Science.gov

Sample records for ecosystem carbon gain

  1. Assessing carbon dynamics in semiarid ecosystems : Balancing potential gains with potential large rapid losses

    SciTech Connect

    Breshears, D. D.; Ebinger, M. H.; Unkefer, P. J.

    2001-01-01

    Photosynthesis and respiration are the largest fluxes into and out of the biosphere (Molles 1999). Consequently, small changes in these fluxes can potentially produce large changes in the storage of carbon in the biosphere. Terrestrial carbon fluxes account for more than half of the carbon transferred between the atmosphere and the earth's surface (about 120 GigaTons/year), and current stores of carbon in terrestrial ecosystem are estimated at 2060 GigaTons. Increasing attention is being focused on the role of managing and sequestering carbon in the terrestrial biosphere as a means for addressing global climate change (IGBP, 1998; U.S. Department of Energy, 1999). Terrestrial ecosystems are widely recognized as a major biological scrubber for atmosphereic CO{sub 2} and their ability to finction as such can be increased significantly over the next 25 years through careful manipulation. The potential for terrestrial carbon gains has been the subject of much attention (Dixon et al., 1994; Masera et al. 1997; Cao and Woodward, 1998; DeLucia et al. 1999). In contrast to other strategies for reducing net carbon emissions, terrestrial sequestration has the potential for rapid implementation. Strategies that focus on soil carbon are likely to be effective because in addition to being a storage pool of carbon, soil carbon also improves site productivity through improving soil quality (e.g., water retention and nutrient availability). The carbon pool in soils is immense and highly dynamic. The flux of carbon into and out of soils is one of the largest uncertainties in the total mass balance of global carbon (NRC, 1999; La1 et al., 1998; Cambardella, 1998). Reducing these uncertainties is key to developing carbon sequestration strategies. Soil carbon pools have been greatly depleted over recent centuries, and there is potential to increase storage of carbon in these soils through effective land management. Whereas carbon in vegetation can be managed directly through land use

  2. Quantifying ecosystem carbon losses and gains following development in New England: A combined field, modeling, and remote sensing approach

    NASA Astrophysics Data System (ADS)

    Raciti, S. M.; Hutyra, L.; Briber, B. M.; Dunn, A. L.; Friedl, M. A.; Woodcock, C.; Zhu, Z.; Olofsson, P.

    2013-12-01

    If current trends continue, the world's urban population may double and urban land area may quadruple over the next 50 years. Despite the rapid expansion of urban areas, the trajectories of carbon losses and gains following development remain poorly quantified. We are using a combination of field measurements, modeling, and remote sensing to advance our ability to measure and monitor trajectories of ecosystem carbon over space and time. To characterize how carbon stocks change across urban-to-rural gradients, we previously established field plots to survey live and dead tree biomass, tree canopy, soil and foliar carbon and nitrogen concentrations, and a range of landscape characteristics (Raciti et al. 2012). In 2013, we extended our field sampling to focus specifically on places that experienced land use and land cover change over the past 35 years. This chronosequence approach was informed by Landsat time series (1982-present) and property records (before 1982). The Landsat time series approach differs from traditional remote-sensing-based land use change detection methods because it leverages the entire Landsat archive of imagery using a Fourier fitting approach (Zhu et al. 2012). The result is a temporally and spatially continuous map of land use and land cover change across the study region. We used these field and remote sensing data to inform a carbon bookkeeping model that estimates changes in past and potential future carbon stocks over time. Here we present preliminary results of this work for eastern Massachusetts.

  3. Photosynthesis, Nitrogen, Their Adjustment and its Effects on Ecosystem Carbon Gain at Elevated CO{sub 2}l. A Comparison of Loblolly and Ponderosa Pines

    SciTech Connect

    Ball, J. Timothy; Eichelmann, Hillar Y.; Tissue, David T.; Lewis, James D.; Picone, Johnn B.; Ross, Peter D.

    1996-12-01

    A functional understanding of terrestrial ecosystem carbon processes is essential for two reasons. First, carbon flow is a most fundamental aspects of ecosystem function as it mediates most of the energy flow in these systems. Second, carbon flow also mediates the majority of energy flow in the global economy and will do for the foreseeable future. The increased atmospheric carbon dioxide and its inevitable flow through global ecosystems will influence ecosystem processes. There is, of course, great interest in the potential of ecosystems to sequester some of the carbon being loaded into the atmosphere by economic activity.

  4. Contrasting Responses of Ecosystem Carbon Gain (Input) and Soil Carbon Efflux (Output) to Warming and Drought Across a European Aridity Gradient

    NASA Astrophysics Data System (ADS)

    Cosby, J.; Reinsch, S.; Koehler, E.; de Dato, G.; Estiarte, M.; Guidolotti, G.; Kovacs-Lang, E.; Dukes, J.; Kröel-Dulay, G.; Larsen, K. S.; Lellei-Kovács, E.; Liberati, D.; Ransijn, J.; Schmidt, I. K.; Smith, A. R.; Sowerby, A.; Emmett, B.

    2015-12-01

    Understanding the relationship between aboveground and belowground processes are crucial to understand if we are to forecast feedbacks between terrestrial carbon (C) dynamics and future climate. To test if climate induced changes in annual aboveground net primary production (ANPP) will drive changes in C loss by soil respiration (Rs) we integrated data across a European temperature and precipitation gradient. Six European shrublands were exposed to year-round, night time warming (+1.5 oC) or repeated drought (-30% annual rain) during the plants growth season for over a decade, using an identical experimental approach. As a result, drought reduced ecosystem C gain as ANPP by 50% (compared to an untreated control) at the driest xeric site with effects reducing in intensity across the aridity gradient to a 15% ANPP-C gain at the wettest hydric site (slope=1.2, R2=0.76). In contrast, reductions in Rs-C loss were of a lower magnitude (0-15%) and increased in intensity across the aridity gradient (slope=-0.44, R2=0.76) if the hydric site was excluded. These results suggest (i) above and belowground C fluxes responses do not track each other in response to drought and (ii) whilst ANPP at our hydric sites follows that predicted from an aridity gradient, Rs responses did not. Results from the warming treatments were generally of lower magnitude and opposite direction indicating different mechanisms were driving responses. Overall, these results suggest that ANPP is more sensitive than Rs to climate stresses and soil respiration C fluxes are not predictable from changes in plant productivity. Indirect effects on soil properties and/or microbial communities need to be explored. As we observed no acclimation of either ANPP or Rs after over a decade of treatments, feedbacks between the terrestrial C cycle and climate may not weaken over decadal timescales at larger, continental scales.

  5. Trophic cascade alters ecosystem carbon exchange

    PubMed Central

    Strickland, Michael S.; Hawlena, Dror; Reese, Aspen; Bradford, Mark A.; Schmitz, Oswald J.

    2013-01-01

    Trophic cascades—the indirect effects of carnivores on plants mediated by herbivores—are common across ecosystems, but their influence on biogeochemical cycles, particularly the terrestrial carbon cycle, are largely unexplored. Here, using a 13C pulse-chase experiment, we demonstrate how trophic structure influences ecosystem carbon dynamics in a meadow system. By manipulating the presence of herbivores and predators, we show that even without an initial change in total plant or herbivore biomass, the cascading effects of predators in this system begin to affect carbon cycling through enhanced carbon fixation by plants. Prolonged cascading effects on plant biomass lead to slowing of carbon loss via ecosystem respiration and reallocation of carbon among plant aboveground and belowground tissues. Consequently, up to 1.4-fold more carbon is retained in plant biomass when carnivores are present compared with when they are absent, owing primarily to greater carbon storage in grass and belowground plant biomass driven largely by predator nonconsumptive (fear) effects on herbivores. Our data highlight the influence that the mere presence of predators, as opposed to direct consumption of herbivores, can have on carbon uptake, allocation, and retention in terrestrial ecosystems. PMID:23776213

  6. Carbon cycling in high-latitude ecosystems

    NASA Technical Reports Server (NTRS)

    Townsend, Alan; Frolking, Stephen; Holland, Elizabeth

    1992-01-01

    The carbon-rich soils and peatlands of high-latitude ecosystems could substantially influence atmospheric concentrations of CO2 and CH4 in a changing climate. Currently, cold, often waterlogged conditions retard decomposition, and release of carbon back to the atmosphere may be further slowed by physical protection of organic matter in permafrost. As a result, many northern ecosystems accumulate carbon over time (Billings et al., 1982; Poole and Miller, 1982), and although such rates of accumulation are low, thousands of years of development have left Arctic ecosystems with an extremely high soil carbon content; Schlesinger's (1984) average value of 20.4 kg C/m(sup 2) leads to a global estimate of 163 x 10(exp 15) g C. All GCM simulations of a doubled CO2 climate predict the greatest warming to occur in the polar regions (Dickinson, 1986; Mitchell, 1989). Given the extensive northern carbon pools and the strong sensitivity of decomposition processes to temperature, even a slight warming of the soil could dramatically alter the carbon balance of Arctic ecosystems. If warming accelerates rates of decomposition more than rates of primary production, a sizeable additional accumulation of CO2 in the atmosphere could occur. Furthermore, CH4 produced in anaerobic soils and peatlands of the Arctic already composes a good percentage of the global efflux (Cicerone and Oremlund, 1988); if northern soils become warmer and wetter as a whole, CH4 emissions could dramatically rise. A robust understanding of the primary controls of carbon fluxes in Arctic ecosystems is critical. As a framework for a systematic examination of these controls, we discussed a conceptual model of regional-scale Arctic carbon turnover, including CH4 production, and based upon the Century soil organic matter model.

  7. Use of Field-based Near Infrared Sensors to Map Soil Carbon in Agricultural Ecosystems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ability to detect changes in soil carbon storage is an important component of verifying sequestration of soil carbon within agricultural ecosystems. Rapid methods of measuring soil carbon such as near infrared spectroscopy have gained considerable interest but problems in accurate measurement still...

  8. Carbon dioxide sequestration in terrestrial ecosystems

    SciTech Connect

    Wisniewski, J.; Dixon, R.K.; Kinsman, J.D.; Sampson, R.N.; Lugo, A.E.

    1993-01-01

    The terrestrial biosphere plays a prominent role in the global carbon (C) cycle. Terrestrial ecosystems are currently accumulating C and it appears feasible to manage existing terrestrial (forest, agronomic, desert) ecosystems to maintain or increase C storage. Forest ecosystems can be managed to sequester and store globally significant amounts of C. Agroecosystems and arid lands could be managed to conserve existing terrestrial C but CO2 sequestration rates by vegetation in these systems is relatively low. Biomass from forest agroecosystems has the potential to be used as an energy source and trees could be used to conserve energy in urban environments. Some ecosystem management practices that result in C sequestration and conservation provide ancillary benefits.

  9. Carbon exchange between ecosystems and atmosphere in the Czech Republic is affected by climate factors.

    PubMed

    Marek, Michal V; Janouš, Dalibor; Taufarová, Klára; Havránková, Kateřina; Pavelka, Marian; Kaplan, Věroslav; Marková, Irena

    2011-05-01

    By comparing five ecosystem types in the Czech Republic over several years, we recorded the highest carbon sequestration potential in an evergreen Norway spruce forest (100%) and an agroecosystem (65%), followed by European beech forest (25%) and a wetland ecosystem (20%). Because of a massive ecosystem respiration, the final carbon gain of the grassland was negative. Climate was shown to be an important factor of carbon uptake by ecosystems: by varying the growing season length (a 22-d longer season in 2005 than in 2007 increased carbon sink by 13%) or by the effect of short- term synoptic situations (e.g. summer hot and dry days reduced net carbon storage by 58% relative to hot and wet days). Carbon uptake is strongly affected by the ontogeny and a production strategy which is demonstrated by the comparison of seasonal course of carbon uptake between coniferous (Norway spruce) and deciduous (European beech) stands. PMID:21345558

  10. Protected area certificates: gaining ground for better ecosystem protection?

    PubMed

    Segerstedt, Anna; Grote, Ulrike

    2015-06-01

    Protected areas are vital to sustain a number of ecosystem services. Yet, many protected areas are underfinanced and lack management effectiveness. Protected area certificates have been suggested as a way to resolve these problems. This instrument would allow land managers to certify an area if it meets certain conservation criteria. The certificates could then be sold on an international market, for example to companies and any consumers that are interested in environmental protection. Some pilot initiatives have been launched, yet little is known about future demand and features of protected area certificates. To fill this knowledge gap, we conduct a choice experiment with close to 400 long-distance tourists from Germany as a potential group of buyers. Our results indicate that the respondents have the highest willingness to pay for certificates that conserve sensitive ecosystems and in addition to this lead to poverty reduction and safeguard water resources. For other attributes such as a greenhouse gas reduction, the preferences are less significant. Overall, the results are rather homogenous irrespective of where the protected areas are located. These insights are important for the future design and marketing of protected area certificates. PMID:25868572

  11. Protected Area Certificates: Gaining Ground for Better Ecosystem Protection?

    NASA Astrophysics Data System (ADS)

    Segerstedt, Anna; Grote, Ulrike

    2015-06-01

    Protected areas are vital to sustain a number of ecosystem services. Yet, many protected areas are underfinanced and lack management effectiveness. Protected area certificates have been suggested as a way to resolve these problems. This instrument would allow land managers to certify an area if it meets certain conservation criteria. The certificates could then be sold on an international market, for example to companies and any consumers that are interested in environmental protection. Some pilot initiatives have been launched, yet little is known about future demand and features of protected area certificates. To fill this knowledge gap, we conduct a choice experiment with close to 400 long-distance tourists from Germany as a potential group of buyers. Our results indicate that the respondents have the highest willingness to pay for certificates that conserve sensitive ecosystems and in addition to this lead to poverty reduction and safeguard water resources. For other attributes such as a greenhouse gas reduction, the preferences are less significant. Overall, the results are rather homogenous irrespective of where the protected areas are located. These insights are important for the future design and marketing of protected area certificates.

  12. Ecosystem carbon fluxes and Amazonian forest metabolism

    NASA Astrophysics Data System (ADS)

    Saleska, Scott; da Rocha, Humberto; Kruijt, Bart; Nobre, Antonio

    Long-term measurements of ecosystem-atmosphere exchanges of carbon, water, and energy, via eddy flux towers, give insight into three key questions about Amazonian forest function. First, what is the carbon balance of Amazon forests? Some towers give accurate site-specific carbon balances, as validated by independent methods, but decisive resolution of the large-scale question will also require integration of remote sensing techniques (to detect and encompass the distribution of naturally induced disturbance states across the landscape of old growth forests) with eddy flux process studies (to characterize the association between carbon balance and forest disturbance states). Second, what is the seasonality of ecosystem metabolism in Amazonian forests? Models have historically simulated dry season declines in photosynthetic metabolism, a consequence of modeled water limitation. Tower sites in equatorial Amazonian forests, however, show that photosynthetic metabolism increases during dry seasons ("green up"), perhaps because deep roots buffer trees from dry season water stress, while phenological rhythms trigger leaf flush, associated with increased solar irradiance. Third, how does ecosystem metabolism vary across biome types and land use patterns? As dry season length increases from equatorial forest, to drier southern forests, to savanna, fluxes show seasonal patterns consistent with increasing water stress, including a switch from dry season green up to "brown down." Land use change in forest ecosystems removes deep roots, artificially inducing the same trend toward brown down. In the final part, this review suggests that eddy tower network and satellite-based insights into seasonal responses provide a model for detecting responses to extreme interannual climate variations that can test whether forests are vulnerable to model-simulated Amazonian forest collapse under climate change.

  13. Predators help protect carbon stocks in blue carbon ecosystems

    NASA Astrophysics Data System (ADS)

    Atwood, Trisha B.; Connolly, Rod M.; Ritchie, Euan G.; Lovelock, Catherine E.; Heithaus, Michael R.; Hays, Graeme C.; Fourqurean, James W.; Macreadie, Peter I.

    2015-12-01

    Predators continue to be harvested unsustainably throughout most of the Earth's ecosystems. Recent research demonstrates that the functional loss of predators could have far-reaching consequences on carbon cycling and, by implication, our ability to ameliorate climate change impacts. Yet the influence of predators on carbon accumulation and preservation in vegetated coastal habitats (that is, salt marshes, seagrass meadows and mangroves) is poorly understood, despite these being some of the Earth's most vulnerable and carbon-rich ecosystems. Here we discuss potential pathways by which trophic downgrading affects carbon capture, accumulation and preservation in vegetated coastal habitats. We identify an urgent need for further research on the influence of predators on carbon cycling in vegetated coastal habitats, and ultimately the role that these systems play in climate change mitigation. There is, however, sufficient evidence to suggest that intact predator populations are critical to maintaining or growing reserves of 'blue carbon' (carbon stored in coastal or marine ecosystems), and policy and management need to be improved to reflect these realities.

  14. BOREAS TE-19 Ecosystem Carbon Balance Model

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Papagno, Andrea (Editor); Frolking, Steve

    2000-01-01

    The BOREAS TE-19 team developed a model called the Spruce and Moss Model (SPAM) designed to simulate the daily carbon balance of a black spruce/moss boreal forest ecosystem. It is driven by daily weather conditions, and consists of four components: (1) soil climate, (2) tree photosynthesis and respiration, (3) moss photosynthesis and respiration, and (4) litter decomposition and associated heterotrophic respiration. The model simulates tree gross and net photosynthesis, wood respiration, live root respiration, moss gross and net photosynthesis, and heterotrophic respiration (decomposition of root litter, young needle and moss litter, and humus). These values can be combined to generate predictions of total site net ecosystem exchange of carbon (NEE), total soil dark respiration (live roots + heterotrophs + live moss), spruce and moss net productivity, and net carbon accumulation in the soil. To date, simulations have been of the BOREAS NSA-OBS and SSA-OBS tower sites, from 1968-95 (except 1990-93). The files include source code and sample input and output files in ASCII format. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Activity Archive Center (DAAC).

  15. Carbon dioxide dynamics in an artificial ecosystem

    NASA Astrophysics Data System (ADS)

    Hu, Enzhu; Hu, Dawei; Tong, Ling; Li, Ming; Fu, Yuming; He, Wenting; Liu, Hong

    An experimental artificial ecosystem was established as a tool to understand the behavior of closed ecosystem and to develop the technology for a future bioregenerative life support system for lunar or planetary exploration. Total effective volume of the system is 0.7 m3 . It consists of a higher plant chamber, an animal chamber and a photo-bioreactor which cultivated lettuce (Lactuca sativa L.), silkworm (Bombyx Mori L.) and microalgae (Chlorella), respectively. For uniform and sustained observations, lettuce and silkworms was cultivated using sequential cultivation method, and microalgae using continuous culture. Four researchers took turns breathing the system air through a tube for brief periods every few hours. A mathematic model, simulating the carbon dioxide dynamics was developed. The main biological parameters concerning photosynthesis of lettuce and microalgae, respiration of silkworms and human were validated by the experimental data. The model described the respiratory relationship between autotrophic and heterotrophic compartments. A control strategy was proposed as a tool for the atmosphere management of the artificial ecosystem.

  16. Net ecosystem production: A comprehensive measure of net carbon accumulation by ecosystems

    USGS Publications Warehouse

    Randerson, J.T.; Chapin, F. S., III; Harden, J.W.; Neff, J.C.; Harmon, M.E.

    2002-01-01

    The conceptual framework used by ecologists and biogeochemists must allow for accurate and clearly defined comparisons of carbon fluxes made with disparate techniques across a spectrum of temporal and spatial scales. Consistent with usage over the past four decades, we define "net ecosystem production" (NEP) as the net carbon accumulation by ecosystems. Past use of this term has been ambiguous, because it has been used conceptually as a measure of carbon accumulation by ecosystems, but it has often been calculated considering only the balance between gross primary production (GPP) and ecosystem respiration. This calculation ignores other carbon fluxes from ecosystems (e.g., leaching of dissolved carbon and losses associated with disturbance). To avoid conceptual ambiguities, we argue that NEP be defined, as in the past, as the net carbon accumulation by ecosystems and that it explicitly incorporate all the carbon fluxes from an ecosystem, including autotrophic respiration, heterotrophic respiration, losses associated with disturbance, dissolved and particulate carbon losses, volatile organic compound emissions, and lateral transfers among ecosystems. Net biome productivity (NBP), which has been proposed to account for carbon loss during episodic disturbance, is equivalent to NEP at regional or global scales. The multi-scale conceptual framework we describe provides continuity between flux measurements made at the scale of soil profiles and chambers, forest inventories, eddy covariance towers, aircraft, and inversions of remote atmospheric flask samples, allowing a direct comparison of NEP estimates made at all temporal and spatial scales.

  17. Quantifying terrestrial ecosystem carbon dynamics in the Jinsha watershed, upper Yangtze, China from 1975 to 2000.

    PubMed

    Zhao, Shuqing; Liu, Shuguang; Yin, Runsheng; Li, Zhengpeng; Deng, Yulin; Tan, Kun; Deng, Xiangzheng; Rothstein, David; Qi, Jiaguo

    2010-03-01

    Quantifying the spatial and temporal dynamics of carbon stocks in terrestrial ecosystems and carbon fluxes between the terrestrial biosphere and the atmosphere is critical to our understanding of regional patterns of carbon budgets. Here we use the General Ensemble biogeochemical Modeling System to simulate the terrestrial ecosystem carbon dynamics in the Jinsha watershed of China's upper Yangtze basin from 1975 to 2000, based on unique combinations of spatial and temporal dynamics of major driving forces, such as climate, soil properties, nitrogen deposition, and land use and land cover changes. Our analysis demonstrates that the Jinsha watershed ecosystems acted as a carbon sink during the period of 1975-2000, with an average rate of 0.36 Mg/ha/yr, primarily resulting from regional climate variation and local land use and land cover change. Vegetation biomass accumulation accounted for 90.6% of the sink, while soil organic carbon loss before 1992 led to a lower net gain of carbon in the watershed, and after that soils became a small sink. Ecosystem carbon sink/source patterns showed a high degree of spatial heterogeneity. Carbon sinks were associated with forest areas without disturbances, whereas carbon sources were primarily caused by stand-replacing disturbances. It is critical to adequately represent the detailed fast-changing dynamics of land use activities in regional biogeochemical models to determine the spatial and temporal evolution of regional carbon sink/source patterns. PMID:19296154

  18. Quantifying terrestrial ecosystem carbon dynamics in the Jinsha watershed, Upper Yangtze, China from 1975 to 2000

    USGS Publications Warehouse

    Zhao, Shuqing

    2010-01-01

    Quantifying the spatial and temporal dynamics of carbon stocks in terrestrial ecosystems and carbon fluxes between the terrestrial biosphere and the atmosphere is critical to our understanding of regional patterns of carbon budgets. Here we use the General Ensemble biogeochemical Modeling System to simulate the terrestrial ecosystem carbon dynamics in the Jinsha watershed of China’s upper Yangtze basin from 1975 to 2000, based on unique combinations of spatial and temporal dynamics of major driving forces, such as climate, soil properties, nitrogen deposition, and land use and land cover changes. Our analysis demonstrates that the Jinsha watershed ecosystems acted as a carbon sink during the period of 1975–2000, with an average rate of 0.36 Mg/ha/yr, primarily resulting from regional climate variation and local land use and land cover change. Vegetation biomass accumulation accounted for 90.6% of the sink, while soil organic carbon loss before 1992 led to a lower net gain of carbon in the watershed, and after that soils became a small sink. Ecosystem carbon sink/source patterns showed a high degree of spatial heterogeneity. Carbon sinks were associated with forest areas without disturbances, whereas carbon sources were primarily caused by stand-replacing disturbances. It is critical to adequately represent the detailed fast-changing dynamics of land use activities in regional biogeochemical models to determine the spatial and temporal evolution of regional carbon sink/source patterns.

  19. Organic carbon hidden in urban ecosystems

    PubMed Central

    Edmondson, Jill L.; Davies, Zoe G.; McHugh, Nicola; Gaston, Kevin J.; Leake, Jonathan R.

    2012-01-01

    Urbanization is widely presumed to degrade ecosystem services, but empirical evidence is now challenging these assumptions. We report the first city-wide organic carbon (OC) budget for vegetation and soils, including under impervious surfaces. Urban soil OC storage was significantly greater than in regional agricultural land at equivalent soil depths, however there was no significant difference in storage between soils sampled beneath urban greenspaces and impervious surfaces, at equivalent depths. For a typical U.K. city, total OC storage was 17.6 kg m−2 across the entire urban area (assuming 0 kg m−2 under 15% of land covered by buildings). The majority of OC (82%) was held in soils, with 13% found under impervious surfaces, and 18% stored in vegetation. We reveal that assumptions underpinning current national estimates of ecosystem OC stocks, as required by Kyoto Protocol signatories, are not robust and are likely to have seriously underestimated the contributions of urban areas. PMID:23236585

  20. Soil carbon sequestration in degraded semiarid agro-ecosystems--perils and potentials.

    PubMed

    Olsson, Lennart; Ardö, Jonas

    2002-09-01

    The Kyoto Protocol opens new possibilities for using the biosphere as a carbon sink. Using agro-ecosystems as carbon sinks may be the most appropriate practice from both environmental and socioeconomic points of view. Degraded agro-ecosystems in Africa might benefit significantly from the improved land management that would be part of a carbon sequestration program. There are vast areas of these agro-ecosystems in Africa and their rehabilitation is an urgent matter. We agree with UNEP that there are potentially important synergies to be made between the Convention on Climate Change, the UN Convention to Combat Desertification and the UN Convention on Biodiversity. In this paper, we have investigated the potential for increasing soil carbon content in semiarid agro-ecosystems in the Sudan and found that increasing fallow periods will result in increased soil carbon content and converting marginal agricultural areas to rangeland will restore the carbon levels to 80% of the natural savannah carbon levels in 100 years. The economic gain from a future carbon sequestration program has the potential of a significant contribution to the household economy in these agro-ecosystems. PMID:12436845

  1. [Seagrass ecosystems: contributions to and mechanisms of carbon sequestration].

    PubMed

    Qiu, Guang-Long; Lin, Hsing-Juh; Li, Zong-Shan; Fan, Hang-Qing; Zhou, Hao-Lang; Liu, Guo-Hua

    2014-06-01

    The ocean's vegetated habitats, in particular seagrasses, mangroves and salt marshes, each capture and store a comparable amount of carbon per year, forming the Earth's blue carbon sinks, the most intense carbon sinks on the planet. Seagrass meadows, characterized by high primary productivity, efficient water column filtration and sediment stability, have a pronounced capacity for carbon sequestration. This is enhanced by low decomposition rates in anaerobic seagrass sediments. The carbon captured by seagrass meadows contributes significantly to the total blue carbon. At a global scale, seagrass ecosystems are carbon sink hot spots and have profound influences on the global carbon cycle. This importance combined with the many other functions of seagrass meadows places them among the most valuable ecosystems in the world. Unfortunately, seagrasses are declining globally at an alarming rate owing to anthropogenic disturbances and climate change, making them also among the most threatened ecosystems on the Earth. The role of coastal systems in carbon sequestration has received far too little attention and thus there are still many uncertainties in evaluating carbon sequestration of global seagrass meadows accurately. To better assess the carbon sequestration of global seagrass ecosystems, a number of scientific issues should be considered with high priorities: 1) more accurate measurements of seagrass coverage at national and global levels; 2) more comprehensive research into species- and location-specific carbon sequestration efficiencies; 3) in-depth exploration of the effects of human disturbance and global climate change on carbon capture and storage by seagrass ecosystems. PMID:25223044

  2. Ecosystem Carbon Stocks of Intertidal Wetlands in Singapore

    NASA Astrophysics Data System (ADS)

    Phang, V. X. H.; Friess, D.; Chou, L. M.

    2014-12-01

    Mangrove forests and seagrass meadows provide numerous ecosystem services, with huge recent interest in their carbon sequestration and storage value. Mangrove forests and seagrass meadows as well as mudflats and sandbars form a continuum of intertidal wetlands, but studies that consider these spatially-linked habitats as a whole are limited. This paper presents the results of a field-based and remote sensing carbon stock assessment, including the first study of the ecosystem carbon stocks of these adjacent habitats in the tropics. Aboveground, belowground and soil organic carbon pools were quantified at Chek Jawa, an intertidal wetland in Singapore. Total ecosystem carbon stocks averaged 499 Mg C ha-1 in the mangrove forest and 140 Mg C ha-1 in the seagrass meadow. Soil organic carbon dominated the total storage in both habitats. In the adjacent mudflats and sandbars, soil organic carbon averaged 143 and 124 Mg C ha-1 respectively. High amount of carbon stored in soil demonstrate the role of intertidal wetlands in sequestering large amount of carbon in sediments accumulated over millennia. High-resolution remote sensing imagery was used to create spatial models that upscaled field-based carbon measurements to the national scale. Field-based data and spatial modeling of ecosystem carbon stocks to the entire island through remote sensing provides a large-scale and holistic carbon stock value, important for the understanding and management of these threatened intertidal ecosystems.

  3. Plant diversity effects on ecosystem evapotranspiration and carbon uptake: a controlled environment (Ecotron) and modeling approach

    NASA Astrophysics Data System (ADS)

    Milcu, Alexandru; Roy, Jacques

    2016-04-01

    Effects of species and functional diversity of plants on ecosystem evapotranspiration and carbon fluxes have been rarely assessed simultaneously. Here we present the results from an experiment that combined a lysimeter setup in a controlled environment facility (Ecotron) with large ecosystem samples/ monoliths originating from a long-term biodiversity experiment ("The Jena Experiment") and a modelling approach. We aimed at (1) quantifying the impact of plant species richness (4 vs. 16 species) on day- and night-time ecosystem water vapor fluxes and carbon uptake, (2) partitioning ecosystem evapotranspiration into evaporation and plant transpiration using the Shuttleworth and Wallace (SW) energy partitioning model, and (3) identifying the most parsimonious predictors of water vapor vapor and CO2 fluxes using plant functional trait-based metrics such as functional diversity and community weighted means. The SW model indicated that at low plant species richness, a higher proportion of the available energy was diverted to evaporation (a non-productive flux), while at higher species richness the proportion of ecosystem transpiration (a production-related water flux) increased. This led to an increased carbon gain per amount of water vapor loss (i.e. increased water use efficiency). While the LAI controlled the carbon and water fluxes, we also found that the diversity of plant functional traits, and in particular of leaf nitrogen concentration are potential important predictors of ecosystem transpiration and carbon uptake and consequently significantly contributed to increase in water use efficiency in communities with higher plant diversity.

  4. Looking skyward to study ecosystem carbon dynamics

    USGS Publications Warehouse

    Dye, Dennis G.

    2012-01-01

    Between May and October 2011 the U.S. Geological Survey (USGS), in cooperation with the U.S. Department of Energy's Atmospheric Radiation Measurement (ARM) program, conducted a field campaign at the ARM Southern Great Plains site in north central Oklahoma to evaluate a new instrument for quantitative image-based monitoring of sky conditions and solar radiation. The High Dynamic Range All-Sky Imaging System (HDR-ASIS) was developed by USGS to support studies of cloud- and aerosol-induced variability in the geometric properties of solar radiation (the sky radiance distribution) and its effects on photosynthesis and uptake of carbon dioxide (CO2) by terrestrial ecosystems. Under a clean, cloudless atmosphere when the Sun is above the horizon, most of the solar radiation reaching an area of the Earth's surface is concentrated in a beam coming directly from the Sun; a relatively small proportion arrives as diffuse radiation from the rest of the sky. Clouds and atmospheric aerosols cause increased scattering of the beam radiation, which increases the proportion of diffuse radiation at the surface.

  5. Using Radiocarbon to Test Models of Ecosystem Carbon Cycling

    NASA Astrophysics Data System (ADS)

    Trumbore, S.; Lin, H.; Randerson, J.

    2007-05-01

    The radiocarbon content of carbon stored in and respired by ecosystems provides a direct measure of ecosystem carbon dynamics that can be directly compared to model predictions. Because carbon cycles through ecosystems on a variety of timescales, the mean age of C in standing biomass and soil organic matter pools is older than the mean age of microbially respired carbon. In turn, each pathway for C transit through ecosystems my respond differently to edaphic conditions; for example, soil organic matter mean age is controlled by factors affecting stabilization of C on very long timescales, such as mineralogy, while a factor like litter quality that effects decomposition rates reflects vegetation and climate characteristics. We compare the radiocarbon signature of heterotrophically respired CO2 across a number of ecosystems with models predicted using the CASA ecosystem model. The major controls of microbially respired CO2 from ecosystems include the residence time of C in living plant pools (i.e. the age of C in litter inputs to soil) and factors that control decomposition rates (litter quality and climate). Major differences between model and measured values at low latitudes are related to how woody debris pools are treated differently in models and measurements. The time lag between photosynthesis and respiration is a key ecosystem property that defines its potential to store or release carbon given variations in annual net primary production. Radiocarbon provides a rare case where models can be directly compared with measurements to provide a test of this parameter.

  6. Ecosystem carbon dioxide fluxes after disturbance in forests of North America

    NASA Astrophysics Data System (ADS)

    Amiro, B. D.; Barr, A. G.; Barr, J. G.; Black, T. A.; Bracho, R.; Brown, M.; Chen, J.; Clark, K. L.; Davis, K. J.; Desai, A. R.; Dore, S.; Engel, V.; Fuentes, J. D.; Goldstein, A. H.; Goulden, M. L.; Kolb, T. E.; Lavigne, M. B.; Law, B. E.; Margolis, H. A.; Martin, T.; McCaughey, J. H.; Misson, L.; Montes-Helu, M.; Noormets, A.; Randerson, J. T.; Starr, G.; Xiao, J.

    2010-10-01

    Disturbances are important for renewal of North American forests. Here we summarize more than 180 site years of eddy covariance measurements of carbon dioxide flux made at forest chronosequences in North America. The disturbances included stand-replacing fire (Alaska, Arizona, Manitoba, and Saskatchewan) and harvest (British Columbia, Florida, New Brunswick, Oregon, Quebec, Saskatchewan, and Wisconsin) events, insect infestations (gypsy moth, forest tent caterpillar, and mountain pine beetle), Hurricane Wilma, and silvicultural thinning (Arizona, California, and New Brunswick). Net ecosystem production (NEP) showed a carbon loss from all ecosystems following a stand-replacing disturbance, becoming a carbon sink by 20 years for all ecosystems and by 10 years for most. Maximum carbon losses following disturbance (g C m-2y-1) ranged from 1270 in Florida to 200 in boreal ecosystems. Similarly, for forests less than 100 years old, maximum uptake (g C m-2y-1) was 1180 in Florida mangroves and 210 in boreal ecosystems. More temperate forests had intermediate fluxes. Boreal ecosystems were relatively time invariant after 20 years, whereas western ecosystems tended to increase in carbon gain over time. This was driven mostly by gross photosynthetic production (GPP) because total ecosystem respiration (ER) and heterotrophic respiration were relatively invariant with age. GPP/ER was as low as 0.2 immediately following stand-replacing disturbance reaching a constant value of 1.2 after 20 years. NEP following insect defoliations and silvicultural thinning showed lesser changes than stand-replacing events, with decreases in the year of disturbance followed by rapid recovery. NEP decreased in a mangrove ecosystem following Hurricane Wilma because of a decrease in GPP and an increase in ER.

  7. Ecosystem carbon dioxide fluxes after disturbance in forests of North America

    NASA Astrophysics Data System (ADS)

    Amiro, B. D.; Barr, A. G.; Barr, J. G.; Black, T. A.; Bracho, R.; Brown, M.; Chen, J.; Clark, K. L.; Davis, K. J.; Desai, A. R.; Dore, S.; Engel, V.; Fuentes, J. D.; Goldstein, A. H.; Goulden, M. L.; Kolb, T. E.; Lavigne, M. B.; Law, B. E.; Margolis, H. A.; Martin, T.; McCaughey, J. H.; Misson, L.; Montes-Helu, M.; Noormets, A.; Randerson, J. T.; Starr, G.; Xiao, J.

    2010-12-01

    Disturbances are important for renewal of North American forests. Here we summarize more than 180 site years of eddy covariance measurements of carbon dioxide flux made at forest chronosequences in North America. The disturbances included stand-replacing fire (Alaska, Arizona, Manitoba, and Saskatchewan) and harvest (British Columbia, Florida, New Brunswick, Oregon, Quebec, Saskatchewan, and Wisconsin) events, insect infestations (gypsy moth, forest tent caterpillar, and mountain pine beetle), Hurricane Wilma, and silvicultural thinning (Arizona, California, and New Brunswick). Net ecosystem production (NEP) showed a carbon loss from all ecosystems following a stand-replacing disturbance, becoming a carbon sink by 20 years for all ecosystems and by 10 years for most. Maximum carbon losses following disturbance (g C m-2y-1) ranged from 1270 in Florida to 200 in boreal ecosystems. Similarly, for forests less than 100 years old, maximum uptake (g C m-2y-1) was 1180 in Florida mangroves and 210 in boreal ecosystems. More temperate forests had intermediate fluxes. Boreal ecosystems were relatively time invariant after 20 years, whereas western ecosystems tended to increase in carbon gain over time. This was driven mostly by gross photosynthetic production (GPP) because total ecosystem respiration (ER) and heterotrophic respiration were relatively invariant with age. GPP/ER was as low as 0.2 immediately following stand-replacing disturbance reaching a constant value of 1.2 after 20 years. NEP following insect defoliations and silvicultural thinning showed lesser changes than stand-replacing events, with decreases in the year of disturbance followed by rapid recovery. NEP decreased in a mangrove ecosystem following Hurricane Wilma because of a decrease in GPP and an increase in ER.

  8. Seagrass ecosystems as a globally significant carbon stock

    NASA Astrophysics Data System (ADS)

    Fourqurean, James W.; Duarte, Carlos M.; Kennedy, Hilary; Marbà, Núria; Holmer, Marianne; Mateo, Miguel Angel; Apostolaki, Eugenia T.; Kendrick, Gary A.; Krause-Jensen, Dorte; McGlathery, Karen J.; Serrano, Oscar

    2012-07-01

    The protection of organic carbon stored in forests is considered as an important method for mitigating climate change. Like terrestrial ecosystems, coastal ecosystems store large amounts of carbon, and there are initiatives to protect these `blue carbon' stores. Organic carbon stocks in tidal salt marshes and mangroves have been estimated, but uncertainties in the stores of seagrass meadows--some of the most productive ecosystems on Earth--hinder the application of marine carbon conservation schemes. Here, we compile published and unpublished measurements of the organic carbon content of living seagrass biomass and underlying soils in 946 distinct seagrass meadows across the globe. Using only data from sites for which full inventories exist, we estimate that, globally, seagrass ecosystems could store as much as 19.9Pg organic carbon; according to a more conservative approach, in which we incorporate more data from surface soils and depth-dependent declines in soil carbon stocks, we estimate that the seagrass carbon pool lies between 4.2 and 8.4Pg carbon. We estimate that present rates of seagrass loss could result in the release of up to 299Tg carbon per year, assuming that all of the organic carbon in seagrass biomass and the top metre of soils is remineralized.

  9. Ecosystem Carbon Storage in Alpine Grassland on the Qinghai Plateau.

    PubMed

    Liu, Shuli; Zhang, Fawei; Du, Yangong; Guo, Xiaowei; Lin, Li; Li, Yikang; Li, Qian; Cao, Guangmin

    2016-01-01

    The alpine grassland ecosystem can sequester a large quantity of carbon, yet its significance remains controversial owing to large uncertainties in the relative contributions of climate factors and grazing intensity. In this study we surveyed 115 sites to measure ecosystem carbon storage (both biomass and soil) in alpine grassland over the Qinghai Plateau during the peak growing season in 2011 and 2012. Our results revealed three key findings. (1) Total biomass carbon density ranged from 0.04 for alpine steppe to 2.80 kg C m-2 for alpine meadow. Median soil organic carbon (SOC) density was estimated to be 16.43 kg C m-2 in alpine grassland. Total ecosystem carbon density varied across sites and grassland types, from 1.95 to 28.56 kg C m-2. (2) Based on the median estimate, the total carbon storage of alpine grassland on the Qinghai Plateau was 5.14 Pg, of which 94% (4.85 Pg) was soil organic carbon. (3) Overall, we found that ecosystem carbon density was affected by both climate and grazing, but to different extents. Temperature and precipitation interaction significantly affected AGB carbon density in winter pasture, BGB carbon density in alpine meadow, and SOC density in alpine steppe. On the other hand, grazing intensity affected AGB carbon density in summer pasture, SOC density in alpine meadow and ecosystem carbon density in alpine grassland. Our results indicate that grazing intensity was the primary contributing factor controlling carbon storage at the sites tested and should be the primary consideration when accurately estimating the carbon storage in alpine grassland. PMID:27494253

  10. Ecosystem Carbon Storage in Alpine Grassland on the Qinghai Plateau

    PubMed Central

    Liu, Shuli; Zhang, Fawei; Du, Yangong; Guo, Xiaowei; Lin, Li; Li, Yikang; Li, Qian; Cao, Guangmin

    2016-01-01

    The alpine grassland ecosystem can sequester a large quantity of carbon, yet its significance remains controversial owing to large uncertainties in the relative contributions of climate factors and grazing intensity. In this study we surveyed 115 sites to measure ecosystem carbon storage (both biomass and soil) in alpine grassland over the Qinghai Plateau during the peak growing season in 2011 and 2012. Our results revealed three key findings. (1) Total biomass carbon density ranged from 0.04 for alpine steppe to 2.80 kg C m-2 for alpine meadow. Median soil organic carbon (SOC) density was estimated to be 16.43 kg C m-2 in alpine grassland. Total ecosystem carbon density varied across sites and grassland types, from 1.95 to 28.56 kg C m-2. (2) Based on the median estimate, the total carbon storage of alpine grassland on the Qinghai Plateau was 5.14 Pg, of which 94% (4.85 Pg) was soil organic carbon. (3) Overall, we found that ecosystem carbon density was affected by both climate and grazing, but to different extents. Temperature and precipitation interaction significantly affected AGB carbon density in winter pasture, BGB carbon density in alpine meadow, and SOC density in alpine steppe. On the other hand, grazing intensity affected AGB carbon density in summer pasture, SOC density in alpine meadow and ecosystem carbon density in alpine grassland. Our results indicate that grazing intensity was the primary contributing factor controlling carbon storage at the sites tested and should be the primary consideration when accurately estimating the carbon storage in alpine grassland. PMID:27494253

  11. Integrating water and carbon fluxes at the ecosystem scale across African ecosystems

    NASA Astrophysics Data System (ADS)

    Merbold, Lutz; Brümmer, Christian; Archibald, Sally; Ardö, Jonas; Arneth, Almut; Brüggemann, Nicolas; de Grandcourt, Agnes; Kergoat, Laurent; Moffat, Antje M.; Mougin, Eric; Nouvellon, Yann; Saint-Andre, Laurent; Saunders, Matthew; Scholes, Robert J.; Veenendaal, Elmar; Kutsch, Werner L.

    2013-04-01

    In this study we report on water and carbon dioxide fluxes, measured using the eddy covariance (EC) technology, from different ecosystems in Sub-Saharan Africa. These sites differed in ecosystem type (C3 plant dominated woodlands to C4 plant dominated grass savannas) and covered the very dry regions of the Sahel (250 mm rainfall, Sudan), the tropical areas in Central Africa (1650 mm in Uganda) further south to the subtropical areas in Botswana, Zambia and South Africa (400-900 mm in precipitation). The link between water and carbon dioxide fluxes were evaluated for time periods (see also the corresponding abstract by Bruemmer et al.) without water limitation during the peak growing season. Our results show that plant stomata control ecosystem scale water and carbon dioxide fluxes and mediate between plant growth and plant survival. On continental scale, this switch between maximizing carbon uptake and minimizing water losses, from here on called the "Carbon-Water-Tipping Point" was positively correlated to the mean annual growing season temperature at each site. Even though similar responses of plants were shown at the individual leaf-level scale this has to our knowledge not yet been shown at the ecosystem scale further suggesting a long-term adaptation of the complete ecosystems to certain climatic regions. It remains unclear how this adaption will influence the ecosystem response to ongoing climate change and according temperature increases and changes in precipitation.

  12. Carbon dynamics and sequestration in urban turfgrass ecosystems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Urbanization is a global trend. Turfgrass covers 1.9% of land in the continental US. Here we review existing literature associated with carbon (C) pools, sequestration, and nitrous oxide emission of urban turfgrass ecosystems. Turfgrasses exhibit significant carbon sequestration (0.34–1.4 Mg ha-1 ye...

  13. Leaf conductance and carbon gain under salt-stressed conditions

    NASA Astrophysics Data System (ADS)

    Volpe, V.; Manzoni, S.; Marani, M.; Katul, G.

    2011-12-01

    Exposure of plants to salt stress is often accompanied by reductions in leaf photosynthesis and in stomatal and mesophyll conductances. To separate the effects of salt stress on these quantities, a model based on the hypothesis that carbon gain is maximized subject to a water loss cost is proposed. The optimization problem of adjusting stomatal aperture for maximizing carbon gain at a given water loss is solved for both a non-linear and a linear biochemical demand function. A key novel theoretical outcome of the optimality hypothesis is an explicit relationship between the stomatal and mesophyll conductances that can be evaluated against published measurements. The approaches here successfully describe gas-exchange measurements reported for olive trees (Olea europea L.) and spinach (Spinacia oleraceaL.) in fresh water and in salt-stressed conditions. Salt stress affected both stomatal and mesophyll conductances and photosynthetic efficiency of both species. The fresh water/salt water comparisons show that the photosynthetic capacity is directly reduced by 30%-40%, indicating that reductions in photosynthetic rates under increased salt stress are not due only to a limitation of CO2diffusion. An increase in salt stress causes an increase in the cost of water parameter (or marginal water use efficiency) exceeding 100%, analogous in magnitude to findings from extreme drought stress studies. The proposed leaf-level approach can be incorporated into physically based models of the soil-plant-atmosphere system to assess how saline conditions and elevated atmospheric CO2 jointly impact transpiration and photosynthesis.

  14. Ecosystem-Level Carbon Stocks in Costa Rican Mangrove Forests

    NASA Astrophysics Data System (ADS)

    Cifuentes, M.

    2012-12-01

    Tropical mangroves provide a wide variety of ecosystem services, including atmospheric carbon sequestration. Because of their high rates of carbon accumulation, the large expected size of their total stocks (from 2 to 5 times greater than those of upland tropical forests), and the alarming rates at which they are being converted to other uses (releasing globally from 0.02 to 0.12 Pg C yr-1), mangroves are receiving increasing attention as additional tools to mitigate climate change. However, data on whole ecosystem-level carbon in tropical mangroves is limited. Here I present the first estimate of ecosystem level carbon stocks in mangrove forests of Central America. I established 28, 125 m-long, sampling transects along the 4 main rivers draining the Térraba-Sierpe National Wetland in the southern Pacific coast of Costa Rica. This area represents 39% of all remaining mangroves in the country (48300 ha). A circular nested plot was placed every 25 m along each transect. Carbon stocks of standing trees, regeneration, the herbaceous layer, litter, and downed wood were measured following internationally-developed methods compatible with IPCC "Good Practice Guidelines". In addition, total soil carbon stocks were determined down to 1 m depth. Together, these carbon estimates represent the ecosystem-carbon stocks of these forests. The average aboveground carbon stocks were 72.5 ± 3.2 MgC ha-1 (range: 9 - 241 MgC ha-1), consistent with results elsewhere in the world. Between 74 and 92% of the aboveground carbon is stored in trees ≥ 5cm dbh. I found a significant correlation between basal area of trees ≥ 5cm dbh and total aboveground carbon. Soil carbon stocks to 1 m depth ranged between 141 y 593 MgC ha-1. Ecosystem-level carbon stocks ranged from 391 MgC ha-1 to 438 MgC ha-1, with a slight increase from south to north locations. Soil carbon stocks represent an average 76% of total ecosystem carbon stocks, while trees represent only 20%. These Costa Rican mangroves

  15. Influence of the Tussock Growth Form on Arctic Ecosystem Carbon Stocks

    NASA Astrophysics Data System (ADS)

    Curasi, S.; Rocha, A. V.; Sonnentag, O.; Wullschleger, S. D.; Myers-Smith, I. H.; Fetcher, N.; Mack, M. C.; Natali, S.; Loranty, M. M.; Parker, T.

    2015-12-01

    The influence of plant growth forms on ecosystem carbon (C) cycling has been under appreciated. In arctic tundra, environmental factors and plant traits of the sedge Eriophorum vaginatum cause the formation of mounds that are dense amalgamations of belowground C called tussocks. Tussocks have important implications for arctic ecosystem biogeochemistry and C stocks, but the environmental and biological factors controlling their size and distribution across the landscape are poorly understood. In order to better understand how landscape variation in tussock size and density impact ecosystem C stocks, we formed the Carbon in Arctic Tussock Tundra (CATT) network and recruited an international team to sample locations across the arctic. The CATT network provided a latitudinal and longitudinal gradient along which to improve our understanding of tussocks' influence on ecosystem structure and function. CATT data revealed important insights into tussock formation across the arctic. Tussock density generally declined with latitude, and tussock size exhibited substantial variation across sites. The relationship between height and diameter was similar across CATT sites indicating that both biological and environmental factors control tussock formation. At some sites, C in tussocks comprised a substantial percentage of ecosystem C stocks that may be vulnerable to climate change. It is concluded that the loss of this growth form would offset C gains from projected plant functional shifts from graminoid to shrub tundra. This work highlights the role of plant growth forms on the magnitude and retention of ecosystem C stocks.

  16. Sustainable carbon uptake - important ecosystem service within sustainable forest management

    NASA Astrophysics Data System (ADS)

    Zorana Ostrogović Sever, Maša; Anić, Mislav; Paladinić, Elvis; Alberti, Giorgio; Marjanović, Hrvoje

    2016-04-01

    Even-aged forest management with natural regeneration under continuous cover (i.e. close to nature management) is considered to be sustainable regarding the yield, biodiversity and stability of forest ecosystems. Recently, in the context of climate change, there is a raising question of sustainable forest management regarding carbon uptake. Aim of this research was to explore whether current close to nature forest management approach in Croatia can be considered sustainable in terms of carbon uptake throughout the life-time of Pedunculate oak forest. In state-owned managed forest a chronosequence experiment was set up and carbon stocks in main ecosystem pools (live biomass, dead wood, litter and mineral soil layer), main carbon fluxes (net primary production, soil respiration (SR), decomposition) and net ecosystem productivity were estimated in eight stands of different age (5, 13, 38, 53, 68, 108, 138 and 168 years) based on field measurements and published data. Air and soil temperature and soil moisture were recorded on 7 automatic mini-meteorological stations and weekly SR measurements were used to parameterize SR model. Carbon balance was estimated at weekly scale for the growing season 2011 (there was no harvesting), as well as throughout the normal rotation period of 140 years (harvesting was included). Carbon stocks in different ecosystem pools change during a stand development. Carbon stocks in forest floor increase with stand age, while carbon stocks in dead wood are highest in young and older stands, and lowest in middle-aged, mature stands. Carbon stocks in mineral soil layer were found to be stable across chronosequence with no statistically significant age-dependent trend. Pedunculate Oak stand, assuming successful regeneration, becomes carbon sink very early in a development phase, between the age of 5 and 13 years, and remains carbon sink even after the age of 160 years. Greatest carbon sink was reached in the stand aged 53 years. Obtained results

  17. Present and Future Carbon Balance of Russia's Northern Ecosystems. Final report

    SciTech Connect

    Chapin, F. Stuart III; Zimov, Sergei A.

    2000-08-28

    Recent increases in the seasonal amplitude of atmospheric CO{sub 2} at high latitudes suggest a widespread biospheric response to high-latitude warming. We have shown that the seasonal amplitude of net ecosystem carbon exchange by northern Siberian ecosystems is greater in disturbed than undisturbed sites, due to increased summer influx and increased winter efflux. Net carbon gain in summer and respiration in winter were greater in a cool than in a warm year, especially in disturbed sites and did not differ between high-arctic and treeline sites, suggesting that high-latitude warming, if it occurred, would have little effect or would reduce seasonal amplitude of carbon exchange. We suggest that increased disturbance contributes significantly to the amplified seasonal cycle of atmospheric CO{sub 2} at high latitudes.

  18. Observing terrestrial ecosystems and the carbon cycle from space

    SciTech Connect

    Schimel, David; Pavlick, Ryan; Fisher, Joshua B.; Asner, Gregory P.; Saatchi, Sassan; Townsend, Philip; Miller, Charles E.; Frankenberg, Christian; Hibbard, Kathleen A.; Cox, Peter

    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 time 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.

  19. Global simulation of the carbon isotope exchange of terrestrial ecosystems

    NASA Astrophysics Data System (ADS)

    Ito, A.; Terao, Y.; Mukai, H.

    2009-12-01

    There remain large uncertainties in our quantification of global carbon cycle, which has close interactions with the climate system and is subject to human-induced global environmental change. Information on carbon isotopes is expected to reduce the uncertainty by providing additional constraints on net atmosphere-ecosystem exchange. This study attempted to simulate the dynamics of carbon isotopes at the global scale, using a process-based terrestrial ecosystem model: Vegetation Integrative SImulator for Trace gases (VISIT). The base-model of carbon cycle (Sim-CYCLE, Ito 2003) has already considered stable carbon isotope composition (13C/12C), and here radioactive carbon isotope (14C) was included. The isotope ratios characterize various aspects of terrestrial carbon cycle, which is difficult to be constrained by sole mass balance. For example, isotopic discrimination by photosynthetic assimilation is closely related with leaf stomatal conductance and composition of C3 and C4 plant in grasslands. Isotopic disequilibrium represents mean residence time of terrestrial carbon pools. In this study, global simulations (spatial resolution 0.5-deg, time-step 1-month) were conducted during the period 1901 to 2100 on the basis of observed and projected atmospheric CO2, climate, and land-use conditions. As anthropogenic CO2 accumulates in the atmosphere, heavier stable carbon isotope (13C) was diluted, while radioactive carbon isotope (14C) is strongly affected by atomic bomb experiments mainly in the 1950s and 1960s. The model simulated the decadal change in carbon isotope compositions. Leaf carbon with shorter mean residence time responded rapidly to the atmospheric change, while plant stems and soil humus showed substantial time-lag, leading to large isotopic disequilibrium. In the future, the isotopic disequilibrium was estimated to augment, due to accelerated rate of anthropogenic CO2 accumulation. Spatial distribution of stable isotope composition (12C/13C, or d13C) was

  20. Ecosystem carbon-water interactions of tropical pasture and afforestation

    NASA Astrophysics Data System (ADS)

    Wolf, S.; Eugster, W.; Buchmann, N.

    2010-12-01

    Despite the importance of tropical ecosystems for global carbon and water cycling, eddy covariance flux measurements in the tropics are still scarce and globally underrepresented within FLUXNET. In addition, previous studies have been predominantly conducted in tropical forests with only very few observations, often unpublished, from other tropical land-use types like pastures, croplands and savannas. As recently emphasized by global synthesis activities, C4 dominated ecosystems account for more than 20 % of terrestrial gross primary production (GPP) but represent less than 20 site-years of data within FLUXNET. Consequently, an expansion of observations for tropical C4 ecosystems is needed to understand their role in the global carbon and water cycling. We have performed comparative eddy covariance measurements of carbon dioxide and water vapour fluxes in a tropical pasture and an adjacent, young afforestation in Panama from 2007 to 2009. Our results show a larger intra-annual variability of CO2 and H2O fluxes at the pasture compared to the afforestation. In addition, the tropical pasture was more sensitive to water limitations and seasonal drought. Moreover, observed differences in water use efficiency (WUE) between both ecosystems tend to become smaller after the establishment phase of the afforestation. Our results highlight the role of land management on ecosystem carbon and water fluxes in the tropics. Implications of our results for further research and synthesis activities will be discussed.

  1. Soil carbon sensitivity to temperature and carbon use efficiency compared across microbial-ecosystem models of varying complexity

    SciTech Connect

    Li, Jianwei; Wang, Gangsheng; Allison, Steven D.; Mayes, Melanie; Luo, Yiqi

    2014-01-01

    Global ecosystem models may require microbial components to accurately predict feedbacks between climate warming and soil decomposition, but it is unclear what parameters and levels of complexity are ideal for scaling up to the globe. Here we conducted a model comparison using a conventional model with first-order decay and three microbial models of increasing complexity that simulate short- to long-term soil carbon dynamics. We focused on soil carbon responses to microbial carbon use efficiency (CUE) and temperature. Three scenarios were implemented in all models: constant CUE (held at 0.31), varied CUE ( 0.016 C 1), and 50 % acclimated CUE ( 0.008 C 1). Whereas the conventional model always showed soil carbon losses with increasing temperature, the microbial models each predicted a temperature threshold above which warming led to soil carbon gain. The location of this threshold depended on CUE scenario, with higher temperature thresholds under the acclimated and constant scenarios. This result suggests that the temperature sensitivity of CUE and the structure of the soil carbon model together regulate the long-term soil carbon response to warming. Equilibrium soil carbon stocks predicted by the microbial models were much less sensitive to changing inputs compared to the conventional model. Although many soil carbon dynamics were similar across microbial models, the most complex model showed less pronounced oscillations. Thus, adding model complexity (i.e. including enzyme pools) could improve the mechanistic representation of soil carbon dynamics during the transient phase in certain ecosystems. This study suggests that model structure and CUE parameterization should be carefully evaluated when scaling up microbial models to ecosystems and the globe.

  2. Infrared sensors to map soil carbon in agricultural ecosystems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Rapid methods of measuring soil carbon such as near-infrared (NIR) and mid-infrared (MIR) diffuse reflectance spectroscopy have gained interest but problems of accurate and precise measurement still persist resulting from the high spatial variability of soil carbon within agricultural landscapes. T...

  3. Spring Hydrology Determines Summer Net Carbon Uptake in Northern Ecosystems

    NASA Technical Reports Server (NTRS)

    Yi, Yonghong; Kimball, John; Reichle, Rolf H.

    2014-01-01

    Increased photosynthetic activity and enhanced seasonal CO2 exchange of northern ecosystems have been observed from a variety of sources including satellite vegetation indices (such as the Normalized Difference Vegetation Index; NDVI) and atmospheric CO2 measurements. Most of these changes have been attributed to strong warming trends in the northern high latitudes (greater than or equal to 50N). Here we analyze the interannual variation of summer net carbon uptake derived from atmospheric CO2 measurements and satellite NDVI in relation to surface meteorology from regional observational records. We find that increases in spring precipitation and snow pack promote summer net carbon uptake of northern ecosystems independent of air temperature effects. However, satellite NDVI measurements still show an overall benefit of summer photosynthetic activity from regional warming and limited impact of spring precipitation. This discrepancy is attributed to a similar response of photosynthesis and respiration to warming and thus reduced sensitivity of net ecosystem carbon uptake to temperature. Further analysis of boreal tower eddy covariance CO2 flux measurements indicates that summer net carbon uptake is positively correlated with early growing-season surface soil moisture, which is also strongly affected by spring precipitation and snow pack based on analysis of satellite soil moisture retrievals. This is attributed to strong regulation of spring hydrology on soil respiration in relatively wet boreal and arctic ecosystems. These results document the important role of spring hydrology in determining summer net carbon uptake and contrast with prevailing assumptions of dominant cold temperature limitations to high-latitude ecosystems. Our results indicate potentially stronger coupling of boreal/arctic water and carbon cycles with continued regional warming trends.

  4. Management and fertility control ecosystem carbon allocation to biomass production

    NASA Astrophysics Data System (ADS)

    Campioli, Matteo; Vicca, Sara; Janssens, Ivan

    2015-04-01

    Carbon (C) allocation within the ecosystem is one of the least understood processes in plant- and geo-sciences. The proportion of the C assimilated through photosynthesis (gross primary production, GPP) that is used for biomass production (BP) is a key variable of the C allocation process and it has been termed as biomass production efficiency (BPE). We investigated the potential drivers of BPE using a global dataset of BP, GPP, BPE and ancillary ecosystem characteristics (vegetation properties, climatic and environmental variables, anthropogenic impacts) for 131 sites comprising six major ecosystem types: forests, grasslands, croplands, tundra, boreal peatlands and marshes. We obtained two major findings. First, site fertility is the key driver of BPE across forests, with nutrient-rich forests allocating 58% of their photosynthates to BP, whereas this fraction is only 42% for nutrient-poor forests. Second, by disentangling the effect of management from the effect of fertility and by integrating all ecosystem types, we observed that BPE is globally not driven by the 'natural' site fertility, but by the positive effect brought by management on the nutrient availability. This resulted in managed ecosystems having substantially larger BPE than natural ecosystems. These findings will crucially improve our elucidation of the human impact on ecosystem functioning and our predictions of the global C cycle.

  5. Endogenous circadian regulation of carbon dioxide exchange in terrestrial ecosystems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We tested the hypothesis that diurnal changes in terrestrial CO2 exchange are driven exclusively by the direct effect of the physical environment on plant physiology. We failed to corroborate this assumption, finding instead large diurnal fluctuations in whole ecosystem carbon assimilation across a ...

  6. Soil carbon sequestration: Quantifying this ecosystem service

    EPA Science Inventory

    Soils have a crucial role in supplying many goods and services that society depends upon on a daily basis. These include food and fiber production, water cleansing and supply, nutrient cycling, waste isolation and degradation. Soils also provide a significant amount of carbon s...

  7. Technical Report: Investigation of Carbon Cycle Processes within a Managed Landscape: An Ecosystem Manipulation and Isotope Tracer Approach

    SciTech Connect

    Griffis, Timothy J; Baker, John M; Billmark, Kaycie

    2009-06-01

    The goal of this research is to provide a better scientific understanding of carbon cycle processes within an agricultural landscape characteristic of the Upper Midwest. This project recognizes the need to study processes at multiple spatial and temporal scales to reduce uncertainty in ecosystem and landscape-scale carbon budgets to provide a sound basis for shaping future policy related to carbon management. Specifically, this project has attempted to answer the following questions: 1. Would the use of cover crops result in a shift from carbon neutral to significant carbon gain in corn-soybean rotation ecosystems of the Upper Midwest? 2. Can stable carbon isotope analyses be used to partition ecosystem respiration into its autotrophic and heterotrophic components? 3. Can this partitioning be used to better understand the fate of crop residues to project changes in the soil carbon reservoir? 4. Are agricultural ecosystems of the Upper Midwest carbon neutral, sinks, or sources? Can the proposed measurement and modeling framework help address landscape-scale carbon budget uncertainties and help guide future carbon management policy?

  8. Contrasting responses of shrubland carbon gain and soil carbon efflux to drought and warming across a European climate gradient

    NASA Astrophysics Data System (ADS)

    Reinsch, Sabine; Koller, Eva; Sowerby, Alwyn; de Dato, Giovanbattista; Estiarte, Marc; Guidolotti, Gabriele; Kovács-Láng, Edit; Kröel-Dulay, György; Lellei-Kovács, Eszter; Larsen, Klaus S.; Liberati, Dario; Penuelas, Josep; Ransijn, Johannes; Schmidt, Inger K.; Smith, Andrew R.; Tietema, Albert; Dukes, Jeffrey S.; Emmett, Bridget A.

    2016-04-01

    Understanding the relationship between above- and belowground processes is crucial if we are to forecast feedbacks between terrestrial carbon (C) dynamics and future climate. To test if climate-induced changes in annual aboveground net primary productivity (aNPP) will drive changes in C loss by soil respiration (Rs), we integrated data across a European temperature and precipitation gradient. For over a decade, six European shrublands were exposed to repeated drought (-30 % annual rain) during the plants' growth season or year-round night-time warming (+1.5 oC), using an identical experimental approach. As a result, drought reduced ecosystem C gain via aNPP by 0-25 % (compared to an untreated control) with the lowest C gain in warm-dry sites and highest in wet-cold sites (R2=0.078, p-value = 0.544, slope = 14.35 %). In contrast, drought induced C loss via Rs was of a lower magnitude (10-20 %) and was most pronounced in warm-dry sites compared to wet-cold sites (R2=0.687, p-value = 0.131, slope = 7.86 %). This suggests that belowground activity (microbes and roots) is stabilizing ecosystem processes and functions in terms of C storage. However, when the drought treatment permanently altered the soil structure at our hydric site, indicating we had exceeded the resilience of the system, the ecosystem C gain was no longer predictable from current (linear) relationships. Results from the warming treatment were generally of lower magnitude and of opposing direction compared to the drought treatment, indicating different mechanisms were driving ecosystem responses. Overall, our results suggest that aNPP is less sensitive than Rs to climate stresses and soil respiration C fluxes are not predictable from changes in plant productivity. Drought and warming effects on aNPP and Rs did not weaken over decadal timescales at larger, continental scales if no catastrophic threshold is passed. However, indirect effects of climate change on soil properties and/or microbial communities

  9. Carbon and nitrogen isotope studies in an arctic ecosystem

    SciTech Connect

    Schell, D.M.

    1989-12-31

    This proposal requests funding for the completion of our current ecological studies at the MS-117 research site at Toolik Lake, Alaska. We have been using a mix of stable and radioisotope techniques to assess the fluxes of carbon and nitrogen within the ecosystem and the implications for long-term carbon storage or loss from the tundra. Several tentative conclusions have emerged from our study including: Tundra in the foothills is no longer accumulating carbon. Surficial radiocarbon abundances show little or no accumulation since 1000--2500 yrs BP. Coastal plain tundra is still accumulating carbon, but the rate of accumulation has dropped in the last few thousand years. Carbon export from watersheds in the Kuparuk and Imnavait Creek drainages are in excess of that expected from estimated primary productivity; and Nitrogen isotope abundances vary between species of plants and along hydrologic gradients.

  10. Carbon and nitrogen isotope studies in an arctic ecosystem

    SciTech Connect

    Schell, D.M.

    1989-01-01

    This proposal requests funding for the completion of our current ecological studies at the MS-117 research site at Toolik Lake, Alaska. We have been using a mix of stable and radioisotope techniques to assess the fluxes of carbon and nitrogen within the ecosystem and the implications for long-term carbon storage or loss from the tundra. Several tentative conclusions have emerged from our study including: Tundra in the foothills is no longer accumulating carbon. Surficial radiocarbon abundances show little or no accumulation since 1000--2500 yrs BP. Coastal plain tundra is still accumulating carbon, but the rate of accumulation has dropped in the last few thousand years. Carbon export from watersheds in the Kuparuk and Imnavait Creek drainages are in excess of that expected from estimated primary productivity; and Nitrogen isotope abundances vary between species of plants and along hydrologic gradients.

  11. Climate, carbon cycling, and deep-ocean ecosystems

    PubMed Central

    Smith, K. L.; Ruhl, H. A.; Bett, B. J.; Billett, D. S. M.; Lampitt, R. S.; Kaufmann, R. S.

    2009-01-01

    Climate variation affects surface ocean processes and the production of organic carbon, which ultimately comprises the primary food supply to the deep-sea ecosystems that occupy ≈60% of the Earth's surface. Warming trends in atmospheric and upper ocean temperatures, attributed to anthropogenic influence, have occurred over the past four decades. Changes in upper ocean temperature influence stratification and can affect the availability of nutrients for phytoplankton production. Global warming has been predicted to intensify stratification and reduce vertical mixing. Research also suggests that such reduced mixing will enhance variability in primary production and carbon export flux to the deep sea. The dependence of deep-sea communities on surface water production has raised important questions about how climate change will affect carbon cycling and deep-ocean ecosystem function. Recently, unprecedented time-series studies conducted over the past two decades in the North Pacific and the North Atlantic at >4,000-m depth have revealed unexpectedly large changes in deep-ocean ecosystems significantly correlated to climate-driven changes in the surface ocean that can impact the global carbon cycle. Climate-driven variation affects oceanic communities from surface waters to the much-overlooked deep sea and will have impacts on the global carbon cycle. Data from these two widely separated areas of the deep ocean provide compelling evidence that changes in climate can readily influence deep-sea processes. However, the limited geographic coverage of these existing time-series studies stresses the importance of developing a more global effort to monitor deep-sea ecosystems under modern conditions of rapidly changing climate. PMID:19901326

  12. Estimating net ecosystem exchange of carbon using the normalized difference vegetation index and an ecosystem model

    SciTech Connect

    Veroustraete, F.; Patyn, J.; Myneni, R.B.

    1996-10-01

    The evaluation and prediction of changes in carbon dynamics at the ecosystem level is a key issue in studies of global change. An operational concept for the determination of carbon fluxes for the Belgian territory is the goal of the presented study. The approach is based on the integration of remotely sensed data into ecosystem models in order to evaluate photosynthetic assimilation and net ecosystem exchange (NEE). Remote sensing can be developed as an operational tool to determine the fraction of absorbed photosynthetically active radiation (fPAR). A review of the methodological approach of mapping fPAR dynamics at the regional scale by means of NOAA11-AVHRR/2 data for the year 1990 is given. The processing sequence from raw radiance values to fPAR is presented. An interesting aspect of incorporating remote sensing derived fPAR in ecosystem models is the potential for modeling actual as opposed to potential vegetation. Further work should prove whether the concepts presented and the assumptions made in this study are valid.

  13. Assessing Effects of Rising Carbon Dioxide Levels on Ocean Ecosystems

    NASA Astrophysics Data System (ADS)

    Lance, Veronica P.

    2009-07-01

    Carbon Productivity Responses to Increased Dissolved Inorganic Carbon Concentrations in Surface Ocean: Exploring the Feasibility of an in Situ Mesoscale Carbon Addition Experiment; Palisades, New York, 23-24 March 2009; To assess the effects of future elevated carbon dioxide (CO2) levels on ocean biogeochemistry and ecosystems, it is desirable to mimic such an environment in nature. A workshop to explore an in situ open ocean mesoscale CO2 perturbation experiment that would simulate the oceanic conditions expected toward the end of this century was held at Lamont-Doherty Earth Observatory at Columbia University (LDEO). The objectives were to evaluate the current understanding of the potential effects on open ocean ecosystems and biogeochemical cycling resulting from carbon chemistry and pH changes in response to increased atmospheric partial pressure of carbon dioxide (pCO2) and to examine the scientific justification and logistical feasibility of an in situ open ocean mesoscale CO2/pH perturbation experiment. The 15 participants represented fields of modeling and physical, geochemical, and biological oceanography.

  14. Influence of the Asian monsoon on net ecosystem carbon exchange in two major ecosystems in Korea

    NASA Astrophysics Data System (ADS)

    Kwon, H.; Kim, J.; Hong, J.; Lim, J.-H.

    2010-05-01

    Considering the feedback in radiation, temperature, and soil moisture with alterations in rainfall patterns, the influence of the changing monsoon on Net Ecosystem CO2 Exchange (NEE) can be critical to the estimation of carbon balance in Asia. In this paper, we examined CO2 fluxes measured by the eddy covariance method from 2004 to 2008 in two major ecosystems in the KoFlux sites in Korea, i.e., the Gwangneung Deciduous forest (GDK) and the Haenam Farmland (HFK). Our objectives were to identify the repeatability of the mid-season depression of NEE encountered at the two sites based on the single-year observation, and to further scrutinize its cause, effect, and interannual variability by using multi-year observations. In both GDK and HFK sites, the mid-season depression of NEE was reproduced each year but with different timing, magnitude, and mechanism. At the GDK site, a predominant factor causing the mid-season depression was a decreased solar radiation and the consequent reduction in Gross Primary Productivity (GPP) during the summer monsoon period. At the HFK site, however, the monsoonal effect was less pronounced and the apparent mid-season depression was mainly a result of the management practices such as cultivation of spring barley and rice transplantation. Other flux observation sites in East Asia also showed a decline in radiation but with a lesser degree during the monsoon season, resulting in less pronounced depression in NEE. In our study, the observed depressions in NEE caused both GDK and HFK sites to become a weaker carbon sink or even a source in the middle of the growing season. On average, the GDK site (with maximum leaf area index of ~5) was a weak carbon sink with NEE of -84 gC m-2 y-1. Despite about 20% larger GPP (of 1321 gC m-2y-1) in comparison with the GDK site, the HFK site (with maximum leaf area index of 3-4) was a weaker carbon sink with NEE of -58 gC m-2 y-1 because of greater ecosystem respiration (of 1263 gC m-2 y-1). These NEE

  15. Organic carbon flow in a swamp-stream ecosystem

    SciTech Connect

    Mulholland, P.J.

    1981-01-01

    An annual organic carbon budget is presented for an 8-km segment of Creeping Swamp, an undisturbed, third-order swamp-stream in the Coastal Plain of North Carolina, USA. Annual input of organic carbon (588 gC/m/sup 2/) was 96% allochthonous and was dominated by leaf litter inputs (36%) and fluvial, dissolved organic carbon (DOC) inputs (31%). Although the swamp-stream was primarily heterotrophic, autochthonous organic carbon input, primarily from filamentous algae, was important during February and March when primary production/ecosystem respiration (P/R) ratios of the flooded portions were near one. Annual output of organic carbon via fluvial processes (214 gC/m/sup 2/), 95% as DOC, was 36% of total annual inputs, indicating that the swamp-stream segment ecosystem was 64% efficient at retaining organic carbon. Organic carbon dynamics in the Creeping Swamp segment were compared to those reported for upland stream segments using indices of organic matter processing suggested by Fisher (1977) and a loading potential index suggested here. Creeping Swamp, while loading at a high rate, retains a much larger portion of its organic carbon inputs than two upland streams. Despite the high degree of retention and oxidation of organic inputs to Creeping Swamp, there is a net annual fluvial export of 21 gC/m/sup 2/, mostly in the dissolved form. Watersheds drained by swamp-streams in the southeastern United States are thought to have large organic carbon exports compared to upland forested drainages, because the stream network covers a much greater proportion of the total watershed area.

  16. Carbon dioxide budget in a temperature grassland ecosystem

    NASA Technical Reports Server (NTRS)

    Kim, Joon; Verma, Shashi B.; Clement, Robert J.

    1992-01-01

    Eddy correlation measurements of CO2 flux made during May-October 1987 and June-August 1989 were employed, in conjunction with simulated data, to examine the net exchange of CO2 in a temperature grassland ecosystem. Simulated estimates of CO2 uptake were used when flux measurements were not available. These estimates were based on daily intercepted photosynthetically active radiation, air temperature, and extractable soil water. Soil CO2 flux and dark respiration of the aerial part of plants were estimated using the relationships developed by Norman et al. (1992) and Polley et al. (1992) at the study site. The results indicate that the CO2 exchange between this ecosystem and the atmosphere is highly variable. The net ecosystem CO2 exchange reached its peak value (12-18 g/sq m d) during the period when the leaf area index was maximum. Drought, a frequent occurrence in this region, can change this ecosystem from a sink to a source for atmospheric CO2. Comparison with data on dry matter indicated that the aboveground biomass accounted for about 45-70 percent of the net carbon uptake, suggesting the importance of the below ground biomass in estimating net primary productivity in this ecosystem.

  17. Biomass carbon pool of forest ecosystems and carbon-containing gas emission from biomass burning in China

    SciTech Connect

    Xiaoke Wang; Yahui Zhuang; Zongwei Feng

    1997-12-31

    With the increasing study on global climatic change, scientists have paid more attention to the role of forest ecosystem in global carbon cycle, especially to the uncertainty of atmospheric carbon source and sink involved in forest ecosystems. However, to date it is lack of the information of forest carbon cycle in China for many studies of global carbon cycle. By investigations of forest ecosystem biomass and experiment of chamber combustion, in this paper it was estimated that the carbon pool of forest ecosystem and the carbon-containing gases released from forest biomass burning in China.

  18. Convergent Evolution towards High Net Carbon Gain Efficiency Contributes to the Shade Tolerance of Palms (Arecaceae)

    PubMed Central

    Ma, Ren-Yi; Zhang, Jiao-Lin; Cavaleri, Molly A.; Sterck, Frank; Strijk, Joeri S.; Cao, Kun-Fang

    2015-01-01

    Most palm species occur in the shaded lower strata of tropical rain forests, but how their traits relate to shade adaptation is poorly understood. We hypothesized that palms are adapted to the shade of their native habitats by convergent evolution towards high net carbon gain efficiency (CGEn), which is given by the maximum photosynthetic rate to dark respiration rate ratio. Leaf mass per area, maximum photosynthetic rate, dark respiration and N and P concentrations were measured in 80 palm species grown in a common garden, and combined with data of 30 palm species growing in their native habitats. Compared to other species from the global leaf economics data, dicotyledonous broad-leaved trees in tropical rainforest or other monocots in the global leaf economics data, palms possessed consistently higher CGEn, achieved by lowered dark respiration and fairly high foliar P concentration. Combined phylogenetic analyses of evolutionary signal and trait evolution revealed convergent evolution towards high CGEn in palms. We conclude that high CGEn is an evolutionary strategy that enables palms to better adapt to shady environments than coexisting dicot tree species, and may convey advantages in competing with them in the tropical forest understory. These findings provide important insights for understanding the evolution and ecology of palms, and for understanding plant shade adaptations of lower rainforest strata. Moreover, given the dominant role of palms in tropical forests, these findings are important for modelling carbon and nutrient cycling in tropical forest ecosystems. PMID:26461108

  19. Convergent Evolution towards High Net Carbon Gain Efficiency Contributes to the Shade Tolerance of Palms (Arecaceae).

    PubMed

    Ma, Ren-Yi; Zhang, Jiao-Lin; Cavaleri, Molly A; Sterck, Frank; Strijk, Joeri S; Cao, Kun-Fang

    2015-01-01

    Most palm species occur in the shaded lower strata of tropical rain forests, but how their traits relate to shade adaptation is poorly understood. We hypothesized that palms are adapted to the shade of their native habitats by convergent evolution towards high net carbon gain efficiency (CGEn), which is given by the maximum photosynthetic rate to dark respiration rate ratio. Leaf mass per area, maximum photosynthetic rate, dark respiration and N and P concentrations were measured in 80 palm species grown in a common garden, and combined with data of 30 palm species growing in their native habitats. Compared to other species from the global leaf economics data, dicotyledonous broad-leaved trees in tropical rainforest or other monocots in the global leaf economics data, palms possessed consistently higher CGEn, achieved by lowered dark respiration and fairly high foliar P concentration. Combined phylogenetic analyses of evolutionary signal and trait evolution revealed convergent evolution towards high CGEn in palms. We conclude that high CGEn is an evolutionary strategy that enables palms to better adapt to shady environments than coexisting dicot tree species, and may convey advantages in competing with them in the tropical forest understory. These findings provide important insights for understanding the evolution and ecology of palms, and for understanding plant shade adaptations of lower rainforest strata. Moreover, given the dominant role of palms in tropical forests, these findings are important for modelling carbon and nutrient cycling in tropical forest ecosystems. PMID:26461108

  20. Changes in the Carbon Cycle of Amazon Ecosystems During the 2010 Drought

    NASA Technical Reports Server (NTRS)

    Potter, Christophera; Klooster, Steven; Hiatt, Cyrus; Genovese, Vanessa; Castilla-Rubino, Juan Carlos

    2011-01-01

    Satellite remote sensing was combined with the NASA-CASA carbon cycle simulation model to evaluate the impact of the 2010 drought (July through September) throughout tropical South America. Results indicated that net primary production (NPP) in Amazon forest areas declined by an average of 7% in 2010 compared to 2008. This represented a loss of vegetation CO2 uptake and potential Amazon rainforest growth of nearly 0.5 Pg C in 2010. The largest overall decline in ecosystem carbon gains by land cover type was predicted for closed broadleaf forest areas of the Amazon River basin, including a large fraction of regularly flooded forest areas. Model results support the hypothesis that soil and dead wood carbon decomposition fluxes of CO2 to the atmosphere were elevated during the drought period of 2010 in periodically flooded forest areas, compared to forests outside the main river floodplains.

  1. A decision framework for identifying models to estimate forest ecosystem services gains from restoration

    USGS Publications Warehouse

    Christin, Zachary; Bagstad, Kenneth J.; Verdone, Michael

    2016-01-01

    Restoring degraded forests and agricultural lands has become a global conservation priority. A growing number of tools can quantify ecosystem service tradeoffs associated with forest restoration. This evolving “tools landscape” presents a dilemma: more tools are available, but selecting appropriate tools has become more challenging. We present a Restoration Ecosystem Service Tool Selector (RESTS) framework that describes key characteristics of 13 ecosystem service assessment tools. Analysts enter information about their decision context, services to be analyzed, and desired outputs. Tools are filtered and presented based on five evaluative criteria: scalability, cost, time requirements, handling of uncertainty, and applicability to benefit-cost analysis. RESTS uses a spreadsheet interface but a web-based interface is planned. Given the rapid evolution of ecosystem services science, RESTS provides an adaptable framework to guide forest restoration decision makers toward tools that can help quantify ecosystem services in support of restoration.

  2. Experiences gained from implementing mandatory buffer strips in Denmark: how can we enhance their ecosystem services?

    NASA Astrophysics Data System (ADS)

    Kronvang, Brian; Hoffmann, Carl Christian; Baattrup-Pedersen, Annette; Hille, Sandra; Rubæk, Gitte; Heckrath, Goswin; Gertz, Flemming; Jensen, Henning; Feuerback, Peter; Strand, John; Stutter, Marc

    2015-04-01

    along watercourses from ca. 50,000 ha to ca. 25,000 ha and at the same time they reduced the width of the mandatory BSs from 10 m to 9 m. The aim of this presentation is to share the experience gained in Denmark on establishing mandatory BSs. Furthermore, we will show some preliminary results from two newly initiated research projects (BUFFERTECH and BALTICSEA2020) that studies how to enhance the ecosystem services provided by buffer strips. We will show how intelligently to guide managers when establishing BSs along watercourses at catchment scale utilizing a combined P-index model for soil erosion and a statistical model for P retention in BSs as well as results obtained from new 'Engineered' or 'Constructed' BSs that delays tile drainage flow from field to streams thereby increasing nutrient retention. Acknowledgement The work is supported by the Strategic Research Foundation/Innovation Fund Denmark project 'BUFFERTECH - Optimization of Ecosystem Services Provided by Buffer Strips Using Novel Technological Methods' (Grant No. 1305-00017B) and the BalticSea2020 project 'Integrerade skyddszoner (IBZ)'.

  3. Global distribution of carbon turnover times in terrestrial ecosystems

    NASA Astrophysics Data System (ADS)

    Carvalhais, Nuno; Forkel, Matthias; Khomik, Myroslava; Bellarby, Jessica; Jung, Martin; Migliavacca, Mirco; Mu, Mingquan; Saatchi, Sassan; Santoro, Maurizio; Thurner, Martin; Weber, Ulrich; Ahrens, Bernhard; Beer, Christian; Cescatti, Alessandro; Randerson, James T.; Reichstein, Markus

    2015-04-01

    The response of the carbon cycle in terrestrial ecosystems to climate variability remains one of the largest uncertainties affecting future projections of climate change. This feedback between the terrestrial carbon cycle and climate is partly determined by the response of carbon uptake and by changes in the residence time of carbon in land ecosystems, which depend on climate, soil, and vegetation type. Thus, it is of foremost importance to quantify the turnover times of carbon in terrestrial ecosystems and its spatial co-variability with climate. Here, we develop a global, spatially explicit and observation-based assessment of whole-ecosystem carbon turnover times (τ) to investigate its co-variation with climate at global scale. Assuming a balance between uptake (gross primary production, GPP) and emission fluxes, τ can be defined as the ratio between the total stock (C_total) and the output or input fluxes (GPP). The estimation of vegetation (C_veg) stocks relies on new remote sensing-based estimates from Saatchi et al (2011) and Thurner et al (2014), while soil carbon stocks (C_soil) are estimated based on state of the art global (Harmonized World Soil Database) and regional (Northern Circumpolar Soil Carbon Database) datasets. The uptake flux estimates are based on global observation-based fields of GPP (Jung et al., 2011). Globally, we find an overall mean global carbon turnover time of 23-4+7 years (95% confidence interval). A strong spatial variability globally is also observed, from shorter residence times in equatorial regions to longer periods at latitudes north of 75°N (mean τ of 15 and 255 years, respectively). The observed latitudinal pattern reflect the clear dependencies on temperature, showing increases from the equator to the poles, which is consistent with our current understanding of temperature controls on ecosystem dynamics. However, long turnover times are also observed in semi-arid and forest-herbaceous transition regions. Furthermore

  4. Ecosystem and Societal Consequences of Ocean versus Atmosphere Carbon Storage

    NASA Astrophysics Data System (ADS)

    Barry, J. P.; Adams, E. E.; Bleck, R.; Caldeira, K.; Carman, K.; Erickson, D.; Kennett, J. P.; Sarmiento, J. L.; Tsouris, C.

    2005-12-01

    Climate stabilization during the next 100 to 200 y will require significant reductions in atmospheric carbon dioxide emissions to avoid large increases in global temperature. While there is only mild disagreement concerning carbon management options such as energy efficiency, alternative energy sources, and even geologic C storage, ocean storage remains controversial, due to its potential impacts for deep-sea ecosystems. A cautionary approach to carbon management might avoid any ocean C storage. However, this approach does not consider the balance between ocean and terrestrial ecosystems, or societal concerns. Using a broader perspective, we might ask whether atmospheric CO2 storage (i.e. the status quo), or deep ocean sequestration is better for Earth's ecosystems and societies? We explored the potential storage capacity of the deep ocean for carbon dioxide, under scenarios producing a 0.2 pH unit reduction, a level similar to observed scale of pH variability in deep ocean basins, which may also represent coarse thresholds for deep-sea ecosystem impacts. Roughly 500 PgC could be stored in the deep ocean to lower pH by 0.2 units, yielding a long term (~250 y) ocean sequestration program of 2 PgCy-1. The mitigation value of such ocean C sequestration for upper ocean and terrestrial systems depends strongly on future emission scenarios. Under a low emission scenario (e.g. SRES scenario A1T, B1; atm CO2 ~575 ppm, global temperature change of ~+2 oC), a 2 PgCy-1 ocean CO2 injection program could mitigate global temperature by ~-0.4 oC (20%) by 2100. This could reduce significantly the number of people at risk of water shortage and tropical diseases, with lesser improvement expected for hunger or coastal flooding. Mitigation for terrestrial and shallow ocean ecosystems is difficult to predict. A 0.4 oC reduction in warming this century is expected to delay the progression of coral reef devastation by roughly 20 y. The mitigation potential of ocean storage under very

  5. Black carbon in grassland ecosystems of the world

    NASA Astrophysics Data System (ADS)

    Rodionov, Andrej; Amelung, Wulf; Peinemann, Norman; Haumaier, Ludwig; Zhang, Xudong; Kleber, Markus; Glaser, Bruno; Urusevskaya, Inga; Zech, Wolfgang

    2010-09-01

    Black carbon (BC) is the product of incomplete burning processes and a significant component of the passive soil organic carbon (SOC) pool. The role of BC in the global carbon cycle is still unclear. This study aimed to quantify and characterize BC in major grassland ecosystems of the world. Twenty-eight representative soil profiles (mainly Mollisols) were sampled in the Russian Steppe, the U.S. Great Plains, the Argentinian Pampa, the Manchurian Plains in China, and the Chernozem region in central Germany. Black carbon contents were estimated using benzene polycarboxylic acids (BPCA) as a molecular marker, and indications about the origin of the BC were derived from bulk and compound-specific δ13C analyses and radiocarbon dating of bulk soil organic matter (SOM). Our findings suggest that between 5% and 30% of SOC stocks consist of BC. Maximum BC contributions to SOC frequently were found at deeper parts of the A horizon with 14C ages younger than 7000 years BP; that is, incorporation of C as charred particles accompanied ecosystem development since the mid-Holocene. Most of this BC formed from local vegetation, as indicated by a 13C isotope signature similar to that of bulk SOM. At some sites, also nonlocal sources contributed to soil BC, e.g., fossil fuel BC inputs at the German sites. Black carbon stocks were highest in Chernozems and lowest in Kastanozems. The Russian Steppe and Chinese Manchurian sites stored about 3-4 times more BC (around 3 kg m-2) than did the other sites because of thicker A horizons that were rich in BC. On a global scale, we estimate that steppe ecosystems contain between 4 and 17 Pg BC.

  6. Freshwater ecology. Experimental nutrient additions accelerate terrestrial carbon loss from stream ecosystems.

    PubMed

    Rosemond, Amy D; Benstead, Jonathan P; Bumpers, Phillip M; Gulis, Vladislav; Kominoski, John S; Manning, David W P; Suberkropp, Keller; Wallace, J Bruce

    2015-03-01

    Nutrient pollution of freshwater ecosystems results in predictable increases in carbon (C) sequestration by algae. Tests of nutrient enrichment on the fates of terrestrial organic C, which supports riverine food webs and is a source of CO2, are lacking. Using whole-stream nitrogen (N) and phosphorus (P) additions spanning the equivalent of 27 years, we found that average terrestrial organic C residence time was reduced by ~50% as compared to reference conditions as a result of nutrient pollution. Annual inputs of terrestrial organic C were rapidly depleted via release of detrital food webs from N and P co-limitation. This magnitude of terrestrial C loss can potentially exceed predicted algal C gains with nutrient enrichment across large parts of river networks, diminishing associated ecosystem services. PMID:25745171

  7. Forest ecosystem carbon on public lands of the United States

    SciTech Connect

    Heath, L.S.

    1995-06-01

    Increasing concentration of greenhouse gases in the atmosphere has prompted nations to investigate strategies to mitigate emissions. One set of strategies involves sequestering carbon in forests, and this requires a way to estimate and project the forest ecosystem carbon budget for all forestland under a range of potential policy options. Carbon was estimated and projected using the FORCARB model, linked to ATLAS, the Aggregate Timberland Assessment System. FORCARB estimates carbon in live trees, detrital wood, forest floor, and soil, and ATLAS tracks timber inventory in terms of volume and land area. Together, these models account for the effects of existing forest inventories, forest growth, land use changes, and harvesting on carbon sequestered on public lands. Forests on both federal and non-federal public lands comprise at least 40% of the forests in the U.S. by land area, and contain a significant portion of the forest carbon budget. Changes in harvesting and fire suppression strategies on public lands noticeably affect the forest carbon budget of the U.S.

  8. Assessing net ecosystem carbon exchange of U.S. terrestrial ecosystems by integrating eddy covariance flux measurements and satellite observations

    Technology Transfer Automated Retrieval System (TEKTRAN)

    More accurate projections of future carbon dioxide concentrations in the atmosphere and associated climate change as well as carbon accounting and climate policy-making depend on improved scientific understanding of the terrestrial carbon cycle. Despite the consensus that U.S. terrestrial ecosystems...

  9. Quantifying Typhoon Impact on Net Carbon Ecosystem Exchange in a Sub-tropical Mangrove Ecosystem

    NASA Astrophysics Data System (ADS)

    Chen, H.; Lu, W.; Yan, G.; Yang, S.; Lin, G.

    2011-12-01

    Although typhoon is a natural disturbance for mangrove forests, research of typhoon impact on net carbon ecosystem exchange (NEE) of mangrove wetlands has not reached final conclusion. In this study we investigated possible effects of typhoons with different forces on the NEE of a subtropical mangrove forest in Fujian, China (117°23'E, 23°55'N). In 2010, Typhoon Lionrock, Fanapi and Megi made landfall with a speed of 23, 35 and 38 m s-1 near our mangrove field station in Zhangjiang Estuary National Mangrove Nature Reserve on September 2, September 20 and October 23, respectively. In October 2009, total of 16 litter traps and an eddy covariance system were instated at this field station. Litter production was monitored at the biweekly intervals while the NEE was measured continuously. The litter production and NEE values were compared before and after each typhoon landed. Strong winds and torrential rains from these typhoons caused the amount of litter production more than double over the same period a year before when there was no typhoon landing. Moreover, about 5~25% green leaves and twigs were found in the litter traps after the typhoons, indicating significant defoliation by the typhoons. Typhoon Lionrock and Fanapi did not significantly reduce NEE, while Typhoo Fanapi reduced gross ecosystem production (GEP) by about 12%. However, NEE was increased by Typhoon Megi, which resulted from lower daily ecosystem respiration (Re) following the typhoon. Our results indicate that, although theses typhoons caused significant defoliation, they had little effect on ecosystem carbon exchange over the short periods following the typhoons.

  10. Whole-ecosystem exposure to elevated carbon dioxide increases total ecosystem carbon and nitrogen in the Mojave Desert

    NASA Astrophysics Data System (ADS)

    Evans, R. D.; Koyama, A.; Sonderegger, D.; Charlet, D.; Newingham, B. A.; Fenstermaker, L.; Ogle, K.; Smith, S. D.; Nowak, R.

    2011-12-01

    Arid ecosystems are predicted to be among the most responsive to global change and their response is globally significant considering their extensive spatial coverage. Although carbon cycling in arid lands is an important component of the global carbon budget, there is substantial uncertainty about the potential impacts of global change drivers, such as elevated CO2, on arid land carbon budgets. Studies suggest that productivity may be stimulated by elevated CO2 directly due to enhanced plant water-use efficiency. The indirect impacts of elevated CO2 on ecosystem productivity may also be constrained by available nitrogen, but little is known about how the importance of the nitrogen constraint or how the nitrogen cycle may be affected by global change drivers. Here we present the carbon and nitrogen mass budgets of a Mojave Desert ecosystem after ten years of exposure to elevated CO2. The Nevada Desert Free-Air Carbon Enrichment Facility (FACE) was established in 1997 to evaluate the response of an intact Mojave Desert ecosystem to elevated CO2. The CO2 concentration of the atmosphere in the elevated treatment was maintained at 513 uL/L until harvest in 2007. At harvest time, all aboveground biomass for 2/3 of each plot was harvested and soils and roots were removed down to 1 m depth and analyzed for total carbon and nitrogen. We observed significantly greater carbon (10,800 versus 9,200 kg C/ha, P=0.004) and nitrogen (1,400 versus 1,100 kg N/ha, P=0.002) in elevated compared to ambient CO2 treatments. Differences between treatments were due solely to greater C and N in soils across all cover types, and no differences were observed in above and belowground plant biomass. Companion research shows that increased soil C was from increased root exudation, microbial residues, and episodic increased litter input under elevated CO2, and these increased C inputs in turn stimulated production of inorganic nitrogen. Results from the Nevada Desert FACE Facility demonstrate

  11. Carbon and nitrogen isotope studies in an arctic aquatic ecosystem

    SciTech Connect

    Schell, D.M.

    1989-01-01

    The Phase II studies of the R4D Program on stream and watershed ecology reflect the accomplishments and accumulation of baseline information obtained during the past studies. Although our rough estimates indicate that nitrogen inputs to the watershed ba lance losses, the carbon fluxes suggest that they are not in equilibrium and that there is a net loss of carbon from the tundra ecosystem through respiration and transport out of the watershed via the stream system. Radiocarbon profiles of soil sections coupled with mass transport calculations revealed that peat accumulation has essentially ceased in the R4D watershed and appears to be in ablative loss. Thus the carbon flux measurements provide validation tests for the PLANTGRO and GAS-HYDRO models of the PHASE II studies. These findings are also important in the context of global CO[sub 2] increases from positive feedback mechanisms in peatlands associated with climatic warming in the subarctic regions.

  12. Carbon and nitrogen isotope studies in an arctic aquatic ecosystem

    SciTech Connect

    Schell, D.M.

    1989-12-31

    The Phase II studies of the R4D Program on stream and watershed ecology reflect the accomplishments and accumulation of baseline information obtained during the past studies. Although our rough estimates indicate that nitrogen inputs to the watershed ba lance losses, the carbon fluxes suggest that they are not in equilibrium and that there is a net loss of carbon from the tundra ecosystem through respiration and transport out of the watershed via the stream system. Radiocarbon profiles of soil sections coupled with mass transport calculations revealed that peat accumulation has essentially ceased in the R4D watershed and appears to be in ablative loss. Thus the carbon flux measurements provide validation tests for the PLANTGRO and GAS-HYDRO models of the PHASE II studies. These findings are also important in the context of global CO{sub 2} increases from positive feedback mechanisms in peatlands associated with climatic warming in the subarctic regions.

  13. Carbon fluxes in ecosystems of Yellowstone National Park predicted from remote sensing data and simulation modeling

    PubMed Central

    2011-01-01

    Background A simulation model based on remote sensing data for spatial vegetation properties has been used to estimate ecosystem carbon fluxes across Yellowstone National Park (YNP). The CASA (Carnegie Ames Stanford Approach) model was applied at a regional scale to estimate seasonal and annual carbon fluxes as net primary production (NPP) and soil respiration components. Predicted net ecosystem production (NEP) flux of CO2 is estimated from the model for carbon sinks and sources over multi-year periods that varied in climate and (wildfire) disturbance histories. Monthly Enhanced Vegetation Index (EVI) image coverages from the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) instrument (from 2000 to 2006) were direct inputs to the model. New map products have been added to CASA from airborne remote sensing of coarse woody debris (CWD) in areas burned by wildfires over the past two decades. Results Model results indicated that relatively cooler and wetter summer growing seasons were the most favorable for annual plant production and net ecosystem carbon gains in representative landscapes of YNP. When summed across vegetation class areas, the predominance of evergreen forest and shrubland (sagebrush) cover was evident, with these two classes together accounting for 88% of the total annual NPP flux of 2.5 Tg C yr-1 (1 Tg = 1012 g) for the entire Yellowstone study area from 2000-2006. Most vegetation classes were estimated as net ecosystem sinks of atmospheric CO2 on annual basis, making the entire study area a moderate net sink of about +0.13 Tg C yr-1. This average sink value for forested lands nonetheless masks the contribution of areas burned during the 1988 wildfires, which were estimated as net sources of CO2 to the atmosphere, totaling to a NEP flux of -0.04 Tg C yr-1 for the entire burned area. Several areas burned in the 1988 wildfires were estimated to be among the lowest in overall yearly NPP, namely the Hellroaring Fire, Mink Fire, and Falls Fire

  14. Impact of cloudiness on net ecosystem exchange of carbon dioxide in different types of forest ecosystems in China

    NASA Astrophysics Data System (ADS)

    Zhang, M.; Yu, G.-R.; Zhang, L.-M.; Sun, X.-M.; Wen, X.-F.; Han, S.-J.; Yan, J.-H.

    2010-02-01

    Clouds can significantly affect carbon exchange process between forest ecosystems and the atmosphere by influencing the quantity and quality of solar radiation received by ecosystem's surface and other environmental factors. In this study, we analyzed the effects of cloudiness on net ecosystem exchange of carbon dioxide (NEE) in a temperate broad-leaved Korean pine mixed forest at Changbaishan (CBS) and a subtropical evergreen broad-leaved forest at Dinghushan (DHS), based on the flux data obtained during June-August from 2003 to 2006. The results showed that the response of NEE of forest ecosystems to photosynthetically active radiation (PAR) differed under clear skies and cloudy skies. Compared with clear skies, the light-saturated maximum photosynthetic rate (Pec,max) at CBS under cloudy skies during mid-growing season (from June to August) increased by 34%, 25%, 4% and 11% in 2003, 2004, 2005 and 2006, respectively. In contrast, Pec,max of the forest ecosystem at DHS was higher under clear skies than under cloudy skies from 2004 to 2006. When the clearness index (kt) ranged between 0.4 and 0.6, the NEE reached its maximum at both CBS and DHS. However, the NEE decreased more dramatically at CBS than at DHS when kt exceeded 0.6. The results indicate that cloudy sky conditions are beneficial to net carbon uptake in the temperate forest ecosystem and the subtropical forest ecosystem. Under clear skies, vapor pressure deficit (VPD) and air temperature increased due to strong light. These environmental conditions led to greater decrease in gross ecosystem photosynthesis (GEP) and greater increase in ecosystem respiration (Re) at CBS than at DHS. As a result, clear sky conditions caused more reduction of NEE in the temperate forest ecosystem than in the subtropical forest ecosystem. The response of NEE of different forest ecosystems to the changes in cloudiness is an important factor that should be included in evaluating regional carbon budgets under climate change

  15. Biotic Processes Regulating the Carbon Balance of Desert Ecosystems

    SciTech Connect

    R. S. Nowak; J. Arnone; L. Fenstermaker; and S. D. Smith

    2005-07-26

    This project provided the funding to operate and maintain the Nevada Desert FACE Facility. This support funds the CO{sub 2}, system repairs and maintenance, basic physical and biological site information, and personnel that are essential for the experiment to continue. They have continued to assess the effects of elevated CO{sub 2} on three key processes: (1) leaf- to plant-level responses of desert vegetation to elevated atmospheric CO{sub 2}; (2) ecosystem-level responses; and (3) integration of plant and ecosystem processes to understand carbon balance of deserts. The focus is the seminal interactions among atmospheric CO{sub 2}, water, and nitrogen that drive desert responses to elevated CO{sub 2} and explicitly address processes that occur across scales (biological, spatial, and temporal).

  16. Long-term increase in forest water-use efficiency observed across ecosystem carbon flux networks

    NASA Astrophysics Data System (ADS)

    Keenan, Trevor; Bohrer, Gil; Dragoni, Danilo; Hollinger, David; Munger, James W.; Schmid, Hans Peter; Richardson, Andrew

    2014-05-01

    Terrestrial plants remove CO2 from the atmosphere through photo- synthesis, a process that is accompanied by the loss of water vapour from leaves. The ratio of water loss to carbon gain, or water-use efficiency, is a key characteristic of ecosystem function that is central to the global cycles of water, energy and carbon. Here we analyse direct, long-term measurements of whole-ecosystem carbon and water exchange. We find a substantial increase in water-use efficiency in temperate and boreal forests of the Northern Hemisphere over the past two decades. We systematically assess various competing hypotheses to explain this trend, and find that the observed increase is most consistent with a strong CO2 fertilization effect. The results suggest a partial closure of stomata - small pores on the leaf surface that regulate gas exchange - to maintain a near- constant concentration of CO2 inside the leaf even under continually increasing atmospheric CO2 levels. The observed increase in forest water-use efficiency is larger than that predicted by existing theory and 13 terrestrial biosphere models. The increase is associated with trends of increasing ecosystem-level photosynthesis and net carbon uptake, and decreasing evapotranspiration. Our findings demonstrate the utility of maintaining long-term eddy-covariance flux measurement sites. The results suggest a shift in the carbon- and water-based economics of terrestrial vegetation, which may require a reassessment of the role of stomatal control in regulating interactions between forests and climate change, and a re-evaluation of coupled vegetation-climate models.

  17. Quantifying the role of fire in the Earth system - Part 2: Impact on the net carbon balance of global terrestrial ecosystems for the 20th century

    SciTech Connect

    Li, Fang; Bond-Lamberty, Benjamin; Levis, Samuel

    2014-03-07

    Fire is the primary terrestrial ecosystem disturbance agent on a global scale. It affects carbon balance of global terrestrial ecosystems by emitting carbon to atmosphere directly and immediately from biomass burning (i.e., fire direct effect), and by changing net ecosystem productivity and land-use carbon loss in post-fire regions due to biomass burning and fire-induced vegetation mortality (i.e., fire indirect effect). Here, we provide the first quantitative assessment about the impact of fire on the net carbon balance of global terrestrial ecosystems for the 20th century, and investigate the roles of fire direct and indirect effects. This study is done by quantifying the difference between the 20th century fire-on and fire-off simulations with NCAR community land model CLM4.5 as the model platform. Results show that fire decreases net carbon gain of the global terrestrial ecosystems by 1.0 Pg C yr-1 average across the 20th century, as a results of fire direct effect (1.9 Pg C yr-1) partly offset by indirect effect (-0.9 Pg C yr-1). Fire generally decreases the average carbon gains of terrestrial ecosystems in post-fire regions, which are significant over tropical savannas and part of forests in North America and the east of Asia. The general decrease of carbon gains in post-fire regions is because fire direct and indirect effects have similar spatial patterns and the former (to decrease carbon gain) is generally stronger. Moreover, the effect of fire on net carbon balance significantly declines prior to ~1970 with trend of 8 Tg C yr-1 due to increasing fire indirect effect and increases afterward with trend of 18 Tg C yr-1 due to increasing fire direct effect.

  18. Carbon Budget and its Dynamics over Northern Eurasia Forest Ecosystems

    NASA Astrophysics Data System (ADS)

    Shvidenko, Anatoly; Schepaschenko, Dmitry; Kraxner, Florian; Maksyutov, Shamil

    2016-04-01

    The presentation contains an overview of recent findings and results of assessment of carbon cycling of forest ecosystems of Northern Eurasia. From a methodological point of view, there is a clear tendency in understanding a need of a Full and Verified Carbon Account (FCA), i.e. in reliable assessment of uncertainties for all modules and all stages of FCA. FCA is considered as a fuzzy (underspecified) system that supposes a system integration of major methods of carbon cycling study (land-ecosystem approach, LEA; process-based models; eddy covariance; and inverse modelling). Landscape-ecosystem approach 1) serves for accumulation of all relevant knowledge of landscape and ecosystems; 2) for strict systems designing the account, 3) contains all relevant spatially distributed empirical and semi-empirical data and models, and 4) is presented in form of an Integrated Land Information System (ILIS). The ILIS includes a hybrid land cover in a spatially and temporarily explicit way and corresponding attributive databases. The forest mask is provided by utilizing multi-sensor remote sensing data, geographically weighed regression and validation within GEO-wiki platform. By-pixel parametrization of forest cover is based on a special optimization algorithms using all available knowledge and information sources (data of forest inventory and different surveys, observations in situ, official statistics of forest management etc.). Major carbon fluxes within the LEA (NPP, HR, disturbances etc.) are estimated based on fusion of empirical data and aggregations with process-based elements by sets of regionally distributed models. Uncertainties within LEA are assessed for each module and at each step of the account. Within method results of LEA and corresponding uncertainties are harmonized and mutually constrained with independent outputs received by other methods based on the Bayesian approach. The above methodology have been applied to carbon account of Russian forests for 2000

  19. Airborne Measurement of Ecosystem Carbon Dynamics over Heterogeneous Landscapes

    NASA Astrophysics Data System (ADS)

    Wade, T. J.; Hill, T. C.; Clement, R.; Moncrieff, J.; Disney, M.; Nichol, C. J.; Williams, M. D.

    2009-12-01

    Terrestrial carbon sinks are currently believed to account for the removal and storage of approximately 25% of anthropogenic carbon emissions from the atmosphere. The processes involved are numerous and complex and many feedbacks are at play. The ability to study the dynamics of different ecosystems at scales meaningful to climatic forcing is essential for understanding the key processes involved and identifying crucial sensitivities and thresholds. Airborne platforms with the requisite instrumentation offer the opportunity to directly measure biological processes and atmospheric structures at scales that are not achievable by ground measurements alone. The current generation of small research aircraft such as the University of Edinburgh’s Diamond HK36TTC ECO Dimona present excellent platforms for measurement of both the atmosphere and terrestrial surface. In this study we present results from airborne CO2/H2O flux measuring campaigns in contrasting climatic systems to quantify spatial patterns in ecosystem photosynthesis. Several airborne campaigns were undertaken in Arctic Finland, as part of the Arctic Biosphere Atmosphere Coupling at Multiple Scales (ABACUS) project (2008), and mainland UK as part of the UK Population Biology Network (UKPopNet) 2009 project, to explore the variability in surface CO2 flux across spatial scales larger than captured using conventional ground based eddy covariance. We discuss the application of our aircraft platform as a tool to address the challenge of understanding carbon dynamics within landscapes of heterogeneous vegetation class, terrain and hydrology using complementary datasets acquired from airborne eddy covariance and remote sensing.

  20. Budgeting Ecosystem - Atmosphere Carbon Exchange in a Subarctic Birch Forest

    NASA Astrophysics Data System (ADS)

    Heliasz, M.; Johansson, T.; Mastepanov, M.; Callaghan, T. V.; Christensen, T. R.

    2008-12-01

    The overarching objective of this project is to work towards a better understanding of ecosystem-atmosphere interactions in a composite subarctic landscape with a focus on measurements and modeling of carbon cycling in birch forest environments. In this presentation we document the interactions between the birch forest (Betula pubescens ssp. czerepanovii) ecosystem and the atmosphere both in terms of greenhouse gas and energy exchanges. The study provides new information on climatic controls of interannual variability in annual carbon and energy exchange. This information is complimented with studies of the effects of insect outbreak disturbance on these annual budgets. Carbon flux data produced since 2003 shows that during the first year of measurements the forest acted as a large net sink of atmospheric carbon. However, during the growing season of 2004 the area was severely affected by an extreme outbreak of the autumnal moth (Epirrita autumnata) resulting in total defoliation of the forest over large areas. This caused the same forest stand to act as a net source of CO2 even during the peak growing season. During the summer of 2008, as part of a special campaign under the International Polar Year, the larger scale variability of the subarctic birch forest carbon fluxes was documented. A mobile eddy covariance tower provided seasonal measurements from six different locations in the catchment of lake Tornetrask which can be compared with longer term, inter-annual data from two permanent flux towers operating continuously in the vicinity of the village of Abisko. The sites were chosen to document possible differences in CO2 fluxes depending on the time since last defoliation which was in 2004 in some areas. Also sites were chosen with different types of birch forest (monocormic, polycormic) and at greatly varying distances to the oceanic influence from the Norwegian coast. This poster will present and discuss preliminary CO2 flux data from all these different

  1. Ecosystem carbon balance and vulnerability of soil carbon in a drained lower coastal plain loblolly pine plantation

    NASA Astrophysics Data System (ADS)

    Noormets, A.; McNulty, S. G.; Gavazzi, M.; Domec, J.; Sun, G.; King, J. S.; Chen, J.

    2008-12-01

    Coastal plain ecosystems comprise only about 5% of total U.S. land area, but the soil carbon density in these ecosystems is about 10-fold higher than in upland ecosystems and they may therefore play a disproportionately large role in ecosystem-climate feedbacks. The role of these ecosystems in continental carbon exchange is largely unclear because they have been underrepresented in flux monitoring networks. We monitored ecosystem carbon fluxes and pools for three years in two lower coastal plain loblolly pine plantations (3 and 17 years of age). The contribution of soil to ecosystem respiration decreased from over 90% immediately following a harvest to about 50% by age 17. The replenishment of soil C through litterfall exceeded heterotrophic respiration (Rh) by 2-9% in two years, but was 30% lower than Rh in the third year, highlighting the vulnerability of soil carbon stocks to interannual climate variability.

  2. Carbon Isotope Composition of Ecosystem Respired Carbon Dioxide in Three Boreal Forest Ecosystems: Measurements and Model Calculations

    NASA Astrophysics Data System (ADS)

    Cai, T.; Flanagan, L. B.

    2007-12-01

    We conducted measurements of seasonal and inter-annual variation in the carbon isotope composition of ecosystem respired CO2 (δR) in aspen, black spruce and jack pine dominated ecosystems in northern Saskatchewan during 2004-2006 as part of the Fluxnet-Canada Research Network. All three sites showed relatively small variation (approximately -26 to -29 per mil) in δR values during the entire study. The measurements were strongly correlated with modeled δ13C values of ecosystem respired CO2. The model calculated leaf CO2 assimilation, stomatal conductance and chloroplast CO2 concentration separately for sunlit and shaded leaves within multiple canopy layers, and, therefore, allowed us to estimate canopy photosynthetic 13C discrimination. All three sites showed variation in canopy 13C discrimination in response to environmental conditions in a manner consistent with well-known leaf-level studies. Specifically, 13C discrimination was positively correlated with soil moisture and negatively correlated with photon flux density, air temperature and vapor pressure deficit. As a consequence a strong diurnal pattern was observed for 13C discrimination. The measured δR values also varied in response to environmental conditions in a manner consistent with well-known leaf-level studies of photosynthetic 13C discrimination, but with a dampened response caused by the contribution of heterotrophic respiration, which had a constant δ13C value. These results indicate that the stable isotope composition of respired CO2 is a useful ecosystem-scale tool to study constraints to photosynthesis and acclimation of ecosystems to environmental stress.

  3. Terrestrial Carbon Sinks in the Brazilian Amazon and Cerrado Region Predicted from MODIS Satellite Data and Ecosystem Modeling

    NASA Technical Reports Server (NTRS)

    Potter, C.; Klooster, S.; Huete, A.; Genovese, V.; Bustamante, M.; Ferreira, L. Guimaraes; deOliveira, R. C., Jr.; Zepp, R.

    2009-01-01

    A simulation model based on satellite observations of monthly vegetation cover from the Moderate Resolution Imaging Spectroradiometer (MODIS) was used to estimate monthly carbon fluxes in terrestrial ecosystems of Brazilian Amazon and Cerrado regions over the period 2000-2004. Net ecosystem production (NEP) flux for atmospheric CO2 in the region for these years was estimated. Consistently high carbon sink fluxes in terrestrial ecosystems on a yearly basis were found in the western portions of the states of Acre and Rondonia and the northern portions of the state of Par a. These areas were not significantly impacted by the 2002-2003 El Nino event in terms of net annual carbon gains. Areas of the region that show periodically high carbon source fluxes from terrestrial ecosystems to the atmosphere on yearly basis were found throughout the state of Maranhao and the southern portions of the state of Amazonas. As demonstrated though tower site comparisons, NEP modeled with monthly MODIS Enhanced Vegetation Index (EVI) inputs closely resembles the measured seasonal carbon fluxes at the LBA Tapajos tower site. Modeling results suggest that the capacity for use of MODIS Enhanced Vegetation Index (EVI) data to predict seasonal uptake rates of CO2 in Amazon forests and Cerrado woodlands is strong.

  4. Terrestrial carbon sinks in the Brazilian Amazon and Cerrado region predicted from MODIS satellite data and ecosystem modeling

    NASA Astrophysics Data System (ADS)

    Potter, C.; Klooster, S.; Huete, A.; Genovese, V.; Bustamante, M.; Guimaraes Ferreira, L.; de Oliveira, R. C., Jr.; Zepp, R.

    2009-06-01

    A simulation model based on satellite observations of monthly vegetation cover from the Moderate Resolution Imaging Spectroradiometer (MODIS) was used to estimate monthly carbon fluxes in terrestrial ecosystems of Brazilian Amazon and Cerrado regions over the period 2000-2004. Net ecosystem production (NEP) flux for atmospheric CO2 in the region for these years was estimated. Consistently high carbon sink fluxes in terrestrial ecosystems on a yearly basis were found in the western portions of the states of Acre and Rondônia and the northern portions of the state of Pará. These areas were not significantly impacted by the 2002-2003 El Niño event in terms of net annual carbon gains. Areas of the region that show periodically high carbon source fluxes from terrestrial ecosystems to the atmosphere on yearly basis were found throughout the state of Maranhão and the southern portions of the state of Amazonas. As demonstrated though tower site comparisons, NEP modeled with monthly MODIS Enhanced Vegetation Index (EVI) inputs closely resembles the measured seasonal carbon fluxes at the LBA Tapajos tower site. Modeling results suggest that the capacity for use of MODIS Enhanced Vegetation Index (EVI) data to predict seasonal uptake rates of CO2 in Amazon forests and Cerrado woodlands is strong.

  5. Terrestrial carbon sinks in the Brazilian Amazon and Cerrado region predicted from MODIS satellite data and ecosystem modeling

    NASA Astrophysics Data System (ADS)

    Potter, C.; Klooster, S.; Huete, A.; Genovese, V.; Bustamante, M.; Guimaraes Ferreira, L.; Cosme de Oliveira Junior, R.; Zepp, R.

    2009-01-01

    A simulation model based on satellite observations of monthly vegetation cover from the Moderate Resolution Imaging Spectroradiometer (MODIS) was used to estimate monthly carbon fluxes in terrestrial ecosystems of Brazilian Amazon and Cerrado regions over the period 2000-2004. Net ecosystem production (NEP) flux for atmospheric CO2 in the region for these years was estimated. Consistently high carbon sink fluxes in terrestrial ecosystems on a yearly basis were found in the western portions of the states of Acre and Rondônia and the northern portions of the state of Pará. These areas were not significantly impacted by the 2002-2003 El Niño event in terms of net annual carbon gains. Areas of the region that show periodically high carbon source fluxes from terrestrial ecosystems to the atmosphere on yearly basis were found throughout the state of Maranhão and the southern portions of the state of Amazonas. As demonstrated though tower site comparisons, NEP modeled with monthly MODIS Enhanced Vegetation Index (EVI) inputs closely resembles the measured seasonal carbon fluxes at the LBA Tapajos tower site. Modeling results suggest that the capacity for use of MODIS Enhanced Vegetation Index (EVI) data to predict seasonal uptake rates of CO2 in Amazon forests and Cerrado woodlands is strong.

  6. Impact of soil movement on carbon sequestration in agricultural ecosystems.

    PubMed

    McCarty, G W; Ritchie, J C

    2002-01-01

    Recent modeling studies indicate that soil erosion and terrestrial sedimentation may establish ecosystem disequilibria that promote carbon (C) sequestration within the biosphere. Movement of upland eroded soil into wetland systems with high net primary productivity may represent the greatest increase in storage capacity potential for C sequestration. The capacity of wetland systems to capture sediments and build up areas of deposition has been documented as well as the ability of these ecosystems to store substantial amounts of C. The purpose of our work was to assess rates of sediment deposition and C storage in a wetland site adjacent to a small first-order stream that drains an agricultural area. The soils of the wetland site consist of a histosol buried by sediments from the agricultural area. Samples of deposited sediments in the riparian zone were collected in 5 cm increments and the concentration of 137Cs was used to determine the 1964 and 1954 deposition layers. Agricultural activity in the watershed has caused increased sediment deposition to the wetland. The recent upland sediment is highly enriched in organic matter indicating that large amounts of organic C have been sequestered within this zone of sediment deposition. Rates of sequestration are much higher than rates that have occurred over the pre-modern history of the wetland. These data indicate the increased sedimentation rates in the wetland ecosystem are associated with increased C sequestration rates. PMID:11822721

  7. Assessing net ecosystem carbon exchange of U S terrestrial ecosystems by integrating eddy covariance flux measurements and satellite observations

    SciTech Connect

    Zhuang, Qianlai; Law, Beverly E.; Baldocchi, Dennis; Ma, Siyan; Chen, Jiquan; Richardson, Andrew; Melillo, Jerry; Davis, Ken J.; Hollinger, D.; Wharton, Sonia; Falk, Matthias; Paw, U. Kyaw Tha; Oren, Ram; Katulk, Gabriel G.; Noormets, Asko; Fischer, Marc; Verma, Shashi; Suyker, A. E.; Cook, David R.; Sun, G.; McNulty, Steven G.; Wofsy, Steve; Bolstad, Paul V; Burns, Sean; Monson, Russell K.; Curtis, Peter; Drake, Bert G.; Foster, David R.; Gu, Lianhong; Hadley, Julian L.; Litvak, Marcy; Martin, Timothy A.; Matamala, Roser; Meyers, Tilden; Oechel, Walter C.; Schmid, H. P.; Scott, Russell L.; Torn, Margaret S.

    2011-01-01

    More accurate projections of future carbon dioxide concentrations in the atmosphere and associated climate change depend on improved scientific understanding of the terrestrial carbon cycle. Despite the consensus that U.S. terrestrial ecosystems provide a carbon sink, the size, distribution, and interannual variability of this sink remain uncertain. Here we report a terrestrial carbon sink in the conterminous U.S. at 0.63 pg C yr 1 with the majority of the sink in regions dominated by evergreen and deciduous forests and savannas. This estimate is based on our continuous estimates of net ecosystem carbon exchange (NEE) with high spatial (1 km) and temporal (8-day) resolutions derived from NEE measurements from eddy covariance flux towers and wall-to-wall satellite observations from Moderate Resolution Imaging Spectroradiometer (MODIS). We find that the U.S. terrestrial ecosystems could offset a maximum of 40% of the fossil-fuel carbon emissions. Our results show that the U.S. terrestrial carbon sink varied between 0.51 and 0.70 pg C yr 1 over the period 2001 2006. The dominant sources of interannual variation of the carbon sink included extreme climate events and disturbances. Droughts in 2002 and 2006 reduced the U.S. carbon sink by 20% relative to a normal year. Disturbances including wildfires and hurricanes reduced carbon uptake or resulted in carbon release at regional scales. Our results provide an alternative, independent, and novel constraint to the U.S. terrestrial carbon sink.

  8. Modeling Root Exudation, Priming and Protection in Soil Carbon Responses to Elevated CO2 from Ecosystem to Global Scales

    NASA Astrophysics Data System (ADS)

    Sulman, B. N.; Phillips, R.; Shevliakova, E.; Oishi, A. C.; Pacala, S. W.

    2014-12-01

    The sensitivity of soil organic carbon (SOC) to changing environmental conditions represents a critical uncertainty in coupled carbon cycle-climate models. Much of this uncertainty arises from our limited understanding of the extent to which plants induce SOC losses (through accelerated decomposition or "priming") or promote SOC gains (via stabilization through physico-chemical protection). We developed a new SOC model, "Carbon, Organisms, Rhizosphere and Protection in the Soil Environment" (CORPSE), to examine the net effect of priming and protection in response to rising atmospheric CO2, and conducted simulations of rhizosphere priming effects at both ecosystem and global scales. At the ecosystem scale, the model successfully captured and explained disparate SOC responses at the Duke and Oak Ridge free-air CO2 enrichment (FACE) experiments. We show that stabilization of "new" carbon in protected SOC pools may equal or exceed microbial priming of "old" SOC in ecosystems with readily decomposable litter (e.g. Oak Ridge). In contrast, carbon losses owing to priming dominate the net SOC response in ecosystems with more resistant litters (e.g. Duke). For global simulations, the model was fully integrated into the Geophysical Fluid Dynamics Laboratory (GFDL) land model LM3. Globally, priming effects driven by enhanced root exudation and expansion of the rhizosphere reduced SOC storage in the majority of terrestrial areas, partially counterbalancing SOC gains from the enhanced ecosystem productivity driven by CO2 fertilization. Collectively, our results suggest that SOC stocks globally depend not only on temperature and moisture, but also on vegetation responses to environmental changes, and that protected C may provide an important constraint on priming effects.

  9. Modeling Environmental Controls on the Carbon Isotope Composition of Ecosystem Respired Carbon Dioxide

    NASA Astrophysics Data System (ADS)

    Cai, T.; Flanagan, L. B.

    2006-12-01

    Our main objective was to test whether the carbon isotope composition of ecosystem respired CO2 varied in response to environmental conditions in a manner consistent with well-known leaf-level studies of photosynthetic 13C discrimination. We developed an ecosystem-scale model that calculated leaf CO2 assimilation, stomatal conductance and chloroplast CO2 concentration separately for sunlit and shaded leaves within multiple canopy layers. The stomatal conductance model was linked to differences in water potential and resistances in the hydraulic pathway between the soil and the tree foliage. This part of the ecosystem model was validated by comparison to leaf-level gas exchange measurements and estimates of ecosystem-scale photosynthesis (GEP). The estimates of GEP were based on eddy covariance measurements of net ecosystem CO2 exchange (NEE) and the Fluxnet-Canada Research Network standard protocol for partitioning NEE into GEP and total ecosystem respiration (TER). The carbon isotope composition of carbohydrate formed during photosynthesis was calculated based on the Farquhar model of isotope effects. Total ecosystem respiration was modeled, based on measured temperature and soil moisture, as the sum of four components (1) above-ground plant, (2) root, (3) litter, and (4) mineral soil. We applied a variety of techniques to allocate the contribution of these different components so that modeled TER was consistent with TER calculated from NEE measurements. The carbon isotope composition of CO2 released during above-ground plant and root respiration was calculated based on an assimilated-weighted average of carbohydrate fixed during a variable number of days previous to the day of respiration. The isotope composition of CO2 released by litter and mineral soil respiration was based on measurements of the δ13C values of these components (we assumed no isotope fractionation during respiration) and held constant in all calculations. The model was compared to

  10. Antarctic sea ice losses drive gains in benthic carbon drawdown.

    PubMed

    Barnes, D K A

    2015-09-21

    Climate forcing of sea-ice losses from the Arctic and West Antarctic are blueing the poles. These losses are accelerating, reducing Earth's albedo and increasing heat absorption. Subarctic forest (area expansion and increased growth) and ice-shelf losses (resulting in new phytoplankton blooms which are eaten by benthos) are the only significant described negative feedbacks acting to counteract the effects of increasing CO2 on a warming planet, together accounting for uptake of ∼10(7) tonnes of carbon per year. Most sea-ice loss to date has occurred over polar continental shelves, which are richly, but patchily, colonised by benthic animals. Most polar benthos feeds on microscopic algae (phytoplankton), which has shown increased blooms coincident with sea-ice losses. Here, growth responses of Antarctic shelf benthos to sea-ice losses and phytoplankton increases were investigated. Analysis of two decades of benthic collections showed strong increases in annual production of shelf seabed carbon in West Antarctic bryozoans. These were calculated to have nearly doubled to >2x10(5) tonnes of carbon per year since the 1980s. Annual production of bryozoans is median within wider Antarctic benthos, so upscaling to include other benthos (combined study species typically constitute ∼3% benthic biomass) suggests an increased drawdown of ∼2.9x10(6) tonnes of carbon per year. This drawdown could become sequestration because polar continental shelves are typically deeper than most modern iceberg scouring, bacterial breakdown rates are slow, and benthos is easily buried. To date, most sea-ice losses have been Arctic, so, if hyperboreal benthos shows a similar increase in drawdown, polar continental shelves would represent Earth's largest negative feedback to climate change. PMID:26394097

  11. [Carbon budget of ecosystem in Changbai Mountain Natural Reserve].

    PubMed

    Zhang, Na; Yu, Guirui; Zhao, Shidong; Yu, Zhenliang

    2003-01-01

    The study used EPPML, a biological geochemistry cycle model that was built, to simulate the carbon budget for ecosystems in Changbai Mountain Natural Reserve. The results indicated that the annual net primary productivity [NPP (carbon)] of the natural reserve was 1.332 x 10(6) t.a-1. The annual NPP of mixed broad-leaved and Korean pine forest and spruce-fir forest were maximal, 0.540 x 10(6) t.a-1 and 0.428 x 10(6) t.a-1 respectively. The area and productivity of the two stands were maximal in Changbai Mountain, therefore, the simulating productivity of the two stands most greatly affect carbon cycle and carbon budget of the natural reserve, and the veracity of the former decides the security of the latter. To sum up, not only did the simulations accord with routines in the relative comparisons between different vegetation belts and climate belts in the whole natural reserve, but also was exact in the absolute comparisons with very disperse data from field survey. Vegetations in the natural reserve had evident carbon sink functions, mainly exhibiting in the increasing of carbon, about 1.058 x 10(6) t.a-1. The annual carbon of mixed broad-leaved and Korean pine forest increased greatest (0.452 x 10(6) t.a-1), secondly spruce-fir forest (0.339 x 10(6) t.a-1). The two stands played crucial roles in the carbon sink for Changbai Mountain, others being Changbai larch forest, broad-leaved forest, meadow, shrub, alpine tundra, subalpine Betula ermanii forest and alpine grass. In 1995, the decomposing carbon of soil organic matter was 0.169 x 10(6) t.a-1 higher than the littering carbon in the natural reserve. There was accumulation of organic matter in the meadow soil and shrub soil. The decomposition and accumulation of soil organic matter was in the nearly balancing condition in the alpine tundra soil and alpine grass soil. The decomposition of organic matter was as one and a half time or double as litterfall in the arbor forest soil. PMID:12708285

  12. Multiple independent constraints help resolve net ecosystem carbon exchange under nutrient limitation

    NASA Astrophysics Data System (ADS)

    Thornton, P. E.; Metcalfe, D.; Oren, R.; Ricciuto, D. M.

    2014-12-01

    The magnitude, spatial distribution, and variability of land net ecosystem exchange of carbon (NEE) are important determinants of the trajectory of atmospheric carbon dioxide concentration. Independent observational constraints provide important clues regarding NEE and its component fluxes, with information available at multiple spatial scales: from cells, to leaves, to entire organisms and collections of organisms, to complex landscapes and up to continental and global scales. Experimental manipulations, ecosystem observations, and process modeling all suggest that the components of NEE (photosynthetic gains, and respiration and other losses) are controlled in part by the availability of mineral nutrients, and that nutrient limitation is a common condition in many biomes. Experimental and observational constraints at different spatial scales provide a complex and sometimes puzzling picture of the nature and degree of influence of nutrient availability on carbon cycle processes. Photosynthetic rates assessed at the cellular and leaf scales are often higher than the observed accumulation of carbon in plant and soil pools would suggest. We infer that a down-regulation process intervenes between carbon uptake and plant growth under conditions of nutrient limitation, and several down-regulation mechanisms have been hypothesized and tested. A recent evaluation of two alternative hypotheses for down-regulation in the light of whole-plant level flux estimates indicates that some plants take up and store extra carbon, releasing it to the environment again on short time scales. The mechanism of release, either as additional autotrophic respiration or as exudation belowground is unclear, but has important consequences for long-term ecosystem state and response to climate change signals. Global-scale constraints from atmospheric concentration and isotopic composition data help to resolve this question, ultimately focusing attention on land use fluxes as the most uncertain

  13. Modelling Plant and Soil Nitrogen Feedbacks Affecting Forest Carbon Gain at High CO2

    NASA Astrophysics Data System (ADS)

    McMurtrie, R. E.; Norby, R. J.; Franklin, O.; Pepper, D. A.

    2007-12-01

    Short-term, direct effects of elevated atmospheric CO2 concentrations on plant carbon gain are relatively well understood. There is considerable uncertainty, however, about longer-term effects, which are influenced by various plant and ecosystem feedbacks. A key feedback in terrestrial ecosystems occurs through changes in plant carbon (C) allocation patterns. For instance, if high CO2 were to increase C allocation to roots, then plants may experience positive feedback through improved plant nutrition. A second type of feedback, associated with decomposition of soil-organic matter, may reduce soil-nutrient availability at high CO2. This paper will consider mechanistic models of both feedbacks. Effects of high CO2 on plant C allocation will be investigated using a simple model of forest net primary production (NPP) that incorporates the primary mechanisms of plant carbon and nitrogen (N) balance. The model called MATE (Model Any Terrestrial Ecosystem) includes an equation for annual C balance that depends on light- saturated photosynthetic rate and therefore on [CO2], and an equation for N balance incorporating an expression for N uptake as a function of root mass. The C-N model is applied to a Free Air CO2 Exchange (FACE) experiment at Oak Ridge National Laboratory (ORNL) in Tennessee, USA, where closed-canopy, monoculture stands of the deciduous hardwood sweetgum ( Liquidambar styraciflua) have been growing at [CO2] of 375 and 550 ppm for ten years. Features of this experiment are that the annual NPP response to elevated CO2 has averaged approximately 25% over seven years, but that annual fine-root production has almost doubled on average, with especially large increases in later years of the experiment (Norby et al. 2006). The model provides a simple graphical approach for analysing effects of elevated CO2 and N supply on leaf/root/wood C allocation and productivity. It simulates increases in NPP and fine-root production at the ORNL FACE site that are consistent

  14. Seasonal changes of water carbon relations in savanna ecosystems

    NASA Astrophysics Data System (ADS)

    Kutsch, W. L.; Merbold, L.; Archibald, S.

    2011-12-01

    During evolution plant species have developed different strategies to optimize the water carbon relations. These stratgies summarize to ecosystem properties. As an example we show how tropical and subtropical savannas and woodlands can respond flexibly to changes in temperature and water availability and thus optimize carbon and water fluxes between land surface and atmosphere. Several phenomena are presented and discussed in this overview from African flux sites in Zambia, Burkina Faso and South Africa: Pre-rain leaf development: Many trees developed new leaves before the first rain appeared. As a consequence of this early timing of leaf flush, the phenological increase of photosynthetic capacity (Amax) was steeper than in temperate forests. Mid-term response of conductance and photosynthesis to soil water relations: The regulation of canopy conductance was temporally changing in two ways: changes due to phenology during the course of the growing season and short-term (hours to days) acclimation to soil water conditions. The most constant parameter was water use efficiency. It was influenced by water vapour pressure deficit (VPD) during the day, but the VPD response curve of water usage only changed slightly during the course of the growing season, and decreased by about 30% during the transition from wet to dry season. The regulation of canopy conductance and photosynthetic capacity were closely related. This observation meets recent leaf-level findings that stomatal closure triggers down-regulation of Rubisco during drought. Our results may show the effects of these processes on the ecosystem scale. Furthermore, we observed that the close relationship between stomatal conductance and photosynthesis resulted in different temperature optima of GPP that were close to the average daytime temperature. Adaptation of respiration to rain pulses: Finally, the response of respiration to rain pulses showed changes throughout the growing season. The first rain events early

  15. Carbon Gain and Photosynthetic Response of Chrysanthemum to Photosynthetic Photon Flux Density Cycles 1

    PubMed Central

    Stoop, Johan M. H.; Willits, Dan H.; Peet, Mary M.; Nelson, Paul V.

    1991-01-01

    Most models of carbon gain as a function of photosynthetic irradiance assume an instantaneous response to increases and decreases in irradiance. High- and low-light-grown plants differ, however, in the time required to adjust to increases and decreases in irradiance. In this study the response to a series of increases and decreases in irradiance was observed in Chrysanthemum × morifolium Ramat. “Fiesta” and compared with calculated values assuming an instantaneous response. There were significant differences between high- and low-light-grown plants in their photosynthetic response to four sequential photosynthetic photon flux density (PPFD) cycles consisting of 5-minute exposures to 200 and 400 micromoles per square meter per second (μmol m−2s−1). The CO2 assimilation rate of high-light-grown plants at the cycle peak increased throughout the PPFD sequence, but the rate of increase was similar to the increase in CO2 assimilation rate observed under continuous high-light conditions. Low-light leaves showed more variability in their response to light cycles with no significant increase in CO2 assimilation rate at the cycle peak during sequential cycles. Carbon gain and deviations from actual values (percentage carbon gain over- or underestimation) based on assumptions of instantaneous response were compared under continuous and cyclic light conditions. The percentage carbon gain overestimation depended on the PPFD step size and growth light level of the leaf. When leaves were exposed to a large PPFD increase, the carbon gain was overestimated by 16 to 26%. The photosynthetic response to 100 μmol m−2 s−1 PPFD increases and decreases was rapid, and the small overestimation of the predicted carbon gain, observed during photosynthetic induction, was almost entirely negated by the carbon gain underestimation observed after a decrease. If the PPFD cycle was 200 or 400 μmol m−2 s−1, high- and low-light leaves showed a carbon gain overestimation of 25

  16. Using carbon oxidation state and ecosystem oxidative ratio to understand terrestrial ecosystem response to elevated CO2

    NASA Astrophysics Data System (ADS)

    Hockaday, W. C.; Masiello, C. A.; Gallagher, M. E.

    2015-12-01

    Here we show that an easily-measured biogeochemical tracer, carbon oxidation state (Cox) can be used to understand ecosystem response to elevated atmospheric CO2 concentrations. We briefly review the use of Cox in understanding C sink estimates, and its role in understanding the coupled nature of carbon and oxygen cycles, which derives from its relationship with ecosystem oxidative ratio (OR). The Cox of a carbon pool provides an integrated measure of all processes that create and destroy organic matter (e.g. photosynthesis, respiration, fire) and therefore, can be used to estimate the oxidative ratio (O2/CO2) of biosphere-atmosphere exchange. Our preliminary data suggest that the OR of temperate hardwood forest and grassland ecosystems are influenced by atmospheric CO2 concentration. The variation in ecosystem Cox with atmospheric CO2 concentration suggest that OR is not a conservative property of terrestrial ecosystems on annual or decadal timescales. In the grassland ecosystem, the Cox of plant biomass increased by as much as 50% across a CO2 concentration gradient of 190 ppm, but the response was highly dependent upon soil properties. In the temperate forest, the Cox of the soil C pool increased by 40% after 9 seasons of CO2 enrichment (by 175 ppm). We will discuss our interpretation of Cox as a proxy and its potential use in studies of coupled O2 and CO2 cycling.

  17. Typhoons exert significant but differential impact on net carbon ecosystem exchange of subtropical mangrove ecosystems in China

    NASA Astrophysics Data System (ADS)

    Chen, H.; Lu, W.; Yan, G.; Yang, S.; Lin, G.

    2014-06-01

    Typhoons are very unpredictable natural disturbances to subtropical mangrove forests in Asian countries, but litter information is available on how these disturbances affect ecosystem level carbon dioxide (CO2) exchange of mangrove wetlands. In this study, we examined short-term effect of frequent strong typhoons on defoliation and net ecosystem CO2 exchange (NEE) of subtropical mangroves, and also synthesized 19 typhoons during a 4-year period between 2009 and 2012 to further investigate the regulation mechanisms of typhoons on ecosystem carbon and water fluxes following typhoon disturbances. Strong wind and intensive rainfall caused defoliation and local cooling effect during typhoon season. Daily total NEE values were decreased by 26-50% following some typhoons (e.g. W28-Nockten, W35-Molave and W35-Lio-Fan), but were significantly increased (43-131%) following typhoon W23-Babj and W38-Megi. The magnitudes and trends of daily NEE responses were highly variable following different typhoons, which were determined by the balance between the variances of gross ecosystem production (GEP) and ecosystem respiration (RE). Furthermore, results from our synthesis indicated that the landfall time of typhoon, wind speed and rainfall were the most important factors controlling the CO2 fluxes following typhoon events. These findings not only indicate that mangrove ecosystems have strong resilience to the frequent typhoon disturbances, but also demonstrate the damage of increasing typhoon intensity and frequency on subtropical mangrove ecosystems under future global climate change scenarios.

  18. Elevated carbon dioxide and ozone alter productivity and ecosystem carbon content in northern temperate forests.

    PubMed

    Talhelm, Alan F; Pregitzer, Kurt S; Kubiske, Mark E; Zak, Donald R; Campany, Courtney E; Burton, Andrew J; Dickson, Richard E; Hendrey, George R; Isebrands, J G; Lewin, Keith F; Nagy, John; Karnosky, David F

    2014-08-01

    Three young northern temperate forest communities in the north-central United States were exposed to factorial combinations of elevated carbon dioxide (CO2 ) and tropospheric ozone (O3 ) for 11 years. Here, we report results from an extensive sampling of plant biomass and soil conducted at the conclusion of the experiment that enabled us to estimate ecosystem carbon (C) content and cumulative net primary productivity (NPP). Elevated CO2 enhanced ecosystem C content by 11%, whereas elevated O3 decreased ecosystem C content by 9%. There was little variation in treatment effects on C content across communities and no meaningful interactions between CO2 and O3 . Treatment effects on ecosystem C content resulted primarily from changes in the near-surface mineral soil and tree C, particularly differences in woody tissues. Excluding the mineral soil, cumulative NPP was a strong predictor of ecosystem C content (r(2) = 0.96). Elevated CO2 enhanced cumulative NPP by 39%, a consequence of a 28% increase in canopy nitrogen (N) content (g N m(-2) ) and a 28% increase in N productivity (NPP/canopy N). In contrast, elevated O3 lowered NPP by 10% because of a 21% decrease in canopy N, but did not impact N productivity. Consequently, as the marginal impact of canopy N on NPP (∆NPP/∆N) decreased through time with further canopy development, the O3 effect on NPP dissipated. Within the mineral soil, there was less C in the top 0.1 m of soil under elevated O3 and less soil C from 0.1 to 0.2 m in depth under elevated CO2 . Overall, these results suggest that elevated CO2 may create a sustained increase in NPP, whereas the long-term effect of elevated O3 on NPP will be smaller than expected. However, changes in soil C are not well-understood and limit our ability to predict changes in ecosystem C content. PMID:24604779

  19. Ecosystem carbon budgeting and soil carbon sequestration in reclaimed mine soil.

    PubMed

    Shrestha, Raj K; Lal, Rattan

    2006-08-01

    Global warming risks from emissions of green house gases (GHGs) by anthropogenic activities, and possible mitigation strategies of terrestrial carbon (C) sequestration have increased the need for the identification of ecosystems with high C sink capacity. Depleted soil organic C (SOC) pools of reclaimed mine soil (RMS) ecosystems can be restored through conversion to an appropriate land use and adoption of recommended management practices (RMPs). The objectives of this paper are to (1) synthesize available information on carbon dioxide (CO2) emissions from coal mining and combustion activities, (2) understand mechanisms of SOC sequestration and its protection, (3) identify factors affecting C sequestration potential in RMSs, (4) review available methods for the estimation of ecosystem C budget (ECB), and (5) identify knowledge gaps to enhance C sink capacity of RMS ecosystems and prioritize research issues. The drastic perturbations of soil by mining activities can accentuate CO2 emission through mineralization, erosion, leaching, changes in soil moisture and temperature regimes, and reduction in biomass returned to the soil. The reclamation of drastically disturbed soils leads to improvement in soil quality and development of soil pedogenic processes accruing the benefit of SOC sequestration and additional income from trading SOC credits. The SOC sequestration potential in RMS depends on amount of biomass production and return to soil, and mechanisms of C protection. The rate of SOC sequestration ranges from 0.1 to 3.1 Mg ha(-1) yr(-1) and 0.7 to 4 Mg ha(-1) yr(-1) in grass and forest RMS ecosystem, respectively. Proper land restoration alone could off-set 16 Tg CO2 in the U.S. annually. However, the factors affecting C sequestration and protection in RMS leading to increase in microbial activity, nutrient availability, soil aggregation, C build up, and soil profile development must be better understood in order to formulate guidelines for development of an

  20. Gaining insight into river ecosystem processes from a large-scale flow experiment

    NASA Astrophysics Data System (ADS)

    Harrison, L.; Pike, A.; Boughton, D. A.

    2015-12-01

    In rivers throughout the world, anthropogenic impacts related to large dams have altered or eliminated the habitat necessary for many aquatic organisms. Flow experiments, both planned and unplanned, provide unique opportunities to evaluate the extent to which alternative dam operations can provide downstream ecological benefits. Here we use an unanticipated, reservoir release on the Santa Ynez River in southern California to investigate how a large flood influenced river ecosystem processes. We directly measured the flood-induced, topographic changes over 80 km of the river and floodplain using two high-resolution field and remote sensing data sets that bracketed the flood event. DEM-differencing of the pre- and post-flood topography was used to calculate shifts in the active channel planform and the net volumetric fluxes in gravel storage along the channel and floodplain. LiDAR and image-based habitat mapping was conducted to quantify the proportion of different habitat units before and after the flood. Large-scale geomorphic changes were observed as a result of the flood, including lateral migration of the river channel, gravel bar formation and the development of off-channel chute habitat. Spatial patterns of gravel storage changed with distance from the dam, with the upper 20 km experiencing a net sediment deficit and the lower 60 km undergoing net deposition. The longitudinal trends in gravel transport and storage reflect differences in the channel gradient, valley confinement and density of floodplain vegetation. We found that the flood nearly doubled the extent of pool habitat, primarily by converting runs to pools and by incising new pools adjacent to valley walls and terraces. The increase in the number of pools was predicted to have positive impacts on steelhead habitat, by providing a broader range of water depths and micro-habitats utilized by different age classes. Results from this study highlight the value of using flow pulses as opportunities to

  1. Global change accelerates carbon assimilation by a wetland ecosystem engineer

    NASA Astrophysics Data System (ADS)

    Caplan, Joshua S.; Hager, Rachel N.; Megonigal, J. Patrick; Mozdzer, Thomas J.

    2015-11-01

    The primary productivity of coastal wetlands is changing dramatically in response to rising atmospheric carbon dioxide (CO2) concentrations, nitrogen (N) enrichment, and invasions by novel species, potentially altering their ecosystem services and resilience to sea level rise. In order to determine how these interacting global change factors will affect coastal wetland productivity, we quantified growing-season carbon assimilation (≈gross primary productivity, or GPP) and carbon retained in living plant biomass (≈net primary productivity, or NPP) of North American mid-Atlantic saltmarshes invaded by Phragmites australis (common reed) under four treatment conditions: two levels of CO2 (ambient and +300 ppm) crossed with two levels of N (0 and 25 g N added m-2 yr-1). For GPP, we combined descriptions of canopy structure and leaf-level photosynthesis in a simulation model, using empirical data from an open-top chamber field study. Under ambient CO2 and low N loading (i.e., the Control), we determined GPP to be 1.66 ± 0.05 kg C m-2 yr-1 at a typical Phragmites stand density. Individually, elevated CO2 and N enrichment increased GPP by 44 and 60%, respectively. Changes under N enrichment came largely from stimulation to carbon assimilation early and late in the growing season, while changes from CO2 came from stimulation during the early and mid-growing season. In combination, elevated CO2 and N enrichment increased GPP by 95% over the Control, yielding 3.24 ± 0.08 kg C m-2 yr-1. We used biomass data to calculate NPP, and determined that it represented 44%-60% of GPP, with global change conditions decreasing carbon retention compared to the Control. Our results indicate that Phragmites invasions in eutrophied saltmarshes are driven, in part, by extended phenology yielding 3.1× greater NPP than native marsh. Further, we can expect elevated CO2 to amplify Phragmites productivity throughout the growing season, with potential implications including accelerated spread

  2. Asymmetric warming significantly affects net primary production, but not ecosystem carbon balances of forest and grassland ecosystems in northern China

    PubMed Central

    Su, Hongxin; Feng, Jinchao; Axmacher, Jan C.; Sang, Weiguo

    2015-01-01

    We combine the process-based ecosystem model (Biome-BGC) with climate change-scenarios based on both RegCM3 model outputs and historic observed trends to quantify differential effects of symmetric and asymmetric warming on ecosystem net primary productivity (NPP), heterotrophic respiration (Rh) and net ecosystem productivity (NEP) of six ecosystem types representing different climatic zones of northern China. Analysis of covariance shows that NPP is significant greater at most ecosystems under the various environmental change scenarios once temperature asymmetries are taken into consideration. However, these differences do not lead to significant differences in NEP, which indicates that asymmetry in climate change does not result in significant alterations of the overall carbon balance in the dominating forest or grassland ecosystems. Overall, NPP, Rh and NEP are regulated by highly interrelated effects of increases in temperature and atmospheric CO2 concentrations and precipitation changes, while the magnitude of these effects strongly varies across the six sites. Further studies underpinned by suitable experiments are nonetheless required to further improve the performance of ecosystem models and confirm the validity of these model predictions. This is crucial for a sound understanding of the mechanisms controlling the variability in asymmetric warming effects on ecosystem structure and functioning. PMID:25766381

  3. Asymmetric warming significantly affects net primary production, but not ecosystem carbon balances of forest and grassland ecosystems in northern China.

    PubMed

    Su, Hongxin; Feng, Jinchao; Axmacher, Jan C; Sang, Weiguo

    2015-01-01

    We combine the process-based ecosystem model (Biome-BGC) with climate change-scenarios based on both RegCM3 model outputs and historic observed trends to quantify differential effects of symmetric and asymmetric warming on ecosystem net primary productivity (NPP), heterotrophic respiration (Rh) and net ecosystem productivity (NEP) of six ecosystem types representing different climatic zones of northern China. Analysis of covariance shows that NPP is significant greater at most ecosystems under the various environmental change scenarios once temperature asymmetries are taken into consideration. However, these differences do not lead to significant differences in NEP, which indicates that asymmetry in climate change does not result in significant alterations of the overall carbon balance in the dominating forest or grassland ecosystems. Overall, NPP, Rh and NEP are regulated by highly interrelated effects of increases in temperature and atmospheric CO2 concentrations and precipitation changes, while the magnitude of these effects strongly varies across the six sites. Further studies underpinned by suitable experiments are nonetheless required to further improve the performance of ecosystem models and confirm the validity of these model predictions. This is crucial for a sound understanding of the mechanisms controlling the variability in asymmetric warming effects on ecosystem structure and functioning. PMID:25766381

  4. Asymmetric warming significantly affects net primary production, but not ecosystem carbon balances of forest and grassland ecosystems in northern China

    NASA Astrophysics Data System (ADS)

    Su, Hongxin; Feng, Jinchao; Axmacher, Jan C.; Sang, Weiguo

    2015-03-01

    We combine the process-based ecosystem model (Biome-BGC) with climate change-scenarios based on both RegCM3 model outputs and historic observed trends to quantify differential effects of symmetric and asymmetric warming on ecosystem net primary productivity (NPP), heterotrophic respiration (Rh) and net ecosystem productivity (NEP) of six ecosystem types representing different climatic zones of northern China. Analysis of covariance shows that NPP is significant greater at most ecosystems under the various environmental change scenarios once temperature asymmetries are taken into consideration. However, these differences do not lead to significant differences in NEP, which indicates that asymmetry in climate change does not result in significant alterations of the overall carbon balance in the dominating forest or grassland ecosystems. Overall, NPP, Rh and NEP are regulated by highly interrelated effects of increases in temperature and atmospheric CO2 concentrations and precipitation changes, while the magnitude of these effects strongly varies across the six sites. Further studies underpinned by suitable experiments are nonetheless required to further improve the performance of ecosystem models and confirm the validity of these model predictions. This is crucial for a sound understanding of the mechanisms controlling the variability in asymmetric warming effects on ecosystem structure and functioning.

  5. Carbon fluxes, evapotranspiration, and water use efficiency of terrestrial ecosystems in China

    NASA Astrophysics Data System (ADS)

    Xiao, J.

    2013-12-01

    The magnitude, spatial patterns, and controlling factors of the carbon and water fluxes of terrestrial ecosystems in China are not well understood due to the lack of ecosystem-level flux observations. We synthesized flux and micrometeorological observations from 22 eddy covariance flux sites across China, and examined the carbon fluxes, evapotranspiration (ET), and water use efficiency (WUE) of terrestrial ecosystems at the annual scale. Our results show that annual carbon and water fluxes exhibited clear latitudinal patterns across sites. Both annual gross primary productivity (GPP) and ecosystem respiration (ER) declined with increasing latitude, leading to a declining pattern in net ecosystem productivity (NEP) with increasing latitude. Annual ET also generally declined with increasing latitude. The spatial patterns of annual carbon and water fluxes were mainly driven by annual temperature, precipitation, and growing season length. Carbon fluxes, ET, and water use efficiency (WUE) varied with vegetation type. Overall, forest and cropland sites had higher annual fluxes than grassland sites, and the annual fluxes of coastal wetland sites were similar to or slightly higher than those of forest sites. Annual WUE was associated with annual precipitation, GPP, and growing season length. Higher-productivity ecosystems (forests and coastal wetlands) also had higher WUE than lower-productivity ecosystems (grasslands and croplands). The strong relationships between annual GPP and ET demonstrated the coupling of the carbon and water cycles. Our results show that forest plantations had high annual net carbon uptake and WUE, and provide larger carbon sequestration capacity than natural forests. The coastal salt marsh and mangrove ecosystems also had high carbon sequestration capacity. Efforts to strengthen China's ecosystem carbon sequestration should focus on ecosystems such as forest plantations in southern China where heat and water are ideal for maintaining high

  6. Insights into the Processing of Carbon by Early Microbial Ecosystems

    NASA Technical Reports Server (NTRS)

    DesMarais, D.; Bebout, B.; Carpenter, S.; Discipulo, S.; Londry, K.; Habicht, K.; Turk, K.

    2003-01-01

    Interactions between Earth and the biosphere that were crucial for early biological evolution also influenced substantially the processes that circulate C between its reservoirs in the atmosphere, ocean, crust and mantle. The C-13 C-12 values of crustal carbonates and organics have recorded changes both in biological discrimination and in the relative rates of burial of organics and carbonates. A full interpretation of these patterns needs further isotopic studies of microbial ecosystems and individual anaerobes. Thus we measured carbon isotope discrimination during autotrophic and heterotrophic growth of pure cultures of sulfate-reducing bacteria and archaea (SRB and SRA). Discrimination during CO2 assimilation is significantly larger than during heterotrophic growth on lactate or acetate. SRB grown lithoautotrophically consumed less than 3% of available CO2 and exhibited substantial discrimination, as follows: Desulfobacterium autotrophicum (alpha 1.0100 to 1.0123), Desulfobacter hydrogenophilus (alpha = 0.0138), and Desulfotomuculum acetoxidans (alpha = 1.0310). Mixotrophic growth of Desulfovibrio desulfuricans on acetate and CO2 resulted in biomass with delta C-13 composition intermediate to that of the substrates. We have recently extended these experiments to include the thermophilic SRA Archeoglobus spp. Ecological forces also influence isotopic discrimination. Accordingly, we quantified the flow of C and other constituents in modern marine cyanobacterial mats, whose ancestry extends back billions of years. Such ecosystem processes shaped the biosignatures that entered sediments and atmospheres. At Guerrero Negro, BCS, Mexico, we examined mats dominated by Microcoleus (subtidal) and Lyngbya (intertidal to supratidal) cyanobacteria. During 24 hour cycles, we observed the exchange of O2 and dissolved inorganic C (DIC) between mats and the overlying water. Microcoleus mats assimilated near-equal amounts of DIC during the day as they released at night, but

  7. Utilization of carbon sources in a northern Brazilian mangrove ecosystem

    NASA Astrophysics Data System (ADS)

    Giarrizzo, Tommaso; Schwamborn, Ralf; Saint-Paul, Ulrich

    2011-12-01

    Carbon and nitrogen stable isotope ratios ( 13C and 15N) and trophic level (TL) estimates based on stomach content analysis and published data were used to assess the contribution of autotrophic sources to 55 consumers in an intertidal mangrove creek of the Curuçá estuary, northern Brazil. Primary producers showed δ 13C signatures ranging between -29.2 and -19.5‰ and δ 15N from 3.0 to 6.3‰. The wide range of the isotopic composition of carbon of consumers (-28.6 to -17.1‰) indicated that different autotrophic sources are important in the intertidal mangrove food webs. Food web segregation structures the ecosystem into three relatively distinct food webs: (i) mangrove food web, where vascular plants contribute directly or indirectly via POM to the most 13C-depleted consumers (e.g. Ucides cordatus and zooplanktivorous food chains); (ii) algal food web, where benthic algae are eaten directly by consumers (e.g. Uca maracoani, mullets, polychaetes, several fishes); (iii) mixed food web where the consumers use the carbon from different primary sources (mainly benthivorous fishes). An IsoError mixing model was used to determine the contributions of primary sources to consumers, based on δ 13C values. Model outputs were very sensitive to the magnitude of trophic isotope fractionation and to the variability in 13C data. Nevertheless, the simplification of the system by a priori aggregation of primary producers allowed interpretable results for several taxa, revealing the segregation into different food webs.

  8. Microbial carbon cycling in Lost City hydrothermal chimneys and other serpentinite-hosted ecosystems (Invited)

    NASA Astrophysics Data System (ADS)

    Brazelton, W. J.; Lang, S. Q.; Morrill, P. L.; Twing, K. I.; Crespo-Medina, M.; Morgan-Smith, D.; Früh-Green, G. L.; Schrenk, M. O.

    2013-12-01

    Ultramafic rocks formed in the Earth's mantle and uplifted into the crust represent an immense but poorly described reservoir of carbon. The biological availability of this rock-hosted carbon reservoir is unknown, but the set of geochemical reactions known as serpentinization can mobilize carbon from the subsurface and trigger the growth of dense microbial communities. Serpentinite-hosted ecosystems such as the chimney biofilms of the Lost City hydrothermal field can support dense populations of bacteria and archaea fueled by the copious quantities of H2 and methane (CH4) released by serpentinization (1-5). The metabolic pathways involved, however, remain unknown, and conventional interpretations of genomic and experimental data are complicated by the unusual carbon speciation in these environments. Carbon dioxide is scarce due to the highly reducing, high pH conditions. Instead, the predominant forms of carbon are CH4 and formate (5). Despite its natural abundance, however, direct evidence for CH4-derived biomass is lacking (1,4,5), and the role of formate is potentially significant but largely unexplored (1,5). To gain a more generalized perspective of carbon cycling in serpentinite-hosted ecosystems, we have recently investigated fluids and rocks collected from serpentinizing ophiolites in California, Canada, and Italy. Our results point to potentially H2-utilizing, autotrophic Betaproteobacteria thriving in shallow, oxic-anoxic transition zones and anaerobic Clostridia inhabiting anoxic, subsurface zones (1,6). The carbon sources utilized by the Clostridia are unknown, but preliminary metagenomic evidence is consistent with a fermentation-style metabolic strategy that may be conducive to an oxidant-limited, subsurface environment. Curiously, despite the abundance of H2 and CH4 in these continental springs, none of the geochemical, genomic, or experimental results obtained thus far contain any evidence for biological methanogenesis (1,6). This is in stark

  9. [A review on carbon and water interactions of forest ecosystem and its impact factors].

    PubMed

    Song, Chun-lin; Sun, Xiang-yang; Wang, Gen-xu

    2015-09-01

    Interaction between carbon and water in forest ecosystem is a coupling process in terrestrial ecosystem, which is an indispensable aspect for the study of forest carbon pool, ecohydrological processes and the responses to global change. In the context of global change, the interaction and coupling of carbon and water in forest ecosystem has attracted much attention among scientists. In this paper, we reviewed the process mechanism of forest carbon and water relationships based on previous studies, which consisted of advance in forest water use efficiency, carbon and water interactions at different scales, scaling, and model simulation. We summed up the factors affecting for- est water and carbon interaction, including water condition, carbon dioxide enrichment, warming, nitrogen deposition, ozone concentration variation, solar radiation, and altitudinal gradients. Finally, we discussed the problems in the previous studies, and prospected the possible future research fields, among which we thought the inherent dynamics mechanism and scaling of forest carbon and water interactions should be enhanced. PMID:26785576

  10. Organic carbon balance and net ecosystem metabolism in Chesapeake Bay

    USGS Publications Warehouse

    Kemp, W.M.; Smith, E.M.; Marvin-DiPasquale, M.; Boynton, W.R.

    1997-01-01

    The major fluxes of organic carbon associated with physical transport and biological metabolism were compiled, analyzed and compared for the mainstem portion of Chesapeake Bay (USA). In addition, 5 independent methods were used to calculate the annual mean net ecosystem metabolism (NEM = production - respiration) for the integrated Bay. These methods, which employed biogeochemical models, nutrient mass-balances anti summation of individual organic carbon fluxes, yielded remarkably similar estimates, with a mean NEM of +50 g C m-2 yr-1 (?? SE = 751, which is approximately 8% of the estimated annual average gross primary production. These calculations suggest a strong cross-sectional pattern in NEM throughout the Bay, wherein net heterotrophic metabolism prevails in the pelagic zones of the main channel, while net autotrophy occurs in the littoral zones which flank the deeper central area. For computational purposes, the estuary was separated into 3 regions along the land-sea gradient: (1) the oligohaline Upper Bay (11% of total area); (2) the mesohaline Mid Bay (36% of area); and (3) the polyhaline Lower Bay (53% of area). A distinct regional trend in NEM was observed along this salinity gradient, with net here(atrophy (NEM = 87 g C m-2 yr-1) in the Upper Bay, balanced metabolism in the Mid Bay and net autotrophy (NEM = +92 g C m-2 yr-1) in the Lower Bay. As a consequence of overall net autotrophy, the ratio of dissolved inorganic nitrogen (DIN) to total organic nitrogen (TON) changed from DIN:TON = 5.1 for riverine inputs to DIN:TON = 0.04 for water exported to the ocean. A striking feature of this organic C mass-balance was the relative dominance of biologically mediated metabolic fluxes compared to physical transport fluxes. The overall ratio of physical TOC inputs (1) to biotic primary production (P) was 0.08 for the whole estuary, but varied dramatically from 2.3 in the Upper Bay to 0.03 in the Mid and Lower Bay regions. Similarly, ecosystem respiration was

  11. Assessing and Monitoring Spatial and Temporal Distributions of Ecosystem Carbon Storage and Changes in the United States

    NASA Astrophysics Data System (ADS)

    Zhu, Z.; Liu, S.; Sleeter, B. M.; Sohl, T. L.; Hawbaker, T. J.; Stackpoole, S. M.

    2011-12-01

    Land changes (land use and ecosystem disturbances) are the primary driver of stability and vulnerability of ecosystem carbon sequestration. Advances in remote sensing and modeling make it possible that carbon storage in relation to land changes can be assessed and monitored at the national and regional scales. Using remote sensing and modeling tools, the U.S. Geological Survey is conducting a national assessment to estimate spatial and temporal distributions of carbon storage in relation to land changes. The assessment covers all major ecosystems: forests, shrub and grasslands, croplands, wetlands, and aquatic systems. Recent land changes (baseline, 1992 to current) are mapped on an annual basis using Landsat imagery; future land changes (current to 2050) are modeled by incorporating IPCC socioeconomic storylines and climate change projections (three storylines and projections used: A1B, A2, and B1, each with multiple GCM runs). Carbon storage in, and transitions between, ecosystems are modeled and estimated annually using biogeochemical models, with the baseline and future potential land use changes and fire disturbances as the primary input. Effects of land changes and management activities are analyzed. A series of regional-scale maps and datasets are produced as deliverables of the assessment. The Great Plains region of the United States is the first region to complete for the assessment. The region encompasses 2.17 million square kilometers from eastern half of Montana south to Texas and east to Minnesota and Iowa. Changes in land use between 1992 and 2050 are pronounced for major ecosystems, including 7-16% gains in agriculture, 8-17% losses of grasslands and 18-19% losses of wetlands under A1B and A2 scenarios. More environmental oriented scenarios such as B1 will see gains in wetlands (15%) while holding areas of other ecosystems stable. For fire disturbances, number, size, and severity of large wildland fires in the region are highly variable, depending on

  12. Modeling the above and below ground carbon and nitrogen stocks in northern high latitude terrestrial ecosystems

    NASA Astrophysics Data System (ADS)

    ElMasri, B.; Jain, A. K.

    2012-12-01

    Climate change is expected to cause warming in the northern high latitudes, but it is still uncertain what the respond of the northern high latitudes ecosystem will be to such warming. One of the biggest scientific questions is to determine whether northern high latitude ecosystem are or will act as a terrestrial carbon sink or source. Therefore, it is essential to understand and quantify the biogeochemical cycle of the northern high latitude ecosystems in order to predict their respond to climate change. Using a land surface model, the Integrated Science Assessment Model (ISAM) with its coupled carbon-nitrogen cycle, we provide a detail quantification of the carbon and nitrogen in the vegetation pools and the soil carbon for the northern high latitude ecosystems. We focus on soil carbon and vegetation carbon and nitrogen, though we provide results for gross primary production (GPP), autotrophic respiration (Ra), net primary production (NPP), net ecosystem exchange (NEE), and heterotrophic respiration (Rh). In addition, we examine the effect of nitrogen limitation on the carbon fluxes and soil carbon. We present the results for several flux tower sites representative of the tundra and the boreal ecosystems as well as for the northern high latitude region. Our results provide a comprehensive assessment of below and above ground carbon and nitrogen pools in the northern high latitude and the model calibrated parameters can be used to improve the results of other land surface models.

  13. Intensity normalization and automatic gain control correction of airborne LiDAR data for classifying a rangeland ecosystem

    NASA Astrophysics Data System (ADS)

    Shrestha, R.; Glenn, N. F.; Spaete, L.; Mitchell, J.

    2011-12-01

    Airborne LiDAR not only records elevation but also the intensity, or the amplitude, of the returning light beam. LiDAR intensity information can be useful for many applications, including landcover classification. Intensity is directly associated with the reflectance of the target surface and can be influenced by factors such as flying altitude and sensor settings. LiDAR intensity data must be calibrated before use and this is especially important for multi-temporal studies where differing flight conditions can cause more variations. Some sensors such as the Leica ALS50 Phase II also records automatic gain control (AGC), which controls the gain of the LiDAR signal, allowing information from low-reflectance surfaces. We demonstrate a post-processing method for calibrating intensity using airborne LiDAR data collected over a sage-steppe ecosystem in southeastern Idaho, USA. Range normalization with respect to the sensor-to-object distance is performed by using smoothed best estimated trajectory information collected at an interval of every second. Optimal parameters for calibrating AGC data are determined by collecting spectral reference data at the time of overflights, in test areas with homogenous backscatter properties. Intensity calibration results are compared with vendor corrected intensity data, and used to perform landcover classification using the Random Forests method. We also test this intensity calibration approach using a separate multi-temporal LiDAR data set collected by the same sensor.

  14. Relationships among carbon inputs, arbuscular mycorrhizal fungi, and soil carbon storage in a monoculture corn ecosystem

    NASA Astrophysics Data System (ADS)

    Castellano, M. J.; Brown, K.; Hofmockel, K.

    2012-12-01

    Carbon inputs are positively associated with soil organic carbon storage. Soil organic carbon can be stored in relatively stable pools through: silt + clay association and aggregation. Current models predict that the proportion of new carbon inputs that can be stabilized by silt + clay and aggregates decreases in proportion to the amount of organic matter already present in the fraction. Accordingly, as the capacity to stabilize organic matter approaches zero (full capacity), the efficiency of organic matter stabilization decreases and a greater proportion of organic matter inputs is respired as CO2 or accumulate as litter or easily mineralizable particulate organic matter. The organic matter storage capacity of silt + clay particles is a function of soil texture and mineralogy whereas aggregate storage capacity is also affected by biological factors such as mycorrhizae abundance. We explored relationships among net primary production (carbon inputs), mycorrhizae, and soil organic matter storage in a long-term monoculture corn ecosystem. Replicated plots of corn were grown with one of five nitrogen fertilizer input rates (0-228 kg ha-1 h-y) to impart differences in net primary productivity. The fertilizer rates had no effect on soil C/N ratio. However, the fertilizer rate was positively associated with mycorrhizae abundance and soil carbon storage. Soil carbon storage increases were the result of an increase in soil aggregate-protected carbon only; silt + clay associated carbon did not differ with fertilizer rate. These results are inconsistent with models that predict aggregate and silt + clay pools reach capacity at similar rates. A positive correlation among soil carbon stored in aggregates and mycorrhizae helps to explain this result.

  15. Fluid mixing technique increases the gain and output power of carbon dioxide laser systems

    NASA Technical Reports Server (NTRS)

    Cool, T. A.

    1970-01-01

    High speed flowing gas system provides uniform mixing in short times compared to flow transit times and carbon dioxide vibrational relaxation times. This system minimizes the effects of surrounding surfaces and provides a uniformly high gain that is independent of dimensions transverse to the flow direction.

  16. Modeling the role of terrestrial ecosystems in the global carbon cycle

    SciTech Connect

    Emanuel, W.R.; Post, W.M.; Shugart, H.H. Jr.

    1980-01-01

    A model for the global biogeochemical cycle of carbon which includes a five-compartment submodel for circulation in terrestrial ecosystems of the world is presented. Although this terrestrial submodel divides carbon into compartments with more functional detail than previous models, the variability in carbon dynamics among ecosystem types and in different climatic zones is not adequately treated. A new model construct which specifically treats this variability by modeling the distribution of ecosystem types as a function of climate on a 0.5/sup 0/ latitude by 0.5/sup 0/ longitude scale of resolution is proposed.

  17. [Ecosystem carbon exchange in Artemisia ordosica shrubland of Ordos Plateau in two different precipitation years].

    PubMed

    Gao, Li; Dong, Ting-Ting; Wang, Yu-Qing; Yan, Zhi-Jian; Baoyin, Tao-ge-tao; Wang, Hui; Dai, Ya-Ting

    2014-08-01

    Characteristics of ecosystem carbon exchange and its impact factors in Artemisia ordosica shrubland in 2011 (low precipitation) and 2012 (high precipitation), Ordos Plateau, were studied using eddy covariance methods. The results showed that the diurnal dynamics of ecosystem carbon exchange could be expressed as single-peak and double-peak curves in the two different precipitation years. In 2011, three carbon absorption peaks and three carbon release peaks of ecosystem carbon exchange presented in the growing season. In 2012, four carbon absorption peaks and one carbon release peak appeared in the growing season. The A. ordosica shrubland was a net carbon sink from June to September and a carbon source in October in 2011. In 2012, A. ordosica shrubland was a net carbon sink in the whole growing season. The amount of carbon fixed by A. ordosica shrubland in the growing season in 2012 was 268.90 mg CO2 x m(-2) x s(-1) higher than that in 2011. The ecosystem carbon exchange of A. ordosica shrubland was controlled by PAR (photosynthetically active radiation) on the day scale, and affected by both abiotic (precipitation and soil water content) and biotic (aboveground net primary, productivity) factors on the growing season scale. PMID:25509064

  18. Effects of management of ecosystem carbon pools and fluxes in grassland ecosystems

    NASA Astrophysics Data System (ADS)

    Ryals, R.; Silver, W. L.

    2010-12-01

    Grasslands represent a large land-use footprint and have considerable potential to sequester carbon (C) in soil. Climate policies and C markets may provide incentives for land managers to pursue strategies that optimize soil C storage, yet we lack robust understanding of C sequestration in grasslands. Previous research has shown that management approaches such as organic amendments or vertical subsoiling can lead to larger soil C pools. These management approaches can both directly and indirectly affect soil C pools. We used well-replicated field experiments to explore the effects of these management strategies on ecosystem C pools and fluxes in two bioclimatic regions of California (Sierra Foothills Research and Extension Center (SFREC) and Nicasio Ranch). Our treatments included an untreated control, compost amendments, plowed (vertical subsoil), and compost + plow. The experiment was conducted over two years allowing us to compare dry (360 mm) and average (632 mm) rainfall conditions. Carbon dioxide (CO2) fluxes were measured weekly using a LI-8100 infrared gas analyzer. Methane (CH4) and nitrous oxide (N2O) fluxes were measured monthly using static flux chambers. Aboveground and belowground biomass were measured at the end of the growing season as an index of net primary productivity (NPP) in the annual plant dominated system. Soil moisture and temperature were measured continuously and averaged on hourly and daily timescales. Soil organic C and N concentrations were measured prior to the application of management treatments and at the ends of each growing season. Soils were collected to a 10 cm depth in year one and at four depth increments (0-10, 10-30, 30-50, and 50-100 cm) in year two. Soil C and N concentrations were converted to content using bulk density values for each plot. During both growing seasons, soil respiration rates were higher in the composted plots and lower in the plowed plots relative to controls at both sites. The effects on C loss via

  19. The Importance of Uncertainty and Sensitivity Analyses in Process-Based Models of Carbon and Nitrogen Cycling in Terrestrial Ecosystems with Particular Emphasis on Forest Ecosystems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Many process-based models of carbon (C) and nitrogen (N) cycles have been developed for terrestrial ecosystems, including forest ecosystems. Existing models are sufficiently well advanced to help decision makers develop sustainable management policies and planning of terrestrial ecosystems, as they ...

  20. Quantifying the role of fire in the Earth system - Part 2: Impact on the net carbon balance of global terrestrial ecosystems for the 20th century

    NASA Astrophysics Data System (ADS)

    Li, F.; Bond-Lamberty, B.; Levis, S.

    2014-03-01

    Fire is the primary form of terrestrial ecosystem disturbance on a global scale. It affects the net carbon balance of terrestrial ecosystems by emitting carbon directly and immediately into the atmosphere from biomass burning (the fire direct effect), and by changing net ecosystem productivity and land-use carbon loss in post-fire regions due to biomass burning and fire-induced vegetation mortality (the fire indirect effect). Here, we provide the first quantitative assessment of the impact of fire on the net carbon balance of global terrestrial ecosystems during the 20th century, and investigate the roles of fire's direct and indirect effects. This is done by quantifying the difference between the 20th century fire-on and fire-off simulations with the NCAR Community Land Model CLM4.5 (prescribed vegetation cover and uncoupled from the atmospheric model) as a model platform. Results show that fire decreases the net carbon gain of global terrestrial ecosystems by 1.0 Pg C yr-1 averaged across the 20th century, as a result of the fire direct effect (1.9 Pg C yr-1) partly offset by the indirect effect (-0.9 Pg C yr-1). Post-fire regions generally experience decreased carbon gains, which is significant over tropical savannas and some North American and East Asian forests. This decrease is due to the direct effect usually exceeding the indirect effect, while they have similar spatial patterns and opposite sign. The effect of fire on the net carbon balance significantly declines until ∼1970 with a trend of 8 Tg C yr-1 due to an increasing indirect effect, and increases subsequently with a trend of 18 Tg C yr-1 due to an increasing direct effect. These results help constrain the global-scale dynamics of fire and the terrestrial carbon cycle.

  1. Contribution of non biological CO2 flows in the net ecosystem carbon balance

    NASA Astrophysics Data System (ADS)

    Serrano-Ortiz, P.; Sanchez-Cañete, E. P.; Roland, M.; Cuezva, S.; Sanchez-Moral, S.; Janssens, I.; Scott, R. L.; Domingo, F.; Godderis, Y.; Kowalski, A. S.

    2011-12-01

    The international micrometeorological tower network (FLUXNET) provides direct ecosystem measurements of carbon dioxide, water vapor and energy flux densities and is a critical source of information for validating and improving models used to study regional and global carbon cycles. In such research, the net ecosystem carbon balance (NECB) has generally been interpreted as biological (photosynthetic and respiratory), and separated into in Gross Primary Production (GPP) and Total Ecosystem Respiration (TER) components using ecophysiological models, neglecting non-biological processes which are therefore not taken into account in ecosystem-scale carbon cycle research. Evidence from some arid lands contradicts the common, unstated hypothesis that the terrestrial NECB always can be interpreted purely in terms of biological processes. On one hand, weathering processes that occur in substrates with carbonates imply consumption or emission of CO2 and therefore short-term contributions to the NECB. In addition, subterranean CO2 storage and ventilation processes may contribute to ecosystem CO2 exchange measured over soils that overlie cavities, macropores and fissures. What is more, non-biological exchange processes can temporally dominate the ecosystem carbon exchange with the atmosphere in areas with carbonate soils, revealing large CO2 release during the dry season. Here we present an overview of the roll of non-biological processes, mainly weathering and subterranean ventilation processes, in the NECB. Using a combination of micrometeorological and subterranean data from (semi-)arid experimental sites, together with adapted WITCH model simulations, we demonstrate the existence of such processes and their main drivers.

  2. Tradeoffs between global warming and day length on the start of the carbon uptake period in seasonally cold ecosystems.

    PubMed

    Wohlfahrt, Georg; Cremonese, Edoardo; Hammerle, Albin; Hörtnagl, Lukas; Galvagno, Marta; Gianelle, Damiano; Marcolla, Barbara; di Cella, Umberto Morra

    2013-12-16

    It is well established that warming leads to longer growing seasons in seasonally cold ecosystems. Whether this goes along with an increase in the net ecosystem carbon dioxide (CO2) uptake is much more controversial. We studied the effects of warming on the start of the carbon uptake period (CUP) of three mountain grasslands situated along an elevational gradient in the Alps. To this end we used a simple empirical model of the net ecosystem CO2 exchange, calibrated and forced with multi-year empirical data from each site. We show that reductions in the quantity and duration of daylight associated with earlier snowmelts were responsible for diminishing returns, in terms of carbon gain, from longer growing seasons caused by reductions in daytime photosynthetic uptake and increases in nighttime losses of CO2. This effect was less pronounced at high, compared to low, elevations, where the start of the CUP occurred closer to the summer solstice when changes in day length and incident radiation are minimal. PMID:24587563

  3. Responses of ecosystem carbon cycling to climate change treatments along an elevation gradient

    USGS Publications Warehouse

    Wu, Zhuoting; Koch, George W.; Dijkstra, Paul; Bowker, Matthew A.; Hungate, Bruce A.

    2011-01-01

    Global temperature increases and precipitation changes are both expected to alter ecosystem carbon (C) cycling. We tested responses of ecosystem C cycling to simulated climate change using field manipulations of temperature and precipitation across a range of grass-dominated ecosystems along an elevation gradient in northern Arizona. In 2002, we transplanted intact plant–soil mesocosms to simulate warming and used passive interceptors and collectors to manipulate precipitation. We measured daytime ecosystem respiration (ER) and net ecosystem C exchange throughout the growing season in 2008 and 2009. Warming generally stimulated ER and photosynthesis, but had variable effects on daytime net C exchange. Increased precipitation stimulated ecosystem C cycling only in the driest ecosystem at the lowest elevation, whereas decreased precipitation showed no effects on ecosystem C cycling across all ecosystems. No significant interaction between temperature and precipitation treatments was observed. Structural equation modeling revealed that in the wetter-than-average year of 2008, changes in ecosystem C cycling were more strongly affected by warming-induced reduction in soil moisture than by altered precipitation. In contrast, during the drier year of 2009, warming induced increase in soil temperature rather than changes in soil moisture determined ecosystem C cycling. Our findings suggest that warming exerted the strongest influence on ecosystem C cycling in both years, by modulating soil moisture in the wet year and soil temperature in the dry year.

  4. Ecosystem carbon storage capacity as affected by disturbance regimes: A general theoretical model

    NASA Astrophysics Data System (ADS)

    Weng, Ensheng; Luo, Yiqi; Wang, Weile; Wang, Han; Hayes, Daniel J.; McGuire, A. David; Hastings, Alan; Schimel, David S.

    2012-09-01

    Disturbances have been recognized as a key factor shaping terrestrial ecosystem states and dynamics. A general model that quantitatively describes the relationship between carbon storage and disturbance regime is critical for better understanding large scale terrestrial ecosystem carbon dynamics. We developed a model (REGIME) to quantify ecosystem carbon storage capacities (E[x]) under varying disturbance regimes with an analytical solution E[x] = U · τE · ?, where U is ecosystem carbon influx, τE is ecosystem carbon residence time, and τ1 is the residence time of the carbon pool affected by disturbances (biomass pool in this study). The disturbance regime is characterized by the mean disturbance interval (λ) and the mean disturbance severity (s). It is a Michaelis-Menten-type equation illustrating the saturation of carbon content with mean disturbance interval. This model analytically integrates the deterministic ecosystem carbon processes with stochastic disturbance events to reveal a general pattern of terrestrial carbon dynamics at large scales. The model allows us to get a sense of the sensitivity of ecosystems to future environmental changes just by a few calculations. According to the REGIME model, for example, approximately 1.8 Pg C will be lost in the high-latitude regions of North America (>45°N) if fire disturbance intensity increases around 5.7 time the current intensity to the end of the twenty-first century, which will require around 12% increases in net primary productivity (NPP) to maintain stable carbon stocks. If the residence time decreased 10% at the same time additional 12.5% increases in NPP are required to keep current C stocks. The REGIME model also lays the foundation for analytically modeling the interactions between deterministic biogeochemical processes and stochastic disturbance events.

  5. Ecosystem carbon storage capacity as affected by disturbance regimes: a general theoretical model

    NASA Astrophysics Data System (ADS)

    Weng, E.; Luo, Y.; Wang, W.; Wang, H.; Hayes, D. J.; McGuire, A. D.; Hastings, A.; Schimel, D.

    2012-12-01

    Disturbances have been recognized as a key factor shaping terrestrial ecosystem states and dynamics. A general model that quantitatively describes the relationship between carbon storage and disturbance regime is critical for better understanding large scale terrestrial ecosystem carbon dynamics. We developed a model (REGIME) to quantify ecosystem carbon storage capacities (E[x]) under varying disturbance regimes with an analytical solution E[x]=UτE λ/(λ+sτ1) , where U is ecosystem carbon influx, τE is ecosystem carbon residence time, and τ1 is the residence time of the carbon pool affected by disturbances (biomass pool in this study). The disturbance regime is characterized by the mean disturbance interval (λ) and the mean disturbance severity (s). It is a Michaelis-Menten type equation illustrating the saturation of carbon content with mean disturbance interval. This model analytically integrates the deterministic ecosystem carbon processes with stochastic disturbance events to reveal a general pattern of terrestrial carbon dynamics at large scales. The model allows us to get a sense of the sensitivity of ecosystems to future environmental changes just by a few calculations. According to the REGIME model , for example, approximately 1.8 Pg C will be lost in the high latitude regions of North America (>45°N) if fire disturbance intensity increases around 5.7 time the current intensity to the end of 21st century, which will require around 12% increases in NPP to maintain stable carbon stocks. If the residence time decreased 10% at the same time additional 12.5% increases in NPP are required to keep current C stocks. The REGIME model also lays the foundation for analytically modeling the interactions between deterministic biogeochemical processes and stochastic disturbance events.

  6. Ecosystem carbon storage capacity as affected by disturbance regimes: A general theoretical model

    SciTech Connect

    Weng, Ensheng; Luo, Yiqi; Wang, Weile; Wang, Han; Hayes, Daniel J; McGuire, A. David; Hastings, Alan; Schimel, David

    2012-01-01

    Disturbances have been recognized as a key factor shaping terrestrial ecosystem states and dynamics. A general model that quantitatively describes the relationship between carbon storage and disturbance regime is critical for better understanding large scale terrestrial ecosystem carbon dynamics. We developed a model (REGIME) to quantify ecosystem carbon storage capacities (E[x]) under varying disturbance regimes with an analytical solution E[x] = U {center_dot} {tau}{sub E} {center_dot} {lambda}{lambda} + s {tau} 1, where U is ecosystem carbon influx, {tau}{sub E} is ecosystem carbon residence time, and {tau}{sub 1} is the residence time of the carbon pool affected by disturbances (biomass pool in this study). The disturbance regime is characterized by the mean disturbance interval ({lambda}) and the mean disturbance severity (s). It is a Michaelis-Menten-type equation illustrating the saturation of carbon content with mean disturbance interval. This model analytically integrates the deterministic ecosystem carbon processes with stochastic disturbance events to reveal a general pattern of terrestrial carbon dynamics at large scales. The model allows us to get a sense of the sensitivity of ecosystems to future environmental changes just by a few calculations. According to the REGIME model, for example, approximately 1.8 Pg C will be lost in the high-latitude regions of North America (>45{sup o} N) if fire disturbance intensity increases around 5.7 time the current intensity to the end of the twenty-first century, which will require around 12% increases in net primary productivity (NPP) to maintain stable carbon stocks. If the residence time decreased 10% at the same time additional 12.5% increases in NPP are required to keep current C stocks. The REGIME model also lays the foundation for analytically modeling the interactions between deterministic biogeochemical processes and stochastic disturbance events.

  7. Effects of temperature, moisture, and permafrost thaw on ecosystem carbon exchange in Alaskan tundra.

    NASA Astrophysics Data System (ADS)

    Natali, S.; Schuur, E. A.; Webb, E.

    2012-12-01

    Carbon has been accumulating in northern high latitude ecosystems for thousands of years because cold and moist conditions have protected soil organic matter from microbial decomposition. Over the past several decades, warming surface air temperatures have been accompanied by thawing of the perennially frozen permafrost layer where much of the accumulated carbon is stored. In addition to its role in carbon storage, permafrost regulates surface hydrology by restricting vertical water flow, thereby maintaining a water table that remains close to the ground surface. In the absence of the permafrost layer, enhanced water drainage will result in increased water table depth and decreased soil moisture. The biological availability of permafrost carbon may increase in a warmer and drier soil environment, as is expected for the region of this study. To determine the effects of warming temperatures and changes in soil moisture on ecosystem carbon exchange, we established a water table drawdown experiment within the footprint of the Carbon in Permafrost Experimental Heating Research (CiPEHR) project, an ecosystem warming experiment in Interior Alaska that warms air and soil temperatures and degrades permafrost. Here we present ecosystem carbon balance results from combined warming and moisture manipulation treatments at the CiPEHR project. Soil warming increased soil temperature by 2-3o C and resulted in a 10% increase in growing season thaw depth. Surprisingly, the additional 2 kg of thawed soil C m-2 in the warmed plots did not increase net growing season CO2 loss from this ecosystem. In contrast, soil warming and permafrost thaw increased growing season CO2 uptake, which was a result of both higher net primary productivity and an inhibition of microbial decomposition by soil saturation at the base of the active layer. The drying treatment (i.e., water table drawdown) decreased soil moisture by 25%, which led to an increase in ecosystem respiration and decrease in net

  8. Ontogeny, understorey light interception and simulated carbon gain of juvenile rainforest evergreens differing in shade tolerance

    PubMed Central

    Lusk, Christopher H.; Pérez-Millaqueo, Manuel Matías; Piper, Frida I.; Saldaña, Alfredo

    2011-01-01

    Background and Aims A long-running debate centres on whether shade tolerance of tree seedlings is mainly a function of traits maximizing net carbon gain in low light, or of traits minimizing carbon loss. To test these alternatives, leaf display, light-interception efficiency, and simulated net daily carbon gain of juvenile temperate evergreens of differing shade tolerance were measured, and how these variables are influenced by ontogeny was queried. Methods The biomass distribution of juveniles (17–740 mm tall) of seven temperate rainforest evergreens growing in low (approx. 4 %) light in the understorey of a second-growth stand was quantified. Daytime and night-time gas exchange rates of leaves were also determined, and crown architecture was recorded digitally. YPLANT was used to model light interception and carbon gain. Results An index of species shade tolerance correlated closely with photosynthetic capacities and respiration rates per unit mass of leaves, but only weakly with respiration per unit area. Accumulation of many leaf cohorts by shade-tolerant species meant that their ratios of foliage area to biomass (LAR) decreased more gradually with ontogeny than those of light-demanders, but also increased self-shading; this depressed the foliage silhouette-to-area ratio (STAR), which was used as an index of light-interception efficiency. As a result, displayed leaf area ratio (LARd = LAR × STAR) of large seedlings was not related to species shade tolerance. Self-shading also caused simulated net daily carbon assimilation rates of shade-tolerant species to decrease with ontogeny, leading to a negative correlation of shade tolerance with net daily carbon gain of large (500 mm tall) seedlings in the understorey. Conclusions The results suggest that efficiency of energy capture is not an important correlate of shade tolerance in temperate rainforest evergreens. Ontogenetic increases in self-shading largely nullify the potential carbon gain advantages expected

  9. Effect of interannual climate variability on carbon storage in Amazonian ecosystems

    USGS Publications Warehouse

    Tian, H.; Melillo, J.M.; Kicklighter, D.W.; McGuire, David A.; Helfrich, J. V. K., III; Moore, B., III; Vorosmarty, C.J.

    1998-01-01

    The Amazon Basin contains almost one-half of the world's undisturbed tropical evergreen forest as well as large areas of tropical savanna. The forests account for about 10 per cent of the world's terrestrial primary productivity and for a similar fraction of the carbon stored in land ecosystems, and short-term field measurements suggest that these ecosystems are globally important carbon sinks. But tropical land ecosystems have experienced substantial interannual climate variability owing to frequent El Nino episodes in recent decades. Of particular importance to climate change policy is how such climate variations, coupled with increases in atmospheric CO2 concentration, affect terrestrial carbon storage. Previous model analyses have demonstrated the importance of temperature in controlling carbon storage. Here we use a transient process-based biogeochemical model of terrestrial ecosystems to investigate interannual variations of carbon storage in undisturbed Amazonian ecosystems in response to climate variability and increasing atmospheric CO2 concentration during the period 1980 to 1994. In El Nino years, which bring hot, dry weather to much of the Amazon region, the ecosystems act as a source of carbon to the atmosphere (up to 0.2 petagrams of carbon in 1987 and 1992). In other years, these ecosystems act as a carbon sink (up to 0.7 Pg C in 1981 and 1993). These fluxes are large; they compare to a 0.3 Pg C per year source to the atmosphere associated with deforestation in the Amazon Basin in the early 1990s. Soil moisture, which is affected by both precipitation and temperature, and which affects both plant and soil processes, appears to be an important control on carbon storage.

  10. Soil Carbon Turnover and the Net Ecosystem Carbon Balance of a Northern Hardwood Forest, Michigan, USA

    NASA Astrophysics Data System (ADS)

    Gough, C. M.; Biswas, S.; Vogel, C. S.; Curtis, P. S.

    2004-12-01

    Soils are a major reservoir of stored carbon (C) in forested ecosystems, containing up to 70% of total ecosystem C. Heterotrophic activity largely dictates the rate of soil C turnover and directly impacts ecosystem C balance. Reliable estimates of net ecosystem productivity (NEP) from ecophysiological and biometric data as well as the refinement of process-based models predicting belowground changes in C storage depend on accurate quantification and partitioning of autotrophic and heterotrophic soil C fluxes. We used field and laboratory measurements of root, microbial and soil respiration in a northern hardwood forest to (1) quantify the annual soil C efflux attributed to heterotrophs and autotrophs from 1999 to 2003; (2) identify the extent to which microclimatic drivers impact interannual variability in microbial activity of the mineral soil and O-horizon; and (3) evaluate the sensitivity of estimated annual NEP to heterotrophic respiration. The study was conducted in an 85-year-old aspen-dominated mixed deciduous forest at the University of Michigan Biological Station Ameriflux site (UMBS ˜Flux) in N. lower Michigan, USA. Soil respiration was monitored from 1999 to 2003. Laboratory incubations of roots, mineral soil and the O-horizon at different temperatures were used to examine the relationship between microclimate and autotrophic and heterotrophic respiration. Empirical models relating root and microbial respiration to temperature were used in combination with soil respiration models and site soil temperature, moisture and root biomass data to estimate the contribution of autotrophic and heterotrophic respiration to total soil C efflux. Heterotrophic soil respiration estimates were combined with other C flux data to calculate annual NEP from 1999 to 2003. Microbially-mediated C turnover was responsible for ˜half of the total annual soil C efflux. Heterotrophic respiration varied by more than 1 Mg C ha-1 yr-1 among years primarily due to interannual

  11. Elevated CO2 and warming influence ecosystem carbon dynamics and evapotranspiration in a semi-arid grassland

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ecosystem carbon dynamics are sensitive to rising CO2 concentrations and warming, but the combined effects of these global change drivers on ecosystem carbon uptake and loss remain a critical uncertainty. Northern mixed grass prairie is expected to be among the most responsive ecosystems to the effe...

  12. Organic Carbon Storage in Four Ecosystem Types in the Karst Region of Southwestern China

    PubMed Central

    Wang, Shijie; Guo, Ke; Yang, Jun; Zhang, Xinshi; Li, Guoqing

    2013-01-01

    Karst ecosystems are important landscape types that cover about 12% of the world's land area. The role of karst ecosystems in the global carbon cycle remains unclear, due to the lack of an appropriate method for determining the thickness of the solum, a representative sampling of the soil and data of organic carbon stocks at the ecosystem level. The karst region in southwestern China is the largest in the world. In this study, we estimated biomass, soil quantity and ecosystem organic carbon stocks in four vegetation types typical of karst ecosystems in this region, shrub grasslands (SG), thorn shrubbery (TS), forest - shrub transition (FS) and secondary forest (F). The results showed that the biomass of SG, TS, FS, and F is 0.52, 0.85, 5.9 and 19.2 kg m−2, respectively and the corresponding organic cabon storage is 0.26, 0.40, 2.83 and 9.09 kg m−2, respectively. Nevertheless, soil quantity and corresponding organic carbon storage are very small in karst habitats. The quantity of fine earth overlaying the physical weathering zone of the carbonate rock of SG, TS, FS and F is 38.10, 99.24, 29.57 and 61.89 kg m−2, respectively, while the corresponding organic carbon storage is only 3.34, 4.10, 2.37, 5.25 kg m−2, respectively. As a whole, ecosystem organic carbon storage of SG, TS, FS, and F is 3.81, 4.72, 5.68 and 15.1 kg m−2, respectively. These are very low levels compared to other ecosystems in non-karst areas. With the restoration of degraded vegetation, karst ecosystems in southwestern China may play active roles in mitigating the increasing CO2 concentration in the atmosphere. PMID:23451047

  13. Bring the catchment hydrology and carbon science together: a simple ecosystem water use efficiency model

    NASA Astrophysics Data System (ADS)

    Cheng, Lei; Zhang, Lu; Wang, Ying-Ping; Chiew, Francis; Canadell, Josep

    2016-04-01

    Water use efficiency (WUE) defined as carbon uptake per unit of water loss by plants or ecosystems is one of most important functional properties in plant sciences. While theory of WUE is quite advanced at leaf-scale, but quite limited at ecosystem scale because of the complexity of interactions among vegetation, soil and climate. In this study, we developed one simple equation for estimating ecosystem WUE with 2 parameters and 5 variables. Using this simple model, we can explain why ecosystem WUE peaks at about 60N, 20N and tropical region globally. Estimated global ecosystem WUE agrees very well with other independent estimates in both magnitude and spatial variability. We also demonstrated that this model can be used to predict quite accurately the global gross primary production (GPP) when estimates of ecosystem water use are available. We estimated global mean annual GPP as 120.7±10.1 Pg(C) year‑1 based on 7 independent estimates of global evapotranspiration. Further analysis shows both global ecosystem WUE and GPP have increased over the last three decades. About 90% of the increased trend in WUE is attributed to increased atmosphere CO2. Increases in GPP is largely driven by increasing WUE. Therefore this simple model provide an important link of catchment hydrology with carbon science community and as an independent approach for estimating ecosystem photosynthetic carbon production from traditional catchment hydrological measurements.

  14. Permafrost carbon-climate feedback in high-altitude ecosystems: evidence from the Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Yang, Y.; Ding, J.; Han, T.; Peng, Y.; Li, F.; Chen, L.; Chen, Y.

    2014-12-01

    Permafrost carbon-climate feedback has received particular interest from the global change research community. However, current evidence is mainly derived from high-latitude ecosystems, with little known about high-altitude ecosystems. In this study, we examined permafrost carbon-climate feedback in alpine grasslands on the Tibetan Plateau from the following three aspects. First, we evaluated soil carbon stock in the top 3 meter by conducting a large-scale soil survey across the study area during the summer of 2013-2014. We found that Tibetan grassland soils store 10.4 Pg C in the upper 3 meter, ~40% larger than previous estimation in the top 1 meter. Second, we examined large-scale patterns of temperature sensitivity of soil carbon decomposition in alpine ecosystems by conducting laboratory incubation experiments, and found that greater temperature sensitivity occurred in those soils with more recalcitrant components. Third, we explored the responses of carbon cycling processes in alpine grasslands to climate warming by conducting OTC experiments. We found that experimental warming stimulated ecosystem respiration, but also increased gross primary production, and thus led to the net carbon accumulation. Overall, these three lines of evidence demonstrate that carbon cycle in high-altitude ecosystems is very sensitive to climate warming.

  15. Plant traits as predictor of ecosystem carbon fluxes - a case study across European grasslands

    NASA Astrophysics Data System (ADS)

    Klumpp, Katja; Bahn, Michael; Acosta, Manuel; Altimir, Nuria; Gimeno, Cristina; Jongen, Marjan; Merbold, Lutz; Moors, Eddy; Pinter, Kistina; Darsonville, Olivier

    2015-04-01

    Predicting ecosystem responses to global change has become a major challenge, particularly as terrestrial ecosystems contribute to the mitigation of global climate change through carbon sequestration. Plant traits are major surrogates of ecosystem physiology may thus help to predict carbon (C) fluxes and their consequences for the delivery of ecosystem services (e.g. C sequestration) across climatic gradients and in changing environments. However, linkages between community abundance-weighted means (CWM) of plant functional traits and ecosystem C fluxes have rarely been tested. It is also not known to what degree traits, which are typically measured at a defined point in time, are suitable for predicting annual C fluxes. We analysed the relationships between ecosystem fluxes and community level plant traits for 13 European grasslands under contrasting climate and management regimes, using multiyear eddy covariance data. Plant traits (specific leaf area SLA, leaf dry matter content LDMC, specific root length SLR) were determined at peak biomass. Analyses showed that GPPmax (at maximum radiation) was related to SLA, SRL and LDMC across sites and management, where GPPmax was an excellent indicator for annual GPP. Similar relations were found between for root density (and -diameter) and ecosystem respiration. Ecosystems respiration at GPPmax was also in line with annual respiration, indicating the strong predictive potential of plant community traits. Our study therefore suggests that above- and belowground community level plant traits are well suited surrogates for predicting ecosystem C fluxes at peak biomass and at annual scale.

  16. Global covariation of carbon turnover times with climate in terrestrial ecosystems.

    PubMed

    Carvalhais, Nuno; Forkel, Matthias; Khomik, Myroslava; Bellarby, Jessica; Jung, Martin; Migliavacca, Mirco; Mu, Mingquan; Saatchi, Sassan; Santoro, Maurizio; Thurner, Martin; Weber, Ulrich; Ahrens, Bernhard; Beer, Christian; Cescatti, Alessandro; Randerson, James T; Reichstein, Markus

    2014-10-01

    The response of the terrestrial carbon cycle to climate change is among the largest uncertainties affecting future climate change projections. The feedback between the terrestrial carbon cycle and climate is partly determined by changes in the turnover time of carbon in land ecosystems, which in turn is an ecosystem property that emerges from the interplay between climate, soil and vegetation type. Here we present a global, spatially explicit and observation-based assessment of whole-ecosystem carbon turnover times that combines new estimates of vegetation and soil organic carbon stocks and fluxes. We find that the overall mean global carbon turnover time is 23(+7)(-4) years (95 per cent confidence interval). On average, carbon resides in the vegetation and soil near the Equator for a shorter time than at latitudes north of 75° north (mean turnover times of 15 and 255 years, respectively). We identify a clear dependence of the turnover time on temperature, as expected from our present understanding of temperature controls on ecosystem dynamics. Surprisingly, our analysis also reveals a similarly strong association between turnover time and precipitation. Moreover, we find that the ecosystem carbon turnover times simulated by state-of-the-art coupled climate/carbon-cycle models vary widely and that numerical simulations, on average, tend to underestimate the global carbon turnover time by 36 per cent. The models show stronger spatial relationships with temperature than do observation-based estimates, but generally do not reproduce the strong relationships with precipitation and predict faster carbon turnover in many semi-arid regions. Our findings suggest that future climate/carbon-cycle feedbacks may depend more strongly on changes in the hydrological cycle than is expected at present and is considered in Earth system models. PMID:25252980

  17. Exploiting heterogeneous environments: does photosynthetic acclimation optimize carbon gain in fluctuating light?

    PubMed Central

    Retkute, Renata; Smith-Unna, Stephanie E.; Smith, Robert W.; Burgess, Alexandra J.; Jensen, Oliver E.; Johnson, Giles N.; Preston, Simon P.; Murchie, Erik H.

    2015-01-01

    Plants have evolved complex mechanisms to balance the efficient use of absorbed light energy in photosynthesis with the capacity to use that energy in assimilation, so avoiding potential damage from excess light. This is particularly important under natural light, which can vary according to weather, solar movement and canopy movement. Photosynthetic acclimation is the means by which plants alter their leaf composition and structure over time to enhance photosynthetic efficiency and productivity. However there is no empirical or theoretical basis for understanding how leaves track historic light levels to determine acclimation status, or whether they do this accurately. We hypothesized that in fluctuating light (varying in both intensity and frequency), the light-response characteristics of a leaf should adjust (dynamically acclimate) to maximize daily carbon gain. Using a framework of mathematical modelling based on light-response curves, we have analysed carbon-gain dynamics under various light patterns. The objective was to develop new tools to quantify the precision with which photosynthesis acclimates according to the environment in which plants exist and to test this tool on existing data. We found an inverse relationship between the optimal maximum photosynthetic capacity and the frequency of low to high light transitions. Using experimental data from the literature we were able to show that the observed patterns for acclimation were consistent with a strategy towards maximizing daily carbon gain. Refinement of the model will further determine the precision of acclimation. PMID:25788730

  18. Long-term increase in forest water-use efficiency observed across ecosystem carbon flux networks (Invited)

    NASA Astrophysics Data System (ADS)

    Keenan, T. F.; Hollinger, D. Y.; Bohrer, G.; Dragoni, D.; Munger, J. W.; Schmid, H. E.; Richardson, A. D.

    2013-12-01

    Terrestrial plants remove CO2 from the atmosphere through photo- synthesis, a process that is accompanied by the loss of water vapour from leaves. The ratio of water loss to carbon gain, or water-use efficiency, is a key characteristic of ecosystem function that is central to the global cycles of water, energy and carbon. Here we analyse direct, long-term measurements of whole-ecosystem carbon and water exchange. We find a substantial increase in water-use efficiency in temperate and boreal forests of the Northern Hemisphere over the past two decades. We systematically assess various competing hypotheses to explain this trend, and find that the observed increase is most consistent with a strong CO2 fertilization effect. The results suggest a partial closure of stomata - small pores on the leaf surface that regulate gas exchange - to maintain a near- constant concentration of CO2 inside the leaf even under continually increasing atmospheric CO2 levels. The observed increase in forest water-use efficiency is larger than that predicted by existing theory and 13 terrestrial biosphere models. The increase is associated with trends of increasing ecosystem-level photosynthesis and net carbon uptake, and decreasing evapotranspiration. Our findings demonstrate the utility of maintaining long-term eddy-covariance flux measurement sites. The results suggest a shift in the carbon- and water-based economics of terrestrial vegetation, which may require a reassessment of the role of stomatal control in regulating interactions between forests and climate change, and a re-evaluation of coupled vegetation-climate models.

  19. Dynamics and structure of carbon storage in the postagrogenic ecosystems of the southern taiga

    NASA Astrophysics Data System (ADS)

    Ryzhova, I. M.; Erokhova, A. A.; Podvezennaya, M. A.

    2014-12-01

    The dynamics and structure of the carbon storage in postagrogenic ecosystems during the natural reforestation of agrosoddy-podzolic soils in the southern taiga zone of European Russia have been considered. Calculation experiments based on the nonlinear model of the carbon cycle in soils (NAMSOM) have revealed different tendencies in the changes of the soil carbon reserves during the postagrogenic succession depending of the preceding land use and the soil texture. It has been shown that, in spite of the possible decrease in the reserves of soil carbon in some cases, the total carbon reserves in the ecosystems always increase during the postagrogenic succession due to the multiple increases in the phytomass and the accumulation of carbon in the litter. Thus, the obtained results indicate the sequestering of carbon in the abandoned lands of the southern taiga of European Russia.

  20. 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. PMID:26232918

  1. Whole ecosystem estimates of carbon exchange and storage in a New England salt marsh

    NASA Astrophysics Data System (ADS)

    Forbrich, I.; Giblin, A.

    2013-12-01

    Salt marshes are wetlands situated at the interface of land and ocean. They are among the most productive ecosystems worldwide and store substantial amounts of carbon as peat. Their long-term stability is dependent on sediment accretion and carbon accumulation to avoid submergence when sea level is rising. Currently, estimates of carbon storage in salt marshes are uncertain because our understanding of the coupling between marsh plant productivity and carbon release to the adjacent ocean is limited. To evaluate the capacity to store carbon as well as the resilience of the ecosystem, long-term studies of carbon cycling considering both vertical and lateral fluxes are necessary. To study the net exchange between marsh and atmosphere, we chose the non-intrusive eddy covariance which allows nearly continuous half hourly flux measurements of net ecosystem exchange (NEE) on the ecosystem scale. Since spring 2012, we have been investigating the marsh-atmosphere exchange of carbon dioxide (CO2) at a Spartina patens high marsh at the Plum Island Ecosystems Long-Term Ecological Research site. Seasonal dynamics of CO2 exchange during summer were controlled by the phenology of S. patens. Preliminary estimates for seasonal carbon storage range from 185 to 228 g C m-2 (5/1/2012 to 10/31/2012). During the winter months we observed small fluxes, but carbon uptake still occurred during the day. We attribute this to microalgae productivity. Winter carbon release is estimated to be approximately 130 g C m-2 (12/6/2012 to 4/30/2013), when uptake by microalgae is not taken into account. This emphasizes the relevance of transitional and cold season carbon cycling for the carbon storage capacity of northern salt marshes, since a large proportion of fixed carbon is released during these periods. Direct tidal effects on the marsh-atmosphere carbon exchange are visible especially during monthly spring tides, when both daytime carbon uptake and night time respiration were reduced during

  2. Carbon storage estimation of main forestry ecosystems in Northwest Yunnan Province using remote sensing data

    NASA Astrophysics Data System (ADS)

    Wang, Jinliang; Wang, Xiaohua; Yue, Cairong; Xu, Tian-shu; Cheng, Pengfei

    2014-05-01

    Estimating regional forest organic carbon pool has became a hot issue in the study of forest ecosystem carbon cycle. The forest ecosystem in Shangri-La County, Northwest Yunnan Province, are well preserved, and the area of Picea Likiangensis, Quercus Aquifolioides, Pinus Densata and Pinus Yunnanensis amounts to 80% of the total arboreal forest area in Shangri-La County. Based on the field measurements, remote sensing data and GIS analysis, three models were established for carbon storage estimation. The remote sensing information model with the highest accuracy were used to calculate the carbon storages of the four main forest ecosystems. The results showed: (1) the total carbon storage of the four forest ecosystems in Shangri-La is 302.984 TgC, in which tree layer, shrub layer, herb layer, litter layer, soil layer are 60.196TgC, 5.433TgC, 1.080TgC, 3.582TgC and 232.692TgC, accounting for 19.87%, 1.79%, 0.36%, 1.18%, 76.80% of the total carbon storage respectively. (2)The order of the carbon storage from high to low is soil layer, tree layer, shrub layer, litter layer and herb layer respectively for the four main forest ecosystems. (3)The total average carbon density of the four main forest ecosystems is 403.480 t/hm2, and the carbon densities of the Picea Likiangensis, Quercus Aquifolioides, Pinus Densata and Pinus Yunnanensis are 576.889 t/hm2, 326.947 t/hm2, 279.993 t/hm2 and 255.792 t/hm2 respectively.

  3. Large Uncertainties in Estimating Grassland Carbon Fluxes: Can Net Ecosystem Production Be Inferred?

    NASA Astrophysics Data System (ADS)

    Cahill, K. N.; Foley, J. A.; Kucharik, C. J.

    2003-12-01

    Despite interest in estimating ecosystem carbon budgets based on easily collected field data, no previous study to our knowledge has compared various methods of estimating total above- and belowground net primary production (NPP) and net ecosystem production (NEP, the annual carbon accumulated by an ecosystem) from commonly measured biomass and soil surface CO2 flux data in grasslands. Here we used field data from two grassland restorations and a row-crop agriculture treatment enrolled in the Conservation Reserve Program as a model for an analysis of methodological uncertainty in estimating ecosystem carbon budgets over a short time period. The goal of this study was to investigate how a range of methods for estimating NPP and NEP suggested in the literature might be used to predict ecosystem carbon budgets based on short-term field measurements. We conclude that it is extremely difficult to close the carbon budget of a temperate grassland using flux-based methods that account for plant-derived carbon inputs and soil surface CO2 losses. Current uncertainties in (1) estimating aboveground NPP, (2) determining belowground NPP, and (3) splitting soil respiration into heterotrophic and autotrophic components strongly affect the magnitude, and even the sign, of NEP. A comparison of these estimates, across a treatment of different plant species mixes and land management, cannot reliably distinguish differences in NEP, nor the absolute sign of the overall carbon budget. These uncertainties likely exist in all grassland carbon budget studies using this approach, so conclusions about whether these systems are truly carbon sinks, or how they should be managed to sequester carbon, must be made with extreme care. Longer-term stocks methods, periodically linked to flux-based measurements of individual processes, may be the only way to close the carbon budget in these systems with any reasonable degree of certainty at the present time.

  4. Global patterns of ecosystem carbon flux in forests: A biometric data-based synthesis

    NASA Astrophysics Data System (ADS)

    Xu, Bing; Yang, Yuanhe; Li, Pin; Shen, Haihua; Fang, Jingyun

    2014-09-01

    Forest ecosystems function as a significant carbon sink for atmospheric carbon dioxide. However, our understanding of global patterns of forest carbon fluxes remains controversial. Here we examined global patterns and environmental controls of forest carbon balance using biometric measurements derived from 243 sites and synthesized from 81 publications around the world. Our results showed that both production and respiration increased with mean annual temperature and exhibited unimodal patterns along a gradient of precipitation. However, net ecosystem production (NEP) initially increased and subsequently declined along gradients of both temperature and precipitation. Our results also indicated that ecosystem production increased during stand development but eventually leveled off, whereas respiration was significantly higher in mature and old forests than in young forests. The residual variation of carbon flux along climatic and age gradients might be explained by other factors such as atmospheric CO2 elevation and disturbances (e.g., forest fire, storm damage, and selective harvest). Heterotrophic respiration (Rh) was positively associated with net primary production (NPP), but the Rh-NPP relationship differed between natural and planted forests: Rh increased exponentially with NPP in natural forests but tended toward saturation with increased NPP in planted forests. Comparison of biometric measurements with eddy covariance observations revealed that ecosystem carbon balance derived from the latter generated higher overall NEP estimates. These results suggest that the eddy covariance observations may overestimate the strength of carbon sinks, and thus, biometric measurements need to be incorporated into global assessments of the forest carbon balance.

  5. Carbon allocation in plants and ecosystems - insights from stable isotope studies

    NASA Astrophysics Data System (ADS)

    Gessler, Arthur

    2014-05-01

    Trees are large global stores of carbon (C) that will be impacted by increased carbon dioxide levels and climate change. However, at present we cannot properly predict the carbon balance of forests in future as we lack knowledge on how plant physiological processes, the transfer of carbon within the plant, carbon storage, and remobilization in the plant tissues as well as the release of carbon from the roots to the soil interact with environmental drivers and ecosystem-scale processes. This paper will summarise how stable isotope techniques can give new insights in the fate of newly assimilated C in plants and ecosystems on time scales from hours to seasons and it will include studies either characterizing temporal and spatial variation in the natural abundance of carbon and oxygen isotopes or applying isotopically enriched tracers. It comprises the assessment of the mechanisms of C partitioning among specific metabolic pathways, between plant organs and into various ecosystem C pools with different residence times. Moreover stable isotopes are highly suitable tools to characterise the role of the phloem, which is the central long-distance conveyer distributing C from source to sinks and thus plays a central role in linking sites and structures of storage, growth and other metabolic activities. A deeper understanding of these processes and their interaction with environmental drivers is critical for predicting how trees and ecosystems will respond to coming global environmental changes, including increased temperature, altered precipitation, and elevated carbon dioxide concentrations.

  6. Responses of terrestrial ecosystems and carbon budgets to current and future environmental variability.

    PubMed

    Medvigy, David; Wofsy, Steven C; Munger, J William; Moorcroft, Paul R

    2010-05-01

    We assess the significance of high-frequency variability of environmental parameters (sunlight, precipitation, temperature) for the structure and function of terrestrial ecosystems under current and future climate. We examine the influence of hourly, daily, and monthly variance using the Ecosystem Demography model version 2 in conjunction with the long-term record of carbon fluxes measured at Harvard Forest. We find that fluctuations of sunlight and precipitation are strongly and nonlinearly coupled to ecosystem function, with effects that accumulate through annual and decadal timescales. Increasing variability in sunlight and precipitation leads to lower rates of carbon sequestration and favors broad-leaved deciduous trees over conifers. Temperature variability has only minor impacts by comparison. We also find that projected changes in sunlight and precipitation variability have important implications for carbon storage and ecosystem structure and composition. Based on Intergovernmental Panel on Climate Change model estimates for changes in high-frequency meteorological variability over the next 100 years, we expect that terrestrial ecosystems will be affected by changes in variability almost as much as by changes in mean climate. We conclude that terrestrial ecosystems are highly sensitive to high-frequency meteorological variability, and that accurate knowledge of the statistics of this variability is essential for realistic predictions of ecosystem structure and functioning. PMID:20404190

  7. Responses of terrestrial ecosystems and carbon budgets to current and future environmental variability

    PubMed Central

    Medvigy, David; Wofsy, Steven C.; Munger, J. William; Moorcroft, Paul R.

    2010-01-01

    We assess the significance of high-frequency variability of environmental parameters (sunlight, precipitation, temperature) for the structure and function of terrestrial ecosystems under current and future climate. We examine the influence of hourly, daily, and monthly variance using the Ecosystem Demography model version 2 in conjunction with the long-term record of carbon fluxes measured at Harvard Forest. We find that fluctuations of sunlight and precipitation are strongly and nonlinearly coupled to ecosystem function, with effects that accumulate through annual and decadal timescales. Increasing variability in sunlight and precipitation leads to lower rates of carbon sequestration and favors broad-leaved deciduous trees over conifers. Temperature variability has only minor impacts by comparison. We also find that projected changes in sunlight and precipitation variability have important implications for carbon storage and ecosystem structure and composition. Based on Intergovernmental Panel on Climate Change model estimates for changes in high-frequency meteorological variability over the next 100 years, we expect that terrestrial ecosystems will be affected by changes in variability almost as much as by changes in mean climate. We conclude that terrestrial ecosystems are highly sensitive to high-frequency meteorological variability, and that accurate knowledge of the statistics of this variability is essential for realistic predictions of ecosystem structure and functioning. PMID:20404190

  8. Stable oxygen isotope and flux partitioning demonstrates understory of an oak savanna contributes up to half of ecosystem carbon and water exchange

    PubMed Central

    Dubbert, Maren; Piayda, Arndt; Cuntz, Matthias; Correia, Alexandra C.; Costa e Silva, Filipe; Pereira, Joao S.; Werner, Christiane

    2014-01-01

    Semi-arid ecosystems contribute about 40% to global net primary production (GPP) even though water is a major factor limiting carbon uptake. Evapotranspiration (ET) accounts for up to 95% of the water loss and in addition, vegetation can also mitigate drought effects by altering soil water distribution. Hence, partitioning of carbon and water fluxes between the soil and vegetation components is crucial to gain mechanistic understanding of vegetation effects on carbon and water cycling. However, the possible impact of herbaceous vegetation in savanna type ecosystems is often overlooked. Therefore, we aimed at quantifying understory vegetation effects on the water balance and productivity of a Mediterranean oak savanna. ET and net ecosystem CO2 exchange (NEE) were partitioned based on flux and stable oxygen isotope measurements and also rain infiltration was estimated. The understory vegetation contributed importantly to total ecosystem ET and GPP with a maximum of 43 and 51%, respectively. It reached water-use efficiencies (WUE; ratio of carbon gain by water loss) similar to cork-oak trees. The understory vegetation inhibited soil evaporation (E) and, although E was large during wet periods, it did not diminish WUE during water-limited times. The understory strongly increased soil water infiltration, specifically following major rain events. At the same time, the understory itself was vulnerable to drought, which led to an earlier senescence of the understory growing under trees as compared to open areas, due to competition for water. Thus, beneficial understory effects are dominant and contribute to the resilience of this ecosystem. At the same time the vulnerability of the understory to drought suggests that future climate change scenarios for the Mediterranean basin threaten understory development. This in turn will very likely diminish beneficial understory effects like infiltration and ground water recharge and therefore ecosystem resilience to drought. PMID

  9. Ecosystem carbon exchange in response to locust outbreaks in a temperate steppe.

    PubMed

    Song, Jian; Wu, Dandan; Shao, Pengshuai; Hui, Dafeng; Wan, Shiqiang

    2015-06-01

    It is predicted that locust outbreaks will occur more frequently under future climate change scenarios, with consequent effects on ecological goods and services. A field manipulative experiment was conducted to examine the responses of gross ecosystem productivity (GEP), net ecosystem carbon dioxide (CO2) exchange (NEE), ecosystem respiration (ER), and soil respiration (SR) to locust outbreaks in a temperate steppe of northern China from 2010 to 2011. Two processes related to locust outbreaks, natural locust feeding and carcass deposition, were mimicked by clipping 80 % of aboveground biomass and adding locust carcasses, respectively. Ecosystem carbon (C) exchange (i.e., GEP, NEE, ER, and SR) was suppressed by locust feeding in 2010, but stimulated by locust carcass deposition in both years (except SR in 2011). Experimental locust outbreaks (i.e., clipping plus locust carcass addition) decreased GEP and NEE in 2010 whereas they increased GEP, NEE, and ER in 2011, leading to neutral changes in GEP, NEE, and SR across the 2 years. The responses of ecosystem C exchange could have been due to the changes in soil ammonium nitrogen, community cover, and aboveground net primary productivity. Our findings of the transient and neutral changes in ecosystem C cycling under locust outbreaks highlight the importance of resistance, resilience, and stability of the temperate steppe in maintaining reliable ecosystem services, and facilitate the projections of ecosystem functioning in response to natural disturbance and climate change. PMID:25663332

  10. How does wind-throw disturbance affect the carbon budget of an upland spruce forest ecosystem?

    NASA Astrophysics Data System (ADS)

    Lindauer, Matthias; Schmid, Hans Peter; Grote, Rüdiger; Mauder, Matthias; Wolpert, Benjamin; Steinbrecher, Rainer

    2014-05-01

    Forests, especially in mid-latitudes are generally designated as large carbon sinks. However, stand-replacing disturbance events like fires, insect-infestations, or severe wind-storms can shift an ecosystem from carbon sink to carbon source within short time and keep it as this for a long time. In Addition, extreme weather situations which promote the occurrence of ecosystem disturbances are likely to increase in the future due to climate change. The development and competition of different vegetation types (spruce vs. grass) as well as soil organic matter (SOM), and their contribution to the net ecosystem exchange (NEE), in such disturbed forest ecosystems are largely unknown. In a large wind-throw area (ca. 600 m diameter, due to cyclone Kyrill in January 2007) within a mature upland spruce forest, where dead-wood has not been removed, in the Bavarian Forest National Park (Lackenberg, 1308 m a.s.l., Bavaria, Germany), fluxes of CO2, water vapor and energy have been measured with the Eddy Covariance (EC) method since 2009. Model simulations (MoBiLE) were used to estimate the GPP components from trees and grassland as well as to differentiate between soil and plant respiration, and to get an idea about the long term behavior of the ecosystems carbon exchange. For 2009, 2010, 2011, 2012, and 2013 estimates of annual Net Ecosystem Exchange (NEE) showed that the wind-throw was a marked carbon source. However, the few remaining trees and newly emerging vegetation (grass, sparse young spruce, etc.) lead to an already strong Gross Ecosystem Production (GEP). Model simulations conformed well with the measurements. To our knowledge, we present the worldwide first long-term measurements of NEE within a non-cleared wind-throw-disturbed forest ecosystem.

  11. Carbon budget estimation of a subarctic catchment using a dynamic ecosystem model at high spatial resolution

    NASA Astrophysics Data System (ADS)

    Tang, J.; Miller, P. A.; Persson, A.; Olefeldt, D.; Pilesjo, P.; Heliasz, M.; Jackowicz-Korczynski, M.; Yang, Z.; Smith, B.; Callaghan, T. V.; Christensen, T. R.

    2015-05-01

    A large amount of organic carbon is stored in high-latitude soils. A substantial proportion of this carbon stock is vulnerable and may decompose rapidly due to temperature increases that are already greater than the global average. It is therefore crucial to quantify and understand carbon exchange between the atmosphere and subarctic/arctic ecosystems. In this paper, we combine an Arctic-enabled version of the process-based dynamic ecosystem model, LPJ-GUESS (version LPJG-WHyMe-TFM) with comprehensive observations of terrestrial and aquatic carbon fluxes to simulate long-term carbon exchange in a subarctic catchment at 50 m resolution. Integrating the observed carbon fluxes from aquatic systems with the modeled terrestrial carbon fluxes across the whole catchment, we estimate that the area is a carbon sink at present and will become an even stronger carbon sink by 2080, which is mainly a result of a projected densification of birch forest and its encroachment into tundra heath. However, the magnitudes of the modeled sinks are very dependent on future atmospheric CO2 concentrations. Furthermore, comparisons of global warming potentials between two simulations with and without CO2 increase since 1960 reveal that the increased methane emission from the peatland could double the warming effects of the whole catchment by 2080 in the absence of CO2 fertilization of the vegetation. This is the first process-based model study of the temporal evolution of a catchment-level carbon budget at high spatial resolution, including both terrestrial and aquatic carbon. Though this study also highlights some limitations in modeling subarctic ecosystem responses to climate change, such as aquatic system flux dynamics, nutrient limitation, herbivory and other disturbances, and peatland expansion, our study provides one process-based approach to resolve the complexity of carbon cycling in subarctic ecosystems while simultaneously pointing out the key model developments for capturing

  12. Carbon Storages in Plantation Ecosystems in Sand Source Areas of North Beijing, China

    PubMed Central

    Liu, Xiuping; Zhang, Wanjun; Cao, Jiansheng; Shen, Huitao; Zeng, Xinhua; Yu, Zhiqiang; Zhao, Xin

    2013-01-01

    Afforestation is a mitigation option to reduce the increased atmospheric carbon dioxide levels as well as the predicted high possibility of climate change. In this paper, vegetation survey data, statistical database, National Forest Resource Inventory database, and allometric equations were used to estimate carbon density (carbon mass per hectare) and carbon storage, and identify the size and spatial distribution of forest carbon sinks in plantation ecosystems in sand source areas of north Beijing, China. From 2001 to the end of 2010, the forest areas increased more than 2.3 million ha, and total carbon storage in forest ecosystems was 173.02 Tg C, of which 82.80 percent was contained in soil in the top 0–100 cm layer. Younger forests have a large potential for enhancing carbon sequestration in terrestrial ecosystems than older ones. Regarding future afforestation efforts, it will be more effective to increase forest area and vegetation carbon density through selection of appropriate tree species and stand structure according to local climate and soil conditions, and application of proper forest management including land-shaping, artificial tending and fencing plantations. It would be also important to protect the organic carbon in surface soils during forest management. PMID:24349223

  13. Losses and recovery of organic carbon from a seagrass ecosystem following disturbance.

    PubMed

    Macreadie, Peter I; Trevathan-Tackett, Stacey M; Skilbeck, Charles G; Sanderman, Jonathan; Curlevski, Nathalie; Jacobsen, Geraldine; Seymour, Justin R

    2015-10-22

    Seagrasses are among the Earth's most efficient and long-term carbon sinks, but coastal development threatens this capacity. We report new evidence that disturbance to seagrass ecosystems causes release of ancient carbon. In a seagrass ecosystem that had been disturbed 50 years ago, we found that soil carbon stocks declined by 72%, which, according to radiocarbon dating, had taken hundreds to thousands of years to accumulate. Disturbed soils harboured different benthic bacterial communities (according to 16S rRNA sequence analysis), with higher proportions of aerobic heterotrophs compared with undisturbed. Fingerprinting of the carbon (via stable isotopes) suggested that the contribution of autochthonous carbon (carbon produced through plant primary production) to the soil carbon pool was less in disturbed areas compared with seagrass and recovered areas. Seagrass areas that had recovered from disturbance had slightly lower (35%) carbon levels than undisturbed, but more than twice as much as the disturbed areas, which is encouraging for restoration efforts. Slow rates of seagrass recovery imply the need to transplant seagrass, rather than waiting for recovery via natural processes. This study empirically demonstrates that disturbance to seagrass ecosystems can cause release of ancient carbon, with potentially major global warming consequences. PMID:26490788

  14. Biomass burning in boreal forests and peatlands: Effects on ecosystem carbon losses and soil carbon stabilization as black carbon

    NASA Astrophysics Data System (ADS)

    Turetsky, M. R.; Kane, E. S.; Benscoter, B.

    2011-12-01

    Climate change has increased both annual area burned and the severity of biomass combustion in some boreal regions. For example, there has been a four-fold increase in late season fires in boreal Alaska over the last decade relative to the previous 50 years. Such changes in the fire regime are expected to stimulate ecosystem carbon losses through fuel combustion, reduced primary production, and increased decomposition. However, biomass burning also will influence the accumulation of black carbon in soils, which could promote long-term soil carbon sequestration. Variations in slope and aspect regulate soil temperatures and drainage conditions, and affect the development of permafrost and thick peat layers. Wet soil conditions in peatlands and permafrost forests often inhibit combustion during wildfires, leading to strong positive correlations between pre- and post- fire organic soil thickness that persist through multiple fire cycles. However, burning can occur in poorly drained ecosystems through smouldering combustion, which has implications for emission ratios of CO2:CH4:CO as well as black carbon formation. Our studies of combustion severity and black carbon concentrations in boreal soils show a negative relationship between concentrations of black carbon and organic carbon in soils post-fire. Relative to well drained stands, poorly drained sites with thick peat layers (such as north-facing stands) had less severe burning and low concentrations of black carbon in mineral soils post-fire. Conversely, drier forests lost a greater proportion of their organic soils during combustion but retained larger black carbon stocks following burning. Overall, we have quantified greater black carbon concentrations in surface mineral soil horizons than in organic soil horizons. This is surprising given that wildfires typically do not consume the entire organic soil layer in boreal forests, and could be indicative of the vulnerability of black carbon formed in organic horizons

  15. Climatic and biotic controls on annual carbon storage in Amazonian ecosystems

    USGS Publications Warehouse

    Tian, H.; Melillo, J.M.; Kicklighter, D.W.; McGuire, A.D.; Helfrich, J., Iii; Moore, B., III; Vorosmarty, C.J.

    2000-01-01

    1 The role of undisturbed tropical land ecosystems in the global carbon budget is not well understood. It has been suggested that inter-annual climate variability can affect the capacity of these ecosystems to store carbon in the short term. In this paper, we use a transient version of the Terrestrial Ecosystem Model (TEM) to estimate annual carbon storage in undisturbed Amazonian ecosystems during the period 1980-94, and to understand the underlying causes of the year-to-year variations in net carbon storage for this region. 2 We estimate that the total carbon storage in the undisturbed ecosystems of the Amazon Basin in 1980 was 127.6 Pg C, with about 94.3 Pg C in vegetation and 33.3 Pg C in the reactive pool of soil organic carbon. About 83% of the total carbon storage occurred in tropical evergreen forests. Based on our model's results, we estimate that, over the past 15 years, the total carbon storage has increased by 3.1 Pg C (+ 2%), with a 1.9-Pg C (+2%) increase in vegetation carbon and a 1.2-Pg C (+4%) increase in reactive soil organic carbon. The modelled results indicate that the largest relative changes in net carbon storage have occurred in tropical deciduous forests, but that the largest absolute changes in net carbon storage have occurred in the moist and wet forests of the Basin. 3 Our results show that the strength of interannual variations in net carbon storage of undisturbed ecosystems in the Amazon Basin varies from a carbon source of 0.2 Pg C/year to a carbon sink of 0.7 Pg C/year. Precipitation, especially the amount received during the drier months, appears to be a major controller of annual net carbon storage in the Amazon Basin. Our analysis indicates further that changes in precipitation combine with changes in temperature to affect net carbon storage through influencing soil moisture and nutrient availability. 4 On average, our results suggest that the undisturbed Amazonian ecosystems accumulated 0.2 Pg C/year as a result of climate

  16. Carbon financing of household water treatment: background, operation and recommendations to improve potential for health gains.

    PubMed

    Hodge, James M; Clasen, Thomas F

    2014-11-01

    Household water treatment (HWT) provides a means for vulnerable populations to take charge of their own drinking water quality as they patiently wait for the pipe to finally reach them. In many low-income countries, however, promoters have not succeeded in scaling up the intervention among the target population or securing its consistent and sustained use. Carbon financing can provide the funding for reaching targeted populations with effective HWT solutions and the incentives to ensure their long-term uptake. Nevertheless, programs have been criticized because they do not actually reduce carbon emissions. We summarize the background and operation of carbon financing of HWT interventions, including the controversial construct of "suppressed demand". We agree that these programs have limited potential to reduce greenhouse gas emissions and that their characterization of trading "carbon for water" is misleading. Nevertheless, we show that the Kyoto Protocol expressly encouraged the use of suppressed demand as a means of allowing low-income countries to benefit from carbon financing provided it is used to advance development priorities such as health. We conclude by recommending changes to existing criteria for eligible HWT programs that will help ensure that they meet the conditions of microbiological effectiveness and actual use that will improve their potential for health gains. PMID:25314642

  17. Effects of Land Use and Climate on Ecosystem Carbon Balance from a Recent National Assessment

    NASA Astrophysics Data System (ADS)

    Zhu, Z.; Liu, S.; Bachelet, D. M.; Sleeter, B. M.; Stackpoole, S. M.; Hawbaker, T. J.; Larson, T.; Reed, B.

    2014-12-01

    A recent ecosystem carbon sequestration assessment estimated that the conterminous United States (CONUS) stored 48.3 Pg of carbon, or 6.14 Kg of carbon per square meter covering all vegetated as well as arid lands in the 48 states. The CONUS is shown to be a strong C sink with an average rate of 431 Tg of carbon up-take per year (ranging from 148-667 TgC/yr) for the first half of 2000s as a baseline. Dissolved carbon transported through aquatic systems and emitted carbon dioxide from water surfaces averaged 142 Tg per year. Emissions from wildfires averaged 14 Tg per year based on a separate analysis using remotely sensed fire areas and burn severities. Wildfires are simulated under future climate scenarios and are projected to increase in area, intensity and emissions in future years. Under combinations of future land use/land cover change and climate scenarios, the net ecosystem carbon balance is projected to remain as a carbon sink for the CONUS but could become weaker by 2050 as compared to the baseline, ranging from 44-579 TgC per year. However, a separate analysis of the assessment noted that future potential rate of carbon sequestration by CONUS ecosystems could be higher (increasing to 503-676 Tg of carbon per year by 2060, depending on climate scenarios) than the present rate. This assumes the ecosystems would be managed with active fire suppression, maintained for natural vegetation cover, and benefited from increased water use efficiency of increased atmosphere carbon dioxide concentration.

  18. Economic innovation and efficiency gains as the driving force for accelerating carbon dioxide emissions

    NASA Astrophysics Data System (ADS)

    Garrett, T. J.

    2012-12-01

    It is normally assumed that gains in energy efficiency are one of the best routes that society has available to it for stabilizing future carbon dioxide emissions. For a given degree of economic productivity less energy is consumed and a smaller quantity of fossil fuels is required. While certainly this observation is true in the instant, it ignores feedbacks in the economic system such that efficiency gains ultimately lead to greater energy consumption: taken as a global whole, they permit civilization to accelerate its expansion into the energy reserves that sustain it. Here this argument is formalized from a general thermodynamic perspective. The core result is that there exists a fixed, time-independent link between a very general representation of global inflation-adjusted economic wealth (units currency) and civilization's total capacity to consume power (units energy per time). Based on 40 years of available statistics covering more than a tripling of global GDP and a doubling of wealth, this constant has a value of 7.1 +/- 0.01 Watts per one thousand 2005 US dollars. Essentially, wealth is power. Civilization grows by dissipating power in order to sustain all its current activities and to incorporate more raw material into its existing structure. Growth of its structure is related to economic production, so more energy efficient economic production facilitates growth. Growth is into the reserves that sustain civilization, in which case there is a positive feedback in the economic system whereby energy efficiency gains ultimately "backfire" if their intended purpose is to reduce energy consumption and carbon dioxide emissions. The analogy that can be made is to a growing child: a healthy child who efficiently incorporates food into her structure grows quickly and is able to consume more in following years. Economically, an argument is made that, for a range of reasons, there are good reasons to refer to efficiency gains as economic "innovation", both for

  19. An Integrated Functional Genomics Consortium to Increase Carbon Sequestration in Poplars: Optimizing Aboveground Carbon Gain

    SciTech Connect

    Karnosky, David F; Podila, G Krishna; Burton, Andrew J

    2009-02-17

    This project used gene expression patterns from two forest Free-Air CO2 Enrichment (FACE) experiments (Aspen FACE in northern Wisconsin and POPFACE in Italy) to examine ways to increase the aboveground carbon sequestration potential of poplars (Populus). The aim was to use patterns of global gene expression to identify candidate genes for increased carbon sequestration. Gene expression studies were linked to physiological measurements in order to elucidate bottlenecks in carbon acquisition in trees grown in elevated CO2 conditions. Delayed senescence allowing additional carbon uptake late in the growing season, was also examined, and expression of target genes was tested in elite P. deltoides x P. trichocarpa hybrids. In Populus euramericana, gene expression was sensitive to elevated CO2, but the response depended on the developmental age of the leaves. Most differentially expressed genes were upregulated in elevated CO2 in young leaves, while most were downregulated in elevated CO2 in semi-mature leaves. In P. deltoides x P. trichocarpa hybrids, leaf development and leaf quality traits, including leaf area, leaf shape, epidermal cell area, stomatal number, specific leaf area, and canopy senescence were sensitive to elevated CO2. Significant increases under elevated CO2 occurred for both above- and belowground growth in the F-2 generation. Three areas of the genome played a role in determining aboveground growth response to elevated CO2, with three additional areas of the genome important in determining belowground growth responses to elevated CO2. In Populus tremuloides, CO2-responsive genes in leaves were found to differ between two aspen clones that showed different growth responses, despite similarity in many physiological parameters (photosynthesis, stomatal conductance, and leaf area index). The CO2-responsive clone shunted C into pathways associated with active defense/response to stress, carbohydrate/starch biosynthesis and subsequent growth. The CO2

  20. A carbon budget of Arizona: Comparing Natural Ecosystems with Emissions from Human Activities

    NASA Astrophysics Data System (ADS)

    Ford, A. C.; Finley, B. K.; Koch, G. W.; Hungate, B. A.

    2011-12-01

    A carbon budget of Arizona was constructed to examine the potential for carbon uptake by the state's ecosystems to mitigate human-caused emissions of greenhouse gases. The NASA-CASA (Carnegie Ames Stanford Approach) carbon flux model was used to estimate annual ecosystem CO2 exchange and the State's 2006 greenhouse gas inventory provided data on emissions from transportation, industry, waste, agriculture, electricity, industrial, and residential fuel use. The net carbon flux from primary production in the eight major land resource areas in the state averaged -1.56 million metric tons of carbon (MMTC) per year between 2001 and 2004. This net uptake from the atmosphere amounts to only 1.5% of statewide anthropogenic emissions of 99 MMTCE per year. Given this large imbalance and that projected climate trends for the region are likely to reduce C stocks in the state's forest and woodland ecosystems, land management to promote ecosystem carbon uptake is not a realistic solution to mitigate Arizona's anthropogenic greenhouse gas emissions.

  1. Water and carbon fluxes from savanna ecosystems of the Volta River watershed, West Africa

    NASA Astrophysics Data System (ADS)

    Freitag, Heiko; Ferguson, Paul R.; Dubois, Kristal; Hayford, Ebenezer Kofi; von Vordzogbe, Vincent; Veizer, Ján

    2008-03-01

    The fluxes of water and carbon from terrestrial ecosystems are coupled via the process of photosynthesis. Constraining the annual water cycle therefore allows first order estimates of annual photosynthetic carbon flux, providing that the components of evapotranspiration can be separated. In this study, an isotope mass-balance equation is utilized to constrain annual evaporation flux, which in turn, is used to determine the amount of water transferred to the atmosphere by plant transpiration. The Volta River watershed in West Africa is dominated by woodland and savanna ecosystems with a significant proportion of C 4 vegetation. Annually, the Volta watershed receives ˜ 380 km 3 of rainfall, ˜ 50% of which is returned to the atmosphere via transpiration. An annual photosynthetic carbon flux of ˜ 170 × 10 12 g C yr - 1 or ˜ 428 g C m - 2 was estimated to be associated with this water vapor flux. Independent estimates of heterotrophic soil respiration slightly exceeded the NPP estimate from this study, implying that the exchange of carbon between the Volta River watershed and the atmosphere was close to being in balance or that terrestrial ecosystems were a small annual source of CO 2 to the atmosphere. In addition to terrestrial carbon flux, the balance of photosynthesis and respiration in Volta Lake was also examined. The lake was found to evade carbon dioxide to the atmosphere although the magnitude of the flux was much smaller than that of the terrestrial ecosystems.

  2. FOREST ECOLOGY. Pervasive drought legacies in forest ecosystems and their implications for carbon cycle models.

    PubMed

    Anderegg, W R L; Schwalm, C; Biondi, F; Camarero, J J; Koch, G; Litvak, M; Ogle, K; Shaw, J D; Shevliakova, E; Williams, A P; Wolf, A; Ziaco, E; Pacala, S

    2015-07-31

    The impacts of climate extremes on terrestrial ecosystems are poorly understood but important for predicting carbon cycle feedbacks to climate change. Coupled climate-carbon cycle models typically assume that vegetation recovery from extreme drought is immediate and complete, which conflicts with the understanding of basic plant physiology. We examined the recovery of stem growth in trees after severe drought at 1338 forest sites across the globe, comprising 49,339 site-years, and compared the results with simulated recovery in climate-vegetation models. We found pervasive and substantial "legacy effects" of reduced growth and incomplete recovery for 1 to 4 years after severe drought. Legacy effects were most prevalent in dry ecosystems, among Pinaceae, and among species with low hydraulic safety margins. In contrast, limited or no legacy effects after drought were simulated by current climate-vegetation models. Our results highlight hysteresis in ecosystem-level carbon cycling and delayed recovery from climate extremes. PMID:26228147

  3. Quantifying regional changes in terrestrial carbon storage by extrapolation from local ecosystem models

    SciTech Connect

    King, A W

    1991-12-31

    A general procedure for quantifying regional carbon dynamics by spatial extrapolation of local ecosystem models is presented Monte Carlo simulation to calculate the expected value of one or more local models, explicitly integrating the spatial heterogeneity of variables that influence ecosystem carbon flux and storage. These variables are described by empirically derived probability distributions that are input to the Monte Carlo process. The procedure provides large-scale regional estimates based explicitly on information and understanding acquired at smaller and more accessible scales.Results are presented from an earlier application to seasonal atmosphere-biosphere CO{sub 2} exchange for circumpolar ``subarctic`` latitudes (64{degree}N-90{degree}N). Results suggest that, under certain climatic conditions, these high northern ecosystems could collectively release 0.2 Gt of carbon per year to the atmosphere. I interpret these results with respect to questions about global biospheric sinks for atmospheric CO{sub 2} .

  4. Pervasive Drought Legacy Effects in Forest Ecosystems and their Carbon Cycle Implications

    NASA Astrophysics Data System (ADS)

    Anderegg, W.; Schwalm, C.; Biondi, F.; Camarero, J. J.; Koch, G. W.; Litvak, M. E.; Ogle, K.; Shaw, J.; Shevliakova, E.; Williams, P.; Wolf, A.; Ziaco, E.; Pacala, S. W.

    2015-12-01

    The impacts of climate extremes on terrestrial ecosystems are poorly understood but central for predicting carbon cycle feedbacks to climate change. Coupled climate-carbon cycle models typically assume that vegetation recovery from extreme drought is immediate and complete, which conflicts with basic plant physiological understanding. We examine the recovery of tree stem growth after severe drought at 1,338 forest sites globally comprising 49,339 site-years and compare it to simulated recovery in climate-vegetation models. We find pervasive and substantial "legacy effects" of reduced growth and incomplete recovery for 1-4 years after severe drought, and that legacy effects are most prevalent in dry ecosystems, Pinaceae, and species with low hydraulic safety margins. In contrast, no or limited legacy effects are simulated in current climate-vegetation models after drought. Our results highlight hysteresis in ecosystem carbon cycling and delayed recovery from climate extremes.

  5. CARBON POOL AND FLUX OF GLOBAL FOREST ECOSYSTEMS

    EPA Science Inventory

    Forest systems cover more than 4.1 x 10 9 hectares of the Earth's land area. lobally, forest vegetation and soils contain about 1146 petagrams of carbon, with approximately 37 percent of this carbon in low-latitude forests, 14 percent in mid-latitudes, and 49 percent in high lati...

  6. Biochemical inventory as a tool to assay ecosystem carbon dynamics

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Global soil carbon (C) stocks (2 x 1018 g C) are large enough that a minor change in soil C dynamics would constitute a major climate feedback. The responses of soil C stocks to experimental manipulations of atmospheric carbon dioxide concentration (CO2) and temperature vary widely in direction and...

  7. Does woody plant encroachment increase ecosystem carbon stocks?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Drylands account for ~30-35% of terrestrial primary production and are an important component of the global carbon cycle. Changes in dryland vegetation thus have implications for carbon uptake and storage. One widely observed change is the conversion of grasslands to shrublands and woodlands. Althou...

  8. Field-Scale Partitioning of Ecosystem Respiration Components Suggests Carbon Stabilization in a Bioenergy Grass Ecosystem

    NASA Astrophysics Data System (ADS)

    Black, C. K.; Miller, J. N.; Masters, M. D.; Bernacchi, C.; DeLucia, E. H.

    2014-12-01

    Annually-harvested agroecosystems have the potential to be net carbon sinks only if their root systems allocate sufficient carbon belowground and if this carbon is then retained as stable soil organic matter. Soil respiration measurements are the most common approach to evaluate the stability of soil carbon at experimental time scales, but valid inferences require the partitioning of soil respiration into root-derived (current-year C) and heterotrophic (older C) components. This partitioning is challenging at the field scale because roots and soil are intricately mixed and physical separation in impossible without disturbing the fluxes to be measured. To partition soil flux and estimate the C sink potential of bioenergy crops, we used the carbon isotope difference between C3 and C4 plant species to quantify respiration from roots of three C4 grasses (maize, Miscanthus, and switchgrass) grown in a site with a mixed cropping history where respiration from the breakdown of old soil carbon has a mixed C3-C4 signature. We used a Keeling plot approach to partition fluxes both at the soil surface using soil chambers and from the whole field using continuous flow sampling of air within and above the canopy. Although soil respiration rates from perennial grasses were higher than those from maize, the isotopic signature of respired carbon indicated that the fraction of soil CO2 flux attributable to current-year vegetation was 1.5 (switchgrass) to 2 (Miscanthus) times greater in perennials than that from maize, indicating that soil CO2 flux came mostly from roots and turnover of soil organic matter was reduced in the perennial crops. This reduction in soil heterotrophic respiration, combined with the much greater quantities of C allocated belowground by perennial grasses compared to maize, suggests that perennial grasses grown as bioenergy crops may be able to provide an additional climate benefit by acting as carbon sinks in addition to reducing fossil fuel consumption.

  9. Coherence between woody carbon uptake and net ecosystem productivity at five eddy-covariance sites

    NASA Astrophysics Data System (ADS)

    Babst, F.; Bouriaud, O.; Papale, D.; Gielen, B.; Janssens, I.; Nikinmaa, E.; Ibrom, A.; Wu, J.; Bernhofer, C.; Koestner, B.; Gruenwald, T.; Seufert, G.; Ciais, P.; Frank, D. C.

    2013-12-01

    Forest growth ranks amongst the most important processes that determine the carbon balance of terrestrial ecosystems. Quantifications of forest carbon cycling can be made e.g. using biometric and eddy-covariance (EC) techniques. Both offer different perspectives on carbon uptake and attempts to combine them have been inconsistent and variably successful in the past. This contributes to persistent uncertainties regarding carbon allocation in forest ecosystems and complicates precise vegetation model parameterization. Aiming to reconcile assessments of carbon cycling from biometric and EC techniques, we measured radial tree growth and wood density at five long-term EC stations across Europe. The resulting records were used to calculate annual carbon uptake during above-ground wood formation and compared to monthly and seasonal CO2-flux measurements. Efforts were made to identify i) the time periods when EC and tree-ring data correspond best in different parts of Europe and ii) the fraction of eddy-fluxes which is associated with changes in above-ground woody carbon stocks. Biometric measurements and net ecosystem productivity (NEP) proved largely compatible at seasonal time scales while relationships with gross primary productivity (GPP) were often weaker. Results suggest a partitioning of sequestered carbon mainly used for volume increase (January-June) and a combination of cell-wall thickening and storage (July-September). The inter-annual variability in above-ground woody carbon uptake was significantly linked with absolute productivity ranging between 69-366 g C m-2 y-1 at boreal and temperate sites, thereby accounting for 10-25% of GPP, 15-32% of TER, and 25-80% of NEP. These findings from sites representing the major European climate zones and tree species contribute to improved quantification of above-ground carbon allocation in forests. Furthermore, they refine knowledge on processes driving ecosystem productivity important for e.g. vegetation models and

  10. Changing sources and sinks of carbon in boreal ecosystems of Interior Alaska: Current and future perspectives

    NASA Astrophysics Data System (ADS)

    Douglas, T. A.; Jones, M.; Hiemstra, C. A.

    2012-12-01

    Future climate scenarios predict a roughly 5°C increase in mean annual air temperatures for the Alaskan Interior over the next 80 years. Increasing temperatures and greater frequency and severity of climate-induced disturbances such as wildfires will be enough to initiate permafrost degradation in many areas of Alaska, leading to major changes in surface hydrology and ecosystem structure and function. This, in turn, is expected to alter the current inventories of carbon sources and sinks in the region and provide a management challenge for carbon itemization efforts. To assist land managers in adapting and planning for potential changes in Interior Alaska carbon cycling we synthesize information on climate, ecosystem processes, vegetation, and soil, permafrost, and hydrologic regimes in Interior Alaska. Our goal is to provide an assessment of the current and likely future regime of Interior Alaska carbon sources and sinks. For our carbon assessment we: 1) synthesize the most recent results from numerous studies on the carbon cycle with a focus on research from the Alaskan boreal biome, 2) assemble a summary of estimates of carbon sources in soil and vegetation in Interior Alaska, 3) categorize carbon sources and sinks for predominant Interior Alaska ecosystems, and 4) identify expected changes in sources and sinks with climate change and human activities. This information is used to provide recommendations on potential actions land managers can take to minimize carbon export from the boreal forest. Though the results from our project are geared primarily toward policy makers and land managers we also provide recommendations for filling research gaps that currently present uncertainty in our understanding of the carbon cycle in boreal forest ecosystems of Interior Alaska.

  11. Effects of high CO2 levels on dynamic photosynthesis: carbon gain, mechanisms, and environmental interactions.

    PubMed

    Tomimatsu, Hajime; Tang, Yanhong

    2016-05-01

    Understanding the photosynthetic responses of terrestrial plants to environments with high levels of CO2 is essential to address the ecological effects of elevated atmospheric CO2. Most photosynthetic models used for global carbon issues are based on steady-state photosynthesis, whereby photosynthesis is measured under constant environmental conditions; however, terrestrial plant photosynthesis under natural conditions is highly dynamic, and photosynthetic rates change in response to rapid changes in environmental factors. To predict future contributions of photosynthesis to the global carbon cycle, it is necessary to understand the dynamic nature of photosynthesis in relation to high CO2 levels. In this review, we summarize the current body of knowledge on the photosynthetic response to changes in light intensity under experimentally elevated CO2 conditions. We found that short-term exposure to high CO2 enhances photosynthetic rate, reduces photosynthetic induction time, and reduces post-illumination CO2 burst, resulting in increased leaf carbon gain during dynamic photosynthesis. However, long-term exposure to high CO2 during plant growth has varying effects on dynamic photosynthesis. High levels of CO2 increase the carbon gain in photosynthetic induction in some species, but have no significant effects in other species. Some studies have shown that high CO2 levels reduce the biochemical limitation on RuBP regeneration and Rubisco activation during photosynthetic induction, whereas the effects of high levels of CO2 on stomatal conductance differ among species. Few studies have examined the influence of environmental factors on effects of high levels of CO2 on dynamic photosynthesis. We identified several knowledge gaps that should be addressed to aid future predictions of photosynthesis in high-CO2 environments. PMID:27094437

  12. Optimization of stomatal conductance for maximum carbon gain under dynamic soil moisture

    NASA Astrophysics Data System (ADS)

    Manzoni, Stefano; Vico, Giulia; Palmroth, Sari; Porporato, Amilcare; Katul, Gabriel

    2013-12-01

    Optimization theories explain a variety of forms and functions in plants. At the leaf scale, it is often hypothesized that carbon gain is maximized, thus providing a quantifiable objective for a mathematical definition of optimality conditions. Eco-physiological trade-offs and limited resource availability introduce natural bounds to this optimization process. In particular, carbon uptake from the atmosphere is inherently linked to water losses from the soil as water is taken up by roots and evaporated. Hence, water availability in soils constrains the amount of carbon that can be taken up and assimilated into new biomass. The problem of maximizing photosynthesis at a given water availability by modifying stomatal conductance, the plant-controlled variable to be optimized, has been traditionally formulated for short time intervals over which soil moisture changes can be neglected. This simplification led to a mathematically open solution, where the undefined Lagrange multiplier of the optimization (equivalent to the marginal water use efficiency, λ) is then heuristically determined via data fitting. Here, a set of models based on different assumptions that account for soil moisture dynamics over an individual dry-down are proposed so as to provide closed analytical expressions for the carbon gain maximization problem. These novel solutions link the observed variability in λ over time, across soil moisture changes, and at different atmospheric CO2 concentrations to water use strategies ranging from intensive, in which all soil water is consumed by the end of the dry-down period, to more conservative, in which water stress is avoided by reducing transpiration.

  13. Contribution of semi-arid ecosystems to interannual variability of the global carbon cycle.

    PubMed

    Poulter, Benjamin; Frank, David; Ciais, Philippe; Myneni, Ranga B; Andela, Niels; Bi, Jian; Broquet, Gregoire; Canadell, Josep G; Chevallier, Frederic; Liu, Yi Y; Running, Steven W; Sitch, Stephen; van der Werf, Guido R

    2014-05-29

    The land and ocean act as a sink for fossil-fuel emissions, thereby slowing the rise of atmospheric carbon dioxide concentrations. Although the uptake of carbon by oceanic and terrestrial processes has kept pace with accelerating carbon dioxide emissions until now, atmospheric carbon dioxide concentrations exhibit a large variability on interannual timescales, considered to be driven primarily by terrestrial ecosystem processes dominated by tropical rainforests. We use a terrestrial biogeochemical model, atmospheric carbon dioxide inversion and global carbon budget accounting methods to investigate the evolution of the terrestrial carbon sink over the past 30 years, with a focus on the underlying mechanisms responsible for the exceptionally large land carbon sink reported in 2011 (ref. 2). Here we show that our three terrestrial carbon sink estimates are in good agreement and support the finding of a 2011 record land carbon sink. Surprisingly, we find that the global carbon sink anomaly was driven by growth of semi-arid vegetation in the Southern Hemisphere, with almost 60 per cent of carbon uptake attributed to Australian ecosystems, where prevalent La Niña conditions caused up to six consecutive seasons of increased precipitation. In addition, since 1981, a six per cent expansion of vegetation cover over Australia was associated with a fourfold increase in the sensitivity of continental net carbon uptake to precipitation. Our findings suggest that the higher turnover rates of carbon pools in semi-arid biomes are an increasingly important driver of global carbon cycle inter-annual variability and that tropical rainforests may become less relevant drivers in the future. More research is needed to identify to what extent the carbon stocks accumulated during wet years are vulnerable to rapid decomposition or loss through fire in subsequent years. PMID:24847888

  14. Convergence of the effect of root hydraulic functioning and root hydraulic redistribution on ecosystem water and carbon balance across divergent forest ecosystems

    NASA Astrophysics Data System (ADS)

    domec, J.; King, J. S.; Ogée, J.; Noormets, A.; Warren, J.; Meinzer, F. C.; Sun, G.; Jordan-Meille, L.; Martineau, E.; Brooks, R. J.; Laclau, J.; Battie Laclau, P.; McNulty, S.

    2012-12-01

    INVITED ABSTRACT: Deep root water uptake and hydraulic redistribution (HR) play a major role in forest ecosystems during drought, but little is known about the impact of climate change on root-zone processes influencing HR and its consequences on water and carbon fluxes. Using data from two old growth sites in the western USA, two mature sites in the eastern USA, one site in southern Brazil, and simulations with the process-based model MuSICA, our objectives were to show that HR can 1) mitigate the effects of soil drying on root functioning, and 2) have important implications for carbon uptake and net ecosystem exchange (NEE). In a dry, old-growth ponderosa pine (USA) and a eucalyptus stand (Brazil) both characterized by deep sandy soils, HR limited the decline in root hydraulic conductivity and increased dry season tree transpiration (T) by up to 30%, which impacted NEE through major increases in gross primary productivity (GPP). The presence of deep-rooted trees did not necessarily imply high rates of HR unless soil texture allowed large water potential gradients to occur, as was the case in the wet old-growth Douglas-fir/mixed conifer stand. At the Duke mixed hardwood forest characterized by a shallow clay-loam soil, modeled HR was low but not negligible, representing annually up to 10% of T, and maintaining root conductance high. At this site, in the absence of HR, it was predicted that annual GPP would have been diminished by 7-19%. At the coastal loblolly pine plantation, characterized by deep organic soil, HR limited the decline in shallow root conductivity by more than 50% and increased dry season T by up to 40%, which increased net carbon gain by the ecosystem by about 400 gC m-2 yr-1, demonstrating the significance of HR in maintaining the stomatal conductance and assimilation capacity of the whole ecosystem. Under future climate conditions (elevated atmospheric [CO2] and temperature), HR is predicted to be reduced by up to 50%; reducing the resilience of

  15. Mycorrhizal mediated feedbacks influence net carbon gain and nutrient uptake in Andropogon gerardii.

    SciTech Connect

    Miller, R. M.; Miller, S. P.; Jastrow, J. D.; Rivetta, C. B.; Environmental Research

    2002-07-01

    The carbon sink strength of arbuscular mycorrhizal fungi (AMF) was investigated by comparing the growth dynamics of mycorrhizal and nonmycorrhizal Andropogon gerardii plants over a wide range of equivalent tissue phosphorus : nitrogen (P : N) ratios. Host growth, apparent photosynthesis (A{sub net}), net C gain (C{sub n}) and P and N uptake were evaluated in sequential harvests of mycorrhizal and nonmycorrhizal A. gerardii plants. Response curves were used to assess the effect of assimilate supply on the mycorrhizal symbiosis in relation to the association of C with N and P. Mycorrhizal plants had higher C{sub n} than nonmycorrhizal plants at equivalent shoot P : N ratios even though colonization did not affect plant dry mass. The higher C{sub n} in mycorrhizal plants was related to both an increase in specific leaf area and enhanced photosynthesis. The additional carbon gain associated with the mycorrhizal condition was not allocated to root biomass. The C{sub n} in the mycorrhizal plants was positively related to the proportion of active colonization in the roots. The calculated difference between C{sub n} values in mycorrhizal and nonmycorrhizal plants, C{sub diff}, appeared to correspond to the sink strength of the AMF and was not an indirect result of enhanced nutrition in mycorrhizal plants.

  16. Ecosystem carbon stocks and sequestration potential of federal lands across the conterminous United States

    USGS Publications Warehouse

    Tan, Zhengxi; Liu, Shuguang; Sohl, Terry L.; Wu, Yiping; Young, Claudia J.

    2015-01-01

    Federal lands across the conterminous United States (CONUS) account for 23.5% of the CONUS terrestrial area but have received no systematic studies on their ecosystem carbon (C) dynamics and contribution to the national C budgets. The methodology for US Congress-mandated national biological C sequestration potential assessment was used to evaluate ecosystem C dynamics in CONUS federal lands at present and in the future under three Intergovernmental Panel on Climate Change Special Report on Emission Scenarios (IPCC SRES) A1B, A2, and B1. The total ecosystem C stock was estimated as 11,613 Tg C in 2005 and projected to be 13,965 Tg C in 2050, an average increase of 19.4% from the baseline. The projected annual C sequestration rate (in kilograms of carbon per hectare per year) from 2006 to 2050 would be sinks of 620 and 228 for forests and grasslands, respectively, and C sources of 13 for shrublands. The federal lands’ contribution to the national ecosystem C budget could decrease from 23.3% in 2005 to 20.8% in 2050. The C sequestration potential in the future depends not only on the footprint of individual ecosystems but also on each federal agency’s land use and management. The results presented here update our current knowledge about the baseline ecosystem C stock and sequestration potential of federal lands, which would be useful for federal agencies to decide management practices to achieve the national greenhouse gas (GHG) mitigation goal.

  17. Spatial and Temporal Patterns of Carbon Storage in Forest Ecosystems on Hainan Island, Southern China

    PubMed Central

    Tang, Xuli; Zhang, Qianmei; Wang, Dong; Yuan, Lianlian; Chen, Xubing

    2014-01-01

    Spatial and temporal patterns of carbon (C) storage in forest ecosystems significantly affect the terrestrial C budget, but such patterns are unclear in the forests in Hainan Province, the largest tropical island in China. Here, we estimated the spatial and temporal patterns of C storage from 1993–2008 in Hainan's forest ecosystems by combining our measured data with four consecutive national forest inventories data. Forest coverage increased from 20.7% in the 1950s to 56.4% in the 2010s. The average C density of 163.7 Mg C/ha in Hainan's forest ecosystems in this study was slightly higher than that of China's mainland forests, but was remarkably lower than that in the tropical forests worldwide. Total forest ecosystem C storage in Hainan increased from 109.51 Tg in 1993 to 279.17 Tg in 2008. Soil C accounted for more than 70% of total forest ecosystem C. The spatial distribution of forest C storage in Hainan was uneven, reflecting differences in land use change and forest management. The potential carbon sequestration of forest ecosystems was 77.3 Tg C if all forested lands were restored to natural tropical forests. To increase the C sequestration potential on Hainan Island, future forest management should focus on the conservation of natural forests, selection of tree species, planting of understory species, and implementation of sustainable practices. PMID:25229628

  18. Ecosystem carbon stocks and sequestration potential of federal lands across the conterminous United States.

    PubMed

    Tan, Zhengxi; Liu, Shuguang; Sohl, Terry L; Wu, Yiping; Young, Claudia J

    2015-10-13

    Federal lands across the conterminous United States (CONUS) account for 23.5% of the CONUS terrestrial area but have received no systematic studies on their ecosystem carbon (C) dynamics and contribution to the national C budgets. The methodology for US Congress-mandated national biological C sequestration potential assessment was used to evaluate ecosystem C dynamics in CONUS federal lands at present and in the future under three Intergovernmental Panel on Climate Change Special Report on Emission Scenarios (IPCC SRES) A1B, A2, and B1. The total ecosystem C stock was estimated as 11,613 Tg C in 2005 and projected to be 13,965 Tg C in 2050, an average increase of 19.4% from the baseline. The projected annual C sequestration rate (in kilograms of carbon per hectare per year) from 2006 to 2050 would be sinks of 620 and 228 for forests and grasslands, respectively, and C sources of 13 for shrublands. The federal lands' contribution to the national ecosystem C budget could decrease from 23.3% in 2005 to 20.8% in 2050. The C sequestration potential in the future depends not only on the footprint of individual ecosystems but also on each federal agency's land use and management. The results presented here update our current knowledge about the baseline ecosystem C stock and sequestration potential of federal lands, which would be useful for federal agencies to decide management practices to achieve the national greenhouse gas (GHG) mitigation goal. PMID:26417074

  19. Ecosystem carbon stocks and sequestration potential of federal lands across the conterminous United States

    PubMed Central

    Tan, Zhengxi; Liu, Shuguang; Sohl, Terry L.; Wu, Yiping; Young, Claudia J.

    2015-01-01

    Federal lands across the conterminous United States (CONUS) account for 23.5% of the CONUS terrestrial area but have received no systematic studies on their ecosystem carbon (C) dynamics and contribution to the national C budgets. The methodology for US Congress-mandated national biological C sequestration potential assessment was used to evaluate ecosystem C dynamics in CONUS federal lands at present and in the future under three Intergovernmental Panel on Climate Change Special Report on Emission Scenarios (IPCC SRES) A1B, A2, and B1. The total ecosystem C stock was estimated as 11,613 Tg C in 2005 and projected to be 13,965 Tg C in 2050, an average increase of 19.4% from the baseline. The projected annual C sequestration rate (in kilograms of carbon per hectare per year) from 2006 to 2050 would be sinks of 620 and 228 for forests and grasslands, respectively, and C sources of 13 for shrublands. The federal lands’ contribution to the national ecosystem C budget could decrease from 23.3% in 2005 to 20.8% in 2050. The C sequestration potential in the future depends not only on the footprint of individual ecosystems but also on each federal agency’s land use and management. The results presented here update our current knowledge about the baseline ecosystem C stock and sequestration potential of federal lands, which would be useful for federal agencies to decide management practices to achieve the national greenhouse gas (GHG) mitigation goal. PMID:26417074

  20. Validity of extrapolating field CO[sub 2] experiments to predict carbon sequestration in natural ecosystems

    SciTech Connect

    Luo, Y. . Biological Sciences Center); Reynolds, J.F. . Dept. of Botany)

    1999-07-01

    One of the ultimate goals of ecosystem carbon dioxide (CO[sub 2]) experiments is to infer the capacity of terrestrial ecosystems to sequester carbon (C) in a CO[sub 2]-enriched world. This modeling study examines C sequestration (C[sub seq]) in natural ecosystems based on CO[sub 2] experiments. Most experiments are conducted by a step increase in CO[sub 2] concentration, whereas natural ecosystems are experiencing a gradual increase in atmospheric CO[sub 2] (C[sub a]). To examine the effects of a step vs. gradual CO[sub 2] increase on ecosystem responses, the authors have developed a terrestrial C sequestration (TCS) model that focuses on C and nitrogen (N) interactions in regulating C[sub seq]. They used the model to: (1) compare C[sub seq] and N demand in response to the step vs. gradual increase in CO[sub 2]; (2) identify mechanisms underlying different ecosystem responses to the step vs. gradual CO[sub 2] forcing; (3) examine key parameters in controlling C[sub seq]; and (4) explore three hypothesized N supply mechanisms in regulating photosynthetic acclimation and C[sub seq].

  1. Tracing pyrogenic carbon (PyC) beyond terrestrial ecosystems

    NASA Astrophysics Data System (ADS)

    Wiedemeier, Daniel B.; Eglinton, Timothy I.; Hanke, Ulrich M.; Schmidt, Michael W. I.

    2015-04-01

    Combustion-derived, pyrogenic carbon (PyC) is a persistent organic carbon fraction. Due to its aromatic and condensed nature (Wiedemeier et al., 2015), it is relatively resistant against chemical and biological degradation in the environment, leading to a comparatively slow turnover, which would support carbon sequestration. PyC is produced on large scales (hundreds of teragrams) in biomass burning events such as wildfires, and by combustion of fossil fuel in industry and traffic. PyC is an inherently terrestrial product and thus has predominantly been investigated in soils and the atmosphere. Much fewer studies are available about the subsequent transport of PyC to rivers and oceans. Recently, awareness has been rising about the mobility of PyC from terrestrial to marine systems and its fate in coastal and abyssal sediments was recognized (Mitra et al, 2014). It is therefore crucial to extend our knowledge about the PyC cycle by tracing PyC through all environmental compartments. By comparing its biogeochemical behavior and budgets to that of other forms of organic carbon, it will eventually be possible to elucidate PyC's total spatiotemporal contribution to carbon sequestration. In this study, we are using a state-of-the-art PyC molecular marker method (Wiedemeier et al., 2013, Gierga et al., 2014) to trace quantity, quality as well as 13C and 14C signature of PyC in selected major river systems around the globe (Godavari, Yellow, Danube, Fraser, Mackenzie and Yukon river). Different size fractions of particulate suspended sediment are being analyzed and compared across a north-south gradient. Previous studies suggested a distinct relationship between the age of plant-derived suspended carbon and the latitude of the river system, indicating slower cycling of plant biomarkers in higher latitudes. We discuss this pattern with respect to PyC, its isotopic signature and quality and the resulting implications for the global carbon and PyC cycle. Gierga et al., 2014

  2. Carbon Transformations Following Landscape Fire: Carbon Loss, Mortality, and Ecosystem Recovery Across the Metolius Watershed, Oregon

    NASA Astrophysics Data System (ADS)

    Meigs, G. W.; Law, B. E.

    2008-12-01

    Since 2002, mixed-severity wildfires have burned more than 65,000 ha in the Eastern Cascades of Oregon. This study quantifies changes in aboveground carbon pools and estimates carbon balance and ecosystem recovery 4-5 years following fire. We integrate results from 64 1-ha field plots, forest inventories, and remote sensing data and focus on four fires that burned 35% of the Metolius Watershed (115,000 ha) in 2002 and 2003. We used a stratified random factorial design across three landscape gradients: 1. forest type (ponderosa pine (PP) and mixed-conifer (MC)); 2. burn severity (unburned, low, moderate, and high overstory mortality); 3. prefire biomass (low to high). The fires created a complex mosaic of burn severity and associated overstory and understory responses. Total aboveground mass was 75% greater in MC forests than in PP forests (mean: 10.21 vs. 5.85 kg C m-2, p < 0.001), and trees dominated both live and dead C pools. Across both forest types, mean aboveground dead mass increased twofold in high severity stands compared to low severity stands. Basal area (BA) mortality was an effective ground-based metric of burn severity that validated the remotely-sensed dNBR severity map. BA mortality ranged from 14% in low severity PP stands to 100% in high severity PP stands, with parallel patterns in MC stands. Postfire conifer seedling density was negatively correlated with burn severity (median range: 10,223 seedlings ha-1 in low severity MC to zero seedlings ha-1in high severity PP), while shrub cover and biomass showed the opposite trend. These diverse understory responses demonstrate a wide range of trajectories across the mixed-severity mosaic that, coupled with overstory productivity and decomposition, will drive short- and long-term patterns of C loss and recovery. We used these field estimates of fire effects to: 1. validate a novel Landsat trajectory-based change detection that measures multiple disturbances, partial disturbance, and recovery and 2

  3. Estimating California ecosystem carbon change using process model and land cover disturbance data: 1951-2000

    USGS Publications Warehouse

    Liu, J.; Vogelmann, J.E.; Zhu, Z.; Key, C.H.; Sleeter, B.M.; Price, D.T.; Chen, J.M.; Cochrane, M.A.; Eidenshink, J.C.; Howard, S.M.; Bliss, N.B.; Jiang, H.

    2011-01-01

    Land use change, natural disturbance, and climate change directly alter ecosystem productivity and carbon stock level. The estimation of ecosystem carbon dynamics depends on the quality of land cover change data and the effectiveness of the ecosystem models that represent the vegetation growth processes and disturbance effects. We used the Integrated Biosphere Simulator (IBIS) and a set of 30- to 60-m resolution fire and land cover change data to examine the carbon changes of California's forests, shrublands, and grasslands. Simulation results indicate that during 1951-2000, the net primary productivity (NPP) increased by 7%, from 72.2 to 77.1TgCyr-1 (1 teragram=1012g), mainly due to CO2 fertilization, since the climate hardly changed during this period. Similarly, heterotrophic respiration increased by 5%, from 69.4 to 73.1TgCyr-1, mainly due to increased forest soil carbon and temperature. Net ecosystem production (NEP) was highly variable in the 50-year period but on average equalled 3.0TgCyr-1 (total of 149TgC). As with NEP, the net biome production (NBP) was also highly variable but averaged -0.55TgCyr-1 (total of -27.3TgC) because NBP in the 1980s was very low (-5.34TgCyr-1). During the study period, a total of 126Tg carbon were removed by logging and land use change, and 50Tg carbon were directly removed by wildland fires. For carbon pools, the estimated total living upper canopy (tree) biomass decreased from 928 to 834TgC, and the understory (including shrub and grass) biomass increased from 59 to 63TgC. Soil carbon and dead biomass carbon increased from 1136 to 1197TgC. Our analyses suggest that both natural and human processes have significant influence on the carbon change in California. During 1951-2000, climate interannual variability was the key driving force for the large interannual changes of ecosystem carbon source and sink at the state level, while logging and fire were the dominant driving forces for carbon balances in several specific

  4. Simulating the effects of fire disturbance and vegetation recovery on boreal ecosystem carbon fluxes

    NASA Astrophysics Data System (ADS)

    Yi, Y.; Kimball, J. S.; Jones, L. A.; Zhao, M.

    2011-12-01

    Fire related disturbance and subsequent vegetation recovery has a major influence on carbon storage and land-atmosphere CO2 fluxes in boreal ecosystems. We applied a synthetic approach combining tower eddy covariance flux measurements, satellite remote sensing and model reanalysis surface meteorology within a terrestrial carbon model framework to estimate fire disturbance and recovery effects on boreal ecosystem carbon fluxes including gross primary production (GPP), ecosystem respiration and net CO2 exchange (NEE). A disturbance index based on MODIS land surface temperature and NDVI was found to coincide with vegetation recovery status inferred from tower chronosequence sites. An empirical algorithm was developed to track ecosystem recovery status based on the disturbance index and used to nudge modeled net primary production (NPP) and surface soil organic carbon stocks from baseline steady-state conditions. The simulations were conducted using a satellite based terrestrial carbon flux model driven by MODIS NDVI and MERRA reanalysis daily surface meteorology inputs. The MODIS (MCD45) burned area product was then applied for mapping recent (post 2000) regional disturbance history, and used with the disturbance index to define vegetation disturbance and recovery status. The model was then applied to estimate regional patterns and temporal changes in terrestrial carbon fluxes across the entire northern boreal forest and tundra domain. A sensitivity analysis was conducted to assess the relative importance of fire disturbance and recovery on regional carbon fluxes relative to assumed steady-state conditions. The explicit representation of disturbance and recovery effects produces more accurate NEE predictions than the baseline steady-state simulations and reduces uncertainty regarding the purported missing carbon sink in the high latitudes.

  5. TEMPERATURE SENSITIVITY OF SOIL RESPIRATION AND ITS EFFECTS ON ECOSYSTEM CARBON BUDGET: NONLINEARITY BEGETS SURPRISES. (R827676)

    EPA Science Inventory

    Nonlinearity is a salient feature in all complex systems, and it certainly characterizes biogeochemical cycles in ecosystems across a wide range of scales. Soil carbon emission is a major source of uncertainty in estimating the terrestrial carbon budget at the ecosystem level ...

  6. Evidence for novel and specialized mycorrhizal parasitism: the orchid Gastrodia confusa gains carbon from saprotrophic Mycena

    PubMed Central

    Ogura-Tsujita, Yuki; Gebauer, Gerhard; Hashimoto, Toshimasa; Umata, Hidetaka; Yukawa, Tomohisa

    2008-01-01

    We investigated the physiological ecology of the Asian non-photosynthetic orchid Gastrodia confusa. We revealed its mycorrhizal partners by using molecular identification and identified its ultimate nutritional source by analysing carbon and nitrogen natural stable isotope abundances. Molecular identification using internal transcribed spacer and large subunit nrDNA sequences showed that G. confusa associates with several species of litter- and wood-decomposer Mycena fungi. The carbon and nitrogen isotope signatures of G. confusa were analysed together with photosynthetic plant reference samples and samples of the ectomycorrhizal epiparasite Monotropa uniflora. We found that G. confusa was highly enriched in 13C but not greatly in 15N, while M. uniflora was highly enriched in both 13C and 15N. The 13C and 15N signatures of G. confusa were the closest to those of the fruit bodies of saprotrophic fungi. Our results demonstrate for the first time using molecular and mass-spectrometric approaches that myco-heterotrophic plants gain carbon through parasitism of wood or litter decaying fungi. Furthermore, we demonstrate that, several otherwise free-living non-mycorrhizal, Mycena can be mycorrhizal partners of orchids. PMID:19004757

  7. Baseline and projected future carbon storage and greenhouse-gas fluxes in ecosystems of Alaska

    USGS Publications Warehouse

    2016-01-01

    This assessment was conducted to fulfill the requirements of section 712 of the Energy Independence and Security Act of 2007 and to contribute to knowledge of the storage, fluxes, and balance of carbon and methane gas in ecosystems of Alaska. The carbon and methane variables were examined for major terrestrial ecosystems (uplands and wetlands) and inland aquatic ecosystems in Alaska in two time periods: baseline (from 1950 through 2009) and future (projections from 2010 through 2099). The assessment used measured and observed data and remote sensing, statistical methods, and simulation models. The national assessment, conducted using the methodology described in SIR 2010-5233, has been completed for the conterminous United States, with results provided in three separate regional reports (PP 1804, PP 1797, and PP 1897).

  8. Photodegradation alleviates the lignin bottleneck for carbon turnover in terrestrial ecosystems.

    PubMed

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

    2016-04-19

    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

  9. Sources and sinks of carbon in boreal ecosystems of interior Alaska: a review

    USGS Publications Warehouse

    Douglas, Thomas A.; Jones, Miriam C.; Hiemstra, Christopher A.

    2014-01-01

    Boreal regions store large quantities of carbon but are increasingly vulnerable to carbon loss due to disturbance and climate warming. The boreal region, underlain by discontinuous permafrost, presents a challenging landscape for itemizing current and potential carbon sources and sinks in the boreal soil and vegetation. The roles of fire, forest succession, and the presence (or absence) of permafrost on carbon cycle, vegetation, and hydrologic processes have been the focus of multidisciplinary research in this area for the past 20 years. However, projections of a warming future climate, an increase in fire severity and extent, and the potential degradation of permafrost could lead to major landscape process changes over the next 20 to 50 years. This provides a major challenge for predicting how the interplay between land management activities and impacts of climate warming will affect carbon sources and sinks in Interior Alaska. To assist land managers in adapting and managing for potential changes in the Interior Alaska carbon cycle we developed this review paper incorporating an overview of the climate, ecosystem processes, vegetation types, and soil regimes in Interior Alaska with a focus on ramifications for the carbon cycle. Our objective is to provide a synthesis of the most current carbon storage estimates and measurements to support policy and land management decisions on how to best manage carbon sources and sinks in Interior Alaska. To support this we have surveyed relevant peer reviewed estimates of carbon stocks in aboveground and belowground biomass for Interior Alaska boreal ecosystems. We have also summarized methane and carbon dioxide fluxes from the same ecosystems. These data have been converted into the same units to facilitate comparison across ecosystem compartments. We identify potential changes in the carbon cycle with climate change and human disturbance including how compounding disturbances can affect the boreal system. Finally, we provide

  10. The Effects of Nitrogen Fertilization of a Corn Ecosystem's Oxidative Ratio and Its Carbon Cycle Implications

    NASA Astrophysics Data System (ADS)

    Gallagher, M. E.; Masiello, C. A.; Hockaday, W. C.; McSwiney, C. P.; Robertson, G. P.

    2008-12-01

    One of the most effective ways to estimate the size of carbon sinks in the terrestrial biosphere and oceans is through paired measurements of atmospheric CO2 and O2 concentrations (e.g. (Keeling et al. 1996)). Successful use of this technique requires knowledge of the oxidative ratio (OR) of the terrestrial biosphere (the ratio of moles of O2 released per moles of CO2 consumed in gas fluxes between the terrestrial biosphere and atmosphere.) Historically the terrestrial biosphere's OR has been assumed to be a constant, approximately 1.1 (e.g. Prentice et al. 2001). However, small shifts in the biosphere's OR values can lead to large variations in the calculated sizes of the terrestrial biosphere and ocean carbon sinks (Randerson et al. 2006). We have recently shown that it is possible to measure the OR of biomass to at least +/- 0.01 units (Masiello et al., 2008), and that there is significant natural variability in ecosystem OR. Ecosystem OR is impacted by human activities. In this presentation, we explore the effects of one major form of anthropogenic ecosystem alteration: nitrogen fertilization. We are measuring ecosystem OR in corn agricultural ecosystems under a range of nitrogen fertilization treatments at the Kellogg Biological Station- Long Term Ecological Research Site (KBS-LTER) in Michigan. We measure OR indirectly, through its relationship with organic carbon oxidation state (Cox) (Masiello et al. 2008). Here we present data showing the effects of varying corn ecosystem nitrogen fertilization rates (from 0 to 202 kg N/ha) on ecosystem OR and the implications it will have on apportionment calculations.

  11. Integrated Carbon Observation System (ICOS) ecosystem network: current state and future perspectives

    NASA Astrophysics Data System (ADS)

    Gielen, B.; Op de Beeck, M.; Ceulemans, R.; Janssens, I.; Loustau, D.; Valentini, R.; Papale, D.

    2013-12-01

    Atmospheric concentrations of greenhouse gases (GHG) such as carbon dioxide (CO2) and methane (CH4) are increasing due to emissions related to human activity, affecting the global climate. Natural sinks remove a fraction of the GHG anthropogenic excess at the global level. The characterization of greenhouse gases atmospheric burden and fluxes, both anthropogenic and natural, are needed at the global and regional scale, making use of all available information in an integrated framework. The Integrated Carbon Observation System (ICOS) research infrastructure will address this issue by providing the community with systematic measurements of a suite of atmospheric, terrestrial ecosystem and oceanic measurements. The ecosystem network comprises three station classes, for which variables are collected with different intensity. These stations are well distributed among the major European ecosystem types and cover most climatic zones in Europe. The Ecosystem Thematic Center (ETC) is coordinating the ICOS ecosystem network providing assistance with instruments and methods, testing and developing new measurement techniques and associated processing algorithms; also ensuring a high level of data standardization, uncertainty analysis and database services in coordination with the ICOS carbon portal. The ETC is also coordinating the drafting of the protocols describing in detail how measurements will be collected at all ecosystem stations, in order to guarantee inter comparability. This is done in close collaboration with experts in the field and with the other existing ecological and meteorological networks (NEON, Ameriflux, ICP -forests, MWO, TERN, ...). This presentation will focus on the current state of the ICOS ecosystem network, on the data products and the potential user community.

  12. Coupling of soil water and dissolved carbon measurements to estimate the carbon flux in forest ecosystems a case study

    NASA Astrophysics Data System (ADS)

    Fink, M.; Krause, P.; Gleixner, G.

    2003-04-01

    We used the 250 year old forest of the national park Hainich, Germany, to estimate carbon storage and export to the ground water in old grown forests. The Hainich is one of the largest deciduous forest ecosystems in middle Europe and the protected area is unmanaged for at least 50 years. It is one of the flux sites of the Carboeurop cluster (www.carboeurop.de) equipped with an eddy covariance system to measure net ecosystem exchange (NEE). Surprisingly NEE of this old grown forest is about 5 t carbon/ha*a. This high amount of carbon uptake can not be explained only by biomass or litter increase. Therefore we quantified the amount of carbon lost as dissolved carbon from the upper soil layer. To determine if carbon is washed out and transported by water fluxes in form of dissolved carbon, the measurement campaign was extended by sophisticated hydrometrical instruments, like frequency domain reflectrometry (FDR) probes, high frequency rain measurement equipment and ceramic plates to take soil water samples. The FDR probes characterize the soil hydrology and quantify the amount of water percolating horizontal and vertical through the soil. In the water samples dissolved organic carbon and dissolved inorganic carbon were determined. Both the quantification of the soil hydrology and the chemical characterization of the soil water enable the calculation of the carbon export from the system. The measurement equipment and layout will be presented and results of dissolved carbon contents in the subsurface water fluxes will be presented. Preliminary estimations of the carbon loss by seepages will be presented also.

  13. Pursuing robust agro-ecosystem functioning through effective soil organic carbon management

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil organic matter is a key indicator of many ecosystem functions, particularly in agricultural systems. With carbon as its majority constituent (~58%), the quantity of soil organic C is a key variable relating production and environmental responses. However, it is argued that depth distribution ...

  14. Stock assessment and balance of organic carbon in the Eastern European steppe ecosystems tree windbreaks

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Reserves and balance of organic carbon in ecosystems of windbreaks planted in the mid-1950s within the Forest-Steppe of Central Eastern Europe were determined from field sampling. Windbreaks were represented by 5-6-row plantings of Populus nigra and Betula pendula ("Streletskaya Steppe"), Acer negun...

  15. Landscape and environmental controls over leaf and ecosystem carbon dioxide fluxes under woody plant expansion

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Many regions of the globe are experiencing a simultaneous change in the dominant plant functional type and regional climatology. We explored how atmospheric temperature and precipitation input control leaf- and ecosystem scale carbon fluxes within a pair of semiarid shrublands that had undergone woo...

  16. FOREST SOIL CARBON SEQUESTRATION: ACCOUNTING FOR THIS VITAL ECOSYSTEM SERVICE

    EPA Science Inventory

    Forests play a crucial role in supplying many goods and services that society depends upon on a daily basis including water supply, production of oxygen, soil protection, building materials, wildlife habitat and recreation. Forests also provide a significant amount of carbon seq...

  17. Effects of Fire on Ecosystem Carbon Exchange in Siberian Larch Forest

    NASA Astrophysics Data System (ADS)

    Natali, S.; Alexander, H. D.; Davydov, S. P.; Loranty, M. M.; Mack, M. C.; Zimov, N.

    2014-12-01

    Fire frequency and severity have been increasing across the Arctic, and fires are expected to intensify as the climate becomes warmer and dryer. Fire plays a prominent role in global carbon cycling through direct emissions of greenhouse gases from organic matter combustion as well as through indirect effects of vegetation changes and permafrost thaw, both of which can impact ecosystem carbon exchange over timescales ranging from years to centuries. We examined the indirect effects of fire (i.e., years to decades timescales) on ecosystem carbon exchange in Siberian larch (Larix cajanderi) forests underlain by continuous permafrost and carbon-rich yedoma deposits. We measured understory net ecosystem exchange (NEE) and ecosystem respiration (Reco) from experimental burns, and from larch stands of varying stand densities occurring within a 75-yr burn scar in the vicinity of Cherskiy, Russia. The plot-level (4 m2) experimental burns were conducted in 2012 and comprise four burn treatments based on residual soil organic layer (SOL) depths: control, low severity (> 8 cm), moderate severity (5-8 cm), and high severity (2-5 cm). After three growing seasons, thaw depth was 6%, 11% and 30% deeper in the low, mid, and high severity burn plots compared to control. Immediately following the burns, Reco declined and was related to burn severity; Reco in the mid and high severity plots was fourfold lower than in low severity and control. In the second and third growing seasons, understory Reco continued to be lower in the burn plots relative to control, but effects of burn severity varied across measurement years. While Reco declined as a result of fire, there was a greater net release of CO2 (i.e., NEE) from the burn plots compared to control because there was limited carbon uptake by the regenerating plant community. In the 75-yr burn, we found that variation in stand density, which was likely related to fire severity, significantly impacted understory CO2 exchange through

  18. Surficial gains and subsoil losses of soil carbon and nitrogen during secondary forest development.

    PubMed

    Mobley, Megan L; Lajtha, Kate; Kramer, Marc G; Bacon, Allan R; Heine, Paul R; Richter, Daniel Deb

    2015-02-01

    Reforestation of formerly cultivated land is widely understood to accumulate above- and belowground detrital organic matter pools, including soil organic matter. However, during 40 years of study of reforestation in the subtropical southeastern USA, repeated observations of above- and belowground carbon documented that significant gains in soil organic matter (SOM) in surface soils (0-7.5 cm) were offset by significant SOM losses in subsoils (35-60 cm). Here, we extended the observation period in this long-term experiment by an additional decade, and used soil fractionation and stable isotopes and radioisotopes to explore changes in soil organic carbon and soil nitrogen that accompanied nearly 50 years of loblolly pine secondary forest development. We observed that accumulations of mineral soil C and N from 0 to 7.5 cm were almost entirely due to accumulations of light-fraction SOM. Meanwhile, losses of soil C and N from mineral soils at 35 to 60 cm were from SOM associated with silt and clay-sized particles. Isotopic signatures showed relatively large accumulations of forest-derived carbon in surface soils, and little to no accumulation of forest-derived carbon in subsoils. We argue that the land use change from old field to secondary forest drove biogeochemical and hydrological changes throughout the soil profile that enhanced microbial activity and SOM decomposition in subsoils. However, when the pine stands aged and began to transition to mixed pines and hardwoods, demands on soil organic matter for nutrients to support aboveground growth eased due to pine mortality, and subsoil organic matter levels stabilized. This study emphasizes the importance of long-term experiments and deep measurements when characterizing soil C and N responses to land use change and the remarkable paucity of such long-term soil data deeper than 30 cm. PMID:25155991

  19. The carbon balance pivot point of southwestern U.S. semiarid ecosystems: Insights from the 21st century drought

    NASA Astrophysics Data System (ADS)

    Scott, Russell L.; Biederman, Joel A.; Hamerlynck, Erik P.; Barron-Gafford, Greg A.

    2015-12-01

    Global-scale studies indicate that semiarid regions strongly regulate the terrestrial carbon sink. However, we lack understanding of how climatic shifts, such as decadal drought, impact carbon sequestration across the wide range of structural diversity in semiarid ecosystems. Therefore, we used eddy covariance measurements to quantify how net ecosystem production of carbon dioxide (NEP) differed with relative grass and woody plant abundance over the last decade of drought in four Southwest U.S. ecosystems. We identified a precipitation "pivot point" in the carbon balance for each ecosystem where annual NEP switched from negative to positive. Ecosystems with grass had pivot points closer to the drought period precipitation than the predrought average, making them more likely to be carbon sinks (and a grass-free shrubland, a carbon source) during the current drought. One reason for this is that the grassland located closest to the shrubland supported higher leaf area and photosynthesis at the same water availability. Higher leaf area was associated with a greater proportion of evapotranspiration being transpiration (T/ET), and therefore with higher ecosystem water use efficiency (gross ecosystem photosynthesis/ET). Our findings strongly show that water availability is a primary driver of both gross and net semiarid productivity and illustrate that structural differences may contribute to the speed at which ecosystem carbon cycling adjusts to climatic shifts.

  20. Improved determination of daytime net ecosystem exchange of carbon dioxide at croplands

    NASA Astrophysics Data System (ADS)

    Zhao, P.; Lüers, J.

    2012-03-01

    The eddy-covariance technique is applied worldwide to acquire information about carbon exchange between a variety of ecosystems and atmosphere, but the data acquisition only covers, on average, two-thirds of the whole year due to system failures and data rejection. Therefore, data must be corrected and data gaps must be filled to provide seasonal or annual budgets. The gap-filing strategies, however, are still under discussion within the research community. Presently the major gap-filling methods work quite well for long-time running sites over slow-developing biosphere surfaces such as long-living evergreen forests, but difficulties appear for short-living and fast-growing croplands. In this study we developed a new Multi-Step Error Filter procedure to gain good-quality data as input for different parameterizations of the light response function of plants for two cropland sites (rice and potatoes), and we could prove that the conventional temperature binning approach is inadequate. The presented time-window scheme showed best results with a four-day time window for the potato field and an eight-day time window for the rice field. The influence of vapor pressure deficit was tested as well, but in our case it plays a minor role at both the potato and the rice fields with the exception of the early growing stage of the potatoes. Completing our research, we suggest an innovative method by introducing a Leaf Area Index factor to capture the seasonal vegetation development. With this method we are now able to fill the large gaps between observation periods when conventional methods are invalid.

  1. Effects of drought - altered seasonality and low rainfall - in net ecosystem carbon exchange of three contrasting Mediterranean ecosystems

    NASA Astrophysics Data System (ADS)

    Pereira, J. S.; Mateus, J. A.; Aires, L. M.; Pita, G.; Pio, C.; Andrade, V.; Banza, J.; David, T. S.; Rodrigues, A.; David, J. S.

    2007-06-01

    Droughts cause reductions in gross primary production (GPP) and also in net ecosystem exchange (NEE), contributing to most of the inter-annual variability in terrestrial carbon sequestration. In seasonally dry climates (Mediterranean) droughts result from reductions in annual rainfall and from changes in rain seasonality. In western Iberia, the hydrological-year (i.e., from October to September) of 2004-2005 was extremely dry, with precipitation 50% below the long-term mean (691 mm in 1961-1990), but 2005-2006 was normal. We compared the carbon fluxes measured by the eddy covariance technique from three contrasting ecosystems in southern Portugal: an evergreen oak woodland (savannah-like) with ca. 21% tree cover; a Mediterranean C3/C4 grassland; and a coppiced eucalyptus plantation. During the dry hydrological-year of 2004-2005, NEE was lowest, the highest sink strength was in the eucalypt plantation (NEE = -399 g C m -2 year-1) as compared to the oak woodland (NEE = -88 g C m -2 year-1), and the grassland (NEE = +49 g C m -2 year -1). The latter was a source of carbon dioxide. The NEE values of the dry year were, however, much lower than those for wetter years, e.g. NEE = -861 g C m-2 year -1 in 2002-2003 in the eucalypt plantation. The NEE of the grassland and the oak savannah in the 2005-2006 hydrological-year, with annual precipitation above the long term mean, were -190 and -120 g C m -2 year-1, respectively. All ecosystems studied increased their rain-use efficiency (GPP per unit of rain volume) increased in dry years. In the case of annual vegetation - grassland and low tree density woodland, however &ndash, rain-use efficiency decreased with severe drought. However, this was more pronounced in the eucalypt plantation due to greater GPP and the use of deep soil water resources. Although both calendar years of 2004 and 2005 had equally low rainfall, the effect of drought on the eucalypt plantation was delayed until the second dry year. This suggests that the

  2. Carbon dioxide exchange in a temperate grassland ecosystem

    NASA Technical Reports Server (NTRS)

    Kim, Joon; Verma, Shashi B.

    1990-01-01

    Carbon dioxide exchange was measured, using the eddy correlation technique, over a tallgrass prairie in northeastern Kansas, U.S.A., during a six-month period in 1987. The diurnal patterns of daytime and nocturnal CO2 fluxes are presented on eight selected days. These days were distributed throughout most of the growing season and covered a wide range of meteorological and soil water conditions. The midday CO2 flux reached a maximum of 1.3 mg/sq m (ground area)/s during early July and was near zero during the dry period in late July. The dependence of the daytime carbon dioxide exchange on pertinent controlling variables, particularly photosynthetically active radiation, vapor pressure deficit, and soil water content is discussed. The nocturnal CO2 flux (soil plus plant respiration) averaged -0.4 m sq m (ground area)/s during early July and was about -0.2 mg sq/m during the dry period.

  3. Responses of carbon gain and growth of Pinus radiata stands to thinning and fertilizing.

    PubMed

    Sheriff, D W

    1996-06-01

    Thinning of forest stands is widely carried out to minimize the slowing of growth of individual stems that follows from increasing competition among trees as they become bigger. After thinning, there is an increase in the growth rate of remaining trees because of an increase in the availability of resources per tree. Often, there is also an increase in foliar efficiency (biomass increase/foliage amount). On sites where mineral nutrient supply is limiting, fertilizers may be applied, often in association with thinning, to boost productivity. Growth responses to fertilizer application depend on an adequate supply of other resources, but also involve nonlinear interactions among mineral nutrients and between nutrients and other growth-limiting environmental factors. The effects of thinning and fertilizing on the carbon gain and growth responses of Pinus radiata D. Don to availability of resources (light, mineral nutrients and water) and to changes in the canopy are discussed. PMID:14871706

  4. Photosynthetic properties of boreal bog plant species and their contribution to ecosystem level carbon sink

    NASA Astrophysics Data System (ADS)

    Korrensalo, Aino; Hájek, Tomas; Alekseychik, Pavel; Rinne, Janne; Vesala, Timo; Mehtätalo, Lauri; Mammarella, Ivan; Tuittila, Eeva-Stiina

    2016-04-01

    Boreal bogs have a low number of plant species, but a large diversity of growth forms. This heterogeneity might explain the seasonally less varying photosynthetic productivity of these ecosystems compared to peatlands with vegetation consisting of fewer growth forms. The differences in photosynthetic properties within bog species and phases of growing season has not been comprehensively studied. Also the role of different plant species for the ecosystem level carbon (C) sink function is insufficiently known. We quantified the seasonal variation of photosynthetic properties in bog plant species and assessed how this variation accounts for the temporal variation in the ecosystem C sink. Photosynthetic light response of 11 vascular plant and 8 Sphagnum moss species was measured monthly over the growing season of 2013. Based on the species' light response parameters, leaf area development and areal coverage, we estimated the ecosystem level gross photosynthesis rate (PG) over the growing season. The level of upscaled PG was verified by comparing it to the ecosystem gross primary production (GPP) estimate calculated based on eddy covariance (EC) measurements. Although photosynthetic parameters differed within plant species and months, these differences were of less importance than expected for the variation in ecosystem level C sink. The most productive plant species at the ecosystem scale were not those with the highest maximum potential photosynthesis per unit of leaf area (Pmax), but those having the largest areal coverage. Sphagnum mosses had 35% smaller Pmax than vascular plants, but had higher photosynthesis at the ecosystem scale throughout the growing season. The contribution of the bog plant species to the ecosystem level PG differed over the growing season. The seasonal variation in ecosystem C sink was mainly controlled by phenology. Sedge PG had a sharp mid-summer peak, but the PG of evergreen shrubs and Sphagna remained rather stable over the growing season

  5. Responses of ecosystem carbon cycle to experimental warming: a meta-analysis.

    PubMed

    Lu, Meng; Zhou, Xuhui; Yang, Qiang; Li, Hui; Luo, Yiqi; Fang, Changming; Chen, Jiakuan; Yang, Xin; Li, Bo

    2013-03-01

    Global warming potentially alters the terrestrial carbon (C) cycle, likely feeding back to further climate warming. However, how the ecosystem C cycle responds and feeds back to warming remains unclear. Here we used a meta-analysis approach to quantify the response ratios of 18 variables of the ecosystem C cycle to experimental warming and evaluated ecosystem C-cycle feedback to climate warming. Our results showed that warming stimulated gross ecosystem photosynthesis (GEP) by 15.7%, net primary production (NPP) by 4.4%, and plant C pools from above- and belowground parts by 6.8% and 7.0%, respectively. Experimental warming accelerated litter mass loss by 6.8%, soil respiration by 9.0%, and dissolved organic C leaching by 12.1%. In addition, the responses of some of those variables to experimental warming differed among the ecosystem types. Our results demonstrated that the stimulation of plant-derived C influx basically offset the increase in warming-induced efflux and resulted in insignificant changes in litter and soil C content, indicating that climate warming may not trigger strong positive C-climate feedback from terrestrial ecosystems. Moreover, the increase in plant C storage together with the slight but not statistically significant decrease of net ecosystem exchange (NEE) across ecosystems suggests that terrestrial ecosystems might be a weak C sink rather than a C source under global climate warming. Our results are also potentially useful for parameterizing and benchmarking land surface models in terms of C cycle responses to climate warming. PMID:23687898

  6. Precipitation legacy effects on dryland ecosystem carbon fluxes: direction, magnitude and biogeochemical carryovers

    NASA Astrophysics Data System (ADS)

    Shen, W.; Jenerette, G. D.; Hui, D.; Scott, R. L.

    2016-01-01

    The precipitation legacy effect, defined as the impact of historical precipitation (PPT) on extant ecosystem dynamics, has been recognized as an important driver in shaping the temporal variability of dryland aboveground net primary production (ANPP) and soil respiration. How the PPT legacy influences whole ecosystem-level carbon (C) fluxes has rarely been quantitatively assessed, particularly at longer temporal scales. We parameterized a process-based ecosystem model to a semiarid savanna ecosystem in the southwestern USA, calibrated and evaluated the model performance based on 7 years of eddy-covariance measurements, and conducted two sets of simulation experiments to assess interdecadal and interannual PPT legacy effects over a 30-year simulation period. The results showed that decreasing the previous period/year PPT (dry legacy) always increased subsequent net ecosystem production (NEP) whereas increasing the previous period/year PPT (wet legacy) decreased NEP. The simulated dry-legacy impacts mostly increased subsequent gross ecosystem production (GEP) and reduced ecosystem respiration (Re), but the wet legacy mostly reduced GEP and increased Re. Although the direction and magnitude of GEP and Re responses to the simulated dry and wet legacies were influenced by both the previous and current PPT conditions, the NEP responses were predominantly determined by the previous PPT characteristics including rainfall amount, seasonality and event size distribution. Larger PPT difference between periods/years resulted in larger legacy impacts, with dry legacies fostering more C sequestration and wet legacies more C release. The carryover of soil N between periods/years was mainly responsible for the GEP responses, while the carryovers of plant biomass, litter and soil organic matter were mainly responsible for the Re responses. These simulation results suggest that previous PPT conditions can exert substantial legacy impacts on current ecosystem C balance, which should

  7. The impact of Indonesian peatland degradation on downstream marine ecosystems and the global carbon cycle.

    PubMed

    Abrams, Jesse F; Hohn, Sönke; Rixen, Tim; Baum, Antje; Merico, Agostino

    2016-01-01

    Tropical peatlands are among the most space-efficient stores of carbon on Earth containing approximately 89 Gt C. Of this, 57 Gt (65%) are stored in Indonesian peatlands. Large-scale exploitation of land, including deforestation and drainage for the establishment of oil palm plantations, is changing the carbon balance of Indonesian peatlands, turning them from a natural sink to a source via outgassing of CO2 to the atmosphere and leakage of dissolved organic carbon (DOC) into the coastal ocean. The impacts of this perturbation to the coastal environment and at the global scale are largely unknown. Here, we evaluate the downstream effects of released Indonesian peat carbon on coastal ecosystems and on the global carbon cycle. We use a biogeochemical box model in combination with novel and literature observations to investigate the impact of different carbon emission scenarios on the combined ocean-atmosphere system. The release of all carbon stored in the Indonesian peat pool, considered as a worst-case scenario, will increase atmospheric pCO2 by 8 ppm to 15 ppm within the next 200 years. The expected impact on the Java Sea ecosystems is most significant on the short term (over a few hundred years) and is characterized by an increase of 3.3% in phytoplankton, 32% in seagrass biomass, and 5% decrease in coral biomass. On the long term, however, the coastal ecosystems will recover to reach near pre-excursion conditions. Our results suggest that the ultimate fate of the peat carbon is in the deep ocean with 69% of it landing in the deep DIC pool after 1000 years, but the effects on the global ocean carbonate chemistry will be marginal. PMID:26416553

  8. Carbon Sequestration and Energy Balance of Turf in the Denver Urban Ecosystem and Adjacent Tallgrass Prairie

    NASA Astrophysics Data System (ADS)

    Thienelt, T.; Anderson, D. E.; Powell, K. M.

    2012-12-01

    Urban ecosystems are currently characterized by rapid growth and are expected to continually expand. They represent an important driver of land use change. A significant component of urban ecosystems is lawns, potentially the single largest irrigated "crop" in the U.S. Between March and October of 2011 and 2012, eddy covariance measurements of net carbon dioxide exchange and evapotranspiration along with energy balance fluxes were conducted for an irrigated, fertilized lawn (rye-bluegrass-mix) in metropolitan Denver and for a nearby tallgrass prairie (big bluestem, switchgrass, cheatgrass, blue grama). Due to the semi-arid climate conditions of the Denver region, differences in management (i.e., irrigation and fertilization) are expected to have a discernible impact on ecosystem productivity and thus on carbon sequestration rates, evapotranspiration, and the partitioning of sensible and latent heat. Data for the 2011 season showed that cumulative evapotranspiration was approximately 600 mm for the urban lawn and 305 mm for the tallgrass prairie; cumulative carbon sequestration was calculated to be 172 and 85 g C/m2, respectively. Also, patterns of carbon exchange differed between the grasslands. In 2011, both sites showed daily net uptake of carbon starting in late May, but the urban lawn displayed greater diurnal variability as well as greater uptake rates in general, especially following fertilization in mid-June. In contrast, the trend of carbon uptake at the prairie site was occasionally reversed following strong convective precipitation events, resulting in a temporary net release of carbon. Preliminary data for the 2012 season (up to early July) indicated an earlier start of net carbon uptake and higher cumulative evapotranspiration for both locations, likely due to a warm spring. The continuing acquisition of data and investigation of these relations will help assess the potential impact of urban growth on regional carbon sequestration.

  9. Process contributions of Australian ecosystems to interannual variations in the carbon cycle

    NASA Astrophysics Data System (ADS)

    Haverd, Vanessa; Smith, Benjamin; Trudinger, Cathy

    2016-05-01

    New evidence is emerging that semi-arid ecosystems dominate interannual variability (IAV) of the global carbon cycle, largely via fluctuating water availability associated with El Niño/Southern Oscillation. Recent evidence from global terrestrial biosphere modelling and satellite-based inversion of atmospheric CO2 point to a large role of Australian ecosystems in global carbon cycle variability, including a large contribution from Australia to the record land sink of 2011. However the specific mechanisms governing this variability, and their bioclimatic distribution within Australia, have not been identified. Here we provide a regional assessment, based on best available observational data, of IAV in the Australian terrestrial carbon cycle and the role of Australia in the record land sink anomaly of 2011. We find that IAV in Australian net carbon uptake is dominated by semi-arid ecosystems in the east of the continent, whereas the 2011 anomaly was more uniformly spread across most of the continent. Further, and in contrast to global modelling results suggesting that IAV in Australian net carbon uptake is amplified by lags between production and decomposition, we find that, at continental scale, annual variations in production are dampened by annual variations in decomposition, with both fluxes responding positively to precipitation anomalies.

  10. Modeling Net Ecosystem Carbon Exchange of Alpine Grasslands with a Satellite-Driven Model

    PubMed Central

    Zhao, Yuping; Zhang, Xianzhou; Fan, Yuzhi; Shi, Peili; He, Yongtao; Yu, Guirui; Li, Yingnian

    2015-01-01

    Estimate of net ecosystem carbon exchange (NEE) between the atmosphere and terrestrial ecosystems, the balance of gross primary productivity (GPP) and ecosystem respiration (Reco) has significant importance for studying the regional and global carbon cycles. Using models driven by satellite data and climatic data is a promising approach to estimate NEE at regional scales. For this purpose, we proposed a semi-empirical model to estimate NEE in this study. In our model, the component GPP was estimated with a light response curve of a rectangular hyperbola. The component Reco was estimated with an exponential function of soil temperature. To test the feasibility of applying our model at regional scales, the temporal variations in the model parameters derived from NEE observations in an alpine grassland ecosystem on Tibetan Plateau were investigated. The results indicated that all the inverted parameters exhibit apparent seasonality, which is in accordance with air temperature and canopy phenology. In addition, all the parameters have significant correlations with the remote sensed vegetation indexes or environment temperature. With parameters estimated with these correlations, the model illustrated fair accuracy both in the validation years and at another alpine grassland ecosystem on Tibetan Plateau. Our results also indicated that the model prediction was less accurate in drought years, implying that soil moisture is an important factor affecting the model performance. Incorporating soil water content into the model would be a critical step for the improvement of the model. PMID:25849325

  11. Greater ecosystem carbon in the Mojave Desert after ten years exposure to elevated CO2

    NASA Astrophysics Data System (ADS)

    Evans, R. D.; Koyama, A.; Sonderegger, D. L.; Charlet, T. N.; Newingham, B. A.; Fenstermaker, L. F.; Harlow, B.; Jin, V. L.; Ogle, K.; Smith, S. D.; Nowak, R. S.

    2014-05-01

    Carbon dioxide is the main greenhouse gas inducing climate change. Increased global CO2 emissions, estimated at 8.4 Pg C yr-1 at present, have accelerated from 1% yr-1 during 1990-1999 to 2.5% yr-1 during 2000-2009 (ref. ). The carbon balance of terrestrial ecosystems is the greatest unknown in the global C budget because the actual magnitude, location and causes of terrestrial sinks are uncertain; estimates of terrestrial C uptake, therefore, are often based on the residuals between direct measurements of the atmospheric sink and well-constrained models of ocean uptake of CO2 (ref. ). Here we report significant terrestrial C accumulation caused by CO2 enhancement to net ecosystem productivity in an intact, undisturbed arid ecosystem following ten years of exposure to elevated atmospheric CO2. Results provide direct evidence that CO2 fertilization substantially increases ecosystem C storage and that arid ecosystems are significant, previously unrecognized, sinks for atmospheric CO2 that must be accounted for in efforts to constrain terrestrial and global C cycles.

  12. Detecting Disturbance and its Impact on Ecosystem Carbon Balance from Global to Regional Scales

    NASA Astrophysics Data System (ADS)

    Ballantyne, A.; Jacobson, A. R.; Anderegg, W.; Poulter, B.; Cooper, L. A.; Smith, W. K.; Miller, J. B.

    2015-12-01

    One of the most vital ecosystem services currently provided by the terrestrial biosphere is the removal of approximately one quarter of the anthropogenic CO2 emitted to the atmosphere. However, as patterns of temperature and precipitation change so is the frequency and intensity of ecosystem disturbance. Despite evidence that ecosystem disturbance regimes have shifted leading to widespread forest mortality, the net effect of disturbance on the carbon (C) balance of forest ecosystems remains uncertain. We will use satellite and atmospheric observations to deconvolve net carbon exchange (NEE) into its component fluxes of gross primary productivity and total respiration (e.g. NEE= GPP - R) at global to regional scales. At the global scale we find that NEE has increased over the last 50 years and appears to have accelerated as a result of diminished R over the last 15 years. However the variance in global NEE has also increased perhaps due to inter-annual variability in R, especially within semi-arid ecosystems. These global trends are not necessarily consistent with regional patterns in the net carbon balance, especially across the western US. Atmospheric mass balance suggests that ecosystems of North America have shifted from a net C sink to a net C source. While prolonged drought across the Western US has likely caused this shift in continental scale NEE, attributing this shift in the net C balance to any one mechanism of disturbance (e.g. drought, insect infestation, and fire) or their interactions is challenging. Lastly, we will evaluate existing observing networks, such as NOAA/ESRL and Ameriflux, and how they can be combined with nascent networks, such as NEON, EarthNetworks, and OCO-2, to identify regional disturbance processes that may be causing increasing variance in the global C cycle.

  13. Increased forest ecosystem carbon and nitrogen storage from nitrogen rich bedrock.

    PubMed

    Morford, Scott L; Houlton, Benjamin Z; Dahlgren, Randy A

    2011-09-01

    Nitrogen (N) limits the productivity of many ecosystems worldwide, thereby restricting the ability of terrestrial ecosystems to offset the effects of rising atmospheric CO(2) emissions naturally. Understanding input pathways of bioavailable N is therefore paramount for predicting carbon (C) storage on land, particularly in temperate and boreal forests. Paradigms of nutrient cycling and limitation posit that new N enters terrestrial ecosystems solely from the atmosphere. Here we show that bedrock comprises a hitherto overlooked source of ecologically available N to forests. We report that the N content of soils and forest foliage on N-rich metasedimentary rocks (350-950 mg N kg(-1)) is elevated by more than 50% compared with similar temperate forest sites underlain by N-poor igneous parent material (30-70 mg N kg(-1)). Natural abundance N isotopes attribute this difference to rock-derived N: (15)N/(14)N values for rock, soils and plants are indistinguishable in sites underlain by N-rich lithology, in marked contrast to sites on N-poor substrates. Furthermore, forests associated with N-rich parent material contain on average 42% more carbon in above-ground tree biomass and 60% more carbon in the upper 30 cm of the soil than similar sites underlain by N-poor rocks. Our results raise the possibility that bedrock N input may represent an important and overlooked component of ecosystem N and C cycling elsewhere. PMID:21886160

  14. The contribution of harvest residue to ecosystem carbon balance over the production cycle of managed forests

    NASA Astrophysics Data System (ADS)

    Noormets, A.; McNulty, S.; Domec, J.; Gavazzi, M. J.; Treasure, E.; Sun, G.; King, J. S.; Chen, J.

    2010-12-01

    It has been proposed that forests could be managed for carbon sequestration to mitigate the increase in atmospheric CO2. However, intensive management tends to deplete ecosystem resources (e.g. nutrients and soil organic matter) that make high productivity possible, thus potentially undermining the sustainability of such practices. In forest ecosystems, we have seen soil carbon loss exceed new litter inputs. While the cause of this loss is not clear, the increased frequency of disturbance associated with harvests and management practices likely contributes to the accelerated decomposition rates. Furthermore, the additional pulse of harvest residue of leaves, branches, roots, and coarse woody debris is likely to contribute to enhanced CO2 emissions. Here we evaluate the magnitude of emissions from post-harvest debris in relation to total ecosystem C budget in two loblolly pine plantations in SE-US, and compare our results to three other pine harvest chronosequences in North America. The initial magnitude of ecosystem respiration decreased and the duration of the source phase increased with latitude such that the integrated source phase emissions were proportional (130-140%) to the amount of CWD left at the site following the harvest. However, this relationship may vary by existing soil carbon and moisture availability. The results will be evaluated in the context of potential sources of uncertainty.

  15. Improving Aboveground Carbon Estimates in Dryland Ecosystems with Airborne LiDAR and Satellite Laser Altimetry

    NASA Astrophysics Data System (ADS)

    Glenn, N. F.; Shrestha, R.; Li, A.; Spaete, L.

    2014-12-01

    Numerous studies have demonstrated the utility of ground and airborne LiDAR data to quantify ecosystem structure. In addition, data from satellite-based laser altimetry (e.g. ICESat's GLAS instrument) have been used to estimate vegetation heights, aboveground carbon, and topography in forested areas. With the upcoming ICESAT-2 satellite scheduled to launch in 2017, we have the potential to map vegetation characteristics and dynamics in other ecosystems, including semiarid and low-height ecosystems, at global and regional scales. The ICESat-2 satellite will include the Advanced Topographic Laser Altimeter System (ATLAS) with a configuration of 6 laser beams with 532 nm wavelength and photon counting detectors. We will demonstrate the potential of ICESat-2 to provide estimates of vegetation structure and topography in a dryland ecosystem by simulating the configuration of the ATLAS mission. We will also examine how airborne LiDAR can be used together with ICESat-2 and other satellite data to achieve estimates of aboveground carbon. We will explore how these data may be used for future monitoring and quantification of spatial and temporal changes in aboveground carbon and topography.

  16. Variability in Ecosystem Carbon Predictions in the CCSM4.0 Ensemble

    NASA Astrophysics Data System (ADS)

    Lombardozzi, D.; Bonan, G. B.; Nychka, D. W.

    2013-12-01

    Ecosystems have the capability to moderate climate change over the twenty-first century by removing carbon dioxide from the atmosphere and storing it in vegetation and soils. The responses of terrestrial carbon pools and fluxes are dependent on environmental variables in the physical climate, but model simulations of the physical climate can be highly uncertain due to unforced variability in the climate system. In this study, we evaluate the magnitude and time dependence of variability in terrestrial carbon pools and fluxes in North America using a 6-member ensemble of Community Climate System Model (CCSM) version 4.0 simulations for Representative Concentration Pathway 8.5 (RCP 8.5). Results indicate large ensemble variability in simulated carbon fluxes, and variability in instantaneous carbon fluxes is larger than in integrated carbon pools. The change in carbon pools in response to climate change ('climate signal') is smaller than the unforced variability 10 years into the future, however, the climate signal is larger than the unforced variability throughout North America by 50 years into the future. These results demonstrate that unforced variability needs to be considered when monitoring and predicting decadal-scale ecosystem responses to climate.

  17. Response of a tundra ecosystem to elevated atmospheric carbon dioxide and CO{sub 2}-induced climate change. [Annual report

    SciTech Connect

    Oechel, W.C.

    1989-12-31

    Predicting the response of northern ecosystems to increases in atmospheric CO{sub 2} and associated climatic change is important for several reasons, including the fact that northern ecosystems contain large stores of carbon, most of which is below ground and because northern ecosystems could conceivably be either sources or sinks for CO{sub 2} under future climatic and atmospheric CO{sub 2} concentrations. The carbon in northern ecosystems is equal to about 20% of the world`s terrestrial carbon and about 70% of the carbon currently in the atmosphere. Eighty-three percent of this carbon is below ground in the seasonally-thawed upper soil layers and in the permanently frozen zone, the permafrost. Because of bogs and permafrost, northern ecosystems are unusual in that they can potentially store significant amounts of carbon over long time periods. Most other mature ecosystems have little capacity for long- term carbon storage. Given the right conditions, northern ecosystems can also release a significant amount of carbon. A substantial amount of the carbon stored in northern ecosystems, and much of the future storage potential, is in the tundra regions. These systems could conceivably act as sources or sinks depending on developing climatic and atmospheric conditions. Our recent work indicates that elevated CO{sub 2} alone will have little effect on carbon storage in the tundra. However, the combination of elevated atmospheric CO{sub 2} (+ 340 ppm) and air temperature (+4{degrees}C) in the absence of any change in soil water table or soil moisture content, should result in significant increases in carbon sequestering in the tundra. However, if changing climate results in a decrease in the water table and soil moisture levels, this may lead to sizeable losses of carbon from the tundra soils.

  18. Turning sunlight into stone: the oxalate-carbonate pathway in a tropical tree ecosystem

    NASA Astrophysics Data System (ADS)

    Cailleau, G.; Braissant, O.; Verrecchia, E. P.

    2011-07-01

    pumped through the roots, leading to carbonate precipitation. The main pools of carbon are clearly identified as the organic matter (the tree and its organic products), the oxalate crystals, and the various carbonate features. A functional model based on field observations and diagenetic investigations with δ13C signatures of the various compartments involved in the local carbon cycle is proposed. It suggests that the iroko ecosystem can act as a long-term carbon sink, as long as the calcium source is related to non-carbonate rocks. Consequently, this carbon sink, driven by the oxalate carbonate pathway around an iroko tree, constitutes a true carbon trapping ecosystem as defined by ecological theory.

  19. Turning sunlight into stone: the oxalate-carbonate pathway in a tropical tree ecosystem

    NASA Astrophysics Data System (ADS)

    Cailleau, G.; Braissant, O.; Verrecchia, E. P.

    2011-02-01

    roots, leading to carbonate precipitation. The main pools of carbon are clearly identified as the organic matter (the tree and its organic products), the oxalate crystals, and the various carbonate features. A functional model based on field observations and diagenetic investigations with δ13C signatures of the various compartments involved in the local carbon cycle is proposed. It suggests that the iroko ecosystem can act as a long-term carbon sink, as long as the calcium source is related to non-carbonate rocks. Consequently, this carbon sink, driven by the oxalate carbonate pathway around an iroko tree, constitutes a true carbon trapping ecosystem as define by the ecological theory.

  20. Carbon budget estimation of a subarctic catchment using a dynamic ecosystem model at high spatial resolution

    NASA Astrophysics Data System (ADS)

    Tang, J.; Miller, P. A.; Persson, A.; Olefeldt, D.; Pilesjö, P.; Heliasz, M.; Jackowicz-Korczynski, M.; Yang, Z.; Smith, B.; Callaghan, T. V.; Christensen, T. R.

    2015-01-01

    Large amount of organic carbon is stored in high latitude soils. A substantial proportion of this carbon stock is vulnerable and may decompose rapidly due to temperature increases that are already greater than the global average. It is therefore crucial to quantify and understand carbon exchange between the atmosphere and subarctic/arctic ecosystems. In this paper, we combine an arctic-enabled version of the process-based dynamic ecosystem model, LPJ-GUESS (version LPJG-WHyMe-TFM) with comprehensive observations of terrestrial and aquatic carbon fluxes to simulate long-term carbon exchange in a subarctic catchment comprising both mineral and peatland soils. The model is applied at 50 m resolution and is shown to be able to capture the seasonality and magnitudes of observed fluxes at this fine scale. The modelled magnitudes of CO2 uptake generally follow the descending sequence: birch forest, non-permafrost Eriophorum, Sphagnum and then tundra heath during the observation periods. The catchment-level carbon fluxes from aquatic systems are dominated by CO2 emissions from streams. Integrated across the whole catchment, we estimate that the area is a carbon sink at present, and will become an even stronger carbon sink by 2080, which is mainly a result of a projected densification of birch forest and its encroachment into tundra heath. However, the magnitudes of the modelled sinks are very dependent on future atmospheric CO2 concentrations. Furthermore, comparisons of global warming potentials between two simulations with and without CO2 increase since 1960 reveal that the increased methane emission from the peatland could double the warming effects of the whole catchment by 2080 in the absence of CO2 fertilization of the vegetation. This is the first process-based model study of the temporal evolution of a catchment-level carbon budget at high spatial resolution, integrating comprehensive and diverse fluxes including both terrestrial and aquatic carbon. Though this

  1. Biotic Processes Regulating the Carbon Balance of Desert Ecosystems - Final Report

    SciTech Connect

    Nowak, Robert S; Smith, Stanley D; Evans, Dave; Ogle, Kiona; Fenstermaker, Lynn

    2012-12-13

    Our results from the 10-year elevated atmospheric CO{sub 2} concentration study at the Nevada Desert FACE (Free-air CO{sub 2} Enrichment) Facility (NDFF) indicate that the Mojave Desert is a dynamic ecosystem with the capacity to respond quickly to environmental changes. The Mojave Desert ecosystem is accumulating carbon (C), and over the 10-year experiment, C accumulation was significantly greater under elevated [CO{sub 2}] than under ambient, despite great fluctuations in C inputs from year to year and even apparent reversals in which [CO{sub 2}] treatment had greater C accumulations.

  2. Comparing carbon storage of Siberian tundra and taiga permafrost ecosystems at very high spatial resolution

    NASA Astrophysics Data System (ADS)

    Siewert, Matthias B.; Hanisch, Jessica; Weiss, Niels; Kuhry, Peter; Maximov, Trofim C.; Hugelius, Gustaf

    2015-10-01

    Permafrost-affected ecosystems are important components in the global carbon (C) cycle that, despite being vulnerable to disturbances under climate change, remain poorly understood. This study investigates ecosystem carbon storage in two contrasting continuous permafrost areas of NE and East Siberia. Detailed partitioning of soil organic carbon (SOC) and phytomass carbon (PC) is analyzed for one tundra (Kytalyk) and one taiga (Spasskaya Pad/Neleger) study area. In total, 57 individual field sites (24 and 33 in the respective areas) have been sampled for PC and SOC, including the upper permafrost. Landscape partitioning of ecosystem C storage was derived from thematic upscaling of field observations using a land cover classification from very high resolution (2 × 2 m) satellite imagery. Nonmetric multidimensional scaling was used to explore patterns in C distribution. In both environments the ecosystem C is mostly stored in the soil (≥86%). At the landscape scale C stocks are primarily controlled by the presence of thermokarst depressions (alases). In the tundra landscape, site-scale variability of C is controlled by periglacial geomorphological features, while in the taiga, local differences in catenary position, soil texture, and forest successions are more important. Very high resolution remote sensing is highly beneficial to the quantification of C storage. Detailed knowledge of ecosystem C storage and ground ice distribution is needed to predict permafrost landscape vulnerability to projected climatic changes. We argue that vegetation dynamics are unlikely to offset mineralization of thawed permafrost C and that landscape-scale reworking of SOC represents the largest potential changes to C cycling.

  3. Changes in ecosystem structure related to the type and extent of woody cover alter carbon dynamics and surface energy exchange in central Texas ecosystems.

    NASA Astrophysics Data System (ADS)

    Litvak, M. E.; Heilman, J.; McInnes, K.; Owens, K.; Kjelgaard, J.; Thijs, A.

    2006-12-01

    Rangeland ecosystems account for almost two thirds the total land area in Texas. Over the past century, heavy livestock grazing and fire suppression coupled with changes in climate have facilitated the expansion of woody species into rangelands throughout the state. Based in part on the assumption that woody species use more water than their herbaceous counterparts, land managers have used a variety of techniques to reduce tree and shrub abundance to combat the loss of forage for cattle. As a result, the structure of rangelands in Texas is complex, characterized by woody vegetation that is patchy in distribution, and continually changing between grassland, savanna and woodland. Despite the large areal extent of Texas rangelands, very little is known about how the observed changes in ecosystem structure impact carbon cycle dynamics and surface energy exchange. To reduce these uncertainties, we explored explicit relationships between structure and function in these ecosystems by comparing tower-based measurements of carbon and water vapor exchange made simultaneously from July 2004-Dec 2005 across three representative land covers in central Texas: open grassland, savanna with 30% Ashe juniper and honey mesquite cover, and closed canopy woodland. Here we report our findings on what impact the type and pattern of woody plant cover has on biological controls and patterns of carbon sequestration, evapotranspiration, and sensitivity to precipitation pulses. Monthly measurements of leaf level gas exchange, soil respiration rates, herbaceous net ecosystem exchange, and sap flow measurements on dominant woody species were used to augment eddy covariance estimates of ecosystem-atmosphere exchange. The addition of woody species significantly increased carbon sequestration in these ecosystems. Net ecosystem production from July 05-Jun 05 in the grassland, savanna and forest ecosystems was -14 g C m-2, -413 g C m-2, -450 g C m-2, respectively. Evapotranspiration was less

  4. Can leaf net carbon gain acclimate to keep up with global warming?

    NASA Astrophysics Data System (ADS)

    Vico, Giulia; Manzoni, Stefano; Way, Danielle; Hurry, Vaughan

    2016-04-01

    Plants are able to adjust their physiological activity to fluctuations and long-term changes in their growing environment. Nevertheless, projected increases in temperature will occur with unprecedented speed. Will global warming exceed the thermal acclimation capacity of leaves, thus reducing net CO2 assimilation? Such a reduction in net CO2 assimilation rate (Anet) in response to warming may deplete ecosystems' net primary productivity, with global impacts on the carbon cycling. Here we combine data on net photosynthetic thermal acclimation to changes in temperature with a probabilistic description of leaf temperature variability. We analytically obtain the probability distribution of the net CO2 assimilation rate as a function of species-specific leaf traits and growing conditions. Using this approach, we study the effects of mean leaf temperature and its variability on average Anet and the frequency of occurrence of sub-optimal thermal conditions. To maximize the net CO2 assimilation in warmer conditions, the thermal optimum for Anet (Topt) must track the growing temperature. Observations suggest that plants' thermal acclimation capacity is limited, so that growing temperatures cannot be tracked by the Topt. It is thus likely that net CO2 assimilation rates will decline in the future. Furthermore, for set leaf traits, large fluctuations in leaf temperature reduce average Anet and increase the frequency of occurrence of sub-optimal conditions for net CO2 assimilation.

  5. Effects of invasive species on ecosystem carbon dynamics in a restored tallgrass prairie

    NASA Astrophysics Data System (ADS)

    Matamala, R.; Graham, S. L.; Cook, D. R.; Gonzalez-Meler, M. A.

    2007-12-01

    Land cover is an important determinant of soil C storage and dynamics. Restoration of degraded ecosystems and soils represents a target sink for offsetting rising atmospheric CO2 levels by increasing carbon sequestration in soils. The Conservation Reserve Program (CRP) and other initiatives to halt land degradation after cessation of cultivation present opportunities to assess the C sequestration potential of restoration practices. Our aim is to study what key ecosystem and climatic components exert the largest leverage for these lands to be sustainable C sinks. When considering controls on ecosystem C cycling, biodiversity has the potential to be a strong biotic influence. Invasive species can disrupt ecosystem processes by exhibiting functional characteristics which are distinct from their native counterparts. Invasive species, while affecting nearly all ecosystems, may pose a particular threat to restorations and impact rates of C accrual. We measured net ecosystem production (NEP) at a 18 years-old restored tallgrass prairie using the eddy covariance technique coupled to biometric estimates of biomass and soil C in a two year study where climatic conditions and plant species dominance varied. In 2005, the prairie restoration was a strong C sink with a NEP 438 gCm-2, despite a pronounced spring drought. In 2006, with above normal precipitation, a Melilotus alba dominance dramatically reduced NEP when compared to 2005. The loss of ecosystem functional diversity that resulted from the dominance of the invasive M. alba led to a 42% reduction in the length of the photosynthetically active season, as compared to the previous year. These results suggest that understudied biotic limitations to NEP may outweigh the effects of more commonly studied abiotic limitations. Ecosystem models and management strategies should consider biotic limitations to NEP in grasslands in order to maximize long term C sequestration of restorations and CRP management practices.

  6. Functional Diversity of Boreal Bog Plant Species Decreases Seasonal Variation of Ecosystem Carbon Sink Function

    NASA Astrophysics Data System (ADS)

    Korrensalo, A.

    2015-12-01

    Species diversity has been found to decrease the temporal variance of productivity of a plant community, and diversity in species responses to environmental factors seems to make a plant community more stable in changing conditions. Boreal bogs are nutrient poor peatland ecosystems where the number of plant species is low but the species differ greatly in their growth form. In here we aim to assess the role of the variation in photosynthesis between species for the temporal variation in ecosystem carbon sink function. To quantify the photosynthetic properties and their seasonal variation for different bog plant species we measured photosynthetic parameters and stress-inducing chlorophyll fluorescence of vascular plant and Sphagnum moss species in a boreal bog over a growing season. We estimated monthly gross photosynthesis (PG) of the whole study site based on species level light response curves and leaf area development. The estimated PG was further compared with a gross primary production (GPP) estimate measured by eddy covariance (EC) technique. The sum of upscaled PG estimates agreed well with the GPP estimate measured by the EC technique. The contributions of the species and species groups to the ecosystem level PG changed over the growing season. The sharp mid-summer peak in sedge PG was balanced by more stable PG of evergreen shrubs and Sphagna. Species abundance rather than differences in photosynthetic properties between species and growth forms determined the most productive plants on the ecosystem scale. Sphagna had lower photosynthesis and clorophyll fluorescence than vascular plants but were more productive on the ecosystem scale throughout the growing season due to their high areal coverage. These results show that the diversity of growth forms stabilizes the seasonal variation of the ecosystem level PG in an ombrotrophic bog ecosystem. This may increase the resilience of the ecosystem to changing environmental conditions.

  7. An eddy covariance derived annual carbon budget for an arctic terrestrial ecosystem (Disko, Greenland)

    NASA Astrophysics Data System (ADS)

    McConnell, Alistair; Lund, Magnus; Friborg, Thomas

    2016-04-01

    Ecosystems with underlying permafrost cover nearly 25% of the ice-free land area in the northern hemisphere and store almost half of the global soil carbon. Future climate changes are predicted to have the most pronounced effect in northern latitudes. These Arctic ecosystems are therefore subject to dramatic changes following thawing of permafrost, glacial retreat, and coastal erosion. The most dramatic effect of permafrost thawing is the accelerated decomposition and potential mobilization of organic matter stored in the permafrost. This will impact global climate through the mobilization of carbon and nitrogen accompanied by release of greenhouses gases, including carbon dioxide. This study presents the initial findings and first full annual carbon (CO2) budget, derived from eddy covariance measurements, for an Arctic landscape in West Greenland. The study site, a terrestrial Arctic maritime climate, is located at Østerlien, near Qeqertarsuaq, on the southern coast of Disko Island in central West Greenland (69° 15' N, 53° 34' W) within the transition zone from continuous to discontinuous permafrost. The mean annual air temperature is -5 C and the annual precipitation as rain is 150-200 mm. Arctic ecosystem feedback mechanisms and processes interact on micro, local and regional scales. This is further complicated by several potential feedback mechanisms likely to occur in permafrost-affected ecosystems, involving the interactions of microorganisms, vegetation and soil. The eddy covariance method allows us to interrogate the processes and drivers of land-atmosphere carbon exchange at extremely high temporary frequency (10 Hz), providing landscape-scale measurements of CO2, H2O and heat fluxes for the site, which are processed to derive daily, monthly and now, annual carbon fluxes. We discuss the scientific methodology, challenges, and analysis, as well as the practical and logistic challenges of working in the Arctic, and present an annual carbon budget

  8. Environmental Controls and Management Effects on Ecosystem Carbon Exchange in Two Grazed Temperate Grasslands

    NASA Astrophysics Data System (ADS)

    Ni Choncubhair, O.; Humphreys, J.; Lanigan, G.

    2013-12-01

    Temperate grasslands constitute over 30% of the Earth's naturally-occurring biomes and make an important contribution towards the partial mitigation of anthropogenic greenhouse gas emissions by terrestrial ecosystems. Accumulation of carbon (C) in grassland systems predominantly takes place in below-ground repositories, enhanced by the presence of a stable soil environment with low carbon turnover rates, active rhizodeposition and high levels of residue and organic inputs. However, this C sequestration is strongly influenced by soil characteristics and climatic variables. Furthermore, in managed pasture systems, carbon exchange across the soil-atmosphere boundary is additionally affected by management activities, such as biomass removal, grazing events and the deposition or application of organic amendments. These biotic and abiotic factors contribute greatly towards the large uncertainty associated with the carbon balance of grassland ecosystems and demand further analysis. In the present study, the controls and drivers of carbon dynamics in two rotationally-grazed grasslands in Ireland were examined. The sites experience similar temperate climatic regimes but differ in soil texture classification and stocking rate. Eddy covariance measurements of net ecosystem exchange of carbon were complemented by regular assessment of standing biomass, leaf cover, harvest exports and organic amendment inputs. Our study showed that mild weather conditions and an extended growing season sustained net C accumulation at both sites for at least ten months of the year. Despite differing soil drainage characteristics, winter fluxes of net carbon exchange and its component fluxes, gross photosynthesis and ecosystem respiration, were highly comparable between the two sites. Management practices during the active growing season exerted a strong influence on both the direction and the rate of C exchange in the grassland systems, with a strong dependence, however, on the timing and

  9. Carbon cycling in a high-arctic marine ecosystem - Young Sound, NE Greenland

    NASA Astrophysics Data System (ADS)

    Rysgaard, Søren; Nielsen, Torkel Gissel

    2006-10-01

    Young Sound is a deep-sill fjord in NE Greenland (74°N). Sea ice usually begins to form in late September and gains a thickness of ∼1.5 m topped with 0-40 cm of snow before breaking up in mid-July the following year. Primary production starts in spring when sea ice algae begin to flourish at the ice-water interface. Most biomass accumulation occurs in the lower parts of the sea ice, but sea ice algae are observed throughout the sea ice matrix. However, sea ice algal primary production in the fjord is low and often contributes only a few percent of the annual phytoplankton production. Following the break-up of ice, the immediate increase in light penetration to the water column causes a steep increase in pelagic primary production. Usually, the bloom lasts until August-September when nutrients begin to limit production in surface waters and sea ice starts to form. The grazer community, dominated by copepods, soon takes advantage of the increased phytoplankton production, and on an annual basis their carbon demand (7-11 g C m -2) is similar to phytoplankton production (6-10 g C m -2). Furthermore, the carbon demand of pelagic bacteria amounts to 7-12 g C m -2 yr -1. Thus, the carbon demand of the heterotrophic plankton is approximately twice the estimated pelagic primary production, illustrating the importance of advected carbon from the Greenland Sea and from land in fuelling the ecosystem. In the shallow parts of the fjord (<40 m) benthic primary producers dominate primary production. As a minimum estimate, a total of 41 g C m -2 yr -1 is fixed by primary production, of which phytoplankton contributes 15%, sea ice algae <1%, benthic macrophytes 62% and benthic microphytes 22%. A high and diverse benthic infauna dominated by polychaetes and bivalves exists in these shallow-water sediments (<40 m), which are colonized by benthic primary producers and in direct contact with the pelagic phytoplankton bloom. The annual benthic mineralization is 32 g C m -2 yr -1 of

  10. How is climate warming altering the carbon cycle of a tundra ecosystem in the Siberian Arctic?

    NASA Astrophysics Data System (ADS)

    Belelli Marchesini, Luca; (Ko) van Huissteden, Jacobus; van der Molen, Michiel; Parmentier, Frans-Jan W.; Maximov, Trofim; Budishchev, Artem; Gallagher, Angela; (Han) Dolman, Albertus J.

    2015-04-01

    Climate has been warming over the the Arctic region with the strongest anomalies taking place in autumn and winter for the period 2000-2010, particularly in northern Eurasia. The quantification of the impact on climate warming on the degradation of permafrost and the associated potential release to the atmosphere of carbon stocked in the soil under the form of greenhouse gases, thus further increasing the radiative forcing of the atmosphere, is currently a matter of scientific debate. The positive trend in primary productivity in the last decades inferred by vegetation indexes (NDVI) and confirmed by observations on the enhanced growth of shrub vegetation represents indeed a contrasting process that, if prevalent could offset GHG emissions or even strengthen the carbon sink over the Arctic tundra. At the site of Kytalyk, in north-eastern Siberia, net fluxes of CO2 at ecosystem scale (NEE) have been monitored by eddy covariance technique since 2003. While presenting the results of the seasonal (snow free period) and inter-annual variability of NEE, conceived as the interplay between meteorological drivers and ecosystem responses, we test the role of climate as the main source of NEE variability in the last decade using a data oriented statistical approach. The impact of the timing and duration of the snow free period on the seasonal carbon budget is also considered. Finally, by including the results of continuous micrometeorological observations of methane fluxes taken during summer 2012, corroborated with seasonal CH4 budgets from two previous shorter campaigns (2008, 2009), as well as an experimentally determined estimate of dissolved organic carbon (DOC) flux, we provide an assessment of the carbon budget and its stability over time. The examined tundra ecosystem was found to sequester CO2 during the snow free season with relatively small inter-annual variability (-97.9±12.1gC m-2) during the last decade and without any evident trend despite the carbon uptake

  11. Global Fire emissions and its impacts on terrestrial ecosystem carbon budget from 1901 to 2010

    NASA Astrophysics Data System (ADS)

    Yang, J.; Tian, H.; Tao, B.; Ren, W.; Wang, Y.; Liu, Y.

    2014-12-01

    As a natural disturbance in the earth system, fire plays a critical role in determining vegetation composition and distribution, atmospheric components, terrestrial carbon budget, and land surface energy balance, which all contribute to climate change. However, the fire regime prior to satellite era (the 1980s) is largely unknown at global level due to the lack of sufficient long-term fire records. Recently, a centurial-scale burned area dataset has been reconstructed at global level based on satellite information and fire model simulation. By incorporating this fire dataset into the Dynamic Land Ecosystem Model (DLEM), we estimated the fire emissions from global fires and analyzed the changes in terrestrial ecosystem carbon budget caused by fire during 1901 - 2010. Our preliminary results indicated that the average global fire emissions is 3.0 Pg C year-1 with a significantly decreasing trend during the study period. The difference between fire-on and fire-off simulations showed that fires reduced both net primary productivity (NPP) and ecosystem heterotrophic respiration (Rh). The immediate post-fire reduction in NPP is stronger than that in Rh, which dampened the Net Ecosystem Productivity; while the long-term post-fire recovery in NPP is much faster than that in Rh. Overall, the post-fire recovery processes sequestrated approximately 50% of the carbon emissions released from fires; the global fire cause a net carbon source at about 1.5 Pg C year-1 during the 110 years. In the 21st century, a large increase in global fire potential and burned area has been reported by previous studies according to climate projections. Our results imply that the future fires regime could produce more GHG emissions and reduce carbon sink size, which in turn cause positive feedbacks to global warming.

  12. Neighborhood structure influences the convergence in light capture efficiency and carbon gain: an architectural approach for cloud forest shrubs.

    PubMed

    Guzmán Q, J Antonio; Cordero S, Roberto A

    2016-06-01

    Although plant competition is recognized as a fundamental factor that limits survival and species coexistence, its relative importance on light capture efficiency and carbon gain is not well understood. Here, we propose a new framework to explain the effects of neighborhood structures and light availability on plant attributes and their effect on plant performance in two understory shade-tolerant species (Palicourea padifolia (Roem. & Schult.) C.M. Taylor & Lorence and Psychotria elata (Swartz)) within two successional stages of a cloud forest in Costa Rica. Features of plant neighborhood physical structure and light availability, estimated by hemispherical photographs, were used to characterize the plant competition. Plant architecture, leaf attributes and gas exchange parameters extracted from the light-response curve were used as functional plant attributes, while an index of light capture efficiency (silhouette to total area ratio, averaged over all viewing angles, STAR) and carbon gain were used as indicators of plant performance. This framework is based in a partial least square Path model, which suggests that changes in plant performance in both species were affected in two ways: (i) increasing size and decreasing distance of neighbors cause changes in plant architecture (higher crown density and greater leaf dispersion), which contribute to lower STAR and subsequently lower carbon gain; and (ii) reductions in light availability caused by the neighbors also decrease plant carbon gain. The effect of neighbors on STAR and carbon gain were similar for the two forests sites, which were at different stages of succession, suggesting that the architectural changes of the two understory species reflect functional convergence in response to plant competition. Because STAR and carbon gain are variables that depend on multiple plant attributes and environmental characteristics, we suggest that changes in these features can be used as a whole-plant response approach to

  13. Determining the Carbon Transport Rate of an Enclosed Tropical Rainforest Ecosystem in Biosphere 2

    NASA Astrophysics Data System (ADS)

    Takagi, Y. A.; Van Haren, J. L.

    2013-12-01

    Determining how carbon moves through a tropical rainforest ecosystem is an important step towards understanding its role as a carbon sink system in the global carbon cycle. The paths by which carbon moves through forest ecosystems are reasonably well known. However, very little is known about how quickly this happens. We will present data from experiments where we isotopically pulse label the atmospheric carbon dioxide within the Biosphere 2 tropical rainforest biome with natural gas derived CO2 (∂13C ~ -40‰ vs. ~ -8.5‰ for ambient air). We are continually monitoring the CO2 concentration and isotope composition of the ambient air along a vertical profile to measure ecosystem gas exchange, and that of six branch-bag and five soil-chamber locations within the Biosphere 2 tropical rainforest, with an Aerodyne Quantum Cascade Laser to trace the labeled carbon (precision for ∂13C = 0.02‰ and CO2 = 0.07ppm, calibrated to NOAA air standards). Environmental parameters such as light, relative humidity, soil moisture, and temperature are monitored at fifteen-minute intervals. We have selected one vine species and three different tree species for branch bag enclosures at two canopy heights that we expect represent the bulk photosynthetic biomass of the rainforest. The soil chambers are distributed randomly. By treating the Biosphere 2 tropical rainforest biome, a glass enclosed ecosystem with 1900m2 of ground, 26700m3 of air, and 92 different plant species, as a model ecosystem, we anticipate to determine carbon transport rates that would otherwise be practically impossible to determine in the real world due to the difficulty of isotopically labeling and monitoring entire canopies or even individual trees, which can reach heights over 60m. The data we have collected thus far will provide a baseline comparison for the labeling data. Comparing the branch bag data with the ecosystem data has helped us determine how well small branches represent the canopy and whole

  14. Evaluation of atmospheric aerosol and tropospheric ozone effects on global terrestrial ecosystem carbon dynamics

    NASA Astrophysics Data System (ADS)

    Chen, Min

    The increasing human activities have produced large amounts of air pollutants ejected into the atmosphere, in which atmospheric aerosols and tropospheric ozone are considered to be especially important because of their negative impacts on human health and their impacts on global climate through either their direct radiative effect or indirect effect on land-atmosphere CO2 exchange. This dissertation dedicates to quantifying and evaluating the aerosol and tropospheric ozone effects on global terrestrial ecosystem dynamics using a modeling approach. An ecosystem model, the integrated Terrestrial Ecosystem Model (iTem), is developed to simulate biophysical and biogeochemical processes in terrestrial ecosystems. A two-broad-band atmospheric radiative transfer model together with the Moderate-Resolution Imaging Spectroradiometer (MODIS) measured atmospheric parameters are used to well estimate global downward solar radiation and the direct and diffuse components in comparison with observations. The atmospheric radiative transfer modeling framework were used to quantify the aerosol direct radiative effect, showing that aerosol loadings cause 18.7 and 12.8 W m -2 decrease of direct-beam Photosynthetic Active Radiation (PAR) and Near Infrared Radiation (NIR) respectively, and 5.2 and 4.4 W m -2 increase of diffuse PAR and NIR, respectively, leading to a total 21.9 W m-2 decrease of total downward solar radiation over the global land surface during the period of 2003-2010. The results also suggested that the aerosol effect may be overwhelmed by clouds because of the stronger extinction and scattering ability of clouds. Applications of the iTem with solar radiation data and with or without considering the aerosol loadings shows that aerosol loading enhances the terrestrial productions [Gross Primary Production (GPP), Net Primary Production (NPP) and Net Ecosystem Production (NEP)] and carbon emissions through plant respiration (RA) in global terrestrial ecosystems over the

  15. Spatial Patterns of Carbon Residence Time and Sequestration Capacity in Terrestrial Ecosystems of the Conterminous USA

    NASA Astrophysics Data System (ADS)

    Zhou, T.; Xu, T.; Luo, Y.

    2005-12-01

    To model carbon (C) sequestration and its spatial pattern, three key parameters need to be quantified: (1) canopy carbon influx; (2) carbon residence time in an ecosystem; and (3) initial values of pool sizes. While spatial distributions of canopy carbon influx have been extensively studied, spatial patterns of carbon residence times have not been carefully characterized. In this study, we conducted an inverse analysis to estimate the carbon residence times in ecosystems of the conterminous US from 12 data sets. The 12 data sets are three NPP data sets (i.e., NPP in leaves, stems, and roots), five biomass data sets (i.e., biomass of leaves, stem, and roots in three soil layers), one litter data set (i.e., fine litter mass), and three SOC data sets in the three soil layers. The inverse analysis was based on a process-based Terrestrial ECOsystem Regional (TECOR) model and used the genetic algorithm for optimal parameter estimation. The inverted residence times and increase trends of net primary production (NPP) were then fed into a forward modeling analysis to map spatial patterns of carbon sequestration capacity. Our analysis estimated that the mean residence time for the whole conterminous US is 46 years with a range from 10 to 150 years. The central Great Plains have the lowest residence times (mean = 28 years, std = 13 years) and the west regions have the highest ones (mean = 64 years, std = 34 years) with the east regions in between (mean = 41 years, std = 20 years). When a 0.5 percent increase of NPP per year was uniformly applied to the whole conterminous US, our forward modeling showed that most of the eastern regions and some of the northwest regions have large carbon sequestration capacity. When a satellite-data-derived spatial distribution of NPP was applied in the forward modeling, it was estimated that the cropland has the largest carbon sequestration capacity followed by the deciduous broadleaf forest, grassland, wooded grassland, and mixed forest. The

  16. Contributions of Land Inventory and Biometrics for Characterizing Disturbance in Ecosystem and Carbon Accounting Models

    NASA Astrophysics Data System (ADS)

    Birdsey, R.; Pan, Y.

    2004-12-01

    Nearly all forest lands of the U.S. are disturbed or affected by disturbance. Each decade about half of the total forest land area is disturbed by harvesting, grazing, wildfire, pests, and other natural causes. Because of the patchy nature of forest disturbances and the amount of edges, a large proportion of undisturbed interior forest area is affected by disturbances. Some ecosystem and carbon accounting models require spatially explicit input data about frequency or effects of disturbance. Current and historical information about forest disturbances includes both geospatial and statistical data. Examples of geospatial data sets from land inventories include maps of insect defoliation and N deposition. Examples of primarily statistical data sets that can be made into geospatial data sets include county-level statistics from forest inventory and other census data about land use or cover. A variety of techniques are available to manipulate statistical data sets into geospatial data sets. Many ecosystem and carbon accounting models lack ability to simulate the dynamics of disturbance and instead only represent potential forest vegetation. Several techniques are being developed in large-scale ecosystem models to address this issue. One approach is illustrated by Production Efficiency Models (PEMs) that use satellite-derived information to estimate vegetation productivity and C changes affected by landscape changes and climatic variability. Models that rely primarily on remote-sensing information lack ability to separate kinds of disturbances that may have similar canopy impacts, such as forest management and land use change. Also, PEMs lack the capacity to detect impacts of global change stressors such as CO2, N deposition and ozone. Another approach is to combine disturbance models with ecosystem models. Such model combinations use different integration approaches. Whether using ecosystem models to provide growth information to parameterize disturbance models, or

  17. Unmasking the effect of a precipitation pulse on the biological processes composing Net Ecosystem Carbon Exchange

    NASA Astrophysics Data System (ADS)

    Lopez-Ballesteros, Ana; Sanchez-Cañete, Enrique P.; Serrano-Ortiz, Penelope; Oyonarte, Cecilio; Kowalski, Andrew S.; Perez-Priego, Oscar; Domingo, Francisco

    2015-04-01

    Drylands occupy 47.2% of the global terrestrial area and are key ecosystems that significantly determine the inter-annual variability of the global carbon balance. However, it is still necessary to delve into the functional behavior of arid and semiarid ecosystems due to the complexity of drivers and interactions between underpinning processes (whether biological or abiotic) that modulate net ecosystem CO2 exchange (NEE). In this context, water inputs are crucial to biological organisms survival in arid ecosystems and frequently arrive via rain events that are commonly stochastic and unpredictable (i.e. precipitation pulses) and strongly control arid land ecosystem structure and function. The eddy covariance technique can be used to investigate the effect of precipitation pulses on NEE, but provide limited understanding of what exactly happens after a rain event. The chief reasons are that, firstly, we cannot measure separately autotrophic and heterotrophic components, and secondly, the partitioning techniques widely utilized to separate Gross Primary Production and Total Ecosystem Respiration, do not work properly in these water-limited ecosystems, resulting in biased estimations of plant and soil processes. Consequently, it is essential to combine eddy covariance measurements with other techniques to disentangle the different biological processes composing NEE that are activated by a precipitation pulse. Accordingly, the main objectives of this work were: (i) to quantify the contribution of precipitation pulse events to annual NEE using the eddy covariance technique in a semiarid steppe located in Almería (Spain), and (ii) to simulate a realistic precipitation pulse in order to understand its effect on the ecosystem, soil and plant CO2 exchanges by using a transitory-state closed canopy chamber, soil respiration chambers and continuous monitoring CO2 sensors inserted in the subsoil. Preliminary results showed, as expected, a delay between soil and plant

  18. Effects of Stand age Structure on Regional Carbon Budgets of Forest Ecosystems

    NASA Astrophysics Data System (ADS)

    Song, C.; Woodcock, C. E.

    2002-12-01

    This study has developed a two-stage modeling scheme to investigate the importance of age structure on regional carbon fluxes for the forests in the Pacific Northwest of the United States. In the first stage, an individual-based forest ecosystem carbon flux model (IntCarb) at stand scale is developed. IntCarb combines components from the ZELIG and CENTURY models to simulate forest growth and development, and heterotrophic respiration, respectively. Stand scale carbon fluxes simulated by IntCarb strongly depend on stand age. Due to its high variablity over large areas, forest age structure has to be taken into account for realistic estimation of carbon budgets. The RegCarb model is developed to estimate regional scale carbon fluxes based on forest age structure and adjusting for the nonrespiratory carbon losses, such as harvesting. Our initial estimate with RegCarb for the Pacific Northwest of the United States found that this region was a tremendous carbon source to the atmosphere from 1890 to 1990 due to intensive logging of old-growth forest, and is becoming a carbon sink since the last decade. Projections for the role of forests in this region in the global carbon cycle in the future strongly depend on the amount of timber to be harvested, i.e. how the age structure of forests in this region is to be altered.

  19. Detecting a Terrestrial Biosphere Sink for Carbon Dioxide: Interannual Ecosystem Modeling for the Mid-1980s

    NASA Technical Reports Server (NTRS)

    Potter, Christopher S.; Klooster, Steven A.; Brooks, Vanessa; Gore, Warren J. (Technical Monitor)

    1998-01-01

    There is considerable uncertainty as to whether interannual variability in climate and terrestrial ecosystem production is sufficient to explain observed variation in atmospheric carbon content over the past 20-30 years. In this paper, we investigated the response of net CO2 exchange in terrestrial ecosystems to interannual climate variability (1983 to 1988) using global satellite observations as drivers for the NASA-CASA (Carnegie-Ames-Stanford Approach) simulation model. This computer model of net ecosystem production (NEP) is calibrated for interannual simulations driven by monthly satellite vegetation index data (NDVI) from the NOAA Advanced Very High Resolution Radiometer (AVHRR) at 1 degree spatial resolution. Major results from NASA-CASA simulations suggest that from 1985 to 1988, the northern middle-latitude zone (between 30 and 60 degrees N) was the principal region driving progressive annual increases in global net primary production (NPP; i.e., the terrestrial biosphere sink for carbon). The average annual increase in NPP over this predominantly northern forest zone was on the order of +0.4 Pg (10 (exp 15) g) C per year. This increase resulted mainly from notable expansion of the growing season for plant carbon fixation toward the zonal latitude extremes, a pattern uniquely demonstrated in our regional visualization results. A net biosphere source flux of CO2 in 1983-1984, coinciding with an El Nino event, was followed by a major recovery of global NEP in 1985 which lasted through 1987 as a net carbon sink of between 0.4 and 2.6 Avg C per year. Analysis of model controls on NPP and soil heterotrophic CO2 fluxes (Rh) suggests that regional warming in northern forests can enhance ecosystem production significantly. In seasonally dry tropical zones, periodic drought and temperature drying effects may carry over with at least a two-year lag time to adversely impact ecosystem production. These yearly patterns in our model-predicted NEP are consistent in

  20. Improving SWAT for simulating water and carbon fluxes of forest ecosystems.

    PubMed

    Yang, Qichun; Zhang, Xuesong

    2016-11-01

    As a widely used watershed model for assessing impacts of anthropogenic and natural disturbances on water quantity and quality, the Soil and Water Assessment Tool (SWAT) has not been extensively tested in simulating water and carbon fluxes of forest ecosystems. Here, we examine SWAT simulations of evapotranspiration (ET), net primary productivity (NPP), net ecosystem exchange (NEE), and plant biomass at ten AmeriFlux forest sites across the U.S. We identify unrealistic radiation use efficiency (Bio_E), large leaf to biomass fraction (Bio_LEAF), and missing phosphorus supply from parent material weathering as the primary causes for the inadequate performance of the default SWAT model in simulating forest dynamics. By further revising the relevant parameters and processes, SWAT's performance is substantially improved. Based on the comparison between the improved SWAT simulations and flux tower observations, we discuss future research directions for further enhancing model parameterization and representation of water and carbon cycling for forests. PMID:27401278

  1. Global sensitivity analysis, probabilistic calibration, and predictive assessment for the data assimilation linked ecosystem carbon model

    NASA Astrophysics Data System (ADS)

    Safta, C.; Ricciuto, D. M.; Sargsyan, K.; Debusschere, B.; Najm, H. N.; Williams, M.; Thornton, P. E.

    2015-07-01

    In this paper we propose a probabilistic framework for an uncertainty quantification (UQ) study of a carbon cycle model and focus on the comparison between steady-state and transient simulation setups. A global sensitivity analysis (GSA) study indicates the parameters and parameter couplings that are important at different times of the year for quantities of interest (QoIs) obtained with the data assimilation linked ecosystem carbon (DALEC) model. We then employ a Bayesian approach and a statistical model error term to calibrate the parameters of DALEC using net ecosystem exchange (NEE) observations at the Harvard Forest site. The calibration results are employed in the second part of the paper to assess the predictive skill of the model via posterior predictive checks.

  2. Integrating flux, satellite, and proximal optical data for an improved understanding of ecosystem carbon uptake

    NASA Astrophysics Data System (ADS)

    Gamon, J. A.; Huemmrich, K. F.; Garrity, S. R.

    2015-12-01

    The different scales and methods of satellite observations and flux measurements present challenges for data integration that can be partly addressed by the addition of scale-appropriate optical sampling. Proximal optical measurement facilitates experimental approaches that can inform upscaling, satellite validation, and lead to better understanding of controls on carbon fluxes and other ecosystem processes. Using the framework of the light-use efficiency model, this presentation will review efforts to explore the controls on ecosystem-atmosphere carbon fluxes using a variety of novel optical sensors and platforms. Topics of appropriate sampling methodology, scaling and data aggregation will also be considered, with examples of how information content and interpretation of optical data can be scale-dependent. Key challenges include informatics solutions that handle large, multi-dimensional data volumes and contextual information, including information about sampling protocols and scale. Key opportunities include the assessment of vegetation functional diversity with optical sensors.

  3. Estimation of Net Ecosystem Carbon Exchange for the Conterminous United States by Combining MODIS and AmeriFlux Data 1961

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Eddy covariance flux towers provide continuous measurements of net ecosystem carbon exchange (NEE) for a wide range of climate and biome types. However, these measurements only represent the carbon fluxes at the scale of the tower footprint. To quantify the net exchange of carbon dioxide between the...

  4. Biophysical regulation of carbon fluxes over an alpine meadow ecosystem in the eastern Tibetan Plateau.

    PubMed

    Wang, Shaoying; Zhang, Yu; Lü, Shihua; Su, Peixi; Shang, Lunyu; Li, Zhaoguo

    2016-06-01

    The eddy covariance method was used to measure net ecosystem CO2 exchange (NEE) between atmosphere and an alpine meadow ecosystem in the eastern Tibetan Plateau of China in 2010. Our results show that photosynthesis was reduced under low air temperature (T a), high vapor pressure deficit (VPD), and medium soil water content (SWC) conditions, when compared to that under other T a (i.e., medium and high), VPD (i.e., low and medium), and SWC (i.e., low and high) conditions. The apparent temperature sensitivity of ecosystem respiration (Q 10) declined with progressing phenology during the growing season and decreased with an increase of soil temperature (T s) during the non-growing season. Increased ecosystem respiration (R eco) was measured during spring soil thawing. By the path analysis, T a, T s, and VPD were the main control factors of CO2 exchange at 30-min scale in this alpine meadow. Integrated NEE, gross primary production (GPP), and R eco over the measured year were -156.4, 1164.3, and 1007.9 g C m(-2), respectively. Zoige alpine meadow was a medium carbon sink based on published data for grassland ecosystems. PMID:26456094

  5. Biophysical regulation of carbon fluxes over an alpine meadow ecosystem in the eastern Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Wang, Shaoying; Zhang, Yu; Lü, Shihua; Su, Peixi; Shang, Lunyu; Li, Zhaoguo

    2015-10-01

    The eddy covariance method was used to measure net ecosystem CO2 exchange (NEE) between atmosphere and an alpine meadow ecosystem in the eastern Tibetan Plateau of China in 2010. Our results show that photosynthesis was reduced under low air temperature (T a), high vapor pressure deficit (VPD), and medium soil water content (SWC) conditions, when compared to that under other T a (i.e., medium and high), VPD (i.e., low and medium), and SWC (i.e., low and high) conditions. The apparent temperature sensitivity of ecosystem respiration (Q 10) declined with progressing phenology during the growing season and decreased with an increase of soil temperature (T s) during the non-growing season. Increased ecosystem respiration (R eco) was measured during spring soil thawing. By the path analysis, T a, T s, and VPD were the main control factors of CO2 exchange at 30-min scale in this alpine meadow. Integrated NEE, gross primary production (GPP), and R eco over the measured year were -156.4, 1164.3, and 1007.9 g C m-2, respectively. Zoige alpine meadow was a medium carbon sink based on published data for grassland ecosystems.

  6. Can We Make Use of Abandoned Land for Carbon Management and Ecosystem Restoration?

    NASA Astrophysics Data System (ADS)

    Yamagata, Y.; Shoyama, K.

    2014-12-01

    Potential conflicts between biodiversity conservation and climate-change mitigation can result in trade-offs in multiple-use land management. This study aimed to detect possible changes in land-use patterns in response to biodiversity conservation and climate-change mitigation measures and the effects on ecosystem services across a watershed. For that purpose, we have developed a new method to combine land-use change scenarios and ecosystem service assessments. We analyzed land-cover change based on past and future scenarios in the rural Kushiro watershed in northern Japan. The analysis showed that if no conservation measures were implemented and the timber and agricultural industry remained small until 2060, supporting and provisioning services would decline due to less land management. Although biodiversity conservation measures are predicted to improve three of the ecosystem services that we studied, carbon sequestration and timber production would be improved to a greater degree by climate-change mitigation measures. The greatest land-cover changes are likely to occur in the unprotected area around the middle reaches of the Kushiro River, and such changes could affect the provision of ecosystem services throughout the entire watershed. Thus, our findings indicate that land-use decisions for the middle reaches of the watershed are particularly important for managing the integrated ecosystem services of the entire watershed for the future.

  7. Biophysical regulation of carbon fluxes over an alpine meadow ecosystem in the eastern Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Wang, Shaoying; Zhang, Yu; Lü, Shihua; Su, Peixi; Shang, Lunyu; Li, Zhaoguo

    2016-06-01

    The eddy covariance method was used to measure net ecosystem CO2 exchange (NEE) between atmosphere and an alpine meadow ecosystem in the eastern Tibetan Plateau of China in 2010. Our results show that photosynthesis was reduced under low air temperature ( T a), high vapor pressure deficit (VPD), and medium soil water content (SWC) conditions, when compared to that under other T a (i.e., medium and high), VPD (i.e., low and medium), and SWC (i.e., low and high) conditions. The apparent temperature sensitivity of ecosystem respiration ( Q 10) declined with progressing phenology during the growing season and decreased with an increase of soil temperature ( T s) during the non-growing season. Increased ecosystem respiration ( R eco) was measured during spring soil thawing. By the path analysis, T a, T s, and VPD were the main control factors of CO2 exchange at 30-min scale in this alpine meadow. Integrated NEE, gross primary production (GPP), and R eco over the measured year were -156.4, 1164.3, and 1007.9 g C m-2, respectively. Zoige alpine meadow was a medium carbon sink based on published data for grassland ecosystems.

  8. Impacts of droughts on carbon sequestration by China's terrestrial ecosystems from 2000 to 2011

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Zhou, Y.; Ju, W.; Wang, S.; Wu, X.; He, M.; Zhu, G.

    2014-05-01

    In recent years, China's terrestrial ecosystems have experienced frequent droughts. How these droughts have affected carbon sequestration by the terrestrial ecosystems is still unclear. In this study, the process-based Boreal Ecosystem Productivity Simulator (BEPS) model, driven by remotely sensed vegetation parameters, was employed to assess the effects of droughts on net ecosystem productivity (NEP) of terrestrial ecosystems in China from 2000 to 2011. Droughts of differing severity, as indicated by a standard precipitation index (SPI), hit terrestrial ecosystems in China extensively in 2001, 2006, 2009, and 2011. The national total annual NEP exhibited the slight decline of -11.3 Tg C yr-2 during the aforementioned years of extensive droughts. The NEP reduction ranged from 61.1 Tg C yr-1 to 168.8 Tg C yr-1. National and regional total NEP anomalies were correlated with the annual mean SPI, especially in Northwest China, North China, Central China, and Southwest China. The reductions in annual NEP in 2001 and 2011 might have been caused by a larger decrease in annual gross primary productivity (GPP) than in annual ecosystem respiration (ER). The reductions experienced in 2009 might be due to a decrease in annual GPP and an increase in annual ER, while reductions in 2006 could stem from a larger increase in ER than in GPP. The effects of droughts on NEP lagged up to 3-6 months, due to different responses of GPP and ER. In eastern China, where is humid and warm, droughts have predominant and short-term lagged influences on NEP. In western regions, cold and arid, the drought effects on NEP were relatively weaker but prone to lasting longer.

  9. A source of terrestrial organic carbon to investigate the browning of aquatic ecosystems.

    PubMed

    Lennon, Jay T; Hamilton, Stephen K; Muscarella, Mario E; Grandy, A Stuart; Wickings, Kyle; Jones, Stuart E

    2013-01-01

    There is growing evidence that terrestrial ecosystems are exporting more dissolved organic carbon (DOC) to aquatic ecosystems than they did just a few decades ago. This "browning" phenomenon will alter the chemistry, physics, and biology of inland water bodies in complex and difficult-to-predict ways. Experiments provide an opportunity to elucidate how browning will affect the stability and functioning of aquatic ecosystems. However, it is challenging to obtain sources of DOC that can be used for manipulations at ecologically relevant scales. In this study, we evaluated a commercially available source of humic substances ("Super Hume") as an analog for natural sources of terrestrial DOC. Based on chemical characterizations, comparative surveys, and whole-ecosystem manipulations, we found that the physical and chemical properties of Super Hume are similar to those of natural DOC in aquatic and terrestrial ecosystems. For example, Super Hume attenuated solar radiation in ways that will not only influence the physiology of aquatic taxa but also the metabolism of entire ecosystems. Based on its chemical properties (high lignin content, high quinone content, and low C:N and C:P ratios), Super Hume is a fairly recalcitrant, low-quality resource for aquatic consumers. Nevertheless, we demonstrate that Super Hume can subsidize aquatic food webs through 1) the uptake of dissolved organic constituents by microorganisms, and 2) the consumption of particulate fractions by larger organisms (i.e., Daphnia). After discussing some of the caveats of Super Hume, we conclude that commercial sources of humic substances can be used to help address pressing ecological questions concerning the increased export of terrestrial DOC to aquatic ecosystems. PMID:24124511

  10. Irrigation and Fertilization Controls on Critical Zone Carbon and Nitrogen cycles in Harvested Ecosystems

    NASA Astrophysics Data System (ADS)

    Parolari, A.; Katul, G. G.; Porporato, A. M.

    2014-12-01

    Feedbacks between hydrology, soil biogeochemistry, and primary productivity raise questions regarding the broader impact of human modifications to one or more of these critical zone processes. In particular, irrigation and nitrogen fertilization are used simultaneously to stimulate agricultural productivity and biomass export; however, together they may lead to unintended downstream consequences such as increased nitrogen leaching or greenhouse gas release. To quantify such trade-offs among ecosystem services and to identify optimal agricultural management practices, an ecosystem model coupling the water, carbon, and nitrogen cycles is studied. The model is forced by stochastic climate and periodic management interventions that include irrigation, fertilization, and harvest. Steady-state solutions of ecosystems under rotational harvest are developed, demonstrating that these ecosystems operate in a limit-cycle. Under constant fertilization and soil moisture conditions, the model predicts an optimal rotation length associated with maximum yield and maximum ecosystem nitrogen use efficiency. Through plant-soil feedbacks mediated by the harvest, intermediate rotation lengths promote short periods of immobilization, which stimulates mineral nitrogen retention. In these systems, increased soil moisture increases non-productive nitrogen losses, especially under long rotations, where mineral nitrogen availability is greatest. Time-variable water and nitrogen input scenarios are also considered and suggest the possibility of an optimal irrigation-fertilization strategy that balances productivity, which provides an economic benefit, and leaching, which may have consequences for aquatic ecosystems in receiving waters. These results highlight several soil C-N cycle responses to management practices that influence the provision of and trade-off between ecosystem services, namely primary productivity and mineral nitrogen export.

  11. A Source of Terrestrial Organic Carbon to Investigate the Browning of Aquatic Ecosystems

    PubMed Central

    Lennon, Jay T.; Hamilton, Stephen K.; Muscarella, Mario E.; Grandy, A. Stuart; Wickings, Kyle; Jones, Stuart E.

    2013-01-01

    There is growing evidence that terrestrial ecosystems are exporting more dissolved organic carbon (DOC) to aquatic ecosystems than they did just a few decades ago. This “browning” phenomenon will alter the chemistry, physics, and biology of inland water bodies in complex and difficult-to-predict ways. Experiments provide an opportunity to elucidate how browning will affect the stability and functioning of aquatic ecosystems. However, it is challenging to obtain sources of DOC that can be used for manipulations at ecologically relevant scales. In this study, we evaluated a commercially available source of humic substances (“Super Hume”) as an analog for natural sources of terrestrial DOC. Based on chemical characterizations, comparative surveys, and whole-ecosystem manipulations, we found that the physical and chemical properties of Super Hume are similar to those of natural DOC in aquatic and terrestrial ecosystems. For example, Super Hume attenuated solar radiation in ways that will not only influence the physiology of aquatic taxa but also the metabolism of entire ecosystems. Based on its chemical properties (high lignin content, high quinone content, and low C:N and C:P ratios), Super Hume is a fairly recalcitrant, low-quality resource for aquatic consumers. Nevertheless, we demonstrate that Super Hume can subsidize aquatic food webs through 1) the uptake of dissolved organic constituents by microorganisms, and 2) the consumption of particulate fractions by larger organisms (i.e., Daphnia). After discussing some of the caveats of Super Hume, we conclude that commercial sources of humic substances can be used to help address pressing ecological questions concerning the increased export of terrestrial DOC to aquatic ecosystems. PMID:24124511

  12. Carbon account of forest ecosystems as a fuzzy system: a case study for Northern Eurasia

    NASA Astrophysics Data System (ADS)

    Shvidenko, A.; Shchepashchenko, D.; Kraxner, F.; Maksyutov, S. S.

    2015-12-01

    We consider practicality of a verified account of Net Ecosystem Carbon Budget for forest ecosystems (FCA) that supposes reliable assessment of uncertainties, i.e. understanding "uncertainty of uncertainties". The FCA is a fuzzy (underspecified) system, of which membership function is inherently stochastic. Thus, any individually used method of FCA is not able to estimate structural uncertainties and usually reported "within method" uncertainties are inevitably partial. Attempting at estimation of "full uncertainties" of the studied system we follow the requirements of applied systems analysis integrating the major methods of terrestrial ecosystems carbon account, assessing the uncertainties "within method" for intermediate and final indicators of FCA with their following mutual constrains. Landscape-ecosystem approach (LEA) 1) serves for strict systems designing the account, 2) contains all relevant spatially distributed empirical and semi-empirical data and models, and 3) is presented in form of an Integrated Land Information System (ILIS). By-pixel parametrization of forest cover is provided by utilizing multi-sensor remote sensing data (12 RS products used) within GEO-wiki platform and other relevant information based on special optimization algorithms. Major carbon fluxes within the LEA (NPP, HR, disturbances etc.) are estimated based on fusion of empirical data with process-based elements by sets of regionally distributed models. Uncertainties within LEA are assessed for each module and at each step of the account. "Within method" results and uncertainties (including LEA, process-based models, eddy covariance, and inverse modelling) are harmonized based on the Bayesian approach. The above methodology have been applied to carbon account of Russian forests for 2000-2010; uncertainties of the FCA for individual years were estimated in limits of 25%. We discussed strengths and weaknesses of the approach, system requirements to different methods of FCA, information

  13. Assessment of Pan-Arctic Soil Moisture, Surface Temperature, and Net Ecosystem Carbon Exchange

    NASA Astrophysics Data System (ADS)

    Nirala, M. L.; Kimball, J.; Njoku, E.; McDonald, K.; Chan, S.; Jones, L.; Oechel, W.; Running, S.

    2006-05-01

    In this paper, we discuss the application of Moderate Resolution Imaging Spectroradiometer (MODIS), Leaf Area Index (LAI), Gross Primary Production (GPP), and Advanced Microwave Scanning Radiometer - EOS (AMSR-E) brightness temperature and soil moisture to derived Net Ecosystem Carbon Exchange (NEE). We also compare the satellite-derived results with ground-based tower CO2 eddy flux observations and Biome- BGC ecosystem process model simulations using site meteorology. We found that AMSR-E brightness temperature-derived surface temperatures compare favorably with site-based temperatures and that sensitivity to air and soil temperatures depend on wavelength, snow cover, freeze-thaw conditions, and the sub-grid scale extent of open water. The surface temperature estimations using the emissivity lookup table approach showed good agreement, as compared to observations on most sites. AMSR-E L3 soil moisture data showed large discrepancies relative to site-based ecosystem model simulations and limited site observations. The soil moisture differences were larger in winter than summer. Satellite-derived carbon model results were consistent with site-based CO2 flux tower observations and detailed ecosystem process model (BIOME-BGC) simulations. The carbon model represents NEE seasonal variability and regional patterns, and the NEE is highly sensitive to LAI, which determines the optimal soil decomposition rate. NEE is a residual of two fluxes: GPP and respiration. Small changes in component fluxes yielded large changes in annual NEE and predicted carbon source/sink behavior, especially for relatively low productivity sites, such as tundra. This work was performed at The University of Montana and the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

  14. Continuous In-situ Measurements of Carbonyl Sulfide (OCS) and Carbon Dioxide Isotopes to Constrain Ecosystem Carbon and Water Exchanges

    NASA Astrophysics Data System (ADS)

    Rastogi, B.; Still, C. J.; Noone, D. C.; Berkelhammer, M. B.; Whelan, M.; Lai, C. T.; Hollinger, D. Y.; Gupta, M.; Leen, J. B.; Huang, Y. W.

    2015-12-01

    Understanding the processes that control the terrestrial exchange of carbon and water are critical for examining the role of forested ecosystems in changing climates. A small but increasing number of studies have identified Carbonyl Sulfide (OCS) as a potential tracer for photosynthesis. OCS is hydrolyzed by an irreversible reaction in leaf mesophyll cells that is catalyzed by the enzyme, carbonic anhydrase. Leaf- level field and greenhouse studies indicate that OCS uptake is controlled by stomatal activity and that the ratio of OCS and CO2 uptake is reasonably constant. Existing studies on ecosystem OCS exchange have been based on laboratory measurements or short field campaigns and therefore little information on OCS exchange in a natural ecosystem over longer timescales is available. The objective of this study is to further assess the stability of OCS as a tracer for canopy photosynthesis in an active forested ecosystem and also to assess its utility for constraining transpiration, since both fluxes are mediated by canopy stomatal conductance. An off-axis integrated cavity output spectroscopy analyzer (Los Gatos Research Inc.) was deployed at the Wind River Experimental Forest in Washington (45.8205°N, 121.9519°W). Canopy air was sampled from four heights as well as the soil to measure vertical gradients of OCS within the canopy, and OCS exchange between the forest and the atmosphere for the growing season. Here we take advantage of simultaneous measurements of the stable isotopologues of H2O and CO2 at corresponding heights as well as NEE (Net Ecosystem Exchange) from eddy covariance measurements to compare GPP (Gross Primary Production) and transpiration estimates from a variety of independent techniques. Our findings also seek to allow assessment of the environmental and ecophysicological controls on evapotranspiration rates, which are projected to change in coming decades, and are otherwise poorly constrained.

  15. Carbon cycle. The dominant role of semi-arid ecosystems in the trend and variability of the land CO₂ sink.

    PubMed

    Ahlström, Anders; Raupach, Michael R; Schurgers, Guy; Smith, Benjamin; Arneth, Almut; Jung, Martin; Reichstein, Markus; Canadell, Josep G; Friedlingstein, Pierre; Jain, Atul K; Kato, Etsushi; Poulter, Benjamin; Sitch, Stephen; Stocker, Benjamin D; Viovy, Nicolas; Wang, Ying Ping; Wiltshire, Andy; Zaehle, Sönke; Zeng, Ning

    2015-05-22

    The growth rate of atmospheric carbon dioxide (CO2) concentrations since industrialization is characterized by large interannual variability, mostly resulting from variability in CO2 uptake by terrestrial ecosystems (typically termed carbon sink). However, the contributions of regional ecosystems to that variability are not well known. Using an ensemble of ecosystem and land-surface models and an empirical observation-based product of global gross primary production, we show that the mean sink, trend, and interannual variability in CO2 uptake by terrestrial ecosystems are dominated by distinct biogeographic regions. Whereas the mean sink is dominated by highly productive lands (mainly tropical forests), the trend and interannual variability of the sink are dominated by semi-arid ecosystems whose carbon balance is strongly associated with circulation-driven variations in both precipitation and temperature. PMID:25999504

  16. Long-Term Release of Carbon Dioxide from Arctic Tundra Ecosystems in Northern Alaska

    NASA Astrophysics Data System (ADS)

    Euskirchen, E. S.; Bret-Harte, M. S.; Edgar, C.; Shaver, G. R.

    2014-12-01

    Recent data syntheses and modeling studies of arctic tundra carbon dioxide (CO2) balance have suggested that the tundra is a CO2 sink, a source or neutral. Much of this uncertainty arises from a lack of data pertaining to winter CO2 flux, as well as how these ecosystems have responded to recent warming trends. Due to a harsh, remote environment, long-term, continuous measurements of arctic tundra CO2 fluxes over the full annual cycle have been non-existent. In September 2007, we began eddy covariance measurements of net ecosystem exchange (NEE, where a negative value denotes a sink) of CO2 in northern Alaska at two ecosystems, heath and wet sedge tundra. These measurements continue to the present, and represent the longest continuous record of arctic tundra NEE currently available. From January 2008 - December 2013, the ecosystems were annual sources of CO2, with the wet sedge tundra acting as a greater source (mean ± standard deviation of 50 ± 30 g C m-2 y-1) than the heath tundra (16 ± 6 g C m-2 y-1). During these same years, the ecosystems were sinks of CO2 in the summer (June - August), with less variability between the ecosystems, -77 ± 15 g C m-2 in the wet sedge tundra, and -70 ± 12 g C m-2 in the heath. Environmental controls over NEE differed between ecosystems and seasons, with the wet sedge tundra acting particularly responsive in terms of CO2 release during periods with warm air temperatures from fall to early winter. During cold winter periods, CO2 release from the snowpack in both ecosystems was related to increases in wind speed and drops in atmospheric pressure. Overall, the measured differences in the annual versus summer NEE illustrate how the sink strength of the tundra can be overestimated if data are only collected during the growing season. Furthermore, eddy covariance measurements of methane (CH4) in the wet sedge tundra during late spring to early fall from 2012 to present show that this ecosystem releases 0.34 ± 11 mg CH4 m-2 d-1

  17. Land Use and Ecosystems Data from the Carbon Dioxide Information Analysis Center (CDIAC)

    DOE Data Explorer

    CDIAC products are indexed and searchable through a customized interface powered by ORNL's Mercury search engine. Products include numeric data packages, publications, trend data, atlases, models, etc. and can be searched for by subject area, keywords, authors, product numbers, time periods, collection sites, spatial references, etc. Some of the collections may also be included in the CDIAC publication titled Trends Online: A Compendium of Global Change Data. Most data sets, many with numerous data files, are free to download from CDIAC's ftp area. Land Use and Ecosystems information includes Terrestrial Carbon Sequestration Data Sets, data sets from Africa and Asia, the Worldwide Organic Soil Carbon and Nitrogen Dataset, and much more.

  18. Contribution of increasing CO2 and climate to carbon storage by ecosystems in the United States

    USGS Publications Warehouse

    Schimel, D.; Melillo, J.; Tian, H.; McGuire, A.D.; Kicklighter, D.; Kittel, T.; Rosenbloom, N.; Running, S.; Thornton, P.; Ojima, D.; Parton, W.; Kelly, R.; Sykes, M.; Neilson, R.; Rizzo, B.

    2000-01-01

    The effects of increasing carbon dioxide (CO2) and climate on net carbon storage in terrestrial ecosystems of the conterminous United States for the period 1895-1993 were modeled with new, detailed historical climate information. For the period 1980-1993, results from an ensemble of three models agree within 25%, simulating a land carbon sink from CO2 and climate effects of 0.08 gigaton of carbon per year. The best estimates of the total sink from inventory data are about three times larger, suggesting that processes such as regrowth on abandoned agricultural land or in forests harvested before 1980 have effects as large as or larger than the direct effects of CO2 and climate. The modeled sink varies by about 100% from year to year as a result of climate variability.

  19. Herbivory makes major contributions to ecosystem carbon and nutrient cycling in tropical forests.

    PubMed

    Metcalfe, Daniel B; Asner, Gregory P; Martin, Roberta E; Silva Espejo, Javier E; Huasco, Walter Huaraca; Farfán Amézquita, Felix F; Carranza-Jimenez, Loreli; Galiano Cabrera, Darcy F; Baca, Liliana Durand; Sinca, Felipe; Huaraca Quispe, Lidia P; Taype, Ivonne Alzamora; Mora, Luzmila Eguiluz; Dávila, Angela Rozas; Solórzano, Marlene Mamani; Puma Vilca, Beisit L; Laupa Román, Judith M; Guerra Bustios, Patricia C; Revilla, Norma Salinas; Tupayachi, Raul; Girardin, Cécile A J; Doughty, Christopher E; Malhi, Yadvinder

    2014-03-01

    The functional role of herbivores in tropical rainforests remains poorly understood. We quantified the magnitude of, and underlying controls on, carbon, nitrogen and phosphorus cycled by invertebrate herbivory along a 2800 m elevational gradient in the tropical Andes spanning 12°C mean annual temperature. We find, firstly, that leaf area loss is greater at warmer sites with lower foliar phosphorus, and secondly, that the estimated herbivore-mediated flux of foliar nitrogen and phosphorus from plants to soil via leaf area loss is similar to, or greater than, other major sources of these nutrients in tropical forests. Finally, we estimate that herbivores consume a significant portion of plant carbon, potentially causing major shifts in the pattern of plant and soil carbon cycling. We conclude that future shifts in herbivore abundance and activity as a result of environmental change could have major impacts on soil fertility and ecosystem carbon sequestration in tropical forests. PMID:24372865

  20. Subsurface Intertidal Microbes: A Cryptic Source Of Organic Carbon For Beach Ecosystems

    NASA Technical Reports Server (NTRS)

    Rothschild, Lynn J.; Giver, Lorraine J.; Alvarez, Teresa (Technical Monitor)

    1994-01-01

    Some freshwater, marine or hotspring beaches have no visible source of primary production, yet beneath the surface is an interstitial photosynthetic microbial community. To assess the significance of this source of organic carbon, we measured in situ carbon fixation rates in an intertidal marine beach through a diurnal cycle. Gross fixation for a transect (99 x 1 m) perpendicular to the shore was approx. 4041 mg C fixed/ day, or approx. 41 mg C fixed/ sq m day. In contrast, an adjacent well-established cyanobacterial (Lyngbya) mat was approx. 12 x as productive (approx. 490 mg C fixed/sq m day). Thus, subsurface sand mats may be an overlooked, yet important, endogenous source of organic carbon for intertidal ecosystems, as well as a sink in the global carbon cycle.

  1. Impact of the 2012 US drought on ecosystem carbon and water fluxes (Invited)

    NASA Astrophysics Data System (ADS)

    Wolf, S.; Baldocchi, D. D.; Fisher, J. B.; Keenan, T. F.

    2013-12-01

    Drought severely impacts biosphere-atmosphere carbon and water fluxes of terrestrial ecosystems by reducing productivity, carbon uptake and water transport to the atmosphere. The 2012 US drought was among the most intense and widespread drought events in the US since the ';Dust Bowl' period in the 1930s. Drought conditions started developing during an exceptionally warm spring, intensified throughout the summer and were most severe in the Central US (Midwest), with devastating effects on agricultural production. Here we synthesize the impact of the 2012 drought on ecosystem carbon and water fluxes across the Contiguous United States using eddy covariance data from 30 AmeriFlux sites and remote sensing data from MODIS. We found widespread reductions in gross primary production and evapotranspiration of up to 50% in the Midwest during the summer months. Drought intensity and duration are directly linked to changes in ecosystem fluxes. As drought frequencies and intensities are predicted to increase in the future, we discuss the implications of our results regarding drought susceptibilities of different land-use types.

  2. Carbon and nitrogen gain during the growth of orchid seedlings in nature.

    PubMed

    Stöckel, Marcus; Těšitelová, Tamara; Jersáková, Jana; Bidartondo, Martin I; Gebauer, Gerhard

    2014-04-01

    For germination and establishment, orchids depend on carbon (C) and nutrients supplied by mycorrhizal fungi. As adults, the majority of orchids then appear to become autotrophic. To compare the proportional C and nitrogen (N) gain from fungi in mycoheterotrophic seedlings and in adults, here we examined in the field C and N stable isotope compositions in seedlings and adults of orchids associated with ectomycorrhizal and saprotrophic fungi. Using a new highly sensitive approach, we measured the isotope compositions of seedlings and adults of four orchid species belonging to different functional groups: fully and partially mycoheterotrophic orchids associated with narrow or broad sets of ectomycorrhizal fungi, and two adult putatively autotrophic orchids associated exclusively with saprotrophic fungi. Seedlings of orchids associated with ectomycorrhizal fungi were enriched in (13) C and (15) N similarly to fully mycoheterotrophic adults. Seedlings of saprotroph-associated orchids were also enriched in (13) C and (15) N, but unexpectedly their enrichment was significantly lower, making them hardly distinguishable from their respective adult stages and neighbouring autotrophic plants. We conclude that partial mycoheterotrophy among saprotroph-associated orchids cannot be identified unequivocally based on C and N isotope compositions alone. Thus, partial mycoheterotrophy may be much more widely distributed among orchids than hitherto assumed. PMID:24444001

  3. SIMULATED CARBON SINK RESPONSE OF SHORTGRASS STEPPE, TALLGRASS PRAIRIE AND FOREST ECOSYSTEMS TO RISING [CO2], TEMPERATURE AND NITROGEN INPUT

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The response of plant ecosystems to environmental change will determine whether the terrestrial biosphere will remain a substantial carbon sink or become a source during the next century. We use two ecosystem models, the Generic Decomposition And Yield model (G’DAY) and the daily time step version o...

  4. Elevated carbon dioxide alters impacts of precipitation pulses on ecosystem photosynthesis and respiration in a semi-arid grassland

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Predicting net carbon (C) balance under future global change scenarios requires a comprehensive understanding of photosynthetic (GPP) and ecosystem respiration (Re) responses to atmospheric CO2 concentration and water availability. We measured net ecosystem exchange of CO2 (NEE), GPP and Re prior to...

  5. The functional role of carbonate-cemented soil horizons in desert ecosystems: Spatial and temporal dynamics of plant water availability

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In water limited ecosystems, soil profile characteristics can control plant community composition and production through their effects on spatial and temporal patterns of plant available water. Little is known, however, about water availability in soil horizons cemented with carbonates (petrocalcic ...

  6. Control of Growth Efficiency in Young Plantation Loblolly Pine and Sweetgum through Irrigation and Fertigation Enhancement of Leaf Carbon Gain

    SciTech Connect

    L. Samuelson

    1999-07-07

    The overall objective of this study was to determine if growth efficiency of young plantation loblolly pine and sweetgum can be maintained by intensive forest management and whether increased carbon gain is the mechanism controlling growth efficiency response to resource augmentation. Key leaf physiological processes were examined over two growing seasons in response to irrigation, fertigation (irrigation with a fertilizer solution), and fertigation plus pest control (pine only). Although irrigation improved leaf net photosynthesis in pine and decreased stomatal sensitivity to vapor pressure deficit in sweetgum, no consistent physiological responses to fertigation were detected in either species. After 4 years of treatment, a 3-fold increase in woody net primary productivity was observed in both species in response to fertigation. Trees supplemented with fertigation and fertigation plus pest control exhibited the largest increases in growth and biomass. Furthermore, growth efficiency was maintained by fertigation and fertigation plus pest control, despite large increases in crown development and self-shading. Greater growth in response to intensive culture was facilitated by significant gains in leaf mass and whole tree carbon gain rather than detectable increases in leaf level processes. Growth efficiency was not maintained by significant increases in leaf level carbon gain but was possibly influenced by changes in carbon allocation to root versus shoot processes.

  7. The impact of intensive forest management on carbon stores in forest ecosystems

    SciTech Connect

    Krankina, O.N.; Harmon, M.E. . Dept. of Forest Science)

    1994-06-01

    The expansion of intensive management of forest resources for timber production with the human population growth may have a profound effect on the role forests play in the global carbon cycle. First, the transition from old-growth to intensively managed second-growth forest with short rotations entails major long-term ecosystems changes including the reduction of total woody biomass. Although the biomass of living trees can be restored within a relatively short period of time, dead wood biomass takes considerably longer to reach pre-harvest levels; therefore commonly used rotations are too short for the latter part of ecosystem to recover fully. As dead trees account for 14--18% of the total woody biomass stores in a natural forest, a considerable amount of carbon can be released if this material is not replaced. Second, economically efficient, intensive forest management systems that include commercial thinning and wood salvage can further reduce the total biomass loading of second-growth forests. Long-term study of live and dead wood in thinning trials in the Pacific Northwest and in northwestern Russia suggest that intensive practices can reduce total woody biomass averaged over rotation to 10--25% that found in a natural old-growth forest. Therefore intensive forest management practices may maximize the supply of raw materials, but they may also generate a major carbon flux into the atmosphere. This flux may be significant despite the fact the land-use type remains the same. Effect of intensive forest management practices should be included in future carbon budgets and in developing forest management strategies aimed at increasing carbon storage in forest ecosystems.

  8. Continuous In-situ Measurements of Carbonyl Sulfide to Constrain Ecosystem Carbon and Water Exchange

    NASA Astrophysics Data System (ADS)

    Rastogi, B.; Kim, Y.; Berkelhammer, M. B.; Noone, D. C.; Lai, C. T.; Hollinger, D. Y.; Bible, K.; Leen, J. B.; Gupta, M.; Still, C. J.

    2014-12-01

    Understanding the processes that control the terrestrial exchange of carbon and water are critical for examining the role of forested ecosystems in changing climates. A small but increasing number of studies have identified Carbonyl Sulfide (OCS) as a potential tracer for photosynthesis. OCS is hydrolyzed by an irreversible reaction in leaf mesophyll cells that is catalyzed by the enzyme, carbonic anhydrase. Leaf-level field and greenhouse studies indicate that OCS uptake is controlled by stomatal activity and that the ratio of OCS and CO2 uptake is reasonably constant. Existing studies on ecosystem OCS exchange have been based on laboratory measurements or short field campaigns and therefore little information on OCS exchange in a natural ecosystem over longer timescales is available. The objective of this study is to further assess the stability of OCS as a tracer for canopy photosynthesis in an active forested ecosystem and also to assess its utility for constraining transpiration, since both fluxes are mediated by canopy stomatal conductance. An off-axis integrated cavity output spectroscopy analyzer (Los Gatos Research Inc.) was deployed at the Wind River Experimental Forest in Washington (45.8205°N, 121.9519°W). Canopy air was sampled from three heights to measure vertical gradients of OCS within the canopy, and OCS exchange between the forest and the atmosphere. Here we take advantage of simultaneous measurements of the stable isotopologues of H2O and CO2 at corresponding heights as well as NEE (Net Ecosystem Exchange) from eddy covariance measurements to compare GPP (Gross Primary Production) and transpiration estimates from a variety of independent techniques. Our findings seek to allow assessment of the environmental and ecophysicological controls on evapotranspiration rates, which are projected to change in coming decades, and are otherwise poorly constrained.

  9. Climate change impacts on stream carbon export from coastal temperate rainforest ecosystems in Alaska (Invited)

    NASA Astrophysics Data System (ADS)

    Hood, E. W.

    2013-12-01

    Coastal temperate rainforests (CTR) in Alaska contain about 10% of the total carbon in the forests of the conterminous United States. CTR ecosystems span a large environmental gradient that ranges from icefields mantling the Coast Mountains to carbon-rich conifer forests along the coastal margin and within the islands of the Alexander Archipelago in the Gulf of Alaska. Riverine dissolved organic carbon (DOC) export from Alaskan CTR ecosystems, which can exceed 2 Tg C yr-1, is large relative to other northern ecosystems as a result of high rates of specific discharge (~2.5 m yr-1) and an abundance of organic soils found in peatlands and forested wetlands. Runoff from glaciers, which are rapidly thinning and retreating, has also been shown to an important contributor to land-to-ocean fluxes of DOC in this region. Downscaled regional climate models suggest that CTR ecosystems in Alaska will become warmer and wetter in coming decades, with uncertain effects on riverine organic matter (OM) export. Changes in watershed OM export are likely to be driven by changes in both hydrology and the availability of OM in terrestrial source pools. However, the impacts of these climate driven changes will vary with watershed landcover across the continuum from icefields to coastal temperate forests. Expected hydrological perturbations include changes in the timing and magnitude of streamflow associated with shifts in: 1) the extent and duration of seasonal snowcover and 2) the mass balance of glaciers and icefields in the Coast Mountains. The availability of OM for export along hydrologic flowpaths will likely be altered by increased soil temperatures and shifts in water table elevations during the summer/fall runoff season. This will be particularly true for organic carbon export from peatlands in which changes in temperature and oxygen availability can strongly impact rates of organic matter decomposition. This talk will explore how climate-driven changes in hydrology and

  10. Precipitation legacy effects on dryland ecosystem carbon fluxes: direction, magnitude and biogeochemical carryovers

    NASA Astrophysics Data System (ADS)

    Shen, W.; Jenerette, G. D.; Hui, D.; Scott, R. L.

    2015-07-01

    The precipitation legacy effect, defined as the impact of historical precipitation (PPT) on extant ecosystem dynamics, has been recognized as an important driver in shaping the temporal variability of dryland aboveground primary production (ANPP) and soil respiration. How the PPT legacy influences whole ecosystem-level carbon (C) fluxes has rarely been quantitatively assessed, particularly at longer temporal scales. We parameterized a process-based ecosystem model to a semiarid savanna ecosystem in southwestern US, calibrated and evaluated the model performance based on 7 years of eddy covariance measurements, and conducted two sets of simulation experiments to assess interdecadal and interannual scale PPT legacy effects over a 30 year simulation period. The results showed that decreasing the previous period/year PPT (dry legacy) always imposed positive impacts on net ecosystem production (NEP) whereas increasing the previous period/year PPT (wet legacy) had negative impacts on NEP. The simulated dry legacy impacts were mostly positive on gross ecosystem production (GEP) and negative on ecosystem respiration (Re) but the wet legacy impacts were mostly negative on GEP and positive on Re. Although the direction and magnitude of GEP and Re responses to the simulated dry and wet legacies were influenced by both the previous and current PPT conditions, the NEP responses were predominantly determined by the previous PPT characteristics including rainfall amount, seasonality and event size distribution. Larger PPT difference between periods/years resulted in larger legacy impacts, with dry legacies fostering more C sequestration and wet legacies more C release. By analyzing the resource pool (C, N, and H2O) responses to the simulated dry and wet legacies, we found that the carryover of soil N between periods/years was mainly responsible for the GEP responses while the carryovers of plant biomass, litter and soil organic matter were mainly responsible for the Re responses

  11. Nitrogen feedbacks increase future terrestrial ecosystem carbon uptake in an individual-based dynamic vegetation model

    NASA Astrophysics Data System (ADS)

    Wårlind, D.; Smith, B.; Hickler, T.; Arneth, A.

    2014-11-01

    Recently a considerable amount of effort has been put into quantifying how interactions of the carbon and nitrogen cycle affect future terrestrial carbon sinks. Dynamic vegetation models, representing the nitrogen cycle with varying degree of complexity, have shown diverging constraints of nitrogen dynamics on future carbon sequestration. In this study, we use LPJ-GUESS, a dynamic vegetation model employing a detailed individual- and patch-based representation of vegetation dynamics, to evaluate how population dynamics and resource competition between plant functional types, combined with nitrogen dynamics, have influenced the terrestrial carbon storage in the past and to investigate how terrestrial carbon and nitrogen dynamics might change in the future (1850 to 2100; one representative "business-as-usual" climate scenario). Single-factor model experiments of CO2 fertilisation and climate change show generally similar directions of the responses of C-N interactions, compared to the C-only version of the model as documented in previous studies using other global models. Under an RCP 8.5 scenario, nitrogen limitation suppresses potential CO2 fertilisation, reducing the cumulative net ecosystem carbon uptake between 1850 and 2100 by 61%, and soil warming-induced increase in nitrogen mineralisation reduces terrestrial carbon loss by 31%. When environmental changes are considered conjointly, carbon sequestration is limited by nitrogen dynamics up to the present. However, during the 21st century, nitrogen dynamics induce a net increase in carbon sequestration, resulting in an overall larger carbon uptake of 17% over the full period. This contrasts with previous results with other global models that have shown an 8 to 37% decrease in carbon uptake relative to modern baseline conditions. Implications for the plausibility of earlier projections of future terrestrial C dynamics based on C-only models are discussed.

  12. Carbon emissions from deforestation in the Brazilian Amazon region predicted from satellite data and ecosystem modeling

    NASA Astrophysics Data System (ADS)

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

    2009-03-01

    A simulation model based on satellite observations of monthly vegetation cover from the Moderate Resolution Imaging Spectroradiometer (MODIS) was used to estimate monthly carbon fluxes in terrestrial ecosystems of Brazilian Amazon and Cerrado regions over the period 2000-2002. The NASA-CASA (Carnegie Ames Stanford Approach) model estimates of annual forest production were used as the basis to generate a prediction for the standing pool of carbon in above-ground biomass (AGB; g C m-2) for forested areas of the Brazilian Amazon region. Plot-level measurements of the residence time of carbon in wood in Amazon forest from Malhi et al. (2006) were interpolated by inverse distance weighting algorithms and used with CASA to generate a new regional map of AGB. Data from the Brazilian PRODES (Estimativa do Desflorestamento da Amazônia) project were used to map deforested areas. Results show that net primary production (NPP) sinks for carbon are highest across the eastern and northern Amazon areas, whereas deforestation sources of CO2 flux from decomposition of residual woody debris are more rapid and less seasonal in the central Amazon than in the eastern and southern areas. Increased woody debris from past deforestation events was predicted to alter the net ecosystem carbon balance of the Amazon region to generate annual CO2 source fluxes at least two times higher than previously predicted by CASA modeling studies. Variations in climate, land cover, and forest burning were predicted to release carbon at rates of 0.5 to 1 Pg C yr-1 from the Brazilian Amazon. When direct carbon emissions from forest burning of between 0.2 and 0.6-1 in the Legal Amazon are overlooked in regional budgets, the year-to-year variations in this net biome flux may appear to be large, whereas our model results implies net biome fluxes had actually been relatively consistent from year to year during the period 2000-2002.

  13. Linking Rainfall Variability and Carbon Cycling in a Green Roof Ecosystem

    NASA Astrophysics Data System (ADS)

    Potts, D. L.; Warren, R. J., II; Ivancic, T. A.

    2015-12-01

    Whereas green roof hydrology is well-studied, these systems present a novel opportunity to examine plant-mediated linkages between rainfall and carbon cycling. For example, green roofs experience dramatic fluctuations in soil moisture because they have limited soil water holding capacity and high rates of evaporation. Stonecrop (Sedum spp.) is widely planted in green roofs and its traits reflect an overall strategy of water conservation. In addition to succulent leaves and a slow growth rate, several stonecrop species possess inducible CAM photosynthesis. We made continuous measurements of ecosystem CO2 exchange, soil temperature (T), and volumetric soil moisture (θ) using a chamber-based automated monitoring system installed on a 3-year old green roof located in Buffalo, New York. Concurrent measurements of net ecosystem CO2 exchange (NEE) and ecosystem respiration (Re) allowed us to estimate gross ecosystem CO2 exchange (GEE). We predicted that CAM photosynthesis by stonecrop would be induced by high T and low θ and would manifest at the ecosystem scale by a reductions in both reduced midday CO2 uptake associated with stomatal closure and nighttime net CO2 efflux as CAM-driven assimilation offset respiratory losses. Not surprisingly, increased T and decreased θ negatively influenced GEE while Re increased in response to increased T and θ. During a period of unusually hot, dry conditions the responses of GEE and Re were reflected in a decline in daytime NEE. However, this decline in NEE was not associated with a similar reduction in nighttime Re suggesting that these conditions were insufficient to induce CAM photosynthesis. Future ecohydrological investigations of green roofs may provide new insights into how rainfall variability interacts with plant traits, community diversity, and edaphic factors to shape ecosystem function.

  14. Response of tundra ecosystems to elevated atmospheric carbon dioxide. [Annual report

    SciTech Connect

    Oechel, W.C.; Grulke, N.E.

    1988-12-31

    Our past research shows that arctic tussock tundra responds to elevated atmospheric CO{sub 2} with marked increases in net ecosystem carbon flux and photosynthetic rates. However, at ambient temperatures and nutrient availabilities, homeostatic adjustments result in net ecosystem flux rates dropping to those found a contemporary CO{sub 2} levels within three years. Evidence for ecosystem-level acclimation in the first season of elevated CO{sub 2} exposure was found in 1987. Photosynthetic rates of Eriophorum vaginatum, the dominant species, adjusts to elevated CO{sub 2} within three weeks. Past research also indicates other changes potentially important to ecosystem structure and function. Elevated CO{sub 2} treatment apparently delays senescence and increases the period of positive photosynthetic activity. Recent results from the 1987 field season verify the results obtained in the 1983--1986 field seasons: Elevated CO{sub 2} resulted in increased ecosystem-level flux rates. Regressions fitted to the seasonal flux rates indicate an apparent 10 d extension of positive CO{sub 2} uptake reflecting a delay of the onset of plant dormancy. This delay in senescence could increase the frost sensitivity of the system. Major end points proposed for this research include the effects of elevated CO{sub 2} and the interaction of elevated atmospheric CO{sub 2} with elevated soil temperature and increased nutrient availability on: (1) Net ecosystem CO{sub 2} flux; (2) Net photosynthetic rates; (3) Patterns and resource controls on homeostatic adjustment in the above processes to elevated CO{sub 2}; (4) Plant-nutrient status, litter quality, and forage quality; (5) Soil-nutrient status; (6) Plant-growth pattern and shoot demography.

  15. Monitoring Ecosystem Carbon and Water Variations During a Severe Drought in the Southwest With AVIRIS and MODIS Sensor Data.

    NASA Astrophysics Data System (ADS)

    Kim, Y.; Huete, A. R.; Didan, K.; Cobb, N.; Koch, G.

    2004-12-01

    We investigated the spatial and temporal variations in vegetation biologic activity across a wide range of ecosystems (desert shrub to conifer forest) in northern Arizona with carbon and water indices derived from fine resolution AVIRIS data and moderate resolution MODIS observations. Leaf level and canopy level surface moisture indices were computed over the range of ecosystems and drought-induced mortality sites with hyperspectral AVIRIS data in the 1240nm and 2100nm water absorption regions. The land surface moisture indices were combined with the vegetation index, carbon measures to map spatial and temporal patterns of above-ground net productivity and analyze ecosystem sensitivity to water availability and precipitation. The coupled water and carbon indices were scaled up to MODIS data for spatial extension and time series analysis over the past 5 years. Land surface moisture and carbon patterns behaved differently across the range of ecosystems and within drought impact sites. Drought impacts were observed in all ecosystems, particularly in tree mortality areas and the grassland and desert areas. Our results show that combined water and carbon indices offer improved sensitivity to ecosystem health assessment and drought detection and analysis. Remotely-sensed land surface water indices combined with the carbon products yielded important information useful in the prediction of vegetation health response to climate change and human land cover modifications.

  16. Carbon sequestration through urban ecosystem services: A case study from Finland.

    PubMed

    Kuittinen, Matti; Moinel, Caroline; Adalgeirsdottir, Kristjana

    2016-09-01

    Plants and soil are natural regulators of atmospheric CO2. Whereas plants sequester atmospheric carbon, soils deposit it for decades. As cities become increasingly more densely built, the available land area for such ecosystem services may decrease. We studied seven different housing areas in the Finnish city of Espoo to ascertain the extent to which site efficiency affects to the ecosystem services if the full life-cycle GHG emissions of these areas are taken into account. The results show that the impact of CO2 uptake through carbon sinks in growing plants and the uptake of soil organic carbon vary greatly. Its share of all emissions varied from a marginal value of 1.2% to a more considerable value of 11.9%. The highest potential was calculated for a detached house located on a large site, while the weakest was calculated for compact apartment blocks. The study revealed that in order to quantify this potential more accurately, several knowledge gaps must first be addressed. These include impartial growth algorithms for Nordic wood species, missing accumulation factors for soil organic carbon in cold climates and statistical maintenance scenarios for gardens. PMID:27213698

  17. Epiphyte dynamics and carbon metabolism in a nutrient enriched Mediterranean seagrass ( Posidonia oceanica ) ecosystem

    NASA Astrophysics Data System (ADS)

    Apostolaki, Eugenia T.; Holmer, Marianne; Marbà, Núria; Karakassis, Ioannis

    2011-08-01

    The study aimed at examining the relationship between epiphyte dynamics and carbon metabolism in seagrass ecosystems under nutrient enrichment. Temporal variability of epiphytes and factors controlling their dynamics (i.e. environmental conditions, substratum availability, substratum stability and herbivore pressure) were assessed in a fish farm impacted and an unaffected Mediterranean seagrass ( Posidonia oceanica) meadow in the Aegean Sea (Greece). The factors controlling epiphyte dynamics responded differently to nutrient enrichment and partly interacted, rendering their cumulative effect on epiphyte load difficult to elucidate. Yet epiphytes accumulated on seagrass leaves near to the fish farm throughout the year, contributing 2 times more in above-ground biomass at cages than the control station. Reduction in substratum availability (i.e. decrease in leaf biomass) and increase in herbivore pressure affected epiphyte load, albeit their effects were not strong enough to counterbalance the effect of nutrient input from fish farm effluents. Moderate yet continuous nutrient input possibly stimulated epiphyte growth in excess of herbivory, shifting the control of epiphytes from top-down to bottom-up. Epiphyte accumulation affected carbon metabolism in the seagrass ecosystem by contributing to enhanced dissolved organic carbon (DOC) release, but seagrass loss was so acute that increased epiphyte cover could not counterbalance the decrease in community carbon production which was mainly driven by seagrass decline.

  18. Spatial Simulation of Land Use based on Terrestrial Ecosystem Carbon Storage in Coastal Jiangsu, China

    PubMed Central

    Chuai, Xiaowei; Huang, Xianjin; Wang, Wanjing; Wu, Changyan; Zhao, Rongqin

    2014-01-01

    This paper optimises projected land-use structure in 2020 with the goal of increasing terrestrial ecosystem carbon storage and simulates its spatial distribution using the CLUE-S model. We found the following: The total carbon densities of different land use types were woodland > water area > cultivated land > built-up land > grassland > shallows. Under the optimised land-use structure projected for 2020, coastal Jiangsu showed the potential to increase carbon storage, and our method was effective even when only considering vegetation carbon storage. The total area will increase by reclamation and the original shallows will be exploited, which will greatly increase carbon storage. For built-up land, rural land consolidation caused the second-largest carbon storage increase, which might contribute the most as the rural population will continue to decrease in the future, while the decrease of cultivated land will contribute the most to carbon loss. The area near the coastline has the greatest possibility for land-use change and is where land management should be especially strengthened. PMID:25011476

  19. The combination of different carbon sources enhances bacterial growth efficiency in aquatic ecosystems.

    PubMed

    Fonte, Ellen S; Amado, André M; Meirelles-Pereira, Frederico; Esteves, Francisco A; Rosado, Alexandre S; Farjalla, Vinicius F

    2013-11-01

    The dissolved organic carbon (DOC) pool is composed of several organic carbon compounds from different carbon sources. Each of these sources may support different bacterial growth rates, but few studies have specifically analyzed the effects of the combination of different carbon sources on bacterial metabolism. In this study, we evaluated the response of several metabolic parameters, including bacterial biomass production (BP), bacterial respiration (BR), bacterial growth efficiency (BGE), and bacterial community structure, on the presence of three DOC sources alone and in combination. We hypothesized that the mixture of different DOC sources would increase the efficiency of carbon use by bacteria (BGE). We established a full-factorial substitutive design (seven treatments) in which the effects of the number and identity of DOC sources on bacterial metabolism were evaluated. We calculated the expected metabolic rates of the combined DOC treatments based on the single-DOC treatments and observed a positive interaction on BP, a negative interaction on BR, and, consequently, a positive interaction on BGE for the combinations. The bacterial community composition appeared to have a minor impact on differences in bacterial metabolism among the treatments. Our data indicate that mixtures of DOC sources result in a more efficient biological use of carbon. This study provides strong evidence that the mixture of different DOC sources is a key factor affecting the role of bacteria in the carbon flux of aquatic ecosystems. PMID:23963223

  20. Carbon Exchange in the Northern High Latitude Terrestrial Ecosystems Over the Last Three Decades

    NASA Astrophysics Data System (ADS)

    Jain, Atul; El-Masri, Bassil; Barman, Rahul

    2013-04-01

    The dynamics of carbon fluxes in the permafrost region is likely to have tremendous impacts for the future global climate. Recently, several ecosystem and land surface models have demonstrated improved permafrost modeling capabilities by incorporating deep soil layers, organic soils, and parameterizing the effects of wind compaction and depth hoar formations, which influence high latitude soil biogeophysics. However, no global study has yet incorporated the combined effects of these biogeophysical improvements. Additionally, the primary focus has been on modeling biogeophysical fluxes rather than on how biogeochemical processes and feedbacks are impacted. In this study, we evaluate how biogeochemistry (carbon and nitrogen dynamics) responds to improved biogeophysics in the high latitudes. We employ a land surface model, the Integrated Science Assessment Model (ISAM), to model the fluxes of water, energy and carbon, as well as the change in active layer depths during the historical period. The ISAM represents fully prognostic carbon and nitrogen cycles, coupled with biogeophysics schemes. Additionally, biogeophysical improvements such as the inclusion of deep soils, organic soils, wind compaction and depth hoar formation effects, which are critical for high-latitude soil thermal dynamics, have been incorporated into the model. The performance of the model is evaluated using observations for active layer depths and carbon fluxes, together with recent estimates for total soil carbon amount in the permafrost region. The soil decomposition module in the ISAM was calibrated with field experiment data, which includes representation of nitrogen mineralization processes.The ISAM modeled carbon, nitrogen and energy fluxes were evaluated for several flux tower sites representative of the tundra and the boreal ecosystems as well as for the northern high latitude region. This is one of the first studies to explore the combined effects of improvements in biogeophysics, coupled

  1. An integrated modeling study of ocean circulation, the ocean carbon cycle, marine ecosystems, and climate change

    NASA Astrophysics Data System (ADS)

    Cao, Long

    The unifying theme of this study is to conduct an extensive exploration of various interactions between ocean circulation, the carbon cycle, marine ecosystems, and climate change using an earth system model of intermediate complexity, ISAM-2.5D (Integrated Science Assessment Model). First, through the simulation of radiocarbon (in terms of Delta14C) it is demonstrated that the inclusion of isopycnal diffusion and a parameterization of eddy-induced circulation in the ISAM-2.5D model yields the most realistic representation of ocean mixing and circulation. Secondly, I demonstrate the value of the simulation of multiple tracers, combined with a variety of observational data, in constraining the ISAM-2.5D model that has been constrained by the simulation of Delta14C. Through the simulation of ocean biogeochemical cycles and CFC-11 and the use of the updated observational data of bomb radiocarbon, I improve the Delta14C-constrained ISAM-2.5D model's performance in simulating ocean circulation and air-sea gas exchange, as well as its credibility in predicting oceanic carbon uptake. Third, I use the ISAM-2.5D model to assess the efficiency of direct carbon injection into the deep ocean with the influence of climate change. It is shown that the consideration of climate change enhances the retention time of injected carbon into the Atlantic Ocean as a result of weakened North Atlantic overturning circulation in a warming climate. However, the climatic effect is insignificant on the efficiency of carbon injection into the Pacific and Indian Oceans. Finally, I quantify that increased atmospheric CO2 concentrations would be mainly responsible for future ocean acidification, including lowering in ocean pH and sea water saturation state with respect to carbonate minerals. The consideration of climate change produces a second-order modification to projected ocean acidification. Therefore, in addition to its radiative effects on climate change, increased atmospheric CO2

  2. Contribution of natural variability to future terrestrial ecosystem carbon balance uncertainties

    NASA Astrophysics Data System (ADS)

    Ahlstroem, A.; Lindstroem, J.; Rummukainen, M.; Smith, B.; Uvo, C. B.

    2012-12-01

    A considerable part of the uncertainty surrounding the magnitude of a future climate change is the response of the terrestrial carbon cycle. One of the largest sources of this uncertainty is the heterogeneity of the predictions of future climate made by different climate models (general circulation models, GCMs). Not only do GCMs differ in their climate sensitivities and in regional distributions of changes in temperature, precipitation and radiation, they also differ markedly in simulated natural variability. To investigate the role of natural variability in the uncertainties induced by differences between climate models we forced the detailed individual based ecosystem model LPJ-GUESS with outputs from four CMIP3 climate models under three SRES CO2 concentration ([CO2]) pathways. Based on results from the ecosystem model, we parameterized a simple global carbon cycle model including only global temperature and [CO2] as the independent variables, scaled by parameters representing natural variability and regionality (α) and the land-to-global warming ratio (γ). Using singular value decomposition of simulated sea surface temperatures, a main driver of inter-annual variability in the climate system, we investigated the dominant patterns of variability and the resulting spatial carbon cycle patterns resulting from applying the four GCMs. We find that the uptake of carbon differs more between climate models than between different [CO2] pathways. Sampling the parameters of the simple carbon cycle model we create 60 "artificial" climate models. Applying the simplified model with these 60 parameterizations plus the original four GCMs under three [CO2] pathways (based on A2, A1B and B1 emission scenarios) resulted in a total of 192 simulations. We applied ANOVA to estimate how much of the variability in the simulated total carbon pool at year 2099 that can be explained by each factor, emission scenario, α and γ. The discrepancies in climate model natural variability

  3. How Argonne's Intense Pulsed Neutron Source came to life and gained its niche : the view from an ecosystem perspective.

    SciTech Connect

    Westfall, C.; Office of The Director

    2008-02-25

    of money to produce science and technology at multipurpose laboratories like Argonne. For example, in the mid-1990s, about the time the IPNS's fortunes were secured, DOE spent more than $6 billion a year to fund nine such facilities, with Argonne's share totaling $500 million. And an important justification for funding these expensive laboratories is that they operate expensive but powerful scientific tools like the IPNS, generally considered too large to be built and managed by universities. Clearly, 'life and death' decision making has a lot to tell us about how the considerable U.S. federal investment in science and technology at national laboratories is actually transacted and, indeed, how a path is cleared or blocked for good science to be produced. Because forces within Argonne, DOE, and the materials science community obviously dictated the changing fortunes of the IPNS, it makes sense to probe the interactions binding these three environments for an understanding of how the IPNS was threatened and how it survived. In other words, sorting out what happened requires analyzing the system that includes all three environments. In an attempt to find a better way to understand its twists and turns, I will view the life-and-death IPNS story through the lens of an ecological metaphor. Employing the ideas and terms that ecologists use to describe what happens in a system of shared resources, that is, an ecosystem, I will describe the IPNS as an organism that vied with competitors for resources to find a niche in the interrelated environments of Argonne, DOE, and the materials science community. I will start with an explanation of the Argonne 'ecosystem' before the advent of the IPNS and then describe how the project struggled to emerge in the 1970s, how it scratched its way to a fragile niche in the early 1980s, and how it adapted and matured through the turn of the 21st century. The paper will conclude with a summary of what the ecosystem perspective shows about the

  4. Analysis of trophic networks and carbon flows in south-eastern Baltic coastal ecosystems

    NASA Astrophysics Data System (ADS)

    Tomczak, Maciej T.; Müller-Karulis, Bärbel; Järv, Leili; Kotta, Jonne; Martin, Georg; Minde, Atis; Põllumäe, Arno; Razinkovas, Arturas; Strake, Solvita; Bucas, Martynas; Blenckner, Thorsten

    2009-04-01

    Carbon flows in five south-eastern Baltic coastal ecosystems (Puck Bay, Curonian Lagoon, Lithuanian coast, Gulf of Riga coast and Pärnu Bay) were compared on the basis of ECOPATH models using 12 common functional groups. The studied systems ranged from the hypertrophic Curonian Lagoon to the mesotrophic Gulf of Riga coast. Interestingly, we found that macrophytes were not consumed by grazers, but rather channelled into the detritus food chain. In all ecosystems fisheries had far reaching impacts on their target species and on the food-web in general. In particular, benthic food-webs were partly affected by indirect fisheries effects. For example, fisheries tend to change the biomass of piscivorous fish, causing a cascading effect on benthivorous fish and macrozoobenthos. These cascades are ecosystem specific and need to be considered when using benthic invertebrates as productivity and eutrophication indicators. Odum’s maturity attributes allowed a ranking of costal ecosystems according to their maturity. Namely, the community development decreased in the following order: Pärnu Bay > Gulf of Riga coast > Lithuanian coast > Puck Bay > Curonian Lagoon.

  5. Siberian tundra ecosystem vegetation and carbon stocks four decades after wildfire

    NASA Astrophysics Data System (ADS)

    Loranty, Michael M.; Natali, Susan M.; Berner, Logan T.; Goetz, Scott J.; Holmes, Robert M.; Davydov, Sergei P.; Zimov, Nikita S.; Zimov, Sergey A.

    2014-11-01

    Tundra ecosystem fire regimes are intensifying with important implications for regional and global carbon (C) and energy dynamics. Although a substantial portion of the tundra biome is located in Russia, the vast majority of accessible studies describe North American tundra fires. Here we use field observations and high-resolution satellite remote sensing observations to describe the effects of wildfire on ecosystem C pools and vegetation communities four decades after fire for a tundra ecosystem in northeastern Siberia. Our analyses reveal no differences between soil physical properties and C pools in burned and unburned tundra, which we attribute to low combustion of organic soil associated with low-severity fire. Field and remote sensing data show no differences in aboveground C pools and vegetation communities indicating recovery to prefire conditions. These results are comparable to observations of ecosystem recovery in North American tundra. An assessment of literature data indicate that the average annual area burned in Russian tundra is an order of magnitude larger than that of Alaskan tundra, highlighting a crucial need to assess Russian tundra fire regimes in order to understand the current and future role of the biome wide fire regime in regional and global C and energy dynamics.

  6. Understanding ecosystems' sub-daily water and carbon flux changes during dry-down events

    NASA Astrophysics Data System (ADS)

    Nelson, Jacob; Jung, Martin; Carvalhais, Nuno; Migliavacca, Mirco; Reichstein, Markus

    2016-04-01

    Sub-daily water and carbon flux patterns give important and sometimes overlooked information about ecosystem processes and land-atmosphere feedbacks. While models often perform well down to daily timescales, they can be uncertain with respect to the diurnal courses, especially during dry-down events where the fraction of T to ET is shifting. We analyzed events from multiple locations for unique pattern changes that were robust across sites. Of particular interest were the divergence of water and carbon fluxes during high radiation periods, which indicates changes in water use efficiency as drought conditions intensified. The validity of attributing the signatures to ecosystem transitions such as changes in phenology, switches in soil evaporation vs transpiration dominance, and physiological stress were evaluated by comparing to site specific sap flow, soil moisture, and remote sensing data. Going forward, these findings can be used to further understand ecosystem physiology under drought conditions, and can also be used to partition of water fluxes and better constrain future models.

  7. Integrating remotely sensed land cover observations and a biogeochemical model for estimating forest ecosystem carbon dynamics

    USGS Publications Warehouse

    Liu, J.; Liu, S.; Loveland, T.R.; Tieszen, L.L.

    2008-01-01

    Land cover change is one of the key driving forces for ecosystem carbon (C) dynamics. We present an approach for using sequential remotely sensed land cover observations and a biogeochemical model to estimate contemporary and future ecosystem carbon trends. We applied the General Ensemble Biogeochemical Modelling System (GEMS) for the Laurentian Plains and Hills ecoregion in the northeastern United States for the period of 1975-2025. The land cover changes, especially forest stand-replacing events, were detected on 30 randomly located 10-km by 10-km sample blocks, and were assimilated by GEMS for biogeochemical simulations. In GEMS, each unique combination of major controlling variables (including land cover change history) forms a geo-referenced simulation unit. For a forest simulation unit, a Monte Carlo process is used to determine forest type, forest age, forest biomass, and soil C, based on the Forest Inventory and Analysis (FIA) data and the U.S. General Soil Map (STATSGO) data. Ensemble simulations are performed for each simulation unit to incorporate input data uncertainty. Results show that on average forests of the Laurentian Plains and Hills ecoregion have been sequestrating 4.2 Tg C (1 teragram = 1012 gram) per year, including 1.9 Tg C removed from the ecosystem as the consequences of land cover change. ?? 2008 Elsevier B.V.

  8. Evaluating two experimental approaches for measuring ecosystem carbon oxidation state and oxidative ratio

    NASA Astrophysics Data System (ADS)

    Masiello, C. A.; Gallagher, M. E.; Randerson, J. T.; Deco, R. M.; Chadwick, O. A.

    2008-09-01

    Degree of oxidation of organic carbon (Cox) is a fundamental property of the carbon cycle, reflecting the synthesis and decomposition of natural organic matter. Cox is also related to ecosystem oxidative ratio (OR), the molar ratio of O2 to CO2 fluxes associated with net ecosystem exchange (NEE). Here we compare two methods for measuring Cox and OR: (1) %C, %H, %N, and %O elemental analysis, and (2) heat of combustion (ΔHc) measured by means of bomb calorimetry coupled with %C elemental analysis (hereafter referred to as calorimetry). Compared with %C, %N, %H, and %O elemental analysis, calorimetry generates Cox and OR data more rapidly and cheaply. However, calorimetric measurements yield less accurate Cox and OR data. We additionally report Cox and OR data for a pair of biomass standards and a suite of biomass samples. The OR values we measured in these samples were less variable than OR data reported in the literature (generated by simultaneous measurement of ecosystem O2 and CO2 gas mixing ratios). Our biomass OR values had a mean of 1.03 and range of 0.99-1.06. These estimates are lower than the OR value of 1.10 that is often used to partition uptake of fossil fuel CO2 between the ocean and the terrestrial biosphere.

  9. Ecosystem scale carbon dioxide balance of two grasslands in Hungary under different weather conditions.

    PubMed

    Pintér, Krisztina; Balogh, J; Nagy, Z

    2010-01-01

    The carbon balance of the sandy pasture (Bugac) and the mountain meadow (Mátra) varied between -171 and 96 gC m(-2) year-1, and -194 and 14 gC m(-2) year(-1), respectively, during the study period (2003-2009). Large part of interannual variability of net ecosystem exchange (NEE) was explained by the variation of the annual sum of precipitation in the sandy grassland ecosystem, while this relationship was weaker in the case of the mountain meadow on heavy clay soil. These different responses are largely explained by soil texture characteristics leading to differences in soil water contents available to plants at the two grasslands. The grassland on heavy clay soil was more sensitive to temporal distribution of rainfall for the same reason. The mountain meadow therefore seems to be more vulnerable to droughts, while the sandy grassland is better adapted to water shortage. The precipitation threshold (annual sum), below which the grassland turns into source of carbon dioxide on annual basis, is only 50-80 mm higher than the 10 years average precipitation sum. In extremely dry years (2003, 2007 and 2009), even the sandy grassland ecosystem was not stable enough to maintain its sink character. PMID:21565771

  10. Spatial and Temporal Patterns of Soil Organic Carbon in Mangrove Forest Ecosystems (Invited)

    NASA Astrophysics Data System (ADS)

    McKee, K. L.

    2010-12-01

    Wetlands are recognized as potentially important carbon sinks, but few studies have focused on tropical and sub-tropical systems that accumulate organic carbon. Soil organic carbon (SOC) density was analyzed in multiple mangrove forests, representing 30 geographic locations and six forest types (total of 230 study plots overall). SOC density varied from 0.002 to 0.1 g cm-3, with an overall average of 0.019 and 0.058 g cm-3 in mineral and organic soils, respectively. Sites spanned a latitudinal range from 37° S to 29° N, and carbon density was correlated with average annual temperature. However, high variation in SOC density within latitude indicated additional influences. At a regional scale, SOC density varied with forest type and generally increased with hydrologic energy. At a site in Panama, SOC density varied spatially with soil pore space, which influenced bulk density and soil temperature—indicating an influence of compaction and/or degree of decomposition. Carbon sequestration rates estimated from surface accretion of organic C were similar in organic (216 g C m-2 yr-1) and mineral (145 g C m-2 yr-1) soil types, but varied across geographic locations (41 to 591 g C m-2 yr-1). Subsurface inputs of carbon, which were estimated using measured rates of root matter accumulation and root carbon content, averaged 121 g m-2 yr-1, but exceeded 400 g m-2 yr-1 at several sites. Depths of mangrove peat varied across sites from < 1 m to over 10 m, indicating the potentially large carbon stores that can develop under certain conditions. Rates of carbon accretion at a site in Belize have varied from 90 to 300 g C m-2 yr-1 over 8000 yr. These patterns indicate spatial and temporal variability in SOC and suggest multiple controls on rates of carbon accumulation in mangrove ecosystems.

  11. Ecosystem Function in Amazon Floodplain Wetlands: Climate Variability, Landscape Dynamics and Carbon Biogeochemistry.

    NASA Astrophysics Data System (ADS)

    Silva, T. S. F.; Melack, J. M.; Sousa, R. N. D.; Ferreira-Ferreira, J.; Streher, A. S.; Fragal, E. H.; Furtado, L. F.; Resende, A. F. D.; Luize, B. G.; Rudorff, C.; Queiroz, H. L.; Schongart, J.; Novo, E. M.

    2015-12-01

    Wetlands comprise 14% of the Amazon basin, and are a major component of the hydrological and biogeochemical cycles. Most of these areas correspond to floodplain ecosystems along the Amazon River and its major tributaries, hosting unique vegetation types that are strongly controlled by annual hydrological fluctuations. The combination of strong environmental filtering and active fluvial dynamics results in a highly heterogeneous landscape, and in physiological linkages between climate variability and ecosystem processes. We will show several years of results obtained within the framework of the LBA program, discussing the interplay between hydroclimatic variability, landscape dynamics, ecosystem functioning and carbon biogeochemistry in the Amazon floodplains. Using optical and microwave remote sensing, we assessed the distribution of major vegetation types and flooding regimes at several locations across the floodplain. Strong variability in vegetation distribution can be observed, with high and low várzea forests ranging from 30% and 34%, respectively, at the upper Solimões River, to 6% and 25% at the lower Solimões, while non-forested habitats and lakes increase from a percent cover of 8% and 10% to 28% and 27%, respectively. Strong variability in local flood regimes was also determined for each vegetation type, revealing a gradient of habitats within each floodplain. As tree growth, diversity and phenology are affected by flood duration, we expect local conditions to strongly impact carbon stocks and cycling at the landscape scale. Fluvial processes also disturb forest patches, ensuring a mixture of age distributions in the landscape, with varying species composition, carbon stocks, and carbon uptake rates. Herbaceous vegetation growth responds very rapidly to changes in hydrological conditions, and modeling based on microwave imagery and in situ observations showed expected changes of up to 50% in annual net primary production between regular and extreme

  12. Carbon-sequestration and ecosystem services in the boreal ecoregion of Alaska

    NASA Astrophysics Data System (ADS)

    Wang, B.; Manies, K.; Labay, K.; Johnson, W. N.; Harden, J. W.

    2011-12-01

    Managing public lands for carbon (C) sequestration is increasingly discussed as a component of national carbon policies. However, management of public land to facilitate carbon sequestration must be considered in the context of other management mandates and the effects on other ecosystem services. Of the United States Fish and Wildlife Service's (USFWS) National Wildlife Refuge lands in Alaska, about 35% are in the boreal ecoregion; primarily in the Intermountain and the Alaska Range Transition ecoregions. These refuges were established to conserve wildlife habitat, fulfill treaty obligations, provide for continued subsistence uses, and ensure necessary water quality and quantity. One of the major factors in determining ecosystem distribution in the boreal ecoregion is disturbance. Fire is the dominant disturbance for Alaska's boreal region. Most USFWS refuge lands are managed with "limited" suppression, where fires burn naturally and are monitored to assure the protection of human life, property, and site specific values (such as historical or religious). However, there is increasing interest in biomass harvest and combustion for local energy production. Harvest and fire can have differing effects on both the spatial and temporal aspects of carbon storage. The current biomass harvest for energy production proposals are considered to be C neutral because they focus on "hazardous" biomass which would burn naturally or in a prescribed burn. The goal of this effort is to explore the relation between C storage and other public land management priorities, as well as, to explore how disturbance type (fire and harvest) affect C storage and boreal ecosystem distribution in the context of wildlife habitat and subsistence use management priorities. We present a conceptual model that defines the linkages among these management priorities, a data gap analysis, and scenarios to be evaluated.

  13. Variability in the Carbon Storage of Seagrass Habitats and Its Implications for Global Estimates of Blue Carbon Ecosystem Service

    PubMed Central

    Lavery, Paul S.; Mateo, Miguel-Ángel; Serrano, Oscar; Rozaimi, Mohammad

    2013-01-01

    The recent focus on carbon trading has intensified interest in ‘Blue Carbon’–carbon sequestered by coastal vegetated ecosystems, particularly seagrasses. Most information on seagrass carbon storage is derived from studies of a single species, Posidonia oceanica, from the Mediterranean Sea. We surveyed 17 Australian seagrass habitats to assess the variability in their sedimentary organic carbon (Corg) stocks. The habitats encompassed 10 species, in mono-specific or mixed meadows, depositional to exposed habitats and temperate to tropical habitats. There was an 18-fold difference in the Corg stock (1.09–20.14 mg Corg cm−3 for a temperate Posidonia sinuosa and a temperate, estuarine P. australis meadow, respectively). Integrated over the top 25 cm of sediment, this equated to an areal stock of 262–4833 g Corg m−2. For some species, there was an effect of water depth on the Corg stocks, with greater stocks in deeper sites; no differences were found among sub-tidal and inter-tidal habitats. The estimated carbon storage in Australian seagrass ecosystems, taking into account inter-habitat variability, was 155 Mt. At a 2014–15 fixed carbon price of A$25.40 t−1 and an estimated market price of $35 t−1 in 2020, the Corg stock in the top 25 cm of seagrass habitats has a potential value of $AUD 3.9–5.4 bill. The estimates of annual Corg accumulation by Australian seagrasses ranged from 0.093 to 6.15 Mt, with a most probable estimate of 0.93 Mt y−1 (10.1 t. km−2 y−1). These estimates, while large, were one-third of those that would be calculated if inter-habitat variability in carbon stocks were not taken into account. We conclude that there is an urgent need for more information on the variability in seagrass carbon stock and accumulation rates, and the factors driving this variability, in order to improve global estimates of seagrass Blue Carbon storage. PMID:24040052

  14. Effects of Elevated CO2 and Nitrogen Deposition on Ecosystem Carbon Fluxes on the Sanjiang Plain Wetland in Northeast China

    PubMed Central

    Wang, Jianbo; Zhu, Tingcheng; Ni, Hongwei; Zhong, Haixiu; Fu, Xiaoling; Wang, Jifeng

    2013-01-01

    Background Increasing atmospheric CO2 and nitrogen (N) deposition across the globe may affect ecosystem CO2 exchanges and ecosystem carbon cycles. Additionally, it remains unknown how increased N deposition and N addition will alter the effects of elevated CO2 on wetland ecosystem carbon fluxes. Methodology/Principal Findings Beginning in 2010, a paired, nested manipulative experimental design was used in a temperate wetland of northeastern China. The primary factor was elevated CO2, accomplished using Open Top Chambers, and N supplied as NH4NO3 was the secondary factor. Gross primary productivity (GPP) was higher than ecosystem respiration (ER), leading to net carbon uptake (measured by net ecosystem CO2 exchange, or NEE) in all four treatments over the growing season. However, their magnitude had interannual variations, which coincided with air temperature in the early growing season, with the soil temperature and with the vegetation cover. Elevated CO2 significantly enhanced GPP and ER but overall reduced NEE because the stimulation caused by the elevated CO2 had a greater impact on ER than on GPP. The addition of N stimulated ecosystem C fluxes in both years and ameliorated the negative impact of elevated CO2 on NEE. Conclusion/Significance In this ecosystem, future elevated CO2 may favor carbon sequestration when coupled with increasing nitrogen deposition. PMID:23818943

  15. Carbon Isotopic Studies of Assimilated and Ecosystem Respired CO2 in a Southeastern Pine Forest. Final Report and Conference Proceedings

    SciTech Connect

    Conte, Maureen H

    2008-04-10

    Carbon dioxide is the major “greenhouse” gas responsible for global warming. Southeastern pine forests appear to be among the largest terrestrial sinks of carbon dioxide in the US. This collaborative study specifically addressed the isotopic signatures of the large fluxes of carbon taken up by photosynthesis and given off by respiration in this ecosystem. By measuring these isotopic signatures at the ecosystem level, we have provided data that will help to more accurately quantify the magnitude of carbon fluxes on the regional scale and how these fluxes vary in response to climatic parameters such as rainfall and air temperature. The focus of the MBL subcontract was to evaluate how processes operating at the physiological and ecosystem scales affects the resultant isotopic signature of plant waxes that are emitted as aerosols into the convective boundary layer. These wax aerosols provide a large-spatial scale integrative signal of isotopic discrimination of atmospheric carbon dioxide by terrestrial photosynthesis (Conte and Weber 2002). The ecosystem studies have greatly expanded of knowledge of wax biosynthetic controls on their isootpic signature The wax aerosol data products produced under this grant are directly applicable as input for global carbon modeling studies that use variations in the concentration and carbon isotopic composition of atmospheric carbon dioxide to quantify the magnitude and spatial and temporal patterns of carbon uptake on the global scale.

  16. Historical and projected carbon balance of mature black spruce ecosystems across north america: The role of carbon-nitrogen interactions

    USGS Publications Warehouse

    Clein, J.S.; McGuire, A.D.; Zhang, X.; Kicklighter, D.W.; Melillo, J.M.; Wofsy, S.C.; Jarvis, P.G.; Massheder, J.M.

    2002-01-01

    The role of carbon (C) and nitrogen (N) interactions on sequestration of atmospheric CO2 in black spruce ecosystems across North America was evaluated with the Terrestrial Ecosystem Model (TEM) by applying parameterizations of the model in which C-N dynamics were either coupled or uncoupled. First, the performance of the parameterizations, which were developed for the dynamics of black spruce ecosystems at the Bonanza Creek Long-Term Ecological Research site in Alaska, were evaluated by simulating C dynamics at eddy correlation tower sites in the Boreal Ecosystem Atmosphere Study (BOREAS) for black spruce ecosystems in the northern study area (northern site) and the southern study area (southern site) with local climate data. We compared simulated monthly growing season (May to September) estimates of gross primary production (GPP), total ecosystem respiration (RESP), and net ecosystem production (NEP) from 1994 to 1997 to available field-based estimates at both sites. At the northern site, monthly growing season estimates of GPP and RESP for the coupled and uncoupled simulations were highly correlated with the field-based estimates (coupled: R2= 0.77, 0.88 for GPP and RESP; uncoupled: R2 = 0.67, 0.92 for GPP and RESP). Although the simulated seasonal pattern of NEP generally matched the field-based data, the correlations between field-based and simulated monthly growing season NEP were lower (R2 = 0.40, 0.00 for coupled and uncoupled simulations, respectively) in comparison to the correlations between field-based and simulated GPP and RESP. The annual NEP simulated by the coupled parameterization fell within the uncertainty of field-based estimates in two of three years. On the other hand, annual NEP simulated by the uncoupled parameterization only fell within the field-based uncertainty in one of three years. At the southern site, simulated NEP generally matched field-based NEP estimates, and the correlation between monthly growing season field-based and

  17. Effects of Nitrogen Deposition on Carbon Sequestration in China as Simulated by Process-Based Ecosystem Models

    NASA Astrophysics Data System (ADS)

    Lu, C.; Tian, H.; Liu, M.; Zhang, C.; Ren, W.; Chen, G.; Xu, X.; Pan, S.; Kicklighter, D.; Melillo, J.; Mu, Q.; Running, S.; Zhao, M.

    2008-12-01

    During the past decades, nitrogen deposition in China has been substantially increased, with mean values higher than those in the United States and Europe. The elevated nitrogen input, as important part of global changes, has greatly altered ecosystem structure and functioning, and thus exerted significant impacts on carbon cycling. In this study, three process-based ecosystem models (BIOME-BGC, DLEM and TEM) are used to explore the effects of increased nitrogen deposition and its combination with other environmental factors on C dynamic of China's terrestrial ecosystems. To illustrate the interactive effects of N deposition with ecosystem components, our simulations also consider multiple changes in climate, CO2, O3 concentration and land use & land cover (LULC) patterns. The model results indicate that raised nitrogen deposition level has enhanced net primary productivity and carbon storage in China during the year 1961 to 2005. Over the past 45 years, nitrogen amendment in China plays a vital role to accumulate carbon into ecosystems, considerably offsetting C release through climatic extremes, LULC changes and increased O3 concentration. It is proved that N deposition and its interaction with other driving forces accelerate carbon sequestration as the greatest contributor, although there apparently exist large uncertainties due to model assumptions and reliability of input dataset. Model inter-comparisons also reveal that N amendment imposes greater impacts on vegetation carbon pool than that on soil carbon pool. Among the models, the net effect of elevated nitrogen deposition on annual NPP ranges from 0.1 to 0.5 Pg C/yr in China from the year 1961 to 2005, while total carbon storage of terrestrial ecosystems has been enhanced by an average of about 5 Pg C in the same period. Key words: nitrogen deposition, carbon sequestration, China, process-based ecosystem models, model inter- comparison

  18. Chamber and Diffusive Based Carbon Flux Measurements in an Alaskan Arctic Ecosystem

    NASA Astrophysics Data System (ADS)

    Wilkman, E.; Oechel, W. C.; Zona, D.

    2013-12-01

    Eric Wilkman, Walter Oechel, Donatella Zona Comprising an area of more than 7 x 106 km2 and containing over 11% of the world's organic matter pool, Arctic terrestrial ecosystems are vitally important components of the global carbon cycle, yet their structure and functioning are sensitive to subtle changes in climate and many of these functional changes can have large effects on the atmosphere and future climate regimes (Callaghan & Maxwell 1995, Chapin et al. 2002). Historically these northern ecosystems have acted as strong C sinks, sequestering large stores of atmospheric C due to photosynthetic dominance in the short summer season and low rates of decomposition throughout the rest of the year as a consequence of cold, nutrient poor, and generally water-logged conditions. Currently, much of this previously stored carbon is at risk of loss to the atmosphere due to accelerated soil organic matter decomposition in warmer future climates (Grogan & Chapin 2000). Although there have been numerous studies on Arctic carbon dynamics, much of the previous soil flux work has been done at limited time intervals, due to both the harshness of the environment and labor and time constraints. Therefore, in June of 2013 an Ultraportable Greenhouse Gas Analyzer (UGGA - Los Gatos Research Inc.) was deployed in concert with the LI-8100A Automated Soil Flux System (LI-COR Biosciences) in Barrow, AK to gather high temporal frequency soil CO2 and CH4 fluxes from a wet sedge tundra ecosystem. An additional UGGA in combination with diffusive probes, installed in the same location, provides year-round soil and snow CO2 and CH4 concentrations. When used in combination with the recently purchased AlphaGUARD portable radon monitor (Saphymo GmbH), continuous soil and snow diffusivities and fluxes of CO2 and CH4 can be calculated (Lehmann & Lehmann 2000). Of particular note, measuring soil gas concentration over a diffusive gradient in this way allows one to separate both net production and

  19. Nitrogen controls on ecosystem carbon sequestration: A model implementation and application to Saskatchewan, Canada

    USGS Publications Warehouse

    Liu, J.; Price, D.T.; Chen, J.M.

    2005-01-01

    A plant-soil nitrogen (N) cycling model was developed and incorporated into the Integrated BIosphere Simulator (IBIS) of Foley et al. [Foley, J.A., Prentice, I.C., Ramankutty, N., Levis, S., Pollard, D., Sitch, S., Haxeltine, A., 1996. An integrated biosphere model of land surface process, terrestrial carbon balance and vegetation dynamics. Global Biogeochem. Cycles 10, 603-628]. In the N-model, soil mineral N regulates ecosystem carbon (C) fluxes and ecosystem C:N ratios. Net primary productivity (NPP) is controlled by feedbacks from both leaf C:N and soil mineral N. Leaf C:N determines the foliar and canopy photosynthesis rates, while soil mineral N determines the N availability for plant growth and the efficiency of biomass construction. Nitrogen controls on the decomposition of soil organic matter (SOM) are implemented through N immobilization and mineralization separately. The model allows greater SOM mineralization at lower mineral N, and conversely, allows greater N immobilization at higher mineral N. The model's seasonal and inter-annual behaviours are demonstrated. A regional simulation for Saskatchewan, Canada, was performed for the period 1851-2000 at a 10 km x 10 km resolution. Simulated NPP was compared with high-resolution (1 km x 1 km) NPP estimated from remote sensing data using the boreal ecosystem productivity simulator (BEPS) [Liu, J., Chen, J.M., Cihlar, J., Park, W.M., 1997. A process-based boreal ecosystem productivity simulator using remote sensing inputs. Remote Sens. Environ. 44, 81-87]. The agreement between IBIS and BEPS, particularly in NPP spatial variation, was considerably improved when the N controls were introduced into IBIS. ?? 2005 Elsevier B.V. All rights reserved.

  20. A coupled carbon and plant hydraulic model to predict ecosystem carbon and water flux responses to disturbance and environmental change

    NASA Astrophysics Data System (ADS)

    Mackay, D. S.; Ewers, B. E.; Roberts, D. E.; McDowell, N. G.; Pendall, E.; Frank, J. M.; Reed, D. E.; Massman, W. J.; Mitra, B.

    2011-12-01

    Changing climate drivers including temperature, humidity, precipitation, and carbon dioxide (CO2) concentrations directly control land surface exchanges of CO2 and water. In a profound way these responses are modulated by disturbances that are driven by or exacerbated by climate change. Predicting these changes is challenging given that the feedbacks between environmental controls, disturbances, and fluxes are complex. Flux data in areas of bark beetle outbreaks in the western U.S.A. show differential declines in carbon and water flux in response to the occlusion of xylem by associated fungi. For example, bark beetle infestation at the GLEES AmeriFlux site manifested in a decline in summer water use efficiency to 60% in the year after peak infestation compared to previous years, and no recovery of carbon uptake following a period of high vapor pressure deficit. This points to complex feedbacks between disturbance and differential ecosystem reaction and relaxation responses. Theory based on plant hydraulics and extending to include links to carbon storage and exhaustion has potential for explaining these dynamics with simple, yet rigorous models. In this spirit we developed a coupled model that combines an existing model of canopy water and carbon flow, TREES [e.g., Loranty et al., 2010], with the Sperry et al., [1998] plant hydraulic model. The new model simultaneously solves carbon uptake and losses along with plant hydraulics, and allows for testing specific hypotheses on feedbacks between xylem dysfunction, stomatal and non-stomatal controls on photosynthesis and carbon allocation, and autotrophic and heterotrophic respiration. These are constrained through gas exchange, root vulnerability to cavitation, sap flux, and eddy covariance data in a novel model complexity-testing framework. Our analysis focuses on an ecosystem gradient spanning sagebrush to subalpine forests. Our modeling results support hypotheses on feedbacks between hydraulic dysfunction and 1) non

  1. Carbon Biogeochemistry: A Stable Isotope Approach to Trophic Dynamics in an Indian Coastal Ecosystem

    NASA Astrophysics Data System (ADS)

    Mathukumalli, B.; Alagappan, R.

    2005-12-01

    Stable isotope(δ13C & δ15N) approach was applied to understand carbon biogeochemistry and trophic dynamics in an Indian coastal mangrove wetland. The δ13C and δ15N values of potential nutrient sources (mangrove plant leaves, lichen, sediment and suspended material) and in seven species of consumers (invertebrates) were measured. The value of δ13C and δ15N isotopes of different potential nutrient sources and the consumers determine the sources of nutrients for the invertebrate consumer community of the mangrove. There is a significant variation in the stable carbon in the nutrient sources; however, δ15N signatures were not significantly different among the different potential nutrient sources. Organic matter in the sediments under the mangrove vegetation was characterized by relatively negatively fractionated and moderately high C:N ratios, indicating that mangrove derived organic matter was the principal diet source for the invertebrate consumer communities in the mangrove ecosystem. Invertebrates in the mangrove showed a wide range of δ13C signatures and are enriched relative to the mangrove leaf stable isotope values. Micro-environmental differences certainly drive the variability in the nutrient sources and consumable nature among the different regions of the ecosystem. Therefore, further research is needed to determine whether carbon assimilation is different from one zone to another.

  2. Dynamical prediction of terrestrial ecosystems and the global carbon cycle: A 25-year hindcast experiment

    NASA Astrophysics Data System (ADS)

    Zeng, Ning; Yoon, Jin-Ho; Vintzileos, Augustin; Collatz, G. James; Kalnay, Eugenia; Mariotti, Annarita; Kumar, Arun; Busalacchi, Antonio; Lord, Stephen

    2008-12-01

    Using a 25-year hindcast experiment, we explore the possibility of seasonal-interannual prediction of terrestrial ecosystems and the global carbon cycle. This has been achieved using a prototype forecasting system in which the dynamic vegetation and terrestrial carbon cycle model VEGAS was forced with 15-member ensemble climate predictions generated by the NOAA/NCEP coupled climate forecasting system (CFS) for the period 1981-2005, with lead times up to 9 months. The results show that the predictability is dominated by the ENSO signal with its major influence on the tropical and subtropical regions, including South America, Indonesia, southern Africa, eastern Australia, western United States, and central Asia. There is also important non-ENSO related predictability such as that associated with midlatitude drought. Comparison of the dynamical prediction results with benchmark statistical prediction methods such as anomaly persistence and damping show that the dynamical method performs significantly better. The hindcasted ecosystem variables and carbon flux show significantly slower decrease in skill at longer lead time compared to the climate forcing variables, partly because of the memories in land and vegetation processes that filter out the higher-frequency noise and sustain the signal.

  3. Tundra ecosystems observed to be CO2 sources due to differential amplification of the carbon cycle.

    PubMed

    Belshe, E F; Schuur, E A G; Bolker, B M

    2013-10-01

    Are tundra ecosystems currently a carbon source or sink? What is the future trajectory of tundra carbon fluxes in response to climate change? These questions are of global importance because of the vast quantities of organic carbon stored in permafrost soils. In this meta-analysis, we compile 40 years of CO2 flux observations from 54 studies spanning 32 sites across northern high latitudes. Using time-series analysis, we investigated if seasonal or annual CO2 fluxes have changed over time, and whether spatial differences in mean annual temperature could help explain temporal changes in CO2 flux. Growing season net CO2 uptake has definitely increased since the 1990s; the data also suggest (albeit less definitively) an increase in winter CO2 emissions, especially in the last decade. In spite of the uncertainty in the winter trend, we estimate that tundra sites were annual CO2 sources from the mid-1980s until the 2000s, and data from the last 7 years show that tundra continue to emit CO2 annually. CO2 emissions exceed CO2 uptake across the range of temperatures that occur in the tundra biome. Taken together, these data suggest that despite increases in growing season uptake, tundra ecosystems are currently CO2 sources on an annual basis. PMID:23953054

  4. Alaska ecosystem carbon fluxes estimated from MODIS satellite data inputs from 2000 to 2010

    PubMed Central

    2013-01-01

    Background Trends in Alaska ecosystem carbon fluxes were predicted from inputs of monthly MODerate resolution Imaging Spectroradiometer (MODIS) vegetation index time-series combined with the NASA-CASA (Carnegie Ames Stanford Approach) carbon cycle simulation model over the past decade. CASA simulates monthly net ecosystem production (NEP) as the difference in carbon fluxes between net primary production (NPP) and soil microbial respiration (Rh). Results Model results showed that NEP on a unit area basis was estimated to be highest (> +10 g C m-2 yr-1) on average over the period 2000 to 2010 within the Major Land Resource Areas (MRLAs) of the Interior Brooks Range Mountains, the Arctic Foothills, and the Western Brooks Range Mountains. The lowest (as negative land C source fluxes) mean NEP fluxes were predicted for the MLRAs of the Cook Inlet Lowlands, the Ahklun Mountains, and Bristol Bay-Northern Alaska Peninsula Lowlands. High levels of interannual variation in NEP were predicted for most MLRAs of Alaska. Conclusions The relatively warm and wet years of 2004 and 2007 resulted in the highest positive NEP flux totals across MLRAs in the northern and western coastal locations in the state (i.e., the Brooks Range Mountains and Arctic Foothills). The relatively cold and dry years of 2001 and 2006 were predicted with the lowest (negative) NEP flux totals for these MLRAs, and likewise across the Ahklun Mountains and the Yukon-Kuskokwim Highlands. PMID:24261829

  5. Sustainability of Carbon Sequestration in Terrestrial Ecosystems: Theoretical Framework and a Case Study

    NASA Astrophysics Data System (ADS)

    Luo, Y.

    2002-12-01

    A sound understanding of the sustainability of terrestrial carbon (C) sequestration is critical for the success of any policies geared to stabilize atmospheric greenhouse concentrations. This includes the controversial Kyoto Protocol and/or other greenhouse strategies by individual countries. However, the sustainability of C sinks and pools has not been carefully studied with either empirical or theoretical approaches. This study establishes a theoretical framework to define the sustainability based on C influx and residence time (t). Ecosystem C influx is determined by canopy photosynthetic capacity, which is regulated by leaf photosynthetic capacity and leaf area index. The residence time represents the capacity of an ecosystem to store C in plant and soil pools (i.e., the C-storage capacity). The C-sequestration capacity in an ecosystem is jointly determined by the canopy photosynthetic capacity and the C-storage capacity. The C-sequestration capacity is maintained in a future global change scenario only if neither the canopy photosynthetic capacity nor the C-storage capacity is up-or down-regulated. In that case, the future rate of terrestrial C sequestration is primarily determined by environmental forcing functions. The forcing functions could be the rising of atmospheric CO2 concentration, forest regrowth, woody plant encroachment, and nitrogen deposition. We applied this framework to the Free-Air CO2 Enrichment (FACE) experiment in Duke Forest, North Carolina, USA. We estimated C influx with a mechanistic canopy model and residence time via inverse analysis of multiple data sets. Our results indicated that neither canopy photosynthetic capacity nor the C-storage capacity was altered by elevated CO2 at this forest site Thus, the current evidence from both experimental observations and inverse analysis suggests that C sequestration in the ecosystem will increase gradually as Ca gradually increases. Nonetheless, the increased C sequestration in terrestrial

  6. Temporal-Spatial Pattern of Carbon Stocks in Forest Ecosystems in Shaanxi, Northwest China.

    PubMed

    Cui, Gaoyang; Chen, Yunming; Cao, Yang

    2015-01-01

    The precise and accurate quantitative evaluation of the temporal and spatial pattern of carbon (C) storage in forest ecosystems is critical for understanding the role of forests in the global terrestrial C cycle and is essential for formulating forest management policies to combat climate change. In this study, we examined the C dynamics of forest ecosystems in Shaanxi, northwest China, based on four forest inventories (1989-1993, 1994-1998, 1999-2003, and 2004-2008) and field-sampling measurements (2012). The results indicate that the total C storage of forest ecosystems in Shaanxi increased by approximately 29.3%, from 611.72 Tg in 1993 to 790.75 Tg in 2008, partially as a result of ecological restoration projects. The spatial pattern of C storage in forest ecosystems mainly exhibited a latitude-zonal distribution across the province, increasing from north (high latitude) to south (low latitude) generally, which signifies the effect of environmental conditions, chiefly water and heat related factors, on forest growth and C sequestration. In addition, different data sources and estimation methods had a significant effect on the results obtained, with the C stocks in 2008 being considerably overestimated (864.55 Tg) and slightly underestimated (778.07 Tg) when measured using the mean C density method and integrated method, respectively. Overall, our results demonstrated that the forest ecosystem in Shaanxi acted as a C sink over the last few decades. However, further studies should be carried out with a focus on adaption of plants to environmental factors along with forest management for vegetation restoration to maximize the C sequestration potential and to better cope with climate change. PMID:26353011

  7. Tree Species Linked to Large Differences in Ecosystem Carbon Distribution in the Boreal Forest of Alaska

    NASA Astrophysics Data System (ADS)

    Melvin, A. M.; Mack, M. C.; Johnstone, J. F.; Schuur, E. A. G.; Genet, H.; McGuire, A. D.

    2014-12-01

    In the boreal forest of Alaska, increased fire severity associated with climate change is altering plant-soil-microbial feedbacks and ecosystem carbon (C) dynamics. The boreal landscape has historically been dominated by black spruce (Picea mariana), a tree species associated with slow C turnover and large soil organic matter (SOM) accumulation. Historically, low severity fires have led to black spruce regeneration post-fire, thereby maintaining slow C cycling rates and large SOM pools. In recent decades however, an increase in high severity fires has led to greater consumption of the soil organic layer (SOL) during fire and subsequent establishment of deciduous tree species in areas previously dominated by black spruce. This shift to a more deciduous dominated landscape has many implications for ecosystem structure and function, as well as feedbacks to global C cycling. To improve our understanding of how boreal tree species affect C cycling, we quantified above- and belowground C stocks and fluxes in adjacent, mid-successional stands of black spruce and Alaska paper birch (Betula neoalaskana) that established following a 1958 fire near Fairbanks, Alaska. Although total ecosystem C pools (aboveground live tree biomass + dead wood + SOL + top 10 cm of mineral soil) were similar for the two stand types, the distribution of C among pools was markedly different. In black spruce, 78% of measured C was found in soil pools, primarily in the SOL, where spruce contained twice the C stored in paper birch (4.8 ± 0.3 vs. 2.4 ± 0.1 kg C m-2). In contrast, aboveground biomass dominated ecosystem C pools in birch forest (6.0 ± 0.3 vs. 2.5 ± 0.2 kg C m-2 in birch and spruce, respectively). Our findings suggest that tree species exert a strong influence over plant-soil-microbial feedbacks and may have long-term effects on ecosystem C sequestration and storage that feedback to the climate system.

  8. Temporal-Spatial Pattern of Carbon Stocks in Forest Ecosystems in Shaanxi, Northwest China

    PubMed Central

    Cui, Gaoyang; Chen, Yunming; Cao, Yang

    2015-01-01

    The precise and accurate quantitative evaluation of the temporal and spatial pattern of carbon (C) storage in forest ecosystems is critical for understanding the role of forests in the global terrestrial C cycle and is essential for formulating forest management policies to combat climate change. In this study, we examined the C dynamics of forest ecosystems in Shaanxi, northwest China, based on four forest inventories (1989–1993, 1994–1998, 1999–2003, and 2004–2008) and field-sampling measurements (2012). The results indicate that the total C storage of forest ecosystems in Shaanxi increased by approximately 29.3%, from 611.72 Tg in 1993 to 790.75 Tg in 2008, partially as a result of ecological restoration projects. The spatial pattern of C storage in forest ecosystems mainly exhibited a latitude-zonal distribution across the province, increasing from north (high latitude) to south (low latitude) generally, which signifies the effect of environmental conditions, chiefly water and heat related factors, on forest growth and C sequestration. In addition, different data sources and estimation methods had a significant effect on the results obtained, with the C stocks in 2008 being considerably overestimated (864.55 Tg) and slightly underestimated (778.07 Tg) when measured using the mean C density method and integrated method, respectively. Overall, our results demonstrated that the forest ecosystem in Shaanxi acted as a C sink over the last few decades. However, further studies should be carried out with a focus on adaption of plants to environmental factors along with forest management for vegetation restoration to maximize the C sequestration potential and to better cope with climate change. PMID:26353011

  9. Quantification of terrestrial ecosystem carbon dynamics in the conterminous United States combining a process-based biogeochemical model and MODIS and AmeriFlux data

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Satellite remote sensing provides continuous temporal and spatial information of terrestrial ecosystems. Using these remote sensing data and eddy flux measurements and biogeochemical models, such as the Terrestrial Ecosystem Model (TEM), should provide a more adequate quantification of carbon dynami...

  10. The carbon balance pivot point of southwestern U.S. semiarid ecosystems: Insights from the 21st century drought

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Global-scale studies indicate that semiarid regions strongly regulate the terrestrial carbon sink. However, we lack understanding of how climatic shifts, such as decadal drought, impact carbon sequestration across the wide-range of structural diversity in semiarid ecosystems. Therefore, we used edd...

  11. Biological and geological carbon sources in a steppe ecosystem in the SE of Spain

    NASA Astrophysics Data System (ADS)

    Rey, Ana; Belelli-Marchesini, Luca; Etiope, Giuseppe; Papale, Dario

    2015-04-01

    Widespread recognition of the importance of soil CO2 efflux as a major source of CO2 to the atmosphere has led to active research. A large soil respiration database and recent reviews have compiled data, methods, and current challenges. However, some processes of soil CO2 production and transport have not received enough attention. In the current soil respiration literature it has mostly been assumed that soil CO2 efflux is the result of biological processes (i.e. soil respiration) but recent studies demonstrate that pedochemical and geological processes, such as geothermal and volcanic CO2 degassing, are potentially important in some areas. We carried out a study in the SE of Spain that showed that wind was the main determinant of the net ecosystem carbon balance with anomalous CO2 fluxes that could not be attributed to biological activity alone and hypothesised the presence of a geo-CO2 source given that the site was located over an tectonic fault in an ancient volcanic area (Rey et al., 2012a). After proving the existence of a geological CO2 source (Rey et al., 2013b), we developed a methodology using parameters of the boundary layer to derive biological (FBIO) and geological (FGEO) components and then partitioned FBIO into gross primary productivity and ecosystem respiration (Rey et al. 2013). We estimated that ca 50% of the carbon emitted annually came from geological sources. Thus these sources can be very important in some regions and confound our estimates of the CO2 exchange attributed to biological activity. This study highlights the need to improve our understanding of the processes involved in ecosystem and soil CO2 efflux and to standardise current methodologies among the scientific community. The complexity of the CO2 production and transport mechanisms will require a much better interdisciplinary integration (Rey 2014). This should be a research priority given the importance of this flux in the global carbon budget.

  12. Soil Organic Carbon and Total Nitrogen Gains in an Old Growth Deciduous Forest in Germany

    PubMed Central

    Schrumpf, Marion; Kaiser, Klaus; Schulze, Ernst-Detlef

    2014-01-01

    Temperate forests are assumed to be organic carbon (OC) sinks, either because of biomass increases upon elevated CO2 in the atmosphere and large nitrogen deposition, or due to their age structure. Respective changes in soil OC and total nitrogen (TN) storage have rarely been proven. We analysed OC, TN, and bulk densities of 100 soil cores sampled along a regular grid in an old-growth deciduous forest at the Hainich National Park, Germany, in 2004 and again in 2009. Concentrations of OC and TN increased significantly from 2004 to 2009, mostly in the upper 0–20 cm of the mineral soil. Changes in the fine earth masses per soil volume impeded the detection of OC changes based on fixed soil volumes. When calculated on average fine earth masses, OC stocks increased by 323±146 g m−2 and TN stocks by 39±10 g m−2 at 0–20 cm soil depth from 2004 to 2009, giving average annual accumulation rates of 65±29 g OC m−2 yr−1 and 7.8±2 g N m−2 yr−1. Accumulation rates were largest in the upper part of the B horizon. Regional increases in forest biomass, either due to recovery of forest biomass from previous forest management or to fertilization by elevated CO2 and N deposition, are likely causes for the gains in soil OC and TN. As TN increased stronger (1.3% yr−1 of existing stocks) than OC (0.9% yr−1), the OC-to-TN ratios declined significantly. Results of regression analyses between changes in OC and TN stocks suggest that at no change in OC, still 3.8 g TN m−2 yr−1 accumulated. Potential causes for the increase in TN in excess to OC are fixation of inorganic N by the clay-rich soil or changes in microbial communities. The increase in soil OC corresponded on average to 6–13% of the estimated increase in net biome productivity. PMID:24586720

  13. Soil organic carbon and total nitrogen gains in an old growth deciduous forest in Germany.

    PubMed

    Schrumpf, Marion; Kaiser, Klaus; Schulze, Ernst-Detlef

    2014-01-01

    Temperate forests are assumed to be organic carbon (OC) sinks, either because of biomass increases upon elevated CO2 in the atmosphere and large nitrogen deposition, or due to their age structure. Respective changes in soil OC and total nitrogen (TN) storage have rarely been proven. We analysed OC, TN, and bulk densities of 100 soil cores sampled along a regular grid in an old-growth deciduous forest at the Hainich National Park, Germany, in 2004 and again in 2009. Concentrations of OC and TN increased significantly from 2004 to 2009, mostly in the upper 0-20 cm of the mineral soil. Changes in the fine earth masses per soil volume impeded the detection of OC changes based on fixed soil volumes. When calculated on average fine earth masses, OC stocks increased by 323 ± 146 g m(-2) and TN stocks by 39 ± 10 g m(-2) at 0-20 cm soil depth from 2004 to 2009, giving average annual accumulation rates of 65 ± 29 g OC m(-2) yr(-1) and 7.8 ± 2 g N m(-2) yr(-1). Accumulation rates were largest in the upper part of the B horizon. Regional increases in forest biomass, either due to recovery of forest biomass from previous forest management or to fertilization by elevated CO2 and N deposition, are likely causes for the gains in soil OC and TN. As TN increased stronger (1.3% yr(-1) of existing stocks) than OC (0.9% yr(-1)), the OC-to-TN ratios declined significantly. Results of regression analyses between changes in OC and TN stocks suggest that at no change in OC, still 3.8 g TN m(-2) yr(-1) accumulated. Potential causes for the increase in TN in excess to OC are fixation of inorganic N by the clay-rich soil or changes in microbial communities. The increase in soil OC corresponded on average to 6-13% of the estimated increase in net biome productivity. PMID:24586720

  14. The influence of ecosystem nitrogen status on carbon cycling in forests

    NASA Astrophysics Data System (ADS)

    Ollinger, S. V.; Smith, M.; Richardson, A.; Hollinger, D. Y.; Martin, M.; Jenkins, J.

    2006-12-01

    The carbon and nitrogen cycles in terrestrial ecosystems are tightly coupled through a shared set of biological processes. The N status of plant canopies exerts a direct influence on carbon assimilation through its well-known effect on net photosynthesis. In soils, both the accumulation of N and the decay of organic matter are often related to the initial C/N ratio of litterfall. Similarly, respiration rates in both roots and foliage have been shown to be positively correlated with tissue N concentrations. These linkages suggest that the N status of ecosystems may provide a useful indicator of their overall C metabolism. Further, evidence from both CO2 and N enrichment experiments indicates that alteration of one cycle can have important implications for the other. This is significant in that global cycles of both C and N have been greatly perturbed by humans. Despite the well-known influence of nitrogen availability on fluxes of carbon, few studies have explicitly examined the role of nitrogen as it pertains to spatial and temporal variation in carbon cycling. This is due, in part, to limited crossover between different scientific communities, but also stems from some very real methodological limitations that make regional-scale assessment of N status difficult. Here, we report on an NACP investigation that examines the degree to which rates of carbon assimilation and growth in forests can be related to both local and regional variation in ecosystem N status. Field measurements from a series of forested research sites within the AmeriFlux network have been combined with hyperspectral remote sensing data from the AVIRIS and Hyperion instruments. Results from a cross-site synthesis indicate a positive relationship between canopy N and the maximum rate of carbon assimilation, as measured by flux towers. Because existing methods of canopy N detection are restricted to small landscapes, a parallel investigation involves developing generalizeable canopy N detection

  15. How have past fire disturbances contributed to the current carbon balance of boreal ecosystems?

    NASA Astrophysics Data System (ADS)

    Yue, C.; Ciais, P.; Zhu, D.; Wang, T.; Peng, S. S.; Piao, S. L.

    2016-02-01

    Boreal fires have immediate effects on regional carbon budgets by emitting CO2 into the atmosphere at the time of burning, but they also have legacy effects by initiating a long-term carbon sink during post-fire vegetation recovery. Quantifying these different effects on the current-day pan-boreal (44-84° N) carbon balance and quantifying relative contributions of legacy sinks by past fires is important for understanding and predicting the carbon dynamics in this region. Here we used the global dynamic vegetation model ORCHIDEE-SPITFIRE (Organising Carbon and Hydrology In Dynamic Ecosystems - SPread and InTensity of FIRE) to attribute the contributions by fires in different decades between 1850 and 2009 to the carbon balance of 2000-2009, taking into account the atmospheric CO2 change and climate change since 1850. The fire module of ORCHIDEE-SPITFIRE was turned off for each decade in turn and was also turned off before and after the decade in question in order to model the legacy carbon trajectory by fires in each past decade. We found that, unsurprisingly, fires that occurred in 2000-2009 are a carbon source (-0.17 Pg C yr-1) for the carbon balance of 2000-2009, whereas fires in all decades before 2000 contribute carbon sinks with a collective contribution of 0.23 Pg C yr-1. This leaves a net fire sink effect of 0.06 Pg C yr-1, or 6.3 % of the simulated regional carbon sink (0.95 Pg C yr-1). Further, fires with an age of 10-40 years (i.e., those that occurred during 1960-1999) contribute more than half of the total sink effect of fires. The small net sink effect of fires indicates that current-day fire emissions are roughly balanced out by legacy sinks. The future role of fires in the regional carbon balance remains uncertain and will depend on whether changes in fires and associated carbon emissions will exceed the enhanced sink effects of previous fires, both being strongly affected by global change.

  16. A model using marginal efficiency of investment to analyse carbon and nitrogen interactions in forested ecosystems

    NASA Astrophysics Data System (ADS)

    Thomas, R. Q.; Williams, M.

    2014-12-01

    Carbon (C) and nitrogen (N) cycles are coupled in terrestrial ecosystems through multiple processes including photosynthesis, tissue allocation, respiration, N fixation, N uptake, and decomposition of litter and soil organic matter. Capturing the constraint of N on terrestrial C uptake and storage has been a focus of the Earth System modelling community. Here we explore the trade-offs and sensitivities of allocating C and N to different tissues in order to optimize the productivity of plants using a new, simple model of ecosystem C-N cycling and interactions (ACONITE). ACONITE builds on theory related to plant economics in order to predict key ecosystem properties (leaf area index, leaf C:N, N fixation, and plant C use efficiency) based on the optimization of the marginal change in net C or N uptake associated with a change in allocation of C or N to plant tissues. We simulated and evaluated steady-state and transient ecosystem stocks and fluxes in three different forest ecosystems types (tropical evergreen, temperate deciduous, and temperate evergreen). Leaf C:N differed among the three ecosystem types (temperate deciduous < tropical evergreen < temperature evergreen), a result that compared well to observations from a global database describing plant traits. Gross primary productivity (GPP) and net primary productivity (NPP) estimates compared well to observed fluxes at the simulation sites. A sensitivity analysis revealed that parameterization of the relationship between leaf N and leaf respiration had the largest influence on leaf area index and leaf C:N. Also, a widely used linear leaf N-respiration relationship did not yield a realistic leaf C:N, while a more recently reported non-linear relationship simulated leaf C:N that compared better to the global trait database than the linear relationship. Overall, our ability to constrain leaf area index and allow spatially and temporally variable leaf C:N can help address challenges simulating these properties in

  17. Partitioning Ecosystem Respiration Using Stable Carbon Isotopes in a Mixed C3 Annual Grassland

    NASA Astrophysics Data System (ADS)

    Tu, K. P.

    2001-12-01

    The stable carbon isotope ratio (δ 13C) of respired CO2 has been used to partition soil respiration into root and microbial components by exploiting the different δ 13C signals from C3 plants growing in a previously C4 dominated system (Rouchette, Angers and Flanagan 1999). We extend this approach and present data that attempts to partition ecosystem respiration using δ 13C analyses of all of the ecosystem compartments in a mixed C3 annual grassland that has not experienced recent C4 inputs. From December 2000 to February 2001 we measured δ 13C-CO2 respired from leaves, roots and sieved soil collected from a winter-active grassland near Ione, California. Two-source mixing models were used to calculate the contribution of each source to total system respiration by comparing their isotope signals to those from whole ecosystem respiration and soil surface efflux. Isotope ratios were measured on 10mL air samples in septum-capped vials using a Finnigan MAT Delta PlusXL IRMS/Gas Bench II interfaced to an autosampler (after Tu et al. 2001). The vials were filled with sample air in the field using a double-holed needle connected in a closed loop to a LI-6200 IRGA and a bottle containing the isolated samples (leaf, root, sieved soil, etc.). Leaves were clipped at ground level and roots and soil were separated by sieving soil cores. Sample δ 13CO2 signatures were determined by plotting the change in δ 13C against the inverse of CO2 concentration. On average, CO2 respired from sieved soil (-27.4o/oo+/-1.4) was slightly more depleted than that from leaves (-27.2o/oo+/-0.5), but much more depleted than the whole ecosystem (-24.9o/oo+/-0.6), the soil surface efflux (-23.8o/oo+/-0.9), and plant roots (-20.5o/oo+/-0.8). Based on these isotope values, leaf respiration comprised 33% of ecosystem respiration with 36% from roots and 31% from soil microbial respiration. Thus, over two-thirds of ecosystem respiration was autotrophic (plant-based) in origin with roughly one

  18. Quantifying thermal constraints on carbon and water fluxes in a mixed-conifer sky island ecosystem

    NASA Astrophysics Data System (ADS)

    Braun, Z.; Minor, R. L.; Potts, D. L.; Barron-Gafford, G. A.

    2012-12-01

    Western North American forests represent a potential, yet uncertain, sink for atmospheric carbon. Revealing how predicted climatic conditions of warmer temperatures and longer inter-storm periods of moisture stress might influence the carbon status of these forests requires a fuller understanding of plant functional responses to abiotic stress. While data related to snow dominated montane ecosystems has become more readily available to parameterize ecosystem function models, there is a paucity of data available for Madrean sky island mixed-conifer forests, which receive about one third of their precipitation from the North American Monsoon. Thus, we quantified ecophysiological responses to moisture and temperature stress in a Madrean mixed-conifer forest near Tucson, Arizona, within the footprint of the Mt. Bigelow Eddy Covariance Tower. In measuring a series of key parameters indicative of carbon and water fluxes within the dominant species across pre-monsoon and monsoon conditions, we were able to develop a broader understanding of what abiotic drivers are most restrictive to plant performance in this ecosystem. Within Pinus ponderosa (Ponderosa Pine), Pseudotsuga menziesii (Douglas Fir), and Pinus strobiformis (Southwestern White Pine) we quantified: (i) the optimal temperature (Topt) for maximum photosynthesis (Amax), (ii) the range of temperatures over which photosynthesis was at least 50% of Amax (Ω50), and (iii) each conifer's water use efficiency (WUE) to relate to the balance between carbon uptake and water loss in this high elevation semiarid ecosystem. Our findings support the prediction that photosynthesis decreases under high temperatures (>30°C) among the three species we measured, regardless of soil moisture status. However, monsoon moisture reduced sensitivity to temperature extremes and fluctuations (Ω50), which substantially magnified total photosynthetic productivity. In particular, wet conditions enhanced Amax the most dramatically for P

  19. Integration of ecosystem services into the carbon footprint of milk of South German dairy farms.

    PubMed

    Robert Kiefer, Lukas; Menzel, Friederike; Bahrs, Enno

    2015-04-01

    Allocation of greenhouse gas emissions (GHG) in Life Cycle Assessments (LCA) is challenging especially when multi-functionality of dairy farms, which do not only produce milk but also meat is considered. Moreover, some farms fulfill a wide range of additional services for society such as management of renewable natural resources as well as preservation of biodiversity and cultural landscapes. Due to the increasing degradation of ecosystems many industrialized as well as developing countries designed payment systems for environmental services. This study examines different allocation methods of GHG for a comparatively large convenience sample of 113 dairy farms located in grassland-based areas of southern Germany. Results are carbon footprints of 1.99 kg CO2eq/kg of fat and protein corrected milk (FPCM) on average if "no allocation" for coupled products is performed. "Physical allocation" results in 1.53 kg CO2eq/kg FPCM and "conventional economic allocation" in 1.66 kg CO2eq/kg FPCM on average if emissions are apportioned between milk and meat. Economic allocation which includes ecosystem services for society based on the farm net income as a new aspect in this study results in a carbon footprint of 1.5 kg CO2eq/kg FPCM on average. System expansion that puts greater emphasis on coupled beef production accounts for a carbon footprint of 0.68 kg CO2eq/kg FPCM on average. Intense milk production systems with higher milk yields show better results based on "no allocation", "physical allocation" and "conventional economic allocation". By contrast, economic allocation, which takes into account ecosystem services favors extensive systems, especially in less favored areas. This shows that carbon footprints of dairy farms should not be examined one-dimensionally based on the amount of milk and meat that is produced on the farm. Rather, a broader perspective is necessary that takes into account the multi-functionality of dairy farms especially in countries where a wide

  20. Rock Outcrops Redistribute Organic Carbon and Nutrients to Nearby Soil Patches in Three Karst Ecosystems in SW China

    PubMed Central

    Wang, Dianjie; Shen, Youxin; Li, Yuhui; Huang, Jin

    2016-01-01

    Emergent rock outcrops are common in terrestrial ecosystems. However, little research has been conducted regarding their surface function in redistributing organic carbon and nutrient fluxes to soils nearby. Water that fell on and ran off 10 individual rock outcrops was collected in three 100 × 100 m plots within a rock desertification ecosystem, an anthropogenic forest ecosystem, and a secondary forest ecosystem between June 2013 and June 2014 in Shilin, SW China. The concentrations of total organic carbon (TOC), total nitrogen (N), total phosphorus (P), and potassium (K) in the water samples were determined during three seasons, and the total amounts received by and flowing out from the outcrops were calculated. In all three ecosystems, TOC and N, P, and K were found throughout the year in both the water received by and delivered to nearby soil patches. Their concentrations and amounts were generally greater in forested ecosystems than in the rock desertification ecosystem. When rock outcrops constituted a high percentage (≥ 30%) of the ground surface, the annual export of rock outcrop runoff contributed a large amount of organic carbon and N, P, and K nutrients to soil patches nearby by comparison to the amount soil patches received via atmospheric deposition. These contributions may increase the spatial heterogeneity of soil fertility within patches, as rock outcrops of different sizes, morphologies, and emergence ratios may surround each soil patch. PMID:27509199

  1. Rock Outcrops Redistribute Organic Carbon and Nutrients to Nearby Soil Patches in Three Karst Ecosystems in SW China.

    PubMed

    Wang, Dianjie; Shen, Youxin; Li, Yuhui; Huang, Jin

    2016-01-01

    Emergent rock outcrops are common in terrestrial ecosystems. However, little research has been conducted regarding their surface function in redistributing organic carbon and nutrient fluxes to soils nearby. Water that fell on and ran off 10 individual rock outcrops was collected in three 100 × 100 m plots within a rock desertification ecosystem, an anthropogenic forest ecosystem, and a secondary forest ecosystem between June 2013 and June 2014 in Shilin, SW China. The concentrations of total organic carbon (TOC), total nitrogen (N), total phosphorus (P), and potassium (K) in the water samples were determined during three seasons, and the total amounts received by and flowing out from the outcrops were calculated. In all three ecosystems, TOC and N, P, and K were found throughout the year in both the water received by and delivered to nearby soil patches. Their concentrations and amounts were generally greater in forested ecosystems than in the rock desertification ecosystem. When rock outcrops constituted a high percentage (≥ 30%) of the ground surface, the annual export of rock outcrop runoff contributed a large amount of organic carbon and N, P, and K nutrients to soil patches nearby by comparison to the amount soil patches received via atmospheric deposition. These contributions may increase the spatial heterogeneity of soil fertility within patches, as rock outcrops of different sizes, morphologies, and emergence ratios may surround each soil patch. PMID:27509199

  2. A dynamical systems analysis of the data assimilation linked ecosystem carbon (DALEC) models

    NASA Astrophysics Data System (ADS)

    Chuter, Anna M.; Aston, Philip J.; Skeldon, Anne C.; Roulstone, Ian

    2015-03-01

    Changes in our climate and environment make it ever more important to understand the processes involved in Earth systems, such as the carbon cycle. There are many models that attempt to describe and predict the behaviour of carbon stocks and stores but, despite their complexity, significant uncertainties remain. We consider the qualitative behaviour of one of the simplest carbon cycle models, the Data Assimilation Linked Ecosystem Carbon (DALEC) model, which is a simple vegetation model of processes involved in the carbon cycle of forests, and consider in detail the dynamical structure of the model. Our analysis shows that the dynamics of both evergreen and deciduous forests in DALEC are dependent on a few key parameters and it is possible to find a limit point where there is stable sustainable behaviour on one side but unsustainable conditions on the other side. The fact that typical parameter values reside close to this limit point highlights the difficulty of predicting even the correct trend without sufficient data and has implications for the use of data assimilation methods.

  3. Temporal dynamics of carbon dioxide and carbon monoxide in the Salt Lake Valley urban ecosystem of northern Utah, USA

    NASA Astrophysics Data System (ADS)

    Bush, S. E.; Ehleringer, J. R.; Hopkins, F. M.; Randerson, J. T.; Lai, C.

    2013-12-01

    Urban ecosystems are a significant source of greenhouse gas emissions. Existing data obtained from surface based measurements of carbon dioxide (CO2) and carbon monoxide (CO) are largely limited to static monitoring stations and show a high degree of temporal and spatial variability both within and across urban areas. Finer scale spatial resolution data of surface measurements were collected to obtain a more comprehensive view of trace gas dynamics at the whole-ecosystem scale, to integrate across space among existing stationary measurement locations, and to provide data for the development and validation of modeled emissions estimates. We utilized a mobile laboratory to obtain high precision measurements of CO2 and CO in the highly urbanized and urbanizing areas across the Salt Lake Valley of northern Utah, USA. Continuous measurements of CO2, CO, and geospatial position data were obtained at a 5-second frequency along a transect route representative of major urban land use types. Data collection across the transect route was repeated thrice daily (morning, afternoon and evening) through all seasons of the year. Preliminary results show significant spatial structure in CO2, CO, and the ratio of CO to CO2 across both diurnal and seasonal time scales. In general, we found higher concentrations of both trace gases as well as the ratio of CO to CO2 in the morning and evening periods compared to the afternoon time periods. In addition, we found higher concentrations of both trace gases and the ratio of CO to CO2 in winter than summer time periods. Our results provide a foundation for the information needed to improve our understanding of whole-ecosystem scale temporal dynamics of CO2 and CO in urban regions.

  4. Rudist bivalve shells as palaeoenvironmental archive: assessing ecological boundary conditions of Barremian subtropical carbonate platform ecosystems

    NASA Astrophysics Data System (ADS)

    Huck, Stefan; Heimhofer, Ulrich

    2013-04-01

    Mid-Cretaceous shoal-water ecosystems have been proven to show characteristic response modes (microencruster blooms, carbonate platform drowning) to major climatic and environmental changes that finally culminated in so-called oceanic anoxic events (OAEs). During most OAEs, the widespread burial of unusual amounts of organic matter in pelagic basins caused a strong carbon-cycle perturbation, expressed as prominent positive carbon-isotope excursion. Stratigraphically, the Aptian OAE1a is marked by a well-defined carbon-isotope pattern (negative spike and subsequent positive anomaly). Judging from high-resolution chemostratigraphic (C, Sr) studies, the observed neritic response modes are diachronous in nature and certain biotic changes (orbitolinid-rich sediments, Lithocodium blooms, carbonate platform drowning) clearly predate the deposition of OAE1a black-shales. The perturbations observed in the neritic realm underline the previously quoted progressive nature of Late Barremian-Early Aptian environmental change. Considering the observed time lag between the earliest biotic perturbations and widespread oceanic anoxia, a volcanic scenario related to the release of large volumes of CO2 during the formation of the Ontong Java large igneous province seems at least likely. The aim of the current project is to reconstruct the evolution of carbonate platform ecosystems in the northern subtropical realm during the early onset of enhanced (submarine) volcanic activity. A Late Barremian carbonate platform succession (Sausset-les-Pins section), deposited on a proximal part of the Provence platform (Marseille area, SE France), has been investigated applying high-resolution chemostratigraphy and detailed sedimentological analysis. The 60-m thick section is composed of peloidal to bioclastic packstones and grainstones rich in rudist bivalves (Urgonian limestones sensu stricto) and subordinate mudstones and wackestones. In order to obtain information on the palaeoecological and

  5. Estimation of Carbon Flux of Forest Ecosystem over Qilian Mountains by BIOME-BGC Model

    NASA Astrophysics Data System (ADS)

    Yan, Min; Tian, Xin; Li, Zengyuan; Chen, Erxue; Li, Chunmei

    2014-11-01

    The gross primary production (GPP) and net ecosystem exchange (NEE) are important indicators for carbon fluxes. This study aims at evaluating the forest GPP and NEE over the Qilian Mountains using meteorological, remotely sensed and other ancillary data at large scale. To realize this, the widely used ecological-process-based model, Biome-BGC, and remote-sensing-based model, MODIS GPP algorithm, were selected for the simulation of the forest carbon fluxes. The combination of these two models was based on calibrating the Biome-BGC by the optimized MODIS GPP algorithm. The simulated GPP and NEE values were evaluated against the eddy covariance observed GPPs and NEEs, and the well agreements have been reached, with R2=0.76, 0.67 respectively.

  6. Climatic Controls of Soil Carbon Cycling Across a Gradient of Sonoran Desert Ecosystems

    NASA Astrophysics Data System (ADS)

    Rasmussen, C.

    2009-04-01

    Arid and semiarid lands cover roughly 36% to 40% of global land area, highlighting the importance these ecosystems play in the global carbon cycle. The controls of arid and semiarid ecosystem carbon cycle processes, such as soil organic matter turnover and mineral weathering, remain poorly understood. To address this knowledge gap, we established a set of long-term soil monitoring sites across a gradient of semiarid ecosystems in the Sonoran Desert of the Southwestern USA. These sites were established as part of the Critical Zone Exploration Network (CZEN), sponsored by the US National Science Foundation. The primary objectives of the Sonoran Desert Environmental Gradient (SDEG) include: (i) characterizing climate forcing controls of soil physical, chemical and biological processes, and the flux of chemical species from soils to surface waters; and (ii) developing predictive models of carbon cycle response to climate and climate change. Particular attention is given to the bimodal precipitation regime characteristic of the SDEG ecosystems and the relative impact of warm versus cold precipitation on biogeochemical processes. The SDEG spans a steep elevation and environmental gradient on granitic parent materials near Tucson, Arizona, USA. Elevation ranges from 800-2650 m a.s.l. with concurrent shifts in climatic regime. Specifically, mean annual air temperature decreases (20-10 °C) and mean annual precipitation increases (30-85 cm) with elevation, with concomitant changes in vegetation from mixed desert-scrub (<1200m) to grass and oak woodlands (1200-1700 m) to pinyon-juniper woodland (1700-2000 m) and ponderosa pine and fir forest (>2000 m). We sampled soil and regolith material from each of vegetation community across the SDEG and established a long-term soil-moisture and temperature monitoring network. Pedon physicochemical data, coupled with elemental mass balance, radiocarbon analyses of soil organic matter, and terrestrial cosmogenic nuclide (10Be) analyses

  7. Large interannual variability in net ecosystem carbon dioxide exchange of a disturbed temperate peatland.

    PubMed

    Aslan-Sungur, Guler; Lee, Xuhui; Evrendilek, Fatih; Karakaya, Nusret

    2016-06-01

    Peatland ecosystems play an important role in the global carbon (C) cycle as significant C sinks. However, human-induced disturbances can turn these sinks into sources of atmospheric CO2. Long-term measurements are needed to understand seasonal and interannual variability of net ecosystem CO2 exchange (NEE) and effects of hydrological conditions and their disturbances on C fluxes. Continuous eddy-covariance measurements of NEE were conducted between August 2010 and April 2014 at Yenicaga temperate peatland (Turkey), which was drained for agricultural usage and for peat mining until 2009. Annual NEE during the three full years of measurement indicated that the peatland acted as a CO2 source with large interannual variability, at rates of 246, 244 and 663 g Cm(-2)yr(-1) for 2011, 2012, and 2013 respectively, except for June 2011, and May to July 2012. The emission strengths were comparable to those found for severely disturbed tropical peatlands. The peak CO2 emissions occurred in the dry summer of 2013 when water table level (WTL) was below a threshold value of -60 cm and soil water content (SCW) below a threshold value of 70% by volume. Water availability index was found to have a stronger explanatory power for variations in monthly ecosystem respiration (ER) than the traditional water status indicators (SCW and WTL). Air temperature, evapotranspiration and vapor pressure deficient were the most significant variables strongly correlated with NEE and its component fluxes of gross primary production and ER. PMID:26950633

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

    PubMed

    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

  9. 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

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

    NASA Astrophysics Data System (ADS)

    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.

  11. Factors controlling the temporal variability of ecosystem respiration and its carbon isotope composition

    NASA Astrophysics Data System (ADS)

    Fassbinder, J.; Griffis, T. J.; Baker, J. M.; Erickson, M.; Billmark, K.; Smith, J.

    2009-12-01

    Ecosystem respiration (FR ) is the major pathway for carbon loss from terrestrial ecosystems. Stable carbon isotope analyses have been used to improve our understanding of the processes controlling ecosystem respiration. In particular, 13CO2 has been used to partition the autotrophic (Fa) and heterotrophic (Fh) contributions to FR. Further, there has been some concern in the literature regarding the temporal variability of the isotopic composition of ecosystem respiration (δR) and its potential influence on ecosystem flux partitioning based on isotope methods. In this study, we used an automated chamber and tunable diode laser system to measure soil respiration (FRs) and its isotopic composition (δRs) in an agricultural ecosystem under a C3/C4 crop rotation. Further, we used the same chamber-TDL system in a climate controlled greenhouse facility with C3/C4 treatments to examine the main factors causing variability in δRs and δR. The chamber data revealed strong diurnal patterns in the isotopic composition of Fh in the agricultural soil plots before crop emergence and in the greenhouse experiments involving bare soils. The diurnal pattern consisted of a sharp enrichment of up to 6‰ from 0700 to 1200 hr followed by a gradual depletion throughout the afternoon and evening. The diurnal signals of FR and soil temperature closely resembled the diurnal signal of δh, but consistently lagged δh by 3 to 4 hours. During peak corn growth, diurnal variation in δRs was strongly influenced by the isotopic composition of root respiration (δas), which enriched nighttime δRs by as much as 7‰ and daytime δRs by as much as 3‰. Chamber and flux-gradient data also indicated considerable seasonal variation in δR during corn growing seasons, ranging from -25‰ at the time of planting to -11‰ during peak growth. Less variation in δR was observed during soybean seasons, with values ranging from -26 to -21‰. Major shifts in δR during corn seasons were consistently

  12. Carbon fluxes in the pelagic ecosystem of the Gulf of Trieste (Northern Adriatic Sea)

    NASA Astrophysics Data System (ADS)

    Umani, Serena Fonda; Malfatti, Francesca; Del Negro, Paola

    2012-12-01

    By measuring a broad suite of physical, chemical, and biological parameters coupled with experiments on grazing efficiency of mesozoo-, microzoo- and heteronano-plankton we were able to depict the seasonal trophic status of the pelagic system in the Gulf of Trieste over a period of 8 years from 1998 to 2005. In winter and spring, primary production exceeded respiration, the autotrophic fraction biomass was higher than the heterotrophic biomass. Moreover, predation on microphytoplankton and autotrophic nanoplankton largely structured the ecosystem and bacterial carbon production accounted for <50% of primary production. The ratio of primary production/respiration was higher than 1 in winter and spring suggesting that pelagic ecosystem was autotrophic whereas in summer and in autumn the ratio was lower than 1 suggesting a shift towards net heterotrophic status. Carbon export was possible in winter and in autumn, and the few data from the sediment trap supported the theoretical rates. Thus since spring most of the C fixed by photosynthesis remained segregated in the surface layer and possibly it was exported to the bottom through grazer fecal pellets. In summer the system was dominated by heterotrophic picoplankton, which showed the highest production rate. In this scenario we hypothesize that the DOC produced during the winter-spring period can sustain a high and active bacterial biomass that is the primary energy source for the whole system. Picoplankton communities were heavily grazed by microzooplankton and heteronano-plankton, moreover predation rates of mesozooplankton on microzooplankton were particularly high in summer. Despite the high variability typical of the coastal areas, the pelagic ecosystem during these 8 years has shifted seasonally from a nutrient-excited state (winter-spring) to a background state (summer-autumn) as it has been observed from open-ocean ecosystem. Understanding the dynamic and the magnitude of this variability-shift is rather

  13. A Terrestrial Ecosystem Full Verified Carbon Accounting for Russian Land: Results and Uncertainty

    NASA Astrophysics Data System (ADS)

    Shvidenko, A.; Schepaschenko, D.; Maksyutov, S.

    2010-12-01

    We present a terrestrial full carbon account (FCA) for Russian land in a spatially explicit form for 2009 and aggregated country-wide annual estimates for 2004-2008. The integrated methodology of the FCA takes into account the fuzzy character of the studied systems. IIASA’s landscape-ecosystem approach (LEA) is used for designing the account boundaries and assessment of major pools and fluxes. An Integrated Land Information System (ILIS) serves as the information background of the FCA. The ILIS is based on a system integration of all available ground data and multi-sensor remote sensing applications. The ILIS includes a georeferenced hybrid land cover (~500 land classes, resolution 1 x 1 km), corresponding attributive datasets and sets of empirical and semi-empirical ecosystem and landscape models. The latter are based on long-period measurements of ecological parameters with corrections - if necessary - due to weather specifics of individual growth seasons. On average, terrestrial ecosystems of Russia served as a sink of roughly 0.6 Pg C yr-1 during the last five years which exceeds the technosphere’s emissions of the country by about one third. Two major fluxes (net primary production and heterotrophic respiration) for all productive lands of the country are estimated at 323 and 204 g C yr-1 m-2, respectively. Disturbance and consumption of plant products comprise from 15 to 20% of the net primary production. Forests serve as a major component of the sink (~85% of the country’s total). Disturbed forests and peatlands, as well as cultivated agricultural lands, are a relatively small carbon source. The interannual variability of the net ecosystem carbon balance are mostly driven by climatic conditions and natural disturbance (fire, insects) of the growth periods and is in limits of 10-15% for the country as a whole, but could exceed 25-30% for large regions with weather anomalies of the vegetation periods. Uncertainty within the LEA was assessed for all

  14. The Legacy of Invasive Species on Ecosystem Carbon Dynamics in a Restored Tallgrass Prairie

    NASA Astrophysics Data System (ADS)

    Matamala, R.; Graham, S.; Cook, D.; Gonzalez-Meler, M.

    2008-12-01

    Restoration of degraded grassland and prairie ecosystems represents a target sink for offsetting rising atmospheric CO2 levels by increasing carbon sequestration in C-depleted soils, as two-thirds of the biomass is allocated belowground. When considering controls on ecosystem C cycling, biodiversity-led productivity has the potential to be a strong biotic influence. However, invasive species can disrupt ecosystem processes by exhibiting functional characteristics which are distinct from their native counterparts. Invasibility has been linked to disturbance history, which might lead to additional vulnerability of managed lands. The restoration of tallgrass prairie at Fermilab, Batavia, IL, is a known C sink, accruing soil organic matter at rates 43 g C m-2 y-1 during the past 20 years. This rate integrates environmental, climatic and vegetation variations that occurred over this period. Typically, the tallgrass prairie is dominated by warm season grasses and forbs with sporadic but recurrent years when invasive species increase productivity. We measured net ecosystem exchange, net ecosystem production (NEP) and soil C at a 19- year-old restored tallgrass prairie in a four year study where plant species dominance varied. In the first year, the prairie restoration was a strong C sink with a NEP 438 g C m-2 despite a pronounced spring drought. During the second year, dominance of the invasive biannual Melilotus alba L., led to a shorter growing season that resulted on a 47% reduction in NEP from the previous year. NEP did not recover in the third year, even when M. alba was present but not dominant and a number of prairie species re-emerged, showing the legacy of the previous year disturbance. At this time soil C for all years and a fourth NEP year is being analyzed. These data suggest that biotic factors can exert large memory effects on NEP and possibly influence the sink capacity of restored ecosystems. Management strategies should aim to control biotic limitations

  15. Relationship between carbon and nitrogen isotope ratios for lower trophic ecosystem in marine environments

    NASA Astrophysics Data System (ADS)

    Aita, M. N.; Ishii, R.; Tadokoro, K.; Smith, S. L.; Wada, E.

    2012-12-01

    To examine the relationship between carbon and nitrogen stable isotope ratios (δ13C and δ15N) along food chains, we analyzed using the data from the Oyashio waters at the western North Pacific (samples collected from March to October 2009), the warm-core ring 86-B derived from the Kuroshio extension region (preserved samples), and previously published data from the Gulf of Alaska and Antarctic Ocean. The statistical analysis suggested a common slope of δ15N versus δ13C (Δδ15N/Δδ13C) among regions. We attribute this similarity to common physiological aspects of feeding processes (e.g., kinetic isotope effects inherent in the processes of amino acid synthesis). We also compared seasonal differences seasonal in Δδ15N/Δδ13C for the euphotic layers of the Oyashio waters. The Δδ15N/Δδ13C slope of the food chain during the spring bloom differs from its common value in other seasons. If we could better understand both carbon and nitrogen trophic fractionation within ecosystems, the stable isotope ratios may help to elucidate migratory behavior of higher trophic levels such as fishes in marine ecosystems as well as frame work of biogeochemical cycles in question.

  16. Erosion and vegetation restoration impacts on ecosystem carbon dynamics in South China

    USGS Publications Warehouse

    Tang, X.; Liu, S.; Zhou, G.

    2010-01-01

    To quantify the consequences of erosion and vegetation restoration on ecosystem C dynamics (a key element in understanding the terrestrial C cycle), field measurements were collected since 1959 at two experimental sites set up on highly disturbed barren land in South China. One site had received vegetation restoration (the restored site) while the other received no planting and remained barren (the barren site). The Erosion-Deposition Carbon Model (EDCM) was used to simulate the ecosystem C dynamics at both sites. The on-site observations in 2007 showed that soil organic C (SOC) storage in the top 80-cm soil layer at the barren site was 50.3 ?? 3.5 Mg C ha-1, half that of the restored site. The SOC and surface soil loss by erosion at the restored site from 1959 to 2007 was 3.7 MgC ha-1 and 2.2 cm, respectively-one-third and one-eighth that of the barren site. The on-site C sequestration in SOC and vegetation at the restored site was 0.67 and 2.5 Mg C ha-1 yr-1, respectively, from 1959 to 2007, driven largely by tree growth and high atmospheric N deposition in the study area. Simulated findings suggested that higher N deposition resulted in higher on-site SOC storage in the soil profile (with SOC in the top 20-cm layer increasing more significantly), and higher on-site ecosystem C sequestration as long as N saturation was not reached. Lacking human-induced vegetation recovery, the barren site remained as barren land from 1959 to 2007 and the on-site C decrease was 0.28 Mg C ha-1 yr-1. Our study clearly indicated that vegetation restoration and burial by soil erosion provide a large potential C sink in terrestrial ecosystems. ?? Soil Science Society of America.

  17. Modeling Potential Distribution and Carbon Dynamics of Natural Terrestrial Ecosystems: A Case Study of Turkey

    PubMed Central

    Evrendilek, Fatih; Berberoglu, Suha; Gulbeyaz, Onder; Ertekin, Can

    2007-01-01

    We derived a simple model that relates the classification of biogeoclimate zones, (co)existence and fractional coverage of plant functional types (PFTs), and patterns of ecosystem carbon (C) stocks to long-term average values of biogeoclimatic indices in a time- and space-varying fashion from climate–vegetation equilibrium models. Proposed Dynamic Ecosystem Classification and Productivity (DECP) model is based on the spatial interpolation of annual biogeoclimatic variables through multiple linear regression (MLR) models and inverse distance weighting (IDW) and was applied to the entire Turkey of 780,595 km2 on a 500 m × 500 m grid resolution. Estimated total net primary production (TNPP) values of mutually exclusive PFTs ranged from 108 ± 26 to 891 ± 207 Tg C yr-1 under the optimal conditions and from 16 ± 7 to 58 ± 23 Tg C yr-1 under the growth-limiting conditions for all the natural ecosystems in Turkey. Total NPP values of coexisting PFTs ranged from 178 ± 36 to 1231 ± 253 Tg C yr-1 under the optimal conditions and from 23 ± 8 to 92 ± 31 Tg C yr-1 under the growth-limiting conditions. The national steady state soil organic carbon (SOC) storage in the surface one meter of soil was estimated to range from 7.5 ± 1.8 to 36.7 ± 7.8 Pg C yr-1 under the optimal conditions and from 1.3 ± 0.7 to 5.8 ± 2.6 Pg C yr-1 under the limiting conditions, with the national range of 1.3 to 36.7 Pg C elucidating 0.1% and 2.8% of the global SOC value (1272.4 Pg C), respectively. Our comparisons with literature compilations indicate that estimated patterns of biogeoclimate zones, PFTs, TNPP and SOC storage by the DECP model agree reasonably well with measurements from field and remotely sensed data.

  18. The contribution of litter derived carbon to winter respiration in an alpine tundra ecosystem

    NASA Astrophysics Data System (ADS)

    Wipf, S.; Siegwolf, R.; Esperschuetz, J.; Hagedorn, F.

    2009-04-01

    Although soil respiration rates from snow-covered ecosystems are relatively low, they add up to a substantial fraction of the annual CO2 efflux over the whole winter, which lasts for more than half of the year in the Alpine. It is still unclear, however, which carbon sources are respired preferentially in winter. In a new experiment at the Stillberg tree line research site near Davos, Switzerland, we added 13C-labelled litter (Leucanthemopsis alpina L.) to an alpine tundra ecosystem and measured its contribution to the CO2 efflux at different soil temperatures over winter. The litter was placed either at the soil surface or at 5 cm depth, and soil temperature was decreased by manually reducing snow depth to half of of that of the control plots. Soil respiration was measured by means of a chamber system, and gas samples were analysed for their isotopic composition. Preliminary results indicate that soil respiration in early winter was about half compared to that measured in late fall. Lower soil temperatures under a shallow snow cover further decreased respiration by 40%. Litter addition increased respiration rates by 10 to 30%. At the beginning of the winter season, a higher respiration rate was found for the plots where litter was applied at the surface than at 5 cm soil depth. This effect, however, decreased with the progression of the winter as later measurements have shown. The isotopic composition of the respired CO2 suggests that carbon from the additional litter contributed about 5 to 15% to the total CO2 efflux, and that this fraction was higher in plots with lower soil temperatures. Our results show considerable and non negligible amounts of C-loss in winter. By exploring the effect of the snow cover and soil temperatures on the decomposition of fresh plant litter, this experiment will give a more detailed insight into the environmental controls of soil respiration processes and the sources of respiratory CO2 release in Alpine ecosystems.

  19. Whole-Ecosystem Labile Carbon Production in a North Temperate Deciduous Forest

    NASA Astrophysics Data System (ADS)

    Gough, C. M.; Flower, C. E.; Vogel, C. S.; Dragoni, D.; Curtis, P. S.

    2008-12-01

    Management for forest carbon (C) sequestration requires knowledge of the fate of photosynthetic C. Labile C is an essential intermediary between C assimilation and growth in deciduous forests, accumulating when photosynthetic C supply exceeds demand and later depleting when reallocated to growth during periods of depressed photosynthesis. We developed a new approach that combined meteorological and biometric C cycling data for a mixed deciduous forest in Michigan, USA, to provide novel estimates of whole-ecosystem labile C production (PLC) and reallocation to growth inferred from the temporal imbalance between carbon supply from canopy net C assimilation (Ac) and C demand for net primary production (NPP). We substantiated these estimates with measurements of Populus grandidentata and Quercus rubra wood non-structural carbohydrate (NSC) concentration and mass over two years. Our analysis showed that half of annual Ac was allocated to PLC rather than to immediate growth. Labile C produced during the latter half of summer later supported dormant-season growth and respiration, with 35% of NPP in a given year requiring labile C stored during previous years. Seasonal changes in wood NSC concentration and mass generally corroborated patterns of labile C production and reallocation to growth. We observed a negative relationship between current-year PLC and NPP, indicating that disparities between same-year meteorological and biometric net ecosystem production (NEP) estimates can arise when C assimilated via photosynthesis, a flux incorporated into meteorological NEP estimates, is diverted away from NPP, a flux included in biometric NEP estimates, and instead allocated to PLC. A large, annually recharging pool of labile C also may buffer growth from climate conditions that immediately affect Ac. We conclude that a broader understanding of labile C production and reallocation across ecosystems may be important to interpreting lagged canopy C cycling and growth processes.

  20. Viral Regulation of Prokaryotic Carbon Metabolism in a Hypereutrophic Freshwater Reservoir Ecosystem (Villerest, France)

    PubMed Central

    Pradeep Ram, Angia Sriram; Colombet, Jonathan; Perriere, Fanny; Thouvenot, Antoine; Sime-Ngando, Télesphore

    2016-01-01

    The current consensus concerning the viral regulation of prokaryotic carbon metabolism is less well-studied, compared to substrate availability. We explored the seasonal and vertical distribution of viruses and its relative influence on prokaryotic carbon metabolism in a hypereutrophic reservoir, Lake Villerest (France). Flow cytometry and transmission electron microscopy (TEM) analyses to determine viral abundance (VA; range = 6.1–63.5 × 107 ml-1) and viral infection rates of prokaryotes (range = 5.3–32%) respectively suggested that both the parameters varied more significantly with depths than with seasons. Prokaryotic growth efficiency (PGE, considered as a proxy of prokaryotic carbon metabolism) calculated from prokaryotic production and respiration measurements (PGE = prokaryotic production/[prokaryotic production + prokaryotic respiration] × 100) varied from 14 to 80% across seasons and depths. Viruses through selective lyses had antagonistic impacts on PGE by regulating key prokaryotic metabolic processes (i.e., production and respiration). Higher viral lysis accompanied by higher respiration rates and lower PGE in the summer (mean = 22.9 ± 10.3%) than other seasons (mean = 59.1 ± 18.6%), led to significant loss of carbon through bacterial-viral loop and shifted the reservoir system to net heterotrophy. Our data therefore suggests that the putative adverse impact of viruses on the growth efficiency of the prokaryotic community can have strong implications on nutrient flux patterns and on the overall ecosystem metabolism in anthropogenic dominated aquatic systems such as Lake Villerest. PMID:26903963

  1. Viral Regulation of Prokaryotic Carbon Metabolism in a Hypereutrophic Freshwater Reservoir Ecosystem (Villerest, France).

    PubMed

    Pradeep Ram, Angia Sriram; Colombet, Jonathan; Perriere, Fanny; Thouvenot, Antoine; Sime-Ngando, Télesphore

    2016-01-01

    The current consensus concerning the viral regulation of prokaryotic carbon metabolism is less well-studied, compared to substrate availability. We explored the seasonal and vertical distribution of viruses and its relative influence on prokaryotic carbon metabolism in a hypereutrophic reservoir, Lake Villerest (France). Flow cytometry and transmission electron microscopy (TEM) analyses to determine viral abundance (VA; range = 6.1-63.5 × 10(7) ml(-1)) and viral infection rates of prokaryotes (range = 5.3-32%) respectively suggested that both the parameters varied more significantly with depths than with seasons. Prokaryotic growth efficiency (PGE, considered as a proxy of prokaryotic carbon metabolism) calculated from prokaryotic production and respiration measurements (PGE = prokaryotic production/[prokaryotic production + prokaryotic respiration] × 100) varied from 14 to 80% across seasons and depths. Viruses through selective lyses had antagonistic impacts on PGE by regulating key prokaryotic metabolic processes (i.e., production and respiration). Higher viral lysis accompanied by higher respiration rates and lower PGE in the summer (mean = 22.9 ± 10.3%) than other seasons (mean = 59.1 ± 18.6%), led to significant loss of carbon through bacterial-viral loop and shifted the reservoir system to net heterotrophy. Our data therefore suggests that the putative adverse impact of viruses on the growth efficiency of the prokaryotic community can have strong implications on nutrient flux patterns and on the overall ecosystem metabolism in anthropogenic dominated aquatic systems such as Lake Villerest. PMID:26903963

  2. High carbon dioxide uptake by subtropical forest ecosystems in the East Asian monsoon region

    PubMed Central

    Yu, Guirui; Chen, Zhi; Piao, Shilong; Peng, Changhui; Ciais, Philippe; Wang, Qiufeng; Li, Xuanran; Zhu, Xianjin

    2014-01-01

    Temperate- and high-latitude forests have been shown to contribute a carbon sink in the Northern Hemisphere, but fewer studies have addressed the carbon balance of the subtropical forests. In the present study, we integrated eddy covariance observations established in the 1990s and 2000s to show that East Asian monsoon subtropical forests between 20°N and 40°N represent an average net ecosystem productivity (NEP) of 362 ± 39 g C m−2 yr−1 (mean ± 1 SE). This average forest NEP value is higher than that of Asian tropical and temperate forests and is also higher than that of forests at the same latitudes in Europe–Africa and North America. East Asian monsoon subtropical forests have comparable NEP to that of subtropical forests of the southeastern United States and intensively managed Western European forests. The total NEP of East Asian monsoon subtropical forests was estimated to be 0.72 ± 0.08 Pg C yr−1, which accounts for 8% of the global forest NEP. This result indicates that the role of subtropical forests in the current global carbon cycle cannot be ignored and that the regional distributions of the Northern Hemisphere's terrestrial carbon sinks are needed to be reevaluated. The young stand ages and high nitrogen deposition, coupled with sufficient and synchronous water and heat availability, may be the primary reasons for the high NEP of this region, and further studies are needed to quantify the contribution of each underlying factor. PMID:24639529

  3. Public Review Draft: A Method for Assessing Carbon Stocks, Carbon Sequestration, and Greenhouse-Gas Fluxes in Ecosystems of the United States Under Present Conditions and Future Scenarios

    USGS Publications Warehouse

    Bergamaschi, Brian A.; Bernknopf, Richard; Clow, David; Dye, Dennis; Faulkner, Stephen; Forney, William; Gleason, Robert; Hawbaker, Todd; Liu, Jinxun; Liu, Shu-Guang; Prisley, Stephen; Reed, Bradley; Reeves, Matthew; Rollins, Matthew; Sleeter, Benjamin; Sohl, Terry; Stackpoole, Sarah; Stehman, Stephen; Striegl, Rob; Wein, Anne; Zhu, Zhi-Liang

    2010-01-01

    The Energy Independence and Security Act of 2007 (EISA), Section 712, authorizes the U.S. Department of the Interior to develop a methodology and conduct an assessment of the Nation's ecosystems focusing on carbon stocks, carbon sequestration, and emissions of three greenhouse gases (GHGs): carbon dioxide, methane, and nitrous oxide. The major requirements include (1) an assessment of all ecosystems (terrestrial systems, such as forests, croplands, wetlands, shrub and grasslands; and aquatic ecosystems, such as rivers, lakes, and estuaries), (2) an estimation of annual potential capacities of ecosystems to increase carbon sequestration and reduce net GHG emissions in the context of mitigation strategies (including management and restoration activities), and (3) an evaluation of the effects of controlling processes, such as climate change, land use and land cover, and wildlfires. The purpose of this draft methodology for public review is to propose a technical plan to conduct the assessment. Within the methodology, the concepts of ecosystems, carbon pools, and GHG fluxes used for the assessment follow conventional definitions in use by major national and international assessment or inventory efforts. In order to estimate current ecosystem carbon stocks and GHG fluxes and to understand the potential capacity and effects of mitigation strategies, the method will use two time periods for the assessment: 2001 through 2010, which establishes a current ecosystem GHG baseline and will be used to validate the models; and 2011 through 2050, which will be used to assess future potential conditions based on a set of projected scenarios. The scenario framework is constructed using storylines of the Intergovernmental Panel on Climate Change (IPCC) Special Report Emission Scenarios (SRES), along with initial reference land-use and land-cover (LULC) and land-management scenarios. An additional three LULC and land-management mitigation scenarios will be constructed for each

  4. Long term carbon fluxes in south eastern U.S. pine ecosystems.

    NASA Astrophysics Data System (ADS)

    Bracho, R. G.; Martin, T.; Gonzalez-Benecke, C. A.; Sharp, J.

    2015-12-01

    Forests in the southeastern U.S. are a critical component of the national carbon balance storing a third of the total forest carbon (C) in conterminous USA. South eastern forests occupy 60% of the land area, with a large fraction dominated by the genus Pinus distributed in almost equal proportions of naturally-regenerated and planted stands. These stands often differ in structure (e.g., stem density, leaf area index (LAI)) and in the intensity with which they are managed (e.g. naturally-regenerated, older pine stands are often managed less intensively, with prescribed fire). We measured C fluxes using the eddy covariance approach (net ecosystem production, -NEP) in planted (Pinus elliottii var. elliottii) and naturally-regenerated mixed stand of long leaf (Pinus palustris Mill) and slash pine (Pinus elliottii var. elliottii) accompanied by biometric estimations of C balance. Measurements spanned more than a decade and included interannual climatic variability ranging from severe droughts (e.g. Palmer Drought severity index (PDSI) averaged -2.7 from January 2000 to May 2002, and -3.3 from June 2006 to April 2008), to years with tropical storms. Annual NEP for the older, naturally-regenerated stand fluctuated from -1.60 to -5.38 Mg C ha-1 yr-1 with an average of -2.73 ± 1.17 Mg C ha-1 yr-1 while in plantations after canopy closure NEP fluctuated from -4.0 to -8.2 Mg C ha-1 yr-1 with an average of -6.17 ± 1.34 Mg C ha-1 yr-1. Annual NEP in naturally-regenerated pine was mainly driven by a combination of water availability and understory burning while in plantations it was driven by water availability after canopy closure. Woody and above ground net primary productivity (NPP) followed gross ecosystem carbon exchange (GEE) in both ecosystems. Naturally-regenerated and planted pine are a strong carbon sink under the current management and environmental fluctuations accumulating 28 and 130 Mg C ha-1 in a decade, respectively, and are among the most productive forests in

  5. Stress differentially impacts reserve pools and root exudation: implications for ecosystem functioning and carbon balance

    NASA Astrophysics Data System (ADS)

    Landhäusser, Simon; Karst, Justine; Wiley, Erin; Gaster, Jacob

    2016-04-01

    Environmental stress can influence carbon assimilation and the accumulation and distribution of carbon between growth, reserves, and exudation; however, it is unclear how these processes vary by different stress types. Partitioning of carbon to growth and reserves in plants might also vary between different organs. Roots reserves are of particular interest as they link the plant with the soil carbon cycle through exudation. Simple models of diffusion across concentration gradients predict the more C reserves in roots, the more C should be exuded from roots. However, the mechanisms underlying the accumulation and loss of C from roots may differ depending on the stress experienced by the plants. In a controlled study we tested whether different types of stresses (shade, cold soil, and drought) have differential effects on the distribution, abundance, and form (sugar vs. starch) of carbohydrates in seedlings, and whether these changes alone could explain differences in root exudation between stress types. Non-structural carbohydrate (NSC) concentration and pool sizes varied by stress type and between organs. Mass-specific C exudation increased with fine root sugar concentration; however, stress type affected exudation independently of reserve concentration. Seedlings exposed to cold soils exuded the most C on a per root mass basis followed by shade and drought. Through 13C labeling, we also found that depending on the stress type, aspen seedlings may be less able to control the loss of C to the soil compared with unstressed seedlings, resulting in more C leaked to the rhizosphere. The loss of C beyond that predicted by simple concentration gradients might have important implications for ecosystem functioning and carbon balance. If stressed plants lose proportionally more carbon to the soil, existing interactions between plants and soils may decouple under stress, and may include unexpected C fluxes between trees, soils and the atmosphere with a changing climate.

  6. Effects of Conversion from Boreal Forest to Arctic Steppe on Soil Communities and Ecosystem Carbon Pools

    NASA Astrophysics Data System (ADS)

    Han, P. D.; Natali, S.; Schade, J. D.; Zimov, N.; Zimov, S. A.

    2014-12-01

    The end of the Pleistocene marked the extinction of a great variety of arctic megafauna, which, in part, led to the conversion of arctic grasslands to modern Siberian larch forest. This shift may have increased the vulnerability of permafrost to thawing because of changes driven by the vegetation shift; the higher albedo of grassland and low insulation of snow trampled by animals may have decreased soil temperatures and reduced ground thaw in the grassland ecosystem, resulting in protection of organic carbon in thawed soil and permafrost. To test these hypothesized impacts of arctic megafauna, we examined an experimental reintroduction of large mammals in northeast Siberia, initiated in 1988. Pleistocene Park now contains 23 horses, three musk ox, one bison, and several moose in addition to the native fauna. The park is 16 square km with a smaller enclosure (< 1 km) where animals spend most of their time and our study was focused. We measured carbon-pools in forested sites (where scat surveys showed low animal use), and grassy sites (which showed higher use), within the park boundaries. We also measured thaw depth and documented the soil invertebrate communities in each ecosystem. There was a substantial difference in number of invertebrates per kg of organic soil between the forest (600 ± 250) and grassland (300 ± 250), though these differences were not statistically significant they suggest faster nutrient turnover in the forest or a greater proportion of decomposition by invertebrates than other decomposers. While thaw depth was deeper in the grassland (60 ± 4 cm) than in the forest (40 ± 6 cm), we did not detect differences in organic layer depth or percent organic matter between grassland and forest. However, soil in the grassland had higher bulk density, and higher carbon stocks in the organic and mineral soil layers. Although deeper thaw depth in the grassland suggests that more carbon is available to microbial decomposers, ongoing temperature monitoring

  7. Incorporating Ecosystem Processes Controlling Carbon Balance Into Models of Coupled Human-Natural Systems

    NASA Astrophysics Data System (ADS)

    Currie, W.; Brown, D. G.; Brunner, A.; Fouladbash, L.; Hadzick, Z.; Hutchins, M.; Kiger, S. E.; Makino, Y.; Nassauer, J. I.; Robinson, D. T.; Riolo, R. L.; Sun, S.

    2012-12-01

    A key element in the study of coupled human-natural systems is the interactions of human populations with vegetation and soils. In human-dominated landscapes, vegetation production and change results from a combination of ecological processes and human decision-making and behavior. Vegetation is often dramatically altered, whether to produce food for humans and livestock, to harvest fiber for construction and other materials, to harvest fuel wood or feedstock for biofuels, or simply for cultural preferences as in the case of residential lawns with sparse trees in the exurban landscape. This alteration of vegetation and its management has a substantial impact on the landscape carbon balance. Models can be used to simulate scenarios in human-natural systems and to examine the integration of processes that determine future trajectories of carbon balance. However, most models of human-natural systems include little integration of the human alteration of vegetation with the ecosystem processes that regulate carbon balance. Here we illustrate a few case studies of pilot-study models that strive for this integration from our research across various types of landscapes. We focus greater detail on a fully developed research model linked to a field study of vegetation and soils in the exurban residential landscape of Southeastern Michigan, USA. The field study characterized vegetation and soil carbon storage in 5 types of ecological zones. Field-observed carbon storage in the vegetation in these zones ranged widely, from 150 g C/m2 in turfgrass zones, to 6,000 g C/m2 in zones defined as turfgrass with sparse woody vegetation, to 16,000 g C/m2 in a zone defined as dense trees and shrubs. Use of these zones facilitated the scaling of carbon pools to the landscape, where the areal mixtures of zone types had a significant impact on landscape C storage. Use of these zones also facilitated the use of the ecosystem process model Biome-BGC to simulate C trajectories and also

  8. Baseline and projected future carbon storage and greenhouse-gas fluxes in ecosystems of the Western United States

    USGS Publications Warehouse

    Zhu, Zhi-Liang; Reed, Bradley C.

    2012-01-01

    This assessment was conducted to fulfill the requirements of section 712 of the Energy Independence and Security Act (EISA) of 2007 and to improve understanding of carbon and greenhouse gas (GHG) fluxes in ecosystems of the Western United States. The assessment examined carbon storage, carbon fluxes, and other GHG fluxes (methane and nitrous oxide) in all major terrestrial ecosystems (forests, grasslands/shrublands, agricultural lands, and wetlands) and aquatic ecosystems (rivers, streams, lakes, reservoirs, and coastal waters) in two time periods: baseline (generally in the first half of the 2010s) and future (projections from baseline to 2050). The assessment was based on measured and observed data collected by the U.S. Geological Survey (USGS) and many other agencies and organizations and used remote sensing, statistical methods, and simulation models.

  9. The combined influence of the main European circulation patterns on carbon uptake by ecosystems

    NASA Astrophysics Data System (ADS)

    Bastos, Ana; Gouveia, Célia; Trigo, Ricardo

    2014-05-01

    Understanding how natural climate variability affects carbon uptake by land and ocean pools is particularly relevant to better characterize human impact on the carbon cycle. Recently, we have contributed to assess the major role played by the El-Niño/Southern Oscillation in driving inter-annual variability (IAV) of carbon uptake by land ecosystems and significantly influencing global CO2 air-borne fraction [1]. Despite the prominent role played by ENSO, other important teleconnections on the hemispheric scale have deserved less attention. On the European scale, the main mode of variability is the North-Atlantic Oscillation (NAO), which controls storm tracks position and drives changes in temperature and precipitation over the whole region, affecting vegetation dynamics [2]. Besides NAO, a few additional large scale circulation patterns the Scandinavian (SC) and East-Atlantic (EA) Patterns, are also known to influence significantly the European climate [3]. Different combinations of these teleconnection polarities have been recently shown to modulate the overall role of the NAO impact location and strength, thus affecting winter temperature and precipitation patterns over Europe [4]. This work aims to answer the following questions: (i) how do NAO, EA and SC affect vegetation carbon uptake IAV? (ii) do the interactions between these three modes have a significant impact on land CO2 IAV? (iii) what is the contribution of the different physical variables to ecosystems' response to these modes? (iv) how well do the state-of-the-art Earth System Models (ESMs) from CMIP5 represent these climate variability modes and the corresponding carbon fluxes? We first analyze observational data to assess the relationships between the different combinations of NAO, SC and EA polarities and IAV of gross and net primary production (GPP and NPP, respectively), as well as the most relevant driving factors of ecosystem's response to those variability patterns. Although the winter state

  10. Implications of accounting for land use in simulations of ecosystem carbon cycling in Africa

    NASA Astrophysics Data System (ADS)

    Lindeskog, M.; Arneth, A.; Bondeau, A.; Waha, K.; Seaquist, J.; Olin, S.; Smith, B.

    2013-11-01

    Dynamic global vegetation models (DGVMs) are important tools for modelling impacts of global change on ecosystem services. However, most models do not take full account of human land management and land use and land cover changes (LULCCs). We integrated croplands and pasture and their management and natural vegetation recovery and succession following cropland abandonment into the LPJ-GUESS DGVM. The revised model was applied to Africa as a case study to investigate the implications of accounting for land use on net ecosystem carbon balance (NECB) and the skill of the model in describing agricultural production and reproducing trends and patterns in vegetation structure and function. The seasonality of modelled monthly fraction of absorbed photosynthetically active radiation (FPAR) was shown to agree well with satellite-inferred normalised difference vegetation index (NDVI). In regions with a large proportion of cropland, the managed land addition improved the FPAR vs. NDVI fit significantly. Modelled 1991-1995 average yields for the seven most important African crops, representing potential optimal yields limited only by climate forcings, were generally higher than reported FAO yields by a factor of 2-6, similar to previous yield gap estimates. Modelled inter-annual yield variations during 1971-2005 generally agreed well with FAO statistics, especially in regions with pronounced climate seasonality. Modelled land-atmosphere carbon fluxes for Africa associated with land use change (0.07 PgC yr-1 release to the atmosphere for the 1980s) agreed well with previous estimates. Cropland management options (residue removal, grass as cover crop) were shown to be important to the land-atmosphere carbon flux for the 20th century.

  11. Holocene Carbon Fluxes and Palaeoproductivity in Aquatic Ecosystems: a Multiproxy, Palaeolimnological Approach

    NASA Astrophysics Data System (ADS)

    Mackay, A. W.; Leng, M. J.; Morley, D. W.; Piotrowska, N.; Rioual, P.; Swann, G. E. A.

    2014-12-01

    Inland waters act as an important control on the global carbon cycle. Deep tectonic lakes may provide a key link between short-term and long-term carbon cycles as buried carbon is essentially locked away from the atmosphere over geological timescales. Here we investigate Holocene carbon dynamics in one of the worlds most important lake ecosystems, Lake Baikal, Siberia. We test the hypothesis that multiple factors play a significant role in determining long-term carbon dynamics in central Asia, and that these factors change in importance over time. Carbon isotopes (δ13C), percentage total organic carbon (%TOC) were analysed during combustion in a Carlo Erba 1500 on-line to a VG Triple Trap and dual-inlet mass spectrometer. A multi-decadal organic geochemistry record (%TOC; δ13C, C/N ratios) was determined on Holocene sediments extracted from a slope terrace c. 600 m deep. Age-depth modelling on radiocarbon-dated pollen extracts was undertaken using 'Bacon', which takes into account variable sediment accumulation rates. Carbon mass accumulation rates (CMAR; g cm-2 yr-1) were estimated at a centennial scale resolution. δ13C values were routinely higher during cool glacial periods (-26 ‰) than during warmer climates (-28 ‰) linked to changes in carbon sources. Diatom productivity & boreal forest expansion were strongly associated with δ13C variability during the early Holocene, but after 8 kyr BP, no relationships are apparent. CMAR were highest during the early Holocene (11.7 - 8 kyr BP) although rates fluctuated considerably. Peak values of 12.5 g cm-2 yr-1 were observed at 10.35 kyr BP before a rapid decline to c. 5.2 g cm-2 yr-1 at 10.05 kyr BP. CMAR declined to lowest Holocene values of 3.5 g cm-2 yr-1 by 3.9 kyr BP at the same time as maximum δ13C values (-27.0 ‰), indicative of low palaeoproductivity. Our data show that measures of palaeoproductivity in Lake Baikal are complex, and during the early Holocene are strongly associated with allochthonous

  12. Effects of Permafrost Thaw on Net Ecosystem Carbon Balance in a Subarctic Peatland

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Roulet, N. T.; Moore, T. R.

    2014-12-01

    This research is to assess changes in net ecosystem carbon balance (NECB) with permafrost thaw in northern peatland: in particular how changes in C biogeochemistry influence NECB. Thawed transects associated with varying stages of permafrost thaw: from palsas with intact permafrost (P), through edge of palsa (EP), dry lawn (DL), wet lawn (WL), edge of thawed pond (ET), pond sedges (PS), to several thawed ponds (TP) in a subarctic peatland in northern Quebec were sampled in the snow free seasons of 2013 and 2014. The exchange of CO2 and CH4, vegetation, dissolved organic C (DOC) concentration and biodegradability, active layer depth, air and peat temperatures, water table depth (WT), pH, and conductivity were measured. Peat temperatures were quite similar among different locations, but the WT decreased significantly along the transect creating varied environmental conditions that supporting different plant communities. From dry to wet area, vegetation abundance and biomass showed reductions of shrubs and lichens, and increases of Sphagnum, grasses and sedges. Pore water pH increased from dry to wet area, and conductivity slightly decreased. Wet thaw area WL, ET and PS had relatively higher season gross ecosystem production (GEP) and higher season ecosystem respiration (ER), but relative similar net ecosystem CO2 exchange (NEE). Only TP had a significant higher positive season NEE. Palsa was the only CH4 sink, and quite high CH4 emissions were found after it thawed. CH4-C release significantly increased from dry to wet in thawed area, which even several times bigger than total C exchange in ET and PS. Generally, wet area had higher DOC concentration and higher DOC biodegradability indicated by lower SUVA254 (except PS which received great influence from pond). All components in the NECB (GEP, ER, CH4, DOC) increased significantly in magnitude from palsa to wet thawed area, and ecosystem C sink turned into source as palsa thawed into PS and TP. These results

  13. High elastic polyurethane/carbon nanotube composite laminate for structure health monitoring by gain shifting of antenna sensing element

    NASA Astrophysics Data System (ADS)

    Olejnik, Robert; Slobodian, Petr; Matyas, Jiri; Gorakh Babar, Dipak

    2016-03-01

    The composite of carbon nanotubes and polyurethane (PU) was prepared by simple filtration technique. The PU nonwoven filtration membrane was prepared by electrospinning. A layer of carbon nanotubes was prepared by vacuum filtration on the surface of PU membrane. The resulting composite was subsequently placed on highly elastic polyurethane substrate. The contribution shows an efficient method of preparing the sensing element for monitoring the state of strain of loaded structures by using highly elastic polyurethane / carbon nanotubes composite. This sensor has been involved as passive antenna with stable resonance frequency of 650 MHz. When it is get deformed in the range from 0 to 3.5% the sensor gain was changing from -39 dB to - 19.45 dB. But if it is get deformed by 15% and again measured strain from 0 to 3.5%, sensor gain was changing from -33 dB to -12.3 dB, which clearly indicates the damage of structure.

  14. Carbon nanotube-based mode-locked wavelength-switchable fiber laser via net gain cross section alteration

    NASA Astrophysics Data System (ADS)

    Latif, A. A.; Mohamad, H.; Abu Bakar, M. H.; Muhammad, F. D.; Mahdi, M. A.

    2016-02-01

    We have proposed and demonstrated a carbon nanotube-based mode-locked erbium-doped fiber laser with switchable wavelength in the C-band wavelength region by varying the net gain cross section of erbium. The carbon nanotube is coated on a tapered fiber to form the saturable absorber for the purpose of mode-locking by exploiting the concept of evanescent field interaction on the tapered fiber with the carbon nanotube in a ring cavity configuration. The propagation loss is adjusted by inducing macrobend losses of the optical fiber in the cavity through a fiber spooling technique. Since the spooling radius can be gradually adjusted to achieve continuous tuning of attenuation, this passive tuning approach can be an alternative to optical tunable attenuator, with freedom of external device integration into the laser cavity. Based on this alteration, the net gain cross section of the laser system can be tailored to three different lasing wavelength ranges; 1533, 1560 nm and both (1533 and 1560 nm) with the minimum pulse duration of 734 fs. The proposed design is simple and stable with high beam quality and good reliability for multiple applications.

  15. The loss of Scottish peatlands: Implications for long-term net gains in coastal Blue Carbon stocks.

    NASA Astrophysics Data System (ADS)

    Austin, William; Smeaton, Craig; Winterton, Cathy; Clarke, Jessica; Smith, Laura; Ward, Hannah; Bennett, Keith

    2016-04-01

    Nearly 66% of Scotland is covered by peat and organic soils, representing over 50% of the UK's soil carbon stocks. Peatland erosion, while partly a natural process, is also accelerated by human activities, such as land management and potentially by the impacts of climate change. We present evidence from the voes (sea lochs or fjords) of Shetland's west coast to suggest that this process may have accelerated since Medieval times. Our work is supported by the analyses of short sediment (Craib) cores (triplicate coring) recovered from 17 sites. We present preliminary chronologies supported by radiocarbon dating and sediment characteristics that highlight both changes in the rate of accumulation and source of sedimentary organic carbon to the west Shetland voes during the late Holocene. Scottish coastal sediments contain a significant Blue Carbon stock, a significant proportion of which derives directly from terrestrial sources. The loss of peatland carbon represents a potentially important contribution (i.e. net gain) in refractory carbon within the marine environment and we present preliminary estimates to assess the significance of these large-scale transfers to the coastal ocean.

  16. Cyclic Occurrence of Fire and Its Role in Carbon Dynamics along an Edaphic Moisture Gradient in Longleaf Pine Ecosystems

    PubMed Central

    Whelan, Andrew; Mitchell, Robert; Staudhammer, Christina; Starr, Gregory

    2013-01-01

    Fire regulates the structure and function of savanna ecosystems, yet we lack understanding of how cyclic fire affects savanna carbon dynamics. Furthermore, it is largely unknown how predicted changes in climate may impact the interaction between fire and carbon cycling in these ecosystems. This study utilizes a novel combination of prescribed fire, eddy covariance (EC) and statistical techniques to investigate carbon dynamics in frequently burned longleaf pine savannas along a gradient of soil moisture availability (mesic, intermediate and xeric). This research approach allowed us to investigate the complex interactions between carbon exchange and cyclic fire along the ecological amplitude of longleaf pine. Over three years of EC measurement of net ecosystem exchange (NEE) show that the mesic site was a net carbon sink (NEE = −2.48 tonnes C ha−1), while intermediate and xeric sites were net carbon sources (NEE = 1.57 and 1.46 tonnes C ha−1, respectively), but when carbon losses due to fuel consumption were taken into account, all three sites were carbon sources (10.78, 7.95 and 9.69 tonnes C ha−1 at the mesic, intermediate and xeric sites, respectively). Nonetheless, rates of NEE returned to pre-fire levels 1–2 months following fire. Consumption of leaf area by prescribed fire was associated with reduction in NEE post-fire, and the system quickly recovered its carbon uptake capacity 30–60 days post fire. While losses due to fire affected carbon balances on short time scales (instantaneous to a few months), drought conditions over the final two years of the study were a more important driver of net carbon loss on yearly to multi-year time scales. However, longer-term observations over greater environmental variability and additional fire cycles would help to more precisely examine interactions between fire and climate and make future predictions about carbon dynamics in these systems. PMID:23335986

  17. Cyclic occurrence of fire and its role in carbon dynamics along an edaphic moisture gradient in longleaf pine ecosystems.

    PubMed

    Whelan, Andrew; Mitchell, Robert; Staudhammer, Christina; Starr, Gregory

    2013-01-01

    Fire regulates the structure and function of savanna ecosystems, yet we lack understanding of how cyclic fire affects savanna carbon dynamics. Furthermore, it is largely unknown how predicted changes in climate may impact the interaction between fire and carbon cycling in these ecosystems. This study utilizes a novel combination of prescribed fire, eddy covariance (EC) and statistical techniques to investigate carbon dynamics in frequently burned longleaf pine savannas along a gradient of soil moisture availability (mesic, intermediate and xeric). This research approach allowed us to investigate the complex interactions between carbon exchange and cyclic fire along the ecological amplitude of longleaf pine. Over three years of EC measurement of net ecosystem exchange (NEE) show that the mesic site was a net carbon sink (NEE = -2.48 tonnes C ha(-1)), while intermediate and xeric sites were net carbon sources (NEE = 1.57 and 1.46 tonnes C ha(-1), respectively), but when carbon losses due to fuel consumption were taken into account, all three sites were carbon sources (10.78, 7.95 and 9.69 tonnes C ha(-1) at the mesic, intermediate and xeric sites, respectively). Nonetheless, rates of NEE returned to pre-fire levels 1-2 months following fire. Consumption of leaf area by prescribed fire was associated with reduction in NEE post-fire, and the system quickly recovered its carbon uptake capacity 30-60 days post fire. While losses due to fire affected carbon balances on short time scales (instantaneous to a few months), drought conditions over the final two years of the study were a more important driver of net carbon loss on yearly to multi-year time scales. However, longer-term observations over greater environmental variability and additional fire cycles would help to more precisely examine interactions between fire and climate and make future predictions about carbon dynamics in these systems. PMID:23335986

  18. Carbon Cycling Studies in Forest and Rangeland Ecosystems of Northern and Central Coastal California

    NASA Astrophysics Data System (ADS)

    Potter, C.; Klooster, S.; Gross, P.; Hiatt, S.; Genovese, V.

    2008-12-01

    The varied topography and micro-climates of northern and central coastal California result in high biodiversity and many different levels of primary production driving regional carbon cycles. Coastal mountains trap moisture from low clouds and fog in summer to supplement rainfall in winter. This creates a favorable micro-environment for coniferous forests, including the southernmost habitat of the coast redwood (Sequoia sempervirens), which grows mainly on lower north-facing slopes in Big Sur. In rain shadows, forests transition to open oak woodland, and then into the more fire-tolerant chaparral and coast scrub. Field sites for our on-going climate change studies on the California northern and central coasts currently include the University of California Santa Cruz Campus Natural Reserve, the US Forest Service Brazil Ranch, and the University of California Big Creek Reserve. We are conducting research at each of these sites to better understand possible impacts of climate change, including: (1) biological and physical capacity of soils to capture carbon and retain plant-essential nutrients; (2) rates of plant-soil water and carbon cycling and energy flow; and (3) recovery mechanisms for disturbances such as invasive weed species, grazing, and wildfire. The NASA-CASA simulation model based on satellite observations of monthly vegetation cover from the Moderate Resolution Imaging Spectroradiometer (MODIS) was used to estimate carbon cycling for much of the central coast as far north as Mendocino County. Net primary production (NPP) of all vegetation cover was mapped at 30-meter resolution for selected years by combining MODIS and Landsat images across the region. Results show annual NPP predictions of between 200-400 grams C per square meter for coastal scrub and 800-1200 grams C per square meter for coastal evergreen forests, Net ecosystem fluxes of carbon will be presented for the region based on NASA-CASA modeling and field measurements of soil respiration fluxes.

  19. Carbon balance of grazed savanna grassland ecosystem in Welgegund, South Africa

    NASA Astrophysics Data System (ADS)

    Räsänen, Matti; Aurela, Mika; Vakkari, Ville; Beukes, Paul; Van Zyl, Pieter; Josipovic, Micky; Venter, Andrew; Jaars, Kerneels; Siebert, Stefan; Laurila, Tuomas; Tuovinen, Juha-Pekka; Rinne, Janne; Laakso, Lauri

    2016-04-01

    Tropical savannas and grasslands are estimated to contribute significantly to the global primary production of all terrestrial vegetation. It is suggested that semi-arid ecosystems dominate the inter-annual variation of the global land carbon sink. Most of the previous carbon flux measurements of African savannas have focused on the areas around national parks or nature reserves. However, large parts of African savannas and grasslands are used for agriculture or cattle grazing and there is a lack of measurements from these areas. In this study, we present carbon dioxide fluxes measured with the eddy covariance method for three years at a grazed savanna grassland in South Africa. The tree cover around the Welgegund measurement site (26°34'10"S, 26°56'21"E, 1480 m.a.s.l.; www.welgegund.org) was around 15% and it was grazed by cattle and sheep. Weekly monitoring of the measurements produced high quality flux measurements and only 33% of the measured flux values were missing or discarded due to e.g. too small turbulence. The inter-annual variation of yearly carbon balance was high. The carbon balance for the years 2010, 2011 and 2012 were -73, 82 and 167 gC m-2 y-1, respectively. The yearly variation in GPP and respiration followed the changes in precipitation, whereas the yearly variation in NEE was not explained by the changes in annual precipitation, the length of rainy season or peak NDVI. However, the number of days when soil was wet, seems to relate to the annual sum of NEE.

  20. Fire alters ecosystem carbon and nutrients but not plant nutrient stoichiometry or composition in tropical savanna.

    PubMed

    Pellegrini, Adam F A; Hedin, Lars O; Staver, A Carla; Govender, Navashni

    2015-05-01

    Fire and nutrients interact to influence the global distribution and dynamics of the savanna biome, but the results of these interactions are both complex and poorly known. A critical but unresolved question is whether short-term losses of carbon and nutrients caused by fire can trigger long-term and potentially compensatory responses in the nutrient stoichiometry of plants, or in the abundance of dinitrogen-fixing trees. There is disagreement in the literature about the potential role of fire on savanna nutrients, and, in turn, on plant stoichiometry and composition. A major limitation has been the lack of fire manipulations over time scales sufficiently long for these interactions to emerge. We use a 58-year, replicated, large-scale, fire manipulation experiment in Kruger National Park (South Africa) in savanna to quantify the effect of fire on (1) distributions of carbon, nitrogen, and phosphorus at the ecosystem scale; (2) carbon: nitrogen: phosphorus stoichiometry of above- and belowground tissues of plant species; and (3) abundance of plant functional groups including nitrogen fixers. Our results show dramatic effects of fire on the relative distribution of nutrients in soils, but that individual plant stoichiometry and plant community composition remained unexpectedly resilient. Moreover, measures of nutrients and carbon stable isotopes allowed us to discount the role of tree cover change in favor of the turnover of herbaceous biomass as the primary mechanism that mediates a transition from low to high 'soil carbon and nutrients in the absence of fire. We conclude that, in contrast to extra-tropical grasslands or closed-canopy forests, vegetation in the savanna biome may be uniquely adapted to nutrient losses caused by recurring fire. PMID:26236841

  1. Mineral carbonation: energy costs of pretreatment options and insights gained from flow loop reaction studies

    SciTech Connect

    Penner, Larry R.; O'Connor, William K.; Dahlin, David C.; Gerdemann, Stephen J.; Rush, Gilbert E.

    2004-01-01

    Sequestration of carbon as a stable mineral carbonate has been proposed to mitigate environmental concerns that carbon dioxide may with time escape from its sequestered matrix using alternative sequestration technologies. A method has been developed to prepare stable carbonate products by reacting CO2 with magnesium silicate minerals in aqueous bicarbonate/chloride media at high temperature and pressure. Because this approach is inherently expensive due to slow reaction rates and high capital costs, studies were conducted to improve the reaction rates through mineral pretreatment steps and to cut expenses through improved reactor technology. An overview is given for the estimated cost of the process including sensitivity to grinding and heating as pretreatment options for several mineral feedstocks. The energy costs are evaluated for each pretreatment in terms of net carbon avoided. New studies with a high-temperature, high-pressure flow-loop reactor have yielded information on overcoming kinetic barriers experienced with processing in stirred autoclave reactors. Repeated tests with the flow-loop reactor have yielded insights on wear and failure of system components, on challenges to maintain and measure flow, and for better understanding of the reaction mechanism.

  2. Hurricane impacts on tree mortality and carbon cycling in coastal forest ecosystems

    NASA Astrophysics Data System (ADS)

    Chambers, J. Q.; Negron-Juarez, R. I.; Zeng, H.; Henkel, T. K.; Baker, D. B.; Saatchi, S. S.

    2008-12-01

    Forests recovering from land-use, the encroachment of woody vegetation, and other ecological processes, cause terrestrial ecosystems to act as a net sinks for atmospheric carbon dioxide. Changes in the strength and sign of this sink over the coming decades are difficult to predict. One process that can act to diminish the terrestrial carbon sink is an increase in disturbance frequency and intensity, which transfers greater amounts of biomass from live to dead respiring pools, and shifts the forest size distribution toward smaller average tree size and lower biomass stocks. A number of studies predict an increase in the frequency of extreme weather events and the intensity of tropical cyclones under a warming climate, which may ultimately result in elevated forest disturbance regimes. Here we present a novel synthetic approach combining detailed ecological field investigations with remote sensing image analysis to provide spatially explicit estimates of forest damage, tree mortality, and biomass loss for U.S. landfalling hurricanes. Analysis results for Hurricane Katrina predicted the death and severe structural damage to about 320 million trees, representing a 100 Tg carbon transfer from live to dead biomass. Under the same wind-field, forest susceptibility to damage was highly tree species dependent, with cypress-tupelo swamp forests exhibiting the greatest resistance. Statistical models were useful for separating storm surge from wind effects on coastal forests. Similar analyses are currently underway for Hurricane Gustav, and will also be presented.

  3. Net ecosystem exchange, gross primary production, and ecosystem respiration of carbon dioxide during barley growing season in rice-barley paddy field of Korea

    NASA Astrophysics Data System (ADS)

    Jung, M.; Shim, K.; Min, S.; Kim, Y.; Kim, S.; So, K.

    2013-12-01

    This study was conducted to measure carbon dioxide exchange between customarily cultivated rice-barley double cropping paddy field and the atmosphere during barley growing season (October 2012 and June 2013) and to estimate carbon dioxide fluxes using agro-meteorological factors (temperature, net radiation etc. ) and barley biomass. The carbon dioxide fluxes were quantified by eddy covariance technique in paddy fields with rice-barley double cropping system, located at the Gimje flux site in the southwestern coast of Korea. The total values of net ecosystem carbon dioxide exchange (NEE), gross primary production (GPP), and ecosystem respiration (Re) were -100.6, 782.7, and 682.5 g C m-2 during barley growing season, respectively. The NEE was tended to keep between 0 and 5 g C m-2 d-1 from sowing date (Oct. 21, 2012) to winter rest stage (Dec. 3, 2012 to Feb. 22, 2013), and gradually decreased in tillering stage (Feb. 23, 2013 to May 5, 2013) with its maximum around heading date, and then started to increase in ripening stage (May 6, 2013 to Jun. 8, 2013). The soil temperature was strongly correlated with the Re (r2=0.86), while the net radiation showed the weak relationship with the GPP during the emergence, seedling, and winter rest stage. The aboveground biomass of barley was significantly correlated with the values of NEE (r2=0.79), GPP (r2=0.83), and Re (r2=0.77), respectively.

  4. Formation, transformation and transport of black carbon (charcoal) in terrestrial and aquatic ecosystems.

    PubMed

    Forbes, M S; Raison, R J; Skjemstad, J O

    2006-10-15

    Black carbon (BC) is ubiquitous in terrestrial environments and its unique physical and chemical properties suggest that it may play an important role in the global carbon budget (GCB). A critical issue is whether the global production of BC results in significant amounts of carbon (C) being removed from the short-term bio-atmospheric carbon cycle and transferred to the long-term geological carbon cycle. Several dozen field and laboratory based studies of BC formation during the burning of biomass have been documented. Findings are difficult to interpret because they have been expressed in an inconsistent manner, and because different physical and chemical methods have been used to derive them. High error terms documented in many of these studies also highlight the problems associated with the quantification of the amount of biomass C consumed in fire, the amount of residue produced and the constituents of that residue. To be able to estimate the potential for BC as a carbon sink, issues regarding its definition, the methods used in its identification and measurement, and the way it is expressed in relation to other components of the carbon cycle need to be addressed. This paper presents BC data in a standard way; BC production as a percentage of the amount of C consumed by fire (BC/CC), which can be readily integrated into a larger carbon budget. Results from previous studies and new data from Australian ecosystems were recalculated in this way. As part of this process, several BC estimates derived solely from physical methods were discarded, based on their inability to accurately identify and quantify the BC component of the post-fire residue. Instead, more focus was placed on BC estimates obtained by chemical methods. This recalculated data lowered the estimate for BC formation in forest fires from 4% to 5% to <3% BC/CC. For savannah and grassland fires a value of <3% is consistent with reported data, but considerable variation among estimates remains. An

  5. Final Report on "Rising CO2 and Long-term Carbon Storage in Terrestrial Ecosystems: An Empirical Carbon Budget Validation"

    SciTech Connect

    J. Patrick Megonigal; Bert G. Drake

    2010-08-27

    The primary goal of this report is to report the results of Grant DE-FG02-97ER62458, which began in 1997 as Grant DOE-98-59-MP-4 funded through the TECO program. However, this project has a longer history because DOE also funded this study from its inception in 1985 through 1997. The original grant was focused on plant responses to elevated CO2 in an intact ecosystem, while the latter grant was focused on belowground responses. Here we summarize the major findings across the 25 years this study has operated, and note that the experiment will continue to run through 2020 with NSF support. The major conclusions of the study to date are: (1 Elevated CO2 stimulated plant productivity in the C3 plant community by ~30% during the 25 year study. The magnitude of the increase in productivity varied interannually and was sometime absent altogether. There is some evidence of down-regulation at the ecosystem level across the 25 year record that may be due to interactions with other factors such as sea-level rise or long-term changes in N supply; (2) Elevated CO2 stimulated C4 productivity by <10%, perhaps due to more efficient water use, but C3 plants at elevated CO2 did not displace C4 plants as predicted; (3) Increased primary production caused a general stimulation of microbial processes, but there were both increases and decreases in activity depending on the specific organisms considered. An increase in methanogenesis and methane emissions implies elevated CO2 may amplify radiative forcing in the case of wetland ecosystems; (4) Elevated CO2 stimulated soil carbon sequestration in the form of an increase in elevation. The increase in elevation is 50-100% of the increase in net ecosystem production caused by elevated CO2 (still under analysis). The increase in soil elevation suggests the elevated CO2 may have a positive outcome for the ability of coastal wetlands to persist despite accelerated sea level rise; (5) Crossing elevated CO2 with elevated N causes the elevated CO

  6. Historical and simulated ecosystem carbon dynamics in Ghana: land use, management, and climate

    NASA Astrophysics Data System (ADS)

    Tan, Z.; Tieszen, L. L.; Tachie-Obeng, E.; Liu, S.; Dieye, A. M.

    2008-06-01

    We used the General Ensemble biogeochemical Modeling System (GEMS) to simulate responses of natural and managed ecosystems to changes in land use, management, and climate for a forest/savanna transitional zone in central Ghana. Model results show that deforestation for crop production during the last century resulted in a substantial reduction in ecosystem carbon (C) stock from 135.4 Mg C ha-1 in 1900 to 77.0 Mg C ha-1 in 2000, and in soil organic C stock within the top 20 cm of soil from 26.6 Mg C ha-1 to 21.2 Mg C ha-1. If no land use change takes place from 2000 through 2100, low and high climate change scenarios (increase in temperature and decrease in precipitation over time) will result in losses of soil organic C stock by 19% and 25%, respectively. A low nitrogen (N) fertilization rate is the principal constraint on current crop production. An increase in N fertilization under the low climate change scenario would increase crop yield by 14% with 30 kg N ha-1 and by 38% with 60 kg N ha-1, leading to an increase in the average soil C stock by 12% and 29%, respectively, in all cropland by 2100. The results suggest that the climate changes in the future from current climate conditions will not necessarily become a determinant control on ecosystem C fluxes and crop production, while a reasonable N fertilization rate is critical to achieve food security and agricultural sustainability in the study area through the 21st century, and current cropping systems could be optimized to make full use of the rainfall resource.

  7. Importance of soil thermal regime in terrestrial ecosystem carbon dynamics in the circumpolar north

    NASA Astrophysics Data System (ADS)

    Jiang, Yueyang; Zhuang, Qianlai; Sitch, Stephen; O'Donnell, Jonathan A.; Kicklighter, David; Sokolov, Andrei; Melillo, Jerry

    2016-07-01

    In the circumpolar north (45-90°N), permafrost plays an important role in vegetation and carbon (C) dynamics. Permafrost thawing has been accelerated by the warming climate and exerts a positive feedback to climate through increasing soil C release to the atmosphere. To evaluate the influence of permafrost on C dynamics, changes in soil temperature profiles should be considered in global C models. This study incorporates a sophisticated soil thermal model (STM) into a dynamic global vegetation model (LPJ-DGVM) to improve simulations of changes in soil temperature profiles from the ground surface to 3 m depth, and its impacts on C pools and fluxes during the 20th and 21st centuries. With cooler simulated soil temperatures during the summer, LPJ-STM estimates ~ 0.4 Pg C yr- 1 lower present-day heterotrophic respiration but ~ 0.5 Pg C yr- 1 higher net primary production than the original LPJ model resulting in an additional 0.8 to 1.0 Pg C yr- 1 being sequestered in circumpolar ecosystems. Under a suite of projected warming scenarios, we show that the increasing active layer thickness results in the mobilization of permafrost C, which contributes to a more rapid increase in heterotrophic respiration in LPJ-STM compared to the stand-alone LPJ model. Except under the extreme warming conditions, increases in plant production due to warming and rising CO2, overwhelm the e nhanced ecosystem respiration so that both boreal forest and arctic tundra ecosystems remain a net C sink over the 21st century. This study highlights the importance of considering changes in the soil thermal regime when quantifying the C budget in the circumpolar north.

  8. Perspectives on the microbial carbon pump with special reference to microbial respiration and ecosystem efficiency in large estuarine systems

    NASA Astrophysics Data System (ADS)

    Dang, H.; Jiao, N.

    2014-07-01

    Although respiration-based oxidation of reduced carbon releases CO2 into the environment, it provides an ecosystem with the metabolic energy for essential biogeochemical processes, including the newly proposed microbial carbon pump (MCP). The efficiency of MCP in heterotrophic microorganisms is related to the mechanisms of energy transduction employed and hence is related to the form of respiration utilized. Anaerobic organisms typically have lower efficiencies of energy transduction and hence lower efficiencies of energy-dependent carbon transformation. This leads to a lower MCP efficiency on a per-cell basis. Substantial input of terrigenous nutrients and organic matter into estuarine ecosystems typically results in elevated heterotrophic respiration that rapidly consumes dissolved oxygen, potentially producing hypoxic and anoxic zones in the water column. The lowered availability of dissolved oxygen and the excessive supply of nutrients such as nitrate from river discharge lead to enhanced anaerobic respiration processes such as denitrification and dissimilatory nitrate reduction to ammonium. Thus, some nutrients may be consumed through anaerobic heterotrophs, instead of being utilized by phytoplankton for autotrophic carbon fixation. In this manner, eutrophied estuarine ecosystems become largely fueled by anaerobic respiratory pathways and their efficiency is less due to lowered ecosystem productivity when compared to healthy and balanced estuarine ecosystems. This situation may have a negative impact on the ecological function and efficiency of the MCP which depends on the supply of both organic carbon and metabolic energy. This review presents our current understanding of the MCP mechanisms from the view point of ecosystem energy transduction efficiency, which has not been discussed in previous literature.

  9. Modeled effect of warming on ecosystem carbon and water dynamics within grassland/old-field ecosystems along a moisture gradient

    Technology Transfer Automated Retrieval System (TEKTRAN)

    As a consequence of steadily increasing concentrations of greenhouse gases in Earth’s atmosphere, average world-wide surface temperature is expected to increase 1.5-6.4°C by the end of the 21st Century. Results from manipulative field experiments and ecosystem modeling indicate that plants and soil...

  10. Carbon Monoxide Based Metabolism and CO Cycling in Anaerobic Microbial Ecosystems

    NASA Astrophysics Data System (ADS)

    Colman, A. S.; Techtmann, S. M.; He, B.; Anderson, M. R.; Robb, F. T.

    2011-12-01

    Carbon monoxide binds tightly to many hemes and other porphyrins, proving toxic to humans and microbes. Nevertheless, CO is an attractive fuel for anaerobic chemolithotrophy for those microbes not impaired by CO's toxicity. CO can be oxidized to CO2 anaerobically through the water-gas-shift reaction by hydrogenogenic carboxydotrophs. CO can also be used by certain homoacetogens in the production of acetate and by certain methanogens in the production of methane, acetate, and formate. CO is not only consumed by microbes, but a diverse range of evidence points towards biogenic production of CO. We present measurements of CO concentrations in dissolved and free phase gases in hot springs in Kamchatka, Russia, and Lassen Volcanic National Park, CA. These measurements implicate microbial CO production as a dominant source of CO in these anaerobic ecosystems. There are few in situ measurements of dissolved CO in microbial mats and sediment pore waters. However, the concentration dependent biochemical and transcriptional responses of carboxydotrophs to CO offer strong evidence for the growth conditions to which these microbes have adapted. CooA is a CO-sensing transcriptional activator found in most anaerobic carboxydotrophs. We interpret the CO-binding properties of CooA in Carboxydothermus hydrogenoformans and Rhodospirillum rubrum as evidence for the ranges of environmental CO concentrations that are frequently encountered in anaerobic ecosystems.

  11. Near-neutral carbon dioxide balance at a seminatural, temperate bog ecosystem

    NASA Astrophysics Data System (ADS)

    Hurkuck, Miriam; Brümmer, Christian; Kutsch, Werner L.

    2016-02-01

    The majority of peatlands in the temperate zone is subjected to drainage and agricultural land use and have been found to be anthropogenic emission hot spots for greenhouse gases. At the same time, many peatlands receive increased atmospheric nitrogen (N) deposition by intensive agricultural practices. Here we provide eddy covariance measurements determining net ecosystem carbon dioxide (CO2) exchange at a protected but moderately drained ombrotrophic bog in Northwestern Germany over three consecutive years. The region is dominated by intensive agricultural land use with total (wet and dry) atmospheric N deposition being about 25 kg N ha-1 yr-1. The investigated peat bog was a small net CO2 sink during all three years ranging from -9 to -73 g C m-2 yr-1. We found temperature- and light-dependent ecosystem respiration (Reco) and gross primary production, respectively, but only weak correlations to water table depths despite large interannual and seasonal variability. Significant short-term effects of atmospheric N deposition on CO2 flux components could not be observed, as the primary controlling factors for N deposition and C sequestration, i.e., fertilization of adjacent fields as well as temperature and light availability, respectively, exceeded potential interactions between the two.

  12. Soil Carbon Stocks in a Shifting Ecosystem; Climate Induced Migration of Mangroves into Salt Marsh

    NASA Astrophysics Data System (ADS)

    Simpson, L.; Osborne, T.; Feller, I. C.

    2015-12-01

    Across the globe, coastal wetland vegetation distributions are changing in response to climate change. The increase in global average surface temperature has already caused shifts in the structure and distribution of many ecological communities. In parts of the southeastern United States, increased winter temperatures have resulted in the poleward range expansion of mangroves at the expense of salt marsh habitat. Our work aims to document carbon storage in the salt marsh - mangrove ecotone and any potential changes in this reservoir that may ensue due to the shifting range of this habitat. Differences in SOM and C stocks along a latitudinal gradient on the east coast of Florida will be presented. The gradient studied spans 342 km and includes pure mangrove habitat, the salt marsh - mangrove ecotone, and pure salt marsh habitat.This latitudinal gradient gives us an exceptional opportunity to document and investigate ecosystem soil C modifications as mangroves transgress into salt marsh habitat due to climatic change.

  13. Integrating Landscape-scale Forest Measurements with Remote Sensing and Ecosystem Models to Improve Carbon Management Decisions

    NASA Astrophysics Data System (ADS)

    Birdsey, R.; Pan, Y.

    2009-05-01

    Managing forests to increase carbon stocks and reduce emissions requires knowledge of how management practices and natural disturbances affect carbon pools over time, and cost-effective techniques for monitoring and reporting. This study improves upon the methodology to collect and integrate the multi-tier monitoring data from the North American Carbon Program (NACP) with management decisions by systematically scaling up intensive forest carbon measurements to land management areas (or landscapes), and reconciling these estimates with ecosystem models and decision-support systems that are driven by remote sensing and national inventories. We propose to use spatial analysis techniques and an ecosystem process model (PnET- CN) to scale up and map observations from flux towers, landscape biometrics, and inventories to areas of approximately 2500 km2 around flux tower sites. The NASA-CASA model is used to derive estimates for the same areas from remote sensing observations by the MODIS sensor, and biophysical maps. We compare and reconcile the top-down and bottom-up approaches, then use the mapped estimates of productivity and biomass that embed consequences of land disturbances and forest age structure as input to decision-support tools. Key information for the decision-support tools includes (1) estimates of carbon stocks and quantified impacts of management activity; (2) estimates of net ecosystem production (NEP) and changes in carbon pools; and (3) estimates of forest/atmosphere carbon fluxes and relevant effects from various environmental controls. This work is relevant to land managers and climate change policy because it supports a need to estimate and report carbon stocks and changes in carbon stocks to state, regional, national, and private greenhouse gas registries. This work builds upon a foundation of work begun in 2001 by the U.S. Forest Service to implement a forest carbon monitoring and observation system at intermediate or "Tier 3" sites as described

  14. Understanding processes contributing to the ecosystem flux of carbonyl sulfide and carbon dioxide in a mixed forest

    NASA Astrophysics Data System (ADS)

    Commane, R.; Baker, I. T.; Berry, J. A.; Munger, J. W.; Wofsy, S. C.

    2014-12-01

    Carbonyl sulfide (OCS) has been proposed as a valuable new measurement for understanding ecosystem carbon fluxes. Net OCS uptake is thought to be a proxy for gross photosynthetic uptake (which can't be directly measured at large scales). However, our understanding of the OCS flux within forest ecosystems, and it's relationship to CO2, has been limited by a lack of long-term measurements of the OCS flux. Throughout 2011, the ecosystem flux of OCS was measured at a mid-latitude deciduous forest (Harvard Forest, MA, US), a site of long-term CO2 flux measurements. In order to understand the processes contributing to the seasonal ecosystem fluxes of OCS and CO2, we used the Simple Biosphere Model (SiB). This is an enzyme-kinetic model that couples the carbon cycle to the surface energy, water and radiation balance through stomatal regulation. The model has been extended to include a coupled representation of OCS uptake by leaves and soil. Here we test these parameterizations against the whole suite of ecosystem fluxes (including OCS flux) measured throughout the year. We also evaluate the effect of longer-term processes (such as phenology and soil moisture stress) on inter annual variation in ecosystem flux and OCS exchange.

  15. [Effect of seasonal high temperature and drought on carbon flux of bamboo forest ecosystem in subtropical region].

    PubMed

    Chen, Xiao-feng; Jiang, Hong; Niu, Xiao-dong; Zhang, Jin-meng; Liu, Yu-li; Fang, Cheng-yuan

    2016-02-01

    The carbon flux of subtropical bamboo forest ecosystem was continuously measured using eddy covariance technique in Anji County of Zhejiang Province, China. The monthly net ecosystem productivity (NEP), ecosystem respiration (Re) and gross ecosystem productivity (GEP) data from 2011 to 2013 were selected to analyze the impacts of seasonal high temperature and drought on the carbon flux of bamboo forest ecosystem. The results showed that there were big differences among annual NEP of bamboo forest from 2011 to 2013. Because of the asynchronization of precipitation and heat, the seasonal high temperature and drought in July and August of 2013 caused significant decline in NEP by 59.9% and 80.0% when compared with the same months in 2011. Correlation analysis of the NEP, Re, GEP and environmental factors suggested that the atmosphere temperatures were significantly correlated with Re and GEP in 2011 and 2013 (P<0.05). However, to air and soil moisture, Re and GEP had different responses, that was, GEP was more vulnerable by the decrease of the soil moisture compared with Re. Besides, the raising of saturation vapour pressure promoted the Re modestly but inhibited the GEP, which was supposed to be the main reason for NEP decrease of bamboo forest ecosystem in Anji, from July to August in 2013. PMID:27396103

  16. [Carbon dynamics of broad-leaved Korean pine forest ecosystem in Changbai Mountains and its responses to climate change].

    PubMed

    Tang, Feng-De; Han, Shi-Jie; Zhang, Jun-Hui

    2009-06-01

    By using process model Sim-CYCLE based on dry matter production theory, this paper estimated the gross primary productivity (GPP), net primary productivity (NPP), net ecosystem productivity (NEP), ecosystem carbon storage (WE), total plant carbon storage (WP), and total soil carbon storage (WS) of broad-leaved Korean pine forest ecosystem in Changbai Mountains from 1982 to 2003, and analyzed the variations of these indices under present climate condition and carbon equilibrium state as well as the responses of these indices to climate change scenarios in the future. Under present climate condition, the estimated GPP, NPP, and NEP were 14.9, 8.7, and 2.7 Mg C x hm(-2) x a(-1), being 2.8 Mg C x hm(-2) x a(-1) less and 1.4 and 0.2 Mg C x hm(-2) x a(-1) higher than the measured values, respectively. The NEP in June-August occupied more than 90% of the annual NEP, and the maximum monthly NEP appeared in July (1.23 Mg C x hm(-2) month(-1)). The estimated WE, WP, and WS were 550.8, 183.8, and 367.0 Mg C x hm(-2), respectively, very close to the measured values. From present climate condition to carbon equilibrium state, the estimated carbon storages of the forest ecosystem increased to some extent, with the GPP and NPP being 17.7 and 7.3 Mg C x hm(-2) x a(-1), respectively, suggesting that the role of the forest ecosystem as a carbon "sink" declined gradually with the increase of carbon storage. A 2 degree C-increment of air temperature did not benefit the increase of GPP, NPP and NEP, while doubling CO2 concentration was in adverse. The effects of the combination of doubling CO2 concentration and 2 degree C-increment of air temperature on the GPP, NPP, and NEP were similar to those of doubling CO2 concentration. The climate change scenario in the future had the same effects both on the carbon storage and on the productivity of the forest ecosystem, which was mainly correlated to the effects of primary productivity on the carbon storage. PMID:19795634

  17. Carbon storage in Chinese grassland ecosystems: Influence of different integrative methods

    PubMed Central

    Ma, Anna; He, Nianpeng; Yu, Guirui; Wen, Ding; Peng, Shunlei

    2016-01-01

    The accurate estimate of grassland carbon (C) is affected by many factors at the large scale. Here, we used six methods (three spatial interpolation methods and three grassland classification methods) to estimate C storage of Chinese grasslands based on published data from 2004 to 2014, and assessed the uncertainty resulting from different integrative methods. The uncertainty (coefficient of variation, CV, %) of grassland C storage was approximately 4.8% for the six methods tested, which was mainly determined by soil C storage. C density and C storage to the soil layer depth of 100 cm were estimated to be 8.46 ± 0.41 kg C m−2 and 30.98 ± 1.25 Pg C, respectively. Ecosystem C storage was composed of 0.23 ± 0.01 (0.7%) above-ground biomass, 1.38 ± 0.14 (4.5%) below-ground biomass, and 29.37 ± 1.2 (94.8%) Pg C in the 0–100 cm soil layer. Carbon storage calculated by the grassland classification methods (18 grassland types) was closer to the mean value than those calculated by the spatial interpolation methods. Differences in integrative methods may partially explain the high uncertainty in C storage estimates in different studies. This first evaluation demonstrates the importance of multi-methodological approaches to accurately estimate C storage in large-scale terrestrial ecosystems. PMID:26883467

  18. After the Storm: Assessing the carbon and nitrogen leaching potential from sediments deposited in aquatic ecosystems

    NASA Astrophysics Data System (ADS)

    Johnson, E. R.; Krieg, C.; Canning, C.; Inamdar, S. P.; Rowland, R. D.

    2015-12-01

    The erosive energy of large storms can mobilize, and subsequently deposit large amounts of sediment in receiving aquatic ecosystems. Depending on the character of the sediments there is potential for leaching or sequestration of carbon (C) and nitrogen (N) from the sediments. This could have significant implications for water quality, aquatic metabolism, and global cycling of C and N. This study examines the fate of these sediments by: (1) determining the amount and quality of organic matter that can be leached into the surrounding water from coarse, medium and fine particle classes (2) assessing the C and N contents of various particles classes and the sources of the sediment through isotopic composition. Bed sediment samples were collected along a 1-2nd order stream (eight locations) in a forested catchment in the Piedmont region of Maryland following a large storm event. Samples were sieved into three particle classes - coarse (2mm-1mm), medium (1mm-250µm) and fine (<250µm). Extractions were performed for each of three particle class sizes by leaching with DI water. Organic matter composition for the extracts was characterized using fluorescence. Stable isotopes of 13C and 15N were determined for bed sediment classes and upland source sediments to identify the origins of the eroded sediments. Extracts with low C:N ratios that also exhibit a higher percent protein and lower percent humic carbon content are considered most labile. Within the bed sediment deposits, differences were found in the distribution of labile compounds between each particle class size. Generally, course particle size exhibited the most labile characteristics, closely followed by medium particle size. Fine particle size exhibited the most refractory characteristics in all locations. These results are critical since climate-change predictions reveal more intense and large storms for the northeast US, with potentially greater impacts on aquatic ecosystems from eroded upland sediments.

  19. Carbon storage in Chinese grassland ecosystems: Influence of different integrative methods.

    PubMed

    Ma, Anna; He, Nianpeng; Yu, Guirui; Wen, Ding; Peng, Shunlei

    2016-01-01

    The accurate estimate of grassland carbon (C) is affected by many factors at the large scale. Here, we used six methods (three spatial interpolation methods and three grassland classification methods) to estimate C storage of Chinese grasslands based on published data from 2004 to 2014, and assessed the uncertainty resulting from different integrative methods. The uncertainty (coefficient of variation, CV, %) of grassland C storage was approximately 4.8% for the six methods tested, which was mainly determined by soil C storage. C density and C storage to the soil layer depth of 100 cm were estimated to be 8.46 ± 0.41 kg C m(-2) and 30.98 ± 1.25 Pg C, respectively. Ecosystem C storage was composed of 0.23 ± 0.01 (0.7%) above-ground biomass, 1.38 ± 0.14 (4.5%) below-ground biomass, and 29.37 ± 1.2 (94.8%) Pg C in the 0-100 cm soil layer. Carbon storage calculated by the grassland classification methods (18 grassland types) was closer to the mean value than those calculated by the spatial interpolation methods. Differences in integrative methods may partially explain the high uncertainty in C storage estimates in different studies. This first evaluation demonstrates the importance of multi-methodological approaches to accurately estimate C storage in large-scale terrestrial ecosystems. PMID:26883467

  20. Carbon storage in Chinese grassland ecosystems: Influence of different integrative methods

    NASA Astrophysics Data System (ADS)

    Ma, Anna; He, Nianpeng; Yu, Guirui; Wen, Ding; Peng, Shunlei

    2016-02-01

    The accurate estimate of grassland carbon (C) is affected by many factors at the large scale. Here, we used six methods (three spatial interpolation methods and three grassland classification methods) to estimate C storage of Chinese grasslands based on published data from 2004 to 2014, and assessed the uncertainty resulting from different integrative methods. The uncertainty (coefficient of variation, CV, %) of grassland C storage was approximately 4.8% for the six methods tested, which was mainly determined by soil C storage. C density and C storage to the soil layer depth of 100 cm were estimated to be 8.46 ± 0.41 kg C m-2 and 30.98 ± 1.25 Pg C, respectively. Ecosystem C storage was composed of 0.23 ± 0.01 (0.7%) above-ground biomass, 1.38 ± 0.14 (4.5%) below-ground biomass, and 29.37 ± 1.2 (94.8%) Pg C in the 0-100 cm soil layer. Carbon storage calculated by the grassland classification methods (18 grassland types) was closer to the mean value than those calculated by the spatial interpolation methods. Differences in integrative methods may partially explain the high uncertainty in C storage estimates in different studies. This first evaluation demonstrates the importance of multi-methodological approaches to accurately estimate C storage in large-scale terrestrial ecosystems.

  1. Degradation State and Sequestration Potential of Carbon in Coastal Wetlands of Texas: Mangrove Vs. Saltmarsh Ecosystems

    NASA Astrophysics Data System (ADS)

    Sterne, A. M. E.; Kaiser, K.; Louchouarn, P.; Norwood, M. J.

    2015-12-01

    The estimated magnitude of the organic carbon (OC) stocks contained in the first meter of US coastal wetland soils represents ~10% of the entire OC stock in US soils (4 vs. 52 Pg, respectively). Because this stock extends to several meters below the surface for many coastal wetlands, it becomes paramount to understand the fate of OC under ecosystem shifts, varying natural environmental constraints, and changing land use. In this project we analyze the major classes of biochemicals including total hydrolysable neutral carbohydrates, enantiomeric amino acids, phenols, and cutins/suberins at two study sites located on the Texas coastline to investigate chemical composition and its controls on organic carbon preservation in mangrove (Avicennia germinans) and saltmarsh grass (Spartina alterniflora) dominated wetlands. Results show neutral carbohydrates and lignin contribute 30-70% and 10-40% of total OC, respectively, in plant litter and surface sediments at both sites. Sharp declines of carbohydrate yields with depth occur parallel to increasing Ac/AlS,V ratios indicating substantial decomposition of both the polysaccharide and lignin components of litter detritus. Contrasts in the compositions and relative abundances of all previously mentioned compound classes are further discussed to examine the role of litter biochemistry in OC preservation. For example, the selective preservation of cellulose over hemicellulose in sediments indicates macromolecular structure plays a key role in preservation between plant types. It is concluded that the chemical composition of litter material controls the composition and magnitude of OC stored in sediments. Ultimately, as these ecosystems transition from one dominant plant type to another, as is currently observed along the Texas coastline, there is the potential for OC sequestration efficiency to shift due to the changing composition of OC input to sediments.

  2. Tunable Diode Laser Measurements of Leaf-scale Carbon Isotope Discrimination and Ecosystem Respired Carbon and Oxygen Isotope Ratios in a Semi-arid Woodland

    NASA Astrophysics Data System (ADS)

    McDowell, N.; Chris, B.; Hanson, D.; Kern, S.; Meyer, C.; Pockman, W.; Powers, H.

    2005-12-01

    We present results and speculative interpretation of leaf-level carbon isotope discrimination and ecosystem respired carbon and oxygen isotope ratios from a semi-arid, C3/C4 woodland located in northern New Mexico, USA. Overstory leaf area index (LAI) is dominated by live juniper (Juniperus monosperma) trees with an LAI value of approximately 1.0 m2 per m2 ground area, and has a seasonally dynamic understory of mixed C3 forbs and C4 grasses and cacti, with a maximum LAI of 0.30 m2 per m2 ground area. Ecosystem respired carbon isotope ratios showed values characteristic of C3 dominated photosynthesis (Keeling plot intercepts of -35 to -22 per mil). Seasonal variation was typical of that found in wetter, C3 dominated forests, as was the dependence on climate (e.g. relationships with vapor pressure deficit, soil water content, and canopy conductance). Leaf-level carbon isotope discrimination of the junipers, measured by coupling a Li-Cor 6400 photosynthesis system to the TDL, provided discrimination-Ci and discrimination-vpd relationships consistent with measured ecosystem respired carbon isotope ratios. The oxygen isotope ratio of ecosystem respiration was dependent on rain water isotope composition, but was correlated with soil water content during rain-free periods. The cumulative effect of vapor pressure deficit after a rain event was tightly correlated with the oxygen isotope ratio of ecosystem respiration, suggesting the primary drivers are evaporative enrichment of soil water and perhaps nocturnal leaf enrichment. Instrument precision for carbon and oxygen isotope ratios of carbon dioxide is 0.06 to 0.18 per mil; however, overall precision is somewhat lower due to pressure and sampling effects.

  3. Diurnal and seasonal variations in carbon dioxide exchange in ecosystems in the Zhangye oasis area, Northwest China.

    PubMed

    Zhang, Lei; Sun, Rui; Xu, Ziwei; Qiao, Chen; Jiang, Guoqing

    2015-01-01

    Quantifying carbon dioxide exchange and understanding the response of key environmental factors in various ecosystems are critical to understanding regional carbon budgets and ecosystem behaviors. For this study, CO2 fluxes were measured in a variety of ecosystems with an eddy covariance observation matrix between June 2012 and September 2012 in the Zhangye oasis area of Northwest China. The results show distinct diurnal variations in the CO2 fluxes in vegetable field, orchard, wetland, and maize cropland. Diurnal variations of CO2 fluxes were not obvious, and their values approached zero in the sandy desert, desert steppe, and Gobi ecosystems. Additionally, daily variations in the Gross Primary Production (GPP), Ecosystem Respiration (Reco) and Net Ecosystem Exchange (NEE) were not obvious in the sandy desert, desert steppe, and Gobi ecosystems. In contrast, the distributions of the GPP, Reco, and NEE show significant daily variations, that are closely related to the development of vegetation in the maize, wetland, orchard, and vegetable field ecosystems. All of the ecosystems are characterized by their carbon absorption during the observation period. The ability to absorb CO2 differed significantly among the tested ecosystems. We also used the Michaelis-Menten equation and exponential curve fitting methods to analyze the impact of Photosynthetically Active Radiation (PAR) on the daytime CO2 flux and impact of air temperature on Reco at night. The results show that PAR is the dominant factor in controlling photosynthesis with limited solar radiation, and daytime CO2 assimilation increases rapidly with PAR. Additionally, the carbon assimilation rate was found to increase slowly with high solar radiation. The light response parameters changed with each growth stage for all of the vegetation types, and higher light response values were observed during months or stages when the plants grew quickly. Light saturation points are different for different species. Nighttime

  4. Diurnal and Seasonal Variations in Carbon Dioxide Exchange in Ecosystems in the Zhangye Oasis Area, Northwest China

    PubMed Central

    Zhang, Lei; Sun, Rui; Xu, Ziwei; Qiao, Chen; Jiang, Guoqing

    2015-01-01

    Quantifying carbon dioxide exchange and understanding the response of key environmental factors in various ecosystems are critical to understanding regional carbon budgets and ecosystem behaviors. For this study, CO2 fluxes were measured in a variety of ecosystems with an eddy covariance observation matrix between June 2012 and September 2012 in the Zhangye oasis area of Northwest China. The results show distinct diurnal variations in the CO2 fluxes in vegetable field, orchard, wetland, and maize cropland. Diurnal variations of CO2 fluxes were not obvious, and their values approached zero in the sandy desert, desert steppe, and Gobi ecosystems. Additionally, daily variations in the Gross Primary Production (GPP), Ecosystem Respiration (Reco) and Net Ecosystem Exchange (NEE) were not obvious in the sandy desert, desert steppe, and Gobi ecosystems. In contrast, the distributions of the GPP, Reco, and NEE show significant daily variations, that are closely related to the development of vegetation in the maize, wetland, orchard, and vegetable field ecosystems. All of the ecosystems are characterized by their carbon absorption during the observation period. The ability to absorb CO2 differed significantly among the tested ecosystems. We also used the Michaelis-Menten equation and exponential curve fitting methods to analyze the impact of Photosynthetically Active Radiation (PAR) on the daytime CO2 flux and impact of air temperature on Reco at night. The results show that PAR is the dominant factor in controlling photosynthesis with limited solar radiation, and daytime CO2 assimilation increases rapidly with PAR. Additionally, the carbon assimilation rate was found to increase slowly with high solar radiation. The light response parameters changed with each growth stage for all of the vegetation types, and higher light response values were observed during months or stages when the plants grew quickly. Light saturation points are different for different species. Nighttime

  5. Modeling Karst Ecosystem-Atmosphere CO2 Exchange: The Importance of Ventilation for Carbonate Geochemistry

    NASA Astrophysics Data System (ADS)

    Roland, M.; Serrano-Ortiz, P.; Godderis, Y.; Kowalski, A. S.; Janssens, I.

    2011-12-01

    Global carbonate weathering is considered a small carbon flux when compared with biogenic CO2 fluxes. This is, however, a question of time and space. In karst regions, it has been shown that biogenic fluxes are not always dominant. CO2 exchange patterns have been reported there that cannot be explained by biological processes: disproportionate outgassing during daytime or nighttime CO2 uptake during periods when all vegetation is senescent. These phenomena have previously been attributed to carbonate weathering reactions or biocrust activity, but their associated CO2 exchange rates are considered too small [Serrano-Ortiz et al., 2010]. Here, we report a novel mechanism through which carbonate weathering, exacerbated by subterranean ventilation, dominates the diel pattern of land-atmosphere CO2 exchange in karst areas. Ventilation is an efficient air mass transfer process (including pressure pumping, deep penetration of eddies and thermal expansion of air) that occurs in all porous media, when pores are connected and not blocked by water. Due to its high porosity and the presence of caves, fissures and cracks, karts systems are very prone to ventilation. When soil CO2 concentrations are rapidly brought into disequilibrium by ventilation, CO2 fluxes associated with carbonate weathering can exceed those associated with biological activity. The biology-based standardized partitioning schemes that are used by a large community of scientists, are then no longer applicable and gas exchange measurements fail to reveal any information on the biological activity. By incorporating ventilation processes into the mineral weathering model WITCH [Goddéris et al., 2006], we were able to quantify the contribution of carbonate geochemistry to the synoptic CO2 fluxes on karst ecosystems. [1] Goddéris, Y., L. M. Francois, A. Probst, J. Schott, D. Moncoulon, D. Labat, and D. Viville (2006), Modelling weathering processes at the catchment scale: The WITCH numerical model, Geochim

  6. Declining plant nitrogen supply and carbon accumulation in ageing primary boreal forest ecosystems

    NASA Astrophysics Data System (ADS)

    Högberg, Mona N.; Yarwood, Stephanie A.; Trumbore, Susan; Högberg, Peter

    2016-04-01

    Boreal forest soils are commonly characterized by a low plant nitrogen (N) supply. A high tree below-ground allocation of carbon (C) to roots and soil microorganisms in response to the shortage of N may lead to high microbial immobilisation of N, thus aggravating the N limitation. We studied the N supply at a Swedish boreal forest ecosystem chronosequence created by new land rising out of the sea due to iso-static rebound. The youngest soils develop with meadows by the coast, followed by a zone of dinitrogen fixing alder trees, and primary boreal conifer forest on ground up to 560 years old. With increasing ecosystem age, the proportion of microbial C out of the total soil C pool from the youngest to the oldest coniferous ecosystem was constant (c. 1-1.5%), whereas immobilised N (microbial N out of total soil N) increased and approached the levels commonly observed in similar boreal coniferous forests (c. 6-7 %), whereas gross N mineralization declined. Simultaneously, plant foliar N % decreased and the natural abundance of N-15 in the soil increased. More specifically, the difference in N-15 between plant foliage and soil increased, which is related to greater retention of N-15 relative to N-14 by ectomycorrhizal fungi as N is taken up from the soil and some N is transferred to the plant host. In the conifer forest, where these changes were greatest, we found increased fungal biomass in the F- and H-horizons of the mor-layer, in which ectomycorrhizal fungi are known to dominate (the uppermost horizon with litter and moss is dominated by saprotrophic fungi). Hence, we propose that the decreasing N supply to the plants and the subsequent decline in plant production in ageing boreal forests is linked to high tree belowground C allocation to C limited ectomycorrhizal fungi (and other soil microorganisms), a strong sink for available soil N. Data on organic matter C-14 suggested that the largest input of recently fixed plant C occurred in the younger coniferous forest

  7. Baseline and projected future carbon storage and greenhouse-gas fluxes in ecosystems of the eastern United States

    USGS Publications Warehouse

    Zhu, Zhi-Liang; Reed, Bradley C.

    2014-01-01

    This assessment was conducted to fulfill the requirements of section 712 of the Energy Independence and Security Act of 2007 and to conduct a comprehensive national assessment of storage and flux (flow) of carbon and the fluxes of other greenhouse gases in ecosystems of the Eastern United States. These carbon and greenhouse gas variables were examined for major terrestrial ecosystems (forests, grasslands/shrublands, agricultural lands, and wetlands) and aquatic ecosystems (rivers, streams, lakes, estuaries, and coastal waters) in the Eastern United States in two time periods: baseline (from 2001 through 2005) and future (projections from the end of the baseline through 2050). The Great Lakes were not included in this assessment due to a lack of input data. The assessment was based on measured and observed data collected by the U.S. Geological Survey and many other agencies and organizations and used remote sensing, statistical methods, and simulation models.

  8. Typhoons exert significant but differential impacts on net ecosystem carbon exchange of subtropical mangrove forests in China

    NASA Astrophysics Data System (ADS)

    Chen, H.; Lu, W.; Yan, G.; Yang, S.; Lin, G.

    2014-10-01

    Typhoons are very unpredictable natural disturbances to subtropical mangrove forests in Asian countries, but little information is available on how these disturbances affect ecosystem level carbon dioxide (CO2) exchange of mangrove wetlands. In this study, we examined short-term effect of frequent strong typhoons on defoliation and net ecosystem CO2 exchange (NEE) of subtropical mangroves, and also synthesized 19 typhoons during a 4-year period between 2009 and 2012 to further investigate the regulation mechanisms of typhoons on ecosystem carbon and water fluxes following typhoon disturbances. Strong wind and intensive rainfall caused defoliation and local cooling effect during the typhoon season. Daily total NEE values decreased by 26-50% following some typhoons (e.g., W28-Nockten, W35-Molave and W35-Lio-Fan), but significantly increased (43-131%) following typhoon W23-Babj and W38-Megi. The magnitudes and trends of daily NEE responses were highly variable following different typhoons, which were determined by the balance between the variances of gross ecosystem production (GEP) and ecosystem respiration (RE). Furthermore, results from our synthesis indicated that the landfall time of typhoon, wind speed and rainfall were the most important factors controlling the CO2 fluxes following typhoon events. These findings indicate that different types of typhoon disturbances can exert very different effects on CO2 fluxes of mangrove ecosystems and that typhoon will likely have larger impacts on carbon cycle processes in subtropical mangrove ecosystems as the intensity and frequency of typhoons are predicted to increase under future global climate change scenarios.

  9. Changes in Ecosystem Carbon Following Afforestation of Post-Mining Sites- A Case Study from Raniganj Coalfield, India

    NASA Astrophysics Data System (ADS)

    Kumar, S.; Maiti, S. K.; Chaudhuri, S.; Ghosh, P.

    2015-12-01

    The concept of changes in ecosystem dynamics of carbon (C) as a function of soil and vegetation developments at post-mining sites is of interest because of its prospective function in mitigating increasing global C-cycle. Forestry reclamation approaches (FRA) for post-mining sites can significantly enhance C storage in minesoils and established species; however the mechanism that not widely assessed to predict changes in ecosystem functions. A chronosequence post-mining sites (2-years, 5-years, 9-years, 15-years and 21-years old reclaimed afforested minesoils at Raniganj Coalfield, India) were investigated to: (i) quantify the amount of soil C accumulating in developing ecosystem; (ii) examine several physiochemical properties and biological processes that govern the rate of C-sequestration; (iii) identify the relationships between C-sequestration and soil properties, and (iv) develop a soil quality index by principal component analysis (PCA). From changes in ecosystem C perspective, although soil organic carbon (Corg) was less in newly developed ecosystem in comparisons to older one (21-years). However, rate of soil C-accumulation was greater (2.6 Mg C ha-1yr-1) in newly formed minesoil ecosystem. The overall microbial indices, dehydrogenase activities (DHA-15.7 µg-1TPF g-1 24 hrs-1); microbial biomass carbon (MBC-368 mg C kg-1); and rates of soil CO2 flux (15 μmol CO2 m-2 s-1) were found highest in older minesoils in comparisons to younger minesoils. PCA showed that three PCs with eigenvalues > 1 explained 74.5% of the total variance in the soil properties. The first PC is mostly characterized by soil nutritional and biological properties; second PC by physical properties and showed a positive correlation with soil C-accumulation and changes in plant species diversity. The present study showed that changes in ecosystem C and nutrients are direct function of enhanced and established forest land use managements.

  10. Influences of changing land use and CO 2 concentration on ecosystem and landscape level carbon and water balances in mountainous terrain of the Stubai Valley, Austria

    NASA Astrophysics Data System (ADS)

    Tenhunen, J.; Geyer, R.; Adiku, S.; Reichstein, M.; Tappeiner, U.; Bahn, M.; Cernusca, A.; Dinh, N. Q.; Kolcun, O.; Lohila, A.; Otieno, D.; Schmidt, M.; Schmitt, M.; Wang, Q.; Wartinger, M.; Wohlfahrt, G.

    2009-05-01

    A process-based spatial simulation model was used to estimate gross primary production, ecosystem respiration, net ecosystem CO 2 exchange and water use by the vegetation in Stubai Valley, Austria at landscape scale. The simulations were run for individual years from early spring to late fall, providing estimates in grasslands for carbon gain, biomass and leaf area development, allocation of photoproducts to the below ground ecosystem compartment, and water use. In the case of evergreen coniferous forests, gas exchange is estimated, but spatial simulation of growth over the single annual cycles is not included. Spatial parameterization of the model is derived for forest LAI based on remote sensing, for soil characteristics by generalization from spatial surveys and for climate drivers from observations at monitoring stations along the elevation gradient and from modelling of incident radiation in complex terrain. Validation of the model was carried out at point scale, and was based on comparison of model output at selected locations with observations along elevation gradients in Stubai Valley and Berchtesgaden National Park, Germany as well as with known trends in ecosystem response documented in the literature. The utility of the model for describing long-term changes in carbon and water balances at landscape scale is demonstrated in the context of land use change that occurred between 1861 and 2002 in Stubai Valley. During this period, coniferous forest increased in extent by ca. 11% of the vegetated area of 1861, primarily in the subalpine zone. Managed grassland decreased by 46%, while abandoned grassland and natural alpine mats increased by 14 and 11%, respectively. At point scale, the formulated model predicts higher canopy conductance in 1861 due to lower atmospheric CO 2 concentration which opens stomata. As a result, water use at point scale decreased by ca. 8% in 2002 in the valley bottoms versus 10% at tree line. At landscape level, the decrease in water

  11. RESOLUTION AND ERROR IN MEASURING LAND-COVER CHANGE: EFFECTS ON ESTIMATING NET CARBON RELEASE FROM MEXICAN TERRESTRIAL ECOSYSTEMS

    EPA Science Inventory

    Reliable estimates of carbon exchange between terrestrial ecosystems and the atmosphere due to land-use change have become increasingly important. One source of land-use changes estimates comes from comparing multi-date remote sensing imagery, though the effect of land-cover clas...

  12. Terrestrial Carbon Sinks in the Brazilian Amazon and Cerrado Region Predicted from MODIS Satellite Data and Ecosystem Modeling

    EPA Science Inventory

    A simulation model based on satellite observations of monthly vegetation cover from the Moderate Resolution Imaging Spectroradiometer (MODIS) was used to estimate monthly carbon fluxes in terrestrial ecosystems of Brazilian Amazon and Cerrado regions over the period 2000-2004. Pr...

  13. Integration of Field Studies and Undergraduate Research into an Interdisciplinary Course: Natural History of Tropical Carbonate Ecosystems

    ERIC Educational Resources Information Center

    Eves, Robert L.; Davis, Larry E.; Brown, D. Gordon; Lamberts, William L.

    2007-01-01

    According to Carl Sagan (1987), "Science is a way of thinking much more than it is a body of knowledge." Field studies and undergraduate research provide students with the best opportunities for "thinking" about science, while at the same time acquiring a body of knowledge. Natural History of Tropical Carbonate Ecosystems is a spring semester…

  14. Shrub encroachment in North American grasslands: Shifts in growth form dominance rapidly alters control of ecosystem carbon inputs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Shrub encroachment into grass-dominated biomes is occurring globally due to a variety of anthropogenic activities, but the consequences for carbon (C) inputs, storage and cycling remain unclear. We studied eight North American graminoid-dominated ecosystems invaded by shrubs, from arctic tundra to ...

  15. The initial performance tests of the Closed Geoshpere Experiment Facility (CGEF) for the investigation of ecosystem carbon cycles

    NASA Astrophysics Data System (ADS)

    Suzuki, S.; Endo, M.; Tsuga, S.; Nitta, K.

    The Closed Geosphere Experiment Facility CGEF is designed to investigate carbon cycles of terrestrial ecosystems because of its airtightness A wetland ecosystem is scheduled to be introduced to the CGEF The size of CGEF is a 5 8 times 8 7 m 2 ground area and 11 9 m average height including 3 1 m soil depth The facility serves as an experimental means for analyzing ecosystem processes on carbon cycles under controlled conditions Air temperature in the CGEF was controlled near setting points The CGEF has heterogeneous light intensity which decreases from south to north Effects of heterogeneity on plants were estimated using pot-grown plants which are scheduled for introduction into the CGEF Amounts of evapotranspiration were higher for the south than north side No significant difference in growth vegetation height and culm density detected between the south and north side Concentrations of N P Na K Ca and Mg in plants show the similar value between south and north side We conclude that there is no serious problem attributable to heterogeneity of light conditions against plants for a growing season The degree of airtightness was investigated for the facility and the air exchange rate was about 6 66 times 10 -3 per hour Thus the carbon budget of the wetland ecosystem is easily investigated by monitoring the product of gaseous carbon CO 2 and CH 4 concentrations and amounts of ventilation in CGEF due to its airtightness The initial performance test shows the CGEF to be a suitable facility for investigating

  16. Using Targeted Active-Learning Exercises and Diagnostic Question Clusters to Improve Students' Understanding of Carbon Cycling in Ecosystems

    ERIC Educational Resources Information Center

    Maskiewicz, April Cordero; Griscom, Heather Peckham; Welch, Nicole Turrill

    2012-01-01

    In this study, we used targeted active-learning activities to help students improve their ways of reasoning about carbon flow in ecosystems. The results of a validated ecology conceptual inventory (diagnostic question clusters [DQCs]) provided us with information about students' understanding of and reasoning about transformation of inorganic and…

  17. Interannual, seasonal, and diel variability in the carbon isotope composition of respiration in a C3/C4 agricultural ecosystem

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The stable carbon isotope ratio 13CO2/12CO2 is a valuable tool for understanding the processes controlling the autotrophic (FRa) and heterotrophic (FRh) contributions to ecosystem respiration (FR) as well as influences of photosynthesis on respiration. There is increasing interest in the temporal va...

  18. Simulating soil carbon accumulation in an upland black spruce ecosystem of interior Alaska: implications for permafrost carbon dynamics to climate change

    NASA Astrophysics Data System (ADS)

    Wang, X.; Yokozawa, M.; Toda, M.; Kushida, K.

    2015-12-01

    Boreal terrestrial ecosystems act as a huge reservoir of organic carbon, most of which is mainly stored in both active-layer soils and permafrost. Recently, many observational studies have revealed that ongoing climate warming has promoted changes in fire regime, which stimulates the permafrost thaw in the boreal area. Consequently, the decomposition rate of the organic and mineral soils will increase and a large amount of CO2 will be released into the atmosphere. The sustained CO2­ release from the soils may create a positive feedback in relation to carbon cycling between the atmosphere and boreal terrestrial ecosystems. However, there still remains substantial uncertainty for evaluating the mechanisms of the carbon cycle feedbacks over centuries. In the present study, we examined the effect of warming and fire episodes on soil carbon dynamics in an upland black spruce ecosystem in interior Alaska, by using a Physical and Biogeochemical Soil Dynamics Model (PB-SDM) which can simulate the feedback cycle of soil organic carbon accumulation with soil thermal and hydrological dynamics. The result indicates that soil carbon accumulation in the organic layer was strongly dominated by increased temperature. In addition, fire events by which a great number of soil layers burned contributed to decrease in soil carbon accumulation largely in the organic layer. On the other hand, remarkably increased temperature conditions (around 9.6℃ by 3000) controlled soil carbon accumulation in the mineral layer and changes in soil decomposition rate accompanying with the shift from frozen to thawed conditions with warming accelerated soil carbon decomposition. It is suggested that future climate warming would result in drastic decrease in the soil carbon stock, largely from the organic layer, whereas the vulnerability of deeper soil carbon to future warming is closely connected to permafrost degradation due to wildfire disturbance.

  19. Soil Organic Carbon for Global Benefits - assessing potential SOC increase under SLM technologies worldwide and evaluating tradeoffs and gains of upscaling SLM technologies

    NASA Astrophysics Data System (ADS)

    Wolfgramm, Bettina; Hurni, Hans; Liniger, Hanspeter; Ruppen, Sebastian; Milne, Eleanor; Bader, Hans-Peter; Scheidegger, Ruth; Amare, Tadele; Yitaferu, Birru; Nazarmavloev, Farrukh; Conder, Malgorzata; Ebneter, Laura; Qadamov, Aslam; Shokirov, Qobiljon; Hergarten, Christian; Schwilch, Gudrun

    2013-04-01

    There is a fundamental mutual interest between enhancing soil organic carbon (SOC) in the world's soils and the objectives of the major global environmental conventions (UNFCCC, UNCBD, UNCCD). While there is evidence at the case study level that sustainable land management (SLM) technologies increase SOC stocks and SOC related benefits, there is no quantitative data available on the potential for increasing SOC benefits from different SLM technologies and especially from case studies in the developing countries, and a clear understanding of the trade-offs related to SLM up-scaling is missing. This study aims at assessing the potential increase of SOC under SLM technologies worldwide, evaluating tradeoffs and gains in up-scaling SLM for case studies in Tajikistan, Ethiopia and Switzerland. It makes use of the SLM technologies documented in the online database of the World Overview of Conservation Approaches and Technologies (WOCAT). The study consists of three components: 1) Identifying SOC benefits contributing to the major global environmental issues for SLM technologies worldwide as documented in the WOCAT global database 2) Validation of SOC storage potentials and SOC benefit predictions for SLM technologies from the WOCAT database using results from existing comparative case studies at the plot level, using soil spectral libraries and standardized documentations of ecosystem service from the WOCAT database. 3) Understanding trade-offs and win-win scenarios of up-scaling SLM technologies from the plot to the household and landscape level using material flow analysis. This study builds on the premise that the most promising way to increase benefits from land management is to consider already existing sustainable strategies. Such SLM technologies from all over the world documented are accessible in a standardized way in the WOCAT online database. The study thus evaluates SLM technologies from the WOCAT database by calculating the potential SOC storage increase and

  20. Inter-annual variability of carbon fluxes in temperate forest ecosystems: effects of biotic and abiotic factors

    NASA Astrophysics Data System (ADS)

    Chen, M.; Keenan, T. F.; Hufkens, K.; Munger, J. W.; Bohrer, G.; Brzostek, E. R.; Richardson, A. D.

    2014-12-01

    Carbon dynamics in terrestrial ecosystems are influenced by both abiotic and biotic factors. Abiotic factors, such as variation in meteorological conditions, directly drive biophysical and biogeochemical processes; biotic factors, referring to the inherent properties of the ecosystem components, reflect the internal regulating effects including temporal dynamics and memory. The magnitude of the effect of abiotic and biotic factors on forest ecosystem carbon exchange has been suggested to vary at different time scales. In this study, we design and conduct a model-data fusion experiment to investigate the role and relative importance of the biotic and abiotic factors for inter-annual variability of the net ecosystem CO2 exchange (NEE) of temperate deciduous forest ecosystems in the Northeastern US. A process-based model (FöBAAR) is parameterized at four eddy-covariance sites using all available flux and biometric measurements. We conducted a "transplant" modeling experiment, that is, cross- site and parameter simulations with different combinations of site meteorology and parameters. Using wavelet analysis and variance partitioning techniques, analysis of model predictions identifies both spatial variant and spatially invariant parameters. Variability of NEE was primarily modulated by gross primary productivity (GPP), with relative contributions varying from hourly to yearly time scales. The inter-annual variability of GPP and NEE is more regulated by meteorological forcing, but spatial variability in certain model parameters (biotic response) has more substantial effects on the inter-annual variability of ecosystem respiration (Reco) through the effects on carbon pools. Both the biotic and abiotic factors play significant roles in modulating the spatial and temporal variability in terrestrial carbon cycling in the region. Together, our study quantifies the relative importance of both, and calls for better understanding of them to better predict regional CO2

  1. High-Resolution Forest Canopy Height Estimation in an African Blue Carbon Ecosystem

    NASA Technical Reports Server (NTRS)

    Lagomasino, David; Fatoyinbo, Temilola; Lee, Seung-Kuk; Simard, Marc

    2015-01-01

    Mangrove forests are one of the most productive and carbon dense ecosystems that are only found at tidally inundated coastal areas. Forest canopy height is an important measure for modeling carbon and biomass dynamics, as well as land cover change. By taking advantage of the flat terrain and dense canopy cover, the present study derived digital surface models (DSMs) using stereophotogrammetric techniques on high-resolution spaceborne imagery (HRSI) for southern Mozambique. A mean-weighted ground surface elevation factor was subtracted from the HRSI DSM to accurately estimate the canopy height in mangrove forests in southern Mozambique. The mean and H100 tree height measured in both the field and with the digital canopy model provided the most accurate results with a vertical error of 1.18-1.84 m, respectively. Distinct patterns were identified in the HRSI canopy height map that could not be discerned from coarse shuttle radar topography mission canopy maps even though the mode and distribution of canopy heights were similar over the same area. Through further investigation, HRSI DSMs have the potential of providing a new type of three-dimensional dataset that could serve as calibration/validation data for other DSMs generated from spaceborne datasets with much larger global coverage. HSRI DSMs could be used in lieu of Lidar acquisitions for canopy height and forest biomass estimation, and be combined with passive optical data to improve land cover classifications.

  2. Controls of Carbon Preservation in Coastal Wetlands of Texas: Mangrove vs. Saltmarsh Ecosystems

    NASA Astrophysics Data System (ADS)

    Sterne, A. M. E.; Louchouarn, P.; Norwood, M. J.; Kaiser, K.

    2014-12-01

    The estimated magnitude of the carbon (C) stocks contained in the first meter of US coastal wetland soils represents ~10% of the entire C stock in US soils (4 vs. 52 Pg, respectively). Because this stock extends to several meters below the surface for many coastal wetlands, it becomes paramount to understand the fate of C under ecosystem shifts, varying natural environmental constraints, and changing land use. In this project we analyze total hydrolysable carbohydrates, amino acids, phenols and stable isotopic data (δ13C) at two study sites located on the Texas coastline to investigate chemical compositions and the stage of decomposition in mangrove and marsh grass dominated wetlands. Carbohydrates are used as specific decomposition indicators of the polysaccharide component of wetland plants, whereas amino acids are used to identify the contribution of microbial biomass, and acid/aldehyde ratios of syringyl (S) and vanillyl (V) phenols (Ac/AlS,V) follow the decomposition of lignin. Preliminary results show carbohydrates account for 30-50 % of organic carbon in plant litter and surface sediments at both sites. Sharp declines of carbohydrate yields with depth occur parallel to increasing Ac/AlS,V ratios indicating substantial decomposition of both the polysaccharide and lignin components of litter detritus. Ecological differences (between marsh grass and mangrove dominated wetlands) are discussed to better constrain the role of litter biochemistry and ecological shifts on C preservation in these anoxic environments.

  3. CARBON DIOXIDE FLUXES IN A CENTRAL HARDWOODS OAK-HICKORY FOREST ECOSYSTEM

    SciTech Connect

    Pallardy, Stephen G.; Gu, Lianhong; Hanson, Paul J; Meyers, T. P.; Wullschleger, Stan D; Yang, Bai; Hosman, K. P.

    2007-01-01

    A long-term experiment to measure carbon and water fluxes was initiated in 2004 as part of the Ameriflux network in a second-growth oak-hickory forest in central Missouri. Ecosystem-scale (~ 1 km2) canopy gas exchange (measured by eddy-covariance methods), vertical CO2 profile sampling and soil respiration along with meteorological parameters were monitored continuously. Early results from this forest located on the western margin of the Eastern Deciduous Forest indicated high peak rates of canopy CO2 uptake (35-40 ?mol m-2 s-1) during the growing season. Canopy CO2 profile measurements indicated substantial accumulation of CO2 (~500 ppm) near the surface in still air at night, venting of this buildup in the morning hours under radiation-induced turbulent air flow, and small vertical gradients of CO2 during most of the subsequent light period with minimum CO2 concentrations in the canopy. Flux of CO2 from the soil ranged from 2 to 8 ?mol m-2 s-1 and increased with temperature. Data from this site and others in the network will also allow characterization of regional spatial variation in carbon fluxes as well as inter-annual differences attributable to climatic events such as droughts.

  4. Carbon balance of the terrestrial biosphere in the twentieth century: analyses of CO2, climate and land use effects with four process-based ecosystem models

    USGS Publications Warehouse

    McGuire, A.D.; Sitch, S.; Clein, J.S.; Dargaville, R.; Esser, G.; Foley, J.; Heimann, Martin; Joos, F.; Kaplan, J.; Kicklighter, D.W.; Meier, R.A.; Melillo, J.M.; Moore, B., III; Prentice, I.C.; Ramankutty, N.; Reichenau, T.; Schloss, A.; Tian, H.; Williams, L.J.; Wittenberg, U.

    2001-01-01

    . The next steps for improving the process-based simulation of historical terrestrial carbon include (1) the transfer of insight gained from stand-level process studies to improve the sensitivity of simulated carbon storage responses to changes in CO2 and climate, (2) improvements in the data sets used to drive the models so that they incorporate the timing, extent, and types of major disturbances, (3) the enhancement of the models so that they consider major crop types and management schemes, (4) development of data sets that identify the spatial extent of major crop types and management schemes through time, and (5) the consideration of the effects of anthropogenic nitrogen deposition. The evaluation of the performance of the models in the context of a more complete consideration of the factors influencing historical terrestrial carbon dynamics is important for reducing uncertainties in representing the role of terrestrial ecosystems in future projections of the Earth system.

  5. Soil and vegetation carbon in urban ecosystems: The importance of urban definition and scale

    NASA Astrophysics Data System (ADS)

    Raciti, S. M.; Hutyra, L.; Rao, P.; Finzi, A. C.

    2011-12-01

    There is conflicting evidence about the importance of soils and vegetation in urban carbon metabolism that is caused, in part, by inconsistent definitions of 'urban' land use. In Massachusetts, the US census estimates that 36% of the state is 'urban', yet remote sensing observations reveal that 50% of this urban area is forest or forested wetlands. While both of these estimates can be correct, the importance of soils and vegetation on the carbon metabolism of urban areas is clearly dependent on whether municipal, physical, or social definitions of urban are applied. We quantified urban ecosystem contributions to terrestrial C pools in the Boston Metropolitan Statistical Area (MSA) using several alternative urban definitions. Aboveground biomass (DBH ≥ 5 cm) for the MSA was 7.2 ± 0.4 kg C/m2, reflecting a high proportion of forest cover. Vegetation C was highest in forest (11.6 ± 0.5 kg C/m2) followed by residential (4.6 ± 0.5 kg C/m2) and then other developed (2.0 ± 0.4 kg C/m2) land uses. Soil C (0 to 10 cm) followed the same pattern of decreasing C concentration from forest, to residential, to other developed land uses (4.1 ± 0.1, 4.0 ± 0.2, and 3.3 ± 0.2 kg C/m2, respectively). Soil N concentrations were higher in urban areas than non-urban areas of the same land use type, except for residential areas, which had similarly high soil N concentrations. Urban soil (1 m depth) and vegetation C stocks spanned a wide range, from 14.4 to 54.5 Tg C and from 4.2 to 27.3 Tg C, respectively, depending on the urban definition that was used. Conclusions about the importance of soils and vegetation in urban ecosystems are very sensitive to the definition of urban used by the investigators. Urban areas are rapidly expanding in their extent; a systematic understanding of how our development patterns influence urban carbon metabolism, including vegetation and soils, is necessary to inform future development choices.

  6. Assessing Actual and Potential Organic Carbon Pools in Southern Taiga and Forest-Steppe Ecosystems of Russia

    NASA Astrophysics Data System (ADS)

    Chernova, Olga; Ryzhova, Irina; Podvezennaya, Marina

    2014-05-01

    Recent debates on climate changes showed the importance of maintaining natural cycles of nutrients and preserving extensive areas of natural ecosystems to ensure sustainability of the biosphere. The size and distribution of nutrient pools within ecosystems are the key characteristics of the biological cycle reflecting changes in the functioning of natural systems. Carbon pools assessed in similar land-use types by different researchers are often poorly comparable due to various calculation algorithms, sampling techniques and sets of field data used. Model-based assessments often yield results that significantly depart from calculations based on actual field data. We estimated the actual and potential natural carbon pools using potential natural vegetation maps, soil maps, up-to-date statistics and results of regional studies. Organic carbon pools in biomass, forest litter, peat and soil were calculated for most typical natural (ecosystems, which experienced the least effect of historic land use) and modern ecosystems for two administrative regions of Russia: 1. Kursk region characterized by high productive natural steppe vegetation with predominance of chernozems - the country's most fertile soils, which were extensively transformed by agricultural activity; 2. Kostroma region, sparsely populated area with still abundant southern taiga forests. The average characteristics of vegetation productivity for natural and some human-modified ecosystems such as coniferous (pine, spruce) and noble broadleaf (oak, linden) forests, swamps, bogs, steppes, bottomland meadows, secondary forests, hayfields, pastures were calculated using the Database on the Productivity of Ecosystems in North Eurasia. The biological productivity of present-day forests and carbon pools in biomass were calculated using the program for assessing forest carbon budget (ROBUL model). Similar characteristics were used for agricultural areas. They were averaged according to crop rotations and recalculated

  7. Diagnosing turnover times of carbon in terrestrial ecosystems to address global climate co-variability and for model evaluation

    NASA Astrophysics Data System (ADS)

    Carvalhais, Nuno; Thurner, Martin; Forkel, Matthias; Beer, Christian; Reichstein, Markus

    2016-04-01

    The response of the global terrestrial carbon cycle to climate change and the associated climate-carbon feedback has been shown to be highly uncertain. Ultimately this response depends on how carbon assimilation by vegetation changes relatively to the effective mean turnover time of carbon in vegetation and soils. Consequently, these turnover times of carbon are expected to depend on vegetation longevity and relative allocation to woody and non-woody biomass, and to litter and soil organic matter decomposition rates, which depend on climate variables, but also soil properties, biological activity and chemical composition of the litter. Data oriented estimates of whole ecosystem carbon turnover rates (τ) are based on global datasets of carbon stocks and fluxes and used to diagnose the co-variability of τ with climate. The overall mean global carbon turnover time estimated is 23 years (with 95% confidence intervals between 19 and 30 years), showing a strong spatial variability ranging from 15 years in equatorial regions to 255 years at latitudes north of 75°N. This latitudinal pattern reflects the expected dependencies of metabolic activity and ecosystem dynamics to temperature. However, a strong local correlation of τ with mean annual precipitation patterns is at least as prevalent as the expected effect of temperature on the global patterns of τ. The comparing between observation-based estimates of τ with current state-of-the-art Earth system models shows a consistent latitudinal pattern but a significant underestimation bias of ˜36% globally. Models consistently show a stronger association of τ to temperature and do not reproduce the observed association to mean annual precipitation in different latitudinal bands. A further breakdown of τ focusing on forest background mortality also shows contrasting regional patterns to those of global vegetation models, suggesting that the treatment of plant mortality may be overly simplistic in different model

  8. Evaluating of simulated carbon flux phenology over a cropland ecosystem in a semiarid area of China with SiBcrop

    NASA Astrophysics Data System (ADS)

    Du, Qun; Liu, Huizhi; Xu, Lujun

    2016-07-01

    The cropland ecosystem in semiarid areas is sensitive to climate change. The accurate representation of crop phenology is important for predicting the carbon and water exchange process. The performance of a newly developed phenological model (SiBcrop) for simulations of carbon flux phenology in a semiarid area ecosystem was evaluated. The results showed that the SiBcrop improved the prediction for daily maximum gross primary production (GPP), and the days GPP reached the maximum value were closer to the observation, compared to SiB3. SiBcrop had a better prediction for both monthly total net ecosystem exchange (NEE) in the growing season than in the dormant season in semiarid areas. The day when the cumulative NEE predicted with SiBcrop became positive was closer to the observation. The observed start date of carbon uptake (CUstart) had a larger annual variation than did the end date of carbon uptake (CUend). SiBcrop had a better prediction for CUstart but poor for CUend, compared to SiB3. There was a longer carbon uptake period (CUP) predicted with SiBcrop than the observed results.

  9. Cumulative response of ecosystem carbon and nitrogen stocks to chronic CO2 exposure in a subtropical oak woodland

    PubMed Central

    Hungate, Bruce A; Dijkstra, Paul; Wu, Zhuoting; Duval, Benjamin D; Day, Frank P; Johnson, Dale W; Megonigal, J Patrick; Brown, Alisha L P; Garland, Jay L

    2013-01-01

    Summary Rising atmospheric carbon dioxide (CO2) could alter the carbon (C) and nitrogen (N) content of ecosystems, yet the magnitude of these effects are not well known. We examined C and N budgets of a subtropical woodland after 11 yr of exposure to elevated CO2. We used open-top chambers to manipulate CO2 during regrowth after fire, and measured C, N and tracer 15N in ecosystem components throughout the experiment. Elevated CO2 increased plant C and tended to increase plant N but did not significantly increase whole-system C or N. Elevated CO2 increased soil microbial activity and labile soil C, but more slowly cycling soil C pools tended to decline. Recovery of a long-term 15N tracer indicated that CO2 exposure increased N losses and altered N distribution, with no effect on N inputs. Increased plant C accrual was accompanied by higher soil microbial activity and increased C losses from soil, yielding no statistically detectable effect of elevated CO2 on net ecosystem C uptake. These findings challenge the treatment of terrestrial ecosystems responses to elevated CO2 in current biogeochemical models, where the effect of elevated CO2 on ecosystem C balance is described as enhanced photosynthesis and plant growth with decomposition as a first-order response. PMID:23718224

  10. Carbon balance of surfaces vs. ecosystems: advantages of measuring eddy covariance and soil respiration simultaneously in dry grassland ecosystems

    NASA Astrophysics Data System (ADS)

    Nagy, Z.; Pintér, K.; Pavelka, M.; Darenová, E.; Balogh, J.

    2011-02-01

    An automated open system for measurement of soil CO2 efflux (Rsc) was developed and calibrated against known fluxes and tested in the field, while measuring soil respiration also by the gradient method (Rsg) at a dry sandy grassland (Bugac, Hungary). Ecosystem respiration (Reco) was measured by the eddy covariance technique. Small chamber size (5 cm in diameter) of the chamber system made it possible to use the chambers also in vegetation gaps, thereby avoiding the necessity of removing shoots, the disturbance of the spatial structure of vegetation and the upper soil layer. Low air flow rates associated with small chamber volume and chamber design allowed the overpressure range to stabilize between 0.05-0.12 Pa. While the correlation between ecosystem and soil CO2 efflux rates as measured by the independent methods was significant, Reco rates were similar or even lower than Rsc in the low flux (up to 2 μmol CO2 m-2 s-1) range, probably due to the larger than assumed storage flux. The gradient method showed both up and downward CO2 fluxes originating from the main rooting zone after rains. Downward fluxes within the soil profile amounted to 15% of the simultaneous upward fluxes and to ~ 7.6% of the total (upward) effluxes during the 3 months study. The upper 5 cm soil layer contributed to ~ 50% of the total soil CO2 efflux. The continuously operated automatic open chamber system and the gradient system makes possible the detection of situations when the eddy system underestimates Reco, gives the lower limit of underestimation (chamber system) and helps in quantifying the downward flux component of soil respiration (gradient method) between the soil layers. These latter (downward) fluxes are expected to seriously affect (1) the Reco vs. temperature response functions and (2) the net ecosystem exchange of CO2 (NEE) vs. photon flux density response functions, therefore potentially affecting also the gap filling procedures and to led to a situation (3) when the

  11. The spatial and temporal shifts of biofuel production in the ecosystem-level carbon and water dynamics in the central plains of US

    NASA Astrophysics Data System (ADS)

    Lin, P.; Brunsell, N. A.

    2011-12-01

    The grasslands of the central plains US are the leading producer of wheat, sorghum and a significant amount of corn and soybean. By linking the food production and energy cycles, increasing demand for ethanol, biodiesel, and food, not only regional ecosystems are altered by the influences of Land-Use Land-Cover (LULC), but it is also a challenge for us to gain more knowledge about the carbon balance on fuel and food. In order to ascertain the impacts of changing LULC on carbon and water dynamics, more specifically, to examine the impacts of altering current land cover to increase biofuel production in this region, we used Normalized Difference Vegetation Index (NDVI) data and precipitation record for the period from 1982 to 2003 to show the temporal dynamics associated with different landcover types as a function of location along the mean precipitation gradient; and then employed Biome-BGC model to estimate key carbon fluxes and storage pools associated with each of the different landcover classes, as well as the fluxes resulting from landcover changes. Results show an increasing trend of NDVI is from the west to the east, which agreed with the spatial distribution of precipitation, however due to some of LULC types are grown by irrigation, precipitation is not the main effect for vegetation development in west portion. However, overall within the study area, indicated by the temporal distributed plots of wavelet analysis for NDVI and precipitation, vegetation dynamics is obviously affected by long-term regional climatic factors, i.e. precipitation, not by short-term or individual local factors instead. On the other hand, by inputting actual land cover and interpolated meteorological data, as well as important ecosystem variables that govern carbon dynamics, we can better define the impacts of biofuel productions; moreover, this ecosystem carbon cycling simulation by Bio-BGC model illustrates that the extent of those landcover responses depend not only on the rate

  12. Carbon and Nitrogen Stocks in the Salt Lake Valley Urban Ecosystem

    NASA Astrophysics Data System (ADS)

    Williamson, J. C.; Dennison, P. E.; Ehleringer, J. R.

    2008-12-01

    Water availability exerts a fundamental control over primary production processes in both managed and unmanaged arid land ecosystems. Societal interest in converting grasslands to urban forest has likely increased primary productivity in many western US cities. The changes in primary productivity have the potential to alter C and N stocks of urban soils. Here, we report on trends in soil C and N storage observed along an urban age gradient spanning a century in the Salt Lake Valley, USA metropolitan area. Our results indicate substantial accumulation of soil organic C and total N beneath residential lawns in this semi-arid region. Soil organic C and total N stocks in the upper 20 cm of lawn soils increased as much as 3-fold following long-term residential use. Average tree biomass of residential parcels increased quickly with age, creating urban forests with standing biomass values similar to nearby coniferous forests. Anthropogenic influence emerged as the dominant source of variation in these stocks across our study area, eclipsing site characteristics such as soil texture and elevation that are commonly important in natural settings. While US cities are prominent exporters of atmospheric C and reactive N, significant gains in C and N stocks may offset a portion of these outputs in well-irrigated cities in dry climates. Observations of regional C and N storage in western US cities should lead to better estimates of sequestration capacities and provide insights into the potential consequence of future water-use policies, including xeriscaping.

  13. Climate extremes and the carbon cycle - a review using an integrated approach with regional examples for forests & native ecosystems -

    NASA Astrophysics Data System (ADS)

    Frank, D.; Reichstein, M.; Bahn, M.; Beer, C.; Ciais, P.; Mahecha, M.; Seneviratne, S. I.; Smith, P.; van Oijen, M.; Walz, A.

    2012-04-01

    The terrestrial carbon cycle provides an important biogeochemical feedback to climate and is itself particularly susceptible to extreme climate events. Climate extremes can override any (positive) effects of mean climate change as shown in European and recent US-American heat waves and dry spells. They can impact the structure, composition, and functioning of terrestrial ecosystems and have the potential to cause rapid carbon losses from accumulated stocks. We review how climate extremes like severe droughts, heat waves, extreme precipitation or storms can cause direct impacts on the CO2 fluxes [e.g. due to extreme temperature and/ or drought events] as well as lagged impacts on the carbon cycle [e.g. via an increased fire risk, or disease outbreaks and pest invasions]. The relative impact of the different climate extremes varies according to climate region and vegetation type. We present lagged effects on plant growth (and mortality) in the year(s) following an extreme event and their impacts on the carbon sequestration of forests and natural ecosystems. Comprehensive regional or even continental quantification with regard to extreme events is missing, and especially compound extreme events, the role of lagged effects and aspects of the return frequency are not studied enough. In a case study of a Mediterranean ecosystem we illustrate that the response of the net carbon balance at ecosystem level to regional climate change is hard to predict as interacting and partly compensating processes are affected and several processes which have the ability to substantially alter the carbon balance are not or not sufficiently represented in state-of-the-art biogeochemical models.

  14. Global Sensitivity Analysis and Parameter Calibration for an Ecosystem Carbon Model

    NASA Astrophysics Data System (ADS)

    Safta, C.; Ricciuto, D. M.; Sargsyan, K.; Najm, H. N.; Debusschere, B.; Thornton, P. E.

    2013-12-01

    We present uncertainty quantification results for a process-based ecosystem carbon model. The model employs 18 parameters and is driven by meteorological data corresponding to years 1992-2006 at the Harvard Forest site. Daily Net Ecosystem Exchange (NEE) observations were available to calibrate the model parameters and test the performance of the model. Posterior distributions show good predictive capabilities for the calibrated model. A global sensitivity analysis was first performed to determine the important model parameters based on their contribution to the variance of NEE. We then proceed to calibrate the model parameters in a Bayesian framework. The daily discrepancies between measured and predicted NEE values were modeled as independent and identically distributed Gaussians with prescribed daily variance according to the recorded instrument error. All model parameters were assumed to have uninformative priors with bounds set according to expert opinion. The global sensitivity results show that the rate of leaf fall (LEAFALL) is responsible for approximately 25% of the total variance in the average NEE for 1992-2005. A set of 4 other parameters, Nitrogen use efficiency (NUE), base rate for maintenance respiration (BR_MR), growth respiration fraction (RG_FRAC), and allocation to plant stem pool (ASTEM) contribute between 5% and 12% to the variance in average NEE, while the rest of the parameters have smaller contributions. The posterior distributions, sampled with a Markov Chain Monte Carlo algorithm, exhibit significant correlations between model parameters. However LEAFALL, the most important parameter for the average NEE, is not informed by the observational data, while less important parameters show significant updates between their prior and posterior densities. The Fisher information matrix values, indicating which parameters are most informed by the experimental observations, are examined to augment the comparison between the calibration and global

  15. Historical and simulated ecosystem carbon dynamics in Ghana: Land use, management, and climate

    USGS Publications Warehouse

    Tan, Z.; Tieszen, L.L.; Tachie-Obeng, E.; Liu, S.; Dieye, A.M.

    2009-01-01

    We used the General Ensemble biogeochemical Modeling System (GEMS) to simulate responses of natural and managed ecosystems to changes in land use and land cover, management, and climate for a forest/savanna transitional zone in central Ghana. Model results show that deforestation for crop production during the 20th century resulted in a substantial reduction in ecosystem carbon (C) stock from 135.4 Mg C ha-1 in 1900 to 77.0 Mg C ha-1 in 2000, and in soil organic C stock within the top 20 cm of soil from 26.6 Mg C ha-1 to 21.2 Mg C ha-1. If no land use change takes place from 2000 through 2100, low and high climate change scenarios (increase in temperature and decrease in precipitation over time) will result in losses of soil organic C stock by 16% and 20%, respectively. A low nitrogen (N) fertilization rate is the principal constraint on current crop production. An increase in N fertilization under the low climate change scenario would lead to an increase in the average crop yield by 21% with 30 kg N ha-1 and by 42% with 60 kg N ha-1 (varying with crop species), accordingly, the average soil C stock would decrease by 2% and increase by 17%, in all cropping systems by 2100. The results suggest that a reasonable N fertilization rate is critical to achieve food security and agricultural sustainability in the study area through the 21st century. Adaptation strategies for climate change in this study area require national plans to support policies and practices that provide adequate N fertilizers to sustain soil C and crop yields and to consider high temperature tolerant crop species if these temperature projections are exceeded. ?? Author(s) 2009.

  16. 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

  17. Historical and simulated ecosystem carbon dynamics in Ghana: land use, management, and climate

    NASA Astrophysics Data System (ADS)

    Tan, Z.; Tieszen, L. L.; Tachie-Obeng, E.; Liu, S.; Dieye, A. M.

    2009-01-01

    We used the General Ensemble biogeochemical Modeling System (GEMS) to simulate responses of natural and managed ecosystems to changes in land use and land cover, management, and climate for a forest/savanna transitional zone in central Ghana. Model results show that deforestation for crop production during the 20th century resulted in a substantial reduction in ecosystem carbon (C) stock from 135.4 Mg C ha-1 in 1900 to 77.0 Mg C ha-1 in 2000, and in soil organic C stock within the top 20 cm of soil from 26.6 Mg C ha-1 to 21.2 Mg C ha-1. If no land use change takes place from 2000 through 2100, low and high climate change scenarios (increase in temperature and decrease in precipitation over time) will result in losses of soil organic C stock by 16% and 20%, respectively. A low nitrogen (N) fertilization rate is the principal constraint on current crop production. An increase in N fertilization under the low climate change scenario would lead to an increase in the average crop yield by 21% with 30 kg N ha-1 and by 42% with 60 kg N ha-1 (varying with crop species), accordingly, the average soil C stock would decrease by 2% and increase by 17%, in all cropping systems by 2100. The results suggest that a reasonable N fertilization rate is critical to achieve food security and agricultural sustainability in the study area through the 21st century. Adaptation strategies for climate change in this study area require national plans to support policies and practices that provide adequate N fertilizers to sustain soil C and crop yields and to consider high temperature tolerant crop species if these temperature projections are exceeded.

  18. Measuring the impact of prescribed fire management on the carbon balance of a flatwoods ecosystem in Kissimmee, Florida

    NASA Astrophysics Data System (ADS)

    Becker, K.; Hinkle, C.

    2012-12-01

    It has been well documented that terrestrial ecosystems have a great potential to store and sequester carbon. Therefore, a former ranch land at the Disney Wilderness Preserve (DWP), Kissimmee, Florida, USA is being restored to native ecosystems and managed to preserve biodiversity and increase carbon storage. Here, we present measurements of C flux from an eddy covariance system located in a longleaf pine flatwoods ecosystem at DWP. C flux measurements were taken at the site before, during, and after a prescribed fire event. C stock measurements were also taken for aboveground biomass immediately before and after the fire, as well as one year post fire. This study indicated that this ecosystem typically serves as a net sink of C. However, the system became a net source of C immediately following the fire event, with a ~40% loss of aboveground C stock, but recovered to a net sink of C within 6 weeks of the fire. Annually this ecosystem was found to serve as a net C sink even with a prescribed fire event, with annual net ecosystem productivity (NEP) of 508 g C/m2 in a non-fire year (2010) and 237 g C/m2 in a fire year (2011). In addition to the fire, it is important to note that the growing season of 2011 was anomalously dry, which likely hindered productivity, and thus the NEP of the fire year would probably be more similar to the non-fire year under more typical hydrologic conditions. Despite the variability of rainfall between years, this study shows that the longleaf pine flatwoods ecosystem provides the service of C sequestration even in the context of frequent prescribed fire management.

  19. The Effect of Climate and Management on Carbon Fluxes of Three U.S. Southern Plains Ecosystems

    NASA Astrophysics Data System (ADS)

    Raz Yaseef, N.; Fischer, M. L.; Billesbach, D. P.; Biraud, S.; Gunter, S. A.; Bradford, J. A.; Torn, M. S.

    2013-12-01

    The Southern Great Plains are characterized by a fine-scale mixture of different land cover types, predominantly winter-wheat and grazed pasture, with relatively small holdings of other crops, native prairie, and switchgrass. Recent droughts and predictions of increased drought in the future have created concern for these ecosystems. We measured ecosystem carbon, water, and energy fluxes with eddy covariance systems in three different ecosystems characteristic to the Southern Great Plains: cultivated cropland, lightly grazed prairie, and new switchgrass fields, for 2 to 10 years. We identified three parameters dominating carbon and water exchange. First, precipitation during the growing season had a larger effect on plant productivity than annual precipitation. Second, summer-growing native prairies and switchgrass observed more seasonal droughts than winter-wheat because of the higher likelihood of dry soil conditions during summer. Third, management practices for crops were effective in suppressing evapotranspiration and decomposition after senescence (harvest and removal of secondary growth), and increased carbon uptake during the growing season (fertilization). Under severe drought conditions, these practices are not sufficient to maintain plant productivity. In light of future projections for wetter springs and drier summers in the Southern Great Plains, our study indicates increased native-ecosystem vulnerability to climate change over time.

  20. Patterns and determinants of potential carbon gain in the C3 evergreen Yucca glauca (Liliaceae) in a C4 grassland.

    PubMed

    Maragni, L A; Knapp, A K; McAllister, C A

    2000-02-01

    Yucca glauca is a C(3) evergreen rosette species locally common in the C(4)-dominated grasslands of the ce