WorldWideScience

Sample records for ecosystem carbon exchange

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

    Science.gov (United States)

    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 ...

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

    Science.gov (United States)

    Victor Resco de Dios; Michael L. Goulden; Kiona Ogle; Andrew D. Richardson; David Y. Hollinger; Eric A. Davidson; Josu G. Alday; Greg A. Barron-Gafford; Arnaud Carrara; Andrew S. Kowalski; Walt C. Oechel; Borja R. Reverter; Russell L. Scott; Ruth K. Varner; Ruben Diaz-Sierra; Jose M. Moreno

    2012-01-01

    It is often assumed that daytime patterns of ecosystem carbon assimilation are mostly driven by direct physiological responses to exogenous environmental cues. Under limited environmental variability, little variation in carbon assimilation should thus be expected unless endogenous plant controls on carbon assimilation, which regulate photosynthesis in time, are active...

  3. Net ecosystem carbon exchange in three contrasting Mediterranean ecosystems – the effect of drought

    Directory of Open Access Journals (Sweden)

    T. S. David

    2007-09-01

    Full Text Available 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

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

    International Nuclear Information System (INIS)

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

    1996-01-01

    The evaluation and prediction of changes in carbon dynamics at the ecosystem level is a key issue in studies of global change. An operational concept for the determination of carbon fluxes for the Belgian territory is the goal of the presented study. The approach is based on the integration of remotely sensed data into ecosystem models in order to evaluate photosynthetic assimilation and net ecosystem exchange (NEE). Remote sensing can be developed as an operational tool to determine the fraction of absorbed photosynthetically active radiation (feAR). A review of the methodological approach of mapping fPAR dynamics at the regional scale by means of NOAA11-A VHRR / 2 data for the year 1990 is given. The processing sequence from raw radiance values to fPAR is presented. An interesting aspect of incorporating remote sensing derived fPAR in ecosystem models is the potential for modeling actual as opposed to potential vegetation. Further work should prove whether the concepts presented and the assumptions made in this study are valid. (NEE). Complex ecosystem models with a highly predictive value for a specific ecosystem are generally not suitable for global or regional applications, since they require a substantial set of ancillary data becoming increasingly larger with increasing complexity of the model. The ideal model for our purpose is one that is simple enough to be used in global scale modeling, and which can be adapted for different ecosystems or vegetation types. The fraction of absorbed photosynthetically active radiation (fPAR) during the growing season determines in part net photosynthesis and phytomass production (Ruimy, 1995). Remotely measured red and near-infrared spectral reflectances can be used to estimate fPAR. Therefore, a possible approach is to estimate net photosynthesis, phytomass, and NEE from a combination of satellite data and an ecosystem model that includes carbon dynamics. It has to be stated that some parts of the work presented in this

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

    Energy Technology Data Exchange (ETDEWEB)

    Zhuang, Qianlai [Purdue University; Law, Beverly E. [Oregon State University; Baldocchi, Dennis [University of California, Berkeley; Ma, Siyan [University of California, Berkeley; Chen, Jiquan [University of Toledo, Toledo, OH; Richardson, Andrew [Harvard University; Melillo, Jerry [Marine Biological Laboratory; Davis, Ken J. [Pennsylvania State University; Hollinger, D. [USDA Forest Service; Wharton, Sonia [University of California, Davis; Falk, Matthias [University of California, Davis; Paw, U. Kyaw Tha [University of California, Davis; Oren, Ram [Duke University; Katulk, Gabriel G. [Duke University; Noormets, Asko [North Carolina State University; Fischer, Marc [Lawrence Berkeley National Laboratory (LBNL); Verma, Shashi [University of Nebraska; Suyker, A. E. [University of Nebraska, Lincoln; Cook, David R. [Argonne National Laboratory (ANL); Sun, G. [USDA Forest Service; McNulty, Steven G. [USDA Forest Service; Wofsy, Steve [Harvard University; Bolstad, Paul V [University of Minnesota; Burns, Sean [University of Colorado, Boulder; Monson, Russell K. [University of Colorado, Boulder; Curtis, Peter [Ohio State University, The, Columbus; Drake, Bert G. [Smithsonian Environmental Research Center, Edgewater, MD; Foster, David R. [Harvard University; Gu, Lianhong [ORNL; Hadley, Julian L. [Harvard University; Litvak, Marcy [University of New Mexico, Albuquerque; Martin, Timothy A. [University of Florida, Gainesville; Matamala, Roser [Argonne National Laboratory (ANL); Meyers, Tilden [NOAA, Oak Ridge, TN; Oechel, Walter C. [San Diego State University; Schmid, H. P. [Indiana University; Scott, Russell L. [USDA ARS; Torn, Margaret S. [Lawrence Berkeley National Laboratory (LBNL)

    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.

  6. Carbon exchanges and their responses to temperature and precipitation in forest ecosystems in Yunnan, Southwest China.

    Science.gov (United States)

    Fei, Xuehai; Song, Qinghai; Zhang, Yiping; Liu, Yuntong; Sha, Liqing; Yu, Guirui; Zhang, Leiming; Duan, Changqun; Deng, Yun; Wu, Chuansheng; Lu, Zhiyun; Luo, Kang; Chen, Aiguo; Xu, Kun; Liu, Weiwei; Huang, Hua; Jin, Yanqiang; Zhou, Ruiwu; Li, Jing; Lin, Youxing; Zhou, Liguo; Fu, Yane; Bai, Xiaolong; Tang, Xianhui; Gao, Jinbo; Zhou, Wenjun; Grace, John

    2018-03-01

    Forest ecosystems play an increasingly important role in the global carbon cycle. However, knowledge on carbon exchanges, their spatio-temporal patterns, and the extent of the key controls that affect carbon fluxes is lacking. In this study, we employed 29-site-years of eddy covariance data to observe the state, spatio-temporal variations and climate sensitivity of carbon fluxes (gross primary productivity (GPP), ecosystem respiration (R eco ), and net ecosystem carbon exchange (NEE)) in four representative forest ecosystems in Yunnan. We found that 1) all four forest ecosystems were carbon sinks (the average NEE was -3.40tCha -1 yr -1 ); 2) contrasting seasonality of the NEE among the ecosystems with a carbon sink mainly during the wet season in the Yuanjiang savanna ecosystem (YJ) but during the dry season in the Xishuangbanna tropical rainforest ecosystem (XSBN), besides an equivalent NEE uptake was observed during the wet/dry season in the Ailaoshan subtropical evergreen broad-leaved forest ecosystem (ALS) and Lijiang subalpine coniferous forest ecosystem (LJ); 3) as the GPP increased, the net ecosystem production (NEP) first increased and then decreased when the GPP>17.5tCha -1 yr -1 ; 4) the precipitation determines the carbon sinks in the savanna ecosystem (e.g., YJ), while temperature did so in the tropical forest ecosystem (e.g., XSBN); 5) overall, under the circumstances of warming and decreased precipitation, the carbon sink might decrease in the YJ but maybe increase in the ALS and LJ, while future strength of the sink in the XSBN is somewhat uncertain. However, based on the redundancy analysis, the temperature and precipitation combined together explained 39.7%, 32.2%, 25.3%, and 29.6% of the variations in the NEE in the YJ, XSBN, ALS and LJ, respectively, which indicates that considerable changes in the NEE could not be explained by variations in the temperature and precipitation. Therefore, the effects of other factors (e.g., CO 2 concentration, N

  7. Ecosystem-atmosphere exchange of carbon in a heathland under future climatic conditions

    DEFF Research Database (Denmark)

    Selsted, Merete Bang

    on ecosystem-atmosphere exchange of carbon in a heathland under future climatic conditions, shows that extended summer drought in combination with elevated temperature will ensure permanent dryer soil conditions, which decreases carbon turnover, while elevated atmospheric CO2 concentrations will increase...... carbon turnover. In the full future climate scenario, carbon turnover is over all expected to increase and the heathland to become a source of atmospheric CO2. The methodology of static chamber CO2 flux measurements and applying the technology in a FACE (free air CO2 enrichment) facility is a challenge...... on the atmospheric CO2 concentration. Photosynthesis and respiration run in parallel during measurements of net ecosystem exchange, and these measurements should therefore be performed with care to both the atmospheric CO2 concentration and the CO2 soil-atmosphere gradient....

  8. Carbon dioxide exchange in the High Arctic - examples from terrestrial ecosystems

    DEFF Research Database (Denmark)

    Grøndahl, L.

    of the growing season, which in combination with high temperatures increased uptake rates. The dry heath ecosystem in general gained carbon during the summer season in the order of magnitude -1.4 gCm-2 up to 32 gCm-2. This result is filling out a gap of knowledge on the response of high Arctic ecosystems...... the measurements conducted in the valley to a regional level. Including information on temporal and spatial variability in air temperature and radiation, together with NDVI and a vegetation map a regional estimate of the CO2 exchange during the summer was provided, elaborating the NDVI based estimate on net carbon...

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

    Directory of Open Access Journals (Sweden)

    M. Zhang

    2010-02-01

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

  10. Identifying Differences in Carbon Exchange among Arctic Ecosystem Types

    NARCIS (Netherlands)

    Williams, M.; Street, L.E.; Wijk, van M.T.; Shaver, G.R.

    2006-01-01

    Our objective was to determine how varied is the response of C cycling to temperature and irradiance in tundra vegetation. We used a large chamber to measure C exchange at 23 locations within a small arctic catchment in Alaska during summer 2003 and 2004. At each location, we determined light

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

    Science.gov (United States)

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

    2008-01-01

    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,...

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

    Science.gov (United States)

    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

  13. Ecosystem-atmosphere exchange of carbon in a heathland under future climatic conditions

    Energy Technology Data Exchange (ETDEWEB)

    Bang Selsted, M

    2010-07-15

    Global change is a reality. Atmospheric CO{sub 2} levels are rising as well as mean global temperature and precipitation patterns are changing. These three environmental factors have separately and in combination effect on ecosystem processes. Terrestrial ecosystems hold large amounts of carbon, why understanding plant and soil responses to such changes are necessary, as ecosystems potentially can ameliorate or accelerate global change. To predict the feedback of ecosystems to the atmospheric CO{sub 2} concentrations experiments imitating global change effects are therefore an important tool. This work on ecosystem-atmosphere exchange of carbon in a heathland under future climatic conditions, shows that extended summer drought in combination with elevated temperature will ensure permanent dryer soil conditions, which decreases carbon turnover, while elevated atmospheric CO{sub 2} concentrations will increase carbon turnover. In the full future climate scenario, carbon turnover is over all expected to increase and the heathland to become a source of atmospheric CO{sub 2}. The methodology of static chamber CO{sub 2} flux measurements and applying the technology in a FACE (free air CO{sub 2} enrichment) facility is a challenge. Fluxes of CO{sub 2} from soil to atmosphere depend on a physical equilibrium between those two medias, why it is important to keep the CO{sub 2} gradient between soil and atmosphere unchanged during measurement. Uptake to plants via photosynthesis depends on a physiological process, which depends strongly on the atmospheric CO{sub 2} concentration. Photosynthesis and respiration run in parallel during measurements of net ecosystem exchange, and these measurements should therefore be performed with care to both the atmospheric CO{sub 2} concentration and the CO{sub 2} soil-atmosphere gradient. (author)

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

    Science.gov (United States)

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

    Czech Academy of Sciences Publication Activity Database

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

    2011-01-01

    Roč. 159, č. 5 (2011), s. 1035-1039 ISSN 0269-7491 R&D Projects: GA MŽP(CZ) SP/1A6/108/07; GA MŠk 2B06068 Institutional research plan: CEZ:AV0Z60870520 Keywords : carbon fluxes * net ecosystem exchange * spruce forest * beech forest * Grassland * agroecosystem * wetland * climate factors Subject RIV: EH - Ecology, Behaviour Impact factor: 3.746, year: 2011

  16. Carbon dioxide exchange in Norway spruce at the shoot, tree and ecosystem scale.

    Science.gov (United States)

    Wallin, G; Linder, S; Lindroth, A; Räntfors, M; Flemberg, S; Grelle, A

    2001-08-01

    Net CO2 exchange in a 35-year-old boreal Norway spruce (Picea abies (L.) Karst.) forest in northern Sweden was measured at the shoot (NSE), tree (NTE) and ecosystem levels (NEE) by means of shoot cuvettes, whole-tree chambers and the eddy covariance technique, respectively. We compared the dynamics of gross primary production (GPP) at the three levels during the course of a single week. The diurnal dynamics of GPP at each level were estimated by subtracting half-hourly or hourly model-estimated values of total respiration (excluding light-dependent respiration) from net CO(2) exchange. The relationship between temperature and total respiration at each level was derived from nighttime measurements of NSE, NTE and NEE over the course of 1 month. There was a strong linear relationship (r2 = 0.93) between the hourly estimates of GPP at the shoot and tree levels, but the correlation between shoot- and ecosystem-level GPP was weaker (r2 = 0.69). However, the correlation between shoot- and ecosystem-level GPP was improved (r2 = 0.88) if eddy covariance measurements were restricted to periods when friction velocity was > or = 0.5 m s(-1). Daily means were less dependent on friction velocity, giving an r2 value of 0.94 between shoot- and ecosystem-level GPP. The correlation between shoot and tree levels also increased when daily means were compared (r2 = 0.98). Most of the measured variation in carbon exchange rate among the shoot, tree and ecosystem levels was the result of periodic low coupling between vegetation and the atmosphere at the ecosystem level. The results validate the use of measurements at the shoot and tree level for analyzing the contribution of different compartments to net ecosystem CO2 exchange.

  17. Examining responses of ecosystem carbon exchange to environmental changes using particle filtering mathod

    Science.gov (United States)

    Yokozawa, M.

    2017-12-01

    Attention has been paid to the agricultural field that could regulate ecosystem carbon exchange by water management and residual treatments. However, there have been less known about the dynamic responses of the ecosystem to environmental changes. In this study, focussing on paddy field, where CO2 emissions due to microbial decomposition of organic matter are suppressed and alternatively CH4 emitted under flooding condition during rice growth season and subsequently CO2 emission following the fallow season after harvest, the responses of ecosystem carbon exchange were examined. We conducted model data fusion analysis for examining the response of cropland-atmosphere carbon exchange to environmental variation. The used model consists of two sub models, paddy rice growth sub-model and soil decomposition sub-model. The crop growth sub-model mimics the rice plant growth processes including formation of reproductive organs as well as leaf expansion. The soil decomposition sub-model simulates the decomposition process of soil organic carbon. Assimilating the data on the time changes in CO2 flux measured by eddy covariance method, rice plant biomass, LAI and the final yield with the model, the parameters were calibrated using a stochastic optimization algorithm with a particle filter method. The particle filter method, which is one of the Monte Carlo filters, enable us to evaluating time changes in parameters based on the observed data until the time and to make prediction of the system. Iterative filtering and prediction with changing parameters and/or boundary condition enable us to obtain time changes in parameters governing the crop production as well as carbon exchange. In this study, we focused on the parameters related to crop production as well as soil carbon storage. As the results, the calibrated model with estimated parameters could accurately predict the NEE flux in the subsequent years. The temperature sensitivity, denoted by Q10s in the decomposition rate of

  18. Net ecosystem carbon dioxide exchange in tropical rainforests - sensitivity to environmental drivers and flux measurement methodology

    Science.gov (United States)

    Fu, Z.; Stoy, P. C.

    2017-12-01

    Tropical rainforests play a central role in the Earth system services of carbon metabolism, climate regulation, biodiversity maintenance, and more. They are under threat by direct anthropogenic effects including deforestation and indirect anthropogenic effects including climate change. A synthesis of the factors that determine the net ecosystem exchange of carbon dioxide (NEE) across multiple time scales in different tropical rainforests has not been undertaken to date. Here, we study NEE and its components, gross primary productivity (GPP) and ecosystem respiration (RE), across thirteen tropical rainforest research sites with 63 total site-years of eddy covariance data. Results reveal that the five ecosystems that have greater carbon uptakes (with the magnitude of GPP greater than 3000 g C m-2 y-1) sequester less carbon - or even lose it - on an annual basis at the ecosystem scale. This counterintuitive result is because high GPP is compensated by similar magnitudes of RE. Sites that provided subcanopy CO2 storage observations had higher average magnitudes of GPP and RE and consequently lower NEE, highlighting the importance of measurement methodology for understanding carbon dynamics in tropical rainforests. Vapor pressure deficit (VPD) constrained GPP at all sites, but to differing degrees. Many environmental variables are significantly related to NEE at time scales greater than one year, and NEE at a rainforest in Malaysia is significantly related to soil moisture variability at seasonal time scales. Climate projections from 13 general circulation models (CMIP5) under representative concentration pathway (RCP) 8.5 suggest that many current tropical rainforest sites on the cooler end of the current temperature range are likely to reach a climate space similar to present-day warmer sites by the year 2050, and warmer sites will reach a climate space not currently experienced. Results demonstrate the need to quantify if mature tropical trees acclimate to heat and

  19. Modeling net ecosystem carbon exchange of alpine grasslands with a satellite-driven model.

    Directory of Open Access Journals (Sweden)

    Wei Yan

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

  20. Carbon dioxide exchange in subarctic ecosystems measured by a micrometeorological technique

    International Nuclear Information System (INIS)

    Aurela, M.

    2005-01-01

    The atmospheric CO 2 concentration and the surface air temperatures have increased since the pre-industrial era, and the increase in both is predicted to continue during the 21st century. The feedback mechanisms between the changing climate and the carbon cycle are complex, and more information is needed about carbon exchange in different ecosystems. Northern Finland lies in the transition zone between boreal forest and tundra where the ecosystems are especially sensitive to any changes in the climate. In 1995-2004, micrometeorological eddy covariance measurements were conducted to yield continuous data on the CO 2 exchange between the atmosphere and the biosphere in northern Finland on four different ecosystems: an aapa mire, a mountain birch forest, a Scots pine forest and a Norway spruce forest. A measurement system enabling year-round measurements in the harsh subarctic conditions was developed and shown to be suitable for long-term exchange studies. A comparison of the CO 2 flux components, photosynthesis and respiration, at different ecosystems in the European subarctic and arctic regions showed that the leaf area index (LAI) is the key determinant of the gross photosynthetic rates, explaining greatest part of the variation between these ecosystems. Respiration did not show such a strong correlation with LAI, but in general, high respiration rates were related to high values of LAI. The first continuous round-the-year measurements of net ecosystem CO 2 exchange on a subarctic wetland were conducted at Kaamanen. The winter-time CO 2 efflux (of about 90 g CO 2 m -2 yr -1 ) was shown to constitute an essential part of the annual CO 2 balance (of -79 g CO 2 m -2 yr -1 in 1997-2002). The annual CO 2 balances at all sites in northern Finland were relatively small compared with those in lower latitudes. The interannual variation of the CO 2 balance at Kaamanen was marked (-15 to -195 g CO 2 m -2 yr -1 ) during the years 1997-2002. The most important factor

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  3. Dynamics in carbon exchange fluxes for a grazed semi-arid savanna ecosystem in West Africa

    DEFF Research Database (Denmark)

    Tagesson, Torbern; Fensholt, Rasmus; Cropley, Ford

    2015-01-01

    variable in scaling carbon fluxes from ground observations using earth observation data. The net ecosystem exchange of carbon dioxide (NEE) 2010-2013 was measured using the eddy covariance technique at a grazed semi-arid savanna site in Senegal, West Africa. Night-time NEE was not related to temperature......-arid savanna sites; half-hourly GPP and Reco peaked at -43μmol CO2m-2s-1 and 20μmol CO2m-2s-1, and daily GPP and Reco peaked at -15gCm-2 and 12gCm-2, respectively. Possible explanations for the high CO2 fluxes are a high fraction of C4 species, alleviated water stress conditions, and a strong grazing pressure...

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

    Science.gov (United States)

    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

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

    International Nuclear Information System (INIS)

    Marek, Michal V.; Janous, Dalibor; Taufarova, Klara; Havrankova, Katerina; Pavelka, Marian; Kaplan, Veroslav; Markova, Irena

    2011-01-01

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

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

    Science.gov (United States)

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

    2011-05-01

    By comparing five ecosystem types in the Czech Republic over several years, we recorded the highest carbon sequestration potential in an evergreen Norway spruce forest (100%) and an agroecosystem (65%), followed by European beech forest (25%) and a wetland ecosystem (20%). Because of a massive ecosystem respiration, the final carbon gain of the grassland was negative. Climate was shown to be an important factor of carbon uptake by ecosystems: by varying the growing season length (a 22-d longer season in 2005 than in 2007 increased carbon sink by 13%) or by the effect of short- term synoptic situations (e.g. summer hot and dry days reduced net carbon storage by 58% relative to hot and wet days). Carbon uptake is strongly affected by the ontogeny and a production strategy which is demonstrated by the comparison of seasonal course of carbon uptake between coniferous (Norway spruce) and deciduous (European beech) stands. Copyright © 2011 Elsevier Ltd. All rights reserved.

  7. North American coastal carbon stocks and exchanges among the coupled ecosystems of tidal wetlands and estuaries

    Science.gov (United States)

    Windham-Myers, L.; Cai, W. J.

    2017-12-01

    The development of the 2nd State of the Carbon Cycle Report (SOCCR-2) has recognized a significant role of aquatic ecosystems, including coastal zones, in reconciling some of the gaps associated with the North American carbon (C) budget. Along with a large community of coauthors, we report major C stocks and fluxes for tidal wetlands and estuaries of Canada, Mexico and the United States. We find divergent patterns between these coupled ecosystems, with tidal wetlands largely serving as CO2 sinks (net autotrophic), and open-water estuaries largely serving as CO2 sources (net heterotrophic). We summarized measurements across 4 continental regions - East Coast, Gulf of Mexico, West Coast, and High Latitudes - to assess spatial variability and datagaps in our understanding of coastal C cycling. Subtracting estuarine outgassing of 10 ± 10 Tg C yr-1 from the tidal wetland uptake of 23 ± 10 Tg C yr-1 leaves a net uptake of the combined system of 13 ± 14 Tg C yr-1. High uncertainty for net atmospheric C exchange in this combined coastal system is further complicated by spatially and temporally dynamic boundaries, as well as terrestrial C sources. Tidal wetlands are among the most productive ecosystems on earth and are capable of continuously accumulating organic C in their sediments as a result of environmental conditions that inhibit organic matter decomposition. Estuaries have more interannual variability in C dynamics than those of tidal wetlands, reflecting the estuarine balance of exchanges with terrestrial watersheds, tidal wetlands, and the continental shelf. Whereas tidal, subtidal and estuarine maps are of limited accuracy at larger scales, North America likely represents less than 1/10 of global distributions of coastal wetland habitats. Coupled land-ocean C flux models are increasingly robust but lacking much of the data needed for parameterization and validation. Accurate boundary maps and synoptic monitoring data on air-water CO2 exchange may be developed

  8. Evaluation and inversion of a net ecosystem carbon exchange model for grasslands and croplands

    Science.gov (United States)

    Herbst, M.; Klosterhalfen, A.; Weihermueller, L.; Graf, A.; Schmidt, M.; Huisman, J. A.; Vereecken, H.

    2017-12-01

    A one-dimensional soil water, heat, and CO2 flux model (SOILCO2), a pool concept of soil carbon turnover (RothC), and a crop growth module (SUCROS) was coupled to predict the net ecosystem exchange (NEE) of carbon. This model, further referred to as AgroC, was extended with routines for managed grassland as well as for root exudation and root decay. In a first step, the coupled model was applied to two winter wheat sites and one upland grassland site in Germany. The model was calibrated based on soil water content, soil temperature, biometric, and soil respiration measurements for each site, and validated in terms of hourly NEE measured with the eddy covariance technique. The overall model performance of AgroC was acceptable with a model efficiency >0.78 for NEE. In a second step, AgroC was optimized with the eddy covariance NEE measurements to examine the effect of various objective functions, constraints, and data-transformations on estimated NEE, which showed a distinct sensitivity to the choice of objective function and the inclusion of soil respiration data in the optimization process. Both, day and nighttime fluxes, were found to be sensitive to the selected optimization strategy. Additional consideration of soil respiration measurements improved the simulation of small positive fluxes remarkably. Even though the model performance of the selected optimization strategies did not diverge substantially, the resulting annual NEE differed substantially. We conclude that data-transformation, definition of objective functions, and data sources have to be considered cautiously when using a terrestrial ecosystem model to determine carbon balances by means of eddy covariance measurements.

  9. Diurnal and seasonal variations in carbon dioxide exchange in ecosystems in the Zhangye oasis area, Northwest China.

    Science.gov (United States)

    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

  10. Large interannual variability in net ecosystem carbon dioxide exchange of a disturbed temperate peatland.

    Science.gov (United States)

    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. Copyright © 2016 Elsevier B.V. All rights reserved.

  11. Environmental controls of daytime leaf carbon exchange: Implications for estimates of ecosystem fluxes in a deciduous forest

    Science.gov (United States)

    Heskel, M.; Tang, J.

    2017-12-01

    Leaf-level photosynthesis and respiration are sensitive to short- and long-term changed in temperature, and how these processes respond to phenological and seasonal transitions and daily temperature variation dictate how carbon is first assimilated and released in terrestrial ecosystems. We examined the short-term temperature response of daytime leaf carbon exchange at Harvard Forest across growing season, with the specific objective to quantify the light inhibition of dark respiration and photorespiration in leaves and use this to better inform daytime carbon assimilation and efflux estimates at the canopy scale. Dark and light respiration increased with measurement temperature and varied seasonally in a proportional manner, with the level of inhibition remaining relatively constant through the growing season. Higher rates of mitochondrial respiration and photorespiration at warmer temperatures drove a lower carbon use efficiency. Using temperature, light, and canopy leaf area index values to drive models, we estimate partitioned ecosystem fluxes and re-calculate gross primary production under multiple scenarios that include and exclude the impact of light inhibition, thermal acclimation, and seasonal variation in physiology. Quantifying the contribution of these `small fluxes' to ecosystem carbon exchange in forests provides a nuanced approach for integrating physiology into regional model estimates derived from eddy covariance and remote-sensing methods.

  12. Diurnal and seasonal variations in carbon dioxide exchange in ecosystems in the Zhangye oasis area, Northwest China.

    Directory of Open Access Journals (Sweden)

    Lei Zhang

    Full Text Available 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

  13. Ecosystem-atmosphere exchange of carbon in a heathland under future climatic conditions

    DEFF Research Database (Denmark)

    Selsted, Merete Bang

    understanding plant and soil responses to such changes are necessary, as ecosystems potentially can ameliorate or accelerate global change. To predict the feedback of ecosystems to the atmospheric CO2 concentrations experiments imitating global change effects are therefore an important tool. This work....... Fluxes of CO2 from soil to atmosphere depend on a physical equilibrium between those two medias, why it is important to keep the CO2 gradient between soil and atmosphere unchanged during measurement. Uptake to plants via photosynthesis depends on a physiological process, which depends strongly...... on the atmospheric CO2 concentration. Photosynthesis and respiration run in parallel during measurements of net ecosystem exchange, and these measurements should therefore be performed with care to both the atmospheric CO2 concentration and the CO2 soil-atmosphere gradient....

  14. The Inter-Annual Variability Analysis of Carbon Exchange in Low Artic Fen Uncovers The Climate Sensitivity And The Uncertainties Around Net Ecosystem Exchange Partitioning

    Science.gov (United States)

    Blanco, E. L.; Lund, M.; Williams, M. D.; Christensen, T. R.; Tamstorf, M. P.

    2015-12-01

    An improvement in our process-based understanding of CO2 exchanges in the Arctic, and their climate sensitivity, is critical for examining the role of tundra ecosystems in changing climates. Arctic organic carbon storage has seen increased attention in recent years due to large potential for carbon releases following thaw. Our knowledge about the exact scale and sensitivity for a phase-change of these C stocks are, however, limited. Minor variations in Gross Primary Production (GPP) and Ecosystem Respiration (Reco) driven by changes in the climate can lead to either C sink or C source states, which likely will impact the overall C cycle of the ecosystem. Eddy covariance data is usually used to partition Net Ecosystem Exchange (NEE) into GPP and Reco achieved by flux separation algorithms. However, different partitioning approaches lead to different estimates. as well as undefined uncertainties. The main objectives of this study are to use model-data fusion approaches to (1) determine the inter-annual variability in C source/sink strength for an Arctic fen, and attribute such variations to GPP vs Reco, (2) investigate the climate sensitivity of these processes and (3) explore the uncertainties in NEE partitioning. The intention is to elaborate on the information gathered in an existing catchment area under an extensive cross-disciplinary ecological monitoring program in low Arctic West Greenland, established under the auspices of the Greenland Ecosystem Monitoring (GEM) program. The use of such a thorough long-term (7 years) dataset applied to the exploration in inter-annual variability of carbon exchange, related driving factors and NEE partition uncertainties provides a novel input into our understanding about land-atmosphere CO2 exchange.

  15. Net ecosystem exchange of CO2 and carbon balance for eight temperate organic soils under agricultural management

    DEFF Research Database (Denmark)

    Elsgaard, Lars; Görres, C.-M.; Hoffmann, Carl Christian

    2012-01-01

    This study presents the first annual estimates of net ecosystem exchange (NEE) of CO2 and net ecosystem carbon balances (NECB) of contrasting Danish agricultural peatlands. Studies were done at eight sites representing permanent grasslands (PG) and rotational (RT) arable soils cropped to barley......, potato or forage grasses in three geo-regional settings. Using an advanced flux-chamber technique, NEE was derived from modelling of ecosystem respiration (ER) and gross primary production (GPP) with temperature and photosynthetically active radiation as driving variables. At PG (n = 3) and RT (n = 5......) sites, NEE (mean ± standard error, SE) was 5.1 ± 0.9 and 8.6 ± 2.0 Mg C ha−1 yr−1, respectively, but with the overall lowest value observed for potato cropping (3.5 Mg C ha−1 yr−1). This was partly attributed to a short-duration vegetation period and drying of the soil especially in potato ridges. NECB...

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    DEFF Research Database (Denmark)

    Niu, Shuli; Luo, Yiqi; Fei, Shenfeng

    2012-01-01

    distributed sites of eddy covariance and quantified the temperature response functions of net ecosystem exchange (NEE), an ecosystem‐level property, to determine whether NEE shows thermal optimality and to explore the underlying mechanisms. We found that the temperature response of NEE followed a peak curve......, with the optimum temperature (corresponding to the maximum magnitude of NEE) being positively correlated with annual mean temperature over years and across sites. Shifts of the optimum temperature of NEE were mostly a result of temperature acclimation of gross primary productivity (upward shift of optimum...... ecosystem–climate change feedbacks. The thermal optimality of NEE has implications for understanding fundamental properties of ecosystems in changing environments and benchmarking global models....

  18. Impacts of tropospheric ozone and climate change on net primary productivity and net carbon exchange of China’s forest ecosystems

    Science.gov (United States)

    Wei Ren; Hanqin Tian; Bo Tao; Art Chappelka; Ge Sun; et al

    2011-01-01

    Aim We investigated how ozone pollution and climate change/variability have interactively affected net primary productivity (NPP) and net carbon exchange (NCE) across China’s forest ecosystem in the past half century. Location Continental China. Methods Using the dynamic land ecosystem model (DLEM) in conjunction with 10-km-resolution gridded historical data sets (...

  19. Ecosystem-scale carbon monoxide exchange and partitioning across major biomes in Europe

    Science.gov (United States)

    Hammerle, Albin; Spielmann, Felix; Kitz, Florian; Ibrom, Andreas; Migliavacca, Mirco; Noe, Steffen; Kolle, Olaf; Moreno, Gerardo; Wohlfahrt, Georg

    2017-04-01

    With an average mole fraction of 100 ppb carbon monoxide (CO) plays a critical role in atmospheric chemistry and has an indirect global warming potential. While sources/sinks of CO on land at least partially cancel out each other and their magnitude is very likely lower compared to other sinks and sources, the magnitude of CO sources and sinks is highly uncertain. Thus 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. Here we present data on continuous eddy covariance measurements of CO-fluxes above different biomes in Europe in combination with soil-chamber flux measurements. Eddy covariance and soil-chamber measurements were conducted during the vegetation periods in 2015 and 2016 at a temperate grassland (AUT), a Mediterranean savanna (ESP), a temperate mixed deciduous (DEN) and a hemi-boreal forest (EST). While a clear diel pattern in ecosystem-scale CO-fluxes could be observed at the two grassland sites, with comparatively high emission rates at daytime conditions and fluxes around zero at night, no such pattern could be found for the two forest sites. Soil-chamber measurements mimicked the ecosystem-scale fluxes with CO-emissions during the day at the grassland ecosystems and slightly negative fluxes at night. Applying different treatments the influence of radiation and the availability of litter on these fluxes could be shown. Furthermore, a two-month rainout experiment revealed hardly any differences in CO soil fluxes between rainout- and control-plots at the grassland site (AUT), unless extremely dry conditions were reached.

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

    International Nuclear Information System (INIS)

    Nikolov, Ned; Zeller, Karl F.

    2003-01-01

    A new biophysical model (FORFLUX) is presented to link ozone deposition with carbon and water cycles in terrestrial ecosystems. - 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 CO 2 - 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 LEAFC3 model 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 CO 2 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

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  3. Net ecosystem exchange of carbon dioxide and water of far eastern Siberian Larch (Larix cajanderii on permafrost

    Directory of Open Access Journals (Sweden)

    A. J. Dolman

    2004-01-01

    Full Text Available Observations of the net ecosystem exchange of water and CO2 were made during two seasons in 2000 and 2001 above a Larch forest in Far East Siberia (Yakutsk. The measurements were obtained by eddy correlation. There is a very sharply pronounced growing season of 100 days when the forest is leaved. Maximum half hourly uptake rates are 18 µmol m-2 s-1; maximum respiration rates are 5 µmol m-2 s-1. Net annual sequestration of carbon was estimated at 160 gCm-2 in 2001. Applying no correction for low friction velocities added 60 g C m-2. The net carbon exchange of the forest was extremely sensitive to small changes in weather that may switch the forest easily from a sink to a source, even in summer. June was the month with highest uptake in 2001. The average evaporation rate of the forest approached 1.46 mm day-1 during the growing season, with peak values of 3 mm day-1 with an estimated annual evaporation of 213 mm, closely approaching the average annual rainfall amount. 2001 was a drier year than 2000 and this is reflected in lower evaporation rates in 2001 than in 2000. The surface conductance of the forest shows a marked response to increasing atmospheric humidity deficits. This affects the CO2 uptake and evaporation in a different manner, with the CO2 uptake being more affected. There appears to be no change in the relation between surface conductance and net ecosystem uptake normalized by the atmospheric humidity deficit at the monthly time scale. The response to atmospheric humidity deficit is an efficient mechanism to prevent severe water loss during the short intense growing season. The associated cost to the sequestration of carbon may be another explanation for the slow growth of these forests in this environment.

  4. Different responses of ecosystem carbon exchange to warming in three types of alpine grassland on the central Qinghai-Tibetan Plateau.

    Science.gov (United States)

    Ganjurjav, Hasbagan; Hu, Guozheng; Wan, Yunfan; Li, Yue; Danjiu, Luobu; Gao, Qingzhu

    2018-02-01

    Climate is a driver of terrestrial ecosystem carbon exchange, which is an important product of ecosystem function. The Qinghai-Tibetan Plateau has recently been subjected to a marked increase in temperature as a consequence of global warming. To explore the effects of warming on carbon exchange in grassland ecosystems, we conducted a whole-year warming experiment between 2012 and 2014 using open-top chambers placed in an alpine meadow, an alpine steppe, and a cultivated grassland on the central Qinghai-Tibetan Plateau. We measured the gross primary productivity, net ecosystem CO 2 exchange (NEE), ecosystem respiration, and soil respiration using a chamber-based method during the growing season. The results show that after 3 years of warming, there was significant stimulation of carbon assimilation and emission in the alpine meadow, but both these processes declined in the alpine steppe and the cultivated grassland. Under warming conditions, the soil water content was more important in stimulating ecosystem carbon exchange in the meadow and cultivated grassland than was soil temperature. In the steppe, the soil temperature was negatively correlated with ecosystem carbon exchange. We found that the ambient soil water content was significantly correlated with the magnitude of warming-induced change in NEE. Under high soil moisture condition, warming has a significant positive effect on NEE, while it has a negative effect under low soil moisture condition. Our results highlight that the NEE in steppe and cultivated grassland have negative responses to warming; after reclamation, the natural meadow would subject to loose more C in warmer condition. Therefore, under future warmer condition, the overextension of cultivated grassland should be avoided and scientific planning of cultivated grassland should be achieved.

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

    Science.gov (United States)

    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

  6. Expanding dryland ecosystem flux datasets enable novel quantification of water availability and carbon exchange in Southwestern North America

    Science.gov (United States)

    Biederman, J. A.; Scott, R. L.; Smith, W. K.; Litvak, M. E.; MacBean, N.

    2017-12-01

    Global-scale studies suggest that water-limited dryland ecosystems dominate the increasing trend in magnitude and interannual variability of the land CO2 sink. However, the terrestrial biosphere models and remote sensing models used in large-scale analyses are poorly constrained by flux measurements in drylands, which are under-represented in global datasets. In this talk, I will address this gap with eddy covariance data from 30 ecosystems across the Southwest 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 each (160 site-years). This extensive dryland dataset enables new approaches including 1) separation of temporal and spatial patterns to infer fast and slow ecosystem responses to change, and 2) partitioning of precipitation into hydrologic losses, evaporation, and ecosystem-available water. I will then compare direct flux measurements with models and remote sensing used to scale fluxes regionally. Combining eddy covariance and streamflow measurements, I will show how evapotranspiration (ET), which is the efflux of soil moisture remaining after hydrologic losses, is a better metric than precipitation of water available to drive ecosystem CO2 exchange. Furthermore, I will present a novel method to partition ET into evaporation and transpiration using the tight coupling of transpiration and photosynthesis. In contrast with typical carbon sink function in wetter, more-studied regions, dryland sites express an annual net carbon uptake varying from -350 to +330 gC m-2. Due to less respiration losses relative to photosynthesis gains during winter, declines in winter precipitation across the Southwest since 1999 are reducing annual net CO2 uptake. Interannual variability of net uptake is larger than for wetter regions, and half the sites pivot between sinks in wet years to sources in dry years. Biospheric and remote sensing models capture only 20-30 % of interannual

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

    NARCIS (Netherlands)

    Niu, S.; Luo, Y.; Fei, S.; Yuan, W.; Schimel, D.; Law, B.E.; Ammann, C.; Moors, E.J.

    2012-01-01

    It is well established that individual organisms can acclimate and adapt to temperature to optimize their functioning. However, thermal optimization of ecosystems, as an assemblage of organisms, has not been examined at broad spatial and temporal scales. • Here, we compiled data from 169 globally

  8. Calcium carbonate phosphate binding ion exchange filtration and accelerated denitrification improve public health standards and combat eutrophication in aquatic ecosystems.

    Science.gov (United States)

    Yanamadala, Vijay

    2005-01-01

    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.

  9. Tidal effects on net ecosystem exchange of carbon in an estuarine wetland

    Science.gov (United States)

    H. Guo; A. Noormets; B. Zhao; J. Chen; G. Sun; Y. Gu; B. Li; J. Chen

    2009-01-01

    One year of continuous data from two eddy-flux towers established along an elevation gradient incoastal Shanghai was analyzed to evaluate the tidal effect on carbon flux (Fc) over an estuarine wetland.The measured wavelet spectra and cospectra of Fc and other environmental factors demonstrated thatthe...

  10. The contribution of mosses to the carbon and water exchange of artic ecosystems: quantification and relationships with system properties

    NARCIS (Netherlands)

    Douma, J.C.; Wijk, van M.T.; Lang, S.I.; Shaver, G.R.

    2007-01-01

    Water vapour and CO2 exchange were measured in moss-dominated vegetation using a gas analyser and a 0.3 × 0.3 m chamber at 17 sites near Abisko, Northern Sweden and 21 sites near Longyearbyen, Svalbard, to quantify the contribution of mosses to ecosystem level fluxes. With the help of a simple

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

    Science.gov (United States)

    J.-C. Domec; J.S. King; A. Noormets; E. Treasure; M.J. Gavazzi; G. Sun; S.G. McNulty

    2010-01-01

    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...

  12. Seasonal reversal of temperature-moisture response of net carbon exchange of biocrusted soils in a cool desert ecosystem.

    Science.gov (United States)

    Tucker, C.; Reed, S.; Howell, A.

    2017-12-01

    Carbon cycling associated with biological soil crusts, which occur in interspaces between vascular plants in drylands globally, may be an important part of the coupled climate-carbon cycle of the Earth system. A major challenge to understanding CO2 fluxes in these systems is that much of the biotic and biogeochemical activity occurs in the upper few mm of the soil surface layer (i.e., the `mantle of fertility'), which exhibits highly dynamic and difficult to measure temperature and moisture fluctuations. Here, we report data collected in a cool desert ecosystem over one year using a multi-sensor approach to simultaneously measuring temperature and moisture of the biocrust surface layer (0-2 mm), and the deeper soil profile (5-20 cm), concurrent with automated measurement of surface soil CO2 effluxes. Our results illuminate robust relationships between microclimate and field CO2 pulses that have previously been difficult to detect and explain. The temperature of the biocrust surface layer was highly variable, ranging from minimum of -9 °C in winter to maximum of 77 °C in summer with a maximum diurnal range of 61 °C. Temperature cycles were muted deeper in the soil profile. During summer, biocrust and soils were usually hot and dry and CO2 fluxes were tightly coupled to pulse wetting events experienced at the biocrust surface, which consistently resulted in net CO2 efflux (i.e., respiration). In contrast, during the winter, biocrust and soils were usually cold and moist, and there was sustained net CO2 uptake via photosynthesis by biocrust organisms, although during cold dry periods CO2 fluxes were minimal. During the milder spring and fall seasons, short wetting events drove CO2 loss, while sustained wetting events resulted in net CO2 uptake. Thus, the upper and lower bounds of net CO2 exchange at a point in time were functions of the seasonal temperature regime, while the actual flux within those bounds was determined by the magnitude and duration of biocrust

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

    Directory of Open Access Journals (Sweden)

    Maren eDubbert

    2014-10-01

    Full Text Available 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

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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.

  16. Carbon allocation in forest ecosystems

    Science.gov (United States)

    Creighton M. Litton; James W. Raich; Michael G. Ryan

    2007-01-01

    Carbon allocation plays a critical role in forest ecosystem carbon cycling. We reviewed existing literature and compiled annual carbon budgets for forest ecosystems to test a series of hypotheses addressing the patterns, plasticity, and limits of three components of allocation: biomass, the amount of material present; flux, the flow of carbon to a component per unit...

  17. Responses of ecosystem carbon dioxide exchange to nitrogen addition in a freshwater marshland in Sanjiang Plain, Northeast China.

    Science.gov (United States)

    Zhang, Lihua; Song, Changchun; Nkrumah, Philip N

    2013-09-01

    It has widely been documented that nitrogen (N) stimulates plant growth and net primary production. But how N affects net ecosystem CO2 exchange (NEE) is still dispute. We conduct an experimental study to assess the response of NEE to N addition in a freshwater marsh. Experimental treatments involved elevated N and control treatments on triplicate 1 m(2) plots. Gas exchange, air temperature, plant biomass and leaf area as well as N% of leaf were measured from 2004 to 2005. The results indicated that N addition initially decreased the CO2 sequestration but the trend changed in the second year. It was concluded that N addition enhanced the greenhouse effect in marshland as far as global warming potential (GWP) is concerned. This increase was attributed to a substantial increase in CH4 and N2O emissions after N addition. We recommended long-term studies to further clarify the effect of N addition on NEE. Copyright © 2013 Elsevier Ltd. All rights reserved.

  18. Climate control of terrestrial carbon exchange across biomes and continents

    DEFF Research Database (Denmark)

    Yi, Chuixiang; Ricciuto, Daniel; Li, Runze

    2010-01-01

    Understanding the relationships between climate and carbon exchange by terrestrial ecosystems is critical to predict future levels of atmospheric carbon dioxide because of the potential accelerating effects of positive climate–carbon cycle feedbacks. However, directly observed relationships betwe...

  19. Climate control of terrestrial carbon exchange across biomes and continents

    NARCIS (Netherlands)

    Yi, C.; Ricciuto, D.; Li, R.; Hendriks, D.M.D.; Moors, E.J.; Valentini, R.

    2010-01-01

    Understanding the relationships between climate and carbon exchange by terrestrial ecosystems is critical to predict future levels of atmospheric carbon dioxide because of the potential accelerating effects of positive climate-carbon cycle feedbacks. However, directly observed relationships between

  20. Climate control of terrestrial carbon exchange across biomes and continents

    NARCIS (Netherlands)

    Yi, C.; Jacobs, C.M.J.; Moors, E.J.; Elbers, J.A.

    2010-01-01

    Understanding the relationships between climate and carbon exchange by terrestrial ecosystems is critical to predict future levels of atmospheric carbon dioxide because of the potential accelerating effects of positive climate–carbon cycle feedbacks. However, directly observed relationships between

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

    Science.gov (United States)

    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

  2. Long term carbon dioxide exchange above a mixed forest in the Belgian Ardennes: evaluation of different approaches to deduce total ecosystem respiration from Eddy covariance measurements

    Science.gov (United States)

    Jérôme, Elisabeth; Aubinet, Marc; Heinesch, Bernard

    2010-05-01

    The general aim of this research is to analyze inter annual variability of carbon dioxide (CO2) fluxes exchanged by a mixed forest located at the Vielsalm experimental site in Belgium. At this site, CO2 flux measurements started in 1996 and are still going on. Thirteen complete years of measurements are thus available. Net Ecosystem Exchange (NEE) inter annual variability may be driven by gross primary productivity (GPP) or Total Ecosystem Respiration (TER), which should thus be both quantified. Using flux partitioning methods, TER is deduced from NEE measurements. GPP is then obtained by subtracting TER from NEE. Initially, a robust estimation of TER is required. This work seeks to compare two independent approaches to assess TER in order to quantify the implications on inter-annual variability. The comparison was performed on twelve complete years. TER estimates can be deduced by extrapolating to the whole day NEE measurements taken during selected night or day periods. In both case, the extrapolation is performed by using a respiration response to temperature. The first approach, referred as the night-time approach, consisted in calculating TER using a temperature response function derived from night-time data sets (Reichstein et al., 2005). The second approach, referred as the daytime approach, consisted in assessing TER from the intercept of the NEE/Photosynthetically Photon Flux Density (PPFD) response (Wohlfahrt et al., 2005). For each approach, different modalities were compared: the use of long term (annual) or short term (15 days) data sets for the night-time approach and the use of different types of regression for the daytime approach. In addition, the impact of the temperature choice was studied for each of the approaches. For the night-time approach, main results showed that air temperature sensitivity of ecosystem respiration derived from annual data did not reflect the short-term air temperature sensitivity. Vielsalm is a summer active ecosystem

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

    Science.gov (United States)

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

    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

  4. Shifting the Arctic Carbon Balance: Effects of a Long-Term Fertilization Experiment and Anomalously Warm Temperatures on Net Ecosystem Exchange in the Alaskan Tundra

    Science.gov (United States)

    Ludwig, S.; Natali, S.; Rastetter, E. B.; Shaver, G. R.; Graham, L. M.; Jastrow, J. D.

    2017-12-01

    The arctic is warming at an accelerated rate relative to the globe. Among the predicted consequences of warming temperatures in the arctic are increased gross primary productivity (GPP), ecosystem respiration (ER), and nutrient availability. The net effect of these changes on the carbon (C) cycle and resulting C balance and feedback to climate change remain unclear. Historically the Arctic has been a C sink, but evidence from recent years suggests some regions in the Arctic are becoming C sources. To predict the role of the Arctic in global C cycling, the mechanisms affecting arctic C balances need to be better resolved. We measured net ecosystem exchange (NEE) in a long-term, multi-level, fertilization experiment at Toolik Lake, AK during an anomalously warm summer. We modeled NEE, ER, and GPP using a Bayesian network model. The best-fit model included Q10 temperature functions and linear fertilization functions for both ER and GPP. ER was more strongly affected by temperature and GPP was driven more by fertilization level. As a result, fertilization increased the C sink capacity, but only at moderate and low temperatures. At high temperatures (>28 °C) the NEE modeled for the highest level of fertilization was not significantly different from zero. In contrast, at ambient nutrient levels modeled NEE was significantly below zero (net uptake) until 35 °C, when it becomes neutral. Regardless of the level of fertilization, NEE never decreased with warming. Temperature in low ranges (5-15°C) had no net effect on NEE, whereas NEE began to increase exponentially with temperature after a threshold of 15°C until becoming a net source to the atmosphere at 37°C. Our results indicate that the C sink strength of tundra ecosystems can be increased with small increases in nutrient availability, but that large increase in nutrient availability can switch tundra ecosystems into C sources under warm conditions. Warming temperatures in tundra ecosystems will only decrease C

  5. NACP North American 8-km Net Ecosystem Exchange and Component Fluxes, 2004

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set provides modeled carbon flux estimates at 8-km spatial resolution over North America for the year 2004 of (1) net ecosystem exchange (NEE) of carbon...

  6. Parallel Computing for Terrestrial Ecosystem Carbon Modeling

    International Nuclear Information System (INIS)

    Wang, Dali; Post, Wilfred M.; Ricciuto, Daniel M.; Berry, Michael

    2011-01-01

    Terrestrial ecosystems are a primary component of research on global environmental change. Observational and modeling research on terrestrial ecosystems at the global scale, however, has lagged behind their counterparts for oceanic and atmospheric systems, largely because the unique challenges associated with the tremendous diversity and complexity of terrestrial ecosystems. There are 8 major types of terrestrial ecosystem: tropical rain forest, savannas, deserts, temperate grassland, deciduous forest, coniferous forest, tundra, and chaparral. The carbon cycle is an important mechanism in the coupling of terrestrial ecosystems with climate through biological fluxes of CO 2 . The influence of terrestrial ecosystems on atmospheric CO 2 can be modeled via several means at different timescales. Important processes include plant dynamics, change in land use, as well as ecosystem biogeography. Over the past several decades, many terrestrial ecosystem models (see the 'Model developments' section) have been developed to understand the interactions between terrestrial carbon storage and CO 2 concentration in the atmosphere, as well as the consequences of these interactions. Early TECMs generally adapted simple box-flow exchange models, in which photosynthetic CO 2 uptake and respiratory CO 2 release are simulated in an empirical manner with a small number of vegetation and soil carbon pools. Demands on kinds and amount of information required from global TECMs have grown. Recently, along with the rapid development of parallel computing, spatially explicit TECMs with detailed process based representations of carbon dynamics become attractive, because those models can readily incorporate a variety of additional ecosystem processes (such as dispersal, establishment, growth, mortality etc.) and environmental factors (such as landscape position, pest populations, disturbances, resource manipulations, etc.), and provide information to frame policy options for climate change

  7. Climate control of terrestrial carbon exchange across biomes and continents

    Science.gov (United States)

    Chuixiang Yi; Daniel Ricciuto; Runze Li; John Wolbeck; Xiyan Xu; Mats Nilsson; John Frank; William J. Massman

    2010-01-01

    Understanding the relationships between climate and carbon exchange by terrestrial ecosystems is critical to predict future levels of atmospheric carbon dioxide because of the potential accelerating effects of positive climate-carbon cycle feedbacks. However, directly observed relationships between climate and terrestrial CO2 exchange with the atmosphere across biomes...

  8. Climatic sensitivity of hydrology and carbon exchanges in boreal peatland ecosystems, with implications on sustainable management of reed canary grass (Phalaris arundinacea, L.) on cutaway peatlands

    Energy Technology Data Exchange (ETDEWEB)

    Gong Jinnan

    2013-11-01

    The aim of the study was to investigate the effects of climate change on soil hydrology and carbon (C) fluxes in boreal peatland ecosystems, with implications for the feasibility of cultivating reed canary grass (Phalaris arundinacea, L; RCG) as a way to restore the C sink in cutaway peatlands under Finnish conditions. First, hydrological models were developed for pristine peatland ecosystems and the cutaway peatlands under RCG cultivation. Concurrently, the hydrological responses to varying climatic forcing and mire types were investigated for these ecosystems. Thereafter, process-based models for estimating the seasonal and annual C exchanges were developed for the pristine mires and cutaway peatlands. The C models incorporated the hydrological models for corresponding ecosystems. Model simulations based on the climate scenarios (ACCLIM, developed by the Finnish Meteorological Institute, FMI) were further carried out to study the impacts of climate change on the C exchanges in the peatland ecosystems during the 21st century. The simulation showed that the water table (WT) in the pristine Finnish mires would draw down slightly during the 21st century. Such a chance in WT would be related to a decrease in the CO{sub 2} sink but an increase in the CH{sub 4} source at the country scale, as driven mainly by the rising temperature (Ta) and increasing precipitation (P). These changes in CO{sub 2}/ CH{sub 4} fluxes would decrease the total C-greenhouse gas (GHG) sink (CO{sub 2} equilibrium) by 68% at the country scale, and the changes would be more pronounced toward the end of the century. The majority of pristine fens in southern and western Finland and the pristine bogs near the coastal areas would become centurial CO{sub 2} sources under the changing climate. On the other hand, the major distribution of fens in northern Finland would act to increase the CH{sub 4} source at the country scale, whereas the CH{sub 4} emission would tend to decrease with WT in the southern

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

    OpenAIRE

    Yanamadala, Vijay

    2005-01-01

    Cultural eutrophication, the process by which a lake becomes rich in dissolved nutrients as a result of point and nonpoint pollutant sources, is a major cause of the loss of natural lake ecosystems throughout the world. The process occurs naturally in all lakes, but phosphate-rich nutrient runoff from sources such as storm drains and agricultural runoff is a major cause of excess phosphate-induced eutrophication. Especially in Madrona Marsh, one of the last remaining vernal marshes in the gre...

  10. Unifying Dynamic Prognostic Phenology, Heterogeneous Soil and Vegetation Fluxes, and Ecosystem Biomass and Carbon Stocks To Predict the Terrestrial Carbon Cycle and Land-Atmosphere Exchanges in the Simple Biosphere Model (SiB4)

    Science.gov (United States)

    Haynes, K. D.; Baker, I. T.; Denning, S.

    2016-12-01

    Future climate projections require process-based models that incorporate the mechanisms and feedbacks controlling the carbon cycle. Over the past three decades, land surface models have been key contributors to Earth system models, evolving from predicting latent (LE) and sensible (SH) heat fluxes to energy and water budgets, momentum transfer, and terrestrial carbon exchange and storage. This study presents the latest version of the Simple Biosphere Model (SiB4), which builds on a compilation of previous versions and adds a new mechanistic-based scheme that fully predicts the terrestrial carbon cycle. The main SiB4 updates can be summarized as follows: (i) Incorporation of carbon pools that use new respiration and transfer methods, (ii) Creation of a new dynamic phenology scheme that uses mechanistic-based seasonal stages, and (iii) Unification of carbon pools, phenology and disturbance to close the carbon cycle. SiB4 removes the dependence on satellite-based vegetation indices, and instead uses a single mathematical framework to prognose self-consistent land-atmosphere exchanges of carbon, water, energy, radiation, and momentum, as well as carbon storage. Since grasslands cover 30% of land and are highly seasonal, we investigated forty grass sites. Diurnal cycles of gross primary productivity (GPP), ecosystem respiration (RE), net ecosystem exchange (NEE), LE and SH have third-quartile root mean squared (RMS) errors less than 2.0 µmol m-2 s-1, 1.9 µmol m-2 s-1, 2.0 µmol m-2 s-1, 42 W m-2, and 78 W m-2, respectively. On the synoptic timeframe, all sites have significant LE correlation coefficients of non-seasonal daily data; and all but one have significant SH correlations. Mean seasonal cycles for leaf area index (LAI), GPP, RE, LE, and SH have third-quartile normalized RMS errors less than 32%, 25%, 28%, 16%, and 48%, respectively. On multi-year timescales, daily correlations of LAI, GPP, RE, and LE are all statistically significant, with third-quartile RMS

  11. Partitioning inter annual variability in net ecosystem exchange between climatic variability and functional change

    International Nuclear Information System (INIS)

    Hui, D.; Luo, Y.; Katul, G.

    2003-01-01

    Inter annual variability in net ecosystem exchange of carbon is investigated using a homogeneity-of-slopes model to identify the function change contributing to inter annual variability, net ecosystem carbon exchange, and night-time ecosystem respiration. Results of employing this statistical approach to a data set collected at the Duke Forest AmeriFlux site from August 1997 to December 2001 are discussed. The results demonstrate that it is feasible to partition the variation in ecosystem carbon fluxes into direct effects of seasonal and inter annual climatic variability and functional change. 51 refs., 4 tabs., 5 figs

  12. NACP North American 8-km Net Ecosystem Exchange and Component Fluxes, 2004

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: This data set provides modeled carbon flux estimates at 8-km spatial resolution over North America for the year 2004 of (1) net ecosystem exchange (NEE) of...

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

    Energy Technology Data Exchange (ETDEWEB)

    Baldocchi, Dennis [Univ. of California, Berkeley, CA (United States)

    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.

  14. Dissolved carbon leaching from soil is a crucial component of the net ecosystem carbon balance

    DEFF Research Database (Denmark)

    Kindler, Reimo; Siemens, Jan; Kaiser, Klaus

    2011-01-01

    ecosystem exchange (NEE) plus carbon inputs with fertilization minus carbon removal with harvest. Carbon leaching increased the net losses from cropland soils by 24–105% (median: 25%). For the majority of forest sites, leaching hardly affected actual net ecosystem carbon balances because of the small...... solubility of CO2 in acidic forest soil solutions and large NEE. Leaching of CH4 proved to be insignificant compared with other fluxes of carbon. Overall, our results show that leaching losses are particularly important for the carbon balance of agricultural systems....

  15. Modeling Carbon Exchange

    Science.gov (United States)

    Sellers, Piers

    2012-01-01

    Model results will be reviewed to assess different methods for bounding the terrestrial role in the global carbon cycle. It is proposed that a series of climate model runs could be scoped that would tighten the limits on the "missing sink" of terrestrial carbon and could also direct future satellite image analyses to search for its geographical location and understand its seasonal dynamics.

  16. Variability in carbon exchange of European croplands

    DEFF Research Database (Denmark)

    Eddy J, Moors; Jacobs, Cor; Jans, Wilma

    2010-01-01

    The estimated net ecosystem exchange (NEE) of CO2 based on measurements at 17 flux sites in Europe for 45 cropping periods showed an average loss of -38 gC m-2 per cropping period. The cropping period is defined as the period after sowing or planting until harvest. The variability taken as the st......The estimated net ecosystem exchange (NEE) of CO2 based on measurements at 17 flux sites in Europe for 45 cropping periods showed an average loss of -38 gC m-2 per cropping period. The cropping period is defined as the period after sowing or planting until harvest. The variability taken...... as the standard deviation of these cropping periods was 251 gC m-2. These numbers do not include lateral inputs such as the carbon content of applied manure, nor the carbon exchange out of the cropping period. Both are expected to have a major effect on the C budget of high energy summer crops such as maize. NEE...... and gross primary production (GPP) can be estimated by crop net primary production based on inventories of biomass at these sites, independent of species and regions. NEE can also be estimated by the product of photosynthetic capacity and the number of days with the average air temperature >5 °C. Yield...

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

    Science.gov (United States)

    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.

  18. An ecosystem carbon database for Canadian forests

    Energy Technology Data Exchange (ETDEWEB)

    Shaw, C.H.; Bhatti, J.S.; Sabourin, K.J.

    2005-07-01

    The forest ecosystem carbon database (FECD) is a compilation of data from more than 700 plots from different forest ecosystems in Canada. It includes more than 60 variables for site, stand and soil characteristics. It is intended for large-scale modelers and analysts working with the carbon budget and dynamics of forest ecosystems, particularly those interested in the response of forest carbon stocks and fluxes to changes in climate and site characteristics. The database includes totals for organic and mineral soil horizons for each plot along with total soil carbon content, tree biomass carbon content by component and total ecosystem carbon content. It is complete for site description information, soil chemistry, stand-level estimates of live tree biomass and carbon components and their totals. Soil carbon content by horizon was also included. The compilation targeted data collected at single points in space, where above ground and below ground carbon levels were measured simultaneously. It was noted that one of the important information gaps lies in the fact that no data was available for the natural disturbance or management histories of the stands where the plots were located. Estimates did not include detrital carbon or root biomass, which can influence the estimates for total ecosystem carbon in some forest types. The preliminary analysis reveals that ecozones can be grouped according to low and high average total biomass carbon content. The groups correlate to ecozones with low and high average total ecosystem carbon. Mineral soil carbon within each group contributes the highest proportion of carbon to the average total ecosystem carbon. It is correlated with a gradient in ecozone climate from cold and dry to warm and wet. 42 refs., 13 tabs., 16 figs.

  19. 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

    Science.gov (United States)

    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.

  20. 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

    International Nuclear Information System (INIS)

    Hadley, J.L.; Kuzeja, P.S.; Singh, S.

    2008-01-01

    This study used the eddy flux method to measure water use and carbon exchange of a red oak forest and an eastern hemlock-dominated forest located in north-central Massachusetts over a period of 2 years. The study demonstrated that water use by the red oak reached approximately 4 mm per day -1 . A maximum rate of 2 mm per day -1 was used by the eastern hemlock forest. Carbon (C) uptake rates were higher in the red oak forest than in the eastern hemlock forest. Measurements of sap flux suggested that transpiration of red oak and black birches in the eastern hemlock forest were approximately twice as high as transpiration rates observed for eastern hemlock. However, annual C storage of eastern hemlock was almost equal to C storage rates of the red oak forest, due to net C uptake by the hemlock during an unusually warm fall and spring. The study showed that C storage by eastern hemlock forests will increase as a result of climatic warming. Although forest water use will decrease as a result of eastern hemlock due to insect disturbances, the replacement of eastern hemlock by deciduous species such as red oak will increase water use during the summer-time in areas where hemlock is a predominant species. 24 refs., 5 tabs., 11 figs

  1. 'Carbon-Money Exchange' to contain global warming and deforestation

    International Nuclear Information System (INIS)

    Nagase, Kozo

    2005-01-01

    This paper builds a basic theory of 'Carbon-Money Exchange' in which carbon as currency in nature's household (ecosystems) and money as currency in humankind's household (economy) are exchanged just like in a foreign exchange. The simple chemical equation below makes it possible (CO 2 →C+O 2 =C+O 2 →CO 2 ). The left-hand side represents the work of plants to remove atmospheric CO 2 . The right-hand side represents the work of humans as fossil fuel consumers to produce it. The exchange of the two currencies is possible by copying the fossil fuel market. The paper concludes that this new exchange can automatically contain global warming and deforestation, replacing onerous emissions trading. Moreover, it could revolutionize the conventional economy, creating counter-capitalism, or 'carbonism'

  2. On Variability in Satellite Terrestrial Chlorophyll Fluorescence Measurements: Relationships with Phenology and Ecosystem-Atmosphere Carbon Exchange, Vegetation Structure, Clouds, and Sun-Satellite Geometry

    Science.gov (United States)

    Joiner, J.; Yoshida, Y.; Guanter, L.; Zhang, Y.; Vasilkov, A. P.; Schaefer, K. M.; Huemmrich, K. F.; Middleton, E.; Koehler, P.; Jung, M.; Tucker, C. J.; Lyapustin, A.; Wang, Y.; Frankenberg, C.; Berry, J. A.; Koster, R. D.; Reichle, R. H.; Lee, J. E.; Kawa, S. R.; Collatz, G. J.; Walker, G. K.; Van der Tol, C.

    2014-12-01

    Over the past several years, there have been several breakthroughs in our ability to detect the very small fluorescence emitted by chlorophyll in vegetation globally from space. There are now multiple instruments in space capable of measuring this signal at varying temporal and spatial resolutions. We will review the state-of-the-art with respect to these relatively new satellite measurements and ongoing studies that examine the relationships with photosynthesis. Now that we have a data record spanning more than seven years, we can examine variations due to seasonal carbon uptake, interannual variability, land-use changes, and water and temperature stress. In addition, we examine how clouds and satellite viewing geometry impact the signal. We compare and contrast these variations with those from popular vegetation indices, such as the Normalized Difference Vegetation Index (NDVI), related to the potential photosynthesis as well as with measurements from flux tower gas exchange measurements and other model-based estimates of Global Primary Productivity (GPP). Vegetation fluorescence can be simulated in global vegetation models as well as with 1D canopy radiative transport models. We will describe how the satellite fluorescence data are being used to evaluate and potentially improve these models.

  3. Ecosystem carbon stocks of micronesian mangrove forests

    Science.gov (United States)

    J. Boone Kauffman; Chris Heider; Thomas G. Cole; Kathleen A. Dwire; Daniel C. Donato

    2011-01-01

    Among the least studied ecosystem services of mangroves is their value as global carbon (C) stocks. This is significant as mangroves are subject to rapid rates of deforestation and therefore could be significant sources of atmospheric emissions. Mangroves could be key ecosystems in strategies addressing the mitigation of climate change though reduced deforestation. We...

  4. Carbon sequestration and natural longleaf pine ecosystem

    Science.gov (United States)

    Ram Thapa; Dean Gjerstad; John Kush; Bruce Zutter

    2010-01-01

    The Southeastern United States was once dominated by a longleaf pine ecosystem which ranged from Virginia to Texas and covered approximately 22 to 36 million ha. The unique fire tolerant species provided the necessary habitat for numerous plant and animal species. Different seasons of prescribed fire have various results on the ecosystem and the carbon which is stored...

  5. Limits on carbon sequestration in arid blue carbon ecosystems.

    Science.gov (United States)

    Schile, Lisa M; Kauffman, J Boone; Crooks, Stephen; Fourqurean, James W; Glavan, Jane; Megonigal, J Patrick

    2017-04-01

    Coastal ecosystems produce and sequester significant amounts of carbon ("blue carbon"), which has been well documented in humid and semi-humid regions of temperate and tropical climates but less so in arid regions where mangroves, marshes, and seagrasses exist near the limit of their tolerance for extreme temperature and salinity. To better understand these unique systems, we measured whole-ecosystem carbon stocks in 58 sites across the United Arab Emirates (UAE) in natural and planted mangroves, salt marshes, seagrass beds, microbial mats, and coastal sabkha (inter- and supratidal unvegetated salt flats). Natural mangroves held significantly more carbon in above- and belowground biomass than other vegetated ecosystems. Planted mangrove carbon stocks increased with age, but there were large differences for sites of similar age. Soil carbon varied widely across sites (2-367 Mg C/ha), with ecosystem averages that ranged from 49 to 156 Mg C/ha. For the first time, microbial mats were documented to contain soil carbon pools comparable to vascular plant-dominated ecosystems, and could arguably be recognized as a unique blue carbon ecosystem. Total ecosystem carbon stocks ranged widely from 2 to 515 Mg C/ha (seagrass bed and mangrove, respectively). Seagrass beds had the lowest carbon stock per unit area, but the largest stock per total area due to their large spatial coverage. Compared to similar ecosystems globally, mangroves and marshes in the UAE have lower plant and soil carbon stocks; however, the difference in soil stocks is far larger than with plant stocks. This incongruent difference between stocks is likely due to poor carbon preservation under conditions of weakly reduced soils (200-350 mV), coarse-grained sediments, and active shoreline migration. This work represents the first attempt to produce a country-wide coastal ecosystem carbon accounting using a uniform sampling protocol, and was motivated by specific policy goals identified by the Abu Dhabi Global

  6. Carbon-nitrogen interactions in forest ecosystems

    DEFF Research Database (Denmark)

    Gundersen, Per; Berg, Bjørn; Currie, W.S.

    This report is a summary of the main results from the EU project “Carbon – Nitrogen Interactions in Forest Ecosystems” (CNTER). Since carbon (C) and nitrogen (N) are bound together in organic matter we studied both the effect of N deposition on C cycling in forest ecosystems, and the effect of C ...

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

    Science.gov (United States)

    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.

  8. 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

    Science.gov (United States)

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

    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,...

  9. Delayed responses of an Arctic ecosystem to an extremely dry summer: impacts on net ecosystem exchange and vegetation functioning

    Science.gov (United States)

    Zona, D.; Lipson, D. A.; Richards, J. H.; Phoenix, G. K.; Liljedahl, A. K.; Ueyama, M.; Sturtevant, C. S.; Oechel, W. C.

    2013-12-01

    The importance and mode of action of extreme events on the global carbon budget are inadequately understood. This includes the differential impact of extreme events on various ecosystem components, lag effects, recovery times, and compensatory processes. Summer 2007 in Barrow, Arctic Alaska, experienced unusually high air temperatures (fifth warmest over a 65 yr period) and record low precipitation (lowest over a 65 yr period). These abnormal conditions resulted in strongly reduced net Sphagnum CO2 uptake, but no effect neither on vascular plant development nor on net ecosystem exchange (NEE) from this arctic tundra ecosystem. Gross primary production (GPP) and ecosystem respiration (Reco) were both generally greater during most of this extreme summer. Cumulative ecosystem C uptake in 2007 was similar to the previous summers, showing the capacity of the ecosystem to compensate in its net ecosystem exchange (NEE) despite the impact on other functions and structure such as substantial necrosis of the Sphagnum layer. Surprisingly, the lowest ecosystem C uptake (2005-2009) was observed during the 2008 summer, i.e the year directly following the extremely summer. In 2008, cumulative C uptake was ∼70% lower than prior years. This reduction cannot solely be attributed to mosses, which typically contribute with ∼40% - of the entire ecosystem C uptake. The minimum summer cumulative C uptake in 2008 suggests that the entire ecosystem experienced difficulty readjusting to more typical weather after experiencing exceptionally warm and dry conditions. Importantly, the return to a substantial cumulative C uptake occurred two summers after the extreme event, which suggest a high resilience of this tundra ecosystem. Overall, these results show a highly complex response of the C uptake and its sub-components to atypically dry conditions. The impact of multiple extreme events still awaits further investigation.

  10. Global variation of carbon use efficiency in terrestrial ecosystems

    Science.gov (United States)

    Tang, Xiaolu; Carvalhais, Nuno; Moura, Catarina; Reichstein, Markus

    2017-04-01

    Carbon use efficiency (CUE), defined as the ratio between net primary production (NPP) and gross primary production (GPP), is an emergent property of vegetation that describes its effectiveness in storing carbon (C) and is of significance for understanding C biosphere-atmosphere exchange dynamics. A constant CUE value of 0.5 has been widely used in terrestrial C-cycle models, such as the Carnegie-Ames-Stanford-Approach model, or the Marine Biological Laboratory/Soil Plant-Atmosphere Canopy Model, for regional or global modeling purposes. However, increasing evidence argues that CUE is not constant, but varies with ecosystem types, site fertility, climate, site management and forest age. Hence, the assumption of a constant CUE of 0.5 can produce great uncertainty in estimating global carbon dynamics between terrestrial ecosystems and the atmosphere. Here, in order to analyze the global variations in CUE and understand how CUE varies with environmental variables, a global database was constructed based on published data for crops, forests, grasslands, wetlands and tundra ecosystems. In addition to CUE data, were also collected: GPP and NPP; site variables (e.g. climate zone, site management and plant function type); climate variables (e.g. temperature and precipitation); additional carbon fluxes (e.g. soil respiration, autotrophic respiration and heterotrophic respiration); and carbon pools (e.g. stem, leaf and root biomass). Different climate metrics were derived to diagnose seasonal temperature (mean annual temperature, MAT, and maximum temperature, Tmax) and water availability proxies (mean annual precipitation, MAP, and Palmer Drought Severity Index), in order to improve the local representation of environmental variables. Additionally were also included vegetation phenology dynamics as observed by different vegetation indices from the MODIS satellite. The mean CUE of all terrestrial ecosystems was 0.45, 10% lower than the previous assumed constant CUE of 0

  11. Net ecosystem CO2 exchange over a larch forest in Hokkaido, Japan

    International Nuclear Information System (INIS)

    Huimin Wang; Saigusa, Nobuko; Yamamoto, Susumu; Kondo, Hiroaki; Hirano, Takashi; Toriyama, Atsushi; Fujinuma, Yasumi

    2004-01-01

    Larch forests are distributed extensively in the east Eurasian continent and are expected to play a significant role in the terrestrial ecosystem carbon cycling process. In view of the fact that studies on carbon exchange for this important biome have been very limited, we have initiated a long-term flux observation in a larch forest ecosystem in Hokkaido in northern Japan since 2000. The net ecosystem CO 2 exchange (NEE) showed large seasonal and diurnal variation. Generally, the larch forest ecosystem released CO 2 in nighttime and assimilated CO 2 in daytime during the growing season from May to October. The ecosystem started to become a net carbon sink in May, reaching a maximum carbon uptake as high as 186 g C m -2 month -1 in June. With the yellowing, senescing and leaf fall, the ecosystem turned into a carbon source in November. During the non-growing season, the larch forest ecosystem became a net source of CO 2 , releasing an average of 16.7 g C m -2 month -1 . Overall, the ecosystem sequestered 141-240 g C m -2 yr -1 in 2001. The NEE was significantly influenced by environmental factors. Respiration of the ecosystem, for example, was exponentially dependent on air temperature, while photosynthesis was related to the incident PAR in a manner consistent with the Michaelis-Menten model. Although the vapor pressure deficit (VPD) was scarcely higher than 15 hPa, the CO 2 uptake rate was also depressed when VPD surpassed 10 hPa (Author)

  12. Spring hydrology determines summer net carbon uptake in northern ecosystems

    International Nuclear Information System (INIS)

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

    2014-01-01

    Increased photosynthetic activity and enhanced seasonal CO 2 exchange of northern ecosystems have been observed from a variety of sources including satellite vegetation indices (such as the normalized difference vegetation index; NDVI) and atmospheric CO 2 measurements. Most of these changes have been attributed to strong warming trends in the northern high latitudes (⩾50° N). Here we analyze the interannual variation of summer net carbon uptake derived from atmospheric CO 2 measurements and satellite NDVI in relation to surface meteorology from regional observational records. We find that increases in spring precipitation and snow pack promote summer net carbon uptake of northern ecosystems independent of air temperature effects. However, satellite NDVI measurements still show an overall benefit of summer photosynthetic activity from regional warming and limited impact of spring precipitation. This discrepancy is attributed to a similar response of photosynthesis and respiration to warming and thus reduced sensitivity of net ecosystem carbon uptake to temperature. Further analysis of boreal tower eddy covariance CO 2 flux measurements indicates that summer net carbon uptake is positively correlated with early growing-season surface soil moisture, which is also strongly affected by spring precipitation and snow pack based on analysis of satellite soil moisture retrievals. This is attributed to strong regulation of spring hydrology on soil respiration in relatively wet boreal and arctic ecosystems. These results document the important role of spring hydrology in determining summer net carbon uptake and contrast with prevailing assumptions of dominant cold temperature limitations to high-latitude ecosystems. Our results indicate potentially stronger coupling of boreal/arctic water and carbon cycles with continued regional warming trends. (letters)

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

    Science.gov (United States)

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

    2014-01-01

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

  14. Climate control of terrestrial carbon exchange across biomes and continents

    Energy Technology Data Exchange (ETDEWEB)

    Yi Chuixiang; Wolbeck, John; Xu Xiyan [School of Earth and Environmental Sciences, Queens College, City University of New York, NY 11367 (United States); Ricciuto, Daniel [Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Li Runze [Department of Statistics, Pennsylvania State University, University Park, PA 16802 (United States); Nilsson, Mats [Department of Forest Ecology, Swedish University of Agricultural Sciences, SE-901 83 Umeaa (Sweden); Aires, Luis [CESAM and Department of Environmental Engineering, School of Technology and Management, Polytechnic Institute of Leiria (Portugal); Albertson, John D [Department of Civil and Environmental Engineering, Duke University, Durham, NC 22708-0287 (United States); Ammann, Christof [Federal Research Station Agroscope Reckenholz-Taenikon, Reckenholzstrasse 191, 8046 Zuerich (Switzerland); Arain, M Altaf [School of Geography and Earth Sciences, McMaster University, Hamilton, ON, L8S 4K1 (Canada); De Araujo, Alessandro C [Instituto Nacional de Pesquisas da Amazonia, Programa LBA, Campus-II, Manaus-Amazonas 69060 (Brazil); Aubinet, Marc [University of Liege, Gembloux Agro-Bio Tech, Unit of Biosystem Physics, 2 Passage des Deportes, 5030 Gembloux (Belgium); Aurela, Mika [Finnish Meteorological Institute, Climate Change Research, FI-00101 Helsinki (Finland); Barcza, Zoltan [Department of Meteorology, Eoetvoes Lorand University, H-1117 Budapest, Pazmany setany 1/A (Hungary); Barr, Alan [Climate Research Division, Environment Canada, Saskatoon, SK, S7N 3H5 (Canada); Berbigier, Paul [INRA, UR1263 EPHYSE, Villenave d' Ornon F-33883 (France); Beringer, Jason [School of Geography and Environmental Science, Monash University, Clayton, Victoria 3800 (Australia); Bernhofer, Christian [Institute of Hydrology and Meteorology, Dresden University of Technology, Pienner Strasse 23, D-01737, Tharandt (Germany)

    2010-07-15

    Understanding the relationships between climate and carbon exchange by terrestrial ecosystems is critical to predict future levels of atmospheric carbon dioxide because of the potential accelerating effects of positive climate-carbon cycle feedbacks. However, directly observed relationships between climate and terrestrial CO{sub 2} exchange with the atmosphere across biomes and continents are lacking. Here we present data describing the relationships between net ecosystem exchange of carbon (NEE) and climate factors as measured using the eddy covariance method at 125 unique sites in various ecosystems over six continents with a total of 559 site-years. We find that NEE observed at eddy covariance sites is (1) a strong function of mean annual temperature at mid- and high-latitudes, (2) a strong function of dryness at mid- and low-latitudes, and (3) a function of both temperature and dryness around the mid-latitudinal belt (45 deg. N). The sensitivity of NEE to mean annual temperature breaks down at {approx} 16 deg. C (a threshold value of mean annual temperature), above which no further increase of CO{sub 2} uptake with temperature was observed and dryness influence overrules temperature influence.

  15. Climate control of terrestrial carbon exchange across biomes and continents

    International Nuclear Information System (INIS)

    Yi Chuixiang; Wolbeck, John; Xu Xiyan; Ricciuto, Daniel; Li Runze; Nilsson, Mats; Aires, Luis; Albertson, John D; Ammann, Christof; Arain, M Altaf; De Araujo, Alessandro C; Aubinet, Marc; Aurela, Mika; Barcza, Zoltan; Barr, Alan; Berbigier, Paul; Beringer, Jason; Bernhofer, Christian

    2010-01-01

    Understanding the relationships between climate and carbon exchange by terrestrial ecosystems is critical to predict future levels of atmospheric carbon dioxide because of the potential accelerating effects of positive climate-carbon cycle feedbacks. However, directly observed relationships between climate and terrestrial CO 2 exchange with the atmosphere across biomes and continents are lacking. Here we present data describing the relationships between net ecosystem exchange of carbon (NEE) and climate factors as measured using the eddy covariance method at 125 unique sites in various ecosystems over six continents with a total of 559 site-years. We find that NEE observed at eddy covariance sites is (1) a strong function of mean annual temperature at mid- and high-latitudes, (2) a strong function of dryness at mid- and low-latitudes, and (3) a function of both temperature and dryness around the mid-latitudinal belt (45 deg. N). The sensitivity of NEE to mean annual temperature breaks down at ∼ 16 deg. C (a threshold value of mean annual temperature), above which no further increase of CO 2 uptake with temperature was observed and dryness influence overrules temperature influence.

  16. Drought and ecosystem carbon cycling

    NARCIS (Netherlands)

    Molen, M.K. van der; Dolman, A.J.; Ciais, P.; Eglin, T.; Gobron, N.; Law, B.E.; Meir, P.; Peters, P.; Philips, O.L.; Reichstein, M.; Chen, T.; Dekker, S.C.; Doubkova, M.; Friedl, M.A.; Jung, M.; Hurk, B.J.J.M. van den; Jeu, R.A.M. de; Kruijt, B.; Ohta, T.; Rebel, K.T.; Plummer, S.; Seneviratne, S.I.; Sitch, S.; Teuling, A.J.; Werf, G.R. van der; Wang, G.

    2011-01-01

    Drought as an intermittent disturbance of the water cycle interacts with the carbon cycle differently than the ‘gradual’ climate change. During drought plants respond physiologically and structurally to prevent excessive water loss according to species-specific water use strategies. This has

  17. Ecosystem carbon stocks in Pinus palustris forests

    Science.gov (United States)

    Lisa Samuelson; Tom Stokes; John R. Butnor; Kurt H. Johnsen; Carlos A. Gonzalez-Benecke; Pete Anderson; Jason Jackson; Lorenzo Ferrari; Tim A. Martin; Wendell P. Cropper

    2014-01-01

    Longleaf pine (Pinus palustris Mill.) restoration in the southeastern United States offers opportunities for carbon (C) sequestration. Ecosystem C stocks are not well understood in longleaf pine forests, which are typically of low density and maintained by prescribed fire. The objectives of this research were to develop allometric equations for...

  18. Carbon sequestration and natural longleaf pine ecosystems

    Science.gov (United States)

    Ralph S. Meldahl; John S. Kush

    2006-01-01

    A fire-maintained longleaf pine (Pinus palustris Mill.) ecosystem may offer the best option for carbon (C) sequestration among the southern pines. Longleaf is the longest living of the southern pines, and products from longleaf pine will sequester C longer than most since they are likely to be solid wood products such as structural lumber and poles....

  19. Biotic, abiotic, and management controls on the net ecosystem CO2 exchange of European mountain grassland ecosystems

    DEFF Research Database (Denmark)

    Wohlfahrt, Georg; Anderson-Dunn, Margaret; Bahn, Michael

    2008-01-01

    The net ecosystem carbon dioxide (CO2) exchange (NEE) of nine European mountain grassland ecosystems was measured during 2002-2004 using the eddy covariance method. Overall, the availability of photosynthetically active radiation (PPFD) was the single most important abiotic influence factor for NEE....... Its role changed markedly during the course of the season, PPFD being a better predictor for NEE during periods favorable for CO2 uptake, which was spring and autumn for the sites characterized by summer droughts (southern sites) and (peak) summer for the Alpine and northern study sites. This general...... pattern was interrupted by grassland management practices, that is, mowing and grazing, when the variability in NEE explained by PPFD decreased in concert with the amount of aboveground biomass (BMag). Temperature was the abiotic influence factor that explained most of the variability in ecosystem...

  20. Estimation of Global 1km-grid Terrestrial Carbon Exchange Part I: Developing Inputs and Modelling

    Science.gov (United States)

    Sasai, T.; Murakami, K.; Kato, S.; Matsunaga, T.; Saigusa, N.; Hiraki, K.

    2015-12-01

    Global terrestrial carbon cycle largely depends on a spatial pattern in land cover type, which is heterogeneously-distributed over regional and global scales. However, most studies, which aimed at the estimation of carbon exchanges between ecosystem and atmosphere, remained within several tens of kilometers grid spatial resolution, and the results have not been enough to understand the detailed pattern of carbon exchanges based on ecological community. Improving the sophistication of spatial resolution is obviously necessary to enhance the accuracy of carbon exchanges. Moreover, the improvement may contribute to global warming awareness, policy makers and other social activities. In this study, we show global terrestrial carbon exchanges (net ecosystem production, net primary production, and gross primary production) with 1km-grid resolution. As methodology for computing the exchanges, we 1) developed a global 1km-grid climate and satellite dataset based on the approach in Setoyama and Sasai (2013); 2) used the satellite-driven biosphere model (Biosphere model integrating Eco-physiological And Mechanistic approaches using Satellite data: BEAMS) (Sasai et al., 2005, 2007, 2011); 3) simulated the carbon exchanges by using the new dataset and BEAMS by the use of a supercomputer that includes 1280 CPU and 320 GPGPU cores (GOSAT RCF of NIES). As a result, we could develop a global uniform system for realistically estimating terrestrial carbon exchange, and evaluate net ecosystem production in each community level; leading to obtain highly detailed understanding of terrestrial carbon exchanges.

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

    Science.gov (United States)

    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 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. © 2014 John Wiley & Sons Ltd.

  2. Measurement-based upscaling of pan Arctic net ecosystem exchange: the PANEEx project

    DEFF Research Database (Denmark)

    Mbufong, Herbert Njuabe; Kusbach, Antonin; Lund, Magnus

    2015-01-01

    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 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 (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...

  3. Organic carbon spiralling in stream ecosystems

    Energy Technology Data Exchange (ETDEWEB)

    Newbold, J D; Mulholland, P J; Elwood, J W; O' Neill, R V

    1982-01-01

    The term spiralling has been used to describe the combined processes of cycling and longitudinal transport in streams. As a measure or organic carbon spiralling, we introduced organic carbon turnover length, S, defined as the average or expected downstream distance travelled by a carbon atom between its entry or fixation in the stream and its oxidation. Using a simple model for organic carbon dynamics in a stream, we show that S is closely related to fisher and Likens' ecosystem efficiency. Unlike efficiency, however, S is independent of the length of the study reach, and values of S determined in streams of differing lengths can be compared. Using data from three different streams, we found the relationship between S and efficiency to agree closely with the model prediction. Hypotheses of stream functioning are discussed in the context of organic carbeon spiralling theory.

  4. Accumulation of carbon in northern mire ecosystems

    Energy Technology Data Exchange (ETDEWEB)

    Tolonen, K.; Turunen, J.; Alm, J. [Joensuu Univ. (Finland). Dept. of Biology; Korhola, A. [Helsinki Univ. (Finland). Lab. of Physical Geography; Jungner, H. [Helsinki Univ. (Finland). Dating Lab.; Vasander, H. [Helsinki Univ. (Finland). Dept. of Forest Ecology

    1996-12-31

    The basic feature in the functional ecology of any mire ecosystem is retardation of the effective decay of organic material resulting in a conspicuous accumulation of plant debris as peat overtime. The carbon accumulation process is slow, and climatic change may have an impact on the carbon cycle of peatlands, therefore, it has been of interest to study the rate of carbon accumulation by geological methods from dated peat strata. The approach is hampered by several facts. First, the mires vary enormously as to their vegetation and hydrology and hence their production and decay properties. It follows that a great number of study sites are needed. Second, the peat in mires expands both vertically and laterally, and this requires a spatial reconstruction of carbon accumulation within a mire basin. Third, simple geological methods cannot account for the actual rate of carbon accumulation in peat, and finally, an additional carbon sink in the mire ecosystems can be the mineral subsoil beneath peat. The proposed warming will perhaps shift northwards the existing climatic mire regimes and, thus, the northern aapa fens will change to Sphagnum bogs that are more effective in sequestering carbon, but distinctly less effective in their CH{sub 4} and N{sub 2}O emanation. The role of mire fires in more remote northern areas may then become another important factor. The answer to the important question of future total sequestration of carbon to peatlands depends on the precipitation and its seasonal distribution pattern. Most climatic scenarios predict a decrease in the evaporation surplus during the summer at northern regions. Presumably, the consequent lowering of the water table would improve growth of forest on mires and simultaneously decrease the methane fluxes from peat. The combined net effect could be a clear restraining of the radiative forcing

  5. Accumulation of carbon in northern mire ecosystems

    Energy Technology Data Exchange (ETDEWEB)

    Tolonen, K; Turunen, J; Alm, J [Joensuu Univ. (Finland). Dept. of Biology; Korhola, A [Helsinki Univ. (Finland). Lab. of Physical Geography; Jungner, H [Helsinki Univ. (Finland). Dating Lab.; Vasander, H [Helsinki Univ. (Finland). Dept. of Forest Ecology

    1997-12-31

    The basic feature in the functional ecology of any mire ecosystem is retardation of the effective decay of organic material resulting in a conspicuous accumulation of plant debris as peat overtime. The carbon accumulation process is slow, and climatic change may have an impact on the carbon cycle of peatlands, therefore, it has been of interest to study the rate of carbon accumulation by geological methods from dated peat strata. The approach is hampered by several facts. First, the mires vary enormously as to their vegetation and hydrology and hence their production and decay properties. It follows that a great number of study sites are needed. Second, the peat in mires expands both vertically and laterally, and this requires a spatial reconstruction of carbon accumulation within a mire basin. Third, simple geological methods cannot account for the actual rate of carbon accumulation in peat, and finally, an additional carbon sink in the mire ecosystems can be the mineral subsoil beneath peat. The proposed warming will perhaps shift northwards the existing climatic mire regimes and, thus, the northern aapa fens will change to Sphagnum bogs that are more effective in sequestering carbon, but distinctly less effective in their CH{sub 4} and N{sub 2}O emanation. The role of mire fires in more remote northern areas may then become another important factor. The answer to the important question of future total sequestration of carbon to peatlands depends on the precipitation and its seasonal distribution pattern. Most climatic scenarios predict a decrease in the evaporation surplus during the summer at northern regions. Presumably, the consequent lowering of the water table would improve growth of forest on mires and simultaneously decrease the methane fluxes from peat. The combined net effect could be a clear restraining of the radiative forcing

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

    Science.gov (United States)

    Paul Selmants; Creighton Litton; Christian P. Giardina; Greg P. Asner

    2014-01-01

    Theory and experiment agree that climate warming will increase carbon fluxes between terrestrial ecosystems and the atmosphere. The effect of this increased exchange on terrestrial carbon storage is less predictable, with important implications for potential feedbacks to the climate system. We quantified how increased mean annual temperature (MAT) affects ecosystem...

  7. [Effect of air temperature and rainfall on wetland ecosystem CO2 exchange in China].

    Science.gov (United States)

    Chu, Xiao-jing; Han, Guang-xuan

    2015-10-01

    Wetland can be a potential efficient sink to reduce global warming due to its higher primary productivity and lower carbon decomposition rate. While there has been a series progress on the influence mechanism of ecosystem CO2 exchange over China' s wetlands, a systematic metaanalysis of data still needs to be improved. We compiled data of ecosystem CO2 exchange of 21 typical wetland vegetation types in China from 29 papers and carried out an integrated analysis of air temperature and precipitation effects on net ecosystem CO2 exchange (NEE), ecosystem respiration (Reco), gross primary productivity (GPP), the response of NEE to PAR, and the response of Reco to temperature. The results showed that there were significant responses (P0.05). Across different Chinese wetlands, both precipitation and temperature had no significant effect on apparent quantum yield (α) or ecosystem respiration in the daytime (Reco,day, P>0.05). The maximum photosynthesis rate (Amax) was remarkably correlated with precipitation (P 0.05). Precipitation was negatively correlated with temperature sensitivity of Reco (Q10, P<0.05). Furthermore, temperature accounted for 35% and 46% of the variations in temperature sensitivity of Reco (Q10) and basal respiration (Rref P<0.05), respectively.

  8. Estimation of Global 1km-grid Terrestrial Carbon Exchange Part II: Evaluations and Applications

    Science.gov (United States)

    Murakami, K.; Sasai, T.; Kato, S.; Niwa, Y.; Saito, M.; Takagi, H.; Matsunaga, T.; Hiraki, K.; Maksyutov, S. S.; Yokota, T.

    2015-12-01

    Global terrestrial carbon cycle largely depends on a spatial pattern in land cover type, which is heterogeneously-distributed over regional and global scales. Many studies have been trying to reveal distribution of carbon exchanges between terrestrial ecosystems and atmosphere for understanding global carbon cycle dynamics by using terrestrial biosphere models, satellite data, inventory data, and so on. However, most studies remained within several tens of kilometers grid spatial resolution, and the results have not been enough to understand the detailed pattern of carbon exchanges based on ecological community and to evaluate the carbon stocks by forest ecosystems in each countries. Improving the sophistication of spatial resolution is obviously necessary to enhance the accuracy of carbon exchanges. Moreover, the improvement may contribute to global warming awareness, policy makers and other social activities. We show global terrestrial carbon exchanges (net ecosystem production, net primary production, and gross primary production) with 1km-grid resolution. The methodology for these estimations are shown in the 2015 AGU FM poster "Estimation of Global 1km-grid Terrestrial Carbon Exchange Part I: Developing Inputs and Modelling". In this study, we evaluated the carbon exchanges in various regions with other approaches. We used the satellite-driven biosphere model (BEAMS) as our estimations, GOSAT L4A CO2 flux data, NEP retrieved by NICAM and CarbonTracer2013 flux data, for period from Jun 2001 to Dec 2012. The temporal patterns for this period were indicated similar trends between BEAMS, GOSAT, NICAM, and CT2013 in many sub-continental regions. Then, we estimated the terrestrial carbon exchanges in each countries, and could indicated the temporal patterns of the exchanges in large carbon stock regions.Global terrestrial carbon cycle largely depends on a spatial pattern of land cover type, which is heterogeneously-distributed over regional and global scales. Many

  9. Carbon dioxide and water vapour exchange in a tropical dry forest as influenced by the North American Monsoon System (NAMS)

    Science.gov (United States)

    To better understand the effects and relationship between precipitation, net ecosystem carbon dioxide (NEE) and water vapor exchange (ET), we report a study conducted in the tropical dry forest (TDF) in the northwest of Mexico. Ecosystem gas exchange was measured using the eddy correlation technique...

  10. Eddy covariance and biometric measurements show that a savanna ecosystem in Southwest China is a carbon sink

    Science.gov (United States)

    Fei, Xuehai; Jin, Yanqiang; Zhang, Yiping; Sha, Liqing; Liu, Yuntong; Song, Qinghai; Zhou, Wenjun; Liang, Naishen; Yu, Guirui; Zhang, Leiming; Zhou, Ruiwu; Li, Jing; Zhang, Shubin; Li, Peiguang

    2017-02-01

    Savanna ecosystems play a crucial role in the global carbon cycle. However, there is a gap in our understanding of carbon fluxes in the savanna ecosystems of Southeast Asia. In this study, the eddy covariance technique (EC) and the biometric-based method (BM) were used to determine carbon exchange in a savanna ecosystem in Southwest China. The BM-based net ecosystem production (NEP) was 0.96 tC ha-1 yr-1. The EC-based estimates of the average annual gross primary productivity (GPP), ecosystem respiration (Reco), and net ecosystem carbon exchange (NEE) were 6.84, 5.54, and -1.30 tC ha-1 yr-1, respectively, from May 2013 to December 2015, indicating that this savanna ecosystem acted as an appreciable carbon sink. The ecosystem was more efficient during the wet season than the dry season, so that it represented a small carbon sink of 0.16 tC ha-1 yr-1 in the dry season and a considerable carbon sink of 1.14 tC ha-1 yr-1 in the wet season. However, it is noteworthy that the carbon sink capacity may decline in the future under rising temperatures and decreasing rainfall. Consequently, further studies should assess how environmental factors and climate change will influence carbon-water fluxes.

  11. Eddy covariance and biometric measurements show that a savanna ecosystem in Southwest China is a carbon sink

    Science.gov (United States)

    Fei, Xuehai; Jin, Yanqiang; Zhang, Yiping; Sha, Liqing; Liu, Yuntong; Song, Qinghai; Zhou, Wenjun; Liang, Naishen; Yu, Guirui; Zhang, Leiming; Zhou, Ruiwu; Li, Jing; Zhang, Shubin; Li, Peiguang

    2017-01-01

    Savanna ecosystems play a crucial role in the global carbon cycle. However, there is a gap in our understanding of carbon fluxes in the savanna ecosystems of Southeast Asia. In this study, the eddy covariance technique (EC) and the biometric-based method (BM) were used to determine carbon exchange in a savanna ecosystem in Southwest China. The BM-based net ecosystem production (NEP) was 0.96 tC ha−1 yr−1. The EC-based estimates of the average annual gross primary productivity (GPP), ecosystem respiration (Reco), and net ecosystem carbon exchange (NEE) were 6.84, 5.54, and −1.30 tC ha−1 yr−1, respectively, from May 2013 to December 2015, indicating that this savanna ecosystem acted as an appreciable carbon sink. The ecosystem was more efficient during the wet season than the dry season, so that it represented a small carbon sink of 0.16 tC ha−1 yr−1 in the dry season and a considerable carbon sink of 1.14 tC ha−1 yr−1 in the wet season. However, it is noteworthy that the carbon sink capacity may decline in the future under rising temperatures and decreasing rainfall. Consequently, further studies should assess how environmental factors and climate change will influence carbon-water fluxes. PMID:28145459

  12. Net ecosystem exchange in a sedge-sphagnum fen at the South of West Siberia, Russia

    Science.gov (United States)

    Dyukarev, Egor

    2017-04-01

    The model of net ecosystem exchange was used to study the influence of different environmental factors and to calculate daily and growing season carbon budget for minerotrophic fen at South of West Siberia, Russia. Minerotrophic sedge-sphagnum fen occupies the central part of the Bakcharskoe bog. The model uses air and soil temperature, incoming photosynthetically active radiation, and leaf area index as the explanatory factors for gross primary production, heterotrophic and autotrophic respiration. The model coefficients were calibrated using data collected by automated soil CO2 flux system with clear long-term chamber. The studied ecosystem is a sink of carbon according to modelling and observation results. This study was supported by Russian Foundation for Basic Researches (grant numbers 16-07-01205 and 16-45-700562.

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

    Science.gov (United States)

    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

  14. Current net ecosystem exchange of CO2 in a young mixed forest: any heritage from the previous ecosystem?

    Science.gov (United States)

    Violette, Aurélie; Heinesch, Bernard; Erpicum, Michel; Carnol, Monique; Aubinet, Marc; François, Louis

    2013-04-01

    For 15 years, networks of flux towers have been developed to determine accurate carbon balance with the eddy-covariance method and determine if forests are sink or source of carbon. However, for prediction of the evolution of carbon cycle and climate, major uncertainties remain on the ecosystem respiration (Reco, which includes the respiration of above ground part of trees, roots respiration and mineralization of the soil organic matter), the gross primary productivity (GPP) and their difference, the net ecosystem exchange (NEE) of forests. These uncertainties are consequences of spatial and inter-annual variability, driven by previous and current climatic conditions, as well as by the particular history of the site (management, diseases, etc.). In this study we focus on the carbon cycle in two mixed forests in the Belgian Ardennes. The first site, Vielsalm, is a mature stand mostly composed of beeches (Fagus sylvatica) and douglas fir (Pseudotsuga menziesii) from 80 to 100 years old. The second site, La Robinette, was covered before 1995 with spruces. After an important windfall and a clear cutting, the site was replanted, between 1995 and 2000, with spruces (Piceas abies) and deciduous species (mostly Betula pendula, Aulnus glutinosa and Salix aurita). The challenge here is to highlight how initial conditions can influence the current behavior of the carbon cycle in a growing stand compared to a mature one, where initial conditions are supposed to be forgotten. A modeling approach suits particularly well for sensitivity tests and estimation of the temporal lag between an event and the ecosystem response. We use the forest ecosystem model ASPECTS (Rasse et al., Ecological Modelling 141, 35-52, 2001). This model predicts long-term forest growth by calculating, over time, hourly NEE. It was developed and already validated on the Vielsalm forest. Modelling results are confronted to eddy-covariance data on both sites from 2006 to 2011. The main difference between both

  15. Carbon and nitrogen stoichiometry across stream ecosystems

    Science.gov (United States)

    Wymore, A.; Kaushal, S.; McDowell, W. H.; Kortelainen, P.; Bernhardt, E. S.; Johnes, P.; Dodds, W. K.; Johnson, S.; Brookshire, J.; Spencer, R.; Rodriguez-Cardona, B.; Helton, A. M.; Barnes, R.; Argerich, A.; Haq, S.; Sullivan, P. L.; López-Lloreda, C.; Coble, A. A.; Daley, M.

    2017-12-01

    Anthropogenic activities are altering carbon and nitrogen concentrations in surface waters globally. The stoichiometry of carbon and nitrogen regulates important watershed biogeochemical cycles; however, controls on carbon and nitrogen ratios in aquatic environments are poorly understood. Here we use a multi-biome and global dataset (tropics to Arctic) of stream water chemistry to assess relationships between dissolved organic carbon (DOC) and nitrate, ammonium and dissolved organic nitrogen (DON), providing a new conceptual framework to consider interactions between DOC and the multiple forms of dissolved nitrogen. We found that across streams the total dissolved nitrogen (TDN) pool is comprised of very little ammonium and as DOC concentrations increase the TDN pool shifts from nitrate to DON dominated. This suggests that in high DOC systems, DON serves as the primary source of nitrogen. At the global scale, DOC and DON are positively correlated (r2 = 0.67) and the average C: N ratio of dissolved organic matter (molar ratio of DOC: DON) across our data set is approximately 31. At the biome and smaller regional scale the relationship between DOC and DON is highly variable (r2 = 0.07 - 0.56) with the strongest relationships found in streams draining the mixed temperate forests of the northeastern United States. DOC: DON relationships also display spatial and temporal variability including latitudinal and seasonal trends, and interactions with land-use. DOC: DON ratios correlated positively with gradients of energy versus nutrient limitation pointing to the ecological role (energy source versus nutrient source) that DON plays with stream ecosystems. Contrary to previous findings we found consistently weak relationships between DON and nitrate which may reflect DON's duality as an energy or nutrient source. Collectively these analyses demonstrate how gradients of DOC drive compositional changes in the TDN pool and reveal a high degree of variability in the C: N ratio

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

    Science.gov (United States)

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

    2014-06-01

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

  17. Turbulence considerations for comparing ecosystem exchange over old-growth and clear-cut stands for limited fetch and complex canopy flow conditions

    Science.gov (United States)

    Sonia Wharton; Matt Schroeder; Kyaw Tha Paw U; Matthias Falk; Ken Bible

    2009-01-01

    Carbon dioxide (CO2), water vapor, and energy fluxes were measured using eddy covariance (EC) methodology over three adjacent evergreen 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...

  18. Hysteresis response of daytime net ecosystem exchange during drought

    Directory of Open Access Journals (Sweden)

    N. Pingintha

    2010-03-01

    Full Text Available Continuous measurements of net ecosystem CO2 exchange (NEE using the eddy-covariance method were made over an agricultural ecosystem in the southeastern US. During optimum environmental conditions, photosynthetically active radiation (PAR was the primary driver controlling daytime NEE, accounting for as much as 67 to 89% of the variation in NEE. However, soil water content became the dominant factor limiting the NEE-PAR response during the peak growth stage. NEE was significantly depressed when high PAR values coincided with very low soil water content. The presence of a counter-clockwise hysteresis of daytime NEE with PAR was observed during periods of water stress. This is a result of the stomatal closure control of photosynthesis at high vapor pressure deficit and enhanced respiration at high temperature. This result is significant since this hysteresis effect limits the range of applicability of the Michaelis-Menten equation and other related expressions in the determination of daytime NEE as a function of PAR. The systematic presence of hysteresis in the response of NEE to PAR suggests that the gap-filling technique based on a non-linear regression approach should take into account the presence of water-limited field conditions. Including this step is therefore likely to improve current evaluation of ecosystem response to increased precipitation variability arising from climatic changes.

  19. Ecosystem Carbon Stocks of Intertidal Wetlands in Singapore

    Science.gov (United States)

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

    2014-12-01

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

  20. Ventilation of subterranean CO2 and Eddy covariance incongruities over carbonate ecosystems

    Directory of Open Access Journals (Sweden)

    F. Domingo

    2010-03-01

    Full Text Available Measurements of CO2 fluxes with Eddy Covariance (EC systems are ongoing over different ecosystems around the world, through different measuring networks, in order to assess the carbon balance of these ecosystems. In carbonate ecosystems, characterized by the presence of subterranean pores and cavities, ventilation of the CO2 accumulated in these cavities and pores can act as an extra source of CO2 exchange between the ecosystem and the atmosphere. In this work we analyse the effect of the subterranean heterogeneity of a carbonate ecosystem on measurements of CO2 fluxes by comparing measurements from two EC systems with distinct footprints. Results showed that both EC systems agreed for measurements of evapotranspiration and of CO2 in periods when respiratory and photosynthetic processes were dominant (biological periods, with a regression slope of 0.99 and 0.97, respectively. However, in periods when the main source of CO2 comes from the ventilation of subterranean pores and cavities (abiotic periods agreement is not good, with a regression slope of 0.6. Ground-penetrating radar measurements of the sub-surface confirmed the existence of high sub-surface heterogeneity that, combined with different footprints, lead to differences in the measurements of the two EC systems. These results show that measurements of CO2 fluxes with Eddy covariance systems over carbonate ecosystems must be taken carefully, as they may not be representative of the ecosystem under consideration.

  1. Dynamical implications of bi-directional resource exchange within a meta-ecosystem.

    Science.gov (United States)

    Rodriguez, Marisabel Rodriguez; Kopp, Darin; Allen, Daniel; Kang, Yun

    2018-05-05

    The exchange of resources across ecosystem boundaries can have large impacts on ecosystem structures and functions at local and regional scales. In this article, we develop a simple model to investigate dynamical implications of bi-directional resource exchanges between two local ecosystems in a meta-ecosystem framework. In our model, we assume that (1) Each local ecosystem acts as both a resource donor and recipient, such that one ecosystem donating resources to another results in a cost to the donating system and a benefit to the recipient; and (2) The costs and benefits of the bi-directional resource exchange between two ecosystems are correlated in a nonlinear fashion. Our model could apply to the resource interactions between terrestrial and aquatic ecosystems that are supported by the literature. Our theoretical results show that bi-directional resource exchange between two ecosystems can indeed generate complicated dynamical outcomes, including the coupled ecosystems having amensalistic, antagonistic, competitive, or mutualistic interactions, with multiple alternative stable states depending on the relative costs and benefits. In addition, if the relative cost for resource exchange for an ecosystem is decreased or the relative benefit for resource exchange for an ecosystem is increased, the production of that ecosystem would increase; however, depending on the local environment, the production of the other ecosystem may increase or decrease. We expect that our work, by evaluating the potential outcomes of resource exchange theoretically, can facilitate empirical evaluations and advance the understanding of spatial ecosystem ecology where resource exchanges occur in varied ecosystems through a complicated network. Copyright © 2018. Published by Elsevier Inc.

  2. Soil carbon effluxes in ecosystems of Forsmark and Laxemar

    Energy Technology Data Exchange (ETDEWEB)

    Tagesson, Torbern (Dept. of Physical Geography and Ecosystem Analysis, Lund Univ. (Sweden))

    2007-12-15

    Soil carbon effluxes were estimated in a number of ecosystems in Laxemar and Forsmark investigations areas. It was done in a young Scots pine (Pinus sylvestris) stand, a wet deciduous stand, a poor fen and an agricultural field in the Laxemar investigation area in south-eastern Sweden (57 deg 5 min N, 16 deg 7 min E) and in a pasture, two Norway spruce (Picea abies) stands, a deciduous forest, a mire, a wet deciduous forest and a clear-cut in the Forsmark investigation area (60 deg 4 min N, 18 deg 2 min E). It was measured with the closed chamber technique in 2005 and 2006. Soil temperature at 10 cm depth, air temperature and photosynthetically active radiation (PAR) were also measured. Exponential regressions with soil respiration against air and soil temperature were used to estimate annual soil respiration. A hyperbolic curve with Gross Primary Production (GPP) against PAR was used for modelling GPP for the growing season in the poor fen and the agricultural area of Laxemar. The exponential regressions with soil respiration against air and soil temperature explained on average 33.6% and 44.0% of the variation, respectively. GPP of the ground vegetation were reducing soil carbon effluxes, in all stands but one of the spruce stands, the deciduous forest, the mire and the wet deciduous forest of Forsmark. The significant (all but spruce 2 in Forsmark) curves with GPP against PAR explained on average 22.7% of the variation in GPP. The cubic regressions with GPP against air temperature were only significant for the poor fen and the agricultural field in Laxemar and it explained on average 34.8% of the variation in GPP for these ecosystems. The exponential regressions with air and soil temperature against soil respiration could be used to temporally extrapolate the occasional field measurements. The hyperbolic curve with GPP against PAR could also be used for temporal extrapolation of GPP for the ecosystems without a tree layer, i.e. the poor fen and the agricultural

  3. Soil carbon effluxes in ecosystems of Forsmark and Laxemar

    International Nuclear Information System (INIS)

    Tagesson, Torbern

    2007-12-01

    Soil carbon effluxes were estimated in a number of ecosystems in Laxemar and Forsmark investigations areas. It was done in a young Scots pine (Pinus sylvestris) stand, a wet deciduous stand, a poor fen and an agricultural field in the Laxemar investigation area in south-eastern Sweden (57 deg 5 min N, 16 deg 7 min E) and in a pasture, two Norway spruce (Picea abies) stands, a deciduous forest, a mire, a wet deciduous forest and a clear-cut in the Forsmark investigation area (60 deg 4 min N, 18 deg 2 min E). It was measured with the closed chamber technique in 2005 and 2006. Soil temperature at 10 cm depth, air temperature and photosynthetically active radiation (PAR) were also measured. Exponential regressions with soil respiration against air and soil temperature were used to estimate annual soil respiration. A hyperbolic curve with Gross Primary Production (GPP) against PAR was used for modelling GPP for the growing season in the poor fen and the agricultural area of Laxemar. The exponential regressions with soil respiration against air and soil temperature explained on average 33.6% and 44.0% of the variation, respectively. GPP of the ground vegetation were reducing soil carbon effluxes, in all stands but one of the spruce stands, the deciduous forest, the mire and the wet deciduous forest of Forsmark. The significant (all but spruce 2 in Forsmark) curves with GPP against PAR explained on average 22.7% of the variation in GPP. The cubic regressions with GPP against air temperature were only significant for the poor fen and the agricultural field in Laxemar and it explained on average 34.8% of the variation in GPP for these ecosystems. The exponential regressions with air and soil temperature against soil respiration could be used to temporally extrapolate the occasional field measurements. The hyperbolic curve with GPP against PAR could also be used for temporal extrapolation of GPP for the ecosystems without a tree layer, i.e. the poor fen and the agricultural

  4. Carbon exchange in Western Siberian watershed mires and implication for the greenhouse effect : A spatial temporal modeling approach

    NARCIS (Netherlands)

    Borren, W.

    2007-01-01

    The vast watershed mires of Western Siberia formed a significant sink of carbon during the Holocene. Because of their large area these mires might play an important role in the carbon exchange between terrestrial ecosystems and the atmosphere. However, estimation of the Holocene and future carbon

  5. Air-sea exchange of carbon dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Bakker, D C.E.; De Baar, H J.W.; De Jong, E; Koning, F A [Netherlands Institute for Sea Research NIOZ, Den Burg Texel (Netherlands)

    1996-12-31

    The greenhouse gas carbon dioxide is emitted by anthropogenic activities. The oceans presumably serve as a net sink for 17 to 39% of these emissions. The objective of this project is to quantify more accurately the locality, seasonality and magnitude of the net air-sea flux of CO2 with emphasis on the South Atlantic Ocean. In situ measurements of the fugacity of CO2 in surface water and marine air, of total dissolved inorganic carbon, alkalinity and of air-sea exchange of CO2 have been made at four Atlantic crossings, in the Southern Ocean, in a Norwegian fjord and in the Dutch coastal zone. Skin temperature was detected during several of the cruises. The data collected in the course of the project support and refine previous findings. Variability of dissolved CO2 in surface water is related in a complex way to biological and physical factors. The carbonate equilibria cause dissolved gaseous CO2 to react in an intricate manner to disturbances. Dissolved gaseous CO2 hardly ever attains equilibrium with the atmospheric CO2 content by means of air-sea exchange, before a new disturbance occurs. Surface water fCO2 changes could be separated in those caused by seasonal warming and those by biological uptake in a Southern Ocean spring. Incorporation of a thermal skin effect and a change of the wind speed interval strongly increased the small net oceanic uptake for the area. The Atlantic crossings point to a relationship between water mass history and surface water CO2 characteristics. In particular, current flow and related heat fluxes leave their imprint on the concentration dissolved gaseous CO2 and on air-sea exchange. In the Dutch coastal zone hydrography and inorganic carbon characteristics of the water were heterogeneous, which yielded variable air-sea exchange of CO2. figs., tabs., refs.

  6. Controls of Carbon Exchange in a Boreal Minerogenic Mire

    Science.gov (United States)

    Nilsson, M.; Sagerfors, J.; Buffam, I.; Eriksson, T.; Grelle, A.; Klemedtsson, L.; Weslien, P.; Laudon, H.; Lindroth, A.

    2008-12-01

    Based on theories on both mire development and their response to environmental change, the current role of mires as a net carbon sink has been questioned. A rigorous evaluation of the contemporary net C-exchange in mires requires direct measurements of all relevant fluxes. We use data on carbon exchange from a boreal minerogenic oligotrophic mire (Degerö Stormyr, 64°11' N, 19°33E) to derive a contemporary carbon budget and to analyze the main controls on the C exchange. Data on the following fluxes were collected: land-atmosphere CO2 (continuous Eddy Covariance measurements, 7 years) and CH4 (static chambers during the snow free period, 4 years) exchange; DOC in precipitation; loss of TOC, CO2 and CH4 through water runoff, 4 years (continuous discharge measurement and regular C-content measurements). The annual land atmosphere exchange of CO2 (NEE) was fairly constant between years and varied between -48 - -61 gCm-2yr-1 during six out of the seven years, despite a large variation in weather combinations, the average being -53 ± 5 gCm-2yr-1. Of the net fixation of atmospheric CO2-C during the net uptake period, i.e. the growing season, approximately a third was lost during the net source period, i.e. the winter period. During the four years with measurements of methane and runoff C-export another third of the growing season uptake was lost from the mire ecosystem as methane and runoff C. While the balance between the length of the NEE uptake and the NEE loss period are most important for the annual net ecosystem carbon balance (NECB) it is central to understand the controls of the spring-summer, and the summer-autumn transitions. The onset of the net C uptake period was controlled by the interaction between the water content and the temperature of the peat moss surface. We interpret this as mainly being a control of the CO2 photosynthesis uptake by the Sphagnum mosses. The transition from being a net C sink to being a net C source is in contrast only controlled

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

    Science.gov (United States)

    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 ~vegetation index, longest monsoon growing season and the highest annual and July-September P. The interannual variations in annual E and NEE were mostly controlled by annual P, July-September NDVI and growing season length during 2002-2009.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2000-08-28

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

  9. Direct and indirect effects of climatic variations on the interannual variability in net ecosystem exchange across terrestrial ecosystems

    Directory of Open Access Journals (Sweden)

    Junjiong Shao

    2016-08-01

    Full Text Available Climatic variables not only directly affect the interannual variability (IAV in net ecosystem exchange of CO2 (NEE but also indirectly drive it by changing the physiological parameters. Identifying these direct and indirect paths can reveal the underlying mechanisms of carbon (C dynamics. In this study, we applied a path analysis using flux data from 65 sites to quantify the direct and indirect climatic effects on IAV in NEE and to evaluate the potential relationships among the climatic variables and physiological parameters that represent physiology and phenology of ecosystems. We found that the maximum photosynthetic rate was the most important factor for the IAV in gross primary productivity (GPP, which was mainly induced by the variation in vapour pressure deficit. For ecosystem respiration (RE, the most important drivers were GPP and the reference respiratory rate. The biome type regulated the direct and indirect paths, with distinctive differences between forests and non-forests, evergreen needleleaf forests and deciduous broadleaf forests, and between grasslands and croplands. Different paths were also found among wet, moist and dry ecosystems. However, the climatic variables can only partly explain the IAV in physiological parameters, suggesting that the latter may also result from other biotic and disturbance factors. In addition, the climatic variables related to NEE were not necessarily the same as those related to GPP and RE, indicating the emerging difficulty encountered when studying the IAV in NEE. Overall, our results highlight the contribution of certain physiological parameters to the IAV in C fluxes and the importance of biome type and multi-year water conditions, which should receive more attention in future experimental and modelling research.

  10. 'Carbon-Money Exchange' to contain global warming and deforestation

    Energy Technology Data Exchange (ETDEWEB)

    Nagase, Kozo E-mail: nagase@de.mbn.or.jp

    2005-07-01

    This paper builds a basic theory of 'Carbon-Money Exchange' in which carbon as currency in nature's household (ecosystems) and money as currency in humankind's household (economy) are exchanged just like in a foreign exchange. The simple chemical equation below makes it possible (CO{sub 2}{yields}C+O{sub 2}=C+O{sub 2}{yields}CO{sub 2}). The left-hand side represents the work of plants to remove atmospheric CO{sub 2}. The right-hand side represents the work of humans as fossil fuel consumers to produce it. The exchange of the two currencies is possible by copying the fossil fuel market. The paper concludes that this new exchange can automatically contain global warming and deforestation, replacing onerous emissions trading. Moreover, it could revolutionize the conventional economy, creating counter-capitalism, or 'carbonism'.

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

    Energy Technology Data Exchange (ETDEWEB)

    King, A W

    1991-12-31

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

  12. 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.

    Science.gov (United States)

    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. Copyright © 2012 Elsevier B.V. All rights reserved.

  13. Precipitation as driver of carbon fluxes in 11 African ecosystems

    NARCIS (Netherlands)

    Merbold, L.; Ardo, J.; Arneth, A.; Scholes, R.J.; Nouvellon, Y.; Grandcourt, de A.; Archibald, S.; Bonnefonds, J.M.; Boulain, N.; Bruemmer, C.; Brueggemann, N.; Cappelaere, B.; Ceschia, E.; El-Khidir, H.A.M.; El-Tahir, B.A.; Falk, U.; Lloyd, J.; Kergoat, L.; Dantec, Le V.; Mougin, E.; Muchinda, M.; Mukelabai, M.M.; Ramier, D.; Roupsard, O.; Timouk, F.; Veenendaal, E.M.; Kutsch, W.L.

    2009-01-01

    This study reports carbon and water fluxes between the land surface and atmosphere in eleven different ecosystems types in Sub-Saharan Africa, as measured using eddy covariance (EC) technology in the first two years of the CarboAfrica network operation. The ecosystems for which data were available

  14. Carbon dioxide fluxes from contrasting ecosystems in the Sudanian Savanna in West Africa.

    Science.gov (United States)

    Quansah, Emmanuel; Mauder, Matthias; Balogun, Ahmed A; Amekudzi, Leonard K; Hingerl, Luitpold; Bliefernicht, Jan; Kunstmann, Harald

    2015-12-01

    The terrestrial land surface in West Africa is made up of several types of savanna ecosystems differing in land use changes which modulate gas exchanges between their vegetation and the overlying atmosphere. This study compares diurnal and seasonal estimates of CO 2 fluxes from three contrasting ecosystems, a grassland, a mixture of fallow and cropland, and nature reserve in the Sudanian Savanna and relate them to water availability and land use characteristics. Over the study period, and for the three study sites, low soil moisture availability, high vapour pressure deficit and low ecosystem respiration were prevalent during the dry season (November to March), but the contrary occurred during the rainy season (May to October). Carbon uptake predominantly took place in the rainy season, while net carbon efflux occurred in the dry season as well as the dry to wet and wet to dry transition periods (AM and ND) respectively. Carbon uptake decreased in the order of the nature reserve, a mixture of fallow and cropland, and grassland. Only the nature reserve ecosystem at the Nazinga Park served as a net sink of CO 2 , mostly by virtue of a several times larger carbon uptake and ecosystem water use efficiency during the rainy season than at the other sites. These differences were influenced by albedo, LAI, EWUE, PPFD and climatology during the period of study. These results suggest that land use characteristics affect plant physiological processes that lead to flux exchanges over the Sudanian Savanna ecosystems. It affects the diurnal, seasonal and annual changes in NEE and its composite signals, GPP and RE. GPP and NEE were generally related as NEE scaled with photosynthesis with higher CO 2 assimilation leading to higher GPP. However, CO 2 effluxes over the study period suggest that besides biomass regrowth, other processes, most likely from the soil might have also contributed to the enhancement of ecosystem respiration.

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

    Science.gov (United States)

    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.

  16. Net carbon exchange across the Arctic tundra-boreal forest transition in Alaska 1981-2000

    Science.gov (United States)

    Thompson, Catharine Copass; McGuire, A.D.; Clein, Joy S.; Chapin, F. S.; Beringer, J.

    2006-01-01

    Shifts in the carbon balance of high-latitude ecosystems could result from differential responses of vegetation and soil processes to changing moisture and temperature regimes and to a lengthening of the growing season. Although shrub expansion and northward movement of treeline should increase carbon inputs, the effects of these vegetation changes on net carbon exchange have not been evaluated. We selected low shrub, tall shrub, and forest tundra sites near treeline in northwestern Alaska, representing the major structural transitions expected in response to warming. In these sites, we measured aboveground net primary production (ANPP) and vegetation and soil carbon and nitrogen pools, and used these data to parameterize the Terrestrial Ecosystem Model. We simulated the response of carbon balance components to air temperature and precipitation trends during 1981-2000. In areas experiencing warmer and dryer conditions, Net Primary Production (NPP) decreased and heterotrophic respiration (R H ) increased, leading to a decrease in Net Ecosystem Production (NEP). In warmer and wetter conditions NPP increased, but the response was exceeded by an increase in R H ; therefore, NEP also decreased. Lastly, in colder and wetter regions, the increase in NPP exceeded a small decline in R H , leading to an increase in NEP. The net effect for the region was a slight gain in ecosystem carbon storage over the 20 year period. This research highlights the potential importance of spatial variability in ecosystem responses to climate change in assessing the response of carbon storage in northern Alaska over the last two decades. ?? Springer 2005.

  17. Quantitative aspects of oxygen and carbon dioxide exchange ...

    African Journals Online (AJOL)

    Quantitative aspects of oxygen and carbon dioxide exchange through the ... ceratophthalmus (Crustacea: Decapoda) during rest and exercise in water and ... intersects zero time on the x-axis, indicating rapid gas exchange at the lung surface.

  18. Carbon cycling and gas exchange in soils

    International Nuclear Information System (INIS)

    Trumbore, S.E.

    1989-01-01

    This thesis summaries three independent projects, each of which describes a method which can be used to study the role of soils in regulating the atmospheric concentrations of CO 2 and other trace gases. The first chapter uses the distribution of natural and bomb produced radiocarbon in fractionated soil organic matter to quantify the turnover of carbon in soils. A comparison of 137 Cs and 14 C in the modern soil profiles indicates that carbon is transported vertically in the soil as dissolved organic material. The remainder of the work reported is concerned with the use of inert trace gases to explore the physical factors which control the seasonal to diel variability in the fluxes of CO 2 and other trace gases from soils. Chapter 2 introduces a method for measuring soil gas exchange rates in situ using sulfur hexafluoride as a purposeful tracer. The measurement method uses standard flux box technology, and includes simultaneous determination of the fluxes and soil atmosphere concentrations of CO 2 and CH 4 . In Chapter 3, the natural tracer 222 Rn is used as an inert analog for exchange both in the soils and forest canopy of the Amazon rain forest

  19. Sustaining the emerging carbon trading industry development: A business ecosystem approach of carbon traders

    International Nuclear Information System (INIS)

    Hu, Guangyu; Rong, Ke; Shi, Yongjiang; Yu, Jing

    2014-01-01

    This paper explores how carbon traders nurture the business ecosystem to sustain the emerging carbon trading industry development. We collected primary data from a multinational carbon trader and its ecosystem partners in China, through the construction of interviews and documentary. The research findings show the carbon trading industry has experienced four-stage evolution with different driving forces; the carbon trader attracted and organized ecosystem partners to facilitate the CDM project owners to create carbon credits and trade them; a systematic business ecosystems approach through the lens of Context, Cooperation and Configuration, initiated by carbon traders, has facilitated the industry development. Our findings also implicate to industrial practitioners and policymakers for sustaining the emerging industry development at both the current- and the post-Kyoto protocol periods. - Highlights: • The carbon trader is a catalyst to link CDM project owner and trading market in China • The evolution of carbon trading industry has four stages with various driving forces. • Nurturing business ecosystems facilitates the carbon trading industry development. • The ecosystem approach works via the lens of Context, Configuration and Cooperation. • The ecosystem approach implicates to carbon trading industry at the post-Kyoto era

  20. Net ecosystem CO2 exchange of a cutover peatland rehabilitated with a transplanted acrotelm

    International Nuclear Information System (INIS)

    Cagampan, J.P.; Waddington, J.M.

    2008-01-01

    Peatlands are an important long-term sink for atmospheric carbon dioxide (CO 2 ). The storage function of peatland ecosystems is significantly impacted by drainage and extraction processes, which can result in the release of significant amounts of CO 2 . This paper investigated the net ecosystem CO 2 exchange of a newly developed extraction-restoration technique that preserved the acrotelm and replaced it directly on the cut surface of the peatlands. The technique used a modified block-cut method with a back-hoe to create a drainage ditch. Actrotelm and surface vegetation were removed and placed to one side, and the peat was mechanically removed. The acrotelm was then transplanted over the older and more decomposed catotelm peat to create a trench topography in which the natural peatland was higher than the extracted zone. Air temperatures, water table levels, and volumetric moisture content levels were measured throughout the experiment. Measurements of CO 2 exchange were taken for the duration of a Spring and summer growing season at 12 sampling locations. Results of the experiment showed that the technique was successful in maintaining moisture conditions similar to those observed in the natural peatlands. However, the peatlands where the technique was used were still net emitters of CO 2 . Recommendations for improving the technique included using more care when removing upper peat layers; limiting surface damage; and reducing spaces and gaps between the transplanted acrotelm. 34 refs., 8 figs

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

    Science.gov (United States)

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

    2003-01-01

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

  2. Carbon source/sink function of a subtropical, eutrophic lake determined from an overall mass balance and a gas exchange and carbon burial balance

    International Nuclear Information System (INIS)

    Yang Hong; Xing Yangping; Xie Ping; Ni Leyi; Rong Kewen

    2008-01-01

    Although studies on carbon burial in lake sediments have shown that lakes are disproportionately important carbon sinks, many studies on gaseous carbon exchange across the water-air interface have demonstrated that lakes are supersaturated with CO 2 and CH 4 causing a net release of CO 2 and CH 4 to the atmosphere. In order to more accurately estimate the net carbon source/sink function of lake ecosystems, a more comprehensive carbon budget is needed, especially for gaseous carbon exchange across the water-air interface. Using two methods, overall mass balance and gas exchange and carbon burial balance, we assessed the carbon source/sink function of Lake Donghu, a subtropical, eutrophic lake, from April 2003 to March 2004. With the overall mass balance calculations, total carbon input was 14 905 t, total carbon output was 4950 t, and net carbon budget was +9955 t, suggesting that Lake Donghu was a great carbon sink. For the gas exchange and carbon burial balance, gaseous carbon (CO 2 and CH 4 ) emission across the water-air interface totaled 752 t while carbon burial in the lake sediment was 9477 t. The ratio of carbon emission into the atmosphere to carbon burial into the sediment was only 0.08. This low ratio indicates that Lake Donghu is a great carbon sink. Results showed good agreement between the two methods with both showing Lake Donghu to be a great carbon sink. This results from the high primary production of Lake Donghu, substantive allochthonous carbon inputs and intensive anthropogenic activity. Gaseous carbon emission accounted for about 15% of the total carbon output, indicating that the total output would be underestimated without including gaseous carbon exchange. - Due to high primary production, substantive allochthonous carbon inputs and intensive anthropogenic acitivity, subtropical, eutrophic Lake Donghu is a great carbon sink

  3. Effects of elevated CO2 and nitrogen deposition on ecosystem carbon fluxes on the Sanjiang plain wetland in Northeast China.

    Science.gov (United States)

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

    2013-01-01

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

  4. Effects of elevated CO2 and nitrogen deposition on ecosystem carbon fluxes on the Sanjiang plain wetland in Northeast China.

    Directory of Open Access Journals (Sweden)

    Jianbo Wang

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

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

    International Nuclear Information System (INIS)

    Yang, Qichun; Zhang, Xuesong

    2016-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Qichun [Joint Global Change Research Institute, Pacific Northwest National Lab, College Park, MD 20740 (United States); Zhang, Xuesong, E-mail: xuesong.zhang@pnnl.gov [Joint Global Change Research Institute, Pacific Northwest National Lab, College Park, MD 20740 (United States); Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, MI 48824 (United States)

    2016-11-01

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

  7. Effects of diffuse radiation on canopy gas exchange processes in a forest ecosystem

    Science.gov (United States)

    Knohl, Alexander; Baldocchi, Dennis D.

    2008-06-01

    Forest ecosystems across the globe show an increase in ecosystem carbon uptake efficiency under conditions with high fraction of diffuse radiation. Here, we combine eddy covariance flux measurements at a deciduous temperate forest in central Germany with canopy-scale modeling using the biophysical multilayer model CANVEG to investigate the impact of diffuse radiation on various canopy gas exchange processes and to elucidate the underlying mechanisms. Increasing diffuse radiation enhances canopy photosynthesis by redistributing the solar radiation load from light saturated sunlit leaves to nonsaturated shade leaves. Interactions with atmospheric vapor pressure deficit and reduced leaf respiration are only of minor importance to canopy photosynthesis. The response strength of carbon uptake to diffuse radiation depends on canopy characteristics such as leaf area index and leaf optical properties. Our model computations shows that both canopy photosynthesis and transpiration increase initially with diffuse fraction, but decrease after an optimum at a diffuse fraction of 0.45 due to reduction in global radiation. The initial increase in canopy photosynthesis exceeds the increase in transpiration, leading to a rise in water-use-efficiency. Our model predicts an increase in carbon isotope discrimination with water-use-efficiency resulting from differences in the leaf-to-air vapor pressure gradient and atmospheric vapor pressure deficit. This finding is in contrast to those predicted with simple big-leaf models that do not explicitly calculate leaf energy balance. At an annual scale, we estimate a decrease in annual carbon uptake for a potential increase in diffuse fraction, since diffuse fraction was beyond the optimum for 61% of the data.

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

    Science.gov (United States)

    Cifuentes, M.

    2012-12-01

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

  9. Seasonal Precipitation Variability Effects on Carbon Exchange in a Tropical Dry Forest of Northwest Mexico

    Science.gov (United States)

    Verduzco, V.; Garatuza-Payan, J.; Yépez, E. A.; Watts, C. J.; Rodriguez, J. C.; Robles-Morua, A.; Vivoni, E. R.

    2015-12-01

    The Tropical Dry Forest (TDF) cover a large area in tropical and subtropical regions in the Americas and its productivity is thought to have an important contribution to the atmospheric carbon fluxes. However, due to this ecosystem complex dynamics, our understanding about the mechanisms controlling net ecosystem exchange is limited. In this study, five years of continue water and carbon fluxes measurements from eddy covariance complemented with remotely sensed vegetation greenness were used to investigate the ecosystem carbon balance of a TDF in the North American Monsoon region under different hydro climatic conditions. We identified a large CO2 efflux at the start of the summer season that is strongly related to the preceding winter precipitation and greenness. Since this CO2 efflux occurs prior to vegetation green-up, we infer a predominant heterotrophic control owed to high decomposition of accumulated labile soil organic matter from prior growing season. Overall, ecosystem respiration has an important effect on the net ecosystem production over the year, but can be overwhelmed by the strength of the primary productivity during the monsoon season. Precipitation characteristics during the monsoon have significant controls on sustaining carbon fixation in the TDF ecosystem into the fall season. A threshold of ~350 to 400 mm of summer precipitation was identify to switch the annual carbon balance in the TDF ecosystem from a net source (+102 g C/m2/yr) to a net sink (-249 g C/m2/yr). This research points at the needs for understanding the potential effects of changing seasonal precipitation patterns on ecosystem dynamics and carbon sequestration in subtropical regions.

  10. Marine ecosystem modeling beyond the box: using GIS to study carbon fluxes in a coastal ecosystem.

    Science.gov (United States)

    Wijnbladh, Erik; Jönsson, Bror Fredrik; Kumblad, Linda

    2006-12-01

    Studies of carbon fluxes in marine ecosystems are often done by using box model approaches with basin size boxes, or highly resolved 3D models, and an emphasis on the pelagic component of the ecosystem. Those approaches work well in the ocean proper, but can give rise to considerable problems when applied to coastal systems, because of the scale of certain ecological niches and the fact that benthic organisms are the dominant functional group of the ecosystem. In addition, 3D models require an extensive modeling effort. In this project, an intermediate approach based on a high resolution (20x20 m) GIS data-grid has been developed for the coastal ecosystem in the Laxemar area (Baltic Sea, Sweden) based on a number of different site investigations. The model has been developed in the context of a safety assessment project for a proposed nuclear waste repository, in which the fate of hypothetically released radionuclides from the planned repository is estimated. The assessment project requires not only a good understanding of the ecosystem dynamics at the site, but also quantification of stocks and flows of matter in the system. The data-grid was then used to set up a carbon budget describing the spatial distribution of biomass, primary production, net ecosystem production and thus where carbon sinks and sources are located in the area. From these results, it was clear that there was a large variation in ecosystem characteristics within the basins and, on a larger scale, that the inner areas are net producing and the outer areas net respiring, even in shallow phytobenthic communities. Benthic processes had a similar or larger influence on carbon fluxes as advective processes in inner areas, whereas the opposite appears to be true in the outer basins. As many radionuclides are expected to follow the pathways of organic matter in the environment, these findings enhance our abilities to realistically describe and predict their fate in the ecosystem.

  11. Marine Ecosystem Modeling Beyond the Box: Using GIS to Study Carbon Fluxes in a Coastal Ecosystem

    International Nuclear Information System (INIS)

    Wijnbladh, Erik; Joensson, Bror Fredrik; Kumblad, Linda

    2006-01-01

    Studies of carbon fluxes in marine ecosystems are often done by using box model approaches with basin size boxes, or highly resolved 3D models, and an emphasis on the pelagic component of the ecosystem. Those approaches work well in the ocean proper, but can give rise to considerable problems when applied to coastal systems, because of the scale of certain ecological niches and the fact that benthic organisms are the dominant functional group of the ecosystem. In addition, 3D models require an extensive modeling effort. In this project, an intermediate approach based on a high resolution (20x20 m) GIS data-grid has been developed for the coastal ecosystem in the Laxemar area (Baltic Sea, Sweden) based on a number of different site investigations. The model has been developed in the context of a safety assessment project for a proposed nuclear waste repository, in which the fate of hypothetically released radionuclides from the planned repository is estimated. The assessment project requires not only a good understanding of the ecosystem dynamics at the site, but also quantification of stocks and flows of matter in the system. The data-grid was then used to set up a carbon budget describing the spatial distribution of biomass, primary production, net ecosystem production and thus where carbon sinks and sources are located in the area. From these results, it was clear that there was a large variation in ecosystem characteristics within the basins and, on a larger scale, that the inner areas are net producing and the outer areas net respiring, even in shallow phyto benthic communities. Benthic processes had a similar or larger influence on carbon fluxes as advective processes in inner areas, whereas the opposite appears to be true in the outer basins. As many radionuclides are expected to follow the pathways of organic matter in the environment, these findings enhance our abilities to realistically describe and predict their fate in the ecosystem

  12. Carbon dioxide exchange in the Arctic

    DEFF Research Database (Denmark)

    Ravn, Nynne Marie Rand

    in further warming. This PhD thesis addresses different aspects of climate change effects on C dynamics in the Arctic. The focus has been on i) changes in ER, age of the C sources, GEP and the net ecosystem exchange (NEE) in response to long- and short-term climate manipulations and ii) comparisons of CO2...... warming indications of emission of old C were observed, though most pronounced in the spring. I found no short-term response of summer warming on GEP at the low arctic heath and the measurements of NEE showed an increased emission of CO2 to the atmosphere during two snow free seasons. Increased winter......-term warming can cause GEP to increase and leave NEE unaltered. Hence, the risk of warming induced long-term positive feedback on climate change might be reduced. The new balance in the C cycling might though be sensitive to limitations of GEP due to for instance late snowmelt or herbivory....

  13. Soil Carbon Inputs and Ecosystem Respiration: a Field Priming Experiment in Arctic Coastal Tundra

    Science.gov (United States)

    Vaughn, L. S.; Zhu, B.; Bimueller, C.; Curtis, J. B.; Chafe, O.; Bill, M.; Abramoff, R. Z.; Torn, M. S.

    2016-12-01

    In Arctic ecosystems, climate change is expected to influence soil carbon stocks through changes in both plant carbon inputs and organic matter decomposition. This study addresses the potential for a priming effect, an interaction between these changes in which root-derived carbon inputs alter SOM decomposition rates via microbial biomass increases, co-metabolism of substrates, induced nitrogen limitation, or other possible mechanisms. The priming effect has been observed in numerous laboratory and greenhouse experiments, and is increasingly included in ecosystem models. Few studies, however, have evaluated the priming effect with in situ field manipulations. In a two-year field experiment in Barrow, Alaska, we tested for a priming effect under natural environmental variability. In September 2014 and August 2015, we added 6.1g of 13C-labeled glucose to 25cm diameter mesocosms, 15cm below the soil surface in the mineral soil layer. Over the following month, we quantified effects on the rate and temperature sensitivity of native (non-glucose) ecosystem respiration and GPP. Following the 2014 treatment, soil samples were collected at 1 and 3 weeks for microbial biomass carbon and 13C/12C analysis, and ion exchange membranes were buried for one week to assess nitrate and ammonium availability. In contrast with many laboratory incubation studies using soils from a broad range of ecosystems, we observed no significant priming effect. In spite of a clear signal of 13C-glucose decomposition in respired CO2 and microbial biomass, we detected no treatment effect on background ecosystem respiration or total microbial biomass carbon. Our findings suggest that glucose taken up by microbes was not used for production of additional SOM-decomposing enzymes, possibly due to stoichiometric limitations on enzyme production. To best inform models representing complex and dynamic ecosystems, this study calls for further research relating theory, laboratory findings, and field

  14. Carbon dynamics and ecosystem diversity of Amazonian peatlands

    Energy Technology Data Exchange (ETDEWEB)

    Laehteenoja, O.

    2011-07-01

    The overall aim was to initiate peatland research in Amazonia, which has been referred to as 'one of the large white spots on the global peatland map'. Specifically, the study was to clarify how common peat accumulation is on Amazonian floodplains, and how extensive and thick peat deposits can be encountered. Secondly, the intention was to study how rapidly Amazonian peatlands sequester carbon, and how much carbon they store and thirdly, to gain some understanding of the diversity of peatland ecosystem types and of the processes forming these ecosystems

  15. Response of CO2 exchange in a tussock tundra ecosystem to permafrost thaw and thermokarst development

    Science.gov (United States)

    Jason Vogel; Edward A.G. Schuur; Christian Trucco; Hanna. Lee

    2009-01-01

    Climate change in high latitudes can lead to permafrost thaw, which in ice-rich soils can result in ground subsidence, or thermokarst. In interior Alaska, we examined seasonal and annual ecosystem CO2 exchange using static and automatic chamber measurements in three areas of a moist acidic tundra ecosystem undergoing varying degrees of permafrost...

  16. Drivers of inter-annual variability in Net Ecosystem Exchange in a semi-arid savanna ecosystem, South Africa

    CSIR Research Space (South Africa)

    Archibald, SA

    2009-01-01

    Full Text Available and filling gaps in eddy-covariance data in semi-arid systems were developed. Net ecosystem exchange (NEE) in these systems occurs as pulses associated with rainfall events, a pattern not well-represented in current standard gap-filling procedures developed...

  17. The carbon balance of terrestrial ecosystems of China

    Directory of Open Access Journals (Sweden)

    Pilli R

    2009-05-01

    Full Text Available A comment is made on a recent letter published on Nature, in which different methodologies are applied to estimate the carbon balance of terrestrial ecosystems of China. A global carbon sink of 0.19-0.26 Pg per year is estimated during the 1980s and 1990s, and it is estimated that in 2006 terrestrial ecosystems have absorbed 28-37 per cent of global carbon emissions in China. Most of the carbon absorption is attributed to large-scale plantation made since the 1980s and shrub recovery. These results will certainly be valuable in the frame of the so-called “REDD” (Reducing Emissions from Deforestation forest Degradation in developing countries mechanism (UN convention on climate change UNFCCC.

  18. Net ecosystem exchange of CO2 and H2O fluxes from irrigated grain sorghum and maize in the Texas High Plains

    Science.gov (United States)

    Net ecosystem exchange (NEE) of carbon dioxide (CO2) and water vapor (H2O) fluxes from irrigated grain sorghum (Sorghum bicolor L. Moench) and maize (Zea mays L.) fields in the Texas High Plains were quantified using the eddy covariance (EC) technique during 2014-2016 growing seasons and examined in...

  19. Modeling and Predicting Carbon and Water Fluxes Using Data-Driven Techniques in a Forest Ecosystem

    Directory of Open Access Journals (Sweden)

    Xianming Dou

    2017-12-01

    Full Text Available Accurate estimation of carbon and water fluxes of forest ecosystems is of particular importance for addressing the problems originating from global environmental change, and providing helpful information about carbon and water content for analyzing and diagnosing past and future climate change. The main focus of the current work was to investigate the feasibility of four comparatively new methods, including generalized regression neural network, group method of data handling (GMDH, extreme learning machine and adaptive neuro-fuzzy inference system (ANFIS, for elucidating the carbon and water fluxes in a forest ecosystem. A comparison was made between these models and two widely used data-driven models, artificial neural network (ANN and support vector machine (SVM. All the models were evaluated based on the following statistical indices: coefficient of determination, Nash-Sutcliffe efficiency, root mean square error and mean absolute error. Results indicated that the data-driven models are capable of accounting for most variance in each flux with the limited meteorological variables. The ANN model provided the best estimates for gross primary productivity (GPP and net ecosystem exchange (NEE, while the ANFIS model achieved the best for ecosystem respiration (R, indicating that no single model was consistently superior to others for the carbon flux prediction. In addition, the GMDH model consistently produced somewhat worse results for all the carbon flux and evapotranspiration (ET estimations. On the whole, among the carbon and water fluxes, all the models produced similar highly satisfactory accuracy for GPP, R and ET fluxes, and did a reasonable job of reproducing the eddy covariance NEE. Based on these findings, it was concluded that these advanced models are promising alternatives to ANN and SVM for estimating the terrestrial carbon and water fluxes.

  20. Storage flux uncertainty impact on eddy covariance net ecosystem exchange measurements

    Science.gov (United States)

    Nicolini, Giacomo; Aubinet, Marc; Feigenwinter, Christian; Heinesch, Bernard; Lindroth, Anders; Mamadou, Ossénatou; Moderow, Uta; Mölder, Meelis; Montagnani, Leonardo; Rebmann, Corinna; Papale, Dario

    2017-04-01

    Complying with several assumption and simplifications, most of the carbon budget studies based on eddy covariance (EC) measurements, quantify the net ecosystem exchange (NEE) by summing the flux obtained by EC (Fc) and the storage flux (Sc). Sc is the rate of change of CO2, within the so called control volume below the EC measurement level, given by the difference in the instantaneous profiles of concentration at the beginning and end of the EC averaging period, divided by the averaging period. While cumulating over time led to a nullification of Sc, it can be significant at short time periods. The approaches used to estimate Sc fluxes largely vary, from measurements based only on a single sampling point (usually located at the EC measurement height) to measurements based on several sampling profiles distributed within the control volume. Furthermore, the number of sampling points within each profile vary, according to their height and the ecosystem typology. It follows that measurement accuracy increases with the sampling intensity within the control volume. In this work we use the experimental dataset collected during the ADVEX campaign in which Sc flux has been measured in three similar forest sites by the use of 5 sampling profiles (towers). Our main objective is to quantify the impact of Sc measurement uncertainty on NEE estimates. Results show that different methods may produce substantially different Sc flux estimates, with problematic consequences in case high frequency (half-hourly) data are needed for the analysis. However, the uncertainty on long-term estimates may be tolerate.

  1. Environmental variation, vegetation distribution, carbon dynamics and water/energy exchange at high latitudes

    Science.gov (United States)

    McGuire, A.D.; Wirth, C.; Apps, M.; Beringer, J.; Clein, J.; Epstein, H.; Kicklighter, D.W.; Bhatti, J.; Chapin, F. S.; De Groot, B.; Efremov, D.; Eugster, W.; Fukuda, M.; Gower, T.; Hinzman, L.; Huntley, B.; Jia, G.J.; Kasischke, E.; Melillo, J.; Romanovsky, V.; Shvidenko, A.; Vaganov, E.; Walker, D.

    2002-01-01

    The responses of high latitude ecosystems to global change involve complex interactions among environmental variables, vegetation distribution, carbon dynamics, and water and energy exchange. These responses may have important consequences for the earth system. In this study, we evaluated how vegetation distribution, carbon stocks and turnover, and water and energy exchange are related to environmental variation spanned by the network of the IGBP high latitude transects. While the most notable feature of the high latitude transects is that they generally span temperature gradients from southern to northern latitudes, there are substantial differences in temperature among the transects. Also, along each transect temperature co-varies with precipitation and photosynthetically active radiation, which are also variable among the transects. Both climate and disturbance interact to influence latitudinal patterns of vegetation and soil carbon storage among the transects, and vegetation distribution appears to interact with climate to determine exchanges of heat and moisture in high latitudes. Despite limitations imposed by the data we assembled, the analyses in this study have taken an important step toward clarifying the complexity of interactions among environmental variables, vegetation distribution, carbon stocks and turnover, and water and energy exchange in high latitude regions. This study reveals the need to conduct coordinated global change studies in high latitudes to further elucidate how interactions among climate, disturbance, and vegetation distribution influence carbon dynamics and water and energy exchange in high latitudes.

  2. Regional Ecosystem-Atmosphere CO2 Exchange Via Atmospheric Budgets

    Energy Technology Data Exchange (ETDEWEB)

    Davis, K J; Richardson, S J; Miles, N L

    2007-03-07

    Inversions of atmospheric CO2 mixing ratio measurements to determine CO2 sources and sinks are typically limited to coarse spatial and temporal resolution. This limits our ability to evaluate efforts to upscale chamber- and stand-level CO2 flux measurements to regional scales, where coherent climate and ecosystem mechanisms govern the carbon cycle. As a step towards the goal of implementing atmospheric budget or inversion methodology on a regional scale, a network of five relatively inexpensive CO2 mixing ratio measurement systems was deployed on towers in northern Wisconsin. Four systems were distributed on a circle of roughly 150-km radius, surrounding one centrally located system at the WLEF tower near Park Falls, WI. All measurements were taken at a height of 76 m AGL. The systems used single-cell infrared CO2 analyzers (Licor, model LI-820) rather than the siginificantly more costly two-cell models, and were calibrated every two hours using four samples known to within ± 0.2 ppm CO2. Tests prior to deployment in which the systems sampled the same air indicate the precision of the systems to be better than ± 0.3 ppm and the accuracy, based on the difference between the daily mean of one system and a co-located NOAA-ESRL system, is consistently better than ± 0.3 ppm. We demonstrate the utility of the network in two ways. We interpret regional CO2 differences using a Lagrangian parcel approach. The difference in the CO2 mixing ratios across the network is at least 2-3 ppm, which is large compared to the accuracy and precision of the systems. Fluxes estimated assuming Lagrangian parcel transport are of the same sign and magnitude as eddy-covariance flux measurements at the centrally-located WLEF tower. These results indicate that the network will be useful in a full inversion model. Second, we present a case study involving a frontal passage through the region. The progression of a front across the network is evident; changes as large as four ppm in one minute

  3. Modeling carbon and nitrogen biogeochemistry in forest ecosystems

    Science.gov (United States)

    Changsheng Li; Carl Trettin; Ge Sun; Steve McNulty; Klaus Butterbach-Bahl

    2005-01-01

    A forest biogeochemical model, Forest-DNDC, was developed to quantify carbon sequestration in and trace gas emissions from forest ecosystems. Forest-DNDC was constructed by integrating two existing moels, PnET and DNDC, with several new features including nitrification, forest litter layer, soil freezing and thawing etc, PnET is a forest physiological model predicting...

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

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Qichun; Zhang, Xuesong

    2016-11-01

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

  5. Geospatial variability of soil CO2-C exchange in the main terrestrial ecosystems of Keller Peninsula, Maritime Antarctica.

    Science.gov (United States)

    Thomazini, A; Francelino, M R; Pereira, A B; Schünemann, A L; Mendonça, E S; Almeida, P H A; Schaefer, C E G R

    2016-08-15

    Soils and vegetation play an important role in the carbon exchange in Maritime Antarctica but little is known on the spatial variability of carbon processes in Antarctic terrestrial environments. The objective of the current study was to investigate (i) the soil development and (ii) spatial variability of ecosystem respiration (ER), net ecosystem CO2 exchange (NEE), gross primary production (GPP), soil temperature (ST) and soil moisture (SM) under four distinct vegetation types and a bare soil in Keller Peninsula, King George Island, Maritime Antarctica, as follows: site 1: moss-turf community; site 2: moss-carpet community; site 3: phanerogamic antarctic community; site 4: moss-carpet community (predominantly colonized by Sanionia uncinata); site 5: bare soil. Soils were sampled at different layers. A regular 40-point (5×8 m) grid, with a minimum separation distance of 1m, was installed at each site to quantify the spatial variability of carbon exchange, soil moisture and temperature. Vegetation characteristics showed closer relation with soil development across the studied sites. ER reached 2.26μmolCO2m(-2)s(-1) in site 3, where ST was higher (7.53°C). A greater sink effect was revealed in site 4 (net uptake of 1.54μmolCO2m(-2)s(-1)) associated with higher SM (0.32m(3)m(-3)). Spherical models were fitted to describe all experimental semivariograms. Results indicate that ST and SM are directly related to the spatial variability of CO2 exchange. Heterogeneous vegetation patches showed smaller range values. Overall, poorly drained terrestrial ecosystems act as CO2 sink. Conversely, where ER is more pronounced, they are associated with intense soil carbon mineralization. The formations of new ice-free areas, depending on the local soil drainage condition, have an important effect on CO2 exchange. With increasing ice/snow melting, and resulting widespread waterlogging, increasing CO2 sink in terrestrial ecosystems is expected for Maritime Antarctica. Copyright

  6. A climate sensitive model of carbon transfer through atmosphere, vegetation and soil in managed forest ecosystems

    Science.gov (United States)

    Loustau, D.; Moreaux, V.; Bosc, A.; Trichet, P.; Kumari, J.; Rabemanantsoa, T.; Balesdent, J.; Jolivet, C.; Medlyn, B. E.; Cavaignac, S.; Nguyen-The, N.

    2012-12-01

    For predicting the future of the forest carbon cycle in forest ecosystems, it is necessary to account for both the climate and management impacts. Climate effects are significant not only at a short time scale but also at the temporal horizon of a forest life cycle e.g. through shift in atmospheric CO2 concentration, temperature and precipitation regimes induced by the enhanced greenhouse effect. Intensification of forest management concerns an increasing fraction of temperate and tropical forests and untouched forests represents only one third of the present forest area. Predicting tools are therefore needed to project climate and management impacts over the forest life cycle and understand the consequence of management on the forest ecosystem carbon cycle. This communication summarizes the structure, main components and properties of a carbon transfer model that describes the processes controlling the carbon cycle of managed forest ecosystems. The model, GO+, links three main components, (i) a module describing the vegetation-atmosphere mass and energy exchanges in 3D, (ii) a plant growth module and a (iii) soil carbon dynamics module in a consistent carbon scheme of transfer from atmosphere back into the atmosphere. It was calibrated and evaluated using observed data collected on coniferous and broadleaved forest stands. The model predicts the soil, water and energy balance of entire rotations of managed stands from the plantation to the final cut and according to a range of management alternatives. It accounts for the main soil and vegetation management operations such as soil preparation, understorey removal, thinnings and clearcutting. Including the available knowledge on the climatic sensitivity of biophysical and biogeochemical processes involved in atmospheric exchanges and carbon cycle of forest ecosystems, GO+ can produce long-term backward or forward simulations of forest carbon and water cycles under a range of climate and management scenarios. This

  7. Wind Erosion Caused by Land Use Changes Significantly Reduces Ecosystem Carbon Storage and Carbon Sequestration Potentials in Grassland

    Science.gov (United States)

    Li, P.; Chi, Y. G.; Wang, J.; Liu, L.

    2017-12-01

    Wind erosion exerts a fundamental influence on the biotic and abiotic processes associated with ecosystem carbon (C) cycle. However, how wind erosion under different land use scenarios will affect ecosystem C balance and its capacity for future C sequestration are poorly quantified. Here, we established an experiment in a temperate steppe in Inner Mongolia, and simulated different intensity of land uses: control, 50% of aboveground vegetation removal (50R), 100% vegetation removal (100R) and tillage (TI). We monitored lateral and vertical carbon flux components and soil characteristics from 2013 to 2016. Our study reveals three key findings relating to the driving factors, the magnitude and consequence of wind erosion on ecosystem C balance: (1) Frequency of heavy wind exerts a fundamental control over the severity of soil erosion, and its interaction with precipitation and vegetation characteristics explained 69% variation in erosion intensity. (2) With increases in land use intensity, the lateral C flux induced by wind erosion increased rapidly, equivalent to 33%, 86%, 111% and 183% of the net ecosystem exchange of the control site under control, 50R, 100R and TI sites, respectively. (3) After three years' treatment, erosion induced decrease in fine fractions led to 31%, 43%, 85% of permanent loss of C sequestration potential in the surface 5cm soil for 50R, 100R and TI sites. Overall, our study demonstrates that lateral C flux associated with wind erosion is too large to be ignored. The loss of C-enriched fine particles not only reduces current ecosystem C content, but also results in irreversible loss of future soil C sequestration potential. The dynamic soil characteristics need be considered when projecting future ecosystem C balance in aeolian landscape. We also propose that to maintain the sustainability of grassland ecosystems, land managers should focus on implementing appropriate land use rather than rely on subsequent managements on degraded soils.

  8. Banking carbon: A review of organic carbon storage and physical factors influencing retention in floodplains and riparian ecosystems

    Science.gov (United States)

    Nicholas A. Sutfin; Ellen E. Wohl; Kathleen A. Dwire

    2016-01-01

    Rivers are dynamic components of the terrestrial carbon cycle and provide important functions in ecosystem processes. Although rivers act as conveyers of carbon to the oceans, rivers also retain carbon within riparian ecosystems along floodplains, with potential for long-term (> 102 years) storage. Research in ecosystem processing emphasizes the...

  9. Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.

    Science.gov (United States)

    Dore, Sabina; Montes-Helu, Mario; Hart, Stephen C; Hungate, Bruce A; Koch, George W; Moon, John B; Finkral, Alex J; Kolb, Thomas E

    2012-10-01

    Carbon uptake by forests is a major sink in the global carbon cycle, helping buffer the rising concentration of CO 2 in the atmosphere, yet the potential for future carbon uptake by forests is uncertain. Climate warming and drought can reduce forest carbon uptake by reducing photosynthesis, increasing respiration, and by increasing the frequency and intensity of wildfires, leading to large releases of stored carbon. Five years of eddy covariance measurements in a ponderosa pine (Pinus ponderosa)-dominated ecosystem in northern Arizona showed that an intense wildfire that converted forest into sparse grassland shifted site carbon balance from sink to source for at least 15 years after burning. In contrast, recovery of carbon sink strength after thinning, a management practice used to reduce the likelihood of intense wildfires, was rapid. Comparisons between an undisturbed-control site and an experimentally thinned site showed that thinning reduced carbon sink strength only for the first two posttreatment years. In the third and fourth posttreatment years, annual carbon sink strength of the thinned site was higher than the undisturbed site because thinning reduced aridity and drought limitation to carbon uptake. As a result, annual maximum gross primary production occurred when temperature was 3 °C higher at the thinned site compared with the undisturbed site. The severe fire consistently reduced annual evapotranspiration (range of 12-30%), whereas effects of thinning were smaller and transient, and could not be detected in the fourth year after thinning. Our results show large and persistent effects of intense fire and minor and short-lived effects of thinning on southwestern ponderosa pine ecosystem carbon and water exchanges. © 2012 Blackwell Publishing Ltd.

  10. Multi-year net ecosystem carbon balance at a horticulture-extracted restored peatland

    Science.gov (United States)

    Nugent, Kelly; Strachan, Ian; Strack, Maria

    2017-04-01

    Restoration of previously extracted peatlands is essential to minimize the impact of drainage and peat removal. Best practices restoration methods have been developed that include ditch blocking, site leveling and reintroducing bog vegetation using the moss layer transfer technique. A long term goal of restoration is the return to a peat accumulating ecosystem. Bois-des-Bel is a cool-temperate bog, located in eastern Quebec, Canada, that was vacuum harvested until 1980 and restored in 1999. While several studies have used discrete (chamber) methods to determine the net carbon exchange from rewetted or restored peatlands, ours appears to be the first to have multiple complete years of net ecosystem carbon exchange from a restored northern peatland. An eddy covariance flux tower instrumented with a sonic anemometer and open-path CO2/H2O and CH4 analyzers was operated continuously over three years to produce a robust estimate of net carbon sequestration. Our initial results indicate that this restored peatland was a consistent moderate annual net sink for CO2, a moderate source of CH4 and had low losses of dissolved organic carbon compared to undisturbed northern latitude peatlands. Closed chambers combined with a fast response CO2/H2O/CH4 analyzer were used to investigate ecohydrological controls on net ecosystem exchange of CO2 (NEE) and CH4 flux from the restored fields and remnant ditches at the site. CH4 release was found to be an order of magnitude higher in the ditches compared to the fields, with non-vegetated ditch showing a greater range in flux compared to areas invaded by Typha latifolia. Bubble magnitude and count were highest in the non-vegetated ditch, followed by Typha plots and were undetectable in the restored fields. The latter may be partially attributed to the high cover of Eriophorum vaginatum in the restored fields, plants that have aerenchymous tissue, as well as a much deeper water table level. While the non-vegetated ditch areas were a steady

  11. Assessing ecosystem carbon stocks of Indonesia's threatened wetland forests

    Science.gov (United States)

    Warren, M.; Kauffman, B.; Murdiyarso, D.; Kurnianto, S.

    2011-12-01

    Over millennia, atmospheric carbon dioxide has been sequestered and stored in Indonesia's tropical wetland forests. Waterlogged conditions impede decomposition, allowing the formation of deep organic soils. These globally significant C pools are highly vulnerable to deforestation, degradation and climate change which can potentially switch their function as C sinks to long term sources of greenhouse gas (GHG) emissions. Also at risk are critical ecosystem services which sustain millions of people and the conservation of unique biological communities. The multiple benefits derived from wetland forest conservation makes them attractive for international C offset programs such as the proposed Reduced Emissions from Deforestation and Degradation (REDD+) mechanism. Yet, ecosystem C pools and fluxes in wetland forests remain poorly quantified. Significant knowledge gaps exist regarding how land use changes impact C dynamics in tropical wetlands, and very few studies have simultaneously assessed above- and belowground ecosystem C pools in Indonesia's freshwater peat swamps and mangroves. In addition, most of what is known about Indonesia's tropical wetland forests is derived from few geographic locations where long-standing research has focused, despite their broad spatial distribution. Here we present results from an extensive survey of ecosystem C stocks across several Indonesian wetland forests. Ecosystem C stocks were measured in freshwater peat swamp forests in West Papua, Central Kalimantan, West Kalimantan, and Sumatra. Carbon storage was also measured for mangrove forests in W. Papua, W. Kalimantan, and Sumatra. One overarching goal of this research is to support the development of REDD+ for tropical wetlands by informing technical issues related to carbon measuring, monitoring, and verification (MRV) and providing baseline data about the variation of ecosystem C storage across and within several Indonesian wetland forests.

  12. Precipitation as driver of carbon fluxes in 11 African ecosystems

    Directory of Open Access Journals (Sweden)

    L. Merbold

    2009-06-01

    Full Text Available This study reports carbon and water fluxes between the land surface and atmosphere in eleven different ecosystems types in Sub-Saharan Africa, as measured using eddy covariance (EC technology in the first two years of the CarboAfrica network operation. The ecosystems for which data were available ranged in mean annual rainfall from 320 mm (Sudan to 1150 mm (Republic of Congo and include a spectrum of vegetation types (or land cover (open savannas, woodlands, croplands and grasslands. Given the shortness of the record, the EC data were analysed across the network rather than longitudinally at sites, in order to understand the driving factors for ecosystem respiration and carbon assimilation, and to reveal the different water use strategies in these highly seasonal environments.

    Values for maximum net carbon assimilation rates (photosynthesis ranged from −12.5 μmol CO2 m−2 s−1 in a dry, open Millet cropland (C4-plants up to −48 μmol CO2 m−2 s−1 for a tropical moist grassland. Maximum carbon assimilation rates were highly correlated with mean annual rainfall (r2=0.74. Maximum photosynthetic uptake rates (Fpmax were positively related to satellite-derived fAPAR. Ecosystem respiration was dependent on temperature at all sites, and was additionally dependent on soil water content at sites receiving less than 1000 mm of rain per year. All included ecosystems dominated by C3-plants, showed a strong decrease in 30-min assimilation rates with increasing water vapour pressure deficit above 2.0 kPa.

  13. Complex terrain influences ecosystem carbon responses to temperature and precipitation

    Science.gov (United States)

    Reyes, W. M.; Epstein, H. E.; Li, X.; McGlynn, B. L.; Riveros-Iregui, D. A.; Emanuel, R. E.

    2017-08-01

    Terrestrial ecosystem responses to temperature and precipitation have major implications for the global carbon cycle. Case studies demonstrate that complex terrain, which accounts for more than 50% of Earth's land surface, can affect ecological processes associated with land-atmosphere carbon fluxes. However, no studies have addressed the role of complex terrain in mediating ecophysiological responses of land-atmosphere carbon fluxes to climate variables. We synthesized data from AmeriFlux towers and found that for sites in complex terrain, responses of ecosystem CO2 fluxes to temperature and precipitation are organized according to terrain slope and drainage area, variables associated with water and energy availability. Specifically, we found that for tower sites in complex terrain, mean topographic slope and drainage area surrounding the tower explained between 51% and 78% of site-to-site variation in the response of CO2 fluxes to temperature and precipitation depending on the time scale. We found no such organization among sites in flat terrain, even though their flux responses exhibited similar ranges. These results challenge prevailing conceptual framework in terrestrial ecosystem modeling that assumes that CO2 fluxes derive from vertical soil-plant-climate interactions. We conclude that the terrain in which ecosystems are situated can also have important influences on CO2 responses to temperature and precipitation. This work has implications for about 14% of the total land area of the conterminous U.S. This area is considered topographically complex and contributes to approximately 15% of gross ecosystem carbon production in the conterminous U.S.

  14. Insight into climate change from the carbon exchange of biocrusts utilizing non-rainfall water.

    Science.gov (United States)

    Ouyang, Hailong; Hu, Chunxiang

    2017-05-31

    Biocrusts are model ecosystems of global change studies. However, light and non-rainfall water (NRW) were previously few considered. Different biocrust types further aggravated the inconsistence. So carbon-exchange of biocrusts (cyanobacteria crusts-AC1/AC2; cyanolichen crust-LC1; chlorolichen crust-LC2; moss crust-MC) utilizing NRW at various temperatures and light-intensities were determined under simulated and insitu mesocosm experiments. Carbon input of all biocrusts were negatively correlated with experimental temperature under all light-intensity with saturated water and stronger light with equivalent NRW, but positively correlated with temperature under weak light with equivalent NRW. LCPs and R/Pg of AC1 were lowest, followed in turn by AC2, LC2 and MC. Thus AC1 had most opportunities to use NRW, and 2.5 °C warming did cause significant changes of carbon exchange. Structural equation models further revealed that air-temperature was most important for carbon-exchange of ACs, but equally important as NRW for LC2 and MC; positive influence of warming on carbon-input in ACs was much stronger than the latter. Therefore, temperature effect on biocrust carbon-input depends on both moisture and light. Meanwhile, the role of NRW, transitional states between ACs, and obvious carbon-fixation differences between lichen crusts should be fully considered in the future study of biocrusts responding to climate change.

  15. [Regional and global estimates of carbon stocks and carbon sequestration capacity in forest ecosystems: A review].

    Science.gov (United States)

    Liu, Wei-wei; Wang, Xiao-ke; Lu, Fei; Ouyang, Zhi-yun

    2015-09-01

    As a dominant part of terrestrial ecosystems, forest ecosystem plays an important role in absorbing atmospheric CO2 and global climate change mitigation. From the aspects of zonal climate and geographical distribution, the present carbon stocks and carbon sequestration capacity of forest ecosystem were comprehensively examined based on the review of the latest literatures. The influences of land use change on forest carbon sequestration were analyzed, and factors that leading to the uncertainty of carbon sequestration assessment in forest ecosystem were also discussed. It was estimated that the current forest carbon stock was in the range of 652 to 927 Pg C and the carbon sequestration capacity was approximately 4.02 Pg C · a(-1). In terms of zonal climate, the carbon stock and carbon sequestration capacity of tropical forest were the maximum, about 471 Pg C and 1.02-1.3 Pg C · a(-1) respectively; then the carbon stock of boreal forest was about 272 Pg C, while its carbon sequestration capacity was the minimum, approximately 0.5 Pg C · a(-1); for temperate forest, the carbon stock was minimal, around 113 to 159 Pg C and its carbon sequestration capacity was 0.8 Pg C · a(-1). From the aspect of geographical distribution, the carbon stock of forest ecosystem in South America was the largest (187.7-290 Pg C), then followed by European (162.6 Pg C), North America (106.7 Pg C), Africa (98.2 Pg C) and Asia (74.5 Pg C), and Oceania (21.7 Pg C). In addition, carbon sequestration capacity of regional forest ecosystem was summed up as listed below: Tropical South America forest was the maximum (1276 Tg C · a(-1)), then were Tropical Africa (753 Tg C · a(-1)), North America (248 Tg C · a(-1)) and European (239 Tg C · a(-1)), and East Asia (98.8-136.5 Tg C · a(-1)) was minimum. To further reduce the uncertainty in the estimations of the carbon stock and carbon sequestration capacity of forest ecosystem, comprehensive application of long-term observation, inventories

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

    Science.gov (United States)

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

    2009-11-17

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

  17. Carbon and energy fluxes in cropland ecosystems: a model-data comparison

    Energy Technology Data Exchange (ETDEWEB)

    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.

  18. Carbon and energy fluxes in cropland ecosystems: a model-data comparison

    Science.gov (United States)

    Lokupitiya, E.; Denning, A. Scott; 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.C.; El Maayar, M.; Fischer, M.; Grant, R.; Hollinger, D.; Izaurralde, C.; Jain, A.; Kucharik, C.J.; 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, Christina; Torn, M.S.; Verbeeck, Hans; Verma, S.B.; Xue, Y.

    2016-01-01

    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.

  19. Testing the performance of a Dynamic Global Ecosystem Model: Water balance, carbon balance, and vegetation structure

    Science.gov (United States)

    Kucharik, Christopher J.; Foley, Jonathan A.; Delire, Christine; Fisher, Veronica A.; Coe, Michael T.; Lenters, John D.; Young-Molling, Christine; Ramankutty, Navin; Norman, John M.; Gower, Stith T.

    2000-09-01

    While a new class of Dynamic Global Ecosystem Models (DGEMs) has emerged in the past few years as an important tool for describing global biogeochemical cycles and atmosphere-biosphere interactions, these models are still largely untested. Here we analyze the behavior of a new DGEM and compare the results to global-scale observations of water balance, carbon balance, and vegetation structure. In this study, we use version 2 of the Integrated Biosphere Simulator (IBIS), which includes several major improvements and additions to the prototype model developed by Foley et al. [1996]. IBIS is designed to be a comprehensive model of the terrestrial biosphere; the model represents a wide range of processes, including land surface physics, canopy physiology, plant phenology, vegetation dynamics and competition, and carbon and nutrient cycling. The model generates global simulations of the surface water balance (e.g., runoff), the terrestrial carbon balance (e.g., net primary production, net ecosystem exchange, soil carbon, aboveground and belowground litter, and soil CO2 fluxes), and vegetation structure (e.g., biomass, leaf area index, and vegetation composition). In order to test the performance of the model, we have assembled a wide range of continental and global-scale data, including measurements of river discharge, net primary production, vegetation structure, root biomass, soil carbon, litter carbon, and soil CO2 flux. Using these field data and model results for the contemporary biosphere (1965-1994), our evaluation shows that simulated patterns of runoff, NPP, biomass, leaf area index, soil carbon, and total soil CO2 flux agree reasonably well with measurements that have been compiled from numerous ecosystems. These results also compare favorably to other global model results.

  20. Can land degradation drive differences in the C exchange of two similar semiarid ecosystems?

    Science.gov (United States)

    López-Ballesteros, Ana; Oyonarte, Cecilio; Kowalski, Andrew S.; Serrano-Ortiz, Penélope; Sánchez-Cañete, Enrique P.; Rosario Moya, M.; Domingo, Francisco

    2018-01-01

    Currently, drylands occupy more than one-third of the global terrestrial surface and are recognized as areas vulnerable to land degradation. The concept of land degradation stems from the loss of an ecosystem's biological productivity due to long-term loss of natural vegetation or depletion of soil nutrients. Drylands' key role in the global carbon (C) balance has been recently demonstrated, but the effects of land degradation on C sequestration by these ecosystems still need to be investigated. In the present study, we compared net C and water vapor fluxes, together with satellite, meteorological and vadose zone (CO2, water content and temperature) measurements, between two nearby (˜ 23 km) experimental sites representing natural (i.e., site of reference) and degraded grazed semiarid grasslands. We utilized data acquired over 6 years from two eddy covariance stations located in southeastern Spain with highly variable precipitation magnitude and distribution. Results show a striking difference in the annual C balances with an average net CO2 exchange of 196 ± 40 (C release) and -23 ± 2 g C m-2 yr-1 (C fixation) for the degraded and natural sites, respectively. At the seasonal scale, differing patterns in net CO2 fluxes were detected over both growing and dry seasons. As expected, during the growing seasons, greater net C uptake over longer periods was observed at the natural site. However, a much greater net C release, probably derived from subterranean ventilation, was measured at the degraded site during drought periods. After subtracting the nonbiological CO2 flux from net CO2 exchange, flux partitioning results point out that, during the 6 years of study, gross primary production, ecosystem respiration and water use efficiency were, on average, 9, 2 and 10 times higher, respectively, at the natural site versus the degraded site. We also tested differences in all monitored meteorological and soil variables and CO2 at 1.50 m belowground was the variable

  1. Initial shifts in nitrogen impact on ecosystem carbon fluxes in an alpine meadow: patterns and causes

    Science.gov (United States)

    Song, Bing; Sun, Jian; Zhou, Qingping; Zong, Ning; Li, Linghao; Niu, Shuli

    2017-09-01

    Increases in nitrogen (N) deposition can greatly stimulate ecosystem net carbon (C) sequestration through positive N-induced effects on plant productivity. However, how net ecosystem CO2 exchange (NEE) and its components respond to different N addition rates remains unclear. Using an N addition gradient experiment (six levels: 0, 2, 4, 8, 16, 32 gN m-2 yr-1) in an alpine meadow on the Qinghai-Tibetan Plateau, we explored the responses of different ecosystem C fluxes to an N addition gradient and revealed mechanisms underlying the dynamic responses. Results showed that NEE, ecosystem respiration (ER), and gross ecosystem production (GEP) all increased linearly with N addition rates in the first year of treatment but shifted to N saturation responses in the second year with the highest NEE (-7.77 ± 0.48 µmol m-2 s-1) occurring under an N addition rate of 8 gN m-2 yr-1. The saturation responses of NEE and GEP were caused by N-induced accumulation of standing litter, which limited light availability for plant growth under high N addition. The saturation response of ER was mainly due to an N-induced saturation response of aboveground plant respiration and decreasing soil microbial respiration along the N addition gradient, while decreases in soil microbial respiration under high N addition were caused by N-induced reductions in soil pH. We also found that various components of ER, including aboveground plant respiration, soil respiration, root respiration, and microbial respiration, responded differentially to the N addition gradient. These results reveal temporal dynamics of N impacts and the rapid shift in ecosystem C fluxes from N limitation to N saturation. Our findings bring evidence of short-term initial shifts in responses of ecosystem C fluxes to increases in N deposition, which should be considered when predicting long-term changes in ecosystem net C sequestration.

  2. Linkages of plant stoichiometry to ecosystem production and carbon fluxes with increasing nitrogen inputs in an alpine steppe.

    Science.gov (United States)

    Peng, Yunfeng; Li, Fei; Zhou, Guoying; Fang, Kai; Zhang, Dianye; Li, Changbin; Yang, Guibiao; Wang, Guanqin; Wang, Jun; Yang, Yuanhe

    2017-12-01

    Unprecedented levels of nitrogen (N) have entered terrestrial ecosystems over the past century, which substantially influences the carbon (C) exchange between the atmosphere and biosphere. Temperature and moisture are generally regarded as the major controllers over the N effects on ecosystem C uptake and release. N-phosphorous (P) stoichiometry regulates the growth and metabolisms of plants and soil organisms, thereby affecting many ecosystem C processes. However, it remains unclear how the N-induced shift in the plant N:P ratio affects ecosystem production and C fluxes and its relative importance. We conducted a field manipulative experiment with eight N addition levels in a Tibetan alpine steppe and assessed the influences of N on aboveground net primary production (ANPP), gross ecosystem productivity (GEP), ecosystem respiration (ER), and net ecosystem exchange (NEE); we used linear mixed-effects models to further determine the relative contributions of various factors to the N-induced changes in these parameters. Our results showed that the ANPP, GEP, ER, and NEE all exhibited nonlinear responses to increasing N additions. Further analysis demonstrated that the plant N:P ratio played a dominate role in shaping these C exchange processes. There was a positive relationship between the N-induced changes in ANPP (ΔANPP) and the plant N:P ratio (ΔN:P), whereas the ΔGEP, ΔER, and ΔNEE exhibited quadratic correlations with the ΔN:P. In contrast, soil temperature and moisture were only secondary predictors for the changes in ecosystem production and C fluxes along the N addition gradient. These findings highlight the importance of plant N:P ratio in regulating ecosystem C exchange, which is crucial for improving our understanding of C cycles under the scenarios of global N enrichment. © 2017 John Wiley & Sons Ltd.

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

    Science.gov (United States)

    Chen, Min

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

  4. Potential Applications of Gosat Based Carbon Budget Products to Refine Terrestrial Ecosystem Model

    Science.gov (United States)

    Kondo, M.; Ichii, K.

    2011-12-01

    Estimation of carbon exchange in terrestrial ecosystem associates with difficulties due to complex entanglement of physical and biological processes: thus, the net ecosystem productivity (NEP) estimated from simulation often differs among process-based terrestrial ecosystem models. In addition to complexity of the system, validation can only be conducted in a point scale since reliable observation is only available from ground observations. With a lack of large spatial data, extension of model simulation to a global scale results in significant uncertainty in the future carbon balance and climate change. Greenhouse gases Observing SATellite (GOSAT), launched by the Japanese space agency (JAXA) in January, 2009, is the 1st operational satellite promised to deliver the net land-atmosphere carbon budget to the terrestrial biosphere research community. Using that information, the model reproducibility of carbon budget is expected to improve: hence, gives a better estimation of the future climate change. This initial analysis is to seek and evaluate the potential applications of GOSAT observation toward the sophistication of terrestrial ecosystem model. The present study was conducted in two processes: site-based analysis using eddy covariance observation data to assess the potential use of terrestrial carbon fluxes (GPP, RE, and NEP) to refine the model, and extension of the point scale analysis to spatial using Carbon Tracker product as a prototype of GOSAT product. In the first phase of the experiment, it was verified that an optimization routine adapted to a terrestrial model, Biome-BGC, yielded the improved result with respect to eddy covariance observation data from AsiaFlux Network. Spatial data sets used in the second phase were consists of GPP from empirical algorithm (e.g. support vector machine), NEP from Carbon Tracker, and RE from the combination of these. These spatial carbon flux estimations was used to refine the model applying the exactly same

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

    Science.gov (United States)

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

    2012-05-01

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

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

    Science.gov (United States)

    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

  7. Cyclic occurrence of fire and its role in carbon dynamics along an edaphic moisture gradient in longleaf pine ecosystems.

    Directory of Open Access Journals (Sweden)

    Andrew Whelan

    Full Text Available Fire regulates the structure and function of savanna ecosystems, yet we lack understanding of how cyclic fire affects savanna carbon dynamics. Furthermore, it is largely unknown how predicted changes in climate may impact the interaction between fire and carbon cycling in these ecosystems. This study utilizes a novel combination of prescribed fire, eddy covariance (EC and statistical techniques to investigate carbon dynamics in frequently burned longleaf pine savannas along a gradient of soil moisture availability (mesic, intermediate and xeric. This research approach allowed us to investigate the complex interactions between carbon exchange and cyclic fire along the ecological amplitude of longleaf pine. Over three years of EC measurement of net ecosystem exchange (NEE show that the mesic site was a net carbon sink (NEE = -2.48 tonnes C ha(-1, while intermediate and xeric sites were net carbon sources (NEE = 1.57 and 1.46 tonnes C ha(-1, respectively, but when carbon losses due to fuel consumption were taken into account, all three sites were carbon sources (10.78, 7.95 and 9.69 tonnes C ha(-1 at the mesic, intermediate and xeric sites, respectively. Nonetheless, rates of NEE returned to pre-fire levels 1-2 months following fire. Consumption of leaf area by prescribed fire was associated with reduction in NEE post-fire, and the system quickly recovered its carbon uptake capacity 30-60 days post fire. While losses due to fire affected carbon balances on short time scales (instantaneous to a few months, drought conditions over the final two years of the study were a more important driver of net carbon loss on yearly to multi-year time scales. However, longer-term observations over greater environmental variability and additional fire cycles would help to more precisely examine interactions between fire and climate and make future predictions about carbon dynamics in these systems.

  8. Moisture effects on temperature sensitivity of CO2 exchange in a subarctic heath ecosystem

    DEFF Research Database (Denmark)

    Illeris, Lotte; Christensen, TR; Mastepanov, M

    2004-01-01

    Carbon fluxes between natural ecosystems and the atmosphere have received increased attention in recent years due to the impact they have on climate. In order to investigate independently how soil moisture and temperature control carbon fluxes into and out of a dry subarctic dwarf shrub dominated...

  9. Carbon and Water Exchanges in a Chronosequence of Temperate White Pine Forest

    Science.gov (United States)

    Arain, M.; Restrepo, N.; Pejam, M.; Khomik, M.

    2003-12-01

    Quantification of carbon sink or source strengths of temperate forest ecosystems, growing in northern mid-latitudes, is essential to resolve uncertainties in carbon balance of the world's terrestrial ecosystems. Long-term flux measurements are needed to quantify seasonal and annual variability of carbon and water exchanges from these ecosystems and to relate the variability to environmental and physiological factors. Such long-term measurements are of particular interest for different stand developmental stages. An understanding of environmental control factors is necessary to improve predictive capabilities of terrestrial carbon and water cycles. A long-term year-round measurement program has been initiated to observe energy, water vapour, and carbon dioxide fluxes in a chronosequence of white pine (Pinus Strobus) forests in southeastern Canada. White pine is an important species in the North American landscape because of its ability to adapt to dry environments. White pine efficiently grows on coarse and sandy soils, where other deciduous and conifer species cannot survive. Generally, it is the first woody species to flourish after disturbances such as fire and clearing. The climate at the study site is temperate, with a mean annual temperature of 8 degree C and a mean annual precipitation of about 800 mm. The growing season is one of the longest in Canada, with at least 150 frost-free days. Measurements at the site began in June 2002 and are continuing at present. Flux measurements at the 60 year old stand are being made using a close-path eddy covariance (EC) system, while fluxes at the three younger stands (30, 15 and 1 year old) are being measured over 10 to 20 day periods using a roving open-path EC system Soil respiration is being measured every 2-weeks across 50-m transects at all four sites using a mobile chamber system (LI-COR 6400). The mature stand was a sink of carbon with annual NEP value of 140 g C m-2 from June 2002 to May 2003. Gross ecosystem

  10. Global variation in the cost of increasing ecosystem carbon

    Science.gov (United States)

    Larjavaara, Markku; Kanninen, Markku; Gordillo, Harold; Koskinen, Joni; Kukkonen, Markus; Käyhkö, Niina; Larson, Anne M.; Wunder, Sven

    2018-01-01

    Slowing the reduction, or increasing the accumulation, of organic carbon stored in biomass and soils has been suggested as a potentially rapid and cost-effective method to reduce the rate of atmospheric carbon increase1. The costs of mitigating climate change by increasing ecosystem carbon relative to the baseline or business-as-usual scenario has been quantified in numerous studies, but results have been contradictory, as both methodological issues and substance differences cause variability2. Here we show, based on 77 standardized face-to-face interviews of local experts with the best possible knowledge of local land-use economics and sociopolitical context in ten landscapes around the globe, that the estimated cost of increasing ecosystem carbon varied vastly and was perceived to be 16-27 times cheaper in two Indonesian landscapes dominated by peatlands compared with the average of the eight other landscapes. Hence, if reducing emissions from deforestation and forest degradation (REDD+) and other land-use mitigation efforts are to be distributed evenly across forested countries, for example, for the sake of international equity, their overall effectiveness would be dramatically lower than for a cost-minimizing distribution.

  11. Effects of Recent Regional Soil Moisture Variability on Global Net Ecosystem CO2 Exchange

    Science.gov (United States)

    Jones, L. A.; Madani, N.; Kimball, J. S.; Reichle, R. H.; Colliander, A.

    2017-12-01

    Soil moisture exerts a major regional control on the inter-annual variability of the global land sink for atmospheric CO2. In semi-arid regions, annual biomass production is closely coupled to variability in soil moisture availability, while in cold-season-affected regions, summer drought offsets the effects of advancing spring phenology. Availability of satellite solar-induced fluorescence (SIF) observations and improvements in atmospheric inversions has led to unprecedented ability to monitor atmospheric sink strength. However, discrepancies still exist between such top-down estimates as atmospheric inversion and bottom-up process and satellite driven models, indicating that relative strength, mechanisms, and interaction of driving factors remain poorly understood. We use soil moisture fields informed by Soil Moisture Active Passive Mission (SMAP) observations to compare recent (2015-2017) and historic (2000-2014) variability in net ecosystem land-atmosphere CO2 exchange (NEE). The operational SMAP Level 4 Carbon (L4C) product relates ground-based flux tower measurements to other bottom-up and global top-down estimates to underlying soil moisture and other driving conditions using data-assimilation-based SMAP Level 4 Soil Moisture (L4SM). Droughts in coastal Brazil, South Africa, Eastern Africa, and an anomalous wet period in Eastern Australia were observed by L4C. A seasonal seesaw pattern of below-normal sink strength at high latitudes relative to slightly above-normal sink strength for mid-latitudes was also observed. Whereas SMAP-based soil moisture is relatively informative for short-term temporal variability, soil moisture biases that vary in space and with season constrain the ability of the L4C estimates to accurately resolve NEE. Such biases might be caused by irrigation and plant-accessible ground-water. Nevertheless, SMAP L4C daily NEE estimates connect top-down estimates to variability of effective driving factors for accurate estimates of regional

  12. Kinetics of the exchange of oxygen between carbon dioxide and carbonate in aqueous solution

    International Nuclear Information System (INIS)

    Tu, C.K.; Silverman, D.N.

    1975-01-01

    A kinetic analysis of the exchange of oxygen between carbon dioxide and carbonate ion in alkaline, aqueous solutions is presented. The exchange was observed by placing 18 O-labeled carbonate, not enriched in 13 C, into solution with 13 C-enriched carbonate, not enriched in 18 O. The rate of depletion of 18 O from the 12 C-containing species and the rate of appearance of 18 O in the 13 C-containing species was measured by mass spectrometry. From these data, the second-order rate constant for the reaction between carbon dioxide and carbonate which results in the exchange of oxygen at 25 0 is 114 +- 11 M -1 sec -1 . It is emphasized that this exchange of oxygen between species of CO 2 in solution must be recognized in studies using 18 O labels to determine the fate of CO 2 in biochemical and physiological processes. (auth)

  13. Strong tidal modulation of net ecosystem exchange in a salt marsh in North Inlet, South Carolina

    Science.gov (United States)

    O'Halloran, T. L.; Smith, E. M.; Bogoev, I.

    2017-12-01

    Along the southeastern US, intertidal salt marshes represent a critical habitat at the interface of the terrestrial and marine environments and perform a variety of ecological functions and services that make them of great economic importance for coastal communities They provide essential fish and shellfish habitat, with a majority of all commercially- and recreationally important fish species being dependent on intertidal marsh habitat during some portion of their life cycle. The penaeid shrimp industry, South Carolina's most economically important fishery, would cease to exist without the critical nursery function provided by intertidal salt marshes. Smooth cordgrass (Spartina alterniflora) is a keystone species in the high salinity marshes of the southeastern U.S., and its functioning is essential to the health and survival of salt marshes under rising sea levels. To better quantify and facilitate prediction of future salt marsh productivity, in May of 2017, we established a new integrated eddy covariance tower system to measure the net ecosystem exchange of carbon in a salt marsh in coastal South Carolina. The tower site is co-located with long-term, ongoing measurements as part of the North Inlet-Winyah Bay National Estuarine Research Reserve (NI-WB NERR). Current sampling conducted within the eddy flux footprint includes: annual measures of the vegetation community at the time of peak biomass; bi-monthly measures of sediment elevation at Sediment Elevation Tables (SETs) located at the upper and lower ends of the flux footprint; monthly sediment porewater salinity and nutrient (ammonium, orthophosphate) and sulfide concentrations; and biannual sediment elevation surveys by RTK-GPS. A suite of water quality measurements are made every 15 minutes in the main creek that floods the marsh platform in the flux footprint. Here we present our first six months of observations investigating the abiotic drivers of productivity on daily (intratidal) to monthly timescales

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

    Science.gov (United States)

    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

  15. A terrestrial ecosystem model (SOLVEG) coupled with atmospheric gas and aerosol exchange processes

    International Nuclear Information System (INIS)

    Katata, Genki; Ota, Masakazu

    2017-01-01

    In order to predict the impact of atmospheric pollutants (gases and aerosols) to the terrestrial ecosystem, new schemes for calculating the processes of dry deposition of gases and aerosols, and water and carbon cycles in terrestrial ecosystems were implemented in the one-dimensional atmosphere-SOiL-VEGetation model, SOLVEG. We made performance tests at various vegetation areas to validate the newly developed schemes. In this report, the detail in each modeled process is described with an instruction how to use the modified SOLVEG. The framework of 'terrestrial ecosystem model' was developed for investigation of a change in water, energy, and carbon cycles associated with global warming and air pollution and its impact on terrestrial ecosystems. (author)

  16. Spatiotemporal variability in carbon exchange fluxes across the Sahel

    DEFF Research Database (Denmark)

    Tagesson, Håkan Torbern; Fensholt, Rasmus; Cappelaere, Bernard

    2016-01-01

    for semi-arid ecosystems. We have synthesized data on the land-atmosphere exchange of CO2 measured with the eddy covariance technique from the six existing sites across the Sahel, one of the largest semi-arid regions in the world. The overall aim of the study is to analyse and quantify the spatiotemporal...... variability in these fluxes and to analyse to which degree spatiotemporal variation can be explained by hydrological, climatic, edaphic and vegetation variables. All ecosystems were C sinks (average ± total error -162 ± 48 g C m-2 y-1), but were smaller when strongly impacted by anthropogenic influences...

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

    Science.gov (United States)

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

    2011-12-01

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

  18. A Constructed Freshwater Wetland Shows Signs of Declining Net Ecosystem Exchange

    Science.gov (United States)

    Anderson, F. E.; Bergamaschi, B. A.; Windham-Myers, L.; Byrd, K. B.; Drexler, J. Z.; Fujii, R.

    2014-12-01

    The USGS constructed a freshwater-wetland complex on Twitchell Island in the Sacramento-San Joaquin Delta (Delta), California, USA, in 1997 and maintained it until 2012 to investigate strategies for biomass accretion and reduction of oxidative soil loss. We studied an area of the wetland complex covered mainly by dense patches of hardstem bulrush (Schoenoplectus acutus) and cattails (Typha spp.), with smaller areas of floating and submerged vegetation, that was maintained at an average depth of 55 cm. Using eddy covariance measurements of carbon and energy fluxes, we found that the combination of water management and the region's Mediterranean climate created conditions where peak growing season daily means of net ecosystem exchange (NEE) reached -45 gCO2 m-2 d-1 and averaged around -30 gCO2 m-2 d-1 between 2002 through 2004. However, when measurements resumed in 2010, NEE rates were a fraction of the rates previously measured, approximately -6 gCO2 m-2 d-1. Interestingly, NEE rates in 2011 doubled compared to 2010 (-13 gCO2 m-2 d-1). Methane fluxes, collected in 2010 to assess a complete atmospheric carbon budget, were positive throughout the year, with daily mean flux values ranging from 50 to 300 mg CH4 m-2 d-1. As a result, methane flux reduced NEE values by approximately one-third, and when the global warming potential was considered, the wetland became a net global warming potential source. We found that carbon cycling in a constructed wetland is complex and can change over annual and decadal timescales. We investigated possible reasons for differences between flux measurements from 2002 to 2004 and those from 2010 and 2011: (1) changes in methodology, (2) differences in weather conditions, (3) differences in gross primary productivity relative to respiration rates, and (4) the amount of living plant tissue relative to brown accumulations of senesced plant litter. We hypothesize that large mats of senesced material within the flux footprint could have

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

    Science.gov (United States)

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

    2016-04-01

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

  20. The exchange of acetaldehyde between plants and the atmosphere: Stable carbon isotope and flux measurements

    Science.gov (United States)

    Jardine, Kolby Jeremiah

    The exchange of acetaldehyde between plant canopies and the atmosphere may significantly influence regional atmospheric chemistry and plant metabolism. While plants are known to both produce and consume acetaldehyde, the exchange of this compound with forested ecosystems is complicated by physical, biological, and chemical processes that range from being poorly understood to completely unknown. This precludes a quantitative understanding of acetaldehyde exchange rates between the atmosphere and the biosphere. In this study, the processes controlling the exchange of acetaldehyde with plant canopies was investigated using concentration, flux, and natural abundance 13C measurements of gas phase acetaldehyde from individual plants, soils, and entire ecosystems. Although previously only considered important in anoxic tissues, it was discovered that acetaldehyde is produced and consumed in leaves through ethanolic fermentation coupled to the pyruvate dehydrogenase bypass system under normal aerobic conditions. These coupled pathways determine the acetaldehyde compensation point, a major factor controlling its exchange with the atmosphere. Carbon isotope analysis suggests a new pathway for acetaldehyde production from plants under stress involving the peroxidation of membrane fatty acids. This pathway may be a major source of acetaldehyde to the atmosphere from plants under biotic and abiotic stresses. Plant stomata were found to be the dominant pathway for the exchange of acetaldehyde with the atmosphere with stomatal conductance influencing both emission and uptake fluxes. In addition, increasing temperature and solar radiation was found to increase the compensation point by increasing the rates of acetaldehyde production relative to consumption. Under ambient conditions, bare soil was neutral to the exchange of acetaldehyde while senescing and decaying leaves were found to be strong source of acetaldehyde to the atmosphere due to increased decomposition processes and

  1. Ecosystem Carbon Emissions from 2015 Forest Fires in Interior Alaska

    Science.gov (United States)

    Potter, Christopher S.

    2018-01-01

    In the summer of 2015, hundreds of wildfires burned across the state of Alaska, and consumed more than 1.6 million ha of boreal forest and wetlands in the Yukon-Koyukuk region. Mapping of 113 large wildfires using Landsat satellite images from before and after 2015 indicated that nearly 60% of this area was burned at moderate-to-high severity levels. Field measurements near the town of Tanana on the Yukon River were carried out in July of 2017 in both unburned and 2015 burned forested areas (nearly adjacent to one-another) to visually verify locations of different Landsat burn severity classes (low, moderate, or high). Results: Field measurements indicated that the loss of surface organic layers in boreal ecosystem fires is a major factor determining post-fire soil temperature changes, depth of thawing, and carbon losses from the mineral topsoil layer. Measurements in forest sites showed that soil temperature profiles to 30 cm depth at burned forest sites increased by an average of 8o - 10o C compared to unburned forest sites. Sampling and laboratory analysis indicated a 65% reduction in soil carbon content and a 58% reduction in soil nitrogen content in severely burned sample sites compared to soil mineral samples from nearby unburned spruce forests. Conclusions: Combined with nearly unprecedented forest areas severely burned in the Interior region of Alaska in 2015, total ecosystem fire emission of carbon to the atmosphere exceeded most previous estimates for the state.

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

    Science.gov (United States)

    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

  3. Estimation of Carbon Flux of Forest Ecosystem over Qilian Mountains by BIOME-BGC Model

    Science.gov (United States)

    Yan, Min; Tian, Xin; Li, Zengyuan; Chen, Erxue; Li, Chunmei

    2014-11-01

    The gross primary production (GPP) and net ecosystem exchange (NEE) are important indicators for carbon fluxes. This study aims at evaluating the forest GPP and NEE over the Qilian Mountains using meteorological, remotely sensed and other ancillary data at large scale. To realize this, the widely used ecological-process-based model, Biome-BGC, and remote-sensing-based model, MODIS GPP algorithm, were selected for the simulation of the forest carbon fluxes. The combination of these two models was based on calibrating the Biome-BGC by the optimized MODIS GPP algorithm. The simulated GPP and NEE values were evaluated against the eddy covariance observed GPPs and NEEs, and the well agreements have been reached, with R2=0.76, 0.67 respectively.

  4. Carbon nanofiber growth on carbon paper for proton exchange membrane fuel cells

    NARCIS (Netherlands)

    Celebi, S.; Nijhuis, T.A.; Schaaf, van der J.; Bruijn, de F.A.; Schouten, J.C.

    2011-01-01

    Homogeneous deposition precipitation (HDP) of nickel has been investigated for the growth of carbon nanofibers (CNFs) on carbon paper for use in proton exchange membrane fuel cells as a gas diffusion layer. Selective CNF growth on only one side of carbon paper is required to transfer the generated

  5. Comparison of a Mass Balance and an Ecosystem Model Approach when Evaluating the Carbon Cycling in a Lake Ecosystem

    International Nuclear Information System (INIS)

    Andersson, Eva; Sobek, Sebastian

    2006-01-01

    Carbon budgets are frequently used in order to understand the pathways of organic matter in ecosystems, and they also have an important function in the risk assessment of harmful substances. We compared two approaches, mass balance calculations and an ecosystem budget, to describe carbon processing in a shallow, oligotrophic hardwater lake. Both approaches come to the same main conclusion, namely that the lake is a net auto trophic ecosystem, in spite of its high dissolved organic carbon and low total phosphorus concentrations. However, there were several differences between the carbon budgets, e.g. in the rate of sedimentation and the air-water flux of CO 2 . The largest uncertainty in the mass balance is the contribution of emergent macrophytes to the carbon cycling of the lake, while the ecosystem budget is very sensitive towards the choice of conversion factors and literature values. While the mass balance calculations produced more robust results, the ecosystem budget gave valuable insights into the pathways of organic matter transfer in the ecosystem. We recommend that when using an ecosystem budget for the risk assessment of harmful substances, mass balance calculations should be performed in parallel in order to increase the robustness of the conclusions

  6. Responses to elevated carbon dioxide in artificial tropical ecosystems

    International Nuclear Information System (INIS)

    Koerner, C.; Arnone, J.A. III

    1992-01-01

    Carbon, nutrient, and water balance as well as key plant and soil processes were simultaneously monitored for humid tropical plant communities treated with CO 2 -enriched atmospheres. Despite vigorous growth, no significant differences in stand biomass, leaf area index, nitrogen or water consumption, or leaf stomatal behavior were detected between ambient and elevated CO 2 treatments. Major responses under elevated CO 2 included massive starch accumulation in the tops of canopies, increased fine-root production, and a doubling of CO 2 evolution from the soil. Stimulated rhizosphere activity was accompanied by increased loss of soil carbon and increased mineral nutrient leaching. This study points at the inadequacy of scaling-up from physiological baseline to ecosystems without accounting for interactions among components, and it emphasizes the urgent need for whole-system experimental approaches in global-change research

  7. Models for transport and fate of carbon, nutrients and point source released radionuclides to an aquatic ecosystem

    Energy Technology Data Exchange (ETDEWEB)

    Kumblad, Linda [Stockholm Univ. (Sweden). Dept. of Systems Ecology; Kautsky, Ulrik [Swedish Nuclear Fuel and Waste Management Co., Stockholm (Sweden)

    2004-09-01

    In this report three ecosystem models are described in terms of structure, initial data, and results. All models are dynamic, mass-balanced and describe the transport and fate of elements in an open aquatic ecosystem. The models are based on ecologically sound principles, provide model results with high resolution and transparency, and are constrained by the nutrient dynamics of the ecosystem itself. The processes driving the transport in all the models are both the biological processes such as primary production, consumption, respiration and excretion, and abiotic e.g. water exchange and air-sea exchange. The first model, the CNP-model, describes the distribution and fluxes of carbon and nutrients for the coastal ecosystem off Forsmark. The second model, the C-14 model, is an extension of the CNP-model and describes the transport and distribution of hypothetically released C-14 from the underground repository SFR-1 to the ecosystem above. The third model, the RN-model, is a generic radionuclide flow model that models the transport and distribution of radionuclides other than C-14 hypothetically discharged to the ecosystem. The model also analyses the importance of some radionuclide specific mechanisms for the radionuclide flow. The generic radionuclide model is also based on the CNP-model, but has radionuclide specific mechanisms connected to each compartment.

  8. Models for transport and fate of carbon, nutrients and point source released radionuclides to an aquatic ecosystem

    International Nuclear Information System (INIS)

    Kumblad, Linda

    2004-09-01

    In this report three ecosystem models are described in terms of structure, initial data, and results. All models are dynamic, mass-balanced and describe the transport and fate of elements in an open aquatic ecosystem. The models are based on ecologically sound principles, provide model results with high resolution and transparency, and are constrained by the nutrient dynamics of the ecosystem itself. The processes driving the transport in all the models are both the biological processes such as primary production, consumption, respiration and excretion, and abiotic e.g. water exchange and air-sea exchange. The first model, the CNP-model, describes the distribution and fluxes of carbon and nutrients for the coastal ecosystem off Forsmark. The second model, the C-14 model, is an extension of the CNP-model and describes the transport and distribution of hypothetically released C-14 from the underground repository SFR-1 to the ecosystem above. The third model, the RN-model, is a generic radionuclide flow model that models the transport and distribution of radionuclides other than C-14 hypothetically discharged to the ecosystem. The model also analyses the importance of some radionuclide specific mechanisms for the radionuclide flow. The generic radionuclide model is also based on the CNP-model, but has radionuclide specific mechanisms connected to each compartment

  9. The role of ecosystem memory in predicting inter-annual variations of the tropical carbon balance.

    Science.gov (United States)

    Bloom, A. A.; Liu, J.; Bowman, K. W.; Konings, A. G.; Saatchi, S.; Worden, J. R.; Worden, H. M.; Jiang, Z.; Parazoo, N.; Williams, M. D.; Schimel, D.

    2017-12-01

    Understanding the trajectory of the tropical carbon balance remains challenging, in part due to large uncertainties in the integrated response of carbon cycle processes to climate variability. Satellite observations atmospheric CO2 from GOSAT and OCO-2, together with ancillary satellite measurements, provide crucial constraints on continental-scale terrestrial carbon fluxes. However, an integrated understanding of both climate forcings and legacy effects (or "ecosystem memory") on the terrestrial carbon balance is ultimately needed to reduce uncertainty on its future trajectory. Here we use the CARbon DAta-MOdel fraMework (CARDAMOM) diagnostic model-data fusion approach - constrained by an array of C cycle satellite surface observations, including MODIS leaf area, biomass, GOSAT solar-induced fluorescence, as well as "top-down" atmospheric inversion estimates of CO2 and CO surface fluxes from the NASA Carbon Monitoring System Flux (CMS-Flux) - to constrain and predict spatially-explicit tropical carbon state variables during 2010-2015. We find that the combined assimilation of land surface and atmospheric datasets places key constraints on the temperature sensitivity and first order carbon-water feedbacks throughout the tropics and combustion factors within biomass burning regions. By varying the duration of the assimilation period, we find that the prediction skill on inter-annual net biospheric exchange is primarily limited by record length rather than model structure and process representation. We show that across all tropical biomes, quantitative knowledge of memory effects - which account for 30-50% of interannual variations across the tropics - is critical for understanding and ultimately predicting the inter-annual tropical carbon balance.

  10. Impact of climate change on carbon cycle in freshwater ecosystems

    Energy Technology Data Exchange (ETDEWEB)

    Kankaala, P.; Ojala, A.; Tulonen, T.; Haapamaeki, J.; Arvola, L. [Helsinki Univ., Lammi (Finland). Lammi Biological Station

    1996-12-31

    The impacts of the expected climate change on Finnish lake ecosystems were studied with the biota of the mesohumic Lake Paeaejaervi, southern Finland. Experimental conditions, from small-scale experiments on single species level to a large-scale ecosystem manipulation, were established to simulate directly the future climate and/or loading of nutrients and dissolved organic matter (DOM) from the drainage area. The experimental studies were accomplished by modelling the carbon flow in the pelagic food web as well as the growth of littoral macrophytes. The main hypothese tested were as follows: As a consequence of the climate change (rising temperature and increasing precipitation) the loading of nutrients and dissolved organic matter (DOM) from the drainage area to the lake will increase. In the pelagic zone this will be first reflected i higher productivity of primary producers and bacteria, but will later affect the entire food chain. Increase in atmospheric CO{sub 2} concentration and ambient temperature as well as longer growing season will enhance the overall productivity of littoral macrophytes. The higher productivity of the littoral zone will be reflected in the pelagic zone an thus may change the whole ecosystem of the lake

  11. Impact of climate change on carbon cycle in freshwater ecosystems

    Energy Technology Data Exchange (ETDEWEB)

    Kankaala, P; Ojala, A; Tulonen, T; Haapamaeki, J; Arvola, L [Helsinki Univ., Lammi (Finland). Lammi Biological Station

    1997-12-31

    The impacts of the expected climate change on Finnish lake ecosystems were studied with the biota of the mesohumic Lake Paeaejaervi, southern Finland. Experimental conditions, from small-scale experiments on single species level to a large-scale ecosystem manipulation, were established to simulate directly the future climate and/or loading of nutrients and dissolved organic matter (DOM) from the drainage area. The experimental studies were accomplished by modelling the carbon flow in the pelagic food web as well as the growth of littoral macrophytes. The main hypothese tested were as follows: As a consequence of the climate change (rising temperature and increasing precipitation) the loading of nutrients and dissolved organic matter (DOM) from the drainage area to the lake will increase. In the pelagic zone this will be first reflected i higher productivity of primary producers and bacteria, but will later affect the entire food chain. Increase in atmospheric CO{sub 2} concentration and ambient temperature as well as longer growing season will enhance the overall productivity of littoral macrophytes. The higher productivity of the littoral zone will be reflected in the pelagic zone an thus may change the whole ecosystem of the lake

  12. Water- and plant-mediated responses of ecosystem carbon fluxes to warming and nitrogen addition on the Songnen grassland in northeast China.

    Directory of Open Access Journals (Sweden)

    Li Jiang

    Full Text Available Understanding how grasslands are affected by a long-term increase in temperature is crucial to predict the future impact of global climate change on terrestrial ecosystems. Additionally, it is not clear how the effects of global warming on grassland productivity are going to be altered by increased N deposition and N addition.In-situ canopy CO(2 exchange rates were measured in a meadow steppe subjected to 4-year warming and nitrogen addition treatments. Warming treatment reduced net ecosystem CO(2 exchange (NEE and increased ecosystem respiration (ER; but had no significant impacts on gross ecosystem productivity (GEP. N addition increased NEE, ER and GEP. However, there were no significant interactions between N addition and warming. The variation of NEE during the four experimental years was correlated with soil water content, particularly during early spring, suggesting that water availability is a primary driver of carbon fluxes in the studied semi-arid grassland.Ecosystem carbon fluxes in grassland ecosystems are sensitive to warming and N addition. In the studied water-limited grassland, both warming and N addition influence ecosystem carbon fluxes by affecting water availability, which is the primary driver in many arid and semiarid ecosystems. It remains unknown to what extent the long-term N addition would affect the turn-over of soil organic matter and the C sink size of this grassland.

  13. Isotopic exchange of carbon-bound hydrogen over geologic timescales

    Science.gov (United States)

    Sessions, Alex L.; Sylva, Sean P.; Summons, Roger E.; Hayes, John M.

    2004-04-01

    The increasing popularity of compound-specific hydrogen isotope (D/H) analyses for investigating sedimentary organic matter raises numerous questions about the exchange of carbon-bound hydrogen over geologic timescales. Important questions include the rates of isotopic exchange, methods for diagnosing exchange in ancient samples, and the isotopic consequences of that exchange. This article provides a review of relevant literature data along with new data from several pilot studies to investigate such issues. Published experimental estimates of exchange rates between organic hydrogen and water indicate that at warm temperatures (50-100°C) exchange likely occurs on timescales of 104 to 108 yr. Incubation experiments using organic compounds and D-enriched water, combined with compound-specific D/H analyses, provide a new and highly sensitive method for measuring exchange at low temperatures. Comparison of δD values for isoprenoid and n-alkyl carbon skeletons in sedimentary organic matter provides no evidence for exchange in young (exchange in ancient (>350 Ma) rocks. Specific rates of exchange are probably influenced by the nature and abundance of organic matter, pore-water chemistry, the presence of catalytic mineral surfaces, and perhaps even enzymatic activity. Estimates of equilibrium fractionation factors between organic H and water indicate that typical lipids will be depleted in D relative to water by ∼75 to 140‰ at equilibrium (30°C). Thus large differences in δD between organic molecules and water cannot be unambiguously interpreted as evidence against hydrogen exchange. A better approach may be to use changes in stereochemistry as a proxy for hydrogen exchange. For example, estimated rates of H exchange in pristane are similar to predicted rates for stereochemical inversion in steranes and hopanes. The isotopic consequences of this exchange remain in question. Incubations of cholestene with D2O indicate that the number of D atoms incorporated during

  14. Similar net ecosystem exchange of beech stands located in France and Denmark

    DEFF Research Database (Denmark)

    Granier, A.; Pilegaard, K.; Jensen, N.O.

    2002-01-01

    Net ecosystem exchange (NEE), as measured with eddy covariance was compared for two European beech stands for the years 1996-1999: a young beech forest (32 year-old) growing in east France, and a mature beech stand (80 year-old) located in Denmark. Those sites are included in the Carboeuroflux....../Carbodata European networks. Except for some short-term differences (1-5 days), the temporal variation of NEE followed similar patterns in both sites. This similarity followed from similar values of. (i) dates of bud break and of leaf fall; (ii) ecosystem respiration rates during winter; (iii) diurnal NEE during...

  15. Function of Wildfire-Deposited Pyrogenic Carbon in Terrestrial Ecosystems

    Directory of Open Access Journals (Sweden)

    Melissa R. A. Pingree

    2017-08-01

    Full Text Available Fire is an important driver of change in most forest, savannah, and prairie ecosystems and fire-altered organic matter, or pyrogenic carbon (PyC, conveys numerous functions in soils of fire-maintained terrestrial ecosystems. Although an exceptional number of recent review articles and books have addressed agricultural soil application of charcoal or biochar, few reviews have addressed the functional role of naturally formed PyC in fire-maintained ecosystems. Recent advances in molecular spectroscopic techniques have helped strengthen our understanding of PyC as a ubiquitous, complex material that is capable of altering soil chemical, physical, and biological properties and processes. The uniquely recalcitrant nature of PyC in soils is partly a result of its stable C = C double-bonded, graphene-like structure and C-rich, N-poor composition. This attribute allows it to persist in soils for hundreds to thousands of years and represent net ecosystem C sequestration in fire-maintained ecosystems. The rapid formation of PyC during wildfire or anthropogenic fire events short-circuits the normally tortuous pathway of recalcitrant soil C formation. Existing literature also suggests that PyC provides an essential role in the cycling of certain nutrients, greatly extending the timeframe by which fires influence soil processes and facilitating recovery in ecosystems where organic matter inputs are low and post-fire surface soil bacterial and fungal activity is reduced. The high surface area of PyC allows for the adsorption a broad spectrum of organic compounds that directly or indirectly influence microbial processes after fire events. Adsorption capacity and microsite conditions created by PyC yields a “charosphere” effect in soil with heightened microbial activity in the vicinity of PyC. In this mini-review, we explore the function of PyC in natural and semi-natural settings, provide a mechanistic approach to understanding these functions, and examine

  16. On the sseparation of net ecosystem exchange into assimilation and ecosystemrespiration: review and improved algorithm

    Czech Academy of Sciences Publication Activity Database

    Reichstein, M.; Falge, E.; Baldocchi, D.; Papale, D.; Aubinet, M.; Berbigier, P.; Bernhofer, Ch.; Buchmann, N.; Gilmanov, T.; Granier, A.; Grunwald, T.; Havránková, Kateřina; Ilvesniemi, H.; Janouš, Dalibor; Knohl, A.; Laurila, T.; Lohila, A.; Loustau, D.; Matteucci, G.; Meyers, T.; Miglietta, F.; Ourcival, J.M.; Pumpanen, J.; Rambal, S.; Rotenberg, E.; Sanz, M.; Tenhunen, J.; Seufert, G.; Vaccari, F.; Vesala, T.; Yakir, D.; Valentini, R.

    2005-01-01

    Roč. 11, č. 9 (2005), s. 1424-1439 ISSN 1354-1013 Institutional research plan: CEZ:AV0Z60870520 Keywords : CO2 fluxes * ecosystem carbon budget * stable isotopes Subject RIV: GK - Forestry Impact factor: 4.075, year: 2005

  17. Equal exchange: Determining a fair price for carbon

    Energy Technology Data Exchange (ETDEWEB)

    Hodes, G.; Kamel, S.

    2007-12-14

    This first volume in the new series CD4CDM Perspective Series focuses on determining an equal exchange between carbon buyers and sellers in CDM transactions. Contributors to this volume represent a wide spectrum of the various market actors that are interacting in order to realize both successful and equitable carbon transactions. The following issues are discussed: Global carbon price dynamics; CDM project risk profiles and/or premiums; Importance of time factors and delivery guarantees; Impact of regulatory drivers and post-Kyoto outlook; Region-specific outlooks; Strategies, contracting models and approaches. (BA)

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

    Science.gov (United States)

    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 (ΔF) 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

  19. UU* filtering of nighttime net ecosystem CO2 exchange flux over forest canopy under strong wind in wintertime

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Junhui

    2005-01-01

    [1]Aubinet, M., Heinesch, B., Longdoz, B., Estimation of the carbon sequestration by a heterogeneous forest: night flux corrections,heterogeneity of the site and inter-annual variability, Global Change Biology, 2002, 8:1053-1071.[2]Charlotte, L.R., Nigel, T.R., Seasonal contribution of CO2 fluxes in the annual C budget of a northern bog, Global Biogeochemical Cycles, 2003, 171029, doi: 10.1029/20029B001889.[3]Baldocchi, D.D., Hicks, B.B., Meyers, T. P., Measuring biosphere-atmosphere exchanges of biologically related gases with micrometeorological methods, Ecology, 1988, 69:1331-1340.[4]Baldocchi, D.D., Assessing ecosystem carbon balance: problems and prospects of the eddy covariance technique, Global change biology, 2003, 9: 478-492.[5]Canadell, J. G., Mooney, H. A., Baldocchi, D. D. et al., Carbon metabolism of the terrestrial biosphere: A multi technique approach for improved understanding, Ecosystems, 2000, 3:115-130.[6]Schmid, H. P., Footprint modeling for vegetation atmosphere exchange studies: a review and perspective, Agricultural and Forest Meteorology, 2002, 113: 159-183.[7]Wofsy, S. C., Goulden, M. L., Munger, J. W. et al., Net exchange on CO2 in a mid-latitude forest, Science, 1993, 260: 1314-1317.[8]Massman, W. J., Lee, X. H., Eddy covariance flux corrections and uncertainties in long-term studies of carbon and energy exchanges,Agricultural and Forest Meteorology, 2002, 113: 121-144.[9]Baldocchi, D. D., Finnigan, J., Wilson, K. et al., On measuring net ecosystem carbon exchange over tall vegetation on complex terrain, Boundary-Layer Meteorology, 2000, 96: 257-291.[10]Anthoni, P. M., Unsworth, M. H., Law, B. E. et al., Seasonal differences in carbon and water vapor exchange in young and old-growth ponderosa pine ecosystems, Agricultural and Forest Meteorology, 2002, 111: 203-222.[11]Paw U, K. T., Baldocchi, D. D., Meyers, T. P. et al., Correction of eddy-covariance measurements incorporating both advective

  20. Boreal mire carbon exchange: sensitivity to climate change and anthropogenic nitrogen and sulfur deposition

    Energy Technology Data Exchange (ETDEWEB)

    Eriksson, Tobias

    2010-07-01

    Boreal peatlands are important long-term sinks of atmospheric carbon and in the same time the largest natural source of methane to the atmosphere. A changing climate as well as deposition of anthropogenically derived pollutants, such as nitrogen and sulfur, has the potential to affect the processes that control the carbon exchange in peatlands. Many of the biogeochemical responses to changed environmental conditions, such as changed plant community composition, are slow and therefore long-term studies are required. In this thesis I have investigated the long-term effects of nitrogen addition, sulfur addition and greenhouse enclosures on carbon exchange by using a field manipulation experiment in a boreal minerogenic, oligotrophic mire after 10-12 years of treatment. Treatment effects on CH{sub 4} emissions, gross primary production (GPP), ecosystem respiration (Reco) and net ecosystem exchange (NEE) were estimated from 1-2 seasons of chamber flux measurements. Treatment effects on potential CH{sub 4} production and oxidation were estimated in incubations of peat from different depth intervals. The effect of nitrogen deposition on carbon accumulation was evaluated in peat cores at different depth intervals. The long-term nitrogen additions have: shifted plant community composition from being dominated by Sphagnum to being dominated by sedges and dwarf shrubs; changed mire surface microtopography so that mean water table is closer to the surface in plots with high nitrogen; increased CH{sub 4} production and emission; increased Reco slightly but have not affected GPP or NEE; reduced the peat height increment, but increased both peat bulk density and carbon content, leading to an unchanged carbon accumulation. The long-term sulfur additions have not reduced CH{sub 4} emissions, only slightly reduced CH{sub 4} production and did not have any effect on the CO{sub 2} carbon exchange. The greenhouse treatment, manifested in increased air and soil temperatures, reduced

  1. Alternative ways of using field-based estimates to calibrate ecosystem models and their implications for ecosystem carbon cycle studies

    Science.gov (United States)

    Y. He; Q. Zhuang; A.D. McGuire; Y. Liu; M. Chen

    2013-01-01

    Model-data fusion is a process in which field observations are used to constrain model parameters. How observations are used to constrain parameters has a direct impact on the carbon cycle dynamics simulated by ecosystem models. In this study, we present an evaluation of several options for the use of observations inmodeling regional carbon dynamics and explore the...

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

    Science.gov (United States)

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

    2014-12-01

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

  3. Assessing the risk of carbon dioxide emissions from blue carbon ecosystems

    KAUST Repository

    Lovelock, Catherine E.

    2017-05-15

    "Blue carbon" ecosystems, which include tidal marshes, mangrove forests, and seagrass meadows, have large stocks of organic carbon (C) in their soils. These carbon stocks are vulnerable to decomposition and - if degraded - can be released to the atmosphere in the form of CO. We present a framework to help assess the relative risk of CO emissions from degraded soils, thereby supporting inclusion of soil C into blue carbon projects and establishing a means to prioritize management for their carbon values. Assessing the risk of CO emissions after various kinds of disturbances can be accomplished through knowledge of both the size of the soil C stock at a site and the likelihood that the soil C will decompose to CO.

  4. Recent patterns and mechanisms of carbon exchange by terrestrial ecosystems

    CSIR Research Space (South Africa)

    Schimel, DS

    2001-11-08

    Full Text Available Èr Biogeochemie, Jena, Germany; 2 IGBP/GAIM, University of New Hampshire, Morse Hall, Durham, NewHampshire 03824, USA; 3 LSCE Unite mixte CEA-CNRS, Bat. 709, CE L'Orme desMerisiers, 91191, Gif sur Yvette France; 4 Laboratoire de BiogeÂochimie Isotopique... deposition is 2 to 4 times higher in Europe compared to the United States40, and land management practices and history differ. In the United States, studies indicate that much (possibly most) of the sink is due to changing land use (including abandonment...

  5. Climate indices strongly influence old-growth forest carbon exchange

    Science.gov (United States)

    Sonia Wharton; Matthias Falk

    2016-01-01

    We present a decade and a half (1998–2013) of carbon dioxide fluxes from an old-growth stand in the American Pacific Northwest to identify ecosystem-level responses to Pacific teleconnection patterns, including the El Niño/Southern Oscillation (ENSO). This study provides the longest, continuous record of old-growth eddy flux data to date from one of the longest running...

  6. Initial shifts in nitrogen impact on ecosystem carbon fluxes in an alpine meadow: patterns and causes

    Directory of Open Access Journals (Sweden)

    B. Song

    2017-09-01

    Full Text Available Increases in nitrogen (N deposition can greatly stimulate ecosystem net carbon (C sequestration through positive N-induced effects on plant productivity. However, how net ecosystem CO2 exchange (NEE and its components respond to different N addition rates remains unclear. Using an N addition gradient experiment (six levels: 0, 2, 4, 8, 16, 32 gN m−2 yr−1 in an alpine meadow on the Qinghai–Tibetan Plateau, we explored the responses of different ecosystem C fluxes to an N addition gradient and revealed mechanisms underlying the dynamic responses. Results showed that NEE, ecosystem respiration (ER, and gross ecosystem production (GEP all increased linearly with N addition rates in the first year of treatment but shifted to N saturation responses in the second year with the highest NEE (−7.77 ± 0.48 µmol m−2 s−1 occurring under an N addition rate of 8 gN m−2 yr−1. The saturation responses of NEE and GEP were caused by N-induced accumulation of standing litter, which limited light availability for plant growth under high N addition. The saturation response of ER was mainly due to an N-induced saturation response of aboveground plant respiration and decreasing soil microbial respiration along the N addition gradient, while decreases in soil microbial respiration under high N addition were caused by N-induced reductions in soil pH. We also found that various components of ER, including aboveground plant respiration, soil respiration, root respiration, and microbial respiration, responded differentially to the N addition gradient. These results reveal temporal dynamics of N impacts and the rapid shift in ecosystem C fluxes from N limitation to N saturation. Our findings bring evidence of short-term initial shifts in responses of ecosystem C fluxes to increases in N deposition, which should be considered when predicting long-term changes in ecosystem net C sequestration.

  7. Simulating forest productivity and surface-atmosphere carbon exchange in the BOREAS study region

    Energy Technology Data Exchange (ETDEWEB)

    Kimball, J.S.; Thornton, P.E.; White, M.A.; Running, S.W. [Montana Univ., Missoula, MT (United States). School of Forestry

    1997-12-31

    Studies have shown that the boreal forest region is in danger of experiencing significant warming and drying in response to increases in atmospheric CO{sub 2} concentration and other greenhouse gases. Since the boreal forest region contains 16-24 per cent of the world`s soil carbon, warming in this region could result in a rapid, large-scale displacement and redistribution of boreal forest, enhanced release of CO{sub 2} to the atmosphere, and an intensification of global warming. A study was conducted in which a process-based, general ecosystem model (BIOME-BGC) was used to simulate daily gross primary production, maintenance and heterotrophic respiration, net primary production and net ecosystem carbon exchange of boreal aspen, jack pine and black spruce. The objective was to integrate point measurements across multiple spatial and temporal scales using process level models of the boreal forest water, energy and biogeochemical cycles. Climate characteristics that control simulated carbon fluxes were also studied. Results showed that trees with large daily evapotranspiration rates and those situated on sandy soils with low water holding capacities were especially vulnerable to increased temperature and drought conditions. Trees subject to frequent water stress during the growing season, particularly older trees that exhibit low photosynthetic and high respiration rates, were on the margin between being annual net sources or sinks for atmospheric carbon. 71 refs., 3 tabs., 5 figs.

  8. Heat exchange performance of stainless steel and carbon foams modified with carbon nano fibers

    NARCIS (Netherlands)

    Tuzovskaya, I.; Pacheco Benito, Sergio; Chinthaginjala, J.K.; Reed, C.P.; Lefferts, Leonardus; van der Meer, Theodorus H.

    2012-01-01

    Carbon nanofibers (CNF), with fishbone and parallel wall structures, were grown by catalytic chemical vapor deposition on the surface of carbon foam and stainless steel foam, in order to improve their heat exchange performance. Enhancement in heat transfer efficiency between 30% and 75% was achieved

  9. How do persistent organic pollutants be coupled with biogeochemical cycles of carbon and nutrients in terrestrial ecosystems under global climate change?

    Energy Technology Data Exchange (ETDEWEB)

    Teng, Ying [Chinese Academy of Sciences, Nanjing (China). Key Lab. of Soil Environment and Pollution Remediation; Griffith Univ., Nathan, QLD (Australia). Environmetnal Futures Centre and School of Biomolecular and Physical Sciences; Xu, Zhihong; Reverchon, Frederique [Griffith Univ., Nathan, QLD (Australia). Environmetnal Futures Centre and School of Biomolecular and Physical Sciences; Luo, Yongming [Chinese Academy of Sciences, Nanjing (China). Key Lab. of Soil Environment and Pollution Remediation

    2012-03-15

    Global climate change (GCC), especially global warming, has affected the material cycling (e.g., carbon, nutrients, and organic chemicals) and the energy flows of terrestrial ecosystems. Persistent organic pollutants (POPs) were regarded as anthropogenic organic carbon (OC) source, and be coupled with the natural carbon (C) and nutrient biogeochemical cycling in ecosystems. The objective of this work was to review the current literature and explore potential coupling processes and mechanisms between POPs and biogeochemical cycles of C and nutrients in terrestrial ecosystems induced by global warming. Global warming has caused many physical, chemical, and biological changes in terrestrial ecosystems. POPs environmental fate in these ecosystems is controlled mainly by temperature and biogeochemical processes. Global warming may accelerate the re-emissions and redistribution of POPs among environmental compartments via soil-air exchange. Soil-air exchange is a key process controlling the fate and transportation of POPs and terrestrial ecosystem C at regional and global scales. Soil respiration is one of the largest terrestrial C flux induced by microbe and plant metabolism, which can affect POPs biotransformation in terrestrial ecosystems. Carbon flow through food web structure also may have important consequences for the biomagnification of POPs in the ecosystems and further lead to biodiversity loss induced by climate change and POPs pollution stress. Moreover, the integrated techniques and biological adaptation strategy help to fully explore the coupling mechanisms, functioning and trends of POPs and C and nutrient biogeochemical cycling processes in terrestrial ecosystems. There is increasing evidence that the environmental fate of POPs has been linked with biogeochemical cycles of C and nutrients in terrestrial ecosystems under GCC. However, the relationships between POPs and the biogeochemical cycles of C and nutrients are still not well understood. Further

  10. Elucidating Carbon Exchange at the Regional Scale Via Airborne Eddy Covariance Flux Measurements

    Science.gov (United States)

    Hannun, R. A.; Wolfe, G. M.; Kawa, S. R.; Newman, P. A.; Hanisco, T. F.; Diskin, G. S.; DiGangi, J. P.; Nowak, J. B.; Barrick, J. D. W.; Thornhill, K. L., II; Noormets, A.; Vargas, R.; Clark, K. L.; Kustas, W. P.

    2017-12-01

    Direct flux observations from aircraft provide a unique tool for probing greenhouse gas (GHG) sources and sinks on a regional scale. Airborne eddy covariance, which relies on high-frequency, simultaneous measurements of fluctuations in concentration and vertical wind speed, is a robust method for quantifying surface-atmosphere exchange. We have assembled and flown an instrument payload onboard the NASA C-23 Sherpa aircraft capable of measuring CO2, CH4, H2O, and heat fluxes. Flights for the Carbon Airborne Flux Experiment (CARAFE) took place during September 2016 and May 2017 based out of Wallops Flight Facility, VA. Flight tracks covered a variety of ecosystems and land-use types in the Mid-Atlantic, including forests, croplands, and wetlands. Carbon fluxes are derived using eddy covariance and wavelet analysis. Our results show a strong drawdown of CO2 and near-zero CH4 emissions from crops and dry-land forest, but seasonally strong CH4 flux from wetland forest. CARAFE flux data will also be compared with observations from several flux towers along the flight path to complement the airborne measurements. We will further assess the effects of land surface type and seasonal variability in carbon exchange. Regional-scale flux observations from CARAFE supply a useful constraint for improving top-down and bottom up estimates of carbon sources and sinks.

  11. Tundra shrub effects on growing season energy and carbon dioxide exchange

    Science.gov (United States)

    Lafleur, Peter M.; Humphreys, Elyn R.

    2018-05-01

    Increased shrub cover on the Arctic tundra is expected to impact ecosystem-atmosphere exchanges of carbon and energy resulting in feedbacks to the climate system, yet few direct measurements of shrub tundra-atmosphere exchanges are available to corroborate expectations. Here we present energy and carbon dioxide (CO2) fluxes measured using the eddy covariance technique over six growing seasons at three closely located tundra sites in Canada’s Low Arctic. The sites are dominated by the tundra shrub Betula glandulosa, but percent cover varies from 17%–60% and average shrub height ranges from 18–59 cm among sites. The site with greatest percent cover and height had greater snow accumulation, but contrary to some expectations, it had similar late-winter albedo and snow melt dates compared to the other two sites. Immediately after snowmelt latent heat fluxes increased more slowly at this site compared to the others. Yet by the end of the growing season there was little difference in cumulative latent heat flux among the sites, suggesting evapotranspiration was not increased with greater shrub cover. In contrast, lower albedo and less soil thaw contributed to greater summer sensible heat flux at the site with greatest shrub cover, resulting in greater total atmospheric heating. Net ecosystem exchange of CO2 revealed the potential for enhanced carbon cycling rates under greater shrub cover. Spring CO2 emissions were greatest at the site with greatest percent cover of shrubs, as was summer net uptake of CO2. The seasonal net sink for CO2 was ~2 times larger at the site with the greatest shrub cover compared to the site with the least shrub cover. These results largely agree with expectations that the growing season feedback to the atmosphere arising from shrub expansion in the Arctic has the potential to be negative for CO2 fluxes but positive for turbulent energy fluxes.

  12. Potential increases in natural disturbance rates could offset forest management impacts on ecosystem carbon stocks.

    Science.gov (United States)

    John B. Bradford; Nicholas R. Jensen; Grant M. Domke; Anthony W. D' Amato

    2013-01-01

    Forested ecosystems contain the majority of the world’s terrestrial carbon, and forest management has implications for regional and global carbon cycling. Carbon stored in forests changes with stand age and is affected by natural disturbance and timber harvesting. We examined how harvesting and disturbance interact to influence forest carbon stocks over the Superior...

  13. Interannual Variations of the Carbon Footprint and Carbon Eco-efficiency in Agro-ecosystem of Beijing, China

    OpenAIRE

    TIAN Zhi-hui; MA Xiao-yan; LIU Rui-han

    2015-01-01

    Suburban farmland ecosystems are known to be affected by intensive land use/cover change (LUCC) during the process of urbanization in Beijing. We investigated inter-annual changes in carbon sequestration, source, footprint, and eco-efficiency from 2004 to 2012 in the agro-ecosystem of suburban Beijing. Our findings indicated that: (1) Carbon sink increased 2.8 percent annually and the average annual carbon storage amount was 1 058 200 t, with food crops constituting the highest proportion at ...

  14. Interannual Variations of the Carbon Footprint and Carbon Eco-efficiency in Agro-ecosystem of Beijing, China

    Directory of Open Access Journals (Sweden)

    TIAN Zhi-hui

    2015-12-01

    Full Text Available Suburban farmland ecosystems are known to be affected by intensive land use/cover change (LUCC during the process of urbanization in Beijing. We investigated inter-annual changes in carbon sequestration, source, footprint, and eco-efficiency from 2004 to 2012 in the agro-ecosystem of suburban Beijing. Our findings indicated that: (1 Carbon sink increased 2.8 percent annually and the average annual carbon storage amount was 1 058 200 t, with food crops constituting the highest proportion at 80.4% of carbon storage in farmland ecosystems, of which maize contributed 68.5% as the largest constituent; (2 Carbon emission in the system showed a gradually decreasing trend, with agricultural chemicals as significant contributors. The annual average carbon emission was 276 000 tons in the Beijing farmland ecosystem, and decreased approximately 1.3 percent per year. The largest amount of carbon emissions came from agricultural chemicals at 85.4%, of which nitrogen fertilizer was the biggest contributor at 83.7%; ( 3 The carbon footprint also showed a decreasing trend along with an ecological surplus of carbon. The average carbon footprint was 5.71 hm2 in the Beijing farmland ecosystem with decreasing rate at 5.5% annually; however, the carbon surplus showed a downward trend due to reduction in the amount of arable land; (4 Finally, the increasing carbon sink capacity led to higher carbon eco-efficiency, with an annual average of 3.854 kg C·kg-1 CE, carbon sequestration was greater than the amount of carbon released. In summary, the agro-ecosystem in suburban Beijing has sustained a relatively high carbon eco-efficiency, and agricultural production continues to have high sustainability potential.

  15. How intensive agriculture affects surface-atmosphere exchange of nitrogen and carbon compounds over peatland

    Science.gov (United States)

    Bruemmer, C.; Richter, U.; Schrader, F.; Hurkuck, M.; Kutsch, W. L.

    2016-12-01

    Mid-latitude peatlands are often exposed to high atmospheric nitrogen deposition when located in close vicinity to agricultural land. As the impacts of altered deposition rates on nitrogen-limited ecosystems are poorly understood, we investigated the surface-atmosphere exchange of several nitrogen and carbon compounds using multiple high-resolution measurement techniques and modeling. Our study site was a protected semi-natural bog ecosystem. Local wind regime and land use in the adjacent area clearly regulated whether total reactive nitrogen (∑Nr) concentrations were ammonia (NH3) or NOx-dominated. Eddy-covariance measurements of NH3 and ∑Nr revealed concentration, temperature and surface wetness-dependent deposition rates. Intermittent periods of NH3 and ∑Nr emission likely attributed to surface water re-emission and soil efflux, respectively, were found, thereby indicating nitrogen oversaturation in this originally N-limited ecosystem. Annual dry plus wet deposition resulted in 20 to 25 kg N ha-1 depending on method and model used, which translated into a four- to fivefold exceedance of the ecosystem-specific critical load. As the bog site had likely been exposed to the observed atmospheric nitrogen burden over several decades, a shift in grass species' composition towards a higher number of nitrophilous plants was already visible. Three years of CO2 eddy flux measurements showed that the site was a small net sink in the range of 33 to 268 g CO2 m-2 yr-1. Methane emissions of 32 g CO2-eq were found to partly offset the sequestered carbon through CO2. Our study demonstrates the applicability of novel micrometeorological measurement techniques in biogeochemical sciences and stresses the importance of monitoring long-term changes in vulnerable ecosystems under anthropogenic pressure and climate change.

  16. An application of plot-scale NDVI in predicting carbon dioxide exchange and leaf area index in heterogeneous subarctic tundra

    Energy Technology Data Exchange (ETDEWEB)

    Dagg, J.; Lafleur, P.

    2010-07-01

    This paper reported on a study that examined the flow of carbon into and out of tundra ecosystems. It is necessary to accurately predict carbon dioxide (CO{sub 2}) exchange in the Tundra because of the impacts of climate change on carbon stored in permafrost. Understanding the relationships between the normalized difference vegetation index (NDVI) and vegetation and CO{sub 2} exchange may explain how small-scale variation in vegetation community extends to remotely sensed estimates of landscape characteristics. In this study, CO{sub 2} fluxes were measured with a portable chamber in a range of Tundra vegetation communities. Biomass and leaf area were measured with destructive harvest, and NDVI was obtained using a hand-held infrared camera. There was a weak correlation between NDVI and leaf area index in some vegetation communities, but a significant correlation between NDVI and biomass, including mosses. NDVI was found to be strongly related to photosynthetic activity and net CO{sub 2} uptake in all vegetation groups. However, NDVI related to ecosystem respiration only in wet sedge. It was concluded that at plot scale, the ability of NDVI to predict ecosystem properties and CO{sub 2} exchange in heterogeneous Tundra vegetation is variable.

  17. An application of plot-scale NDVI in predicting carbon dioxide exchange and leaf area index in heterogeneous subarctic tundra

    International Nuclear Information System (INIS)

    Dagg, J.; Lafleur, P.

    2010-01-01

    This paper reported on a study that examined the flow of carbon into and out of tundra ecosystems. It is necessary to accurately predict carbon dioxide (CO 2 ) exchange in the Tundra because of the impacts of climate change on carbon stored in permafrost. Understanding the relationships between the normalized difference vegetation index (NDVI) and vegetation and CO 2 exchange may explain how small-scale variation in vegetation community extends to remotely sensed estimates of landscape characteristics. In this study, CO 2 fluxes were measured with a portable chamber in a range of Tundra vegetation communities. Biomass and leaf area were measured with destructive harvest, and NDVI was obtained using a hand-held infrared camera. There was a weak correlation between NDVI and leaf area index in some vegetation communities, but a significant correlation between NDVI and biomass, including mosses. NDVI was found to be strongly related to photosynthetic activity and net CO 2 uptake in all vegetation groups. However, NDVI related to ecosystem respiration only in wet sedge. It was concluded that at plot scale, the ability of NDVI to predict ecosystem properties and CO 2 exchange in heterogeneous Tundra vegetation is variable.

  18. Sediment carbon and nutrient fluxes from cleared and intact temperate mangrove ecosystems and adjacent sandflats.

    Science.gov (United States)

    Bulmer, Richard H; Schwendenmann, Luitgard; Lohrer, Andrew M; Lundquist, Carolyn J

    2017-12-01

    The loss of mangrove ecosystems is associated with numerous impacts on coastal and estuarine function, including sediment carbon and nutrient cycling. In this study we compared in situ fluxes of carbon dioxide (CO 2 ) from the sediment to the atmosphere, and fluxes of dissolved inorganic nutrients and oxygen across the sediment-water interface, in intact and cleared mangrove and sandflat ecosystems in a temperate estuary. Measurements were made 20 and 25months after mangrove clearance, in summer and winter, respectively. Sediment CO 2 efflux was over two-fold higher from cleared than intact mangrove ecosystems at 20 and 25months after mangrove clearance. The higher CO 2 efflux from the cleared site was explained by an increase in respiration of dead root material along with sediment disturbance following mangrove clearance. In contrast, sediment CO 2 efflux from the sandflat site was negligible (≤9.13±1.18mmolm -2 d -1 ), associated with lower sediment organic matter content. The fluxes of inorganic nutrients (NH 4 + , NO x and PO 4 3- ) from intact and cleared mangrove sediments were low (≤20.37±18.66μmolm -2 h - 1 ). The highest NH 4 + fluxes were measured at the sandflat site (69.21±13.49μmolm -2 h - 1 ). Lower inorganic nutrient fluxes within the cleared and intact mangrove sites compared to the sandflat site were associated with lower abundance of larger burrowing macrofauna. Further, a higher fraction of organic matter, silt and clay content in mangrove sediments may have limited nutrient exchange. Copyright © 2017 Elsevier B.V. All rights reserved.

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

    Science.gov (United States)

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

    2011-12-01

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

  20. Simulating forest productivity and surface-atmosphere carbon exchange in the BOREAS study region.

    Science.gov (United States)

    Kimball, John S.; Thornton, Peter E.; White, Mike A.; Running, Steven W.

    1997-01-01

    A process-based, general ecosystem model (BIOME-BGC) was used to simulate daily gross primary production, maintenance and heterotrophic respiration, net primary production and net ecosystem carbon exchange of boreal aspen, jack pine and black spruce stands. Model simulations of daily net carbon exchange of the ecosystem (NEE) explained 51.7% (SE = 1.32 g C m(-2) day(-1)) of the variance in daily NEE derived from stand eddy flux measurements of CO(2) during 1994. Differences between measured and simulated results were attributed to several factors including difficulties associated with measuring nighttime CO(2) fluxes and model assumptions of site homogeneity. However, comparisons between simulations and field data improved markedly at coarser time-scales. Model simulations explained 66.1% (SE = 0.97 g C m(-2) day(-1)) of the variance in measured NEE when 5-day means of daily results were compared. Annual simulations of aboveground net primary production ranged from 0.6-2.4 Mg C ha(-1) year(-1) and were concurrent with results derived from tree increment core measurements and allometric equations. Model simulations showed that all of the sites were net sinks (0.1-4.1 Mg C ha(-1) year(-1)) of atmospheric carbon for 1994. Older conifer stands showed narrow margins between uptake of carbon by net photosynthesis and carbon release through respiration. Younger stands were more productive than older stands, primarily because of lower maintenance respiration costs. However, all sites appeared to be less productive than temperate forests. Productivity simulations were strongly linked to stand morphology and site conditions. Old jack pine and aspen stands showed decreased productivity in response to simulated low soil water contents near the end of the 1994 growing season. Compared with the aspen stand, the jack pine stand appeared better adapted to conserve soil water through lower daily evapotranspiration losses but also exhibited a narrower margin between daily net

  1. Estimating Carbon Stocks and Atmospheric Exchange of Depressional Marshes on the Central Florida Landscape

    Science.gov (United States)

    Benscoter, B.; McClellan, M. D.; Benavides, V.; Harshbarger, D.; Comas, X.

    2014-12-01

    Depressional marshes are ubiquitous throughout central and south Florida. Often distributed within a matrix of sandy pine flatwoods and hammocks, these wetlands have a seasonally variable water table, alternating between inundation and complete drydown. Though these landforms are typically small individually, they comprise a substantial component of the landscape and provide vital habitat for an array of flora and fauna. Given their fluctuating hydrology, conditions for soil and plant carbon (C) exchange mechanisms can vary greatly both spatially and temporally. In this study, we are developing a C budget for depressional marsh landforms by assessing ecosystem carbon exchange along an ecotone gradient and quantifying belowground C stocks using non-invasive geophysical methods (ground penetrating radar, GPR) at the Disney Wilderness Preserve (DWP) in Kissimmee, FL, USA. Using a series of closed chambers transecting the marsh from the center outward into the surrounding flatwoods, we are quantifying the effects of seasonal water table change on the magnitude of C exchange. Three dimensional GPR surveys were used to quantify peat layer thickness, and were constrained with direct core sampling to verify subsurface lithology and to assess peat C content. Using the relationship between landform surface area and belowground C volume, we assessed the cumulative C storage in depressional marshes across the DWP landscape. In conjunction with a nearby eddy covariance tower and seasonal hydrologic data, these response functions will help to evaluate the contribution of these small but widespread landscape features on regional C cycling.

  2. Multiyear high-resolution carbon exchange over European croplands from the integration of observed crop yields into CarbonTracker Europe

    Science.gov (United States)

    Combe, Marie; Vilà-Guerau de Arellano, Jordi; de Wit, Allard; Peters, Wouter

    2016-04-01

    Carbon exchange over croplands plays an important role in the European carbon cycle over daily-to-seasonal time scales. Not only do crops occupy one fourth of the European land area, but their photosynthesis and respiration are large and affect CO2 mole fractions at nearly every atmospheric CO2 monitoring site. A better description of this crop carbon exchange in our CarbonTracker Europe data assimilation system - which currently treats crops as unmanaged grasslands - could strongly improve its ability to constrain terrestrial carbon fluxes. Available long-term observations of crop yield, harvest, and cultivated area allow such improvements, when combined with the new crop-modeling framework we present. This framework can model the carbon fluxes of 10 major European crops at high spatial and temporal resolution, on a 12x12 km grid and 3-hourly time-step. The development of this framework is threefold: firstly, we optimize crop growth using the process-based WOrld FOod STudies (WOFOST) agricultural crop growth model. Simulated yields are downscaled to match regional crop yield observations from the Statistical Office of the European Union (EUROSTAT) by estimating a yearly regional parameter for each crop species: the yield gap factor. This step allows us to better represent crop phenology, to reproduce the observed multiannual European crop yields, and to construct realistic time series of the crop carbon fluxes (gross primary production, GPP, and autotrophic respiration, Raut) on a fine spatial and temporal resolution. Secondly, we combine these GPP and Raut fluxes with a simple soil respiration model to obtain the total ecosystem respiration (TER) and net ecosystem exchange (NEE). And thirdly, we represent the horizontal transport of carbon that follows crop harvest and its back-respiration into the atmosphere during harvest consumption. We distribute this carbon using observations of the density of human and ruminant populations from EUROSTAT. We assess the model

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

    Science.gov (United States)

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

    1997-01-01

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

  4. FLUXNET: A new tool to study the temporal and spatial variability of ecosystem-scale carbon dioxide, water vapor, and energy flux densities

    DEFF Research Database (Denmark)

    Baldocchi, D.; Falge, E.; Gu, L.

    2001-01-01

    FLUXNET is a global network of micrometeorological flux measurement site's that measure the exchanges of carbon dioxide, water vapor, and energy between the biosphere and atmosphere. At present over 140 sites are operating on a long-term and continuous basis. Vegetation under study includes...... of annual ecosystem carbon and water balances, to quantify the response of stand-scale carbon dioxide and water vapor flux densities to controlling biotic and abiotic factors, and to validate a hierarchy of soil-plant-atmosphere trace gas exchange models. Findings so far include 1) net CO2 exchange......, it provides infrastructure for compiling, archiving, and distributing carbon, water, and energy flux measurement, and meteorological, plant, and soil data to the science community. (Data and site information are available online at the FLUXNET Web site, http://www-eosdis.oml.gov/FLUXNTET/.) Second...

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

    Science.gov (United States)

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

    2015-03-13

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

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

    Science.gov (United States)

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

    2015-03-01

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

  7. Methane and carbon dioxide exchange in a post-extraction, unrestored peatland in Eastern Quebec, Canada

    Science.gov (United States)

    Rankin, Tracy; Strachan, Ian; Strack, Maria

    2017-04-01

    Peatlands, in their pristine state, are important long-term sinks of carbon. The extraction of peat for agricultural purposes or for biofuel leads to a shift in the carbon dynamics. Changes in environmental conditions post extraction may also allow for invasive species to establish and spread across the peatland. Many studies have shown the benefits and advantages of various restoration management practices, but few studies have explored the carbon exchange from unrestored peatlands. Our study reports the methane (CH4) and carbon dioxide (CO2) fluxes from a post-extraction, unrestored peatland in Eastern Québec at both the plant community scale using static chambers, and at the ecosystem scale using an eddy covariance flux tower, over two complete years. Extraction of the Saint-Alexandre-de-Kamouraska peatland (SAK) started in the early 1970's and was halted in 1999. No restoration efforts have been implemented and the remnant ditches remain unblocked. The site consists of sparse patches of Eriophorum and a vast area of bare peat. Consequently, SAK is an overall source of carbon to the atmosphere, releasing an annual total of 153 g C m-2 and 241 g C m-2 in CO2 emissions for 2014 and 2015, respectively, and an average annual total of 1 g C m-2yr-1 in CH4 emissions. Phragmites and Typha, both invasive species, have established themselves in the ditches and are sources of methane; partly explaining the increased emissions in carbon fluxes to the atmosphere post extraction. Results from this study will help managers assess the importance of post-extraction peatland restoration, by comparing the differences in CO2 and CH4 exchange between restored and unrestored peatlands.

  8. Absorption of carbon dioxide and isotope exchange rate of carbon in a reaction system between carbon dioxide and carbamic acid

    International Nuclear Information System (INIS)

    Takeshita, Kenji; Kitamoto, Asashi

    1985-01-01

    The performance of isotope separation of carbon-13 by chemical exchange between carbon dioxide and carbamic acid was studied. The working fluid used in the study was a solution of DNBA, (C 4 H 9 ) 2 NH and n-octane mixture. Factors related to the isotope exchange rate were measured, such as the absorption rate of carbon dioxide into the solution of DNBA and n-octane, the isotope exchange rate and the separation factor in the reaction between CO 2 and carbamic acid. The absorption of CO 2 into the working fluid was the sum of chemical absorption by DNBA and physical absorption by n-octane. The absorption of carbon dioxide into the working fluid was negligible at temperatures over 90 0 C, but increased gradually at lower temperatures. Carbon dioxide was absorbed into DNBA by chemical absorption, and DNBA was converted to carbamic acid by the reaction. The reaction for synthesis and decomposition of carbamic acid was reversible. The separation factor in equilibrium reached a large value at lower temperatures. The isotope exchange rate between gas and liquid was proportional to the product of the concentration of carbamic acid and the concentration of CO 2 by physical absorption. The isotope separation of carbon by chemical exchange reaction is better operated under the conditions of lower temperature and higher pressure. (author)

  9. Net ecosystem exchange and energy fluxes measured with the eddy covariance technique in a western Siberian bog

    Directory of Open Access Journals (Sweden)

    P. Alekseychik

    2017-08-01

    Full Text Available Very few studies of ecosystem–atmosphere exchange involving eddy covariance data have been conducted in Siberia, with none in the western Siberian middle taiga. This work provides the first estimates of carbon dioxide (CO2 and energy budgets in a typical bog of the western Siberian middle taiga based on May–August measurements in 2015. The footprint of measured fluxes consisted of a homogeneous mixture of tree-covered ridges and hollows with the vegetation represented by typical sedges and shrubs. Generally, the surface exchange rates resembled those of pine-covered bogs elsewhere. The surface energy balance closure approached 100 %. Net CO2 uptake was comparatively high, summing up to 202 gC m−2 for the four measurement months, while the Bowen ratio was seasonally stable at 28 %. The ecosystem turned into a net CO2 source during several front passage events in June and July. The periods of heavy rain helped keep the water table at a sustainably high level, preventing a usual drawdown in summer. However, because of the cloudy and rainy weather, the observed fluxes might rather represent the special weather conditions of 2015 than their typical magnitudes.

  10. Long term carbon fluxes in south eastern U.S. pine ecosystems.

    Science.gov (United States)

    Bracho, R. G.; Martin, T.; Gonzalez-Benecke, C. A.; Sharp, J.

    2015-12-01

    Forests in the southeastern U.S. are a critical component of the national carbon balance storing a third of the total forest carbon (C) in conterminous USA. South eastern forests occupy 60% of the land area, with a large fraction dominated by the genus Pinus distributed in almost equal proportions of naturally-regenerated and planted stands. These stands often differ in structure (e.g., stem density, leaf area index (LAI)) and in the intensity with which they are managed (e.g. naturally-regenerated, older pine stands are often managed less intensively, with prescribed fire). We measured C fluxes using the eddy covariance approach (net ecosystem production, -NEP) in planted (Pinus elliottii var. elliottii) and naturally-regenerated mixed stand of long leaf (Pinus palustris Mill) and slash pine (Pinus elliottii var. elliottii) accompanied by biometric estimations of C balance. Measurements spanned more than a decade and included interannual climatic variability ranging from severe droughts (e.g. Palmer Drought severity index (PDSI) averaged -2.7 from January 2000 to May 2002, and -3.3 from June 2006 to April 2008), to years with tropical storms. Annual NEP for the older, naturally-regenerated stand fluctuated from -1.60 to -5.38 Mg C ha-1 yr-1 with an average of -2.73 ± 1.17 Mg C ha-1 yr-1 while in plantations after canopy closure NEP fluctuated from -4.0 to -8.2 Mg C ha-1 yr-1 with an average of -6.17 ± 1.34 Mg C ha-1 yr-1. Annual NEP in naturally-regenerated pine was mainly driven by a combination of water availability and understory burning while in plantations it was driven by water availability after canopy closure. Woody and above ground net primary productivity (NPP) followed gross ecosystem carbon exchange (GEE) in both ecosystems. Naturally-regenerated and planted pine are a strong carbon sink under the current management and environmental fluctuations accumulating 28 and 130 Mg C ha-1 in a decade, respectively, and are among the most productive forests in

  11. Establishing a Supervised Classification of Global Blue Carbon Mangrove Ecosystems

    Science.gov (United States)

    Baltezar, P.

    2016-12-01

    Understanding change in mangroves over time will aid forest management systems working to protect them from over exploitation. Mangroves are one of the most carbon dense terrestrial ecosystems on the planet and are therefore a high priority for sustainable forest management. Although they represent 1% of terrestrial cover, they could account for about 10% of global carbon emissions. The foundation of this analysis uses remote sensing to establish a supervised classification of mangrove forests for discrete regions in the Zambezi Delta of Mozambique and the Rufiji Delta of Tanzania. Open-source mapping platforms provided a dynamic space for analyzing satellite imagery in the Google Earth Engine (GEE) coding environment. C-Band Synthetic Aperture Radar data from Sentinel 1 was used in the model as a mask by optimizing SAR parameters. Exclusion metrics identified within Global Land Surface Temperature data from MODIS and the Shuttle Radar Topography Mission were used to accentuate mangrove features. Variance was accounted for in exclusion metrics by statistically calculating thresholds for radar, thermal, and elevation data. Optical imagery from the Landsat 8 archive aided a quality mosaic in extracting the highest spectral index values most appropriate for vegetative mapping. The enhanced radar, thermal, and digital elevation imagery were then incorporated into the quality mosaic. Training sites were selected from Google Earth imagery and used in the classification with a resulting output of four mangrove cover map models for each site. The model was assessed for accuracy by observing the differences between the mangrove classification models to the reference maps. Although the model was over predicting mangroves in non-mangrove regions, it was more accurately classifying mangrove regions established by the references. Future refinements will expand the model with an objective degree of accuracy.

  12. Nitrogen Cycling from Increased Soil Organic Carbon Contributes Both Positively and Negatively to Ecosystem Services in Wheat Agro-Ecosystems

    Directory of Open Access Journals (Sweden)

    Jeda Palmer

    2017-05-01

    Full Text Available Soil organic carbon (SOC is an important and manageable property of soils that impacts on multiple ecosystem services through its effect on soil processes such as nitrogen (N cycling and soil physical properties. There is considerable interest in increasing SOC concentration in agro-ecosystems worldwide. In some agro-ecosystems, increased SOC has been found to enhance the provision of ecosystem services such as the provision of food. However, increased SOC may increase the environmental footprint of some agro-ecosystems, for example by increasing nitrous oxide emissions. Given this uncertainty, progress is needed in quantifying the impact of increased SOC concentration on agro-ecosystems. Increased SOC concentration affects both N cycling and soil physical properties (i.e., water holding capacity. Thus, the aim of this study was to quantify the contribution, both positive and negative, of increased SOC concentration on ecosystem services provided by wheat agro-ecosystems. We used the Agricultural Production Systems sIMulator (APSIM to represent the effect of increased SOC concentration on N cycling and soil physical properties, and used model outputs as proxies for multiple ecosystem services from wheat production agro-ecosystems at seven locations around the world. Under increased SOC, we found that N cycling had a larger effect on a range of ecosystem services (food provision, filtering of N, and nitrous oxide regulation than soil physical properties. We predicted that food provision in these agro-ecosystems could be significantly increased by increased SOC concentration when N supply is limiting. Conversely, we predicted no significant benefit to food production from increasing SOC when soil N supply (from fertiliser and soil N stocks is not limiting. The effect of increasing SOC on N cycling also led to significantly higher nitrous oxide emissions, although the relative increase was small. We also found that N losses via deep drainage were

  13. Nitrogen Cycling from Increased Soil Organic Carbon Contributes Both Positively and Negatively to Ecosystem Services in Wheat Agro-Ecosystems.

    Science.gov (United States)

    Palmer, Jeda; Thorburn, Peter J; Biggs, Jody S; Dominati, Estelle J; Probert, Merv E; Meier, Elizabeth A; Huth, Neil I; Dodd, Mike; Snow, Val; Larsen, Joshua R; Parton, William J

    2017-01-01

    Soil organic carbon (SOC) is an important and manageable property of soils that impacts on multiple ecosystem services through its effect on soil processes such as nitrogen (N) cycling and soil physical properties. There is considerable interest in increasing SOC concentration in agro-ecosystems worldwide. In some agro-ecosystems, increased SOC has been found to enhance the provision of ecosystem services such as the provision of food. However, increased SOC may increase the environmental footprint of some agro-ecosystems, for example by increasing nitrous oxide emissions. Given this uncertainty, progress is needed in quantifying the impact of increased SOC concentration on agro-ecosystems. Increased SOC concentration affects both N cycling and soil physical properties (i.e., water holding capacity). Thus, the aim of this study was to quantify the contribution, both positive and negative, of increased SOC concentration on ecosystem services provided by wheat agro-ecosystems. We used the Agricultural Production Systems sIMulator (APSIM) to represent the effect of increased SOC concentration on N cycling and soil physical properties, and used model outputs as proxies for multiple ecosystem services from wheat production agro-ecosystems at seven locations around the world. Under increased SOC, we found that N cycling had a larger effect on a range of ecosystem services (food provision, filtering of N, and nitrous oxide regulation) than soil physical properties. We predicted that food provision in these agro-ecosystems could be significantly increased by increased SOC concentration when N supply is limiting. Conversely, we predicted no significant benefit to food production from increasing SOC when soil N supply (from fertiliser and soil N stocks) is not limiting. The effect of increasing SOC on N cycling also led to significantly higher nitrous oxide emissions, although the relative increase was small. We also found that N losses via deep drainage were minimally

  14. Modeling Carbon Turnover in Five Terrestrial Ecosystems in the Boreal Zone Using Multiple Criteria of Acceptance

    International Nuclear Information System (INIS)

    Karlberg, Louise; Gustafsson, David; Jansson, Per-Erik

    2006-01-01

    Estimates of carbon fluxes and turnover in ecosystems are key elements in the understanding of climate change and in predicting the accumulation of trace elements in the biosphere. In this paper we present estimates of carbon fluxes and turnover times for five terrestrial ecosystems using a modeling approach. Multiple criteria of acceptance were used to parameterize the model, thus incorporating large amounts of multi-faceted empirical data in the simulations in a standardized manner. Mean turnover times of carbon were found to be rather similar between systems with a few exceptions, even though the size of both the pools and the fluxes varied substantially. Depending on the route of the carbon through the ecosystem, turnover times varied from less than one year to more than one hundred, which may be of importance when considering trace element transport and retention. The parameterization method was useful both in the estimation of unknown parameters, and to identify variability in carbon turnover in the selected ecosystems

  15. Carbon fluxes of surfaces vs. ecosystems. Advantages of measuring eddy covariance and soil respiration simultaneously in dry grassland ecosystems

    Czech Academy of Sciences Publication Activity Database

    Nagy, Z.; Pintér, K.; Pavelka, Marian; Dařenová, Eva; Balogh, J.

    2011-01-01

    Roč. 8, č. 9 (2011), s. 2523-2534 ISSN 1726-4170 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0073 Institutional research plan: CEZ:AV0Z60870520 Keywords : carbon fluxes * ecosystems * grassland ecoystems * measuring eddy covariance * soil respiration Subject RIV: EH - Ecology, Behaviour Impact factor: 3.859, year: 2011

  16. Modelling the decadal trend of ecosystem carbon fluxes demonstrates the important role of functional changes in a temperate deciduous forest

    DEFF Research Database (Denmark)

    Wu, Jian; Jansson, P.E.; van der Linden, Leon

    2013-01-01

    Temperate forests are globally important carbon sinks and stocks. Trends in net ecosystem exchange have been observed in a Danish beech forest and this trend cannot be entirely attributed to changing climatic drivers. This study sought to clarify the mechanisms responsible for the observed trend...... for nitrogen demand during mast years is supported by the inter-annual variability in the estimated parameters. The inter-annual variability of photosynthesis parameters was fundamental to the simulation of the trend in carbon fluxes in the investigated beech forest and this demonstrates the importance......, the latent and sensible heat fluxes and the CO2 fluxes decreased the parameter uncertainty considerably compared to using CO2 fluxes as validation data alone. The fitted model was able to simulate the observed carbon fluxes well (R2=0.8, mean error=0.1gCm−2d−1) but did not reproduce the decadal (1997...

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

    Science.gov (United States)

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

    2014-01-01

    Three young northern temperate forest communities in the north-central United States were exposed to factorial combinations of elevated carbon dioxide (CO2) and tropospheric ozone (O3) for 11 years. Here, we report results from an extensive sampling of plant biomass and soil conducted at the conclusion of the experiment that enabled us to estimate ecosystem carbon (C) content and cumulative net primary productivity (NPP). Elevated CO2 enhanced ecosystem C content by 11%, whereas elevated O3 decreased ecosystem C content by 9%. There was little variation in treatment effects on C content across communities and no meaningful interactions between CO2 and O3. Treatment effects on ecosystem C content resulted primarily from changes in the near-surface mineral soil and tree C, particularly differences in woody tissues. Excluding the mineral soil, cumulative NPP was a strong predictor of ecosystem C content (r2 = 0.96). Elevated CO2 enhanced cumulative NPP by 39%, a consequence of a 28% increase in canopy nitrogen (N) content (g N m−2) and a 28% increase in N productivity (NPP/canopy N). In contrast, elevated O3 lowered NPP by 10% because of a 21% decrease in canopy N, but did not impact N productivity. Consequently, as the marginal impact of canopy N on NPP (ΔNPP/ΔN) decreased through time with further canopy development, the O3 effect on NPP dissipated. Within the mineral soil, there was less C in the top 0.1 m of soil under elevated O3 and less soil C from 0.1 to 0.2 m in depth under elevated CO2. Overall, these results suggest that elevated CO2 may create a sustained increase in NPP, whereas the long-term effect of elevated O3 on NPP will be smaller than expected. However, changes in soil C are not well-understood and limit our ability to predict changes in ecosystem C content. PMID:24604779

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

    Science.gov (United States)

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

    2014-08-01

    Three young northern temperate forest communities in the north-central United States were exposed to factorial combinations of elevated carbon dioxide (CO2 ) and tropospheric ozone (O3 ) for 11 years. Here, we report results from an extensive sampling of plant biomass and soil conducted at the conclusion of the experiment that enabled us to estimate ecosystem carbon (C) content and cumulative net primary productivity (NPP). Elevated CO2 enhanced ecosystem C content by 11%, whereas elevated O3 decreased ecosystem C content by 9%. There was little variation in treatment effects on C content across communities and no meaningful interactions between CO2 and O3 . Treatment effects on ecosystem C content resulted primarily from changes in the near-surface mineral soil and tree C, particularly differences in woody tissues. Excluding the mineral soil, cumulative NPP was a strong predictor of ecosystem C content (r(2) = 0.96). Elevated CO2 enhanced cumulative NPP by 39%, a consequence of a 28% increase in canopy nitrogen (N) content (g N m(-2) ) and a 28% increase in N productivity (NPP/canopy N). In contrast, elevated O3 lowered NPP by 10% because of a 21% decrease in canopy N, but did not impact N productivity. Consequently, as the marginal impact of canopy N on NPP (∆NPP/∆N) decreased through time with further canopy development, the O3 effect on NPP dissipated. Within the mineral soil, there was less C in the top 0.1 m of soil under elevated O3 and less soil C from 0.1 to 0.2 m in depth under elevated CO2 . Overall, these results suggest that elevated CO2 may create a sustained increase in NPP, whereas the long-term effect of elevated O3 on NPP will be smaller than expected. However, changes in soil C are not well-understood and limit our ability to predict changes in ecosystem C content. © 2014 The Authors Global Change Biology Published by John Wiley & Sons Ltd.

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

    Science.gov (United States)

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

    2010-01-01

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

  20. Estimating global "blue carbon" emissions from conversion and degradation of vegetated coastal ecosystems.

    Directory of Open Access Journals (Sweden)

    Linwood Pendleton

    Full Text Available Recent attention has focused on the high rates of annual carbon sequestration in vegetated coastal ecosystems--marshes, mangroves, and seagrasses--that may be lost with habitat destruction ('conversion'. Relatively unappreciated, however, is that conversion of these coastal ecosystems also impacts very large pools of previously-sequestered carbon. Residing mostly in sediments, this 'blue carbon' can be released to the atmosphere when these ecosystems are converted or degraded. Here we provide the first global estimates of this impact and evaluate its economic implications. Combining the best available data on global area, land-use conversion rates, and near-surface carbon stocks in each of the three ecosystems, using an uncertainty-propagation approach, we estimate that 0.15-1.02 Pg (billion tons of carbon dioxide are being released annually, several times higher than previous estimates that account only for lost sequestration. These emissions are equivalent to 3-19% of those from deforestation globally, and result in economic damages of $US 6-42 billion annually. The largest sources of uncertainty in these estimates stems from limited certitude in global area and rates of land-use conversion, but research is also needed on the fates of ecosystem carbon upon conversion. Currently, carbon emissions from the conversion of vegetated coastal ecosystems are not included in emissions accounting or carbon market protocols, but this analysis suggests they may be disproportionally important to both. Although the relevant science supporting these initial estimates will need to be refined in coming years, it is clear that policies encouraging the sustainable management of coastal ecosystems could significantly reduce carbon emissions from the land-use sector, in addition to sustaining the well-recognized ecosystem services of coastal habitats.

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

    Science.gov (United States)

    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

  2. Modelling carbon fluxes of forest and grassland ecosystems in Western Europe using the CARAIB dynamic vegetation model: evaluation against eddy covariance data.

    Science.gov (United States)

    Henrot, Alexandra-Jane; François, Louis; Dury, Marie; Hambuckers, Alain; Jacquemin, Ingrid; Minet, Julien; Tychon, Bernard; Heinesch, Bernard; Horemans, Joanna; Deckmyn, Gaby

    2015-04-01

    Eddy covariance measurements are an essential resource to understand how ecosystem carbon fluxes react in response to climate change, and to help to evaluate and validate the performance of land surface and vegetation models at regional and global scale. In the framework of the MASC project (« Modelling and Assessing Surface Change impacts on Belgian and Western European climate »), vegetation dynamics and carbon fluxes of forest and grassland ecosystems simulated by the CARAIB dynamic vegetation model (Dury et al., iForest - Biogeosciences and Forestry, 4:82-99, 2011) are evaluated and validated by comparison of the model predictions with eddy covariance data. Here carbon fluxes (e.g. net ecosystem exchange (NEE), gross primary productivity (GPP), and ecosystem respiration (RECO)) and evapotranspiration (ET) simulated with the CARAIB model are compared with the fluxes measured at several eddy covariance flux tower sites in Belgium and Western Europe, chosen from the FLUXNET global network (http://fluxnet.ornl.gov/). CARAIB is forced either with surface atmospheric variables derived from the global CRU climatology, or with in situ meteorological data. Several tree (e.g. Pinus sylvestris, Fagus sylvatica, Picea abies) and grass species (e.g. Poaceae, Asteraceae) are simulated, depending on the species encountered on the studied sites. The aim of our work is to assess the model ability to reproduce the daily, seasonal and interannual variablility of carbon fluxes and the carbon dynamics of forest and grassland ecosystems in Belgium and Western Europe.

  3. Organic carbon sedimentation rates in Asian mangrove coastal ecosystems estimated by 210PB chronology

    International Nuclear Information System (INIS)

    Tateda, Y.; Wattayakorn, G.; Nhan, D.D.; Kasuya, Y.

    2004-01-01

    Organic carbon balance estimation of mangrove coastal ecosystem is important for understanding of Asian coastal carbon budget/flux calculation in global carbon cycle modelling which is powerful tool for the prediction of future greenhouse gas effect and evaluation of countermeasure preference. Especially, the organic carbon accumulation rate in mangrove ecosystem was reported to be important sink of carbon as well as that in boreal peat accumulation. For the estimation of 10 3 years scale organic carbon accumulation rates in mangrove coastal ecosystems, 14 C was used as long term chronological tracer, being useful in pristine mangrove forest reserve area. While in case of mangrove plantation of in coastal area, the 210 Pb is suitable for the estimation of decades scale estimation by its half-life. Though it has possibility of bio-/physical- turbation effect in applying 210 Pb chronology that is offset in case of 10 3 years scale estimation, especially in Asian mangrove ecosystem where the anthropogenic physical turbation by coastal fishery is vigorous.In this paper, we studied the organic carbon and 210 Pb accumulation rates in subtropical mangrove coastal ecosystems in Japan, Vietnam and Thailand with 7 Be analyses to make sure the negligible effect of above turbation effects on organic carbon accumulation. We finally concluded that 210 Pb was applicable to estimate organic carbon accumulation rates in these ecosystems even though the physical-/bio-turbation is expected. The measured organic carbon accumulation rates using 210 Pb in mangrove coastal ecosystems of Japan, Vietnam and Thailand were 0.067 4.0 t-C ha -1 y -1 . (author)

  4. Methane- and dissolved organic carbon-fueled microbial loop supports a tropical subterranean estuary ecosystem

    NARCIS (Netherlands)

    Brankovits, D.; Pohlman, J.W.; Niemann, H.; Leigh, M.B.; Leewis, M.C.; Becker, K.W.; Iliffe, T.M.; Alvarez, F.; Lehmann, M.F.; Phillips, B.

    2017-01-01

    Subterranean estuaries extend inland into density-stratified coastal carbonate aquifers containing a surprising diversity of endemic animals (mostly crustaceans) within a highly oligotrophic habitat. How complex ecosystems (termed anchialine) thrive in this globally distributed, cryptic environment

  5. Evaluating the Effects of Fire on Semi-Arid Savanna Ecosystem Productivity Using Integrated Spectral and Gas Exchange Measurements

    Science.gov (United States)

    Raub, H. D.; Jimenez, J. R.; Gallery, R. E.; Sutter, L., Jr.; Barron-Gafford, G.; Smith, W. K.

    2017-12-01

    Drylands account for 40% of the land surface and have been identified as increasingly important in driving interannual variability of the land carbon sink. Yet, understanding of dryland seasonal ecosystem productivity dynamics - termed Gross Primary Productivity (GPP) - is limited due to complex interactions between vegetation health, seasonal drought dynamics, a paucity of long-term measurements across these under-studied regions, and unanticipated disturbances from varying fire regimes. For instance, fire disturbance has been found to either greatly reduce post-fire GPP through vegetation mortality or enhance post-fire GPP though increased resource availability (e.g., water, light, nutrients, etc.). Here, we explore post-fire ecosystem recovery by evaluating seasonal GPP dynamics for two Ameriflux eddy covariance flux tower sites within the Santa Rita Experimental Range of southeastern Arizona: 1) the US-SRG savanna site dominated by a mix of grass and woody mesquite vegetation that was burned in May 2017, and 2) the US-SRM savanna site dominated by similar vegetation but unburned for the full measurement record. For each site, we collected leaf-level spectral and gas exchange measurements, as well as leaf-level chemistry and soil chemistry to characterize differences in nutrient availability and microbial activity throughout the 2017 growing season. From spectral data, we derived and evaluated multiple common vegetation metrics, including normalized difference vegetation index (NDVI), photochemical reflectivity index (PRI), near-infrared reflectance (NIRv), and MERIS terrestrial chlorophyll index (MTCI). Early results suggest rates of photosynthesis were enhanced at the burned site, with productivity increasing immediately following the onset of monsoonal precipitation; whereas initial photosynthesis at the unburned site remained relatively low following first monsoonal rains. MTCI values for burned vegetation appear to track higher levels of leaf-level nitrogen

  6. Lessons from simultaneous measurements of soil respiration and net ecosystem exchange of CO2 in temperate forests

    Science.gov (United States)

    Renchon, A.; Pendall, E.

    2017-12-01

    Land-surface exchanges of CO2 play a key role in ameliorating or exacerbating climate change. The eddy-covariance method allows direct measurement of net ecosystem-atmosphere exchange of CO2 (NEE), but partitioning daytime NEE into its components - gross primary productivity (GPP) and ecosystem respiration (RE) - remains challenging. Continuous measurements of soil respiration (RS), along with flux towers, have the potential to better constrain data and models of RE and GPP. We use simultaneous half-hourly NEE and RS data to: (1) compare the short-term (fortnightly) apparent temperature sensitivity (Q10) of nighttime RS and RE; (2) assess whether daytime RS can be estimated using nighttime response functions; and (3) compare the long-term (annual) responses of nighttime RS and nighttime RE to interacting soil moisture and soil temperature. We found that nighttime RS has a lower short-term Q10 than nighttime RE. This suggests that the Q10 of nighttime RE is strongly influenced by the Q10 of nighttime above-ground respiration, or possibly by a bias in RE measurements. The short-term Q10 of RS and RE decreased with increasing temperature. In general, daytime RS could be estimated using nighttime RS temperature and soil moisture (r2 = 0.9). However, this results from little to no diurnal variation in RS, and estimating daytime RS as the average of nighttime RS gave similar results (r2 = 0.9). Furthermore, we observed a day-night hysteresis of RS response to temperature, especially when using air temperature and sometimes when using soil temperature at 5cm depth. In fact, during some months, soil respiration observations were lower during daytime compared to nighttime, despite higher temperature in daytime. Therefore, daytime RS modelled from nighttime RS temperature response was overestimated during these periods. RS and RE responses to the combination of soil moisture and soil temperature were similar, and consistent with the DAMM model of soil-C decomposition. These

  7. Carbon storage in mangrove and peatland ecosystems: A preliminary account from plots in Indonesia

    Science.gov (United States)

    Daniel Murdiyarso; Daniel Donato; J. Boone Kauffman; Sofyan Kurnianto; Melanie Stidham; Markku. Kanninen

    2009-01-01

    Tropical mangroves and peat swamp forests provide numerous ecosystem services, including nutrient cycling, sediment trapping, protection from cyclones and tsunamis, habitat for numerous organisms (many economically important) and wood for lumber and fuel (Ellison 2008). Among the most important of these functions--but poorly quantified--is ecosystem carbon (C) storage...

  8. An integrated model of soil, hydrology, and vegetation for carbon dynamics in wetland ecosystems

    Science.gov (United States)

    Yu Zhang; Changsheng Li; Carl C. Trettin; Harbin Li; Ge Sun

    2002-01-01

    Wetland ecosystems are an important component in global carbon (C) cycles and may exert a large influence on global clinlate change. Predictions of C dynamics require us to consider interactions among many critical factors of soil, hydrology, and vegetation. However, few such integrated C models exist for wetland ecosystems. In this paper, we report a simulation model...

  9. Burrowing herbivores alter soil carbon and nitrogen dynamics in a semi-arid ecosystem, Argentina

    Science.gov (United States)

    Kenneth L. Clark; Lyn C. Branch; Jose L. Hierro; Diego Villarreal

    2016-01-01

    Activities of burrowing herbivores, including movement of soil and litter and deposition of waste material, can alter the distribution of labile carbon (C) and nitrogen (N) in soil, affecting spatial patterning of nutrient dynamics in ecosystems where they are abundant. Their role in ecosystem processes in surface soil has been studied extensively, but effects of...

  10. A method for assessing carbon stocks, carbon sequestration, and greenhouse-gas fluxes in ecosystems of the United States under present conditions and future scenarios

    Science.gov (United States)

    Bergamaschi, Brian A.; Bernknopf, Richard; Clow, David; Dye, Dennis; Faulkner, Stephen; Forney, William; Gleason, Robert; Hawbaker, Todd; Liu, Jinxun; Liu, Shu-Guang; Prisley, Stephen; Reed, Bradley; Reeves, Matthew; Rollins, Matthew; Sleeter, Benjamin; Sohl, Terry; Stackpoole, Sarah; Stehman, Stephen; Striegl, Robert G.; Wein, Anne; Zhu, Zhi-Liang; Zhu, Zhi-Liang

    2010-01-01

    solicited to construct these scenarios.The methods for mapping the current LULC and ecosystem disturbances will require the extensive use of both remote-sensing data and field-survey data (for example, forest inventories) to capture and characterize landscape-changing events. For potential LULC changes and ecosystem disturbances, key drivers such as socioeconomic and climate changes will be used in addition to the biophysical data. The result of these analyses will be a series of maps for each future year for each scenario. These annual maps will form the basis for estimating carbon storage and GHG emissions. For terrestrial ecosystems, carbon storage, carbon-sequestration capacities, and GHG emissions under the present conditions and future scenarios will be assessed using the LULC-change and ecosystem-disturbance estimates in map format with a spatially explicit biogeochemical ensemble modeling system that incorporates properties of management activities (such as tillage or harvesting) and properties of individual ecosystems (such as energy exchange, vegetation characteristics, hydrological cycling, and soil attributes). For aquatic ecosystems, carbon burial in sediments and fluxes of GHG are functions of the present and future potential stream flow and sediment transport and will be assessed using empirical hydrological modeling methods. Validation and uncertainty analysis methods described in the methodology will follow established guidelines to assess the quality of the assessment results.The U.S. Environmental Protection Agency’s Level II ecoregions map will be the practical instrument for developing and delivering assessment results. Consequently, the ecoregion (there are 22 modified ecoregions) will be the reporting unit of the assessment because the scenarios, assessment results, validation, and uncertainty analysis will be produced at that scale. The implementation of these methods will require collaborations among various Federal agencies, State agencies

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

    Science.gov (United States)

    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

  12. Impacts of urbanization on carbon balance in terrestrial ecosystems of the Southern United States

    International Nuclear Information System (INIS)

    Zhang Chi; Tian Hanqin; Chen, Guangsheng; Chappelka, Arthur; Xu Xiaofeng; Ren Wei; Hui Dafeng; Liu Mingliang; Lu Chaoqun; Pan, Shufen; Lockaby, Graeme

    2012-01-01

    Using a process-based Dynamic Land Ecosystem Model, we assessed carbon dynamics of urbanized/developed lands in the Southern United States during 1945–2007. The results indicated that approximately 1.72 (1.69–1.77) Pg (1P = 10 15 ) carbon was stored in urban/developed lands, comparable to the storage of shrubland or cropland in the region. Urbanization resulted in a release of 0.21 Pg carbon to the atmosphere during 1945–2007. Pre-urbanization vegetation type and time since land conversion were two primary factors determining the extent of urbanization impacts on carbon dynamics. After a rapid decline of carbon storage during land conversion, an urban ecosystem gradually accumulates carbon and may compensate for the initial carbon loss in 70–100 years. The carbon sequestration rate of urban ecosystem diminishes with time, nearly disappearing in two centuries after land conversion. This study implied that it is important to take urbanization effect into account for assessing regional carbon balance. - Highlights: ► A series of spatial and temporal urban/developed land maps were generated. ► Urbanization effects on regional carbon dynamics were studied with a process-based Dynamic Land Ecosystem Model (DLEM). ► Carbon storage of urban/developed land was comparable to that stored in cropland and shrubland in the Southern United States. ► Pre-urbanization vegetation type and time since land conversion were two primary factors determining the extent of urbanization impacts on carbon dynamics. ► Urbanization resulted in carbon emission, but established urban areas may gradually accumulate carbon over time. - Urbanization has resulted in carbon release to the atmosphere, but established urban areas may gradually accumulate carbon over time.

  13. How ecological restoration alters ecosystem services: an analysis of carbon sequestration in China's Loess Plateau.

    Science.gov (United States)

    Feng, Xiaoming; Fu, Bojie; Lu, Nan; Zeng, Yuan; Wu, Bingfang

    2013-10-03

    Restoring disturbed and over-exploited ecosystems is important to mitigate human pressures on natural ecosystems. China has launched an ambitious national ecosystem restoration program called Grain to Green Program (GTGP) over the last decade. By using remote sensing techniques and ecosystem modelling, we quantitatively evaluated the changes in ecosystem carbon sequestration since China's GTGP program during period of 2000-2008. It was found the NPP and NEP in this region had steadily increased after the initiative of the GTGP program, and a total of 96.1 Tg of additional carbon had been sequestered during that period. Changes in soil carbon storage were lagged behind and thus insignificant over the period, but was expected to follow in the coming decades. As a result, the Loess Plateau ecosystem had shifted from a net carbon source in 2000 to a net carbon sink in 2008. The carbon sequestration efficiency was constrained by precipitation, and appropriate choices of restoration types (trees, shrubs, and grasses) in accordance to local climate are critical for achieving the best benefit/cost efficiency.

  14. A diagnostic study of temperature controls on global terrestrial carbon exchange

    International Nuclear Information System (INIS)

    Vukicevic, Tomislava; Schimel, David

    2001-01-01

    The observed interannual variability of atmospheric CO 2 reflects short-term variability in sources and sinks of CO 2 . Analyses using 13 C and O 2 suggest that much of the observed interannual variability is due to changes in terrestrial CO 2 exchange. First principles, empirical correlations and process models suggest a link between climate variation and net ecosystem exchange, but the scaling of ecological process studies to the globe is notoriously difficult. We sought to identify a component of global CO 2 exchange that varied coherently with land temperature anomalies using an inverse modeling approach. We developed a family of simplified spatially aggregated ecosystem models (designated K-model versions) consisting of five compartments: atmospheric CO 2 , live vegetation, litter, and two soil pools that differ in turnover times. The pools represent cumulative differences from mean storage due to temperature variability and can thus have positive or negative values. Uptake and respiration of CO 2 are assumed to be linearly dependent on temperature. One model version includes a simple representation of the nitrogen cycle in which changes in the litter and soil carbon pools result in stoichiometric release of plant-available nitrogen, the other omits the nitrogen feedback. The model parameters were estimated by inversion of the model against global temperature and CO 2 anomaly data using the variational method. We found that the temperature sensitivity of carbon uptake (NPP) was less than that of respiration in all model versions. Analyses of model and data also showed that temperature anomalies trigger ecosystem changes on multiple, lagged time-scales. Other recent studies have suggested a more active land biosphere at Northern latitudes in response to warming and longer growing seasons. Our results indicate that warming should increase NPP, consistent with this theory, but that respiration should increase more than NPP, leading to decreased or negative NEP. A

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

    Science.gov (United States)

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

    1998-01-01

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

  16. Seasonal variation in carbon dioxide exchange over a Mediterranean annual grassland in California

    Energy Technology Data Exchange (ETDEWEB)

    Xu, L; Baldocchi, D

    2004-05-01

    Understanding how environmental variables affect the processes that regulate the carbon flux over grassland is critical for large-scale modeling research, since grasslands comprise almost one-third of the earth's natural vegetation. To address this issue, fluxes of CO{sub 2} (F{sub c}, flux toward the surface is negative) were measured over a Mediterranean, annual grassland in California, USA for 2 years with the eddy covariance method. To interpret the biotic and abiotic factors that modulate F{sub c} over the course of a year we decomposed net ecosystem CO{sub 2} exchange into its constituent components, ecosystem respiration (R{sub eco}) and gross primary production (GPP). Daytime R{sub eco} was extrapolated from the relationship between temperature and nighttime F{sub c} under high turbulent conditions. Then, GPP was estimated by subtracting daytime values of F{sub c} from daytime estimates of R{sub eco}. Results show that most of carbon exchange, both photosynthesis and respiration, was limited to the wet season (typically from October to mid-May). Seasonal variations in GPP followed closely to changes in leaf area index, which in turn was governed by soil moisture, available sunlight and the timing of the last frost. In general, R{sub eco} was an exponential function of soil temperature, but with season-dependent values of Q{sub 10}. The temperature-dependent respiration model failed immediately after rain events, when large pulses of R{sub eco} were observed. Respiration pulses were especially notable during the dry season when the grass was dead and were the consequence of quickly stimulated microbial activity. Integrated values of GPP, R{sub eco}, and net ecosystem exchange (NEE) were 867, 735, and -132g C m{sup -2}, respectively, for the 2000-2001 season, and 729, 758, and 29g C m{sup -2} for the 2001-2002 season. Thus, the grassland was a moderate carbon sink during the first season and a weak carbon source during the second season. In contrast to a

  17. Sensitivity of temperate desert steppe carbon exchange to seasonal droughts and precipitation variations in Inner Mongolia, China.

    Science.gov (United States)

    Yang, Fulin; Zhou, Guangsheng

    2013-01-01

    Arid grassland ecosystems have significant interannual variation in carbon exchange; however, it is unclear how environmental factors influence carbon exchange in different hydrological years. In this study, the eddy covariance technique was used to investigate the seasonal and interannual variability of CO₂ flux over a temperate desert steppe in Inner Mongolia, China from 2008 to 2010. The amounts and times of precipitation varied significantly throughout the study period. The precipitation in 2009 (186.4 mm) was close to the long-term average (183.9±47.6 mm), while the precipitation in 2008 (136.3 mm) and 2010 (141.3 mm) was approximately a quarter below the long-term average. The temperate desert steppe showed carbon neutrality for atmospheric CO₂ throughout the study period, with a net ecosystem carbon dioxide exchange (NEE) of -7.2, -22.9, and 26.0 g C m⁻² yr⁻¹ in 2008, 2009, and 2010, not significantly different from zero. The ecosystem gained more carbon in 2009 compared to other two relatively dry years, while there was significant difference in carbon uptake between 2008 and 2010, although both years recorded similar annual precipitation. The results suggest that summer precipitation is a key factor determining annual NEE. The apparent quantum yield and saturation value of NEE (NEE(sat)) and the temperature sensitivity coefficient of ecosystem respiration (R(eco)) exhibited significant variations. The values of NEE(sat) were -2.6, -2.9, and -1.4 µmol CO₂ m⁻² s⁻¹ in 2008, 2009, and 2010, respectively. Drought suppressed both the gross primary production (GPP) and R(eco), and the drought sensitivity of GPP was greater than that of R(eco). The soil water content sensitivity of GPP was high during the dry year of 2008 with limited soil moisture availability. Our results suggest the carbon balance of this temperate desert steppe was not only sensitive to total annual precipitation, but also to its seasonal distribution.

  18. Sensitivity of temperate desert steppe carbon exchange to seasonal droughts and precipitation variations in Inner Mongolia, China.

    Directory of Open Access Journals (Sweden)

    Fulin Yang

    Full Text Available Arid grassland ecosystems have significant interannual variation in carbon exchange; however, it is unclear how environmental factors influence carbon exchange in different hydrological years. In this study, the eddy covariance technique was used to investigate the seasonal and interannual variability of CO₂ flux over a temperate desert steppe in Inner Mongolia, China from 2008 to 2010. The amounts and times of precipitation varied significantly throughout the study period. The precipitation in 2009 (186.4 mm was close to the long-term average (183.9±47.6 mm, while the precipitation in 2008 (136.3 mm and 2010 (141.3 mm was approximately a quarter below the long-term average. The temperate desert steppe showed carbon neutrality for atmospheric CO₂ throughout the study period, with a net ecosystem carbon dioxide exchange (NEE of -7.2, -22.9, and 26.0 g C m⁻² yr⁻¹ in 2008, 2009, and 2010, not significantly different from zero. The ecosystem gained more carbon in 2009 compared to other two relatively dry years, while there was significant difference in carbon uptake between 2008 and 2010, although both years recorded similar annual precipitation. The results suggest that summer precipitation is a key factor determining annual NEE. The apparent quantum yield and saturation value of NEE (NEE(sat and the temperature sensitivity coefficient of ecosystem respiration (R(eco exhibited significant variations. The values of NEE(sat were -2.6, -2.9, and -1.4 µmol CO₂ m⁻² s⁻¹ in 2008, 2009, and 2010, respectively. Drought suppressed both the gross primary production (GPP and R(eco, and the drought sensitivity of GPP was greater than that of R(eco. The soil water content sensitivity of GPP was high during the dry year of 2008 with limited soil moisture availability. Our results suggest the carbon balance of this temperate desert steppe was not only sensitive to total annual precipitation, but also to its seasonal distribution.

  19. A new estimate of carbon for Bangladesh forest ecosystems with their spatial distribution and REDD+ implications

    DEFF Research Database (Denmark)

    Mukul, Sharif A.; Biswas, Shekhar R.; Rashid, A. Z. M. Manzoor

    2014-01-01

    In tropical developing countries, reducing emissions from deforestation and forest degradation (REDD+) is becoming an important mechanism for conserving forests and protecting biodiversity. A key prerequisite for any successful REDD+ project, however, is obtaining baseline estimates of carbon...... in forest ecosystems. Using available published data, we provide here a new and more reliable estimate of carbon in Bangladesh forest ecosystems, along with their geo-spatial distribution. Our study reveals great variability in carbon density in different forests and higher carbon stock in the mangrove...... ecosystems, followed by in hill forests and in inland Sal (Shorea robusta) forests in the country. Due to its coverage, degraded nature, and diverse stakeholder engagement, the hill forests of Bangladesh can be used to obtain maximum REDD+ benefits. Further research on carbon and biodiversity in under...

  20. Vegetation Structure Controls Carbon Sequestration Potential in a Savannah Ecosystem of Mt. Kilimanjaro Region

    Science.gov (United States)

    Becker, J. N.; Gutlein, A.; Sierra Cornejo, N.; Ralf, K.; Hertel, D.; Kuzyakov, Y.

    2016-12-01

    The savannah biome is a hotspot for biodiversity and wildlife conservation in Africa and recently got in the focus of research on carbon (C) sequestration. Savanna ecosystems are increasingly pressured by climate and land-use changes, especially around populous areas such as the Mt. Kilimanjaro region. Savanna vegetation consists of grassland with isolated trees and is therefore characterized by high spatial variation and patchiness of canopy cover and aboveground biomass. Both are major regulators for soil ecological properties and soil-atmospheric trace gas exchange (CO2, N2O, CH4), especially in water-limited environments. Our objectives were to determine spatial trends in soil properties and trace-gas fluxes during the dry season and to relate above- and belowground processes and attributes. 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 each sampling point (0-10 & 10-30 cm depth) we measured soil 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. The tree species had no effect on soil parameters and gas fluxes under the crown. CEC, C and N fractions decreased up to 50% outside the crown-covered area. Tree leaf litter had a far lower C:N ratio than leaf litter of the C4-grass species. δ13C in soil under the crowns shifted about 15% in the direction of tree leaf litter δ13C compared to soil in open area reflecting the tree litter contribution to soil organic matter. The microbial C:N ratio and CO2 efflux were about 30% higher in the open area and strongly dependent on mineral N availability. This indicates N limitation and low C-use efficiency in soil under open grassland. We conclude that the spatial

  1. Organic carbon storage in four ecosystem types in the karst region of southwestern China.

    Directory of Open Access Journals (Sweden)

    Yuguo Liu

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

  2. Spatially explicit simulation of peatland hydrology and carbon dioxide exchange

    International Nuclear Information System (INIS)

    Sonnentag, O.

    2008-01-01

    A recent version of the Boreal Ecosystem Productivity Simulator (BEPS) was extended and modified to include northern peatlands. This thesis evaluated the BEPS-TerrainLab using observations made at the Mer Bleue bog located near Ottawa, Ontario, and the Sandhill fen located near Prince Albert, Saskatchewan. The code was revised to represent the multi-layer canopy and processes related to energy, water vapour and carbon dioxide fluxes through remotely-sensed leaf area index (LAI) maps. A quick and reliable method was also developed to determine shrub LAI with the LAI-2000 plant canopy analyzer. A large number of LAI data was collected at the Mer Bleue bog for the development of a new remote sensing-based methodology using multiple end member spectral unmixing to allow for separate tree and shrub LAI mapping in ombrotrophic peatlands. The methodology was also adapted for use in minerotrophic peatlands and their surrounding landscapes. These LAI maps within the BEPS-TerrainLab represented the tree and shrub layers of the Mer Bleue bog and the tree and shrub/sedge layers of the Sandhill fen. The study examined the influence of mesoscale topography (Mer Bleue bog) and macro- and mesoscale topography (Sandhill fen) on wetness, evapotranspiration, and gross primary productivity during the snow-free period of 2004. The results suggested that a peatland type-specific differentiation of macro- and mesoscale topographic effects on hydrology should be included in future peatland ecosystem modelling efforts in order to allow for a more realistic simulation of the soil water balance in peatlands and to reduce uncertainties in carbon dioxide and methane annual fluxes from wetlands

  3. Spatially explicit simulation of peatland hydrology and carbon dioxide exchange

    Energy Technology Data Exchange (ETDEWEB)

    Sonnentag, O.

    2008-08-01

    A recent version of the Boreal Ecosystem Productivity Simulator (BEPS) was extended and modified to include northern peatlands. This thesis evaluated the BEPS-TerrainLab using observations made at the Mer Bleue bog located near Ottawa, Ontario, and the Sandhill fen located near Prince Albert, Saskatchewan. The code was revised to represent the multi-layer canopy and processes related to energy, water vapour and carbon dioxide fluxes through remotely-sensed leaf area index (LAI) maps. A quick and reliable method was also developed to determine shrub LAI with the LAI-2000 plant canopy analyzer. A large number of LAI data was collected at the Mer Bleue bog for the development of a new remote sensing-based methodology using multiple end member spectral unmixing to allow for separate tree and shrub LAI mapping in ombrotrophic peatlands. The methodology was also adapted for use in minerotrophic peatlands and their surrounding landscapes. These LAI maps within the BEPS-TerrainLab represented the tree and shrub layers of the Mer Bleue bog and the tree and shrub/sedge layers of the Sandhill fen. The study examined the influence of mesoscale topography (Mer Bleue bog) and macro- and mesoscale topography (Sandhill fen) on wetness, evapotranspiration, and gross primary productivity during the snow-free period of 2004. The results suggested that a peatland type-specific differentiation of macro- and mesoscale topographic effects on hydrology should be included in future peatland ecosystem modelling efforts in order to allow for a more realistic simulation of the soil water balance in peatlands and to reduce uncertainties in carbon dioxide and methane annual fluxes from wetlands.

  4. Upland Trees Contribute to Exchange of Nitrous Oxide (N2O) in Forest Ecosystems

    Science.gov (United States)

    Tian, H.; Thompson, R.; Canadell, J.; Winiwarter, W.; Machacova, K.; Maier, M.; Halmeenmäki, E.; Svobodova, K.; Lang, F.; Pihlatie, M.; Urban, O.

    2017-12-01

    The increase in atmospheric nitrous oxide (N2O) concentration contributes to the acceleration of the greenhouse effect. However, the role of trees in the N2O exchange of forest ecosystems is still an open question. While the soils of temperate and boreal forests were shown to be a natural source of N2O, trees have been so far overlooked in the forest N2O inventories. We determined N2O fluxes in common tree species of boreal and temperate forests: Scots pine (Pinus sylvestris), Norway spruce (Picea abies), downy and silver birch (Betula pubescens, B. pendula), and European beech (Fagus sylvatica). We investigated (1) whether these tree species exchange N2O with the atmosphere under natural field conditions, (2) how the tree N2O fluxes contribute to the forest N2O balance, and (3) whether these fluxes show seasonal dynamics. The studies were performed in a boreal forest (SMEAR II station, Finland; June 2014 - May 2015) and two temperate mountain forests (White Carpathians, Czech Republic; Black Forest, Germany; June and July 2015). Fluxes of N2O in mature tree stems and forest floor were measured using static chamber systems followed by chromatographic and photo-acoustic analyses of N2O concentration changes. Pine, spruce and birch trees were identified as net annual N2O sources. Spruce was found the strongest emitter (0.27 mg ha-1 h-1) amounting thus up to 2.5% of forest floor N2O emissions. All tree species showed a substantial seasonality in stem N2O flux that was related to their physiological activity and climatic variables. In contrast, stems of beech trees growing at soils consuming N2O may act as a substantial sink of N2O from the atmosphere. Consistent N2O consumption by tree stems ranging between -12.1 and -35.2 mg ha-1 h-1 and contributing by up to 3.4% to the forest floor N2O uptake is a novel finding in contrast to current studies presenting trees as N2O emitters. To understand these fluxes, N2O exchange of photoautotrophic organisms associated with

  5. Modelling carbon cycle of agro-forest ecosystems in Lombardy (Italy

    Directory of Open Access Journals (Sweden)

    Colombo R

    2009-09-01

    Full Text Available In this paper we present a methodology for the estimation of Gross Primary Production (GPP, Net Primary Production (NPP and Net Ecosystem Production (NEP for the main agricultural and forest ecosystems of the Lombardia Region (Italy. The MOD17 model was parameterized according to the different agro-forestry ecosystems and applied at regional scale by using satellite data with a spatial resolution of 250m. The high spatial resolution along with fine classification agro-forestry ecosystems has allowed to accurately analyze the carbon budget of an extremely fragmented and complex environment such as the Lombardia Region. Modeling results showed the role of the forests in the carbon budget at regional scale and represent important information layer for the spatial analysis and for inferring the inter-annual variability of carbon sequestration due to impacts of extreme events and recent climate change (e.g., drought, heat wave, flooding, fires.

  6. Simulating carbon and water fluxes at Arctic and boreal ecosystems in Alaska by optimizing the modified BIOME-BGC with eddy covariance data

    Science.gov (United States)

    Ueyama, M.; Kondo, M.; Ichii, K.; Iwata, H.; Euskirchen, E. S.; Zona, D.; Rocha, A. V.; Harazono, Y.; Nakai, T.; Oechel, W. C.

    2013-12-01

    To better predict carbon and water cycles in Arctic ecosystems, we modified a process-based ecosystem model, BIOME-BGC, by introducing new processes: change in active layer depth on permafrost and phenology of tundra vegetation. The modified BIOME-BGC was optimized using an optimization method. The model was constrained using gross primary productivity (GPP) and net ecosystem exchange (NEE) at 23 eddy covariance sites in Alaska, and vegetation/soil carbon from a literature survey. The model was used to simulate regional carbon and water fluxes of Alaska from 1900 to 2011. Simulated regional fluxes were validated with upscaled GPP, ecosystem respiration (RE), and NEE based on two methods: (1) a machine learning technique and (2) a top-down model. Our initial simulation suggests that the original BIOME-BGC with default ecophysiological parameters substantially underestimated GPP and RE for tundra and overestimated those fluxes for boreal forests. We will discuss how optimization using the eddy covariance data impacts the historical simulation by comparing the new version of the model with simulated results from the original BIOME-BGC with default ecophysiological parameters. This suggests that the incorporation of the active layer depth and plant phenology processes is important to include when simulating carbon and water fluxes in Arctic ecosystems.

  7. Constraining the Exchange of Carbon and Nitrogen in Eastern Long Island Sound

    Science.gov (United States)

    Byrd, A.; Warren, J. K.; Vlahos, P.; Whitney, M. M.

    2017-12-01

    Long Island Sound (LIS) is an urban estuary on the US east coast that undergoes seasonal hypoxia in its western and central regions. Currently, the budgets of both carbon and nitrogen in LIS remain unbalanced, despite their importance to the efficient and strategic management of the health of coastal and aquatic ecosystems. In this study, we evaluated the exchange values of C and N at the mouth of LIS (the Race), in order to constrain export through this important boundary. Discreet water samples were collected during four 15 km transects over the Race at five stations and three depths each station to resolve the temporal variability over a complete tidal cycle, in order to assess both net flux and variations across the tidal period. By evaluating both the particulate and dissolved pools of carbon (POC, PIC, DOC, DIC) and nitrogen (PON, DON, DIN) during the spring, summer and winter (high and low flow conditions) and pairing these measurements with physical data, we were able to identify a variety of forcing and export regimes. Preliminary results indicate the importance of spatial and tidal variability on flux estimates and show little or no export (and sometimes import) of nitrogen and significant export of organic carbon.

  8. Modelling the diurnal and seasonal dynamics of soil CO2 exchange in a semiarid ecosystem with high plant–interspace heterogeneity

    Directory of Open Access Journals (Sweden)

    J. Gong

    2018-01-01

    Full Text Available We used process-based modelling to investigate the roles of carbon-flux (C-flux components and plant–interspace heterogeneities in regulating soil CO2 exchanges (FS in a dryland ecosystem with sparse vegetation. To simulate the diurnal and seasonal dynamics of FS, the modelling considered simultaneously the CO2 production, transport and surface exchanges (e.g. biocrust photosynthesis, respiration and photodegradation. The model was parameterized and validated with multivariate data measured during the years 2013–2014 in a semiarid shrubland ecosystem in Yanchi, northwestern China. The model simulation showed that soil rewetting could enhance CO2 dissolution and delay the emission of CO2 produced from rooting zone. In addition, an ineligible fraction of respired CO2 might be removed from soil volumes under respiration chambers by lateral water flows and root uptakes. During rewetting, the lichen-crusted soil could shift temporally from net CO2 source to sink due to the activated photosynthesis of biocrust but the restricted CO2 emissions from subsoil. The presence of plant cover could decrease the root-zone CO2 production and biocrust C sequestration but increase the temperature sensitivities of these fluxes. On the other hand, the sensitivities of root-zone emissions to water content were lower under canopy, which may be due to the advection of water flows from the interspace to canopy. To conclude, the complexity and plant–interspace heterogeneities of soil C processes should be carefully considered to extrapolate findings from chamber to ecosystem scales and to predict the ecosystem responses to climate change and extreme climatic events. Our model can serve as a useful tool to simulate the soil CO2 efflux dynamics in dryland ecosystems.

  9. Modelling the diurnal and seasonal dynamics of soil CO2 exchange in a semiarid ecosystem with high plant-interspace heterogeneity

    Science.gov (United States)

    Gong, Jinnan; Wang, Ben; Jia, Xin; Feng, Wei; Zha, Tianshan; Kellomäki, Seppo; Peltola, Heli

    2018-01-01

    We used process-based modelling to investigate the roles of carbon-flux (C-flux) components and plant-interspace heterogeneities in regulating soil CO2 exchanges (FS) in a dryland ecosystem with sparse vegetation. To simulate the diurnal and seasonal dynamics of FS, the modelling considered simultaneously the CO2 production, transport and surface exchanges (e.g. biocrust photosynthesis, respiration and photodegradation). The model was parameterized and validated with multivariate data measured during the years 2013-2014 in a semiarid shrubland ecosystem in Yanchi, northwestern China. The model simulation showed that soil rewetting could enhance CO2 dissolution and delay the emission of CO2 produced from rooting zone. In addition, an ineligible fraction of respired CO2 might be removed from soil volumes under respiration chambers by lateral water flows and root uptakes. During rewetting, the lichen-crusted soil could shift temporally from net CO2 source to sink due to the activated photosynthesis of biocrust but the restricted CO2 emissions from subsoil. The presence of plant cover could decrease the root-zone CO2 production and biocrust C sequestration but increase the temperature sensitivities of these fluxes. On the other hand, the sensitivities of root-zone emissions to water content were lower under canopy, which may be due to the advection of water flows from the interspace to canopy. To conclude, the complexity and plant-interspace heterogeneities of soil C processes should be carefully considered to extrapolate findings from chamber to ecosystem scales and to predict the ecosystem responses to climate change and extreme climatic events. Our model can serve as a useful tool to simulate the soil CO2 efflux dynamics in dryland ecosystems.

  10. Effect of climate warming on the annual terrestrial net ecosystem CO2 exchange globally in the boreal and temperate regions.

    Science.gov (United States)

    Zhang, Zhiyuan; Zhang, Renduo; Cescatti, Alessandro; Wohlfahrt, Georg; Buchmann, Nina; Zhu, Juan; Chen, Guanhong; Moyano, Fernando; Pumpanen, Jukka; Hirano, Takashi; Takagi, Kentaro; Merbold, Lutz

    2017-06-08

    The net ecosystem CO 2 exchange is the result of the imbalance between the assimilation process (gross primary production, GPP) and ecosystem respiration (RE). The aim of this study was to investigate temperature sensitivities of these processes and the effect of climate warming on the annual terrestrial net ecosystem CO 2 exchange globally in the boreal and temperate regions. A database of 403 site-years of ecosystem flux data at 101 sites in the world was collected and analyzed. Temperature sensitivities of rates of RE and GPP were quantified with Q 10 , defined as the increase of RE (or GPP) rates with a temperature rise of 10 °C. Results showed that on the annual time scale, the intrinsic temperature sensitivity of GPP (Q 10sG ) was higher than or equivalent to the intrinsic temperature sensitivity of RE (Q 10sR ). Q 10sG was negatively correlated to the mean annual temperature (MAT), whereas Q 10sR was independent of MAT. The analysis of the current temperature sensitivities and net ecosystem production suggested that temperature rise might enhance the CO 2 sink of terrestrial ecosystems both in the boreal and temperate regions. In addition, ecosystems in these regions with different plant functional types should sequester more CO 2 with climate warming.

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

    Science.gov (United States)

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

    2015-10-01

    Recently, the number and amount of biogenically emitted volatile organic compounds (VOCs) has been discussed vigorously. 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 by the eddy covariance (EC) method. Detectable fluxes were observed for twelve compounds, dominated by isoprene, which comprised over 65 % of the total flux emission. The daily average of the total VOC emission was 9.5 nmol m-2 s-1. Methanol had the highest concentration and accounted for the largest deposition. Methanol seemed to be deposited to dew, as the deposition happened in the early morning, right after the calculated surface temperature came closest to the calculated dew point temperature. We estimated that up to 27 % of the upward flux of methyl vinyl ketone (MVK) and methacrolein (MACR) originated from atmospheric oxidation of isoprene. A comparison between two flux detection methods (classical/visual and automated) was made. Their respective advantages and disadvantages were discussed and the differences in their results shown. Both provide comparable results; however we recommend the automated method with a compound filter, which combines the fast analysis and better flux detection, without the overestimation due to double counting.

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

    Directory of Open Access Journals (Sweden)

    S. Schallhart

    2016-06-01

    Full Text Available 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.

  13. A carbon budget for the aquatic ecosystem above SFR in Oeregrundsgrepen

    International Nuclear Information System (INIS)

    Kumblad, L

    1999-07-01

    The potential hazards of radionuclide release to humans and the environment is regularly evaluated in safety assessments of SFR, the final repository for radioactive operational waste. SFR handles, since 1988, low and intermediate level nuclear waste from Swedish nuclear power plants, medical care attendance, industries and research laboratories and is located in the bedrock 50 meters under the seabed of Oeregrundsgrepen in the southern Bothnian Sea. This report presents a description of the aquatic ecosystem and a carbon budget for the area above SFR with the aim to include ecosystem dynamics in the present safety assessment of the repository (SAFE). The carbon budget will support SAFE by facilitating evaluations of transport and fate of radionuclides, primarily 14 C, in case of a release from the repository and describe the ecosystem structure and function. Furthermore, 14 C is the dose-dominant radionuclide in the repository which most likely will follow the general carbon flow in the ecosystem if there should be a release. The carbon budget was based on biomass and flow of carbon between thirteen functional groups (including POC and DOC) in the ecosystem above SFR and the results indicates that the organisms are self-sufficient on carbon and that the area exports carbon corresponding to approximately 50% of the annual primary production. The largest organic carbon pool is DOC (one and a half time larger than the total biomass) and the major functional organism groups are the macrophytes (37% of the total biomass), benthic macrofauna (36%), and the microphytes (11%). The soft bottom and phytobenthic communities seem to have important roles in the ecosystem since these communities comprise the main part of the living carbon in the studied area

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

    Science.gov (United States)

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

    2014-05-01

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

  15. A carbon budget for the aquatic ecosystem above SFR in Oeregrundsgrepen

    Energy Technology Data Exchange (ETDEWEB)

    Kumblad, L [Stockholm Univ. (Sweden). Dept. of Systems Ecology

    1999-07-01

    The potential hazards of radionuclide release to humans and the environment is regularly evaluated in safety assessments of SFR, the final repository for radioactive operational waste. SFR handles, since 1988, low and intermediate level nuclear waste from Swedish nuclear power plants, medical care attendance, industries and research laboratories and is located in the bedrock 50 meters under the seabed of Oeregrundsgrepen in the southern Bothnian Sea. This report presents a description of the aquatic ecosystem and a carbon budget for the area above SFR with the aim to include ecosystem dynamics in the present safety assessment of the repository (SAFE). The carbon budget will support SAFE by facilitating evaluations of transport and fate of radionuclides, primarily {sup 14}C, in case of a release from the repository and describe the ecosystem structure and function. Furthermore, {sup 14}C is the dose-dominant radionuclide in the repository which most likely will follow the general carbon flow in the ecosystem if there should be a release. The carbon budget was based on biomass and flow of carbon between thirteen functional groups (including POC and DOC) in the ecosystem above SFR and the results indicates that the organisms are self-sufficient on carbon and that the area exports carbon corresponding to approximately 50% of the annual primary production. The largest organic carbon pool is DOC (one and a half time larger than the total biomass) and the major functional organism groups are the macrophytes (37% of the total biomass), benthic macrofauna (36%), and the microphytes (11%). The soft bottom and phytobenthic communities seem to have important roles in the ecosystem since these communities comprise the main part of the living carbon in the studied area.

  16. Forest biodiversity, carbon and other ecosystem services: relationships and impacts of deforestation and forest degradation

    Science.gov (United States)

    Ian D. Thompson; Joice Ferreira; Toby Gardner; Manuel Guariguata; Lian Pin Koh; Kimiko Okabe; Yude Pan; Christine B. Schmitt; Jason Tylianakis; Jos Barlow; Valerie Kapos; Werner A. Kurz; John A. Parrotta; Mark D. Spalding; Nathalie van Vliet

    2012-01-01

    REDD+ actions should be based on the best science and on the understanding that forests can provide more than a repository for carbon but also offer a wide range of services beneficial to people. Biodiversity underpins many ecosystem services, one of which is carbon sequestration, and individual species’ functional traits play an important role in determining...

  17. Pervasive drought legacies in forest ecosystems and their implications for carbon cycle models

    Science.gov (United States)

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

    2015-01-01

    The impacts of climate extremes on terrestrial ecosystems are poorly understood but important for predicting carbon cycle feedbacks to climate change. Coupled climate-carbon cycle models typically assume that vegetation recovery from extreme drought is immediate and complete, which conflicts with the understanding of basic plant physiology. We examined the recovery of...

  18. Effects of nutrient additions on ecosystem carbon cycle in a Puerto Rican tropical wet forest

    Science.gov (United States)

    YIQING LI; MING XU; XIAOMING ZOU

    2006-01-01

    Wet tropical forests play a critical role in global ecosystem carbon (C) cycle, but C allocation and the response of different C pools to nutrient addition in these forests remain poorly understood. We measured soil organic carbon (SOC), litterfall, root biomass, microbial biomass and soil physical and chemical properties in a wet tropical forest from May 1996 to July...

  19. Organic carbon dynamics in mangrove ecosystems: a review

    NARCIS (Netherlands)

    Kristensen, E.; Bouillon, S.; Dittmar, T.; Marchand, C.

    2008-01-01

    Our current knowledge on production, composition, transport, pathways and transformations of organic carbon in tropical mangrove environments is reviewed and discussed. Organic carbon entering mangrove foodwebs is either produced autochthonously or imported by tides and/or rivers. Mangrove litter

  20. Summertime elemental mercury exchange of temperate grasslands on an ecosystem-scale

    Science.gov (United States)

    Fritsche, J.; Wohlfahrt, G.; Ammann, C.; Zeeman, M.; Hammerle, A.; Obrist, D.; Alewell, C.

    2013-01-01

    In order to estimate the air-surface mercury exchange of grasslands in temperate climate regions, fluxes of gaseous elemental mercury (GEM) were measured at two sites in Switzerland and one in Austria during summer 2006. Two classic micrometeorological methods (aerodynamic and modified Bowen ratio) have been applied to estimate net GEM exchange rates and to determine the response of the GEM flux to changes in environmental conditions (e.g. heavy rain, summer ozone) on an ecosystem-scale. Both methods proved to be appropriate to estimate fluxes on time scales of a few hours and longer. Average dry deposition rates up to 4.3 ng m−2 h−1 and mean deposition velocities up to 0.10 cm s−1 were measured, which indicates that during the active vegetation period temperate grasslands are a small net sink for atmospheric mercury. With increasing ozone concentrations depletion of GEM was observed, but could not be quantified from the flux signal. Night-time deposition fluxes of GEM were measured and seem to be the result of mercury co-deposition with condensing water. Effects of grass cuts could also be observed, but were of minor magnitude. PMID:24348525

  1. Summertime elemental mercury exchange of temperate grasslands on an ecosystem-scale

    Directory of Open Access Journals (Sweden)

    J. Fritsche

    2008-12-01

    Full Text Available In order to estimate the air-surface mercury exchange of grasslands in temperate climate regions, fluxes of gaseous elemental mercury (GEM were measured at two sites in Switzerland and one in Austria during summer 2006. Two classic micrometeorological methods (aerodynamic and modified Bowen ratio have been applied to estimate net GEM exchange rates and to determine the response of the GEM flux to changes in environmental conditions (e.g. heavy rain, summer ozone on an ecosystem-scale. Both methods proved to be appropriate to estimate fluxes on time scales of a few hours and longer. Average dry deposition rates up to 4.3 ng m−2 h−1 and mean deposition velocities up to 0.10 cm s−1 were measured, which indicates that during the active vegetation period temperate grasslands are a small net sink for atmospheric mercury. With increasing ozone concentrations depletion of GEM was observed, but could not be quantified from the flux signal. Night-time deposition fluxes of GEM were measured and seem to be the result of mercury co-deposition with condensing water. Effects of grass cuts could also be observed, but were of minor magnitude.

  2. Estimation of daytime net ecosystem CO2 exchange over balsam fir forests in eastern Canada : combining averaged tower-based flux measurements with remotely sensed MODIS data

    International Nuclear Information System (INIS)

    Hassan, Q.K.; Bourque, C.P.A.; Meng, F-R.

    2006-01-01

    Considerable attention has been placed on the unprecedented increases in atmospheric carbon dioxide (CO 2 ) emissions and associated changes in global climate change. This article developed a practical approach for estimating daytime net CO 2 fluxes generated over balsam fir dominated forest ecosystems in the Atlantic Maritime ecozone of eastern Canada. The study objectives were to characterize the light use efficiency and ecosystem respiration for young to intermediate-aged balsam fir forest ecosystems in New Brunswick; relate tower-based measurements of daytime net ecosystem exchange (NEE) to absorbed photosynthetically active radiation (APAR); use a digital elevation model of the province to enhance spatial calculations of daily photosynthetically active radiation and APAR under cloud-free conditions; and generate a spatial calculation of daytime NEE for a balsam fir dominated region in northwestern New Brunswick. The article identified the study area and presented the data requirements and methodology. It was shown that the seasonally averaged daytime NEE and APAR values are strongly correlated. 36 refs., 2 tabs., 10 figs

  3. Marine ecosystem community carbon and nutrient uptake stoichiometry under varying ocean acidification during the PeECE III experiment

    Directory of Open Access Journals (Sweden)

    R. G. J. Bellerby

    2008-11-01

    Full Text Available Changes to seawater inorganic carbon and nutrient concentrations in response to the deliberate CO2 perturbation of natural plankton assemblages were studied during the 2005 Pelagic Ecosystem CO2 Enrichment (PeECE III experiment. Inverse analysis of the temporal inorganic carbon dioxide system and nutrient variations was used to determine the net community stoichiometric uptake characteristics of a natural pelagic ecosystem perturbed over a range of pCO2 scenarios (350, 700 and 1050 μatm. Nutrient uptake showed no sensitivity to CO2 treatment. There was enhanced carbon production relative to nutrient consumption in the higher CO2 treatments which was positively correlated with the initial CO2 concentration. There was no significant calcification response to changing CO2 in Emiliania huxleyi by the peak of the bloom and all treatments exhibited low particulate inorganic carbon production (~15 μmol kg−1. With insignificant air-sea CO2 exchange across the treatments, the enhanced carbon uptake was due to increase organic carbon production. The inferred cumulative C:N:P stoichiometry of organic production increased with CO2 treatment from 1:6.3:121 to 1:7.1:144 to 1:8.25:168 at the height of the bloom. This study discusses how ocean acidification may incur modification to the stoichiometry of pelagic production and have consequences for ocean biogeochemical cycling.

  4. Feedback of global warming to soil carbon cycling in forest ecosystems

    International Nuclear Information System (INIS)

    Nakane, Kaneyuki

    1993-01-01

    Thus in this study the simulation of soil carbon cycling and dynamics of its storage in several types of mature forests developed from the cool-temperate to the tropics was carried out for quantitatively assessing carbon loss from the soil under several scenarios of global warming, based on the model of soil carbon cycling in forest ecosystems (Nakane et al. 1984, 1987 and Nakane 1992). (J.P.N.)

  5. Seven years of recent European net terrestrial carbon dioxide exchange constrained by atmospheric observations

    NARCIS (Netherlands)

    Peters, W.; Krol, M. C.; van der Werf, G. R.; Houweling, S.; Jones, C. D.; Hughes, J.; Schaefer, K.; Masarie, K. A.; Jacobson, A. R.; Miller, J. B.; Cho, C. H.; Ramonet, M.; Schmidt, M.; Ciattaglia, L.; Apadula, F.; Heltai, D.; Meinhardt, F.; di Sarra, A. G.; Piacentino, S.; Sferlazzo, D.; Aalto, T.; Hatakka, J.; StröM, J.; Haszpra, L.; Meijer, H. A J; van Der Laan, S.; Neubert, R. E M; Jordan, A.; Rodó, X.; Morguí, J. A.; Vermeulen, A. T.; Popa, Maria Elena; Rozanski, K.; Zimnoch, M.; Manning, A. C.; Leuenberger, M.; Uglietti, C.; Dolman, A. J.; Ciais, P.; Heimann, M.; Tans, P.

    2010-01-01

    We present an estimate of net ecosystem exchange (NEE) of CO2 in Europe for the years 2001-2007. It is derived with a data assimilation that uses a large set of atmospheric CO2 mole fraction observations (∼70 000) to guide relatively simple descriptions of terrestrial and oceanic net exchange, while

  6. Seven years of recent European net terrestrial carbon dioxide exchange constrained by atmospheric observations

    NARCIS (Netherlands)

    Peters, W.; Krol, M.C.; Werf, van der G.R.; Houweling, S.; Jones, C.D.; Hughes, J.; Schaefer, K.; Masarie, K.A.

    2010-01-01

    We present an estimate of net ecosystem exchange (NEE) of CO2 in Europe for the years 2001–2007. It is derived with a data assimilation that uses a large set of atmospheric CO2 mole fraction observations (~70 000) to guide relatively simple descriptions of terrestrial and oceanic net exchange, while

  7. Carbon dioxide exchange in three tundra sites show a dissimilar response to environmental variables

    DEFF Research Database (Denmark)

    Mbufong, Herbert Njuabe; Lund, Magnus; Christensen, Torben Røjle

    2015-01-01

    variability. An improved understanding of the control of ancillary variables on net ecosystem exchange (NEE), gross primary production (GPP) and ecosystem respiration (Re) will improve the accuracy with which CO2 exchange seasonality in Arctic tundra ecosystems is modelled. Fluxes were measured with the eddy...... Lake. Growing season NEE correlated mainly to cumulative radiation and temperature-related variables at Zackenberg, while at Daring Lake the same variables showed significant correlations with the partitioned fluxes (GPP and Re). Stordalen was temperature dependent during the growing season. This study...

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

    Science.gov (United States)

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

    2013-01-01

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

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

    Science.gov (United States)

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

    2000-01-01

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

  10. Fire frequency drives decadal changes in soil carbon and nitrogen and ecosystem productivity

    Science.gov (United States)

    Pellegrini, Adam F. A.; Ahlström, Anders; Hobbie, Sarah E.; Reich, Peter B.; Nieradzik, Lars P.; Staver, A. Carla; Scharenbroch, Bryant C.; Jumpponen, Ari; Anderegg, William R. L.; Randerson, James T.; Jackson, Robert B.

    2018-01-01

    Fire frequency is changing globally and is projected to affect the global carbon cycle and climate. However, uncertainty about how ecosystems respond to decadal changes in fire frequency makes it difficult to predict the effects of altered fire regimes on the carbon cycle; for instance, we do not fully understand the long-term effects of fire on soil carbon and nutrient storage, or whether fire-driven nutrient losses limit plant productivity. Here we analyse data from 48 sites in savanna grasslands, broadleaf forests and needleleaf forests spanning up to 65 years, during which time the frequency of fires was altered at each site. We find that frequently burned plots experienced a decline in surface soil carbon and nitrogen that was non-saturating through time, having 36 per cent (±13 per cent) less carbon and 38 per cent (±16 per cent) less nitrogen after 64 years than plots that were protected from fire. Fire-driven carbon and nitrogen losses were substantial in savanna grasslands and broadleaf forests, but not in temperate and boreal needleleaf forests. We also observe comparable soil carbon and nitrogen losses in an independent field dataset and in dynamic model simulations of global vegetation. The model study predicts that the long-term losses of soil nitrogen that result from more frequent burning may in turn decrease the carbon that is sequestered by net primary productivity by about 20 per cent of the total carbon that is emitted from burning biomass over the same period. Furthermore, we estimate that the effects of changes in fire frequency on ecosystem carbon storage may be 30 per cent too low if they do not include multidecadal changes in soil carbon, especially in drier savanna grasslands. Future changes in fire frequency may shift ecosystem carbon storage by changing soil carbon pools and nitrogen limitations on plant growth, altering the carbon sink capacity of frequently burning savanna grasslands and broadleaf forests.

  11. CMIP5 land surface models systematically underestimate inter-annual variability of net ecosystem exchange in semi-arid southwestern North America.

    Science.gov (United States)

    MacBean, N.; Scott, R. L.; Biederman, J. A.; Vuichard, N.; Hudson, A.; Barnes, M.; Fox, A. M.; Smith, W. K.; Peylin, P. P.; Maignan, F.; Moore, D. J.

    2017-12-01

    Recent studies based on analysis of atmospheric CO2 inversions, satellite data and terrestrial biosphere model simulations have suggested that semi-arid ecosystems play a dominant role in the interannual variability and long-term trend in the global carbon sink. These studies have largely cited the response of vegetation activity to changing moisture availability as the primary mechanism of variability. However, some land surface models (LSMs) used in these studies have performed poorly in comparison to satellite-based observations of vegetation dynamics in semi-arid regions. Further analysis is therefore needed to ensure semi-arid carbon cycle processes are well represented in global scale LSMs before we can fully establish their contribution to the global carbon cycle. In this study, we evaluated annual net ecosystem exchange (NEE) simulated by CMIP5 land surface models using observations from 20 Ameriflux sites across semi-arid southwestern North America. We found that CMIP5 models systematically underestimate the magnitude and sign of NEE inter-annual variability; therefore, the true role of semi-arid regions in the global carbon cycle may be even more important than previously thought. To diagnose the factors responsible for this bias, we used the ORCHIDEE LSM to test different climate forcing data, prescribed vegetation fractions and model structures. Climate and prescribed vegetation do contribute to uncertainty in annual NEE simulations, but the bias is primarily caused by incorrect timing and magnitude of peak gross carbon fluxes. Modifications to the hydrology scheme improved simulations of soil moisture in comparison to data. This in turn improved the seasonal cycle of carbon uptake due to a more realistic limitation on photosynthesis during water stress. However, the peak fluxes are still too low, and phenology is poorly represented for desert shrubs and grasses. We provide suggestions on model developments needed to tackle these issues in the future.

  12. Assessing wildlife benefits and carbon storage from restored and natural coastal marshes in the Nisqually River Delta: Determining marsh net ecosystem carbon balance

    Science.gov (United States)

    Anderson, Frank; Bergamaschi, Brian; Windham-Myers, Lisamarie; Woo, Isa; De La Cruz, Susan; Drexler, Judith; Byrd, Kristin; Thorne, Karen M.

    2016-06-24

    Working in partnership since 1996, the U.S. Fish and Wildlife Service and the Nisqually Indian Tribe have restored 902 acres of tidally influenced coastal marsh in the Nisqually River Delta (NRD), making it the largest estuary-restoration project in the Pacific Northwest to date. Marsh restoration increases the capacity of the estuary to support a diversity of wildlife species. Restoration also increases carbon (C) production of marsh plant communities that support food webs for wildlife and can help mitigate climate change through long-term C storage in marsh soils.In 2015, an interdisciplinary team of U.S. Geological Survey (USGS) researchers began to study the benefits of carbon for wetland wildlife and storage in the NRD. Our primary goals are (1) to identify the relative importance of the different carbon sources that support juvenile chinook (Oncorhynchus tshawytscha) food webs and contribute to current and historic peat formation, (2) to determine the net ecosystem carbon balance (NECB) in a reference marsh and a restoration marsh site, and (3) to model the sustainability of the reference and restoration marshes under projected sea-level rise conditions along with historical vegetation change. In this fact sheet, we focus on the main C sources and exchanges to determine NECB, including carbon dioxide (CO2) uptake through plant photosynthesis, the loss of CO2 through plant and soil respiration, emissions of methane (CH4), and the lateral movement or leaching loss of C in tidal waters.

  13. Water and carbon dynamics in selected ecosystems in China

    Science.gov (United States)

    Ge Sun; J. Sun; G. Zhou

    2009-01-01

    Global climate change and unprecedented socioeconomic evelopment have resulted in tremendous environmental, ecological and resource stress on China’s continued growth.Among the numerous challenges, nothing is more pressing than ecosystem degradation as evidenced by the regional-scale air and water pollution, groundwater...

  14. Precipitation as driver of carbon fluxes in 11 African ecosystems

    CSIR Research Space (South Africa)

    Merbold, L

    2008-01-01

    Full Text Available operation. The ecosystems for which data were available ranged in mean annual rainfall from 320mm (Sudan) to 1150mm (The Republic of Congo) and include a spectrum of vegetation types (or land cover) (open savannas, woodlands, croplands and grasslands). Given...

  15. Wildland fire emissions, carbon, and climate: Seeing the forest and the trees - A cross-scale assessment of wildfire and carbon dynamics in fire-prone, forested ecosystems

    Science.gov (United States)

    Rachel A. Loehman; Elizabeth Reinhardt; Karin L. Riley

    2014-01-01

    Wildfires are an important component of the terrestrial carbon cycle and one of the main pathways for movement of carbon from the land surface to the atmosphere. Fires have received much attention in recent years as potential catalysts for shifting landscapes from carbon sinks to carbon sources. Unless structural or functional ecosystem shifts occur, net carbon balance...

  16. [Carbon sequestration status of forest ecosystems in Ningxia Hui Autonomous Region].

    Science.gov (United States)

    Gao, Yang; Jin, Jing-Wei; Cheng, Ji-Min; Su, Ji-Shuai; Zhu, Ren-Bin; Ma, Zheng-Rui; Liu, Wei

    2014-03-01

    Based on the data of Ningxia Hui Autonomous Region forest resources inventory, field investigation and laboratory analysis, this paper studied the carbon sequestration status of forest ecosystems in Ningxia region, estimated the carbon density and storage of forest ecosystems, and analyzed their spatial distribution characteristics. The results showed that the biomass of each forest vegetation component was in the order of arbor layer (46.64 Mg x hm(-2)) > litterfall layer (7.34 Mg x hm(-2)) > fine root layer (6.67 Mg x hm(-2)) > shrub-grass layer (0.73 Mg x hm(-2)). Spruce (115.43 Mg x hm(-2)) and Pinus tabuliformis (94.55 Mg x hm(-2)) had higher vegetation biomasses per unit area than other tree species. Over-mature forest had the highest arbor carbon density among the forests with different ages. However, the young forest had the highest arbor carbon storage (1.90 Tg C) due to its widest planted area. Overall, the average carbon density of forest ecosystems in Ningxia region was 265.74 Mg C x hm(-2), and the carbon storage was 43.54 Tg C. Carbon density and storage of vegetation were 27.24 Mg C x hm(-2) and 4.46 Tg C, respectively. Carbon storage in the soil was 8.76 times of that in the vegetation. In the southern part of Ningxia region, the forest carbon storage was higher than in the northern part, where the low C storage was mainly related to the small forest area and young forest age structure. With the improvement of forest age structure and the further implementation of forestry ecoengineering, the forest ecosystems in Ningxia region would achieve a huge carbon sequestration potential.

  17. Ozone effects on Sphagnum mosses, carbon dioxide exchange and methane emission in boreal peatland microcosms

    International Nuclear Information System (INIS)

    Niemi, Riikka; Holopainen, Toini; Martikainen, Pertti J.; Silvola, Jouko

    2002-01-01

    Microcosms of a boreal peatland originating from an oligotrophic fen in Eastern Finland were fumigated under four ozone concentrations (0, 50, 100 and 150 ppb O 3 ) in laboratory growth chambers during two separate experiments (autumn and summer) for 4 and 6 weeks, respectively. Ozone effects on Sphagnum mosses and the fluxes of carbon dioxide and methane were evaluated. In both experiments, the three Sphagnum species studied showed only a few significant responses to ozone. In the autumn experiment, membrane permeability of S. angustifolium, measured as conductivity and magnesium leakage, was significantly higher under ozone fumigation (P=0.005 and 2 exchange during the 6-week-long summer experiment, but dark ecosystem respiration was transiently increased by ozone concentration of 100 ppb after 14 days of exposure (P<0.05). Fumigation with 100 ppb of ozone, however, more than doubled (P<0.05) methane emission from the peatland monoliths. Our results suggest that increasing tropospheric ozone concentration may cause substantial changes in the carbon gas cycling of boreal peatlands, even though these changes are not closely associated with the changes in Sphagnum vegetation

  18. Effects of nitrogen deposition on carbon cycle in terrestrial ecosystems of China

    DEFF Research Database (Denmark)

    Chen, Hao; Li, Dejun; Gurmesa, Geshere Abdisa

    2015-01-01

    Nitrogen (N) deposition in China has increased greatly, but the general impact of elevated N deposition on carbon (C) dynamics in Chinese terrestrial ecosystems is not well documented. In this study we used a meta-analysis method to compile 88 studies on the effects of N deposition C cycling...... and rate of N addition. Overall, our findings suggest that 1) decreased below-ground plant C pool may limit long-term soil C sequestration; and 2) it is better to treat N-rich and N-limited ecosystems differently in modeling effects of N deposition on ecosystem C cycle....

  19. Impacts of Human Induced Nitrogen Deposition on Ecosystem Carbon Sequestration and Water Balance in China

    Science.gov (United States)

    Sheng, M.; Yang, D.; Tang, J.; Lei, H.

    2017-12-01

    Enhanced plant biomass accumulation in response to elevated atmospheric CO2 concentration could dampen the future rate of increase in CO2 levels and associated climate warming. However, many experiments around the world reported that nitrogen availability could limit the sustainability of the ecosystems' response to elevated CO2. In the recent 20 years, atmospheric nitrogen deposition, primarily from fossil fuel combustion, has increased sharply about 25% in China and meanwhile, China has the highest carbon emission in the world, implying a large opportunity to increase vegetation greenness and ecosystem carbon sequestration. Moreover, the water balance of the ecosystem will also change. However, in the future, the trajectory of increasing nitrogen deposition from fossil fuel use is to be controlled by the government policy that shapes the energy and industrial structure. Therefore, the historical and future trajectories of nitrogen deposition are likely very different, and it is imperative to understand how changes in nitrogen deposition will impact the ecosystem carbon sequestration and water balance in China. We here use the Community Land Model (CLM 4.5) to analyze how the change of nitrogen deposition has influenced and will influence the ecosystem carbon and water cycle in China at a high spatial resolution (0.1 degree). We address the following questions: 1) what is the contribution of the nitrogen deposition on historical vegetation greenness? 2) How does the change of nitrogen deposition affect the carbon sequestration? 3) What is its influence to water balance? And 4) how different will be the influence of the nitrogen deposition on ecosystem carbon and water cycling in the future?

  20. Ecosystem services and biogeochemical cycles on a global scale: valuation of water, carbon and nitrogen processes

    International Nuclear Information System (INIS)

    Watanabe, Marcos D.B.; Ortega, Enrique

    2011-01-01

    Ecosystem services (ES) are provided by healthy ecosystems and are fundamental to support human life. However, natural systems have been degraded all over the world and the process of degradation is partially attributed to the lack of knowledge regarding the economic benefits associated with ES, which usually are not captured in the market. To valuate ES without using conventional approaches, such as the human's willingness-to-pay for ecosystem goods and services, this paper uses a different method based on Energy Systems Theory to estimate prices for biogeochemical flows that affect ecosystem services by considering their emergy content converted to equivalent monetary terms. Ecosystem services related to water, carbon and nitrogen biogeochemical flows were assessed since they are connected to a range of final ecosystem services including climate regulation, hydrological regulation, food production, soil formation and others. Results in this paper indicate that aquifer recharge, groundwater flow, carbon dioxide sequestration, methane emission, biological nitrogen fixation, nitrous oxide emission and nitrogen leaching/runoff are the most critical biogeochemical flows in terrestrial systems. Moreover, monetary values related to biogeochemical flows on a global scale could provide important information for policymakers concerned with payment mechanisms for ecosystem services and costs of greenhouse gas emissions.

  1. Potential increases in natural disturbance rates could offset forest management impacts on ecosystem carbon stocks

    Science.gov (United States)

    Bradford, John B.; Jensen, Nicholas R.; Domke, Grant M.; D’Amato, Anthony W.

    2013-01-01

    Forested ecosystems contain the majority of the world’s terrestrial carbon, and forest management has implications for regional and global carbon cycling. Carbon stored in forests changes with stand age and is affected by natural disturbance and timber harvesting. We examined how harvesting and disturbance interact to influence forest carbon stocks over the Superior National Forest, in northern Minnesota. Forest inventory data from the USDA Forest Service, Forest Inventory and Analysis program were used to characterize current forest age structure and quantify the relationship between age and carbon stocks for eight forest types. Using these findings, we simulated the impact of alternative management scenarios and natural disturbance rates on forest-wide terrestrial carbon stocks over a 100-year horizon. Under low natural mortality, forest-wide total ecosystem carbon stocks increased when 0% or 40% of planned harvests were implemented; however, the majority of forest-wide carbon stocks decreased with greater harvest levels and elevated disturbance rates. Our results suggest that natural disturbance has the potential to exert stronger influence on forest carbon stocks than timber harvesting activities and that maintaining carbon stocks over the long-term may prove difficult if disturbance frequency increases in response to climate change.

  2. Modelling the soil carbon cycle of pine ecosystems

    International Nuclear Information System (INIS)

    Nakane, K.

    1994-01-01

    Soil carbon cycling rates and carbon budgets were calculated for stands of four pine species. Pinus sylvestris (at Jaedraaas, Sweden), P. densiflora (Hiroshima, Japan), P. elliottii (Florida, USA) and P. radiata (Canberra, Australia), using a simulation model driven by daily observations of mean air temperature and precipitation. Inputs to soil carbon through litterfall differ considerably among the four pine forests, but the accumulation of the A 0 layer and humus in mineral soil is less variable. Decomposition of the A 0 layer and humus is fastest for P. densiflora and slowest for P. sylvestris stands with P. radiata and P. elliottii intermediate. The decomposition rate is lower for the P. elliottii stand than for P. densiflora in spite of its higher temperatures and slightly higher precipitation. Seasonal changes in simulated soil carbon are observed only for the A 0 layer at the P. densiflora site. Simulated soil respiration rates vary seasonally in three stands (P. sylvestris, P. densiflora and P. radiata). In simulations for pine trees planted on bare soil, all soil organic matter fractions except the humus in mineral soil recover to half their asymptotic values within 30 to 40 years of planting for P. sylvestris and P. densiflora, compared with 10 to 20 years for P. radiata and P. elliottii. The simulated recovery of soil carbon following clear-cutting is fastest for the P. elliottii stand and slowest for P. sylvestris. Management of P. elliottii and P. radiata stands on 40-years rotations is sustainable because carbon removed through harvest is restored in the interval between successive clear-cuts. However p. densiflora and P. sylvestris stands may be unable to maintain soil carbon under such a short rotation. High growth rates of P. elliottii and p. radiata stands in spite of relatively poor soil conditions and slow carbon cycling may be related to the physiological responses of species to environmental conditions. (Abstract Truncated)

  3. Evaluation of Sustainability of the Carbon and Silicon Ecosystem: From Nanoparticles to Macroworld

    Science.gov (United States)

    Dolin, V.

    Rapid development of nanotechnologies has led to a complicated problem of utilization, storage and treatment of waste nanodevices of silicon and carbon origin. The processes of physico-chemical and biogeochemical destruction of carbon—silicon—uranium nanoparticles of Chernobyl origin has been studied. The period of half-destruction assessed by leaching of different radionuclide from particles is between 5 and 25 years. Natural ecosystems are generally of carbon and silicon origin. The behavior of radionuclide in natural media is observed over a period of 20 years. For the balance calculations we have utilized the Geochemical Transition Factor (GTF) that represents the quantity of substance, which is accumulated by living matter from the area unit. The main part of total carbon is involved in biogeochemical cycles in the forest ecosystem. Anthropogenic activity leads to a considerable imbalance of carbon isotopes. The distribution of carbon isotopes between different biotic levels demonstrates that radiocarbon of artificial emission is substantially less bio-available than those from natural sources. The environmental ability to recovery, lies in decontamination of carbon trophic circuits, is an order of magnitude greater than the rate of natural attenuation and corresponds to the removal of artificial matter from natural silicon media. The modern sustainability of the silicon and carbon ecosystem is determined by an insignificant quantity of artificial matter involved in biogeochemical cycles.

  4. Modeling the influence of snow cover on low Arctic net ecosystem exchange

    International Nuclear Information System (INIS)

    Luus, K A; Kelly, R E J; Lin, J C; Humphreys, E R; Lafleur, P M; Oechel, W C

    2013-01-01

    The Arctic net ecosystem exchange (NEE) of CO 2 between the land surface and the atmosphere is influenced by the timing of snow onset and melt. The objective of this study was to examine whether uncertainty in model estimates of NEE could be reduced by representing the influence of snow on NEE using remote sensing observations of snow cover area (SCA). Observations of NEE and time-lapse images of SCA were collected over four locations at a low Arctic site (Daring Lake, NWT) in May–June 2010. Analysis of these observations indicated that SCA influences NEE, and that good agreement exists between SCA derived from time-lapse images, Landsat and MODIS. MODIS SCA was therefore incorporated into the vegetation photosynthesis respiration model (VPRM). VPRM was calibrated using observations collected in 2005 at Daring Lake. Estimates of NEE were then generated over Daring Lake and Ivotuk, Alaska (2004–2007) using VPRM formulations with and without explicit representations of the influence of SCA on respiration and/or photosynthesis. Model performance was assessed by comparing VPRM output against unfilled eddy covariance observations from Daring Lake and Ivotuk (2004–2007). The uncertainty in VPRM estimates of NEE was reduced when respiration was estimated as a function of air temperature when SCA ≤ 50% and as a function of soil temperature when SCA > 50%. (letter)

  5. Gap filling strategies for defensible annual sums of net ecosystem exchange

    DEFF Research Database (Denmark)

    Falge, E.; Baldocchi, D.; Olson, R.

    2001-01-01

    ecosystem exchange (F-NEE) responses are being made among biome types, phenology patterns, and stress conditions. The comparisons are usually performed on annual sums of F-NEE; however, the average data coverage during a year is only 65%. Therefore, robust and consistent gap filling methods are required. We...... is investigated. The difference between annual F-NEE filled by MDV compared to F-NEE filled by Regr. ranged from -45 to +200 g C m(-2) per year (MDV-Regr.). Comparing LookUp and Regr. methods resulted in a difference (LookUp-Regr.) ranging from -30 to +150g Cm-2 per year. We also investigated the impact...... of replacing measurements at night, when turbulent mixing is insufficient. The nighttime correction for low friction velocities (u(*)) shifted annual F-NEE on average by +77 g C m(-2) per year, but in certain cases as much as +185 g C m-2 per year. Our results emphasize the need to standardize gap filling...

  6. Seasonal variations in carbon dioxide exchange in an alpine wetland meadow on the Qinghai-Tibetan Plateau

    Directory of Open Access Journals (Sweden)

    L. Zhao

    2010-04-01

    Full Text Available Alpine wetland meadow could functions as a carbon sink due to it high soil organic content and low decomposition. However, the magnitude and dynamics of carbon stock in alpine wetland ecosystems are not well quantified. Therefore, understanding how environmental variables affect the processes that regulate carbon fluxes in alpine wetland meadow on the Qinghai-Tibetan Plateau is critical. To address this issue, Gross Primary Production (GPP, Ecosystem Respiration (Reco, and Net Ecosystem Exchange (NEE were examined in an alpine wetland meadow using the eddy covariance method from October 2003 to December 2006 at the Haibei Research Station of the Chinese Academy of Sciences. Seasonal patterns of GPP and Reco were closely associated with leaf area index (LAI. The Reco showed a positive exponential to soil temperature and relatively low Reco occurred during the non-growing season after a rain event. This result is inconsistent with the result observed in alpine shrubland meadow. In total, annual GPP were estimated at 575.7, 682.9, and 630.97 g C m−2 in 2004, 2005, and 2006, respectively. Meanwhile, the Reco were equal to 676.8, 726.4, 808.2 g C m−2, and thus the NEE were 101.1, 44.0 and 173.2 g C m−2. These results indicated that the alpine wetland meadow was a moderately source of carbon dioxide (CO2. The observed carbon dioxide fluxes in the alpine wetland meadow were higher than other alpine meadow such as Kobresia humilis meadow and shrubland meadow.

  7. Carbon payments for mangrove conservation: ecosystem constraints and uncertainties of sequestration potential

    International Nuclear Information System (INIS)

    Alongi, Daniel M.

    2011-01-01

    Natural ecosystem change over time is an often unconsidered issue for PES and REDD+ schemes, and a lack of consideration of thermodynamic limitations has led to misconceptions and oversimplifications regarding ecosystem services, especially for tropical mangrove forests. Mangroves are non-linear, non-equilibrium systems uniquely adapted to a highly dynamic boundary where shorelines are continually evolving and sea-level ever changing, and rarely conform to classical concepts of forest development and succession. Not all mangroves accumulate carbon and rates of forest floor accretion are directly linked to the frequency of tidal inundation. Carbon payments in either a PES or REDD+ scheme are dependent on the rate of carbon sequestration, not the size of C stocks, so site selection must be ordinarily confined to the sea edge. Gas emissions and net ecosystem production (NEP) are linked to forest age, particularly for monospecific plantations. Planting of mixed-species forests is recommended to maximize biodiversity, food web connectivity and NEP. Old-growth forests are the prime ecosystems for carbon sequestration, and policy must give priority to schemes to maintain their existence. Large uncertainties exist in carbon sequestration potential of mangroves, and such limitations must be factored into the design, timeframe and execution of PES and REDD+ schemes.

  8. Modelling carbon and water flows in terrestrial ecosystems in the boreal zone - examples from Oskarshamn

    Energy Technology Data Exchange (ETDEWEB)

    Karlberg, Louise [Stockholm Environment Institute (SEI), Stockholm (Sweden); Gu stafsson, David; Jansson, Per-Erik [Royal Inst. of Technology, Dept. of Land and Water Resources Engineering, Stockholm (Sweden)

    2007-12-15

    Carbon budgets and mean residence times were estimated in four hypothetical ecosystems. The greatest uncertainties in the estimations lie in the calculation of fluxes to and from the field layer. A parametrisation method based on multiple criteria, synthesising a wide range of empirical knowledge on ecosystem behaviour, proved to be useful both in the estimation of unknown parameters, to demonstrate model sensitivity, and to identify processes where our current knowledge is limited. The parameterizations derived from the study of the hypothetical systems were used to estimate site-specific carbon and water budgets for four ecosystems located within the Oskarshamn study-area. Measured soil respiration was used to calibrate the simulations. An analysis of the simulated carbon fluxes indicated that two of the ecosystems, namely the grassland and the spruce forest, were net sources of carbon dioxide, while the alder and the pine forest were net sinks of CO{sub 2}. In the former case, this was interpreted as a result of recent drainage of the organogenic soils and the concurrent increase in decomposition. The results from the study conformed rather well with results from a previous study on carbon budgets from the Oskarshamn study area.

  9. Modelling carbon and water flows in terrestrial ecosystems in the boreal zone - examples from Oskarshamn

    International Nuclear Information System (INIS)

    Karlberg, Louise; Gu stafsson, David; Jansson, Per-Erik

    2007-12-01

    Carbon budgets and mean residence times were estimated in four hypothetical ecosystems. The greatest uncertainties in the estimations lie in the calculation of fluxes to and from the field layer. A parametrisation method based on multiple criteria, synthesising a wide range of empirical knowledge on ecosystem behaviour, proved to be useful both in the estimation of unknown parameters, to demonstrate model sensitivity, and to identify processes where our current knowledge is limited. The parameterizations derived from the study of the hypothetical systems were used to estimate site-specific carbon and water budgets for four ecosystems located within the Oskarshamn study-area. Measured soil respiration was used to calibrate the simulations. An analysis of the simulated carbon fluxes indicated that two of the ecosystems, namely the grassland and the spruce forest, were net sources of carbon dioxide, while the alder and the pine forest were net sinks of CO 2 . In the former case, this was interpreted as a result of recent drainage of the organogenic soils and the concurrent increase in decomposition. The results from the study conformed rather well with results from a previous study on carbon budgets from the Oskarshamn study area

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

    Energy Technology Data Exchange (ETDEWEB)

    Sather, Nichole K. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Borde, Amy B. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Diefenderfer, Heida L. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Serkowski, John A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Coleman, Andre M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Johnson, Gary E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2013-12-01

    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.

  11. Uncertainties in mapping forest carbon in urban ecosystems.

    Science.gov (United States)

    Chen, Gang; Ozelkan, Emre; Singh, Kunwar K; Zhou, Jun; Brown, Marilyn R; Meentemeyer, Ross K

    2017-02-01

    Spatially explicit urban forest carbon estimation provides a baseline map for understanding the variation in forest vertical structure, informing sustainable forest management and urban planning. While high-resolution remote sensing has proven promising for carbon mapping in highly fragmented urban landscapes, data cost and availability are the major obstacle prohibiting accurate, consistent, and repeated measurement of forest carbon pools in cities. This study aims to evaluate the uncertainties of forest carbon estimation in response to the combined impacts of remote sensing data resolution and neighborhood spatial patterns in Charlotte, North Carolina. The remote sensing data for carbon mapping were resampled to a range of resolutions, i.e., LiDAR point cloud density - 5.8, 4.6, 2.3, and 1.2 pt s/m 2 , aerial optical NAIP (National Agricultural Imagery Program) imagery - 1, 5, 10, and 20 m. Urban spatial patterns were extracted to represent area, shape complexity, dispersion/interspersion, diversity, and connectivity of landscape patches across the residential neighborhoods with built-up densities from low, medium-low, medium-high, to high. Through statistical analyses, we found that changing remote sensing data resolution introduced noticeable uncertainties (variation) in forest carbon estimation at the neighborhood level. Higher uncertainties were caused by the change of LiDAR point density (causing 8.7-11.0% of variation) than changing NAIP image resolution (causing 6.2-8.6% of variation). For both LiDAR and NAIP, urban neighborhoods with a higher degree of anthropogenic disturbance unveiled a higher level of uncertainty in carbon mapping. However, LiDAR-based results were more likely to be affected by landscape patch connectivity, and the NAIP-based estimation was found to be significantly influenced by the complexity of patch shape. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. Studying biosphere-atmosphere exchange of CO2 through Carbon-13 stable isotopes

    NARCIS (Netherlands)

    Velde, van der I.R.

    2015-01-01

    Summary Thesis ‘Studying biosphere-atmosphere exchange of CO2 through

    carbon-13 stable isotopes’

    Ivar van der Velde

    Making predictions of future climate is difficult, mainly due to large uncertainties in the carbon cycle. The rate at which carbon is stored in the oceans and

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

    Science.gov (United States)

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

    2012-12-01

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

  14. Simulating the carbon balance in reclaimed forest ecosystems with the FORECAST model

    Energy Technology Data Exchange (ETDEWEB)

    Welham, C. [British Columbia Univ., Vancouver, BC (Canada). Dept. of Forest Sciences, Forest Ecosystem Simulation Group; ForRx Consulting, Belcarra, BC (Canada); 3GreenTree Ecosystem Services Ltd., Belcarra, BC (Canada)

    2010-07-01

    Large emission sources are beginning to report their carbon footprint on an annual basis as a result of government mandates, shareholder demand for disclosure of a company's risk to climate change, and as part of corporate social responsibility initiatives. Oil sands mining is a carbon intensive activity from the perspective of carbon dioxide emissions. The intensity of carbon emissions can be mitigated through technological and process innovations. However, reclamation is the only mining-related activity that directly removes atmospheric carbon dioxide. This presentation described a modeling exercise that had 3 principal objectives, notably to simulate the carbon balance in a developing reclaimed upland forest ecosystem; to explore the relative change in carbon pools over time; and to compare the carbon balance of the reclaimed ecosystem to its natural analogue. The presentation provided a description of the model and methodology and discussed the simulation protocol. Imperial Oil's Kearl Lake operation, which was used as a test case, showed that approximately 83,000 tonnes of carbon dioxide per hectare can be sequestered per year as a result of reclamation. tabs., figs.

  15. Precipitation as driver of carbon fluxes in 11 African ecosystems

    CSIR Research Space (South Africa)

    Merbold, L

    2009-01-01

    Full Text Available ). Given the shortness of the record, the EC data were analysed across the network rather than longitudinally at sites, in order to under- stand the driving factors for ecosystem respiration and car- bon assimilation, and to reveal the different water... by Schulze et al. (1994) and the thick solid regression line shows the regression for the eleven African sites. (n=11) variability in the global terrestrial cycles of water and car- bon (Williams et al., 2007; Weber et al., 2009). More- over, all African...

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

    Science.gov (United States)

    Liu, Jinxun; Vogelmann, James E.; Zhu, Zhiliang; Key, Carl H.; Sleeter, Benjamin M.; Price, D.T.; Chen, Jing M.; Cochrane, Mark A.; Eidenshink, Jeffery C.; Howard, Stephen M.; Bliss, Norman B.; Jiang, Hong

    2011-01-01

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

  17. Ecosystem services and climate change: Understanding the differences and identifying opportunities for forest carbon

    Science.gov (United States)

    Robert L. Deal; Crystal Raymond; David L. Peterson; Cindy. Glick

    2010-01-01

    There are a number of misunderstandings about “ecosystem services” and “climate change” and these terms are often used incorrectly to describe different concepts. These concepts address different issues and objectives but have some important integrating themes relating to carbon and carbon sequestration. In this paper, we provide definitions and distinctions between...

  18. Studies on sorption of plutonium on inorganic exchangers from sodium carbonate medium

    Energy Technology Data Exchange (ETDEWEB)

    Pius, I C; Charyulu, M M; Sivaramakrishnan, C K [Fuel Chemistry Division, Bhabha Atomic Research Centre, Mumbai (India); Venkataramani, B [Chemistry Division, Bhabha Atomic Research Centre, Mumbai (India)

    1994-06-01

    Sorption of Pu(IV) from sodium carbonate medium has been investigated by using different inorganic exchangers alumina, silica gel and hydrous titanium oxide. Distribution ratios of Pu(IV) for its sorption on these exchangers from sodium carbonate medium were found to be sufficiently high indicating the suitability of these exchangers for the removal of Pu(IV). The presence of uranium and dibutyl phosphate do not have any effect on distribution ratio. The 10% Pu(IV) breakthrough capacities for above exchangers have been determined with 5 ml bed at a flow rate of 30 ml/hour. (author). 4 refs., 2 tabs.

  19. Exploring the ecosystem engineering ability of Red Sea shallow benthic habitats using stocks and fluxes in carbon biogeochemistry

    KAUST Repository

    Baldry, Kimberlee

    2017-12-01

    The coastal ocean is a marginal region of the global ocean, but is home to metabolically intense ecosystems which increase the structural complexity of the benthos. These ecosystems have the ability to alter the carbon chemistry of surrounding waters through their metabolism, mainly through processes which directly release or consume carbon dioxide. In this way, coastal habitats can engineer their environment by acting as sources or sinks of carbon dioxide and altering their environmental chemistry from the regional norm. In most coastal water masses, it is difficult to resolve the ecosystem effect on coastal carbon biogeochemistry due to the mixing of multiple offshore end members, complex geography or the influence of variable freshwater inputs. The Red Sea provides a simple environment for the study of ecosystem processes at a coastal scale as it contains only one offshore end-member and negligible freshwater inputs due to the arid climate of adjacent land. This work explores the ability of three Red Sea benthic coastal habitats (coral reefs, seagrass meadows and mangrove forests) to create characteristic ecosystem end-members, which deviate from the biogeochemistry of offshore source waters. This is done by both calculating non-conservative deviations in carbonate stocks collected over each ecosystem, and by quantifying net carbonate fluxes (in seagrass meadows and mangrove forests only) using 24 hour incubations. Results illustrate that carbonate stocks over ecosystems conform to broad ecosystem trends, which are different to the offshore end-member, and are influenced by inherited properties from surrounding ecosystems. Carbonate fluxes also show ecosystem dependent trends and further illustrate the importance of sediment processes in influencing CaCO3 fluxes in blue carbon benthic habitats, which warrants further attention. These findings show the respective advantages of studying both carbonate stocks and fluxes of coastal benthic ecosystems in order to

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

    Science.gov (United States)

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

    2014-01-01

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

  1. The causal nexus between carbon dioxide emissions and agricultural ecosystem-an econometric approach.

    Science.gov (United States)

    Asumadu-Sarkodie, Samuel; Owusu, Phebe Asantewaa

    2017-01-01

    Achieving a long-term food security and preventing hunger include a better nutrition through sustainable systems of production, distribution, and consumption. Nonetheless, the quest for an alternative to increasing global food supply to meet the growing demand has led to the use of poor agricultural practices that promote climate change. Given the contribution of the agricultural ecosystem towards greenhouse gas (GHG) emissions, this study investigated the causal nexus between carbon dioxide emissions and agricultural ecosystem by employing a data spanning from 1961 to 2012. Evidence from long-run elasticity shows that a 1 % increase in the area of rice paddy harvested will increase carbon dioxide emissions by 1.49 %, a 1 % increase in biomass-burned crop residues will increase carbon dioxide emissions by 1.00 %, a 1 % increase in cereal production will increase carbon dioxide emissions by 1.38 %, and a 1 % increase in agricultural machinery will decrease carbon dioxide emissions by 0.09 % in the long run. There was a bidirectional causality between carbon dioxide emissions, cereal production, and biomass-burned crop residues. The Granger causality shows that the agricultural ecosystem in Ghana is sensitive to climate change vulnerability.

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

    Science.gov (United States)

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

    2016-04-19

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

  3. Spatial and temporal patterns of carbon storage in forest ecosystems on Hainan island, southern China.

    Science.gov (United States)

    Ren, Hai; Li, Linjun; Liu, Qiang; Wang, Xu; Li, Yide; Hui, Dafeng; Jian, Shuguang; Wang, Jun; Yang, Huai; Lu, Hongfang; Zhou, Guoyi; Tang, Xuli; Zhang, Qianmei; Wang, Dong; Yuan, Lianlian; Chen, Xubing

    2014-01-01

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

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

    Science.gov (United States)

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

    2015-01-01

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

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

    Science.gov (United States)

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

    2015-10-13

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

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

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

  8. Vulnerability and resilience of the carbon exchange o a subarctic peatland to an extreme winter event

    DEFF Research Database (Denmark)

    Parmentier, Frans-Jan W.; Rasse, Daniel P.; Lund, Magnus

    2018-01-01

    impact of this event. Our results indicate that gross primary production (GPP) exhibited a delayed response to temperature following snowmelt. From snowmelt up to the peak of summer, this reduced carbon uptake by 14 (0-24) g Cm-2 (similar to 12% of GPP in that period)-similar to the effect of interannual......Extreme winter events that damage vegetation are considered an important climatic cause of arctic browning-a reversal of the greening trend of the region-and possibly reduce the carbon uptake of northern ecosystems. Confirmation of a reduction in CO2 uptake due to winter damage, however, remains...... event. The warm summer also increased ecosystem respiration, which limited net carbon uptake. This study shows that damage from a single extreme winter event can have an ecosystem-wide impact on CO2 uptake, and highlights the importance of including winter-induced shrub damage in terrestrial ecosystem...

  9. Aspects of the carbon cycle in terrestrial ecosystems of Northeastern Smaaland

    Energy Technology Data Exchange (ETDEWEB)

    Tagesson, Torbern [Lund Univ., Geobiosphere Science Centre (Sweden). Physical Geography and Ecosystems Analysis

    2006-02-15

    Boreal and temperate ecosystems of the northern hemisphere are important for the future development of global climate. In this study, the carbon cycle has been studied in a pine forest, a meadow, a spruce forest and two deciduous forests in the Simpevarp investigation area in southern Sweden (57 deg 5 min N, 34 deg 55 min E). Ground respiration and ground Gross Primary Production (GPP) has been measured three times during spring 2004 with the closed chamber technique. Soil temperature, soil moisture and Photosynthetically Active Radiation (PAR) were also measured. An exponential regression with ground respiration against soil temperature was used to extrapolate respiration over spring 2004. A logarithmic regression with ground GPP against PAR was used to extrapolate GPP in meadow over spring 2004. Ground respiration is affected by soil temperature in all ecosystems but pine, but still it only explains a small part of the variation in respiration and this indicates that other abiotic factors also have an influence. Soil moisture affects respiration in spruce and one of the deciduous ecosystems. A comparison between measured and extrapolated ground respiration indicated that soil temperature could be used to extrapolate ground respiration. PAR is the main factor influencing GPP in all ecosystems but pine, still it could not be used to extrapolate GPP in meadow since too few measurements were done and they were from different periods of spring. Soil moisture did not have any significant effect on GPP. A Dynamic Global Vegetation Model, a DGVM called LPJ-GUESS, was downscaled to the Simpevarp investigation area. The downscaled DGVM was evaluated against measured respiration and soil organic acids for all five ecosystems. In meadow, it was evaluated against Net Primary Production, NPP. For the forest ecosystems, it was evaluated against tree layer carbon pools. The evaluation indicated that the DGVM is reasonably well downscaled to the Simpevarp investigation area and

  10. Aspects of the carbon cycle in terrestrial ecosystems of Northeastern Smaaland

    International Nuclear Information System (INIS)

    Tagesson, Torbern

    2006-02-01

    Boreal and temperate ecosystems of the northern hemisphere are important for the future development of global climate. In this study, the carbon cycle has been studied in a pine forest, a meadow, a spruce forest and two deciduous forests in the Simpevarp investigation area in southern Sweden (57 deg 5 min N, 34 deg 55 min E). Ground respiration and ground Gross Primary Production (GPP) has been measured three times during spring 2004 with the closed chamber technique. Soil temperature, soil moisture and Photosynthetically Active Radiation (PAR) were also measured. An exponential regression with ground respiration against soil temperature was used to extrapolate respiration over spring 2004. A logarithmic regression with ground GPP against PAR was used to extrapolate GPP in meadow over spring 2004. Ground respiration is affected by soil temperature in all ecosystems but pine, but still it only explains a small part of the variation in respiration and this indicates that other abiotic factors also have an influence. Soil moisture affects respiration in spruce and one of the deciduous ecosystems. A comparison between measured and extrapolated ground respiration indicated that soil temperature could be used to extrapolate ground respiration. PAR is the main factor influencing GPP in all ecosystems but pine, still it could not be used to extrapolate GPP in meadow since too few measurements were done and they were from different periods of spring. Soil moisture did not have any significant effect on GPP. A Dynamic Global Vegetation Model, a DGVM called LPJ-GUESS, was downscaled to the Simpevarp investigation area. The downscaled DGVM was evaluated against measured respiration and soil organic acids for all five ecosystems. In meadow, it was evaluated against Net Primary Production, NPP. For the forest ecosystems, it was evaluated against tree layer carbon pools. The evaluation indicated that the DGVM is reasonably well downscaled to the Simpevarp investigation area and

  11. The increasing importance of atmospheric demand for ecosystem water and carbon fluxes

    Science.gov (United States)

    Kimberly A. Novick; Darren L. Ficklin; Paul C. Stoy; Christopher A. Williams; Gil Bohrer; Andrew C. Oishi; Shirley A. Papuga; Peter D. Blanken; Asko Noormets; Benjamin N. Sulman; Russell L. Scott; Lixin Wang; Richard P. Phillips

    2016-01-01

    Soil moisture supply and atmospheric demand for water independently limit-and profoundly affect-vegetation productivity and water use during periods of hydrologic stress1-4. Disentangling the impact of these two drivers on ecosystem carbon and water cycling is difficult because they are often correlated, and experimental tools for manipulating...

  12. Spring feeding by pink-footed geese reduces carbon stocks and sink strength in tundra ecosystems

    NARCIS (Netherlands)

    van der Wal, Rene; Sjogersten, Sofie; Woodin, Sarah J.; Cooper, Elisabeth J.; Jonsdottir, Ingibjorg S.; Kuijper, Dries; Fox, Tony A. D.; Huiskes, A. D.

    Tundra ecosystems are widely recognized as precious areas and globally important carbon (C) sinks, yet our understanding of potential threats to these habitats and their large soil C store is limited. Land-use changes and conservation measures in temperate regions have led to a dramatic expansion of

  13. Spring feeding by pink-footed geese reduces carbon stocks and sink strength in tundra ecosystems

    NARCIS (Netherlands)

    Van der Wal, R.; Sjögersten, S.; Woodin, S.J.; Cooper, E.J.; Jónsdóttir, I.S.; Kuijper, D.; Fox, A.D.; Huiskes, A.H.L.

    2007-01-01

    Tundra ecosystems are widely recognized as precious areas and globally important carbon (C) sinks, yet our understanding of potential threats to these habitats and their large soil C store is limited. Land-use changes and conservation measures in temperate regions have led to a dramatic expansion of

  14. Analyzing the ecosystem carbon dynamics of four European coniferous forests using a biogeochemistry model

    NARCIS (Netherlands)

    Churkina, G.; Tenhunen, J.; Thornton, P.; Falge, E.; Elbers, J.A.; Erhard, M.; Grünwald, T.; Kowalski, A.; Rannik, Ü.; Sprinz, D.

    2003-01-01

    This paper provides the first steps toward a regional-scale analysis of carbon (C) budgets. We explore the ability of the ecosystem model BIOME-BGC to estimate the daily and annual C dynamics of four European coniferous forests and shifts in these dynamics in response to changing environmental

  15. Potential Effects of Organic Carbon Production on Ecosystems and Drinking Water Quality

    Directory of Open Access Journals (Sweden)

    Larry R. Brown

    2003-10-01

    Full Text Available Restoration of tidal wetlands in the Sacramento-San Joaquin Delta (Delta is an important component of the Ecosystem Restoration Program of the CALFED Bay-Delta Program (CALFED. CALFED is a collaborative effort among state and federal agencies to restore the ecological health and improve water management of the Delta and San Francisco Bay (Bay. Tidal wetland restoration is intended to provide valuable habitat for organisms and to improve ecosystem productivity through export of various forms of organic carbon, including both algae and plant detritus. However, the Delta also provides all or part of the drinking water for over 22 million Californians. In this context, increasing sources of organic carbon may be a problem because of the potential increase in the production of trihalomethanes and other disinfection by-products created during the process of water disinfection. This paper reviews the existing information about the roles of organic carbon in ecosystem function and drinking water quality in the Bay-Delta system, evaluates the potential for interaction, and considers major uncertainties and potential actions to reduce uncertainty. In the last 10 years, substantial progress has been made on the role of various forms of organic carbon in both ecosystem function and drinking water quality; however, interactions between the two have not been directly addressed. Several ongoing studies are beginning to address these interactions, and the results from these studies should reduce uncertainty and provide focus for further research.

  16. Short and long-term impacts of nitrogen deposition on carbon sequestration by forest ecosystems

    NARCIS (Netherlands)

    Vries, de W.; Du, E.; Butterbach-Bahl, K.

    2014-01-01

    The carbon to nitrogen response of forest ecosystems depends on the possible occurrence of nitrogen limitation versus possible co-limitations by other drivers, such as low temperature or availability of phosphorus. A combination of nitrogen retention estimates and stoichiometric scaling is used to

  17. Carbon Sequestration in Terrestrial Ecosystems: A Status Report on R and D Progress

    International Nuclear Information System (INIS)

    Jacobs, G.K.

    2001-01-01

    Sequestration of carbon in terrestrial ecosystems is a low-cost option that may be available in the near-term to mitigate increasing atmospheric CO(sub 2) concentrations, while providing additional benefits. Storing carbon in terrestrial ecosystems can be achieved through maintenance of standing aboveground biomass, utilization of aboveground biomass in long-lived products, or protection of carbon (organic and inorganic) compounds present in soils. There are potential co-benefits from efforts to sequester carbon in terrestrial ecosystems. For example, long-lived valuable products (wood) are produced, erosion would be reduced, soil productivity could be improved through increased capacity to retain water and nutrients, and marginal lands could be improved and riparian ecosystems restored. Another unique feature of the terrestrial sequestration option is that it is the only option that is ''reversible'' should it become desirable or permissible. For example, forests that are created are thus investments which could be harvested should CO(sub 2) emissions be reduced in other ways to acceptable levels 50-100 years from now

  18. The effect of atmospheric carbon dioxide elevation on plant growth in freshwater ecosystems

    NARCIS (Netherlands)

    Schippers, P.; Vermaat, J.; Klein, de J.J.M.; Mooij, W.M.

    2004-01-01

    The authors developed a dynamic model to investigate the effect of atmospheric carbon dioxide (CO2) increase on plant growth in freshwater ecosystems. Steady-state simulations were performed to analyze the response of phytoplankton and submerged macrophytes to atmospheric CO2 elevation from 350 to

  19. The effect of atmospheric carbon dioxide elevation on plant growth in freshwater ecosystems

    NARCIS (Netherlands)

    Schippers, P.; Vermaat, J.E.; de Klein, J.; Mooij, W.M.

    2004-01-01

    We developed a dynamic model to investigate the effect of atmospheric carbon dioxide (CO2) increase on plant growth in freshwater ecosystems. Steady-state simulations were performed to analyze the response of phytoplankton and submerged macrophytes to atmospheric CO2 elevation from 350 to 700 ppm.

  20. Growing season length as a key factor of cumulative net ecosystem exchange over the pine forest ecosystems in Europe

    Czech Academy of Sciences Publication Activity Database

    Danielewska, A.; Urbaniak, M.; Olejnik, Janusz

    2015-01-01

    Roč. 29, č. 2 (2015), s. 129-135 ISSN 0236-8722 Institutional support: RVO:67179843 Keywords : forest * carbon dioxide * eddy covariance * growing season length Subject RIV: EH - Ecology, Behaviour Impact factor: 1.067, year: 2015

  1. [Simulating of carbon fluxes in bamboo forest ecosystem using BEPS model based on the LAI assimilated with Dual Ensemble Kalman Filter].

    Science.gov (United States)

    Li, Xue Jian; Mao, Fang Jie; Du, Hua Qiang; Zhou, Guo Mo; Xu, Xiao Jun; Li, Ping Heng; Liu, Yu Li; Cui, Lu

    2016-12-01

    LAI is one of the most important observation data in the research of carbon cycle of forest ecosystem, and it is also an important parameter to drive process-based ecosystem model. The Moso bamboo forest (MBF) and Lei bamboo forest (LBF) were selected as the study targets. Firstly, the MODIS LAI time series data during 2014-2015 was assimilated with Dual Ensemble Kalman Filter method. Secondly, the high quality assimilated MBF LAI and LBF LAI were used as input dataset to drive BEPS model for simulating the gross primary productivity (GPP), net ecosystem exchange (NEE) and total ecosystem respiration (TER) of the two types of bamboo forest ecosystem, respectively. The modeled carbon fluxes were evaluated by the observed carbon fluxes data, and the effects of different quality LAI inputs on carbon cycle simulation were also studied. The LAI assimilated using Dual Ensemble Kalman Filter of MBF and LBF were significantly correlated with the observed LAI, with high R 2 of 0.81 and 0.91 respectively, and lower RMSE and absolute bias, which represented the great improvement of the accuracy of MODIS LAI products. With the driving of assimilated LAI, the modeled GPP, NEE, and TER were also highly correlated with the flux observation data, with the R 2 of 0.66, 0.47, and 0.64 for MBF, respectively, and 0.66, 0.45, and 0.73 for LBF, respectively. The accuracy of carbon fluxes modeled with assimilated LAI was higher than that acquired by the locally adjusted cubic-spline capping method, in which, the accuracy of mo-deled NEE for MBF and LBF increased by 11.2% and 11.8% at the most degrees, respectively.

  2. Environmental controls on the carbon isotope composition of ecosystem-respired CO{sub 2} in contrasting forest ecosystems in Canada and the USA

    Energy Technology Data Exchange (ETDEWEB)

    Alstad, K.P. [Lethbridge Univ., Lethbridge, AB (Canada). Dept. of Biological Sciences; Toledo Univ., Toledo, OH (United States). Dept. of Environmental Sciences; Flanagan, L.B. [Lethbridge Univ., Lethbridge, AB (Canada). Dept. of Biological Sciences; Lai, C.T. [Utah Univ., Salt Lake City, UT (United States); San Diego State Univ., San Diego, CA (United States); Ehleringer, J.R. [Utah Univ., Salt Lake City, UT (United States)

    2007-10-15

    Eleven forest ecosystems in Canada and the United States were compared in order to test for differences among forest {delta}{sup 13} carbon (C) responses to seasonal variations in environmental conditions from May to October 2004. Carbon isotope composition of ecosystem-respired carbon dioxide (CO{sub 2}) was considered as a proxy for short-term changes in photosynthetic discrimination. The study compared coniferous and deciduous forests, as well as forests in boreal and coastal environments. It was hypothesized that the carbon isotope composition of ecosystem-respired CO{sub 2} varied in a manner consistent with results obtained in leaf-level studies. Results of the study showed that higher R{sup 2} values were obtained for coastal ecosystems. The relationships between {delta}{sup 13}C{sub R} and environmental conditions were consistent with results obtained from leaf-level studies. Vapour pressure deficits and soil temperatures were significant determinants of variations in {delta}{sup 13}C{sub R} in the boreal forest ecosystem. Variations in {delta}{sup 13}C{sub R} in the coastal forest ecosystem correlated with changes in photosynthetic photon flux (PPF). It was concluded that {delta}{sup 13}C{sub R} measurements can be used to assess yearly variations in ecosystem physiological responses to changing environmental conditions. 59 refs., 7 tabs., 6 figs.

  3. Canopy uptake of atmospheric N deposition at a conifer forest: part I -canopy N budget, photosynthetic efficiency and net ecosystem exchange

    International Nuclear Information System (INIS)

    Sievering, H.; Tomaszewski, T.; Torizzo, J.

    2007-01-01

    Global carbon cycle assessments of anthropogenic nitrogen (N) deposition influences on carbon sequestration often assume enhanced sequestration results. This assumption was evaluated at a Rocky Mountains spruce-fir forest. Forest canopy N uptake (CNU) of atmospheric N deposition was estimated by combining event wet and throughfall N fluxes with gradient measured HNO 3 and NH 3 as well as inferred (NO x and particulate N) dry fluxes. Approximately 80% of the growing-season 3 kg N/ha total deposition is retained in canopy foliage and branches. This CNU constitutes ∼1/3 of canopy growing season new N supply at this conifer forest site. Daytime net ecosystem exchange (NEE) significantly (P = 0.006) and negatively (CO 2 uptake) correlated with CNU. Multiple regression indicates ∼20% of daytime NEE may be attributed to CNU (P < 0.02); more than soil water content. A wet deposition N-amendment study (Tomaszewski and Sievering), at canopy spruce branches, increased their growing-season CNU by 40-50% above ambient. Fluorometry and gas exchange results show N-amended spruce branches had greater photosynthetic efficiency and higher carboxylation rates than control and untreated branches. N-amended branches had 25% less photoinhibition, with a 5-9% greater proportion of foliar-N-in-Rubisco. The combined results provide, partly, a mechanistic explanation for the NEE dependence on CNU

  4. Sources and sinks of carbonyl sulfide in a mountain grassland and relationships to the carbon dioxide exchange

    Science.gov (United States)

    Spielmann, Felix M.; Kitz, Florian; Hammerle, Albin; Gerdel, Katharina; Wohlfahrt, Georg

    2016-04-01

    The trace gas carbonyl sulfide (COS) has been proposed as a tracer for canopy gross primary production (GPP), canopy transpiration and stomatal conductance of plant canopies in the last few years. COS enters the plant leaf through the stomata and diffuses through the intercellular space, the cell wall, the plasma membrane and the cytosol like CO2. It is then catalyzed by the enzyme carbonic anhydrase (CA) in a one-way reaction to H2S and CO2. This one-way flux into the leaf makes COS a promising tracer for the GPP. However there is growing evidence, that plant leaves aren't the only contributors to the ecosystem flux of COS. Therefor the COS uptake of soil microorganisms also containing CA and abiotic COS production might have to be accounted for when using COS as a tracer at the ecosystem scale. The overarching objective of this study was to quantify the relationship between the ecosystem-scale exchange of COS, CO2 and H2O and thus to test for the potential of COS to be used as a tracer for the plant canopy CO2 and H2O exchange. More specifically we aimed at quantifying the contribution of the soil to the ecosystem-scale COS exchange in order to understand complications that may arise due to a non-negligible soil COS exchange. In May 2015 we set up our quantum cascade laser (QCL) (Aerodyne Research Inc., MA, USA) at a temperate mountain grassland in Stubai Valley close to the village of Neustift, Austria. Our site lies at the valley bottom and is an intensively managed mountain grassland, which is cut 3-4 times a year. With the QCL we were able to measure concurrently the concentrations of COS, CO2, H2O (and CO) at a frequency of 10 Hz with minimal noise. This allowed us to conduct ecosystem-scale eddy covariance measurements. The eddy covariance flux measurements revealed that the COS uptake continues at night, which we confirmed was not caused by soil microorganisms, as the soil exchange was close to neutral during nighttime. Instead, the nocturnal COS uptake

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

    International Nuclear Information System (INIS)

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

    2015-01-01

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

  6. Differential response of carbon fluxes to climate in three peatland ecosystems that vary in the presence and stability of permafrost

    Science.gov (United States)

    Euskirchen, Eugenie S; Edgar, C.W.; Turetsky, M.R.; Waldrop, Mark P.; Harden, Jennifer W.

    2016-01-01

    Changes in vegetation and soil properties following permafrost degradation and thermokarst development in peatlands may cause changes in net carbon storage. To better understand these dynamics, we established three sites in Alaska that vary in permafrost regime, including a black spruce peat plateau forest with stable permafrost, an internal collapse scar bog formed as a result of thermokarst, and a rich fen without permafrost. Measurements include year-round eddy covariance estimates of carbon dioxide (CO2), water, and energy fluxes, associated environmental variables, and methane (CH4) fluxes at the collapse scar bog. The ecosystems all acted as net sinks of CO2 in 2011 and 2012, when air temperature and precipitation remained near long-term means. In 2013, under a late snowmelt and late leaf out followed by a hot, dry summer, the permafrost forest and collapse scar bog were sources of CO2. In this same year, CO2 uptake in the fen increased, largely because summer inundation from groundwater inputs suppressed ecosystem respiration. CO2 exchange in the permafrost forest and collapse scar bog was sensitive to warm air temperatures, with 0.5 g C m−2 lost each day when maximum air temperature was very warm (≥29°C). The bog lost 4981 ± 300 mg CH4 m−2 between April and September 2013, indicating that this ecosystem acted as a significant source of both CO2 and CH4 to the atmosphere in 2013. These results suggest that boreal peatland responses to warming and drying, both of which are expected to occur in a changing climate, will depend on permafrost regime.

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

    Science.gov (United States)

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

    2015-12-01

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

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

    Directory of Open Access Journals (Sweden)

    G. Cailleau

    2011-07-01

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

  9. Geographic distribution of soluble salts, exchangeable sodium and calcium carbonate in the Caribbean Region of Colombia

    International Nuclear Information System (INIS)

    Pulido, Carlos E

    2000-01-01

    A research was carried out to establish the distribution of soluble salts, exchangeable sodium and calcium carbonate in the soils of the Caribbean Region. The results show that 28,3% (3.506.033 ha) of the soils have problems related to salinity. The soils of the arid and semiarid zones and those belonging to the sea plain are affected severely by soluble salts, exchangeable sodium and calcium carbonate

  10. Mineral carbonation of gaseous carbon dioxide using a clay-hosted cation exchange reaction.

    Science.gov (United States)

    Kang, Il-Mo; Roh, Ki-Min

    2013-01-01

    The mineral carbonation method is still a challenge in practical application owing to: (1) slow reaction kinetics, (2) high reaction temperature, and (3) continuous mineral consumption. These constraints stem from the mode of supplying alkaline earth metals through mineral acidification and dissolution. Here, we attempt to mineralize gaseous carbon dioxide into calcium carbonate, using a cation exchange reaction of vermiculite (a species of expandable clay minerals). The mineralization is operated by draining NaCI solution through vermiculite powders and continuously dropping into the pool of NaOH solution with CO2 gas injected. The mineralization temperature is regulated here at 293 and 333 K for 15 min. As a result of characterization, using an X-ray powder diffractometer and a scanning electron microscopy, two types of pure CaCO3 polymorphs (vaterite and calcite) are identified as main reaction products. Their abundance and morphology are heavily dependent on the mineralization temperature. Noticeably, spindle-shaped vaterite, which is quite different from a typical vaterite morphology (polycrystalline spherulite), forms predominantly at 333 K (approximately 98 wt%).

  11. Combining multiple ecosystem productivity measurements to constrain carbon uptake estimates in semiarid grasslands and shrublands

    Science.gov (United States)

    Maurer, G. E.; Krofcheck, D. J.; Collins, S. L.; Litvak, M. E.

    2016-12-01

    Recent observational and modeling studies have indicated that semiarid ecosystems are more dynamic contributors to the global carbon budget than once thought. Semiarid carbon fluxes, however, are generally small, with high interannual and spatial variability, which suggests that validating their global significance may depend on examining multiple productivity measures and their associated uncertainties and inconsistencies. We examined ecosystem productivity from eddy covariance (NEE), harvest (NPP), and terrestrial biome models (NEPm) at two very similar grassland sites and one creosote shrubland site in the Sevilleta National Wildlife Refuge of central New Mexico, USA. Our goal was to assess site and methodological correspondence in annual carbon uptake, patterns of interannual variability, and measurement uncertainty. One grassland site was a perennial carbon source losing 30 g C m-2 per year on average, while the other two sites were carbon sources or sinks depending on the year, with average net uptake of 5 and 25 g C m-2 per year at the grassland and shrubland site, respectively. Uncertainty values for cumulative annual NEE overlapped between the three sites in most years. When combined, aboveground and belowground annual NPP measurements were 15% higher than annual NEE values and did not confirm a loss of carbon at any site in any year. Despite differences in mean site carbon balance, year-to-year changes in cumulative annual NEE and NPP were similar at all sites with years 2010 and 2013 being favorable for carbon uptake and 2011 and 2012 being unfavorable at all sites. Modeled NEPm data for a number of nearby grid cells reproduced only a fraction of the observed range in carbon uptake and its interannual variability. These three sites are highly similar in location and climate and multiple carbon flux measurements confirm the high interannual variability in carbon flux. The exact magnitude of these fluxes, however, remains difficult to discern.

  12. Carbon-water Cycling in the Critical Zone: Understanding Ecosystem Process Variability Across Complex Terrain

    Energy Technology Data Exchange (ETDEWEB)

    Barnard, Holly [Univ. of Colorado, Boulder, CO (United States); Brooks, Paul [Univ. of Utah, Salt Lake City, UT (United States); Univ. of Arizona, Tucson, AZ (United States)

    2016-06-16

    One of the largest knowledge gaps in environmental science is the ability to understand and predict how ecosystems will respond to future climate variability. The links between vegetation, hydrology, and climate that control carbon sequestration in plant biomass and soils remain poorly understood. Soil respiration is the second largest carbon flux of terrestrial ecosystems, yet there is no consensus on how respiration will change as water availability and temperature co-vary. To address this knowledge gap, we use the variation in soil development and topography across an elevation and climate gradient on the Front Range of Colorado to conduct a natural experiment that enables us to examine the co-evolution of soil carbon, vegetation, hydrology, and climate in an accessible field laboratory. The goal of this project is to further our ability to combine plant water availability, carbon flux and storage, and topographically driven hydrometrics into a watershed scale predictive model of carbon balance. We hypothesize: (i) landscape structure and hydrology are important controls on soil respiration as a result of spatial variability in both physical and biological drivers: (ii) variation in rates of soil respiration during the growing season is due to corresponding shifts in belowground carbon inputs from vegetation; and (iii) aboveground carbon storage (biomass) and species composition are directly correlated with soil moisture and therefore, can be directly related to subsurface drainage patterns.

  13. Linking ecosystem scale vegetation change to shifts in carbon and water cycling: the consequences of widespread piñon mortality in the Southwest

    Energy Technology Data Exchange (ETDEWEB)

    Litvak, Marcy Ellen [University of New Mexico

    2012-10-01

    The southwestern United States experienced an extended drought from 1999-2002 which led to widespread coniferous tree mortality. Piñon-juniper (PJ) woodlands, which occupy 24 million ha throughout the Southwest, were extremely vulnerable to this drought. An abrupt die-off of 40 to 95% of piñon pine (Pinus edulis) and 2-25% of juniper (Juniperus monosperma) across 1.5 million ha triggered rapid and extensive changes in the structure of PJ woodlands with potentially large, yet unknown, consequences for ecosystem services and feedbacks between the carbon cycle and climate system. Given the spatial extent of PJ woodlands (3rd largest biome in the US) and climatic predictions of increased frequency and intensity of drought in the region, it is crucial to understand the consequences of these disturbances on regional carbon and energy dynamics, biogeochemical processes and atmospheric CO2. The overall objective of our research was to quantify what impact widespread mortality of piñon trees has for carbon and water cycling in PJ woodlands. Our specific objectives for this proposal were: 1) Quantify the carbon, water and energy exchange trajectory after mortality in PJ woodlands; 2) Determine the mechanisms controlling the response and recovery of ecosystem production and respiration processes following large-scale piñon mortality; 3) Use the relationships we measure between ecosystem structure and function PJ woodlands recover from mortality to scale the results of our study up to the regional scale.

  14. Society and Ecosystem Carbon Budget through Life Cycle Assessment: Results from Asian Drylands

    Science.gov (United States)

    Chen, J.

    2017-12-01

    Land use, land cover changes, and ecosystem-specific management practices are recognized for their roles in mediating the climatic effects on ecosystem structure and function. A major challenge is that our understanding and forecasting of ecosystem functions, such as C fluxes, cannot rely solely on conventional biophysical regulations from the local ecosystem to the global scale. A second challenge lies in quantifying the magnitude of the C fluxes from managed ecosystems and landscapes over the lifetime of the C cycle, and to deduct the various energy inputs during management. Our specific challenge here is to quantify the landscape-scale C footprint of both managed agricultural-forest landscapes and people - the societal input and engagement in ecosystem studies. Using the East Asia Drylands (Chen et al., 2013) and an agricultural watershed in southwestern Michigan as a test bed, the mechanisms (carbon as an example) from both human activities and biophysical changes on ecosystem C dynamics at different temporal and spatial scales are proposed to be explored by modeling total net ecosystem C production (physical and social C fluxes), performing a spatially-explicit life cycle assessment (LCA) on the total C production. Remote sensing technology, available geospatial data, records of management practices, surveys of historical practices, a land surface model, and in situ measurements of C fluxes are all needed to achieve our objectives. Our case study calls for direct involvement of society as both the driver and beneficiary of ecosystem dynamics. Reference Chen, J., Wan, S., Henebry, G., Qi, J., Gutman, G., Sun, G., and Kappas, M. (Eds.) 2013. Dryland East Asia (DEA): Land Dynamics Amid Social And Climate Change. HEP and De Gruyter, 470 pp.

  15. Carbon Dynamics of Pinus palustris Ecosystems Following Drought

    Directory of Open Access Journals (Sweden)

    Gregory Starr

    2016-04-01

    Full Text Available Drought can affect forest structure and function at various spatial and temporal scales. Forest response and recovery from drought may be a result of position within landscape. Longleaf pine forests in the United States have been observed to reduce their carbon sequestration capacity during drought. We collected eddy covariance data at the ends of an edaphic longleaf pine gradient (xeric and mesic sites over seven years; two years of normal rainfall were followed by 2.5 years of drought, then 2.5 years of normal or slightly above-average rainfall. Drought played a significant role in reducing the physiological capacity of the sites and was compounded when prescribed fire occurred during the same periods. The mesic site has a 40% greater basal area then the xeric site, which accounts for its larger sequestration capacity; however, both sites show the same range of variance in fluxes over the course of the study. Following drought, both sites became carbon sinks. However, the xeric site had a longer carry-over effect and never returned to pre-drought function. Although this study encompassed seven years, we argue that longer studies with greater spatial variance must be undertaken to develop a more comprehensive understanding of forest response to changing climate.

  16. The Arctic Ocean marine carbon cycle: evaluation of air-sea CO2 exchanges, ocean acidification impacts and potential feedbacks

    Directory of Open Access Journals (Sweden)

    N. R. Bates

    2009-11-01

    Full Text Available At present, although seasonal sea-ice cover mitigates atmosphere-ocean gas exchange, the Arctic Ocean takes up carbon dioxide (CO2 on the order of −66 to −199 Tg C year−1 (1012 g C, contributing 5–14% to the global balance of CO2 sinks and sources. Because of this, the Arctic Ocean has an important influence on the global carbon cycle, with the marine carbon cycle and atmosphere-ocean CO2 exchanges sensitive to Arctic Ocean and global climate change feedbacks. In the near-term, further sea-ice loss and increases in phytoplankton growth rates are expected to increase the uptake of CO2 by Arctic Ocean surface waters, although mitigated somewhat by surface warming in the Arctic. Thus, the capacity of the Arctic Ocean to uptake CO2 is expected to alter in response to environmental changes driven largely by climate. These changes are likely to continue to modify the physics, biogeochemistry, and ecology of the Arctic Ocean in ways that are not yet fully understood. In surface waters, sea-ice melt, river runoff, cooling and uptake of CO2 through air-sea gas exchange combine to decrease the calcium carbonate (CaCO3 mineral saturation states (Ω of seawater while seasonal phytoplankton primary production (PP mitigates this effect. Biological amplification of ocean acidification effects in subsurface waters, due to the remineralization of organic matter, is likely to reduce the ability of many species to produce CaCO3 shells or tests with profound implications for Arctic marine ecosystems

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

    Science.gov (United States)

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

    2011-08-31

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

  18. Evaluation of a hierarchy of models reveals importance of substrate limitation for predicting carbon dioxide and methane exchange in restored wetlands

    Science.gov (United States)

    Oikawa, P. Y.; Jenerette, G. D.; Knox, S. H.; Sturtevant, C.; Verfaillie, J.; Dronova, I.; Poindexter, C. M.; Eichelmann, E.; Baldocchi, D. D.

    2017-01-01

    Wetlands and flooded peatlands can sequester large amounts of carbon (C) and have high greenhouse gas mitigation potential. There is growing interest in financing wetland restoration using C markets; however, this requires careful accounting of both CO2 and CH4 exchange at the ecosystem scale. Here we present a new model, the PEPRMT model (Peatland Ecosystem Photosynthesis Respiration and Methane Transport), which consists of a hierarchy of biogeochemical models designed to estimate CO2 and CH4 exchange in restored managed wetlands. Empirical models using temperature and/or photosynthesis to predict respiration and CH4 production were contrasted with a more process-based model that simulated substrate-limited respiration and CH4 production using multiple carbon pools. Models were parameterized by using a model-data fusion approach with multiple years of eddy covariance data collected in a recently restored wetland and a mature restored wetland. A third recently restored wetland site was used for model validation. During model validation, the process-based model explained 70% of the variance in net ecosystem exchange of CO2 (NEE) and 50% of the variance in CH4 exchange. Not accounting for high respiration following restoration led to empirical models overestimating annual NEE by 33-51%. By employing a model-data fusion approach we provide rigorous estimates of uncertainty in model predictions, accounting for uncertainty in data, model parameters, and model structure. The PEPRMT model is a valuable tool for understanding carbon cycling in restored wetlands and for application in carbon market-funded wetland restoration, thereby advancing opportunity to counteract the vast degradation of wetlands and flooded peatlands.

  19. Ecosystem Model Performance at Wetlands: Results from the North American Carbon Program Site Synthesis

    Science.gov (United States)

    Sulman, B. N.; Desai, A. R.; Schroeder, N. M.; NACP Site Synthesis Participants

    2011-12-01

    Northern peatlands contain a significant fraction of the global carbon pool, and their responses to hydrological change are likely to be important factors in future carbon cycle-climate feedbacks. Global-scale carbon cycle modeling studies typically use general ecosystem models with coarse spatial resolution, often without peatland-specific processes. Here, seven ecosystem models were used to simulate CO2 fluxes at three field sites in Canada and the northern United States, including two nutrient-rich fens and one nutrient-poor, sphagnum-dominated bog, from 2002-2006. Flux residuals (simulated - observed) were positively correlated with measured water table for both gross ecosystem productivity (GEP) and ecosystem respiration (ER) at the two fen sites for all models, and were positively correlated with water table at the bog site for the majority of models. Modeled diurnal cycles at fen sites agreed well with eddy covariance measurements overall. Eddy covariance GEP and ER were higher during dry periods than during wet periods, while model results predicted either the opposite relationship or no significant difference. At the bog site, eddy covariance GEP had no significant dependence on water table, while models predicted higher GEP during wet periods. All models significantly over-estimated GEP at the bog site, and all but one over-estimated ER at the bog site. Carbon cycle models in peatland-rich regions could be improved by incorporating better models or measurements of hydrology and by inhibiting GEP and ER rates under saturated conditions. Bogs and fens likely require distinct treatments in ecosystem models due to differences in nutrients, peat properties, and plant communities.

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

    Energy Technology Data Exchange (ETDEWEB)

    Nowak, Robert S [UNR; Smith, Stanley D [UNLV; Evans, Dave [WSU; Ogle, Kiona [ASU; Fenstermaker, Lynn [DRI

    2012-12-13

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

  1. Nitrogen, organic carbon and sulphur cycling in terrestrial ecosystems: linking nitrogen saturation to carbon limitation of soil microbial processes

    Czech Academy of Sciences Publication Activity Database

    Kopáček, Jiří; Cosby, B. J.; Evans, C. D.; Hruška, J.; Moldan, F.; Oulehle, F.; Šantrůčková, H.; Tahovská, K.; Wright, R. F.

    2013-01-01

    Roč. 115, 1-3 (2013), s. 33-51 ISSN 0168-2563. [BIOGEOMON : international symposium on ecosystem behavior /7./. Northport, 15.07.2012-20.07.2012] R&D Projects: GA ČR(CZ) GAP504/12/1218 Institutional support: RVO:60077344 Keywords : nitrogen * carbon * sulphur * acidification * forest soil * modelling Subject RIV: DJ - Water Pollution ; Quality Impact factor: 3.730, year: 2013

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

    Science.gov (United States)

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

    2015-11-01

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

  3. Seven years of recent European net terrestrial carbon dioxide exchange constrained by atmospheric observations

    NARCIS (Netherlands)

    Peters, W.; Krol, M; van der Werf, G. R.; Houweling, S.; Jones, C. D.; Hughes, J.; Schaefer, K.; Masarie, K. A.; Jacobson, A. R.; Miller, J. B.; Cho, C. H.; Ramonet, M.; Schmidt, M.; Ciattaglia, L.; Apadula, F.; Helta, D.; Meinhardt, F.; di Sarra, A. G.; Piacentino, S.; Sferlazzo, D.; Aalto, T.; Hatakka, J.; Strom, J.; Haszpra, L.; Meijer, H. A. J.; van der Laan, S.; Neubert, R. E. M.; Jordan, A.; Rodo, X.; Morgui, J. -A.; Vermeulen, A. T.; Popa, E.; Rozanski, K.; Zimnoch, M.; Manning, A. C.; Leuenberger, M.; Uglietti, C.; Dolman, A. J.; Ciais, P.; Heimann, M.; Tans, P. P.; Heltai, D.; Ström, J.

    We present an estimate of net ecosystem exchange (NEE) of CO(2) in Europe for the years 2001-2007. It is derived with a data assimilation that uses a large set of atmospheric CO(2) mole fraction observations (similar to 70 000) to guide relatively simple descriptions of terrestrial and oceanic net

  4. Carbon dioxide and water vapour exchange from understory species in boreal forest.

    NARCIS (Netherlands)

    Heijmans, M.M.P.D.; Arp, W.J.; Chapin, F.S.

    2004-01-01

    Although recent eddy covariance measurements in boreal forests provide CO2 and energy exchange data for the whole ecosystem, very little is known about the role of the understory vegetation. We conducted chamber flux measurements in an Alaskan black spruce forest in order to compare CO2 and water

  5. Diagnosis and Quantification of Climatic Sensitivity of Carbon Fluxes in Ensemble Global Ecosystem Models

    Science.gov (United States)

    Wang, W.; Hashimoto, H.; Milesi, C.; Nemani, R. R.; Myneni, R.

    2011-12-01

    Terrestrial ecosystem models are primary scientific tools to extrapolate our understanding of ecosystem functioning from point observations to global scales as well as from the past climatic conditions into the future. However, no model is nearly perfect and there are often considerable structural uncertainties existing between different models. Ensemble model experiments thus become a mainstream approach in evaluating the current status of global carbon cycle and predicting its future changes. A key task in such applications is to quantify the sensitivity of the simulated carbon fluxes to climate variations and changes. Here we develop a systematic framework to address this question solely by analyzing the inputs and the outputs from the models. The principle of our approach is to assume the long-term (~30 years) average of the inputs/outputs as a quasi-equlibrium of the climate-vegetation system while treat the anomalies of carbon fluxes as responses to climatic disturbances. In this way, the corresponding relationships can be largely linearized and analyzed using conventional time-series techniques. This method is used to characterize three major aspects of the vegetation models that are mostly important to global carbon cycle, namely the primary production, the biomass dynamics, and the ecosystem respiration. We apply this analytical framework to quantify the climatic sensitivity of an ensemble of models including CASA, Biome-BGC, LPJ as well as several other DGVMs from previous studies, all driven by the CRU-NCEP climate dataset. The detailed analysis results are reported in this study.

  6. Responses in Arctic marine carbon cycle processes: conceptual scenarios and implications for ecosystem function

    Directory of Open Access Journals (Sweden)

    Helen S. Findlay

    2015-04-01

    Full Text Available The Arctic Ocean is one of the fastest changing oceans, plays an important role in global carbon cycling and yet is a particularly challenging ocean to study. Hence, observations tend to be relatively sparse in both space and time. How the Arctic functions, geophysically, but also ecologically, can have significant consequences for the internal cycling of carbon, and subsequently influence carbon export, atmospheric CO2 uptake and food chain productivity. Here we assess the major carbon pools and associated processes, specifically summarizing the current knowledge of each of these processes in terms of data availability and ranges of rates and values for four geophysical Arctic Ocean domains originally described by Carmack & Wassmann (2006: inflow shelves, which are Pacific-influenced and Atlantic-influenced; interior, river-influenced shelves; and central basins. We attempt to bring together knowledge of the carbon cycle with the ecosystem within each of these different geophysical settings, in order to provide specialist information in a holistic context. We assess the current state of models and how they can be improved and/or used to provide assessments of the current and future functioning when observational data are limited or sparse. In doing so, we highlight potential links in the physical oceanographic regime, primary production and the flow of carbon within the ecosystem that will change in the future. Finally, we are able to highlight priority areas for research, taking a holistic pan-Arctic approach.

  7. Moving beyond the exchange value in the nonmarket valuation of ecosystem services

    Science.gov (United States)

    Karen E. Allen; Rebecca Moore

    2016-01-01

    There has been much discussion across the ecosystem services literature as to the role of economic valuation in identifying ecosystem service values and shaping policy. This article demonstrates a non-typical use of a nonmarket valuation technique known as the stated choice experiment (CE) for understanding a range of public preferences for stream-related...

  8. Carbon dioxide exchange rates from short- and long-hydroperiod Everglades freshwater marsh

    Science.gov (United States)

    K. L. Jimenez; G. Starr; C. L. Staudhammer; J. L. Schedlbauer; H. W. Loescher; Sparkle L Malone; S. F. Oberbauer

    2012-01-01

    Everglades freshwater marshes were once carbon sinks, but human-driven hydrologic changes have led to uncertainty about the current state of their carbon dynamics. To investigate the effect of hydrology on CO2 exchange, we used eddy covariance measurements for 2 years (2008-2009) in marl (short-hydroperiod) and peat (long-hydroperiod) wetlands in Everglades National...

  9. Insights from a network of long-term measurements of biosphere-atmospheric exchanges of water vapor and carbon dioxide in southern Arizona

    Science.gov (United States)

    Scott, R. L.; Barron-Gafford, G.; Biederman, J. A.

    2016-12-01

    Around one-third of Earth's land surface is classified as semiarid, and carbon dioxide exchange in these regions has been shown to be an important regulator of both the trend and interannual variability of the terrestrial carbon sink. Fifteen years ago, when we began making measurements of biosphere-atmospheric exchanges of energy, water vapor, and carbon dioxide using eddy covariance in southern Arizona USA, there was paucity of semiarid observations in flux networks like Ameriflux. We started by establishing riparian sites across a woody plant encroachment gradient to quantify the productivity and consumptive plant water use along a iconic and ecologically important desert river. Soon thereafter, we added semiarid grassland, shrubland, and savanna sites that do not have access to groundwater in order to better understand how water limitation and changes in vegetation structure affect ecosystem productivity. Here, we highlight the value of multiyear, multisite flux data for addressing regional to global scale problems associated with groundwater pumping, land cover change, drought, and climate change. For the riparian sites, we find that ecosystem water availability is altered by vegetation structure such that ecosystems with more deeply rooted trees have higher productivity but at a cost of greater groundwater use. For the non-riparian sites, precipitation strongly controls ecosystem water availability and the resultant productivity, but differences in ecosystem structure impact water use efficiency due to the partitioning of evapotranspiration into its component sources. Also, the productivity at sites with more grass, and less woody, plants responds more quickly to precipitation fluctuations including long-term drought conditions. In semiarid regions, variability in water and carbon fluxes is much larger than in more mesic climes. Across our riparian and non-riparian sites, access to more stable groundwater reserves reduces variability in water and carbon

  10. Insights from a network of long-term measurements of biosphere-atmospheric exchanges of water vapor and carbon dioxide in a water-limited semiarid region

    Science.gov (United States)

    Scott, Russell; Biederman, Joel

    2017-04-01

    Around one-third of Earth's land surface is classified as semiarid, and carbon dioxide exchange in these regions has been shown to be an important regulator of both the trend and interannual variability of the terrestrial carbon sink. Fifteen years ago, when we began making measurements of biosphere-atmospheric exchanges of energy, water vapor, and carbon dioxide using eddy covariance in southern Arizona USA, there was paucity of semiarid observations in flux networks like AmeriFlux and EuroFlux. We started by establishing riparian sites across a woody plant encroachment gradient to quantify the productivity and consumptive plant water use along a iconic and ecologically important desert river. Soon thereafter, we added semiarid grassland, shrubland, and savanna sites that do not have access to groundwater in order to better understand how water limitation and changes in vegetation structure affect ecosystem productivity. Here, we highlight the value of multiyear, multisite flux data for addressing regional to global scale problems associated with groundwater pumping, land cover change, drought, and climate change. For the riparian sites, we find that ecosystem water availability is altered by vegetation structure such that ecosystems with more deeply rooted trees have higher productivity but at a cost of greater groundwater use. For the non-riparian sites, precipitation strongly controls ecosystem water availability and the resultant productivity, but differences in ecosystem structure impact water use efficiency due to the partitioning of evapotranspiration into its component sources. Also, the productivity at sites with more grass, and less woody, plants responds more quickly to precipitation fluctuations including long-term drought conditions. In semiarid regions, variability in water and carbon fluxes is much larger than in more mesic climes. Across our riparian and non-riparian sites, access to more stable groundwater reserves reduces variability in water and

  11. Electrochemically Controlled Ion-exchange Property of Carbon Nanotubes/Polypyrrole Nanocomposite in Various Electrolyte Solutions

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Daiwon [Pacific Northwest National Laboratory, 902 Battelle Boulevard P.O. Box 999 Richland WA 99352 USA; Zhu, Chengzhou [School of Mechanical and Materials Engineering, Washington State University, Pullman, Washington 99164-2920 United States; Fu, Shaofang [School of Mechanical and Materials Engineering, Washington State University, Pullman, Washington 99164-2920 United States; Du, Dan [School of Mechanical and Materials Engineering, Washington State University, Pullman, Washington 99164-2920 United States; Engelhard, Mark H. [Pacific Northwest National Laboratory, 902 Battelle Boulevard P.O. Box 999 Richland WA 99352 USA; Lin, Yuehe [Pacific Northwest National Laboratory, 902 Battelle Boulevard P.O. Box 999 Richland WA 99352 USA; School of Mechanical and Materials Engineering, Washington State University, Pullman, Washington 99164-2920 United States

    2016-09-15

    The electrochemically controlled ion-exchange properties of multi-wall carbon nanotube (MWNT)/electronically conductive polypyrrole (PPy) polymer composite in the various electrolyte solutions have been investigated. The ion-exchange behavior, rate and capacity of the electrochemically deposited polypyrrole with and without carbon nanotube (CNT) were compared and characterized using cyclic voltammetry (CV), chronoamperometry (CA), electrochemical quartz crystal microbalance (EQCM), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). It has been found that the presence of carbon nanotube backbone resulted in improvement in ion-exchange rate, stability of polypyrrole, and higher anion loading capacity per PPy due to higher surface area, electronic conductivity, porous structure of thin film, and thinner film thickness providing shorter diffusion path. Chronoamperometric studies show that electrically switched anion exchange could be completed more than 10 times faster than pure PPy thin film. The anion selectivity of CNT/PPy film is demonstrated using X-ray photoelectron spectroscopy (XPS).

  12. Comparing ecosystem and soil respiration: Review and key challenges of tower-based and soil mesurements

    Science.gov (United States)

    The net ecosystem exchange (NEE) is the difference between ecosystem CO2 assimilation and CO2 losses to the atmosphere. Ecosystem respiration (Reco), the efflux of CO2 from the ecosystem to the atmosphere, includes the soil-to-atmosphere carbon flux (i.e., soil respiration; Rsoil) and aboveground pl...

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

    Science.gov (United States)

    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.

  14. The effect of charge exchange with neutral deuterium on carbon emission in JET divertor plasmas

    International Nuclear Information System (INIS)

    Maggi, C.; Horton, L.; Summers, H.

    1999-11-01

    High density, low temperature divertor plasma operation in tokamaks results in large neutral deuterium concentrations in the divertor volume. In these conditions, low energy charge transfer reactions between neutral deuterium and the impurity ions can in principle enhance the impurity radiative losses and thus help to reduce the maximum heat load to the divertor target. A quantitative study of the effect of charge exchange on carbon emission is presented, applied to the JET divertor. Total and state selective effective charge exchange recombination rate coefficients were calculated in the collisional radiative picture. These coefficients were coupled to divertor and impurity transport models to study the effect of charge exchange on the measured carbon spectral emission in JET divertor discharges. The sensitivity of the effect of charge exchange to the assumptions in the impurity transport model was also investigated. A reassessment was made of fundamental charge exchange cross section data in support of this study. (author)

  15. Can mud (silt and clay) concentration be used to predict soil organic carbon content within seagrass ecosystems?

    KAUST Repository

    Serrano, Oscar; Lavery, P. S.; Duarte, Carlos M.; Kendrick, Gary A.; Calafat, Antoni; York, P.; Steven, Andy; Macreadie, Peter I.

    2016-01-01

    The emerging field of blue carbon science is seeking cost-effective ways to estimate the organic carbon content of soils that are bound by coastal vegetated ecosystems. Organic carbon (C-org) content in terrestrial soils and marine sediments has

  16. Methods for calculating forest ecosystem and harvested carbon with standard estimates for forest types of the United States

    Science.gov (United States)

    James E. Smith; Linda S. Heath; Kenneth E. Skog; Richard A. Birdsey

    2006-01-01

    This study presents techniques for calculating average net annual additions to carbon in forests and in forest products. Forest ecosystem carbon yield tables, representing stand-level merchantable volume and carbon pools as a function of stand age, were developed for 51 forest types within 10 regions of the United States. Separate tables were developed for...

  17. Projecting the spatiotemporal carbon dynamics of the Greater Yellowstone Ecosystem from 2006 to 2050.

    Science.gov (United States)

    Huang, Shengli; Liu, Shuguang; Liu, Jinxun; Dahal, Devendra; Young, Claudia; Davis, Brian; Sohl, Terry L; Hawbaker, Todd J; Sleeter, Ben; Zhu, Zhiliang

    2015-12-01

    Climate change and the concurrent change in wildfire events and land use comprehensively affect carbon dynamics in both spatial and temporal dimensions. The purpose of this study was to project the spatial and temporal aspects of carbon storage in the Greater Yellowstone Ecosystem (GYE) under these changes from 2006 to 2050. We selected three emission scenarios and produced simulations with the CENTURY model using three General Circulation Models (GCMs) for each scenario. We also incorporated projected land use change and fire occurrence into the carbon accounting. The three GCMs showed increases in maximum and minimum temperature, but precipitation projections varied among GCMs. Total ecosystem carbon increased steadily from 7,942 gC/m 2 in 2006 to 10,234 gC/m 2 in 2050 with an annual rate increase of 53 gC/m 2 /year. About 56.6% and 27% of the increasing rate was attributed to total live carbon and total soil carbon, respectively. Net Primary Production (NPP) increased slightly from 260 gC/m 2 /year in 2006 to 310 gC/m 2 /year in 2050 with an annual rate increase of 1.22 gC/m 2 /year. Forest clear-cutting and fires resulted in direct carbon removal; however, the rate was low at 2.44 gC/m 2 /year during 2006-2050. The area of clear-cutting and wildfires in the GYE would account for 10.87% of total forested area during 2006-2050, but the predictive simulations demonstrated different spatial distributions in national forests and national parks. The GYE is a carbon sink during 2006-2050. The capability of vegetation is almost double that of soil in terms of sequestering extra carbon. Clear-cutting and wildfires in GYE will affect 10.87% of total forested area, but direct carbon removal from clear-cutting and fires is 109.6 gC/m 2 , which accounts for only 1.2% of the mean ecosystem carbon level of 9,056 gC/m 2 , and thus is not significant.

  18. [Effects of drying and wetting cycles induced by tides on net ecosystem exchange of CO2 over a salt marsh in the Yellow River Delta, China.

    Science.gov (United States)

    He, Wen Jun; Han, Guang Xuan; Xu, Yan Ning; Zhang, Xi Tao; Wang, An Dong; Che, Chun Guang; Sun, Bao Yu; Zhang, Xiao Shuai

    2018-01-01

    As a unique hydrological characteristic, the tidal action can strongly affect carbon balance in a salt marsh despite their short duration. Using the eddy covariance technique, we measured the net ecosystem CO 2 exchange (NEE) and its environmental factors and tidal change over a salt marsh in the Yellow River Delta. It aimed to investigate the effect of tidal process and drying and wetting cycles induced by tides on NEE. The results showed that the tidal process promoted the daytime CO 2 uptake, but it didn't clearly affect the nighttime CO 2 release. Tidal inundation was a major factor influencing daytime NEE. The diurnal change of NEE showed a distinct U-shaped curve on both drought and wet stages, but not with substantial variation in its amplitude during the drought stage. The drying and wetting cycles enhanced the absorption of daytime CO 2 . Under drought stage, the mean of the maximum photosynthetic rate (A max ), apparent quantum yield (α) and ecosystem respiration (R eco ) were higher than those in wet stage. In addition, the drying and wetting cycles suppressed the nighttime CO 2 release from the salt marsh but increased its temperature sensitivity.

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

    Science.gov (United States)

    Potter, Christopher; Klooster, Steven; Crabtree, Robert; Huang, Shengli; Gross, Peggy; Genovese, Vanessa

    2011-08-11

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

  20. The Role of Driving Factors in Historical and Projected Carbon Dynamics in Wetland Ecosystems of Alaska

    Science.gov (United States)

    Lyu, Z.; Helene, G.; He, Y.; Zhuang, Q.; McGuire, A. D.; Bennett, A.; Breen, A. L.; Clein, J.; Euskirchen, E. S.; Johnson, K. D.; Kurkowski, T. A.; Pastick, N. J.; Rupp, S. T.; Wylie, B. K.; Zhu, Z.

    2017-12-01

    Wetlands are important terrestrial ecosystems in Alaska. It is important to understand and assess their role in the regional carbon dynamics in response to historical and projected environmental conditions. A coupled modeling framework that incorporates a fire disturbance model and two biogeochemical models was used to assess the relative influence of changing climate, atmospheric carbon dioxide (CO2) concentration, and fire regime on the historical and future carbon balance in wetland ecosystems of the four main Landscape Conservation Cooperatives (LCCs) of Alaska. Simulations were conducted for the historical period (1950-2009) and future projection period (2010-2099). These simulations estimate that the total carbon (C) storage in wetland ecosystems of Alaska is 5556 Tg C in 2009, with 89% of the C stored in soils. An estimated 175 Tg C was lost during the historical period, which is attributed to greater C lost from the Northwest Boreal LCC than C gained from the other three LCCs. The simulations for the projection period were conducted for six different scenarios driven by climate forcings from two different climate models for each of three CO2 emission scenarios. The mean total carbon storage increased 3.94 Tg C/yr by 2099, with variability among the simulations ranging from 2.02 Tg C/yr to 4.42 Tg C/yr. Across the four LCCs, the largest relative C storage increase occurred in the Arctic and North Pacific LCCs. These increases were primarily driven by increases in net primary production (NPP) that were greater than increases in heterotrophic respiration and fire emissions. Our analysis further indicates that NPP increase was primarily driven by CO2 fertilization ( 5% per 100 ppmv increase) as well as by increases in air temperature ( 1% per ° increase). Increases air temperature were estimated to be the primary cause for a projected 47.7% mean increase in wetlands biogenic CH4 emissions among the simulations ( 15% per ° increase). The combined effects of

  1. Inferring CO2 Fluxes from OCO-2 for Assimilation into Land Surface Models to Calculate Net Ecosystem Exchange

    Science.gov (United States)

    Prouty, R.; Radov, A.; Halem, M.; Nearing, G. S.

    2016-12-01

    Investigations of mid to high latitude atmospheric CO2 show a growing seasonal amplitude. Land surface models poorly predict net ecosystem exchange (NEE) and are unable to substantiate these sporadic observations. An investigation of how the biosphere has reacted to changes in atmospheric CO2 is essential to our understanding of potential climate-vegetation feedbacks. A global, seasonal investigation of CO2-flux is then necessary in order to assimilate into land surface models for improving the prediction of annual NEE. The Atmospheric Radiation Measurement program (ARM) of DOE collects CO2-flux measurements (in addition to CO2 concentration and various other meteorological quantities) at several towers located around the globe at half hour temporal frequencies. CO2-fluxes are calculated via the eddy covariance technique, which utilizes CO2-densities and wind velocities to calculate CO2-fluxes. The global coverage of CO2 concentrations as provided by the Orbiting Carbon Observatory (OCO-2) provide satellite-derived CO2 concentrations all over the globe. A framework relating the satellite-inferred CO2 concentrations collocated with the ground-based ARM as well as Ameriflux stations would enable calculations of CO2-fluxes far from the station sites around the entire globe. Regression techniques utilizing deep-learning neural networks may provide such a framework. Additionally, meteorological reanalysis allows for the replacement of the ARM multivariable meteorological variables needed to infer the CO2-fluxes. We present the results of inferring CO2-fluxes from OCO-2 CO2 concentrations for a two year period, Sept. 2014- Sept. 2016 at the ARM station located near Oklahoma City. A feed-forward neural network (FFNN) is used to infer relationships between the following data sets: F([ARM CO2-density], [ARM Meteorological Data]) = [ARM CO2-Flux] F([OCO-2 CO2-density],[ARM Meteorological Data]) = [ARM CO2-Flux] F([ARM CO2-density],[Meteorological Reanalysis]) = [ARM CO2-Flux

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

    Directory of Open Access Journals (Sweden)

    Bin Wang

    Full Text Available 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

  3. Climate control of terrestrial carbon exchange across biomes and continents

    Czech Academy of Sciences Publication Activity Database

    Yi, C.; Ricciuto, D.; Marek, Michal V.

    2010-01-01

    Roč. 5, č. 3 (2010), s. 034007 ISSN 1748-9326 Institutional research plan: CEZ:AV0Z60870520 Keywords : NEE * climate control * terrestrial carbon sequestration * temperature * dryness * eddy flux * biomes * photosynthesis * respiration * global carbon cycle Subject RIV: EH - Ecology, Behaviour Impact factor: 3.049, year: 2010

  4. Photosynthesis, Nitrogen, Their Adjustment and its Effects on Ecosystem Carbon Gain at Elevated CO(sub 2)l. A Comparison of Loblolly and Ponderosa Pines; FINAL

    International Nuclear Information System (INIS)

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

    1996-01-01

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

  5. Drought resistance across California ecosystems: Evaluating changes in carbon dynamics using satellite imagery

    Science.gov (United States)

    Malone, Sparkle; Tulbure, Mirela; Pérez-Luque, Antonio J.; Assal, Timothy J.; Bremer, Leah; Drucker, Debora; Hillis, Vicken; Varela, Sara; Goulden, Michael

    2016-01-01

    Drought is a global issue that is exacerbated by climate change and increasing anthropogenic water demands. The recent occurrence of drought in California provides an important opportunity to examine drought response across ecosystem classes (forests, shrublands, grasslands, and wetlands), which is essential to understand how climate influences ecosystem structure and function. We quantified ecosystem resistance to drought by comparing changes in satellite-derived estimates of water-use efficiency (WUE = net primary productivity [NPP]/evapotranspiration [ET]) under normal (i.e., baseline) and drought conditions (ΔWUE = WUE2014 − baseline WUE). With this method, areas with increasing WUE under drought conditions are considered more resilient than systems with declining WUE. Baseline WUE varied across California (0.08 to 3.85 g C/mm H2O) and WUE generally increased under severe drought conditions in 2014. Strong correlations between ΔWUE, precipitation, and leaf area index (LAI) indicate that ecosystems with a lower average LAI (i.e., grasslands) also had greater C-uptake rates when water was limiting and higher rates of carbon-uptake efficiency (CUE = NPP/LAI) under drought conditions. We also found that systems with a baseline WUE ≤ 0.4 exhibited a decline in WUE under drought conditions, suggesting that a baseline WUE ≤ 0.4 might be indicative of low drought resistance. Drought severity, precipitation, and WUE were identified as important drivers of shifts in ecosystem classes over the study period. These findings have important implications for understanding climate change effects on primary productivity and C sequestration across ecosystems and how this may influence ecosystem resistance in the future.

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

    Science.gov (United States)

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

    2014-05-01

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

  7. Advances in Estimating Current and Future Effects of Climate and Management on Forest Ecosystem Carbon and Water Dynamics at Multiple Scales

    Science.gov (United States)

    Law, B. E.; Still, C. J.; Hudiburg, T. W.; Buotte, P.; Hanson, C. V.

    2017-12-01

    As we examine the integrated effects of climate variability, atmospheric CO2, and land management actions on terrestrial carbon and water processes within regions, and evaluate mitigation and adaptation options, we want our analysis to be as accurate as possible to reduce the risk of negative impacts from management decisions. The use of global land models at regional scales requires modifications for realistic projections. Model evaluation reveals knowledge and data gaps in species sensitivities to climate extremes and responses to land use change and management actions such as restoration. For example, a combination of sapflux and AmeriFlux tower measurements identifies seasonal shifts in the proportion of water vapor exchange that is due to tree transpiration, as well as changes in tree water-use efficiency associated with climate variation. Thermal measurements from an unmanned aerial system quantify canopy temperatures reached during extreme heat events, as well as tree-to-tree thermal variations, which can be related to transpiration dynamics. Diagnosis of land model performance across climate/vegetation gradients includes the combination of atmospheric CO2/CO/H2O observations from aircraft, a tall tower network, and a mobile platform, combined with inverse modeling. This approach identified an ecoregion where the Community Land Model (CLM4.5) underestimated net ecosystem production by 28%, suggesting model challenges in high productivity forests with high soil nitrogen and deep organic soils. We use land-model output of net ecosystem production, harvest and fire emissions to estimate net ecosystem carbon balance, which is input to a Life-Cycle Assessment of wood product use to estimate net carbon emissions to the atmosphere for harvest scenarios and bioenergy production. Such robust and interdisciplinary approaches are needed to more accurately quantify impacts on ecosystems and "what the atmosphere sees" in terms of greenhouse gas sources and impacts on

  8. Variability in the carbon storage of seagrass habitats and its implications for global estimates of blue carbon ecosystem service.

    Directory of Open Access Journals (Sweden)

    Paul S Lavery

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

  9. The exchange of inorganic carbon on the Canadian Beaufort Shelf

    Science.gov (United States)

    Mol, Jacoba; Thomas, Helmuth; Hu, Xianmin; Myers, Paul G.

    2017-04-01

    The Mackenzie Shelf in the southeastern Beaufort Sea is an area that has experienced large changes in the past several decades as warming, sea-ice loss, and increased river discharge have altered carbon cycling. Upwelling and downwelling events are common on the shelf, caused by strong, fluctuating along-shore winds and resulting cross-shelf Ekman transport. Downwelling carries inorganic carbon and other remineralization products off the shelf and into the deep basin for possible long-term storage in the world oceans. Upwelling carries water high in dissolved inorganic carbon (DIC) and nutrients from the Pacific-origin upper halocline layer (UHL) onto the shelf. Profiles of DIC and total alkalinity (TA) taken in August and September of 2014 are used to investigate the cycling of inorganic carbon on the Mackenzie Shelf. The along-shore and cross-shelf transport of inorganic carbon is quantified using velocity field output from a simulation of the Arctic and Northern Hemisphere Atlantic (ANHA4) configuration of the Nucleus of European Modelling of the Ocean (NEMO) model. A strong upwelling event prior to sampling on the Mackenzie Shelf is analyzed and the resulting influence on the carbonate system, including the saturation state of aragonite and pH levels, is investigated. TA and δ18O are used to examine water mass distributions in the study area and analyze the influence of Pacific Water, Mackenzie River freshwater, and sea-ice melt on carbon dynamics and air-sea fluxes of CO2 in the surface mixed layer. Understanding carbon transfer in this seasonally dynamic environment is key in order to quantify the importance of Arctic shelf regions to the global carbon cycle and to provide a basis for understanding how its role will respond to the aforementioned changes in the regional marine system.

  10. The role of driving factors in historical and projected carbon dynamics of upland ecosystems in Alaska

    Science.gov (United States)

    Genet, Hélène; He, Yujie; Lyu, Zhou; McGuire, A. David; Zhuang, Qianlai; Clein, Joy S.; D'Amore, David; Bennett, Alec; Breen, Amy; Biles, Frances; Euskirchen, Eugénie S.; Johnson, Kristofer; Kurkowski, Tom; Schroder, Svetlana (Kushch); Pastick, Neal J.; Rupp, T. Scott; Wylie, Bruce K.; Zhang, Yujin; Zhou, Xiaoping; Zhu, Zhiliang

    2018-01-01

    It is important to understand how upland ecosystems of Alaska, which are estimated to occupy 84% of the state (i.e., 1,237,774 km2), are influencing and will influence state‐wide carbon (C) dynamics in the face of ongoing climate change. We coupled fire disturbance and biogeochemical models to assess the relative effects of changing atmospheric carbon dioxide (CO2), climate, logging and fire regimes on the historical and future C balance of upland ecosystems for the four main Landscape Conservation Cooperatives (LCCs) of Alaska. At the end of the historical period (1950–2009) of our analysis, we estimate that upland ecosystems of Alaska store ~50 Pg C (with ~90% of the C in soils), and gained 3.26 Tg C/yr. Three of the LCCs had gains in total ecosystem C storage, while the Northwest Boreal LCC lost C (−6.01 Tg C/yr) because of increases in fire activity. Carbon exports from logging affected only the North Pacific LCC and represented less than 1% of the state's net primary production (NPP). The analysis for the future time period (2010–2099) consisted of six simulations driven by climate outputs from two climate models for three emission scenarios. Across the climate scenarios, total ecosystem C storage increased between 19.5 and 66.3 Tg C/yr, which represents 3.4% to 11.7% increase in Alaska upland's storage. We conducted additional simulations to attribute these responses to environmental changes. This analysis showed that atmospheric CO2 fertilization was the main driver of ecosystem C balance. By comparing future simulations with constant and with increasing atmospheric CO2, we estimated that the sensitivity of NPP was 4.8% per 100 ppmv, but NPP becomes less sensitive to CO2increase throughout the 21st century. Overall, our analyses suggest that the decreasing CO2 sensitivity of NPP and the increasing sensitivity of heterotrophic respiration to air temperature, in addition to the increase in C loss from wildfires weakens the C sink from upland

  11. The role of driving factors in historical and projected carbon dynamics of upland ecosystems in Alaska.

    Science.gov (United States)

    Genet, Hélène; He, Yujie; Lyu, Zhou; McGuire, A David; Zhuang, Qianlai; Clein, Joy; D'Amore, David; Bennett, Alec; Breen, Amy; Biles, Frances; Euskirchen, Eugénie S; Johnson, Kristofer; Kurkowski, Tom; Kushch Schroder, Svetlana; Pastick, Neal; Rupp, T Scott; Wylie, Bruce; Zhang, Yujin; Zhou, Xiaoping; Zhu, Zhiliang

    2018-01-01

    It is important to understand how upland ecosystems of Alaska, which are estimated to occupy 84% of the state (i.e., 1,237,774 km 2 ), are influencing and will influence state-wide carbon (C) dynamics in the face of ongoing climate change. We coupled fire disturbance and biogeochemical models to assess the relative effects of changing atmospheric carbon dioxide (CO 2 ), climate, logging and fire regimes on the historical and future C balance of upland ecosystems for the four main Landscape Conservation Cooperatives (LCCs) of Alaska. At the end of the historical period (1950-2009) of our analysis, we estimate that upland ecosystems of Alaska store ~50 Pg C (with ~90% of the C in soils), and gained 3.26 Tg C/yr. Three of the LCCs had gains in total ecosystem C storage, while the Northwest Boreal LCC lost C (-6.01 Tg C/yr) because of increases in fire activity. Carbon exports from logging affected only the North Pacific LCC and represented less than 1% of the state's net primary production (NPP). The analysis for the future time period (2010-2099) consisted of six simulations driven by climate outputs from two climate models for three emission scenarios. Across the climate scenarios, total ecosystem C storage increased between 19.5 and 66.3 Tg C/yr, which represents 3.4% to 11.7% increase in Alaska upland's storage. We conducted additional simulations to attribute these responses to environmental changes. This analysis showed that atmospheric CO 2 fertilization was the main driver of ecosystem C balance. By comparing future simulations with constant and with increasing atmospheric CO 2 , we estimated that the sensitivity of NPP was 4.8% per 100 ppmv, but NPP becomes less sensitive to CO 2 increase throughout the 21st century. Overall, our analyses suggest that the decreasing CO 2 sensitivity of NPP and the increasing sensitivity of heterotrophic respiration to air temperature, in addition to the increase in C loss from wildfires weakens the C sink from upland

  12. Multi-temporal Linkages of Net Ecosystem Exchanges (NEE) with the Climatic and Ecohydrologic Drivers in a Florida Everglades Short-hydroperiod Freshwater Marsh

    Science.gov (United States)

    Zaki, M. T.; Abdul-Aziz, O. I.; Ishtiaq, K. S.

    2017-12-01

    Wetlands are considered one of the most productive and ecologically valuable ecosystems on earth. We investigated the multi-temporal linkages of net ecosystem exchange (NEE) with the relevant climatic and ecohydrological drivers for a Florida Everglades short-hydroperiod freshwater wetland. Hourly NEE observations and the associated driving variables during 2008-12 were collected from the AmeriFlux and EDEN databases, and then averaged for the four temporal scales (1-day, 8-day, 15-day, and 30-day). Pearson correlation and factor analysis were employed to identify the interrelations and grouping patterns among the participatory variables for each time scale. The climatic and ecohydrological linkages of NEE were then reliably estimated using bootstrapped (1000 iterations) partial least squares regressions by resolving multicollinearity. The analytics identified four bio-physical components exhibiting relatively robust interrelations and grouping patterns with NEE across the temporal scales. In general, NEE was most strongly linked with the `radiation-energy (RE)' component, while having a moderate linkage with the `temperature-hydrology (TH)' and `aerodynamic (AD)' components. However, the `ambient atmospheric CO2 (AC)' component was very weakly linked to NEE. Further, RE and TH had a decreasing trend with the increasing time scales (1-30 days). In contrast, the linkages of AD and AC components increased from 1-day to 8-day scales, and then remained relatively invariable at the longer scales of aggregation. The estimated linkages provide insights into the dominant biophysical process components and drivers of ecosystem carbon in the Everglades. The invariant linking pattern and linkages would help to develop low-dimensional models to reliably predict CO2 fluxes from the tidal freshwater wetlands.

  13. Modelling carbon and water exchange of a grazed pasture in New Zealand constrained by eddy covariance measurements.

    Science.gov (United States)

    Kirschbaum, Miko U F; Rutledge, Susanna; Kuijper, Isoude A; Mudge, Paul L; Puche, Nicolas; Wall, Aaron M; Roach, Chris G; Schipper, Louis A; Campbell, David I

    2015-04-15

    We used two years of eddy covariance (EC) measurements collected over an intensively grazed dairy pasture to better understand the key drivers of changes in soil organic carbon stocks. Analysing grazing systems with EC measurements poses significant challenges as the respiration from grazing animals can result in large short-term CO2 fluxes. As paddocks are grazed only periodically, EC observations derive from a mosaic of paddocks with very different exchange rates. This violates the assumptions implicit in the use of EC methodology. To test whether these challenges could be overcome, and to develop a tool for wider scenario testing, we compared EC measurements with simulation runs with the detailed ecosystem model CenW 4.1. Simulations were run separately for 26 paddocks around the EC tower and coupled to a footprint analysis to estimate net fluxes at the EC tower. Overall, we obtained good agreement between modelled and measured fluxes, especially for the comparison of evapotranspiration rates, with model efficiency of 0.96 for weekly averaged values of the validation data. For net ecosystem productivity (NEP) comparisons, observations were omitted when cattle grazed the paddocks immediately around the tower. With those points omitted, model efficiencies for weekly averaged values of the validation data were 0.78, 0.67 and 0.54 for daytime, night-time and 24-hour NEP, respectively. While not included for model parameterisation, simulated gross primary production also agreed closely with values inferred from eddy covariance measurements (model efficiency of 0.84 for weekly averages). The study confirmed that CenW simulations could adequately model carbon and water exchange in grazed pastures. It highlighted the critical role of animal respiration for net CO2 fluxes, and showed that EC studies of grazed pastures need to consider the best approach of accounting for this important flux to avoid unbalanced accounting. Copyright © 2015. Published by Elsevier B.V.

  14. Productivity and carbon dioxide exchange of leguminous crops: estimates from flux tower measurements

    Science.gov (United States)

    Gilmanov, Tagir G.; Baker, John M.; Bernacchi, Carl J.; Billesbach, David P.; Burba, George G.; Castro, Saulo; Chen, Jiquan; Eugster, Werner; Fischer, Marc L.; Gamon, John A.; Gebremedhin, Maheteme T.; Glenn, Aaron J.; Griffis, Timothy J.; Hatfield, Jerry L.; Heuer, Mark W.; Howard, Daniel M.; Leclerc, Monique Y.; Loescher, Henry W.; Marloie, Oliver; Meyers, Tilden P.; Olioso, Albert; Phillips, Rebecca L.; Prueger, John H.; Skinner, R. Howard; Suyker, Andrew E.; Tenuta, Mario; Wylie, Bruce K.

    2014-01-01

    Net CO2 exchange data of legume crops at 17 flux tower sites in North America and three sites in Europe representing 29 site-years of measurements were partitioned into gross photosynthesis and ecosystem respiration by using the nonrectangular hyperbolic light-response function method. The analyses produced net CO2 exchange data and new ecosystem-scale ecophysiological parameter estimates for legume crops determined at diurnal and weekly time steps. Dynamics and annual totals of gross photosynthesis, ecosystem respiration, and net ecosystem production were calculated by gap filling with multivariate nonlinear regression. Comparison with the data from grain crops obtained with the same method demonstrated that CO2 exchange rates and ecophysiological parameters of legumes were lower than those of maize (Zea mays L.) but higher than for wheat (Triticum aestivum L.) crops. Year-round annual legume crops demonstrated a broad range of net ecosystem production, from sinks of 760 g CO2 m–2 yr–1 to sources of –2100 g CO2 m–2 yr–1, with an average of –330 g CO2 m–2 yr–1, indicating overall moderate CO2–source activity related to a shorter period of photosynthetic uptake and metabolic costs of N2 fixation. Perennial legumes (alfalfa, Medicago sativa L.) were strong sinks for atmospheric CO2, with an average net ecosystem production of 980 (range 550–1200) g CO2 m–2 yr–1.

  15. Toward a consistency cross-check of eddy covariance flux-based and biometric estimates of ecosystem carbon balance

    NARCIS (Netherlands)

    Luyssaert, S.; Reichstein, M.; Schulze, E.D.; Janssens, I.A.; Law, B.E.; Papale, D.; Dragoni, D.; Goulden, M.L.; Granier, A.; Kutch, W.L.; Linder, S.; Matteucci, G.; Moors, E.J.; Munger, J.W.; Pilegaard, K.; Saunders, M.; Falge, E.M.

    2009-01-01

    Quantification of an ecosystem's carbon balance and its components is pivotal for understanding both ecosystem functioning and global cycling. Several methods are being applied in parallel to estimate the different components of the CO2 balance. However, different methods are subject to different

  16. ISLSCP II Air-Sea Carbon Dioxide Gas Exchange

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set contains the calculated net ocean-air carbon dioxide (CO2) flux and sea-air CO2 partial pressure (pCO2) difference. The estimates are based on...

  17. Carbon sequestration capacity in a semiarid ecosystem: A carbon balance approach

    International Nuclear Information System (INIS)

    Almagro, M.; Lopez, J.; Boix-Fayos, C.; Albaladejo, J.; Martinez-Mena, M.

    2009-01-01

    Here, we used two C balance approaches to estimate total below ground C allocation (TBCA) in three representative land uses in a Mediterranean ecosystem (late-successional forest, abandoned agricultural field, rainfed olive grove). Our objectives were: 1) to asses the response of TBCA and its components to changes in land use; 2) to evaluate how soil water erosion and changes in C stored in roots, soil and litter layer altered our estimates of TBCA; 3) to determine annual net ecosystem productivity, and examine C allocation patterns at each land use. (Author) 4 refs.

  18. Carbon exchange in biological soil crust communities under differential temperatures and soil water contents: implications for global change

    Science.gov (United States)

    Grote, Edmund E.; Belnap, Jayne; Housman, David C.; Sparks, Jed P.

    2010-01-01

    Biological soil crusts (biocrusts) are an integral part of the soil system in arid regions worldwide, stabilizing soil surfaces, aiding vascular plant establishment, and are significant sources of ecosystem nitrogen and carbon. Hydration and temperature primarily control ecosystem CO2 flux in these systems. Using constructed mesocosms for incubations under controlled laboratory conditions, we examined the effect of temperature (5-35 1C) and water content (WC, 20-100%) on CO2 exchange in light cyanobacterially dominated) and dark cyanobacteria/lichen and moss dominated) biocrusts of the cool Colorado Plateau Desert in Utah and the hot Chihuahuan Desert in New Mexico. In light crusts from both Utah and New Mexico, net photosynthesis was highest at temperatures 430 1C. Net photosynthesis in light crusts from Utah was relatively insensitive to changes in soil moisture. In contrast, light crusts from New Mexico tended to exhibit higher rates of net photosynthesis at higher soil moisture. Dark crusts originating from both sites exhibited the greatest net photosynthesis at intermediate soil water content (40-60%). Declines in net photosynthesis were observed in dark crusts with crusts from Utah showing declines at temperatures 425 1C and those originating from New Mexico showing declines at temperatures 435 1C. Maximum net photosynthesis in all crust types from all locations were strongly influenced by offsets in the optimal temperature and water content for gross photosynthesis compared with dark respiration. Gross photosynthesis tended to be maximized at some intermediate value of temperature and water content and dark respiration tended to increase linearly. The results of this study suggest biocrusts are capable of CO2 exchange under a wide range of conditions. However, significant changes in the magnitude of this exchange should be expected for the temperature and precipitation changes suggested by current climate models.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-06-01

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

  20. Ecosystem carbon and radiative fluxes: a global synthesis based on the FLUXNET network.

    Science.gov (United States)

    Cescatti, A.

    2009-04-01

    Solar radiation is the most important environmental factor driving the temporal and spatial variability of the gross primary productivity (GPP) in terrestrial ecosystems. At the ecosystem scale, the light use efficiency (LUE) depends not only on radiation quantity but also on radiation "quality" both in terms of spectral composition and angular distribution. The day-to-day variations in LUE are largely determined by changes in the ratio of diffuse to total radiation. The relative importance of the concurrent variation in total incoming radiation and in LUE is essential to estimate the sign and the magnitude of the GPP sensitivity to radiation. Despite the scientific relevance of this issue, a global assessment on the sensitivity of GPP to the variations of Phar is still missing. Such an analysis is needed to improve our understanding of the current and future impacts of aerosols and cloud cover on the spatio-temporal variability of GPP. The current availability of ecosystem carbon fluxes, together with separate measurements of incoming direct and diffuse Phar at a large number of flux sites, offers the unique opportunity to extend the previous investigation, both in terms of ecosystem, spatial and climate coverage, and to address questions about the internal (e.g. leaf area index, canopy structure) and external (e.g. cloudiness, covarying meteorology) factors affecting the ecosystem sensitivity to radiation geometry. For this purpose half-hourly measurements of carbon fluxes and radiation have been analyzed at about 220 flux sites for a total of about 660 site-years. This analysis demonstrates that the sensitivity of GPP to incoming radiation varies across the different plant functional types and is correlated with the leaf area index and the local climatology. In particular, the sensitivity of GPP to changes in incoming diffuse light maximizes for the broadleaved forests of the Northern Hemisphere.

  1. Carbon dioxide exchange of the Arctic tundra in the northern part of European Russia

    DEFF Research Database (Denmark)

    Kiepe, Isabell; Johansson, Paul Torbjörn; Friborg, Thomas

    Northern Russia has been subject to many speculations in relation to climatic change effects and greenhouse gas (GHG) exchange but still little scientific evidence is available for this region. There is low abundance of continuous Arctic GHG exchange measurements deploying eddy covariance technique...... 70 cm in the hummocky areas. The climate is continental with a mean annual air temperature (1995-2007) of about -9.4 °C (Vorkuta). To determine the greenhouse balance of this area the eddy covariance technique was used in the late period of the growing season of 2007. In this study we focus...... on the transition period at the end of the growth season, which is a part of the year when predicted changes in temperature is likely to have the most pronounced effects on the exchange of GHGs. The net ecosystem CO2 exchange reflects two important influences on the opposed fluxes, gross photosynthesis...

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

    Science.gov (United States)

    Kuittinen, Matti; Moinel, Caroline; Adalgeirsdottir, Kristjana

    2016-09-01

    Plants and soil are natural regulators of atmospheric CO2. Whereas plants sequester atmospheric carbon, soils deposit it for decades. As cities become increasingly more densely built, the available land area for such ecosystem services may decrease. We studied seven different housing areas in the Finnish city of Espoo to ascertain the extent to which site efficiency affects to the ecosystem services if the full life-cycle GHG emissions of these areas are taken into account. The results show that the impact of CO2 uptake through carbon sinks in growing plants and the uptake of soil organic carbon vary greatly. Its share of all emissions varied from a marginal value of 1.2% to a more considerable value of 11.9%. The highest potential was calculated for a detached house located on a large site, while the weakest was calculated for compact apartment blocks. The study revealed that in order to quantify this potential more accurately, several knowledge gaps must first be addressed. These include impartial growth algorithms for Nordic wood species, missing accumulation factors for soil organic carbon in cold climates and statistical maintenance scenarios for gardens. Copyright © 2016 Elsevier B.V. All rights reserved.

  3. Mangrove Carbon Stocks and Ecosystem Cover Dynamics in Southwest Madagascar and the Implications for Local Management

    Directory of Open Access Journals (Sweden)

    Lisa Benson

    2017-05-01

    Full Text Available Of the numerous ecosystem services mangroves provide, carbon storage is gaining particular attention for its potential role in climate change mitigation strategies. Madagascar contains 2% of the world’s mangroves, over 20% of which is estimated to have been deforested through charcoal production, timber extraction and agricultural development. This study presents a carbon stock assessment of the mangroves in Helodrano Fagnemotse in southwest Madagascar alongside an analysis of mangrove land-cover change from 2002 to 2014. Similar to other mangrove ecosystems in East Africa, higher stature, closed-canopy mangroves in southwest Madagascar were estimated to contain 454.92 (±26.58 Mg·C·ha−1. Although the mangrove extent in this area is relatively small (1500 ha, these mangroves are of critical importance to local communities and anthropogenic pressures on coastal resources in the area are increasing. This was evident in both field observations and remote sensing analysis, which indicated an overall net loss of 3.18% between 2002 and 2014. Further dynamics analysis highlighted widespread transitions of dense, higher stature mangroves to more sparse mangrove areas indicating extensive degradation. Harnessing the value that the carbon stored within these mangroves holds on the voluntary carbon market could generate revenue to support and incentivise locally-led sustainable mangrove management, improve livelihoods and alleviate anthropogenic pressures.

  4. Models for transport and fate of carbon, nutrients and radionuclides in the aquatic ecosystem at Oeregrundsgrepen

    International Nuclear Information System (INIS)

    Erichsen, Anders Christian; Moehlenberg, Flemming; Closter, Rikke Margrethe; Sandberg, Johannes

    2010-06-01

    The aim of the work was to provide supplementary input to the risk assessment of a planned final nuclear waste repository at Forsmark. The main deliverable was a computed water exchange between basins in the Forsmark marine area for the period 6500 BC to 9000 AD - based on the hydrodynamic modelling - to be used as input to the landscape dose model. In addition and what is described in this report, a second deliverable was development and application of high-resolution models for the marine ecosystem and radionuclide processes. The purpose of this deliverable was to illustrate the spatial and temporal variation in important processes and parameters, while constituting a complement to previous modelling approaches and providing supporting information to discussions of the marine ecosystem, parameters and variation (see Chapter 4 and 6).To this end, a hydrodynamic model of high temporal and spatial resolution was constructed and calibrated for the Forsmark area. An ecosystem model was then developed and coupled to the hydrodynamic model. In turn, a detailed radionuclide model was coupled to the ecosystem model to provide detailed predictions of radionuclide transport and accumulation in the coastal ecosystem. The ecosystem and radionuclide models were developed in the equation solver MIKE ECOLab that links seamless to the MIKE3 FM hydrodynamic model. The 'standard' ECOLab ecosystem model was extended with six biological state variables, perennial macroalgae, benthic herbivors, detritus feeders, planktivorus fish and, benthic predators representing the relict isopod Saduria and cod. In contrast to the ecosystem model, the radionuclide model was developed from scratch but building on the structure of the ecosystem model and using the output (process rates linking state variables) from the ecosystem model as input to the radionuclide model. Both the ecosystem model and the radionuclide model were run for several years (5-8 years) to bring state variables into quasi

  5. Models for transport and fate of carbon, nutrients and radionuclides in the aquatic ecosystem at Oeregrundsgrepen

    Energy Technology Data Exchange (ETDEWEB)

    Erichsen, Anders Christian; Moehlenberg, Flemming; Closter, Rikke Margrethe; Sandberg, Johannes [DHI, Hoersholm (Denmark)

    2010-06-15

    The aim of the work was to provide supplementary input to the risk assessment of a planned final nuclear waste repository at Forsmark. The main deliverable was a computed water exchange between basins in the Forsmark marine area for the period 6500 BC to 9000 AD - based on the hydrodynamic modelling - to be used as input to the landscape dose model. In addition and what is described in this report, a second deliverable was development and application of high-resolution models for the marine ecosystem and radionuclide processes. The purpose of this deliverable was to illustrate the spatial and temporal variation in important processes and parameters, while constituting a complement to previous modelling approaches and providing supporting information to discussions of the marine ecosystem, parameters and variation (see Chapter 4 and 6).To this end, a hydrodynamic model of high temporal and spatial resolution was constructed and calibrated for the Forsmark area. An ecosystem model was then developed and coupled to the hydrodynamic model. In turn, a detailed radionuclide model was coupled to the ecosystem model to provide detailed predictions of radionuclide transport and accumulation in the coastal ecosystem. The ecosystem and radionuclide models were developed in the equation solver MIKE ECOLab that links seamless to the MIKE3 FM hydrodynamic model. The 'standard' ECOLab ecosystem model was extended with six biological state variables, perennial macroalgae, benthic herbivors, detritus feeders, planktivorus fish and, benthic predators representing the relict isopod Saduria and cod. In contrast to the ecosystem model, the radionuclide model was developed from scratch but building on the structure of the ecosystem model and using the output (process rates linking state variables) from the ecosystem model as input to the radionuclide model. Both the ecosystem model and the radionuclide model were run for several years (5-8 years) to bring state variables into quasi

  6. Separation of uranium from sodium carbonate - sodium bicarbonate eluate by ion exchange method

    International Nuclear Information System (INIS)

    Sakane, Kohji; Hirotsu, Takahiro; Fujii, Ayako; Katoh, Shunsaku; Sugasaka, Kazuhiko

    1982-01-01

    The ion exchange method was used for separating uranium from the eluate (0.5 N Na 2 CO 3 -0.5 N NaHCO 3 ) that was obtained in the extraction process of uranium from natural sea water by using the titanium-activated carbon composite adsorbent. Uranium in the eluate containing 3 mg/1 uranium was adsorbed by ion exchange resin (Amberlite IRA-400), and was eluted with the eluant (5 % NaCl-0.5 % Na 2 CO 3 ). The concentration ratio of uranium in the final concentrated-eluate became more than 20 times. The eluting solution to the adsorbent and the eluant to the resin could be repeatedly used in the desorption-ion exchange process. Sodium carbonate was consumed at the desorption step, and sodium bicarbonate was consumed at the ion exchange step. The concentration ratio of uranium was found to decrease as chloride ion in the eluate increased. (author)

  7. Separation of uranium from sodium carbonate-sodium bicarbonate eluate by ion exchange method

    International Nuclear Information System (INIS)

    Sakane, Kohji; Hirotsu, Takahiro; Fujii, Ayako; Katoh, Shunsaku; Sugasaka, Kazuhiko

    1982-01-01

    The ion exchange method was used for separating uranium from the eluate (0.5 N Na 2 CO 3 -0.5 N NaHCO 3 ) that was obtained in the extraction process of uranium from natural sea water by using the titanium-activated carbon composite adsorbent. Uranium in the eluate containing 3 mg/l uranium was adsorbed by ion exchange resin (Amberlite IRA-400), and was eluted with the eluent (5% NaCl-0.5% Na 2 CO 3 ). The concentration ratio of uranium in the final concentrated-eluate became more than 20 times. The eluting solution to the adsorbent and the eluant to the resin could be repeatedly used in the desorption-ion exchange process. Sodium carbonate was consumed at the desorption step, and sodium bicarbonate was consumed at the ion exchange step. The concentration ratio of uranium was found to decrease as chloride ion in the eluate increased. (author)

  8. Carbon exchange fluxes over peatlands in Western Siberia: Possible feedback between land-use change and climate change.

    Science.gov (United States)

    Fleischer, Elisa; Khashimov, Ilhom; Hölzel, Norbert; Klemm, Otto

    2016-03-01

    The growing demand for agricultural products has been leading to an expansion and intensification of agriculture around the world. More and more unused land is currently reclaimed in the regions of the former Soviet Union. Driven by climate change, the Western Siberian grain belt might, in a long-term, even expand into the drained peatland areas to the North. It is crucial to study the consequences of this land-use change with respect to the carbon cycling as this is still a major knowledge gap. We present for the first time data on the atmosphere-ecosystem exchange of carbon dioxide and methane of an arable field and a neighboring unused grassland on peat soil in Western Siberia. Eddy covariance measurements were performed over one vegetation period. No directed methane fluxes were found due to an effective drainage of the study sites. The carbon dioxide fluxes appeared to be of high relevance for the global carbon and greenhouse gas cycles. They showed very site-specific patterns resulting from the development of vegetation: the persistent plants of the grassland were able to start photosynthesizing soon after snow melt, while the absence of vegetation on the managed field lead to a phase of emissions until the oat plants started to grow in June. The uptake peak of the oat field is much later than that of the grassland, but larger due to a rapid plant growth. Budgeting the whole measurement period, the grassland served as a carbon sink, whereas the oat field was identified to be a carbon source. The conversion from non-used grasslands on peat soil to cultivated fields in Western Siberia is therefore considered to have a positive feedback on climate change. Copyright © 2015 Elsevier B.V. All rights reserved.

  9. Bicarbonate adsorption band of the chromatography for carbon isotope separation using anion exchangers

    International Nuclear Information System (INIS)

    Takeda, Kunihiko; Obanawa, Heiichiro; Hata, Masahisa; Sato, Katsuya

    1985-01-01

    The equilibria of bicarbonate ion between two phases were studied for the carbon isotope separation using anion exchangers. The condition of the formation of a bicarbonate adsorption band was quantitatively discussed. The formation of the adsorption band depends on the difference of S-potential which is the sum of the standard redection chemical potentials and L-potential which is the sum of the reduction chemical potential. The isotopic separation factor observed was about 1.012, independent of the concentrations of acid and alkali in the solutions. The isotopic separation factor was considered to be determined by the reaction of bicarbonate ion on anion exchangers and carbon dioxide dissolved in solutions. The enriched carbon isotope whose isotopic abundance ratio ( 13 C/ 12 C) was 1.258 was obtained with the column packed with anion exchangers. (author)

  10. Potential Carbon Stock Changes in Arizona's Ecosystems Due to Projected Climate Change

    Science.gov (United States)

    Finley, B. K.; Ironside, K.; Hungate, B. A.; Hurteau, M.; Koch, G. W.

    2011-12-01

    Climate change can alter the role of plants and soils as sources or sinks of atmospheric carbon dioxide and result in changes in long-term carbon storage. To understand the sensitivity of Arizona's ecosystems to climate change, we quantified the present carbon stocks in Arizona's major ecosystem types using the NASA-CASA (Carnegie Ames Stanford Approach) model. Carbon stocks for each vegetation type included surface mineral soil, dead wood litter, standing wood and live leaf biomass. The total Arizona ecosystem carbon stock is presently 1775 MMtC, 545 MMtC of which is in Pinus ponderosa and Pinus edulis forests and woodlands. Evergreen forest vegetation, predominately Pinus ponderosa, has the largest current C density at 11.3 kgC/m2, while Pinus edulis woodlands have a C density of 6.0 kgC/m2. A change in climate will impact the suitable range for each tree species, and consequentially the amount of C stored. Present habitat ranges for these tree species are projected to have widespread mortality and likely will be replaced by herbaceous species, resulting in a loss of C stored. We evaluated the C storage implications over the 2010 to 2099 period of climate change based on output from GCMs with contrasting projections for the southwestern US: MPI-ECHAM5, which projects warming and reduced precipitation, and UKMO-HadGEM, which projects warming and increased precipitation. These projected changes are end points of a spectrum of possible future climate scenarios. The vegetation distribution models used describe potential suitable habitat, and we assumed that the growth rate for each vegetation type would be one-third of the way to full C density for each 30 year period up to 2099. With increasing temperature and decreasing precipitation predictions under the MPI-ECHAM5 model, P. ponderosa and P. edulis vegetation show a decrease in carbon stored from 545 MMtC presently to 116 MMtC. With the combined increase in temperature and precipitation, C storage in these

  11. Assessing the risk of carbon dioxide emissions from blue carbon ecosystems

    KAUST Repository

    Lovelock, Catherine E.; Atwood, Trisha; Baldock, Jeff; Duarte, Carlos M.; Hickey, Sharyn; Lavery, Paul S.; Masque, Pere; Macreadie, Peter I.; Ricart, Aurora M.; Serrano, Oscar; Steven, Andy

    2017-01-01

    to the atmosphere in the form of CO. We present a framework to help assess the relative risk of CO emissions from degraded soils, thereby supporting inclusion of soil C into blue carbon projects and establishing a means to prioritize management for their carbon

  12. Photochemically induced carbon dioxide production as a mechanism for carbon loss from plant litter in arid ecosystems

    Science.gov (United States)

    Brandt, L. A.; Bohnet, C.; King, J. Y.

    2009-06-01

    We investigated the potential for abiotic mineralization to carbon dioxide (CO2) via photodegradation to account for carbon (C) loss from plant litter under conditions typical of arid ecosystems. We exposed five species of grass and oak litter collected from arid and mesic sites to a factorial design of ultraviolet (UV) radiation (UV pass, UV block), and sterilization under dry conditions in the laboratory. UV pass treatments produced 10 times the amount of CO2 produced in UV block treatments. CO2 production rates were unaffected by litter chemistry or sterilization. We also exposed litter to natural solar radiation outdoors on clear, sunny days close to the summer solstice at midlatitudes and found that UV radiation (280-400 nm) accounted for 55% of photochemically induced CO2 production, while shortwave visible radiation (400-500 nm) accounted for 45% of CO2 production. Rates of photochemically induced CO2 production on a per-unit-mass basis decreased with litter density, indicating that rates depend on litter surface area. We found no evidence for leaching, methane production, or facilitation of microbial decomposition as alternative mechanisms for significant photochemically induced C loss from litter. We conclude that abiotic mineralization to CO2 is the primary mechanism by which C is lost from litter during photodegradation. We estimate that CO2 production via photodegradation could be between 1 and 4 g C m-2 a-1 in arid ecosystems in the southwestern United States. Taken together with low levels of litter production in arid systems, photochemical mineralization to CO2 could account for a significant proportion of annual carbon loss from litter in arid ecosystems.

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

    Science.gov (United States)

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

    2011-01-01

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

  14. Changes in the carbon cycle of Amazon ecosystems during the 2010 drought

    Energy Technology Data Exchange (ETDEWEB)

    Potter, Christopher [NASA Ames Research Center, Moffett Field, CA (United States); Klooster, Steven; Hiatt, Cyrus; Genovese, Vanessa [California State University Monterey Bay, Seaside, CA (United States); Castilla-Rubio, Juan Carlos, E-mail: chris.potter@nasa.gov [Planetary Skin Institute, Silicon Valley, CA (United States)

    2011-07-15

    Satellite remote sensing was combined with the NASA-CASA (Carnegie Ames Stanford Approach) carbon cycle simulation model to evaluate the impact of the 2010 drought (July through September) throughout tropical South America. Results indicated that net primary production in Amazon forest areas declined by an average of 7% in 2010 compared to 2008. This represented a loss of vegetation CO{sub 2} uptake and potential Amazon rainforest growth of nearly 0.5 Pg C in 2010. The largest overall decline in ecosystem carbon gains by land cover type was predicted for closed broadleaf forest areas of the Amazon river basin, including a large fraction of regularly flooded forest areas. Model results support the hypothesis that soil and dead wood carbon decomposition fluxes of CO{sub 2} to the atmosphere were elevated during the drought period of 2010 in periodically flooded forest areas, compared to those for forests outside the main river floodplains.

  15. Changes in the carbon cycle of Amazon ecosystems during the 2010 drought

    International Nuclear Information System (INIS)

    Potter, Christopher; Klooster, Steven; Hiatt, Cyrus; Genovese, Vanessa; Castilla-Rubio, Juan Carlos

    2011-01-01

    Satellite remote sensing was combined with the NASA-CASA (Carnegie Ames Stanford Approach) carbon cycle simulation model to evaluate the impact of the 2010 drought (July through September) throughout tropical South America. Results indicated that net primary production in Amazon forest areas declined by an average of 7% in 2010 compared to 2008. This represented a loss of vegetation CO 2 uptake and potential Amazon rainforest growth of nearly 0.5 Pg C in 2010. The largest overall decline in ecosystem carbon gains by land cover type was predicted for closed broadleaf forest areas of the Amazon river basin, including a large fraction of regularly flooded forest areas. Model results support the hypothesis that soil and dead wood carbon decomposition fluxes of CO 2 to the atmosphere were elevated during the drought period of 2010 in periodically flooded forest areas, compared to those for forests outside the main river floodplains.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1988-12-31

    Our past research shows that arctic tus