iTREE: Long-term variability of tree growth in a changing environment - identifying physiological mechanisms using stable C and O isotopes in tree rings.

NASA Astrophysics Data System (ADS)

Siegwolf, R. T. W.; Buchmann, N.; Frank, D.; Joos, F.; Kahmen, A.; Treydte, K.; Leuenberger, M.; Saurer, M.

2012-04-01

Trees play are a critical role in the carbon cycle - their photosynthetic assimilation is one of the largest terrestrial carbon fluxes and their standing biomass represents the largest carbon pool of the terrestrial biosphere. Understanding how tree physiology and growth respond to long-term environmental change is pivotal to predict the magnitude and direction of the terrestrial carbon sink. iTREE is an interdisciplinary research framework to capitalize on synergies among leading dendroclimatologists, plant physiologists, isotope specialists, and global carbon cycle modelers with the objectives of reducing uncertainties related to tree/forest growth in the context of changing natural environments. Cross-cutting themes in our project are tree rings, stable isotopes, and mechanistic modelling. We will (i) establish a European network of tree-ring based isotope time-series to retrodict interannual to long-term tree physiological changes, (ii) conduct laboratory and field experiments to adapt a mechanistic isotope model to derive plant physiological variables from tree-ring isotopes, (iii) implement this model into a dynamic global vegetation model, and perform subsequent model-data validation exercises to refine model representation of plant physiological processes and (iv) attribute long-term variation in tree growth to plant physiological and environmental drivers, and identify how our refined knowledge revises predictions of the coupled carbon-cycle climate system. We will contribute to i) advanced quantifications of long-term variation in tree growth across Central Europe, ii) novel long-term information on key physiological processes that underlie variations in tree growth, and iii) improved carbon cycle models that can be employed to revise predictions of the coupled carbon-cycle climate system. Hence iTREE will significantly contribute towards a seamless understanding of the responses of terrestrial ecosystems to long-term environmental change, and ultimately help reduce uncertainties of the magnitude and direction of the past and future terrestrial carbon sink.

Selective consumption and metabolic allocation of terrestrial and algal carbon determine allochthony in lake bacteria.

PubMed

Guillemette, François; Leigh McCallister, S; Del Giorgio, Paul A

2016-06-01

Here we explore strategies of resource utilization and allocation of algal versus terrestrially derived carbon (C) by lake bacterioplankton. We quantified the consumption of terrestrial and algal dissolved organic carbon, and the subsequent allocation of these pools to bacterial growth and respiration, based on the δ(13)C isotopic signatures of bacterial biomass and respiratory carbon dioxide (CO2). Our results confirm that bacterial communities preferentially remove algal C from the terrestrially dominated organic C pool of lakes, but contrary to current assumptions, selectively allocate this autochthonous substrate to respiration, whereas terrestrial C was preferentially allocated to biosynthesis. The results provide further evidence of a mechanism whereby inputs of labile, algal-derived organic C may stimulate the incorporation of a more recalcitrant, terrestrial C pool. This mechanism resulted in a counterintuitive pattern of high and relatively constant levels of allochthony (~76%) in bacterial biomass across lakes that otherwise differ greatly in productivity and external inputs.

Selective consumption and metabolic allocation of terrestrial and algal carbon determine allochthony in lake bacteria

PubMed Central

Guillemette, François; Leigh McCallister, S; del Giorgio, Paul A

2016-01-01

Here we explore strategies of resource utilization and allocation of algal versus terrestrially derived carbon (C) by lake bacterioplankton. We quantified the consumption of terrestrial and algal dissolved organic carbon, and the subsequent allocation of these pools to bacterial growth and respiration, based on the δ13C isotopic signatures of bacterial biomass and respiratory carbon dioxide (CO2). Our results confirm that bacterial communities preferentially remove algal C from the terrestrially dominated organic C pool of lakes, but contrary to current assumptions, selectively allocate this autochthonous substrate to respiration, whereas terrestrial C was preferentially allocated to biosynthesis. The results provide further evidence of a mechanism whereby inputs of labile, algal-derived organic C may stimulate the incorporation of a more recalcitrant, terrestrial C pool. This mechanism resulted in a counterintuitive pattern of high and relatively constant levels of allochthony (~76%) in bacterial biomass across lakes that otherwise differ greatly in productivity and external inputs. PMID:26623544

Analysis of Terrestrial Carbon Stocks in a Small Catchment of Northeastern Siberia

NASA Astrophysics Data System (ADS)

Heard, K.; Natali, S.; Bunn, A. G.; Loranty, M. M.; Kholodov, A. L.; Schade, J. D.; Berner, L. T.; Spektor, V.; Zimov, N.; Alexander, H. D.

2015-12-01

As arctic terrestrial ecosystems comprise about one-third of the global terrestrial ecosystem carbon total, understanding arctic carbon cycling and the feedback of terrestrial carbon pools to accelerated warming is an issue of global concern. For this research, we examined above- and belowground carbon stocks in a larch-dominated catchment underlain by yedoma and located within the Kolyma River watershed in northeastern Siberia. We quantified carbon stocks in vegetation, active layer, and permafrost, and we assessed the correlation between plant and active layer carbon pools and four environmental correlates — slope, solar insolation, canopy density, and leaf area index ­— at 20 sites. Carbon in the active layer was approximately four times greater than aboveground carbon pools (972 g C m-2), and belowground carbon to 1 m depth was approximately 18 times greater than aboveground carbon pools. Canopy density and slope had a robust positive association with aboveground carbon pools, and soil moisture was positively related to %C in organic, thawed mineral and permafrost soil. Thaw depth was negatively correlated with moss cover and larch biomass, highlighting the importance of vegetation and surface characteristics on permafrost carbon vulnerability. These data suggest that landscape and ecosystem characteristics affect carbon accumulation and storage, but they also play an important role in stabilizing permafrost carbon pools.

Towards a paradigm shift in the modeling of soil organic carbon decomposition for earth system models

NASA Astrophysics Data System (ADS)

He, Yujie

Soils are the largest terrestrial carbon pools and contain approximately 2200 Pg of carbon. Thus, the dynamics of soil carbon plays an important role in the global carbon cycle and climate system. Earth System Models are used to project future interactions between terrestrial ecosystem carbon dynamics and climate. However, these models often predict a wide range of soil carbon responses and their formulations have lagged behind recent soil science advances, omitting key biogeochemical mechanisms. In contrast, recent mechanistically-based biogeochemical models that explicitly account for microbial biomass pools and enzyme kinetics that catalyze soil carbon decomposition produce notably different results and provide a closer match to recent observations. However, a systematic evaluation of the advantages and disadvantages of the microbial models and how they differ from empirical, first-order formulations in soil decomposition models for soil organic carbon is still needed. This dissertation consists of a series of model sensitivity and uncertainty analyses and identifies dominant decomposition processes in determining soil organic carbon dynamics. Poorly constrained processes or parameters that require more experimental data integration are also identified. This dissertation also demonstrates the critical role of microbial life-history traits (e.g. microbial dormancy) in the modeling of microbial activity in soil organic matter decomposition models. Finally, this study surveys and synthesizes a number of recently published microbial models and provides suggestions for future microbial model developments.

Environmental forcing of terrestrial carbon isotope excursion amplification across five Eocene hyperthermals

NASA Astrophysics Data System (ADS)

Bowen, G. J.; Abels, H.

2015-12-01

Abrupt changes in the isotope composition of exogenic carbon pools accompany many major episodes of global change in the geologic record. The global expression of this change in substrates that reflect multiple carbon pools provides important evidence that many events reflect persistent, global redistribution of carbon between reduced and oxidized stocks. As the diversity of records documenting any event grows, however, discrepancies in the expression of carbon isotope change among substrates are almost always revealed. These differences in magnitude, pace, and pattern of change can complicate interpretations of global carbon redistribution, but under ideal circumstances can also provide additional information on changes in specific environmental and biogeochemical systems that accompanied the global events. Here we evaluate possible environmental influences on new terrestrial records of the negative carbon isotope excursions (CIEs) associated with multiple hyperthermals of the Early Eocene, which show a common pattern of amplified carbon isotope change in terrestrial paleosol carbonate records relative to that recorded in marine substrates. Scaling relationships between climate and carbon-cycle proxies suggest that that the climatic (temperature) impact of each event scaled proportionally with the magnitude of its marine CIE, likely implying that all events involved release of reduced carbon with a similar isotopic composition. Amplification of the terrestrial CIEs, however, does not scale with event magnitude, being proportionally less for the first, largest event (the PETM). We conduct a sensitivity test of a coupled plant-soil carbon isotope model to identify conditions that could account for the observed CIE scaling. At least two possibilities consistent with independent lines of evidence emerge: first, varying effects of pCO2 change on photosynthetic carbon isotope discrimination under changing background pCO2, and second, contrasting changes in regional hydroclimate during the PETM and subsequent hyperthermals. These mechanisms have very different implications for the reconstruction of environmental conditions, and resolving the correct interpretation will require new, complimentary records of plant and soil conditions associated with the Early Eocene hyperthermals.

Ecosystem carbon storage does not vary with mean annual temperature in Hawaiian tropical montane wet forests.

PubMed

Selmants, Paul C; Litton, Creighton M; Giardina, Christian P; Asner, Gregory P

2014-09-01

Theory and experiment agree that climate warming will increase carbon fluxes between terrestrial ecosystems and the atmosphere. The effect of this increased exchange on terrestrial carbon storage is less predictable, with important implications for potential feedbacks to the climate system. We quantified how increased mean annual temperature (MAT) affects ecosystem carbon storage in above- and belowground live biomass and detritus across a well-constrained 5.2 °C MAT gradient in tropical montane wet forests on the Island of Hawaii. This gradient does not systematically vary in biotic or abiotic factors other than MAT (i.e. dominant vegetation, substrate type and age, soil water balance, and disturbance history), allowing us to isolate the impact of MAT on ecosystem carbon storage. Live biomass carbon did not vary predictably as a function of MAT, while detrital carbon declined by ~14 Mg of carbon ha(-1) for each 1 °C rise in temperature - a trend driven entirely by coarse woody debris and litter. The largest detrital pool, soil organic carbon, was the most stable with MAT and averaged 48% of total ecosystem carbon across the MAT gradient. Total ecosystem carbon did not vary significantly with MAT, and the distribution of ecosystem carbon between live biomass and detritus remained relatively constant across the MAT gradient at ~44% and ~56%, respectively. These findings suggest that in the absence of alterations to precipitation or disturbance regimes, the size and distribution of carbon pools in tropical montane wet forests will be less sensitive to rising MAT than predicted by ecosystem models. This article also provides needed detail on how individual carbon pools and ecosystem-level carbon storage will respond to future warming. © 2014 John Wiley & Sons Ltd.

Incorporating incorporating economic models into seasonal pool conservation planning

USGS Publications Warehouse

Freeman, Robert C.; Bell, Kathleen P.; Calhoun, Aram J.K.; Loftin, Cyndy

2012-01-01

Massachusetts, New Jersey, Connecticut, and Maine have adopted regulatory zones around seasonal (vernal) pools to conserve terrestrial habitat for pool-breeding amphibians. Most amphibians require access to distinct seasonal habitats in both terrestrial and aquatic ecosystems because of their complex life histories. These habitat requirements make them particularly vulnerable to land uses that destroy habitat or limit connectivity (or permeability) among habitats. Regulatory efforts focusing on breeding pools without consideration of terrestrial habitat needs will not ensure the persistence of pool-breeding amphibians. We used GIS to combine a discrete-choice, parcel-scale economic model of land conversion with a landscape permeability model based on known habitat requirements of wood frogs (Lithobates sylvaticus) in Maine (USA) to examine permeability among habitat elements for alternative future scenarios. The economic model predicts future landscapes under different subdivision open space and vernal pool regulatory requirements. Our model showed that even “no build” permit zones extending 76 m (250 ft) outward from the pool edge were insufficient to assure permeability among required habitat elements. Furthermore, effectiveness of permit zones may be inconsistent due to interactions with other growth management policies, highlighting the need for local and state planning for the long-term persistence of pool-breeding amphibians in developing landscapes.

Insights into soil carbon dynamics across climatic gradients from carbon-pool specific radiocarbon analyses

NASA Astrophysics Data System (ADS)

van der Voort, Tessa Sophia; Hagedorn, Frank; McIntyre, Cameron; Zell, Claudia; Eglinton, Timothy Ian

2017-04-01

Soil carbon constitutes the largest terrestrial reservoir of organic carbon, and therefore understanding the mechanisms and drivers of carbon stabilization is crucial, especially in the framework of climate change. The understanding of the dependence of soil organic turnover in specific carbon pools as related to e.g. climate, soil texture and mineralogy is limited. In this framework, radiocarbon constitutes a uniquely powerful tool that help to unravel carbon dynamics from decadal to millennial timescales. This project combines bulk and pool-specific radiocarbon analyses in the top and deep soil on a wide range of forested soils that span a large climatic gradient (MAT 1.3-9.2°C, MAP 600 to 2100 mm m-2y-1). These well-studies sites are part of the Long-Term Forest Ecosystem Research (LWF) program of the Swiss Federal Institute for Forest, Snow and Landscape research (WSL). This study aims to combine the insights gained from bulk and pool-specific turnover to environmental conditions and molecular composition of soil carbon. The pools investigated span the mineral-associated (occluded and heavy fractions from density fractionation) and potentially water-soluble (free light fractions from density fractionation and water extractable organic carbon) organic carbon fractions. Pool-specific radiocarbon work is augmented by the measurement of abundance of compounds such as alkanes, fatty acids and lignin phenols on a subset of samples. Initial results show disparate patterns depending on soil type and in particular soil texture, which could be indicative of various stabilization mechanisms in different soils. Overall, this study provides new insights into the controls of soil organic matter dynamics as related to environmental conditions, in particular in specific sub-pools of carbon.

Carbon Inputs From Riparian Vegetation Limit Oxidation of Physically Bound Organic Carbon Via Biochemical and Thermodynamic Processes

NASA Astrophysics Data System (ADS)

Graham, Emily B.; Tfaily, Malak M.; Crump, Alex R.; Goldman, Amy E.; Bramer, Lisa M.; Arntzen, Evan; Romero, Elvira; Resch, C. Tom; Kennedy, David W.; Stegen, James C.

2017-12-01

In light of increasing terrestrial carbon (C) transport across aquatic boundaries, the mechanisms governing organic carbon (OC) oxidation along terrestrial-aquatic interfaces are crucial to future climate predictions. Here we investigate the biochemistry, metabolic pathways, and thermodynamics corresponding to OC oxidation in the Columbia River corridor using ultrahigh-resolution C characterization. We leverage natural vegetative differences to encompass variation in terrestrial C inputs. Our results suggest that decreases in terrestrial C deposition associated with diminished riparian vegetation induce oxidation of physically bound OC. We also find that contrasting metabolic pathways oxidize OC in the presence and absence of vegetation and—in direct conflict with the "priming" concept—that inputs of water-soluble and thermodynamically favorable terrestrial OC protect bound-OC from oxidation. In both environments, the most thermodynamically favorable compounds appear to be preferentially oxidized regardless of which OC pool microbiomes metabolize. In turn, we suggest that the extent of riparian vegetation causes sediment microbiomes to locally adapt to oxidize a particular pool of OC but that common thermodynamic principles govern the oxidation of each pool (i.e., water-soluble or physically bound). Finally, we propose a mechanistic conceptualization of OC oxidation along terrestrial-aquatic interfaces that can be used to model heterogeneous patterns of OC loss under changing land cover distributions.

Effects of nitrogen deposition on carbon cycle in terrestrial ecosystems of China: A meta-analysis.

PubMed

Chen, Hao; Li, Dejun; Gurmesa, Geshere A; Yu, Guirui; Li, Linghao; Zhang, Wei; Fang, Huajun; Mo, Jiangming

2015-11-01

Nitrogen (N) deposition in China has increased greatly, but the general impact of elevated N deposition on carbon (C) dynamics in Chinese terrestrial ecosystems is not well documented. In this study we used a meta-analysis method to compile 88 studies on the effects of N deposition C cycling on Chinese terrestrial ecosystems. Our results showed that N addition did not change soil C pools but increased above-ground plant C pool. A large decrease in below-ground plant C pool was observed. Our result also showed that the impacts of N addition on ecosystem C dynamics depend on ecosystem type and rate of N addition. Overall, our findings suggest that 1) decreased below-ground plant C pool may limit long-term soil C sequestration; and 2) it is better to treat N-rich and N-limited ecosystems differently in modeling effects of N deposition on ecosystem C cycle. Copyright © 2015 Elsevier Ltd. All rights reserved.

Multimolecular tracers of terrestrial carbon transfer across the pan-Arctic: 14C characteristics of sedimentary carbon components and their environmental controls

NASA Astrophysics Data System (ADS)

Feng, Xiaojuan; Gustafsson, Örjan; Holmes, R. Max; Vonk, Jorien E.; van Dongen, Bart E.; Semiletov, Igor P.; Dudarev, Oleg V.; Yunker, Mark B.; Macdonald, Robie W.; Wacker, Lukas; Montluçon, Daniel B.; Eglinton, Timothy I.

2015-11-01

Distinguishing the sources, ages, and fate of various terrestrial organic carbon (OC) pools mobilized from heterogeneous Arctic landscapes is key to assessing climatic impacts on the fluvial release of carbon from permafrost. Through molecular 14C measurements, including novel analyses of suberin- and/or cutin-derived diacids (DAs) and hydroxy fatty acids (FAs), we compared the radiocarbon characteristics of a comprehensive suite of terrestrial markers (including plant wax lipids, cutin, suberin, lignin, and hydroxy phenols) in the sedimentary particles from nine major arctic and subarctic rivers in order to establish a benchmark assessment of the mobilization patterns of terrestrial OC pools across the pan-Arctic. Terrestrial lipids, including suberin-derived longer-chain DAs (C24,26,28), plant wax FAs (C24,26,28), and n-alkanes (C27,29,31), incorporated significant inputs of aged carbon, presumably from deeper soil horizons. Mobilization and translocation of these "old" terrestrial carbon components was dependent on nonlinear processes associated with permafrost distributions. By contrast, shorter-chain (C16,18) DAs and lignin phenols (as well as hydroxy phenols in rivers outside eastern Eurasian Arctic) were much more enriched in 14C, suggesting incorporation of relatively young carbon supplied by runoff processes from recent vegetation debris and surface layers. Furthermore, the radiocarbon content of terrestrial markers is heavily influenced by specific OC sources and degradation status. Overall, multitracer molecular 14C analysis sheds new light on the mobilization of terrestrial OC from arctic watersheds. Our findings of distinct ages for various terrestrial carbon components may aid in elucidating fate of different terrestrial OC pools in the face of increasing arctic permafrost thaw.

Climatic and Edaphic Effects on the Turnover and Composition of Mineral-Associated Soil Organic Matter in Temperate Deciduous Forests

NASA Astrophysics Data System (ADS)

Jastrow, J. D.; Calderon, F. J.; McFarlane, K. J.; Porras, R. C.; Torn, M. S.; Guilderson, T. P.; Hanson, P. J.

2013-12-01

Soil organic matter (SOM) is the largest reservoir of carbon (C) in terrestrial ecosystems. But, efforts to predict future changes in soil C stocks are challenged by our incomplete understanding of how soil C pools stabilized by different mechanisms will respond to changing climatic conditions and other environmental forcing factors. One approach to quantifying soil C pools of differing stability is to physically fractionate SOM into (1) a free light fraction representing an unprotected C pool, (2) an occluded light fraction characterizing a pool physically protected within aggregates, and (3) a mineral-associated dense fraction approximating a pool stabilized by organomineral interactions. Although the two light fractions are generally considered to be relatively homogenous pools, any assumption that the dense fraction represents a homogenous pool is problematic. To explore the potential for reducing the heterogeneity within the dense fraction, we isolated acid-hydrolyzable and acid-resistant C pools from the dense fraction at four sites representing a range of soil types and the climatic extent of Eastern deciduous forest. Soils were collected from before and after 14C-enriched leaf-litter manipulations at each site. Across all sites, 50-75% of the C in the dense fraction was acid-hydrolyzable, and the mean turnover time of C in this fraction was 1-2 orders of magnitude faster (~35-350 y) than that of the acid-resistant fraction (~300-1500 y). Remarkably, in some cases leaf-derived 14C accounted for up to about 5% of the C in one or both dense fraction pools after only 2 years, demonstrating the existence of a very rapid turnover component within both pools at some sites. Characterization of these mineral-associated C pools by mid-infrared spectroscopy showed variations in C chemistry across sites and site differences in the types of C isolated by hydrolysis. Taken together, these results demonstrate considerable differences within the Eastern deciduous forest in the dynamics of mineral-associated soil C pools that can be related to variations in climate, soil texture, and bioturbation.

Redefining fine roots improves understanding of belowground contributions to terrestrial biosphere processes

DOE PAGES

McCormack, M. Luke; Dickie, Ian A.; Eissenstat, David M.; ...

2015-03-10

Fine roots acquire essential soil resources and mediate biogeochemical cycling in terrestrial ecosystems. Estimates of carbon and nutrient allocation to build and maintain these structures remain uncertain due to challenges in consistent measurement and interpretation of fine-root systems. We define fine roots as all roots less than or equal to 2 mm in diameter, yet it is now recognized that this approach fails to capture the diversity of form and function observed among fine-root orders. We demonstrate how order-based and functional classification frameworks improve our understanding of dynamic root processes in ecosystems dominated by perennial plants. In these frameworks, finemore » roots are separated into either individual root orders or functionally defined into a shorter-lived absorptive pool and a longer-lived transport fine root pool. Furthermore, using these frameworks, we estimate that fine-root production and turnover represent 22% of terrestrial net primary production globally a ca. 30% reduction from previous estimates assuming a single fine-root pool. In the future we hope to develop tools to rapidly differentiate functional fine-root classes, explicit incorporation of mycorrhizal fungi in fine-root studies, and wider adoption of a two-pool approach to model fine roots provide opportunities to better understand belowground processes in the terrestrial biosphere.« less

Carbon pools in China’s terrestrial ecosystems: New estimates based on an intensive field survey

PubMed Central

Tang, Xuli; Zhao, Xia; Bai, Yongfei; Wang, Wantong; Zhao, Yongcun; Wan, Hongwei; Xie, Zongqiang; Shi, Xuezheng; Wu, Bingfang; Wang, Gengxu; Yan, Junhua; Ma, Keping; Du, Sheng; Li, Shenggong; Han, Shijie; Ma, Youxin; Hu, Huifeng; Yang, Yuanhe; Han, Wenxuan; He, Hongling; Yu, Guirui; Fang, Jingyun; Zhou, Guoyi

2018-01-01

China’s terrestrial ecosystems have functioned as important carbon sinks. However, previous estimates of carbon budgets have included large uncertainties owing to the limitations of sample size, multiple data sources, and inconsistent methodologies. In this study, we conducted an intensive field campaign involving 14,371 field plots to investigate all sectors of carbon stocks in China’s forests, shrublands, grasslands, and croplands to better estimate the regional and national carbon pools and to explore the biogeographical patterns and potential drivers of these pools. The total carbon pool in these four ecosystems was 79.24 ± 2.42 Pg C, of which 82.9% was stored in soil (to a depth of 1 m), 16.5% in biomass, and 0.60% in litter. Forests, shrublands, grasslands, and croplands contained 30.83 ± 1.57 Pg C, 6.69 ± 0.32 Pg C, 25.40 ± 1.49 Pg C, and 16.32 ± 0.41 Pg C, respectively. When all terrestrial ecosystems are taken into account, the country’s total carbon pool is 89.27 ± 1.05 Pg C. The carbon density of the forests, shrublands, and grasslands exhibited a strong correlation with climate: it decreased with increasing temperature but increased with increasing precipitation. Our analysis also suggests a significant sequestration potential of 1.9–3.4 Pg C in forest biomass in the next 10–20 years assuming no removals, mainly because of forest growth. Our results update the estimates of carbon pools in China’s terrestrial ecosystems based on direct field measurements, and these estimates are essential to the validation and parameterization of carbon models in China and globally. PMID:29666314

Soil Carbon Residence Time in the Arctic - Potential Drivers of Past and Future Change

NASA Astrophysics Data System (ADS)

Huntzinger, D. N.; Fisher, J.; Schwalm, C. R.; Hayes, D. J.; Stofferahn, E.; Hantson, W.; Schaefer, K. M.; Fang, Y.; Michalak, A. M.; Wei, Y.

2017-12-01

Carbon residence time is one of the most important factors controlling carbon cycling in ecosystems. Residence time depends on carbon allocation and conversion among various carbon pools and the rate of organic matter decomposition; all of which rely on environmental conditions, primarily temperature and soil moisture. As a result, residence time is an emergent property of models and a strong determinant of terrestrial carbon storage capacity. However, residence time is poorly constrained in process-based models due, in part, to the lack of data with which to benchmark global-scale models in order to guide model improvements and, ultimately, reduce uncertainty in model projections. Here we focus on improving the understanding of the drivers to observed and simulated carbon residence time in the Arctic-Boreal region (ABR). Carbon-cycling in the ABR represents one of the largest sources of uncertainty in historical and future projections of land-atmosphere carbon dynamics. This uncertainty is depicted in the large spread of terrestrial biospheric model (TBM) estimates of carbon flux and ecosystem carbon pool size in this region. Recent efforts, such as the Arctic-Boreal Vulnerability Experiment (ABoVE), have increased the availability of spatially explicit in-situ and remotely sensed carbon and ecosystem focused data products in the ABR. Together with simulations from Multi-scale Synthesis and Terrestrial Model Intercomparison Project (MsTMIP), we use these observations to evaluate the ability of models to capture soil carbon stocks and changes in the ABR. Specifically, we compare simulated versus observed soil carbon residence times in order to evaluate the functional response and sensitivity of modeled soil carbon stocks to changes in key environmental drivers. Understanding how simulated carbon residence time compares with observations and what drives these differences is critical for improving projections of changing carbon dynamics in the ABR and globally.

Variation in active and passive resource inputs to experimental pools: mechanisms and possible consequences for food webs

USGS Publications Warehouse

Kraus, Johanna M.; Pletcher, Leanna T.; Vonesh, James R.

2010-01-01

1. Cross-ecosystem movements of resources, including detritus, nutrients and living prey, can strongly influence food web dynamics in recipient habitats. Variation in resource inputs is thought to be driven by factors external to the recipient habitat (e.g. donor habitat productivity and boundary conditions). However, inputs of or by ‘active’ living resources may be strongly influenced by recipient habitat quality when organisms exhibit behavioural habitat selection when crossing ecosystem boundaries. 2. To examine whether behavioural responses to recipient habitat quality alter the relative inputs of ‘active’ living and ‘passive’ detrital resources to recipient food webs, we manipulated the presence of caged predatory fish and measured biomass, energy and organic content of inputs to outdoor experimental pools of adult aquatic insects, frog eggs, terrestrial plant matter and terrestrial arthropods. 3. Caged fish reduced the biomass, energy and organic matter donated to pools by tree frog eggs by ∼70%, but did not alter insect colonisation or passive allochthonous inputs of terrestrial arthropods and plant material. Terrestrial plant matter and adult aquatic insects provided the most energy and organic matter inputs to the pools (40–50%), while terrestrial arthropods provided the least (7%). Inputs of frog egg were relatively small but varied considerably among pools and over time (3%, range = 0–20%). Absolute and proportional amounts varied by input type. 4. Aquatic predators can strongly affect the magnitude of active, but not passive, inputs and that the effect of recipient habitat quality on active inputs is variable. Furthermore, some active inputs (i.e. aquatic insect colonists) can provide similar amounts of energy and organic matter as passive inputs of terrestrial plant matter, which are well known to be important. Because inputs differ in quality and the trophic level they subsidise, proportional changes in input type could have strong effects on recipient food webs. 5. Cross-ecosystem resource inputs have previously been characterised as donor-controlled. However, control by the recipient food web could lead to greater feedback between resource flow and consumer dynamics than has been appreciated so far.

How well do we succeed in modeling the global soil carbon pools?

NASA Astrophysics Data System (ADS)

Viskari, T.; Liski, J.

2017-12-01

Terrestrial carbon pools are a crucial part of the global carbon cycle. Carbon from vegetation is deposited to the soil, which in turn releases carbon dioxide back to the atmosphere through heterotrophic respiration. The resulting soil carbon storage in the largest on land. While there are continuous efforts to improve the modeling of global soil carbon and how this storage is affected by climate change, this research requires still a more reliable baseline on how well the models estimate the current global soil carbon pools. Especially such comparisons are important for identifying the major challenges in the current soil carbon models. Here, we used the Yasso soil carbon model to create a global soil carbon map at a 0.5 degree resolution based on the available climate, land cover and vegetation productivity information. Yasso model describes the soil carbon cycling by pools that represent the breaking down of dead organic matter. We compared the model results to a measurement based projection of global soil carbon pools, and we examined the differences and spatial correlations between the two maps. In our findings, the modelled predictions captured the overall soil carbon distributions within 5 kgCm-2 on 63 % of the land area. The spatial distributions fit each other as well. The average soil carbon is smaller with the Yasso prediction ( 8.5 kg m-2) than with the measurement map ( 10 kg m-2) and there are notable areas, such as Siberia and Southern North America, where there are large differences between the model predictions and measurements. These results not only encourage future development of soil carbon models, but also highlight problem areas to focus and improve upon.

Ecohydrological dynamics of peatlands and adjacent upland forests in the Rocky Mountains

NASA Astrophysics Data System (ADS)

Millar, D.; Parsekian, A.; Mercer, J.; Ewers, B. E.; Mackay, D. S.; Williams, D. G.; Cooper, D. J.; Ronayne, M. J.

2017-12-01

Mountain peatlands are susceptible to a changing climate via changes in the water cycle. Understanding the impacts of such changes requires knowledge of the hydrological processes within these peatlands and in the upland forests that supply them with water. We investigated hydrological processes in peatland catchments in the Rocky Mountains by developing empirical models of groundwater dynamics, and are working to improve subsurface water dynamics in a ecohydrological process model, the Terrestrial Regional Ecosystem Exchange Simulator (TREES). Results from empirical models showed major differences in water budget components between two peatlands with differing climate, vegetation, and hydrogeological settings. Several-fold higher rates of evapotranspiration from the saturated zone, and groundwater inflow were observed for a sloping fen in southern Wyoming than that of a basin fen in southwestern Colorado, where rainfall was two-fold higher due to stronger influence of the North American monsoon. We also present ongoing work coupling stable water isotope and borehole nuclear magnetic resonance analyses to test which soil water pools (bound or mobile) are used by dominant upland and peatland vegetation in two catchments in southern Wyoming. These data are being used to test whether the root hydraulic mechanisms in TREES can simulate water uptake from these two soil water pools, and sap flux measurements are being used to evaluate simulated transpiration. Preliminary results from this work suggest that upland vegetation utilize tightly-bound soil water pools, as these pools comprise the largest amount of subsurface water (> 80%) in the vadose zone long after snow melt. Conversely, it appears that herbaceous peatland hydrophytes may preferentially utilize mobile soil water pools, since their roots extend below the water table. The results of this work are expected to increase predictive understanding of hydrological processes in these important ecosystems.

Temperature acclimation of photosynthesis and respiration: A key uncertainty in the carbon cycle-climate feedback

NASA Astrophysics Data System (ADS)

Lombardozzi, Danica L.; Bonan, Gordon B.; Smith, Nicholas G.; Dukes, Jeffrey S.; Fisher, Rosie A.

2015-10-01

Earth System Models typically use static responses to temperature to calculate photosynthesis and respiration, but experimental evidence suggests that many plants acclimate to prevailing temperatures. We incorporated representations of photosynthetic and leaf respiratory temperature acclimation into the Community Land Model, the terrestrial component of the Community Earth System Model. These processes increased terrestrial carbon pools by 20 Pg C (22%) at the end of the 21st century under a business-as-usual (Representative Concentration Pathway 8.5) climate scenario. Including the less certain estimates of stem and root respiration acclimation increased terrestrial carbon pools by an additional 17 Pg C (~40% overall increase). High latitudes gained the most carbon with acclimation, and tropical carbon pools increased least. However, results from both of these regions remain uncertain; few relevant data exist for tropical and boreal plants or for extreme temperatures. Constraining these uncertainties will produce more realistic estimates of land carbon feedbacks throughout the 21st century.

Effects of Litter and Nutrient Additions on Soil Carbon Cycling in a Tropical Forest

NASA Astrophysics Data System (ADS)

Cusack, D. F.; Halterman, S.; Turner, B. L.; Tanner, E.; Wright, S. J.

2014-12-01

Soil carbon (C) dynamics present one of the largest sources of uncertainty in global C cycle models, with tropical forest soils containing some of the largest terrestrial C stocks. Drastic changes in soil C storage and loss are likely to occur if global change alters plant net primary production (NPP) and/or nutrient availability in these ecosystems. We assessed the effects of litter removal and addition, as well as fertilization with nitrogen (N), phosphorus (P), and/or potassium (K), on soil C stocks in a tropical seasonal forest in Panama after ten and sixteen years, respectively. We used a density fractionation scheme to assess manipulation effects on rapidly and slowly cycling pools of C. Soil samples were collected in the wet and dry seasons from 0-5 cm and 5-10 cm depths in 15- 45x45 m plots with litter removal, 2x litter addition, and control (n=5), and from 32- 40x40 m fertilization plots with factorial additions of N, P, and K. We hypothesized that litter addition would increase all soil C fractions, but that the magnitude of the effect on rapidly-cycling C would be dampened by a fertilization effect. Results for the dry season show that the "free light" C fraction, or rapidly cycling soil C pool, was significantly different among the three litter treatments, comprising 5.1 ± 0.9 % of total soil mass in the litter addition plots, 2.7 ± 0.3 % in control plots, and 1.0 ± 0.1 % in litter removal plots at the 0-5cm depth (means ± one standard error, p < 0.05). Bulk soil C results are similar to observed changes in the rapidly cycling C pool for the litter addition and removal. Fertilization treatments on average diminished this C pool size relative to control plots, although there was substantial variability among fertilization treatments. In particular, addition of N and P together did not significantly alter rapidly cycling C pool sizes (4.1 ± 1.2 % of total soil mass) relative to controls (3.5 ± 0.4 %), whereas addition of P alone resulted in significantly smaller rapidly cycling C pools (1.8 ± 0.4 %, p < 0.05). These results demonstrate that changes in tropical forest NPP have high potential to alter the storage and cycling of C in C-rich soils, and that secondary fertilization effects are likely.

Abundant carbon substrates drive extremely high sulfate reduction rates and methane fluxes in Prairie Pothole Wetlands.

PubMed

Dalcin Martins, Paula; Hoyt, David W; Bansal, Sheel; Mills, Christopher T; Tfaily, Malak; Tangen, Brian A; Finocchiaro, Raymond G; Johnston, Michael D; McAdams, Brandon C; Solensky, Matthew J; Smith, Garrett J; Chin, Yu-Ping; Wilkins, Michael J

2017-08-01

Inland waters are increasingly recognized as critical sites of methane emissions to the atmosphere, but the biogeochemical reactions driving such fluxes are less well understood. The Prairie Pothole Region (PPR) of North America is one of the largest wetland complexes in the world, containing millions of small, shallow wetlands. The sediment pore waters of PPR wetlands contain some of the highest concentrations of dissolved organic carbon (DOC) and sulfur species ever recorded in terrestrial aquatic environments. Using a suite of geochemical and microbiological analyses, we measured the impact of sedimentary carbon and sulfur transformations in these wetlands on methane fluxes to the atmosphere. This research represents the first study of coupled geochemistry and microbiology within the PPR and demonstrates how the conversion of abundant labile DOC pools into methane results in some of the highest fluxes of this greenhouse gas to the atmosphere ever reported. Abundant DOC and sulfate additionally supported some of the highest sulfate reduction rates ever measured in terrestrial aquatic environments, which we infer to account for a large fraction of carbon mineralization in this system. Methane accumulations in zones of active sulfate reduction may be due to either the transport of free methane gas from deeper locations or the co-occurrence of methanogenesis and sulfate reduction. If both respiratory processes are concurrent, any competitive inhibition of methanogenesis by sulfate-reducing bacteria may be lessened by the presence of large labile DOC pools that yield noncompetitive substrates such as methanol. Our results reveal some of the underlying mechanisms that make PPR wetlands biogeochemical hotspots, which ultimately leads to their critical, but poorly recognized role in regional greenhouse gas emissions. © 2017 John Wiley & Sons Ltd.

Abundant carbon substrates drive extremely high sulfate reduction rates and methane fluxes in Prairie Pothole Wetlands

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dalcin Martins, Paula; Hoyt, David W.; Bansal, Sheel

Inland waters are increasingly recognized as critical sites of methane emissions to the atmosphere, but the biogeochemical reactions driving such fluxes are less well understood. The Prairie Pothole Region (PPR) of North America is one of the largest wetland complexes in the world, containing millions of small, shallow wetlands. The sediment pore waters of PPR wetlands contain some of the highest concentrations of dissolved organic carbon (DOC) and sulfur species ever recorded in terrestrial aquatic environments. Using a suite of geochemical and microbiological analyses we measured the impact of sedimentary carbon and sulfur transformations in these wetlands on methane fluxesmore » to the atmosphere. This research represents the first study of coupled geochemistry and microbiology within the PPR, and demonstrates how the conversion of abundant labile DOC pools into methane results in some of the highest fluxes of this greenhouse gas to the atmosphere ever reported. Abundant DOC and sulfate additionally supported some of the highest sulfate reduction rates ever measured in terrestrial aquatic environments, which we infer to account for a large fraction of carbon mineralization in this system. Methane accumulations in zones of active sulfate reduction may be due to either the transport of free methane gas from deeper locations, or the co-occurrence of methanogenesis and sulfate reduction. If both respiratory processes are concurrent, any competitive inhibition of methanogenesis by sulfate-reducing bacteria may be lessened by the presence of large labile DOC pools that yield non-competitive substrates such as methanol. Our results reveal some of the underlying mechanisms that make PPR wetlands biogeochemical hotspots, which ultimately leads to their critical, but poorly recognized role in regional greenhouse gas emissions.« less

Distribution, Source and Fate of Dissolved Organic Matter in Shelf Seas

NASA Astrophysics Data System (ADS)

Carr, N.; Mahaffey, C.; Hopkins, J.; Sharples, J.; Williams, R. G.; Davis, C. E.

2016-02-01

Dissolved organic matter (DOM) is a complex array of molecules containing carbon (DOC), nitrogen (DON) and phosphorous (DOP), and represents the largest pool of organic matter in the marine environment. DOM in the sea originates from a variety of sources, including allochthonous inputs of terrestrial DOM from land via rivers, and autochthonous inputs through in-situ biotic processes that include phytoplankton exudation, grazing and cell lysis. Marine DOM is a substrate for bacterial growth and can act as a source of nutrients for autotrophs. However, a large component of DOM is biologically refractory. This pool is carbon-rich and nutrient-poor, and can transport and store its compositional elements over large areas and on long time scales. The role of DOM in the shelf seas is currently unclear, despite these regions acting as conduits between the land and open ocean, and also being highly productive ecosystems. Using samples collected across the Northwest European Shelf Sea, we studied the distribution, source, seasonality and potential fate of DOM using a combination of analytical tools, including analysis of amino acids, DOM absorbance spectra and excitation emission matrices, in conjunction with parallel factor analysis (PARAFAC). Strong cross shelf and seasonal gradients in DOM source and lability were found. We observed a strong seasonally dependent significant correlation between salinity and terrestrial DOM in the bottom mixed layer, an enrichment of DOM at the shelf edge in winter and a three-fold increase in fresh marine DOM coinciding with the timing of a spring bloom. Together, our findings illustrate the dynamic nature of DOM in shelf seas over a seasonal cycle and, highlight the potential for DOM to play a key role in the carbon cycle in these regions.

Abundant carbon substrates drive extremely high sulfate reduction rates and methane fluxes in Prairie Pothole Wetlands

USGS Publications Warehouse

Martins, Paula; Hoyt, David W.; Bansal, Sheel; Mills, Christopher T.; Tfaily, Malak; Tangen, Brian; Finocchiaro, Raymond; Johnston, Michael D.; McAdams, Brandon C.; Solensky, Matthew J.; Smith, Garrett J.; Chin, Yu-Ping; Wilkins, Michael J.

2017-01-01

Inland waters are increasingly recognized as critical sites of methane emissions to the atmosphere, but the biogeochemical reactions driving such fluxes are less well understood. The Prairie Pothole Region (PPR) of North America is one of the largest wetland complexes in the world, containing millions of small, shallow wetlands. The sediment pore waters of PPR wetlands contain some of the highest concentrations of dissolved organic carbon (DOC) and sulfur species ever recorded in terrestrial aquatic environments. Using a suite of geochemical and microbiological analyses, we measured the impact of sedimentary carbon and sulfur transformations in these wetlands on methane fluxes to the atmosphere. This research represents the first study of coupled geochemistry and microbiology within the PPR and demonstrates how the conversion of abundant labile DOC pools into methane results in some of the highest fluxes of this greenhouse gas to the atmosphere ever reported. Abundant DOC and sulfate additionally supported some of the highest sulfate reduction rates ever measured in terrestrial aquatic environments, which we infer to account for a large fraction of carbon mineralization in this system. Methane accumulations in zones of active sulfate reduction may be due to either the transport of free methane gas from deeper locations or the co-occurrence of methanogenesis and sulfate reduction. If both respiratory processes are concurrent, any competitive inhibition of methanogenesis by sulfate-reducing bacteria may be lessened by the presence of large labile DOC pools that yield noncompetitive substrates such as methanol. Our results reveal some of the underlying mechanisms that make PPR wetlands biogeochemical hotspots, which ultimately leads to their critical, but poorly recognized role in regional greenhouse gas emissions.

Effects of predators on fish and crayfish survival in intermittent streams

USGS Publications Warehouse

Dekar, Matthew P.; Magoulick, Daniel D.

2013-01-01

Predation from aquatic and terrestrial predators arc important factors structuring the size and depth distribution of aquatic prey. We conducted mesocosm and tethering experiments on Little Mulberry Creek in northwest Arkansas during low flows to examine the effects of predators on fish and crayfish survival in intermittent streams Using shallow artificial pools (10 cm deep) and predator exclusions, we tested the hypothesis that large-bodied fish are at greater risk from terrestrial predators in shallow habitats compared to small-bodied individuals. Twenty-four circular pools (12 open top. 12 closed top) were stocked with two size classes of Campostoma anomalum (Central Stonerller) and deployed systematically in a single stream pool. In addition, we used a crayfish tethering experiment to test the hypothesis that the survival of small and large crayfish is greater in shallow and deep habitats, respectively. We tethered two size classes of Orconectes meeki meeki (Meek's Crayfish) along shallow and deep transects in two adjacent stream pools and measured survival for 15 days. During both experiments, we monitored the presence or absence of predators by visual observation and from scat surveys. We demonstrated a negative effect of terrestrial predators on Central Stonerller survival in the artificial pools, and larger individuals were more susceptible to predation. In contrast, small crayfish experienced low survival at all depths and large crayfish were preyed upon much less intensively during the tethering study, particularly in the pool with larger substrate. More studies are needed to understand how stream drying and environmental heterogeneity influence the complex interactions between predator and prey populations in intermittent streams.

Impacts of large-scale climatic disturbances on the terrestrial carbon cycle.

PubMed

Erbrecht, Tim; Lucht, Wolfgang

2006-07-27

The amount of carbon dioxide in the atmosphere steadily increases as a consequence of anthropogenic emissions but with large interannual variability caused by the terrestrial biosphere. These variations in the CO2 growth rate are caused by large-scale climate anomalies but the relative contributions of vegetation growth and soil decomposition is uncertain. We use a biogeochemical model of the terrestrial biosphere to differentiate the effects of temperature and precipitation on net primary production (NPP) and heterotrophic respiration (Rh) during the two largest anomalies in atmospheric CO2 increase during the last 25 years. One of these, the smallest atmospheric year-to-year increase (largest land carbon uptake) in that period, was caused by global cooling in 1992/93 after the Pinatubo volcanic eruption. The other, the largest atmospheric increase on record (largest land carbon release), was caused by the strong El Niño event of 1997/98. We find that the LPJ model correctly simulates the magnitude of terrestrial modulation of atmospheric carbon anomalies for these two extreme disturbances. The response of soil respiration to changes in temperature and precipitation explains most of the modelled anomalous CO2 flux. Observed and modelled NEE anomalies are in good agreement, therefore we suggest that the temporal variability of heterotrophic respiration produced by our model is reasonably realistic. We therefore conclude that during the last 25 years the two largest disturbances of the global carbon cycle were strongly controlled by soil processes rather then the response of vegetation to these large-scale climatic events.

Impacts of large-scale climatic disturbances on the terrestrial carbon cycle

PubMed Central

Erbrecht, Tim; Lucht, Wolfgang

2006-01-01

Background The amount of carbon dioxide in the atmosphere steadily increases as a consequence of anthropogenic emissions but with large interannual variability caused by the terrestrial biosphere. These variations in the CO2 growth rate are caused by large-scale climate anomalies but the relative contributions of vegetation growth and soil decomposition is uncertain. We use a biogeochemical model of the terrestrial biosphere to differentiate the effects of temperature and precipitation on net primary production (NPP) and heterotrophic respiration (Rh) during the two largest anomalies in atmospheric CO2 increase during the last 25 years. One of these, the smallest atmospheric year-to-year increase (largest land carbon uptake) in that period, was caused by global cooling in 1992/93 after the Pinatubo volcanic eruption. The other, the largest atmospheric increase on record (largest land carbon release), was caused by the strong El Niño event of 1997/98. Results We find that the LPJ model correctly simulates the magnitude of terrestrial modulation of atmospheric carbon anomalies for these two extreme disturbances. The response of soil respiration to changes in temperature and precipitation explains most of the modelled anomalous CO2 flux. Conclusion Observed and modelled NEE anomalies are in good agreement, therefore we suggest that the temporal variability of heterotrophic respiration produced by our model is reasonably realistic. We therefore conclude that during the last 25 years the two largest disturbances of the global carbon cycle were strongly controlled by soil processes rather then the response of vegetation to these large-scale climatic events. PMID:16930463

Sinks for nitrogen inputs in terrestrial ecosystems: a meta-analysis of 15N tracer field studies

USGS Publications Warehouse

Templer, P.H.; Mack, M.C.; Chapin, F. S.; Christenson, L.M.; Compton, J.E.; Crook, H.D.; Currie, W.S.; Curtis, C.J.; Dail, D.B.; D'Antonio, C. M.; Emmett, B.A.; Epstein, H.E.; Goodale, C.L.; Gundersen, P.; Hobbie, S.E.; Holland, K.; Hooper, D.U.; Hungate, B.A.; Lamontagne, S.; Nadelhoffer, K.J.; Osenberg, C.W.; Perakis, S.S.; Schleppi, P.; Schimel, J.; Schmidt, I.K.; Sommerkorn, M.; Spoelstra, J.; Tietema, A.; Wessel, W.W.; Zak, D.R.

2012-01-01

Effects of anthropogenic nitrogen (N) deposition and the ability of terrestrial ecosystems to store carbon (C) depend in part on the amount of N retained in the system and its partitioning among plant and soil pools. We conducted a meta-analysis of studies at 48 sites across four continents that used enriched 15N isotope tracers in order to synthesize information about total ecosystem N retention (i.e., total ecosystem 15N recovery in plant and soil pools) across natural systems and N partitioning among ecosystem pools. The greatest recoveries of ecosystem 15N tracer occurred in shrublands (mean, 89.5%) and wetlands (84.8%) followed by forests (74.9%) and grasslands (51.8%). In the short term (15N tracer application), total ecosystem 15N recovery was negatively correlated with fine-root and soil 15N natural abundance, and organic soil C and N concentration but was positively correlated with mean annual temperature and mineral soil C:N. In the longer term (3–18 months after 15N tracer application), total ecosystem 15N retention was negatively correlated with foliar natural-abundance 15N but was positively correlated with mineral soil C and N concentration and C: N, showing that plant and soil natural-abundance 15N and soil C:N are good indicators of total ecosystem N retention. Foliar N concentration was not significantly related to ecosystem 15N tracer recovery, suggesting that plant N status is not a good predictor of total ecosystem N retention. Because the largest ecosystem sinks for 15N tracer were below ground in forests, shrublands, and grasslands, we conclude that growth enhancement and potential for increased C storage in aboveground biomass from atmospheric N deposition is likely to be modest in these ecosystems. Total ecosystem 15N recovery decreased with N fertilization, with an apparent threshold fertilization rate of 46 kg N·ha-1·yr-1 above which most ecosystems showed net losses of applied 15N tracer in response to N fertilizer addition.

The potential of detecting intermediate-scale biomass and canopy interception in a coniferous forest using cosmic-ray neutron intensity measurements and neutron transport modeling

NASA Astrophysics Data System (ADS)

Andreasen, M.; Looms, M. C.; Bogena, H. R.; Desilets, D.; Zreda, M. G.; Sonnenborg, T. O.; Jensen, K. H.

2014-12-01

The water stored in the various compartments of the terrestrial ecosystem (in snow, canopy interception, soil and litter) controls the exchange of the water and energy between the land surface and the atmosphere. Therefore, measurements of the water stored within these pools are critical for the prediction of e.g. evapotranspiration and groundwater recharge. The detection of cosmic-ray neutron intensity is a novel non-invasive method for the quantification of continuous intermediate-scale soil moisture. The footprint of the cosmic-ray neutron probe is a hemisphere of a few hectometers and subsurface depths of 10-70 cm depending on wetness. The cosmic-ray neutron method offers measurements at a scale between the point-scale measurements and large-scale satellite retrievals. The cosmic-ray neutron intensity is inversely correlated to the hydrogen stored within the footprint. Overall soil moisture represents the largest pool of hydrogen and changes in the soil moisture clearly affect the cosmic-ray neutron signal. However, the neutron intensity is also sensitive to variations of hydrogen in snow, canopy interception and biomass offering the potential to determine water content in such pools from the signal. In this study we tested the potential of determining canopy interception and biomass using cosmic-ray neutron intensity measurements within the framework of the Danish Hydrologic Observatory (HOBE) and the Terrestrial Environmental Observatories (TERENO). Continuous measurements at the ground and the canopy level, along with profile measurements were conducted at towers at forest field sites. Field experiments, including shielding the cosmic-ray neutron probes with cadmium foil (to remove lower-energy neutrons) and measuring reference intensity rates at complete water saturated conditions (on the sea close to the HOBE site), were further conducted to obtain an increased understanding of the physics controlling the cosmic-ray neutron transport and the equipment used. Additionally, neutron transport modeling, using the extended version of the Monte Carlo N-Particle Transport Code, was conducted. The responses of the reference condition, different amounts of biomass, soil moisture and canopy interception on the cosmic-ray neutron intensity were simulated and compared to the measurements.

Sinks for nitrogen inputs in terrestrial ecosystems: a meta-analysis of 15N tracer field studies.

PubMed

Templer, P H; Mack, M C; Chapin, F S; Christenson, L M; Compton, J E; Crook, H D; Currie, W S; Curtis, C J; Dail, D B; D'Antonio, C M; Emmett, B A; Epstein, H E; Goodale, C L; Gundersen, P; Hobbie, S E; Holland, K; Hooper, D U; Hungate, B A; Lamontagne, S; Nadelhoffer, K J; Osenberg, C W; Perakis, S S; Schleppi, P; Schimel, J; Schmidt, I K; Sommerkorn, M; Spoelstra, J; Tietema, A; Wessel, W W; Zak, D R

2012-08-01

Effects of anthropogenic nitrogen (N) deposition and the ability of terrestrial ecosystems to store carbon (C) depend in part on the amount of N retained in the system and its partitioning among plant and soil pools. We conducted a meta-analysis of studies at 48 sites across four continents that used enriched 15N isotope tracers in order to synthesize information about total ecosystem N retention (i.e., total ecosystem 15N recovery in plant and soil pools) across natural systems and N partitioning among ecosystem pools. The greatest recoveries of ecosystem 15N tracer occurred in shrublands (mean, 89.5%) and wetlands (84.8%) followed by forests (74.9%) and grasslands (51.8%). In the short term (< 1 week after 15N tracer application), total ecosystem 15N recovery was negatively correlated with fine-root and soil 15N natural abundance, and organic soil C and N concentration but was positively correlated with mean annual temperature and mineral soil C:N. In the longer term (3-18 months after 15N tracer application), total ecosystem 15N retention was negatively correlated with foliar natural-abundance 15N but was positively correlated with mineral soil C and N concentration and C:N, showing that plant and soil natural-abundance 15N and soil C:N are good indicators of total ecosystem N retention. Foliar N concentration was not significantly related to ecosystem 15N tracer recovery, suggesting that plant N status is not a good predictor of total ecosystem N retention. Because the largest ecosystem sinks for 15N tracer were below ground in forests, shrublands, and grasslands, we conclude that growth enhancement and potential for increased C storage in aboveground biomass from atmospheric N deposition is likely to be modest in these ecosystems. Total ecosystem 15N recovery decreased with N fertilization, with an apparent threshold fertilization rate of 46 kg N x ha(-1) x yr(-1) above which most ecosystems showed net losses of applied 15N tracer in response to N fertilizer addition.

The energetic consequences of habitat structure for forest stream salmonids.

PubMed

Naman, Sean M; Rosenfeld, Jordan S; Kiffney, Peter M; Richardson, John S

2018-05-08

1.Increasing habitat availability (i.e. habitat suitable for occupancy) is often assumed to elevate the abundance or production of mobile consumers; however, this relationship is often nonlinear (threshold or unimodal). Identifying the mechanisms underlying these nonlinearities is essential for predicting the ecological impacts of habitat change, yet the functional forms and ultimate causation of consumer-habitat relationships are often poorly understood. 2.Nonlinear effects of habitat on animal abundance may manifest through physical constraints on foraging that restrict consumers from accessing their resources. Subsequent spatial incongruence between consumers and resources should lead to unimodal or saturating effects of habitat availability on consumer production if increasing the area of habitat suitable for consumer occupancy comes at the expense of habitats that generate resources. However, the shape of this relationship could be sensitive to cross-ecosystem prey subsidies, which may be unrelated to recipient habitat structure and result in more linear habitat effects on consumer production. 3.We investigated habitat-productivity relationships for juveniles of stream-rearing Pacific salmon and trout (Oncorhynchus spp.), which typically forage in low-velocity pool habitats, while their prey (drifting benthic invertebrates) are produced upstream in high-velocity riffles. However, juvenile salmonids also consume subsidies of terrestrial invertebrates that may be independent of pool-riffle structure. 4.We measured salmonid biomass production in 13 experimental enclosures each containing a downstream pool and upstream riffle, spanning a gradient of relative pool area (14-80% pool). Increasing pool relative to riffle habitat area decreased prey abundance, leading to a nonlinear saturating effect on fish production. We then used bioenergetics model simulations to examine how the relationship between pool area and salmonid biomass is affected by varying levels of terrestrial subsidy. Simulations indicated that increasing terrestrial prey inputs linearized the effect of habitat availability on salmonid biomass, while decreasing terrestrial inputs exaggerated a 'hump-shaped' effect. 5.Our results imply that nonlinear effects of habitat availability on consumer production can arise from trade-offs between habitat suitable for consumer occupancy and habitat that generates prey. However, cross-ecosystem prey subsidies can effectively decouple this trade-off and modify consumer-habitat relationships in recipient systems. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Vertical and seasonal dynamics of fungal communities in boreal Scots pine forest soil.

PubMed

Santalahti, Minna; Sun, Hui; Jumpponen, Ari; Pennanen, Taina; Heinonsalo, Jussi

2016-11-01

Fungal communities are important for carbon (C) transformations in boreal forests that are one of the largest C pools in terrestrial ecosystems, warranting thus further investigation of fungal community dynamics in time and space. We investigated fungal diversity and community composition seasonally and across defined soil horizons in boreal Scots pine forest in Finland using 454 pyrosequencing. We collected a total of 120 samples from five vertical soil horizons monthly from March to October; in March, under snow. Boreal forest soil generally harbored diverse fungal communities across soil horizons. The communities shifted drastically and rapidly over time. In late winter, saprotrophs dominated the community and were replaced by ectomycorrhizal fungi during the growing season. Our studies are among the first to dissect the spatial and temporal dynamics in boreal forest ecosystems and highlights the ecological importance of vertically distinct communities and their rapid seasonal dynamics. As climate change is predicted to result in warmer and longer snow-free winter seasons, as well as increase the rooting depth of trees in boreal forest, the seasonal and vertical distribution of fungal communities may change. These changes are likely to affect the organic matter decomposition by the soil-inhabiting fungi and thus alter organic C pools. © FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Probing metabolic processes of intact soil microbial communities using position-specific 13C-labeled glucose

NASA Astrophysics Data System (ADS)

Fairbanks, D. E.; Hungate, B. A.; KOCH, G. W.; Schwartz, E.; Dijkstra, P.

2012-12-01

Soils represent one of the largest carbon pools in the terrestrial biosphere and fluxes into or out of this pool may feedback to current climate change. Understanding the mechanisms behind microbial processes regulating C cycling, microbial turnover, and soil organic matter stabilization is hindered by our lack of understanding of the details of microbial physiology in soils. Position-specific 13C labeled metabolic tracers are proposed as a new way to probe microbial community energy production, biosynthesis, C use efficiency (the proportion of substrate incorporated into microbial biomass), and enables the determination of C fluxes through the various C metabolic pathways. We determined the 13CO2 production from microbial communities within a one hour time frame by adding six isotopomers (1-13C, 2-13C, 3-13C, 4-13C, 5-13C, 6-13C) of glucose in parallel incubations using a young volcanic soil (Pinyon-juniper wood, near Sunset Crater, Flagstaff, Arizona). We compared the measured rates of position-specific 13CO2 production with modeled results based on glucose (1-13C and U-13C) and pyruvate (1-13C and 2,3-13C) incubations. These labeling and modeling techniques may improve our ability to analyze the biochemistry and ecophysiology of intact soil microbial communities.

Impact of atmospheric and terrestrial CO2 feedbacks on fertilization-induced marine carbon uptake

NASA Astrophysics Data System (ADS)

Oschlies, A.

2009-04-01

The sensitivity of oceanic CO2 uptake to alterations in the marine biological carbon pump, such as brought about by natural or purposeful ocean fertilization, has repeatedly been investigated by studies employing numerical biogeochemical ocean models. It is shown here that the results of such ocean-centered studies are very sensitive to the assumption made about the response of the carbon reservoirs on the atmospheric side of the sea surface. Assumptions made include prescribed atmospheric pCO2, an interactive atmospheric CO2 pool exchanging carbon with the ocean but not with the terrestrial biosphere, and an interactive atmosphere that exchanges carbon with both oceanic and terrestrial carbon pools. The impact of these assumptions on simulated annual to millennial oceanic carbon uptake is investigated for a hypothetical increase in the C:N ratio of the biological pump and for an idealized enhancement of phytoplankton growth. Compared to simulations with interactive atmosphere, using prescribed atmospheric pCO2 overestimates the sensitivity of the oceanic CO2 uptake to changes in the biological pump, by about 2%, 25%, 100%, and >500% on annual, decadal, centennial, and millennial timescales, respectively. Adding an interactive terrestrial carbon pool to the atmosphere-ocean model system has a small effect on annual timescales, but increases the simulated fertilization-induced oceanic carbon uptake by about 4%, 50%, and 100% on decadal, centennial, and millennial timescales, respectively. On longer than decadal timescales, a substantial fraction of oceanic carbon uptake induced by natural or purposeful ocean fertilization may not come from the atmosphere but from the terrestrial biosphere.

Afforestation effects on soil carbon storage in the United States: a synthesis

Treesearch

L.E. Nave; C.W. Swanston; U. Mishra; K.J. Nadelhoffer

2013-01-01

Afforestation (tree establishment on nonforested land) is a management option for increasing terrestrial C sequestration and mitigating rising atmospheric carbon dioxide because, compared to nonforested land uses, afforestation increases C storage in aboveground pools. However, because terrestrial ecosystems typically store most of their C in soils, afforestation...

Balancing the Energy Pendulum.

ERIC Educational Resources Information Center

MacKinnon, Sharon

1987-01-01

The city of Kitchener, Ontario, has installed a heat recovery loop in one indoor pool, all indoor swimming pools use pool covers, and two have solar heating. Energy is saved in two ice arenas by low-emissivity ceilings, and in the largest arena by a heat recovery system. (MLF)

Carbon Pool Dynamics in the Lower Fraser Basin from 1827 to 1990

PubMed

Boyle; Lavkulich

1997-05-01

/ To understand the total impact of humans on the carbon cycle, themodeling and quantifying of the transfer of carbon from terrestrial pools tothe atmosphere is becoming more critical. Using previously published data,this research sought to assess the change in carbon pools caused by humans inthe Lower Fraser Basin (LFB) in British Columbia, Canada, since 1827 anddefine the long-term, regional contribution of carbon to the atmosphere. Theresults indicate that there has been a transfer of 270 Mt of carbon frombiomass pools in the LFB to other pools, primarily the atmosphere. The majorlosses of biomass carbon have been from logged forests (42%), wetlands(14%), and soils (43%). Approximately 48% of the forestbiomass, almost 20% of the carbon of the LFB, lies within old-growthforest, which covers only 19% of the study area. Landfills are nowbecoming a major sink of carbon, containing 5% of the biomass carbonin the LFB, while biomass carbon in buildings, urban vegetation, mammals, andagriculture is negligible. Approximately 26% of logged forest biomasswould still be in a terrestrial biomass pool, leaving 238 Mt of carbon thathas been released to the atmosphere. On an area basis, this is 29 times theaverage global emissions of carbon, providing an indication of the pastcontributions of developed countries such as Canada to global warming andpossible contributions from further clearing of rainforest in both tropicaland temperate regions.KEY WORDS: Carbon pools; Global warming; Carbon release to atmosphere;Greenhouse effect

Imaging soil litter decomposition: Integrating sychrotron-based elemental and molecular imaging techniques

EPA Science Inventory

Forest ecosystems contain approximately one-half of the Earths terrestrial carbon (C) (1146 Pg), with two-thirds (787 Pg) of this pool residing in forest soils. Given the magnitude of the forest soil C pool, it is critical to understand the mechanisms that control soil organic ma...

pyhector: A Python interface for the simple climate model Hector

DOE PAGES

Willner, Sven N.; Hartin, Corinne; Gieseke, Robert

2017-04-01

Here, pyhector is a Python interface for the simple climate model Hector (Hartin et al. 2015) developed in C++. Simple climate models like Hector can, for instance, be used in the analysis of scenarios within integrated assessment models like GCAM1, in the emulation of complex climate models, and in uncertainty analyses. Hector is an open-source, object oriented, simple global climate carbon cycle model. Its carbon cycle consists of a one pool atmosphere, three terrestrial pools which can be broken down into finer biomes or regions, and four carbon pools in the ocean component. The terrestrial carbon cycle includes primary productionmore » and respiration fluxes. The ocean carbon cycle circulates carbon via a simplified thermohaline circulation, calculating air-sea fluxes as well as the marine carbonate system. The model input is time series of greenhouse gas emissions; as example scenarios for these the Pyhector package contains the Representative Concentration Pathways (RCPs)2.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Willner, Sven N.; Hartin, Corinne; Gieseke, Robert

Here, pyhector is a Python interface for the simple climate model Hector (Hartin et al. 2015) developed in C++. Simple climate models like Hector can, for instance, be used in the analysis of scenarios within integrated assessment models like GCAM1, in the emulation of complex climate models, and in uncertainty analyses. Hector is an open-source, object oriented, simple global climate carbon cycle model. Its carbon cycle consists of a one pool atmosphere, three terrestrial pools which can be broken down into finer biomes or regions, and four carbon pools in the ocean component. The terrestrial carbon cycle includes primary productionmore » and respiration fluxes. The ocean carbon cycle circulates carbon via a simplified thermohaline circulation, calculating air-sea fluxes as well as the marine carbonate system. The model input is time series of greenhouse gas emissions; as example scenarios for these the Pyhector package contains the Representative Concentration Pathways (RCPs)2.« less

Evidence for the respiration of ancient terrestrial organic C in northern temperate lakes and streams

PubMed Central

McCallister, S. Leigh; del Giorgio, Paul A.

2012-01-01

Northern rivers and lakes process large quantities of organic and inorganic carbon from the surrounding terrestrial ecosystems. These external carbon inputs fuel widespread CO2 supersaturation in continental waters, and the resulting CO2 emissions from lakes and rivers are now recognized as a globally significant loss of terrestrial production to the atmosphere. Whereas the magnitude of emissions has received much attention, the pathways of C delivery and processing that generate these emissions are still not well-understood. CO2 outgassing in aquatic systems has been unequivocally linked to microbial degradation and respiration of terrestrial organic carbon (OC), but the nature (i.e., age and source) of this OC respired in surface waters is largely unknown. We present direct radiocarbon measurements of OC respired by bacteria in freshwater aquatic systems, specifically temperate lakes and streams in Québec. Terrestrial OC fuels much of the respiration in these systems, and our results show that a significant fraction of the respired terrestrial OC is old (in the range of 1,000–3,000 y B.P.). Because the bulk OC pools in these lakes is relatively young, our results also suggest selective removal of an old but highly bioreactive terrestrial OC pool and its conversion to CO2 by bacteria. The respiration of ancient 14C-depleted terrestrial C in northern lakes and rivers provides a biological link between contemporary aquatic carbon biogeochemistry and paleo-conditions in the watershed, and it implies the aquatic-mediated return to the atmosphere of C putatively considered permanently stored, thus challenging current models of long-term C storage in terrestrial reservoirs. PMID:23027957

Demographic consequences of terrestrial habitat loss for pool-breeding amphibians: predicting extinction risks associated with inadequate size of buffer zones.

PubMed

Harper, Elizabeth B; Rittenhouse, Tracy A G; Semlitsch, Raymond D

2008-10-01

Much of the biodiversity associated with isolated wetlands requires aquatic and terrestrial habitat to maintain viable populations. Current federal wetland regulations in the United States do not protect isolated wetlands or extend protection to surrounding terrestrial habitat. Consequently, some land managers, city planners, and policy makers at the state and local levels are making an effort to protect these wetland and neighboring upland habitats. Balancing human land-use and habitat conservation is challenging, and well-informed land-use policy is hindered by a lack of knowledge of the specific risks of varying amounts of habitat loss. Using projections of wood frog (Rana sylvatica) and spotted salamander (Ambystoma maculatum) populations, we related the amount of high-quality terrestrial habitat surrounding isolated wetlands to the decline and risk of extinction of local amphibian populations. These simulations showed that current state-level wetland regulations protecting 30 m or less of surrounding terrestrial habitat are inadequate to support viable populations of pool-breeding amphibians. We also found that species with different life-history strategies responded differently to the loss and degradation of terrestrial habitat. The wood frog, with a short life span and high fecundity, was most sensitive to habitat loss and isolation, whereas the longer-lived spotted salamander with lower fecundity was most sensitive to habitat degradation that lowered adult survival rates. Our model results demonstrate that a high probability of local amphibian population persistence requires sufficient terrestrial habitat, the maintenance of habitat quality, and connectivity among local populations. Our results emphasize the essential role of adequate terrestrial habitat to the maintenance of wetland biodiversity and ecosystem function and offer a means of quantifying the risks associated with terrestrial habitat loss and degradation.

Impact of atmospheric and terrestrial CO2 feedbacks on fertilization-induced marine carbon uptake

NASA Astrophysics Data System (ADS)

Oschlies, A.

2009-08-01

The sensitivity of oceanic CO2 uptake to alterations in the marine biological carbon pump, such as brought about by natural or purposeful ocean fertilization, has repeatedly been investigated by studies employing numerical biogeochemical ocean models. It is shown here that the results of such ocean-centered studies are very sensitive to the assumption made about the response of the carbon reservoirs on the atmospheric side of the sea surface. Assumptions made include prescribed atmospheric pCO2, an interactive atmospheric CO2 pool exchanging carbon with the ocean but not with the terrestrial biosphere, and an interactive atmosphere that exchanges carbon with both oceanic and terrestrial carbon pools. The impact of these assumptions on simulated annual to millennial oceanic carbon uptake is investigated for a hypothetical increase in the C:N ratio of the biological pump and for an idealized enhancement of phytoplankton growth. Compared to simulations with interactive atmosphere, using prescribed atmospheric pCO2 overestimates the sensitivity of the oceanic CO2 uptake to changes in the biological pump, by about 2%, 25%, 100%, and >500% on annual, decadal, centennial, and millennial timescales, respectively. The smaller efficiency of the oceanic carbon uptake under an interactive atmosphere is due to the back flux of CO2 that occurs when atmospheric CO2 is reduced. Adding an interactive terrestrial carbon pool to the atmosphere-ocean model system has a small effect on annual timescales, but increases the simulated fertilization-induced oceanic carbon uptake by about 4%, 50%, and 100% on decadal, centennial, and millennial timescales, respectively, for pCO2 sensitivities of the terrestrial carbon storage in the middle range of the C4MIP models (Friedlingstein et al., 2006). For such sensitivities, a substantial fraction of oceanic carbon uptake induced by natural or purposeful ocean fertilization originates, on timescales longer than decades, not from the atmosphere but from the terrestrial biosphere.

The significance of carbon-enriched dust for global carbon accounting

USDA-ARS?s Scientific Manuscript database

Soil carbon stores amount to 54% of the terrestrial carbon pool and twice the atmospheric carbon pool, but soil organic carbon (SOC) can be transient. There is an ongoing debate about whether soils are a net source or sink of carbon, and understanding the role of aeolian processes in SOC erosion, tr...

When bulk density methods matter: Implications for estimating soil organic carbon pools in rocky soils

USDA-ARS?s Scientific Manuscript database

Resolving uncertainty in the carbon cycle is paramount to refining climate predictions. Soil organic carbon (SOC) is a major component of terrestrial C pools, and accuracy of SOC estimates are only as good as the measurements and assumptions used to obtain them. Dryland soils account for a substanti...

Stimulation of terrestrial ecosystem carbon storage by nitrogen addition: a meta-analysis

PubMed Central

Yue, Kai; Peng, Yan; Peng, Changhui; Yang, Wanqin; Peng, Xin; Wu, Fuzhong

2016-01-01

Elevated nitrogen (N) deposition alters the terrestrial carbon (C) cycle, which is likely to feed back to further climate change. However, how the overall terrestrial ecosystem C pools and fluxes respond to N addition remains unclear. By synthesizing data from multiple terrestrial ecosystems, we quantified the response of C pools and fluxes to experimental N addition using a comprehensive meta-analysis method. Our results showed that N addition significantly stimulated soil total C storage by 5.82% ([2.47%, 9.27%], 95% CI, the same below) and increased the C contents of the above- and below-ground parts of plants by 25.65% [11.07%, 42.12%] and 15.93% [6.80%, 25.85%], respectively. Furthermore, N addition significantly increased aboveground net primary production by 52.38% [40.58%, 65.19%] and litterfall by 14.67% [9.24%, 20.38%] at a global scale. However, the C influx from the plant litter to the soil through litter decomposition and the efflux from the soil due to microbial respiration and soil respiration showed insignificant responses to N addition. Overall, our meta-analysis suggested that N addition will increase soil C storage and plant C in both above- and below-ground parts, indicating that terrestrial ecosystems might act to strengthen as a C sink under increasing N deposition. PMID:26813078

Landscape Disturbance History and Belowground Carbon Dynamics.

NASA Astrophysics Data System (ADS)

Marin-Spiotta, E.; Smith, A. P.; Atkinson, E. E.; Chaopricha, N. T.

2014-12-01

Earth system models vary in their predictions of carbon (C) uptake and release by the terrestrial biosphere, partly due to great uncertainties in the response of soils, one of the largest C reservoirs. The world's soils play a major role in the exchange of greenhouse gases with the atmosphere, in sustaining primary production, and in providing food security. Despite this, the sensitivity of soils to disturbance is highly uncertain. One reason for this is geographic variability in the importance of different mechanisms regulating soil C turnover. Most of our understanding of factors influencing soil organic C dynamics comes from research in temperate soils, despite the major role of tropical soils in the global C cycle. Even in the tropics, the diversity of soil environments is grossly underrepresented in the literature. This has important implications for predictions of soil C change across latitudes. We discuss results from the response of soil C pools and microbial communities to land use legacies on two contrasting tropical soil environments. Uncertainties in the response of soil C to disturbance also stem from a historic focus on shallow depths and the assumption that deep soil C is unreactive to landscape change. Growing evidence indicates that soil C pools in deep mineral horizons can be sensitive to changes in land cover and climate. This realization highlights the need to reassess the source of soil C at depth and the processes contributing to its stabilization. We discuss results from the interaction between multiple disturbances: drought, fire and erosion, on the accumulation of soil C at depths beyond those typically included in regional or global inventories. Our data show that deep soil C can be reactive and be a potential source of C if reconnected to the atmosphere. A deeper, mechanistic appreciation for a landscape's history of disturbance is critical for predicting feedbacks between the terrestrial biosphere and the climate system.

Differential mobilization of terrestrial carbon pools in Eurasian Arctic river basins.

PubMed

Feng, Xiaojuan; Vonk, Jorien E; van Dongen, Bart E; Gustafsson, Örjan; Semiletov, Igor P; Dudarev, Oleg V; Wang, Zhiheng; Montluçon, Daniel B; Wacker, Lukas; Eglinton, Timothy I

2013-08-27

Mobilization of Arctic permafrost carbon is expected to increase with warming-induced thawing. However, this effect is challenging to assess due to the diverse processes controlling the release of various organic carbon (OC) pools from heterogeneous Arctic landscapes. Here, by radiocarbon dating various terrestrial OC components in fluvially and coastally integrated estuarine sediments, we present a unique framework for deconvoluting the contrasting mobilization mechanisms of surface vs. deep (permafrost) carbon pools across the climosequence of the Eurasian Arctic. Vascular plant-derived lignin phenol (14)C contents reveal significant inputs of young carbon from surface sources whose delivery is dominantly controlled by river runoff. In contrast, plant wax lipids predominantly trace ancient (permafrost) OC that is preferentially mobilized from discontinuous permafrost regions, where hydrological conduits penetrate deeper into soils and thermokarst erosion occurs more frequently. Because river runoff has significantly increased across the Eurasian Arctic in recent decades, we estimate from an isotopic mixing model that, in tandem with an increased transfer of young surface carbon, the proportion of mobilized terrestrial OC accounted for by ancient carbon has increased by 3-6% between 1985 and 2004. These findings suggest that although partly masked by surface carbon export, climate change-induced mobilization of old permafrost carbon is well underway in the Arctic.

Temporal change in soil carbon stability at a paired old-growth douglas-fir forest/clear-cut site

EPA Science Inventory

Forest ecosystems are estimated to contain one-half of the total terrestrial carbon (C) pool (1146 Pg), with two-thirds of this C (787 Pg) residing in forest soils. Given the magnitude of this C pool, it is critical to understand the effects of forest management practices on soil...

Comparison between remote sensing and a dynamic vegetation model for estimating terrestrial primary production of Africa.

PubMed

Ardö, Jonas

2015-12-01

Africa is an important part of the global carbon cycle. It is also a continent facing potential problems due to increasing resource demand in combination with climate change-induced changes in resource supply. Quantifying the pools and fluxes constituting the terrestrial African carbon cycle is a challenge, because of uncertainties in meteorological driver data, lack of validation data, and potentially uncertain representation of important processes in major ecosystems. In this paper, terrestrial primary production estimates derived from remote sensing and a dynamic vegetation model are compared and quantified for major African land cover types. Continental gross primary production estimates derived from remote sensing were higher than corresponding estimates derived from a dynamic vegetation model. However, estimates of continental net primary production from remote sensing were lower than corresponding estimates from the dynamic vegetation model. Variation was found among land cover classes, and the largest differences in gross primary production were found in the evergreen broadleaf forest. Average carbon use efficiency (NPP/GPP) was 0.58 for the vegetation model and 0.46 for the remote sensing method. Validation versus in situ data of aboveground net primary production revealed significant positive relationships for both methods. A combination of the remote sensing method with the dynamic vegetation model did not strongly affect this relationship. Observed significant differences in estimated vegetation productivity may have several causes, including model design and temperature sensitivity. Differences in carbon use efficiency reflect underlying model assumptions. Integrating the realistic process representation of dynamic vegetation models with the high resolution observational strength of remote sensing may support realistic estimation of components of the carbon cycle and enhance resource monitoring, providing suitable validation data is available.

Estimating aboveground live understory vegetation carbon in the United States

NASA Astrophysics Data System (ADS)

Johnson, Kristofer D.; Domke, Grant M.; Russell, Matthew B.; Walters, Brian; Hom, John; Peduzzi, Alicia; Birdsey, Richard; Dolan, Katelyn; Huang, Wenli

2017-12-01

Despite the key role that understory vegetation plays in ecosystems and the terrestrial carbon cycle, it is often overlooked and has few quantitative measurements, especially at national scales. To understand the contribution of understory carbon to the United States (US) carbon budget, we developed an approach that relies on field measurements of understory vegetation cover and height on US Department of Agriculture Forest Service, Forest Inventory and Analysis (FIA) subplots. Allometric models were developed to estimate aboveground understory carbon. A spatial model based on stand characteristics and remotely sensed data was also applied to estimate understory carbon on all FIA plots. We found that most understory carbon was comprised of woody shrub species (64%), followed by nonwoody forbs and graminoid species (35%) and seedlings (1%). The largest estimates were found in temperate or warm humid locations such as the Pacific Northwest and southeastern US, thus following the same broad trend as aboveground tree biomass. The average understory aboveground carbon density was estimated to be 0.977 Mg ha-1, for a total estimate of 272 Tg carbon across all managed forest land in the US (approximately 2% of the total aboveground live tree carbon pool). This estimate is more than twice as low as previous FIA modeled estimates that did not rely on understory measurements, suggesting that this pool may currently be overestimated in US National Greenhouse Gas reporting.

Limits to soil carbon stability; Deep, ancient soil carbon decomposition stimulated by new labile organic inputs

USDA-ARS?s Scientific Manuscript database

Soil carbon (C) pools store about one-third of the total terrestrial organic carbon. Deep soil C pools (below 1 m) are thought to be stable due to their low biodegradability, but little is known about soil microbial processes and carbon dynamics below the soil surface, or how global change might aff...

Carbon storage in managed forests of the northern Great Lake States

Treesearch

Jeanette L. Rollinger; Terry F. Strong

1996-01-01

Carbon (C) storage in forest ecosystems is a significant part of the total terrestrial C pool, and may potentially be manipulated as an important C sink. The influence of management on C pools must be understood before guidelines can be suggested for maximizing C sequestration in forests. Studies of hardwood, red pine (Pinus resinosa Ait.), aspen and...

Large-Scale Impact Cratering and Early Earth Evolution

NASA Technical Reports Server (NTRS)

Grieve, R. A. F.; Cintala, M. J.

1997-01-01

The surface of the Moon attests to the importance of large-scale impact in its early crustal evolution. Previous models of the effects of a massive bombardment on terrestrial crustal evolution have relied on analogies with the Moon, with allowances for the presence of water and a thinner lithosphere. It is now apparent that strict lunar-terrestrial analogies are incorrect because of the "differential scaling" of crater dimensions and melt volumes with event size and planetary gravity. Impact melt volumes and "ancient cavity dimensions for specific impacts were modeled according to previous procedures. In the terrestrial case, the melt volume (V(sub m)) exceeds that of the transient cavity (V(sub tc)) at diameters > or = 400 km. This condition is reached on the Moon only with transient cavity diameters > or = 3000 km, equivalent to whole Moon melting. The melt volumes in these large impact events are minimum estimates, since, at these sizes, the higher temperature of the target rocks at depth will increase melt production. Using the modification-scaling relation of Croft, a transient cavity diameter of about 400 km in the terrestrial environment corresponds to an expected final impact "basin" diameter of about 900 km. Such a "basin" would be comparable in dimensions to the lunar basin Orientale. This 900-km "basin" on the early Earth, however, would not have had the appearance of Orientale. It would have been essentially a melt pool, and, morphologically, would have had more in common with the palimpsests structures on Callisto and Ganymede. With the terrestrial equivalents to the large multiring basins of the Moon being manifested as muted palimpsest-like structures filled with impact melt, it is unlikely they played a role in establishing the freeboard on the early Earth. The composition of the massive impact melt sheets (> 10 (exp 7) cu km) produced in "basin-forming" events on the early Earth would have most likely ranged from basaltic to more mafic for the largest impacts, where the melt volume would have reached well into the mantle. Any contribution from adiabatic melting or shock heating of the asthenosphere would have had similar mafic compositions. The depth of the melt sheets is unknown but would have been in the multilkilometer range. Bodies of basaltic melt > or = 300 m thick differentiate in the terrestrial environment, with the degree of differentiation being a function of the thickness of the body. We therefore expect that these thick, closed-system melt pools would have differentiated into an ultramafic-mafic base and felsic top. If only 10% of the impact melt produced in a single event creating a 400-km diameter transient cavity evolved into felsic differentiates, they would be comparable in volume to the Columbia River basalts. It has been estimated that at least 200 impact events of this size or larger occurred on the early Earth during a period of heavy bombardment. We speculate that these massive differentiated melt sheets may have had a role in the formation of the initial felsic component of the Earth's crust. Additional information is contained in the original.

Sources and fate of sediment organic matter in Asia's largest brackish water lagoon and nearby mangrove ecosystem

NASA Astrophysics Data System (ADS)

Mukherjee, R.; Muduli, P. R.; Barik, S.; Kumar, S.

2017-12-01

Coastal lagoons and mangrove ecosystems regularly undergo natural (tidal) and anthropogenic (riverine inputs) forcings. After effects of these forcings cause coastal environments to sustain high biological production leading to high suspended organic matter (OM) and hence fast sedimentation and accumulation of OM in sediments.The different sources of OM and its burial in tropical lacustrine and mangrove systems have been rarely studied in detail with a few reports from Indian estuaries. The present study attempts to understand the sources and fate organic matter at two Ramsar sites, viz. Chilika Lake (Asia's largest brackish water lagoon) and nearby Bhitarkanika mangroves, located in the east coast of India. We measured nitrogen and carbon content (% N and % C) and isotopic composition (δ13Corg and δ15N) of OM at different depths in eight and three sediment cores collected from the Chilika lagoon and Bhitarkanika mangroves, respectively. Overall, the mean δ13Corg and % C in the lagoon were ‒21.10 ± 0.79 ‰ and 0.84 ± 0.47 %, respectively; whereas the same for mangrove cores were ‒24.56 ± 0.80 ‰ and 1.04 ± 0.26 %, respectively. Similarly, average δ15N and % N in the lagoon cores were 4.15 ± 0.63 ‰ and 0.11 ± 0.05 %, respectively; for mangrove cores the values were 4.28 ± 0.50 ‰ and 0.07 ± 0.01 %, respectively. Preliminary analysis of the isotopic composition (δ13Corg and δ15N) and elemental ratios indicates that organic carbon in the sediment at Bhitarkanika mangrove was of terrigenous, marine and in situ origin, whereas cores of Chilika lagoon showed predominantly marine signature. No relationship between δ13Corg of suspended and sediment in the Chilika lagoon indicates these two organic pools to be not directly coupled. End member mixing model in the mangrove ecosystem indicate on an average 50 % terrestrial contribution to the OM pool.

Independent effects of heart-head distance and caudal blood pooling on blood pressure regulation in aquatic and terrestrial snakes.

PubMed

Seymour, Roger S; Arndt, Joachim O

2004-03-01

Changes in orientation in a gravitational field markedly alter the patterns of blood pressure and flow in animals, especially tall or long ones such as giraffes or snakes. Vertical orientation tends to reduce blood flow and pressure in the head for two major reasons. First, the increased vertical blood column above the heart creates a gravitational hydrostatic pressure against which the heart must work. Second, expansion of dependent vessels in the lower extremities causes blood pooling and reduces return of venous blood to the heart, thereby lowering flow and pressure. For most animals, it is difficult to separate these two effects, but snakes offer the possibility of bending the animal in the region of the heart and manipulating the two ends of the body independently. We studied baroregulatory responses in terrestrial pythons (Liasis fuscus) and aquatic file snakes (Acrochordus arafurae) by tilting only the front or rear parts and then the whole animal. Changes in head blood pressure during partial tilts added up to the change during full tilt. The vertical distance to the head had twice as much influence on head blood pressure than did blood pooling in the pythons and four times as much in file snakes. This accounts for the cephalad location of the heart in terrestrial species compared with aquatic ones.

Partial coupling and differential regulation of biologically and photochemically labile dissolved organic carbon across boreal aquatic networks

NASA Astrophysics Data System (ADS)

Lapierre, J.-F.; del Giorgio, P. A.

2014-10-01

Despite the rapidly increasing volume of research on the biological and photochemical degradation of DOC (dissolved organic carbon) in aquatic environments, little is known of the large-scale patterns in biologically and photochemically degradable DOC (BDOC and PDOC, respectively) in continental watersheds, and on the links that exist between these two key properties that greatly influence the flow of carbon from continents to oceans. Here we explored the patterns in the concentrations and proportions of BDOC and PDOC across hundreds of boreal lakes, rivers and wetlands spanning a large range of system trophic status and terrestrial influence, and compared the drivers of these two reactive pools of DOC at the landscape level. Using standardized incubations of natural waters, we found that the concentrations of BDOC and PDOC covaried across all systems studied but were nevertheless related to different pools of dissolved organic matter (DOM; identified by fluorescence analyses) in ambient waters. Concentrations of nutrients and protein-like fluorescent DOM (FDOM) explained nearly half of the variation in BDOC, whereas PDOC was exclusively predicted by DOM optical properties, consistent with the photochemical degradability of specific FDOM pools that we experimentally determined. The concentrations of colored DOM (CDOM), which we use here as a proxy of terrestrial influence, almost entirely accounted for the observed relationship between FDOM and the concentrations of both BDOC and PDOC. The concentrations of CDOM and of the putative biolabile fluorescence component shifted from complete decoupling in clear-water environments to strong coupling in darker streams and wetlands. This suggests a baseline autochthonous BDOC pool fueled by internal production that is gradually overwhelmed by land-derived BDOC as terrestrial influence increases across landscape gradients. The importance of land as a major source of both biologically and photochemically degradable DOC for continental watersheds resulted in a partial coupling of those carbon pools in natural freshwaters, despite fundamental contrasts in terms of their composition and regulation.

Partial coupling and differential regulation of biologically and photo-chemically labile dissolved organic carbon across boreal aquatic networks

NASA Astrophysics Data System (ADS)

Lapierre, J.-F.; del Giorgio, P. A.

2014-05-01

Despite the rapidly increasing volume of research on the biological and photochemical degradation of DOC in aquatic environments, little is known on the large-scale patterns in biologically and photo-chemically degradable DOC (Bd-DOC and Pd-DOC, respectively) in continental watersheds, and on the links that exist between these two key properties that greatly influence the flow of carbon from continents to oceans. Here we explore the patterns of Bd- and Pd-DOC across hundreds of boreal lakes, rivers and wetlands spanning a large range of system trophy and terrestrial influence, and compared the drivers of these two reactive pools of DOC at the landscape level. Using standardized incubations of natural waters, we found that the concentrations of Bd- and Pd-DOC co-varied across all systems studied but were nevertheless related to different pools of dissolved organic matter (DOM, identified by fluorescence analyses) in ambient waters. A combination of nutrients and protein-like DOM explained nearly half of the variation in Bd-DOC, whereas Pd-DOC was exclusively predicted by DOM optical properties, consistent with the photochemical degradability of specific fluorescent DOM (FDOM) pools that we experimentally determined. The concentrations of colored DOM (CDOM), a proxy of terrestrial influence, almost entirely accounted for the observed relationship between FDOM and the concentrations of both Bd- and Pd-DOC. The concentrations of CDOM and of the putative bio-labile fluorescence component shifted from complete decoupling in clear-water environments to strong coupling in browner streams and wetlands. This suggests a baseline autochthonous Bd-DOC pool fuelled by internal production that is gradually overwhelmed by land-derived Bd-DOC as terrestrial influence increases across landscape gradients. The importance of land as a major source of both biologically and photo-chemically degradable DOC for continental watersheds resulted in a partial coupling of those carbon pools in natural freshwaters, despite fundamental contrasts in terms of their composition and regulation.

Methodology for estimating soil carbon for the forest carbon budget model of the United States, 2001

Treesearch

L. S. Heath; R. A. Birdsey; D. W. Williams

2002-01-01

The largest carbon (C) pool in United States forests is the soil C pool. We present methodology and soil C pool estimates used in the FORCARB model, which estimates and projects forest carbon budgets for the United States. The methodology balances knowledge, uncertainties, and ease of use. The estimates are calculated using the USDA Natural Resources Conservation...

Total C and N Pools and fluxes vary with time, soil temperature, and moisture along an elevation, precipitation, and vegetation gradient in southern Appalachian Forests

Treesearch

Jennifer D. Knoepp; Craig R. See; James M. Vose; Chelcy F. Miniat; James S. Clark

2018-01-01

The interactions of terrestrial C pools and fluxes with spatial and temporal variation in climate are not well understood. We conducted this study in the southern Appalachian Mountains where complex topography provides variability in temperature, precipitation, and forest communities. In 1990, we established five large plots across an elevation gradient...

State High-Risk Pools: An Update on the Minnesota Comprehensive Health Association

PubMed Central

Spencer, Donna; Burke, Courtney E.

2011-01-01

State health insurance high-risk pools are a key component of the US health care system's safety net, because they provide health insurance to the “uninsurable.” In 2007, 34 states had individual high-risk pools, which covered more than 200 000 people at a total cost of $1.8 billion. We examine the experience of the largest and oldest pool in the nation, the Minnesota Comprehensive Health Association, to document key issues facing state high-risk pools in enrollment and financing. We also considered the role and future of high-risk pools in light of national health care finance reform. PMID:21228286

Bayesian Evaluation of Dynamical Soil Carbon Models Using Soil Carbon Flux Data

NASA Astrophysics Data System (ADS)

Xie, H. W.; Romero-Olivares, A.; Guindani, M.; Allison, S. D.

2017-12-01

2016 was Earth's hottest year in the modern temperature record and the third consecutive record-breaking year. As the planet continues to warm, temperature-induced changes in respiration rates of soil microbes could reduce the amount of carbon sequestered in the soil organic carbon (SOC) pool, one of the largest terrestrial stores of carbon. This would accelerate temperature increases. In order to predict the future size of the SOC pool, mathematical soil carbon models (SCMs) describing interactions between the biosphere and atmosphere are needed. SCMs must be validated before they can be chosen for predictive use. In this study, we check two SCMs called CON and AWB for consistency with observed data using Bayesian goodness of fit testing that can be used in the future to compare other models. We compare the fit of the models to longitudinal soil respiration data from a meta-analysis of soil heating experiments using a family of Bayesian goodness of fit metrics called information criteria (IC), including the Widely Applicable Information Criterion (WAIC), the Leave-One-Out Information Criterion (LOOIC), and the Log Pseudo Marginal Likelihood (LPML). These IC's take the entire posterior distribution into account, rather than just one outputted model fit line. A lower WAIC and LOOIC and larger LPML indicate a better fit. We compare AWB and CON with fixed steady state model pool sizes. At equivalent SOC, dissolved organic carbon, and microbial pool sizes, CON always outperforms AWB quantitatively by all three IC's used. AWB monotonically improves in fit as we reduce the SOC steady state pool size while fixing all other pool sizes, and the same is almost true for CON. The AWB model with the lowest SOC is the best performing AWB model, while the CON model with the second lowest SOC is the best performing model. We observe that AWB displays more changes in slope sign and qualitatively displays more adaptive dynamics, which prevents AWB from being fully ruled out for predictive use, but based on IC's, CON is clearly the superior model for fitting the data. Hence, we demonstrate that Bayesian goodness of fit testing with information criteria helps us rigorously determine the consistency of models with data. Models that demonstrate their consistency to multiple data sets with our approach can then be selected for further refinement.

Terrestrial and marine perspectives on modeling organic matter degradation pathways.

PubMed

Burd, Adrian B; Frey, Serita; Cabre, Anna; Ito, Takamitsu; Levine, Naomi M; Lønborg, Christian; Long, Matthew; Mauritz, Marguerite; Thomas, R Quinn; Stephens, Brandon M; Vanwalleghem, Tom; Zeng, Ning

2016-01-01

Organic matter (OM) plays a major role in both terrestrial and oceanic biogeochemical cycles. The amount of carbon stored in these systems is far greater than that of carbon dioxide (CO2 ) in the atmosphere, and annual fluxes of CO2 from these pools to the atmosphere exceed those from fossil fuel combustion. Understanding the processes that determine the fate of detrital material is important for predicting the effects that climate change will have on feedbacks to the global carbon cycle. However, Earth System Models (ESMs) typically utilize very simple formulations of processes affecting the mineralization and storage of detrital OM. Recent changes in our view of the nature of this material and the factors controlling its transformation have yet to find their way into models. In this review, we highlight the current understanding of the role and cycling of detrital OM in terrestrial and marine systems and examine how this pool of material is represented in ESMs. We include a discussion of the different mineralization pathways available as organic matter moves from soils, through inland waters to coastal systems and ultimately into open ocean environments. We argue that there is strong commonality between aspects of OM transformation in both terrestrial and marine systems and that our respective scientific communities would benefit from closer collaboration. © 2015 John Wiley & Sons Ltd.

Climatic role of terrestrial ecosystem under elevated CO2 : a bottom-up greenhouse gases budget.

PubMed

Liu, Shuwei; Ji, Cheng; Wang, Cong; Chen, Jie; Jin, Yaguo; Zou, Ziheng; Li, Shuqing; Niu, Shuli; Zou, Jianwen

2018-05-07

The net balance of greenhouse gas (GHG) exchanges between terrestrial ecosystems and the atmosphere under elevated atmospheric carbon dioxide (CO 2 ) remains poorly understood. Here, we synthesise 1655 measurements from 169 published studies to assess GHGs budget of terrestrial ecosystems under elevated CO 2 . We show that elevated CO 2 significantly stimulates plant C pool (NPP) by 20%, soil CO 2 fluxes by 24%, and methane (CH 4 ) fluxes by 34% from rice paddies and by 12% from natural wetlands, while it slightly decreases CH 4 uptake of upland soils by 3.8%. Elevated CO 2 causes insignificant increases in soil nitrous oxide (N 2 O) fluxes (4.6%), soil organic C (4.3%) and N (3.6%) pools. The elevated CO 2 -induced increase in GHG emissions may decline with CO 2 enrichment levels. An elevated CO 2 -induced rise in soil CH 4 and N 2 O emissions (2.76 Pg CO 2 -equivalent year -1 ) could negate soil C enrichment (2.42 Pg CO 2 year -1 ) or reduce mitigation potential of terrestrial net ecosystem production by as much as 69% (NEP, 3.99 Pg CO 2 year -1 ) under elevated CO 2 . Our analysis highlights that the capacity of terrestrial ecosystems to act as a sink to slow climate warming under elevated CO 2 might have been largely offset by its induced increases in soil GHGs source strength. © 2018 John Wiley & Sons Ltd/CNRS.

Dissolved Organic Nitrogen Inputs from Wastewater Treatment Plant Effluents Increase Responses of Planktonic Metabolic Rates to Warming.

PubMed

Vaquer-Sunyer, Raquel; Conley, Daniel J; Muthusamy, Saraladevi; Lindh, Markus V; Pinhassi, Jarone; Kritzberg, Emma S

2015-10-06

Increased anthropogenic pressures on coastal marine ecosystems in the last century are threatening their biodiversity and functioning. Global warming and increases in nutrient loadings are two major stressors affecting these systems. Global warming is expected to increase both atmospheric and water temperatures and increase precipitation and terrestrial runoff, further increasing organic matter and nutrient inputs to coastal areas. Dissolved organic nitrogen (DON) concentrations frequently exceed those of dissolved inorganic nitrogen in aquatic systems. Many components of the DON pool have been shown to supply nitrogen nutrition to phytoplankton and bacteria. Predictions of how global warming and eutrophication will affect metabolic rates and dissolved oxygen dynamics in the future are needed to elucidate their impacts on biodiversity and ecosystem functioning. Here, we experimentally determine the effects of simultaneous DON additions and warming on planktonic community metabolism in the Baltic Sea, the largest coastal area suffering from eutrophication-driven hypoxia. Both bacterioplankton community composition and metabolic rates changed in relation to temperature. DON additions from wastewater treatment plant effluents significantly increased the activation energies for community respiration and gross primary production. Activation energies for community respiration were higher than those for gross primary production. Results support the prediction that warming of the Baltic Sea will enhance planktonic respiration rates faster than it will for planktonic primary production. Higher increases in respiration rates than in production may lead to the depletion of the oxygen pool, further aggravating hypoxia in the Baltic Sea.

Mineral surface-reactive metabolites secreted during fungal decomposition contribute to the formation of soil organic matter.

PubMed

Wang, Tao; Tian, Zhaomo; Bengtson, Per; Tunlid, Anders; Persson, Per

2017-12-01

Soil organic matter (SOM) constitutes the largest terrestrial C pool. An emerging, untested, view is that oxidation and depolymerization of SOM by microorganisms promote the formation of SOM-mineral associations that is critical for SOM stabilization. To test this hypothesis, we performed laboratory-scale experiments involving one ectomycorrhizal and one saprotrophic fungus that represent the two major functional groups of microbial decomposers in the boreal forest soils. Fungal decomposition enhanced the retention of SOM on goethite, partly because of oxidative modifications of organic matter (OM) by the fungi. Moreover, both fungi secreted substantial amounts (> 10% new biomass C) of aromatic metabolites that also contributed to an enhanced mineral retention of OM. Our study demonstrates that soil fungi can form mineral-stabilized SOM not only by oxidative conversion of the SOM but also by synthesizing mineral surface-reactive metabolites. Metabolites produced by fungal decomposers can play a yet overlooked role in the formation and stabilization of SOM. © 2017 Society for Applied Microbiology and John Wiley & Sons Ltd.

Beyond clay: Towards an improved set of variables for predicting soil organic matter content

USGS Publications Warehouse

Rasmussen, Craig; Heckman, Katherine; Wieder, William R.; Keiluweit, Marco; Lawrence, Corey R.; Berhe, Asmeret Asefaw; Blankinship, Joseph C.; Crow, Susan E.; Druhan, Jennifer; Hicks Pries, Caitlin E.; Marin-Spiotta, Erika; Plante, Alain F.; Schadel, Christina; Schmiel, Joshua P.; Sierra, Carlos A.; Thompson, Aaron; Wagai, Rota

2018-01-01

Improved quantification of the factors controlling soil organic matter (SOM) stabilization at continental to global scales is needed to inform projections of the largest actively cycling terrestrial carbon pool on Earth, and its response to environmental change. Biogeochemical models rely almost exclusively on clay content to modify rates of SOM turnover and fluxes of climate-active CO2 to the atmosphere. Emerging conceptual understanding, however, suggests other soil physicochemical properties may predict SOM stabilization better than clay content. We addressed this discrepancy by synthesizing data from over 5,500 soil profiles spanning continental scale environmental gradients. Here, we demonstrate that other physicochemical parameters are much stronger predictors of SOM content, with clay content having relatively little explanatory power. We show that exchangeable calcium strongly predicted SOM content in water-limited, alkaline soils, whereas with increasing moisture availability and acidity, iron- and aluminum-oxyhydroxides emerged as better predictors, demonstrating that the relative importance of SOM stabilization mechanisms scales with climate and acidity. These results highlight the urgent need to modify biogeochemical models to better reflect the role of soil physicochemical properties in SOM cycling.

A River Model Intercomparison Project in Preparation for SWOT

NASA Astrophysics Data System (ADS)

David, C. H.; Andreadis, K.; Famiglietti, J. S.; Beighley, E.; Boone, A. A.; Yamazaki, D.; Paiva, R. C. D.; Fleischmann, A. S.; Collischonn, W.; Fisher, C. K.; Kim, H.; Biancamaria, S.

2017-12-01

The Surface Water and Ocean Topography (SWOT) mission is currently scheduled to launch at the beginning of next decade. SWOT is expected to retrieve unprecedented measurements of water extent, elevation, and slope in the largest terrestrial water bodies. Such potential transformative information motivates the investigation of our ability to ingest the associated data into continental-scale models of terrestrial hydrology. In preparation for the expected SWOT observations, an inter-comparison of continental-scale river models is being performed. This comparison experiment focuses on four of the world's largest river basins: the Amazon, the Mississippi, the Niger, and the Saint-Lawrence. This ongoing project focuses on two main research questions: 1) How can we best prepare for the expected SWOT continental to global measurements before SWOT even flies?, and 2) What is the added value of including SWOT terrestrial measurements into global hydro models for enhancing our understanding of the terrestrial water cycle and the climate system? We present here the results of the second year of this project which now includes simulations from six numerical models of rivers over the Mississippi and sheds light on the implications of various modeling choices on simulation quality as well as on the potential impact of SWOT observations.

Soil carbon and belowground carbon balance of a short-rotation coppice: assessments from three different approaches.

PubMed

Berhongaray, Gonzalo; Verlinden, Melanie S; Broeckx, Laura S; Janssens, Ivan A; Ceulemans, Reinhart

2017-02-01

Uncertainty in soil carbon (C) fluxes across different land-use transitions is an issue that needs to be addressed for the further deployment of perennial bioenergy crops. A large-scale short-rotation coppice (SRC) site with poplar ( Populus ) and willow ( Salix ) was established to examine the land-use transitions of arable and pasture to bioenergy. Soil C pools, output fluxes of soil CO 2 , CH 4 , dissolved organic carbon (DOC) and volatile organic compounds, as well as input fluxes from litter fall and from roots, were measured over a 4-year period, along with environmental parameters. Three approaches were used to estimate changes in the soil C. The largest C pool in the soil was the soil organic carbon (SOC) pool and increased after four years of SRC from 10.9 to 13.9 kg C m -2 . The belowground woody biomass (coarse roots) represented the second largest C pool, followed by the fine roots (Fr). The annual leaf fall represented the largest C input to the soil, followed by weeds and Fr. After the first harvest, we observed a very large C input into the soil from high Fr mortality. The weed inputs decreased as trees grew older and bigger. Soil respiration averaged 568.9 g C m -2  yr -1 . Leaching of DOC increased over the three years from 7.9 to 14.5 g C m -2 . The pool-based approach indicated an increase of 3360 g C m -2 in the SOC pool over the 4-year period, which was high when compared with the -27 g C m -2 estimated by the flux-based approach and the -956 g C m -2 of the combined eddy-covariance + biometric approach. High uncertainties were associated to the pool-based approach. Our results suggest using the C flux approach for the assessment of the short-/medium-term SOC balance at our site, while SOC pool changes can only be used for long-term C balance assessments.

Genetic legacy of the deep subsurface recorded in the outflow channel of a terrestrial serpentinizing seep (Luzon, the Philippines)

NASA Astrophysics Data System (ADS)

Woycheese, K. M.; Meyer-Dombard, D. R.; Cardace, D.; Arcilla, C. A.

2014-12-01

The deep subsurface microbial community represents the largest biome on Earth, yet accessing this deep biosphere is challenging. Fluids seep along fractures from aquifers that may support diverse microbial communities, living off hydrogen gas generated by radiolysis, serpentinization, or thermogenic reactions. A serpentinizing seep, emanating fluids as high as pH 11.27, was found to accrete meters-long carbonate terraces in the Zambales ophiolite range (Luzon, the Philippines). Samples were collected at several locations along the Poon Bato (PB) River, focusing primarily on the pools and terraces formed by carbonate rimstone (Figure 1). As serpentinizing fluids are exposed to the atmosphere, dynamic niches are established in surface sediments. We propose that the high pH, reducing, high Ca+2 fluid pool terraces reflect remnants of deep subsurface microbial communities, based on high-throughput 16S rRNA sequencing data. In total, eight samples were collected for environmental DNA analysis. Post-sequence analysis revealed a total of 927126 counts, with an average of 115890.75 counts per sample. Many taxa aligned with cultured representatives of serpentinizing seep-associated taxa, including Bacteroidetes, Clostrida, Chloroflexi, Methylococcales, and Xanthomonadales. Geochemical data indicates an average fluid temperature of 28.9°C, and pH that varies from 9.22-11.27. Total carbon wt.% of solids was highest in a shallow pool shaped by boulders, where calcite precipitation occurred over nearly every surface. Dissolved oxygen (DO%) was highest at PB1 main pool (60%), although a calcite skin had formed along the air-water interface. Dissolved inorganic carbon (DIC) at PB1 main pool was 1.3 ppm, while at PB2 main pool, the DIC was higher (6.0 ppm). The lack of calcite skin may allow more direct access to atmospheric carbon dioxide at PB2. The isotopic value of carbon-13 was depleted at PB1 relative to PB2 (δ13C VPDB -25.4 ‰ versus δ13C VPDB ‰ -17.5, respectively). The DOC concentration at PB1 main pool was 0.3 ppm and 1.15 ppm at PB2. Given the low DIC concentrations at PB1, it is suggested that heterotrophy may dominate over autotrophy in the system. This suggests that the highly reducing, high pH fluids emanating from fluid seeps at Poon Bato influence surface communities via inundation with serpentinizing fluid.

Effects of surface-water and groundwater inflows and outflows on the hydrology of the Tsala Apopka Lake Basin in Citrus County, Florida

USGS Publications Warehouse

Sepúlveda, Nicasio; Fulkerson, Mark; Basso, Ron; Ryan, Patrick J.

2018-05-21

The U.S. Geological Survey, in cooperation with the Southwest Florida Water Management District, initiated a study to quantify the inflows and outflows in the Floral City, Inverness, and Hernando pools of the Tsala Apopka Lake Basin in Citrus County, Florida. This study assesses hydrologic changes in pool stages, groundwater levels, spring flows, and streamflows caused by the diversion of streamflow from the Withlacoochee River to the Tsala Apopka Lake Basin through water-control structures. A surface-water/groundwater flow model was developed using hydraulic parameters for lakes, streams, the unsaturated zone, and the underlying surficial and Upper Floridan aquifers estimated using an inverse modeling calibration technique. After calibration, the model was used to assess the relation between inflows and outflows in the Tsala Apopka Lake Basin and changes in pool stages.Simulation results using the calibrated surface-water/groundwater flow model showed that leakage rates from the pools to the Upper Floridan aquifer were largest at the deep lake cells and that these leakage rates to the Upper Floridan aquifer were the highest in the model area. Downward leakage to the Upper Floridan aquifer occurred beneath most of the extent of the Floral City, Inverness, and Hernando pools. These leakage rates depended on the lakebed leakance and the difference between lake stages and heads in the Upper Floridan aquifer. Leakage rates were higher for the Floral City pool than for the Inverness pool, and higher for the Inverness pool than for the Hernando pool. Lakebed leakance was higher for the Floral City pool than for the Hernando pool, and higher for the Hernando pool than for the Inverness pool.Simulation results showed that the average recharge rate to the surficial aquifer was 10.3 inches per year for the 2004 to 2012 simulation period. Areas that recharge the surficial aquifer covered about 86 percent of the model area. Simulations identified areas along segments of the Withlacoochee River and within land-surface depressions that receive water from the surficial aquifer. Recharge rates were largest in physiographic regions having a deep water table. Simulated heads in the Upper Floridan aquifer indicated the general flow directions in the active flow model area were from the northeast toward the southwest and then westward toward the coast, and from the southeast toward the northwest and then westward toward the coast, consistent with flow directions inferred from the estimated potentiometric surface map for May 2010. The largest inflow in the water budget of the Upper Floridan aquifer was downward leakage from the overlying hydrogeologic unit. The largest outflow in the water budget of the Upper Floridan aquifer was spring flow.The calibrated surface-water and groundwater flow model was used to simulate hydrologic scenarios that included changes in rainfall rates, projected increases in groundwater pumping rates for 2025 and 2035, no flow for the 2004–12 period through the eight water-control structures in the Tsala Apopka Lake Basin, and the removal of the Inglis Dam and the Inglis Bypass Spillway on Lake Rousseau. Scenario simulation results were compared to annual average calibrated water levels and flows from 2004 to 2012. Simulated declines in the Tsala Apopka Lake pool stages under the 10-percent lower rainfall scenario were about 0.8, 0.3, and 1.3 feet (ft) for the Floral City, Inverness, and Hernando pools, respectively. Simulated groundwater levels under the same scenario declined up to 5.4 ft in the surficial aquifer and up to 2.9 ft in the Upper Floridan aquifer. Under the projected increases in groundwater pumping rates for 2035 that represented an increase of 36 percent from average 2004 to 2012 pumping rates, the simulated declines in the Floral City, Inverness, and Hernando pool stages were, in downstream order, 0.02, 0.06, and 0.04 ft. The largest drawdown under the projected increases in groundwater pumping rates for 2035 was 2.1 ft in the surficial aquifer and about 1.8 ft in the Upper Floridan aquifer. A scenario of decreased rainfall by 10 percent caused greater declines in water levels and pool stages than projected increases in groundwater pumping rates. The simulation with no flow through the eight Tsala Apopka Lake water-control structures resulted in simulated declines in average pool stage of 1.8, 1.9, and 0.5 ft in the Floral City, Inverness, and Hernando pools, respectively. The simulated removal of the two water-control structures in Lake Rousseau caused flow to increase at Rainbow Springs by 28 cubic feet per second, an increase of 4.7 percent from the average calibrated flow for 2004 to 2012.

How big is the influence of biogenic silicon pools on short-term changes in water-soluble silicon in soils? Implications from a study of a 10-year-old soil-plant system

NASA Astrophysics Data System (ADS)

Puppe, Daniel; Höhn, Axel; Kaczorek, Danuta; Wanner, Manfred; Wehrhan, Marc; Sommer, Michael

2017-11-01

The significance of biogenic silicon (BSi) pools as a key factor for the control of Si fluxes from terrestrial to aquatic ecosystems has been recognized for decades. However, while most research has been focused on phytogenic Si pools, knowledge of other BSi pools is still limited. We hypothesized that different BSi pools influence short-term changes in the water-soluble Si fraction in soils to different extents. To test our hypothesis we took plant (Calamagrostis epigejos, Phragmites australis) and soil samples in an artificial catchment in a post-mining landscape in the state of Brandenburg, Germany. We quantified phytogenic (phytoliths), protistic (diatom frustules and testate amoeba shells) and zoogenic (sponge spicules) Si pools as well as Tiron-extractable and water-soluble Si fractions in soils at the beginning (t0) and after 10 years (t10) of ecosystem development. As expected the results of Tiron extraction showed that there are no consistent changes in the amorphous Si pool at Chicken Creek (Hühnerwasser) as early as after 10 years. In contrast to t0 we found increased water-soluble Si and BSi pools at t10; thus we concluded that BSi pools are the main driver of short-term changes in water-soluble Si. However, because total BSi represents only small proportions of water-soluble Si at t0 (< 2 %) and t10 (2.8-4.3 %) we further concluded that smaller (< 5 µm) and/or fragile phytogenic Si structures have the biggest impact on short-term changes in water-soluble Si. In this context, extracted phytoliths (> 5 µm) only amounted to about 16 % of total Si contents of plant materials of C. epigejos and P. australis at t10; thus about 84 % of small-scale and/or fragile phytogenic Si is not quantified by the used phytolith extraction method. Analyses of small-scale and fragile phytogenic Si structures are urgently needed in future work as they seem to represent the biggest and most reactive Si pool in soils. Thus they are the most important drivers of Si cycling in terrestrial biogeosystems.

Bacterial production in the water column of small streams highly depends on terrestrial dissolved organic carbon

NASA Astrophysics Data System (ADS)

Graeber, Daniel; Poulsen, Jane R.; Rasmussen, Jes J.; Kronvang, Brian; Zak, Dominik; Kamjunke, Norbert

2016-04-01

In the recent years it has become clear that the largest part of the terrestrial dissolved organic carbon (DOC) pool is removed on the way from the land to the ocean. Yet it is still unclear, where in the freshwater systems terrestrial DOC is actually taken up, and for streams DOC uptake was assumed to happen mostly at the stream bottom (benthic zone). However, a recent monitoring study implies that water column but not benthic bacteria are strongly affected by the amount and composition of DOM entering streams from the terrestrial zone. We conducted an experiment to compare the reaction of the bacterial production and heterotrophic uptake in the water column and the benthic zone to a standardized source of terrestrial DOC (leaf leachate from Beech litter). In detail, we sampled gravel and water from eight streams with a gradient in stream size and land use. For each stream four different treatments were incubated at 16°C for three days and each stream: filtered stream water with gravel stones (representing benthic zone bacteria) or unfiltered stream water (representing water column bacteria), both either with (n = 5) or, without (n = 3) leaf leachate. We found that the bacterial uptake of leaf litter DOC was higher for the benthic zone likely due to the higher bacterial production compared to the water column. In contrast, the bacterial production per amount of leaf leachate DOC taken up was significantly higher for the bacteria in the water column than for those in the benthic zone. This clearly indicates a higher growth efficiency with the leaf leachate DOC for the bacteria in the water column than in the benthic zone. We found a high variability for the growth efficiency in the water column, which was best explained by a negative correlation of the DOC demand with stream width (R² = 0.86, linear correlation of log-transformed data). This was not the case for the benthic zone bacteria (R² = 0.02). This implies that water column bacteria in very small streams are more dependent on terrestrial DOC sources for their growth than those in larger streams. Based on this experiment and literature data we hypothesize that: I) The response of the bacterial production to terrestrial DOC in the water column is stronger than for the benthic zone and is decreasing with increasing stream size, likely due to the increase of autochthonous DOC production within the stream. II) Independent of stream size there is only a small reaction to terrestrial DOC for the bacterial production in the benthic zone, either due to internal DOC production or a stronger dependency on particulate organic carbon. We propose that this terrestrial DOC dependency concept is generally applicable, however, its potential underlying mechanisms and concept predictions need to be tested further for other stream and river ecosystems.

Inferring terrestrial photosynthetic light use efficiency of temperate ecosystems from space

Treesearch

Thomas Hilker; Nicholas C. Coops; Forest G. Hall; Caroline J. Nichol; Alexei Lyapustin; T. Andrew Black; Michael A. Wulder; Ray Leuning; Alan Barr; David Y. Hollinger; Bill Munger; Compton J. Tucker

2011-01-01

Terrestrial ecosystems absorb about 2.8 Gt C yr−1, which is estimated to be about a quarter of the carbon emitted from fossil fuel combustion. However, the uncertainties of this sink are large, on the order of ±40%, with spatial and temporal variations largely unknown. One of the largest factors contributing to the uncertainty is photosynthesis,...

Effects of climate extremes on the terrestrial carbon cycle: concepts, processes and potential future impacts

PubMed Central

Frank, Dorothea; Reichstein, Markus; Bahn, Michael; Thonicke, Kirsten; Frank, David; Mahecha, Miguel D; Smith, Pete; van der Velde, Marijn; Vicca, Sara; Babst, Flurin; Beer, Christian; Buchmann, Nina; Canadell, Josep G; Ciais, Philippe; Cramer, Wolfgang; Ibrom, Andreas; Miglietta, Franco; Poulter, Ben; Rammig, Anja; Seneviratne, Sonia I; Walz, Ariane; Wattenbach, Martin; Zavala, Miguel A; Zscheischler, Jakob

2015-01-01

Extreme droughts, heat waves, frosts, precipitation, wind storms and other climate extremes may impact the structure, composition and functioning of terrestrial ecosystems, and thus carbon cycling and its feedbacks to the climate system. Yet, the interconnected avenues through which climate extremes drive ecological and physiological processes and alter the carbon balance are poorly understood. Here, we review the literature on carbon cycle relevant responses of ecosystems to extreme climatic events. Given that impacts of climate extremes are considered disturbances, we assume the respective general disturbance-induced mechanisms and processes to also operate in an extreme context. The paucity of well-defined studies currently renders a quantitative meta-analysis impossible, but permits us to develop a deductive framework for identifying the main mechanisms (and coupling thereof) through which climate extremes may act on the carbon cycle. We find that ecosystem responses can exceed the duration of the climate impacts via lagged effects on the carbon cycle. The expected regional impacts of future climate extremes will depend on changes in the probability and severity of their occurrence, on the compound effects and timing of different climate extremes, and on the vulnerability of each land-cover type modulated by management. Although processes and sensitivities differ among biomes, based on expert opinion, we expect forests to exhibit the largest net effect of extremes due to their large carbon pools and fluxes, potentially large indirect and lagged impacts, and long recovery time to regain previous stocks. At the global scale, we presume that droughts have the strongest and most widespread effects on terrestrial carbon cycling. Comparing impacts of climate extremes identified via remote sensing vs. ground-based observational case studies reveals that many regions in the (sub-)tropics are understudied. Hence, regional investigations are needed to allow a global upscaling of the impacts of climate extremes on global carbon–climate feedbacks. PMID:25752680

Effects of climate extremes on the terrestrial carbon cycle: concepts, processes and potential future impacts.

PubMed

Frank, Dorothea; Reichstein, Markus; Bahn, Michael; Thonicke, Kirsten; Frank, David; Mahecha, Miguel D; Smith, Pete; van der Velde, Marijn; Vicca, Sara; Babst, Flurin; Beer, Christian; Buchmann, Nina; Canadell, Josep G; Ciais, Philippe; Cramer, Wolfgang; Ibrom, Andreas; Miglietta, Franco; Poulter, Ben; Rammig, Anja; Seneviratne, Sonia I; Walz, Ariane; Wattenbach, Martin; Zavala, Miguel A; Zscheischler, Jakob

2015-08-01

Extreme droughts, heat waves, frosts, precipitation, wind storms and other climate extremes may impact the structure, composition and functioning of terrestrial ecosystems, and thus carbon cycling and its feedbacks to the climate system. Yet, the interconnected avenues through which climate extremes drive ecological and physiological processes and alter the carbon balance are poorly understood. Here, we review the literature on carbon cycle relevant responses of ecosystems to extreme climatic events. Given that impacts of climate extremes are considered disturbances, we assume the respective general disturbance-induced mechanisms and processes to also operate in an extreme context. The paucity of well-defined studies currently renders a quantitative meta-analysis impossible, but permits us to develop a deductive framework for identifying the main mechanisms (and coupling thereof) through which climate extremes may act on the carbon cycle. We find that ecosystem responses can exceed the duration of the climate impacts via lagged effects on the carbon cycle. The expected regional impacts of future climate extremes will depend on changes in the probability and severity of their occurrence, on the compound effects and timing of different climate extremes, and on the vulnerability of each land-cover type modulated by management. Although processes and sensitivities differ among biomes, based on expert opinion, we expect forests to exhibit the largest net effect of extremes due to their large carbon pools and fluxes, potentially large indirect and lagged impacts, and long recovery time to regain previous stocks. At the global scale, we presume that droughts have the strongest and most widespread effects on terrestrial carbon cycling. Comparing impacts of climate extremes identified via remote sensing vs. ground-based observational case studies reveals that many regions in the (sub-)tropics are understudied. Hence, regional investigations are needed to allow a global upscaling of the impacts of climate extremes on global carbon-climate feedbacks. © 2015 The Authors. Global Change Biology published by John Wiley & Sons Ltd.

Complete and draft genome sequences of six members of the Aquificales.

PubMed

Reysenbach, Anna-Louise; Hamamura, N; Podar, M; Griffiths, E; Ferreira, S; Hochstein, R; Heidelberg, J; Johnson, J; Mead, D; Pohorille, A; Sarmiento, M; Schweighofer, K; Seshadri, R; Voytek, M A

2009-03-01

The Aquificales are widespread in marine and terrestrial hydrothermal environments. Here, we report the complete and draft genome sequences of six new members of the Aquificales: two marine species, Persephonella marina strain EX-H1 and Hydrogenivirga strain 128-5-R1 (from the East Pacific Rise, 9 degrees 50.3'N, 104 degrees 17.5'W, and the Eastern Lau Spreading Center, 176 degrees 11.5'W, 20 degrees 45.8'S, respectively), and four terrestrial isolates, Sulfurihydrogenibium azorense strain Az-Fu1, Sulfurihydrogenibium yellowstonense strain SS-5, and Sulfurihydrogenibium strain Y03AOP1 (from Furnas, Azores, Portugal, and Calcite Springs and Obsidian Pool in Yellowstone National Park, United States, respectively), and the only thermoacidophilic isolate, Hydrogenobaculum strain Y04AAS1 (from a stream adjacent to Obsidian Pool). Significant differences among the different species exist that include nitrogen metabolism, hydrogen utilization, chemotaxis, and signal transduction, providing insights into their ecological niche adaptations.

Nonautonomous linear system of the terrestrial carbon cycle

NASA Astrophysics Data System (ADS)

Luo, Y.

2012-12-01

Carbon cycle has been studied by uses of observation through various networks, field and laboratory experiments, and simulation models. Much less has been done on theoretical thinking and analysis to understand fundament properties of carbon cycle and then guide observatory, experimental, and modeling research. This presentation is to explore what would be the theoretical properties of terrestrial carbon cycle and how those properties can be used to make observatory, experimental, and modeling research more effective. Thousands of published data sets from litter decomposition and soil incubation studies almost all indicate that decay processes of litter and soil organic carbon can be well described by first order differential equations with one or more pools. Carbon pool dynamics in plants and soil after disturbances (e.g., wildfire, clear-cut of forests, and plows of soil for cropping) and during natural recovery or ecosystem restoration also exhibit characteristics of first-order linear systems. Thus, numerous lines of empirical evidence indicate that the terrestrial carbon cycle can be adequately described as a nonautonomous linear system. The linearity reflects the nature of the carbon cycle that carbon, once fixed by photosynthesis, is linearly transferred among pools within an ecosystem. The linear carbon transfer, however, is modified by nonlinear functions of external forcing variables. In addition, photosynthetic carbon influx is also nonlinearly influenced by external variables. This nonautonomous linear system can be mathematically expressed by a first-order linear ordinary matrix equation. We have recently used this theoretical property of terrestrial carbon cycle to develop a semi-analytic solution of spinup. The new methods have been applied to five global land models, including NCAR's CLM and CABLE models and can computationally accelerate spinup by two orders of magnitude. We also use this theoretical property to develop an analytic framework to decompose modeled carbon cycle into a few traceable components so as to facilitate model intercompsirosn, benchmark analysis, and data assimilation of global land models.

NATIVE PLANTS FOR OPTIMIZING CARBON SEQUESTRATION IN RECLAIMED LANDS

DOE Office of Scientific and Technical Information (OSTI.GOV)

P. UNKEFER; M. EBINGER; ET AL

Carbon emissions and atmospheric concentrations are expected to continue to increase through the next century unless major changes are made in the way carbon is managed. Managing carbon has emerged as a pressing national energy and environmental need that will drive national policies and treaties through the coming decades. Addressing carbon management is now a major priority for DOE and the nation. One way to manage carbon is to use energy more efficiently to reduce our need for major energy and carbon source-fossil fuel combustion. Another way is to increase our use of low-carbon and carbon free fuels and technologies.more » A third way, and the focus of this proposal, is carbon sequestration, in which carbon is captured and stored thereby mitigating carbon emissions. Sequestration of carbon in the terrestrial biosphere has emerged as the principle means by which the US will meet its near-term international and economic requirements for reducing net carbon emissions (DOE Carbon Sequestration: State of the Science. 1999; IGBP 1998). Terrestrial carbon sequestration provides three major advantages. First, terrestrial carbon pools and fluxes are of sufficient magnitude to effectively mitigate national and even global carbon emissions. The terrestrial biosphere stores {approximately}2060 GigaTons of carbon and transfers approximately 120 GigaTons of carbon per year between the atmosphere and the earth's surface, whereas the current global annual emissions are about 6 GigaTons. Second, we can rapidly and readily modify existing management practices to increase carbon sequestration in our extensive forest, range, and croplands. Third, increasing soil carbon is without negative environment consequences and indeed positively impacts land productivity. The terrestrial carbon cycle is dependent on several interrelationships between plants and soils. Because the soil carbon pool ({approximately}1500 Giga Tons) is approximately three times that in terrestrial vegetation ({approximately}560 GigaTons), the principal focus of terrestrial sequestration efforts is to increase soil carbon. But soil carbon ultimately derives from vegetation and therefore must be managed indirectly through aboveground management of vegetation and nutrients. Hence, the response of whole ecosystems must be considered in terrestrial carbon sequestration strategies.« less

The Influence of Submarine Groundwater Discharge on Nearshore Marine Dissolved Organic Carbon Reactivity, Concentration Dynamics, and Offshore Export

NASA Astrophysics Data System (ADS)

Goodridge, B.

2017-12-01

Dissolved organic carbon (DOC) is the largest pool of reduced carbon in the oceans, with a reservoir equivalent to atmospheric CO2. In nearshore marine regions, DOC sources include primary production, terrestrial DOC delivered by river discharge, and/or terrestrial and marine DOC delivered via submarine groundwater discharge (SGD). While the importance of SGD to coastal carbon cycling has been implicated, the actual influence of this process on nearshore carbon dynamics and offshore export has not been explicitly identified. This study, conducted at a predominantly marine-influenced intertidal beach-nearshore ocean system along the Santa Barbara, California coastline, aimed to address this knowledge gap. I coupled dark, temperature-controlled laboratory incubations, radioisotopic (Rn-222) SGD estimates, and a DOC box model to identify the influence of pore water mixing with seawater on nearshore DOC reactivity, concentration dynamics, and offshore export. Even with a relatively low volumetric contribution, SGD pore water mixing altered nearshore DOC reactivity, and elevated the nearshore DOC concentration by 0.9 to 5.6 µmol L-1 over nearshore seawater residence times ranging from 1 to 6 days. These elevated DOC concentrations were equivalent to 1.2 to 7.5% of the mean offshore DOC concentration taken during the summer months in the Santa Barbara Channel, when the coastal water column is highly thermally stratified. Despite the challenge of assessing carbon dynamics in physically and biogeochemically complex nearshore marine regions, this study demonstrates the need for future investigations to assess and account for SGD as a non-trivial component of coastal marine carbon cycles.

Lake secondary production fueled by rapid transfer of low molecular weight organic carbon from terrestrial sources to aquatic consumers.

PubMed

Berggren, M; Ström, L; Laudon, H; Karlsson, J; Jonsson, A; Giesler, R; Bergström, A-K; Jansson, M

2010-07-01

Carbon of terrestrial origin often makes up a significant share of consumer biomass in unproductive lake ecosystems. However, the mechanisms for terrestrial support of lake secondary production are largely unclear. By using a modelling approach, we show that terrestrial export of dissolved labile low molecular weight carbon (LMWC) compounds supported 80% (34-95%), 54% (19-90%) and 23% (7-45%) of the secondary production by bacteria, protozoa and metazoa, respectively, in a 7-km(2) boreal lake (conservative to liberal estimates in brackets). Bacterial growth on LMWC was of similar magnitude as that of primary production (PP), and grazing on bacteria effectively channelled the LMWC carbon to higher trophic levels. We suggest that rapid turnover of forest LMWC pools enables continuous export of fresh photosynthates and other labile metabolites to aquatic systems, and that substantial transfer of LMWC from terrestrial sources to lake consumers can occur within a few days. Sequestration of LMWC of terrestrial origin, thus, helps explain high shares of terrestrial carbon in lake organisms and implies that lake food webs can be closely dependent on recent terrestrial PP.

Heterogeneity in leaf litter decomposition in a temporary Mediterranean stream during flow fragmentation.

PubMed

Abril, Meritxell; Muñoz, Isabel; Menéndez, Margarita

2016-05-15

In temporary Mediterranean streams, flow fragmentation during summer droughts originates an ephemeral mosaic of terrestrial and aquatic habitat types. The heterogeneity of habitat types implies a particular ecosystem functioning in temporary streams that is still poorly understood. We assessed the initial phases of leaf litter decomposition in selected habitat types: running waters, isolated pools and moist and dry streambed sediments. We used coarse-mesh litter bags containing Populus nigra leaves to examine decomposition rates, microbial biomass, macroinvertebrate abundance and dissolved organic carbon (DOC) release rates in each habitat type over an 11-day period in late summer. We detected faster decomposition rates in aquatic (running waters and isolated pools) than in terrestrial habitats (moist and dry streambed sediments). Under aquatic conditions, decomposition was characterized by intense leaching and early microbial colonization, which swiftly started to decompose litter. Microbial colonization in isolated pools was primarily dominated by bacteria, whereas in running waters fungal biomass predominated. Under terrestrial conditions, leaves were most often affected by abiotic processes that resulted in small mass losses. We found a substantial decrease in DOC release rates in both aquatic habitats within the first days of the study, whereas DOC release rates remained relatively stable in the moist and dry sediments. This suggests that leaves play different roles as a DOC source during and after flow fragmentation. Overall, our results revealed that leaf decomposition is heterogeneous during flow fragmentation, which has implications related to DOC utilization that should be considered in future regional carbon budgets. Copyright © 2016 Elsevier B.V. All rights reserved.

A molecular palaeobiological exploration of arthropod terrestrialization

PubMed Central

Carton, Robert; Edgecombe, Gregory D.

2016-01-01

Understanding animal terrestrialization, the process through which animals colonized the land, is crucial to clarify extant biodiversity and biological adaptation. Arthropoda (insects, spiders, centipedes and their allies) represent the largest majority of terrestrial biodiversity. Here we implemented a molecular palaeobiological approach, merging molecular and fossil evidence, to elucidate the deepest history of the terrestrial arthropods. We focused on the three independent, Palaeozoic arthropod terrestrialization events (those of Myriapoda, Hexapoda and Arachnida) and showed that a marine route to the colonization of land is the most likely scenario. Molecular clock analyses confirmed an origin for the three terrestrial lineages bracketed between the Cambrian and the Silurian. While molecular divergence times for Arachnida are consistent with the fossil record, Myriapoda are inferred to have colonized land earlier, substantially predating trace or body fossil evidence. An estimated origin of myriapods by the Early Cambrian precedes the appearance of embryophytes and perhaps even terrestrial fungi, raising the possibility that terrestrialization had independent origins in crown-group myriapod lineages, consistent with morphological arguments for convergence in tracheal systems. This article is part of the themed issue ‘Dating species divergences using rocks and clocks’. PMID:27325830

Soil Organic Carbon Loss: An Overlooked Factor in the Carbon Sequestration Potential of Enhanced Mineral Weathering

NASA Astrophysics Data System (ADS)

Dietzen, Christiana; Harrison, Robert

2016-04-01

Weathering of silicate minerals regulates the global carbon cycle on geologic timescales. Several authors have proposed that applying finely ground silicate minerals to soils, where organic acids would enhance the rate of weathering, could increase carbon uptake and mitigate anthropogenic CO2 emissions. Silicate minerals such as olivine could replace lime, which is commonly used to remediate soil acidification, thereby sequestering CO2 while achieving the same increase in soil pH. However, the effect of adding this material on soil organic matter, the largest terrestrial pool of carbon, has yet to be considered. Microbial biomass and respiration have been observed to increase with decreasing acidity, but it is unclear how long the effect lasts. If the addition of silicate minerals promotes the loss of soil organic carbon through decomposition, it could significantly reduce the efficiency of this process or even create a net carbon source. However, it is possible that this initial flush of microbial activity may be compensated for by additional organic matter inputs to soil pools due to increases in plant productivity under less acidic conditions. This study aimed to examine the effects of olivine amendments on soil CO2 flux. A liming treatment representative of typical agricultural practices was also included for comparison. Samples from two highly acidic soils were split into groups amended with olivine or lime and a control group. These samples were incubated at 22°C and constant soil moisture in jars with airtight septa lids. Gas samples were extracted periodically over the course of 2 months and change in headspace CO2 concentration was determined. The effects of enhanced mineral weathering on soil organic matter have yet to be addressed by those promoting this method of carbon sequestration. This project provides the first data on the potential effects of enhanced mineral weathering in the soil environment on soil organic carbon pools.

Soil properties of mangroves in contrasting geomorphic settings within the Zambezi River Delta, Mozambique

Treesearch

Christina E. Stringer; Carl C. Trettin; Stan Zarnoch

2016-01-01

Mangroves are well-known for their numerous ecosystem services, including sequestering a significant carbon stock, with soils accounting for the largest pool. The soil carbon pool is dependent on the carbon content and bulk density. Our objective was to assess the spatial variability of mangrove soil physical and chemical properties within the Zambezi River Delta and...

Comparing the influence of wildfire and prescribed burns on watershed nitrogen biogeochemistry using 15N natural abundance in terrestrial and aquatic ecosystem components.

PubMed

Stephan, Kirsten; Kavanagh, Kathleen L; Koyama, Akihiro

2015-01-01

We evaluated differences in the effects of three low-severity spring prescribed burns and four wildfires on nitrogen (N) biogeochemistry in Rocky Mountain headwater watersheds. We compared paired (burned/unburned) watersheds of four wildfires and three spring prescribed burns for three growing seasons post-fire. To better understand fire effects on the entire watershed ecosystem, we measured N concentrations and δ15N in both the terrestrial and aquatic ecosystems components, i.e., soil, understory plants in upland and riparian areas, streamwater, and in-stream moss. In addition, we measured nitrate reductase activity in foliage of Spiraea betulifolia, a dominant understory species. We found increases of δ15N and N concentrations in both terrestrial and aquatic ecosystem N pools after wildfire, but responses were limited to terrestrial N pools after prescribed burns indicating that N transfer from terrestrial to aquatic ecosystem components did not occur in low-severity prescribed burns. Foliar δ15N differed between wildfire and prescribed burn sites; the δ15N of foliage of upland plants was enriched by 2.9 ‰ (difference between burned and unburned watersheds) in the first two years after wildfire, but only 1.3 ‰ after prescribed burns. In-stream moss δ15N in wildfire-burned watersheds was enriched by 1.3 ‰, but there was no response by moss in prescription-burned watersheds, mirroring patterns of streamwater nitrate concentrations. S. betulifolia showed significantly higher nitrate reductase activity two years after wildfires relative to corresponding unburned watersheds, but no such difference was found after prescribed burns. These responses are consistent with less altered N biogeochemistry after prescribed burns relative to wildfire. We concluded that δ15N values in terrestrial and aquatic plants and streamwater nitrate concentrations after fire can be useful indicators of the magnitude and duration of fire effects and the fate of post-fire available N.

Comparing the Influence of Wildfire and Prescribed Burns on Watershed Nitrogen Biogeochemistry Using 15N Natural Abundance in Terrestrial and Aquatic Ecosystem Components

PubMed Central

Stephan, Kirsten; Kavanagh, Kathleen L.; Koyama, Akihiro

2015-01-01

We evaluated differences in the effects of three low-severity spring prescribed burns and four wildfires on nitrogen (N) biogeochemistry in Rocky Mountain headwater watersheds. We compared paired (burned/unburned) watersheds of four wildfires and three spring prescribed burns for three growing seasons post-fire. To better understand fire effects on the entire watershed ecosystem, we measured N concentrations and δ15N in both the terrestrial and aquatic ecosystems components, i.e., soil, understory plants in upland and riparian areas, streamwater, and in-stream moss. In addition, we measured nitrate reductase activity in foliage of Spiraea betulifolia, a dominant understory species. We found increases of δ15N and N concentrations in both terrestrial and aquatic ecosystem N pools after wildfire, but responses were limited to terrestrial N pools after prescribed burns indicating that N transfer from terrestrial to aquatic ecosystem components did not occur in low-severity prescribed burns. Foliar δ15N differed between wildfire and prescribed burn sites; the δ15N of foliage of upland plants was enriched by 2.9 ‰ (difference between burned and unburned watersheds) in the first two years after wildfire, but only 1.3 ‰ after prescribed burns. In-stream moss δ15N in wildfire-burned watersheds was enriched by 1.3 ‰, but there was no response by moss in prescription-burned watersheds, mirroring patterns of streamwater nitrate concentrations. S. betulifolia showed significantly higher nitrate reductase activity two years after wildfires relative to corresponding unburned watersheds, but no such difference was found after prescribed burns. These responses are consistent with less altered N biogeochemistry after prescribed burns relative to wildfire. We concluded that δ15N values in terrestrial and aquatic plants and streamwater nitrate concentrations after fire can be useful indicators of the magnitude and duration of fire effects and the fate of post-fire available N. PMID:25885257

Long-term changes in aluminum fractions of drainage waters in two forest catchments with contrasting lithology.

PubMed

Krám, Pavel; Hruska, Jakub; Driscoll, Charles T; Johnson, Chris E; Oulehle, Filip

2009-11-01

Aluminum (Al) chemistry was studied in soils and waters of two catchments covered by spruce (Picea abies) monocultures in the Czech Republic that represent geochemical end-members of terrestrial and aquatic sensitivity to acidic deposition. The acid-sensitive Lysina catchment, underlain by granite, was compared to the acid-resistant Pluhův Bor catchment on serpentine. Organically-bound Al was the largest pool of reactive soil Al at both sites. Very high median total Al (Alt) concentrations (40 micromol L(-1)) and inorganic monomeric Al (Ali) concentrations (27 micromol L(-1)) were observed in acidic (pH 4.0) stream water at Lysina in the 1990s and these concentrations decreased to 32 micromol L(-1) (Alt) and 13 micromol L(-1) (Ali) in the 2000s. The potentially toxic Ali fraction decreased in response to long-term decreases in acidic deposition, but Ali remained the largest fraction. However, the organic monomeric (Alo) and particulate (Alp) fractions increased in the 2000s at Lysina. In contrast to Lysina, marked increases of Alt concentrations in circum-neutral waters at Pluhův Bor were observed in the 2000s in comparison with the 1990s. These increases were entirely due to the Alp fraction, which increased more than 3-fold in stream water and up to 8-fold in soil water in the A horizon. Increase of Alp coincided with dissolved organic carbon (DOC) increases. Acidification recovery may have increased the content of colloidal Al though the coagulation of monomeric Al.

Allochthonous carbon is a major regulator to bacterial growth and community composition in subarctic freshwaters

PubMed Central

Roiha, Toni; Peura, Sari; Cusson, Mathieu; Rautio, Milla

2016-01-01

In the subarctic region, climate warming and permafrost thaw are leading to emergence of ponds and to an increase in mobility of catchment carbon. As carbon of terrestrial origin is increasing in subarctic freshwaters the resource pool supporting their microbial communities and metabolism is changing, with consequences to overall aquatic productivity. By sampling different subarctic water bodies for a one complete year we show how terrestrial and algal carbon compounds vary in a range of freshwaters and how differential organic carbon quality is linked to bacterial metabolism and community composition. We show that terrestrial drainage and associated nutrients supported higher bacterial growth in ponds and river mouths that were influenced by fresh terrestrial carbon than in large lakes with carbon from algal production. Bacterial diversity, however, was lower at sites influenced by terrestrial carbon inputs. Bacterial community composition was highly variable among different water bodies and especially influenced by concentrations of dissolved organic carbon (DOC), fulvic acids, proteins and nutrients. Furthermore, a distinct preference was found for terrestrial vs. algal carbon among certain bacterial tribes. The results highlight the contribution of the numerous ponds to cycling of terrestrial carbon in the changing subarctic and arctic regions. PMID:27686416

Allochthonous carbon is a major regulator to bacterial growth and community composition in subarctic freshwaters.

PubMed

Roiha, Toni; Peura, Sari; Cusson, Mathieu; Rautio, Milla

2016-09-30

In the subarctic region, climate warming and permafrost thaw are leading to emergence of ponds and to an increase in mobility of catchment carbon. As carbon of terrestrial origin is increasing in subarctic freshwaters the resource pool supporting their microbial communities and metabolism is changing, with consequences to overall aquatic productivity. By sampling different subarctic water bodies for a one complete year we show how terrestrial and algal carbon compounds vary in a range of freshwaters and how differential organic carbon quality is linked to bacterial metabolism and community composition. We show that terrestrial drainage and associated nutrients supported higher bacterial growth in ponds and river mouths that were influenced by fresh terrestrial carbon than in large lakes with carbon from algal production. Bacterial diversity, however, was lower at sites influenced by terrestrial carbon inputs. Bacterial community composition was highly variable among different water bodies and especially influenced by concentrations of dissolved organic carbon (DOC), fulvic acids, proteins and nutrients. Furthermore, a distinct preference was found for terrestrial vs. algal carbon among certain bacterial tribes. The results highlight the contribution of the numerous ponds to cycling of terrestrial carbon in the changing subarctic and arctic regions.

Altered soil microbial community at elevated CO2 leads to loss of soil carbon

PubMed Central

Carney, Karen M.; Hungate, Bruce A.; Drake, Bert G.; Megonigal, J. Patrick

2007-01-01

Increased carbon storage in ecosystems due to elevated CO2 may help stabilize atmospheric CO2 concentrations and slow global warming. Many field studies have found that elevated CO2 leads to higher carbon assimilation by plants, and others suggest that this can lead to higher carbon storage in soils, the largest and most stable terrestrial carbon pool. Here we show that 6 years of experimental CO2 doubling reduced soil carbon in a scrub-oak ecosystem despite higher plant growth, offsetting ≈52% of the additional carbon that had accumulated at elevated CO2 in aboveground and coarse root biomass. The decline in soil carbon was driven by changes in soil microbial composition and activity. Soils exposed to elevated CO2 had higher relative abundances of fungi and higher activities of a soil carbon-degrading enzyme, which led to more rapid rates of soil organic matter degradation than soils exposed to ambient CO2. The isotopic composition of microbial fatty acids confirmed that elevated CO2 increased microbial utilization of soil organic matter. These results show how elevated CO2, by altering soil microbial communities, can cause a potential carbon sink to become a carbon source. PMID:17360374

Mudskippers and Their Genetic Adaptations to an Amphibious Lifestyle.

PubMed

You, Xinxin; Sun, Min; Li, Jia; Bian, Chao; Chen, Jieming; Yi, Yunhai; Yu, Hui; Shi, Qiong

2018-02-07

Mudskippers are the largest group of amphibious teleost fish that are uniquely adapted to live on mudflats. During their successful transition from aqueous life to terrestrial living, these fish have evolved morphological and physiological modifications of aerial vision and olfaction, higher ammonia tolerance, aerial respiration, improved immunological defense against terrestrial pathogens, and terrestrial locomotion using protruded pectoral fins. Comparative genomic and transcriptomic data have been accumulated and analyzed for understanding molecular mechanisms of the terrestrial adaptations. Our current review provides a general introduction to mudskippers and recent research advances of their genetic adaptations to the amphibious lifestyle, which will be helpful for understanding the evolutionary transition of vertebrates from water to land. Our insights into the genomes and transcriptomes will also support molecular breeding, functional identification, and natural compound screening.

Impact basins on Venus and some interplanetary comparisons

NASA Technical Reports Server (NTRS)

Spudis, Paul D.; Sharpton, Virgil L.

1993-01-01

Impact is one of the many processes that have shaped the surface of Venus. The largest impact craters, basins, are important features affecting the evolution of the terrestrial planets. Because Venus has an atmosphere, a gravity similar to Earth's, and a surface target with a high geothermal gradient, venusian basins provide an important comparative set of data to test our ideas about basin-forming impacts and their geological effects on the evolution of the crusts of the terrestrial planets.

Representation of Dissolved Organic Carbon in the JULES Dynamic Global Vegetation Model

NASA Astrophysics Data System (ADS)

Nakhavali, Mahdi; Friedlingstein, Pierre; Guenet, Bertrand; Ciais, Philip

2017-04-01

Current global models of the carbon cycle consider only vertical gas exchanges between terrestrial or oceanic reservoirs and the atmosphere, hence not considering lateral transport of carbon from the continent to the oceans. This also means that such models implicitly consider that all the CO2 which is not respired to the atmosphere is stored on land, hence overestimating the land sink of carbon. Moving toward a boundless carbon cycle that is integrating the whole continuum from land to ocean to atmosphere is needed in order to better understand Earth's carbon cycle and to make more reliable projection of its future. Here we present an original representation of Dissolved Organic Carbon (DOC) processes in the Joint UK Land Environment Simulator (JULES). The standard version of JULES represent energy, water and carbon cycles and exchanges with the atmosphere, but only account for water run-off, not including export of carbon from terrestrial ecosystems to the aquatic environments. The aim of the project is to include in JULES a representation of DOC production in terrestrial soils, due to incomplete decomposition of organic matter, its decomposition to the atmosphere, and its export to the river network by leaching. In new developed version of JULES (JULES-DOCM), DOC pools, based on their decomposition rate, are classified into labile and recalcitrant within 3 meters of soil. Based on turnover rate, DOC coming from plant material pools and microbial biomass is directed to labile pool, while DOC from humus is directed to recalcitrant pool. Both of these pools have free (dissolved) and locked (adsorbed) form where just the free pool is subjected to decomposition and leaching. DOC production and decomposition are controlled by rate modifiers (moisture, temperature, vegetation fraction and decomposition rate) at each soil layer. Decomposed DOC is released to the atmosphere following a fixed carbon use efficiency. Leaching accounts for both surface (runoff) and subsurface (groundwater) components and is parameterized as Top soil leaching (from top 20cm) and Bottom soil leaching (down to 3 meters) depending on DOC concentration and runoff leaving that layer. The model parameters are calibrated against specific sites (Brasschaat, Hainich and Carlow) for which observations of DOC concentration and leaching are available. Tuning is performed optimizing parameters such as DOC labile and recalcitrant resident time, DOC vertical distribution and CUE. Once this calibration has been performed at the site level, the model is used for global simulations with the major historical forcing (climate, atmospheric CO2 and land-use changes) in order to estimate the changes of DOC export and their attribution to anthropogenic activities.

[Roles of soil dissolved organic carbon in carbon cycling of terrestrial ecosystems: a review].

PubMed

Li, Ling; Qiu, Shao-Jun; Liu, Jing-Tao; Liu, Qing; Lu, Zhao-Hua

2012-05-01

Soil dissolved organic carbon (DOC) is an active fraction of soil organic carbon pool, playing an important role in the carbon cycling of terrestrial ecosystems. In view of the importance of the carbon cycling, this paper summarized the roles of soil DOC in the soil carbon sequestration and greenhouse gases emission, and in considering of our present ecological and environmental problems such as soil acidification and climate warming, discussed the effects of soil properties, environmental factors, and human activities on the soil DOC as well as the response mechanisms of the DOC. This review could be helpful to the further understanding of the importance of soil DOC in the carbon cycling of terrestrial ecosystems and the reduction of greenhouse gases emission.

Terrestrial cycling of 13CO2 by photosynthesis, respiration, and biomass burning in SiBCASA

NASA Astrophysics Data System (ADS)

van der Velde, I. R.; Miller, J. B.; Schaefer, K.; van der Werf, G. R.; Krol, M. C.; Peters, W.

2014-12-01

We present an enhanced version of the SiBCASA terrestrial biosphere model that is extended with (a) biomass burning emissions from the SiBCASA carbon pools using remotely sensed burned area from the Global Fire Emissions Database (GFED), (b) an isotopic discrimination scheme that calculates 13C signatures of photosynthesis and autotrophic respiration, and (c) a separate set of 13C pools to carry isotope ratios into heterotrophic respiration. We quantify in this study the terrestrial exchange of CO2 and 13CO2 as a function of environmental changes in humidity and biomass burning. The implementation of biomass burning yields similar fluxes as CASA-GFED both in magnitude and spatial patterns. The implementation of isotope exchange gives a global mean discrimination value of 15.2‰, ranges between 4 and 20‰ depending on the photosynthetic pathway in the plant, and compares favorably (annually and seasonally) with other published values. Similarly, the isotopic disequilibrium is similar to other studies that include a small effect of biomass burning as it shortens the turnover of carbon. In comparison to measurements, a newly modified starch/sugar storage pool propagates the isotopic discrimination anomalies to respiration much better. In addition, the amplitude of the drought response by SiBCASA is lower than suggested by the measured isotope ratios. We show that a slight increase in the stomatal closure for large vapor pressure deficit would amplify the respired isotope ratio variability. Our study highlights the importance of isotope ratio observations of 13C to assess and improve biochemical models like SiBCASA, especially with regard to the allocation and turnover of carbon and the responses to drought.

Metabolic Patterns in Spirodela polyrhiza Revealed by 15N Stable Isotope Labeling of Amino Acids in Photoautotrophic, Heterotrophic, and Mixotrophic Growth Conditions

PubMed Central

Evans, Erin M.; Freund, Dana M.; Sondervan, Veronica M.; Cohen, Jerry D.; Hegeman, Adrian D.

2018-01-01

In this study we describe a [15N] stable isotopic labeling study of amino acids in Spirodela polyrhiza (common duckweed) grown under three different light and carbon input conditions which represent unique potential metabolic modes. Plants were grown with a light cycle, either with supplemental sucrose (mixotrophic) or without supplemental sucrose (photoautotrophic) and in the dark with supplemental sucrose (heterotrophic). Labeling patterns, pool sizes (both metabolically active and inactive), and kinetics/turnover rates were estimated for 17 of the proteinogenic amino acids. Estimation of these parameters followed several overall trends. First, most amino acids showed plateaus in labeling patterns of <100% [15N]-labeling, indicating the possibility of a large proportion of amino acids residing in metabolically inactive metabolite pools. Second, total pool sizes appear largest in the dark (heterotrophic) condition, whereas active pool sizes appeared to be largest in the light with sucrose (mixotrophic) growth condition. In contrast turnover measurements based on pool size were highest overall in the light with sucrose experiment, with the exception of leucine/isoleucine, lysine, and arginine, which all showed higher turnover in the dark. K-means clustering analysis also revealed more rapid turnover in the light treatments with many amino acids clustering in lower-turnover groups. Emerging insights from other research were also supported, such as the prevalence of alternate pathways for serine metabolism in non-photosynthetic cells. These data provide extensive novel information on amino acid pool size and kinetics in S. polyrhiza and can serve as groundwork for future metabolic studies. PMID:29904627

Metabolic Patterns in Spirodela polyrhiza Revealed by 15N Stable Isotope Labeling of Amino Acids in Photoautotrophic, Heterotrophic, and Mixotrophic Growth Conditions.

PubMed

Evans, Erin M; Freund, Dana M; Sondervan, Veronica M; Cohen, Jerry D; Hegeman, Adrian D

2018-01-01

In this study we describe a [ 15 N] stable isotopic labeling study of amino acids in Spirodela polyrhiza (common duckweed) grown under three different light and carbon input conditions which represent unique potential metabolic modes. Plants were grown with a light cycle, either with supplemental sucrose (mixotrophic) or without supplemental sucrose (photoautotrophic) and in the dark with supplemental sucrose (heterotrophic). Labeling patterns, pool sizes (both metabolically active and inactive), and kinetics/turnover rates were estimated for 17 of the proteinogenic amino acids. Estimation of these parameters followed several overall trends. First, most amino acids showed plateaus in labeling patterns of <100% [ 15 N]-labeling, indicating the possibility of a large proportion of amino acids residing in metabolically inactive metabolite pools. Second, total pool sizes appear largest in the dark (heterotrophic) condition, whereas active pool sizes appeared to be largest in the light with sucrose (mixotrophic) growth condition. In contrast turnover measurements based on pool size were highest overall in the light with sucrose experiment, with the exception of leucine/isoleucine, lysine, and arginine, which all showed higher turnover in the dark. K-means clustering analysis also revealed more rapid turnover in the light treatments with many amino acids clustering in lower-turnover groups. Emerging insights from other research were also supported, such as the prevalence of alternate pathways for serine metabolism in non-photosynthetic cells. These data provide extensive novel information on amino acid pool size and kinetics in S. polyrhiza and can serve as groundwork for future metabolic studies.

Metabolic patterns in Spirodela polyrhiza revealed by 15N stable isotope labeling of amino acids in photoautotrophic, heterotrophic, and mixotrophic growth conditions

NASA Astrophysics Data System (ADS)

Evans, Erin M.; Freund, Dana M.; Sondervan, Veronica M.; Cohen, Jerry D.; Hegeman, Adrian D.

2018-05-01

In this study we describe a [15N] stable isotopic labeling study of amino acids in Spirodela polyrhiza (common duckweed) grown under three different light and carbon input conditions which represent unique potential metabolic modes. Plants were grown with a light cycle, either with supplemental sucrose (mixotrophic) or without supplemental sucrose (photoautotrophic) and in the dark with supplemental sucrose (heterotrophic). Labeling patterns, pool sizes (both metabolically active and inactive), and kinetics/turnover rates were estimated for fifteen of the proteinogenic amino acids. Estimation of these parameters followed several overall trends. First, most amino acids showed plateaus in labeling patterns of less than 100% [15N]-labeling, indicating the possibility of a large proportion of amino acids residing in metabolically inactive metabolite pools. Second, total pool sizes appear largest in the dark (heterotrophic) condition, whereas active pool sizes appeared to be largest in the light with sucrose (mixotrophic) growth condition. In contrast turnover measurements based on pool size were highest overall in the light with sucrose experiment, with the exception of leucine/isoleucine, lysine, and arginine, which all showed higher turnover in the dark. K-means clustering analysis also revealed more rapid turnover in the light treatments with many amino acids clustering in lower-turnover groups. Emerging insights from other research were also supported, such as the prevalence of alternate pathways for serine metabolism in non-photosynthetic cells. These data provide extensive novel information on amino acid pool size and kinetics in S. polyrhiza and can serve as groundwork for future metabolic studies.

Complete and Draft Genome Sequences of Six Members of the Aquificales▿

PubMed Central

Reysenbach, Anna-Louise; Hamamura, N.; Podar, M.; Griffiths, E.; Ferreira, S.; Hochstein, R.; Heidelberg, J.; Johnson, J.; Mead, D.; Pohorille, A.; Sarmiento, M.; Schweighofer, K.; Seshadri, R.; Voytek, M. A.

2009-01-01

The Aquificales are widespread in marine and terrestrial hydrothermal environments. Here, we report the complete and draft genome sequences of six new members of the Aquificales: two marine species, Persephonella marina strain EX-H1 and Hydrogenivirga strain 128-5-R1 (from the East Pacific Rise, 9°50.3′N, 104°17.5′W, and the Eastern Lau Spreading Center, 176°11.5′W, 20°45.8′S, respectively), and four terrestrial isolates, Sulfurihydrogenibium azorense strain Az-Fu1, Sulfurihydrogenibium yellowstonense strain SS-5, and Sulfurihydrogenibium strain Y03AOP1 (from Furnas, Azores, Portugal, and Calcite Springs and Obsidian Pool in Yellowstone National Park, United States, respectively), and the only thermoacidophilic isolate, Hydrogenobaculum strain Y04AAS1 (from a stream adjacent to Obsidian Pool). Significant differences among the different species exist that include nitrogen metabolism, hydrogen utilization, chemotaxis, and signal transduction, providing insights into their ecological niche adaptations. PMID:19136599

Complete and draft genome sequences of six members of the aquificales

USGS Publications Warehouse

Reysenbach, A.-L.; Hamamura, N.; Podar, M.; Griffiths, E.; Ferreira, S.; Hochstein, R.; Heidelberg, J.; Johnson, J.; Mead, D.; Pohorille, A.; Sarmiento, M.; Sehweighofer, K.; Seshadri, R.; Voytek, M.A.

2009-01-01

The Aquificales are widespread in marine and terrestrial hydrothermal environments. Here, we report the complete and draft genome sequences of six new members of the Aquificales: two marine species, Persephonella marina strain EX-H1 and Hydrogenivirga strain 128-5-R1 (from the East Pacific Rise, 9??50.3???N, 104??17.5???W, and the Eastern Lau Spreading Center, 176??11.5???W, 20??45.8???S, respectively), and four terrestrial isolates, Sulfuri-hydrogenibium azorense strain Az-Ful, Sulfurihydrogenibium yellowstonense strain SS-5, and Sulfurihydro-genibium strain Y03AOP1 (from Furnas, Azores, Portugal, and Calcite Springs and Obsidian Pool in Yellowstone National Park, United States, respectively), and the only thermoacidophilic isolate, Hydrogenobaculum strain Y04AAS1 (from a stream adjacent to Obsidian Pool). Significant differences among the different species exist that include nitrogen metabolism, hydrogen utilization, Chemotaxis, and signal transduction, providing insights into their ecological niche adaptations. Copyright ?? 2009, American Society for Microbiology. All Rights Reserved.

Biogenic and non-biogenic Si pools in terrestrial ecosystems: results from a novel analysis method

NASA Astrophysics Data System (ADS)

Barao, Lucia; Vandevenne, Floor; Clymans, Wim; Meire, Patrick; Frings, Patrick; Conley, Daniel; Struyf, Eric

2015-04-01

Silicon (Si) is a chemical element frequently associated with highly abundant silicate minerals in the Earth crust. Over millions of years, the interaction of such minerals with the atmosphere and hydrosphere produces a myriad of processed compounds, and the mineral weathering consumes CO2 during the process. The weathering of minerals also triggers the export of dissolved Si (DSi) to coastal waters and the ocean. Here, DSi is deposited in diatom frustules, in an amorphous biogenic form (BSi). Diatoms account for 50% of the primary production and are crucial for the export of carbon into the deep sea. In recent years, it was acknowledged that terrestrial systems filter the Si transition from the terrestrial mineral to the marine and coastal biological pool, by the incorporation of DSi into plants. In this process, DSi is taken up by roots together with other nutrients and precipitates in plant cells in amorphous structures named phytoliths. After dead, plant tissues become mixed in the top soil, where BSi is available for dissolution and will control the DSi availability in short time scales. Additionally, Si originated from soil forming processes can also significantly interfere with the global cycle. The Si cycle in terrestrial ecosystems is a key factor to coastal ecology, plant ecology, biogeochemistry and agro-sciences, but the high variability of different biogenic and non-biogenic Si pools remains as an obstacle to obtain accurate measurements. The traditional methods, developed to isolate diatoms in ocean sediments, only account for simple mineral corrections. In this dissertation we have adapted a novel continuous analysis method (during alkaline extraction) that uses Si-Al ratios and reactivity to differ biogenic from non-biogenic fractions. The method was originally used in marine sediments, but we have developed it to be applicable in a wide range of terrestrial, aquatic and coastal ecosystems. We first focused on soils under strong human impact in temperate (European) zones, since cultivation influences the Si cycle with multiple consequences for the environment. Results showed that the intensity of the human pressure in the agricultural systems defines the level of BSi depletion, but parent material and weathering degree can also provide the soil with other reactive non BSi fractions. Secondly we analysed the influence of non-BSi pools of volcanic origin in soils and sediments subjected to volcanic activity. Results showed that a separation method is fundamental in these systems with volcanic shards and strongly weathered products, both of which are also significantly prone to dissolution in the common alkaline sequential extractions. We conclude that the application of a method that discriminates between Si fractions is mandatory to correctly understand the Si dynamics in terrestrial ecosystems. Although time-consuming and subjected to some limitations, the continuous analysis can be used for this purpose. Future challenges remain however for identifying fractions that cannot be differentiated on either reactivity or Si-Al ratio and for correlating the reactivity of fractions extracted in alkaline environments with the availability in situ.

Greenhouse gas efflux from an impacted Malaysian tropical peat swamp (Invited)

NASA Astrophysics Data System (ADS)

Waldron, S.; Vihermaa, L. E.; Evers, S.; Garnett, M.; Newton, J.; Padfield, R.

2013-12-01

Tropical peatlands constitute ~11% of global peatland area and ~12% of the global peat C pool. Malaysia alone contains 10% of tropical peats. Due to rising global demands for food and biofuels, SE-Asia peat swamp forest ecosystems are threatened by increasing amounts of drainage, fire and conversion to plantation. These processes can change the GHG emissions and thus net ecosystem C balance. However, in comparison to temperate and boreal peatlands, there is a lack of data on terrestrial-aquatic-atmospheric carbon transfer from tropical peatlands, both those that are little disturbed and those facing anthropogenic pressures. Lateral transport of soil-respired carbon, and fluvial respiration or UV-oxidation of terrestrial DOC primes atmospheric carbon dioxide efflux. We now know that DOC lost from disturbed tropical peat swamp forests can be centuries to millennia old and originates deep within the peat column - this carbon may fuel efflux of old carbon dioxide and so anthropogenic land-use change renders the older, slower carbon cycles shorter and faster. Currently we have no knowledge of how significant ';older-slower' terrestrial-aquatic-atmospheric cycles are in disturbed tropical peatlands. Further, in some areas for commercial reasons, or by conservation bodies trying to minimise peat habitat loss, logged peats have been left to regenerate. Consequently, unpicking the legacy of multiple land uses on magnitude, age and source of GHG emissions is challenging but required to support land management decisions and projections of response to a changing climate. Here, we present the results of our first field campaign in July 2013 to the Raja Musa and Sungai Karang Peat Swamp Forest Reserves in North Selangor, Malaysia. This is one of Malaysia's largest oceanic peat swamps, and has been selectively logged and drained for 80 years, but is now subject to a 30 year logging ban to aid forest regeneration and build up wood stocks. From sites subject to different land use, we will present measurements of i) spatial variation in fluvial carbon dioxide and methane concentrations and associated efflux rates, and ii) the stable carbon isotopic composition of DIC and novel determination of the age of the effluxed carbon dioxide. From this we can consider if younger-faster or older-slower carbon cycling dominates the terrestrial-aquatic-atmospheric C transfer during this dry period sampling.

Towards a global understanding of vertical soil carbon dynamics: meta-analysis of soil 14C data

NASA Astrophysics Data System (ADS)

hatte, C.; Balesdent, J.; Guiot, J.

2012-12-01

Soil represents the largest terrestrial storage mechanism for atmospheric carbon from photosynthesis, with estimates ranging from 1600 Pg C within the top 1 meter to 2350 Pg C for the top 3 meters. These values are at least 2.5 times greater than atmospheric C pools. Small changes in soil organic carbon storage could result in feedback to atmospheric CO2 and the sensitivity of soil organic matter to changes in temperature, and precipitation remains a critical area of research with respect to the global carbon cycle. As an intermediate storage mechanism for organic material through time, the vertical profile of carbon generally shows an age continuum with depth. Radiocarbon provides critical information for understanding carbon exchanges between soils and atmosphere, and within soil layers. Natural and "bomb" radiocarbon has been used to demonstrate the importance and nature of the soil carbon response to climatic and human impacts on decadal to millennial timescales. Radiocarbon signatures of bulk, or chemically or physically fractionated soil, or even of specific organic compounds, offer one of the only ways to infer terrestrial carbon turnover times or test ecosystem carbon models. We compiled data from the literature on radiocarbon distribution on soil profiles and characterized each study according to the following categories: soil type, analyzed organic fraction, location (latitude, longitude, elevation), climate (temperature, precipitation), land use and sampling year. Based on the compiled data, soil carbon 14C profiles were reconstructed for each of the 226 sites. We report here partial results obtained by statistical analyses of portion of this database, i.e. bulk and bulk-like organic matter and sampling year posterior to 1980. We highlight here 14C vertical pattern in relationship with external parameters (climate, location and land use).

Temporal deconvolution of vascular plant signatures delivered to coastal sediments

NASA Astrophysics Data System (ADS)

Vonk, J.; Drenzek, N. J.; Hughen, K. A.; Stanley, R.; Montluçon, D. B.; McIntyre, C.; Southon, J. R.; Santos, G.; Andersson, A.; Sköld, M.; Eglinton, T. I.

2017-12-01

Presently, relatively little is known about the amount of time that lapses between the photosynthetic fixation of carbon by vascular land plants and its incorporation into the marine sedimentary record. It is clear that there are multiple potential intermediate storage pools and transport trajectories that vascular plant carbon may experience, and the age of vascular plant carbon accumulating in marine sediments will reflect these different pre-depositional histories. Here we use molecular-level radiocarbon (14C) analysis to develop down-core 14C profiles for higher plant leaf wax-derived fatty acids isolated from sediments from three sites across a 60-degrees latitudinal gradient (Cariaco Basin, Saanich Inlet, and Mackenzie Delta). The sediment profiles were used as a direct measure of the storage and transport times experienced by these biomolecular tracer compounds. Residence times are evaluated by comparing these records to the 14C history of atmospheric CO2. Using a modeling framework, we conclude that there is, in addition to a variable "young" pool, a millennial pool of compounds that consists of 49-78 % of the fractional contribution of organic carbon (OC) that exhibits variable ages for the different depositional settings. For the Mackenzie Delta sediments, we find a mean age of the millennial pool of 28 ky, suggesting pre-aging in permafrost soils, whereas the millennial pool in Saanich Inlet and Cariaco Basin sediments is younger with 7.9 and 2.4-3.2 ky, respectively, suggesting limited storage in terrestrial reservoirs. The "young" pool, conditionally defined as < 50 years showed clear annual contributions for Saanich Inlet and Mackenzie Delta sediments (24% and 16% of young pool, respectively) that can likely be explained by transport of OC from steep hillside slopes near the Saanich Inlet and annual spring flood deposition in the Mackenzie Delta. These results show that a significant fraction of vascular plant C in deltaic and marine settings undergoes pre-aging in terrestrial reservoirs. The age distribution, reflecting storage and transport times, depends on landscape-specific factors such as local topography, hydrographic characteristics, and degree of soil build-up and preservation.

Enhanced detection of terrestrial gamma-ray flashes by AGILE.

PubMed

Marisaldi, M; Argan, A; Ursi, A; Gjesteland, T; Fuschino, F; Labanti, C; Galli, M; Tavani, M; Pittori, C; Verrecchia, F; D'Amico, F; Østgaard, N; Mereghetti, S; Campana, R; Cattaneo, P W; Bulgarelli, A; Colafrancesco, S; Dietrich, S; Longo, F; Gianotti, F; Giommi, P; Rappoldi, A; Trifoglio, M; Trois, A

2015-11-16

At the end of March 2015 the onboard software configuration of the Astrorivelatore Gamma a Immagini Leggero (AGILE) satellite was modified in order to disable the veto signal of the anticoincidence shield for the minicalorimeter instrument. The motivation for such a change was the understanding that the dead time induced by the anticoincidence prevented the detection of a large fraction of Terrestrial Gamma-Ray Flashes (TGFs). The configuration change was highly successful resulting in an increase of one order of magnitude in TGF detection rate. As expected, the largest fraction of the new events has short duration (<100 μs), and part of them has simultaneous association with lightning sferics detected by the World Wide Lightning Location Network. The new configuration provides the largest TGF detection rate surface density (TGFs/km 2 /yr) to date, opening prospects for improved correlation studies with lightning and atmospheric parameters on short spatial and temporal scales along the equatorial region.

Transient dynamics of terrestrial carbon storage: Mathematical foundation and its applications

DOE PAGES

Luo, Yiqi; Shi, Zheng; Lu, Xingjie; ...

2017-01-12

Terrestrial ecosystems have absorbed roughly 30% of anthropogenic CO 2 emissions over the past decades, but it is unclear whether this carbon (C) sink will endure into the future. Despite extensive modeling and experimental and observational studies, what fundamentally determines transient dynamics of terrestrial C storage under global change is still not very clear. Here we develop a new framework for understanding transient dynamics of terrestrial C storage through mathematical analysis and numerical experiments. Our analysis indicates that the ultimate force driving ecosystem C storage change is the C storage capacity, which is jointly determined by ecosystem C input (e.g.,more » net primary production, NPP) and residence time. Since both C input and residence time vary with time, the C storage capacity is time-dependent and acts as a moving attractor that actual C storage chases. The rate of change in C storage is proportional to the C storage potential, which is the difference between the current storage and the storage capacity. The C storage capacity represents instantaneous responses of the land C cycle to external forcing, whereas the C storage potential represents the internal capability of the land C cycle to influence the C change trajectory in the next time step. The influence happens through redistribution of net C pool changes in a network of pools with different residence times. Moreover, this and our other studies have demonstrated that one matrix equation can replicate simulations of most land C cycle models (i.e., physical emulators). As a result, simulation outputs of those models can be placed into a three-dimensional (3-D) parameter space to measure their differences. The latter can be decomposed into traceable components to track the origins of model uncertainty. In addition, the physical emulators make data assimilation computationally feasible so that both C flux- and pool-related datasets can be used to better constrain model predictions of land C sequestration. Altogether, this new mathematical framework offers new approaches to understanding, evaluating, diagnosing, and improving land C cycle models.« less

Transient dynamics of terrestrial carbon storage: Mathematical foundation and its applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luo, Yiqi; Shi, Zheng; Lu, Xingjie

Terrestrial ecosystems have absorbed roughly 30% of anthropogenic CO 2 emissions over the past decades, but it is unclear whether this carbon (C) sink will endure into the future. Despite extensive modeling and experimental and observational studies, what fundamentally determines transient dynamics of terrestrial C storage under global change is still not very clear. Here we develop a new framework for understanding transient dynamics of terrestrial C storage through mathematical analysis and numerical experiments. Our analysis indicates that the ultimate force driving ecosystem C storage change is the C storage capacity, which is jointly determined by ecosystem C input (e.g.,more » net primary production, NPP) and residence time. Since both C input and residence time vary with time, the C storage capacity is time-dependent and acts as a moving attractor that actual C storage chases. The rate of change in C storage is proportional to the C storage potential, which is the difference between the current storage and the storage capacity. The C storage capacity represents instantaneous responses of the land C cycle to external forcing, whereas the C storage potential represents the internal capability of the land C cycle to influence the C change trajectory in the next time step. The influence happens through redistribution of net C pool changes in a network of pools with different residence times. Moreover, this and our other studies have demonstrated that one matrix equation can replicate simulations of most land C cycle models (i.e., physical emulators). As a result, simulation outputs of those models can be placed into a three-dimensional (3-D) parameter space to measure their differences. The latter can be decomposed into traceable components to track the origins of model uncertainty. In addition, the physical emulators make data assimilation computationally feasible so that both C flux- and pool-related datasets can be used to better constrain model predictions of land C sequestration. Altogether, this new mathematical framework offers new approaches to understanding, evaluating, diagnosing, and improving land C cycle models.« less

Transient dynamics of terrestrial carbon storage: Mathematical foundation and numeric examples

DOE PAGES

Luo, Yiqi; Shi, Zheng; Lu, Xingjie; ...

2016-09-16

Terrestrial ecosystems absorb roughly 30% of anthropogenic CO 2 emissions since preindustrial era, but it is unclear whether this carbon (C) sink will endure into the future. Despite extensive modeling, experimental, and observational studies, what fundamentally determines transient dynamics of terrestrial C storage under climate change is still not very clear. Here we develop a new framework for understanding transient dynamics of terrestrial C storage through mathematical analysis and numerical experiments. Our analysis indicates that the ultimate force driving ecosystem C storage change is the C storage capacity, which is jointly determined by ecosystem C input (e.g., net primary production,more » NPP) and residence time. Since both C input and residence time vary with time, the C storage capacity is time-dependent and acts as a moving attractor that actual C storage chases. The rate of change in C storage is proportional to the C storage potential, the difference between the current storage and the storage capacity. The C storage capacity represents instantaneous responses of the land C cycle to external forcing, whereas the C storage potential represents the internal capability of the land C cycle to influence the C change trajectory in the next time step. The influence happens through redistribution of net C pool changes in a network of pools with different residence times. Furthermore, this and our other studies have demonstrated that one matrix equation can exactly replicate simulations of most land C cycle models (i.e., physical emulators). As a result, simulation outputs of those models can be placed into a three-dimensional (3D) parameter space to measure their differences. The latter can be decomposed into traceable components to track the origins of model uncertainty. Moreover, the emulators make data assimilation computationally feasible so that both C flux- and pool-related datasets can be used to better constrain model predictions of land C sequestration. We also propose that the C storage potential be the targeted variable for research, market trading, and government negotiation for C credits.« less

Transient dynamics of terrestrial carbon storage: Mathematical foundation and numeric examples

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luo, Yiqi; Shi, Zheng; Lu, Xingjie

Terrestrial ecosystems absorb roughly 30% of anthropogenic CO 2 emissions since preindustrial era, but it is unclear whether this carbon (C) sink will endure into the future. Despite extensive modeling, experimental, and observational studies, what fundamentally determines transient dynamics of terrestrial C storage under climate change is still not very clear. Here we develop a new framework for understanding transient dynamics of terrestrial C storage through mathematical analysis and numerical experiments. Our analysis indicates that the ultimate force driving ecosystem C storage change is the C storage capacity, which is jointly determined by ecosystem C input (e.g., net primary production,more » NPP) and residence time. Since both C input and residence time vary with time, the C storage capacity is time-dependent and acts as a moving attractor that actual C storage chases. The rate of change in C storage is proportional to the C storage potential, the difference between the current storage and the storage capacity. The C storage capacity represents instantaneous responses of the land C cycle to external forcing, whereas the C storage potential represents the internal capability of the land C cycle to influence the C change trajectory in the next time step. The influence happens through redistribution of net C pool changes in a network of pools with different residence times. Furthermore, this and our other studies have demonstrated that one matrix equation can exactly replicate simulations of most land C cycle models (i.e., physical emulators). As a result, simulation outputs of those models can be placed into a three-dimensional (3D) parameter space to measure their differences. The latter can be decomposed into traceable components to track the origins of model uncertainty. Moreover, the emulators make data assimilation computationally feasible so that both C flux- and pool-related datasets can be used to better constrain model predictions of land C sequestration. We also propose that the C storage potential be the targeted variable for research, market trading, and government negotiation for C credits.« less

Observing terrestrial ecosystems and the carbon cycle from space

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schimel, David; Pavlick, Ryan; Fisher, Joshua B.

2015-02-06

Modeled terrestrial ecosystem and carbon cycle feedbacks contribute substantial uncertainty to projections of future climate. The limitations of current observing networks contribute to this uncertainty. Here we present a current climatology of global model predictions and observations for photosynthesis, biomass, plant diversity and plant functional diversity. Carbon cycle tipping points occur in terrestrial regions where fluxes or stocks are largest, and where biological variability is highest, the tropics and Arctic/Boreal zones. Global observations are predominately in the mid-latitudes and are sparse in high and low latitude ecosystems. Observing and forecasting ecosystem change requires sustained observations of sufficient density in timemore » and space in critical regions. Using data and theory available now, we can develop a strategy to detect and forecast terrestrial carbon cycle-climate interactions, by combining in situ and remote techniques.« less

Precipitation and nitrogen interactions in arid ecosystems

USDA-ARS?s Scientific Manuscript database

Arid and semi-arid ecosystems are among the most impoverished terrestrial systems in terms of water and nitrogen (N) availability. Productivity (NPP) is generally low, soil N pools are small and N loss through percolation is assumed to be negligible. Increased water availability can stimulate both N...

Impacts and Benefits of a Satellite Power System on the Electric Utility Industry

NASA Technical Reports Server (NTRS)

Winer, B. M.

1977-01-01

The purpose of this limited study was to investigate six specific issues associated with interfacing a Satellite Power System (5 GW) with large (by present standards) terrestrial power pools to a depth sufficient to determine if certain interface problems and/or benefits exist and what future studies of these problems are required. The issues investigated are as follows: (1) Stability of Power Pools Containing a 5 GWe SPS; (2) Extra Reserve Margin Required to Maintain the Reliability of Power Pools Containing a 5 GWe SPS; (3) Use of the SPS in Load Following Service (i.e. in two independent pools whose times of peak demand differ by three hours); (4) Ownership of the SPS and its effect on SPS Usage and Utility Costs; (5) Utility Sharing of SPS related RD and D Costs; (6) Utility Liability for SPS Related Hazards.

Long Term Large Scale river nutrient changes across the UK

NASA Astrophysics Data System (ADS)

Bell, Victoria; Naden, Pam; Tipping, Ed; Davies, Helen; Davies, Jessica; Dragosits, Ulli; Muhammed, Shibu; Quinton, John; Stuart, Marianne; Whitmore, Andy; Wu, Lianhai

2017-04-01

During recent decades and centuries, pools and fluxes of Carbon, Nitrogen and Phosphorus (C, N and P) in UK rivers and ecosystems have been transformed by the spread and fertiliser-based intensification of agriculture (necessary to sustain human populations), by atmospheric pollution, by human waste (rising in line with population growth), and now by climate change. The principal objective of the UK's NERC-funded Macronutrients LTLS research project has been to account for observable terrestrial and aquatic pools, concentrations and fluxes of C, N and P on the basis of past inputs, biotic and abiotic interactions, and transport processes. More specifically, over the last 200 years, what have been the temporal responses of plant and soil nutrient pools in different UK catchments to nutrient enrichment, and what have been the consequent effects on nutrient transfers from land to the atmosphere, freshwaters and estuaries? The work described here addresses the second question by providing an integrated quantitative description of the interlinked land and water pools and annual fluxes of C, N and P for UK catchments over time. A national-scale modelling environment has been developed, combining simple physically-based gridded models that can be parameterised using recent observations before application to long timescales. The LTLS Integrated Model (LTLS-IM) uses readily-available driving data (climate, land-use, nutrient inputs, topography), and model estimates of both terrestrial and freshwater nutrient loads have been compared with measurements from sites across the UK. Here, the focus is on the freshwater nutrient component of the LTLS-IM, but the terrestrial nutrient inputs required for this are provided by models of nutrient processes in semi-natural and agricultural systems, and from simple models of nutrients arising from human waste. In the freshwater model, lateral routing of dissolved and particulate nutrients and within-river processing such as denitrification, decomposition and chlorophyll growth are undertaken, and the effects of groundwater storage and processes in lakes connected to the river network can be included. Following assessment against observations of terrestrial and nutrient fluxes in rivers across the UK, the LTLS-IM has been run nationally for 200 years (1800 to 2010), and the work presented here provides, for the first time, national, regional or catchment estimates of the origins and trends in riverine nutrients in the period following the industrial revolution. Ongoing work is now exploring the effects of future climate, waste water treatment and land-management scenarios on water quality, and the effects of nutrient enrichment on the development of eutrophication in rivers.

On the Regulation of the Pacific Warm Pool Temperature

NASA Technical Reports Server (NTRS)

Chou, Ming-Dah; Chou, Sue-Hsien; Chan, Pui-King; Lau, William K. M. (Technical Monitor)

2002-01-01

In the tropical western Pacific, regions of the highest sea surface temperature (SST) and the largest cloud cover are found to have the largest surface heating, primarily due to the weak evaporative cooling associated with weak winds. This situation is in variance with the suggestions that the temperature in the Pacific warm pool is regulated either by the reduced solar heating due to an enhanced cloudiness or by the enhanced evaporative cooling due to an elevated SST. It is clear that an enhanced surface heating in an enhanced convection region is not sustainable and must be interrupted by variations in large-scale atmospheric circulation. As the deep convective regions shift away from regions of high SST due primarily to seasonal variation and secondarily to interannual variation of the large-scale atmospheric and oceanic circulation, both trade wind and evaporative cooling in the high SST region increase, leading to a reduction in SST. We conclude that the evaporative cooling associated with the seasonal and interannual variations of trade winds in the primary factor that prevent the warm pool SST from increasing to a value much higher than what is observed.

Matrix approaches to assess terrestrial nitrogen scheme in CLM4.5

NASA Astrophysics Data System (ADS)

Du, Z.

2017-12-01

Terrestrial carbon (C) and nitrogen (N) cycles have been commonly represented by a series of balance equations to track their influxes into and effluxes out of individual pools in earth system models (ESMs). This representation matches our understanding of C and N cycle processes well but makes it difficult to track model behaviors. To overcome these challenges, we developed a matrix approach, which reorganizes the series of terrestrial C and N balance equations in the CLM4.5 into two matrix equations based on original representation of C and N cycle processes and mechanisms. The matrix approach would consequently help improve the comparability of models and data, evaluate impacts of additional model components, facilitate benchmark analyses, model intercomparisons, and data-model fusion, and improve model predictive power.

An Alternative Default Soil Organic Carbon Method for National GHG Inventory Reporting to the UNFCCC

NASA Astrophysics Data System (ADS)

Ogle, S. M.; Gurung, R.; Klepfer, A.; Spencer, S.; Breidt, J.

2016-12-01

Estimating soil organic C stocks is challenging because of the large amount of data needed to evaluate the impact of land use and management on this terrestrial C pool. Moreover, some of the required data are rarely collected by governments through surveys programs, and are not typically available in remote sensing products. Examples include data on organic amendments, cover crops, crop rotation sequences, vegetated fallows, and fertilization practices. Due to these difficulties, only about 20% of the countries report soil organic C stock changes in their national communications to the UNFCCC. Yet, C sequestration in soils represents one of the least expensive options for reducing greenhouse gas emissions, and has the largest potential for mitigation in the agricultural sector. In order to facilitate reporting, we developed an alternative approach to the current default method provided by the Intergovernmental Panel on Climate Change (IPCC) for estimating soil organic C stock changes in mineral soils. The alternative method estimates the steady-state C stocks for a three pool model given annual crop yields or net primary production as the main input, along with monthly average temperature, total precipitation and soil texture data. Yield data are commonly available in a national agricultural census, and global datasets exists with adequate data for weather and soil texture if national datasets are not available. Tillage and irrigation data are also needed to address the impact of these practices on decomposition rates. The change in steady-state stocks is assumed to occur over a few decades. A Bayesian analysis framework has been developed to derive probability distribution functions for the parameters, and the method is being applied in a global analysis of soil organic carbon stock changes.

Effect of increasing CO2 on the terrestrial carbon cycle

PubMed Central

Schimel, David; Fisher, Joshua B.

2015-01-01

Feedbacks from the terrestrial carbon cycle significantly affect future climate change. The CO2 concentration dependence of global terrestrial carbon storage is one of the largest and most uncertain feedbacks. Theory predicts the CO2 effect should have a tropical maximum, but a large terrestrial sink has been contradicted by analyses of atmospheric CO2 that do not show large tropical uptake. Our results, however, show significant tropical uptake and, combining tropical and extratropical fluxes, suggest that up to 60% of the present-day terrestrial sink is caused by increasing atmospheric CO2. This conclusion is consistent with a validated subset of atmospheric analyses, but uncertainty remains. Improved model diagnostics and new space-based observations can reduce the uncertainty of tropical and temperate zone carbon flux estimates. This analysis supports a significant feedback to future atmospheric CO2 concentrations from carbon uptake in terrestrial ecosystems caused by rising atmospheric CO2 concentrations. This feedback will have substantial tropical contributions, but the magnitude of future carbon uptake by tropical forests also depends on how they respond to climate change and requires their protection from deforestation. PMID:25548156

Early studies reported extreme findings with large variability: a meta-epidemiologic study in the field of endocrinology.

PubMed

Wang, Zhen; Alahdab, Fares; Almasri, Jehad; Haydour, Qusay; Mohammed, Khaled; Abu Dabrh, Abd Moain; Prokop, Larry J; Alfarkh, Wedad; Lakis, Sumaya; Montori, Victor M; Murad, Mohammad Hassan

2016-04-01

To evaluate the presence of extreme findings and fluctuation in effect size in endocrinology. We systematically identified all meta-analyses published in 2014 in the field of endocrinology. Within each meta-analysis, the effect size of the primary binary outcome was compared across studies according to their order of publication. We pooled studies using the DerSimonian and Laird random-effects method. Heterogeneity was evaluated using the I(2) and tau(2). Twelve percent of the included 100 meta-analyses reported the largest effect size in the very first published study. The largest effect size occurred in the first 2 earliest studies in 31% of meta-analyses. When the effect size was the largest in the first published study, it was three times larger than the final pooled effect (ratio of rates, 3.26; 95% confidence interval: 1.80, 5.90). The largest heterogeneity measured by I(2) was observed in 18% of the included meta-analyses when combining the first 2 studies or 17% when combing the first 3 studies. In endocrinology, early studies reported extreme findings with large variability. This behavior of the evidence needs to be taken into account when used to formulate clinical policies. Copyright © 2016 Elsevier Inc. All rights reserved.

Vulnerability of Permafrost Soil Carbon to Climate Warming: Evaluating Controls on Microbial Community Composition

USDA-ARS?s Scientific Manuscript database

Abstract: Despite the fact that permafrost soils contain up to half of the carbon (C) in terrestrial pools, we have a poor understanding of the controls on decomposition in thawed permafrost. Global climate models assume that decomposition increases linearly with temperature, yet decomposition in th...

An introduction to mid-Atlantic seasonal pools

USGS Publications Warehouse

Brown, L.J.; Jung, R.E.

2005-01-01

Seasonal pools, also known as vernal ponds, provide important ecological services to the mid-Atlantic region. This publication serves as an introduction to seasonal pool ecology and management; it also provides tools for exploring seasonal pools, including a full-color field guide to wildlife. Seasonal pools are defined as having four distinctive features: surface water isolation, periodic drying, small size and shallow depth, and support of a characteristic biological community. Seasonal pools experience regular drying that excludes populations of predatory fish. Thus, pools in the mid-Atlantic region provide critical breeding habitat for amphibian and invertebrate species (e.g., spotted salamander (Ambystoma maculatum), wood frog (Rana sylvatica), and fairy shrimp (Order Anostraca)) that would be at increased risk of predation in more permanent waters. The distinctive features of seasonal pools also make them vulnerable to human disturbance. In the mid-Atlantic region, land-use changes pose the greatest challenges to seasonal pool conservation. Seasonal pools are threatened by direct loss (e.g., filling or draining of the pool) as well as by destruction and fragmentation of adjoining terrestrial habitat. Many of the species that depend on seasonal pools for breeding spend the majority of their lives in the surrounding lands that extend a radius of 1000 feet or more from the pools; these vital habitats are being transected by roads and converted to other land uses. Other threats to seasonal pools include biological introductions and removals, mosquito control practices, amphibian diseases, atmospheric deposition, and climate change. The authors recommend a three-pronged strategy for seasonal pool conservation and management in the mid-Atlantic region: education and research, inventory and monitoring of seasonal pools, and landscape-level planning and management.

Non-labile Soil Nitrogen Retention beneath Three Tree Species in a Tropical Plantation

Treesearch

Jason P. Kaye; Dan Binkley; Xiaoming Zou

2002-01-01

Soil organic matter is the largest sink for N additions to forests. Species composition may affect soilNretention by altering the amount or proportion of added N stored in non-labile organic pools. We measured 15N tracer retention in labile and non-labile pools of surface (0–20 cm) mineral soils, 7 yr after the tracer was applied to a 9 yr-old Puerto Rican tree...

Contribution of soil respiration to the global carbon equation.

PubMed

Xu, Ming; Shang, Hua

2016-09-20

Soil respiration (Rs) is the second largest carbon flux next to GPP between the terrestrial ecosystem (the largest organic carbon pool) and the atmosphere at a global scale. Given their critical role in the global carbon cycle, Rs measurement and modeling issues have been well reviewed in previous studies. In this paper, we briefly review advances in soil organic carbon (SOC) decomposition processes and the factors affecting Rs. We examine the spatial and temporal distribution of Rs measurements available in the literature and found that most of the measurements were conducted in North America, Europe, and East Asia, with major gaps in Africa, East Europe, North Asia, Southeast Asia, and Australia, especially in dry ecosystems. We discuss the potential problems of measuring Rs on slope soils and propose using obliquely-cut soil collars to solve the existing problems. We synthesize previous estimates of global Rs flux and find that the estimates ranged from 50 PgC/yr to 98 PgC/yr and the error associated with each estimation was also high (4 PgC/yr to 33.2 PgC/yr). Using a newly integrated database of Rs measurements and the MODIS vegetation map, we estimate that the global annual Rs flux is 94.3 PgC/yr with an estimation error of 17.9 PgC/yr at a 95% confidence level. The uneven distribution of Rs measurements limits our ability to improve the accuracy of estimation. Based on the global estimation of Rs flux, we found that Rs is highly correlated with GPP and NPP at the biome level, highlighting the role of Rs in global carbon budgets. Copyright © 2016. Published by Elsevier GmbH.

Processes regulating progressive nitrogen limitation under elevated carbon dioxide: a meta-analysis

NASA Astrophysics Data System (ADS)

Liang, J.; Qi, X.; Souza, L.; Luo, Y.

2015-10-01

Nitrogen (N) cycle has the potential to regulate climate change through its influence on carbon (C) sequestration. Although extensive researches have been done to explore whether or not progressive N limitation (PNL) occurs under CO2 enrichment, a comprehensive assessment of the processes that regulate PNL is still lacking. Here, we quantitatively synthesized the responses of all major processes and pools in terrestrial N cycle with meta-analysis of CO2 experimental data available in the literature. The results showed that CO2 enrichment significantly increased N sequestration in plant and litter pools but not in soil pool. Thus, the basis of PNL occurrence partially exists. However, CO2 enrichment also significantly increased the N influx via biological N fixation, but decreased the N efflux via leaching. In addition, no general diminished CO2 fertilization effect on plant growth over time was observed. Overall, our analyses suggest that the extra N supply by the increased biological N fixation and decreased leaching may potentially alleviate PNL under elevated CO2 conditions. Moreover, our synthesis showed that CO2 enrichment increased soil ammonium (NH4+) but decreased nitrate (NO3-). The different responses of NH4+ and NO3-, and the consequent biological processes, may result in changes in soil microenvironment, community structures and above-belowground interactions, which could potentially affect the terrestrial biogeochemical cycles and the feedback to climate change.

Biosphere model simulations of interannual variability in terrestrial 13C/12C exchange

NASA Astrophysics Data System (ADS)

van der Velde, I. R.; Miller, J. B.; Schaefer, K.; Masarie, K. A.; Denning, S.; White, J. W. C.; Tans, P. P.; Krol, M. C.; Peters, W.

2013-09-01

Previous studies suggest that a large part of the variability in the atmospheric ratio of 13CO2/12CO2originates from carbon exchange with the terrestrial biosphere rather than with the oceans. Since this variability is used to quantitatively partition the total carbon sink, we here investigate the contribution of interannual variability (IAV) in biospheric exchange to the observed atmospheric 13C variations. We use the Simple Biosphere - Carnegie-Ames-Stanford Approach biogeochemical model, including a detailed isotopic fractionation scheme, separate 12C and 13C biogeochemical pools, and satellite-observed fire disturbances. This model of 12CO2 and 13CO2 thus also produces return fluxes of 13CO2from its differently aged pools, contributing to the so-called disequilibrium flux. Our simulated terrestrial 13C budget closely resembles previously published model results for plant discrimination and disequilibrium fluxes and similarly suggests that variations in C3 discrimination and year-to-year variations in C3and C4 productivity are the main drivers of their IAV. But the year-to-year variability in the isotopic disequilibrium flux is much lower (1σ=±1.5 PgC ‰ yr-1) than required (±12.5 PgC ‰ yr-1) to match atmospheric observations, under the common assumption of low variability in net ocean CO2 fluxes. This contrasts with earlier published results. It is currently unclear how to increase IAV in these drivers suggesting that SiBCASA still misses processes that enhance variability in plant discrimination and relative C3/C4productivity. Alternatively, 13C budget terms other than terrestrial disequilibrium fluxes, including possibly the atmospheric growth rate, must have significantly different IAV in order to close the atmospheric 13C budget on a year-to-year basis.

Work Program. Fiscal Year 1969 for The Department of the Army. Research and Development in Training, Motivation, and Leadership

DTIC Science & Technology

1969-01-01

job requiremeits in these skills , and (2) developing technique.; for improving literacy skills through training. In addition, manpower pools for a given...job requirements in these skills , and (2) developing techniques for improving literacy skills through training. In addition, manpower pools for a...visual and psychomotor skills -for accurate .nd’efficient operation, and performance variations among gunners are the largest source of error in system

Non-labile Soil 15Nitrogen Retention beneath Three Tree Species in a Tropical Plantation

Treesearch

Jason P. Kaye; Dan Binkley; Xiaoming Zou

2002-01-01

Soil organic matter is the largest sink for N additions to forests.Species composition may affect soilNretention by altering the amount or proportion of added N stored in non-labile organic pools. We measured 15N tracer retention in labile and non-labile pools of surface (0–20 cm) mineral soils, 7 yr after the tracer was applied to a 9 yr-old Puerto Rican tree...

Isotopic and anatomical evidence of an herbivorous diet in the Early Tertiary giant bird Gastornis. Implications for the structure of Paleocene terrestrial ecosystems

NASA Astrophysics Data System (ADS)

Angst, D.; Lécuyer, C.; Amiot, R.; Buffetaut, E.; Fourel, F.; Martineau, F.; Legendre, S.; Abourachid, A.; Herrel, A.

2014-04-01

The mode of life of the early Tertiary giant bird Gastornis has long been a matter of controversy. Although it has often been reconstructed as an apex predator feeding on small mammals, according to other interpretations, it was in fact a large herbivore. To determine the diet of this bird, we analyze here the carbon isotope composition of the bone apatite from Gastornis and contemporaneous herbivorous mammals. Based on 13C-enrichment measured between carbonate and diet of carnivorous and herbivorous modern birds, the carbonate δ13C values of Gastornis bone remains, recovered from four Paleocene and Eocene French localities, indicate that this bird fed on plants. This is confirmed by a morphofunctional study showing that the reconstructed jaw musculature of Gastornis was similar to that of living herbivorous birds and unlike that of carnivorous forms. The herbivorous Gastornis was the largest terrestrial tetrapod in the Paleocene biota of Europe, unlike the situation in North America and Asia, where Gastornis is first recorded in the early Eocene, and the largest Paleocene animals were herbivorous mammals. The structure of the Paleocene terrestrial ecosystems of Europe may have been similar to that of some large islands, notably Madagascar, prior to the arrival of humans.

Conservation of Terrestrial Vertebrates in a Global Hotspot of Karst Area in Southwestern China

PubMed Central

Luo, Zhenhua; Tang, Songhua; Jiang, Zhigang; Chen, Jing; Fang, Hongxia; Li, Chunwang

2016-01-01

The karst area of southwest China (KASC) is the largest piece of karst landscape on the earth and a global biodiversity hot-spot with high concentrations of endemic species. Although a number of nature reserves (NRs) have been established across the region, the representativeness of biodiversity of the NR system is still unknown. Based on comprehensive literature and field surveys, and intensive consultations with zoologists and wildlife managers, we compiled distributions of 1,204 terrestrial vertebrate species and 271 NRs in KASC. We found Jinxiu, Mengla, Hekou, and Jinghong have the richest amphibian species; Jinxiu has the highest species richness of reptiles; Jinghong, Menghai, and Mengla have the largest numbers of avian species; whereas, Mengla, Longzhou, and Ningming have the greatest mammalian diversity in the region. Gap analysis among NR system, species richness pattern, and five biogeographic indicators found insufficient representation of the NR system on territorial vertebrate diversity. The conservation effectiveness in Guizhou Province was much lower than that in Guangxi and Yunnan Provinces. Under-representation and over-representation simultaneously occurred in many of the ecoregions, elevation classes, vegetation types, landcover categories, and human disturbance intensity gradients. For conservation of terrestrial vertebrates in KASC, several suggestions were presented in this study. PMID:27228463

Conservation of Terrestrial Vertebrates in a Global Hotspot of Karst Area in Southwestern China.

PubMed

Luo, Zhenhua; Tang, Songhua; Jiang, Zhigang; Chen, Jing; Fang, Hongxia; Li, Chunwang

2016-05-26

The karst area of southwest China (KASC) is the largest piece of karst landscape on the earth and a global biodiversity hot-spot with high concentrations of endemic species. Although a number of nature reserves (NRs) have been established across the region, the representativeness of biodiversity of the NR system is still unknown. Based on comprehensive literature and field surveys, and intensive consultations with zoologists and wildlife managers, we compiled distributions of 1,204 terrestrial vertebrate species and 271 NRs in KASC. We found Jinxiu, Mengla, Hekou, and Jinghong have the richest amphibian species; Jinxiu has the highest species richness of reptiles; Jinghong, Menghai, and Mengla have the largest numbers of avian species; whereas, Mengla, Longzhou, and Ningming have the greatest mammalian diversity in the region. Gap analysis among NR system, species richness pattern, and five biogeographic indicators found insufficient representation of the NR system on territorial vertebrate diversity. The conservation effectiveness in Guizhou Province was much lower than that in Guangxi and Yunnan Provinces. Under-representation and over-representation simultaneously occurred in many of the ecoregions, elevation classes, vegetation types, landcover categories, and human disturbance intensity gradients. For conservation of terrestrial vertebrates in KASC, several suggestions were presented in this study.

Minefields Associated with Mining Data from Peer-reviewed Literature

EPA Science Inventory

The USEPA’s ECOTOX database is the largest compilation of ecotoxicity study results, providing information on the adverse effects of single chemical stressors to ecologically relevant aquatic and terrestrial species. The primary source of data included in the ECOTOX database is t...

Wildland fire emissions, carbon, and climate: Science overview and knowledge needs

Treesearch

William T. Sommers; Rachel A. Loehman; Colin C. Hardy

2014-01-01

Wildland fires have influenced the global carbon cycle for 420 million years of Earth history, interacting with climate to define vegetation characteristics and distributions, trigger abrupt ecosystem shifts, and move carbon among terrestrial and atmospheric pools. Carbon dioxide (CO2) is the dominant driver of ongoing climate change and the principal emissions...

Long-term effects of wetland harvesting practices on productivity and carbon pools

Treesearch

Scott McKee; Mike Aust; John Seiler; Brian Strahm

2012-01-01

Forested wetlands are valued for social and ecological benefits including filtering sediments, uptake of nutrients, carbon storage, reduction of flood depths, protection of shorelines and streambanks, and provision of terrestrial and aquatic wildlife habitat (Walbridge 1993, Kellison and Young 1997, Brady and Weil 2002). Although the importance of wetland functions are...

A review on the role of organic inputs in maintaining soil carbon pool of the terrestrial ecosystem

USDA-ARS?s Scientific Manuscript database

Among the numerous sources of greenhouse gases, emissions of CO2 are affected considerably by changes in the extent of and type of land use, e.g., intensive agriculture, deforestation, urbanization, conversion of natural agricultural ecosystems, soil erosion, and wetland drainage. As a feasible opti...

Marine-influenced microbial communities inhabit terrestrial hot springs on a remote island volcano.

PubMed

Stewart, Lucy C; Stucker, Valerie K; Stott, Matthew B; de Ronde, Cornel E J

2018-07-01

Raoul Island is a subaerial island volcano approximately 1000 km northeast of New Zealand. Its caldera contains a circumneutral closed-basin volcanic lake and several associated pools, as well as intertidal coastal hot springs, all fed by a hydrothermal system sourced from both meteoric water and seawater. Here, we report on the geochemistry, prokaryotic community diversity, and cultivatable abundance of thermophilic microorganisms of four terrestrial features and one coastal feature on Raoul. Hydrothermal fluid contributions to the volcanic lake and pools make them brackish, and consequently support unusual microbial communities dominated by Planctomycetes, Chloroflexi, Alphaproteobacteria, and Thaumarchaeota, as well as up to 3% of the rare sister phylum to Cyanobacteria, Candidatus Melainabacteria. The dominant taxa are mesophilic to moderately thermophilic, phototrophic, and heterotrophic marine groups related to marine Planctomycetaceae. The coastal hot spring/shallow hydrothermal vent community is similar to other shallow systems in the Western Pacific Ocean, potentially due to proximity and similarities of geochemistry. Although rare in community sequence data, thermophilic methanogens, sulfur-reducers, and iron-reducers are present in culture-based assays.

Processes regulating progressive nitrogen limitation under elevated carbon dioxide: a meta-analysis

NASA Astrophysics Data System (ADS)

Liang, Junyi; Qi, Xuan; Souza, Lara; Luo, Yiqi

2016-05-01

The nitrogen (N) cycle has the potential to regulate climate change through its influence on carbon (C) sequestration. Although extensive research has explored whether or not progressive N limitation (PNL) occurs under CO2 enrichment, a comprehensive assessment of the processes that regulate PNL is still lacking. Here, we quantitatively synthesized the responses of all major processes and pools in the terrestrial N cycle with meta-analysis of CO2 experimental data available in the literature. The results showed that CO2 enrichment significantly increased N sequestration in the plant and litter pools but not in the soil pool, partially supporting one of the basic assumptions in the PNL hypothesis that elevated CO2 results in more N sequestered in organic pools. However, CO2 enrichment significantly increased the N influx via biological N fixation and the loss via N2O emission, but decreased the N efflux via leaching. In addition, no general diminished CO2 fertilization effect on plant growth was observed over time up to the longest experiment of 13 years. Overall, our analyses suggest that the extra N supply by the increased biological N fixation and decreased leaching may potentially alleviate PNL under elevated CO2 conditions in spite of the increases in plant N sequestration and N2O emission. Moreover, our syntheses indicate that CO2 enrichment increases soil ammonium (NH4+) to nitrate (NO3-) ratio. The changed NH4+/NO3- ratio and subsequent biological processes may result in changes in soil microenvironments, above-belowground community structures and associated interactions, which could potentially affect the terrestrial biogeochemical cycles. In addition, our data synthesis suggests that more long-term studies, especially in regions other than temperate ones, are needed for comprehensive assessments of the PNL hypothesis.

Forest soil carbon oxidation state and oxidative ratio responses to elevated CO 2

DOE PAGES

Hockaday, William C.; Gallagher, Morgan E.; Masiello, Caroline A.; ...

2015-09-21

The oxidative ratio (OR) of the biosphere is the stoichiometric ratio (O 2/CO 2) of gas exchange by photosynthesis and respiration a key parameter in budgeting calculations of the land and ocean carbon sinks. Carbon cycle-climate feedbacks could alter the OR of the biosphere by affecting the quantity and quality of organic matter in plant biomass and soil carbon pools. Here, this study considers the effect of elevated atmospheric carbon dioxide concentrations ([CO 2]) on the OR of a hardwood forest after nine growing seasons of Free-Air CO 2 Enrichment. We measured changes in the carbon oxidation state (C ox)more » of biomass and soil carbon pools as a proxy for the ecosystem OR. The OR of net primary production, 1.039, was not affected by elevated [CO 2]. However, the C ox of the soil carbon pool was 40% higher at elevated [CO 2], and the estimated OR values for soil respiration increased from 1.006 at ambient [CO 2] to 1.054 at elevated [CO 2]. A biochemical inventory of the soil organic matter ascribed the increases in C ox and OR to faster turnover of reduced substrates, lignin and lipids, at elevated [CO 2]. This implicates the heterotrophic soil community response to elevated [CO 2] as a driver of disequilibrium in the ecosystem OR. The oxidation of soil carbon pool constitutes an unexpected terrestrial O 2 sink. Carbon budgets constructed under the assumption of OR equilibrium would equate such a terrestrial O 2 sink to CO 2 uptake by the ocean. We find that the potential for climate-driven disequilibriua in the cycling of O 2 and CO 2 warrants further investigation.« less

Networking our science to characterize the state, vulnerabilities, and management opportunities of soil organic matter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harden, Jennifer W.; Hugelius, Gustaf; Ahlstrom, Anders

Here, soil organic matter supports the Earth’s ability to sustain terrestrial ecosystems, provide food and fiber, and retain the largest pool of actively cycling carbon (C). Over 75% of the soil organic carbon (SOC) in the top meter of soil is directly affected by human land use. Large land areas have lost SOC as a result of land use practices, yet there are compensatory opportunities to enhance land productivity and SOC storage in degraded lands through improved management practices. Large areas with and without intentional management are also being subjected to rapid changes in climate, making many SOC stocks vulnerablemore » to losses by decomposition or disturbance. In order to quantify potential SOC losses or sequestration at field, regional, and global scales, measurements for detecting changes in SOC are needed. Such measurements and soil-management best practices should be based on well-established and emerging scientific understanding of processes of C stabilization and destabilization over various timescales, soil types, and spatial scales. As newly engaged members of the International Soil Carbon Network, we have identified gaps in data, modeling, and communication that underscore the need for an open, shared network to frame and guide the study of soil organic matter and C and their management for sustained production and climate regulation.« less

Effects of temperature and grazing on soil organic carbon storage in grasslands along the Eurasian steppe eastern transect.

PubMed

Zhao, Yanyun; Ding, Yong; Hou, Xiangyang; Li, Frank Yonghong; Han, Wenjun; Yun, Xiangjun

2017-01-01

Soil represents the largest terrestrial organic carbon pool. To address global climate change, it is essential to explore the soil organic carbon storage patterns and their controlling factors. We investigated the soil organic carbon density (SOCD) in 48 grassland sites along the Eurasian steppe eastern transect (ESET) region, which covers the Inner Mongolia grassland subregion and Mongolia grasslands subregion. Specifically, we analyzed the SOCD in the top 30 cm soil layer and its relationships with climatic variables, soil texture, grazing intensity and community biomass productivity. The results showed that the average SOCD of the ESET was 4.74 kg/m2, and the SOCD of the Inner Mongolia grassland subregion (4.11 kg/m2) was significantly lower than that of the Mongolia grassland subregion (5.79 kg/m2). Significant negative relationships were found between the SOCD and the mean annual temperature (MAT), mean annual precipitation (MAP) and grazing intensity in the ESET region. The MAT and grazing intensity were identified as the major factors influencing the SOCD in the ESET region; the MAP and MAT were the major factors influencing the SOCD in the Inner Mongolia grassland subregion; and the MAT and soil pH were the major factors influencing the SOCD in the Mongolia grassland subregion.

Glacial forcing of central Indonesian hydroclimate since 60,000 y B.P.

PubMed Central

Russell, James M.; Vogel, Hendrik; Konecky, Bronwen L.; Bijaksana, Satria; Huang, Yongsong; Melles, Martin; Wattrus, Nigel; Costa, Kassandra; King, John W.

2014-01-01

The Indo-Pacific warm pool houses the largest zone of deep atmospheric convection on Earth and plays a critical role in global climate variations. Despite the region’s importance, changes in Indo-Pacific hydroclimate on orbital timescales remain poorly constrained. Here we present high-resolution geochemical records of surface runoff and vegetation from sediment cores from Lake Towuti, on the island of Sulawesi in central Indonesia, that continuously span the past 60,000 y. We show that wet conditions and rainforest ecosystems on Sulawesi present during marine isotope stage 3 (MIS3) and the Holocene were interrupted by severe drying between ∼33,000 and 16,000 y B.P. when Northern Hemisphere ice sheets expanded and global temperatures cooled. Our record reveals little direct influence of precessional orbital forcing on regional climate, and the similarity between MIS3 and Holocene climates observed in Lake Towuti suggests that exposure of the Sunda Shelf has a weaker influence on regional hydroclimate and terrestrial ecosystems than suggested previously. We infer that hydrological variability in this part of Indonesia varies strongly in response to high-latitude climate forcing, likely through reorganizations of the monsoons and the position of the intertropical convergence zone. These findings suggest an important role for the tropical western Pacific in amplifying glacial–interglacial climate variability. PMID:24706841

Networking our science to characterize the state, vulnerabilities, and management opportunities of soil organic matter

USGS Publications Warehouse

Harden, Jennifer W.; Hugelius, Gustaf; Ahlström, Anders; Blankinship, Joseph C.; Bond-Lamberty, Ben; Lawrence, Corey; Loisel, Julie; Malhotra, Avni; Jackson, Robert B.; Ogle, Stephen M.; Phillips, Claire; Ryals, Rebecca; Todd-Brown, Katherine; Vargas, Rodrigo; Vergara, Sintana E.; Cotrufo, M. Francesca; Keiluweit, Marco; Heckman, Katherine; Crow, Susan E.; Silver, Whendee L.; DeLonge, Marcia; Nave, Lucas E.

2018-01-01

Soil organic matter (SOM) supports the Earth's ability to sustain terrestrial ecosystems, provide food and fiber, and retains the largest pool of actively cycling carbon. Over 75% of the soil organic carbon (SOC) in the top meter of soil is directly affected by human land use. Large land areas have lost SOC as a result of land use practices, yet there are compensatory opportunities to enhance productivity and SOC storage in degraded lands through improved management practices. Large areas with and without intentional management are also being subjected to rapid changes in climate, making many SOC stocks vulnerable to losses by decomposition or disturbance. In order to quantify potential SOC losses or sequestration at field, regional, and global scales, measurements for detecting changes in SOC are needed. Such measurements and soil-management best practices should be based on well established and emerging scientific understanding of processes of C stabilization and destabilization over various timescales, soil types, and spatial scales. As newly engaged members of the International Soil Carbon Network, we have identified gaps in data, modeling, and communication that underscore the need for an open, shared network to frame and guide the study of SOM and SOC and their management for sustained production and climate regulation.

Networking our science to characterize the state, vulnerabilities, and management opportunities of soil organic matter

DOE PAGES

Harden, Jennifer W.; Hugelius, Gustaf; Ahlstrom, Anders; ...

2017-10-05

Here, soil organic matter supports the Earth’s ability to sustain terrestrial ecosystems, provide food and fiber, and retain the largest pool of actively cycling carbon (C). Over 75% of the soil organic carbon (SOC) in the top meter of soil is directly affected by human land use. Large land areas have lost SOC as a result of land use practices, yet there are compensatory opportunities to enhance land productivity and SOC storage in degraded lands through improved management practices. Large areas with and without intentional management are also being subjected to rapid changes in climate, making many SOC stocks vulnerablemore » to losses by decomposition or disturbance. In order to quantify potential SOC losses or sequestration at field, regional, and global scales, measurements for detecting changes in SOC are needed. Such measurements and soil-management best practices should be based on well-established and emerging scientific understanding of processes of C stabilization and destabilization over various timescales, soil types, and spatial scales. As newly engaged members of the International Soil Carbon Network, we have identified gaps in data, modeling, and communication that underscore the need for an open, shared network to frame and guide the study of soil organic matter and C and their management for sustained production and climate regulation.« less

Effects of temperature and grazing on soil organic carbon storage in grasslands along the Eurasian steppe eastern transect

PubMed Central

Hou, Xiangyang; Li, Frank Yonghong; Han, Wenjun; Yun, Xiangjun

2017-01-01

Soil represents the largest terrestrial organic carbon pool. To address global climate change, it is essential to explore the soil organic carbon storage patterns and their controlling factors. We investigated the soil organic carbon density (SOCD) in 48 grassland sites along the Eurasian steppe eastern transect (ESET) region, which covers the Inner Mongolia grassland subregion and Mongolia grasslands subregion. Specifically, we analyzed the SOCD in the top 30 cm soil layer and its relationships with climatic variables, soil texture, grazing intensity and community biomass productivity. The results showed that the average SOCD of the ESET was 4.74 kg/m2, and the SOCD of the Inner Mongolia grassland subregion (4.11 kg/m2) was significantly lower than that of the Mongolia grassland subregion (5.79 kg/m2). Significant negative relationships were found between the SOCD and the mean annual temperature (MAT), mean annual precipitation (MAP) and grazing intensity in the ESET region. The MAT and grazing intensity were identified as the major factors influencing the SOCD in the ESET region; the MAP and MAT were the major factors influencing the SOCD in the Inner Mongolia grassland subregion; and the MAT and soil pH were the major factors influencing the SOCD in the Mongolia grassland subregion. PMID:29084243

Changes in Landscape-level Carbon Balance of an Arctic Coastal Plain Tundra Ecosystem Between 1970-2100, in Response to Projected Climate Change

NASA Astrophysics Data System (ADS)

Lara, M. J.; McGuire, A. D.; Euskirchen, E. S.; Genet, H.; Sloan, V. L.; Iversen, C. M.; Norby, R. J.; Zhang, Y.; Yuan, F.

2014-12-01

Northern permafrost regions are estimated to cover 16% of the global soil area and account for approximately 50% of the global belowground organic carbon pool. However, there are considerable uncertainties regarding the fate of this soil carbon pool with projected climate warming over the next century. In northern Alaska, nearly 65% of the terrestrial surface is composed of polygonal tundra, where geomorphic land cover types such as high-, flat-, and low-center polygons influence local surface hydrology, plant community composition, nutrient and biogeochemical cycling, over small spatial scales. Due to the lack of representation of these fine-scale geomorphic types and ecosystem processes, in large-scale terrestrial ecosystem models, future uncertainties are large for this tundra region. In this study, we use a new version of the terrestrial ecosystem model (TEM), that couples a dynamic vegetation model (in which plant functional types compete for water, nitrogen, and light) with a dynamic soil organic model (in which temperature, moisture, and associated organic/inorganic carbon and nitrogen pools/fluxes vary together in vertically resolved layers) to simulate ecosystem carbon balance. We parameterized and calibrated this model using data specific to the local climate, vegetation, and soil associated with tundra geomorphic types. We extrapolate model results at a 1km2 resolution across the ~1800 km2 Barrow Peninsula using a tundra geomorphology map, describing ten dominant geomorphic tundra types (Lara et al. submitted), to estimate the likely change in landscape-level carbon balance between 1970 and 2100 in response to projected climate change. Preliminary model runs for this region indicated temporal variability in carbon and active layer dynamics, specific to tundra geomorphic type over time. Overall, results suggest that it is important to consider small-scale discrete polygonal tundra geomorphic types that control local structure and function in regional estimates of carbon balance in northern Alaska.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luo, Yiqi; Shi, Zheng; Lu, Xingjie

Terrestrial ecosystems have absorbed roughly 30 % of anthropogenic CO 2 emissions over the past decades, but it is unclear whether this carbon (C) sink will endure into the future. Despite extensive modeling and experimental and observational studies, what fundamentally determines transient dynamics of terrestrial C storage under global change is still not very clear. Here we develop a new framework for understanding transient dynamics of terrestrial C storage through mathematical analysis and numerical experiments. Our analysis indicates that the ultimate force driving ecosystem C storage change is the C storage capacity, which is jointly determined by ecosystem C inputmore » (e.g., net primary production, NPP) and residence time. Since both C input and residence time vary with time, the C storage capacity is time-dependent and acts as a moving attractor that actual C storage chases. The rate of change in C storage is proportional to the C storage potential, which is the difference between the current storage and the storage capacity. The C storage capacity represents instantaneous responses of the land C cycle to external forcing, whereas the C storage potential represents the internal capability of the land C cycle to influence the C change trajectory in the next time step. The influence happens through redistribution of net C pool changes in a network of pools with different residence times. Moreover, this and our other studies have demonstrated that one matrix equation can replicate simulations of most land C cycle models (i.e., physical emulators). As a result, simulation outputs of those models can be placed into a three-dimensional (3-D) parameter space to measure their differences. The latter can be decomposed into traceable components to track the origins of model uncertainty. In addition, the physical emulators make data assimilation computationally feasible so that both C flux- and pool-related datasets can be used to better constrain model predictions of land C sequestration. Overall, this new mathematical framework offers new approaches to understanding, evaluating, diagnosing, and improving land C cycle models.« less

Morphological and molecular characterization and phylogenetic relationships of a new species of trypanosome in Tapirus terrestris (lowland tapir), Trypanosoma terrestris sp. nov., from Atlantic Rainforest of southeastern Brazi.

PubMed

Acosta, Igor da Cunha Lima; da Costa, Andrea Pereira; Nunes, Pablo Henrique; Gondim, Maria Fernanda Naegeli; Gatti, Andressa; Rossi, João Luiz; Gennari, Solange Maria; Marcili, Arlei

2013-12-11

The Lowland tapir (Tapirus terrestris) is the largest Brazilian mammal and despite being distributed in various Brazilian biomes, it is seriously endangered in the Atlantic Rainforest. These hosts were never evaluated for the presence of Trypanosoma parasites. The Lowland tapirs were captured in the Brazilian southeastern Atlantic Rainforest, Espírito Santo state. Trypanosomes were isolated by hemoculture, and the molecular phylogeny based on small subunit rDNA (SSU rDNA) and glycosomal-3-phosphate dehydrogenase (gGAPDH) gene sequences and the ultrastructural features seen via light microscopy and scanning and transmission electron microscopy are described. Phylogenetic trees using combined SSU rDNA and gGAPDH data sets clustered the trypanosomes of Lowland tapirs, which were highly divergent from other trypanosome species. The phylogenetic position and morphological discontinuities, mainly in epimastigote culture forms, made it possible to classify the trypanosomes from Lowland tapirs as a separate species. The isolated trypanosomes from Tapirus terrestris are a new species, Trypanosoma terrestris sp. n., and were positioned in a new Trypanosoma clade, named T. terrestris clade.

Morphological and molecular characterization and phylogenetic relationships of a new species of trypanosome in Tapirus terrestris (lowland tapir), Trypanosoma terrestris sp. nov., from Atlantic Rainforest of southeastern Brazi

PubMed Central

2013-01-01

Background The Lowland tapir (Tapirus terrestris) is the largest Brazilian mammal and despite being distributed in various Brazilian biomes, it is seriously endangered in the Atlantic Rainforest. These hosts were never evaluated for the presence of Trypanosoma parasites. Methods The Lowland tapirs were captured in the Brazilian southeastern Atlantic Rainforest, Espírito Santo state. Trypanosomes were isolated by hemoculture, and the molecular phylogeny based on small subunit rDNA (SSU rDNA) and glycosomal-3-phosphate dehydrogenase (gGAPDH) gene sequences and the ultrastructural features seen via light microscopy and scanning and transmission electron microscopy are described. Results Phylogenetic trees using combined SSU rDNA and gGAPDH data sets clustered the trypanosomes of Lowland tapirs, which were highly divergent from other trypanosome species. The phylogenetic position and morphological discontinuities, mainly in epimastigote culture forms, made it possible to classify the trypanosomes from Lowland tapirs as a separate species. Conclusions The isolated trypanosomes from Tapirus terrestris are a new species, Trypanosoma terrestris sp. n., and were positioned in a new Trypanosoma clade, named T. terrestris clade. PMID:24330660

Puncturevine seed response to postemergence herbicides

USDA-ARS?s Scientific Manuscript database

Puncturevine (Tribulus terrestris) continues to plague growers, vegetation managers, and home gardeners. Puncturevine is a summer annual weed with spiny fruits that split into five segments, each containing one to four seeds. The seed nearest the pointed end of the bur is the largest and usually ge...

Multiscale analyses of solar-induced florescence and gross primary production

USDA-ARS?s Scientific Manuscript database

Remotely sensed solar induced fluorescence (SIF) has shown great promise for probing spatiotemporal variations in terrestrial gross primary production (GPP), the largest component flux of the global carbon cycle. However, scale mismatches between SIF and ground-based GPP have posed challenges toward...

Regional Scale Photochemical Model Evaluation of Total Mercury Wet Deposition and Speciated Ambient Mercury

EPA Science Inventory

Methylmercury is a known neurotoxin with deleterious health effects on humans and wildlife. Atmospheric deposition is the largest source of mercury loading to most terrestrial and aquatic ecosystems. Regional scale air quality models are needed to quantify mercury deposition resu...

Influence of Plants on Chlorine Cycling in Terrestrial Environments

NASA Astrophysics Data System (ADS)

Montelius, Malin; Thiry, Yves; Marang, Laura; Ranger, Jacques; Cornelis, Jean-Thomas; Svensson, Teresia; Bastviken, David

2016-04-01

Chlorine (Cl), one of the 20 most abundant elements on Earth, is crucial for life as a regulator of cellular ionic strength and an essential co-factor in photosynthesis. Chlorinated organic compounds (Clorg) molecules are surprisingly abundant in soils, in fact many studies during the last decades show that Clorg typically account for more than 60% of the total soil Cl pool in boreal and temperate forest soils and frequently exceed chloride (Cl-) levels. The natural and primarily biotic formation of this Clorg pool has been confirmed experimentally but the detailed content of the Clorg pool and the reasons for its high abundance remains puzzling and there is a lack of Cl budgets for different ecosystems. Recently, the radioisotope 36Cl has caused concerns because of presence in radioactive waste, a long half-life (301 000 years), potential high mobility, and limited knowledge about Cl residence times, speciation and uptake by organisms in terrestrial environments. The chlorination of organic molecules may influence the pool of available Cl- to organisms and thereby the Cl cycling dynamics. This will prolong residence times of total Cl in the soil-vegetation system, which affects exposure times in radioactive 36Cl isotope risk assessments. We tested to what extent the dominating tree species influences the overall terrestrial Cl cycling and the balance between Cl- and Clorg. Total Cl and Clorg were measured in different tree compartments and soil horizons in the Breuil experimental forest, Bourgogne, established in 1976 and located at Breuil-Chenue in Eastern France. The results from this field experiment show how the dominating tree species affected Cl cycling and accumulation over a time period of 30 years. Cl uptake by trees as well as content of both total Cl and Clorg in soil humus was much higher in experimental plots with coniferous forests compared to deciduous forests. The amounts of Clorg found in plant tissue indicate significant Clorg production inside trees in addition to substantial soil production of Clorg. A large and tree species dependent "luxury" Cl uptake, rapidly released through the leaves and returned to the soil as throughfall, was indicated for some tree species. The physiology of dominating tree species, along with tree-related soil microbial communities, thus appears more important for the local Cl levels and cycling than atmospheric Cl deposition.

The Effects of Elevated CO2 on a Subtropical Scrub Oak-Palmetto Plant Community

NASA Technical Reports Server (NTRS)

Vieglais, David; Hinkle, C. Ross; Drake, Bert

1995-01-01

A 2.5 year (1992-1995) pilot study was conducted on the effects of twice ambient CO2 on native scrub oak-palmetto vegetation at Kennedy Space Center (KSC). The effects suggest that rising atmospheric CO2 will increase terrestrial carbon and alter the distribution of carbon among the different pools of carbon.

Decomposition rates of American chestnut (Castanea dentata) wood and implications for coarse woody debris pools

Treesearch

Arjan de Bruijn; Eric J. Gustafson; Daniel M. Kashian; Harmony J. Dalgleish; Brian R. Sturtevant; Douglass F. Jacobs

2014-01-01

Observations of the rapid growth and slow decomposition of American chestnut (Castanea dentata (Marsh.) Borkh.) suggest that its reintroduction could enhance terrestrial carbon (C) sequestration. A suite of decomposition models was fit with decomposition data from coarse woody debris (CWD) sampled in Wisconsin and Virginia, U.S. The optimal (two-...

Soil organic nitrogen mineralization across a global latitudinal gradient

Treesearch

D.L. Jones; K. Kielland; F.L. Sinclair; R.A. Dahlgren; K.K. Newsham; J.F. Farrar; D.V. Murphy

2009-01-01

Understanding and accurately predicting the fate of carbon and nitrogen in the terrestrial biosphere remains a central goal in ecosystem science. Amino acids represent a key pool of C and N in soil, and their availability to plants and microorganisms has been implicated as a major driver in regulating ecosystem functioning. Because of potential differences in...

Conservation Priorities for Terrestrial Birds in the Northeastern United States

Treesearch

Kenneth V. Rosenberg; Jeffrey V. Wells

2005-01-01

As part of the Partners in Flight (PIF) bird-conservation planning process, we assessed breeding land bird species according to seven categories of population vulnerability to derive a priority species pool in each of 12 physiographic areas that overlap the northeastern U.S. We then grouped species into the following habitat-species suites: (1) boreal-mountaintop...

Carbon pools in stream-riparian corridors: legacy of disturbance along mountain streams of south-eastern Wyoming

Treesearch

Claire M. Ruffing; Kathleen A. Dwire; Melinda D. Daniels

2016-01-01

Streams and their accompanying riparian environments are intrinsic components of terrestrial carbon cycling. However, they have been understudied in terms of the magnitude of their storage components and the role of disturbance in determining carbon storage capacity. This study presents partial carbon budgets for stream-riparian corridors along six study...

Nitrogen in rock: Occurrences and biogeochemical implications

USGS Publications Warehouse

Holloway, J.M.; Dahlgren, R.A.

2002-01-01

There is a growing interest in the role of bedrock in global nitrogen cycling and potential for increased ecosystem sensitivity to human impacts in terrains with elevated background nitrogen concentrations. Nitrogen-bearing rocks are globally distributed and comprise a potentially large pool of nitrogen in nutrient cycling that is frequently neglected because of a lack of routine analytical methods for quantification. Nitrogen in rock originates as organically bound nitrogen associated with sediment, or in thermal waters representing a mixture of sedimentary, mantle, and meteoric sources of nitrogen. Rock nitrogen concentrations range from trace levels (>200 mg N kg -1) in granites to ecologically significant concentrations exceeding 1000 mg N kg -1 in some sedimentary and metasedimentary rocks. Nitrate deposits accumulated in arid and semi-arid regions are also a large potential pool. Nitrogen in rock has a potentially significant impact on localized nitrogen cycles. Elevated nitrogen concentrations in water and soil have been attributed to weathering of bedrock nitrogen. In some environments, nitrogen released from bedrock may contribute to nitrogen saturation of terrestrial ecosystems (more nitrogen available than required by biota). Nitrogen saturation results in leaching of nitrate to surface and groundwaters, and, where soils are formed from ammonium-rich bedrock, the oxidation of ammonium to nitrate may result in soil acidification, inhibiting revegetation in certain ecosystems. Collectively, studies presented in this article reveal that geologic nitrogen may be a large and reactive pool with potential for amplification of human impacts on nitrogen cycling in terrestrial and aquatic ecosystems.

Organochlorine Turnover in Forest Ecosystems: The Missing Link in the Terrestrial Chlorine Cycle

DOE Office of Scientific and Technical Information (OSTI.GOV)

A Leri; S Myneni

Research in the last 20 years has shown that chlorine undergoes transformations between inorganic and organic forms as part of a complex biogeochemical cycle in terrestrial systems. Natural organochlorine production appears to be associated with the decomposition of plant material on the soil surface, though the chlorine cycle budget implies that a proportion of natural organochlorine enters soil through plant litter and atmospheric deposition as well. Organochlorine compounds may form through biotic and abiotic pathways, but the rates and magnitude of production in the field remain undefined. We have performed a time-dependent trace of chlorine concentration through forest ecosystems, revealingmore » distinct fractions of naturally produced organochlorine in plant biomass. Aliphatic organochlorine constitutes an intrinsic component of healthy leaves that persists through senescence and humification of the plant material, making a substantial contribution to the pool of soil organochlorine. Plant leaves also contain soluble aromatic organochlorine compounds that leach from leaf litter during early decay stages. As decay progresses, high concentrations of insoluble aromatic organochlorine accrue in the humus, through de novo production as well as adsorption. The rates of aromatic organochlorine production and degradation vary seasonally and conversely. This study presents the first unambiguous evidence that there exist multiple pools of chlorinated organic matter in the soil environment and that leaf litter deposition makes a significant and refractory contribution to the soil organochlorine pool, providing key insights into the biogeochemical chlorine cycle.« less

Application of sulphur isotope ratios to examine weaning patterns and freshwater fish consumption in Roman Oxfordshire, UK

NASA Astrophysics Data System (ADS)

Nehlich, Olaf; Fuller, Benjamin T.; Jay, Mandy; Mora, Alice; Nicholson, Rebecca A.; Smith, Colin I.; Richards, Michael P.

2011-09-01

This study investigates the application of sulphur isotope ratios (δ 34S) in combination with carbon (δ 13C) and nitrogen (δ 15N) ratios to understand the influence of environmental sulphur on the isotopic composition of archaeological human and faunal remains from Roman era sites in Oxfordshire, UK. Humans ( n = 83), terrestrial animals ( n = 11), and freshwater fish ( n = 5) were analysed for their isotope values from four locations in the Thames River Valley, and a broad range of δ 34S values were found. The δ 34S values from the terrestrial animals were highly variable (-13.6‰ to +0.5‰), but the δ 34S values of the fish were clustered and 34S-depleted (-20.9‰ to -17.3‰). The results of the faunal remains suggest that riverine sulphur influenced the terrestrial sulphur isotopic signatures. Terrestrial animals were possibly raised on the floodplains of the River Thames, where highly 34S-depleted sulphur influenced the soil. The humans show the largest range of δ 34S values (-18.8‰ to +9.6‰) from any archaeological context to date. No differences in δ 34S values were found between the males (-7.8 ± 6.0‰) and females (-5.3 ± 6.8‰), but the females had a linear correlation ( R2 = 0.71; p < 0.0001) between their δ 15N and δ 34S compositions. These δ 34S results suggest a greater dietary variability for the inhabitants of Roman Oxfordshire than previously thought, with some individuals eating solely terrestrial protein resources and others showing a diet almost exclusively based on freshwater protein such as fish. Such large dietary variability was not visible by analysing only the carbon and nitrogen isotope ratios, and this research represents the largest and most detailed application of δ 34S analysis to examine dietary practices (including breastfeeding and weaning patterns) during the Romano-British Period.

Agricultural conversion without external water and nutrient inputs reduces terrestrial vegetation productivity

USGS Publications Warehouse

Smith, W. Kolby; Cleveland, Cory C.; Reed, Sasha C.; Running, Steven W.

2014-01-01

Driven by global population and standard of living increases, humanity co-opts a growing share of the planet's natural resources resulting in many well-known environmental trade-offs. In this study, we explored the impact of agriculture on a resource fundamental to life on Earth: terrestrial vegetation growth (net primary production; NPP). We demonstrate that agricultural conversion has reduced terrestrial NPP by ~7.0%. Increases in NPP due to agricultural conversion were observed only in areas receiving external inputs (i.e., irrigation and/or fertilization). NPP reductions were found for ~88% of agricultural lands, with the largest reductions observed in areas formerly occupied by tropical forests and savannas (~71% and ~66% reductions, respectively). Without policies that explicitly consider the impact of agricultural conversion on primary production, future demand-driven increases in agricultural output will likely continue to drive net declines in global terrestrial productivity, with potential detrimental consequences for net ecosystem carbon storage and subsequent climate warming.

Chapter 5: Wolverine

Treesearch

Vivian Banci

1994-01-01

The wolverine (Gulo gulo) is the largest-bodied terrestrial mustelid. Its distribution is circumpolar; it occupies the tundra, taiga, and forest zones of North America and Eurasia (Wilson 1982). North American wolverines are considered the same species as those in Eurasia. They are usually thought of as creatures of northern wilderness and remote...

Will nitrogen deposition mitigate warming-increased soil respiration in a young subtropical plantation?

Treesearch

Xiaofei Liu; Zhijie Yang; Chengfang Lin; Christian P. Giardina; Decheng Xiong; Weisheng Lin; Shidong Chen; Chao Xu; Guangshui Chen; Jinsheng Xie; Yiqing Li; Yusheng Yang

2017-01-01

Global change such as climate warming and nitrogen (N) deposition is likely to alter terrestrial carbon (C) cycling, including soil respiration (Rs), the largest CO2 source from soils to the atmosphere. To examine the effects of warming, N addition and their interactions on Rs, we...

Habitat and Grazing Influence on Terrestrial Ants in Subtropical Grasslands and Savannas of Argentina

USDA-ARS?s Scientific Manuscript database

The maintenance of species diversity in modified and natural habitats is a central focus of conservation biology. The Iberá Nature Reserve (INR) protects highly diverse ecosystems in northeastern Argentina, including one of the largest freshwater wetlands in South America. Livestock grazing is one o...

Modelling C3 photosynthesis from the chloroplast to the ecosystem

USDA-ARS?s Scientific Manuscript database

Globally, photosynthesis accounts for the largest flux of CO2 from the atmosphere into ecosystems and is the driving process for terrestrial ecosystem function. The importance of accurate predictions of photosynthesis over a range of plant growth conditions led to the development of a C3 photosynthe...

Insertion sequences enrichment in extreme Red sea brine pool vent.

PubMed

Elbehery, Ali H A; Aziz, Ramy K; Siam, Rania

2017-03-01

Mobile genetic elements are major agents of genome diversification and evolution. Limited studies addressed their characteristics, including abundance, and role in extreme habitats. One of the rare natural habitats exposed to multiple-extreme conditions, including high temperature, salinity and concentration of heavy metals, are the Red Sea brine pools. We assessed the abundance and distribution of different mobile genetic elements in four Red Sea brine pools including the world's largest known multiple-extreme deep-sea environment, the Red Sea Atlantis II Deep. We report a gradient in the abundance of mobile genetic elements, dramatically increasing in the harshest environment of the pool. Additionally, we identified a strong association between the abundance of insertion sequences and extreme conditions, being highest in the harshest and deepest layer of the Red Sea Atlantis II Deep. Our comparative analyses of mobile genetic elements in secluded, extreme and relatively non-extreme environments, suggest that insertion sequences predominantly contribute to polyextremophiles genome plasticity.

Perspectives on the age and distribution of large wood in riparian carbon pools

Treesearch

Richard P. Guyette; William G. Cole; Daniel C. Dey; Rose-Marie Muzkia

2002-01-01

Most knowledge of carbon budgets is derived from the productivity and sequestration of carbon in terrestrial and marine ecosystems. Less is known of carbon stored in riparian areas associated with lakes and rivers. Case studies of the age distribution of carbon in aquatic large wood (C1w) from two different landscapes with different drainage...

Stream nitrogen responses to fire in the Southeastern U.S.

Treesearch

James M. Vose; Stephanie H. Laseter; Steve G. McNulty

2005-01-01

Fire can play a significant role in runoff, sediment yield, and nitrate transport in aquatic and terrestrial ecosystems in the southeast US. The typical impact of fire is an immediate change in the physical properties of the soil and forest floor surface, followed by mid- and long-term changes in biological pools and cycling processes. Depending upon the severity of...

Retention of phosphorus in highly weathered soils under a lowland Amazonian forest ecosystem

Treesearch

M. E. McGroddy; W. L. Silver; Jr. de Oliveira; W. Z. de Mello; M. Keller

2008-01-01

The low available phosphorus (P) pools typical of highly weathered tropical forest soils are thought to result from a combination of export of phosphorus via erosion and leaching as well as chemical reactions resulting in physically and chemically protected P compounds. Despite the low apparent P availability, these soils support some of the highest terrestrial net...

Soil nitrogen accretion along a floodplain terrace chronosequence in northwest Alaska: Influence of the nitrogen-fixing shrub Shepherdia Canadensis

Treesearch

Charles Rhoades; Dan Binkley; Hlynur Oskarsson; Robert Stottlemyer

2008-01-01

Nitrogen enters terrestrial ecosystems through multiple pathways during primary succession. We measured accumulation of total soil nitrogen and changes in inorganic nitrogen (N) pools across a 300-y sequence of river terraces in northwest Alaska and assessed the contribution of the nitrogen-fixing shrub Shepherdia canadensis. Our work compared 5...

Photosynthetic carbon metabolism in seagrasses C-labeling evidence for the c(3) pathway.

PubMed

Andrews, T J; Abel, K M

1979-04-01

The delta(13)C values of several seagrasses were considerably less negative than those of terrestrial C(3) plants and tended toward those of terrestrial C(4) plants. However, for Thalassia hemprichii (Ehrenb.) Aschers and Halophila spinulosa (R. Br.) Aschers, phosphoglycerate and other C(3) cycle intermediates predominated among the early labeled products of photosynthesis in (14)C-labeled seawater (more than 90% at the earliest times) and the labeling pattern at longer times was brought about by the operation of the C(3) pathway. Malate and aspartate together accounted for only a minor fraction of the total fixed label at all times and the kinetic data of this labeling were not at all consistent with these compounds being early intermediates in seagrass photosynthesis. Pulse-chase (14)C-labeling studies further substantiated these conclusions. Significant labeling of photorespiratory intermediates was observed in all experiments. The kinetics of total fixation of label during some steady-state and pulse-chase experiments suggested that there may be an intermediate pool of inorganic carbon of variable size closely associated with the leaves, either externally or internally. Such a pool may be one cause for the C(4)-like carbon isotope ratios of seagrasses.

An Evaluation of Fish ELS Data: Is it Predictive?

EPA Science Inventory

As with higher vertebrate animal alternatives, balance between reducing the use of animals in testing without impairing or increasing uncertainty in risk assessment is needed. Testing demands for long-term (chronic) fish toxicity represents the third largest pool of needs follo...

A meta-analysis of soil biodiversity impacts on the carbon cycle

NASA Astrophysics Data System (ADS)

de Graaff, M.-A.; Adkins, J.; Kardol, P.; Throop, H. L.

2015-03-01

Loss of biodiversity impacts ecosystem functions, such as carbon (C) cycling. Soils are the largest terrestrial C reservoir, containing more C globally than the biotic and atmospheric pools together. As such, soil C cycling, and the processes controlling it, has the potential to affect atmospheric CO2 concentrations and subsequent climate change. Despite the growing evidence of links between plant diversity and soil C cycling, there is a dearth of information on whether similar relationships exist between soil biodiversity and C cycling. This knowledge gap occurs even though there has been increased recognition that soil communities display high levels of both taxonomic and functional diversity and are key drivers of fluxes of C between the atmosphere and terrestrial ecosystems. Here, we used meta-analysis and regression analysis to quantitatively assess how soil biodiversity affects soil C cycling pools and processes (i.e., soil C respiration, litter decomposition, and plant biomass). We compared the response of process variables to changes in diversity both within and across groups of soil organisms that differed in body size, a grouping that typically correlates with ecological function. When studies that manipulated both within- and across-body size group diversity were included in the meta-analysis, loss of diversity significantly reduced soil C respiration (-27.5%) and plant tissue decomposition (-18%) but did not affect above- or belowground plant biomass. The loss of within-group diversity significantly reduced soil C respiration, while loss of across-group diversity did not. Decomposition was negatively affected both by loss of within-group and across-group diversity. Furthermore, loss of microbial diversity strongly reduced soil C respiration (-41%). In contrast, plant tissue decomposition was negatively affected by loss of soil faunal diversity but was unaffected by loss of microbial diversity. Taken together, our findings show that loss of soil biodiversity strongly impacts on soil C cycling processes, and highlight the importance of diversity across groups of organisms (e.g., primary consumers and secondary decomposers) for maintaining full functionality of C cycle processes. However, our understanding of the complex relationships between soil biodiversity and C cycling processes is currently limited by the sheer number of methodological concerns associated with these studies, which can greatly overestimate or underestimate the impact of soil biodiversity on soil C cycling, challenging extrapolation to natural field settings. Future studies should attempt to further elucidate the relative importance of taxonomic diversity (species numbers) versus functional diversity.

Sources, degradation and transport of terrigenous organic carbon on the East Siberian Arctic Shelf Seas

NASA Astrophysics Data System (ADS)

Tesi, Tommaso; Semiletov, Igor; Dudarev, Oleg; Gustafsson, Örjan

2013-04-01

Recent studies suggest that the present hydrological regime increase observed in the Arctic rivers is mainly the consequence of the changes in permafrost conditions as a result of climate warming. Given the enormous amount of carbon stored in coastal and terrestrial permafrost the potentially increased supply from this large carbon pool to the coastal Arctic Ocean, possibly associated with a translocated release to the atmosphere as CO2, is considered a plausible scenario in a warming climate. However, there is not sufficient information regarding the reactivity of terrigenous material once supplied to the Arctic Ocean. In this study, we address this critical issue by examining the organic composition of surface sediments collected over extensive scales on the East Siberian Arctic Shelf (ESAS) as part of the International Siberian Shelf Study (ISSS). The ESAS represents by far the largest shelf of the Arctic Ocean. Samples were collected from the inner- to the outer-shelf following the sediment transport pathway in a region between the Lena and the Kolyma rivers. The analytical approach includes the characterization of marine and land-derived carbon using a large number of molecular biomarkers obtained by alkaline CuO oxidation such as lignin-phenols, cutin-derived products, p-hydroxy benzenes, benzoic acids, fatty acids, and dicarboxylic acids. Our results indicated high concentrations of terrigenous material in shallow sediments and a marked decrease of terrestrial biomarkers with increasing distance from the coastline. In parallel, lignin-based degradation proxies suggested highly altered terrigenous carbon in mid- and outer-shelf sediments compared to coastal sediments. Furthermore, the ratio of cutin-derived products over lignin significantly increased along the sediment transport pathway. Considering that cutin is considered to be intrinsically more reactive compared to lignin, high values of this ratio off the coastal region were interpreted as selective transport of fine sediments relatively rich in cutin. Finally, in addition to degradation and sorting processes, our results indicated dilution of land-derived material with marine phytodetritus with increasing distance from the shore. Results from our study indicate that the benthic sediment transport system in the ESAS is quite dynamic and acts as an efficient incinerator of terrigenous material as observed in mid-latitude settings. Therefore, considering the mega-pool of terrigenous carbon susceptible to remobilization because of climate-induced changes, our results suggest future limited burial of this material in mid- and outer-shelf deposits.

Mudskippers and Their Genetic Adaptations to an Amphibious Lifestyle

PubMed Central

You, Xinxin; Sun, Min; Li, Jia; Bian, Chao; Chen, Jieming; Yu, Hui; Shi, Qiong

2018-01-01

Simple Summary Mudskippers are an interesting group of goggle-eyed amphibious fish that can live both in water and on land. They are a useful model for obtaining insights into the genetic mechanisms underlying the terrestrial adaptations of amphibious fish. This review summarizes the morphological and physiological modifications of representative mudskippers, and focuses on the recent advancement of genomic studies on their genetic adaptations to the amphibious lifestyle. Abstract Mudskippers are the largest group of amphibious teleost fish that are uniquely adapted to live on mudflats. During their successful transition from aqueous life to terrestrial living, these fish have evolved morphological and physiological modifications of aerial vision and olfaction, higher ammonia tolerance, aerial respiration, improved immunological defense against terrestrial pathogens, and terrestrial locomotion using protruded pectoral fins. Comparative genomic and transcriptomic data have been accumulated and analyzed for understanding molecular mechanisms of the terrestrial adaptations. Our current review provides a general introduction to mudskippers and recent research advances of their genetic adaptations to the amphibious lifestyle, which will be helpful for understanding the evolutionary transition of vertebrates from water to land. Our insights into the genomes and transcriptomes will also support molecular breeding, functional identification, and natural compound screening. PMID:29414871

Coming down from the trees: Is terrestrial activity in Bornean orangutans natural or disturbance driven?

PubMed Central

Ancrenaz, Marc; Sollmann, Rahel; Meijaard, Erik; Hearn, Andrew J.; Ross, Joanna; Samejima, Hiromitsu; Loken, Brent; Cheyne, Susan M.; Stark, Danica J.; Gardner, Penny C.; Goossens, Benoit; Mohamed, Azlan; Bohm, Torsten; Matsuda, Ikki; Nakabayasi, Miyabi; Lee, Shan Khee; Bernard, Henry; Brodie, Jedediah; Wich, Serge; Fredriksson, Gabriella; Hanya, Goro; Harrison, Mark E.; Kanamori, Tomoko; Kretzschmar, Petra; Macdonald, David W.; Riger, Peter; Spehar, Stephanie; Ambu, Laurentius N.; Wilting, Andreas

2014-01-01

The orangutan is the world's largest arboreal mammal, and images of the red ape moving through the tropical forest canopy symbolise its typical arboreal behaviour. Records of terrestrial behaviour are scarce and often associated with habitat disturbance. We conducted a large-scale species-level analysis of ground-based camera-trapping data to evaluate the extent to which Bornean orangutans Pongo pygmaeus come down from the trees to travel terrestrially, and whether they are indeed forced to the ground primarily by anthropogenic forest disturbances. Although the degree of forest disturbance and canopy gap size influenced terrestriality, orangutans were recorded on the ground as frequently in heavily degraded habitats as in primary forests. Furthermore, all age-sex classes were recorded on the ground (flanged males more often). This suggests that terrestrial locomotion is part of the Bornean orangutan's natural behavioural repertoire to a much greater extent than previously thought, and is only modified by habitat disturbance. The capacity of orangutans to come down from the trees may increase their ability to cope with at least smaller-scale forest fragmentation, and to cross moderately open spaces in mosaic landscapes, although the extent of this versatility remains to be investigated. PMID:24526001

Soil organic carbon dynamics following afforestation in the Loess Plateau of China

NASA Astrophysics Data System (ADS)

Lu, N.; Liski, J.; Chang, R. Y.; Akujärvi, A.; Wu, X.; Jin, T. T.; Wang, Y. F.; Fu, B. J.

2013-07-01

Soil organic carbon (SOC) is the largest terrestrial carbon pool and sensitive to land use and cover change; its dynamics is critical for carbon cycling in terrestrial ecosystems and the atmosphere. In this study, we combined a modeling approach and field measurements to examine the temporal dynamics of SOC following afforestation of former arable land at six sites under different climatic conditions in the Loess Plateau during 1980-2010. The results showed that the measured mean SOC increased to levels higher than before afforestation when taking the last measurements (i.e., at age 25 to 30 yr), although it decreased in the first few years at the wetter sites. The accumulation rates of SOC were 1.58 to 6.22% yr-1 in the upper 20 cm and 1.62 to 5.15% yr-1 in the upper 40 cm of soil. The simulations reproduced the basic characteristics of measured SOC dynamics, suggesting that litter input and climatic factors (temperature and precipitation) were the major causes for SOC dynamics and the differences among the sites. They explained 88-96, 48-86 and 57-74% of the variations in annual SOC changes at the soil depths of 0-20, 0-40, and 0-100 cm, respectively. Notably, the simulated SOC decreased during the first few years at all the sites, although the magnitudes of decreases were small at the drier sites. This suggested that the modeling may be advantageous in capturing SOC changes at finer time scale. The discrepancy between the simulation and measurement was a result of uncertainties in model structure, data input, and sampling design. Our findings indicated that afforestation promoted soil carbon sequestration at the study sites, which is favorable for further restoration of the vegetation and environment. Afforestation activities should decrease soil disturbances to reduce carbon release in the early stage. The long-term strategy for carbon fixation capability of the plantations should also consider the climate and site conditions, species adaptability, and successional stage of recovery.

Quantifying Fast and Slow Responses of Terrestrial Carbon Exchange across a Water Availability Gradient in North American Flux Sites

NASA Astrophysics Data System (ADS)

Biederman, J. A.; Scott, R. L.; Goulden, M.

2014-12-01

Climate change is predicted to increase the frequency and severity of water limitation, altering terrestrial ecosystems and their carbon exchange with the atmosphere. Here we compare site-level temporal sensitivity of annual carbon fluxes to interannual variations in water availability against cross-site spatial patterns over a network of 19 eddy covariance flux sites. This network represents one order of magnitude in mean annual productivity and includes western North American desert shrublands and grasslands, savannahs, woodlands, and forests with continuous records of 4 to 12 years. Our analysis reveals site-specific patterns not identifiable in prior syntheses that pooled sites. We interpret temporal variability as an indicator of ecosystem response to annual water availability due to fast-changing factors such as leaf stomatal response and microbial activity, while cross-site spatial patterns are used to infer ecosystem adjustment to climatic water availability through slow-changing factors such as plant community and organic carbon pools. Using variance decomposition, we directly quantify how terrestrial carbon balance depends on slow- and fast-changing components of gross ecosystem production (GEP) and total ecosystem respiration (TER). Slow factors explain the majority of variance in annual net ecosystem production (NEP) across the dataset, and their relative importance is greater at wetter, forest sites than desert ecosystems. Site-specific offsets from spatial patterns of GEP and TER explain one third of NEP variance, likely due to slow-changing factors not directly linked to water, such as disturbance. TER and GEP are correlated across sites as previously shown, but our site-level analysis reveals surprisingly consistent linear relationships between these fluxes in deserts and savannahs, indicating fast coupling of TER and GEP in more arid ecosystems. Based on the uncertainty associated with slow and fast factors, we suggest a framework for improved prediction of terrestrial carbon balance. We will also present results of ongoing work to quantify fast and slow contributions to the relationship between evapotranspiration and precipitation across a precipitation gradient.

Biological and land use controls on the isotopic composition of aquatic carbon in the Upper Mississippi River Basin

NASA Astrophysics Data System (ADS)

Voss, Britta M.; Wickland, Kimberly P.; Aiken, George R.; Striegl, Robert G.

2017-08-01

Riverine ecosystems receive organic matter (OM) from terrestrial sources, internally produce new OM, and biogeochemically cycle and modify organic and inorganic carbon. Major gaps remain in the understanding of the relationships between carbon sources and processing in river systems. Here we synthesize isotopic, elemental, and molecular properties of dissolved organic carbon (DOC), particulate organic carbon (POC), and dissolved inorganic carbon (DIC) in the Upper Mississippi River (UMR) system above Wabasha, MN, including the main stem Mississippi River and its four major tributaries (Minnesota, upper Mississippi, St. Croix, and Chippewa Rivers). Our goal was to elucidate how biological processing modifies the chemical and isotopic composition of aquatic carbon pools during transport downstream in a large river system with natural and man-made impoundments. Relationships between land cover and DOC carbon-isotope composition, absorbance, and hydrophobic acid content indicate that DOC retains terrestrial carbon source information, while the terrestrial POC signal is largely replaced by autochthonous organic matter, and DIC integrates the influence of in-stream photosynthesis and respiration of organic matter. The UMR is slightly heterotrophic throughout the year, but pools formed by low-head navigation dams and natural impoundments promote a shift toward autotrophic conditions, altering aquatic ecosystem dynamics and POC and DIC compositions. Such changes likely occur in all major river systems affected by low-head dams and need to be incorporated into our understanding of inland water carbon dynamics and processes controlling CO2 emissions from rivers, as new navigation and flood control systems are planned for future river and water resources management.

Biological and land use controls on the isotopic composition of aquatic carbon in the Upper Mississippi River Basin

USGS Publications Warehouse

Voss, Britta; Wickland, Kimberly P.; Aiken, George R.; Striegl, Robert G.

2017-01-01

Riverine ecosystems receive organic matter (OM) from terrestrial sources, internally produce new OM, and biogeochemically cycle and modify organic and inorganic carbon. Major gaps remain in the understanding of the relationships between carbon sources and processing in river systems. Here we synthesize isotopic, elemental, and molecular properties of dissolved organic carbon (DOC), particulate organic carbon (POC), and dissolved inorganic carbon (DIC) in the Upper Mississippi River (UMR) system above Wabasha, MN, including the main stem Mississippi River and its four major tributaries (Minnesota, upper Mississippi, St. Croix, and Chippewa Rivers). Our goal was to elucidate how biological processing modifies the chemical and isotopic composition of aquatic carbon pools during transport downstream in a large river system with natural and man-made impoundments. Relationships between land cover and DOC carbon-isotope composition, absorbance, and hydrophobic acid content indicate that DOC retains terrestrial carbon source information, while the terrestrial POC signal is largely replaced by autochthonous organic matter, and DIC integrates the influence of in-stream photosynthesis and respiration of organic matter. The UMR is slightly heterotrophic throughout the year, but pools formed by low-head navigation dams and natural impoundments promote a shift towards autotrophic conditions, altering aquatic ecosystem dynamics and POC and DIC composition. Such changes likely occur in all major river systems affected by low-head dams and need to be incorporated into our understanding of inland water carbon dynamics and processes controlling CO2 emissions from rivers, as new navigation and flood control systems are planned for future river and water resources management.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Campbell, J. E.; Berry, J. A.; Seibt, U.

Growth in terrestrial gross primary production (GPP) may provide a feedback for climate change, but there is still strong disagreement on the extent to which biogeochemical processes may suppress this GPP growth at the ecosystem to continental scales. The consequent uncertainty in modeling of future carbon storage by the terrestrial biosphere constitutes one of the largest unknowns in global climate projections for the next century. Here we provide a global, measurement-based estimate of historical GPP growth using long-term atmospheric carbonyl sulfide (COS) records derived from ice core, firn, and ambient air samples. We interpret these records using a model thatmore » relates changes in the COS concentration to changes in its sources and sinks, the largest of which is proportional to GPP. The COS history was most consistent with simulations that assume a large historical GPP growth. Carbon-climate models that assume little to no GPP growth predicted trajectories of COS concentration over the anthropogenic era that differ from those observed. Continued COS monitoring may be useful for detecting ongoing changes in GPP while extending the ice core record to glacial cycles could provide further opportunities to evaluate earth system models.« less

Impact of changes in GRACE derived terrestrial water storage on vegetation growth in Eurasia

NASA Astrophysics Data System (ADS)

A, G.; Velicogna, I.; Kimball, J. S.; Kim, Y.

2015-12-01

We use GRACE-derived terrestrial water storage (TWS) and ERA-interim air temperature, as proxy for available water and temperature constraints on vegetation productivity, inferred from MODIS satellite normalized difference vegetation index (NDVI), in Northern Eurasia during 2002-2011. We investigate how changes in TWS affect the correlation between NDVI and temperature during the non-frozen season. We find that vegetation growth exhibits significant spatial and temporal variability associated with varying trend in TWS and temperature. The largest NDVI gains occur over boreal forests associated with warming and wetting. The largest NDVI losses occur over grasslands in the Southwestern Ob associated with regional drying and cooling, with dominant constraint from TWS. Over grasslands and temperate forests in the Southeast Ob and South Yenisei, wetting and cooling lead to a dominant temperature constraint due to the relaxation of TWS constraints. Overall, we find significant monthly correlation of NDVI with TWS and temperature over 35% and 50% of the domain, respectively. These results indicate that water availability (TWS) plays a major role in modulating Eurasia vegetation response to temperature changes.

Controls on terrestrial carbon feedbacks by productivity versus turnover in the CMIP5 Earth System Models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koven, C. D.; Chambers, J. Q.; Georgiou, K.

To better understand sources of uncertainty in projections of terrestrial carbon cycle feedbacks, we present an approach to separate the controls on modeled carbon changes. We separate carbon changes into four categories using a linearized, equilibrium approach: those arising from changed inputs (productivity-driven changes), and outputs (turnover-driven changes), of both the live and dead carbon pools. Using Coupled Model Intercomparison Project Phase 5 (CMIP5) simulations for five models, we find that changes to the live pools are primarily explained by productivity-driven changes, with only one model showing large compensating changes to live carbon turnover times. For dead carbon pools, themore » situation is more complex as all models predict a large reduction in turnover times in response to increases in productivity. This response arises from the common representation of a broad spectrum of decomposition turnover times via a multi-pool approach, in which flux-weighted turnover times are faster than mass-weighted turnover times. This leads to a shift in the distribution of carbon among dead pools in response to changes in inputs, and therefore a transient but long-lived reduction in turnover times. Since this behavior, a reduction in inferred turnover times resulting from an increase in inputs, is superficially similar to priming processes, but occurring without the mechanisms responsible for priming, we call the phenomenon "false priming", and show that it masks much of the intrinsic changes to dead carbon turnover times as a result of changing climate. These patterns hold across the fully coupled, biogeochemically coupled, and radiatively coupled 1 % yr −1 increasing CO 2 experiments. We disaggregate inter-model uncertainty in the globally integrated equilibrium carbon responses to initial turnover times, initial productivity, fractional changes in turnover, and fractional changes in productivity. For both the live and dead carbon pools, inter-model spread in carbon changes arising from initial conditions is dominated by model disagreement on turnover times, whereas inter-model spread in carbon changes from fractional changes to these terms is dominated by model disagreement on changes to productivity in response to both warming and CO 2 fertilization. However, the lack of changing turnover time control on carbon responses, for both live and dead carbon pools, in response to the imposed forcings may arise from a common lack of process representation behind changing turnover times (e.g., allocation and mortality for live carbon; permafrost, microbial dynamics, and mineral stabilization for dead carbon), rather than a true estimate of the importance of these processes.« less

Controls on terrestrial carbon feedbacks by productivity versus turnover in the CMIP5 Earth System Models

DOE PAGES

Koven, C. D.; Chambers, J. Q.; Georgiou, K.; ...

2015-09-07

To better understand sources of uncertainty in projections of terrestrial carbon cycle feedbacks, we present an approach to separate the controls on modeled carbon changes. We separate carbon changes into four categories using a linearized, equilibrium approach: those arising from changed inputs (productivity-driven changes), and outputs (turnover-driven changes), of both the live and dead carbon pools. Using Coupled Model Intercomparison Project Phase 5 (CMIP5) simulations for five models, we find that changes to the live pools are primarily explained by productivity-driven changes, with only one model showing large compensating changes to live carbon turnover times. For dead carbon pools, themore » situation is more complex as all models predict a large reduction in turnover times in response to increases in productivity. This response arises from the common representation of a broad spectrum of decomposition turnover times via a multi-pool approach, in which flux-weighted turnover times are faster than mass-weighted turnover times. This leads to a shift in the distribution of carbon among dead pools in response to changes in inputs, and therefore a transient but long-lived reduction in turnover times. Since this behavior, a reduction in inferred turnover times resulting from an increase in inputs, is superficially similar to priming processes, but occurring without the mechanisms responsible for priming, we call the phenomenon "false priming", and show that it masks much of the intrinsic changes to dead carbon turnover times as a result of changing climate. These patterns hold across the fully coupled, biogeochemically coupled, and radiatively coupled 1 % yr −1 increasing CO 2 experiments. We disaggregate inter-model uncertainty in the globally integrated equilibrium carbon responses to initial turnover times, initial productivity, fractional changes in turnover, and fractional changes in productivity. For both the live and dead carbon pools, inter-model spread in carbon changes arising from initial conditions is dominated by model disagreement on turnover times, whereas inter-model spread in carbon changes from fractional changes to these terms is dominated by model disagreement on changes to productivity in response to both warming and CO 2 fertilization. However, the lack of changing turnover time control on carbon responses, for both live and dead carbon pools, in response to the imposed forcings may arise from a common lack of process representation behind changing turnover times (e.g., allocation and mortality for live carbon; permafrost, microbial dynamics, and mineral stabilization for dead carbon), rather than a true estimate of the importance of these processes.« less

Generation and migration of petroleum in the Mahakam delta, Indonesia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Durand, B.; Bessereau, G.; Doligez, B.

1988-08-01

The Mahakam delta, located east of Kalimantan, Indonesia, contains sediments of Miocene-Pliocene age. Their thickness may reach more than 8,000 m in places, and sections which have been drilled are generally overpressured below 3,000 to 4,000 m. Petroleum was formed essentially from a kerogen originating in terrestrial land plants grown in an equatorial climate. The kerogen may occur either dispersed in clays or concentrated in humic coal beds. Petroleum potential (oil and gas) of this kerogen at the beginning of catagenesis is 200-250 mg HC/g organic carbon on the average (as measured by Rock-Eval pyrolysis) but is highly variable aroundmore » this mean value (100-400 mg HC/g organic carbon approximately). Although the kerogen is of terrestrial origin, the kerogen-containing sediments have the capacity to produce and expel oil at depth, as shown by large quantities of oil pooled in sandy reservoirs together with gas in a relatively small area. Depth of top oil kitchen varies from 2,500 to 4,000 m and is greater in synclines than on top of structures. Present isotherms follow more or less the same pattern. Migration is very recent and is till at work. Light hydrocarbons have migrated farther from their source than heavy ones did. Thus condensate in pooled gas and the density of pooled oil tend to increase with depth. These variations of oil and gas compositions along secondary and tertiary migration routes are likely to be provoked by evaporative fractionation processes.« less

Consequences of simulating terrestrial N dynamics for projecting future terrestrial C storage

NASA Astrophysics Data System (ADS)

Zaehle, S.; Friend, A. D.; Friedlingstein, P.

2009-04-01

We present results of a new land surface model, O-CN, which includes a process-based coupling between the terrestrial cycling of energy, water, carbon, and nitrogen. The model represents the controls of the terrestrial nitrogen (N) cycling on carbon (C) pools and fluxes through photosynthesis, respiration, changes in allocation patterns, as well as soil organic matter decomposition, and explicitly accounts for N leaching and gaseous losses. O-CN has been shown to give realistic results in comparison to observations at a wide range of scales, including in situ flux measurements, productivity databases, and atmospheric CO2 concentration data. Notably, O-CN simulates realistic responses of net primary productivity, foliage area, and foliage N content to elevated atmospheric [CO2] as evidenced at free air carbon dioxide enrichment (FACE) sites (Duke, Oak Ridge). We re-examine earlier model-based assessments of the terrestrial C sequestration potential using a global transient O-CN simulation driven by increases in atmospheric [CO2], N deposition and climatic changes over the 21st century. We find that accounting for terrestrial N cycling about halves the potential to store C in response to increases in atmospheric CO2 concentrations; mainly due to a reduction of the net C uptake in temperate and boreal forests. Nitrogen deposition partially alleviates the effect of N limitation, but is by far not sufficient to compensate for the effect completely. These findings underline the importance of an accurate representation of nutrient limitations in future projections of the terrestrial net CO2 exchanges and therefore land-climate feedback studies.

Networking our science to characterize the state, vulnerabilities, and management opportunities of soil organic matter.

PubMed

Harden, Jennifer W; Hugelius, Gustaf; Ahlström, Anders; Blankinship, Joseph C; Bond-Lamberty, Ben; Lawrence, Corey R; Loisel, Julie; Malhotra, Avni; Jackson, Robert B; Ogle, Stephen; Phillips, Claire; Ryals, Rebecca; Todd-Brown, Katherine; Vargas, Rodrigo; Vergara, Sintana E; Cotrufo, M Francesca; Keiluweit, Marco; Heckman, Katherine A; Crow, Susan E; Silver, Whendee L; DeLonge, Marcia; Nave, Lucas E

2018-02-01

Soil organic matter (SOM) supports the Earth's ability to sustain terrestrial ecosystems, provide food and fiber, and retains the largest pool of actively cycling carbon. Over 75% of the soil organic carbon (SOC) in the top meter of soil is directly affected by human land use. Large land areas have lost SOC as a result of land use practices, yet there are compensatory opportunities to enhance productivity and SOC storage in degraded lands through improved management practices. Large areas with and without intentional management are also being subjected to rapid changes in climate, making many SOC stocks vulnerable to losses by decomposition or disturbance. In order to quantify potential SOC losses or sequestration at field, regional, and global scales, measurements for detecting changes in SOC are needed. Such measurements and soil-management best practices should be based on well established and emerging scientific understanding of processes of C stabilization and destabilization over various timescales, soil types, and spatial scales. As newly engaged members of the International Soil Carbon Network, we have identified gaps in data, modeling, and communication that underscore the need for an open, shared network to frame and guide the study of SOM and SOC and their management for sustained production and climate regulation. © 2017 The Authors. Global Change Biology Published by John Wiley & Sons Ltd.

Estimation of soil organic carbon in forests of the United States

NASA Astrophysics Data System (ADS)

Domke, G. M.; Perry, C. H.; Walters, B. F.; Woodall, C. W.; Nave, L. E.; Swanston, C.

2015-12-01

Soil organic carbon (SOC) is the largest terrestrial carbon (C) sink on earth and management of this pool is a critical component of global efforts to mitigate atmospheric C concentrations. Soil organic carbon is also a key indicator of soil quality as it affects essential biological, chemical, and physical soil functions such as nutrient cycling, water retention, and soil structure maintenance. Much of the SOC on earth is found in forest ecosystems and is thought to be relatively stable. That said, there is growing evidence that SOC may be sensitive to disturbance and global change drivers. In the United States (US), SOC in forests is monitored by the national forest inventory (NFI) conducted by the Forest Inventory and Analysis (FIA) program within the US Department of Agriculture, Forest Service. The FIA program currently uses SOC predictions based on SSURGO/STATSGO data to populate the NFI. Most of estimates of SOC in forests from the SSURGO/STATSGO data are based primarily upon expert opinion and lack systematic field observations. The FIA program has been consistently measuring soil attributes as part of the NFI since 2001 and has amassed an extensive inventory of SOC in forests in the conterminous US and coastal Alaska. Here we present estimates of SOC obtained using data from the NFI and International Soil Carbon Network and describe the modeling framework used to compile estimates for United Nations Framework Convention on Climate Change reporting.

Why do orangutans leave the trees? Terrestrial behavior among wild Bornean orangutans (Pongo pygmaeus wurmbii) at Tuanan, Central Kalimantan.

PubMed

Ashbury, Alison M; Posa, Mary Rose C; Dunkel, Lynda P; Spillmann, Brigitte; Atmoko, S Suci Utami; van Schaik, Carel P; van Noordwijk, Maria A

2015-11-01

Orangutans (genus Pongo) are the largest arboreal mammals, but Bornean orangutans (P. pygmaeus spp.) also spend time on the ground. Here, we investigate ground use among orangutans using 32,000 hr of direct focal animal observations from a well-habituated wild population of Bornean orangutans (P. p. wurmbii) living in a closed-canopy swamp forest at Tuanan, Central Kalimantan, Indonesia. Ground use did not change with increasing observation time of well-habituated individuals, suggesting it was not an artifact of observer presence. Flanged males spent the most time on the ground (ca. 5% of active time), weaned immatures the least (around 1%). Females and immatures descended mainly to feed, especially on termites, whereas flanged males traveled more while on the ground. Flanged males may travel more inconspicuously, and perhaps also faster, when moving on the ground. In addition, orangutans engaged in ground-specific behavior, including drinking from and bathing in swamp pools. Supplementary records from 20 ground-level camera traps, totaling 3986 trap days, confirmed the observed age-sex biases in ground use at Tuanan. We conclude that ground use is a natural part of the Bornean orangutan behavioral repertoire, however it remains unclear to what extent food scarcity and canopy structure explain population differences in ground use. © 2015 Wiley Periodicals, Inc.

The age of the meteorite recovery surfaces of Roosevelt County, New Mexico, USA

NASA Technical Reports Server (NTRS)

Zolensky, Michael E.; Rendell, Helen M.; Wilson, Ivan; Wells, Gordon L.

1992-01-01

We have obtained minimum age estimates for the sand units underlying the two largest meteorite deflation surfaces in Roosevelt County, New Mexico, USA, using thermoluminescence dating techniques. The dates obtained ranged from 53.5 (+/- 5.4) to 95.2 (+/- 9.5) ka, and must be considered lower limits for the terrestrial ages of the meteorites found within these specific deflation surfaces. These ages greatly exceed previous measurements from adjacent meteorite-producing deflation basins. We find that Roosevelt County meteorites are probably terrestrial contemporaries of the meteorites found at most accumulation zones in Antarctica. The apparent high meteorite accumulation rate reported for Roosevelt County by Zolensky et al. (1990) is incorrect, as it used an age of 16 ka for all Roosevelt County recovery surfaces. We conclude that the extreme variability of terrestrial ages of the Roosevelt County deflation surfaces effectively precludes their use for calculations of the meteorite accumulation rate at the Earth's surface.

Hidden dental diversity in the oldest terrestrial apex predator Dimetrodon.

PubMed

Brink, Kirstin S; Reisz, Robert R

2014-01-01

Paleozoic sphenacodontid synapsids are the oldest known fully terrestrial apex predators. Dimetrodon and other sphenacodontids are the first terrestrial vertebrates to have strong heterodonty, massive skulls and well-developed labio-lingually compressed and recurved teeth with mesial and distal cutting edges (carinae). Here we reveal that the dentition of Dimetrodon and other sphenacodontids is diverse. Tooth morphology includes simple carinae with smooth cutting edges and elaborate enamel features, including the first occurrence of cusps and true denticles (ziphodonty) in the fossil record. A time-calibrated phylogenetic analysis indicates that changes in dental morphology occur in the absence of any significant changes in skull morphology, suggesting that the morphological change is associated with changes in feeding style and trophic interactions in these ecosystems. In addition, the available evidence indicates that ziphodonty evolved for the first time in the largest known species of the genus Dimetrodon and independently from the ziphodont teeth observed in some therapsids.

Processes regulating progressive nitrogen limitation under elevated carbon dioxide: A meta-analysis

DOE PAGES

Liang, Junyi; Qi, Xuan; Souza, Lara; ...

2016-05-10

Here, the nitrogen (N) cycle has the potential to regulate climate change through its influence on carbon (C) sequestration. Although extensive research has explored whether or not progressive N limitation (PNL) occurs under CO 2 enrichment, a comprehensive assessment of the processes that regulate PNL is still lacking. Here, we quantitatively synthesized the responses of all major processes and pools in the terrestrial N cycle with meta-analysis of CO 2 experimental data available in the literature. The results showed that CO 2 enrichment significantly increased N sequestration in the plant and litter pools but not in the soil pool, partiallymore » supporting one of the basic assumptions in the PNL hypothesis that elevated CO 2 results in more N sequestered in organic pools. However, CO 2 enrichment significantly increased the N influx via biological N fixation and the loss via N 2O emission, but decreased the N efflux via leaching. In addition, no general diminished CO 2 fertilization effect on plant growth was observed over time up to the longest experiment of 13 years. Overall, our analyses suggest that the extra N supply by the increased biological N fixation and decreased leaching may potentially alleviate PNL under elevated CO 2 conditions in spite of the increases in plant N sequestration and N 2O emission. Moreover, our syntheses indicate that CO 2 enrichment increases soil ammonium (NH 4 +) to nitrate (NO 3 –) ratio. The changed NH 4 +/NO 3 – ratio and subsequent biological processes may result in changes in soil microenvironments, above-belowground community structures and associated interactions, which could potentially affect the terrestrial biogeochemical cycles. In addition, our data synthesis suggests that more long-term studies, especially in regions other than temperate ones, are needed for comprehensive assessments of the PNL hypothesis.« less

Changes in Carbon Chemistry and Stability Along Deep Tropical Soil Profiles at the Luquillo Critical Zone Observatory

NASA Astrophysics Data System (ADS)

Stone, M.; Hockaday, W. C.; Plante, A. F.

2014-12-01

Tropical forests are the largest terrestrial carbon (C) sink, and tropical forest soils contribute disproportionately to the poorly-characterized deep soil C pool. The goal of this study was to evaluate how carbon chemistry and stability change with depth in tropical forest soils formed on two contrasting parent materials. We used soils from pits excavated to 140 cm depth that were stratified across two soil types (Oxisols and Inceptisols) at the Luquillo Critical Zone Observatory in northeast Puerto Rico. We used 13C nuclear magnetic resonance (NMR) spectroscopy to characterize soil C chemistry and differential scanning calorimetry (DSC) coupled with evolved gas analysis (CO2-EGA) to evaluate the thermal stability of soil C during ramped combustion. Thirty-four samples with an initial C concentration ≥1% were chosen from discrete depth intervals (0, 30, 60, 90 & 140 cm) for 13C NMR analysis, while DSC was performed on 122 samples that included the NMR sample set and additional samples at 20, 50, 80 and 110 cm depth. Preliminary 13C NMR results indicate higher alkyl : O-alkyl ratios and an enrichment of aliphatic and proteinaceous C with depth, compared with greater aromatic and carbohydrate signals in surface soils. The energy density of soil C (J mg-1 C) also declined significantly with depth. In Oxisols, most CO2 evolution from combustion occurred around 300ºC, while most CO2 evolution occurred at higher temperatures (400-500ºC) in Inceptisols. Our findings suggest soil C is derived primarily of plant biomolecules in surface soils and becomes increasingly microbial with depth. Soil matrix-mediated differences in C transport and preservation may result in differences in C chemistry between the two soil types and a more thermally labile C pool in the Oxisols. We suggest that energy-poor substrates, combined with potentially stronger organo-mineral interactions in subsoils, may explain the long-term stability of deep C in highly weathered tropical soils.

Vulnerability of permafrost carbon to climate change: implications for the global carbon cycle

Treesearch

Edward A.G. Schuur; James Bockheim; Josep G. Canadell; Eugenie Euskirchen; Christopher B. Field; Sergey V. Goryachkin; Stefan Hagemann; Peter Kuhry; Peter M. Lafleur; Hanna Lee; Galina Mazhitova; Frederick E. Nelson; Annette Rinke; Vladimir E. Romanovsky; Nikolay Shiklomanov; Charles Tarnocai; Sergey Venevsky; Jason G. Vogel; Sergei A. Zimov

2008-01-01

Thawing permafrost and the resulting microbial decomposition of previously frozen organic carbon (C) is one of the most significant potential feedbacks from terrestrial ecosystems to the atmosphere in a changing climate. In this article we present an overview of the global permafrost C pool and of the processes that might transfer this C into the atmosphere, as well as...

Regional carbon cycle responses to 25 years of variation in climate and disturbance in the US Pacific Northwest

Treesearch

David P. Turner; William D. Ritts; Robert E. Kennedy; Andrew N. Gray; Zhiqiang Yang

2016-01-01

Variation in climate, disturbance regime, and forest management strongly influence terrestrial carbon sources and sinks. Spatially distributed, process-based, carbon cycle simulation models provide a means to integrate information on these various influences to estimate carbon pools and flux over large domains. Here we apply the Biome-BGC model over the four-state...

Effects of model structural uncertainty on carbon cycle projections: biological nitrogen fixation as a case study

NASA Astrophysics Data System (ADS)

Wieder, William R.; Cleveland, Cory C.; Lawrence, David M.; Bonan, Gordon B.

2015-04-01

Uncertainties in terrestrial carbon (C) cycle projections increase uncertainty of potential climate feedbacks. Efforts to improve model performance often include increased representation of biogeochemical processes, such as coupled carbon-nitrogen (N) cycles. In doing so, models are becoming more complex, generating structural uncertainties in model form that reflect incomplete knowledge of how to represent underlying processes. Here, we explore structural uncertainties associated with biological nitrogen fixation (BNF) and quantify their effects on C cycle projections. We find that alternative plausible structures to represent BNF result in nearly equivalent terrestrial C fluxes and pools through the twentieth century, but the strength of the terrestrial C sink varies by nearly a third (50 Pg C) by the end of the twenty-first century under a business-as-usual climate change scenario representative concentration pathway 8.5. These results indicate that actual uncertainty in future C cycle projections may be larger than previously estimated, and this uncertainty will limit C cycle projections until model structures can be evaluated and refined.

Resources and energetics determined dinosaur maximal size

PubMed Central

McNab, Brian K.

2009-01-01

Some dinosaurs reached masses that were ≈8 times those of the largest, ecologically equivalent terrestrial mammals. The factors most responsible for setting the maximal body size of vertebrates are resource quality and quantity, as modified by the mobility of the consumer, and the vertebrate's rate of energy expenditure. If the food intake of the largest herbivorous mammals defines the maximal rate at which plant resources can be consumed in terrestrial environments and if that limit applied to dinosaurs, then the large size of sauropods occurred because they expended energy in the field at rates extrapolated from those of varanid lizards, which are ≈22% of the rates in mammals and 3.6 times the rates of other lizards of equal size. Of 2 species having the same energy income, the species that uses the most energy for mass-independent maintenance of necessity has a smaller size. The larger mass found in some marine mammals reflects a greater resource abundance in marine environments. The presumptively low energy expenditures of dinosaurs potentially permitted Mesozoic communities to support dinosaur biomasses that were up to 5 times those found in mammalian herbivores in Africa today. The maximal size of predatory theropods was ≈8 tons, which if it reflected the maximal capacity to consume vertebrates in terrestrial environments, corresponds in predatory mammals to a maximal mass less than a ton, which is what is observed. Some coelurosaurs may have evolved endothermy in association with the evolution of feathered insulation and a small mass. PMID:19581600

Resources and energetics determined dinosaur maximal size.

PubMed

McNab, Brian K

2009-07-21

Some dinosaurs reached masses that were approximately 8 times those of the largest, ecologically equivalent terrestrial mammals. The factors most responsible for setting the maximal body size of vertebrates are resource quality and quantity, as modified by the mobility of the consumer, and the vertebrate's rate of energy expenditure. If the food intake of the largest herbivorous mammals defines the maximal rate at which plant resources can be consumed in terrestrial environments and if that limit applied to dinosaurs, then the large size of sauropods occurred because they expended energy in the field at rates extrapolated from those of varanid lizards, which are approximately 22% of the rates in mammals and 3.6 times the rates of other lizards of equal size. Of 2 species having the same energy income, the species that uses the most energy for mass-independent maintenance of necessity has a smaller size. The larger mass found in some marine mammals reflects a greater resource abundance in marine environments. The presumptively low energy expenditures of dinosaurs potentially permitted Mesozoic communities to support dinosaur biomasses that were up to 5 times those found in mammalian herbivores in Africa today. The maximal size of predatory theropods was approximately 8 tons, which if it reflected the maximal capacity to consume vertebrates in terrestrial environments, corresponds in predatory mammals to a maximal mass less than a ton, which is what is observed. Some coelurosaurs may have evolved endothermy in association with the evolution of feathered insulation and a small mass.

Constant replenishment from circulating monocytes maintains the macrophage pool in adult intestine

PubMed Central

Scott, Charlotte L.; Perdiguero, Elisa Gomez; Geissmann, Frederic; Henri, Sandrine; Malissen, Bernard; Osborne, Lisa C.; Artis, David; Mowat, Allan McI.

2014-01-01

The paradigm that resident macrophages in steady-state tissues are derived from embryonic precursors has never been investigated in the intestine, which contains the largest pool of macrophages. Using fate mapping models and monocytopenic mice, together with bone marrow chimeric and parabiotic models, we show that embryonic precursors seeded the intestinal mucosa and demonstrated extensive in situ proliferation in the neonatal period. However these cells did not persist in adult intestine. Instead, they were replaced around the time of weaning by the CCR2-dependent influx of Ly6Chi monocytes that differentiated locally into mature, anti-inflammatory macrophages. This process was driven largely by the microbiota and had to be continued throughout adult life to maintain a normal intestinal macrophage pool. PMID:25151491

Aquatic CAM photosynthesis: a brief history of its discovery

USGS Publications Warehouse

Keeley, Jon E.

2014-01-01

Aquatic CAM (Crassulacean Acid Metabolism) photosynthesis was discovered while investigating an unrelated biochemical pathway concerned with anaerobic metabolism. George Bowes was a significant contributor to this project early in its infancy. Not only did he provide me with some valuable perspectives on peer review rejections, but by working with his gas exchange system I was able to take our initial observations of diel fluctuations in malic acid to the next level, showing this aquatic plant exhibited dark CO2 uptake. CAM is universal in all aquatic species of the worldwide Lycophyta genus Isoetes and non-existent in terrestrial Isoetes. Outside of this genus aquatic CAM has a limited occurrence in three other families, including the Crassulaceae. This discovery led to fascinating adventures in the highlands of the Peruvian Andes in search of Stylites, a terrestrial relative of Isoetes. Stylites is a plant that is hermetically sealed from the atmosphere and obtains all of its carbon from terrestrial sources and recycles carbon through CAM. Considering the Mesozoic origin of Isoetes in shallow pools, coupled with the fact that aquatic Isoetes universally possess CAM, suggests the earliest evolution of CAM photosynthesis was most likely not in terrestrial plants.

Measurement of soil carbon oxidation state and oxidative ratio by 13C nuclear magnetic resonance

USGS Publications Warehouse

Hockaday, W.C.; Masiello, C.A.; Randerson, J.T.; Smernik, R.J.; Baldock, J.A.; Chadwick, O.A.; Harden, J.W.

2009-01-01

The oxidative ratio (OR) of the net ecosystem carbon balance is the ratio of net O2 and CO2 fluxes resulting from photosynthesis, respiration, decomposition, and other lateral and vertical carbon flows. The OR of the terrestrial biosphere must be well characterized to accurately estimate the terrestrial CO2 sink using atmospheric measurements of changing O2 and CO2 levels. To estimate the OR of the terrestrial biosphere, measurements are needed of changes in the OR of aboveground and belowground carbon pools associated with decadal timescale disturbances (e.g., land use change and fire). The OR of aboveground pools can be measured using conventional approaches including elemental analysis. However, measuring the OR of soil carbon pools is technically challenging, and few soil OR data are available. In this paper we test three solid-state nuclear magnetic resonance (NMR) techniques for measuring soil OR, all based on measurements of the closely related parameter, organic carbon oxidation state (Cox). Two of the three techniques make use of a molecular mixing model which converts NMR spectra into concentrations of a standard suite of biological molecules of known C ox. The third technique assigns Cox values to each peak in the NMR spectrum. We assess error associated with each technique using pure chemical compounds and plant biomass standards whose Cox and OR values can be directly measured by elemental analyses. The most accurate technique, direct polarization solid-state 13C NMR with the molecular mixing model, agrees with elemental analyses to ??0.036 Cox units (??0.009 OR units). Using this technique, we show a large natural variability in soil Cox and OR values. Soil Cox values have a mean of -0.26 and a range from -0.45 to 0.30, corresponding to OR values of 1.08 ?? 0.06 and a range from 0.96 to 1.22. We also estimate the OR of the carbon flux from a boreal forest fire. Analysis of soils from nearby intact soil profiles imply that soil carbon losses associated with the fire had an OR of 1.091 (??0.003). Fire appears to be a major factor driving the soil C pool to higher oxidation states and lower OR values. Episodic fluxes caused by disturbances like fire may have substantially different ORs from ecosystem respiration fluxes and therefore should be better quantified to reduce uncertainties associated with our understanding of the global atmospheric carbon budget. Copyright 2009 by the American Geophysical Union.

High-severity wildfire effects on carbon stocks and emissions in fuels treated and untreated forest

Treesearch

Malcolm P. North; Matthew D. Hurteau

2011-01-01

Forests contain the world's largest terrestrial carbonstocks, but in seasonally dry environments stock stability can be compromised if burned by wildfire, emitting carbon back to the atmosphere. Treatments to reduce wildfireseverity can reduce emissions, but with an immediate cost of reducing carbonstocks. In this study we examine the tradeoffs in...

Global spread and control of avian influenza

USDA-ARS?s Scientific Manuscript database

H5 and H7 high pathogenicity avian influenza (HPAI) viruses emerge from the mutation of H5 and H7 low pathogenicity avian influenza viruses (LPAI) after circulation in terrestrial poultry for a few weeks to years. There have been 42 distinct HPAI epizootics since 1959. The largest being the H5N1 A/G...

Biophysical control of whole tree transpiration under an urban environment in Northern China

Treesearch

Lixin Chen; Zhiqiang Zhang; Zhandong Li; Jianwu Tang; Peter Caldwell; et al

2011-01-01

Urban reforestation in China has led to increasing debate about the impact of urban trees and forests on water resources. Although transpiration is the largest water flux leaving terrestrial ecosystems, little is known regarding whole tree transpiration in urban environments. In this study, we quantified urban tree transpiration at various temporal scales and examined...

Community College Alumni: Predicting Who Gives

ERIC Educational Resources Information Center

Skari, Lisa Ann

2014-01-01

Due to the decrease in public funding, community colleges are in a position where they need to generate private gifts. Alumni represent the largest untapped pool of prospective donors, and the success of alumni giving at 4-year institutions illustrates the potential that exists for community colleges. To develop effective fundraising strategies,…

Carbon and nitrogen balances for six shrublands across Europe

NASA Astrophysics Data System (ADS)

Beier, Claus; Emmett, Bridget A.; Tietema, Albert; Schmidt, Inger K.; PeñUelas, Josep; LáNg, Edit KováCs; Duce, Pierpaolo; de Angelis, Paolo; Gorissen, Antonie; Estiarte, Marc; de Dato, Giovanbattista D.; Sowerby, Alwyn; KröEl-Dulay, GyöRgy; Lellei-KováCs, Eszter; Kull, Olevi; Mand, Pille; Petersen, Henning; Gjelstrup, Peter; Spano, Donatella

2009-12-01

Shrublands constitute significant and important parts of European landscapes providing a large number of important ecosystem services. Biogeochemical cycles in these ecosystems have gained little attention relative to forests and grassland systems, but data on such cycles are required for developing and testing ecosystem models. As climate change progresses, the potential feedback from terrestrial ecosystems to the atmosphere through changes in carbon stocks, carbon sequestration, and general knowledge on biogeochemical cycles becomes increasingly important. Here we present carbon and nitrogen balances of six shrublands along a climatic gradient across the European continent. The aim of the study was to provide a basis for assessing the range and variability in carbon storage in European shrublands. Across the sites the net carbon storage in the systems ranged from 1,163 g C m-2 to 18,546 g C m-2, and the systems ranged from being net sinks (126 g C m-2 a-1) to being net sources (-536 g C m-2 a-1) of carbon with the largest storage and sink of carbon at wet and cold climatic conditions. The soil carbon store dominates the carbon budget at all sites and in particular at the site with a cold and wet climate where soil C constitutes 95% of the total carbon in the ecosystem. Respiration of carbon from the soil organic matter pool dominated the carbon loss at all sites while carbon loss from aboveground litter decomposition appeared less important. Total belowground carbon allocation was more than 5 times aboveground litterfall carbon which is significantly greater than the factor of 2 reported in a global analysis of forest data. Nitrogen storage was also dominated by the soil pools generally showing small losses except when atmospheric N input was high. The study shows that in the future a climate-driven land cover change between grasslands and shrublands in Europe will likely lead to increased ecosystem C where shrublands are promoted and less where grasses are promoted. However, it also emphasizes that if feedbacks on the global carbon cycle are to be predicted it is critically important to quantify and understand belowground carbon allocation and processes as well as soil carbon pools, particularly on wet organic soils, rather than plant functional change as the soil stores dominate the overall budget and fluxes of carbon.

Assessing the effect of elevated carbon dioxide on soil carbon: a comparison of four meta-analyses.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hungate, B. A.; van Groenigen, K.; Six, J.

2009-08-01

Soil is the largest reservoir of organic carbon (C) in the terrestrial biosphere and soil C has a relatively long mean residence time. Rising atmospheric carbon dioxide (CO{sub 2}) concentrations generally increase plant growth and C input to soil, suggesting that soil might help mitigate atmospheric CO{sub 2} rise and global warming. But to what extent mitigation will occur is unclear. The large size of the soil C pool not only makes it a potential buffer against rising atmospheric CO{sub 2}, but also makes it difficult to measure changes amid the existing background. Meta-analysis is one tool that can overcomemore » the limited power of single studies. Four recent meta-analyses addressed this issue but reached somewhat different conclusions about the effect of elevated CO{sub 2} on soil C accumulation, especially regarding the role of nitrogen (N) inputs. Here, we assess the extent of differences between these conclusions and propose a new analysis of the data. The four meta-analyses included different studies, derived different effect size estimates from common studies, used different weighting functions and metrics of effect size, and used different approaches to address nonindependence of effect sizes. Although all factors influenced the mean effect size estimates and subsequent inferences, the approach to independence had the largest influence. We recommend that meta-analysts critically assess and report choices about effect size metrics and weighting functions, and criteria for study selection and independence. Such decisions need to be justified carefully because they affect the basis for inference. Our new analysis, with a combined data set, confirms that the effect of elevated CO{sub 2} on net soil C accumulation increases with the addition of N fertilizers. Although the effect at low N inputs was not significant, statistical power to detect biogeochemically important effect sizes at low N is limited, even with meta-analysis, suggesting the continued need for long-term experiments.« less

Discrimination of communication vocalizations by single neurons and groups of neurons in the auditory midbrain.

PubMed

Schneider, David M; Woolley, Sarah M N

2010-06-01

Many social animals including songbirds use communication vocalizations for individual recognition. The perception of vocalizations depends on the encoding of complex sounds by neurons in the ascending auditory system, each of which is tuned to a particular subset of acoustic features. Here, we examined how well the responses of single auditory neurons could be used to discriminate among bird songs and we compared discriminability to spectrotemporal tuning. We then used biologically realistic models of pooled neural responses to test whether the responses of groups of neurons discriminated among songs better than the responses of single neurons and whether discrimination by groups of neurons was related to spectrotemporal tuning and trial-to-trial response variability. The responses of single auditory midbrain neurons could be used to discriminate among vocalizations with a wide range of abilities, ranging from chance to 100%. The ability to discriminate among songs using single neuron responses was not correlated with spectrotemporal tuning. Pooling the responses of pairs of neurons generally led to better discrimination than the average of the two inputs and the most discriminating input. Pooling the responses of three to five single neurons continued to improve neural discrimination. The increase in discriminability was largest for groups of neurons with similar spectrotemporal tuning. Further, we found that groups of neurons with correlated spike trains achieved the largest gains in discriminability. We simulated neurons with varying levels of temporal precision and measured the discriminability of responses from single simulated neurons and groups of simulated neurons. Simulated neurons with biologically observed levels of temporal precision benefited more from pooling correlated inputs than did neurons with highly precise or imprecise spike trains. These findings suggest that pooling correlated neural responses with the levels of precision observed in the auditory midbrain increases neural discrimination of complex vocalizations.

Gigantism, temperature and metabolic rate in terrestrial poikilotherms

PubMed Central

Makarieva, Anastassia M; Gorshkov, Victor G; Li, Bai-Lian

2005-01-01

The mechanisms dictating upper limits to animal body size are not well understood. We have analysed body length data for the largest representatives of 24 taxa of terrestrial poikilotherms from tropical, temperate and polar environments. We find that poikilothermic giants on land become two–three times shorter per each 10 degrees of decrease in ambient temperature. We quantify that this diminution of maximum body size accurately compensates the drop of metabolic rate dictated by lower temperature. This supports the idea that the upper limit to body size within each taxon can be set by a temperature-independent critical minimum value of mass-specific metabolic rate, a fall below which is not compatible with successful biological performance. PMID:16191647

Role of soil texture, clay mineralogy, location, and temperature in coarse wood decomposition - a mesocosm experiment

Treesearch

Cinzia Fissore; Martin F. Jurgensen; James Pickens; Chris Miller; Deborah Page-Dumroese; Christian P. Giardina

2016-01-01

Of all the major pools of terrestrial carbon (C), the dynamics of coarse woody debris (CWD) are the least understood. In contrast to soils and living vegetation, the study of CWD has rarely relied on ex situ methods for elaborating controls on decomposition rates. In this study, we report on a mesocosm incubation experiment examining how clay amount (8%, 16%,...

Terrestrial Carbon Fluxes from Deforestation in the Brazilian Amazon and Cerrado Regions Predicted from MODIS Satellite Data and Ecosystem Modeling

NASA Astrophysics Data System (ADS)

Klooster, S.; Potter, C.; Genovese, V.

2008-12-01

The NASA-CASA (Carnegie Ames Stanford Approach) simulation model based on satellite observations of monthly vegetation cover from the Moderate Resolution Imaging Spectroradiometer (MODIS) was used to estimate tropical forest and savanna (Cerrado) carbon pools for the Brazilian Amazon region over the period 2000-2004. Adjustments for mean age of forest stands were carried out across the region, resulting in a new mapping of aboveground biomass pools based on MODIS satellite data. Yearly maps of newly deforested lands from the Brazilian PRODES (Programa de calculo do desflorestamento da Amazonia ) project were combined with these NASA-CASA biomass predictions to generate seasonal budgets of potential carbon and nitrogen trace gas losses from biomass burning events. Simulations of plant residue and soil carbon decomposition were conducted in the NASA-CASA model during and following deforestation events to track the fate of aboveground biomass pools that were cut and burned each year across the region.

Large wood influence on stream metabolism at a reach-scale in the Assabet River, Massachusetts

NASA Astrophysics Data System (ADS)

David, G. C. L.; Snyder, N. P.; Rosario, G. M.

2016-12-01

Total stream metabolism (TSM) represents the transfer of carbon through a channel by both primary production and respiration, and thus represents the movement of energy through a watershed. Large wood (LW) creates geomorphically complex channels by diverting flows, altering shear stresses on the channel bed and banks, and pool development. The increase in habitat complexity around LW is expected to increase TSM, but this change has not been directly measured. In this study, we measured changes in TSM around a LW jam in a Massachusetts river. Dissolved oxygen (DO) time series data are used to quantify gross primary production (GPP), ecosystem respiration (ER), which equal TSM when summed. Two primary objectives of this study are to (1) assess changes in TSM around LW and (2) compare empirical methods of deriving TSM to Grace et al.'s (2015) BASE model. We hypothesized that LW would increase TSM by providing larger pools, increasing coverage for fish and macroinvertebrates, increasing organic matter accumulation, and providing a place for primary producers to anchor and grow. The Assabet River is a 78 km2 drainage basin in central Massachusetts that provides public water supply to 7 towns. A change in TSM over a reach-scale was assessed using two YSI 6-Series Multiparameter Water Quality sondes over a 140 m long pool-riffle open meadow section. The reach included 6 pools and one LW jam. Every two weeks from July to November 2015, the sondes were moved to different pools. The sondes collected DO, temperature, depth, pH, salinity, light intensity, and turbidity at 15-minute intervals. Velocity (V) and discharge (Q) were measured weekly around the sondes and at established cross sections. Instantaneous V and Q were calculated for each sonde by modeling flows in HEC-RAS. Overall, TSM was heavily influenced by the pool size and indirectly to the LW jam which was associated with the largest pool. The largest error in TSM calculations is related to the empirically calculated reaeration flux (k), which represents oxygen inputs from the atmosphere. We used two well-established empirical equations to compare k values to the BASE model. The model agreed with empirically derived values during intermediate and high Q. Modeled GPP and ER diverged, sometimes by an order of magnitude, from the empirically derived results during the lowest flows.

Scale-dependent performances of CMIP5 earth system models in simulating terrestrial vegetation carbon

NASA Astrophysics Data System (ADS)

Jiang, L.; Luo, Y.; Yan, Y.; Hararuk, O.

2013-12-01

Mitigation of global changes will depend on reliable projection for the future situation. As the major tools to predict future climate, Earth System Models (ESMs) used in Coupled Model Intercomparison Project Phase 5 (CMIP5) for the IPCC Fifth Assessment Report have incorporated carbon cycle components, which account for the important fluxes of carbon between the ocean, atmosphere, and terrestrial biosphere carbon reservoirs; and therefore are expected to provide more detailed and more certain projections. However, ESMs are never perfect; and evaluating the ESMs can help us to identify uncertainties in prediction and give the priorities for model development. In this study, we benchmarked carbon in live vegetation in the terrestrial ecosystems simulated by 19 ESMs models from CMIP5 with an observationally estimated data set of global carbon vegetation pool 'Olson's Major World Ecosystem Complexes Ranked by Carbon in Live Vegetation: An Updated Database Using the GLC2000 Land Cover Product' by Gibbs (2006). Our aim is to evaluate the ability of ESMs to reproduce the global vegetation carbon pool at different scales and what are the possible causes for the bias. We found that the performance CMIP5 ESMs is very scale-dependent. While CESM1-BGC, CESM1-CAM5, CESM1-FASTCHEM and CESM1-WACCM, and NorESM1-M and NorESM1-ME (they share the same model structure) have very similar global sums with the observation data but they usually perform poorly at grid cell and biome scale. In contrast, MIROC-ESM and MIROC-ESM-CHEM simulate the best on at grid cell and biome scale but have larger differences in global sums than others. Our results will help improve CMIP5 ESMs for more reliable prediction.

Pool spacing, channel morphology, and the restoration of tidal forested wetlands of the Columbia River, U.S.A.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Diefenderfer, Heida L.; Montgomery, David R.

2008-10-09

Tidal forested wetlands have sustained substantial areal losses, and restoration practitioners lack a description of many ecosystem structures associated with these late-successional systems in which surface water is a significant controlling factor on the flora and fauna. The roles of large woody debris in terrestrial and riverine ecosystems have been well described compared to functions in tidal areas. This study documents the role of large wood in forcing channel morphology in Picea-sitchensis (Sitka spruce) dominated freshwater tidal wetlands in the floodplain of the Columbia River, U.S.A. near the Pacific coast. The average pool spacing documented in channel surveys of threemore » freshwater tidal forested wetlands near Grays Bay were 2.2 ± 1.3, 2.3 ± 1.2, and 2.5 ± 1.5. There were significantly greater numbers of pools on tidal forested wetland channels than on a nearby restoration site. On the basis of pool spacing and the observed sequences of log jams and pools, the tidal forested wetland channels were classified consistent with a forced step-pool class. Tidal systems, with bidirectional flow, have not previously been classified in this way. The classification provides a useful basis for restoration project design and planning in historically forested tidal freshwater areas, particularly in regard to the use of large wood in restoration actions and the development of pool habitats for aquatic species. Significant modifications by beaver on these sites warrant further investigation to explore the interactions between these animals and restoration actions affecting hydraulics and channel structure in tidal areas.« less

Phylogeography and spatial structure of the lowland tapir (Tapirus terrestris, Perissodactyla: Tapiridae) in South America.

PubMed

Ruiz-García, Manuel; Vásquez, Catalina; Sandoval, Sergio; Kaston, Franz; Luengas-Villamil, Kelly; Shostell, Joseph Mark

2016-07-01

We sequenced the mitochondrial cytochrome b gene of 141 lowland tapirs (Tapirus terrestris) - representing the largest geographical distribution sample of this species studied across of South America to date. We compare our new data regard to two previous works on population structure and molecular systematics of T. terrestris. Our data agree with the Thoisy et al.'s work in (1) the Northern Western Amazon basin was the area with the highest gene diversity levels in T. terrestris, being probably the area of initial diversification; (2) there was no clear association between haplogroups and specific geographical areas; (3) there were clear population decreases during the last glacial maximum for the different haplogroups detected, followed by population expansions during the Holocene; and (4) our temporal splits among different T. terrestris haplogroups coincided with the first molecular clock approach carried out by these authors (fossil calibration). Nevertheless, our study disagreed regard to other aspects of the Thoisy et al.'s claims: (1) meanwhile, they detected four relevant clades in their data, we put forward six different relevant clades; (2) the Amazon River was not a strong barrier for haplotype dispersion in T. terrestris; and (3) we found reciprocal monophyly between T. terrestris and T. pinchaque. Additionally, we sequenced 42 individuals (T. terrestris, T. pinchaque, T. bairdii, and the alleged "new species", T. kabomani) for three concatenated mitochondrial genes (Cyt-b, COI, and COII) agreeing quite well with the view of Voss et al., and against of the claims of Cozzuol et al. Tapirus kabomani should be not considered as a full species with the results obtained throughout the mitochondrial sequences.

Composition and fate of terrigenous organic matter along the Arctic land-ocean continuum in East Siberia: Insights from biomarkers and carbon isotopes

NASA Astrophysics Data System (ADS)

Tesi, Tommaso; Semiletov, Igor; Hugelius, Gustaf; Dudarev, Oleg; Kuhry, Peter; Gustafsson, Örjan

2014-05-01

Climate warming is predicted to translocate terrigenous organic carbon (TerrOC) to the Arctic Ocean and affect the marine biogeochemistry at high latitudes. The magnitude of this translocation is currently unknown, so is the climate response. The fate of the remobilized TerrOC across the Arctic shelves represents an unconstrained component of this feedback. The present study investigated the fate of permafrost carbon along the land-ocean continuum by characterizing the TerrOC composition in three different terrestrial carbon pools from Siberian permafrost (surface organic rich horizon, mineral soil active layer, and Ice Complex deposit) and marine sediments collected on the extensive East Siberian Arctic Shelf (ESAS). High levels of lignin phenols and cutin acids were measured in all terrestrial samples analyzed indicating that these compounds can be used to trace the heterogeneous terrigenous material entering the Arctic Ocean. In ESAS sediments, comparison of these terrigenous biomarkers with other TerrOC proxies (bulk δ13C/Δ14C and HMW lipid biomarkers) highlighted contrasting across-shelf trends. These differences could indicate that TerrOC in the ESAS is made up of several pools that exhibit contrasting reactivity toward oxidation during the transport. In this reactive spectrum, lignin is the most reactive, decreasing up to three orders of magnitude from the inner- to the outer-shelf while the decrease of HMW wax lipid biomarkers was considerably less pronounced. Alternatively, degradation might be negligible while sediment sorting during the across-shelf transport could be the major physical forcing that redistributes different TerrOC pools characterized by different matrix-association.

pyhector: A Python interface for the simple climate model Hector

DOE Office of Scientific and Technical Information (OSTI.GOV)

N Willner, Sven; Hartin, Corinne; Gieseke, Robert

2017-04-01

Pyhector is a Python interface for the simple climate model Hector (Hartin et al. 2015) developed in C++. Simple climate models like Hector can, for instance, be used in the analysis of scenarios within integrated assessment models like GCAM1, in the emulation of complex climate models, and in uncertainty analyses. Hector is an open-source, object oriented, simple global climate carbon cycle model. Its carbon cycle consists of a one pool atmosphere, three terrestrial pools which can be broken down into finer biomes or regions, and four carbon pools in the ocean component. The terrestrial carbon cycle includes primary production andmore » respiration fluxes. The ocean carbon cycle circulates carbon via a simplified thermohaline circulation, calculating air-sea fluxes as well as the marine carbonate system (Hartin et al. 2016). The model input is time series of greenhouse gas emissions; as example scenarios for these the Pyhector package contains the Representative Concentration Pathways (RCPs)2. These were developed to cover the range of baseline and mitigation emissions scenarios and are widely used in climate change research and model intercomparison projects. Using DataFrames from the Python library Pandas (McKinney 2010) as a data structure for the scenarios simplifies generating and adapting scenarios. Other parameters of the Hector model can easily be modified when running the model. Pyhector can be installed using pip from the Python Package Index.3 Source code and issue tracker are available in Pyhector's GitHub repository4. Documentation is provided through Readthedocs5. Usage examples are also contained in the repository as a Jupyter Notebook (Pérez and Granger 2007; Kluyver et al. 2016). Courtesy of the Mybinder project6, the example Notebook can also be executed and modified without installing Pyhector locally.« less

Utilizing Forest Inventory and Analysis Data, Remote Sensing, and Ecosystem Models for National Forest System Carbon Assessments

Treesearch

Alexa J. Dugan; Richard A. Birdsey; Sean P. Healey; Christopher Woodall; Fangmin Zhang; Jing M. Chen; Alexander Hernandez; James B. McCarter

2015-01-01

Forested lands, representing the largest terrestrial carbon sink in the United States, offset 16% of total U.S. carbon dioxide emissions through carbon sequestration. Meanwhile, this carbon sink is threatened by deforestation, climate change and natural disturbances. As a result, U.S. Forest Service policies require that National Forests assess baseline carbon stocks...

Remote sensing of channels and riparian zones with a narrow-beam aquatic-terrestrial LIDAR

Treesearch

Jim McKean; Dave Nagel; Daniele Tonina; Philip Bailey; Charles Wayne Wright; Carolyn Bohn; Amar Nayegandhi

2009-01-01

The high-resolution Experimental Advanced Airborne Research LIDAR (EAARL) is a new technology for cross-environment surveys of channels and floodplains. EAARL measurements of basic channel geometry, such as wetted cross-sectional area, are within a few percent of those from control field surveys. The largest channel mapping errors are along stream banks. The LIDAR data...

Plant community composition as a predictor of regional soil carbon storage in Alaskan boreal black spruce ecosystems

Treesearch

T.N. Hollingsworth; E.A.G. Schuur; F.S. III Chapin; M.D. Walker

2008-01-01

The boreal forest is the largest terrestrial biome in North America and holds a large portion of the world's reactive soil carbon. Therefore, understanding soil carbon accumulation on a landscape or regional scale across the boreal forest is useful for predicting future soil carbon storage. Here, we examined the relationship between floristic composition and...

A framework for assessing global change risks to forest carbon stocks in the United States

Treesearch

Christopher W. Woodall; Grant M. Domke; Karin L. Riley; Christopher M. Oswalt; Susan J. Crocker; Gary W. Yohe

2013-01-01

Among terrestrial environments, forests are not only the largest long-term sink of atmospheric carbon (C), but are also susceptible to global change themselves, with potential consequences including alterations of C cycles and potential C emission. To inform global change risk assessment of forest C across large spatial/temporal scales, this study constructed and...

Consequences of alternative tree-level biomass estimation procedures on U.S. forest carbon stock estimates

Treesearch

Grant M. Domke; Christopher W. Woodall; James E. Smith; James A. Westfall; Ronald E. McRoberts

2012-01-01

Forest ecosystems are the largest terrestrial carbon sink on earth and their management has been recognized as a relatively cost-effective strategy for offsetting greenhouse gas emissions. Forest carbon stocks in the U.S. are estimated using data from the USDA Forest Service, Forest Inventory and Analysis (FIA) program. In an attempt to balance accuracy with...

Observations of cross-Saharan transport of water vapour via cycle of cold pools and moist convection

NASA Astrophysics Data System (ADS)

Trzeciak, Tomasz; Garcia-Carreras, Luis; Marsham, John H.

2017-04-01

Very limited observational data has previously limited our ability to study meteorological processes in the Sahara. The Sahara is a key component of the West African monsoon and the world's largest dust source, but its representation is a major uncertainty in global models. Past studies have shown that there is a persistent warm and dry model bias throughout the Sahara, and this has been attributed to the lack of convectively-generated cold pools in the model, which can ventilate the central Sahara from its margins. Here we present an observed case from June 2012 which explains how cold pools are able to transport water vapour across a large area of the Sahara over a period of several days. A daily cycle is found to occur, where deep convection in the evening generates moist cold pools that then feed the next day's convection; the new convection in turn generates new cold pools, providing a vertical recycling of moisture. Trajectories driven by analyses can capture the general direction of transport, but not its full extent, especially at night when cold pools are most active, highlighting the difficulties for models to capture these processes. These results show the importance of cold pools for moisture transport, dust and clouds in the region, and demonstrate the need to include these processes in models to improve the representation of the Saharan atmosphere.

Insects and allies associated with bromeliads: a review

PubMed Central

Frank, J. H.; Lounibos, L. P.

2009-01-01

Summary Bromeliads are a Neotropical plant family (Bromeliaceae) with about 2,900 described species. They vary considerably in architecture. Many impound water in their inner leaf axils to form phytotelmata (plant pools), providing habitat for terrestrial arthropods with aquatic larvae, while their outer axils provide terraria for an assemblage of fully terrestrial arthropods. Many bromeliads are epiphytic. Dominant terrestrial arthropods with aquatic larvae inhabiting bromeliad phytotelmata are typically larvae of Diptera, of which at least 16 families have been reported, but in some circumstances are Coleoptera, of which only three families have been reported. Other groups include crabs and the insect orders Odonata, Plecoptera, and Trichoptera, plus Hemiptera with adults active on the water surface. The hundreds of arthropod species are detritivores or predators and do not harm their host plants. Many of them are specialists to this habitat. Terrestrial arthropods with terrestrial larvae inhabiting bromeliad terraria include many more arachnid and insect orders, but relatively few specialists to this habitat. They, too, are detritivores or predators. Arthropod herbivores, especially Curculionidae (Coleoptera) and Lepidoptera, consume leaves, stems, flowers, pollen, and roots of bromeliads. Some herbivores consume nectar, and some of these and other arthropods provide pollination and even seed-dispersal. Ants have complex relationships with bromeliads, a few being herbivores, some guarding the plants from herbivory, and some merely nesting in bromeliad terraria. A few serve as food for carnivorous bromeliads, which also consume other terrestrial insects. Bromeliads are visited by far more species of arthropods than breed in them. This is especially notable during dry seasons, when bromeliads provide moist refugia. PMID:20209047

Influence of Prescribed Fire on Ecosystem Biomass, Carbon, and Nitrogen in a Pinyon Juniper Woodland

USDA-ARS?s Scientific Manuscript database

Pinyon and juniper woodland encroachment associated with climate change and land use history in the Great Basin is thought to provide offsets for carbon emissions. However, the largest pools of carbon in arid landscapes are typically found in soils, and aboveground biomass cannot be considered long ...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Genda, H.; Kobayashi, H.; Kokubo, E., E-mail: genda@elsi.jp

In our solar system, Mars-sized protoplanets frequently collided with each other during the last stage of terrestrial planet formation, called the giant impact stage. Giant impacts eject a large amount of material from the colliding protoplanets into the terrestrial planet region, which may form debris disks with observable infrared excesses. Indeed, tens of warm debris disks around young solar-type stars have been observed. Here we quantitatively estimate the total mass of ejected materials during the giant impact stages. We found that ∼0.4 times the Earth’s mass is ejected in total throughout the giant impact stage. Ejected materials are ground down bymore » collisional cascade until micron-sized grains are blown out by radiation pressure. The depletion timescale of these ejected materials is determined primarily by the mass of the largest body among them. We conducted high-resolution simulations of giant impacts to accurately obtain the mass of the largest ejected body. We then calculated the evolution of the debris disks produced by a series of giant impacts and depleted by collisional cascades to obtain the infrared excess evolution of the debris disks. We found that the infrared excess is almost always higher than the stellar infrared flux throughout the giant impact stage (∼100 Myr) and is sometimes ∼10 times higher immediately after a giant impact. Therefore, giant impact stages would explain the infrared excess from most observed warm debris disks. The observed fraction of stars with warm debris disks indicates that the formation probability of our solar-system-like terrestrial planets is approximately 10%.« less

From solid to liquid: assessing the release of organic matter into soil solution in response to land-use conversion in Brazilian Oxisols

NASA Astrophysics Data System (ADS)

James, Jason; Gross, Cole; Dwivedi, Pranjal; Bernardi, Rodolpho; Guerrini, Irae; Harrison, Rob; Butman, David

2017-04-01

Recent advances in freshwater research indicate that roughly double the quantity of carbon is exported from soils to streams and rivers than was previously estimated, and that the age of carbon exported from major rivers globally increases with greater human disturbance in the watershed. This implies that human land-use can release old, previously mineral-associated C into solution with subsequent export to groundwater and ultimately freshwater systems where terrestrial organic matter is either mineralized to CO2, stored in aquatic sediments, or exported to the ocean. Consequently, it is important to understand the mechanisms that cause the release of SOM that is mineral-bound into solution in response to human disturbance and land-use change. Research methods have been established to examine both the fast turnover, dissolved pool of soil organic matter (SOM), as well as the slow turnover, mineral-associated pool. However, to better characterize the response of the total SOM pool to disturbance, it is necessary to understand the interactions between these functional pools by examining them both simultaneously. This study seeks to examine the interaction between dissolved organic matter (DOM) and bulk SOM throughout the soil profile in response to conversion of Brazilian Cerrado (savannah forest) to Eucalyptus plantation forest on the same soil type. The water-extractable organic matter was obtained from soil samples down to 150 cm, characterized using fluorescence and NMR spectroscopy, and carbon-dated. Simultaneously, bulk mineral soil samples were analyzed for microbial biomass, carbon content and age, and characterized using Fourier Transform Infrared Spectroscopy. SOM spectra were obtained by washing subsamples with sodium hypochlorite and subtracting the subsequent mineral matrix spectra from bulk soil spectra. Preliminary results show that microbial biomass decreases much more quickly with depth than DOM, suggesting that C released into solution from deeper horizons may be less likely to be intercepted, and thus preferentially leached to groundwater. Native Cerrado forests had substantially more roots compared to Eucalyptus, and also released substantially larger quantities of DOM from their O horizons. Processes operating at the interface between solid and liquid, terrestrial and aquatic are a key unknown in the global carbon cycle. This research permits a unique snapshot into the relationship between DOM and SOM and the response of these pools to land-use change in Brazil.

Differential Millennial-scale Responses of Terrestrial Carbon Cycling Dynamics to Warming from two Contrasting Lake Catchments in Arctic Alaska

NASA Astrophysics Data System (ADS)

Longo, W. M.; Huang, Y.; Russell, J. M.; Giblin, A. E.; McNichol, A. P.; Xu, L.; Daniels, W.

2016-12-01

Earth's permafrost carbon (C) reservoir is more than twice as large as global atmospheric C and its vulnerability to warming makes it a significant potential feedback to climate change. Predicted rates of warming could result in the release of 5 to 15% of permafrost C to the atmosphere by 2100 (Schuur et al., 2015); however the uncertainty around this estimate hinders our ability to quantify the arctic temperature-carbon feedback. To elucidate the long-term response of terrestrial C to warming in regions underlain by continuous permafrost, we present geologic records of changes in temperature and terrestrial C cycling dynamics from sediment cores from two contrasting lake catchments in arctic Alaska. The sediment records feature independent chronologies, biomarker-based temperature reconstructions, and geochemical measurements of vascular plant biomarkers (lignin phenols) that provide insight into terrestrial carbon quality, its release from permafrost soils and its transit time on the landscape. Our results indicate that both abrupt and sustained increases in temperature over the past 20,000 years resulted in increased carbon normalized yields of lignin phenols (Λ8, Λ6), which indicate increased mobilization of terrestrial organic carbon from permafrost soils. Lignin phenol indicators of terrestrial carbon quality (Ad:Al(s), Ad:Al(v)), indicated that carbon quality decreased with increasing temperature. These results demonstrate covariation between temperature and both the decay of terrestrial organic matter and lignin alteration resulting from dissolution and sorption processes. Compound specific radiocarbon analyses of lignin phenols and their offsets from depositional ages quantify transit times of terrestrial carbon on the landscape. These measurements revealed the presence of a persistent "pre-aged" terrestrial organic carbon pool, which is likely sourced from degrading permafrost. We also observe different responses of terrestrial organic carbon cycling to temperature that depend on landscape characteristics. C cycling responses are pronounced in the low-relief, Pleistocene-aged catchment of lake E5, and more muted in Lake Fog 2, which exists in a higher-relief and younger catchment. Mechanisms differentiating the responses of these catchments are discussed.

Experimental Testing and Numerical Modeling of Spray Cooling Under Terrestrial Gravity Conditions

DTIC Science & Technology

2005-01-01

running safely. Mudawar (2000) identifies two heat flux ranges relative to the amount of heat dissipation. The high-flux range includes heat fluxes on...inferior to those of water ( Mudawar , 2000). Phase change cooling can exist in several forms, or cooling schemes. Pool boiling may be used in...addition to reducing the significant effects of flow orientation ( Mudawar , 2000). It is not fully known how low gravity affects flow boiling, as

Matrix approach to uncertainty assessment and reduction for modeling terrestrial carbon cycle

NASA Astrophysics Data System (ADS)

Luo, Y.; Xia, J.; Ahlström, A.; Zhou, S.; Huang, Y.; Shi, Z.; Wang, Y.; Du, Z.; Lu, X.

2017-12-01

Terrestrial ecosystems absorb approximately 30% of the anthropogenic carbon dioxide emissions. This estimate has been deduced indirectly: combining analyses of atmospheric carbon dioxide concentrations with ocean observations to infer the net terrestrial carbon flux. In contrast, when knowledge about the terrestrial carbon cycle is integrated into different terrestrial carbon models they make widely different predictions. To improve the terrestrial carbon models, we have recently developed a matrix approach to uncertainty assessment and reduction. Specifically, the terrestrial carbon cycle has been commonly represented by a series of carbon balance equations to track carbon influxes into and effluxes out of individual pools in earth system models. This representation matches our understanding of carbon cycle processes well and can be reorganized into one matrix equation without changing any modeled carbon cycle processes and mechanisms. We have developed matrix equations of several global land C cycle models, including CLM3.5, 4.0 and 4.5, CABLE, LPJ-GUESS, and ORCHIDEE. Indeed, the matrix equation is generic and can be applied to other land carbon models. This matrix approach offers a suite of new diagnostic tools, such as the 3-dimensional (3-D) parameter space, traceability analysis, and variance decomposition, for uncertainty analysis. For example, predictions of carbon dynamics with complex land models can be placed in a 3-D parameter space (carbon input, residence time, and storage potential) as a common metric to measure how much model predictions are different. The latter can be traced to its source components by decomposing model predictions to a hierarchy of traceable components. Then, variance decomposition can help attribute the spread in predictions among multiple models to precisely identify sources of uncertainty. The highly uncertain components can be constrained by data as the matrix equation makes data assimilation computationally possible. We will illustrate various applications of this matrix approach to uncertainty assessment and reduction for terrestrial carbon cycle models.

Lignin Contribution to the Global Carbon Pool: Investigating the Abiotic Modification of Lignin by Reactive Oxygen Species

NASA Astrophysics Data System (ADS)

Waggoner, Derek Charles

Evidence suggests that reactive oxygen species (ROS), largely generated through photochemical processes, are important in transforming the chemical composition of the large pool of terrestrially-derived dissolved organic matter (DOM) exported from land to water annually. However, due to the challenges inherent in isolating the effects of individual ROS on DOM composition, the role of ROS in the photochemical alteration of DOM remains poorly characterized. The main focus of the studies within this dissertation aim to more thoroughly characterize the alterations to lignin, used as an analog for terrestrial DOM, resulting from reactions with ROS. To investigate the possibility that the alteration of lignin, through reactions involving ROS, could lead to the production of compounds not recognized as having terrestrial origin, lignin-derived DOM was prepared from a sample of Atlantic white cedar (Chamaecyparis thyoides) and used for a number of studies. Lignin-derived DOM was independently exposed to hydroxyl radical (•OH) generated by Fenton reaction, singlet oxygen (1O2) produced using the photosensitizer Rose Bengal, and superoxide (O2-•) via stable potassium superoxide solution, under controlled laboratory conditions to accentuate how each ROS is responsible for the alteration of lignin. Advanced analytical techniques including high performance liquid chromatography (HPLC), nuclear magnetic resonance (NMR), and Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS), were employed to characterize alteration to lignin taking place following various ROS treatments. Results of these studies have shown distinct differences in the types of new compounds observed from exposure to each ROS as well as ROS reactivity. The alteration of lignin to compounds not typically associated with terrestrial DOM has been demonstrated upon exposure to ROS. It is also suggested that ROS could selectively react with different fractions of lignin like compounds based largely on oxygen content. Additionally, results indicate that partially oxidized lignin could react further with ROS to generate compounds resembling condensed aromatic-like compounds, previously believed to be primarily pyrogenic in origin, as well as alicyclic compounds commonly observed in marine DOM.

Geometric factors influencing the diet of vertebrate predators in marine and terrestrial environments

PubMed Central

Carbone, Chris; Codron, Daryl; Scofield, Conrad; Clauss, Marcus; Bielby, Jon; Enquist, Brian

2014-01-01

Predator–prey relationships are vital to ecosystem function and there is a need for greater predictive understanding of these interactions. We develop a geometric foraging model predicting minimum prey size scaling in marine and terrestrial vertebrate predators taking into account habitat dimensionality and biological traits. Our model predicts positive predator–prey size relationships on land but negative relationships in the sea. To test the model, we compiled data on diets of 794 predators (mammals, snakes, sharks and rays). Consistent with predictions, both terrestrial endotherm and ectotherm predators have significantly positive predator–prey size relationships. Marine predators, however, exhibit greater variation. Some of the largest predators specialise on small invertebrates while others are large vertebrate specialists. Prey–predator mass ratios were generally higher for ectothermic than endothermic predators, although dietary patterns were similar. Model-based simulations of predator–prey relationships were consistent with observed relationships, suggesting that our approach provides insights into both trends and diversity in predator–prey interactions. PMID:25265992

Rock-Eval analysis of French forest soils: the influence of depth, soil and vegetation types on SOC thermal stability and bulk chemistry

NASA Astrophysics Data System (ADS)

Soucemarianadin, Laure; Cécillon, Lauric; Baudin, François; Cecchini, Sébastien; Chenu, Claire; Mériguet, Jacques; Nicolas, Manuel; Savignac, Florence; Barré, Pierre

2017-04-01

Soil organic matter (SOM) is the largest terrestrial carbon pool and SOM degradation has multiple consequences on key ecosystem properties like nutrients cycling, soil emissions of greenhouse gases or carbon sequestration potential. With the strong feedbacks between SOM and climate change, it becomes particularly urgent to develop reliable routine methodologies capable of indicating the turnover time of soil organic carbon (SOC) stocks. Thermal analyses have been used to characterize SOM and among them, Rock-Eval 6 (RE6) analysis of soil has shown promising results in the determination of in-situ SOC biogeochemical stability. This technique combines a phase of pyrolysis followed by a phase of oxidation to provide information on both the SOC bulk chemistry and thermal stability. We analyzed with RE6 a set of 495 soils samples from 102 permanent forest sites of the French national network for the long-term monitoring of forest ecosystems (''RENECOFOR'' network). Along with covering pedoclimatic variability at a national level, these samples include a range of 5 depths up to 1 meter (0-10 cm, 10-20 cm, 20-40 cm, 40-80 cm and 80-100 cm). Using RE6 parameters that were previously shown to be correlated to short-term (hydrogen index, HI; T50 CH pyrolysis) or long-term (T50 CO2 oxidation and HI) SOC persistence, and that characterize SOM bulk chemical composition (oxygen index, OI and HI), we tested the influence of depth (n = 5), soil class (n = 6) and vegetation type (n = 3; deciduous, coniferous-fir, coniferous-pine) on SOM thermal stability and bulk chemistry. Results showed that depth was the dominant discriminating factor, affecting significantly all RE6 parameters. With depth, we observed a decrease of the thermally labile SOC pool and an increase of the thermally stable SOC pool, along with an oxidation and a depletion of hydrogen-rich moieties of the SOC. Soil class and vegetation type had contrasted effects on the RE6 parameters but both affected significantly T50 CO2 oxidation with, for instance, entic Podzols and dystric Cambisols containing relatively more thermally stable SOC in the deepest layer than hypereutric/calcaric Cambisols. Moreover, soils in deciduous plots contained a higher proportion of thermally stable SOC than soils in coniferous plots. This study shows that RE6 analysis constitutes a fast and cost effective way to qualitatively estimate SOM turnover and to discuss its ecosystem drivers. It offers promising prospects towards a quantitative estimation of SOC turnover and the development of RE6-based indicators related to the size of the different SOC kinetic pools.

Projecting large-scale area changes in land use and land cover for terrestrial carbon analyses.

Treesearch

Ralph J. Alig; Brett J. Butler

2004-01-01

One of the largest changes in US forest type areas over the last half-century has involved pine types in the South. The area of planted pine has increased more than 10-fold since 1950, mostly on private lands. Private landowners have responded to market incentives and government programs, including subsidized afforestation on marginal agricultural land. Timber harvest...

Long-term effects of silviculture on soil carbon storage: does vegetation control make a difference?

Treesearch

Robert F. Powers; Matt D. Busse; Karis J. McFarlane; Jianwei Zhang; David H. Young

2012-01-01

Forests and the soils beneath them are Earth’s largest terrestrial sinks for atmospheric carbon (C) and healthy forests provide a partial check against atmospheric rises in CO2. Consequently, there is global interest in crediting forest managers who enhance C retention. Interest centres on C acquisition and storage in trees. Less is directed to...

Irreducible Uncertainty in Terrestrial Carbon Projections

NASA Astrophysics Data System (ADS)

Lovenduski, N. S.; Bonan, G. B.

2016-12-01

We quantify and isolate the sources of uncertainty in projections of carbon accumulation by the ocean and terrestrial biosphere over 2006-2100 using output from Earth System Models participating in the 5th Coupled Model Intercomparison Project. We consider three independent sources of uncertainty in our analysis of variance: (1) internal variability, driven by random, internal variations in the climate system, (2) emission scenario, driven by uncertainty in future radiative forcing, and (3) model structure, wherein different models produce different projections given the same emission scenario. Whereas uncertainty in projections of ocean carbon accumulation by 2100 is 100 Pg C and driven primarily by emission scenario, uncertainty in projections of terrestrial carbon accumulation by 2100 is 50% larger than that of the ocean, and driven primarily by model structure. This structural uncertainty is correlated with emission scenario: the variance associated with model structure is an order of magnitude larger under a business-as-usual scenario (RCP8.5) than a mitigation scenario (RCP2.6). In an effort to reduce this structural uncertainty, we apply various model weighting schemes to our analysis of variance in terrestrial carbon accumulation projections. The largest reductions in uncertainty are achieved when giving all the weight to a single model; here the uncertainty is of a similar magnitude to the ocean projections. Such an analysis suggests that this structural uncertainty is irreducible given current terrestrial model development efforts.

Mercury deposition and re-emission pathways in boreal forest soils investigated with Hg isotope signatures.

PubMed

Jiskra, Martin; Wiederhold, Jan G; Skyllberg, Ulf; Kronberg, Rose-Marie; Hajdas, Irka; Kretzschmar, Ruben

2015-06-16

Soils comprise the largest terrestrial mercury (Hg) pool in exchange with the atmosphere. To predict how anthropogenic emissions affect global Hg cycling and eventually human Hg exposure, it is crucial to understand Hg deposition and re-emission of legacy Hg from soils. However, assessing Hg deposition and re-emission pathways remains difficult because of an insufficient understanding of the governing processes. We measured Hg stable isotope signatures of radiocarbon-dated boreal forest soils and modeled atmospheric Hg deposition and re-emission pathways and fluxes using a combined source and process tracing approach. Our results suggest that Hg in the soils was dominantly derived from deposition of litter (∼90% on average). The remaining fraction was attributed to precipitation-derived Hg, which showed increasing contributions in older, deeper soil horizons (up to 27%) indicative of an accumulation over decades. We provide evidence for significant Hg re-emission from organic soil horizons most likely caused by nonphotochemical abiotic reduction by natural organic matter, a process previously not observed unambiguously in nature. Our data suggest that Histosols (peat soils), which exhibit at least seasonally water-saturated conditions, have re-emitted up to one-third of previously deposited Hg back to the atmosphere. Re-emission of legacy Hg following reduction by natural organic matter may therefore be an important pathway to be considered in global models, further supporting the need for a process-based assessment of land/atmosphere Hg exchange.

Influences of kerogen-rich bedrock on the molecular and isotopic composition of modern soils; implications for global C cycling

NASA Astrophysics Data System (ADS)

Longbottom, T. L.; Hockaday, W. C.

2016-12-01

Kerogen represents the largest terrestrial organic carbon (OC) reservoir on earth and is vulnerable to remineralization upon exposure to earth's atmosphere. Oxidative weathering of ancient sedimentary organic matter is an immensely transformative process with poorly-constrained mechanisms and flux values in contemporary carbon cycle models. The weathered residuum of organic-rich mudrocks serves as parent material for many modern soils, and it is likely that the structure and dynamics of the resulting soil organic matter pool is inherited directly from kerogen-rich bedrock. We used a combination of solid-state 13-C nuclear magnetic resonance (NMR) spectroscopy, and carbon isotope techniques to describe molecular and isotopic changes that occur throughout oxidative weathering of marine kerogens, and the subsequent formation of modern soils, in two outcropping Cretaceous mudstones of the Eagle Ford and Pepper Formations in central, TX. Gradational production of O-containing functionalities was observed, coupled with reductions in characteristically abundant polymethylenic components of type II kerogens. Organic matter structural parameters, derived from C-H dephasing NMR experiments, also provide the basis for a novel weathering index that accounts for the degree of post-sedimentary diagenetic alteration of samples along the kerogen-soil continuum. Molecular and isotopic mixing models were employed in estimating the proportions of modern and ancient C in soils, as increased incorporation and vulnerability of ancient OC under climatic shifts in temperature and/or precipitation is likely.

West Nile Virus Outbreak in Houston and Harris County, Texas, USA, 2014.

PubMed

Martinez, Diana; Murray, Kristy O; Reyna, Martin; Arafat, Raouf R; Gorena, Roberto; Shah, Umair A; Debboun, Mustapha

2017-08-01

Since 2002, West Nile virus (WNV) has been detected every year in Houston and the surrounding Harris County, Texas. In 2014, the largest WNV outbreak to date occurred, comprising 139 cases and causing 2 deaths. Additionally, 1,286 WNV-positive mosquito pools were confirmed, the most reported in a single mosquito season.

Initial Breakdown Pulse Amplitudes in Intracloud and Cloud-to-Ground Lightning Flashes

NASA Astrophysics Data System (ADS)

Marshall, T. C.; Smith, E. M.; Stolzenburg, M.; Karunarathne, S.; Siedlecki, R. D., II

2017-12-01

This study analyzes the largest initial breakdown (IB) pulse in flashes from three storms in Florida. The study was motivated in part by the possibility that IB pulses of IC flashes may cause of terrestrial gamma-ray flashes (TGFs). The range-normalized, zero-to-peak amplitude of the largest IB pulse within each flash was determined along with its altitude, duration, and occurrence time in the flash. Appropriate data were available for 40 intracloud (IC) and 32 cloud-to-ground (CG) flashes. Histograms of the magnitude of the largest IB pulse amplitude by flash type were similar, with mean (median) values of 1.49 (1.05) V/m for IC flashes and -1.35 (-0.87) V/m for CG flashes. The mean amplitude of the largest IC IB pulses are substantially smaller (roughly an order of magnitude smaller) than the few known pulse amplitudes of TGF events and TGF candidate events. The largest IB pulse in 30 IC flashes showed a weak inverse relation between pulse amplitude and altitude. Amplitude of the largest IB pulse for 25 CG flashes showed no altitude correlation. Duration of the largest IB pulse in ICs averaged twice as long as in CGs (96 μs versus 46 μs); all of the CG durations were <100 μs. Among the ICs, there is a positive relation between largest IB pulse duration and amplitude; the linear correlation coefficient is 0.385 with outliers excluded. The largest IB pulse in IC flashes typically occurred at a longer time after the first IB pulse (average 4.1 ms) than was the case in CG flashes (average 0.6 ms). In both flash types, the largest IB pulse was the first IB pulse in about 30% of the cases.

Pooling procurement in the Belgian hospital sector.

PubMed

Hebert, Guy

2011-01-01

The Belgian hospital sector is following the example of a number of other European countries and for more than ten years now, has been striving to pool its medical supplies and equipment purchases in a bid to reduce costs. The various experiments of which we are aware come under both opportunist purchases and initiatives which are designed to encourage local-regional contracts. These attempts have now all come to nothing or are struggling in the absence of a structured and professional approach. In 2005, the Saint Luc University Clinic in Brussels decided to set up a high-performance purchasing department, the aim being to centre its initiatives around TCO or Total Cost of Ownership. Following an analysis of the various experiments into pooling procurement in hospitals in Europe, the Saint Luc University Clinic decided on a central procurement agency model, in accordance with new legislation on public procurement. This article seeks to highlight the prerequisites which are vital for a procurement pooling initiative, without underestimating the risks and limitations of implementing such a change in procurement practices. The Mercure central procurement agency is now the largest interhospital purchasing structure in Belgium.

Comprehensive analysis of correlation coefficients estimated from pooling heterogeneous microarray data

PubMed Central

2013-01-01

Background The synthesis of information across microarray studies has been performed by combining statistical results of individual studies (as in a mosaic), or by combining data from multiple studies into a large pool to be analyzed as a single data set (as in a melting pot of data). Specific issues relating to data heterogeneity across microarray studies, such as differences within and between labs or differences among experimental conditions, could lead to equivocal results in a melting pot approach. Results We applied statistical theory to determine the specific effect of different means and heteroskedasticity across 19 groups of microarray data on the sign and magnitude of gene-to-gene Pearson correlation coefficients obtained from the pool of 19 groups. We quantified the biases of the pooled coefficients and compared them to the biases of correlations estimated by an effect-size model. Mean differences across the 19 groups were the main factor determining the magnitude and sign of the pooled coefficients, which showed largest values of bias as they approached ±1. Only heteroskedasticity across the pool of 19 groups resulted in less efficient estimations of correlations than did a classical meta-analysis approach of combining correlation coefficients. These results were corroborated by simulation studies involving either mean differences or heteroskedasticity across a pool of N > 2 groups. Conclusions The combination of statistical results is best suited for synthesizing the correlation between expression profiles of a gene pair across several microarray studies. PMID:23822712

Context-dependent environmental quality standards of soil nitrate for terrestrial plant communities.

PubMed

van Goethem, Thomas M W J; Schipper, Aafke M; Wamelink, G W Wieger; Huijbregts, Mark A J

2016-10-01

Environmental quality standards (EQS) specify the maximum permissible concentration or level of a specific environmental stressor. Here, a procedure is proposed to derive EQS that are specific to a representative species pool and conditional on confounding environmental factors. To illustrate the procedure, a dataset was used with plant species richness observations of grasslands and forests and accompanying soil nitrate-N and pH measurements collected from 981 sampling sites in the Netherlands. Species richness was related to soil nitrate-N and pH with quantile regression allowing for interaction effects. The resulting regression models were used to derive EQS for nitrate conditional on pH, quantified as the nitrate-N concentrations at a specific pH level corresponding with a species richness equal to 95% of the species pool, for both grasslands and forest communities. The EQS varied between 1.8 mg/kg nitrate-N at pH 9-65 mg/kg nitrate-N at pH 4. EQS for forests and grasslands were similar, but EQS based on Red List species richness were considerably lower (more stringent) than those based on overall species richness, particularly at high pH levels. The results indicate that both natural background pH conditions and Red List species are important factors to consider in the derivation of EQS for soil nitrate-N for terrestrial ecosystems. Copyright © 2016 Elsevier Ltd. All rights reserved.

Commissioned Review. Carbon: freshwater plants

USGS Publications Warehouse

Keeley, J.E.; Sandquist, D.R.

1992-01-01

δ13C values for freshwater aquatic plant matter varies from −11 to −50‰ and is not a clear indicator of photosynthetic pathway as in terrestrial plants. Several factors affect δ13C of aquatic plant matter. These include: (1) The δ13C signature of the source carbon has been observed to range from +1‰ for HCO3− derived from limestone to −30‰ for CO2 derived from respiration. (2) Some plants assimilate HCO3−, which is –7 to –11‰ less negative than CO2. (3) C3, C4, and CAM photosynthetic pathways are present in aquatic plants. (4) Diffusional resistances are orders of magnitude greater in the aquatic environment than in the aerial environment. The greater viscosity of water acts to reduce mixing of the carbon pool in the boundary layer with that of the bulk solution. In effect, many aquatic plants draw from a finite carbon pool, and as in terrestrial plants growing in a closed system, biochemical discrimination is reduced. In standing water, this factor results in most aquatic plants having a δ13C value similar to the source carbon. Using Farquhar's equation and other physiological data, it is possible to use δ13C values to evaluate various parameters affecting photosynthesis, such as limitations imposed by CO2 diffusion and carbon source.

Chloromethane release from carbonaceous meteorite affords new insight into Mars lander findings

NASA Astrophysics Data System (ADS)

Keppler, Frank; Harper, David B.; Greule, Markus; Ott, Ulrich; Sattler, Tobias; Schöler, Heinz F.; Hamilton, John T. G.

2014-11-01

Controversy continues as to whether chloromethane (CH3Cl) detected during pyrolysis of Martian soils by the Viking and Curiosity Mars landers is indicative of organic matter indigenous to Mars. Here we demonstrate CH3Cl release (up to 8 μg/g) during low temperature (150-400°C) pyrolysis of the carbonaceous chondrite Murchison with chloride or perchlorate as chlorine source and confirm unequivocally by stable isotope analysis the extraterrestrial origin of the methyl group (δ2H +800 to +1100‰, δ13C -19.2 to +10‰,). In the terrestrial environment CH3Cl released during pyrolysis of organic matter derives from the methoxyl pool. The methoxyl pool in Murchison is consistent both in magnitude (0.044%) and isotope signature (δ2H +1054 +/- 626‰, δ13C +43.2 +/- 38.8‰,) with that of the CH3Cl released on pyrolysis. Thus CH3Cl emissions recorded by Mars lander experiments may be attributed to methoxyl groups in undegraded organic matter in meteoritic debris reaching the Martian surface being converted to CH3Cl with perchlorate or chloride in Martian soil. However we cannot discount emissions arising additionally from organic matter of indigenous origin. The stable isotope signatures of CH3Cl detected on Mars could potentially be utilized to determine its origin by distinguishing between terrestrial contamination, meteoritic infall and indigenous Martian sources.

Chloromethane release from carbonaceous meteorite affords new insight into Mars lander findings.

PubMed

Keppler, Frank; Harper, David B; Greule, Markus; Ott, Ulrich; Sattler, Tobias; Schöler, Heinz F; Hamilton, John T G

2014-11-13

Controversy continues as to whether chloromethane (CH3Cl) detected during pyrolysis of Martian soils by the Viking and Curiosity Mars landers is indicative of organic matter indigenous to Mars. Here we demonstrate CH3Cl release (up to 8 μg/g) during low temperature (150-400°C) pyrolysis of the carbonaceous chondrite Murchison with chloride or perchlorate as chlorine source and confirm unequivocally by stable isotope analysis the extraterrestrial origin of the methyl group (δ(2)H +800 to +1100‰, δ(13)C -19.2 to +10‰,). In the terrestrial environment CH3Cl released during pyrolysis of organic matter derives from the methoxyl pool. The methoxyl pool in Murchison is consistent both in magnitude (0.044%) and isotope signature (δ(2)H +1054 ± 626‰, δ(13)C +43.2 ± 38.8‰,) with that of the CH3Cl released on pyrolysis. Thus CH3Cl emissions recorded by Mars lander experiments may be attributed to methoxyl groups in undegraded organic matter in meteoritic debris reaching the Martian surface being converted to CH3Cl with perchlorate or chloride in Martian soil. However we cannot discount emissions arising additionally from organic matter of indigenous origin. The stable isotope signatures of CH3Cl detected on Mars could potentially be utilized to determine its origin by distinguishing between terrestrial contamination, meteoritic infall and indigenous Martian sources.

Spatial scales of carbon flow in a river food web

USGS Publications Warehouse

Finlay, J.C.; Khandwala, S.; Power, M.E.

2002-01-01

Spatial extents of food webs that support stream and river consumers are largely unknown, but such information is essential for basic understanding and management of lotic ecosystems. We used predictable variation in algal ??13C with water velocity, and measurements of consumer ??13C and ??15N to examine carbon flow and trophic structure in food webs of the South Fork Eel River in Northern California. Analyses of ??13C showed that the most abundant macroinvertebrate groups (collector-gatherers and scrapers) relied on algae from local sources within their riffle or shallow pool habitats. In contrast, filter-feeding invertebrates in riffles relied in part on algal production derived from upstream shallow pools. Riffle invertebrate predators also relied in part on consumers of pool-derived algal carbon. One abundant taxon drifting from shallow pools and riffles (baetid mayflies) relied on algal production derived from the habitats from which they dispersed. The trophic linkage from pool algae to riffle invertebrate predators was thus mediated through either predation on pool herbivores dispersing into riffles, or on filter feeders. Algal production in shallow pool habitats dominated the resource base of vertebrate predators in all habitats at the end of the summer. We could not distinguish between the trophic roles of riffle algae and terrestrial detritus, but both carbon sources appeared to play minor roles for vertebrate consumers. In shallow pools, small vertebrates, including three-spined stickleback (Gasterosteus aculeatus), roach (Hesperoleucas symmetricus), and rough-skinned newts (Taricha granulosa), relied on invertebrate prey derived from local pool habitats. During the most productive summer period, growth of all size classes of steelhead and resident rainbow trout (Oncorhynchus mykiss) in all habitats (shallow pools, riffles, and deep unproductive pools) was largely derived from algal production in shallow pools. Preliminary data suggest that the strong role of shallow pool algae in riffle steelhead growth during summer periods was due to drift of pool invertebrates to riffles, rather than movement of riffle trout. Data for ??15N showed that resident rainbow trout (25-33 cm standard length) in deep pools preyed upon small size classes of juvenile steelhead that were most often found in riffles or shallow pools. While many invertebrate consumers relied primarily on algal production derived from local habitats, our study shows that growth of top predators in the river is strongly linked to food webs in adjacent habitats. These results suggest a key role for emigration of aquatic prey in determining carbon flow to top predators.

'invisible' DOM in hourly-resolved headwater river records from Northern Amazonia

NASA Astrophysics Data System (ADS)

Pereira, R.; Bovolo, C.; Spencer, R. G.; Hernes, P. J.; Tipping, E.; Vieth-Hillebrand, A.; Chappell, N.; Lewis-Franklin, A.; Parkin, G.; Wagner, T.

2012-12-01

Global river networks annually process ~3 billion tonnes of organic carbon but only ~17% reaches the ocean. These estimates suggest rivers are not mere transportation pipes but biogeochemical reactors. Inland waters are therefore fundamental to the understanding of carbon and nutrient interactions between land and ocean. Within these global estimates, tropical rivers contribute ~two-thirds of the global dissolved organic matter flux to the ocean. Recent studies suggest that up to 50% of the CO2 outgassed from tropical rivers is derived from terrestrial organic matter and that the terrestrial-aquatic interface in river headwaters are hotspots of biochemical activity. However, to date, most tropical riverine studies focus on the main river stem or mouth and therefore the dynamics of tropical headwater organic matter cycling within the global carbon cycle are unknown. We present a geochemical and hydrological time-series (sub-hourly resolution) of river water DOC concentration, source and composition from a pristine lowland rainforest headwater of the Burro Burro River, a tributary of the Essequibo River, the 3rd largest river in S. America. We show that during and after a rainstorm event, DOC concentrations increase an order of magnitude (10 to 114mg/L) in less than 30 mins, far exceeding the entire seasonal DOC range measured in 2010 and 2011 (17-28mg/L). The source (δ13C-DOC) of DOC during the rainstorm event changes from microbial/aquatic (-21.9‰ to -25.7‰) at low/intermediate DOC concentration to C3 vegetation supply (-26.8‰ to -30.3‰) during peak DOC flushing. First radiocarbon data shows that riverine DOC is relatively young (106.8-110.9 %modern), however, tropical soils suggest a potential for organic matter to be preserved (360-1200 BP). The fundamental relationship between DOC and coloured dissolved organic matter (CDOM), measured as UV absorbance (SUVA254), holds only for low riverine DOC concentrations with proportionally high lignin contribution, whereas high levels in DOC are not explained by humic substances. Size exclusion chromatography confirms that the DOM pool is divided into two main fractions, humic substances and 'invisible' DOM, or 'iDOM'. The latter group includes non UV-absorbing organic compounds of mono- and oligosaccharides, alcohols, aldehydes, ketones and amino sugars. Our new records from Guyana show that whilst lignin phenols are present and closely track the UV absorbance (R2 = 0.97), it is iDOM that dominates the total DOC pool at peak concentrations (up to 84%). Notably, iDOM is still found in the main Burro Burro River (20-40%), indicating that iDOM has some potential to survive transport downstream. The results suggest that DOC could be significantly underestimated in tropical systems due to the observed decoupling of DOC, water colour (CDOM) and river flux related to large amounts of iDOM entering the river during rainstorm events and wet seasons. Furthermore, given that headwaters represent roughly 50-85% of the total area of tropical river catchments, it is likely that iDOM is a significant component of the terrestrial carbon and nutrient cycles. It is therefore necessary to conduct further field studies that will produce high resolution (temporal and spatial) geochemical records from a large number of tropical systems to better quantify the role of tropical inland waters in carbon and nutrient cycling.

Dynamics of Inorganic Nutrients in Intertidal Sediments: Porewater, Exchangeable, and Intracellular Pools

PubMed Central

Garcia-Robledo, Emilio; Bohorquez, Julio; Corzo, Alfonso; Jimenez-Arias, Juan L.; Papaspyrou, Sokratis

2016-01-01

The study of inorganic nutrients dynamics in shallow sediments usually focuses on two main pools: porewater (PW) nutrients and exchangeable (EX) ammonium and phosphate. Recently, it has been found that microphytobenthos (MPB) and other microorganisms can accumulate large amounts of nutrients intracellularly (IC), highlighting the biogeochemical importance of this nutrient pool. Storing nutrients could support the growth of autotrophs when nutrients are not available, and could also provide alternative electron acceptors for dissimilatory processes such as nitrate reduction. Here, we studied the magnitude and relative importance of these three nutrient pools (PW, IC, and EX) and their relation to chlorophylls (used as a proxy for MPB abundance) and organic matter (OM) contents in an intertidal mudflat of Cadiz Bay (Spain). MPB was localized in the first 4 mm of the sediment and showed a clear seasonal pattern; highest chlorophylls content was found during autumn and lowest during spring-summer. The temporal and spatial distribution of nutrients pools and MPB were largely correlated. Ammonium was higher in the IC and EX fractions, representing on average 59 and 37% of the total ammonium pool, respectively. Similarly, phosphate in the IC and EX fractions accounted on average for 40 and 31% of the total phosphate pool, respectively. Nitrate in the PW was low, suggesting low nitrification activity and rapid consumption. Nitrate accumulated in the IC pool during periods of moderate MPB abundance, being up to 66% of the total nitrate pool, whereas it decreased when chlorophyll concentration peaked likely due to a high nitrogen demand. EX-Nitrate accounted for the largest fraction of total sediment nitrate, 66% on average. The distribution of EX-Nitrate was significantly correlated with chlorophyll and OM, which probably indicates a relation of this pool to an increased availability of sites for ionic adsorption. This EX-Nitrate pool could represent an alternative nitrate source with significant concentrations available to the microbial community, deeper in the sediment below the oxic layer. PMID:27303370

Dynamics of Inorganic Nutrients in Intertidal Sediments: Porewater, Exchangeable, and Intracellular Pools.

PubMed

Garcia-Robledo, Emilio; Bohorquez, Julio; Corzo, Alfonso; Jimenez-Arias, Juan L; Papaspyrou, Sokratis

2016-01-01

The study of inorganic nutrients dynamics in shallow sediments usually focuses on two main pools: porewater (PW) nutrients and exchangeable (EX) ammonium and phosphate. Recently, it has been found that microphytobenthos (MPB) and other microorganisms can accumulate large amounts of nutrients intracellularly (IC), highlighting the biogeochemical importance of this nutrient pool. Storing nutrients could support the growth of autotrophs when nutrients are not available, and could also provide alternative electron acceptors for dissimilatory processes such as nitrate reduction. Here, we studied the magnitude and relative importance of these three nutrient pools (PW, IC, and EX) and their relation to chlorophylls (used as a proxy for MPB abundance) and organic matter (OM) contents in an intertidal mudflat of Cadiz Bay (Spain). MPB was localized in the first 4 mm of the sediment and showed a clear seasonal pattern; highest chlorophylls content was found during autumn and lowest during spring-summer. The temporal and spatial distribution of nutrients pools and MPB were largely correlated. Ammonium was higher in the IC and EX fractions, representing on average 59 and 37% of the total ammonium pool, respectively. Similarly, phosphate in the IC and EX fractions accounted on average for 40 and 31% of the total phosphate pool, respectively. Nitrate in the PW was low, suggesting low nitrification activity and rapid consumption. Nitrate accumulated in the IC pool during periods of moderate MPB abundance, being up to 66% of the total nitrate pool, whereas it decreased when chlorophyll concentration peaked likely due to a high nitrogen demand. EX-Nitrate accounted for the largest fraction of total sediment nitrate, 66% on average. The distribution of EX-Nitrate was significantly correlated with chlorophyll and OM, which probably indicates a relation of this pool to an increased availability of sites for ionic adsorption. This EX-Nitrate pool could represent an alternative nitrate source with significant concentrations available to the microbial community, deeper in the sediment below the oxic layer.

Observation of Wetland Dynamics with Global Navigation Satellite Signals Reflectometry

NASA Astrophysics Data System (ADS)

Zuffada, C.; Shah, R.; Nghiem, S. V.; Cardellach, E.; Chew, C. C.

2015-12-01

Wetland dynamics is crucial to changes in both atmospheric methane and terrestrial water storage. The Intergovernmental Panel on Climate Change's Fifth Assessment Report (IPCC AR5) highlights the role of wetlands as a key driver of methane (CH4) emission, which is more than one order of magnitude stronger than carbon dioxide as a greenhouse gas in the centennial time scale. Among the multitude of methane emission sources (hydrates, livestock, rice cultivation, freshwaters, landfills and waste, fossil fuels, biomass burning, termites, geological sources, and soil oxidation), wetlands constitute the largest contributor with the widest uncertainty range of 177-284 Tg(CH4) yr-1 according to the IPCC estimate. Wetlands are highly susceptible to climate change that might lead to wetland collapse. Such wetland destruction would decrease the terrestrial water storage capacity and thus contribute to sea level rise, consequently exacerbating coastal flooding problems. For both methane change and water storage change, wetland dynamics is a crucial factor with the largest uncertainty. Nevertheless, a complete and consistent map of global wetlands still needs to be obtained as the Ramsar Convention calls for a wetlands inventory and impact assessment. We develop a new method for observations of wetland change using Global Navigation Satellite Signals Reflectometry (GNSS-R) signatures for global wetland mapping in synergy with the existing capability, not only as a static inventory but also as a temporal dataset, to advance the capability for monitoring the dynamics of wetland extent relevant to addressing the science issues of CH4 emission change and terrestrial water storage change. We will demonstrate the capability of the new GNSS-R method over a rice field in the Ebro Delta wetland in Spain.

Soil organic carbon dynamics of black locust plantations in the middle Loess Plateau area of China

NASA Astrophysics Data System (ADS)

Lu, N.; Liski, J.; Chang, R. Y.; Akujärvi, A.; Wu, X.; Jin, T. T.; Wang, Y. F.; Fu, B. J.

2013-11-01

Soil organic carbon (SOC) is the largest terrestrial carbon pool and sensitive to land use and cover change; its dynamics are critical for carbon cycling in terrestrial ecosystems and the atmosphere. In this study, we combined a modeling approach and field measurements to examine the temporal dynamics of SOC following afforestation (Robinia pseudoacacia) of former arable land at six sites under different climatic conditions in the Loess Plateau during 1980-2010, where the annual mean precipitation ranging from 450 mm to 600 mm. The results showed that the measured mean SOC increased to levels higher than before afforestation when taking the last measurements (i.e., at age 25 to 30 yr) at all the sites, although it decreased at the wetter sites in the first few years. The accumulation rates of SOC were 1.58 to 6.22% yr-1 in the upper 20 cm and 1.62 to 5.15% yr-1in the upper 40 cm of soil. The simulations reproduced the basic characteristics of measured SOC dynamics, suggesting that litter input and climatic factors (temperature and precipitation) were the major causes for SOC dynamics and the differences among the sites. They explained 88-96, 48-86 and 57-74% of the variations in annual SOC changes at the soil depths of 0-20, 0-40, and 0-100 cm, respectively. Notably, the simulated SOC decreased during the first few years at all the sites, although the magnitudes of decreases were smaller at the drier sites. This suggested that the modeling may be advantageous in capturing SOC changes at finer timescale. The discrepancy between the simulation and measurement was a result of uncertainties in model structure, data input, and sampling design. Our findings indicated that afforestation promoted soil carbon sequestration at the study sites during 1980-2010. Afforestation activities should decrease soil disturbances to reduce carbon release in the early stage. The long-term strategy for carbon fixation capability of the plantations should also consider the climate and site conditions, species adaptability, and successional stage of recovery.

Evaluating the role of land cover and climate uncertainties in computing gross primary production in Hawaiian Island ecosystems

Treesearch

Heather L. Kimball; Paul C. Selmants; Alvaro Moreno; Steve W. Running; Christian P. Giardina; Benjamin Poulter

2017-01-01

Gross primary production (GPP) is the Earth’s largest carbon flux into the terrestrial biosphere and plays a critical role in regulating atmospheric chemistry and global climate. The Moderate Resolution Imaging Spectrometer (MODIS)-MOD17 data product is a widely used remote sensing-based model that provides global estimates of spatiotemporal trends in GPP. When the...

Simulating Multi-Scale Fate and Transport of Mercury from Atmospheric Deposition to Receiving Surface Waters Across and Through the Terrestrial Landscape in a Coastal Plain Watershed (McTier Creek, SC)

EPA Science Inventory

Mercury (Hg) is the toxicant responsible for the largest number of fish advisories across the United States, with 1.1 million river miles under advisory. The processes governing fate and transport of Hg in streams and rivers are not well understood, in large part, because these s...

Interaction Between the Celestial and the Terrestrial Reference Frames

NASA Technical Reports Server (NTRS)

Gordon, David; MacMillan, Dan; Bolotin, Sergei; Le Bail, Karine; Gipson, John; Ma, Chopo

2010-01-01

Effects of International Celestial Reference Frame (ICRF2) on the Terrestrial Reference Frames (TRF), CRF and EOP's, The ICRF2 became official on Jan. 1, 2010. It includes positions of 3414 compact radio astronomical sources observed with VLBI, a fivefold increase from the first ICRF. Numerous new VLBI models were used and the most unstable sources were treated as arc parameters to avoid distortions of the frame. The ICRF2 has a noise floor of 40 micro-arc-seconds and an axis stability of 10 micro-arc-seconds. It was aligned with the ICRS using 138 stable sources common to ICRF2 and ICRF-Ext2. Maintenance of ICRF2 is to be made using 295 defining sources chosen for their historical positional stability, minimal source structure, and sky distribution. Their stability and their more uniform sky distribution eliminate the two largest weaknesses of ICRF I. The switchover to ICRF2 has some small effects on the TRF, CRF and Earth Orientation Parameters (EOP). A CRF based on ICRF2 shows a relative rotation of 40 micro-arc-seconds, mostly about the Y-axis. Small shifts are also seen in the EOP's, the largest being 11 micro-arc-seconds in X-pole. Some small but insignificant differences are also seen in the TRF. These results will be presented and discussed.

Examining the role of shrub expansion and fire in Arctic plant silica cycling

NASA Astrophysics Data System (ADS)

Carey, J.; Fetcher, N.; Parker, T.; Rocha, A. V.; Tang, J.

2017-12-01

All terrestrial plants accumulate silica (SiO2) to some degree, although the amount varies by species type, functional group, and environmental conditions. Silica improves overall plant fitness, providing protection from a variety of biotic and abiotic stressors. Plant silica uptake serves to retain silica in terrestrial landscapes, influencing silica export rates from terrestrial to marine systems. These export rates are important because silica is often the limiting nutrient for primary production by phytoplankton in coastal waters. Understanding how terrestrial plant processes influence silica export rates to oceanic systems is of interest on the global scale, but nowhere is this issue more important than in the Arctic, where marine diatoms rely on silica for production in large numbers and terrestrial runoff largely influences marine biogeochemistry. Moreover, the rapid rate of change occurring in the Arctic makes understanding plant silica dynamics timely, although knowledge of plant silica cycling in the region is in its infancy. This work specifically examines how shrub expansion, permafrost thaw, and fire regimes influence plant silica behavior in the Alaskan Arctic. We quantified silica accumulation in above and belowground portions of three main tundra types found in the Arctic (wet sedge, moist acidic, moist non-acidic tundra) and scaled these values to estimate how shrub expansion alters plant silica accumulation rates. Results indicate that shrub expansion via warming will increase silica storage in Arctic land plants due to the higher biomass associated with shrub tundra, whereas conversion of tussock to wet sedge tundra via permafrost thaw would produce the opposite effect in the terrestrial plant BSi pool. We also examined silica behavior in plants exposed to fire, finding that post-fire growth results in elevated plant silica uptake. Such changes in the size of the terrestrial vegetation silica reservoir could have direct consequences for the rates and timing of silica delivery to coastal receiving waters in the Arctic.

Terrestrial gross carbon dioxide uptake: global distribution and covariation with climate.

PubMed

Beer, Christian; Reichstein, Markus; Tomelleri, Enrico; Ciais, Philippe; Jung, Martin; Carvalhais, Nuno; Rödenbeck, Christian; Arain, M Altaf; Baldocchi, Dennis; Bonan, Gordon B; Bondeau, Alberte; Cescatti, Alessandro; Lasslop, Gitta; Lindroth, Anders; Lomas, Mark; Luyssaert, Sebastiaan; Margolis, Hank; Oleson, Keith W; Roupsard, Olivier; Veenendaal, Elmar; Viovy, Nicolas; Williams, Christopher; Woodward, F Ian; Papale, Dario

2010-08-13

Terrestrial gross primary production (GPP) is the largest global CO(2) flux driving several ecosystem functions. We provide an observation-based estimate of this flux at 123 +/- 8 petagrams of carbon per year (Pg C year(-1)) using eddy covariance flux data and various diagnostic models. Tropical forests and savannahs account for 60%. GPP over 40% of the vegetated land is associated with precipitation. State-of-the-art process-oriented biosphere models used for climate predictions exhibit a large between-model variation of GPP's latitudinal patterns and show higher spatial correlations between GPP and precipitation, suggesting the existence of missing processes or feedback mechanisms which attenuate the vegetation response to climate. Our estimates of spatially distributed GPP and its covariation with climate can help improve coupled climate-carbon cycle process models.

Stochastic late accretion to Earth, the Moon, and Mars.

PubMed

Bottke, William F; Walker, Richard J; Day, James M D; Nesvorny, David; Elkins-Tanton, Linda

2010-12-10

Core formation should have stripped the terrestrial, lunar, and martian mantles of highly siderophile elements (HSEs). Instead, each world has disparate, yet elevated HSE abundances. Late accretion may offer a solution, provided that ≥0.5% Earth masses of broadly chondritic planetesimals reach Earth's mantle and that ~10 and ~1200 times less mass goes to Mars and the Moon, respectively. We show that leftover planetesimal populations dominated by massive projectiles can explain these additions, with our inferred size distribution matching those derived from the inner asteroid belt, ancient martian impact basins, and planetary accretion models. The largest late terrestrial impactors, at 2500 to 3000 kilometers in diameter, potentially modified Earth's obliquity by ~10°, whereas those for the Moon, at ~250 to 300 kilometers, may have delivered water to its mantle.

Organic horizon and mineral soil mercury along three clear-cut forest chronosequences across the northeastern USA.

PubMed

Richardson, Justin B; Petrenko, Chelsea L; Friedland, Andrew J

2017-12-01

Mercury (Hg) is a globally distributed pollutant trace metal that has been increasing in terrestrial environments due to rising anthropogenic emissions. Vegetation plays an important role in Hg sequestration in forested environments, but increasing tree removal for biofuels and wood products may affect this process. The long-term effect of clear-cutting on forest soil Hg remains uncertain, since most studies are limited to measuring changes for < 10 years following a single harvest event. The chronosequence approach, which substitutes space for time using forest stands of different ages since clear-cutting, allows for investigation of processes occurring over decades to centuries. Here, we utilized three clear-cut forest soil chronosequences across the northeastern USA to understand Hg accumulation and retention over several decades. Total Hg concentrations and pools were quantified for five soil depth increments along three chronosequences. Our results showed Hg concentrations and pools decreased in the initial 20 years following clear-cutting. Mineral soil Hg pools decreased 21-53% (7-14 mg m -2 ) between 1-5-year-old stands and 15-25-year-old stands but mineral soil Hg pools recovered in 55-140-year-old stands to similar values as measured in 1-5-year-old stands. Our study is one of the first to demonstrate a decrease and recovery in Hg pool size. These changes in Hg did not correspond with changes in bulk density, soil C, or pH. We utilized a simple two-box model to determine how different Hg fluxes affected organic and mineral soil horizon Hg pools. Our simple model suggests that changes in litterfall and volatilization rates could have caused the observed changes in organic horizon Hg pools. However, only increases in leaching could reproduce observed decreases to mineral soil Hg pools. Further studies are needed to determine the mechanism of Hg loss from forest soils following clear-cutting.

Tracing Carbon Cycling in the Atmosphere and Oceans During the Cretaceous Ocean Anoxic Event 2 (OAE2, 94Ma)

NASA Astrophysics Data System (ADS)

Moran, S. A. M.; Boudinot, F. G.; Dildar, N.; Sepúlveda, J.

2017-12-01

We present a high-resolution record of compound-specific stable carbon isotope data from short-chain—aquatic algae—and long-chain n-alkanes—terrestrial plants—preserved in sedimentary sequences from the Smokey Hollow #1 (SH1) core in the Grand Staircase Escalante National Monument in southern Utah. The study area covered by SH1 core was situated at the western margin of the Western Interior Seaway during the Cretaceous Ocean Anoxic Event (OAE2, 94Ma.), and was characterized by high sedimentation rates and enhanced preservation of both marine and terrestrial organic matter. Short- and long-chain n-alkanes were isolated and purified from branched and cyclic aliphatic hydrocarbons using an optimized urea adduction protocol, and δ13Cn-alkane was measured using a Thermo MAT253 GC-C-IR-MS. We use the δ13Cn-alkane from aquatic and terrestrial sources to better understand carbon cycle interactions in the oceanic and atmospheric carbon pools across this event. Our results indicate that the δ13C of terrestrial plants experienced a faster and more pronounced positive carbon isotope excursion compared to marine sources. We will discuss how these results can inform models of carbon cycle interactions between the ocean and the atmosphere during greenhouse climates, and how they can be used to trace possible sources of CO2.

Photodegradation alleviates the lignin bottleneck for carbon turnover in terrestrial ecosystems

PubMed Central

Austin, Amy T.; Méndez, M. Soledad; Ballaré, Carlos L.

2016-01-01

A mechanistic understanding of the controls on carbon storage and losses is essential for our capacity to predict and mitigate human impacts on the global carbon cycle. Plant litter decomposition is an important first step for carbon and nutrient turnover, and litter inputs and losses are essential in determining soil organic matter pools and the carbon balance in terrestrial ecosystems. Photodegradation, the photochemical mineralization of organic matter, has been recently identified as a mechanism for previously unexplained high rates of litter mass loss in arid lands; however, the global significance of this process as a control on carbon cycling in terrestrial ecosystems is not known. Here we show that, across a wide range of plant species, photodegradation enhanced subsequent biotic degradation of leaf litter. Moreover, we demonstrate that the mechanism for this enhancement involves increased accessibility to plant litter carbohydrates for microbial enzymes. Photodegradation of plant litter, driven by UV radiation, and especially visible (blue–green) light, reduced the structural and chemical bottleneck imposed by lignin in secondary cell walls. In leaf litter from woody species, specific interactions with UV radiation obscured facilitative effects of solar radiation on biotic decomposition. The generalized effect of sunlight exposure on subsequent microbial activity, mediated by increased accessibility to cell wall polysaccharides, suggests that photodegradation is quantitatively important in determining rates of mass loss, nutrient release, and the carbon balance in a broad range of terrestrial ecosystems. PMID:27044070

Unifying latitudinal gradients in range size and richness across marine and terrestrial systems

PubMed Central

Tomašových, Adam; Kennedy, Jonathan D.; Betzner, Tristan J.; Kuehnle, Nicole Bitler; Edie, Stewart; Kim, Sora; Supriya, K.; White, Alexander E.; Rahbek, Carsten; Huang, Shan; Price, Trevor D.; Jablonski, David

2016-01-01

Many marine and terrestrial clades show similar latitudinal gradients in species richness, but opposite gradients in range size—on land, ranges are the smallest in the tropics, whereas in the sea, ranges are the largest in the tropics. Therefore, richness gradients in marine and terrestrial systems do not arise from a shared latitudinal arrangement of species range sizes. Comparing terrestrial birds and marine bivalves, we find that gradients in range size are concordant at the level of genera. Here, both groups show a nested pattern in which narrow-ranging genera are confined to the tropics and broad-ranging genera extend across much of the gradient. We find that (i) genus range size and its variation with latitude is closely associated with per-genus species richness and (ii) broad-ranging genera contain more species both within and outside of the tropics when compared with tropical- or temperate-only genera. Within-genus species diversification thus promotes genus expansion to novel latitudes. Despite underlying differences in the species range-size gradients, species-rich genera are more likely to produce a descendant that extends its range relative to the ancestor's range. These results unify species richness gradients with those of genera, implying that birds and bivalves share similar latitudinal dynamics in net species diversification. PMID:27147094

Research Needs for Carbon Management in Agriculture, Forestry and Other Land Uses

NASA Astrophysics Data System (ADS)

Negra, C.; Lovejoy, T.; Ojima, D. S.; Ashton, R.; Havemann, T.; Eaton, J.

2009-12-01

Improved management of terrestrial carbon in agriculture, forestry, and other land use sectors is a necessary part of climate change mitigation. It is likely that governments will agree in Copenhagen in December 2009 to incentives for improved management of some forms of terrestrial carbon, including maintaining existing terrestrial carbon (e.g., avoiding deforestation) and creating new terrestrial carbon (e.g., afforestation, soil management). To translate incentives into changes in land management and terrestrial carbon stocks, a robust technical and scientific information base is required. All terrestrial carbon pools (and other greenhouse gases from the terrestrial system) that interact with the atmosphere at timescales less than centuries, and all land uses, have documented mitigation potential, however, most activity has focused on above-ground forest biomass. Despite research advances in understanding emissions reduction and sequestration associated with different land management techniques, there has not yet been broad-scale implementation of land-based mitigation activity in croplands, peatlands, grasslands and other land uses. To maximize long-term global terrestrial carbon volumes, further development of relevant data, methodologies and technologies are needed to complement policy and financial incentives. The Terrestrial Carbon Group, in partnership with UN-REDD agencies, the World Bank and CGIAR institutions, is reviewing literature, convening leading experts and surveying key research institutions to develop a Roadmap for Terrestrial Carbon: Research Needs for Implementation of Carbon Management in Agriculture, Forestry and Other Land Uses. This work will summarize the existing knowledge base for emissions reductions and sequestration through land management as well as the current availability of tools and methods for measurement and monitoring of terrestrial carbon. Preliminary findings indicate a number of areas for future work. Enhanced information systems and process-level understanding of historical, current and potential emissions and sequestration in grasslands, drylands, wetlands and peatlands are needed. Research and information synthesis have not been equally distributed across regions of the world. Monitoring and reporting guidance and capacity vary across and among geographic scales and sectors. There are concerns about continuity and interpretation capability for commonly used remote sensing data products. Most research synthesis and data compilation occurs at the international level although some institutions work across scales both supporting location-specific research and development and synthesizing information up to regional and international scales. This presentation will describe findings from the Roadmap for Terrestrial Carbon for: (1) critical science and technology gaps, globally and in specific regions, for improved management and quantification of terrestrial carbon; (2) technical investments and research priorities for acceleration of avoided emissions and sequestration of terrestrial carbon; (3) opportunities for multi-lateral, multi-scale coordination and integration across research institutions.

Towards a global assessment of pyrogenic carbon from vegetation fires

NASA Astrophysics Data System (ADS)

Dittmar, Thorsten; Santín, Cristina; Doerr, Stefan; Kane, Evan; Masiello, Caroline; Ohlson, Mikael; De La Rosa, Jose Maria; Preston, Caroline

2016-04-01

The production of pyrogenic carbon (PyC; a continuum of organic carbon (C) ranging from partially charred biomass and charcoal to soot) is a widely acknowledged C sink, with the latest estimates indicating that ~50% of the PyC produced by vegetation fires potentially sequesters C over centuries. Nevertheless, the quantitative importance of PyC in the global C balance remains contentious, and therefore, PyC is rarely considered in global C cycle and climate studies. Here we examine the robustness of existing evidence and identify the main research gaps in the production, fluxes and fate of PyC from vegetation fires. Much of the previous work on PyC production has focused on selected components of total PyC generated in vegetation fires, likely leading to underestimates. We suggest that global PyC production could be in the range of 116-385 Tg C per year, that is ~0.2-0.6% of the annual terrestrial net primary production. According to our estimations, atmospheric emissions of soot/black C might be a smaller fraction of total PyC (<2%) than previously reported. Research on the fate of PyC in the environment has mainly focused on its degradation pathways, and its accumulation and resilience either in situ (surface soils) or in ultimate sinks (marine sediments). Off-site transport, transformation and PyC storage in intermediate pools are often overlooked, which could explain the fate of a substantial fraction of the PyC mobilized annually. Rivers carry about 25-28 Tg dissolved PyC per year into the ocean where it accumulates in dissolved form over ten-thousands of year to one of the largest PyC pool on Earth. The riverine flux of suspended (particulate) PyC is largely unconstrained to date. We propose new research directions addressing gaps in the global PyC cycle to fully understand the importance of the products of burning in global C cycle dynamics. This presentation is based largely on a recent review by the same group of authors (Santín et al., 2016, Global Change Biology 22, 76-91, doi: 10.1111/gcb.12985).

Tropical rain forest biogeochemistry in a warmer world: initial results from a novel warming experiment in a Puerto Rico tropical forest

NASA Astrophysics Data System (ADS)

Reed, S.; Cavaleri, M. A.; Alonso-Rodríguez, A. M.; Kimball, B. A.; Wood, T. E.

2016-12-01

Tropical forests represent one of the planet's most active biogeochemical engines. They account for the dominant proportion of Earth's live terrestrial plant biomass, nearly one-third of all soil carbon, and exchange more CO2 with the atmosphere than any other biome. In the coming decades, the tropics will experience extraordinary changes in temperature, and our understanding of how this warming will affect biogeochemical cycling remains notably poor. Given the large amounts of carbon tropical forests store and cycle, it is no surprise that our limited ability to characterize tropical forest responses to climate change may represent the largest hurdle in accurately predicting Earth's future climate. Here we describe initial results from the world's first tropical forest field warming experiment, where forest understory plants and soils are being warmed 4 °C above ambient temperatures. This Tropical Responses to Altered Climate Experiment (TRACE) was established in a rain forest in Puerto Rico to investigate the effects of increased temperature on key biological processes that control tropical forest carbon cycling, and to establish the steps that need to be taken to resolve the uncertainties surrounding tropical forest responses to warming. In this talk we will describe the experimental design, as well as the wide range of measurements being conducted. We will also present results from the initial phase of warming, including data on how increased temperatures from infrared lamp warming affected soil moisture, soil respiration rates, a suite of carbon pools, soil microbial biomass, nutrient availability, and the exchange of elements between leaf litter and soil. These data represent a first look into tropical rain forest responses to an experimentally-warmed climate in the field, and provide exciting insight into the non-linear ways tropical biogeochemical cycles respond to change. Overall, we strive to improve Earth System Model parameterization of the pools and fluxes of water, carbon, and nutrients in tropical forested ecosystems and the data shown will highlight how these cycles are coupled and independently altered by warming.

Effect of catchment land use and soil type on the concentration, quality, and bacterial degradation of riverine dissolved organic matter.

PubMed

Autio, Iida; Soinne, Helena; Helin, Janne; Asmala, Eero; Hoikkala, Laura

2016-04-01

We studied the effects of catchment characteristics (soil type and land use) on the concentration and quality of dissolved organic matter (DOM) in river water and on the bacterial degradation of terrestrial DOM. The share of organic soil was the strongest predictor of high concentrations of dissolved organic carbon, nitrogen, and phosphorus (DOC, DON, and DOP, respectively), and was linked to DOM quality. Soil type was more important than land use in determining the concentration and quality of riverine DOM. On average, 5-9 % of the DOC and 45 % of the DON were degraded by the bacterial communities within 2-3 months. Simultaneously, the proportion of humic-like compounds in the DOM pool increased. Bioavailable DON accounted for approximately one-third of the total bioavailable dissolved nitrogen, and thus, terrestrial DON can markedly contribute to the coastal plankton dynamics and support the heterotrophic food web.

The Second State of the Carbon Cycle Report: A Scientific Basis for Policy and Management Decisions

NASA Astrophysics Data System (ADS)

Birdsey, R.; Mayes, M. A.; Reed, S.; Najjar, R.; Romero-Lankao, P.

2017-12-01

The second "State of the Carbon Cycle of North America Report" (SOCCR-2) includes an overview of the North American carbon budget and future projections, the consequences of changes to the carbon budget, details of the carbon budget in major terrestrial and aquatic ecosystems (including coastal ocean waters), information about anthropogenic drivers, and implications for policy and carbon management. SOCCR-2 includes new focus areas such as soil carbon, arctic and boreal ecosystems, tribal lands, and greater emphasis on aquatic systems and the role of societal drivers and decision making on the carbon cycle. In addition, methane is considered to a greater extent than before. SOCCR-2 will contribute to the next U.S. National Climate Assessment, as well as providing information to support science-based management decisions and policies that include climate change mitigation and adaptation in Canada, the United States, and Mexico. Although the Report is still in the review process, preliminary findings indicate that North America is a net emitter of carbon dioxide and methane to the atmosphere, and that natural sinks offset about 25% of emitted carbon dioxide. Combustion of fossil fuels represents the largest source of emissions, but show a decreasing trend over the last decade and a lower share (20%) of the global total compared with the previous decade. Forests, soils, grasslands, and coastal oceans comprise the largest carbon sinks, while emissions from inland waters are a significant source of carbon dioxide. The Report also documents the lateral transfers of carbon among terrestrial ecosystems and from terrestrial to near-coastal ecosystems, to complete the carbon cycle accounting. Further, the Report explores the consequences of rising atmospheric carbon dioxide on terrestrial and oceanic systems, and the capacity of these systems to continue to act as carbon sinks based on the drivers of future carbon cycle changes, including carbon-climate feedbacks, atmospheric composition, nutrient availability, and human activity and management decisions. SOCCR-2 highlights key data gaps in carbon accounting frameworks, uncertainties in modeling and estimation approaches, and integrated frameworks for improving our understanding of the North American carbon cycle.

Estimating Asian terrestrial carbon fluxes from CONTRAIL aircraft and surface CO2 observations for the period 2006 to 2010

NASA Astrophysics Data System (ADS)

Zhang, H. F.; Chen, B. Z.; van der Laan-Luijkx, I. T.; Machida, T.; Matsueda, H.; Sawa, Y.; Fukuyama, Y.; Labuschagne, C.; Langenfelds, R.; van der Schoot, M.; Xu, G.; Yan, J. W.; Zhou, L. X.; Tans, P. P.; Peters, W.

2013-10-01

Current estimates of the terrestrial carbon fluxes in Asia ("Asia" refers to lands as far west as the Urals and is divided into Boreal Eurasia, Temperate Eurasia and tropical Asia based on TransCom regions) show large uncertainties particularly in the boreal and mid-latitudes and in China. In this paper, we present an updated carbon flux estimate for Asia by introducing aircraft CO2 measurements from the CONTRAIL (Comprehensive Observation Network for Trace gases by Airline) program into an inversion modeling system based on the CarbonTracker framework. We estimated the averaged annual total Asian terrestrial land CO2 sink was about -1.56 Pg C yr-1 over the period 2006-2010, which offsets about one-third of the fossil fuel emission from Asia (+4.15 Pg C yr-1). The uncertainty of the terrestrial uptake estimate was derived from a set of sensitivity tests and ranged from -1.07 to -1.80 Pg C yr-1, comparable to the formal Gaussian error of ±1.18 Pg C yr-1 (1-sigma). The largest sink was found in forests, predominantly in coniferous forests (-0.64 Pg C yr-1) and mixed forests (-0.14 Pg C yr-1); and the second and third large carbon sinks were found in grass/shrub lands and crop lands, accounting for -0.44 Pg C yr-1 and -0.20 Pg C yr-1, respectively. The peak-to-peak amplitude of inter-annual variability (IAV) was 0.57 Pg C yr-1 ranging from -1.71 Pg C yr-1 to -2.28 Pg C yr-1. The IAV analysis reveals that the Asian CO2 sink was sensitive to climate variations, with the lowest uptake in 2010 concurrent with summer flood/autumn drought and the largest CO2 sink in 2009 owing to favorable temperature and plentiful precipitation conditions. We also found the inclusion of the CONTRAIL data in the inversion modeling system reduced the uncertainty by 11% over the whole Asian region, with a large reduction in the southeast of Boreal Eurasia, southeast of Temperate Eurasia and most Tropical Asian areas.

Temporary wetlands: Challenges and solutions to conserving a ‘disappearing’ ecosystem

USGS Publications Warehouse

Calhoun, Aram J.K.; Mushet, David M.; Bell, Kathleen P.; Boix, Dani; Fitzsimons, James A.; Isselin-Nondedeu, Francis

2017-01-01

Frequent drying of ponded water, and support of unique, highly specialized assemblages of often rare species, characterize temporary wetlands, such as vernal pools, gilgais, and prairie potholes. As small aquatic features embedded in a terrestrial landscape, temporary wetlands enhance biodiversity and provide aesthetic, biogeochemical, and hydrologic functions. Challenges to conserving temporary wetlands include the need to: (1) integrate freshwater and terrestrial biodiversity priorities; (2) conserve entire ‘pondscapes’ defined by connections to other aquatic and terrestrial systems; (3) maintain natural heterogeneity in environmental gradients across and within wetlands, especially gradients in hydroperiod; (4) address economic impact on landowners and developers; (5) act without complete inventories of these wetlands; and (6) work within limited or non-existent regulatory protections. Because temporary wetlands function as integral landscape components, not singly as isolated entities, their cumulative loss is ecologically detrimental yet not currently part of the conservation calculus. We highlight approaches that use strategies for conserving temporary wetlands in increasingly human-dominated landscapes that integrate top-down management and bottom-up collaborative approaches. Diverse conservation activities (including education, inventory, protection, sustainable management, and restoration) that reduce landowner and manager costs while achieving desired ecological objectives will have the greatest probability of success in meeting conservation goals.

Investigation of amino acid δ 13C signatures in bone collagen to reconstruct human palaeodiets using liquid chromatography-isotope ratio mass spectrometry

NASA Astrophysics Data System (ADS)

Choy, Kyungcheol; Smith, Colin I.; Fuller, Benjamin T.; Richards, Michael P.

2010-11-01

This research presents the individual amino acid δ 13C values in bone collagen of humans ( n = 9) and animals ( n = 27) from two prehistoric shell midden sites in Korea. We obtained complete baseline separation of 16 of the 18 amino acids found in bone collagen by using liquid chromatography-isotope ratio mass spectrometry (LC-IRMS). The isotopic results reveal that the humans and animals in the two sites had similar patterns in essential amino acids (EAAs) and non-essential amino acids (NEAAs). The EAA and NEAA δ 13C values in humans are intermediate between those in marine and terrestrial animals. However, the threonine δ 13C values in humans and animals measured in this study are more highly enriched than those of other amino acids. At both sites, all amino acids in marine animals are 13C-enriched relative to those of the terrestrial animals. The isotopic evidence suggests that the Tongsamdong human had EAAs and NEAAs from marine food resources, while the Nukdo humans mainly had EAAs from terrestrial food resources but obtained NEAAs from both terrestrial and marine resources. The δ 13C isotopic differences in amino acids between marine and terrestrial animals were the largest for glycine (NEAA) and histidine (EAA) and the smallest for tyrosine (NEAA) and phenylalanine (EAA). In addition, threonine among the EAAs also had a large difference (˜8‰) in δ 13C values between marine and terrestrial animals, and has the potential to be used as an isotopic marker in palaeodietary studies. Threonine δ 13C values were used in conjunction with the established Δ 13C Glycine-phenylalanine values and produced three distinct dietary groups (terrestrial, omnivorous, and marine). In addition, threonine δ 13C values and Δ 13C Serine-phenylalanine values were discovered to separate between two dietary groups (terrestrial vs. marine), and these δ 13C values may provide a potential new indicator for investigating the distinction between marine and terrestrial protein sources in human diets.

A cross-site comparison of factors controlling streamwater carbon flux in western North American catchments (Invited)

NASA Astrophysics Data System (ADS)

Brooks, P. D.; Biederman, J. A.; Condon, K.; Chorover, J.; McIntosh, J. C.; Meixner, T.; Perdrial, J. N.

2013-12-01

Increasing variability in climate is expected to alter the amount and form of terrestrial carbon in stream water both directly, through changes in the magnitude and timing of discharge, and indirectly through changes in land cover following disturbance (e.g. drought, fire, or insect driven mortality). Predicting how these changes will impact individual stream-catchment ecosystems however, is hampered by a lack of concurrent observations on both dissolved and particulate carbon flux across a range of spatial, temporal, and discharge scales. Because carbon is strongly coupled to most biogeochemical reactions within both aquatic and terrestrial ecosystems, this represents a critical unknown in predicting the response of catchment-ecosystems to concurrent changes in climate and land cover. This presentation will address this issue using a meta-analysis of dissolved organic, dissolved inorganic, and particulate organic carbon fluxes from multiple locations, including undisturbed sites along a climate gradient from desert rivers to seasonally snow-covered, forested mountain catchments, and sites disturbed by both fire and extensive, insect driven mortality. Initial analyses suggest that dissolved (organic and inorganic) and particulate fluxes respond differently to various types of disturbance and depend on interactions between changes in size of mobile carbon pools and changes in hydrologic routing of carbon to streamwater. Anomalously large fluxes of both dissolved and particulate organic matter are associated with episodic changes in hydrologic routing (e.g. storm floods; snowmelt) that connect normally hydrologically isolated carbon pools (e.g. surficial hillslope soils) with surface water. These events are often of short duration as the supply of mobile carbon is exhausted in short term flushing response. In contrast, disturbances that increase the size of the mobile carbon pool (e.g. widespread vegetation mortality) result smaller proportional increases in concentrations, but these elevated concentrations persist for a longer period of time as increased solute sources are transported to surface water through persistent, subsurface flowpaths.

The Tropical Western Hemisphere Warm Pool

NASA Astrophysics Data System (ADS)

Wang, C.; Enfield, D. B.

2002-12-01

The paper describes and examines variability of the tropical Western Hemisphere warm pool (WHWP) of water warmer than 28.5oC. The WHWP is the second-largest tropical warm pool on Earth. Unlike the Eastern Hemisphere warm pool in the western Pacific, which straddles the equator, the WHWP is entirely north of the equator. At various stages of development the WHWP extends over parts of the eastern North Pacific, the Gulf of Mexico, the Caribbean, and the western tropical North Atlantic. It has a large seasonal cycle and its interannual fluctuations of area and intensity are significant. Surface heat fluxes warm the WHWP through the boreal spring to an annual maximum of SST and WHWP area in the late summer/early fall, associated with eastern North Pacific and Atlantic hurricane activities and rainfall from northern South America to the southern tier of the United States. Observations suggest that a positive ocean-atmosphere feedback operating through longwave radiation and associated cloudiness seems to operate in the WHWP. During winter preceding large warm pool, there is an alteration of the Walker and Hadley circulation cells that serves as a "tropospheric bridge" for transferring Pacific ENSO effects to the Atlantic sector and inducing initial warming of warm pool. Associated with the warm SST anomalies is a decrease in sea level pressure anomalies and an anomalous increase in atmospheric convection and cloudiness. The increase in convective activity and cloudiness results in less net longwave radiation loss from the sea surface, which then reinforces SST anomalies.

Influence of prescribed fire on ecosystem biomass, carbon, and nitrogen in a pinyon juniper woodland

Treesearch

Benjamin M. Rau; Robin Tausch; Alicia Reiner; Dale W. Johnson; Jeanne C. Chambers; Robert R. Blank; Annmarrie Lucchesi

2010-01-01

Increases in pinyon and juniper woodland cover associated with land-use history are suggested to provide offsets for carbon emissions in arid regions. However, the largest pools of carbon in arid landscapes are typically found in soils, and aboveground biomass cannot be considered long-term storage in fire-prone ecosystems. Also, the objectives of carbon storage may...

Community phylogenetic diversity of cyanobacterial mats associated with geothermal springs along a tropical intertidal gradient.

PubMed

Jing, Hongmei; Lacap, Donnabella C; Lau, Chui Yim; Pointing, Stephen B

2006-04-01

The 16S rRNA gene-defined bacterial diversity of tropical intertidal geothermal vents subject to varying degrees of seawater inundation was investigated. Shannon-Weaver diversity estimates of clone library-derived sequences revealed that the hottest pools located above the mean high-water mark that did not experience seawater inundation were most diverse, followed by those that were permanently submerged below the mean low-water mark. Pools located in the intertidal were the least biodiverse, and this is attributed to the fluctuating conditions caused by periodic seawater inundation rather than physicochemical conditions per se. Phylogenetic analysis revealed that a ubiquitous Oscillatoria-like phylotype accounted for 83% of clones. Synechococcus-like phylotypes were also encountered at each location, whilst others belonging to the Chroococcales, Oscillatoriales, and other non-phototrophic bacteria occurred only at specific locations along the gradient. All cyanobacterial phylotypes displayed highest phylogenetic affinity to terrestrial thermophilic counterparts rather than marine taxa.

Goddard Visiting Scientist Program

NASA Technical Reports Server (NTRS)

2000-01-01

Under this Indefinite Delivery Indefinite Quantity (IDIQ) contract, USRA was expected to provide short term (from I day up to I year) personnel as required to provide a Visiting Scientists Program to support the Earth Sciences Directorate (Code 900) at the Goddard Space Flight Center. The Contractor was to have a pool, or have access to a pool, of scientific talent, both domestic and international, at all levels (graduate student to senior scientist), that would support the technical requirements of the following laboratories and divisions within Code 900: 1) Global Change Data Center (902); 2) Laboratory for Atmospheres (Code 910); 3) Laboratory for Terrestrial Physics (Code 920); 4) Space Data and Computing Division (Code 930); 5) Laboratory for Hydrospheric Processes (Code 970). The research activities described below for each organization within Code 900 were intended to comprise the general scope of effort covered under the Visiting Scientist Program.

Mineral-associated organic matter: are we now on the right path to accurately measuring and modelling it?

NASA Astrophysics Data System (ADS)

Cotrufo, M. F.

2017-12-01

Mineral-associated organic matter (MAOM) is the largest and most persistent pool of carbon in soil. Understanding and correctly modeling its dynamic is key to suggest management practices that can augment soil carbon storage for climate change mitigation, as well as increase soil organic matter (SOM) stocks to support soil health on the long-term. In the Microbial Efficiency Mineral Stabilization (MEMS) framework we proposed that, contrary to what originally thought, this form of persistent SOM is derived from the labile components of plant inputs, through their efficient microbial processing. I will present results from several experiments using dual isotope labeling of plant inputs that largely confirm this opinion, and point to the key role of dissolved organic matter in MAOM formation, and to the dynamic nature of the outer layer of MAOM. I will also show how we are incorporating this understanding in a new SOM model, which uses physically defined measurable pools rather than turnover-defined pools to forecast C cycling in soil.

Role of Western Hemisphere Warm Pool in Rapid Climate Changes over the Western North Pacific

NASA Astrophysics Data System (ADS)

Kug, Jong-Seong; Park, Jae-Heung; An, Soon-Il

2017-04-01

Oceanic states over the western North Pacific (WNP), which is surrounded by heavily populated countries, are closely tied to the lives of the people in East Asia in regards to both climate and socioeconomics. As global warming continues, remarkable increases in sea surface temperature (SST) and sea surface height (SSH) have been observed in the WNP in recent decades. Here, we show that the SST increase in the western hemisphere warm pool (WHWP), which is the second largest warm pool on the globe, has contributed considerably to the rapid surface warming and sea level rise in the WNP via its remote teleconnection along the Pacific Intertropical Convergence Zone (ITCZ). State-of-the-art climate models strongly support the role of the WHWP not only on interannual time sales but also in long-term climate projections. We expect that understanding the processes initiated by the WHWP-SST could permit better forecasts of western North Pacific climate and the further development of the socioeconomics of East Asia.

Laser pulse heating of steel mixing with WC particles in a irradiated region

NASA Astrophysics Data System (ADS)

Shuja, S. Z.; Yilbas, B. S.; Ali, H.; Karatas, C.

2016-12-01

Laser pulse heating of steel mixing with tungsten carbide (WC) particles is carried out. Temperature field in the irradiated region is simulated in line with the experimental conditions. In the analysis, a laser pulse parameter is introduced, which defines the laser pulse intensity distribution at the irradiated surface. The influence of the laser parameter on the melt pool size and the maximum temperature increase in the irradiated region is examined. Surface temperature predictions are compared with the experimental data. In addition, the distribution of WC particles and their re-locations in the treated layer, due to combination of the natural convection and Marangoni currents, are predicted. The findings are compared to the experimental data. It is found that surface temperature predictions agree well with the experimental data. The dislocated WC particles form a streamlining in the near region of the melt pool wall, which agree with the experimental findings. The Gaussian distribution of the laser pulse intensity results in the maximum peak temperature and the maximum flow velocity inside the melt pool. In this case, the melt pool depth becomes the largest as compared to those corresponding to other laser pulse intensity distributions at the irradiated surface.

Black Carbon in Estuarine (Coastal) High-molecular-weight Dissolved Organic Matter

NASA Technical Reports Server (NTRS)

Mannino, Antonio; Harvey, H. Rodger

2003-01-01

Dissolved organic matter (DOM) in the ocean constitutes one of the largest pools of organic carbon in the biosphere, yet much of its composition is uncharacterized. Observations of black carbon (BC) particles (by-products of fossil fuel combustion and biomass burning) in the atmosphere, ice, rivers, soils and marine sediments suggest that this material is ubiquitous, yet the contribution of BC to the ocean s DOM pool remains unknown. Analysis of high-molecular-weight DOM isolated from surface waters of two estuaries in the northwest Atlantic Ocean finds that BC is a significant component of DOM, suggesting that river-estuary systems are important exporters of BC to the ocean through DOM. We show that BC comprises 4-7% of the dissolved organic carbon (DOC) at coastal ocean sites, which supports the hypothesis that the DOC pool is the intermediate reservoir in which BC ages prior to sedimentary deposition. Flux calculations suggest that BC could be as important as vascular plant-derived lignin in terms of carbon inputs to the ocean. Production of BC sequesters fossil fuel- and biomass-derived carbon into a refractory carbon pool. Hence, BC may represent a significant sink for carbon to the ocean.

Laboratory experiments on the impact disruption of iron meteorites at temperature of near-Earth space

NASA Astrophysics Data System (ADS)

Katsura, Takekuni; Nakamura, Akiko M.; Takabe, Ayana; Okamoto, Takaya; Sangen, Kazuyoshi; Hasegawa, Sunao; Liu, Xun; Mashimo, Tsutomu

2014-10-01

Iron meteorites and some M-class asteroids are generally understood to be fragments that were originally part of cores of differentiated planetesimals or part of local melt pools on primitive bodies. The parent bodies of iron meteorites may have formed in the terrestrial planet region, from which they were then scattered into the main belt (Bottke, W.F., Nesvorný, D., Grimm, R.E., Morbidelli, A., O'Brien, D.P. [2006]. Nature 439, 821-824). Therefore, a wide range of collisional events at different mass scales, temperatures, and impact velocities would have occurred between the time when the iron was segregated and the impact that eventually exposed the iron meteorites to interplanetary space. In this study, we performed impact disruption experiments of iron meteorite specimens as projectiles or targets at room temperature to increase understanding of the disruption process of iron bodies in near-Earth space. Our iron specimens (as projectiles or targets) were almost all smaller in size than their counterparts (as targets or projectiles, respectively). Experiments of impacts of steel specimens were also conducted for comparison. The fragment mass distribution of the iron material was different from that of rocks. In the iron fragmentation, a higher percentage of the mass was concentrated in larger fragments, probably due to the ductile nature of the material at room temperature. The largest fragment mass fraction f was dependent not only on the energy density but also on the size d of the specimen. We assumed a power-law dependence of the largest fragment mass fraction to initial peak pressure P0 normalized by a dynamic strength, Y, which was defined to be dependent on the size of the iron material. A least squares fit to the data of iron meteorite specimens resulted in the following relationship: f∝∝d, indicating a large size dependence of f. Additionally, the deformation of the iron materials in high-velocity shots was found to be most significant when the initial pressure greatly exceeded the dynamic strength of the material.

What can molecular dynamics simulations reveal about the stability of proteinaceous soil organic matter on mineral surfaces?

NASA Astrophysics Data System (ADS)

Andersen, A.; Reardon, P. N.; Chacon, S. S.; Qafoku, N. P.; Washton, N.; Kleber, M.

2015-12-01

With the increased attention on climate change and the role of increasing atmospheric CO2 levels in global warming, the need for an accurate depiction of the carbon cycling processes involved in the Earth's three major carbon pools, i.e., atmosphere, terrestrial systems, and oceans has never been greater. Within the terrestrial system, soil organic matter (SOM) represents an important carbon sub-pool. Complexation of SOM with mineral interfaces and particles is believed to protect SOM from possible biotic and abiotic transformation and mineralization to carbon dioxide. However, obtaining a molecular scale picture of the interactions of the various types of SOM with a variety of soil minerals is a challenging endeavor, especially for experimental techniques. Molecular scale simulations techniques can be applied to study the atomistic, molecular, and nanoscale aspects of SOM-mineral associations, and, therefore, and aid in filling current knowledge gaps in the potential fate and stability of SOM in soil systems. Here, we will discuss our recent results from large-scale molecular dynamics simulation of protein, GB1, and its interaction with clay and oxide/hydroxide minerals (i.e., kaolinite, Na+-MMT, Ca2+-MMT, goethite, and birnessite) including a comparison of structural changes of the protein by, protein orientation with respect to, degree of protein binding to, and mobility on the mineral surfaces. Our molecular simulations indicate that these mineral surfaces, with the exception of birnessite, potentially preserve the physical properties of the GB1 protein.

Chloromethane release from carbonaceous meteorite affords new insight into Mars lander findings

PubMed Central

Keppler, Frank; Harper, David B.; Greule, Markus; Ott, Ulrich; Sattler, Tobias; Schöler, Heinz F.; Hamilton, John T. G.

2014-01-01

Controversy continues as to whether chloromethane (CH3Cl) detected during pyrolysis of Martian soils by the Viking and Curiosity Mars landers is indicative of organic matter indigenous to Mars. Here we demonstrate CH3Cl release (up to 8 μg/g) during low temperature (150–400°C) pyrolysis of the carbonaceous chondrite Murchison with chloride or perchlorate as chlorine source and confirm unequivocally by stable isotope analysis the extraterrestrial origin of the methyl group (δ2H +800 to +1100‰, δ13C −19.2 to +10‰,). In the terrestrial environment CH3Cl released during pyrolysis of organic matter derives from the methoxyl pool. The methoxyl pool in Murchison is consistent both in magnitude (0.044%) and isotope signature (δ2H +1054 ± 626‰, δ13C +43.2 ± 38.8‰,) with that of the CH3Cl released on pyrolysis. Thus CH3Cl emissions recorded by Mars lander experiments may be attributed to methoxyl groups in undegraded organic matter in meteoritic debris reaching the Martian surface being converted to CH3Cl with perchlorate or chloride in Martian soil. However we cannot discount emissions arising additionally from organic matter of indigenous origin. The stable isotope signatures of CH3Cl detected on Mars could potentially be utilized to determine its origin by distinguishing between terrestrial contamination, meteoritic infall and indigenous Martian sources. PMID:25394222

Precocity in a tiny titanosaur from the Cretaceous of Madagascar.

PubMed

Curry Rogers, Kristina; Whitney, Megan; D'Emic, Michael; Bagley, Brian

2016-04-22

Sauropod dinosaurs exhibit the largest ontogenetic size range among terrestrial vertebrates, but a dearth of very young individuals has hindered understanding of the beginning of their growth trajectory. A new specimen of Rapetosaurus krausei sheds light on early life in the smallest stage of one of the largest dinosaurs. Bones record rapid growth rates and hatching lines, indicating that this individual weighed ~3.4 kilograms at hatching. Just several weeks later, when it likely succumbed to starvation in a drought-stressed ecosystem, it had reached a mass of ~40 kilograms and was ~35 centimeters tall at the hip. Unexpectedly, Rapetosaurus limb bones grew isometrically throughout their development. Cortical remodeling, limb isometry, and thin calcified hypertrophic metaphyseal cartilages indicate an active, precocial growth strategy. Copyright © 2016, American Association for the Advancement of Science.

Neovenatorid theropods are apex predators in the Late Cretaceous of North America.

PubMed

Zanno, Lindsay E; Makovicky, Peter J

2013-01-01

Allosauroid theropods were a diverse and widespread radiation of Jurassic-Cretaceous megapredators. Achieving some of the largest body sizes among theropod dinosaurs, these colossal hunters dominated terrestrial ecosystems until a faunal turnover redefined apex predator guild occupancy during the final 20 million years of the Cretaceous. Here we describe a giant new species of allosauroid--Siats meekerorum gen. et sp. nov.--providing the first evidence for the cosmopolitan clade Neovenatoridae in North America. Siats is the youngest allosauroid yet discovered from the continent and demonstrates that the clade endured there into the Late Cretaceous. The discovery provides new evidence for ecologic sympatry of large allosauroids and small-bodied tyrannosauroids. These data support the hypothesis that extinction of Allosauroidea in terrestrial ecosystems of North America permitted ecological release of tyrannosauroids, which went on to dominate end-Cretaceous food webs.

Observed Structure and Characteristics of Cold Pools over Tropical Oceans using Vector Wind Retrievals and WRF simulations

NASA Astrophysics Data System (ADS)

Garg, P.; Nesbitt, S. W.; Lang, T. J.; Chronis, T.; Thayer, J. D.; Hence, D. A.

2017-12-01

Cold pools generated in the wake of convective activity can enhance the surface sensible heat flux, latent heat flux, and also changes in evaporation out of, and fresh water flux into, the ocean. Recent studies have shown that over the open ocean, cold pool outflow boundaries and their intersections can organize and initiate a spectrum of deep convective clouds, which is a key driver of shallow and deep convection over conditionally-unstable tropical oceans. The primary goal of this study is to understand the structure and characteristics of cold pools over the tropical oceans using observations. With the idea that cold pools will have strong wind gradients at their boundaries, we use ASCAT vector wind retrievals. We identify regions of steep gradients in wind vectors as gradient features (GFs), akin to cold pools. Corresponding to these GFs, sensible and latent heat fluxes were calculated using the observed winds and background temperatures from MERRA-2 reanalysis. To evaluate the proposed technique, cold pools were observed using S-PolKa radar from the DYNAMO/AMIE field campaign in the Indian Ocean for the period of 1 October 2011 to 31 March 2012 and were compared with ASCAT GFs. To relate the thermodynamic and kinematic characteristics of observed and simulated cold pools, simulations were carried out on WRF on a 3-km domain explicitly. The areas of cold pools were identified in the models using virtual temperature (Tv), which is a direct measure of air density, while GFs were identified using model simulated winds. Quantitative measures indicate that GFs are highly correspondent with model-simulated cold pools. In global measurements of cold pools from 2007-2015, it is possible to examine the characteristics of GFs across all tropical ocean basins, and relate them to meteorological conditions, as well as the characteristics of the parent precipitation systems. Our results indicate that while there is a general relationship between the amount of precipitation and the number of cold pools, the largest cold pools exist over the Eastern Pacific basin, where the most stratiform rain is produced from oceanic MCSs. It is anticipated that improved understanding of cold pools, which are a primary triggering mechanism of oceanic shallow and deep convection, will improve prediction of this important component of the climate system.

A spectral-structural bag-of-features scene classifier for very high spatial resolution remote sensing imagery

NASA Astrophysics Data System (ADS)

Zhao, Bei; Zhong, Yanfei; Zhang, Liangpei

2016-06-01

Land-use classification of very high spatial resolution remote sensing (VHSR) imagery is one of the most challenging tasks in the field of remote sensing image processing. However, the land-use classification is hard to be addressed by the land-cover classification techniques, due to the complexity of the land-use scenes. Scene classification is considered to be one of the expected ways to address the land-use classification issue. The commonly used scene classification methods of VHSR imagery are all derived from the computer vision community that mainly deal with terrestrial image recognition. Differing from terrestrial images, VHSR images are taken by looking down with airborne and spaceborne sensors, which leads to the distinct light conditions and spatial configuration of land cover in VHSR imagery. Considering the distinct characteristics, two questions should be answered: (1) Which type or combination of information is suitable for the VHSR imagery scene classification? (2) Which scene classification algorithm is best for VHSR imagery? In this paper, an efficient spectral-structural bag-of-features scene classifier (SSBFC) is proposed to combine the spectral and structural information of VHSR imagery. SSBFC utilizes the first- and second-order statistics (the mean and standard deviation values, MeanStd) as the statistical spectral descriptor for the spectral information of the VHSR imagery, and uses dense scale-invariant feature transform (SIFT) as the structural feature descriptor. From the experimental results, the spectral information works better than the structural information, while the combination of the spectral and structural information is better than any single type of information. Taking the characteristic of the spatial configuration into consideration, SSBFC uses the whole image scene as the scope of the pooling operator, instead of the scope generated by a spatial pyramid (SP) commonly used in terrestrial image classification. The experimental results show that the whole image as the scope of the pooling operator performs better than the scope generated by SP. In addition, SSBFC codes and pools the spectral and structural features separately to avoid mutual interruption between the spectral and structural features. The coding vectors of spectral and structural features are then concatenated into a final coding vector. Finally, SSBFC classifies the final coding vector by support vector machine (SVM) with a histogram intersection kernel (HIK). Compared with the latest scene classification methods, the experimental results with three VHSR datasets demonstrate that the proposed SSBFC performs better than the other classification methods for VHSR image scenes.

Inverse modeling of the terrestrial carbon flux in China with flux covariance among inverted regions

NASA Astrophysics Data System (ADS)

Wang, H.; Jiang, F.; Chen, J. M.; Ju, W.; Wang, H.

2011-12-01

Quantitative understanding of the role of ocean and terrestrial biosphere in the global carbon cycle, their response and feedback to climate change is required for the future projection of the global climate. China has the largest amount of anthropogenic CO2 emission, diverse terrestrial ecosystems and an unprecedented rate of urbanization. Thus information on spatial and temporal distributions of the terrestrial carbon flux in China is of great importance in understanding the global carbon cycle. We developed a nested inversion with focus in China. Based on Transcom 22 regions for the globe, we divide China and its neighboring countries into 17 regions, making 39 regions in total for the globe. A Bayesian synthesis inversion is made to estimate the terrestrial carbon flux based on GlobalView CO2 data. In the inversion, GEOS-Chem is used as the transport model to develop the transport matrix. A terrestrial ecosystem model named BEPS is used to produce the prior surface flux to constrain the inversion. However, the sparseness of available observation stations in Asia poses a challenge to the inversion for the 17 small regions. To obtain additional constraint on the inversion, a prior flux covariance matrix is constructed using the BEPS model through analyzing the correlation in the net carbon flux among regions under variable climate conditions. The use of the covariance among different regions in the inversion effectively extends the information content of CO2 observations to more regions. The carbon flux over the 39 land and ocean regions are inverted for the period from 2004 to 2009. In order to investigate the impact of introducing the covariance matrix with non-zero off-diagonal values to the inversion, the inverted terrestrial carbon flux over China is evaluated against ChinaFlux eddy-covariance observations after applying an upscaling methodology.

Studying dissolved organic carbon export from the Penobscot Watershed in to Gulf of Maine using Regional Hydro-Ecological Simulation System (RHESSys)

NASA Astrophysics Data System (ADS)

Rouhani, S. F. B. B.; Schaaf, C.; Douglas, E. M.; Choate, J. S.; Yang, Y.; Kim, J.

2014-12-01

The movement of Dissolved Organic Carbon (DOC) from terrestrial system into aquatic system plays an important role for carbon sequestration in ecosystems and affects the formation of soil organic matters.Carbon cycling, storage, and transport to marine systems have become critical issues in global-change science, especially with regard to northern latitudes (Freeman et al., 2001; Benner et al., 2004). DOC, as an important composition of the carbon cycling, leaches from the terrestrial watersheds is a large source of marine DOC. The Penobscot River basin in north-central Maine is the second largest watershed in New England, which drains in to Gulf of Maine. Approximately 89% of the watershed is forested (Griffith and Alerich, 1996).Studying temporal and spatial changes in DOC export can help us to understand terrestrial carbon cycling and to detect any shifts from carbon sink to carbon source or visa versa in northern latitude forested ecosystems.Despite for the importance of understanding carbon cycling in terrestrial and aquatic biogeochemistry, the Doc export, especially the combination of DOC production from bio-system and DOC transportation from the terrestrial in to stream has been lightly discussed in most conceptual or numerical models. The Regional Hydro-Ecological Simulation System (RHESSys), which has been successfully applied in many study sites, is a physical process based terrestrial model that has the ability to simulate both the source and transportation of DOC by combining both hydrological and ecological processes. The focus of this study is on simulating the DOC concentration and flux from the land to the water using RHESSys in the Penobscot watershed. The simulated results will be compared with field measurement of DOC from the watershed to explore the spatial and temporal DOC export pattern. This study will also enhance our knowledge to select sampling locations properly and also improve our understanding on DOC production and transportation in terrestrial forest ecosystem.

Activation of old carbon by erosion of coastal and subsea permafrost in Arctic Siberia.

PubMed

Vonk, J E; Sánchez-García, L; van Dongen, B E; Alling, V; Kosmach, D; Charkin, A; Semiletov, I P; Dudarev, O V; Shakhova, N; Roos, P; Eglinton, T I; Andersson, A; Gustafsson, O

2012-09-06

The future trajectory of greenhouse gas concentrations depends on interactions between climate and the biogeosphere. Thawing of Arctic permafrost could release significant amounts of carbon into the atmosphere in this century. Ancient Ice Complex deposits outcropping along the ~7,000-kilometre-long coastline of the East Siberian Arctic Shelf (ESAS), and associated shallow subsea permafrost, are two large pools of permafrost carbon, yet their vulnerabilities towards thawing and decomposition are largely unknown. Recent Arctic warming is stronger than has been predicted by several degrees, and is particularly pronounced over the coastal ESAS region. There is thus a pressing need to improve our understanding of the links between permafrost carbon and climate in this relatively inaccessible region. Here we show that extensive release of carbon from these Ice Complex deposits dominates (57 ± 2 per cent) the sedimentary carbon budget of the ESAS, the world’s largest continental shelf, overwhelming the marine and topsoil terrestrial components. Inverse modelling of the dual-carbon isotope composition of organic carbon accumulating in ESAS surface sediments, using Monte Carlo simulations to account for uncertainties, suggests that 44 ± 10 teragrams of old carbon is activated annually from Ice Complex permafrost, an order of magnitude more than has been suggested by previous studies. We estimate that about two-thirds (66 ± 16 per cent) of this old carbon escapes to the atmosphere as carbon dioxide, with the remainder being re-buried in shelf sediments. Thermal collapse and erosion of these carbon-rich Pleistocene coastline and seafloor deposits may accelerate with Arctic amplification of climate warming.

Singlet oxygen in the coupled photochemical and biochemical oxidation of dissolved organic matter.

PubMed

Cory, Rose M; McNeill, Kristopher; Cotner, James P; Amado, Andre; Purcell, Jeremiah M; Marshall, Alan G

2010-05-15

Dissolved organic matter (DOM) is a significant (>700 Pg) global C pool. Transport of terrestrial DOM to the inland waters and coastal zones represents the largest flux of reduced C from land to water (215 Tg yr(-1)) (Meybeck, M. Am. J. Sci. 1983, 282, 401-450). Oxidation of DOM by interdependent photochemical and biochemical processes largely controls the fate of DOM entering surface waters. Reactive oxygen species (ROS) have been hypothesized to play a significant role in the photooxidation of DOM, because they may oxidize the fraction of DOM that is inaccessible to direct photochemical degradation by sunlight. We followed the effects of photochemically produced singlet oxygen ((1)O(2)) on DOM by mass spectrometry with (18)O-labeled oxygen, to understand how (1)O(2)-mediated transformations of DOM may lead to altered DOM bioavailability. The photochemical oxygen uptake by DOM attributed to (1)O(2) increased with DOM concentration, yet it remained a minority contributor to photochemical oxygen uptake even at very high DOM concentrations. When DOM samples were exposed to (1)O(2)-generating conditions (Rose Bengal and visible light), increases were observed in DOM constituents with higher oxygen content and release of H(2)O(2) was detected. Differential effects of H(2)O(2) and (1)O(2)-treated DOM showed that (1)O(2)-treated DOM led to slower bacterial growth rates relative to unmodified DOM. Results of this study suggested that the net effect of the reactions between singlet oxygen and DOM may be production of partially oxidized substrates with correspondingly lower potential biological energy yield.

The effect of long-term changes in plant inputs on soil carbon stocks

NASA Astrophysics Data System (ADS)

Georgiou, K.; Li, Z.; Torn, M. S.

2017-12-01

Soil organic carbon (SOC) is the largest actively-cycling terrestrial reservoir of C and an integral component of thriving natural and managed ecosystems. C input interventions (e.g., litter removal or organic amendments) are common in managed landscapes and present an important decision for maintaining healthy soils in sustainable agriculture and forestry. Furthermore, climate and land-cover change can also affect the amount of plant C inputs that enter the soil through changes in plant productivity, allocation, and rooting depth. Yet, the processes that dictate the response of SOC to such changes in C inputs are poorly understood and inadequately represented in predictive models. Long-term litter manipulations are an invaluable resource for exploring key controls of SOC storage and validating model representations. Here we explore the response of SOC to long-term changes in plant C inputs across a range of biomes and soil types. We synthesize and analyze data from long-term litter manipulation field experiments, and focus our meta-analysis on changes to total SOC stocks, microbial biomass carbon, and mineral-associated (`protected') carbon pools and explore the relative contribution of above- versus below-ground C inputs. Our cross-site data comparison reveals that divergent SOC responses are observed between forest sites, particularly for treatments that increase C inputs to the soil. We explore trends among key variables (e.g., microbial biomass to SOC ratios) that inform soil C model representations. The assembled dataset is an important benchmark for evaluating process-based hypotheses and validating divergent model formulations.

Impacts of peatland and permafrost changes on the terrestrial carbon storage over the last 21 ka

NASA Astrophysics Data System (ADS)

Spahni, Renato; Stocker, Benjamin D.; Joos, Fortunat

2014-05-01

Paleoclimate records and global climate-carbon cycle models suggest a net increase in land carbon (C) storage between 300 and 700 Pg C (1 Pg C = 1015 g C) during the transition from the last glacial maximum (LGM), the Holocene up to the preindustrial period. Peat accumulation rate records imply an increase in peatland C of ~600 Pg C over the course of the Holocene. In high northern latitudes mineral and organic soils are subject to permafrost formation, which is believed to have been more extensive during glacial compared to interglacial periods. Soil C in permafrost regions represents the largest inert C pool on land at present. The spatio-temporal evolution, however, of C stocks in soils and vegetation remains poorly quantified and is uncertain. Here, the Land surface Processes and eXchanges (LPX-Bern) Dynamic Global Vegetation Model is applied in transient simulations to explore the evolution of permafrost, peatland and vegetation C over the last 21'000 years. The model is forced with temperature and precipitation output from the Trace-21ka climate simulation, and dynamically simulates the formation and disappearance of peatlands and permafrost soils, vegetation distribution and C stocks. Results indicate that peatlands and permfrost areas existed further south in the LGM, in agreement with available proxy information, and that their associated C was lost during the transition into the Holocene. The simulated loss of inert C is over-compensated by vegetation regrowth. The timing of the C relocation on land is compared to observational evidence from paleoclimate archives and estimates from ocean C inventory changes.

Colonization and development of stream communities across a 200-year gradient in Glacier Bay National Park, Alaska

USGS Publications Warehouse

Milner, Alexander M.; Knudsen, E. Eric; Soiseth, Chad; Robertson, Anne L.; Schell, Don; Phillips, Ian T.; Magnusson, Katrina

2000-01-01

In May 1997, physical and biological variables were studied in 16 streams of different ages and contrasting stages of development following glacial recession in Glacier Bay National Park, southeast Alaska. The number of microcrustacean and macroinvertebrate taxa and juvenile fish abundance and diversity were significantly greater in older streams. Microcrustacean diversity was related to the amount of instream wood and percent pool habitat, while the number of macroinvertebrate taxa was related to bed stability, amount of instream wood, and percent pool habitat. The percent contribution of Ephemeroptera to stream benthic communities increased significantly with stream age and the amount of coarse benthic organic matter. Juvenile Dolly Varden (Salvelinus malma) were dominant in the younger streams, but juvenile coho salmon (Oncorhynchus kisutch) abundance was greater in older streams associated with increased pool habitat. Upstream lakes significantly influenced channel stability, percent Chironomidae, total macroinvertebrate and meiofaunal abundance, and percent fish cover. Stable isotope analyses indicated nitrogen enrichment from marine sources in macroinvertebrates and juvenile fish in older streams with established salmon runs. The findings are encapsulated in a conceptual summary of stream development that proposes stream assemblages to be determined by direct interactions with the terrestrial, marine, and lake ecosystems.

Photosynthetic pathway diversity in a seasonal pool community

USGS Publications Warehouse

Keeley, Jon E.

1999-01-01

1. Photosynthetic pathway diversity was evaluated for the dominant species in a seasonally aquatic community in the south-western USA using 14C pulse-chase techniques.2. Under submerged conditions, only about half of the species were clearly C3, three of the 15 dominants were CAM, one species was C4 and three were potentially assimilating carbon with both C3 and C4 fixation.3. During the brief terrestrial stage in the life history of these amphibious plants, both the CAM and the C3 + C4 species switched to C3, whereas the C4 species did not switch.4. Numerous variations were apparent; for example, the C4 species, while exhibiting a biochemical pathway indistinguishable from terrestrial C4 plants, lacked Kranz anatomy in the aquatic foliage. Also, despite well-developed CAM in several species, others exhibited low-level diel changes in acidity, apparently not indicative of CAM.5. Species with C4 or CAM CO2 concentrating mechanisms lacked the capacity for bicarbonate uptake, an alternative CO2 concentrating mechanism found in certain C3 species in this community.6. Rubisco/PEPC in aquatic foliage was higher in C3 species than in C4, CAM or putative C3 + C4species. In the terrestrial phase, as expected, the switch from CAM or C3 + C4 to strictly C3assimilation was associated with a substantial increase in Rubisco/PEPC. Quite unexpected, however, was the substantial increase in this ratio in terrestrial C3 foliage. It is hypothesized that submerged C3 plants utilize PEPC for recycling of respiratory CO2 and/or C4 phototrophism under field conditions of limited CO2 and O2 saturation, and this is lost in the terrestrial foliage.

The decadal state of the terrestrial carbon cycle: Global retrievals of terrestrial carbon allocation, pools, and residence times

PubMed Central

Bloom, A. Anthony; Exbrayat, Jean-François; van der Velde, Ivar R.; Feng, Liang; Williams, Mathew

2016-01-01

The terrestrial carbon cycle is currently the least constrained component of the global carbon budget. Large uncertainties stem from a poor understanding of plant carbon allocation, stocks, residence times, and carbon use efficiency. Imposing observational constraints on the terrestrial carbon cycle and its processes is, therefore, necessary to better understand its current state and predict its future state. We combine a diagnostic ecosystem carbon model with satellite observations of leaf area and biomass (where and when available) and soil carbon data to retrieve the first global estimates, to our knowledge, of carbon cycle state and process variables at a 1° × 1° resolution; retrieved variables are independent from the plant functional type and steady-state paradigms. Our results reveal global emergent relationships in the spatial distribution of key carbon cycle states and processes. Live biomass and dead organic carbon residence times exhibit contrasting spatial features (r = 0.3). Allocation to structural carbon is highest in the wet tropics (85–88%) in contrast to higher latitudes (73–82%), where allocation shifts toward photosynthetic carbon. Carbon use efficiency is lowest (0.42–0.44) in the wet tropics. We find an emergent global correlation between retrievals of leaf mass per leaf area and leaf lifespan (r = 0.64–0.80) that matches independent trait studies. We show that conventional land cover types cannot adequately describe the spatial variability of key carbon states and processes (multiple correlation median = 0.41). This mismatch has strong implications for the prediction of terrestrial carbon dynamics, which are currently based on globally applied parameters linked to land cover or plant functional types. PMID:26787856

Salmon-derived nitrogen in terrestrial invertebrates from coniferous forests of the Pacific Northwest

PubMed Central

2002-01-01

Background Bi-directional flow of nutrients between marine and terrestrial ecosystems can provide essential resources that structure communities in transitional habitats. On the Pacific coast of North America, anadromous salmon (Oncorhynchus spp.) constitute a dominant nutrient subsidy to aquatic habitats and riparian vegetation, although the contribution to terrestrial habitats is not well established. We use a dual isotope approach of δ15N and δ13C to test for the contribution of salmon nutrients to multiple trophic levels of litter-based terrestrial invertebrates below and above waterfalls that act as a barrier to salmon migration on two watersheds in coastal British Columbia. Results Invertebrates varied predictably in δ15N with enrichment of 3–8‰ below the falls compared with above the falls in all trophic groups on both watersheds. We observed increasing δ15N levels in our invertebrate groups with increasing consumption of dietary protein. Invertebrates varied in δ13C but did not always vary predictably with trophic level or habitat. From 19.4 to 71.5% of invertebrate total nitrogen was originally derived from salmon depending on taxa, watershed, and degree of fractionation from the source. Conclusions Enrichment of δ15N in the invertebrate community below the falls in conjunction with the absence of δ13C enrichment suggests that enrichment in δ15N occurs primarily through salmon-derived nitrogen subsidies to litter, soil and vegetation N pools rather than from direct consumption of salmon tissue or salmon tissue consumers. Salmon nutrient subsidies to terrestrial habitats may result in shifts in invertebrate community structure, with subsequent implications for higher vertebrate consumers, particularly the passerines. PMID:11914157

Wnt Signaling Specifies Anteroposterior Progenitor Zone Identity in the Drosophila Visual Center.

PubMed

Suzuki, Takumi; Trush, Olena; Yasugi, Tetsuo; Takayama, Rie; Sato, Makoto

2016-06-15

During brain development, various types of neuronal populations are produced from different progenitor pools to produce neuronal diversity that is sufficient to establish functional neuronal circuits. However, the molecular mechanisms that specify the identity of each progenitor pool remain obscure. Here, we show that Wnt signaling is essential for the specification of the identity of posterior progenitor pools in the Drosophila visual center. In the medulla, the largest component of the visual center, different types of neurons are produced from two progenitor pools: the outer proliferation center (OPC) and glial precursor cells (GPCs; also known as tips of the OPC). We found that OPC-type neurons are produced from the GPCs at the expense of GPC-type neurons when Wnt signaling is suppressed in the GPCs. In contrast, GPC-type neurons are ectopically induced when Wnt signaling is ectopically activated in the OPC. These results suggest that Wnt signaling is necessary and sufficient for the specification of the progenitor pool identity. We also found that Homothorax (Hth), which is temporally expressed in the OPC, is ectopically induced in the GPCs by suppression of Wnt signaling and that ectopic induction of Hth phenocopies the suppression of Wnt signaling in the GPCs. Thus, Wnt signaling is involved in regionalization of the fly visual center through the specification of the progenitor pool located posterior to the medulla by suppressing Hth expression. Brain consists of considerably diverse neurons of different origins. In mammalian brain, excitatory and inhibitory neurons derive from the dorsal and ventral telencephalon, respectively. Multiple progenitor pools also contribute to the neuronal diversity in fly brain. However, it has been unclear how differences between these progenitor pools are established. Here, we show that Wnt signaling, an evolutionarily conserved signaling, is involved in the process that establishes the differences between these progenitor pools. Because β-catenin signaling, which is under the control of Wnt ligands, specifies progenitor pool identity in the developing mammalian thalamus, Wnt signaling-mediated specification of progenitor pool identity may be conserved in insect and mammalian brains. Copyright © 2016 the authors 0270-6474/16/366503-11$15.00/0.

Ecology. Three-Gorges Dam--experiment in habitat fragmentation?

PubMed

Wu, Jianguo; Huang, Jianhui; Han, Xingguo; Xie, Zongqiang; Gao, Xianming

2003-05-23

Habitat fragmentation is the primary cause of the loss of biodiversity and ecosystem services, but its underlying processes and mechanisms remain poorly understood. Studies of islands and insular terrestrial habitats are essential for improving our understanding of habitat fragmentation. We argue that the Three-Gorges Dam, the largest that humans have ever created, presents a unique grand-scale natural experiment that allows ecologists to address a range of critical questions concerning the theory and practice of biodiversity conservation.

Evaluation of Planning for Fish and Wildlife at Corps of Engineers Reservoirs, Eufaula Reservoir Project, Oklahoma.

DTIC Science & Technology

1982-09-01

Eufaula Lake, the largest body of water in Oklahoma, extends into McIntosh, Haskell, Pittsburg and Olwiulgee counties , Oklahoma. Construction of the...TABLES iv LIST OF FIGURES vii PROJECT PERSONNEL viii INTRODUCTION 1 Location I Authorization 1 Physical Features 3 Area Description 4 WILDLIFE RESULTS AND...TableLa I Eufaula Lake Project. Summary of pertinent physical 4 characteristics. 2 Eufaula Project. Comparison of terrestrial habitat 9 affected by

The Origin of Life in a Terrestrial Hydrothermal Pool? The Importance of a Catalytic Surface

NASA Astrophysics Data System (ADS)

Sydow, L. A.; Bennett, P.

2013-12-01

A premise of one chemoautotrophic theory for the origin of life is that a recurring reaction catalyzed on the charged surfaces of pyrite served as the first metabolism and was later enveloped by a primitive cellular membrane. This proposed 'surface metabolism' is analogous to the reductive acetyl-CoA pathway (Wächtershäuser 1988) and requires the abiotic formation of methanethiol (CH3SH), the simplest of the alkyl thiols, which would serve the role of coenzyme-A in the surface metabolism. Abiogenic CH3SH has not previously been identified in terrestrial hot springs, but it has been produced in the laboratory under hydrothermal conditions in the presence of a catalyst, usually FeS. Its formation would occur via the following reactions, with reaction 2 requiring catalysis: CO2 + 2H2S --> CS2 + 2H2O (1) CS2 + 3H2 --> CH3SH + H2S (2) We have identified CH3SH in Cinder Pool, an acid-sulfate-chloride hot spring in Yellowstone National Park. This spring is unusual in that it contains a subaqueous molten sulfur layer (~18 m depth) and thousands of iron-sulfur-spherules floating on the surface, which are created by gas bubbling through the molten floor of the spring. Analysis with EDS has shown that cinder material, largely composed of elemental sulfur, also contains trace iron sulfide minerals, meaning it could serve as a reactive and catalytic surface for abiogenic CH3SH formation in Cinder Pool. Furthermore, the cinders themselves are highly porous, and these void spaces could trap necessary reactants near the catalytic surface. Gas samples were collected from Cinder pool in fall of 2011 using the bubble strip method. One sample contained measurable quantities of CH3SH, and all samples contained related reactant sulfur gases such as large amounts of H2S, and smaller amounts of CS2 and dimethyl disulfide. Laboratory microcosm experiments were conducted to replicate these findings in a sterile environment to ensure CH3SH generation was abiotic. Analog Cinder Pool water and either FeS, FeS2, or cinders collected from the pool itself were incubated with H2, CO2, and CS2 as reaction gases for over a week at pool temperatures. An experiment was also conducted without CS2 to see if the solid materials could act as the sole source of sulfur. All of the experimental solids were capable of catalyzing CH3SH production when CS2 was added. Without added CS2, however, only cinders produced CH3SH, while FeS and FeS2 bottles could only make small amounts of H2S. Presumably, the large amount of elemental sulfur in the cinders creates enough H2S for the subsequent generation of CS2 then CH3SH, which is catalyzed by the trace iron-sulfide they also contain. Cinders act as an excellent reaction surface for CH3SH generation, and a similar material may have played a significant part in the advent of life on earth.

Nitrogen Deposition: A Component of Global Change Analyses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Norby, Richard J.

1997-12-31

The global cycles of carbon and nitrogen are being perturbed by human activities that increase the transfer from large pools of nonreactive forms of the elements to reactive forms that are essential to the functioning of the terrestrial biosphere. The cycles are closely linked at all scales, and global change analyses must consider carbon and nitrogen cycles together. The increasing amount of nitrogen originating from fossil fuel combustion and deposited to terrestrial ecosystems as nitrogen oxides could increase the capacity of ecosystems to sequester carbon thereby removing some of the excess carbon dioxide from the atmosphere and slowing the developmentmore » of greenhouse warming. Several global and ecosystem models have calculated the amount of carbon sequestration that can be attributed to nitrogen deposition based on assumptions about the allocation of nitrogen among ecosystem components with different carbon-nitrogen ratios. They support the premise that nitrogen deposition is responsible for a an increasing terrestrial carbon sink since industrialization began, but there are large uncertainties related to the continued capacity of ecosystems to retain exogenous nitrogen. Whether terrestrial ecosystems continue to sequester additional carbon will depend in part on their response to increasing atmospheric carbon dioxide concentrations, which is widely thought to be constrained by limited nitrogen availability. Ecosystem models generally support the conclusion that the responses of ecosystems to increasing concentrations of carbon dioxide will be larger, and the range of possible responses will be wider, in ecosystems with increased nitrogen inputs originating as atmospheric deposition.« less

ATLANTIC-CAMTRAPS: a dataset of medium and large terrestrial mammal communities in the Atlantic Forest of South America.

PubMed

Lima, Fernando; Beca, Gabrielle; Muylaert, Renata L; Jenkins, Clinton N; Perilli, Miriam L L; Paschoal, Ana Maria O; Massara, Rodrigo L; Paglia, Adriano P; Chiarello, Adriano G; Graipel, Maurício E; Cherem, Jorge J; Regolin, André L; Oliveira Santos, Luiz Gustavo R; Brocardo, Carlos R; Paviolo, Agustín; Di Bitetti, Mario S; Scoss, Leandro M; Rocha, Fabiana L; Fusco-Costa, Roberto; Rosa, Clarissa A; Da Silva, Marina X; Hufnagell, Ludmila; Santos, Paloma M; Duarte, Gabriela T; Guimarães, Luiza N; Bailey, Larissa L; Rodrigues, Flávio Henrique G; Cunha, Heitor M; Fantacini, Felipe M; Batista, Graziele O; Bogoni, Juliano A; Tortato, Marco A; Luiz, Micheli R; Peroni, Nivaldo; De Castilho, Pedro V; Maccarini, Thiago B; Filho, Vilmar Picinatto; Angelo, Carlos De; Cruz, Paula; Quiroga, Verónica; Iezzi, María E; Varela, Diego; Cavalcanti, Sandra M C; Martensen, Alexandre C; Maggiorini, Erica V; Keesen, Fabíola F; Nunes, André V; Lessa, Gisele M; Cordeiro-Estrela, Pedro; Beltrão, Mayara G; De Albuquerque, Anna Carolina F; Ingberman, Bianca; Cassano, Camila R; Junior, Laury Cullen; Ribeiro, Milton C; Galetti, Mauro

2017-11-01

Our understanding of mammal ecology has always been hindered by the difficulties of observing species in closed tropical forests. Camera trapping has become a major advance for monitoring terrestrial mammals in biodiversity rich ecosystems. Here we compiled one of the largest datasets of inventories of terrestrial mammal communities for the Neotropical region based on camera trapping studies. The dataset comprises 170 surveys of medium to large terrestrial mammals using camera traps conducted in 144 areas by 74 studies, covering six vegetation types of tropical and subtropical Atlantic Forest of South America (Brazil and Argentina), and present data on species composition and richness. The complete dataset comprises 53,438 independent records of 83 species of mammals, includes 10 species of marsupials, 15 rodents, 20 carnivores, eight ungulates and six armadillos. Species richness averaged 13 species (±6.07 SD) per site. Only six species occurred in more than 50% of the sites: the domestic dog Canis familiaris, crab-eating fox Cerdocyon thous, tayra Eira barbara, south American coati Nasua nasua, crab-eating raccoon Procyon cancrivorus and the nine-banded armadillo Dasypus novemcinctus. The information contained in this dataset can be used to understand macroecological patterns of biodiversity, community, and population structure, but also to evaluate the ecological consequences of fragmentation, defaunation, and trophic interactions. © 2017 by the Ecological Society of America.

Study of terrestrial carbon cycling as impacted by mountaintop coal mining in the Southern Appalachian forest region using carbon elemental and isotopic data and remote sensing of land cover change

NASA Astrophysics Data System (ADS)

Fox, J. F.; Campbell, J. E.; Martin, D.

2008-12-01

The need to quantify the impact of human disturbance upon carbon flux and storage has been recently highlighted in order to more accurately budget carbon. One understudied but critical area of research is surface coal mining's impact on terrestrial carbon storage and sediment carbon transport processes-which has been identified as potentially important to understanding fluxes in global carbon budgeting. While national attention has focused on U.S. coal production to maintain a vibrant economy, scientists are concerned that increased coal production could have unforeseen environmental implications if the relationship between coal mining practices and the environment is not better understood. This issue is particularly important to the coal mining region of the Southern Appalachian forest region, which has been responsible for 23.3% of the coal produced in the United States over the past twenty years and seen approximately 300,000 ha of forested land disturbed by surface coal mining during that time period. Our presentation provides results that focus upon terrestrial carbon cycling as impacted by mountaintop coal mining in the Southern Appalachian forest region. In order to study carbon redistribution due to the mining disturbance, our methods make use of measurements of total organic carbon, total organic nitrogen, and carbon and nitrogen stable isotopes of soils and eroded sediments collected in the region as well as published data, consultation with experts and remote sensing of land cover change. It was found that disturbed terrestrial carbon, including soil C, non-soil or plant C, and geogenic C, is approximately 10% of the carbon emitted to the atmosphere during coal combusting and transportation and mining of coal. Quantification of the fate of terrestrial carbon in different pools is provided and discussed including the fate atmosphere during recovery of the terrestrial system; newly deposited coal fragments within the terrestrial soil reservoir; and carbon that is eroded to streams in mined watersheds with different levels of disturbance.

Influence of Three Contrasting Detrital Carbon Sources on Planktonic Bacterial Metabolism in a Mesotrophic Lake.

PubMed

Wehr; Petersen; Findlay

1999-01-01

Abstract Lakes receive organic carbon from a diversity of sources which vary in their contribution to planktonic microbial food webs. We conducted a mesocosm study to test the effects of three different detrital carbon sources (algae, aquatic macrophytes, terrestrial leaves) on several measures of microbial metabolism in a small meso-eutrophic lake (DOC approximately 5 mg/L). Small DOC additions (DeltaC < 1 mg/L) affected bacterial numbers, growth, and pathways of carbon acquisition. Macrophyte and leaf detritus significantly increased TDP and color, but bacterial densities initially (+12 h) were unaffected. After 168 h, densities in systems amended with terrestrial detritus were 60% less than in controls, while production rates in mesocosms with macrophyte detritus were 4-fold greater. Detritus treatments resulted in greater per-cell production rates either through stable cell numbers and greater growth rates (macrophyte-C) or lower densities with stable production rates (terrestrial-C). After only 12 h, rates of leucine aminopeptidase (LAPase) activity were 2.5x greater in macrophyte-C systems than in controls, but LAPase and beta-N-acetylglucosamindase activities in systems amended with terrestrial-C were only 50% of rates in controls. After 168 h, beta-xylosidase rates were significantly greater in communities with terrestrial and phytoplankton detritus. Microbial utilization of >20% of 102 carbon sources tested were affected by at least one detritus addition. Macrophyte-C had positive (6% of substrates) and negative (14%) effects on substrate use; terrestrial detritus had mainly positive effects. An ordination based on carbon-use profiles (+12 h) revealed a cluster of macrophyte-amended communities with greater use of psicose, lactulose, and succinamic acid; controls and algal-detritus systems were more effective in metabolizing two common sugars and cellobiose. After 168 h, communities receiving terrestrial detritus were most tightly clustered, exhibiting greater use of raffinose, pyroglutamic acid, and sebacic acid. Results suggest that pelagic bacterial communities respond to changes in organic carbon source rapidly and by different routes, including shifts in per-cell production rates and variations in degradation of a variety of compounds comprising the DOC pool.

Ceres and the terrestrial planets impact cratering record

NASA Astrophysics Data System (ADS)

Strom, R. G.; Marchi, S.; Malhotra, R.

2018-03-01

Dwarf planet Ceres, the largest object in the Main Asteroid Belt, has a surface that exhibits a range of crater densities for a crater diameter range of 5-300 km. In all areas the shape of the craters' size-frequency distribution is very similar to those of the most ancient heavily cratered surfaces on the terrestrial planets. The most heavily cratered terrain on Ceres covers ∼15% of its surface and has a crater density similar to the highest crater density on <1% of the lunar highlands. This region of higher crater density on Ceres probably records the high impact rate at early times and indicates that the other 85% of Ceres was partly resurfaced after the Late Heavy Bombardment (LHB) at ∼4 Ga. The Ceres cratering record strongly indicates that the period of Late Heavy Bombardment originated from an impactor population whose size-frequency distribution resembles that of the Main Belt Asteroids.

The 30/20 GHz mixed user architecture development study: Executive summary

NASA Technical Reports Server (NTRS)

1979-01-01

The baseline 30/30 GHz satellite communication system, designed for cost-effective communications in the years 1990 to 2000, incorporates on-board satellite demodulation and routing of individual 64 kbps digital voice-grade circuits. This level of routing flexibility is necessary to provide efficient communications to the large number of direct-to-user terminals (DTU) projected. The circuit interfacing hardware is distributed among all the DTU and master control stations. The switching circuitry which provides full interconnectivity between 30 to 45 thousand circuits is in the satellite. The DTU terminal cost, perhaps the largest element in the system cost, represents the largest economic value element of the system because it avoids using terrestrial signal distribution and routing and the charges associated with these functions. Satellite baseline design and power requirements for the system are examined.

Survey of the Urban Bell in the Belfry of St. Trinity Church in Krosno

NASA Astrophysics Data System (ADS)

Oleniacz, Grzegorz; Skrzypczak, Izabela; Ślęczka, Lucjan; Świętoń, Tomasz; Rymar, Marta

2017-06-01

Urban is one of the three bells in the belfry of St. Trinity Church in Krosno. It is the largest one, with diameter equal to 1,535 mm and it is commonly considered as one of the largest historical bells in Poland. The total mass of all the three bells is close to 4,200 kilograms, so the dynamic actions produced by swinging have a great effect on the supporting structure and on the tower. However, the exact weight of the biggest bell isn't known, and for safety reasons it should be estimated in order to verify the real dynamic forces affecting the structure. The paper describes the method of Urban bell's survey using terrestrial laser scanning and a total station as a task to estimate its weight by determining its volume.

A general scaling law reveals why the largest animals are not the fastest.

PubMed

Hirt, Myriam R; Jetz, Walter; Rall, Björn C; Brose, Ulrich

2017-08-01

Speed is the fundamental constraint on animal movement, yet there is no general consensus on the determinants of maximum speed itself. Here, we provide a general scaling model of maximum speed with body mass, which holds across locomotion modes, ecosystem types and taxonomic groups. In contrast to traditional power-law scaling, we predict a hump-shaped relationship resulting from a finite acceleration time for animals, which explains why the largest animals are not the fastest. This model is strongly supported by extensive empirical data (474 species, with body masses ranging from 30 μg to 100 tonnes) from terrestrial as well as aquatic ecosystems. Our approach unravels a fundamental constraint on the upper limit of animal movement, thus enabling a better understanding of realized movement patterns in nature and their multifold ecological consequences.

Mars Crustal Remanent Magnetism: An Extinct Dynamo Leaves a Record of Field Reversals in the Heavily Cratered Highlands

NASA Technical Reports Server (NTRS)

Connerney, John E.; Acuna, Mario H.; Ness, Norman F.; Wasilewski, Peter J.

1999-01-01

The Mars Global Surveyor spacecraft, in a highly elliptical polar orbit about Mars, obtained vector magnetic field measurements just above the surface of Mars (altitudes > 100 kilometers). Crustal magnetization, largely confined to the most ancient, heavily cratered Mars highlands, is frequently organized in east-west trending linear features, the largest of which extends over 2000 km. A representative set of survey passes are modeled using uniformly magnetized thin plates and a generalized inverse methodology. Crustal remanent magnetization exceeds that deduced for the largest terrestrial magnetic anomalies by more than an order of magnitude. Groups of quasi-parallel linear features of alternating magnetic polarity are found. They are reminiscent of similar magnetic features associated with sea floor spreading and crustal genesis on Earth but with a much larger spatial scale.

Brain architecture of the largest living land arthropod, the Giant Robber Crab Birgus latro (Crustacea, Anomura, Coenobitidae): evidence for a prominent central olfactory pathway?

PubMed Central

2010-01-01

Background Several lineages within the Crustacea conquered land independently during evolution, thereby requiring physiological adaptations for a semi-terrestrial or even a fully terrestrial lifestyle. Birgus latro Linnaeus, 1767, the giant robber crab or coconut crab (Anomura, Coenobitidae), is the largest land-living arthropod and inhabits Indo-Pacific islands such as Christmas Island. B. latro has served as a model in numerous studies of physiological aspects related to the conquest of land by crustaceans. From an olfactory point of view, a transition from sea to land means that molecules need to be detected in gas phase instead of in water solution. Previous studies have provided physiological evidence that terrestrial hermit crabs (Coenobitidae) such as B. latro have a sensitive and well differentiated sense of smell. Here we analyze the brain, in particular the olfactory processing areas of B. latro, by morphological analysis followed by 3 D reconstruction and immunocytochemical studies of synaptic proteins and a neuropeptide. Results The primary and secondary olfactory centers dominate the brain of B. latro and together account for ca. 40% of the neuropil volume in its brain. The paired olfactory neuropils are tripartite and composed of more than 1,000 columnar olfactory glomeruli, which are radially arranged around the periphery of the olfactory neuropils. The glomeruli are innervated ca. 90,000 local interneurons and ca. 160,000 projection neurons per side. The secondary olfactory centers, the paired hemiellipsoid neuropils, are targeted by the axons of these olfactory projection neurons. The projection neuron axonal branches make contact to ca. 250.000 interneurons (per side) associated with the hemiellipsoid neuropils. The hemiellipsoid body neuropil is organized into parallel neuropil lamellae, a design that is quite unusual for decapod crustaceans. The architecture of the optic neuropils and areas associated with antenna two suggest that B. latro has visual and mechanosensory skills that are comparable to those of marine Crustacea. Conclusions In parallel to previous behavioral findings that B. latro has aerial olfaction, our results indicate that their central olfactory pathway is indeed most prominent. Similar findings from the closely related terrestrial hermit crab Coenobita clypeatus suggest that in Coenobitidae, olfaction is a major sensory modality processed by the brain, and that for these animals, exploring the olfactory landscape is vital for survival in their terrestrial habitat. Future studies on terrestrial members of other crustacean taxa such as Isopoda, Amphipoda, Astacida, and Brachyura will shed light on how frequently the establishment of an aerial sense of olfaction evolved in Crustacea during the transition from sea to land. Amounting to ca. 1,000,000, the numbers of interneurons that analyse the olfactory input in B. latro brains surpasses that in other terrestrial arthropods, as e.g. the honeybee Apis mellifera or the moth Manduca sexta, by two orders of magnitude suggesting that B. latro in fact is a land-living arthropod that has devoted a substantial amount of nervous tissue to the sense of smell. PMID:20831795

Fishing down the largest coral reef fish species.

PubMed

Fenner, Douglas

2014-07-15

Studies on remote, uninhabited, near-pristine reefs have revealed surprisingly large populations of large reef fish. Locations such as the northwestern Hawaiian Islands, northern Marianas Islands, Line Islands, U.S. remote Pacific Islands, Cocos-Keeling Atoll and Chagos archipelago have much higher reef fish biomass than islands and reefs near people. Much of the high biomass of most remote reef fish communities lies in the largest species, such as sharks, bumphead parrots, giant trevally, and humphead wrasse. Some, such as sharks and giant trevally, are apex predators, but others such as bumphead parrots and humphead wrasse, are not. At many locations, decreases in large reef fish species have been attributed to fishing. Fishing is well known to remove the largest fish first, and a quantitative measure of vulnerability to fishing indicates that large reef fish species are much more vulnerable to fishing than small fish. The removal of large reef fish by fishing parallels the extinction of terrestrial megafauna by early humans. However large reef fish have great value for various ecological roles and for reef tourism. Copyright © 2014 Elsevier Ltd. All rights reserved.

Empty forest or empty rivers? A century of commercial hunting in Amazonia.

PubMed

Antunes, André P; Fewster, Rachel M; Venticinque, Eduardo M; Peres, Carlos A; Levi, Taal; Rohe, Fabio; Shepard, Glenn H

2016-10-01

The Amazon basin is the largest and most species-rich tropical forest and river system in the world, playing a pivotal role in global climate regulation and harboring hundreds of traditional and indigenous cultures. It is a matter of intense debate whether the ecosystem is threatened by hunting practices, whereby an "empty forest" loses critical ecological functions. Strikingly, no previous study has examined Amazonian ecosystem resilience through the perspective of the massive 20th century international trade in furs and skins. We present the first historical account of the scale and impacts of this trade and show that whereas aquatic species suffered basin-wide population collapse, terrestrial species did not. We link this differential resilience to the persistence of adequate spatial refuges for terrestrial species, enabling populations to be sustained through source-sink dynamics, contrasting with unremitting hunting pressure on more accessible aquatic habitats. Our findings attest the high vulnerability of aquatic fauna to unregulated hunting, particularly during years of severe drought. We propose that the relative resilience of terrestrial species suggests a marked opportunity for managing, rather than criminalizing, contemporary traditional subsistence hunting in Amazonia, through both the engagement of local people in community-based comanagement programs and science-led conservation governance.

Abrupt Climate Change in the Atlantic Ocean During the Last 20,000 Years: Insights from Multi-Element Analyses of Benthic and Planktic Foraminifera and a Coupled OA-GCM

DTIC Science & Technology

2005-09-01

paleoceanographic and terrestrial climate proxies . Greenland ice cores, in particular, provide evidence of large amplitude, very rapid climate change during...received the most attention because it is the largest Holocene excursion in the GISP2 810 record [Alley et al., 1997]. Multiple proxies in Greenland ice...latitude North Atlantic foraminiferal-based proxies such as modem analogue technique [Marchal et al., 2002; Risebrobakken et al., 2003], but

Microbial degradation of terrigenous dissolved organic matter and potential consequences for carbon cycling in brown-water streams.

PubMed

Fasching, Christina; Behounek, Barbara; Singer, Gabriel A; Battin, Tom J

2014-05-15

Streams receive substantial terrestrial deliveries of dissolved organic matter (DOM). The chromophoric (CDOM) fraction of terrestrial deliveries confers the brown colour to streamwater, often understood as browning, and plays a central role in aquatic photochemistry and is generally considered resistant to microbial metabolism. To assess the relevance of terrigenous DOM for carbon fluxes mediated by stream microorganisms, we determined the bioavailable fraction of DOM and microbial carbon use efficiency (CUE), and related these measures to partial pressure of CO2 in headwater streams spanning across a browning gradient. Fluorescence and absorbance analyses revealed high molecular weight and aromaticity, and elevated contributions from humic-like components to characterize terrestrial CDOM. We found that microorganisms metabolized this material at the cost of low CUE and shifted its composition (from fluorescence and absorbance) towards less aromatic and low-molecular weight compounds. Respiration (from CUE) was related to CO2 supersaturation in streams and this relationship was modulated by DOM composition. Our findings imply that terrigenous DOM is respired by microorganisms rather than incorporated into their biomass, and that this channelizes terrigenous carbon to the pool of CO2 potentially outgassing from streams into the atmosphere. This finding may gain relevance as major terrigenous carbon stores become mobilized and browning progresses.

Microbial degradation of terrigenous dissolved organic matter and potential consequences for carbon cycling in brown-water streams

PubMed Central

Fasching, Christina; Behounek, Barbara; Singer, Gabriel A.; Battin, Tom J.

2014-01-01

Streams receive substantial terrestrial deliveries of dissolved organic matter (DOM). The chromophoric (CDOM) fraction of terrestrial deliveries confers the brown colour to streamwater, often understood as browning, and plays a central role in aquatic photochemistry and is generally considered resistant to microbial metabolism. To assess the relevance of terrigenous DOM for carbon fluxes mediated by stream microorganisms, we determined the bioavailable fraction of DOM and microbial carbon use efficiency (CUE), and related these measures to partial pressure of CO2 in headwater streams spanning across a browning gradient. Fluorescence and absorbance analyses revealed high molecular weight and aromaticity, and elevated contributions from humic-like components to characterize terrestrial CDOM. We found that microorganisms metabolized this material at the cost of low CUE and shifted its composition (from fluorescence and absorbance) towards less aromatic and low-molecular weight compounds. Respiration (from CUE) was related to CO2 supersaturation in streams and this relationship was modulated by DOM composition. Our findings imply that terrigenous DOM is respired by microorganisms rather than incorporated into their biomass, and that this channelizes terrigenous carbon to the pool of CO2 potentially outgassing from streams into the atmosphere. This finding may gain relevance as major terrigenous carbon stores become mobilized and browning progresses. PMID:24828296

Terrestrial Waters and Sea Level Variations on Interannual Time Scale

NASA Technical Reports Server (NTRS)

Llovel, W.; Becker, M.; Cazenave, A.; Jevrejeva, S.; Alkama, R.; Decharme, B.; Douville, H.; Ablain, M.; Beckley, B.

2011-01-01

On decadal to multi-decadal time scales, thermal expansion of sea waters and land ice loss are the main contributors to sea level variations. However, modification of the terrestrial water cycle due to climate variability and direct anthropogenic forcing may also affect sea level. For the past decades, variations in land water storage and corresponding effects on sea level cannot be directly estimated from observations because these are almost non-existent at global continental scale. However, global hydrological models developed for atmospheric and climatic studies can be used for estimating total water storage. For the recent years (since mid-2002), terrestrial water storage change can be directly estimated from observations of the GRACE space gravimetry mission. In this study, we analyse the interannual variability of total land water storage, and investigate its contribution to mean sea level variability at interannual time scale. We consider three different periods that, each, depend on data availability: (1) GRACE era (2003-2009), (2) 1993-2003 and (3) 1955-1995. For the GRACE era (period 1), change in land water storage is estimated using different GRACE products over the 33 largest river basins worldwide. For periods 2 and 3, we use outputs from the ISBA-TRIP (Interactions between Soil, Biosphere, and Atmosphere-Total Runoff Integrating Pathways) global hydrological model. For each time span, we compare change in land water storage (expressed in sea level equivalent) to observed mean sea level, either from satellite altimetry (periods 1 and 2) or tide gauge records (period 3). For each data set and each time span, a trend has been removed as we focus on the interannual variability. We show that whatever the period considered, interannual variability of the mean sea level is essentially explained by interannual fluctuations in land water storage, with the largest contributions arising from tropical river basins.

Inferring Phytoplankton, Terrestrial Plant and Bacteria Bulk δ¹³C Values from Compound Specific Analyses of Lipids and Fatty Acids

PubMed Central

Taipale, Sami J.; Peltomaa, Elina; Hiltunen, Minna; Jones, Roger I.; Hahn, Martin W.; Biasi, Christina; Brett, Michael T.

2015-01-01

Stable isotope mixing models in aquatic ecology require δ13C values for food web end members such as phytoplankton and bacteria, however it is rarely possible to measure these directly. Hence there is a critical need for improved methods for estimating the δ13C ratios of phytoplankton, bacteria and terrestrial detritus from within mixed seston. We determined the δ13C values of lipids, phospholipids and biomarker fatty acids and used these to calculate isotopic differences compared to the whole-cell δ13C values for eight phytoplankton classes, five bacterial taxa, and three types of terrestrial organic matter (two trees and one grass). The lipid content was higher amongst the phytoplankton (9.5±4.0%) than bacteria (7.3±0.8%) or terrestrial matter (3.9±1.7%). Our measurements revealed that the δ13C values of lipids followed phylogenetic classification among phytoplankton (78.2% of variance was explained by class), bacteria and terrestrial matter, and there was a strong correlation between the δ13C values of total lipids, phospholipids and individual fatty acids. Amongst the phytoplankton, the isotopic difference between biomarker fatty acids and bulk biomass averaged -10.7±1.1‰ for Chlorophyceae and Cyanophyceae, and -6.1±1.7‰ for Cryptophyceae, Chrysophyceae and Diatomophyceae. For heterotrophic bacteria and for type I and type II methane-oxidizing bacteria our results showed a -1.3±1.3‰, -8.0±4.4‰, and -3.4±1.4‰ δ13C difference, respectively, between biomarker fatty acids and bulk biomass. For terrestrial matter the isotopic difference averaged -6.6±1.2‰. Based on these results, the δ13C values of total lipids and biomarker fatty acids can be used to determine the δ13C values of bulk phytoplankton, bacteria or terrestrial matter with ± 1.4‰ uncertainty (i.e., the pooled SD of the isotopic difference for all samples). We conclude that when compound-specific stable isotope analyses become more widely available, the determination of δ13C values for selected biomarker fatty acids coupled with established isotopic differences, offers a promising way to determine taxa-specific bulk δ13C values for the phytoplankton, bacteria, and terrestrial detritus embedded within mixed seston. PMID:26208114

Microbiological investigations on the water of a thermal bath at Budapest.

PubMed

Szuróczki, Sára; Kéki, Zsuzsa; Káli, Szandra; Lippai, Anett; Márialigeti, Károly; Tóth, Erika

2016-06-01

Thermal baths are unique aquatic environments combining a wide variety of natural and anthropogenic ecological factors, which also appear in their microbiological state. There is limited information on the microbiology of thermal baths in their complexity, tracking community shifts from the thermal wells to the pools. In the present study, the natural microbial community of well and pool waters in Gellért bath was studied in detail by cultivation-based techniques. To isolate bacteria, 10% R2A and minimal synthetic media (with "bath water") with agar-agar and gellan gum were used after prolonged incubation time; moreover, polyurethane blocks covered with media were also applied. Strains were identified by sequencing their 16S rRNA gene after grouping them by amplified rDNA restriction analysis. From each sample, the dominance of Alphaproteobacteria was characteristic though their diversity differed among samples. Members of Actinobacteria, Firmicutes, Beta- and Gamma-proteobacteria, Deinococcus-Thermus, and Bacteroidetes were also identified. Representatives of Deinococcus-Thermus phylum appeared only in the pool water. The largest groups in the pool water belonged to the Tistrella and Chelatococcus genera. The most dominant member in the well water was a new taxon, its similarity to Hartmannibacter diazotrophicus as closest relative was 93.93%.

Evaluation of the BD GeneOhm assay using the rotor-gene 6000 platform for rapid detection of methicillin-resistant Staphylococcus aureus from pooled screening swabs.

PubMed

Smith, Melvyn Howard; Hodgson, Julian; Eltringham, Ian Joseph

2010-12-01

As health services move toward universal methicillin-resistant Staphylococcus aureus (MRSA) screening for hospital admissions, the most cost-effective approach is yet to be defined. In this study, one of the largest to date, we evaluated the performance of the BD GeneOhm MRSA assay on the Rotor-Gene 6000 thermal cycler, using samples taken directly from pooled MRSA screens. Results were compared with the same assay performed on the Smart-Cycler II platform and overnight broth culture. Samples yielding discrepant results were subjected to detailed analysis with an in-house PCR and patient note review. A total of 1,428 pooled MRSA screens were tested. Sensitivities and specificities of 85.3% and 95.8% for the Rotor-Gene and 81% and 95.7% for the Smart-Cycler were obtained, compared with broth enrichment. The sensitivity of the BD GeneOhm assay was increased to 100% when the results of in-house PCR and patient note review were taken into account. This study demonstrates that the Rotor-Gene 6000 thermal cycler is a reliable platform for use with the BD GeneOhm assay. It also proves that commercial PCR can be performed direct on pooled samples in selective broth, without the need for overnight incubation.

Estimation of biogeochemical climate regulation services in Chinese forest ecosystems

NASA Astrophysics Data System (ADS)

Zhang, Y.; Li, S.

2016-12-01

As the global climate is changing, the climate regulation service of terrestrial ecosystem has been widely studied. Forests, as one of the most important terrestrial ecosystem types, is the biggest carbon pool or sink on land and can regulate climate through both biophysical and biogeochemical means. China is a country with vast forested areas and a variety of forest ecosystems types. Although current studies have related the climate regulation service of forest in China with biophysical or biogeochemical mechanism, there is still a lack of quantitative estimation of climate regulation services, especially for the biogeochemical climate regulation service. The GHGV (greenhouse gas value) is an indicator that can quantify the biochemical climate regulation service using ecosystems' stored organic matter, annual greenhouse gas flux, and potential greenhouse gas exchange rates during disturbances over a multiple year time frame. Therefore, we used GHGV to estimate the contribution of China's ten main forest types to biogeochemical climate regulation and generate the pattern of biochemical climate regulation service in Chinese forest ecosystems.

Evaluation of passive samplers for the collection of dissolved organic matter in streams.

PubMed

Warner, Daniel L; Oviedo-Vargas, Diana; Royer, Todd V

2015-01-01

Traditional sampling methods for dissolved organic matter (DOM) in streams limit opportunities for long-term studies due to time and cost constraints. Passive DOM samplers were constructed following a design proposed previously which utilizes diethylaminoethyl (DEAE) cellulose as a sampling medium, and they were deployed throughout a temperate stream network in Indiana. Two deployments of the passive samplers were conducted, during which grab samples were frequently collected for comparison. Differences in DOM quality between sites and sampling methods were assessed using several common optical analyses. The analyses revealed significant differences in optical properties between sampling methods, with the passive samplers preferentially collecting terrestrial, humic-like DOM. We assert that the differences in DOM composition from each sampling method were caused by preferential binding of complex humic compounds to the DEAE cellulose in the passive samplers. Nonetheless, the passive samplers may provide a cost-effective, integrated sample of DOM in situations where the bulk DOM pool is composed mainly of terrestrial, humic-like compounds.

Reactivity and mobility of new and old mercury deposition in a boreal forest ecosystem during the first year of the METAALICUS study

USGS Publications Warehouse

Hintelmann, H.; Harris, R.; Heyes, A.; Hurley, J.P.; Kelly, C.A.; Krabbenhoft, D.P.; Lindberg, S.; Rudd, J.W.M.; Scott, K.J.; St. Louis, V.L.

2002-01-01

The METAALICUS (Mercury Experiment To Assess Atmospheric Loading In Canada and the US) project is a whole ecosystem experiment designed to study the activity, mobility, and availability of atmospherically deposited mercury. To investigate the dynamics of mercury newly deposited onto a terrestrial ecosystem, an enriched stable isotope of mercury (202Hg) was sprayed onto a Boreal forest subcatchment in an experiment that allowed us, for the first time, to monitor the fate of "new" mercury in deposition and to distinguish it from native mercury historically stored in the ecosystem. Newly deposited mercury was more reactive than the native mercury with respect to volatilization and methylation pathways. Mobility through runoff was very low and strongly decreased with time because of a rapid equilibration with the large native pool of "bound" mercury. Over one season, only ???8% of the added 202Hg volatilized to the atmosphere and less than 1% appeared in runoff. Within a few months, approximately 66% of the applied 202Hg remained associated with above ground vegetation, with the rest being incorporated into soils. The fraction of 202Hg bound to vegetation was much higher than seen for native Hg (<5% vegetation), suggesting that atmospherically derived mercury enters the soil pool with a time delay, after plants senesce and decompose. The initial mobility of mercury received through small rain events or dry deposition decreased markedly in a relatively short time period, suggesting that mercury levels in terrestrial runoff may respond slowly to changes in mercury deposition rates.

Grain Yield Observations Constrain Cropland CO2 Fluxes Over Europe

NASA Astrophysics Data System (ADS)

Combe, M.; de Wit, A. J. W.; Vilà-Guerau de Arellano, J.; van der Molen, M. K.; Magliulo, V.; Peters, W.

2017-12-01

Carbon exchange over croplands plays an important role in the European carbon cycle over daily to seasonal time scales. A better description of this exchange in terrestrial biosphere models—most of which currently treat crops as unmanaged grasslands—is needed to improve atmospheric CO2 simulations. In the framework we present here, we model gross European cropland CO2 fluxes with a crop growth model constrained by grain yield observations. Our approach follows a two-step procedure. In the first step, we calculate day-to-day crop carbon fluxes and pools with the WOrld FOod STudies (WOFOST) model. A scaling factor of crop growth is optimized regionally by minimizing the final grain carbon pool difference to crop yield observations from the Statistical Office of the European Union. In a second step, we re-run our WOFOST model for the full European 25 × 25 km gridded domain using the optimized scaling factors. We combine our optimized crop CO2 fluxes with a simple soil respiration model to obtain the net cropland CO2 exchange. We assess our model's ability to represent cropland CO2 exchange using 40 years of observations at seven European FluxNet sites and compare it with carbon fluxes produced by a typical terrestrial biosphere model. We conclude that our new model framework provides a more realistic and strongly observation-driven estimate of carbon exchange over European croplands. Its products will be made available to the scientific community through the ICOS Carbon Portal and serve as a new cropland component in the CarbonTracker Europe inverse model.

Forecasting Responses of a Northern Peatland Carbon Cycle to Elevated CO2 and a Gradient of Experimental Warming

NASA Astrophysics Data System (ADS)

Jiang, Jiang; Huang, Yuanyuan; Ma, Shuang; Stacy, Mark; Shi, Zheng; Ricciuto, Daniel M.; Hanson, Paul J.; Luo, Yiqi

2018-03-01

The ability to forecast ecological carbon cycling is imperative to land management in a world where past carbon fluxes are no longer a clear guide in the Anthropocene. However, carbon-flux forecasting has not been practiced routinely like numerical weather prediction. This study explored (1) the relative contributions of model forcing data and parameters to uncertainty in forecasting flux- versus pool-based carbon cycle variables and (2) the time points when temperature and CO2 treatments may cause statistically detectable differences in those variables. We developed an online forecasting workflow (Ecological Platform for Assimilation of Data (EcoPAD)), which facilitates iterative data-model integration. EcoPAD automates data transfer from sensor networks, data assimilation, and ecological forecasting. We used the Spruce and Peatland Responses Under Changing Experiments data collected from 2011 to 2014 to constrain the parameters in the Terrestrial Ecosystem Model, forecast carbon cycle responses to elevated CO2 and a gradient of warming from 2015 to 2024, and specify uncertainties in the model output. Our results showed that data assimilation substantially reduces forecasting uncertainties. Interestingly, we found that the stochasticity of future external forcing contributed more to the uncertainty of forecasting future dynamics of C flux-related variables than model parameters. However, the parameter uncertainty primarily contributes to the uncertainty in forecasting C pool-related response variables. Given the uncertainties in forecasting carbon fluxes and pools, our analysis showed that statistically different responses of fast-turnover pools to various CO2 and warming treatments were observed sooner than slow-turnover pools. Our study has identified the sources of uncertainties in model prediction and thus leads to improve ecological carbon cycling forecasts in the future.

International Medical Graduates in the US Physician Workforce and Graduate Medical Education: Current and Historical Trends.

PubMed

Ahmed, Awad A; Hwang, Wei-Ting; Thomas, Charles R; Deville, Curtiland

2018-04-01

Data show that international medical graduates (IMGs), both US and foreign born, are more likely to enter primary care specialties and practice in underserved areas. Comprehensive assessments of representation trends for IMGs in the US physician workforce are limited. We reported current and historical representation trends for IMGs in the graduate medical education (GME) training pool and US practicing physician workforce. We compared representation for the total GME and active practicing physician pools with the 20 largest residency specialties. A 2-sided test was used for comparison, with P  < .001 considered significant. To assess significant increases in IMG GME trainee representation for the total pool and each of the specialties from 1990-2015, the slope was estimated using simple linear regression. IMGs showed significantly greater representation among active practicing physicians in 4 specialties: internal medicine (39%), neurology (31%), psychiatry (30%), and pediatrics (25%). IMGs in GME showed significantly greater representation in 5 specialties: pathology (39%), internal medicine (39%), neurology (36%), family medicine (32%), and psychiatry (31%; all P  < .001). Over the past quarter century, IMG representation in GME has increased by 0.2% per year in the total GME pool, and 1.1% per year for family medicine, 0.5% for obstetrics and gynecology and general surgery, and 0.3% for internal medicine. IMGs make up nearly a quarter of the total GME pool and practicing physician workforce, with a disproportionate share, and larger increases over our study period in certain specialties.

Land use change and terrestrial carbon stocks in Senegal

USGS Publications Warehouse

Woomer, P.L.; Tieszen, L.L.; Tappan, G.; Toure, A.; Sall, M.

2004-01-01

Environmental degradation resulting from long-term drought and land use change has affected terrestrial carbon (C) stocks within Africa's Sahel. We estimated Senegal's terrestrial carbon stocks in 1965, 1985, and 2000 using an inventory procedure involving satellite images revealing historical land use change, and recent field measurements of standing carbon stocks occurring in soil and plants. Senegal was divided into eight ecological zones containing 11 land uses. In 2000, savannas, cultivated lands, forests, and steppes were the four largest land uses in Senegal, occupying 70, 22, 2.7, and 2.3 percent of Senegal's 199,823 km2. System C stocks ranged from 9 t C ha−1 in degraded savannas in the north, to 113 t C ha−1 in the remnant forests of the Senegal River Valley. This approach resulted in estimated total C stocks of 1019 and 727 MT C between 1965 and 2000, respectively, indicating a loss of 292 MT C over 35 years. The proportion of C residing in biomass decreased with time, from 55 percent in 1965 to 38 percent in 2000. Calculated terrestrial C flux for 1993 was −7.5 MT C year−1 and had declined by 17 percent over the previous 18 years. Most of the terrestrial C flux in 1993 was attributed to biomass C reduction. Human disturbance accounted for only 22 percent of biomass C loss in 1993, suggesting that the effects of long-term Sahelian drought continue to play an overriding role in ecosystem change. Some carbon mitigation strategies for Senegal were investigated, including potential C sequestration levels. Opportunities for C mitigation exist but are constrained by available knowledge and access to resources.

The carbon balance of terrestrial ecosystems in China.

PubMed

Piao, Shilong; Fang, Jingyun; Ciais, Philippe; Peylin, Philippe; Huang, Yao; Sitch, Stephen; Wang, Tao

2009-04-23

Global terrestrial ecosystems absorbed carbon at a rate of 1-4 Pg yr(-1) during the 1980s and 1990s, offsetting 10-60 per cent of the fossil-fuel emissions. The regional patterns and causes of terrestrial carbon sources and sinks, however, remain uncertain. With increasing scientific and political interest in regional aspects of the global carbon cycle, there is a strong impetus to better understand the carbon balance of China. This is not only because China is the world's most populous country and the largest emitter of fossil-fuel CO(2) into the atmosphere, but also because it has experienced regionally distinct land-use histories and climate trends, which together control the carbon budget of its ecosystems. Here we analyse the current terrestrial carbon balance of China and its driving mechanisms during the 1980s and 1990s using three different methods: biomass and soil carbon inventories extrapolated by satellite greenness measurements, ecosystem models and atmospheric inversions. The three methods produce similar estimates of a net carbon sink in the range of 0.19-0.26 Pg carbon (PgC) per year, which is smaller than that in the conterminous United States but comparable to that in geographic Europe. We find that northeast China is a net source of CO(2) to the atmosphere owing to overharvesting and degradation of forests. By contrast, southern China accounts for more than 65 per cent of the carbon sink, which can be attributed to regional climate change, large-scale plantation programmes active since the 1980s and shrub recovery. Shrub recovery is identified as the most uncertain factor contributing to the carbon sink. Our data and model results together indicate that China's terrestrial ecosystems absorbed 28-37 per cent of its cumulated fossil carbon emissions during the 1980s and 1990s.

ON THE NOTION OF WELL-DEFINED TECTONIC REGIMES FOR TERRESTRIAL PLANETS IN THIS SOLAR SYSTEM AND OTHERS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lenardic, A.; Crowley, J. W., E-mail: ajns@rice.edu, E-mail: jwgcrowley@gmail.com

2012-08-20

A model of coupled mantle convection and planetary tectonics is used to demonstrate that history dependence can outweigh the effects of a planet's energy content and material parameters in determining its tectonic state. The mantle convection-surface tectonics system allows multiple tectonic modes to exist for equivalent planetary parameter values. The tectonic mode of the system is then determined by its specific geologic and climatic history. This implies that models of tectonics and mantle convection will not be able to uniquely determine the tectonic mode of a terrestrial planet without the addition of historical data. Historical data exists, to variable degrees,more » for all four terrestrial planets within our solar system. For the Earth, the planet with the largest amount of observational data, debate does still remain regarding the geologic and climatic history of Earth's deep past but constraints are available. For planets in other solar systems, no such constraints exist at present. The existence of multiple tectonic modes, for equivalent parameter values, points to a reason why different groups have reached different conclusions regarding the tectonic state of extrasolar terrestrial planets larger than Earth ({sup s}uper-Earths{sup )}. The region of multiple stable solutions is predicted to widen in parameter space for more energetic mantle convection (as would be expected for larger planets). This means that different groups can find different solutions, all potentially viable and stable, using identical models and identical system parameter values. At a more practical level, the results argue that the question of whether extrasolar terrestrial planets will have plate tectonics is unanswerable and will remain so until the temporal evolution of extrasolar planets can be constrained.« less

Sensitivity and Tolerance of Riparian Arthropod Communities to Altered Water Resources along a Drying River

PubMed Central

McCluney, Kevin E.; Sabo, John L.

2014-01-01

Background Rivers around the world are drying with increasing frequency, but little is known about effects on terrestrial animal communities. Previous research along the San Pedro River in southeastern AZ, USA, suggests that changes in the availability of water resources associated with river drying lead to changes in predator abundance, community composition, diversity, and abundance of particular taxa of arthropods, but these observations have not yet been tested manipulatively. Methods and Results In this study, we constructed artificial pools in the stream bed adjacent to a drying section of the San Pedro River and maintained them as the river dried. We compared pitfall trapped arthropods near artificial pools to adjacent control sites where surface waters temporarily dried. Assemblage composition changed differentially at multiple taxonomic levels, resulting in different assemblages at pools than at control sites, with multiple taxa and richness of carabid beetle genera increasing at pools but not at controls that dried. On the other hand, predator biomass, particularly wolf spiders, and diversity of orders and families were consistently higher at control sites that dried. These results suggest an important role for colonization dynamics of pools, as well as the ability of certain taxa, particularly burrowing wolf spiders, to withstand periods of temporary drying. Conclusions Overall, we found some agreement between this manipulative study of water resources and a previous analysis of river drying that showed shifts in composition, changes in diversity, and declines in abundance of certain taxa (e.g. carabid beetles). However, colonization dynamics of pools, as well as compensatory strategies of predatory wolf spiders seem to have led to patterns that do not match previous research, with control sites maintaining high diversity, despite drying. Tolerance of river drying by some species may allow persistence of substantial diversity in the face of short-term drying. The long-term effects of drying remain to be investigated. PMID:25295874

Sensitivity and tolerance of Riparian arthropod communities to altered water resources along a drying river.

PubMed

McCluney, Kevin E; Sabo, John L

2014-01-01

Rivers around the world are drying with increasing frequency, but little is known about effects on terrestrial animal communities. Previous research along the San Pedro River in southeastern AZ, USA, suggests that changes in the availability of water resources associated with river drying lead to changes in predator abundance, community composition, diversity, and abundance of particular taxa of arthropods, but these observations have not yet been tested manipulatively. In this study, we constructed artificial pools in the stream bed adjacent to a drying section of the San Pedro River and maintained them as the river dried. We compared pitfall trapped arthropods near artificial pools to adjacent control sites where surface waters temporarily dried. Assemblage composition changed differentially at multiple taxonomic levels, resulting in different assemblages at pools than at control sites, with multiple taxa and richness of carabid beetle genera increasing at pools but not at controls that dried. On the other hand, predator biomass, particularly wolf spiders, and diversity of orders and families were consistently higher at control sites that dried. These results suggest an important role for colonization dynamics of pools, as well as the ability of certain taxa, particularly burrowing wolf spiders, to withstand periods of temporary drying. Overall, we found some agreement between this manipulative study of water resources and a previous analysis of river drying that showed shifts in composition, changes in diversity, and declines in abundance of certain taxa (e.g. carabid beetles). However, colonization dynamics of pools, as well as compensatory strategies of predatory wolf spiders seem to have led to patterns that do not match previous research, with control sites maintaining high diversity, despite drying. Tolerance of river drying by some species may allow persistence of substantial diversity in the face of short-term drying. The long-term effects of drying remain to be investigated.

[Effects of land use change on carbon storage in terrestrial ecosystem].

PubMed

Yang, Jingcheng; Han, Xingguo; Huang, Jianhui; Pan, Qingmin

2003-08-01

Terrestrial ecosystem is an important carbon pool, which plays a crucial role in carbon biogeochemical cycle. Human activities such as fossil fuel combustion and land use change have resulted in carbon fluxes from terrestrial ecosystem to the atmosphere, which increased the atmospheric CO2 concentration, and reinforced the greenhouse effect. Land use change affects the structure and function of the terrestrial ecosystem, which causes its change of carbon storage. To a great extent, the change of carbon storage lies in the type of ecosystem and the change of land use patterns. The conversion of forest to agricultural land and pasture causes a large reduction of carbon storage in vegetation and soil, and the decrease of soil carbon concentration is mainly caused by the reduction of detritus, the acceleration of soil organic matter decomposition, and the destroy of physical protection to organic matter due to agricultural practices. The loss of soil organic matter appears at the early stage after deforestation, and the loss rate is influenced by many factors and soil physical, chemical and biological processes. The conversion of agricultural land and pasture to forest and many conservative agricultural practices can sequester atmospheric carbon in vegetation and soil. Vegetation can sequester large amounts of carbon from atmosphere, while carbon accumulation in soil varies greatly because of farming history and soil spatial heterogeneity. Conservative agricultural practices such as no-tillage, reasonable cropping system, and fertilization can influence soil physical and chemical characters, plant growth, quality and quantity of stubble, and soil microbial biomass and its activity, and hence, maintain and increase soil carbon concentration.

Different sources and degradation state of dissolved, particulate, and sedimentary organic matter along the Eurasian Arctic coastal margin

NASA Astrophysics Data System (ADS)

Karlsson, Emma; Gelting, Johan; Tesi, Tommaso; van Dongen, Bart; Andersson, August; Semiletov, Igor; Charkin, Alexander; Dudarev, Oleg; Gustafsson, Örjan

2016-06-01

Thawing Arctic permafrost causes massive fluvial and erosional releases of dissolved and particulate organic carbon (DOC and POC) to coastal waters. Here we investigate how different sources and degradation of remobilized terrestrial carbon may affect large-scale carbon cycling, by comparing molecular and dual-isotope composition of waterborne high molecular weight DOC (>1 kD, aka colloidal OC), POC, and sedimentary OC (SOC) across the East Siberian Arctic Shelves. Lignin phenol fingerprints demonstrate a longitudinal trend in relative contribution of terrestrial sources to coastal OC. Wax lipids and cutins were not detected in colloidal organic carbon (COC), in contrast to POC and SOC, suggesting that different terrestrial carbon pools partition into different aquatic carrier phases. The Δ14C signal suggests overwhelmingly contemporary sources for COC, while POC and SOC are dominated by old C from Ice Complex Deposit (ICD) permafrost. Monte Carlo source apportionment (δ13C, Δ14C) constrained that COC was dominated by terrestrial OC from topsoil permafrost (65%) and marine plankton (25%) with smaller contribution ICD and other older permafrost stocks (9%). This distribution is likely a result of inherent compositional matrix differences, possibly driven by organomineral associations. Modern OC found suspended in the surface water may be more exposed to degradation, in contrast to older OC that preferentially settles to the seafloor where it may be degraded on a longer timescale. The different sources which partition into DOC, POC, and SOC appear to have vastly different fates along the Eurasian Arctic coastal margin and may possibly respond on different timescales to climate change.

Burning transformations: Fire history effects on organic matter processing from hillslopes to streams

NASA Astrophysics Data System (ADS)

Barnes, R. T.; Gilbertson, A.; Maxwell, K.

2017-12-01

Disturbance strongly regulates material and energy flows, changing ecosystem pattern and process. An increase in the size and severity of fire, particularly in the Intermountain West, over the last several decades is expected to continue due to a warming climate. Predicting how fire will alter the net ecosystem carbon balance requires us to understand how carbon is stored, processed, and transferred. Here we present results from paired watersheds focused on five 2002 severe fires in Colorado to examine how organic matter is processed along the hillslope and within the stream. Comparing soil samples and water extractable organic matter (WEOM) between burned and unburned sites illustrates the impact of fire: burned soils have 50% organic matter (OM) content as unburned soils, regardless of geomorphic position. While a smaller pool, soil OM (SOM) in burned sites is more susceptible to microbial degradation (p<0.001 for 4 of 6 sites), especially in systems with slower vegetative recovery. This is explained, in part, to the water extractable organic matter (WEOM) from unburned soils having a higher C:N than burned sites (p<0.02). This shift in SOM quality is likely due to differing OM inputs (e.g. grasses and forbes vs. trees in burned vs. unburned sites). Comparing results from intact soil column experiments to soil extractions and stream samples, suggests that the majority of this soil derived WEOM does not make it to the stream, potentially getting sorbed deeper in the mineral rich, organic poor, portion of the soil. Interestingly, the systematic shifts in OM amounts and quality (as measured by SUVA, E2:E3, and fluorescence) within the terrestrial system in response to fire, are not seen in stream exports. As such, while there are significant relationships (p<0.05) between stream DOM quality, DOM bioavailability, and stream metabolism, burned watersheds are not exporting DOM that is more bioavailable. In addition, despite different terrestrial OM pools, burned and unburned watersheds export statistically similar amounts of DOM per unit area, suggesting that a larger fraction of OM is transferred from the terrestrial to aquatic ecosystem within fire affected landscapes.

Competition between plant functional types in the Canadian Terrestrial Ecosystem Model (CTEM) v. 2.0

NASA Astrophysics Data System (ADS)

Melton, J. R.; Arora, V. K.

2015-06-01

The Canadian Terrestrial Ecosystem Model (CTEM) is the interactive vegetation component in the Earth system model of the Canadian Centre for Climate Modelling and Analysis. CTEM models land-atmosphere exchange of CO2 through the response of carbon in living vegetation, and dead litter and soil pools, to changes in weather and climate at timescales of days to centuries. Version 1.0 of CTEM uses prescribed fractional coverage of plant functional types (PFTs) although, in reality, vegetation cover continually adapts to changes in climate, atmospheric composition, and anthropogenic forcing. Changes in the spatial distribution of vegetation occur on timescales of years to centuries as vegetation distributions inherently have inertia. Here, we present version 2.0 of CTEM which includes a representation of competition between PFTs based on a modified version of the Lotka-Volterra (L-V) predator-prey equations. Our approach is used to dynamically simulate the fractional coverage of CTEM's seven natural, non-crop PFTs which are then compared with available observation-based estimates. Results from CTEM v. 2.0 show the model is able to represent the broad spatial distributions of its seven PFTs at the global scale. However, differences remain between modelled and observation-based fractional coverages of PFTs since representing the multitude of plant species globally, with just seven non-crop PFTs, only captures the large scale climatic controls on PFT distributions. As expected, PFTs that exist in climate niches are difficult to represent either due to the coarse spatial resolution of the model, and the corresponding driving climate, or the limited number of PFTs used. We also simulate the fractional coverages of PFTs using unmodified L-V equations to illustrate its limitations. The geographic and zonal distributions of primary terrestrial carbon pools and fluxes from the versions of CTEM that use prescribed and dynamically simulated fractional coverage of PFTs compare reasonably well with each other and observation-based estimates. The parametrization of competition between PFTs in CTEM v. 2.0 based on the modified L-V equations behaves in a reasonably realistic manner and yields a tool with which to investigate the changes in spatial distribution of vegetation in response to future changes in climate.

Competition between plant functional types in the Canadian Terrestrial Ecosystem Model (CTEM) v. 2.0

NASA Astrophysics Data System (ADS)

Melton, J. R.; Arora, V. K.

2016-01-01

The Canadian Terrestrial Ecosystem Model (CTEM) is the interactive vegetation component in the Earth system model of the Canadian Centre for Climate Modelling and Analysis. CTEM models land-atmosphere exchange of CO2 through the response of carbon in living vegetation, and dead litter and soil pools, to changes in weather and climate at timescales of days to centuries. Version 1.0 of CTEM uses prescribed fractional coverage of plant functional types (PFTs) although, in reality, vegetation cover continually adapts to changes in climate, atmospheric composition and anthropogenic forcing. Changes in the spatial distribution of vegetation occur on timescales of years to centuries as vegetation distributions inherently have inertia. Here, we present version 2.0 of CTEM, which includes a representation of competition between PFTs based on a modified version of the Lotka-Volterra (L-V) predator-prey equations. Our approach is used to dynamically simulate the fractional coverage of CTEM's seven natural, non-crop PFTs, which are then compared with available observation-based estimates. Results from CTEM v. 2.0 show the model is able to represent the broad spatial distributions of its seven PFTs at the global scale. However, differences remain between modelled and observation-based fractional coverage of PFTs since representing the multitude of plant species globally, with just seven non-crop PFTs, only captures the large-scale climatic controls on PFT distributions. As expected, PFTs that exist in climate niches are difficult to represent either due to the coarse spatial resolution of the model, and the corresponding driving climate, or the limited number of PFTs used. We also simulate the fractional coverage of PFTs using unmodified L-V equations to illustrate its limitations. The geographic and zonal distributions of primary terrestrial carbon pools and fluxes from the versions of CTEM that use prescribed and dynamically simulated fractional coverage of PFTs compare reasonably well with each other and observation-based estimates. The parametrization of competition between PFTs in CTEM v. 2.0 based on the modified L-V equations behaves in a reasonably realistic manner and yields a tool with which to investigate the changes in spatial distribution of vegetation in response to future changes in climate.

Characterization of Organic Matter Sources within a Matrix of Land Use in Northeast Utah

NASA Astrophysics Data System (ADS)

Kelso, J. E.; Baker, M. A.

2017-12-01

Dynamics of organic matter (OM) sources in natural aquatic systems have been studied for decades, but urban studies have revealed additional, less studied, OM sources such as stormwater, lawn clippings, and wastewater effluent. Traditionally the OM pool in freshwater systems has been defined as a homogenous pool of varying size classes: course particulate, fine particulate and dissolved OM. Our goal was to identify and quantify the composition of fine particulate OM (FPOM), and dissolved OM (DOM) as derived from autochthonous, terrestrial, and potential anthropogenic sources. We hypothesized anthropogenic changes in land use have increased the proportion of autochthonous sources of OM. We sampled OM at 33 sites in four watersheds in northeast Utah that encompass a range of land uses. Stable isotopes of carbon, nitrogen, and deuterium were collected for all size classes of OM, and DOM was analyzed with a spectrofluorometer. Stable isotopes were used to estimate the proportion of autochthonous and terrestrial sources of OM. Fluorescence indices and a PARAFAC model were created from DOM excitation emission matrices (EEMs). FPOM appeared to be a mixture of autochthonous and terrestrial sources but overlap in endmember isotope values made quantifying the proportion of each source difficult. Higher deuterium values (-120 to -80‰) were associated with sites receiving wastewater effluent, while sites with agriculture, forest, and urban land use had lower deuterium isotope values (-200 to -110). DOM Excitation Emission Matrices were resolved into a 5-component PARAFAC model. The percent of protein-like DOM components tended to be higher in urban versus non-urban sites (mean 35%, S.D. 12% versus mean 25%, S.D. 15%). We concluded deuterium isotopes may be used as a tracer or wastewater effluent and DOM is composed of more labile, protein-like DOM with increased wastewater input. A greater understanding of the sources of OM can inform management and policy decisions aimed at mitigating the effects of OM pollution. For example, evaluating tradeoffs between mitigating the effects of OM inputs from cattle grazing versus building or improving waste water treatment facilities can be further explored.

Similarities in Photodegradation of Cyanobacteria-Derived and Marine Fluorescent Dissolved Organic Matter

NASA Astrophysics Data System (ADS)

Ianiri, H. L.; Timko, S.; Gonsior, M.

2016-02-01

Marine dissolved organic matter (DOM) is one of the largest reduced carbon reservoirs on Earth, yet we only have a limited understanding of its production, cycling, degradation, and overall structure. It was previously believed that a significant portion of refractory dissolved organic carbon (RDOC) in the ocean was derived from terrestrial sources, however recent studies indicated that the majority of marine DOM might be produced in situ by marine biota. Previous research has found that terrestrial and microbial DOM fluorescent signatures are similar, complicating the identification of the origins of marine fluorescent DOM (FDOM). However, photodegradation kinetics of terrestrial and microbial-derived DOM are expected to be different due to their assumed different chemical compositions. In this study we analyzed for the first time the photodegradation kinetics of microbial-derived DOM originating from different cyanobacteria strains. Cyanobacterial-derived DOM were exposed to simulated sunlight for a total of 20 hours while recording excitation emission matrix (EEM) fluorescence every twenty minutes to observe the photodegradation of this specific FDOM. Parallel Factor Analysis (PARAFAC) was applied to deconvolute the EEM matrices into six separate components. The photodegradation kinetics was then calculated for each component and compared with previously obtained photodegradation data of marine and terrestrial FDOM. This six component PARAFAC model was similar to those generated from open ocean data and global DOM data sets. The "humic-like" FDOM was also found in cyanobacteria FDOM and showed similar fluorescence intensities and percent fluorescence loss when compared to marine DOM. The degradation kinetics of the "humic-like" component of microbial-derived DOM was faster than that of terrestrial-derived DOM, and marine FDOM samples showed degradation kinetics more similar to microbial-derived FDOM. This indicates marine FDOM is more similar in chemical composition to microbial-derived FDOM than terrestrial-derived FDOM, supporting the hypothesis that the majority of marine FDOM is produced in situ.

Degraded tropical rain forests possess valuable carbon storage opportunities in a complex, forested landscape.

PubMed

Alamgir, Mohammed; Campbell, Mason J; Turton, Stephen M; Pert, Petina L; Edwards, Will; Laurance, William F

2016-07-20

Tropical forests are major contributors to the terrestrial global carbon pool, but this pool is being reduced via deforestation and forest degradation. Relatively few studies have assessed carbon storage in degraded tropical forests. We sampled 37,000 m(2) of intact rainforest, degraded rainforest and sclerophyll forest across the greater Wet Tropics bioregion of northeast Australia. We compared aboveground biomass and carbon storage of the three forest types, and the effects of forest structural attributes and environmental factors that influence carbon storage. Some degraded forests were found to store much less aboveground carbon than intact rainforests, whereas others sites had similar carbon storage to primary forest. Sclerophyll forests had lower carbon storage, comparable to the most heavily degraded rainforests. Our findings indicate that under certain situations, degraded forest may store as much carbon as intact rainforests. Strategic rehabilitation of degraded forests could enhance regional carbon storage and have positive benefits for tropical biodiversity.

Degraded tropical rain forests possess valuable carbon storage opportunities in a complex, forested landscape

PubMed Central

Alamgir, Mohammed; Campbell, Mason J.; Turton, Stephen M.; Pert, Petina L.; Edwards, Will; Laurance, William F.

2016-01-01

Tropical forests are major contributors to the terrestrial global carbon pool, but this pool is being reduced via deforestation and forest degradation. Relatively few studies have assessed carbon storage in degraded tropical forests. We sampled 37,000 m2 of intact rainforest, degraded rainforest and sclerophyll forest across the greater Wet Tropics bioregion of northeast Australia. We compared aboveground biomass and carbon storage of the three forest types, and the effects of forest structural attributes and environmental factors that influence carbon storage. Some degraded forests were found to store much less aboveground carbon than intact rainforests, whereas others sites had similar carbon storage to primary forest. Sclerophyll forests had lower carbon storage, comparable to the most heavily degraded rainforests. Our findings indicate that under certain situations, degraded forest may store as much carbon as intact rainforests. Strategic rehabilitation of degraded forests could enhance regional carbon storage and have positive benefits for tropical biodiversity. PMID:27435389

Degraded tropical rain forests possess valuable carbon storage opportunities in a complex, forested landscape

NASA Astrophysics Data System (ADS)

Alamgir, Mohammed; Campbell, Mason J.; Turton, Stephen M.; Pert, Petina L.; Edwards, Will; Laurance, William F.

2016-07-01

Tropical forests are major contributors to the terrestrial global carbon pool, but this pool is being reduced via deforestation and forest degradation. Relatively few studies have assessed carbon storage in degraded tropical forests. We sampled 37,000 m2 of intact rainforest, degraded rainforest and sclerophyll forest across the greater Wet Tropics bioregion of northeast Australia. We compared aboveground biomass and carbon storage of the three forest types, and the effects of forest structural attributes and environmental factors that influence carbon storage. Some degraded forests were found to store much less aboveground carbon than intact rainforests, whereas others sites had similar carbon storage to primary forest. Sclerophyll forests had lower carbon storage, comparable to the most heavily degraded rainforests. Our findings indicate that under certain situations, degraded forest may store as much carbon as intact rainforests. Strategic rehabilitation of degraded forests could enhance regional carbon storage and have positive benefits for tropical biodiversity.

Freshwater savings from marine protein consumption

NASA Astrophysics Data System (ADS)

Gephart, Jessica A.; Pace, Michael L.; D'Odorico, Paolo

2014-01-01

Marine fisheries provide an essential source of protein for many people around the world. Unlike alternative terrestrial sources of protein, marine fish production requires little to no freshwater inputs. Consuming marine fish protein instead of terrestrial protein therefore represents freshwater savings (equivalent to an avoided water cost) and contributes to a low water footprint diet. These water savings are realized by the producers of alternative protein sources, rather than the consumers of marine protein. This study quantifies freshwater savings from marine fish consumption around the world by estimating the water footprint of replacing marine fish with terrestrial protein based on current consumption patterns. An estimated 7 600 km3 yr-1 of water is used for human food production. Replacing marine protein with terrestrial protein would require an additional 350 km3 yr-1 of water, meaning that marine protein provides current water savings of 4.6%. The importance of these freshwater savings is highly uneven around the globe, with savings ranging from as little as 0 to as much as 50%. The largest savings as a per cent of current water footprints occur in Asia, Oceania, and several coastal African nations. The greatest national water savings from marine fish protein occur in Southeast Asia and the United States. As the human population increases, future water savings from marine fish consumption will be increasingly important to food and water security and depend on sustainable harvest of capture fisheries and low water footprint growth of marine aquaculture.

Reconciling the temperature dependence of respiration across timescales and ecosystem types.

PubMed

Yvon-Durocher, Gabriel; Caffrey, Jane M; Cescatti, Alessandro; Dossena, Matteo; del Giorgio, Paul; Gasol, Josep M; Montoya, José M; Pumpanen, Jukka; Staehr, Peter A; Trimmer, Mark; Woodward, Guy; Allen, Andrew P

2012-07-26

Ecosystem respiration is the biotic conversion of organic carbon to carbon dioxide by all of the organisms in an ecosystem, including both consumers and primary producers. Respiration exhibits an exponential temperature dependence at the subcellular and individual levels, but at the ecosystem level respiration can be modified by many variables including community abundance and biomass, which vary substantially among ecosystems. Despite its importance for predicting the responses of the biosphere to climate change, it is as yet unknown whether the temperature dependence of ecosystem respiration varies systematically between aquatic and terrestrial environments. Here we use the largest database of respiratory measurements yet compiled to show that the sensitivity of ecosystem respiration to seasonal changes in temperature is remarkably similar for diverse environments encompassing lakes, rivers, estuaries, the open ocean and forested and non-forested terrestrial ecosystems, with an average activation energy similar to that of the respiratory complex (approximately 0.65 electronvolts (eV)). By contrast, annual ecosystem respiration shows a substantially greater temperature dependence across aquatic (approximately 0.65 eV) versus terrestrial ecosystems (approximately 0.32 eV) that span broad geographic gradients in temperature. Using a model derived from metabolic theory, these findings can be reconciled by similarities in the biochemical kinetics of metabolism at the subcellular level, and fundamental differences in the importance of other variables besides temperature—such as primary productivity and allochthonous carbon inputs—on the structure of aquatic and terrestrial biota at the community level.

Terrestrial water fluxes dominated by transpiration.

PubMed

Jasechko, Scott; Sharp, Zachary D; Gibson, John J; Birks, S Jean; Yi, Yi; Fawcett, Peter J

2013-04-18

Renewable fresh water over continents has input from precipitation and losses to the atmosphere through evaporation and transpiration. Global-scale estimates of transpiration from climate models are poorly constrained owing to large uncertainties in stomatal conductance and the lack of catchment-scale measurements required for model calibration, resulting in a range of predictions spanning 20 to 65 per cent of total terrestrial evapotranspiration (14,000 to 41,000 km(3) per year) (refs 1, 2, 3, 4, 5). Here we use the distinct isotope effects of transpiration and evaporation to show that transpiration is by far the largest water flux from Earth's continents, representing 80 to 90 per cent of terrestrial evapotranspiration. On the basis of our analysis of a global data set of large lakes and rivers, we conclude that transpiration recycles 62,000 ± 8,000 km(3) of water per year to the atmosphere, using half of all solar energy absorbed by land surfaces in the process. We also calculate CO2 uptake by terrestrial vegetation by connecting transpiration losses to carbon assimilation using water-use efficiency ratios of plants, and show the global gross primary productivity to be 129 ± 32 gigatonnes of carbon per year, which agrees, within the uncertainty, with previous estimates. The dominance of transpiration water fluxes in continental evapotranspiration suggests that, from the point of view of water resource forecasting, climate model development should prioritize improvements in simulations of biological fluxes rather than physical (evaporation) fluxes.

Water level management and contaminant exposure to tree swallows nesting on the Upper Mississippi River

USGS Publications Warehouse

Custer, T.W.; Dummer, P.M.; Custer, Christine M.; Li, A.U.; Warburton, D.; Melancon, M.J.; Hoffman, D.J.; Matson, C.W.; Bickham, J.W.

2007-01-01

The U.S. Army Corps of Engineers conducted a water drawdown on Navigation Pool 8 of the Upper Mississippi River during the summers of 2001 and 2002 to increase aquatic vegetation production and thereby improve fish and wildlife habitat. Flooding of previously dried wetlands, however, may increase the rate of mercury methylation and make mercury more available to terrestrial vertebrates that feed in aquatic environments. Our objective was to determine if mercury, other elements, and organochlorine contaminants were more available to vertebrates following the 2001 drawdown. Tree swallow (Tachycineta bicolor) eggs and nestlings were collected at two sites on Pool 8 and a nearby Reference site in 2000 (pre-2001 drawdown), 2001 (pre-2001 drawdown) and 2002 (post-2001 drawdown) and tissues were analyzed for mercury, other elements, and organochlorine contaminants. Bioindicator measurements of genetic damage, oxidative stress, ethoxyresorufin-O-dealkylase activity, and the ratio of liver to nestling mass were also measured in nestlings at all sites and all years. Based on a multivariate analysis, the 2001 drawdown of Pool 8 did not influence element concentrations, organochlorine concentrations, or bioindicator response. Concentrations of inorganic and organochlorine contaminants in tree swallow eggs and nestlings were not at toxic levels. Hatching success did not differ among years and was comparable to the nationwide average.

Manganese biogeochemistry in a central Czech Republic catchment

USGS Publications Warehouse

Navratil, T.; Shanley, J.B.; Skrivan, P.; Kram, P.; Mihaljevic, M.; Drahota, P.

2007-01-01

Mn biogeochemistry was studied from 1994 to 2003 in a small forested catchment in the central Czech Republic using the watershed mass balance approach together with measurements of internal stores and fluxes. Mn inputs in bulk deposition were relatively constant during a period of sharply decreasing acidic deposition, suggesting that the Mn source was terrestrial, and not from fossil fuel combustion. Mn inputs in bulk deposition and Mn supplied by weathering each averaged 13 mg m-2 year-1 (26 mg m -2 year-1 total input), whereas Mn export in streamwater and groundwater averaged 43 mg m-2 year-1. Thus an additional Mn source is needed to account for 17 mg m-2 year -1. Internal fluxes and pools of Mn were significantly greater than annual inputs and outputs. Throughfall Mn flux was 70 mg m-2 year-1, litterfall Mn flux was 103 mg m-2 year -1, and Mn net uptake by vegetation was 62 mg m-2 year-1. Large pools of labile or potentially labile Mn were present in biomass and surficial soil horizons. Small leakages from these large pools likely supply the additional Mn needed to close the watershed mass balance. This leakage may reflect an adjustment of the ecosystem to recent changes in atmospheric acidity. ?? 2007 Springer Science+Business Media B.V.

Dinosaurs, dragons, and dwarfs: The evolution of maximal body size

PubMed Central

Burness, Gary P.; Diamond, Jared; Flannery, Timothy

2001-01-01

Among local faunas, the maximum body size and taxonomic affiliation of the top terrestrial vertebrate vary greatly. Does this variation reflect how food requirements differ between trophic levels (herbivores vs. carnivores) and with taxonomic affiliation (mammals and birds vs. reptiles)? We gathered data on the body size and food requirements of the top terrestrial herbivores and carnivores, over the past 65,000 years, from oceanic islands and continents. The body mass of the top species was found to increase with increasing land area, with a slope similar to that of the relation between body mass and home range area, suggesting that maximum body size is determined by the number of home ranges that can fit into a given land area. For a given land area, the body size of the top species decreased in the sequence: ectothermic herbivore > endothermic herbivore > ectothermic carnivore > endothermic carnivore. When we converted body mass to food requirements, the food consumption of a top herbivore was about 8 times that of a top carnivore, in accord with the factor expected from the trophic pyramid. Although top ectotherms were heavier than top endotherms at a given trophic level, lower metabolic rates per gram of body mass in ectotherms resulted in endotherms and ectotherms having the same food consumption. These patterns explain the size of the largest-ever extinct mammal, but the size of the largest dinosaurs exceeds that predicted from land areas and remains unexplained. PMID:11724953

Ancient DNA evidence supports the contribution of Di-Qiang people to the han Chinese gene pool.

PubMed

Zhao, Yong-Bin; Li, Hong-Jie; Li, Sheng-Nan; Yu, Chang-Chun; Gao, Shi-Zhu; Xu, Zhi; Jin, Li; Zhu, Hong; Zhou, Hui

2011-02-01

Han Chinese is the largest ethnic group in the world. During its development, it gradually integrated with many neighboring populations. To uncover the origin of the Han Chinese, ancient DNA analysis was performed on the remains of 46 humans (1700 to 1900 years ago) excavated from the Taojiazhai site in Qinghai province, northwest of China, where the Di-Qiang populations had previously lived. In this study, eight mtDNA haplogroups (A, B, D, F, M*, M10, N9a, and Z) and one Y-chromosome haplogroup (O3) were identified. All analyses show that the Taojiazhai population presents close genetic affinity to Tibeto-Burman populations (descendants of Di-Qiang populations) and Han Chinese, suggesting that the Di-Qiang populations may have contributed to the Han Chinese genetic pool. 2010 Wiley-Liss, Inc.

The Deoxynucleoside Triphosphate Triphosphohydrolase Activity of SAMHD1 Protein Contributes to the Mitochondrial DNA Depletion Associated with Genetic Deficiency of Deoxyguanosine Kinase*

PubMed Central

Franzolin, Elisa; Salata, Cristiano; Bianchi, Vera; Rampazzo, Chiara

2015-01-01

The dNTP triphosphohydrolase SAMHD1 is a nuclear antiviral host restriction factor limiting HIV-1 infection in macrophages and a major regulator of dNTP concentrations in human cells. In normal human fibroblasts its expression increases during quiescence, contributing to the small dNTP pool sizes of these cells. Down-regulation of SAMHD1 by siRNA expands all four dNTP pools, with dGTP undergoing the largest relative increase. The deoxyguanosine released by SAMHD1 from dGTP can be phosphorylated inside mitochondria by deoxyguanosine kinase (dGK) or degraded in the cytosol by purine nucleoside phosphorylase. Genetic mutations of dGK cause mitochondrial (mt) DNA depletion in noncycling cells and hepato-cerebral mtDNA depletion syndrome in humans. We studied if SAMHD1 and dGK interact in the regulation of the dGTP pool during quiescence employing dGK-mutated skin fibroblasts derived from three unrelated patients. In the presence of SAMHD1 quiescent mutant fibroblasts manifested mt dNTP pool imbalance and mtDNA depletion. When SAMHD1 was silenced by siRNA transfection the composition of the mt dNTP pool approached that of the controls, and mtDNA copy number increased, compensating the depletion to various degrees in the different mutant fibroblasts. Chemical inhibition of purine nucleoside phosphorylase did not improve deoxyguanosine recycling by dGK in WT cells. We conclude that the activity of SAMHD1 contributes to the pathological phenotype of dGK deficiency. Our results prove the importance of SAMHD1 in the regulation of all dNTP pools and suggest that dGK inside mitochondria has the function of recycling the deoxyguanosine derived from endogenous dGTP degraded by SAMHD1 in the nucleus. PMID:26342080

The Influence of Land-Use Change on Soil and Dissolved Organic Matter Age, Lability, and Chemical Characteristics in Brazilian Oxisols

NASA Astrophysics Data System (ADS)

James, J. N.; Harrison, R. B.; Gross, C. D.; Dwivedi, P.; Myers, T.; Butman, D. E.

2017-12-01

Recent advances in freshwater research indicate that the age of carbon exported from major rivers globally increases with greater human disturbance in the watershed. This implies that human land-use can release old, previously mineral-associated C into solution with subsequent export to groundwater and ultimately freshwater systems where terrestrial organic matter is either mineralized to CO2, stored in aquatic sediments, or exported to the ocean. It is important to understand the mechanisms that cause the release of mineral-bound soil organic matter (SOM) into solution in response to human disturbance and land-use change. To better characterize the response of the total soil organic matter (SOM) pool to disturbance, this study examines the interactions between dissolved and bulk soil pools in response to conversion of Brazilian Cerrado (savannah forest) to Eucalyptus plantations. Water-extractable organic matter (WEOM) was obtained from soil samples down to 150 cm at 4 sites in Sao Paulo State, Brazil. These WEOM samples were characterized using fluorescence and NMR spectroscopy, incubated to assess biolability, and carbon-dated. Simultaneously, bulk mineral soil samples were analyzed for microbial biomass, carbon content and age, and characterized using Fourier Transform Infrared Spectroscopy. FTIR spectra of SOM were obtained by washing subsamples with sodium hypochlorite and subtracting the subsequent mineral matrix spectra from bulk soil spectra. Preliminary results show that microbial biomass decreases much more quickly with depth than WEOM, suggesting that C released into solution from deeper horizons may be less likely to be intercepted, and thus preferentially leached to groundwater. Native Cerrado forests had substantially more roots compared to Eucalyptus, and also released substantially larger quantities of WEOM from their O horizons. Furthermore, the age of WEOM released under Eucalyptus forest was more similar in age to bulk SOM, while Cerrado forest WEOM was substantially younger than the bulk SOM. Processes operating at the interface between solid and liquid, terrestrial and aquatic are a key unknown in the global carbon cycle. This research permits a unique snapshot into the relationship between DOM and SOM and the response of these pools to forest conversion and management in Brazil.

Spatio-temporal variability in the distribution of ground-dwelling riparian spiders and their potential role in water-to-land energy transfer along Hong Kong forest streams

PubMed Central

Yuen, Elaine Y.L.

2015-01-01

Terrestrial predators have been shown to aggregate along stream margins during periods when the emergence of adult aquatic insects is high. Such aggregation may be especially evident when terrestrial surroundings are relatively unproductive, and there are steep productivity gradients across riparia. In tropical forests, however, the productivity of inland terrestrial habitats may decrease the resource gradient across riparia, thus lessening any tendency of terrestrial predators to aggregate along stream margins. We elucidated the spatio-temporal variability in the distribution of ground-dwelling spiders and terrestrial arthropod prey within the riparia of two forest streams in tropical Hong Kong by sampling arthropods along transects at different distances from the streams during the wet and dry seasons. Environmental variables that may have influenced spider distributions were also measured. The vast majority of ground-dwelling predators along all transects at both sites were spiders. Of the three most abundant spiders captured along stream margins, Heteropoda venatoria (Sparassidae) and Draconarius spp. (Agelenidae) were terrestrially inclined and abundant during both seasons. Only Pardosa sumatrana (Lycosidae) showed some degree of aggregation at the stream banks, indicating a potential reliance on aquatic insect prey. Circumstantial evidence supports this notion, as P. sumatrana was virtually absent during the dry season when aquatic insect emergence was low. In general, forest-stream riparia in Hong Kong did not appear to be feeding hotspots for ground-dwelling predators. The lack of aggregation in ground-dwelling spiders in general may be attributed to the low rates of emergence of aquatic insects from the study streams compared to counterpart systems, as well as the potentially high availability of terrestrial insect prey in the surrounding forest. Heteropoda venatoria, the largest of the three spiders maintained a high biomass (up to 28 mg dry weight/m2) in stream riparia, exceeding the total standing stock of all other spiders by 2–80 times. The biomass and inland distribution of H. venatoria could make it a likely conduit for the stream-to-land transfer of energy. PMID:26246974

The Profitability of a Birthing Center a Cost Finding Analysis of a Not-for-Profit Hospital.

DTIC Science & Technology

1997-03-01

bed-days in each DRG. The supply, equipment and dietary cost pools were distributed using this methodology. Supplies and drugs made-up the largest...Large Freestanding Birth Center of Low-Income Women. Journal of Nurse Midwifery 39 (2) (March-April): 112-8. Duboff, Robert S. 1992. Marketing to...Spitzer, Matthew C. 1995. Birth Centers - Economy, Safety, and Empowerment. Journal of Nurse Midwifery 40 (4) (July-August): 371-5. Stone, Patricia W

Allogeneic killing by earthworm effector cells.

PubMed

Suzuki, M M; Cooper, E L

1995-01-01

We observed spontaneous allogeneic cytotoxicity by coelomocytes (Lumbricus terrestris) using three assays: trypan blue, lactate dehydrogenase release and chromium-51 release. Cell-cell contact may not be essential to effect cytotoxicity, since killing of allogeneic cells occurred in pooled allogeneic coelomic fluid derived from worms raised in two different geographic locales. We observed no significant spontaneous cytotoxicity against autogeneic target coelomocytes haptenated with 2,4,6-trinitrobenzene sulfonic acid; however, coelomocytes effected significant spontaneous cytotoxicity against haptenated allogeneic targets. These results support the view that earthworm coelomocytes can act as effector cells that can specifically kill nonself target cells.

KENNEDY SPACE CENTER, FLA. - On Launch Complex 17-B, Cape Canaveral Air Force Station, the first stage of a Delta II rocket is lifted up the mobile service tower. Below the rocket is the flame trench, and in the foreground is the overflow pool. The rocket is being erected to launch the Space InfraRed Telescope Facility (SIRTF). Consisting of an 0.85-meter telescope and three cryogenically cooled science instruments, SIRTF is one of NASA's largest infrared telescopes to be launched. SIRTF will obtain images and spectra by detecting the infrared energy, or heat, radiated by objects in space. Most of this infrared radiation is blocked by the Earth's atmosphere and cannot be observed from the ground.

NASA Image and Video Library

2003-07-18

KENNEDY SPACE CENTER, FLA. - On Launch Complex 17-B, Cape Canaveral Air Force Station, the first stage of a Delta II rocket is lifted up the mobile service tower. Below the rocket is the flame trench, and in the foreground is the overflow pool. The rocket is being erected to launch the Space InfraRed Telescope Facility (SIRTF). Consisting of an 0.85-meter telescope and three cryogenically cooled science instruments, SIRTF is one of NASA's largest infrared telescopes to be launched. SIRTF will obtain images and spectra by detecting the infrared energy, or heat, radiated by objects in space. Most of this infrared radiation is blocked by the Earth's atmosphere and cannot be observed from the ground.

Characteristics of electron distributions observed during large amplitude whistler wave events in the magnetosphere

NASA Astrophysics Data System (ADS)

Wilson, L. B., III; Cattell, C. A.; Kellogg, P. J.; Goetz, K.; Wygant, J.; Breneman, A. W.; Kersten, K.

2010-12-01

We present a statistical study of the characteristics of electron distributions associated with large amplitude whistler waves inside the terrestrial magnetosphere using waveform capture data as an addition of the study by Kellogg et al., [2010b]. We identified three types of electron distributions observed simultaneously with the whistler waves including beam-like, beam/flattop, and anisotropic distributions. The whistlers exhibited different characteristics dependent upon the observed electron distributions. The majority of the waveforms observed in our study have f/fce ≤ 0.5 and are observed primarily in the radiation belts outside the plasmapause simultaneously with anisotropic electron distributions. We also present an example waveform capture of the largest magnetic field amplitude (≥ 8 nT pk-pk) whistler wave measured in the radiation belts. The majority of the largest amplitude whistlers occur during magnetically active periods (AE > 200 nT).

A hydrological budget (2002-2008) for a large subtropical wetland ecosystem indicates marine groundwater discharge accompanies diminished freshwater flow

USGS Publications Warehouse

Saha, Amartya K.; Moses, Christopher S.; Price, Rene M.; Engel, Victor; Smith, Thomas J.; Anderson, Gordon

2012-01-01

Water budget parameters are estimated for Shark River Slough (SRS), the main drainage within Everglades National Park (ENP) from 2002 to 2008. Inputs to the water budget include surface water inflows and precipitation while outputs consist of evapotranspiration, discharge to the Gulf of Mexico and seepage losses due to municipal wellfield extraction. The daily change in volume of SRS is equated to the difference between input and outputs yielding a residual term consisting of component errors and net groundwater exchange. Results predict significant net groundwater discharge to the SRS peaking in June and positively correlated with surface water salinity at the mangrove ecotone, lagging by 1 month. Precipitation, the largest input to the SRS, is offset by ET (the largest output); thereby highlighting the importance of increasing fresh water inflows into ENP for maintaining conditions in terrestrial, estuarine, and marine ecosystems of South Florida.

O-16 excesses in Murchison and Murray hibonites - A case against a late supernova injection origin of isotopic anomalies in O, Mg, Ca, and Ti

NASA Technical Reports Server (NTRS)

Fahey, A. J.; Goswami, J. N.; Mckeegan, K. D.; Zinner, E. K.

1987-01-01

Ion probe measurements of the oxygen isotopic composition of seven hibonite samples from the CM chondrites Murchison and Murray are reported. All samples show large O-16 excesses relative to terrestrial oxygen. The data for all samples plot along the carbonaceous chondrite O-16-rich mixing line and show no evidence for isotopic mass fractionation effects characteristic of FUN inclusions. These hibonites have the largest Ca-48 and Ti-50 isotopic anomalies found to date; thus there is no intrinsic relationship between anomalies of a nucleosynthetic origin and isotopic mass fractionation effects. The large O-16 excess seen in the sample with the largest measured Ca-48 and Ti-50 depletions argues against a late injection of exotic material from a nearby supernova as a source for the isotopic anomalies.

Characteristics of Electron Distributions Observed During Large Amplitude Whistler Wave Events in the Magnetosphere

NASA Technical Reports Server (NTRS)

Wilson, Lynn B., III

2010-01-01

We present a statistical study of the characteristics of electron distributions associated with large amplitude whistler waves inside the terrestrial magnetosphere using waveform capture data as an addition of the study by Kellogg et al., [2010b]. We identified three types of electron distributions observed simultaneously with the whistler waves including beam-like, beam/flattop, and anisotropic distributions. The whistlers exhibited different characteristics dependent upon the observed electron distributions. The majority of the waveforms observed in our study have f/fce < or = 0.5 and are observed primarily in the radiation belts outside the plasmapause simultaneously with anisotropic electron distributions. We also present an example waveform capture of the largest magnetic field amplitude (> or = 8 nT pk-pk) whistler wave measured in the radiation belts. The majority of the largest amplitude whistlers occur during magnetically active periods (AE > 200 nT).

A giant Late Triassic ichthyosaur from the UK and a reinterpretation of the Aust Cliff ‘dinosaurian’ bones

PubMed Central

De la Salle, Paul; Massare, Judy A.; Gallois, Ramues

2018-01-01

The largest reported ichthyosaurs lived during the Late Triassic (~235–200 million years ago), and isolated, fragmentary bones could be easily mistaken for those of dinosaurs because of their size. We report the discovery of an isolated bone from the lower jaw of a giant ichthyosaur from the latest Triassic of Lilstock, Somerset, UK. It documents that giant ichthyosaurs persisted well into the Rhaetian Stage, and close to the time of the Late Triassic extinction event. This specimen has prompted the reinterpretation of several large, roughly cylindrical bones from the latest Triassic (Rhaetian Stage) Westbury Mudstone Formation from Aust Cliff, Gloucestershire, UK. We argue here that the Aust bones, previously identified as those of dinosaurs or large terrestrial archosaurs, are jaw fragments from giant ichthyosaurs. The Lilstock and Aust specimens might represent the largest ichthyosaurs currently known. PMID:29630618

Collapse of the world's largest herbivores.

PubMed

Ripple, William J; Newsome, Thomas M; Wolf, Christopher; Dirzo, Rodolfo; Everatt, Kristoffer T; Galetti, Mauro; Hayward, Matt W; Kerley, Graham I H; Levi, Taal; Lindsey, Peter A; Macdonald, David W; Malhi, Yadvinder; Painter, Luke E; Sandom, Christopher J; Terborgh, John; Van Valkenburgh, Blaire

2015-05-01

Large wild herbivores are crucial to ecosystems and human societies. We highlight the 74 largest terrestrial herbivore species on Earth (body mass ≥100 kg), the threats they face, their important and often overlooked ecosystem effects, and the conservation efforts needed to save them and their predators from extinction. Large herbivores are generally facing dramatic population declines and range contractions, such that ~60% are threatened with extinction. Nearly all threatened species are in developing countries, where major threats include hunting, land-use change, and resource depression by livestock. Loss of large herbivores can have cascading effects on other species including large carnivores, scavengers, mesoherbivores, small mammals, and ecological processes involving vegetation, hydrology, nutrient cycling, and fire regimes. The rate of large herbivore decline suggests that ever-larger swaths of the world will soon lack many of the vital ecological services these animals provide, resulting in enormous ecological and social costs.

Collapse of the world’s largest herbivores

PubMed Central

Ripple, William J.; Newsome, Thomas M.; Wolf, Christopher; Dirzo, Rodolfo; Everatt, Kristoffer T.; Galetti, Mauro; Hayward, Matt W.; Kerley, Graham I. H.; Levi, Taal; Lindsey, Peter A.; Macdonald, David W.; Malhi, Yadvinder; Painter, Luke E.; Sandom, Christopher J.; Terborgh, John; Van Valkenburgh, Blaire

2015-01-01

Large wild herbivores are crucial to ecosystems and human societies. We highlight the 74 largest terrestrial herbivore species on Earth (body mass ≥100 kg), the threats they face, their important and often overlooked ecosystem effects, and the conservation efforts needed to save them and their predators from extinction. Large herbivores are generally facing dramatic population declines and range contractions, such that ~60% are threatened with extinction. Nearly all threatened species are in developing countries, where major threats include hunting, land-use change, and resource depression by livestock. Loss of large herbivores can have cascading effects on other species including large carnivores, scavengers, mesoherbivores, small mammals, and ecological processes involving vegetation, hydrology, nutrient cycling, and fire regimes. The rate of large herbivore decline suggests that ever-larger swaths of the world will soon lack many of the vital ecological services these animals provide, resulting in enormous ecological and social costs. PMID:26601172

Modelling the sensitivity of soil mercury storage to climate-induced changes in soil carbon pools

NASA Astrophysics Data System (ADS)

Hararuk, O.; Obrist, D.; Luo, Y.

2013-04-01

Substantial amounts of mercury (Hg) in the terrestrial environment reside in soils and are associated with soil organic carbon (C) pools, where they accumulated due to increased atmospheric deposition resulting from anthropogenic activities. The purpose of this study was to examine potential sensitivity of surface soil Hg pools to global change variables, particularly affected by predicted changes in soil C pools, in the contiguous US. To investigate, we included a soil Hg component in the Community Land Model based on empirical statistical relationships between soil Hg / C ratios and precipitation, latitude, and clay; and subsequently explored the sensitivity of soil C and soil Hg densities (i.e., areal-mass) to climate scenarios in which we altered annual precipitation, carbon dioxide (CO2) concentrations and temperature. Our model simulations showed that current sequestration of Hg in the contiguous US accounted for 15 230 metric tons of Hg in the top 0-40 cm of soils, or for over 300 000 metric tons when extrapolated globally. In the simulations, US soil Hg pools were most sensitive to changes in precipitation because of strong effects on soil C pools, plus a direct effect of precipitation on soil Hg / C ratios. Soil Hg pools were predicted to increase beyond present-day values following an increase in precipitation amounts and decrease following a reduction in precipitation. We found pronounced regional differences in sensitivity of soil Hg to precipitation, which were particularly high along high-precipitation areas along the West and East Coasts. Modelled increases in CO2 concentrations to 700 ppm stimulated soil C and Hg accrual, while increased air temperatures had small negative effects on soil C and Hg densities. The combined effects of increased CO2, increased temperature and increased or decreased precipitation were strongly governed by precipitation and CO2 showing pronounced regional patterns. Based on these results, we conclude that the combination of precipitation and CO2 should be emphasised when assessing how climate-induced changes in soil C may affect sequestration of Hg in soils.

Soil erosion, sedimentation and the carbon cycle

NASA Astrophysics Data System (ADS)

Cammeraat, L. H.; Kirkels, F.; Kuhn, N. J.

2012-04-01

Historically soil erosion focused on the effects of on-site soil quality loss and consequently reduced crop yields, and off-site effects related to deposition of material and water quality issues such as increased sediment loads of rivers. In agricultural landscapes geomorphological processes reallocate considerable amounts of soil and soil organic carbon (SOC). The destiny of SOC is of importance because it constitutes the largest C pool of the fast carbon cycle, and which cannot only be understood by looking at the vertical transfer of C from soil to atmosphere. Therefore studies have been carried out to quantify this possible influence of soil erosion and soil deposition and which was summarized by Quinton et al. (2010) by "We need to consider soils as mobile systems to make accurate predictions about the consequences of global change for terrestrial biogeochemical cycles and climate feedbacks". Currently a debate exists on the actual fate of SOC in relation to the global carbon cycle, represented in a controversy between researchers claiming that erosion is a sink, and those who claim the opposite. This controversy is still continuing as it is not easy to quantify and model the dominating sink and source processes at the landscape scale. Getting insight into the balance of the carbon budget requires a comprehensive research of all relevant processes at broad spatio-temporal scales, from catchment to regional scales and covering the present to the late Holocene. Emphasising the economic and societal benefits, the merits for scientific knowledge of the carbon cycle and the potential to sequester carbon and consequently offset increasing atmospheric CO2 concentrations, make the fate of SOC in agricultural landscapes a high-priority research area. Quinton, J.N., Govers, G., Van Oost, K., Bardgett, R.D., 2010. The impact of agricultural soil erosion on biogeochemical cycling. Nature Geosci, 3, 311-314.

Low black carbon concentration in agricultural soils of central and northern Ethiopia.

PubMed

Yli-Halla, Markku; Rimhanen, Karoliina; Muurinen, Johanna; Kaseva, Janne; Kahiluoto, Helena

2018-08-01

Soil carbon (C) represents the largest terrestrial carbon stock and is key for soil productivity. Major fractions of soil C consist of organic C, carbonates and black C. The turnover rate of black C is lower than that of organic C, and black C abundance decreases the vulnerablility of soil C stock to decomposition under climate change. The aim of this study was to determine the distribution of soil C in different pools and impact of agricultural management on the abundance of different species. Soil C fractions were quantified in the topsoils (0-15cm) of 23 sites in the tropical highlands of Ethiopia. The sites in central Ethiopia represented paired plots of agroforestry and adjacent control plots where cereal crops were traditionally grown in clayey soils. In the sandy loam and loam soils of northern Ethiopia, the pairs represented restrained grazing with adjacent control plots with free grazing, and terracing with cereal-based cropping with adjacent control plots without terracing. Soil C contained in carbonates, organic matter and black C along with total C was determined. The total C median was 1.5% (range 0.3-3.6%). The median proportion of organic C was 85% (range 53-94%), 6% (0-41%) for carbonate C and 6% (4-21%) for black C. An increase was observed in the organic C and black C fractions attributable to agroforestry and restrained grazing. The very low concentration of the relatively stable black C fraction and the dominance of organic C in these Ethiopian soils suggest vulnerability to degradation and the necessity for cultivation practices maintaining the C stock. Copyright © 2018 Elsevier B.V. All rights reserved.

Manganese Driven Carbon Oxidation along Oxic-Anoxic Interfaces in Forest Soils

NASA Astrophysics Data System (ADS)

Jones, M. E.; Keiluweit, M.

2017-12-01

Soils are the largest and most dynamic terrestrial carbon pool, storing a total of 3000 Pg of C - more than the atmosphere and biosphere combined. Because microbial oxidation determines the proportion of carbon that is either stored in the soil or emitted as climate active CO2, its rate directly impacts the global carbon cycle. Recently, a strong correlation between oxidation rates and manganese (Mn) content has been observed in forest soils globally, leading researchers conclude that Mn "is the single main factor governing" the oxidation of plant-derived particulate organic carbon (POC). Many soils are characterized by steep oxygen gradients, forming oxic-anoxic transitions that enable rapid redox cycling of Mn. Oxic-anoxic interfaces have been shown to promote fungal Mn oxidation and the formation of ligand-stabilized Mn(III), which ranks second only to superoxide as the most powerful oxidizing agent in the environment. Here we examined fungal Mn(III) formation along redox gradients in forest soils and their impact on POC oxidation rates. In both field and laboratory settings, oxic-anoxic transition zones showed the greatest Mn(III) concentrations, along with enhanced fungal growth, oxidative potential, production of soluble oxidation products, and CO2 production. Additional electrochemical and X-ray (micro)spectroscopic analyses indicated that oxic-anoxic interfaces represent ideal niches for fungal Mn(III) formation, owing to the ready supply of Mn(II), ligands and O2. Combined, our results suggest that POC oxidation relies on fungal Mn cycling across oxic-anoxic interfaces to produce Mn(III) based oxidants. Because predicted changes in the frequency and timing of precipitation dramatically alter soil moisture regimes in forest soils, understanding the mechanistic link between Mn cycling and carbon oxidation along oxic-anoxic interfaces is becoming increasingly important.

Global carbon sequestration in tidal, saline wetland soils

USGS Publications Warehouse

Chmura, G.L.; Anisfeld, S.C.; Cahoon, D.R.; Lynch, J.C.

2003-01-01

Wetlands represent the largest component of the terrestrial biological carbon pool and thus play an important role in global carbon cycles. Most global carbon budgets, however, have focused on dry land ecosystems that extend over large areas and have not accounted for the many small, scattered carbon-storing ecosystems such as tidal saline wetlands. We compiled data for 154 sites in mangroves and salt marshes from the western and eastern Atlantic and Pacific coasts, as well as the Indian Ocean, Mediterranean Ocean, and Gulf of Mexico. The set of sites spans a latitudinal range from 22.4??S in the Indian Ocean to 55.5??N in the northeastern Atlantic. The average soil carbon density of mangrove swamps (0.055 ?? 0.004 g cm-3) is significantly higher than the salt marsh average (0.039 ?? 0.003 g cm-3). Soil carbon density in mangrove swamps and Spartina patens marshes declines with increasing average annual temperature, probably due to increased decay rates at higher temperatures. In contrast, carbon sequestration rates were not significantly different between mangrove swamps and salt marshes. Variability in sediment accumulation rates within marshes is a major control of carbon sequestration rates masking any relationship with climatic parameters. Globally, these combined wetlands store at least 44.6 Tg C yr-1 and probably more, as detailed areal inventories are not available for salt marshes in China and South America. Much attention has been given to the role of freshwater wetlands, particularly northern peatlands, as carbon sinks. In contrast to peatlands, salt marshes and mangroves release negligible amounts of greenhouse gases and store more carbon per unit area. Copyright 2003 by the American Geophysical Union.

Assessment of MODIS-derived indices (2001-2013) to drought across Taiwan's forests

NASA Astrophysics Data System (ADS)

Chang, Chung-Te; Wang, Hsueh-Ching; Huang, Cho-ying

2018-05-01

Tropical and subtropical ecosystems, the largest terrestrial carbon pools, are very susceptible to the variability of seasonal precipitation. However, the assessment of drought conditions in these regions is often overlooked due to the preconceived notion of the presence of high humidity. Drought indices derived from remotely sensed imagery have been commonly used for large-scale monitoring, but feasibility of drought assessment may vary across regions due to climate regimes and local biophysical conditions. Therefore, this study aims to evaluate the feasibility of 11 commonly used MODIS-derived vegetation/drought index in the forest regions of Taiwan through comparison with the station-based standardized precipitation index with a 3-month time scale (SPI3). The drought indices were further transformed (standardized anomaly, SA) to make them better delineate the spatiotemporal variations of drought conditions. The results showed that the Normalized Difference Infrared Index utilizing the near-infrared and shortwave infrared bands (NDII6) may be more superior to other indices in delineating drought patterns. Overall, the NDII6 SA-SPI3 pair yielded the highest correlation (mean r ± standard deviation = 0.31 ± 0.13) and was most significant in central and south Taiwan ( r = 0.50-0.90) during the cold, dry season (January and April). This study illustrated that the NDII6 is suitable to delineate drought conditions in a relatively humid region. The results suggested the better performance of the NDII6 SA-SPI3 across the high climate gradient, especially in the regions with dramatic interannual amplifications of rainfall. This synthesis was conducted across a wide bioclimatic gradient, and the findings could be further generalized to a much broader geographical extent.

Drought sensitivity of Amazonian carbon balance revealed by atmospheric measurements

NASA Astrophysics Data System (ADS)

Gatti, L. V.; Gloor, M.; Miller, J. B.; Doughty, C. E.; Malhi, Y.; Domingues, L. G.; Basso, L. S.; Martinewski, A.; Correia, C. S. C.; Borges, V. F.; Freitas, S.; Braz, R.; Anderson, L. O.; Rocha, H.; Grace, J.; Phillips, O. L.; Lloyd, J.

2014-02-01

Feedbacks between land carbon pools and climate provide one of the largest sources of uncertainty in our predictions of global climate. Estimates of the sensitivity of the terrestrial carbon budget to climate anomalies in the tropics and the identification of the mechanisms responsible for feedback effects remain uncertain. The Amazon basin stores a vast amount of carbon, and has experienced increasingly higher temperatures and more frequent floods and droughts over the past two decades. Here we report seasonal and annual carbon balances across the Amazon basin, based on carbon dioxide and carbon monoxide measurements for the anomalously dry and wet years 2010 and 2011, respectively. We find that the Amazon basin lost 0.48+/-0.18 petagrams of carbon per year (PgCyr-1) during the dry year but was carbon neutral (0.06+/-0.1PgCyr-1) during the wet year. Taking into account carbon losses from fire by using carbon monoxide measurements, we derived the basin net biome exchange (that is, the carbon flux between the non-burned forest and the atmosphere) revealing that during the dry year, vegetation was carbon neutral. During the wet year, vegetation was a net carbon sink of 0.25+/-0.14PgCyr-1, which is roughly consistent with the mean long-term intact-forest biomass sink of 0.39+/-0.10PgCyr-1 previously estimated from forest censuses. Observations from Amazonian forest plots suggest the suppression of photosynthesis during drought as the primary cause for the 2010 sink neutralization. Overall, our results suggest that moisture has an important role in determining the Amazonian carbon balance. If the recent trend of increasing precipitation extremes persists, the Amazon may become an increasing carbon source as a result of both emissions from fires and the suppression of net biome exchange by drought.

The role of minerals and mean annual temperature on soil carbon accumulation: A modeling analysis

NASA Astrophysics Data System (ADS)

Abramoff, R. Z.; Georgiou, K.; Tang, J.; Torn, M. S.; Riley, W. J.

2016-12-01

Soil organic carbon (SOC) is the largest actively cycling terrestrial C pool with mean residence times that can exceed 10,000 years. There is strong evidence suggesting that SOC dynamics depend on soil temperature and C inputs to soil through net primary production (NPP), but it is unclear what the relative importance of these factors is relative to SOC protection by minerals. Recent empirical studies have suggested that mineral protection explains more variation in SOC stock sizes and C respiration fluxes than does NPP or climate. Our previous modeling has demonstrated that representing the chemistry of mineral sorption in a microbially-explicit model affects the temperature sensitivity of SOC dynamics. We apply this modeling framework to interpret observations of SOC stocks, mineral surface availability, mean annual temperature (MAT), and NPP collected along a 4,000 km transect in South America. We use a Random Forest machine learning algorithm and regression to analyze our model output and the empirical data. This analysis shows that mineral surface availability is the dominant control over C respiration and SOC stock, and is substantially larger than the effects of belowground NPP. We further show that minerals interact with MAT to determine the observed range of SOC stocks along this transect in the present day, as well as projected SOC stocks under long-term warming. Our model-data comparison suggests that soil mineralogy and MAT will explain the majority of the spatial variation in SOC stock over decadal-to-millennial timescales. We extend the analysis of these interactions using the ACME Land Model (ALM) coupled with an explicit representation of microbes, minerals, and vertical transport of solutes and gases. The model results confirm the dominant effects of minerals on organic matter decomposition throughout the soil column.

Deep instability of deforested tropical peatlands revealed by fluvial organic carbon fluxes.

PubMed

Moore, Sam; Evans, Chris D; Page, Susan E; Garnett, Mark H; Jones, Tim G; Freeman, Chris; Hooijer, Aljosja; Wiltshire, Andrew J; Limin, Suwido H; Gauci, Vincent

2013-01-31

Tropical peatlands contain one of the largest pools of terrestrial organic carbon, amounting to about 89,000 teragrams (1 Tg is a billion kilograms). Approximately 65 per cent of this carbon store is in Indonesia, where extensive anthropogenic degradation in the form of deforestation, drainage and fire are converting it into a globally significant source of atmospheric carbon dioxide. Here we quantify the annual export of fluvial organic carbon from both intact peat swamp forest and peat swamp forest subject to past anthropogenic disturbance. We find that the total fluvial organic carbon flux from disturbed peat swamp forest is about 50 per cent larger than that from intact peat swamp forest. By carbon-14 dating of dissolved organic carbon (which makes up over 91 per cent of total organic carbon), we find that leaching of dissolved organic carbon from intact peat swamp forest is derived mainly from recent primary production (plant growth). In contrast, dissolved organic carbon from disturbed peat swamp forest consists mostly of much older (centuries to millennia) carbon from deep within the peat column. When we include the fluvial carbon loss term, which is often ignored, in the peatland carbon budget, we find that it increases the estimate of total carbon lost from the disturbed peatlands in our study by 22 per cent. We further estimate that since 1990 peatland disturbance has resulted in a 32 per cent increase in fluvial organic carbon flux from southeast Asia--an increase that is more than half of the entire annual fluvial organic carbon flux from all European peatlands. Our findings emphasize the need to quantify fluvial carbon losses in order to improve estimates of the impact of deforestation and drainage on tropical peatland carbon balances.

Organic carbon storage change in China's urban landfills from 1978-2014

NASA Astrophysics Data System (ADS)

Ge, Shidong; Zhao, Shuqing

2017-10-01

China has produced increasingly large quantities of waste associated with its accelerated urbanization and economic development and deposited these wastes into landfills, potentially sequestering carbon. However, the magnitude of the carbon storage in China’s urban landfills and its spatial and temporal change remain unclear. Here, we estimate the total amount of organic carbon (OC) stored in China's urban landfills between 1978 and 2014 using a first order organic matter decomposition model and data compiled from literature review and statistical yearbooks. Our results show that total OC stored in China’s urban landfills increased nearly 68-fold from the 1970s to the 2010s, and reached 225.2-264.5 Tg C (95% confidence interval, hereafter) in 2014. Construction waste was the largest OC pool (128.4-157.5 Tg C) in 2014, followed by household waste (67.7-83.8 Tg C), and sewage sludge was the least (19.7-34.1 Tg C). Carbon stored in urban landfills accounts for more than 10% of the country’s carbon stocks in urban ecosystems. The annual increase (i.e. sequestration rate) of OC in urban landfills in the 2010s (25.1 ± 4.3 Tg C yr-1, mean ± 2SD, hereafter) is equivalent to 1% of China's carbon emissions from fossil fuel combustion and cement production during the same period, but represents about 9% of the total terrestrial carbon sequestration in the country. Our study clearly indicates that OC dynamics in landfills should not be neglected in regional to national carbon cycle studies as landfills not only account for a substantial part of the carbon stored in urban ecosystems but also have a respectable contribution to national carbon sequestration.

ORCHIDEE-MICT (v8.4.1), a land surface model for the high latitudes: model description and validation

NASA Astrophysics Data System (ADS)

Guimberteau, Matthieu; Zhu, Dan; Maignan, Fabienne; Huang, Ye; Yue, Chao; Dantec-Nédélec, Sarah; Ottlé, Catherine; Jornet-Puig, Albert; Bastos, Ana; Laurent, Pierre; Goll, Daniel; Bowring, Simon; Chang, Jinfeng; Guenet, Bertrand; Tifafi, Marwa; Peng, Shushi; Krinner, Gerhard; Ducharne, Agnès; Wang, Fuxing; Wang, Tao; Wang, Xuhui; Wang, Yilong; Yin, Zun; Lauerwald, Ronny; Joetzjer, Emilie; Qiu, Chunjing; Kim, Hyungjun; Ciais, Philippe

2018-01-01

The high-latitude regions of the Northern Hemisphere are a nexus for the interaction between land surface physical properties and their exchange of carbon and energy with the atmosphere. At these latitudes, two carbon pools of planetary significance - those of the permanently frozen soils (permafrost), and of the great expanse of boreal forest - are vulnerable to destabilization in the face of currently observed climatic warming, the speed and intensity of which are expected to increase with time. Improved projections of future Arctic and boreal ecosystem transformation require improved land surface models that integrate processes specific to these cold biomes. To this end, this study lays out relevant new parameterizations in the ORCHIDEE-MICT land surface model. These describe the interactions between soil carbon, soil temperature and hydrology, and their resulting feedbacks on water and CO2 fluxes, in addition to a recently developed fire module. Outputs from ORCHIDEE-MICT, when forced by two climate input datasets, are extensively evaluated against (i) temperature gradients between the atmosphere and deep soils, (ii) the hydrological components comprising the water balance of the largest high-latitude basins, and (iii) CO2 flux and carbon stock observations. The model performance is good with respect to empirical data, despite a simulated excessive plant water stress and a positive land surface temperature bias. In addition, acute model sensitivity to the choice of input forcing data suggests that the calibration of model parameters is strongly forcing-dependent. Overall, we suggest that this new model design is at the forefront of current efforts to reliably estimate future perturbations to the high-latitude terrestrial environment.

Organic carbon storage change in China's urban landfills from 1978 to 2014

NASA Astrophysics Data System (ADS)

Ge, S.; Zhao, S.

2017-12-01

China has produced increasingly large quantities of waste associated with her accelerated urbanization and economic development and deposited these wastes into landfills potentially sequestering carbon. However, the magnitude of the carbon storage in China's urban landfills and its spatial and temporal change remain unclear. Here, we estimate the total amount of organic carbon (OC) stored in China's urban landfills between 1978 and 2014 using a first order organic matter decomposition model and data compiled from literature review and statistical yearbooks. Our results show that total OC stored in China's urban landfills increased nearly 68 folds from the 1970s to the 2010s, and reached 225.2 - 264.5 Tg C (95% confidence interval, hereafter) in 2014. Construction waste was the largest OC pool (128.4 - 157.5 Tg C) in 2014, followed by household waste (67.7 - 83.8 Tg C), and sewage sludge was the least (19.7 - 34.1 Tg C). Carbon stored in urban landfills accounts for more than 10% of the country's carbon stocks in urban ecosystems. The annual increase (i.e., sequestration rate) of OC in urban landfills in the 2010s (25.1 ± 4.3 Tg C yr-1, mean±2SD, hereafter) is equivalent to 1% of China's carbon emissions from fossil fuel combustion and cement production during the same period, but represents about 9% of the total terrestrial carbon sequestration in the country. Our study clearly indicates that OC dynamics in landfills should not be neglected in regional to national carbon cycle studies as landfills not only account for a substantial part of the carbon stored in urban ecosystems but also contribute respectably to national carbon sequestration.

Assessment of MODIS-derived indices (2001-2013) to drought across Taiwan's forests

NASA Astrophysics Data System (ADS)

Chang, Chung-Te; Wang, Hsueh-Ching; Huang, Cho-ying

2017-12-01

Tropical and subtropical ecosystems, the largest terrestrial carbon pools, are very susceptible to the variability of seasonal precipitation. However, the assessment of drought conditions in these regions is often overlooked due to the preconceived notion of the presence of high humidity. Drought indices derived from remotely sensed imagery have been commonly used for large-scale monitoring, but feasibility of drought assessment may vary across regions due to climate regimes and local biophysical conditions. Therefore, this study aims to evaluate the feasibility of 11 commonly used MODIS-derived vegetation/drought index in the forest regions of Taiwan through comparison with the station-based standardized precipitation index with a 3-month time scale (SPI3). The drought indices were further transformed (standardized anomaly, SA) to make them better delineate the spatiotemporal variations of drought conditions. The results showed that the Normalized Difference Infrared Index utilizing the near-infrared and shortwave infrared bands (NDII6) may be more superior to other indices in delineating drought patterns. Overall, the NDII6 SA-SPI3 pair yielded the highest correlation (mean r ± standard deviation = 0.31 ± 0.13) and was most significant in central and south Taiwan (r = 0.50-0.90) during the cold, dry season (January and April). This study illustrated that the NDII6 is suitable to delineate drought conditions in a relatively humid region. The results suggested the better performance of the NDII6 SA-SPI3 across the high climate gradient, especially in the regions with dramatic interannual amplifications of rainfall. This synthesis was conducted across a wide bioclimatic gradient, and the findings could be further generalized to a much broader geographical extent.

Two-dimensional NMR spectroscopy strongly enhances soil organic matter composition analysis

NASA Astrophysics Data System (ADS)

Soucemarianadin, Laure; Erhagen, Björn; Öquist, Mats; Nilsson, Mats; Hedenström, Mattias; Schleucher, Jürgen

2016-04-01

Soil organic matter (SOM) is the largest terrestrial carbon pool and strongly affects soil properties. With climate change, understanding SOM processes and turnover and how they could be affected by increasing temperatures becomes critical. This is particularly key for organic soils as they represent a huge carbon pool in very sensitive ecosystems, like boreal ecosystems and peatlands. Nevertheless, characterization of SOM molecular composition, which is essential to elucidate soil carbon processes, is not easily achieved, and further advancements in that area are greatly needed. Solid-state one-dimensional (1D) 13C nuclear magnetic resonance (NMR) spectroscopy is often used to characterize its molecular composition, but only provides data on a few major functional groups, which regroup many different molecular fragments. For instance, in the carbohydrates region, signals of all monosaccharides present in many different polymers overlap. This overlap thwarts attempts to identify molecular moieties, resulting in insufficient information to characterize SOM composition. Here we show that two-dimensional (2D) liquid-state 1H-13C NMR spectra provided much richer data on the composition of boreal plant litter and organic surface soil. The 2D spectra indeed resolved overlaps observed in 1D 13C spectra and displayed signals from hundreds of identifiable molecular groups. For example, in the aromatics region, signals from individual lignin units could be recognized. It was hence possible to follow the fate of specific structural moieties in soils. We observed differences between litter and soil samples, and were able to relate them to the decomposition of identifiable moieties. Sample preparation and data acquisition were both simple and fast. Further, using multivariate data analysis, we aimed at linking the detailed chemical fingerprints of SOM to turnover rates in a soil incubation experiment. With the multivariate models, we were able to identify specific molecular moieties correlated to variability in the temperature response of organic matter decomposition, as assessed by Q10. Thus, 2D NMR methods, and their combination with multivariate analysis, can greatly improve analysis of litter and SOM composition, thereby facilitating elucidation of their roles in biogeochemical and ecological processes that are so critical to foresee associated feedback mechanisms on SOM turnover as a result of global environmental change.

Effects of Management on Soil Carbon Pools in California Rangeland Ecosystems

NASA Astrophysics Data System (ADS)

Silver, W. L.; Ryals, R.; Lewis, D. J.; Creque, J.; Wacker, M.; Larson, S.

2008-12-01

Rangeland ecosystems managed for livestock production represent the largest land-use footprint globally, covering more than one-quarter of the world's land surface (Asner et al. 2004). In California, rangelands cover an estimated 17 million hectares or approximately 40% of the land area (FRAP 2003). These ecosystems have considerable potential to sequester carbon (C) in soil and offset greenhouse gas emissions through changes in land management practices. Climate policies and C markets may provide incentives for rangeland managers to pursue strategies that optimize soil C storage, yet we lack a thorough understanding of the effects of management on soil C pools in rangelands over time and space. We sampled soil C pools on rangelands in a 260 km2 region of Marin and Sonoma counties to determine if patterns in soil C storage exist with management. Replicate soil samples were collected from 35 fields that spanned the dominant soil orders, plant communities, and management practices in the region while controlling for slope and bioclimatic zone (n = 1050). Management practices included organic amendments, intensive (dairy) and extensive (other) grazing practices, and subsoiling. Soil C pools ranged from approximately 50 to 140 Mg C ha-1 to 1 m depth, with a mean of 99 ± 22 (sd) Mg C ha-1. Differences among sites were due primarily to C concentrations, which exhibited a much larger coefficient of variation than bulk density at all depths. There were no statistically significant differences among the dominant soil orders. Subsoiling appeared to significantly increase soil C content in the top 50 cm, even though subsoiling had only occurred for the first time the previous Nov. Organic amendments also appeared to greatly increase soil C pools, and was the dominant factor that distinguished soil C pools in intensive and extensive land uses. Our results indicate that management has the potential to significantly increase soil C pools. Future research will determine the location of sequestered C within the soil matrix and its turnover time.

Simulated Nitrogen Deposition has Minor Effects on Ecosystem Pools and Fluxes of Energy, Elements, and Biochemicals in a Northern Hardwoods Forest

NASA Astrophysics Data System (ADS)

Talhelm, A. F.; Pregitzer, K. S.; Burton, A. J.; Xia, M.; Zak, D. R.

2017-12-01

The elemental and biochemical composition of plant tissues is an important influence on primary productivity, decomposition, and other aspects of biogeochemistry. Human activity has greatly altered biogeochemical cycles in ecosystems downwind of industrialized regions through atmospheric nitrogen deposition, but most research on these effects focuses on individual elements or steps in biogeochemical cycles. Here, we quantified pools and fluxes of biomass, the four major organic elements (carbon, oxygen, hydrogen, nitrogen), four biochemical fractions (lignin, structural carbohydrates, cell walls, and soluble material), and energy in a mature northern hardwoods forest in Michigan. We sampled the organic and mineral soil, fine and coarse roots, leaf litter, green leaves, and wood for chemical analyses. We then combined these data with previously published and archival information on pools and fluxes within this forest, which included replicated plots receiving either ambient deposition or simulated nitrogen deposition (3 g N m-2 yr-1 for 18 years). Live wood was the largest pool of energy and all elements and biochemical fractions. However, the production of wood, leaf litter, and fine roots represented similar fluxes of carbon, hydrogen, oxygen, cell wall material, and energy, while nitrogen fluxes were dominated by leaf litter and fine roots. Notably, the flux of lignin via fine roots was 70% higher than any other flux. Experimental nitrogen deposition had relatively few significant effects, increasing foliar nitrogen, increasing the concentration of lignin in the soil organic horizon and decreasing pools of all elements and biochemical fractions in the soil organic horizon except nitrogen, lignin, and structural carbohydrates. Overall, we found that differences in tissue chemistry concentrations were important determinants of ecosystem-level pools and fluxes, but that nitrogen deposition had little effect on concentrations, pools, or fluxes in this mature forest. Disclaimer: The views expressed in this poster are those of the authors and do not necessarily represent the views or policies of the U.S. EPA.

Trophodynamic linkage between river runoff and coastal fishery yield elucidated by stable isotope data in the Gulf of Lions (NW Mediterranean).

PubMed

Darnaude, Audrey M; Salen-Picard, Chantal; Polunin, Nicholas V C; Harmelin-Vivien, Mireille L

2004-02-01

The link between climate-driven river runoff and sole fishery yields observed in the Gulf of Lions (NW Mediterranean) was analysed using carbon- and nitrogen stable isotopes along the flatfish food webs. Off the Rhone River, the main terrestrial (river POM) and marine (seawater POM) sources of carbon differed in delta(13)C (-26.11 per thousand and -22.36 per thousand, respectively). Surface sediment and suspended POM in plume water exhibited low delta(13)C (-24.38 per thousand and -24.70 per thousand, respectively) that differed more from the seawater POM than from river POM, demonstrating the dominance of terrestrial material in those carbon pools. Benthic invertebrates showed a wide range in delta(15)N (mean 4.30 per thousand to 9.77 per thousand ) and delta(13)C (mean -23.81 per thousand to -18.47 per thousand ), suggesting different trophic levels, diets and organic sources. Among the macroinvertebrates, the surface (mean delta(13)C -23.71 per thousand ) and subsurface (mean delta(13)C -23.81 per thousand ) deposit-feeding polychaetes were particularly (13)C depleted, indicating that their carbon was mainly derived from terrestrial material. In flatfish, delta(15)N (mean 9.42 to 10.93 per thousand ) and delta(13)C (mean -19.95 per thousand to -17.69 per thousand ) varied among species, indicating differences in food source and terrestrial POM use. A significant negative correlation was observed between the percentage by weight of polychaetes in the diet and the delta(13)C of flatfish white muscle. Solea solea (the main polychaete feeder) had the lowest mean delta(13)C, Arnoglossus laterna and Buglossidium luteum (crustacean, mollusc and polychaete feeders) had intermediate values, and Solea impar (mollusc feeder) and Citharus linguatula (crustacean and fish feeder) exhibited the highest delta(13)C. Two different benthic food webs were thus identified off the Rhone River, one based on marine planktonic carbon and the other on the terrestrial POM carried by the river. Deposit-feeding polychaetes were responsible for the main transfer of terrestrial POM to upper trophic levels, linking sole population dynamics to river runoff fluctuations.

Comparing Terrestrial Organic Carbon Cycle Dynamics in Interglacial and Glacial Climates in the South American Tropics

NASA Astrophysics Data System (ADS)

Fornace, K. L.; Galy, V.; Hughen, K. A.

2014-12-01

The application of compound-specific radiocarbon dating to molecular biomarkers has allowed for tracking of specific organic carbon pools as they move through the environment, providing insight into complex processes within the global carbon cycle. Here we use this technique to investigate links between glacial-interglacial climate change and terrestrial organic carbon cycling in the catchments of Cariaco Basin and Lake Titicaca, two tropical South American sites with well-characterized climate histories since the last glacial period. By comparing radiocarbon ages of terrestrial biomarkers (leaf wax compounds) with deposition ages in late glacial and Holocene sediments, we are able to gauge the storage time of these compounds in the catchments in soils, floodplains, etc. before transport to marine or lacustrine sediments. We are also able to probe the effects of temperature and hydrologic change individually by taking advantage of opposite hydrologic trends at the two sites: while both were colder during the last glacial period, precipitation at Titicaca decreased from the last glacial period to the Holocene, but the late glacial was marked by drier conditions at Cariaco. Preliminary data from both sites show a wide range of apparent ages of long-chain n-fatty acids (within error of 0 to >10,000 years older than sediment), with the majority showing ages on the order of several millennia at time of deposition and age generally increasing with chain length. While late glacial leaf waxes appear to be older relative to sediment than those deposited in the Holocene at both sites, at Cariaco we find a ~2-3 times larger glacial-interglacial age difference than at Titicaca. We hypothesize that at Titicaca the competing influences of wetter and colder conditions during the last glacial period, which respectively tend to increase and decrease the rate of organic carbon turnover on land, served to minimize the contrast between glacial and interglacial leaf wax storage time compared to Cariaco where temperature and hydrologic change may have acted in concert on the rate of terrestrial carbon turnover. This study has important implications for understanding the effects of large climate change on terrestrial carbon storage, as well as applications of terrestrial biomarkers for paleoclimate records.

Estimation of distribution overlap of urn models.

PubMed

Hampton, Jerrad; Lladser, Manuel E

2012-01-01

A classical problem in statistics is estimating the expected coverage of a sample, which has had applications in gene expression, microbial ecology, optimization, and even numismatics. Here we consider a related extension of this problem to random samples of two discrete distributions. Specifically, we estimate what we call the dissimilarity probability of a sample, i.e., the probability of a draw from one distribution not being observed in [Formula: see text] draws from another distribution. We show our estimator of dissimilarity to be a [Formula: see text]-statistic and a uniformly minimum variance unbiased estimator of dissimilarity over the largest appropriate range of [Formula: see text]. Furthermore, despite the non-Markovian nature of our estimator when applied sequentially over [Formula: see text], we show it converges uniformly in probability to the dissimilarity parameter, and we present criteria when it is approximately normally distributed and admits a consistent jackknife estimator of its variance. As proof of concept, we analyze V35 16S rRNA data to discern between various microbial environments. Other potential applications concern any situation where dissimilarity of two discrete distributions may be of interest. For instance, in SELEX experiments, each urn could represent a random RNA pool and each draw a possible solution to a particular binding site problem over that pool. The dissimilarity of these pools is then related to the probability of finding binding site solutions in one pool that are absent in the other.

Growth and mortality of larval sunfish in backwaters of the upper Mississippi River

USGS Publications Warehouse

Zigler, S.J.; Jennings, C.A.

1993-01-01

The authors estimated the growth and mortality of larval sunfish Lepomis spp. in backwater habitats of the upper Mississippi River with an otolith-based method and a length-based method. Fish were sampled with plankton nets at one station in Navigation Pools 8 and 14 in 1989 and at two stations in Pool 8 in 1990. For both methods, growth was modeled with an exponential equation, and instantaneous mortality was estimated by regressing the natural logarithm of fish catch for each 1-mm size-group against the estimated age of the group, which was derived from the growth equations. At two of the stations, the otolith-based method provided more precise estimates of sunfish growth than the length-based method. We were able to compare length-based and otolith-based estimates of sunfish mortality only at the two stations where we caught the largest numbers of sunfish. Estimates of mortality were similar for both methods in Pool 14, where catches were higher, but the length-based method gave significantly higher estimates in Pool 8, where the catches were lower. The otolith- based method required more laboratory analysis, but provided better estimates of the growth and mortality than the length-based method when catches were low. However, the length-based method was more cost- effective for estimating growth and mortality when catches were large.

Multiyear Downstream Response to Dam Removal on the White Salmon River, WA

NASA Astrophysics Data System (ADS)

Wilcox, A. C.; O'Connor, J. E.; Major, J. J.

2017-12-01

The 2011 removal of the 38 m tall Condit Dam on the White Salmon River, Washington was one of the largest dam removals to date, in terms of both dam height and sediment release. We examined the multiyear geomorphic response to this event, through 2015, including in a bedrock-confined canyon and in a less-confined, backwater-influenced pool reach near the river's mouth, to the large, rapid influx of fine reservoir sediment produced by the breach and to subsequent sediment transfer in the free-flowing White Salmon River. In the canyon reach, aggraded sediments were rapidly eroded from riffles, returning them toward pre-breach bed elevations within weeks, but pool aggradation persisted for longer. The downstream, less-confined reach transformed from a deep pool to a narrower pool-riffle channel with alternate bars; multiyear observations showed persistence of bars and of this new and distinct morphology. This downstream reach marks a rare case in post-dam removal channel response; in most dam removals, channels have rapidly reverted toward pre-removal morphology, as in the canyon reach here. Comparison of the multiyear geomorphic evolution of the White Salmon River to other recent large dam removals in the U.S. allows evaluation of the relative influences of antecedent channel morphology, post-breach hydrology, and dam removal style, as well as providing a basis for predicting responses to future dam removals.

Empty forest or empty rivers? A century of commercial hunting in Amazonia

PubMed Central

Antunes, André P.; Fewster, Rachel M.; Venticinque, Eduardo M.; Peres, Carlos A.; Levi, Taal; Rohe, Fabio; Shepard, Glenn H.

2016-01-01

The Amazon basin is the largest and most species-rich tropical forest and river system in the world, playing a pivotal role in global climate regulation and harboring hundreds of traditional and indigenous cultures. It is a matter of intense debate whether the ecosystem is threatened by hunting practices, whereby an “empty forest” loses critical ecological functions. Strikingly, no previous study has examined Amazonian ecosystem resilience through the perspective of the massive 20th century international trade in furs and skins. We present the first historical account of the scale and impacts of this trade and show that whereas aquatic species suffered basin-wide population collapse, terrestrial species did not. We link this differential resilience to the persistence of adequate spatial refuges for terrestrial species, enabling populations to be sustained through source-sink dynamics, contrasting with unremitting hunting pressure on more accessible aquatic habitats. Our findings attest the high vulnerability of aquatic fauna to unregulated hunting, particularly during years of severe drought. We propose that the relative resilience of terrestrial species suggests a marked opportunity for managing, rather than criminalizing, contemporary traditional subsistence hunting in Amazonia, through both the engagement of local people in community-based comanagement programs and science-led conservation governance. PMID:27757421

Socio-economic and ecological impacts of global protected area expansion plans

PubMed Central

Visconti, Piero; Bakkenes, Michel; Smith, Robert J.; Joppa, Lucas; Sykes, Rachel E.

2015-01-01

Several global strategies for protected area (PA) expansion have been proposed to achieve the Convention on Biological Diversity's Aichi target 11 as a means to stem biodiversity loss, as required by the Aichi target 12. However, habitat loss outside PAs will continue to affect habitats and species, and PAs may displace human activities into areas that might be even more important for species persistence. Here we measure the expected contribution of PA expansion strategies to Aichi target 12 by estimating the extent of suitable habitat available for all terrestrial mammals, with and without additional protection (the latter giving the counterfactual outcome), under different socio-economic scenarios and consequent land-use change to 2020. We found that expanding PAs to achieve representation targets for ecoregions under a Business-as-usual socio-economic scenario will result in a worse prognosis than doing nothing for more than 50% of the world's terrestrial mammals. By contrast, targeting protection towards threatened species can increase the suitable habitat available to over 60% of terrestrial mammals. Even in the absence of additional protection, an alternative socio-economic scenario, adopting progressive changes in human consumption, leads to positive outcomes for mammals globally and to the largest improvements for wide-ranging species. PMID:26460136

Soils associated to different tree communities do not elicit predictable responses in lake bacterial community structure and function.

PubMed

Ruiz-González, Clara; Archambault, Esther; Laforest-Lapointe, Isabelle; Del Giorgio, Paul A; Kembel, Steven W; Messier, Christian; Nock, Charles A; Beisner, Beatrix E

2018-06-14

Freshwater bacterioplankton communities are influenced by the inputs of material and bacteria from the surrounding landscape, yet few studies have investigated how different terrestrial inputs affect bacterioplankton. We examined whether the addition of soils collected under various tree species combinations differentially influences lake bacterial communities. Lake water was incubated for 6 days following addition of five different soils. We assessed the taxonomic composition (16S rRNA gene sequencing) and metabolic activity (Biolog Ecoplates) of lake bacteria with and without soil addition, and compared these to initial soil communities. Soil bacterial assemblages showed a strong influence of tree composition, but such community differences were not reflected in the structure of lake communities that developed during the experiment. Bacterial taxa showing the largest abundance increases during incubation were initially present in both lake water and across most soils, and were related to Cytophagales, Burkholderiales and Rhizobiales. No clear metabolic profiles based on inoculum source were found, yet soil-amended communities used 60% more substrate than non-inoculated communities. Overall, we show that terrestrial inputs influence aquatic communities by stimulating the growth and activity of certain ubiquitous taxa distributed across the terrestrial-aquatic continuum, yet different forest soils did not cause predictable changes in lake bacterioplankton assemblages.

Evolution of extreme body size disparity in monitor lizards (Varanus).

PubMed

Collar, David C; Schulte, James A; Losos, Jonathan B

2011-09-01

Many features of species' biology, including life history, physiology, morphology, and ecology are tightly linked to body size. Investigation into the causes of size divergence is therefore critical to understanding the factors shaping phenotypic diversity within clades. In this study, we examined size evolution in monitor lizards (Varanus), a clade that includes the largest extant lizard species, the Komodo dragon (V. komodoensis), as well as diminutive species that are nearly four orders of magnitude smaller in adult body mass. We demonstrate that the remarkable body size disparity of this clade is a consequence of different selective demands imposed by three major habitat use patterns-arboreality, terrestriality, and rock-dwelling. We reconstructed phylogenetic relationships and ancestral habitat use and applied model selection to determine that the best-fitting evolutionary models for species' adult size are those that infer oppositely directed adaptive evolution associated with terrestriality and rock-dwelling, with terrestrial lineages evolving extremely large size and rock-dwellers becoming very small. We also show that habitat use affects the evolution of several ecologically important morphological traits independently of body size divergence. These results suggest that habitat use exerts a strong, multidimensional influence on the evolution of morphological size and shape disparity in monitor lizards. © 2011 The Author(s).

Socio-economic and ecological impacts of global protected area expansion plans.

PubMed

Visconti, Piero; Bakkenes, Michel; Smith, Robert J; Joppa, Lucas; Sykes, Rachel E

2015-11-05

Several global strategies for protected area (PA) expansion have been proposed to achieve the Convention on Biological Diversity's Aichi target 11 as a means to stem biodiversity loss, as required by the Aichi target 12. However, habitat loss outside PAs will continue to affect habitats and species, and PAs may displace human activities into areas that might be even more important for species persistence. Here we measure the expected contribution of PA expansion strategies to Aichi target 12 by estimating the extent of suitable habitat available for all terrestrial mammals, with and without additional protection (the latter giving the counterfactual outcome), under different socio-economic scenarios and consequent land-use change to 2020. We found that expanding PAs to achieve representation targets for ecoregions under a Business-as-usual socio-economic scenario will result in a worse prognosis than doing nothing for more than 50% of the world's terrestrial mammals. By contrast, targeting protection towards threatened species can increase the suitable habitat available to over 60% of terrestrial mammals. Even in the absence of additional protection, an alternative socio-economic scenario, adopting progressive changes in human consumption, leads to positive outcomes for mammals globally and to the largest improvements for wide-ranging species. © 2015 The Author(s).

Seasonal body size reductions with warming covary with major body size gradients in arthropod species.

PubMed

Horne, Curtis R; Hirst, Andrew G; Atkinson, David

2017-03-29

Major biological and biogeographical rules link body size variation with latitude or environmental temperature, and these rules are often studied in isolation. Within multivoltine species, seasonal temperature variation can cause substantial changes in adult body size, as subsequent generations experience different developmental conditions. Yet, unlike other size patterns, these common seasonal temperature-size gradients have never been collectively analysed. We undertake the largest analysis to date of seasonal temperature-size gradients in multivoltine arthropods, including 102 aquatic and terrestrial species from 71 global locations. Adult size declines in warmer seasons in 86% of the species examined. Aquatic species show approximately 2.5-fold greater reduction in size per °C of warming than terrestrial species, supporting the hypothesis that greater oxygen limitation in water than in air forces aquatic species to exhibit greater plasticity in body size with temperature. Total percentage change in size over the annual cycle appears relatively constant with annual temperature range but varies between environments, such that the overall size reduction in aquatic-developing species (approx. 31%) is almost threefold greater than in terrestrial species (approx. 11%). For the first time, we show that strong correlations exist between seasonal temperature-size gradients, laboratory responses and latitudinal-size clines, suggesting that these patterns share common drivers. © 2017 The Author(s).

Decoding the Substrate Supply to Human Neuronal Nitric Oxide Synthase

PubMed Central

Habermeier, Alice; Closs, Ellen I.

2013-01-01

Nitric oxide, produced by the neuronal nitric oxide synthase (nNOS) from L-arginine is an important second messenger molecule in the central nervous system: It influences the synthesis and release of neurotransmitters and plays an important role in long-term potentiation, long-term depression and neuroendocrine secretion. However, under certain pathological conditions such as Alzheimer’s or Parkinson’s disease, stroke and multiple sclerosis, excessive NO production can lead to tissue damage. It is thus desirable to control NO production in these situations. So far, little is known about the substrate supply to human nNOS as a determinant of its activity. Measuring bioactive NO via cGMP formation in reporter cells, we demonstrate here that nNOS in both, human A673 neuroepithelioma and TGW-nu-I neuroblastoma cells can be fast and efficiently nourished by extracellular arginine that enters the cells via membrane transporters (pool I that is freely exchangeable with the extracellular space). When this pool was depleted, NO synthesis was partially sustained by intracellular arginine sources not freely exchangeable with the extracellular space (pool II). Protein breakdown made up by far the largest part of pool II in both cell types. In contrast, citrulline to arginine conversion maintained NO synthesis only in TGW-nu-I neuroblastoma, but not A673 neuroepithelioma cells. Histidine mimicked the effect of protease inhibitors causing an almost complete nNOS inhibition in cells incubated additionally in lysine that depletes the exchangeable arginine pool. Our results identify new ways to modulate nNOS activity by modifying its substrate supply. PMID:23874440

Cation regulation by the terrestrial isopod Armadillidium vulgare (Crustacea: Isopoda: Oniscidea) during dehydration in air.

PubMed

Koh, Huishan; Wright, Jonathan

2011-06-01

Many terrestrial arthropods display tight osmotic and ionic regulation of the hemolymph during dehydration. In this study, we sought to quantify the level of regulation of the major hemolymph cations in the terrestrial isopod Armadillidium vulgare (Isopoda, Oniscidea). Inulin space measurements showed that the hemolymph comprises 52 ± 2.2% of the hydrated water content but contributes 71 ± 9.8% of water losses during desiccation. Hemolymph concentrations of Na+, K+ and Ca²+ were measured in variably dehydrated animals using ion-selective microelectrodes and compared with predicted concentrations assuming no regulation. Na+ and Ca²+ are quite tightly regulated, showing respective concentration increases of 20.8% and 7.1% following a 50% reduction in hemolymph volume, but K+ showed no measurable regulation. The excreted cation fraction during desiccation is negligible. Sites of ion sequestration were examined by injecting ²²Na and ⁴⁵Ca into the hemolymph of hydrated animals and assaying tissue-specific activities following dehydration. Na+ is apparently sequestered non-specifically by an unknown mechanism. Ca²+ accumulates in the dorsal somatic tissues, possibly in the calcium pool of the cuticle. How A. vulgare avoids significant disruptions of E(m) and neuromuscular function in the absence of K+ regulation, and how it sequesters Na+, both pose intriguing challenges for future work. Copyright © 2011 Elsevier Inc. All rights reserved.

Marine microbial L-asparaginase: Biochemistry, molecular approaches and applications in tumor therapy and in food industry.

PubMed

Izadpanah Qeshmi, Fatemeh; Homaei, Ahmad; Fernandes, Pedro; Javadpour, Sedigheh

2018-03-01

The marine environment is a rich source of biological and chemical diversity. It covers more than 70% of the Earth's surface and features a wide diversity of habitats, often displaying extreme conditions, where marine organisms thrive, offering a vast pool for microorganisms and enzymes. Given the dissimilarity between marine and terrestrial habitats, enzymes and microorganisms, either novel or with different and appealing features as compared to terrestrial counterparts, may be identified and isolated. L-asparaginase (E.C. 3.5.1.1), is among the relevant enzymes that can be obtained from marine sources. This amidohydrolase acts on L-asparagine and produce L-aspartate and ammonia, accordingly it has an acknowledged chemotherapeutic application, namely in acute lymphoblastic leukemia. Moreover, L-asparaginase is also of interest in the food industry as it prevents acrylamide formation. Terrestrial organisms have been largely tapped for L-asparaginases, but most failed to comply with criteria for practical applications, whereas marine sources have only been marginally screened. This work provides an overview on the relevant features of this enzyme and the framework for its application, with a clear emphasis on the use of L-asparaginase from marine sources. The review envisages to highlight the unique properties of marine L-asparaginases that could make them good candidates for medical applications and industries, especially in food safety. Copyright © 2018 Elsevier GmbH. All rights reserved.

A review on the role of organic inputs in maintaining the soil carbon pool of the terrestrial ecosystem.

PubMed

Bhattacharya, Satya Sundar; Kim, Ki-Hyun; Das, Subhasish; Uchimiya, Minori; Jeon, Byong Hun; Kwon, Eilhann; Szulejko, Jan E

2016-02-01

Among the numerous sources of greenhouse gases, emissions of CO2 are considerably affected by changes in the extent and type of land use, e.g., intensive agriculture, deforestation, urbanization, soil erosion, or wetland drainage. As a feasible option to control emissions from the terrestrial ecosystems, the scientific community has explored the possibility of enhancing soil carbon (C) storage capacity. Thus, restoration of damaged lands through conservation tillage, crop rotation, cover cropping, reforestation, sub-soiling of compacted lands, sustainable water management practices, and organic manuring are the major antidotes against attenuation of soil organic C (SOC) stocks. In this research, we focused on the effect of various man-made activities on soil biotic organics (e.g., green-, farm-yard manure, and composts) to understand how C fluxes from various sources contribute to the establishment of a new equilibrium in the terrestrial ecosystems. Although such inputs substitute a portion of chemical fertilizers, they all undergo activities that augment the rate and extent of decay to deplete the SOC bank. Here, we provide perspectives on the balancing factors that control the mineralization rate of organic matter. Our arguments are placed in the background of different land use types and their impacts on forests, agriculture, urbanization, soil erosion, and wetland destruction. Copyright © 2015 Elsevier Ltd. All rights reserved.

Identifying the core seed bank of a complex boreal bacterial metacommunity.

PubMed

Ruiz-González, Clara; Niño-García, Juan Pablo; Kembel, Steven W; Del Giorgio, Paul A

2017-09-01

Seed banks are believed to contribute to compositional changes within and across microbial assemblages, but the application of this concept to natural communities remains challenging. Here we describe the core seed bank of a bacterial metacommunity from a boreal watershed, using the spatial distribution of bacterial operational taxonomic units (OTUs) across 223 heterogeneous terrestrial, aquatic and phyllosphere bacterial assemblages. Taxa were considered potential seeds if they transitioned from rare to abundant somewhere within the metacommunity and if they were ubiquitous and able to persist under unfavorable conditions, the latter assessed by checking their presence in three deeply sequenced samples (one soil, one river and one lake, 2.2-3 million reads per sample). We show that only a small fraction (13%) of all detected OTUs constitute a metacommunity seed bank that is shared between all terrestrial and aquatic communities, but not by phyllosphere assemblages, which seem to recruit from a different taxa pool. Our results suggest directional recruitment driven by the flow of water in the landscape, since most aquatic sequences were associated to OTUs found in a single deeply-sequenced soil sample, but only 45% of terrestrial sequences belonged to OTUs found in the two deeply-sequenced aquatic communities. Finally, we hypothesize that extreme rarity, and its interplay with water residence time and growth rates, may further constrain the size of the potential seed bank.

Diversification of Nitrogen Sources in Various Tundra Vegetation Types in the High Arctic

PubMed Central

Skrzypek, Grzegorz; Wojtuń, Bronisław; Richter, Dorota; Jakubas, Dariusz; Wojczulanis-Jakubas, Katarzyna; Samecka-Cymerman, Aleksandra

2015-01-01

Low nitrogen availability in the high Arctic represents a major constraint for plant growth, which limits the tundra capacity for carbon retention and determines tundra vegetation types. The limited terrestrial nitrogen (N) pool in the tundra is augmented significantly by nesting seabirds, such as the planktivorous Little Auk (Alle alle). Therefore, N delivered by these birds may significantly influence the N cycling in the tundra locally and the carbon budget more globally. Moreover, should these birds experience substantial negative environmental pressure associated with climate change, this will adversely influence the tundra N-budget. Hence, assessment of bird-originated N-input to the tundra is important for understanding biological cycles in polar regions. This study analyzed the stable nitrogen composition of the three main N-sources in the High Arctic and in numerous plants that access different N-pools in ten tundra vegetation types in an experimental catchment in Hornsund (Svalbard). The percentage of the total tundra N-pool provided by birds, ranged from 0–21% in Patterned-ground tundra to 100% in Ornithocoprophilous tundra. The total N-pool utilized by tundra plants in the studied catchment was built in 36% by birds, 38% by atmospheric deposition, and 26% by atmospheric N2-fixation. The stable nitrogen isotope mixing mass balance, in contrast to direct methods that measure actual deposition, indicates the ratio between the actual N-loads acquired by plants from different N-sources. Our results enhance our understanding of the importance of different N-sources in the Arctic tundra and the used methodological approach can be applied elsewhere. PMID:26376204

Diversification of Nitrogen Sources in Various Tundra Vegetation Types in the High Arctic.

PubMed

Skrzypek, Grzegorz; Wojtuń, Bronisław; Richter, Dorota; Jakubas, Dariusz; Wojczulanis-Jakubas, Katarzyna; Samecka-Cymerman, Aleksandra

2015-01-01

Low nitrogen availability in the high Arctic represents a major constraint for plant growth, which limits the tundra capacity for carbon retention and determines tundra vegetation types. The limited terrestrial nitrogen (N) pool in the tundra is augmented significantly by nesting seabirds, such as the planktivorous Little Auk (Alle alle). Therefore, N delivered by these birds may significantly influence the N cycling in the tundra locally and the carbon budget more globally. Moreover, should these birds experience substantial negative environmental pressure associated with climate change, this will adversely influence the tundra N-budget. Hence, assessment of bird-originated N-input to the tundra is important for understanding biological cycles in polar regions. This study analyzed the stable nitrogen composition of the three main N-sources in the High Arctic and in numerous plants that access different N-pools in ten tundra vegetation types in an experimental catchment in Hornsund (Svalbard). The percentage of the total tundra N-pool provided by birds, ranged from 0-21% in Patterned-ground tundra to 100% in Ornithocoprophilous tundra. The total N-pool utilized by tundra plants in the studied catchment was built in 36% by birds, 38% by atmospheric deposition, and 26% by atmospheric N2-fixation. The stable nitrogen isotope mixing mass balance, in contrast to direct methods that measure actual deposition, indicates the ratio between the actual N-loads acquired by plants from different N-sources. Our results enhance our understanding of the importance of different N-sources in the Arctic tundra and the used methodological approach can be applied elsewhere.

Effects of the hippopotamus on the chemistry and ecology of a changing watershed.

PubMed

Stears, Keenan; McCauley, Douglas J; Finlay, Jacques C; Mpemba, James; Warrington, Ian T; Mutayoba, Benezeth M; Power, Mary E; Dawson, Todd E; Brashares, Justin S

2018-05-29

Cross-boundary transfers of nutrients can profoundly shape the ecology of recipient systems. The common hippopotamus, Hippopotamus amphibius , is a significant vector of such subsidies from terrestrial to river ecosystems. We compared river pools with high and low densities of H. amphibius to determine how H. amphibius subsidies shape the chemistry and ecology of aquatic communities. Our study watershed, like many in sub-Saharan Africa, has been severely impacted by anthropogenic water abstraction reducing dry-season flow to zero. We conducted observations for multiple years over wet and dry seasons to identify how hydrological variability influences the impacts of H. amphibius During the wet season, when the river was flowing, we detected no differences in water chemistry and nutrient parameters between pools with high and low densities of H. amphibius Likewise, the diversity and abundance of fish and aquatic insect communities were indistinguishable. During the dry season, however, high-density H. amphibiu s pools differed drastically in almost all measured attributes of water chemistry and exhibited depressed fish and insect diversity and fish abundance compared with low-density H. amphibius pools. Scaled up to the entire watershed, we estimate that H. amphibius in this hydrologically altered watershed reduces dry-season fish abundance and indices of gamma-level diversity by 41% and 16%, respectively, but appears to promote aquatic invertebrate diversity. Widespread human-driven shifts in hydrology appear to redefine the role of H. amphibius , altering their influence on ecosystem diversity and functioning in a fashion that may be more severe than presently appreciated.

Estimating Sources and Fluxes of Dissolved and Particulate Organic Matter in UK Rivers

NASA Astrophysics Data System (ADS)

Adams, Jessica; Tipping, Edward; Quinton, John; Old, Gareth

2014-05-01

Over the past two centuries, pools and fluxes of carbon, nitrogen and phosphorus in UK ecosystems have been altered by intensification of agriculture, land use change and atmospheric pollution leading to acidification and eutrophication of surface waters. In addition to this, climate change is now also predicted to substantially impact these systems. The CEH Long Term Large Scale (LTLS) project therefore aims to simulate the pools and fluxes of carbon, nitrogen and phosphorus and their stoichiometry during the cycling process. Through the N14C model, simulations of the release of C, N and P through drainage water and erosion processes will be predicted using historical climate data, which will be tested using contemporary data. For present data, water from four UK catchments (Ribble, Wiltshire Avon, Conwy, Dee) were collected at the tidal limit of each river, which included a combination of high and low flow samples predicted using 5 day forecasts and local weather station data. These samples were filtered, centrifuged and sent to the NERC radiocarbon facility for analysis by accelerator mass spectrometry (AMS) to obtain both PO14C and DO14C data. Radiocarbon enables a unique and dynamic way of estimating long term turnover rates of organic matter, and has proven to be an invaluable tool for measuring upland terrestrial and aquatic systems. It has however, been scarcely used in larger, lowland river systems. Since the riverine organic matter captured is likely to have originated from terrestrial and riparian sources, the radiocarbon data will be a rigorous test of the model's ability to simulate the coupling of erosion and leaching processes, and stoichiometric relationships between C:N:P.

Optimization of Terrestrial Ecosystem Model Parameters Using Atmospheric CO2 Concentration Data With the Global Carbon Assimilation System (GCAS)

NASA Astrophysics Data System (ADS)

Chen, Zhuoqi; Chen, Jing M.; Zhang, Shupeng; Zheng, Xiaogu; Ju, Weiming; Mo, Gang; Lu, Xiaoliang

2017-12-01

The Global Carbon Assimilation System that assimilates ground-based atmospheric CO2 data is used to estimate several key parameters in a terrestrial ecosystem model for the purpose of improving carbon cycle simulation. The optimized parameters are the leaf maximum carboxylation rate at 25°C (Vmax25), the temperature sensitivity of ecosystem respiration (Q10), and the soil carbon pool size. The optimization is performed at the global scale at 1° resolution for the period from 2002 to 2008. The results indicate that vegetation from tropical zones has lower Vmax25 values than vegetation in temperate regions. Relatively high values of Q10 are derived over high/midlatitude regions. Both Vmax25 and Q10 exhibit pronounced seasonal variations at middle-high latitudes. The maxima in Vmax25 occur during growing seasons, while the minima appear during nongrowing seasons. Q10 values decrease with increasing temperature. The seasonal variabilities of Vmax25 and Q10 are larger at higher latitudes. Optimized Vmax25 and Q10 show little seasonal variabilities at tropical regions. The seasonal variabilities of Vmax25 are consistent with the variabilities of LAI for evergreen conifers and broadleaf evergreen forests. Variations in leaf nitrogen and leaf chlorophyll contents may partly explain the variations in Vmax25. The spatial distribution of the total soil carbon pool size after optimization is compared favorably with the gridded Global Soil Data Set for Earth System. The results also suggest that atmospheric CO2 data are a source of information that can be tapped to gain spatially and temporally meaningful information for key ecosystem parameters that are representative at the regional and global scales.

Insights into archaeal evolution and symbiosis from the genomes of a nanoarchaeon and its inferred crenarchaeal host from Obsidian Pool, Yellowstone National Park.

PubMed

Podar, Mircea; Makarova, Kira S; Graham, David E; Wolf, Yuri I; Koonin, Eugene V; Reysenbach, Anna-Louise

2013-04-22

A single cultured marine organism, Nanoarchaeum equitans, represents the Nanoarchaeota branch of symbiotic Archaea, with a highly reduced genome and unusual features such as multiple split genes. The first terrestrial hyperthermophilic member of the Nanoarchaeota was collected from Obsidian Pool, a thermal feature in Yellowstone National Park, separated by single cell isolation, and sequenced together with its putative host, a Sulfolobales archaeon. Both the new Nanoarchaeota (Nst1) and N. equitans lack most biosynthetic capabilities, and phylogenetic analysis of ribosomal RNA and protein sequences indicates that the two form a deep-branching archaeal lineage. However, the Nst1 genome is more than 20% larger, and encodes a complete gluconeogenesis pathway as well as the full complement of archaeal flagellum proteins. With a larger genome, a smaller repertoire of split protein encoding genes and no split non-contiguous tRNAs, Nst1 appears to have experienced less severe genome reduction than N. equitans. These findings imply that, rather than representing ancestral characters, the extremely compact genomes and multiple split genes of Nanoarchaeota are derived characters associated with their symbiotic or parasitic lifestyle. The inferred host of Nst1 is potentially autotrophic, with a streamlined genome and simplified central and energetic metabolism as compared to other Sulfolobales. Comparison of the N. equitans and Nst1 genomes suggests that the marine and terrestrial lineages of Nanoarchaeota share a common ancestor that was already a symbiont of another archaeon. The two distinct Nanoarchaeota-host genomic data sets offer novel insights into the evolution of archaeal symbiosis and parasitism, enabling further studies of the cellular and molecular mechanisms of these relationships. This article was reviewed by Patrick Forterre, Bettina Siebers (nominated by Michael Galperin) and Purification Lopez-Garcia.

Land-Use Impacts on the Terrestrial Carbon Cycle: An Integrative Tool for Resource Assessment and Planning

NASA Astrophysics Data System (ADS)

Sleeter, B. M.; Liu, J.; Zhu, Z.; Hawbaker, T. J.

2014-12-01

Human land use and natural processes contribute to the ability of ecosystems to store and sequester carbon and offset greenhouse gas emissions. Changes in land use (e.g. agricultural cultivation, timber harvest, urban development, and other land management strategies) and natural processes (e.g. climate, wildfire, disease, storm, and insect outbreak) drive the dynamics of ecosystem carbon pools. These carbon dynamics operate at different spatial and temporal scales, making it challenging to track the changes in a single integrative framework. Landowners, managers, and policy makers require data, information, and tools on the relative contributions of these drivers of ecosystem carbon stocks and fluxes in order to evaluate alternative policies and management strategies designed to increase carbon storage and sequestration. In this paper we explore preliminary results from efforts to simulate changes in ecosystem carbon at ecoregional scales, resulting from anthropogenic land use, wildfire, natural vegetation change, and climate variability under a range of future conditions coherent with a range of global change scenarios. Simulations track the fate of carbon across several pools, including living biomass, deadwood, litter, soil, and wood products. Carbon fluxes are estimated based on simulations from the Integrated Biosphere Simulator model (IBIS). Downscaled land-use projections from the Special Report on Emission Scenarios and Representative Concentration Pathways drive changes in land use, along with extrapolations based on local-scale data. We discuss the sensitivity of the model to individual drivers, and the overall uncertainty associated with the wide range of scenario projections, as well as explore alternative policy and management outcomes and their ability to increase carbon storage in terrestrial ecosystems.

BLAZE, a novel Fire-Model for the CABLE Land-Surface Model applied to a Re-Assessment of the Australian Continental Carbon Budget

NASA Astrophysics Data System (ADS)

Nieradzik, L. P.; Haverd, V. E.; Briggs, P.; Meyer, C. P.; Canadell, J.

2015-12-01

Fires play a major role in the carbon-cycle and the development of global vegetation, especially on the continent of Australia, where vegetation is prone to frequent fire occurences and where regional composition and stand-age distribution is regulated by fire. Furthermore, the probable changes of fire behaviour under a changing climate are still poorly understood and require further investigation.In this presentation we introduce the fire-model BLAZE (BLAZe induced land-atmosphere flux Estimator), designed for a novel approach to simulate fire-frequencies, fire-intensities, fire related fluxes and the responses in vegetation. Fire frequencies are prescribed using SIMFIRE (Knorr et al., 2014) or GFED3 (e.g. Giglio et al., 2013). Fire-Line-Intensity (FLI) is computed from meteorological information and fuel loads which are state variables within the C-cycle component of CABLE (Community Atmosphere-Biosphere-Land Exchange model). This FLI is used as an input to the tree-demography model POP(Population-Order-Physiology; Haverd et al., 2014). Within POP the fire-mortality depends on FLI and tree height distribution. Intensity-dependent combustion factors (CF) are then generated for and applied to live and litter carbon pools as well as the transfers from live pools to litter caused by fire. Thus, both fire and stand characteristics are taken into account which has a legacy effect on future events. Gross C-CO2 emissions from Australian wild fires are larger than Australian territorial fossil fuel emissions. However, the net effect of fire on the Australian terrestrial carbon budget is unknown. We address this by applying the newly-developed fire module, integrated within the CABLE land surface model, and optimised for the Australian region, to a reassessment of the Australian Terrestrial Carbon Budget.

Stable carbon and nitrogen isotope composition of aquatic and terrestrial plants of the San Francisco Bay estuarine system

USGS Publications Warehouse

Cloern, J.E.; Canuel, E.A.; Harris, D.

2002-01-01

We report measurements of seasonal variability in the C-N stable isotope ratios of plants collected across the habitat mosaic of San Francisco Bay, its marshes, and its tributary river system. Analyses of 868 plant samples were binned into 10 groups (e.g., terrestrial riparian, freshwater phytoplankton, salt marsh) to determine whether C-N isotopes can be used as biomarkers for tracing the origins of organic matter in this river-marsh-estuary complex. Variability of ??13C and ??15N was high (???5-10???) within each plant group, and we identified three modes of variability: (1) between species and their microhabitats, (2) over annual cycles of plant growth and senescence, and (3) between living and decomposing biomass. These modes of within-group variability obscure any source-specific isotopic signatures, confounding the application of C-N isotopes for identifying the origins of organic matter. A second confounding factor was large dissimilarity between the ??13C-??15N of primary producers and the organic-matter pools in the seston and sediments. Both confounding factors impede the application of C-N isotopes to reveal the food supply to primary consumers in ecosystems supporting diverse autotrophs and where the isotopic composition of organic matter has been transformed and become distinct from that of its parent plant sources. Our results support the advice of others: variability of C-N stable isotopes within all organic-matter pools is high and must be considered in applications of these isotopes to trace trophic linkages from primary producers to primary consumers. Isotope-based approaches are perhaps most powerful when used to complement other tools, such as molecular biomarkers, bioassays, direct measures of production, and compilations of organic-matter budgets.

Calcium Induces Long-Term Legacy Effects in a Subalpine Ecosystem

PubMed Central

Schaffner, Urs; Alewell, Christine; Eschen, René; Matthies, Diethart; Spiegelberger, Thomas; Hegg, Otto

2012-01-01

Human activities have transformed a significant proportion of the world’s land surface, with profound effects on ecosystem processes. Soil applications of macronutrients such as nitrate, phosphorus, potassium or calcium are routinely used in the management of croplands, grasslands and forests to improve plant health or increase productivity. However, while the effects of continuous fertilization and liming on terrestrial ecosystems are well documented, remarkably little is known about the legacy effect of historical fertilization and liming events in terrestrial ecosystems and of the mechanisms involved. Here, we show that more than 70 years after the last application of lime on a subalpine grassland, all major soil and plant calcium pools were still significantly larger in limed than in unlimed plots, and that the resulting shift in the soil calcium/aluminium ratio continues to affect ecosystem services such as primary production. The difference in the calcium content of the vegetation and the topmost 10 cm of the soil in limed vs. unlimed plots amounts to approximately 19.5 g m−2, equivalent to 16.3% of the amount that was added to the plots some 70 years ago. In contrast, plots that were treated with nitrogen-phosphorus-potassium fertilizer in the 1930s did not differ from unfertilized plots in any of the soil and vegetation characteristics measured. Our findings suggest that the long-term legacy effect of historical liming is due to long-term storage of added calcium in stable soil pools, rather than a general increase in nutrient availability. Our results demonstrate that single applications of calcium in its carbonated form can profoundly and persistently alter ecosystem processes and services in mountain ecosystems. PMID:23284779

Report of the 22nd Annual Congress of the International Liver Transplantation Society.

PubMed

Diaz, Geraldine C; Zerillo, Jeron; Singhal, Ashish; Hibi, Taizo; Vitale, Alessandro; Levitsky, Josh; Renz, John F

2017-02-01

The 2016 Annual Congress of the International Liver Transplantation Society was held in Seoul, South Korea in May. The 22nd Congress marked the largest multidisciplinary liver transplantation meeting in Asia since 2010. The principal themes were living donation, allocation, immunosuppression, machine preservation, novel treatment of hepatitis C, and expansion of the deceased-donor allograft pool. This report presents select abstracts from the scientific sessions within the context of the published literature to serve as a quick reference.

Infectivity and Transmissibility of Avian H9N2 Influenza Viruses in Pigs

PubMed Central

Wang, Jia; Wu, Maocai; Hong, Wenshan; Fan, Xiaohui; Chen, Rirong; Zheng, Zuoyi; Zeng, Yu; Huang, Ren; Zhang, Yu; Lam, Tommy Tsan-Yuk; Smith, David K.

2016-01-01

ABSTRACT The H9N2 influenza viruses that are enzootic in terrestrial poultry in China pose a persistent pandemic threat to humans. To investigate whether the continuous circulation and adaptation of these viruses in terrestrial poultry increased their infectivity to pigs, we conducted a serological survey in pig herds with H9N2 viruses selected from the aquatic avian gene pool (Y439 lineage) and the enzootic terrestrial poultry viruses (G1 and Y280 lineages). We also compared the infectivity and transmissibility of these viruses in pigs. It was found that more than 15% of the pigs sampled from 2010 to 2012 in southern China were seropositive to either G1 or Y280 lineage viruses, but none of the sera were positive to the H9 viruses from the Y439 lineage. Viruses of the G1 and Y280 lineages were able to infect experimental pigs, with detectable nasal shedding of the viruses and seroconversion, whereas viruses of the Y439 lineage did not cause a productive infection in pigs. Thus, adaptation and prevalence in terrestrial poultry could lead to interspecies transmission of H9N2 viruses from birds to pigs. Although H9N2 viruses do not appear to be continuously transmissible among pigs, repeated introductions of H9 viruses to pigs naturally increase the risk of generating mammalian-adapted or reassorted variants that are potentially infectious to humans. This study highlights the importance of monitoring the activity of H9N2 viruses in terrestrial poultry and pigs. IMPORTANCE H9N2 subtype of influenza viruses has repeatedly been introduced into mammalian hosts, including humans and pigs, so awareness of their activity and evolution is important for influenza pandemic preparedness. However, since H9N2 viruses usually cause mild or even asymptomatic infections in mammalian hosts, they may be overlooked in influenza surveillance. Here, we found that the H9N2 viruses established in terrestrial poultry had higher infectivity in pigs than those from aquatic birds, which suggests that adaptation of the H9N2 viruses in terrestrial poultry might have increased the infectivity of the virus to mammals. Therefore, monitoring the prevalence and evolution of H9 viruses prevalent in terrestrial birds and conducting risk assessment of their threat to mammals are critical for evaluating the pandemic potential of this virus. PMID:26764002

Infectivity and Transmissibility of Avian H9N2 Influenza Viruses in Pigs.

PubMed

Wang, Jia; Wu, Maocai; Hong, Wenshan; Fan, Xiaohui; Chen, Rirong; Zheng, Zuoyi; Zeng, Yu; Huang, Ren; Zhang, Yu; Lam, Tommy Tsan-Yuk; Smith, David K; Zhu, Huachen; Guan, Yi

2016-01-13

The H9N2 influenza viruses that are enzootic in terrestrial poultry in China pose a persistent pandemic threat to humans. To investigate whether the continuous circulation and adaptation of these viruses in terrestrial poultry increased their infectivity to pigs, we conducted a serological survey in pig herds with H9N2 viruses selected from the aquatic avian gene pool (Y439 lineage) and the enzootic terrestrial poultry viruses (G1 and Y280 lineages). We also compared the infectivity and transmissibility of these viruses in pigs. It was found that more than 15% of the pigs sampled from 2010 to 2012 in southern China were seropositive to either G1 or Y280 lineage viruses, but none of the sera were positive to the H9 viruses from the Y439 lineage. Viruses of the G1 and Y280 lineages were able to infect experimental pigs, with detectable nasal shedding of the viruses and seroconversion, whereas viruses of the Y439 lineage did not cause a productive infection in pigs. Thus, adaptation and prevalence in terrestrial poultry could lead to interspecies transmission of H9N2 viruses from birds to pigs. Although H9N2 viruses do not appear to be continuously transmissible among pigs, repeated introductions of H9 viruses to pigs naturally increase the risk of generating mammalian-adapted or reassorted variants that are potentially infectious to humans. This study highlights the importance of monitoring the activity of H9N2 viruses in terrestrial poultry and pigs. H9N2 subtype of influenza viruses has repeatedly been introduced into mammalian hosts, including humans and pigs, so awareness of their activity and evolution is important for influenza pandemic preparedness. However, since H9N2 viruses usually cause mild or even asymptomatic infections in mammalian hosts, they may be overlooked in influenza surveillance. Here, we found that the H9N2 viruses established in terrestrial poultry had higher infectivity in pigs than those from aquatic birds, which suggests that adaptation of the H9N2 viruses in terrestrial poultry might have increased the infectivity of the virus to mammals. Therefore, monitoring the prevalence and evolution of H9 viruses prevalent in terrestrial birds and conducting risk assessment of their threat to mammals are critical for evaluating the pandemic potential of this virus. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

Quantifying carbon budget and nitrous oxide emissions of terrestrial ecosystems in the Eurasian Arctic and the Dry Latitudinal Belt of Northern Eurasia

NASA Astrophysics Data System (ADS)

Zhuang, Q.; Yu, T.; Qu, Y.; Kicklighter, D. W.; Melillo, J. M.; Sokolov, A. P.; Reilly, J. M.; Monier, E.

2017-12-01

The largest increase of surface air temperature and related climate extremes has occurred in Northern Eurasia in recent decades, and is projected to continue during the 21st century. The changing climate will affect the fate of the large reservoir of organic matter stored in the region. Given a large amount of carbon-based gases CO2 and CH4 is exchanged between the atmosphere and land ecosystems, we hypothesize that the emissions of another potent greenhouse gas N2O are not small. This study used a process-based biogeochemistry model to estimate soil N2O emissions in Northern Eurasia for the latter half of the 20th century and the 21st century. We find that, in the latter half of the 20th century, there was a slight decreasing trend for the regional N2O emissions from 1.4 Tg N yr-1 to 1.17 Tg N yr-1. Boreal forests are the largest source due to their large area and high flux density. Two contrasting climate scenarios with no-policy and policy for future greenhouse gas emissions and with different climate sensitivities (high, medium and low) of a global climate model are used to drive the biogeochemistry model for the 21st century. Simulations indicate that there will be an increasing trend of N2O emissions under the no-policy climate scenario. By 2100, the emissions are 1.28, 1.40 and 1.73 Tg N yr-1 under climate conditions projected considering low, intermediate, and high level of climate sensitivity, respectively. In contrast, under the policy climate scenarios, there will be a decreasing trend and the emissions are 0.89, 1.02, and 1.06 Tg N yr-1 by 2100, respectively. This study suggests that the large increase of air temperature will enhance regional N2O emissions. Future changes in precipitation and depleting organic nitrogen pools also play a role in affecting future emission strengths in Northern Eurasia. In this presentation, we will also present ensemble simulations of carbon budget for the Dry Latitudinal Belt of Northern Eurasia under various future climate conditions.

Effects of Recombinant Human Growth Hormone for Osteoporosis: Systematic Review and Meta-Analysis.

PubMed

Atkinson, Hayden F; Moyer, Rebecca F; Yacoub, Daniel; Coughlin, Dexter; Birmingham, Trevor B

2017-03-01

Our objective was to evaluate the efficacy of recombinant human growth hormone (GH) on bone mineral density (BMD) in persons age 50 and older, with normal pituitary function, with or at risk for developing osteoporosis. We systematically reviewed randomized clinical trials (RCTs), searching six databases, and conducted meta-analyses to examine GH effects on BMD of the lumbar spine and femoral neck. Data for fracture incidence, bone metabolism biomarkers, and adverse events were also extracted and analysed. Thirteen RCTs met the eligibility criteria. Pooled effect sizes suggested no significant GH effect on BMD. Pooled effect sizes were largest, but nonsignificant, when compared to placebo. GH had a significant effect on several bone metabolism biomarkers. A significantly higher rate of adverse events was observed in the GH groups. Meta-analysis of RCTs suggests that GH treatment for persons with or at risk for developing osteoporosis results in very small, nonsignificant increases in BMD.

Late Miocene - Pliocene Evolution of the Pacific Warm Pool and Cold Tongue: Implications for El Niño

NASA Astrophysics Data System (ADS)

Zhang, Y.; Pagani, M.

2011-12-01

The Western Pacific Warm Pool of the tropical Pacific Ocean retains the largest and warmest sea surface water body on Earth, while the eastern equatorial Pacific is characterized by strong upwelling of cold, nutrient-rich deep waters, termed the Pacific cold tongue. Evolution of the Pacific warm pool and cold tongue are important because they control the circum-Pacific climate and impact the globe via El Niño - Southern Oscillation (ENSO) teleconnections. Sea surface temperature (SST) reconstructions using a single site from the warm pool (ODP 806) and two sites from the cold tongue (ODP 846, 847) suggest that the temperature of the warm pool was "stable" throughout the Plio-Pleistocene, whereas the cold tongue was much warmer in the Pliocene and subsequently cooled. The absence of an east-west Pacific temperature gradient during the early Pliocene is the basis for the "permanent El Niño" hypothesis. However, annually-resolved fossil coral and evaporite records found 3-7 years climate variability during the Pliocene warm period and late Miocene, challenging a "permanent" or invariant climate state. Here we present a multi-proxy (TEX86, UK37, Mg/Ca), multi-site reconstruction of the late Miocene - Pliocene (ca. 12 Ma - 3 Ma) SST in the Pacific warm pool (ODP 806, ODP 769 in the Sulu Sea, ODP 1143 in the South China Sea) and the cold tongue (ODP 850, 849, 846). Our results show that the cold tongue was even warmer in the late Miocene than the Pliocene, and that the warm pool cooled 2-3°C from the late Miocene into the Pliocene - in contrast to the invariant character previously assumed. Temperature comparison between different sites suggests that the warm pool may have expanded in size in the late Miocene. Although eastern and western ends of the tropical Pacific were warmer, a persistent, but low east-west temperature gradient (~3°C) is apparent. This agrees with recent studies which have shown ENSO-related frequency of climate change in the late Miocene and early Pliocene.

Asynchronous marine-terrestrial signals of the last deglacial warming in East Asia associated with low- and high-latitude climate changes.

PubMed

Xu, Deke; Lu, Houyuan; Wu, Naiqin; Liu, Zhenxia; Li, Tiegang; Shen, Caiming; Wang, Luo

2013-06-11

A high-resolution multiproxy record, including pollen, foraminifera, and alkenone paleothermometry, obtained from a single core (DG9603) from the Okinawa Trough, East China Sea (ECS), provided unambiguous evidence for asynchronous climate change between the land and ocean over the past 40 ka. On land, the deglacial stage was characterized by rapid warming, as reflected by paleovegetation, and it began ca. 15 kaBP, consistent with the timing of the last deglacial warming in Greenland. However, sea surface temperature estimates from foraminifera and alkenone paleothermometry increased around 20-19 kaBP, as in the Western Pacific Warm Pool (WPWP). Sea surface temperatures in the Okinawa Trough were influenced mainly by heat transport from the tropical western Pacific Ocean by the Kuroshio Current, but the epicontinental vegetation of the ECS was influenced by atmospheric circulation linked to the northern high-latitude climate. Asynchronous terrestrial and marine signals of the last deglacial warming in East Asia were thus clearly related to ocean currents and atmospheric circulation. We argue that (i) early warming seawater of the WPWP, driven by low-latitude insolation and trade winds, moved northward via the Kuroshio Current and triggered marine warming along the ECS around 20-19 kaBP similar to that in the WPWP, and (ii) an almost complete shutdown of the Atlantic Meridional Overturning Circulation ca. 18-15 kaBP was associated with cold Heinrich stadial-1 and delayed terrestrial warming during the last deglacial warming until ca. 15 kaBP at northern high latitudes, and hence in East Asia. Terrestrial deglacial warming therefore lagged behind marine changes by ca. 3-4 ka.

Effects of carbon turnover time on terrestrial ecosystem carbon storage

NASA Astrophysics Data System (ADS)

Yan, Yaner; Zhou, Xuhui; Jiang, Lifeng; Luo, Yiqi

2017-12-01

Carbon (C) turnover time is a key factor in determining C storage capacity in various plant and soil pools as well as terrestrial C sink in a changing climate. However, the effects of C turnover time on ecosystem C storage have not been well explored. In this study, we compared mean C turnover times (MTTs) of ecosystem and soil, examined their variability to climate, and then quantified the spatial variation in ecosystem C storage over time from changes in C turnover time and/or net primary production (NPP). Our results showed that mean ecosystem MTT based on gross primary production (GPP; MTTEC_GPP = Cpool/GPP, 25.0 ± 2.7 years) was shorter than soil MTT (MTTsoil = Csoil/NPP, 35.5 ± 1.2 years) and NPP-based ecosystem MTT (MTTEC_NPP = Cpool/NPP, 50.8 ± 3 years; Cpool and Csoil referred to ecosystem or soil C storage, respectively). On the biome scale, temperature is the best predictor for MTTEC (R2 = 0.77, p < 0.001) and MTTsoil (R2 = 0.68, p < 0.001), while the inclusion of precipitation in the model did not improve the performance of MTTEC (R2 = 0.76, p < 0.001). Ecosystem MTT decreased by approximately 4 years from 1901 to 2011 when only temperature was considered, resulting in a large C release from terrestrial ecosystems. The resultant terrestrial C release caused by the decrease in MTT only accounted for about 13.5 % of that due to the change in NPP uptake (159.3 ± 1.45 vs. 1215.4 ± 11.0 Pg C). However, the larger uncertainties in the spatial variation of MTT than temporal changes could lead to a greater impact on ecosystem C storage, which deserves further study in the future.

Reducing the uncertainty in the projection of the terrestrial carbon cycle by fusing models with remote sensing data

NASA Astrophysics Data System (ADS)

Serbin, S.; Shiklomanov, A. N.; Viskari, T.; Desai, A. R.; Townsend, P. A.; Dietze, M.

2015-12-01

Modeling global change requires accurate representation of terrestrial carbon (C), energy and water fluxes. In particular, capturing the properties of vegetation canopies that describe the radiation regime are a key focus for global change research because the properties related to radiation utilization and penetration within plant canopies provide an important constraint on terrestrial ecosystem productivity, as well as the fluxes of water and energy from vegetation to the atmosphere. As such, optical remote sensing observations present an important, and as yet relatively untapped, source of observations that can be used to inform modeling activities. In particular, high-spectral resolution optical data at the leaf and canopy scales offers the potential for an important and direct data constraint on the parameterization and structure of the radiative transfer model (RTM) scheme within ecosystem models across diverse vegetation types, disturbance and management histories. In this presentation we highlight ongoing work to integrate optical remote sensing observations, specifically leaf and imaging spectroscopy (IS) data across a range of forest ecosystems, into complex ecosystem process models within an efficient computational assimilation framework as a means to improve the description of canopy optical properties, vegetation composition, and modeled radiation balance. Our work leverages the Predictive Ecosystem Analyzer (PEcAn; http://www.pecanproject.org/) ecoinformatics toolbox together with a RTM module designed for efficient assimilation of leaf and IS observations to inform vegetation optical properties as well as associated plant traits. Ultimately, an improved understanding of the radiation balance of ecosystems will provide a better constraint on model projections of energy balance, vegetation composition, and carbon pools and fluxes thus allowing for a better diagnosis of the vulnerability of terrestrial ecosystems in response to global change.

Asynchronous marine-terrestrial signals of the last deglacial warming in East Asia associated with low- and high-latitude climate changes

PubMed Central

Xu, Deke; Lu, Houyuan; Wu, Naiqin; Liu, Zhenxia; Li, Tiegang; Shen, Caiming; Wang, Luo

2013-01-01

A high-resolution multiproxy record, including pollen, foraminifera, and alkenone paleothermometry, obtained from a single core (DG9603) from the Okinawa Trough, East China Sea (ECS), provided unambiguous evidence for asynchronous climate change between the land and ocean over the past 40 ka. On land, the deglacial stage was characterized by rapid warming, as reflected by paleovegetation, and it began ca. 15 kaBP, consistent with the timing of the last deglacial warming in Greenland. However, sea surface temperature estimates from foraminifera and alkenone paleothermometry increased around 20–19 kaBP, as in the Western Pacific Warm Pool (WPWP). Sea surface temperatures in the Okinawa Trough were influenced mainly by heat transport from the tropical western Pacific Ocean by the Kuroshio Current, but the epicontinental vegetation of the ECS was influenced by atmospheric circulation linked to the northern high-latitude climate. Asynchronous terrestrial and marine signals of the last deglacial warming in East Asia were thus clearly related to ocean currents and atmospheric circulation. We argue that (i) early warming seawater of the WPWP, driven by low-latitude insolation and trade winds, moved northward via the Kuroshio Current and triggered marine warming along the ECS around 20–19 kaBP similar to that in the WPWP, and (ii) an almost complete shutdown of the Atlantic Meridional Overturning Circulation ca. 18–15 kaBP was associated with cold Heinrich stadial-1 and delayed terrestrial warming during the last deglacial warming until ca. 15 kaBP at northern high latitudes, and hence in East Asia. Terrestrial deglacial warming therefore lagged behind marine changes by ca. 3–4 ka. PMID:23720306

Terrestrial N Cycling And C Storage: Some Insights From A Process-based Land Surface Model

NASA Astrophysics Data System (ADS)

Zaehle, S.; Friend, A. D.; Friedlingstein, P.

2008-12-01

We present results of a new land surface model, O-CN, which includes a process-based coupling between the terrestrial cycling of energy, water, carbon, and nitrogen. The model represents the controls of the terrestrial nitrogen (N) cycling on carbon (C) pools and fluxes through photosynthesis, respiration, changes in allocation, and soil organic matter decomposition, and explicitly accounts for N leaching and gaseous losses. O-CN has been shown to give realistic results in comparison to observations at a wide range of scales, including in situ flux measurements, productivity databases, and atmospheric CO2 concentration data. O-CN is run for three free air carbon dioxide enrichment (FACE) sites (Duke, Oak Ridge, Aspen), and reproduces observed magnitudes of changes in net primary productivity, foliage area and foliage N content. Several alternative hypotheses concerning the control of N on vegetation growth and decomposition, including effects of diluting foliage N concentrations, down-regulation of photosynthesis and respiration, acclimation of C allocation patterns and biological N fixation, are tested with respect to their effect on long- term C sequestration estimate. Differences in initial N availability, small transient changes in N inputs and the assumed plasticity of C:N stoichiometry can lead to substantial differences in the simulated long-term changes in productivity and C sequestration. We discuss the capacity of observations obtained at FACE sites to evaluate these alternative hypotheses, and investigate implications of a transient versus instantaneous increase in atmospheric carbon dioxide for the magnitude of the simulated limiting effect of N on C cycling. Finally, we re-examine earlier model-based assessments of the terrestrial C sequestration potential using a global transient O-CN simulation driven by increases in atmospheric CO2, N deposition and climatic changes over the 21st century.

Yearly fluctuation of the spring phytoplankton bloom in south San Francisco Bay - An example of ecological variability at the land-sea interface

USGS Publications Warehouse

Cloern, James E.; Jassby, Alan D.

1995-01-01

Estuaries are transitional ecosystems at the interface of the terrestrial and marine realms. Their unique physiographic position gives rise to large spatial variability, and to dynamic temporal variability resulting, in part, from a variety of forces and fluxes at the oceanic and terrestrial boundaries. River flow, in particular, is an important mechanism for delivering watershed-derived materials such as fresh water, sediments, and nutrients; each of these quantities in turn directly influences the physical structure and biological communities of estuaries. With this setting in mind, we consider here the general proposition that estuarine variability at the yearly time scale can be caused by annual fluctuations in river flow. We use a “long-term” (15-year) time series of phytoplankton biomass variability in South San Francisco Bay (SSFB), a lagoon-type estuary in which phytoplankton primary production is the largest source of organic carbon (Jassby et al. 1993).

The Atmospheres of the Terrestrial Planets:Clues to the Origins and Early Evolution of Venus, Earth, and Mars

NASA Technical Reports Server (NTRS)

Baines, Kevin H.; Atreya, Sushil K.; Bullock, Mark A.; Grinspoon, David H,; Mahaffy, Paul; Russell, Christopher T.; Schubert, Gerald; Zahnle, Kevin

2015-01-01

We review the current state of knowledge of the origin and early evolution of the three largest terrestrial planets - Venus, Earth, and Mars - setting the stage for the chapters on comparative climatological processes to follow. We summarize current models of planetary formation, as revealed by studies of solid materials from Earth and meteorites from Mars. For Venus, we emphasize the known differences and similarities in planetary bulk properties and composition with Earth and Mars, focusing on key properties indicative of planetary formation and early evolution, particularly of the atmospheres of all three planets. We review the need for future in situ measurements for improving our understanding of the origin and evolution of the atmospheres of our planetary neighbors and Earth, and suggest the accuracies required of such new in situ data. Finally, we discuss the role new measurements of Mars and Venus have in understanding the state and evolution of planets found in the habitable zones of other stars.

The database of the PREDICTS (Projecting Responses of Ecological Diversity In Changing Terrestrial Systems) project.

PubMed

Hudson, Lawrence N; Newbold, Tim; Contu, Sara; Hill, Samantha L L; Lysenko, Igor; De Palma, Adriana; Phillips, Helen R P; Alhusseini, Tamera I; Bedford, Felicity E; Bennett, Dominic J; Booth, Hollie; Burton, Victoria J; Chng, Charlotte W T; Choimes, Argyrios; Correia, David L P; Day, Julie; Echeverría-Londoño, Susy; Emerson, Susan R; Gao, Di; Garon, Morgan; Harrison, Michelle L K; Ingram, Daniel J; Jung, Martin; Kemp, Victoria; Kirkpatrick, Lucinda; Martin, Callum D; Pan, Yuan; Pask-Hale, Gwilym D; Pynegar, Edwin L; Robinson, Alexandra N; Sanchez-Ortiz, Katia; Senior, Rebecca A; Simmons, Benno I; White, Hannah J; Zhang, Hanbin; Aben, Job; Abrahamczyk, Stefan; Adum, Gilbert B; Aguilar-Barquero, Virginia; Aizen, Marcelo A; Albertos, Belén; Alcala, E L; Del Mar Alguacil, Maria; Alignier, Audrey; Ancrenaz, Marc; Andersen, Alan N; Arbeláez-Cortés, Enrique; Armbrecht, Inge; Arroyo-Rodríguez, Víctor; Aumann, Tom; Axmacher, Jan C; Azhar, Badrul; Azpiroz, Adrián B; Baeten, Lander; Bakayoko, Adama; Báldi, András; Banks, John E; Baral, Sharad K; Barlow, Jos; Barratt, Barbara I P; Barrico, Lurdes; Bartolommei, Paola; Barton, Diane M; Basset, Yves; Batáry, Péter; Bates, Adam J; Baur, Bruno; Bayne, Erin M; Beja, Pedro; Benedick, Suzan; Berg, Åke; Bernard, Henry; Berry, Nicholas J; Bhatt, Dinesh; Bicknell, Jake E; Bihn, Jochen H; Blake, Robin J; Bobo, Kadiri S; Bóçon, Roberto; Boekhout, Teun; Böhning-Gaese, Katrin; Bonham, Kevin J; Borges, Paulo A V; Borges, Sérgio H; Boutin, Céline; Bouyer, Jérémy; Bragagnolo, Cibele; Brandt, Jodi S; Brearley, Francis Q; Brito, Isabel; Bros, Vicenç; Brunet, Jörg; Buczkowski, Grzegorz; Buddle, Christopher M; Bugter, Rob; Buscardo, Erika; Buse, Jörn; Cabra-García, Jimmy; Cáceres, Nilton C; Cagle, Nicolette L; Calviño-Cancela, María; Cameron, Sydney A; Cancello, Eliana M; Caparrós, Rut; Cardoso, Pedro; Carpenter, Dan; Carrijo, Tiago F; Carvalho, Anelena L; Cassano, Camila R; Castro, Helena; Castro-Luna, Alejandro A; Rolando, Cerda B; Cerezo, Alexis; Chapman, Kim Alan; Chauvat, Matthieu; Christensen, Morten; Clarke, Francis M; Cleary, Daniel F R; Colombo, Giorgio; Connop, Stuart P; Craig, Michael D; Cruz-López, Leopoldo; Cunningham, Saul A; D'Aniello, Biagio; D'Cruze, Neil; da Silva, Pedro Giovâni; Dallimer, Martin; Danquah, Emmanuel; Darvill, Ben; Dauber, Jens; Davis, Adrian L V; Dawson, Jeff; de Sassi, Claudio; de Thoisy, Benoit; Deheuvels, Olivier; Dejean, Alain; Devineau, Jean-Louis; Diekötter, Tim; Dolia, Jignasu V; Domínguez, Erwin; Dominguez-Haydar, Yamileth; Dorn, Silvia; Draper, Isabel; Dreber, Niels; Dumont, Bertrand; Dures, Simon G; Dynesius, Mats; Edenius, Lars; Eggleton, Paul; Eigenbrod, Felix; Elek, Zoltán; Entling, Martin H; Esler, Karen J; de Lima, Ricardo F; Faruk, Aisyah; Farwig, Nina; Fayle, Tom M; Felicioli, Antonio; Felton, Annika M; Fensham, Roderick J; Fernandez, Ignacio C; Ferreira, Catarina C; Ficetola, Gentile F; Fiera, Cristina; Filgueiras, Bruno K C; Fırıncıoğlu, Hüseyin K; Flaspohler, David; Floren, Andreas; Fonte, Steven J; Fournier, Anne; Fowler, Robert E; Franzén, Markus; Fraser, Lauchlan H; Fredriksson, Gabriella M; Freire, Geraldo B; Frizzo, Tiago L M; Fukuda, Daisuke; Furlani, Dario; Gaigher, René; Ganzhorn, Jörg U; García, Karla P; Garcia-R, Juan C; Garden, Jenni G; Garilleti, Ricardo; Ge, Bao-Ming; Gendreau-Berthiaume, Benoit; Gerard, Philippa J; Gheler-Costa, Carla; Gilbert, Benjamin; Giordani, Paolo; Giordano, Simonetta; Golodets, Carly; Gomes, Laurens G L; Gould, Rachelle K; Goulson, Dave; Gove, Aaron D; Granjon, Laurent; Grass, Ingo; Gray, Claudia L; Grogan, James; Gu, Weibin; Guardiola, Moisès; Gunawardene, Nihara R; Gutierrez, Alvaro G; Gutiérrez-Lamus, Doris L; Haarmeyer, Daniela H; Hanley, Mick E; Hanson, Thor; Hashim, Nor R; Hassan, Shombe N; Hatfield, Richard G; Hawes, Joseph E; Hayward, Matt W; Hébert, Christian; Helden, Alvin J; Henden, John-André; Henschel, Philipp; Hernández, Lionel; Herrera, James P; Herrmann, Farina; Herzog, Felix; Higuera-Diaz, Diego; Hilje, Branko; Höfer, Hubert; Hoffmann, Anke; Horgan, Finbarr G; Hornung, Elisabeth; Horváth, Roland; Hylander, Kristoffer; Isaacs-Cubides, Paola; Ishida, Hiroaki; Ishitani, Masahiro; Jacobs, Carmen T; Jaramillo, Víctor J; Jauker, Birgit; Hernández, F Jiménez; Johnson, McKenzie F; Jolli, Virat; Jonsell, Mats; Juliani, S Nur; Jung, Thomas S; Kapoor, Vena; Kappes, Heike; Kati, Vassiliki; Katovai, Eric; Kellner, Klaus; Kessler, Michael; Kirby, Kathryn R; Kittle, Andrew M; Knight, Mairi E; Knop, Eva; Kohler, Florian; Koivula, Matti; Kolb, Annette; Kone, Mouhamadou; Kőrösi, Ádám; Krauss, Jochen; Kumar, Ajith; Kumar, Raman; Kurz, David J; Kutt, Alex S; Lachat, Thibault; Lantschner, Victoria; Lara, Francisco; Lasky, Jesse R; Latta, Steven C; Laurance, William F; Lavelle, Patrick; Le Féon, Violette; LeBuhn, Gretchen; Légaré, Jean-Philippe; Lehouck, Valérie; Lencinas, María V; Lentini, Pia E; Letcher, Susan G; Li, Qi; Litchwark, Simon A; Littlewood, Nick A; Liu, Yunhui; Lo-Man-Hung, Nancy; López-Quintero, Carlos A; Louhaichi, Mounir; Lövei, Gabor L; Lucas-Borja, Manuel Esteban; Luja, Victor H; Luskin, Matthew S; MacSwiney G, M Cristina; Maeto, Kaoru; Magura, Tibor; Mallari, Neil Aldrin; Malone, Louise A; Malonza, Patrick K; Malumbres-Olarte, Jagoba; Mandujano, Salvador; Måren, Inger E; Marin-Spiotta, Erika; Marsh, Charles J; Marshall, E J P; Martínez, Eliana; Martínez Pastur, Guillermo; Moreno Mateos, David; Mayfield, Margaret M; Mazimpaka, Vicente; McCarthy, Jennifer L; McCarthy, Kyle P; McFrederick, Quinn S; McNamara, Sean; Medina, Nagore G; Medina, Rafael; Mena, Jose L; Mico, Estefania; Mikusinski, Grzegorz; Milder, Jeffrey C; Miller, James R; Miranda-Esquivel, Daniel R; Moir, Melinda L; Morales, Carolina L; Muchane, Mary N; Muchane, Muchai; Mudri-Stojnic, Sonja; Munira, A Nur; Muoñz-Alonso, Antonio; Munyekenye, B F; Naidoo, Robin; Naithani, A; Nakagawa, Michiko; Nakamura, Akihiro; Nakashima, Yoshihiro; Naoe, Shoji; Nates-Parra, Guiomar; Navarrete Gutierrez, Dario A; Navarro-Iriarte, Luis; Ndang'ang'a, Paul K; Neuschulz, Eike L; Ngai, Jacqueline T; Nicolas, Violaine; Nilsson, Sven G; Noreika, Norbertas; Norfolk, Olivia; Noriega, Jorge Ari; Norton, David A; Nöske, Nicole M; Nowakowski, A Justin; Numa, Catherine; O'Dea, Niall; O'Farrell, Patrick J; Oduro, William; Oertli, Sabine; Ofori-Boateng, Caleb; Oke, Christopher Omamoke; Oostra, Vicencio; Osgathorpe, Lynne M; Otavo, Samuel Eduardo; Page, Navendu V; Paritsis, Juan; Parra-H, Alejandro; Parry, Luke; Pe'er, Guy; Pearman, Peter B; Pelegrin, Nicolás; Pélissier, Raphaël; Peres, Carlos A; Peri, Pablo L; Persson, Anna S; Petanidou, Theodora; Peters, Marcell K; Pethiyagoda, Rohan S; Phalan, Ben; Philips, T Keith; Pillsbury, Finn C; Pincheira-Ulbrich, Jimmy; Pineda, Eduardo; Pino, Joan; Pizarro-Araya, Jaime; Plumptre, A J; Poggio, Santiago L; Politi, Natalia; Pons, Pere; Poveda, Katja; Power, Eileen F; Presley, Steven J; Proença, Vânia; Quaranta, Marino; Quintero, Carolina; Rader, Romina; Ramesh, B R; Ramirez-Pinilla, Martha P; Ranganathan, Jai; Rasmussen, Claus; Redpath-Downing, Nicola A; Reid, J Leighton; Reis, Yana T; Rey Benayas, José M; Rey-Velasco, Juan Carlos; Reynolds, Chevonne; Ribeiro, Danilo Bandini; Richards, Miriam H; Richardson, Barbara A; Richardson, Michael J; Ríos, Rodrigo Macip; Robinson, Richard; Robles, Carolina A; Römbke, Jörg; Romero-Duque, Luz Piedad; Rös, Matthias; Rosselli, Loreta; Rossiter, Stephen J; Roth, Dana S; Roulston, T'ai H; Rousseau, Laurent; Rubio, André V; Ruel, Jean-Claude; Sadler, Jonathan P; Sáfián, Szabolcs; Saldaña-Vázquez, Romeo A; Sam, Katerina; Samnegård, Ulrika; Santana, Joana; Santos, Xavier; Savage, Jade; Schellhorn, Nancy A; Schilthuizen, Menno; Schmiedel, Ute; Schmitt, Christine B; Schon, Nicole L; Schüepp, Christof; Schumann, Katharina; Schweiger, Oliver; Scott, Dawn M; Scott, Kenneth A; Sedlock, Jodi L; Seefeldt, Steven S; Shahabuddin, Ghazala; Shannon, Graeme; Sheil, Douglas; Sheldon, Frederick H; Shochat, Eyal; Siebert, Stefan J; Silva, Fernando A B; Simonetti, Javier A; Slade, Eleanor M; Smith, Jo; Smith-Pardo, Allan H; Sodhi, Navjot S; Somarriba, Eduardo J; Sosa, Ramón A; Soto Quiroga, Grimaldo; St-Laurent, Martin-Hugues; Starzomski, Brian M; Stefanescu, Constanti; Steffan-Dewenter, Ingolf; Stouffer, Philip C; Stout, Jane C; Strauch, Ayron M; Struebig, Matthew J; Su, Zhimin; Suarez-Rubio, Marcela; Sugiura, Shinji; Summerville, Keith S; Sung, Yik-Hei; Sutrisno, Hari; Svenning, Jens-Christian; Teder, Tiit; Threlfall, Caragh G; Tiitsaar, Anu; Todd, Jacqui H; Tonietto, Rebecca K; Torre, Ignasi; Tóthmérész, Béla; Tscharntke, Teja; Turner, Edgar C; Tylianakis, Jason M; Uehara-Prado, Marcio; Urbina-Cardona, Nicolas; Vallan, Denis; Vanbergen, Adam J; Vasconcelos, Heraldo L; Vassilev, Kiril; Verboven, Hans A F; Verdasca, Maria João; Verdú, José R; Vergara, Carlos H; Vergara, Pablo M; Verhulst, Jort; Virgilio, Massimiliano; Vu, Lien Van; Waite, Edward M; Walker, Tony R; Wang, Hua-Feng; Wang, Yanping; Watling, James I; Weller, Britta; Wells, Konstans; Westphal, Catrin; Wiafe, Edward D; Williams, Christopher D; Willig, Michael R; Woinarski, John C Z; Wolf, Jan H D; Wolters, Volkmar; Woodcock, Ben A; Wu, Jihua; Wunderle, Joseph M; Yamaura, Yuichi; Yoshikura, Satoko; Yu, Douglas W; Zaitsev, Andrey S; Zeidler, Juliane; Zou, Fasheng; Collen, Ben; Ewers, Rob M; Mace, Georgina M; Purves, Drew W; Scharlemann, Jörn P W; Purvis, Andy

2017-01-01

The PREDICTS project-Projecting Responses of Ecological Diversity In Changing Terrestrial Systems (www.predicts.org.uk)-has collated from published studies a large, reasonably representative database of comparable samples of biodiversity from multiple sites that differ in the nature or intensity of human impacts relating to land use. We have used this evidence base to develop global and regional statistical models of how local biodiversity responds to these measures. We describe and make freely available this 2016 release of the database, containing more than 3.2 million records sampled at over 26,000 locations and representing over 47,000 species. We outline how the database can help in answering a range of questions in ecology and conservation biology. To our knowledge, this is the largest and most geographically and taxonomically representative database of spatial comparisons of biodiversity that has been collated to date; it will be useful to researchers and international efforts wishing to model and understand the global status of biodiversity.

Nitrogen isotope and trace metal analyses from the Mingolsheim core (Germany): Evidence for redox variations across the Triassic-Jurassic boundary

NASA Astrophysics Data System (ADS)

Quan, Tracy M.; van de Schootbrugge, Bas; Field, M. Paul; Rosenthal, Yair; Falkowski, Paul G.

2008-06-01

The Triassic-Jurassic (T-J) boundary was one of the largest but least understood mass extinction events in the Phanerozoic. We measured bulk organic nitrogen and carbon isotopes and trace metal concentrations from a core near Mingolsheim (Germany) to infer paleoenvironmental conditions associated with this event. Poorly fossiliferous claystones across the boundary have relatively low δ15N values and low concentrations of redox-sensitive elements, characteristic of an oxic environment with significant terrestrial input. The Early Jurassic features enrichment in δ15N coincident with high redox-sensitive element concentrations, indicating an increase in water column denitrification and decreased oxygen concentrations. These redox state variations are concordant with shifts in abundance and species composition in terrestrial and marine microflora. We propose that the mass extinction at the T-J boundary was caused by a series of events resulting in a long period of stratification, deep-water hypoxia, and denitrification in this region of the Tethys Ocean basin.

Synchronous turnover of flora, fauna, and climate at the Eocene-Oligocene Boundary in Asia

NASA Astrophysics Data System (ADS)

Sun, Jimin; Ni, Xijun; Bi, Shundong; Wu, Wenyu; Ye, Jie; Meng, Jin; Windley, Brian F.

2014-12-01

The Eocene-Oligocene Boundary (~34 million years ago) marks one of the largest extinctions of marine invertebrates in the world oceans and of mammalian fauna in Europe and Asia in the Cenozoic era. A shift to a cooler climate across this boundary has been suggested as the cause of this extinction in the marine environment, but there is no manifold evidence for a synchronous turnover of flora, fauna and climate at the Eocene-Oligocene Boundary in a single terrestrial site in Asia to support this hypothesis. Here we report new data of magnetostratigraphy, pollen and climatic proxies in the Asian interior across the Eocene-Oligocene Boundary; our results show that climate change forced a turnover of flora and fauna, suggesting there was a change from large-size perissodactyl-dominant fauna in forests under a warm-temperate climate to small rodent/lagomorph-dominant fauna in forest-steppe in a dry-temperate climate across the Eocene-Oligocene Boundary. These data provide a new terrestrial record for this significant Cenozoic environmental event.

Synchronous turnover of flora, fauna, and climate at the Eocene-Oligocene Boundary in Asia.

PubMed

Sun, Jimin; Ni, Xijun; Bi, Shundong; Wu, Wenyu; Ye, Jie; Meng, Jin; Windley, Brian F

2014-12-12

The Eocene-Oligocene Boundary (~34 million years ago) marks one of the largest extinctions of marine invertebrates in the world oceans and of mammalian fauna in Europe and Asia in the Cenozoic era. A shift to a cooler climate across this boundary has been suggested as the cause of this extinction in the marine environment, but there is no manifold evidence for a synchronous turnover of flora, fauna and climate at the Eocene-Oligocene Boundary in a single terrestrial site in Asia to support this hypothesis. Here we report new data of magnetostratigraphy, pollen and climatic proxies in the Asian interior across the Eocene-Oligocene Boundary; our results show that climate change forced a turnover of flora and fauna, suggesting there was a change from large-size perissodactyl-dominant fauna in forests under a warm-temperate climate to small rodent/lagomorph-dominant fauna in forest-steppe in a dry-temperate climate across the Eocene-Oligocene Boundary. These data provide a new terrestrial record for this significant Cenozoic environmental event.

A large and persistent carbon sink in the world's forests

USGS Publications Warehouse

Pan, Y.; Birdsey, R.A.; Fang, J.; Houghton, R.; Kauppi, P.E.; Kurz, W.A.; Phillips, O.L.; Shvidenko, A.; Lewis, S.L.; Canadell, J.G.; Ciais, P.; Jackson, R.B.; Pacala, S.W.; McGuire, A.D.; Piao, S.; Rautiainen, A.; Sitch, S.; Hayes, D.

2011-01-01

The terrestrial carbon sink has been large in recent decades, but its size and location remain uncertain. Using forest inventory data and long-term ecosystem carbon studies, we estimate a total forest sink of 2.4 ?? 0.4 petagrams of carbon per year (Pg C year-1) globally for 1990 to 2007. We also estimate a source of 1.3 ?? 0.7 Pg C year-1 from tropical land-use change, consisting of a gross tropical deforestation emission of 2.9 ?? 0.5 Pg C year-1 partially compensated by a carbon sink in tropical forest regrowth of 1.6 ?? 0.5 Pg C year-1. Together, the fluxes comprise a net global forest sink of 1.1 ?? 0.8 Pg C year-1, with tropical estimates having the largest uncertainties. Our total forest sink estimate is equivalent in magnitude to the terrestrial sink deduced from fossil fuel emissions and land-use change sources minus ocean and atmospheric sinks.

Seasonal Changes of DOC Composition of Rivers in Temperate Monsoon Climates

NASA Astrophysics Data System (ADS)

Oh, N. H.; Shin, Y.; Lee, E. J.; Hur, J.

2014-12-01

The spatial and seasonal dynamics of dissolved organic carbon (DOC) composition and biodegradability were investigated for the five largest rivers in the Republic of Korea during the years 2012 - 2013 using dark incubation experiments and spectroscopic measurements, including parallel factor analysis (PARAFAC). The DOC concentrations of the rivers in relatively steep and forest-dominated basins were <~2 mg L-1, and remained relatively constant over the seasons. In contrast, those of the rivers influenced by urban and agricultural activities rose up to 5.4 mg L-1, which was decreased to ~2 mg L-1 during the summer monsoon period, indicating that increased precipitation had the effect of dilution. Among the fluorescence components, terrestrial humic-like components were dominant in all the rivers except for one, where tyrosine- or tryptophan-like compounds were the major component. However, terrestrial humic-like components became dominant in all five of the rivers after high precipitation which occurred during the monsoon season, during which ~76% of the annual precipitation was received. Considering that 64% of South Korea is forested, our results suggest that the forests could be a large source of riverine DOC, elevating the DOC loads during monsoon rainfall. Although more DOC could be degraded when DOC input increased, regardless of its sources, the percent biodegradability was reduced with increased proportions of terrestrially derived and aromatic compounds. These results suggest that the relatively stable and terrestrial humic-like compounds released during the monsoon rainfall could reduce the potential of microbial respiration of riverine DOC and evasion of river CO2 to the atmosphere, despite of the increase in the DOC load.

Untangling above- and belowground mycorrhizal fungal networks in tropical orchids.

PubMed

Leake, J R; Cameron, D D

2012-10-01

Orchids typically depend on fungi for establishment from seeds, forming mycorrhizal associations with basidiomycete fungal partners in the polyphyletic group rhizoctonia from early stages of germination, sometimes with very high specificity. This has raised important questions about the roles of plant and fungal phylogenetics, and their habitat preferences, in controlling which fungi associate with which plants. In this issue of Molecular Ecology, Martos et al. (2012) report the largest network analysis to date for orchids and their mycorrhizal fungi, sampling a total of over 450 plants from nearly half the 150 tropical orchid species on Reunion Island, encompassing its main terrestrial and epiphytic orchid genera. The authors found a total of 95 operational taxonomic units of mycorrhizal fungi and investigated the architecture and nestedness of their bipartite networks with 73 orchid species. The most striking finding was a major ecological barrier between above- and belowground mycorrhizal fungal networks, despite both epiphytic and terrestrial orchids often associating with closely related taxa across all three major lineages of rhizoctonia fungi. The fungal partnerships of the epiphytes and terrestrial species involved a diversity of fungal taxa in a modular network architecture, with only about one in ten mycorrhizal fungi partnering orchids in both groups. In contrast, plant and fungal phylogenetics had weak or no effects on the network. This highlights the power of recently developed ecological network analyses to give new insights into controls on plant-fungal symbioses and raises exciting new hypotheses about the differences in properties and functioning of mycorrhiza in epiphytic and terrestrial orchids. © 2012 Blackwell Publishing Ltd.

ORCHILEAK (revision 3875): a new model branch to simulate carbon transfers along the terrestrial-aquatic continuum of the Amazon basin

NASA Astrophysics Data System (ADS)

Lauerwald, Ronny; Regnier, Pierre; Camino-Serrano, Marta; Guenet, Bertrand; Guimberteau, Matthieu; Ducharne, Agnès; Polcher, Jan; Ciais, Philippe

2017-10-01

Lateral transfer of carbon (C) from terrestrial ecosystems into the inland water network is an important component of the global C cycle, which sustains a large aquatic CO2 evasion flux fuelled by the decomposition of allochthonous C inputs. Globally, estimates of the total C exports through the terrestrial-aquatic interface range from 1.5 to 2.7 Pg C yr-1 (Cole et al., 2007; Battin et al., 2009; Tranvik et al., 2009), i.e. of the order of 2-5 % of the terrestrial NPP. Earth system models (ESMs) of the climate system ignore these lateral transfers of C, and thus likely overestimate the terrestrial C sink. In this study, we present the implementation of fluvial transport of dissolved organic carbon (DOC) and CO2 into ORCHIDEE (Organising Carbon and Hydrology in Dynamic Ecosystems), the land surface scheme of the Institut Pierre-Simon Laplace ESM. This new model branch, called ORCHILEAK, represents DOC production from canopy and soils, DOC and CO2 leaching from soils to streams, DOC decomposition, and CO2 evasion to the atmosphere during its lateral transport in rivers, as well as exchange with the soil carbon and litter stocks on floodplains and in swamps. We parameterized and validated ORCHILEAK for the Amazon basin, the world's largest river system with regard to discharge and one of the most productive ecosystems in the world. With ORCHILEAK, we are able to reproduce observed terrestrial and aquatic fluxes of DOC and CO2 in the Amazon basin, both in terms of mean values and seasonality. In addition, we are able to resolve the spatio-temporal variability in C fluxes along the canopy-soil-water continuum at high resolution (1°, daily) and to quantify the different terrestrial contributions to the aquatic C fluxes. We simulate that more than two-thirds of the Amazon's fluvial DOC export are contributed by the decomposition of submerged litter. Throughfall DOC fluxes from canopy to ground are about as high as the total DOC inputs to inland waters. The latter, however, are mainly sustained by litter decomposition. Decomposition of DOC and submerged plant litter contributes slightly more than half of the CO2 evasion from the water surface, while the remainder is contributed by soil respiration. Total CO2 evasion from the water surface equals about 5 % of the terrestrial NPP. Our results highlight that ORCHILEAK is well suited to simulate carbon transfers along the terrestrial-aquatic continuum of tropical forests. It also opens the perspective that provided parameterization, calibration and validation is performed for other biomes, the new model branch could improve the quantification of the global terrestrial C sink and help better constrain carbon cycle-climate feedbacks in future projections.

Terrestrial ecosystem process model Biome-BGCMuSo v4.0: summary of improvements and new modeling possibilities

NASA Astrophysics Data System (ADS)

Hidy, Dóra; Barcza, Zoltán; Marjanović, Hrvoje; Zorana Ostrogović Sever, Maša; Dobor, Laura; Gelybó, Györgyi; Fodor, Nándor; Pintér, Krisztina; Churkina, Galina; Running, Steven; Thornton, Peter; Bellocchi, Gianni; Haszpra, László; Horváth, Ferenc; Suyker, Andrew; Nagy, Zoltán

2016-12-01

The process-based biogeochemical model Biome-BGC was enhanced to improve its ability to simulate carbon, nitrogen, and water cycles of various terrestrial ecosystems under contrasting management activities. Biome-BGC version 4.1.1 was used as a base model. Improvements included addition of new modules such as the multilayer soil module, implementation of processes related to soil moisture and nitrogen balance, soil-moisture-related plant senescence, and phenological development. Vegetation management modules with annually varying options were also implemented to simulate management practices of grasslands (mowing, grazing), croplands (ploughing, fertilizer application, planting, harvesting), and forests (thinning). New carbon and nitrogen pools have been defined to simulate yield and soft stem development of herbaceous ecosystems. The model version containing all developments is referred to as Biome-BGCMuSo (Biome-BGC with multilayer soil module; in this paper, Biome-BGCMuSo v4.0 is documented). Case studies on a managed forest, cropland, and grassland are presented to demonstrate the effect of model developments on the simulation of plant growth as well as on carbon and water balance.

Methodology for astronaut reconditioning research.

PubMed

Beard, David J; Cook, Jonathan A

2017-01-01

Space medicine offers some unique challenges, especially in terms of research methodology. A specific challenge for astronaut reconditioning involves identification of what aspects of terrestrial research methodology hold and which require modification. This paper reviews this area and presents appropriate solutions where possible. It is concluded that spaceflight rehabilitation research should remain question/problem driven and is broadly similar to the terrestrial equivalent on small populations, such as rare diseases and various sports. Astronauts and Medical Operations personnel should be involved at all levels to ensure feasibility of research protocols. There is room for creative and hybrid methodology but careful systematic observation is likely to be more achievable and fruitful than complex trial based comparisons. Multi-space agency collaboration will be critical to pool data from small groups of astronauts with the accepted use of standardised outcome measures across all agencies. Systematic reviews will be an essential component. Most limitations relate to the inherent small sample size available for human spaceflight research. Early adoption of a co-operative model for spaceflight rehabilitation research is therefore advised. Copyright © 2016 Elsevier Ltd. All rights reserved.

Preliminary design of an advanced Stirling system for terrestrial solar energy conversion

NASA Astrophysics Data System (ADS)

White, M. A.; Noble, J. E.; Emigh, S. G.; Ross, B. A.; Lehmann, G. A.

A preliminary design was generated for an advanced Stirling conversion system (ASCS) that will be capable of delivering about 25 kW of electric power to an electric utility grid. Stirling engines are being evaluated for terrestrial solar applications. A two-year task to complete detailed design, fabrication, assembly and testing of an ASCS prototype began in April, 1990. The ASCS is designed to deliver maximum power per year over a range of solar inputs with a design life of 30 years (60,000 h). The ACSC has a long-term cost goal of about $450 per kilowatt, exclusive of the 11-m parabolic dish concentrator. The proposed system includes a Stirling engine with high-pressure hydraulic output, coupled with a bent axis variable displacement hydraulic motor and a rotary induction generator. The major thrusts of the preliminary design are described, including material selection for the hot-end components, heat transport system (reflux pool boiler) design, system thermal response, improved manufacturability, FMECA/FTA analysis, updated manufacturing cost estimate, and predicted system performance.

Preliminary design of an advanced Stirling system for terrestrial solar energy conversion

NASA Technical Reports Server (NTRS)

White, M. A.; Noble, J. E.; Emigh, S. G.; Ross, B. A.; Lehmann, G. A.

1990-01-01

A preliminary design was generated for an advanced Stirling conversion system (ASCS) that will be capable of delivering about 25 kW of electric power to an electric utility grid. Stirling engines are being evaluated for terrestrial solar applications. A two-year task to complete detailed design, fabrication, assembly and testing of an ASCS prototype began in April, 1990. The ASCS is designed to deliver maximum power per year over a range of solar inputs with a design life of 30 years (60,000 h). The ACSC has a long-term cost goal of about $450 per kilowatt, exclusive of the 11-m parabolic dish concentrator. The proposed system includes a Stirling engine with high-pressure hydraulic output, coupled with a bent axis variable displacement hydraulic motor and a rotary induction generator. The major thrusts of the preliminary design are described, including material selection for the hot-end components, heat transport system (reflux pool boiler) design, system thermal response, improved manufacturability, FMECA/FTA analysis, updated manufacturing cost estimate, and predicted system performance.

Partitioning nitrogen losses by natural abundance nitrogen isotope composition in a process-based statistical modelling framework

NASA Astrophysics Data System (ADS)

Dong, Ning; Wright, Ian; Prentice, Iain Colin

2017-04-01

Natural abundance of the stable isotope 15N is an under-utilized resource for research on the global terrestrial nitrogen cycle. Mass balance considerations suggest that if reactive N inputs have a roughly constant isotopic signature, soil δ15N should be mainly determined by the fraction of N losses by leaching - which barely discriminates against 15N - versus gaseous N losses, which discriminate strongly against 15N. We defined simple process-oriented functions of runoff (frunoff) and soil temperature (ftemp) and investigated the dependencies of soil and foliage δ15N (from global compilations of both types of measurement) on their ratio. Both plant and soil δ15N were found to systematically increase with ftemp/frunoff. Consistent with previous analyses, foliage δ15N was offset (more negative) with respect to soil δ15N, with significant differences in this offset between (from largest to smallest offset) ericoid, ectomycorrhizal, arbuscular mycorrhizal and non-mycorrhizal associated plants. δ15N values tend to be large and positive in the driest environments and to decline as frunoff increases, while also being lower in cold environments and increasing as ftemp increases. The fitted statistical model was used to estimate the gaseous fraction of total N losses from ecosystems (fgas) on a global grid basis. In common with earlier results, the largest values of fgas are predicted in the tropics and semi-arid subtropics. This analysis provides an indirectly estimated global mapping of fgas, which could be used as an improved benchmark for terrestrial nitrogen cycle models.

Strontium source and depth of uptake shifts with substrate age in semiarid ecosystems

NASA Astrophysics Data System (ADS)

Coble, Ashley A.; Hart, Stephen C.; Ketterer, Michael E.; Newman, Gregory S.; Kowler, Andrew L.

2015-06-01

Without exogenous rock-derived nutrient sources, terrestrial ecosystems may eventually regress or reach a terminal steady state, but the degree to which exogenous nutrient sources buffer or slow to a theoretical terminal steady state remains unclear. We used strontium isotope ratios (87Sr/86Sr) as a tracer and measured 87Sr/86Sr values in aeolian dust, soils, and vegetation across a well-constrained 3 Myr semiarid substrate age gradient to determine (1) whether the contribution of atmospheric sources of rock-derived nutrients to soil and vegetation pools varied with substrate age and (2) to determine if the depth of uptake varied with substrate age. We found that aeolian-derived nutrients became increasingly important, contributing as much as 71% to plant-available soil pools and tree (Pinus edulis) growth during the latter stages of ecosystem development in a semiarid climate. The depth of nutrient uptake increased on older substrates, demonstrating that trees in arid regions can acquire nutrients from greater depths as ecosystem development progresses presumably in response to nutrient depletion in the more weathered surface soils. Our results demonstrate that global and regional aeolian transport of nutrients to local ecosystems is a vital process for ecosystem development in arid regions. Furthermore, these aeolian nutrient inputs contribute to deep soil nutrient pools, which become increasingly important for maintaining plant productivity over long time scales.

Fish and Wildlife Habitat Changes Resulting from Construction of a Nine-Foot Channel on Pools 24, 25, and 26 of the Mississippi River and the Lower Illinois River,

DTIC Science & Technology

1979-04-01

adjustment) by subtracting the conversion factor of 7.345. Terrestrial Coumunities Wetland Plants Aquatic and moist soil plant acreages were obtained...hft U tumd b mm as as "off usls oso$ Fd.- a fl mm .to 16011 md rumo Ut mo eve -1 to the amen leawso way. ase speasee topsuita of no. man ineuS to P.1...productive marsh areas, but has recreated mud flats available for moist soil food production. The acres of mud flats nov exceed the number present

Salt marsh-mangrove ecotones: using structural gradients to investigate the effects of woody plant encroachment on plant-soil interactions and ecosystem carbon pools

USGS Publications Warehouse

Yando, Erik S.; Osland, Michael J.; Willis, Jonathan M; Day, Richard H.; Krauss, Ken W.; Hester, Mark W.

2016-01-01

Synthesis: Our results indicate that the ecological implications of woody plant encroachment in tidal saline wetlands are dependent upon precipitation controls of plant–soil interactions. Although the above-ground effects of mangrove expansion are consistently large, below-ground influences of mangrove expansion appear to be greatest along low-rainfall coasts where salinities are high and marshes being replaced are carbon poor and dominated by succulent plants. Collectively, these findings complement those from terrestrial ecosystems and reinforce the importance of considering rainfall and plant–soil interactions within predictions of the ecological effects of woody plant encroachment.

Homoacetogenesis in Deep-Sea Chloroflexi, as Inferred by Single-Cell Genomics, Provides a Link to Reductive Dehalogenation in Terrestrial Dehalococcoidetes.

PubMed

Sewell, Holly L; Kaster, Anne-Kristin; Spormann, Alfred M

2017-12-19

The deep marine subsurface is one of the largest unexplored biospheres on Earth and is widely inhabited by members of the phylum Chloroflexi In this report, we investigated genomes of single cells obtained from deep-sea sediments of the Peruvian Margin, which are enriched in such Chloroflexi 16S rRNA gene sequence analysis placed two of these single-cell-derived genomes (DscP3 and Dsc4) in a clade of subphylum I Chloroflexi which were previously recovered from deep-sea sediment in the Okinawa Trough and a third (DscP2-2) as a member of the previously reported DscP2 population from Peruvian Margin site 1230. The presence of genes encoding enzymes of a complete Wood-Ljungdahl pathway, glycolysis/gluconeogenesis, a Rhodobacter nitrogen fixation (Rnf) complex, glyosyltransferases, and formate dehydrogenases in the single-cell genomes of DscP3 and Dsc4 and the presence of an NADH-dependent reduced ferredoxin:NADP oxidoreductase (Nfn) and Rnf in the genome of DscP2-2 imply a homoacetogenic lifestyle of these abundant marine Chloroflexi We also report here the first complete pathway for anaerobic benzoate oxidation to acetyl coenzyme A (CoA) in the phylum Chloroflexi (DscP3 and Dsc4), including a class I benzoyl-CoA reductase. Of remarkable evolutionary significance, we discovered a gene encoding a formate dehydrogenase (FdnI) with reciprocal closest identity to the formate dehydrogenase-like protein (complex iron-sulfur molybdoenzyme [CISM], DET0187) of terrestrial Dehalococcoides/Dehalogenimonas spp. This formate dehydrogenase-like protein has been shown to lack formate dehydrogenase activity in Dehalococcoides/Dehalogenimonas spp. and is instead hypothesized to couple HupL hydrogenase to a reductive dehalogenase in the catabolic reductive dehalogenation pathway. This finding of a close functional homologue provides an important missing link for understanding the origin and the metabolic core of terrestrial Dehalococcoides/Dehalogenimonas spp. and of reductive dehalogenation, as well as the biology of abundant deep-sea Chloroflexi IMPORTANCE The deep marine subsurface is one of the largest unexplored biospheres on Earth and is widely inhabited by members of the phylum Chloroflexi In this report, we investigated genomes of single cells obtained from deep-sea sediments and provide evidence for a homacetogenic lifestyle of these abundant marine Chloroflexi Moreover, genome signature and key metabolic genes indicate an evolutionary relationship between these deep-sea sediment microbes and terrestrial, reductively dehalogenating Dehalococcoides . Copyright © 2017 Sewell et al.

Geologic map of the Artemis Chasma quadrangle (V-48), Venus

USGS Publications Warehouse

Bannister, Roger A.; Hansen, Vicki L.

2010-01-01

Artemis, named for the Greek goddess of the hunt, represents an approximately 2,600 km diameter circular feature on Venus, and it may represent the largest circular structure in our solar system. Artemis, which lies between the rugged highlands of Aphrodite Terra to the north and relatively smooth lowlands to the south, includes an interior topographic high surrounded by the 2,100-km-diameter, 25- to 200-km-wide, 1- to 2-km-deep circular trough, called Artemis Chasma, and an outer rise that grades outward into the surrounding lowland. Although several other chasmata exist in the area and globally, other chasmata have generally linear trends that lack the distinctive circular pattern of Artemis Chasma. The enigmatic nature of Artemis has perplexed researchers since Artemis Chasma was first identified in Pioneer Venus data. Although Venus' surface abounds with circular to quasi-circular features at a variety of scales, including from smallest to largest diameter features: small shield edifices (>1 km), large volcanic edifices (100-1,000 km), impact craters (1-270 km), coronae (60-1,010 km), volcanic rises and crustal plateaus (~1,500-2,500 km), Artemis defies classification into any of these groups. Artemis dwarfs Venus' largest impact crater, Mead (~280 km diameter); Artemis also lacks the basin topography, multiple ring structures, and central peak expected for large impact basins. Topographically, Artemis resembles some Venusian coronae; however Artemis is an order of magnitude larger than the average corona (200 km) and about twice the size of Heng-O Corona (which is 1,010 km in diameter), the largest of Venusian coronae. In map view Artemis' size and shape resemble volcanic rises and crustal plateaus; however, both of these classes of features differ topographically from Artemis. Volcanic rises and crustal plateaus form broad domical regions, and steep-sided regions with flat tops, respectively; furthermore, neither rises nor plateaus include circular troughs. So although it seems clear what Artemis is not, there is little consensus about what Artemis is, much less how Artemis formed. Debate during the past decade has resulted in the proposal of at least four hypotheses for Artemis' formation. The first (herein referred to as H1) is that Artemis Chasma represents a zone of northwest-directed convergence and subduction. The second hypothesis (herein referred to as H2) is that Artemis consists of a composite structure with a part of its interior region marking the exposure of deformed ductile deep-crustal rocks analogous to a terrestrial metamorphic core complex. The third (herein referred to as H3) is that Artemis reflects the surface expression of an ancient (>3.5 Ga) huge bolide impact event on cold strong lithosphere. The fourth hypothesis (herein referred to as H4) is that Artemis marks the surface expression of a deep mantle plume. Each of these hypotheses holds different implications for Venus geodynamics and evolution processes, and for terrestrial planet processes in general. Viability of H1 would provide support that terrestrial-like plate-tectonic processes once occurred on Earth's sister planet. The feasibility of H2 would require high values of crustal extension and therefore imply that significant horizontal displacements occurred on Venus-displacement that may or may not be related to terrestrial-like plate-tectonic processes. The possibility of H3 would suggest that Venus' surface is extremely old, and that Venus has experienced very little dynamic activity for the last 3.5 billion years or more; this would further imply that Venus is essentially tectonically dead, and has been for most of its history. This view contrasts strongly with studies that highlight a rich history of Venus including activity at least as young as 750 million years ago, and quite likely up to the present. If H4 has credibility, then Artemis could provide clues to cooling mechanisms of Earth's sister planet. Each of these hypotheses

Influence of intermittent stream connectivity on water quality and salmonid survivorship.

NASA Astrophysics Data System (ADS)

Hildebrand, J.; Woelfle-Erskine, C. A.; Larsen, L.

2014-12-01

Anthropogenic stress and climate change are causing an increasing number of California streams to become intermittent and are driving earlier and more severe summertime drying. The extent to which emerging water conservation alternatives impact flows or habitat quality (e.g. temperature, DO) for salmonids remains poorly understood. Here, we investigate the proximal drivers of salmonid mortality over a range of connectivity conditions during summertime intermittency in Salmon Creek watershed, Sonoma County, CA. Through extensive sampling in paired subwatersheds over a period of two years, we tested the hypothesis that accumulation of readily bioavailable DOC in poorly flushed pools drives DO decline associated with loss of salmonids. We then traced the origin and flow pathways of DOC throughout the watershed using Parallel Factor Analysis (PARAFAC). We obtained samples for DOC and stable isotope analyses at monthly intervals from 20 piezometers and surface water in the study reaches and from private wells and springs distributed throughout the watersheds. We also obtained in situ DO, conductivity and pH readings within stream study reaches. We determined DOC quality by SUVA (specific UV absorbance) and fluorescence index. We calculated stream metabolism rates using the single station method. In pools instrumented with DO sensors, we compared changing DOC quality during the summer months to changes in DO concentrations and stream metabolism. Our results show that the duration of complete disconnection of pools during the summer months and stream metabolic rates are positively correlated with salmonid mortality. Furthermore, our results indicate that salmonid mortality is greatest in disconnected pools with low DOC fluorescence indices and high SUVA values, indicative of terrestrially derived DOC and little or no groundwater inflow. Conversely low salmonid mortality was found in disconnected pools with high fluorescence index and low SUVA, indicative of microbially derived DOC. These pools showed clear signs of hyporheic inflow during summertime drying despite complete surficial disconnection. PARAFAC analysis pinpointed groundwater sources of hyporheic flow in the watershed, suggesting that targeted aquifer recharge may contribute to salmonid recovery by augmenting flow in summer refugia.

Denitrification across landscapes and waterscapes: A synthesis

USGS Publications Warehouse

Seitzinger, S.; Harrison, J.A.; Böhlke, J.K.; Bouwman, A.F.; Lowrance, R.; Peterson, B.; Tobias, C.; Van Drecht, G.

2006-01-01

Denitrification is a critical process regulating the removal of bioavailable nitrogen (N) from natural and human-altered systems. While it has been extensively studied in terrestrial, freshwater, and marine systems, there has been limited communication among denitrification scientists working in these individual systems. Here, we compare rates of denitrification and controlling factors across a range of ecosystem types. We suggest that terrestrial, freshwater, and marine systems in which denitrification occurs can be organized along a continuum ranging from (1) those in which nitrification and denitrification are tightly coupled in space and time to (2) those in which nitrate production and denitrification are relatively decoupled.In aquatic ecosystems, N inputs influence denitrification rates whereas hydrology and geomorphology influence the proportion of N inputs that are denitrified. Relationships between denitrification and water residence time and N load are remarkably similar across lakes, river reaches, estuaries, and continental shelves.Spatially distributed global models of denitrification suggest that continental shelf sediments account for the largest portion (44%) of total global denitrification, followed by terrestrial soils (22%) and oceanic oxygen minimum zones (OMZs; 14%). Freshwater systems (groundwater, lakes, rivers) account for about 20% and estuaries 1% of total global denitrification. Denitrification of land-based N sources is distributed somewhat differently. Within watersheds, the amount of land-based N denitrified is generally highest in terrestrial soils, with progressively smaller amounts denitrified in groundwater, rivers, lakes and reservoirs, and estuaries. A number of regional exceptions to this general trend of decreasing denitrification in a downstream direction exist, including significant denitrification in continental shelves of N from terrestrial sources. Though terrestrial soils and groundwater are responsible for much denitrification at the watershed scale, per-area denitrification rates in soils and groundwater (kg N·km−2·yr−1) are, on average, approximately one-tenth the per-area rates of denitrification in lakes, rivers, estuaries, continental shelves, or OMZs. A number of potential approaches to increase denitrification on the landscape, and thus decrease N export to sensitive coastal systems exist. However, these have not generally been widely tested for their effectiveness at scales required to significantly reduce N export at the whole watershed scale.

Thermal Impact of Gas Flares on the Biological Activity of Soils

NASA Astrophysics Data System (ADS)

Yevdokimov, I. V.; Yusupov, I. A.; Larionova, A. A.; Bykhovets, S. S.; Glagolev, M. V.; Shavnin, S. A.

2017-12-01

Global warming can lead to a significant transformation of the structure of terrestrial ecosystems and changes in the mode of functioning of their components. In this connection, studies of soil respiration, particularly of the biological activity of soils under forest exposed to warm impact of flaring flare are of scientific and practical interests. A long-term experimental plot was established in a lichen pine forest on the Albic Podzols (Arenic) (Khanty-Mansi Autonomous Area-Yugra). Sampling and measurements were carried out in the areas at the distances of 70, 90, and 130 m from the flare with the strong, moderate, and weak heating effects, respectively. In the zone of the maximum heating effect, the soil temperature was by 1.3°C higher, and the rate of CO2 emission from the surface in situ was greater by 18% compared to the zone with weak impact of the flare. Along with increasing CO2 emissions, organic matter accumulated due to increasing the stable pool. The parameters of the microbial biomass, basal respiration, and the input of labile organic matter pool increased with the distance from the flare.

Frequency of progression from acute to chronic pancreatitis and risk factors: a meta-analysis.

PubMed

Sankaran, Sharanya J; Xiao, Amy Y; Wu, Landy M; Windsor, John A; Forsmark, Christopher E; Petrov, Maxim S

2015-11-01

Acute pancreatitis (AP) and chronic pancreatitis (CP) traditionally have been thought to be distinct diseases, but there is evidence that AP can progress to CP. Little is known about the mechanisms of pancreatitis progression. We performed a meta-analysis to quantify the frequency of transition of AP to CP and identify risk factors for progression. We searched PubMed, Scopus, and Embase for studies of patients with AP who developed CP, published from 1966 through November 2014. Pooled prevalence and 95% confidence intervals (CIs) were calculated for these outcomes, and sensitivity, subgroup, and meta-regression analyses were conducted. We analyzed 14 studies, which included a total of 8492 patients. The pooled prevalence of recurrent AP was 22% (95% CI, 18%-26%), and the pooled prevalence of CP was 10% (95% CI, 6%-15%). Sensitivity analyses yielded a pooled prevalence of CP of 10% (95% CI, 4%-19%) and 36% (95% CI, 20%-53%) in patients after the first occurrence and recurrent AP, respectively. Subgroup analyses found alcohol use and smoking to be the largest risk factors for the development of CP, with pooled prevalence values of 65% (95% CI, 48%-56%) and 61% (95% CI, 47%-73%), respectively. Meta-regression analysis found that men were more likely than women to transition from AP to CP. Ten percent of patients with a first episode of AP and 36% of patients with recurrent AP develop CP; the risk is higher among smokers, alcoholics, and men. Prospective clinical studies are needed to study pancreatitis progression. Copyright © 2015 AGA Institute. Published by Elsevier Inc. All rights reserved.

Multigene assessment of the species boundaries and sexual status of the basidiomycetous yeasts Cryptococcus flavescens and C. terrestris (Tremellales).

PubMed

Yurkov, Andrey; Guerreiro, Marco A; Sharma, Lav; Carvalho, Cláudia; Fonseca, Álvaro

2015-01-01

Cryptococcus flavescens and C. terrestris are phenotypically indistinguishable sister species that belong to the order Tremellales (Tremellomycetes, Basidiomycota) and which may be mistaken for C. laurentii based on phenotype. Phylogenetic separation between C. flavescens and C. terrestris was based on rDNA sequence analyses, but very little is known on their intraspecific genetic variability or propensity for sexual reproduction. We studied 59 strains from different substrates and geographic locations, and used a multilocus sequencing (MLS) approach complemented with the sequencing of mating type (MAT) genes to assess genetic variation and reexamine the boundaries of the two species, as well as their sexual status. The following five loci were chosen for MLS: the rDNA ITS-LSU region, the rDNA IGS1 spacer, and fragments of the genes encoding the largest subunit of RNA polymerase II (RPB1), the translation elongation factor 1 alpha (TEF1) and the p21-activated protein kinase (STE20). Phylogenetic network analyses confirmed the genetic separation of the two species and revealed two additional cryptic species, for which the names Cryptococcus baii and C. ruineniae are proposed. Further analyses of the data revealed a high degree of genetic heterogeneity within C. flavescens as well as evidence for recombination between lineages detected for this species. Strains of C. terrestris displayed higher levels of similarity in all analysed genes and appear to make up a single recombining group. The two MAT genes (STE3 and SXI1/SXI2) sequenced for C. flavescens strains confirmed the potential for sexual reproduction and suggest the presence of a tetrapolar mating system with a biallelic pheromone/receptor locus and a multiallelic HD locus. In C. terrestris we could only sequence STE3, which revealed a biallelic P/R locus. In spite of the strong evidence for sexual recombination in the two species, attempts at mating compatible strains of both species on culture media were unsuccessful.

Composition and transformation of dissolved organic matter in the Baltic Sea

NASA Astrophysics Data System (ADS)

Seidel, Michael; Manecki, Marcus; Herlemann, Daniel P. R.; Deutsch, Barbara; Schulz-Bull, Detlef; Jürgens, Klaus; Dittmar, Thorsten

2017-05-01

The processing of terrestrial dissolved organic matter (DOM) in coastal shelf seas is an important part of the global carbon cycle, yet, it is still not well understood. One of the largest brackish shelf seas, the Baltic Sea in northern Europe, is characterized by high freshwater input from sub-arctic rivers and limited water exchange with the Atlantic Ocean via the North Sea. We studied the molecular and isotopic composition and turnover of solid-phase extractable (SPE) DOM and its transformation along the salinity and redox continuum of the Baltic Sea during spring and autumn. We applied ultrahigh-resolution mass spectrometry and other geochemical and biological approaches. Our data demonstrate a large influx of terrestrial riverine DOM, especially into the northern part of the Baltic Sea. The DOM composition in the central Baltic Sea changed seasonally and was mainly related to autochthonous production by phytoplankton in spring. Especially in the northern, river-dominated basins, a major fraction of riverine DOM was removed, likely by bio- and photo-degradation. We estimate that the removal rate of terrestrial DOM in the Baltic Sea (Bothnian Bay to the Danish Straits/Kattegat area) is 1.6 - 1.9 Tg C per year which is 43 to 51% of the total riverine input. The export of terrestrial DOM from the Danish Straits/Kattegat area towards the North Sea is 1.8 - 2.1 Tg C per year. Due to the long residence time of terrestrial DOM in the Baltic Sea (total of ca. 12 years), seasonal variations caused by bio- and photo-transformations and riverine discharge are dampened, resulting in a relatively invariant DOM molecular and isotopic signature exported to the North Sea. In the deep stagnant basins of the Baltic Sea, the DOM composition and dissolved organic nitrogen concentrations changed seasonally, likely because of vertical particle transport and subsequent degradation releasing DOM. DOM in the deep anoxic basins was also enriched in sulfur-containing organic molecules, pointing to abiotic sulfurization of DOM under sulfidic conditions.

Statistical Analysis of Terrestrial Water Storage Change Over Southwestern United States

NASA Astrophysics Data System (ADS)

Eibedingil, I. G.; Mubako, S. T.; Hargrove, W. L.; Espino, A. C.

2017-12-01

A warming trend over recent decades has aggravated water resource challenges in the arid southwestern region of the United States (U.S.). An increase in temperature, coupled with decreasing snowpack and rainfall have impacted the region's cities, ecosystems, and agriculture. The region is the largest contributor of agricultural products to the U.S. market resulting from irrigation. Water use through irrigation is stressing already limited terrestrial water resources. Population growth in recent decades has also led to increased water demand. This study utilizes products of the Gravity Recovery and Climate Experiment (GRACE) twin satellites experiment in MATLAB and ArcGIS to examine terrestrial water storage changes in the southwestern region of the U.S., comprised of the eight states of Texas, California, Nevada, Utah, Arizona, Colorado, New Mexico, and Oklahoma. Linear trend analysis was applied to the equivalent water-height data of terrestrial water storage changes (TWSC), precipitation, and air temperature. Correlation analysis was performed on couplings of TWSC - precipitation and TWSC - air temperature to examine the impact of temperature and precipitation on the region's water resources. Our preliminary results show a decreasing trend of TWSC from April 2002 to July 2016 in almost all parts of the region. Precipitation shows a decreasing trend from March 2000 to March 2017 for most of the region, except for sparse areas of increased precipitation near the northwestern coast of California, and a belt running from Oklahoma through the middle of Texas to the El Paso/New Mexico border. From April 2002 to December 2014, air temperature exhibited a negative trend for most of the region, except a larger part of California and a small location in central Texas. Correlation between TWSC and precipitation was mostly positive, but a negative trend was observed when TWSC and air temperature were correlated. The study contributes to the understanding of terrestrial water storage trends and their relationship with climatic variables, crucial for implementing appropriate adaptation and mitigation policies and strategies, and managing water demand.

A case study on the historical peninsula of Istanbul based on three-dimensional modeling by using photogrammetry and terrestrial laser scanning.

PubMed

Ergun, Bahadir; Sahin, Cumhur; Baz, Ibrahim; Ustuntas, Taner

2010-06-01

Terrestrial laser scanning is a popular methodology that is used frequently in the process of documenting historical buildings and cultural heritage. The historical peninsula region sprawls over an area of approximately 1,500 ha and is one of the main aggregate areas of the historical buildings in Istanbul. In this study, terrestrial laser scanning and close range photogrammetry techniques are integrated into each other to create a 3D city model of this part of Istanbul, including some of the buildings that represent the most brilliant areas of Byzantine and Ottoman Empires. Several terrestrial laser scanners with their different specifications were used to solve various geometric scanning problems for distinct areas of the subject city. Photogrammetric method was used for the documentation of the façades of these historical buildings for architectural purposes. This study differentiates itself from the similar ones by its application process that focuses on the geometry, the building texture, and density of the study area. Nowadays, the largest-scale studies among 3D modeling studies, in terms of the methodology of measurement, are urban modeling studies. Because of this large scale, the application of 3D urban modeling studies is executed in a gradual way. In this study, a modeling method based on the façades of the streets was used. In addition, the complimentary elements for the process of modeling were combined in several ways. A street model was presented as a sample, as being the subject of the applied study. In our application of 3D modeling, the modeling based on close range photogrammetry and the data of combined calibration with the data of terrestrial laser scanner were used in a compatible way. The final work was formed with the pedestal data for 3D visualization.

Multigene Assessment of the Species Boundaries and Sexual Status of the Basidiomycetous Yeasts Cryptococcus flavescens and C. terrestris (Tremellales)

PubMed Central

Sharma, Lav; Carvalho, Cláudia; Fonseca, Álvaro

2015-01-01

Cryptococcus flavescens and C. terrestris are phenotypically indistinguishable sister species that belong to the order Tremellales (Tremellomycetes, Basidiomycota) and which may be mistaken for C. laurentii based on phenotype. Phylogenetic separation between C. flavescens and C. terrestris was based on rDNA sequence analyses, but very little is known on their intraspecific genetic variability or propensity for sexual reproduction. We studied 59 strains from different substrates and geographic locations, and used a multilocus sequencing (MLS) approach complemented with the sequencing of mating type (MAT) genes to assess genetic variation and reexamine the boundaries of the two species, as well as their sexual status. The following five loci were chosen for MLS: the rDNA ITS-LSU region, the rDNA IGS1 spacer, and fragments of the genes encoding the largest subunit of RNA polymerase II (RPB1), the translation elongation factor 1 alpha (TEF1) and the p21-activated protein kinase (STE20). Phylogenetic network analyses confirmed the genetic separation of the two species and revealed two additional cryptic species, for which the names Cryptococcus baii and C. ruineniae are proposed. Further analyses of the data revealed a high degree of genetic heterogeneity within C. flavescens as well as evidence for recombination between lineages detected for this species. Strains of C. terrestris displayed higher levels of similarity in all analysed genes and appear to make up a single recombining group. The two MAT genes (STE3 and SXI1/SXI2) sequenced for C. flavescens strains confirmed the potential for sexual reproduction and suggest the presence of a tetrapolar mating system with a biallelic pheromone/receptor locus and a multiallelic HD locus. In C. terrestris we could only sequence STE3, which revealed a biallelic P/R locus. In spite of the strong evidence for sexual recombination in the two species, attempts at mating compatible strains of both species on culture media were unsuccessful. PMID:25811603

Reading comprehension and its underlying components in second-language learners: A meta-analysis of studies comparing first- and second-language learners.

PubMed

Melby-Lervåg, Monica; Lervåg, Arne

2014-03-01

We report a systematic meta-analytic review of studies comparing reading comprehension and its underlying components (language comprehension, decoding, and phonological awareness) in first- and second-language learners. The review included 82 studies, and 576 effect sizes were calculated for reading comprehension and underlying components. Key findings were that, compared to first-language learners, second-language learners display a medium-sized deficit in reading comprehension (pooled effect size d = -0.62), a large deficit in language comprehension (pooled effect size d = -1.12), but only small differences in phonological awareness (pooled effect size d = -0.08) and decoding (pooled effect size d = -0.12). A moderator analysis showed that characteristics related to the type of reading comprehension test reliably explained the variation in the differences in reading comprehension between first- and second-language learners. For language comprehension, studies of samples from low socioeconomic backgrounds and samples where only the first language was used at home generated the largest group differences in favor of first-language learners. Test characteristics and study origin reliably contributed to the variations between the studies of language comprehension. For decoding, Canadian studies showed group differences in favor of second-language learners, whereas the opposite was the case for U.S. studies. Regarding implications, unless specific decoding problems are detected, interventions that aim to ameliorate reading comprehension problems among second-language learners should focus on language comprehension skills.

Pooled versus separate tree-ring δD measurements, and implications for reconstruction of the Arctic Oscillation in northwestern China.

PubMed

Liu, Xiaohong; An, Wenling; Treydte, Kerstin; Wang, Wenzhi; Xu, Guobao; Zeng, Xiaomin; Wu, Guoju; Wang, Bo; Zhang, Xuanwen

2015-04-01

Stable hydrogen isotope ratios (δD) in tree rings are an attractive but still rarely explored terrestrial archive of past climatic information. Because the preparation of the cellulose nitrate for δD measurements requires more wood and a longer preparation time than preparation techniques for other isotopes in cellulose (δ18O or δ13C), it is challenging to obtain high-resolution records, especially for slow-growing trees at high elevations and in boreal regions. Here, we tested whether annually pooled samples of Qinghai spruce (Picea crassifolia Kom.) trees from northwestern China provided results similar to those derived as the mean of individual measurements of the same trees and whether the resulting chronologies recorded useful climate information. Inter-tree variability of δD was higher than that of measured ring width for the same trees. We found higher and significant coherence between pooled and mean isotope chronologies than that among the individual series. It showed a logarithmic relationship between ring mass and δD; however, accounting for the influence of ring mass on δD values only slightly improved the strength of climatic signals in the pooled records. Tree-ring δD was significantly positively correlated with the mean, maximum, and minimum temperatures during the previous winter and with maximum temperature during the current August, and significantly negatively correlated with precipitation in the previous November to January and the current July. The winter climate signal seems to dominate tree-ring δD through the influence of large-scale atmospheric circulation patterns, i.e. the Arctic Oscillation. These results will facilitate reconstruction of winter atmospheric circulation patterns over northwestern China based on a regional tree-ring δD networks. Copyright © 2015 Elsevier B.V. All rights reserved.

Experimental Investigation of Pool Boiling Heat Transfer Enhancement in Microgravity in the Presence of Electric Fields

NASA Technical Reports Server (NTRS)

Herman, Cila

1996-01-01

Boiling is an effective mode of heat transfer since high heat flux levels are possible driven by relatively small temperature differences. The high heat transfer coefficients associated with boiling have made the use of these processes increasingly attractive to aerospace engineering. Applications of this type include compact evaporators in the thermal control of aircraft avionics and spacecraft environments, heat pipes, and use of boiling to cool electronic equipment. In spite of its efficiency, cooling based on liquid-vapor phase change processes has not yet found wide application in aerospace engineering due to specific problems associated with the low gravity environment. After a heated surface has reached the superheat required for the initiation of nucleate boiling, bubbles will start forming at nucleation sites along the solid interface by evaporation of the liquid. Bubbles in contact with the wall will continue growing by this mechanism until they detach. In terrestrial conditions, bubble detachment is determined by the competition between body forces (e.g. buoyancy) and surface tension forces that act to anchor the bubble along the three phase contact line. For a given body force potential and a balance of tensions along the three phase contact line, bubbles must reach a critical size before the body force can cause them to detach from the wall. In a low gravity environment the critical bubble size for detachment is much larger than under terrestrial conditions, since buoyancy is a less effective means of bubble removal. Active techniques of heat transfer enhancement in single phase and phase change processes by utilizing electric fields have been the subject of intensive research during recent years. The field of electrohydrodynamics (EHD) deals with the interactions between electric fields, flow fields and temperature fields. Previous studies indicate that in terrestrial applications nucleate boiling heat transfer can be increased by a factor of 50 as compared to values obtained for the same system without electric fields. Imposing an external electric field holds the promise to improve pool boiling heat transfer in low gravity, since a phase separation force other than gravity is introduced. The goal of our research is to experimentally investigate the potential of EHD and the mechanisms responsible for EHD heat transfer enhancement in boiling in low gravity conditions.

A gigantic new dinosaur from Argentina and the evolution of the sauropod hind foot.

PubMed

González Riga, Bernardo J; Lamanna, Matthew C; Ortiz David, Leonardo D; Calvo, Jorge O; Coria, Juan P

2016-01-18

Titanosauria is an exceptionally diverse, globally-distributed clade of sauropod dinosaurs that includes the largest known land animals. Knowledge of titanosaurian pedal structure is critical to understanding the stance and locomotion of these enormous herbivores and, by extension, gigantic terrestrial vertebrates as a whole. However, completely preserved pedes are extremely rare among Titanosauria, especially as regards the truly giant members of the group. Here we describe Notocolossus gonzalezparejasi gen. et sp. nov. from the Upper Cretaceous of Mendoza Province, Argentina. With a powerfully-constructed humerus 1.76 m in length, Notocolossus is one of the largest known dinosaurs. Furthermore, the complete pes of the new taxon exhibits a strikingly compact, homogeneous metatarsus--seemingly adapted for bearing extraordinary weight--and truncated unguals, morphologies that are otherwise unknown in Sauropoda. The pes underwent a near-progressive reduction in the number of phalanges along the line to derived titanosaurs, eventually resulting in the reduced hind foot of these sauropods.

A gigantic new dinosaur from Argentina and the evolution of the sauropod hind foot

PubMed Central

González Riga, Bernardo J.; Lamanna, Matthew C.; Ortiz David, Leonardo D.; Calvo, Jorge O.; Coria, Juan P.

2016-01-01

Titanosauria is an exceptionally diverse, globally-distributed clade of sauropod dinosaurs that includes the largest known land animals. Knowledge of titanosaurian pedal structure is critical to understanding the stance and locomotion of these enormous herbivores and, by extension, gigantic terrestrial vertebrates as a whole. However, completely preserved pedes are extremely rare among Titanosauria, especially as regards the truly giant members of the group. Here we describe Notocolossus gonzalezparejasi gen. et sp. nov. from the Upper Cretaceous of Mendoza Province, Argentina. With a powerfully-constructed humerus 1.76 m in length, Notocolossus is one of the largest known dinosaurs. Furthermore, the complete pes of the new taxon exhibits a strikingly compact, homogeneous metatarsus—seemingly adapted for bearing extraordinary weight—and truncated unguals, morphologies that are otherwise unknown in Sauropoda. The pes underwent a near-progressive reduction in the number of phalanges along the line to derived titanosaurs, eventually resulting in the reduced hind foot of these sauropods. PMID:26777391

A lost generation of impact structures: Imaging the Arctic and Antarctic in magnetics and gravity

NASA Astrophysics Data System (ADS)

Purucker, M. E.

2017-12-01

The process of convection that drives plate tectonics has fragmented the early record on the continents, and subducted it in the oceans. Erosion blurs the upper surfaces of impact structures exposed to the atmosphere beyond recognition after a few million years. The largest confirmed impact structures on the Earth are Vredefort, Chicxulub, and Sudbury, with crater diameters averaging 150 km, and maximum ages of about 2 Ga. Contrast this with the situation at Mars or the Moon, where the largest confirmed impact structures have diameters of 2000 km, and ages of 4 Ga. The giant impact basins that form the most ancient, and most prominent, visible structures on the other terrestrial planets and moons have vanished on the Earth. Only with the use of techniques like magnetics and gravity is it possible to see deeper within the crust. We identify possible impact structure(s) in the Arctic and Antarctic in this way, and discuss techniques that can be used to confirm or refute these identifications.

Fugitives from the Hungaria region: Close encounters and impacts with terrestrial planets

NASA Astrophysics Data System (ADS)

Galiazzo, M. A.; Bazsó, Á.; Dvorak, R.

2013-08-01

Hungaria asteroids, whose orbits occupy the region in element space between 1.78

Higher-than-predicted saltation threshold wind speeds on Titan.

PubMed

Burr, Devon M; Bridges, Nathan T; Marshall, John R; Smith, James K; White, Bruce R; Emery, Joshua P

2015-01-01

Titan, the largest satellite of Saturn, exhibits extensive aeolian, that is, wind-formed, dunes, features previously identified exclusively on Earth, Mars and Venus. Wind tunnel data collected under ambient and planetary-analogue conditions inform our models of aeolian processes on the terrestrial planets. However, the accuracy of these widely used formulations in predicting the threshold wind speeds required to move sand by saltation, or by short bounces, has not been tested under conditions relevant for non-terrestrial planets. Here we derive saltation threshold wind speeds under the thick-atmosphere, low-gravity and low-sediment-density conditions on Titan, using a high-pressure wind tunnel refurbished to simulate the appropriate kinematic viscosity for the near-surface atmosphere of Titan. The experimentally derived saltation threshold wind speeds are higher than those predicted by models based on terrestrial-analogue experiments, indicating the limitations of these models for such extreme conditions. The models can be reconciled with the experimental results by inclusion of the extremely low ratio of particle density to fluid density on Titan. Whereas the density ratio term enables accurate modelling of aeolian entrainment in thick atmospheres, such as those inferred for some extrasolar planets, our results also indicate that for environments with high density ratios, such as in jets on icy satellites or in tenuous atmospheres or exospheres, the correction for low-density-ratio conditions is not required.

Autumn photoproduction of carbon monoxide in Jiaozhou Bay, China

NASA Astrophysics Data System (ADS)

Ren, Chunyan; Yang, Guipeng; Lu, Xiaolan

2014-06-01

Carbon monoxide (CO) plays a significant role in global warming and atmospheric chemistry. Global oceans are net natural sources of atmospheric CO. CO at surface ocean is primarily produced from the photochemical degradation of chromophoric dissolved organic matter (CDOM). In this study, the effects of photobleaching, temperature and the origin (terrestrial or marine) of CDOM on the apparent quantum yields (AQY) of CO were studied for seawater samples collected from Jiaozhou Bay. Our results demonstrat that photobleaching, temperature and the origin of CDOM strongly affected the efficiency of CO photoproduction. The concentration, absorbance and fluorescence of CDOM exponentially decreased with increasing light dose. Terrestrial riverine organic matter could be more prone to photodegradation than the marine algae-derived one. The relationships between CO AQY and the dissolved organic carbon-specific absorption coefficient at 254 nm for the photobleaching study were nonlinear, whereas those of the original samples were strongly linear. This suggests that: 1) terrestrial riverine CDOM was more efficient than marine algae-derived CDOM for CO photoproduction; 2) aromatic and olefinic moieties of the CDOM pool were affected more strongly by degradation processes than by aliphatic ones. Water temperature and the origin of CDOM strongly affected the efficiency of CO photoproduction. The photoproduction rate of CO in autumn was estimated to be 31.98 μmol m-2 d-1 and the total DOC photomineralization was equivalent to 3.25%-6.35% of primary production in Jiaozhou Bay. Our results indicate that CO photochemistry in coastal areas is important for oceanic carbon cycle.

15N/14N variations in Cretaceous Atlantic sedimentary sequences: implication for past changes in marine nitrogen biogeochemistry

USGS Publications Warehouse

Rau, G.H.; Arthur, M.A.; Dean, W.E.

1987-01-01

At two locations in the Atlantic Ocean (DSDP Sites 367 and 530) early to middle Cretaceous organic-carbon-rich beds ("black shales") were found to have significantly lower ??15N values (lower 15N/14N ratios) than adjacent organic-carbon-poor beds (white limestones or green claystones). While these lithologies are of marine origin, the black strata in particular have ??15N values that are significantly lower than those previously found in the marine sediment record and most contemporary marine nitrogen pools. In contrast, black, organic-carbon-rich beds at a third site (DSDP Site 603) contain predominantly terrestrial organic matter and have C- and N-isotopic compositions similar to organic matter of modern terrestrial origin. The recurring 15N depletion in the marine-derived Cretaceous sequences prove that the nitrogen they contain is the end result of an episodic and atypical biogeochemistry. Existing isotopic and other data indicate that the low 15N relative abundance is the consequence of pelagic rather than post-depositional processes. Reduced ocean circulation, increased denitrification, and, hence, reduced euphotic zone nitrate availability may have led to Cretaceous phytoplankton assemblages that were periodically dominated by N2-fixing blue-green algae, a possible source of this sediment 15N-depletion. Lack of parallel isotopic shifts in Cretaceous terrestrially-derived nitrogen (Site 603) argues that the above change in nitrogen cycling during this period did not extend beyond the marine environment. ?? 1987.

The Atmospheric Supply of Terrestrial Authigenic Phosphate Minerals to Open Marine Sediments

NASA Astrophysics Data System (ADS)

Flaum, J. A.; Jacobson, A. D.; Sageman, B. B.

2007-12-01

Authigenic P-bearing minerals (Pauth), such as carbonate fluorapatite, form within shallow marine sediments as biological processes degrade organic matter and release associated phosphate to the dissolved pool during early diagenesis. Thus, Pauth is commonly used as a proxy for productivity in modern and ancient marine depositional environments. To help refine this proxy and further improve understanding of the marine P cycle, we investigated if dust deposition could supply terrestrially derived Pauth and other P-bearing phases to modern marine sediments. We used the SEDEX sequential extraction procedure to quantify the occurrence of P in ten samples of loess from the Chinese Loess Plateau, a major source of dust to the North Pacific Ocean (NPO). On average, 40% of the total P within Chinese Loess occurs as Pauth, 33% as detrital apatite (Pdet), 17% in organic matter (Porg), and 10% bound to Fe-Al oxides (Pox). Using eolian dust and total P accumulation rates reported for core LL44-GC3 taken from the central NPO, we find that ~86% of the total P accumulation within the central NPO could originate from the atmospheric deposition of Pauth and Pdet. Hence, productivity estimates based upon total P accumulation for this site are likely lower than previously estimated. Our findings suggest that marine productivity studies predicated on the measurement of Pauth need to quantify the fraction of Pauth supplied from terrestrial sources. This may be even more significant along continental margins where rivers can supply sediments with high concentrations of Pauth minerals.

Transient simulations of historical climate change including interactive carbon emissions from land-use change.

NASA Astrophysics Data System (ADS)

Matveev, A.; Matthews, H. D.

2009-04-01

Carbon fluxes from land conversion are among the most uncertain variables in our understanding of the contemporary carbon cycle, which limits our ability to estimate both the total human contribution to current climate forcing and the net effect of terrestrial biosphere changes on atmospheric CO2 increases. The current generation of coupled climate-carbon models have made significant progress in simulating the coupled climate and carbon cycle response to anthropogenic CO2 emissions, but do not typically include land-use change as a dynamic component of the simulation. In this work we have incorporated a book-keeping land-use carbon accounting model into the University of Victoria Earth System Climate Model (UVic ESCM), and intermediate-complexity coupled climate-carbon model. The terrestrial component of the UVic ESCM allows an aerial competition of five plant functional types (PFTs) in response to climatic conditions and area availability, and tracks the associated changes in affected carbon pools. In order to model CO2 emissions from land conversion in the terrestrial component of the model, we calculate the allocation of carbon to short and long-lived wood products following specified land-cover change, and use varying decay timescales to estimate CO2 emissions. We use recently available spatial datasets of both crop and pasture distributions to drive a series of transient simulations and estimate the net contribution of human land-use change to historical carbon emissions and climate change.

Interactions among roots, mycorrhizas and free-living microbial communities differentially impact soil carbon processes

DOE PAGES

Moore, Jessica A. M.; Jiang, Jiang; Patterson, Courtney M.; ...

2015-10-20

Plant roots, their associated microbial community and free-living soil microbes interact to regulate the movement of carbon from the soil to the atmosphere, one of the most important and least understood fluxes of terrestrial carbon. Our inadequate understanding of how plant-microbial interactions alter soil carbon decomposition may lead to poor model predictions of terrestrial carbon feedbacks to the atmosphere. Roots, mycorrhizal fungi and free-living soil microbes can alter soil carbon decomposition through exudation of carbon into soil. Exudates of simple carbon compounds can increase microbial activity because microbes are typically carbon limited. When both roots and mycorrhizal fungi are presentmore » in the soil, they may additively increase carbon decomposition. However, when mycorrhizas are isolated from roots, they may limit soil carbon decomposition by competing with free-living decomposers for resources. We manipulated the access of roots and mycorrhizal fungi to soil insitu in a temperate mixed deciduous forest. We added 13C-labelled substrate to trace metabolized carbon in respiration and measured carbon-degrading microbial extracellular enzyme activity and soil carbon pools. We used our data in a mechanistic soil carbon decomposition model to simulate and compare the effects of root and mycorrhizal fungal presence on soil carbon dynamics over longer time periods. Contrary to what we predicted, root and mycorrhizal biomass did not interact to additively increase microbial activity and soil carbon degradation. The metabolism of 13C-labelled starch was highest when root biomass was high and mycorrhizal biomass was low. These results suggest that mycorrhizas may negatively interact with the free-living microbial community to influence soil carbon dynamics, a hypothesis supported by our enzyme results. Our steady-state model simulations suggested that root presence increased mineral-associated and particulate organic carbon pools, while mycorrhizal fungal presence had a greater influence on particulate than mineral-associated organic carbon pools.Synthesis. Our results suggest that the activity of enzymes involved in organic matter decomposition was contingent upon root-mycorrhizal-microbial interactions. Using our experimental data in a decomposition simulation model, we show that root-mycorrhizal-microbial interactions may have longer-term legacy effects on soil carbon sequestration. Lastly, our study suggests that roots stimulate microbial activity in the short term, but contribute to soil carbon storage over longer periods of time.« less

Interactions among roots, mycorrhizas and free-living microbial communities differentially impact soil carbon processes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moore, Jessica A. M.; Jiang, Jiang; Patterson, Courtney M.

Plant roots, their associated microbial community and free-living soil microbes interact to regulate the movement of carbon from the soil to the atmosphere, one of the most important and least understood fluxes of terrestrial carbon. Our inadequate understanding of how plant-microbial interactions alter soil carbon decomposition may lead to poor model predictions of terrestrial carbon feedbacks to the atmosphere. Roots, mycorrhizal fungi and free-living soil microbes can alter soil carbon decomposition through exudation of carbon into soil. Exudates of simple carbon compounds can increase microbial activity because microbes are typically carbon limited. When both roots and mycorrhizal fungi are presentmore » in the soil, they may additively increase carbon decomposition. However, when mycorrhizas are isolated from roots, they may limit soil carbon decomposition by competing with free-living decomposers for resources. We manipulated the access of roots and mycorrhizal fungi to soil insitu in a temperate mixed deciduous forest. We added 13C-labelled substrate to trace metabolized carbon in respiration and measured carbon-degrading microbial extracellular enzyme activity and soil carbon pools. We used our data in a mechanistic soil carbon decomposition model to simulate and compare the effects of root and mycorrhizal fungal presence on soil carbon dynamics over longer time periods. Contrary to what we predicted, root and mycorrhizal biomass did not interact to additively increase microbial activity and soil carbon degradation. The metabolism of 13C-labelled starch was highest when root biomass was high and mycorrhizal biomass was low. These results suggest that mycorrhizas may negatively interact with the free-living microbial community to influence soil carbon dynamics, a hypothesis supported by our enzyme results. Our steady-state model simulations suggested that root presence increased mineral-associated and particulate organic carbon pools, while mycorrhizal fungal presence had a greater influence on particulate than mineral-associated organic carbon pools.Synthesis. Our results suggest that the activity of enzymes involved in organic matter decomposition was contingent upon root-mycorrhizal-microbial interactions. Using our experimental data in a decomposition simulation model, we show that root-mycorrhizal-microbial interactions may have longer-term legacy effects on soil carbon sequestration. Lastly, our study suggests that roots stimulate microbial activity in the short term, but contribute to soil carbon storage over longer periods of time.« less

Apparatus for Cold, Pressurized Biogeochemical Experiments

NASA Technical Reports Server (NTRS)

Amashukeli, Xenia; Pappalardo, Robert T.; Connon, Stephanie A.; Gleeson, Damhnait F.

2010-01-01

A laboratory apparatus has been devised as a means of studying plausible biogeochemical reactions under high-pressure, low-temperature aqueous, anaerobic conditions like those conjectured to prevail in a liquid water ocean on Europa (the fourth largest moon of the planet Jupiter). The experiments to be performed by use of this apparatus are intended to enhance understanding of how life (if any) could originate and evolve in the Europa ocean environment. Inasmuch as terrestrial barophilic, psychrophilic organisms that thrive under anaerobic conditions are used in the experiments, the experiments may also contribute to terrestrial biogeochemistry. The apparatus (see figure) includes a bolt-closure reaction vessel secured inside a refrigerator that maintains a temperature of 4 C. Pressurized water is supplied to the interior of the vessel by a hydrostatic pump, which is attached to the vessel via high-pressure fittings. The terrestrial organisms used in the experiments thus far have been several facultative barophilic, psychrophilic stains of Shewanella bacteria. In the experiments, these organisms have been tested for reduction of ferric ion by growing them in the presence of a ferric food source under optimized terrestrial conditions. The short-term goal of these experiments has been to select Shewanella strains that exhibit iron-reduction capability and test their ability to facilitate biogeochemical reduction of iron under temperature and pressure conditions imitating those in Europa s ocean. It is anticipated, that, once growth under Europa-like conditions has been achieved, the selected Shewanella strains will be used to facilitate biogeochemical reactions of sulfate and carbonate with hydrogen gas. Any disequilibrium of the products with the environment would be interpreted as signifying biogenic activity and the possibility of life in Europa s ocean.

Impacts of the Central Atlantic Magmatic Province on the Terrestrial Carbon Cycle in Western Pangea

NASA Astrophysics Data System (ADS)

Knobbe, T.; Suarez, C. A.

2014-12-01

Carbon isotope analysis of bulk organic and inorganic carbon preserved in the lacustrine deposits of the late Triassic to Jurassic Moenave Formation were analyzed to construct a carbon isotope chemostratigraphic profile of western Pangea. Negative carbon isotope excursions (NCIE) are characteristic of the Late Triassic and are attributed to the effects of the Central Atlantic Magmatic Province (CAMP) on climate and the global C-cycle. The aerial extent of the CAMP basalts is the largest in Earth's history spanning four continents with an area of ~ 7 x 106 km2 and a volume of 3 to 11 x 106 km3. Carbon isotope and paleontological evidence has shown that the end Triassic extinction is near synchronous to the CAMP and likely spurred on the extinction event as well as an increase in global temperatures of 2 - 2.5°C. Global correlations of NCIEs between marine and terrestrial strata provide a connection between the CAMP basalts and the end-Triassic extinction. Preliminary data collected at Potter Canyon, Arizona reveal a 5.5 ‰ decrease in δ13Corganic and a 2.75‰ decrease in δ13Ccarbonate in the lower portion of the Whitmore Point Member. These NCIEs indicate the global carbon cycle perturbation caused by the CAMP is recorded in lacustrine sediments of the Whitmore Point Member in southern Utah and northern Arizona. Additional samples collected at high sampling frequencies at other locations in the Whitmore Point Member will corroborate the terrestrial impacts of the CAMP perturbation at these locations across the region. Correlation of NCIES associated with the CAMP and any identified microfossils of the Whitmore Point Member will also illustrate the global effects of increased atmospheric CO2 on the terrestrial environment and biota.

Spatial distribution and influence factors of interprovincial terrestrial physical geographical names in China

NASA Astrophysics Data System (ADS)

Zhang, S.; Wang, Y.; Ju, H.

2017-12-01

The interprovincial terrestrial physical geographical entities are the key areas of regional integrated management. Based on toponomy dictionaries and different thematic maps, the attributes and the spatial extent of the interprovincial terrestrial physical geographical names (ITPGN, including terrain ITPGN and water ITPGN) were extracted. The coefficient of variation and Moran's I were combined together to measure the spatial variation and spatial association of ITPGN. The influencing factors of the distribution of ITPGN and the implications for the regional management were further discussed. The results showed that 11325 ITPGN were extracted, including 7082 terrain ITPGN and 4243 water ITPGN. Hunan Province had the largest number of ITPGN in China, and Shanghai had the smallest number. The spatial variance of the terrain ITPGN was larger than that of the water ITPGN, and the ITPGN showed a significant agglomeration phenomenon in the southern part of China. Further analysis showed that the number of ITPGN was positively related with the relative elevation and the population where the relative elevation was lower than 2000m and the population was less than 50 million. But the number of ITPGN showed a negative relationship with the two factors when their values became larger, indicating a large number of unnamed entities existed in complex terrain areas and a decreasing number of terrestrial physical geographical entities in densely populated area. Based on these analysis, we suggest the government take the ITPGN as management units to realize a balance development between different parts of the entities and strengthen the geographical names census and the nomination of unnamed interprovincial physical geographical entities. This study also demonstrated that the methods of literature survey, coefficient of variation and Moran's I can be combined to enhance the understanding of the spatial pattern of ITPGN.

Contributions of wildland fire to terrestrial ecosystem carbon dynamics in North America from 1990 to 2012

USGS Publications Warehouse

Chen, Guangsheng; Hayes, Daniel J.; McGuire, A. David

2017-01-01

Burn area and the frequency of extreme fire events have been increasing during recent decades in North America, and this trend is expected to continue over the 21st century. While many aspects of the North American carbon budget have been intensively studied, the net contribution of fire disturbance to the overall net carbon flux at the continental scale remains uncertain. Based on national scale, spatially explicit and long-term fire data, along with the improved model parameterization in a process-based ecosystem model, we simulated the impact of fire disturbance on both direct carbon emissions and net terrestrial ecosystem carbon balance in North America. Fire-caused direct carbon emissions were 106.55 ± 15.98 Tg C/yr during 1990–2012; however, the net ecosystem carbon balance associated with fire was −26.09 ± 5.22 Tg C/yr, indicating that most of the emitted carbon was resequestered by the terrestrial ecosystem. Direct carbon emissions showed an increase in Alaska and Canada during 1990–2012 as compared to prior periods due to more extreme fire events, resulting in a large carbon source from these two regions. Among biomes, the largest carbon source was found to be from the boreal forest, primarily due to large reductions in soil organic matter during, and with slower recovery after, fire events. The interactions between fire and environmental factors reduced the fire-caused ecosystem carbon source. Fire disturbance only caused a weak carbon source as compared to the best estimate terrestrial carbon sink in North America owing to the long-term legacy effects of historical burn area coupled with fast ecosystem recovery during 1990–2012.

Hydrological changes of DOM composition and biodegradability of rivers in temperate monsoon climates

NASA Astrophysics Data System (ADS)

Shin, Yera; Lee, Eun-Ju; Jeon, Young-Joon; Hur, Jin; Oh, Neung-Hwan

2016-09-01

The spatial and hydrological dynamics of dissolved organic matter (DOM) composition and biodegradability were investigated for the five largest rivers in the Republic of Korea (South Korea) during the years 2012-2013 using incubation experiments and spectroscopic measurements, which included parallel factor analysis (PARAFAC). The lower reaches of the five rivers were selected as windows showing the integrated effects of basin biogeochemistry of different land use under Asian monsoon climates, providing an insight on consistency of DOM dynamics across multiple sites which could be difficult to obtain from a study on an individual river. The mean dissolved organic carbon (DOC) concentrations of the five rivers were relatively low, ranging from 1.4 to 3.4 mg L-1, due to the high slope and low percentage of wetland cover in the basin. Terrestrial humic- and fulvic-like components were dominant in all the rivers except for one, where protein-like compounds were up to ∼80%. However, terrestrial components became dominant in all five of the rivers after high precipitation during the summer monsoon season, indicating the strong role of hydrology on riverine DOM compositions for the basins under Asian monsoon climates. Considering that 64% of South Korea is forested, our results suggest that the forests could be a large source of riverine DOM, elevating the DOM loads during monsoon rainfall. Although more DOM was degraded when DOM input increased, regardless of its sources, the percent biodegradability was reduced with increased proportions of terrestrially derived aromatic compounds. The shift in DOM quality towards higher percentages of aromatic terrestrial compounds may alter the balance of the carbon cycle of coastal ecosystems by changing microbial metabolic processes if climate extremes such as heavy storms and typhoons become more frequent due to climate change.

Spatial variations in geochemical characteristics of the modern Mackenzie Delta sedimentary system

NASA Astrophysics Data System (ADS)

Vonk, Jorien E.; Giosan, Liviu; Blusztajn, Jerzy; Montlucon, Daniel; Graf Pannatier, Elisabeth; McIntyre, Cameron; Wacker, Lukas; Macdonald, Robie W.; Yunker, Mark B.; Eglinton, Timothy I.

2015-12-01

The Mackenzie River in Canada is by far the largest riverine source of sediment and organic carbon (OC) to the Arctic Ocean. Therefore the transport, degradation and burial of OC along the land-to-ocean continuum for this riverine system is important to study both regionally and as a dominant representative of Arctic rivers. Here, we apply sedimentological (grain size, mineral surface area), and organic and inorganic geochemical techniques (%OC, δ13C-OC and Δ14C-OC, 143Nd/144Nd, δ2H and δ18O, major and trace elements) on particulate, bank, channel and lake surface sediments from the Mackenzie Delta, as well as on surface sediments from the Mackenzie shelf in the Beaufort Sea. Our data show a hydrodynamic sorting effect resulting in the accumulation of finer-grained sediments in lake and shelf deposits. A general decrease in organic carbon (OC) to mineral surface area ratios from river-to-sea furthermore suggests a loss of mineral-bound terrestrial OC during transport through the delta and deposition on the shelf. The net isotopic value of the terrestrial OC that is lost en route, derived from relationships between δ13C, OC and surface area, is -28.5‰ for δ13C and -417‰ for Δ14C. We calculated that OC burial efficiencies are around 55%, which are higher (∼20%) than other large river systems such as the Amazon. Old sedimentary OC ages, up to 12 14C-ky, suggest the delivery of both a petrogenic OC source (with an estimated contribution of 19 ± 9%) as well as a pre-aged terrestrial OC source. We calculated the 14C-age of this pre-aged, biogenic, component to be about 6100 yrs, or -501‰, which illustrates that terrestrial OC in the watershed can reside for millennia in soils before being released into the river. Surface sediments in lakes across the delta (n = 20) showed large variability in %OC (0.92-5.7%) and δ13C (-30.7‰ to -23.5‰). High-closure lakes, flooding only at exceptionally high water levels, hold high sedimentary OC contents (>2.5%) and young biogenic OC with a terrestrial or an autochthonous source whereas no-closure lakes, permanently connected to a river channel, hold sediments with pre-aged, terrestrial OC. The intermediate low-closure lakes, flooding every year during peak discharge, display the largest variability in OC content, age and source, likely reflecting variability in for example the length of river-lake connections, the distance to sediment source and the number of intermediate settling basins. Bank, channel and suspended sediment show variable 143Nd/144Nd values, yet there is a gradual but distinct spatial transition in 143Nd/144Nd (nearly three ε units; from -11.4 to -13.9) in the detrital fraction of lake surface sediments from the western to the eastern delta. This reflects the input of younger Peel River catchment material in the west and input of older geological source material in the east, and suggests that lake sediments can be used to assess variability in source watershed patterns across the delta.

CAM Photosynthesis in Submerged Aquatic Plants

USGS Publications Warehouse

Keeley, J.E.

1998-01-01

Crassulacean acid metabolism (CAM) is a CO2-concentrating mechanism selected in response to aridity in terrestrial habitats, and, in aquatic environments, to ambient limitations of carbon. Evidence is reviewed for its presence in five genera of aquatic vascular plants, including Isoe??tes, Sagittaria, Vallisneria, Crassula, and Littorella. Initially, aquatic CAM was considered by some to be an oxymoron, but some aquatic species have been studied in sufficient detail to say definitively that they possess CAM photosynthesis. CO2-concentrating mechanisms in photosynthetic organs require a barrier to leakage; e.g., terrestrial C4 plants have suberized bundle sheath cells and terrestrial CAM plants high stomatal resistance. In aquatic CAM plants the primary barrier to CO2 leakage is the extremely high diffusional resistance of water. This, coupled with the sink provided by extensive intercellular gas space, generates daytime CO2(Pi) comparable to terrestrial CAM plants. CAM contributes to the carbon budget by both net carbon gain and carbon recycling, and the magnitude of each is environmentally influenced. Aquatic CAM plants inhabit sites where photosynthesis is potentially limited by carbon. Many occupy moderately fertile shallow temporary pools that experience extreme diel fluctuations in carbon availability. CAM plants are able to take advantage of elevated nighttime CO2 levels in these habitats. This gives them a competitive advantage over non-CAM species that are carbon starved during the day and an advantage over species that expend energy in membrane transport of bicarbonate. Some aquatic CAM plants are distributed in highly infertile lakes, where extreme carbon limitation and light are important selective factors. Compilation of reports on diel changes in titratable acidity and malate show 69 out of 180 species have significant overnight accumulation, although evidence is presented discounting CAM in some. It is concluded that similar proportions of the aquatic and terrestrial floras have evolved CAM photosynthesis. Aquatic Isoe??tes (Lycophyta) represent the oldest lineage of CAM plants and cladistic analysis supports an origin for CAM in seasonal wetlands, from which it has radiated into oligotrophic lakes and into terrestrial habitats. Temperate Zone terrestrial species share many characteristics with amphibious ancestors, which in their temporary terrestrial stage, produce functional stomata and switch from CAM to C3. Many lacustrine Isoe??tes have retained the phenotypic plasticity of amphibious species and can adapt to an aerial environment by development of stomata and switching to C3. However, in some neotropical alpine species, adaptations to the lacustrine environment are genetically fixed and these constitutive species fail to produce stomata or loose CAM when artificially maintained in an aerial environment. It is hypothesized that neotropical lacustrine species may be more ancient in origin and have given rise to terrestrial species, which have retained most of the characteristics of their aquatic ancestry, including astomatous leaves, CAM and sediment-based carbon nutrition.

Herbivory and eutrophication mediate grassland plant nutrient responses across a global climatic gradient

USGS Publications Warehouse

Anderson, T. Michael; Griffith, Daniel M.; Grace, James B.; Lind, Eric M.; Adler, Peter B.; Biederman, Lori A.; Blumenthal, Dana M.; Daleo, Pedro; Firn, Jennifer; Hagenah, Nicole; Harpole, W. Stanley; MacDougall, Andrew S.; McCulley, Rebecca L.; Prober, Suzanne M.; Risch, Anita C.; Sankaran, Mahesh; Schütz, Martin; Seabloom, Eric W.; Stevens, Carly J.; Sullivan, Lauren; Wragg, Peter; Borer, Elizabeth T.

2018-01-01

Plant stoichiometry, the relative concentration of elements, is a key regulator of ecosystem functioning and is also being altered by human activities. In this paper we sought to understand the global drivers of plant stoichiometry and compare the relative contribution of climatic vs. anthropogenic effects. We addressed this goal by measuring plant elemental (C, N, P and K) responses to eutrophication and vertebrate herbivore exclusion at eighteen sites on six continents. Across sites, climate and atmospheric N deposition emerged as strong predictors of plot‐level tissue nutrients, mediated by biomass and plant chemistry. Within sites, fertilization increased total plant nutrient pools, but results were contingent on soil fertility and the proportion of grass biomass relative to other functional types. Total plant nutrient pools diverged strongly in response to herbivore exclusion when fertilized; responses were largest in ungrazed plots at low rainfall, whereas herbivore grazing dampened the plant community nutrient responses to fertilization. Our study highlights (1) the importance of climate in determining plant nutrient concentrations mediated through effects on plant biomass, (2) that eutrophication affects grassland nutrient pools via both soil and atmospheric pathways and (3) that interactions among soils, herbivores and eutrophication drive plant nutrient responses at small scales, especially at water‐limited sites.

Spatial and seasonal variations in mobile carbohydrates in Pinus cembra in the timberline ecotone of the Central Austrian Alps.

PubMed

Gruber, A; Pirkebner, D; Oberhuber, W; Wieser, G

2011-03-01

To test whether the altitudinal limit of tree growth is determined by carbons shortage or by a limitation in growth we investigated non structural carbohydrates and their components starch and total soluble sugars in Pinus cembra trees along an elevational gradient in the timberline ecotone of the Central Austrian Alps. NSC contents in needles, branches, stems, and coarse roots were measured throughout an entire growing season. At the tissue level NSC contents were not significantly more abundant in treeline trees as compared to trees at lower elevations. Along our 425 m elevational transect from the closed forest to the treeline we failed to find a stable elevational trend in the total NSC pool of entire trees and observed within season increases in the tree's NSC pool that can be attributed to an altitudinal increase in leaf mass as needles contained the largest NSC fraction of the whole tree NSC pool. Furthermore, whole tree NSC contents were positively correlated with net photosynthetic capacity. Although our observed NSC characteristics do not support the hypothesis that tree life at their upper elevational limit is determined by an insufficient carbon balance we found no consistent confirmation for the sink limitation hypothesis.

Spatial and seasonal variations in mobile carbohydrates in Pinus cembra in the timberline ecotone of the Central Austrian Alps

PubMed Central

Gruber, A.; Pirkebner, D.; Oberhuber, W.; Wieser, G.

2011-01-01

To test whether the altitudinal limit of tree growth is determined by carbons shortage or by a limitation in growth we investigated non structural carbohydrates and their components starch and total soluble sugars in Pinus cembra trees along an elevational gradient in the timberline ecotone of the Central Austrian Alps. NSC contents in needles, branches, stems, and coarse roots were measured throughout an entire growing season. At the tissue level NSC contents were not significantly more abundant in treeline trees as compared to trees at lower elevations. Along our 425 m elevational transect from the closed forest to the treeline we failed to find a stable elevational trend in the total NSC pool of entire trees and observed within season increases in the tree’s NSC pool that can be attributed to an altitudinal increase in leaf mass as needles contained the largest NSC fraction of the whole tree NSC pool. Furthermore, whole tree NSC contents were positively correlated with net photosynthetic capacity. Although our observed NSC characteristics do not support the hypothesis that tree life at their upper elevational limit is determined by an insufficient carbon balance we found no consistent confirmation for the sink limitation hypothesis. PMID:22003357

Herbivory and eutrophication mediate grassland plant nutrient responses across a global climatic gradient.

PubMed

Anderson, T Michael; Griffith, Daniel M; Grace, James B; Lind, Eric M; Adler, Peter B; Biederman, Lori A; Blumenthal, Dana M; Daleo, Pedro; Firn, Jennifer; Hagenah, Nicole; Harpole, W Stanley; MacDougall, Andrew S; McCulley, Rebecca L; Prober, Suzanne M; Risch, Anita C; Sankaran, Mahesh; Schütz, Martin; Seabloom, Eric W; Stevens, Carly J; Sullivan, Lauren L; Wragg, Peter D; Borer, Elizabeth T

2018-04-01

Plant stoichiometry, the relative concentration of elements, is a key regulator of ecosystem functioning and is also being altered by human activities. In this paper we sought to understand the global drivers of plant stoichiometry and compare the relative contribution of climatic vs. anthropogenic effects. We addressed this goal by measuring plant elemental (C, N, P and K) responses to eutrophication and vertebrate herbivore exclusion at eighteen sites on six continents. Across sites, climate and atmospheric N deposition emerged as strong predictors of plot-level tissue nutrients, mediated by biomass and plant chemistry. Within sites, fertilization increased total plant nutrient pools, but results were contingent on soil fertility and the proportion of grass biomass relative to other functional types. Total plant nutrient pools diverged strongly in response to herbivore exclusion when fertilized; responses were largest in ungrazed plots at low rainfall, whereas herbivore grazing dampened the plant community nutrient responses to fertilization. Our study highlights (1) the importance of climate in determining plant nutrient concentrations mediated through effects on plant biomass, (2) that eutrophication affects grassland nutrient pools via both soil and atmospheric pathways and (3) that interactions among soils, herbivores and eutrophication drive plant nutrient responses at small scales, especially at water-limited sites. © 2018 by the Ecological Society of America.

Quantifying Standing Dead Tree Volume and Structural Loss with Voxelized Terrestrial Lidar Data

NASA Astrophysics Data System (ADS)

Popescu, S. C.; Putman, E.

2017-12-01

Standing dead trees (SDTs) are an important forest component and impact a variety of ecosystem processes, yet the carbon pool dynamics of SDTs are poorly constrained in terrestrial carbon cycling models. The ability to model wood decay and carbon cycling in relation to detectable changes in tree structure and volume over time would greatly improve such models. The overall objective of this study was to provide automated aboveground volume estimates of SDTs and automated procedures to detect, quantify, and characterize structural losses over time with terrestrial lidar data. The specific objectives of this study were: 1) develop an automated SDT volume estimation algorithm providing accurate volume estimates for trees scanned in dense forests; 2) develop an automated change detection methodology to accurately detect and quantify SDT structural loss between subsequent terrestrial lidar observations; and 3) characterize the structural loss rates of pine and oak SDTs in southeastern Texas. A voxel-based volume estimation algorithm, "TreeVolX", was developed and incorporates several methods designed to robustly process point clouds of varying quality levels. The algorithm operates on horizontal voxel slices by segmenting the slice into distinct branch or stem sections then applying an adaptive contour interpolation and interior filling process to create solid reconstructed tree models (RTMs). TreeVolX estimated large and small branch volume with an RMSE of 7.3% and 13.8%, respectively. A voxel-based change detection methodology was developed to accurately detect and quantify structural losses and incorporated several methods to mitigate the challenges presented by shifting tree and branch positions as SDT decay progresses. The volume and structural loss of 29 SDTs, composed of Pinus taeda and Quercus stellata, were successfully estimated using multitemporal terrestrial lidar observations over elapsed times ranging from 71 - 753 days. Pine and oak structural loss rates were characterized by estimating the amount of volumetric loss occurring in 20 equal-interval height bins of each SDT. Results showed that large pine snags exhibited more rapid structural loss in comparison to medium-sized oak snags in this study.

Extensive survey of terrestrial organic carbon in surface sediments of the East Siberian Sea

NASA Astrophysics Data System (ADS)

Vonk, Jorien; Gustafsson, Örjan; Alling, Vanja; Sánchez-García, Laura; van Dongen, Bart; Andersson, Per; Dudarev, Oleg; Semiletov, Igor; Eglinton, Tim

2010-05-01

The East Siberian Sea (ESS) is the largest and shallowest continental shelf sea of the Arctic Ocean, yet it is the least explored. The perenially frozen tundra and taiga of the circum-Arctic coastal area holds approximately half of the global belowground carbon pool. Significant amounts of terrestrial organic carbon (terrOC) are exported with the Great Siberian Arctic rivers to the shelf seas. In addition, the carbon-rich, ice-bound Yedoma coasts in East Siberia release significant amounts of Pleistocene carbon through thermal degradation and coastal erosion. The fate of these large-scale releases of terrOC in the East Siberian Shelf Sea is still poorly understood. The urgency of this research is accentuated by the fact that the East-Siberian Arctic landmass is experiencing the strongest climate warming on Earth, with a great potential for various carbon-climate feedback links. During the International Siberian Shelf Study 2008 (ISSS-08), a 50-day research expedition onboard the Russian vessel Yakob Smirnitskiy in late summer 2008, we obtained surface sediments from over 60 ESS locations. The data obtained after bulk analyses of these sediments are combined with results obtained from previous ESS campaigns in 2003 and 2004 to facilitate a comprehensive investigation of the ESS surface sediment composition. Sedimentary OC contents were between 0.13 and 3.7% (median 1.02%, interquartile range 0.563) with the highest values near the Indigirka and Kolyma river mouths and in the Long Strait. Stable carbon isotope values were in the range of -27.4 to -21.2 per mill (median -25.3 per mill, interquartile range 2.04), with more depleted values close to the coast. A clear transition was observed east of 170° E with more enriched values, signalling a regime shift with stronger influence of the Pacific Ocean. The terrOC fraction in the surface sediments was estimated from the 13C data to be on average 70% for ESS as a whole, with maximal values of 90-100% (along most of the coastline and in Sannikov and Dmitry Laptev Strait) and minimal values of 10-35% (outer shelf and Long Strait). An extensive set of bulk organic 14C data of the sedimentary OC in the ESS will also be interpreted with respect to relative contributions of coastal Yedoma erosion versus river input. Based on published and calculated (calculated from ISSS08 sediment cores) sedimentation velocities, we estimated terrOC burial sink on the East Siberian Shelf Sea.

Carbon dioxide dynamics in a lake and a reservoir on a tropical island (Bali, Indonesia).

PubMed

Macklin, Paul A; Suryaputra, I Gusti Ngurah Agung; Maher, Damien T; Santos, Isaac R

2018-01-01

Water-to-air carbon dioxide fluxes from tropical lakes and reservoirs (artificial lakes) may be an important but understudied component of global carbon fluxes. Here, we investigate the seasonal dissolved carbon dioxide (CO2) dynamics in a lake and a reservoir on a tropical volcanic island (Bali, Indonesia). Observations were performed over four seasonal surveys in Bali's largest natural lake (Lake Batur) and largest reservoir (Palasari Reservoir). Average CO2 partial pressures in the natural lake and reservoir were 263.7±12.2 μatm and 785.0±283.6 μatm respectively, with the highest area-weighted partial pressures in the wet season for both systems. The strong correlations between seasonal mean values of dissolved oxygen (DO) and pCO2 in the natural lake (r2 = 0.92) suggest that surface water metabolism was an important driver of CO2 dynamics in this deep system. Radon (222Rn, a natural groundwater discharge tracer) explained up to 77% of the variability in pCO2 in the shallow reservoir, suggesting that groundwater seepage was the major CO2 driver in the reservoir. Overall, the natural lake was a sink of atmospheric CO2 (average fluxes of -2.8 mmol m-2 d-1) while the reservoir was a source of CO2 to the atmosphere (average fluxes of 7.3 mmol m-2 d-1). Reservoirs are replacing river valleys and terrestrial ecosystems, particularly throughout developing tropical regions. While the net effect of this conversion on atmospheric CO2 fluxes remains to be resolved, we speculate that reservoir construction will partially offset the CO2 sink provided by deep, volcanic, natural lakes and terrestrial environments.

Adaptations in the structure and innervation of follicle-sinus complexes to an aquatic environment as seen in the Florida manatee (Trichechus manatus latirostris).

PubMed

Sarko, Diana K; Reep, Roger L; Mazurkiewicz, Joseph E; Rice, Frank L

2007-09-20

Florida manatees are large-bodied aquatic herbivores that use large tactile vibrissae for several purposes. Facial vibrissae are used to forage in a turbid water environment, and the largest perioral vibrissae can also grasp and manipulate objects. Other vibrissae distributed over the entire postfacial body appear to function as a lateral line system. All manatee vibrissae emanate from densely innervated follicle-sinus complexes (FSCs) like those in other mammals, although proportionately larger commensurate with the caliber of the vibrissae. As revealed by immunofluorescence, all manatee FSCs have many types of C, Adelta and Abeta innervation including Merkel, club, and longitudinal lanceolate endings at the level of the ring sinus, but they lack other types such as reticular and spiny endings at the level of the cavernous sinus. As in non-whisking terrestrial species, the inner conical bodies of facial FSCs are well innervated but lack Abeta-fiber terminals. Importantly, manatee FSCs have two unique types of Abeta-fiber endings. First, all of the FSCs have exceptionally large-caliber axons that branch to terminate as novel, gigantic spindle-like endings located at the upper ring sinus. Second, facial FSCs have smaller caliber Abeta fibers that terminate in the trabeculae of the cavernous sinus as an ending that resembles a Golgi tendon organ. In addition, the largest perioral vibrissae, which are used for grasping, have exceptionally well-developed medullary cores that have a structure and dense small-fiber innervation resembling that of tooth pulp. Other features of the epidermis and upper dermis structure and innervation differ from that seen in terrestrial mammals. Copyright (c) 2007 Wiley-Liss, Inc.

Complete genome sequence of Thermosphaera aggregans type strain (M11TL).

PubMed

Spring, Stefan; Rachel, Reinhard; Lapidus, Alla; Davenport, Karen; Tice, Hope; Copeland, Alex; Cheng, Jan-Fang; Lucas, Susan; Chen, Feng; Nolan, Matt; Bruce, David; Goodwin, Lynne; Pitluck, Sam; Ivanova, Natalia; Mavromatis, Konstantinos; Ovchinnikova, Galina; Pati, Amrita; Chen, Amy; Palaniappan, Krishna; Land, Miriam; Hauser, Loren; Chang, Yun-Juan; Jeffries, Cynthia C; Brettin, Thomas; Detter, John C; Tapia, Roxanne; Han, Cliff; Heimerl, Thomas; Weikl, Fabian; Brambilla, Evelyne; Göker, Markus; Bristow, James; Eisen, Jonathan A; Markowitz, Victor; Hugenholtz, Philip; Kyrpides, Nikos C; Klenk, Hans-Peter

2010-06-15

Thermosphaera aggregans Huber et al. 1998 is the type species of the genus Thermosphaera, which comprises at the time of writing only one species. This species represents archaea with a hyperthermophilic, heterotrophic, strictly anaerobic and fermentative phenotype. The type strain M11TL(T) was isolated from a water-sediment sample of a hot terrestrial spring (Obsidian Pool, Yellowstone National Park, Wyoming). Here we describe the features of this organism, together with the complete genome sequence and annotation. The 1,316,595 bp long single replicon genome with its 1,410 protein-coding and 47 RNA genes is a part of the Genomic Encyclopedia of Bacteria and Archaea project.

The grape cluster, metal particle 63344,1. [in lunar coarse fines

NASA Technical Reports Server (NTRS)

Goldstein, J. I.; Axon, H. J.; Agrell, S. O.

1975-01-01

The grape cluster metal particle 63344,1 found in lunar coarse fines is examined using the scanning electron microscope (SEM), electron microprobe, and an optical microscope. This metal particle is approximately 0.5 cm in its largest dimension and consists of hundreds of metallic globules welded together to form a structure somewhat like a bunch of grapes. Electron microprobe analysis for Fe, Ni, Co, P, and S in the metal was carried out using wavelength dispersive detectors. No primary solidification structure is observed in the globules, and the particle is slow cooled from the solidification temperature (nearly 1300 C) taking days to probably months to reach 600 C. Two mechanisms for the formation of globules are proposed. One mechanism involves the primary impact of an iron meteorite which produces a metallic liquid and vapor phase. The second mechanism involves the formation of a liquid pool of metal after impact of an iron meteorite projectile followed by a secondary impact in the liquid metal pool.

Continental-scale water fluxes from continuous GPS observations of Earth surface loading

NASA Astrophysics Data System (ADS)

Borsa, A. A.; Agnew, D. C.; Cayan, D. R.

2015-12-01

After more than a decade of observing annual oscillations of Earth's surface from seasonal snow and water loading, continuous GPS is now being used to model time-varying terrestrial water fluxes on the local and regional scale. Although the largest signal is typically due to the seasonal hydrological cycle, GPS can also measure subtle surface deformation caused by sustained wet and dry periods, and to estimate the spatial distribution of the underlying terrestrial water storage changes. The next frontier is expanding this analysis to the continental scale and paving the way for incorporating GPS models into the National Climate Assessment and into the observational infrastructure for national water resource management. This will require reconciling GPS observations with predictions from hydrological models and with remote sensing observations from a suite of satellite instruments (e.g. GRACE, SMAP, SWOT). The elastic Earth response which transforms surface loads into vertical and horizontal displacements is also responsible for the contamination of loading observations by tectonic and anthropogenic transients, and we discuss these and other challenges to this new application of GPS.

Synchronous turnover of flora, fauna, and climate at the Eocene–Oligocene Boundary in Asia

PubMed Central

Sun, Jimin; Ni, Xijun; Bi, Shundong; Wu, Wenyu; Ye, Jie; Meng, Jin; Windley, Brian F.

2014-01-01

The Eocene–Oligocene Boundary (~34 million years ago) marks one of the largest extinctions of marine invertebrates in the world oceans and of mammalian fauna in Europe and Asia in the Cenozoic era. A shift to a cooler climate across this boundary has been suggested as the cause of this extinction in the marine environment, but there is no manifold evidence for a synchronous turnover of flora, fauna and climate at the Eocene–Oligocene Boundary in a single terrestrial site in Asia to support this hypothesis. Here we report new data of magnetostratigraphy, pollen and climatic proxies in the Asian interior across the Eocene–Oligocene Boundary; our results show that climate change forced a turnover of flora and fauna, suggesting there was a change from large-size perissodactyl-dominant fauna in forests under a warm-temperate climate to small rodent/lagomorph-dominant fauna in forest-steppe in a dry-temperate climate across the Eocene–Oligocene Boundary. These data provide a new terrestrial record for this significant Cenozoic environmental event. PMID:25501388

Analysis of data from the plasma composition experiment on the International Sun-Earth Explorer (ISEE 1)

NASA Technical Reports Server (NTRS)

Lennartsson, O. W.

1994-01-01

The Lockheed plasma composition experiment on the ISEE 1 spacecraft has provided one of the largest and most varied sets of data on earth's energetic plasma environment, covering both the solar wind, well beyond the bow shock, and the near equatorial magnetosphere to a distance of almost 23 earth radii. This report is an overview of the last four years of data analysis and archiving. The archiving for NSSDC includes most data obtained during the initial 28-months of instrument operation, from early November 1977 through the end of February 1980. The data products are a combination of spectra (mass and energy angle) and velocity moments. A copy of the data user's guide and examples of the data products are attached as appendix A. The data analysis covers three major areas: solar wind ions upstream and downstream of the day side bowshock, especially He(++) ions; terrestrial ions flowing upward from the auroral regions, especially H(+), O(+), and He(+) ions; and ions of both solar and terrestrial origins in the tail plasma sheet and lobe regions. Copies of publications are attached.

Temporally inter-comparable maps of terrestrial wilderness and the Last of the Wild

NASA Astrophysics Data System (ADS)

Allan, James R.; Venter, Oscar; Watson, James E. M.

2017-12-01

Wilderness areas, defined as areas free of industrial scale activities and other human pressures which result in significant biophysical disturbance, are important for biodiversity conservation and sustaining the key ecological processes underpinning planetary life-support systems. Despite their importance, wilderness areas are being rapidly eroded in extent and fragmented. Here we present the most up-to-date temporally inter-comparable maps of global terrestrial wilderness areas, which are essential for monitoring changes in their extent, and for proactively planning conservation interventions to ensure their preservation. Using maps of human pressure on the natural environment for 1993 and 2009, we identified wilderness as all 'pressure free' lands with a contiguous area >10,000 km2. These places are likely operating in a natural state and represent the most intact habitats globally. We then created a regionally representative map of wilderness following the well-established 'Last of the Wild' methodology; which identifies the 10% area with the lowest human pressure within each of Earth's 60 biogeographic realms, and identifies the ten largest contiguous areas, along with all contiguous areas >10,000 km2.

A test of the hypothesis that impact-induced fractures are preferred sites for later tectonic activity

NASA Technical Reports Server (NTRS)

Solomon, Sean C.; Duxbury, Elizabeth D.

1987-01-01

Impact cratering has been an important process in the solar system. The cratering event is generally accompanied by faulting in adjacent terrain. Impact-induced faults are nearly ubiquitous over large areas on the terrestrial planets. The suggestion is made that these fault systems, particularly those associated with the largest impact features are preferred sites for later deformation in response to lithospheric stresses generated by other processes. The evidence is a perceived clustering of orientations of tectonic features either radial or concentric to the crater or basin in question. An opportunity exists to test this suggestion more directly on Earth. The terrestrial continents contain more than 100 known or probable impact craters, with associated geological structures mapped to varying levels of detail. Prime facie evidence for reactivation of crater-induced faults would be the occurrence of earthquakes on these faults in response to the intraplate stress field. Either an alignment of epicenters with mapped fault traces or fault plane solutions indicating slip on a plane approximately coincident with that inferred for a crater-induced fault would be sufficient to demonstrate such an association.

The “χ” of the Matter: Testing the Relationship between Paleoenvironments and Three Theropod Clades

PubMed Central

Sales, Marcos A. F.; Lacerda, Marcel B.; Horn, Bruno L. D.; de Oliveira, Isabel A. P.; Schultz, Cesar L.

2016-01-01

The view of spinosaurs as dinosaurs of semi-aquatic habits and strongly associated with marginal and coastal habitats are deeply rooted in both scientific and popular knowledge, but it was never statistically tested. Inspired by a previous analysis of other dinosaur clades and major paleoenvironmental categories, here we present our own statistical evaluation of the association between coastal and terrestrial paleoenvironments and spinosaurids, along with other two theropod taxa: abelisaurids and carcharodontosaurids. We also included a taphonomic perspective and classified the occurrences in categories related to potential biases in order to better address our interpretations. Our main results can be summarized as follows: 1) the taxon with the largest amount of statistical evidence showing it positively associated to coastal paleoenvironments is Spinosauridae; 2) abelisaurids and carcharodontosaurids had more statistical evidence showing them positively associated with terrestrial paleoenvironments; 3) it is likely that spinosaurids also occupied spatially inland areas in a way somehow comparable at least to carcharodontosaurids; 4) abelisaurids may have been more common than the other two taxa in inland habitats. PMID:26829315

Meiofauna as descriptor of tourism-induced changes at sandy beaches.

PubMed

Gheskiere, Tom; Vincx, Magda; Weslawski, Jan Marcin; Scapini, Felicita; Degraer, Steven

2005-08-01

Tourism has long been considered as a 'clean industry' with almost no negative effects on the environment. This study demonstrated, in two different coastal systems (Mediterranean and Baltic), that tourism related activities are particularly affecting the sandy beach meio- and nematofauna in the upper beach zone, the specific ecotone in which many meiofauna species from both the marine and the terrestrial environment congregate. Tourist upper beaches are characterized by a lower % total organic matter (%TOM), lower densities, lower diversities (absence of Insecta, Harpacticoida, Oligochaeta, terrestrial nematodes and marine Ironidae nematodes) and higher community stress compared to nearby non-tourist locations. The %TOM was found to be the single most important factor for the observed differences in meiofauna assemblage structure at tourist versus non-tourist beaches in both the Mediterranean and the Baltic region. The free-living nematode assemblages from tourist upper zones depart significantly from expectations based on random selections from the regional nematode species pool. Furthermore upper zone assemblages are characterised by a low species diversity consisting of taxonomically closely related nematode species with r-strategist features. Generally, faunal differences between tourist and non-tourist beaches are decreasing towards the lower beach zones.