WorldWideScience

Sample records for carbon fluxes resulting

  1. The primary results for the mixed carbon material used for high flux steady-state tokamak operation in China

    International Nuclear Information System (INIS)

    Guo, Q.G.; Li, J.G.; Zhai, G.T.; Liu, L.; Song, J.R.; Zhang, L.F.; He, Y.X.; Chen, J.L.

    2001-01-01

    Several types of carbon mixed materials have been developed in China to be used for high flux steady-state tokamak operation. Performance evaluation of these materials is necessary to determine their applicability as PFCs for high flux steady state. This paper describes the primary results of carbon mixed materials and the effects of dopants on properties are primarily discussed. Test results reveal that bulk boronized graphite has excellent physical and mechanical properties while their thermal conductivity is no more than 73 W/m K due to the formation of a uniform boron-carbon solid solution. In case of multi-element doped graphite, titanium dopant or a decreased boron content is favorable to enhance thermal conductivity. A kind of doped graphite has been developed with thermal conductivity as high as 278 W/m K by optimizing the compositions. Correlations among compositions, microstructure and properties of such doped graphite are discussed

  2. Impact of hydrological variations on modeling of peatland CO2 fluxes: Results from the North American Carbon Program site synthesis

    Science.gov (United States)

    Sulman, Benjamin N.; Desai, Ankur R.; Schroeder, Nicole M.; Ricciuto, Dan; Barr, Alan; Richardson, Andrew D.; Flanagan, Lawrence B.; Lafleur, Peter M.; Tian, Hanqin; Chen, Guangsheng; Grant, Robert F.; Poulter, Benjamin; Verbeeck, Hans; Ciais, Philippe; Ringeval, Bruno; Baker, Ian T.; Schaefer, Kevin; Luo, Yiqi; Weng, Ensheng

    2012-03-01

    Northern peatlands are likely to be important in future carbon cycle-climate feedbacks due to their large carbon pools and vulnerability to hydrological change. Use of non-peatland-specific models could lead to bias in modeling studies of peatland-rich regions. Here, seven ecosystem models were used to simulate CO2fluxes at three wetland sites in Canada and the northern United States, including two nutrient-rich fens and one nutrient-poor,sphagnum-dominated bog, over periods between 1999 and 2007. Models consistently overestimated mean annual gross ecosystem production (GEP) and ecosystem respiration (ER) at all three sites. Monthly flux residuals (simulated - observed) were correlated with measured water table for GEP and ER at the two fen sites, but were not consistently correlated with water table at the bog site. Models that inhibited soil respiration under saturated conditions had less mean bias than models that did not. Modeled diurnal cycles agreed well with eddy covariance measurements at fen sites, but overestimated fluxes at the bog site. Eddy covariance GEP and ER at fens were higher during dry periods than during wet periods, while models predicted either the opposite relationship or no significant difference. At the bog site, eddy covariance GEP did not depend on water table, while simulated GEP was higher during wet periods. Carbon cycle modeling in peatland-rich regions could be improved by incorporating wetland-specific hydrology and by inhibiting GEP and ER under saturated conditions. Bogs and fens likely require distinct plant and soil parameterizations in ecosystem models due to differences in nutrients, peat properties, and plant communities.

  3. Hydrothermal replacement of biogenic and abiogenic aragonite by Mg-carbonates - Relation between textural control on effective element fluxes and resulting carbonate phase

    Science.gov (United States)

    Jonas, Laura; Müller, Thomas; Dohmen, Ralf; Immenhauser, Adrian; Putlitz, Benita

    2017-01-01

    Dolomitization, i.e., the secondary replacement of calcite or aragonite (CaCO3) by dolomite (CaMg[CO3]2), is one of the most volumetrically important carbonate diagenetic processes. It occurs under near surface and shallow burial conditions and can significantly modify rock properties through changes in porosity and permeability. Dolomitization fronts are directly coupled to fluid pathways, which may be related to the initial porosity/permeability of the precursor limestone, an existing fault network or secondary porosity/permeability created through the replacement reaction. In this study, the textural control on the replacement of biogenic and abiogenic aragonite by Mg-carbonates, that are typical precursor phases in the dolomitization process, was experimentally studied under hydrothermal conditions. Aragonite samples with different textural and microstructural properties exhibiting a compact (inorganic aragonite single crystal), an intermediate (bivalve shell of Arctica islandica) and open porous structure (skeleton of coral Porites sp.) were reacted with a solution of 0.9 M MgCl2 and 0.015 M SrCl2 at 200 °C. The replacement of aragonite by a Ca-bearing magnesite and a Mg-Ca carbonate of non-stoichiometric dolomitic composition takes place via a dissolution-precipitation process and leads to the formation of a porous reaction front that progressively replaces the aragonite precursor. The reaction leads to the development of porosity within the reaction front and distinctive microstructures such as gaps and cavities at the reaction interface. The newly formed reaction rim consists of chemically distinct phases separated by sharp boundaries. It was found that the number of phases and their chemical variation decreases with increasing initial porosity and reactive surface area. This observation is explained by variations in effective element fluxes that result in differential chemical gradients in the fluid within the pore space of the reaction rim. Observed

  4. Diurnal Change of Soil Carbon Flux of Binhai New District

    Science.gov (United States)

    Wang, T. F.; Mao, T. Y.; Ye, W.

    2018-05-01

    In order to investigate the factors influencing diurnal change of soil carbon flux of Binhai New District. Field observation experiments were carried out by using LC pro-SD photosynthetic apparatus. The diurnal changes of soil carbon flux and its environmental factors such as atmosphere temperature and soil temperature were analysed. The results indicated that soil carbon flux appeared single diurnal pattern. The diurnal average of soil carbon flux ranked from 0.2761 to 2.3367μmo1/m2/s. Soil carbon flux varied significantly among different land use regimes(Pequations (Pquadratic correlations between soil carbon flux and soil temperature (10cm). And soil temperature could account for more than 32.27% of the soil carbon flux changes (P<0.05, R2=0.3227-0.7465).

  5. Assessing Ecosystem Drought Response in CLM 4.5 Using Site-Level Flux and Carbon-Isotope Measurements: Results From a Pacific Northwest Coniferous Forest

    Science.gov (United States)

    Duarte, H.; Raczka, B. M.; Koven, C. D.; Ricciuto, D. M.; Lin, J. C.; Bowling, D. R.; Ehleringer, J. R.

    2015-12-01

    The frequency, extent, and severity of droughts are expected to increase in the western United States as climate changes occur. The combination of warmer temperature, larger vapor pressure deficit, reduced snowfall and snow pack, earlier snow melt, and extended growing seasons is expected to lead to an intensification of summer droughts, with a direct impact on ecosystem productivity and therefore on the carbon budget of the region. In this scenario, an accurate representation of ecosystem drought response in land models becomes fundamental, but the task is challenging, especially in regards to stomatal response to drought. In this study we used the most recent release of the Community Land Model (CLM 4.5), which now includes photosynthetic carbon isotope discrimination and revised photosynthesis and hydrology schemes, among an extensive list of updates. We evaluated the model's performance at a coniferous forest site in the Pacific northwest (Wind River AmeriFlux Site), characterized by a climate that has a strong winter precipitation component followed by a summer drought. We ran the model in offline mode (i.e., decoupled from an atmospheric model), forced by observed meteorological data, and used site observations (e.g., surface fluxes, biomass values, and carbon isotope data) to assess the model. Previous field observations indicated a significant negative correlation between soil water content and the carbon isotope ratio of ecosystem respiration (δ13CR), suggesting that δ13CR was closely related to the photosynthetic discrimination against 13CO2 as controlled by stomatal conductance. We used these observations and latent-heat flux measurements to assess the modeled stomatal conductance values and their responses to extended summer drought. We first present the model results, followed by a discussion of potential CLM model improvements in stomatal conductance responses and in the representation of soil water stress (parameter βt) that would more precisely

  6. Rivers of Carbon: Carbon Fluxes in a Watershed Context

    Science.gov (United States)

    Wohl, E.; Tom, B.; Hovius, N.

    2017-12-01

    Research within the past decade has identified the roles of diverse terrestrial processes in mobilizing terrestrial carbon from bedrock, soil, and vegetation and in redistributing this carbon among the atmosphere, biota, geosphere, and oceans. Rivers are central to carbon redistribution, serving as the primary initial receptor of mobilized terrestrial carbon, as well as governing the proportions of carbon sequestered within sediment, transported to oceans, or released to the atmosphere. We use a riverine carbon budget to examine how key questions regarding carbon dynamics can be addressed across diverse spatial and temporal scales from sub-meter areas over a few hours on a single gravel bar to thousands of square kilometers over millions of years across an entire large river network. The portion of the budget applying to the active channel(s) takes the form of ,in which Cs is organic carbon storage over time t. Inputs are surface and subsurface fluxes from uplands (CIupl) and the floodplain (CIfp), including fossil, soil, and biospheric organic carbon; surface and subsurface fluxes of carbon dioxide to the channel (CICO2); and net primary productivity in the channel (CINPP). Outputs occur via respiration within the channel and carbon dioxide emissions (COgas) and fluxes of dissolved and particulate organic carbon to the floodplain and downstream portions of the river network (COriver). The analogous budget for the floodplain portion of a river corridor is .

  7. Remote sensing mapping of carbon and energy fluxes over forests

    NARCIS (Netherlands)

    Roerink, G.J.; Wit, de A.J.W.; Pelgrum, H.; Mücher, C.A.

    2001-01-01

    This report presents the results of the EU project "Carbon and water fluxes of Mediterranean forests and impacts of land use/cover changes". The objectives of the project can be summarized as follows: (I) surface energy balance mapping using remote sensing, (ii) carbon uptake mapping using remote

  8. Mapping carbon flux uncertainty and selecting optimal locations for future flux towers in the Great Plains

    Science.gov (United States)

    Gu, Yingxin; Howard, Daniel M.; Wylie, Bruce K.; Zhang, Li

    2012-01-01

    Flux tower networks (e. g., AmeriFlux, Agriflux) provide continuous observations of ecosystem exchanges of carbon (e. g., net ecosystem exchange), water vapor (e. g., evapotranspiration), and energy between terrestrial ecosystems and the atmosphere. The long-term time series of flux tower data are essential for studying and understanding terrestrial carbon cycles, ecosystem services, and climate changes. Currently, there are 13 flux towers located within the Great Plains (GP). The towers are sparsely distributed and do not adequately represent the varieties of vegetation cover types, climate conditions, and geophysical and biophysical conditions in the GP. This study assessed how well the available flux towers represent the environmental conditions or "ecological envelopes" across the GP and identified optimal locations for future flux towers in the GP. Regression-based remote sensing and weather-driven net ecosystem production (NEP) models derived from different extrapolation ranges (10 and 50%) were used to identify areas where ecological conditions were poorly represented by the flux tower sites and years previously used for mapping grassland fluxes. The optimal lands suitable for future flux towers within the GP were mapped. Results from this study provide information to optimize the usefulness of future flux towers in the GP and serve as a proxy for the uncertainty of the NEP map.

  9. Anthropogenic perturbation of the carbon fluxes from land to ocean

    KAUST Repository

    Regnier, Pierre

    2013-06-09

    A substantial amount of the atmospheric carbon taken up on land through photosynthesis and chemical weathering is transported laterally along the aquatic continuum from upland terrestrial ecosystems to the ocean. So far, global carbon budget estimates have implicitly assumed that the transformation and lateral transport of carbon along this aquatic continuum has remained unchanged since pre-industrial times. A synthesis of published work reveals the magnitude of present-day lateral carbon fluxes from land to ocean, and the extent to which human activities have altered these fluxes. We show that anthropogenic perturbation may have increased the flux of carbon to inland waters by as much as 1.0 Pg C yr -1 since pre-industrial times, mainly owing to enhanced carbon export from soils. Most of this additional carbon input to upstream rivers is either emitted back to the atmosphere as carbon dioxide (∼0.4 Pg C yr -1) or sequestered in sediments (∼0.5 Pg C yr -1) along the continuum of freshwater bodies, estuaries and coastal waters, leaving only a perturbation carbon input of ∼0.1 Pg C yr -1 to the open ocean. According to our analysis, terrestrial ecosystems store ∼0.9 Pg C yr -1 at present, which is in agreement with results from forest inventories but significantly differs from the figure of 1.5 Pg C yr -1 previously estimated when ignoring changes in lateral carbon fluxes. We suggest that carbon fluxes along the land-ocean aquatic continuum need to be included in global carbon dioxide budgets.

  10. Carbon dioxide fluxes from an urban area in Beijing

    Science.gov (United States)

    Song, Tao; Wang, Yuesi

    2012-03-01

    A better understanding of urban carbon dioxide (CO 2) emissions is important for quantifying urban contributions to the global carbon budget. From January to December 2008, CO 2 fluxes were measured, by eddy covariance at 47 m above ground on a meteorological tower in a high-density residential area in Beijing. The results showed that the urban surface was a net source of CO 2 in the atmosphere. Diurnal flux patterns were similar to those previously observed in other cities and were largely influenced by traffic volume. Carbon uptake by both urban vegetation during the growing season and the reduction of fuel consumption for domestic heating resulted in less-positive daily fluxes in the summer. The average daily flux measured in the summer was 0.48 mg m - 2 s - 1 , which was 82%, 35% and 36% lower than those in the winter, spring and autumn, respectively. The reduction of vehicles on the road during the 29th Olympic and Paralympic Games had a significant impact on CO 2 flux. The flux of 0.40 mg m - 2 s - 1 for September 2008 was approximately 0.17 mg m - 2 s - 1 lower than the flux for September 2007. Annual CO 2 emissions from the study site were estimated at 20.6 kg CO 2 m - 2 y - 1 , considerably higher than yearly emissions obtained from other urban and suburban landscapes.

  11. The NASA Carbon Airborne Flux Experiment (CARAFE: instrumentation and methodology

    Directory of Open Access Journals (Sweden)

    G. M. Wolfe

    2018-03-01

    Full Text Available The exchange of trace gases between the Earth's surface and atmosphere strongly influences atmospheric composition. Airborne eddy covariance can quantify surface fluxes at local to regional scales (1–1000 km, potentially helping to bridge gaps between top-down and bottom-up flux estimates and offering novel insights into biophysical and biogeochemical processes. The NASA Carbon Airborne Flux Experiment (CARAFE utilizes the NASA C-23 Sherpa aircraft with a suite of commercial and custom instrumentation to acquire fluxes of carbon dioxide, methane, sensible heat, and latent heat at high spatial resolution. Key components of the CARAFE payload are described, including the meteorological, greenhouse gas, water vapor, and surface imaging systems. Continuous wavelet transforms deliver spatially resolved fluxes along aircraft flight tracks. Flux analysis methodology is discussed in depth, with special emphasis on quantification of uncertainties. Typical uncertainties in derived surface fluxes are 40–90 % for a nominal resolution of 2 km or 16–35 % when averaged over a full leg (typically 30–40 km. CARAFE has successfully flown two missions in the eastern US in 2016 and 2017, quantifying fluxes over forest, cropland, wetlands, and water. Preliminary results from these campaigns are presented to highlight the performance of this system.

  12. The NASA Carbon Airborne Flux Experiment (CARAFE): instrumentation and methodology

    Science.gov (United States)

    Wolfe, Glenn M.; Kawa, S. Randy; Hanisco, Thomas F.; Hannun, Reem A.; Newman, Paul A.; Swanson, Andrew; Bailey, Steve; Barrick, John; Thornhill, K. Lee; Diskin, Glenn; DiGangi, Josh; Nowak, John B.; Sorenson, Carl; Bland, Geoffrey; Yungel, James K.; Swenson, Craig A.

    2018-03-01

    The exchange of trace gases between the Earth's surface and atmosphere strongly influences atmospheric composition. Airborne eddy covariance can quantify surface fluxes at local to regional scales (1-1000 km), potentially helping to bridge gaps between top-down and bottom-up flux estimates and offering novel insights into biophysical and biogeochemical processes. The NASA Carbon Airborne Flux Experiment (CARAFE) utilizes the NASA C-23 Sherpa aircraft with a suite of commercial and custom instrumentation to acquire fluxes of carbon dioxide, methane, sensible heat, and latent heat at high spatial resolution. Key components of the CARAFE payload are described, including the meteorological, greenhouse gas, water vapor, and surface imaging systems. Continuous wavelet transforms deliver spatially resolved fluxes along aircraft flight tracks. Flux analysis methodology is discussed in depth, with special emphasis on quantification of uncertainties. Typical uncertainties in derived surface fluxes are 40-90 % for a nominal resolution of 2 km or 16-35 % when averaged over a full leg (typically 30-40 km). CARAFE has successfully flown two missions in the eastern US in 2016 and 2017, quantifying fluxes over forest, cropland, wetlands, and water. Preliminary results from these campaigns are presented to highlight the performance of this system.

  13. QUANTIFYING FOREST ABOVEGROUND CARBON POOLS AND FLUXES USING MULTI-TEMPORAL LIDAR A report on field monitoring, remote sensing MMV, GIS integration, and modeling results for forestry field validation test to quantify aboveground tree biomass and carbon

    Energy Technology Data Exchange (ETDEWEB)

    Lee Spangler; Lee A. Vierling; Eva K. Stand; Andrew T. Hudak; Jan U.H. Eitel; Sebastian Martinuzzi

    2012-04-01

    Sound policy recommendations relating to the role of forest management in mitigating atmospheric carbon dioxide (CO{sub 2}) depend upon establishing accurate methodologies for quantifying forest carbon pools for large tracts of land that can be dynamically updated over time. Light Detection and Ranging (LiDAR) remote sensing is a promising technology for achieving accurate estimates of aboveground biomass and thereby carbon pools; however, not much is known about the accuracy of estimating biomass change and carbon flux from repeat LiDAR acquisitions containing different data sampling characteristics. In this study, discrete return airborne LiDAR data was collected in 2003 and 2009 across {approx}20,000 hectares (ha) of an actively managed, mixed conifer forest landscape in northern Idaho, USA. Forest inventory plots, established via a random stratified sampling design, were established and sampled in 2003 and 2009. The Random Forest machine learning algorithm was used to establish statistical relationships between inventory data and forest structural metrics derived from the LiDAR acquisitions. Aboveground biomass maps were created for the study area based on statistical relationships developed at the plot level. Over this 6-year period, we found that the mean increase in biomass due to forest growth across the non-harvested portions of the study area was 4.8 metric ton/hectare (Mg/ha). In these non-harvested areas, we found a significant difference in biomass increase among forest successional stages, with a higher biomass increase in mature and old forest compared to stand initiation and young forest. Approximately 20% of the landscape had been disturbed by harvest activities during the six-year time period, representing a biomass loss of >70 Mg/ha in these areas. During the study period, these harvest activities outweighed growth at the landscape scale, resulting in an overall loss in aboveground carbon at this site. The 30-fold increase in sampling density

  14. Carbon stocks and flux in French forests

    International Nuclear Information System (INIS)

    Dupouey, Jean-Luc; Pignard, Gerome; Badeau, Vincent; Thimonier, A.; Dhote, Jean-Francois; Nepveu, G.; Berges, L.; Augusto, L.; Belkacem, S.; Nys, C.

    2000-01-01

    Forests contain most of the carbon stored in the earth's biomass (81 %) and could play a role in CO 2 mitigation to a certain extent. We estimate French forest carbon stocks in biomass to be 860 MtC on 14.5 million hectares of forests, and 1,140 MtC in forest soils. Total carbon in the 14.5 million hectares of French forests is estimated at 2,000 MtC. Average annual flux for the 1979/91 period is 10.5 MtC/y, i.e. 10 % of national fossil fuel emissions. The main causes of this net carbon uptake are the rapid increase of forest area, increasing productivity due to environmental changes, ageing or, in some localized areas, more intensive silviculture practices. These carbon sinks are not offset by the harvesting level which remains low on average (61 % of the annual volume growth). Forestry carbon mitigation options applicable in France are discussed. The need for global economic and ecological budgets (including carbon stocks, soil fertility and biodiversity) of the possible alternatives is stressed. (authors)

  15. Impact of land use change on the land atmosphere carbon flux of South and South East Asia: A Synthesis of Dynamic Vegetation Model Results

    Science.gov (United States)

    Cervarich, M.; Shu, S.; Jain, A. K.; Poulter, B.; Stocker, B.; Arneth, A.; Viovy, N.; Kato, E.; Wiltshire, A.; Koven, C.; Sitch, S.; Zeng, N.; Friedlingstein, P.

    2015-12-01

    Understanding our present day carbon cycle and possible solutions to recent increases in atmospheric carbon dioxide is dependent upon quantifying the terrestrial carbon budget. Currently, global land cover and land use change is estimated to emit 0.9 PgC yr-1 compared to emissions due to fossil fuel combustion and cement production of 8.4 PgC yr-1. South and Southeast Asia (India, Nepal, Bhutan, Bangladesh, Burma, Thailand, Laos, Vietnam, Cambodia, Malaysia, Philippines, Indonesia, Pakistan, Myanmar, and Singapore) is a region of rapid land cover and land use change due to the continuous development of agriculture, deforestation, reforestation, afforestation, and the increased demand of land for people to live. In this study, we synthesize outputs of nine models participated in Global Carbon Budget Project to identify the carbon budget of South and southeast Asia, diagnose the contribution of land cover and land use change to carbon emissions and assess areas of uncertainty in the suite of models. Uncertainty is determined using the standard deviation and the coefficient of variation of net ecosystem exchange and its component parts. Results show the region's terrestrial biosphere was a source of carbon emissions from the 1980 to the early 1990s. During the same time period, land cover and land use change increasingly contributed to carbon emission. In the most recent two decades, the region became a carbon sink since emission due to land cover land use changes. Spatially, the greatest total emissions occurred in the tropical forest of Southeast Asia. Additionally, this is the subregion with the greatest uncertainty and greatest biomass. Model uncertainty is shown to be proportional to total biomass. The atmospheric impacts of ENSO are shown to suppress the net biosphere productivity in South and Southeast Asia leading to years of increased carbon emissions.

  16. Methane and Carbon Dioxide Concentrations and Fluxes in Amazon Floodplains

    Science.gov (United States)

    Melack, J. M.; MacIntyre, S.; Forsberg, B.; Barbosa, P.; Amaral, J. H.

    2016-12-01

    Field studies on the central Amazon floodplain in representative aquatic habitats (open water, flooded forests, floating macrophytes) combine measurements of methane and carbon dioxide concentrations and fluxes to the atmosphere over diel and seasonal times with deployment of meteorological sensors and high-resolution thermistors and dissolved oxygen sondes. A cavity ringdown spectrometer is used to determine gas concentrations, and floating chambers and bubble collectors are used to measure fluxes. To further understand fluxes, we measured turbulence as rate of dissipation of turbulent kinetic energy based on microstructure profiling. These results allow calculations of vertical mixing within the water column and of air-water exchanges using surface renewal models. Methane and carbon dioxide fluxes varied as a function of season, habitat and water depth. High CO2 fluxes at high water are related to high pCO2; low pCO2 levels at low water result from increased phytoplankton uptake. CO2 fluxes are highest at turbulent open water sites, and pCO2 is highest in macrophyte beds. Fluxes and pCH4 are high in macrophyte beds.

  17. Carbon fluxes from an urban tropical grassland

    International Nuclear Information System (INIS)

    Ng, B.J.L.; Hutyra, L.R.; Nguyen, H.; Cobb, A.R.; Kai, F.M.; Harvey, C.; Gandois, L.

    2015-01-01

    Turfgrass covers a large fraction of the urbanized landscape, but the carbon exchange of urban lawns is poorly understood. We used eddy covariance and flux chambers in a grassland field manipulative experiment to quantify the carbon mass balance in a Singapore tropical turfgrass. We also assessed how management and variations in environmental factors influenced CO 2 respiration. Standing aboveground turfgrass biomass was 80 gC m −2 , with a mean ecosystem respiration of 7.9 ± 1.1 μmol m −2  s −1 . The contribution of autotrophic respiration was 49–76% of total ecosystem respiration. Both chamber and eddy covariance measurements suggest the system was in approximate carbon balance. While we did not observe a significant relationship between the respiration rates and soil temperature or moisture, daytime fluxes increased during the rainy interval, indicating strong overall moisture sensitivity. Turfgrass biomass is small, but given its abundance across the urban landscape, it significantly influences diurnal CO 2 concentrations. - Highlights: • We measured urban turfgrass CO 2 respiration rates and soil characteristics. • Mean observed ecosystem respiration was 7.9 ± 1.1 μmol m −2  s −1 . • Soil temperature and moisture were largely insignificant drivers of observed flux. - We found a Singapore urban turfgrass to be approximately carbon neutral, with a mean ecosystem respiration of 7.9 ± 1.1 μmol m −2  s −1

  18. 1km Global Terrestrial Carbon Flux: Estimations and Evaluations

    Science.gov (United States)

    Murakami, K.; Sasai, T.; Kato, S.; Saito, M.; Matsunaga, T.; Hiraki, K.; Maksyutov, S. S.

    2017-12-01

    Estimating global scale of the terrestrial carbon flux change with high accuracy and high resolution is important to understand global environmental changes. Furthermore the estimations of the global spatiotemporal distribution may contribute to the political and social activities such as REDD+. In order to reveal the current state of terrestrial carbon fluxes covering all over the world and a decadal scale. The satellite-based diagnostic biosphere model is suitable for achieving this purpose owing to observing on the present global land surface condition uniformly at some time interval. In this study, we estimated the global terrestrial carbon fluxes with 1km grids by using the terrestrial biosphere model (BEAMS). And we evaluated our new carbon flux estimations on various spatial scales and showed the transition of forest carbon stocks in some regions. Because BEAMS required high resolution meteorological data and satellite data as input data, we made 1km interpolated data using a kriging method. The data used in this study were JRA-55, GPCP, GOSAT L4B atmospheric CO2 data as meteorological data, and MODIS land product as land surface satellite data. Interpolating process was performed on the meteorological data because of insufficient resolution, but not on MODIS data. We evaluated our new carbon flux estimations using the flux tower measurement (FLUXNET2015 Datasets) in a point scale. We used 166 sites data for evaluating our model results. These flux sites are classified following vegetation type (DBF, EBF, ENF, mixed forests, grass lands, croplands, shrub lands, Savannas, wetlands). In global scale, the BEAMS estimations was underestimated compared to the flux measurements in the case of carbon uptake and release. The monthly variations of NEP showed relatively high correlations in DBF and mixed forests, but the correlation coefficients of EBF, ENF, and grass lands were less than 0.5. In the meteorological factors, air temperature and solar radiation showed

  19. Planck intermediate results - LII. Planet flux densities

    DEFF Research Database (Denmark)

    Akrami, Y.; Ashdown, M.; Aumont, J.

    2017-01-01

    Measurements of flux density are described for five planets, Mars, Jupiter, Saturn, Uranus, and Neptune, across the six Planck High Frequency Instrument frequency bands (100–857 GHz) and these are then compared with models and existing data. In our analysis, we have also included estimates...... of the brightness of Jupiter and Saturn at the three frequencies of the Planck Low Frequency Instrument (30, 44, and 70 GHz). The results provide constraints on the intrinsic brightness and the brightness time-variability of these planets. The majority of the planet flux density estimates are limited by systematic...... errors, but still yield better than 1% measurements in many cases. Applying data from Planck HFI, the Wilkinson Microwave Anisotropy Probe (WMAP), and the Atacama Cosmology Telescope (ACT) to a model that incorporates contributions from Saturn’s rings to the planet’s total flux density suggests a best...

  20. Upscaling Our Approach to Peatland Carbon Sequestration: Remote Sensing as a Tool for Carbon Flux Estimation.

    Science.gov (United States)

    Lees, K.; Khomik, M.; Clark, J. M.; Quaife, T. L.; Artz, R.

    2017-12-01

    Peatlands are an important part of the Earth's carbon cycle, comprising approximately a third of the global terrestrial carbon store. However, peatlands are sensitive to climatic change and human mismanagement, and many are now degraded and acting as carbon sources. Restoration work is being undertaken at many sites around the world, but monitoring the success of these schemes can be difficult and costly using traditional methods. A landscape-scale alternative is to use satellite data in order to assess the condition of peatlands and estimate carbon fluxes. This work focuses on study sites in Northern Scotland, where parts of the largest blanket bog in Europe are being restored from forest plantations. A combination of laboratory and fieldwork has been used to assess the Net Ecosystem Exchange (NEE), Gross Primary Productivity (GPP) and respiration of peatland sites in different conditions, and the climatic vulnerability of key peat-forming Sphagnum species. The results from these studies have been compared with spectral data in order to evaluate the extent to which remote sensing can function as a source of information for peatland health and carbon flux models. This work considers particularly the effects of scale in calculating peatland carbon flux. Flux data includes chamber and eddy covariance measurements of carbon dioxide, and radiometric observations include both handheld spectroradiometer results and satellite images. Results suggest that despite the small-scale heterogeneity and unique ecosystem factors in blanket bogs, remote sensing can be a useful tool in monitoring peatland health and carbon sequestration. In particular, this study gives unique insights into the relationships between peatland vegetation, carbon flux and spectral reflectance.

  1. Fluxes of Methane and Carbon Dioxide from a Subarctic Lake

    DEFF Research Database (Denmark)

    Jammet, Mathilde Manon

    ) and carbon dioxide (CO2) with the atmosphere. Yet uncertainties in the magnitude and drivers of these fluxes remain, partly due to a lack of direct observations covering all seasons of the year, but also because of the diversity in measurement methods that often miss components of the transport processes......Ongoing climate warming is expected to affect the carbon functioning of subarctic ecosystems. Lakes and wetlands, which are common ecosystems of the high northern latitudes, are of utmost interest in this context because they exchange large amounts of the climate-forcing gases methane (CH4......-out and the release of CH4 and CO2 was established. These results underline the crucial importance of shoulder seasons in the annual carbon emissions from seasonally frozen lakes. Overall, the lake was an important annual source of carbon to the atmosphere, partially compensating the higher, annual sink function...

  2. Partitioning of net carbon dioxide flux measured by automatic transparent chamber

    Science.gov (United States)

    Dyukarev, EA

    2018-03-01

    Mathematical model was developed for describing carbon dioxide fluxes at open sedge-sphagnum fen during growing season. The model was calibrated using the results of observations from automatic transparent chamber and it allows us to estimate autotrophic, heterotrophic and ecosystem respiration fluxes, gross and net primary vegetation production, and the net carbon balance.

  3. Carbon fluxes of Kobresia pygmaea pastures on the Tibetan Plateau

    Science.gov (United States)

    Foken, T.; Biermann, T.; Babel, W.; Ma, Y.

    2013-12-01

    With an approximate cover of 450,000 km2 on the Tibetan Plateau (TP), the Cyperaceae Kobresia pygmaea forms he world's largest alpine ecosystem. This species, especially adapted to grazing pressure, grows to a height of only 2-6 cm and can be found in an altitudinal range of 4000 to 5960 m a.s.l. A special characteristic of this ecosystem is the stable turf layer, which is built up from roots and plays a significant role in protecting soil from erosion. This is of great importance since soils on the TP store 2.5 % of the global soil organic carbon stocks. The aim of the investigation was the study of the carbon storage and the impact of human-induced land use change on these Kobresia pygmaea pastures. We therefore applied eddy-covariance measurements and modelling as a long-term control of the fluxes between the atmosphere and the pastures and 13C labelling for the investigation of flux partitioning, and chamber measurements to investigate the degradation of the pastures. Combining CO2 budgets observed in 2010 with eddy-covariance measurements and relative partitioning of Carbon fluxes estimated with 13C labelling enabled us to characterise the C turnover for the vegetation period with absolute fluxes within the plant-soil-atmosphere continuum. These results revealed that this ecosystem indeed stores a great amount of C in below-ground pools, especially in the root turf layer. To further investigate the importance of the root layer, the experiments in 2012 focused on flux measurements over the different surface types which make up the heterogeneity of the Kobresia pygmaea pastures and might result from degradation due to extensive grazing. The three surface types investigated with a LiCOR long-term monitoring chamber system include Kobresia pygmaea with intact turf layer (IRM), a surface type where the turf layer is still present but the vegetation is sparse and mainly consists of Cryptogam crusts (DRM) and finally areas without the turf layer (BS). According to

  4. Quantification of net carbon flux from plastic greenhouse vegetable cultivation: A full carbon cycle analysis

    International Nuclear Information System (INIS)

    Wang Yan; Xu Hao; Wu Xu; Zhu Yimei; Gu Baojing; Niu Xiaoyin; Liu Anqin; Peng Changhui; Ge Ying; Chang Jie

    2011-01-01

    Plastic greenhouse vegetable cultivation (PGVC) has played a vital role in increasing incomes of farmers and expanded dramatically in last several decades. However, carbon budget after conversion from conventional vegetable cultivation (CVC) to PGVC has been poorly quantified. A full carbon cycle analysis was used to estimate the net carbon flux from PGVC systems based on the combination of data from both field observations and literatures. Carbon fixation was evaluated at two pre-selected locations in China. Results suggest that: (1) the carbon sink of PGVC is 1.21 and 1.23 Mg C ha -1 yr -1 for temperate and subtropical area, respectively; (2) the conversion from CVC to PGVC could substantially enhance carbon sink potential by 8.6 times in the temperate area and by 1.3 times in the subtropical area; (3) the expansion of PGVC usage could enhance the potential carbon sink of arable land in China overall. - Highlights: → We used full carbon (C) cycle analysis to estimate the net C flux from cultivation. → The plastic greenhouse vegetable cultivation system in China can act as a C sink. → Intensified agricultural practices can generate C sinks. → Expansion of plastic greenhouse vegetable cultivation can enhance regional C sink. - The conversion from conventional vegetable cultivation to plastic greenhouse vegetable cultivation could substantially enhance carbon sink potential by 8.6 and 1.3 times for temperate and subtropical area, respectively.

  5. Inverse carbon dioxide flux estimates for the Netherlands

    Energy Technology Data Exchange (ETDEWEB)

    Meesters, A.G.C.A.; Tolk, L.F.; Dolman, A.J. [Faculty of Earth and Life Sciences, VU University, Amsterdam (Netherlands); Peters, W.; Hutjes, R.W.A.; Vellinga, O.S.; Elbers, J.A. [Department Meteorology and Air Quality, Wageningen University and Research Centre, Wageningen (Netherlands); Vermeulen, A.T. [Biomass, Coal and Environmental Research, Energy research Center of the Netherlands ECN, Petten (Netherlands); Van der Laan, S.; Neubert, R.E.M.; Meijer, H.A.J. [Centre for Isotope Research, Energy and Sustainability Research Institute Groningen, University of Groningen, Groningen (Netherlands)

    2012-10-26

    CO2 fluxes for the Netherlands and surroundings are estimated for the year 2008, from concentration measurements at four towers, using an inverse model. The results are compared to direct CO2 flux measurements by aircraft, for 6 flight tracks over the Netherlands, flown multiple times in each season. We applied the Regional Atmospheric Mesoscale Modeling system (RAMS) coupled to a simple carbon flux scheme (including fossil fuel), which was run at 10 km resolution, and inverted with an Ensemble Kalman Filter. The domain had 6 eco-regions, and inversions were performed for the four seasons separately. Inversion methods with pixel-dependent and -independent parameters for each eco-region were compared. The two inversion methods, in general, yield comparable flux averages for each eco-region and season, whereas the difference from the prior flux may be large. Posterior fluxes co-sampled along the aircraft flight tracks are usually much closer to the observations than the priors, with a comparable performance for both inversion methods, and with best performance for summer and autumn. The inversions showed more negative CO2 fluxes than the priors, though the latter are obtained from a biosphere model optimized using the Fluxnet database, containing observations from more than 200 locations worldwide. The two different crop ecotypes showed very different CO2 uptakes, which was unknown from the priors. The annual-average uptake is practically zero for the grassland class and for one of the cropland classes, whereas the other cropland class had a large net uptake, possibly because of the abundance of maize there.

  6. Carbon and energy fluxes from China's largest freshwater lake

    Science.gov (United States)

    Gan, G.; LIU, Y.

    2017-12-01

    Carbon and energy fluxes between lakes and the atmosphere are important aspects of hydrology, limnology, and ecology studies. China's largest freshwater lake, the Poyang lake experiences tremendous water-land transitions periodically throughout the year, which provides natural experimental settings for the study of carbon and energy fluxes. In this study, we use the eddy covariance technique to explore the seasonal and diurnal variation patterns of sensible and latent heat fluxes of Poyang lake during its high-water and low-water periods, when the lake is covered by water and mudflat, respectively. We also determine the annual NEE of Poyang lake and the variations of NEE's components: Gross Primary Productivity (GPP) and Ecosystem Respiration (Re). Controlling factors of seasonal and diurnal variations of carbon and energy fluxes are analyzed, and land cover impacts on the variation patterns are also studied. Finally, the coupling between the carbon and energy fluxes are analyzed under different atmospheric, boundary stability and land cover conditions.

  7. Soil Carbon Dioxide Production and Surface Fluxes: Subsurface Physical Controls

    Science.gov (United States)

    Risk, D.; Kellman, L.; Beltrami, H.

    Soil respiration is a critical determinant of landscape carbon balance. Variations in soil temperature and moisture patterns are important physical processes controlling soil respiration which need to be better understood. Relationships between soil respi- ration and physical controls are typically addressed using only surface flux data but other methods also exist which permit more rigorous interpretation of soil respira- tion processes. Here we use a combination of subsurface CO_{2} concentrations, surface CO_{2} fluxes and detailed physical monitoring of the subsurface envi- ronment to examine physical controls on soil CO_{2} production at four climate observatories in Eastern Canada. Results indicate that subsurface CO_{2} produc- tion is more strongly correlated to the subsurface thermal environment than the surface CO_{2} flux. Soil moisture was also found to have an important influence on sub- surface CO_{2} production, particularly in relation to the soil moisture - soil profile diffusivity relationship. Non-diffusive profile CO_{2} transport appears to be im- portant at these sites, resulting in a de-coupling of summertime surface fluxes from subsurface processes and violating assumptions that surface CO_{2} emissions are the result solely of diffusion. These results have implications for the study of soil respiration across a broad range of terrestrial environments.

  8. Salp contributions to vertical carbon flux in the Sargasso Sea

    Science.gov (United States)

    Stone, Joshua P.; Steinberg, Deborah K.

    2016-07-01

    We developed a one-dimensional model to estimate salp contributions to vertical carbon flux at the Bermuda Atlantic Time-series Study (BATS) site in the North Atlantic subtropical gyre for a 17-yr period (April 1994 to December 2011). We based the model parameters on published rates of salp physiology and experimentally determined sinking and decomposition rates of salp carcasses. Salp grazing was low during non-bloom conditions, but routinely exceeded 100% of chlorophyll standing stock and primary production during blooms. Fecal pellet production was the largest source of salp carbon flux (78% of total), followed by respiration below 200 m (19%), sinking of carcasses (3%), and DOC excretion below 200 m (salp-mediated carbon flux. Seasonally, salp flux was higher during spring-summer than fall-winter, due to seasonal changes in species composition and abundance. Salp carbon export to 200 m was on average 2.3 mg C m-2 d-1 across the entire time series. This is equivalent to 11% of the mean 200 m POC flux measured by sediment traps in the region. During years with significant salp blooms, however, annually-averaged salp carbon export was the equivalent of up to 60% of trap POC flux at 200 m. Salp carbon flux attenuated slowly, and at 3200 m the average modeled carbon from salps was 109% of the POC flux measured in sediment traps at that depth. Migratory and carcass carbon export pathways should also be considered (alongside fecal pellet flux) as facilitating carbon export to sequestration depths in future studies.

  9. Accounting for urban biogenic fluxes in regional carbon budgets.

    Science.gov (United States)

    Hardiman, Brady S; Wang, Jonathan A; Hutyra, Lucy R; Gately, Conor K; Getson, Jackie M; Friedl, Mark A

    2017-08-15

    Many ecosystem models incorrectly treat urban areas as devoid of vegetation and biogenic carbon (C) fluxes. We sought to improve estimates of urban biomass and biogenic C fluxes using existing, nationally available data products. We characterized biogenic influence on urban C cycling throughout Massachusetts, USA using an ecosystem model that integrates improved representation of urban vegetation, growing conditions associated with urban heat island (UHI), and altered urban phenology. Boston's biomass density is 1/4 that of rural forests, however 87% of Massachusetts' urban landscape is vegetated. Model results suggest that, kilogram-for-kilogram, urban vegetation cycles C twice as fast as rural forests. Urban vegetation releases (R E ) and absorbs (GEE) the equivalent of 11 and 14%, respectively, of anthropogenic emissions in the most urban portions of the state. While urban vegetation in Massachusetts fully sequesters anthropogenic emissions from smaller cities in the region, Boston's UHI reduces annual C storage by >20% such that vegetation offsets only 2% of anthropogenic emissions. Asynchrony between temporal patterns of biogenic and anthropogenic C fluxes further constrains the emissions mitigation potential of urban vegetation. However, neglecting to account for biogenic C fluxes in cities can impair efforts to accurately monitor, report, verify, and reduce anthropogenic emissions. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. A Carbon Flux Super Site. New Insights and Innovative Atmosphere-Terrestrial Carbon Exchange Measurements and Modeling

    Energy Technology Data Exchange (ETDEWEB)

    Leclerc, Monique Y. [The University of Georgia Research Foundation, Athens, GA (United States)

    2014-11-17

    This final report presents the main activities and results of the project “A Carbon Flux Super Site: New Insights and Innovative Atmosphere-Terrestrial Carbon Exchange Measurements and Modeling” from 10/1/2006 to 9/30/2014. It describes the new AmeriFlux tower site (Aiken) at Savanna River Site (SC) and instrumentation, long term eddy-covariance, sodar, microbarograph, soil and other measurements at the site, and intensive field campaigns of tracer experiment at the Carbon Flux Super Site, SC, in 2009 and at ARM-CF site, Lamont, OK, and experiments in Plains, GA. The main results on tracer experiment and modeling, on low-level jet characteristics and their impact on fluxes, on gravity waves and their influence on eddy fluxes, and other results are briefly described in the report.

  11. The impact of lateral carbon fluxes on the European carbon balance

    International Nuclear Information System (INIS)

    Ciais, P.; Hauglustaine, D.; Borges, A.V.; Abril, G.; Meybeck, M.; Folberth, G.; Janssens, I.A.

    2008-01-01

    To date, little is known about the impact of processes which cause lateral carbon fluxes over continents, and from continents to oceans on the CO 2 - and carbon budgets at local, regional and continental scales. Lateral carbon fluxes contribute to regional carbon budgets as follows: Ecosystem CO 2 sink=Ecosystem carbon accumulation + Lateral carbon fluxes. We estimated the contribution of wood and food product trade, of emission and oxidation of reduced carbon species, and of river erosion and transport as lateral carbon fluxes to the carbon balance of Europe (EU-25). The analysis is completed by new estimates of the carbon fluxes of coastal seas. We estimated that lateral transport (all processes combined) is a flux of 165 Tg C yr -1 at the scale of EU-25. The magnitude of lateral transport is thus comparable to current estimates of carbon accumulation in European forests. The main process contributing to the total lateral flux out of Europe is the flux of reduced carbon compounds, corresponding to the sum of non-CO 2 gaseous species (CH 4 , CO, hydrocarbons,... ) emitted by ecosystems and exported out of the European boundary layer by the large scale atmospheric circulation. (authors)

  12. Carbon dioxide, water vapour and energy fluxes over a semi ...

    Indian Academy of Sciences (India)

    42

    of energy fluxes showed dominance of latent heat fluxes over sensible heat flux. .... for measurement of air temperature, rainfall, relative humidity, wind speed etc. ... within the radius of 100 m around the tower by using plant canopy analyzer ..... 2001), similar mechanisms might operate in our study resulting in flux deficit.

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

    Science.gov (United States)

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

    2011-12-01

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

  14. Evaluation of Site and Continental Terrestrial Carbon Cycle Simulations with North American Flux Tower Observations

    Science.gov (United States)

    Raczka, B. M.; Davis, K. J.; Regional-Interim Synthesis Participants, N.; Site Level Interim Synthesis, N.; Regional/Continental Interim Synthesis Team

    2010-12-01

    Terrestrial carbon models are widely used to diagnose past ecosystem-atmosphere carbon flux responses to climate variability, and are a critical component of coupled climate-carbon model used to predict global climate change. The North American Carbon Program (NACP) Interim Regional and Site Interim Synthesis activities collected a broad sampling of terrestrial carbon model results run at both regional and site level. The Regional Interim Synthesis Activity aims to determine our current knowledge of the carbon balance of North America by comparing the flux estimates provided by the various terrestrial carbon cycle models. Moving beyond model-model comparison is challenging, however, because no continental-scale reference values exist to validate modeled fluxes. This paper presents an effort to evaluate the continental-scale flux estimates of these models using North American flux tower observations brought together by the Site Interim Synthesis Activity. Flux towers present a standard for evaluation of the modeled fluxes, though this evaluation is challenging because of the mismatch in spatial scales between the spatial resolution of continental-scale model runs and the size of a flux tower footprint. We compare model performance with flux tower observations at monthly and annual integrals using the statistical criteria of normalized standard deviation, correlation coefficient, centered root mean square deviation and chi-squared. Models are evaluated individually and according to common model characteristics including spatial resolution, photosynthesis, soil carbon decomposition and phenology. In general all regional models are positively biased for GPP, Re and NEE at both annual and monthly time scales. Further analysis links this result to a positive bias in many solar radiation reanalyses. Positively biased carbon fluxes are also observed for enzyme-kinetic models and models using no nitrogen limitation for soil carbon decomposition. While the former result is

  15. Forest disturbance and North American carbon flux

    Science.gov (United States)

    S. N. Goward; J. G. Masek; W. Cohen; G. Moisen; G. J. Collatz; S. Healey; R. A. Houghton; C. Huang; R. Kennedy; B. Law; S. Powell; D. Turner; M. A. Wulder

    2008-01-01

    North America's forests are thought to be a significant sink for atmospheric carbon. Currently, the rate of sequestration by forests on the continent has been estimated at 0.23 petagrams of carbon per year, though the uncertainty about this estimate is nearly 50%. This offsets about 13% of the fossil fuel emissions from the continent [Pacala et al., 2007]. However...

  16. Evaluation of statistical protocols for quality control of ecosystem carbon dioxide fluxes

    Science.gov (United States)

    Jorge F. Perez-Quezada; Nicanor Z. Saliendra; William E. Emmerich; Emilio A. Laca

    2007-01-01

    The process of quality control of micrometeorological and carbon dioxide (CO2) flux data can be subjective and may lack repeatability, which would undermine the results of many studies. Multivariate statistical methods and time series analysis were used together and independently to detect and replace outliers in CO2 flux...

  17. Measurement of carbon dioxide fluxes in a free-air carbon dioxide enrichment experiment using the closed flux chamber technique

    DEFF Research Database (Denmark)

    Selsted, Merete Bang; Ambus, Per; Michelsen, Anders

    2011-01-01

    Carbon dioxide (CO2) fluxes, composing net ecosystem exchange (NEE), ecosystem respiration (ER), and soil respiration (SR) were measured in a temperate heathland exposed to elevated CO2 by the FACE (free-air carbon enrichment) technique, raising the atmospheric CO2 concentration from c. 380 μmol...

  18. Carbon Fluxes at the AmazonFACE Research Site

    Science.gov (United States)

    Norby, R.; De Araujo, A. C.; Cordeiro, A. L.; Fleischer, K.; Fuchslueger, L.; Garcia, S.; Hofhansl, F.; Garcia, M. N.; Grandis, A.; Oblitas, E.; Pereira, I.; Pieres, N. M.; Schaap, K.; Valverde-Barrantes, O.

    2017-12-01

    experiment. Although carbon fluxes on small plots cannot be expected to represent the fluxes across the wider and more diverse region, our integrated measurements, coupled with a model framework, provide a strong foundation for understanding the mechanistic basis of responses and for extending results of experimental CO2 fertilization to the wider region.

  19. 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.

  20. Carbon fluxes on North American rangelands

    Science.gov (United States)

    Tony Svejcar; Raymond Angell; James A. Bradford; William Dugas; William Emmerich; Albert B. Frank; Tagir Gilmanov; Marshall Haferkamp; Douglas A. Johnson; Herman Mayeux; Pat Mielnick; Jack Morgan; Nicanor Z. Saliendra; Gerald E. Schuman; Phillip L. Sims; Kereith Snyder

    2008-01-01

    Rangelands account for almost half of the earth's land surface and may play an important role in the global carbon (C) cycle. We studied net ecosystem exchange (NEE) of C on eight North American rangeland sites over a 6-yr period. Management practices and disturbance regimes can influence NEE; for consistency, we compared ungrazed and undisturbed rangelands...

  1. Chapter 9: Carbon fluxes across regions.

    Science.gov (United States)

    Beverly E. Law; Dave Turner; John Campbell; Michael Lefsky; Michael Guzy; Osbert Sun; Steve Van Tuyl; Warren Cohen

    2006-01-01

    Scaling biogeochemical processes to regions, continents, and the globe is critical for understanding feedbacks between the biosphere and atmosphere in the analysis of global change. This includes the effects of changing atmospheric carbon dioxide, climate, disturbances, and increasing nitrogen deposition from air pollution (Ehleringer and Field 1993, Vitousek et al....

  2. Monitoring carbon dioxide from space: Retrieval algorithm and flux inversion based on GOSAT data and using CarbonTracker-China

    Science.gov (United States)

    Yang, Dongxu; Zhang, Huifang; Liu, Yi; Chen, Baozhang; Cai, Zhaonan; Lü, Daren

    2017-08-01

    Monitoring atmospheric carbon dioxide (CO2) from space-borne state-of-the-art hyperspectral instruments can provide a high precision global dataset to improve carbon flux estimation and reduce the uncertainty of climate projection. Here, we introduce a carbon flux inversion system for estimating carbon flux with satellite measurements under the support of "The Strategic Priority Research Program of the Chinese Academy of Sciences—Climate Change: Carbon Budget and Relevant Issues". The carbon flux inversion system is composed of two separate parts: the Institute of Atmospheric Physics Carbon Dioxide Retrieval Algorithm for Satellite Remote Sensing (IAPCAS), and CarbonTracker-China (CT-China), developed at the Chinese Academy of Sciences. The Greenhouse gases Observing SATellite (GOSAT) measurements are used in the carbon flux inversion experiment. To improve the quality of the IAPCAS-GOSAT retrieval, we have developed a post-screening and bias correction method, resulting in 25%-30% of the data remaining after quality control. Based on these data, the seasonal variation of XCO2 (column-averaged CO2 dry-air mole fraction) is studied, and a strong relation with vegetation cover and population is identified. Then, the IAPCAS-GOSAT XCO2 product is used in carbon flux estimation by CT-China. The net ecosystem CO2 exchange is -0.34 Pg C yr-1 (±0.08 Pg C yr-1), with a large error reduction of 84%, which is a significant improvement on the error reduction when compared with in situ-only inversion.

  3. Relevance of methodological choices for accounting of land use change carbon fluxes

    Science.gov (United States)

    Pongratz, Julia; Hansis, Eberhard; Davis, Steven

    2015-04-01

    To understand and potentially steer how humans shape land-climate interactions it is important to accurately attribute greenhouse gas fluxes from land use and land cover change (LULCC) in space and time. However, such accounting of carbon fluxes from LULCC generally requires choosing from multiple options of how to attribute the fluxes to regions and to LULCC activities. Applying a newly-developed and spatially-explicit bookkeeping model, BLUE ("bookkeeping of land use emissions"), we quantify LULCC carbon fluxes and attribute them to land-use activities and countries by a range of different accounting methods. We present results with respect to a Kyoto Protocol-like ``commitment'' accounting period, using land use emissions of 2008-12 as example scenario. We assess the effect of accounting methods that vary (1) the temporal evolution of carbon stocks, (2) the state of the carbon stocks at the beginning of the period, (3) the temporal attribution of carbon fluxes during the period, and (4) treatment of LULCC fluxes that occurred prior to the beginning of the period. We show that the methodological choices result in grossly different estimates of carbon fluxes for the different attribution definitions. The global net flux in the accounting period varies between 4.3 Pg(C) uptake and 15.2 Pg(C) emissions, depending on the accounting method. Regional results show different modes of variation. This finding has implications for both political and scientific considerations: Not all methodological choices are currently specified under the UNFCCC treaties on land use, land-use change and forestry. Yet, a consistent accounting scheme is crucial to assure comparability of individual LULCC activities, quantify their relevance for the global annual carbon budget, and assess the effects of LULCC policies.

  4. Soil surface CO2 fluxes and the carbon budget of a grassland

    Science.gov (United States)

    Norman, J. M.; Garcia, R.; Verma, S. B.

    1992-01-01

    Measurements of soil surface CO2 fluxes are reported for three sites within the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE) area, and simple empirical equations are fit to the data to provide predictions of soil fluxes from environmental observations. A prototype soil chamber, used to make the flux measurements, is described and tested by comparing CO2 flux measurements to a 40-L chamber, a 1-m/cu chamber, and eddy correlation. Results suggest that flux measurements with the prototype chamber are consistent with measurements by other methods to within about 20 percent. A simple empirical equation based on 10-cm soil temperature, 0- to 10-cm soil volumetric water content, and leaf area index predicts the soil surface CO2 flux with a rms error of 1.2 micro-mol sq m/s for all three sites. Further evidence supports using this equation to evaluate soil surface CO2 during the 1987 FIFE experiment. The soil surface CO2 fluxes when averaged over 24 hours are comparable to daily gross canopy photosynthetic rates. For 6 days of data the net daily accumulation of carbon is about 0.6 g CO2 sq m/d; this is only a few percent of the daily gross accumulation of carbon by photosynthesis. As the soil became drier in 1989, the net accumulation of carbon by the prairie increased, suggesting that the soil flux is more sensitive to temperature and drought than the photosynthetic fluxes.

  5. High-Flux Carbon Molecular Sieve Membranes for Gas Separation.

    Science.gov (United States)

    Richter, Hannes; Voss, Hartwig; Kaltenborn, Nadine; Kämnitz, Susanne; Wollbrink, Alexander; Feldhoff, Armin; Caro, Jürgen; Roitsch, Stefan; Voigt, Ingolf

    2017-06-26

    Carbon membranes have great potential for highly selective and cost-efficient gas separation. Carbon is chemically stable and it is relative cheap. The controlled carbonization of a polymer coating on a porous ceramic support provides a 3D carbon material with molecular sieving permeation performance. The carbonization of the polymer blend gives turbostratic carbon domains of randomly stacked together sp 2 hybridized carbon sheets as well as sp 3 hybridized amorphous carbon. In the evaluation of the carbon molecular sieve membrane, hydrogen could be separated from propane with a selectivity of 10 000 with a hydrogen permeance of 5 m 3 (STP)/(m 2 hbar). Furthermore, by a post-synthesis oxidative treatment, the permeation fluxes are increased by widening the pores, and the molecular sieve carbon membrane is transformed from a molecular sieve carbon into a selective surface flow carbon membrane with adsorption controlled performance and becomes selective for carbon dioxide. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. 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.

  7. Overview of NASA's Carbon Monitoring System Flux-Pilot Project

    Science.gov (United States)

    Pawson, Steven; Gunson, Michael R.; Jucks, Kenneth

    2011-01-01

    NASA's space-based observations of physical, chemical and biological parameters in the Earth System along with state-of-the-art modeling capabilities provide unique capabilities for analyses of the carbon cycle. The Carbon Monitoring System is developing an exploratory framework for detecting carbon in the environment and its changes, with a view towards contributing to national and international monitoring activities. The Flux-Pilot Project aims to provide a unified view of land-atmosphere and ocean-atmosphere carbon exchange, using observation-constrained models. Central to the project is the application of NASA's satellite observations (especially MODIS), the ACOS retrievals of the JAXA-GOSAT observations, and the "MERRA" meteorological reanalysis produced with GEOS-S. With a primary objective of estimating uncertainty in computed fluxes, two land- and two ocean-systems are run for 2009-2010 and compared with existing flux estimates. An transport model is used to evaluate simulated CO2 concentrations with in-situ and space-based observations, in order to assess the realism of the fluxes and how uncertainties in fluxes propagate into atmospheric concentrations that can be more readily evaluated. Finally, the atmospheric partial CO2 columns observed from space are inverted to give new estimates of surface fluxes, which are evaluated using the bottom-up estimates and independent datasets. The focus of this presentation will be on the science goals and current achievements of the pilot project, with emphasis on how policy-relevant questions help focus the scientific direction. Examples include the issue of what spatio-temporal resolution of fluxes can be detected from polar-orbiting satellites and whether it is possible to use space-based observations to separate contributions to atmospheric concentrations of (say) fossil-fuel and biological activity

  8. Monitoring Forest Carbon Stocks and Fluxes in the Congo Basin

    OpenAIRE

    2010-01-01

    The Central African Forests Commission (COMIFAC) and its partners (OFAC, USAID, EC-JRC, OSFAC, WWF, WRI, WCS, GOFC-GOLD, START, UN-FAO) organized an international conference on "Monitoring of Carbon stocks and fluxes in the Congo Basin" in Brazzaville, Republic of Congo, 2-4 February 2010. The conference brought together leading international specialists to discuss approaches for quantifying stocks and flows of carbon in tropical forests of the Congo Basin. The conference provided a unique op...

  9. Assessing FPAR Source and Parameter Optimization Scheme in Application of a Diagnostic Carbon Flux Model

    Energy Technology Data Exchange (ETDEWEB)

    Turner, D P; Ritts, W D; Wharton, S; Thomas, C; Monson, R; Black, T A

    2009-02-26

    The combination of satellite remote sensing and carbon cycle models provides an opportunity for regional to global scale monitoring of terrestrial gross primary production, ecosystem respiration, and net ecosystem production. FPAR (the fraction of photosynthetically active radiation absorbed by the plant canopy) is a critical input to diagnostic models, however little is known about the relative effectiveness of FPAR products from different satellite sensors nor about the sensitivity of flux estimates to different parameterization approaches. In this study, we used multiyear observations of carbon flux at four eddy covariance flux tower sites within the conifer biome to evaluate these factors. FPAR products from the MODIS and SeaWiFS sensors, and the effects of single site vs. cross-site parameter optimization were tested with the CFLUX model. The SeaWiFs FPAR product showed greater dynamic range across sites and resulted in slightly reduced flux estimation errors relative to the MODIS product when using cross-site optimization. With site-specific parameter optimization, the flux model was effective in capturing seasonal and interannual variation in the carbon fluxes at these sites. The cross-site prediction errors were lower when using parameters from a cross-site optimization compared to parameter sets from optimization at single sites. These results support the practice of multisite optimization within a biome for parameterization of diagnostic carbon flux models.

  10. Carbon nanotube/carbon nanotube composite AFM probes prepared using ion flux molding

    Science.gov (United States)

    Chesmore, Grace; Roque, Carrollyn; Barber, Richard

    The performance of carbon nanotube-carbon nanotube composite (CNT/CNT composite) atomic force microscopy (AFM) probes is compared to that of conventional Si probes in AFM tapping mode. The ion flux molding (IFM) process, aiming an ion beam at the CNT probe, aligns the tip to a desired angle. The result is a relatively rigid tip that is oriented to offset the cantilever angle. Scans using these probes reveal an improvement in image accuracy over conventional tips, while allowing higher aspect ratio imaging of 3D surface features. Furthermore, the lifetimes of CNT-CNT composite tips are observed to be longer than both conventional tips and those claimed for other CNT technologies. Novel applications include the imaging of embiid silk. Supported by the Clare Boothe Luce Research Scholars Award and Carbon Design Innovations.

  11. Partitioning Water Vapor and Carbon Dioxide Fluxes using Correlation Analysis

    Science.gov (United States)

    Scanlon, T. M.

    2008-12-01

    A variety of methods are currently available to partition water vapor fluxes (into components of transpiration and direct evaporation) and carbon dioxide fluxes (into components of photosynthesis and respiration), using chambers, isotopes, and regression modeling approaches. Here, a methodology is presented that accounts for correlations between high-frequency measurements of water vapor (q) and carbon dioxide (c) concentrations being influenced by their non-identical source-sink distributions and the relative magnitude of their constituent fluxes. Flux-variance similarity assumptions are applied separately to the stomatal and the non-stomatal exchange, and the flux components are identified by considering the q-c correlation. Water use efficiency for the vegetation, and how it varies with respect to vapor pressure deficit, is the only input needed for this approach that uses standard eddy covariance measurements. The method is demonstrated using data collected over a corn field throughout a growing season. In particular, the research focuses on the partitioning of the water flux with the aim of improving how direct evaporation is handled in soil-vegetation- atmosphere transfer models over the course of wetting and dry-down cycles.

  12. 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

  13. Changes in ocean circulation and carbon storage are decoupled from air-sea CO2 fluxes

    Science.gov (United States)

    Marinov, I.; Gnanadesikan, A.

    2011-02-01

    The spatial distribution of the air-sea flux of carbon dioxide is a poor indicator of the underlying ocean circulation and of ocean carbon storage. The weak dependence on circulation arises because mixing-driven changes in solubility-driven and biologically-driven air-sea fluxes largely cancel out. This cancellation occurs because mixing driven increases in the poleward residual mean circulation result in more transport of both remineralized nutrients and heat from low to high latitudes. By contrast, increasing vertical mixing decreases the storage associated with both the biological and solubility pumps, as it decreases remineralized carbon storage in the deep ocean and warms the ocean as a whole.

  14. Grasland Stable Isotope Flux Measurements: Three Isotopomers of Carbon Dioxide Measured by QCL Spectroscopy

    Science.gov (United States)

    Zeeman, M. J.; Tuzson, B.; Eugster, W.; Werner, R. A.; Buchmann, N.; Emmenegger, L.

    2007-12-01

    To improve our understanding of greenhouse gas dynamics of managed ecosystems such as grasslands, we not only need to investigate the effects of management (e.g., grass cuts) and weather events (e.g., rainy days) on carbon dioxide fluxes, but also need to increase the time resolution of our measurements. Thus, for the first time, we assessed respiration and assimilation fluxes with high time resolution (5Hz) stable isotope measurements at an intensively managed farmland in Switzerland (Chamau, 400m ASL). Two different methods were used to quantify fluxes of carbon dioxide and associated fluxes of stable carbon isotopes: (1) the flux gradient method, and (2) the eddy covariance method. During a week long intensive measurement campaign, we (1) measured mixing ratios of carbon dioxide isotopomers (12C16O2, 12C16O18O, 13C16O2) with a Quantum Cascade Laser (QCL, Aerodyne Inc.) spectroscope and (2) collected air samples for isotope analyses (13C/12C) and (18O/16O) of carbon dioxide by Isotope Ratio Mass Spectrometry (IRMS, Finnigan) every two hours, concurrently along a height profile (z = 0.05; 0.10; 0.31; 2.15m). In the following week, the QCL setup was used for closed-path eddy covariance flux measurement of the carbon dioxide isotopomers, with the air inlet located next to an open-path Infra Red Gas Analyzers (IRGA, LiCor 7500) used simultaneously for carbon dioxide measurements. During this second week, an area of grass inside the footprint was cut and harvested after several days. The first results of in-field continuous QCL measurements of carbon dioxide mixing ratios and their stable isotopic ratios show good agreement with IRGA measurements and isotope analysis of flask samples by IRMS. Thus, QCL spectroscopy is a very promising tool for stable isotope flux investigations.

  15. Fluxes of particulate organic carbon in the East China Sea in summer

    Directory of Open Access Journals (Sweden)

    C.-C. Hung

    2013-10-01

    Full Text Available To understand carbon cycling in marginal seas better, particulate organic carbon (POC concentrations, POC fluxes and primary production (PP were measured in the East China Sea (ECS in summer 2007. Higher concentrations of POC were observed in the inner shelf, and lower POC values were found in the outer shelf. Similar to POC concentrations, elevated uncorrected POC fluxes (720–7300 mg C m−2 d−1 were found in the inner shelf, and lower POC fluxes (80–150 mg C m−2 d−1 were in the outer shelf, respectively. PP values (~ 340–3380 mg C m−2 d−1 had analogous distribution patterns to POC fluxes, while some of PP values were significantly lower than POC fluxes, suggesting that contributions of resuspended particles to POC fluxes need to be appropriately corrected. A vertical mixing model was used to correct effects of bottom sediment resuspension, and the lowest and highest corrected POC fluxes were in the outer shelf (58 ± 33 mg C m−2 d−1 and the inner shelf (785 ± 438 mg C m−2 d−1, respectively. The corrected POC fluxes (486 to 785 mg C m−2 d−1 in the inner shelf could be the minimum value because we could not exactly distinguish the effect of POC flux from Changjiang influence with turbid waters. The results suggest that 27–93% of the POC flux in the ECS might be from the contribution of resuspension of bottom sediments rather than from the actual biogenic carbon sinking flux. While the vertical mixing model is not a perfect model to solve sediment resuspension because it ignores biological degradation of sinking particles, Changjiang plume (or terrestrial inputs and lateral transport, it makes significant progress in both correcting the resuspension problem and in assessing a reasonable quantitative estimate of POC flux in a marginal sea.

  16. Evaluation of NASA's Carbon Monitoring System (CMS) Flux Pilot: Terrestrial CO2 Fluxes

    Science.gov (United States)

    Fisher, J. B.; Polhamus, A.; Bowman, K. W.; Collatz, G. J.; Potter, C. S.; Lee, M.; Liu, J.; Jung, M.; Reichstein, M.

    2011-12-01

    NASA's Carbon Monitoring System (CMS) flux pilot project combines NASA's Earth System models in land, ocean and atmosphere to track surface CO2 fluxes. The system is constrained by atmospheric measurements of XCO2 from the Japanese GOSAT satellite, giving a "big picture" view of total CO2 in Earth's atmosphere. Combining two land models (CASA-Ames and CASA-GFED), two ocean models (ECCO2 and NOBM) and two atmospheric chemistry and inversion models (GEOS-5 and GEOS-Chem), the system brings together the stand-alone component models of the Earth System, all of which are run diagnostically constrained by a multitude of other remotely sensed data. Here, we evaluate the biospheric land surface CO2 fluxes (i.e., net ecosystem exchange, NEE) as estimated from the atmospheric flux inversion. We compare against the prior bottom-up estimates (e.g., the CASA models) as well. Our evaluation dataset is the independently derived global wall-to-wall MPI-BGC product, which uses a machine learning algorithm and model tree ensemble to "scale-up" a network of in situ CO2 flux measurements from 253 globally-distributed sites in the FLUXNET network. The measurements are based on the eddy covariance method, which uses observations of co-varying fluxes of CO2 (and water and energy) from instruments on towers extending above ecosystem canopies; the towers integrate fluxes over large spatial areas (~1 km2). We present global maps of CO2 fluxes and differences between products, summaries of fluxes by TRANSCOM region, country, latitude, and biome type, and assess the time series, including timing of minimum and maximum fluxes. This evaluation shows both where the CMS is performing well, and where improvements should be directed in further work.

  17. Seasonal analyses of carbon dioxide and energy fluxes above an oil palm plantation using the eddy covariance method

    Science.gov (United States)

    Ibrahim, Anis; Haniff Harun, Mohd; Yusup, Yusri

    2017-04-01

    A study presents the measurements of carbon dioxide and latent and sensible heat fluxes above a mature oil palm plantation on mineral soil in Keratong, Pahang, Peninsular Malaysia. The sampling campaign was conducted over an 25-month period, from September 2013 to February 2015 and May 2016 to November 2016, using the eddy covariance method. The main aim of this work is to assess carbon dioxide and energy fluxes over this plantation at different time scales, seasonal and diurnal, and determine the effects of season and relevant meteorological parameters on the latter fluxes. Energy balance closure analyses gave a slope between latent and sensible heat fluxes and total incoming energy to be 0.69 with an R2 value of 0.86 and energy balance ratio of 0.80. The averaged net radiation was 108 W m-2. The results show that at the diurnal scale, carbon dioxide, latent and sensible heat fluxes exhibited a clear diurnal trend where carbon dioxide flux was at its minimum - 3.59 μmol m-2 s-1 in the mid-afternoon and maximum in the morning while latent and sensible behaved conversely to the carbon dioxide flux. The average carbon dioxide flux was - 0.37 μmol m-2 s-1. At the seasonal timescale, carbon dioxide fluxes did not show any apparent trend except during the Northeast Monsoon where the highest variability of the monthly means of carbon dioxide occurred.

  18. Management effects on carbon fluxes in boreal forests (Invited)

    Science.gov (United States)

    Lindroth, A.; Mölder, M.; Lagergren, F.; Vestin, P.; Hellström, M.; Sundqvist, E.; Norunda Bgs Team

    2010-12-01

    Disturbance by management or natural causes such as wind throw or fire are believed to be one of the main factors that are controlling the carbon balance of vegetation. In Northern Europe a large fraction of the forest area is managed with clear cutting and thinning as the main silvicultural methods. The effect of clear-cutting on carbon dioxide exchanges were studied in different chrono-sequences located in Sweden, Finland, UK and France, respectively. The combined results from these studies showed that a simple model could be developed describing relative net ecosystem exchange as a function of relative rotation length (age). A stand with a rotation length of 100 years, typical for Swedish conditions, looses substantial amounts of carbon during the first 12-15 years and the time it takes to reach cumulative balance after clear-cut, is 25-30 years. The mean net ecosystem exchange over the whole rotation length equals 50% of the maximum uptake. An interesting question is if it is possible to harvest without the substantial carbon losses that take place after clear-cutting. Selective harvest by thinning could potentially be such a method. We therefore studied the effect of thinning on soil and ecosystem carbon fluxes in a mixed pine and spruce forest in Central Sweden, the Norunda forest, located in the semi-boreal zone at 60.08°N, 17.48 °E. The CO2 fluxes from the forest were measured by eddy covariance method and soil effluxes were measured by automatic chambers. Maximum canopy height of the ca. 100 years-old forest was 28 m. The stand was composed of ca 72% pine, 28% before the thinning while the composition after the thinning became 82% pine and 18% spruce. The thinning was made in November/December 2008 in a half- circle from the tower with a radius of 200 m. The LAI decreased from 4.5 to 2.8 after the thinning operation. Immediately after the thinning, we found significantly higher soil effluxes, probably due to increased decomposition of dead roots. The

  19. Numerical cell model investigating cellular carbon fluxes in Emiliania huxleyi.

    Science.gov (United States)

    Holtz, Lena-Maria; Wolf-Gladrow, Dieter; Thoms, Silke

    2015-01-07

    Coccolithophores play a crucial role in the marine carbon cycle and thus it is interesting to know how they will respond to climate change. After several decades of research the interplay between intracellular processes and the marine carbonate system is still not well understood. On the basis of experimental findings given in literature, a numerical cell model is developed that describes inorganic carbon fluxes between seawater and the intracellular sites of calcite precipitation and photosynthetic carbon fixation. The implemented cell model consists of four compartments, for each of which the carbonate system is resolved individually. The four compartments are connected to each other via H(+), CO2, and HCO3(-) fluxes across the compartment-confining membranes. For CO2 accumulation around RubisCO, an energy-efficient carbon concentrating mechanism is proposed that relies on diffusive CO2 uptake. At low external CO2 concentrations and high light intensities, CO2 diffusion does not suffice to cover the carbon demand of photosynthesis and an additional uptake of external HCO3(-) becomes essential. The model is constrained by data of Emiliania huxleyi, the numerically most abundant coccolithophore species in the present-day ocean. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

  20. Regional variations in the fluxes of foraminifera carbonate, coccolithophorid carbonate and biogenic opal in the northern Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Ramaswamy, V.; Gaye, B.

    Mass fluxes of diatom opal, planktonic foraminifera carbonate and coccolithophorid carbonate were measured with time-series sediment traps at six sites in the Arabian Sea, Bay of Bengal and Equatorial Indian Ocean (EIOT). The above fluxes were...

  1. Carbon Flux to the Atmosphere from Land-Use Changes: 1850 to 1990

    Energy Technology Data Exchange (ETDEWEB)

    Houghton, R.A.

    2001-02-22

    The database documented in this numeric data package, a revision to a database originally published by the Carbon Dioxide Information Analysis Center (CDIAC) in 1995, consists of annual estimates, from 1850 through 1990, of the net flux of carbon between terrestrial ecosystems and the atmosphere resulting from deliberate changes in land cover and land use, especially forest clearing for agriculture and the harvest of wood for wood products or energy. The data are provided on a year-by-year basis for nine regions (North America, South and Central America, Europe, North Africa and the Middle East, Tropical Africa, the Former Soviet Union, China, South and Southeast Asia, and the Pacific Developed Region) and the globe. Some data begin earlier than 1850 (e.g., for six regions, areas of different ecosystems are provided for the year 1700) or extend beyond 1990 (e.g., fuelwood harvest in South and Southeast Asia, by forest type, is provided through 1995). The global net flux during the period 1850 to 1990 was 124 Pg of carbon (1 petagram = 10{sup 15} grams). During this period, the greatest regional flux was from South and Southeast Asia (39 Pg of carbon), while the smallest regional flux was from North Africa and the Middle East (3 Pg of carbon). For the year 1990, the global total net flux was estimated to be 2.1 Pg of carbon.

  2. Aspect as a Driver of Soil Carbon and Water Fluxes in Desert Environments

    Science.gov (United States)

    Sutter, L., Jr.; Barron-Gafford, G.; Sanchez-Canete, E. P.

    2016-12-01

    Within dryland environments, precipitation and incoming energy are the primary determinants of carbon and water cycling. We know aspect can influence how much sun energy reaches the ground surface, but how does this spatial feature of the landscape propagate into temporal moisture and carbon flux dynamics? We made parallel measurements across north and south-facing slopes to examine the effects of aspect on soil temperature and moisture and the resulting soil carbon and water flux rates within a low elevation, desert site in the Santa Catalina-Jemez Critical Zone Observatory. We coupled spatially distributed measurements at a single point in time with diel patterns of soil fluxes at singular point and in response to punctuated rain events. Reponses concerning aspect after spring El Niño rainfall events were complex, with higher cumulative carbon flux on the south-facing slope two weeks post rain, despite higher daily flux values starting on the north-facing slope ten days after the rain. Additional summer monsoon rain events and dry season measurements will give further insights into patterns under hotter conditions of periodic inter-storm drought. We will complete a year-round carbon and water flux budget of this site by measuring throughout the winter rainfall months. Ultimately, our work will illustrate the interactive effects of a range of physical factors on soil fluxes. Critical zone soil dynamics, especially within dryland environments, are very complex, but capturing the uncertainty around these flux is necessary to understand concerning vertical carbon and water exchange and storage.

  3. Measurements of flux and isotopic composition of soil carbon dioxide

    International Nuclear Information System (INIS)

    Gorczyca, Z.; Rozanski, K.; Kuc, T.

    2002-01-01

    The flux and isotope composition of soil CO 2 has been regularly measured at three sites located in the southern Poland, during the time period: January 1998 - October 2000. They represent typical ecosystems appearing in central Europe: (i) mixed forest; (ii) cultivated agricultural field; (iii) grassland. To monitor the flux and isotopic composition of soil CO 2 , a method based on the inverted cup principle was adopted. The flux of soil CO 2 reveals distinct seasonal fluctuations, with maximum values up to ca. 25 mmol/m 2 /h during sommer months and around ten times lower values during winter time. Also significant differences among the monitored sites were detected, the flux density of this gas being highest for the mixed forest site and ca. two times lower for the cultivated grassland. Carbon-13 content of the soil CO 2 reveals little seasonal variability, with δ 13 C values essentially reflecting the isotopic composition of the soil organic matter and the vegetation type. The carbon-14 content of soil CO 2 flux also reveals slight seasonality, with lower δ 14 C values recorded during winter time. Significantly lower δ 14 C values recorded during winter time. Significantly lower δ 14 C values were recorded at depth. (author)

  4. Carbon Fluxes and Transport Along the Terrestrial Aquatic Continuum

    Science.gov (United States)

    Butman, D. E.; Kolka, R.; Fennel, K.; Stackpoole, S. M.; Trettin, C.; Windham-Myers, L.

    2017-12-01

    Terrestrial wetlands, inland surface waters, tidal wetlands and estuaries, and the coastal ocean are distinct aquatic ecosystems that integrate carbon (C) fluxes and processing among the major earth system components: the continents, oceans, and atmosphere. The development of the 2nd State of the Carbon Cycle Report (SOCCR2) noted that incorporating the C cycle dynamics for these ecosystems was necessary to reconcile some of the gaps associated with the North American C budget. We present major C stocks and fluxes for Canada, Mexico and the United States. North America contains nearly 42% of the global terrestrial wetland area. Terrestrial wetlands, defined as soils that are seasonally or permanently inundated or saturated, contain significant C stocks equivalent to 174,000 Tg C in the top 40 cm of soil. While terrestrial wetlands are a C sink of approximately 64 Tg C yr-1, they also emit 21 Tg of CH4 yr-1. Inland waters are defined as lakes, reservoirs, rivers, and streams. Carbon fluxes, which include lateral C export to the coast, riverine and lacustrine CO2 emissions, and C burial in lakes and reservoirs are estimated at 507 Tg yr-1. Estuaries and tidal wetlands assimilate C and nutrients from uplands and rivers, and their total C stock is 1,323 Tg C in the top 1 m of soils and sediment. Accounting for soil accretion, lateral C flux, and CO2 assimilation and emission, tidal wetlands and estuaries are net sinks with a total flux equal to 6 Tg C yr-1. The coastal ocean and sea shelfs, defined as non-estuarine waters within 200 nautical miles (370 km) of the coast, function as net sinks, with the air-sea exchange of CO2 estimated at 150 Tg C yr-1. In total, fluxes from these four aquatic ecosystems are equal to a loss of 302 Tg C yr-1. Including these four discrete fluxes in this assessment demonstrates the importance of linking hydrology and biogeochemical cycling to evaluate the impacts of climate change and human activities on carbon fluxes across the

  5. Dissolved Carbon Fluxes During the 2017 Mississippi River Flood

    Science.gov (United States)

    Reiman, J. H.; Xu, Y. J.

    2017-12-01

    The Mississippi River drains approximately 3.2 million square kilometres of land and discharges about 680 cubic kilometres of water into the Northern Gulf of Mexico annually, acting as a significant medium for carbon transport from land to the ocean. A few studies have documented annual carbon fluxes in the river, however it is unclear whether floods can create riverine carbon pulses. Such information is critical in understanding the effects that extreme precipitation events may have on carbon transport under the changing climate. We hypothesize that carbon concentration and mass loading will increase in response to an increase in river discharge, creating a carbon pulse, and that the source of carbon varies from river rising to falling due to terrestrial runoff processes. This study investigated dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) loadings during the 2017 Mississippi River early-summer flood. Water samples were taken from the Mississippi River at Baton Rouge on the rising limb, crest, and falling limb of the flood. All samples were analysed for concentrations of DOC, DIC, and their respective isotopic signature (δ13C). Partial pressure of carbon dioxide (pCO2) was also recorded in the field at each sampling trip. Additionally, the water samples were analysed for nutrients, dissolved metals, and suspended solids, and in-situ measurements were made on water temperature, pH, dissolved oxygen, and specific conductance. The preliminary findings suggest that carbon species responded differently to the flood event and that δ13C values were dependent on river flood stage. This single flood event transported a large quantity of carbon, indicating that frequent large pulses of riverine carbon should be expected in the future as climate change progresses.

  6. Intercomparison of terrestrial carbon fluxes and carbon use efficiency simulated by CMIP5 Earth System Models

    Science.gov (United States)

    Kim, Dongmin; Lee, Myong-In; Jeong, Su-Jong; Im, Jungho; Cha, Dong Hyun; Lee, Sanggyun

    2017-12-01

    This study compares historical simulations of the terrestrial carbon cycle produced by 10 Earth System Models (ESMs) that participated in the fifth phase of the Coupled Model Intercomparison Project (CMIP5). Using MODIS satellite estimates, this study validates the simulation of gross primary production (GPP), net primary production (NPP), and carbon use efficiency (CUE), which depend on plant function types (PFTs). The models show noticeable deficiencies compared to the MODIS data in the simulation of the spatial patterns of GPP and NPP and large differences among the simulations, although the multi-model ensemble (MME) mean provides a realistic global mean value and spatial distributions. The larger model spreads in GPP and NPP compared to those of surface temperature and precipitation suggest that the differences among simulations in terms of the terrestrial carbon cycle are largely due to uncertainties in the parameterization of terrestrial carbon fluxes by vegetation. The models also exhibit large spatial differences in their simulated CUE values and at locations where the dominant PFT changes, primarily due to differences in the parameterizations. While the MME-simulated CUE values show a strong dependence on surface temperatures, the observed CUE values from MODIS show greater complexity, as well as non-linear sensitivity. This leads to the overall underestimation of CUE using most of the PFTs incorporated into current ESMs. The results of this comparison suggest that more careful and extensive validation is needed to improve the terrestrial carbon cycle in terms of ecosystem-level processes.

  7. Scaling-up of CO2 fluxes to assess carbon sequestration in rangelands of Central Asia

    Science.gov (United States)

    Bruce K. Wylie; Tagir G. Gilmanov; Douglas A. Johnson; Nicanor Z. Saliendra; Larry L. Tieszen; Ruth Anne F. Doyle; Emilio A. Laca

    2006-01-01

    Flux towers provide temporal quantification of local carbon dynamics at specific sites. The number and distribution of flux towers, however, are generally inadequate to quantify carbon fluxes across a landscape or ecoregion. Thus, scaling up of flux tower measurements through use of algorithms developed from remote sensing and GIS data is needed for spatial...

  8. Relationships between carbon fluxes and environmental factors in a drip-irrigated, film-mulched cotton field in arid region

    OpenAIRE

    Li, Xiaoyu; Liu, Lijuan; Yang, Huijin; Li, Yan

    2018-01-01

    Environmental factors and human activities play important roles in carbon fixation and emissions generated from croplands. Eddy covariance measurements in a drip-irrigated, film-mulched cotton field were used to analyze the relationships between carbon fluxes and environmental factors in Wulanwusu, northern Xinjiang, an arid region of Northwest China. Our results showed that the cumulative net carbon flux (NEE) was -304.8 g C m-2 (a strong sink) over the whole cotton growing season in 2012, w...

  9. Urban Evapotranspiration and Carbon Dioxide Flux in Miami - Dade, Florida

    Science.gov (United States)

    Bernier, T.; Hopper, W.

    2010-12-01

    Atmospheric Carbon Dioxide (CO2) concentrations are leading indicators of secular climate change. With increasing awareness of the consequences of climate change, methods for monitoring this change are becoming more important daily. Of particular interest is the carbon dioxide exchange between natural and urban landscapes and the correlation of atmospheric CO2 concentrations. Monitoring Evapotranspiration (ET) is important for assessments of water availability for growing populations. ET is surprisingly understudied in the hydrologic cycle considering ET removes as much as 80 to over 100% of precipitation back into the atmosphere as water vapor. Lack of understanding in spatial and temporal ET estimates can limit the credibility of hydrologic water budgets designed to promote sustainable water use and resolve water-use conflicts. Eddy covariance (EC) methods are commonly used to estimate ET and CO2 fluxes. The EC platform consist of a (CSAT) 3-D Sonic Anemometer and a Li-Cor Open Path CO2/ H2O Analyzer. Measurements collected at 10 Hz create a very large data sets. A EC flux tower located in the Snapper Creek Well Field as part of a study to estimate ET for the Miami Dade County Water and Sewer project. Data has been collected from December 17, 2009 to August 30, 2010. QA/QC is performed with the EdiRe data processing software according to Ameri-flux protocols. ET estimates along with other data--latent-heat flux, sensible-heat flux, rainfall, air temperature, wind speed and direction, solar irradiance, net radiation, soil-heat flux and relative humidity--can be used to aid in the development of water management policies and regulations. Currently, many financial institutions have adopted an understanding about baseline environmental monitoring. The “Equator Principle” is an example of a voluntary standard for managing social and environmental risk in project financing and has changed the way in which projects are financed.

  10. Genetic algorithm based adaptive neural network ensemble and its application in predicting carbon flux

    Science.gov (United States)

    Xue, Y.; Liu, S.; Hu, Y.; Yang, J.; Chen, Q.

    2007-01-01

    To improve the accuracy in prediction, Genetic Algorithm based Adaptive Neural Network Ensemble (GA-ANNE) is presented. Intersections are allowed between different training sets based on the fuzzy clustering analysis, which ensures the diversity as well as the accuracy of individual Neural Networks (NNs). Moreover, to improve the accuracy of the adaptive weights of individual NNs, GA is used to optimize the cluster centers. Empirical results in predicting carbon flux of Duke Forest reveal that GA-ANNE can predict the carbon flux more accurately than Radial Basis Function Neural Network (RBFNN), Bagging NN ensemble, and ANNE. ?? 2007 IEEE.

  11. Quantifying and predicting historical and future patterns of carbon fluxes from the North American Continent to Ocean

    Science.gov (United States)

    Tian, H.; Zhang, B.; Xu, R.; Yang, J.; Yao, Y.; Pan, S.; Lohrenz, S. E.; Cai, W. J.; He, R.; Najjar, R. G.; Friedrichs, M. A. M.; Hofmann, E. E.

    2017-12-01

    Carbon export through river channels to coastal waters is a fundamental component of the global carbon cycle. Changes in the terrestrial environment, both natural (e.g., climatic change, enriched CO2 concentration, and elevated ozone concentration) and anthropogenic (e.g, deforestation, cropland expansion, and urbanization) have greatly altered carbon production, stocks, decomposition, movement and export from land to river and ocean systems. However, the magnitude and spatiotemporal patterns of lateral carbon fluxes from land to oceans and the underlying mechanisms responsible for these fluxes remain far from certain. Here we applied a process-based land model with explicit representation of carbon processes in stream and rivers (Dynamic Land Ecosystem Model: DLEM 2.0) to examine how changes in climate, land use, atmospheric CO2, and nitrogen deposition have affected the carbon fluxes from North American continent to Ocean during 1980-2015. Our simulated results indicated that terrestrial carbon export shows substantially spatial and temporal variability. Of the five sub-regions (Arctic coast, Pacific coast, Gulf of Mexico, Atlantic coast, and Great lakes), the Arctic sub-region provides the highest DOC flux, whereas the Gulf of Mexico sub-region provided the highest DIC flux. However, terrestrial carbon export to the arctic oceans showed increasing trends for both DOC and DIC, whereas DOC and DIC export to the Gulf of Mexico decreased in the recent decades. Future pattern of riverine carbon fluxes would be largely dependent on the climate change and land use scenarios.

  12. Time series measurements of carbon fluxes from a mangrove-dominated estuary

    Science.gov (United States)

    Volta, C.; Ho, D. T.; Friederich, G.; Del Castillo, C. E.; Engel, V. C.; Bhat, M.

    2017-12-01

    Mangrove ecosystems are among the most important and productive coastal ecosystems globally, and due to their high productivity and rapid carbon cycling, these ecosystems are important modulators of carbon fluxes from the land to the ocean and between the water and the atmosphere. Therefore, they may play a crucial role in the global carbon cycle and climate. Nonetheless, to date, estimates of carbon fluxes in mangrove-dominated estuaries are associated with large uncertainties, because studies have typically focused on limited spatial and temporal scales. For the first time, continuous time series measurements of temperature, salinity, CDOM, pH and pCO2 covering both the dry and the wet seasons were made in Shark River, a tidal estuary in the largest contiguous mangrove forest in North America. The measurements were made at two permanent stations along the estuarine domain, and allowed estimates of net dissolved carbon export from the Shark River to the Gulf of Mexico, as well as the CO2 emissions to the atmosphere to be made at seasonal and annual timescales. Results reveal that, compared to the dry season, the wet season was characterized by higher dissolved carbon export and CO2 emissions, due to meteorological, hydrological, and biogeochemical processes. Additionally, an analysis of relationships between hydrodynamic control factors (i.e. water discharge and water level) in the upstream freshwater marsh and carbon fluxes in the Shark River highlighted the importance of developing good water management strategies in the future. Finally, the study estimated the social cost of carbon fluxes in the Shark River estuary as a contribution to carbon accounting in mangrove ecosystems.

  13. Growth of carbon nanocone arrays on a metal catalyst: The effect of carbon flux ionization

    International Nuclear Information System (INIS)

    Levchenko, I.; Khachan, J.; Vladimirov, S. V.; Ostrikov, K.

    2008-01-01

    The growth of carbon nanocone arrays on metal catalyst particles by deposition from a low-temperature plasma is studied by multiscale Monte Carlo/surface diffusion numerical simulation. It is demonstrated that the variation in the degree of ionization of the carbon flux provides an effective control of the growth kinetics of the carbon nanocones, and leads to the formation of more uniform arrays of nanostructures. In the case of zero degree of ionization (neutral gas process), a width of the distribution of nanocone heights reaches 360 nm with the nanocone mean height of 150 nm. When the carbon flux of 75% ionization is used, the width of the distribution of nanocone heights decreases to 100 nm, i.e., by a factor of 3.6. A higher degree of ionization leads to a better uniformity of the metal catalyst saturation and the nanocone growth, thus contributing to the formation of more height-uniform arrays of carbon nanostructures.

  14. Oxyanion flux characterization using passive flux meters: Development and field testing of surfactant-modified granular activated carbon

    Science.gov (United States)

    Lee, Jimi; Rao, P. S. C.; Poyer, Irene C.; Toole, Robyn M.; Annable, M. D.; Hatfield, K.

    2007-07-01

    We report here on the extension of Passive Flux Meter (PFM) applications for measuring fluxes of oxyanions in groundwater, and present results for laboratory and field studies. Granular activated carbon, with and without impregnated silver (GAC and SI-GAC, respectively), was modified with a cationic surfactant, hexadecyltrimethylammonium (HDTMA), to enhance the anion exchange capacity (AEC). Langmuir isotherm sorption maxima for oxyanions measured in batch experiments were in the following order: perchlorate >> chromate > selenate, consistent with their selectivity. Linear sorption isotherms for several alcohols suggest that surfactant modification of GAC and SI-GAC reduced (˜ 30-45%) sorption of alcohols by GAC. Water and oxyanion fluxes (perchlorate and chromate) measured by deploying PFMs packed with surfactant-modified GAC (SM-GAC) or surfactant-modified, silver-impregnated GAC (SM-SI-GAC) in laboratory flow chambers were in close agreement with the imposed fluxes. The use of SM-SI-GAC as a PFM sorbent was evaluated at a field site with perchlorate contamination of a shallow unconfined aquifer. PFMs packed with SM-SI-GAC were deployed in three existing monitoring wells with a perchlorate concentration range of ˜ 2.5 to 190 mg/L. PFM-measured, depth-averaged, groundwater fluxes ranged from 1.8 to 7.6 cm/day, while depth-averaged perchlorate fluxes varied from 0.22 to 1.7 g/m 2/day. Groundwater and perchlorate flux distributions measured in two PFM deployments closely matched each other. Depth-averaged Darcy fluxes measured with PFMs were in line with an estimate from a borehole dilution test, but much smaller than those based on hydraulic conductivity and head gradients; this is likely due to flow divergence caused by well-screen clogging. Flux-averaged perchlorate concentrations measured with PFM deployments matched concentrations in groundwater samples taken from one well, but not in two other wells, pointing to the need for additional field testing. Use of

  15. The impact of biosolids application on organic carbon and carbon dioxide fluxes in soil.

    Science.gov (United States)

    Wijesekara, Hasintha; Bolan, Nanthi S; Thangavel, Ramesh; Seshadri, Balaji; Surapaneni, Aravind; Saint, Christopher; Hetherington, Chris; Matthews, Peter; Vithanage, Meththika

    2017-12-01

    A field study was conducted on two texturally different soils to determine the influences of biosolids application on selected soil chemical properties and carbon dioxide fluxes. Two sites, located in Manildra (clay loam) and Grenfell (sandy loam), in Australia, were treated at a single level of 70 Mg ha -1 biosolids. Soil samples were analyzed for SOC fractions, including total organic carbon (TOC), labile, and non-labile carbon contents. The natural abundances of soil δ 13 C and δ 15 N were measured as isotopic tracers to fingerprint carbon derived from biosolids. An automated soil respirometer was used to measure in-situ diurnal CO 2 fluxes, soil moisture, and temperature. Application of biosolids increased the surface (0-15 cm) soil TOC by > 45% at both sites, which was attributed to the direct contribution from residual carbon in the biosolids and also from the increased biomass production. At both sites application of biosolids increased the non-labile carbon fraction that is stable against microbial decomposition, which indicated the soil carbon sequestration potential of biosolids. Soils amended with biosolids showed depleted δ 13 C, and enriched δ 15 N indicating the accumulation of biosolids residual carbon in soils. The in-situ respirometer data demonstrated enhanced CO 2 fluxes at the sites treated with biosolids, indicating limited carbon sequestration potential. However, addition of biosolids on both the clay loam and sandy loam soils found to be effective in building SOC than reducing it. Soil temperature and CO 2 fluxes, indicating that temperature was more important for microbial degradation of carbon in biosolids than soil moisture. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. Increased terrestrial to ocean sediment and carbon fluxes in the northern Chesapeake Bay associated with twentieth century land alteration

    Science.gov (United States)

    Saenger, C.; Cronin, T. M.; Willard, D.; Halka, J.; Kerhin, R.

    2008-01-01

    We calculated Chesapeake Bay (CB) sediment and carbon fluxes before and after major anthropogenic land clearance using robust monitoring, modeling and sedimentary data. Four distinct fluxes in the estuarine system were considered including (1) the flux of eroded material from the watershed to streams, (2) the flux of suspended sediment at river fall lines, (3) the burial flux in tributary sediments, and (4) the burial flux in main CB sediments. The sedimentary maximum in Ambrosia (ragweed) pollen marked peak land clearance (~1900 a.d.). Rivers feeding CB had a total organic carbon (TOC)/total suspended solids of 0.24??0.12, and we used this observation to calculate TOC fluxes from sediment fluxes. Sediment and carbon fluxes increased by 138-269% across all four regions after land clearance. Our results demonstrate that sediment delivery to CB is subject to significant lags and that excess post-land clearance sediment loads have not reached the ocean. Post-land clearance increases in erosional flux from watersheds, and burial in estuaries are important processes that must be considered to calculate accurate global sediment and carbon budgets. ?? 2008 Coastal and Estuarine Research Federation.

  17. How can mountaintop CO2 observations be used to constrain regional carbon fluxes?

    Science.gov (United States)

    Lin, John C.; Mallia, Derek V.; Wu, Dien; Stephens, Britton B.

    2017-05-01

    Despite the need for researchers to understand terrestrial biospheric carbon fluxes to account for carbon cycle feedbacks and predict future CO2 concentrations, knowledge of these fluxes at the regional scale remains poor. This is particularly true in mountainous areas, where complex meteorology and lack of observations lead to large uncertainties in carbon fluxes. Yet mountainous regions are often where significant forest cover and biomass are found - i.e., areas that have the potential to serve as carbon sinks. As CO2 observations are carried out in mountainous areas, it is imperative that they are properly interpreted to yield information about carbon fluxes. In this paper, we present CO2 observations at three sites in the mountains of the western US, along with atmospheric simulations that attempt to extract information about biospheric carbon fluxes from the CO2 observations, with emphasis on the observed and simulated diurnal cycles of CO2. We show that atmospheric models can systematically simulate the wrong diurnal cycle and significantly misinterpret the CO2 observations, due to erroneous atmospheric flows as a result of terrain that is misrepresented in the model. This problem depends on the selected vertical level in the model and is exacerbated as the spatial resolution is degraded, and our results indicate that a fine grid spacing of ˜ 4 km or less may be needed to simulate a realistic diurnal cycle of CO2 for sites on top of the steep mountains examined here in the American Rockies. In the absence of higher resolution models, we recommend coarse-scale models to focus on assimilating afternoon CO2 observations on mountaintop sites over the continent to avoid misrepresentations of nocturnal transport and influence.

  18. Thermodynamic Cconstraints on Coupled Carbonate-Pyrite Weathering Dynamics and Carbon Fluxes

    Science.gov (United States)

    Winnick, M.; Maher, K.

    2017-12-01

    Chemical weathering within the critical zone regulates global biogeochemical cycles, atmospheric composition, and the supply of key nutrients to terrestrial and aquatic ecosystems. Recent studies suggest that thermodynamic limits on solute production act as a first-order control on global chemical weathering rates; however, few studies have addressed the factors that set these thermodynamic limits in natural systems. In this presentation, we investigate the effects of soil CO2 concentrations and pyrite oxidation rates on carbonate dissolution and associated carbon fluxes in the East River watershed in Colorado, using concentration-discharge relationships and thermodynamic constraints. Within the shallow subsurface, soil respiration rates and moisture content determine the extent of carbonic acid-promoted carbonate dissolution through their modulation of soil pCO2 and the balance of open- v. closed-system weathering processes. At greater depths, pyrite oxidation generates sulfuric acid, which alters the approach to equilibrium of infiltrating waters. Through comparisons of concentration-discharge data and reactive transport model simulations, we explore the conditions that determine whether sulfuric acid reacts to dissolve additional carbonate mineral or instead reacts with alkalinity already in solution - the balance of which determines watershed carbon flux budgets. Our study highlights the importance of interactions between the chemical structure of the critical zone and the hydrologic regulation of flowpaths in determining concentration-discharge relationships and overall carbon fluxes.

  19. Steel slag carbonation in a flow-through reactor system: the role of fluid-flux.

    Science.gov (United States)

    Berryman, Eleanor J; Williams-Jones, Anthony E; Migdisov, Artashes A

    2015-01-01

    Steel production is currently the largest industrial source of atmospheric CO2. As annual steel production continues to grow, the need for effective methods of reducing its carbon footprint increases correspondingly. The carbonation of the calcium-bearing phases in steel slag generated during basic oxygen furnace (BOF) steel production, in particular its major constituent, larnite {Ca2SiO4}, which is a structural analogue of olivine {(MgFe)2SiO4}, the main mineral subjected to natural carbonation in peridotites, offers the potential to offset some of these emissions. However, the controls on the nature and efficiency of steel slag carbonation are yet to be completely understood. Experiments were conducted exposing steel slag grains to a CO2-H2O mixture in both batch and flow-through reactors to investigate the impact of temperature, fluid flux, and reaction gradient on the dissolution and carbonation of steel slag. The results of these experiments show that dissolution and carbonation of BOF steel slag are more efficient in a flow-through reactor than in the batch reactors used in most previous studies. Moreover, they show that fluid flux needs to be optimized in addition to grain size, pressure, and temperature, in order to maximize the efficiency of carbonation. Based on these results, a two-stage reactor consisting of a high and a low fluid-flux chamber is proposed for CO2 sequestration by steel slag carbonation, allowing dissolution of the slag and precipitation of calcium carbonate to occur within a single flow-through system. Copyright © 2014. Published by Elsevier B.V.

  20. 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

  1. 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.

  2. Changes in ocean circulation and carbon storage are decoupled from air-sea CO2 fluxes

    OpenAIRE

    A. Gnanadesikan; I. Marinov

    2010-01-01

    The spatial distribution of the air-sea flux of carbon dioxide is a poor indicator of the underlying ocean circulation and of ocean carbon storage. The weak dependence on circulation arises because mixing-driven changes in solubility-driven and biologically-driven air-sea fluxes largely cancel out. This cancellation occurs because mixing driven increases in the poleward residual mean circulation results in more transport of both remineralized nutrients and heat from low to high latitudes. By ...

  3. Carbon-carbon composite and copper-composite bond damages for high flux component controlled fusion

    International Nuclear Information System (INIS)

    Chevet, G.

    2010-01-01

    Plasma facing components constitute the first wall in contact with plasma in fusion machines such as Tore Supra and ITER. These components have to sustain high heat flux and consequently elevated temperatures. They are made up of an armour material, the carbon-carbon composite, a heat sink structure material, the copper chromium zirconium, and a material, the OFHC copper, which is used as a compliant layer between the carbon-carbon composite and the copper chromium zirconium. Using different materials leads to the apparition of strong residual stresses during manufacturing, because of the thermal expansion mismatch between the materials, and compromises the lasting operation of fusion machines as damage which appeared during manufacturing may propagate. The objective of this study is to understand the damage mechanisms of the carbon-carbon composite and the composite-copper bond under solicitations that plasma facing components may suffer during their life. The mechanical behaviours of carbon-carbon composite and composite-copper bond were studied in order to define the most suitable models to describe these behaviours. With these models, thermomechanical calculations were performed on plasma facing components with the finite element code Cast3M. The manufacturing of the components induces high stresses which damage the carbon-carbon composite and the composite-copper bond. The damage propagates during the cooling down to room temperature and not under heat flux. Alternative geometries for the plasma facing components were studied to reduce damage. The relation between the damage of the carbon-carbon composite and its thermal conductivity was also demonstrated. (author) [fr

  4. 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

  5. A regional high-resolution carbon flux inversion of North America for 2004

    Science.gov (United States)

    Schuh, A. E.; Denning, A. S.; Corbin, K. D.; Baker, I. T.; Uliasz, M.; Parazoo, N.; Andrews, A. E.; Worthy, D. E. J.

    2010-05-01

    Resolving the discrepancies between NEE estimates based upon (1) ground studies and (2) atmospheric inversion results, demands increasingly sophisticated techniques. In this paper we present a high-resolution inversion based upon a regional meteorology model (RAMS) and an underlying biosphere (SiB3) model, both running on an identical 40 km grid over most of North America. Current operational systems like CarbonTracker as well as many previous global inversions including the Transcom suite of inversions have utilized inversion regions formed by collapsing biome-similar grid cells into larger aggregated regions. An extreme example of this might be where corrections to NEE imposed on forested regions on the east coast of the United States might be the same as that imposed on forests on the west coast of the United States while, in reality, there likely exist subtle differences in the two areas, both natural and anthropogenic. Our current inversion framework utilizes a combination of previously employed inversion techniques while allowing carbon flux corrections to be biome independent. Temporally and spatially high-resolution results utilizing biome-independent corrections provide insight into carbon dynamics in North America. In particular, we analyze hourly CO2 mixing ratio data from a sparse network of eight towers in North America for 2004. A prior estimate of carbon fluxes due to Gross Primary Productivity (GPP) and Ecosystem Respiration (ER) is constructed from the SiB3 biosphere model on a 40 km grid. A combination of transport from the RAMS and the Parameterized Chemical Transport Model (PCTM) models is used to forge a connection between upwind biosphere fluxes and downwind observed CO2 mixing ratio data. A Kalman filter procedure is used to estimate weekly corrections to biosphere fluxes based upon observed CO2. RMSE-weighted annual NEE estimates, over an ensemble of potential inversion parameter sets, show a mean estimate 0.57 Pg/yr sink in North America

  6. Tree age, disturbance history, and carbon stocks and fluxes in subalpine Rocky Mountain forests

    Science.gov (United States)

    J.B. Bradford; R.A. Birdsey; L.A. Joyce; M.G. Ryan

    2008-01-01

    Forest carbon stocks and fluxes vary with forest age, and relationships with forest age are often used to estimate fluxes for regional or national carbon inventories. Two methods are commonly used to estimate forest age: observed tree age or time since a known disturbance. To clarify the relationships between tree age, time since disturbance and forest carbon storage...

  7. Changes in ocean circulation and carbon storage are decoupled from air-sea CO2 fluxes

    Directory of Open Access Journals (Sweden)

    A. Gnanadesikan

    2011-02-01

    Full Text Available The spatial distribution of the air-sea flux of carbon dioxide is a poor indicator of the underlying ocean circulation and of ocean carbon storage. The weak dependence on circulation arises because mixing-driven changes in solubility-driven and biologically-driven air-sea fluxes largely cancel out. This cancellation occurs because mixing driven increases in the poleward residual mean circulation result in more transport of both remineralized nutrients and heat from low to high latitudes. By contrast, increasing vertical mixing decreases the storage associated with both the biological and solubility pumps, as it decreases remineralized carbon storage in the deep ocean and warms the ocean as a whole.

  8. Bioavailable dissolved and particulate organic carbon flux from coastal temperate rainforest watersheds

    Science.gov (United States)

    Fellman, J.; Hood, E. W.; D'Amore, D. V.; Moll, A.

    2017-12-01

    Coastal temperate rainforest (CTR) watersheds of southeast Alaska have dense soil carbon stocks ( 300 Mg C ha-1) and high specific discharge (1.5-7 m yr-1) driven by frontal storms from the Gulf of Alaska. As a result, dissolved organic carbon (DOC) fluxes from Alaskan CTR watersheds are estimated to exceed 2 Tg yr-1; however, little is known about the export of particulate organic carbon (POC). The magnitude and bioavailability of this land-to-ocean flux of terrigenous organic matter ultimately determines how much metabolic energy is translocated to downstream and coastal marine ecosystems in this region. We sampled streamwater weekly from May through October from four watersheds of varying landcover (gradient of wetland to glacial coverage) to investigate changes in the concentration and flux of DOC and POC exported to the coastal ocean. We also used headspace analysis of CO2 following 14 day laboratory incubations to determine the flux of bioavailable DOC and POC exported from CTR watersheds. Across all sites, bioavailable DOC concentrations ranged from 0.2 to 1.9 mg L-1 but were on average 0.6 mg L-1. For POC, bioavailable concentrations ranged from below detection to 0.3 mg L-1 but were on average 0.1 mg L-1. The concentration, flux and bioavailability of DOC was higher than for POC highlighting the potential importance of DOC as a metabolic subsidy to downstream and coastal environments. Ratios of DOC to POC decreased during high flow events because the increase in POC concentrations with discharge exceeds that for DOC. Overall, our findings suggest that projected increases in precipitation and storm intensity will drive changes in the speciation, magnitude and bioavailability of the organic carbon flux from CTR watersheds.

  9. The "Carbon Data Explorer": Web-Based Space-Time Visualization of Modeled Carbon Fluxes

    Science.gov (United States)

    Billmire, M.; Endsley, K. A.

    2014-12-01

    The visualization of and scientific "sense-making" from large datasets varying in both space and time is a challenge; one that is still being addressed in a number of different fields. The approaches taken thus far are often specific to a given academic field due to the unique questions that arise in different disciplines, however, basic approaches such as geographic maps and time series plots are still widely useful. The proliferation of model estimates of increasing size and resolution further complicates what ought to be a simple workflow: Model some geophysical phenomen(on), obtain results and measure uncertainty, organize and display the data, make comparisons across trials, and share findings. A new tool is in development that is intended to help scientists with the latter parts of that workflow. The tentatively-titled "Carbon Data Explorer" (http://spatial.mtri.org/flux-client/) enables users to access carbon science and related spatio-temporal science datasets over the web. All that is required to access multiple interactive visualizations of carbon science datasets is a compatible web browser and an internet connection. While the application targets atmospheric and climate science datasets, particularly spatio-temporal model estimates of carbon products, the software architecture takes an agnostic approach to the data to be visualized. Any atmospheric, biophysical, or geophysical quanity that varies in space and time, including one or more measures of uncertainty, can be visualized within the application. Within the web application, users have seamless control over a flexible and consistent symbology for map-based visualizations and plots. Where time series data are represented by one or more data "frames" (e.g. a map), users can animate the data. In the "coordinated view," users can make direct comparisons between different frames and different models or model runs, facilitating intermodal comparisons and assessments of spatio-temporal variability. Map

  10. Soil fluxes of carbonyl sulfide (COS), carbon monoxide, and carbon dioxide in a boreal forest in southern Finland

    Science.gov (United States)

    Sun, Wu; Kooijmans, Linda M. J.; Maseyk, Kadmiel; Chen, Huilin; Mammarella, Ivan; Vesala, Timo; Levula, Janne; Keskinen, Helmi; Seibt, Ulli

    2018-02-01

    Soil is a major contributor to the biosphere-atmosphere exchange of carbonyl sulfide (COS) and carbon monoxide (CO). COS is a tracer with which to quantify terrestrial photosynthesis based on the coupled leaf uptake of COS and CO2, but such use requires separating soil COS flux, which is unrelated to photosynthesis, from ecosystem COS uptake. For CO, soil is a significant natural sink that influences the tropospheric CO budget. In the boreal forest, magnitudes and variabilities of soil COS and CO fluxes remain poorly understood. We measured hourly soil fluxes of COS, CO, and CO2 over the 2015 late growing season (July to November) in a Scots pine forest in Hyytiälä, Finland. The soil acted as a net sink of COS and CO, with average uptake rates around 3 pmol m-2 s-1 for COS and 1 nmol m-2 s-1 for CO. Soil respiration showed seasonal dynamics controlled by soil temperature, peaking at around 4 µmol m-2 s-1 in late August and September and dropping to 1-2 µmol m-2 s-1 in October. In contrast, seasonal variations of COS and CO fluxes were weak and mainly driven by soil moisture changes through diffusion limitation. COS and CO fluxes did not appear to respond to temperature variation, although they both correlated well with soil respiration in specific temperature bins. However, COS : CO2 and CO : CO2 flux ratios increased with temperature, suggesting possible shifts in active COS- and CO-consuming microbial groups. Our results show that soil COS and CO fluxes do not have strong variations over the late growing season in this boreal forest and can be represented with the fluxes during the photosynthetically most active period. Well-characterized and relatively invariant soil COS fluxes strengthen the case for using COS as a photosynthetic tracer in boreal forests.

  11. Changes to the Carbon and Energy fluxes in a Northern Peatland with Thawing Permafrost

    Science.gov (United States)

    Harder, S. R.; Roulet, N. T.; Crill, P. M.; Strachan, I. B.

    2017-12-01

    The maintenance of thaw of high carbon density landscapes in the permafrost region ultimately depends of how the energy balance is partitioned as temperatures and precipitation change, yet there are comparatively few energy balance studies, especially in peatlands that contain permafrost. While permafrost peatlands are currently net sinks of carbon, as Arctic temperatures rise and permafrost thaws, the future of these ecosystems and their capacity for carbon uptake is in question. Since 2012 we have been measuring the spatially integrated CO2, energy and water vapour fluxes from the Stordalen peatland (68°22'N, 19°03'E) using eddy covariance (EC). The Stordalen peatland is a heterogeneous peatland in the discontinuous permafrost zone where permafrost thaw is actively occurring, resulting in large changes to the landscape from year to year. Areas where permafrost is present are elevated by up to 1.5 m compared to the areas where permafrost has thawed causing differences in water table depth, peat temperatures, snow distribution, vegetation community and therefore in the carbon and energy fluxes. Our EC tower is located on the edge of a permafrost peat plateau (or palsa) where one fetch measures fluxes from an area underlain by permafrost and the other fetch sees the portion of the peatland where the permafrost has thawed. Within each sector, we have an array of soil temperature and water content sensors to determine the physical characteristics of each fetch. Extensive vegetation surveys (based on plant functional types or PFTs) have also been conducted to run a footprint analysis on the flux data to complete a comparative analysis of the magnitude and variability of the carbon and energy exchanges from PFT. The footprint analysis allows us to explain the difference in energy and carbon fluxes by examining the ecological, biogeochemical and physical characteristics within each footprint. We see distinctly different energy partitioning between the fetches

  12. Southern Ocean Carbon Dioxide and Oxygen Fluxes Detected by SOCCOM Biogeochemical Profiling Floats

    Science.gov (United States)

    Sarmiento, J. L.; Bushinksy, S.; Gray, A. R.

    2016-12-01

    The Southern Ocean is known to play an important role in the global carbon cycle, yet historically our measurements of this remote region have been sparse and heavily biased towards summer. Here we present new estimates of air-sea fluxes of carbon dioxide and oxygen calculated with measurements from autonomous biogeochemical profiling floats. At high latitudes in and southward of the Antarctic Circumpolar Current, we find a significant flux of CO2 from the ocean to the atmosphere during 2014-2016, which is particularly enhanced during winter months. These results suggest that previous estimates may be biased towards stronger Southern Ocean CO2 uptake due to undersampling in winter. We examine various implications of having a source of CO2 that is higher than previous estimates. We also find that CO2:O2 flux ratios north of the Subtropical Front are positive, consistent with the fluxes being driven by changes in solubility, while south of the Polar Front biological processes and upwelling of deep water combine to produce a negative CO2:O2 flux ratio.

  13. 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.

  14. Pyroclastic Eruption Boosts Organic Carbon Fluxes Into Patagonian Fjords

    Science.gov (United States)

    Mohr, Christian H.; Korup, Oliver; Ulloa, Héctor; Iroumé, Andrés.

    2017-11-01

    Fjords and old-growth forests store large amounts of organic carbon. Yet the role of episodic disturbances, particularly volcanic eruptions, in mobilizing organic carbon in fjord landscapes covered by temperate rainforests remains poorly quantified. To this end, we estimated how much wood and soils were flushed to nearby fjords following the 2008 eruption of Chaitén volcano in south-central Chile, where pyroclastic sediments covered >12 km2 of pristine temperate rainforest. Field-based surveys of forest biomass, soil organic content, and dead wood transport reveal that the reworking of pyroclastic sediments delivered 66,500 + 14,600/-14,500 tC of large wood to two rivers entering the nearby Patagonian fjords in less than a decade. A similar volume of wood remains in dead tree stands and buried beneath pyroclastic deposits ( 79,900 + 21,100/-16,900 tC) or stored in active river channels (5,900-10,600 tC). We estimate that bank erosion mobilized 132,300+21,700/-30,600 tC of floodplain forest soil. Eroded and reworked forest soils have been accreting on coastal river deltas at >5 mm yr-1 since the eruption. While much of the large wood is transported out of the fjord by long-shore drift, the finer fraction from eroded forest soils is likely to be buried in the fjords. We conclude that the organic carbon fluxes boosted by rivers adjusting to high pyroclastic sediment loads may remain elevated for up to a decade and that Patagonian temperate rainforests disturbed by excessive loads of pyroclastic debris can be episodic short-lived carbon sources.

  15. High-flux water desalination with interfacial salt sieving effect in nanoporous carbon composite membranes

    KAUST Repository

    Chen, Wei; Chen, Shuyu; Liang, Tengfei; Zhang, Qiang; Fan, Zhongli; Yin, Hang; Huang, Kuo-Wei; Zhang, Xixiang; Lai, Zhiping; Sheng, Ping

    2018-01-01

    Freshwater flux and energy consumption are two important benchmarks for the membrane desalination process. Here, we show that nanoporous carbon composite membranes, which comprise a layer of porous carbon fibre structures grown on a porous ceramic

  16. Methane Flux and Authigenic Carbonate in Shallow Sediments Overlying Methane Hydrate Bearing Strata in Alaminos Canyon, Gulf of Mexico

    Directory of Open Access Journals (Sweden)

    Joseph P. Smith

    2014-09-01

    Full Text Available In June 2007 sediment cores were collected in Alaminos Canyon, Gulf of Mexico across a series of seismic data profiles indicating rapid transitions between the presence of methane hydrates and vertical gas flux. Vertical profiles of dissolved sulfate, chloride, calcium, magnesium, and dissolved inorganic carbon (DIC concentrations in porewaters, headspace methane, and solid phase carbonate concentrations were measured at each core location to investigate the cycling of methane-derived carbon in shallow sediments overlying the hydrate bearing strata. When integrated with stable carbon isotope ratios of DIC, geochemical results suggest a significant fraction of the methane flux at this site is cycled into the inorganic carbon pool. The incorporation of methane-derived carbon into dissolved and solid inorganic carbon phases represents a significant sink in local carbon cycling and plays a role in regulating the flux of methane to the overlying water column at Alaminos Canyon. Targeted, high-resolution geochemical characterization of the biogeochemical cycling of methane-derived carbon in shallow sediments overlying hydrate bearing strata like those in Alaminos Canyon is critical to quantifying methane flux and estimating methane hydrate distributions in gas hydrate bearing marine sediments.

  17. The interaction of the flux errors and transport errors in modeled atmospheric carbon dioxide concentrations

    Science.gov (United States)

    Feng, S.; Lauvaux, T.; Butler, M. P.; Keller, K.; Davis, K. J.; Jacobson, A. R.; Schuh, A. E.; Basu, S.; Liu, J.; Baker, D.; Crowell, S.; Zhou, Y.; Williams, C. A.

    2017-12-01

    Regional estimates of biogenic carbon fluxes over North America from top-down atmospheric inversions and terrestrial biogeochemical (or bottom-up) models remain inconsistent at annual and sub-annual time scales. While top-down estimates are impacted by limited atmospheric data, uncertain prior flux estimates and errors in the atmospheric transport models, bottom-up fluxes are affected by uncertain driver data, uncertain model parameters and missing mechanisms across ecosystems. This study quantifies both flux errors and transport errors, and their interaction in the CO2 atmospheric simulation. These errors are assessed by an ensemble approach. The WRF-Chem model is set up with 17 biospheric fluxes from the Multiscale Synthesis and Terrestrial Model Intercomparison Project, CarbonTracker-Near Real Time, and the Simple Biosphere model. The spread of the flux ensemble members represents the flux uncertainty in the modeled CO2 concentrations. For the transport errors, WRF-Chem is run using three physical model configurations with three stochastic perturbations to sample the errors from both the physical parameterizations of the model and the initial conditions. Additionally, the uncertainties from boundary conditions are assessed using four CO2 global inversion models which have assimilated tower and satellite CO2 observations. The error structures are assessed in time and space. The flux ensemble members overall overestimate CO2 concentrations. They also show larger temporal variability than the observations. These results suggest that the flux ensemble is overdispersive. In contrast, the transport ensemble is underdispersive. The averaged spatial distribution of modeled CO2 shows strong positive biogenic signal in the southern US and strong negative signals along the eastern coast of Canada. We hypothesize that the former is caused by the 3-hourly downscaling algorithm from which the nighttime respiration dominates the daytime modeled CO2 signals and that the latter

  18. Water-carbon Links in a Tropical Forest: How Interbasin Groundwater Flow Affects Carbon Fluxes and Ecosystem Carbon Budgets

    Energy Technology Data Exchange (ETDEWEB)

    Genereux, David [North Carolina State Univ., Raleigh, NC (United States); Osburn, Christopher [North Carolina State Univ., Raleigh, NC (United States); Oberbauer, Steven [Florida Intl Univ., Miami, FL (United States); Oviedo Vargas, Diana [North Carolina State Univ., Raleigh, NC (United States); Dierick, Diego [Florida Intl Univ., Miami, FL (United States)

    2017-03-27

    This report covers the outcomes from a quantitative, interdisciplinary field investigation of how carbon fluxes and budgets in a lowland tropical rainforest are affected by the discharge of old regional groundwater into streams, springs, and wetlands in the forest. The work was carried out in a lowland rainforest of Costa Rica, at La Selva Biological Station. The research shows that discharge of regional groundwater high in dissolved carbon dioxide represents a significant input of carbon to the rainforest "from below", an input that is on average larger than the carbon input "from above" from the atmosphere. A stream receiving discharge of regional groundwater had greatly elevated emissions of carbon dioxide (but not methane) to the overlying air, and elevated downstream export of carbon from its watershed with stream flow. The emission of deep geological carbon dioxide from stream water elevates the carbon dioxide concentrations in air above the streams. Carbon-14 tracing revealed the presence of geological carbon in the leaves and stems of some riparian plants near streams that receive inputs of regional groundwater. Also, discharge of regional groundwater is responsible for input of dissolved organic matter with distinctive chemistry to rainforest streams and wetlands. The discharge of regional groundwater in lowland surface waters has a major impact on the carbon cycle in this and likely other tropical and non-tropical forests.

  19. A method for measuring element fluxes in an undisturbed soil: nitrogen and carbon from earthworms

    International Nuclear Information System (INIS)

    Bouche, M.B.

    1984-01-01

    Data on chemical cycles, as nitrogen or carbon cycles, are extrapolated to the fields or ecosystems without the possibility for checking conclusions; i.e. from scientific knowledge (para-ecology). A new method, by natural introduction of an earthworm compartment into an undisturbed soil, with earthworms labelled both by isotopes ( 15 N, 14 C) and by staining is described. This method allows us to measure fluxes of chemicals. The first results, gathered during the improvement of the method in partly artificial conditions, are cross-checked with other data given by direct observation in the field. Measured flux (2.2 mg N/g fresh mass empty gut/day/15 0 C) is far more important than para-ecological estimations; animal metabolism plays directly an important role in nitrogen and carbon cycles. (author)

  20. Measurement of boron and carbon fluxes in cosmic rays with the PAMELA experiment

    Energy Technology Data Exchange (ETDEWEB)

    Adriani, O.; Bongi, M. [Department of Physics and Astronomy, University of Florence, I-50019 Sesto Fiorentino, Florence (Italy); Barbarino, G. C. [Department of Physics, University of Naples " Federico II," I-80126 Naples (Italy); Bazilevskaya, G. A. [Lebedev Physical Institute, RU-119991 Moscow (Russian Federation); Bellotti, R.; Bruno, A. [Department of Physics, University of Bari, I-70126 Bari (Italy); Boezio, M.; Bonvicini, V.; Carbone, R. [INFN, Sezione di Trieste, I-34149 Trieste (Italy); Bogomolov, E. A. [Ioffe Physical Technical Institute, RU-194021 St. Petersburg (Russian Federation); Bottai, S. [INFN, Sezione di Florence, I-50019 Sesto Fiorentino, Florence (Italy); Cafagna, F. [INFN, Sezione di Bari, I-70126 Bari (Italy); Campana, D. [INFN, Sezione di Naples, I-80126 Naples (Italy); Carlson, P. [KTH, Department of Physics, and the Oskar Klein Centre for Cosmoparticle Physics, AlbaNova University Centre, SE-10691 Stockholm (Sweden); Casolino, M.; De Donato, C.; De Santis, C.; De Simone, N. [INFN, Sezione di Rome " Tor Vergata," I-00133 Rome (Italy); Castellini, G. [IFAC, I-50019 Sesto Fiorentino, Florence (Italy); Danilchenko, I. A. [National Research Nuclear University MEPhI, RU-115409 Moscow (Russian Federation); and others

    2014-08-20

    The propagation of cosmic rays inside our galaxy plays a fundamental role in shaping their injection spectra into those observed at Earth. One of the best tools to investigate this issue is the ratio of fluxes for secondary and primary species. The boron-to-carbon (B/C) ratio, in particular, is a sensitive probe to investigate propagation mechanisms. This paper presents new measurements of the absolute fluxes of boron and carbon nuclei as well as the B/C ratio from the PAMELA space experiment. The results span the range 0.44-129 GeV/n in kinetic energy for data taken in the period 2006 July to 2008 March.

  1. CARBON STORAGE AND FLUXES IN PONDEROSA PINE AT DIFFERENT SUCCESSIONAL STAGES

    Science.gov (United States)

    We compared carbon storage and fluxes in young and old ponderosa pine stands in Oregon, including plant and soil storage, net primary productivity, respiration fluxes, and eddy flux estimates of net ecosystem exchange. The young site (Y site) was previously an old-growth pondero...

  2. Forest inventory-based estimation of carbon stocks and flux in California forests in 1990.

    Science.gov (United States)

    Jeremy S. Fried; Xiaoping. Zhou

    2008-01-01

    Estimates of forest carbon stores and flux for California circa 1990 were modeled from forest inventory data in support of California’s legislatively mandated greenhouse gas inventory. Reliable estimates of live-tree carbon stores and flux on timberlands outside of national forest could be calculated from periodic inventory data collected in the 1980s and 1990s;...

  3. Methane and carbon dioxide fluxes over a lake: comparison between eddy covariance, floating chambers and boundary layer method

    Directory of Open Access Journals (Sweden)

    K.-M. Erkkilä

    2018-01-01

    Full Text Available Freshwaters bring a notable contribution to the global carbon budget by emitting both carbon dioxide (CO2 and methane (CH4 to the atmosphere. Global estimates of freshwater emissions traditionally use a wind-speed-based gas transfer velocity, kCC (introduced by Cole and Caraco, 1998, for calculating diffusive flux with the boundary layer method (BLM. We compared CH4 and CO2 fluxes from BLM with kCC and two other gas transfer velocities (kTE and kHE, which include the effects of water-side cooling to the gas transfer besides shear-induced turbulence, with simultaneous eddy covariance (EC and floating chamber (FC fluxes during a 16-day measurement campaign in September 2014 at Lake Kuivajärvi in Finland. The measurements included both lake stratification and water column mixing periods. Results show that BLM fluxes were mainly lower than EC, with the more recent model kTE giving the best fit with EC fluxes, whereas FC measurements resulted in higher fluxes than simultaneous EC measurements. We highly recommend using up-to-date gas transfer models, instead of kCC, for better flux estimates. BLM CO2 flux measurements had clear differences between daytime and night-time fluxes with all gas transfer models during both stratified and mixing periods, whereas EC measurements did not show a diurnal behaviour in CO2 flux. CH4 flux had higher values in daytime than night-time during lake mixing period according to EC measurements, with highest fluxes detected just before sunset. In addition, we found clear differences in daytime and night-time concentration difference between the air and surface water for both CH4 and CO2. This might lead to biased flux estimates, if only daytime values are used in BLM upscaling and flux measurements in general. FC measurements did not detect spatial variation in either CH4 or CO2 flux over Lake Kuivajärvi. EC measurements, on the other hand, did not show any spatial variation in CH4 fluxes but did show a clear difference

  4. 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

  5. Response of carbon fluxes and climate to orbital forcing changes in the Community Climate System Model

    Science.gov (United States)

    Jochum, M.; Peacock, S.; Moore, J. K.; Lindsay, K. T.

    2009-12-01

    A global general circulation model coupled to an ocean ecosystem model is used to quantify the response of carbon fluxes and climate to changes in orbital forcing. Compared to the present-day simulation, the simulation with the Earth's orbital parameters from 115,000 years ago features significantly cooler northern high latitudes, but only moderately cooler southern high latitudes. This asymmetry is explained by a 30% reduction of the strength of the Atlantic Meridional Overturning Circulation that is caused by an increased Arctic sea-ice export and a resulting freshening of the North Atlantic. The strong northern high-latitude cooling and the direct insolation induced tropical warming lead to global shifts in precipitation and winds to the order of 10-20%. These climate shifts lead to regional differences in air-sea carbon fluxes of the same order. However, the differences in global net carbon fluxes are insignificant. This surprising result is due to several effects, two of which stand out: Firstly, colder sea surface temperature leads to a more effective solubility pump but also to increased sea-ice concentration which blocks air-sea exchange; and secondly, the weakening of Southern Ocean winds, which is predicted by some idealized studies, is small compared to its interannual variability.

  6. SIERRA-Flux: Measuring Regional Surface Fluxes of Carbon Dioxide, Methane, and Water Vapor from an Unmanned Aircraft System

    Science.gov (United States)

    Fladeland; Yates, Emma Louise; Bui, Thaopaul Van; Dean-Day, Jonathan; Kolyer, Richard

    2011-01-01

    The Eddy-Covariance Method for quantifying surface-atmosphere fluxes is a foundational technique for measuring net ecosystem exchange and validating regional-to-global carbon cycle models. While towers or ships are the most frequent platform for measuring surface-atmosphere exchange, experiments using aircraft for flux measurements have yielded contributions to several large-scale studies including BOREAS, SMACEX, RECAB by providing local-to-regional coverage beyond towers. The low-altitude flight requirements make airborne flux measurements particularly dangerous and well suited for unmanned aircraft.

  7. Tidal wetland fluxes of dissolved organic carbon and sediment at Browns Island, California: initial evaluation

    Science.gov (United States)

    Ganju, N.K.; Bergamaschi, B.; Schoellhamer, D.H.

    2003-01-01

    Carbon and sediment fluxes from tidal wetlands are of increasing concern in the Sacramento-San Joaquin River Delta (Delta), because of drinking water issues and habitat restoration efforts. Certain forms of dissolved organic carbon (DOC) react with disinfecting chemicals used to treat drinking water, to form disinfection byproducts (DBPs), some of which are potential carcinogens. The contribution of DBP precursors by tidal wetlands is unknown. Sediment transport to and from tidal wetlands determines the potential for marsh accretion, thereby affecting habitat formation.Water, carbon, and sediment flux were measured in the main channel of Browns Island, a tidal wetland located at the confluence of Suisun Bay and the Delta. In-situ instrumentation were deployed between May 3 and May 21, 2002. Water flux was measured using acoustic Doppler current profilers and the index-velocity method. DOC concentrations were measured using calibrated ultraviolet absorbance and fluorescence instruments. Suspended-sediment concentrations were measured using a calibrated nephelometric turbidity sensor. Tidally averaged water flux through the channel was dependent on water surface elevations in Suisun Bay. Strong westerly winds resulted in higher water surface elevations in the area east of Browns Island, causing seaward flow, while subsiding winds reversed this effect. Peak ebb flow transported 36% more water than peak flood flow, indicating an ebb-dominant system. DOC concentrations were affected strongly by porewater drainage from the banks of the channel. Peak DOC concentrations were observed during slack after ebb, when the most porewater drained into the channel. Suspended-sediment concentrations were controlled by tidal currents that mobilized sediment from the channel bed, and stronger tides mobilized more sediment than the weaker tides. Sediment was transported mainly to the island during the 2-week monitoring period, though short periods of export occurred during the spring

  8. Carbon dioxide flux measurements from a coastal Douglas-fir forest floor

    International Nuclear Information System (INIS)

    Drewitt, G.B.

    2002-01-01

    This thesis examined the process that affects the exchange of carbon between the soil and the atmosphere with particular attention to the large amounts of carbon stored in soils in the form of decaying organic matter. This forest floor measuring study was conducted in 2000 at a micro-meteorological tower flux site in a coastal temperature Douglas-fir forest. The measuring study involved half hourly measurements of both carbon dioxide and below-ground carbon dioxide storage. Measurements were taken at 6 locations between April and December to include a large portion of the growing season. Eddy covariance (EC) measurements of carbon dioxide flux above the forest floor over a two month period in the summer and the autumn were compared with forest floor measurements. Below-ground carbon dioxide mixing ratios of soil air were measured at 6 depths between 0.02 to 1 m using gas diffusion probes and a syringe sampling method. Maximum carbon dioxide fluxes measured by the soil chambers varied by a factor of 3 and a high spatial variability in soil carbon dioxide flux was noted. Forest floor carbon dioxide fluxes measured by each of the chambers indicated different sensitivities to soil temperature. Hysteresis in the flux temperature relationship over the year was evident. Reliable below-canopy EC measurements of the forest floor carbon dioxide flux were difficult to obtain because of the every low wind speeds below the forest canopy. The amount of carbon dioxde present in the soil increased rapidly with depth near the surface but less rapidly deeper in the soil. It was suggested that approximately half of the carbon dioxide produced below-ground comes from between the soil surface and the first 0.15 m of depth. Carbon dioxide fluxes from the floor of a Douglas-fir forest were found to be large compared to other, less productive ecosystems

  9. [Simulation of water and carbon fluxes in harvard forest area based on data assimilation method].

    Science.gov (United States)

    Zhang, Ting-Long; Sun, Rui; Zhang, Rong-Hua; Zhang, Lei

    2013-10-01

    Model simulation and in situ observation are the two most important means in studying the water and carbon cycles of terrestrial ecosystems, but have their own advantages and shortcomings. To combine these two means would help to reflect the dynamic changes of ecosystem water and carbon fluxes more accurately. Data assimilation provides an effective way to integrate the model simulation and in situ observation. Based on the observation data from the Harvard Forest Environmental Monitoring Site (EMS), and by using ensemble Kalman Filter algorithm, this paper assimilated the field measured LAI and remote sensing LAI into the Biome-BGC model to simulate the water and carbon fluxes in Harvard forest area. As compared with the original model simulated without data assimilation, the improved Biome-BGC model with the assimilation of the field measured LAI in 1998, 1999, and 2006 increased the coefficient of determination R2 between model simulation and flux observation for the net ecosystem exchange (NEE) and evapotranspiration by 8.4% and 10.6%, decreased the sum of absolute error (SAE) and root mean square error (RMSE) of NEE by 17.7% and 21.2%, and decreased the SAE and RMSE of the evapotranspiration by 26. 8% and 28.3%, respectively. After assimilated the MODIS LAI products of 2000-2004 into the improved Biome-BGC model, the R2 between simulated and observed results of NEE and evapotranspiration was increased by 7.8% and 4.7%, the SAE and RMSE of NEE were decreased by 21.9% and 26.3%, and the SAE and RMSE of evapotranspiration were decreased by 24.5% and 25.5%, respectively. It was suggested that the simulation accuracy of ecosystem water and carbon fluxes could be effectively improved if the field measured LAI or remote sensing LAI was integrated into the model.

  10. Observation-based modelling of permafrost carbon fluxes with accounting for deep carbon deposits and thermokarst activity

    Science.gov (United States)

    Schneider von Deimling, T.; Grosse, G.; Strauss, J.; Schirrmeister, L.; Morgenstern, A.; Schaphoff, S.; Meinshausen, M.; Boike, J.

    2015-06-01

    High-latitude soils store vast amounts of perennially frozen and therefore inert organic matter. With rising global temperatures and consequent permafrost degradation, a part of this carbon stock will become available for microbial decay and eventual release to the atmosphere. We have developed a simplified, two-dimensional multi-pool model to estimate the strength and timing of future carbon dioxide (CO2) and methane (CH4) fluxes from newly thawed permafrost carbon (i.e. carbon thawed when temperatures rise above pre-industrial levels). We have especially simulated carbon release from deep deposits in Yedoma regions by describing abrupt thaw under newly formed thermokarst lakes. The computational efficiency of our model allowed us to run large, multi-centennial ensembles under various scenarios of future warming to express uncertainty inherent to simulations of the permafrost carbon feedback. Under moderate warming of the representative concentration pathway (RCP) 2.6 scenario, cumulated CO2 fluxes from newly thawed permafrost carbon amount to 20 to 58 petagrams of carbon (Pg-C) (68% range) by the year 2100 and reach 40 to 98 Pg-C in 2300. The much larger permafrost degradation under strong warming (RCP8.5) results in cumulated CO2 release of 42 to 141 Pg-C and 157 to 313 Pg-C (68% ranges) in the years 2100 and 2300, respectively. Our estimates only consider fluxes from newly thawed permafrost, not from soils already part of the seasonally thawed active layer under pre-industrial climate. Our simulated CH4 fluxes contribute a few percent to total permafrost carbon release yet they can cause up to 40% of total permafrost-affected radiative forcing in the 21st century (upper 68% range). We infer largest CH4 emission rates of about 50 Tg-CH4 per year around the middle of the 21st century when simulated thermokarst lake extent is at its maximum and when abrupt thaw under thermokarst lakes is taken into account. CH4 release from newly thawed carbon in wetland

  11. Observation-based modelling of permafrost carbon fluxes with accounting for deep carbon deposits and thermokarst activity

    Directory of Open Access Journals (Sweden)

    T. Schneider von Deimling

    2015-06-01

    Full Text Available High-latitude soils store vast amounts of perennially frozen and therefore inert organic matter. With rising global temperatures and consequent permafrost degradation, a part of this carbon stock will become available for microbial decay and eventual release to the atmosphere. We have developed a simplified, two-dimensional multi-pool model to estimate the strength and timing of future carbon dioxide (CO2 and methane (CH4 fluxes from newly thawed permafrost carbon (i.e. carbon thawed when temperatures rise above pre-industrial levels. We have especially simulated carbon release from deep deposits in Yedoma regions by describing abrupt thaw under newly formed thermokarst lakes. The computational efficiency of our model allowed us to run large, multi-centennial ensembles under various scenarios of future warming to express uncertainty inherent to simulations of the permafrost carbon feedback. Under moderate warming of the representative concentration pathway (RCP 2.6 scenario, cumulated CO2 fluxes from newly thawed permafrost carbon amount to 20 to 58 petagrams of carbon (Pg-C (68% range by the year 2100 and reach 40 to 98 Pg-C in 2300. The much larger permafrost degradation under strong warming (RCP8.5 results in cumulated CO2 release of 42 to 141 Pg-C and 157 to 313 Pg-C (68% ranges in the years 2100 and 2300, respectively. Our estimates only consider fluxes from newly thawed permafrost, not from soils already part of the seasonally thawed active layer under pre-industrial climate. Our simulated CH4 fluxes contribute a few percent to total permafrost carbon release yet they can cause up to 40% of total permafrost-affected radiative forcing in the 21st century (upper 68% range. We infer largest CH4 emission rates of about 50 Tg-CH4 per year around the middle of the 21st century when simulated thermokarst lake extent is at its maximum and when abrupt thaw under thermokarst lakes is taken into account. CH4 release from newly thawed carbon in

  12. Climate Warming Can Increase Soil Carbon Fluxes Without Decreasing Soil Carbon Stocks in Boreal Forests

    Science.gov (United States)

    Ziegler, S. E.; Benner, R. H.; Billings, S. A.; Edwards, K. A.; Philben, M. J.; Zhu, X.; Laganiere, J.

    2016-12-01

    Ecosystem C fluxes respond positively to climate warming, however, the net impact of changing C fluxes on soil organic carbon (SOC) stocks over decadal scales remains unclear. Manipulative studies and global-scale observations have informed much of the existing knowledge of SOC responses to climate, providing insights on relatively short (e.g. days to years) and long (centuries to millennia) time scales, respectively. Natural climate gradient studies capture integrated ecosystem responses to climate on decadal time scales. Here we report the soil C reservoirs, fluxes into and out of those reservoirs, and the chemical composition of inputs and soil organic matter pools along a mesic boreal forest climate transect. The sites studied consist of similar forest composition, successional stage, and soil moisture but differ by 5.2°C mean annual temperature. Carbon fluxes through these boreal forest soils were greatest in the lowest latitude regions and indicate that enhanced C inputs can offset soil C losses with warming in these forests. Respiration rates increased by 55% and the flux of dissolved organic carbon from the organic to mineral soil horizons tripled across this climate gradient. The 2-fold increase in litterfall inputs to these soils coincided with a significant increase in the organic horizon C stock with warming, however, no significant difference in the surface mineral soil C stocks was observed. The younger mean age of the mineral soil C ( 70 versus 330 YBP) provided further evidence for the greater turnover of SOC in the warmer climate soils. In spite of these differences in mean radiocarbon age, mineral SOC exhibited chemical characteristics of highly decomposed material across all regions. In contrast with depth trends in soil OM diagenetic indices, diagenetic shifts with latitude were limited to increases in C:N and alkyl to O-alkyl ratios in the overlying organic horizons in the warmer relative to the colder regions. These data indicate that the

  13. Metabolic Flux Analysis of Shewanella spp. Reveals Evolutionary Robustness in Central Carbon Metabolism

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Yinjie J.; Martin, Hector Garcia; Dehal, Paramvir S.; Deutschbauer, Adam; Llora, Xavier; Meadows, Adam; Arkin, Adam; Keasling, Jay D.

    2009-08-19

    Shewanella spp. are a group of facultative anaerobic bacteria widely distributed in marine and fresh-water environments. In this study, we profiled the central metabolic fluxes of eight recently sequenced Shewanella species grown under the same condition in minimal med-ium with [3-13C] lactate. Although the tested Shewanella species had slightly different growth rates (0.23-0.29 h31) and produced different amounts of acetate and pyruvate during early exponential growth (pseudo-steady state), the relative intracellular metabolic flux distributions were remarkably similar. This result indicates that Shewanella species share similar regulation in regard to central carbon metabolic fluxes under steady growth conditions: the maintenance of metabolic robustness is not only evident in a single species under genetic perturbations (Fischer and Sauer, 2005; Nat Genet 37(6):636-640), but also observed through evolutionary related microbial species. This remarkable conservation of relative flux profiles through phylogenetic differences prompts us to introduce the concept of metabotype as an alternative scheme to classify microbial fluxomics. On the other hand, Shewanella spp. display flexibility in the relative flux profiles when switching their metabolism from consuming lactate to consuming pyruvate and acetate.

  14. Interannual variation of carbon fluxes from three contrasting evergreen forests: the role of forest dynamics and climate.

    Science.gov (United States)

    Sierra, Carlos A; Loescher, Henry W; Harmon, Mark E; Richardson, Andrew D; Hollinger, David Y; Perakis, Steven S

    2009-10-01

    Interannual variation of carbon fluxes can be attributed to a number of biotic and abiotic controls that operate at different spatial and temporal scales. Type and frequency of disturbance, forest dynamics, and climate regimes are important sources of variability. Assessing the variability of carbon fluxes from these specific sources can enhance the interpretation of past and current observations. Being able to separate the variability caused by forest dynamics from that induced by climate will also give us the ability to determine if the current observed carbon fluxes are within an expected range or whether the ecosystem is undergoing unexpected change. Sources of interannual variation in ecosystem carbon fluxes from three evergreen ecosystems, a tropical, a temperate coniferous, and a boreal forest, were explored using the simulation model STANDCARB. We identified key processes that introduced variation in annual fluxes, but their relative importance differed among the ecosystems studied. In the tropical site, intrinsic forest dynamics contributed approximately 30% of the total variation in annual carbon fluxes. In the temperate and boreal sites, where many forest processes occur over longer temporal scales than those at the tropical site, climate controlled more of the variation among annual fluxes. These results suggest that climate-related variability affects the rates of carbon exchange differently among sites. Simulations in which temperature, precipitation, and radiation varied from year to year (based on historical records of climate variation) had less net carbon stores than simulations in which these variables were held constant (based on historical records of monthly average climate), a result caused by the functional relationship between temperature and respiration. This suggests that, under a more variable temperature regime, large respiratory pulses may become more frequent and high enough to cause a reduction in ecosystem carbon stores. Our results

  15. Interannual variation of carbon fluxes from three contrasting evergreen forests: The role of forest dynamics and climate

    Science.gov (United States)

    Sierra, C.A.; Loescher, H.W.; Harmon, M.E.; Richardson, A.D.; Hollinger, D.Y.; Perakis, S.S.

    2009-01-01

    Interannual variation of carbon fluxes can be attributed to a number of biotic and abiotic controls that operate at different spatial and temporal scales. Type and frequency of disturbance, forest dynamics, and climate regimes are important sources of variability. Assessing the variability of carbon fluxes from these specific sources can enhance the interpretation of past and current observations. Being able to separate the variability caused by forest dynamics from that induced by climate will also give us the ability to determine if the current observed carbon fluxes are within an expected range or whether the ecosystem is undergoing unexpected change. Sources of interannual variation in ecosystem carbon fluxes from three evergreen ecosystems, a tropical, a temperate coniferous, and a boreal forest, were explored using the simulation model STANDCARB. We identified key processes that introduced variation in annual fluxes, but their relative importance differed among the ecosystems studied. In the tropical site, intrinsic forest dynamics contributed ?? 30% of the total variation in annual carbon fluxes. In the temperate and boreal sites, where many forest processes occur over longer temporal scales than those at the tropical site, climate controlled more of the variation among annual fluxes. These results suggest that climate-related variability affects the rates of carbon exchange differently among sites. Simulations in which temperature, precipitation, and radiation varied from year to year (based on historical records of climate variation) had less net carbon stores than simulations in which these variables were held constant (based on historical records of monthly average climate), a result caused by the functional relationship between temperature and respiration. This suggests that, under a more variable temperature regime, large respiratory pulses may become more frequent and high enough to cause a reduction in ecosystem carbon stores. Our results also show

  16. Maintenance metabolism and carbon fluxes in Bacillus species

    Directory of Open Access Journals (Sweden)

    Decasper Seraina

    2008-06-01

    Full Text Available Abstract Background Selection of an appropriate host organism is crucial for the economic success of biotechnological processes. A generally important selection criterion is a low maintenance energy metabolism to reduce non-productive consumption of substrate. We here investigated, whether various bacilli that are closely related to Bacillus subtilis are potential riboflavin production hosts with low maintenance metabolism. Results While B. subtilis exhibited indeed the highest maintenance energy coefficient, B. licheniformis and B. amyloliquefaciens exhibited only statistically insignificantly reduced maintenance metabolism. Both B. pumilus and B. subtilis (natto exhibited irregular growth patterns under glucose limitation such that the maintenance metabolism could not be determined. The sole exception with significantly reduced maintenance energy requirements was the B. licheniformis strain T380B. The frequently used spo0A mutation significantly increased the maintenance metabolism of B. subtilis. At the level of 13C-detected intracellular fluxes, all investigated bacilli exhibited a significant flux through the pentose phosphate pathway, a prerequisite for efficient riboflavin production. Different from all other species, B. subtilis featured high respiratory tricarboxylic acid cycle fluxes in batch and chemostat cultures. In particular under glucose-limited conditions, this led to significant excess formation of NADPH of B. subtilis, while anabolic consumption was rather balanced with catabolic NADPH formation in the other bacilli. Conclusion Despite its successful commercial production of riboflavin, B. subtilis does not seem to be the optimal cell factory from a bioenergetic point of view. The best choice of the investigated strains is the sporulation-deficient B. licheniformis T380B strain. Beside a low maintenance energy coefficient, this strain grows robustly under different conditions and exhibits only moderate acetate overflow, hence

  17. Carbon conversion efficiency and central metabolic fluxes in developing sunflower (Helianthus annuus L.) embryos.

    Science.gov (United States)

    Alonso, Ana P; Goffman, Fernando D; Ohlrogge, John B; Shachar-Hill, Yair

    2007-10-01

    The efficiency with which developing sunflower embryos convert substrates into seed storage reserves was determined by labeling embryos with [U-(14)C6]glucose or [U-(14)C5]glutamine and measuring their conversion to CO2, oil, protein and other biomass compounds. The average carbon conversion efficiency was 50%, which contrasts with a value of over 80% previously observed in Brassica napus embryos (Goffman et al., 2005), in which light and the RuBisCO bypass pathway allow more efficient conversion of hexose to oil. Labeling levels after incubating sunflower embryos with [U-(14)C4]malate indicated that some carbon from malate enters the plastidic compartment and contributes to oil synthesis. To test this and to map the underlying pattern of metabolic fluxes, separate experiments were carried out in which embryos were labeled to isotopic steady state using [1-(13)C1]glucose, [2-(13)C1]glucose, or [U-(13)C5]glutamine. The resultant labeling in sugars, starch, fatty acids and amino acids was analyzed by NMR and GC-MS. The fluxes through intermediary metabolism were then quantified by computer-aided modeling. The resulting flux map accounted well for the labeling data, was in good agreement with the observed carbon efficiency, and was further validated by testing for agreement with gas exchange measurements. The map shows that the influx of malate into oil is low and that flux through futile cycles (wasting ATP) is low, which contrasts with the high rates previously determined for growing root tips and heterotrophic cell cultures.

  18. Acidification, not carbonation, is the major regulator of carbon fluxes in the coccolithophore Emiliania huxleyi.

    Science.gov (United States)

    Kottmeier, Dorothee M; Rokitta, Sebastian D; Rost, Björn

    2016-07-01

    A combined increase in seawater [CO2 ] and [H(+) ] was recently shown to induce a shift from photosynthetic HCO3 (-) to CO2 uptake in Emiliania huxleyi. This shift occurred within minutes, whereas acclimation to ocean acidification (OA) did not affect the carbon source. To identify the driver of this shift, we exposed low- and high-light acclimated E. huxleyi to a matrix of two levels of dissolved inorganic carbon (1400, 2800 μmol kg(-1) ) and pH (8.15, 7.85) and directly measured cellular O2 , CO2 and HCO3 (-) fluxes under these conditions. Exposure to increased [CO2 ] had little effect on the photosynthetic fluxes, whereas increased [H(+) ] led to a significant decline in HCO3 (-) uptake. Low-light acclimated cells overcompensated for the inhibition of HCO3 (-) uptake by increasing CO2 uptake. High-light acclimated cells, relying on higher proportions of HCO3 (-) uptake, could not increase CO2 uptake and photosynthetic O2 evolution consequently became carbon-limited. These regulations indicate that OA responses in photosynthesis are caused by [H(+) ] rather than by [CO2 ]. The impaired HCO3 (-) uptake also provides a mechanistic explanation for lowered calcification under OA. Moreover, it explains the OA-dependent decrease in photosynthesis observed in high-light grown phytoplankton. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

  19. Migrant biomass and respiratory carbon flux by zooplankton and micronekton in the subtropical northeast Atlantic Ocean (Canary Islands)

    Science.gov (United States)

    Ariza, A.; Garijo, J. C.; Landeira, J. M.; Bordes, F.; Hernández-León, S.

    2015-05-01

    Diel Vertical Migration (DVM) in marine ecosystems is performed by zooplankton and micronekton, promoting a poorly accounted export of carbon to the deep ocean. Major efforts have been made to estimate carbon export due to gravitational flux and to a lesser extent, to migrant zooplankton. However, migratory flux by micronekton has been largely neglected in this context, due to its time-consuming and difficult sampling. In this paper, we evaluated gravitational and migratory flux due to the respiration of zooplankton and micronekton in the northeast subtropical Atlantic Ocean (Canary Islands). Migratory flux was addressed by calculating the biomass of migrating components and measuring the electron transfer system (ETS) activity in zooplankton and dominant species representing micronekton (Euphausia gibboides, Sergia splendens and Lobianchia dofleini). Our results showed similar biomass in both components. The main taxa contributing to DVM within zooplankton were juvenile euphausiids, whereas micronekton were mainly dominated by fish, followed by adult euphausiids and decapods. The contribution to respiratory flux of zooplankton (3.4 ± 1.9 mg C m-2 d-1) was similar to that of micronekton (2.9 ± 1.0 mg C m-2 d-1). In summary, respiratory flux accounted for 53% (range 23-71) of the gravitational flux measured at 150 m depth (11.9 ± 5.8 mg C m-2 d-1). However, based on larger migratory ranges and gut clearance rates, micronekton are expected to be the dominant component that contributes to carbon export in deeper waters. Micronekton estimates in this paper as well as those in existing literature, although variable due to regional differences and difficulties in calculating their biomass, suggest that carbon fluxes driven by this community are important for future models of the biological carbon pump.

  20. 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.

  1. Inorganic carbon fluxes across the vadose zone of planted and unplanted soil mesocosms

    DEFF Research Database (Denmark)

    Thaysen, Eike Marie; Jacques, D.; Jessen, S.

    2014-01-01

    The efflux of carbon dioxide (CO2) from soils influences atmospheric CO2 concentrations and thereby climate change. The partitioning of inorganic carbon (C) fluxes in the vadose zone between emission to the atmosphere and to the groundwater was investigated to reveal controlling underlying...... mechanisms. Carbon dioxide partial pressure in the soil gas (pCO(2)), alkalinity, soil moisture and temperature were measured over depth and time in unplanted and planted (barley) mesocosms. The dissolved inorganic carbon (DIC) percolation flux was calculated from the pCO(2), alkalinity and the water flux...... to calculate the soil CO2 production. Carbon dioxide fluxes were modeled using the HP1 module of the Hydrus 1-D software. The average CO2 effluxes to the atmosphere from unplanted and planted mesocosm ecosystems during 78 days of experiment were 0.1 +/- 0.07 and 4.9 +/- 0.07 mu mol Cm-2 s(-1), respectively...

  2. Impacts of revised PFTs on JULES simulated carbon and moisture fluxes

    Science.gov (United States)

    Harper, Anna; Cox, Peter; Sitch, Stephen; Mercado, Lina; Luke, Catherine; Jupp, Tim; Wiltshire, Andy; Jones, Chris; Friedlingstein, Pierre

    2013-04-01

    JULES is the land surface model in the Hadley Centre GCM, which is used for investigations of climate and climate change. We analyze the impacts on the simulated carbon and moisture fluxes of extending the PFTs in a manner consistent with observed leaf traits. The model currently represents global vegetation with five PFTs (needleleaf and broadleaf trees, C3 and C4 grasses, and shrubs). We add three new PFTs to delineate between deciduous and evergreen trees and shrubs. Since the inception of JULES in the late 90's, a tremendous amount of new data linking leaf traits and potential photosynthesis is available. We use data from the TRY plant trait data base to revise the relationships between leaf area, leaf lifespan, leaf nitrogen content, and Vcmax. In addition, JULES now includes a canopy radiation scheme based on fractions of sunlit and shaded leaves at 10 levels in the canopy. This results in a vertical distribution of nitrogren and Vcmax through the canopy and enables multilayer scaling from leaf to canopy level photosynthesis. The scheme is more physically realistic than previous canopy radiation schemes, but remains to be evaluated outside of the Tropics. Within the constraints of observed values, we optimize new parameter values related to the canopy radiation and photosynthesis, using optimization software developed at the University of Exeter. Impacts on simulated GPP, respiration, and latent heat flux are examined. In particular, we are interested in a better understanding of carbon cycle dynamics in tropical forests. Using data from TRY, carbon fluxes are improved across all PFTs compared to observations from Fluxnet tower sites. We adopt a regional analysis to compare JULES fluxes in certain regions (e.g. tropical forests, and boreal and tropical shrub-dominated landscapes).

  3. Spatial and temporal variability of urban fluxes of methane, carbon monoxide and carbon dioxide above London, UK

    Directory of Open Access Journals (Sweden)

    C. Helfter

    2016-08-01

    Full Text Available We report on more than 3 years of measurements of fluxes of methane (CH4, carbon monoxide (CO and carbon dioxide (CO2 taken by eddy-covariance in central London, UK. Mean annual emissions of CO2 in the period 2012–2014 (39.1 ± 2.4 ktons km−2 yr−1 and CO (89 ± 16 tons km−2 yr−1 were consistent (within 1 and 5 % respectively with values from the London Atmospheric Emissions Inventory, but measured CH4 emissions (72 ± 3 tons km−2 yr−1 were over two-fold larger than the inventory value. Seasonal variability was large for CO with a winter to summer reduction of 69 %, and monthly fluxes were strongly anti-correlated with mean air temperature. The winter increment in CO emissions was attributed mainly to vehicle cold starts and reduced fuel combustion efficiency. CO2 fluxes were 33 % higher in winter than in summer and anti-correlated with mean air temperature, albeit to a lesser extent than for CO. This was attributed to an increased demand for natural gas for heating during the winter. CH4 fluxes exhibited moderate seasonality (21 % larger in winter, and a spatially variable linear anti-correlation with air temperature. Differences in resident population within the flux footprint explained up to 90 % of the spatial variability of the annual CO2 fluxes and up to 99 % for CH4. Furthermore, we suggest that biogenic sources of CH4, such as wastewater, which is unaccounted for by the atmospheric emissions inventories, make a substantial contribution to the overall budget and that commuting dynamics in and out of central business districts could explain some of the spatial and temporal variability of CO2 and CH4 emissions. To our knowledge, this study is unique given the length of the data sets presented, especially for CO and CH4 fluxes. This study offers an independent assessment of "bottom-up" emissions inventories and demonstrates that the urban sources of CO and CO2 are well characterized in

  4. Large carbon dioxide fluxes from headwater boreal and sub-boreal streams.

    Science.gov (United States)

    Venkiteswaran, Jason J; Schiff, Sherry L; Wallin, Marcus B

    2014-01-01

    Half of the world's forest is in boreal and sub-boreal ecozones, containing large carbon stores and fluxes. Carbon lost from headwater streams in these forests is underestimated. We apply a simple stable carbon isotope idea for quantifying the CO2 loss from these small streams; it is based only on in-stream samples and integrates over a significant distance upstream. We demonstrate that conventional methods of determining CO2 loss from streams necessarily underestimate the CO2 loss with results from two catchments. Dissolved carbon export from headwater catchments is similar to CO2 loss from stream surfaces. Most of the CO2 originating in high CO2 groundwaters has been lost before typical in-stream sampling occurs. In the Harp Lake catchment in Canada, headwater streams account for 10% of catchment net CO2 uptake. In the Krycklan catchment in Sweden, this more than doubles the CO2 loss from the catchment. Thus, even when corrected for aquatic CO2 loss measured by conventional methods, boreal and sub-boreal forest carbon budgets currently overestimate carbon sequestration on the landscape.

  5. 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

  6. Assessing glycolytic flux alterations resulting from genetic perturbations in E. coli using a biosensor

    DEFF Research Database (Denmark)

    Lehning, Christina Eva; Siedler, Solvej; Ellabaan, Mostafa M Hashim

    2017-01-01

    validated the glycolytic flux dependency of the biosensor in a range of different carbon sources in six different E. coli strains and during mevalonate production. Furthermore, we studied the flux-altering effects of genome-wide single gene knock-outs in E. coli in a multiplex FlowSeq experiment. From...... a library consisting of 2126 knock-out mutants, we identified 3 mutants with high-flux and 95 mutants with low-flux phenotypes that did not have severe growth defects. This approach can improve our understanding of glycolytic flux regulation improving metabolic models and engineering efforts....

  7. The role of forest disturbance in global forest mortality and terrestrial carbon fluxes

    Science.gov (United States)

    Pugh, Thomas; Arneth, Almut; Smith, Benjamin; Poulter, Benjamin

    2017-04-01

    Large-scale forest disturbance dynamics such as insect outbreaks, wind-throw and fires, along with anthropogenic disturbances such as logging, have been shown to turn forests from carbon sinks into intermittent sources, often quite dramatically so. There is also increasing evidence that disturbance regimes in many regions are changing as a result of climatic change and human land-management practices. But how these landscape-scale events fit into the wider picture of global tree mortality is not well understood. Do such events dominate global carbon turnover, or are their effects highly regional? How sensitive is global terrestrial carbon exchange to realistic changes in the occurrence rate of such disturbances? Here, we combine recent advances in global satellite observations of stand-replacing forest disturbances and in compilations of forest inventory data, with a global terrestrial ecosystem model which incorporates an explicit representation of the role of disturbance in forest dynamics. We find that stand-replacing disturbances account for a fraction of wood carbon turnover that varies spatially from less than 5% in the tropical rainforest to ca. 50% in the mid latitudes, and as much as 90% in some heavily-managed regions. We contrast the size of the land-atmosphere carbon flux due to this disturbance with other components of the terrestrial carbon budget. In terms of sensitivity, we find a quasi log-linear relationship of disturbance rate to total carbon storage. Relatively small changes in disturbance rates at all latitudes have marked effects on vegetation carbon storage, with potentially very substantial implications for the global terrestrial carbon sink. Our results suggest a surprisingly small effect of disturbance type on large-scale forest vegetation dynamics and carbon storage, with limited evidence of widespread increases in nitrogen limitation as a result of increasing future disturbance. However, the influence of disturbance type on soil carbon

  8. Sputtering yields of carbon based materials under high particle flux with low energy

    Science.gov (United States)

    Nakamura, K.; Nagase, A.; Dairaku, M.; Akiba, M.; Araki, M.; Okumura, Y.

    1995-04-01

    A new ion source which can produce high particle flux beams at low energies has been developed. This paper presents preliminary results on the sputtering yield of the carbon fiber reinforced composites (CFCs) measured with the new ion source. The sputtering yields of 1D and 2D CFCs, which are candidate materials for the divertor armour tiles, have been measured by the weight loss method under the hydrogen and deuterium particle fluxes of 2 ˜ 7 × 10 20/m 2 s at 50 ˜ 150 eV. Preferential sputtering of the matrix was observed on CFCs which included the matrix of 40 ˜ 60 w%. The energy dependence of the sputtering yields was weak. The sputtering yields of CFCs normally irradiated with deuterium beam were from 0.073 to 0.095, and were around three times larger than those with hydrogen beam.

  9. Sputtering yields of carbon based materials under high particle flux with low energy

    International Nuclear Information System (INIS)

    Nakamura, K.; Nagase, A.; Dairaku, M.; Akiba, M.; Araki, M.; Okumura, Y.

    1995-01-01

    A new ion source which can produce high particle flux beams at low energies has been developed. This paper presents preliminary results on the sputtering yield of the carbon fiber reinforced composites (CFCs) measured with the new ion source. The sputtering yields of 1D and 2D CFCs, which are candidate materials for the divertor armour tiles, have been measured by the weight loss method under the hydrogen and deuterium particle fluxes of 2 similar 7x10 20 /m 2 s at 50 similar 150 eV. Preferential sputtering of the matrix was observed on CFCs which included the matrix of 40 similar 60 w%. The energy dependence of the sputtering yields was weak. The sputtering yields of CFCs normally irradiated with deuterium beam were from 0.073 to 0.095, and were around three times larger than those with hydrogen beam. ((orig.))

  10. Technical Note: Mesocosm approach to quantify dissolved inorganic carbon percolation fluxes

    DEFF Research Database (Denmark)

    Thaysen, Eike Marie; Jessen, S.; Ambus, Per

    2014-01-01

    unplanted soil. Carbon dioxide partial pressure (pCO(2)), alkalinity, soil moisture and temperature were measured with depth and time, and DIC in the percolate was quantified using a sodium hydroxide trap. Results showed good reproducibility between two replicate mesocosms. The pCO(2) varied between 0.......2 and 1.1 %, and the alkalinity was 0.1-0.6 meq L-1. The measured cumulative effluent DIC flux over the 78-day experimental period was 185-196 mg L-1 m(-2) and in the same range as estimates derived from pCO(2) and alkalinity in samples extracted from the side of the mesocosm column and the drainage flux...

  11. Carbon Dioxide and Methane Flux Related to Forest Type and Managed and Unmanaged Conditions in the Great Dismal Swamp, USA

    Science.gov (United States)

    Gutenberg, L. W.; Krauss, K.; Qu, J. J.; Hogan, D. M.; Zhu, Z.; Xu, C.

    2017-12-01

    The Great Dismal Swamp in Virginia and North Carolina, USA, has been greatly impacted by human use and management for the last few hundred years through logging, ditching, and draining. Today, the once dominant cedar, cypress and pocosin forest types are fragmented due to logging and environmental change. Maple-gum forest has taken over more than half the remaining area of the swamp ecosystem, which is now a National Wildlife Refuge and State Park. The peat soils and biomass store a vast quantity of carbon compared with the size of the refuge, but this store is threatened by fire and drying. This study looks at three of the main forest types in the GDS— maple-sweet gum, tall pine pocosin, and Atlantic white cedar— in terms of their carbon dioxide and methane soil flux. Using static chambers to sample soil gas flux in locally representative sites, we found that cedar sites showed a higher carbon dioxide flux rate as the soil temperature increased than maple sites, and the rate of carbon dioxide flux decreased as soil moisture increased faster in cedar sites than in maple sites. Methane flux increased as temperature increased for pocosin, but decreased with temperature for cedar and maple. All of the methane fluxes increased as soil moisture increased. Cedar average carbon dioxide flux was statistically significantly different from both maple and pocosin. These results show that soil carbon gas flux depends on soil moisture and temperature, which are factors that are changing due to human actions, as well as on forest type, which is also the result of human activity. Some of these variables may be adjustable by the managers of the land. Variables other than forest type, temperature and soil moisture/inundation may also play a role in influencing soil flux, such as stand age, tree height, composition of the peat and nutrient availability, and source of moisture as some sites are more influenced by groundwater from ditches and some more by rainfall depending on the

  12. Can Carbon Fluxes Explain Differences in Soil Organic Carbon Storage under Aspen and Conifer Forest Overstories?

    Directory of Open Access Journals (Sweden)

    Antra Boča

    2017-04-01

    Full Text Available Climate- and management-induced changes in tree species distributions are raising questions regarding tree species-specific effects on soil organic carbon (SOC storage and stability. Quaking aspen (Populus tremuloides Michx. is the most widespread tree species in North America, but fire exclusion often promotes the succession to conifer dominated forests. Aspen in the Western US have been found to store more SOC in the mineral soil than nearby conifers, but we do not yet fully understand the source of this differential SOC accumulation. We measured total SOC storage (0–50 cm, characterized stable and labile SOC pools, and quantified above- and belowground litter inputs and dissolved organic carbon (DOC fluxes during snowmelt in plots located in N and S Utah, to elucidate the role of foliage vs. root detritus in SOC storage and stabilization in both ecosystems. While leaf litterfall was twice as high under aspen as under conifers, input of litter-derived DOC with snowmelt water was consistently higher under conifers. Fine root (<2 mm biomass, estimated root detritus input, and root-derived DOC fluxes were also higher under conifers. A strong positive relationship between root and light fraction C content suggests that root detritus mostly fueled the labile fraction of SOC. Overall, neither differences in above- and belowground detritus C inputs nor in detritus-derived DOC fluxes could explain the higher and more stable SOC pools under aspen. We hypothesize that root–microbe–soil interactions in the rhizosphere are more likely to drive these SOC pool differences.

  13. LBA-ECO LC-39 Modeled Carbon Flux from Deforestation, Mato Grosso, Brazil: 2000-2006

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set contains modeled estimates of carbon flux, biomass, and annual burning emissions across the Brazilian state of Mato Grosso from 2000-2006. The model,...

  14. LBA-ECO LC-39 Modeled Carbon Flux from Deforestation, Mato Grosso, Brazil: 2000-2006

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: This data set contains modeled estimates of carbon flux, biomass, and annual burning emissions across the Brazilian state of Mato Grosso from 2000-2006....

  15. The assessment of water vapour and carbon dioxide fluxes above arable crops - a comparison of methods

    Energy Technology Data Exchange (ETDEWEB)

    Schaaf, S.; Daemmgen, U.; Burkart, S. [Federal Agricultural Research Centre, Inst. of Agroecology, Braunschweig (Germany); Gruenhage, L. [Justus-Liebig-Univ., Inst. for Plant Ecology, Giessen (Germany)

    2005-04-01

    Vertical fluxes of water vapour and carbon dioxide obtained from gradient, eddy covariance (closed and open path systems) and chamber measurements above arable crops were compared with the directly measured energy balance and the harvested net biomass carbon. The gradient and chamber measurements were in the correct order of magnitude, whereas the closed path eddy covariance system showed unacceptably small fluxes. Correction methods based on power spectra analysis yielded increased fluxes. However, the energy balance could not be closed satisfactorily. The application of the open path system proved to be successful. The SVAT model PLATIN which had been adapted to various arable crops was able to depict the components of the energy balance adequately. Net carbon fluxes determined with the corrected closed path data sets, chamber, and SVAT model equal those of the harvested carbon. (orig.)

  16. Towards a better understanding of microbial carbon flux in the sea

    Czech Academy of Sciences Publication Activity Database

    Gasol, J.M.; Pinhassi, J.; Alonso-Sáez, L.; Ducklow, H.; Herndl, G. J.; Koblížek, Michal; Labrenz, M.; Luo, Y.; Morán, X. A. G.; Reinthaler, T.; Simon, M.

    2008-01-01

    Roč. 53, - (2008), s. 21-38 ISSN 0948-3055 Institutional research plan: CEZ:AV0Z50200510 Keywords : carbon flux * microbioal ecology * ocean Subject RIV: EE - Microbiology, Virology Impact factor: 2.190, year: 2008

  17. 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.

  18. Ecosystem carbon storage and flux in upland/peatland watersheds in northern Minnesota. Chapter 9.

    Science.gov (United States)

    David F. Grigal; Peter C. Bates; Randall K. Kolka

    2011-01-01

    Carbon (C) storage and fluxes (inputs and outputs of C per unit time) are central issues in global change. Spatial patterns of C storage on the landscape, both that in soil and in biomass, are important from an inventory perspective and for understanding the biophysical processes that affect C fluxes. Regional and national estimates of C storage are uncertain because...

  19. Spatiotemporal dynamics of carbon dioxide and methane fluxes from agricultural and restored wetlands in the California Delta

    Science.gov (United States)

    Hatala, Jaclyn Anne

    The Sacramento-San Joaquin Delta in California was drained for agriculture and human settlement over a century ago, resulting in extreme rates of soil subsidence and release of CO2 to the atmosphere from peat oxidation. Because of this century-long ecosystem carbon imbalance where heterotrophic respiration exceeded net primary productivity, most of the land surface in the Delta is now up to 8 meters below sea level. To potentially reverse this trend of chronic carbon loss from Delta ecosystems, land managers have begun converting drained lands back to flooded ecosystems, but at the cost of increased production of CH4, a much more potent greenhouse gas than CO2. To evaluate the impacts of inundation on the biosphere-atmophere exchange of CO2 and CH4 in the Delta, I first measured and analyzed net fluxes of CO2 and CH4 for two continuous years with the eddy covariance technique in a drained peatland pasture and a recently re-flooded rice paddy. This analysis demonstrated that the drained pasture was a consistent large source of CO2 and small source of CH 4, whereas the rice paddy was a mild sink for CO2 and a mild source of CH4. However more importantly, this first analysis revealed nuanced complexities for measuring and interpreting patterns in CO2 and CH4 fluxes through time and space. CO2 and CH4 fluxes are inextricably linked in flooded ecosystems, as plant carbon serves as the primary substrate for the production of CH4 and wetland plants also provide the primary transport pathway of CH4 flux to the atmosphere. At the spatially homogeneous rice paddy during the summer growing season, I investigated rapid temporal coupling between CO2 and CH4 fluxes. Through wavelet Granger-causality analysis, I demonstrated that daily fluctuations in growing season gross ecosystem productivity (photosynthesis) exert a stronger control than temperature on the diurnal pattern in CH4 flux from rice. At a spatially heterogeneous restored wetland site, I analyzed the spatial coupling

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

    Science.gov (United States)

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

    2013-12-01

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

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

    Science.gov (United States)

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

    2017-08-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Dalcin Martins, Paula [Microbiology Department, The Ohio State University, Columbus OH 43210 USA; Hoyt, David W. [Environmental Molecular Sciences Laboratory, Richland WA 99350 USA; Bansal, Sheel [United States Geological Survey - Northern Prairie Wildlife Research Center, Jamestown ND 58401 USA; Mills, Christopher T. [United States Geological Survey, Crustal Geophysics and Geochemistry Science Center, Building 20, Denver Federal Center Denver CO 80225 USA; Tfaily, Malak [Environmental Molecular Sciences Laboratory, Richland WA 99350 USA; Tangen, Brian A. [United States Geological Survey - Northern Prairie Wildlife Research Center, Jamestown ND 58401 USA; Finocchiaro, Raymond G. [United States Geological Survey - Northern Prairie Wildlife Research Center, Jamestown ND 58401 USA; Johnston, Michael D. [School of Earth Sciences, The Ohio State University, Columbus OH 43210 USA; McAdams, Brandon C. [School of Earth Sciences, The Ohio State University, Columbus OH 43210 USA; Solensky, Matthew J. [United States Geological Survey - Northern Prairie Wildlife Research Center, Jamestown ND 58401 USA; Smith, Garrett J. [Microbiology Department, The Ohio State University, Columbus OH 43210 USA; Chin, Yu-Ping [School of Earth Sciences, The Ohio State University, Columbus OH 43210 USA; Wilkins, Michael J. [Microbiology Department, The Ohio State University, Columbus OH 43210 USA; School of Earth Sciences, The Ohio State University, Columbus OH 43210 USA

    2017-02-23

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

  3. Anthropogenic perturbation of the carbon fluxes from land to ocean

    KAUST Repository

    Regnier, Pierre; Friedlingstein, Pierre; Ciais, Philippe; Mackenzie, Fred T.; Gruber, Nicolas; Janssens, Ivan A.; Laruelle, Goulven G.; Lauerwald, Ronny; Luyssaert, Sebastiaan; Andersson, Andreas J.; Arndt, Sandra; Arnosti, Carol; Borges, Alberto V.; Dale, Andrew W.; Gallego-Sala, Angela; Goddé ris, Yves; Goossens, Nicolas; Hartmann, Jens; Heinze, Christoph; Ilyina, Tatiana; Joos, Fortunat; LaRowe, Douglas E.; Leifeld, Jens; Meysman, Filip J. R.; Munhoven, Guy; Raymond, Peter A.; Spahni, Renato; Suntharalingam, Parvadha; Thullner, Martin

    2013-01-01

    to enhanced carbon export from soils. Most of this additional carbon input to upstream rivers is either emitted back to the atmosphere as carbon dioxide (∼0.4 Pg C yr -1) or sequestered in sediments (∼0.5 Pg C yr -1) along the continuum of freshwater bodies

  4. Spatially Explicit Simulation of Mesotopographic Controls on Peatland Hydrology and Carbon Fluxes

    Science.gov (United States)

    Sonnentag, O.; Chen, J. M.; Roulet, N. T.

    2006-12-01

    A number of field carbon flux measurements, paleoecological records, and model simulations have acknowledged the importance of northern peatlands in terrestrial carbon cycling and methane emissions. An important parameter in peatlands that influences both net primary productivity, the net gain of carbon through photosynthesis, and decomposition under aerobic and anaerobic conditions, is the position of the water table. Biological and physical processes involved in peatland carbon dynamics and their hydrological controls operate at different spatial scales. The highly variable hydraulic characteristics of the peat profile and the overall shape of the peat body as defined by its surface topography at the mesoscale (104 m2) are of major importance for peatland water table dynamics. Common types of peatlands include bogs with a slightly domed centre. As a result of the convex profile, their water supply is restricted to atmospheric inputs, and water is mainly shed by shallow subsurface flow. From a modelling perspective the influence of mesotopographic controls on peatland hydrology and thus carbon balance requires that process-oriented models that examine the links between peatland hydrology, ecosystem functioning, and climate must incorporate some form of lateral subsurface flow consideration. Most hydrological and ecological modelling studies in complex terrain explicitly account for the topographic controls on lateral subsurface flow through digital elevation models. However, modelling studies in peatlands often employ simple empirical parameterizations of lateral subsurface flow, neglecting the influence of peatlands low relief mesoscale topography. Our objective is to explicitly simulate the mesotopographic controls on peatland hydrology and carbon fluxes using the Boreal Ecosystem Productivity Simulator (BEPS) adapted to northern peatlands. BEPS is a process-oriented ecosystem model in a remote sensing framework that takes into account peatlands multi

  5. Rerouting of carbon flux in a glycogen mutant of cyanobacteria assessed via isotopically non-stationary 13 C metabolic flux analysis.

    Science.gov (United States)

    Hendry, John I; Prasannan, Charulata; Ma, Fangfang; Möllers, K Benedikt; Jaiswal, Damini; Digmurti, Madhuri; Allen, Doug K; Frigaard, Niels-Ulrik; Dasgupta, Santanu; Wangikar, Pramod P

    2017-10-01

    Cyanobacteria, which constitute a quantitatively dominant phylum, have attracted attention in biofuel applications due to favorable physiological characteristics, high photosynthetic efficiency and amenability to genetic manipulations. However, quantitative aspects of cyanobacterial metabolism have received limited attention. In the present study, we have performed isotopically non-stationary 13 C metabolic flux analysis (INST- 13 C-MFA) to analyze rerouting of carbon in a glycogen synthase deficient mutant strain (glgA-I glgA-II) of the model cyanobacterium Synechococcus sp. PCC 7002. During balanced photoautotrophic growth, 10-20% of the fixed carbon is stored in the form of glycogen via a pathway that is conserved across the cyanobacterial phylum. Our results show that deletion of glycogen synthase gene orchestrates cascading effects on carbon distribution in various parts of the metabolic network. Carbon that was originally destined to be incorporated into glycogen gets partially diverted toward alternate storage molecules such as glucosylglycerol and sucrose. The rest is partitioned within the metabolic network, primarily via glycolysis and tricarboxylic acid cycle. A lowered flux toward carbohydrate synthesis and an altered distribution at the glucose-1-phosphate node indicate flexibility in the network. Further, reversibility of glycogen biosynthesis reactions points toward the presence of futile cycles. Similar redistribution of carbon was also predicted by Flux Balance Analysis. The results are significant to metabolic engineering efforts with cyanobacteria where fixed carbon needs to be re-routed to products of interest. Biotechnol. Bioeng. 2017;114: 2298-2308. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  6. Observations and modeling of aboveground tree carbon stocks and fluxes following a bark beetle outbreak in the western United States

    Science.gov (United States)

    Eric M. Pfeifer; Jeffrey A. Hicke; Arjan J.H. Meddens

    2011-01-01

    Bark beetle epidemics result in tree mortality across millions of hectares in North America. However, few studies have quantified impacts on carbon (C) cycling. In this study, we quantified the immediate response and subsequent trajectories of stand-level aboveground tree C stocks and fluxes using field measurements and modeling for a location in central Idaho, USA...

  7. B33C-0612: Evaluation of Simulated Biospheric Carbon Dioxide Fluxes and Atmospheric Concentrations Using Global in Situ Observations

    Science.gov (United States)

    Philip, Sajeev; Johnson, Matthew S.; Potter, Christopher S.; Genovese, Vanessa

    2016-01-01

    Atmospheric mixing ratios of carbon dioxide (CO2) are largely controlled by anthropogenic emission sources and biospheric sources/sinks. Global biospheric fluxes of CO2 are controlled by complex processes facilitating the exchange of carbon between terrestrial ecosystems and the atmosphere. These processes which play a key role in these terrestrial ecosystem-atmosphere carbon exchanges are currently not fully understood, resulting in large uncertainties in the quantification of biospheric CO2 fluxes. Current models with these inherent deficiencies have difficulties simulating the global carbon cycle with high accuracy. We are developing a new modeling platform, GEOS-Chem-CASA by integrating the year-specific NASA-CASA (National Aeronautics and Space Administration - Carnegie Ames Stanford Approach) biosphere model with the GEOS-Chem (Goddard Earth Observation System-Chemistry) chemical transport model to improve the simulation of atmosphere-terrestrial ecosystem carbon exchange. We use NASA-CASA to explicitly represent the exchange of CO2 between terrestrial ecosystem and atmosphere by replacing the baseline GEOS-Chem land net CO2 flux and forest biomass burning CO2 emissions. We will present the estimation and evaluation of these "bottom-up" land CO2 fluxes, simulated atmospheric mixing ratios, and forest disturbance changes over the last decade. In addition, we will present our initial comparison of atmospheric column-mean dry air mole fraction of CO2 predicted by the model and those retrieved from NASA's OCO-2 (Orbiting Carbon Observatory-2) satellite instrument and model-predicted surface CO2 mixing ratios with global in situ observations. This evaluation is the first step necessary for our future work planned to constrain the estimates of biospheric carbon fluxes through "top-down" inverse modeling, which will improve our understanding of the processes controlling atmosphere-terrestrial ecosystem greenhouse gas exchanges, especially over regions which lack in

  8. Impact of mountain pine beetle induced mortality on forest carbon and water fluxes

    International Nuclear Information System (INIS)

    E Reed, David; Ewers, Brent E; Pendall, Elise

    2014-01-01

    Quantifying impacts of ecological disturbance on ecosystem carbon and water fluxes will improve predictive understanding of biosphere—atmosphere feedbacks. Tree mortality caused by mountain pine bark beetles (Dendroctonus ponderosae) is hypothesized to decrease photosynthesis and water flux to the atmosphere while increasing respiration at a rate proportional to mortality. This work uses data from an eddy-covariance flux tower in a bark beetle infested lodgepole pine (Pinus contorta) forest to test ecosystem responses during the outbreak. Analyses were conducted on components of carbon (C) and water fluxes in response to disturbance and environmental factors (solar radiation, soil water content and vapor pressure deficit). Maximum CO 2 uptake did not change as tree basal area mortality increased from 30 to 78% over three years of beetle disturbance. Growing season evapotranspiration varied among years while ecosystem water use efficiency (the ratio of net CO 2 uptake to water vapor loss) did not change. Between 2009 and 2011, canopy water conductance increased from 98.6 to 151.7 mmol H 2 O m −2 s −1 . Ecosystem light use efficiency of photosynthesis increased, with quantum yield increasing by 16% during the outbreak as light increased below the mature tree canopy and illuminated remaining vegetation more. Overall net ecosystem productivity was correlated with water flux and hence water availability. Average weekly ecosystem respiration, derived from light response curves and standard Ameriflux protocols for CO 2 flux partitioning into respiration and gross ecosystem productivity, did not change as mortality increased. Separate effects of increased respiration and photosynthesis efficiency largely canceled one another out, presumably due to increased diffuse light in the canopy and soil organic matter decomposition resulting in no change in net CO 2 exchange. These results agree with an emerging consensus in the literature demonstrating CO 2 and H 2 O dynamics

  9. Aeolian nutrient fluxes following wildfire in sagebrush steppe: implications for soil carbon storage

    Directory of Open Access Journals (Sweden)

    N. J. Hasselquist

    2011-12-01

    Full Text Available Pulses of aeolian transport following fire can profoundly affect the biogeochemical cycling of nutrients in semi-arid and arid ecosystems. Our objective was to determine horizontal nutrient fluxes occurring in the saltation zone during an episodic pulse of aeolian transport that occurred following a wildfire in a semi-arid sagebrush steppe ecosystem in southern Idaho, USA. We also examined how temporal trends in nutrient fluxes were affected by changes in particle sizes of eroded mass as well as nutrient concentrations associated with different particle size classes. In the burned area, total carbon (C and nitrogen (N fluxes were as high as 235 g C m−1 d−1 and 19 g N m−1 d−1 during the first few months following fire, whereas C and N fluxes were negligible in an adjacent unburned area throughout the study. Temporal variation in C and N fluxes following fire was largely attributable to the redistribution of saltation-sized particles. Total N and organic C concentrations in the soil surface were significantly lower in the burned relative to the unburned area one year after fire. Our results show how an episodic pulse of aeolian transport following fire can affect the spatial distribution of soil C and N, which, in turn, can have important implications for soil C storage. These findings demonstrate how an ecological disturbance can exacerbate a geomorphic process and highlight the need for further research to better understand the role aeolian transport plays in the biogeochemical cycling of C and N in recently burned landscapes.

  10. 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

  11. Disturbance and climate effects on carbon stocks and fluxes across western Oregon USA.

    Science.gov (United States)

    B.E. Law; D. Turner; J. Campbell; O.J. Sun; S. Van Tuyl; W.D. Ritts; W.B. Cohen

    2004-01-01

    We used a spatially nested hierarchy of field and remote-sensing observations and a process model, Biome-BGC, to produce a carbon budget for the forested region of Oregon, and to determine the relative influence of differences in climate and disturbance among the ecoregions on carbon stocks and fluxes. The simulations suggest that annual net uptake (net ecosystem...

  12. Quantifying aboveground forest carbon pools and fluxes from repeat LiDAR surveys

    Science.gov (United States)

    Andrew T. Hudak; Eva K. Strand; Lee A. Vierling; John C. Byrne; Jan U. H. Eitel; Sebastian Martinuzzi; Michael J. Falkowski

    2012-01-01

    Sound forest policy and management decisions to mitigate rising atmospheric CO2 depend upon accurate methodologies to quantify forest carbon pools and fluxes over large tracts of land. LiDAR remote sensing is a rapidly evolving technology for quantifying aboveground biomass and thereby carbon pools; however, little work has evaluated the efficacy of repeat LiDAR...

  13. Organic carbon fluxes in the Atlantic and the Southern Ocean: relationship to primary production compiled from satellite radiometer data

    Science.gov (United States)

    Fischer, G.; Ratmeyer, V.; Wefer, G.

    Fluxes of organic carbon normalised to a depth of 1000 m from 18 sites in the Atlantic and the Southern Ocean are presented, comprising nine biogeochemical provinces as defined by Longhurst et al. (1995. Journal of Plankton Research 17, 1245-1271). For comparison with primary production, we used a recent compilation of primary production values derived from CZCS data (Antoine et al., 1996. Global Biogeochemical Cycles 10, 57-69). In most cases, the seasonal patterns stood reasonably well in accordance with the carbon fluxes. Particularly, organic carbon flux records from two coastal sites off northwest and southwest Africa displayed a more distinct correlation to the primary production in sectors (1×1°) which are situated closer to the coastal environments. This was primarily caused by large upwelling filaments streaming far offshore, resulting in a cross-shelf carbon transport. With respect to primary production, organic carbon export to a water depth of 1000 m, and the fraction of primary production exported to a depth of 1000 m (export fraction=EF 1000), we were able to distinguish between: (1) the coastal environments with highest values (EF 1000=1.75-2.0%), (2) the eastern equatorial upwelling area with moderately high values (EF 1000=0.8-1.1%), (3) and the subtropical oligotrophic gyres that yielded lowest values (EF 1000=0.6%). Carbon export in the Southern Ocean was low to moderate, and the EF 1000 value seems to be quite low in general. Annual organic carbon fluxes were proportional to primary production, and the export fraction EF 1000 increased with primary production up to 350 gC m -2 yr-1. Latitudinal variations in primary production were reflected in the carbon flux pattern. A high temporal variability of primary production rates and a pronounced seasonality of carbon export were observed in the polar environments, in particular in coastal domains, although primary production (according to Antoine et al., 1996. Global Biogeochemical Cycles 10, 57

  14. Anthropogenic and climatic influences on carbon fluxes from eastern North America to the Atlantic Ocean: A process-based modeling study

    Science.gov (United States)

    Tian, Hanqin; Yang, Qichun; Najjar, Raymond G.; Ren, Wei; Friedrichs, Marjorie A. M.; Hopkinson, Charles S.; Pan, Shufen

    2015-04-01

    The magnitude, spatiotemporal patterns, and controls of carbon flux from land to the ocean remain uncertain. Here we applied a process-based land model with explicit representation of carbon processes in streams and rivers to examine how changes in climate, land conversion, management practices, atmospheric CO2, and nitrogen deposition affected carbon fluxes from eastern North America to the Atlantic Ocean, specifically the Gulf of Maine (GOM), Middle Atlantic Bight (MAB), and South Atlantic Bight (SAB). Our simulation results indicate that the mean annual fluxes (±1 standard deviation) of dissolved organic carbon (DOC), particulate organic carbon (POC), and dissolved inorganic carbon (DIC) in the past three decades (1980-2008) were 2.37 ± 0.60, 1.06 ± 0.20, and 3.57 ± 0.72 Tg C yr-1, respectively. Carbon export demonstrated substantial spatial and temporal variability. For the region as a whole, the model simulates a significant decrease in riverine DIC fluxes from 1901 to 2008, whereas there were no significant trends in DOC or POC fluxes. In the SAB, however, there were significant declines in the fluxes of all three forms of carbon, and in the MAB subregion, DIC and POC fluxes declined significantly. The only significant trend in the GOM subregion was an increase in DIC flux. Climate variability was the primary cause of interannual variability in carbon export. Land conversion from cropland to forest was the primary factor contributing to decreases in all forms of C export, while nitrogen deposition and fertilizer use, as well as atmospheric CO2 increases, tended to increase DOC, POC, and DIC fluxes.

  15. The atmospheric signal of terrestrial carbon isotopic discrimination and its implication for partitioning carbon fluxes

    International Nuclear Information System (INIS)

    Miller, John B.; Tans, Pieter P.; Conway, Thomas J.; White, James W.C.; Vaughn, Bruce W.

    2003-01-01

    The 13 C/ 12 C ratio in atmospheric carbon dioxide has been measured in samples taken in the NOAA/CMDL network since 1991. By examining the relationship between weekly anomalies in 13 C and CO 2 at continental sites in the network, we infer temporal and spatial values for the isotopic signature of terrestrial CO 2 fluxes. We can convert these isotopic signatures to values of discrimination if we assume the atmospheric starting point for photosynthesis. The average discrimination in the Northern Hemisphere between 30 and 50 deg N is calculated to be 16.6 ± 0.2 per mil. In contrast to some earlier modeling studies, we find no strong latitudinal gradient in discrimination. However, we do observe that discrimination in Eurasia is larger than in North America, which is consistent with two modeling studies. We also observe a possible trend in the North American average of discrimination toward less discrimination. There is no apparent trend in the Eurasian average or at any individual sites. However, there is interannual variability on the order of 2 per mil at several sites and regions. Finally, we calculate the northern temperate terrestrial CO 2 flux replacing our previous discrimination values of about 18 per mil with the average value of 16.6 calculated in this study. We find this enhances the terrestrial sink by about 0.4 GtC/yr

  16. Drivers of seasonality in Arctic carbon dioxide fluxes

    DEFF Research Database (Denmark)

    Mbufong, Herbert Njuabe

    , while there were no discernable drivers of CO2 fluxes in Stordalen, growing season length showed significant controls on net ecosystem exchange (NEE) in Zackenberg and with gross primary production (GPP) and ecosystem respiration (Re) in Daring Lake. This is important considering the recent observations...... compensates for the shorter growing season due to increase snow cover and duration. Other drivers of growing season CO2 fluxes were mainly air temperature, growing degree days and photosynthetic active radiation in a high and a low Arctic tundra ecosystem. Upscaling Arctic tundra NEE based on an acquired...... understanding of the drivers of NEE during this research venture, shows an estimation of reasonable fluxes at three independent sites in low Arctic Alaska. However, this later project is still ongoing and its findings are only preliminary....

  17. Land-Use Influences Carbon Fluxes in Northern Kazakhstan

    Science.gov (United States)

    An understanding of carbon cycling is important to maintain sustainable rangeland ecosystems. Rangelands in the western U.S. are similar to those in Central Asia. We used a combination of meteorological and computer modeling techniques to quantitatively assess carbon loss and gain for four major l...

  18. 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.

  19. 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

  20. 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.

  1. Temporal and spatial variations of soil carbon dioxide, methane, and nitrous oxide fluxes in a Southeast Asian tropical rainforest

    Science.gov (United States)

    Itoh, M.; Kosugi, Y.; Takanashi, S.; Hayashi, Y.; Kanemitsu, S.; Osaka, K.; Tani, M.; Nik, A. R.

    2010-09-01

    To clarify the factors controlling temporal and spatial variations of soil carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) fluxes, we investigated these gas fluxes and environmental factors in a tropical rainforest in Peninsular Malaysia. Temporal variation of CO2 flux in a 2-ha plot was positively related to soil water condition and rainfall history. Spatially, CO2 flux was negatively related to soil water condition. When CO2 flux hotspots were included, no other environmental factors such as soil C or N concentrations showed any significant correlation. Although the larger area sampled in the present study complicates explanations of spatial variation of CO2 flux, our results support a previously reported bipolar relationship between the temporal and spatial patterns of CO2 flux and soil water condition observed at the study site in a smaller study plot. Flux of CH4 was usually negative with little variation, resulting in the soil at our study site functioning as a CH4 sink. Both temporal and spatial variations of CH4 flux were positively related to the soil water condition. Soil N concentration was also related to the spatial distribution of CH4 flux. Some hotspots were observed, probably due to CH4 production by termites, and these hotspots obscured the relationship between both temporal and spatial variations of CH4 flux and environmental factors. Temporal variation of N2O flux and soil N2O concentration was large and significantly related to the soil water condition, or in a strict sense, to rainfall history. Thus, the rainfall pattern controlled wet season N2O production in soil and its soil surface flux. Spatially, large N2O emissions were detected in wet periods at wetter and anaerobic locations, and were thus determined by soil physical properties. Our results showed that, even in Southeast Asian rainforests where distinct dry and wet seasons do not exist, variation in the soil water condition related to rainfall history controlled the

  2. Combining Observations in the Reflective Solar and Thermal Domains for Improved Mapping of Carbon, Water and Energy FLuxes

    Science.gov (United States)

    Houborg, Rasmus; Anderson, Martha; Kustas, Bill; Rodell, Matthew

    2011-01-01

    This study investigates the utility of integrating remotely sensed estimates of leaf chlorophyll (C(sub ab)) into a thermal-based Two-Source Energy Balance (TSEB) model that estimates land-surface CO2 and energy fluxes using an analytical, light-use-efficiency (LUE) based model of canopy resistance. Day to day variations in nominal LUE (LUE(sub n)) were assessed for a corn crop field in Maryland U.S.A. through model calibration with CO2 flux tower observations. The optimized daily LUE(sub n) values were then compared to estimates of C(sub ab) integrated from gridded maps of chlorophyll content weighted over the tower flux source area. Changes in Cab exhibited a curvilinear relationship with corresponding changes in daily calibrated LUE(sub n) values derived from the tower flux data, and hourly water, energy and carbon flux estimation accuracies from TSEB were significantly improved when using C(sub ab) for delineating spatio-temporal variations in LUE(sub n). The results demonstrate the synergy between thermal infrared and shortwave reflective wavebands in producing valuable remote sensing data for monitoring of carbon and water fluxes.

  3. Inorganic carbon fluxes on the Mackenzie Shelf of the Beaufort Sea

    Science.gov (United States)

    Mol, Jacoba; Thomas, Helmuth; Myers, Paul G.; Hu, Xianmin; Mucci, Alfonso

    2018-02-01

    The Mackenzie Shelf in the southeastern Beaufort Sea is a region 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, resulting in cross-shelf Ekman transport, and an alternating estuarine and anti-estuarine circulation. Downwelling carries dissolved inorganic carbon (DIC) and other remineralization products off the shelf and into the deep basin for possible long-term storage in the world's oceans. Upwelling carries DIC and nutrient-rich waters 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 carbon on the Mackenzie Shelf. The along-shore transport of water and the cross-shelf transport of DIC are 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) framework. A strong upwelling event prior to sampling on the Mackenzie Shelf took place, bringing CO2-rich (elevated pCO2) water from the UHL onto the shelf bottom. The maximum on-shelf DIC flux was estimated at 16.9×103 mol C d-1 m-2 during the event. The maximum on-shelf transport of DIC through the upwelling event was found to be 65±15×10-3 Tg C d-1. TA and the oxygen isotope ratio of water (δ18O-H2O) are used to examine water-mass distributions in the study area and to investigate the influence of Pacific Water, Mackenzie River freshwater, and sea-ice melt on carbon dynamics and air-sea fluxes of carbon dioxide (CO2) in the surface mixed layer. Understanding carbon transfer in this seasonally dynamic environment is key to quantify the importance of Arctic shelf regions to the global carbon cycle and provide a basis for understanding how it will

  4. Inorganic carbon fluxes on the Mackenzie Shelf of the Beaufort Sea

    Directory of Open Access Journals (Sweden)

    J. Mol

    2018-02-01

    Full Text Available The Mackenzie Shelf in the southeastern Beaufort Sea is a region 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, resulting in cross-shelf Ekman transport, and an alternating estuarine and anti-estuarine circulation. Downwelling carries dissolved inorganic carbon (DIC and other remineralization products off the shelf and into the deep basin for possible long-term storage in the world's oceans. Upwelling carries DIC and nutrient-rich waters 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 carbon on the Mackenzie Shelf. The along-shore transport of water and the cross-shelf transport of DIC are 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 framework. A strong upwelling event prior to sampling on the Mackenzie Shelf took place, bringing CO2-rich (elevated pCO2 water from the UHL onto the shelf bottom. The maximum on-shelf DIC flux was estimated at 16.9×103 mol C d−1 m−2 during the event. The maximum on-shelf transport of DIC through the upwelling event was found to be 65±15×10−3 Tg C d−1. TA and the oxygen isotope ratio of water (δ18O-H2O are used to examine water-mass distributions in the study area and to investigate the influence of Pacific Water, Mackenzie River freshwater, and sea-ice melt on carbon dynamics and air–sea fluxes of carbon dioxide (CO2 in the surface mixed layer. Understanding carbon transfer in this seasonally dynamic environment is key to quantify the importance of Arctic shelf regions to the global carbon cycle and provide a basis

  5. Transient pressure and productivity analysis in carbonate geothermal reservoirs with changing external boundary flux

    Directory of Open Access Journals (Sweden)

    Wang Dongying

    2017-01-01

    Full Text Available In this paper, a triple-medium flow model for carbonate geothermal reservoirs with an exponential external boundary flux is established. The pressure solution under constant production conditions in Laplace space is solved. The geothermal wellbore pressure change considering wellbore storage and skin factor is obtained by Stehfest numerical inversion. The well test interpretation charts and Fetkovich production decline chart for carbonate geothermal reservoirs are proposed for the first time. The proposed Fetkovich production decline curves are applied to analyze the production decline behavior. The results indicate that in carbonate geothermal reservoirs with exponential external boundary flux, the pressure derivative curve contains a triple dip, which represents the interporosity flow between the vugs or matrix and fracture system and the invading flow of the external boundary flux. The interporosity flow of carbonate geothermal reservoirs and changing external boundary flux can both slow down the extent of production decline and the same variation tendency is observed in the Fetkovich production decline curve.

  6. Modeling of the carbon dioxide fluxes in European Russia peat bogs

    Energy Technology Data Exchange (ETDEWEB)

    Kurbatova, J; Tatarinov, F; Varlagin, A; Shalukhina, N; Olchev, A [A N Severtsov Institute of Ecology and Evolution of RAS, Leninsky Prospekt 33, Moscow 119071 (Russian Federation); Li, C, E-mail: kurbatova.j@gmail.co [Institute for the Study of Earth, Oceans and Space, University of New Hampshire, Durham, NH 03824 (United States)

    2009-10-15

    A process-based model (Forest-DNDC) was applied to describe the possible impacts of climate change on carbon dioxide (CO{sub 2}) fluxes from a peat bog in European Russia. In the first step, Forest-DNDC was tested against CO{sub 2} fluxes measured by the eddy covariance method on an oligotrophic bog in a representative region of the southern taiga (56 deg. N 33 deg. E). The results of model validations show that Forest-DNDC is capable of quantifying the CO{sub 2} fluxes from the bog ecosystem. In the second step, the validated model was used to estimate how the expected future changes of the air temperature and water table depth could affect the C dynamics in the bogs. It was shown that a decrease in the water table and an increase in temperature influence significantly the CO{sub 2} exchange between our bog ecosystem and the atmosphere. Under elevated temperature and deepened water table the bog ecosystems could become a significant source of atmospheric CO{sub 2}.

  7. Potential for using remote sensing to estimate carbon fluxes across northern peatlands - A review.

    Science.gov (United States)

    Lees, K J; Quaife, T; Artz, R R E; Khomik, M; Clark, J M

    2018-02-15

    Peatlands store large amounts of terrestrial carbon and any changes to their carbon balance could cause large changes in the greenhouse gas (GHG) balance of the Earth's atmosphere. There is still much uncertainty about how the GHG dynamics of peatlands are affected by climate and land use change. Current field-based methods of estimating annual carbon exchange between peatlands and the atmosphere include flux chambers and eddy covariance towers. However, remote sensing has several advantages over these traditional approaches in terms of cost, spatial coverage and accessibility to remote locations. In this paper, we outline the basic principles of using remote sensing to estimate ecosystem carbon fluxes and explain the range of satellite data available for such estimations, considering the indices and models developed to make use of the data. Past studies, which have used remote sensing data in comparison with ground-based calculations of carbon fluxes over Northern peatland landscapes, are discussed, as well as the challenges of working with remote sensing on peatlands. Finally, we suggest areas in need of future work on this topic. We conclude that the application of remote sensing to models of carbon fluxes is a viable research method over Northern peatlands but further work is needed to develop more comprehensive carbon cycle models and to improve the long-term reliability of models, particularly on peatland sites undergoing restoration. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

  8. Variability of carbon and water fluxes following climate extremes over a tropical forest in southwestern Amazonia.

    Directory of Open Access Journals (Sweden)

    Marcelo Zeri

    Full Text Available The carbon and water cycles for a southwestern Amazonian forest site were investigated using the longest time series of fluxes of CO2 and water vapor ever reported for this site. The period from 2004 to 2010 included two severe droughts (2005 and 2010 and a flooding year (2009. The effects of such climate extremes were detected in annual sums of fluxes as well as in other components of the carbon and water cycles, such as gross primary production and water use efficiency. Gap-filling and flux-partitioning were applied in order to fill gaps due to missing data, and errors analysis made it possible to infer the uncertainty on the carbon balance. Overall, the site was found to have a net carbon uptake of ≈5 t C ha(-1 year(-1, but the effects of the drought of 2005 were still noticed in 2006, when the climate disturbance caused the site to become a net source of carbon to the atmosphere. Different regions of the Amazon forest might respond differently to climate extremes due to differences in dry season length, annual precipitation, species compositions, albedo and soil type. Longer time series of fluxes measured over several locations are required to better characterize the effects of climate anomalies on the carbon and water balances for the whole Amazon region. Such valuable datasets can also be used to calibrate biogeochemical models and infer on future scenarios of the Amazon forest carbon balance under the influence of climate change.

  9. Rapid forest recovery of carbon and water fluxes after a tropical firestorm

    Science.gov (United States)

    Brando, P. M.; Silverio, D. V.; Migliavacca, M.; Santos, C.; Kolle, O.; Balch, J.; Maracahipes, L.; Bustamante, M.; Coe, M. T.; Trumbore, S.

    2017-12-01

    Forest disturbances interact synergistically and drive potentially large and persistent degradation of ecosystem services in the tropics. Here we analyze multi-year measurements of carbon (C) and water (evapotranspiration; ET) fluxes in forests recovering from 7 years of prescribed fires. Located in southeast Amazonia, the experimental forest consisted of three 50-ha plots burned annually, triennially, or not at all between 2004-2010. During the subsequent seven-year recovery period from 2011 to present, tree survivorship and biomass sharply declined, with aboveground C stocks decreasing by 70-94% along forest edges. While vegetation regrowth in the forest understory triggered partial canopy closure, light-demanding grasses covered roughly the same area in 2015 that they did in 2012. However, the spatial distribution of grasses drastically changed, while C4 grass species replaced C3 ones. Surprisingly, the observed alterations in forest structure and dynamics rendered minor or no changes in total C fluxes and ET, probably because plants in the burned forest increased light- and reduced ecosystem water-use efficiency. Hence, delayed post-fire mortality of large trees can reduce forest C stocks and create opportunities for the establishment of invasive grasses, Yet, post-fire vegetation growth can rapidly restore C uptake and ET by optimizing resources use. These results show that tropical forests can rapidly recover the capacity to cycle water and carbon following disturbances, but also that a full recovery of biomass and vegetation dominance may take many years or decades.

  10. High heat flux actively cooled plasma facing components development, realization and first results in Tore Supra

    International Nuclear Information System (INIS)

    Grosman, A.

    2004-01-01

    The development, design, manufacture and testing of actively cooled high heat flux plasma facing components (PFC) has been an essential stage towards long powerful tokamak operations for Tore-Supra, it lasted about 10 years. This paper deals with the toroidal pumped limiter (TPL) that is able to sustain up to 10 MW/m 2 of nominal heat flux. This device is based on hardened copper alloy heat sink structures covered by a carbon fiber composite armour, it resulted in the manufacturing of 600 elementary components, called finger elements, to achieve the 7.6 m 2 TPL. This assembly has been operating in Tore-Supra since spring 2002. Some difficulties occurred during the manufacturing phase, the valuable industrial experience is summarized in the section 2. The permanent monitoring of PFC surface temperature all along the discharge is performed by a set of 6 actively cooled infrared endoscopes. The heat flux monitoring and control issue but also the progress made in our understanding of the deuterium retention in long discharges are described in the section 3. (A.C.)

  11. High heat flux actively cooled plasma facing components development, realization and first results in Tore Supra

    Energy Technology Data Exchange (ETDEWEB)

    Grosman, A. [Association Euratom-CEA, Centre d' Etudes de Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee

    2004-07-01

    The development, design, manufacture and testing of actively cooled high heat flux plasma facing components (PFC) has been an essential stage towards long powerful tokamak operations for Tore-Supra, it lasted about 10 years. This paper deals with the toroidal pumped limiter (TPL) that is able to sustain up to 10 MW/m{sup 2} of nominal heat flux. This device is based on hardened copper alloy heat sink structures covered by a carbon fiber composite armour, it resulted in the manufacturing of 600 elementary components, called finger elements, to achieve the 7.6 m{sup 2} TPL. This assembly has been operating in Tore-Supra since spring 2002. Some difficulties occurred during the manufacturing phase, the valuable industrial experience is summarized in the section 2. The permanent monitoring of PFC surface temperature all along the discharge is performed by a set of 6 actively cooled infrared endoscopes. The heat flux monitoring and control issue but also the progress made in our understanding of the deuterium retention in long discharges are described in the section 3. (A.C.)

  12. Global Monthly CO2 Flux Inversion Based on Results of Terrestrial Ecosystem Modeling

    Science.gov (United States)

    Deng, F.; Chen, J.; Peters, W.; Krol, M.

    2008-12-01

    Most of our understanding of the sources and sinks of atmospheric CO2 has come from inverse studies of atmospheric CO2 concentration measurements. However, the number of currently available observation stations and our ability to simulate the diurnal planetary boundary layer evolution over continental regions essentially limit the number of regions that can be reliably inverted globally, especially over continental areas. In order to overcome these restrictions, a nested inverse modeling system was developed based on the Bayesian principle for estimating carbon fluxes of 30 regions in North America and 20 regions for the rest of the globe. Inverse modeling was conducted in monthly steps using CO2 concentration measurements of 5 years (2000 - 2005) with the following two models: (a) An atmospheric transport model (TM5) is used to generate the transport matrix where the diurnal variation n of atmospheric CO2 concentration is considered to enhance the use of the afternoon-hour average CO2 concentration measurements over the continental sites. (b) A process-based terrestrial ecosystem model (BEPS) is used to produce hourly step carbon fluxes, which could minimize the limitation due to our inability to solve the inverse problem in a high resolution, as the background of our inversion. We will present our recent results achieved through a combination of the bottom-up modeling with BEPS and the top-down modeling based on TM5 driven by offline meteorological fields generated by the European Centre for Medium Range Weather Forecast (ECMFW).

  13. Carbon stocks and fluxes in managed peatlands in northern Borneo

    Science.gov (United States)

    Arn Teh, Yit; Manning, Frances; Cook, Sarah; Zin Zawawi, Norliyana; Sii, Longwin; Hill, Timothy; Page, Susan; Whelan, Mick; Evans, Chris; Gauci, Vincent; Chocholek, Melanie; Khoon Kho, Lip

    2017-04-01

    Oil palm is the largest agricultural crop in the tropics and accounts for 13 % of current tropical land area. Patterns of land-atmosphere exchange from oil palm ecosystems therefore have potentially important implications for regional and global C budgets due to the large scale of land conversion. This is particularly true for oil palm plantations on peat because of the large C stocks held by tropical peat soils that are potential sensitivity to human disturbance. Here we report preliminary findings on C stocks and fluxes from a long-term, multi-scale project in Sarawak, Malaysia that aims to quantify the impacts of oil palm conversion on C and greenhouse gas fluxes from oil palm recently established on peat. Land-atmosphere fluxes were determined using a combination of top-down and bottom-up methods (eddy covariance, canopy/stem and soil flux measurements, net primary productivity). Fluvial fluxes were determined by quantifying rates of dissolved and particulate organic C export. Ecosystem C dynamics were determined using the intensive C plot method, which quantified all major C stocks and fluxes, including plant and soil stocks, leaf litterfall, aboveground biomass production, root production, stem/canopy respiration, root-rhizosphere respiration, and heterotrophic soil respiration. Preliminary analysis indicates that vegetative aboveground biomass in these 7 year old plantations was 8.9-11.9 Mg C ha-1, or approximately one-quarter of adjacent secondary forest. Belowground biomass was 5.6-6.5 Mg C ha-1; on par with secondary forests. Soil C stocks in the 0-30 cm depth was 233.1-240.8 Mg C ha-1, or 32-36% greater than soil C stocks in secondary forests at the same depth (176.8 Mg C ha-1). Estimates of vegetative aboveground and belowground net primary productivity were 1.3-1.7 Mg C ha-1 yr-1 and 0.8-0.9 Mg C ha-1 yr-1, respectively. Fruit brunch production was approximately 67 Mg C ha-1over 7 yearsor 9.6 Mg C ha-1 yr-1. Total soil respiration rates were 18 Mg C ha

  14. 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,...

  15. Stockage de carbone et flux de gaz à effet de serre en prairie (synthèse bibliographique

    Directory of Open Access Journals (Sweden)

    Jérôme, E.

    2013-01-01

    Full Text Available Carbon sequestration and greenhouse gas fluxes in grassland. A review. Grassland carbon (C sequestration can play an important role in mitigating total greenhouse gas (GHG emissions of livestock production systems. An accurate inventory of livestock production system contribution to GHG emissions requires to think in terms of global budget, by considering both the GHG sources and the mitigation potential trough grassland soil carbon sequestration. There is a huge variability in C and GHG balances of grasslands that is mainly due to management practices and climatic conditions. The present article shows that, to reduce the uncertainties of the results, long term measurements at the field scale are necessary. Also, it shows the importance of taking into account the fluxes of the three main GHGs (carbon dioxide, nitrous oxide, methane into account when calculating the GHG budget. This article also highlights the need for a better understanding of the mechanisms driving the fluxes, in relation to environmental factors and management practices, in order to propose mitigation strategies able to enhance soil carbon sequestration in soils and to reduce methane and nitrous oxide emissions.

  16. Modeling Biogeochemical-Physical Interactions and Carbon Flux in the Sargasso Sea (Bermuda Atlantic Time-series Study site)

    Science.gov (United States)

    Signorini, Sergio R.; McClain, Charles R.; Christian, James R.

    2001-01-01

    An ecosystem-carbon cycle model is used to analyze the biogeochemical-physical interactions and carbon fluxes in the Bermuda Atlantic Time-series Study (BATS) site for the period of 1992-1998. The model results compare well with observations (most variables are within 8% of observed values). The sea-air flux ranges from -0.32 to -0.50 mol C/sq m/yr, depending upon the gas transfer algorithm used. This estimate is within the range (-0.22 to -0.83 mol C/sq m/yr) of previously reported values which indicates that the BATS region is a weak sink of atmospheric CO2. The overall carbon balance consists of atmospheric CO2 uptake of 0.3 Mol C/sq m/yr, upward dissolved inorganic carbon (DIC) bottom flux of 1.1 Mol C/sq m/yr, and carbon export of 1.4 mol C/sq m/yr via sedimentation. Upper ocean DIC levels increased between 1992 and 1996 at a rate of approximately 1.2 (micro)mol/kg/yr, consistent with observations. However, this trend was reversed during 1997-1998 to -2.7 (micro)mol/kg/yr in response to hydrographic changes imposed by the El Nino-La Nina transition, which were manifested in the Sargasso Sea by the warmest SST and lowest surface salinity of the period (1992-1998).

  17. High-flux water desalination with interfacial salt sieving effect in nanoporous carbon composite membranes

    Science.gov (United States)

    Chen, Wei; Chen, Shuyu; Liang, Tengfei; Zhang, Qiang; Fan, Zhongli; Yin, Hang; Huang, Kuo-Wei; Zhang, Xixiang; Lai, Zhiping; Sheng, Ping

    2018-04-01

    Freshwater flux and energy consumption are two important benchmarks for the membrane desalination process. Here, we show that nanoporous carbon composite membranes, which comprise a layer of porous carbon fibre structures grown on a porous ceramic substrate, can exhibit 100% desalination and a freshwater flux that is 3-20 times higher than existing polymeric membranes. Thermal accounting experiments demonstrated that the carbon composite membrane saved over 80% of the latent heat consumption. Theoretical calculations combined with molecular dynamics simulations revealed the unique microscopic process occurring in the membrane. When the salt solution is stopped at the openings to the nanoscale porous channels and forms a meniscus, the vapour can rapidly transport across the nanoscale gap to condense on the permeate side. This process is driven by the chemical potential gradient and aided by the unique smoothness of the carbon surface. The high thermal conductivity of the carbon composite membrane ensures that most of the latent heat is recovered.

  18. High-flux water desalination with interfacial salt sieving effect in nanoporous carbon composite membranes

    KAUST Repository

    Chen, Wei

    2018-03-05

    Freshwater flux and energy consumption are two important benchmarks for the membrane desalination process. Here, we show that nanoporous carbon composite membranes, which comprise a layer of porous carbon fibre structures grown on a porous ceramic substrate, can exhibit 100% desalination and a freshwater flux that is 3-20 times higher than existing polymeric membranes. Thermal accounting experiments demonstrated that the carbon composite membrane saved over 80% of the latent heat consumption. Theoretical calculations combined with molecular dynamics simulations revealed the unique microscopic process occurring in the membrane. When the salt solution is stopped at the openings to the nanoscale porous channels and forms a meniscus, the vapour can rapidly transport across the nanoscale gap to condense on the permeate side. This process is driven by the chemical potential gradient and aided by the unique smoothness of the carbon surface. The high thermal conductivity of the carbon composite membrane ensures that most of the latent heat is recovered.

  19. Evaluations of carbon fluxes estimated by top-down and bottom-up approaches

    Science.gov (United States)

    Murakami, K.; Sasai, T.; Kato, S.; Hiraki, K.; Maksyutov, S. S.; Yokota, T.; Nasahara, K.; Matsunaga, T.

    2013-12-01

    There are two types of estimating carbon fluxes using satellite observation data, and these are referred to as top-down and bottom-up approaches. Many uncertainties are however still remain in these carbon flux estimations, because the true values of carbon flux are still unclear and estimations vary according to the type of the model (e.g. a transport model, a process based model) and input data. The CO2 fluxes in these approaches are estimated by using different satellite data such as the distribution of CO2 concentration in the top-down approach and the land cover information (e.g. leaf area, surface temperature) in the bottom-up approach. The satellite-based CO2 flux estimations with reduced uncertainty can be used efficiently for identifications of large emission area and carbon stocks of forest area. In this study, we evaluated the carbon flux estimates from two approaches by comparing with each other. The Greenhouse gases Observing SATellite (GOSAT) has been observing atmospheric CO2 concentrations since 2009. GOSAT L4A data product is the monthly CO2 flux estimations for 64 sub-continental regions and is estimated by using GOSAT FTS SWIR L2 XCO2 data and atmospheric tracer transport model. We used GOSAT L4A CO2 flux as top-down approach estimations and net ecosystem productions (NEP) estimated by the diagnostic type biosphere model BEAMS as bottom-up approach estimations. BEAMS NEP is only natural land CO2 flux, so we used GOSAT L4A CO2 flux after subtraction of anthropogenic CO2 emissions and oceanic CO2 flux. We compared with two approach in temperate north-east Asia region. This region is covered by grassland and crop land (about 60 %), forest (about 20 %) and bare ground (about 20 %). The temporal variation for one year period was indicated similar trends between two approaches. Furthermore we show the comparison of CO2 flux estimations in other sub-continental regions.

  20. A low-frequency wave motion mechanism enables efficient energy transport in carbon nanotubes at high heat fluxes.

    Science.gov (United States)

    Zhang, Xiaoliang; Hu, Ming; Poulikakos, Dimos

    2012-07-11

    The great majority of investigations of thermal transport in carbon nanotubes (CNTs) in the open literature focus on low heat fluxes, that is, in the regime of validity of the Fourier heat conduction law. In this paper, by performing nonequilibrium molecular dynamics simulations we investigated thermal transport in a single-walled CNT bridging two Si slabs under constant high heat flux. An anomalous wave-like kinetic energy profile was observed, and a previously unexplored, wave-dominated energy transport mechanism is identified for high heat fluxes in CNTs, originated from excited low frequency transverse acoustic waves. The transported energy, in terms of a one-dimensional low frequency mechanical wave, is quantified as a function of the total heat flux applied and is compared to the energy transported by traditional Fourier heat conduction. The results show that the low frequency wave actually overtakes traditional Fourier heat conduction and efficiently transports the energy at high heat flux. Our findings reveal an important new mechanism for high heat flux energy transport in low-dimensional nanostructures, such as one-dimensional (1-D) nanotubes and nanowires, which could be very relevant to high heat flux dissipation such as in micro/nanoelectronics applications.

  1. Narrowband Bio-Indicator Monitoring of Temperate Forest Carbon Fluxes in Northeastern China

    Directory of Open Access Journals (Sweden)

    Quanzhou Yu

    2014-09-01

    Full Text Available Developments in hyperspectral remote sensing techniques during the last decade have enabled the use of narrowband indices to evaluate the role of forest ecosystem variables in estimating carbon (C fluxes. In this study, narrowband bio-indicators derived from EO-1 Hyperion data were investigated to determine whether they could capture the temporal variation and estimate the spatial variability of forest C fluxes derived from eddy covariance tower data. Nineteen indices were divided into four categories of optical indices: broadband, chlorophyll, red edge, and light use efficiency. Correlation tests were performed between the selected vegetation indices, gross primary production (GPP, and ecosystem respiration (Re. Among the 19 indices, five narrowband indices (Chlorophyll Index RedEdge 710, scaled photochemical reflectance index (SPRI*enhanced vegetation index (EVI, SPRI*normalized difference vegetation index (NDVI, MCARI/OSAVI[705, 750] and the Vogelmann Index, and one broad band index (EVI had R-squared values with a good fit for GPP and Re. The SPRI*NDVI has the highest significant coefficients of determination with GPP and Re (R2 = 0.86 and 0.89, p < 0.0001, respectively. SPRI*NDVI was used in atmospheric inverse modeling at regional scales for the estimation of C fluxes. We compared the GPP spatial patterns inversed from our model with corresponding results from the Vegetation Photosynthesis Model (VPM, the Boreal Ecosystems Productivity Simulator model, and MODIS MOD17A2 products. The inversed GPP spatial patterns from our model of SPRI*NDVI had good agreement with the output from the VPM model. The normalized difference nitrogen index was well correlated with measured C net ecosystem exchange. Our findings indicated that narrowband bio-indicators based on EO-1 Hyperion images could be used to predict regional C flux variations for Northeastern China’s temperate broad-leaved Korean pine forest ecosystems.

  2. Fluvial organic carbon flux from an eroding peatland catchment, southern Pennines, UK

    Directory of Open Access Journals (Sweden)

    R. R. Pawson

    2008-03-01

    Full Text Available This study investigates for the first time the relative importance of dissolved organic carbon (DOC and particulate organic carbon (POC in the fluvial carbon flux from an actively eroding peatland catchment in the southern Pennines, UK. Event scale variability in DOC and POC was examined and the annual flux of fluvial organic carbon was estimated for the catchment. At the event scale, both DOC and POC were found to increase with discharge, with event based POC export accounting for 95% of flux in only 8% of the time. On an annual cycle, exports of 35.14 t organic carbon (OC are estimated from the catchment, which represents an areal value of 92.47 g C m−2 a−1. POC was the most significant form of organic carbon export, accounting for 80% of the estimated flux. This suggests that more research is required on both the fate of POC and the rates of POC export in eroding peatland catchments.

  3. Seasonal variation of carbon fluxes in a sparse savanna in semi arid Sudan

    Directory of Open Access Journals (Sweden)

    El-Tahir Bashir

    2008-12-01

    Full Text Available Abstract Background Large spatial, seasonal and annual variability of major drivers of the carbon cycle (precipitation, temperature, fire regime and nutrient availability are common in the Sahel region. This causes large variability in net ecosystem exchange and in vegetation productivity, the subsistence basis for a major part of the rural population in Sahel. This study compares the 2005 dry and wet season fluxes of CO2 for a grass land/sparse savanna site in semi arid Sudan and relates these fluxes to water availability and incoming photosynthetic photon flux density (PPFD. Data from this site could complement the current sparse observation network in Africa, a continent where climatic change could significantly impact the future and which constitute a weak link in our understanding of the global carbon cycle. Results The dry season (represented by Julian day 35–46, February 2005 was characterized by low soil moisture availability, low evapotranspiration and a high vapor pressure deficit. The mean daily NEE (net ecosystem exchange, Eq. 1 was -14.7 mmol d-1 for the 12 day period (negative numbers denote sinks, i.e. flux from the atmosphere to the biosphere. The water use efficiency (WUE was 1.6 mmol CO2 mol H2O-1 and the light use efficiency (LUE was 0.95 mmol CO2 mol PPFD-1. Photosynthesis is a weak, but linear function of PPFD. The wet season (represented by Julian day 266–273, September 2005 was, compared to the dry season, characterized by slightly higher soil moisture availability, higher evapotranspiration and a slightly lower vapor pressure deficit. The mean daily NEE was -152 mmol d-1 for the 8 day period. The WUE was lower, 0.97 mmol CO2 mol H2O-1 and the LUE was higher, 7.2 μmol CO2 mmol PPFD-1 during the wet season compared to the dry season. During the wet season photosynthesis increases with PPFD to about 1600 μmol m-2s-1 and then levels off. Conclusion Based on data collected during two short periods, the studied ecosystem

  4. Carbon allocation and carbon isotope fluxes in the plant-soil-atmosphere continuum: a review

    Directory of Open Access Journals (Sweden)

    N. Brüggemann

    2011-11-01

    Full Text Available The terrestrial carbon (C cycle has received increasing interest over the past few decades, however, there is still a lack of understanding of the fate of newly assimilated C allocated within plants and to the soil, stored within ecosystems and lost to the atmosphere. Stable carbon isotope studies can give novel insights into these issues. In this review we provide an overview of an emerging picture of plant-soil-atmosphere C fluxes, as based on C isotope studies, and identify processes determining related C isotope signatures. The first part of the review focuses on isotopic fractionation processes within plants during and after photosynthesis. The second major part elaborates on plant-internal and plant-rhizosphere C allocation patterns at different time scales (diel, seasonal, interannual, including the speed of C transfer and time lags in the coupling of assimilation and respiration, as well as the magnitude and controls of plant-soil C allocation and respiratory fluxes. Plant responses to changing environmental conditions, the functional relationship between the physiological and phenological status of plants and C transfer, and interactions between C, water and nutrient dynamics are discussed. The role of the C counterflow from the rhizosphere to the aboveground parts of the plants, e.g. via CO2 dissolved in the xylem water or as xylem-transported sugars, is highlighted. The third part is centered around belowground C turnover, focusing especially on above- and belowground litter inputs, soil organic matter formation and turnover, production and loss of dissolved organic C, soil respiration and CO2 fixation by soil microbes. Furthermore, plant controls on microbial communities and activity via exudates and litter production as well as microbial community effects on C mineralization are reviewed. A further part of the paper is dedicated to physical interactions between soil CO2 and the soil matrix, such as

  5. Dynamical and biogeochemical control on the decadal variability of ocean carbon fluxes

    Directory of Open Access Journals (Sweden)

    R. Séférian

    2013-04-01

    Full Text Available Several recent observation-based studies suggest that ocean anthropogenic carbon uptake has slowed down due to the impact of anthropogenic forced climate change. However, it remains unclear whether detected changes over the recent time period can be attributed to anthropogenic climate change or rather to natural climate variability (internal plus naturally forced variability alone. One large uncertainty arises from the lack of knowledge on ocean carbon flux natural variability at the decadal time scales. To gain more insights into decadal time scales, we have examined the internal variability of ocean carbon fluxes in a 1000 yr long preindustrial simulation performed with the Earth System Model IPSL-CM5A-LR. Our analysis shows that ocean carbon fluxes exhibit low-frequency oscillations that emerge from their year-to-year variability in the North Atlantic, the North Pacific, and the Southern Ocean. In our model, a 20 yr mode of variability in the North Atlantic air-sea carbon flux is driven by sea surface temperature variability and accounts for ~40% of the interannual regional variance. The North Pacific and the Southern Ocean carbon fluxes are also characterised by decadal to multi-decadal modes of variability (10 to 50 yr that account for 20–40% of the interannual regional variance. These modes are driven by the vertical supply of dissolved inorganic carbon through the variability of Ekman-induced upwelling and deep-mixing events. Differences in drivers of regional modes of variability stem from the coupling between ocean dynamics variability and the ocean carbon distribution, which is set by large-scale secular ocean circulation.

  6. Can pelagic net heterotrophy account for carbon fluxes from eastern Canadian lakes?

    Energy Technology Data Exchange (ETDEWEB)

    Dubois, Kristal, E-mail: kristal.dubois@gmail.com [Ottawa-Carleton Geoscience Center, University of Ottawa, 140 Louis Pasteur, Ottawa, Ontario, K1N 6N5 (Canada); Carignan, Richard [Departement des Sciences Biologiques, Universite de Montreal C.P. 6128, succ. Centre-Ville, Montreal, Quebec, H3C 3J7 (Canada); Veizer, Jan [Ottawa-Carleton Geoscience Center, University of Ottawa, 140 Louis Pasteur, Ottawa, Ontario, K1N 6N5 (Canada)

    2009-05-15

    Lakes worldwide are commonly oversaturated with CO{sub 2}, however the source of this CO{sub 2} oversaturation is not well understood. To examine the magnitude of the C flux to the atmosphere and determine if an excess of respiration (R) over gross primary production (GPP) is sufficient to account for this C flux, metabolic parameters and stable isotopes of dissolved O{sub 2} and C were measured in 23 Quebec lakes. All of the lakes sampled were oversaturated with CO{sub 2} over the sampling period, on average 221 {+-} 25%. However, little evidence was found to conclude that this CO{sub 2} oversaturation was the result of an excess of pelagic R over GPP. In lakes Croche and a l'Ours, where CO{sub 2} flux, R and GPP were measured weekly, the annual difference between pelagic GPP and R, or net primary production (NPP), was not sufficient to account for the size of the CO{sub 2} flux to the atmosphere. In Lac Croche average annual NPP was 14.4 mg C m{sup -2} d{sup -1} while the average annual flux of CO{sub 2} to the atmosphere was 34 mg C m{sup -2} d{sup -1}. In Lac a l'Ours average annual NPP was -9.1 mg C m{sup -2} d{sup -1} while the average annual flux of CO{sub 2} to the atmosphere was 55 mg C m{sup -2} d{sup -1}. In all of the lakes sampled, O{sub 2} saturation averaged 104.0 {+-} 1.7% during the ice-free season and the isotopic composition of dissolved O{sub 2} ({delta}{sup 18}O{sub DO}) was 22.9 {+-} 0.3 per mille , lower than atmospheric values and indicative of net autotrophy. Carbon evasion was not a function of R, nor did the isotopic signature of dissolved CO{sub 2} in the lakes present evidence of excess R over GPP. External inputs of C must therefore subsidize the lake to explain the continued CO{sub 2} oversaturation. The isotopic composition of dissolved inorganic C ({delta}{sup 13}C{sub DIC}) indicates that the CO{sub 2} oversaturation cannot be attributed to in situ aerobic respiration. {delta}{sup 13}C{sub DIC} reveals a source of excess

  7. On the choice of the driving temperature for eddy-covariance carbon dioxide flux partitioning

    Directory of Open Access Journals (Sweden)

    G. Lasslop

    2012-12-01

    Full Text Available Networks that merge and harmonise eddy-covariance measurements from many different parts of the world have become an important observational resource for ecosystem science. Empirical algorithms have been developed which combine direct observations of the net ecosystem exchange of carbon dioxide with simple empirical models to disentangle photosynthetic (GPP and respiratory fluxes (Reco. The increasing use of these estimates for the analysis of climate sensitivities, model evaluation and calibration demands a thorough understanding of assumptions in the analysis process and the resulting uncertainties of the partitioned fluxes. The semi-empirical models used in flux partitioning algorithms require temperature observations as input, but as respiration takes place in many parts of an ecosystem, it is unclear which temperature input – air, surface, bole, or soil at a specific depth – should be used. This choice is a source of uncertainty and potential biases. In this study, we analysed the correlation between different temperature observations and nighttime NEE (which equals nighttime respiration across FLUXNET sites to understand the potential of the different temperature observations as input for the flux partitioning model. We found that the differences in the correlation between different temperature data streams and nighttime NEE are small and depend on the selection of sites. We investigated the effects of the choice of the temperature data by running two flux partitioning algorithms with air and soil temperature. We found the time lag (phase shift between air and soil temperatures explains the differences in the GPP and Reco estimates when using either air or soil temperatures for flux partitioning. The impact of the source of temperature data on other derived ecosystem parameters was estimated, and the strongest impact was found for the temperature sensitivity. Overall, this study suggests that the

  8. Can pelagic net heterotrophy account for carbon fluxes from eastern Canadian lakes?

    International Nuclear Information System (INIS)

    Dubois, Kristal; Carignan, Richard; Veizer, Jan

    2009-01-01

    Lakes worldwide are commonly oversaturated with CO 2 , however the source of this CO 2 oversaturation is not well understood. To examine the magnitude of the C flux to the atmosphere and determine if an excess of respiration (R) over gross primary production (GPP) is sufficient to account for this C flux, metabolic parameters and stable isotopes of dissolved O 2 and C were measured in 23 Quebec lakes. All of the lakes sampled were oversaturated with CO 2 over the sampling period, on average 221 ± 25%. However, little evidence was found to conclude that this CO 2 oversaturation was the result of an excess of pelagic R over GPP. In lakes Croche and a l'Ours, where CO 2 flux, R and GPP were measured weekly, the annual difference between pelagic GPP and R, or net primary production (NPP), was not sufficient to account for the size of the CO 2 flux to the atmosphere. In Lac Croche average annual NPP was 14.4 mg C m -2 d -1 while the average annual flux of CO 2 to the atmosphere was 34 mg C m -2 d -1 . In Lac a l'Ours average annual NPP was -9.1 mg C m -2 d -1 while the average annual flux of CO 2 to the atmosphere was 55 mg C m -2 d -1 . In all of the lakes sampled, O 2 saturation averaged 104.0 ± 1.7% during the ice-free season and the isotopic composition of dissolved O 2 (δ 18 O DO ) was 22.9 ± 0.3 per mille , lower than atmospheric values and indicative of net autotrophy. Carbon evasion was not a function of R, nor did the isotopic signature of dissolved CO 2 in the lakes present evidence of excess R over GPP. External inputs of C must therefore subsidize the lake to explain the continued CO 2 oversaturation. The isotopic composition of dissolved inorganic C (δ 13 C DIC ) indicates that the CO 2 oversaturation cannot be attributed to in situ aerobic respiration. δ 13 C DIC reveals a source of excess C enriched in 13 C, which may be accounted for by anaerobic sediment respiration or groundwater inputs followed by kinetic isotope fractionation during degassing

  9. Measurements of carbon dioxide and heat fluxes during monsoon ...

    Indian Academy of Sciences (India)

    An increase in carbon dioxide (CO2) concentrations in the atmosphere due to ... The changes in land ... the air quality and climate models. 2. ... soon period of 2011 as a part Cloud Aerosol .... density effects due to heat and water vapour trans-.

  10. Carbon pools and flux in U.S. forest products

    Science.gov (United States)

    Linda S. Heath; Richard A. Birdsey; Clark Row; Andrew J. Plantinga

    1996-01-01

    Increasing recognition that anthropogenic CO2 and other greenhouse gas emissions may effect climate change has prompted research studies on global carbon (C) budgets and international agreements for action. At the United Nations Conference on Environment and Development in 1992, world leaders and citizens gathered and initiated the Framework...

  11. 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...

  12. Fluxes and burial of particulate organic carbon along the Adriatic mud-wedge (Mediterranean Sea)

    Science.gov (United States)

    Tesi, T.; Langone, L.; Giani, M.; Ravaioli, M.; Miserocchi, S.

    2012-04-01

    Clinoform-shaped deposits are ubiquitous sedimentological bodies of modern continental margins, including both carbonate and silicoclastic platforms. They formed after the attainment of the modern sea level high-stand (mid-late Holocene) when river outlets and shoreline migrated landward. As clinoform-shape deposits are essential building blocks of the infill of sedimentary basins, they are sites of intense organic carbon (OC) deposition and account for a significant fraction of OC burial in the ocean during interglacial periods. In this study, we focused on sigmoid clinoforms that are generally associated with low-energy environments. In particular, we characterized the modern accumulation and burial of OC along the late-Holocene sigmoid in the Western Adriatic Sea (Mediterranean Sea). This sedimentary body consists of a mud wedge recognizable on seismic profiles as a progradational unit lying on top the maximum flooding surface that marks the time of maximum landward shift of the shoreline attained around 5.5 kyr cal BP. In the last two decades, several projects have investigated sediment dynamics and organic geochemistry along the Adriatic mud wedge (e.g., PRISMA, EURODELTA, EuroSTRATAFORM, PASTA, CIPE, VECTOR). All these studies increased our understanding of strata formation and organic matter cycling in this epicontinental margin. The overarching goal of this study was to combine the results gained during these projects with newly acquired data to assess fluxes to seabed and burial efficiency of organic carbon along the uppermost strata of the Adriatic mud-wedge. Our study benefited of an extensive number of radionuclide-based (Pb-210, and Cs-137) sediment accumulation rates and numerous biogeochemical data of surface sediments and sediment cores (organic carbon, total nitrogen, radiocarbon measurements, carbon stable isotopes, and biomarkers). In addition, because the accumulation of river-borne sediment may or may not be linked to a specific source, another

  13. Carbon dioxide and methane fluxes from arctic mudboils

    International Nuclear Information System (INIS)

    Wilson, K.S.; Humphreys, E.R.

    2010-01-01

    Carbon-rich ecosystems in the Arctic have large stores of soil carbon. However, small changes in climate have the potential to change the carbon (C) balance. This study examined how changes in ecosystem structure relate to differences in the exchange of greenhouse gases, notably carbon dioxide (CO 2 ) and methane (CH 4 ), between the atmosphere and soil. In particular, it examined low-center mudboils to determine the influence that this distinct form of patterned ground in the Arctic may have on the overall C balance of Tundra ecosystems. The net ecosystem exchange of carbon dioxide (NEE) was measured along with methane efflux along a 35-m transect intersecting two mudboils in a wet sedge fen in Canada's Southern Arctic during the summer of 2008. Mudboil features revealed significant variations in vegetation, soil temperature and thaw depth, and soil organic matter content along this transect. Variations in NEE were attributed to changes in the amount of vascular vegetation, but CO 2 and CH 4 effluxes were similar among the two mudboil and the sedge fen sampling areas. The study showed that vegetation played a key role in limiting temporal variations in CH 4 effluxes through plant mediated transport in both mudboil and sedge fen sampling areas. The negligible vascular plant colonization in one of the mudboils was likely due to more active frost heave processes. Growth and decomposition of cryptogamic organisms along with inflow of dissolved organic C and warmer soil temperatures may have been the cause of the rather high CO 2 and CH 4 efflux in this mudboil area.

  14. Humin to Human: Organic carbon, sediment, and water fluxes along river corridors in a changing world

    Energy Technology Data Exchange (ETDEWEB)

    Sutfin, Nicholas Alan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-11-20

    This is a presentation with slides on What does it mean to be human? ...humin?; River flow and Hydrographs; Snake River altered hydrograph (Marston et al., 2005); Carbon dynamics are important in rivers; Rivers and streams as carbon sink; Reservoirs for organic carbon; Study sites in Colorado; River morphology; Soil sample collection; Surveys at RMNP; Soil organic carbon content at RMNP; Abandoned channels and Cutoffs; East River channel migration and erosion; Linking hydrology to floodplain sediment flux; Impact of Extreme Floods on Floodplain Sediment; Channel Geometry: RMNP; Beavers dams and multithread channels; Geomorphology and carbon in N. St. Vrain Creek; Geomorphology and carbon along the East River; Geomorphology and carbon in N. St. Vrain Creek; San Marcos River, etc.

  15. Carbon and water fluxes and footprints in tropical agricultural systems under rainfed and irrigated conditions

    Science.gov (United States)

    Johnson, M. S.; Lathuilliere, M. J.; Morillas, L.; Dalmagro, H. J.; D'Acunha, B.; Kim, Y.; Suarez, A.; Couto, E. G.

    2017-12-01

    In this talk, we will summarize results obtained using three tropical agricultural water observatories in Guanacaste, Costa Rica and Mato Grosso, Brazil. These flux towers and associated sensors enable detailed assessments of carbon use and water use efficiencies for crops under rain-fed and irrigated conditions. In addition to directly assessing water consumption from crops via eddy covariance, determination of water footprints and water use efficiencies using sensors and integrating it with remotely sensed data make it possible to (i) evaluate and compare different irrigation systems used in the study regions (drip, pivot and flood irrigation), (ii) assess the effect of irrigation over the local water balance to identify vulnerabilities associated with intensive water extraction for irrigation, and (iii) study the effect of inter-annual water availability fluctuations on crop water use. We conclude by comparing volumetric water footprints for crops, their carbon footprints, and water and carbon use efficiencies of crops produced under business-as-usual and alternative soil and water management scenarios.

  16. Change of chemical bond and wettability of polylacticacid implanted with high-flux carbon ion

    International Nuclear Information System (INIS)

    Zhang Jizhong; Kang Jiachen; Zhang Xiaoji; Zhou Hongyu

    2008-01-01

    Polylacticacid (PLA) was submitted to high-flux carbon ion implantation with energy of 40 keV. It was investigated to the effect of ion fluence (1 x 10 12 -1 x 10 15 ions/cm 2 ) on the properties of the polymer. X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), wettability, and roughness were employed to study change of structure and properties of the as-implanted PLA samples. Six carbon bonds, that is, C, C-H, C-O-C, C-O, O-C-O, and >C=O, were observed on surfaces of the as-implanted PLA samples. The intensities of various chemical bonds changed with increasing ion fluence. AFM images displayed that there was irradiation damage and that it was related closely with ion fluence. At fluence as high as 1 x 10 15 ions/cm 2 surface-restructuring phenomenum took place on the surface of the PLA. Wettability was also affected by the variation on the fluence. With increasing ion fluence, the water contact angle of the as-implanted PLA samples changed gradually reaching a maximum of 76.5 deg. with 1 x 10 13 ions/cm 2 . The experimental results revealed that carbon ion fluence strongly affected surface chemical bond, morphology, wettability, and roughness of the PLA samples

  17. A land-use and land-cover modeling strategy to support a national assessment of carbon stocks and fluxes

    Science.gov (United States)

    Sohl, Terry L.; Sleeter, Benjamin M.; Zhu, Zhi-Liang; Sayler, Kristi L.; Bennett, Stacie; Bouchard, Michelle; Reker, Ryan R.; Hawbaker, Todd; Wein, Anne; Liu, Shu-Guang; Kanengieter, Ronald; Acevedo, William

    2012-01-01

    Changes in land use, land cover, disturbance regimes, and land management have considerable influence on carbon and greenhouse gas (GHG) fluxes within ecosystems. Through targeted land-use and land-management activities, ecosystems can be managed to enhance carbon sequestration and mitigate fluxes of other GHGs. National-scale, comprehensive analyses of carbon sequestration potential by ecosystem are needed, with a consistent, nationally applicable land-use and land-cover (LULC) modeling framework a key component of such analyses. The U.S. Geological Survey has initiated a project to analyze current and projected future GHG fluxes by ecosystem and quantify potential mitigation strategies. We have developed a unique LULC modeling framework to support this work. Downscaled scenarios consistent with IPCC Special Report on Emissions Scenarios (SRES) were constructed for U.S. ecoregions, and the FORE-SCE model was used to spatially map the scenarios. Results for a prototype demonstrate our ability to model LULC change and inform a biogeochemical modeling framework for analysis of subsequent GHG fluxes. The methodology was then successfully used to model LULC change for four IPCC SRES scenarios for an ecoregion in the Great Plains. The scenario-based LULC projections are now being used to analyze potential GHG impacts of LULC change across the U.S.

  18. Effects of ocean acidification and hydrodynamic conditions on carbon metabolism and dissolved organic carbon (DOC) fluxes in seagrass populations.

    Science.gov (United States)

    Egea, Luis G; Jiménez-Ramos, Rocío; Hernández, Ignacio; Bouma, Tjeerd J; Brun, Fernando G

    2018-01-01

    Global change has been acknowledged as one of the main threats to the biosphere and its provision of ecosystem services, especially in marine ecosystems. Seagrasses play a critical ecological role in coastal ecosystems, but their responses to ocean acidification (OA) and climate change are not well understood. There have been previous studies focused on the effects of OA, but the outcome of interactions with co-factors predicted to alter during climate change still needs to be addressed. For example, the impact of higher CO2 and different hydrodynamic regimes on seagrass performance remains unknown. We studied the effects of OA under different current velocities on productivity of the seagrass Zostera noltei, using changes in dissolved oxygen as a proxy for the seagrass carbon metabolism, and release of dissolved organic carbon (DOC) in a four-week experiment using an open-water outdoor mesocosm. Under current pH conditions, increasing current velocity had a positive effect on productivity, but this depended on shoot density. However, this positive effect of current velocity disappeared under OA conditions. OA conditions led to a significant increase in gross production rate and respiration, suggesting that Z. noltei is carbon-limited under the current inorganic carbon concentration of seawater. In addition, an increase in non-structural carbohydrates was found, which may lead to better growing conditions and higher resilience in seagrasses subjected to environmental stress. Regarding DOC flux, a direct and positive relationship was found between current velocity and DOC release, both under current pH and OA conditions. We conclude that OA and high current velocity may lead to favourable growth scenarios for Z. noltei populations, increasing their productivity, non-structural carbohydrate concentrations and DOC release. Our results add new dimensions to predictions on how seagrass ecosystems will respond to climate change, with important implications for the

  19. Effects of ocean acidification and hydrodynamic conditions on carbon metabolism and dissolved organic carbon (DOC fluxes in seagrass populations.

    Directory of Open Access Journals (Sweden)

    Luis G Egea

    Full Text Available Global change has been acknowledged as one of the main threats to the biosphere and its provision of ecosystem services, especially in marine ecosystems. Seagrasses play a critical ecological role in coastal ecosystems, but their responses to ocean acidification (OA and climate change are not well understood. There have been previous studies focused on the effects of OA, but the outcome of interactions with co-factors predicted to alter during climate change still needs to be addressed. For example, the impact of higher CO2 and different hydrodynamic regimes on seagrass performance remains unknown. We studied the effects of OA under different current velocities on productivity of the seagrass Zostera noltei, using changes in dissolved oxygen as a proxy for the seagrass carbon metabolism, and release of dissolved organic carbon (DOC in a four-week experiment using an open-water outdoor mesocosm. Under current pH conditions, increasing current velocity had a positive effect on productivity, but this depended on shoot density. However, this positive effect of current velocity disappeared under OA conditions. OA conditions led to a significant increase in gross production rate and respiration, suggesting that Z. noltei is carbon-limited under the current inorganic carbon concentration of seawater. In addition, an increase in non-structural carbohydrates was found, which may lead to better growing conditions and higher resilience in seagrasses subjected to environmental stress. Regarding DOC flux, a direct and positive relationship was found between current velocity and DOC release, both under current pH and OA conditions. We conclude that OA and high current velocity may lead to favourable growth scenarios for Z. noltei populations, increasing their productivity, non-structural carbohydrate concentrations and DOC release. Our results add new dimensions to predictions on how seagrass ecosystems will respond to climate change, with important

  20. Carbon Monitoring System Flux for Fossil Fuel L4 V1 (CMSFluxFossilfuel) at GES DISC

    Data.gov (United States)

    National Aeronautics and Space Administration — This dataset provides the Carbon Flux for Fossil Fuel. The NASA Carbon Monitoring System (CMS) is designed to make significant contributions in characterizing,...

  1. Ballast minerals and the sinking carbon flux in the ocean: carbon-specific respiration rates and sinking velocity of marine snow aggregates

    Directory of Open Access Journals (Sweden)

    M. H. Iversen

    2010-09-01

    Full Text Available Recent observations have shown that fluxes of ballast minerals (calcium carbonate, opal, and lithogenic material and organic carbon fluxes are closely correlated in the bathypelagic zones of the ocean. Hence it has been hypothesized that incorporation of biogenic minerals within marine aggregates could either protect the organic matter from decomposition and/or increase the sinking velocity via ballasting of the aggregates. Here we present the first combined data on size, sinking velocity, carbon-specific respiration rate, and composition measured directly in three aggregate types; Emiliania huxleyi aggregates (carbonate ballasted, Skeletonema costatum aggregates (opal ballasted, and aggregates made from a mix of both E. huxleyi and S. costatum (carbonate and opal ballasted. Overall average carbon-specific respiration rate was ~0.13 d−1 and did not vary with aggregate type and size. Ballasting from carbonate resulted in 2- to 2.5-fold higher sinking velocities than those of aggregates ballasted by opal. We compiled literature data on carbon-specific respiration rate and sinking velocity measured in aggregates of different composition and sources. Compiled carbon-specific respiration rates (including this study vary between 0.08 d−1 and 0.20 d−1. Sinking velocity increases with increasing aggregate size within homogeneous sources of aggregates. When compared across different particle and aggregate sources, however, sinking velocity appeared to be independent of particle or aggregate size. The carbon-specific respiration rate per meter settled varied between 0.0002 m−1 and 0.0030 m−1, and decreased with increasing aggregate size. It was lower for calcite ballasted aggregates as compared to that of similar sized opal ballasted aggregates.

  2. Metabolic fluxes in the central carbon metabolism of Dinoroseobacter shibae and Phaeobacter gallaeciensis, two members of the marine Roseobacter clade

    Directory of Open Access Journals (Sweden)

    Rabus Ralf

    2009-09-01

    Full Text Available Abstract Background In the present work the central carbon metabolism of Dinoroseobacter shibae and Phaeobacter gallaeciensis was studied at the level of metabolic fluxes. These two strains belong to the marine Roseobacter clade, a dominant bacterial group in various marine habitats, and represent surface-associated, biofilm-forming growth (P. gallaeciensis and symbiotic growth with eukaryotic algae (D. shibae. Based on information from recently sequenced genomes, a rich repertoire of pathways has been identified in the carbon core metabolism of these organisms, but little is known about the actual contribution of the various reactions in vivo. Results Using 13C labelling techniques in specifically designed experiments, it could be shown that glucose-grown cells of D. shibae catabolise the carbon source exclusively via the Entner-Doudoroff pathway, whereas alternative routes of glycolysis and the pentose phosphate pathway are obviously utilised for anabolic purposes only. Enzyme assays confirmed this flux pattern and link the lack of glycolytic flux to the absence of phosphofructokinase activity. The previously suggested formation of phosphoenolpyruvate from pyruvate during mixotrophic CO2 assimilation was found to be inactive under the conditions studied. Moreover, it could be shown that pyruvate carboxylase is involved in CO2 assimilation and that the cyclic respiratory mode of the TCA cycle is utilised. Interestingly, the use of intracellular pathways was highly similar for P. gallaeciensis. Conclusion The present study reveals the first insight into pathway utilisation within the Roseobacter group. Fluxes through major intracellular pathways of the central carbon metabolism, which are closely linked to the various important traits found for the Roseobacter clade, could be determined. The close similarity of fluxes between the two physiologically rather different species might provide the first indication of more general key properties among

  3. Multi-annual fluxes of carbon dioxide from an intensively cultivated temperate peatland

    Science.gov (United States)

    Cumming, Alex; Balzter, Heiko; Evans, Chris; Kaduk, Joerg; Morrison, Ross; Page, Susan

    2016-04-01

    East Anglia contains the largest continuous area of lowland fen peatlands in the United Kingdom (UK) which store vast quantities of terrestrial carbon (C) that have accrued over millennia. These long term C stores have largely been drained and converted for agricultural land use over the last 400 years due to their high agricultural production potential. Initial drainage of these peatlands leads to surface lowering and peat wastage. Prolonged exposure of carbon dense peat soils to oxygen through continued agricultural management results in sustained losses of carbon dioxide (CO₂) to the atmosphere. An increasing population in the UK has the potential to put further stress on these productive but rapidly diminishing Grade 1 agricultural land. Improving our understanding of land management impacts on CO₂ emissions from these soils is crucial to improving their longevity as an important store of C and as an economic resource. Our measurements at an intensively cultivated lowland peatland in Norfolk, UK, are the first multi-annual record using the micrometeorological eddy covariance (EC) technique to measure CO₂ fluxes associated with the production of horticultural salad crops. Three full years of flux measurements over leek (2013), lettuce (2014) and celery (2015) cropping systems found that the site was a net annual source of CO₂ with a net ecosystem exchange (NEE) of 6.59, 7.84 and 7.71 t C-CO₂ ha-1 a-1 respectively. The leek crop, with its longer growing period, had a lower annual NEE due to its long growth period from early spring through to late autumn, whereas the shorter growing periods of lettuce and celery meant their peak growth (CO₂ uptake, Gross Primary Productivity, GPP) took place during early/mid-summer with post-harvest weeds exploiting the later growing season but exhibited lower CO₂ assimilation than the leek crop. Periods of high CO₂ emissions from the soil to the atmosphere were measured during mechanical disruptions to the soils

  4. Moss and soil contributions to the annual net carbon flux of a maturing boreal forest

    Science.gov (United States)

    Harden, J.W.; O'Neill, K. P.; Trumbore, S.E.; Veldhuis, H.; Stocks, B.J.

    1997-01-01

    We used input and decomposition data from 14C studies of soils to determine rates of vertical accumulation of moss combined with carbon storage inventories on a sequence of burns to model how carbon accumulates in soils and moss after a stand-killing fire. We used soil drainage - moss associations and soil drainage maps of the old black spruce (OBS) site at the BOREAS northern study area (NSA) to areally weight the contributions of each moderately well drained, feathermoss areas; poorly drained sphagnum - feathermoss areas; and very poorly drained brown moss areas to the carbon storage and flux at the OBS NSA site. On this very old (117 years) complex of black spruce, sphagnum bog veneer, and fen systems we conclude that these systems are likely sequestering 0.01-0.03 kg C m-2 yr-' at OBS-NSA today. Soil drainage in boreal forests near Thompson, Manitoba, controls carbon storage and flux by controlling moss input and decomposition rates and by controlling through fire the amount and quality of carbon left after burning. On poorly drained soils rich in sphagnum moss, net accumulation and long-term storage of carbon is higher than on better drained soils colonized by feathermosses. The carbon flux of these contrasting ecosystems is best characterized by soil drainage class and stand age, where stands recently burned are net sources of CO2, and maturing stands become increasingly stronger sinks of atmospheric CO2. This approach to measuring carbon storage and flux presents a method of scaling to larger areas using soil drainage, moss cover, and stand age information.

  5. Carbon dioxide in northern high latitude oceans: Anthropogenic increase and air-sea flux variability

    International Nuclear Information System (INIS)

    Omar, Abdirahman M.

    2003-01-01

    in the meltwater pool during summer, associated with changes in temperature of the inflowing Atlantic Water, is found to give rise to variations in the annual cycle of fCO2s''w. During cold years, sea ice extends south of the polar front and melts in the Atlantic sector. This results in a reduced heating and earlier stratification of the surface water during summer, with the latter triggering a rapid and strong phytoplankton bloom. As a consequence, cold years are characterized by a stronger and shorter lived fCO2 s ''w drawdown during summer. However, significant differences are not found between the annual mean air-sea CO2 fluxes computed for cold and warm years. In this study, fCO2''s''w was calculated by applying an empirical relationship to a 23-year time series of apparent oxygen utilization, seawater temperature, salinity, and phosphate, which have been grouped into cold and warm years. The result was combined with data of atmospheric mole fraction of CO2 and wind speed to calculate the air-sea flux of CO2. Seasonal sea ice formation and subsequent brine rejection produce high density brine-enriched Shelf Water (BSW) in Storfjorden. It is shown that sea ice formation is accompanied by a seaward flux of atmospheric CO2 (paper III). This was inferred by using inorganic carbon and auxiliary hydrographic and nutrient data collected during four cruises from 1999 to 2002. The inferred flux is 12 times higher for the part of the fjord where open water and/or thin ice conditions prevail throughout the winter. By extrapolating this result to the entire Arctic Ocean, it is estimated that sea ice formation during winter can account for an uptake of atmospheric CO2 of around 50x 10''1''2 g C yr ''-''1. Further, it is speculated that changes in the areal extent of sea ice formation in the Arctic Ocean at the end of this century may triple this uptake. The mean winter time air-sea CO2 flux in the northern North Atlantic is found to be 0.1 G ton, with an interannual

  6. Carbon dioxide in northern high latitude oceans: Anthropogenic increase and air-sea flux variability

    Energy Technology Data Exchange (ETDEWEB)

    Omar, Abdirahman M.

    2003-07-01

    , changes in the meltwater pool during summer, associated with changes in temperature of the inflowing Atlantic Water, is found to give rise to variations in the annual cycle of fCO2s''w. During cold years, sea ice extends south of the polar front and melts in the Atlantic sector. This results in a reduced heating and earlier stratification of the surface water during summer, with the latter triggering a rapid and strong phytoplankton bloom. As a consequence, cold years are characterized by a stronger and shorter lived fCO2{sup s}''w drawdown during summer. However, significant differences are not found between the annual mean air-sea CO2 fluxes computed for cold and warm years. In this study, fCO2''s''w was calculated by applying an empirical relationship to a 23-year time series of apparent oxygen utilization, seawater temperature, salinity, and phosphate, which have been grouped into cold and warm years. The result was combined with data of atmospheric mole fraction of CO2 and wind speed to calculate the air-sea flux of CO2. Seasonal sea ice formation and subsequent brine rejection produce high density brine-enriched Shelf Water (BSW) in Storfjorden. It is shown that sea ice formation is accompanied by a seaward flux of atmospheric CO2 (paper III). This was inferred by using inorganic carbon and auxiliary hydrographic and nutrient data collected during four cruises from 1999 to 2002. The inferred flux is 12 times higher for the part of the fjord where open water and/or thin ice conditions prevail throughout the winter. By extrapolating this result to the entire Arctic Ocean, it is estimated that sea ice formation during winter can account for an uptake of atmospheric CO2 of around 50x 10''1''2 g C yr ''-''1. Further, it is speculated that changes in the areal extent of sea ice formation in the Arctic Ocean at the end of this century may triple this uptake. The mean winter time air-sea CO2

  7. Estimation of Surface Temperature and Heat Flux by Inverse Heat Transfer Methods Using Internal Temperatures Measured While Radiantly Heating a Carbon/Carbon Specimen up to 1920 F

    Science.gov (United States)

    Pizzo, Michelle; Daryabeigi, Kamran; Glass, David

    2015-01-01

    The ability to solve the heat conduction equation is needed when designing materials to be used on vehicles exposed to extremely high temperatures; e.g. vehicles used for atmospheric entry or hypersonic flight. When using test and flight data, computational methods such as finite difference schemes may be used to solve for both the direct heat conduction problem, i.e., solving between internal temperature measurements, and the inverse heat conduction problem, i.e., using the direct solution to march forward in space to the surface of the material to estimate both surface temperature and heat flux. The completed research first discusses the methods used in developing a computational code to solve both the direct and inverse heat transfer problems using one dimensional, centered, implicit finite volume schemes and one dimensional, centered, explicit space marching techniques. The developed code assumed the boundary conditions to be specified time varying temperatures and also considered temperature dependent thermal properties. The completed research then discusses the results of analyzing temperature data measured while radiantly heating a carbon/carbon specimen up to 1920 F. The temperature was measured using thermocouple (TC) plugs (small carbon/carbon material specimens) with four embedded TC plugs inserted into the larger carbon/carbon specimen. The purpose of analyzing the test data was to estimate the surface heat flux and temperature values from the internal temperature measurements using direct and inverse heat transfer methods, thus aiding in the thermal and structural design and analysis of high temperature vehicles.

  8. 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.

  9. Diagnosing the influence of model structure on the simulation of water, energy and carbon fluxes on bark beetle infested forests

    Science.gov (United States)

    Gochis, D. J.; Gutmann, E. D.; Brooks, P. D.; Reed, D. E.; Ewers, B. E.; Pendall, E.; Biederman, J. A.; Harpold, A. A.; Barnard, H. R.; Hu, J.

    2011-12-01

    Forest dynamics induced by insect infestation can have a significant, local impact on plant physiological regulation of water, energy and carbon fluxes. Rapid mortality succeeded by more gradually varying land cover changes are presently thought to initiate a cascade of changes to water, energy and carbon budgets at the forest stand scale. Initial model sensitivity results have suggested very strong changes in land-atmosphere exchanges of these variables. Specifically, model results from the Noah land surface model, a relatively simple model, have suggested that loss of transpiration function may result in a nearly 50% increase in seasonal soil moisture values and similar increases in runoff production for locations in the central Rocky Mountains. However, differing model structures, such as the representation of plant canopy architecture, snowpack dynamics, dynamic vegetation and hillslope hydrologic processes, may significantly confound the synthesis of results from different modeling systems. We assess the performance of new suite of model simulations from three different land surface models of differing model structures and complexity levels against a comprehensive set of field observations of land surface flux and state variables. The focus of the analysis is in diagnosing how model structure influences changes in energy, water and carbon budget partitioning prior to and following insect infestation. Specific emphasis in this presentation is placed on verifying variables that characterize top of canopy and within canopy energy and water fluxes. We conclude the presentation with a set of recommendations about the advantages and disadvantages of various model structures in their simulation of insect driven forest dynamics.

  10. A case study of carbon fluxes from land change in the southwest Brazilian Amazon

    Science.gov (United States)

    Barrett, K.; Rogan, J.; Eastman, J.R.

    2009-01-01

    Worldwide, land change is responsible for one-fifth of anthropogenic carbon emissions. In Brazil, three-quarters of carbon emissions originate from land change. This study represents a municipal-scale study of carbon fluxes from vegetation in Rio Branco, Brazil. Land-cover maps of pasture, forest, and secondary growth from 1993, 1996, 1999, and 2003 were produced using an unsupervised classification method (overall accuracy = 89%). Carbon fluxes from land change over the decade of imagery were estimated from transitions between land-cover categories for each time interval. This article presents new methods for estimating emissions reductions from carbon stored in the vegetation that replaces forests (e.g., pasture) and sequestration by new (>10-15 years) forests, which reduced gross emissions by 16, 15, and 22% for the period of 1993-1996, 1996-1999, and 1999-2003, respectively. The methods used in the analysis are broadly applicable and provide a comprehensive characterization of regional-scale carbon fluxes from land change.

  11. Carbon and nitrogen fluxes in the North Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Naqvi, S.W.A.; Naik, H.; DeSouza, W.; Narvekar, P.V.; Paropkari, A.L.; Bange, H.W.

    , the reverse is probably true for the burial. Notwithstanding these uncertainties, it seems reasonable to conclude that the POC delivery by rivers substantially exceeds sedimentary organic carbon burial in the NEIO. In spite of the higher sedimentation... in the NEIO has been reported to range from 0.3 to 2.5 (average 1.4) Tg N yr -1 (Schäfer et al., 1993). This is slightly higher than the DIN delivery by rivers. Rate of N 2 -fixation in the NEIO has not been measured so far. However, it is probably much...

  12. Impact of climatic change on ocean carbon fluxes. Role of the decadal variability

    International Nuclear Information System (INIS)

    Seferian, Roland

    2013-01-01

    Since the industrial revolution, oceans have absorbed roughly one quarter of the anthropogenic emissions of CO 2 , slowing down climate change. The evolution of the ocean carbon sink, paralleled to the anthropogenic CO 2 emissions, is ruled by the CO 2 as well as climate. Influence of atmospheric CO 2 in the recent evolution of the ocean carbon sink is well understood whilst this is not the case for the climate's one. Indeed, some authors claim that the recent variations of the ocean CO 2 sink can be attributed to climate change, whereas some others suggest that these latter are controlled by a decadal variability, which is poorly understood. In this thesis, we address question relative to the role of the decadal variability of the ocean carbon fluxes through the mean of numerical modeling. On one hand, we have demonstrated that ocean carbon fluxes exhibit decadal fluctuations within the high latitudes oceans. These fluctuations displays modes of 10 to 50-year long which account for 20 to 40% of the year-to-year variability. Thanks to Detection and Attribution methods applied to RECCAP project's reconstructions (1960-2005), we have then assessed whether the occurrence of fluctuations at decadal time scale could hamper the detection of the climate contribution to the recent evolution of ocean carbon fluxes. We have shown that the climate contribution is indeed not detected in the high latitude oceans due to the presence of decadal mode of variability. In the low latitude oceans instead, the weaker fluctuations of ocean carbon fluxes at decadal time scale favor the detection of climate influence in the recent variations of the CO 2 fluxes. (author) [fr

  13. Flux

    DEFF Research Database (Denmark)

    Ravn, Ib

    . FLUX betegner en flyden eller strømmen, dvs. dynamik. Forstår man livet som proces og udvikling i stedet for som ting og mekanik, får man et andet billede af det gode liv end det, som den velkendte vestlige mekanicisme lægger op til. Dynamisk forstået indebærer det gode liv den bedst mulige...... kanalisering af den flux eller energi, der strømmer igennem os og giver sig til kende i vore daglige aktiviteter. Skal vores tanker, handlinger, arbejde, samvær og politiske liv organiseres efter stramme og faste regelsæt, uden slinger i valsen? Eller skal de tværtimod forløbe ganske uhindret af regler og bånd...

  14. Organic carbon fluxes in stemflow, throughfall and rainfall in an olive orchard

    Science.gov (United States)

    Lombardo, L.; Vanwalleghem, T.; Gomez, J. A.

    2012-04-01

    The importance of rainfall distribution under the vegetation canopy for nutrient cycling of forest ecosystems has been widely studied (e.g. Kolkai et al., 1999, Bath et al., 2011). It has been demonstrated how throughfall and stemflow reach the soil as chemically-enriched water, by incorporating soluble organic and inorganic particles deriving from plant exudates and from atmospheric depositions (dryfall and wetfall) present on the surfaces of the plant (leaves, bark, fruits). Dissolved (DOC) and particulate (POC) organic carbon inputs from stem- and canopy-derived hydrologic fluxes are small but important components of the natural carbon cycle. DOC has also the capability to form complexes that control the transport and solubility of heavy metals in surface and ground waters, being composed for the most part (75-90%) of fulvic, humic or tanninic compounds, and for the resting part of molecules like carbohydrates, hydrocarbons, waxes, fatty acids, amino and hydroxy acids. However, very little data is available for agricultural tree crops, especially olive trees. In this sense, the objective of this work is to investigate the concentration and fluxes of organic carbon in rainfall, throughfall, and stemflow in a mature olive orchard located in Cordoba, in Southern Spain and to relate them to rainfall characteristics and tree physiology. The measurements started in October 2011. Four high density polyethylene bottles with 18-cm-diameter polyethylene funnels for throughfall collection were placed beneath the canopy of each of the three selected olive trees; four more collectors were placed in open spaces in the same orchard for rainfall sampling. Stemflow was collected through PVC spiral tubes wrapped around the trunks and leading into collection bins. The throughflow sampling points were chosen randomly. Total and dissolved organic carbon concentrations in unfiltered (TOC) and filtered (0.45 µm membrane filter, DOC) collected waters were measured using a TOC analyzer

  15. Carbon, Water and Heat Fluxes Comparison between Two Subtropical Mangroves Sites, Southeastern China

    Science.gov (United States)

    Liu, F.; Lin, G., Sr.; Lu, W.; Chen, H.

    2014-12-01

    Due to the numerous ecological services provided by mangroves and its vital ecological role, the monitor of mangrove ecosystem in China receives a growing concern. We deployed eddy covariance system and meteorological instrument to continuously monitor the exchange of CO2 flux, water vapor, heat flux and meteorological factors of mangrove ecosystem on Guangdong and Fujian province in 2012, namely GDGQ and FJYX. The major species of two sites were similar, and by 2012 were on average 2.8~3.3 m in height. Climatically, temperature, net radiation and rainfall have significant seasonal difference, all reaching peak values during the summer wet season. Based on the results available, two sites were strong carbon sink in annual scale. The cumulative NEP in GDGQ (667.92 g C m-2 year-1) was lower than that in FJYX (848.31 g C m-2 year-1), but respiration (Rd) was opposite, 1433.80 g C m-2 year-1 for GDGQ and 1345.13 g C m-2 year-1 for FJYX. Tidal inundation decreased nighttime Rd by ~0.82 μ mol m-2 s-1 in GDGQ and ~0.99 μ mol m-2 s-1 in FJYX. The diurnal patterns of sensible (Hs) and latent heat fluxes (LE) of two sites were both single peak, and peak values both occurred at 12:00~14:00. Hs of GDGQ was higher than FJYX during nighttime and lower in daytime, but LE of GDGQ was lower than FJYX during nighttime. Evapotranspiration (ET) of two sites presented similar seasonal pattern, reaching highest value in July and lowest value in January. ET of whole year were 892.66 mm and 1051.76mm for GDGQ and FJYX. Daily WUE was strong negatively correlated to salinity in in FJYX, but the pattern of GDGQ was less distinct. Due to its high salinity stress and long-time inundation, water use efficiency (WUE) of GDGQ was higher than FJYX in all months. Soil heat flux (G) was quite small when compared to other heat flux, but both had obvious diurnal pattern in two sites. G was positively correlated to air temperature and G variation range of GDGQ (-8.68 ~5.51 w m-2) was greater than

  16. Analyzing the causes and spatial pattern of the European 2003 carbon flux anomaly using seven models

    Directory of Open Access Journals (Sweden)

    M. Vetter

    2008-04-01

    Full Text Available Globally, the year 2003 is associated with one of the largest atmospheric CO2 rises on record. In the same year, Europe experienced an anomalously strong flux of CO2 from the land to the atmosphere associated with an exceptionally dry and hot summer in Western and Central Europe. In this study we analyze the magnitude of this carbon flux anomaly and key driving ecosystem processes using simulations of seven terrestrial ecosystem models of different complexity and types (process-oriented and diagnostic. We address the following questions: (1 how large were deviations in the net European carbon flux in 2003 relative to a short-term baseline (1998–2002 and to longer-term variations in annual fluxes (1980 to 2005, (2 which European regions exhibited the largest changes in carbon fluxes during the growing season 2003, and (3 which ecosystem processes controlled the carbon balance anomaly .

    In most models the prominence of 2003 anomaly in carbon fluxes declined with lengthening of the reference period from one year to 16 years. The 2003 anomaly for annual net carbon fluxes ranged between 0.35 and –0.63 Pg C for a reference period of one year and between 0.17 and –0.37 Pg C for a reference period of 16 years for the whole Europe.

    In Western and Central Europe, the anomaly in simulated net ecosystem productivity (NEP over the growing season in 2003 was outside the 1σ variance bound of the carbon flux anomalies for 1980–2005 in all models. The estimated anomaly in net carbon flux ranged between –42 and –158 Tg C for Western Europe and between 24 and –129 Tg C for Central Europe depending on the model used. All models responded to a dipole pattern of the climate anomaly in 2003. In Western and Central Europe NEP was reduced due to heat and drought. In contrast, lower than normal temperatures and higher air humidity decreased NEP over Northeastern Europe. While models agree on the sign of changes in

  17. Black carbon network in Mexico. First Results

    Science.gov (United States)

    Barrera, Valter; Peralta, Oscar; Granado, Karen; Ortinez, Abraham; Alvarez-Ospina, Harry; Espinoza, Maria de la Luz; Castro, Telma

    2017-04-01

    After the United Nations Framework Convention on Climate Change celebrated in Paris 2016, many countries should adopt some mechanisms in the next years to contribute to mitigate greenhouse gas emissions and support sustainable development. Mexico Government has adopted an unconditional international commitment to carry out mitigation actions that would result in the reduction of 51% in black carbon (BC) emissions by year 2030. However, many BC emissions have been calculated by factor emissions. Since optical measurements of environmental BC concentrations can vary according the different components and their subsequence wavelength measure, it's important to obtain more accurate values. BC is formally defined as an ideally light-absorbing substance composed by carbon (Bond et al., 2013), and is the second main contributor (behind Carbon Dioxide; CO2) to positive radiative forcing (Ramanathan and Carmichael, 2008). Recently, BC has been used as an additional indicator in air quality management in some cities because is emitted from the incomplete combustion of fossil fuels, biofuel and biomass burning in both anthropogenic and it is always emitted with other particles and gases, such as organic carbon (OC), nitrogen oxides (NOx), and sulfur dioxide (SO2). Black Carbon, PM2.5 and pollutant gases were measured from January 2015 to December 2015 at three main cities in Mexico, and two other places to evaluate the BC concentration levels in the country. The urban background sites (Mexico City, Monterrey, Guadalajara, MXC-UB, GDL-UB, MTY-UB), a sub-urban background site (Juriquilla, Queretaro, JUR-SUB) and a regional background site (Altzomoni, ALT-RB). Results showed the relationship between BC and PM2.5 in the 3 large cities, with BC/PM2.5 ratios near 0.14 to 0.09 and a high BC-CO relationship in all the year in Mexico City, who showed that mobile sources are a common, at least in cities with a non-significant biomass burning emission related to agriculture or coal

  18. Carbon dioxide, methane and nitrous oxide fluxes from a fire chronosequence in subarctic boreal forests of Canada.

    Science.gov (United States)

    Köster, Egle; Köster, Kajar; Berninger, Frank; Aaltonen, Heidi; Zhou, Xuan; Pumpanen, Jukka

    2017-12-01

    Forest fires are one of the most important natural disturbances in boreal forests, and their occurrence and severity are expected to increase as a result of climate warming. A combination of factors induced by fire leads to a thawing of the near-surface permafrost layer in subarctic boreal forest. Earlier studies reported that an increase in the active layer thickness results in higher carbon dioxide (CO 2 ) and methane (CH 4 ) emissions. We studied changes in CO 2 , CH 4 and nitrous oxide (N 2 O) fluxes in this study, and the significance of several environmental factors that influence the greenhouse gas (GHG) fluxes at three forest sites that last had fires in 2012, 1990 and 1969, and we compared these to a control area that had no fire for at least 100years. The soils in our study acted as sources of CO 2 and N 2 O and sinks for CH 4 . The elapsed time since the last forest fire was the only factor that significantly influenced all studied GHG fluxes. Soil temperature affected the uptake of CH 4 , and the N 2 O fluxes were significantly influenced by nitrogen and carbon content of the soil, and by the active layer depth. Results of our study confirm that the impacts of a forest fire on GHGs last for a rather long period of time in boreal forests, and are influenced by the fire induced changes in the ecosystem. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Simulation and sensitivity analysis of carbon storage and fluxes in the New Jersey Pinelands

    Science.gov (United States)

    Zewei Miao; Richard G. Lathrop; Ming Xu; Inga P. La Puma; Kenneth L. Clark; John Hom; Nicholas Skowronski; Steve. Van Tuyl

    2011-01-01

    A major challenge in modeling the carbon dynamics of vegetation communities is the proper parameterization and calibration of eco-physiological variables that are critical determinants of the ecosystem process-based model behavior. In this study, we improved and calibrated a biochemical process-based WxBGC model by using in situ AmeriFlux eddy covariance tower...

  20. Spatial and temporal variations in net carbon flux during HAPEX-Sahel.

    NARCIS (Netherlands)

    Moncrieff, J.B.; Monteny, B.; Verhoef, A.; Friborg, Th.; Elbers, J.; Kabat, P.; DeBruin, H.; Soegaard, H.; Jarvis, P.G.; Taupin, J.D.

    1997-01-01

    Micrometeorological measurements of the surface flux of carbon dioxide were made at a number of spatially separate sites within the HAPEX-Sahel experimental area. Differences in the timing of plant development caused by differences in rainfall (both quantity and frequency) over the experimental area

  1. SEASONAL SOIL FLUXES OF CARBON MONOXIDE IN BURNED AND UNBURNED BRAZILIAN SAVANNAS

    Science.gov (United States)

    Soil-atmosphere fluxes of carbon monoxide (CO) were measured from September 1999 through November 2000 in savanna areas in central Brazil (Cerrado) under different fire regimes using transparent and opaque static chambers. Studies focused on two vegetation types, cerrado stricto...

  2. Fast nanostructured carbon microparticle synthesis by one-step high-flux plasma processing

    NARCIS (Netherlands)

    Aussems, D. U. B.; Bystrov, K.; Dogan, I.; Arnas, C.; Cabié, M.; Neisius, T.; Rasinski, M.; Zoethout, E.; Lipman, P.; van de Sanden, M. C. M.; Morgan, T. W.

    2017-01-01

    This study demonstrates a fast one-step synthesis method for nanostructured carbon microparticles on graphite samples using high-flux plasma exposure. These structures are considered as potential candidates for energy applications such as Li-ion batteries and supercapacitors. The samples were

  3. Fast nanostructured carbon microparticle synthesis by one-step high-flux plasma processing

    NARCIS (Netherlands)

    Aussems, D.U.B.; Bystrov, K.E.; Doǧan, I.; Arnas, C.; Cabié, M.; Neisius, T.; Rasinski, M.; Lipman, P.J.L.; van de Sanden, M.C.M.; Morgan, T.W.

    This study demonstrates a fast one-step synthesis method for nanostructured carbon microparticles on graphite samples using high-flux plasma exposure. These structures are considered as potential candidates for energy applications such as Li-ion batteries and supercapacitors. The samples were

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

    Science.gov (United States)

    B. D. Amiro; A. G. Barr; J. G. Barr; T. A. Black; R. Bracho; al. et.

    2010-01-01

    [1] Disturbances are important for renewal of North American forests. Here we summarize more than 180 site years of eddy covariance measurements of carbon dioxide flux made at forest chronosequences in North America. The disturbances included standreplacing fire (Alaska, Arizona, Manitoba, and Saskatchewan) and harvest (British Columbia, Florida, New Brunswick, Oregon...

  5. Effects of ocean acidification on pelagic carbon fluxes in a mesocosm experiment

    NARCIS (Netherlands)

    Spilling, K.; Schulz, K.G.; Paul, A.J.; Boxhammer, T.; Achterberg, E.P.; Hornick, T.; Lischka, S.; Stuhr, A.; Bermúdez, R.; Czerny, J.; Crawfurd, K.; Brussaard, C.P.D.; Grossart, H.-P.; Riebesell, U.

    2016-01-01

    About a quarter of anthropogenic CO2 emissions are currently taken up by the oceans, decreasing seawater pH. We performed a mesocosm experiment in the Baltic Sea in order to investigate the consequences of increasing CO2 levels on pelagic carbon fluxes. A gradient of different CO2 scenarios, ranging

  6. Behaviour of carbon dioxide and water vapour flux densities from a disturbed raised peat bog

    NARCIS (Netherlands)

    Nieveen, J.P.; Jacobs, A.F.G.

    2002-01-01

    Measurements of carbon dioxide and water vapour flux densities were carried out for a disturbed raised peat bog in the north of the Netherlands during an 18 month continuous experiment. Tussock grass (sp. Molinea caerulae) mainly dominated the vegetation of the bog area. The maximum leaf area index

  7. 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.

  8. Magnitude and Uncertainty of Carbon Pools and Fluxes in the US Forests

    Science.gov (United States)

    Harris, N.; Saatchi, S. S.; Fore, A.; Yu, Y.; Woodall, C. W.; Ganguly, S.; Nemani, R. R.; Hagen, S.; Birdsey, R.; Brown, S.; Salas, W.; Johnson, K. D.

    2015-12-01

    Sassan Saatchi1,2, Stephan Hagen3, Christopher Woodall4 , Sangram Ganguly,5 Nancy Harris6, Sandra Brown7, Timothy Pearson7, Alexander Fore1, Yifan Yu1, Rama Nemani5, Gong Zhang5, William Salas4, Roger Cooke81 NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA2 Institute of Environment and Sustainability, University of California, Los Angeles, CA, 90095, USA3 Applied Geosolutions, 55 Main Street Suit 125, Newmarket, NH 03857, USA4 USDA Forest Service, Northern Research Station, Saint Paul, MN 55108, USA5 NASA Ames Research Center, Moffett Field, CA 94035, USA6 Forests Program, World Resources Institute, Washington, DC, 20002, USA7 Winrock International, Ecosystem Services Unit, Arlington, VA 22202, USA8 Risk Analysis Resources for the Future, Washington DC 20036-1400Assessment of the carbon sinks and sources associated with greenhouse gas (GHG) fluxes across the US forestlands is a priority of the national climate mitigation policy. However, estimates of fluxes from the land sector are less precise compared to other sectors because of the large sources of uncertainty in quantifying the carbon pools, emissions, and removals associated with anthropogenic (land use) and natural changes in the US forestlands. As part of the NASA's Carbon Monitoring System, we developed a methodology based on a combination of ground inventory and space observations to develop spatially refined carbon pools and fluxes including the gross emissions and sequestration of carbon at each 1-ha land unit across the forestlands in the continental United States (CONUS) for the period of 2006-2010. Here, we provide the magnitude and uncertainty of multiple pools and fluxes of the US forestlands and outline the observational requirements to reduce the uncertainties for developing national climate mitigation policies based on the carbon sequestration capacity of the US forest lands. Keywords: forests, carbon pools, greenhouse gas, land use, attribution

  9. Dissolved organic carbon fluxes from soils in the Alaskan coastal temperate rainforest

    Science.gov (United States)

    D'Amore, D. V.; Edwards, R.; Hood, E. W.; Herendeen, P. A.; Valentine, D.

    2011-12-01

    Soil saturation and temperature are the primary factors that influence soil carbon cycling. Interactions between these factors vary by soil type, climate, and landscape position, causing uncertainty in predicting soil carbon flux from. The soils of the North American perhumid coastal temperate rainforest (NCTR) store massive amounts of carbon, yet there is no estimate of dissolved organic carbon (DOC) export from different soil types in the region. There are also no working models that describe the influence of soil saturation and temperature on the export of DOC from soils. To address this key information gap, we measured soil water table elevation, soil temperature, and soil and stream DOC concentrations to calculate DOC flux across a soil hydrologic gradient that included upland soils, forested wetland soils, and sloping bog soils in the NCTR of southeast Alaska. We found that increased soil temperature and frequent fluctuations of soil water tables promoted the export of large quantities of DOC from wetland soils and relatively high amounts of DOC from mineral soils. Average area-weighted DOC flux ranged from 7.7 to 33.0 g C m-2 y-1 across a gradient of hydropedologic soil types. The total area specific export of carbon as DOC for upland, forested wetland and sloping bog catchments was 77, 306, and 329 Kg C ha-1 y-1 respectively. The annual rate of carbon export from wetland soils in this region is among the highest reported in the literature. These findings highlight the importance of terrestrial-aquatic fluxes of DOC as a pathway for carbon loss in the NCTR.

  10. The LandCarbon Web Application: Advanced Geospatial Data Delivery and Visualization Tools for Communication about Ecosystem Carbon Sequestration and Greenhouse Gas Fluxes

    Science.gov (United States)

    Thomas, N.; Galey, B.; Zhu, Z.; Sleeter, B. M.; Lehmer, E.

    2015-12-01

    The LandCarbon web application (http://landcarbon.org) is a collaboration between the U.S. Geological Survey and U.C. Berkeley's Geospatial Innovation Facility (GIF). The LandCarbon project is a national assessment focused on improved understanding of carbon sequestration and greenhouse gas fluxes in and out of ecosystems related to land use, using scientific capabilities from USGS and other organizations. The national assessment is conducted at a regional scale, covers all 50 states, and incorporates data from remote sensing, land change studies, aquatic and wetland data, hydrological and biogeochemical modeling, and wildfire mapping to estimate baseline and future potential carbon storage and greenhouse gas fluxes. The LandCarbon web application is a geospatial portal that allows for a sophisticated data delivery system as well as a suite of engaging tools that showcase the LandCarbon data using interactive web based maps and charts. The web application was designed to be flexible and accessible to meet the needs of a variety of users. Casual users can explore the input data and results of the assessment for a particular area of interest in an intuitive and interactive map, without the need for specialized software. Users can view and interact with maps, charts, and statistics that summarize the baseline and future potential carbon storage and fluxes for U.S. Level 2 Ecoregions for 3 IPCC emissions scenarios. The application allows users to access the primary data sources and assessment results for viewing and download, and also to learn more about the assessment's objectives, methods, and uncertainties through published reports and documentation. The LandCarbon web application is built on free and open source libraries including Django and D3. The GIF has developed the Django-Spillway package, which facilitates interactive visualization and serialization of complex geospatial raster data. The underlying LandCarbon data is available through an open application

  11. Changing Land Use from Cotton to Bioenergy Crops in the Southern Great Plains: Implications on Carbon and Water Vapor Fluxes

    Science.gov (United States)

    Rajan, N.; Sharma, S.

    2016-12-01

    We are facing an unprecedented challenge in securing America's energy future. To address this challenge, increased biofuel crop production is needed. Although first-generation biofuels like corn ethanol are available, second-generation biofuels are gaining importance because they don't directly compete with food production. Second-generation biofuels are made from the by-products of intensive agriculture or from less-intensive agriculture on more marginal lands. The Southwestern U.S. Cotton Belt can play a significant role in this effort through a change from more conventional crops (like continuous cotton) to second-generation biofuel feedstocks (biomass sorghum and perennial grasses). While we believe there would be environmental benefits associated with this change in land use, their exact nature and magnitude have not been investigated for this region. The overall goal of the proposed study was to investigate the water and carbon (C) fluxes associated with the change in agricultural land use to biofuels-dominated cropping systems in the semi-arid Southwestern U.S. Cotton Belt region. Eddy covariance flux towers were established at selected producer fields (cotton, perennial grasses and biomass sorghum) in the Southern Great Plains region. The fluxes of carbon dioxide, water vapor and sensible heat between the surface and the atmosphere will be measured throughout the year. The results have demonstrated that the dynamics of C and water vapor fluxes for these agroecosystems were strongly affected by environmental variables, management factors, and crop phenology. Detailed results will be presented at the meeting.

  12. User-Friendly Predictive Modeling of Greenhouse Gas (GHG) Fluxes and Carbon Storage in Tidal Wetlands

    Science.gov (United States)

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

    2015-12-01

    We developed user-friendly empirical models to predict instantaneous fluxes of CO2 and CH4 from coastal wetlands based on a small set of dominant hydro-climatic and environmental drivers (e.g., photosynthetically active radiation, soil temperature, water depth, and soil salinity). The dominant predictor variables were systematically identified by applying a robust data-analytics framework on a wide range of possible environmental variables driving wetland greenhouse gas (GHG) fluxes. The method comprised of a multi-layered data-analytics framework, including Pearson correlation analysis, explanatory principal component and factor analyses, and partial least squares regression modeling. The identified dominant predictors were finally utilized to develop power-law based non-linear regression models to predict CO2 and CH4 fluxes under different climatic, land use (nitrogen gradient), tidal hydrology and salinity conditions. Four different tidal wetlands of Waquoit Bay, MA were considered as the case study sites to identify the dominant drivers and evaluate model performance. The study sites were dominated by native Spartina Alterniflora and characterized by frequent flooding and high saline conditions. The model estimated the potential net ecosystem carbon balance (NECB) both in gC/m2 and metric tonC/hectare by up-scaling the instantaneous predicted fluxes to the growing season and accounting for the lateral C flux exchanges between the wetlands and estuary. The entire model was presented in a single Excel spreadsheet as a user-friendly ecological engineering tool. The model can aid the development of appropriate GHG offset protocols for setting monitoring plans for tidal wetland restoration and maintenance projects. The model can also be used to estimate wetland GHG fluxes and potential carbon storage under various IPCC climate change and sea level rise scenarios; facilitating an appropriate management of carbon stocks in tidal wetlands and their incorporation into a

  13. The European forest sector: past and future carbon budget and fluxes under different management scenarios

    Science.gov (United States)

    Pilli, Roberto; Grassi, Giacomo; Kurz, Werner A.; Fiorese, Giulia; Cescatti, Alessandro

    2017-05-01

    The comprehensive analysis of carbon stocks and fluxes of managed European forests is a prerequisite to quantify their role in biomass production and climate change mitigation. We applied the Carbon Budget Model (CBM) to 26 European countries, parameterized with country information on the historical forest age structure, management practices, harvest regimes and the main natural disturbances. We modeled the C stocks for the five forest pools plus harvested wood products (HWPs) and the fluxes among these pools from 2000 to 2030. The aim is to quantify, using a consistent modeling framework for all 26 countries, the main C fluxes as affected by land-use changes, natural disturbances and forest management and to assess the impact of specific harvest and afforestation scenarios after 2012 on the mitigation potential of the EU forest sector. Substitution effects and the possible impacts of climate are not included in this analysis. Results show that for the historical period from 2000 to 2012 the net primary productivity (NPP) of the forest pools at the EU level is on average equal to 639 Tg C yr-1. The losses are dominated by heterotrophic respiration (409 Tg C yr-1) and removals (110 Tg C yr-1), with direct fire emissions being only 1 Tg C yr-1, leading to a net carbon stock change (i.e., sink) of 110 Tg C yr-1. Fellings also transferred 28 Tg C yr-1 of harvest residues from biomass to dead organic matter pools. The average annual net sector exchange (NSE) of the forest system, i.e., the carbon stock changes in the forest pools including HWP, equals a sink of 122 Tg C yr-1 (i.e., about 19 % of the NPP) for the historical period, and in 2030 it reaches 126, 101 and 151 Tg C yr-1, assuming constant, increasing (+20 %) and decreasing (-20 %) scenarios, respectively, of both harvest and afforestation rates compared to the historical period. Under the constant harvest rate scenario, our findings show an incipient aging process of the forests existing in 1990: although NPP

  14. Seasonality and variability of coccolithophore fluxes in response to diverse oceanographic regimes in the Bay of Bengal: Sediment trap results

    Digital Repository Service at National Institute of Oceanography (India)

    Mergulhao, L.P.; Guptha, M.V.S.; Unger, D.; Murty, V.S.N.

    carbonate and diatom opal fluxes continued to increase. Tanaka and Kawahata (2001) reported that the calculated coccolith- CaCO3 fluxes ranged between 6.8 and 49.6 mg m-2day-1 and contributed 23.3% of total CaCO3 flux in the west Caroline Basin...

  15. The effect of typhoon on particulate organic carbon flux in the southern East China Sea

    Directory of Open Access Journals (Sweden)

    C.-C. Hung

    2010-10-01

    Full Text Available Severe tropical storms play an important role in triggering phytoplankton blooms, but the extent to which such storms influence biogenic carbon flux from the euphotic zone is unclear. In 2008, typhoon Fengwong provided a unique opportunity to study the in situ biological responses including phytoplankton blooms and particulate organic carbon fluxes associated with a severe storm in the southern East China Sea (SECS. After passage of the typhoon, the sea surface temperature (SST in the SECS was markedly cooler (∼25 to 26 °C than before typhoon passage (∼28 to 29 °C. The POC flux 5 days after passage of the typhoon was 265 ± 14 mg C m−2 d−1, which was ∼1.7-fold that (140–180 mg C m−2 d−1 recorded during a period (June–August, 2007 when no typhoons occurred. A somewhat smaller but nevertheless significant increase in POC flux (224–225 mg C m−2 d−1 was detected following typhoon Sinlaku which occurred approximately 1 month after typhoon Fengwong, indicating that typhoon events can increase biogenic carbon flux efficiency in the SECS. Remarkably, phytoplankton uptake accounted for only about 5% of the nitrate injected into the euphotic zone by typhoon Fengwong. It is likely that phytoplankton population growth was constrained by a combination of light limitation and grazing pressure. Modeled estimates of new/export production were remarkably consistent with the average of new and export production following typhoon Fengwong. The same model suggested that during non-typhoon conditions approximately half of the export of organic carbon occurs via convective mixing of dissolved organic carbon, a conclusion consistent with earlier work at comparable latitudes in the open ocean.

  16. Carbon flux from plants to soil microbes is highly sensitive to nitrogen addition and biochar amendment

    Science.gov (United States)

    Kaiser, C.; Solaiman, Z. M.; Kilburn, M. R.; Clode, P. L.; Fuchslueger, L.; Koranda, M.; Murphy, D. V.

    2012-04-01

    The release of carbon through plant roots to the soil has been recognized as a governing factor for soil microbial community composition and decomposition processes, constituting an important control for ecosystem biogeochemical cycles. Moreover, there is increasing awareness that the flux of recently assimilated carbon from plants to the soil may regulate ecosystem response to environmental change, as the rate of the plant-soil carbon transfer will likely be affected by increased plant C assimilation caused by increasing atmospheric CO2 levels. What has received less attention so far is how sensitive the plant-soil C transfer would be to possible regulations coming from belowground, such as soil N addition or microbial community changes resulting from anthropogenic inputs such as biochar amendments. In this study we investigated the size, rate and sensitivity of the transfer of recently assimilated plant C through the root-soil-mycorrhiza-microbial continuum. Wheat plants associated with arbuscular mycorrhizal fungi were grown in split-boxes which were filled either with soil or a soil-biochar mixture. Each split-box consisted of two compartments separated by a membrane which was penetrable for mycorrhizal hyphae but not for roots. Wheat plants were only grown in one compartment while the other compartment served as an extended soil volume which was only accessible by mycorrhizal hyphae associated with the plant roots. After plants were grown for four weeks we used a double-labeling approach with 13C and 15N in order to investigate interactions between C and N flows in the plant-soil-microorganism system. Plants were subjected to an enriched 13CO2 atmosphere for 8 hours during which 15NH4 was added to a subset of split-boxes to either the root-containing or the root-free compartment. Both, 13C and 15N fluxes through the plant-soil continuum were monitored over 24 hours by stable isotope methods (13C phospho-lipid fatty acids by GC-IRMS, 15N/13C in bulk plant

  17. Constraining Marsh Carbon Budgets Using Long-Term C Burial and Contemporary Atmospheric CO2 Fluxes

    Science.gov (United States)

    Forbrich, I.; Giblin, A. E.; Hopkinson, C. S.

    2018-03-01

    Salt marshes are sinks for atmospheric carbon dioxide that respond to environmental changes related to sea level rise and climate. Here we assess how climatic variations affect marsh-atmosphere exchange of carbon dioxide in the short term and compare it to long-term burial rates based on radiometric dating. The 5 years of atmospheric measurements show a strong interannual variation in atmospheric carbon exchange, varying from -104 to -233 g C m-2 a-1 with a mean of -179 ± 32 g C m-2 a-1. Variation in these annual sums was best explained by differences in rainfall early in the growing season. In the two years with below average rainfall in June, both net uptake and Normalized Difference Vegetation Index were less than in the other three years. Measurements in 2016 and 2017 suggest that the mechanism behind this variability may be rainfall decreasing soil salinity which has been shown to strongly control productivity. The net ecosystem carbon balance was determined as burial rate from four sediment cores using radiometric dating and was lower than the net uptake measured by eddy covariance (mean: 110 ± 13 g C m-2 a-1). The difference between these estimates was significant and may be because the atmospheric measurements do not capture lateral carbon fluxes due to tidal exchange. Overall, it was smaller than values reported in the literature for lateral fluxes and highlights the importance of investigating lateral C fluxes in future studies.

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

    Science.gov (United States)

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

    2013-12-01

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

  19. Modeling the radiative effects of biomass burning aerosols on carbon fluxes in the Amazon region

    Science.gov (United States)

    Moreira, Demerval S.; Longo, Karla M.; Freitas, Saulo R.; Yamasoe, Marcia A.; Mercado, Lina M.; Rosário, Nilton E.; Gloor, Emauel; Viana, Rosane S. M.; Miller, John B.; Gatti, Luciana V.; Wiedemann, Kenia T.; Domingues, Lucas K. G.; Correia, Caio C. S.

    2017-12-01

    Every year, a dense smoke haze covers a large portion of South America originating from fires in the Amazon Basin and central parts of Brazil during the dry biomass burning season between August and October. Over a large portion of South America, the average aerosol optical depth at 550 nm exceeds 1.0 during the fire season, while the background value during the rainy season is below 0.2. Biomass burning aerosol particles increase scattering and absorption of the incident solar radiation. The regional-scale aerosol layer reduces the amount of solar energy reaching the surface, cools the near-surface air, and increases the diffuse radiation fraction over a large disturbed area of the Amazon rainforest. These factors affect the energy and CO2 fluxes at the surface. In this work, we applied a fully integrated atmospheric model to assess the impact of biomass burning aerosols in CO2 fluxes in the Amazon region during 2010. We address the effects of the attenuation of global solar radiation and the enhancement of the diffuse solar radiation flux inside the vegetation canopy. Our results indicate that biomass burning aerosols led to increases of about 27 % in the gross primary productivity of Amazonia and 10 % in plant respiration as well as a decline in soil respiration of 3 %. Consequently, in our model Amazonia became a net carbon sink; net ecosystem exchange during September 2010 dropped from +101 to -104 TgC when the aerosol effects are considered, mainly due to the aerosol diffuse radiation effect. For the forest biome, our results point to a dominance of the diffuse radiation effect on CO2 fluxes, reaching a balance of 50-50 % between the diffuse and direct aerosol effects for high aerosol loads. For C3 grasses and savanna (cerrado), as expected, the contribution of the diffuse radiation effect is much lower, tending to zero with the increase in aerosol load. Taking all biomes together, our model shows the Amazon during the dry season, in the presence of high

  20. Modeling the radiative effects of biomass burning aerosols on carbon fluxes in the Amazon region

    Directory of Open Access Journals (Sweden)

    D. S. Moreira

    2017-12-01

    Full Text Available Every year, a dense smoke haze covers a large portion of South America originating from fires in the Amazon Basin and central parts of Brazil during the dry biomass burning season between August and October. Over a large portion of South America, the average aerosol optical depth at 550 nm exceeds 1.0 during the fire season, while the background value during the rainy season is below 0.2. Biomass burning aerosol particles increase scattering and absorption of the incident solar radiation. The regional-scale aerosol layer reduces the amount of solar energy reaching the surface, cools the near-surface air, and increases the diffuse radiation fraction over a large disturbed area of the Amazon rainforest. These factors affect the energy and CO2 fluxes at the surface. In this work, we applied a fully integrated atmospheric model to assess the impact of biomass burning aerosols in CO2 fluxes in the Amazon region during 2010. We address the effects of the attenuation of global solar radiation and the enhancement of the diffuse solar radiation flux inside the vegetation canopy. Our results indicate that biomass burning aerosols led to increases of about 27 % in the gross primary productivity of Amazonia and 10 % in plant respiration as well as a decline in soil respiration of 3 %. Consequently, in our model Amazonia became a net carbon sink; net ecosystem exchange during September 2010 dropped from +101 to −104 TgC when the aerosol effects are considered, mainly due to the aerosol diffuse radiation effect. For the forest biome, our results point to a dominance of the diffuse radiation effect on CO2 fluxes, reaching a balance of 50–50 % between the diffuse and direct aerosol effects for high aerosol loads. For C3 grasses and savanna (cerrado, as expected, the contribution of the diffuse radiation effect is much lower, tending to zero with the increase in aerosol load. Taking all biomes together, our model shows the Amazon during the dry

  1. Modelling the genesis of equatorial podzols: age and implications for carbon fluxes

    Science.gov (United States)

    Doupoux, Cédric; Merdy, Patricia; Régina Montes, Célia; Nunan, Naoise; José Melfi, Adolpho; José Ribeiro Pereira, Osvaldo; Lucas, Yves

    2017-05-01

    Amazonian podzols store huge amounts of carbon and play a key role in transferring organic matter to the Amazon River. In order to better understand their C dynamics, we modelled the formation of representative Amazonian podzol profiles by constraining both total carbon and radiocarbon. We determined the relationships between total carbon and radiocarbon in organic C pools numerically by setting constant C and 14C inputs over time. The model was an effective tool for determining the order of magnitude of the carbon fluxes and the time of genesis of the main carbon-containing horizons, i.e. the topsoil and deep Bh. We performed retrocalculations to take into account the bomb carbon in the young topsoil horizons (calculated apparent 14C age from 62 to 109 years). We modelled four profiles representative of Amazonian podzols, two profiles with an old Bh (calculated apparent 14C age 6.8 × 103 and 8.4 × 103 years) and two profiles with a very old Bh (calculated apparent 14C age 23.2 × 103 and 25.1 × 103 years). The calculated fluxes from the topsoil to the perched water table indicate that the most waterlogged zones of the podzolized areas are the main source of dissolved organic matter found in the river network. It was necessary to consider two Bh carbon pools to accurately represent the carbon fluxes leaving the Bh as observed in previous studies. We found that the genesis time of the studied soils was necessarily longer than 15 × 103 and 130 × 103 years for the two younger and two older Bhs, respectively, and that the genesis time calculated considering the more likely settings runs to around 15 × 103-25 × 103 and 150 × 103-250 × 103 years, respectively.

  2. Sedimentary record of water column trophic conditions and sediment carbon fluxes in a tropical water reservoir (Valle de Bravo, Mexico).

    Science.gov (United States)

    Carnero-Bravo, Vladislav; Merino-Ibarra, Martín; Ruiz-Fernández, Ana Carolina; Sanchez-Cabeza, Joan Albert; Ghaleb, Bassam

    2015-03-01

    Valle de Bravo (VB) is the main water reservoir of the Cutzamala hydraulic system, which provides 40% of the drinking water consumed in the Mexico City Metropolitan Area and exhibits symptoms of eutrophication. Nutrient (C, N and P) concentrations were determined in two sediment cores to reconstruct the water column trophic evolution of the reservoir and C fluxes since its creation in 1947. Radiometric methods ((210)Pb and (137)Cs) were used to obtain sediment chronologies, using the presence of pre-reservoir soil layers in one of the cores as an independent chronological marker. Mass accumulation rates ranged from 0.12 to 0.56 g cm(-2) year(-1) and total organic carbon (TOC) fluxes from 122 to 380 g m(-2) year(-1). Total N ranged 4.9-48 g m(-2) year(-1), and total P 0.6-4.2 g m(-2) year(-1). The sedimentary record shows that all three (C, N and P) fluxes increased significantly after 1991, in good agreement with the assessed trophic evolution of VB and with historic and recent real-time measurements. In the recent years (1992-2006), the TOC flux to the bottom of VB (average 250 g m(-2) year(-1), peaks 323 g m(-2) year(-1)) is similar to that found in highly eutrophic reservoirs and impoundments. Over 1/3 of the total C burial since dam construction, circa 70,000 t, has occurred in this recent period. These results highlight the usefulness of the reconstruction of carbon and nutrient fluxes from the sedimentary record to assess carbon burial and its temporal evolution in freshwater ecosystems.

  3. A Contemporary Assessment of Lateral Fluxes of Organic Carbon in Inland Waters of the USA and Delivery to Coastal Waters

    Science.gov (United States)

    Boyer, E. W.; Alexander, R. B.; Smith, R. A.; Shih, J.; Schwarz, G. E.

    2010-12-01

    Organic carbon (OC) is a critical water quality characteristic in surface waters, as it is an important component of the energy balance and food chains in freshwater and estuarine aquatic ecosystems, is significant in the mobilization and transport of contaminants along flow paths, and is associated with the formation of known carcinogens in drinking water supplies. The importance of OC dynamics on water quality has been recognized, but challenges remain in quantitatively addressing processes controlling OC fluxes over broad spatial scales in a hydrological context. Here, we: 1) quantified lateral OC fluxes in rivers, streams, and reservoirs across the nation; 2) partitioned how much organic carbon that is stored in lakes, rivers and streams comes from allochthonous sources (produced in the terrestrial landscape) versus autochthonous sources (produced in-stream by primary production); and 3) estimated the delivery of dissolved and total forms of organic carbon to coastal estuaries and embayments. To accomplish this, we developed national-scale models of organic carbon in U.S. surface waters using the spatially referenced regression on watersheds (SPARROW) technique. This approach uses mechanistic formulations, imposes mass balance constraints, and provides a formal parameter estimation structure to statistically estimate sources and fate of OC in terrestrial and aquatic ecosystems. We make use of a GIS based framework to describe sources of organic matter and characteristics of the landscape that affect its fate and transport, from spatial databases providing characterizations of climate, land cover, primary productivity, topography, soils, geology, and water routing. We calibrated and evaluated the model with statistical estimates of organic carbon loads that were observed at 1,125 monitoring stations across the nation. Our results illustrate spatial patterns and magnitudes OC loadings in rivers and reservoirs, highlighting hot spots and suggesting origins of the

  4. Particle flux and temperature dependence of carbon impurity production from an inertially-cooled limiter in tore supra

    International Nuclear Information System (INIS)

    DeMichelis, C.; Monier-Garbet, P.; Guilhem, D.

    1998-01-01

    A visible endoscope system and an infrared camera system have been used to study the flux of carbon from an inertially-cooled graphite limiter in Tore Supra. From the variation in the carbon flux with plasma parameters new data have been obtained describing the dependence of radiation enhanced sublimation (RES) and chemical sputtering on incident ion flux. Other characteristics of RES under plasma operation conditions have also been studied. The dependence of RES on incident deuterium particle flux density is found to be in reasonable agreement with the expected particle flux scaling over a range of particle fluxes varying by a factor ∼ 25, extending the present scaling to higher flux density values. Chemical sputtering has been observed, but only in regions of the limiter with low incident deuterium fluxes. Values inferred for the chemical sputtering yield are similar to those measured with a temperature controlled test limiter in Textor. (author)

  5. Carbon and nitrogen accumulation and fluxes on Landscape Evolution Observatory (LEO) slopes

    Science.gov (United States)

    Dontsova, K.; Volk, M.; Webb, C.; Hunt, E.; Tfaily, M. M.; Van Haren, J. L. M.; Sengupta, A.; Chorover, J.; Troch, P.; Ruiz, J.

    2017-12-01

    Carbon accumulation on the landscapes in organic and inorganic forms is an important sink of CO2 from the atmosphere. Formation and preservation of organic compounds is accompanied by N fixation from the atmosphere and cycling in the soil. Model slopes of Landscape Evolution Observatory present unique opportunity to examine carbon and nitrogen buildup on the landscapes during soil formation processes, such as weathering of primary minerals and microbial activity, due to low original levels of C and N, tight control over environmental conditions, and high spatial and temporal density of measurements. This presents results of inorganic and organic C and N measurements in the cores collected in LEO slopes after several years of exposure to the rainfall, as well as soil solution measurements collected through 496 samplers on each of three model slopes and in seepage. We observed significant spatially distributed accumulation of both C (organic and inorganic) and N in soil profiles. We also observed differences in the composition of organic compounds in the solid and solution phases depending on location on the slope indicating formation of heterogeneity as soils develop. This works indicates potential of physical models to help understand accumulation and fluxes of C and N on natural landscapes.

  6. Integrating tracer-based metabolomics data and metabolic fluxes in a linear fashion via Elementary Carbon Modes.

    Science.gov (United States)

    Pey, Jon; Rubio, Angel; Theodoropoulos, Constantinos; Cascante, Marta; Planes, Francisco J

    2012-07-01

    Constraints-based modeling is an emergent area in Systems Biology that includes an increasing set of methods for the analysis of metabolic networks. In order to refine its predictions, the development of novel methods integrating high-throughput experimental data is currently a key challenge in the field. In this paper, we present a novel set of constraints that integrate tracer-based metabolomics data from Isotope Labeling Experiments and metabolic fluxes in a linear fashion. These constraints are based on Elementary Carbon Modes (ECMs), a recently developed concept that generalizes Elementary Flux Modes at the carbon level. To illustrate the effect of our ECMs-based constraints, a Flux Variability Analysis approach was applied to a previously published metabolic network involving the main pathways in the metabolism of glucose. The addition of our ECMs-based constraints substantially reduced the under-determination resulting from a standard application of Flux Variability Analysis, which shows a clear progress over the state of the art. In addition, our approach is adjusted to deal with combinatorial explosion of ECMs in genome-scale metabolic networks. This extension was applied to infer the maximum biosynthetic capacity of non-essential amino acids in human metabolism. Finally, as linearity is the hallmark of our approach, its importance is discussed at a methodological, computational and theoretical level and illustrated with a practical application in the field of Isotope Labeling Experiments. Copyright © 2012 Elsevier Inc. All rights reserved.

  7. Carbon Dioxide Transfer Through Sea Ice: Modelling Flux in Brine Channels

    Science.gov (United States)

    Edwards, L.; Mitchelson-Jacob, G.; Hardman-Mountford, N.

    2010-12-01

    For many years sea ice was thought to act as a barrier to the flux of CO2 between the ocean and atmosphere. However, laboratory-based and in-situ observations suggest that while sea ice may in some circumstances reduce or prevent transfer (e.g. in regions of thick, superimposed multi-year ice), it may also be highly permeable (e.g. thin, first year ice) with some studies observing significant fluxes of CO2. Sea ice covered regions have been observed to act both as a sink and a source of atmospheric CO2 with the permeability of sea ice and direction of flux related to sea ice temperature and the presence of brine channels in the ice, as well as seasonal processes such as whether the ice is freezing or thawing. Brine channels concentrate dissolved inorganic carbon (DIC) as well as salinity and as these dense waters descend through both the sea ice and the surface ocean waters, they create a sink for CO2. Calcium carbonate (ikaite) precipitation in the sea ice is thought to enhance this process. Micro-organisms present within the sea ice will also contribute to the CO2 flux dynamics. Recent evidence of decreasing sea ice extent and the associated change from a multi-year ice to first-year ice dominated system suggest the potential for increased CO2 flux through regions of thinner, more porous sea ice. A full understanding of the processes and feedbacks controlling the flux in these regions is needed to determine their possible contribution to global CO2 levels in a future warming climate scenario. Despite the significance of these regions, the air-sea CO2 flux in sea ice covered regions is not currently included in global climate models. Incorporating this carbon flux system into Earth System models requires the development of a well-parameterised sea ice-air flux model. In our work we use the Los Alamos sea ice model, CICE, with a modification to incorporate the movement of CO2 through brine channels including the addition of DIC processes and ice algae production to

  8. Vertical and lateral flux on the continental slope off Pakistan: correlation of sediment core and trap results

    Science.gov (United States)

    Schulz, H.; von Rad, U.

    2014-06-01

    Due to the lack of bioturbation, the varve-laminated muds from the oxygen minimum zone (OMZ) off Pakistan provide a unique opportunity to precisely determine the vertical and lateral sediment fluxes in the nearshore part of the northeastern Arabian Sea. West of Karachi (Hab area), the results of two sediment trap stations (EPT and WPT) were correlated with 16 short sediment cores on a depth transect crossing the OMZ. The top of a distinct, either reddish- or light-gray silt layer, 210Pb-dated as AD 1905 ± 10, was used as an isochronous stratigraphic marker bed to calculate sediment accumulation rates. In one core, the red and gray layer were separated by a few (5-10) thin laminae. According to our varve model, this contributes water column above. All traps on the steep Makran continental slope show exceptionally high, pulsed winter fluxes of up to 5000 mg m-2 d-1. Based on core results, the flux at the seafloor amounts to 4000 mg m-2 d-1 and agrees remarkably well with the bulk winter flux of material, as well as with the flux of the individual bulk components of organic carbon, calcium carbonate and opal. However, due to the extreme mass of remobilized matter, the high winter flux events exceeded the capacity of the shallow traps. Based on our comparisons, we argue that high-flux events must occur regularly during winter within the upper OMZ off Pakistan to explain the high accumulations rates. These show distribution patterns that are a negative function of water depth and distance from the shelf. Some of the sediment fractions show marked shifts in accumulation rates near the lower boundary of the OMZ. For instance, the flux of benthic foraminifera is lowered but stable below ~1200-1300 m. However, flux and sedimentation in the upper eastern Makran area are dominated by the large amount of laterally advected fine-grained material and by the pulsed nature of the resuspension events at the upper margin during winter.

  9. Response of air-sea carbon fluxes and climate to orbital forcing changes in the Community Climate System Model

    Science.gov (United States)

    Jochum, M.; Peacock, S.; Moore, K.; Lindsay, K.

    2010-07-01

    A global general circulation model coupled to an ocean ecosystem model is used to quantify the response of carbon fluxes and climate to changes in orbital forcing. Compared to the present-day simulation, the simulation with the Earth's orbital parameters from 115,000 years ago features significantly cooler northern high latitudes but only moderately cooler southern high latitudes. This asymmetry is explained by a 30% reduction of the strength of the Atlantic Meridional Overturning Circulation that is caused by an increased Arctic sea ice export and a resulting freshening of the North Atlantic. The strong northern high-latitude cooling and the direct insolation induced tropical warming lead to global shifts in precipitation and winds to the order of 10%-20%. These climate shifts lead to regional differences in air-sea carbon fluxes of the same order. However, the differences in global net air-sea carbon fluxes are small, which is due to several effects, two of which stand out: first, colder sea surface temperature leads to a more effective solubility pump but also to increased sea ice concentration which blocks air-sea exchange, and second, the weakening of Southern Ocean winds that is predicted by some idealized studies occurs only in part of the basin, and is compensated by stronger winds in other parts.

  10. Redistribution of carbon flux in Torulopsis glabrata by altering vitamin and calcium level.

    Science.gov (United States)

    Liu, Liming; Li, Yin; Zhu, Yang; Du, Guocheng; Chen, Jian

    2007-01-01

    Manipulation of cofactor (thiamine, biotin and Ca(2+)) levels as a potential tool to redistribute carbon flux was studied in Torulopsis glabrata. With sub-optimization of vitamin in fermentation medium, the carbon flux was blocked at the key node of pyruvate, and 69 g/L pyruvate was accumulated. Increasing the concentrations of thiamine and biotin could selectively open the valve of carbon flux from pyruvate to pyruvate dehydrogenase complex, the pyruvate carboxylase (PC) pathway and the channel into the TCA cycle, leading to the over-production of alpha-ketoglutarate. In addition, the activity of PC was enhanced with Ca(2+) present in fermentation medium. By combining high concentration's vitamins and CaCO(3) as the pH buffer, a batch culture was conducted in a 7-L fermentor, with the pyruvate concentration decreased to 21.8 g/L while alpha-ketoglutarate concentration increased to 43.7 g/L. Our study indicated that the metabolic flux could be redistributed to overproduce desired metabolites with manipulating the cofactor levels. Furthermore, the manipulation of vitamin level provided an alternative tool to realize metabolic engineering goals.

  11. Changes in Soil Carbon Stocks and Fluxes in Response to Altered Above- and Belowground Vegetation Inputs

    Science.gov (United States)

    Marañón-Jiménez, S.; Schuetze, C.; Cuntz, M.; García-Quirós, I.; Dienstbach, L.; Schrumpf, M.; Rebmann, C.

    2016-12-01

    The stimulation of vegetation productivity in response to rising atmospheric CO2 concentrations can potentially compensate climate change feedbacks. However, this will depend on the allocation of C resources of vegetation into biomass production versus root exudates and on the feedbacks with soil microorganisms. These dynamic adjustments of vegetation will result on changes in above- and belowground productivity and on the amount of C exported to root exudates. Consequent alteration of litter and rhizosphere detritus inputs to the soil and their interaction on controlling soil C sequestration capacity has been, however, rarely assessed. We hypothesize that above- and belowground vegetation exert a synergistic control of soil CO2 emissions, and that the activation of soil organic matter mineralization by the addition of labile organic substrates (i.e.: the priming effect) is altered by changes in the amount and in the quality of the carbon inputs. In order to elucidate these questions, different levels of litter addition were implemented on trenched (root exclusion) and non-trenched plots (with roots) in a temperate deciduous forest. Changes in the sensitivity of soil respiration to temperature and moisture were detected by measuring CO2 fluxes continuously at high temporal resolution with automatic chambers, whereas the spatial and seasonal variability was determined using portable chambers. Annual changes in soil carbon and nitrogen stocks provide additional information on the soil carbon sequestration in response to above- and belowground inputs. Both roots and litter inputs significantly enhanced soil CO2 effluxes soon after the implementation of the experiment. We detected synergistic effects between roots and litter inputs on soil CO2 emissions: When roots were present, carbon mineralized in response to litter addition was much higher than the total amount of carbon added in litter (ca. 170 g C m-2 y-1). Preliminary results of this study suggest that labile

  12. Evaluation of carbon fluxes and trends (2000-2008) in the Greater Platte River Basin: a sustainability study on the potential biofuel feedstock development

    Science.gov (United States)

    Gu, Yingxin; Wylie, Bruce K.; Zhang, Li; Gilmanov, Tagir G.

    2012-01-01

    This study evaluates the carbon fluxes and trends and examines the environmental sustainability (e.g., carbon budget, source or sink) of the potential biofuel feedstock sites identified in the Greater Platte River Basin (GPRB). A 9-year (2000–2008) time series of net ecosystem production (NEP), a measure of net carbon absorption or emission by ecosystems, was used to assess the historical trends and budgets of carbon flux for grasslands in the GPRB. The spatially averaged annual NEP (ANEP) for grassland areas that are possibly suitable for biofuel expansion (productive grasslands) was 71–169 g C m−2 year−1 during 2000–2008, indicating a carbon sink (more carbon is absorbed than released) in these areas. The spatially averaged ANEP for areas not suitable for biofuel feedstock development (less productive or degraded grasslands) was −47 to 69 g C m−2 year−1 during 2000–2008, showing a weak carbon source or a weak carbon sink (carbon emitted is nearly equal to carbon absorbed). The 9-year pre-harvest cumulative ANEP was 1166 g C m−2 for the suitable areas (a strong carbon sink) and 200 g C m−2 for the non-suitable areas (a weak carbon sink). Results demonstrate and confirm that our method of dynamic modeling of ecosystem performance can successfully identify areas desirable and sustainable for future biofuel feedstock development. This study provides useful information for land managers and decision makers to make optimal land use decisions regarding biofuel feedstock development and sustainability.

  13. Planktic foraminifer and coccolith contribution to carbonate export fluxes over the central Kerguelen Plateau

    Science.gov (United States)

    Rembauville, M.; Meilland, J.; Ziveri, P.; Schiebel, R.; Blain, S.; Salter, I.

    2016-05-01

    We report the contribution of planktic foraminifers and coccoliths to the particulate inorganic carbon (PIC) export fluxes collected over an annual cycle (October 2011/September 2012) on the central Kerguelen Plateau in the Antarctic Zone (AAZ) south of the Polar Front (PF). The seasonality of PIC flux was decoupled from surface chlorophyll a concentration and particulate organic carbon (POC) fluxes and was characterized by a late summer (February) maximum. This peak was concomitant with the highest satellite-derived sea surface PIC and corresponded to a Emiliania huxleyi coccoliths export event that accounted for 85% of the annual PIC export. The foraminifer contribution to the annual PIC flux was much lower (15%) and dominated by Turborotalita quinqueloba and Neogloboquadrina pachyderma. Foraminifer export fluxes were closely related to the surface chlorophyll a concentration, suggesting food availability as an important factor regulating the foraminifer's biomass. We compared size-normalized test weight (SNW) of the foraminifers with previously published SNW from the Crozet Islands using the same methodology and found no significant difference in SNW between sites for a given species. However, the SNW was significantly species-specific with a threefold increase from T. quinqueloba to Globigerina bulloides. The annual PIC:POC molar ratio of 0.07 was close to the mean ratio for the global ocean and lead to a low carbonate counter pump effect (~5%) compared to a previous study north of the PF (6-32%). We suggest that lowers counter pump effect south of the PF despite similar productivity levels is due to a dominance of coccoliths in the PIC fluxes and a difference in the foraminifers species assemblage with a predominance of polar species with lower SNW.

  14. Modelling biogeochemical processes in sediments from the north-western Adriatic Sea: response to enhanced particulate organic carbon fluxes

    Science.gov (United States)

    Brigolin, Daniele; Rabouille, Christophe; Bombled, Bruno; Colla, Silvia; Vizzini, Salvatrice; Pastres, Roberto; Pranovi, Fabio

    2018-03-01

    This work presents the result of a study carried out in the north-western Adriatic Sea, by combining two different types of biogeochemical models with field sampling efforts. A longline mussel farm was taken as a local source of perturbation to the natural particulate organic carbon (POC) downward flux. This flux was first quantified by means of a pelagic model of POC deposition coupled to sediment trap data, and its effects on sediment bioirrigation capacity and organic matter (OM) degradation pathways were investigated constraining an early diagenesis model by using original data collected in sediment porewater. The measurements were performed at stations located inside and outside the area affected by mussel farm deposition. Model-predicted POC fluxes showed marked spatial and temporal variability, which was mostly associated with the dynamics of the farming cycle. Sediment trap data at the two sampled stations (inside and outside of the mussel farm) showed average POC background flux of 20.0-24.2 mmol C m-2 d-1. The difference of organic carbon (OC) fluxes between the two stations was in agreement with model results, ranging between 3.3 and 14.2 mmol C m-2 d-1, and was primarily associated with mussel physiological conditions. Although restricted, these changes in POC fluxes induced visible effects on sediment biogeochemistry. Observed oxygen microprofiles presented a 50 % decrease in oxygen penetration depth (from 2.3 to 1.4 mm), accompanied by an increase in the O2 influx at the station below the mussel farm (19-31 versus 10-12 mmol O2 m-2 d-1) characterised by higher POC flux. Dissolved inorganic carbon (DIC) and NH4+ concentrations showed similar behaviour, with a more evident effect of bioirrigation underneath the farm. This was confirmed through constraining the early diagenesis model, of which calibration leads to an estimation of enhanced and shallower bioirrigation underneath the farm: bioirrigation rates of 40 yr-1 and irrigation depth of 15 cm were

  15. Variability in carbon dioxide fluxes for dense urban, suburban and woodland environments in southern England

    Science.gov (United States)

    Ward, Helen; Kotthaus, Simone; Grimmond, C. Sue; Bjorkegren, Alex; Wilkinson, Matt; Morrison, Will; Evans, Jon; Morison, James; Christen, Andreas

    2014-05-01

    The net exchange of carbon dioxide between the surface and atmosphere can be measured using the eddy covariance technique. Fluxes from a dense urban environment (central London), a suburban landscape (Swindon) and a woodland ecosystem (Alice Holt) are compared. All sites are located in southern England and experience similar climatic and meteorological conditions, yet have very different land cover. The signatures of anthropogenic and biogenic processes are explored at various (daily, seasonal and annual) timescales. Particular emphasis is placed on identifying the mixture of controls that determine the flux. In summer, there are clear similarities between the suburban and woodland sites, as the diurnal behaviour is dominated by photosynthetic uptake. In winter, however, vegetation is largely dormant and human activity determines the pattern of fluxes at the urban and suburban sites. Emissions from building heating augment the net release of carbon dioxide in cold months. Road use is a major contributor to the total emissions, and the diurnal cycle in the observed fluxes reflects this: in central London roads are busy throughout the day, whereas in Swindon a double-peaked rush-hour signal is evident. The net exchange of carbon dioxide is estimated for each site and set in context with other studies around the world. Central London has the smallest proportion of vegetation and largest emissions amongst study sites in the literature to date. Although Swindon's appreciable vegetation fraction helps to offset the anthropogenic emissions, even in summertime the 24h total flux is usually positive, indicating carbon release. Comparison of these three sites in a similar region demonstrates the effects of increasing urban density and changing land use on the atmosphere. Findings are relevant in terms of characterising the behaviour of urban surfaces and for quantifying the impact of anthropogenic activities.

  16. BOREAS TGB-12 Soil Carbon and Flux Data of NSA-MSA in Raster Format

    Science.gov (United States)

    Hall, Forrest G. (Editor); Knapp, David E. (Editor); Rapalee, Gloria; Davidson, Eric; Harden, Jennifer W.; Trumbore, Susan E.; Veldhuis, Hugo

    2000-01-01

    The BOREAS TGB-12 team made measurements of soil carbon inventories, carbon concentration in soil gases, and rates of soil respiration at several sites. This data set provides: (1) estimates of soil carbon stocks by horizon based on soil survey data and analyses of data from individual soil profiles; (2) estimates of soil carbon fluxes based on stocks, fire history, drain-age, and soil carbon inputs and decomposition constants based on field work using radiocarbon analyses; (3) fire history data estimating age ranges of time since last fire; and (4) a raster image and an associated soils table file from which area-weighted maps of soil carbon and fluxes and fire history may be generated. This data set was created from raster files, soil polygon data files, and detailed lab analysis of soils data that were received from Dr. Hugo Veldhuis, who did the original mapping in the field during 1994. Also used were soils data from Susan Trumbore and Jennifer Harden (BOREAS TGB-12). The binary raster file covers a 733-km 2 area within the NSA-MSA.

  17. Proteomic analysis of the seed development in Jatropha curcas: from carbon flux to the lipid accumulation.

    Science.gov (United States)

    Liu, Hui; Wang, Cuiping; Komatsu, Setsuko; He, Mingxia; Liu, Gongshe; Shen, Shihua

    2013-10-08

    To characterize the metabolic signatures of lipid accumulation in Jatropha curcas seeds, comparative proteomic technique was employed to profile protein changes during the seed development. Temporal changes in comparative proteome were examined using gels-based proteomic technique at six developmental stages for lipid accumulation. And 104 differentially expressed proteins were identified by MALDI-TOF/TOF tandem mass spectrometry. These protein species were classified into 10 functional categories, and the results demonstrated that protein species related to energy and metabolism were notably accumulated and involved in the carbon flux to lipid accumulation that occurs primarily from early to late stage in seed development. Glycolysis and oxidative pentose phosphate pathways were the major pathways of producing carbon flux, and the glucose-6-phosphate and triose-phosphate are the major carbon source for fatty acid synthesis. Lipid analysis revealed that fatty acid accumulation initiated 25days after flowering at the late stage of seed development of J. curcas. Furthermore, C16:0 was initially synthesized as the precursor for the elongation to C18:1 and C18:2 in the developing seeds of J. curcas. Together, the metabolic signatures on protein changes in seed development provide profound knowledge and perspective insights into understanding lipid network in J. curcas. Due to the abundant oil content in seeds, Jatropha curcas seeds are being considered as the ideal materials for biodiesel. Although several studies had carried out the transcriptomic project to study the genes expression profiles in seed development of J. curcas, these ESTs hadn't been confirmed by qRT-PCR. Yet, the seed development of J. curcas had been described for a pool of developing seeds instead of being characterized systematically. Moreover, cellular metabolic events are also controlled by protein-protein interactions, posttranslational protein modifications, and enzymatic activities which

  18. CO2 and CH4 fluxes and carbon balance in the atmospheric interaction of boreal peatlands

    International Nuclear Information System (INIS)

    Alm, J.

    1997-01-01

    Release of CO 2 from peat was studied using IR analyzer in a range of boreal peatlands under varying nutrient status and moisture conditions. Root associated CO 2 efflux was separated from the total release by experiments both in the field and in a greenhouse. Emissions of CO 2 and CH 4 (the latter by gas chromatography) were measured during the snow-covered period and their contribution to the annual fluxes of these gases was inspected. Ecosystem exchange of CO 2 under varying irradiation, temperature and moisture conditions was measured at different microsites at two peatland sites with different nutrient ecology. One site represented minerotrophic conditions during a wet growing season and the other site ombrotrophic conditions during an exceptionally dry growing season. Annual carbon balances were compiled for the two sites, and the role of the microsites in the annual carbon balance and CH 4 release was studied. The Holocene history of CO 2 sequestration and CH 4 emission dynamics in a raised mire were simulated using lateral and vertical growth rates derived from radiocarbon ages of peat samples from mire bottom and vertical cores. The model was formulated for a geographic information system (GIS). Artificial or natural lowering of water table increased CO 2 release from peat. A drought lasting from late May to July caused a 90 g C m 2 net loss in the annual C balance of a natural ombrotrophic bog. In drained forested sites the increase in peat CO 2 release could be even 100 %, but the development of the tree layer at least partially compensated for these losses. Wet conditions induced a net accumulation of 67 g C m -2 a -1 in the minerotrophic fen site, while the long term average accumulation rate is estimated to be only 15 g C m -2 a -1 for Finnish fens. Carbon balance in boreal peatlands is thus extremely sensitive to year-to-year climatic variations. Root activity of vascular plants contributed to the total peat CO 2 efflux by 10-40 % as root respiration

  19. Summer carbon dioxide and water vapor fluxes across a range of northern peatlands

    Science.gov (United States)

    Humphreys, Elyn R.; Lafleur, Peter M.; Flanagan, Lawrence B.; Hedstrom, Newell; Syed, Kamran H.; Glenn, Aaron J.; Granger, Raoul

    2006-12-01

    Northern peatlands are a diverse group of ecosystems varying along a continuum of hydrological, chemical, and vegetation gradients. These ecosystems contain about one third of the global soil carbon pool, but it is uncertain how carbon and water cycling processes and response to climate change differ among peatland types. This study examines midsummer CO2 and H2O fluxes measured using the eddy covariance technique above seven northern peatlands including a low-shrub bog, two open poor fens, two wooded moderately rich fens, and two open extreme-rich fens. Gross ecosystem production and ecosystem respiration correlated positively with vegetation indices and with each other. Consequently, 24-hour net ecosystem CO2 exchange was similar among most of the sites (an average net carbon sink of 1.5 ± 0.2 g C m-2 d-1) despite large differences in water table depth, water chemistry, and plant communities. Evapotranspiration was primarily radiatively driven at all sites but a decline in surface conductance with increasing water vapor deficit indicated physiological restrictions to transpiration, particularly at the peatlands with woody vegetation and less at the peatlands with 100% Sphagnum cover. Despite these differences, midday evapotranspiration ranged only from 0.21 to 0.34 mm h-1 owing to compensation among the factors controlling evapotranspiration. Water use efficiency varied among sites primarily as a result of differences in productivity and plant functional type. Although peatland classification includes a great variety of ecosystem characteristics, peatland type may not be an effective way to predict the magnitude and characteristics of midsummer CO2 and water vapor exchanges.

  20. Incoming Shortwave Fluxes at the Surface--A Comparison of GCM Results with Observations.

    Science.gov (United States)

    Garratt, J. R.

    1994-01-01

    Evidence is presented that the exam surface net radiation calculated in general circulation models at continental surfaces is mostly due to excess incoming shortwave fluxes. Based on long-term observations from 22 worldwide inland stations and results from four general circulation models the overestimate in models of 20% (11 W m2) in net radiation on an annual basis compares with 6% (9 W m2) for shortwave fluxes for the same 22 locations, or 9% (18 W m2) for a larger set of 93 stations (71 having shortwave fluxes only). For annual fluxes, these differences appear to be significant.

  1. 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

  2. Carbon Flux of Down Woody Materials in Forests of the North Central United States

    International Nuclear Information System (INIS)

    Woodall, C.W.

    2010-01-01

    Across large scales, the carbon (C) flux of down woody material (DWM) detrital pools has largely been simulated based on forest stand attributes (e.g., stand age and forest type). The annual change in forest DWM C stocks and other attributes (e.g., size and decay class changes) was assessed using a forest inventory in the north central United States to provide an empirical assessment of strategic-scale DWM C flux. Using DWM inventory data from the USDA Forest Service's Forest Inventory and Analysis program, DWM C stocks were found to be relatively static across the study region with an annual flux rate not statistically different from zero. Mean C flux rates across the study area were -0.25, -0.12, -0.01, and -0.04 (Mg/ha/yr) for standing live trees, standing dead trees, coarse woody debris, and fine woody debris, respectively. Flux rates varied in their both magnitude and status (emission/sequestration) by forest types, latitude, and DWM component size. Given the complex dynamics of DWM C flux, early implementation of inventory re measurement, and relatively low sample size, numerous future research directions are suggested.

  3. Integration of ground and satellite data to estimate the forest carbon fluxes of a Mediterranean region

    Science.gov (United States)

    Chiesi, M.; Maselli, F.; Moriondo, M.; Fibbi, L.; Bindi, M.; Running, S. W.

    2009-04-01

    reference series of monthly gross primary production (GPP) estimates. In particular this model estimates forest GPP as function of photosynthetically active radiation absorbed by vegetation (Veroustraete et al., 2002) combined with ground based estimates of incoming solar radiation and air temperature. These GPP values are used as reference data to both calibrate and integrate the functions of a more complex bio-geochemical model, BIOME-BGC, which is capable of simulating all main ecosystem processes. This model requires: daily climate data, information on the general environment (i.e. soil, vegetation and site conditions) and parameters describing the ecophysiological characteristics of vegetation. Both C-Fix and BIOME-BGC compute GPP as an expression of total, or potential, productivity of an ecosystem in equilibrium with the environment. This makes the GPP estimates of the two models practically inter-comparable and opens the possibility of using the more accurate GPP estimates of C-Fix to both calibrate BIOME-BGC and stabilize its outputs (Chiesi et al., 2007). In particular, by integrating BIOME-BGC respiration estimates to those of C-Fix, forest fluxes for the entire region are obtained, which are referable to ecosystems at equilibrium (climax) condition. These estimates are converted into NPP and NEE of real forests relying on a specifically developed conceptual framework which uses the ratio of actual over potential stand volume as indicator of ecosystem distance from climax. The accuracy of the estimated net carbon exchanges is finally evaluated against ground data derived from a recent forest inventory and from two eddy covariance flux towers located in Tuscany (San Rossore and Lecceto). The results of both these comparisons were quite positive, indicating the good capability of the method for forest carbon flux estimation in Mediterranean areas.

  4. Complementarity of flux- and biometric-based data to constrain parameters in a terrestrial carbon model

    Directory of Open Access Journals (Sweden)

    Zhenggang Du

    2015-03-01

    Full Text Available To improve models for accurate projections, data assimilation, an emerging statistical approach to combine models with data, have recently been developed to probe initial conditions, parameters, data content, response functions and model uncertainties. Quantifying how many information contents are contained in different data streams is essential to predict future states of ecosystems and the climate. This study uses a data assimilation approach to examine the information contents contained in flux- and biometric-based data to constrain parameters in a terrestrial carbon (C model, which includes canopy photosynthesis and vegetation–soil C transfer submodels. Three assimilation experiments were constructed with either net ecosystem exchange (NEE data only or biometric data only [including foliage and woody biomass, litterfall, soil organic C (SOC and soil respiration], or both NEE and biometric data to constrain model parameters by a probabilistic inversion application. The results showed that NEE data mainly constrained parameters associated with gross primary production (GPP and ecosystem respiration (RE but were almost invalid for C transfer coefficients, while biometric data were more effective in constraining C transfer coefficients than other parameters. NEE and biometric data constrained about 26% (6 and 30% (7 of a total of 23 parameters, respectively, but their combined application constrained about 61% (14 of all parameters. The complementarity of NEE and biometric data was obvious in constraining most of parameters. The poor constraint by only NEE or biometric data was probably attributable to either the lack of long-term C dynamic data or errors from measurements. Overall, our results suggest that flux- and biometric-based data, containing different processes in ecosystem C dynamics, have different capacities to constrain parameters related to photosynthesis and C transfer coefficients, respectively. Multiple data sources could also

  5. Revised estimates of the annual net flux of carbon to the atmosphere from changes in land use and land management 1850-2000

    International Nuclear Information System (INIS)

    Houghton, R.A.

    2003-01-01

    Recent analyses of land-use change in the US and China, together with the latest estimates of tropical deforestation and afforestation from the FAO, were used to calculate a portion of the annual flux of carbon between terrestrial ecosystems and the atmosphere. The calculated flux includes only that portion of the flux resulting from direct human activity. In most regions, activities included the conversion of natural ecosystems to cultivated lands and pastures, including shifting cultivation, harvest of wood (for timber and fuel) and the establishment of tree plantations. In the US, woody encroachment and woodland thickening as a result of fire suppression were also included. The calculated flux of carbon does not include increases or decreases in carbon storage as a result of environmental changes (e.g.; increasing concentrations of CO 2 , N deposition, climatic change or pollution). Globally, the long-term (1850-2000) flux of carbon from changes in land use and management released 156 PgC to the atmosphere, about 60% of it from the tropics. Average annual fluxes during the 1980s and 1990s were 2.0 and 2.2 PgC/yr, respectively, dominated by releases of carbon from the tropics. Outside the tropics, the average net flux of carbon attributable to land-use change and management decreased from a source of 0.06 PgC/yr during the 1980s to a sink of 0.02 PgC/yr during the 1990s. According to the analyses summarized here, changes in land use were responsible for sinks in North America and Europe and for small sources in other non-tropical regions. The revisions were as large as 0.3 PgC/yr in individual regions but were largely offsetting, so that the global estimate for the 1980s was changed little from an earlier estimate. Uncertainties and recent improvements in the data used to calculate the flux of carbon from land-use change are reviewed, and the results are compared to other estimates of flux to evaluate the extent to which processes other than land-use change and

  6. Emergent Exoplanet Flux: Review of the Spitzer Results

    OpenAIRE

    Deming, Drake

    2008-01-01

    Observations using the Spitzer Space Telescope provided the first detections of photons from extrasolar planets. Spitzer observations are allowing us to infer the temperature structure, composition, and dynamics of exoplanet atmospheres. The Spitzer studies extend from many hot Jupiters, to the hot Neptune orbiting GJ436. Here I review the current status of Spitzer secondary eclipse observations, and summarize the results from the viewpoint of what is robust, what needs more work, and what th...

  7. The effect of assimilating satellite derived soil moisture in SiBCASA on simulated carbon fluxes in Boreal Eurasia

    NARCIS (Netherlands)

    van der Molen, M. K.; de Jeu, R. A. M.; Wagner, W.; van der Velde, I. R.; Kolari, P.; Kurbatova, J.; Varlagin, A.; Maximov, T. C.; Kononov, A. V.; Ohta, T.; Kotani, A.; Krol, M. C.; Peters, W.

    2015-01-01

    Boreal Eurasia is a region where the interaction between droughts and the carbon cycle may have significant impacts on the global carbon cycle. Yet the region is extremely data sparse with respect to meteorology, soil moisture and carbon fluxes as compared to e.g. Europe. To better constrain our

  8. Understanding the behavior of carbon dioxide and surface energy fluxes in semiarid Salt Lake Valley, Utah, USA

    Science.gov (United States)

    Ramamurthy, Prathap

    This dissertation reports the findings from the Salt Lake Valley flux study. The Salt Lake Valley flux study was designed to improve our understanding of the complex land-atmosphere interactions in urban areas. The flux study used the eddy covariance technique to quantify carbon dioxide and surface energy budget in the semiarid Salt Lake Valley. Apart from quantifying fluxes, the study has also added new insight into the nature of turbulent scalar transport in urban areas and has addressed some of the complications in using Eddy Covariance technique in urban areas. As part of this experiment, eddy fluxes of CO2 and surface energy fluxes were measured at two sites, with distinct urban landforms; One site was located in a suburban neighborhood with substantial vegetative cover, prototypical of many residential neighborhoods in the valley. The other CO2 site was in a preurban surrounding that resembled the Salt Lake Valley before it was urbanized. The two sites were intentionally chosen to illustrate the impact of urbanization on CO 2 and surface energy flux cycles. Results indicate that the suburban site acted as a sink of CO2 during the midday period due to photosynthesis and acted as a source of CO2 during the evening and nighttime periods. The vegetative cover around the suburban site also had a significant impact on the surface energy fluxes. Contribution from latent heat flux was substantially high at the suburban site during the summer months compared to sensible heat. The turbulence investigation found that the general behavior of turbulence was very much influenced by local factors and the statistics did not always obey Monin-Obukhov Similarity parameters. This investigation also found that the scalar (co)spectra observed at the suburban site were characterized by multiple peaks and were different compared to (co)spectra reported over forest and crop canopies. The study also observed multiscale CO2 transport at the suburban site during the convective period

  9. Understanding and Projecting Climate and Human Impacts on Terrestrial-Coastal Carbon and Nutrient Fluxes

    Science.gov (United States)

    Lohrenz, S. E.; Cai, W. J.; Tian, H.; He, R.; Fennel, K.

    2017-12-01

    Changing climate and land use practices have the potential to dramatically alter coupled hydrologic-biogeochemical processes and associated movement of water, carbon and nutrients through various terrestrial reservoirs into rivers, estuaries, and coastal ocean waters. Consequences of climate- and land use-related changes will be particularly evident in large river basins and their associated coastal outflow regions. Here, we describe a NASA Carbon Monitoring System project that employs an integrated suite of models in conjunction with remotely sensed as well as targeted in situ observations with the objectives of describing processes controlling fluxes on land and their coupling to riverine, estuarine and ocean ecosystems. The nature of our approach, coupling models of terrestrial and ocean ecosystem dynamics and associated carbon processes, allows for assessment of how societal and human-related land use, land use change and forestry and climate-related change affect terrestrial carbon transport as well as export of materials through watersheds to the coastal margins. Our objectives include the following: 1) Provide representation of carbon processes in the terrestrial ecosystem to understand how changes in land use and climatic conditions influence the export of materials to the coastal ocean, 2) Couple the terrestrial exports of carbon, nutrients and freshwater to a coastal biogeochemical model and examine how different climate and land use scenarios influence fluxes across the land-ocean interface, and 3) Project future changes under different scenarios of climate and human impact, and support user needs related to carbon management and other activities (e.g., water quality, hypoxia, ocean acidification). This research is providing information that will contribute to determining an overall carbon balance in North America as well as describing and predicting how human- and climate-related changes impact coastal water quality including possible effects of coastal

  10. 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.

  11. 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...

  12. A data assimilation framework for constraining upscaled cropland carbon flux seasonality and biometry with MODIS

    Directory of Open Access Journals (Sweden)

    O. Sus

    2013-04-01

    Full Text Available Agroecosystem models are strongly dependent on information on land management patterns for regional applications. Land management practices play a major role in determining global yield variability, and add an anthropogenic signal to the observed seasonality of atmospheric CO2 concentrations. However, there is still little knowledge on spatial and temporal variability of important farmland activities such as crop sowing dates, and thus these remain rather crudely approximated within carbon cycle studies. In this study, we present a framework allowing for spatio-temporally resolved simulation of cropland carbon fluxes under observational constraints on land management and canopy greenness. We apply data assimilation methodology in order to explicitly account for information on sowing dates and model leaf area index. MODIS 250 m vegetation index data were assimilated both in batch-calibration for sowing date estimation and sequentially for improved model state estimation, using the ensemble Kalman filter (EnKF, into a crop carbon mass balance model (SPAc. In doing so, we are able to quantify the multiannual (2000–2006 regional carbon flux and biometry seasonality of maize–soybean crop rotations surrounding the Bondville Ameriflux eddy covariance site, averaged over 104 pixel locations within the wider area. (1 Validation at the Bondville site shows that growing season C cycling is simulated accurately with MODIS-derived sowing dates, and we expect that this framework allows for accurate simulations of C cycling at locations for which ground-truth data are not available. Thus, this framework enables modellers to simulate current (i.e. last 10 yr carbon cycling of major agricultural regions. Averaged over the 104 field patches analysed, relative spatial variability for biometry and net ecosystem exchange ranges from ∼7% to ∼18%. The annual sign of net biome productivity is not significantly different from carbon neutrality. (2 Moreover

  13. 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.

  14. Simulation of Forest Carbon Fluxes Using Model Incorporation and Data Assimilation

    Directory of Open Access Journals (Sweden)

    Min Yan

    2016-07-01

    Full Text Available This study improved simulation of forest carbon fluxes in the Changbai Mountains with a process-based model (Biome-BGC using incorporation and data assimilation. Firstly, the original remote sensing-based MODIS MOD_17 GPP (MOD_17 model was optimized using refined input data and biome-specific parameters. The key ecophysiological parameters of the Biome-BGC model were determined through the Extended Fourier Amplitude Sensitivity Test (EFAST sensitivity analysis. Then the optimized MOD_17 model was used to calibrate the Biome-BGC model by adjusting the sensitive ecophysiological parameters. Once the best match was found for the 10 selected forest plots for the 8-day GPP estimates from the optimized MOD_17 and from the Biome-BGC, the values of sensitive ecophysiological parameters were determined. The calibrated Biome-BGC model agreed better with the eddy covariance (EC measurements (R2 = 0.87, RMSE = 1.583 gC·m−2·d−1 than the original model did (R2 = 0.72, RMSE = 2.419 gC·m−2·d−1. To provide a best estimate of the true state of the model, the Ensemble Kalman Filter (EnKF was used to assimilate five years (of eight-day periods between 2003 and 2007 of Global LAnd Surface Satellite (GLASS LAI products into the calibrated Biome-BGC model. The results indicated that LAI simulated through the assimilated Biome-BGC agreed well with GLASS LAI. GPP performances obtained from the assimilated Biome-BGC were further improved and verified by EC measurements at the Changbai Mountains forest flux site (R2 = 0.92, RMSE = 1.261 gC·m−2·d−1.

  15. Greenhouse gas flux measurements in a forestry-drained peatland indicate a large carbon sink

    Directory of Open Access Journals (Sweden)

    A. Lohila

    2011-11-01

    Full Text Available Drainage for forestry purposes increases the depth of the oxic peat layer and leads to increased growth of shrubs and trees. Concurrently, the production and uptake of the greenhouse gases carbon dioxide (CO2, methane (CH4 and nitrous oxide (N2O change: due to the accelerated decomposition of peat in the presence of oxygen, drained peatlands are generally considered to lose peat carbon (C. We measured CO2 exchange with the eddy covariance (EC method above a drained nutrient-poor peatland forest in southern Finland for 16 months in 2004–2005. The site, classified as a dwarf-shrub pine bog, had been ditched about 35 years earlier. CH4 and N2O fluxes were measured at 2–5-week intervals with the chamber technique. Drainage had resulted in a relatively little change in the water table level, being on average 40 cm below the ground in 2005. The annual net ecosystem exchange was −870 ± 100 g CO2 m−2 yr−1 in the calendar year 2005, indicating net CO2 uptake from the atmosphere. The site was a small sink of CH4 (−0.12 g CH4 m−2 yr−1 and a small source of N2O (0.10 g N2O m−2 yr−1. Photosynthesis was detected throughout the year when the air temperature exceeded −3 °C. As the annual accumulation of C in the above and below ground tree biomass (175 ± 35 g C m−2 was significantly lower than the accumulation observed by the flux measurement (240 ± 30 g C m−2, about 65 g C m−2 yr−1 was likely to have accumulated as organic matter into the peat soil. This is a higher average accumulation rate than previously reported for natural northern peatlands, and the first time C accumulation has been shown by EC measurements to occur in a forestry-drained peatland. Our results suggest that forestry

  16. Crystal growth of carbonate apatite using a CaCO3 flux.

    Science.gov (United States)

    Suetsugu, Y; Tanaka, J

    1999-09-01

    Single crystals of carbonate apatite were grown using a CaCO3 flux under an Ar gas pressure of 55 MPa. The crystals obtained were observed by scanning electron microscopy, optical microscopy and X-ray diffraction. Electron probe microanalyses and thermal analyses were performed. CO3 ions in planar triangle form replaced both OH sites and PO4 tetrahedral sites in the apatite structure: in particular, the OH sites were perfectly substituted by CO3 ions using this method.

  17. Changing fluxes of carbon and other solutes from the Mekong River.

    Science.gov (United States)

    Li, Siyue; Bush, Richard T

    2015-11-02

    Rivers are an important aquatic conduit that connects terrestrial sources of dissolved inorganic carbon (DIC) and other elements with oceanic reservoirs. The Mekong River, one of the world's largest rivers, is firstly examined to explore inter-annual fluxes of dissolved and particulate constituents during 1923-2011 and their associated natural or anthropogenic controls. Over this period, inter-annual fluxes of dissolved and particulate constituents decrease, while anthropogenic activities have doubled the relative abundance of SO4(2-), Cl(-) and Na(+). The estimated fluxes of solutes from the Mekong decrease as follows (Mt/y): TDS (40.4) > HCO3(-) (23.4) > Ca(2+) (6.4) > SO4(2-) (3.8) > Cl(-) (1.74)~Na(+) (1.7) ~ Si (1.67) > Mg(2+) (1.2) > K(+ 0.5). The runoff, land cover and lithological composition significantly contribute to dissolved and particulate yields globally. HCO3(-) and TDS yields are readily predicted by runoff and percent of carbonate, while TSS yield by runoff and population density. The Himalayan Rivers, including the Mekong, are a disproportionally high contributor to global riverine carbon and other solute budgets, and are of course underlined. The estimated global riverine HCO3(-) flux (Himalayan Rivers included) is 34,014 × 10(9) mol/y (0.41 Pg C/y), 3915 Mt/y for solute load, including HCO3(-), and 13,553 Mt/y for TSS. Thereby this study illustrates the importance of riverine solute delivery in global carbon cycling.

  18. Simulation of Forest Carbon Fluxes Using Model Incorporation and Data Assimilation

    OpenAIRE

    Min Yan; Xin Tian; Zengyuan Li; Erxue Chen; Xufeng Wang; Zongtao Han; Hong Sun

    2016-01-01

    This study improved simulation of forest carbon fluxes in the Changbai Mountains with a process-based model (Biome-BGC) using incorporation and data assimilation. Firstly, the original remote sensing-based MODIS MOD_17 GPP (MOD_17) model was optimized using refined input data and biome-specific parameters. The key ecophysiological parameters of the Biome-BGC model were determined through the Extended Fourier Amplitude Sensitivity Test (EFAST) sensitivity analysis. Then the optimized MOD_17 mo...

  19. Response of ecosystem carbon fluxes to drought events in a poplar plantation in Northern China

    Science.gov (United States)

    Jie Zhou; Zhiqiang Zhang; Ge Sun; Xianrui Fang; Tonggang Zha; Steve McNulty; Jiquan Chen; Ying Jin; Asko Noormets

    2013-01-01

    Poplar plantations are widely used for timber production and ecological restoration in northern China,a region that experiences frequent droughts and water scarcity. An open-path eddy-covariance (EC)system was used to continuously measure the carbon,water,and energy fluxes in a poplar plantation during the growing season (i.e., April–October)over the period 2006–2008...

  20. Diurnal and Seasonal Variations of Eddy-Covariance Carbon Dioxide Fluxes Above an Urban Wetland, Partitioned by Vegetation Cover

    Science.gov (United States)

    Schafer, K. V.; Duman, T.

    2017-12-01

    The New Jersey Meadowlands are an urban brackish marsh with a long history of human activity causing disturbances and alterations. Carbon emissions were measured from two sites in the Meadowlands, a natural site and a restored site, using eddy-covariance (EC) from 2014 to 2016. At each site, the EC towers were placed at the interface of two vegetation covers, allowing capturing this aspect of the wetland's heterogeneity. Using footprint modeling and light response curves we were able to partition measured fluxes between vegetation cover types and compare CO2 fluxes from patches of invasive versus native wetland vegetation communities. We show that further separating the data into seasonal and diurnal fluxes reveals patterns in CO2 fluxes that allow determining the nature of each vegetation cover as a source or sink for CO2. Our results also show that CO2 emissions from the restored wetland are significantly higher than the natural wetland. Areas of invasive Phragmites australis at the natural site had the lowest CO2 release rates during winter. These were consistently lower in magnitude than summer daytime uptake, therefore making this part of the wetland a CO2 sink. Areas planted with native Spartina alterniflora at the restored site had the largest uptake during daytime, therefore seemingly justifying restoration activities. However, they also had the highest emission rates during summer nighttime, and therefore the daily summer net uptake was not the highest compared with other vegetation covers. Furthermore, emissions from the restored site during winter were larger compared to the natural site, indicating that restoration activities might have led to a significant increase of carbon release from the wetland. Thus, during the study period the restored wetland acted as a carbon source.

  1. The Net Carbon Flux due to Deforestation and Forest Re-Growth in the Brazilian Amazon: Analysis using a Process-Based Model

    Science.gov (United States)

    Hirsch, A. I.; Little, W. S.; Houghton, R. A.; Scott, N. A.; White, J. D.

    2004-01-01

    We developed a process-based model of forest growth, carbon cycling, and land cover dynamics named CARLUC (for CARbon and Land Use Change) to estimate the size of terrestrial carbon pools in terra firme (non-flooded) forests across the Brazilian Legal Amazon and the net flux of carbon resulting from forest disturbance and forest recovery from disturbance. Our goal in building the model was to construct a relatively simple ecosystem model that would respond to soil and climatic heterogeneity that allows us to study of the impact of Amazonian deforestation, selective logging, and accidental fire on the global carbon cycle. This paper focuses on the net flux caused by deforestation and forest re-growth over the period from 1970-1998. We calculate that the net flux to the atmosphere during this period reached a maximum of approx. 0.35 PgC/yr (1PgC = 1 x 10(exp I5) gC) in 1990, with a cumulative release of approx. 7 PgC from 1970- 1998. The net flux is higher than predicted by an earlier study by a total of 1 PgC over the period 1989-1 998 mainly because CARLUC predicts relatively high mature forest carbon storage compared to the datasets used in the earlier study. Incorporating the dynamics of litter and soil carbon pools into the model increases the cumulative net flux by approx. 1 PgC from 1970-1998, while different assumptions about land cover dynamics only caused small changes. The uncertainty of the net flux, calculated with a Monte-Carlo approach, is roughly 35% of the mean value (1 SD).

  2. Carbon exchange fluxes over peatlands in Western Siberia: Possible feedback between land-use change and climate change

    Energy Technology Data Exchange (ETDEWEB)

    Fleischer, Elisa, E-mail: elisa.fleischer@uni-muenster.de [Institute of Landscape Ecology, Climatology Research Group, University of Münster, Münster (Germany); Khashimov, Ilhom, E-mail: nixonlp@mail.ru [Institute of Earth Science, Physical Geography and Geoecology Department, Tyumen State University, Tyumen (Russian Federation); Hölzel, Norbert, E-mail: nhoelzel@uni-muenster.de [Institute of Landscape Ecology, Biodiversity and Ecosystem Research Group, University of Münster, Münster (Germany); Klemm, Otto, E-mail: otto.klemm@uni-muenster.de [Institute of Landscape Ecology, Climatology Research Group, University of Münster, Münster (Germany)

    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. - Highlights: • Grasslands on drained peat soil can act as carbon sinks. • Arable fields on drained peat act as carbon sources due to long phases of bare soil. • CH{sub 4} emissions from drained peatlands seem to play a smaller role than CO{sub 2} fluxes. • Conversion from grassland to arable field has

  3. Revised methane emissions factors and spatially distributed annual carbon fluxes for global livestock.

    Science.gov (United States)

    Wolf, Julie; Asrar, Ghassem R; West, Tristram O

    2017-09-29

    Livestock play an important role in carbon cycling through consumption of biomass and emissions of methane. Recent research suggests that existing bottom-up inventories of livestock methane emissions in the US, such as those made using 2006 IPCC Tier 1 livestock emissions factors, are too low. This may be due to outdated information used to develop these emissions factors. In this study, we update information for cattle and swine by region, based on reported recent changes in animal body mass, feed quality and quantity, milk productivity, and management of animals and manure. We then use this updated information to calculate new livestock methane emissions factors for enteric fermentation in cattle, and for manure management in cattle and swine. Using the new emissions factors, we estimate global livestock emissions of 119.1 ± 18.2 Tg methane in 2011; this quantity is 11% greater than that obtained using the IPCC 2006 emissions factors, encompassing an 8.4% increase in enteric fermentation methane, a 36.7% increase in manure management methane, and notable variability among regions and sources. For example, revised manure management methane emissions for 2011 in the US increased by 71.8%. For years through 2013, we present (a) annual livestock methane emissions, (b) complete annual livestock carbon budgets, including carbon dioxide emissions, and (c) spatial distributions of livestock methane and other carbon fluxes, downscaled to 0.05 × 0.05 degree resolution. Our revised bottom-up estimates of global livestock methane emissions are comparable to recently reported top-down global estimates for recent years, and account for a significant part of the increase in annual methane emissions since 2007. Our results suggest that livestock methane emissions, while not the dominant overall source of global methane emissions, may be a major contributor to the observed annual emissions increases over the 2000s to 2010s. Differences at regional and local scales may help

  4. 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.

  5. Boiling Heat Transfer Coefficients of Nanofluids Containing Carbon Nanotubes up to Critical Heat Fluxes

    International Nuclear Information System (INIS)

    Park, Ki Jung; Lee, Yohan; Jung, Dong Soo; Shim, Sang Eun

    2011-01-01

    In this study, the nucleate pool boiling heat transfer coefficients (HTCs) and critical heat flux (CHF) for a smooth and square flat heater in a pool of pure water with and without carbon nanotubes (CNTs) dispersed at 60 .deg. C were measured. Tested aqueous nanofluids were prepared using CNTs with volume concentrations of 0.0001%, 0.001%, and 0.01%. The CNTs were dispersed by chemically treating them with an acid in the absence of any polymers. The results showed that the pool boiling HTCs of the nanofluids are higher than those of pure water in the entire nucleate boiling regime. The acid-treated CNTs led to the deposition of a small amount of CNTs on the surface, and the CNTs themselves acted as heat-transfer-enhancing particles, owing to their very high thermal conductivity. There was a significant increase in the CHF- up to 150%-when compared to that of pure water containing CNTs with a volume concentration of 0.001%. This is attributed to the change in surface characteristics due to the deposition of a very thin layer of CNTs on the surface. This layer delays nucleate boiling and causes a reduction in the size of the large vapor canopy around the CHF. This results in a significant increase in the CHF

  6. Seasonal Variations of Carbon Dioxide, Water Vapor and Energy Fluxes in Tropical Indian Mangroves

    Directory of Open Access Journals (Sweden)

    Suraj Reddy Rodda

    2016-02-01

    Full Text Available We present annual estimates of the net ecosystem exchange (NEE of carbon dioxide (CO2 accumulated over one annual cycle (April 2012 to March 2013 in the world’s largest mangrove ecosystem, Sundarbans (India, using the eddy covariance method. An eddy covariance flux tower was established in April 2012 to study the seasonal variations of carbon dioxide fluxes due to soil and vegetation-atmosphere interactions. The half-hourly maximum of the net ecosystem exchange (NEE varied from −6 µmol·m−2·s−1 during the summer (April to June 2012 to −10 µmol·m−2·s−1 during the winter (October to December 2012, whereas the half-hourly maximum of H2O flux varied from 5.5 to 2.5 mmol·m−2·s−1 during October 2013 and July 2013, respectively. During the study period, the study area was a carbon dioxide sink with an annual net ecosystem productivity (NEP = −NEE of 249 ± 20 g·C m−2·year−1. The mean annual evapotranspiration (ET was estimated to be 1.96 ± 0.33 mm·day−1. The gap-filled NEE was also partitioned into Gross Primary Productivity (GPP and Ecosystem Respiration (Re. The total GPP and Re over the study area for the annual cycle were estimated to be1271 g C m−2·year−1 and 1022 g C m−2·year−1, respectively. The closure of the surface energy balance accounted for of about 78% of the available energy during the study period. Our findings suggest that the Sundarbans mangroves are currently a substantial carbon sink, indicating that the protection and management of these forests would lead as a strategy towards reduction in carbon dioxide emissions.

  7. Evaluation of the DayCent model to predict carbon fluxes in French crop sites

    Science.gov (United States)

    Fujisaki, Kenji; Martin, Manuel P.; Zhang, Yao; Bernoux, Martial; Chapuis-Lardy, Lydie

    2017-04-01

    Croplands in temperate regions are an important component of the carbon balance and can act as a sink or a source of carbon, depending on pedoclimatic conditions and management practices. Therefore the evaluation of carbon fluxes in croplands by modelling approach is relevant in the context of global change. This study was part of the Comete-Global project funded by the multi-Partner call FACCE JPI. Carbon fluxes, net ecosystem exchange (NEE), leaf area index (LAI), biomass, and grain production were simulated at the site level in three French crop experiments from the CarboEurope project. Several crops were studied, like winter wheat, rapeseed, barley, maize, and sunflower. Daily NEE was measured with eddy covariance and could be partitioned between gross primary production (GPP) and total ecosystem respiration (TER). Measurements were compared to DayCent simulations, a process-based model predicting plant production and soil organic matter turnover at daily time step. We compared two versions of the model: the original one with a simplified plant module and a newer version that simulates LAI. Input data for modelling were soil properties, climate, and management practices. Simulations of grain yields and biomass production were acceptable when using optimized crop parameters. Simulation of NEE was also acceptable. GPP predictions were improved with the newer version of the model, eliminating temporal shifts that could be observed with the original model. TER was underestimated by the model. Predicted NEE was more sensitive to soil tillage and nitrogen applications than measured NEE. DayCent was therefore a relevant tool to predict carbon fluxes in French crops at the site level. The introduction of LAI in the model improved its performance.

  8. A long-term simulation of forest carbon fluxes over the Qilian Mountains

    Science.gov (United States)

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

    2016-10-01

    In this work, we integrated a remote-sensing-based (the MODIS MOD_17 Gross Primary Productivity (GPP) model (MOD_17)) and a process-based (the Biome-BioGeochemical Cycles (Biome-BGC) model) ecological model in order to estimate long-term (from 2000 to 2012) forest carbon fluxes over the Qilian Mountains in northwest China, a cold and arid forest ecosystem. Our goal was to obtain an accurate and quantitative simulation of spatial GPP patterns using the MOD_17 model and a temporal description of forest processes using the Biome-BGC model. The original MOD_17 model was first optimized using a biome-specific parameter, observed meteorological data, and reproduced fPAR at the eddy covariance site. The optimized MOD_17 model performed much better (R2 = 0.91, RMSE = 5.19 gC/m2/8d) than the original model (R2 = 0.47, RMSE = 20.27 gC/m2/8d). The Biome-BGC model was then calibrated using GPP for 30 representative forest plots selected from the optimized MOD_17 model. The calibrated Biome-BGC model was then driven in order to estimate forest GPP, net primary productivity (NPP), and net ecosystem exchange (NEE). GPP and NEE were validated against two-year (2010 and 2011) EC measurements (R2 = 0.79, RMSE = 1.15 gC/m2/d for GPP; and R2 = 0.69, RMSE = 1.087 gC/m2/d for NEE). NPP estimates from 2000 to 2012 were then compared to dendrochronological measurements (R2 = 0.73, RMSE = 24.46 gC/m2/yr). Our results indicated that integration of the two models can be used for estimating carbon fluxes with good accuracy and a high temporal and spatial resolution. Overall, NPP displayed a downward trend, with an average rate of 0.39 gC/m2/yr, from 2000 and 2012 over the Qilian Mountains. Simulated average annual NPP yielded higher values for the southeast as compared to the northwest. The most positive correlative climatic factor to average annual NPP was downward shortwave radiation. The vapor pressure deficit, and mean temperature and precipitation yielded negative correlations to average

  9. Final Technical Report: The effects of climate, forest age, and disturbance history on carbon and water processes at AmeriFlux sites across gradients in Pacific Northwest forests

    Energy Technology Data Exchange (ETDEWEB)

    Law, Beverly E. [Oregon State Univ., Corvallis, OR (United States)

    2016-12-03

    Investigate the effects of disturbance and climate variables on processes controlling carbon and water processes at AmeriFlux cluster sites in semi-arid and mesic forests in Oregon. The observations were made at three existing and productive AmeriFlux research sites that represent climate and disturbance gradients as a natural experiment of the influence of climatic and hydrologic variability on carbon sequestration and resulting atmospheric CO2 feedback that includes anomalies during the warm/ dry phase of the Pacific Decadal Oscillation.

  10. CarbonTracker-Lagrange: A Framework for Greenhouse Gas Flux Estimation at Regional to Continental Scales

    Science.gov (United States)

    Andrews, A. E.

    2016-12-01

    CarbonTracker-Lagrange (CT-L) is a flexible modeling framework developed to take advantage of newly available atmospheric data for CO2 and other long-lived gases such as CH4 and N2O. The North American atmospheric CO2 measurement network has grown from three sites in 2004 to >100 sites in 2015. The US network includes tall tower, mountaintop, surface, and aircraft sites in the NOAA Global Greenhouse Gas Reference Network along with sites maintained by university, government and private sector researchers. The Canadian network is operated by Environment and Climate Change Canada. This unprecedented dataset can provide spatially and temporally resolved CO2 emissions and uptake flux estimates and quantitative information about drivers of variability, such as drought and temperature. CT-L is a platform for systematic comparison of data assimilation techniques and evaluation of assumed prior, model and observation errors. A novel feature of CT-L is the optimization of boundary values along with surface fluxes, leveraging vertically resolved data available from NOAA's aircraft sampling program. CT-L uses observation footprints (influence functions) from the Weather Research and Forecasting/Stochastic Time-Inverted Lagrangian Transport (WRF-STILT) modeling system to relate atmospheric measurements to upwind fluxes and boundary values. Footprints are pre-computed and the optimization algorithms are efficient, so many variants of the calculation can be performed. Fluxes are adjusted using Bayesian or Geostatistical methods to provide optimal agreement with observations. Satellite measurements of CO2 and CH4 from GOSAT are available starting in July 2009 and from OCO-2 since September 2014. With support from the NASA Carbon Monitoring System, we are developing flux estimation strategies that use remote sensing and in situ data together, including geostatistical inversions using satellite retrievals of solar-induced chlorophyll fluorescence. CT-L enables quantitative

  11. Public Review Draft: A Method for Assessing Carbon Stocks, Carbon Sequestration, and Greenhouse-Gas Fluxes in Ecosystems of the United States Under Present Conditions and Future Scenarios

    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

    storyline to enhance carbon sequestration and reduce GHG fluxes in ecosystems. Input from regional experts and stakeholders will be solicited to construct realistic and meaningful scenarios. The methods for mapping the current LULC and ecosystem disturbances will require the extensive use of both remote-sensing data and in-situ (for example, forest inventory data) to capture and characterize landscape-change events. For future potential LULC and ecosystem disturbances, key drivers such as socioeconomic, policy, and climate assumptions will be used in addition to biophysical data. The product 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 current and projected future conditions will be assessed using the LULC 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 elevation, vegetation characteristics, and soil attributes). For aquatic ecosystems, carbon burial in sediments and GHG fluxes are functions of the current and projected future stream flow and sediment transports, and therefore will be assessed using empirical 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 (which delineates 24 ecoregions for the Nation) will be the practical instrument for developing and delivering assessment results. Consequently, the ecoregion will be the reporting unit of the assessment because the mitigation scenarios, assessment results, validation, and uncertainty analysis will be

  12. Energy, water vapor and carbon fluxes in Andean agroecosystems: conceptualization and methodological standardization

    Directory of Open Access Journals (Sweden)

    Angela María Castaño Marín

    2017-01-01

    Full Text Available This paper presents the conceptualization, methodological adjustment and experimental application of the micrometeorological technique eddy covariance - EC, to measure energy, water vapor and CO2 fluxes in two coffee agroecosystems: the first under full sunlight, and the second under shade, both with equatorial Andean hillslope conditions. With a footprint and fetch calculation, the required distance from the edge of the field in the prevailing wind direction to the EC tower is three times higher under shade than full sun. The shaded agroecosystem reached maximum average carbon fixation rates of 21.26 ± 2.469 μmolCO2.m-2s-1 ( = 0.05 (61% higher than under 100% sunlight which gives a high carbon sink capacity to the association of coffee plants with shading Pigeon peas (Cajanus cajan L. The average evapotranspiration rate was 2.33 ± 0.0102 mm.d-1 ( = 0.05 and 2.08 ± 0.00732 mm.d-1 under shade and 100% sunlight, respectively. The proportion of net radiation that reached the soil was 2% under shade and 4% under 100% sunlight. Likewise, the soil energy loss during the night was lower under shade, indicating less day-night temperature range in the latter agroecosystem. The methodological adjustment and the results of this first work using EC in Colombian coffee plantations, contribute to the development of reliable research regarding gas and energy exchanges between the atmosphere and ecosystems in conditions of the equatorial Andean hillslope.

  13. 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...

  14. Superfine powdered activated carbon (S-PAC) coatings on microfiltration membranes: Effects of milling time on contaminant removal and flux.

    Science.gov (United States)

    Amaral, Pauline; Partlan, Erin; Li, Mengfei; Lapolli, Flavio; Mefford, O Thompson; Karanfil, Tanju; Ladner, David A

    2016-09-01

    In microfiltration processes for drinking water treatment, one method of removing trace contaminants is to add powdered activated carbon (PAC). Recently, a version of PAC called superfine PAC (S-PAC) has been under development. S-PAC has a smaller particle size and thus faster adsorption kinetics than conventionally sized PAC. Membrane coating performance of various S-PAC samples was evaluated by measuring adsorption of atrazine, a model micropollutant. S-PACs were created in-house from PACs of three different materials: coal, wood, and coconut shell. Milling time was varied to produce S-PACs pulverized with different amounts of energy. These had different particles sizes, but other properties (e.g. oxygen content), also differed. In pure water the coal based S-PACs showed superior atrazine adsorption; all milled carbons had over 90% removal while the PAC had only 45% removal. With addition of calcium and/or NOM, removal rates decreased, but milled carbons still removed more atrazine than PAC. Oxygen content and specific external surface area (both of which increased with longer milling times) were the most significant predictors of atrazine removal. S-PAC coatings resulted in loss of filtration flux compared to an uncoated membrane and smaller particles caused more flux decline than larger particles; however, the data suggest that NOM fouling is still more of a concern than S-PAC fouling. The addition of calcium improved the flux, especially for the longer-milled carbons. Overall the data show that when milling S-PAC with different levels of energy there is a tradeoff: smaller particles adsorb contaminants better, but cause greater flux decline. Fortunately, an acceptable balance may be possible; for example, in these experiments the coal-based S-PAC after 30 min of milling achieved a fairly high atrazine removal (overall 80%) with a fairly low flux reduction (under 30%) even in the presence of NOM. This suggests that relatively short duration (low energy

  15. 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.

  16. SiB3 Modeled Global 1-degree Hourly Biosphere-Atmosphere Carbon Flux, 1998-2006

    Data.gov (United States)

    National Aeronautics and Space Administration — The Simple Biosphere Model, Version 3 (SiB3) was used to produce a global data set of hourly carbon fluxes between the atmosphere and the terrestrial biosphere for...

  17. Fluxes of carbon dioxide and methane from diverse aquatic environments in an agricultural landscape

    Science.gov (United States)

    Stanley, E. H.; Crawford, J. T.; Loken, L. C.; Casson, N. J.; Gubbins, N. J.; Oliver, S. K.

    2014-12-01

    The contribution of aquatic environments to landscape carbon cycling is particularly apparent in carbon- and water-rich regions. Such areas arguably represent an end member in terms of the relative significance of aquatic carbon cycling, while dry, carbon-poor zones are the likely opposing end member. Not surprisingly, most limnological attention has focused on these former regions, leaving open questions as to how aquatic systems in other locales influence larger-scale carbon dynamics. This includes human-dominated landscapes where agricultural and urban land uses can fundamentally alter carbon dynamics. Surveys of streams, ponds, and lakes in a southern Wisconsin landscape highlight three findings relevant to understanding the role of these aquatic systems in larger-scale carbon dynamics. First, streams and ponds had unexpectedly high summertime concentrations in and fluxes of CO2 and CH4. These values were approximately an order of magnitude greater than for less disturbed, forest and wetland-dominated landscapes in northern Wisconsin. Second, while mean C gas concentrations in lakes were lower than in streams and ponds, detailed spatial measurements demonstrate variability in surface water CO2 (43-1090 ppm pCO2) and CH4 (6-839 ppm pCH4) within a lake on a single day is similar to that observed among 25 streams included in our survey (260-6000 ppm pCO2; 50-600 ppm pCH4). This small-scale heterogeneity highlights a basic challenge for upscaling site-specific data collected at one or a few points to the whole lake and across lakes. Third, while agricultural and urban ecosystems are not necessarily carbon-rich environments, area-specific carbon storage in streams and ponds is substantial (up to 3000-5000 g C per m2). Further, carbon storage was strongly related to CH4 concentrations in streams, as C-rich sediments provided both an environment and substrate to fuel methanogenesis. The picture that emerges of C processing in aquatic environments throughout this human

  18. How temporal patterns in rainfall determine the geomorphology and carbon fluxes of tropical peatlands

    Science.gov (United States)

    Hoyt, Alison M.; Gandois, Laure; Eri, Jangarun; Dommain, René; Abu Salim, Kamariah; Kai, Fuu Ming; Haji Su’ut, Nur Salihah; Harvey, Charles F.

    2017-01-01

    Tropical peatlands now emit hundreds of megatons of carbon dioxide per year because of human disruption of the feedbacks that link peat accumulation and groundwater hydrology. However, no quantitative theory has existed for how patterns of carbon storage and release accompanying growth and subsidence of tropical peatlands are affected by climate and disturbance. Using comprehensive data from a pristine peatland in Brunei Darussalam, we show how rainfall and groundwater flow determine a shape parameter (the Laplacian of the peat surface elevation) that specifies, under a given rainfall regime, the ultimate, stable morphology, and hence carbon storage, of a tropical peatland within a network of rivers or canals. We find that peatlands reach their ultimate shape first at the edges of peat domes where they are bounded by rivers, so that the rate of carbon uptake accompanying their growth is proportional to the area of the still-growing dome interior. We use this model to study how tropical peatland carbon storage and fluxes are controlled by changes in climate, sea level, and drainage networks. We find that fluctuations in net precipitation on timescales from hours to years can reduce long-term peat accumulation. Our mathematical and numerical models can be used to predict long-term effects of changes in temporal rainfall patterns and drainage networks on tropical peatland geomorphology and carbon storage. PMID:28607068

  19. How temporal patterns in rainfall determine the geomorphology and carbon fluxes of tropical peatlands.

    Science.gov (United States)

    Cobb, Alexander R; Hoyt, Alison M; Gandois, Laure; Eri, Jangarun; Dommain, René; Abu Salim, Kamariah; Kai, Fuu Ming; Haji Su'ut, Nur Salihah; Harvey, Charles F

    2017-06-27

    Tropical peatlands now emit hundreds of megatons of carbon dioxide per year because of human disruption of the feedbacks that link peat accumulation and groundwater hydrology. However, no quantitative theory has existed for how patterns of carbon storage and release accompanying growth and subsidence of tropical peatlands are affected by climate and disturbance. Using comprehensive data from a pristine peatland in Brunei Darussalam, we show how rainfall and groundwater flow determine a shape parameter (the Laplacian of the peat surface elevation) that specifies, under a given rainfall regime, the ultimate, stable morphology, and hence carbon storage, of a tropical peatland within a network of rivers or canals. We find that peatlands reach their ultimate shape first at the edges of peat domes where they are bounded by rivers, so that the rate of carbon uptake accompanying their growth is proportional to the area of the still-growing dome interior. We use this model to study how tropical peatland carbon storage and fluxes are controlled by changes in climate, sea level, and drainage networks. We find that fluctuations in net precipitation on timescales from hours to years can reduce long-term peat accumulation. Our mathematical and numerical models can be used to predict long-term effects of changes in temporal rainfall patterns and drainage networks on tropical peatland geomorphology and carbon storage.

  20. Relationships between carbon fluxes and environmental factors in a drip-irrigated, film-mulched cotton field in arid region.

    Directory of Open Access Journals (Sweden)

    Xiaoyu Li

    Full Text Available Environmental factors and human activities play important roles in carbon fixation and emissions generated from croplands. Eddy covariance measurements in a drip-irrigated, film-mulched cotton field were used to analyze the relationships between carbon fluxes and environmental factors in Wulanwusu, northern Xinjiang, an arid region of Northwest China. Our results showed that the cumulative net carbon flux (NEE was -304.8 g C m-2 (a strong sink over the whole cotton growing season in 2012, which was more than that in cotton cropland without plastic film mulching and drip-irrigation. Moreover, when time is scaled up from a half-hour to a month, the correlations of gross primary production (GPP to air temperature (Tair, net solar radiation (Rn and soil water content (SWC gradually become stronger due to ecosystem resistance and resilience as well as the protection of plastic film mulching. The GPP is more strongly correlated with Rn than Tair at time scales from minutes to days, while it reverses at time scales from days to weeks. This outcome is largely determined by the biochemical characteristics of photosynthesis. SWC and vapor pressure deficit (VPD at all time scales are weakly correlated with GPP because plastic film mulching and regularly drip-irrigation allow soil to maintain sufficient water.

  1. Modeling the large-scale effects of surface moisture heterogeneity on wetland carbon fluxes in the West Siberian Lowland

    Directory of Open Access Journals (Sweden)

    T. J. Bohn

    2013-10-01

    Full Text Available We used a process-based model to examine the role of spatial heterogeneity of surface and sub-surface water on the carbon budget of the wetlands of the West Siberian Lowland over the period 1948–2010. We found that, while surface heterogeneity (fractional saturated area had little overall effect on estimates of the region's carbon fluxes, sub-surface heterogeneity (spatial variations in water table depth played an important role in both the overall magnitude and spatial distribution of estimates of the region's carbon fluxes. In particular, to reproduce the spatial pattern of CH4 emissions recorded by intensive in situ observations across the domain, in which very little CH4 is emitted north of 60° N, it was necessary to (a account for CH4 emissions from unsaturated wetlands and (b use spatially varying methane model parameters that reduced estimated CH4 emissions in the northern (permafrost half of the domain (and/or account for lower CH4 emissions under inundated conditions. Our results suggest that previous estimates of the response of these wetlands to thawing permafrost may have overestimated future increases in methane emissions in the permafrost zone.

  2. Decoding the Secrets of Carbon Preservation and GHG Flux in Lower-Latitude Peatlands

    Science.gov (United States)

    Richardson, C. J.; Flanagan, N. E.; Wang, H.; Ho, M.; Hodgkins, S. B.; Cooper, W. T.; Chanton, J.; Winton, S.

    2017-12-01

    The mechanisms regulating peat decomposition and C carbon storage in peatlands are poorly understood, particularly with regard to the importance of the biochemical compounds produced by different plant species and in turn peat quality controls on C storage and GHG flux. To examine the role of carbon quality in C accretion in northern compared to tropical peatlands we completed field and lab studies on bog peats collected in Minnesota, North Carolina, Florida and Peru to answer three fundamental questions; 1) is tropical peat more recalcitrant than northern peat 2) does the addition of aromatic and phenolic C compounds increase towards the tropics 3) do differences in the chemical structure of organic matter explain variances in carbon storage and GHG flux in tropical versus northern peatlands? Our main hypothesize is that high concentrations of phenolics and aromatic C compounds produced in shrub and tree plant communities in peatlands coupled with the fire production of biochar aromatics in peatlands may provide a dual biogeochemical latch mechanism controlling microbial decomposition of peat even under higher temperatures and seasonal drought. By comparing the peat bog soil cores collected from the MN peat bogs, NC Pocosins, FL Everglades and Peru palm swamps we find that the soils in the shrub-dominant Pocosin contain the highest phenolics, which microbial studies indicate have the strongest resistance to microbial decomposition. A chemical comparison of plant driven peat carbon quality along a north to south latitudinal gradient indicates that tropical peatlands have higher aromatic compounds, and enhanced phenolics, especially after light fires, which enhances C storage and affect GHG flux across the latitudinal gradient.

  3. Oxygen permeation flux through La1-ySryFeO3 limited by the carbon monoxide oxidation rate

    NARCIS (Netherlands)

    van Hassel, B.A.; van Hassel, B.A.; ten Elshof, Johan E.; Bouwmeester, Henricus J.M.

    1995-01-01

    The oxygen permeation flux through La1-ySryFeO3-δ (y = 0.1, 0.2) in a large oxygen partial pressure gradient (air/CO, CO2 mixture) was found to be limited by the carbon monoxide oxidation rate at the low oxygen partial pressure side of the membrane. The oxygen permeation flux through the membrane

  4. Variability in carbon dioxide fluxes among six winter wheat paddocks managed under different tillage and grazing practices

    Science.gov (United States)

    Carbon dioxide (CO2) fluxes from six winter wheat (Triticum aestivum L.) paddocks (grain only, graze-grain, and graze-out) managed under conventional till (CT) and no-till (NT) systems were synthesized for the 2016-2017 growing season to compare the magnitudes and seasonal dynamics of CO2 fluxes and...

  5. Global sampling of the seasonal changes in vegetation biophysical properties and associated carbon flux dynamics: using the synergy of information captured by spectral time series

    Science.gov (United States)

    Campbell, P. K. E.; Huemmrich, K. F.; Middleton, E.; Voorhis, S.; Landis, D.

    2016-12-01

    Spatial heterogeneity and seasonal dynamics in vegetation function contribute significantly to the uncertainties in regional and global CO2 budgets. High spectral resolution imaging spectroscopy ( 10 nm, 400-2500 nm) provides an efficient tool for synoptic evaluation of the factors significantly affecting the ability of the vegetation to sequester carbon and to reflect radiation, due to changes in vegetation chemical and structural composition. EO-1 Hyperion has collected more than 15 years of repeated observations for vegetation studies, and currently Hyperion time series are available for study of vegetation carbon dynamics at a number of FLUX sites. This study presents results from the analysis of EO-1 Hyperion and FLUX seasonal composites for a range of ecosystems across the globe. Spectral differences and seasonal trends were evaluated for each vegetation type and specific phenology. Evaluating the relationships between CO2 flux parameters (e.g., Net ecosystem production - NEP; Gross Ecosystem Exchange - GEE, CO2 flux, μmol m-2 s-1) and spectral parameters for these very different ecosystems, high correlations were established to parameters associated with canopy water and chlorophyll content for deciduous, and photosynthetic function for conifers. Imaging spectrometry provided high spatial resolution maps of CO2 fluxes absorbed by vegetation, and was efficient in tracing seasonal flux dynamics. This study will present examples for key ecosystem tipes to demonstrate the ability of imaging spectrometry and EO-1 Hyperion to map and compare CO2 flux dynamics across the globe.

  6. Evidence for carbon flux shortage and strong carbon/nitrogen interactions in pea nodules at early stages of water stress.

    Science.gov (United States)

    Gálvez, Loli; González, Esther M; Arrese-Igor, Cesar

    2005-09-01

    Symbiotic N2 fixation in legume nodules declines under a wide range of environmental stresses. A high correlation between N2 fixation decline and sucrose synthase (SS; EC 2.4.1.13) activity down-regulation has been reported, although it has still to be elucidated whether a causal relationship between SS activity down-regulation and N2 fixation decline can be established. In order to study the likely C/N interactions within nodules and the effects on N2 fixation, pea plants (Pisum sativum L. cv. Sugar snap) were subjected to progressive water stress by withholding irrigation. Under these conditions, nodule SS activity declined concomitantly with apparent nitrogenase activity. The levels of UDP-glucose, glucose-1-phosphate, glucose-6-phosphate, and fructose-6-phosphate decreased in water-stressed nodules compared with unstressed nodules. Drought also had a marked effect on nodule concentrations of malate, succinate, and alpha-ketoglutarate. Moreover, a general decline in nodule adenylate content was detected. NADP+-dependent isocitrate dehydrogenase (ICDH; EC 1.1.1.42) was the only enzyme whose activity increased as a result of water deficit, compensating for a possible C/N imbalance and/or supplying NADPH in circumstances that the pentose phosphate pathway was impaired, as suggested by the decline in glucose-6-phosphate dehydrogenase (G6PDH; EC 1.1.1.49) activity. The overall results show the occurrence of strong C/N interactions in nodules subjected to water stress and support a likely limitation of carbon flux that might be involved in the decline of N2 fixation under drought.

  7. Lateral transport of soil carbon and land−atmosphere CO2 flux induced by water erosion in China

    Science.gov (United States)

    Yue, Yao; Ni, Jinren; Ciais, Philippe; Piao, Shilong; Wang, Tao; Huang, Mengtian; Borthwick, Alistair G. L.; Li, Tianhong; Wang, Yichu; Chappell, Adrian; Van Oost, Kristof

    2016-01-01

    Soil erosion by water impacts soil organic carbon stocks and alters CO2 fluxes exchanged with the atmosphere. The role of erosion as a net sink or source of atmospheric CO2 remains highly debated, and little information is available at scales larger than small catchments or regions. This study attempts to quantify the lateral transport of soil carbon and consequent land−atmosphere CO2 fluxes at the scale of China, where severe erosion has occurred for several decades. Based on the distribution of soil erosion rates derived from detailed national surveys and soil carbon inventories, here we show that water erosion in China displaced 180 ± 80 Mt C⋅y−1 of soil organic carbon during the last two decades, and this resulted a net land sink for atmospheric CO2 of 45 ± 25 Mt C⋅y−1, equivalent to 8–37% of the terrestrial carbon sink previously assessed in China. Interestingly, the “hotspots,” largely distributed in mountainous regions in the most intensive sink areas (>40 g C⋅m−2⋅y−1), occupy only 1.5% of the total area suffering water erosion, but contribute 19.3% to the national erosion-induced CO2 sink. The erosion-induced CO2 sink underwent a remarkable reduction of about 16% from the middle 1990s to the early 2010s, due to diminishing erosion after the implementation of large-scale soil conservation programs. These findings demonstrate the necessity of including erosion-induced CO2 in the terrestrial budget, hence reducing the level of uncertainty. PMID:27247397

  8. Lateral transport of soil carbon and land-atmosphere CO2 flux induced by water erosion in China.

    Science.gov (United States)

    Yue, Yao; Ni, Jinren; Ciais, Philippe; Piao, Shilong; Wang, Tao; Huang, Mengtian; Borthwick, Alistair G L; Li, Tianhong; Wang, Yichu; Chappell, Adrian; Van Oost, Kristof

    2016-06-14

    Soil erosion by water impacts soil organic carbon stocks and alters CO2 fluxes exchanged with the atmosphere. The role of erosion as a net sink or source of atmospheric CO2 remains highly debated, and little information is available at scales larger than small catchments or regions. This study attempts to quantify the lateral transport of soil carbon and consequent land-atmosphere CO2 fluxes at the scale of China, where severe erosion has occurred for several decades. Based on the distribution of soil erosion rates derived from detailed national surveys and soil carbon inventories, here we show that water erosion in China displaced 180 ± 80 Mt C⋅y(-1) of soil organic carbon during the last two decades, and this resulted a net land sink for atmospheric CO2 of 45 ± 25 Mt C⋅y(-1), equivalent to 8-37% of the terrestrial carbon sink previously assessed in China. Interestingly, the "hotspots," largely distributed in mountainous regions in the most intensive sink areas (>40 g C⋅m(-2)⋅y(-1)), occupy only 1.5% of the total area suffering water erosion, but contribute 19.3% to the national erosion-induced CO2 sink. The erosion-induced CO2 sink underwent a remarkable reduction of about 16% from the middle 1990s to the early 2010s, due to diminishing erosion after the implementation of large-scale soil conservation programs. These findings demonstrate the necessity of including erosion-induced CO2 in the terrestrial budget, hence reducing the level of uncertainty.

  9. Evaluation and uncertainty analysis of regional-scale CLM4.5 net carbon flux estimates

    Science.gov (United States)

    Post, Hanna; Hendricks Franssen, Harrie-Jan; Han, Xujun; Baatz, Roland; Montzka, Carsten; Schmidt, Marius; Vereecken, Harry

    2018-01-01

    Modeling net ecosystem exchange (NEE) at the regional scale with land surface models (LSMs) is relevant for the estimation of regional carbon balances, but studies on it are very limited. Furthermore, it is essential to better understand and quantify the uncertainty of LSMs in order to improve them. An important key variable in this respect is the prognostic leaf area index (LAI), which is very sensitive to forcing data and strongly affects the modeled NEE. We applied the Community Land Model (CLM4.5-BGC) to the Rur catchment in western Germany and compared estimated and default ecological key parameters for modeling carbon fluxes and LAI. The parameter estimates were previously estimated with the Markov chain Monte Carlo (MCMC) approach DREAM(zs) for four of the most widespread plant functional types in the catchment. It was found that the catchment-scale annual NEE was strongly positive with default parameter values but negative (and closer to observations) with the estimated values. Thus, the estimation of CLM parameters with local NEE observations can be highly relevant when determining regional carbon balances. To obtain a more comprehensive picture of model uncertainty, CLM ensembles were set up with perturbed meteorological input and uncertain initial states in addition to uncertain parameters. C3 grass and C3 crops were particularly sensitive to the perturbed meteorological input, which resulted in a strong increase in the standard deviation of the annual NEE sum (σ ∑ NEE) for the different ensemble members from ˜ 2 to 3 g C m-2 yr-1 (with uncertain parameters) to ˜ 45 g C m-2 yr-1 (C3 grass) and ˜ 75 g C m-2 yr-1 (C3 crops) with perturbed forcings. This increase in uncertainty is related to the impact of the meteorological forcings on leaf onset and senescence, and enhanced/reduced drought stress related to perturbation of precipitation. The NEE uncertainty for the forest plant functional type (PFT) was considerably lower (σ ∑ NEE ˜ 4.0-13.5 g C

  10. Implications of elevated CO2 on pelagic carbon fluxes in an Arctic mesocosm study – an elemental mass balance approach

    Directory of Open Access Journals (Sweden)

    J. Czerny

    2013-05-01

    Full Text Available Recent studies on the impacts of ocean acidification on pelagic communities have identified changes in carbon to nutrient dynamics with related shifts in elemental stoichiometry. In principle, mesocosm experiments provide the opportunity of determining temporal dynamics of all relevant carbon and nutrient pools and, thus, calculating elemental budgets. In practice, attempts to budget mesocosm enclosures are often hampered by uncertainties in some of the measured pools and fluxes, in particular due to uncertainties in constraining air–sea gas exchange, particle sinking, and wall growth. In an Arctic mesocosm study on ocean acidification applying KOSMOS (Kiel Off-Shore Mesocosms for future Ocean Simulation, all relevant element pools and fluxes of carbon, nitrogen and phosphorus were measured, using an improved experimental design intended to narrow down the mentioned uncertainties. Water-column concentrations of particulate and dissolved organic and inorganic matter were determined daily. New approaches for quantitative estimates of material sinking to the bottom of the mesocosms and gas exchange in 48 h temporal resolution as well as estimates of wall growth were developed to close the gaps in element budgets. However, losses elements from the budgets into a sum of insufficiently determined pools were detected, and are principally unavoidable in mesocosm investigation. The comparison of variability patterns of all single measured datasets revealed analytic precision to be the main issue in determination of budgets. Uncertainties in dissolved organic carbon (DOC, nitrogen (DON and particulate organic phosphorus (POP were much higher than the summed error in determination of the same elements in all other pools. With estimates provided for all other major elemental pools, mass balance calculations could be used to infer the temporal development of DOC, DON and POP pools. Future elevated pCO2 was found to enhance net autotrophic community carbon

  11. Anthropogenic Heat Flux Estimation from Space: Results of the second phase of the URBANFLUXES Project

    Science.gov (United States)

    Chrysoulakis, Nektarios; Marconcini, Mattia; Gastellu-Etchegorry, Jean-Philippe; Grimmond, Sue; Feigenwinter, Christian; Lindberg, Fredrik; Del Frate, Fabio; Klostermann, Judith; Mitraka, Zina; Esch, Thomas; Landier, Lucas; Gabey, Andy; Parlow, Eberhard; Olofson, Frans

    2017-04-01

    The H2020-Space project URBANFLUXES (URBan ANthrpogenic heat FLUX from Earth observation Satellites) investigates the potential of Copernicus Sentinels to retrieve anthropogenic heat flux, as a key component of the Urban Energy Budget (UEB). URBANFLUXES advances the current knowledge of the impacts of UEB fluxes on urban heat island and consequently on energy consumption in cities. In URBANFLUXES, the anthropogenic heat flux is estimated as a residual of UEB. Therefore, the rest UEB components, namely, the net all-wave radiation, the net change in heat storage and the turbulent sensible and latent heat fluxes are independently estimated from Earth Observation (EO), whereas the advection term is included in the error of the anthropogenic heat flux estimation from the UEB closure. The Discrete Anisotropic Radiative Transfer (DART) model is employed to improve the estimation of the net all-wave radiation balance, whereas the Element Surface Temperature Method (ESTM), adjusted to satellite observations is used to improve the estimation the estimation of the net change in heat storage. Furthermore the estimation of the turbulent sensible and latent heat fluxes is based on the Aerodynamic Resistance Method (ARM). Based on these outcomes, QF is estimated by regressing the sum of the turbulent heat fluxes versus the available energy. In-situ flux measurements are used to evaluate URBANFLUXES outcomes, whereas uncertainties are specified and analyzed. URBANFLUXES is expected to prepare the ground for further innovative exploitation of EO in scientific activities (climate variability studies at local and regional scales) and future and emerging applications (sustainable urban planning, mitigation technologies) to benefit climate change mitigation/adaptation. This study presents the results of the second phase of the project and detailed information on URBANFLUXES is available at: http://urbanfluxes.eu

  12. Seasonal effects of irrigation on land-atmosphere latent heat, sensible heat, and carbon fluxes in semiarid basin

    Science.gov (United States)

    Zeng, Yujin; Xie, Zhenghui; Liu, Shuang

    2017-02-01

    Irrigation, which constitutes ˜ 70 % of the total amount of freshwater consumed by the human population, is significantly impacting land-atmosphere fluxes. In this study, using the improved Community Land Model version 4.5 (CLM4.5) with an active crop model, two high-resolution (˜ 1 km) simulations investigating the effects of irrigation on latent heat (LH), sensible heat (SH), and carbon fluxes (or net ecosystem exchange, NEE) from land to atmosphere in the Heihe River basin in northwestern China were conducted using a high-quality irrigation dataset compiled from 1981 to 2013. The model output and measurements from remote sensing demonstrated the capacity of the developed models to reproduce ecological and hydrological processes. The results revealed that the effects of irrigation on LH and SH are strongest during summer, with a LH increase of ˜ 100 W m-2 and a SH decrease of ˜ 60 W m-2 over intensely irrigated areas. However, the reactions are much weaker during spring and autumn when there is much less irrigation. When the irrigation rate is below 5 mm day-1, the LH generally increases, whereas the SH decreases with growing irrigation rates. However, when the irrigation threshold is in excess of 5 mm day-1, there is no accrued effect of irrigation on the LH and SH. Irrigation produces opposite effects to the NEE during spring and summer. During the spring, irrigation yields more discharged carbon from the land to the atmosphere, increasing the NEE value by 0.4-0.8 gC m-2 day-1, while the summer irrigation favors crop fixing of carbon from atmospheric CO2, decreasing the NEE value by ˜ 0.8 gC m-2 day-1. The repercussions of irrigation on land-atmosphere fluxes are not solely linked to the irrigation amount, and other parameters (especially the temperature) also control the effects of irrigation on LH, SH, and NEE.

  13. Diffusive component of the vertical flux of particulate organic carbon in the north polar Atlantic

    Directory of Open Access Journals (Sweden)

    Małgorzata Stramska

    2006-12-01

    Full Text Available The diffusive component of the vertical flux of particulate organiccarbon (POC from the surface ocean layer has been estimatedusing a combination of the mixed layer model and ocean colordata from the SeaWiFS satellite. The calculations were carriedout for an example location in the north polar Atlantic centeredat 75°N and 0°E for the time period of 1998-2004.The satellite estimates of surface POC derived using a regional ocean coloralgorithm were applied as an input to the model driven by localsurface heat and momentum fluxes. For each year of the examinedperiod, the diffusive POC flux was estimated at 200-m depth fromApril through December. The highest flux is generally observedin the late fall as a result of increased heat loss and convectionalmixing of surface waters. A relatively high diffusive POC fluxis also observed in early spring, when surface waters are weaklystratified. In addition, the model results demonstrate significantinterannual variability. The highest diffusive POC flux occurredin 1999 (about 4500 mg m-2 over the 9-month period. In 1998 and 2002 the estimated flux was about two orders of magnitudelower. The interannual variability of the diffusive POC fluxis associated with mixed layer dynamics and underscores the importanceof atmospheric forcing for POC export from the surface layerto the ocean's interior.

  14. 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.

  15. Multi-model analysis of terrestrial carbon cycles in Japan: reducing uncertainties in model outputs among different terrestrial biosphere models using flux observations

    Science.gov (United States)

    Ichii, K.; Suzuki, T.; Kato, T.; Ito, A.; Hajima, T.; Ueyama, M.; Sasai, T.; Hirata, R.; Saigusa, N.; Ohtani, Y.; Takagi, K.

    2009-08-01

    Terrestrial biosphere models show large uncertainties when simulating carbon and water cycles, and reducing these uncertainties is a priority for developing more accurate estimates of both terrestrial ecosystem statuses and future climate changes. To reduce uncertainties and improve the understanding of these carbon budgets, we investigated the ability of flux datasets to improve model simulations and reduce variabilities among multi-model outputs of terrestrial biosphere models in Japan. Using 9 terrestrial biosphere models (Support Vector Machine-based regressions, TOPS, CASA, VISIT, Biome-BGC, DAYCENT, SEIB, LPJ, and TRIFFID), we conducted two simulations: (1) point simulations at four flux sites in Japan and (2) spatial simulations for Japan with a default model (based on original settings) and an improved model (based on calibration using flux observations). Generally, models using default model settings showed large deviations in model outputs from observation with large model-by-model variability. However, after we calibrated the model parameters using flux observations (GPP, RE and NEP), most models successfully simulated seasonal variations in the carbon cycle, with less variability among models. We also found that interannual variations in the carbon cycle are mostly consistent among models and observations. Spatial analysis also showed a large reduction in the variability among model outputs, and model calibration using flux observations significantly improved the model outputs. These results show that to reduce uncertainties among terrestrial biosphere models, we need to conduct careful validation and calibration with available flux observations. Flux observation data significantly improved terrestrial biosphere models, not only on a point scale but also on spatial scales.

  16. The Labrador Sea during the Last Glacial Maximum: Calcite dissolution or low biogenic carbonate fluxes?

    Science.gov (United States)

    Marshall, Nicole; de Vernal, Anne; Mucci, Alfonso; Filippova, Alexandra; Kienast, Markus

    2017-04-01

    Low concentrations of biogenic carbonate characterize the sediments deposited in the Labrador Sea during the last glaciation. This may reflect poor calcite preservation and/or low biogenic carbonate productivity and fluxes. Regional bottom water ventilation was reduced during the Last Glacial Maximum (LGM), so the calcite lysocline might have been shallower than at present in the deep Labrador Sea making dissolution of calcite shells in the deep Labrador Sea possible. To address the issue, a multi-proxy approach based on micropaleontological counts (coccoliths, foraminifers, palynomorphs) and biogeochemical analyses (alkenones) was applied in the investigation of core HU2008-029-004-PC recovered in the northwestern Labrador Sea. Calcite dissolution indices based on the relative abundance benthic foraminifera shells to their organic linings as well as on fragmentation of planktonic foraminifera shells were used to evaluate changes in calcite dissolution/ preservation since the LGM. In addition, the ratio of the concentrations of coccoliths, specifically of the alkenone-producer Emiliania huxleyi, and alkenones (Emiliania huxleyi: alkenones) was explored as a potential new proxy of calcite dissolution. A sharp increase in coccoliths, foraminifers and organic linings from nearly none to substantial concentrations at 12 ka, reflect a jump to significantly greater biogenic fluxes at the glacial-interglacial transition. Furthermore, conventional dissolution indices (shells/linings of benthic foraminifera and fragmentation of planktic foraminifers) reveal that dissolution is not likely responsible for the lower glacial abundances of coccoliths and foraminifers. Only the low Emiliania huxleyi: alkenones ratios in glacial sediments could be interpreted as evidence of increased dissolution during the LGM. Given the evidence of allochthonous alkenone input into the glacial Labrador Sea, the latter observations must be treated with caution. Overall, the records indicate that

  17. Changes of soil carbon dioxide, methane, and nitrous oxide fluxes in relation to land use/cover management.

    Science.gov (United States)

    Kooch, Yahya; Moghimian, Negar; Bayranvand, Mohammad; Alberti, Giorgio

    2016-06-01

    Conversions of land use/cover are associated with changes in soil properties and biogeochemical cycling, with implications for carbon (C), nitrogen (N), and trace gas fluxes. In an attempt to provide a comprehensive evaluation of the significance of different land uses (Alnus subcordata plantation, Taxodium distichum plantation, agriculture, and deforested areas) on soil features and on the dynamics of greenhouse gas (GHG) fluxes at local scale, this study was carried out in Mazandaran province, northern Iran. Sixteen samples per land use, from the top 10 cm of soil, were taken, from which bulk density, texture, water content, pH, organic C, total N, microbial biomass of C and N, and earthworm density/biomass were determined. In addition, the seasonal changes in the fluxes of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) were monitored over a year. Our results indicated that the different land uses were different in terms of soil properties and GHG fluxes. Even though the amount of the GHG varied widely during the year, the highest CO2 and CH4 fluxes (0.32 mg CO2 m(-2) day(-1) and 0.11 mg CH4 m(-2) day(-1), respectively) were recorded in the deforested areas. N2O flux was higher in Alnus plantation (0.18 mg N2O m(-2) day(-1)) and deforested areas (0.17 mg N2O m(-2) day(-1)) than at agriculture site (0.05 mg N2O m(-2) day(-1)) and Taxodium plantation (0.03 mg N2O m(-2) day(-1)). This study demonstrated strong impacts of land use change on soil-atmosphere trace gas exchanges and provides useful observational constraints for top-down and bottom-up biogeochemistry models.

  18. Using a spatially-distributed hydrologic biogeochemistry model with nitrogen transport to study the spatial variation of carbon stocks and fluxes in a Critical Zone Observatory

    Science.gov (United States)

    Shi, Y.; Eissenstat, D. M.; He, Y.; Davis, K. J.

    2017-12-01

    Most current biogeochemical models are 1-D and represent one point in space. Therefore, they cannot resolve topographically driven land surface heterogeneity (e.g., lateral water flow, soil moisture, soil temperature, solar radiation) or the spatial pattern of nutrient availability. A spatially distributed forest biogeochemical model with nitrogen transport, Flux-PIHM-BGC, has been developed by coupling a 1-D mechanistic biogeochemical model Biome-BGC (BBGC) with a spatially distributed land surface hydrologic model, Flux-PIHM, and adding an advection dominated nitrogen transport module. Flux-PIHM is a coupled physically based model, which incorporates a land-surface scheme into the Penn State Integrated Hydrologic Model (PIHM). The land surface scheme is adapted from the Noah land surface model, and is augmented by adding a topographic solar radiation module. Flux-PIHM is able to represent the link between groundwater and the surface energy balance, as well as land surface heterogeneities caused by topography. In the coupled Flux-PIHM-BGC model, each Flux-PIHM model grid couples a 1-D BBGC model, while nitrogen is transported among model grids via surface and subsurface water flow. In each grid, Flux-PIHM provides BBGC with soil moisture, soil temperature, and solar radiation, while BBGC provides Flux-PIHM with spatially-distributed leaf area index. The coupled Flux-PIHM-BGC model has been implemented at the Susquehanna/Shale Hills Critical Zone Observatory. The model-predicted aboveground vegetation carbon and soil carbon distributions generally agree with the macro patterns observed within the watershed. The importance of abiotic variables (including soil moisture, soil temperature, solar radiation, and soil mineral nitrogen) in predicting aboveground carbon distribution is calculated using a random forest. The result suggests that the spatial pattern of aboveground carbon is controlled by the distribution of soil mineral nitrogen. A Flux-PIHM-BGC simulation

  19. 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

  20. Carbon-flux distribution within Streptomyces coelicolor metabolism: a comparison between the actinorhodin-producing strain M145 and its non-producing derivative M1146.

    Directory of Open Access Journals (Sweden)

    Fabien Coze

    Full Text Available Metabolic Flux Analysis is now viewed as essential to elucidate the metabolic pattern of cells and to design appropriate genetic engineering strategies to improve strain performance and production processes. Here, we investigated carbon flux distribution in two Streptomyces coelicolor A3 (2 strains: the wild type M145 and its derivative mutant M1146, in which gene clusters encoding the four main antibiotic biosynthetic pathways were deleted. Metabolic Flux Analysis and (13C-labeling allowed us to reconstruct a flux map under steady-state conditions for both strains. The mutant strain M1146 showed a higher growth rate, a higher flux through the pentose phosphate pathway and a higher flux through the anaplerotic phosphoenolpyruvate carboxylase. In that strain, glucose uptake and the flux through the Krebs cycle were lower than in M145. The enhanced flux through the pentose phosphate pathway in M1146 is thought to generate NADPH enough to face higher needs for biomass biosynthesis and other processes. In both strains, the production of NADPH was higher than NADPH needs, suggesting a key role for nicotinamide nucleotide transhydrogenase for redox homeostasis. ATP production is also likely to exceed metabolic ATP needs, indicating that ATP consumption for maintenance is substantial.Our results further suggest a possible competition between actinorhodin and triacylglycerol biosynthetic pathways for their common precursor, acetyl-CoA. These findings may be instrumental in developing new strategies exploiting S. coelicolor as a platform for the production of bio-based products of industrial interest.

  1. Sensitivity of water and carbon fluxes to climate changes from 1960 to 2100 in European forest ecosystems

    NARCIS (Netherlands)

    Davi, H.; Dufrêne, E.; Francois, C.; Maire, Le G.; Loustau, D.; Bosc, A.; Rambal, S.; Granier, A.; Moors, E.J.

    2006-01-01

    The effects of climate changes on carbon and water fluxes are quantified using a physiologically multi-layer, process-based model containing a carbon allocation model and coupled with a soil model (CASTANEA). The model is first evaluated on four EUROFLUX sites using eddy covariance data, which

  2. Fluxes of dissolved organic carbon and nitrogen to the northern Indian Ocean from the Indian monsoonal rivers

    Digital Repository Service at National Institute of Oceanography (India)

    Krishna, M.S.; Prasad, V.R.; Sarma, V.V.S.S.; Reddy, N.P.C.; Hemalatha, K.P.J.; Rao, Y.V.

    normalized fluxes of DOC and DON were found to be higher in the estuaries located in the southwestern than the estuaries from other regions of India. It was attributed to relatively higher soil organic carbon, biomass carbon, and heavy rainfall in catchment...

  3. Topographically Driven Lateral Water Fluxes and Their Influence on Carbon Assimilation of a Black Spruce Ecosystem.

    Science.gov (United States)

    Govind, A.; Chen, J. M.; Margolis, H.; Bernier, P. Y.

    2006-12-01

    Current estimates of ecophysiological indicators overlook the effects of topographically-driven lateral flow of soil water. We hypothesize that topographically driven lateral water flows over the landscape have significant influence on the terrestrial carbon cycle. To this end, we simulated the hydrological controls on carbon cycle processes in a black spruce forest in central Quebec, Canada, using the Boreal Ecosystem Productivity Simulator (BEPS) at a daily time step. We accounted for lateral surface and subsurface flows in BEPS by incorporating a distributed, process-oriented hydrological procedure. The results show that modeled dynamics of ecophysiological processes such as evapotranspiration (ET) and photosynthesis (GPP) are consistent with the spatial variation of land cover, topography, soil texture, and leaf area index. Simulated ET and GPP averaged within the footprint of an eddy covariance tower in the watershed agree well with flux measurements with R2=0.77 and 0.83 for ET and GPP, respectively. For ET simulation, much of the remaining discrepancies are found in the winter when the model underestimates snow sublimation. For GPP, there is an underestimation in the fall coinciding with a mid growing season drought, showing the high sensitivity of the model to the soil water status. The key processes controlling primary production were hydraulic limitations for water transfer from soil, roots, stems and leaves through stomatal conductance. Therefore, a further understanding of soil water dynamics is warranted. Comparison with the soil water content of the footprint- averaged unsaturated zone showed that the model captured the annual trend. We also simulated the variations in the water table as well as the mid growing season drought, with a reasonable accuracy(R2=0.68). The foot print average water budget reveals that the annual precipitation of 835mm is partitioned into 282mm of ET, 541 mm of subsurface runoff, and 6 mm of storage change. To test the

  4. A Mechanistically Informed User-Friendly Model to Predict Greenhouse Gas (GHG) Fluxes and Carbon Storage from Coastal Wetlands

    Science.gov (United States)

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

    2015-12-01

    We present a user-friendly modeling tool on MS Excel to predict the greenhouse gas (GHG) fluxes and estimate potential carbon sequestration from the coastal wetlands. The dominant controls of wetland GHG fluxes and their relative mechanistic linkages with various hydro-climatic, sea level, biogeochemical and ecological drivers were first determined by employing a systematic data-analytics method, including Pearson correlation matrix, principal component and factor analyses, and exploratory partial least squares regressions. The mechanistic knowledge and understanding was then utilized to develop parsimonious non-linear (power-law) models to predict wetland carbon dioxide (CO2) and methane (CH4) fluxes based on a sub-set of climatic, hydrologic and environmental drivers such as the photosynthetically active radiation, soil temperature, water depth, and soil salinity. The models were tested with field data for multiple sites and seasons (2012-13) collected from the Waquoit Bay, MA. The model estimated the annual wetland carbon storage by up-scaling the instantaneous predicted fluxes to an extended growing season (e.g., May-October) and by accounting for the net annual lateral carbon fluxes between the wetlands and estuary. The Excel Spreadsheet model is a simple ecological engineering tool for coastal carbon management and their incorporation into a potential carbon market under a changing climate, sea level and environment. Specifically, the model can help to determine appropriate GHG offset protocols and monitoring plans for projects that focus on tidal wetland restoration and maintenance.

  5. 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)

    Zhiliang Zhu; Brian Bergamaschi; Richard Bernknopf; David Clow; Dennis Dye; Stephen Faulkner; William Forney; Robert Gleason; Todd Hawbaker; Jinxun Liu; Shuguang Liu; Stephen Prisley; Bradley Reed; Matthew Reeves; Matthew Rollins; Benjamin Sleeter; Terry Sohl; Sarah Stackpoole; Stephen Stehman; Robert Striegl; Anne Wein

    2010-01-01

    This methodology was developed to fulfill a requirement by the Energy Independence and Security Act of 2007 (EISA). The EISA legislation mandates the U.S. Department of the Interior (DOI) to develop a methodology and conduct an assessment of carbon storage, carbon sequestration, and fluxes of three principal greenhouse gases (GHG) for the Nation's ecosystems. The...

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

    Science.gov (United States)

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

    2017-12-01

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

  7. Interannual Variability of Carbon Dioxide, Methane and Nitrous Oxide Fluxes in Subarctic European Russian Tundra

    Science.gov (United States)

    Marushchak, M. E.; Voigt, C.; Gil, J.; Lamprecht, R. E.; Trubnikova, T.; Virtanen, T.; Kaverin, D.; Martikainen, P. J.; Biasi, C.

    2017-12-01

    Southern tundra landscapes are particularly vulnerable to climate warming, permafrost thaw and associated landscape rearrangement due to near-zero permafrost temperatures. The large soil C and N stocks of subarctic tundra may create a positive feedback for warming if released to the atmosphere at increased rates. Subarctic tundra in European Russia is a mosaic of land cover types, which all play different roles in the regional greenhouse gas budget. Peat plateaus - massive upheaved permafrost peatlands - are large storehouses of soil carbon and nitrogen, but include also bare peat surfaces that act as hot-spots for both carbon dioxide and nitrous oxide emissions. Tundra wetlands are important for the regional greenhouse gas balance since they show high rates of methane emissions and carbon uptake. The most dominant land-form is upland tundra vegetated by shrubs, lichens and mosses, which displays a close-to-neutral balance with respect to all three greenhouse gases. The study site Seida (67°03'N, 62°56'E), located in the discontinuous permafrost zone of Northeast European Russia, incorporates all these land forms and has been an object for greenhouse gas investigations since 2007. Here, we summarize the growing season fluxes of carbon dioxide, methane and nitrous oxide measured by chamber techniques over the study years. We analyzed the flux time-series together with the local environmental data in order to understand the drivers of interannual variability. Detailed soil profile measurements of greenhouse gas concentrations, soil moisture and temperature provide insights into soil processes underlying the net emissions to the atmosphere. The multiannual time-series allows us to assess the importance of the different greenhouse gases and landforms to the overall climate forcing of the study region.

  8. Effects of experimental nitrogen deposition on peatland carbon pools and fluxes: a modeling analysis

    Science.gov (United States)

    Wu, Y.; Blodau, C.; Moore, T. R.; Bubier, J. L.; Juutinen, S.; Larmola, T.

    2014-07-01

    Nitrogen (N) pollution of peatlands alters their carbon (C) balances, yet long-term effects and controls are poorly understood. We applied the model PEATBOG to analyze impacts of long-term nitrogen (N) fertilization on C cycling in an ombrotrophic bog. Simulations of summer gross ecosystem production (GEP), ecosystem respiration (ER) and net ecosystem exchange (NEE) were evaluated against 8 years of observations and extrapolated for 80 years to identify potential effects of N fertilization and factors influencing model behavior. The model successfully simulated moss decline and raised GEP, ER and NEE on fertilized plots. GEP was systematically overestimated in the model compared to the field data due to high tolerance of Sphagnum to N deposition in the model. Model performance regarding the 8 year response of GEP and NEE to N was improved by introducing an N content threshold shifting the response of photosynthesis capacity to N content in shrubs and graminoids from positive to negative at high N contents. Such changes also eliminated the competitive advantages of vascular species and led to resilience of mosses in the long-term. Regardless of the large changes of C fluxes over the short-term, the simulated GEP, ER and NEE after 80 years depended on whether a graminoid- or shrub-dominated system evolved. When the peatland remained shrub-Sphagnum dominated, it shifted to a C source after only 10 years of fertilization at 6.4 g N m-2 yr-1, whereas this was not the case when it became graminoid-dominated. The modeling results thus highlight the importance of ecosystem adaptation and reaction of plant functional types to N deposition, when predicting the future C balance of N-polluted cool temperate bogs.

  9. Effects of experimental nitrogen deposition on peatland carbon pools and fluxes: a modelling analysis

    Science.gov (United States)

    Wu, Y.; Blodau, C.; Moore, T. R.; Bubier, J.; Juutinen, S.; Larmola, T.

    2015-01-01

    Nitrogen (N) pollution of peatlands alters their carbon (C) balances, yet long-term effects and controls are poorly understood. We applied the model PEATBOG to explore impacts of long-term nitrogen (N) fertilization on C cycling in an ombrotrophic bog. Simulations of summer gross ecosystem production (GEP), ecosystem respiration (ER) and net ecosystem exchange (NEE) were evaluated against 8 years of observations and extrapolated for 80 years to identify potential effects of N fertilization and factors influencing model behaviour. The model successfully simulated moss decline and raised GEP, ER and NEE on fertilized plots. GEP was systematically overestimated in the model compared to the field data due to factors that can be related to differences in vegetation distribution (e.g. shrubs vs. graminoid vegetation) and to high tolerance of vascular plants to N deposition in the model. Model performance regarding the 8-year response of GEP and NEE to N input was improved by introducing an N content threshold shifting the response of photosynthetic capacity (GEPmax) to N content in shrubs and graminoids from positive to negative at high N contents. Such changes also eliminated the competitive advantages of vascular species and led to resilience of mosses in the long-term. Regardless of the large changes of C fluxes over the short-term, the simulated GEP, ER and NEE after 80 years depended on whether a graminoid- or shrub-dominated system evolved. When the peatland remained shrub-Sphagnum-dominated, it shifted to a C source after only 10 years of fertilization at 6.4 g N m-2 yr-1, whereas this was not the case when it became graminoid-dominated. The modelling results thus highlight the importance of ecosystem adaptation and reaction of plant functional types to N deposition, when predicting the future C balance of N-polluted cool temperate bogs.

  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. Carbon and water fluxes from ponderosa pine forests disturbed by wildfire and thinning.

    Science.gov (United States)

    Dore, S; Kolb, T E; Montes-Helu, M; Eckert, S E; Sullivan, B W; Hungate, B A; Kaye, J P; Hart, S C; Koch, G W; Finkral, A

    2010-04-01

    Disturbances alter ecosystem carbon dynamics, often by reducing carbon uptake and stocks. We compared the impact of two types of disturbances that represent the most likely future conditions of currently dense ponderosa pine forests of the southwestern United States: (1) high-intensity fire and (2) thinning, designed to reduce fire intensity. High-severity fire had a larger impact on ecosystem carbon uptake and storage than thinning. Total ecosystem carbon was 42% lower at the intensely burned site, 10 years after burning, than at the undisturbed site. Eddy covariance measurements over two years showed that the burned site was a net annual source of carbon to the atmosphere whereas the undisturbed site was a sink. Net primary production (NPP), evapotranspiration (ET), and water use efficiency were lower at the burned site than at the undisturbed site. In contrast, thinning decreased total ecosystem carbon by 18%, and changed the site from a carbon sink to a source in the first posttreatment year. Thinning also decreased ET, reduced the limitation of drought on carbon uptake during summer, and did not change water use efficiency. Both disturbances reduced ecosystem carbon uptake by decreasing gross primary production (55% by burning, 30% by thinning) more than total ecosystem respiration (TER; 33-47% by burning, 18% by thinning), and increased the contribution of soil carbon dioxide efflux to TER. The relationship between TER and temperature was not affected by either disturbance. Efforts to accurately estimate regional carbon budgets should consider impacts on carbon dynamics of both large disturbances, such as high-intensity fire, and the partial disturbance of thinning that is often used to prevent intense burning. Our results show that thinned forests of ponderosa pine in the southwestern United States are a desirable alternative to intensively burned forests to maintain carbon stocks and primary production.

  12. 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.

  13. The importance of forest structure for carbon fluxes of the Amazon rainforest

    Science.gov (United States)

    Rödig, Edna; Cuntz, Matthias; Rammig, Anja; Fischer, Rico; Taubert, Franziska; Huth, Andreas

    2018-05-01

    Precise descriptions of forest productivity, biomass, and structure are essential for understanding ecosystem responses to climatic and anthropogenic changes. However, relations between these components are complex, in particular for tropical forests. We developed an approach to simulate carbon dynamics in the Amazon rainforest including around 410 billion individual trees within 7.8 million km2. We integrated canopy height observations from space-borne LIDAR in order to quantify spatial variations in forest state and structure reflecting small-scale to large-scale natural and anthropogenic disturbances. Under current conditions, we identified the Amazon rainforest as a carbon sink, gaining 0.56 GtC per year. This carbon sink is driven by an estimated mean gross primary productivity (GPP) of 25.1 tC ha‑1 a‑1, and a mean woody aboveground net primary productivity (wANPP) of 4.2 tC ha‑1 a‑1. We found that successional states play an important role for the relations between productivity and biomass. Forests in early to intermediate successional states are the most productive, and woody above-ground carbon use efficiencies are non-linear. Simulated values can be compared to observed carbon fluxes at various spatial resolutions (>40 m). Notably, we found that our GPP corresponds to the values derived from MODIS. For NPP, spatial differences can be observed due to the consideration of forest successional states in our approach. We conclude that forest structure has a substantial impact on productivity and biomass. It is an essential factor that should be taken into account when estimating current carbon budgets or analyzing climate change scenarios for the Amazon rainforest.

  14. Modelling biogeochemical processes in sediments from the north-western Adriatic Sea: response to enhanced particulate organic carbon fluxes

    Directory of Open Access Journals (Sweden)

    D. Brigolin

    2018-03-01

    Full Text Available This work presents the result of a study carried out in the north-western Adriatic Sea, by combining two different types of biogeochemical models with field sampling efforts. A longline mussel farm was taken as a local source of perturbation to the natural particulate organic carbon (POC downward flux. This flux was first quantified by means of a pelagic model of POC deposition coupled to sediment trap data, and its effects on sediment bioirrigation capacity and organic matter (OM degradation pathways were investigated constraining an early diagenesis model by using original data collected in sediment porewater. The measurements were performed at stations located inside and outside the area affected by mussel farm deposition. Model-predicted POC fluxes showed marked spatial and temporal variability, which was mostly associated with the dynamics of the farming cycle. Sediment trap data at the two sampled stations (inside and outside of the mussel farm showed average POC background flux of 20.0–24.2 mmol C m−2 d−1. The difference of organic carbon (OC fluxes between the two stations was in agreement with model results, ranging between 3.3 and 14.2 mmol C m−2 d−1, and was primarily associated with mussel physiological conditions. Although restricted, these changes in POC fluxes induced visible effects on sediment biogeochemistry. Observed oxygen microprofiles presented a 50 % decrease in oxygen penetration depth (from 2.3 to 1.4 mm, accompanied by an increase in the O2 influx at the station below the mussel farm (19–31 versus 10–12 mmol O2 m−2 d−1 characterised by higher POC flux. Dissolved inorganic carbon (DIC and NH4+ concentrations showed similar behaviour, with a more evident effect of bioirrigation underneath the farm. This was confirmed through constraining the early diagenesis model, of which calibration leads to an estimation of enhanced and shallower bioirrigation underneath the farm

  15. [Effect of seasonal high temperature and drought on carbon flux of bamboo forest ecosystem in subtropical region].

    Science.gov (United States)

    Chen, Xiao-feng; Jiang, Hong; Niu, Xiao-dong; Zhang, Jin-meng; Liu, Yu-li; Fang, Cheng-yuan

    2016-02-01

    The carbon flux of subtropical bamboo forest ecosystem was continuously measured using eddy covariance technique in Anji County of Zhejiang Province, China. The monthly net ecosystem productivity (NEP), ecosystem respiration (Re) and gross ecosystem productivity (GEP) data from 2011 to 2013 were selected to analyze the impacts of seasonal high temperature and drought on the carbon flux of bamboo forest ecosystem. The results showed that there were big differences among annual NEP of bamboo forest from 2011 to 2013. Because of the asynchronization of precipitation and heat, the seasonal high temperature and drought in July and August of 2013 caused significant decline in NEP by 59.9% and 80.0% when compared with the same months in 2011. Correlation analysis of the NEP, Re, GEP and environmental factors suggested that the atmosphere temperatures were significantly correlated with Re and GEP in 2011 and 2013 (P<0.05). However, to air and soil moisture, Re and GEP had different responses, that was, GEP was more vulnerable by the decrease of the soil moisture compared with Re. Besides, the raising of saturation vapour pressure promoted the Re modestly but inhibited the GEP, which was supposed to be the main reason for NEP decrease of bamboo forest ecosystem in Anji, from July to August in 2013.

  16. Discharge power dependence of carbon dust flux in a divertor simulator

    International Nuclear Information System (INIS)

    Nishiyama, Katsushi; Morita, Yasuhiko; Uchida, Giichiro; Yamashita, Daisuke; Kamataki, Kunihiro; Seo, Hyunwoong; Itagaki, Naho; Koga, Kazunori; Shiratani, Masaharu; Ashikawa, Naoko; Masuzaki, Suguru; Nishimura, Kiyohiko; Sagara, Akio; Bornholdt, Sven; Kersten, Holger

    2013-01-01

    In fusion devices, dust particles are generated due to plasma–wall interactions and may cause safety or operational problems. Therefore it is necessary to clarify the generation and transport mechanisms of dust particles. Here we have measured energy influx from H 2 plasmas toward a graphite target using a calorimetric probe and compared the results with the dust flux toward a dust collecting substrate set on the reactor wall. The dust flux decreases with increasing the energy influx. For the higher discharge power, the more number of dust particles tend to redeposit onto the graphite target due to the higher ion drag force and hence the dust flux toward the reactor wall becomes smaller. The results show that dust inventory depends strongly on energy influx to graphite divertor plates in fusion devices

  17. The continuous UV flux of alpha lyrae: NON-LTE results

    International Nuclear Information System (INIS)

    Snijders, M.A.J.

    1977-01-01

    Non--LTE calculations for the ultraviolet C I and Si I continuous opacity show that LTE results overestimate the importance of these sources of opacity and underestimate the emergent flux in α Lyr. The largest errors occur between 1100 and 1160 A where the predicted flux in non--LTE is as much as 50 times larger than in LTE, in reasonable accord with Copernicus observations.The discrepancy between LTE models and observations has been interpreted by Praderie et al. to result from the existence of a chromosphere. Until a self--consistent non-LTE model atmosphere becomes available, such an interpretation is premature

  18. The continuous UV flux of Alpha Lyrae - Non-LTE results

    Science.gov (United States)

    Snijders, M. A. J.

    1977-01-01

    Non-LTE calculations for the ultraviolet C I and Si I continuous opacity show that LTE results overestimate the importance of these sources of opacity and underestimate the emergent flux in Alpha Lyr. The largest errors occur between 1100 and 1160 A, where the predicted flux in non-LTE is as much as 50 times larger than in LTE, in reasonable accord with Copernicus observations. The discrepancy between LTE models and observations has been interpreted to result from the existence of a chromosphere. Until a self-consistent non-LTE model atmosphere becomes available, such an interpretation is premature.

  19. Seasonal variation of carbon fluxes in a sparse savanna in semi arid Sudan.

    Science.gov (United States)

    Ardö, Jonas; Mölder, Meelis; El-Tahir, Bashir Awad; Elkhidir, Hatim Abdalla Mohammed

    2008-12-01

    Large spatial, seasonal and annual variability of major drivers of the carbon cycle (precipitation, temperature, fire regime and nutrient availability) are common in the Sahel region. This causes large variability in net ecosystem exchange and in vegetation productivity, the subsistence basis for a major part of the rural population in Sahel. This study compares the 2005 dry and wet season fluxes of CO2 for a grass land/sparse savanna site in semi arid Sudan and relates these fluxes to water availability and incoming photosynthetic photon flux density (PPFD). Data from this site could complement the current sparse observation network in Africa, a continent where climatic change could significantly impact the future and which constitute a weak link in our understanding of the global carbon cycle. The dry season (represented by Julian day 35-46, February 2005) was characterized by low soil moisture availability, low evapotranspiration and a high vapor pressure deficit. The mean daily NEE (net ecosystem exchange, Eq. 1) was -14.7 mmol d-1 for the 12 day period (negative numbers denote sinks, i.e. flux from the atmosphere to the biosphere). The water use efficiency (WUE) was 1.6 mmol CO2 mol H2O-1 and the light use efficiency (LUE) was 0.95 mmol CO2 mol PPFD-1. Photosynthesis is a weak, but linear function of PPFD. The wet season (represented by Julian day 266-273, September 2005) was, compared to the dry season, characterized by slightly higher soil moisture availability, higher evapotranspiration and a slightly lower vapor pressure deficit. The mean daily NEE was -152 mmol d-1 for the 8 day period. The WUE was lower, 0.97 mmol CO2 mol H2O-1 and the LUE was higher, 7.2 mumol CO2 mmol PPFD-1 during the wet season compared to the dry season. During the wet season photosynthesis increases with PPFD to about 1600 mumol m-2s-1 and then levels off. Based on data collected during two short periods, the studied ecosystem was a sink of carbon both during the dry and wet season

  20. 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.

  1. 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.

  2. Rising Mean Annual Temperature Increases Carbon Flux and Alters Partitioning, but Does Not Change Ecosystem Carbon Storage in Hawaiian Tropical Montane Wet Forest

    Science.gov (United States)

    Litton, C. M.; Giardina, C. P.; Selmants, P.

    2014-12-01

    Terrestrial ecosystem carbon (C) storage exceeds that in the atmosphere by a factor of four, and represents a dynamic balance among C input, allocation, and loss. This balance is likely being altered by climate change, but the response of terrestrial C cycling to warming remains poorly quantified, particularly in tropical forests which play a disproportionately large role in the global C cycle. Over the past five years, we have quantified above- and belowground C pools and fluxes in nine permanent plots spanning a 5.2°C mean annual temperature (MAT) gradient (13-18.2°C) in Hawaiian tropical montane wet forest. This elevation gradient is unique in that substrate type and age, soil type, soil water balance, canopy vegetation, and disturbance history are constant, allowing us to isolate the impact of long-term, whole ecosystem warming on C input, allocation, loss and storage. Across the gradient, soil respiration, litterfall, litter decomposition, total belowground C flux, aboveground net primary productivity, and estimates of gross primary production (GPP) all increase linearly and positively with MAT. Carbon partitioning is dynamic, shifting from below- to aboveground with warming, likely in response to a warming-induced increase in the cycling and availability of soil nutrients. In contrast to observed patterns in C flux, live biomass C, soil C, and total ecosystem C pools remained remarkably constant with MAT. There was also no difference in soil bacterial taxon richness, phylogenetic diversity, or community composition with MAT. Taken together these results indicate that in tropical montane wet forests, increased temperatures in the absence of water limitation or disturbance will accelerate C cycling, will not alter ecosystem C storage, and will shift the products of photosynthesis from below- to aboveground. These results agree with an increasing number of studies, and collectively provide a unique insight into anticipated warming-induced changes in tropical

  3. The carbon fluxes in different successional stages: modelling the dynamics of tropical montane forests in South Ecuador

    Directory of Open Access Journals (Sweden)

    Sebastian Paulick

    2017-05-01

    Full Text Available Background Tropical forests play an important role in the global carbon (C cycle. However, tropical montane forests have been studied less than tropical lowland forests, and their role in carbon storage is not well understood. Montane forests are highly endangered due to logging, land-use and climate change. Our objective was to analyse how the carbon balance changes during forest succession. Methods In this study, we used a method to estimate local carbon balances that combined forest inventory data with process-based forest models. We utilised such a forest model to study the carbon balance of a tropical montane forest in South Ecuador, comparing two topographical slope positions (ravines and lower slopes vs upper slopes and ridges. Results The simulation results showed that the forest acts as a carbon sink with a maximum net ecosystem exchange (NEE of 9.3 Mg C∙(ha∙yr−1 during its early successional stage (0–100 years. In the late successional stage, the simulated NEE fluctuated around zero and had a variation of 0.77 Mg C∙(ha∙yr –1. The simulated variability of the NEE was within the range of the field data. We discovered several forest attributes (e.g., basal area or the relative amount of pioneer trees that can serve as predictors for NEE for young forest stands (0–100 years but not for those in the late successional stage (500–1,000 years. In case of young forest stands these correlations are high, especially between stand basal area and NEE. Conclusion In this study, we used an Ecuadorian study site as an example of how to successfully link a forest model with forest inventory data, for estimating stem-diameter distributions, biomass and aboveground net primary productivity. To conclude, this study shows that process-based forest models can be used to investigate the carbon balance of tropical montane forests. With this model it is possible to find hidden relationships between forest attributes and forest carbon fluxes

  4. Variations of iron flux and organic carbon remineralization in a subterranean estuary caused by interannual variations in recharge

    Science.gov (United States)

    Roy, Moutusi; Martin, Jonathan B.; Cable, Jaye E.; Smith, Christopher G.

    2013-01-01

    We determine the inter-annual variations in diagenetic reaction rates of sedimentary iron (Fe ) in an east Florida subterranean estuary and evaluate the connection between metal fluxes and recharge to the coastal aquifer. Over the three-year study period (from 2004 to 2007), the amount of Fe-oxides reduced at the study site decreased from 192 g/yr to 153 g/yr and associated organic carbon (OC) remineralization decreased from 48 g/yr to 38 g/yr. These reductions occurred although the Fe-oxide reduction rates remained constant around 1 mg/cm2/yr. These results suggest that changes in flow rates of submarine groundwater discharge (SGD) related to changes in precipitation may be important to fluxes of the diagenetic reaction products. Rainfall at a weather station approximately 5 km from the field area decreased from 12.6 cm/month to 8.4 cm/month from 2004 to 2007. Monthly potential evapotranspiration (PET) calculated from Thornthwaite’s method indicated potential evapotranspiration cycled from about 3 cm/month in the winter to about 15 cm/month in the summer so that net annual recharge to the aquifer decreased from 40 cm in 2004 to -10 cm in 2007. Simultaneously, with the decrease in recharge of groundwater, freshwater SGD decreased by around 20% and caused the originally 25 m wide freshwater seepage face to decrease in width by about 5 m. The smaller seepage face reduced the area under which Fe-oxides were undergoing reductive dissolution. Consequently, the observed decrease in Fe flux is controlled by hydrology of the subterranean estuary. These results point out the need to better understand linkages between temporal variations in diagenetic reactions and changes in flow within subterranean estuaries in order to accurately constrain their contribution to oceanic fluxes of solutes from subterranean estuaries.

  5. Variations of iron flux and organic carbon remineralization in a subterranean estuary caused by inter-annual variations in recharge

    Science.gov (United States)

    Roy, Moutusi; Martin, Jonathan B.; Cable, Jaye E.; Smith, Christopher G.

    2013-02-01

    We determine the inter-annual variations in diagenetic reaction rates of sedimentary iron (Fe) in an east Florida subterranean estuary and evaluate the connection between metal fluxes and recharge to the coastal aquifer. Over the three years study period (from 2004 to 2007), the amount of Fe-oxides reduced at the study site decreased from 192 to 153 g/yr and associated organic carbon (OC) remineralization decreased from 48 to 38 g/yr. These reductions occurred although the Fe-oxide reduction rates remained constant around 1 mg/cm2/yr. These results suggest that changes in flow rates of submarine groundwater discharge (SGD) related to changes in precipitation may be important to fluxes of the diagenetic reaction products. Rainfall at a weather station approximately 5 km from the field area decreased from 12.6 to 8.4 cm/month from 2004 to 2007. Monthly potential evapotranspiration (PET) calculated from Thornthwaite's method indicated potential evapotranspiration cycled from about 3 cm/month in the winter to about 15 cm/month in the summer so that net annual recharge to the aquifer decreased from 40 cm in 2004 to -10 cm in 2007. Simultaneously with the decrease in recharge of groundwater, freshwater SGD decreased by around 20% and caused the originally 25 m wide freshwater seepage face to decrease in width by about 5 m. The smaller seepage face reduced the area under which Fe-oxides were undergoing reductive dissolution. Consequently, the observed decrease in Fe flux is controlled by hydrology of the subterranean estuary. These results point out the need to better understand linkages between temporal variations in diagenetic reactions and changes in flow within subterranean estuaries in order to accurately constrain their contribution to oceanic fluxes of solutes from subterranean estuaries.

  6. 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.

  7. Rich soil carbon and nitrogen but low atmospheric greenhouse gas fluxes from North Sulawesi mangrove swamps in Indonesia.

    Science.gov (United States)

    Chen, Guang C; Ulumuddin, Yaya I; Pramudji, Sastro; Chen, Shun Y; Chen, Bin; Ye, Yong; Ou, Dan Y; Ma, Zhi Y; Huang, Hao; Wang, Jing K

    2014-07-15

    The soil to atmosphere fluxes of greenhouse gases N2O, CH4 and CO2 and their relationships with soil characteristics were investigated in three tropical oceanic mangrove swamps (Teremaal, Likupang and Kema) in North Sulawesi, Indonesia. Mangrove soils in North Sulawesi were rich in organic carbon and nitrogen, but the greenhouse gas fluxes were low in these mangroves. The fluxes ranged -6.05-13.14 μmol m(-2)h(-1), -0.35-0.61 μmol m(-2)h(-1) and -1.34-3.88 mmol m(-2)h(-1) for N2O, CH4 and CO2, respectively. The differences in both N2O and CH4 fluxes among different mangrove swamps and among tidal positions in each mangrove swamp were insignificant. CO2 flux was influenced only by mangrove swamps and the value was higher in Kema mangrove. None of the measured soil parameters could explain the variation of CH4 fluxes among the sampling plots. N2O flux was negatively related to porewater salinity, while CO2 flux was negatively correlated with water content and organic carbon. This study suggested that the low gas emissions due to slow metabolisms would lead to the accumulations of organic matters in North Sulawesi mangrove swamps. Copyright © 2014 Elsevier B.V. All rights reserved.

  8. Synthesizing Global and Local Datasets to Estimate Jurisdictional Forest Carbon Fluxes in Berau, Indonesia.

    Science.gov (United States)

    Griscom, Bronson W; Ellis, Peter W; Baccini, Alessandro; Marthinus, Delon; Evans, Jeffrey S; Ruslandi

    2016-01-01

    Forest conservation efforts are increasingly being implemented at the scale of sub-national jurisdictions in order to mitigate global climate change and provide other ecosystem services. We see an urgent need for robust estimates of historic forest carbon emissions at this scale, as the basis for credible measures of climate and other benefits achieved. Despite the arrival of a new generation of global datasets on forest area change and biomass, confusion remains about how to produce credible jurisdictional estimates of forest emissions. We demonstrate a method for estimating the relevant historic forest carbon fluxes within the Regency of Berau in eastern Borneo, Indonesia. Our method integrates best available global and local datasets, and includes a comprehensive analysis of uncertainty at the regency scale. We find that Berau generated 8.91 ± 1.99 million tonnes of net CO2 emissions per year during 2000-2010. Berau is an early frontier landscape where gross emissions are 12 times higher than gross sequestration. Yet most (85%) of Berau's original forests are still standing. The majority of net emissions were due to conversion of native forests to unspecified agriculture (43% of total), oil palm (28%), and fiber plantations (9%). Most of the remainder was due to legal commercial selective logging (17%). Our overall uncertainty estimate offers an independent basis for assessing three other estimates for Berau. Two other estimates were above the upper end of our uncertainty range. We emphasize the importance of including an uncertainty range for all parameters of the emissions equation to generate a comprehensive uncertainty estimate-which has not been done before. We believe comprehensive estimates of carbon flux uncertainty are increasingly important as national and international institutions are challenged with comparing alternative estimates and identifying a credible range of historic emissions values.

  9. Burial fluxes and source apportionment of carbon in culture areas of Sanggou Bay over the past 200 years

    Institute of Scientific and Technical Information of China (English)

    LIU Sai; HUANG Jiansheng; YANG Qian; YANG Shu; YANG Guipeng; SUN Yao

    2015-01-01

    In this study, we assessed the burial fluxes and source appointment of different forms of carbon in core sediments collected from culture areas in the Sanggou Bay, and preliminarily analyzed the reasons for the greater proportion of inorganic carbon burial fluxes (BFTIC). The average content of total carbon (TC) in the Sanggou Bay was 2.14%. Total organic carbon (TOC) accounted for a small proportion in TC, more than 65% of which derived from terrigenous organic carbon (Ct), and while the proportion of marine-derived organic carbon (Ca) increased significantly since the beginning of large-scale aquaculture. Total inorganic carbon (TIC) accounted for 60%–75%of TC, an average of which was 60%, with a maximum up to 90% during flourishing periods (1880–1948) of small natural shellfish derived from seashells inorganic carbon (Shell-IC). The TC burial fluxes ranged from 31 g/(m2·a) to 895 g/(m2·a) with an average of 227 g/(m2·a), which was dominated by TIC (about 70%). Shell-IC was the main source of TIC and even TC. As the main food of natural shellfish, biogenic silica (BSi) negatively correlated with BFTIC through affecting shellfish breeding. BFTIC of Sta. S1, influenced greatly by the Yellow Sea Coastal Current, had a certain response to Pacific Decadal Oscillation (PDO) in some specific periods.

  10. Simple additive simulation overestimates real influence: altered nitrogen and rainfall modulate the effect of warming on soil carbon fluxes.

    Science.gov (United States)

    Ni, Xiangyin; Yang, Wanqin; Qi, Zemin; Liao, Shu; Xu, Zhenfeng; Tan, Bo; Wang, Bin; Wu, Qinggui; Fu, Changkun; You, Chengming; Wu, Fuzhong

    2017-08-01

    Experiments and models have led to a consensus that there is positive feedback between carbon (C) fluxes and climate warming. However, the effect of warming may be altered by regional and global changes in nitrogen (N) and rainfall levels, but the current understanding is limited. Through synthesizing global data on soil C pool, input and loss from experiments simulating N deposition, drought and increased precipitation, we quantified the responses of soil C fluxes and equilibrium to the three single factors and their interactions with warming. We found that warming slightly increased the soil C input and loss by 5% and 9%, respectively, but had no significant effect on the soil C pool. Nitrogen deposition alone increased the soil C input (+20%), but the interaction of warming and N deposition greatly increased the soil C input by 49%. Drought alone decreased the soil C input by 17%, while the interaction of warming and drought decreased the soil C input to a greater extent (-22%). Increased precipitation stimulated the soil C input by 15%, but the interaction of warming and increased precipitation had no significant effect on the soil C input. However, the soil C loss was not significantly affected by any of the interactions, although it was constrained by drought (-18%). These results implied that the positive C fluxes-climate warming feedback was modulated by the changing N and rainfall regimes. Further, we found that the additive effects of [warming × N deposition] and [warming × drought] on the soil C input and of [warming × increased precipitation] on the soil C loss were greater than their interactions, suggesting that simple additive simulation using single-factor manipulations may overestimate the effects on soil C fluxes in the real world. Therefore, we propose that more multifactorial experiments should be considered in studying Earth systems. © 2016 John Wiley & Sons Ltd.

  11. How Choice of Depth Horizon Influences the Estimated Spatial Patterns and Global Magnitude of Ocean Carbon Export Flux

    Science.gov (United States)

    Palevsky, Hilary I.; Doney, Scott C.

    2018-05-01

    Estimated rates and efficiency of ocean carbon export flux are sensitive to differences in the depth horizons used to define export, which often vary across methodological approaches. We evaluate sinking particulate organic carbon (POC) flux rates and efficiency (e-ratios) in a global earth system model, using a range of commonly used depth horizons: the seasonal mixed layer depth, the particle compensation depth, the base of the euphotic zone, a fixed depth horizon of 100 m, and the maximum annual mixed layer depth. Within this single dynamically consistent model framework, global POC flux rates vary by 30% and global e-ratios by 21% across different depth horizon choices. Zonal variability in POC flux and e-ratio also depends on the export depth horizon due to pronounced influence of deep winter mixing in subpolar regions. Efforts to reconcile conflicting estimates of export need to account for these systematic discrepancies created by differing depth horizon choices.

  12. Upper ocean carbon flux determined by the 234Th approach and sediment traps using size-fractionated POC and 234Th data from the Golf of Mexico

    International Nuclear Information System (INIS)

    Hung, Chin-Chang; Roberts, Kimberly A.; Santschi, Peter H.; Guo, Laodong

    2004-01-01

    Size-fractionated particulate 234 Th and particulate organic carbon (POC) fluxes were measured in the Gulf of Mexico during 2000 and 2001 in order to obtain a better estimation of upper ocean organic carbon export out of the euphotic zone within cold core and warm core rings, and to assess the relative merit of sediment trap and POC/ 234 Th methods. In 2000, the flux of POC measured by sediment traps at 120 m ranged from 60 to 148 mg C m -2 d -1 , while 234 Th-derived POC fluxes in large particles (>53 μm) varied from 18 to 61 mg C m -2 d -1 using the ratio of POC/ 234 Th at 120 m, and from 51 to 163 mg C m -2 d -1 using an average ratio of POC/ 234 Th for the upper 120 m water column. In 2001, the fluxes of POC measured by traps deployed at 120 m water depth ranged from 39 to 48 mg C m -2 d -1 , while the 234 Th-derived POC fluxes in large particles (>53 μm) varied from 7 to 37 mg C m -2 d -1 using a ratio of POC/ 234 Th at 120 m, and from 37 to 45 mg C m -2 d -1 using an average ratio of POC/ 234 Th within the 0-120 m interval. The results show that POC fluxes estimated by the 234 Th method using the average ratio of POC/ 234 Th within the euphotic zone are similar to those measured by sediment traps. Furthermore, the results demonstrate that the variability in POC export fluxes estimated by the 234 Th/ 238 U disequilibrium approach is strongly related to the ratio of POC/ 234 Th that is taken, and for which we have independent evidence that it may be controlled by the chemical composition of the suspended particles. The results also reveal that using POC/ 234 Th ratios in small particles may result in an estimate of the POC export flux that is considerably higher than when using POC/ 234 Th ratios in large particles (>53 μm). The POC flux calculated from ratios in large particles is, however, more comparable to the POC flux determined directly by sediment traps, but both of these estimates are much lower than that determined by using the POC/ 234 Th ratios in

  13. Tree Stress and Mortality from Emerald Ash Borer Does Not Systematically Alter Short-Term Soil Carbon Flux in a Mixed Northeastern U.S. Forest

    Directory of Open Access Journals (Sweden)

    Jaclyn Hatala Matthes

    2018-01-01

    Full Text Available Invasive insect pests are a common disturbance in temperate forests, but their effects on belowground processes in these ecosystems are poorly understood. This study examined how aboveground disturbance might impact short-term soil carbon flux in a forest impacted by emerald ash borer (Agrilus planipennis Fairmaire in central New Hampshire, USA. We anticipated changes to soil moisture and temperature resulting from tree mortality caused by emerald ash borer, with subsequent effects on rates of soil respiration and methane oxidation. We measured carbon dioxide emissions and methane uptake beneath trees before, during, and after infestation by emerald ash borer. In our study, emerald ash borer damage to nearby trees did not alter soil microclimate nor soil carbon fluxes. While surprising, the lack of change in soil microclimate conditions may have been a result of the sandy, well-drained soil in our study area and the diffuse spatial distribution of canopy ash trees and subsequent canopy light gaps after tree mortality. Overall, our results indicate that short-term changes in soil carbon flux following insect disturbances may be minimal, particularly in forests with well-drained soils and a mixed-species canopy.

  14. Partitioning CO2 fluxes with isotopologue measurements and modeling to understand mechanisms of forest carbon sequestration

    Energy Technology Data Exchange (ETDEWEB)

    Saleska, Scott [Univ. of Arizona, Tucson, AZ (United States); Davidson, Eric [Univ. of Arizona, Tucson, AZ (United States); Finzi, Adrien [Boston Univ., MA (United States); Wehr, Richdard [Harvard Univ., Cambridge, MA (United States); Moorcroft, Paul [Harvard Univ., Cambridge, MA (United States)

    2016-01-28

    1. Objectives This project combines automated in situ observations of the isotopologues of CO2 with root observations, novel experimental manipulations of belowground processes, and isotope-enabled ecosystem modeling to investigate mechanisms of below- vs. aboveground carbon sequestration at the Harvard Forest Environmental Measurements Site (EMS). The proposed objectives, which have now been largely accomplished, include: A. Partitioning of net ecosystem CO2 exchange (NEE) into photosynthesis and respiration using long-term continuous observations of the isotopic composition of NEE, and analysis of their dynamics ; B. Investigation of the influence of vegetation phenology on the timing and magnitude of carbon allocated belowground using measurements of root growth and indices of belowground autotrophic vs. heterotrophic respiration (via trenched plots and isotope measurements); C. Testing whether plant allocation of carbon belowground stimulates the microbial decomposition of soil organic matter, using in situ rhizosphere simulation experiments wherein realistic quantities of artificial isotopically-labeled exudates are released into the soil; and D. Synthesis and interpretation of the above data using the Ecosystem Demography Model 2 (ED2). 2. Highlights Accomplishments: • Our isotopic eddy flux record has completed its 5th full year and has been used to independently estimate ecosystem-scale respiration and photosynthesis. • Soil surface chamber isotopic flux measurements were carried out during three growing seasons, in conjunction with a trenching manipulation. Key findings to date (listed by objective): A. Partitioning of Net Ecosystem Exchange: 1. Ecosystem respiration is lower during the day than at night—the first robust evidence of the inhibition of leaf respiration by light (the “Kok effect”) at the ecosystem scale. 2. Because it neglects the Kok effect, the standard NEE partitioning approach overestimates ecosystem photosynthesis (by ~25%) and

  15. Influence of the Particle Length of Carbon Nanotube for Pool Boiling Critical Heat Flux Enhancement of Nanofluids

    International Nuclear Information System (INIS)

    Park, Sung Seek; Kim, Yong Hwan; Kim, Nam Jin

    2013-01-01

    The results of this experiment were that the CHF of the two nanofluids increased along with the volumetric fraction until 0.001 vol%, and the two types of nanofluids are the highest CHF at 0.001 vol%. Also, the results show clearly that the rate of CHF increase of the CM-100 MWCNT nanofluid with longer-length nanoparticles is higher than that of the CM-95 MWNCT nanofluid. These results indicate that the length of carbon nanotube influences the pool boiling CHF of carbon nanotube nanofluid and that long-length MWCNT, as above-noted, offers a superior effect in this regard. Boiling heat transfer is used in a variety of industrial processes and applications, such as refrigeration, power generation, heat exchangers, cooling of high-power electronics components and cooling of nuclear reactors. The critical heat flux (CHF) phenomenon is the thermal limit during a boiling heat transfer phase change; at the CHF point the heat transfer is maximised, followed by a drastic degradation after the CHF point. The consequence is a substantial increase in wall temperature which may result in physical failure phenomenon of heat transfer systems. Therefore, the CHF is important being considered in the cooling device design, such as nuclear reactor and nuclear fuels, steam generators, high-density electronic component, etc. And, CHF enhancement is essential for safety of heat transfer system. Recently, CHF reported increased when applied to the nanofluids, with its high (higher-than-base-fluid) thermal characteristic in the nuclear power plant system. Therefore, in this study, carried out the pool boiling CHF experiments by the particle length using carbon nanotube nanofluids, and the results are compared and analyzed for the CHF enhancement. The pool boiling CHF of experiments of carbon nanotube nanofluids carried out by the length of particles and the various concentrations

  16. Baseline and projected future carbon storage and greenhouse-gas fluxes in the Great Plains region of the United States

    Science.gov (United States)

    Bouchard, Michelle; Butman, David; Hawbaker, Todd; Li, Zhengpeng; Liu, Jinxun; Liu, Shu-Guang; McDonald, Cory; Reker, Ryan R.; Sayler, Kristi; Sleeter, Benjamin; Sohl, Terry; Stackpoole, Sarah; Wein, Anne; Zhu, Zhi-Liang; Zhu, Zhi-Liang

    2011-01-01

    This assessment was conducted to fulfill the requirements of section 712 of the Energy Independence and Security Act (EISA) of 2007 and to improve understanding of carbon and greenhouse gas (GHG) fluxes in the Great Plains region in the central part of the United States. The assessment examined carbon storage, carbon fluxes, and other GHG fluxes (methane and nitrous oxide) in all major terrestrial ecosystems (forests, grasslands/shrublands, agricultural lands, and wetlands) and freshwater aquatic systems (rivers, streams, lakes, and impoundments) in two time periods: baseline (generally in the first half of the 2010s) and future (projections from baseline to 2050). The assessment was based on measured and observed data collected by the U.S. Geological Survey (USGS) and many other agencies and organizations and used remote sensing, statistical methods, and simulation models.

  17. Integrative measurements focusing on carbon, energy and water fluxes at the forest site 'Hohes Holz' and the grassland 'Grosses Bruch'

    Science.gov (United States)

    Rebmann, Corinna; Claudia, Schütze; Sara, Marañón-Jiménez; Sebastian, Gimper; Matthias, Zink; Luis, Samaniego; Matthias, Cuntz

    2017-04-01

    The reduction of greenhouse gas (GHG) emissions and the optimization of Carbon sequestration by ecosystems have become priority objectives for current climate change policies. In this context, the long term research project TERENO and the research infrastructure ICOS have been established. The eddy covariance technique allows obtaining an integrative estimate of the ecosystem carbon, water and energy balances at the ecosystem level. The relative contributions of evaporation and transpiration as well as carbon sources and sinks need, however, to be determined separately for thorough process understanding. Two different ecosystem observatories have recently been established in the Magdeburger Börde: a deciduous forest (Hohes Holz) and a meadow (Grosses Bruch). A comprehensive system of instrumentation provides continuous data for the evaluation of energy, water and carbon fluxes at the 1500 ha large forest site, including a 50 m high eddy covariance (EC) tower for micrometeorological investigations in different heights above and below canopy, throughfall and stem flow sensors, a soil moisture and temperature sensor network, soil respiration chambers, sap flow sensors, and ancillary analysis of trees such a dendrometer and leaf area index measurements. Eddy covariance measurements allow the assessment of the carbon (Net Ecosystem Exchange, NEE) and water balance at the ecosystem scale. To better understand the contributing processes we partition water und carbon fluxes of the forest ecosystem by different methods. Tower-based data of NEE are therefore complemented and validated by continuous automatic and manual campaign measurements of soil effluxes and their drivers. Water fluxes into the ecosystem are partitioned by stem flow and throughfall measurements and a distributed soil moisture network. Gap fraction in the forest has a strong influence on the distribution on the water fluxes and is therefore determined on a regular basis. Since the establishment of the

  18. Mesocosm-Scale Experimental Quantification of Plant-Fungi Associations on Carbon Fluxes and Mineral Weathering

    Science.gov (United States)

    Andrews, M. Y.; Palmer, B.; Leake, J. R.; Banwart, S. A.; Beerling, D. J.

    2009-12-01

    The rise of land plants in the Paleozoic is classically implicated as driving lower atmospheric CO2 levels through enhanced weathering of Ca and Mg bearing silicate minerals. However, this view overlooks the fact that plants coevolved with associated mycorrhizal fungi over this time, with many of the weathering processes usually ascribed to plants actually being driven by the combined activities of roots and mycorrhizal fungi. Here we present initial results from a novel mesocosm-scale laboratory experiment designed to allow investigation of plant-driven carbon flux and mineral weathering at different soil depths under ambient (400 ppm) and elevated (1500 ppm) atmospheric CO2. Four species of plants were chosen to address evolutionary trends in symbiotic mycorrhizal association and rooting depth on biologically driven silicate weathering under the different CO2 regimes. Gymnosperms were used to investigate potential differences in weathering capabilities of two fungal symbioses: Sequoia sempervirens and Metasequoia glyptostroboides (arbuscular mycorrhizal, AM) and Pinus sylvestris (ectomycorrhizal, EM), and the shallow rooted ancient fern, Osmunda regalis, used to provide a contrast to the three more deeply rooted trees. Plants were grown in a cylindrical mesocosm with four horizontal inserts at each depth. These inserts are a mesh-covered dual-core unit whereby an inner core containing silicate minerals can be rotated within an outer core. The mesh excludes roots from the cylinders allowing fungal-rock pairings to be examined at each depth. Each core contains either basalt or granite, each with severed (rotated cores) or intact (static cores) mycorrhizae. This system provides a unique opportunity to examine the ability of a plant to weather minerals with and without its symbiotic fungi. Preliminary results indicate marked differences in nutritional and water requirements, and response to elevated CO2 between the species. The bulk solution chemistries (p

  19. Episodic Salinization of Urban Rivers: Potential Impacts on Carbon, Cation, and Nutrient Fluxes

    Science.gov (United States)

    Haq, S.; Kaushal, S.

    2017-12-01

    Human dominated watersheds are subjected to an array of salt inputs (e.g. road salts), and in urban areas, infrastructure and impervious surfaces quickly drain applied road salts into the river channel. As a result, many streams experience episodic salinization over the course of hours to days following a snow event (e.g. road salt pulse), and long-term salinization over the course of seasons to decades. Salinization of streams can release contaminants (e.g. heavy metals), reduce biodiversity, and degrade drinking water quality. We investigated the water quality effects of episodic salinization in urban streams. Sediment and streamwater were incubated from twelve sites in the Baltimore-Washington Metropolitan Area under a range of sodium chloride treatments in a lab environment to mimic a vertical stream column with a sediment-water interface undergoing episodic salinization, and to characterize relationships between experimental salinization and nutrient/cation fluxes. Eight sites (Baltimore) exhibit a land use gradient and are routinely monitored within the Baltimore Ecosystem Study LTER project, and four sites (Washington DC) are suburban and offer a contrasting lithology and physiographic province. Our research suggests that salinization can mobilize total dissolved nitrogen, soluble reactive phosphorous, and base cations; potentially due to coupled biotic-abiotic processes, such as ion exchange, rapid nitrification, pH changes, and chloride-organic matter dispersal. The impact of salinization on dissolved inorganic and organic carbon varied between sites, potentially due to sediment composition, organic matter content, and ambient water quality. We contrasted the experimental results with measurements of salinization (specific conductance) and nutrients (nitrate) from real-time sensors operated by the US Geological Survey that encompass the same watersheds as our experimental sites. Sensor data was analyzed to provide insight on the timescales of salinity

  20. A Decade of Carbon Flux Measurements with Annual and Perennial Crop Rotations on the Canadian Prairies

    Science.gov (United States)

    Amiro, B. D.; Tenuta, M.; Gao, X.; Gervais, M.

    2016-12-01

    The Fluxnet database has over 100 cropland sites, some of which have long-term (over a decade) measurements. Carbon neutrality is one goal of sustainable agriculture, although measurements over many annual cropping systems have indicated that soil carbon is often lost. Croplands are complex systems because the CO2 exchange depends on the type of crop, soil, weather, and management decisions such as planting date, nutrient fertilization and pest management strategy. Crop rotations are often used to decrease pest pressure, and can range from a simple 2-crop system, to have 4 or more crops in series. Carbon dioxide exchange has been measured using the flux-gradient technique since 2006 in agricultural systems in Manitoba, Canada. Two cropping systems are being followed: one that is a rotation of annual crops (corn, faba bean, spring wheat, rapeseed, barley, spring wheat, corn, soybean, spring wheat, soybean); and the other with a perennial phase of alfalfa/grass in years 3 to 6. Net ecosystem production ranged from a gain of 330 g C m-2 y-1 in corn to a loss of 75 g C m-2 y-1 in a poor spring-wheat crop. Over a decade, net ecosystem production for the annual cropping system was not significantly different from zero (carbon neutral), but the addition of the perennial phase increased the sink to 130 g C m-2 y-1. Once harvest removals were included, there was a net loss of carbon ranging from 77 g C m-2 y-1 in the annual system to 52 g C m-2 y-1 in the annual-perennial system; but neither of these were significantly different from zero. Termination of the perennial phase of the rotation only caused short-term increases in respiration. We conclude that both these systems were close to carbon-neutral over a decade even though they were tilled with a short growing season (90 to 130 days). We discuss the need for more datasets on agricultural systems to inform management options to increase the soil carbon sink.

  1. An analysis of the decadal variability of Carbon fluxes in three evergreen European forests through modelling

    Science.gov (United States)

    Delpierre, N.; Dufrêne, E.

    2009-04-01

    With several sites measuring mass and energy turbulent fluxes for more than ten years, the CarboEurope database appears as a valuable resource for addressing the question of the determinism of the interannual variability of carbon (C) and water balances in forests ecosystems. Apart from major climate-driven anomalies during the anomalous 2003 summer and 2007 spring, little is known about the factors driving interannual variability (IAV) of the C balance in forest ecosystems. We used the CASTANEA process-based model to simulate the C and W fluxes and balances of three European evergreen forests for the 2000-2007 period (FRPue Quercus ilex, 44°N; DETha Picea abies, 51°N; FIHyy Pinus sylvestris, 62°N). The model fairly reproduced the day-to-day variability of measured fluxes, accounting for 70-81%, 77-91% and 59-90% of the daily variance of measured NEP, GPP and TER, respectively. However, the model was challenged in representing the IAV of fluxes integrated on an annual time scale. It reproduced ca. 80% of the interannual variance of measured GPP, but no significant relationship could be established between annual measured and modelled NEP or TER. Accordingly, CASTANEA appeared as a suitable tool for disentangling the influence of climate and biological processes on GPP at mutiple time scales. We show that climate and biological processes relative influences on the modelled GPP vary from year to year in European evergreen forests. Water-stress related and phenological processes (i.e. release of the winter thermal constraint on photosynthesis in evergreens) appear as primary drivers for the particular 2003 and 2007 years, respectively, but the relative influence of other climatic factors widely varies for less remarkable years at all sites. We discuss shortcomings of the method, as related to the influence of compensating errors in the simulated fluxes, and assess the causes of the model poor ability to represent the IAV of the annual sums of NEP and TER.

  2. Thermal-based modeling of coupled carbon, water, and energy fluxes using nominal light use efficiencies constrained by leaf chlorophyll observations

    KAUST Repository

    Schull, M. A.

    2015-03-11

    Recent studies have shown that estimates of leaf chlorophyll content (Chl), defined as the combined mass of chlorophyll a and chlorophyll b per unit leaf area, can be useful for constraining estimates of canopy light use efficiency (LUE). Canopy LUE describes the amount of carbon assimilated by a vegetative canopy for a given amount of absorbed photosynthetically active radiation (APAR) and is a key parameter for modeling land-surface carbon fluxes. A carbon-enabled version of the remote-sensing-based two-source energy balance (TSEB) model simulates coupled canopy transpiration and carbon assimilation using an analytical sub-model of canopy resistance constrained by inputs of nominal LUE (βn), which is modulated within the model in response to varying conditions in light, humidity, ambient CO2 concentration, and temperature. Soil moisture constraints on water and carbon exchange are conveyed to the TSEB-LUE indirectly through thermal infrared measurements of land-surface temperature. We investigate the capability of using Chl estimates for capturing seasonal trends in the canopy βn from in situ measurements of Chl acquired in irrigated and rain-fed fields of soybean and maize near Mead, Nebraska. The results show that field-measured Chl is nonlinearly related to βn, with variability primarily related to phenological changes during early growth and senescence. Utilizing seasonally varying βn inputs based on an empirical relationship with in situ measured Chl resulted in improvements in carbon flux estimates from the TSEB model, while adjusting the partitioning of total water loss between plant transpiration and soil evaporation. The observed Chl-βn relationship provides a functional mechanism for integrating remotely sensed Chl into the TSEB model, with the potential for improved mapping of coupled carbon, water, and energy fluxes across vegetated landscapes.

  3. Estimating carbon flux phenology with satellite-derived land surface phenology and climate drivers for different biomes: a synthesis of AmeriFlux observations.

    Directory of Open Access Journals (Sweden)

    Wenquan Zhu

    Full Text Available Carbon Flux Phenology (CFP can affect the interannual variation in Net Ecosystem Exchange (NEE of carbon between terrestrial ecosystems and the atmosphere. In this study, we proposed a methodology to estimate CFP metrics with satellite-derived Land Surface Phenology (LSP metrics and climate drivers for 4 biomes (i.e., deciduous broadleaf forest, evergreen needleleaf forest, grasslands and croplands, using 159 site-years of NEE and climate data from 32 AmeriFlux sites and MODIS vegetation index time-series data. LSP metrics combined with optimal climate drivers can explain the variability in Start of Carbon Uptake (SCU by more than 70% and End of Carbon Uptake (ECU by more than 60%. The Root Mean Square Error (RMSE of the estimations was within 8.5 days for both SCU and ECU. The estimation performance for this methodology was primarily dependent on the optimal combination of the LSP retrieval methods, the explanatory climate drivers, the biome types, and the specific CFP metric. This methodology has a potential for allowing extrapolation of CFP metrics for biomes with a distinct and detectable seasonal cycle over large areas, based on synoptic multi-temporal optical satellite data and climate data.

  4. Carbon Flux Through the Giant Barrel Sponge Xestospongia testudinaria in the Red Sea

    KAUST Repository

    Wooster, Michael K.

    2017-11-01

    Sponges have important ecological functions on coral reefs because they are regionally abundant, competitively dominant, and process large volumes of seawater. The sponge loop hypothesis proposes that sponges consume dissolved organic carbon (DOC) and then releases the carbon as shed cellular detritus back to the reef benthos. Within this context, we examined the carbon flux mediated by the giant barrel sponge, Xestospongia testudinaria, on reefs in the Red Sea, where sponge abundance is comparatively low relative to coral reefs elsewhere, such as the Caribbean. Seawater samples were collected from the incurrent and excurrent (In-Ex) flow of 40 sponges from inshore, mid-shelf, and offshore reefs between 18° and 22°N latitude off the coast of Saudi Arabia. Concentrations of DOC and living particulate organic carbon (LPOC) were significantly higher in incurrent (ambient) seawater on inshore reefs than mid-shelf and offshore reefs. Consistent with studies of X. muta in the Caribbean, the diet of X. testudinaria is comprised primarily of DOC; mean values of the nutritional components across all sites were 60.5% DOC, 35.7% detritus, and 3.8% LPOC. Taking into account the specific filtration rates of nutritional components and oxygen consumption of sponges across the inshore-offshore gradient, there is evidence (1) of a threshold concentration of DOC below which sponges cease to be net consumers of DOC, and (2) that sponges on offshore reefs are food-limited. Contrary to the sponge loop hypothesis, there was no evidence that X. testudinaria, returned DOC to the benthos in the form of detritus, but was, instead, a net consumer of detritus from the water column. Unlike the cryptic, interstitial sponges that were studied to advance the sponge-loop hypothesis, emergent sponges may have an alternate pathway for returning DOC to the benthos by converting it to sponge biomass rather than sponge detritus.

  5. Beaver-mediated lateral hydrologic connectivity, fluvial carbon and nutrient flux, and aquatic ecosystem metabolism

    Science.gov (United States)

    Wegener, Pam; Covino, Tim; Wohl, Ellen

    2017-06-01

    River networks that drain mountain landscapes alternate between narrow and wide valley segments. Within the wide segments, beaver activity can facilitate the development and maintenance of complex, multithread planform. Because the narrow segments have limited ability to retain water, carbon, and nutrients, the wide, multithread segments are likely important locations of retention. We evaluated hydrologic dynamics, nutrient flux, and aquatic ecosystem metabolism along two adjacent segments of a river network in the Rocky Mountains, Colorado: (1) a wide, multithread segment with beaver activity; and, (2) an adjacent (directly upstream) narrow, single-thread segment without beaver activity. We used a mass balance approach to determine the water, carbon, and nutrient source-sink behavior of each river segment across a range of flows. While the single-thread segment was consistently a source of water, carbon, and nitrogen, the beaver impacted multithread segment exhibited variable source-sink dynamics as a function of flow. Specifically, the multithread segment was a sink for water, carbon, and nutrients during high flows, and subsequently became a source as flows decreased. Shifts in river-floodplain hydrologic connectivity across flows related to higher and more variable aquatic ecosystem metabolism rates along the multithread relative to the single-thread segment. Our data suggest that beaver activity in wide valleys can create a physically complex hydrologic environment that can enhance hydrologic and biogeochemical buffering, and promote high rates of aquatic ecosystem metabolism. Given the widespread removal of beaver, determining the cumulative effects of these changes is a critical next step in restoring function in altered river networks.

  6. BOREAS RSS-8 BIOME-BGC SSA Simulation of Annual Water and Carbon Fluxes

    Science.gov (United States)

    Hall, Forrest G. (Editor); Nickeson, Jaime (Editor); Kimball, John

    2000-01-01

    The BOREAS RSS-8 team performed research to evaluate the effect of seasonal weather and landcover heterogeneity on boreal forest regional water and carbon fluxes using a process-level ecosystem model, BIOME-BGC, coupled with remote sensing-derived parameter maps of key state variables. This data set contains derived maps of landcover type and crown and stem biomass as model inputs to determine annual evapotranspiration, gross primary production, autotrophic respiration, and net primary productivity within the BOREAS SSA-MSA, at a 30-m spatial resolution. Model runs were conducted over a 3-year period from 1994-1996; images are provided for each of those years. The data are stored in binary image format. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

  7. ForC: a global database of forest carbon stocks and fluxes.

    Science.gov (United States)

    Anderson-Teixeira, Kristina J; Wang, Maria M H; McGarvey, Jennifer C; Herrmann, Valentine; Tepley, Alan J; Bond-Lamberty, Ben; LeBauer, David S

    2018-06-01

    Forests play an influential role in the global carbon (C) cycle, storing roughly half of terrestrial C and annually exchanging with the atmosphere more than five times the carbon dioxide (CO 2 ) emitted by anthropogenic activities. Yet, scaling up from field-based measurements of forest C stocks and fluxes to understand global scale C cycling and its climate sensitivity remains an important challenge. Tens of thousands of forest C measurements have been made, but these data have yet to be integrated into a single database that makes them accessible for integrated analyses. Here we present an open-access global Forest Carbon database (ForC) containing previously published records of field-based measurements of ecosystem-level C stocks and annual fluxes, along with disturbance history and methodological information. ForC expands upon the previously published tropical portion of this database, TropForC (https://doi.org/10.5061/dryad.t516f), now including 17,367 records (previously 3,568) representing 2,731 plots (previously 845) in 826 geographically distinct areas. The database covers all forested biogeographic and climate zones, represents forest stands of all ages, and currently includes data collected between 1934 and 2015. We expect that ForC will prove useful for macroecological analyses of forest C cycling, for evaluation of model predictions or remote sensing products, for quantifying the contribution of forests to the global C cycle, and for supporting international efforts to inventory forest carbon and greenhouse gas exchange. A dynamic version of ForC is maintained at on GitHub (https://GitHub.com/forc-db), and we encourage the research community to collaborate in updating, correcting, expanding, and utilizing this database. ForC is an open access database, and we encourage use of the data for scientific research and education purposes. Data may not be used for commercial purposes without written permission of the database PI. Any publications using For

  8. Declines in the dissolved organic carbon (DOC) concentration and flux from the UK

    Science.gov (United States)

    Worrall, Fred; Howden, Nicholas J. K.; Burt, Tim P.; Bartlett, Rebecca

    2018-01-01

    Increased concentrations of dissolved organic carbon (DOC) have been reported for many catchments across the northern hemisphere. Hypotheses to explain the increase have varied (eg. increasing air temperature or recovery from acidification) but one test of alternative hypotheses is the trend over the recent decade, with the competing hypotheses predicting: continuing increase; the rate of increase declining with time; and even decrease in concentration. In this study, records of DOC concentration in non-tidal rivers across the UK were examined for the period 2003-2012. The study found that: Of the 62 decade-long concentration trends that could be examined, 3 showed a significant increase, 17 experienced no significant change and 42 showed a significant decrease; in 28 of the 42 significant decreases, a significant step change was apparent with step changes being a decrease in concentration in every case. Of the 118 sites where annual flux and concentration records were available from 1974, 28 showed a significant step change down in flux and 52 showed a step down in concentration. The modal year of the step changes was 2000 with no step changes observed before 1982. At the UK national scale, DOC flux peaked in 2005 at 1354 ktonnes C/yr (5.55 tonnes C/km2/yr) but has declined since. The study suggests that there is a disconnection between DOC records from large catchments at their tidal limits and complementary records from headwater catchments, which means that mechanisms believed to be driving increases in DOC concentrations in headwaters will not necessarily be those controlling trends in DOC concentration further downstream. We propose that the changes identified here have been driven by changes in in-stream processing and changes brought about by the Urban Waste Water Treatment Directive. Therefore, signals identified in headwater catchments may bear little relation to those observed in large rivers much further downstream and vice versa.

  9. Effect of spatial sampling from European flux towers for estimating carbon and water fluxes with artificial neural network

    DEFF Research Database (Denmark)

    Papale, D.; Black, T Andrew; Carvalhais, Nuno

    2015-01-01

    -output relationships, while prediction for conditions outside the training domain is generally uncertain. In this work, artificial neural networks (ANNs) were used for the prediction of gross primary production (GPP) and latent heat flux (LE) on local and European scales with the aim to assess the portion...

  10. 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.

  11. Estimation of fractional contribution of root respiration to a forest-floor CO2 flux using carbon isotopes

    International Nuclear Information System (INIS)

    Hachiya, Masashi; Moriizumi, Jun; Yamazawa, Hiromi

    2010-01-01

    Efflux of soil respired carbon dioxide(CO 2 ) is very important component for the global carbon cycle and dynamics of 14 C in environment, and to predict the global climate changes caused by increasing CO 2 concentrations in the atmosphere. There are two components that generate CO 2 in soil, soil organic matter decomposition and root respiration. Although the former is relatively well understood, the root-derived CO 2 efflux has not been evaluated sufficiently. The objective of our research is to estimate depth profile of the root respiration rate. Thus we developed a box model which calculates the depth profile. In this paper, we discussed about (1) the adequacy of calculated result by comparing it to the to observed soil respired CO 2 flux with trenching method and (2) sensitivity of the box model to uncertainty in the input data. The result showed that the depth profile of root respiration rate decreased with soil depth. This is attributed to the distribution of fine roots which dominate root respiration. The model results reasonable agreed with the measurement results and characteristics of root respiration. The output of the model was robust to the variation of the input data. (author)

  12. Site-specific global warming potentials of biogenic CO2 for bioenergy: contributions from carbon fluxes and albedo dynamics

    International Nuclear Information System (INIS)

    Cherubini, Francesco; Bright, Ryan M; Strømman, Anders H

    2012-01-01

    Production of biomass for bioenergy can alter biogeochemical and biogeophysical mechanisms, thus affecting local and global climate. Recent scientific developments have mainly embraced impacts from land use changes resulting from area-expanded biomass production, with several extensive insights available. Comparably less attention, however, has been given to the assessment of direct land surface–atmosphere climate impacts of bioenergy systems under rotation such as in plantations and forested ecosystems, whereby land use disturbances are only temporary. Here, following IPCC climate metrics, we assess bioenergy systems in light of two important dynamic land use climate factors, namely, the perturbation in atmospheric carbon dioxide (CO 2 ) concentration caused by the timing of biogenic CO 2 fluxes, and temporary perturbations to surface reflectivity (albedo). Existing radiative forcing-based metrics can be adapted to include such dynamic mechanisms, but high spatial and temporal modeling resolution is required. Results show the importance of specifically addressing the climate forcings from biogenic CO 2 fluxes and changes in albedo, especially when biomass is sourced from forested areas affected by seasonal snow cover. The climate performance of bioenergy systems is highly dependent on biomass species, local climate variables, time horizons, and the climate metric considered. Bioenergy climate impact studies and accounting mechanisms should rapidly adapt to cover both biogeochemical and biogeophysical impacts, so that policy makers can rely on scientifically robust analyses and promote the most effective global climate mitigation options. (letter)

  13. A comprehensive set of benchmark tests for a land surface model of simultaneous fluxes of water and carbon at both the global and seasonal scale

    Directory of Open Access Journals (Sweden)

    E. Blyth

    2011-04-01

    Full Text Available Evaluating the models we use in prediction is important as it allows us to identify uncertainties in prediction as well as guiding the priorities for model development. This paper describes a set of benchmark tests that is designed to quantify the performance of the land surface model that is used in the UK Hadley Centre General Circulation Model (JULES: Joint UK Land Environment Simulator. The tests are designed to assess the ability of the model to reproduce the observed fluxes of water and carbon at the global and regional spatial scale, and on a seasonal basis. Five datasets are used to test the model: water and carbon dioxide fluxes from ten FLUXNET sites covering the major global biomes, atmospheric carbon dioxide concentrations at four representative stations from the global network, river flow from seven catchments, the seasonal mean NDVI over the seven catchments and the potential land cover of the globe (after the estimated anthropogenic changes have been removed. The model is run in various configurations and results are compared with the data.

    A few examples are chosen to demonstrate the importance of using combined use of observations of carbon and water fluxes in essential in order to understand the causes of model errors. The benchmarking approach is suitable for application to other global models.

  14. Net carbon flux of dead wood in forests of the Eastern US.

    Science.gov (United States)

    Woodall, C W; Russell, M B; Walters, B F; D'Amato, A W; Fraver, S; Domke, G M

    2015-03-01

    Downed dead wood (DDW) in forest ecosystems is a C pool whose net flux is governed by a complex of natural and anthropogenic processes and is critical to the management of the entire forest C pool. As empirical examination of DDW C net flux has rarely been conducted across large scales, the goal of this study was to use a remeasured inventory of DDW C and ancillary forest attributes to assess C net flux across forests of the Eastern US. Stocks associated with large fine woody debris (diameter 2.6-7.6 cm) decreased over time (-0.11 Mg ha(-1) year(-1)), while stocks of larger-sized coarse DDW increased (0.02 Mg ha(-1) year(-1)). Stocks of total DDW C decreased (-0.14 Mg ha(-1) year(-1)), while standing dead and live tree stocks both increased, 0.01 and 0.44 Mg ha(-1) year(-1), respectively. The spatial distribution of DDW C stock change was highly heterogeneous with random forests model results indicating that management history, live tree stocking, natural disturbance, and growing degree days only partially explain stock change. Natural disturbances drove substantial C transfers from the live tree pool (≈-4 Mg ha(-1) year(-1)) to the standing dead tree pool (≈3 Mg ha(-1) year(-1)) with only a minimal increase in DDW C stocks (≈1 Mg ha(-1) year(-1)) in lower decay classes, suggesting a delayed transfer of C to the DDW pool. The assessment and management of DDW C flux is complicated by the diversity of natural and anthropogenic forces that drive their dynamics with the scale and timing of flux among forest C pools remaining a large knowledge gap.

  15. Simulating carbon and water cycles of larch forests in East Asia by the BIOME-BGC model with AsiaFlux data

    Science.gov (United States)

    Ueyama, M.; Ichii, K.; Hirata, R.; Takagi, K.; Asanuma, J.; Machimura, T.; Nakai, Y.; Ohta, T.; Saigusa, N.; Takahashi, Y.; Hirano, T.

    2010-03-01

    Larch forests are widely distributed across many cool-temperate and boreal regions, and they are expected to play an important role in global carbon and water cycles. Model parameterizations for larch forests still contain large uncertainties owing to a lack of validation. In this study, a process-based terrestrial biosphere model, BIOME-BGC, was tested for larch forests at six AsiaFlux sites and used to identify important environmental factors that affect the carbon and water cycles at both temporal and spatial scales. The model simulation performed with the default deciduous conifer parameters produced results that had large differences from the observed net ecosystem exchange (NEE), gross primary productivity (GPP), ecosystem respiration (RE), and evapotranspiration (ET). Therefore, we adjusted several model parameters in order to reproduce the observed rates of carbon and water cycle processes. This model calibration, performed using the AsiaFlux data, substantially improved the model performance. The simulated annual GPP, RE, NEE, and ET from the calibrated model were highly consistent with observed values. The observed and simulated GPP and RE across the six sites were positively correlated with the annual mean air temperature and annual total precipitation. On the other hand, the simulated carbon budget was partly explained by the stand disturbance history in addition to the climate. The sensitivity study indicated that spring warming enhanced the carbon sink, whereas summer warming decreased it across the larch forests. The summer radiation was the most important factor that controlled the carbon fluxes in the temperate site, but the VPD and water conditions were the limiting factors in the boreal sites. One model parameter, the allocation ratio of carbon between belowground and aboveground, was site-specific, and it was negatively correlated with the annual climate of annual mean air temperature and total precipitation. Although this study substantially

  16. Seasonal effects of irrigation on land-atmosphere latent heat, sensible heat and carbon fluxes in semi-arid basin

    Science.gov (United States)

    Xie, Zhenghui; Zeng, Yujin

    2017-04-01

    Irrigation, which constitutes 70% of the total amount of fresh water consumed by the human population, is significantly impacting the land-atmosphere fluxes. In this study, using the improved Community Land Model version 4.5 (CLM 4.5) with an active crop model, two high resolution ( 1 km) simulations investigating the effects of irrigation on Latent Heat (LH), Sensible Heat (SH) and Carbon Fluxes (or net ecosystem exchange, NEE) from land to atmosphere on the Heihe River Basin in northwestern China were conducted using a high-quality irrigation dataset compiled from 1981 to 2013. The model output and measurements from remote sensing demonstrated the capacity and viability of the developed models to reproduce ecological and hydrological processes. The results revealed the effects of irrigation on LH and SH are strongest during summer with a LH increase of 100 W/m2 and a SH decrease of 60 W/m2 over intensely irrigated areas. However, the reactions are much weaker during spring and autumn when there is much less irrigation. When the irrigation rate below 5 mm/day, the LH generally increases, whereas the SH decreases with growing irrigation rates. However, when the irrigation threshold is in excess of 5 mm/day, there is no accrued effect of irrigation on the LH and SH. Irrigation produces opposite effects to the NEE during spring and summer. During the spring, irrigation yields more discharged carbon from the land to the atmosphere, increasing the NEE value by 0.4-0.8 gC/m2/day, while the summer irrigation favors crop fixing of carbon from atmospheric CO2, decreasing the NEE value by 0.8 gC/m2/day. The repercussions of irrigation on land-atmosphere fluxes are not solely linked to the irrigation amount, and other parameters (especially the temperature) also control the effects of irrigation on LH, SH and NEE. The study indicates that how a land surface model with high spatial resolution can represent crop growing and its effects over basin scale.

  17. Application of Crunch-Flow Routines to Constrain Present and Past Carbon Fluxes at Gas-Hydrate Bearing Sites

    Energy Technology Data Exchange (ETDEWEB)

    Torres, Marta [Oregon State Univ., Corvallis, OR (United States). College of Earth, Ocean, and Atmospheric Sciences

    2014-01-31

    In November 2012, Oregon State University initiated the project entitled: Application of Crunch-Flow routines to constrain present and past carbon fluxes at gas-hydrate bearing sites. Within this project we developed Crunch-Flow based modeling modules that include important biogeochemical processes that need to be considered in gas hydrate environments. Our modules were applied to quantify carbon cycling in present and past systems, using data collected during several DOE-supported drilling expeditions, which include the Cascadia margin in US, Ulleung Basin in South Korea, and several sites drilled offshore India on the Bay of Bengal and Andaman Sea. Specifically, we completed modeling efforts that: 1) Reproduce the compositional and isotopic profiles observed at the eight drilled sites in the Ulleung Basin that constrain and contrast the carbon cycling pathways at chimney (high methane flux) and non-chimney sites (low methane, advective systems); 2) Simulate the Ba record in the sediments to quantify the past dynamics of methane flux in the southern Hydrate Ridge, Cascadia margin; and 3) Provide quantitative estimates of the thickness of individual mass transport deposits (MTDs), time elapsed after the MTD event, rate of sulfate reduction in the MTD, and time required to reach a new steady state at several sites drilled in the Krishna-Godavari (K-G) Basin off India. In addition we developed a hybrid model scheme by coupling a home-made MATLAB code with CrunchFlow to address the methane transport and chloride enrichment at the Ulleung Basins chimney sites, and contributed the modeling component to a study focusing on pore-scale controls on gas hydrate distribution in sediments from the Andaman Sea. These efforts resulted in two manuscripts currently under review, and contributed the modeling component of another pare, also under review. Lessons learned from these efforts are the basis of a mini-workshop to be held at Oregon State University (Feb 2014) to instruct

  18. Annual benthic metabolism and organic carbon fluxes in a semi-enclosed Mediterranean bay dominated by the macroalgae Caulerpa prolifera.

    Directory of Open Access Journals (Sweden)

    Sergio eRuiz-Halpern

    2014-12-01

    Full Text Available Coastal areas play an important role on carbon cycling. Elucidating the dynamics on the production, transport and fate of organic carbon is relevant to gain a better understanding of the role coastal areas play in the global carbon budget. Here, we assess the metabolic status and associated organic carbon fluxes of a semi-enclosed Mediterranean bay supporting a meadow of Caulerpa prolifera. We test whether the EDOC pool is a significant component of the organic carbon pool and associated fluxes in this ecosystem. The Bay of Portocolom was in net metabolic balance on a yearly basis, but heterotrophic during the summer months. Community respiration (CR was positively correlated to C. prolifera biomass, while net community production (NCP had a negative correlation. The benthic compartment represented, on average, 72.6 ± 5.2 % of CR and 86.8 ± 4.5 % of gross primary production (GPP. Dissolved organic carbon (DOC production peaked in summer and was always positive, with the incubations performed in the dark almost doubling the flux of those performed in the light. Exchangeable dissolved organic carbon (EDOC, however, oscillated between production and uptake, being completely recycled within the system and representing around 14% of the DOC flux. The pools of bottom and surface DOC were high for an oligotrophic environment, and were positively correlated to the pool of EDOC. Thus, despite being in metabolic balance, this ecosystem acted as a conduit for organic carbon (OC, as it is able to export OC to adjacent areas derived from allochtonous inputs during heterotrophic conditions. These inputs likely come from groundwater discharge, human activity in the watershed, delivered to the sediments through the high capacity of C. prolifera to remove particles from the water column, and from the air-water exchange of EDOC, demonstrating that these communities are a major contributor to the cycling of OC in coastal embayments.

  19. Negative effects of climate change on upland grassland productivity and carbon fluxes are not attenuated by nitrogen status.

    Science.gov (United States)

    Eze, Samuel; Palmer, Sheila M; Chapman, Pippa J

    2018-05-09

    Effects of climate change on managed grassland carbon (C) fluxes and biomass production are not well understood. In this study, we investigated the individual and interactive effects of experimental warming (+3 °C above ambient summer daily range of 9-12 °C), supplemental precipitation (333 mm +15%) and drought (333 mm -23%) on plant biomass, microbial biomass C (MBC), net ecosystem exchange (NEE) and dissolved organic C (DOC) flux in soil cores from two upland grasslands of different soil nitrogen (N) status (0.54% and 0.37%) in the UK. After one month of acclimation to ambient summer temperature and precipitation, five replicate cores of each treatment were subjected to three months of experimental warming, drought and supplemental precipitation, based on the projected regional summer climate by the end of the 21st Century, in a fully factorial design. NEE and DOC flux were measured throughout the experimental duration, alongside other environmental variables including soil temperature and moisture. Plant biomass and MBC were determined at the end of the experiment. Results showed that warming plus drought resulted in a significant decline in belowground plant biomass (-29 to -37%), aboveground plant biomass (-35 to -77%) and NEE (-13 to -29%), regardless of the N status of the soil. Supplemental precipitation could not reverse the negative effects of warming on the net ecosystem C uptake and plant biomass production. This was attributed to physiological stress imposed by warming which suggests that future summer climate will reduce the C sink capacity of the grasslands. Due to the low moisture retention observed in this study, and to verify our findings, it is recommended that future experiments aimed at measuring soil C dynamics under climate change should be carried out under field conditions. Longer term experiments are recommended to account for seasonal and annual variability, and adaptive changes in biota. Copyright © 2018 Elsevier B.V. All

  20. 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.

  1. Soil Carbon Dioxide and Methane Fluxes in a Costa Rican Premontane Wet Forest

    Science.gov (United States)

    Hempel, L. A.; Schade, G. W.; Pfohl, A.

    2011-12-01

    A significant amount of the global terrestrial biomass is found in tropical forests, and soil respiration is a vital part of its carbon cycling. However, data on soil trace gas flux rates in the tropics are sparse, especially from previously disturbed regions. To expand the database on carbon cycling in the tropics, this study examined soil flux rate and its variability for CO2 and CH4 in a secondary premontane wet forest south of Arenal Volcano in Costa Rica. Data were collected over a six-week period in June and July 2011 during the transition from dry to wet season. Trace gas sampling was performed at three sub-canopy sites of different elevations. The soil is of volcanic origin with a low bulk density, likely an Andisol. An average KCl pH of 4.8 indicates exchangeable aluminum is present, and a NaF pH>11 indicates the soil is dominated by short-range order minerals. Ten-inch diameter PVC rings were used as static flux chambers without soil collars. To find soil CO2 efflux rates, a battery-powered LICOR 840A CO2-H2O Gas Analyzer was used to take measurements in the field, logging CO2 concentration every ten seconds. Additionally, six, 10-mL Nylon syringes were filled with gas samples at 0, 1, 7, 14, 21, and 28 minutes after closing the chambers. These samples were analyzed the same day with a SRI 8610 Gas Chromatograph for concentrations of CO2 and CH4. The average CO2 efflux calculated was 1.7±0.8E-2 g/m2/min, and did not differ between the applied analytical methods. Soil respiration depended strongly on soil moisture, with decreasing efflux rates at higher water-filled pore space values. An annual soil respiration rate of 8.5E3 g/m2/yr was estimated by applying the observed relationship between soil moisture and CO2 efflux to annual soil moisture measurements. The relatively high respiration rates could be caused by the high soil moisture and low soil bulk density, providing optimal conditions for microbial respiration. Several diurnal sampling periods at

  2. A Data-Centered Collaboration Portal to Support Global Carbon-Flux Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Agarwal, Deborah A. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States); Humphrey, Marty [Univ. of Virginia, Charlottesville, VA (United States); Beekwilder, Norm [Univ. of Virginia, Charlottesville, VA (United States); Jackson, Keith [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States); Goode, Monte [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States); van Ingen, Catharine [Microsoft. San Francisco, CA (United States)

    2009-04-07

    Carbon-climate, like other environmental sciences, has been changing. Large-scalesynthesis studies are becoming more common. These synthesis studies are often conducted by science teams that are geographically distributed and on datasets that are global in scale. A broad array of collaboration and data analytics tools are now available that could support these science teams. However, building tools that scientists actually use is hard. Also, moving scientists from an informal collaboration structure to one mediated by technology often exposes inconsistencies in the understanding of the rules of engagement between collaborators. We have developed a scientific collaboration portal, called fluxdata.org, which serves the community of scientists providing and analyzing the global FLUXNET carbon-flux synthesis dataset. Key things we learned or re-learned during our portal development include: minimize the barrier to entry, provide features on a just-in-time basis, development of requirements is an on-going process, provide incentives to change leaders and leverage the opportunity they represent, automate as much as possible, and you can only learn how to make it better if people depend on it enough to give you feedback. In addition, we also learned that splitting the portal roles between scientists and computer scientists improved user adoption and trust. The fluxdata.org portal has now been in operation for ~;;1.5 years and has become central to the FLUXNET synthesis efforts.

  3. Carbon and water fluxes above a cacao plantation in Sulawesi, Indonesia

    Science.gov (United States)

    Falk, U.; Ibrom, A.

    2003-04-01

    and June 2002 until now eddy-covariance measurements have been performed above a Cacao plantation in Nopu measuring time series of water vapour, CO2, air temperature, three-dimensional wind vector, photosyntetic active radiation and the surface temperature of the Cacao canopy at 10 Hz. Additionally, net radiation balance and soil heat fluxes have been measured. In order to assess the carbon input caused by the humans living in the ecosystem, a mapping of the site area has been carried out, including investigations of consumption of fire wood and use of machines, like generators for example. In order to obtain the energy balance equation of the canopy surface, also the radiation balance and the heat flux into the canopy have to be evaluated.

  4. Reviews and syntheses: Anthropogenic perturbations to carbon fluxes in Asian river systems – concepts, emerging trends, and research challenges

    Directory of Open Access Journals (Sweden)

    J.-H. Park

    2018-05-01

    Full Text Available Human activities are drastically altering water and material flows in river systems across Asia. These anthropogenic perturbations have rarely been linked to the carbon (C fluxes of Asian rivers that may account for up to 40–50 % of the global fluxes. This review aims to provide a conceptual framework for assessing the human impacts on Asian river C fluxes, along with an update on anthropogenic alterations of riverine C fluxes. Drawing on case studies conducted in three selected rivers (the Ganges, Mekong, and Yellow River and other major Asian rivers, the review focuses on the impacts of river impoundment and pollution on CO2 outgassing from the rivers draining South, Southeast, and East Asian regions that account for the largest fraction of river discharge and C exports from Asia and Oceania. A critical examination of major conceptual models of riverine processes against observed trends suggests that to better understand altered metabolisms and C fluxes in anthropogenic land-water-scapes, or riverine landscapes modified by human activities, the traditional view of the river continuum should be complemented with concepts addressing spatial and temporal discontinuities created by human activities, such as river impoundment and pollution. Recent booms in dam construction on many large Asian rivers pose a host of environmental problems, including increased retention of sediment and associated C. A small number of studies that measured greenhouse gas (GHG emissions in dammed Asian rivers have reported contrasting impoundment effects: decreased GHG emissions from eutrophic reservoirs with enhanced primary production vs. increased emissions from the flooded vegetation and soils in the early years following dam construction or from the impounded reaches and downstream estuaries during the monsoon period. These contrasting results suggest that the rates of metabolic processes in the impounded and downstream reaches can vary greatly longitudinally

  5. Reviews and syntheses: Anthropogenic perturbations to carbon fluxes in Asian river systems - concepts, emerging trends, and research challenges

    Science.gov (United States)

    Park, Ji-Hyung; Nayna, Omme K.; Begum, Most S.; Chea, Eliyan; Hartmann, Jens; Keil, Richard G.; Kumar, Sanjeev; Lu, Xixi; Ran, Lishan; Richey, Jeffrey E.; Sarma, Vedula V. S. S.; Tareq, Shafi M.; Xuan, Do Thi; Yu, Ruihong

    2018-05-01

    Human activities are drastically altering water and material flows in river systems across Asia. These anthropogenic perturbations have rarely been linked to the carbon (C) fluxes of Asian rivers that may account for up to 40-50 % of the global fluxes. This review aims to provide a conceptual framework for assessing the human impacts on Asian river C fluxes, along with an update on anthropogenic alterations of riverine C fluxes. Drawing on case studies conducted in three selected rivers (the Ganges, Mekong, and Yellow River) and other major Asian rivers, the review focuses on the impacts of river impoundment and pollution on CO2 outgassing from the rivers draining South, Southeast, and East Asian regions that account for the largest fraction of river discharge and C exports from Asia and Oceania. A critical examination of major conceptual models of riverine processes against observed trends suggests that to better understand altered metabolisms and C fluxes in anthropogenic land-water-scapes, or riverine landscapes modified by human activities, the traditional view of the river continuum should be complemented with concepts addressing spatial and temporal discontinuities created by human activities, such as river impoundment and pollution. Recent booms in dam construction on many large Asian rivers pose a host of environmental problems, including increased retention of sediment and associated C. A small number of studies that measured greenhouse gas (GHG) emissions in dammed Asian rivers have reported contrasting impoundment effects: decreased GHG emissions from eutrophic reservoirs with enhanced primary production vs. increased emissions from the flooded vegetation and soils in the early years following dam construction or from the impounded reaches and downstream estuaries during the monsoon period. These contrasting results suggest that the rates of metabolic processes in the impounded and downstream reaches can vary greatly longitudinally over time as a

  6. Accounting for representativeness errors in the inversion of atmospheric constituent emissions: application to the retrieval of regional carbon monoxide fluxes

    Directory of Open Access Journals (Sweden)

    Mohammad Reza Koohkan

    2012-07-01

    Full Text Available A four-dimensional variational data assimilation system (4D-Var is developed to retrieve carbon monoxide (CO fluxes at regional scale, using an air quality network. The air quality stations that monitor CO are proximity stations located close to industrial, urban or traffic sources. The mismatch between the coarsely discretised Eulerian transport model and the observations, inferred to be mainly due to representativeness errors in this context, lead to a bias (average simulated concentrations minus observed concentrations of the same order of magnitude as the concentrations. 4D-Var leads to a mild improvement in the bias because it does not adequately handle the representativeness issue. For this reason, a simple statistical subgrid model is introduced and is coupled to 4D-Var. In addition to CO fluxes, the optimisation seeks to jointly retrieve influence coefficients, which quantify each station's representativeness. The method leads to a much better representation of the CO concentration variability, with a significant improvement of statistical indicators. The resulting increase in the total inventory estimate is close to the one obtained from remote sensing data assimilation. This methodology and experiments suggest that information useful at coarse scales can be better extracted from atmospheric constituent observations strongly impacted by representativeness errors.

  7. Carbon stocks and fluxes in the high latitudes: using site-levelbreak data to evaluate Earth system models

    DEFF Research Database (Denmark)

    Chadburn, S. E.; Krinner, G.; Porada, P.

    2017-01-01

    from northward expansion of vegetation under climate warming. Here we evaluate the simulation of tundra carbon stocks and fluxes in three land surface schemes that each form part of major Earth system models (JSBACH, Germany; JULES, UK; ORCHIDEE, France). We use a site-level approach in which...

  8. Carbon and Water Fluxes in a Drained Coastal Clearcut and a Pine Plantation in Eastern North Carolina

    Science.gov (United States)

    J. L. Deforest; Ge Sun; A. Noormets; J. Chen; Steve McNulty; M. Gavazzi; Devendra M. Amatya; R. W. Skaggs

    2006-01-01

    The effects of clear-cutting and cultivating for timber on ecosystem carbon and water fluxes were evaluated by comparative measurements of two drained coastal wetland systems in the North Carolina coastal plain. Measurements were conducted from January through September, 2005 in a recent clearcut (CC) of native hardwoods and a loblolly pine (Pinus tacda...

  9. Bioturbation and dissolved organic matter enhance contaminant fluxes from sediment treated with powdered and granular activated carbon

    NARCIS (Netherlands)

    Kupryianchyk, D.; Noori, A.; Rakowska, M.I.; Grotenhuis, J.T.C.; Koelmans, A.A.

    2013-01-01

    Sediment amendment with activated carbon (AC) is a promising technique for in situ sediment remediation. To date it is not clear whether this technique sufficiently reduces sediment-to-water fluxes of sediment-bound hydrophobic organic chemicals (HOCs) in the presence of bioturbators. Here, we

  10. Spatial variability and controls over biomass stocks, carbon fluxes, and resource-use efficiencies across forest ecosystems

    NARCIS (Netherlands)

    Fernández-Martínez, Marcos; Vicca, Sara; Janssens, Ivan A.; Luyssaert, Sebastiaan; Campioli, Matteo; Sardans, Jordi; Estiarte, Marc; Peñuelas, Josep

    2014-01-01

    Key message: Stand age, water availability, and the length of the warm period are the most influencing controls of forest structure, functioning, and efficiency. We aimed to discern the distribution and controls of plant biomass, carbon fluxes, and resource-use efficiencies of forest ecosystems

  11. Dissolved organic carbon in water fluxes of Eucalyptus grandis plantations in northeastern Entre Ríos Province, Argentina

    Science.gov (United States)

    Natalia Tesón; Víctor H Conzonno; Marcelo F Arturi; Jorge L Frangi

    2014-01-01

    Water fluxes in tree plantations and other ecosystems carry dissolved organic carbon (DOC) provided by atmospheric inputs, autotrophic and heterotrophic metabolisms and from the lysis of dead material. These compounds may be colorless or provide a yellow-to-brown color to water and may also absorb visible light due to the presence of chromophores in the chemical...

  12. 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

  13. Spatiotemporal variations in CO2 flux in a fringing reef simulated using a novel carbonate system dynamics model

    Science.gov (United States)

    Watanabe, A.; Yamamoto, T.; Nadaoka, K.; Maeda, Y.; Miyajima, T.; Tanaka, Y.; Blanco, A. C.

    2013-03-01

    A carbonate system dynamics (CSD) model was developed in a fringing reef on the east coast of Ishigaki Island, southwest Japan, by incorporating organic and inorganic carbon fluxes (photosynthesis and calcification), air-sea gas exchanges, and benthic cover of coral and seagrass into a three-dimensional hydrodynamic model. The CSD model could reproduce temporal variations in dissolved inorganic carbon (DIC) and total alkalinity in coral zones, but not in seagrass meadows. The poor reproduction in seagrass meadows can be attributed to significant contributions of submarine groundwater discharge as well as misclassification of remotely sensed megabenthos in this area. In comparison with offshore areas, the reef acted as a CO2 sink during the observation period when it was averaged over 24 h. The CSD model also indicated large spatiotemporal differences in the carbon dioxide (CO2) sink/source, possibly related to hydrodynamic features such as effective offshore seawater exchange and neap/spring tidal variation. This suggests that the data obtained from a single point observation may lead to misinterpretation of the overall trend and thus should be carefully considered. The model analysis also showed that the advective flux of DIC from neighboring grids is several times greater than local biological flux of DIC and is three orders of magnitude greater than the air-sea gas flux at the coral zone. Sensitivity tests in which coral or seagrass covers were altered revealed that the CO2 sink potential was much more sensitive to changes in coral cover than seagrass cover.

  14. The contribution of various types of settling particles to the flux of organic carbon in the Gulf of St. Lawrence

    Science.gov (United States)

    Romero-Ibarra, Nancy; Silverberg, Norman

    2011-10-01

    The contents of 31 samples from free-drifting sediment traps deployed in the Gulf of St. Lawrence (GSL) were analyzed for the individual contribution of the different types of particles encountered to the total particulate organic carbon (POC) flux. Two trap models were used in 1993-1994: small traps at 50 m depth and large traps at 50 and 150 m. Total POC fluxes averaged 42 mg C m -2 d -1 for the more reliable large trap and 149 mg C m -2 d -1 for the small trap. The POC fluxes were attributed to different classes of particles based upon microscopically determined particle dimensions and carbon/volume algorithms available in the literature. Fecal pellets, followed by phytoplankton, were the major attributable components, with important contributions by microzooplankton, particularly during the summer of 1994. The mean fluxes for pellets (6 and 60 mg C m -2 d -1, for the large and small traps, respectively) and phytoplankton (3.2 and 42.9 mg C m -2 d -1) were in the range of those encountered in other areas of moderate primary productivity. Mean zooplankton carbon fluxes (1.8 and 8.5 mg C m -2 d -1, respectively), however, reflect higher than average zooplankton abundances in the GSL. The C fluxes of specific algal groups confirmed the existence of three trophic regimes previously identified from water column studies and numeric cell fluxes: (1) a period when diatoms were dominant during the spring, (2) a longer interval, which was dominated by dinoflagellates at most others times of the year, and (3) a period of transition during summer. Carbon of animal origin dominated the attributable flux, including an important fraction associated with heterotrophic dinoflagellates. The contribution of marine snow to the total flux (estimated as the difference between the total POC flux and the sum of the attributed components) frequently amounted to more than 60%. The true importance of marine snow remains uncertain, however, because the errors associated with each of the

  15. Contribution of trees and grasses to ecosystem fluxes of water, carbon, and energy throughout the seasons under different nutrient availability

    Science.gov (United States)

    El-Madany, T. S.; Migliavacca, M.; Perez-Priego, O.; Luo, Y.; Moreno, G.; Carrara, A.; Kolle, O.; Reichstein, M.

    2017-12-01

    In semi-arid savanna type ecosystems, the carbon and water cycle are closely related to each other. Water availability is the main driver for the development and phenology of the vegetation, especially for annual plants. Depending on tree density, nutrient availability and species the contribution of the tree- and the herbaceous layer to ecosystem fluxes can vary substantially. We present data from an ecosystem scale nutrient manipulation experiment within a Mediterranean savanna type ecosystem which is used for cattle. The footprint areas of two out of three ecosystem eddy co-variance (EC) towers were fertilized with nitrogen (NT) and nitrogen plus phosphorous (NPT) while the third one served as the control tower (CT). At each ecosystem EC-tower an additional herbaceous layer tower was installed that only sampled fluxes from the herbaceous layer. Under certain assumptions flux differences between the ecosystem EC and the herbaceous layer EC systems can be considered as the contribution of the trees to the ecosystem fluxes. Based on phenology of the herbaceous layer estimated through green-chromatic-coordinates from digital imagery the year was separated into spring, senescence, regreening, and winter. The focus of the analysis is (i) the evaluation of the method and how it works throughout the different seasons and (ii) the quantification of the contribution of trees and grasses to ecosystem fluxes of water, carbon, and energy under different environmental conditions and nutrient stoichiometry. The contribution of the trees to total ecosystem fluxes is variable in time. Especially, during the beginning of the senescence period high evapotranspiration rates and largest carbon uptake are measured while the contribution to sensible heat fluxes is largest during the end of the summer. During the regreening and winter the contribution of ET is relatively constant around 0.25 mm d-1. During the peak of the greenness ET and carbon flux of the herbaceous EC tower are

  16. Changes in ecosystem carbon pool and soil CO2 flux following post-mine reclamation in dry tropical environment, India.

    Science.gov (United States)

    Ahirwal, Jitendra; Maiti, Subodh Kumar; Singh, Ashok Kumar

    2017-04-01

    Open strip mining of coal results in loss of natural carbon (C) sink and increased emission of CO 2 into the atmosphere. A field study was carried out at five revegetated coal mine lands (7, 8, 9, 10 and 11years) to assess the impact of the reclamation on soil properties, accretion of soil organic C (SOC) and nitrogen (N) stock, changes in ecosystem C pool and soil CO 2 flux. We estimated the presence of C in the tree biomass, soils, litter and microbial biomass to determine the total C sequestration potential of the post mining reclaimed land. To determine the C sequestration of the reclaimed ecosystem, soil CO 2 flux was measured along with the CO 2 sequestration. Reclaimed mine soil (RMS) fertility increased along the age of reclamation and decreases with the soil depths that may be attributed to the change in mine soils characteristics and plant growth. After 7 to 11years of reclamation, SOC and N stocks increased two times. SOC sequestration (1.71MgCha -1 year -1 ) and total ecosystem C pool (3.72MgCha -1 year -1 ) increased with the age of reclamation (CO 2 equivalent: 13.63MgCO 2 ha -1 year -1 ). After 11years of reclamation, soil CO 2 flux (2.36±0.95μmolm -2 s -1 ) was found four times higher than the natural forest soils (Shorea robusta Gaertn. F). The study shows that reclaimed mine land can act as a source/sink of CO 2 in the terrestrial ecosystem and plays an important role to offset increased emission of CO 2 in the atmosphere. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Modifying the Soil and Water Assessment Tool to simulate cropland carbon flux: Model development and initial evaluation

    International Nuclear Information System (INIS)

    Zhang, Xuesong; Izaurralde, R. César; Arnold, Jeffrey G.; Williams, Jimmy R.; Srinivasan, Raghavan

    2013-01-01

    Climate change is one of the most compelling modern issues and has important implications for almost every aspect of natural and human systems. The Soil and Water Assessment Tool (SWAT) model has been applied worldwide to support sustainable land and water management in a changing climate. However, the inadequacies of the existing carbon algorithm in SWAT limit its application in assessing impacts of human activities on CO 2 emission, one important source of greenhouse gasses (GHGs) that traps heat in the earth system and results in global warming. In this research, we incorporate a revised version of the CENTURY carbon model into SWAT to describe dynamics of soil organic matter (SOM)-residue and simulate land–atmosphere carbon exchange. We test this new SWAT-C model with daily eddy covariance (EC) observations of net ecosystem exchange (NEE) and evapotranspiration (ET) and annual crop yield at six sites across the U.S. Midwest. Results show that SWAT-C simulates well multi-year average NEE and ET across the spatially distributed sites and capture the majority of temporal variation of these two variables at a daily time scale at each site. Our analyses also reveal that performance of SWAT-C is influenced by multiple factors, such as crop management practices (irrigated vs. rainfed), completeness and accuracy of input data, crop species, and initialization of state variables. Overall, the new SWAT-C demonstrates favorable performance for simulating land–atmosphere carbon exchange across agricultural sites with different soils, climate, and management practices. SWAT-C is expected to serve as a useful tool for including carbon flux into consideration in sustainable watershed management under a changing climate. We also note that extensive assessment of SWAT-C with field observations is required for further improving the model and understanding potential uncertainties of applying it across large regions with complex landscapes. - Highlights: • Expanding the SWAT

  18. Modifying the Soil and Water Assessment Tool to simulate cropland carbon flux: Model development and initial evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xuesong; Izaurralde, R. César [Joint Global Change Research Institute, Pacific Northwest National Laboratory and University of Maryland, College Park, MD 20740 (United States); Arnold, Jeffrey G. [Grassland, Soil and Water Research Laboratory USDA-ARS, Temple, TX 76502 (United States); Williams, Jimmy R. [Blackland Research and Extension Center, AgriLIFE Research, 720 E. Blackland Road, Temple, TX 76502 (United States); Srinivasan, Raghavan [Spatial Sciences Laboratory in the Department of Ecosystem Science and Management, Texas A and M University, College Stations, TX 77845 (United States)

    2013-10-01

    Climate change is one of the most compelling modern issues and has important implications for almost every aspect of natural and human systems. The Soil and Water Assessment Tool (SWAT) model has been applied worldwide to support sustainable land and water management in a changing climate. However, the inadequacies of the existing carbon algorithm in SWAT limit its application in assessing impacts of human activities on CO{sub 2} emission, one important source of greenhouse gasses (GHGs) that traps heat in the earth system and results in global warming. In this research, we incorporate a revised version of the CENTURY carbon model into SWAT to describe dynamics of soil organic matter (SOM)-residue and simulate land–atmosphere carbon exchange. We test this new SWAT-C model with daily eddy covariance (EC) observations of net ecosystem exchange (NEE) and evapotranspiration (ET) and annual crop yield at six sites across the U.S. Midwest. Results show that SWAT-C simulates well multi-year average NEE and ET across the spatially distributed sites and capture the majority of temporal variation of these two variables at a daily time scale at each site. Our analyses also reveal that performance of SWAT-C is influenced by multiple factors, such as crop management practices (irrigated vs. rainfed), completeness and accuracy of input data, crop species, and initialization of state variables. Overall, the new SWAT-C demonstrates favorable performance for simulating land–atmosphere carbon exchange across agricultural sites with different soils, climate, and management practices. SWAT-C is expected to serve as a useful tool for including carbon flux into consideration in sustainable watershed management under a changing climate. We also note that extensive assessment of SWAT-C with field observations is required for further improving the model and understanding potential uncertainties of applying it across large regions with complex landscapes. - Highlights: • Expanding the

  19. 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.

  20. Experimental results on performance improvement of doped carbon-base materials

    International Nuclear Information System (INIS)

    Xu Zengyu

    2002-01-01

    Carbon-base materials is one of candidate plasma facing materials and have been widely used in current tokamak facilities in the world. But some defect properties are presented on high yield of chemical sputtering , high yield of radiation enhancement sublimate (RES), cracking after heat flux and so on. It can be improved by doped some little other elements into the carbon-base materials, such as boron, silicon, titanium and so on. Experimental results indicate that it is feasible and successful to improve thermo-physics and chemical properties of carbon-base materials by multi-element doped. Doped 12 % silicon can strained RES and chemical sputtering yield do not changed. It is the same level of chemical sputtering yield for B 4 C from 3 % to 10 % , but their resistance thermal shock properties ability increases with B 4 C increases

  1. High energy flux thermo-mechanical test of 1D-carbon-carbon fibre composite prototypes for the SPIDER diagnostic calorimeter

    International Nuclear Information System (INIS)

    De Muri, M.; Pasqualotto, R.; Dalla Palma, M.; Cervaro, V.; Fasolo, D.; Franchin, L.; Tollin, M.; Serianni, G.; Cavallin, T.; Greuner, H.; Böswirth, B.

    2014-01-01

    Operation of the thermonuclear fusion experiment ITER requires additional heating via injection of neutral beams from accelerated negative ions. In the SPIDER test facility, under construction in Padova, the production of negative ions will be studied and optimised. STRIKE (Short-Time Retractable Instrumented Kalorimeter Experiment) is a diagnostic used to characterise the SPIDER beam during short pulse operation (several seconds) to verify if the beam meets the ITER requirements about the maximum allowed beam non-uniformity (below ±10%). The major components of STRIKE are 16 1D-CFC (Carbon-Carbon Fibre Composite) tiles, observed at the rear side by a thermal camera. This contribution gives an overview of some tests under high energy particle flux, aimed at verifying the thermo-mechanical behaviour of several CFC prototype tiles. The tests were performed in the GLADIS facility at IPP (Max-Plank-Institut für Plasmaphysik), Garching. Dedicated linear and nonlinear simulations were carried out to interpret the experiments and a comparison of the experimental data with the simulation results is presented. The results of some morphological and structural studies on the material after exposure to the GLADIS beam are also given

  2. The surface energy, water, carbon flux and their intercorrelated seasonality in a global climate-vegetation coupled model

    International Nuclear Information System (INIS)

    Li Dan.; Jinjun Ji

    2007-01-01

    The sensible and latent heat fluxes, representatives of the physical exchange processes of energy and water between land and air, are the two crucial variables controlling the surface energy partitioning related to temperature and humidity. The net primary production (NPP), the major carbon flux exchange between vegetation and atmosphere, is of great importance for the terrestrial ecosystem carbon cycle. The fluxes are simulated by a two-way coupled model, Atmosphere-Vegetation Interaction Model-Global Ocean-Atmosphere-Land System Model (AVIM-GOALS) in which the surface physical and physiological processes are coupled with general circulation model (GCM), and the global spatial and temporal variation of the fluxes is studied. The simulated terrestrial surface physical fluxes are consistent with the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis (ERA40) in the global distribution, but the magnitudes are generally 20-40 W/m 2 underestimated. The annual NPP agrees well with the International Geosphere Biosphere Programme (IGBP) NPP data except for the lower value in northern high latitudes. The surface physical fluxes, leaf area index (LAI) and NPP of the global mid-latitudes, especially between 30 deg N-50 deg N, show great variation in annual oscillation amplitudes. And all physical and biological fields in northern mid-latitudes have the largest seasonality with a high statistical significance of 99.9%. The seasonality of surface physical fluxes, LAI and NPP are highly correlated with each other. The meridional three-peak pattern of seasonal change emerges in northern mid-latitudes, which indicates the interaction of topographical gradient variation of surface fluxes and vegetation phenology on these three latitudinal belts

  3. Hydrocarbon and Carbon Dioxide Fluxes from Natural Gas Well Pad Soils and Surrounding Soils in Eastern Utah.

    Science.gov (United States)

    Lyman, Seth N; Watkins, Cody; Jones, Colleen P; Mansfield, Marc L; McKinley, Michael; Kenney, Donna; Evans, Jordan

    2017-10-17

    We measured fluxes of methane, nonmethane hydrocarbons, and carbon dioxide from natural gas well pad soils and from nearby undisturbed soils in eastern Utah. Methane fluxes varied from less than zero to more than 38 g m -2 h -1 . Fluxes from well pad soils were almost always greater than from undisturbed soils. Fluxes were greater from locations with higher concentrations of total combustible gas in soil and were inversely correlated with distance from well heads. Several lines of evidence show that the majority of emission fluxes (about 70%) were primarily due to subsurface sources of raw gas that migrated to the atmosphere, with the remainder likely caused primarily by re-emission of spilled liquid hydrocarbons. Total hydrocarbon fluxes during summer were only 39 (16, 97)% as high as during winter, likely because soil bacteria consumed the majority of hydrocarbons during summer months. We estimate that natural gas well pad soils account for 4.6 × 10 -4 (1.6 × 10 -4 , 1.6 × 10 -3 )% of total emissions of hydrocarbons from the oil and gas industry in Utah's Uinta Basin. Our undisturbed soil flux measurements were not adequate to quantify rates of natural hydrocarbon seepage in the Uinta Basin.

  4. Estimating daily forest carbon fluxes using a combination of ground and remotely sensed data

    Science.gov (United States)

    Chirici, Gherardo; Chiesi, Marta; Corona, Piermaria; Salvati, Riccardo; Papale, Dario; Fibbi, Luca; Sirca, Costantino; Spano, Donatella; Duce, Pierpaolo; Marras, Serena; Matteucci, Giorgio; Cescatti, Alessandro; Maselli, Fabio

    2016-02-01

    Several studies have demonstrated that Monteith's approach can efficiently predict forest gross primary production (GPP), while the modeling of net ecosystem production (NEP) is more critical, requiring the additional simulation of forest respirations. The NEP of different forest ecosystems in Italy was currently simulated by the use of a remote sensing driven parametric model (modified C-Fix) and a biogeochemical model (BIOME-BGC). The outputs of the two models, which simulate forests in quasi-equilibrium conditions, are combined to estimate the carbon fluxes of actual conditions using information regarding the existing woody biomass. The estimates derived from the methodology have been tested against daily reference GPP and NEP data collected through the eddy correlation technique at five study sites in Italy. The first test concerned the theoretical validity of the simulation approach at both annual and daily time scales and was performed using optimal model drivers (i.e., collected or calibrated over the site measurements). Next, the test was repeated to assess the operational applicability of the methodology, which was driven by spatially extended data sets (i.e., data derived from existing wall-to-wall digital maps). A good estimation accuracy was generally obtained for GPP and NEP when using optimal model drivers. The use of spatially extended data sets worsens the accuracy to a varying degree, which is properly characterized. The model drivers with the most influence on the flux modeling strategy are, in increasing order of importance, forest type, soil features, meteorology, and forest woody biomass (growing stock volume).

  5. Parameter sensitivity and uncertainty of the forest carbon flux model FORUG : a Monte Carlo analysis

    Energy Technology Data Exchange (ETDEWEB)

    Verbeeck, H.; Samson, R.; Lemeur, R. [Ghent Univ., Ghent (Belgium). Laboratory of Plant Ecology; Verdonck, F. [Ghent Univ., Ghent (Belgium). Dept. of Applied Mathematics, Biometrics and Process Control

    2006-06-15

    The FORUG model is a multi-layer process-based model that simulates carbon dioxide (CO{sub 2}) and water exchange between forest stands and the atmosphere. The main model outputs are net ecosystem exchange (NEE), total ecosystem respiration (TER), gross primary production (GPP) and evapotranspiration. This study used a sensitivity analysis to identify the parameters contributing to NEE uncertainty in the FORUG model. The aim was to determine if it is necessary to estimate the uncertainty of all parameters of a model to determine overall output uncertainty. Data used in the study were the meteorological and flux data of beech trees in Hesse. The Monte Carlo method was used to rank sensitivity and uncertainty parameters in combination with a multiple linear regression. Simulations were run in which parameters were assigned probability distributions and the effect of variance in the parameters on the output distribution was assessed. The uncertainty of the output for NEE was estimated. Based on the arbitrary uncertainty of 10 key parameters, a standard deviation of 0.88 Mg C per year per NEE was found, which was equal to 24 per cent of the mean value of NEE. The sensitivity analysis showed that the overall output uncertainty of the FORUG model could be determined by accounting for only a few key parameters, which were identified as corresponding to critical parameters in the literature. It was concluded that the 10 most important parameters determined more than 90 per cent of the output uncertainty. High ranking parameters included soil respiration; photosynthesis; and crown architecture. It was concluded that the Monte Carlo technique is a useful tool for ranking the uncertainty of parameters of process-based forest flux models. 48 refs., 2 tabs., 2 figs.

  6. An incubation system to trace carbon fluxes in soil - First experimental

    Science.gov (United States)

    Thiessen*, Stefany; Gleixner, Gerd; Reichstein, Markus

    2010-05-01

    Soils contain the largest carbon pool in terrestrial ecosystems and it is widely assumed that a considerable fraction of this pool might be mobilized by global warming. Numerous investigations have proven that soil respiration is a mixture of several source, like root rhizosphere and soil organic matter (SOM) degradation. However, little is still known about soil carbon dynamics and the influence of microbes on this process. We developed an incubation system to perform multitracer experiments to quantify the contribution of microorganisms to carbon turnover from different carbon sources. A natural 13C label was used to mark carbon sources. The old carbon in the SOM held a depleted 13C3 signal and newly added C was enriched in 13C4. Accordingly, in the experiment we quantified the relative respiration of carbon from added sugars and soil organic matter by microbial groups, with additional application of fungicide (cycloheximide). A root free arable soil was divided into three sets, all with depleted C3 soil, but varied in terms of the added material: one with C4 glucose, a second with C4 glucose combined with fungicide and the last one with water application only, as control. To characterize microbial communities and estimate microbial biomass we extract phospholipid fatty acids (PLFA). Furthermore, by measuring the isotopic ratio of the PLFA it was also possible to identify microorganisms that metabolised the traced material. Preliminary results showed that the glucose application stimulated microbial growth in the beginning, but afterwards the microbial biomass decreased again over time. However, a change in the microbial community composition could not be observed, regardless to the kind of added material. Nevertheless, the respiration response slowed down after the fungicide application, and a second respiration pulse was induced by this application. This was probably due to reactivation of the fungi, after the effect of the fungicide expired.

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

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    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

  8. A Remote Sensing-based Characterization of the Urban Heat Island and its Implications for Modeled Estimates of Urban Biogenic Carbon Fluxes in Boston, MA.

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    Wang, J.; Friedl, M. A.; Hutyra, L.; Hardiman, B. S.

    2015-12-01

    Urban land use occupies a small but critical proportion of global land area for the carbon cycle, and in the coming decades, urban land area is expected to nearly double. Conversion of natural land cover to urban land cover imposes myriad ecological effects, including increased land surface and air temperatures via the urban heat island effect. In this study, we characterize the seasonal and spatial characteristics of the urban heat island over Boston, MA and estimate its consequences on biogenic carbon fluxes with a remote sensing-based model. Using a 12-year time series of emissivity- and atmospherically-corrected land surface temperatures from Landsat TM and ETM+ imagery, we find a high degree of spatial heterogeneity and consistent seasonal patterns in the thermal properties of Boston, controlled mainly by variations in vegetative cover. Field measurements of surface air temperature across an urbanization gradient show season- and vegetation-dependent patterns consistent with those observed in the Landsat data. With a fused data set that combines surface air temperature, MODIS, and Landsat observations, we modify and run the Vegetation Photosynthesis and Respiration Model (VPRM) to explore 1) how elevated temperatures affect diurnal and seasonal patterns of hourly urban biogenic carbon fluxes in Massachusetts in 2013 and 2014 and 2) to what extent these fluxes follow spatial patterns found in the urban heat island. Model modifications simulate the ecological effects of urbanization, including empirical adjustments to reanalysis-driven air temperatures (up to 5 K) and ecosystem respiration reduced by impervious surface area. Model results reveal spatio-temporal patterns consistent with strong land use and vegetation cover controls on biogenic carbon fluxes, with non-trivial biogenic annual net ecosystem exchange occurring in urban and suburban areas (up to -2.5 MgC/ha/yr). We specifically consider the feedbacks between Boston's urban heat island and landscape

  9. Carbon dioxide fluxes from a degraded woodland in West Africa and their responses to main environmental factors.

    Science.gov (United States)

    Ago, Expedit Evariste; Serça, Dominique; Agbossou, Euloge Kossi; Galle, Sylvie; Aubinet, Marc

    2015-12-01

    In West Africa, natural ecosystems such as woodlands are the main source for energy, building poles and livestock fodder. They probably behave like net carbon sinks, but there are only few studies focusing on their carbon exchange with the atmosphere. Here, we have analyzed CO 2 fluxes measured for 17 months by an eddy-covariance system over a degraded woodland in northern Benin. Specially, temporal evolution of the fluxes and their relationships with the main environmental factors were investigated between the seasons. This study shows a clear response of CO 2 absorption to photosynthetic photon flux density (Q p ), but it varies according to the seasons. After a significant and long dry period, the ecosystem respiration (R) has increased immediately to the first significant rains. No clear dependency of ecosystem respiration on temperature has been observed. The degraded woodlands are probably the "carbon neutral" at the annual scale. The net ecosystem exchange (NEE) was negative during wet season and positive during dry season, and its annual accumulation was equal to +29 ± 16 g C m -2 . The ecosystem appears to be more efficient in the morning and during the wet season than in the afternoon and during the dry season. This study shows diurnal and seasonal contrasted variations in the CO 2 fluxes in relation to the alternation between dry and wet seasons. The Nangatchori site is close to the equilibrium state according to its carbon exchanges with the atmosphere. The length of the observation period was too short to justify the hypothesis about the "carbon neutrality" of the degraded woodlands at the annual scale in West Africa. Besides, the annual net ecosystem exchange depends on the intensity of disturbances due to the site management system. Further research works are needed to define a woodland management policy that might keep these ecosystems as carbon sinks.

  10. Carbon stocks and fluxes in tropical lowland dipterocarp rainforests in Sabah, Malaysian Borneo.

    Directory of Open Access Journals (Sweden)

    Philippe Saner

    Full Text Available Deforestation in the tropics is an important source of carbon C release to the atmosphere. To provide a sound scientific base for efforts taken to reduce emissions from deforestation and degradation (REDD+ good estimates of C stocks and fluxes are important. We present components of the C balance for selectively logged lowland tropical dipterocarp rainforest in the Malua Forest Reserve of Sabah, Malaysian Borneo. Total organic C in this area was 167.9 Mg C ha⁻¹±3.8 (SD, including: Total aboveground (TAGC: 55%; 91.9 Mg C ha⁻¹±2.9 SEM and belowground carbon in trees (TBGC: 10%; 16.5 Mg C ha⁻¹±0.5 SEM, deadwood (8%; 13.2 Mg C ha⁻¹±3.5 SEM and soil organic matter (SOM: 24%; 39.6 Mg C ha⁻¹±0.9 SEM, understory vegetation (3%; 5.1 Mg C ha⁻¹±1.7 SEM, standing litter (<1%; 0.7 Mg C ha⁻¹±0.1 SEM and fine root biomass (<1%; 0.9 Mg C ha⁻¹±0.1 SEM. Fluxes included litterfall, a proxy for leaf net primary productivity (4.9 Mg C ha⁻¹ yr⁻¹±0.1 SEM, and soil respiration, a measure for heterotrophic ecosystem respiration (28.6 Mg C ha⁻¹ yr⁻¹±1.2 SEM. The missing estimates necessary to close the C balance are wood net primary productivity and autotrophic respiration.Twenty-two years after logging TAGC stocks were 28% lower compared to unlogged forest (128 Mg C ha⁻¹±13.4 SEM; a combined weighted average mean reduction due to selective logging of -57.8 Mg C ha⁻¹ (with 95% CI -75.5 to -40.2. Based on the findings we conclude that selective logging decreased the dipterocarp stock by 55-66%. Silvicultural treatments may have the potential to accelerate the recovery of dipterocarp C stocks to pre-logging levels.

  11. Observing Carbon Dioxide Fluxes on a Corn Field and a Native Savanna in the Colombian Orinoco River Region Using Eddy Covariance

    Science.gov (United States)

    Morales-Rincon, L. A.; Jimenez-Pizarro, R.; Rodríguez, N.

    2016-12-01

    The Orinoco River basin is expected to become Colombia's largest farming belt in the near future. Agriculture and land use change are the most important greenhouse gas (GHG) source in Colombia and one of the most important globally. At the same time, agriculture is one of the few economic sectors that is also able to act as a sink, e.g. through soil carbon storage. Emissions are largely determined by agricultural practices, thus practice identification and C flux monitoring are of paramount importance for mitigation alternative identification. During second semester of 2015, we measured CO2 fluxes over a commercial corn filed the Colombian Orinoco River Region using enclosed-path eddy covariance. The plot behaved as a CO2 sink during crop development. We found that inter-crop activities played a key role in defining whether the area acted as a net source or sink. Quantifying C fluxes at under local soil and meteorological conditions provides new high quality scientific information, which could be incorporated into a wider evaluation of agroindustry process, e.g. through the C footprint. We will also present ongoing carbon flux measurements in a native savanna and will discuss on the possibility of extrapolating our result to wider areas using process based models.

  12. Carbon stocks and fluxes in the high latitudes: using site-level data to evaluate Earth system models

    Science.gov (United States)

    Chadburn, Sarah E.; Krinner, Gerhard; Porada, Philipp; Bartsch, Annett; Beer, Christian; Belelli Marchesini, Luca; Boike, Julia; Ekici, Altug; Elberling, Bo; Friborg, Thomas; Hugelius, Gustaf; Johansson, Margareta; Kuhry, Peter; Kutzbach, Lars; Langer, Moritz; Lund, Magnus; Parmentier, Frans-Jan W.; Peng, Shushi; Van Huissteden, Ko; Wang, Tao; Westermann, Sebastian; Zhu, Dan; Burke, Eleanor J.

    2017-11-01

    It is important that climate models can accurately simulate the terrestrial carbon cycle in the Arctic due to the large and potentially labile carbon stocks found in permafrost-affected environments, which can lead to a positive climate feedback, along with the possibility of future carbon sinks from northward expansion of vegetation under climate warming. Here we evaluate the simulation of tundra carbon stocks and fluxes in three land surface schemes that each form part of major Earth system models (JSBACH, Germany; JULES, UK; ORCHIDEE, France). We use a site-level approach in which comprehensive, high-frequency datasets allow us to disentangle the importance of different processes. The models have improved physical permafrost processes and there is a reasonable correspondence between the simulated and measured physical variables, including soil temperature, soil moisture and snow. We show that if the models simulate the correct leaf area index (LAI), the standard C3 photosynthesis schemes produce the correct order of magnitude of carbon fluxes. Therefore, simulating the correct LAI is one of the first priorities. LAI depends quite strongly on climatic variables alone, as we see by the fact that the dynamic vegetation model can simulate most of the differences in LAI between sites, based almost entirely on climate inputs. However, we also identify an influence from nutrient limitation as the LAI becomes too large at some of the more nutrient-limited sites. We conclude that including moss as well as vascular plants is of primary importance to the carbon budget, as moss contributes a large fraction to the seasonal CO2 flux in nutrient-limited conditions. Moss photosynthetic activity can be strongly influenced by the moisture content of moss, and the carbon uptake can be significantly different from vascular plants with a similar LAI. The soil carbon stocks depend strongly on the rate of input of carbon from the vegetation to the soil, and our analysis suggests that

  13. Thermal performance analysis of a flat heat pipe working with carbon nanotube-water nanofluid for cooling of a high heat flux heater

    Science.gov (United States)

    Arya, A.; Sarafraz, M. M.; Shahmiri, S.; Madani, S. A. H.; Nikkhah, V.; Nakhjavani, S. M.

    2018-04-01

    Experimental investigation on the thermal performance of a flat heat pipe working with carbon nanotube nanofluid is conducted. It is used for cooling a heater working at high heat flux conditions up to 190 kW/m2. The heat pipe is fabricated from aluminium and is equipped with rectangular fin for efficient cooling of condenser section. Inside the heat pipe, a screen mesh was inserted as a wick structure to facilitate the capillary action of working fluid. Influence of different operating parameters such as heat flux, mass concentration of carbon nanotubes and filling ratio of working fluid on thermal performance of heat pipe and its thermal resistance are investigated. Results showed that with an increase in heat flux, the heat transfer coefficient in evaporator section of the heat pipe increases. For filling ratio, however, there is an optimum value, which was 0.8 for the test heat pipe. In addition, CNT/water enhanced the heat transfer coefficient up to 40% over the deionized water. Carbon nanotubes intensified the thermal performance of wick structure by creating a fouling layer on screen mesh structure, which changes the contact angle of liquid with the surface, intensifying the capillary forces.

  14. London atmospheric Hydrogen and Carbon Monoxide: 12 year record, fluxes, and diurnal studies.

    Science.gov (United States)

    Lanoisellé, M.; Fisher, R. E.; Sriskantharajah, S.; Lowry, D.; Fowler, C. M. R.; Nisbet, E. G.

    2009-04-01

    Atmospheric hydrogen (H2) and carbon monoxide (CO) have been measured at the Royal Holloway site, 30km WSW of London, for 12 years. This site receives air that has passed over London when there are easterly winds and cleaner, background air when the wind comes from the SW. H2 and CO mixing ratios are measured continuously at 30 minute intervals on a Trace Analytical Reduction Gas Detector coupled to a HP5890 GC since September 1996, and on a Peak Performer I (or PP1) since July 2007 at 5 minute intervals. Both instruments use 2 1/8" packed columns in series: a Unibeads 1S and a Molecular Sieve 5A. The PP1 detector (Reduced Compound Photometer) is an updated version of the old RGD2, and both use zero air as the carrier gas. CO is calibrated twice a month against NOAA-CMDL standards (mixing ratios range: 186 to 300 ppb). H2 was uncalibrated until 2006, but is now calibrated monthly against internal standards (range 530 to 750 ppb) measured at MPI-Jena as part of the Eurohydros project. A linearity correction is applied to each instrument, based on the standard measurements. A secondary standard is measured before each sample on the GC-RGD and another one is measured 4 to 6 times in a row twice a day on the PP1. A target gas is measured daily on both instruments since September 2008. The secondary standards and the target gas are dry ambient air in 70L stainless steel tanks filled to a pressure of 8 bars. Comparison of results from the two instruments suggests that for the most part the data are in good agreement, but an interlaboratory round robin comparison exercise for the Eurohydros project showed that the RGD is not linear at low values of CO. This is particularly noticeable for CO levels below 150 ppb. The long-term record of CO at Royal Holloway shows a significant decline since the start of the record: the annual mean CO mixing ratio in 2008 was three times lower than in 1997. Flux calculations, by ratio against 222Rn, CH4 and CO2, suggest CO emissions

  15. Carbon Stocks and Fluxes in Tropical Lowland Dipterocarp Rainforests in Sabah, Malaysian Borneo

    Science.gov (United States)

    Saner, Philippe; Loh, Yen Yee; Ong, Robert C.; Hector, Andy

    2012-01-01

    Deforestation in the tropics is an important source of carbon C release to the atmosphere. To provide a sound scientific base for efforts taken to reduce emissions from deforestation and degradation (REDD+) good estimates of C stocks and fluxes are important. We present components of the C balance for selectively logged lowland tropical dipterocarp rainforest in the Malua Forest Reserve of Sabah, Malaysian Borneo. Total organic C in this area was 167.9 Mg C ha−1±3.8 (SD), including: Total aboveground (TAGC: 55%; 91.9 Mg C ha−1±2.9 SEM) and belowground carbon in trees (TBGC: 10%; 16.5 Mg C ha−1±0.5 SEM), deadwood (8%; 13.2 Mg C ha−1±3.5 SEM) and soil organic matter (SOM: 24%; 39.6 Mg C ha−1±0.9 SEM), understory vegetation (3%; 5.1 Mg C ha−1±1.7 SEM), standing litter (logging TAGC stocks were 28% lower compared to unlogged forest (128 Mg C ha−1±13.4 SEM); a combined weighted average mean reduction due to selective logging of −57.8 Mg C ha−1 (with 95% CI −75.5 to −40.2). Based on the findings we conclude that selective logging decreased the dipterocarp stock by 55–66%. Silvicultural treatments may have the potential to accelerate the recovery of dipterocarp C stocks to pre-logging levels. PMID:22235319

  16. Sinking rates and ballast composition of particles in the Atlantic Ocean: implications for the organic carbon fluxes to the deep ocean

    Science.gov (United States)

    Fischer, G.; Karakaş, G.

    2009-01-01

    The flux of materials to the deep sea is dominated by larger, organic-rich particles with sinking rates varying between a few meters and several hundred meters per day. Mineral ballast may regulate the transfer of organic matter and other components by determining the sinking rates, e.g. via particle density. We calculated particle sinking rates from mass flux patterns and alkenone measurements applying the results of sediment trap experiments from the Atlantic Ocean. We have indication for higher particle sinking rates in carbonate-dominated production systems when considering both regional and seasonal data. During a summer coccolithophorid bloom in the Cape Blanc coastal upwelling off Mauritania, particle sinking rates reached almost 570 m per day, most probably due the fast sedimentation of densely packed zooplankton fecal pellets, which transport high amounts of organic carbon associated with coccoliths to the deep ocean despite rather low production. During the recurring winter-spring blooms off NW Africa and in opal-rich production systems of the Southern Ocean, sinking rates of larger particles, most probably diatom aggregates, showed a tendency to lower values. However, there is no straightforward relationship between carbonate content and particle sinking rates. This could be due to the unknown composition of carbonate and/or the influence of particle size and shape on sinking rates. It also remains noticeable that the highest sinking rates occurred in dust-rich ocean regions off NW Africa, but this issue deserves further detailed field and laboratory investigations. We obtained increasing sinking rates with depth. By using a seven-compartment biogeochemical model, it was shown that the deep ocean organic carbon flux at a mesotrophic sediment trap site off Cape Blanc can be captured fairly well using seasonal variable particle sinking rates. Our model provides a total organic carbon flux of 0.29 Tg per year down to 3000 m off the NW African upwelling

  17. Multi-model analysis of terrestrial carbon cycles in Japan: limitations and implications of model calibration using eddy flux observations

    Directory of Open Access Journals (Sweden)

    K. Ichii

    2010-07-01

    Full Text Available Terrestrial biosphere models show large differences when simulating carbon and water cycles, and reducing these differences is a priority for developing more accurate estimates of the condition of terrestrial ecosystems and future climate change. To reduce uncertainties and improve the understanding of their carbon budgets, we investigated the utility of the eddy flux datasets to improve model simulations and reduce variabilities among multi-model outputs of terrestrial biosphere models in Japan. Using 9 terrestrial biosphere models (Support Vector Machine – based regressions, TOPS, CASA, VISIT, Biome-BGC, DAYCENT, SEIB, LPJ, and TRIFFID, we conducted two simulations: (1 point simulations at four eddy flux sites in Japan and (2 spatial simulations for Japan with a default model (based on original settings and a modified model (based on model parameter tuning using eddy flux data. Generally, models using default model settings showed large deviations in model outputs from observation with large model-by-model variability. However, after we calibrated the model parameters using eddy flux data (GPP, RE and NEP, most models successfully simulated seasonal variations in the carbon cycle, with less variability among models. We also found that interannual variations in the carbon cycle are mostly consistent among models and observations. Spatial analysis also showed a large reduction in the variability among model outputs. This study demonstrated that careful validation and calibration of models with available eddy flux data reduced model-by-model differences. Yet, site history, analysis of model structure changes, and more objective procedure of model calibration should be included in the further analysis.

  18. Multi-model analysis of terrestrial carbon cycles in Japan: limitations and implications of model calibration using eddy flux observations

    Science.gov (United States)

    Ichii, K.; Suzuki, T.; Kato, T.; Ito, A.; Hajima, T.; Ueyama, M.; Sasai, T.; Hirata, R.; Saigusa, N.; Ohtani, Y.; Takagi, K.

    2010-07-01

    Terrestrial biosphere models show large differences when simulating carbon and water cycles, and reducing these differences is a priority for developing more accurate estimates of the condition of terrestrial ecosystems and future climate change. To reduce uncertainties and improve the understanding of their carbon budgets, we investigated the utility of the eddy flux datasets to improve model simulations and reduce variabilities among multi-model outputs of terrestrial biosphere models in Japan. Using 9 terrestrial biosphere models (Support Vector Machine - based regressions, TOPS, CASA, VISIT, Biome-BGC, DAYCENT, SEIB, LPJ, and TRIFFID), we conducted two simulations: (1) point simulations at four eddy flux sites in Japan and (2) spatial simulations for Japan with a default model (based on original settings) and a modified model (based on model parameter tuning using eddy flux data). Generally, models using default model settings showed large deviations in model outputs from observation with large model-by-model variability. However, after we calibrated the model parameters using eddy flux data (GPP, RE and NEP), most models successfully simulated seasonal variations in the carbon cycle, with less variability among models. We also found that interannual variations in the carbon cycle are mostly consistent among models and observations. Spatial analysis also showed a large reduction in the variability among model outputs. This study demonstrated that careful validation and calibration of models with available eddy flux data reduced model-by-model differences. Yet, site history, analysis of model structure changes, and more objective procedure of model calibration should be included in the further analysis.

  19. Quantifying Sources and Fluxes of Aquatic Carbon in U.S. Streams and Reservoirs Using Spatially Referenced Regression Models

    Science.gov (United States)

    Boyer, E. W.; Smith, R. A.; Alexander, R. B.; Schwarz, G. E.

    2004-12-01

    Organic carbon (OC) is a critical water quality characteristic in riverine systems that is an important component of the aquatic carbon cycle and energy balance. Examples of processes controlled by OC interactions are complexation of trace metals; enhancement of the solubility of hydrophobic organic contaminants; formation of trihalomethanes in drinking water; and absorption of visible and UV radiation. Organic carbon also can have indirect effects on water quality by influencing internal processes of aquatic ecosystems (e.g. photosynthesis and autotrophic and heterotrophic activity). The importance of organic matter dynamics on water quality has been recognized, but challenges remain in quantitatively addressing OC processes over broad spatial scales in a hydrological context. In this study, we apply spatially referenced watershed models (SPARROW) to statistically estimate long-term mean-annual rates of dissolved- and total- organic carbon export in streams and reservoirs across the conterminous United States. We make use of a GIS framework for the analysis, describing sources, transport, and transformations of organic matter from spatial databases providing characterizations of climate, land use, primary productivity, topography, soils, and geology. This approach is useful because it illustrates spatial patterns of organic carbon fluxes in streamflow, highlighting hot spots (e.g., organic-rich environments in the southeastern coastal plain). Further, our simulations provide estimates of the relative contributions to streams from allochthonous and autochthonous sources. We quantify surface water fluxes of OC with estimates of uncertainty in relation to the overall US carbon b