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Sample records for comparing ecosystem exchange

  1. Comparing the Net Ecosystem Exchange of Two Cropping Systems for Dairy Feed Production

    NASA Astrophysics Data System (ADS)

    Sulaiman, M. F.; Wagner-Riddle, C.; Brown, S. E.

    2015-12-01

    A three-year study was conducted from 2012 to 2014 to determine the net CO2 fluxes from corn and hay, the two main feed crops used in dairy production. The aim of this study is to better understand the net ecosystem exchange (NEE) in annual and perennial cropping systems used in dairy production to benefit greenhouse gas emission model developments and the life cycle analysis of dairy production. The study was conducted on two 4-ha plots where one plot was a 5-year old hayfield and the other plot was planted in a continuous cycle corn. All plots were continuously monitored using the flux-gradient method deployed with a tunable diode laser trace gas analyzer and sonic anemometers. All plots received dairy manure as fertilizer applied according to common practice. The cumulative NEE for the three years of the study was -873.15 g C m-2 for corn and -409.36 g C m-2 for hay. Differences in respiration between the two cropping systems was found to be the larger factor compared to differences in gross ecosystem production (GEP) that resulted in the contrasting cumulative NEE where cumulative respiration for the three years for hay was 3094.23 g C m-2 as opposed to 2078.11 g C m-2 for corn. Cumulative GEP for the three years was 3503.60 and 2951.31 g C m-2 for hay and corn respectively. Inter-annual and inter-crop variability of the NEE, GEP and respiration will be discussed in relation to biomass production, climatic conditions and crop physiological characteristics.

  2. Comparing net ecosystem carbon dioxide exchange at adjacent commercial bioenergy and conventional cropping systems in Lincolnshire, United Kingdom

    NASA Astrophysics Data System (ADS)

    Morrison, Ross; Brooks, Milo; Evans, Jonathan; Finch, Jon; Rowe, Rebecca; Rylett, Daniel; McNamara, Niall

    2016-04-01

    The conversion of agricultural land to bioenergy plantations represents one option in the national and global effort to reduce greenhouse gas emissions whilst meeting future energy demand. Despite an increase in the area of (e.g. perennial) bioenergy crops in the United Kingdom and elsewhere, the biophysical and biogeochemical impacts of large scale conversion of arable and other land cover types to bioenergy cropping systems remain poorly characterised and uncertain. Here, the results of four years of eddy covariance (EC) flux measurements of net ecosystem CO2 exchange (NEE) obtained at a commercial farm in Lincolnshire, United Kingdom (UK) are reported. CO2 flux measurements are presented and compared for arable crops (winter wheat, oilseed rape, spring barely) and plantations of the perennial biofuel crops Miscanthus x. giganteus (C4) and short rotation coppice (SRC) willow (Salix sp.,C3). Ecosystem light and temperature response functions were used to analyse and compare temporal trends and spatial variations in NEE across the three land covers. All three crops were net in situ sinks for atmospheric CO2 but were characterised by large temporal and between site variability in NEE. Environmental and biological controls driving the spatial and temporal variations in CO2 exchange processes, as well as the influences of land management, will be analysed and discussed.

  3. Thermal adaptation of net ecosystem exchange

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Thermal adaptation of gross primary production and ecosystem respiration has been well documented over broad thermal gradients. However, no study has examined their interaction as a function of temperature, i.e. the thermal responses of net ecosystem exchange of carbon (NEE). In this study, we const...

  4. Modeling ecosystem CO[sub 2] exchange in Harvard Forest

    SciTech Connect

    Amthor, J.S.; Goulden, M.L. Harvard Univ, Cambridge, MA )

    1993-06-01

    A new model of forest ecosystem CO[sub 2] and energy exchange (FORPHYS) was tested (i.e., validated) with eddy-correlation measurements of net atmosphere/biosphere CO[sub 2] exchange at Harvard Forest. FORPHYS predictions were comparable to measured whole-ecosystem CO[sub 2] exchange rates. The leaf physiology component of FORPHYS combines a radiation transfer model; a modified Farquhar model of photosynthesis and photorespiration; a physically based model of leaf energy exchange, transpiration, and temperature; a leaf respiration model; and a dynamic model of stomatal conductance. Maintenance respiration of all tree organs is based on temperature and nitrogen content. Growth and growth respiration are modeled according to the quantitative biosynthesis model of Penning de Vries. Soil CO[sub 2] exchange is modeled empirically, based on environmental factors. FORPHYS is used to identify, in a quantitative manner, the processes underlying net ecosystem exchange of carbon and energy. The ultimate goal of the model is to predict effects of environmental change, in particular increasing atmospheric CO[sub 2] and temperature, on forest ecosystem carbon exchange and storage.

  5. Turbulence Considerations for Comparing Ecosystem Exchange over Old-Growth and Clear-Cut Stands For Limited Fetch and Complex Canopy Flow Conditions

    SciTech Connect

    Wharton, S; Schroeder, M; Paw U, K T; Falk, M; Bible, K

    2009-01-08

    Carbon dioxide, water vapor and energy fluxes were measured using eddy covariance (EC) methodology over three adjacent forests in southern Washington State to identify stand-level age-effects on ecosystem exchange. The sites represent Douglas-fir forest ecosystems at two contrasting successional stages: old-growth (OG) and early seral (ES). Here we present eddy flux and meteorological data from two early seral stands and the Wind River AmeriFlux old-growth forest during the growing season (March-October) in 2006 and 2007. We show an alternative approach to the usual friction velocity (u*) method for determining periods of adequate atmospheric boundary layer (ABL) mixing based on the ratio of mean horizontal ({bar u}) and vertical ({bar w}) wind flow to a modified turbulent kinetic energy scale (uTKE). This new parameter in addition to footprint modeling showed that daytime CO{sub 2} fluxes (F{sub NEE}) in small clear-cuts (< 10 hectares) can be measured accurately with EC if micrometeorological conditions are carefully evaluated. Peak midday CO{sub 2} fluxes (F{sub NEE} = -14.0 to -12.3 {micro}mol m{sup -2} s{sup -1}) at OG were measured in April in both 2006 and 2007 before bud break when air and soil temperatures and vapor pressure deficit were relatively low, and soil moisture and light levels were favorable for photosynthesis. At the early seral stands, peak midday CO{sub 2} fluxes (F{sub NEE} = -11.0 to -8.7 {micro}mol m{sup -2} s{sup -1}) were measured in June and July while spring-time CO{sub 2} fluxes were much smaller (F{sub NEE} = -3.8 to -3.6 {micro}mol m{sup -2} s{sup -1}). Overall, we measured lower evapotranspiration (OG = 230 mm; ES = 297 mm) higher midday F{sub NEE} (OG F{sub NEE} = -9.0 {micro}mol m{sup -2} s{sup -1}; ES F{sub NEE} = -7.3 {micro}mol m{sup -2} s{sup -1}) and higher Bowen ratios (OG {beta} = 2.0. ES {beta} = 1.2) at the old-growth forest than at the ES sites during the summer months (May-August). Eddy covariance studies such as ours

  6. Trophic cascade alters ecosystem carbon exchange.

    PubMed

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

    2013-07-02

    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 (13)C 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.

  7. Response of a sedge wetland to sub-ambient atmospheric CO2 concentrations: Comparing field measurements to modeled ecosystem gas exchange.

    NASA Astrophysics Data System (ADS)

    Rasse, D. P.; Unterkoffler, B.; Peresta, G.; Francois, L. M.; Gerard, J.; Drake, B. G.

    2002-05-01

    Low rubisco carboxylation and water use efficiency responses to sub-ambient atmospheric CO2 concentration constrain plant productivity. . How would a present day ecosystem respond to conditions that prevailed between 14000 BC and 7000 BC, as the atmospheric CO2 concentration increased from 190 to 260 ppmv following the last ice age? The objective of our study was to evaluate the response of a natural ecosystem to reduced atmospheric CO2 concentrations by field measurements and by mechanistic simulation modeling. Because of our extensive databases of Scirpus olneyi response to elevated CO2 and a comprehensive mechanistic model developed specifically for this ecosystem, we conducted our study on native stands of this salt marsh plant. In the present study, net CO2 assimilation rates were measured for present ambient(PE)- and 2xPE -CO2-grown Scirpus olneyi exposed to 165, 265, 365, 515, and 715 ppmv CO2 in open top chambers. As compared to ambient conditions, maximum assimilation rates were approximately divided by a factor 2 at the sub ambient level of 265 ppmv and by a factor 3 at 165 ppmv. Plants grown at 2xPE-CO2 displayed lower assimilation rates than PE-CO2 plants irrespective of the CO2 concentration at which measurements were conducted. The simulation model, previously developed with PE-CO2 and 2xPE-CO2 data from our databases was calibrated with the sub-ambient CO2 data from this study. These results raise the possibility that plants grown at sub-ambient levels of atmospheric CO2 would acclimate by increasing the amounts of rubisco and the stomatal density. But could the cost of these adaptations be met by plants growing at cooler temperatures, less water, and shorter growing seasons which would have accompanied low atmospheric CO2 ? Model estimates of plant productivity from 14000 BC to pre-industrial conditions will be presented, together with an analysis of nitrogen availability impacts on this productivity.

  8. Comparative review of multifunctionality and ecosystem services in sustainable agriculture.

    PubMed

    Huang, Jiao; Tichit, Muriel; Poulot, Monique; Darly, Ségolène; Li, Shuangcheng; Petit, Caroline; Aubry, Christine

    2015-02-01

    Two scientific communities with broad interest in sustainable agriculture independently focus on multifunctional agriculture or ecosystem services. These communities have limited interaction and exchange, and each group faces research challenges according to independently operating paradigms. This paper presents a comparative review of published research in multifunctional agriculture and ecosystem services. The motivation for this work is to improve communication, integrate experimental approaches, and propose areas of consensus and dialog for the two communities. This extensive analysis of publication trends, ideologies, and approaches enables formulation of four main conclusions. First, the two communities are closely related through their use of the term "function." However, multifunctional agriculture considers functions as agricultural activity outputs and prefers farm-centred approaches, whereas ecosystem services considers ecosystem functions in the provision of services and prefers service-centred approaches. Second, research approaches to common questions in these two communities share some similarities, and there would be great value in integrating these approaches. Third, the two communities have potential for dialog regarding the bundle of ecosystem services and the spectrum of multifunctional agriculture, or regarding land sharing and land sparing. Fourth, we propose an integrated conceptual framework that distinguishes six groups of ecosystem services and disservices in the agricultural landscape, and combines the concepts of multifunctional agriculture and ecosystem services. This integrated framework improves applications of multifunctional agriculture and ecosystem services for operational use. Future research should examine if the framework can be readily adapted for modelling specific problems in agricultural management.

  9. 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

  10. Greenhouse gas exchange in tropical mountain ecosystems in Tanzania

    NASA Astrophysics Data System (ADS)

    Gerschlauer, Friederike; Kikoti, Imani; Kiese, Ralf

    2014-05-01

    Tropical mountain ecosystems with their mostly immense biodiversity are important regions for natural resources but also for agricultural production. Their supportive ecosystem processes are particularly vulnerable to the combined impacts of global warming and the conversion of natural to human-modified landscapes. Data of impacts of climate and land use change on soil-atmosphere interactions due to GHG (CO2, CH4, and N2O) exchange from these ecosystems are still scarce, in particular for Africa. Tropical forest soils are underestimated as sinks for atmospheric CH4 with regard to worldwide GHG budgets (Werner et al. 2007, J GEOPHYS RES Vol. 112). Even though these soils are an important source for the atmospheric N2O budget, N2O emissions from tropical forest ecosystems are still poorly characterized (Castaldi et al. 2013, Biogeosciences 10). To obtain an insight of GHG balances of selected ecosystems soil-atmosphere exchange of N2O, CH4 and CO2 was investigated along the southern slope of Mt. Kilimanjaro, Tanzania. We will present results for tropical forests in three different altitudes (lower montane, Ocotea, and Podocarpus forest), home garden (extensive agro-forestry), and coffee plantation (intensive agro-forestry). Therefore we used a combined approach consisting of a laboratory parameterization experiment (3 temperature and 2 moisture levels) and in situ static chamber measurements for GHG exchange. Field measurements were conducted during different hygric seasons throughout two years. Seasonal variation of temperature and especially of soil moisture across the different ecosystems resulted in distinct differences in GHG exchange. In addition environmental parameters like soil bulk density and substrate availability varying in space strongly influenced the GHG fluxes within sites. The results from parameterization experiments and in situ measurements show that natural forest ecosystems and extensive land use had higher uptakes of CH4. For the investigated

  11. 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 ...

  12. Growing season net ecosystem CO2 exchange of two desert ecosystems with alkaline soils in Kazakhstan.

    PubMed

    Li, Longhui; Chen, Xi; van der Tol, Christiaan; Luo, Geping; Su, Zhongbo

    2014-01-01

    Central Asia is covered by vast desert ecosystems, and the majority of these ecosystems have alkaline soils. Their contribution to global net ecosystem CO2 exchange (NEE) is of significance simply because of their immense spatial extent. Some of the latest research reported considerable abiotic CO2 absorption by alkaline soil, but the rate of CO2 absorption has been questioned by peer communities. To investigate the issue of carbon cycle in Central Asian desert ecosystems with alkaline soils, we have measured the NEE using eddy covariance (EC) method at two alkaline sites during growing season in Kazakhstan. The diurnal course of mean monthly NEE followed a clear sinusoidal pattern during growing season at both sites. Both sites showed significant net carbon uptake during daytime on sunny days with high photosynthetically active radiation (PAR) but net carbon loss at nighttime and on cloudy and rainy days. NEE has strong dependency on PAR and the response of NEE to precipitation resulted in an initial and significant carbon release to the atmosphere, similar to other ecosystems. These findings indicate that biotic processes dominated the carbon processes, and the contribution of abiotic carbon process to net ecosystem CO2 exchange may be trivial in alkaline soil desert ecosystems over Central Asia.

  13. Net ecosystem carbon exchange in three contrasting Mediterranean ecosystems - the effect of drought

    NASA Astrophysics Data System (ADS)

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

    2007-09-01

    Droughts reduce gross primary production (GPP) and ecosystem respiration (Reco), 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 changes in rain seasonality. We compared carbon fluxes measured by the eddy covariance technique in three contrasting ecosystems in southern Portugal: an evergreen oak woodland (savannah-like) with ca.~21% tree crown cover, a grassland dominated by herbaceous annuals and a coppiced short-rotation eucalyptus plantation. During the experimental period (2003-2006) the eucalyptus plantation was always the strongest sink for carbon: net ecosystem exchange rate (NEE) between -861 and -399 g C m-2 year-1. The oak woodland and the grassland were much weaker sinks for carbon: NEE varied in the oak woodland between -140 and -28 g C m-2 year-1 and in the grassland between -190 and +49 g C m-2 year-1. The eucalyptus stand had higher GPP and a lower proportion of GPP spent in respiration than the other systems. The higher GPP resulted from high leaf area duration (LAD), as a surrogate for the photosynthetic photon flux density absorbed by the canopy. The eucalyptus had also higher rain use efficiency (GPP per unit of rain volume) and light use efficiency (the daily GPP per unit incident photosynthetic photon flux density) than the other two ecosystems. The effects of a severe drought could be evaluated during the hydrological-year (i.e., from October to September) of 2004-2005. Between October 2004 and June 2005 the precipitation was only 40% of the long-term average. In 2004-2005 all ecosystems had GPP lower than in wetter years and carbon sequestration was strongly restricted (less negative NEE). The grassland was a net source of carbon dioxide (+49 g C m-2 year-1). In the oak woodland a large proportion of GPP resulted from carbon assimilated by its annual vegetation component, which was strongly affected by

  14. 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.

  15. The Importance of Winter for Controlling the Growing Season Net Ecosystem Exchange (NEE) of Boreal Forests

    NASA Astrophysics Data System (ADS)

    Oquist, M. G.; Peichl, M.; Ottosson Lofvenius, M.; Nilsson, M. B.

    2014-12-01

    It is becoming increasingly apparent that the winter season of high latitudes can be important for controlling a range of ecological and biogeochemical properties of northern ecosystems. Here we evaluate the importance of winter conditions on the carbon exchange between boreal forest systems and the atmosphere during the following growing season in order to elucidate any influence of inter-seasonal "memory" effects on carbon exchange properties of boreal forest ecosystems. The study is based on 5 years of continuous eddy covariance measurements at two ca 50 year old Norway spruce stands situated in mid- and northern Sweden, respectively (a total of 10 site years). The growing season net ecosystem exchange (NEE) ranged from -530 to -60 g C m-2 (negative values indicates carbon sinks). Environmental conditions during the growing season (e.g. temperature, radiation, length) only weakly explained the year-to-year variability in NEE. In contrast, up to 75% of the variation could be explained by the severity of the preceding winter (defined as the lowest observed average weekly air temperature) using an exponential response function. After warm winters the carbon sink properties were high as compared to those observed after cold winters. The winter conditions markedly affected the systems potential for carbon uptake in early summer. This presentation will address the potential mechanisms underpinning the observed correlations linking growing season carbon exchange to the conditions of the preceding winter. The influence of winter on the partitioned carbon fluxes of ecosystem respiration and gross primary productivity, respectively, will also be addressed. The results strongly indicate that controls on boreal forest carbon exchange can transcend across seasons. Understanding these mechanisms are integral for understanding the environmental drivers of atmospheric carbon exchange, allowing for accurate predictions of boreal forest NEE under both present and future climates.

  16. Phenological control over ecosystem-atmosphere carbon exchange (Invited)

    NASA Astrophysics Data System (ADS)

    Monson, R. K.; Moore, D. J.; Scott-Denton, L.; Burns, S. P.

    2010-12-01

    Our understanding of ecosystem-atmosphere carbon fluxes has been improved over the past decade in large part due to the maturation of observational records from networks of flux towers and the development of model-data assimilation techniques from which insight into carbon cycle processes can be extracted. Some of the earliest analyses of the observation record revealed that interannual phenological variation in forest ecosystems has a significant influence on the annual cumulative net rate of CO2 uptake from the atmosphere. In winter-deciduous forest ecosystems, phenological variability in the timing of bud break in the spring, and the early-season rate at which the forest reaches its seasonal maximum leaf area index, have large effects on the ultimate annual sum for net ecosystem CO2 exchange (NEE). In snow-controlled evergreen forests, the timing at which snow melt or soil thaw occurs, and liquid water becomes available to drive diurnal increases in stomatal conductance, the spring 'phenological switch-on' can be abrupt and the capacity for the forest to reach its seasonal maximum NEE can occur within a few days. The relatively high sensitivity of ecosystem carbon budgets to variability in phenology renders it difficult to accurately model system dynamics, especially for evergreen forests. Recent model-data assimilation studies have found large errors in the ability of the models to replicate observations of NEE at the seasonal-to-annual time scales, in large part due to inadequacies in how they capture spring and fall phenology thresholds and early- and late-season dynamics in the state of the photosynthetic apparatus. In our own studies of interannual variation in NEE in the evergreen subalpine forest at Niwot Ridge, Colorado, we have not been able to accurately represent spring phenology dynamics and their influence on annual NEE using the Simple Evapotranspiration and Net Photosynthesis (SIPNET) model without explicit consideration of snowmelt dynamics. In

  17. 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

    flooding. To partition the net flux into its component fluxes gross primary production (GPP) and ecosystem respiration (Reco), these tidal influences have to be incorporated in the NEE model. Differences in GPP and Reco during high tide and low tide events can be used to constrain estimates of lateral carbon transport. These will need to be compared to direct measurements of tidal carbon fluxes to determine how much of the reduction in atmospheric fluxes is due to metabolic changes and how much is due to the exchange of carbon between the marsh and water.

  18. Sensitivity of Prosopis velutina to Summer Rainfall and Consequences for Seasonal Patterns of Ecosystem Carbon Exchange

    NASA Astrophysics Data System (ADS)

    Potts, D. L.; Cable, J. M.; Scott, R. L.; Williams, D. G.; Goodrich, D. C.; Huxman, T. E.

    2005-12-01

    Future changes in dryland vegetation composition will interact with climate variability to influence carbon and water cycling in unforeseen ways. Observed increases in the density of woody plants in North America's savanna ecosystems may be an important terrestrial carbon sink and could alter patterns of regional hydrologic cycling. During the 2005 growing season we compared seasonal patterns of Prosopis velutina plant water status and leaf gas exchange in upland and riparian savannas. Previous work suggested the plant size class constrained alluvial groundwater access and that mature individuals were less sensitive to the onset of summer rains at the riparian site. We predicted that at the upland site, where groundwater was unavailable, mature and juvenile plants would respond similarly to the onset of summer rains. Furthermore, we predicted that this increased sensitivity by the dominant vegetation to seasonal rainfall would be reflected in NEE data collected by eddy-covariance at both sites. Results indicate that mesquite performance and the duration and magnitude of ecosystem carbon exchanges are tightly linked to precipitation at the upland site. Comparing upland and riparian sites demonstrates how seasonal pattern of precipitation, plant-available alluvial groundwater and vegetation structure interact to govern ecosystem carbon balance in savanna ecosystems.

  19. Long term trends of carbon dioxide exchange in a tundra ecosystem affected by permafrost thaw

    NASA Astrophysics Data System (ADS)

    Schuur, E. A.; Bracho, R. G.; Belshe, F.; Crummer, K. G.; Hicks Pries, C.; Krapek, J.; Natali, S.; Pegoraro, E.; Salmon, V.; Trucco, C.; Vogel, J. G.; Webb, E.

    2013-12-01

    Arctic warming has led to permafrost degradation and ground subsidence as a result of ground ice melting. Frozen soil organic matter that thaws can increase carbon (C) emissions to the atmosphere via respiration, but this can be offset in part by increases in plant growth. The balance of plant and microbial processes, and how they change through time, will determine how permafrost ecosystems influence future climate change via the C cycle. This study addressed this question both on short (interannual) and longer (decadal) time periods by measuring C fluxes over a ten-year period at three sites that represent a gradient of time since permafrost thaw. All three sites are upland tundra ecosystems located in Interior Alaska but differed in the extent of permafrost thaw and ground subsidence. Results showed an increasing growing season (May - September) trend in gross primary productivity, net ecosystem exchange, aboveground net primary productivity, and annual net ecosystem exchange at all sites over the study period from 2004-2013. In contrast, there was no directional change in annual and growing season ecosystem respiration, or mass loss from decomposition of a common cellulose substrate. The increasing trends over time as well as inter site differences most closely followed variation in growing season thaw depth over the same time period. During the study period, sites with more permafrost degradation (deeper seasonal thaw) had significantly greater gross primary productivity compared to where degradation was least, but also greater growing season ecosystem respiration. Adding in winter respiration decreased, in part, the summer C sink and left the site with the most permafrost degradation near C neutral, with the other sites annual C sinks. However, annual C balance was strongly dependent on winter respiration, which, compared to the growing season, was relatively data-poor due to extreme environmental conditions. Measurements of growing season and annual C

  20. Effects of water and nitrogen addition on ecosystem carbon exchange in a meadow steppe.

    PubMed

    Wang, Yunbo; Jiang, Qi; Yang, Zhiming; Sun, Wei; Wang, Deli

    2015-01-01

    A changing precipitation regime and increasing nitrogen deposition are likely to have profound impacts on arid and semiarid ecosystem C cycling, which is often constrained by the timing and availability of water and nitrogen. However, little is known about the effects of altered precipitation and nitrogen addition on grassland ecosystem C exchange. We conducted a 3-year field experiment to assess the responses of vegetation composition, ecosystem productivity, and ecosystem C exchange to manipulative water and nitrogen addition in a meadow steppe. Nitrogen addition significantly stimulated aboveground biomass and net ecosystem CO2 exchange (NEE), which suggests that nitrogen availability is a primary limiting factor for ecosystem C cycling in the meadow steppe. Water addition had no significant impacts on either ecosystem C exchange or plant biomass, but ecosystem C fluxes showed a strong correlation with early growing season precipitation, rather than whole growing season precipitation, across the 3 experimental years. After we incorporated water addition into the calculation of precipitation regimes, we found that monthly average ecosystem C fluxes correlated more strongly with precipitation frequency than with precipitation amount. These results highlight the importance of precipitation distribution in regulating ecosystem C cycling. Overall, ecosystem C fluxes in the studied ecosystem are highly sensitive to nitrogen deposition, but less sensitive to increased precipitation.

  1. Effects of Water and Nitrogen Addition on Ecosystem Carbon Exchange in a Meadow Steppe

    PubMed Central

    Wang, Yunbo; Jiang, Qi; Yang, Zhiming; Sun, Wei; Wang, Deli

    2015-01-01

    A changing precipitation regime and increasing nitrogen deposition are likely to have profound impacts on arid and semiarid ecosystem C cycling, which is often constrained by the timing and availability of water and nitrogen. However, little is known about the effects of altered precipitation and nitrogen addition on grassland ecosystem C exchange. We conducted a 3-year field experiment to assess the responses of vegetation composition, ecosystem productivity, and ecosystem C exchange to manipulative water and nitrogen addition in a meadow steppe. Nitrogen addition significantly stimulated aboveground biomass and net ecosystem CO2 exchange (NEE), which suggests that nitrogen availability is a primary limiting factor for ecosystem C cycling in the meadow steppe. Water addition had no significant impacts on either ecosystem C exchange or plant biomass, but ecosystem C fluxes showed a strong correlation with early growing season precipitation, rather than whole growing season precipitation, across the 3 experimental years. After we incorporated water addition into the calculation of precipitation regimes, we found that monthly average ecosystem C fluxes correlated more strongly with precipitation frequency than with precipitation amount. These results highlight the importance of precipitation distribution in regulating ecosystem C cycling. Overall, ecosystem C fluxes in the studied ecosystem are highly sensitive to nitrogen deposition, but less sensitive to increased precipitation. PMID:26010888

  2. Growing season ecosystem and leaf-level gas exchange of an exotic and native semiarid bunchgrass.

    PubMed

    Hamerlynck, Erik P; Scott, Russell L; Moran, M Susan; Keefer, Timothy O; Huxman, Travis E

    2010-07-01

    The South African grass, Lehmann lovegrass (Eragrostis lehmanniana), may alter ecosystem processes across extensive semiarid grasslands and savannahs of western North America. We compared volumetric soil moisture (theta), total and green tissue leaf area index (LAI), ecosystem (i.e. whole-plant and soil), and leaf-level gas exchange of Lehmann lovegrass and the native bush muhly (Muhlenbergia porteri) over the 2008 monsoon season in a semiarid savanna in southern Arizona, USA, to see if these were consistent with high productivity associated with lovegrass invasive success. theta across 0-5 and 0-25 cm was higher while evapotranspiration (ET) was similar between lovegrass and bush muhly plots, except shortly after rainfall, when ET was 32-81% higher in lovegrass plots. Lehmann lovegrass had lower, quickly developing LAI with greater leaf proportions than bush muhly. When early season theta was high, net ecosystem CO(2) exchange (NEE) was similar, but as storm frequency and theta declined, NEE was more negative in lovegrass (-0.69 to -3.00 micromol m(-2) s(-1)) than bush muhly (+1.75 to -1.55 micromol m(-2) s(-1)). Ecosystem respiration (R (eco)) responded quickly to monsoon onset and late-season rains, and was lower in lovegrass (2.44-3.74 micromol m(-2) s(-1)) than bush muhly (3.60-5.3 micromol m(-2) s(-1)) across the season. Gross ecosystem photosynthesis (GEP) was greater in Lehmann lovegrass, concurrent with higher leaf-level photosynthesis and stomatal conductance. We conclude that canopy structure facilitates higher theta under Lehmann lovegrass, reducing phenological constraints and stomatal limitations to whole-plant carbon uptake through the short summer monsoon growing season.

  3. Scaling hyporheic exchange and its influence on biogeochemical reactions in aquatic ecosystems

    USGS Publications Warehouse

    O'Connor, B.L.; Harvey, J.W.

    2008-01-01

    Hyporheic exchange and biogeochemical reactions are difficult to quantify because of the range in fluid-flow and sediment conditions inherent to streams, wetlands, and nearshore marine ecosystems. Field measurements of biogeochemical reactions in aquatic systems are impeded by the difficulty of measuring hyporheic flow simultaneously with chemical gradients in sediments. Simplified models of hyporheic exchange have been developed using Darcy's law generated by flow and bed topography at the sediment-water interface. However, many modes of transport are potentially involved (molecular diffusion, bioturbation, advection, shear, bed mobility, and turbulence) with even simple models being difficult to apply in complex natural systems characterized by variable sediment sizes and irregular bed geometries. In this study, we synthesize information from published hyporheic exchange investigations to develop a scaling relationship for estimating mass transfer in near-surface sediments across a range in fluid-flow and sediment conditions. Net hyporheic exchange was quantified using an effective diffusion coefficient (De) that integrates all of the various transport processes that occur simultaneously in sediments, and dimensional analysis was used to scale De to shear stress velocity, roughness height, and permeability that describe fluid-flow and sediment characteristics. We demonstrated the value of the derived scaling relationship by using it to quantify dissolved oxygen (DO) uptake rates on the basis of DO profiles in sediments and compared them to independent flux measurements. The results support a broad application of the De scaling relationship for quantifying coupled hyporheic exchange and biogeochemical reaction rates in streams and other aquatic ecosystems characterized by complex fluid-flow and sediment conditions.

  4. 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.

  5. Contrasting tropical estuarine ecosystem functioning and stability: A comparative study

    NASA Astrophysics Data System (ADS)

    Villanueva, Maria Ching

    2015-03-01

    A comparative study of the Sine-saloum (Senegal) and Gambia (The Gambia) estuaries was performed based on trophic model outputs that describe the system structure and functioning. These trophic models were constructed such as to differentiate main energetic flows in the systems and express how climate change may have impacted ecosystem resilience to change. Estuarine fish assemblages are highly resilient despite exposure to vast hydrodynamic variations and stress. Coupled with strong anthropogenic-driven stresses such as fisheries and climate change, ecosystems may undergo severe regime shifts that may weaken their resilience and stability. Taxonomically related and morphologically similar species do not necessarily play similar ecological roles in these two ecosystems. Biomass and production in the Sine-saloum are concentrated at trophic levels (TLs) 2 and 3, while for the Gambia, both are concentrated at TL3. Higher TL biomasses in Gambia compared to Sine-Saloum may be explained by the latter ecosystem being characterized by inverse hypersalinity. Higher TL of production in Sine-Saloum is due to higher exploitations compared to Gambia where fishing activities are still less developed. High production and consumption rates of some groups in both ecosystems indicate high system productivity. Elevated productivity may be due to higher abundance of juvenile fishes in most groups that utilize the latter as refuge and/or nursery zones. Both ecosystems are phytoplankton-driven. Differences in group trophic and ecological roles are mainly due to adaptive responses of these species to seasonal and long-term climate and anthropogenic stressors. System indicators suggest different levels of ecosystem resilience and stability as a function of biodiversity. Relevance of other observations on ecosystem functioning and indicators in relation to perturbation is discussed.

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. The ICOS Ecosystem network and Thematic Center: an infrastructure to monitor and better understand the ecosystem GHGs exchanges

    NASA Astrophysics Data System (ADS)

    Papale, D.; Ceulemans, R.; Janssens, I.; Loustau, D.; Valentini, R.

    2012-12-01

    The ICOS Ecosystem network is part of the ICOS European Research Infrastructure (www.icos-infrastructure.eu) together with the Atmospheric and Ocean networks. The ICOS Ecosystem includes highly standardized monitoring sites based on commercially available instruments embedded into an integrated system that is coordinated by the ICOS Ecosystem Thematic Center (ETC) which is responsible for the methodologies advancement, data processing and data distribution. The ecosystem monitoring activity will involve human intervention in field activities and for this reason rigorously standardized protocol for field ecosystem measurements are in preparation also in coordination with others international related activities. The core measurement in the ICOS Ecosystem sites are the main GHGs fluxes that include CO2, H2O, CH4 and N2O, using the eddy covariance method and chambers for the soil effluxes. To better interpret and understand the GHGs exchanges a full series of meteorological data (including spectral reflectance measurements and full radiation and water balance) are also collected and the sites are characterized in terms of carbon stocks, nutrients availability and management and disturbance history. Centralized raw data processing, QAQC and uncertainty estimation, test and development of new methodologies and techniques, assistance to the network and chemical analysis and long term storage of the vegetation and soil samples are the main activities where the ETC is responsible. The ETC, based in Italy and with sections in Belgium and France, is under construction and will be operative in 2013. The Ecosystem network, including the variables collected, the protocols under preparation and the data access and data use policies will be presented together with the Ecosystem Thematic Center role and development strategy. The aim is to identify and discuss integration and collaboration with others similar initiatives, also thanks to the support of the COOPEUS European project

  11. The ICOS Ecosystem network and Thematic Center: an infrastructure to monitor and better understand the ecosystem GHGs exchanges

    NASA Astrophysics Data System (ADS)

    Janssens, Ivan; Papale, Dario; Ceulemans, Reinhart; Gielen, Bert; Loustau, Denis; de Beeck, Maarten Op; Valentini, Riccardo

    2013-04-01

    The ICOS Ecosystem network is part of the ICOS European Research Infrastructure (www.icos-infrastructure.eu) together with the Atmospheric and Ocean networks. The ecosystem network includes highly standardized monitoring sites based on commercially available instruments embedded into an integrated system that is coordinated by the ICOS Ecosystem Thematic Center (ETC), which is also responsible for the methodologies advancement, data processing and data distribution. The ecosystem monitoring activity will involve human intervention in field activities and for this reason rigorously standardized protocol for field ecosystem measurements are in preparation also in coordination with others international related activities. The core measurement in the ICOS Ecosystem sites are the main GHGs fluxes that include CO2, H2O, CH4 and N2O, using the eddy covariance method and chambers for the soil effluxes. To better interpret and understand the GHGs exchanges a full series of meteorological data (including spectral reflectance measurements and full radiation and water balance) are also collected and the sites are characterized in terms of carbon stocks, nutrients availability and management and disturbance history. Centralized raw data processing, QAQC and uncertainty estimation, test and development of new methodologies and techniques, assistance to the network and chemical analysis and long term storage of the vegetation and soil samples are the main activities where the ETC is responsible. The ETC, based in Italy and with sections in Belgium and France, is under construction and will be operative in 2013. We present the actual status of the Ecosystem network, including the variables collected, the protocols under preparation, the data access and data use policies and the Ecosystem Thematic Center role and development strategy, with special emphasis on the approaches followed to reach high level of to standardization together with the uncertainty quantification.

  12. Combining Ballast Water Exchange and Treatment To Maximize Prevention of Species Introductions to Freshwater Ecosystems.

    PubMed

    Briski, Elizabeta; Gollasch, Stephan; David, Matej; Linley, R Dallas; Casas-Monroy, Oscar; Rajakaruna, Harshana; Bailey, Sarah A

    2015-08-18

    The most effective way to manage species transfers is to prevent their introduction via vector regulation. Soon, international ships will be required to meet numeric ballast discharge standards using ballast water treatment (BWT) systems, and ballast water exchange (BWE), currently required by several countries, will be phased out. However, there are concerns that BWT systems may not function reliably in fresh and/or turbid water. A land-based evaluation of simulated "BWE plus BWT" versus "BWT alone" demonstrated potential benefits of combining BWE with BWT for protection of freshwater ecosystems. We conducted ship-based testing to compare the efficacy of "BWE plus BWT" versus "BWT alone" on voyages starting with freshwater ballast. We tested the hypotheses that there is an additional effect of "BWE plus BWT" compared to "BWT alone" on the reduction of plankton, and that taxa remaining after "BWE plus BWT" will be marine (low risk for establishment at freshwater recipient ports). Our study found that BWE has significant additional effect on the reduction of plankton, and this effect increases with initial abundance. As per expectations, "BWT alone" tanks contained higher risk freshwater or euryhaline taxa at discharge, while "BWE plus BWT" tanks contained mostly lower risk marine taxa unlikely to survive in recipient freshwater ecosystems.

  13. Drivers of long-term variability in CO2 net ecosystem exchange in a temperate peatland

    NASA Astrophysics Data System (ADS)

    Helfter, C.; Campbell, C.; Dinsmore, K. J.; Drewer, J.; Coyle, M.; Anderson, M.; Skiba, U.; Nemitz, E.; Billett, M. F.; Sutton, M. A.

    2014-10-01

    Land-atmosphere exchange of carbon dioxide (CO2) in peatlands exhibits marked seasonal and inter-annual variability, which subsequently affects the carbon sink strength of catchments across multiple temporal scales. Long-term studies are needed to fully capture the natural variability and therefore identify the key hydrometeorological drivers in the net ecosystem exchange (NEE) of CO2. NEE has been measured continuously by eddy-covariance at Auchencorth Moss, a temperate lowland peatland in central Scotland, since 2002. Hence this is one of the longest peatland NEE studies to date. For 11 yr, the site was a consistent, yet variable, atmospheric CO2 sink ranging from -5.2 to -135.9 g CO2-C m-2 yr-1 (mean of -64.1 ± 33.6 g CO2-C m-2 yr-1). Inter-annual variability in NEE was positively correlated to the length of the growing season. Mean winter air temperature explained 87% of the inter-annual variability in the sink strength of the following summer, indicating a phenological memory-effect. Plant productivity exhibited a marked hysteresis with respect to photosynthetically active radiation (PAR) over the growing season, indicative of two separate growth regimes. Ecosystem respiration (Reco) and gross primary productivity (GPP) were closely correlated (ratio 0.74), suggesting that autotrophic processes were dominant. Whilst the site was wet most of the year (water table depth <5 cm) there were indications that heterotrophic respiration was enhanced by drought, which also depressed GPP. NEE was compared to 5 other peatland sites which have published long-term NEE records. The CO2 uptake rate during the growing season was comparable to 3 other European sites, however the emission rate during the dormant season was significantly higher.

  14. Relative linkages of climatic and environmental drivers/fluxes with net ecosystem exchanges of six diverse terrestrial ecosystems

    NASA Astrophysics Data System (ADS)

    Abdul-Aziz, O.; Ishtiaq, K. S.

    2013-12-01

    We analyzed ecosystem-scale, half-hourly net ecosystem exchange (NEE) data along with the environmental drivers and heat fluxes for six distinct ecosystems of the AmeriFlux network. Multivariate pattern recognition techniques such as Principal Component Analysis (PCA) and Factor Analysis (FA) were applied to investigate potential groupings in participatory variables and their relative linkages. Normalized multiple regression models were developed in order to extract the statistically significant predictors of NEE from the data matrix and compute their relative weights. Radiation components (net radiation and photosynthetically active radiation) along with the ecosystem water and energy fluxes (latent and soil heat fluxes) displayed dictating weights on NEE followed by temperature related variables (air temperature, soil temperature and vapor pressure deficit). Velocity factors (wind speed and friction velocity) were less explanatory in describing the half hourly fluxes of NEE. Developed linear models showed acceptable accuracy (ratio of root mean square error to observations' standard deviation, RSR: 0.48-0.68) and fitting efficiency (coefficient of determination, R2: 0.54-0.77) in explaining NEE. Overall, environmental drivers and fluxes showed relatively analogous association with NEE among the six separate ecoregions representing diversity in climate, hydrology, and vegetation types. The findings can guide the development of appropriate mechanistic and empirical models for spatio-temporally robust predictions of NEE and potential carbon sequestration from diverse terrestrial ecosystems.

  15. Net ecosystem CO2 exchange of a primary tropical peat swamp forest in Sarawak, Malaysia

    NASA Astrophysics Data System (ADS)

    Tang Che Ing, A.; Stoy, P. C.; Melling, L.

    2014-12-01

    Tropical peat swamp forests are widely recognized as one of the world's most efficient ecosystems for the sequestration and storage of carbon through both their aboveground biomass and underlying thick deposits of peat. As the peat characteristics exhibit high spatial and temporal variability as well as the structural and functional complexity of forests, tropical peat ecosystems can act naturally as both carbon sinks and sources over their life cycles. Nonetheless, few reports of studies on the ecosystem-scale CO2 exchange of tropical peat swamp forests are available to-date and their present roles in the global carbon cycle remain uncertain. To quantify CO2 exchange and unravel the prevailing factors and potential underlying mechanism regulating net CO2 fluxes, an eddy covariance tower was erected in a tropical peat swamp forest in Sarawak, Malaysia. We observed that the diurnal and seasonal patterns of net ecosystem CO2 exchange (NEE) and its components (gross primary productivity (GPP) and ecosystem respiration (RE)) varied between seasons and years. Rates of NEE declined in the wet season relative to the dry season. Conversely, both the gross primary productivity (GPP) and ecosystem respiration (RE) were found to be higher during the wet season than the dry season, in which GPP was strongly negatively correlated with NEE. The average annual NEE was 385 ± 74 g C m-2 yr-1, indicating the primary peat swamp forest functioned as net source of CO2 to the atmosphere over the observation period.

  16. 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.

  17. Characterization of total ecosystem-scale biogenic VOC exchange at a Mediterranean oak-hornbeam forest

    NASA Astrophysics Data System (ADS)

    Schallhart, Simon; Rantala, Pekka; Nemitz, Eiko; Taipale, Ditte; Tillmann, Ralf; Mentel, Thomas F.; Loubet, Benjamin; Gerosa, Giacomo; Finco, Angelo; Rinne, Janne; Ruuskanen, Taina M.

    2016-06-01

    Recently, the number and amount of biogenically emitted volatile organic compounds (VOCs) has been discussed in great detail. Depending on the ecosystem, the published number varies between a dozen and several hundred compounds. We present ecosystem exchange fluxes from a mixed oak-hornbeam forest in the Po Valley, Italy. The fluxes were measured by a proton transfer reaction-time-of-flight (PTR-ToF) mass spectrometer and calculated using the eddy covariance (EC) method. Detectable fluxes were observed for up to 29 compounds, dominated by isoprene, which comprised over 60 % of the total upward flux (on a molar basis). The daily average of the total VOC upward flux was 10.4 nmol m-2 s-1. Methanol had the highest concentration and accounted for the largest downward flux. Methanol seemed to be deposited to dew, as the downward flux happened in the early morning, right after the calculated surface temperature came closest to the calculated dew point temperature.We estimated that up to 30 % of the upward flux of methyl vinyl ketone (MVK) and methacrolein (MACR) originated from atmospheric oxidation of isoprene. A comparison between two methods for the flux detection (manual and automated) was made. Their respective advantages and disadvantages were discussed and the differences in their results shown. Both provide comparable results.

  18. Prerequisites for application of hyperbolic relaxed eddy accumulation on managed grasslands and alternative net ecosystem exchange flux partitioning

    NASA Astrophysics Data System (ADS)

    Riederer, M.; Hübner, J.; Ruppert, J.; Brand, W. A.; Foken, T.

    2014-12-01

    Relaxed eddy accumulation is still applied in ecosystem sciences for measuring trace gas fluxes. On managed grasslands, the length of time between management events and the application of relaxed eddy accumulation has an essential influence on the determination of the proportionality factor b and thus on the resulting flux. In this study this effect is discussed for the first time. Also, scalar similarity between proxy scalars and scalars of interest is affected until the ecosystem has completely recovered. Against this background, CO2 fluxes were continuously measured and 13CO2 isofluxes were determined with a high measurement precision on two representative days in summer 2010. Moreover, a common method for the partitioning of the net ecosystem exchange into assimilation and respiration based on temperature and light response was compared with an isotopic approach directly based on the isotope discrimination of the biosphere. This approach worked well on the grassland site and could enhance flux partitioning results by better reproducing the environmental conditions.

  19. Drivers of long-term variability in CO2 net ecosystem exchange in a temperate peatland

    NASA Astrophysics Data System (ADS)

    Helfter, C.; Campbell, C.; Dinsmore, K. J.; Drewer, J.; Coyle, M.; Anderson, M.; Skiba, U.; Nemitz, E.; Billett, M. F.; Sutton, M. A.

    2015-03-01

    Land-atmosphere exchange of carbon dioxide (CO2) in peatlands exhibits marked seasonal and inter-annual variability, which subsequently affects the carbon (C) sink strength of catchments across multiple temporal scales. Long-term studies are needed to fully capture the natural variability and therefore identify the key hydrometeorological drivers in the net ecosystem exchange (NEE) of CO2. Since 2002, NEE has been measured continuously by eddy-covariance at Auchencorth Moss, a temperate lowland peatland in central Scotland. Hence this is one of the longest peatland NEE studies to date. For 11 years, the site was a consistent, yet variable, atmospheric CO2 sink ranging from -5.2 to -135.9 g CO2-C m-2 yr-1 (mean of -64.1 ± 33.6 g CO2-C m-2 yr-1). Inter-annual variability in NEE was positively correlated to the length of the growing season. Mean winter air temperature explained 87% of the inter-annual variability in the sink strength of the following summer, indicating an effect of winter climate on local phenology. Ecosystem respiration (Reco) was enhanced by drought, which also depressed gross primary productivity (GPP). The CO2 uptake rate during the growing season was comparable to three other sites with long-term NEE records; however, the emission rate during the dormant season was significantly higher. To summarise, the NEE of the peatland studied is modulated by two dominant factors: - phenology of the plant community, which is driven by winter air temperature and impacts photosynthetic potential and net CO2 uptake during the growing season (colder winters are linked to lower summer NEE), - water table level, which enhanced soil respiration and decreased GPP during dry spells. Although summer dry spells were sporadic during the study period, the positive effects of the current climatic trend towards milder winters on the site's CO2 sink strength could be offset by changes in precipitation patterns especially during the growing season.

  20. Isotopic air sampling in a tallgrass prairie to partition net ecosystem CO2 exchange

    NASA Astrophysics Data System (ADS)

    Lai, Chun-Ta; Schauer, Andrew J.; Owensby, Clenton; Ham, Jay M.; Ehleringer, James R.

    2003-09-01

    Stable isotope ratios of various ecosystem components and net ecosystem exchange (NEE) CO2 fluxes were measured in a C3-C4 mixture tallgrass prairie near Manhattan, Kansas. The July 2002 study period was chosen because of contrasting soil moisture contents, which allowed us to address the effects of drought on photosynthetic CO2 uptake and isotopic discrimination. Significantly higher NEE fluxes were observed for both daytime uptake and nighttime respiration during well-watered conditions when compared to a drought period. Given these differences, we investigated two carbon-flux partitioning questions: (1) What proportions of NEE were contributed by C3 versus C4 species? (2) What proportions of NEE fluxes resulted from canopy assimilation versus ecosystem respiration? To evaluate these questions, air samples were collected every 2 hours during daytime for 3 consecutive days at the same height as the eddy covariance system. These air samples were analyzed for both carbon isotope ratios and CO2 concentrations to establish an empirical relationship for isoflux calculations. An automated air sampling system was used to collect nighttime air samples to estimate the carbon isotope ratios of ecosystem respiration (δR) at weekly intervals for the entire growing season. Models of C3 and C4 photosynthesis were employed to estimate bulk canopy intercellular CO2 concentration in order to calculate photosynthetic discrimination against 13C. Our isotope/NEE results showed that for this grassland, C4 vegetation contributed ˜80% of the NEE fluxes during the drought period and later ˜100% of the NEE fluxes in response to an impulse of intense precipitation. For the entire growing season, the C4 contribution ranged from ˜68% early in the spring to nearly 100% in the late summer. Using an isotopic approach, the calculated partitioned respiratory fluxes were slightly greater than chamber-measured estimates during midday under well-watered conditions. In addition, time series

  1. Comparative biogeochemistry-ecosystem-human interactions on dynamic continental margins

    NASA Astrophysics Data System (ADS)

    Levin, Lisa A.; Liu, Kon-Kee; Emeis, Kay-Christian; Breitburg, Denise L.; Cloern, James; Deutsch, Curtis; Giani, Michele; Goffart, Anne; Hofmann, Eileen E.; Lachkar, Zouhair; Limburg, Karin; Liu, Su-Mei; Montes, Enrique; Naqvi, Wajih; Ragueneau, Olivier; Rabouille, Christophe; Sarkar, Santosh Kumar; Swaney, Dennis P.; Wassman, Paul; Wishner, Karen F.

    2015-01-01

    The oceans' continental margins face strong and rapid change, forced by a combination of direct human activity, anthropogenic CO2-induced climate change, and natural variability. Stimulated by discussions in Goa, India at the IMBER IMBIZO III, we (1) provide an overview of the drivers of biogeochemical variation and change on margins, (2) compare temporal trends in hydrographic and biogeochemical data across different margins, (3) review ecosystem responses to these changes, (4) highlight the importance of margin time series for detecting and attributing change and (5) examine societal responses to changing margin biogeochemistry and ecosystems. We synthesize information over a wide range of margin settings in order to identify the commonalities and distinctions among continental margin ecosystems. Key drivers of biogeochemical variation include long-term climate cycles, CO2-induced warming, acidification, and deoxygenation, as well as sea level rise, eutrophication, hydrologic and water cycle alteration, changing land use, fishing, and species invasion. Ecosystem responses are complex and impact major margin services. These include primary production, fisheries production, nutrient cycling, shoreline protection, chemical buffering, and biodiversity. Despite regional differences, the societal consequences of these changes are unarguably large and mandate coherent actions to reduce, mitigate and adapt to multiple stressors on continental margins.

  2. Comparative biogeochemistry-ecosystem-human interactions on dynamic continental margins

    USGS Publications Warehouse

    Levin, Lisa A.; Liu, Kon-Kee; Emeis, Kay-Christian; Breitburg, Denise L.; Cloern, James; Deutsch, Curtis; Giani, Michele; Goffart, Anne; Hofmann, Eileen E.; Lachkar, Zouhair; Limburg, Karin; Liu, Su-Mei; Montes, Enrique; Naqvi, Wajih; Ragueneau, Olivier; Rabouille, Christophe; Sarkar, Santosh Kumar; Swaney, Dennis P.; Wassman, Paul; Wishner, Karen F.

    2014-01-01

    The ocean’s continental margins face strong and rapid change, forced by a combination of direct human activity, anthropogenic CO2-induced climate change, and natural variability. Stimulated by discussions in Goa, India at the IMBER IMBIZO III, we (1) provide an overview of the drivers of biogeochemical variation and change on margins, (2) compare temporal trends in hydrographic and biogeochemical data across different margins (3) review ecosystem responses to these changes, (4) highlight the importance of margin time series for detecting and attributing change and (5) examine societal responses to changing margin biogeochemistry and ecosystems. We synthesize information over a wide range of margin settings in order to identify the commonalities and distinctions among continental margin ecosystems. Key drivers of biogeochemical variation include long-term climate cycles, CO2-induced warming, acidification, and deoxygenation, as well as sea level rise, eutrophication, hydrologic and water cycle alteration, changing land use, fishing, and species invasion. Ecosystem responses are complex and impact major margin services including primary production, fisheries production, nutrient cycling, shoreline protection, chemical buffering, and biodiversity. Despite regional differences, the societal consequences of these changes are unarguably large and mandate coherent actions to reduce, mitigate and adapt to multiple stressors on continental margins.

  3. Partitioning interannual variability in net ecosystem exchange between climatic variability and functional change.

    PubMed

    Hui, Dafeng; Luo, Yiqi; Katul, Gabriel

    2003-05-01

    Interannual variability (IAV) in net ecosystem exchange of carbon (NEE) is a critical factor in projections of future ecosystem changes. However, our understanding of IAV is limited because of the difficulty in isolating its numerous causes. We proposed that IAV in NEE is primarily caused by climatic variability, through its direct effects on photosynthesis and respiration and through its indirect effects on carbon fluxes (i.e., the parameters that govern photosynthesis and respiration), hereafter called functional change. We employed a homogeneity-of-slopes model to identify the functional change contributing to IAV in NEE and nighttime ecosystem respiration (RE). The model uses multiple regression analysis to relate NEE and RE with climatic variables for individual years and for all years. If the use of different slopes for each year significantly improves the model fitting compared to the use of one slope for all years, we consider that functional change exists, at least on annual time scales. With the functional change detected, we then partition the observed variation in NEE or RE to four components, namely, the functional change, the direct effect of interannual climatic variability, the direct effect of seasonal climatic variation, and random error. Application of this approach to a data set collected at the Duke Forest AmeriFlux site from August 1997 to December 2001 indicated that functional change, interannual climatic variability, seasonal climatic variation and random error explained 9.9, 8.9, 59.9 and 21.3%, respectively, of the observed variation in NEE and 13.1, 5.0, 38.1 and 43.8%, respectively, of the observed variation in RE.

  4. Comparing nocturnal eddy covariance measurements to estimates of ecosystem respiration made by scaling chamber measurements at six coniferous boreal sites

    USGS Publications Warehouse

    Lavigne, M.B.; Ryan, M.G.; Anderson, D.E.; Baldocchi, D.D.; Crill, P.M.; Fitzjarrald, D.R.; Goulden, M.L.; Gower, S.T.; Massheder, J.M.; McCaughey, J.H.; Rayment, M.; Striegl, R. G.

    1997-01-01

    During the growing season, nighttime ecosystem respiration emits 30–100% of the daytime net photosynthetic uptake of carbon, and therefore measurements of rates and understanding of its control by the environment are important for understanding net ecosystem exchange. Ecosystem respiration can be measured at night by eddy covariance methods, but the data may not be reliable because of low turbulence or other methodological problems. We used relationships between woody tissue, foliage, and soil respiration rates and temperature, with temperature records collected on site to estimate ecosystem respiration rates at six coniferous BOREAS sites at half-hour or 1-hour intervals, and then compared these estimates to nocturnal measurements of CO2 exchange by eddy covariance. Soil surface respiration was the largest source of CO2 at all sites (48–71%), and foliar respiration made a large contribution to ecosystem respiration at all sites (25–43%). Woody tissue respiration contributed only 5–15% to ecosystem respiration. We estimated error for the scaled chamber predictions of ecosystem respiration by using the uncertainty associated with each respiration parameter and respiring biomass value. There was substantial uncertainty in estimates of foliar and soil respiration because of the spatial variability of specific respiration rates. In addition, more attention needs to be paid to estimating foliar respiration during the early part of the growing season, when new foliage is growing, and to determining seasonal trends of soil surface respiration. Nocturnal eddy covariance measurements were poorly correlated to scaled chamber estimates of ecosystem respiration (r2=0.06–0.27) and were consistently lower than scaled chamber predictions (by 27% on average for the six sites). The bias in eddy covariance estimates of ecosystem respiration will alter estimates of gross assimilation in the light and of net ecosystem exchange rates over extended periods.

  5. Effect of grazing and canopy on Mediterranean ecosystem functioning: Carbon dioxide exchange and the dynamics of carbon and nutrient pools

    NASA Astrophysics Data System (ADS)

    Mirzaei, Heydar; Tenhunen, John; Hossein, Zaman; Li, Yuelin; Otieno, Dennis

    2010-05-01

    Mediterranean ecosystems occupy less than 5 % of the Earth's surface, yet they contain about 20 % of the world's flora, including important components in grasslands. In this study, important ecosystem functions (CO2 exchange, biomass production and nutrient uptake of the herbaceous layer of a Mediterranean grassland ecosystem) at Herdade da Mitra, in Portugal were studied. The main objectives of this project were, to understand effects of grazing and canopy layer (overstory) on ecosystem functioning respectively. The canopy layer consists of some woody species mainly Quercus ilex and Qu. Suber. Results showed that trees added considerable amounts of nutrients to the soil beneath their canopies, and had the potential to facilitate understory production. Although there was no significant difference in total biomass accumulation between understory and open locations. Analysis of soil N concentration revealed higher soil N under the trees when compared to those in open areas. Although NEE was limited by light intensity in the understory, model projection of GPP showed no difference between the understory and the open locations in their potential assimilatory capacity but depending on the locations (open vs understory), grazing influenced CO2 exchange processes differently. We found no significant differences in GPP between grazed and ungrazed sites in the open locations, while large differences occurred in the understory, with lower NEE in the grazed as compared to the ungrazed locations. Significant differences, however, occurred between the two locations in ecosystem respiration, showing higher respiration in grazed location in the open site while in the understory site respiration was similar in both grazed and ungrazed locations. Foliar N concentration in understory and open sites showed a different pattern, as the ungrazed location in the understory indicated lower values compared to grazed locations, although in the open sites, ungrazed locations exhibited larger

  6. Simulating the impacts of land use in northwest Europe on Net Ecosystem Exchange (NEE): the role of arable ecosystems, grasslands and forest plantations in climate change mitigation.

    PubMed

    Abdalla, Mohamed; Saunders, Matthew; Hastings, Astley; Williams, Mike; Smith, Pete; Osborne, Bruce; Lanigan, Gary; Jones, Mike B

    2013-11-01

    In this study, we compared measured and simulated Net Ecosystem Exchange (NEE) values from three wide spread ecosystems in the southeast of Ireland (forest, arable and grassland), and investigated the suitability of the DNDC (the DeNitrification-DeComposition) model to estimate present and future NEE. Although, the field-DNDC version overestimated NEE at temperatures >5 °C, forest-DNDC under-estimated NEE at temperatures >5 °C. The results suggest that the field/forest DNDC models can successfully estimate changes in seasonal and annual NEE from these ecosystems. Differences in NEE were found to be primarily land cover specific. The annual NEE was similar for the grassland and arable sites, but due to the contribution of exported carbon, the soil carbon increased at the grassland site and decreased at the arable site. The NEE of the forest site was an order of magnitude larger than that of the grassland or arable ecosystems, with large amounts of carbon stored in woody biomass and the soil. The average annual NEE, GPP and Reco values over the measurement period were -904, 2379 and 1475 g C m(-2) (forest plantations), -189, 906 and 715 g C m(-2) (arable systems) and -212, 1653 and 1444 g C m(-2) (grasslands), respectively. The average RMSE values were 3.8 g C m(-2) (forest plantations), 0.12 g C m(-2) (arable systems) and 0.21 g C m(-2) (grasslands). When these models were run with climate change scenarios to 2060, predictions show that all three ecosystems will continue to operate as carbon sinks. Further, climate change may decrease the carbon sink strength in the forest plantations by up to 50%. This study supports the use of the DNDC model as a valid tool to predict the consequences of climate change on NEE from different ecosystems.

  7. CO2 exchange and evapotranspiration across dryland ecosystems of southwestern North America.

    PubMed

    Biederman, Joel A; Scott, Russell L; Bell, Tom W; Bowling, David R; Dore, Sabina; Garatuza-Payan, Jaime; Kolb, Thomas E; Krishnan, Praveena; Krofcheck, Dan J; Litvak, Marcy E; Maurer, Gregory E; Meyers, Tilden P; Oechel, Walter C; Papuga, Shirley A; Ponce-Campos, Guillermo E; Rodriguez, Julio C; Smith, William K; Vargas, Rodrigo; Watts, Christopher J; Yepez, Enrico A; Goulden, Michael L

    2017-03-13

    Global-scale studies suggest that dryland ecosystems dominate an increasing trend in the magnitude and interannual variability of the land CO2 sink. However, such analyses are poorly constrained by measured CO2 exchange in drylands. Here we address this observation gap with eddy covariance data from 25 sites in the water-limited Southwest region of North America with observed ranges in annual precipitation of 100 - 1000 mm, annual temperatures of 2 - 25 °C, and records of 3 - 10 years (150 site-years in total). Annual fluxes were integrated using site-specific ecohydrologic years to group precipitation with resulting ecosystem exchanges. We found a wide range of carbon sink/source function, with mean annual net ecosystem production (NEP) varying from -350 to +330 gCm(-2) across sites with diverse vegetation types, contrasting with the more constant sink typically measured in mesic ecosystems. In this region, only forest-dominated sites were consistent carbon sinks. Interannual variability of NEP, gross ecosystem production (GEP) and ecosystem respiration (Reco ) was larger than for mesic regions, and half the sites switched between functioning as C sinks/C sources in wet/dry years. The sites demonstrated coherent responses of GEP and NEP to anomalies in annual evapotranspiration (ET), used here as a proxy for annually available water after hydrologic losses. Notably, GEP and Reco were negatively related to temperature, both interannually within site and spatially across sites, in contrast to positive temperature effects commonly reported for mesic ecosystems. Models based on MODIS satellite observations matched the cross-site spatial pattern in mean annual GEP but consistently underestimated mean annual ET by ~50%. Importantly, the MODIS-based models captured only 20-30% of interannual variation magnitude. These results suggest the contribution of this dryland region to variability of regional to global CO2 exchange may be up to 3 - 5 times larger than current

  8. Comparing resource pulses in aquatic and terrestrial ecosystems.

    PubMed

    Nowlin, Weston H; Vanni, Michael J; Yang, Louie H

    2008-03-01

    Resource pulses affect productivity and dynamics in a diversity of ecosystems, including islands, forests, streams, and lakes. Terrestrial and aquatic systems differ in food web structure and biogeochemistry; thus they may also differ in their responses to resource pulses. However, there has been a limited attempt to compare responses across ecosystem types. Here, we identify similarities and differences in the causes and consequences of resource pulses in terrestrial and aquatic systems. We propose that different patterns of food web and ecosystem structure in terrestrial and aquatic systems lead to different responses to resource pulses. Two predictions emerge from a comparison of resource pulses in the literature: (1) the bottom-up effects of resource pulses should transmit through aquatic food webs faster because of differences in the growth rates, life history, and stoichiometry of organisms in aquatic vs. terrestrial systems, and (2) the impacts of resource pulses should also persist longer in terrestrial systems because of longer generation times, the long-lived nature of many terrestrial resource pulses, and reduced top-down effects of consumers in terrestrial systems compared to aquatic systems. To examine these predictions, we use a case study of a resource pulse that affects both terrestrial and aquatic systems: the synchronous emergence of periodical cicadas (Magicicada spp.) in eastern North American forests. In general, studies that have examined the effects of periodical cicadas on terrestrial and aquatic systems support the prediction that resource pulses transmit more rapidly in aquatic systems; however, support for the prediction that resource pulse effects persist longer in terrestrial systems is equivocal. We conclude that there is a need to elucidate the indirect effects and long-term implications of resource pulses in both terrestrial and aquatic ecosystems.

  9. Interannual variability of Net Ecosystem CO2 Exchange and its component fluxes in a subalpine Mediterranean ecosystem (SE Spain)

    NASA Astrophysics Data System (ADS)

    Chamizo, Sonia; Serrano-Ortiz, Penélope; Sánchez-Cañete, Enrique P.; Domingo, Francisco; Arnau-Rosalén, Eva; Oyonarte, Cecilio; Pérez-Priego, Óscar; López-Ballesteros, Ana; Kowalski, Andrew S.

    2015-04-01

    Recent decades under climate change have seen increasing interest in quantifying the carbon (C) balance of different terrestrial ecosystems, and their behavior as sources or sinks of C. Both CO2 exchange between terrestrial ecosystems and the atmosphere and identification of its drivers are key to understanding land-surface feedbacks to climate change. The eddy covariance (EC) technique allows measurements of net ecosystem C exchange (NEE) from short to long time scales. In addition, flux partitioning models can extract the components of net CO2 fluxes, including both biological processes of photosynthesis or gross primary production (GPP) and respiration (Reco), and also abiotic drivers like subsoil CO2 ventilation (VE), which is of particular relevance in semiarid environments. The importance of abiotic processes together with the strong interannual variability of precipitation, which strongly affects CO2 fluxes, complicates the accurate characterization of the C balance in semiarid landscapes. In this study, we examine 10 years of interannual variability of NEE and its components at a subalpine karstic plateau, El Llano de los Juanes, in the Sierra de Gádor (Almería, SE Spain). Results show annual NEE ranging from 55 g C m-2 (net emission) to -54 g C m-2 (net uptake). Among C flux components, GPP was the greatest contributing 42-57% of summed component magnitudes, while contributions by Reco and VE ranged from 27 to 46% and from 3 to 18%, respectively. Annual precipitation during the studied period exhibited high interannual variability, ranging from 210 mm to 1374 mm. Annual precipitation explained 50% of the variance in Reco, 59% of that in GPP, and 56% for VE. While Reco and GPP were positively correlated with annual precipitation (correlation coefficient, R, of 0.71 and 0.77, respectively), VE showed negative correlation with this driver (R = -0.74). During the driest year (2004-2005), annual GPP and Reco reached their lowest values, while contribution of

  10. Carbon exchange of organic soils ecosystems of the world

    SciTech Connect

    Armentano, T.V.; Menges, E.S.; Molofsky, J.; Lawler, D.J.

    1984-03-01

    Because the annual uptake and release of CO/sub 2/ by the earth's biota (50-100 x 10/sup 9/ t/yr (10/sup 9/ t = 1 Gt)) is 10-20 times larger than the recent annual combustion of fossil fuel (5 Gt/yr), understanding the global carbon cycle requires detailed consideration of relatively small alterations in regional photosynthesis or in the oxidation of carbon stored in the major biological pools. This report presents an original synthesis of data on wetland carbon sinks and releases. Computer simulations of wetland conversions and altered carbon balance were used to estimate carbon uptake and release rates in the tropical and temperate zones. A major goal of this study was to determine whether the world's wetlands, considered as a single global carbon pool, have been appreciably altered by human intervention since 1800. For soil carbon exchangers, only wetlands with organic soils are important because, when functioning naturally, they remove carbon from the atmosphere and retain it over long periods of time. Both tropical and temperature zone wetlands have been sequestering carbon from the atmosphere for the past 5000-10,000 years, thus forming a long-term natural carbon sink of potential significance. Prior to human intervention, the annual sequestering in this sink is estimated here to have been 0.14 Ft of carbon, three-quarters of which occurred in the temperate zone.

  11. Seven-Year Trends of Carbon Dioxide Exchange in a Tundra Ecosystem Affected by Long-Term Permafrost Thaw

    NASA Astrophysics Data System (ADS)

    Schuur, E. A.; Trucco, C.; Natali, S.; Belshe, E. F.; Bracho, R.; Vogel, J. G.; Hicks Pries, C. E.; Webb, E.

    2012-12-01

    Arctic warming has led to permafrost degradation and ground subsidence as a result of ground ice melting. Frozen soil organic matter that thaws can increase carbon (C) emissions to the atmosphere via respiration, but this can be offset in part by increases in plant growth. The balance of plant and microbial processes, and how they change through time, will determine how permafrost ecosystems influence future climate change via the C cycle. This study addressed this question both on short (interannual) and longer (decadal) time periods by measuring C fluxes over a seven-year period at three sites that represent a gradient of time since permafrost thaw. All three sites are upland tundra ecosystems located in Interior Alaska but differed in the extent of permafrost thaw and ground subsidence. Results showed an increasing growing season (May - September) trend in gross primary productivity, net ecosystem exchange, aboveground net primary productivity, and annual net ecosystem exchange at all sites over the seven-year study period from 2004-2010. In contrast, there was no directional change in annual and growing season ecosystem respiration, or mass loss from decomposition of a common cellulose substrate. The increasing trends over time as well as inter site differences most closely followed variation in growing season thaw depth over the same time period. During the seven-year period, sites with more permafrost degradation (deeper seasonal thaw) had significantly greater gross primary productivity compared to where degradation was least, but also greater growing season ecosystem respiration. Adding in winter respiration decreased, in part, the summer C sink and left the site with the most permafrost degradation near C neutral, with the other sites annual C sinks. However, annual C balance was strongly dependent on winter respiration, which, compared to the growing season, was relatively data-poor due to extreme environmental conditions. As a result, we cannot yet

  12. Influence of understory greenness on trace gas and energy exchange in forested ecosystems

    NASA Astrophysics Data System (ADS)

    Swetish, J.; Papuga, S. A.; Litvak, M. E.; Barron-Gafford, G. A.; Mitra, B.

    2012-12-01

    Forested ecosystems are important sources and sinks of carbon, water, and energy - affecting land surface - atmosphere interactions at multiple scales. Understanding how forested ecosystems will respond to climate change is critical for quantifying how they will feedback with the climate system. Addressing this need is challenging in forested ecosystems because of their complex structure and composition, both vertically and horizontally. Here we highlight the different functioning of the main overstory canopy and the more seasonal understory. Both the overstory and the understory contribute differently to the exchange of carbon, water and energy with the atmosphere. Both eddy covariance measurements and remotely sensed products can provide ecosystem-scale estimates of trace gas and energy flux, but the contribution of the understory to these estimates remains relatively unexplored. In this study, we aim to address the contribution of the understory to ecosystem-scale carbon uptake. Specifically, we ask the following questions: (1) how big is the contribution of the understory to ecosystem carbon uptake?; (2) at what times of year is the understory contribution important?; (3) does the eddy covariance carbon uptake signal (NEE-) reflect the greening up dynamics of the understory?; (4) is the greening up dynamics of the understory captured in our remotely-sensed products?; and (5) can remotely-sensed vegetation products such as MODIS-derived NDVI and EVI accurately reflect ecosystem-scale carbon uptake dynamics? To address these questions, we use three years of eddy covariance data from two similar subalpine mixed-conifer ecosystems within the Jemez River Basin - Santa Catalina Mountain Critical Zone Observatory (JRB-SCM CZO). The mixed-conifer site at the JRB is at roughly 3000 m and has substantial understory, while the mixed-conifer ecosystem of the SCM is at roughly 2500 m has very minimal understory. Within the footprint of the eddy covariance towers at both

  13. Carbondioxide exchange of biological soil crusts compared to disturbed soil / sand in semi arid areas

    NASA Astrophysics Data System (ADS)

    Wilske, B.; Yakir, D.; Burgheimer, J.; Karnieli, A.; Zaady, E.; Kesselmeier, J.

    2003-04-01

    Sparse vegetation in semi arid and arid lands is associated with low productivity and minor contribution to biosphere-atmosphere exchange of greenhouse gases, on an area basis. Dryland ecosystems, however, cover large land areas that are continuously increasing. Two third of global population live in semi arid and arid regions and its direct impact contributes to the expansion of dryland ecosystems. Satellite images at the start of the wet season in natural dryland ecosystems clearly show significant photosynthetic activity at a time when most vascular plants are yet inactive or undeveloped, indicating a possibly neglected CO_2 sink. This can likely be assigned to the so-called biological soil crusts (BSC) that consist of poikilohydric microphytes such as cyanobacteria, lichens, green algae, and mosses, which can rapidly recover photosynthesis in response to the earliest water supply. Such non-vascular vegetation activities are an important feature of dryland ecosystems worldwide, often complementary to that of vascular plants. We report on the rates of CO_2 exchange of BSC as measured at two field sites in the northern Negev desert during six months during 2001/2002. Peak rates of net photosynthesis (1.5 - 2 μmol m-2 s-1) were in the range observed in vascular plants, but periods with low or no activities were considerable. Rates of CO_2 exchange of BSC was always compared with that of bare soil / sand. This allowed both estimating net local land surface exchange, and assessing the influence of disturbance, mainly by uncontrolled land use, of the highly vulnerable BSC ecosystems. Simultaneous measurements of spectral reflectance properties of BSC in this study aim to allow calibration of airborne remote sensing for large-scale BSC activity studies.

  14. Scalar Profile Assimilation Into a Multi-Layer Model of Canopy-Atmosphere Exchange: Toward Optimal Estimation of Net Ecosystem Exchange

    NASA Astrophysics Data System (ADS)

    Drewry, D. T.; Albertson, J. D.; Katul, G.

    2003-12-01

    A major focus of current research efforts in land-atmosphere exchange is the modeling and quantification of carbon dioxide, water vapor and energy fluxes between forested ecosystems and the atmosphere. Mechanistic models of the coupled physical and biological processes that determine the magnitude of scalar fluxes have been developed and tested at many sites under a variety of environmental conditions. High frequency eddy covariance measurements of scalar fluxes are often used to test these canopy exchange models. Concurrent observations of carbon dioxide concentration profiles within the canopy airspace are frequently left unutilized in such modeling studies. We explore the assimilation of the information contained in these concentration profile measurements to constrain forward model estimates of net ecosystem exchange (NEE). A high-resolution, one-dimensional multi-layer model of canopy-atmosphere dynamics, including turbulent transport, vertical radiation interception, photosynthesis, stomatal conductance and respiration, is implemented and tested against eddy covariance flux measurements taken at the Duke Forest. A simple assimilation scheme is used to compare the results of forward model integrations both with and without the assimilated profile information. Implications are discussed for the optimal merger of data and models for the estimation of NEE.

  15. 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.

  16. Enhanced Seasonal Exchange of CO2 by Northern Ecosystems - Observations and Models

    NASA Astrophysics Data System (ADS)

    Graven, H. D.; Keeling, R. F.; Piper, S. C.; Patra, P. K.; Stephens, B. B.; Wofsy, S. C.; Welp, L. R.; Sweeney, C.; Tans, P. P.; Kelley, J. J.; Daube, B. C.; Kort, E. A.; Santoni, G.; Bent, J. D.; Thomas, R.; Prentice, I. C.

    2014-12-01

    Long-term measurements of atmospheric CO2 have revealed increasing amplitude in seasonal variations at Northern Hemisphere sites. In a recent paper1, we extended the analysis of seasonal CO2 amplitude using aircraft data from 1958-61 and 2009-11 and found large increases of 50% in the mid-troposphere north of 45°N. Changes in amplitude south of 45°N were less than 25%. The observations indicate that seasonal CO2 exchanges with northern terrestrial ecosystems must have increased by 30-60% over the past 50 years. The increased exchange is likely widespread over northern ecosystems but it must be focused in boreal forests to match the observed spatial pattern in the aircraft data. Small decreases in seasonal CO2 exchange of subtropical and tropical regions may also contribute to CO2 amplitude changes. The required increases in seasonal CO2 exchange in northern ecosystems are larger than simulated by terrestrial models, indicating the models do not capture substantial ecological changes occurring since 1960. This presentation will give an overview of the recent paper1, highlighting the atmospheric evidence for a dominant influence from boreal forests and from the main growing season months. It will also expand on the investigation of modeled changes in seasonal CO2 flux using CMIP5 and other model intercomparisons, including the modeled influences of carbon vs climate drivers. 1. Graven et al. 2013, Enhanced Seasonal Exchange of CO2 by Northern Ecosystems Since 1960, Science, 341, 6150, 1085-1089. DOI: 10.1126/science.1239207

  17. Carbon dioxide and water vapor exchange by young and old ponderosa pine ecosystems during a dry summer.

    PubMed

    Law, B E; Goldstein, A H; Anthoni, P M; Unsworth, M H; Panek, J A; Bauer, M R; Fracheboud, J M; Hultman, N

    2001-03-01

    We investigated key factors controlling mass and energy exchange by a young (6-year-old) ponderosa pine (Pinus ponderosa Laws.) plantation on the west side of the Sierra Nevada Mountains and an old-growth ponderosa pine forest (mix of 45- and 250-year-old trees) on the east side of the Cascade Mountains, from June through September 1997. At both sites, we operated eddy covariance systems above the canopy to measure net ecosystem exchange of carbon dioxide and water vapor, and made concurrent meteorological and ecophysiological measurements. Our objective was to understand and compare the controls on ecosystem processes in these two forests. Precipitation is much higher in the young plantation than in the old-growth forest (1660 versus 550 mm year-1), although both forests experienced decreasing soil water availability and increasing vapor pressure deficits (D) as the summer of 1997 progressed. As a result, drought stress increased at both sites during this period, and changes in D strongly influenced ecosystem conductance and net carbon uptake. Ecosystem conductance for a given D was higher in the young pine plantation than in the old-growth forest, but decreased dramatically following several days of high D in late summer, possibly because of xylem cavitation. Net CO2 exchange generally decreased with conductance at both sites, although values were roughly twice as high at the young site. Simulations with the 3-PG model, which included the effect of tree age on fluxes, suggest that, during the fall through spring period, milder temperatures and ample water availability at the young site provide better conditions for photosynthesis than at the old pine site. Thus, over the long-term, the young site can carry more leaf area, and the climatic conditions between fall and spring offset the more severe limitations imposed by summer drought.

  18. Growing Season Length as a Key Factor of Cumulative Net Ecosystem Exchange Over the Pine Forest Ecosystems in Europe

    NASA Astrophysics Data System (ADS)

    Danielewska, Alina; Urbaniak, Marek; Olejnik, Janusz

    2015-04-01

    The Scots pine is one of the most important species in European and Asian forests. Due to a widespread occurrence of pine forests, their significance in the energy and mass exchange between the Earth surface and the atmosphere is also important, particularly in the context of climate change and greenhouse gases balance. The aim of this work is to present the relationship between the average annual net ecosystem productivity and growing season length, latitude and air temperature (tay) over Europe. Therefore, CO2 flux measurement data from eight European pine dominated forests were used. The observations suggest that there is a correlation between the intensity of CO2 uptake or emission by a forest stand and the above mentioned parameters. Based on the obtained results, all of the selected pine forest stands were CO2 sinks, except a site in northern Finland. The carbon dioxide uptake increased proportionally with the increase of growing season length (9.212 g C m-2 y-1 per day of growing season, R2 = 0.53, p = 0.0399). This dependency showed stronger correlation and higher statistical significance than both relationships between annual net ecosystem productivity and air temperature (R2 = 0.39, p = 0.096) and annual net ecosystem productivity and latitude (R2 = 0.47, p = 0.058). The CO2 emission surpassed assimilation in winter, early spring and late autumn. Moreover, the appearance of late, cold spring and early winter, reduced annual net ecosystem productivity. Therefore, the growing season length can be considered as one of the main factor affecting the annual carbon budget of pine forests.

  19. Exchange of carbonyl sulfide (COS), a potential tracer of gross primary productivity, between grassland ecosystem components and the atmosphere

    NASA Astrophysics Data System (ADS)

    Whelan, M.; Rhew, R. C.

    2013-12-01

    Recently, measurements of carbonyl sulfide (COS) exchange have been used as an independent constraint for estimates of gross primary productivity over terrestrial ecosystems and continents. CO2 is both taken up and released by plants, whereas COS is usually only consumed and at a predictable ratio to CO2. Most of the underlying theoretical assumptions of this method have been verified, however the problem of parsing leaf exchange from other terrestrial sources and sinks of COS is still under investigation. In ecosystems that experience distinct periods of growing and senescence, it is possible to assess COS fluxes in situ when no green plants are present and compare to measurements during the growing season. Taking advantage of this seasonal pattern, we have investigated COS exchange from March 2012 to March 2013 in a Mediterranean grassland outside of Santa Cruz, CA, U.S.A (37.0°N, 122°W). Through lab-based incubation experiments, we found that net COS uptake of grassland soil can be reduced by increased soil moisture. We evaluated this claim in the field with monthly field deployments of static flux chambers over the in-tact soil and plant system. In the dry summer, artificial rain amendments caused COS net uptake to decrease, sometimes leading to overall net production to the atmosphere, in agreement with lab experiments. During the wet growing season, water additions caused over 2x increase in COS uptake from the atmosphere. Contrary to what has been previously claimed, soil exchange of COS is not negligible in grassland ecosystems.

  20. Net Ecosystem Exchange and Net Biome Productivity of different land use in eastern Germany

    NASA Astrophysics Data System (ADS)

    Grünwald, Thomas; Prescher, Anne-Katrin; Bernhofer, Christian

    2010-05-01

    The carbon (CO2-C) budgets of a managed forest (spruce), grassland and a cropland (crop rotation) have been determined and compared. The sites are part of the Tharandt cluster which features low intersite variability in climate due to the small distances between the sites. This allows the comparison of management effects on the carbon budget of different land use among other things. At the forest site, continuous CO2 flux measurements are available from 1997 to 2008, the common observation period of the grassland and cropland sites was 2005 to 2008. With regard to annual net ecosystem exchange NEE (based on eddy covariance flux measurements), the forest showed the highest net sink (-698 g C m-2 (1999) to -444 g C m-2 (2003)). In contrast the grassland and cropland sites were significantly lower sinks in terms of NEE (-177 g C m-2 (2004) to -62 g C m-2 (2005) and -115 g C m-2 (2005) to -32 g C m-2 (2007 and 2008), respectively). To quantify the net biome productivity (NBP) carbon exports due to thinning or harvest as well as carbon imports due to organic fertilisation are considered besides NEE. Carbon exports and imports change the carbon budget in terms of NBP. At the forest site only the 2002 NBP is a carbon source (+221 g C m-2) due to the thinning in April 2002 when around 43 m3 ha-1 solid wood was removed from the ecosystem. After the thinning the annual NEE is reduced by around 100 g C m-2 until 2007. The grassland NBP alternated between carbon source and sink (+25 g C m-2 (2008) to -28 g C m-2 (2006)) indicating the carbon balance was approximately neutral. Low NEE and NBP values at the grassland site were a consequence of carbon export due to several cuts per year. The NBP of the cropland ecosystem was mainly influenced by the crop type (winter or spring crop) and the application of organic fertiliser (manure) resulting in carbon budgets between +484 g C m-2 (2007) and -89 g C m-2 (2006). The different timing and length of the growing season of winter and

  1. Interannual variability of net ecosystem CO2 exchange in a suburban landscape

    NASA Astrophysics Data System (ADS)

    McFadden, J.; Hiller, R.

    2010-12-01

    Turfgrass lawns are a ubiquitous feature of North American cities and suburbs. In the continental United States, lawns cover an estimated area of 163,800 km2 (Milesi et al. 2005). Yet most of what we know about CO2 exchange in urban landscapes is related to the dominant fossil fuel emission terms, whereas relatively few direct measurements have been made of the CO2 uptake by and release from the land itself. This represents an important gap because urbanization in recent decades has been characterized by increasing per-capita land consumption and most of it has taken place in the suburbs, which have a higher percent cover of greenspace compared to the central areas of cities. Here, we report results from the KUOM tall tower flux site located in a first-ring suburban residential neighborhood of Minneapolis-Saint Paul, Minnesota, USA. From November 2005 to June 2009 we concurrently measured CO2, water vapor, and energy fluxes from a mobile tower over an extensive unirrigated turfgrass field that was similar to residential lawns. The annual net ecosystem exchange (NEE) of CO2 ranged from a sink of -78 g C m-2 to a source of 86 g C m-2. We analyzed the interannual variability with respect to differences in winter respiration, the date of spring green-up and fall senescence, growing-season length, the maximum growth rate in spring, and seasonal drought. The long-term goal of this research is to understand how developed land use affects regional carbon budgets and to explore how these impacts may change with management practices and urban development patterns.

  2. Active atmosphere-ecosystem exchange of the vast majority of detected volatile organic compounds.

    PubMed

    Park, J-H; Goldstein, A H; Timkovsky, J; Fares, S; Weber, R; Karlik, J; Holzinger, R

    2013-08-09

    Numerous volatile organic compounds (VOCs) exist in Earth's atmosphere, most of which originate from biogenic emissions. Despite VOCs' critical role in tropospheric chemistry, studies for evaluating their atmosphere-ecosystem exchange (emission and deposition) have been limited to a few dominant compounds owing to a lack of appropriate measurement techniques. Using a high-mass resolution proton transfer reaction-time of flight-mass spectrometer and an absolute value eddy-covariance method, we directly measured 186 organic ions with net deposition, and 494 that have bidirectional flux. This observation of active atmosphere-ecosystem exchange of the vast majority of detected VOCs poses a challenge to current emission, air quality, and global climate models, which do not account for this extremely large range of compounds. This observation also provides new insight for understanding the atmospheric VOC budget.

  3. Bi-directional exchange of ammonia in a pine forest ecosystem - a model sensitivity analysis

    NASA Astrophysics Data System (ADS)

    Moravek, Alexander; Hrdina, Amy; Murphy, Jennifer

    2016-04-01

    Ammonia (NH3) is a key component in the global nitrogen cycle and of great importance for atmospheric chemistry, neutralizing atmospheric acids and leading to the formation of aerosol particles. For understanding the role of NH3 in both natural and anthropogenically influenced environments, the knowledge of processes regulating its exchange between ecosystems and the atmosphere is essential. A two-layer canopy compensation point model is used to evaluate the NH3 exchange in a pine forest in the Colorado Rocky Mountains. The net flux comprises the NH3 exchange of leaf stomata, its deposition to leaf cuticles and exchange with the forest ground. As key parameters the model uses in-canopy NH3 mixing ratios as well as leaf and soil emission potentials measured at the site in summer 2015. A sensitivity analysis is performed to evaluate the major exchange pathways as well as the model's constraints. In addition, the NH3 exchange is examined for an extended range of environmental conditions, such as droughts or varying concentrations of atmospheric pollutants, in order to investigate their influence on the overall net exchange.

  4. Impacts of Precipitation Diurnal Timing on Ecosystem Carbon Exchanges in Grasslands: A Synthesis of AmeriFlux Data

    NASA Astrophysics Data System (ADS)

    Song, X.; Xu, X.; Tweedie, C. E.

    2015-12-01

    Drylands have been found playing an important role regulating the seasonality of global atmospheric carbon dioxide concentrations. Precipitation is a primary control of ecosystem carbon exchanges in drylands where a large proportion of the annual total rainfall arrives through a small number of episodic precipitation events. While a large number of studies use the concept of "precipitation pulses" to explore the effects of short-term precipitation events on dryland ecosystem function, few have specifically evaluated the importance of the diurnal timing of these events. The primary goal of this study was to determine how the diurnal timing of rainfall events impacts land-atmosphere net ecosystem CO2 exchanges (NEE) and ecosystem respiration in drylands. Our research leverages a substantial and existing long-term database (AmeriFlux) that describes NEE, Reco and meteorological conditions at 11 sites situated in different dryland ecosystems in South West America. All sites employ the eddy covariance technique to measure land-atmosphere the CO2 exchange rates between atmosphere and ecosystem. Data collected at these sites range from 4 to 10 years, totaling up to 73 site-years. We found that episodic precipitation events stimulate not only vegetation photosynthesis but also ecosystem respiration. Specifically, the morning precipitation events decrease photosynthesis function at daytime and increase ecosystem respiration at nighttime; the afternoon precipitation events do not stimulate ecosystem photosynthesis at daytime, while stimulate ecosystem respiration; the night precipitations suppress photosynthesis at daytime, and enhance ecosystem respiration at nighttime.

  5. Evaluation of Growing Season Milestones, Using Eddy Covariance Time-Series of Net Ecosystem Exchange

    NASA Astrophysics Data System (ADS)

    Pastorello, G.; Faybishenko, B.; Poindexter, C.; Menzer, O.; Agarwal, D.; Papale, D.; Baldocchi, D. D.

    2014-12-01

    Common methods for determining timing of plants' developmental events, such as direct observation and remote sensing of NDVI, usually produce data of temporal resolution on the order of one week or more. This limitation can make observing subtle trends across years difficult. The goal of this presentation is to demonstrate a conceptual approach and a computational technique to quantify seasonal, annual and long-term phenological indices and patterns, based on continuous eddy covariance measurements of net ecosystem exchange (NEE) measured at eddy covariance towers in the AmeriFlux network. Using a comprehensive time series analysis of NEE fluxes in different climatic zones, we determined multiple characteristics (and their confidence intervals) of the growing season including: the initiation day—the day when canopy photosynthesis development starts, the photosynthesis stabilization day - the day when the development process of canopy photosynthesis starts to slow down and gradually moves toward stabilization, and the growing season effective termination day. We also determined the spring photosynthetic development velocity and the fall photosynthetic development velocity. The results of calculations using NEE were compared with those from temperature and precipitation data measured at the same AmeriFlux tower stations, as well as with the in-situ directly observed phenological records. The results of calculations of phenological indices from the NEE time-series collected at AmeriFlux sites can be used to constrain the application of other time- and labor-intensive sensing methods and to reduce the uncertainty in identifying trends in the timing of phenological indices.

  6. Dynamic exchanges between DOM and POM pools in coastal and inland aquatic ecosystems: A review.

    PubMed

    He, Wei; Chen, Meilian; Schlautman, Mark A; Hur, Jin

    2016-05-01

    Dynamic exchanges between dissolved organic matter (DOM) and particulate organic matter (POM) plays a critical role in organic carbon cycling in coastal and inland aquatic ecosystems, interactions with aquatic organisms, mobility and bioavailability of pollutants, among many other ecological and geochemical phenomena. Although DOM-POM exchange processes have been widely studied from different aspects, little to no effort has been made to date to provide a comprehensive, mechanistic, and micro-spatial schema for understanding various exchange processes occurring in different aquatic ecosystems in a unified way. The phenomena occurring between DOM and POM were explained here with the homogeneous and heterogeneous mechanisms. In the homogeneous mechanism, the participating components are only organic matter (OM) constituents themselves with aggregation and dissolution involved, whereas OM is associated with other components such as minerals and particulate colloids in the heterogeneous counterpart. Besides the generally concerned processes of aggregation/dissolution and adsorption/desorption, other ecological factors such as sunlight and organisms can also participate in DOM-POM exchanges through altering the chemical nature of OM. Despite the limitation of current analytical technologies, many unknown and/or unquantified processes need to be identified to unravel the complicated exchanges of OM between its dissolved and particulate states. Based on the review of several previous mathematical models, we proposed a unified conceptual model to describe all major dynamic exchange mechanisms on the basis of exergy theory. More knowledge of dynamic DOM-POM exchanges is warranted to overcome the potential problems arising from a simple division of OM into dissolved versus particulate states and to further develop more sophisticated mathematic models.

  7. 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

  8. Water and nitrogen availability co-control ecosystem CO2 exchange in a semiarid temperate steppe.

    PubMed

    Zhang, Xiaolin; Tan, Yulian; Li, Ang; Ren, Tingting; Chen, Shiping; Wang, Lixin; Huang, Jianhui

    2015-10-23

    Both water and nitrogen (N) availability have significant effects on ecosystem CO2 exchange (ECE), which includes net ecosystem productivity (NEP), ecosystem respiration (ER) and gross ecosystem photosynthesis (GEP). How water and N availability influence ECE in arid and semiarid grasslands is still uncertain. A manipulative experiment with additions of rainfall, snow and N was conducted to test their effects on ECE in a semiarid temperate steppe of northern China for three consecutive years with contrasting natural precipitation. ECE increased with annual precipitation but approached peak values at different precipitation amount. Water addition, especially summer water addition, had significantly positive effects on ECE in years when the natural precipitation was normal or below normal, but showed trivial effect on GEP when the natural precipitation was above normal as effects on ER and NEP offset one another. Nitrogen addition exerted non-significant or negative effects on ECE when precipitation was low but switched to a positive effect when precipitation was high, indicating N effect triggered by water availability. Our results indicate that both water and N availability control ECE and the effects of future precipitation changes and increasing N deposition will depend on how they can change collaboratively in this semiarid steppe ecosystem.

  9. Modeling approaches to describe H2O and CO2 exchange in mare ecosystems

    NASA Astrophysics Data System (ADS)

    Olchev, A.; Novenko, E.; Volkova, E.

    2012-04-01

    The modern climatic conditions is strongly influenced by both internal variability of climatic system, and various external natural and anthropogenic factors (IPCC 2007). Significant increase of concentration of greenhouse gases in the atmosphere and especially the growth of atmospheric CO2 due to human activity are considered as the main factors that are responsible for global warming and climate changes. A significant part of anthropogenic CO2 is absorbed from the atmosphere by land biota and especially by vegetation cover. However, it is still not completely clear what is the role of different land ecosystems and especially forests and mares in global cycles of H2O and CO2 and what is a sensitivity of these ecosystems to climate changes. Within the frameworks of this study the spatial and temporal variability of H2O and CO2 fluxes in different types of mare ecosystems of the forest-steppe zone in European part of Russia was described using modeling approaches and results of field measurements. For this modeling and experimental study the mare ecosystems of Tula region were selected. The Tula region is located mostly in the forest-steppe zone and it is unique area for such studies because almost all existed types of mare ecosystems of Northern Eurasia distinguished by a geomorphological position, water and mineral supply can be found there. Most mares in Tula region have a relatively small size and surrounded by very heterogeneous forests that make not possible an application of the classical measuring and modeling approaches e.g. an eddy covariance technique or one-dimensional H2O and CO2 exchange models for flux estimation in such sites. In our study to describe the radiation, sensible heat, H2O and CO2 exchange between such heterogeneous mare ecosystems and the atmosphere a three-dimensional model Forbog-3D and one-dimensional Mixfor-SVAT were applied. The main concept used in the Forbog-3D and Mixfor-SVAT models is an aggregated description of physical and

  10. Long term effects of fen restoration: Parameterization of net ecosystem exchange models along a land use-degradation gradient

    NASA Astrophysics Data System (ADS)

    Bergmann, L.; Drösler, M.; Schultz, R.; Freibauer, A.; Jungkunst, H.; Höll, B.

    2010-05-01

    In combination with fluctuating water regimes and extreme variations in weather conditions expected through climate change, continual disturbance to the soils through peat use poses a risk to the carbon storage capacities and sequestration potentials of peatlands. Restoration and/ or extensive use of peatlands are strategies to optimize vegetation and hydrological balance within these sensitive ecosystems. Our goal was to determine the long term effects of fen restoration on CO2 fluxes and to identify the driving parameters causing differential fluxes along a disturbance gradient. This study aimed specifically to provide a CO2-C flux dataset to determine net ecosystem exchange (NEE) in restored temperate fens ecosystems. A climate controlled chamber system was used for measuring instantaneous NEE over the entire year in the Donauried in 2005 and in the Loisach-Kochelsee fens in 2006, both in southern Germany. The sites were chosen to represent both a management gradient (from intensive grasslands and crops to long-term restored Carex lawns) and a water table gradient (-78 cm below surface to -1 cm below surface). NEE was measured using the closed chamber technique, allowing for separation of NEE into gross ecosystem production (GEP) and ecosystem respiration (Reco). In both study areas, management strongly influenced ecosystem respiration and GPP and thus NEE, where Reco remained a strong determinant of NEE balances. Whereas the managed-degraded sites are acting as sources of CO2, a positive effect of restoration is seen in terms of NEE exchange. The restored sites are either acting as significant sinks for CO2 (Donauried old restored sites) or are have significantly lower emissions as the managed-degraded sites. NEE values ranged from 1041 g CO2-C m2 a1source to the atmosphere in a two cut grassland to a -130 g CO2-C m2 a1sinkin the long-term restored unmanaged Carex paniculata site. Reco was highest in grassland sites and lowest in the restored Carex sites. A

  11. 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...

  12. Net ecosystem exchange over heterogeneous Arctic tundra: Scaling between chamber and eddy covariance measurements

    NASA Astrophysics Data System (ADS)

    Fox, Andrew M.; Huntley, Brian; Lloyd, Colin R.; Williams, Mathew; Baxter, Robert

    2008-06-01

    Net ecosystem exchange (NEE) was estimated for an area of tundra near Abisko using both eddy covariance (EC) data and chamber measurements. This area of tundra is heterogeneous with six principal elements forming a landscape mosaic. Chamber measurements in patches of the individual mosaic elements were used to model NEE as a function of irradiance and temperature. The area around the EC mast was mapped, and a footprint model was used to simulate the varying source fraction attributable to each mosaic element. Various upscaling approaches were used to estimate NEE for comparison with NEE calculated from the EC observations. The results showed that EC measurements made for such a heterogeneous site are robust to the variations in NEE between mosaic elements that also vary substantially in their source fractions. However, they also revealed a large (˜60%) bias in the absolute magnitude of the cumulative negative NEE for a 40-day study period simulated by various upscaling approaches when compared to the value calculated from the EC observations. The magnitude of this bias, if applied to estimates for the entire tundra region, is substantial in relation to other components of the global carbon budget. Various hypotheses to account for this bias are discussed and, where possible, evaluated. A need is identified for more systematic sampling strategies when performing chamber measurements in order to assess the extent to which subjectivity of chamber location may account for much of the observed bias. If this is the origin of the bias, then upscaling approaches using chamber measurements may generally overestimate CO2 uptake.

  13. Time Resolved Measurement of Ecosystem-Atmosphere NH3 Exchange Using the Eddy Covariance Technique

    NASA Astrophysics Data System (ADS)

    Fischer, M. L.; Littlejohn, D.

    2005-12-01

    Quantifying ammonia fluxes between the land surface and atmosphere is required for effective control of air quality, improving agricultural practices, and understanding natural ecosystem function. Ammonia (NH3) is emitted in large but uncertain amounts from animal agriculture, in lesser amounts from imperfect use of nitrogen fertilizers in crop agriculture, from catalytic converters used on automobiles and other energy related industrial processes, and exchanged between the ecosystem and atmosphere by natural ecosystem processes on vast spatial scales. To address the need for accurate, time-resolved NH3 flux measurements, we have developed an eddy covariance (EC) instrument for direct measurements of NH3 flux. EC flux measurements of NH3 were not previously possible because instruments were not sufficiently sensitive at high frequencies required to capture rapid variations in surface layer NH3 concentrations. To overcome this hurdle we combined a tunable-diode-laser (TDL) spectrometer with a fast-response NH3 sampling inlet and automated pulse-response calibration system. Laboratory tests of the inlet system demonstrate that the response to 10 ppb step in NH3 concentration is well described by a double exponential model with (1/e) times of 0.3 (85% response) and 1.5 (15% response) seconds. This response combined with a routinely measured instrument stability of ~ 0.1 ppb (on 30 minute timescales) indicates that the instrumental contribution to noise in NH3 flux measurements is ~ 0.2 umol NH3 m-2 hr-1, sufficient to stringently test models for NH3 exchange under most conditions. Recent results of field work to verify the instrument performance and observe examples of NH3 exchange will be presented.

  14. Winds induce CO2 exchange with the atmosphere and vadose zone transport in a karstic ecosystem

    NASA Astrophysics Data System (ADS)

    Sánchez-Cañete, Enrique P.; Oyonarte, Cecilio; Serrano-Ortiz, Penélope; Curiel Yuste, Jorge; Pérez-Priego, Oscar; Domingo, Francisco; Kowalski, Andrew S.

    2016-08-01

    Research on the subterranean CO2 dynamics has focused individually on either surface soils or bedrock cavities, neglecting the interaction of both systems as a whole. In this regard, the vadose zone contains CO2-enriched air (ca. 5% by volume) in the first meters, and its exchange with the atmosphere can represent from 10 to 90% of total ecosystem CO2 emissions. Despite its importance, to date still lacking are reliable and robust databases of vadose zone CO2 contents that would improve knowledge of seasonal-annual aboveground-belowground CO2 balances. Here we study 2.5 years of vadose zone CO2 dynamics in a semiarid ecosystem. The experimental design includes an integrative approach to continuously measure CO2 in vertical and horizontal soil profiles, following gradients from surface to deep horizons and from areas of net biological CO2 production (under plants) to areas of lowest CO2 production (bare soil), as well as a bedrock borehole representing karst cavities and ecosystem-scale exchanges. We found that CO2 followed similar seasonal patterns for the different layers, with the maximum seasonal values of CO2 delayed with depth (deeper more delayed). However, the behavior of CO2 transport differed markedly among layers. Advective transport driven by wind induced CO2 emission both in surface soil and bedrock, but with negligible effect on subsurface soil, which appears to act as a buffer impeding rapid CO2 exchanges. Our study provides the first evidence of enrichment of CO2 under plant, hypothesizing that CO2-rich air could come from root zone or by transport from deepest layers through cracks and fissures.

  15. Comparing Measures of Estuarine Ecosystem Production in a ...

    EPA Pesticide Factsheets

    Anthropogenic nutrient enrichments and concerted efforts at nutrient reductions, compounded with the influences of climate change, are likely changing the net ecosystem production (NEP) of our coastal systems. To quantify these changes, scientists monitor a range of physical, chemical, and biological parameters sampled at various frequencies. Water column chlorophyll concentrations are arguably the most commonly used indicator of net phytoplankton production, as well as a coarse indicator of NEP. We compared parameters that estimate production, including chlorophyll, across an experimental nutrient gradient and in situ in both well-mixed and stratified estuarine environments. Data from an experiment conducted in the early 1980s in mesocosms designed to replicate a well-mixed mid-Narragansett Bay (Rhode Island) water column were used to correlate changes in chlorophyll concentrations, pH, dissolved oxygen (O2), dissolved inorganic nitrogen, phosphate, and silicate concentrations, cell counts, and 14C carbon uptake measurements across a range of nutrient enrichments. The pH, O2, nutrient, and cell count measurements reflected seasonal cycles of spring blooms followed by late summer/early fall respiration periods across nutrient enrichments. Chlorophyll concentrations were more variable and rates of 14C productivity were inconsistent with observed trends in nutrient concentrations, pH, and O2 concentrations. Similar comparisons were made using data from a well-mixe

  16. Estimation of Ecosystem Parameters of the Community Land Model with DREAM: Evaluation of the Potential for Upscaling Net Ecosystem Exchange

    NASA Astrophysics Data System (ADS)

    Hendricks Franssen, H. J.; Post, H.; Vrugt, J. A.; Fox, A. M.; Baatz, R.; Kumbhar, P.; Vereecken, H.

    2015-12-01

    Estimation of net ecosystem exchange (NEE) by land surface models is strongly affected by uncertain ecosystem parameters and initial conditions. A possible approach is the estimation of plant functional type (PFT) specific parameters for sites with measurement data like NEE and application of the parameters at other sites with the same PFT and no measurements. This upscaling strategy was evaluated in this work for sites in Germany and France. Ecosystem parameters and initial conditions were estimated with NEE-time series of one year length, or a time series of only one season. The DREAM(zs) algorithm was used for the estimation of parameters and initial conditions. DREAM(zs) is not limited to Gaussian distributions and can condition to large time series of measurement data simultaneously. DREAM(zs) was used in combination with the Community Land Model (CLM) v4.5. Parameter estimates were evaluated by model predictions at the same site for an independent verification period. In addition, the parameter estimates were evaluated at other, independent sites situated >500km away with the same PFT. The main conclusions are: i) simulations with estimated parameters reproduced better the NEE measurement data in the verification periods, including the annual NEE-sum (23% improvement), annual NEE-cycle and average diurnal NEE course (error reduction by factor 1,6); ii) estimated parameters based on seasonal NEE-data outperformed estimated parameters based on yearly data; iii) in addition, those seasonal parameters were often also significantly different from their yearly equivalents; iv) estimated parameters were significantly different if initial conditions were estimated together with the parameters. We conclude that estimated PFT-specific parameters improve land surface model predictions significantly at independent verification sites and for independent verification periods so that their potential for upscaling is demonstrated. However, simulation results also indicate

  17. Post-Fire Evapotranspiration and Net Ecosystem Exchange over A Semi-Arid Grassland in Arizona

    NASA Astrophysics Data System (ADS)

    Krishnan, P.; Meyers, T. P.; Heuer, M.

    2015-12-01

    The seasonal and interannual variability of evapotranspiration (E) and net ecosystem exchange (NEE) following a fire disturbance over a semi -arid grassland located on the Audubon Research Ranch in south western Arizona (31.5907N, 110.5104W, elevation 1496 m), USA, and their relationships to environmental variables were examined using continuous measurements of water vapour and CO2 fluxes made from first week of June 2002 to 2009 using the eddy covariance technique. The research ranch was established in 1969 as an ecological research preserve and it is now one of the largest ungrazed, privately managed grassland sites in Arizona. A wild fire occurred in April - May 2002, and burned all the standing vegetation and litter on in research ranch (~38,000 acres) including 500 acres of grassland. The mean annual temperature and precipitation (P) at this site were ~16 deg C and ~370 mm, respectively. More than 60% of the annual P was received during the North American monsoon period (July-September) with the lowest annual P in the drought years of 2004 and 2009. Drastic changes in albedo, vegetation growth and evapotranspiration occurred following the onset of the monsoon season in July. The ecosystem was mostly a carbon sink during monsoon period. Daily total evapotranspiration during July-August increased from 2 mm d-1 in 2002 to >3 mm d-1 in 2007. The mean annual E over the site was during 2003 -2009 was 352 ±75 mm. With the onset of monsoon the ecosystem turned to carbon sink in 2002, with daily total net ecosystem exchange (NEE) varying up to ~<-2 g C m-2, by mid-July to August 2002. It was followed by one of the driest monsoon period on the record (2003) with <50% of normal July-September P. Because of this, the recovery of the ecosystem was delayed. During 2002-2009, the ecosystem was mostly a carbon source except in 2006 an year with high growing season Normalized-difference vegetation index, longest monsoon growing season and the highest annual and July

  18. Spatial Distribution of Hydrologic Ecosystem Service Estimates: Comparing Two Models

    NASA Astrophysics Data System (ADS)

    Dennedy-Frank, P. J.; Ghile, Y.; Gorelick, S.; Logsdon, R. A.; Chaubey, I.; Ziv, G.

    2014-12-01

    We compare estimates of the spatial distribution of water quantity provided (annual water yield) from two ecohydrologic models: the widely-used Soil and Water Assessment Tool (SWAT) and the much simpler water models from the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) toolbox. These two models differ significantly in terms of complexity, timescale of operation, effort, and data required for calibration, and so are often used in different management contexts. We compare two study sites in the US: the Wildcat Creek Watershed (2083 km2) in Indiana, a largely agricultural watershed in a cold aseasonal climate, and the Upper Upatoi Creek Watershed (876 km2) in Georgia, a mostly forested watershed in a temperate aseasonal climate. We evaluate (1) quantitative estimates of water yield to explore how well each model represents this process, and (2) ranked estimates of water yield to indicate how useful the models are for management purposes where other social and financial factors may play significant roles. The SWAT and InVEST models provide very similar estimates of the water yield of individual subbasins in the Wildcat Creek Watershed (Pearson r = 0.92, slope = 0.89), and a similar ranking of the relative water yield of those subbasins (Spearman r = 0.86). However, the two models provide relatively different estimates of the water yield of individual subbasins in the Upper Upatoi Watershed (Pearson r = 0.25, slope = 0.14), and very different ranking of the relative water yield of those subbasins (Spearman r = -0.10). The Upper Upatoi watershed has a significant baseflow contribution due to its sandy, well-drained soils. InVEST's simple seasonality terms, which assume no change in storage over the time of the model run, may not accurately estimate water yield processes when baseflow provides such a strong contribution. Our results suggest that InVEST users take care in situations where storage changes are significant.

  19. Seven-year trends of CO2 exchange in a tundra ecosystem affected by long-term permafrost thaw

    NASA Astrophysics Data System (ADS)

    Trucco, Christian; Schuur, Edward A. G.; Natali, Susan M.; Belshe, E. Fay; Bracho, Rosvel; Vogel, Jason

    2012-06-01

    Arctic warming has led to permafrost degradation and ground subsidence, created as a result of ground ice melting. Frozen soil organic matter that thaws can increase carbon (C) emissions to the atmosphere, but this can be offset in part by increases in plant growth. The balance of plant and microbial processes, and how this balance changes through time, determines how permafrost ecosystems influence future climate change via the C cycle. This study addressed this question both on short (interannual) and longer (decadal) time periods by measuring C fluxes over a seven-year period at three sites representing a gradient of time since permafrost thaw. All three sites were upland tundra ecosystems located in Interior Alaska but differed in the extent of permafrost thaw and ground subsidence. Results showed an increasing growing season (May - September) trend in gross primary productivity (GPP), net ecosystem exchange (NEE), aboveground net primary productivity (ANPP), and annual NEE at all sites over the seven year study period from 2004 to 2010, but no change in annual and growing season ecosystem respiration (Reco). These trends appeared to most closely follow increases in the depth to permafrost that occurred over the same time period. During the seven-year period, sites with more permafrost degradation had significantly greater GPP compared to where degradation was least, but also greater growing season Reco. Adding in winter Reco decreased, in part, the summer C sink and left only the site with the most permafrost degradation C neutral, with the other sites still C sinks. Annual C balance was strongly dependent on winter Reco, which, compared to the growing season, was relatively data-poor due to extreme environmental conditions. As a result, we cannot yet conclude whether the increased NEE in the growing season is truly sustained on an annual basis. If it turns out that winter measurements shown here are an underestimate, we may indeed find these systems are

  20. Structure, function and evolution of the gas exchangers: comparative perspectives

    PubMed Central

    Maina, JN

    2002-01-01

    Over the evolutionary continuum, animals have faced similar fundamental challenges of acquiring molecular oxygen for aerobic metabolism. Under limitations and constraints imposed by factors such as phylogeny, behaviour, body size and environment, they have responded differently in founding optimal respiratory structures. A quintessence of the aphorism that ‘necessity is the mother of invention’, gas exchangers have been inaugurated through stiff cost–benefit analyses that have evoked transaction of trade-offs and compromises. Cogent structural–functional correlations occur in constructions of gas exchangers: within and between taxa, morphological complexity and respiratory efficiency increase with metabolic capacities and oxygen needs. Highly active, small endotherms have relatively better-refined gas exchangers compared with large, inactive ectotherms. Respiratory structures have developed from the plain cell membrane of the primeval prokaryotic unicells to complex multifunctional ones ofthe modern Metazoa. Regarding the respiratory medium used to extract oxygen from, animal life has had only two choices – water or air – within the biological range of temperature and pressure the only naturally occurring respirable fluids. In rarer cases, certain animalshave adapted to using both media. Gills (evaginated gas exchangers) are the primordial respiratory organs: they are the archetypal water breathing organs. Lungs (invaginated gas exchangers) are the model air breathing organs. Bimodal (transitional) breathers occupy the water–air interface. Presentation and exposure of external (water/air) and internal (haemolymph/blood) respiratory media, features determined by geometric arrangement of the conduits, are important features for gas exchange efficiency: counter-current, cross-current, uniform pool and infinite pool designs have variably developed. PMID:12430953

  1. Sensitivity analysis of a model of CO2 exchange in tundra ecosystems by the adjoint method

    SciTech Connect

    Waelbroek, C.; Louis, J.F. |

    1995-02-01

    A model of net primary production (NPP), decomposition, and nitrogen cycling in tundra ecosystems has been developed. The adjoint technique is used to study the sensitivity of the computed annual net CO2 flux to perturbation in initial conditions, climatic inputs, and model`s main parameters describing current seasonal CO2 exchange in wet sedge tundra at Barrow, Alaska. The results show that net CO2 flux is most sensitive to parameters characterizing litter chemical composition and more sensitive to decomposition parameters than to NPP parameters. This underlines the fact that in nutrient-limited ecosystems, decomposition drives net CO2 exchange by controlling mineralization of main nutrients. The results also indicate that the short-term (1 year) response of wet sedge tundra to CO2-induced warming is a significant increase in CO2 emission, creating a positive feedback to atmosphreic CO2 accumulation. However, a cloudiness increase during the same year can severely alter this response and lead to either a slight decrease or a strong increase in emitted CO2, depending on its exact timing. These results demonstrate that the adjoint method is well suited to study systems encountering regime changes, as a single run of the adjoint model provides sensitivities of the net CO2 flux to perturbations in all parameters and variables at any time of the year. Moreover, it is shown that large errors due to the presence of thresholds can be avoided by first delimiting the range of applicability of the adjoint results.

  2. Sensitivity analysis of a model of CO2 exchange in tundra ecosystems by the adjoint method

    NASA Technical Reports Server (NTRS)

    Waelbroek, C.; Louis, J.-F.

    1995-01-01

    A model of net primary production (NPP), decomposition, and nitrogen cycling in tundra ecosystems has been developed. The adjoint technique is used to study the sensitivity of the computed annual net CO2 flux to perturbation in initial conditions, climatic inputs, and model's main parameters describing current seasonal CO2 exchange in wet sedge tundra at Barrow, Alaska. The results show that net CO2 flux is most sensitive to parameters characterizing litter chemical composition and more sensitive to decomposition parameters than to NPP parameters. This underlines the fact that in nutrient-limited ecosystems, decomposition drives net CO2 exchange by controlling mineralization of main nutrients. The results also indicate that the short-term (1 year) response of wet sedge tundra to CO2-induced warming is a significant increase in CO2 emission, creating a positive feedback to atmosphreic CO2 accumulation. However, a cloudiness increase during the same year can severely alter this response and lead to either a slight decrease or a strong increase in emitted CO2, depending on its exact timing. These results demonstrate that the adjoint method is well suited to study systems encountering regime changes, as a single run of the adjoint model provides sensitivities of the net CO2 flux to perturbations in all parameters and variables at any time of the year. Moreover, it is shown that large errors due to the presence of thresholds can be avoided by first delimiting the range of applicability of the adjoint results.

  3. Controls for ecosystem methane exchange are time-scale specifc and shift during the growing season of a temperate fen

    NASA Astrophysics Data System (ADS)

    Sachs, T.; Koebsch, F.; Jurasinski, G.; Koch, M.; Hofmann, J.; Glatzel, S.

    2014-12-01

    Wetlands are the largest natural sources for atmospheric methane (CH4). In wetlands with permanent shallow inundation, the seasonal variation of CH4 exchange is mainly controlled by temperature and phenology. In addition, ecosystem CH4 exchange varies considerably on smaller temporal scales such as days or weeks. Several single processes that control CH4 emissions on the local soil-plant-atmosphere continuum are well investigated, but their interaction on ecosystem level is not well understood yet. We applied wavelet analysis to a quasi-continuous Eddy Covariance CH4 flux time series to describe the temporal variation of ecosystem CH4 exchange within the growing season of a permanently inundated temperate fen. Moreover, we addressed time scale-specific controls and investigated whether their impact changes during the course of the growing season. On large time scales of two weeks to three months, temperature explained most of the variation in ecosystem CH4 exchange. In general, the temperature in the shallow water column had the largest impact as explanatory variable, however, air temperature and soil temperature became increasingly important as explanatory variables when water level dropped slightly up to June. The diurnal variation of ecosystem CH4 exchange shifted during the course of the growing season: During a short time period at the end of April, plant activity (expressed by canopy photosynthesis) caused a diurnal variation of ecosystem CH4 exchange with peak time around noon. In the following weeks, the daily cycle of convective mixing within the water column (expressed by the water temperature gradient) gradually gained importance and caused high night-time CH4 emissions, thereby levelling off the diurnal CH4 emission pattern. Moreover, shear-induced turbulence caused short-term fluctuations of ecosystem CH4 exchange on time scales up to two hours. Our study highlights the need for multi-scale approaches that consider the non-stationarity of the

  4. Comparative analysis of compact heat exchangers for application as the intermediate heat exchanger for advanced nuclear reactors

    SciTech Connect

    Bartel, N.; Chen, M.; Utgikar, V. P.; Sun, X.; Kim, I. -H.; Christensen, R.; Sabharwall, P.

    2015-04-04

    A comparative evaluation of alternative compact heat exchanger designs for use as the intermediate heat exchanger in advanced nuclear reactor systems is presented in this article. Candidate heat exchangers investigated included the Printed circuit heat exchanger (PCHE) and offset strip-fin heat exchanger (OSFHE). Both these heat exchangers offer high surface area to volume ratio (a measure of compactness [m2/m3]), high thermal effectiveness, and overall low pressure drop. Helium–helium heat exchanger designs for different heat exchanger types were developed for a 600 MW thermal advanced nuclear reactor. The wavy channel PCHE with a 15° pitch angle was found to offer optimum combination of heat transfer coefficient, compactness and pressure drop as compared to other alternatives. The principles of the comparative analysis presented here will be useful for heat exchanger evaluations in other applications as well.

  5. Comparative analysis of compact heat exchangers for application as the intermediate heat exchanger for advanced nuclear reactors

    DOE PAGES

    Bartel, N.; Chen, M.; Utgikar, V. P.; ...

    2015-04-04

    A comparative evaluation of alternative compact heat exchanger designs for use as the intermediate heat exchanger in advanced nuclear reactor systems is presented in this article. Candidate heat exchangers investigated included the Printed circuit heat exchanger (PCHE) and offset strip-fin heat exchanger (OSFHE). Both these heat exchangers offer high surface area to volume ratio (a measure of compactness [m2/m3]), high thermal effectiveness, and overall low pressure drop. Helium–helium heat exchanger designs for different heat exchanger types were developed for a 600 MW thermal advanced nuclear reactor. The wavy channel PCHE with a 15° pitch angle was found to offer optimummore » combination of heat transfer coefficient, compactness and pressure drop as compared to other alternatives. The principles of the comparative analysis presented here will be useful for heat exchanger evaluations in other applications as well.« less

  6. Carbonyl sulfide exchange on an ecosystem scale: soil represents a dominant sink for atmospheric COS

    NASA Astrophysics Data System (ADS)

    Kuhn, U.; Ammann, C.; Wolf, A.; Meixner, F. X.; Andreae, M. O.; Kesselmeier, J.

    The soil/plant/atmosphere exchange of carbonyl sulfide (COS) was investigated in an open oak woodland ecosystem at a rural site in northern California. Measurements of atmospheric concentrations of COS were made in June and in December 1994. We found a significant diel cycle with a drop of COS levels by approximately 150 ppt during the night in both seasons. The mean COS daytime background mixing ratios showed a distinct seasonal difference with 465±77 ppt in summer and 375±56 ppt in winter. The nighttime bulk COS flux into the ecosystem was estimated using a micrometeorological model. To address the observed depletion of COS during stable nocturnal boundary layer conditions, the potential of various ecosystem compartments to act as a sink for COS was investigated. Studies using dynamic enclosures flushed with ambient air excluded vegetation as an important sink during nighttime due to high stomatal resistance. Results from soil chamber measurements indicate that the soil can act as a dominant sink for atmospheric COS.

  7. Autochamber measurements of Net Ecosystem (CO2) Exchange at a subarctic mire in Northern Sweden

    NASA Astrophysics Data System (ADS)

    Walthall, M.; Parker-Smith, X.; Lawrence, R. D.; Crill, P. M.

    2015-12-01

    Northern latitude wetlands (>~50°N) are characterized by cold and wet conditions that result in low decomposition rates for plant litter. This process promotes the sequestration of carbon (C) in the form of organic matter (i.e. peat) and the formation of widespread peatands. Peatlands, particularly in the Northern Hemisphere, have accumulated C by removing atmospheric CO2 for approximately the past 10,000 years. Historically, peatlands represent a net C sink; however, increases in the global average temperature could alter peatlands ability to store carbon. With a warming climate and permafrost thaw, the pool of once stable soil organic C available for decomposition is increasing. Like all terrestrial ecosystems, a number of environmental factors (e.g. peat temperature and vegetation) play important roles in governing the fate of C in peatlands. Projected climate change is expected to affect these regulating factors. Subarctic peatlands in zones of discontinuous permafrost are experiencing widespread environmental changes due to climate warming. In this study, we present net ecosystem (CO2) exchange and δ13C-CO2 data from Stordalen Mire in northern Sweden (68°22'N, 19°03'E). Measurements were made using a quantum cascade laser spectrometer connected to automatic chambers placed in the three predominant ecosystems (a dry, elevated Palsa; an intermediate thaw regime dominated by Sphagnum spp. and; a completely thawed, inundated site dominated by Eriophorum angustifolium). Team was mentored by Mr. Ryan Lawrence from The University of New Hampshire.

  8. Pan-Arctic modelling of net ecosystem exchange of CO2.

    PubMed

    Shaver, G R; Rastetter, E B; Salmon, V; Street, L E; van de Weg, M J; Rocha, A; van Wijk, M T; Williams, M

    2013-08-19

    Net ecosystem exchange (NEE) of C varies greatly among Arctic ecosystems. Here, we show that approximately 75 per cent of this variation can be accounted for in a single regression model that predicts NEE as a function of leaf area index (LAI), air temperature and photosynthetically active radiation (PAR). The model was developed in concert with a survey of the light response of NEE in Arctic and subarctic tundras in Alaska, Greenland, Svalbard and Sweden. Model parametrizations based on data collected in one part of the Arctic can be used to predict NEE in other parts of the Arctic with accuracy similar to that of predictions based on data collected in the same site where NEE is predicted. The principal requirement for the dataset is that it should contain a sufficiently wide range of measurements of NEE at both high and low values of LAI, air temperature and PAR, to properly constrain the estimates of model parameters. Canopy N content can also be substituted for leaf area in predicting NEE, with equal or greater accuracy, but substitution of soil temperature for air temperature does not improve predictions. Overall, the results suggest a remarkable convergence in regulation of NEE in diverse ecosystem types throughout the Arctic.

  9. Growing season ecosystem and leaf-level gas exchange of an exotic and native semiarid bunchgrass

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The extensive spread of the South African grass, Lehmann lovegrass (Eragrostis lehmanniana) may potentially alter ecological and hydrological processes across semiarid grasslands and savannahs of western North America. We compared volumetric soil moisture (Q), ecosystem (i.e. whole-plant and soil) ...

  10. Multivariate Comparative Analysis of Stock Exchanges: The European Perspective

    NASA Astrophysics Data System (ADS)

    Koralun-Bereźnicka, Julia

    The aim of the research is to perform a multivariate comparative analysis of 20 European stock exchanges in order to identify the main similarities between the objects. Due to the convergence process of capital markets in Europe the similarities between stock exchanges could be expected to increase over time. The research is meant to show whether and how these similarities change. Consequently, the distances between clusters of similar stock exchanges should become less significant, which the analysis also aims at verifying. The basis of comparison is a set of 48 monthly variables from the period January, 2003 to December, 2006. The variables are classified into three categories: size of the market, equity trading and bonds. The paper aims at identifying the clusters of alike stock exchanges and at finding the characteristic features of each of the distinguished groups. The obtained categorization to some extent corresponds with the division of the European Union into “new” and “old” member countries. Clustering method, performed for each quarter separately, also reveals that the classification is fairly stable in time. The factor analysis, which was carried out to reduce the number of variables, reveals three major factors behind the data, which are related with the earlier mentioned categories of variables.

  11. Uncertainties in the Net Ecosystem Exchange of Europe and North America

    NASA Astrophysics Data System (ADS)

    Tomelleri, E.; Migliavacca, M.; Carvalhais, N.; Reichstein, M.

    2008-12-01

    Here present a thorough upscaling of carbon balance estimates from eddy covariance flux towers to Europe and North America with an estimate of uncertainties by means of model data integration techniques. Model parameter regionalization approaches aim to spatially discriminate ecosystem properties, embodying the concept that different parameters control different processes hence requiring different extrapolation strategies. In this perspective, the consideration of a multivariate space for model parameter extrapolation strategies should rely on spatially distributed variables, supporting the identification of upscaling regions. This target can be partly achieved by the use of variables derived from remote sensing as model drivers. These act as weights for the flux variability in the upscaling exercise, by adding information about the spatial structure in the land surface exchanges. In this perspective, the quantification of the FLUXNET representativeness and heterogeneity is fundamental to assess the upscaling potential of both model parameters and observed processes. These issues can be better addressed for geographical regions such as Europe or North America where FLUXNET, albeit confined to individual sites, is already gaining pseudo- spatial characteristics. We integrated eddy covariance measurements, partitioned into primary productivity and ecosystem respiration into the parameterization of a primary productivity empirical light-use efficiency model combined with a semi-empirical respiration model. We stratified the measurement sites per ecosystem type and climate classification. For the integration we adopted a Markov Chain Monte Carlo approach, which permitted us to estimate a posteriori joint probability functions of model parameters. These were used for extrapolating uncertainties of the regional carbon budgets for Europe and North America. For doing this, the Markovian Chains of model parameters from each site/year optimization were sub-sampled in such a

  12. The impact of land use on the net ecosystem CO2 exchanges in the West African Sudanian Savannas

    NASA Astrophysics Data System (ADS)

    Mauder, Matthias; Quansah, Emmanuel; Annor, Thompson; Balogun, Ahmed A.; Amekudzi, Leonard K.; Bliefernicht, Jan; Heinzeller, Dominikus; Kunstmann, Harald

    2016-04-01

    The land surface in West Africa has been considerably changed within the past decade due to various anthropogenic measures such as an increased agricultural activity. However, the impact of these land use changes on land-atmosphere exchange processes such as net ecosystems exchange is not well known for this highly vulnerable region. To tackle this problem, the effects of land use on the net ecosystem exchange of CO2 (NEE) along a transect of three contrasting ecosystems have been investigated on seasonal and annual time scales using the Eddy Covariance method. The ecosystems were grassland (GL), a mixture of fallow and cropland (CR) in the Upper East Region of Ghana, and a nature reserve (NR) near Pô in the Nahouri Province of Burkina Faso. The results for January to December 2013 showed that the ecosystems of the three sites served as net sinks of CO2 during the rainy season (May to October) and net sources of CO2 during the dry season (November to April). However, NR was a net sink of CO2 during the wet to dry transition period (November to December). On an annual timescale, only NR served as a net sink of CO2 from the atmosphere into the ecosystem, while the others were net sources of CO2 into the atmosphere. Furthermore, the study revealed that the three contrasting ecosystems responded to environmental and physiological factors based on the ecosystem functional types. This suggests that land use and land use management may play a significant role in the diurnal to annual sequestration and efflux patterns of NEE and its composite fluxes, gross primary production (GPP) and ecosystem respiration (ER), over the West African Sudanian Savannas.

  13. Modeling net ecosystem exchange of carbon dioxide in a beetle-attacked subalpine forest using a data-constrained ecosystem model

    NASA Astrophysics Data System (ADS)

    Peckham, S. D.; Ewers, B. E.; Mackay, D. S.; Frank, J. M.; Massman, W. J.; Ryan, M. G.; Scott, H.; Pendall, E.

    2012-12-01

    The mountain pine and spruce bark beetles and associated blue-stain fungi have caused widespread mortality in the forests of the western U.S. during the past decade, impacting over 1.6 Mha in Northern Colorado and Southeast Wyoming alone. Both the beetles and fungi they carry block tree xylem and eventually cause mortality due to hydraulic failure. Previous studies of bark beetle mortality in Canadian forests have suggested a net loss of carbon following beetle attack. This study aimed to determine if forests in the southern Rocky Mountains showed a similar response. We simulated carbon fluxes over a time period of six years (2005-2010) at the Glacier Lakes Ecosystem Experiment sites (GLEES) Ameriflux site using the Terrestrial Regional Ecosystem Exchange Simulator (TREES) model. This time period included a beetle infestation during the last three years that resulted in mortality of 51% of the spruce trees that accounted for 90% of the spruce basal area. Model estimates of net ecosystem exchange of CO2 (NEE) were compared to eddy-covariance measurements before, during, and after beetle attack. Model predictions of NEE were generated two ways, 1) using the standard set of maintenance respiration coefficients, and 2) constraining modeled respiration using equations derived from field measurements of stem, leaf, and soil respiration at GLEES, and were compared to NEE observations before, during, and after the presence of bark beetles. Model changes included both simple modification of the exponential temperature response curve (Q10) and adding new equations based on both temperature and live tissue nitrogen content. Pre-beetle observed growing season mean NEE averaged -1.49 μmol C m-2 s-1 and simulation means ranged from -4.10 to 0.64 μmol C m-2 s-1. Changing the model's computation of maintenance respiration to incorporate site-specific temperature response (Q10) resulted in an over-prediction of nighttime NEE by up to 100%, but a 10-30% improvement during the day

  14. Can we see the Forest for the Trees? Toward an Ecological/Ecosystem Basis for Remote Sensing of Carbon Exchange.

    NASA Astrophysics Data System (ADS)

    Sims, D. A.; Oechel, W.; Rahman, F.; Gamon, J. A.

    2003-12-01

    Although a top-down approach focusing on the "forest" as a whole would seem to make sense for remote sensing estimates of global vegetation/atmosphere carbon exchange, many current models take a bottom-up, scaling approach that focuses on the "trees". This bias is understandable since most of us, including the authors of this presentation, began our careers studying eco-physiology at the leaf and single plant levels. It may also reflect the scarcity of data relating carbon fluxes to spectral reflectance at sufficiently large scales. This is unfortunate since relationships that are important at small scales are not necessarily the same ones that are most important at larger scales. Although large-scale measurements of carbon flux (from eddy covariance) and reflectance (from satellites) have been available for some time, direct comparisons have been difficult due to mismatches in their temporal and spatial scales. Development of tram systems for measurement of spectral reflectance in the footprints of eddy covariance towers (Specnet) is one approach to providing a better match between these scales. In this presentation we will compare relationships at ecosystem, plant and leaf scales. The degree of correlation between physiological and morphological (canopy structure) characteristics increased with increasing spatial scale. At the leaf and plant level photosynthetic light use efficiency (LUE) is largely independent of vegetation greenness and absorbed photosynthetically active radiation (APAR). However, our measurements at the ecosystem level suggest a strong correlation between LUE and vegetation greenness. Consequently, estimation of LUE as a parameter independent of vegetation greenness may not be as crucial as would be suggested by leaf and individual plant relationships. Although major disturbances temporarily upset the LUE/greenness relationship, we have found that vegetation rapidly re-establishes this equilibrium once the disturbance is removed. Another bias

  15. Comparative assessment of the methods for exchangeable acidity measuring

    NASA Astrophysics Data System (ADS)

    Vanchikova, E. V.; Shamrikova, E. V.; Bespyatykh, N. V.; Zaboeva, G. A.; Bobrova, Yu. I.; Kyz"yurova, E. V.; Grishchenko, N. V.

    2016-05-01

    A comparative assessment of the results of measuring the exchangeable acidity and its components by different methods was performed for the main mineral genetic horizons of texturally-differentiated gleyed and nongleyed soddy-podzolic and gley-podzolic soils of the Komi Republic. It was shown that the contents of all the components of exchangeable soil acidity determined by the Russian method (with potassium chloride solution as extractant, c(KCl) = 1 mol/dm3) were significantly higher than those obtained by the international method (with barium chloride solution as extractant, c(BaCl2) = 0.1 mol/dm3). The error of the estimate of the concentration of H+ ions extracted with barium chloride solution equaled 100%, and this allowed only qualitative description of this component of the soil acidity. In the case of the extraction with potassium chloride, the error of measurements was 50%. It was also shown that the use of potentiometric titration suggested by the Russian method overestimates the results of soil acidity measurement caused by the exchangeable metal ions (Al(III), Fe(III), and Mn(II)) in comparison with the atomic emission method.

  16. 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

  17. Use of micrometeorological techniques to study the isotopic exchange in ecosystems

    NASA Astrophysics Data System (ADS)

    Santos, E.; Wagner-Riddle, C.; Brown, S. E.; Stropes, K.

    2015-12-01

    The combination of micrometeorological techniques with high frequency concentration measurements of stable isotopes are a powerful tool to study the temporal dynamics of isotope signatures at the ecosystem level. The objective of this study was to study the isotopic composition of the net CO2 exchange (NEE) above and with corn and tall grass canopies. Profiles of stable isotopes of CO2 (12C-CO2, 13C-CO2 and 18O-CO2) were measured using tunable diode laser trace gas analyzers and multiport sampling systems in corn (12C-CO2 and 13C-CO2, only) and tall grass canopies. These measurements were combined with the flux gradient method and Lagrangian dispersion analysis to estimate the isotopic signatures of the net CO2 flux. The use of a gradient of a concentration threshold to screen half hourly period improved the estimates of flux signatures by the isotope flux ratio approach. The Langrangian dispersion analysis and the isotope flux ratio method estimates showed good agreement above the corn canopy, indicating that the former method can be a viable alternative to study the isotopic exchange within plant canopies. The 13CO2 composition of NEE showed a downward trend near the end of the growing season, which may be related to a reduction of autotrophic respiration in the soil.

  18. Measurement-based upscaling of Pan Arctic Net Ecosystem Exchange: the PANEEx project

    NASA Astrophysics Data System (ADS)

    Njuabe Mbufong, Herbert; Kusbach, Antonin; Lund, Magnus; Persson, Andreas; Christensen, Torben R.; Tamstorf, Mikkel P.; Connolly, John

    2016-04-01

    The high variability in Arctic tundra net ecosystem exchange (NEE) of carbon (C) can be attributed to the high spatial heterogeneity of Arctic tundra due to the complex topography. Current models of C exchange handle the Arctic as either a single or few ecosystems, responding to environmental change in the same manner. In this study, we developed and tested a simple pan Arctic NEE (PANEEx) model using the Misterlich light response curve (LRC) function with photosynthetic photon flux density (PPFD) as the main driving variable. Model calibration was carried out with eddy covariance carbon dioxide (CO2) data from 12 Arctic tundra sites. The model input parameters (Fcsat, Rd and α) were estimated as a function of air temperature (AirT) and leaf area index (LAI) and represent specific characteristics of the NEE-PPFD relationship, including the saturation flux, dark respiration and initial light use efficiency, respectively. LAI and air temperature were respectively estimated from empirical relationships with remotely sensed normalized difference vegetation index (NDVI) and land surface temperature (LST). These are available as MODIS Terra product MOD13Q1 and MOD11A1 respectively. Therefore, no specific knowledge of the vegetation type is required. The PANEEx model captures the spatial heterogeneity of the Arctic tundra and was effective in simulating 77% of the measured fluxes (r2 = 0.72, p < 0.001) at the 12 sites used in the calibration of the model. Further, the model effectively estimates NEE in three disparate Alaskan ecosystems (heath, tussock and fen) with an estimation ranging between 10 - 36% of the measured fluxes. We suggest that the poor agreement between the measured and modeled NEE may result from the disparity between ground-based measured LAI (used in model calibration) and remotely sensed LAI (estimated from NDVI and used in NEE estimation). Moreover, our results suggests that using simple linear regressions may be inadequate as parameters estimated

  19. Biophysical drivers of net ecosystem exchange in shrublands of the northern Chihuahuan Desert

    NASA Astrophysics Data System (ADS)

    Jaimes, A.; Laney, C.; Tweedie, C. E.

    2013-12-01

    In the northern Chihuahuan Desert, large areas of southern New Mexico that were formerly dominated by perennial grasses, including black grama (Bouteloua eriopa) and mesa dropseed (Sporobolus flexus) have been replaced by desert shrubland species, in particular creosote bush (Larrea tridentata) and honey mesquite (Prosopis glandulosa). Recent studies suggest that these changes in land cover have the ability to modify near surface microclimate such as soil water holding capacity, albedo, carbon dioxide sequestration, and increases in local air temperature, respiration, sensible heat and evapotranspiration. Despite the recognized importance of the consequences of land cover change in the ecosystem, the rates and tipping points at which these changes occur are not well understood. This knowledge is key to improve predictions in regional and global models, as the region is expected to go through an imminent transition from warm to warmer climate in this century. This study analyze three years of data (2010-2012) from our multi sensor platform situated on the USDA ARS Jornada Experimental Range (JER), about 25 km northeast of Las Cruces, New Mexico, USA. A robust data set that combines high frequency micrometeorological data, plot phenology estimates and spectral indices was used. A combination of statistical analyses based on clustering methods (self-organizing maps) and simple nonparametric regression techniques (regression trees) were used to identify factors controlling fluxes and likely biophysical thresholds and tipping points indicative of different functional system states. Both analyses were implemented through the use of Neural Network Toolbox and Statistics toolbox within MATLAB 7.0. During the period of study the shrubland acted as a carbon sink ranging between -105 to -134 gCO2 m-2 y-1. The largest variation between years in the annual estimated fluxes was the slight decrease of total annual net ecosystem exchange during 2011 (-105 g m-2 s-1) in comparison

  20. Simultaneous reproduction of global carbon exchange and storage of terrestrial forest ecosystems

    NASA Astrophysics Data System (ADS)

    Kondo, M.; Ichii, K.

    2012-12-01

    Understanding the mechanism of the terrestrial carbon cycle is essential for assessing the impact of climate change. Quantification of both carbon exchange and storage is the key to the understanding, but it often associates with difficulties due to complex entanglement of environmental and physiological factors. Terrestrial ecosystem models have been the major tools to assess the terrestrial carbon budget for decades. Because of its strong association with climate change, carbon exchange has been more rigorously investigated by the terrestrial biosphere modeling community. Seeming success of model based assessment of carbon budge often accompanies with the ill effect, substantial misrepresentation of storage. In practice, a number of model based analyses have paid attention solely on terrestrial carbon fluxes and often neglected carbon storage such as forest biomass. Thus, resulting model parameters are inevitably oriented to carbon fluxes. This approach is insufficient to fully reduce uncertainties about future terrestrial carbon cycles and climate change because it does not take into account the role of biomass, which is equivalently important as carbon fluxes in the system of carbon cycle. To overcome this issue, a robust methodology for improving the global assessment of both carbon budget and storage is needed. One potentially effective approach to identify a suitable balance of carbon allocation proportions for each individual ecosystem. Carbon allocations can influence the plant growth by controlling the amount of investment acquired from photosynthesis, as well as carbon fluxes by controlling the carbon content of leaves and litter, both are active media for photosynthesis and decomposition. Considering those aspects, there may exist the suitable balance of allocation proportions enabling the simultaneous reproduction of carbon budget and storage. The present study explored the existence of such suitable balances of allocation proportions, and examines the

  1. Contrasting the patterns of aspen forest and sagebrush shrubland gross ecosystem exchange in montane Idaho, USA

    NASA Astrophysics Data System (ADS)

    Fellows, A.; Flerchinger, G. N.; Seyfried, M. S.

    2015-12-01

    We investigated the environmental controls on Gross Ecosystem Exchange (GEE) at an aspen forest and a sagebrush shrubland in southwest Idaho. The two sites were situated within a mosaic of vegetation that included temperate deciduous trees, shrublands, and evergreen conifer trees. The distribution of vegetation was presumably linked to water availability; aspen were located in wetter high-elevations sites, topographic drainages, or near snow drifts. Local temperatures have increased by ~2-3 °C over the past 50 years and less precipitation has arrived as snow. These ongoing changes in weather may impact snow water redistribution, plant-water availability, and plant-thermal stress, with associated impacts on vegetation health and production. We used eddy covariance to measure the exchange of water and carbon dioxide above the two sites and partitioned the net carbon flux to determine GEE. The sagebrush record was from 2003-2007 and the aspen record was from 2007-12. The region experienced a modest-to-severe drought in 2007, with ~73% of typical precipitation. We found that aspen were local "hotspots" for carbon exchange; peak rates of aspen GEE were ~ 60% greater than the peak rates of sagebrush GEE. Light, temperature, and water availability were dominant controls on the seasonality of GEE at both sites. Sagebrush and aspen were dormant during winter, limited by cold temperatures during winter and early spring, and water availability during mid-late summer. The onset of summer drought was typically later in the aspen than in the sagebrush. Drifting snow, lateral water redistribution, or increased rooting depths may have increased water availability in the aspen stand. Seasonal patterns of observed soil moisture and evaporation indicated aspen were rooted to >= 1 m. The sagebrush and aspen both responded strongly to the 2007 drought; peak GEE decreased by ~75%, peak GEE shifted to earlier parts of the year, and mid-summer GEE was decreased. We consider potential

  2. Precipitation regulates the response of net ecosystem CO2 exchange to environmental variation on U.S. rangelands

    Technology Transfer Automated Retrieval System (TEKTRAN)

    For virtually all terrestrial ecosystems, the balance between photosynthetic uptake of carbon dioxide (CO2) and CO2 loss to respiration varies among years in response to inter-annual variation in climate. Variability in CO2 exchange results from inter-annual differences in (1) climatic variables at ...

  3. ELEVATED CO2 AND TEMPERATURE ALTER THE ECOSYSTEM C EXCHANGE IN A YOUNG DOUGLAS FIR MESOCOSM EXPERIMENT

    EPA Science Inventory

    We investigated the effects of elevated CO2 (EC) [ambient CO2 (AC) + 190 ppm] and elevated temperature (ET) [ambient temperature (AT) + 3.6 °C] on net ecosystem exchange (NEE) of seedling Douglas fir (Pseudotsuga menziesii) mesocosms. As the study utilized seedlings in reconstruc...

  4. Invasive C4 Perennial Grass Alters Net Ecosystem Exchange in Mixed C3/C4 Savanna Grassland

    NASA Astrophysics Data System (ADS)

    Basham, T. S.; Litvak, M.

    2006-12-01

    The invasion of ecosystems by non-native plants that differ from native plants in physiological characteristics and phenology has the potential to alter ecosystem function. In Texas and other regions of the southern central plains of the United States, the introduced C4 perennial grass, Bothriochloa ischaemum, invades C3/C4 mixed grasslands and savannas, resulting in decreased plant community diversity (Gabbard 2003; Harmoney et al 2004). The objective of this study was to quantify how the conversion of these mixed grass communities to C4 dominated, B. ischaemum monocultures impacts carbon cycling and sequestration. Seasonal measurements of Net Ecosystem Exchange (NEE) of CO2, leaf level gas exchange and soil respiration were compared between savanna grassland plots composed of either naturally occurring B. ischaemum monocultures or native mixed grasses (n=16). NEE was measured using a closed system chamber that attached to permanently installed stainless steel bases. Temperature, soil moisture, aerial percent species cover and leaf area index were also monitored in plots to explain variability in measured responses. Results showed that NEE differed seasonally between invaded and native plots due to 1) greater leaf surface area per unit ground area in invaded plots, 2) differences in phenological patterns of plant activity and 3) differences in responses to water limitation between invaded and native plots. Cold season and summer drought NEE were driven primarily by belowground respiration in both plot types, however spring uptake activity commenced two months later in invaded plots. This later start in invaded plots was compensated for by greater uptake throughout the growing season and in particular during the drier summer months. Differences in NEE between plot types were not due to differences in soil respiration nor were they due to greater leaf level photosynthetic capabilities of B. ischaemum relative to the dominant native grasses. NEE, soil respiration and

  5. Effects of grazing on ecosystem CO₂ exchange in a meadow grassland on the Tibetan Plateau during the growing season.

    PubMed

    Chen, Ji; Shi, Weiyu; Cao, Junji

    2015-02-01

    Effects of human activity on ecosystem carbon fluxes (e.g., net ecosystem exchange (NEE), ecosystem respiration (R(eco)), and gross ecosystem exchange (GEE)) are crucial for projecting future uptake of CO2 in terrestrial ecosystems. However, how ecosystem that carbon fluxes respond to grazing exclusion is still under debate. In this study, a field experiment was conducted to study the effects of grazing exclusion on R(eco), NEE, and GEE with three treatments (free-range grazing (FG) and grazing exclusion for 3 and 5 years (GE3 and GE5, respectively)) in a meadow grassland on the Tibetan Plateau. Our results show that grazing exclusion significantly increased NEE by 47.37 and 15.84%, and R eco by 33.14 and 4.29% under GE3 and GE5 plots, respectively, although carbon sinks occurred in all plots during the growing season, with values of 192.11, 283.12, and 222.54 g C m(-2) for FG, GE3, and GE5, respectively. Interestingly, grazing exclusion increased temperature sensitivity (Q10) of R eco with larger increases at the beginning and end of growing season (i.e., May and October, respectively). Soil temperature and soil moisture were key factors on controlling the diurnal and seasonal variations of R(eco), NEE, and GEE, with soil temperature having a stronger influence. Therefore, the combined effects of grazing and temperature suggest that grazing should be taken into consideration in assessing global warming effects on grassland ecosystem CO2 exchange.

  6. Surface-Water Exchanges for Streams Entering Lakes Compared with Shoreline Exchanges in General

    NASA Astrophysics Data System (ADS)

    Naranjo, R. C.; Allander, K.; Neilson, B. T.; Niswonger, R. G.; Constantz, J. E.

    2013-12-01

    Streamflow and thermal patterns suggest that stream/streambed exchanges are more dynamic than lake/sediment exchanges along the nearby shoreline. A synoptic field program was carried out in September 2012 for Lake Tahoe NV, when baseflow is dominant and diurnal temperature patterns are large as alpine night temperatures cool tributary waters to well below lake water temperatures. Two streams with significant adjoining lakeshores were chosen for thermal and hydraulic instrumentation, with continuous logging and periodic water quality sampling. Due to partial channelization, Incline Creek flows and discharges nearly perpendicular to the shoreline on the lake's north shore, while in a natural setting Marlette Creek forms a summer barrier sandbar at its mouth on the lake's eastern shore. A suite of measurements were gathered, including continuous surface and subsurface water levels and temperatures, as well as periodic samples of nutrients and field parameters. For Incline Creek, the thermal and hydraulic patterns were monitored 1.3 m upstream of the mouth, across the mouth of the stream, and 1.3 m into the lake. These data were compared with data collected at equivalent locations along the shoreline away from the stream. Initial results reveal considerably more dynamic spatial and temporal patterns of exchange associated with the stream. For Marlette Creek, a barrier sandbar forms and spreads across the mouth as baseflow recession extends to the fall, and by September streamflow only directly reaches the lake during predawn hours when evapotranspiration is at a minimum. During September 2012, there was ponding behind the barrier sandbar resulting in stream-originated groundwater rapidly flowing through the sandbar, with high dissolved oxygen gradients approaching the lake. As a result of these synoptic results, a more extensive monitoring program was developed for September 2013, with additional instrumentation including automated seepage meters and infrared imaging

  7. Disentangling leaf area and environmental effects on the response of the net ecosystem CO2 exchange to diffuse radiation

    PubMed Central

    Wohlfahrt, Georg; Hammerle, Albin; Haslwanter, Alois; Bahn, Michael; Tappeiner, Ulrike; Cernusca, Alexander

    2013-01-01

    There is an ongoing discussion about why the net ecosystem CO2 exchange (NEE) of some ecosystems is less sensitive to diffuse radiation than others and about the role other environmental factors play in determining the response of NEE to diffuse radiation. Using a six-year data set from a temperate mountain grassland in Austria we show that differences between ecosystems may be reconciled based on their green area index (GAI; square meter green plant area per square meter ground area) - the sensitivity to diffuse radiation increasing with GAI. Our data suggest diffuse radiation to have a negligible influence on NEE below a GAI of 2 m2 m−2. Changes in air/soil temperature and air humidity concurrent with the fraction of diffuse radiation were found to amplify the sensitivity of the investigated temperate mountain grassland ecosystem to diffuse radiation. PMID:24347740

  8. Plant carbon-nutrient interactions control CO{sub 2} exchange in Alaskan wet sedge tundra ecosystems

    SciTech Connect

    Johnson, L.C.; Shaver, G.R.; Cades, D.H.; Rastetter, E.; Nadelhoffer, K.; Giblin, A.; Laundre, J.; Stanley, A.

    2000-02-01

    The authors explored the long-term (8-yr) effects of separate field manipulations of temperature and nutrient availability on carbon balance in wet sedge tundra near the Arctic Long Term Ecological Research (LTER) site at Toolik Lake, Alaska. Their goals were (1) to assess the relative importance of chronic warming (with field greenhouses) and increased N and P availability (by fertilization) in controlling gross ecosystem photosynthesis, ecosystem respiration, and ultimately ecosystem C balance; and (2) to attempt to partition ecosystem responses to these treatments between plant and soil contributions. The authors present results of the effects of these manipulations on whole-system CO{sub 2} exchange over seasonal and duel cycles, and on nonrhizosphere soil microbial respiration using in situ soil incubations.

  9. Inter-annual variability in Alaskan net ecosystem CO2 exchange

    NASA Astrophysics Data System (ADS)

    Luus, Kristina; Lindaas, Jakob; Commane, Roisin; Euskirchen, Eugenie; Oechel, Walter; Zona, Donatella; Chang, Rachel; Kelly, Richard; Miller, Charles; Wofsy, Steven; Lin, John

    2015-04-01

    The high-latitude biospheric carbon cycle's responses to climate change are predicted to have an important role in determining future atmospheric concentrations of CO2. In response to warming soil and air temperatures, Arctic wetlands have been observed to increase rates of both soil C efflux and vegetation C uptake through photosynthesis. However, insights into the regional-scale consequences of these processes for net C uptake have been limited by the large uncertainties existing in process-based model estimates of Arctic net ecosystem CO2 exchange (NEE). The Polar Vegetation Photosynthesis and Respiration Model (PolarVPRM) instead provides data-driven, satellite-based estimates of high-latitude NEE, using a framework which specifically accounts for polar influences on NEE. PolarVPRM calculates NEE as the sum of respiration (R) and gross ecosystem exchange (GEE), where GEE refers to the light-dependent portion of NEE: NEE= -GEE + R. Meteorological inputs for PolarVPRM are provided by the North American Regional Reanalysis (NARR), and land surface inputs are acquired from the Moderate Resolution Imaging Spectroradiometer (MODIS). Growing season R is calculated from air temperature, and subnivean R is calculated according to soil temperature. GEE is calculated according to shortwave radiation, air temperature, and MODIS-derived estimates of soil moisture and vegetation biomass. Previously, model validation has indicated that PolarVPRM showed reasonably good agreement with eddy covariance observations at nine North American Arctic sites, of which three were used for calibration purposes. For this project, PolarVPRM NEE was calculated year-round across Alaska at a three-hourly temporal resolution and a spatial resolution of 1 6°×1 4° (latitude × longitude). The objective of this work was to gain insight into inter-annual variability in Alaskan NEE, R and GEE, and an understanding of which meteorological and land surface drivers account for these observed patterns

  10. Land use affects the net ecosystem CO(2) exchange and its components in mountain grasslands.

    PubMed

    Schmitt, M; Bahn, M; Wohlfahrt, G; Tappeiner, U; Cernusca, A

    2010-08-01

    Changes in land use and management have been strongly affecting mountain grassland, however, their effects on the net ecosystem exchange of CO(2) (NEE) and its components have not yet been well documented. We analysed chamber-based estimates of NEE, gross primary productivity (GPP), ecosystem respiration (R) and light use efficiency (LUE) of six mountain grasslands differing in land use and management, and thus site fertility, for the growing seasons of 2002 to 2008. The main findings of the study are that: (1) land use and management affected seasonal NEE, GPP and R, which all decreased from managed to unmanaged grasslands; (2) these changes were explained by differences in leaf area index (LAI), biomass and leaf-area-independent changes that were likely related to photosynthetic physiology; (3) diurnal variations of NEE were primarily controlled by photosynthetically active photon flux density and soil and air temperature; seasonal variations were associated with changes in LAI; (4) parameters of light response curves were generally closely related to each other, and the ratio of R at a reference temperature/ maximum GPP was nearly constant across the sites; (5) similarly to our study, maximum GPP and R for other grasslands on the globe decreased with decreasing land use intensity, while their ratio remained remarkably constant. We conclude that decreasing intensity of management and, in particular, abandonment of mountain grassland lead to a decrease in NEE and its component processes. While GPP and R are generally closely coupled during most of the growing season, GPP is more immediately and strongly affected by land management (mowing, grazing) and season. This suggests that management and growing season length, as well as their possible future changes, may play an important role for the annual C balance of mountain grassland.

  11. Characteristics of net CO2 exchange during the growing season over the alpine steppe ecosystem on the Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Zhu, Zhikun; Ma, Yaoming; Li, Maoshan; Han, Cunbo; Chao, Xu; Meng, Chunchun

    2013-04-01

    Based on open-path eddy covariance measurement data of the alpine steppe ecosystem at Nam Co Monitoring and Research Station for Multisphere Interactions, CAS (NAMORS) from May to September in 2008 and 2009, the characteristics of the NEE (net ecosystem exchange) for the two growing seasons was analyzed. The average temperature was 7.5° and 9.1° in this two summer, respectively. And the total precipitation from May to September was 493.1 mm and 327 mm in 2008 and 2009, respectively. The rainy season arrived later in 2009. Especially in the early period of the growing season (May to July), the precipitation (129mm) was only half of that in 2008 (261mm). So compared with the 2008, there was a warm and dry growing season in 2009. The results showed that: (1) The CO2 concentration was low during daytime but high in nighttime in both growing season. It had an inverse correlation between VPD (vapor pressure deficit). The mean value in 2008 was 365.4 mg•m-3 and lower than that in 2009 (375.7 mg•m-3 ). (2) The NEE had diurnal variation. During daytime (08:00~19:00), alpine steppe uptakes CO2, but net CO2 emission occured in the nighttime (20:00~23:00, 00:00~08:00 ) for both growing season. The monthly mean NEE was 1.49, 3.09 and 2.7 g CO2 m-2 day-1 from June to August in 2008, while 0.94, 1.2 and 2.82 g CO2 m-2 day-1 in 2009, respectively . (3) The ecosystem respiration was influenced significantly by the soil moisture and soil temperature. When the alpine steppe ecosystem did not threaten by water, it had lower Q10 (the monthly mean Q10 was 2.06 in July and August in2008), but higher Q10 (3.88 in July 2009) when drought stress happened.

  12. Ecosystem CO2 exchange during the snow-covered season in a boreal peatland, Sweden

    NASA Astrophysics Data System (ADS)

    Zhao, Junbin; Peichl, Matthias; Nilsson, Mats

    2014-05-01

    In high latitude areas, ecosystem CO2 emission in the snow-covered season (SCS) is a crucial part of annual carbon budget, which may account for 33-90% of the summer uptake. As snow pack development is sensitive to the warming climate, the change of CO2 flux in SCS is widely concerned, which, however, is still poorly understood. We used the 12-year CO2 exchange data (2001-2012) from an eddy covariance system in a minerogenic mire in Sweden, where the snow-covered season lasts for about 6 months in a year, to evaluate inter-annual change of CO2 flux in SCS and explore the underlying environmental controllers. Sum of net ecosystem CO2 exchange (NEE) in SCS varied from 8.19 to 32.13 gC m-2 (CO2 release), which accounted for 11-41% of the net CO2 uptake during non-snow-covered period of each year. Over the studied years, the NEE during SCS performed a trend of decline (-1.58 gC m-2 year-1), which was attributed to the decreased daily NEE rather than the variation in the duration of SCS. However, we found no single environmental factor that was responsible for the trend. Over the whole SCS, snow depth did not show direct impact on the day-to-day variation of NEE but acted as an important role in insulating the environment below snow pack from the atmosphere. Daily NEE during the period with a deep snow cover (i.e. snow depth >30cm) was relatively lower and was not affected by air or soil temperature. In contrast, the period with a shallow snow cover (i.e. snow depth < 30cm), which was usually shorter, emitted more CO2 and the NEE was influenced by both air and soil temperatures as well as photosynthetically active radiation. At the end of SCS, snow melt usually lasted for about a month and during this period, NEE was jointly driven by air temperature and photosynthetically active radiation. Given a trend of CO2 emission decline in SCS over 2001-2012 and the influence of temperature on day-to-day NEE variation, our results suggest that winter time CO2 flux is an

  13. 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

  14. Comparing two tools for ecosystem service assessments regarding water resources decisions.

    PubMed

    Dennedy-Frank, P James; Muenich, Rebecca Logsdon; Chaubey, Indrajeet; Ziv, Guy

    2016-07-15

    We present a comparison of two ecohydrologic models commonly used for planning land management to assess the production of hydrologic ecosystem services: the Soil and Water Assessment Tool (SWAT) and the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) annual water yield model. We compare these two models at two distinct sites in the US: the Wildcat Creek Watershed in Indiana and the Upper Upatoi Creek Watershed in Georgia. The InVEST and SWAT models provide similar estimates of the spatial distribution of water yield in Wildcat Creek, but very different estimates of the spatial distribution of water yield in Upper Upatoi Creek. The InVEST model may do a poor job estimating the spatial distribution of water yield in the Upper Upatoi Creek Watershed because baseflow provides a significant portion of the site's total water yield, which means that storage dynamics which are not modeled by InVEST may be important. We also compare the ability of these two models, as well as one newly developed set of ecosystem service indices, to deliver useful guidance for land management decisions focused on providing hydrologic ecosystem services in three particular decision contexts: environmental flow ecosystem services, ecosystem services for potable water supply, and ecosystem services for rainfed irrigation. We present a simple framework for selecting models or indices to evaluate hydrologic ecosystem services as a way to formalize where models deliver useful guidance.

  15. Comparing soil biogeochemical processes in novel and natural boreal forest ecosystems

    NASA Astrophysics Data System (ADS)

    Quideau, S. A.; Swallow, M. J. B.; Prescott, C. E.; Grayston, S. J.; Oh, S.-W.

    2013-08-01

    Emulating the variability that exists in the natural landscape prior to disturbance should be a goal of soil reconstruction and land reclamation efforts following resource extraction. Long-term ecosystem sustainability within reclaimed landscapes can only be achieved with the re-establishment of biogeochemical processes between reconstructed soils and plants. In this study, we assessed key soil biogeochemical attributes (nutrient availability, organic matter composition, and microbial communities) in reconstructed, novel, anthropogenic ecosystems, covering different reclamation treatments following open-cast mining for oil extraction. We compared the attributes to those present in a range of natural soils representative of mature boreal forest ecosystems in the same area of Northern Alberta. Soil nutrient availability was determined in situ with resin probes, organic matter composition was described with 13C nuclear magnetic resonance spectroscopy and soil microbial community structure was characterized using phospholipid fatty acid analysis. Significant differences among natural ecosystems were apparent in nutrient availability and seemed more related to the dominant tree cover than to soil type. When analyzed together, all natural forests differed significantly from the novel ecosystems, in particular with respect to soil organic matter composition. However, there was some overlap between the reconstructed soils and some of the natural ecosystems in nutrient availability and microbial communities, but not in organic matter characteristics. Hence, our results illustrate the importance of considering the range of natural landscape variability and including several soil biogeochemical attributes when comparing novel, anthropogenic ecosystems to the mature ecosystems that constitute ecological targets.

  16. Comparing soil biogeochemical processes in novel and natural boreal forest ecosystems

    NASA Astrophysics Data System (ADS)

    Quideau, S. A.; Swallow, M. J. B.; Prescott, C. E.; Grayston, S. J.; Oh, S.-W.

    2013-04-01

    Emulating the variability that exists in the natural landscape prior to disturbance should be a goal of soil reconstruction and land reclamation efforts following resource extraction. Long-term ecosystem sustainability within reclaimed landscapes can only be achieved with the re-establishment of biogeochemical processes between reconstructed soils and plants. In this study, we assessed key soil biogeochemical attributes (nutrient availability, organic matter composition, and microbial communities) in reconstructed, novel, anthropogenic ecosystems covering different reclamation treatments following open-cast mining for oil extraction. We compared the attributes to those present in a range of natural soils representative of mature boreal forest ecosystems in the same area of northern Alberta. Soil nutrient availability was determined in situ with resin probes, organic matter composition was described with 13C nuclear magnetic resonance spectroscopy and soil microbial community structure was characterized using phospholipid fatty acid analysis. Significant differences among natural ecosystems were apparent in nutrient availability and seemed more related to the dominant tree cover than to soil type. When analyzed together, all natural forests differed significantly from the novel ecosystems, in particular with respect to soil organic matter composition. However, there was some overlap between the reconstructed soils and some of the natural ecosystems in nutrient availability and microbial communities, but not in organic matter characteristics. Hence, our results illustrate the importance of considering the range of natural landscape variability, and including several soil biogeochemical attributes when comparing novel, anthropogenic ecosystems to the mature ecosystems that constitute ecological targets.

  17. H2O and CO2 exchange between a sphagnum mire ecosystem and the atmosphere

    NASA Astrophysics Data System (ADS)

    Olchev, Alexander; Volkova, Elena; Karataeva, Tatiana; Novenko, Elena

    2013-04-01

    part of the mire in June and reached 6.8+-4.2 mkmol m-2 s-1. In July the net CO2 flux is lower and doesn't not exceed -4.2 +- 2.8 mkmol m-2 s-1. Maximal values of H2O flux (0.23 +- 0.10 mm hour-1) was observed in August in central part of the mire. Do describe the spatial pattern of the H2O and CO2 exchange within the mire ecosystem a three dimensional model 3D Forbog-3D was applied. The model operates with the horizontal grid resolution - 2 m x 2 m, vertical resolution - 1 m, and primary time step - 1 hour. Forbog-3D uses data about position of each individual tree around the mire, mean height, crown and stem diameters of the trees to simulate patterns of plant and leaf area densities of a forest stand. The model algorithm describing solar radiation transfer through a forest canopy considers direct and diffuse radiation penetrating through gaps in the canopy, transmitted by leaves and reflected from leaves, bark and soil surface. It uses information about the 3D structure of each tree species in the forest stand, and about the optical properties of their leaves and bark. It takes into account clumping and gapping of foliage, spatial variations in leaf orientation angles and site topography. The study was supported by grants 11-04-97538-r_center_a, 11-04-01622-a and 11-05-00557-a of the Russian Foundation of the Basic Research (RFBR) and the grant of the government of Russian Federation (11.G34.31.0079).

  18. Are BVOC exchanges in agricultural ecosystems overestimated? Insights from fluxes measured in a maize field over a whole growing season

    NASA Astrophysics Data System (ADS)

    Bachy, Aurélie; Aubinet, Marc; Schoon, Niels; Amelynck, Crist; Bodson, Bernard; Moureaux, Christine; Heinesch, Bernard

    2016-04-01

    Although maize is the second most important crop worldwide, and the most important C4 crop, no study on biogenic volatile organic compounds (BVOCs) has yet been conducted on this crop at ecosystem scale and over a whole growing season. This has led to large uncertainties in cropland BVOC emission estimations. This paper seeks to fill this gap by presenting, for the first time, BVOC fluxes measured in a maize field at ecosystem scale (using the disjunct eddy covariance by mass scanning technique) over a whole growing season in Belgium. The maize field emitted mainly methanol, although exchanges were bi-directional. The second most exchanged compound was acetic acid, which was taken up mainly in the growing season. Bi-directional exchanges of acetaldehyde, acetone and other oxygenated VOCs also occurred, whereas the terpenes, benzene and toluene exchanges were small, albeit significant. Surprisingly, BVOC exchanges were of the same order of magnitude on bare soil and on well developed vegetation, suggesting that soil is a major BVOC reservoir in agricultural ecosystems. Quantitatively, the maize BVOC emissions observed were lower than those reported in other maize, crops and grasses studies. The standard emission factors (SEFs) estimated in this study (231 ± 19 µg m-2 h-1 for methanol, 8 ± 5 µg m-2 h-1 for isoprene and 4 ± 6 µg m-2 h-1 for monoterpenes) were also much lower than those currently used by models for C4 crops, particularly for terpenes. These results suggest that maize fields are small BVOC exchangers in north-western Europe, with a lower BVOC emission impact than that modelled for growing C4 crops in this part of the world. They also reveal the high variability in BVOC exchanges across world regions for maize and suggest that SEFs should be estimated for each region separately.

  19. The Consequences of a Two Water Source Ecosystem on the Surface Carbon and Water Exchange in a Semiarid Riparian Woodland

    NASA Astrophysics Data System (ADS)

    Scott, R. L.; Watts, C.; Goodrich, D.; Martens, D.; Hultine, K.; Yepez Gonzalez, E.; Huxman, T.; Lin, G.

    2002-12-01

    A multi-year, multidisciplinary study was conducted to improve our understanding of the carbon and water exchange from a dominant, riparian mesquite (Prosopis velutina) ecosystem. Accordingly, we have used a variety of measurements including above and below-canopy eddy covariance, sap flow, soil/plant respiration, stable isotopes, soil moisture, and water table height to monitor key ecosystem processes and forcing. Groundwater table fluctuations and tree functioning (phenology, carbon uptake, transpiration) were well correlated suggesting that the trees rely principally on this 11 m deep, stable water source. The functioning of the understory plants and soil microbes, however, were dependent on recent precipitation. This bifurcation of water sources between overstory and understory resulted in interesting and unusual ecosystem fluxes. The tree water use was nearly constant before and after the arrival of the summer monsoon whereas the understory functioning changed dramatically. The apparent increase in total ecosystem photosynthesis during the rainy season, however, did not lead to a rise in net ecosystem carbon exchange. Rather, the net uptake of carbon decreased due to the substantial increase in respiration, which was fueled by precipitation, warm nighttime temperatures and an abundant source of deposited tree litter.

  20. Hydraulic redistribution of soil water by roots affects whole-stand evapotranspiration and net ecosystem carbon exchange.

    PubMed

    Domec, Jean-Christophe; King, John S; Noormets, Asko; Treasure, Emrys; Gavazzi, Michael J; Sun, Ge; McNulty, Steven G

    2010-07-01

    *Hydraulic redistribution (HR) of water via roots from moist to drier portions of the soil occurs in many ecosystems, potentially influencing both water use and carbon assimilation. *By measuring soil water content, sap flow and eddy covariance, we investigated the temporal variability of HR in a loblolly pine (Pinus taeda) plantation during months of normal and below-normal precipitation, and examined its effects on tree transpiration, ecosystem water use and carbon exchange. *The occurrence of HR was explained by courses of reverse flow through roots. As the drought progressed, HR maintained soil moisture above 0.15 cm(3) cm(-3) and increased transpiration by 30-50%. HR accounted for 15-25% of measured total site water depletion seasonally, peaking at 1.05 mm d(-1). The understory species depended on water redistributed by the deep-rooted overstory pine trees for their early summer water supply. Modeling carbon flux showed that in the absence of HR, gross ecosystem productivity and net ecosystem exchange could be reduced by 750 and 400 g C m(-2) yr(-1), respectively. *Hydraulic redistribution mitigated the effects of soil drying on understory and stand evapotranspiration and had important implications for net primary productivity by maintaining this whole ecosystem as a carbon sink.

  1. Promoting Value for Consumers: Comparing Individual Health Insurance Markets Inside and Outside the ACA's Exchanges.

    PubMed

    McCue, Michael J; Hall, Mark A

    2016-06-01

    The new health insurance exchanges are the core of the Affordable Care Act's (ACA) insurance reforms, but insurance markets beyond the exchanges also are affected by the reforms. This issue brief compares the markets for individual coverage on and off of the exchanges, using insurers' most recent projections for ACA-compliant policies. In 2016, insurers expect that less than one-fifth of ACA-compliant coverage will be sold outside of the exchanges. Insurers that sell mostly through exchanges devote a greater portion of their premium dollars to medical care than do insurers selling only off of the exchanges, because exchange insurers project lower administrative costs and lower profit margins. Premium increases on exchange plans are less than those for off-exchange plans, in large part because exchange enrollment is projected to shift to closed-network plans. Finally, initial concerns that insurers might seek to segregate higher-risk subscribers on the exchanges have not been realized.

  2. The Oncor Geodatabase for the Columbia Estuary Ecosystem Restoration Program: Handbook of Data Reduction Procedures, Workbooks, and Exchange Templates

    SciTech Connect

    Sather, Nichole K.; Borde, Amy B.; Diefenderfer, Heida L.; Serkowski, John A.; Coleman, Andre M.; Johnson, Gary E.

    2013-12-31

    This Handbook of Data Reduction Procedures, Workbooks, and Exchange Templates is designed to support the Oncor geodatabase for the Columbia Estuary Ecosystem Restoration Program (CEERP). The following data categories are covered: water-surface elevation and temperature, sediment accretion rate, photo points, herbaceous wetland vegetation cover, tree plots and site summaries, fish catch and density, fish size, fish diet, fish prey, and Chinook salmon genetic stock identification. The handbook is intended for use by scientists collecting monitoring and research data for the CEERP. The ultimate goal of Oncor is to provide quality, easily accessible, geospatial data for synthesis and evaluation of the collective performance of CEERP ecosystem restoration actions at a program scale.

  3. 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...

  4. Long-term impacts of peatland restoration on the net ecosystem exchange (NEE) of blanket bogs in Northern Scotland.

    NASA Astrophysics Data System (ADS)

    Hambley, Graham; Hill, Timothy; Saunders, Matthew; Arn Teh, Yit

    2016-04-01

    Unmanaged peatlands represent an important long-term C sink and thus play an important part of the global C cycle. Despite covering only 12 % of the UK land area, peatlands are estimated to store approximately 20 times more carbon than the UK's forests, which cover 13% of the land area. The Flow Country of Northern Scotland is the largest area of contiguous blanket bog in the UK, and one of the biggest in Europe, covering an area in excess of 4000 km2 and plays a key role in mediating regional atmospheric exchanges of greenhouse gases (GHGs) such as carbon dioxide (CO2), and water vapour (H2O). However, these peatlands underwent significant afforestation in the 1980s, when over 670 km2 of blanket bog were drained and planted with Sitka spruce (Picea sitchensis) and Lodgepole pine (Pinus contorta). This resulted in modifications to hydrology, micro-topography, vegetation and soil properties all of which are known to influence the production, emission and sequestration of key GHGs. Since the late 1990s restoration work has been carried out to remove forest plantations and raise water tables, by drain blocking, to encourage the recolonisation of Sphagnum species and restore ecosystem functioning. Here, we report findings of NEE and its constituent fluxes, GPP and Reco, from a study investigating the impacts of restoration on C dynamics over a chronosequence of restored peatlands. The research explored the role of environmental variables and microtopography in modulating land-atmosphere exchanges, using a multi-scale sampling approach that incorporated eddy covariance measurements with dynamic flux chambers. Key age classes sampled included an undrained peatland; an older restored peatland (17 years old); and a more recently restored site (12 years old). The oldest restored site showed the strongest uptake of C, with an annual assimilation rate of 858 g C m-2 yr-1 compared to assimilation rates of 501g C m-2 yr-1 and 575g C m-2 yr-1 from the younger restored site and

  5. 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.

  6. Intercomparisons of Prognostic, Diagnostic, and Inversion Modeling Approaches for Estimation of Net Ecosystem Exchange over the Pacific Northwest Region

    NASA Astrophysics Data System (ADS)

    Turner, D. P.; Jacobson, A. R.; Nemani, R. R.

    2013-12-01

    The recent development of large spatially-explicit datasets for multiple variables relevant to monitoring terrestrial carbon flux offers the opportunity to estimate the terrestrial land flux using several alternative, potentially complimentary, approaches. Here we developed and compared regional estimates of net ecosystem exchange (NEE) over the Pacific Northwest region of the U.S. using three approaches. In the prognostic modeling approach, the process-based Biome-BGC model was driven by distributed meteorological station data and was informed by Landsat-based coverages of forest stand age and disturbance regime. In the diagnostic modeling approach, the quasi-mechanistic CFLUX model estimated net ecosystem production (NEP) by upscaling eddy covariance flux tower observations. The model was driven by distributed climate data and MODIS FPAR (the fraction of incident PAR that is absorbed by the vegetation canopy). It was informed by coarse resolution (1 km) data about forest stand age. In both the prognostic and diagnostic modeling approaches, emissions estimates for biomass burning, harvested products, and river/stream evasion were added to model-based NEP to get NEE. The inversion model (CarbonTracker) relied on observations of atmospheric CO2 concentration to optimize prior surface carbon flux estimates. The Pacific Northwest is heterogeneous with respect to land cover and forest management, and repeated surveys of forest inventory plots support the presence of a strong regional carbon sink. The diagnostic model suggested a stronger carbon sink than the prognostic model, and a much larger sink that the inversion model. The introduction of Landsat data on disturbance history served to reduce uncertainty with respect to regional NEE in the diagnostic and prognostic modeling approaches. The FPAR data was particularly helpful in capturing the seasonality of the carbon flux using the diagnostic modeling approach. The inversion approach took advantage of a global

  7. Enhanced seasonal CO2 exchange caused by amplified plant productivity in northern ecosystems

    NASA Astrophysics Data System (ADS)

    Forkel, Matthias; Carvalhais, Nuno; Rödenbeck, Christian; Keeling, Ralph; Heimann, Martin; Thonicke, Kirsten; Zaehle, Sönke; Reichstein, Markus

    2016-04-01

    Atmospheric monitoring has shown an increase in the seasonal cycle of carbon dioxide (CO2) in high northern latitudes (> 40°N) since the 1960s. The much stronger increase of the seasonal CO2 amplitude in high latitudes compared to low latitudes suggests that northern ecosystems are experiencing large changes in carbon cycle dynamics. However the underlying mechanisms are not yet fully understood and current climate/carbon cycle models under-estimate observed changes in the seasonal CO2 amplitude. Here we aim to explain the observed latitudinal gradient of seasonal CO2 amplitude trends by contrasting observations from long-term monitoring sites of atmospheric CO2 concentration, satellite observation of vegetation greenness, and global observation-based datasets of gross primary production and net biome productivity, with results from the LPJmL dynamic global vegetation model coupled to the TM3 atmospheric transport model. Our results demonstrate that the latitudinal gradient of the enhanced seasonal CO2 amplitude is mainly driven by positive trends in photosynthetic carbon uptake caused by recent climate change and mediated by changing vegetation cover in boreal and arctic ecosystems. Climate change affects processes such as plant physiology, phenology, water availability, and vegetation dynamics, ultimately leading to increased plant productivity and vegetation cover in northern ecosystems in the last decades. Thereby photosynthetic carbon uptake has reacted much more strongly to warming than respiratory carbon release processes. Continued long-term observation of atmospheric CO2 together with ground and satellite observations of land surface and vegetation dynamics will be the key to detect, model, and better predict changes in high-latitude land/carbon cycle dynamics.

  8. Biosphere/atmosphere CO2 exchange in tundra ecosystems - Community characteristics and relationships with multispectral surface reflectance

    NASA Technical Reports Server (NTRS)

    Whiting, Gary J.; Bartlett, David S.; Fan, Song-Miao; Bakwin, Peter S.; Wofsy, Steven C.

    1992-01-01

    CO2 exchange rates were measured at selected tundra sites near Bethel, Alaska using portable, climate-controlled, instrumented enclosures. The empirically modeled exchange rate for a representative area of vegetated tundra was 1.2 +/- 1.2 g/sq m/d, compared to a tower-measured exchange over the same time period of 1.1 +.0- 1.2 g/sq m/d. Net exchange in response to varying light levels was compared to wet meadow and dry upland tundra, and to the net exchange measured by the micrometeoroidal tower technique. The multispectral reflectance properties of the sites were measured and related to exchange rates in order to provide a quantitative foundation for the use of satellite remote sensing to monitor biosphere/atmosphere CO2 exchange in the tundra biome.

  9. Biosphere/atmosphere CO[sub 2] exchange in tundra ecosystems - community characteristics and relationships with multispectral surface reflectance

    SciTech Connect

    Whiting, G.J.; Bartlett, D.S.; Fan, Songmiao; Bakwin, P.S.; Wofsy, S.C. New Hampshire Univ., Durham Harvard Univ., Cambridge, MA )

    1992-10-01

    CO2 exchange rates were measured at selected tundra sites near Bethel, Alaska using portable, climate-controlled, instrumented enclosures. The empirically modeled exchange rate for a representative area of vegetated tundra was 1.2 +/- 1.2 g/sq m/d, compared to a tower-measured exchange over the same time period of 1.1 +.0- 1.2 g/sq m/d. Net exchange in response to varying light levels was compared to wet meadow and dry upland tundra, and to the net exchange measured by the micrometeoroidal tower technique. The multispectral reflectance properties of the sites were measured and related to exchange rates in order to provide a quantitative foundation for the use of satellite remote sensing to monitor biosphere/atmosphere CO[sub 2] exchange in the tundra biome. 28 refs.

  10. What are the instrumentation requirements for measuring the isotopic composition of net ecosystem exchange of CO2 using eddy covariance methods?

    PubMed

    Saleska, Scott R; Shorter, Joanne H; Herndon, Scott; Jiménez, Rodrigo; McManus, J Barry; Munger, J William; Nelson, David D; Zahniser, Mark S

    2006-06-01

    Better quantification of isotope ratios of atmosphere-ecosystem exchange of CO2 could substantially improve our ability to probe underlying physiological and ecological mechanisms controlling ecosystem carbon exchange, but the ability to make long-term continuous measurements of isotope ratios of exchange fluxes has been limited by measurement difficulties. In particular, direct eddy covariance methods have not yet been used for measuring the isotopic composition of ecosystem fluxes. In this article, we explore the feasibility of such measurements by (a) proposing a general criterion for judging whether a sensor's performance is sufficient for making such measurements (the criterion is met when the contribution of sensor error to the flux measurement error is comparable to or less than the contribution of meteorological noise inherently associated with turbulence flux measurements); (b) using data-based numerical simulations to quantify the level of sensor precision and stability required to meet this criterion for making direct eddy covariance measurements of the 13C/12C ratio of CO2 fluxes above a specific ecosystem (a mid-latitude temperate forest in central Massachusetts, USA); (c) testing whether the performance of a new sensor-a prototype pulsed quantum cascade laser (QCL) based isotope-ratio absorption spectrometer (and plausible improvements thereon)-is sufficient for meeting the criterion in this ecosystem. We found that the error contribution from a prototype sensor (approximately 0.2 per thousand, 1 SD of 10 s integrations) to total isoflux measurement error was comparable to (1.5 to 2x) the irreducible 'meteorological' noise inherently associated with turbulent flux measurements above this ecosystem (daytime measurement error SD of approximately 60% of flux versus meteorological noise of 30-40% for instantaneous half-hour fluxes). Our analysis also shows that plausible instrument improvements (increase of sensor precision to approximately 0.1 per

  11. Ecosystem-atmosphere exchange of CO2 in a temperate herbaceous peatland in the Sanjiang Plain of northeast China

    USGS Publications Warehouse

    Zhu, Xiaoyan; Song, Changchun; Swarzenski, Christopher M.; Guo, Yuedong; Zhang, Xinhow; Wang, Jiaoyue

    2015-01-01

    Northern peatlands contain a considerable share of the terrestrial carbon pool, which will be affected by future climatic variability. Using the static chamber technique, we investigated ecosystem respiration and soil respiration over two growing seasons (2012 and 2013) in a Carex lasiocarpa-dominated peatland in the Sanjiang Plain in China. We synchronously monitored the environmental factors controlling CO2 fluxes. Ecosystem respiration during these two growing seasons ranged from 33.3 to 506.7 mg CO2–C m−2 h−1. Through step-wise regression, variations in soil temperature at 10 cm depth alone explained 73.7% of the observed variance in log10(ER). The mean Q10 values ranged from 2.1 to 2.9 depending on the choice of depth where soil temperature was measured. The Q10 value at the 10 cm depth (2.9) appears to be a good representation for herbaceous peatland in the Sanjiang Plain when applying field-estimation based Q10values to current terrestrial ecosystem models due to the most optimized regression coefficient (63.2%). Soil respiration amounted to 57% of ecosystem respiration and played a major role in peatland carbon balance in our study. Emphasis on ecosystem respiration from temperate peatlands in the Sanjiang Plain will improve our basic understanding of carbon exchange between peatland ecosystem and the atmosphere.

  12. [CO2-exchange in tundra ecosystems of Vaygach Island during the unusually warm and dry vegetation season].

    PubMed

    Zamolodchikov, D G

    2015-01-01

    In summer of 2013, field studies of CO2-exchange in tundra ecosystems of Vaygach Island have been conducted using the chamber method. The models are developed that establish relationships between CO2 fluxes and key ecological factors such as temperature, photosynthetic active radiation, leaf mass of vascular plants, and depth of thawing. According to the model estimates, in 2013 vegetation season tundra ecosystems of Vaygach Island have been appearing to be a CO2 source to the atmosphere (31.9 ± 17.1 g C m(-2) season(-1)) with gross primary production equal to 136.6 ± 18.9 g C m(-2) season(-1) and ecosystem respiration of 168.5 ± ± 18.4 g C m(-2) season(-1). Emission of CO2 from the soil surface (soil respiration) has been equal, on the average, to 67.3% of the ecosystem respiration. The reason behind carbon losses by tundra ecosystems seems to be unusually warm and dry weather conditions in 2013 summer. The air temperature during summer months has been twice as high as the climatic norm for 1961-1990. Last decades, researches in the circumpolar Arctic revealed a growing trend to the carbon sink from the atmosphere to tundra ecosystems. This trend can be interrupted by unusually warm weather situations becoming more frequent and of larger scale.

  13. 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

  14. Are BVOC exchanges in agricultural ecosystems overestimated? Insights from fluxes measured in a maize field over a whole growing season

    NASA Astrophysics Data System (ADS)

    Bachy, Aurélie; Aubinet, Marc; Schoon, Niels; Amelynck, Crist; Bodson, Bernard; Moureaux, Christine; Heinesch, Bernard

    2016-04-01

    Maize is the most important C4 crop worldwide. It is also the second most important crop worldwide (C3 and C4 mixed), and is a dominant crop in some world regions. Therefore, it can potentially influence local climate and air quality through its exchanges of gases with the atmosphere. Among others, biogenic volatile organic compounds (BVOC) are known to influence the atmospheric composition and thereby modify greenhouse gases lifetime and pollutant formation in the atmosphere. However, so far, only two studies have dealt with BVOC exchanges from maize. Moreover, these studies were conducted on a limited range of meteorological and phenological conditions, so that the knowledge of BVOC exchanges by this crop remains poor. Here, we present the first BVOC measurement campaign performed at ecosystem-scale on a maize field during a whole growing season. It was carried out in the Lonzée Terrestrial Observatory (LTO), an ICOS site. BVOC fluxes were measured by the disjunct by mass-scanning eddy covariance technique with a proton transfer reaction mass spectrometer for BVOC mixing ratios measurements. Outstanding results are (i) BVOC exchanges from soil were as important as BVOC exchanges from maize itself; (ii) BVOC exchanges observed on our site were much lower than exchanges observed by other maize studies, even under normalized temperature and light conditions, (iii) they were also lower than those observed on other crops grown in Europe. Lastly (iv), BVOC exchanges observed on our site under standard environmental conditions, i.e., standard emission factors SEF, were much lower than those currently considered by BVOC exchange up-scaling models. From those observations, we deduced that (i) soil BVOC exchanges should be better understood and should be incorporated in terrestrial BVOC exchanges models, and that (ii) SEF for the C4 crop plant functional type cannot be evaluated at global scale but should be determined for each important agronomic and pedo-climatic region

  15. Empirically constrained estimates of Alaskan regional Net Ecosystem Exchange of CO2, 2012-2014

    NASA Astrophysics Data System (ADS)

    Commane, R.; Lindaas, J.; Benmergui, J. S.; Luus, K. A.; Chang, R. Y. W.; Miller, S. M.; Henderson, J.; Karion, A.; Miller, J. B.; Sweeney, C.; Miller, C. E.; Lin, J. C.; Oechel, W. C.; Zona, D.; Euskirchen, E. S.; Iwata, H.; Ueyama, M.; Harazono, Y.; Veraverbeke, S.; Randerson, J. T.; Daube, B. C.; Pittman, J. V.; Wofsy, S. C.

    2015-12-01

    We present data-driven estimates of the regional net ecosystem exchange of CO2 across Alaska for three years (2012-2014) derived from CARVE (Carbon in the Arctic Reservoirs Vulnerability Experiment) aircraft measurements. Integrating optimized estimates of annual NEE, we find that the Alaskan region was a small sink of CO2 during 2012 and 2014, but a significant source of CO2 in 2013, even before including emissions from the large forest fire season during 2013. We investigate the drivers of this interannual variability, and the larger spring and fall emissions of CO2 in 2013. To determine the optimized fluxes, we couple the Polar Weather Research and Forecasting (PWRF) model with the Stochastic Time-Inverted Lagrangian Transport (STILT) model, to produce footprints of surface influence that we convolve with a remote-sensing driven model of NEE across Alaska, the Polar Vegetation Photosynthesis and Respiration Model (Polar-VPRM). For each month we calculate a spatially explicit additive flux (∆F) by minimizing the difference between the measured profiles of the aircraft CO2 data and the modeled profiles, using a framework that combines a uniform correction at regional scales and a Bayesian inversion of residuals at smaller scales. A rigorous estimate of total uncertainty (including atmospheric transport, measurement error, etc.) was made with a combination of maximum likelihood estimation and Monte Carlo error propagation. Our optimized fluxes are consistent with other measurements on multiple spatial scales, including CO2 mixing ratios from the CARVE Tower near Fairbanks and eddy covariance flux towers in both boreal and tundra ecosystems across Alaska. For times outside the aircraft observations (Dec-April) we use the un-optimized polar-VPRM, which has shown good agreement with both tall towers and eddy flux data outside the growing season. This approach allows us to robustly estimate the annual CO2 budget for Alaska and investigate the drivers of both the

  16. Long-term dynamics of production, respiration, and net CO2 exchange in two sagebrush-steppe ecosystems

    USGS Publications Warehouse

    Gilmanov, T.G.; Svejcar, T.J.; Johnson, D.A.; Angell, R.F.; Saliendra, Nicanor Z.; Wylie, B.K.

    2006-01-01

    We present a synthesis of long-term measurements of CO2 exchange in 2 US Intermountain West sagebrush-steppe ecosystems. The locations near Burns, Oregon (1995-2001), and Dubois, Idaho (1996-2001), are part of the AgriFlux Network of the Agricultural Research Service, United States Department of Agriculture. Measurements of net ecosystem CO2 exchange (F c) during the growing season were continuously recorded at flux towers using the Bowen ratio-energy balance technique. Data were partitioned into gross primary productivity (Pg) and ecosystem respiration (Re) using the light-response function method. Wintertime fluxes were measured during 1999/2000 and 2000/2001 and used to model fluxes in other winters. Comparison of daytime respiration derived from light-response analysis with nighttime tower measurements showed close correlation, with daytime respiration being on the average higher than nighttime respiration. Maxima of Pg and Re at Burns were both 20 g CO2?? m-2??d-1 in 1998. Maxima of Pg and R e at Dubois were 37 and 35 g CO2??m -2??d-1, respectively, in 1997. Mean annual gross primary production at Burns was 1 111 (range 475-1 715) g CO2?? m-2??y-1 about 30% lower than that at Dubois (1 602, range 963-2 162 g CO2??m-2??y-1). Across the years, both ecosystems were net sinks for atmospheric CO2 with a mean net ecosystem CO2 exchange of 82 g CO2?? m-2??y-1 at Burns and 253 g CO2?? m-2??y-1 at Dubois, but on a yearly basis either site could be a C sink or source, mostly depending on precipitation timing and amount. Total annual precipitation is not a good predictor of carbon sequestration across sites. Our results suggest that Fc should be partitioned into Pg and Re components to allow prediction of seasonal and yearly dynamics of CO2 fluxes.

  17. Effects of Pre-industrial and Future Atmospheric CO2 concentration on Net Ecosystem Exchange on Arid and Semi-Arid Ecosystems

    NASA Astrophysics Data System (ADS)

    Kalhori, A. A. M.; Deutschman, D.; Cheng, Y.; Oechel, W. C.

    2014-12-01

    Ecosystem carbon dioxide flux was studied between 1997 and 2000 under six different CO2 concentrations (250 ppm, 350 ppm, 450 ppm, 550 ppm, 650 ppm, and 750 ppm) using CO2 LT (CO2 controlled, naturally Lit, Temperature controlled) null balance chambers in Southern California chaparral dominated by Adenostoma fasciculatum. The purpose of this study is to evaluate possible effects of altered levels of atmospheric CO2 concentrations on carbon fluxes in a natural chaparral ecosystem. Here we present that the increase of CO2 from near pre-industrial levels of around 250 ppm to recent past CO2 levels of 350 ppm are sufficient to increase NEE. These data indicate that chaparral ecosystems will increase carbon sequestration under elevated CO2 levels and that under elevated atmospheric CO2 there will be greater sink or reduced source of ecosystem CO2 to the atmosphere as a result of improved moisture status. The effect of elevated CO2 on increasing NEE was greatest during the warm and dry season versus the cold and wet season. Further, it appears that increasing atmospheric CO2 will have greater relative effects in areas of increasing water stress as CO2 treatment effects on NEE were greater in modestly dry years and with longer periods of drought. The daily maximum NEE difference between the lowest (250 ppm) and the highest (750 ppm) CO2 concentrations treatments for January was -0.127gC m-2 h-1, but for June was -0.267 gC m-2 h-1 in this study, which was a 210 percent increase. The differences between the lower treatments and higher treatments were greater in the later years indicating there was an accumulative effect. Cumulative of net ecosystem exchange (gC m-2) between 1/1/1997 and 1/1/2001 under six different CO2 concentration is presented in the figure attached.

  18. Net ecosystem exchange of CO2 with rapidly changing high Arctic landscapes.

    PubMed

    Emmerton, Craig A; St Louis, Vincent L; Humphreys, Elyn R; Gamon, John A; Barker, Joel D; Pastorello, Gilberto Z

    2016-03-01

    High Arctic landscapes are expansive and changing rapidly. However, our understanding of their functional responses and potential to mitigate or enhance anthropogenic climate change is limited by few measurements. We collected eddy covariance measurements to quantify the net ecosystem exchange (NEE) of CO2 with polar semidesert and meadow wetland landscapes at the highest latitude location measured to date (82°N). We coupled these rare data with ground and satellite vegetation production measurements (Normalized Difference Vegetation Index; NDVI) to evaluate the effectiveness of upscaling local to regional NEE. During the growing season, the dry polar semidesert landscape was a near-zero sink of atmospheric CO2 (NEE: -0.3 ± 13.5 g C m(-2) ). A nearby meadow wetland accumulated over 300 times more carbon (NEE: -79.3 ± 20.0 g C m(-2) ) than the polar semidesert landscape, and was similar to meadow wetland NEE at much more southerly latitudes. Polar semidesert NEE was most influenced by moisture, with wetter surface soils resulting in greater soil respiration and CO2 emissions. At the meadow wetland, soil heating enhanced plant growth, which in turn increased CO2 uptake. Our upscaling assessment found that polar semidesert NDVI measured on-site was low (mean: 0.120-0.157) and similar to satellite measurements (mean: 0.155-0.163). However, weak plant growth resulted in poor satellite NDVI-NEE relationships and created challenges for remotely detecting changes in the cycling of carbon on the polar semidesert landscape. The meadow wetland appeared more suitable to assess plant production and NEE via remote sensing; however, high Arctic wetland extent is constrained by topography to small areas that may be difficult to resolve with large satellite pixels. We predict that until summer precipitation and humidity increases enough to offset poor soil moisture retention, climate-related changes to productivity on polar semideserts may be restricted.

  19. Net Ecosystem Exchange of CO2 with Rapidly Changing High Arctic Landscapes

    NASA Astrophysics Data System (ADS)

    Emmerton, C. A.

    2015-12-01

    High Arctic landscapes are expansive and changing rapidly. However our understanding of their functional responses and potential to mitigate or enhance anthropogenic climate change is limited by few measurements. We collected eddy covariance measurements to quantify the net ecosystem exchange (NEE) of CO2 with polar semidesert and meadow wetland landscapes at the highest-latitude location measured to date (82°N). We coupled these rare data with ground and satellite vegetation production measurements (Normalized Difference Vegetation Index; NDVI) to evaluate the effectiveness of upscaling local to regional NEE. During the growing season, the dry polar semidesert landscape was a near zero sink of atmospheric CO2 (NEE: -0.3±13.5 g C m-2). A nearby meadow wetland accumulated over two magnitudes more carbon (NEE: -79.3±20.0 g C m-2) than the polar semidesert landscape, and was similar to meadow wetland NEE at much more southern latitudes. Polar semidesert NEE was most influenced by moisture, with wetter surface soils resulting in greater soil respiration and CO2 emissions. At the meadow wetland, soil heating enhanced plant growth, which in turn increased CO2 uptake. Our upscaling assessment found that polar semidesert NDVI measured on site was low (mean: 0.120-0.157) and similar to satellite measurements (mean: 0.155-0.163). However, weak plant growth resulted in poor satellite NDVI-NEE relationships and created challenges for remotely-detecting changes in the cycling of carbon on the polar semidesert landscape. The meadow wetland appeared more suitable to assess plant production and NEE via remote-sensing, however high Arctic wetland extent is constrained by topography to small areas that may be difficult to resolve with large satellite pixels. We predict that until summer precipitation and humidity increases substantially, climate-related changes of dry high Arctic landscapes may be restricted by poor soil moisture retention, and therefore have some inertia against

  20. 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

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

    PubMed

    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.

  2. Differential Responses of Net Ecosystem Exchange of Carbon Dioxide to Light and Temperature between Spring and Neap Tides in Subtropical Mangrove Forests

    PubMed Central

    Li, Qing; Lu, Weizhi; Chen, Hui; Luo, Yiqi; Lin, Guanghui

    2014-01-01

    The eddy flux data with field records of tidal water inundation depths of the year 2010 from two mangroves forests in southern China were analyzed to investigate the tidal effect on mangrove carbon cycle. We compared the net ecosystem exchange (NEE) and its responses to light and temperature, respectively, between spring tide and neap tide inundation periods. For the most time of the year 2010, higher daytime NEE values were found during spring tides than during neap tides at both study sites. Regression analysis of daytime NEE to photosynthetically active radiation (PAR) using the Landsberg model showed increased sensitivity of NEE to PAR with higher maximum photosynthetic rate during spring tides than neap tides. In contrast, the light compensation points acquired from the regression function of the Landsberg model were smaller during spring tides than neap tides in most months. The dependence of nighttime NEE on soil temperature was lower under spring tide than under neap tides. All these results above indicated that ecosystem carbon uptake rates of mangrove forests were strengthened, while ecosystem respirations were inhibited during spring tides in comparison with those during neap tides, which needs to be considered in modeling mangrove ecosystem carbon cycle under future sea level rise scenarios. PMID:25133267

  3. Differential responses of net ecosystem exchange of carbon dioxide to light and temperature between spring and neap tides in subtropical mangrove forests.

    PubMed

    Li, Qing; Lu, Weizhi; Chen, Hui; Luo, Yiqi; Lin, Guanghui

    2014-01-01

    The eddy flux data with field records of tidal water inundation depths of the year 2010 from two mangroves forests in southern China were analyzed to investigate the tidal effect on mangrove carbon cycle. We compared the net ecosystem exchange (NEE) and its responses to light and temperature, respectively, between spring tide and neap tide inundation periods. For the most time of the year 2010, higher daytime NEE values were found during spring tides than during neap tides at both study sites. Regression analysis of daytime NEE to photosynthetically active radiation (PAR) using the Landsberg model showed increased sensitivity of NEE to PAR with higher maximum photosynthetic rate during spring tides than neap tides. In contrast, the light compensation points acquired from the regression function of the Landsberg model were smaller during spring tides than neap tides in most months. The dependence of nighttime NEE on soil temperature was lower under spring tide than under neap tides. All these results above indicated that ecosystem carbon uptake rates of mangrove forests were strengthened, while ecosystem respirations were inhibited during spring tides in comparison with those during neap tides, which needs to be considered in modeling mangrove ecosystem carbon cycle under future sea level rise scenarios.

  4. 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.

  5. On the additional information content of hyperspectral remote sensing data for estimating ecosystem carbon dioxde and energy exchange

    NASA Astrophysics Data System (ADS)

    Wohlfahrt, Georg; Hammerle, Albin; Tomelleri, Enrico

    2015-04-01

    Radiation reflected back from an ecosystem carries a spectral signature resulting from the interaction of radiation with the vegetation canopy and the underlying soil and thus allows drawing conclusions about the structure and functioning of an ecosystem. When this information is linked to a model of the leaf CO2 exchange, the ecosystem-scale CO2 exchange can be simulated. A well-known and very simplistic example for this approach is the light-use efficiency (LUE) model proposed by Monteith which links the flux of absorbed photosynthetically active radiation times a LUE parameter, both of which may be estimated based on remote sensing data, to predict the ecosystem gross photosynthesis. Here we explore the ability of a more elaborate approach by using near-surface remote sensing of hyperspectral reflected radiation, eddy covariance CO2 and energy flux measurements and a coupled radiative transfer and soil-vegetation-atmosphere-transfer (SVAT) model. Our main objective is to understand to what degree the joint assimilation of hyperspectral reflected radiation and eddy covariance flux measurements into the model helps to better constrain model parameters. To this end we use the SCOPE model, a combination of the well-known PROSAIL model and a SVAT model, and the Bayesian inversion algorithm DREAM. In order to explicitly link reflectance in the visible light and the leaf CO2 exchange, a novel parameterisation of the maximum carboxylation capacity parameter (Vcmax) on the leaf a+b chlorophyll content parameter of PROSAIL is introduced. Results are discussed with respect to the additional information content the hyperspectral data yield for simulating canopy photosynthesis.

  6. Ecosystem carbon balance in a drier future: land-atmosphere exchanges of CO2, water and energy across semiarid southwestern North America

    NASA Astrophysics Data System (ADS)

    Biederman, J. A.; Scott, R. L.; Goulden, M.; Litvak, M. E.; Kolb, T.; Yépez, E. A.; Oechel, W. C.; Meyers, T. P.; Papuga, S. A.; Ponce-Campos, G.; Krofcheck, D. J.; Maurer, G. E.; Dore, S.; Garatuza, J.; Bell, T. W.; Krishnan, P.

    2015-12-01

    The southwest US and northwest Mexico are predicted to become warmer and drier, increasing disturbance, shifting ecosystem composition, and altering global CO2 cycling. However, direct measurements of ecosystem land-atmosphere carbon and water exchange in this region have lagged behind those in wetter regions. In this presentation we present a synthesis of CO2, water, and energy exchanges made at 25 Southwest eddy covariance sites (3-10 years each, n = 174 years). This regional gradient includes desert shrublands, grasslands, savannas, and forests and spans ranges of 200 - 800 mm in mean annual precipitation and 2 - 24 ⁰C mean annual temperature, a climate space that has been underrepresented in flux databases and publications. We compare measured fluxes against state-of-the-art remote sensing and modeling products representing current best regional estimates. We find that 65% of annual net ecosystem production of CO2 (NEP) is explained by water availability. Meanwhile, most of the unexplained NEP variability is related to site-specific differences persisting over the observation years, suggesting slow-changing controls such as demography (plant type, age, structure) and legacies of disturbance. Disturbances that kill plants without removing biomass, such as drought, tend to decrease productivity and increase respiration, shifting sites from carbon sinks to sources. However, following disturbances that removed biomass, such as fire, both productivity and respiration decline, with minimal impacts on NEP. Remote sensing and modeling match mean CO2 uptake measurements across spatial gradients in climate and plant functional type. However, measured uptake reveals 200-400% greater interannual variability than model estimates. High variability and sensitivity to water help us understand why semiarid ecosystems dominate the interannual variability of the terrestrial carbon sink in global accounting studies.

  7. A comparative assessment of tools for ecosystem services quantification and valuation

    USGS Publications Warehouse

    Bagstad, Kenneth J.; Semmens, Darius; Waage, Sissel; Winthrop, Robert

    2013-01-01

    To enter widespread use, ecosystem service assessments need to be quantifiable, replicable, credible, flexible, and affordable. With recent growth in the field of ecosystem services, a variety of decision-support tools has emerged to support more systematic ecosystem services assessment. Despite the growing complexity of the tool landscape, thorough reviews of tools for identifying, assessing, modeling and in some cases monetarily valuing ecosystem services have generally been lacking. In this study, we describe 17 ecosystem services tools and rate their performance against eight evaluative criteria that gauge their readiness for widespread application in public- and private-sector decision making. We describe each of the tools′ intended uses, services modeled, analytical approaches, data requirements, and outputs, as well time requirements to run seven tools in a first comparative concurrent application of multiple tools to a common location – the San Pedro River watershed in southeast Arizona, USA, and northern Sonora, Mexico. Based on this work, we offer conclusions about these tools′ current ‘readiness’ for widespread application within both public- and private-sector decision making processes. Finally, we describe potential pathways forward to reduce the resource requirements for running ecosystem services models, which are essential to facilitate their more widespread use in environmental decision making.

  8. The strength of contributions from topography mismatch and measurement filtering to simulated net ecosystem exchange in complex terrain

    NASA Astrophysics Data System (ADS)

    Brooks, B.; Desai, A. R.; Stephens, B. B.; Jacobson, A. R.

    2011-12-01

    Global scale carbon cycle inverse models provide invaluable information for the construction of empirically based carbon budgets based on in situ measurements. In landscapes of predominantly smooth topography inverse carbon cycle models are useful for diagnosing the magnitude and climate sensitivity of different regional carbon sinks. However, in landscapes of predominately complex topography inversion model results come with strong caveats for two reasons: 1) Coarse gridding of model topography can lead the model to sample observations at elevations far above the model surface, and 2) Transport wind fields over smoothed model representations of mountain regions are not always sufficiently resolved to inform the model about the source region for assimilated measurements. The uncertainty contributed by incorrect winds and topography mismatches (e.g., differences between the actual measurement elevation and model surface on the order of 1,000 m) is thought to be smaller for higher resolution regional inversion models (e.g., Gockede et al., 2010; Schuh et al. 2010), but these uncertainties are not well constrained for larger scale inversion systems (e.g., Peters et al., 2010), which are one of few ways for determining the relative priority of regional sinks. In this work we examine the effects on net ecosystem exchange (NEE) for a global scale inversion system when 1) topography mismatches are ameliorated, and 2) subset observations consistent with model resolution are used rather than observation-based subsets. Our focus is to use an example inversion model system, CarbonTracker (Peters et al., 2007; 2010), driven by CO2 mixing ratio measurements, including the RACCOON Network in the United States Mountain West (raccoon.ucar.edu), to quantify and compare the contribution to NEE from tower elevation mismatches and filtering strategies across biomes and and in terms of forecast skill (model data mismatch). We further compare our results to the differences in NEE over

  9. Inverse modeling of seasonal drought effects on canopy CO2/H2O exchange in three Mediterranean ecosystems

    NASA Astrophysics Data System (ADS)

    Reichstein, Markus; Tenhunen, John; Roupsard, Olivier; Ourcival, Jean-Marc; Rambal, Serge; Miglietta, Franco; Peressotti, Alessandro; Pecchiari, Marco; Tirone, Giampiero; Valentini, Riccardo

    2003-12-01

    We present a two-criteria inverse modeling approach to analyze the effects of seasonal drought on ecosystem gas exchange at three Mediterranean sites. The three sites include two nearly monospecific Quercus ilex L. forests, one on karstic limestone (Puéchabon), the other on fluvial sand with access to groundwater (Castelporziano), and a typical multispecies shrubland on limestone (Arca di Noè). A canopy gas exchange model Process Pixel Net Ecosystem Exchange (PROXELNEE), which contains the Farquhar photosynthesis model coupled to stomatal conductance via the Ball-Berry model, was inverted in order to estimate the seasonal time course of canopy parameters from hourly values of ecosystem gross carbon uptake and transpiration. It was shown that an inverse estimation of leaf-level parameters was impossible when optimizing against ecosystem H2O or CO2 fluxes alone (unidentifiable parameters). In contrast, a criterion that constrained the optimization against both H2O and CO2 fluxes yielded stable estimates of leaf-level parameters. Two separate model inversions were implemented to test two alternative hypotheses about the response to drought: a reduction in active leaf area as a result of patchy stomatal closure or a change in photosynthetic capacities. In contrast to a previously tested hypothesis of classical (uniform) stomatal control, both hypotheses were equally able to describe the seasonality of carbon uptake and transpiration on all three sites, with a decline during the drought and recovery after autumn rainfall. Large reductions of up to 80%, in either active leaf area or photosynthetic capacities, were necessary to describe the observed carbon and water fluxes at the end of the drought period. With a threshold-type relationship, soil water content was an excellent predictor of these changes. With the drought-dependent parameter changes included, the canopy model explains 80-90% of the variance of hourly gross CO2 uptake (root mean squared error (RMSE): 1

  10. Net ecosystem CO2 exchange and evapotranspiration of a sphagnum mire: field measurements and model simulations

    NASA Astrophysics Data System (ADS)

    Olchev, Alexander; Volkova, Elena; Karataeva, Tatiana; Zatsarinnaya, Dina; Novenko, Elena

    2014-05-01

    The spatial and temporal variability of net ecosystem exchange of CO2 (NEE) and evapotranspiration (ET) of a karst-hole sphagnum peat mire situated at the boundary between broad-leaved and forest-steppe zones in the central part of European Russia (54.06N, 37.59E, 260 m a.s.l.) was described using results of field measurements and simulations with Mixfor-3D model. The area of the mire is about 1.2 ha and it is surrounded by a broadleaved forest stand. It is a typical peat mire according to water and mineral supply as well as to vegetation composition. The vegetation of the peripheral parts of the mire is typical eutrophic whereas the vegetation in its central part is represented by meso-oligothrophic plant communities. To describe the spatial variability of NEE and ET within the mire a portable measuring system consisting of a transparent ventilated chamber combined with an infrared CO2 and H2O analyzer LI-840A (Li-Cor, USA) was used. The measurements were provided along a transect from the southern peripheral part of the mire to its center under sunny clear-sky weather conditions in the period from May to September of 2012 and from May 2013 to October 2013. The chamber method was used for measurements of NEE and ET fluxes because of small size of the mire, a very uniform surrounding forest stand and the mosaic mire vegetation. All these factors promote very heterogeneous exchange conditions within the mire and make it difficult to apply, for example, an eddy covariance method that is widely used for flux measurements in the field. The results of the field measurements showed a significant spatial and temporal variability of NEE and ET that was mainly influenced by incoming solar radiation, air temperature and ground water level. During the entire growing season the central part of the mire was a sink of CO2 for the atmosphere (up to 6.8±4.2 µmol m-2 s-1 in June) whereas its peripheral part, due to strong shading by the surrounding forest, was mainly a source of

  11. Hydrological exchanges and Organic Matter dynamics in highly vulnerable tidal wetland ecosystems at the land-ocean interface

    NASA Astrophysics Data System (ADS)

    Tzortziou, M.; Neale, P.; Megonigal, P.; Loughner, C.

    2014-12-01

    Occupying a critical interface between the land and the sea, tidal wetlands are amongst the most ecologically valuable and economically important ecosystems on Earth, but also especially vulnerable to human pressures and climate change. These rich in biodiversity and highly productive ecosystems are hot spots of biogeochemical transformations, consistently exchanging Organic Matter with adjacent estuarine waters through tidal flushing. Here we discuss new results on the amount and directions of biogeochemical exchanges at the tidal wetland-estuary interface. Detailed microbial and photochemical degradation experiments and high resolution bio-optical observations in tidal freshwater and salt marsh systems of the Eastern US coast provide insights on the quality and fate of the organic compounds exported from tidal marshes and their influence on near-shore biological processes, biogeochemical cycles and optical variability. Impacts of anthropogenic activities and resulting air-pollution are also discussed. High resolution model runs were performed using the Community Multi-scale Air Quality (CMAQ) model, to examine atmospheric composition along the shoreline where processes such as sea and bay breeze circulations often favor the accumulation and air-deposition of atmospheric pollutants, impacting biogeochemical processes in sensitive tidal wetland ecosystems.

  12. Larval outbreaks in West Greenland: Instant and subsequent effects on tundra ecosystem productivity and CO2 exchange.

    PubMed

    Lund, Magnus; Raundrup, Katrine; Westergaard-Nielsen, Andreas; López-Blanco, Efrén; Nymand, Josephine; Aastrup, Peter

    2017-02-01

    Insect outbreaks can have important consequences for tundra ecosystems. In this study, we synthesise available information on outbreaks of larvae of the noctuid moth Eurois occulta in Greenland. Based on an extensive dataset from a monitoring programme in Kobbefjord, West Greenland, we demonstrate effects of a larval outbreak in 2011 on vegetation productivity and CO2 exchange. We estimate a decreased carbon (C) sink strength in the order of 118-143 g C m(-2), corresponding to 1210-1470 tonnes C at the Kobbefjord catchment scale. The decreased C sink was, however, counteracted the following years by increased primary production, probably facilitated by the larval outbreak increasing nutrient turnover rates. Furthermore, we demonstrate for the first time in tundra ecosystems, the potential for using remote sensing to detect and map insect outbreak events.

  13. [Characteristics of net ecosystem flux exchanges over Stipa krylovii steppe in Inner Mongolia].

    PubMed

    Yang, Juan; Zhou, Guang-Sheng; Wang, Yun-Long; Wang, Yu-Hui

    2008-03-01

    Based on an entire year continuous measurement of surface fluxes by eddy covariance (EC) tower and micro-climate gradient observation system, the diurnal and seasonal dynamics of net ecosystem fluxes including carbon, water, and heat fluxes over Stipa krylovii steppe in Inner Mongolia were investigated. The results indicated that the diurnal pattern of carbon fluxes during growing season could be expressed as U curve. S. krylovii steppe ecosystem emitted CO2 before the sunrise and absorbed CO2 after the sunrise, with the maximum CO2 uptake around noon. The ecosystem had weaker CO2 uptake after the noon, and turned to emit CO2 after sunset. The CO2 uptake by S. krylovii steppe ecosystem reached the maximum in September, followed in August, and got the minimum in October. The diurnal dynamic patterns of sensible heat flux (Hs) and latent heat flux (LE) could be expressed as inverse U curves. The Hs and LE over S. krylovii steppe ecosystem were positive during the daytime, while Hs was negative and LE was close to zero during the nighttime. The ecosystem had the highest Hs and LE in May and September, respectively. In winter, the steppe acted as a weak carbon source, with the CO2 flux being small; while in summer, it became an obvious carbon sink.

  14. A top-down approach of surface carbonyl sulfide exchange by a Mediterranean oak forest ecosystem in southern France

    NASA Astrophysics Data System (ADS)

    Belviso, Sauveur; Reiter, Ilja Marco; Loubet, Benjamin; Gros, Valérie; Lathière, Juliette; Montagne, David; Delmotte, Marc; Ramonet, Michel; Kalogridis, Cerise; Lebegue, Benjamin; Bonnaire, Nicolas; Kazan, Victor; Gauquelin, Thierry; Fernandez, Catherine; Genty, Bernard

    2016-12-01

    The role that soil, foliage, and atmospheric dynamics have on surface carbonyl sulfide (OCS) exchange in a Mediterranean forest ecosystem in southern France (the Oak Observatory at the Observatoire de Haute Provence, O3HP) was investigated in June of 2012 and 2013 with essentially a top-down approach. Atmospheric data suggest that the site is appropriate for estimating gross primary production (GPP) directly from eddy covariance measurements of OCS fluxes, but it is less adequate for scaling net ecosystem exchange (NEE) to GPP from observations of vertical gradients of OCS relative to CO2 during the daytime. Firstly, OCS and carbon dioxide (CO2) diurnal variations and vertical gradients show no net exchange of OCS at night when the carbon fluxes are dominated by ecosystem respiration. This contrasts with other oak woodland ecosystems of a Mediterranean climate, where nocturnal uptake of OCS by soil and/or vegetation has been observed. Since temperature, water, and organic carbon content of soil at the O3HP should favor the uptake of OCS, the lack of nocturnal net uptake would indicate that its gross consumption in soil is compensated for by emission processes that remain to be characterized. Secondly, the uptake of OCS during the photosynthetic period was characterized in two different ways. We measured ozone (O3) deposition velocities and estimated the partitioning of O3 deposition between stomatal and non-stomatal pathways before the start of a joint survey of OCS and O3 surface concentrations. We observed an increasing trend in the relative importance of the stomatal pathway during the morning hours and synchronous steep drops of mixing ratios of OCS (amplitude in the range of 60-100 ppt) and O3 (amplitude in the range of 15-30 ppb) after sunrise and before the break up of the nocturnal boundary layer. The uptake of OCS by plants was also characterized from vertical profiles. However, the time window for calculation of the ecosystem relative uptake (ERU) of OCS

  15. Comparing strengths and weaknesses of three ecosystem services modelling tools in a diverse UK river catchment.

    PubMed

    Sharps, Katrina; Masante, Dario; Thomas, Amy; Jackson, Bethanna; Redhead, John; May, Linda; Prosser, Havard; Cosby, Bernard; Emmett, Bridget; Jones, Laurence

    2017-01-29

    Ecosystem services modelling tools can help land managers and policy makers evaluate the impacts of alternative management options or changes in land use on the delivery of ecosystem services. As the variety and complexity of these tools increases, there is a need for comparative studies across a range of settings, allowing users to make an informed choice. Using examples of provisioning and regulating services (water supply, carbon storage and nutrient retention), we compare three spatially explicit tools - LUCI (Land Utilisation and Capability Indicator), ARIES (Artificial Intelligence for Ecosystem Services) and InVEST (Integrated Valuation of Ecosystem Services and Tradeoffs). Models were parameterised for the UK and applied to a temperate catchment with widely varying land use in North Wales. Although each tool provides quantitative mapped output, can be applied in different contexts, and can work at local or national scale, they differ in the approaches taken and underlying assumptions made. In this study, we focus on the wide range of outputs produced for each service and discuss the differences between each modelling tool. Model outputs were validated using empirical data for river flow, carbon and nutrient levels within the catchment. The sensitivity of the models to land-use change was tested using four scenarios of varying severity, evaluating the conversion of grassland habitat to woodland (0-30% of the landscape). We show that, while the modelling tools provide broadly comparable quantitative outputs, each has its own unique features and strengths. Therefore the choice of tool depends on the study question.

  16. Atmospheric N deposition and feedbacks on net ecosystem CO2 exchange at a semi-natural peatland site

    NASA Astrophysics Data System (ADS)

    Hurkuck, Miriam; Brümmer, Christian; Spott, Oliver; Flessa, Heinz; Kutsch, Werner L.

    2013-04-01

    Large areas of Northern Germany have been converted from natural peat bogs to arable land and were subjected to draining and peat cutting in the past. The few protected peatland areas remaining are affected by high nitrogen (N) deposition. This is the case at our study site - a semi-natural raised bog - which although located in a natural park, is surrounded by highly fertilized agricultural land and highly emitting animal husbandry farms. In this study, we use a combined approach of two independent methods to quantify atmospheric N deposition. We further investigate possible feedbacks of seasonal variation in N deposition on net ecosystem CO2 exchange (NEE). Fluxes of ammonia (NH3) and its atmospheric reactants are measured by a KAPS-denuder system. Additionally, total N input from the atmosphere into a soil-plant model ecosystem is investigated by a 15N dilution method called 'Integrated Total Nitrogen Input' (ITNI). With this approach, we allocate atmospheric N after its uptake by the ecosystem into its different fractions and investigate both plant-species effects (Lolium multiflorum, Eriophorum vaginatum) and influences of the plant biomass production induced by different amounts of fertilizer addition. Continuous eddy-covariance measurements are carried out to measure NEE. Maximum NH3 depositions of 0.41 ± 0.04 kg ha-1 week-1 were found in spring 2012. The proportion of fluxes of other N compounds such as HNO3, aerosol NH4 and NO3 was usually around 20 % of total dry N measured by KAPS denuders. In total, dry N deposition was 11.2 ± 0.9 kg N ha-1 yr-1 over the first year of experiments. Complemented with wet N measurements using bulk samplers, total N depositions of about 25.0 kg ha-1 yr-1 were found. The mean atmospheric N uptake determined with the ITNI system was 3.99 ± 0.82 mg N g-1 dry weight from July to October 2011. About two third of total deposited airborne N was allocated in above-ground plant biomass and roots. Upscaling of data based on pot

  17. Comparing Individual Health Coverage On and Off the Affordable Care Act's Insurance Exchanges.

    PubMed

    McCue, Michael J; Hall, Mark A

    2015-08-01

    The new health insurance exchanges are the core of the Affordable Care Act's (ACA) reforms, but how the law improves the nonsubsidized portion of the individual market is also important. This issue brief compares products sold on and off the exchanges to gain insight into how the ACA's market reforms are functioning. Initial concerns that insurers might seek to enroll lower-risk customers outside the exchanges have not been realized. Instead, more-generous benefit plans, which appeal to people with health problems, constitute a greater portion of plans sold off-exchange than those sold on-exchange. Although insur­ers that sell mostly on the exchanges incur an additional fee, they still devote a greater portion of their premium dollars to medical care. Their projected admin­istrative costs and profit margins are lower than are those of insurers selling only off the exchanges.

  18. Acclimation of ecosystem CO2 exchange in the Alaskan Arctic in response to decadal climate warming

    PubMed

    Oechel; Vourlitis; Hastings; Zulueta; Hinzman; Kane

    2000-08-31

    Long-term sequestration of carbon in Alaskan Arctic tundra ecosystems was reversed by warming and drying of the climate in the early 1980s, resulting in substantial losses of terrestrial carbon. But recent measurements suggest that continued warming and drying has resulted in diminished CO2 efflux, and in some cases, summer CO2 sink activity. Here we compile summer CO2 flux data for two Arctic ecosystems from 1960 to the end of 1998. The results show that a return to summer sink activity has come during the warmest and driest period observed over the past four decades, and indicates a previously undemonstrated capacity for ecosystems to metabolically adjust to long-term (decadal or longer) changes in climate. The mechanisms involved are likely to include changes in nutrient cycling, physiological acclimation, and population and community reorganization. Nevertheless, despite the observed acclimation, the Arctic ecosystems studied are still annual net sources of CO2 to the atmosphere of at least 40 g C m(-2) yr(-1), due to winter release of CO2, implying that further climate change may still exacerbate CO2 emissions from Arctic ecosystems.

  19. Annual net ecosystem exchanges of carbon dioxide and methane from a temperate brackish marsh: should the focus of marsh restoration be on brackish environments?

    NASA Astrophysics Data System (ADS)

    Windham-Myers, L.; Anderson, F. E.; Bergamaschi, B. A.; Ferner, M. C.; Schile, L. M.; Spinelli, G.

    2015-12-01

    The exchange and transport of carbon in tidally driven, saline marsh ecosystems provide habitat and trophic support for coastal wildlife and fisheries, while potentially accumulating and storing carbon at some of the highest rates compared to other ecosystems. However, due to the predicted rise in sea level over the next century, the preservation and restoration of estuarine habitats is necessary to compensate for their expected decline. In addition, restoration of these marsh systems can also reduce the impacts of global climate change as they assimilate as much carbon as their freshwater counterparts, while emitting less methane due to the higher concentrations of sulfate in seawater. Unfortunately, in brackish marshes, with salinity concentrations less than 18 parts per thousand (ppt), simple relationships between methane production, salinity and sulfate concentrations are not well known. Here we present the net ecosystem exchange (NEE) of carbon dioxide and methane, as calculated by the eddy covariance method, from a brackish marsh ecosystem in the San Francisco Estuary where salinity ranges from oligohaline (0.5-5 ppt) to mesohaline (5-18 ppt) conditions. Daily rates of carbon dioxide and methane NEE ranged from approximately 10 gC-CO2 m-2 d-1 and 0 mgC-CH4 m-2 d-1, during the winter to -15 gC-CO2 m-2 d-1 and 30 mgC-CH4 m-2 d-1, in the summer growing season. A comparison between similar measurements made from freshwater wetlands in the Sacramento-San Joaquin Delta found that the daily rates of carbon dioxide NEE were similar, but daily rates of methane NEE were just a small fraction (0-15%). Our research also shows that the daily fluxes of carbon dioxide and methane at the brackish marsh were highly variable and may be influenced by the tidal exchanges of seawater. Furthermore, the observed decline in methane production from summer to fall may have resulted from a rise in salinity and/or a seasonal decline in water and air temperatures. Our research goals are

  20. Ambient ammonia in terrestrial ecosystems: a comparative study in the Tennessee Valley, USA.

    PubMed

    Allen, Ridwaana; Myles, LaToya; Heuer, Mark W

    2011-06-15

    Atmospheric ammonia has been shown to degrade regional air quality and affect environmental health. In-situ measurements of ammonia are needed to determine how ambient concentrations vary in different ecosystems and the extent to which emission sources contribute to those levels. The objective of this study was to measure and compare ammonia concentrations in two Tennessee Valley (USA) ecosystems: a forested rural area and a metropolitan site adjacent to a main transportation route. Integrated samples of atmospheric ammonia were collected with annular denuder systems for ~4 weeks during the summer of 2009 in both ecosystems. Ancillary measurements of meteorological variables, such as wind direction and precipitation, were also conducted to determine any relationships with ammonia concentration. Measurements in the two ecosystems revealed ammonia concentrations that were mostly representative of background levels. Arithmetic means were 1.57±0.68 μg m(-3) at the metropolitan site and 1.60±0.77 μg m(-3) in the forest. The geometric mean concentrations for both sites were ~1.46 μg m(-3). Wind direction, and to a lesser extent air temperature and precipitation, did influence measured concentrations. At the metropolitan site, ammonia concentrations were slightly higher in winds emanating from the direction of the interstate highway. Meteorological variables, such as wind direction, and physical factors, such as topography, can affect measurement of ambient ammonia concentrations, especially in ecosystems distant from strong emission sources. The 12-h integrated sampling method used in this study was unable to measure frequent changes in ambient ammonia concentrations and illustrates the need for measurements with higher temporal resolution, at least ~1-2h, in a variety of diverse ecosystems to determine the behavior of atmospheric ammonia and its environmental effects.

  1. Investigation of gas exchange processes in peat bog ecosystems by means of innovative Raman gas spectroscopy.

    PubMed

    Frosch, Torsten; Keiner, Robert; Michalzik, Beate; Fischer, Bernhard; Popp, Jürgen

    2013-02-05

    Highly sensitive Raman gas spectroscopy is introduced for simultaneous real time analysis of O(2), CO(2), CH(4), and N(2) in order to elucidate the dynamics of greenhouse gases evolving from climate-sensitive ecosystems. The concentrations and fluxes of this suite of biogenic gases were quantified in the head space of a water-saturated, raised peat bog ecotron. The intact peat bog, exhibiting various degradation stages of peat and sphagnum moss, was exposed to various light regimes in order to determine important ecosystem parameters such as the maximum photosynthesis rate of the sphagnum as well as the extent of soil and plant respiration. Miniaturized Raman gas spectroscopy was proven to be an extremely versatile analytical technique that allows for onsite multigas analysis in high temporal resolution. Therefore it is an urgently needed tool for elucidation of complex biochemical processes especially in climate-sensitive ecosystems and consequently for the estimation of climate-relevant gas budgets.

  2. Comparative analysis of European wide marine ecosystem shifts: a large-scale approach for developing the basis for ecosystem-based management.

    PubMed

    Möllmann, Christian; Conversi, Alessandra; Edwards, Martin

    2011-08-23

    Abrupt and rapid ecosystem shifts (where major reorganizations of food-web and community structures occur), commonly termed regime shifts, are changes between contrasting and persisting states of ecosystem structure and function. These shifts have been increasingly reported for exploited marine ecosystems around the world from the North Pacific to the North Atlantic. Understanding the drivers and mechanisms leading to marine ecosystem shifts is crucial in developing adaptive management strategies to achieve sustainable exploitation of marine ecosystems. An international workshop on a comparative approach to analysing these marine ecosystem shifts was held at Hamburg University, Institute for Hydrobiology and Fisheries Science, Germany on 1-3 November 2010. Twenty-seven scientists from 14 countries attended the meeting, representing specialists from seven marine regions, including the Baltic Sea, the North Sea, the Barents Sea, the Black Sea, the Mediterranean Sea, the Bay of Biscay and the Scotian Shelf off the Canadian East coast. The goal of the workshop was to conduct the first large-scale comparison of marine ecosystem regime shifts across multiple regional areas, in order to support the development of ecosystem-based management strategies.

  3. Impact of inter-annual climatic variability on ecosystem carbon exchange in two grazed temperate grasslands with contrasting drainage regimes

    NASA Astrophysics Data System (ADS)

    Choncubhair, Órlaith Ní; Humphreys, James; Lanigan, Gary

    2014-05-01

    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. Predicted future warming is expected to increase productivity in temperate zones, thereby enhancing rates of terrestrial carbon sequestration. However, the susceptibility of many ecosystems, including grasslands, to extreme climatic events and inter-annual variability has been demonstrated previously. Temperature anomalies as well as modifications in the temporal pattern and quantity of precipitation alter the balance between carbon uptake and release processes and a mechanistic understanding of ecosystem response to such changes is still lacking. In the present study, the impact of extreme inter-annual variability in summer rainfall and temperature on carbon dynamics in two rotationally-grazed grasslands in Ireland was examined. The sites experience similar temperate climatic regimes but differ in soil drainage characteristics. 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. The summers of 2012 and 2013 showed contrasting climatic conditions, with summer precipitation 93% higher and 25% lower respectively than long-term means. In addition, soil temperatures were 7% lower and 11% higher than expected. Cool, wet conditions in 2012 facilitated net carbon uptake for more than ten months of the year at the poorly-drained site, however the ecosystem switched to a net source of carbon in 2013 during months with significantly reduced rainfall. In contrast, net C

  4. Ecosystem-Atmosphere Exchange of Carbon, Water and Energy over a Mixed Deciduous Forest in the Midwest

    SciTech Connect

    Danilo Dragoni; Hans Peter Schmid; C.S.B. Grimmond; J.C. Randolph; J.R. White

    2012-12-17

    During the project period we continued to conduct long-term (multi-year) measurements, analysis, and modeling of energy and mass exchange in and over a deciduous forest in the Midwestern United States, to enhance the understanding of soil-vegetation-atmosphere exchange of carbon. At the time when this report was prepared, results from nine years of measurements (1998 - 2006) of above canopy CO2 and energy fluxes at the AmeriFlux site in the Morgan-Monroe State Forest, Indiana, USA (see Table 1), were available on the Fluxnet database, and the hourly CO2 fluxes for 2007 are presented here (see Figure 1). The annual sequestration of atmospheric carbon by the forest is determined to be between 240 and 420 g C m-2 a-1 for the first ten years. These estimates are based on eddy covariance measurements above the forest, with a gap-filling scheme based on soil temperature and photosynthetically active radiation. Data gaps result from missing data or measurements that were rejected in qua)lity control (e.g., during calm nights). Complementary measurements of ecological variables (i.e. inventory method), provided an alternative method to quantify net carbon uptake by the forest, partition carbon allocation in each ecosystem components, and reduce uncertainty on annual net ecosystem productivity (NEP). Biometric datasets are available on the Fluxnext database since 1998 (with the exclusion of 2006). Analysis for year 2007 is under completion.

  5. Estimating Pan Arctic Net Ecosystem Exchange using Functional Relationships with Air temperature, Leaf Area Index and Photosynthetic Active Radiation

    NASA Astrophysics Data System (ADS)

    Mbufong, H.; Kusbach, A.; Lund, M.; Persson, A.; Christensen, T. R.; Tamstorf, M. P.; Connolly, J.

    2015-12-01

    The high variability in Arctic tundra net ecosystem exchange (NEE) of carbon (C) is often attributed to the high spatial heterogeneity of Arctic tundra. Current models of carbon exchange thus handle the Arctic as either a single or few ecosystems, responding to environmental change in the same manner. In this study, we developed and tested a simple NEE model using the Misterlich light response curve (LRC) function with photosynthetic photon flux density (PPFD) as the main driving variable. Model calibration was carried out with eddy covariance carbon dioxide data from 12 Arctic tundra sites. The model input parameters (fcsat, Rd and α) were estimated as a function of air temperature and leaf area index (LAI) and represent specific characteristics of the NEE-PPFD relationship. They describe the saturation flux, dark respiration and initial light use efficiency, respectively. While remotely sensed LAI is readily available as a MODIS Terra product (MCD15A3), air temperature was estimated from a direct relationship with MODIS land surface temperature (MOD11A2, LST). Therefore, no specific knowledge of the vegetation type is required. Preliminary results show the model captures the spatial heterogeneity of the Arctic tundra but so far, overestimates NEE on all 17 test sites which include heaths, bogs, fens, and tussock tundra vegetation. The final updated results and error assessment will be presented at the conference in December.

  6. Energy and CO2 exchanges and influencing factors in spring wheat ecosystem along the Heihe River, northwestern China

    NASA Astrophysics Data System (ADS)

    Sun, Shuchen; Shao, Ming'an; Gao, Hongbei

    2016-12-01

    Spring wheat ( Triticum aestivum Linn.) is an important crop for food security in the desert-oasis farmland in the middle reaches of the Heihe River in northwestern China. We measured fluxes using eddy covariance and meteorological parameters to explore the energy fluxes and the relationship between CO2 flux and climate change in this region during the wheat growing seasons in 2013 and 2014. The energy balance closures were 70.5% and 72.7% in the 2013 and 2014 growing season, respectively. The wheat ecosystem had distinct seasonal and diurnal dynamics of CO2 fluxes with U-shaped curves. The accumulated net ecosystemic CO2 exchanges (NEE) were -111.6 and -142.2 g C/m2 in 2013 and 2014 growing season, respectively. The ecosystem generally acted as a CO2 sink during the growing season but became a CO2 source after the wheat harvest. A correlation analysis indicated that night-time CO2 fluxes were exponentially dependent on air temperature and soil temperature at a depth of 5 cm but were not correlated with soil-water content, water-vapour pressure, or vapour-pressure deficit. CO2 flux was not correlated with the meteorological parameters during daytime. However, irrigation and precipitation, may complicate the response of CO2 fluxes to other meteorological parameters.

  7. Thermal optimality of net ecosystem exchange of carbon dioxide and underlying mechanisms

    Technology Transfer Automated Retrieval System (TEKTRAN)

    It has been well established that individual organisms can acclimate and adapt to temperature change to optimize their performance (i.e., achieve thermal optimality). However, whether ecosystems with an assembly of organisms would also undergo thermal optimization has not been examined on a broader ...

  8. Interannual responses of net ecosystem CO2 exchange and NEP of intact tallgrass prairie ecosystems to an anomalously warm year under elevated atmospheric CO2

    NASA Astrophysics Data System (ADS)

    Arnone, John; Jasoni, Richard; Coulombe, William; Verburg, Paul

    2014-05-01

    Increases in anthropogenic greenhouse gas (GHG) levels in the atmosphere continue to warm the troposphere and cause a higher frequency and intensity of extremely warm climatic events. Because the terrestrial biosphere strongly influences the fluxes of CO2, the most important GHG, to and from the atmosphere globally, quantification of the responses of these ecosystems to extremely warm years is essential to project how ecosystem process such as net ecosystem CO2 exchange (NEE) and net ecosystem productivity (NEP) will be affected, and to predict how these responses will impact atmospheric CO2 levels. Our earlier research with intact grassland ecosystems using the EcoCELL large-scale controlled environment facility under present day atmospheric CO2 concentrations demonstrated a 1-2 year lagged recovery time of NEE and NEP (with NEP= net primary productivity [NPP] minus heterotrophic respiration [Rh]) in response to exposure to an anomalously (+4° C) warm year (Arnone et al. 2008-Nature 455:383-386). This lagged effect was attributed to large reductions in NPP during the warm year and then a 1-year delayed increase in Rh followed in the next year by a recovery. Responses of NPP resulted primarily from decreases in leaf stomatal conductance and photosynthesis caused by warming-induced high vapor pressure deficits (VPDs) and drying soil in the rooting zone. Lagged responses in Rh resulted from dry surface soils occurring during the anomalously warm year followed by a recovery in soil moisture in the following year, with carbon fixed and deposited in the rhizosphere during warm year-in addition to carbon fixed and deposited in the rhizosphere during the year following-able to be decomposed in the year after the temperature extreme. Given the large modulating role that these hydrologic factors (VPD, soil moisture) played in defining responses of NEE and NEP to an extremely warm year, and the fact that elevated atmospheric CO2 concentrations can alleviate these hydrologic

  9. Differences in Net Ecosystem Exchange for an intensely managed watershed using a lumped, regional model and a mechanistic, hillslope-scale model

    NASA Astrophysics Data System (ADS)

    Wilson, C. G.; Wacha, K.; Papanicolaou, T.; Stanier, C. O.; Jamroensan, A.

    2014-12-01

    In this study, Net Ecosystem Exchange (NEE), and its components Gross Ecosystem Exchange (GEE) and Ecosystem Respiration (RESP), were compared from a lumped, regional model and a mechanistic, hillslope-scale model to determine if the effects of land management on the carbon cycle are captured by larger-scale biosphere models that determine CO2 sources and sinks. WRF-VPRM (Weather Research & Forecasting - Vegetation Photosynthesis & Respiration Model) is a regional-scale model that uses simulated downward shortwave radiation and surface temperatures, along with satellite-derived land cover indices and eddy flux tower-derived parameters to estimate biosphere CO2 fluxes with empirical equations. The DAYCENT biogeochemical model coupled with the Watershed Erosion Prediction Project model (WEPP), which simulates changes in soil carbon stocks due to different land management and the resulting enhanced erosion, can also quantify biosphere CO2 fluxes. Both models (i.e., WRF-VPRM and WEPP-DAYCENT) were used to quantify GEE, RESP, and NEE for the summer of 2008 in the IML-CZO Clear Creek watershed of the U.S. Midwest to examine the role of land management heterogeneity in CO2 exchanges between the biosphere and atmosphere. Comparing average daily GEE rates from WRF-VPRM (-11.0 ± 5.2 g C/m2/d) with WEPP-DAYCENT average values weighted per land use area in the watershed (-10.2 ± 1.5 g C/m2/d) showed no significant differences (t-test; p=0.08). In contrast, daily RESP values were different between the two models. Daily respiration rates were relatively constant for WRF-VPRM (6.0 ± 0.8 g C/m2/d), while WEPP-DAYCENT values for each management practice were significantly greater (7.2 ± 1.8 g C/m2/d; t-test, p<0.001) with the land uses experiencing tillage having the widest ranges. WEPP-DAYCENT accounts for the effects of land management and net erosion/deposition on total SOC stocks and tillage impacts on respiration by increasing decomposition from the breaking of soil

  10. Comparing Acquisition of Exchange-Based and Signed Mands With Children With Autism

    PubMed Central

    Barlow, Kathryn E.; Tiger, Jeffrey H.; Slocum, Sarah K.; Miller, Sarah J.

    2013-01-01

    Therapists and educators frequently teach alternative-communication systems, such as picture exchanges or manual signs, to individuals with developmental disabilities who present with expressive language deficits. Michael (1985) recommended a taxonomy for alternative communication systems that differentiated between selection-based systems in which each response is topographically identical (e.g., card selection and exchange systems) and topography-based systems in which each response is topographically distinct (e.g., signed language). We compared the efficiency of training picture exchanges and signs with 3 participants who presented with severe language deficits; all participants acquired the picture-exchange responses more readily. PMID:23814367

  11. The Development of Community-Based Health Information Exchanges: A Comparative Assessment of Organizational Models

    ERIC Educational Resources Information Center

    Champagne, Tiffany

    2013-01-01

    The purpose of this dissertation research was to critically examine the development of community-based health information exchanges (HIEs) and to comparatively analyze the various models of exchanges in operation today nationally. Specifically this research sought to better understand several aspects of HIE: policy influences, organizational…

  12. Comparing the performance of two ecosystem models in the North Atlantic

    NASA Astrophysics Data System (ADS)

    Daewel, Ute; Samuelsen, Annette

    2015-04-01

    Comparing different biogeochemical models allows for understanding process interactions within model formulations and hence constitutes a good starting point for advanced model development. But 3d biogeochemical models are combinations of coupled modules, representing different aspects of the ecosystem (i.e. physics, ecosystem dynamics, carbon chemistry), and a set of different forcing fields. This creates difficulties in understanding the results from inter-model comparison studies as differences between model results might either stem from each of the modules or from the choice of the forcing fields. Here we present an inter-model comparison study for the North Atlantic ecosystem using two different NPZD type ecosystem models (NORWECOM and ECOSMO) solved in exactly the same physical setup. This approach allows disentangling differences and uncertainties caused by the chosen NPZD model and better understanding the choice of model formulation and parameterisation. Both models were coupled to a North Atlantic version of HYCOM (HYbrid Coordinate Ocean model) forced by the ERA-interim atmospheric reanalysis. ECOSMO is a model originally developed for the North Sea and Baltic Sea ecosystem that has previously been successfully applied to the Barents Sea ecosystem. It resolves 15 state variables including nitrate, ammonia, phosphate, silicate, oxygen, 2 types of phytoplankton, diatoms and flagellates, and 2 types of zooplankton, divided in functional groups based on their feeding preferences, DOM, detritus, opal and 3 types of sediments. This version of NORWECOM in contrast has earlier been used to simulate the North Atlantic ecosystem. It contains 11 state variables including nitrate, phosphate, silicate, oxygen, diatoms and flagellates, 2 size classes of zooplankton, 2 types of detritus, and opal. The aim of the study is to understand the relevance of different model formulation and parameterisations for the solution of the model system and to use this information to

  13. Response of net ecosystem CO2 exchange and evapotranspiration of boreal forest ecosystems to projected future climate changes: results of a modeling study

    NASA Astrophysics Data System (ADS)

    Olchev, Alexander; Kurbatova, Julia

    2014-05-01

    It is presented the modeling results describing the possible response of net ecosystem exchange of CO2 (NEE), gross (GPP) and net (NPP) primary production, as well as evapotranspiration (ET) of spruce forest ecosystems situated at central part of European part of Russia at the southern boundary of boreal forest community to projected future changes of climatic conditions and forest species composition. A process-based MixFor-SVAT model (Olchev et al 2002, 2008, 2009) has been used to describe the CO2 and H2O fluxes under present and projected future climate conditions. The main advantage of MixFor-SVAT is its ability not only to describe seasonal and daily dynamics of total CO2 and H2O fluxes at an ecosystem level, but also to adequately estimate the contributions of soil, forest understorey, and various tree species in overstorey into total ecosystem fluxes taking into account their individual responses to changes in environmental conditions as well as the differences in structure and biophysical properties. Results of modeling experiments showed that projected changes of climate conditions (moderate scenario A1B IPCC) and forest species composition at the end of 21 century can lead to small increase of annual evapotranspiration as well as to growth of NEE, GPP and NPP of the forests in case if the projected increase in temperature and elevated CO2 in the atmosphere in future will be strictly balanced with growth of available nutrients and water in plant and soil. It is obvious that any deficit of e.g. nitrogen in leaves (due to reduced transpiration, nitrogen availability in soil, etc.) may lead to decreases in the photosynthesis and respiration rates of trees and, as a consequence, to decreases in the GPP and NEE of entire forest ecosystem. Conducted modeling experiments have demonstrated that a 20% reduction of available nitrogen in tree leaves in a monospesific spruce forest stand may result in a 14% decrease in NEE, a 8% decrease in NPP, and a 4% decrease in

  14. Ecosystem Warming Affects Vertical Distribution of Leaf Gas Exchange Properties and Water Relations of Spring Wheat

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The vertical distribution of gas exchange and water relations responses to full-season in situ infrared (IR) warming were evaluated for hard red spring wheat (Triticum aestivum L. cv. Yecora Rojo) grown in an open field in a semiarid desert region of the Southwest USA. A Temperature Free-Air Contro...

  15. Effects of vegetation structure on soil carbon, nutrients and greenhouse gas exchange in a savannah ecosystem of Mount Kilimanjaro Region

    NASA Astrophysics Data System (ADS)

    Becker, J.

    2015-12-01

    The savannah biome is a hotspot for biodiversity and wildlife conservation in Africa and recently got in the focus of research on carbon sequestration. Savannah ecosystems are under strong pressure from climate and land-use change, especially around populous areas like the Mt. Kilimanjaro region. Savannah vegetation consists of grassland with isolated trees and is therefore characterized by high spatial variation of canopy cover, aboveground biomass and root structure. The canopy structure is a major regulator for soil ecological parameters and soil-atmospheric trace gas exchange (CO2, N2O, CH4) in water limited environments. The spatial distribution of these parameters and the connection between above and belowground processes are important to understand and predict ecosystem changes and estimate its vulnerability. Our objective was to determine spatial trends and changes of soil parameters and relate their variability to the vegetation structure. We chose three trees from each of the two most dominant species (Acacia nilotica and Balanites aegyptiaca) in our research area. For each tree, we selected transects with nine sampling points of the same relative distances to the stem. At these each sampling point a soil core was taken and separated in 0-10 cm and 10-30 cm depth. We measured soil carbon (C) and nitrogen (N) storage, microbial biomass C and N, Natural δ13C, soil respiration, available nutrients, pH, cation exchange capacity (CEC) as well as root biomass and -density, soil temperature and soil water content. Concentrations and stocks of C and N fractions, CEC and K+ decreased up to 50% outside the crown covered area. Microbial C:N ratio and CO2 efflux was about 30% higher outside the crown. This indicates N limitation and low C use efficiency in soil outside the crown area. We conclude that the spatial structure of aboveground biomass in savanna ecosystems leads to a spatial variance in nutrient limitation. Therefore, the capability of a savanna ecosystem

  16. Environment and phenology: CO2 net ecosystem exchange and CO2 flux partitioning at an acid and oligotrophic mire system in northern Sweden

    NASA Astrophysics Data System (ADS)

    Gažovič, Michal; Peichl, Matthias; Vermeij, Ilse; Limpens, Juul; Nilsson, Mats. B.

    2015-04-01

    Static chamber and environmental measurements in combination with vegetation indices (i.e. vascular green area (VGA) and the greenness chromatic color index (gcc) derived from digital camera images) were used to investigate effects of environment and phenology on the CO2 net ecosystem exchange (NEE) and CO2 flux partitioning at the Degerö Stormyr site in northern Sweden (64°11' 23.565" N, 19°33' 55.291 E) during two environmentally different years. Our measurement design included a control plot, a moss plot (where vascular plants were removed by clipping) and four heterotrophic respiration (RH) collars (where all green moss and vascular plant biomass were removed) to partition between soil heterotrophic and plant autotrophic (moss and vascular plants) respiration (RA), as well as between moss and vascular plant gross primary production (GPP). Environmental conditions, especially the shallow snow cover, peat soil frost and cold spring in 2014 caused delayed onset of spring green up, reduced soil respiration flux and reduced GPP of vascular plants. Soil temperature measured in 26 cm depth started to rise from spring temperatures of ~ 0.6 °C in 2013 and 0.15 °C in 2014 about 20 days earlier in 2013 compared to 2014. With earlier onset of the growing season and higher soil temperatures in 2013, heterotrophic soil respiration was higher in year 2013 than in year 2014. In 2013, RH dominated the total ecosystem respiration in all months but June and August. On contrary, autotrophic respiration dominated ecosystem respiration in all months of 2014. In both years, vascular plants and mosses were more or less equally contributing to autotrophic respiration. We measured higher GPP in year 2013 compared to year 2014. Also VGA and gcc were higher in spring and throughout the rest of 2013 compared to 2014. The onset of VGA was delayed by ~ 10 days in 2014. In general, total GPP was dominated by GPP of vascular plants in both years, although moss GPP had substantial

  17. Net ecosystem exchange of carbon dioxide and evapotranspiration response of a high elevation Rocky Mountain (Wyoming, USA) forest to a bark beetle epidemic

    NASA Astrophysics Data System (ADS)

    Frank, J. M.; Massman, W. J.; Ewers, B. E.

    2011-12-01

    Bark beetle epidemics have caused major disturbance in the forests of western North America where significant tree mortality alters the balance of ecosystem photosynthesis, carbon balance, and water exchange. In this study we investigate the change in the growing-season light-response of net ecosystem exchange of carbon dioxide (NEE) and evapotranspiration (ET) in a high elevation Rocky Mountain forest over the three years preceding and three years following a bark beetle outbreak. The GLEES AmeriFlux site (southeastern Wyoming, USA) is located in a high elevation subalpine forest dominated by Engelmann spruce (Picea engelmannii) and subalpine fir (Abies lasiocarpa) and recently experienced an epidemic of spruce beetle (Dendroctonus rufipennis). The peak beetle outbreak occurred in 2008, and has impacted 35% of the stems and 90% of the basal area of Engelmann spruce, which accounts for 30% of the trees and 70% of the basal area of the forest. Two semi-empirical light response curves for eddy-covariance carbon flux were compared, with a logistic sigmoid performing better because of residual bias than a rectangular hyperbola (Michaelis-Menten) at estimating the quantum yield of photosynthesis. In the first two years after the peak beetle outbreak the original quantum yield of 0.015 mol mol-1 was reduced by 25%. By the third year it was reduced by a half, which was composed of declines of 45% in the ecosystem's responses to diffuse radiation and 60% to direct radiation. The light-saturated rate of photosynthesis decreased by 10% in the first two years post outbreak, and fell by 40% in the third year. After the peak outbreak, the cumulative NEE over the growing season was reduced by over a half from a sink of 185 gC m-2 to 80 gC m-2, and by the third year it was reduced to near zero, or carbon neutral. The change in the ET response to light was similar in all years after the peak outbreak where the slope of the response curve was decreased by 25%. This led to a

  18. Ecosystem scale VOC exchange measurements at Bosco Fontana (IT) and Hyytiälä (FI)

    NASA Astrophysics Data System (ADS)

    Schallhart, S.; Rantala, P.; Taipale, R.; Nemitz, E.; Tillmann, R.; Mentel, T. F.; Ruuskanen, T.; Rinne, J.

    2013-12-01

    The ozone production and destruction mechanisms in the troposphere depend on the abundance of NOx and volatile organic compounds (VOCs). As the latter originate not only from human activities, but to a large extent from vegetation it is important to quantify these biogenic sources as well. The VOC-fluxes were measured in Bosco Fontana forest as a part of an intensive measurement campaign of the Eclaire project, which investigates how climate change alters the threat of air pollution. Measurements were carried out at the Nature Reserve 'Bosco della Fontana' in the Po valley, Italy. The area of the forest is 198 ha and the dominanting tree species are Quercus robur (English oak), Quercus cerris (Turkey oak) and Carpinus betulus (hornbeam). The fluxes were measured on at a height of 32 metres using the eddy covariance method. A PTR-TOF (Ionicon Analytik, Austria) measured volatile organic compounds up to a mass of 300 atomic mass units. The instrument is capable of recording full spectra of VOCs in real-time with a resolution of 10 Hz. In addition to the mass spectrometer a 3D Anemometer was placed next to the inlet. Results will be presented and compared with disjunct eddy covariance measurements (Taipale et al. 2011) from a Pinus sylvestris (Scots Pine) dominated forest in Hyytiälä, Finland. The two forests are characterized by a different emission profile; the Bosco Fontana forest emits large amounts of isoprene, whereas the terpenoid emissions from Hyytiälä forest are dominated by monoterpenes. The magnitude of the emissions differs as emission from Bosco Fontana is much higher. The monoterpene emission from Bosco Fontana is likely to follow different dynamics than that from Hyytiälä as it correlates well with the radiation. This leads to the conclusion, that monoterpenes are released right after they are produced (de novo). In Hyytiälä the emissions are light and temperature dependent, which is caused by de novo and storage emissions. Pines have large

  19. Selenium and sulfur in exchange reactions: a comparative study.

    PubMed

    Steinmann, Daniel; Nauser, Thomas; Koppenol, Willem H

    2010-10-01

    Cysteamine reduces selenocystamine to form hemiselenocystamine and then cystamine. The rate constants are k(1) = 1.3 × 10(5) M(-1) s(-1); k(-1) = 2.6 × 10(7) M(-1) s(-1); k(2) = 11 M(-1) s(-1); and k(-2) = 1.4 × 10(3) M(-1) s(-1), respectively. Rate constants for reactions of cysteine/selenocystine are similar. Reaction rates of selenium as a nucleophile and as an electrophile are 2-3 and 4 orders of magnitude higher, respectively, than those of sulfur. Sulfides and selenides are comparable as leaving groups.

  20. The REFLEX project: Comparing different algorithms and implementations for the inversion of a terrestrial ecosystem model against eddy covariance data

    SciTech Connect

    Fox, Andrew; Williams, Mathew; Richardson, Andrew D.; Cameron, David; Gove, Jeffrey H.; Quaife, Tristan; Ricciuto, Daniel M; Reichstein, Markus; Tomelleri, Enrico; Trudinger, Cathy; Van Wijk, Mark T.

    2009-10-01

    We describe a model-data fusion (MDF) inter-comparison project (REFLEX), which compared various algorithms for estimating carbon (C) model parameters consistent with both measured carbon fluxes and states and a simple C model. Participants were provided with the model and with both synthetic net ecosystem exchange (NEE) ofCO2 and leaf area index (LAI) data, generated from the model with added noise, and observed NEE and LAI data from two eddy covariance sites. Participants endeavoured to estimate model parameters and states consistent with the model for all cases over the two years for which data were provided, and generate predictions for one additional year without observations. Nine participants contributed results using Metropolis algorithms, Kalman filters and a genetic algorithm. For the synthetic data case, parameter estimates compared well with the true values. The results of the analyses indicated that parameters linked directly to gross primary production (GPP) and ecosystem respiration, such as those related to foliage allocation and turnover, or temperature sensitivity of heterotrophic respiration,were best constrained and characterised. Poorly estimated parameters were those related to the allocation to and turnover of fine root/wood pools. Estimates of confidence intervals varied among algorithms, but several algorithms successfully located the true values of annual fluxes from synthetic experiments within relatively narrow 90% confidence intervals, achieving>80% success rate and mean NEE confidence intervals <110 gCm-2 year-1 for the synthetic case. Annual C flux estimates generated by participants generally agreed with gap-filling approaches using half-hourly data. The estimation of ecosystem respiration and GPP through MDF agreed well with outputs from partitioning studies using half-hourly data. Confidence limits on annual NEE increased by an average of 88% in the prediction year compared to the previous year, when data were available. Confidence

  1. Estimation of the Net Ecosystem CO2 Exchange of Chaparral Using Eddy Covariance, remote sensing and Biome-BGC

    NASA Astrophysics Data System (ADS)

    Luo, H.; Oechel, W. C.; Sims, D.; Heinsch, F.; Kimball, J.

    2003-12-01

    The chaparral ecosystem ranges from California to Arizona, USA, and into Nuevo Leon and Tamaulipas, eastern Mexico. Tower-based eddy covariance and measurements above the canopy of a young stand (10 years old) and an old stand (>100 years old) have been conducted at Sky Oaks Biological Field Station, San Diego, USA, for 5 years to quantify the seasonal and annual variation in the net ecosystem CO2 exchange (NEE) of the chaparral ecosystem. Both stands are a C sink on an annual basis. Surprisingly, and contrary to the hypothesis by Odum, the old, mature, "scenscent" stand was as large of a C sink as the young stand. The stands tended to be net sinks during the wet seasons, and net sources during the dry seasons. Seasonal changes in carbon flux reflected changes of light use efficiency and were well correlated with two remote sensing indices of leaf pigment composition (NDVI and PRI). This implied the possibility of using remote sensing to estimate ecosystem CO2 balance. Two practical tram systems with optical sensors were set within the footprint of each eddy covariance tower in the young stand and old stand at Sky Oaks. This comparison between data from the eddy tower and spectral reflectance from remote sensing presented a good correlation between CO2 flux and NDVI corrected to a constant solar angle, which indicated that remote sensing is a very promising tool for the estimation of carbon fluxes in a chaparral ecosystem. To develop methods for scaling eddy flux measurements to the surrounding region, Biome-BGC model and MODIS results were introduced into the analysis. The eddy covariance data illustrated sink NEE patterns during wet seasons and source patterns during dry seasons, while the data simulated from Biome-BGC presented a net sink pattern throughout the whole year. The GPP simulated from Biome-BGC was lower than the estimate from MODIS, and their GPP yearly patterns were also different. Peak GPP from Biome-BGC was around June, while MODIS showed the peak

  2. A multiscale and multidisciplinary investigation of ecosystem-atmosphere CO2 exchange over the rocky mountains of colorado

    USGS Publications Warehouse

    Sun, Jielun; Oncley, S.P.; Burns, Sean P.; Stephens, B.B.; Lenschow, D.H.; Campos, T.; Monson, Russell K.; Schimel, D.S.; Sacks, W.J.; De Wekker, S. F. J.; Lai, C.-T.; Lamb, B.; Ojima, D.; Ellsworth, P.Z.; Sternberg, L.S.L.; Zhong, S.; Clements, C.; Moore, D.J.P.; Anderson, D.E.; Watt, A.S.; Hu, Jiawen; Tschudi, M.; Aulenbach, S.; Allwine, E.; Coons, T.

    2010-01-01

    A field study combined with modeling investigation demonstrated that the organization of CO2 transport by mountain terrain strongly affects the regional CO2 budget. Atmospheric dynamics can lead to complicated flows generated by inhomogeneous landscapes, topography or synoptic weather systems. The field campaign conducted of a ground deployment, the Carbon in the Mountain Experiment (CME04), and an aircraft deployment of the national Center for Atmospheric Research (NCAR) C-130, the Airborne Carbon in the Mountains Experiment (ACME04) over the period of spring to fall of 2004 to cover the seasonal variation of ecosystem-atmosphere carbon exchange. The role of the mountain circulation in CO2 transport can be played over seemingly flat terrain by mesoscale flows generated by various physical processes. The three dimensional observation strategy considered can also be applied over flat terrain.

  3. Estimation of net ecosystem carbon exchange for the conterminous United States by combining MODIS and AmeriFlux data

    SciTech Connect

    Xiao, Jingfeng; Zhuang, Qianlai; Baldocchi, Dennis; Ma, Siyan; Law, Beverly E.; Richardson, Andrew D; Chen, Jiquan; Oren, Ram

    2008-10-01

    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 terrestrial biosphere and the atmosphere for regions or continents, flux tower measurements need to be extrapolated to these large areas. Here we used remotely sensed data from the Moderate Resolution Imaging Spectrometer (MODIS) instrument on board the National Aeronautics and Space Administration s (NASA) Terra satellite to scale up AmeriFlux NEE measurements to the continental scale.We first combined MODIS and AmeriFlux data for representative U.S. ecosystems to develop a predictive NEE model using a modified regression tree approach. The predictive model was trained and validated using eddy flux NEE data over the periods 2000 2004 and 2005 2006, respectively. We found that the model predicted NEE well (r = 0.73, p < 0.001). We then applied the model to the continental scale and estimated NEE for each 1 km 1 km cell across the conterminous U.S. for each 8-day interval in 2005 using spatially explicit MODIS data. The model generally captured the expected spatial and seasonal patterns of NEE as determined from measurements and the literature. Our study demonstrated that our empirical approach is effective for scaling up eddy flux NEE measurements to the continental scale and producing wall-to-wall NEE estimates across multiple biomes. Our estimates may provide an independent dataset from simulations with biogeochemical models and inverse modeling approaches for examining the spatiotemporal patterns of NEE and constraining terrestrial carbon budgets over large areas.

  4. Sensitivity analysis of a model of CO{sub 2} exchange in tundra ecosystems by the adjoint method

    SciTech Connect

    Waelbroeck, C.; Louis, J.F.

    1995-02-20

    A model of net primary production (NPP), decomposition, and nitrogen cycling in tundra ecosystems has been developed. The adjoint technique is used to study the sensitivity of the computed annual net CO{sub 2} flux to perturbations in initial conditions, climatic inputs, and model`s main parameters describing current seasonal CO{sub 2} exchange in wet sedge tundra at Barrow, Alaska. The results show that net CO{sub 2} flux is more sensitive to decomposition parameters than to NPP parameters. This underlines the fact that in nutrient-limited ecosystems, decomposition drives net CO{sub 2} exchange by controlling mineralization of main nutrients. The results also indicate that the short-term (1 year) response of wet sedge tundra to CO{sub 2}-induced warming is a significant increase in CO{sub 2} emission, creating a positive feedback to atmospheric CO{sub 2} accumulation. However, a cloudiness increase during the same year can severely alter this response and lead to either a slight decrease or a strong increase in emitted CO{sub 2}, depending on its exact timing. These results demonstrate that the adjoint method is well suited to study systems encountering regime changes, as a single run of the adjoint model provides sensitivities of the net CO{sub 2} flux to perturbations in all parameters and variables at any time of the year. Moreover, it is shown that large errors due to the presence of thresholds can be avoided by first delimiting the range of applicability of the adjoint results. 38 refs., 10 figs., 7 tabs.

  5. Estimation of Net Ecosystem Carbon Exchange for the Conterminous UnitedStates by Combining MODIS and AmeriFlux Data

    SciTech Connect

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

    2009-03-06

    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 terrestrial biosphere and the atmosphere for regions or continents, flux tower measurements need to be extrapolated to these large areas. Here we used remotely-sensed data from the Moderate Resolution Imaging Spectrometer (MODIS) instrument on board NASA's Terra satellite to scale up AmeriFlux NEE measurements to the continental scale. We first combined MODIS and AmeriFlux data for representative U.S. ecosystems to develop a predictive NEE model using a regression tree approach. The predictive model was trained and validated using NEE data over the periods 2000-2004 and 2005-2006, respectively. We found that the model predicted NEE reasonably well at the site level. We then applied the model to the continental scale and estimated NEE for each 1 km x 1 km cell across the conterminous U.S. for each 8-day period in 2005 using spatially-explicit MODIS data. The model generally captured the expected spatial and seasonal patterns of NEE. Our study demonstrated that our empirical approach is effective for scaling up eddy flux NEE measurements to the continental scale and producing wall-to-wall NEE estimates across multiple biomes. Our estimates may provide an independent dataset from simulations with biogeochemical models and inverse modeling approaches for examining the spatiotemporal patterns of NEE and constraining terrestrial carbon budgets for large areas.

  6. Estimation of net ecosystem carbon exchange for the conterminous United States by combining MODIS and AmeriFlux data

    SciTech Connect

    Xiao, Jingfeng; Zhuang, Qianlai; Baldocchi, Dennis D.; Bolstad, Paul V.; Burns, Sean P.; Chen, Jiquan; Cook, David R.; Curtis, Peter S.; Drake, Bert G.; Foster, David R.; Gu, Lianhong; Hadley, Julian L.; Hollinger, David Y.; Katul, Gabriel G.; Law, Beverly E.; Litvak, Marcy; Ma, Siyan; Martin, Timothy A.; Matamala, Roser; McNulty, Steve; Meyers, Tilden P.; Monson, Russell K.; Munger, J. William; Noormets, Asko; Oechel, Walter C.; Oren, Ram; Richardson, Andrew D.; Schmid, Hans Peter; Scott, Russell L.; Starr, Gregory; Sun, Ge; Suyker, Andrew E.; Torn, Margaret S.; Paw, Kyaw; Verma, Shashi B.; Wharton, Sonia; Wofsy, Steven C.

    2008-10-01

    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 terrestrial biosphere and the atmosphere for regions or continents, flux tower measurements need to be extrapolated to these large areas. Here we used remotely sensed data from the Moderate Resolution Imaging Spectrometer (MODIS) instrument on board the National Aeronautics and Space Administration's (NASA) Terra satellite to scale up AmeriFlux NEE measurements to the continental scale. We first combined MODIS and AmeriFlux data for representative U.S. ecosystems to develop a predictive NEE model using a modified regression tree approach. The predictive model was trained and validated using eddy flux NEE data over the periods 2000-2004 and 2005-2006, respectively. We found that the model predicted NEE well (r = 0.73, p < 0.001). We then applied the model to the continental scale and estimated NEE for each 1 km x 1 km cell across the conterminous U.S. for each 8-day interval in 2005 using spatially explicit MODIS data. The model generally captured the expected spatial and seasonal patterns of NEE as determined from measurements and the literature. Our study demonstrated that our empirical approach is effective for scaling up eddy flux NEE measurements to the continental scale and producing wall-to-wall NEE estimates across multiple biomes. Our estimates may provide an independent dataset from simulations with biogeochemical models and inverse modeling approaches for examining the spatiotemporal patterns of NEE and constraining terrestrial carbon budgets over large areas.

  7. El Niño Southern Oscillation (ENSO) enhances CO2 exchange rates in freshwater Marsh ecosystems in the Florida everglades.

    PubMed

    Malone, Sparkle L; Staudhammer, Christina L; Oberbauer, Steven F; Olivas, Paulo; Ryan, Michael G; Schedlbauer, Jessica L; Loescher, Henry W; Starr, Gregory

    2014-01-01

    This research examines the relationships between El Niño Southern Oscillation (ENSO), water level, precipitation patterns and carbon dioxide (CO2) exchange rates in the freshwater wetland ecosystems of the Florida Everglades. Data was obtained over a 5-year study period (2009-2013) from two freshwater marsh sites located in Everglades National Park that differ in hydrology. At the short-hydroperiod site (Taylor Slough; TS) and the long-hydroperiod site (Shark River Slough; SRS) fluctuations in precipitation patterns occurred with changes in ENSO phase, suggesting that extreme ENSO phases alter Everglades hydrology which is known to have a substantial influence on ecosystem carbon dynamics. Variations in both ENSO phase and annual net CO2 exchange rates co-occurred with changes in wet and dry season length and intensity. Combined with site-specific seasonality in CO2 exchanges rates, El Niño and La Niña phases magnified season intensity and CO2 exchange rates at both sites. At TS, net CO2 uptake rates were higher in the dry season, whereas SRS had greater rates of carbon sequestration during the wet season. As La Niña phases were concurrent with drought years and extended dry seasons, TS became a greater sink for CO2 on an annual basis (-11 to -110 g CO2 m-2 yr-1) compared to El Niño and neutral years (-5 to -43.5 g CO2 m-2 yr-1). SRS was a small source for CO2 annually (1.81 to 80 g CO2 m-2 yr-1) except in one exceptionally wet year that was associated with an El Niño phase (-16 g CO2 m-2 yr-1). Considering that future climate predictions suggest a higher frequency and intensity in El Niño and La Niña phases, these results indicate that changes in extreme ENSO phases will significantly alter CO2 dynamics in the Florida Everglades.

  8. El Niño Southern Oscillation (ENSO) Enhances CO2 Exchange Rates in Freshwater Marsh Ecosystems in the Florida Everglades

    PubMed Central

    Malone, Sparkle L.; Staudhammer, Christina L.; Oberbauer, Steven F.; Olivas, Paulo; Ryan, Michael G.; Schedlbauer, Jessica L.; Loescher, Henry W.; Starr, Gregory

    2014-01-01

    This research examines the relationships between El Niño Southern Oscillation (ENSO), water level, precipitation patterns and carbon dioxide (CO2) exchange rates in the freshwater wetland ecosystems of the Florida Everglades. Data was obtained over a 5-year study period (2009–2013) from two freshwater marsh sites located in Everglades National Park that differ in hydrology. At the short-hydroperiod site (Taylor Slough; TS) and the long-hydroperiod site (Shark River Slough; SRS) fluctuations in precipitation patterns occurred with changes in ENSO phase, suggesting that extreme ENSO phases alter Everglades hydrology which is known to have a substantial influence on ecosystem carbon dynamics. Variations in both ENSO phase and annual net CO2 exchange rates co-occurred with changes in wet and dry season length and intensity. Combined with site-specific seasonality in CO2 exchanges rates, El Niño and La Niña phases magnified season intensity and CO2 exchange rates at both sites. At TS, net CO2 uptake rates were higher in the dry season, whereas SRS had greater rates of carbon sequestration during the wet season. As La Niña phases were concurrent with drought years and extended dry seasons, TS became a greater sink for CO2 on an annual basis (−11 to −110 g CO2 m−2 yr−1) compared to El Niño and neutral years (−5 to −43.5 g CO2 m−2 yr−1). SRS was a small source for CO2 annually (1.81 to 80 g CO2 m−2 yr−1) except in one exceptionally wet year that was associated with an El Niño phase (−16 g CO2 m−2 yr−1). Considering that future climate predictions suggest a higher frequency and intensity in El Niño and La Niña phases, these results indicate that changes in extreme ENSO phases will significantly alter CO2 dynamics in the Florida Everglades. PMID:25521299

  9. Elevated CO(2) and temperature alter net ecosystem C exchange in a young Douglas fir mesocosm experiment.

    PubMed

    Tingey, David T; Lee, E Henry; Phillips, Donald L; Rygiewicz, Paul T; Waschmann, Ronald S; Johnson, Mark G; Olszyk, David M

    2007-11-01

    We investigated the effects of elevated CO(2) (EC) [ambient CO(2) (AC) + 190 ppm] and elevated temperature (ET) [ambient temperature (AT) + 3.6 degrees C] on net ecosystem exchange (NEE) of seedling Douglas fir (Pseudotsuga menziesii) mesocosms. As the study utilized seedlings in reconstructed soil-litter-plant systems, we anticipated greater C losses through ecosystem respiration (R(e)) than gains through gross photosynthesis (GPP), i.e. negative NEE. We hypothesized that: (1) EC would increase GPP more than R(e), resulting in NEE being less negative; and (2) ET would increase R(e) more than GPP, resulting in NEE being more negative. We also evaluated effects of CO(2) and temperature on light inhibition of dark respiration. Consistent with our hypothesis, NEE was a smaller C source in EC, not because EC increased photosynthesis but rather because of decreased respiration resulting in less C loss. Consistent with our hypothesis, NEE was more negative in ET because R(e) increased more than GPP. The light level that inhibited respiration varied seasonally with little difference among CO(2) and temperature treatments. In contrast, the degree of light inhibition of respiration was greater in AC than EC. In our system, respiration was the primary control on NEE, as EC and ET caused greater changes in respiration than photosynthesis.

  10. Modeling coupled interactions of carbon, water, and ozone exchange between terrestrial ecosystems and the atmosphere. I: model description.

    PubMed

    Nikolov, Ned; Zeller, Karl F

    2003-01-01

    A new biophysical model (FORFLUX) is presented to study the simultaneous exchange of ozone, carbon dioxide, and water vapor between terrestrial ecosystems and the atmosphere. The model mechanistically couples all major processes controlling ecosystem flows trace gases and water implementing recent concepts in plant eco-physiology, micrometeorology, and soil hydrology. FORFLUX consists of four interconnected modules-a leaf photosynthesis model, a canopy flux model, a soil heat-, water- and CO2- transport model, and a snow pack model. Photosynthesis, water-vapor flux and ozone uptake at the leaf level are computed by the LEAFC3 sub-model. The canopy module scales leaf responses to a stand level by numerical integration of the LEAFC3model over canopy leaf area index (LAI). The integration takes into account (1) radiative transfer inside the canopy, (2) variation of foliage photosynthetic capacity with canopy depth, (3) wind speed attenuation throughout the canopy, and (4) rainfall interception by foliage elements. The soil module uses principles of the diffusion theory to predict temperature and moisture dynamics within the soil column, evaporation, and CO2 efflux from soil. The effect of soil heterogeneity on field-scale fluxes is simulated employing the Bresler-Dagan stochastic concept. The accumulation and melt of snow on the ground is predicted using an explicit energy balance approach. Ozone deposition is modeled as a sum of three fluxes- ozone uptake via plant stomata, deposition to non-transpiring plant surfaces, and ozone flux into the ground. All biophysical interactions are computed hourly while model projections are made at either hourly or daily time step. FORFLUX represents a comprehensive approach to studying ozone deposition and its link to carbon and water cycles in terrestrial ecosystems.

  11. Unexpected sensitivity of the annual net ecosystem exchange to the high frequency loss corrections in a grazed grassland site in Belgium

    NASA Astrophysics Data System (ADS)

    Mamadou, Ossenatou; Gourlez de la Motte, Louis; De Ligne, Anne; Bernard, Heineisch; Aubinet, Marc

    2016-04-01

    Although widely used to measure CO2 and other gas fluxes, the eddy covariance technique still needs methodological improvements. This research focuses on the high frequency loss corrections, which are especially important when using a closed-path infrared gas analyzer. We compared three approaches to implement these corrections for CO2 fluxes and evaluated their impact on the carbon balance at the Dorinne Terrestrial Observatory (DTO), an intensively grazed grassland site in Belgium. The carbon balance at DTO is also the object of a separate analysis (Gourlez de la Motte et al., Geophysical Research Abstract, Vol. 18, EGU2016-6813-1, 2016). In the first approach, the computation of correction factors was based on the measured sensible heat cospectra ('local' cospectra), whereas the other two were based on theoretical models (Kaimal et al., 1972). The correction approaches were validated by comparing the nighttime eddy covariance CO2 fluxes corrected with each approach and in situ soil respiration measurements. We found that the local cospectra differed from the Kaimal theoretical shape, although the site could not be considered 'difficult' (i.e., fairly flat, homogeneous, low vegetation, sufficient measurement height), appearing less peaked in the inertial subrange. This difference greatly affected the correction factor, especially for night fluxes. Night fluxes measured by eddy covariance were found to be in good agreement with in situ soil respiration measurements when corrected with local cospectra and to be overestimated when corrected with Kaimal cospectra. As the difference between correction factors was larger in stable than unstable conditions, this acts as a selective systematic error and has an important impact on annual fluxes. On the basis of a 4-year average, at DTO, the errors reach 71-150 g C m-2 y-1 for net ecosystem exchange (NEE), 280-562 g C m-2 y-1 for total ecosystem respiration (TER) and 209-412 g C m-2 y-1 for gross primary productivity (GPP

  12. Regional Ecosystem Carbon Exchange in the Southern Great Plains: Measurements, Modeling, and Scaling

    NASA Astrophysics Data System (ADS)

    Torn, M. S.; Riley, W. J.; Biraud, S. C.; Fischer, M. L.; Billesbach, D. S.; Berry, J. A.

    2007-12-01

    The extremely heterogeneous landscape of the ARM (Atmospheric Radiation Measurement) Climate Research Facility (ACRF) in the U.S. Southern Great Plains is representative of the southern boundary of the NACP Midwest intensive experiment. The area is largely agricultural with vegetation cover type and status that vary on sub- kilometer scales. In this study we developed, applied, and tested a "bottom- up" approach to inferring terrestrial C exchanges at fine scales (down to 250 m). Measurements at the ACRF include a 60 m tower instrumented with eddy covariance (ECOR) systems at several heights, about 20 permanent ECOR towers, several portable ECOR systems, many atmospheric and cloud sensing systems, and regular balloon sonde and aircraft measurements. We applied the land-surface model ISOLSM (with recent modifications to the plant physiological submodel) forced with OK and KS Mesonet climate datasets and MODIS vegetation indices. A method to infer vegetation cover type using satellite data and archetypal LAI annual profiles was developed and successfully tested against USDA census data for the region. The model's net CO2 exchange estimates were calibrated and tested using eddy correlation data from the dominant surface covers. Three years spanning a substantial precipitation gradient (2003 - 2005) were then simulated. Large differences in annual regional CO2 exchanges were predicted corresponding to expected system responses to available moisture. Spatial scaling analysis from 250 m to 100 km indicated that homogenizing LAI and vegetation cover can impact annual NEE substantially, including changing the region from a predicted net CO2 source to a net sink. Further, differences in NEE associated with spatial scaling differed between years, indicating that accurate bottom-up NEE estimates in this heterogeneous region require fine-scale analysis approaches.

  13. Comparing approaches to spatially explicit ecosystem service modeling: a case study from the San Pedro River, Arizona

    USGS Publications Warehouse

    Bagstad, Kenneth J.; Semmens, Darius J.; Winthrop, Robert

    2013-01-01

    Although the number of ecosystem service modeling tools has grown in recent years, quantitative comparative studies of these tools have been lacking. In this study, we applied two leading open-source, spatially explicit ecosystem services modeling tools – Artificial Intelligence for Ecosystem Services (ARIES) and Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) – to the San Pedro River watershed in southeast Arizona, USA, and northern Sonora, Mexico. We modeled locally important services that both modeling systems could address – carbon, water, and scenic viewsheds. We then applied managerially relevant scenarios for urban growth and mesquite management to quantify ecosystem service changes. InVEST and ARIES use different modeling approaches and ecosystem services metrics; for carbon, metrics were more similar and results were more easily comparable than for viewsheds or water. However, findings demonstrate similar gains and losses of ecosystem services and conclusions when comparing effects across our scenarios. Results were more closely aligned for landscape-scale urban-growth scenarios and more divergent for a site-scale mesquite-management scenario. Follow-up studies, including testing in different geographic contexts, can improve our understanding of the strengths and weaknesses of these and other ecosystem services modeling tools as they move closer to readiness for supporting day-to-day resource management.

  14. Net ecosystem CO2 exchange measured by autochambers during the snow-covered season at a temperate peatland

    NASA Astrophysics Data System (ADS)

    Bubier, Jill; Crill, Patrick; Mosedale, Andrew

    2002-12-01

    Net ecosystem exchange of CO2 was measured at a temperate peatland in southeastern New Hampshire. Classified as a mineral-poor fen owing to deep, water-logged peats that are influenced to a limited extent by groundwater, the ecosystem is dominated by plants such as sedges (Carex spp.) and evergreen shrubs. Ten automatic chambers measured fluxes every 3 h by sampling changes in headspace concentration of CO2 from November 2000 through March 2001. The fen was covered in snow for most of this period and CO2 was emitted from the snow pack throughout the winter. The largest fluxes were associated with ground temperatures of 0°C and with declining atmospheric pressure. CO2 effluxes up to 3 µmol m-2 s-1 were recorded when the ground temperature reached the thaw point. Fluxes were lower when the ground temperature rose above 0°C, however, suggesting that the large fluxes were associated with a build up and release of stored CO2 degassing as soon as the ground thawed, or by enhanced microbial activity associated with freeze-thaw dynamics. The large number of thaw events coupled with frequent short-term releases of CO2 suggest that degassing occurred on a regular basis with changes in atmospheric pressure and/or microbial decomposition occurred beneath the snowpack. The extent of soil freezing prior to thaw was also an important factor, with colder soils yielding smaller CO2 emissions upon thaw. Although most of the observed CO2 flux was efflux from the ecosystem, occasional CO2 uptake by the ecosystem of up to 1 µmol m-2 s-1 was also observed, indicating small rates of photosynthesis even during winter. Photosynthesis occurred only when the ground temperature was >0°C. The implications for a warmer climate are unclear. If warmer winter temperatures yield less snow in the temperate region, then soils could freeze more deeply and result in lower CO

  15. Comparative diversity analysis in sandy littoral ecosystems of the western Mediterranean

    NASA Astrophysics Data System (ADS)

    Colombini, I.; Fallaci, M.; Milanesi, F.; Scapini, F.; Chelazzi, L.

    2003-10-01

    A comparative faunal analysis was carried out in sandy littoral localities differing both morphologically and in human impact. The study sites were located in the western Mediterranean basin along the coasts of Morocco, Tunisia, the Maltese Islands and Italy. These were typical beach-dune ecosystems more (Smir, Morocco; Zouara, Tunisia; Burano, Italy) or less (Ir-Ramla tat-Torri, Malta and Ir-Ramla l-Hamra, Gozo) structurally developed accordingly. Species richness was evaluated using standard trapping techniques with pitfall traps along the transects perpendicular to the shoreline. Only isopods and coleopterans were used in the analysis. In each locality, an analysis was conducted on both the beach and the dune separately, and on the entire ecosystem in the two seasons (spring and autumn). Species were studied both quantitatively and qualitatively using ecological coefficients (relative abundance) and Fisher's diversity index. To evaluate the evenness of the community, Shannon-Weaver index was calculated and compared with Brillouin index. For both indices, the maximum values were computed and were used to obtain the evenness of the community through Pielou index. In addition, Simpson's dominance index was considered. Percentages of similarities between localities were analysed in the two seasons and in total using the Renkonen index. The overall analysis showed that general trends could be found for both orders that were studied and gave indications on habitat quality. The study showed that when monitoring was carried out systematically both in space and time, arthropods could be used as important tool to assess beach health.

  16. Multiple Flux Footprints, Flux Divergences and Boundary Layer Mixing Ratios: Studies of Ecosystem-Atmosphere CO2 Exchange Using the WLEF Tall Tower.

    NASA Astrophysics Data System (ADS)

    Davis, K. J.; Bakwin, P. S.; Yi, C.; Cook, B. D.; Wang, W.; Denning, A. S.; Teclaw, R.; Isebrands, J. G.

    2001-05-01

    Long-term, tower-based measurements using the eddy-covariance method have revealed a wealth of detail about the temporal dynamics of netecosystem-atmosphere exchange (NEE) of CO2. The data also provide a measure of the annual net CO2 exchange. The area represented by these flux measurements, however, is limited, and doubts remain about possible systematic errors that may bias the annual net exchange measurements. Flux and mixing ratio measurements conducted at the WLEF tall tower as part of the Chequamegon Ecosystem-Atmosphere Study (ChEAS) allow for unique assessment of the uncertainties in NEE of CO2. The synergy between flux and mixing ratio observations shows the potential for comparing inverse and eddy-covariance methods of estimating NEE of CO2. Such comparisons may strengthen confidence in both results and begin to bridge the huge gap in spatial scales (at least 3 orders of magnitude) between continental or hemispheric scale inverse studies and kilometer-scale eddy covariance flux measurements. Data from WLEF and Willow Creek, another ChEAS tower, are used to estimate random and systematic errors in NEE of CO2. Random uncertainty in seasonal exchange rates and the annual integrated NEE, including both turbulent sampling errors and variability in enviromental conditions, is small. Systematic errors are identified by examining changes in flux as a function of atmospheric stability and wind direction, and by comparing the multiple level flux measurements on the WLEF tower. Nighttime drainage is modest but evident. Systematic horizontal advection occurs during the morning turbulence transition. The potential total systematic error appears to be larger than random uncertainty, but still modest. The total systematic error, however, is difficult to assess. It appears that the WLEF region ecosystems were a small net sink of CO2 in 1997. It is clear that the summer uptake rate at WLEF is much smaller than that at most deciduous forest sites, including the nearby

  17. Comparing the Development of Transversal Skills between Virtual and Physical Exchanges

    ERIC Educational Resources Information Center

    Van der Velden, Bart; Millner, Sophie; Van der Heijden, Casper

    2016-01-01

    This paper aims to compare the impact on the development of transversal skills, such as self-esteem, of virtual and physical exchanges. This is done by comparing the Europe on the Edge programme to the results of the Erasmus Impact Study. In doing so it fills the need that has been expressed in the telecollaboration field to study the impact of…

  18. EXCHANGE

    SciTech Connect

    Boltz, J.C.

    1992-09-01

    EXCHANGE is published monthly by the Idaho National Engineering Laboratory (INEL), a multidisciplinary facility operated for the US Department of Energy (DOE). The purpose of EXCHANGE is to inform computer users about about recent changes and innovations in both the mainframe and personal computer environments and how these changes can affect work being performed at DOE facilities.

  19. Mercury isotopes in a forested ecosystem: Implications for air-surface exchange dynamics and the global mercury cycle

    NASA Astrophysics Data System (ADS)

    Demers, Jason D.; Blum, Joel D.; Zak, Donald R.

    2013-01-01

    ABSTRACT Forests mediate the biogeochemical cycling of mercury (Hg) between the atmosphere and terrestrial ecosystems; however, there remain many gaps in our understanding of these processes. Our objectives in this study were to characterize Hg isotopic composition within forests, and use natural abundance stable Hg isotopes to track sources and reveal mechanisms underlying the cycling of Hg. We quantified the stable Hg isotopic composition of foliage, forest floor, mineral soil, precipitation, and total gaseous mercury (THg(g)) in the atmosphere and in evasion from soil, in 10-year-old aspen forests at the Rhinelander FACE experiment in northeastern Wisconsin, USA. The effect of increased atmospheric CO2 and O3 concentrations on Hg isotopic composition was small relative to differences among forest ecosystem components. Precipitation samples had δ202Hg values of -0.74 to 0.06‰ and ∆199Hg values of 0.16 to 0.82‰. Atmospheric THg(g) had δ202Hg values of 0.48 to 0.93‰ and ∆199Hg values of -0.21 to -0.15‰. Uptake of THg(g) by foliage resulted in a large (-2.89‰) shift in δ202Hg values; foliage displayed δ202Hg values of -2.53 to -1.89‰ and ∆199Hg values of -0.37 to -0.23‰. Forest floor samples had δ202Hg values of -1.88 to -1.22‰ and ∆199Hg values of -0.22 to -0.14‰. Mercury isotopes distinguished geogenic sources of Hg and atmospheric derived sources of Hg in soil, and showed that precipitation Hg only accounted for ~16% of atmospheric Hg inputs. The isotopic composition of Hg evasion from the forest floor was similar to atmospheric THg(g); however, there were systematic differences in δ202Hg values and MIF of even isotopes (∆200Hg and ∆204Hg). Mercury evasion from the forest floor may have arisen from air-surface exchange of atmospheric THg(g), but was not the emission of legacy Hg from soils, nor re-emission of wet-deposition. This implies that there was net atmospheric THg(g) deposition to the forest soils. Furthermore, MDF of

  20. Net ecosystem CO2 exchange of an invasive plant infestation: new insights on the effects of phenology and management practices on structure and functioning

    NASA Astrophysics Data System (ADS)

    Sonnentag, Oliver; Detto, Matteo; Runkle, Benjamin; Hatala, Jaclyn; Vargas, Rodrigo; Kelly, Maggi; Baldocchi, Dennis

    2010-05-01

    effects of measurement year and flowering/ mowing on the variable parameters of the non-linear responses of FA to light and FAR to air temperature. We address two specific questions with our research. First, how do year-round grazing and spring mowing affect the timing (i.e., onset) of pepperweed's key phenological phases? Second, we focus on pepperweed flowering, the spectrally most notable phenological phase. Thus we ask does the onset of flowering trigger changes in structural canopy development (i.e., z0m) and functioning (i.e., FA; FAR)? Over the summers (1 May - 30 September) of 2007 and 2009 the site was either almost neutral with respect to CO2 (-26 g C m-2 period-1 in 2007) or a moderate net CO2 source (89 g C m-2 period-1 in 2009). In contrast, the pepperweed infestation acted as a net CO2 sink (-162 g C m-2 period-1) over the summer of 2008 when the site was mowed once in May during flowering to reduce the reproductive success of pepperweed. Preliminary results show that year-round grazing inhibited the accumulation of dead stalks causing earlier pepperweed green-up. The onset of flowering had no substantial impact on z0m. In contrast, the onset of flowering significantly reduced maximum photosynthetic capacity compared to non-flowering pepperweed, resulting in reduced photosynthetic CO2 uptake. Similarly, FAR was slightly reduced in response to flowering, most likely due to the due to the close coupling of growth respiration to FA. In contrast, mowing early during flowering prevented the decrease in photosynthetic CO2 uptake and the associated decrease in FAR due to immediate pepperweed regrowth. Our study highlights the impact of invasive plants' unique ecophysiological features and applied management practices on net ecosystem CO2 exchange of infested ecosystems.

  1. Ecosystem CO2/H2O fluxes are explained by hydraulically limited gas exchange during tree mortality from spruce bark beetles

    NASA Astrophysics Data System (ADS)

    Frank, John M.; Massman, William J.; Ewers, Brent E.; Huckaby, Laurie S.; Negrón, José F.

    2014-06-01

    Disturbances are increasing globally due to anthropogenic changes in land use and climate. This study determines whether a disturbance that affects the physiology of individual trees can be used to predict the response of the ecosystem by weighing two competing hypothesis at annual time scales: (a) changes in ecosystem fluxes are proportional to observable patterns of mortality or (b) to explain ecosystem fluxes the physiology of dying trees must also be incorporated. We evaluate these hypotheses by analyzing 6 years of eddy covariance flux data collected throughout the progression of a spruce beetle (Dendroctonus rufipennis) epidemic in a Wyoming Engelmann spruce (Picea engelmannii)-subalpine fir (Abies lasiocarpa) forest and testing for changes in canopy conductance (gc), evapotranspiration (ET), and net ecosystem exchange (NEE) of CO2. We predict from these hypotheses that (a) gc, ET, and NEE all diminish (decrease in absolute magnitude) as trees die or (b) that (1) gc and ET decline as trees are attacked (hydraulic failure from beetle-associated blue-stain fungi) and (2) NEE diminishes both as trees are attacked (restricted gas exchange) and when they die. Ecosystem fluxes declined as the outbreak progressed and the epidemic was best described as two phases: (I) hydraulic failure caused restricted gc, ET (28 ± 4% decline, Bayesian posterior mean ± standard deviation), and gas exchange (NEE diminished 13 ± 6%) and (II) trees died (NEE diminished 51 ± 3% with minimal further change in ET to 36 ± 4%). These results support hypothesis b and suggest that model predictions of ecosystem fluxes following massive disturbances must be modified to account for changes in tree physiological controls and not simply observed mortality.

  2. Eddy covariance measurements of annual carbon dioxide exchange in two natural ecosystems of the northwestern Italian Alps

    NASA Astrophysics Data System (ADS)

    Galvagno, Marta; Migliavacca, Mirco; Cremonese, Edoardo; Busetto, Lorenzo; Cogliati, Sergio; Colombo, Roberto; Manca, Giovanni; Meroni, Michele; Morra di Cella, Umberto; Rossini, Micol

    2010-05-01

    In consequence of the relationship between climate change and atmospheric greenhouse gases concentrations, a prime issue of recent researches is the quantification of the carbon balance of terrestrial biomes. In the last decades an increasing number of monitoring sites has recently been implemented worldwide, with the aim to better understand and quantify how inter-annual climate fluctuations affect net carbon exchange and the length of growing season over different vegetation types, land uses and climates. Eddy covariance (EC) technique is a widespread method that provide a direct measure of net carbon dioxide exchange across the biosphere-atmosphere interface by measuring the covariance between fluctuations in vertical wind velocity and CO2 mixing ratio. Two long-term monitoring sites have been equipped in the northwest Italian Alps (Aosta Valley) with the aim of quantify the annual carbon dioxide sequestration by grassland and forest ecosystems in relation to climate change. Grasslands and European larch forests (Larix decidua, Mill.) are the most representative vegetation types of this alpine region. The grassland site, located at an elevation of 2160 m asl, has been equipped in summer 2008 in an abandoned pasture with Nardus stricta as dominant species. European larch stand is located at 2050 m asl, at a distance of ~8 km from the grassland, and measurements has started in winter 2009. Both sites have been equipped with the same eddy flux system mounted at 2.5 m and 20 m above the ground in the grassland and in the larch forest, respectively. Both sites were equipped with a basic EC system: a3D sonic anemometer and an open-path infrared gas analyser (LI-7500, LICOR Inc.). Along EC the main meteorological variables are measured (e.g. air temperature, humidity, precipitation, photosynthetically active radiation, PAR, , soil water content, snow height etc..). In order to link annual sites productivity to the growing seasons length, phenological observations are

  3. [Evaluation of remote sensing extraction methods for vegetation phenology based on flux tower net ecosystem carbon exchange data].

    PubMed

    Mou, Min-Jie; Zhu, Wen-Quan; Wang, Ling-Li; Xu, Ying-Jun; Liu, Jian-Hong

    2012-02-01

    Taking the vegetation phenological metrics derived from the net ecosystem carbon exchange (NEE) data of 72 flux towers in North America as the references, a comprehensive evaluation was conducted on the three typical classes of remote sensing extraction methods (threshold method, moving average method, and function fitting method) for vegetation phenology from the aspects of feasibility and accuracy. The results showed that the local midpoint threshold method had the highest feasibility and accuracy for extracting vegetation phenology, followed by the first derivative method based on fitted Logistic function. The feasibility and accuracy of moving average method were determined by the moving window size. As for the MODJS 16 d composited time-series normalized difference vegetation index (NDVI), the moving average method had preferable performance when the window size was set as 15. The global threshold method performed quite poor in the feasibility and accuracy. Though the values of the phenological metrics extracted by the curvature change rate method based on fitted Logistic function and the corresponding ones derived from NEE data had greater differences, there existed a strong correlation between them, indicating that the vegetation phenological metrics extracted by the curvature change rate method could reflect the real temporal and spatial variations of vegetation phenology.

  4. CO2 and CH4 exchanges between land ecosystems and the atmosphere in northern high latitudes over the 21st century

    USGS Publications Warehouse

    Zhuang, Q.; Melillo, J.M.; Sarofim, M.C.; Kicklighter, D.W.; McGuire, A.D.; Felzer, B.S.; Sokolov, A.; Prinn, R.G.; Steudler, P.A.; Hu, S.

    2006-01-01

    Terrestrial ecosystems of the northern high latitudes (above 50??N) exchange large amounts of CO2 and CH4 with the atmosphere each year. Here we use a process-based model to estimate the budget of CO 2 and CH4 of the region for current climate conditions and for future scenarios by considering effects of permafrost dynamics, CO 2 fertilization of photosynthesis and fire. We find that currently the region is a net source of carbon to the atmosphere at 276 Tg C yr -1. We project that throughout the 21st century, the region will most likely continue as a net source of carbon and the source will increase by up to 473 Tg C yr-1 by the end of the century compared to the current emissions. However our coupled carbon and climate model simulations show that these emissions will exert relatively small radiative forcing on global climate system compared to large amounts of anthropogenic emissions. Copyright 2006 by the American Geophysical Union.

  5. Seasonal and inter-annual variability of the net ecosystem CO2 exchange of a temperate mountain grassland: effects of climate and management

    PubMed Central

    Wohlfahrt, Georg; Hammerle, Albin; Haslwanter, Alois; Bahn, Michael; Tappeiner, Ulrike; Cernusca, Alexander

    2013-01-01

    The role and relative importance of climate and cutting for the seasonal and inter-annual variability of the net ecosystem CO2 (NEE) of a temperate mountain grassland was investigated. Eddy covariance CO2 flux data and associated measurements of the green area index and the major environmental driving forces acquired during 2001-2006 at the study site Neustift (Austria) were analyzed. Driven by three cutting events per year which kept the investigated grassland in a stage of vigorous growth, the seasonal variability of NEE was primarily modulated by gross primary productivity (GPP). The role of environmental parameters in modulating the seasonal variability of NEE was obscured by the strong response of GPP to changes in the amount of green area, as well as the cutting-mediated decoupling of phenological development and the seasonal course of climate drivers. None of the climate and management metrics examined was able to explain the inter-annual variability of annual NEE. This is thought to result from (1) a high covariance between GPP and ecosystem respiration (Reco) at the annual time scale which results in a comparatively small inter-annual variation of NEE, (2) compensating effects between carbon exchange during and outside the management period, and (3) changes in the biotic response to rather than the climate variables per se. GPP was more important in modulating inter-annual variations in NEE in spring and before the first and second cut, while Reco explained a larger fraction of the inter-annual variability of NEE during the remaining, in particular the post-cut, periods. PMID:24383047

  6. Comparative impacts of two major hurricane seasons on the Neuse River and western Pamlico Sound ecosystems

    PubMed Central

    Burkholder, JoAnn; Eggleston, David; Glasgow, Howard; Brownie, Cavell; Reed, Robert; Janowitz, Gerald; Posey, Martin; Melia, Greg; Kinder, Carol; Corbett, Reide; Toms, David; Alphin, Troy; Deamer, Nora; Springer, Jeffrey

    2004-01-01

    Ecosystem-level impacts of two hurricane seasons were compared several years after the storms in the largest lagoonal estuary in the U.S., the Albemarle–Pamlico Estuarine System. A segmented linear regression flow model was developed to compare mass-water transport and nutrient loadings to a major artery, the Neuse River Estuary (NRE), and to estimate mean annual versus storm-related volume delivery to the NRE and Pamlico Sound. Significantly less water volume was delivered by Hurricane Fran (1996), but massive fish kills occurred in association with severe dissolved oxygen deficits and high contaminant loadings (total nitrogen, total phosphorus, suspended solids, and fecal bacteria). The high water volume of the second hurricane season (Hurricanes Dennis, Floyd, and Irene in 1999) delivered generally comparable but more dilute contaminant loads, and no major fish kills were reported. There were no discernable long-term adverse impacts on water quality. Populations of undesirable organisms, such as toxic dinoflagellates, were displaced down-estuary to habitats less conducive for growth. The response of fisheries was species-dependent: there was no apparent impact of the hurricanes on commercial landings of bivalve molluscs or shrimp. In contrast, interacting effects of hurricane floodwaters in 1999 and intensive fishing pressure led to striking reductions in blue crabs. Overall, the data support the premise that, in shallow estuaries frequently disturbed by hurricanes, there can be relatively rapid recovery in water quality and biota, and benefit from the scouring activity of these storms. PMID:15199179

  7. Carbonyl sulfide exchange in soils for better estimates of ecosystem carbon uptake

    DOE PAGES

    Whelan, Mary E.; Hilton, Timothy W.; Berry, Joseph A.; ...

    2016-03-21

    Carbonyl sulfide (COS) measurements are one of the emerging tools to better quantify gross primary production (GPP), the largest flux in the global carbon cycle. COS is a gas with a similar structure to CO2; COS uptake is thought to be a proxy for GPP. However, soils are a potential source or sink of COS. This study presents a framework for understanding soil–COS interactions. Excluding wetlands, most of the few observations of isolated soils that have been made show small uptake of atmospheric COS. Recently, a series of studies at an agricultural site in the central United States found soilmore » COS production under hot conditions an order of magnitude greater than fluxes at other sites. To investigate the extent of this phenomenon, soils were collected from five new sites and incubated in a variety of soil moisture and temperature states. We found that soils from a desert, an oak savannah, a deciduous forest, and a rainforest exhibited small COS fluxes, behavior resembling previous studies. However, soil from an agricultural site in Illinois, >800 km away from the initial central US study site, demonstrated comparably large soil fluxes under similar conditions. These new data suggest that, for the most part, soil COS interaction is negligible compared to plant uptake of COS. We present a model that anticipates the large agricultural soil fluxes so that they may be taken into account. Furthermore, while COS air-monitoring data are consistent with the dominance of plant uptake, improved interpretation of these data should incorporate the soil flux parameterizations suggested here.« less

  8. Carbonyl sulfide exchange in soils for better estimates of ecosystem carbon uptake

    NASA Astrophysics Data System (ADS)

    Whelan, Mary E.; Hilton, Timothy W.; Berry, Joseph A.; Berkelhammer, Max; Desai, Ankur R.; Campbell, J. Elliott

    2016-03-01

    Carbonyl sulfide (COS) measurements are one of the emerging tools to better quantify gross primary production (GPP), the largest flux in the global carbon cycle. COS is a gas with a similar structure to CO2; COS uptake is thought to be a proxy for GPP. However, soils are a potential source or sink of COS. This study presents a framework for understanding soil-COS interactions. Excluding wetlands, most of the few observations of isolated soils that have been made show small uptake of atmospheric COS. Recently, a series of studies at an agricultural site in the central United States found soil COS production under hot conditions an order of magnitude greater than fluxes at other sites. To investigate the extent of this phenomenon, soils were collected from five new sites and incubated in a variety of soil moisture and temperature states. We found that soils from a desert, an oak savannah, a deciduous forest, and a rainforest exhibited small COS fluxes, behavior resembling previous studies. However, soil from an agricultural site in Illinois, > 800 km away from the initial central US study site, demonstrated comparably large soil fluxes under similar conditions. These new data suggest that, for the most part, soil COS interaction is negligible compared to plant uptake of COS. We present a model that anticipates the large agricultural soil fluxes so that they may be taken into account. While COS air-monitoring data are consistent with the dominance of plant uptake, improved interpretation of these data should incorporate the soil flux parameterizations suggested here.

  9. Carbonyl sulfide exchange in soils for better estimates of ecosystem carbon uptake

    NASA Astrophysics Data System (ADS)

    Whelan, M. E.; Hilton, T. W.; Berry, J. A.; Berkelhammer, M.; Desai, A. R.; Campbell, J. E.

    2015-08-01

    Carbonyl sulfide (COS) measurements are one of the emerging tools to better quantify gross primary production (GPP), the largest flux in the global carbon cycle. COS is a gas with a similar structure to CO2; COS uptake is thought to be a proxy for GPP. However, soils are a potential source or sink of COS. This study presents a framework for understanding soil-COS interactions. Excluding wetlands, most of the few observations of isolated soils that have been made show small uptake of atmospheric COS. Recently, a series of studies at an agricultural site in the central United States found soil COS production under hot conditions an order of magnitude greater than fluxes at other sites. To investigate the extent of this phenomenon, soils were collected from 5 new sites and incubated in a variety of soil moisture and temperature states. We found that soils from a desert, an oak savannah, a deciduous forest, and a rainforest exhibited small COS fluxes, behavior resembling previous studies. However, soil from an agricultural site in Illinois, > 800 km away from the initial central US study site, demonstrated comparably large soil fluxes under similar conditions. These new data suggest that, for the most part, soil COS interaction is negligible compared to plant uptake of COS. We present a model that anticipates the large agricultural soil fluxes so that they may be taken into account. While COS air-monitoring data are consistent with the dominance of plant uptake, improved interpretation of these data should incorporate the soil flux parameterizations suggested here.

  10. Carbonyl sulfide exchange in soils for better estimates of ecosystem carbon uptake

    SciTech Connect

    Whelan, Mary E.; Hilton, Timothy W.; Berry, Joseph A.; Berkelhammer, Max; Desai, Ankur R.; Campbell, J. Elliott

    2016-03-21

    Carbonyl sulfide (COS) measurements are one of the emerging tools to better quantify gross primary production (GPP), the largest flux in the global carbon cycle. COS is a gas with a similar structure to CO2; COS uptake is thought to be a proxy for GPP. However, soils are a potential source or sink of COS. This study presents a framework for understanding soil–COS interactions. Excluding wetlands, most of the few observations of isolated soils that have been made show small uptake of atmospheric COS. Recently, a series of studies at an agricultural site in the central United States found soil COS production under hot conditions an order of magnitude greater than fluxes at other sites. To investigate the extent of this phenomenon, soils were collected from five new sites and incubated in a variety of soil moisture and temperature states. We found that soils from a desert, an oak savannah, a deciduous forest, and a rainforest exhibited small COS fluxes, behavior resembling previous studies. However, soil from an agricultural site in Illinois, >800 km away from the initial central US study site, demonstrated comparably large soil fluxes under similar conditions. These new data suggest that, for the most part, soil COS interaction is negligible compared to plant uptake of COS. We present a model that anticipates the large agricultural soil fluxes so that they may be taken into account. Furthermore, while COS air-monitoring data are consistent with the dominance of plant uptake, improved interpretation of these data should incorporate the soil flux parameterizations suggested here.

  11. Mathematical modeling of the "plant community -soil-like substrate -gas exchange with the human" closed ecosystem

    NASA Astrophysics Data System (ADS)

    Barkhatov, Yuri; Gubanov, Vladimir; Tikhomirov, Alexander A.; Degermendzhy, Andrey G.

    A mathematical model of the "plant community -soil-like substrate -gas exchange with the human" experimental biological life support system (BLSS) has been constructed to predict its functioning and estimate feasibility of controlling it. The mathematical model consists of three compartments -two `phytotron' models (with wheat and radish) and the `mycotron' model (for mushrooms). The following components are included in the model: edible mushrooms (mushroom fruit bodies and mycelium); wheat; radish; straw (processed by mycelium); dead organic matter in the phytotron (separately for the wheat unit and for the radish unit); worms; worms' coprolites; vermicompost used as a soil-like substrate (SLS); bacterial microflora; min-eral nitrogen, phosphorus and iron; products of the system intended for humans (wheat grains, radish roots and mushroom fruit bodies); oxygen and carbon dioxide. Under continuous gas exchange, the mass exchange between the compartments occurs at the harvesting time. The conveyor character of the closed ecosystem functioning has been taken into account -the num-ber of culture age groups can be regulated (in experiments -4 and 8 age groups). The conveyor cycle duration can be regulated as well. The module is designed for the food and gas exchange requirements of 1/30 of a virtually present human. Aim of model analysis is determination of investigation direction in real experimental BLSS. The model allows doing dynamic calcu-lations of closure coefficient based on the main elements taken into account in the model and evaluating all dynamic components of the system under different conditions and modes of its operation, especially under the conditions that can hardly be created experimentally. One of the sustainability conditions can be long-duration functioning of the system under the light-ing that is far from the optimum. The mathematical model of the system can demonstrate variants of its sustainable functioning or ruin under various critical

  12. Quantification of net ecosystem exchange sampling within two mature boreal aspen stands using airborne LiDAR and a flux footprint model: Scaling to MODIS

    NASA Astrophysics Data System (ADS)

    Chasmer, L. E.; Kljun, N.; Hopkinson, C.; Petrone, R. M.; Milne, T.; Giroux, K.; Black, T. A.; Devito, K. J.; Canadian Carbon Program; Head Project

    2010-12-01

    Exchanges of CO2 and H2O are often measured by eddy covariance within relatively homogeneous ecosystems, where the spatial variability of vegetation structural characteristics and ground surface topography are relatively non-varying. Therefore, scalars transported from source/sink areas are representative of site average characteristics, regardless of wind direction and atmospheric turbulence. Despite relatively high confidence in the efficacy of measured exchanges within homogeneous ecosystems (barring meteorological and technical problems, etc.), site representativeness of the larger area may be questionable. For example, ecosystems represented by eddy covariance are often more heterogeneous than those measured. On the other hand, deployment of eddy covariance within sites containing variable land cover types may be prone to biased site averages if sampling does not represent similar landscape characteristics within the region. By combining remote sensing data, estimates of source/sink areas, and net ecosystem exchanges (NEE), vegetation and topographical characteristics associated with the frequency of sampling may be quantified. Sample frequency may then be used to classify and scale fluxes to the larger region. The following study integrates a flux footprint model parameterisation with three-dimensional characteristics of the ground, understory, and canopy measured using airborne Light Detection and Ranging (LiDAR) and NEE within two contrasting mature boreal aspen/mixed ecosystems. The objectives of the study are to 1) quantify the frequency distribution of source/sink contributions of CO2 to eddy covariance; 2) classify canopy, understory and topographical characteristics of the footprint climatology to quantify biases in NEE; 3) determine the dominance of sites (e.g. their representativeness) within the larger basin; 4) Evaluate the effectiveness of eddy covariance placement for MODIS product validation.

  13. Integration of Satellite Estimates of Daily Inundation Extent into a Land Surface Ecosystem-Atmosphere Gas Exchange Model: Impacts on Methane Modeling

    NASA Astrophysics Data System (ADS)

    Galantowicz, J. F.; Wei, L. H.; Samanta, A.; Picton, J.; Zhang, B.; Lu, C.; Yang, J.; Tian, H.; Eluszkiewicz, J.; Nehrkorn, T.; Mountain, M.

    2013-12-01

    Soil moisture and the spatial extent of soil saturation, transient inundation, and wetland ecosystems are key determinants of greenhouse gas (GHG, e.g., methane) emissions from the land surface to the atmosphere. We are investigating how near-daily surface water and soil moisture observations such as those expected from NASA's planned Soil Moisture Active-Passive (SMAP) mission could be integrated into an ecosystem-atmosphere gas exchange model to improve its estimates of GHG fluxes. SMAP, to be launched in November 2014, will combine ~3-km resolution synthetic aperture radar (SAR), ~40-km-resolution L-band radiometry, and 3-day revisit period to make a novel dataset expected to provide inundation and soil moisture estimates superior to alternative methods at that temporal-spatial scale. We test the potential impact of this new data source using the Dynamic Land Surface Ecosystem Model (DLEM). DLEM quantifies regional fluxes of methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O) given atmospheric forcing data, with soil saturation as a prognostic variable. In this presentation, we discuss the results of integrating DLEM CH4 emission model products with time-varying subgrid inundation extent estimates from satellite remote sensing observations of North America. To emulate SMAP observations, we have derived a new daily inundation fraction dataset for 2008-2010 using data from NASA's Advanced Microwave Scanning Radiometer-EOS (AMSR-E). To test data-model integration, we created a testbed composed of two separate multi-year DLEM runs in which subgrid land cover conditions were artificially prescribed: one run with maximum wetlands coverage and one with no wetlands. We can combine CH4 products from the two runs using our daily inundation fraction estimates or other inundation representations such that the combination approximates CH4 flux results from a model with explicit inundation forcing. The testbed allows us to simulate a larger array of mixed-grid cases

  14. Comparative floc-bed sediment trace element partitioning across variably contaminated aquatic ecosystems.

    PubMed

    Elliott, Amy V C; Plach, Janina M; Droppo, Ian G; Warren, Lesley A

    2012-01-03

    Significantly higher concentrations of Ag, As, Cu, Ni and Co are found in floc compared to bed sediments across six variably impacted aquatic ecosystems. In contrast to the observed element and site-specific bed sediment trace element (TE) partitioning patterns, floc TE sequestration is consistently dominated by amorphous oxyhydroxides (FeOOH), which account for 30-79% of floc total TE concentrations, irrespective of system physico-chemistry or elements involved. FeOOH consistently occur in significantly higher concentrations in floc than within bed sediments. Further, comparative concentration factors indicate significantly higher TE reactivity of floc-FeOOH relative to sediment-FeOOH in all systems investigated, indicating that both the greater abundance and higher reactivity of floc-FeOOH contribute to enhanced floc TE uptake. Results indicate that floc-organics (live cells and exopolymeric substances, EPS) directly predict floc-FeOOH concentrations, suggesting an organic structural role in the collection/templating of FeOOH. This, in turn, facilitates the sequestration of TEs associated with floc-FeOOH formation, imparting the conserved FeOOH "signature" on floc TE geochemistry across sites. Results demonstrate that the organic rich nature of floc exerts an important control over TE geochemistry in aquatic environments, ultimately creating a distinct solid with differing controls over TE behavior than bed sediments in close proximity (<0.5 m).

  15. Forecasting net ecosystem CO2 exchange in a subalpine forest using model data assimilation combined with simulated climate and weather generation

    NASA Astrophysics Data System (ADS)

    Scott-Denton, Laura E.; Moore, David J. P.; Rosenbloom, Nan A.; Kittel, Timothy G. F.; Burns, Sean P.; Schimel, David S.; Monson, Russell K.

    2013-06-01

    Forecasting the carbon uptake potential of terrestrial ecosystems in the face of future climate change has proven challenging. Process models, which have been increasingly used to study ecosystem-atmosphere carbon and water exchanges when conditioned with tower-based eddy covariance data, have the potential to inform us about biogeochemical processes in future climate regimes, but only if we can reconcile the spatial and temporal scales used for observed fluxes and projected climate. Here, we used weather generator and ecosystem process models conditioned on observed weather dynamics and carbon/water fluxes, and embedded them within climate projections from a suite of six Earth Systems Models. Using this combination of models, we studied carbon cycle processes in a subalpine forest within the context of future (2080-2099) climate regimes. The assimilation of daily averaged, observed net ecosystem CO2 exchange (NEE) and evapotranspiration (ET) into the ecosystem process model resulted in retrieval of projected NEE with a level of accuracy that was similar to that following the assimilation of half-daily averaged observations; the assimilation of 30 min averaged fluxes or monthly averaged fluxes caused degradation in the model's capacity to accurately simulate seasonal patterns in observed NEE. Using daily averaged flux data with daily averaged weather data projected for the period 2080-2099, we predicted greater forest net CO2 uptake in response to a lengthening of the growing season. These results contradict our previous observations of reduced CO2 uptake in response to longer growing seasons in the current (1999-2008) climate regime. The difference between these analyses is due to a projected increase in the frequency of rain versus snow during warmer winters of the future. Our results demonstrate the sensitivity of modeled processes to local variation in meteorology, which is often left unresolved in traditional approaches to earth systems modeling, and the

  16. Effects of winter temperature and summer drought on net ecosystem exchange of CO2 in a temperate peatland

    NASA Astrophysics Data System (ADS)

    Helfter, Carole; Campbell, Claire; Dinsmore, Kerry; Drewer, Julia; Coyle, Mhairi; Anderson, Margaret; Skiba, Ute; Nemitz, Eiko; Billett, Michael; Sutton, Mark

    2014-05-01

    Northern peatlands are one of the most important global sinks of atmospheric carbon dioxide (CO2); their ability to sequester C is a natural feedback mechanism controlled by climatic variables such as precipitation, temperature, length of growing season and period of snow cover. In the UK it has been predicted that peatlands could become a net source of carbon in response to climate change with climate models predicting a rise in global temperature of ca. 3oC between 1961-1990 and 2100. Land-atmosphere exchange of CO2in peatlands exhibits marked seasonal and inter-annual variations, which have significant short- and long-term effects on carbon sink strength. Net ecosystem exchange (NEE) of CO2 has been measured continuously by eddy-covariance (EC) at Auchencorth Moss (55° 47'32 N, 3° 14'35 W, 267 m a.s.l.), a temperate peatland in central Scotland, since 2002. Auchencorth Moss is a low-lying, ombrotrophic peatland situated ca. 20 km south-west of Edinburgh. Peat depth ranges from 5 m and the site has a mean annual precipitation of 1155 mm. The vegetation present within the flux measurement footprint comprises mixed grass species, heather and substantial areas of moss species (Sphagnum spp. and Polytrichum spp.). The EC system consists of a LiCOR 7000 closed-path infrared gas analyser for the simultaneous measurement of CO2 and water vapour and of a Gill Windmaster Pro ultrasonic anemometer. Over the 10 year period, the site was a consistent yet variable sink of CO2 ranging from -34.1 to -135.9 g CO2-C m-2 yr-1 (mean of -69.1 ± 33.6 g CO2-C m-2 yr-1). Inter-annual variability in NEE was positively correlated to the length of the growing seasons and mean winter air temperature explained 93% of the variability in summertime sink strength, indicating a phenological memory-effect. Plant development and productivity were stunted by colder winters causing a net reduction in the annual carbon sink strength of this peatland where autotrophic processes are thought to be

  17. Changes in net ecosystem productivity and greenhouse gas exchange with fertilization of Douglas fir: Mathematical modeling in ecosys

    NASA Astrophysics Data System (ADS)

    Grant, R. F.; Black, T. A.; Jassal, R. S.; Bruemmer, C.

    2010-12-01

    The application of nitrogen fertilizers to Douglas fir forests is known to raise net ecosystem productivity (NEP), but also N2O emissions, the CO2 equivalent of which may offset gains in NEP when accounting for net greenhouse gas (GHG) exchange. However, total changes in NEP and N2O emissions caused by fertilizer between times of application and harvest, while needed for national GHG inventories, are difficult to quantify except through modeling. In this study, integrated hypotheses for soil and plant N processes within the ecosystem model ecosys were tested against changes in CO2 and N2O fluxes recorded with eddy covariance (EC) and surface flux chambers for 1 year after applying 20 g N m-2 of urea to a mature Douglas fir stand in British Columbia. Parameters from annual regressions of hourly modeled versus measured CO2 fluxes conducted before and after fertilization were unchanged (b = 1.0, R2 = 0.8, RMSD = 3.4 μmol m-2 s-1), indicating that model hypotheses for soil and plant N processes did not introduce bias into CO2 fluxes modeled after fertilization. These model hypotheses were then used to project changes in NEP and GHG exchange attributed to the fertilizer during the following 10 years until likely harvest of the Douglas fir stand. Increased CO2 uptake caused modeled and EC-derived annual NEP to rise from 443 and 386 g C m-2 in the year before fertilization to 591 and 547 g C m-2 in the year after. These gains contributed to a sustained rise in modeled wood C production with fertilization, which was partly offset by a decline in soil C attributed in the model to reduced root C productivity and litterfall. Gains in net CO2 uptake were further offset in the model by a rise of 0.74 g N m-2 yr-1 in N2O emissions during the first year after fertilization, which was consistent with one of 1.05 g N m-2 yr-1 estimated from surface flux chamber measurements. Further N2O emissions were neither modeled nor measured after the first year. At the end of the 11 year

  18. Calcium Carbonate Phosphate Binding Ion Exchange Filtration and Accelerated Denitrification Improve Public Health Standards and Combat Eutrophication in Aquatic Ecosystems

    PubMed Central

    Yanamadala, Vijay

    2010-01-01

    Hektoen agar. Initial analyses suggest a strong correlation between phosphate concentrations and bacterial populations; a 66% decrease in phosphate resulted in a 35% reduction in bacterial populations and a 45% reduction in enteropathogenic populations. Likewise, a strong correlation was shown between calcium carbonate concentrations and bacterial reduction greater than that which can be attributed to the phosphate reduction alone. This was followed by the construction of various phosphate binding calcium carbonate filters, which used the ion exchange principle, including a spring loading filter, PVC pipe filter, and a galvanized filter. All were tested with the aid of Stoke's law formulation. The experiment was extremely successful in designing a working phosphate-binding and ammonia-reducing filter, and a large-scale agitator-clarifier filter system is currently being planned for construction in Madrona Marsh; this filter will reduce phosphate and ammonia levels substantially in the following years, bringing ecological, economical, and health-related improvements to the overall ecosystem and habitat. PMID:16381147

  19. Biodiversity mediates top-down control in eelgrass ecosystems: a global comparative-experimental approach.

    PubMed

    Duffy, J Emmett; Reynolds, Pamela L; Boström, Christoffer; Coyer, James A; Cusson, Mathieu; Donadi, Serena; Douglass, James G; Eklöf, Johan S; Engelen, Aschwin H; Eriksson, Britas Klemens; Fredriksen, Stein; Gamfeldt, Lars; Gustafsson, Camilla; Hoarau, Galice; Hori, Masakazu; Hovel, Kevin; Iken, Katrin; Lefcheck, Jonathan S; Moksnes, Per-Olav; Nakaoka, Masahiro; O'Connor, Mary I; Olsen, Jeanine L; Richardson, J Paul; Ruesink, Jennifer L; Sotka, Erik E; Thormar, Jonas; Whalen, Matthew A; Stachowicz, John J

    2015-07-01

    Nutrient pollution and reduced grazing each can stimulate algal blooms as shown by numerous experiments. But because experiments rarely incorporate natural variation in environmental factors and biodiversity, conditions determining the relative strength of bottom-up and top-down forcing remain unresolved. We factorially added nutrients and reduced grazing at 15 sites across the range of the marine foundation species eelgrass (Zostera marina) to quantify how top-down and bottom-up control interact with natural gradients in biodiversity and environmental forcing. Experiments confirmed modest top-down control of algae, whereas fertilisation had no general effect. Unexpectedly, grazer and algal biomass were better predicted by cross-site variation in grazer and eelgrass diversity than by global environmental gradients. Moreover, these large-scale patterns corresponded strikingly with prior small-scale experiments. Our results link global and local evidence that biodiversity and top-down control strongly influence functioning of threatened seagrass ecosystems, and suggest that biodiversity is comparably important to global change stressors.

  20. From carbon numbers to ecosystem services: usable results comparing natural versus managed lands

    NASA Astrophysics Data System (ADS)

    Bachelet, D. M.; Ferschweiler, K.; Sheehan, T.; Sleeter, B. M.; Zhu, Z.

    2015-12-01

    We ran the MC2 dynamic vegetation model for the conterminous US at 30 arc sec with and without land use and fire suppression for several climate change scenarios. We translated model results into key ecosystem services (ES) such as climate regulation through carbon uptake and sequestration (global climate) or through transpiration (regional climate) as well as water provision through runoff and throughflow. We also projected timber production and gauged the risk of production lost to fire and/or drought by simulating fuel loads and forest vigor annually through the 21st century. We calculated the rising irrigation demand for agricultural land which, coupled with available information on groundwater resources, could help plan for future cropping systems. By combining these results we can evaluate land cover value across the country in terms of quantity and quality of services rendered. By comparing projections with and without landuse and fire suppression we can illustrate differences in regulating and provisioning services between managed and natural lands.

  1. Determination of The Carbon and Water Vapour Net Ecosystem Exchange Rates In The Swiss Pre-alps - A Contribution To The Carbomont Project

    NASA Astrophysics Data System (ADS)

    Furger, M.; Siegwolf, R. T. W.; Eugster, W.

    A major objective of the Carbomont project is the analysis of the source/sink re- lationship of various biogenic and anthropogenic species in European mountainous ecosystems. PSI contributes to these studies with two sub-projects. The first one de- termines the carbon and water vapour net ecosystem exchange (NEE) rates of selected ecosystem segments, while the other one investigates the partitioning of the NEE into its carbon dioxide source and sink components. The NEE will be determined with eddy covariance (EC) methods for two different ecosystems (abandoned versus in- tensively managed pasture) and shall provide information on their long-term carbon source or sink relation. By analysing the stable isotope 13C/12C and 18O/16O ratio in the carbon dioxide from the soil, the canopy, and the atmosphere above the canopy, the ecosystem carbon dioxide flux can be quantitatively partitioned. In combination with the EC method, the sink and source strength of different flux components can be quantified. The field measurements will take place in Seebodenalp in Central Switzer- land. The site is located at an altitude of about 1000 m above sea level. Measurements are planned for the growing seasons of 2002, 2003 and 2004.

  2. Soil warming effect on net ecosystem exchange of carbon dioxide during the transition from winter carbon source to spring carbon sink in a temperate urban lawn.

    PubMed

    Zhou, Xiaoping; Wang, Xiaoke; Tong, Lei; Zhang, Hongxing; Lu, Fei; Zheng, Feixiang; Hou, Peiqiang; Song, Wenzhi; Ouyang, Zhiyun

    2012-01-01

    The significant warming in urban environment caused by the combined effects of global warming and heat island has stimulated widely development of urban vegetations. However, it is less known of the climate feedback of urban lawn in warmed environment. Soil warming effect on net ecosystem exchange (NEE) of carbon dioxide during the transition period from winter to spring was investigated in a temperate urban lawn in Beijing, China. The NEE (negative for uptake) under soil warming treatment (temperature was about 5 degrees C higher than the ambient treatment as a control) was -0.71 micromol/(m2 x sec), the ecosytem was a CO2 sink under soil warming treatment, the lawn ecosystem under the control was a CO2 source (0.13 micromol/(m2 x sec)), indicating that the lawn ecosystem would provide a negative feedback to global warming. There was no significant effect of soil warming on nocturnal NEE (i.e., ecosystem respiration), although the soil temperature sensitivity (Q10) of ecosystem respiration under soil warming treatment was 3.86, much lower than that in the control (7.03). The CO2 uptake was significantly increased by soil warming treatment that was attributed to about 100% increase of alpha (apparent quantum yield) and Amax (maximum rate of photosynthesis). Our results indicated that the response of photosynthesis in urban lawn is much more sensitive to global warming than respiration in the transition period.

  3. Two years with extreme and little snowfall: effects on energy partitioning and surface energy exchange in a high-Arctic tundra ecosystem

    NASA Astrophysics Data System (ADS)

    Stiegler, Christian; Lund, Magnus; Røjle Christensen, Torben; Mastepanov, Mikhail; Lindroth, Anders

    2016-07-01

    Snow cover is one of the key factors controlling Arctic ecosystem functioning and productivity. In this study we assess the impact of strong variability in snow accumulation during 2 subsequent years (2013-2014) on the land-atmosphere interactions and surface energy exchange in two high-Arctic tundra ecosystems (wet fen and dry heath) in Zackenberg, Northeast Greenland. We observed that record-low snow cover during the winter 2012/2013 resulted in a strong response of the heath ecosystem towards low evaporative capacity and substantial surface heat loss by sensible heat fluxes (H) during the subsequent snowmelt period and growing season. Above-average snow accumulation during the winter 2013/2014 promoted summertime ground heat fluxes (G) and latent heat fluxes (LE) at the cost of H. At the fen ecosystem a more muted response of LE, H and G was observed in response to the variability in snow accumulation. Overall, the differences in flux partitioning and in the length of the snowmelt periods and growing seasons during the 2 years had a strong impact on the total accumulation of the surface energy balance components. We suggest that in a changing climate with higher temperature and more precipitation the surface energy balance of this high-Arctic tundra ecosystem may experience a further increase in the variability of energy accumulation, partitioning and redistribution.

  4. Comparing Measures of Estuarine Ecosystem Production in a Temperate New England Estuary

    EPA Science Inventory

    Anthropogenic nutrient enrichments and concerted efforts at nutrient reductions, compounded with the influences of climate change, are likely changing the net ecosystem production (NEP) of our coastal systems. To quantify these changes, scientists monitor a range of physical, che...

  5. Old and Not-So-Old: Examining Changes in Forest Ecosystem Carbon Exchange With Stand Age in the Upper Midwest U.S.

    NASA Astrophysics Data System (ADS)

    Desai, A. R.; Cook, B.; Davis, K. J.; Bolstad, P.; Carey, E.; Martin, J.; Kreller, L.; Wang, W.

    2003-12-01

    Forest stand age is an important determinant of ecosystem carbon uptake. Though there are biometric measurements and ecological models for forests of all ages, there are few stand-scale eddy-flux measurements of net carbon exchange in older forests, though the number is increasing. In order to scale carbon fluxes from sites to regions, where stands of multiple ages may exist, it is necessary to measure to the effect of stand age on carbon exchange. Measuring the effect of stand age on carbon exchange is also necessary when trying to predict future or past carbon exchange (scaling across time). Many researchers have noted that site disturbance history is the fundamental factor in determining carbon uptake by forests over time scales of decades to centuries. The 8,500 ha Sylvania Wilderness in the upper peninsula of Michigan is one of several large tracts of old-growth forest in the Midwest. Trees range from 0-350 years old. Primary species are sugar maple, eastern hemlock and yellow birch. Catastrophic disturbance is rare. A research plot near the wilderness was established in late 2001 to measure the net ecosystem exchange (NEE) of carbon and water using eddy-flux, component flux and biometric methods. This site is part of the Chequamegon Ecosystem Atmosphere Study (ChEAS, http://cheas.psu.edu), a loose affiliation of researchers conducting carbon and water research in northern Wisconsin and upper Michigan. Another similar research plot within ChEAS and not far from Sylvania is the Willow Creek mature uplands site. This forest is about 70 years old and the primary species are sugar maple, basswood and green ash. The site had presettlement old-growth vegetation similar to what is currently seen in the Sylvania Wilderness. Thus, the carbon exchange seen at Sylvania may be representative of carbon uptake at Willow Creek had it not been logged in the early 20th century, and may also represent the future (or past) carbon uptake for similar forests in northern Wisconsin

  6. Comparing bioenergy production sites in the Southeastern US regarding ecosystem service supply and demand.

    PubMed

    Meyer, Markus A; Chand, Tanzila; Priess, Joerg A

    2015-01-01

    Biomass for bioenergy is debated for its potential synergies or tradeoffs with other provisioning and regulating ecosystem services (ESS). This biomass may originate from different production systems and may be purposefully grown or obtained from residues. Increased concerns globally about the sustainable production of biomass for bioenergy has resulted in numerous certification schemes focusing on best management practices, mostly operating at the plot/field scale. In this study, we compare the ESS of two watersheds in the southeastern US. We show the ESS tradeoffs and synergies of plantation forestry, i.e., pine poles, and agricultural production, i.e., wheat straw and corn stover, with the counterfactual natural or semi-natural forest in both watersheds. The plantation forestry showed less distinct tradeoffs than did corn and wheat production, i.e., for carbon storage, P and sediment retention, groundwater recharge, and biodiversity. Using indicators of landscape composition and configuration, we showed that landscape planning can affect the overall ESS supply and can partly determine if locally set environmental thresholds are being met. Indicators on landscape composition, configuration and naturalness explained more than 30% of the variation in ESS supply. Landscape elements such as largely connected forest patches or more complex agricultural patches, e.g., mosaics with shrub and grassland patches, may enhance ESS supply in both of the bioenergy production systems. If tradeoffs between biomass production and other ESS are not addressed by landscape planning, it may be reasonable to include rules in certification schemes that require, e.g., the connectivity of natural or semi-natural forest patches in plantation forestry or semi-natural landscape elements in agricultural production systems. Integrating indicators on landscape configuration and composition into certification schemes is particularly relevant considering that certification schemes are governance

  7. Comparing Bioenergy Production Sites in the Southeastern US Regarding Ecosystem Service Supply and Demand

    PubMed Central

    Meyer, Markus A.; Chand, Tanzila; Priess, Joerg A.

    2015-01-01

    Biomass for bioenergy is debated for its potential synergies or tradeoffs with other provisioning and regulating ecosystem services (ESS). This biomass may originate from different production systems and may be purposefully grown or obtained from residues. Increased concerns globally about the sustainable production of biomass for bioenergy has resulted in numerous certification schemes focusing on best management practices, mostly operating at the plot/field scale. In this study, we compare the ESS of two watersheds in the southeastern US. We show the ESS tradeoffs and synergies of plantation forestry, i.e., pine poles, and agricultural production, i.e., wheat straw and corn stover, with the counterfactual natural or semi-natural forest in both watersheds. The plantation forestry showed less distinct tradeoffs than did corn and wheat production, i.e., for carbon storage, P and sediment retention, groundwater recharge, and biodiversity. Using indicators of landscape composition and configuration, we showed that landscape planning can affect the overall ESS supply and can partly determine if locally set environmental thresholds are being met. Indicators on landscape composition, configuration and naturalness explained more than 30% of the variation in ESS supply. Landscape elements such as largely connected forest patches or more complex agricultural patches, e.g., mosaics with shrub and grassland patches, may enhance ESS supply in both of the bioenergy production systems. If tradeoffs between biomass production and other ESS are not addressed by landscape planning, it may be reasonable to include rules in certification schemes that require, e.g., the connectivity of natural or semi-natural forest patches in plantation forestry or semi-natural landscape elements in agricultural production systems. Integrating indicators on landscape configuration and composition into certification schemes is particularly relevant considering that certification schemes are

  8. Disentangling the confounding effects of PAR and air temperature on net ecosystem exchange in time and scale

    NASA Astrophysics Data System (ADS)

    yang, Z.; Chen, J.; Becker, R.; Chu, H.; Xie, J.; Shao, C.

    2013-12-01

    Net ecosystem exchange of CO2 (NEE) in temperate forests is modulated by microclimatic factors. The effects of those factors differ at different time scales and during different time periods. Some of them are correlated across a number of time scales, so their effects on NEE are confounded by each other. PAR and air temperature (Ta) are among the two most important drivers of NEE in temperate forests, and among the two most correlated microclimatic factors. PAR and Ta have similar daily, seasonal, and annual cycles. Their influence on NEE is confounded by each other and entangled together especially at those scales. In this study, we tried to disentangle the confounding effects of them on NEE at different time scales and during different time periods. To accomplish this objective, we applied the innovative spectral analysis techniques including Continuous Wavelet Transformation (CWT), Cross Wavelet Transformation (XWT), Wavelet Coherent (WTC), and Partial Wavelet Coherence (PWC) on seven years time series (2004-2010) of PAR, Ta and NEE from the Ohio Oak Openings site (N 41.5545°, W 83.8438°), USA for spectral analysis. We found that PAR is the major driver at short time scales (e.g. semidiurnal and daily) and Ta is the major driver at long time scales (e.g. seasonal and annual). At daily scale during growing seasons, PAR is anti-phase with NEE with no time delay while Ta lagged PAR about 2-3 hours, which could be explained by the strong dependence of photosynthesis on PAR and a 2-3 hours lags of the daily course of Ta to PAR. At daily scale during non-growing season, NEE has little variation and thus neither Ta nor PAR has high common wavelet power and significant coherence with NEE. At annual scale, Ta is anti-phase with NEE and PAR leads NEE about 34 days, which could be explained by the strong dependence of LAI dynamics on Ta and the lag between the LAI/biomass development and the progress of sunlight. We also found that NEE distributes most of its variation

  9. Warmer temperatures stimulate respiration and reduce net ecosystem productivity in a northern Great Plains grassland: Analysis of CO2 exchange in automatic chambers

    NASA Astrophysics Data System (ADS)

    Flanagan, L. B.

    2013-12-01

    The interacting effects of altered temperature and precipitation are expected to have significant consequences for ecosystem net carbon storage. Here I report the results of an experiment that evaluated the effects of elevated temperature and altered precipitation on ecosystem CO2 exchange in a northern Great Plains grassland, near Lethbridge, Alberta Canada. Open-top chambers were used to establish an experiment in 2012 with three treatments (control, warmed, warmed plus 50% of normal precipitation input). A smaller experiment with only the two temperature treatments (control and warmed) was conducted in 2013. Continuous half-hourly net CO2 exchange measurements were made using nine automatic chambers during May-October in both years. My objectives were to determine the sensitivity of the ecosystem carbon budget to temperature and moisture manipulations, and to test for direct and indirect effects of the environmental changes on ecosystem CO2 exchange. The experimental manipulations resulted primarily in a significant increase in air temperature in the warmed treatment plots. A cumulative net loss of carbon or negative net ecosystem productivity (NEP) occurred during May through September in the warmed treatment (NEP = -659 g C m-2), while in the control treatment there was a cumulative net gain of carbon (NEP = +50 g C m-2). An eddy covariance system that operated at the site, over a footprint region that was not influenced by the experimental treatments, also showed a net gain of carbon by the ecosystem. The reduced NEP was due to higher plant and soil respiration rates in the warmed treatment that appeared to be caused by a combination of: (i) higher carbon substrate availability indirectly stimulating soil respiration in the warmed relative to the control treatment, and (ii) a strong increase in leaf respiration likely caused by a shift in electron partitioning to the alternative pathway respiration in the warmed treatment, particularly when exposed to high

  10. Comparing marine and terrestrial ecosystems: Implications for the design of coastal marine reserves

    USGS Publications Warehouse

    Carr, M.H.; Neigel, J.E.; Estes, J.A.; Andelman, S.; Warner, R.R.; Largier, J. L.

    2003-01-01

    Concepts and theory for the design and application of terrestrial reserves is based on our understanding of environmental, ecological, and evolutionary processes responsible for biological diversity and sustainability of terrestrial ecosystems and how humans have influenced these processes. How well this terrestrial-based theory can be applied toward the design and application of reserves in the coastal marine environment depends, in part, on the degree of similarity between these systems. Several marked differences in ecological and evolutionary processes exist between marine and terrestrial ecosystems as ramifications of fundamental differences in their physical environments (i.e., the relative prevalence of air and water) and contemporary patterns of human impacts. Most notably, the great extent and rate of dispersal of nutrients, materials, holoplanktonic organisms, and reproductive propagules of benthic organisms expand scales of connectivity among near-shore communities and ecosystems. Consequently, the "openness" of marine populations, communities, and ecosystems probably has marked influences on their spatial, genetic, and trophic structures and dynamics in ways experienced by only some terrestrial species. Such differences appear to be particularly significant for the kinds of organisms most exploited and targeted for protection in coastal marine ecosystems (fishes and macroinvertebrates). These and other differences imply some unique design criteria and application of reserves in the marine environment. In explaining the implications of these differences for marine reserve design and application, we identify many of the environmental and ecological processes and design criteria necessary for consideration in the development of the analytical approaches developed elsewhere in this Special Issue.

  11. Mechanistic insights on the responses of plant and ecosystem gas exchange to global environmental change: lessons from Biosphere 2.

    PubMed

    Gonzalez-Meler, Miquel A; Rucks, Jessica S; Aubanell, Gerard

    2014-09-01

    Scaling up leaf processes to canopy/ecosystem level fluxes is critical for examining feedbacks between vegetation and climate. Collectively, studies from Biosphere 2 Laboratory have provided important insight of leaf-to-ecosystem investigations of multiple environmental parameters that were not before possible in enclosed or field studies. B2L has been a testing lab for the applicability of new technologies such as spectral approaches to detect spatial and temporal changes in photosynthesis within canopies, or for the development of cavity ring-down isotope applications for ecosystem evapotranspiration. Short and long term changes in atmospheric CO2, drought or temperature allowed for intensive investigation of the interactions between photosynthesis and leaf, soil and ecosystem respiration. Experiments conducted in the rainforest biome have provided some of the most comprehensive dataset to date on the effects of climate change variables on tropical ecosystems. Results from these studies have been later corroborated in natural rainforest ecosystems and have improved the predictive capabilities of models that now show increased resilience of tropics to climate change. Studies of temperature and CO2 effects on ecosystem respiration and its leaf and soil components have helped reconsider the use of simple first-order kinetics for characterizing respiration in models. The B2L also provided opportunities to quantify the rhizosphere priming effect, or establish the relationships between net primary productivity, atmospheric CO2 and isoprene emissions.

  12. Ecosystem modeling of coastal acidification and hypoxia and structural uncertainties in the representation of sediment-water exchanges

    EPA Science Inventory

    Numerical ecosystem models of coastal acidification (CA) and hypoxia have been developed to synthesize current scientific understanding and provide predictions for nutrient management and policy. However, there is not a scientific consensus about the structure of these models an...

  13. Hydrological Controls on Ecosystem CO2 and CH4 Exchange in a MIXED Tundra and a FEN within an Arctic Landscape UNDER Current and Future Climates

    NASA Astrophysics Data System (ADS)

    Grant, R. F.; Humphreys, E.; Lafleur, P.

    2014-12-01

    Variation in CO2 and CH4 exchange in years with contrasting weather is strongly affected by hydrology in landscapes underlain by permafrost. Hypotheses for this variation were incorporated into the ecosystem model ecosys which simulated CO2 and CH4 fluxes along a topographic gradient within an arctic landscape at Daring Lake, NWT, Canada. Fluxes modelled at mixed tundra and fen sites within the gradient were compared with CO2 fluxes measured at eddy covariance towers from 2006 to 2009, and with CH4 fluxes measured with surface chambers in 2008. Slopes and correlation coefficients from regressions of modelled vs. measured CO2 fluxes were 1.0 ± 0.1 and 0.7 - 0.8 for both sites in all years. At the mixed tundra site, rises in net CO2 uptake in warmer years with earlier snowmelt were constrained by midafternoon declines in CO2 influxes when vapor pressure deficits (D) exceeded 1.5 kPa, and by rises in CO2 effluxes with greater active layer depth (ALD). Consequently annual net CO2 uptake at this site rose little with warming. At the fen site, CO2 influxes declined less with D and CO2 effluxes rose less with warming, so that rises in net CO2 uptake in warmer years were greater than those at the mixed tundra site. The greater declines in CO2 influxes with warming at the mixed tundra site were modelled from greater soil-plant-atmosphere water potential gradients that developed in drier soil, and the smaller rises in CO2 effluxes with warming at the fen site were modelled from O2 constraints to heterotrophic and below-ground autotrophic respiration that limited their responses to greater ALD. Modelled and measured CH4 exchange during July and August indicated very small influxes at the mixed tundra site, and larger emissions at the fen site. Emissions of CH4 modelled during soil freezing in October - November contributed about one-third of the annual total, and so should be included in estimates of annual emissions. These contrasting responses to warming under current

  14. Modelling the impact of soil Carbonic Anhydrase on the net ecosystem exchange of OCS at Harvard forest using the MuSICA model

    NASA Astrophysics Data System (ADS)

    Launois, Thomas; Ogée, Jérôme; Commane, Roisin; Wehr, Rchard; Meredith, Laura; Munger, Bill; Nelson, David; Saleska, Scott; Wofsy, Steve; Zahniser, Mark; Wingate, Lisa

    2016-04-01

    The exchange of CO2 between the terrestrial biosphere and the atmosphere is driven by photosynthetic uptake and respiratory loss, two fluxes currently estimated with considerable uncertainty at large scales. Model predictions indicate that these biosphere fluxes will be modified in the future as CO2 concentrations and temperatures increase; however, it still unclear to what extent. To address this challenge there is a need for better constraints on land surface model parameterisations. Additional atmospheric tracers of large-scale CO2 fluxes have been identified as potential candidates for this task. In particular carbonyl sulphide (OCS) has been proposed as a complementary tracer of gross photosynthesis over land, since OCS uptake by plants is dominated by carbonic anhydrase (CA) activity, an enzyme abundant in leaves that catalyses CO2 hydration during photosynthesis. However, although the mass budget at the ecosystem is dominated by the flux of OCS into leaves, some OCS is also exchanged between the atmosphere and the soil and this component of the budget requires constraining. In this study, we adapted the process-based isotope-enabled model MuSICA (Multi-layer Simulator of the Interactions between a vegetation Canopy and the Atmosphere) to include the transport, reaction, diffusion and production of OCS within a forested ecosystem. This model was combined with 3 years (2011-2013) of in situ measurements of OCS atmospheric concentration profiles and fluxes at the Harvard Forest (Massachussets, USA) to test hypotheses on the mechanisms responsible for CA-driven uptake by leaves and soils as well as possible OCS emissions during litter decomposition. Model simulations over the three years captured well the impact of diurnally and seasonally varying environmental conditions on the net ecosystem OCS flux. A sensitivity analysis on soil CA activity and soil OCS emission rates was also performed to quantify their impact on the vertical profiles of OCS inside the

  15. Causes of interannual variability in ecosystem-atmosphere CO2 exchange in a northern Wisconsin forest using a Bayesian model calibration

    SciTech Connect

    Ricciuto, Daniel M; Butler, Martha; Davis, Kenneth; Cook, Bruce D

    2008-01-01

    Carbon dioxide fluxes were examined over the growing seasons of 2002 and 2003 from 14 different sites in Upper Midwest (USA) to assess spatial variability of ecosystem-atmosphere CO2 exchange. These sites were exposed to similar temperature/precipitation regimes and spanned a range of vegetation types typical of the region (northern hardwood, mixed forest, red pine, jack pine, pine barrens and shrub wetland). The hardwood and red pine sites also spanned a range of stand ages (young, intermediate, mature). While seasonal changes in net ecosystem exchange (NEE) and photosynthetic parameters were coherent across the 2 years at most sites, changes in ecosystem respiration (ER) and gross ecosystem production (GEP) were not. Canopy height and vegetation type were important variables for explaining spatial variability of CO2 fluxes across the region. Light-use efficiency (LUE) was not as strongly correlated to GEP as maximum assimilation capacity (Amax). A bottom-up multi-tower land cover aggregated scaling of CO2 flux to a 2000 km(2) regional flux estimate found June to August 2003 NEE, ER and GEP to be -290 +/- 89, 408 +/- 48, and 698 +/- 73 gC m(-2), respectively. Aggregated NEE, ER and GEP were 280% larger, 32% smaller and 3% larger, respectively, than that observed from a regionally integrating 447 m tall flux tower. However, when the tall tower fluxes were decomposed using a footprint-weighted influence function and then re-aggregated to a regional estimate, the resulting NEE, ER and GEP were within 11% of the multi-tower aggregation. Excluding wetland and young stand age sites from the aggregation worsened the comparison to observed fluxes. These results provide insight on the range of spatial sampling, replication, measurement error and land cover accuracy needed for multi-tiered bottom-up scaling of CO2 fluxes in heterogeneous regions such as the Upper Midwest, USA. (C) 2007 Elsevier B.V. All rights reserved.

  16. 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.

  17. Comparative analysis of carbon, water, and energy exchanges in co-located mid-latitude forests at various stages of development

    NASA Astrophysics Data System (ADS)

    Williams, C. A.; Munger, J. W.; Hadley, J.; Fitzjarrald, D. R.

    2010-12-01

    Biosphere-atmosphere exchanges of mass and energy vary with forest type, stand age, and following disturbance, but the degree, character, and persistence of these variations remain poorly understood. This work explores such gradients by synthesizing across a local network of flux tower sites within Harvard Forest (central Massachusetts). We examine how CO2, H2O, and energy exchanges compare among mature and intermediate aged deciduous forests, a mature hemlock forest, and a newly instrumented site in the early stages of secondary succession following a recent clearcut. We find markedly lower growing season evapotranspiration in the hemlock stand compared to adjacent deciduous forests, lower still in the revegetating clearcut. Daytime net ecosystem carbon exchange follows a similar pattern, with highest uptake in the deciduous forests, intermediate in the hemlock site, and lowest in the clearcut. This is true despite sizeable midday uptake in the clearcut during the second growing season post-harvest. Large nighttime CO2 emissions from the clearcut indicate high respiration rates of the early succession vegetation as well as vigorous decomposition of the abundant woody debris and litter left onsite after harvest. Surface albedo and corresponding net radiation are both surprisingly consistent across these adjacent cover types. Implications for water resources and carbon balance of New England landscapes will be discussed, particularly within the contexts of human and natural disturbances, such as harvesting and Hemlock Wooly Adelgid infestations.

  18. Digital photography for assessing the link between vegetation phenology and CO2 exchange in two contrasting northern ecosystems

    NASA Astrophysics Data System (ADS)

    Linkosalmi, Maiju; Aurela, Mika; Tuovinen, Juha-Pekka; Peltoniemi, Mikko; Tanis, Cemal M.; Arslan, Ali N.; Kolari, Pasi; Böttcher, Kristin; Aalto, Tuula; Rainne, Juuso; Hatakka, Juha; Laurila, Tuomas

    2016-09-01

    Digital repeat photography has become a widely used tool for assessing the annual course of vegetation phenology of different ecosystems. By using the green chromatic coordinate (GCC) as a greenness measure, we examined the feasibility of digital repeat photography for assessing the vegetation phenology in two contrasting high-latitude ecosystems. Ecosystem-atmosphere CO2 fluxes and various meteorological variables were continuously measured at both sites. While the seasonal changes in GCC were more obvious for the ecosystem that is dominated by annual plants (open wetland), clear seasonal patterns were also observed for the evergreen ecosystem (coniferous forest). Daily and seasonal time periods with sufficient solar radiation were determined based on images of a grey reference plate. The variability in cloudiness had only a minor effect on GCC, and GCC did not depend on the sun angle and direction either. The daily GCC of wetland correlated well with the daily photosynthetic capacity estimated from the CO2 flux measurements. At the forest site, the correlation was high in 2015 but there were discernible deviations during the course of the summer of 2014. The year-to-year differences were most likely generated by meteorological conditions, with higher temperatures coinciding with higher GCCs. In addition to depicting the seasonal course of ecosystem functioning, GCC was shown to respond to environmental changes on a timescale of days. Overall, monitoring of phenological variations with digital images provides a powerful tool for linking gross primary production and phenology.

  19. Combining Microbial Enzyme Kinetics Models with Light Use Efficiency Models to Predict CO2 and CH4 Ecosystem Exchange from Flooded and Drained Peatland Systems

    NASA Astrophysics Data System (ADS)

    Oikawa, P. Y.; Jenerette, D.; Knox, S. H.; Sturtevant, C. S.; Verfaillie, J. G.; Baldocchi, D. D.

    2014-12-01

    Under California's Cap-and-Trade program, companies are looking to invest in land-use practices that will reduce greenhouse gas (GHG) emissions. The Sacramento-San Joaquin River Delta is a drained cultivated peatland system and a large source of CO2. To slow soil subsidence and reduce CO2 emissions, there is growing interest in converting drained peatlands to wetlands. However, wetlands are large sources of CH4 that could offset CO2-based GHG reductions. The goal of our research is to provide accurate measurements and model predictions of the changes in GHG budgets that occur when drained peatlands are restored to wetland conditions. We have installed a network of eddy covariance towers across multiple land use types in the Delta and have been measuring CO2 and CH4 ecosystem exchange for multiple years. In order to upscale these measurements through space and time we are using these data to parameterize and validate a process-based biogeochemical model. To predict gross primary productivity (GPP), we are using a simple light use efficiency (LUE) model which requires estimates of light, leaf area index and air temperature and can explain 90% of the observed variation in GPP in a mature wetland. To predict ecosystem respiration we have adapted the Dual Arrhenius Michaelis-Menten (DAMM) model. The LUE-DAMM model allows accurate simulation of half-hourly net ecosystem exchange (NEE) in a mature wetland (r2=0.85). We are working to expand the model to pasture, rice and alfalfa systems in the Delta. To predict methanogenesis, we again apply a modified DAMM model, using simple enzyme kinetics. However CH4 exchange is complex and we have thus expanded the model to predict not only microbial CH4 production, but also CH4 oxidation, CH4 storage and the physical processes regulating the release of CH4 to the atmosphere. The CH4-DAMM model allows accurate simulation of daily CH4 ecosystem exchange in a mature wetland (r2=0.55) and robust estimates of annual CH4 budgets. The LUE

  20. Analysis of the influence of climatic and physiological parameters on the net ecosystem carbon exchange of an apple orchard

    NASA Astrophysics Data System (ADS)

    Zanotelli, Damiano; Montagnani, Leonardo; Scandellari, Francesca; Tagliavini, Massimo

    2013-04-01

    Net ecosystem carbon exchange (NEE) of an apple orchard located in South Tyrol (Caldaro, Bolzano, Italy) was monitored continuously since March 2009 via eddy covariance technique. Contemporary measurements of the main environmental parameters (temperature, photosynthetic active photon flux density, soil water content, vapor pressure deficit) were taken at the same field site. Leaf Area Index was also determined biometrically starting from spring 2010. Objectives of this work were (i) to assess the influence of these environmental and physiological parameters on NEE, (ii) to set up a model capable to fill large gap occurring in the dataset and (iii) predict inter-annual variability of fluxes based on the measurements of the selected explanatory variables. Daily cumulated values of the response variable (NEE, g C d-1) and mean daily value of the five explanatory variables considered (air T, ° C; SWC, m3m-3; PPFD, μmol m-2s-1; VPD, hPa, LAI m2m-2) were used in this analysis. The complex interactions between the explanatory variables and NEE were analyzed with the tree model approach which draws a picture of the complexity of data structure and highlights the explanatory variable that explain the greater amount of deviance of the response variable. NEE variability was mostly explained by LAI and PPFD. The most positive values of NEE occurred below the LAI threshold of 1.16 m2m-2 while above that LAI threshold and with an average daily PPFD above 13.2 μmol m-2s-1, the orchard resulted always a sink of carbon (negative daily NEE). On half of the available data (only alternate months of the considered period were considered), a stepwise multiple regression approach was used to model NEE using the variables indicated above. Simplification by deletion of the non-significant terms was carried out until all parameters where highly significant (p < 0.05) and a significant increase in deviance was observed when deleting further variables. Since heteroscedasticity and non

  1. Comparative dynamics of pelagic and benthic micro-algae in a coastal ecosystem

    NASA Astrophysics Data System (ADS)

    Chatterjee, Arnab; Klein, Cécile; Naegelen, Aurore; Claquin, Pascal; Masson, Annick; Legoff, Manon; Amice, Erwan; L'Helguen, Stéphane; Chauvaud, Laurent; Leynaert, Aude

    2013-11-01

    Together with phytoplankton, microphytobenthos (MPB) play an important role in the overall food web structure of coastal ecosystems by regulating nutrient fluxes, oxygen concentration and sediment stability in the ecosystem. Although there are many studies on phytoplankton, MPB dynamics in the subtidal zone are largely unknown. In this study, we carried out a whole-year survey to investigate the seasonal dynamics of phytoplankton and MPB biomass simultaneously in relation to the environmental physico-chemical parameters. We show that phytoplankton and MPB do not follow the same dynamics with MPB being the first to increase in the season. It constitutes a large energy input to the ecosystem from the beginning of spring (with 60% of the total biomass until April). The system then moves from a system dominated by benthic biomass in early spring to a system where the pelagic biomass dominates. Among resources that MPB and phytoplankton have to share, light seems to trigger the MPB bloom as soon as maximum bottom PAR is reached, i.e. one month earlier than the phytoplankton bloom in the water column. With regard to nutrients, the lack of phosphorus can be put forward to explain the decline of MPB biomass at the beginning of April, whereas the phytoplankton decline in the first week of May coincides to silicic acid deficiency. Dissolved inorganic nitrogen then becomes potentially limiting in the water column until the end of October. Competition with macroalgae at the bottom and grazing were also considered as being possible factors for the disparate course of phytoplankton and MPB dynamics. Further investigations are needed to give a more detailed picture on the interactions and feedback loops between MPB and phytoplankton. However, although benthic-pelagic relationships are complex, this study indicates the need to integrate such fundamental coupling to a thorough understanding of ecosystem dynamics and functions.

  2. Impact of urbanization on natural ecosystem service values: a comparative study.

    PubMed

    Zang, Shuying; Wu, Changshan; Liu, Hang; Na, Xiaodong

    2011-08-01

    With rapid population growth and rural to-urban migration in many Chinese cities, a large amount of natural lands have been converted to urban and agricultural lands recently. During this process of land conversion, economic development and quality of life improvement are considered as major goals, and their influences on ecological systems have often been neglected. The degradation of natural ecological systems due to land use change, however, has become severe,and may require immediate attentions from urban planners and local governments. Taking HaDaQi industrial corridor, Heilongjiang Province, China,as a case study area, this paper examined the trend of land use changes during 1990–2005, and quantified their influences on natural eco system service values. In particular, this study applied two major valuation methods, and examined whether different valuation methods generate significantly different results. Analysis of results suggests that human dominated land uses (e.g., urban and agriculture)have expanded rapidly at the cost of natural lands (e.g., wetlands and forest). Due to these land use changes, the total ecosystem service value decreased 29% (2.26% annually) from 1990 to 2005 when the first method was applied, and this rate is estimated to be 15.7% (1.13% annually)with the second approach. Moreover, the annual rate of ecosystem service value decline during 2000–2005 is about four times higher than that in 1990–2000 with both methods, suggesting much more severe ecosystem degradation during 2000–2005.

  3. Comparative behavior of three long-lived radionuclides in forest ecosystems

    SciTech Connect

    Auerbach, S.I.

    1986-01-01

    This paper deals with studies in three forest ecosystems in eastern Tennessee, an area of rich temperate deciduous forests, sometimes referred to as mixed mesophytic forests. Two of these forest ecosystems were contaminated as a result of waste disposal operations. The third was experimentally tagged with millicurie quantities of /sup 137/Cs. One of these ecosystems is a floodplain forest that is typical of this region. This forest has been growing on alluvial soils since 1944. Prior to that time the area was a temporary holding pond within White Oak Creek which received radioactive effluents from ORNL. Radiocesium was deposited in the pond sediments as were /sup 90/Sr, /sup 239/Pu, /sup 241/Am, and other radionuclides. The dam which created the pond failed in late 1944, and the area was allowed to revert to natural conditions. The result was the development of a floodplain forest consisting of three different forest communities. The soils are fertile alluvials representative of bottomlands. The overstory tree species are principally ash, sycamore, boxelder, willow, and sweetgum (Fraxinus americana L., Plantanus occidentalis L., Acer negundo L., Salix nigra Marsh, and Liquidambar styraciflua L., respectively).

  4. Response of NDVI, biomass, and ecosystem gas exchange to long-term warming and fertilization in wet sedge tundra.

    PubMed

    Boelman, Natalie T; Stieglitz, Marc; Rueth, Heather M; Sommerkorn, Martin; Griffin, Kevin L; Shaver, Gaius R; Gamon, John A

    2003-05-01

    This study explores the relationship between the normalized difference vegetation index (NDVI), aboveground plant biomass, and ecosystem C fluxes including gross ecosystem production (GEP), ecosystem respiration (ER) and net ecosystem production. We measured NDVI across long-term experimental treatments in wet sedge tundra at the Toolik Lake LTER site, in northern Alaska. Over 13 years, N and P were applied in factorial experiments (N, P and N + P), air temperature was increased using greenhouses with and without N + P fertilizer, and light intensity (photosynthetically active photon flux density) was reduced by 50% using shade cloth. Within each treatment plot, NDVI, aboveground biomass and whole-system CO(2) flux measurements were made at the same sampling points during the peak-growing season of 2001. We found that across all treatments, NDVI is correlated with aboveground biomass ( r(2)=0.84), GEP ( r(2)=0.75) and ER ( r(2)=0.71), providing a basis for linking remotely sensed NDVI to aboveground biomass and ecosystem carbon flux.

  5. The Seasonal Cycle of Satellite Chlorophyll Fluorescence Observations and its Relationship to Vegetation Phenology and Ecosystem Atmosphere Carbon Exchange

    NASA Technical Reports Server (NTRS)

    Joiner, J.; Yoshida, Y.; Vasilkov, A. P.; Schaefer, K.; Jung, M.; Guanter, L.; Zhang, Y; Garrity, S.; Middleton, E. M.; Huemmrich, K. F.; Gu, L.; Marchesini, L. Belelli

    2014-01-01

    Mapping of terrestrial chlorophyll uorescence from space has shown potentialfor providing global measurements related to gross primary productivity(GPP). In particular, space-based fluorescence may provide information onthe length of the carbon uptake period that can be of use for global carboncycle modeling. Here, we examine the seasonal cycle of photosynthesis asestimated from satellite fluorescence retrievals at wavelengths surroundingthe 740nm emission feature. These retrievals are from the Global OzoneMonitoring Experiment 2 (GOME-2) flying on the MetOp A satellite. Wecompare the fluorescence seasonal cycle with that of GPP as estimated froma diverse set of North American tower gas exchange measurements. Because the GOME-2 has a large ground footprint (40 x 80km2) as compared with that of the flux towers and requires averaging to reduce random errors, we additionally compare with seasonal cycles of upscaled GPP in the satellite averaging area surrounding the tower locations estimated from the Max Planck Institute for Biogeochemistry (MPI-BGC) machine learning algorithm. We also examine the seasonality of absorbed photosynthetically-active radiation(APAR) derived with reflectances from the MODerate-resolution Imaging Spectroradiometer (MODIS). Finally, we examine seasonal cycles of GPP as produced from an ensemble of vegetation models. Several of the data-driven models rely on satellite reflectance-based vegetation parameters to derive estimates of APAR that are used to compute GPP. For forested sites(particularly deciduous broadleaf and mixed forests), the GOME-2 fluorescence captures the spring onset and autumn shutoff of photosynthesis as delineated by the tower-based GPP estimates. In contrast, the reflectance-based indicators and many of the models tend to overestimate the length of the photosynthetically-active period for these and other biomes as has been noted previously in the literature. Satellite fluorescence measurements therefore show potential for

  6. Net ecosystem exchange from five land-use transitions to bioenergy crops from four locations across the UK - The Ecosystem Land Use Modelling & Soil Carbon GHG Flux Trial (ELUM) project.

    NASA Astrophysics Data System (ADS)

    Xenakis, Georgios; Perks, Mike; Harris, Zoe M.; McCalmont, Jon; Rylett, Daniel; Brooks, Milo; Evans, Jonathan G.; Finch, Jon; Rowe, Rebecca; Morrison, Ross; Alberti, Giorgio; Donnison, Ian; Siebicke, Lukas; Morison, James; Taylor, Gail; McNamara, Niall P.

    2016-04-01

    A major part of international agreements on combating climate change is the conversion from a fossil fuel economy to a low carbon economy. Bioenergy crops have been proposed as a way to improve energy security while reducing CO2 emissions to help mitigate the effects of climate change. However, the impact of land-use change from a traditional land use (e.g., arable and grassland) to bioenergy cropping systems on greenhouse gas balance (GHG) and carbon stocks are poorly quantified at this time. The Ecosystem Land Use Modelling & Soil Carbon GHG Flux Trial (ELUM) project was commissioned and funded by the Energy Technologies Institute (ETI) to provide scientific evidence within the UK on a range of land-use conversions (LUC) to bioenergy crops. The ELUM network consists of seven partners investigating five LUCs in four locations including Scotland, Wales, North and South England. Transitions included grasslands to short rotation forestry (SRF), to short rotation coppice willow (SRC) and to Miscanthus and arable to SRC and Miscanthus Measurements of net ecosystem exchange (NEE) along with continuous measurements of meteorological conditions were made at seven sub-sites over a two-year period. Results showed that, over two years, two of the land-uses, a grassland in South England and a grassland conversion to Miscanthus in Wales were net sources of carbon. The greatest carbon sink was into the SRF site in Scotland followed by the SRC willow in South England. The annual terrestrial ecosystem respiration (TER) for the SRC willow in North and South Sussex sites were similar, but the annual GPP at the South England site was about 27% higher than that the North England site. Establishing a long term network will allow us to continue monitoring the effects of land use change on whole ecosystem carbon balance, providing an insight into which types of LUC are suitable for bioenergy cropping in the UK.

  7. The Seasonal and Diurnal Patterns of net Ecosystem CO2 Exchange in a Subtropical Montane Cloud Forest.

    NASA Astrophysics Data System (ADS)

    Chu, H.; Lai, C.; Wu, C.; Hsia, Y.

    2008-12-01

    CO2 fluxes were measured by an open/closed path eddy covariance system at a natural regenerated 50-years-old yellow cypress (Chamaecyparis obtusa var. formosana) forest at Chi-Lan Mountain site (CLM site, 24°35'N, 121°25'E, 1650 m elevation), north-eastern Taiwan. CLM site is located at a relative uniform south-eastern-facing valley slope (15°) characterized with year round fog occurrence and diurnal mountain-valley wind and can be classified as subtropical montane cloud forest. Based on measurement from July 2007 to June 2008, seasonal and diurnal patterns of CO2 fluxes were described and patterns under different cloudiness and foggy conditions were presented. Comparing with other cypress forests in temperate region, there is only a weak seasonal pattern of the CO2 fluxes at CLM site. Throughout the year, average incident photosynthetically active radiation in summer was almost the double of that in winter, whereas the difference of mean daytime CO2 fluxes among seasons was much less than the seasonal light difference. During summer when light intensity was higher, mean daytime CO2 fluxes reached -7.5 μmol/m2/s in July and -8.8 μmol/m2/s in August. As heavy fog accounted for 64% and 67% of the time in November and February, mean daytime CO2 fluxes dropped to -6.9 and -6.1 μmol/m2/s respectively. With comparable higher incident radiation intensity (>1000 μmol/m2/s), the CO2 fluxes were higher in overcast days than in clear days. In July 2007, clear days accounted for 30% of the month, light intensity reached its peak at midday, and however, CO2 fluxes didn't reach its highest value in the meanwhile. Canopy conductance calculated from the Penman-Monteith equation and measured latent heat fluxes both showed a midday depression at clear days, which indicated the regulation of transpiration by plant physiological mechanism. With comparable lower incident radiation intensity (<1000 μmol/m2/s), the CO2 fluxes were higher in overcast days than in foggy days. The

  8. CH4 exchanges of the natural ecosystems in China during the past three decades: The role of wetland extent and its dynamics

    NASA Astrophysics Data System (ADS)

    Wei, Da; Wang, Xiaodan

    2016-09-01

    CH4 is the second largest contributor to human-induced global warming. However, large uncertainties still exist regarding the magnitude and temporal variation of CH4 exchanges in China's natural ecosystems, especially under climate changes. In this study, we assessed its uncertainty and temporal variation during 1979-2012, by integrating a biogeochemical model, extensive in situ measurements, and various sources of wetland maps. Uncertainty analyses suggested that previous studies might have underestimated CH4 emissions, primarily due to bias in wetland extents in NE China. After that, 1 km resolution wetland maps were used to drive the model, together with a 0.1° resolution climate data set. The model showed that China's natural wetlands emitted 4.56 ± 1.24 Tg CH4 yr-1 during the 1980s, which decreased to 3.86 ± 1.09 Tg CH4 yr-1 in the 2000s, mainly due to wetland drainage in NE China. However, recent glacier-melt-induced wetland expansion has enhanced CH4 emissions by 28% on the Tibetan Plateau since the 1980s. The magnitude of CH4 uptake by the natural ecosystems has remained relatively stable, e.g., -2.57 ± 0.18 and -2.70 ± 0.19 Tg CH4 yr-1 in the 1980s and 2000s, respectively. In summary, the net CH4 balance of China's natural ecosystems has shown a decreasing pattern, i.e., 1.99 ± 1.42 and 1.16 ± 1.28 Tg CH4 yr-1 in the 1980s and 2000s, respectively, despite distinct regional differences between NE China and the Tibetan Plateau. Furthermore, this study emphasizes the correct representation of wetland extent and its dynamics, i.e., wetland drainage in populated regions and wetland expansion in glacier-fed regions, in driving the decadal CH4 exchange magnitude.

  9. Comparing Ion Exchange Adsorbents for Nitrogen Recovery from Source-Separated Urine.

    PubMed

    Tarpeh, William A; Udert, Kai M; Nelson, Kara L

    2017-02-21

    Separate collection of urine, which is only 1% of wastewater volume but contains the majority of nitrogen humans excrete, can potentially reduce the costs and energy input of wastewater treatment and facilitate recovery of nitrogen for beneficial use. Ion exchange was investigated for recovery of nitrogen as ammonium from urine for use as a fertilizer or disinfectant. Cation adsorption curves for four adsorbents (clinoptilolite, biochar, Dowex 50, and Dowex Mac 3) were compared in pure salt solutions, synthetic urine, and real stored urine. Competition from sodium and potassium present in synthetic and real urine did not significantly decrease ammonium adsorption for any of the adsorbents. Dowex 50 and Dowex Mac 3 showed nearly 100% regeneration efficiencies. Estimated ion exchange reactor volumes to capture the nitrogen for 1 week from a four-person household were lowest for Dowex Mac 3 (5 L) and highest for biochar (19 L). Although Dowex Mac 3 had the highest adsorption capacity, material costs ($/g N removed) were lower for clinoptilolite and biochar because of their substantially lower unit cost.

  10. Precipitation regulates the response of net ecosystem CO2 exchange to environmental variation on U.S. rangelands

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Rangelands occupy about 50% of the Earth’s land surface and thus play an important role in the terrestrial carbon (C) cycle. For rangelands and other terrestrial ecosystems, the balance between photosynthetic uptake of carbon dioxide (CO2) and CO2 loss to respiration varies among years in response ...

  11. Comparative Ecology of H2 Cycling in Organotrophic and Phototrophic Ecosystems

    NASA Technical Reports Server (NTRS)

    Hoehler, Tori M.; Alperin, Marc J.; Albert, Daniel B.; Bebout, Brad M.; Martens, Christopher S.; DesMarais, David J.; DeVincenzi, Don (Technical Monitor)

    2001-01-01

    The simple biochemistry of H2 is critical to a large number of microbial processes, affecting the interaction of organisms with each other and with the environment. The sensitivity of these many processes to H2 can be described quantitatively, at a basic thermodynamic level. This shared dependence on H2 may provide a means for interpreting the ecology and system-level biogeochemistry of widely variant microbial ecosystems on a common (and quantitative) level. Understanding the factors that control H2 itself is a critical prerequisite. Here, we examine two ecosystems that vary widely with respect to H2 cycling. In anoxic, 'organotrophic' sediments from Cape Lookout Bight (North Carolina, USA), H2 partial pressures are strictly maintained at low, steady-state levels by H2-consuming organisms, in a fashion that can be quantitatively predicted by simple thermodynamic calculations. In phototrophic microbial mats from Baja, Mexico, H2 partial pressures are instead controlled by the activity of light-sensitive H2-producing organisms. In consequence, H2 partial pressures within the system fluctuate by orders of magnitude on hour-long time scales. The differences in H2 cycling subsequently impact H2-sensitive microbial processes, such as methanogenesis. For example, the presence of sulfate in the organotrophic system always yielded low levels of H2 that were inhibitory to methanogenesis; however, the elevated levels of H2 in the phototrophic system favored methane production at significant levels, even in the presence of high sulfate concentrations. The myriad of other H2-sensitive microbial processes are expected to exhibit similar behavior.

  12. Marine ecosystem health status assessment through integrative biomarker indices: a comparative study after the Prestige oil spill "Mussel Watch".

    PubMed

    Marigómez, Ionan; Garmendia, Larraitz; Soto, Manu; Orbea, Amaia; Izagirre, Urtzi; Cajaraville, Miren P

    2013-04-01

    Five integrative biomarker indices are compared: Bioeffects Assessment Index (BAI), Health Status Index (HSI), integrated biological response (IBR), ecosystem health condition chart (EHCC) and Integrative Biomarker Index (IBI). They were calculated on the basis of selected biomarker data collected in the framework of the Prestige oil spill (POS) Mussel Watch monitoring (2003-2006) carried out in Galicia and the Bay of Biscay. According to the BAI, the health status of mussels was severely affected by POS and signals of recovery were evidenced in Galicia after April-04 and in Biscay Bay after April-05. The HSI (computed by an expert system) revealed high levels of environmental stress in 2003 and a recovery trend from April-04 to April-05. In July-05, the health status of mussels worsened but in October-05 and April-06 healthy condition was again recorded in almost all localities. IBR/n and IBI indicated that mussel health was severely affected in 2003 and improved from 2004 onwards. EHCC reflected a deleterious environmental condition in 2003 and a recovery trend after April-04, although a healthy ecosystem condition was not achieved in April-06 yet. Whereas BAI and HSI provide a basic indication of the ecosystem health status, star plots accompanying IBR/n and IBI provide complementary information concerning the mechanisms of biological response to environmental insult. Overall, although the integrative indices based on biomarkers show different sensitivity, resolution and informative output, all of them provide coherent information, useful to simplify the interpretation of biological effects of pollution in marine pollution monitoring. Each others' advantages, disadvantages and applicability for ecosystem health assessment are discussed.

  13. Carbon exchange and quantum efficiency of ecosystem carbon storage in mature deciduous and old-growth coniferous forest in central New England in 2001

    NASA Astrophysics Data System (ADS)

    Hadley, J. L.; Urbanski, S. P.

    2002-12-01

    Carbon storage in forests of the northeastern U.S. and adjacent Canada may be a significant carbon sink, as forests and soils in this region have recovered after agricultural abandonment in the 19th century. Data collected during the 1990's showed that an area of 70 to 100 year old deciduous forest on abandoned farmland in central Massachusetts stored an average of 2.0 Mg C/ha/yr in trees and soil. During 2001 we measured carbon exchange and environmental parameters (above-canopy air temperature, atmospheric humidity, photosynthetically active radiation (PAR) and soil temperature) in both the 70-100 year old deciduous forest and in a nearby eastern hemlock (Tsuga canadensis L.)-dominated forest with trees up to 220 years old that was never cleared for agricultural use. The deciduous forest stored more than 4 Mg C/ ha in 2001, far higher than in any previous year since measurements started in 1991. Highest monthly deciduous forest carbon storage (1.8 - 1.9 Mg ha-1 month-1) occurred in July and August. The hemlock forest stored about 3 Mg C/ha, with peak storage in April and May (0.8 - 0.9Mg C ha-1 month-1), and little or no C storage during August. The differences in carbon storage between the two forests were related to differences in quantum use efficiency. Quantum efficiency of ecosystem carbon storage in the foliated deciduous forest averaged about 0.16 g C /mol PAR and was insensitive to temperature after leaf maturation. In contrast, the average hemlock forest quantum efficiency declined from about 0.10 g C /mol PAR at daily average above-canopy air temperature (T{a}{v}{g}) = 5 oC to zero quantum efficiency (no net carbon storage) at T{a}{v}{g} = 23 oC. Optimum temperatures for carbon storage in the hemlock forest occurred in April. Differences between the two forests are likely due primarily to a higher maximum photosynthetic rate and a more positive temperature response of leaf-level photosynthesis in red oak (the dominant deciduous species) as compared with

  14. Exotic Spartina alterniflora invasion alters ecosystem-atmosphere exchange of CH4 and N2O and carbon sequestration in a coastal salt marsh in China.

    PubMed

    Yuan, Junji; Ding, Weixin; Liu, Deyan; Kang, Hojeong; Freeman, Chris; Xiang, Jian; Lin, Yongxin

    2015-04-01

    Coastal salt marshes are sensitive to global climate change and may play an important role in mitigating global warming. To evaluate the impacts of Spartina alterniflora invasion on global warming potential (GWP) in Chinese coastal areas, we measured CH4 and N2O fluxes and soil organic carbon sequestration rates along a transect of coastal wetlands in Jiangsu province, China, including open water; bare tidal flat; and invasive S. alterniflora, native Suaeda salsa, and Phragmites australis marshes. Annual CH4 emissions were estimated as 2.81, 4.16, 4.88, 10.79, and 16.98 kg CH4 ha(-1) for open water, bare tidal flat, and P. australis, S. salsa, and S. alterniflora marshes, respectively, indicating that S. alterniflora invasion increased CH4 emissions by 57-505%. In contrast, negative N2O fluxes were found to be significantly and negatively correlated (P < 0.001) with net ecosystem CO2 exchange during the growing season in S. alterniflora and P. australis marshes. Annual N2O emissions were 0.24, 0.38, and 0.56 kg N2O ha(-1) in open water, bare tidal flat and S. salsa marsh, respectively, compared with -0.51 kg N2O ha(-1) for S. alterniflora marsh and -0.25 kg N2O ha(-1) for P. australis marsh. The carbon sequestration rate of S. alterniflora marsh amounted to 3.16 Mg C ha(-1) yr(-1) in the top 100 cm soil profile, a value that was 2.63- to 8.78-fold higher than in native plant marshes. The estimated GWP was 1.78, -0.60, -4.09, and -1.14 Mg CO2 eq ha(-1) yr(-1) in open water, bare tidal flat, P. australis marsh and S. salsa marsh, respectively, but dropped to -11.30 Mg CO2 eq ha(-1) yr(-1) in S. alterniflora marsh. Our results indicate that although S. alterniflora invasion stimulates CH4 emissions, it can efficiently mitigate increases in atmospheric CO2 and N2O along the coast of China.

  15. Controls on carbon and energy exchange by a black spruce-moss ecosystem: Testing the mathematical model Ecosys with data from the BOREAS Experiment

    NASA Astrophysics Data System (ADS)

    Grant, R. F.; Jarvis, P. G.; Massheder, J. M.; Hale, S. E.; Moncrieff, J. B.; Rayment, M.; Scott, S. L.; Berry, J. A.

    2001-03-01

    Stomatal limitations to mass and energy exchange over boreal black spruce forests may be caused by low needle N concentrations that limit CO2 fixation rates. These low concentrations may be caused by low N uptake rates from cold boreal soils with high soil C:N ratios and by low N deposition rates from boreal atmospheres. A mathematical model of terrestrial ecosystems ecosys was used to examine the likelihood that slow N cycling could account for the low rates of mass and energy exchange measured over a 115-year old boreal spruce/moss forest as part of the Boreal Ecosystem-Atmosphere Study (BOREAS). In the model, net N mineralization was slowed by the high C:N ratios measured in the forest floor and by high lignin contents in spruce litterfall. Slow mineralization caused low N uptake rates and hence high C:N ratios in spruce and moss leaves that reduced specific activities and areal densities of rubisco and chlorophyll. Consequent low CO2 fixation rates caused low stomatal conductances and transpiration rates which in turn caused high soil water contents. Wet soils, in conjunction with large accumulations of surface detritus generated by slow litter mineralization, caused low soil temperatures that further slowed mineralization rates. Model outputs for ecosystem N status were corroborated by low needle N concentrations (< 10 mg g-1), stomatal conductances (< 0.05 mol m-2 s-1) and CO2 fixation rates (< 6 μmol m-2 s-1), and by high canopy Bowen ratios (1.5-2.0) and low canopy net CO2 exchange rates (< 10 μmol m-2 s-1) measured over the black spruce/moss forest at the BOREAS site. Modeled C accumulation rates of 60 (wood) + 10 (soil) = 70 g C m-2 yr-1 were consistent with estimates from aggregated CO2 fluxes measured over the spruce canopy and from allometric equations developed for black spruce in Canadian boreal forests. Model projections under IS92a climate change indicate that rates of wood C accumulation would rise and those of soil C accumulation would decline

  16. Comparing the impact of the 2003 and 2010 heatwaves on Net Ecosystem Production in Europe

    NASA Astrophysics Data System (ADS)

    Bastos, A. F.; Gouveia, C. M.; Trigo, R. M.

    2012-12-01

    Climate variability is known to influence primary productivity on land ecosystems (Nemani et al., 2003). In particular, extreme climatic events such as major droughts and heatwaves are known to have severe impact on primary productivity and, therefore, to affect significantly the carbon dioxide uptake by land ecosystems at regional (Ciais et al., 2005) or even global scale (Zhao and Running, 2010). In the last decade, Europe was struck by two outstanding heatwaves, the 2003 event in Western Europe and the recent 2010 episode over Eastern Europe. Both were characterised by record breaking temperatures at the daily, weekly, monthly and seasonal scales, although the amplitude and spatial extent of the 2010 mega-heatwave surpassed the 2003 event (Barriopedro et al., 2011). This work aims to assess the influence of both mega-heatwaves on seasonal and yearly Net Ecosystem Production (NEP). The work relies on monthly NEP data derived from satellite imagery obtained from MODIS (Moderate Resolution Imaging Spectroradiometer) sensor at 1km spatial resolution. Data were selected for the period between 2000 and 2011 over a region extending from 34.6 oN to 73.5 oN and 12.1 oW to 46.8 oE, covering Eurasia. In 2010 very low NEP anomalies are observed over a very large area in Eastern Europe, at the monthly, seasonal and yearly scale. In western Russia, yearly NEP anomalies fall below 50% of average cumulative NEP. These widespread negative anomalous values of NEP fields over the western Russia region match the patterns of very high temperature values combined with below-average precipitation, at the seasonal (summer) scale. Moreover, the impact of the heatwave is not only evident at the regional level but also at the wider continental (European) scale and is significantly more extensive and intense than the corresponding heatwave of 2003 in Western Europe (Ciais et al., 2005). References: Barriopedro, D., E. M. Fischer, J. Luterbacher, R. M. Trigo, and R. Garcia-Herrera (2011

  17. Comparing biodiversity effects among ecosystem engineers of contrasting strength: macrofauna diversity in Zostera noltii and Spartina anglica vegetations

    NASA Astrophysics Data System (ADS)

    Bouma, Tjeerd J.; Ortells, Victor; Ysebaert, Tom

    2009-03-01

    Whereas it is well known that ecosystem engineers can have a large influence on biodiversity, underlying mechanisms are still not fully clear. We try to enhance insight by comparing biodiversity effects of two neighboring intertidal, clonal, ecosystem engineering plant species that modify the physical environmental parameters in a similar way, but with a different magnitude. Macrobenthic assemblages were compared between meadows of the seagrass Zostera noltii, small patches (≤0.5 m Ø) and large areas (≫5 m Ø) of the emergent halophyte Spartina anglica and the surrounding bare tidal mudflat (control). Multivariate analyses revealed that the mudflat benthic assemblage and Zostera meadow assemblage showed highest similarities, whereas the Spartina marsh assemblage showed the highest dissimilarity with these two areas. Whereas the descriptive nature of our study limits interpretation of the data, some clear patterns were observed. For all vegetated areas, species diversity was lower compared to the unvegetated mudflat, and we observed a strong shift from endo- towards epibenthic species, suggesting that increased above-ground habitat complexity may be a main driving process in our system. As there were no clear patterns related to feeding types, food availability/productivity appeared to be of minor importance in structuring the benthic assemblages. Nevertheless, animals were in general smaller in vegetated areas. Patchiness had a distinct positive effect on biodiversity.

  18. Comparative ecology of H2 cycling in sedimentary and phototrophic ecosystems

    NASA Technical Reports Server (NTRS)

    Hoehler, Tori M.; Albert, Daniel B.; Alperin, Marc J.; Bebout, Brad M.; Martens, Christopher S.; Des Marais, David J.

    2002-01-01

    The simple biochemistry of H2 is critical to a large number of microbial processes, affecting the interaction of organisms with each other and with the environment. The sensitivity of each of these processes to H2 can be described collectively, through the quantitative language of thermodynamics. A necessary prerequisite is to understand the factors that, in turn, control H2 partial pressures. These factors are assessed for two distinctly different ecosystems. In anoxic sediments from Cape Lookout Bight (North Carolina, USA), H2 partial pressures are strictly maintained at low, steady-state levels by H2-consuming organisms, in a fashion that can be quantitatively predicted by simple thermodynamic calculations. In phototrophic microbial mats from Baja California (Mexico), H2 partial pressures are controlled by the activity of light-sensitive H2-producing organisms, and consequently fluctuate over orders of magnitude on a daily basis. The differences in H2 cycling can subsequently impact any of the H2-sensitive microbial processes in these systems. In one example, methanogenesis in Cape Lookout Bight sediments is completely suppressed through the efficient consumption of H2 by sulfate-reducing bacteria; in contrast, elevated levels of H2 prevail in the producer-controlled phototrophic system, and methanogenesis occurs readily in the presence of 40 mM sulfate.

  19. Ecosystem structure and fishing impacts in the northwestern Mediterranean Sea using a food web model within a comparative approach

    NASA Astrophysics Data System (ADS)

    Corrales, Xavier; Coll, Marta; Tecchio, Samuele; Bellido, José María; Fernández, Ángel Mario; Palomera, Isabel

    2015-08-01

    We developed an ecological model to characterize the structure and functioning of the marine continental shelf and slope area of the northwestern Mediterranean Sea, from Toulon to Cape La Nao (NWM model), in the early 2000s. The model included previously modeled areas in the NW Mediterranean (the Gulf of Lions and the Southern Catalan Sea) and expanded their ranges, covering 45,547 km2, with depths from 0 to 1000 m. The study area was chosen to specifically account for the connectivity between the areas and shared fish stocks and fleets. Input data were based on local scientific surveys and fishing statistics, published data on stomach content analyses, and the application of empirical equations to estimate consumption and production rates. The model was composed of 54 functional groups, from primary producers to top predators, and Spanish and French fishing fleets were considered. Results were analyzed using ecological indicators and compared with outputs from ecosystem models developed in the Mediterranean Sea and the Gulf of Cadiz prior to this study. Results showed that the main trophic flows were associated with detritus, phytoplankton, zooplankton and benthic invertebrates. Several high trophic level organisms (such as dolphins, benthopelagic cephalopods, large demersal fishes from the continental shelf, and other large pelagic fishes), and the herbivorous salema fish, were identified as keystone groups within the ecosystem. Results confirmed that fishing impact was high and widespread throughout the food web. The comparative approach highlighted that, despite productivity differences, the ecosystems shared common features in structure and functioning traits such as the important role of detritus, the dominance of the pelagic fraction in terms of flows and the importance of benthic-pelagic coupling.

  20. [Effects of drip irrigation with plastic mulching on the net primary productivity, soil heterotrophic respiration, and net CO2 exchange flux of cotton field ecosystem in Xinjiang, Northwest China].

    PubMed

    Li, Zhi-Guo; Zhang, Run-Hua; Lai, Dong-Mei; Yan, Zheng-Yue; Jiang, Li; Tian, Chang-Yan

    2012-04-01

    In April-October, 2009, a field experiment was conducted to study the effects of drip irrigation with plastic mulching (MD) on the net primary productivity (NPP), soil heterotrophic respiration (Rh) , and net CO2 exchange flux (NEF(CO2)) of cotton field ecosystem in Xinjiang, taking the traditional flood irrigation with no mulching (NF) as the control. With the increasing time, the NPP, Rh, and NEF(CO2) in treatments MD and NF all presented a trend of increasing first and decreased then. As compared with NF, MD increased the aboveground and belowground biomass and the NPP of cotton, and decreased the Rh. Over the whole growth period, the Rh in treatment MD (214 g C x m(-2)) was smaller than that in treatment NF (317 g C x m(-2)), but the NEF(CO2) in treatment MD (1030 g C x m(-2)) was higher than that in treatment NF (649 g C x m(-2)). Treatment MD could fix the atmospheric CO2 approximately 479 g C x m(-2) higher than treatment NF. Drip irrigation with plastic mulching could promote crop productivity while decreasing soil CO2 emission, being an important agricultural measure for the carbon sequestration and emission reduction of cropland ecosystems in arid area.

  1. Control over ecosystem CO2 exchange by winter snow versus summer rain in a subalpine coniferous forest

    NASA Astrophysics Data System (ADS)

    Monson, R. K.; Moore, D. J.; Scott-Denton, L.; Rosenbloom, N.; Kittel, T.

    2008-12-01

    Subalpine forests in the Western U.S. depend on both winter snow and summer rain to provide water. Recent observations have shown a widespread decline in the snowpack of mountain ecosystems in the Western U.S. that is coupled to wintertime high temperature anomalies. Twenty-one coupled GCM models have predicted that this trend will continue. These same models predict changes in the summer precipitation regime, though with less consistency. In order to better understand the partitioning of soil water between winter snow and summer rain, we have been studying the seasonal 2H/1H signatures of these two water sources, as well as stem water (expressed as δD, or delta deuterium). Our analysis revealed that all three dominant tree species (spruce, pine and fir) relied on snowmelt water, to a varying extent, for the entire season. By mid-summer, however, the average contribution of rain water to tree xylem water had increased. We used the isotopic data of seasonal trends in water use to parameterize the SIPNET ecosystem process model. Using the model, we predicted that during warmer years the forest will more water stress with concomitantly lower midsummer photosynthesis rates. Given future climate projections for the Colorado Front Range of the Rocky Mountains, with associated earlier spring snow melt and reduced spring snowpacks, our analysis revealed that there will likely be more reliance on summer rains for CO2 uptake by Rocky Mountain subalpine forests.

  2. Biophysical controls on interannual variability in ecosystem-scale CO2 and CH4 exchange in a California rice paddy

    NASA Astrophysics Data System (ADS)

    Knox, Sara Helen; Matthes, Jaclyn Hatala; Sturtevant, Cove; Oikawa, Patricia Y.; Verfaillie, Joseph; Baldocchi, Dennis

    2016-03-01

    We present 6.5 years of eddy covariance measurements of fluxes of methane (FCH4) and carbon dioxide (FCO2) from a flooded rice paddy in Northern California, USA. A pronounced warming trend throughout the study associated with drought and record high temperatures strongly influenced carbon (C) budgets and provided insights into biophysical controls of FCO2 and FCH4. Wavelet analysis indicated that photosynthesis (gross ecosystem production, GEP) induced the diel pattern in FCH4, but soil temperature (Ts) modulated its amplitude. Forward stepwise linear models and neural networking modeling were used to assess the variables regulating seasonal FCH4. As expected due to their competence in modeling nonlinear relationships, neural network models explained considerably more of the variance in daily average FCH4 than linear models. During the growing season, GEP and water levels typically explained most of the variance in daily average FCH4. However, Ts explained much of the interannual variability in annual and growing season CH4 sums. Higher Ts also increased the annual and growing season ratio of FCH4 to GEP. The observation that the FCH4 to GEP ratio scales predictably with Ts may help improve global estimates of FCH4 from rice agriculture. Additionally, Ts strongly influenced ecosystem respiration, resulting in large interannual variability in the net C budget at the paddy, emphasizing the need for long-term measurements particularly under changing climatic conditions.

  3. Reconciling estimates of the contemporary North American carbon balance among terrestrial biosphere models, atmospheric inversions and a new approach for estimating net ecosystem exchange from inventory-based data

    SciTech Connect

    Hayes, Daniel J; Turner, David P; Stinson, Graham; Mcguire, David; Wei, Yaxing; West, Tristram O.; Heath, Linda S.; De Jong, Bernardus; McConkey, Brian G.; Birdsey, Richard A.; Kurz, Werner; Jacobson, Andrew; Huntzinger, Deborah; Pan, Yude; Post, Wilfred M; Cook, Robert B

    2012-01-01

    We develop an approach for estimating net ecosystem exchange (NEE) using inventory-based information over North America (NA) for a recent 7-year period (ca. 2000 2006). The approach notably retains information on the spatial distribution of NEE, or the vertical exchange between land and atmosphere of all non-fossil fuel sources and sinks of CO2, while accounting for lateral transfers of forest and crop products as well as their eventual emissions. The total NEE estimate of a 327 252 TgC yr1 sink for NA was driven primarily by CO2 uptake in the Forest Lands sector (248 TgC yr1), largely in the Northwest and Southeast regions of the US, and in the Crop Lands sector (297 TgC yr1), predominantly in the Midwest US states. These sinks are counteracted by the carbon source estimated for the Other Lands sector (+218 TgC yr1), where much of the forest and crop products are assumed to be returned to the atmosphere (through livestock and human consumption). The ecosystems of Mexico are estimated tobe a small net source (+18 TgC yr1) due to land use change between 1993 and 2002. We compare these inventorybased estimates with results from a suite of terrestrial biosphere and atmospheric inversion models, where the mean continental-scale NEE estimate for each ensemble is 511 TgC yr1 and 931 TgC yr1, respectively. In the modeling approaches, all sectors, including Other Lands, were generally estimated to be a carbon sink, driven in part by assumed CO2 fertilization and/or lack of consideration of carbon sources from disturbances and product emissions. Additional fluxes not measured by the inventories, although highly uncertain, could add an additional 239 TgC yr1 to the inventory-based NA sink estimate, thus suggesting some convergence with the modeling approaches.

  4. Reconciling estimates of the contemporary North American carbon balance among terrestrial biosphere models, atmospheric inversions, and a new approach for estimating net ecosystem exchange from inventory-based data

    USGS Publications Warehouse

    Hayes, Daniel J.; Turner, David P.; Stinson, Graham; McGuire, A. David; Wei, Yaxing; West, Tristram O.; Heath, Linda S.; de Jong, Bernardus; McConkey, Brian G.; Birdsey, Richard A.; Kurz, Werner A.; Jacobson, Andrew R.; Huntzinger, Deborah N.; Pan, Yude; Post, W. Mac; Cook, Robert B.

    2012-01-01

    We develop an approach for estimating net ecosystem exchange (NEE) using inventory-based information over North America (NA) for a recent 7-year period (ca. 2000–2006). The approach notably retains information on the spatial distribution of NEE, or the vertical exchange between land and atmosphere of all non-fossil fuel sources and sinks of CO2, while accounting for lateral transfers of forest and crop products as well as their eventual emissions. The total NEE estimate of a -327 ± 252 TgC yr-1 sink for NA was driven primarily by CO2 uptake in the Forest Lands sector (-248 TgC yr-1), largely in the Northwest and Southeast regions of the US, and in the Crop Lands sector (-297 TgC yr-1), predominantly in the Midwest US states. These sinks are counteracted by the carbon source estimated for the Other Lands sector (+218 TgC yr-1), where much of the forest and crop products are assumed to be returned to the atmosphere (through livestock and human consumption). The ecosystems of Mexico are estimated to be a small net source (+18 TgC yr-1) due to land use change between 1993 and 2002. We compare these inventory-based estimates with results from a suite of terrestrial biosphere and atmospheric inversion models, where the mean continental-scale NEE estimate for each ensemble is -511 TgC yr-1 and -931 TgC yr-1, respectively. In the modeling approaches, all sectors, including Other Lands, were generally estimated to be a carbon sink, driven in part by assumed CO2 fertilization and/or lack of consideration of carbon sources from disturbances and product emissions. Additional fluxes not measured by the inventories, although highly uncertain, could add an additional -239 TgC yr-1 to the inventory-based NA sink estimate, thus suggesting some convergence with the modeling approaches.

  5. Floral diversity in desert ecosystems: Comparing field sampling to image analyses in assessing species cover

    PubMed Central

    2013-01-01

    Background Developing a quick and reliable technique to estimate floral cover in deserts will assist in monitoring and management. The present attempt was to estimate plant cover in the UAE desert using both digital photography and field sampling. Digital photographs were correlated with field data to estimate floral cover in moderately (Al-Maha) and heavily (DDCR) grazed areas. The Kruskal-Wallis test was also used to assess compatibility between the two techniques within and across grazing intensities and soil substrates. Results Results showed that photographs could be a reliable technique within the sand dune substrate under moderate grazing (r = 0.69). The results were very poorly correlated (r =−0.24) or even inversely proportional (r =−0.48) when performed within DDCR. Overall, Chi-square values for Al-Maha and DDCR were not significant at P > 0.05, indicating similarities between the two methods. At the soil type level, the Kruskal-Wallis analysis was not significant (P > 0.05), except for gravel plains (P < 0.05). Across grazing intensities and soil substrates, the two techniques were in agreement in ranking most plant species, except for Lycium shawii. Conclusions Consequently, the present study has proven that digital photography could not be used reliably to asses floral cover, while further testing is required to support such claim. An image-based sampling approach of plant cover at the species level, across different grazing and substrate variations in desert ecosystems, has its uses, but results are to be cautiously interpreted. PMID:23758667

  6. Comparative sensitivity to the fungicide tebuconazole of biofilm and plankton microbial communities in freshwater ecosystems.

    PubMed

    Artigas, J; Pascault, N; Bouchez, A; Chastain, J; Debroas, D; Humbert, J F; Leloup, J; Tadonleke, R D; ter Halle, A; Pesce, S

    2014-01-15

    Stream and lake ecosystems in agricultural watersheds are exposed to fungicide inputs that can threaten the structure and functioning of aquatic microbial communities. This research analyzes the impact of the triazole fungicide tebuconazole (TBZ) on natural biofilm and plankton microbial communities from sites presenting different degrees of agricultural contamination. Biofilm and plankton communities from less-polluted (LP) and polluted (P) sites were exposed to nominal concentrations of 0 (control), 2 and 20 μg TBZ L(-1) in 3-week microcosm experiments. Descriptors of microbial community structure (bacterial density and chlorophyll-a concentration) and function (bacterial respiration and production and photosynthesis) were analyzed to chart the effects of TBZ and the kinetics of TBZ attenuation in water during the experiments. The results showed TBZ-induced effects on biofilm function (inhibition of substrate-induced respiration and photosynthetic activity), especially in LP-site communities, whereas plankton communities experienced a transitory stimulation of bacterial densities in communities from both LP and P sites. TBZ attenuation was stronger in biofilm (60-75%) than plankton (15-18%) experiments, probably due to greater adsorption on biofilms. The differences between biofilm and plankton responses to TBZ were likely explained by differences in community structure (presence of extracellular polymeric substances (EPS) matrix) and microbial composition. Biofilm communities also exhibited different sensitivity levels according to their in-field pre-exposure to fungicide, with P-site communities demonstrating adaptation capacities to TBZ. This study indicates that TBZ toxicity to non-targeted aquatic microbial communities essentially composed by microalgae and bacteria was moderate, and that its effects varied between stream and lake microbial communities.

  7. Eddy covariance flux measurements of net ecosystem carbon dioxide exchange from a lowland peatland flux tower network in England and Wales

    NASA Astrophysics Data System (ADS)

    Morrison, Ross; Balzter, Heiko; Burden, Annette; Callaghan, Nathan; Cumming, Alenander; Dixon, Simon; Evans, Jonathan; Kaduk, Joerg; Page, Susan; Pan, Gong; Rayment, Mark; Ridley, Luke; Rylett, Daniel; Worrall, Fred; Evans, Christopher

    2016-04-01

    Peatlands store disproportionately large amounts of soil carbon relative to other terrestrial ecosystems. Over recent decades, the large amount of carbon stored as peat has proved vulnerable to a range of land use pressures as well as the increasing impacts of climate change. In temperate Europe and elsewhere, large tracts of lowland peatland have been drained and converted to agricultural land use. Such changes have resulted in widespread losses of lowland peatland habitat, land subsidence across extensive areas and the transfer of historically accumulated soil carbon to the atmosphere as carbon dioxide (CO2). More recently, there has been growth in activities aiming to reduce these impacts through improved land management and peatland restoration. Despite a long history of productive land use and management, the magnitude and controls on greenhouse gas emissions from lowland peatland environments remain poorly quantified. Here, results of surface-atmosphere measurements of net ecosystem CO2 exchange (NEE) from a network of seven eddy covariance (EC) flux towers located at a range of lowland peatland ecosystems across the United Kingdom (UK) are presented. This spatially-dense peatland flux tower network forms part of a wider observation programme aiming to quantify carbon, water and greenhouse gas balances for lowland peatlands across the UK. EC measurements totalling over seventeen site years were obtained at sites exhibiting large differences in vegetation cover, hydrological functioning and land management. The sites in the network show remarkable spatial and temporal variability in NEE. Across sites, annual NEE ranged from a net sink of -194 ±38 g CO2-C m-2 yr-1 to a net source of 784±70 g CO2-C m-2 yr-1. The results suggest that semi-natural sites remain net sinks for atmospheric CO2. Sites that are drained for intensive agricultural production range from a small net sink to the largest observed source for atmospheric CO2 within the flux tower network

  8. Diurnal and Seasonal Variations in the Net Ecosystem CO2 Exchange of a Pasture in the Three-River Source Region of the Qinghai−Tibetan Plateau

    PubMed Central

    Wang, Bin; Jin, Haiyan; Li, Qi; Chen, Dongdong; Zhao, Liang; Tang, Yanhong; Kato, Tomomichi; Gu, Song

    2017-01-01

    Carbon dioxide (CO2) exchange between the atmosphere and grassland ecosystems is very important for the global carbon balance. To assess the CO2 flux and its relationship to environmental factors, the eddy covariance method was used to evaluate the diurnal cycle and seasonal pattern of the net ecosystem CO2 exchange (NEE) of a cultivated pasture in the Three-River Source Region (TRSR) on the Qinghai−Tibetan Plateau from January 1 to December 31, 2008. The diurnal variations in the NEE and ecosystem respiration (Re) during the growing season exhibited single-peak patterns, the maximum and minimum CO2 uptake observed during the noon hours and night; and the maximum and minimum Re took place in the afternoon and early morning, respectively. The minimum hourly NEE rate and the maximum hourly Re rate were −7.89 and 5.03 μmol CO2 m−2 s−1, respectively. The NEE and Re showed clear seasonal variations, with lower values in winter and higher values in the peak growth period. The highest daily values for C uptake and Re were observed on August 12 (−2.91 g C m−2 d−1) and July 28 (5.04 g C m−2 day−1), respectively. The annual total NEE and Re were −140.01 and 403.57 g C m−2 year−1, respectively. The apparent quantum yield (α) was −0.0275 μmol μmol−1 for the entire growing period, and the α values for the pasture’s light response curve varied with the leaf area index (LAI), air temperature (Ta), soil water content (SWC) and vapor pressure deficit (VPD). Piecewise regression results indicated that the optimum Ta and VPD for the daytime NEE were 14.1°C and 0.65 kPa, respectively. The daytime NEE decreased with increasing SWC, and the temperature sensitivity of respiration (Q10) was 3.0 during the growing season, which was controlled by the SWC conditions. Path analysis suggested that the soil temperature at a depth of 5 cm (Tsoil) was the most important environmental factor affecting daily variations in NEE during the growing season, and the

  9. Diurnal and Seasonal Variations in the Net Ecosystem CO2 Exchange of a Pasture in the Three-River Source Region of the Qinghai-Tibetan Plateau.

    PubMed

    Wang, Bin; Jin, Haiyan; Li, Qi; Chen, Dongdong; Zhao, Liang; Tang, Yanhong; Kato, Tomomichi; Gu, Song

    2017-01-01

    Carbon dioxide (CO2) exchange between the atmosphere and grassland ecosystems is very important for the global carbon balance. To assess the CO2 flux and its relationship to environmental factors, the eddy covariance method was used to evaluate the diurnal cycle and seasonal pattern of the net ecosystem CO2 exchange (NEE) of a cultivated pasture in the Three-River Source Region (TRSR) on the Qinghai-Tibetan Plateau from January 1 to December 31, 2008. The diurnal variations in the NEE and ecosystem respiration (Re) during the growing season exhibited single-peak patterns, the maximum and minimum CO2 uptake observed during the noon hours and night; and the maximum and minimum Re took place in the afternoon and early morning, respectively. The minimum hourly NEE rate and the maximum hourly Re rate were -7.89 and 5.03 μmol CO2 m-2 s-1, respectively. The NEE and Re showed clear seasonal variations, with lower values in winter and higher values in the peak growth period. The highest daily values for C uptake and Re were observed on August 12 (-2.91 g C m-2 d-1) and July 28 (5.04 g C m-2 day-1), respectively. The annual total NEE and Re were -140.01 and 403.57 g C m-2 year-1, respectively. The apparent quantum yield (α) was -0.0275 μmol μmol-1 for the entire growing period, and the α values for the pasture's light response curve varied with the leaf area index (LAI), air temperature (Ta), soil water content (SWC) and vapor pressure deficit (VPD). Piecewise regression results indicated that the optimum Ta and VPD for the daytime NEE were 14.1°C and 0.65 kPa, respectively. The daytime NEE decreased with increasing SWC, and the temperature sensitivity of respiration (Q10) was 3.0 during the growing season, which was controlled by the SWC conditions. Path analysis suggested that the soil temperature at a depth of 5 cm (Tsoil) was the most important environmental factor affecting daily variations in NEE during the growing season, and the photosynthetic photon flux

  10. 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.

  11. Partitioning net ecosystem carbon exchange into net assimilation and respiration using 13CO2 measurements: A cost-effective sampling strategy

    NASA Astrophysics Data System (ADS)

    OgéE, J.; Peylin, P.; Ciais, P.; Bariac, T.; Brunet, Y.; Berbigier, P.; Roche, C.; Richard, P.; Bardoux, G.; Bonnefond, J.-M.

    2003-06-01

    The current emphasis on global climate studies has led the scientific community to set up a number of sites for measuring the long-term biosphere-atmosphere net CO2 exchange (net ecosystem exchange, NEE). Partitioning this flux into its elementary components, net assimilation (FA), and respiration (FR), remains necessary in order to get a better understanding of biosphere functioning and design better surface exchange models. Noting that FR and FA have different isotopic signatures, we evaluate the potential of isotopic 13CO2 measurements in the air (combined with CO2 flux and concentration measurements) to partition NEE into FR and FA on a routine basis. The study is conducted at a temperate coniferous forest where intensive isotopic measurements in air, soil, and biomass were performed in summer 1997. The multilayer soil-vegetation-atmosphere transfer model MuSICA is adapted to compute 13CO2 flux and concentration profiles. Using MuSICA as a "perfect" simulator and taking advantage of the very dense spatiotemporal resolution of the isotopic data set (341 flasks over a 24-hour period) enable us to test each hypothesis and estimate the performance of the method. The partitioning works better in midafternoon when isotopic disequilibrium is strong. With only 15 flasks, i.e., two 13CO2 nighttime profiles (to estimate the isotopic signature of FR) and five daytime measurements (to perform the partitioning) we get mean daily estimates of FR and FA that agree with the model within 15-20%. However, knowledge of the mesophyll conductance seems crucial and may be a limitation to the method.

  12. Material exchange and food web of seagrass beds in the Sylt-Rømø Bight: how significant are community changes at the ecosystem level?

    NASA Astrophysics Data System (ADS)

    Asmus, H.; Asmus, R.

    2000-07-01

    Material exchange, biodiversity and trophic transfer within the food web were investigated in two different types of intertidal seagrass beds: a sheltered, dense Zostera marina bed and a more exposed, sparse Z. noltii bed, in the Northern Wadden Sea. Both types of Zostera beds show a seasonal development of above-ground biomass, and therefore measurements were carried out during the vegetation period in summer. The exchange of particles and nutrients between seagrass beds and the overlying water was measured directly using an in situ flume. Particle sedimentation [carbon (C), nitrogen (N) and phosphorus (P) constituents] from the water column prevailed in dense seagrass beds. In the sheltered, dense seagrass bed, a net particle uptake was found even on windy days (7-8 Beaufort). Dissolved inorganic N and orthophosphate were mainly taken up by the dense seagrass bed. At times of strong winds, nutrients were released from the benthic community to tidal waters. In a budget calculation of total N and total P, the dense seagrass beds were characterised as a material sink. The seagrass beds with sparse Z. noltii were a source of particles even during calm weather. The uptake of dissolved inorganic N in the sparse seagrass bed was low but significant, while the uptake of inorganic phosphate and silicate by seagrasses and their epiphytes was exceeded by release processes from the sediment into the overlying water. Estimates at the ecosystem level showed that material fluxes of seagrass beds in the Sylt-Rømø Bight are dominated by the dense type of Zostera beds. Therefore, seagrass beds act as a sink for particles and for dissolved inorganic nutrients. During storms, seagrass beds are distinct sources for inorganic nutrients. The total intertidal area of the Sylt-Rømø Bight could be described as a sink for particles and a source for dissolved nutrients. This balance of the material budget was estimated by either including or excluding seagrass beds. Including the

  13. Grassland and cropland net ecosystem production of the U.S. Great Plains: Regression tree model development and comparative analysis

    USGS Publications Warehouse

    Wylie, Bruce K.; Howard, Daniel; Dahal, Devendra; Gilmanov, Tagir; Ji, Lei; Zhang, Li; Smith, Kelcy

    2016-01-01

    This paper presents the methodology and results of two ecological-based net ecosystem production (NEP) regression tree models capable of up scaling measurements made at various flux tower sites throughout the U.S. Great Plains. Separate grassland and cropland NEP regression tree models were trained using various remote sensing data and other biogeophysical data, along with 15 flux towers contributing to the grassland model and 15 flux towers for the cropland model. The models yielded weekly mean daily grassland and cropland NEP maps of the U.S. Great Plains at 250 m resolution for 2000–2008. The grassland and cropland NEP maps were spatially summarized and statistically compared. The results of this study indicate that grassland and cropland ecosystems generally performed as weak net carbon (C) sinks, absorbing more C from the atmosphere than they released from 2000 to 2008. Grasslands demonstrated higher carbon sink potential (139 g C·m−2·year−1) than non-irrigated croplands. A closer look into the weekly time series reveals the C fluctuation through time and space for each land cover type.

  14. Dynamics of water vapor and energy exchanges above two contrasting Sudanian climate ecosystems in Northern Benin (West Africa)

    NASA Astrophysics Data System (ADS)

    Mamadou, Ossénatou; Galle, Sylvie; Cohard, Jean-Martial; Peugeot, Christophe; Kounouhewa, Basile; Biron, Romain; Hector, Basile; Zannou, Arnaud Bruno

    2016-10-01

    Natural ecosystems in sub-Saharan Africa are experiencing intense changes that will probably modify land surface feedbacks and consequently the regional climate. In this study, we have analyzed water vapor (QLE) and sensible heat (QH) fluxes over a woodland (Bellefoungou, BE) and a cultivated area (Nalohou, NA) in the Sudanian climate of Northern Benin, using 2 years (from July 2008 to June 2010) of eddy covariance measurements. The evaporative fraction (EF) response to environmental and surface variables was investigated at seasonal scale. Soil moisture was found to be the main environmental factor controlling energy partitioning. During the wet seasons, EF was rather stable with an average of 0.75 ± 0.07 over the woodland and 0.70 ± 0.025 over the cultivated area. This means that 70-75% of the available energy was changed into actual evapotranspiration during the investigated wet seasons depending on the vegetation type. The cumulative annual actual evapotranspiration (AET) varied between 730 ± 50 mm yr-1 at the NA site and 1040 ± 70 mm yr-1 at the BE site. With similar weather conditions at the two sites, the BE site showed 30% higher AET values than the NA site. The sensible heat flux QH at the cultivated site was always higher than that of the woodland site, but observed differences were much less than those of QLE. In a land surface conversion context, these differences are expected to impact both atmospheric dynamics and the hydrological cycle.

  15. The Net Exchange Between Terrestrial Ecosystems and the Atmosphere as a Result of Changes in Land Use

    NASA Technical Reports Server (NTRS)

    Houghton, R. A.

    1998-01-01

    The general purpose of this research was to improve and update (to 1990) estimates of the net flux of carbon between the world's terrestrial ecosystems and the atmosphere from changes in land use (e.g., deforestation and reforestation). The estimates are important for understanding the global carbon cycle, and for predicting future concentrations of atmospheric CO2 that will result from emissions. The emphasis of the first year's research was on the northern temperate zone and boreal forests, where the greatest discrepancy exists between estimates of flux. Forest inventories suggest net sinks of 0.6 PgC/yr; inversion analyses based on atmospheric data and models suggest much larger sinks 2-3.6 PgC/yr (e.g., Tans et al. 1990, Ciais et al. 1995). The work carried out with this grant calculated the flux attributable to changes in land use. The estimated flux was somewhat smaller than the flux calculated from inventory data suggesting that environmental changes have led to a small accumulation of carbon in forests that exceeds the accumulation expected from past rates of harvest. Two publications have described these results (Houghton 1996, 1998). The large difference between these estimates and those obtained with atmospheric data and models remains unexplained. The recent estimate of a 1.7 PgC/yr sink in North America, alone (Fan et al. 1998), is particularly difficult to explain. That part of the sink attributable to land-use change, however, is defined as a result of this grant.

  16. Comparative Efficacy of the Picture Exchange Communication System (PECS) versus a Speech-Generating Device: Effects on Requesting Skills

    ERIC Educational Resources Information Center

    Boesch, Miriam C.; Wendt, Oliver; Subramanian, Anu; Hsu, Ning

    2013-01-01

    An experimental, single-subject research study investigated the comparative efficacy of the Picture Exchange Communication System (PECS) versus a speech-generating device (SGD) in developing requesting skills for three elementary-age children with severe autism and little to no functional speech. Results demonstrated increases in requesting…

  17. Utilizing continuous measurements of delta^{13}C_r, delta18O_r, and net ecosystem exchange of CO_2 and H_2O to understand the effects of inter-annual variability in drought on ecosystem functioning

    NASA Astrophysics Data System (ADS)

    Osuna, J. L.; McDowell, N. G.; Shim, J. H.; Rahn, T.; Pockman, W.

    2011-12-01

    In the semi-arid Southwestern US, seasonal drought has strengthened in recent years due to both a decrease in winter precipitation and delayed onset of the summer monsoon. A process-based understanding of ecosystem response to increased drought stress is vital to predicting the long-term stability of semi-arid biomes. To understand the processes responsible for inter-annual and seasonal variability in net ecosystem carbon and water fluxes, we compared nearly continuous measurements of ecosystem scale respiration (R_e) from an eddy covariance system with the stable carbon and oxygen isotope signals in ecosystem respired CO_2 (delta^{13}C_r and delta^{18}O_r) measured continuously by a tunable diode laser spectrometer (TDL) sampling at various canopy heights at the same site. The study site, at Los Alamos National Laboratory, converted from pitilde{n}on juniper woodland to juniper woodland after over 90% of pitilde{n}ons died in 2002-2003 following multiple years of enhanced drought leaving a high necromass at the site. We analyzed the relationships between the Bowen ratio, delta^{18}O_r, daily and annual accumulated NEE, and delta^{13}C_r to understand the (de)coupling between the response of transpiration and respiration under varying degrees of drought stress. Additionally, we explored the variability in the lag and intensity of ecosystem response to precipitation pulses depending on antecedent conditions. The response of delta^{18}O_r was more consistent across years and seasons whereas variability in the contribution of autotrophic versus heterotrophic respiration appeared to cause differing responses of delta^{13}C_r to drought stress and precipitation pulses. This result was supported by the diurnal CO_2 and H_2O fluxes indicating nearly immediate transpirational water loss initiated by most precipitation pulses. Annual accumulated precipitation (versus pulse size) was a better indicator of delta^{13}C_ r response (i.e. relative contributions of autotrophic

  18. Process coupling and control over the response of net ecosystem CO2 exchange to climate variability and insect disturbance in subalpine forests of the Western US

    NASA Astrophysics Data System (ADS)

    Monson, R. K.; Moore, D. J.; Trahan, N. A.; Scott-Denton, L.; Burns, S. P.; Hu, J.; Bowling, D. R.

    2011-12-01

    Following ten years of studies in subalpine forest ecosystems of the Western US, we have concluded that the tight coupling between gross primary productivity (GPP) and the autotrophic component of soil respiration (Ra) drives responses of net ecosystem CO2 exchange (NEE) to climate variability and insect disturbance. This insight has been gained through long-term eddy flux observations, manipulative plot experiments, analyses of dynamics in the stable isotope compositions of CO2 and H2O, and chamber gas-exchange measurements. Using past observations from these studies, we deployed model-data assimilation techniques and forecast weather/climate modeling to estimate how the coupling between GPP and Ra is likely to affect future (Year 2100) dynamics in NEE. The amount of winter snow and its melting dynamics in the spring represents the dominant control over interannual variation in GPP. Using the SIPNET ecosystem process model, combined with knowledge about the stable isotope content of different water sources, we estimated that approximately 75% of growing season GPP is coupled to the use of snowmelt water, whereas approximately 25% is coupled to summer rain. The tight coupling between GPP and winter snow pack drives a similar tight coupling between soil respiration (Rs) and winter snow pack. Manipulation of snow pack on forest plots has shown that Rs increases with increased snow pack, and this effect disappears when trees are girdled, which stops the transfer of GPP to roots and the soil rhizosphere. Higher-than-normal winter snowpacks cause the carbon isotope ratios of soil-respired CO2 to be depleted in 13C, reflecting a signal of lower photosynthetic water-use efficiency in the GPP that is transferred to the soil rhizosphere. Large-scale forest disturbance due to catastrophic tree mortality from mountain pine beetle attack causes an initial (2-3 year) reduction in Rs, which is attributable to the loss of GPP and its effect on Ra. This near-term reduction in Rs

  19. Effect of non-homogeneity in flux footprint on the interpretation of seasonal, annual, and interannual ecosystem carbon exchange

    NASA Astrophysics Data System (ADS)

    Griebel, A.; Bennett, L. T.; Metzen, D.; Cleverly, J. R.; Burba, G. G.; Arndt, S. K.

    2015-12-01

    Carbon flux measurements using the eddy covariance method rely on several assumptions, including reasonably uniform terrain and homogenous vegetation. These are not always possible in complex terrain, structurally variable native vegetation or in disturbed ecosystems. Consequently, an increasing number of flux sites are located over not fully homogeneous areas. This implies that observed year-to-year variations in CO2 budgets may not always be related only to changes in the key driving factors such as weather, canopy state and physiology, but may also be affected by differences in the flux footprints between years. This may bias budget estimates over many locations, since a large number of flux sites are affected by wind channelling, contrasting climatic conditions with wind direction (e.g. maritime sites) and by variations of continental-scale climate patterns that modify prevailing wind directions. We tested the effects of a non-homogeneous footprint on annual carbon estimates for an evergreen forest, where the combination of terrain, weather and anthropogenic management shaped the local forest structure. Interactions among these factors caused the key drivers regulating carbon fluxes (such as LAI, temperature, VPD and turbulence) to vary significantly with wind direction, and their combinations resulted in pronounced carbon sequestration 'hotspots' that impacted instantaneous fluxes. These were most distinctive during the summer months, and they varied in extent and magnitude depending on prevailing weather. Consequently, interannual variations in footprints affected up to 18.9% of seasonal estimates during the summer months, and up to 23.1% of annual carbon budget estimates. The footprint-related bias was largest at 48.7% under 'ideal' uptake conditions (clear sky, mid-day during summer). We further present a procedure to recognise and quantify the apparent interannual variations in carbon estimates attributable to year-to-year variations in flux footprint.

  20. Hyporheic exchange and fulvic acid redox reactions in an Alpine stream/wetland ecosystem, Colorado Front Range.

    PubMed

    Miller, Matthew P; McKnight, Diane M; Cory, Rose M; Williams, Mark W; Runkel, Robert L

    2006-10-01

    The influence of hyporheic zone interactions on the redox state of fulvic acids and other redox active species was investigated in an alpine stream and adjacent wetland, which is a more reducing environment. A tracer injection experiment using bromide (Br-) was conducted in the stream system. Simulations with a transport model showed that rates of exchange between the stream and hyporheic zone were rapid (alpha approximately 10(-3) s(-1)). Parallel factor analysis of fluorescence spectra was used to quantifythe redox state of dissolved fulvic acids. The rate coefficient for oxidation of reduced fulvic acids (lambda = 6.5 x 10(-3) s(-1)) in the stream indicates that electron-transfer reactions occur over short time scales. The rate coefficients for decay of ammonium (lambda = 1.2 x 10(-3) s(-1)) and production of nitrate (lambda = -1.0 x 10(-3) s(-1)) were opposite in sign but almost equal in magnitude. Our results suggest that fulvic acids are involved in rapid electron-transfer processes in and near the stream channel and may be important in determining ecological energy flow at the catchment scale.

  1. Hyporheic exchange and fulvic acid redox reactions in an alpine stream/wetland ecosystem, Colorado front range

    USGS Publications Warehouse

    Miller, Matthew P.; McKnight, Diane M.; Cory, R.M.; Williams, Mark W.; Runkel, Robert L.

    2006-01-01

    The influence of hyporheic zone interactions on the redox state of fulvic acids and other redox active species was investigated in an alpine stream and adjacent wetland, which is a more reducing environment. A tracer injection experiment using bromide (Br-) was conducted in the stream system. Simulations with a transport model showed that rates of exchange between the stream and hyporheic zone were rapid (?? ??? 10-3 s -1). Parallel factor analysis of fluorescence spectra was used to quantify the redox state of dissolved fulvic acids. The rate coefficient for oxidation of reduced fulvic acids (?? = 6.5 ?? 10-3 s -1) in the stream indicates that electron-transfer reactions occur over short time scales. The rate coefficients for decay of ammonium (?? = 1.2 ?? 10-3 s-1) and production of nitrate (?? = -1.0 ?? 10-3 s-1) were opposite in sign but almost equal in magnitude. Our results suggest that fulvic acids are involved in rapid electron-transfer processes in and near the stream channel and may be important in determining ecological energy flow at the catchment scale. ?? 2006 American Chemical Society.

  2. On the difference in the net ecosystem exchange of CO2 between deciduous and evergreen forests in the southeastern United States.

    PubMed

    Novick, Kimberly A; Oishi, A Christopher; Ward, Eric J; Siqueira, Mario B S; Juang, Jehn-Yih; Stoy, Paul C

    2015-02-01

    The southeastern United States is experiencing a rapid regional increase in the ratio of pine to deciduous forest ecosystems at the same time it is experiencing changes in climate. This study is focused on exploring how these shifts will affect the carbon sink capacity of southeastern US forests, which we show here are among the strongest carbon sinks in the continental United States. Using eight-year-long eddy covariance records collected above a hardwood deciduous forest (HW) and a pine plantation (PP) co-located in North Carolina, USA, we show that the net ecosystem exchange of CO2 (NEE) was more variable in PP, contributing to variability in the difference in NEE between the two sites (ΔNEE) at a range of timescales, including the interannual timescale. Because the variability in evapotranspiration (ET) was nearly identical across the two sites over a range of timescales, the factors that determined the variability in ΔNEE were dominated by those that tend to decouple NEE from ET. One such factor was water use efficiency, which changed dramatically in response to drought and also tended to increase monotonically in nondrought years (P < 0.001 in PP). Factors that vary over seasonal timescales were strong determinants of the NEE in the HW site; however, seasonality was less important in the PP site, where significant amounts of carbon were assimilated outside of the active season, representing an important advantage of evergreen trees in warm, temperate climates. Additional variability in the fluxes at long-time scales may be attributable to slowly evolving factors, including canopy structure and increases in dormant season air temperature. Taken together, study results suggest that the carbon sink in the southeastern United States may become more variable in the future, owing to a predicted increase in drought frequency and an increase in the fractional cover of southern pines.

  3. A comparative modeling study of soil water dynamics in a desert ecosystem

    NASA Astrophysics Data System (ADS)

    Kemp, Paul R.; Reynolds, James F.; Pachepsky, Yakov; Chen, Jia-Lin

    1997-01-01

    We compared three different soil water models to evaluate the extent to which variation in plant growth form and cover and soil texture along a topographic gradient interact to affect relative rates of evaporation and transpiration under semiarid conditions. The models all incorporated one-dimensional distribution of water in the soil and had separate functions for loss of water through transpiration and soil evaporation but differed in the degree of mechanism and emphasis. PALS-SW (Patch Arid Lands Simulator-Soil Water) is a mechanistic model that includes soil water fluxes and emphasizes the physiological control of water loss by different plant life forms along the gradient. 2DSOIL is a mechanistic model that emphasizes the physical aspects of soil water fluxes. SWB (Soil Water Budget) is a simple water budget model that has no soil water redistribution and includes simplified schemes for soil evaporation and transpiration by different life forms. The model predictions were compared to observed soil water distributions at five positions along the gradient. All models predicted soil water distributions reasonably well and, for the most part, predicted similar trends along the transect in the fractions of water lost as soil evaporation versus transpiration. Transpiration was lowest (about 40% of total evapotranspiration (ET)) for the creosote bush community, which had the lowest plant cover (30% peak cover). The fraction of ET as transpiration increased with increasing plant cover, with 2DSOIL predicting the highest transpiration (60% of total ET) for the mixed vegetation community (60% peak cover) on relatively fine textured soil and PALSr SW predicting highest transpiration (69% of total ET) for the mixed vegetation community (70% peak cover) on relatively coarse textured soil. The community type had an effect on the amount of water lost as transpiration primarily via depth and distribution of roots. In this respect, PALS-SW predicted greatest differences among

  4. Early Season Goose Grazing Has a Greater Effect Than Advancement of the Growing Season on Net Ecosystem Exchange in a Sub-Arctic Coastal Wetland of Western Alaska

    NASA Astrophysics Data System (ADS)

    Leffler, A. J.; Choi, R. T.; Beard, K. H.; Schmutz, J. A.; Welker, J. M.

    2014-12-01

    The wetlands of the Yukon-Kuskokwim Delta in western Alaska are important breeding areas for geese and are experiencing rapid climate change. Growing seasons now begin earlier but geese have not advanced their breeding enough to match the advancement of spring. Consequently, geese enter a greener system that may be less nutritious than in the past because grasses and sedges have highest nutrient density shortly following emergence. One consequence of this changing phenology is that vegetation consumed by geese and returned as feces may have a different carbon to nitrogen ratio than in the past, which may influence net ecosystem exchange (NEE). We examine the effect of the advancement of the growing season and different arrival times by Brant Geese on NEE. Our study consists of six experimental blocks, each with nine plots. Half of the plots are warmed to advance the growing season. Two plots each receive early, mid, and late season grazing; the remaining two plots are not grazed and there is one control plot. In one block, we monitor NEE hourly with an automatic gas exchange system. In the other blocks, survey measurements of NEE and ecosystem respiration (ER) are made periodically with a portable system. Geese remove considerable vegetation from the system and maintain "grazing lawns" <1 cm tall of high quality forage. Plots grazed in the early summer were net sources of C to the atmosphere, releasing ca. 2-4 g m-2 d-1. Non-grazed plots were C sinks of similar magnitude. Grazing had little effect on ER but an advanced growing season enhanced ER in the plots by ca. 0.5 μmol m-2 s-1. We observed a similar advanced growing season effect on NEE that we attribute to enhanced ER. Consequently, the larger influence on NEE in the system is grazing and this influence is through removal of photosynthetic tissue. Grazing by Brant Geese shifts large areas of this coastal wetland to a C source while advanced growing season only reduces the strength of the C sink.

  5. Strong Links Between Teleconnections and Ecosystem Exchange Found at a Pacific Northwest Old-Growth Forest from Flux Tower and MODIS EVI Data

    SciTech Connect

    Wharton, S; Chasmer, L; Falk, M; Paw U, K T

    2009-03-12

    Variability in three Pacific teleconnection patterns are examined to see if net carbon exchange at a low-elevation, old-growth forest is affected by climatic changes associated with these periodicities. Examined are the Pacific Decadal Oscillation (PDO), Pacific/North American Oscillation (PNA) and El Nino-Southern Oscillation (ENSO). We use nine years of eddy covariance CO{sub 2}, H{sub 2}O and energy fluxes measured at the Wind River AmeriFlux site, Washington, USA and eight years of tower-pixel remote sensing data from the Moderate Resolution Imaging Spectroradiometer (MODIS) to address this question. We compute a new Composite Climate Index (CCI) based on the three Pacific Oscillations to divide the measurement period into positive- (2003 and 2005), negative- (1999 and 2000) and neutral-phase climate years (2001, 2002, 2004, 2006 and 2007). The forest transitioned from an annual net carbon sink (NEP = + 217 g C m{sup -2} year{sup -1}, 1999) to a source (NEP = - 100 g C m{sup -2} year{sup -1}, 2003) during two dominant teleconnection patterns. Net ecosystem productivity (NEP), water use efficiency (WUE) and light use efficiency (LUE) were significantly different (P < 0.01) during positive (NEP = -0.27 g C m{sup -2} day{sup -1}, WUE = 4.1 mg C/g H{sub 2}O, LUE = 0.94 g C MJ{sup -1}) and negative (NEP = +0.37 g C m{sup -2} day{sup -1}, WUE = 3.4 mg C/g H{sub 2}O, LUE = 0.83 g C MJ{sup -1}) climate phases. The CCI was linked to variability in the MODIS Enhanced Vegetation Index (EVI) but not to MODIS Fraction of absorbed Photosynthetically Active Radiation (FPAR). EVI was highest during negative climate phases (1999 and 2000) and was positively correlated with NEP and showed potential for using MODIS to estimate teleconnection-driven anomalies in ecosystem CO{sub 2} exchange in old-growth forests. This work suggests that any increase in the strength or frequency of ENSO coinciding with in-phase, low frequency Pacific oscillations (PDO and PNA) will likely increase

  6. Evaluating stomatal ozone fluxes in WRF-Chem: Comparing ozone uptake in Mediterranean ecosystems

    NASA Astrophysics Data System (ADS)

    Rydsaa, J. H.; Stordal, F.; Gerosa, G.; Finco, A.; Hodnebrog, Ø.

    2016-10-01

    The development of modelling tools for estimating stomatal uptake of surface ozone in vegetation is important for the assessment of potential damage induced due to both current and future near surface ozone concentrations. In this study, we investigate the skill in estimating ozone uptake in plants by the Weather Research and Forecasting model coupled with chemistry (WRF-Chem) V3.6.1, with the Wesely dry deposition scheme. To validate the stomatal uptake of ozone, the model simulations were compared with field measurements of three types of Mediterranean vegetation, over seven different periods representing various meteorological conditions. Some systematic biases in modelled ozone fluxes are revealed; the lack of an explicit and time varying dependency on plants' water availability results in overestimated daytime ozone stomatal fluxes particularly in dry periods. The optimal temperature in the temperature response function is likely too low for the woody species tested here. Also, too low nighttime stomatal conductance leads to underestimation of ozone uptake during night. We demonstrate that modelled stomatal ozone flux is improved by accounting for vapor pressure deficit in the ambient air. Based on the results of the overall comparison to measured fluxes, we propose that additional improvements to the stomatal conductance parameterization should be implemented before applying the modelling system for estimating ozone doses and potential damage to vegetation.

  7. Comparative daily dynamics of mycorrhizal fungal hyphae across differing ecosystems using an automated minirhizotron and sensor network

    NASA Astrophysics Data System (ADS)

    Allen, M. F.

    2013-05-01

    allow us to undertake comparative analyses of soil organisms, such as fungi, on time scale at which the respond to changing weather events and to track individual hyphae to determine turnover, the crucial missing datapoint in carbon modeling. They also tell us that each different ecosystem responds differently, and non-linearly to changes in T and SM, with dramatic shifts in C fluxes. If we are to obtain a mechanistic understanding of global carbon dynamics, we need to understand how soil organisms respond to both fine-scale and coarse scale shifts in different ecosystems.

  8. A comparative study of ion exchange kinetics in zinc/lead-modified zeolite-clinoptilolite systems.

    PubMed

    Trgo, M; Perić, J; Medvidović, N Vukojević

    2006-08-25

    The kinetics of zinc and lead ions removal by modified zeolite-clinoptilolite has been investigated. The rate of the ion exchange process for lead ions is faster than for zinc ions, as well as the time needed to reach the equilibrium. The ion exchange capacity of zeolite of lead ions is doubly higher than that of zinc ions. Diffusion models according to the Vermeulen's approximation, the parabolic diffusion model and the homogeneous diffusion model have been tested with the experimental data of ion exchange for zinc and lead. For both systems examined, the best fit of the models proposed with the experimental data was shown by the Vermeulen's approximation and the homogeneous diffusion model with t-->t(infinity). The diffusion coefficients are calculated from kinetic models of lead ions they are of the order of 10(-6)cm(2)/min, constant for all examined initial concentrations and not dependent on time. The diffusion coefficients in the system of zinc ions is of the order of 10(-8)cm(2)/min, also independent of initial concentrations, but decreasing with time from the beginning of ion exchange to the equilibrium.

  9. Research on Study Abroad, Mobility, and Student Exchange in Comparative Education Scholarship

    ERIC Educational Resources Information Center

    Streitwieser, Bernhard T.; Le, Emily; Rust, Val

    2012-01-01

    For many years there has been research on study abroad, student mobility and international student exchange; however in the last two decades the volume and scope of this work has increased significantly. There are now specific academic journals, a host of new books each year, expansive reports by international research organizations, and an…

  10. Comparing Acquisition of Exchange-Based and Signed Mands with Children with Autism

    ERIC Educational Resources Information Center

    Barlow, Kathryn E.; Tiger, Jeffrey H.; Slocum, Sarah K.; Miller, Sarah J.

    2013-01-01

    Therapists and educators frequently teach alternative-communication systems, such as picture exchanges or manual signs, to individuals with developmental disabilities who present with expressive language deficits. Michael (1985) recommended a taxonomy for alternative communication systems that differentiated between selection-based systems in…

  11. Comparative analysis of feeding ecology of capelin from two shelf ecosystems, off Newfoundland and in the Barents Sea

    NASA Astrophysics Data System (ADS)

    Dalpadado, Padmini; Mowbray, Fran

    2013-07-01

    Four years of capelin (Mallotus villosus) diet data were examined from each of two ecosystems where capelin are an important forage species, the NW Atlantic off Newfoundland and the Barents Sea. Trophic studies from the two areas showed that, the Total Fullness Index (TFI), which reflects the diet weight, was significantly lower in capelin off Newfoundland compared to the Barents Sea, suggestive of poorer feeding conditions for Newfoundland capelin during the study period. In both regions, the copepod, Calanus finmarchicus dominated the diet of smaller capelin (<12 cm) comprising over half of their stomach content. However, there was a major difference in the diet of larger capelin. In the Barents Sea, a pronounced shift in the diet from copepods to krill, mostly Thysanoessa inermis, was observed in larger capelin (>12 cm), with krill being the largest contributor to the diet weight. In contrast, off Newfoundland, copepods remained the most important prey in larger capelin. In both ecosystems arctic amphipods, mostly dominated by Themisto libellula, contributed a small amount to the diet of larger capelin but were nearly absent in the diet of smaller fish. Findings for Newfoundland waters contradict past studies where krill (T. raschii) seems to have been a major component in the diet, especially for mature capelin. In both systems diurnal patterns in TFI indicated that daytime feeding was more successful. In general, a short efficient food chain (phytoplankton via Calanus or herbivorous krill to capelin) was observed in both regions. The extent of consumption of carnivorous zooplankton such as hyperiid amphipods may lengthen the trophic levels and thus reduce efficiency of energy transfer.

  12. Comparative genomics analysis of Streptococcus isolates from the human small intestine reveals their adaptation to a highly dynamic ecosystem.

    PubMed

    Van den Bogert, Bartholomeus; Boekhorst, Jos; Herrmann, Ruth; Smid, Eddy J; Zoetendal, Erwin G; Kleerebezem, Michiel

    2013-01-01

    The human small-intestinal microbiota is characterised by relatively large and dynamic Streptococcus populations. In this study, genome sequences of small-intestinal streptococci from S. mitis, S. bovis, and S. salivarius species-groups were determined and compared with those from 58 Streptococcus strains in public databases. The Streptococcus pangenome consists of 12,403 orthologous groups of which 574 are shared among all sequenced streptococci and are defined as the Streptococcus core genome. Genome mining of the small-intestinal streptococci focused on functions playing an important role in the interaction of these streptococci in the small-intestinal ecosystem, including natural competence and nutrient-transport and metabolism. Analysis of the small-intestinal Streptococcus genomes predicts a high capacity to synthesize amino acids and various vitamins as well as substantial divergence in their carbohydrate transport and metabolic capacities, which is in agreement with observed physiological differences between these Streptococcus strains. Gene-specific PCR-strategies enabled evaluation of conservation of Streptococcus populations in intestinal samples from different human individuals, revealing that the S. salivarius strains were frequently detected in the small-intestine microbiota, supporting the representative value of the genomes provided in this study. Finally, the Streptococcus genomes allow prediction of the effect of dietary substances on Streptococcus population dynamics in the human small-intestine.

  13. Assessment of Metal Toxicity in Marine Ecosystems: Comparative Toxicity Potentials for Nine Cationic Metals in Coastal Seawater.

    PubMed

    Dong, Yan; Rosenbaum, Ralph K; Hauschild, Michael Z

    2016-01-05

    This study is a first attempt to develop globally applicable and spatially differentiated marine comparative toxicity potentials (CTPs) or ecotoxicity characterization factors for metals in coastal seawater for use in life cycle assessment. The toxicity potentials are based exclusively on marine ecotoxicity data and take account of metal speciation and bioavailability. CTPs were developed for nine cationic metals (Cd, Cr(III), Co, Cu(II), Fe(III), Mn, Ni, Pb, and Zn) in 64 large marine ecosystems (LMEs) covering all coastal waters in the world. The results showed that the CTP of a specific metal varies 3-4 orders of magnitude across LMEs, largely due to different seawater residence times. Therefore, the highest toxicity potential for metals was found in the LMEs with the longest seawater residence times. Across metals, the highest CTPs were observed for Cd, Pb, and Zn. At the concentration levels occurring in coastal seawaters, Fe acts not as a toxic agent but as an essential nutrient and thus has CTPs of zero.

  14. Using a Regional Cluster of AmeriFlux Sites in Central California to Advance Our Knowledge on Decadal-Scale Ecosystem-Atmosphere Carbon Dioxide Exchange

    SciTech Connect

    Baldocchi, Dennis

    2015-03-24

    Continuous eddy convariance measurements of carbon dioxide, water vapor and heat were measured continuously between an oak savanna and an annual grassland in California over a 4 year period. These systems serve as representative sites for biomes in Mediterranean climates and experience much seasonal and inter-annual variability in temperature and precipitation. These sites hence serve as natural laboratories for how whole ecosystem will respond to warmer and drier conditions. The savanna proved to be a moderate sink of carbon, taking up about 150 gC m-2y-1 compared to the annual grassland, which tended to be carbon neutral and often a source during drier years. But this carbon sink by the savanna came at a cost. This ecosystem used about 100 mm more water per year than the grassland. And because the savanna was darker and rougher its air temperature was about 0.5 C warmer. In addition to our flux measurements, we collected vast amounts of ancillary data to interpret the site and fluxes, making this site a key site for model validation and parameterization. Datasets consist of terrestrial and airborne lidar for determining canopy structure, ground penetrating radar data on root distribution, phenology cameras monitoring leaf area index and its seasonality, predawn water potential, soil moisture, stem diameter and physiological capacity of photosynthesis.

  15. The CROSTVOC project - an integrated approach to study the effect of stress on BVOC exchange between agricultural crops and grassland ecosystems and the atmosphere

    NASA Astrophysics Data System (ADS)

    Amelynck, Crist; Heinesch, Bernard; Aubinet, Marc; Bachy, Aurélie; Delaplace, Pierre; Digrado, Anthony; du Jardin, Patrick; Fauconnier, Marie-Laure; Mozaffar, Ahsan; Schoon, Niels

    2015-04-01

    Global changes in atmospheric composition and climate are expected to affect BVOC exchange between terrestrial vegetation and the atmosphere through changes in the drivers of constitutive BVOC emissions and by increases in frequency and intensity of biotic or abiotic stress episodes. Indeed, several studies indicate changes in the emission patterns of constitutive BVOCs and emission of stress-induced BVOCs following heat, drought and oxidative stress, amongst others. Relating changes in BVOC emissions to the occurrence of one or multiple stressors in natural environmental conditions is not straightforward and only few field studies have dealt with it, especially for agricultural crop and grassland ecosystems. The CROSTVOC project aims to contribute in filling this knowledge gap in three ways. Firstly, it aims at performing long-term BVOC emission field measurements from maize (Zea mays L.) and wheat (Triticum aestivum L.), two important crop species on the global scale, and from grassland. This should lead to a better characterization of (mainly oxygenated) BVOC emissions from these understudied ecosystems, allowing a better representation of those emissions in air quality and atmospheric chemistry and transport models. BVOC fluxes are obtained by the Disjunct Eddy Covariance by mass scanning (DEC-MS) technique, using a hs-PTR-MS instrument for BVOC analysis. Secondly, the eddy covariance BVOC flux measurements (especially at the grassland site) will be accompanied by ozone flux, chlorophyll fluorescence, photosynthesis and soil moisture measurements, amongst others, to allow linking alterations in BVOC emissions to stress episodes. Simultaneously, automated dynamic enclosures will be deployed in order to detect specific abiotic and biotic stress markers by PTR-MS and identify them unambiguously by GC-MS. Thirdly, the field measurements will be accompanied by laboratory BVOC flux measurements in an environmental chamber in order to better disentangle the responses

  16. Comparative respiratory morphology: themes and principles in the design and construction of the gas exchangers.

    PubMed

    Maina, J N

    2000-02-15

    Along the evolutionary continuum, a kaleidoscope of gas exchangers has evolved from the simple cell membrane of the primeval unicells. The most momentous events in this process were: the intensification of molecular oxygen in the biosphere and its appropriation into aerobic metabolism, the rise of multicellular organisms, the development of a circulatory system and carrier pigments in blood, the advocacy of air breathing, adoption of suctional breathing, and the shift to endothermy. To satisfy species-specific needs for oxygen, some constraints were overcome through transactions that obliged certain compromises and trade-offs. Optimal designs of the gas exchangers for particular phylogenetic levels of development, habitat, and lifestyle have developed only so far as to satisfy prescribed needs. The efficiency of the human lung, for example, falls well below those of certain taxa that are considered to be relatively "less advanced." Utilizing different resources and strategies, in fascinating processes of conformity, different groups of animals have developed similar respiratory structures. In most cases, the analogy reflects evolutionary convergence in response to corresponding selective pressures rather than common ancestry. Anat Rec (New Anat) 261:25-44, 2000.

  17. Hydrogen Exchange Mass Spectrometry of Related Proteins with Divergent Sequences: A Comparative Study of HIV-1 Nef Allelic Variants

    NASA Astrophysics Data System (ADS)

    Wales, Thomas E.; Poe, Jerrod A.; Emert-Sedlak, Lori; Morgan, Christopher R.; Smithgall, Thomas E.; Engen, John R.

    2016-06-01

    Hydrogen exchange mass spectrometry can be used to compare the conformation and dynamics of proteins that are similar in tertiary structure. If relative deuterium levels are measured, differences in sequence, deuterium forward- and back-exchange, peptide retention time, and protease digestion patterns all complicate the data analysis. We illustrate what can be learned from such data sets by analyzing five variants (Consensus G2E, SF2, NL4-3, ELI, and LTNP4) of the HIV-1 Nef protein, both alone and when bound to the human Hck SH3 domain. Regions with similar sequence could be compared between variants. Although much of the hydrogen exchange features were preserved across the five proteins, the kinetics of Nef binding to Hck SH3 were not the same. These observations may be related to biological function, particularly for ELI Nef where we also observed an impaired ability to downregulate CD4 surface presentation. The data illustrate some of the caveats that must be considered for comparison experiments and provide a framework for investigations of other protein relatives, families, and superfamilies with HX MS.

  18. A comparative study of linear and non-linear regression analysis for ammonium exchange by clinoptilolite zeolite.

    PubMed

    Karadag, Dogan; Koc, Yunus; Turan, Mustafa; Ozturk, Mustafa

    2007-06-01

    Ammonium ion exchange from aqueous solution using clinoptilolite zeolite was investigated at laboratory scale. Batch experimental studies were conducted to evaluate the effect of various parameters such as pH, zeolite dosage, contact time, initial ammonium concentration and temperature. Freundlich and Langmuir isotherm models and pseudo-second-order model were fitted to experimental data. Linear and non-linear regression methods were compared to determine the best fitting of isotherm and kinetic model to experimental data. The rate limiting mechanism of ammonium uptake by zeolite was determined as chemical exchange. Non-linear regression has better performance for analyzing experimental data and Freundlich model was better than Langmuir to represent equilibrium data.

  19. The effects of clouds and aerosols on net ecosystem CO2 exchange over semi-arid Loess Plateau of Northwest China

    NASA Astrophysics Data System (ADS)

    Jing, X.; Huang, J.; Wang, G.; Higuchi, K.; Bi, J.; Sun, Y.; Yu, H.; Wang, T.

    2010-09-01

    The impacts of clouds and atmospheric aerosols on the terrestrial carbon cycle at semi-arid Loess Plateau in Northwest China are investigated, by using the observation data obtained at the SACOL (Semi-Arid Climate and Environment Observatory of Lanzhou University) site. Daytime (solar elevation angles of larger than 50°) net ecosystem exchange (NEE) of CO2 obtained during the midgrowing season (July-August) are analyzed with respect to variations in the diffuse radiation, cloud cover and aerosol optical depth (AOD). Results show a significant impact by clouds on the CO2 uptake by the grassland (with smaller LAI values) located in a semi-arid region, quite different from areas covered by forests and crops. The light saturation levels in the canopy are low, with a value of about 434.8 W m-2. Thus, under overcast conditions of optically thick clouds, the CO2 uptake increases with increasing clearness index (the ratio of global solar radiation received at the Earth surface to the extraterrestrial irradiance at a plane parallel to the Earth surface), and a maximum CO2 uptake and light use efficiency of vegetation occur with the clearness index of about 0.37 and lower air temperature. Under other sky conditions, CO2 uptake decreases with cloudiness but light use efficiency is enhanced, due to increased diffuse fraction of PAR. Additionally, under cloudy conditions, changes in the NEE of CO2 also result from the interactions of many environmental factors, especially the air temperature. In contrast to its response to changes in solar radiation, the carbon uptake shows a slightly negative response to increased AOD. The reason for the difference in the response of the semi-arid grassland from that of the forest and crop lands may be due to the difference in the canopy's architectural structure.

  20. Ecosystem CO2 and CH4 exchange in a mixed tundra and a fen within a hydrologically diverse Arctic landscape: 2. Modeled impacts of climate change

    NASA Astrophysics Data System (ADS)

    Grant, R. F.

    2015-07-01

    Climate change will have important effects on arctic productivity and greenhouse gas exchange. These changes were projected by the model ecosys under an Special Report on Emissions Scenarios (SRES) A2 scenario over the 21st century for a landscape including an upland tundra and a lowland fen at Daring Lake, NWT. Rising temperatures and precipitation caused increases in active layer depths (ALD) and eventual formation of taliks, particularly in the fen, which were attributed to heat advection from warmer and more intense precipitation and downslope flow. These changes raised net primary productivity from more rapid N mineralization and uptake, driven by more rapid heterotrophic respiration and increasing deciduous versus evergreen plant functional types. Consequently, gains in net ecosystem productivity (NEP) of 29 and 10 g C m-2 yr-1 were modeled in the tundra and fen after 90 years. However, CH4 emissions modeled from the fen rose sharply from direct effects of increasing soil temperatures and greater ALD on fermenter and methanogenic populations and from indirect effects of increasing sedge growth, which hastened transfer of CH4 through porous roots to the atmosphere. After 90 years, landscape CH4 emissions increased from 1.1 to 5.2 g C m-2 yr-1 while landscape NEP increased from 34 to 46 g C m-2 yr-1. Positive feedback to radiative forcing from increases in CH4 emissions more than offset negative feedback from increases in NEP. This feedback was largely attributed to rises in CH4 emission caused by heat advection from increasing precipitation, the impacts of which require greater attention in arctic climate change studies.

  1. Ecosystem CO2 and CH4 Exchange in a Mixed Tundra and a Fen Within an Arctic Landscape: Modeled Impacts of Climate Change

    NASA Astrophysics Data System (ADS)

    Grant, R. F.

    2015-12-01

    Climate change will have important effects on arctic productivity and greenhouse gas exchange. These changes were projected by the model ecosys under an SRES A2 scenario over the 21st century for a landscape including an upland tundra and a lowland fen at Daring Lake, NWT. Rising temperatures and precipitation caused increases in active layer depths (ALD) and eventual formation of taliks, particularly in the fen, which were attributed to heat advection from warmer and more intense precipitation and downslope flow. These changes raised net primary productivity from more rapid N mineralization and uptake, driven by more rapid heterotrophic respiration and increasing deciduous vs. evergreen plant functional types. Consequently gains in net ecosystem productivity (NEP) of 29 and 10 g C m-2 y-1 were modelled in the tundra and fen after 90 years. However CH4 emissions modelled from the fen rose sharply from direct effects of increasing soil temperatures and greater ALD on fermenter and methanogenic populations, and from indirect effects of increasing sedge growth which hastened transfer of CH4 through porous roots to the atmosphere. After 90 years, landscape CH4 emissions increased from 1.1 to 5.2 g C m-2 y-1 while landscape NEP increased from 34 to 46 g C m-2 y-1. Positive feedback to radiative forcing from increases in CH4 emissions more than offset negative feedback from increases in NEP. This feedback was largely attributed to rises in CH4 emission caused by heat advection from increasing precipitation, the impacts of which require greater attention in arctic climate change studies.

  2. Comparative Calculation of Heat Exchange with the Ground in Residential Building Including Periodes of Heat Waves

    NASA Astrophysics Data System (ADS)

    Staszczuk, Anna; Kuczyński, Tadeusz; Wojciech, Magdalena; Ziembicki, Piotr

    2016-06-01

    The paper provides verification of 3D transient ground-coupled model to calculation of heat exchange between ground and typical one-storey, passive residential building. The model was performed with computer software WUFI®plus and carried out to estimate the indoor air temperatures during extending hot weather periods. For verifying the results of calculations performed by the WUFI®plus software, the most recent version of EnergyPlus software version was used. Comparison analysis of calculation results obtained with the two above mentioned calculation method was made for two scenarios of slab on ground constructions: without thermal insulation and with thermal insulation under the whole slab area. Comprehensive statistical analysis was done including time series analysis and descriptive statistics parameters.

  3. Comparing patterns of ecosystem service consumption and perceptions of range management between ethnic herders in Inner Mongolia and Mongolia

    NASA Astrophysics Data System (ADS)

    Zhen, L.; Ochirbat, B.; Lv, Y.; Wei, Y. J.; Liu, X. L.; Chen, J. Q.; Yao, Z. J.; Li, F.

    2010-01-01

    Ecosystems in the Central Asian Plateau, which includes the Mongolian Plateau, are becoming increasingly sensitive to human interventions, leading to deterioration of already fragile ecosystems. The goal of this paper is to illustrate human dependence on an ecosystem by identifying patterns of resource consumption in this region and investigating the knowledge and perceptions of herders living in these ecosystems. Data on consumption in the two regions were collected using structured questionnaires delivered to a total of 252 herders from Mongolia and China's Inner Mongolia. Meat and other animal products remain the dominant food items for most households, accompanied by various vegetables and cereals. This unbalanced diet leads to excessive consumption of protein and fat from animal sources. The major energy sources used by herders are fuelwood, animal dung, crop residues, and dry grass, but consumption patterns differed between the two areas. Mongolian herders rely more heavily on livestock for meeting their consumption needs than herders in Inner Mongolia. Herder knowledge and perceptions of ecosystem conditions and consumption of resources differed between Mongolia and Inner Mongolia, reflecting the influence of different state policies. The data reported and the conclusions drawn are relevant for developing resource management policies for the Mongolian Plateau, but also provide useful insights for any region where livestock production dominates the use of rangeland resources.

  4. The Grammar of Exchange: A Comparative Study of Reciprocal Constructions Across Languages

    PubMed Central

    Majid, Asifa; Evans, Nicholas; Gaby, Alice; Levinson, Stephen C.

    2010-01-01

    Cultures are built on social exchange. Most languages have dedicated grammatical machinery for expressing this. To demonstrate that statistical methods can also be applied to grammatical meaning, we here ask whether the underlying meanings of these grammatical constructions are based on shared common concepts. To explore this, we designed video stimuli of reciprocated actions (e.g., “giving to each other”) and symmetrical states (e.g., “sitting next to each other”), and with the help of a team of linguists collected responses from 20 languages around the world. Statistical analyses revealed that many languages do, in fact, share a common conceptual core for reciprocal meanings but that this is not a universally expressed concept. The recurrent pattern of conceptual packaging found across languages is compatible with the view that there is a shared non-linguistic understanding of reciprocation. But, nevertheless, there are considerable differences between languages in the exact extensional patterns, highlighting that even in the domain of grammar semantics is highly language-specific. PMID:21713188

  5. Comparing the short and long term stability of biodegradable, ceramic and cation exchange membranes in microbial fuel cells.

    PubMed

    Winfield, Jonathan; Chambers, Lily D; Rossiter, Jonathan; Ieropoulos, Ioannis

    2013-11-01

    The long and short-term stability of two porous dependent ion exchange materials; starch-based compostable bags (BioBag) and ceramic, were compared to commercially available cation exchange membrane (CEM) in microbial fuel cells. Using bi-directional polarisation methods, CEM exhibited power overshoot during the forward sweep followed by significant power decline over the reverse sweep (38%). The porous membranes displayed no power overshoot with comparably smaller drops in power during the reverse sweep (ceramic 8%, BioBag 5.5%). The total internal resistance at maximum power increased by 64% for CEM compared to 4% (ceramic) and 6% (BioBag). Under fixed external resistive loads, CEM exhibited steeper pH reductions than the porous membranes. Despite its limited lifetime, the BioBag proved an efficient material for a stable microbial environment until failing after 8 months, due to natural degradation. These findings highlight porous separators as ideal candidates for advancing MFC technology in terms of cost and operation stability.

  6. Do inverse ecosystem models accurately reconstruct plankton trophic flows? Comparing two solution methods using field data from the California Current

    NASA Astrophysics Data System (ADS)

    Stukel, Michael R.; Landry, Michael R.; Ohman, Mark D.; Goericke, Ralf; Samo, Ty; Benitez-Nelson, Claudia R.

    2012-03-01

    Despite the increasing use of linear inverse modeling techniques to elucidate fluxes in undersampled marine ecosystems, the accuracy with which they estimate food web flows has not been resolved. New Markov Chain Monte Carlo (MCMC) solution methods have also called into question the biases of the commonly used L2 minimum norm (L 2MN) solution technique. Here, we test the abilities of MCMC and L 2MN methods to recover field-measured ecosystem rates that are sequentially excluded from the model input. For data, we use experimental measurements from process cruises of the California Current Ecosystem (CCE-LTER) Program that include rate estimates of phytoplankton and bacterial production, micro- and mesozooplankton grazing, and carbon export from eight study sites varying from rich coastal upwelling to offshore oligotrophic conditions. Both the MCMC and L 2MN methods predicted well-constrained rates of protozoan and mesozooplankton grazing with reasonable accuracy, but the MCMC method overestimated primary production. The MCMC method more accurately predicted the poorly constrained rate of vertical carbon export than the L 2MN method, which consistently overestimated export. Results involving DOC and bacterial production were equivocal. Overall, when primary production is provided as model input, the MCMC method gives a robust depiction of ecosystem processes. Uncertainty in inverse ecosystem models is large and arises primarily from solution under-determinacy. We thus suggest that experimental programs focusing on food web fluxes expand the range of experimental measurements to include the nature and fate of detrital pools, which play large roles in the model.

  7. Growing season variability of net ecosystem CO2 exchange and evapotranspiration of a sphagnum mire in the broad-leaved forest zone of European Russia

    NASA Astrophysics Data System (ADS)

    Olchev, A.; Volkova, E.; Karataeva, T.; Novenko, E.

    2013-09-01

    The spatial and temporal variability of net ecosystem exchange (NEE) of CO2 and evapotranspiration (ET) of a karst-hole sphagnum peat mire situated at the boundary between broad-leaved and forest-steppe zones in the central part of European Russia in the Tula region was described using results from field measurements. NEE and ET were measured using a portable measuring system consisting of a transparent ventilated chamber combined with an infrared CO2/H2O analyzer, LI-840A (Li-Cor, USA) along a transect from the southern peripheral part of the mire to its center under sunny clear-sky weather conditions in the period from May to September of 2012 and in May 2013. The results of the field measurements showed significant spatial and temporal variability of NEE and ET that was mainly influenced by incoming solar radiation and ground water level. The seasonal patterns of NEE and ET within the mire were quite different. During the entire growing season the central part of the mire was a sink of CO2 for the atmosphere. NEE reached maximal values in June-July (-6.8 ± 4.2 μmol m-2 s-1). The southern peripheral part of the mire, due to strong shading by the surrounding forest, was a sink of CO2 for the atmosphere in June-July only. ET reached maximal values in the well-lighted central parts of the mire in May (0.34 ± 0.20 mm h-1) mainly because of high air and surface temperatures and the very wet upper peat horizon and sphagnum moss. Herbaceous species made the maximum contribution to the total gross primary production (GPP) in both the central and the peripheral parts of the mire. The contribution of sphagnum to the total GPP of these plant communities was relatively small and ranged on sunny days of July-August from -1.1 ± 1.1 mgC g-1 of dry weight (DW) per hour in the peripheral zone of the mire to -0.6 ± 0.2 mgC g-1 DW h-1 at the mire center. The sphagnum layer made the maximum contribution to total ET at the mire center (0.25 ± 0.10 mm h-1) and the herbaceous

  8. Trace metal biogeochemistry in mangrove ecosystems: a comparative assessment of acidified (by acid sulfate soils) and non-acidified sites.

    PubMed

    Nath, Bibhash; Birch, Gavin; Chaudhuri, Punarbasu

    2013-10-01

    The generation of acidity and subsequent mobilization of toxic metals induced by acid sulfate soils (ASSs) are known to cause severe environmental damage to many coastal wetlands and estuaries of Australia and worldwide. Mangrove ecosystems serve to protect coastal environments, but are increasingly threatened from such ASS-induced acidification due to variable hydrological conditions (i.e., inundation-desiccation cycles). However, the impact of such behaviors on trace metal distribution, bio-availability and accumulation in mangrove tissues, i.e., leaves and pneumatophores, are largely unknown. In this study, we examined how ASS-induced acidifications controlled trace metal distribution and bio-availability in gray mangrove (Avicennia marina) soils and in tissues in the Kooragang wetland, New South Wales, Australia. We collected mangrove soils, leaves and pneumatophores from a part of the wetland acidified from ASS (i.e., an affected site) for detailed biogeochemical studies. The results were compared with samples collected from a natural intertidal mangrove forest (i.e., a control site) located within the same wetland. Soil pH (mean: 5.90) indicated acidic conditions in the affected site, whereas pH was near-neutral (mean: 7.17) in the control site. The results did not show statistically significant differences in near-total and bio-available metal concentrations, except for Fe and Mn, between affected and control sites. Iron concentrations were significantly (p values≤0.001) greater in the affected site, whereas Mn concentrations were significantly (p values≤0.001) greater in the control site. However, large proportions of near-total metals were potentially bio-available in control sites. Concentrations of Fe and Ni were significantly (p values≤0.001) greater in leaves and pneumatophores of the affected sites, whereas Mn, Cu, Pb and Zn were greater in control sites. The degree of metal bio-accumulation in leaves and pneumatophores suggest contrasting

  9. Warming and Carbon Dioxide Enrichment Alter Plant Production and Ecosystem gas Exchange in a Semi-Arid Grassland Through Direct Responses to Global Change Factors and Indirect Effects on Water Relations

    NASA Astrophysics Data System (ADS)

    Morgan, J. A.; Pendall, E.; Williams, D. G.; Bachman, S.; Dijkstra, F. A.; Lecain, D. R.; Follett, R.

    2007-12-01

    were highly species specific. Ecosystem-level gas exchange measurements indicated that interactions between watering and CO2 enrichment increased C cycling over a range of soil moisture conditions, although watering had a greater relative impact on C fluxes than CO2 enrichment. Results from the combined warming and CO2 enrichment experiment in 2007 indicate soil fluxes of CO2 increased with elevated CO2 and warming, but decreased with warming later in the year compared to un-heated controls. Soil CH4 uptake was enhanced by elevated CO2 but reduced by warming, particularly later in the year. Soil fluxes of N2O were unaffected by treatment. These preliminary results indicate potentially strong feedbacks between carbon cycling and warming are mediated by ecosystem processes in this semiarid rangeland.

  10. Evaluating the agreement between measurements and models of net ecosystem exchange at different times and time scales using wavelet coherence: an example using data from the North American Carbon Program Site-Level Interim Synthesis

    NASA Astrophysics Data System (ADS)

    Stoy, P. C.; Dietze, M.; Richardson, A. D.; Vargas, R.; Barr, A. G.; Anderson, R. S.; Arain, M. A.; Baker, I. T.; Black, T. A.; Chen, J. M.; Cook, R. B.; Gough, C. M.; Grant, R. F.; Hollinger, D. Y.; Izaurralde, R. C.; Kucharik, C. J.; Lafleur, P.; Law, B. E.; Liu, S.; Lokupitiya, E.; Luo, Y.; Munger, J. W.; Peng, C.; Poulter, B.; Price, D. T.; Ricciuto, D. M.; Riley, W. J.; Sahoo, A. K.; Schaefer, K.; Schwalm, C. R.; Tian, H.; Verbeeck, H.; Weng, E.

    2013-02-01

    Earth system processes exhibit complex patterns across time, as do the models that seek to replicate these processes. Model output may or may not be significantly related to observations at different times and on different frequencies. Conventional model diagnostics provide an aggregate view of model-data agreement, but usually do not identify the time and frequency patterns of model misfit, leaving unclear the steps required to improve model response to environmental drivers that vary on characteristic frequencies. Wavelet coherence can quantify the times and frequencies at which models and measurements are significantly different. We applied wavelet coherence to interpret the predictions of twenty ecosystem models from the North American Carbon Program (NACP) Site-Level Interim Synthesis when confronted with eddy covariance-measured net ecosystem exchange (NEE) from ten ecosystems with multiple years of available data. Models were grouped into classes with similar approaches for incorporating phenology, the calculation of NEE, and the inclusion of foliar nitrogen (N). Models with prescribed, rather than prognostic, phenology often fit NEE observations better on annual to interannual time scales in grassland, wetland and agricultural ecosystems. Models that calculate NEE as net primary productivity (NPP) minus heterotrophic respiration (HR) rather than gross ecosystem productivity (GPP) minus ecosystem respiration (ER) fit better on annual time scales in grassland and wetland ecosystems, but models that calculate NEE as GPP - ER were superior on monthly to seasonal time scales in two coniferous forests. Models that incorporated foliar nitrogen (N) data were successful at capturing NEE variability on interannual (multiple year) time scales at Howland Forest, Maine. Combined with previous findings, our results suggest that the mechanisms driving daily and annual NEE variability tend to be correctly simulated, but the magnitude of these fluxes is often erroneous

  11. Evaluating the agreement between measurements and models of net ecosystem exchange at different times and timescales using wavelet coherence: an example using data from the North American Carbon Program Site-Level Interim Synthesis

    NASA Astrophysics Data System (ADS)

    Stoy, P. C.; Dietze, M. C.; Richardson, A. D.; Vargas, R.; Barr, A. G.; Anderson, R. S.; Arain, M. A.; Baker, I. T.; Black, T. A.; Chen, J. M.; Cook, R. B.; Gough, C. M.; Grant, R. F.; Hollinger, D. Y.; Izaurralde, R. C.; Kucharik, C. J.; Lafleur, P.; Law, B. E.; Liu, S.; Lokupitiya, E.; Luo, Y.; Munger, J. W.; Peng, C.; Poulter, B.; Price, D. T.; Ricciuto, D. M.; Riley, W. J.; Sahoo, A. K.; Schaefer, K.; Schwalm, C. R.; Tian, H.; Verbeeck, H.; Weng, E.

    2013-11-01

    Earth system processes exhibit complex patterns across time, as do the models that seek to replicate these processes. Model output may or may not be significantly related to observations at different times and on different frequencies. Conventional model diagnostics provide an aggregate view of model-data agreement, but usually do not identify the time and frequency patterns of model-data disagreement, leaving unclear the steps required to improve model response to environmental drivers that vary on characteristic frequencies. Wavelet coherence can quantify the times and timescales at which two time series, for example time series of models and measurements, are significantly different. We applied wavelet coherence to interpret the predictions of 20 ecosystem models from the North American Carbon Program (NACP) Site-Level Interim Synthesis when confronted with eddy-covariance-measured net ecosystem exchange (NEE) from 10 ecosystems with multiple years of available data. Models were grouped into classes with similar approaches for incorporating phenology, the calculation of NEE, the inclusion of foliar nitrogen (N), and the use of model-data fusion. Models with prescribed, rather than prognostic, phenology often fit NEE observations better on annual to interannual timescales in grassland, wetland and agricultural ecosystems. Models that calculated NEE as net primary productivity (NPP) minus heterotrophic respiration (HR) rather than gross ecosystem productivity (GPP) minus ecosystem respiration (ER) fit better on annual timescales in grassland and wetland ecosystems, but models that calculated NEE as GPP minus ER were superior on monthly to seasonal timescales in two coniferous forests. Models that incorporated foliar nitrogen (N) data were successful at capturing NEE variability on interannual (multiple year) timescales at Howland Forest, Maine. The model that employed a model-data fusion approach often, but not always, resulted in improved fit to data, suggesting

  12. Coupled cryoconite ecosystem structure-function relationships are revealed by comparing bacterial communities in alpine and Arctic glaciers.

    PubMed

    Edwards, Arwyn; Mur, Luis A J; Girdwood, Susan E; Anesio, Alexandre M; Stibal, Marek; Rassner, Sara M E; Hell, Katherina; Pachebat, Justin A; Post, Barbara; Bussell, Jennifer S; Cameron, Simon J S; Griffith, Gareth Wyn; Hodson, Andrew J; Sattler, Birgit

    2014-08-01

    Cryoconite holes are known as foci of microbial diversity and activity on polar glacier surfaces, but are virtually unexplored microbial habitats in alpine regions. In addition, whether cryoconite community structure reflects ecosystem functionality is poorly understood. Terminal restriction fragment length polymorphism and Fourier transform infrared metabolite fingerprinting of cryoconite from glaciers in Austria, Greenland and Svalbard demonstrated cryoconite bacterial communities are closely correlated with cognate metabolite fingerprints. The influence of bacterial-associated fatty acids and polysaccharides was inferred, underlining the importance of bacterial community structure in the properties of cryoconite. Thus, combined application of T-RFLP and FT-IR metabolite fingerprinting promises high throughput, and hence, rapid assessment of community structure-function relationships. Pyrosequencing revealed Proteobacteria were particularly abundant, with Cyanobacteria likely acting as ecosystem engineers in both alpine and Arctic cryoconite communities. However, despite these generalities, significant differences in bacterial community structures, compositions and metabolomes are found between alpine and Arctic cryoconite habitats, reflecting the impact of local and regional conditions on the challenges of thriving in glacial ecosystems.

  13. Comparative study on performance of a zigzag printed circuit heat exchanger with various channel shapes and configurations

    NASA Astrophysics Data System (ADS)

    Lee, Sang-Moon; Kim, Kwang-Yong

    2013-07-01

    Comparative study has been performed with various channel cross-sectional shapes and channel configurations of a zigzag printed circuit heat exchanger (PCHE), which has been considered as a heat exchanging device for the gas turbine based generation systems. Three-dimensional Reynolds-averaged Navier-Stokes equations and heat transfer equations are solved to analyze conjugate heat transfer in the zigzag channels. The shear stress transport model with a low Reynolds number wall treatment is used as a turbulence closure. The global Nusselt number, Colburn j-factor, effectiveness, and friction factor are used to estimate the thermal-hydraulic performance of the PCHE. Four different shapes of channel cross section (semicircular, rectangular, trapezoidal, and circular) and four different channel configurations are tested to determine their effects on thermal-hydraulic performance. The rectangular channel shows the best thermal performance but the worst hydraulic performance, while the circular channel shows the worst thermal performance. The Colburn j-factor and friction factor are found to be inversely proportional to the Reynolds number in cold channels, while the effectiveness and global Nusselt number are proportional to the Reynolds number.

  14. [Comparative analysis of gas exchange and cardiorespiratory systems reactions to increasing normobaric hypoxia and physical load of swimmers and skiers].

    PubMed

    Krivoshchekin, S G; Divert, V E; Mel'nikov, V N; Vodianitskiĭ, S N; Girenko, L A

    2013-01-01

    Qualification comparable groups of young men engaged in cyclic kinds of sports were tested with stepwise accruing loads on bicycle ergometer and 25-minute exponential increasing normobaric hypoxia to final concentration of 10% oxygen. Group of skiers, having the greatest values of the maximal oxygen consumption at muscular work, show the relaxed cardiorespiratory reactions and more falling of blood oxygen in the hypoxia. The swimmers, having restrictions of ventilatory function in the course of trainings, form preadaptation to hypoxia with changes of external respiration and gas exchange functions that allows at hypoxia to better oxygen sate the blood in lungs. The joint assessment of aerobic capacity at physical work and physiological reactions to hypoxia shows the direct relation between individual maximal oxygen consumption and the descent rate of blood oxygen saturation at accruing hypoxia that can be useful at an assessment of a sportsman functional state and its correction at training processes.

  15. Comparative study of glycated hemoglobin by ion exchange chromatography and affinity binding nycocard reader in type 2 diabetes mellitus.

    PubMed

    Gautam, N; Dubey, R K; Jayan, A; Nepaune, Y; Padmavathi, P; Chaudhary, S; Jha, S K; Sinha, A K

    2014-12-01

    The aim of this study was to compare the level of glycated hemoglobin (HbA1c) in type 2 Diabetes Mellitus (DM) patients by two different methods namely Ion Exchange Chromatography and Affinity Binding Nycocard Reader. This is a cross-sectional study conducted on confirmed type 2 diabetes mellitus patients (n = 100) who visited Out Patients Department of the Universal College of Medical Sciences Teaching hospital, Bhairahawa, Nepal from November 2012 to March 2013. The diagnosis of diabetes mellitus was done on the basis of their fasting (164.46 ± 45.33 mg/dl) and random (187.93 ± 78.02 mg/dl) serum glucose level along with clinical history highly suggestive of type 2 DM. The HbA1c values of (7.8 ± 1.9%) and (8.0 ± 2.2%) were found in DM patients as estimated by those two different methods respectively. The highest frequency was observed in HbA1c > 8.0% indicating maximum cases were under very poor glycemic control. However, there were no significant differences observed in HbA1c value showing both methods are comparable in nature and can be used in lab for ease of estimation. The significant raised in HbA1c indicates complications associated with DM and monitoring of therapy become hard for those patients. Despite having standard reference method for HbA1c determination, the availability of report at the time of the patient visit can be made easy by using Nycocard Reader and Ion Exchange Chromatography techniques without any delay in communicating glycemic control, clinical decision-making and changes in treatment regimen.

  16. Comparing projections of future changes in runoff and water resources from hydrological and ecosystem models in ISI-MIP

    NASA Astrophysics Data System (ADS)

    Davie, J. C. S.; Falloon, P. D.; Kahana, R.; Dankers, R.; Betts, R.; Portmann, F. T.; Clark, D. B.; Itoh, A.; Masaki, Y.; Nishina, K.; Fekete, B.; Tessler, Z.; Liu, X.; Tang, Q.; Hagemann, S.; Stacke, T.; Pavlick, R.; Schaphoff, S.; Gosling, S. N.; Franssen, W.; Arnell, N.

    2013-02-01

    Projections of future changes in runoff can have important implications for water resources and flooding. In this study, runoff projections from ISI-MIP (Inter-sectoral Impact Model Intercomparison Project) simulations forced with HadGEM2-ES bias-corrected climate data under the Representative Concentration Pathway 8.5 have been analysed. Projections of change from the baseline period (1981-2010) to the future (2070-2099) from a number of different ecosystems and hydrological models were studied. The differences between projections from the two types of model were looked at globally and regionally. Typically, across different regions the ecosystem models tended to project larger increases and smaller decreases in runoff than the hydrological models. However, the differences varied both regionally and seasonally. Sensitivity experiments were also used to investigate the contributions of varying CO2 and allowing vegetation distribution to evolve on projected changes in runoff. In two out of four models which had data available from CO2 sensitivity experiments, allowing CO2 to vary was found to increase runoff more than keeping CO2 constant, while in two models runoff decreased. This suggests more uncertainty in runoff responses to elevated CO2 than previously considered. As CO2 effects on evapotranspiration via stomatal conductance and leaf-area index are more commonly included in ecosystems models than in hydrological models, this may partially explain some of the difference between model types. Keeping the vegetation distribution static in JULES runs had much less effect on runoff projections than varying CO2, but this may be more pronounced if looked at over a longer timescale as vegetation changes may take longer to reach a new state.

  17. Trophic modeling of the Northern Humboldt Current Ecosystem, Part I: Comparing trophic linkages under La Niña and El Niño conditions

    NASA Astrophysics Data System (ADS)

    Tam, Jorge; Taylor, Marc H.; Blaskovic, Verónica; Espinoza, Pepe; Michael Ballón, R.; Díaz, Erich; Wosnitza-Mendo, Claudia; Argüelles, Juan; Purca, Sara; Ayón, Patricia; Quipuzcoa, Luis; Gutiérrez, Dimitri; Goya, Elisa; Ochoa, Noemí; Wolff, Matthias

    2008-10-01

    The El Niño of 1997-98 was one of the strongest warming events of the past century; among many other effects, it impacted phytoplankton along the Peruvian coast by changing species composition and reducing biomass. While responses of the main fish resources to this natural perturbation are relatively well known, understanding the ecosystem response as a whole requires an ecotrophic multispecies approach. In this work, we construct trophic models of the Northern Humboldt Current Ecosystem (NHCE) and compare the La Niña (LN) years in 1995-96 with the El Niño (EN) years in 1997-98. The model area extends from 4°S-16°S and to 60 nm from the coast. The model consists of 32 functional groups of organisms and differs from previous trophic models of the Peruvian system through: (i) division of plankton into size classes to account for EN-associated changes and feeding preferences of small pelagic fish, (ii) increased division of demersal groups and separation of life history stages of hake, (iii) inclusion of mesopelagic fish, and (iv) incorporation of the jumbo squid ( Dosidicus gigas), which became abundant following EN. Results show that EN reduced the size and organization of energy flows of the NHCE, but the overall functioning (proportion of energy flows used for respiration, consumption by predators, detritus and export) of the ecosystem was maintained. The reduction of diatom biomass during EN forced omnivorous planktivorous fish to switch to a more zooplankton-dominated diet, raising their trophic level. Consequently, in the EN model the trophic level increased for several predatory groups (mackerel, other large pelagics, sea birds, pinnipeds) and for fishery catch. A high modeled biomass of macrozooplankton was needed to balance the consumption by planktivores, especially during EN condition when observed diatoms biomass diminished dramatically. Despite overall lower planktivorous fish catches, the higher primary production required-to-catch ratio implied a

  18. Ecosystem Services

    EPA Pesticide Factsheets

    Ecosystem goods and services are the many life-sustaining benefits we receive from nature and contribute to environmental and human health and well-being. Ecosystem-focused research will develop methods to measure ecosystem goods and services.

  19. Comparative studies on performance of radiation-induced and thermal cross-linked ion-exchange membrane for water electrolysis

    NASA Astrophysics Data System (ADS)

    Chakrabarty, Tina; Jasti, Amaranadh; Goel, N. K.; Shahi, Vinod K.; Sabharwal, Sunil

    2011-07-01

    Radiation-induced and thermal cross-linked sulfonated poly(ether sulfone) (SPS)-sulfonated poly(ether ether ketone) (SPK) composite ion-exchange membranes (SPS/SPK(γ) and SPS/SPK(T), respectively) were prepared. Their performances for water electrolysis were comparatively assessed. Thermal cross-linked membrane (SPS/SPK(T)) showed cross-linking of part functional groups (-SO 3H) and thus deterioration in membrane conductivity. While, radiation-induced cross-linked membrane (SPS/SPK(γ)) avoided any cross-linking between functional groups and thus conductivity. Electrolysis performances of these membranes were evaluated in comparison with Nafion117 membrane. Relatively low current efficiency (CE) for SPS/SPK and SPS/SPK(T) membranes was due to their high mass transfer (water) via electro-osmotic drag, which was negligible for SPS/SPK(γ) membrane. SPS/SPK(γ) membrane exhibited comparable stabilities and water splitting performance with Nafion117 membrane, which revealed its suitability as substitute for electrochemical applications.

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

    PubMed Central

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

    2015-01-01

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

  1. How does a land use change from annual food crop to perennial energy crop affect the CO2 balance? A study on net ecosystem exchange of carbon dioxide from Danish fen peatland grown with spring barley and reed canary grass

    NASA Astrophysics Data System (ADS)

    Kandel, T. P.; Elsgaard, L.; Lærke, P. E.

    2012-04-01

    It is important to evaluate how land use change from annual arable food crop to perennial energy crop cultivation changes the carbon balance in cultivated peatland. We measured CO2 balance in a riparian fen peatland used for growing reed canary grass (RCG) and spring barley (SB) on adjacent field plots for a complete year with a dynamic closed chamber. Carbon dioxide fluxes measured with chamber were divided into a light dependent part as gross photosynthesis (GP) and a light independent part as ecosystem respiration (RE). GP and RE in both cropping system showed a strong seasonal pattern with weather condition and vegetation. A high ecosystem respiration in RCG (1532 ± 32 g CO2-C m-2) and SB (1080 ± 32 g CO2-C m-2) during growing season was offset by higher gross photosynthesis in RCG (-1782 ± 53 g CO2-C m-2) and SB (-1225 ± 59 g CO2-C m-2)making both cropping system net sink of CO2 during the growing season. The estimated gross photosynthesis in cold-season from October to March was 17% and 6% of annual GP in SB and RCG plots, respectively. This higher uptake of CO2 during cold-season in SB plots was caused by growth of volunteer grass during winter which was completely suppressed in RCG plots due to its invasive nature. Both GP and REwere significantly higher in RCG plots than SB plots in an annual scale but net ecosystem exchange was not significantly different. Total estimated annual ecosystem respirations were 1887 ± 10 g CO2-C m-2 in RCG plots and 1288 ± 12 g CO2-C m-2 in SB plots. Similarly, total estimated annual GP were 1885 ± 100 g CO2-C m-2in RCG plots and 1408 ± 24 g CO2-C m-2 in SB plots making a net ecosystem exchange of 2 ± 88 g CO2-C m-2 in RCG plots and -120 ± 25 g CO2-C m-2 in SB plots.

  2. An assessment of the trophic structure of the Bay of Biscay continental shelf food web: Comparing estimates derived from an ecosystem model and isotopic data

    NASA Astrophysics Data System (ADS)

    Lassalle, G.; Chouvelon, T.; Bustamante, P.; Niquil, N.

    2014-01-01

    Comparing outputs of ecosystem models with estimates derived from experimental and observational approaches is important in creating valuable feedback for model construction, analyses and validation. Stable isotopes and mass-balanced trophic models are well-known and widely used as approximations to describe the structure of food webs, but their consistency has not been properly established as attempts to compare these methods remain scarce. Model construction is a data-consuming step, meaning independent sets for validation are rare. Trophic linkages in the French continental shelf of the Bay of Biscay food webs were recently investigated using both methodologies. Trophic levels for mono-specific compartments representing small pelagic fish and marine mammals and multi-species functional groups corresponding to demersal fish and cephalopods, derived from modelling, were compared with trophic levels calculated from independent carbon and nitrogen isotope ratios. Estimates of the trophic niche width of those species, or groups of species, were compared between these two approaches as well. A significant and close-to-one positive (rSpearman2 = 0.72 , n = 16, p < 0.0001) correlation was found between trophic levels estimated by Ecopath modelling and those derived from isotopic signatures. Differences between estimates were particularly low for mono-specific compartments. No clear relationship existed between indices of trophic niche width derived from both methods. Given the wide recognition of trophic levels as a useful concept in ecosystem-based fisheries management, propositions were made to further combine these two approaches.

  3. Water use and carbon exchange of red oak- and eastern hemlock-dominated forests in the northeastern USA: implications for ecosystem-level effects of hemlock woolly adelgid.

    PubMed

    Hadley, Julian L; Kuzeja, Paul S; Daley, Michael J; Phillips, Nathan G; Mulcahy, Thomas; Singh, Safina

    2008-04-01

    Water use and carbon exchange of a red oak-dominated (Quercus rubra L.) forest and an eastern hemlock-dominated (Tsuga canadensis L.) forest, each located within the Harvard Forest in north-central Massachusetts, were measured for 2 years by the eddy flux method. Water use by the red oak forest reached 4 mm day(-1), compared to a maximum of 2 mm day(-1) by the eastern hemlock forest. Maximal carbon (C) uptake rate was also higher in the red oak forest than in the eastern hemlock forest (about 25 versus 15 micromol m(-2) s(-1)). Sap flux measurements indicated that transpiration of red oak, and also of black birch (Betula lenta L.), which frequently replaces eastern hemlock killed by hemlock woolly adelgid (Adelges tsugae Annand.), were almost twice that of eastern hemlock. Despite the difference between species in maximum summertime C assimilation rate, annual C storage of the eastern hemlock forest almost equaled that of the red oak forest because of net C uptake by eastern hemlock during unusually warm fall and spring weather, and a near-zero C balance during the winter. Thus, the effect on C storage of replacing eastern hemlock forest with a forest dominated by deciduous species is unclear. Carbon storage by eastern hemlock forests during fall, winter and spring is likely to increase in the event of climate warming, although this may be offset by C loss during hotter summers. Our results indicate that, although forest water use will decrease immediately following eastern hemlock mortality due to the hemlock woolly adelgid, the replacement of eastern hemlock by deciduous species such as red oak will likely increase summertime water use over current rates in areas where hemlock is a major forest species.

  4. Combining tower mixing ratio and community model data to estimate regional-scale net ecosystem carbon exchange by boundary layer inversion over four flux towers in the United States

    NASA Astrophysics Data System (ADS)

    Dang, Xuerui; Lai, Chun-Ta; Hollinger, David Y.; Schauer, Andrew J.; Xiao, Jingfeng; Munger, J. William; Owensby, Clenton; Ehleringer, James R.

    2011-09-01

    We evaluated an idealized boundary layer (BL) model with simple parameterizations using vertical transport information from community model outputs (NCAR/NCEP Reanalysis and ECMWF Interim Analysis) to estimate regional-scale net CO2 fluxes from 2002 to 2007 at three forest and one grassland flux sites in the United States. The BL modeling approach builds on a mixed-layer model to infer monthly average net CO2 fluxes using high-precision mixing ratio measurements taken on flux towers. We compared BL model net ecosystem exchange (NEE) with estimates from two independent approaches. First, we compared modeled NEE with tower eddy covariance measurements. The second approach (EC-MOD) was a data-driven method that upscaled EC fluxes from towers to regions using MODIS data streams. Comparisons between modeled CO2 and tower NEE fluxes showed that modeled regional CO2 fluxes displayed interannual and intra-annual variations similar to the tower NEE fluxes at the Rannells Prairie and Wind River Forest sites, but model predictions were frequently different from NEE observations at the Harvard Forest and Howland Forest sites. At the Howland Forest site, modeled CO2 fluxes showed a lag in the onset of growing season uptake by 2 months behind that of tower measurements. At the Harvard Forest site, modeled CO2 fluxes agreed with the timing of growing season uptake but underestimated the magnitude of observed NEE seasonal fluctuation. This modeling inconsistency among sites can be partially attributed to the likely misrepresentation of atmospheric transport and/or CO2 gradients between ABL and the free troposphere in the idealized BL model. EC-MOD fluxes showed that spatial heterogeneity in land use and cover very likely explained the majority of the data-model inconsistency. We show a site-dependent atmospheric rectifier effect that appears to have had the largest impact on ABL CO2 inversion in the North American Great Plains. We conclude that a systematic BL modeling approach

  5. Climatic influences on net ecosystem CO2 exchange during the transition from wintertime carbon source to springtime carbon sink in a high-elevation, subalpine forest.

    PubMed

    Monson, Russell K; Sparks, Jed P; Rosenstiel, Todd N; Scott-Denton, Laura E; Huxman, Travis E; Harley, Peter C; Turnipseed, Andrew A; Burns, Sean P; Backlund, Brant; Hu, Jia

    2005-11-01

    The transition between wintertime net carbon loss and springtime net carbon assimilation has an important role in controlling the annual rate of carbon uptake in coniferous forest ecosystems. We studied the contributions of springtime carbon assimilation to the total annual rate of carbon uptake and the processes involved in the winter-to-spring transition across a range of scales from ecosystem CO2 fluxes to chloroplast photochemistry in a coniferous, subalpine forest. We observed numerous initiations and reversals in the recovery of photosynthetic CO2 uptake during the initial phase of springtime recovery in response to the passage of alternating warm- and cold-weather systems. Full recovery of ecosystem carbon uptake, whereby the 24-h cumulative sum of NEE (NEEdaily) was consistently negative, did not occur until 3-4 weeks after the first signs of photosynthetic recovery. A key event that preceded full recovery was the occurrence of isothermality in the vertical profile of snow temperature across the snow pack; thus, providing consistent daytime percolation of melted snow water through the snow pack. Interannual variation in the cumulative annual NEE (NEEannual) was mostly explained by variation in NEE during the snow-melt period (NEEsnow-melt), not variation in NEE during the snow-free part of the growing season (NEEsnow-free). NEEsnow-melt was highest in those years when the snow melt occurred later in the spring, leading us to conclude that in this ecosystem, years with earlier springs are characterized by lower rates of NEEannual, a conclusion that contrasts with those from past studies in deciduous forest ecosystems. Using studies on isolated branches we showed that the recovery of photosynthesis occurred through a series of coordinated physiological and biochemical events. Increasing air temperatures initiated recovery through the upregulation of PSII electron transport caused in part by disengagement of thermal energy dissipation by the carotenoid

  6. [Energy and mass exchange and the productivity of the main ecosystems of Siberia (from eddy covariance measurements). 1. Heat balance structure in the vegetation season].

    PubMed

    Chebakova, N M; Vygodskaia, N N; Arnet, A; Belelli Markezini, L; Kolle, O; Kurbatova, Iu A; Parfenova, E I; Valentini, R; Vaganov, E A; Shul'tse, E D

    2013-01-01

    Direct measurements of heat balance (turbulent heat transfer and evaporation heat consumption) by the method of turbulent pulsations in 1998-2000 and 2002-2004 were used to obtain information on the daily, seasonal, and annual dynamics of energy fluxes and mass transfer between the atmosphere and the typical ecosystems of Siberia (middle-taiga pine forest and raised bog, true four-grass steppe, with the use of data for typical tundra) along the Yenisei meridian (90 degrees E).

  7. Comparative Analysis of Reproductive Traits in Black-Chinned Tilapia Females from Various Coastal Marine, Estuarine and Freshwater Ecosystems

    PubMed Central

    Kantoussan, Justin; Ndiaye, Papa; Thiaw, Omar Thiom; Albaret, Jean-Jacques

    2012-01-01

    The black-chinned tilapia Sarotherodon melanotheron is a marine teleost characterised by an extreme euryhalinity. However, beyond a certain threshold at very high salinity, the species exhibits impaired growth and precocious reproduction. In this study, the relationships between reproductive parameters, environmental salinity and condition factor were investigated in wild populations of this species that were sampled in two consecutive years (2003 and 2004) from three locations in Senegal with different salinities: Guiers lake (freshwater, 0 psu), Hann bay (seawater, 37 psu) and Saloum estuary (hypersaline water, 66–127 psu). The highest absolute fecundity and spawning weight were recorded in seawater by comparison to either freshwater or hypersaline water whereas the poorest condition factors were observed in the most saline sampling site. These results reflect higher resource allocation to the reproduction due to the lowest costs of adaptation to salinity in seawater (the natural environment of this species) rather than differences in food resources at sites and/or efficiency at foraging and prey availability. Fecundities, oocyte size as well as spawning weight were consistent from year to year. However, the relative fecundity in the Saloum estuary varied significantly between the dry and rainy raisons with higher values in the wet season, which seems to reflect seasonal variations in environmental salinity. Such a reproductive tactic of producing large amounts of eggs in the rainy season when the salinity in the estuary was lower, would give the fry a better chance at survival and therefore assures a high larval recruitment. An inverse correlation was found between relative fecundity and oocyte size at the two extreme salinity locations, indicating that S. melanotheron has different reproductive strategies in these ecosystems. The adaptive significance of these two reproductive modes is discussed in regard to the heavy osmotic constraint imposed by extreme

  8. Comparative analysis of reproductive traits in black-chinned tilapia females from various coastal marine, estuarine and freshwater ecosystems.

    PubMed

    Guèye, Moussa; Tine, Mbaye; Kantoussan, Justin; Ndiaye, Papa; Thiaw, Omar Thiom; Albaret, Jean-Jacques

    2012-01-01

    The black-chinned tilapia Sarotherodon melanotheron is a marine teleost characterised by an extreme euryhalinity. However, beyond a certain threshold at very high salinity, the species exhibits impaired growth and precocious reproduction. In this study, the relationships between reproductive parameters, environmental salinity and condition factor were investigated in wild populations of this species that were sampled in two consecutive years (2003 and 2004) from three locations in Senegal with different salinities: Guiers lake (freshwater, 0 psu), Hann bay (seawater, 37 psu) and Saloum estuary (hypersaline water, 66-127 psu). The highest absolute fecundity and spawning weight were recorded in seawater by comparison to either freshwater or hypersaline water whereas the poorest condition factors were observed in the most saline sampling site. These results reflect higher resource allocation to the reproduction due to the lowest costs of adaptation to salinity in seawater (the natural environment of this species) rather than differences in food resources at sites and/or efficiency at foraging and prey availability. Fecundities, oocyte size as well as spawning weight were consistent from year to year. However, the relative fecundity in the Saloum estuary varied significantly between the dry and rainy raisons with higher values in the wet season, which seems to reflect seasonal variations in environmental salinity. Such a reproductive tactic of producing large amounts of eggs in the rainy season when the salinity in the estuary was lower, would give the fry a better chance at survival and therefore assures a high larval recruitment. An inverse correlation was found between relative fecundity and oocyte size at the two extreme salinity locations, indicating that S. melanotheron has different reproductive strategies in these ecosystems. The adaptive significance of these two reproductive modes is discussed in regard to the heavy osmotic constraint imposed by extreme

  9. Comparative Use of a Caribbean Mesophotic Coral Ecosystem and Association with Fish Spawning Aggregations by Three Species of Shark.

    PubMed

    Pickard, Alexandria E; Vaudo, Jeremy J; Wetherbee, Bradley M; Nemeth, Richard S; Blondeau, Jeremiah B; Kadison, Elizabeth A; Shivji, Mahmood S

    2016-01-01

    Understanding of species interactions within mesophotic coral ecosystems (MCEs; ~ 30-150 m) lags well behind that for shallow coral reefs. MCEs are often sites of fish spawning aggregations (FSAs) for a variety of species, including many groupers. Such reproductive fish aggregations represent temporal concentrations of potential prey that may be drivers of habitat use by predatory species, including sharks. We investigated movements of three species of sharks within a MCE and in relation to FSAs located on the shelf edge south of St. Thomas, United States Virgin Islands. Movements of 17 tiger (Galeocerdo cuvier), seven lemon (Negaprion brevirostris), and six Caribbean reef (Carcharhinus perezi) sharks tagged with acoustic transmitters were monitored within the MCE using an array of acoustic receivers spanning an area of 1,060 km2 over a five year period. Receivers were concentrated around prominent grouper FSAs to monitor movements of sharks in relation to these temporally transient aggregations. Over 130,000 detections of telemetered sharks were recorded, with four sharks tracked in excess of 3 years. All three shark species were present within the MCE over long periods of time and detected frequently at FSAs, but patterns of MCE use and orientation towards FSAs varied both spatially and temporally among species. Lemon sharks moved over a large expanse of the MCE, but concentrated their activities around FSAs during grouper spawning and were present within the MCE significantly more during grouper spawning season. Caribbean reef sharks were present within a restricted portion of the MCE for prolonged periods of time, but were also absent for long periods. Tiger sharks were detected throughout the extent of the acoustic array, with the MCE representing only portion of their habitat use, although a high degree of individual variation was observed. Our findings indicate that although patterns of use varied, all three species of sharks repeatedly utilized the MCE and

  10. Comparative Use of a Caribbean Mesophotic Coral Ecosystem and Association with Fish Spawning Aggregations by Three Species of Shark

    PubMed Central

    Pickard, Alexandria E.; Vaudo, Jeremy J.; Wetherbee, Bradley M.; Nemeth, Richard S.; Blondeau, Jeremiah B.; Kadison, Elizabeth A.; Shivji, Mahmood S.

    2016-01-01

    Understanding of species interactions within mesophotic coral ecosystems (MCEs; ~ 30–150 m) lags well behind that for shallow coral reefs. MCEs are often sites of fish spawning aggregations (FSAs) for a variety of species, including many groupers. Such reproductive fish aggregations represent temporal concentrations of potential prey that may be drivers of habitat use by predatory species, including sharks. We investigated movements of three species of sharks within a MCE and in relation to FSAs located on the shelf edge south of St. Thomas, United States Virgin Islands. Movements of 17 tiger (Galeocerdo cuvier), seven lemon (Negaprion brevirostris), and six Caribbean reef (Carcharhinus perezi) sharks tagged with acoustic transmitters were monitored within the MCE using an array of acoustic receivers spanning an area of 1,060 km2 over a five year period. Receivers were concentrated around prominent grouper FSAs to monitor movements of sharks in relation to these temporally transient aggregations. Over 130,000 detections of telemetered sharks were recorded, with four sharks tracked in excess of 3 years. All three shark species were present within the MCE over long periods of time and detected frequently at FSAs, but patterns of MCE use and orientation towards FSAs varied both spatially and temporally among species. Lemon sharks moved over a large expanse of the MCE, but concentrated their activities around FSAs during grouper spawning and were present within the MCE significantly more during grouper spawning season. Caribbean reef sharks were present within a restricted portion of the MCE for prolonged periods of time, but were also absent for long periods. Tiger sharks were detected throughout the extent of the acoustic array, with the MCE representing only portion of their habitat use, although a high degree of individual variation was observed. Our findings indicate that although patterns of use varied, all three species of sharks repeatedly utilized the MCE

  11. Comparable hydrogen isotopic fractionation of plant leaf wax n-alkanoic acids in arid and humid subtropical ecosystems

    NASA Astrophysics Data System (ADS)

    Gao, Li; Zheng, Mei; Fraser, Matthew; Huang, Yongsong

    2014-02-01

    Leaf wax hydrogen isotope proxies have been widely used to reconstruct past hydrological changes. However, published reconstructions have given little consideration for the potentially variable hydrogen isotopic fractionation relative to precipitation (ɛwax-p) under different climate and environmental settings. Chief among various potential factors controlling fractionation is relative humidity, which is known to strongly affect oxygen isotopic ratios of plant cellulose, but its effect on hydrogen isotopic fractionation of leaf waxes is still ambiguous. Analyses of lake surface sediments and individual modern plants have provided valuable information on the variability of ɛwax-p, but both approaches have significant limitations. Here, we present an alternative method to obtain the integrated, time-resolved ecosystem-level ɛwax-p values, by analyzing modern aerosol samples collected weekly from arid (Arizona lowlands) and humid subtropical (Atlanta, Georgia) environments during the main growth season. Because aerosol samples mainly reflect regional leaf wax resources, the extreme contrast in the hydroclimate and associated vegetation assemblages between our study sites allows us to rigorously assess the impact of relative humidity and associated vegetation assemblages on leaf wax hydrogen isotopic fractionation. We show there is only minor difference (mostly <10‰) in the mean ɛwax-p values in the two end-member environments. One possible explanation is that the positive isotopic effects of low relative humidity are offset by progressive replacement of trees with grasses that have a more negative apparent fractionation. Our results represent an important step toward quantitative interpretation of leaf wax hydrogen isotopic records.

  12. A Screening-Level Approach for Comparing Risks Affecting Aquatic Ecosystem Services over Socio-Environmental Gradients

    NASA Astrophysics Data System (ADS)

    Harmon, T. C.; Conde, D.; Villamizar, S. R.; Reid, B.; Escobar, J.; Rusak, J.; Hoyos, N.; Scordo, F.; Perillo, G. M.; Piccolo, M. C.; Zilio, M.; Velez, M.

    2015-12-01

    Assessing risks to aquatic ecosystems services (ES) is challenging and time-consuming, and effective strategies for prioritizing more detailed assessment efforts are needed. We propose a screening-level risk analysis (SRA) approach that scales ES risk using socioeconomic and environmental indices to capture anthropic and climatic pressures, as well as the capacity for institutional responses to those pressures. The method considers ES within a watershed context, and uses expert input to prioritize key services and the associated pressures that threaten them. The SRA approach focuses on estimating ES risk affect factors, which are the sum of the intensity factors for all hazards or pressures affecting the ES. We estimate the pressure intensity factors in a novel manner, basing them on the nation's (i) human development (proxied by Inequality-adjusted Human Development Index, IHDI), (ii) environmental regulatory and monitoring state (Environmental Performance Index, EPI) and (iii) the current level of water stress in the watershed (baseline water stress, BWS). Anthropic intensity factors for future conditions are derived from the baseline values based on the nation's 10-year trend in IHDI and EPI; ES risks in nations with stronger records of change are rewarded more/penalized less in estimates for good/poor future management scenarios. Future climatic intensity factors are tied to water stress estimates based on two general circulation model (GCM) outcomes. We demonstrate the method for an international array of six sites representing a wide range of socio-environmental settings. The outcomes illustrate novel consequences of the scaling scheme. Risk affect factors may be greater in a highly developed region under intense climatic pressure, or in less well-developed regions due to human factors (e.g., poor environmental records). As a screening-level tool, the SRA approach offers considerable promise for ES risk comparisons among watersheds and regions so that

  13. Cost-effectiveness of heat and moisture exchangers compared to usual care for pulmonary rehabilitation after total laryngectomy in Poland.

    PubMed

    Retèl, Valesca P; van den Boer, Cindy; Steuten, Lotte M G; Okła, Sławomir; Hilgers, Frans J; van den Brekel, Michiel W

    2015-09-01

    The beneficial physical and psychosocial effects of heat and moisture exchangers (HMEs) for pulmonary rehabilitation of laryngectomy patients are well evidenced. However, cost-effectiveness in terms of costs per additional quality-adjusted life years (QALYs) has not yet been investigated. Therefore, a model-based cost-effectiveness analysis of using HMEs versus usual care (UC) (including stoma covers, suction system and/or external humidifier) for patients after laryngectomy was performed. Primary outcomes were costs, QALYs and incremental cost-effectiveness ratio (ICER). Secondary outcomes were pulmonary infections, and sleeping problems. The analysis was performed from a health care perspective of Poland, using a time horizon of 10 years and cycle length of 1 year. Transition probabilities were derived from various sources, amongst others a Polish randomized clinical trial. Quality of life data was derived from an Italian study on similar patients. Data on frequencies and mortality-related tracheobronchitis and/or pneumonia were derived from a Europe-wide survey amongst head and neck cancer experts. Substantial differences in quality-adjusted survival between the use of HMEs (3.63 QALYs) versus UC (2.95 QALYs) were observed. Total health care costs/patient were 39,553 PLN (9465 Euro) for the HME strategy and 4889 PLN (1168 Euro) for the UC strategy. HME use resulted in fewer pulmonary infections, and less sleeping problems. We could conclude that given the Polish threshold of 99,000 PLN/QALY, using HMEs is cost-effective compared to UC, resulting in 51,326 PLN/QALY (12,264 Euro/QALY) gained for patients after total laryngectomy. For the hospital period alone (2 weeks), HMEs were cost-saving: less costly and more effective.

  14. A comparative interregional analysis of selected data from LANDSAT-1 and EREP for the inventory and monitoring of natural ecosystems

    NASA Technical Reports Server (NTRS)

    Poulton, C. E.

    1975-01-01

    Comparative statistics were presented on the capability of LANDSAT-1 and three of the Skylab remote sensing systems (S-190A, S-190B, S-192) for the recognition and inventory of analogous natural vegetations and landscape features important in resource allocation and management. Two analogous regions presenting vegetational zonation from salt desert to alpine conditions above the timberline were observed, emphasizing the visual interpretation mode in the investigation. An hierarchical legend system was used as the basic classification of all land surface features. Comparative tests were run on image identifiability with the different sensor systems, and mapping and interpretation tests were made both in monocular and stereo interpretation with all systems except the S-192. Significant advantage was found in the use of stereo from space when image analysis is by visual or visual-machine-aided interactive systems. Some cost factors in mapping from space are identified. The various image types are compared and an operational system is postulated.

  15. No effect of seed source on multiple aspects of ecosystem functioning during ecological restoration: cultivars compared to local ecotypes of dominant grasses

    PubMed Central

    Baer, Sara G; Gibson, David J; Gustafson, Danny J; Benscoter, Allison M; Reed, Lewis K; Campbell, Ryan E; Klopf, Ryan P; Willand, Jason E; Wodika, Ben R

    2014-01-01

    Genetic principles underlie recommendations to use local seed, but a paucity of information exists on the genetic distinction and ecological consequences of using different seed sources in restorations. We established a field experiment to test whether cultivars and local ecotypes of dominant prairie grasses were genetically distinct and differentially influenced ecosystem functioning. Whole plots were assigned to cultivar and local ecotype grass sources. Three subplots within each whole plot were seeded to unique pools of subordinate species. The cultivar of the increasingly dominant grass, Sorghastrum nutans, was genetically different than the local ecotype, but genetic diversity was similar between the two sources. There were no differences in aboveground net primary production, soil carbon accrual, and net nitrogen mineralization rate in soil between the grass sources. Comparable productivity of the grass sources among the species pools for four years shows functional equivalence in terms of biomass production. Subordinate species comprised over half the aboveground productivity, which may have diluted the potential for documented trait differences between the grass sources to influence ecosystem processes. Regionally developed cultivars may be a suitable alternative to local ecotypes for restoration in fragmented landscapes with limited gene flow between natural and restored prairie and negligible recruitment by seed. PMID:24567751

  16. Developing and Applications of a Gap-filling Model for Eddy covariance CO2 Flux: Evaluating the Net Ecosystem Exchange of a Subtropical Evergreen Forest after a Server Environmental Disturbance

    NASA Astrophysics Data System (ADS)

    Li, M.; CHEN, Y.

    2013-12-01

    Successful eddy covariance (EC) applications often challenged by several difficulties, including non-ideal micrometeorological conditions, instrument failures, measurement limitations, and lacking consistent footprint area. Consequently, the resultant gaps in the time series of EC measurements limit the use of these dataset and cause the uncertainty in a range of 1 to 2 ton C/ha/yr for evaluating net ecosystem exchange (NEE) after different CO2 gap-filling procedures (Saigusa et al., 2013). It is crucial to develop a suitable gap-filling model for EC CO2 flux observations to provide reliable long-term surface fluxes for numerous applications. In this study, a gap-filling model was developed for EC CO2 flux by linking the gap-filled water vapor fluxes estimated by Chen et al. (2012) and the optimal nearest QC/QA passed CO2 fluxes for interpolating CO2 flux gaps. Considering the atmosphere characteristics and controlling mechanisms of CO2 fluxes, measured hydrometerological and flux data at the Lien-Hua-Chih (LHC) experimental watershed were separated into clear sky and cloudy/nighttime conditions. The successful applications of our gap-filling approaches were examined with various sizes of artificial CO2 gaps. Without any significant environmental disturbance in 2012, the annual NEE of this subtropical evergreen forest was estimated around 6.7 ton C/ha/yr as the amount of terrestrial CO2 sequestration. The effect of sever Typhoon Soulik (11-13, July, 2013) invasion on several ecosystem variables, such as changes of intrinsic water use efficiency, leaf area index, and canopy storage capacity, will be investigated to propose indicators for estimating NEE variations in association with environmental disturbances at this forest ecosystem.

  17. The comparative effects of gamma radiation and in situ alpha particles on five strong-base anion exchange resins

    SciTech Connect

    Marsh, S.F.

    1991-01-01

    The effects of external gamma radiation and in situ alpha particles were measured on a recently available, macroporous, strong-base polyvinylpyridine resin and on four strong-base polystyrene anion exchange resins. Each resin was irradiated in 7 M nitric acid to 1--10 megaGray of gamma radiation from external {sup 60}Co, or to 5--14 megaGray of alpha particles from sorbed {sup 238}Pu. Each irradiated resin was measured for changes in dry weight, wet volume, weak-base and strong-base chloride exchange capacities, and exchange capacities for Pu(4) from nitric acid. Alpha-induced resin damage was significantly less than that caused by an equivalent dose of gamma radiation. The polyvinylpyridine resin offers the greatest resistance to damage from gamma radiation and from alpha particles. 5 refs., 1 figs. 5 tabs.

  18. Ecosystem Journalism

    ERIC Educational Resources Information Center

    Robertson, Amy; Mahlin, Kathryn

    2005-01-01

    If the organisms in a prairie ecosystem created a newspaper, what would it look like? What important news topics of the ecosystem would the organisms want to discuss? Imaginative and enthusiastic third-grade students were busy pondering these questions as they tried their hands at "ecosystem journalism." The class had recently completed…

  19. Natural ecosystems

    USGS Publications Warehouse

    Fleishman, Erica; Belnap, Jayne; Cobb, Neil; Enquist, Carolyn A.F.; Ford, Karl; MacDonald, Glen; Pellant, Mike; Schoennagel, Tania; Schmit, Lara M.; Schwartz, Mark; van Drunick, Suzanne; Westerling, Anthony LeRoy; Keyser, Alisa; Lucas, Ryan

    2013-01-01

    Natural Ecosystems analyzes the association of observed changes in climate with changes in the geographic distributions and phenology (the timing of blossoms or migrations of birds) for Southwestern ecosystems and their species, portraying ecosystem disturbances—such as wildfires and outbreaks of forest pathogens—and carbon storage and release, in relation to climate change.

  20. Ecosystem Jenga!

    ERIC Educational Resources Information Center

    Umphlett, Natalie; Brosius, Tierney; Laungani, Ramesh; Rousseau, Joe; Leslie-Pelecky, Diandra L.

    2009-01-01

    To give students a tangible model of an ecosystem and have them experience what could happen if a component of that ecosystem were removed; the authors developed a hands-on, inquiry-based activity that visually demonstrates the concept of a delicately balanced ecosystem through a modification of the popular game Jenga. This activity can be…

  1. Mercury vapor air-surface exchange measured by collocated micrometeorological and enclosure methods - Part I: Data comparability and method characteristics

    NASA Astrophysics Data System (ADS)

    Zhu, W.; Sommar, J.; Lin, C.-J.; Feng, X.

    2015-01-01

    Reliable quantification of air-biosphere exchange flux of elemental mercury vapor (Hg0) is crucial for understanding the global biogeochemical cycle of mercury. However, there has not been a standard analytical protocol for flux quantification, and little attention has been devoted to characterize the temporal variability and comparability of fluxes measured by different methods. In this study, we deployed a collocated set of micrometeorological (MM) and dynamic flux chamber (DFC) measurement systems to quantify Hg0 flux over bare soil and low standing crop in an agricultural field. The techniques include relaxed eddy accumulation (REA), modified Bowen ratio (MBR), aerodynamic gradient (AGM) as well as dynamic flux chambers of traditional (TDFC) and novel (NDFC) designs. The five systems and their measured fluxes were cross-examined with respect to magnitude, temporal trend and correlation with environmental variables. Fluxes measured by the MM and DFC methods showed distinct temporal trends. The former exhibited a highly dynamic temporal variability while the latter had much more gradual temporal features. The diurnal characteristics reflected the difference in the fundamental processes driving the measurements. The correlations between NDFC and TDFC fluxes and between MBR and AGM fluxes were significant (R>0.8, p<0.05), but the correlation between DFC and MM fluxes were from weak to moderate (R=0.1-0.5). Statistical analysis indicated that the median of turbulent fluxes estimated by the three independent MM techniques were not significantly different. Cumulative flux measured by TDFC is considerably lower (42% of AGM and 31% of MBR fluxes) while those measured by NDFC, AGM and MBR were similar (<10% difference). This suggests that incorporating an atmospheric turbulence property such as friction velocity for correcting the DFC-measured flux effectively bridged the gap between the Hg0 fluxes measured by enclosure and MM techniques. Cumulated flux measured by REA

  2. Exchange Program Teenagers Compare Life in Denmark and the U.S.A. Occasional Papers in Intercultural Learning No. 10.

    ERIC Educational Resources Information Center

    Bresee, Dana E.

    Thirty teenage exchange students from Denmark and the United States were interviewed concerning the differences they perceived in the two cultures. Salient differences were cited in the domains of family rules, education and schools, use of alcohol, romantic relationships and sexuality, communication and friendships, ethnic differences and…

  3. An algebraic/graphical tool to compare ecosystems with respect to their pollution V: cluster analysis and Hasse diagrams.

    PubMed

    Pudenz, S; Brüggemann, R; Luther, B; Kaune, A; Kreimes, K

    2000-06-01

    In case of large data matrices comparative evaluations of objects/regions with the technique of Hasse diagrams may be troublesome due to a messy system of lines in the graphical representation. Here fuzzy clustering leads to useful simplifications because regions with slightly different pollution pattern are grouped together. However, fuzzy clustering implies to introduce a threshold value for the membership of an object to a cluster and to select the best number of clusters. Therefore many arbitrarities evolve. Within the systematic study presented here we found that some objects are very stable against variations of the threshold value and the number of cluster whereas other objects behaves different. According to their behaviour we investigated a classification of the objects. Formal Concept Analysis shows that in some cases specific pollution pattern imply the membership to one of these classes. For example objects which are characterized by high Pb-, Zn-concentration and moderate S-concentration imply a high stability against variants of the clustering process. Further implications are described in the paper.

  4. Sensitivity of mesquite shrubland CO2 exchange to precipitation in contrasting landscape settings.

    PubMed

    Potts, Daniel L; Scott, Russell L; Cable, Jessica M; Huxman, Travis E; Williams, David G

    2008-10-01

    In semiarid ecosystems, physiography (landscape setting) may interact with woody-plant and soil microbe communities to constrain seasonal exchanges of material and energy at the ecosystem scale. In an upland and riparian shrubland, we examined the seasonally dynamic linkage between ecosystem CO2 exchange, woody-plant water status and photosynthesis, and soil respiration responses to summer rainfall. At each site, we compared tower-based measurements of net ecosystem CO2 exchange (NEE) with ecophysiological measurements among velvet mesquite (Prosopis velutina Woot.) in three size classes and soil respiration in sub-canopy and inter-canopy micro-sites. Monsoonal rainfall influenced a greater shift in the magnitude of ecosystem CO2 assimilation in the upland shrubland than in the riparian shrubland. Mesquite water status and photosynthetic gas exchange were closely linked to the onset of the North American monsoon in the upland shrubland. In contrast, the presence of shallow alluvial groundwater in the riparian shrubland caused larger size classes of mesquite to be physiologically insensitive to monsoonal rains. In both shrublands, soil respiration was greatest beneath mesquite canopies and was coupled to shallow soil moisture abundance. Physiography, through its constraint on the physiological sensitivity of deeply rooted woody plants, may interact with plant-mediated rates of soil respiration to affect the sensitivity of semiarid-ecosystem carbon exchange in response to episodic rainfall.

  5. Flowering phenology of invasive alien plant species compared with native species in three Mediterranean-type ecosystems

    PubMed Central

    Godoy, Oscar; Richardson, David M.; Valladares, Fernando; Castro-Díez, Pilar

    2009-01-01

    Background and Aims Flowering phenology is a potentially important component of success of alien species, since elevated fecundity may enhance invasiveness. The flowering patterns of invasive alien plant species and related natives were studied in three regions with Mediterranean-type climate: California, Spain and South Africa's Cape region. Methods A total of 227 invasive–native pairs were compared for seven character types across the regions, with each pair selected on the basis that they shared the same habitat type within a region, had a common growth form and pollination type, and belonged to the same family or genus. Key Results Invasive alien plant species have different patterns of flowering phenology from native species in the three regions. Whether the alien species flower earlier, later or at the same time as natives depends on the climatic regime in the native range of the aliens and the proportion of species in the invasive floras originating from different regions. Species invading at least two of the regions displayed the same flowering pattern, showing that flowering phenology is a conservative trait. Invasive species with native ranges in temperate climates flower earlier than natives, those from Mediterranean-type climates at the same time, and species from tropical climates flower later. In California, where the proportion of invaders from the Mediterranean Basin is high, the flowering pattern did not differ between invasive and native species, whereas in Spain the high proportion of tropical species results in a later flowering than natives, and in the Cape region early flowering than natives was the result of a high proportion of temperate invaders. Conclusions Observed patterns are due to the human-induced sympatry of species with different evolutionary histories whose flowering phenology evolved under different climatic regimes. The severity of the main abiotic filters imposed by the invaded regions (e.g. summer drought) has not been

  6. Methylotrophic bacteria symbiosis with the higher plants as means of minimization of the lower hydrocarbons concentration during artificial ecosystem gas exchange

    NASA Astrophysics Data System (ADS)

    Berkovich, Yuliy; Smolyanina, Svetlana; Moukhamedieva, Lana; Mardanov, Robert; Doronina, Nina; Ivanova, Ekaterina

    Plant growth unit should be included in the LSS for the space vehicles for vitamin greens supply and psychological support of cosmonauts during long-term missions. The lower hydrocarbons such as methane, methanol, methylated sulfuric compounds and methylated amines, ethylene and so on, are the natural products of human and plant metabolism and usually considered as the air pollutions. It is shown, that one way to decrease the lower hydrocarbons concentration in the artificial ecosystems could be colonization of the plants by methylotrophic bacteria. The aerobic methylotrophic bacteria possess unique ability to use methane and its oxidized or replaced derivatives without food damage and human, animals or plants infection. We have found that methylotrophic bacteria are the phyto-symbiotic bacteria: they stimulate growth and development of the colonized plants because of synthesizing cytokinins and auxins, and vitamin B12.Two collection strains of the obligate methylotrophic bacteria - Methylovorus mays C and Methylomonas metanica S - were chosen because of their high activity to assimilate the lower hydrocarbons due to functioning of methanoldehydrogenase, methanmonooxigenase and ribulose monophosphate cycle enzymes system.Colonization of the leaf cabbage Brassica chinensis L. by these strains led to approximately 30 % reduce of methanol and methane concentration in the air inside phytotron. Experimental estimations of the influence of methylotrophic bacteria on leafy greens growth and development are obtained.

  7. The influence of environmental variability on silicate exchange rates between sediment and water in a shallow-water coastal ecosystem, the Seto Inland Sea, Japan.

    PubMed

    Srithongouthai, Sarawut; Sonoyama, Yu-Ichi; Tada, Kuninao; Montani, Shigeru

    2003-01-01

    Silicate regeneration was determined in a shallow-water coastal ecosystem (Shido Bay, the Seto Inland Sea, Japan) during 1999-2000. The present study was carried out directly by core incubation and by determining gradients of dissolved silicate (DSi) in the pore water. Incubated fluxes ranged from 25.5 to 132.6 mgSim(-2)d(-1), and were 1.6-21.6 times greater than diffusive fluxes (5.4-43.3 mgSim(-2)d(-1)). The disparity between fluxes measured by core incubation and modeling pore water indicated that other physical, chemical or biological processes, in addition to diffusion of DSi from below, contribute to DSi fluxes measured during the incubation of undisturbed cores. A regression analysis revealed that water temperature and salinity explained 24% and 23%, respectively, of season to season variability in incubated fluxes. Microphytobenthos was responsible for 37% of the variability in measured rate of DSi fluxes, with greatly reducing DSi release rates due to their own DSi demand. Moreover, the inverse relationship between the DSi fluxes and biogenic silica (Bio-Si) concentrations in the surface sediment, suggested that about 41% of the variability in the DSi fluxes were explained by Bio-Si concentrations in the surface sediment. As a result, Shido Bay showed silicate regeneration of incubated cores to be a consequence of Bio-Si dissolution depending on microphytobenthos, temperature and salinity, while diffusive fluxes appeared to be limited by DSi in the pore water. An annual average of DSi flux (68.7+/-32.9 mgSim(-2)d(-1)) from the sediments to the water column corresponds to 38% of DSi, required for primary production by phytoplankton in Shido Bay.

  8. Obscuring ecosystem function with application of the ecosystem services concept.

    PubMed

    Peterson, Markus J; Hall, Damon M; Feldpausch-Parker, Andrea M; Peterson, Tarla Rai

    2010-02-01

    Conservationists commonly have framed ecological concerns in economic terms to garner political support for conservation and to increase public interest in preserving global biodiversity. Beginning in the early 1980s, conservation biologists adapted neoliberal economics to reframe ecosystem functions and related biodiversity as ecosystem services to humanity. Despite the economic success of programs such as the Catskill/Delaware watershed management plan in the United States and the creation of global carbon exchanges, today's marketplace often fails to adequately protect biodiversity. We used a Marxist critique to explain one reason for this failure and to suggest a possible, if partial, response. Reframing ecosystem functions as economic services does not address the political problem of commodification. Just as it obscures the labor of human workers, commodification obscures the importance of the biota (ecosystem workers) and related abiotic factors that contribute to ecosystem functions. This erasure of work done by ecosystems impedes public understanding of biodiversity. Odum and Odum's radical suggestion to use the language of ecosystems (i.e., emergy or energy memory) to describe economies, rather than using the language of economics (i.e., services) to describe ecosystems, reverses this erasure of the ecosystem worker. Considering the current dominance of economic forces, however, implementing such solutions would require social changes similar in magnitude to those that occurred during the 1960s. Niklas Luhmann argues that such substantive, yet rapid, social change requires synergy among multiple societal function systems (i.e., economy, education, law, politics, religion, science), rather than reliance on a single social sphere, such as the economy. Explicitly presenting ecosystem services as discreet and incomplete aspects of ecosystem functions not only allows potential economic and environmental benefits associated with ecosystem services, but also

  9. Controls of Net Ecosystem Exchange at an Old Field, a Pine Plantation, and a Hardwood Forest under Identical Climatic and Edaphic Conditions-Isotopic Studies

    SciTech Connect

    Chanton, J. P.; Mortazavi, B.

    2004-11-04

    During the past year we have submitted two manuscripts. 1. Mortazavi, B., J. Chanton, J.L. Prater, A.C. Oishi, R. Oren and G. Katul. Temporal variability in 13C of respired CO2 in a pine and a hardwood forest subject to similar climatic conditions (in Press). Oecologia 2. Mortazavi, B. and J. P. Chanton. Use of Keeling plots for determining sources of dissolved organic carbon in nearshore and open ocean systems (Published in Limnology and Oceanography (2004) Vol 49 pages 102-108). 3. Mortazavi, B., J. L. Prater, and J. P. Chanton (2004). A field-based method for simultaneous measurements of the 18O and 13C of soil CO2 efflux. Biogeosciences Vol 1:1-16 Most recent products delivered: Mortazavi, B. and J. P. Chanton. Abiotic and biotic controls on the 13C of respired CO2 in the southeastern US forest mosaics and a new technique for measuring the of soil CO2 efflux. Joint Biosphere Stable Isotope Network (US) and Stable Isotopes in Biosphere Atmosphere Exchange (EU) 2004 Meeting, Interlaken, Switzerland, March 31-April 4, 2004. Mortazavi, B., J. Chanton, J.L. Prater, A.C. Oishi, R. Oren and G. Katul. Temporal variability in 13C of respired CO2 in a pine and a hardwood forest subject to similar climatic conditions. American Geophysical Union Fall Meeting, San Francisco, USA, December 8-12, 2003. Prater, J., Mortazavi, B. and J. P. Chanton. Measurement of discrimination against 13C during photosynthesis and quantification of the short-term variability of 13C over a diurnal cycle. American Geophysical Union Fall Meeting, San Francisco, USA, December 8-12, 2003.

  10. Carbon exchange between the mantle and the crust and its effect upon the atmosphere: Today compared to Archean time

    NASA Technical Reports Server (NTRS)

    Desmarais, D.

    1986-01-01

    Paleobiologists now recognize that the Earth's biosphere has been profoundly affected by geologic processes. One very important process is the dissipation of heat which has been generated by radioactivity and/or stored within the earth. Heat flow is responsible for crustal movements and therefore it is the principal architect for constructing the environments (e.g. shallow marine, continental, etc.) wherein life developed and flourished. Heat flow has also influenced the movements of volatile elements (e.g. C, N, H, S, rare gases, etc.) both within the Earth's crust and between the crust and mantle. The inventory of these elements in the Earth's crust is important, not just because some of them constitute the building blocks of organic matter, but also because they influence the biosphere's climate. The purpose of this work is to evaluate how the decline of heat flow over the course of the Earth's history has influenced the carbon inventory in the Earth's crust. Such an evaluation must first consider whether the rate at which carbon is presently being exchanged between the mantle and crust is sufficient to play an important role in controlling the crustal inventory. Secondly, this exchange of carbon must be reevaluated in the context of the Precambrian Earth's environment. One very important consideration is that the upper mantle was perhaps 300 C hotter 3 b.y. ago than it is today.

  11. Adsorptive removal of emerging polyfluoroalky substances F-53B and PFOS by anion-exchange resin: A comparative study.

    PubMed

    Gao, Yanxin; Deng, Shubo; Du, Ziwen; Liu, Kai; Yu, Gang

    2017-02-05

    Chrome plating is an important emission source of perfluorinated compounds (PFCs) industrial uses in China, where two commercial products potassium 2-(6-chloro-1,1,2,2,3,3,4,4,5,5,6,6-dodecafluorohexyloxy) (F-53B) and perfluorooctane sulfonate (PFOS) are applied as mist suppressant, causing non-negligible environmental risk. In this paper, anion-exchange resin IRA67 was evaluated for F-53B and PFOS removal from simulated and actual wastewater. Adsorption kinetics exhibited higher adsorption velocity and capacity of IRA67 for PFOS than F-53B due to their difference in molecular structures. Adsorption isotherms demonstrated the adsorption capacity of F-53B and PFOS on IRA67 was 4.2mmol/g and 5.5mmol/g, respectively. Because of the deprotonating of amine groups, solution pH had significant effect on IRA67 at pH>10. The results indicated that besides anion exchange other interactions including hydrophobic interaction and the formation of micelles or hemi-micelles were all involved in adsorption process. Coexisting sulfate and chromate in wastewater decreased adsorption capacities of F-53B and PFOS. The spent resin could be regenerated by the NaCl/NaOH and methanol mixed solution. In the mixed system and actual wastewater IRA67 can simultaneously remove F-53B and PFOS without obvious preference but the removal percent can be affected by competitive effect.

  12. Managing riverine landscapes as meta-ecosystems

    NASA Astrophysics Data System (ADS)

    Tockner, K.

    2014-12-01

    Aquatic and terrestrial ecosystems are tightly linked through energy, material, information, and organism flows. At the landscape scale, these reciprocal flows are controlled by the composition, configuration, boundary conditions and linkage of individual ecosystem types, thereby forming so-called meta-ecosystems. The relative importance of individual ecosystem types depends on the intrinsic properties (so-called "ecosystem traits"), the setting within the landscape, and the characteristics of interfaces that control cross-system fluxes. For example, the juxtaposition of particular ecosystem types (i.e. their composition and configuration) may alter the magnitude of landscape processes as well as the directions of flow among ecosystem types. Therefore, the meta-ecosystem concept provides a framework to quantify ecosystem diversity, a neglected component of biodiversity, and to test its effects on genetic and species diversity as well as the functional performance in coupled ecosystems. Given their topographic position at the lowest point in the landscape, aquatic ecosystems are particularly susceptible to influences exerted by their surrounding terrestrial environment, both the immediately adjacent riparian zones and the entire catchment that they drain. Questions that need to be tackled may include: What are the consequences of exchange pulses between aquatic and terrestrial ecosystems on the functional performance of individual ecosystems? What are the mechanisms and processes underlying structural and functional biodiversity at aquatic-terrestrial interfaces? In this respect, the meta-ecosystem concept might be very helpful in landscape management and in ecosystem design and engineering.

  13. AQUATIC ECOSYSTEMS,

    EPA Science Inventory

    Aquatic ecosystems are a vital part of the urban water cycle (and of urban areas more broadly), and, if healthy, provide a range of goods and services valued by humans (Meyer 1997). For example, aquatic ecosystems (e.g., rivers, lakes, wetlands) provide potable water, food resou...

  14. Soil-atmospheric exchange of CO2, CH4, and N2O in three subtropical forest ecosystems in southern China

    USGS Publications Warehouse

    Tang, X.; Liu, S.; Zhou, G.; Zhang, Dongxiao; Zhou, C.

    2006-01-01

    The magnitude, temporal, and spatial patterns of soil-atmospheric greenhouse gas (hereafter referred to as GHG) exchanges in forests near the Tropic of Cancer are still highly uncertain. To contribute towards an improvement of actual estimates, soil-atmospheric CO2, CH4, and N2O fluxes were measured in three successional subtropical forests at the Dinghushan Nature Reserve (hereafter referred to as DNR) in southern China. Soils in DNR forests behaved as N2O sources and CH4 sinks. Annual mean CO2, N2O, and CH4 fluxes (mean ?? SD) were 7.7 ?? 4.6MgCO2-Cha-1 yr-1, 3.2 ?? 1.2 kg N2ONha-1 yr-1, and 3.4 ?? 0.9 kgCH4-Cha-1 yr-1, respectively. The climate was warm and wet from April through September 2003 (the hot-humid season) and became cool and dry from October 2003 through March 2004 (the cool-dry season). The seasonality of soil CO2 emission coincided with the seasonal climate pattern, with high CO2 emission rates in the hot-humid season and low rates in the cool-dry season. In contrast, seasonal patterns of CH4 and N2O fluxes were not clear, although higher CH4 uptake rates were often observed in the cool-dry season and higher N2O emission rates were often observed in the hot-humid season. GHG fluxes measured at these three sites showed a clear increasing trend with the progressive succession. If this trend is representative at the regional scale, CO2 and N2O emissions and CH4 uptake in southern China may increase in the future in light of the projected change in forest age structure. Removal of surface litter reduced soil CO2 effluxes by 17-44% in the three forests but had no significant effect on CH4 absorption and N2O emission rates. This suggests that microbial CH4 uptake and N2O production was mainly related to the mineral soil rather than in the surface litter layer. ?? 2006 Blackwell Publishing Ltd.

  15. Driving terrestrial ecosystem models from space

    NASA Technical Reports Server (NTRS)

    Waring, R. H.

    1993-01-01

    Regional air pollution, land-use conversion, and projected climate change all affect ecosystem processes at large scales. Changes in vegetation cover and growth dynamics can impact the functioning of ecosystems, carbon fluxes, and climate. As a result, there is a need to assess and monitor vegetation structure and function comprehensively at regional to global scales. To provide a test of our present understanding of how ecosystems operate at large scales we can compare model predictions of CO2, O2, and methane exchange with the atmosphere against regional measurements of interannual variation in the atmospheric concentration of these gases. Recent advances in remote sensing of the Earth's surface are beginning to provide methods for estimating important ecosystem variables at large scales. Ecologists attempting to generalize across landscapes have made extensive use of models and remote sensing technology. The success of such ventures is dependent on merging insights and expertise from two distinct fields. Ecologists must provide the understanding of how well models emulate important biological variables and their interactions; experts in remote sensing must provide the biophysical interpretation of complex optical reflectance and radar backscatter data.

  16. Pulmonary rehabilitation after total laryngectomy: a randomized cross-over clinical trial comparing two different heat and moisture exchangers (HMEs).

    PubMed

    Herranz, Jesús; Espiño, María Alvarez; Morado, Carolina Ogen

    2013-09-01

    Post-laryngectomy heat and moisture exchanger (HME) use is known to have a beneficial effect on tracheal climate, pulmonary symptoms and related aspects. This study aims to investigate differences in clinical effects between the first and second generation Provox HMEs. The second generation (Provox XtraHME) has better humidification properties than the first generation (Provox HME), and has been shown to further improve tracheal climate. Forty-five laryngectomized patients, who were already using an HME, participated in a prospective, randomized cross-over clinical study in which each HME was used for 6 weeks. Results showed that for most parameters studied, the second generation HME performed equally well or better than the first generation HME. The improvement in tracheal climate translated into patients reporting significantly less tracheal dryness with the second generation than with the first generation (p = 0.039). Using an HME with better humidification properties is related to a reduction in tracheal dryness in our study population.

  17. A COMPARATIVE ANALYSIS OF NUTRIENT LOADING, NUTRIENT RETENTION AND NET ECOSYSTEM METABOLISM IN THREE TIDAL RIVER ESTUARIES DIFFERING PREDOMINATELY BY THEIR WATERSHED LAND USE TYPES.

    EPA Science Inventory

    Abstract and oral presentation for the Estuarine Research Federation Conference.

    Estuarine retention of watershed nutrient loads, system-wide nutrient biogeochemical fluxes, and net ecosystem metabolism (NEM) were determined in three estuaries exhibiting differing magnitud...

  18. Visiting Scholar Exchange Reports.

    ERIC Educational Resources Information Center

    Rubin, Kyna, Ed.

    1986-01-01

    Provides reports of four United States scholars who visited China as part of the Visiting Scholar Exchange Program. The titles of the reports are (1) "China Journey: A Political Scientist's Look at Yan'an," (2) "The Social Consequences of Land Reclamation in Chinese Coastal Ecosystems," (3) "Anthropology Lectures in South…

  19. Quantum and Ecosystem Entropies

    NASA Astrophysics Data System (ADS)

    Kirwan, A. D.

    2008-06-01

    Ecosystems and quantum gases share a number of superficial similarities including enormous numbers of interacting elements and the fundamental role of energy in such interactions. A theory for the synthesis of data and prediction of new phenomena is well established in quantum statistical mechanics. The premise of this paper is that the reason a comparable unifying theory has not emerged in ecology is that a proper role for entropy has yet to be assigned. To this end, a phase space entropy model of ecosystems is developed. Specification of an ecosystem phase space cell size based on microbial mass, length, and time scales gives an ecosystem uncertainty parameter only about three orders of magnitude larger than Planck’s constant. Ecosystem equilibria is specified by conservation of biomass and total metabolic energy, along with the principle of maximum entropy at equilibria. Both Bose - Einstein and Fermi - Dirac equilibrium conditions arise in ecosystems applications. The paper concludes with a discussion of some broader aspects of an ecosystem phase space.

  20. Exchange frequency in replica exchange molecular dynamics

    NASA Astrophysics Data System (ADS)

    Sindhikara, Daniel; Meng, Yilin; Roitberg, Adrian E.

    2008-01-01

    The effect of the exchange-attempt frequency on sampling efficiency is studied in replica exchange molecular dynamics (REMD). We show that sampling efficiency increases with increasing exchange-attempt frequency. This conclusion is contrary to a commonly expressed view in REMD. Five peptides (1-21 residues long) are studied with a spectrum of exchange-attempt rates. Convergence rates are gauged by comparing ensemble properties between fixed length test REMD simulations and longer reference simulations. To show the fundamental correlation between exchange frequency and convergence time, a simple model is designed and studied, displaying the same basic behavior of much more complex systems.

  1. Comparative studies on exchange reactions of hexafluoroacetylacetonate in bis(hexafluoroacetylacetonato)(dimethyl sulfoxide)dioxouranium(VI) in nonaqueous solvent and supercritical CO(2).

    PubMed

    Kachi, Yoshihiro; Kayaki, Yoshihito; Tsukahara, Takehiko; Ikariya, Takao; Ikeda, Yasuhisa

    2008-01-07

    Exchange reactions of hexafluoroacetylacetonate (hfacac) in UO2(hfacac)2DMSO (DMSO = dimethyl sulfoxide) in o-C6D4Cl2 and supercritical CO2 (sc-CO2) have been studied using the NMR line-broadening method to compare reactivity in a nonaqueous solvent with that in sc-CO2. It was found that the exchange rates of hfacac in both systems are dependent on the concentration of the enol isomer ([Henol]) of hexafluoroacetylacetone and become slow with an increase in the concentration of free DMSO ([DMSO]). The exchange reaction between free and coordinated DMSO in UO2(hfacac)2DMSO has been also examined in o-C6D4Cl2 and sc-CO2. As a result, the exchange rate of DMSO was found to depend on [DMSO]. From these results, the hfacac exchange reactions in UO2(hfacac)2DMSO in o-C6D4Cl2 and sc-CO2 were proposed to proceed through the mechanism that the ring-opening for one of two coordinated hfacac in UO2(hfacac)2DMSO is the rate-determining step, and the resulting vacant site is coordinated by the incoming Henol, followed by the proton transfer from Henol to hfacac and the ring closure of unidentate hfacac. The rate constants at 60 degrees C and the activation parameters (DeltaH and DeltaS) for the ring-opening path are 35.8 +/- 3.2 s(-1), 57.8 +/- 2.7 kJ.mol(-1), and -42.9 +/- 7.7 J.mol(-1).K(-1) for the o-C6D4Cl2 system, and 518 +/- 50 s(-1), 18.9 +/- 1.8 kJ.mol(-1), and -138 +/- 5 J.mol(-1).K(-1) for the sc-CO2 system, respectively. Differences in kinetic parameters between sc-CO2 and o-C6D4Cl2 systems were proposed to be attributed to the solute-solvent interactions such as Lewis acid-Lewis base interactions and hydrogen bondings between sc-CO2 and beta-diketones.

  2. Comparative effects of climate on ecosystem nitrogen and soil biogeochemistry in U.S. national parks. FY 2001 Annual Report (Res. Rept. No. 94)

    USGS Publications Warehouse

    Stottlemyer, R.; Edmonds, R.; Scherbarth, L.; Urbanczyk, K.; Van Miegroet, H.; Zak, J.

    2002-01-01

    In 1998, the USGS Global Change program funded research for a network of Long-Term Reference Ecosystems initially established in national parks and funded by the National Park Service. The network included Noland Divide, Great Smoky Mountains National Park, Tennessee; Pine Canyon, Big Ben National park, Texas; West Twin Creek, Olympic National Park, Washingtona?? Wallace Lake, Isle Royale National Park, Michigan; and the Asik watershed, Noatak National Preserve, Alaska. The watershed ecosystem model was used since this approach permits additional statistical power in detection of trends among variables, and the watershed in increasingly a land unit used in resource management and planning. The ecosystems represent a major fraction of lands administered by the National Park Service, and were chosen generally for the contrasts among sites. For example, tow of the site, Noland and West Twin, are characterized by high precipitation amounts, but Noland receives some of the highest atmospheric nitrogen (N) inputs in North America. In contrast, Pine Canyon and Asik are warm and cold desert sites respectively. The Asik watershed receives <1% the atmospheric N inputs Noland receives. The Asik site is at the northern extent (treeline) of the boreal biome in the North America while Wallace is at the southern ecotone between boreal and northern hardwoods. The research goal for these sites is to gain a basic understanding of ecosystem structure and function, and the response to global change especially atmospheric inputs and climate.

  3. Commonalities of carbon dioxide exchange in semiarid regions with monsoon and Mediterranean climates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Semiarid ecosystems with monsoon climates receive precipitation during the warm season while Mediterranean systems are characteristically wet in the cool season and dry in the summer. Comparing biosphere-atmosphere carbon exchange across these two climate regimes can yield information about the int...

  4. Flux frequency analysis of seasonally dry ecosystem fluxes in two unique biomes of Sonora Mexico

    NASA Astrophysics Data System (ADS)

    Verduzco, V. S.; Yepez, E. A.; Robles-Morua, A.; Garatuza, J.; Rodriguez, J. C.; Watts, C.

    2013-05-01

    Complex dynamics from the interactions of ecosystems processes makes difficult to model the behavior of ecosystems fluxes of carbon and water in response to the variation of environmental and biological drivers. Although process oriented ecosystem models are critical tools for studying land-atmosphere fluxes, its validity depends on the appropriate parameterization of equations describing temporal and spatial changes of model state variables and their interactions. This constraint often leads to discrepancies between model simulations and observed data that reduce models reliability especially in arid and semiarid ecosystems. In the semiarid north western Mexico, ecosystem processes are fundamentally controlled by the seasonality of water and the intermittence of rain pulses which are conditions that require calibration of specific fitting functions to describe the response of ecosystem variables (i.e. NEE, GPP, ET, respiration) to these wetting and drying periods. The goal is to find functions that describe the magnitude of ecosystem fluxes during individual rain pulses and the seasonality of the ecosystem. Relaying on five years of eddy covariance flux data of a tropical dry forest and a subtropical shrubland we present a flux frequency analysis that describe the variation of net ecosystem exchange (NEE) of CO2 to highlight the relevance of pulse driven dynamics controlling this flux. Preliminary results of flux frequency analysis of NEE indicate that these ecosystems are strongly controlled by the frequency distribution of rain. Also, the output of fitting functions for NEE, GPP, ET and respiration using semi-empirical functions applied at specific rain pulses compared with season-long statistically generated simulations do not agree. Seasonality and the intrinsic nature of individual pulses have different effects on ecosystem flux responses. This suggests that relationships between the nature of seasonality and individual pulses can help improve the

  5. Latent heat exchange in the boreal and arctic biomes.

    PubMed

    Kasurinen, Ville; Alfredsen, Knut; Kolari, Pasi; Mammarella, Ivan; Alekseychik, Pavel; Rinne, Janne; Vesala, Timo; Bernier, Pierre; Boike, Julia; Langer, Moritz; Belelli Marchesini, Luca; van Huissteden, Ko; Dolman, Han; Sachs, Torsten; Ohta, Takeshi; Varlagin, Andrej; Rocha, Adrian; Arain, Altaf; Oechel, Walter; Lund, Magnus; Grelle, Achim; Lindroth, Anders; Black, Andy; Aurela, Mika; Laurila, Tuomas; Lohila, Annalea; Berninger, Frank

    2014-11-01

    In this study latent heat flux (λE) measurements made at 65 boreal and arctic eddy-covariance (EC) sites were analyses by using the Penman-Monteith equation. Sites were stratified into nine different ecosystem types: harvested and burnt forest areas, pine forests, spruce or fir forests, Douglas-fir forests, broadleaf deciduous forests, larch forests, wetlands, tundra and natural grasslands. The Penman-Monteith equation was calibrated with variable surface resistances against half-hourly eddy-covariance data and clear differences between ecosystem types were observed. Based on the modeled behavior of surface and aerodynamic resistances, surface resistance tightly control λE in most mature forests, while it had less importance in ecosystems having shorter vegetation like young or recently harvested forests, grasslands, wetlands and tundra. The parameters of the Penman-Monteith equation were clearly different for winter and summer conditions, indicating that phenological effects on surface resistance are important. We also compared the simulated λE of different ecosystem types under meteorological conditions at one site. Values of λE varied between 15% and 38% of the net radiation in the simulations with mean ecosystem parameters. In general, the simulations suggest that λE is higher from forested ecosystems than from grasslands, wetlands or tundra-type ecosystems. Forests showed usually a tighter stomatal control of λE as indicated by a pronounced sensitivity of surface resistance to atmospheric vapor pressure deficit. Nevertheless, the surface resistance of forests was lower than for open vegetation types including wetlands. Tundra and wetlands had higher surface resistances, which were less sensitive to vapor pressure deficits. The results indicate that the variation in surface resistance within and between different vegetation types might play a significant role in energy exchange between terrestrial ecosystems and atmosphere. These results suggest the need

  6. 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...

  7. A comparative meta-analysis of maximal aerobic metabolism of vertebrates: implications for respiratory and cardiovascular limits to gas exchange.

    PubMed

    Hillman, Stanley S; Hancock, Thomas V; Hedrick, Michael S

    2013-02-01

    Maximal aerobic metabolic rates (MMR) in vertebrates are supported by increased conductive and diffusive fluxes of O(2) from the environment to the mitochondria necessitating concomitant increases in CO(2) efflux. A question that has received much attention has been which step, respiratory or cardiovascular, provides the principal rate limitation to gas flux at MMR? Limitation analyses have principally focused on O(2) fluxes, though the excess capacity of the lung for O(2) ventilation and diffusion remains unexplained except as a safety factor. Analyses of MMR normally rely upon allometry and temperature to define these factors, but cannot account for much of the variation and often have narrow phylogenetic breadth. The unique aspect of our comparative approach was to use an interclass meta-analysis to examine cardio-respiratory variables during the increase from resting metabolic rate to MMR among vertebrates from fish to mammals, independent of allometry and phylogeny. Common patterns at MMR indicate universal principles governing O(2) and CO(2) transport in vertebrate cardiovascular and respiratory systems, despite the varied modes of activities (swimming, running, flying), different cardio-respiratory architecture, and vastly different rates of metabolism (endothermy vs. ectothermy). Our meta-analysis supports previous studies indicating a cardiovascular limit to maximal O(2) transport and also implicates a respiratory system limit to maximal CO(2) efflux, especially in ectotherms. Thus, natural selection would operate on the respiratory system to enhance maximal CO(2) excretion and the cardiovascular system to enhance maximal O(2) uptake. This provides a possible evolutionary explanation for the conundrum of why the respiratory system appears functionally over-designed from an O(2) perspective, a unique insight from previous work focused solely on O(2) fluxes. The results suggest a common gas transport blueprint, or Bauplan, in the vertebrate clade.

  8. Defining Ecosystem Assets for Natural Capital Accounting.

    PubMed

    Hein, Lars; Bagstad, Ken; Edens, Bram; Obst, Carl; de Jong, Rixt; Lesschen, Jan Peter

    2016-01-01

    In natural capital accounting, ecosystems are assets that provide ecosystem services to people. Assets can be measured using both physical and monetary units. In the international System of Environmental-Economic Accounting, ecosystem assets are generally valued on the basis of the net present value of the expected flow of ecosystem services. In this paper we argue that several additional conceptualisations of ecosystem assets are needed to understand ecosystems as assets, in support of ecosystem assessments, ecosystem accounting and ecosystem management. In particular, we define ecosystems' capacity and capability to supply ecosystem services, as well as the potential supply of ecosystem services. Capacity relates to sustainable use levels of multiple ecosystem services, capability involves prioritising the use of one ecosystem service over a basket of services, and potential supply considers the ability of ecosystems to generate services regardless of demand for these services. We ground our definitions in the ecosystem services and accounting literature, and illustrate and compare the concepts of flow, capacity, capability, and potential supply with a range of conceptual and real-world examples drawn from case studies in Europe and North America. Our paper contributes to the development of measurement frameworks for natural capital to support environmental accounting and other assessment frameworks.

  9. Non-use Economic Values for Little-Known Aquatic Species at Risk: Comparing Choice Experiment Results from Surveys Focused on Species, Guilds, and Ecosystems

    NASA Astrophysics Data System (ADS)

    Rudd, Murray A.; Andres, Sheri; Kilfoil, Mary

    2016-09-01

    Accounting for non-market economic values of biological diversity is important to fully assess the benefits of environmental policies and regulations. This study used three choice experiments (species-, guild-, and ecosystem-based surveys) in parallel to quantify non-use values for little-known aquatic species at risk in southern Ontario. Mean willingness-to-pay (WTP) ranged from 9.45 to 21.41 per listing status increment under Canada's Species at Risk Act for both named and unnamed little-known species. Given the broad range of valuable ecosystem services likely to accrue to residents from substantial increases in water quality and the rehabilitation of coastal wetlands, the difference in WTP between species- and ecosystem-based surveys seemed implausibly small. It appeared that naming species—the `iconization' of species in two of the three surveys—had an important effect on WTP. The results suggest that reasonable annual household-level WTP values for little-known aquatic species may be 10 to 25 per species or 10 to 20 per listing status increment. The results highlighted the utility of using parallel surveys to triangulate on non-use economic values for little-known species at risk.

  10. Effects of different elevated CO2 concentrations on chlorophyll contents, gas exchange, water use efficiency, and PSII activity on C3 and C4 cereal crops in a closed artificial ecosystem.

    PubMed

    Wang, Minjuan; Xie, Beizhen; Fu, Yuming; Dong, Chen; Hui, Liu; Guanghui, Liu; Liu, Hong

    2015-12-01

    Although terrestrial CO2 concentrations [CO2] are not expected to reach 1000 μmol mol(-1) (or ppm) for many decades, CO2 levels in closed systems such as growth chambers and greenhouses can easily exceed this concentration. CO2 levels in life support systems (LSS) in space can exceed 10,000 ppm (1 %). In order to understand how photosynthesis in C4 plants may respond to elevated CO2, it is necessary to determine if leaves of closed artificial ecosystem grown plants have a fully developed C4 photosynthetic apparatus, and whether or not photosynthesis in these leaves is more responsive to elevated [CO2] than leaves of C3 plants. To address this issue, we evaluated the response of gas exchange, water use efficiency, and photosynthetic efficiency of PSII by soybean (Glycine max (L.) Merr., 'Heihe35') of a typical C3 plant and maize (Zea mays L., 'Susheng') of C4 plant under four CO2 concentrations (500, 1000, 3000, and 5000 ppm), which were grown under controlled environmental conditions of Lunar Palace 1. The results showed that photosynthetic pigment by the C3 plants of soybean was more sensitive to elevated [CO2] below 3000 ppm than the C4 plants of maize. Elevated [CO2] to 1000 ppm induced a higher initial photosynthetic rate, while super-elevated [CO2] appeared to negate such initial growth promotion for C3 plants. The C4 plant had the highest ETR, φPSII, and qP under 500-3000 ppm [CO2], but then decreased substantially at 5000 ppm [CO2] for both species. Therefore, photosynthetic down-regulation and a decrease in photosynthetic electron transport occurred by both species in response to super-elevated [CO2] at 3000 and 5000 ppm. Accordingly, plants can be selected for and adapt to the efficient use of elevated CO2 concentration in LSS.

  11. Status of whitebarkpine in the Greater Yellowstone Ecosystem: A step-trend analysis comparing 2004-2007 to 2008-2011

    USGS Publications Warehouse

    Shanahan, Erin; Irvine, Kathryn M.; Roberts, Dave; Litt, Andrea R.; Legg, Kristin; Daley, Rob; Chambers, Nina

    2014-01-01

    Whitebark pine (Pinus albicaulis) is a foundation and keystone species in upper subalpine environments of the northern Rocky Mountains that strongly influences the biodiversity and productivity of high-elevation ecosystems (Tomback et al. 2001, Ellison et al. 2005). Throughout its historic range, whitebark pine has decreased significantly as a major component of high-elevation forests. As a result, it is critical to understand the challenges to whitebark pine—not only at the tree and stand level, but also as these factors influence the distribution of whitebark pine across the Greater Yellowstone Ecosystem (GYE). In 2003, the National Park Service (NPS) Greater Yellowstone Inventory & Monitoring Network identified whitebark pine as one of twelve significant natural resource indicators or vital signs to monitor (Jean et al. 2005, Fancy et al. 2009) and initiated a long-term, collaborative monitoring program. Partners in this effort include the U.S. Geological Survey, U.S. Forest Service, and Montana State University with representatives from each comprising the Greater Yellowstone Whitebark Pine Monitoring Working Group. The objectives of the monitoring program are to assess trends in (1) the proportion of live, whitebark pine trees (>1.4-m tall) infected with white pine blister rust (blister rust); (2) to document blister rust infection severity by the occurrence and location of persisting and new infections; (3) to determine mortality of whitebark pine trees and describe potential factors contributing to the death of trees; and (4) to assess the multiple components of the recruitment of understory whitebark pine into the reproductive population. In this report we summarize the past eight years (2004-2011) of whitebark pine status and trend monitoring in the GYE. Our study area encompasses six national forests (NF), two national parks (NP), as well as state and private lands in portions of Wyoming, Montana, and Idaho; this area is collectively described as the

  12. Ecosystem services provided by bats.

    PubMed

    Kunz, Thomas H; Braun de Torrez, Elizabeth; Bauer, Dana; Lobova, Tatyana; Fleming, Theodore H

    2011-03-01

    Ecosystem services are the benefits obtained from the environment that increase human well-being. Economic valuation is conducted by measuring the human welfare gains or losses that result from changes in the provision of ecosystem services. Bats have long been postulated to play important roles in arthropod suppression, seed dispersal, and pollination; however, only recently have these ecosystem services begun to be thoroughly evaluated. Here, we review the available literature on the ecological and economic impact of ecosystem services provided by bats. We describe dietary preferences, foraging behaviors, adaptations, and phylogenetic histories of insectivorous, frugivorous, and nectarivorous bats worldwide in the context of their respective ecosystem services. For each trophic ensemble, we discuss the consequences of these ecological interactions on both natural and agricultural systems. Throughout this review, we highlight the research needed to fully determine the ecosystem services in question. Finally, we provide a comprehensive overview of economic valuation of ecosystem services. Unfortunately, few studies estimating the economic value of ecosystem services provided by bats have been conducted to date; however, we outline a framework that could be used in future studies to more fully address this question. Consumptive goods provided by bats, such as food and guano, are often exchanged in markets where the market price indicates an economic value. Nonmarket valuation methods can be used to estimate the economic value of nonconsumptive services, including inputs to agricultural production and recreational activities. Information on the ecological and economic value of ecosystem services provided by bats can be used to inform decisions regarding where and when to protect or restore bat populations and associated habitats, as well as to improve public perception of bats.

  13. Defining ecosystem assets for natural capital accounting

    USGS Publications Warehouse

    Hein, Lars; Bagstad, Kenneth J.; Edens, Bram; Obst, Carl; de Jong, Rixt; Lesschen, Jan Peter

    2016-01-01

    In natural capital accounting, ecosystems are assets that provide ecosystem services to people. Assets can be measured using both physical and monetary units. In the international System of Environmental-Economic Accounting, ecosystem assets are generally valued on the basis of the net present value of the expected flow of ecosystem services. In this paper we argue that several additional conceptualisations of ecosystem assets are needed to understand ecosystems as assets, in support of ecosystem assessments, ecosystem accounting and ecosystem management. In particular, we define ecosystems’ capacity and capability to supply ecosystem services, as well as the potential supply of ecosystem services. Capacity relates to sustainable use levels of multiple ecosystem services, capability involves prioritising the use of one ecosystem service over a basket of services, and potential supply considers the ability of ecosystems to generate services regardless of demand for these services. We ground our definitions in the ecosystem services and accounting literature, and illustrate and compare the concepts of flow, capacity, capability, and potential supply with a range of conceptual and real-world examples drawn from case studies in Europe and North America. Our paper contributes to the development of measurement frameworks for natural capital to support environmental accounting and other assessment frameworks.

  14. Defining Ecosystem Assets for Natural Capital Accounting

    PubMed Central

    Hein, Lars; Bagstad, Ken; Edens, Bram; Obst, Carl; de Jong, Rixt; Lesschen, Jan Peter

    2016-01-01

    In natural capital accounting, ecosystems are assets that provide ecosystem services to people. Assets can be measured using both physical and monetary units. In the international System of Environmental-Economic Accounting, ecosystem assets are generally valued on the basis of the net present value of the expected flow of ecosystem services. In this paper we argue that several additional conceptualisations of ecosystem assets are needed to understand ecosystems as assets, in support of ecosystem assessments, ecosystem accounting and ecosystem management. In particular, we define ecosystems’ capacity and capability to supply ecosystem services, as well as the potential supply of ecosystem services. Capacity relates to sustainable use levels of multiple ecosystem services, capability involves prioritising the use of one ecosystem service over a basket of services, and potential supply considers the ability of ecosystems to generate services regardless of demand for these services. We ground our definitions in the ecosystem services and accounting literature, and illustrate and compare the concepts of flow, capacity, capability, and potential supply with a range of conceptual and real-world examples drawn from case studies in Europe and North America. Our paper contributes to the development of measurement frameworks for natural capital to support environmental accounting and other assessment frameworks. PMID:27828969

  15. Ecosystem Service Valuation Assessments for Protected Area Management: A Case Study Comparing Methods Using Different Land Cover Classification and Valuation Approaches.

    PubMed

    Whitham, Charlotte E L; Shi, Kun; Riordan, Philip

    2015-01-01

    Accurate and spatially-appropriate ecosystem service valuations are vital for decision-makers and land managers. Many approaches for estimating ecosystem service value (ESV) exist, but their appropriateness under specific conditions or logistical limitations is not uniform. The most accurate techniques are therefore not always adopted. Six different assessment approaches were used to estimate ESV for a National Nature Reserve in southwest China, across different management zones. These approaches incorporated two different land-use land cover (LULC) maps and development of three economic valuation techniques, using globally or locally-derived data. The differences in ESV across management zones for the six approaches were largely influenced by the classifications of forest and farmland and how they corresponded with valuation coefficients. With realistic limits on access to time, data, skills and resources, and using acquired estimates from globally-relevant sources, the Buffer zone was estimated as the most valuable (2.494 million ± 1.371 million CNY yr(-1) km(-2)) and the Non-protected zone as the least valuable (770,000 ± 4,600 CNY yr(-1) km(-2)). However, for both LULC maps, when using the locally-based and more time and skill-intensive valuation approaches, this pattern was generally reversed. This paper provides a detailed practical example of how ESV can differ widely depending on the availability and appropriateness of LULC maps and valuation approaches used, highlighting pitfalls for the managers of protected areas.

  16. Unravelling the Carbon and Sulphur Metabolism in Coastal Soil Ecosystems Using Comparative Cultivation-Independent Genome-Level Characterisation of Microbial Communities

    PubMed Central

    Yousuf, Basit; Kumar, Raghawendra; Mishra, Avinash; Jha, Bhavanath

    2014-01-01

    Bacterial autotrophy contributes significantly to the overall carbon balance, which stabilises atmospheric CO2 concentration and decelerates global warming. Little attention has been paid to different modes of carbon/sulphur metabolism mediated by autotrophic bacterial communities in terrestrial soil ecosystems. We studied these pathways by analysing the distribution and abundance of the diagnostic metabolic marker genes cbbM, apsA and soxB, which encode for ribulose-1,5-bisphosphate carboxylase/oxygenase, adenosine phosphosulphate reductase and sulphate thiohydrolase, respectively, among different contrasting soil types. Additionally, the abundance of community members was assessed by quantifying the gene copy numbers for 16S rRNA, cbbL, cbbM, apsA and soxB. Distinct compositional differences were observed among the clone libraries, which revealed a dominance of phylotypes associated with carbon and sulphur cycling, such as Gammaproteobacteria (Thiohalomonas, Allochromatium, Chromatium, Thiomicrospira) and Alphaproteobacteria (Rhodopseudomonas, Rhodovulum, Paracoccus). The rhizosphere soil was devoid of sulphur metabolism, as the soxB and apsA genes were not observed in the rhizosphere metagenome, which suggests the absence or inadequate representation of sulphur-oxidising bacteria. We hypothesise that the novel Gammaproteobacteria sulphur oxidisers might be actively involved in sulphur oxidation and inorganic carbon fixation, particularly in barren saline soil ecosystems, suggesting their significant putative ecological role and contribution to the soil carbon pool. PMID:25225969

  17. Unravelling the carbon and sulphur metabolism in coastal soil ecosystems using comparative cultivation-independent genome-level characterisation of microbial communities.

    PubMed

    Yousuf, Basit; Kumar, Raghawendra; Mishra, Avinash; Jha, Bhavanath

    2014-01-01

    Bacterial autotrophy contributes significantly to the overall carbon balance, which stabilises atmospheric CO2 concentration and decelerates global warming. Little attention has been paid to different modes of carbon/sulphur metabolism mediated by autotrophic bacterial communities in terrestrial soil ecosystems. We studied these pathways by analysing the distribution and abundance of the diagnostic metabolic marker genes cbbM, apsA and soxB, which encode for ribulose-1,5-bisphosphate carboxylase/oxygenase, adenosine phosphosulphate reductase and sulphate thiohydrolase, respectively, among different contrasting soil types. Additionally, the abundance of community members was assessed by quantifying the gene copy numbers for 16S rRNA, cbbL, cbbM, apsA and soxB. Distinct compositional differences were observed among the clone libraries, which revealed a dominance of phylotypes associated with carbon and sulphur cycling, such as Gammaproteobacteria (Thiohalomonas, Allochromatium, Chromatium, Thiomicrospira) and Alphaproteobacteria (Rhodopseudomonas, Rhodovulum, Paracoccus). The rhizosphere soil was devoid of sulphur metabolism, as the soxB and apsA genes were not observed in the rhizosphere metagenome, which suggests the absence or inadequate representation of sulphur-oxidising bacteria. We hypothesise that the novel Gammaproteobacteria sulphur oxidisers might be actively involved in sulphur oxidation and inorganic carbon fixation, particularly in barren saline soil ecosystems, suggesting their significant putative ecological role and contribution to the soil carbon pool.

  18. Effect of environmental variables and stand structure on ecosystem respiration components in a Mediterranean beech forest.

    PubMed

    Guidolotti, Gabriele; Rey, Ana; D'Andrea, Ettore; Matteucci, Giorgio; De Angelis, Paolo

    2013-09-01

    The temporal variability of ecosystem respiration (RECO) has been reported to have important effects on the temporal variability of net ecosystem exchange, the net amount of carbon exchanged between an ecosystem and the atmosphere. However, our understanding of ecosystem respiration is rather limited compared with photosynthesis or gross primary productivity, particularly in Mediterranean montane ecosystems. In order to investigate how environmental variables and forest structure (tree classes) affect different respiration components and RECO in a Mediterranean beech forest, we measured soil, stem and leaf CO2 efflux rates with dynamic chambers and RECO by the eddy-covariance technique over 1 year (2007-2008). Ecosystem respiration showed marked seasonal variation, with the highest rates in spring and autumn and the lowest in summer. We found that the soil respiration (SR) was mainly controlled by soil water content below a threshold value of 0.2 m(3) m(-3), above which the soil temperature explained temporal variation in SR. Stem CO2 effluxes were influenced by air temperature and difference between tree classes with higher rates measured in dominant trees than in co-dominant ones. Leaf respiration (LR) varied significantly between the two canopy layers considered. Non-structural carbohydrates were a very good predictor of LR variability. We used these measurements to scale up respiration components to ecosystem respiration for the whole canopy and obtained cumulative amounts of carbon losses over the year. Based on the up-scaled chamber measurements, the relative contributions of soil, stem and leaves to the total annual CO2 efflux were: 56, 8 and 36%, respectively. These results confirm that SR is the main contributor of ecosystem respiration and provided an insight on the driving factors of respiration in Mediterranean montane beech forests.

  19. Electronic and magnetic properties of X2YZ and XYZ Heusler compounds: a comparative study of density functional theory with different exchange-correlation potentials

    NASA Astrophysics Data System (ADS)

    Rai, D. P.; Sandeep; Shankar, A.; Pradhan Sakhya, Anup; Sinha, T. P.; Khenata, R.; Ghimire, M. P.; Thapa, R. K.

    2016-07-01

    The electronic and magnetic properties of Heusler compounds X2YZ and XYZ (X = Co, Ni, Pt, Fe; Y = Mn, Cr, Vi; Z = Al, Sb, Ga) are investigated by using the density functional theory with generalized gradient approximation (GGA), GGA plus U (LSDA+U), and modified Becke-Johnson (mBJ) exchange potential. It is found that the half-metallic gaps are generally widened reasonably by LSDA+U and mBJ as compared to the conventional GGA. For the Co-based Heusler compounds the inclusion of U in GGA leads to a larger minority band gap while it is destroyed for Fe2VAl and NiMnSb. The magnetic properties of Co2VSi and Co2VSn are well defined within LSDA+U and mBJ with an exact integer value of magnetic moment. The band gaps of Fe2VAl and CoMnSb given by mBJ are in good agreement with the available experimental data of x-ray absorption spectroscopy. Except for the reasonably larger band gap, the mBJ band structure is almost same as that of GGA but is remarkably different from that of LSDA+U.

  20. On the functional role of tree species in two forest ecosystems

    NASA Astrophysics Data System (ADS)

    Kutsch, Werner Leo; Herbst, Mathias; Liu, Chunjiang

    2010-05-01

    ,max in deciduous forests can be explained by a combined effect of LAI and some species-specific reference leaf traits, rather than by the plasticity index or by pure LAI. In a second study we compared a mixed canopy of Fagus sylvatica and Fraxinus excelsior to a pure Fagus sylvatica stand during a drought period in summer 2006. Leaf gas exchange measurements suggested that beech trees responded faster and stronger to soil drought and changed stomatal sensitivity to leaf to air water vapour pressure deficit, while ash trees remained more progressive. Scaling these results in a modelling approach resulted in an lower impact of drought in a two-species canopy than in a beech monoculture and an increase of the Fraxinus contribution to total ecosystem carbon uptake. Both results support the hypothesis that multi-species canopies may buffer unfavourable environmental constraints and increase efficiency in the use of resources.

  1. A Comparative Study of Weights and Sizes of Flat-Plate Exhaust-Gas-to-Air Heat Exchangers with and without Fins

    DTIC Science & Technology

    1947-07-01

    tests of both heat exchangers, air or-d exhauj’t-gaa flow rates wtre mnr.sur’sd with venturi motors located downstream from the heat exchanger. Air...cas— flow ratoa aa di.torrin.jd froo the venturi notor. TEST rBOCEDUPE Flii^it toatJn3 of tho host exchangers wr.3 conduced to evaluate their tho...Static pressures upstrean and downctroTa frca tho hoat- oxchangor core wore raacurod with etat5c tubos , and air flow rates ware raacurcd vith n vonturi

  2. Soil and litter exchange of reactive trace gases

    EPA Science Inventory

    The soil and litter play an important role in the exchange of trace gases between terrestrial ecosystems and the atmosphere. - The exchange of ammonia between vegetation and the atmosphere is highly influenced by soil and litter emissions especially in managed ecosystems (grassla...

  3. [Comparative morpho-functional characteristics of the organs of the reproductive system of small mammals under conditions of anthropogenic transformation of Southern Ural steppe ecosystems].

    PubMed

    Shevliuk, N N; Blinova, E V; Bokov, D A; Demina, L L; Elina, E E; Meshkova, O A; Ryskulov, M F

    2013-01-01

    The morpho-functional characteristics of reproductive organs of small mammals--striped field mouse (Apodemus agrarius Pallas, 1771), house mouse (Mus musculus Linnaeus, 1758), wood mouse (Sylvaemus uralensis Pallas, 1811), common vole (Microtus arvalis Pallas, 1778), bank vole (Clethrionomys glareolus Schreber, 1780), steppe lemming (Lagurus lagurus Pallas, 1773), little suslik (Spermophilus pygmaeus Pallas, 1778), and red-heeked suslik (Spermophilus major Pallas, 1779)--belonging to the populations inhabiting anthropogenically modified steppe landscapes (zones influenced by the ferrous metallurgy plants and gas processing plant, as well as the territory of the large city) were studied using histological, electron microscopic, immunocytochemical and morphometric methods. In animals studied, inhabiting technologically modified ecosystems, in contrast to those from ecologically safe regions, the testis demonstrated the increased destruction of spermatogenic epithelium. In the ovaries, the accelerated exhaustion of follicular reserve was detected. The increased embryonic death rate was also observed. The portion of the animals participating in reproduction was enlarged, the female fecundity was increased, while the age at puberty was decreased. Among the animal species studied, the variable degree of stability against the effect of the negative factors was demonstrated.

  4. Multiple colonizations lead to cryptic biodiversity in an island ecosystem: comparative phylogeography of anchialine shrimp species in the Ryukyu Archipelago, Japan.

    PubMed

    Weese, David A; Fujita, Yoshihisa; Santos, Scott R

    2013-09-01

    Archipelagos of the Indo-West Pacific are considered to be among the richest in the world in biodiversity, and phylogeographic studies generally support either the center of origin or the center of accumulation hypothesis to explain this pattern. To differentiate between these competing hypotheses for organisms from the Indo-West Pacific anchialine ecosystem, defined as coastal bodies of mixohaline water fluctuating with the tides but having no direct oceanic connections, we investigated the genetic variation, population structure, and evolutionary history of three caridean shrimp species (Antecaridina lauensis, Halocaridinides trigonophthalma, and Metabetaeus minutus) in the Ryukyu Archipelago, Japan. We used two mitochondrial genes--cytochrome c oxidase subunit I (COI) and large ribosomal subunit (16S-rDNA)--complemented with genetic examination of available specimens from the same or closely related species from the Indian and Pacific Oceans. In the Ryukyus, each species encompassed 2-3 divergent (9.52%-19.2% COI p-distance) lineages, each having significant population structure and varying geographic distributions. Phylogenetically, the A. lauensis and M. minutus lineages in the Ryukyus were more closely related to ones from outside the archipelago than to one another. These results, when interpreted in the context of Pacific oceanographic currents and geologic history of the Ryukyus, imply multiple colonizations of the archipelago by the three species, consistent with the center of accumulation hypothesis. While this study contributes toward understanding the biodiversity, ecology, and evolution of organisms in the Ryukyus and the Indo-West Pacific, it also has potential utility in establishing conservation strategies for anchialine fauna of the Pacific Basin in general.

  5. Air-surface exchange of Hg0 measured by collocated micrometeorological and enclosure methods - Part 1: Data comparability and method characteristics

    NASA Astrophysics Data System (ADS)

    Zhu, W.; Sommar, J.; Lin, C.-J.; Feng, X.

    2014-09-01

    Reliable quantification of air-biosphere exchange flux of elemental mercury vapor (Hg0) is crucial for understanding global biogeochemical cycle of mercury. However, there has not been a standard analytical protocol for flux quantification, and little attention has been devoted to characterize the temporal variability and comparability of fluxes measured by different methods. In this study, we deployed a collocated set of micro-meteorological (MM) and enclosure measurement systems to quantify Hg0 flux over bare soil and low standing crop in an agricultural field. The techniques include relaxed eddy accumulation (REA), modified Bowen-ratio (MBR), aerodynamic gradient (AGM) as well as dynamic flux chambers of traditional (TDFC) and novel (NDFC) designs. The five systems and their measured fluxes were cross-examined with respect to magnitude, temporal trend and sensitivity to environmental variables. Fluxes measured by the MM and DFC methods showed distinct temporal trends. The former exhibited a highly dynamic temporal variability while the latter had much gradual temporal features. The diurnal characteristics reflected the difference in the fundamental processes driving the measurements. The correlations between NDFC and TDFC fluxes and between MBR and AGM fluxes were significant (R > 0.8, p < 0.05), but the correlation between DFC and MM instantaneous fluxes were from weak to moderate (R = 0.1-0.5). Statistical analysis indicated that the median of turbulent fluxes estimated by the three independent MM-techniques were not significantly different. Cumulative flux measured by TDFC is considerably lower (42% of AGM and 31% of MBR fluxes) while those measured by NDFC, AGM and MBR were similar (< 10% difference). This implicates that the NDFC technique, which accounts for internal friction velocity, effectively bridged the gap in measured Hg0 flux compared to MM techniques. Cumulated flux measured by REA was ~60% higher than the gradient-based fluxes. Environmental

  6. Climate change and viticulture in Mediterranean climates: the complex response of socio-ecosystems. A comparative case study from France and Australia (1955-2040)

    NASA Astrophysics Data System (ADS)

    Lereboullet, A.-L.; Beltrando, G.; Bardsley, D. K.

    2012-04-01

    The wine industry is very sensitive to extreme weather events, especially to temperatures above 35°C and drought. In a context of global climate change, Mediterranean climate regions are predicted to experience higher variability in rainfall and temperatures and an increased occurrence of extreme weather events. Some viticultural systems could be particularly at risk in those regions, considering their marginal position in the growth climatic range of Vitis vinifera, the long commercial lifespan of a vineyard, the high added-value of wine and the volatile nature of global markets. The wine industry, like other agricultural systems, is inserted in complex networks of climatic and non-climatic (other physical, economical, social and legislative) components, with constant feedbacks. We use a socio-ecosystem approach to analyse the adaptation of two Mediterranean viticultural systems to recent and future increase of extreme weather events. The present analysis focuses on two wine regions with a hot-summer Mediterranean climate (CSb type in the Köppen classification): Côtes-du-Roussillon in southern France and McLaren Vale in southern Australia. Using climate data from two synoptic weather stations, Perpignan (France) and Adelaide (Australia), with time series running from 1955 to 2010, we highlight changes in rainfall patterns and an increase in the number of days with Tx >35°c since the last three decades in both regions. Climate models (DRIAS project data for France and CSIRO Mk3.5 for Australia) project similar trends in the future. To date, very few projects have focused on an international comparison of the adaptive capacity of viticultural systems to climate change with a holistic approach. Here, the analysis of climate data was complemented by twenty in-depth semi-structured interviews with key actors of the two regional wine industries, in order to analyse adaptation strategies put in place regarding recent climate evolution. This mixed-methods approach

  7. Carbon monoxide exchange and partitioning of a managed mountain meadow

    NASA Astrophysics Data System (ADS)

    Wohlfahrt, G.; Hammerle, A.; Kitz, F.; Spielmann, F.

    2015-12-01

    With an average mole fraction of 100 ppb carbon monoxide (CO) plays a critical role in atmospheric chemistry and thus has an indirect global warming potential. While sources/sinks of CO on land at least partially cancel out each other, the magnitude of CO sources and sinks is highly uncertain. Even if direct CO fluxes from/to land ecosystems are very much likely clearly lower in magnitude compared to anthropogenic emissions, biomass burning, emissions from chemical precursors and the OH sink, it may be premature to neglect any direct contributions of land ecosystems to the CO budget. In addition, changes in global climate and resulting changes in global productivity may require re-evaluating older data and assumptions. One major reason for the large uncertainty is a general scarcity of empirical data. An additional factor contributing to the uncertainty is the lack of ecosystem-scale CO exchange measurements, i.e. CO flux data that encompass all sources and sinks within an ecosystem. Here we present data on continuous eddy covariance measurements of CO-fluxes above a managed mountain grassland in combination with soil chamber flux measurements, within- and above-canopy concentration profiles and an inverse Lagrangian analysis to disentangle sinks and sources of CO. Preliminary results show the grassland ecosystem to be a net source for CO during daytime, with increasing flux rates at higher solar radiation. At night, if at all, the meadow is a slight sink for CO. The same holds true for soil flux measurements.

  8. Effects of experimental water table and temperature manipulations on ecosystem CO2 fluxes in an Alaskan rich fen

    USGS Publications Warehouse

    Chivers, M.R.; Turetsky, M.R.; Waddington, J.M.; Harden, J.W.; McGuire, A.D.

    2009-01-01

    Peatlands store 30% of the world's terrestrial soil carbon (C) and those located at northern latitudes are expected to experience rapid climate warming. We monitored growing season carbon dioxide (CO2) fluxes across a factorial design of in situ water table (control, drought, and flooded plots) and soil warming (control vs. warming via open top chambers) treatments for 2 years in a rich fen located just outside the Bonanza Creek Experimental Forest in interior Alaska. The drought (lowered water table position) treatment was a weak sink or small source of atmospheric CO2 compared to the moderate atmospheric CO2 sink at our control. This change in net ecosystem exchange was due to lower gross primary production and light-saturated photosynthesis rather than increased ecosystem respiration. The flooded (raised water table position) treatment was a greater CO2 sink in 2006 due largely to increased early season gross primary production and higher light-saturated photosynthesis. Although flooding did not have substantial effects on rates of ecosystem respiration, this water table treatment had lower maximum respiration rates and a higher temperature sensitivity of ecosystem respiration than the control plot. Surface soil warming increased both ecosystem respiration and gross primary production by approximately 16% compared to control (ambient temperature) plots, with no net effect on net ecosystem exchange. Results from this rich fen manipulation suggest that fast responses to drought will include reduced ecosystem C storage driven by plant stress, whereas inundation will increase ecosystem C storage by stimulating plant growth. ?? 2009 Springer Science+Business Media, LLC.

  9. Ecosystem service valuations of mangrove ecosystems to inform decision making and future valuation exercises.

    PubMed

    Mukherjee, Nibedita; Sutherland, William J; Dicks, Lynn; Hugé, Jean; Koedam, Nico; Dahdouh-Guebas, Farid

    2014-01-01

    The valuation of ecosystem services is a complex process as it includes several dimensions (ecological, socio-cultural and economic) and not all of these can be quantified in monetary units. The aim of this paper is to conduct an ecosystem services valuation study for mangroves ecosystems, the results of which can be used to inform governance and management of mangroves. We used an expert-based participatory approach (the Delphi technique) to identify, categorize and rank the various ecosystem services provided by mangrove ecosystems at a global scale. Subsequently we looked for evidence in the existing ecosystem services literature for monetary valuations of these ecosystem service categories throughout the biogeographic distribution of mangroves. We then compared the relative ranking of ecosystem service categories between the monetary valuations and the expert based analysis. The experts identified 16 ecosystem service categories, six of which are not adequately represented in the literature. There was no significant correlation between the expert based valuation (the Delphi technique) and the economic valuation, indicating that the scope of valuation of ecosystem services needs to be broadened. Acknowledging this diversity in different valuation approaches, and developing methodological frameworks that foster the pluralism of values in ecosystem services research, are crucial for maintaining the credibility of ecosystem services valuation. To conclude, we use the findings of our dual approach to valuation to make recommendations on how to assess and manage the ecosystem services provided by mangrove ecosystems.

  10. Ecosystem Service Valuations of Mangrove Ecosystems to Inform Decision Making and Future Valuation Exercises

    PubMed Central

    Mukherjee, Nibedita; Sutherland, William J.; Dicks, Lynn; Hugé, Jean; Koedam, Nico; Dahdouh-Guebas, Farid

    2014-01-01

    The valuation of ecosystem services is a complex process as it includes several dimensions (ecological, socio-cultural and economic) and not all of these can be quantified in monetary units. The aim of this paper is to conduct an ecosystem services valuation study for mangroves ecosystems, the results of which can be used to inform governance and management of mangroves. We used an expert-based participatory approach (the Delphi technique) to identify, categorize and rank the various ecosystem services provided by mangrove ecosystems at a global scale. Subsequently we looked for evidence in the existing ecosystem services literature for monetary valuations of these ecosystem service categories throughout the biogeographic distribution of mangroves. We then compared the relative ranking of ecosystem service categories between the monetary valuations and the expert based analysis. The experts identified 16 ecosystem service categories, six of which are not adequately represented in the literature. There was no significant correlation between the expert based valuation (the Delphi technique) and the economic valuation, indicating that the scope of valuation of ecosystem services needs to be broadened. Acknowledging this diversity in different valuation approaches, and developing methodological frameworks that foster the pluralism of values in ecosystem services research, are crucial for maintaining the credibility of ecosystem services valuation. To conclude, we use the findings of our dual approach to valuation to make recommendations on how to assess and manage the ecosystem services provided by mangrove ecosystems. PMID:25243852

  11. Contributions of biogenic volatile organic compounds to net ecosystem carbon flux in a ponderosa pine plantation

    NASA Astrophysics Data System (ADS)

    Bouvier-Brown, Nicole C.; Schade, Gunnar W.; Misson, Laurent; Lee, Anita; McKay, Megan; Goldstein, Allen H.

    2012-12-01

    When assessing net ecosystem exchange (NEE) and net ecosystem carbon balance (NECB), respiration is generally assumed to be the only significant loss of carbon to the atmosphere. However, carbon is also emitted from ecosystems in the form of biogenic volatile organic compounds (BVOCs). Here we consider the magnitude of systematic difference caused by omitting this additional carbon loss from the net ecosystem carbon balance, as compared to the NEE term, of the ponderosa pine plantation at Blodgett Forest. We find that 9.4 (range 6.2-12.5) g C m-2 yr-1 were emitted from this ecosystem as BVOCs. This is 4.0 (2.0-7.9) % of annual NEE, and neglecting this additional loss of carbon causes an overestimation of carbon storage for this rapidly growing commercial forest plantation. For ecosystems that are not storing carbon as rapidly, where photosynthesis and respiration are more closely balanced, ignoring BVOC emission may cause a larger error in the estimation of NECB.

  12. An invasive riparian tree reduces stream ecosystem efficiency via a recalcitrant organic matter subsidy.

    PubMed

    Mineau, Madeleine M; Baxter, Golden V; Marcarelli, Amy M; Minshall, G Wayne

    2012-07-01

    A disturbance, such as species invasion, can alter the exchange of materials and organisms between ecosystems, with potential consequences for the function of both ecosystems. Russian olive (Elaeagnus angustifolia) is an exotic tree invading riparian corridors in the western United States, and may alter stream organic matter budgets by increasing allochthonous litter and by reducing light via shading, in turn decreasing in-stream primary production. We used a before-after invasion comparison spanning 35 years to show that Russian olive invasion increased allochthonous litter nearly 25-fold to an invaded vs. a control reach of a stream, and we found that this litter decayed more slowly than native willow. Despite a mean 50% increase in canopy cover by Russian olive and associated shading, there were no significant changes in gross primary production. Benthic organic matter storage increased fourfold after Russian olive invasion compared to pre-invasion conditions, but there were no associated changes in stream ecosystem respiration or organic matter export. Thus, estimated stream ecosystem efficiency (ratio of ecosystem respiration to organic matter input) decreased 14%. These findings show that invasions of nonnative plant species in terrestrial habitats can alter resource fluxes to streams with consequences for whole-ecosystem functions.

  13. Juvenile Rhus glabra leaves have higher temperatures and lower gas exchange rates than mature leaves when compared in the field during periods of high irradiance.

    PubMed

    Snider, John L; Choinski, John S; Wise, Robert R

    2009-05-01

    We sought to test the hypothesis that stomatal development determines the timing of gas exchange competency, which then influences leaf temperature through transpirationally driven leaf cooling. To test this idea, daily patterns of gas exchange and leaflet temperature were obtained from leaves of two distinctively different developmental stages of smooth sumac (Rhus glabra) grown in its native habitat. Juvenile and mature leaves were also sampled for ultrastructural studies of stomatal development. When plants were sampled in May-June, the hypothesis was supported: juvenile leaflets were (for part of the day) from 1.4 to 6.0 degrees C warmer than mature leaflets and as much as 2.0 degrees C above ambient air temperature with lower stomatal conductance and photosynthetic rates than mature leaflets. When measurements were taken from July to October, no significant differences were observed, although mature leaflet gas exchange rates declined to the levels of the juvenile leaves. The gas exchange data were supported by the observations that juvenile leaves had approximately half the number of functional stomata on a leaf surface area basis as did mature leaves. It was concluded that leaf temperature and stage of leaf development in sumac are strongly linked with the higher surface temperatures observed in juvenile leaflets in the early spring possibly being involved in promoting photosynthesis and leaf expansion when air temperatures are cooler.

  14. Comparing the Picture Exchange Communication System and the iPad™ for Communication of Students with Autism Spectrum Disorder and Developmental Delay

    ERIC Educational Resources Information Center

    Hill, Doris Adams; Flores, Margaret M.

    2014-01-01

    Both picture exchange, a low-tech picturebased communication system, and technologybased interventions, such as the iPad™ with communication application, are emerging treatments for students with autism spectrum disorder (ASD), according to the National Autism Center (2009). Recently, investigations regarding the use of the Apple iPad™ to…

  15. Net exchanges of CO2, CH4 and N2O between the terrestrial ecosystems and the atmosphere in boreal and arctic region: Towards a full greenhouse gas budget

    NASA Astrophysics Data System (ADS)

    Zhang, B.; Tian, H.; Lu, C.; Yang, J.; Kamaljit, K.; Pan, S.

    2014-12-01

    Boreal and arctic terrestrial ecosystem is a unique ecological region due to large portion of wetland and permafrost distribution. Increasing disturbances, like permafrost-thaw, fire event, climate extreme, would greatly change the patterns and variations of greenhouse gas emission and further affect the feedback between terrestrial ecosystem and climate change. Carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) accounted for more than 85% of the radioactive forcing (RF) due to long-lived greenhouse gases. However, few studies have considered the full budget of three gases together in this region. In this study, we used a process-based model (Dynamic Land Ecosystem Model), driven by multiple global change factors, to quantify the magnitude, spatial and temporal variation of CO2, CH4 and N2O across the boreal and arctic regions. Simulated results have been evaluated against field observations, inventory-based and atmospheric inversion estimates. By implementing a set of factorial simulations, we further quantify the relative contribution of climate, atmospheric composition, fire to the CO2, CH4 and N2O fluxes. Continued warming climate potentially could shift the inter-annual and intra-annual variation of greenhouse gases fluxes. The understanding of full budget in this region could provide insights for reasonable future projection, which is also crucial for developing effective mitigation strategies.

  16. Microplastic in Aquatic Ecosystems.

    PubMed

    Ivleva, Natalia P; Wiesheu, Alexandra C; Niessner, Reinhard

    2017-02-06

    The contamination of marine and freshwater ecosystems with plastic, and especially with microplastic (MP), is a global ecological problem of increasing scientific concern. This has stimulated a great deal of research on the occurrence of MP, interaction of MP with chemical pollutants, the uptake of MP by aquatic organisms, and the resulting (negative) impact of MP. Herein, we review the major issues of MP in aquatic environments, with the principal aims 1) to characterize the methods applied for MP analysis (including sampling, processing, identification and quantification), indicate the most reliable techniques, and discuss the required further improvements; 2) to estimate the abundance of MP in marine/freshwater ecosystems and clarify the problems that hamper the comparability of such results; and 3) to summarize the existing literature on the uptake of MP by living organisms. Finally, we identify knowledge gaps, suggest possible strategies to assess environmental risks arising from MP, and discuss prospects to minimize MP abundance in aquatic ecosystems.

  17. Linking plant and ecosystem functional biogeography

    PubMed Central

    Reichstein, Markus; Bahn, Michael; Mahecha, Miguel D.; Kattge, Jens; Baldocchi, Dennis D.

    2014-01-01

    Classical biogeographical observations suggest that ecosystems are strongly shaped by climatic constraints in terms of their structure and function. On the other hand, vegetation function feeds back on the climate system via biosphere–atmosphere exchange of matter and energy. Ecosystem-level observations of this exchange reveal very large functional biogeographical variation of climate-relevant ecosystem functional properties related to carbon and water cycles. This variation is explained insufficiently by climate control and a classical plant functional type classification approach. For example, correlations between seasonal carbon-use efficiency and climate or environmental variables remain below 0.6, leaving almost 70% of variance unexplained. We suggest that a substantial part of this unexplained variation of ecosystem functional properties is related to variations in plant and microbial traits. Therefore, to progress with global functional biogeography, we should seek to understand the link between organismic traits and flux-derived ecosystem properties at ecosystem observation sites and the spatial variation of vegetation traits given geoecological covariates. This understanding can be fostered by synergistic use of both data-driven and theory-driven ecological as well as biophysical approaches. PMID:25225392

  18. Complete genome sequence and comparative analysis of Acetobacter pasteurianus 386B, a strain well-adapted to the cocoa bean fermentation ecosystem

    PubMed Central

    2013-01-01

    Background Acetobacter pasteurianus 386B, an acetic acid bacterium originating from a spontaneous cocoa bean heap fermentation, proved to be an ideal functional starter culture for coca bean fermentations. It is able to dominate the fermentation process, thereby resisting high acetic acid concentrations and temperatures. However, the molecular mechanisms underlying its metabolic capabilities and niche adaptations are unknown. In this study, whole-genome sequencing and comparative genome analysis was used to investigate this strain’s mechanisms to dominate the cocoa bean fermentation process. Results The genome sequence of A. pasteurianus 386B is composed of a 2.8-Mb chromosome and seven plasmids. The annotation of 2875 protein-coding sequences revealed important characteristics, including several metabolic pathways, the occurrence of strain-specific genes such as an endopolygalacturonase, and the presence of mechanisms involved in tolerance towards various stress conditions. Furthermore, the low number of transposases in the genome and the absence of complete phage genomes indicate that this strain might be more genetically stable compared with other A. pasteurianus strains, which is an important advantage for the use of this strain as a functional starter culture. Comparative genome analysis with other members of the Acetobacteraceae confirmed the functional properties of A. pasteurianus 386B, such as its thermotolerant nature and unique genetic composition. Conclusions Genome analysis of A. pasteurianus 386B provided detailed insights into the underlying mechanisms of its metabolic features, niche adaptations, and tolerance towards stress conditions. Combination of these data with previous experimental knowledge enabled an integrated, global overview of the functional characteristics of this strain. This knowledge will enable improved fermentation strategies and selection of appropriate acetic acid bacteria strains as functional starter culture for cocoa bean

  19. Sustaining the Landscape: A Method for Comparing Current and Desired Future Conditions of Forest Ecosystems in the North Cumberland Plateau and Mountains

    SciTech Connect

    Druckenbrod, D.L.

    2004-12-22

    This project initiates an integrated-landscape conservation approach within the Northern Cumberlands Project Area in Tennessee and Kentucky. The mixed mesophytic forests within the Cumberland Plateau and Mountains are among the most diverse in North America; however, these forests have been impacted by and remain threatened from changes in land use across this landscape. The integrated-landscape conservation approach presented in this report outlines a sequence of six conservation steps. This report considers the first three of these steps in two, successive stages. Stage 1 compares desired future conditions (DFCs) and current prevailing conditions (CPCs) at the landscape-scale utilizing remote sensing imagery, remnant forests, and descriptions of historical forest types within the Cumberland Plateau. Subsequently, Stage 2 compares DFCs and CPCs for at-risk forest types identified in Stage 1 utilizing structural, compositional, or functional attributes from USFS Forest Inventory and Analysis data. Ecological indicators will be developed from each stage that express the gaps between these two realizations of the landscape. The results from these first three steps will directly contribute to the final three steps of the integrated-landscape conservation approach by providing guidance for the generation of new conservation strategies in the Northern Cumberland Plateau and Mountains.

  20. Comparative Intradermal Tuberculin Testing of Free-Ranging African Buffaloes (Syncerus caffer) Captured for Ex Situ Conservation in the Kafue Basin Ecosystem in Zambia.

    PubMed

    Munang'andu, Hetron Mweemba; Siamudaala, Victor; Matandiko, Wigganson; Nambota, Andrew; Muma, John Bwalya; Mweene, Aaron Simanyengwe; Munyeme, Musso

    2011-01-01

    Bovine tuberculosis (BTB) is endemic in African buffaloes (Syncerus caffer) in some National Parks in Southern Africa, whilst no studies have been conducted on BTB on buffalo populations in Zambia. The increased demand for ecotourism and conservation of the African buffalo on private owned game ranches has prompted the Zambian Wildlife Authority (ZAWA) and private sector in Zambia to generate a herd of "BTB-free buffaloes" for ex situ conservation. In the present study, 86 African buffaloes from four different herds comprising a total of 530 animals were investigated for the presence of BTB for the purpose of generating "BTB free" buffalo for ex-situ conservation. Using the comparative intradermal tuberculin test (CIDT) the BTB status at both individual animal and herd level was estimated to be 0.0% by the CIDT technique. Compared to Avian reactors only, a prevalence of 5.8% was determined whilst for Bovine-only reactors a prevalence of 0.0% was determined. These results suggest the likelihood of buffalo herds in the Kafue National Park being free of BTB.

  1. Comparative Intradermal Tuberculin Testing of Free-Ranging African Buffaloes (Syncerus caffer) Captured for Ex Situ Conservation in the Kafue Basin Ecosystem in Zambia

    PubMed Central

    Munang'andu, Hetron Mweemba; Siamudaala, Victor; Matandiko, Wigganson; Nambota, Andrew; Muma, John Bwalya; Mweene, Aaron Simanyengwe; Munyeme, Musso

    2011-01-01

    Bovine tuberculosis (BTB) is endemic in African buffaloes (Syncerus caffer) in some National Parks in Southern Africa, whilst no studies have been conducted on BTB on buffalo populations in Zambia. The increased demand for ecotourism and conservation of the African buffalo on private owned game ranches has prompted the Zambian Wildlife Authority (ZAWA) and private sector in Zambia to generate a herd of “BTB-free buffaloes” for ex situ conservation. In the present study, 86 African buffaloes from four different herds comprising a total of 530 animals were investigated for the presence of BTB for the purpose of generating “BTB free” buffalo for ex-situ conservation. Using the comparative intradermal tuberculin test (CIDT) the BTB status at both individual animal and herd level was estimated to be 0.0% by the CIDT technique. Compared to Avian reactors only, a prevalence of 5.8% was determined whilst for Bovine-only reactors a prevalence of 0.0% was determined. These results suggest the likelihood of buffalo herds in the Kafue National Park being free of BTB. PMID:21776347

  2. Nitrogen cycling process rates across urban ecosystems.

    PubMed

    Reisinger, Alexander J; Groffman, Peter M; Rosi-Marshall, Emma J

    2016-09-21

    Nitrogen (N) pollution of freshwater, estuarine, and marine ecosystems is widespread and has numerous environmental and economic impacts. A portion of this excess N comes from urban watersheds comprised of natural and engineered ecosystems which can alter downstream N export. Studies of urban N cycling have focused on either specific ecosystems or on watershed-scale mass balances. Comparisons of specific N transformations across ecosystems are required to contextualize rates from individual studies. Here we reviewed urban N cycling in terrestrial, aquatic, and engineered ecosystems, and compared N processing in these urban ecosystem types to native reference ecosystems. We found that net N mineralization and net nitrification rates were enhanced in urban forests and riparian zones relative to reference ecosystems. Denitrification was highly variable across urban ecosystem types, but no significant differences were found between urban and reference denitrification rates. When focusing on urban streams, ammonium uptake was more rapid than nitrate uptake in urban streams. Additionally, reduction of stormwater runoff coupled with potential decreases in N concentration suggests that green infrastructure may reduce downstream N export. Despite multiple environmental stressors in urban environments, ecosystems within urban watersheds can process and transform N at rates similar to or higher than reference ecosystems.

  3. Optimization of Heat Exchangers

    SciTech Connect

    Ivan Catton

    2010-10-01

    The objective of this research is to develop tools to design and optimize heat exchangers (HE) and compact heat exchangers (CHE) for intermediate loop heat transport systems found in the very high temperature reator (VHTR) and other Generation IV designs by addressing heat transfer surface augmentation and conjugate modeling. To optimize heat exchanger, a fast running model must be created that will allow for multiple designs to be compared quickly. To model a heat exchanger, volume averaging theory, VAT, is used. VAT allows for the conservation of mass, momentum and energy to be solved for point by point in a 3 dimensional computer model of a heat exchanger. The end product of this project is a computer code that can predict an optimal configuration for a heat exchanger given only a few constraints (input fluids, size, cost, etc.). As VAT computer code can be used to model characteristics )pumping power, temperatures, and cost) of heat exchangers more quickly than traditional CFD or experiment, optimization of every geometric parameter simultaneously can be made. Using design of experiment, DOE and genetric algorithms, GE, to optimize the results of the computer code will improve heat exchanger disign.

  4. Air-water oxygen exchange in a large whitewater river

    USGS Publications Warehouse

    Hall, Robert O.; Kennedy, Theodore A.; Rosi-Marshall, Emma J.

    2012-01-01

    Air-water gas exchange governs fluxes of gas into and out of aquatic ecosystems. Knowing this flux is necessary to calculate gas budgets (i.e., O2) to estimate whole-ecosystem metabolism and basin-scale carbon budgets. Empirical data on rates of gas exchange for streams, estuaries, and oceans are readily available. However, there are few data from large rivers and no data from whitewater rapids. We measured gas transfer velocity in the Colorado River, Grand Canyon, as decline in O2 saturation deficit, 7 times in a 28-km segment spanning 7 rapids. The O2 saturation deficit exists because of hypolimnetic discharge from Glen Canyon Dam, located 25 km upriver from Lees Ferry. Gas transfer velocity (k600) increased with slope of the immediate reach. k600 was -1 in flat reaches, while k600 for the steepest rapid ranged 3600-7700 cm h-1, an extremely high value of k600. Using the rate of gas exchange per unit length of water surface elevation (Kdrop, m-1), segment-integrated k600 varied between 74 and 101 cm h-1. Using Kdrop we scaled k600 to the remainder of the Colorado River in Grand Canyon. At the scale corresponding to the segment length where 80% of the O2 exchanged with the atmosphere (mean length = 26.1 km), k600 varied 4.5-fold between 56 and 272 cm h-1 with a mean of 113 cm h-1. Gas transfer velocity for the Colorado River was higher than those from other aquatic ecosystems because of large rapids. Our approach of scaling k600 based on Kdrop allows comparing gas transfer velocity across rivers with spatially heterogeneous morphology.

  5. Molecular comparative assessment of the microbial ecosystem in rumen and faeces of goats fed alfalfa hay alone or combined with oats.

    PubMed

    Mohammadzadeh, Hamid; Yáñez-Ruiz, David R; Martínez-Fernandez, Gonzalo; Abecia, Leticia

    2014-10-01

    The objective of this work was to compare the biomass and community structure of bacteria, protozoa and archaea communities in samples of rumen and faeces of goats and to what extent the diet (alfalfa hay with or without supplemented oats) offered to them exert an influence. Four cannulated adult goats fistulated in the rumen were used in a cross over design experiment in two experimental periods of 26 days, consisting in 14 days of adaptation, 7 days of sampling rumen contents and 5 days of digestibility measurement. Bacterial, protozoa and archaeal biomass and the communities' structure was assessed by real time PCR (qPCR) and denaturing gradient gel electrophoresis (DGGE), respectively. The numbers of archaea and bacteria in both rumen and faeces were higher and lower, respectively, in animals fed AH diet (P < 0.005). Contrary, protozoal numbers were not affected by the diet but were lower (P < 0.001) in faeces than in rumen. The analysis of the community structure revealed a consistently different population in structure in rumen and faeces for the three studied microbial groups and that supplementing alfalfa hay with oats led to a decrease in the similarity between sites in the rumen and faeces: similarity indexes for bacteria (57 and 27%), archaea (26 and 9%) and protozoa (62 and 22%) in animals fed AH and AHO diets, respectively.

  6. Simulation modeling of estuarine ecosystems

    NASA Technical Reports Server (NTRS)

    Johnson, R. W.

    1980-01-01

    A simulation model has been developed of Galveston Bay, Texas ecosystem. Secondary productivity measured by harvestable species (such as shrimp and fish) is evaluated in terms of man-related and controllable factors, such as quantity and quality of inlet fresh-water and pollutants. This simulation model used information from an existing physical parameters model as well as pertinent biological measurements obtained by conventional sampling techniques. Predicted results from the model compared favorably with those from comparable investigations. In addition, this paper will discuss remotely sensed and conventional measurements in the framework of prospective models that may be used to study estuarine processes and ecosystem productivity.

  7. Conservation Planning for Ecosystem Services

    PubMed Central

    Chan, Kai M. A; Shaw, M. Rebecca; Cameron, David R; Underwood, Emma C; Daily, Gretchen C

    2006-01-01

    Despite increasing attention to the human dimension of conservation projects, a rigorous, systematic methodology for planning for ecosystem services has not been developed. This is in part because flows of ecosystem services remain poorly characterized at local-to-regional scales, and their protection has not generally been made a priority. We used a spatially explicit conservation planning framework to explore the trade-offs and opportunities for aligning conservation goals for biodiversity with six ecosystem services (carbon storage, flood control, forage production, outdoor recreation, crop pollination, and water provision) in the Central Coast ecoregion of California, United States. We found weak positive and some weak negative associations between the priority areas for biodiversity conservation and the flows of the six ecosystem services across the ecoregion. Excluding the two agriculture-focused services—crop pollination and forage production—eliminates all negative correlations. We compared the degree to which four contrasting conservation network designs protect biodiversity and the flow of the six services. We found that biodiversity conservation protects substantial collateral flows of services. Targeting ecosystem services directly can meet the multiple ecosystem services and biodiversity goals more efficiently but cannot substitute for targeted biodiversity protection (biodiversity losses of 44% relative to targeting biodiversity alone). Strategically targeting only biodiversity plus the four positively associated services offers much promise (relative biodiversity losses of 7%). Here we present an initial analytical framework for integrating biodiversity and ecosystem services in conservation planning and illustrate its application. We found that although there are important potential trade-offs between conservation for biodiversity and for ecosystem services, a systematic planning framework offers scope for identifying valuable synergies. PMID

  8. Estimating agro-ecosystem carbon balance of northern Japan, and comparing the change in carbon stock by soil inventory and net biome productivity.

    PubMed

    Li, Xi; Toma, Yo; Yeluripati, Jagadeesh; Iwasaki, Shinya; Bellingrath-Kimura, Sonoko D; Jones, Edward O; Hatano, Ryusuke

    2016-06-01

    Soil C sequestration in croplands is deemed to be one of the most promising greenhouse gas mitigation options for agriculture. We have used crop-level yields, modeled heterotrophic respiration (Rh) and land use data to estimate spatio-temporal changes in regional scale net primary productivity (NPP), plant C inputs, and net biome productivity (NBP) in northern Japan's arable croplands and grasslands for the period of 1959-2011. We compared the changes in C stocks derived from estimated NBP and using repeated inventory datasets for each individual land use type from 2005 to 2011. For the entire study region of 2193 ha, overall annual plant C inputs to the soil constituted 37% of total region NPP. Plant C inputs in upland areas (excluding bush/fallow) could be predicted by climate variables. Overall NBP for all land use types increased from -1.26MgCha(-1)yr(-1) in 1959-0.26 Mg Cha(-1)yr(-1) in 2011. However, upland and paddy fields showed a decreased in NBP over the period of 1959-2011, under the current C input scenario. From 1988, an increase in agricultural abandonment (bush/fallow) and grassland cover caused a slow increase in the regional C pools. The comparison of carbon budgets using the NBP estimation method and the soil inventory method indicated no significant difference between the two methods. Our results showed C loss in upland crops, paddy fields and sites that underwent land use change from paddy field to upland sites. We also show C gain in grassland from 2005 to 2011. An underestimation of NBP or an overestimation of repeated C inventories cannot be excluded, but either method may be suitable for tracking absolute changes in soil C, considering the uncertainty associated with these methods.

  9. Ecosystem gross CO2 fluxes in a tropical rainforest estimated from carbonyl sulfide (COS)

    NASA Astrophysics Data System (ADS)

    Seibt, U. H.; Maseyk, K. S.; Lett, C.; Juarez, S.; Sun, W.

    2014-12-01

    Carbonyl sulfide (COS) is a promising new tracer to constrain the gross CO2 fluxes of land ecosystems, particularly in tropical forests where CO2 flux partitioning is often problematic due to the absence of turbulent flow at night. Since vegetation COS and CO2 uptake during photosynthesis is closely coupled, the gross fluxes of photosynthesis and respiration can be quantified through the concurrent measurements of COS and CO2. We measured ecosystem COS and CO2 exchange over four months in a tropical rainforest at La Selva, Costa Rica. We observed a strong ecosystem uptake of COS with a diel signal that was similar but not identical to net CO2 fluxes. Soils at the site mostly acted as COS sinks, correlated with soil moisture. The COS and CO2 data were used to calculate canopy photosynthesis (approx. GPP) from net ecosystem CO2 exchange (NEE) based on the empirical relationship of leaf relative uptake of COS and CO2. Mid-day COS-based GPP estimates ranged from -10 to -15 μmol m-2 s-1, compared to NEE of -5 to -10 μmol m-2 s-1. Ecosystem respiration, calculated as the difference of NEE and GPP, ranged from 5 to 10 μmol m-2 s-1, similar to previous estimates of 5 to 9 μmol m-2 s-1 from CO2 flux partitioning and respiration component measurements at the site. Our results support the application of COS as a new tool in ecosystem flux partitioning that may be particularly useful in tropical forests.

  10. Carbon and energy fluxes in cropland ecosystems: a model-data comparison

    SciTech Connect

    Lokupitiya, E.; Denning, A. S.; Schaefer, K.; Ricciuto, D.; Anderson, R.; Arain, M. A.; Baker, I.; Barr, A. G.; Chen, G.; Chen, J. M.; Ciais, P.; Cook, D. R.; Dietze, M.; El Maayar, M.; Fischer, M.; Grant, R.; Hollinger, D.; Izaurralde, C.; Jain, A.; Kucharik, C.; Li, Z.; Liu, S.; Li, L.; Matamala, R.; Peylin, P.; Price, D.; Running, S. W.; Sahoo, A.; Sprintsin, M.; Suyker, A. E.; Tian, H.; Tonitto, C.; Torn, M.; Verbeeck, Hans; Verma, S. B.; Xue, Y.

    2016-06-03

    Croplands are highly productive ecosystems that contribute to land–atmosphere exchange of carbon, energy, and water during their short growing seasons. We evaluated and compared net ecosystem exchange (NEE), latent heat flux (LE), and sensible heat flux (H) simulated by a suite of ecosystem models at five agricultural eddy covariance flux tower sites in the central United States as part of the North American Carbon Program Site Synthesis project. Most of the models overestimated H and underestimated LE during the growing season, leading to overall higher Bowen ratios compared to the observations. Most models systematically under predicted NEE, especially at rain-fed sites. Certain crop-specific models that were developed considering the high productivity and associated physiological changes in specific crops better predicted the NEE and LE at both rain-fed and irrigated sites. Models with specific parameterization for different crops better simulated the inter-annual variability of NEE for maize-soybean rotation compared to those models with a single generic crop type. Stratification according to basic model formulation and phenological methodology did not explain significant variation in model performance across these sites and crops. The under prediction of NEE and LE and over prediction of H by most of the models suggests that models developed and parameterized for natural ecosystems cannot accurately predict the more robust physiology of highly bred and intensively managed crop ecosystems. When coupled in Earth System Models, it is likely that the excessive physiological stress simulated in many land surface component models leads to overestimation of temperature and atmospheric boundary layer depth, and underestimation of humidity and CO2 seasonal uptake over agricultural regions.

  11. Improving policy and practice to promote equity and social justice - a qualitative comparative analysis building on key learnings from a twinning exchange between England and the US.

    PubMed

    Blanchard, Claire; Narle, Ginder; Gibbs, Martin; Ruddock, Charmaine; Grady, Michael; Brookes, Chris; Hopkins, Trevor; Norwood, Jayne

    2013-12-01

    Community health promotion interventions, targeted at marginalised populations and focusing on addressing the social determinants of health (SDH) to reduce health inequalities and addressing the processes of exclusion, are an important strategy to prevent and control non-communicable diseases (NCDs) and promote the health of underprivileged and under-resourced groups. This article builds on key lessons learnt from a learning exchange between Communities for Health in England and the Racial and Ethnic Approaches to Community Health across the US (REACH US) communities that are tackling health inequities. It presents a qualitative analysis further capturing information about specific community interventions involved in the exchange and identifying lessons learnt. This exchange was led by a partnership between the US Centers for Disease Control and Prevention, the International Union for Health Promotion and Education, the Department of Health of England, Health Action Partnership International, and Learning for Public Health West Midlands. These efforts provide interesting insights for further research, priority areas of action for policy and practice to address the SDH and to promote and sustain equity and social justice globally. The article highlights some key lessons about the use of data, assets-based community interventions and the importance of good leadership in times of crisis and adversity. Whilst complex and time-consuming to arrange, such programmes have the potential to offer other countries including the global south new insights and perspectives that will in turn contribute to the SDH field and provide concrete strategies and actions that effectively reduce inequities and promote the health of our societies. The key learnings have the potential to contribute to the global community and growing documentation on evidence of effective efforts in the reduction of health inequities.

  12. Reconciling estimates of the contemporary North American carbon balance among terrestrial biosphere models, atmospheric inversions and a new approach for estimating net ecosystem exchange from inventory-based data

    SciTech Connect

    Hayes, D. J.; Turner, D. P.; Stinson, Graham; McGuire, A. David; Wei, Yaxing; West, Tristram O.; Heath, L.; deJong, B.; McConkey, Brian; Birdsey, Richard A.; Kurz, Werner; Jacobson, Andy; Huntzinger, Deborah N.; Pan, Y.; Post, W. M.; Cook, R. B.

    2012-04-02

    While fossil fuel emissions are calculated with relatively high precision, understanding the fate of those emissions with respect to sequestration in terrestrial ecosystems requires data and methods that can reduce uncertainties in the diagnosis of land-based CO2 sinks. The wide range in the land surface flux estimates is related to a number of factors, but most generally because of the different methodologies used to develop estimates of carbon stocks and flux, and the uncertainties inherent in each approach. The alternative approaches to estimating continental scale carbon fluxes that we explored here can be broadly classified as applying a top-down or bottom-up perspective. Top-down approaches calculate land-atmosphere carbon fluxes based on atmospheric budgets and inverse modeling. Bottom-up approaches rely primarily on measurements of carbon stock changes (the inventory approach) or on spatially distributed simulations of carbon stocks and/or fluxes using process-based modeling (the forward modelapproach).