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Sample records for affecting carbon fluxes

  1. Do volcanic emissions affect carbon gas fluxes in peatlands?

    NASA Astrophysics Data System (ADS)

    Harrison, Nicola; Delmelle, Pierre; Toet, Sylvia; Gauci, Vincent; Ineson, Phil

    2010-05-01

    Recently, a link has been suggested between volcanic deposition of SO4 and the suppression of CH4 emissions in northern peatlands (Gauci et al., 2008). This link stems from the widely accepted idea that acid rain SO4 additions to peatlands can cause a shift in microbial communities as SO4 reducing bacteria out-compete methanogens for substrates, which results in a suppression of CH4 emission. However, volcanic emissions contain besides S other chemically reactive species that are potentially harmful to the environment. In particular, gaseous and particulate F emissions from volcanoes constitute a steady or intermittent source of F emission and deposition into the environment both close to the source and within fallout range of large eruptions. The objective of this study was to investigate the effect of volcanic depositions of SO4, both alone and in combination with F, on CH4 emission in peatlands. Peat mesocosms collected from Pennine uplands in the UK were treated with weekly pulses of Na2SO4 and NaF over 20 weeks in doses of 74 kg SO4/ ha and 13.5 and 135 kg F /ha. CH4 emissions were measured at regular intervals by taking headspace samples, which were analysed by GC-FID. CO2 fluxes were also measured using a portable Infra Red Gas Analyser (IRGA). No significant differences in CH4 and CO2 emissions were observed for any of the treatments when compared to the controls, which had only received deionised water. These findings are in contrast with previous studies where SO4 reduces CH4 emission in peatlands. The reason for this is unclear but may be due to the heterogeneous nature of peat soils. An alternative explanation relates to the previous history of the soils used in the mesocosms which are known to have been previously exposed to large volumes of anthropogenic S pollution. This may have caused microbial communities to evolve and become acclimatised to high levels of S addition. In either case, the assumption that CH4 suppression in peatlands occurs upon

  2. Carbon dioxide flux as affected by tillage and irrigation in soil converted from perennial forages to annual crops

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Among greenhouse gases, carbon dioxide (CO2) is one of the most significant contributors to regional and global warming as well as climatic change. However, CO2 flux from the soil surface to the atmosphere can be affected by modifications in soil physical properties resulting from changes in land ma...

  3. Climatic Versus Biotic Constraints on Carbon and Water Fluxes in Seasonally Drought-affected Ponderosa Pine Ecosystems. Chapter 2

    NASA Technical Reports Server (NTRS)

    Schwarz, P. A.; Law, B. E.; Williams, M.; Irvine, J.; Kurpius, M.; Moore, D.

    2005-01-01

    We investigated the relative importance of climatic versus biotic controls on gross primary production (GPP) and water vapor fluxes in seasonally drought-affected ponderosa pine forests. The study was conducted in young (YS), mature (MS), and old stands (OS) over 4 years at the AmeriFlux Metolius sites. Model simulations showed that interannual variation of GPP did not follow the same trends as precipitation, and effects of climatic variation were smallest at the OS (50%), and intermediate at the YS (<20%). In the young, developing stand, interannual variation in leaf area has larger effects on fluxes than climate, although leaf area is a function of climate in that climate can interact with age-related shifts in carbon allocation and affect whole-tree hydraulic conductance. Older forests, with well-established root systems, appear to be better buffered from effects of seasonal drought and interannual climatic variation. Interannual variation of net ecosystem exchange (NEE) was also lowest at the OS, where NEE is controlled more by interannual variation of ecosystem respiration, 70% of which is from soil, than by the variation of GPP, whereas variation in GPP is the primary reason for interannual changes in NEE at the YS and MS. Across spatially heterogeneous landscapes with high frequency of younger stands resulting from natural and anthropogenic disturbances, interannual climatic variation and change in leaf area are likely to result in large interannual variation in GPP and NEE.

  4. Processes Affecting Carbon Fluxes of Grassland Ecosystems Under Elevated CO{sub 2}

    SciTech Connect

    Owensby, C.E.; Ham, J.M.; Rice, C.W.; Knapp, A.K.

    1998-03-14

    Final report of a project which exposed native tallgrass prairie to twice-ambient atmospheric CO{sub 2}. Improved water use efficiency increased biomass production and increased soil organic matter. Twice ambient CO{sub 2} decreased canopy evapotranspiration by 22%, but, maintained an increased net carbon sequestration.

  5. How Seasonal Drought Affect Carbon and Water Fluxes of Alternative Energy Crops in the US?

    NASA Astrophysics Data System (ADS)

    Joo, E.; Hussain, M. Z.; Zeri, M.; Masters, M.; Gomez-Casanovas, N.; DeLucia, E. H.; Bernacchi, C.

    2014-12-01

    The cellulosic biomass of Switchgrass (Panicum virgatum L.), Miscanthus (Miscanthus giganteus) and native prairie are considered candidate second-generation biofuels, potentially resulting in partial replacement annual row crops within the Midwestern US. There is an increasing focus to study the environmental impact of agricultural crops, however not much is known on the influence on the energy, carbon and water cycles of energy crops, especially under drought conditions. This study compares the impact of drought episodes (in 2011 and 2012) on evapotranspiration (ET), net ecosystem productivity (NEP) and water use efficiency (WUE; equals to NEP/ET) for Switchgrass (SW), Miscanthus (MXG), Maize (MZ) and native prairie (NP) grown in Central Illinois using the eddy covariance technique. Due to the prolonged drought and the rapid growth development with increasing ET of MXG in 2012, large water deficit (precipitation-ET) was observed for each species up to the highest deficit of -360 mm for this species. The gross primary production (GPP) of MZ was radically decreased by the drought in 2011 and 2012, while SW and NP were not influenced. MXG increased NEP throughout the typically wet and drought years, mainly due to the decrease in respiration and by the largest GPP upon the drought in 2012. Despite having the largest water deficit, MXG showed an enhanced WUE of 12.8 and 11.4 Kg C ha-1mm-1 in 2011 and 2012, respectively, in comparison to years typical to the region with WUE of 3.7-7.3 Kg C ha-1mm-1. Other species did not show a significant enhancement of WUE. Therefore we conclude that out of the studied species, MXG has more access to water, and uses this water the most efficiently to store carbon, under drought conditions.

  6. Suspended particulate matter fluxes along with their associated metals, organic matter and carbonates in a coastal Mediterranean area affected by mining activities.

    PubMed

    Helali, Mohamed Amine; Zaaboub, Noureddine; Oueslati, Walid; Added, Ayed; Aleya, Lotfi

    2016-03-15

    A study of suspended particulate matter (SPM) fluxes along with their associated metals, organic matter and carbonates, was conducted off the Mejerda River outlet in May 2011 and in March and July 2012 at depths of 10, 20 and 40 m using sediment traps. SPM fluxes are more significant near the Mejerda outlet, especially in winter, but dissipate further offshore. Normalization reveals that the Mejerda is a major source of Pb, Zn, Cd, Cu, Ni, and Co, all of which are the result of human activities. In contrast, Fe, Mn and N are of authigenic origin. The enrichment factor shows that Pb, Zn and especially Cd are the most highly polluting metals off the Mejerda outlet. This confirms the trend observed on the shores of the Mejerda prodelta and is consistent with the type of mining activities conducted in the Mejerda catchment. PMID:26869095

  7. Carbon Dioxide Flux Measurement Systems (CO2Flux) Handbook

    SciTech Connect

    Fischer, M

    2005-01-01

    The Southern Great Plains (SGP) carbon dioxide flux (CO2 flux) measurement systems provide half-hour average fluxes of CO2, H2O (latent heat), and sensible heat. The fluxes are obtained by the eddy covariance technique, which computes the flux as the mean product of the vertical wind component with CO2 and H2O densities, or estimated virtual temperature. A three-dimensional sonic anemometer is used to obtain the orthogonal wind components and the virtual (sonic) temperature. An infrared gas analyzer is used to obtain the CO2 and H2O densities. A separate sub-system also collects half-hour average measures of meteorological and soil variables from separate 4-m towers.

  8. Modeling vertical carbon flux from zooplankton respiration

    NASA Astrophysics Data System (ADS)

    Packard, Theodore T.; Gómez, May

    2013-03-01

    The transport of carbon from ocean surface waters to the deep sea is a critical factor in calculations of planetary carbon cycling and climate change. This vertical carbon flux is currently thought to support the respiration of all the organisms in the water column below the surface, the respiration of the organisms in the benthos, as well as the carbon lost to deep burial. Accordingly, for conditions where the benthic respiration and the carbon burial are small relative to the respiration in the water column, and where horizontal fluxes are known or negligible, the carbon flux can be calculated by integrating the vertical profile of the water-column plankton respiration rate. Here, this has been done for the zooplankton component of the vertical carbon flux from measurements of zooplankton ETS activity south of the Canary Island Archipelago. From zooplankton ETS activity depth profiles, zooplankton respiration depth profiles were calculated and using the equations for the profiles as models, the epipelagic (3.05 μmol CO2 m-3 h-1), mesopelagic (112.82 nmol CO2 m-3 h-1), and bathypelagic (27.89 nmol CO2 m-3 h-1) zooplankton respiration for these waters were calculated. Then, by integration of the depth-normalized respiration profiles, zooplankton-associated carbon flux profiles below 150 m were calculated. These had an uncertainty of ±40%. At the station level (local regional variation) the variability was ±114% (n = 16). At 150 m and 500 m the average passive carbon flux associated with the zooplankton was 36 (±114%) and 20 (±113%) μmol C m-2 h-1. The carbon transfer efficiency (Teff) from the 150 to the 500 m levels averaged 51 ± 21% and a new metric, the nutrient retention efficiency (NRE), averaged 49 ± 21%. This metric is an index of the efficiency with which nutrients are maintained in the epipelagic zone and is directly related to the respiration in the water column. The carbon flux equation describing the pooled data (n = 16) was 131.14Z-0.292. Using

  9. A Brazilian network of carbon flux stations

    NASA Astrophysics Data System (ADS)

    Roberti, Débora R.; Acevedo, Otávio C.; Moraes, Osvaldo L. L.

    2012-05-01

    First Brasflux Workshop; Santa Maria, Rio Grande do Sul, Brazil, 14-15 November 2011 Last November, 33 researchers participated in a workshop to establish Brasflux, the Brazilian network of carbon flux stations, with the objective of integrating previous efforts and planning for the future. Among the participants were those leading ongoing flux observation projects and others planning to establish flux stations in the near future. International scientists also participated to share the experiences gained with other networks. The need to properly characterize terrestrial ecosystems for their roles in the global carbon, water, and energy budgets has motivated the implementation of hundreds of micrometeorological research sites throughout the world in recent years. The eddy covariance (EC) technique for turbulent flux determination is the preferred method to provide integral information on ecosystematmosphere exchanges. Integrating the observations regionally and globally has proven to be an effective approach to maximizing the usefulness of this technique for carbon cycle studies at multiple scales.

  10. Foliar uptake, carbon fluxes and water status are affected by the timing of daily fog in saplings from a threatened cloud forest.

    PubMed

    Berry, Z Carter; White, Joseph C; Smith, William K

    2014-05-01

    In cloud forests, foliar uptake (FU) of water has been reported for numerous species, possibly acting to relieve daily water and carbon stress. While the prevalence of FU seems common, how daily variation in fog timing may affect this process has not been studied. We examined the quantity of FU, water potentials, gas exchange and abiotic variation at the beginning and end of a 9-day exposure to fog in a glasshouse setting. Saplings of Abies fraseri (Pursh) Poir. and Picea rubens Sarg. were exposed to morning (MF), afternoon (AF) or evening fog (EF) regimes to assess the ability to utilize fog water at different times of day and after sustained exposure to simulated fog. The greatest amount of FU occurred during MF (up to 50%), followed by AF (up to 23%) and then EF, which surprisingly had no FU. There was also a positive relationship between leaf conductance and FU, suggesting a role of stomata in FU. Moreover, MF and AF lead to the greatest improvements in daily water balance and carbon gain, respectively. Foliar uptake was important for improving plant ecophysiology but was influenced by diurnal variation in fog. With climate change scenarios predicting changes to cloud patterns and frequency that will likely alter diurnal patterns, cloud forests that rely on this water subsidy could be affected.

  11. Gas and aerosol fluxes. [emphasizing sulfur, nitrogen, and carbon

    NASA Technical Reports Server (NTRS)

    Martens, C. S.

    1980-01-01

    The development of remote sensing techniques to address the global need for accurate distribution and flux determinations of both man made and natural materials which affect the chemical composition of the atmosphere, the heat budget of the Earth, and the depletion, of stratospheric ozone is considered. Specifically, trace gas fluxes, sea salt aerosol production, and the effect of sea surface microlayer on gas and aerosol fluxes are examined. Volatile sulfur, carbon, nitrogen, and halocarbon compounds are discussed including a statement of the problem associated with each compound or group of compounds, a brief summary of current understanding, and suggestions for needed research.

  12. How does hillslope position control carbon fluxes from peat soils?

    NASA Astrophysics Data System (ADS)

    Boothroyd, I.; Worrall, F.; Allott, T.

    2012-04-01

    Peatlands represent a significant terrestrial carbon stock, with an estimated 445.69 Gtonnes of carbon stored globally (Joosten 2009). In the UK, peatlands are estimated to store 1.75 Gtonnes of carbon (Joosten 2009), yet most of the upland blanket bogs that dominate peatland forms in the UK are in a damaged condition from erosion or land management practices. As such they could be releasing carbon and their restoration could be of benefit to the UK government in terms of climate change mitigation targets through the benefits of avoided carbon losses. In order to realise any possible benefit of management intervention upon peatlands accurate carbon budget models are required to assess the carbon balance of peatlands. To reduce uncertainty in model output a greater understanding of peatland function is required (Ostle et al., 2009). As part of this, topographical and hydrological controls need to be characterised in more detail. Landscape scale features such as gullies (McNamara et al., 2008) and drainage ditches (Wallage et al., 2006; Gibson et al., 2009) have been shown to affect carbon fluxes from peatlands, but slope position and its role on carbon fluxes has not yet been considered. A 12 month field study was carried out from June 2010 - June 2011 in the Peak District, UK, to assess the role that hillslope position has upon carbon flux from peat soils. Changes in hydrology, carbon dioxide flux and dissolved organic carbon (DOC) concentration across four hillslope positions: topslope, upper midslope, lower midslope and bottomslope were observed. Results showed that there was a significant slope effect for both DOC and CO2 effluxes but that the effect upon CO2 was explained by changes in the depth to the water table across the slope.

  13. Can subterranean cave systems affect soil CO2 fluxes?

    NASA Astrophysics Data System (ADS)

    Krajnc, Bor; Ferlan, Mitja; Ogrinc, Nives

    2015-04-01

    Main factors affecting soil CO2 fluxes in most ecosystems are soil temperature and soil moisture. Nevertheless occasionally high soil CO2 fluxes were observed at carst areas, which could result from ventilation of subterranean cavities (Ferlan et al., 2011). The aim of this work was to determine the influence of cave ventilation to soil CO2 fluxes. Research was done in a dead-end passage of Postojna cave (Pisani rov) and on the surface area above the passage (Velika Jeršanova dolina) in south-western Slovenia. Inside the cave we measured CO2 concentrations, its carbon (13C) stable isotope composition, 222Rn activity concentrations, temperatures and air pressure. At the surface we had chosen two sampling plots; test plot above the cave and control. At both plots we measured soil CO2 fluxes with automatic chambers, CO2 concentrations, temperatures and carbon stable isotope composition of soil air at three different depths (0.2 m, 0.5 m and 0.8 m) and different meteorological parameters such as: air temperature, air pressure, wind speed an precipitation. To detect the cave influence, we compared two surface CO2 flux measurements with air temperatures and changes of CO2 concentrations in the cave atmosphere. Our results on CO2 concentrations in the gallery of the cave indicated that the ventilation of this particular gallery also depends on outside air temperatures. Outside temperature increased and corresponded to higher CO2 concentrations, whereas at lower temperatures (T < 9 oC) cave started to ventilate and exhaled CO2 reach air through unknown fissures and cracks. At the control plot the soil CO2 fluxes were in a good correlation with soil temperatures (r = 0.789, p =0.01), where greater soil temperatures correspond to greater soil CO2 fluxes. Soil CO2 fluxes at the plot above the cave did not show statistically significant correlations with soil temperatures or soil moisture indicating that other factors possibly cave ventilation could influence it. References

  14. Carbon Fluxes on the Florida shelf

    NASA Astrophysics Data System (ADS)

    Robbins, L. L.; Knorr, P. O.; Liu, X. S.; Byrne, R.; Gledhill, D. K.

    2008-12-01

    Lack of baseline data on carbonate saturation state and pCO2 fluxes on the west Florida shelf, a low- gradient calcium carbonate platform, constrains the ability of managers and scientists to predict aspects of ecosystem change. Ecosystem change may result from a number of factors, such as climate change, ocean acidification, riverine and groundwater contribution, and biogeochemical cycling. Maps and models of pCO2 fluxes and carbonate saturation state are needed for the Florida shelf where significant decline of carbonate ecosystems, fishery habitats, and calcifying organisms are predicted over the next decade. To address critical information gaps and an incomplete understanding of nearshore carbon flux variability, the U.S. Geological Survey (USGS) is conducting a field campaign with the University of South Florida (USF) and National Oceanographic and Atmospheric Administration (NOAA) to acquire baseline pCO2, pH, total dissolved inorganic carbon (DIC), and total alkalinity (TA) on the west Florida shelf. These data are being used to model nearshore to offshore regional pCO2 and carbonate saturation state and, in conjunction with acquired habitat data, will be used to describe and interpret habitat change over time. Using the Multiparameter Inorganic Carbon Analyzer (MICA) developed by USF, data on air and sea pCO2, pH, DIC, and TA were collected underway during July and August 2008 cruises on the west Florida shelf. Maps depicting carbonate saturation state of the marine water, underlying sediment, and habitat data show varying relations. An additional cruise is planned for winter 2009.

  15. Fluxes of dissolved organic carbon from Chesapeake Bay sediments

    SciTech Connect

    Burdige, D.J.; Homstead, J. )

    1994-08-01

    Benthic fluxes of dissolved organic carbon (DOC) were measured over an annual cycle at two contrasting sites in Chesapeake Bay. At an organic-rich, sulfidic site in the mesohaline portion of the Bay (site M) DOC fluxes from the sediments ranged from 1.4 to 2.9 mmol/m[sup 2]/d. Measured benthic DOC fluxes at site M corresponded to [approximately]3-13% of the depth-integrated benthic C remineralization rates ([Sigma]OCR), and agreed well with calculated diffusive DOC fluxes based on porewater DOC profiles. This agreement suggests that DOC fluxes from site M sediments were likely controlled by molecular diffusion. The second site that was studied is a heavily bioturbated site in the southern Bay (site S). The activity of macrobenthos did not appear to enhance DOC fluxes from these sediments, since measured benthic DOC fluxes (>0.5 mmol/m[sup 2]/d) were lower than those at site M. The ratios of benthic DOC fluxes to [Sigma]OCR values at site S were also slightly smaller than those observed at site M. Benthic DOC fluxes from Chesapeake Bay sediments do not appear to significantly affect the transport of DOC through this estuary, although uncertainties in the reactivity of DOC in estuaries makes this conclusion somewhat tentative at this time. However, when these results are used to make a lower limit estimate of the globally integrated benthic DOC flux from marine sediments, a value similar to that previously calculated by Burdige et al. is obtained. This observation further supports suggestions in this paper about the importance of benthic DOC fluxes in the oceanic C cycle.

  16. Estimates of carbon cycle surface fluxes from the NASA Carbon Monitoring System Flux Pilot Project

    NASA Astrophysics Data System (ADS)

    Bowman, K. W.; Liu, J.; Lee, M.; Gurney, K. R.; Menemenlis, D.; Brix, H.; Hill, C. N.; Denning, S.; Haynes, K.; Baker, I. T.; Henze, D. K.; Bousserez, N.; Marland, G.; Marland, E.; Badurek, C. A.

    2013-12-01

    The goal of NASA Carbon Monitoring Study (CMS) Flux Pilot Project is to incorporate the full suite of NASA observational, modeling, and assimilation capabilities in order to attribute changes in globally distributed CO2 concentrations to spatially resolved surface fluxes across the entire carbon cycle. To that end, CMS has initiated a coordinated effort between land surface, ocean, fossil fuel, and atmospheric scientists to provide global estimates of CO2 constrained by satellite observations and informed by contemporaneous estimates of 'bottom up' fluxes from land surface, ocean, and fossil fuel models. The CMS Flux has evolved to incorporate a spatially explicit fossil fuel data assimilation system (FFDAS), an updated ECCO2 Darwin biogeochemical adjoint ocean state estimation system, and the new Simple Biospheric Model (Sib4) terrestrial ecosystem model. We compare GOSAT xCO2 observations, processed by the JPL ACOS v33, to predicted CMS Flux atmospheric CO2 concentrations for 2010-2011, and attribute the differences to spatially-resolved fluxes. We examine these fluxes in terms of interannual variability, correlative satellite measurements, and uncertainty across the carbon cycle

  17. Carbon Flux in Drylands: The Forgotten Dimensions?

    NASA Astrophysics Data System (ADS)

    Wainwright, J.; Turnbull, L.

    2014-12-01

    There has been a significant emphasis recently on the rôle of vegetation change and land degradation in drylands on carbon sequestration and the provision of related ecosystem services. Studies have typically focussed on the storage of carbon in biomass over short timescales. Over intermediate timescales, an important component of carbon-related ecohydrological processes is the way in which carbon is transferred from biomass to soil organic matter. These transfers are also significantly affected by land degradation via erosion processes which result in redistribution and net loss of carbon from the local system. Many drylands are underlain by significant stores of inorganic carbon, some of which is deposited from aeolian material, but vertical transfer from the surface stores is also an important process. Numerous studies suggest that these stores are in place from thousands to millions of years and thus contain carbon that has long been taken out of the global cycle. As progressive land degradation occurs, these stores are increasingly being exposed at the surface, and thus reactivated as part of the global cycle. In the context of climate change where increasingly stormy conditions are likely to accelerate the mobilization of sediment and associated carbon, and where increasingly acidic rainfall exacerbates dissolution of inorganic carbon, there is the potential for a significant addition to atmospheric carbon at regional and global scales. We will evaluate the relative importance of this mechanism compared to sequestration in vegetation and discuss the implications for maximizing ecosystem-service provision in drylands.

  18. Carbon Flux Explorer observations of ocean carbon sedimentation

    NASA Astrophysics Data System (ADS)

    Bishop, J. K.; Wood, T.

    2011-12-01

    The strength of natural biotic organic carbon sedimentation from the base of sunlit zone of the ocean is estimated to be 10 Pg C/y globally. This biological sequestration of carbon to deeper waters plays a key role in the atmophere/ocean carbon balance. It is impossible to predict whether the ocean biological carbon pump will strengthen or weaken in the face of climate change and ocean acidification because there are scant observations of the sinking carbon flux and remineralization in the upper 1000 m. We report progress on the development and deployment of the fully robotic and autonomous Ocean Carbon Flux Explorer (CFE) which is designed to follow hourly variations of carbon sedimentation for seasons at depths to 1500 m. The CFE relays observations to shore in real time via Iridium satellite links. The Carbon Flux Explorer is the integration of the Scripps Sounding Oceanographic Lagrangian Observer (SOLO) with the LBNL/UC Berkeley Optical Sedimentation Recorder (OSR). The OSR intercepts sinking particles and images them using dark field, transmitted, and transmitted cross polarized modes of illumination. OSR's modified to collect samples have been deployed to enable translation image data on particle albedo, optical density, and birefringence to carbon units. Our aim is fully autonomous operations in 2012. In this progress update, we report highlights of CFE deployments in the Santa Catalina Basin (October 2010, May 2011) and Santa Cruz Basin (May 2011), and California Current waters (August through September 2011). In many cases CFE data shows order of magnitude variation of particle sedimentation on diurnal time scales, a view of sedimentation here-to-fore not attained.

  19. Growth media simulating ileal and colonic environments affect the intracellular proteome and carbon fluxes of enterohemorrhagic Escherichia coli O157:H7 strain EDL933.

    PubMed

    Polzin, Sabrina; Huber, Claudia; Eylert, Eva; Elsenhans, Ines; Eisenreich, Wolfgang; Schmidt, Herbert

    2013-06-01

    In this study, the intracellular proteome of Escherichia coli O157:H7 strain EDL933 was analyzed by two-dimensional gel electrophoresis and matrix-assisted laser desorption ionization-time-of-flight (MALDI-TOF) spectrometry after growth in simulated ileal environment media (SIEM) and simulated colonic environment media (SCEM) under aerobic and microaerobic conditions. Differentially expressed intracellular proteins were identified and allocated to functional protein groups. Moreover, metabolic fluxes were analyzed by isotopologue profiling with [U-(13)C(6)]glucose as a tracer. The results of this study show that EDL933 responds with differential expression of a complex network of proteins and metabolic pathways, reflecting the high metabolic adaptability of the strain. Growth in SIEM and SCEM is obviously facilitated by the upregulation of nucleotide biosynthesis pathway proteins and could be impaired by exposition to 50 µM 6-mercaptopurine under aerobic conditions. Notably, various stress and virulence factors, including Shiga toxin, were expressed without having contact with a human host.

  20. Expression and knockdown of the PEPC1 gene affect carbon flux in the biosynthesis of triacylglycerols by the green alga Chlamydomonas reinhardtii.

    PubMed

    Deng, Xiaodong; Cai, Jiajia; Li, Yajun; Fei, Xiaowen

    2014-11-01

    The regulation of lipid biosynthesis is important in photosynthetic eukaryotic cells. This regulation is facilitated by the direct synthesis of fatty acids and triacylglycerol (TAG), and by other controls of the main carbon metabolic pathway. In this study, knockdown of the mRNA expression of the Chlamydomonas phosphoenolpyruvate carboxylase isoform 1 (CrPEPC1) gene by RNA interference increased TAG level by 20 % but decreased PEPC activities in the corresponding transgenic algae by 39-50 %. The decrease in CrPEPC1 expression increased the expression of TAG biosynthesis-related genes, such as acyl-CoA:diacylglycerol acyltransferase and phosphatidate phosphatase. Conversely, CrPEPC1 over-expression decreased TAG level by 37 % and increased PEPC activities by 157-184 %. These observations suggest that the lipid content of algal cells can be controlled by regulating the CrPEPC1 gene. PMID:24966045

  1. Soil carbon flux following pulse precipitation events in the shortgrass steppe

    USGS Publications Warehouse

    Munson, S.M.; Benton, T.J.; Lauenroth, W.K.; Burke, I.C.

    2010-01-01

    Pulses of water availability characterize semiarid and arid ecosystems. Most precipitation events in these ecosystems are small (???10 mm), but can stimulate carbon flux. The large proportion of carbon stored belowground and small carbon inputs create the potential for these small precipitation events to have large effects on carbon cycling. Land-use change can modify these effects through alteration of the biota and soil resources. The goal of our research was to determine how small precipitation events (2, 5, and 10 mm) affected the dynamics of soil carbon flux and water loss in previously cultivated Conservation Reserve Program (CRP) fields and undisturbed shortgrass steppe. Total carbon loss and duration of elevated carbon flux increased as event size increased in all field types. Time since cultivation increased in importance for carbon flux as event size increased. A comparison of water loss rates to carbon flux suggests that water is limiting to carbon flux for the smallest events, but is less limiting for events above 5 mm. We also describe how water availability interacts with temperature in controlling carbon flux rate. We conclude that small precipitation events have the potential for large short-term losses of carbon in the shortgrass steppe. ?? 2009 The Ecological Society of Japan.

  2. Monitoring Energy and Carbon Fluxes in a Mediterranean City

    NASA Astrophysics Data System (ADS)

    Marras, S.; Sirca, C.; Bellucco, V.; Arca, A.; Ventura, A.; Duce, P.; Spano, D.

    2015-12-01

    Cities and the surrounding areas play an important role in altering and/or contributing to the natural processes of the Earth system. Specifically, cities affect the amount and partitioning of energy fluxes, as well as the carbon budget. It is recognized that increased greenhouse gases (GHG) concentration (mainly carbon dioxide) and air temperature values are typically experienced by cities, due to their structural and morphological characteristics and to human activities in urban areas (such as traffic, domestic heating/cooling, etc.). This will impact the urban climate. Reducing the impact of urbanization on climate requires the knowledge of the interactions and links between human activities and the land-atmosphere system. Each city has different characteristics and conditions, so planning strategies helping in reducing carbon emissions should take into account local features. In this contest, monitoring activities are crucial to study the exchange of energy, water, and carbon over the city, evaluate their impact on human livability, and understand the role of the city on climate. A research activity is carried out in the Mediterranean city of Sassari, in the North of Sardinia island (Italy) to monitor urban fluxes and distinguish the main sources of GHG emissions, which could help the municipality to identify possible actions for reducing them. An Eddy Covariance tower was set up in the city center to directly monitor energy and carbon exchanges at half-hourly time step. Even if the measurement period only consists of few months, the daily trend of urban fluxes clearly shows that traffic is one of the main carbon emission sources, while the contribution of vegetation in sequestering carbon is low due to the reduced amount of green areas in the measurements footprint (< 20%). In addition, differences between working days and holiday periods can be distinguished.

  3. Carbon in, Carbon out: Reevaluating Carbon Fluxes in Subduction Zones

    NASA Astrophysics Data System (ADS)

    Manning, C. E.; Kelemen, P. B.

    2015-12-01

    Subduction zones exert a fundamental control on the deep carbon cycle. We reevaluated carbon inputs and outputs in convergent margins considering new estimates of C concentration in subducting mantle peridotites, carbonate solubility in aqueous fluids along subduction geotherms, melting and diapirism of carbon-bearing metasediments, and diffuse degassing from arcs. Our updated estimate of carbon inputs to the global subduction system, which includes estimates for C in altered peridotite, is 40-66 megatons carbon/year (MtC/y). We find that estimates of C lost from slabs (14-66 MtC/y) must take into account the high CaCO3 solubility in aqueous fluids, which contributes significant C that must be added to that derived from mineral decarbonation reactions. When taken together with hydrous silicate and carbonatite melts and metasediment diapirs, nearly all C can be scavenged from subducting lithosphere. The return of C to the atmosphere via arc-volcano degassing is only 18-43 MtC/y, but consideration deep volatile saturation of arc magmas, magma ponding in the middle and deep arc crust, and CO2 venting in forearcs can account for the remaining C lost from the slab. Thus, whereas previous studies concluded that about half the subducting carbon is returned to the convecting mantle, we find that relatively little carbon may be recycled. If so, substantial quantities of carbon are stored in the mantle lithosphere and crust and the carbon content of the mantle lithosphere + crust + ocean + atmosphere must be increasing, at least over the last 5-10 My. This is consistent with inferences from noble gas data. Recycled carbon in diamonds is a small fraction of the global carbon inventory.

  4. Reduced soil wettability can affect greenhouse gas fluxes

    NASA Astrophysics Data System (ADS)

    Urbanek, Emilia; Qassem, Khalid

    2015-04-01

    Soil moisture is known to be an important factor affecting the carbon (C) dynamics in soils including decomposition of organic matter and exchange of gases like CO2 and CH4 between the soil and the atmosphere. Most studies and process models looking at the soil C dynamics assume, however, that soils are easily wettable and water is relatively uniformly distributed within the soil pores. Most soils, however, do not wet spontaneously when dry or moderately moist, but instead exhibit some degree of soil water repellency (i.e. hydrophobicity), which can restrict infiltration and conductivity of water for weeks or months. This is world-wide occurring phenomenon which affects all soil textural types but is particularly common under permanent vegetation e.g. forest, grass and shrub vegetation. Soil water repellency is most profound during drier seasons, when the soil moisture content is relatively low. Although prolonged contact with water can gradually decrease water repellency, some soils do not recover to being completely wettable even after very wet winter months or substantial rainfall events. It has been recognized that with the predicted climatic changes the phenomenon of soil water repellency will become even more pronounced and severe, additionally it may occur in the areas and climatic zones where the effect have not been currently recognized. One of the main implications of soil water repellency is restricted water infiltration and reduced conductivity, which results in reduced soil water availability for plants and soil biota, even after prolonged periods of rainfall. As the process of C mineralization and consequently CO2 efflux from soil is driven by the accessibility of organic matter to decomposing organisms, which in turn is directly dependent on (i) soil moisture and (ii) soil temperature it is, therefore hypothesised that carbon decomposition and CO2 efflux in water repellent soils will also be affected when soil in the water repellent state. The CO2

  5. Organic carbon and carbonate fluxes: Links to climate change

    NASA Astrophysics Data System (ADS)

    Loubere, Paul; Siedlecki, Samantha A.; Bradtmiller, Louisa I.

    2007-03-01

    This volume is a compendium of articles derived from a Chapman conference entitled "The Role of Marine Organic Carbon and Carbonate Fluxes in Driving Global Climate Change, Past and Future", which was held at Woods Hole Oceanographic Institution in July, 2005. The conference divided the topic into units as follows: concepts and models, production of particulate matter, fluxes through the water column, and sediment record of past fluxes. The volume follows this 'vertically stratified' approach, and we use the same units to organize the articles. The Chapman conference on which this volume is based was made possible by support from The American Geophysical Union (Chapman Conference Program), the National Science Foundation, The Ocean and Climate Change Institute at Woods Hole Oceanographic Institution, and the Analytical Center for Climate and Environmental Change at Northern Illinois University. We extend special thanks to Terry Joyce at the Ocean and Climate Change Institute for his administrative help. Also, we particularly appreciated the hard work of Andrew Daly at WHOI and Melissa Ficek at AGU who managed the conference details, making it a pleasant event. The articles in this volume benefited from evaluations given by a dedicated, and most helpful, group of reviewers. It was gratifying to reach out to the community and receive such a valuable contribution of thought and expertise. We gratefully acknowledge our reviewers. Finally, we acknowledge the help and advice of John Milliman, editor for Deep-Sea Research II, who helped us attain the high standards of publication with the journal.

  6. Fluxes of carbon dioxide at Thetford Forest

    NASA Astrophysics Data System (ADS)

    Jarvis, P. G.; Stewart, J. B.; Meir, P.

    2007-01-01

    The Thetford Project (1968-1976) was a keystone project for the newly established Institute of Hydrology. Its primary objective was to elucidate the processes underlying evaporation of transpired water and intercepted rainfall from plantation forest, so as to explain hydrological observations that more water was apparently returned to the atmosphere from plantations than from grassland and heathland. The primary approach was to determine the fluxes of water vapour from a stand of Scots pine, situated within a larger area of plantations of Scots and Corsican pine, in Thetford Forest, East Anglia, UK, using the Bowen ratio approach. In 1976, advantage was taken of the methodology developed to add measurement of profiles of carbon dioxide concentration so as to enable the fluxes of CO2 also to be calculated. A team from Aberdeen and Edinburgh Universities collected 914 hours of 8-point CO2 concentration profiles, largely between dawn and dusk, on days from March to October, and the data from an "elite" data set of 710 hours have been analysed. In conditions of moderate temperature (<25°C) and specific humidity deficit (<15 g kg-1 with high solar irradiance (>500 W m-2), CO2 uptake reached relatively high rates for pine of up to 20 µmol m-2 s-1 in the middle of the day. This rate of CO2 uptake is higher than has been recently found for four Scots pine forests in continental Europe during July 1997. However, the year of 1976 was exceptionally hot and dry, with air temperatures reaching 30°C and the water deficit in the top 3 m of soil at the site of 152 mm by August. Air temperatures of over 25°C led to large specific humidity deficits, approaching 20 g kg-1, and associated severe reductions in CO2 uptake, as well as in evaporation. However, when specific humidity deficits dropped below c. 15 g kg-1 on succeeding days, generally as a result of lower air temperatures rather than lower solar irradiance, there was rapid recovery in both uptake and evaporation, thus

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

    NASA Astrophysics Data System (ADS)

    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 (<0.1%). Thalia democratica, Salpa fusiformis, Salpa aspera, Wheelia cylindrica, and Iasis zonaria were the five highest contributors, accounting for 95% of total 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.

  8. Linking soil functions to carbon fluxes and stocks

    NASA Astrophysics Data System (ADS)

    Olesen, Jørgen E.

    2014-05-01

    Farming practices causing declining returns and inputs of carbon (C) to soils pose threats to sustainable soil functioning by reducing availability of organic matter for soil microbial activities and by affecting soil structure, and soil C stocks that contribute to regulating greenhouse gas emissions. Declines in soil C also affect availability and storage capacity of a range of essential plant nutrients thus affecting needs for external inputs. Soil degradation is considered a serious problem in Europe and a large part of the degradation is caused by agricultural activity with intensive cultivation in arable and mixed farming system contributing to several soil threats. About 45% of European soils are estimated to have low SOM content, principally in southern Europe, but also in areas of France, UK and Germany. The European SOC stocks follow a clear north to south gradient with cooler temperatures favouring higher stocks. However, SOC stocks strongly depend on soil and land management, and there is thus a potential to both increase and lose SOC, although the potential to increase SOC strongly depends on incentives and structures for implementing improved management. Understanding the role of soil C may be better conceptualised by using a soil C flow and stocks concept to assess the impact of C management on crop productivity, soil organic C stocks and other ecosystem services. This concept distinguishes C flows and stocks, which may be hypothesized to have distinctly different effects on biological, chemical and physical soil functions. By separating the roles of carbon flows from the role of carbon stocks, it may become possible to better identify critical levels not only of soil carbon stocks, but also critical levels of carbon inputs, which directly relate to needs for crop and soil management measures. Such critical soil carbon stocks may be linked to soil mineralogy through complexed organic carbon on clay and silt surfaces. Critical levels of soil carbon

  9. Empirically Modeling Carbon Fluxes over the Northern Great Plains Grasslands

    NASA Astrophysics Data System (ADS)

    Zhang, L.; Wylie, B. K.; Ji, L.; Gilmanov, T.; Tieszen, L. L.

    2007-12-01

    Grasslands cover nearly one-fifth of the global terrestrial surface and store most of their carbon below ground. The grassland ecosystem in the Great Plains occupies over 1.5 million km2 of land area and is the primary resource for livestock production in North America. However, the contributions of grasslands to local and regional carbon budgets remain uncertain due to the lack of carbon flux data for the expansive grassland ecosystems under various managements, land uses, and climate variability. A quantitative understanding of carbon fluxes across these systems is essential for developing regional, national, and global carbon budgets and providing guidance to policy makers and managers when substantial conversion to biofuels are implemented. Additionally, these estimates will provide insights into how the grassland ecosystem will respond to future climate and what systems are sustainable and offer net carbon sinks. This knowledge base and decisions support tools are needed for developing land management strategies for the region under a variety of environmental conditions and land use options. In the past, we used a remote sensing-based piecewise regression (PWR) model to estimate the grassland carbon fluxes in the northern Great Plains using the 1-km SPOT VEGETATION normalized difference vegetation index (NDVI) data. We estimated the carbon fluxes through integrated spatial databases and remotely sensed extrapolations of flux tower data to regional scales. The PWR model was applied to derive an empirical relationship between environmental variables and tower-based measurements. The PWR equations were then applied through time and space to estimate carbon fluxes across the study area at 1-km resolution. We now improve this modeling approach by 1) using Moderate Resolution Imaging Spectroradiometer (MODIS) data with higher temporal, spatial, and spectral resolutions (8-day, 500-m, and 7-band) as input; 2) incorporating the actual vegetation evapotranspiration

  10. Inorganic carbon speciation and fluxes in the Congo River

    NASA Astrophysics Data System (ADS)

    Wang, Zhaohui Aleck; Bienvenu, Dinga Jean; Mann, Paul J.; Hoering, Katherine A.; Poulsen, John R.; Spencer, Robert G. M.; Holmes, Robert M.

    2013-02-01

    Seasonal variations in inorganic carbon chemistry and associated fluxes from the Congo River were investigated at Brazzaville-Kinshasa. Small seasonal variation in dissolved inorganic carbon (DIC) was found in contrast with discharge-correlated changes in pH, total alkalinity (TA), carbonate species, and dissolved organic carbon (DOC). DIC was almost always greater than TA due to the importance of CO2*, the sum of dissolved CO2 and carbonic acid, as a result of low pH. Organic acids in DOC contributed 11-61% of TA and had a strong titration effect on water pH and carbonate speciation. The CO2* and bicarbonate fluxes accounted for ~57% and 43% of the DIC flux, respectively. Congo River surface water released CO2 at a rate of ~109 mol m-2 yr-1. The basin-wide DIC yield was ~8.84 × 104 mol km-2 yr-1. The discharge normalized DIC flux to the ocean amounted to 3.11 × 1011 mol yr-1. The DOC titration effect on the inorganic carbon system may also be important on a global scale for regulating carbon fluxes in rivers.

  11. A Lagrangian Assimilation System for North American Carbon Flux Estimates

    NASA Astrophysics Data System (ADS)

    Chen, H.; He, W., Sr.; Peters, W.; Andrews, A. E.; Jacobson, A. R.; Sweeney, C.; Baker, I. T.; van der Laan-Luijkx, I. T.; van der Velde, I.; Tans, P. P.

    2015-12-01

    Understanding biospheric CO2 fluxes is paramount for climate studies to be able to analyze the responses of terrestrial ecosystems to climate change. To improve North American carbon flux estimates, we have built a new data assimilation system that couples the contemporary global carbon cycle model CarbonTracker with the Weather Research and Forecasting/Stochastic Time-Inverted Lagrangian Transport (WRF-STILT) model (referred as CarbonTracker-WRF-STILT). The current CarbonTracker-WRF-STILT system assimilates atmospheric observations of CO2 mole fractions at eight tower sites in North America and optimizes the a priori carbon fluxes from the simple biosphere (SiB) model. The system employs a two-lag Ensemble Kalman smoother to optimize scaling factors for both biospheric fluxes and the boundary conditions every 10 days. We will present the optimized carbon fluxes for North America for 2010, and compare them with the results from the CT2013B and CTE2014. To estimate the transport uncertainties, we also plan to test an alternative Lagrangian transport model Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT) driven by the NAM12 meteorological fields. In the following step, the CarbonTracker-WRF-STILT system will be adapted to assimilate multiple tracers, e.g. CO2 and carbonyl sulfide (COS) to simultaneously optimize photosynthesis (Gross Primary Production, GPP) and respiration.

  12. Sensitivity analysis of an Ocean Carbon Cycle Model in the North Atlantic: an investigation of parameters affecting the air-sea CO2 flux, primary production and export of detritus

    NASA Astrophysics Data System (ADS)

    Scott, V.; Kettle, H.; Merchant, C. J.

    2010-12-01

    The sensitivity of the biological parameters in a nutrient-phytoplankton-zooplankton-detritus (NPZD) model in the calculation of the air-sea CO2 flux, primary production and detrital export is analysed. The NPZD model is the Hadley Centre Ocean Carbon Cycle model (HadOCC) from the UK Met Office, used in the Hadley Centre Coupled Model 3 (HadCM3) and FAst Met Office and Universities Simulator (FAMOUS) GCMs. Here, HadOCC is coupled to the 1-D General Ocean Turbulence Model (GOTM) and forced with European Centre for Medium-Range Weather Forecasting meteorology to undertake a sensitivity analysis of its twenty biological parameters. Analyses are performed at three sites in the EuroSITES European Ocean Observatory Network: the Central Irminger Sea (60° N 40° W), the Porcupine Abyssal Plain (49° N 16° W) and the European Station for Time series in the Ocean Canary Islands (29° N 15° W) to assess variability in parameter sensitivities at different locations in the North Atlantic Ocean. Reasonable changes to the values of key parameters are shown to have a large effect on the calculation of the air-sea CO2 flux, primary production, and export of biological detritus to the deep ocean. Changes in the values of key parameters have a greater effect in more productive regions than in less productive areas. We perform the analysis using one-at-a-time perturbations and using a statistical emulator, and compare results. The most sensitive parameters are generic to many NPZD ocean ecosystem models. The air-sea CO2 flux is most influenced by variation in the parameters that control phytoplankton growth, detrital sinking and carbonate production by phytoplankton (the rain ratio). Primary production is most sensitive to the parameters that define the shape of the photosythesis-irradiance curve. Export production is most sensitive to the parameters that control the rate of detrital sinking and the remineralisation of detritus.

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

    USGS Publications Warehouse

    Gu, Y.; Howard, D.M.; Wylie, B.K.; Zhang, L.

    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.

  14. Coupling soil Carbon Fluxes, Soil Microbes, and High-Resolution Carbon Profiling in Permafrost Transitions

    NASA Astrophysics Data System (ADS)

    Anderson, C.; Stegen, J.; Bond-Lamberty, B. P.; Tfaily, M. M.; Huang, M.; Liu, Y.

    2015-12-01

    Microbial communities play a central role in the functioning of natural ecosystems by heavily influencing biogeochemical cycles. Understanding how shifts in the environment are tied to shifts in biogeochemical rates via changes in microbial communities is particularly relevant in high latitude terrestrial systems underlain by permafrost due to vast carbon stocks currently stored within thawing permafrost. There is limited understanding, however, of the interplay among soil-atmosphere CO2 fluxes, microbial communities, and SOM chemical composition. To address this knowledge gap, we leverage the distinct spatial transitions in permafrost-affected soils at the Caribou Poker Creek Research Watershed, a 104 km2 boreal watershed ~50 km north of Fairbanks, AK. We integrate a variety of data to gain new knowledge of the factors that govern observed patterns in the rates of soil CO2 fluxes associated with permafrost to non-permafrost transition zones. We show that nonlinearities in fluxes are influenced by depth to permafrost, tree stand structure, and soil C composition. Further, using 16S sequencing methods we explore microbial community assembly processes and their connection to CO2 flux across spatial scales, and suggest a path to more mechanistically link microbes to large-scale biogeochemical cycles. Lastly, we use the Community Land Model (CLM) to compare Earth System Model predictions of soil C cycling with empirical measurements. Deviations between CLM predictions and field observations of CO2 flux and soil C stocks will provide insight for how the model may be improved through inclusion of additional biotic (e.g., microbial community composition) and abiotic (e.g., organic carbon composition) features, which will be critical to improve the predictive power of climate models in permafrost-affected regions.

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

    NASA Astrophysics Data System (ADS)

    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; Goddéris, 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

    2013-08-01

    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.

  16. Hydrologic support of carbon dioxide flux revealed by whole-lake carbon budgets

    USGS Publications Warehouse

    Stets, E.G.; Striegl, R.G.; Aiken, G.R.; Rosenberry, D.O.; Winter, T.C.

    2009-01-01

    Freshwater lakes are an important component of the global carbon cycle through both organic carbon (OC) sequestration and carbon dioxide (CO 2) emission. Most lakes have a net annual loss of CO2 to the atmosphere and substantial current evidence suggests that biologic mineralization of allochthonous OC maintains this flux. Because net CO 2 flux to the atmosphere implies net mineralization of OC within the lake ecosystem, it is also commonly assumed that net annual CO2 emission indicates negative net ecosystem production (NEP). We explored the relationship between atmospheric CO2 emission and NEP in two lakes known to have contrasting hydrologie characteristics and net CO2 emission. We calculated NEP for calendar year 2004 using whole-lake OC and inorganic carbon (IC) budgets, NEPoc and NEPIC, respectively, and compared the resulting values to measured annual CO 2 flux from the lakes. In both lakes, NEPIc and NEP Ic were positive, indicating net autotrophy. Therefore CO2 emission from these lakes was apparently not supported by mineralization of allochthonous organic material. In both lakes, hydrologie CO2 inputs, as well as CO2 evolved from netcalcite precipitation, could account for the net CO2 emission. NEP calculated from diel CO2 measurements was also affected by hydrologie inputs of CO2. These results indicate that CO2 emission and positive NEP may coincide in lakes, especially in carbonate terrain, and that all potential geologic, biogeochemical, and hydrologie sources of CO2 need to be accounted for when using CO2 concentrations to infer lake NEP. Copyright 2009 by the American Geophysical Union.

  17. Aquatic carbon fluxes from the conterminous US and Alaska

    NASA Astrophysics Data System (ADS)

    Butman, D. E.; Stackpoole, S. M.; Stets, E.; McDonald, C.; Clow, D. W.; Striegl, R. G.

    2015-12-01

    In 2007, the First State of the Carbon Cycle Report estimated that rivers exported ~ 35 Tg-C yr-1 to coastal systems and reservoirs in the US served as sink of ~ 25 Tg-C yr-1 through sedimentation, each reported with 95% confidence that the estimate was within 100%. Significant progress has been made to constrain and improve these estimates by carefully considering how inland water ecosystems dynamically process, transport, and sequester carbon with attention given to the gaseous evasion of carbon across the air-water interface, a component that was not included in the 2007 estimates. As part of the U.S. Geological Survey's LandCarbon program, we present the first integrated assessment of freshwater carbon cycling for the conterminous US and Alaska. We estimate that 147 (95% confidence interval of 101- 208) Tg-C yr-1 is exported downstream or emitted to the atmosphere and sedimentation stores 22 (95% confidence interval of 10-68) Tg-C yr-1 in lakes and reservoirs. We show that there is significant regional variation in aquatic carbon flux, but verify that emission across stream and river surfaces represents the dominant removal flux at 85 Tg-C yr-1, or 58% of the total aquatic carbon flux. These new estimates for aquatic carbon fluxes indicate that inland waters must be considered in the context of national scale carbon accounting. For the conterminous US, we compare our results to the output of Terrestrial Biosphere Models. Analysis suggests that within the current modelling framework, calculations of Net Ecosystem Production may be overestimated by as much as 27%. Reconciliation of mass-flux interactions between terrestrial and aquatic carbon sources and sinks will require significant additional field data collection and modelling capacity.

  18. Organic Carbon Fluxes in a Stressed Groundwater System

    NASA Astrophysics Data System (ADS)

    Baker, A.; Graham, P. W.; Grbich, N.; Chinu, K.; Yu, D.

    2013-12-01

    Dissolved Organic Carbon (DOC) flux in groundwater is poorly understood: influenced by recharge, extraction and surface processes. We reviewed existing datasets for DOC concentration and flux in Australian groundwater systems. In a temperate, semi-arid, Australian research site we measured variations in DOC content during a series of high intensity extraction and recovery events in the surrounding aquifer and abstracted groundwater. Groundwater was abstracted from a fractured basalt / metasediment aquifer overlain by residual soils and flanked by a Quaternary alluvial channel. Groundwater systems included the fractured rock system interconnected with the alluvial aquifer through a leaky aquitard and a perched aquifer held at the soil bedrock interface. Prior to and throughout the test, groundwater samples were collected from wells within the fractured rock, alluvial aquifer and soil bedrock interface and analysed for DOC. Initial DOC concentrations in the upper aquifer were ~2 mg/L, following pumping concentrations increased 36 mg/L (ave) peaking at 72 mg/L. In the lower aquifer initial TOC concentrations were ~1.6 mg/L, during pumping levels increased to 3.98 mg/L (ave) peaking at 14.32 mg/L. Results indicate the fractured rock aquifers ability to recharge was exceeded during intense pumping periods and a larger component of water was drawn from the upper aquifer. This increased the volume of water being drawn through the soil profile and increased DOC content in abstracted groundwater. Hydrological setting, well construction and pumping regime are likely to affect the concentration of DOC within abstracted groundwater. Further attention to abstracted groundwater as a component in terrestrial DOC fluxes is warranted.

  19. Carbon dioxide fluxes from an urban area in Beijing

    NASA Astrophysics Data System (ADS)

    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.

  20. Soil carbon dioxide fluxes in relation to physical properties as influenced by management practices

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Among greenhouse gases, carbon dioxide (CO2) is one of the most significant contributors to regional and global warming as well as climatic change. However, CO2 flux from the soil surface to the atmosphere can be affected by modifications in soil physical properties resulting from changes in land ma...

  1. Information for seasonal models of carbon fluxes in terrestrial biomes

    SciTech Connect

    King, A.W.; DeAngelis, D.L.

    1985-06-01

    This report is a compilation of information that can be used in developing seasonal carbon flux models for several principal terrestrial biome types. The information includes flux data as well as models made either to simulate such data or to deduce fluxes not directly measurable. The report is divided into three sections that examine (1) photosynthetic production, (2) litterfall, and (3) decomposition during a year. The sections on photosynthetic production and decomposition discuss a large number of models that relate the processes to basic abiotic variables in each of several biome types. The information on litterfall, however, is largely empirical phenology data. A fourth section demonstrates the application of this compiled information to a compartment model of seasonal carbon flux in terrestrial biomes. 14 figs., 12 tabs.

  2. Arogenate Dehydratase Isoenzymes Profoundly and Differentially Modulate Carbon Flux into Lignins*

    PubMed Central

    Corea, Oliver R. A.; Ki, Chanyoung; Cardenas, Claudia L.; Kim, Sung-Jin; Brewer, Sarah E.; Patten, Ann M.; Davin, Laurence B.; Lewis, Norman G.

    2012-01-01

    How carbon flux differentially occurs in vascular plants following photosynthesis for protein formation, phenylpropanoid metabolism (i.e. lignins), and other metabolic processes is not well understood. Our previous discovery/deduction that a six-membered arogenate dehydratase (ADT1–6) gene family encodes the final step in Phe biosynthesis in Arabidopsis thaliana raised the fascinating question whether individual ADT isoenzymes (or combinations thereof) differentially modulated carbon flux to lignins, proteins, etc. If so, unlike all other lignin pathway manipulations that target cell wall/cytosolic processes, this would be the first example of a plastid (chloroplast)-associated metabolic process influencing cell wall formation. Homozygous T-DNA insertion lines were thus obtained for five of the six ADTs and used to generate double, triple, and quadruple knockouts (KOs) in different combinations. The various mutants so obtained gave phenotypes with profound but distinct reductions in lignin amounts, encompassing a range spanning from near wild type levels to reductions of up to ∼68%. In the various KOs, there were also marked changes in guaiacyl:syringyl ratios ranging from ∼3:1 to 1:1, respectively; these changes were attributed to differential carbon flux into vascular bundles versus that into fiber cells. Laser microscope dissection/pyrolysis GC/MS, histochemical staining/lignin analyses, and pADT::GUS localization indicated that ADT5 preferentially affects carbon flux into the vascular bundles, whereas the adt3456 knock-out additionally greatly reduced carbon flux into fiber cells. This plastid-localized metabolic step can thus profoundly differentially affect carbon flux into lignins in distinct anatomical regions and provides incisive new insight into different factors affecting guaiacyl:syringyl ratios and lignin primary structure. PMID:22311980

  3. Global estimates of boreal forest carbon stocks and flux

    NASA Astrophysics Data System (ADS)

    Bradshaw, Corey J. A.; Warkentin, Ian G.

    2015-05-01

    The boreal ecosystem is an important global reservoir of stored carbon and a haven for diverse biological communities. The natural disturbance dynamics there have historically been driven by fire and insects, with human-mediated disturbances increasing faster than in other biomes globally. Previous research on the total boreal carbon stock and predictions of its future flux reveal high uncertainty in regional patterns. We reviewed and standardised this extensive body of quantitative literature to provide the most up-to-date and comprehensive estimates of the global carbon balance in the boreal forest. We also compiled century-scale predictions of the carbon budget flux. Our review and standardisation confirmed high uncertainty in the available data, but there is evidence that the region's total carbon stock has been underestimated. We found a total carbon store of 367.3 to 1715.8 Pg (1015 g), the mid-point of which (1095 Pg) is between 1.3 and 3.8 times larger than any previous mean estimates. Most boreal carbon resides in its soils and peatlands, although estimates are highly uncertain. We found evidence that the region might become a net carbon source following a reduction in carbon uptake rate from at least the 1980s. Given that the boreal potentially constitutes the largest terrestrial carbon source in the world, in one of the most rapidly warming parts of the globe (Walsh, 2014), how we manage these stocks will be influential on future climate dynamics.

  4. Climate and Biological Controls of Carbon Fluxes along latitudinal gradients

    NASA Astrophysics Data System (ADS)

    Luo, Y.; Yuan, J.; Niu, S.

    2012-12-01

    It has not been carefully examined whether relative importance of climate and biological controls of carbon fluxes is similar among various ecosystem types along latitudinal gradients from the tropical to polar region. We hypothesize that except tropical regions, there is a consistent pattern of climate and biological controls of carbon fluxes across all the other ecosystems. We tested the hypothesis by analyzing data of net ecosystem exchange (NEE) from nearly 200 eddy-flux towers distributed worldwide and simulated gross primary production (GPP) from the Australian Community Atmosphere Land Exchange (CABLE) model. Specifically, we estimated yearly NEE (i.e., NEP), carbon uptake period (CUP) and seasonal maximum of NEE (NEE¬_max) from eddy-flux data. Similarly, we estimated CUP, GPP_max, seasonal maximum leaf area index (LAI_max), and Vcmax from the model across the globe. Our regression analysis indicates that NEP is very tightly correlated with the product of CUP and NEE_max cross all sites. Similarly, simulated GPP is highly correlated with the product of CUP and GPP_max over the globe in the CABLE model. CUP is related to phenology and represents climate control of carbon fluxes while NEE_max or GPP_max is determined by biological processes and thus represents biological control of carbon processes. We further analyzed relationships of GPP_max with LAI_max and Vcmax individually or in combination. GPP_max is highly correlated with them. This talk will present results of our analysis and explain our hypothesis test regarding relative importance of biological and climate controls of carbon fluxes along the latitudinal gradients.

  5. Effects of Land Use History on Soil Carbon Dioxide Flux in Ecuadorian Páramo Grasslands

    NASA Astrophysics Data System (ADS)

    McKnight, J.; Harden, C. P.

    2014-12-01

    Soil carbon dioxide (CO2) respiration is a primary mechanism for soil carbon (C) loss and is intricately linked to processes that affect soil C storage. As a result, land-use changes that affect soil CO2 flux (Flux) rates can significantly influence regional C budgets. The páramo grasslands of the high altitude Ecuadorian Andes are important in regional C budgets due to large soil C stocks. Though some forms of land use history have been shown to reduce soil C and affect known drivers of Flux, such as soil moisture (MS) and soil temperature (TS), the effect of land use history on Flux and its role in páramo soil C budgets remains poorly understood. This study investigated Flux differences among sites representing four land-use histories (PA-páramo; PAB-páramo recently burned; NA-native forest; PI-planted pine forest) and assessed the role of MS and TS on Flux rates within and across sites. Flux, MS, and TS were measured over a 3-week period at the Mazar Wildlife Reserve in southern Ecuador. Flux varied significantly among site pairs, except PI and NA. Flux rates were highest in the PI (5.79 g CO2-C m-2 d-1) and NA sites (5.59 g CO2-C m-2 d-1), with Flux rates at PA and PAB of 4.84 g CO2-C m-2 d-1 and 3.76 g CO2-C m-2 d-1, respectively. MS ranged from 29% at PI to 55% at PA, with grass sites having higher MS than forested sites. On average, páramo soils were ~3°C warmer than forested soil, with PI warmer than NA. Across all sites, Flux was weakly, negatively correlated with MS. Flux and TS were positively correlated within each site except PAB; the strongest correlation (p<0.0001) was observed at PI. Our results show that in the Ecuadorian Andes, Flux is significantly affected by land use history with higher Flux rates observed in forested areas than in páramo grasslands. To our knowledge, these are the first Flux rates reported for the Ecuadorian páramo region.

  6. Carbon dioxide flux across a forest-field ecotone.

    PubMed

    Golley, F; Bakker, S; Hamazaki, T

    1992-08-01

    CO2 flux of a deciduous forest and an old-field surface, and the ecotone between these two typical southern U.S. ecological communities, was studied in July, 1989. Rates of CO2 flux were greatest in the old field and least in the forest plots. The ecotone showed the greatest variation in CO2 flux. These differences appear to be due to differences in soil surface temperature, the old field being more exposed to direct solar radiation. The ecotonal community represents a landscape property which should be considered in studies of the transfer of carbon across the soil-atmosphere boundary.

  7. Microbial Carbon Cycling in Permafrost-Affected Soils

    SciTech Connect

    Vishnivetskaya, T.; Liebner, Susanne; Wilhelm, Ronald; Wagner, Dirk

    2011-01-01

    The Arctic plays a key role in Earth s climate system as global warming is predicted to be most pronounced at high latitudes and because one third of the global carbon pool is stored in ecosystems of the northern latitudes. In order to improve our understanding of the present and future carbon dynamics in climate sensitive permafrost ecosystems, present studies concentrate on investigations of microbial controls of greenhouse gas fluxes, on the activity and structure of the involved microbial communities, and on their response to changing environmental conditions. Permafrost-affected soils can function as both a source and a sink for carbon dioxide and methane. Under anaerobic conditions, caused by flooding of the active layer and the effect of backwater above the permafrost table, the mineralization of organic matter can only be realized stepwise by specialized microorganisms. Important intermediates of the organic matter decomposition are hydrogen, carbon dioxide and acetate, which can be further reduced to methane by methanogenic archaea. Evolution of methane fluxes across the subsurface/atmosphere boundary will thereby strongly depend on the activity of anaerobic methanogenic archaea and obligately aerobic methane oxidizing proteobacteria, which are known to be abundant and to significantly reduce methane emissions in permafrost-affected soils. Therefore current studies on methane-cycling microorganisms are the object of particular attention in permafrost studies, because of their key role in the Arctic methane cycle and consequently of their significance for the global methane budget.

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

    NASA Technical Reports Server (NTRS)

    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

  9. Closing the North American Carbon Budget: Continental Margin Fluxes Matter!

    NASA Astrophysics Data System (ADS)

    Najjar, R.; Benway, H. M.; Siedlecki, S. A.; Boyer, E. W.; Cai, W. J.; Coble, P. G.; Cross, J. N.; Friedrichs, M. A.; Goni, M. A.; Griffith, P. C.; Herrmann, M.; Lohrenz, S. E.; Mathis, J. T.; McKinley, G. A.; Pilskaln, C. H.; Smith, R. A.; Alin, S. R.

    2015-12-01

    Despite their relatively small surface area, continental margins are regions of intense carbon and nutrient processing, export and exchange, and thus have a significant impact on global biogeochemical cycles. In response to recommendations for regional synthesis and carbon budget estimation for North America put forth in the North American Continental Margins workshop report (Hales et al., 2008), the Ocean Carbon and Biogeochemistry (OCB) Program and North American Carbon Program (NACP) began coordinating a series of collaborative, interdisciplinary Coastal CARbon Synthesis (CCARS) research activities in five coastal regions of North America (Atlantic Coast, Pacific Coast, Gulf of Mexico, Arctic, Laurentian Great Lakes) to improve quantitative assessments of the North American carbon budget. CCARS workshops and collaborative research activities have resulted in the development of regional coastal carbon budgets based on recent literature- and model-based estimates of major carbon fluxes with estimated uncertainties. Numerous peer-reviewed papers and presentations by involved researchers have highlighted these findings and provided more in-depth analyses of processes underlying key carbon fluxes in continental margin systems. As a culminating outcome of these synthesis efforts, a comprehensive science plan highlights key knowledge gaps identified during this synthesis and provides explicit guidance on future research and observing priorities in continental margin systems to help inform future agency investments in continental margins research. This presentation will provide an overview of regional and flux-based (terrestrial inputs, biological transformations, sedimentary processes, atmospheric exchanges, lateral carbon transport) synthesis findings and key recommendations in the science plan, as well as a set of overarching priorities and recommendations on observations and modeling approaches for continental margin systems.

  10. Comparison of buried soil sensors, surface chambers and above ground measurements of carbon dioxide fluxes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil carbon dioxide (CO2) flux is an important component of the terrestrial carbon cycle. Accurate measurements of soil CO2 flux aids determinations of carbon budgets. In this study, we investigated soil CO2 fluxes with time and depth and above ground CO2 fluxes in a bare field. CO2 concentrations w...

  11. Carbon monoxide fluxes over a managed mountain meadow

    NASA Astrophysics Data System (ADS)

    Hörtnagl, Lukas; Hammerle, Albin; Wohlfahrt, Georg

    2014-05-01

    Carbon monoxide (CO) is a toxic trace gas with an atmospheric lifetime of 1-3 months and an average atmospheric concentration of 100 ppb. CO mole fractions exhibit a pronounced seasonal cycle with lows in summer and highs in winter. Carbon monoxide has an indirect global warming potential by increasing the lifetime of methane (CH4), as the main sink of CO is the reaction with the hydroxyl (OH) radical, which in turn is also the main sink for CH4. Regarding the warming potential, it is estimated that 100 kg CO are equivalent to an emission of 5 kg CH4. In addition, carbon monoxide interferes with the building and destruction of ozone. Emission into and uptake from the atmosphere of CO are thus relevant for global climate and regional air quality. Sources and sinks of CO on a global scale are still highly uncertain, mainly due to general scarcity of empirical data and the lack of ecosystem-scale CO exchange measurements, i.e. CO flux data that encompass all sources and sinks within an ecosystem. Here we present eddy covariance CO fluxes over a managed temperate mountain grassland near Neustift, Austria, whereby volume mixing ratios of CO were quantified by a dual-laser mid-infrared quantum cascade laser (QCL). First analyses of fluxes captured in April 2013 showed that the QCL is well able to capture CO fluxes at the study site during springtime. During the same time period, both significant net uptake and deposition of CO were observed, with high emission and deposition fluxes on the order of +/- 5 nmol m-2 s-1, respectively. In addition, CO fluxes exhibited a clear diurnal cycle during certain time periods, indicating a continuous release or uptake of the compound with peak flux rates around noon. In this presentation, we will analyze 12 months of carbon monoxide fluxes between January and December 2013 with regard to possible abiotic and biotic drivers of CO exchange. As an additional step towards a full understanding of the greenhouse gas exchange of the meadow

  12. Rerouting carbon flux to enhance photosynthetic productivity.

    PubMed

    Ducat, Daniel C; Avelar-Rivas, J Abraham; Way, Jeffrey C; Silver, Pamela A

    2012-04-01

    The bioindustrial production of fuels, chemicals, and therapeutics typically relies upon carbohydrate inputs derived from agricultural plants, resulting in the entanglement of food and chemical commodity markets. We demonstrate the efficient production of sucrose from a cyanobacterial species, Synechococcus elongatus, heterologously expressing a symporter of protons and sucrose (cscB). cscB-expressing cyanobacteria export sucrose irreversibly to concentrations of >10 mM without culture toxicity. Moreover, sucrose-exporting cyanobacteria exhibit increased biomass production rates relative to wild-type strains, accompanied by enhanced photosystem II activity, carbon fixation, and chlorophyll content. The genetic modification of sucrose biosynthesis pathways to minimize competing glucose- or sucrose-consuming reactions can further improve sucrose production, allowing the export of sucrose at rates of up to 36.1 mg liter(-1) h illumination(-1). This rate of production exceeds that of previous reports of targeted, photobiological production from microbes. Engineered S. elongatus produces sucrose in sufficient quantities (up to ∼80% of total biomass) such that it may be a viable alternative to sugar synthesis from terrestrial plants, including sugarcane. PMID:22307292

  13. Rerouting Carbon Flux To Enhance Photosynthetic Productivity

    PubMed Central

    Ducat, Daniel C.; Avelar-Rivas, J. Abraham; Way, Jeffrey C.

    2012-01-01

    The bioindustrial production of fuels, chemicals, and therapeutics typically relies upon carbohydrate inputs derived from agricultural plants, resulting in the entanglement of food and chemical commodity markets. We demonstrate the efficient production of sucrose from a cyanobacterial species, Synechococcus elongatus, heterologously expressing a symporter of protons and sucrose (cscB). cscB-expressing cyanobacteria export sucrose irreversibly to concentrations of >10 mM without culture toxicity. Moreover, sucrose-exporting cyanobacteria exhibit increased biomass production rates relative to wild-type strains, accompanied by enhanced photosystem II activity, carbon fixation, and chlorophyll content. The genetic modification of sucrose biosynthesis pathways to minimize competing glucose- or sucrose-consuming reactions can further improve sucrose production, allowing the export of sucrose at rates of up to 36.1 mg liter−1 h illumination−1. This rate of production exceeds that of previous reports of targeted, photobiological production from microbes. Engineered S. elongatus produces sucrose in sufficient quantities (up to ∼80% of total biomass) such that it may be a viable alternative to sugar synthesis from terrestrial plants, including sugarcane. PMID:22307292

  14. Rerouting Carbon Flux To Enhance Photosynthetic Productivity

    SciTech Connect

    Ducat, DC; Avelar-Rivas, JA; Way, JC; Silver, PA

    2012-03-23

    The bioindustrial production of fuels, chemicals, and therapeutics typically relies upon carbohydrate inputs derived from agricultural plants, resulting in the entanglement of food and chemical commodity markets. We demonstrate the efficient production of sucrose from a cyanobacterial species, Synechococcus elongatus, heterologously expressing a symporter of protons and sucrose (cscB). cscB-expressing cyanobacteria export sucrose irreversibly to concentrations of >10 mM without culture toxicity. Moreover, sucrose-exporting cyanobacteria exhibit increased biomass production rates relative to wild-type strains, accompanied by enhanced photosystem II activity, carbon fixation, and chlorophyll content. The genetic modification of sucrose biosynthesis pathways to minimize competing glucose-or sucrose-consuming reactions can further improve sucrose production, allowing the export of sucrose at rates of up to 36.1 mg liter(-1) h illumination(-1). This rate of production exceeds that of previous reports of targeted, photobiological production from microbes. Engineered S. elongatus produces sucrose in sufficient quantities (up to similar to 80% of total biomass) such that it may be a viable alternative to sugar synthesis from terrestrial plants, including sugarcane.

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

    PubMed

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

    2015-01-01

    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.

  16. Branchfall dominates annual carbon flux across lowland Amazonian forests

    NASA Astrophysics Data System (ADS)

    Marvin, David C.; Asner, Gregory P.

    2016-09-01

    Tropical forests play an important role in the global carbon cycle, but knowledge of interannual variation in the total tropical carbon flux and constituent carbon pools is highly uncertain. One such pool, branchfall, is an ecologically important dynamic with links to nutrient cycling, forest productivity, and drought. Identifying and quantifying branchfall over large areas would reveal the role of branchfall in carbon and nutrient cycling. Using data from repeat airborne light detection and ranging campaigns across a wide array of lowland Amazonian forest landscapes totaling nearly 100 000 ha, we find that upper canopy gaps—driven by branchfall—are pervasive features of every landscape studied, and are seven times more frequent than full tree mortality. Moreover, branchfall comprises a major carbon source on a landscape basis, exceeding that of tree mortality by 21%. On a per hectare basis, branchfall and tree mortality result in 0.65 and 0.72 Mg C ha-1 yr-1 gross source of carbon to the atmosphere, respectively. Reducing uncertainties in annual gross rates of tropical forest carbon flux, for example by incorporating large-scale branchfall dynamics, is crucial for effective policies that foster conservation and restoration of tropical forests. Additionally, large-scale branchfall mapping offers ecologists a new dimension of disturbance monitoring and potential new insights into ecosystem structure and function.

  17. An Assessment of Global Organic Carbon Flux Along Continental Margins

    NASA Technical Reports Server (NTRS)

    Thunell, Robert

    2004-01-01

    This project was designed to use real-time and historical SeaWiFS and AVHRR data, and real-time MODIS data in order to estimate the global vertical carbon flux along continental margins. This required construction of an empirical model relating surface ocean color and physical variables like temperature and wind to vertical settling flux at sites co-located with sediment trap observations (Santa Barbara Basin, Cariaco Basin, Gulf of California, Hawaii, and Bermuda, etc), and application of the model to imagery in order to obtain spatially-weighted estimates.

  18. Biogenic carbon fluxes from global agricultural production and consumption

    SciTech Connect

    Wolf, Julie; West, Tristram O.; Le Page, Yannick LB; Kyle, G. Page; Zhang, Xuesong; Collatz, George; Imhoff, Marc L.

    2015-10-01

    Quantification of biogenic carbon fluxes from agricultural lands is needed to generate comprehensive bottom-up estimates of net carbon exchange for global and regional carbon monitoring. We estimated global agricultural carbon fluxes associated with annual crop net primary production (NPP), harvested biomass, and consumption of biomass by humans and livestock. These estimates were combined for a single estimate of net carbon exchange (NCE) and spatially distributed to 0.05 degree resolution using MODIS satellite land cover data. Global crop NPP in 2011 was estimated at 5.25 ± 0.46 Pg C yr-1, of which 2.05 ± 0.05 Pg C yr-1 was harvested and 0.54 Pg C yr-1 was collected from crop residues for livestock fodder. Total livestock feed intake in 2011 was 2.42 ± 0.21 Pg C yr-1, of which 2.31 ± 0.21 Pg C yr-1 was emitted as CO2, 0.07 ± 0.01 Pg C yr-1 was emitted as CH4, and 0.04 Pg C yr-1 was contained within milk and egg production. Livestock grazed an estimated 1.27 Pg C yr-1 in 2011, which constituted 52.4% of total feed intake. Global human food intake was 0.57 ± 0.03 Pg C yr-1 in 2011, the majority of which is respired as CO2. Completed global cropland carbon budgets accounted for the ultimate use of ca. 80% of harvested biomass. The spatial distribution of these fluxes may be used for global carbon monitoring, estimation of regional uncertainty, and for use as input to Earth system models.

  19. Effect of restoration on carbon fluxes in urban temperate wetlands

    NASA Astrophysics Data System (ADS)

    Schafer, K. V.; Tripathee, R.; Bohrer, G.

    2012-12-01

    Carbon sequestration as an ecosystem service, has received attraction as a climate change mitigating strategy. The restoration of wetlands has also been an integral part of US management policy, since the clean water act came into effect. How restoration impacts carbon fluxes, however, has seldom been reported. A record of over three years of net carbon exchange from a restored urban temperate wetland, shows that fluxes decreased by 50% concomitant with the management of Phragmites australis, an invasive plant species that has been eliminated by 2011, thus all aboveground biomass has been removed. Likewise, aboveground biomass decreased for Spartina alterniflora, the restored, native species over the same time period as well. The majority of the biomass resides belowground. Comparison between the managed urban wetland and an unmanaged recently restored site nearby shows that the fluxes in the unmanaged wetland in 2011 were significantly higher than those of the managed wetland. Thus, managing wetlands by removing Phragmites may cause diminishing carbon sequestration potential by these wetlands

  20. Mapping carbon dioxide flux in semiarid grasslands using optical remote sensing

    NASA Astrophysics Data System (ADS)

    Holifield Collins, Chandra Deberta

    Increasing atmospheric levels of carbon dioxide (CO2) and the potential impact on climate change has caused an increased effort to more accurately quantify terrestrial sources and sinks. Semiarid grasslands cover a significant portion of the Earth's land surface and may be an important sink for atmospheric CO2. This study was conducted to examine the role semiarid grasslands play in the carbon cycle. The relation between surface reflectance and temperature obtained from satellite imagery was used to determine a Water Deficit Index (WDI) to estimate distributed plant transpiration rates for a point in time. Due to the relationship between transpiration and plant CO2 uptake, WDI was directly related to CO2 flux. Satellite images were acquired for a five-year period (1996-2000) during which transpiration and net CO2 flux were measured for a semiarid grassland site in southeastern Arizona. Manual and automatic chamber data were also collected in 2005 and 2006 and used to assess the spatial variability of nighttime soil respiration. Spatial analysis showed the most influential factor affecting nighttime respiration was aspect, where flux from North-facing slopes was significantly (P < 0.05) higher than on South-facing slopes. A strong linear relationship (R2 = 0.97) existed between WDI-derived instantaneous net CO2 flux and daytime net CO2 flux estimates, and was used to generate maps of distributed daytime net CO2 flux. A linear relationship (R2 = 0.88) was also found between daytime and nighttime net CO2 flux, and used in combination with maps of daytime net CO2 flux to create maps of daily net CO2 flux. This study indicated that remote sensing offers an operational, physically-based means of obtaining daily net CO2 flux in semiarid grasslands.

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

    NASA Astrophysics Data System (ADS)

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

    2003-12-01

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

  2. Effects of tropospheric ozone on methane and carbon dioxide fluxes from peatland mesocosms

    NASA Astrophysics Data System (ADS)

    Toet, Sylvia; Oliver, Vikki; Helgason, Thorunn; Peacock, Simon; Barnes, Jeremy; Ineson, Phil; Ashmore, Mike

    2010-05-01

    gross photosynthesis has been enhanced by elevated ozone up till now. The latter may partly be explained by higher net biomass Sphagnum production observed at elevated ozone. Leaf biomass and stomatal conductance of Schoenus nigricans were not affected by ozone. Additional soil and plant data will be presented that may help unravel the mechanisms underling the observed changes in greenhouse gas fluxes. Hence, the results imply that increases in global background ozone concentrations that are predicted by models in the northern hemisphere over the 21st century may lead to a negative feedback on methane emissions from peatland ecosystems. This study will be continued with methane emission and high-frequency carbon dioxide flux measurements and more detailed process studies, including stable isotope tracer studies, providing key information for long-term predictions of ozone impacts on carbon dynamics in peatland ecosystems.

  3. Geomorphogenesis and Carbon Fluxes of Tropical Peat Domes

    NASA Astrophysics Data System (ADS)

    Cobb, A.; Hoyt, A.; Dommain, R.; Harvey, C. F.

    2015-12-01

    Tropical peatlands sequester and release globally significant quantities of carbon dioxide as peat domes grow and subside on millennial time scales. Research to date indicates that the hydrologic feedback between water table depth and peat accumulation is fundamentally similar across tropical peatlands, but peat accumulation and fluxes cannot always be spatially uniform across the landscape because peat accumulates in domes. We show that upscaling from local measurements to landscape fluxes of CO2 and CH4 requires (1) sampling in both the growing interiors and the static margins of peat domes, and (2) use of topographical data from the peatland. Similarly, inference of past carbon sequestration from dated peat cores requires a model for the partitioning of peatlands into domes by drainage networks.

  4. Particle size distribution and estimated carbon flux across the Arabian Sea oxygen minimum zone

    NASA Astrophysics Data System (ADS)

    Roullier, F.; Berline, L.; Guidi, L.; Durrieu De Madron, X.; Picheral, M.; Sciandra, A.; Pesant, S.; Stemmann, L.

    2014-08-01

    The goal of the Arabian Sea section of the TARA oceans expedition was to study large particulate matter (LPM > 100 μm) distributions and possible impact of associated midwater biological processes on vertical carbon export through the oxygen minimum zone (OMZ) of this region. We propose that observed spatial patterns in LPM distribution resulted from the timing and location of surface phytoplankton bloom, lateral transport, microbial processes in the core of the OMZ, and enhanced biological processes mediated by bacteria and zooplankton at the lower oxycline. Indeed, satellite-derived net primary production maps showed that the northern stations of the transect were under the influence of a previous major bloom event while the most southern stations were in a more oligotrophic situation. Lagrangian simulations of particle transport showed that deep particles of the northern stations could originate from the surface bloom while the southern stations could be considered as driven by 1-D vertical processes. In the first 200 m of the OMZ core, minima in nitrate concentrations and the intermediate nepheloid layer (INL) coincided with high concentrations of 100 μm < LPM < 200 μm. These particles could correspond to colonies of bacteria or detritus produced by anaerobic microbial activity. However, the calculated carbon flux through this layer was not affected. Vertical profiles of carbon flux indicate low flux attenuation in the OMZ, with a Martin model b exponent value of 0.22. At three stations, the lower oxycline was associated to a deep nepheloid layer, an increase of calculated carbon flux and an increase in mesozooplankton abundance. Enhanced bacterial activity and zooplankton feeding in the deep OMZ is proposed as a mechanism for the observed deep particle aggregation. Estimated lower flux attenuation in the upper OMZ and re-aggregation at the lower oxycline suggest that OMZ may be regions of enhanced carbon flux to the deep sea relative to non OMZ regions.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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

  7. Cross-scale impact of climate temporal variability on ecosystem water and carbon fluxes

    NASA Astrophysics Data System (ADS)

    Paschalis, Athanasios; Fatichi, Simone; Katul, Gabriel G.; Ivanov, Valeriy Y.

    2015-09-01

    While the importance of ecosystem functioning is undisputed in the context of climate change and Earth system modeling, the role of short-scale temporal variability of hydrometeorological forcing (~1 h) on the related ecosystem processes remains to be fully understood. Various impacts of meteorological forcing variability on water and carbon fluxes across a range of scales are explored here using numerical simulations. Synthetic meteorological drivers that highlight dynamic features of the short temporal scale in series of precipitation, temperature, and radiation are constructed. These drivers force a mechanistic ecohydrological model that propagates information content into the dynamics of water and carbon fluxes for an ensemble of representative ecosystems. The focus of the analysis is on a cross-scale effect of the short-scale forcing variability on the modeled evapotranspiration and ecosystem carbon assimilation. Interannual variability of water and carbon fluxes is emphasized in the analysis. The main study inferences are summarized as follows: (a) short-scale variability of meteorological input does affect water and carbon fluxes across a wide range of time scales, spanning from the hourly to the annual and longer scales; (b) different ecosystems respond to the various characteristics of the short-scale variability of the climate forcing in various ways, depending on dominant factors limiting system productivity; (c) whenever short-scale variability of meteorological forcing influences primarily fast processes such as photosynthesis, its impact on the slow-scale variability of water and carbon fluxes is small; and (d) whenever short-scale variability of the meteorological forcing impacts slow processes such as movement and storage of water in the soil, the effects of the variability can propagate to annual and longer time scales.

  8. Methane and carbon dioxide fluxes in a hydrologically changed wetland in Canada

    NASA Astrophysics Data System (ADS)

    Fleischer, Elisa; Berger, Sina; Burger, Magdalena; Forsyth, Jordan; Goebel, Marie; Wagner-Riddle, Claudia; Blodau, Christian; Klemm, Otto

    2015-04-01

    Northern peatlands store about 30 % of the global soil carbon and account for a significant contribution to methane emissions from natural sources. The carbon cycle in peatland ecosystems is very sensitive to hydrological changes so that it is important to quantify and analyze the direction and magnitude of carbon fluxes under such conditions. For example, increased water levels might decrease the carbon dioxide uptake and increase methane emissions. The Luther Bog in Ontario, Canada, has been flooded to create a reservoir in 1952. This changed the hydrological regime of the adjacent areas and the question arises whether the changed ecosystem acts as a sink or source for carbon, and how it affects global warming. In 2014, an eddy covariance measurement station was operated there from May to October to quantify the exchange of water vapor, carbon dioxide and methane between the bog and the atmosphere. The station was located in an area that got wetter through the construction of the dam. The magnitude and direction of the methane fluxes were independent from daily patterns. The constantly high water level excluded the effect of temperature changes on the methane production. A seasonal variation with increased emissions during the summer period was visible despite the slightly decreased water level. However, the difference was small. The study site was found to be a clear methane source. The carbon dioxide fluxes showed typical diurnal courses. Their magnitude was relatively constant during the measurement period apart from a slight decrease in fall. The uptake of carbon clearly overweighed the carbon loss, meaning that the bog is sequestering carbon. However, considering the global warming potential of carbon dioxide and methane the effect on climate change is only slightly negative. This points out that even changed wetland ecosystems can keep their important function of sequestering carbon and thereby counteract global warming. A comparison and combination of this

  9. [Hydrochemical Characteristics and the Dissolved Inorganic Carbon Flux in Liuzhou Section of Liujiang Basin].

    PubMed

    Yuan, Ya-qiong; He, Shi-yi; Yu, Shi; Sun, Ping-an; Wang, Yan-xue; Wu, Zhao-yun; Li, Xin-gui; Xie, Ming-xian; Liu, Wen; Li, Rui; Zhang, Hua-sheng

    2015-07-01

    An important aspect of the current global change research is using river chemical composition to reveal the chemical weathering process and its effect of carbon sink. In this study, water samples were collected and analyzed 2 ~3 times per month from January to December in 2013. The hydrochemistry belonged to HCO3-Ca type. Ca+ and HCO3- were the main cation and anion, which reflected that the hydrochemical characteristics of river were mainly affected by the dissolution of carbonate rock. The concentration of main ions varied with the seasons, which reflected that the crest value occurred in winter, followed by those in autumn and spring, and the lowest value was observed in summer. Due to the interaction of effect of dilution and effect of C2, the seasonal variation of Ca2+ and HCO3- showed that the highest value was in autumn and the lowest value was in summer. The seasonal variation law of other ions should be attributed to the effect of dilution or agricultural activities or combined action of them. Both carbonic acid and sulfuric acid took part in the chemical weathering of carbonate rocks as evidenced by stoichiometric analysis. Besides, the δ34S of sulfate ion of the river waters (δ34S: from 7. 65 per thousand to 8. 55 per thousand) showed that SO2- was originated mainly from oxidation of sulfide minerals in ore deposits and acid rain. Chemical mass balance method was applied to estimate the proportion of HCO- coming from carbonate weathering by sulfuric acid. The result was 28. 26% . On this basis, the total carbon flux of carbon ( by CO2 calculation) in Liuzhou section calculated month by month was about 8. 95 x 10(5) t . a-1. What's more, the carbon flux showed a positive correlation with flow, which implied that the discharge of catchment was the main influencing factor of carbon flux rather than the HCO3- concentration. PMID:26489309

  10. [Hydrochemical Characteristics and the Dissolved Inorganic Carbon Flux in Liuzhou Section of Liujiang Basin].

    PubMed

    Yuan, Ya-qiong; He, Shi-yi; Yu, Shi; Sun, Ping-an; Wang, Yan-xue; Wu, Zhao-yun; Li, Xin-gui; Xie, Ming-xian; Liu, Wen; Li, Rui; Zhang, Hua-sheng

    2015-07-01

    An important aspect of the current global change research is using river chemical composition to reveal the chemical weathering process and its effect of carbon sink. In this study, water samples were collected and analyzed 2 ~3 times per month from January to December in 2013. The hydrochemistry belonged to HCO3-Ca type. Ca+ and HCO3- were the main cation and anion, which reflected that the hydrochemical characteristics of river were mainly affected by the dissolution of carbonate rock. The concentration of main ions varied with the seasons, which reflected that the crest value occurred in winter, followed by those in autumn and spring, and the lowest value was observed in summer. Due to the interaction of effect of dilution and effect of C2, the seasonal variation of Ca2+ and HCO3- showed that the highest value was in autumn and the lowest value was in summer. The seasonal variation law of other ions should be attributed to the effect of dilution or agricultural activities or combined action of them. Both carbonic acid and sulfuric acid took part in the chemical weathering of carbonate rocks as evidenced by stoichiometric analysis. Besides, the δ34S of sulfate ion of the river waters (δ34S: from 7. 65 per thousand to 8. 55 per thousand) showed that SO2- was originated mainly from oxidation of sulfide minerals in ore deposits and acid rain. Chemical mass balance method was applied to estimate the proportion of HCO- coming from carbonate weathering by sulfuric acid. The result was 28. 26% . On this basis, the total carbon flux of carbon ( by CO2 calculation) in Liuzhou section calculated month by month was about 8. 95 x 10(5) t . a-1. What's more, the carbon flux showed a positive correlation with flow, which implied that the discharge of catchment was the main influencing factor of carbon flux rather than the HCO3- concentration.

  11. Aeolian nutrient fluxes following wildfire in sagebrush steppe: Implications for soil carbon storage

    USGS Publications Warehouse

    Hasselquist, N.J.; Germino, M.J.; Sankey, J.B.; Ingram, L.J.; Glenn, N.F.

    2011-01-01

    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 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. ?? 2011 Author(s).

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

    NASA Astrophysics Data System (ADS)

    Hasselquist, N. J.; Germino, M. J.; Sankey, J. B.; Ingram, L. J.; Glenn, N. F.

    2011-08-01

    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 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.

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

    NASA Astrophysics Data System (ADS)

    Babel, Wolfgang; Biermann, Tobias; Falge, Eva; Ingrisch, Johannes; Leonbacher, Jürgen; Schleuss, Per; Kuzyakov, Yakov; Ma, Yaoming; Miehe, Georg; Foken, Thomas

    2014-05-01

    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

  14. Particles size distribution and carbon flux across the Arabian Sea Oxygen Minimum Zone

    NASA Astrophysics Data System (ADS)

    Roullier, F.; Berline, L.; Guidi, L.; Sciandra, A.; Durrieu De Madron, X.; Picheral, M.; Pesant, S.; Stemmann, L.

    2013-12-01

    The goal of the Arabian Sea section of the TARA oceans expedition was to study Large Particulate Matter (LPM > 100 μm) distributions and possible impact of associated midwater biological processes on vertical carbon export through the Oxygen Minimum Zone (OMZ) of this region. We found that spatial patterns in LPM distribution resulted from the timing and location of surface phytoplankton bloom, lateral transport, microbial processes in the core of the OMZ, and zooplankton activity at the lower oxycline. Indeed, satellite-derived net primary production maps showed that the northern stations of the transect were under the influence of a previous major bloom event while, the most southern stations were in a more oligotrophic situation. Lagrangian simulations of particle transport showed that deep particles of the northern stations could originate from the surface bloom while the southern stations could be considered as driven by 1-D vertical processes. In the first 200 m of the OMZ core, minima in nitrate concentrations and the Intermediate Nepheloid Layer (INL) coincided with high concentrations of 100 μm < LPM < 200 μm. These particles could correspond to colonies of bacteria or detritus produced by anaerobic microbial activity. However, the calculated carbon flux through this layer was not affected. Vertical profiles of carbon flux indicate low flux attenuation in the OMZ, with a Martin model b exponent value of 0.22. At the lower oxycline, a deep nepheloid layer was associated to an increase of carbon flux and an increase in mesozooplankton abundance. Zooplankton feeding on un-mineralized sinking particles in the OMZ is proposed as a mechanism for the observed deep particle aggregation. These results suggest that OMZ may be regions of enhanced carbon flux to the deep sea relative to non-OMZ regions.

  15. [Effects of CO2 storage flux on carbon budget of forest ecosystem].

    PubMed

    Zhang, Mi; Wen, Xue-fa; Yu, Gui-rui; Zhang, Lei-ming; Fu, Yu-ling; Sun, Xiao-min; Han, Shi-jie

    2010-05-01

    Carbon dioxide (CO2) storage flux in the air space below measurement height of eddy covariance is very important to correctly evaluate net ecosystem exchange of CO2 (NEE) between forest ecosystem and atmosphere. This study analyzed the dynamic variation of CO2 storage flux and its effects on the carbon budget of a temperate broad-leaved Korean pine mixed forest at Changbai Mountains, based on the eddy covariance flux data and the vertical profile of CO2 concentration data. The CO2 storage flux in this forest ecosystem had typical diurnal variation, with the maximum variation appeared during the transition from stable atmospheric layer to unstable atmospheric layer. The CO2 storage flux calculated by the change in CO2 concentration throughout a vertical profile was not significantly different from that calculated by the change in CO2 concentration at the measurement height of eddy covariance. The NEE of this forest ecosystem was underestimated by 25% and 19% at night and at daytime, respectively, without calculating the CO2 storage flux at half-hour scale, and was underestimated by 10% and 25% at daily scale and annual scale, respectively. Without calculating the CO2 storage flux in this forest ecosystem, the parameters of Michaelis-Menten equation and Lloyd-Taylor equation were underestimated, and the ecosystem apparent quantum yield (alpha) and the ecosystem respiration rate (Rref) at the reference temperature were mostly affected. The gross primary productivity (GPP) and ecosystem respiration (Re) of this forest ecosystem were underestimated about 20% without calculating the CO2 storage flux at half-hour, daily scale, and annual scale.

  16. Testing the Need for Replication of Eddy Covariance Carbon Dioxide Flux Measurements over Agricultural Fields

    NASA Astrophysics Data System (ADS)

    Taylor, A. M.; Amiro, B. D.; Gervais, M.

    2015-12-01

    The eddy covariance method directly measures carbon dioxide (CO2) fluxes for long periods of time and with footprints up to hundreds of meters in size. Any ecosystem process that alters how gases and energy move between the atmosphere and soil/vegetation can affect these fluxes. Eddy covariance is vulnerable to systematic errors and uncertainy, particular through relying on assumptions about surface characteristics. Additionally, spatial variation within a site can cause more uncertainty in these measurements and lack of replication in many eddy covariance studies makes statistical analysis of carbon fluxes challenging. We tested if there are significant differences between co-located and simultaneous CO2 flux measurements over a uniform crop surface, and if the differences increase if we measure different flux footprint areas over the same field. During the summer of 2014, three matched instrumented 2.5-m high towers were co-located and then periodically separated by moving at 50 m intervals along a north-south transect on an alfalfa/trefoil field and a spring wheat field in Southern Manitoba, Canada to compare CO­2 fluxes. Georeferenced leaf area index measurements were taken in 50 m grid of each field to establish uniformity of the source/sink within a footprint. Diurnal differences of similar magnitude in the CO2 ­fluxes were found in both the co-located experiment and the spatially separated intervals. Despite rigorous calibration during the experiment, some differences were caused by the measurement systems rather than by variation within the field. Interpretation of the spatial variation in leaf area index is being used to determine the contribution caused by difference in source/sink contributions to the flux footprint areas when the towers were spatially separated.

  17. Mantle carbon fluxes and reservoirs: A status update

    NASA Astrophysics Data System (ADS)

    Hirschmann, M. M.

    2015-12-01

    Carbon masses in and fluxes from the mantle are topics of intense community interest, but remain uncertain. Recent (2010-2015) estimates of ridge carbon fluxes and total mantle C concentrations each vary by a factors of 30 (0.3-8.4 X 1014 g CO2/year) and 38 (20-765 ppm C), respectively. Early estimates of C fluxes at ridges depended chiefly on C/3He ratios, but the recognition of kinetic C/He fractionation during degassing renders these estimates unsound. Methods based on CO2/Nb and CO2/Ba ratios benefit from a greatly expanded set of observations of minimally degassed MORB glasses and melt inclusions, as well as new constraints on the Nb and Ba concentrations of mean oceanic crust. Quite liberal bounds on MORB CO2/Nb and CO2/Ba of 550±250 and 125±50, combined with the ALLMORB (Gale et al. 2013) or global average MORB of Arevalo and McDonough (2010) concentrations of Nb and Ba yield fluxes of 2.1±1.3 X 1014 g CO2/year, thereby reducing the ridge flux uncertainty to a factor of 4. The C flux from oceanic islands, however, remains almost entirely unconstrained. For bulk mantle C, estimates based on He and Ar suffer from problems similar to those related to fluxes - C/He/Ar are strongly fractionated by degassing. As the upper mantle reservoir is well-constrained by sampling from MORB, uncertainty derives chiefly from the deep (OIB source) reservoir . High average mantle C (e.g. 300 or 765 ppm C; Dasgupta and Hirschmann, 2010; Marty, 2012) requires a deep C-rich reservoir that is a large fraction of the mantle (>30%), which means that it must be in part primitive (i.e. it is volatile-rich but cannot be chiefly recycled) and is too large to be "hidden", so should be sampled by OIB. Assuming source Ba and Nb concentrations similar to primitive mantle, bulk mantle with 300 or 765 ppm C require OIB sources with CO2/Ba >700-1400 and CO2/Nb>2800-5200, and would produce magmas (with appropriate Ba and Nb concentrations for OIB) with 20-40 wt.% CO2. These are far beyond any

  18. CarbonTracker-Lagrange: A model-data assimilation system for North American carbon flux estimates

    NASA Astrophysics Data System (ADS)

    He, Wei; Chen, Huilin; van der Velde, Ivar; Andrews, Arlyn; Sweeney, Colm; Baker, Ian; Ju, Weimin; van der Laan-Luijkx, Ingrid; Tans, Pieter; Peters, Wouter

    2016-04-01

    Understanding the regional carbon fluxes is of great importance for climate-related studies. To derive these carbon fluxes, atmospheric inverse modeling methods are often used. Different from global inverse modeling, regional studies need to deal with lateral boundary conditions (BCs) at the outer atmospheric domain studied. Also, regional inverse modeling systems typically use a higher spatial resolution and can be more computation-intensive. In this study, we implement a regional inverse modeling system for atmospheric CO₂ based on the CarbonTracker framework. We combine it with a high-resolution Lagrangian transport model, the Stochastic Time-Inverted Lagrangian Transport model driven by the Weather Forecast and Research meteorological fields (WRF-STILT). The new system uses independent information from aircraft CO₂ profiles to optimize lateral BCs, while simultaneously optimizing biosphere fluxes with near-surface CO₂ observations from tall towers. This Lagrangian transport model with precalculated footprints is computational more efficient than using an Eulerian model. We take SiBCASA biosphere model results as prior NEE from the terrestrial biosphere. Three different lateral BCs, derived from CarbonTracker North America mole fraction fields, CarbonTracker Europe mole fraction fields and an empirical BC from NOAA aircraft profiles, are employed to investigate the influence of BCs. To estimate the uncertainties of the optimized fluxes from the system and to determine the impacts of system setup on biosphere flux covariances, BC uncertainties and model-data mismatches, we tested various prior biosphere fluxes and BCs. To estimate the transport uncertainties, we also tested an alternative Lagrangian transport model Hybrid Single Particle Lagrangian Integrated Trajectory Model driven by the North American Mesoscale Forecast System meteorological fields (HYSPLIT-NAM12). Based on the above tests, we achieved an ensemble of inverse estimates from our system

  19. Carbon flux rerouting during Mycobacterium tuberculosis growth arrest

    PubMed Central

    Shi, Lanbo; Sohaskey, Charles D.; Pfeiffer, Carmen; Datta, Pratik; Parks, Michael; McFadden, Johnjoe; North, Robert J.; Gennaro, Maria L.

    2010-01-01

    Summary A hallmark of the Mycobacterium tuberculosis life cycle is the pathogen’s ability to switch between replicative and non-replicative states in response to host immunity. Transcriptional profiling by qPCR of ~50 M. tuberculosis genes involved in central and lipid metabolism revealed a re-routing of carbon flow associated with bacterial growth arrest during mouse lung infection. Carbon rerouting was marked by a switch from metabolic pathways generating energy and biosynthetic precursors in growing bacilli to pathways for storage compound synthesis during growth arrest. Results of flux balance analysis using an in silico metabolic network were consistent with the transcript abundance data obtained in vivo. Similar transcriptional changes were seen in vitro when M. tuberculosis cultures were treated with bacteriostatic stressors under different nutritional conditions. Thus, altered expression of key metabolic genes reflects growth rate changes rather than changes in substrate availability. A model describing carbon flux rerouting was formulated that (i) provides a coherent interpretation of the adaptation of M. tuberculosis metabolism to immunity-induced stress and (ii) identifies features common to mycobacterial dormancy and stress responses of other organisms. PMID:21091505

  20. Multi-property modeling of ocean basin carbon fluxes

    NASA Technical Reports Server (NTRS)

    Volk, Tyler

    1988-01-01

    The objectives of this project were to elucidate the causal mechanisms in some of the most important features of the global ocean/atomsphere carbon system. These included the interaction of physical and biological processes in the seasonal cycle of surface water pCo2, and links between productivity, surface chlorophyll, and the carbon cycle that would aid global modeling efforts. In addition, several other areas of critical scientific interest involving links between the marine biosphere and the global carbon cycle were successfully pursued; specifically, a possible relation between phytoplankton emitted DMS and climate, and a relation between the location of calcium carbonate burial in the ocean and metamorphic source fluxes of CO2 to the atmosphere. Six published papers covering the following topics are summarized: (1) Mass extinctions, atmospheric sulphur and climatic warming at the K/T boundary; (2) Sensitivity of climate and atmospheric CO2 to deep-ocean and shallow-ocean carbonate burial; (3) Controls on CO2 sources and sinks in the earthscale surface ocean; (4) pre-anthropogenic, earthscale patterns of delta pCO2 between ocean and atmosphere; (5) Effect on atmospheric CO2 from seasonal variations in the high latitude ocean; and (6) Limitations or relating ocean surface chlorophyll to productivity.

  1. Carbon Fluxes and Ocean Acidification in the Irminger Sea

    NASA Astrophysics Data System (ADS)

    Turk, Daniela; Barkhouse, Ryan; Olafsson, Jon; Olafsdottir, Solveig; Gulev, Sergej; Wallace, Doug

    2016-04-01

    Complex horizontal and vertical circulation in the Irminger and Labrador Seas has the potential to influence global ocean circulation and climate patterns. Deep water formation coupled with strong winds, and high rates of primary productivity in spring and summer result in these regions of the North Atlantic acting as strong sinks for atmospheric carbon dioxide. An increase in surface water pCO2 over the past two decades at a rate greater than that of the atmosphere has been observed and indicates a decrease in the air-sea pCO2 difference, the driving force of the air-sea CO2 flux. In response to the increasing pCO2, the surface water pH and the aragonite saturation states (Ωar) show a decreasing trend. Much of the previous work in the region has occurred on a few repeated transects over time, or in specific regions the Irminger basin. There is therefore a need for surveys of carbon parameters with broader horizontal spatial coverage to determine the CO2 fluxes and the effect of ocean acidification (OA) in the Irminger Sea. Here, we estimate surface pCO2 and CO2 fluxes, and Ωar over a large portion of the Irminger Sea and adjacent waters in the summer of 2013. These estimates are based on measurements of total alkalinity (TA) and pH from discrete samples in the upper 100m, collected at 83 stations on two cruises during the International Redfish Survey. The present study is designed to provide a baseline of inorganic carbon parameters for future, long-term study in the region. The large spatial scope of this study, and planned future work, will provide data that will help contextualize measures from repeated transect studies, underway measures, as well as measures from fixed observatories such those deployed by Ocean Observatories Initiative (OOI).

  2. Fluxes of carbon, phosphorylation, and redox intermediates during growth of Saccharomyces cerevisiae on different carbon sources

    SciTech Connect

    Cortassa, S.; Aon, J.C.; Aon, M.A.

    1995-07-20

    In the present work the authors developed a method for estimating anabolic fluxes when yeast are growing on various carbon substrates (glucose, glycerol, lactate, pyruvate, acetate, or ethanol) in minimal medium. Fluxes through the central amphibolic pathways were calculated from the product of the total required amount of a specified carbon intermediate times the growth rate. The required amount of each carbon intermediate was estimated from the experimentally determined macromolecular composition of cells grown in each carbon source and the monomer composition of macromolecules. Substrates sharing most metabolic pathways such as ethanol and acetate, despite changes in the macromolecular composition, namely carbohydrate content, did not show large variations in the overall fluxes through the main amphibolic pathways. For instance, in order to supply anabolic precursors to sustain growth rates in the range of 0.16/h to 0.205/h, similar large fluxes through Acetyl CoA synthase were required by acetate or ethanol. The V{sub max} activities of key enzymes of the main amphibolic pathways measured in permeabilized yeast cells allowed to confirm, qualitatively, the operation of those pathways for all substrates and were consistent on most substrates with the estimate fluxes required to sustain growth.

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

    USGS Publications Warehouse

    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

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  5. Nitrogen and carbon interactions in controlling terrestrial greenhouse gas fluxes

    NASA Astrophysics Data System (ADS)

    Ineson, Phil; Toet, Sylvia; Christiansen, Jesper

    2016-04-01

    The increased input of N to terrestrial systems may have profound impacts on net greenhouse gas (GHGs) fluxes and, consequently, our future climate; however, fully capturing and quantifying these interactions under field conditions urgently requires new, more efficient, measurement approaches. We have recently developed and deployed a novel system for the automation of terrestrial GHG flux measurements at the chamber and plot scales, using the approach of 'flying' a single measurement chamber to multiple points in an experimental field arena. As an example of the value of this approach, we shall describe the results from a field experiment investigating the interactions between increasing inorganic nitrogen (N) and carbon (C) additions on net ecosystem exchanges of N2O, CH4 and CO2, enabling the simultaneous application of 25 treatments, replicated five times in a fully replicated block field design. We will describe how the ability to deliver automated GHG flux measurements, highly replicated in space and time, has revealed hitherto unreported findings on N and C interactions in field soil. In our experiments we found insignificant N2O fluxes from bare field soil, even at very high inorganic N addition rates, but the interactive addition of even small amounts of available C resulted in very large and rapid N2O fluxes. The SkyGas experimental system enabled investigation of the underlying interacting response surfaces on the fluxes of the major soil-derived GHGs (CO2, CH4 and N2O) to increasing N and C inputs, and revealed unexpected interactions. In addition to these results we will also discuss some of the technical problems which have been overcome in developing these 'flying' systems and the potential of the systems for automatically screening the impacts of large numbers of treatments on GHG fluxes, and other ecosystem responses, under field conditions. We describe here technological advances that can facilitate the development of more robust GHG mitigation

  6. Carbon flux assessment in cow-calf grazing systems.

    PubMed

    Chiavegato, M B; Rowntree, J E; Powers, W J

    2015-08-01

    Greenhouse gas (GHG) fluxes and soil organic carbon (SOC) accumulation in grassland ecosystems are intimately linked to grazing management. This study assessed the carbon equivalent flux (Ceq) from 1) an irrigated, heavily stocked, low-density grazing system, 2) a nonirrigated, lightly stocked, high-density grazing system, and 3) a grazing-exclusion pasture site on the basis of the GHG emissions from pasture soils and enteric methane emissions from cows grazing different pasture treatments. Soil organic carbon and total soil nitrogen stocks were measured but not included in Ceq determination because of study duration and time needed to observe a change in soil composition. Light- and heavy-stocking systems had 36% and 43% greater Ceq than nongrazed pasture sites, respectively ( < 0.01). The largest contributor to increased Ceq from grazing systems was enteric CH emissions, which represented 15% and 32% of the overall emissions for lightly and heavily stocked grazing systems, respectively. Across years, grazing systems also had increased nitrous oxide (N2O; < 0.01) and CH emissions from pasture soils ( < 0.01) compared with nongrazed pasture sites but, overall, minimally contributed to total emissions. Results indicate no clear difference in Ceqflux between the grazing systems studied when SOC change is not incorporated ( = 0.11). A greater stocking rate potentially increased total SOC stock ( = 0.02), the addition of SOC deeper into the soil horizon ( = 0.01), and soil OM content to 30 cm ( < 0.01). The incorporation of long-term annual carbon sequestration into the determination of Ceq could change results and possibly differentiate the grazing systems studied. PMID:26440199

  7. Comparing the CarbonTracker and TM5-4DVar data assimilation systems for CO2 surface flux inversions

    NASA Astrophysics Data System (ADS)

    Babenhauserheide, A.; Basu, S.; Houweling, S.; Peters, W.; Butz, A.

    2015-03-01

    Data assimilation systems allow for estimating surface fluxes of greenhouse gases from atmospheric concentration measurements. Good knowledge about fluxes is essential to understand how climate change affects ecosystems and to characterize feedback mechanisms. Based on assimilation of more than one year of atmospheric in-situ concentration measurements, we compare the performance of two established data assimilation models, CarbonTracker and TM5-4DVar, for CO2 flux estimation. CarbonTracker uses an Ensemble Kalman Filter method to optimize fluxes on ecoregions. TM5-4DVar employs a 4-D variational method and optimizes fluxes on a 6° × 4° longitude/latitude grid. Harmonizing the input data allows analyzing the strengths and weaknesses of the two approaches by direct comparison of the modelled concentrations and the estimated fluxes. We further assess the sensitivity of the two approaches to the density of observations and operational parameters such as temporal and spatial correlation lengths. Our results show that both models provide optimized CO2 concentration fields of similar quality. In Antarctica CarbonTracker underestimates the wintertime CO2 concentrations, since its 5-week assimilation window does not allow for adjusting the far-away surface fluxes in response to the detected concentration mismatch. Flux estimates by CarbonTracker and TM5-4DVar are consistent and robust for regions with good observation coverage, regions with low observation coverage reveal significant differences. In South America, the fluxes estimated by TM5-4DVar suffer from limited representativeness of the few observations. For the North American continent, mimicking the historical increase of measurement network density shows improving agreement between CarbonTracker and TM5-4DVar flux estimates for increasing observation density.

  8. Comparing the CarbonTracker and M5-4DVar data assimilation systems for CO2 surface flux inversions

    NASA Astrophysics Data System (ADS)

    Babenhauserheide, A.; Basu, S.; Houweling, S.; Peters, W.; Butz, A.

    2015-09-01

    Data assimilation systems allow for estimating surface fluxes of greenhouse gases from atmospheric concentration measurements. Good knowledge about fluxes is essential to understand how climate change affects ecosystems and to characterize feedback mechanisms. Based on the assimilation of more than 1 year of atmospheric in situ concentration measurements, we compare the performance of two established data assimilation models, CarbonTracker and TM5-4DVar (Transport Model 5 - Four-Dimensional Variational model), for CO2 flux estimation. CarbonTracker uses an ensemble Kalman filter method to optimize fluxes on ecoregions. TM5-4DVar employs a 4-D variational method and optimizes fluxes on a 6° × 4° longitude-latitude grid. Harmonizing the input data allows for analyzing the strengths and weaknesses of the two approaches by direct comparison of the modeled concentrations and the estimated fluxes. We further assess the sensitivity of the two approaches to the density of observations and operational parameters such as the length of the assimilation time window. Our results show that both models provide optimized CO2 concentration fields of similar quality. In Antarctica CarbonTracker underestimates the wintertime CO2 concentrations, since its 5-week assimilation window does not allow for adjusting the distant surface fluxes in response to the detected concentration mismatch. Flux estimates by CarbonTracker and TM5-4DVar are consistent and robust for regions with good observation coverage, regions with low observation coverage reveal significant differences. In South America, the fluxes estimated by TM5-4DVar suffer from limited representativeness of the few observations. For the North American continent, mimicking the historical increase of the measurement network density shows improving agreement between CarbonTracker and TM5-4DVar flux estimates for increasing observation density.

  9. Switchgrass cultivars differentially affect soil carbon stabilization

    NASA Astrophysics Data System (ADS)

    Adkins, J.; Jastrow, J. D.; Wullschleger, S. D.; De Graaff, M.

    2012-12-01

    Soil organic carbon (SOC) storage depends on the amount and quality of plant-derived carbon (C) inputs to soil, which is largely regulated by plant roots via the processes of root turnover and exudation. While we know that plant roots mediate SOC stabilization, we do not fully understand which root characteristics specifically promote soil C storage. With this study we asked whether roots with coarse root systems versus roots with finely branched root systems differentially affect soil C stabilization. In order to answer this question, we collected soil cores (4.8 cm diameter, to a depth of 30 cm) from directly over the crown of six switchgrass (Panicum virgatum L.) cultivars that differed in root architecture. Specifically, three cultivars had fibrous root systems (i.e. high specific root length) and three had coarse root systems (i.e. low specific root length). The cultivars (C4 species) were grown in a C3 grassland for four years, allowing us to use isotopic fractionation techniques to assess differences in soil C input and stabilization. The cores were divided into depth increments of 10 cm and the soils were sieved (2mm). Soil from each depth increment was dispersed by shaking for 16 hours in a NaHMP solution to isolate coarse particulate organic matter (C-POM), fine particulate organic matter (F-POM), silt, and clay-sized fractions. Samples of soil fractions across all depths were analyzed for C and N contents as well as δ13C signature. We found that the relative abundance of the different soil fractions and associated δ13C signatures differed significantly among cultivars. These results indicate that switchgrass cultivars can differentially impact soil carbon inputs and stabilization. We hypothesize that these differences may be driven by variability in root architectures.

  10. Phytolith-Occluded Carbon Pools and Fluxes: New Estimates

    NASA Astrophysics Data System (ADS)

    Reyerson, P. E.; Alexandre, A. E.; Santos, G.

    2015-12-01

    Phytoliths are microscopic grains of silica (SiO2•nH2O) formed within plants. The biomineralization process typically encapsulates small quantities of carbon termed phytC. Upon decomposition, phytoliths are released from biomass and into soils. Recent research has suggested that phytC may be a large sink of atmospheric CO2 in soils. Important steps, therefore, are to quantify phytC cycling across ecosystems and to measure it's importance relative to the organic C cycle as a whole. Thus, information regarding phytC pool sizes and flux rates are needed. To an extent this has been performed. PhytC quantities can be easily estimated as long as 1) phytolith quantities and 2) the amount of C present in phytoliths are known. The quantity of C within phytoliths is still a subject of debate, but recent work has found quantities of less than 0.22%. Older studies, which rely on extraction methods which are now known to incompletely remove surface organic residues, have found phytC quantities from 1% to 20%. Hence, studies of phytC cycling using outdated methods may lead to overestimates. In order to re-estimate phytC dynamics, we compiled an extensive list of published works which document phytolith pools in above-ground biomass and soils, as well as flux rates. From these data phytC quantities were calculated using revised estimates of phytolith C percentages. PhytC quantities were also compared to total organic C (TOC) pools and fluxes. These calculations were then extrapolated to biome and global scales. At the biome scale, our results indicate that phytC within living biomass and soil pools as well as fluxes are one to two orders of magnitude smaller than previously estimated. PhytC is generally less than 0.01% of biomass TOC, and less than 1% of soil TOC. Annual phytC fluxes are less than 0.01% of TOC fluxes. At the global scale, annual phytC production is approximately 0.01% to 0.10% of gross C production. The findings of the present study suggest that direct C

  11. Autonomous Particle Recognition and Analysis of Carbon Flux Explorer Imagery

    NASA Astrophysics Data System (ADS)

    Hamilton, C. M.; Bishop, J. K.; Wood, T.

    2013-12-01

    The biologically mediated export, or sedimentation, of particulate organic carbon to ocean depths below 100 m is approximately 10 Pg C per year and is highly variable in space and time. Despite the need to understand the biological drivers for export and the depth dependence of carbon remineralization for carbon cycle prediction, there are scant observations of sedimentation dynamics in the upper 1000 m. The Carbon Flux Explorer (CFE) is a robotic ocean profiling system, which combines the Scripps Sounding Oceanographic Lagrangian Observer (SOLO) and the LBNL/Berkeley optical sedimentation recorder. The CFE is designed to conduct high-frequency (hourly) observations of particulate organic and inorganic carbon sedimentation to kilometer depths, absent of ships, in all sea conditions, be reprogrammable and adaptive once deployed, and relay data to shore in near real time via Iridium satellite links for seasons to years. The CFE operates by sequentially imaging settled particles at ~15 micrometer size resolution in transmitted, transmitted cross-polarized, and dark field illumination. At present, these images must be stored on the CFE until recovery. In other words, the CFE is deployable in the context of multi-month long process studies. Here we present progress on particle recognition and quantification methodology, which will enable a 100,000:1 compression of image data needed for efficient satellite telemetry and fully autonomous real-time operation. Our methodology includes corrective thresh-holding, cross imaging comparison, distinction of aggregates from organisms, and the classification of particle properties including particle fractal dimension. We also look at these findings in context of particle vertical velocity, float performance, and oceanic conditions. Data analysis examples drawing on recent CFE missions to California coastal and offshore waters and to the subarctic N Pacific ocean, some lasting 41 days, will be presented.

  12. Barium and carbon fluxes in the Canadian Arctic Archipelago

    NASA Astrophysics Data System (ADS)

    Thomas, Helmuth; Shadwick, Elizabeth; Dehairs, Frank; Lansard, Bruno; Mucci, Alfonso; Navez, Jacques; Gratton, Yves; Prowe, Friederike; Chierici, Melissa; Fransson, Agneta; Papakyriakou, Tim N.; Sternberg, Erika; Miller, Lisa A.; Tremblay, Jean-ÉRic; Monnin, Christophe

    2011-09-01

    The seasonal and spatial variability of dissolved Barium (Ba) in the Amundsen Gulf, southeastern Beaufort Sea, was monitored over a full year from September 2007 to September 2008. Dissolved Ba displays a nutrient-type behavior: the maximum water column concentration is located below the surface layer. The highest Ba concentrations are typically observed at river mouths, the lowest concentrations are found in water masses of Atlantic origin. Barium concentrations decrease eastward through the Canadian Arctic Archipelago. Barite (BaSO4) saturation is reached at the maximum dissolved Ba concentrations in the subsurface layer, whereas the rest of the water column is undersaturated. A three end-member mixing model comprising freshwater from sea-ice melt and rivers, as well as upper halocline water, is used to establish their relative contributions to the Ba concentrations in the upper water column of the Amundsen Gulf. Based on water column and riverine Ba contributions, we assess the depletion of dissolved Ba by formation and sinking of biologically bound Ba (bio-Ba), from which we derive an estimate of the carbon export production. In the upper 50 m of the water column of the Amundsen Gulf, riverine Ba accounts for up to 15% of the available dissolved Ba inventory, of which up to 20% is depleted by bio-Ba formation and export. Since riverine inputs and Ba export occur concurrently, the seasonal variability of dissolved Ba in the upper water column is moderate. Assuming a fixed organic carbon to bio-Ba flux ratio, carbon export out of the surface layer is estimated at 1.8 ± 0.45 mol C m-2 yr-1. Finally, we propose a climatological carbon budget for the Amundsen Gulf based on recent literature data and our findings, the latter bridging the surface and subsurface water carbon cycles.

  13. Barium and Carbon fluxes in the Canadian Arctic Archipelago

    NASA Astrophysics Data System (ADS)

    Thomas, H.; Shadwick, E. H.; Woule Ebongue, V.; Lansard, B.; Navez, J.; Gratton, Y.; Prowe, F.; Mucci, A.; Chierici, M.; Fransson, A.; Papakyriakou, T. N.; Sternberg, E.; Miller, L. A.

    2010-12-01

    The seasonal and spatial variability of dissolved Barium (Ba) in the Amundsen Gulf, southeastern Beaufort Sea, was monitored over a full year from September 2007 to September 2008. Barium displays a nutrient-type behavior with the highest concentrations observed at river mouths. The water column maximum is located at the base of the surface layer with lower concentrations above and below. The lowest concentrations are found in water masses of Atlantic origin, and Ba concentrations decrease eastward through the Canadian Arctic Archipelago. A three end-member mixing model comprising fresh water from sea-ice melt and rivers, as well as upper halocline water, was used to establish their relative contributions to the surface waters of the Amundsen Gulf. Based on water column and riverine Ba contributions, we assess the Ba depletion by particle sinking and subsequently estimate the carbon export production. In the upper 50 m of the water column of Amundsen Gulf, riverine Ba accounts for up to 15% of the dissolved Ba inventory, whereas up to 20% of the dissolved Ba inventory is depleted by barite (BaSO4) formation and export. Since riverine inputs and Ba export occur concurrently, the seasonal variability of dissolved Ba is moderate. Assuming a fixed organic carbon to barite flux ratio, carbon export out of the surface layer is estimated at 2 mol C m-2 yr-1. Finally, we propose a climatological carbon budget for the Amundsen Gulf based on recent literature data and our findings, the latter bridging the surface and subsurface water carbon cycles. This work is a contribution to the Canadian IPY programs CFL and GEOTRACES, to ArcticNet as well as to the IGBP/IHDP core project LOICZ.

  14. Carbon fluxes in the Arabian Sea: Export versus recycling

    NASA Astrophysics Data System (ADS)

    Rixen, Tim; Gaye, Birgit; Ramaswamy, Venkitasubramani

    2016-04-01

    The organic carbon pump strongly influences the exchange of carbon between the ocean and the atmosphere. It is known that it responds to global change but the magnitude and the direction of change are still unpredictable. Sediment trap experiments carried out at various sites in the Arabian Sea between 1986 and 1998 have shown differences in the functioning of the organic carbon pump (OCP). An OCP driven by eukaryotic phytoplankton operated in the upwelling region off Oman and during the spring bloom in the northern Arabian Sea. Cyanobacteria capable of fixing nitrogen seem to dominate the phytoplankton community during all other seasons. The export driven by cyanobacteria was much lower than the export driven by eukaryotic phytoplankton. Productivity and nutrient availability seems to be a main factor controlling fluxes during blooms of eukaryotic phytoplankton. The ballast effect caused by inputs of dust into the ocean and its incorporation into sinking particles seems to be the main factor controlling the export during times when cyanobacteria dominate the phytoplankton community. C/N ratios of organic matter exported from blooms dominated by nitrogen fixing cyanobacteria are enhanced and, furthermore, indicate a more efficient recycling of nutrients at shallower water depth. This implies that the bacterial-driven OCP operates more in a recycling mode that keeps nutrients closer to the euphotic zone whereas the OCP driven by eukaryotic phytoplankton reduces the recycling of nutrients by exporting them into greater water-depth.

  15. Hydroclimatic Controls over Global Variations in Phenology and Carbon Flux

    NASA Technical Reports Server (NTRS)

    Koster, Randal; Walker, G.; Thornton, Patti; Collatz, G. J.

    2012-01-01

    The connection between phenological and hydroclimatological variations are quantified through joint analyses of global NDVI, LAI, and precipitation datasets. The global distributions of both NDVI and LAI in the warm season are strongly controlled by three quantities: mean annual precipitation, the standard deviation of annual precipitation, and Budyko's index of dryness. Upon demonstrating that these same basic (if biased) relationships are produced by a dynamic vegetation model (the dynamic vegetation and carbon storage components of the NCAR Community Land Model version 4 combined with the water and energy balance framework of the Catchment Land Surface Model of the NASA Global Modeling and Assimilation Office), we use the model to perform a sensitivity study focusing on how phenology and carbon flux might respond to climatic change. The offline (decoupled from the atmosphere) simulations show us, for example, where on the globe a given small increment in precipitation mean or variability would have the greatest impact on carbon uptake. The analysis framework allows us in addition to quantify the degree to which climatic biases in a free-running GCM are manifested as biases in simulated phenology.

  16. [Biogeneous carbon fluxes in the boreal forests of Central Siberia].

    PubMed

    Vedrova, É F

    2011-01-01

    The assessments of the carbon pool and rate of plant biomass production, phytodetritus destruction, new formations of humic matters, and removal of water-soluble decomposition products for the forest ecosystems of the forest tundra and the northern and southern parts of the Central Siberian taiga were given. The rates of the main processes (organic-matter production and degradation) were demonstrated to be balanced in the ecosystems of the forest tundra. The larch forests of the northern taiga serve as a stock for a C atmosphere, which are equivalent to 32-34% of net primary production (NPP). The secondary birch growth where the understory needle-leaved trees have been formed and the primary old-growth fir forests are characterized by the balance of the main carbon fluxes in the southern taiga. The birch forests where the understory trees are just being formed and the fir forests at the age of 50-90 years serve as a stock for an average of 26% of carbon extracted as dioxide to make NPP. PMID:21442909

  17. Carbon dioxide fluxes associated with synoptic weather events over a southern inland water

    NASA Astrophysics Data System (ADS)

    Liu, H.; Zhang, Q.; Gao, Z.

    2015-12-01

    Evidence indicates that inland waters play an important role in regional and global carbon budget through releasing a substantial carbon into the atmosphere. To better quantify how environmental variables affect CO2 exchange between inland waters and the atmosphere and its temporal variations, we have conducted direct, long-term measurements of CO2 fluxes across the water-atmosphere interface over a large southern open water of Ross Barnett Reservoir in central Mississippi. Our data indicate that large CO2 flux pulses occurred occasionally throughout the course of a year with the duration of a few days for each pulse. Here we analyzed and demonstrated that these CO2 flux pulses were associated with the passages of synoptic weather events. Our preliminary results indicated that these synoptic weather events (e.g., extratropical clones and cold air bursts) led to the enhanced mechanical mixing due to increasing wind speeds and the instability of the atmospheric surface layer due to the decreasing air temperature. As a consequence, in-water processes were also substantially altered accordingly. Due to the dramatic decrease in air temperature caused by the events, the temperature in the water surface layer was largely reduced, generating in-water convection conditions and thus leading to the increased depths of the mixing layer in the water, as reflected by the water temperature profiles. The enhanced mechanical mixing in the atmospheric surface layer may have further contributed to the deepened mixing layer in the water. Our suggestions suggest that high CO2 effluxes during the pulse events were largely attributed to changes in the water-side physical processes that are directly linked to rapid changes in atmospheric processes associated with synoptic weather events. Given its substantial contribution of CO2 flux pulses to carbon emission, such physical processes should be taken into account when carbon emissions from inland waters are quantified.

  18. Influence of Leaf Area Index Prescriptions on Simulations of Heat, Moisture, and Carbon Fluxes

    NASA Technical Reports Server (NTRS)

    Kala, Jatin; Decker, Mark; Exbrayat, Jean-Francois; Pitman, Andy J.; Carouge, Claire; Evans, Jason P.; Abramowitz, Gab; Mocko, David

    2013-01-01

    Leaf-area index (LAI), the total one-sided surface area of leaf per ground surface area, is a key component of land surface models. We investigate the influence of differing, plausible LAI prescriptions on heat, moisture, and carbon fluxes simulated by the Community Atmosphere Biosphere Land Exchange (CABLEv1.4b) model over the Australian continent. A 15-member ensemble monthly LAI data-set is generated using the MODIS LAI product and gridded observations of temperature and precipitation. Offline simulations lasting 29 years (1980-2008) are carried out at 25 km resolution with the composite monthly means from the MODIS LAI product (control simulation) and compared with simulations using each of the 15-member ensemble monthly-varying LAI data-sets generated. The imposed changes in LAI did not strongly influence the sensible and latent fluxes but the carbon fluxes were more strongly affected. Croplands showed the largest sensitivity in gross primary production with differences ranging from -90 to 60 %. PFTs with high absolute LAI and low inter-annual variability, such as evergreen broadleaf trees, showed the least response to the different LAI prescriptions, whilst those with lower absolute LAI and higher inter-annual variability, such as croplands, were more sensitive. We show that reliance on a single LAI prescription may not accurately reflect the uncertainty in the simulation of the terrestrial carbon fluxes, especially for PFTs with high inter-annual variability. Our study highlights that the accurate representation of LAI in land surface models is key to the simulation of the terrestrial carbon cycle. Hence this will become critical in quantifying the uncertainty in future changes in primary production.

  19. Dynamics of carbon fluxes above a hemiboreal mixed forest

    NASA Astrophysics Data System (ADS)

    Krasnova, Alisa; Noe, Steffen M.; Niinemets, Ülo; Krasnov, Dmitrii

    2015-04-01

    Forest ecosystems are a major part of the biosphere and control land surface-atmosphere interactions. They influence atmospheric composition and climate significantly being sources and sinks of trace gases and energy. Mixed stands of both coniferous and deciduous tree species are characterized by greater seasonal variability of forest microclimate, canopy shape and density, length of growing season and plant activity and higher biota diversity and compared to pure boreal forests. These factors coupled with physical environment (atmospheric and meteorological conditions, soil properties) influence CO2 exchange between forest and the atmosphere. To explore complex interactions within ecosystem-atmosphere continuum of hemiboreal forest SMEAR Estonia station was established in Järvselja, Estonia. A 24 m height scaffolding tower located in a forest stand dominated by Norway spruce (Picea abies (L.) Karst.) with co-domination of Silver birch (Betula pendula Roth.) and Black alder (Alnus glutinosa L.) was used to study eddy-covariance fluxes of CO2. We present the results from the first continuous EC measurements over a hemiboreal mixed forest performed in 2011-2012. The focus of the study is on diurnal and annual dynamics of carbon fluxes and the influence of main environmental drivers.

  20. Upper ocean mixing controls the seasonality of planktonic foraminifer fluxes and associated strength of the carbonate pump in the oligotrophic North Atlantic

    NASA Astrophysics Data System (ADS)

    Salmon, K. H.; Anand, P.; Sexton, P. F.; Conte, M.

    2015-01-01

    Oligotrophic regions represent up to 75% of Earth's open-ocean environments. They are thus areas of major importance in understanding the plankton community dynamics and biogeochemical fluxes. Here we present fluxes of total planktonic foraminifera and 11 planktonic foraminifer species measured at the Oceanic Flux Program (OFP) time series site in the oligotrophic Sargasso Sea, subtropical western North Atlantic Ocean. Foraminifera flux was measured at 1500 m water depth, over two ~ 2.5-year intervals: 1998-2000 and 2007-2010. We find that foraminifera flux was closely correlated with total mass flux, carbonate and organic carbon fluxes. We show that the planktonic foraminifera flux increases approximately 5-fold during the winter-spring, contributing up to ~ 40% of the total carbonate flux. This was primarily driven by increased fluxes of deeper-dwelling globorotaliid species, which contributed up to 90% of the foraminiferal-derived carbonate during late winter-early spring. Interannual variability in total foraminifera flux, and in particular fluxes of the deep-dwelling species (Globorotalia truncatulinoides, Globorotalia hirsuta and Globorotalia inflata), was related to differences in seasonal mixed layer dynamics affecting the strength of the spring phytoplankton bloom and export flux, and by the passage of mesoscale eddies. As these heavily calcified, dense carbonate tests of deeper-dwelling species (3 times denser than surface dwellers) have greater sinking rates, this implies a high seasonality of the biological carbonate pump in oligotrophic oceanic regions. Our data suggest that climate cycles, such as the North Atlantic Oscillation, which modulates nutrient supply into the euphotic zone and the strength of the spring bloom, may also in turn modulate the production and flux of these heavily calcified deep-dwelling foraminifera by increasing their food supply, thereby intensifying the biological carbonate pump.

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

    USGS Publications Warehouse

    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

  2. Carbon Dioxide Flux in Mixed-grass Prairie: Response to Interannual Variation in Rainfall and Grazing History

    NASA Astrophysics Data System (ADS)

    Esposito, D.

    2002-12-01

    Grasslands are an important biome in the exchange of carbon between the biosphere and the atmosphere. However, our understanding of how carbon flux varies due to changes in precipitation, including drought conditions and land use history (grazing intensity) is only rudimentary. In this study we have evaluated the effects of adequate precipitation versus drought on net carbon flux, ecosystem respiration, and gross photosynthesis over three years (1998, 1999, and 2002) using chamber techniques. In addition, during 2002 measurements were taken across three grazing regimes (light, heavy, and ungrazed). Precipitation, or lack thereof, in 2002 made for a drought year compared to 1998 and 1999. The maximum rate of net carbon flux was lowest in 2002 at 3 mmol m-2 s-1 and highest in 1998 at 9 mmol m-2 s-1. Due to the drought conditions of 2002 grazing history had no affect on net flux rates. We propose that precipitation is the overriding factor that controls carbon flux in the mixed-grass prairie ecosystem, while land use has only marginal effects. Further data collected in a non-drought year is needed to corroborate this land use hypothesis.

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

    NASA Astrophysics Data System (ADS)

    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

  4. Trophic pathways and carbon flux patterns in the Laptev Sea

    NASA Astrophysics Data System (ADS)

    Schmid, Michael K.; Piepenburg, Dieter; Golikov, Alexander A.; Juterzenka, Karen von; Petryashov, Victor V.; Spindler, Michael

    2006-10-01

    The Laptev Sea is a high-Arctic epicontinental sea north of Siberia (Russia) that is one of the least understood regions of the world’s ocean. It is characterized by a shallow and broad shelf plateau, high influx of river water, sediments and nutrients during summer, long-lasting sea-ice cover from October to May, and the formation of a narrow flaw-lead polynya off the fast-ice edge during winter. Here, we describe results of a German-Russian research project (1993-present), presenting the distribution patterns and dynamics of its marine flora and fauna, as well as pathways and processes of coupling between sea-ice, water-column and sea-floor biota. Three ecological zones are distinguished along a combined east-west and Lena-impact gradient, differing in the composition of pelagic and benthic communities. In general, high Chl a concentrations in the sediments indicate a tight coupling between sympagic and pelagic primary production and nutrient supply to the benthos throughout the entire Laptev Sea. However, there were pronounced regional differences between the ecological zones in magnitude of primary production and trophic dynamics. Primary production during the ice-free summer was highest in the estuarine zone most strongly influenced by the Lena River (210 mg C m -2 day -1). The western and northeastern Laptev Sea yielded 55 and 95 mg C m -2 day -1, respectively. Moreover, the zones differed in the partitioning of carbon flux between zooplankton and benthic food webs. In the Lena zone zooplankton carbon demand was about 31 mg C m -2 day -1 whereas in the western zone it was 21 mg C m -2 day -1 and in the eastern zone 4 mg C m -2 day -1. Total benthic carbon demand was 32 mg C m -2 day -1 for the Lena zone, 56 mg C m -2 day -1 in the western zone and 100 mg C m -2 day -1 in the northeastern zone. A carbon budget constructed for the Laptev Sea indicates that (1) a high proportion of primary production is channelled through the benthic trophic web, bypassing the

  5. Aeolian nutrient fluxes following wildfire in sagebrush steppe: Implications for soil carbon storage

    USGS Publications Warehouse

    Hasselquist, N.J.; Germino, M.J.; Sankey, J.B.; Ingram, L.J.; Glenn, N.F.

    2011-01-01

    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. ?? Author(s) 2011. CC Attribution 3.0 License.

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

    NASA Astrophysics Data System (ADS)

    Hasselquist, N. J.; Germino, M. J.; Sankey, J. B.; Ingram, L. J.; Glenn, N. F.

    2011-12-01

    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.

  7. Nitrogen, tillage, and crop rotation effects on carbon dioxide and methane fluxes from irrigated cropping systems.

    PubMed

    Alluvione, Francesco; Halvorson, Ardell D; Del Grosso, Stephen J

    2009-01-01

    Long-term effects of tillage intensity, N fertilization, and crop rotation on carbon dioxide (CO(2)) and methane (CH(4)) flux from semiarid irrigated soils are poorly understood. We evaluated effects of: (i) tillage intensity [no-till (NT) and conventional moldboard plow tillage (CT)] in a continuous corn rotation; (ii) N fertilization levels [0-246 kg N ha(-1) for corn (Zea mays L.); 0 and 56 kg N ha(-1) for dry bean (Phaseolus vulgaris L.); 0 and 112 kg N ha(-1) for barley (Hordeum distichon L.)]; and (iii) crop rotation under NT soil management [corn-barley (NT-CB); continuous corn (NT-CC); corn-dry bean (NT-CDb)] on CO(2) and CH(4) flux from a clay loam soil. Carbon dioxide and CH(4) fluxes were monitored one to three times per week using vented nonsteady state closed chambers. No-till reduced (14%) growing season (154 d) cumulative CO(2) emissions relative to CT (NT: 2.08 Mg CO(2)-C ha(-1); CT: 2.41 Mg CO(2)-C ha(-1)), while N fertilization had no effect. Significantly lower (18%) growing season CO(2) fluxes were found in NT-CDb than NT-CC and NT-CB (11.4, 13.2 and 13.9 kg CO(2)-C ha(-1)d(-1) respectively). Growing season CH(4) emissions were higher in NT (20.2 g CH(4) ha(-1)) than in CT (1.2 g CH(4) ha(-1)). Nitrogen fertilization and cropping rotation did not affect CH(4) flux. Implementation of NT for 7 yr with no N fertilization was not adequate for restoring the CH(4) oxidation capacity of this clay loam soil relative to CT plowed and fertilized soil.

  8. Constraining surface carbon fluxes using in situ measurements of carbonyl sulfide and carbon dioxide

    NASA Astrophysics Data System (ADS)

    Berkelhammer, M.; Asaf, D.; Still, C.; Montzka, S.; Noone, D.; Gupta, M.; Provencal, R.; Chen, H.; Yakir, D.

    2014-02-01

    Understanding the processes that control the terrestrial exchange of carbon is critical for assessing atmospheric CO2 budgets. Carbonyl sulfide (COS) is taken up by vegetation during photosynthesis following a pathway that mirrors CO2 but has a small or nonexistent emission component, providing a possible tracer for gross primary production. Field measurements of COS and CO2 mixing ratios were made in forest, senescent grassland, and riparian ecosystems using a laser absorption spectrometer installed in a mobile trailer. Measurements of leaf fluxes with a branch-bag gas-exchange system were made across species from 10 genera of trees, and soil fluxes were measured with a flow-through chamber. These data show (1) the existence of a narrow normalized daytime uptake ratio of COS to CO2 across vascular plant species of 1.7, providing critical information for the application of COS to estimate photosynthetic CO2 fluxes and (2) a temperature-dependent normalized uptake ratio of COS to CO2 from soils. Significant nighttime uptake of COS was observed in broad-leafed species and revealed active stomatal opening prior to sunrise. Continuous high-resolution joint measurements of COS and CO2 concentrations in the boundary layer are used here alongside the flux measurements to partition the influence that leaf and soil fluxes and entrainment of air from above have on the surface carbon budget. The results provide a number of critical constraints on the processes that control surface COS exchange, which can be used to diagnose the robustness of global models that are beginning to use COS to constrain terrestrial carbon exchange.

  9. Defaunation affects carbon storage in tropical forests

    PubMed Central

    Bello, Carolina; Galetti, Mauro; Pizo, Marco A.; Magnago, Luiz Fernando S.; Rocha, Mariana F.; Lima, Renato A. F.; Peres, Carlos A.; Ovaskainen, Otso; Jordano, Pedro

    2015-01-01

    Carbon storage is widely acknowledged as one of the most valuable forest ecosystem services. Deforestation, logging, fragmentation, fire, and climate change have significant effects on tropical carbon stocks; however, an elusive and yet undetected decrease in carbon storage may be due to defaunation of large seed dispersers. Many large tropical trees with sizeable contributions to carbon stock rely on large vertebrates for seed dispersal and regeneration, however many of these frugivores are threatened by hunting, illegal trade, and habitat loss. We used a large data set on tree species composition and abundance, seed, fruit, and carbon-related traits, and plant-animal interactions to estimate the loss of carbon storage capacity of tropical forests in defaunated scenarios. By simulating the local extinction of trees that depend on large frugivores in 31 Atlantic Forest communities, we found that defaunation has the potential to significantly erode carbon storage even when only a small proportion of large-seeded trees are extirpated. Although intergovernmental policies to reduce carbon emissions and reforestation programs have been mostly focused on deforestation, our results demonstrate that defaunation, and the loss of key ecological interactions, also poses a serious risk for the maintenance of tropical forest carbon storage. PMID:26824067

  10. Defaunation affects carbon storage in tropical forests.

    PubMed

    Bello, Carolina; Galetti, Mauro; Pizo, Marco A; Magnago, Luiz Fernando S; Rocha, Mariana F; Lima, Renato A F; Peres, Carlos A; Ovaskainen, Otso; Jordano, Pedro

    2015-12-01

    Carbon storage is widely acknowledged as one of the most valuable forest ecosystem services. Deforestation, logging, fragmentation, fire, and climate change have significant effects on tropical carbon stocks; however, an elusive and yet undetected decrease in carbon storage may be due to defaunation of large seed dispersers. Many large tropical trees with sizeable contributions to carbon stock rely on large vertebrates for seed dispersal and regeneration, however many of these frugivores are threatened by hunting, illegal trade, and habitat loss. We used a large data set on tree species composition and abundance, seed, fruit, and carbon-related traits, and plant-animal interactions to estimate the loss of carbon storage capacity of tropical forests in defaunated scenarios. By simulating the local extinction of trees that depend on large frugivores in 31 Atlantic Forest communities, we found that defaunation has the potential to significantly erode carbon storage even when only a small proportion of large-seeded trees are extirpated. Although intergovernmental policies to reduce carbon emissions and reforestation programs have been mostly focused on deforestation, our results demonstrate that defaunation, and the loss of key ecological interactions, also poses a serious risk for the maintenance of tropical forest carbon storage.

  11. Defaunation affects carbon storage in tropical forests.

    PubMed

    Bello, Carolina; Galetti, Mauro; Pizo, Marco A; Magnago, Luiz Fernando S; Rocha, Mariana F; Lima, Renato A F; Peres, Carlos A; Ovaskainen, Otso; Jordano, Pedro

    2015-12-01

    Carbon storage is widely acknowledged as one of the most valuable forest ecosystem services. Deforestation, logging, fragmentation, fire, and climate change have significant effects on tropical carbon stocks; however, an elusive and yet undetected decrease in carbon storage may be due to defaunation of large seed dispersers. Many large tropical trees with sizeable contributions to carbon stock rely on large vertebrates for seed dispersal and regeneration, however many of these frugivores are threatened by hunting, illegal trade, and habitat loss. We used a large data set on tree species composition and abundance, seed, fruit, and carbon-related traits, and plant-animal interactions to estimate the loss of carbon storage capacity of tropical forests in defaunated scenarios. By simulating the local extinction of trees that depend on large frugivores in 31 Atlantic Forest communities, we found that defaunation has the potential to significantly erode carbon storage even when only a small proportion of large-seeded trees are extirpated. Although intergovernmental policies to reduce carbon emissions and reforestation programs have been mostly focused on deforestation, our results demonstrate that defaunation, and the loss of key ecological interactions, also poses a serious risk for the maintenance of tropical forest carbon storage. PMID:26824067

  12. Unsaturated zone carbon dioxide flux, mixing, and isotopic composition at the USGS Amargosa Desert Research Site

    NASA Astrophysics Data System (ADS)

    Conaway, C. H.; Thordsen, J. J.; Thomas, B.; Haase, K.; Moreo, M. T.; Walvoord, M. A.; Andraski, B. J.; Stonestrom, D. A.

    2015-12-01

    Elevated concentrations of tritium, radiocarbon, and volatile organic compounds at the USGS Amargosa Desert Research Site, adjacent to a low-level radioactive waste disposal facility, have stimulated research on factors affecting transport of these contaminants. This research includes an examination of unsaturated zone carbon dioxide (CO2) fluxes, mixing, and isotopic composition, which can help in understanding these factors. In late April 2015 we collected 76 soil-gas samples in multi-layer foil bags from existing 1.5-m deep tubes, both inside and outside the low-level waste area, as well as from two 110-m-deep multilevel gas-sampling boreholes and a distant background site. These samples were analyzed for carbon dioxide concentration and isotopic composition by direct injection into a cavity ring-down spectrometer. Graphical analysis of results indicates mixing of CO2 characteristic of the root zone (δ13C -18 ‰ VPDB), deep soil gas of the capillary fringe (-20‰), and CO2 produced by microbial respiration of organic matter disposed in the waste area trenches (-28‰). Land-surface boundary conditions are being constrained by the application of a novel non-dispersive infrared sensor and traditional concentration and flux measurements, including discrete CO2 flux data using a gas chamber method to complement continuous data from surface- and tower-based CO2 sensors. These results shed light on radionuclide and VOC mobilization and transport mechanisms from this and similar waste disposal facilities.

  13. Two decades of carbon flux from forests of the Pacific northwest

    SciTech Connect

    Cohen, W.B.; Fiorella, M.; Harmon, M.E.; Wallin, D.O.

    1996-12-01

    Earth`s climate is greatly influenced by carbon dioxide concentrations in the atmosphere. Besides combustion of fossil fuels, another important anthropogenic source of atmospheric carbon is associated with deforestation, especially in primary forests, which can store large amounts of carbon in the form of organic biomass. There are a number of problems with models of carbon flux previously developed. The authors are developing a strategy to estimate regional carbon fluxes designed to overcome many of them. This article describes the modeling strategy and the results of the carbon flux modeling in forest of the Pacific Northwest region of the USA using the following topic areas: C flux modeling strategy, demonstration of modeling strategy, significance to regional and global carbon cycle, and resource management implications. 53 refs., 7 figs., 1 tab.

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

    EPA Science Inventory

    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...

  15. Carbon flux estimation by using ACTM for the period 2002-2011

    NASA Astrophysics Data System (ADS)

    Saeki, T.; Patra, P. K.; Kawa, S. R.; Collatz, G. J.

    2013-12-01

    We have estimated carbon flux by using an AGCM (atmospheric general circulation model)-based Chemistry Transport Model (ACTM) in a Bayesian synthesis inversion framework. Firstly, all efforts have been made to check the good performance of ACTM for the representation of synoptic to inter-hemispheric transport time scales using the simulations of SF6, 222Radon, CO2, CH4 and N2O concentrations and comparisons with observations. Thus we expect relatively less bias in estimated carbon fluxes by the inversion. Carbon fluxes were estimated for 84 regions (54 lands + 30 oceans) over the globe during the period of 2002-2011 with CO2 concentration from GLOBALVIEW (2012). Seasonally varying a priori fluxes for atmosphere-ocean exchange are taken from Takahashi et al. (2002, 2009). Interannually varying a priori fossil fuel fluxes (incl. cement production) are taken from EDGAR4.2. 3-hourly and monthly terrestrial biosphere fluxes are taken from the Carnegie Ames and Stanford Approach (CASA) terrestrial biosphere model at the NASA/GSFC. As a result of time-dependent inversions, differences in predicted fluxes with the 3-hourly CASA fluxes and the monthly CASA fluxes are found remarkably in North and South Americas and Australia. Estimated carbon fluxes for ocean regions are almost independent of a priori fluxes (Takahashi et al., 2002 or 2009) except for Southern Ocean. Other sensitivity tests on prior flux dependencies and site selection will be shown in the presentation.

  16. Spatial patterns and climate drivers of carbon fluxes in terrestrial ecosystems of China.

    PubMed

    Yu, Gui-Rui; Zhu, Xian-Jin; Fu, Yu-Ling; He, Hong-Lin; Wang, Qiu-Feng; Wen, Xue-Fa; Li, Xuan-Ran; Zhang, Lei-Ming; Zhang, Li; Su, Wen; Li, Sheng-Gong; Sun, Xiao-Min; Zhang, Yi-Ping; Zhang, Jun-Hui; Yan, Jun-Hua; Wang, Hui-Min; Zhou, Guang-Sheng; Jia, Bing-Rui; Xiang, Wen-Hua; Li, Ying-Nian; Zhao, Liang; Wang, Yan-Fen; Shi, Pei-Li; Chen, Shi-Ping; Xin, Xiao-Ping; Zhao, Feng-Hua; Wang, Yu-Ying; Tong, Cheng-Li

    2013-03-01

    Understanding the dynamics and underlying mechanism of carbon exchange between terrestrial ecosystems and the atmosphere is one of the key issues in global change research. In this study, we quantified the carbon fluxes in different terrestrial ecosystems in China, and analyzed their spatial variation and environmental drivers based on the long-term observation data of ChinaFLUX sites and the published data from other flux sites in China. The results indicate that gross ecosystem productivity (GEP), ecosystem respiration (ER), and net ecosystem productivity (NEP) of terrestrial ecosystems in China showed a significantly latitudinal pattern, declining linearly with the increase of latitude. However, GEP, ER, and NEP did not present a clear longitudinal pattern. The carbon sink functional areas of terrestrial ecosystems in China were mainly located in the subtropical and temperate forests, coastal wetlands in eastern China, the temperate meadow steppe in the northeast China, and the alpine meadow in eastern edge of Qinghai-Tibetan Plateau. The forest ecosystems had stronger carbon sink than grassland ecosystems. The spatial patterns of GEP and ER in China were mainly determined by mean annual precipitation (MAP) and mean annual temperature (MAT), whereas the spatial variation in NEP was largely explained by MAT. The combined effects of MAT and MAP explained 79%, 62%, and 66% of the spatial variations in GEP, ER, and NEP, respectively. The GEP, ER, and NEP in different ecosystems in China exhibited 'positive coupling correlation' in their spatial patterns. Both ER and NEP were significantly correlated with GEP, with 68% of the per-unit GEP contributed to ER and 29% to NEP. MAT and MAP affected the spatial patterns of ER and NEP mainly by their direct effects on the spatial pattern of GEP.

  17. Comparing carbon dioxide (CO2) flux between no-till and conventional tillage agriculture in Lesotho

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil management practices can either sequester or emit carbon (C). Feeding seven billion people mandates that soils be used intensively for food production, but how these soils are managed greatly impacts soil fluxes of carbon dioxide (CO2). However, the lack of CO2 flux measurements on African subs...

  18. Carbon, Water and Energy Fluxes in an African Savanna Ecosystem

    NASA Astrophysics Data System (ADS)

    Hanan, N. P.; Scholes, R. J.; Privette, J. L.

    2001-12-01

    Eddy covariance measurements of the turbulent fluxes of CO2, water and energy, and associated micrometeorological and biophysical measurements, have been made at a site in the Kruger National Park (KNP), South Africa, since April 2000. The study site is located in the southern region of KNP in a gently undulating landscape on granite substrate, with drainage lines 2-3 km apart and ridge tops 30-40 meters above the valley floors. The climate is semi-arid subtropical, with hot, rainy summers, warm dry winters and annual average rainfall of 550-650 mm. The soils of the catena vary between coarse-textured sand near the ridge-tops and finer-textured loamy-sand on the mid-slope and valley floors. The vegetation also differs along the catena, with broad-leaved tree species and low palatability grasses on the sandy soil and bi-pinnate tree species and more palatable grasses on the loam soils. The natural disturbance regime of the site includes fire, at return intervals of 3-8 years, as well as grazing and browsing by numerous species of wild ungulate. Results from the first 18 months of flux measurements are presented, contrasting an unusually wet growing season (1999-2000), followed by a dry-season fire, and a growing season with more average rainfall (2000-2001). The functional and phenological differences between broad-leaf and fine-leaf savanna are explored, and the carbon and water dynamics of the savanna systems interpreted in the context of seasonal weather variation, soil type and nutrient status.

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

    NASA Technical Reports Server (NTRS)

    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.

  20. Estimating carbon and energy fluxes in arctic tundra

    NASA Astrophysics Data System (ADS)

    Gokkaya, K.; Jiang, Y.; Rastetter, E.; Shaver, G. R.; Rocha, A. V.

    2013-12-01

    Arctic ecosystems are undergoing a very rapid change due to climate change and their response to climate change has important implications for the global energy budget and carbon (C) cycling. Therefore, it is important to understand how (C) and energy fluxes in the Arctic will respond to climate change. However, attribution of these responses to climate is challenging because measured fluxes are the sum of multiple processes that respond differently to environmental factors. For example, net ecosystem exchange of CO2 (NEE) is the net result of gross (C) uptake by plant photosynthesis (GPP) and (C) loss by ecosystem respiration (ER) and similarly, evapotranspiration (i.e. latent energy, LE) is the sum of transpiration and evaporation. Partitioning of NEE into GPP and ER requires nighttime measurements of NEE, when photosynthesis does not take place, to be extrapolated to daytime. This is challenging in the Arctic because of the long photoperiod during the growing season and the errors involved during the extrapolation. Transpiration (energy), photosynthesis (carbon), and vegetation phenology are inherently coupled because leaf stomata are the primary regulators of gas exchange. Our objectives in this study are to i) estimate canopy resistance (Rc) based on a light use efficiency model, ii) utilize the estimated Rc to predict GPP and transpiration using a coupled C and energy model and thus improve the partitioning of NEE and LE, and iii) to test ensemble Kalman filter (EnKF) to estimate model parameters and improve model predictions. Results from one growing season showed that the model predictions can explain 75 and 71% of the variance in GPP and LE in the Arctic tundra ecosystem, respectively. When the model was embedded within the EnKF for estimating Rc, the amount of variance explained for GPP increased to 81% but there was no improvement for the prediction of LE. This suggests that the factors controlling LE are not fully integrated in the model such as the

  1. Carbon Monoxide Affecting Planetary Atmospheric Chemistry

    NASA Astrophysics Data System (ADS)

    He, Chao; Horst, Sarah

    2016-10-01

    Atmospheric hazes are present in a range of solar system and extrasolar planetary atmospheres, and organic hazes, such as that in Titan's atmosphere, could be a source of prebiotic molecules.1 However, the chemistry occurring in planetary atmospheres and the resulting chemical structures are still not clear. Numerous experimental simulations2 have been carried out in the laboratory to understand the chemistry in N2/CH4 atmospheres, but very few simulations4 have included CO in their initial gas mixtures, which is an important component in many N2/CH4 atmospheres including Titan, Triton, and Pluto.3 Here we have conducted a series of atmosphere simulation experiments using AC glow discharge (cold plasma) as energy source to irradiate reactions in gas mixtures of CO, CH4, and N2 with a range of CO mixing ratios (from 0, 0.05%, 0.2%, 0.5%, 1%, 2.5%, to 5%) at low temperature (~100 K). Gas phase products are monitored during the reaction by quadrupole mass spectrometer (MS), and solid phase products are analyzed by solution-state nuclear magnetic resonance spectroscopy (NMR). MS results show that with the increase of CO in the initial gases, the production of nitrogenous organic molecules increases while the production of hydrogen molecules decreases in the gas phase. NMR measurements of the solid phase products show that with the increase of CO, hydrogen atoms bonded to nitrogen or oxygen in unsaturated structures increase while those bonded to saturated carbon decrease, which means more unsaturated species and less saturated species formed with the addition of CO. MS and NMR results demonstrate that the inclusion of CO affects the compositions of both gas and solid phase products, indicating that CO has an important impact on the chemistry occurring in our experiments and probably in planetary atmospheres.1. Hörst, S. M., et al. 2012, AsBio, 12, 8092. Cable, M. L., et al. 2012, Chem. Rev., 112, 18823. Lutz, B. L., et al. 1983, Sci, 220, 1374; Greaves, J. S., et al

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

    NASA Astrophysics Data System (ADS)

    Xiao, J.

    2013-12-01

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

  3. Influence of water table on carbon dioxide, carbon monoxide, and methane fluxes from taiga bog microcosms

    SciTech Connect

    Funk, D.W.; Pullmann, E.R.; Peterson, K.M.

    1994-09-01

    Hydrological changes, particularly alterations in water table level, may largely overshadow the more direct effects of global temperature increase upon carbon cycling in arctic and subarctic wetlands. Frozen cores (n=40) of intact soils and vegetation were collected from a bog near Fairbanks, Alaska, and fluxes of CO{sub 2}, CH{sub 4}, and Co in response to water table variation were studied under controlled conditions in the Duke University phytotron. Core microcosms thawed to a 20-cm depth over 30 days under a 20 hour photoperiod with a day/night temperature regime of 20/10{degrees}C. After 30 days the water table in 20 microcosms was decreased from the soil surface to -15 cm and maintained at the soil surface in 20 control cores. Outward fluxes of CO{sub 2} (9-16 g m{sup -2}d{sup -1}) and CO (3-4 mg m{sup -2}d{sup -1}) were greatest during early thaw and decreased to near zero for both gases before the water table treatment started. Lower water table tripled CO{sub 2} flux to the atmosphere when compared with control cores. Carbon monoxide was emitted at low rates from high water table cores and consumed by low water table cores. Methane fluxes were low (<1 mg m{sup -2}d{sup -1}) in all cores during thaw. High water table cores increased CH{sub 4} flux to 8-9 mg m{sup -2}d{sup -1} over 70 days and remained high relative to the low water table cores (<0.74 mg m{sup -2}d{sup -1}). Although drying of wetland taiga soils may decrease CH{sub 4} emissions to the atmosphere, the associated increase in CO{sub 2} due to aerobic respiration will likely increase the global warming potential of gas emissions from these soils. 43 refs., 4 figs.

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

    NASA Astrophysics Data System (ADS)

    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.

  5. Impacts of observation-driven trait variation on carbon fluxes in an earth system projection

    NASA Astrophysics Data System (ADS)

    Verheijen, Lieneke; van Bodegom, Peter; Aerts, Rien; Brovkin, Victor

    2014-05-01

    Climate projections are still highly uncertain and differences in predicted terrestrial global carbon budgets by earth system models (ESMs) are large, both with respect to the size and direction of change. Part of these uncertainties in the land carbon dynamics are caused by differences in the modeled functional responses of vegetation in reaction to climatic drivers. In reality, changes in vegetation responses to the environment are driven by processes like species plasticity, acclimation, (genotypic) adaptation, species turnover and shifts in species abundances. These processes can cause shifts within community mean trait values, which in turn are will affect carbon fluxes to and from the system. Because most current dynamic global vegetation models (DGVMs, the terrestrial part of ESMs) are not species based, these processes are not or poorly modeled. The recent availability of a large trait database (TRY-database), including both field measurements and experimental data, enables parameterization of the models with observational trait data. Many community mean trait values correlate with local environmental conditions. Such trait-climate relationships can be used to model variation in traits in DGVMs and allow for spatial and temporal variation in functional vegetation responses. The aim of this study was to identify the impacts of observation-driven trait variation on modeled carbon fluxes in climate projections. We determined and incorporated relationships between observational trait and climate data for each plant functional type (PFT) in the DGVM JSBACH. Within each grid cell, traits were varied every year, based on the local climatic conditions in the model. We also included CO2 acclimation of traits based on FACE-experiments, as projections concern elevated CO2 concentrations. Impacts on global carbon budgets were large; in the simulation with variable traits the high latitudes (temperate, boreal and arctic areas) were stronger carbon sinks and the tropical

  6. Dissolved Carbon Flux and Mass Balance From a Wetland-Dominated Karstic Headwater Catchment

    NASA Astrophysics Data System (ADS)

    Duval, T. P.; Waddington, J. M.; Branfireun, B. A.

    2009-05-01

    between the wetland types. Significant stream recharge back into the dolomite occurred through the calcareous fen, resulting in the peatland acting as a net 'sink' of DOC and DIC, which was stronger in the drier summer than the wetter autumn. The stream became unconfined through the cedar swamp, with appreciable depression storage that resulted in the wetland becoming a greater net sink of DOC and DIC in the autumn when increased stream discharge into the swamp resulted in greater depression storage. The marsh received significant groundwater inputs from the karstic dolomite, diluting the stream of DOC, but increasing the flux of DIC, resulting in the wetland acting as a sink of DOC but a source of DIC. These data demonstrate that the presence of calcareous bedrock overwhelms the influence of wetland sediments on the dynamics of terrestrial-stream linkages to carbon transport, and that groundwater systems and wetland type can significantly affect the stream-borne flux of carbon from watersheds.

  7. Decadal-Scale Increases in Dissolved Carbon Flux from the Western Canadian Arctic to the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Tank, S. E.; Striegl, R. G.; McClelland, J. W.; Kokelj, S. V.

    2014-12-01

    The chemical signature of large rivers has a clear effect on the chemistry and biology of the nearshore ocean. At the same time, the flux of riverine constituents to coastal environments can be used to understand changes occurring over broad terrestrial landscapes. This is particularly relevant in the Arctic, where rivers have a disproportionate impact on nearshore ocean function. Additionally, change is playing out rapidly in Arctic regions, as permafrost thaw and changes in temperature and hydrology are exposing previously frozen soils, changing the nature of hydrological linkages between land and water, and affecting the seasonality of riverine chemistry and flux. Here, we examine a 40-year dataset of point-measurement alkalinity (largely dissolved inorganic carbon) and dissolved organic carbon (DOC) concentrations near the mouth of the Mackenzie River, in addition to similar data from four of the Mackenzie's major sub-catchments. These datasets are coupled with continuous discharge records, and capture flow from the fourth largest river discharging to the Arctic Ocean. Trends near the Mackenzie mouth show that annual fluxes of both alkalinity and DOC are increasing over time, with the proportional changes in DOC (approximately 16% per decade) being much greater than those for alkalinity (approximately 4% per decade). Seasonally, this increase in total flux occurs largely in the winter and late summer, for both constituents. Sub-catchment datasets indicate that these fluxes are increasing in northern, but not southern, sub-catchment regions. These results have clear implications for nearshore ocean function in the western Canadian Arctic. Increases in DOC may fuel increased bacterial metabolism, while differences in the magnitude of change in alkalinity and DOC flux may modify coastal aragonite saturation. Overall, the changing flux of dissolved carbon near the mouth of the Mackenzie River documents broad-scale changes in the carbon cycle of this region, both on

  8. Upper ocean mixing controls the seasonality of planktonic foraminifer fluxes and associated strength of the carbonate pump in the oligotrophic North Atlantic

    NASA Astrophysics Data System (ADS)

    Salmon, K. H.; Anand, P.; Sexton, P. F.; Conte, M.

    2014-08-01

    Oligotrophic regions represent up to 75% of Earth's open-ocean environments, and are typically characterized by nutrient-limited upper-ocean mixed layers. They are thus areas of major importance in understanding the plankton community dynamics and biogeochemical fluxes. Here we present fluxes of total planktonic foraminifera and eleven planktonic foraminifer species from a bi-weekly sediment trap time series in the oligotrophic Sargasso Sea, subtropical western North Atlantic Ocean at 1500 m water depth, over two ∼2.5 year intervals, 1998-2000 and 2007-2010. Foraminifera flux was closely correlated with total mass flux and with carbonate and organic carbon fluxes. We show that the planktonic foraminifera flux increases approximately five-fold during the winter-spring, contributing up to ∼40% of the total carbonate flux, driven primarily by increased fluxes of deeper dwelling ("globorotaliid") species. Interannual variability in total foraminifera flux, and in particular fluxes of the deep dwelling Globorotalia truncatulinoides, Globorotalia hirsuta, Globorotalia inflata, were related to differences in seasonal mixed layer dynamics affecting the strength of the spring phytoplankton bloom and export flux, and by the passage of mesoscale eddies. The heavily calcified, dense carbonate tests of deeper dwelling species (3 times denser than surface dwellers) can contribute up to 90% of the foraminiferal-derived carbonate in this region during late winter-early spring, implying a high seasonality of the biological carbonate pump in oligotrophic oceanic regions. Our data suggest that climate cycles, such as the North Atlantic Oscillation, that modulate the depth of the mixed layer, intensity of nutrient upwelling and primary production could also modulate the strength of the biological carbonate pump in the oligotrophic North Atlantic.

  9. Constraining future terrestrial carbon cycle projections using observation-based water and carbon flux estimates.

    PubMed

    Mystakidis, Stefanos; Davin, Edouard L; Gruber, Nicolas; Seneviratne, Sonia I

    2016-06-01

    The terrestrial biosphere is currently acting as a sink for about a third of the total anthropogenic CO2  emissions. However, the future fate of this sink in the coming decades is very uncertain, as current earth system models (ESMs) simulate diverging responses of the terrestrial carbon cycle to upcoming climate change. Here, we use observation-based constraints of water and carbon fluxes to reduce uncertainties in the projected terrestrial carbon cycle response derived from simulations of ESMs conducted as part of the 5th phase of the Coupled Model Intercomparison Project (CMIP5). We find in the ESMs a clear linear relationship between present-day evapotranspiration (ET) and gross primary productivity (GPP), as well as between these present-day fluxes and projected changes in GPP, thus providing an emergent constraint on projected GPP. Constraining the ESMs based on their ability to simulate present-day ET and GPP leads to a substantial decrease in the projected GPP and to a ca. 50% reduction in the associated model spread in GPP by the end of the century. Given the strong correlation between projected changes in GPP and in NBP in the ESMs, applying the constraints on net biome productivity (NBP) reduces the model spread in the projected land sink by more than 30% by 2100. Moreover, the projected decline in the land sink is at least doubled in the constrained ensembles and the probability that the terrestrial biosphere is turned into a net carbon source by the end of the century is strongly increased. This indicates that the decline in the future land carbon uptake might be stronger than previously thought, which would have important implications for the rate of increase in the atmospheric CO2 concentration and for future climate change. PMID:26732346

  10. Constraining future terrestrial carbon cycle projections using observation-based water and carbon flux estimates.

    PubMed

    Mystakidis, Stefanos; Davin, Edouard L; Gruber, Nicolas; Seneviratne, Sonia I

    2016-06-01

    The terrestrial biosphere is currently acting as a sink for about a third of the total anthropogenic CO2  emissions. However, the future fate of this sink in the coming decades is very uncertain, as current earth system models (ESMs) simulate diverging responses of the terrestrial carbon cycle to upcoming climate change. Here, we use observation-based constraints of water and carbon fluxes to reduce uncertainties in the projected terrestrial carbon cycle response derived from simulations of ESMs conducted as part of the 5th phase of the Coupled Model Intercomparison Project (CMIP5). We find in the ESMs a clear linear relationship between present-day evapotranspiration (ET) and gross primary productivity (GPP), as well as between these present-day fluxes and projected changes in GPP, thus providing an emergent constraint on projected GPP. Constraining the ESMs based on their ability to simulate present-day ET and GPP leads to a substantial decrease in the projected GPP and to a ca. 50% reduction in the associated model spread in GPP by the end of the century. Given the strong correlation between projected changes in GPP and in NBP in the ESMs, applying the constraints on net biome productivity (NBP) reduces the model spread in the projected land sink by more than 30% by 2100. Moreover, the projected decline in the land sink is at least doubled in the constrained ensembles and the probability that the terrestrial biosphere is turned into a net carbon source by the end of the century is strongly increased. This indicates that the decline in the future land carbon uptake might be stronger than previously thought, which would have important implications for the rate of increase in the atmospheric CO2 concentration and for future climate change.

  11. A Bayesian Deconvolution Approach to Partitioning Soil Respiration: Coupling Carbon Flux and Isotope Data with Process-based Flux and Mixing Models

    NASA Astrophysics Data System (ADS)

    Ogle, K.; Cable, J. M.; Huxman, T. E.

    2006-12-01

    The respiratory loss of carbon from terrestrial ecosystems is a major carbon flux affecting local, regional, and global carbon cycling. Such losses (e.g., soil CO2 efflux), however, are often overly simplified in biogeochemical models compared to processes such as photosynthesis. This discrepancy is partly due to the difficulty associated with partitioning soil respiration (or CO2 efflux) into its various components (e.g., autotrophic vs. heterotrophic). Different components operate at dissimilar temporal and spatial scales, thus estimation of their relative activity based on bulk soil efflux measurements is challenging. Hence, development of a robust, biophysically-inspired method for partitioning the different components is paramount to teasing- apart the mechanisms underlying carbon source-sink dynamics within and across diverse landscapes. Towards this goal, we developed a semi-mechanistic Bayesian deconvolution modeling approach for partitioning soil respiration into its component sources. While the sources can be broadly categorized as autotrophic or heterotrophic, the fundamental sources of biogenic CO2 efflux arises from specific interactions between plants, micro-organisms, and the soil environment. Potential sources have been identified based on their different turnover rates and functional roles, including, (1) activity of roots, (2) rhizomicrobial (e.g., mycorrhiza) respiration, (3) microbial decomposition of plant tissues, (4) microbial activity primed by root exudation, and (5) microbial decomposition of soil organic matter. The relative contribution of each source to soil CO2 efflux can vary within the soil matrix, depending on spatial and temporal variability in soil properties, resource and substrate availability, and microclimate. Our Bayesian deconvolution framework allows for simultaneous analysis of multiple data sources related to soil respiration dynamics, and the data are analyzed within the context of process-based models. The data include

  12. Inventory and burial fluxes of Black Carbon in the Swedish continental shelf sediments

    NASA Astrophysics Data System (ADS)

    Sánchez-García, L.; Cato, I.; Gustafsson, Ö.

    2009-04-01

    Highly condensed black carbon (BC) particles, mainly derived from incomplete combustion of biomass and fossil fuel, are involved in several important processes in the biogeosphere [1], including sedimentary carbon burial, sequestration of organic pollutants in soils and sediments, affecting Earth's radiative heat balance and even human respiratory health. BC is commonly found to constitute several to 20% of total sedimentary carbon, and thus plays an important but poorly constrained role in the global biogeospheric carbon cycle. Sequestration of biogenic carbon as BC is a direct sink of the element from the rapidly cycling atmosphere-biosphere reservoirs, whereas burial of petrogenic/fossil BC is simply a conversion of one form of geological carbon to another [2]. Considerable emphasis has been made on the relevant role this recalcitrant form of organic matter (OM) may play on the global C cycle and yet large uncertainty exists around BC detection and quantification. This work seeks to provide a large-scale estimate of the reservoir and burial sink flux of BC in sediments from the extensive Swedish continental shelf (SCS), as a first approach to global inventories. To this end, a total of 120 sediment samples were collected from the Exclusive Economic Zone (EEZ) along the ?2000 km SCS stretch. The most recalcitrant fraction of the sedimentary OM was isolated and determined by means of a commonly applied method in biogeochemical studies of soils and sediments: chemo-thermal oxidation at 375˚ C in air (CTO-375). The obtained BC concentration was used to estimate the inventory and burial flux of BC in the SCS surface sediments, following [3], which takes into account key geophysical and geochemical properties of the nine distinct sedimentary regimes of the SCS that was separately assessed. Globally representative values of the sediment properties (e.g. density of dried sediments, bioturbated mixing depth, sedimentation rate or porosity over the mixed depth) were

  13. Modeling the Relative Importance of Nutrient and Carbon Loads, Boundary Fluxes, and Sediment Fluxes on Gulf of Mexico Hypoxia.

    PubMed

    Feist, Timothy J; Pauer, James J; Melendez, Wilson; Lehrter, John C; DePetro, Phillip A; Rygwelski, Kenneth R; Ko, Dong S; Kreis, Russell G

    2016-08-16

    The Louisiana continental shelf in the northern Gulf of Mexico experiences bottom water hypoxia in the summer. In this study, we applied a biogeochemical model that simulates dissolved oxygen concentrations on the shelf in response to varying riverine nutrient and organic carbon loads, boundary fluxes, and sediment fluxes. Five-year model simulations demonstrated that midsummer hypoxic areas were most sensitive to riverine nutrient loads and sediment oxygen demand from settled organic carbon. Hypoxic area predictions were also sensitive to nutrient and organic carbon fluxes from lateral boundaries. The predicted hypoxic area decreased with decreases in nutrient loads, but the extent of change was influenced by the method used to estimate model boundary concentrations. We demonstrated that modeling efforts to predict changes in hypoxic area on the continental shelf in relationship to changes in nutrients should include representative boundary nutrient and organic carbon concentrations and functions for estimating sediment oxygen demand that are linked to settled organic carbon derived from water-column primary production. On the basis of our model analyses using the most representative boundary concentrations, nutrient loads would need to be reduced by 69% to achieve the Gulf of Mexico Nutrient Task Force Action Plan target hypoxic area of 5000 km(2). PMID:27406634

  14. Modeling the Relative Importance of Nutrient and Carbon Loads, Boundary Fluxes, and Sediment Fluxes on Gulf of Mexico Hypoxia.

    PubMed

    Feist, Timothy J; Pauer, James J; Melendez, Wilson; Lehrter, John C; DePetro, Phillip A; Rygwelski, Kenneth R; Ko, Dong S; Kreis, Russell G

    2016-08-16

    The Louisiana continental shelf in the northern Gulf of Mexico experiences bottom water hypoxia in the summer. In this study, we applied a biogeochemical model that simulates dissolved oxygen concentrations on the shelf in response to varying riverine nutrient and organic carbon loads, boundary fluxes, and sediment fluxes. Five-year model simulations demonstrated that midsummer hypoxic areas were most sensitive to riverine nutrient loads and sediment oxygen demand from settled organic carbon. Hypoxic area predictions were also sensitive to nutrient and organic carbon fluxes from lateral boundaries. The predicted hypoxic area decreased with decreases in nutrient loads, but the extent of change was influenced by the method used to estimate model boundary concentrations. We demonstrated that modeling efforts to predict changes in hypoxic area on the continental shelf in relationship to changes in nutrients should include representative boundary nutrient and organic carbon concentrations and functions for estimating sediment oxygen demand that are linked to settled organic carbon derived from water-column primary production. On the basis of our model analyses using the most representative boundary concentrations, nutrient loads would need to be reduced by 69% to achieve the Gulf of Mexico Nutrient Task Force Action Plan target hypoxic area of 5000 km(2).

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

    SciTech Connect

    Leclerc, Monique Y.

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  17. How Glassy States Affect Brown Carbon Production?

    NASA Astrophysics Data System (ADS)

    Liu, P.; Li, Y.; Wang, Y.; Bateman, A. P.; Zhang, Y.; Gong, Z.; Gilles, M. K.; Martin, S. T.

    2015-12-01

    Secondary organic material (SOM) can become light-absorbing (i.e. brown carbon) via multiphase reactions with nitrogen-containing species such as ammonia and amines. The physical states of SOM, however, potentially slow the diffusion of reactant molecules in organic matrix under conditions that semisolids or solids prevail, thus inhibiting the browning reaction pathways. In this study, the physical states and the in-particle diffusivity were investigated by measuring the evaporation kinetics of both water and organics from aromatic-derived SOMs using a quartz-crystal-microbalance (QCM). The results indicate that the SOMs derived from aromatic precursors toluene and m-xylene became solid (glassy) and the in particle diffusion was significantly impeded for sufficiently low relative humidity ( < 20% RH) at 293 K. Optical properties and the AMS spectra were measured for toluene-derived SOM after ammonia exposure at varied RHs. The results suggest that the production of light-absorbing nitrogen-containing compounds from multiphase reactions with ammonia was kinetically limited in the glassy organic matrix, which otherwise produce brown carbon. The results of this study have significant implications for production and optical properties of brown carbon in urban atmospheres that ultimately influence the climate and tropospheric photochemistry.

  18. Purification ability and carbon dioxide flux from surface flow constructed wetlands treating sewage treatment plant effluent.

    PubMed

    Wu, Haiming; Lin, Li; Zhang, Jian; Guo, Wenshan; Liang, Shuang; Liu, Hai

    2016-11-01

    In this study, a two-year experiment was carried out to investigate variation of carbon dioxide (CO2) flux from free water surface constructed wetlands (FWS CW) systems treating sewage treatment plant effluent, and treatment performance was also evaluated. The better 74.6-76.6% COD, 92.7-94.4% NH4(+)-N, 60.1-84.7% TN and 49.3-70.7% TP removal efficiencies were achieved in planted CW systems compared with unplanted systems. The planted CW was a net CO2 sink, while the unplanted CW was a net CO2 source in the entire study period. An obvious annual and seasonal variability of CO2 fluxes from different wetland systems was also presented with the average CO2 flux ranging from -592.83mgm(-2)h(-1) to 553.91mgm(-2)h(-1) during 2012-2013. In addition, the net exchange of CO2 between CW systems and the atmosphere was significantly affected by air temperature, and the presence of plants also had the significant effect on total CO2 emissions.

  19. Purification ability and carbon dioxide flux from surface flow constructed wetlands treating sewage treatment plant effluent.

    PubMed

    Wu, Haiming; Lin, Li; Zhang, Jian; Guo, Wenshan; Liang, Shuang; Liu, Hai

    2016-11-01

    In this study, a two-year experiment was carried out to investigate variation of carbon dioxide (CO2) flux from free water surface constructed wetlands (FWS CW) systems treating sewage treatment plant effluent, and treatment performance was also evaluated. The better 74.6-76.6% COD, 92.7-94.4% NH4(+)-N, 60.1-84.7% TN and 49.3-70.7% TP removal efficiencies were achieved in planted CW systems compared with unplanted systems. The planted CW was a net CO2 sink, while the unplanted CW was a net CO2 source in the entire study period. An obvious annual and seasonal variability of CO2 fluxes from different wetland systems was also presented with the average CO2 flux ranging from -592.83mgm(-2)h(-1) to 553.91mgm(-2)h(-1) during 2012-2013. In addition, the net exchange of CO2 between CW systems and the atmosphere was significantly affected by air temperature, and the presence of plants also had the significant effect on total CO2 emissions. PMID:27544264

  20. Response of total belowground carbon flux and soil organic carbon storage to increasing mean annual temperature in Hawaiian tropical montane wet forest.

    NASA Astrophysics Data System (ADS)

    Giardina, C. P.; Litton, C. M.; Crow, S. E.

    2011-12-01

    Controls on the allocation of carbon belowground by plants and the retention of this carbon as new soil organic carbon are poorly quantified, yet exert a large influence on the carbon balance of the terrestrial biosphere. While many studies have now quantified total belowground carbon flux (TBCF), and general global patterns have been identified, rigorous field tests of the effects of climate variables on TBCF do not yet exist, and the conversion of TBCF into soil organic carbon - particularly long-lived soil organic carbon - has received little attention. These represent critical gaps in our understanding of terrestrial carbon cycling, and currently severely constrain efforts to model climate change impacts on belowground carbon processes and storage. We have established a model mean annual temperature gradient spanning 5.2°C in Hawaiian tropical montane wet forests where soil type and age, soil moisture balance, vegetation composition, and disturbance history do not co-vary with temperature. We found that TBCF increases by a factor of two over the 5.2°C MAT gradient in response to increasing ecosystem productivity, while total soil carbon storage is constant. These findings suggest that as temperatures warm, there will be a significant increase in TBCF and belowground carbon process leading to increased flux of CO2 from soils as soil respiration, but that soil organic carbon storage will be relatively insensitive to warming - at least where moisture availability is not affected by rising temperatures. While short-term responses to warming may differ, this study represents long-term insight into the impacts of rising temperatures on belowground carbon cycling and assumes that ecosystem characteristics will change with warming as quantified across this MAT gradient.

  1. Carbon dioxide and methane fluxes in drained tropical peat before and after hydrological restoration.

    PubMed

    Jauhiainen, Jyrki; Limin, Suwido; Silvennoinen, Hanna; Vasander, Harri

    2008-12-01

    Present tropical peat deposits are the outcome of net carbon removal from the atmosphere and form one of the largest terrestrial organic carbon stores on the Earth. Reclamation of pristine tropical peatland areas in Southeast Asia increased strikingly during the last half of the 20th century. Drainage due to land-use change is one of the main driving factors accelerating carbon loss from the ecosystem. Dams were built in drainage-affected peatland area canals in Central Kalimantan, Indonesia, in order to evaluate major patterns in gaseous carbon dioxide and methane fluxes and in peat hydrology immediately before and after hydrologic restoration. The sites included peat swamp forest and deforested burned area, both affected by drainage for nearly 10 years. Higher annual minimum soil water table levels prevailed on both sites after restoration; the deforested site water table level prevailed considerably longer near the peat surface, and the forest water table level remained for a longer period in the topmost 30 cm peat profile after restoration. Forest soil gas fluxes were clearly higher in comparison to the deforested area. Cumulative forest floor CO2 emissions (7305-7444 g x m(-2) x yr(-1); 166.0-169.2 mol CO2 x m(-2) x yr(-1)) and the deforested site CO2 emissions (2781-2608 g x m(-2) x yr(-1); 63.2-59.3 mol CO2 x m(-2) x yr(-1)) did not markedly reflect the notably differing hydrological conditions the year before and after restoration. The forest floor was a weak CH4 sink (-0.208 to -0.368 g x m(-2) x yr(-1); -13.0 to -22.9 mmol CH4 x m(-2) x yr(-1)) and the deforested site a comparable CH4 source (0.197-0.275 g x m(-2) x yr(-1); 12.3-17.1 mmol CH4 x m(-2) x yr(-1)) in the study period. In general, higher soil water table levels had a relatively small effect on the annual CH4 emission budgets. In the two site types the gas flux response into hydrological conditions in degraded tropical peat can be attributed to differing CO2 and CH4 dynamics, peat physical

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

    NASA Astrophysics Data System (ADS)

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

    2008-03-01

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

  3. Estimating carbon flux phenology with satellite-derived land surface phenology and climate drivers for different biomes: a synthesis of AmeriFlux observations.

    PubMed

    Zhu, Wenquan; Chen, Guangsheng; Jiang, Nan; Liu, Jianhong; Mou, Minjie

    2013-01-01

    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. Estimating Carbon Flux Phenology with Satellite-Derived Land Surface Phenology and Climate Drivers for Different Biomes: A Synthesis of AmeriFlux Observations

    PubMed Central

    Zhu, Wenquan; Chen, Guangsheng; Jiang, Nan; Liu, Jianhong; Mou, Minjie

    2013-01-01

    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. PMID:24386441

  5. Organic and inorganic carbon fluxes in a tropical river system (Tana River, Kenya) during contrasting wet seasons

    NASA Astrophysics Data System (ADS)

    Geeraert, Naomi; Omengo, Fred O.; Bouillon, Steven; Borges, Alberto V.; Govers, Gerard

    2015-04-01

    Tropical river systems are often subjected to strong seasonality; in the Tana River (Kenya), for example, ~60% of the annual discharge takes place during a 4-month period. As different carbon pools are transported by the river, seasonal differences in carbon fluxes will also occur. This can furthermore be enhanced or attenuated due to changes in the intensity of carbon transformation processes, such as microbial respiration and primary production, during the wet season. Besides that, seasonal flooding of flood plains or flooded forest is known to be a major driver of the biogeochemical and ecological functioning of tropical rivers ("flood pulse concept") and has been shown to be one of the major drivers of the CO2 emissions from the Amazon River. We monitored the fluxes of different carbon pools at two sites spaced 385 km apart along the lower Tana River (Kenya), which is characterized by a highly seasonal flow regime. Water samples were taken at daily resolution during three wet seasons. During one of those seasons (May-June 2013), considerable flooding took place between both stations, while the other two wet seasons (Oct-Nov 2012 and April-May 2014) were characterised by several distinct discharge peaks, without leading to substantial overbank flooding. The flux of particulate organic carbon (POC) was observed to decrease in the downstream direction by 8 to 33% during all measurement periods. Fluxes of dissolved organic carbon (DOC) also decreased in the downstream direction during the wet seasons without flooding (by 10-38%) but increased drastically (increase of 231%) during the wet season with flooding. The dissolved inorganic carbon (DIC) flux increased downstream (by 6% to 62%) during all measurement periods. The total carbon flux (POC+DOC+DIC) increased by 33% in the wet season with flooding (2013), but decreased by 23% and 3%, respectively, during the 2012 and 2014 wet seasons. Flooding thus affected the relative contribution of different C pools to the

  6. Integrating Aircraft, Tower fluxes, MODIS and Biome-BGC to Study Carbon Dioxide and Water Vapor Fluxes over Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Qian, Y.; Oechel, W. C.; Zulueta, R. C.; Verfaillie, J.; Kwon, H.; Heinsch, F.; Kimball, J.

    2003-12-01

    To understand carbon and water dynamics of susceptible Arctic Tundra ecosystem, intensive and integrated methods are implemented on the North Slope of Artic Alaska, including eddy covariance, remote sensing and ecosystem models. Tower-based eddy covariance instruments have strongly ability to measure long-term temporal trend, and aircraft-based flux measurements is able to assess spatial variations efficiently. Both of complemental measurements have been used on this region for several years. The Aircraft (Sky Arrow ERA 650) with eddy covariance and remote sensors flied at 100 km scale over 115 hours in 2001. The aircraft fluxes are compared to tower fluxes at Barrow, Atqasuk and potable tower. The correlation of aircraft fluxes and MODIS NDVI, EVI and LAI are addressed. MODIS GPP, PSN, NPP are validated by tower measurement at long-term temporal scale and by aircraft measurement at larger spatial scale. The process-based ecosystem model, Biome-BGC, is run at five sites: Barrow, Atqasuk, Ivotuk, Toolik Lake, Prudhoe Bay. While the model can computer components of CO2 flux that cannot be directly monitored, the comparisons of model outputs and aircraft, tower measurements are used to help improve the model estimate ability. The intercomparison of model and MODIS is also discussed in this paper. Key words: Arctic tundra, trace-gas flux, aircraft-based, eddy covariance, MODIS, Biome-BGC

  7. A rheostat mechanism governs the bifurcation of carbon flux in mycobacteria

    PubMed Central

    Murima, Paul; Zimmermann, Michael; Chopra, Tarun; Pojer, Florence; Fonti, Giulia; Dal Peraro, Matteo; Alonso, Sylvie; Sauer, Uwe; Pethe, Kevin; McKinney, John D.

    2016-01-01

    Fatty acid metabolism is an important feature of the pathogenicity of Mycobacterium tuberculosis during infection. Consumption of fatty acids requires regulation of carbon flux bifurcation between the oxidative TCA cycle and the glyoxylate shunt. In Escherichia coli, flux bifurcation is regulated by phosphorylation-mediated inhibition of isocitrate dehydrogenase (ICD), a paradigmatic example of post-translational mechanisms governing metabolic fluxes. Here, we demonstrate that, in contrast to E. coli, carbon flux bifurcation in mycobacteria is regulated not by phosphorylation but through metabolic cross-activation of ICD by glyoxylate, which is produced by the glyoxylate shunt enzyme isocitrate lyase (ICL). This regulatory circuit maintains stable partitioning of fluxes, thus ensuring a balance between anaplerosis, energy production, and precursor biosynthesis. The rheostat-like mechanism of metabolite-mediated control of flux partitioning demonstrates the importance of allosteric regulation during metabolic steady-state. The sensitivity of this regulatory mechanism to perturbations presents a potentially attractive target for chemotherapy. PMID:27555519

  8. A rheostat mechanism governs the bifurcation of carbon flux in mycobacteria.

    PubMed

    Murima, Paul; Zimmermann, Michael; Chopra, Tarun; Pojer, Florence; Fonti, Giulia; Dal Peraro, Matteo; Alonso, Sylvie; Sauer, Uwe; Pethe, Kevin; McKinney, John D

    2016-01-01

    Fatty acid metabolism is an important feature of the pathogenicity of Mycobacterium tuberculosis during infection. Consumption of fatty acids requires regulation of carbon flux bifurcation between the oxidative TCA cycle and the glyoxylate shunt. In Escherichia coli, flux bifurcation is regulated by phosphorylation-mediated inhibition of isocitrate dehydrogenase (ICD), a paradigmatic example of post-translational mechanisms governing metabolic fluxes. Here, we demonstrate that, in contrast to E. coli, carbon flux bifurcation in mycobacteria is regulated not by phosphorylation but through metabolic cross-activation of ICD by glyoxylate, which is produced by the glyoxylate shunt enzyme isocitrate lyase (ICL). This regulatory circuit maintains stable partitioning of fluxes, thus ensuring a balance between anaplerosis, energy production, and precursor biosynthesis. The rheostat-like mechanism of metabolite-mediated control of flux partitioning demonstrates the importance of allosteric regulation during metabolic steady-state. The sensitivity of this regulatory mechanism to perturbations presents a potentially attractive target for chemotherapy. PMID:27555519

  9. Reevaluating carbon fluxes in subduction zones, what goes down, mostly comes up.

    PubMed

    Kelemen, Peter B; Manning, Craig E

    2015-07-28

    Carbon fluxes in subduction zones can be better constrained by including new estimates of carbon concentration in subducting mantle peridotites, consideration of carbonate solubility in aqueous fluid along subduction geotherms, and diapirism of carbon-bearing metasediments. Whereas previous studies concluded that about half the subducting carbon is returned to the convecting mantle, we find that relatively little carbon may be recycled. If so, input from subduction zones into the overlying plate is larger than output from arc volcanoes plus diffuse venting, and substantial quantities of carbon are stored in the mantle lithosphere and crust. Also, if the subduction zone carbon cycle is nearly closed on time scales of 5-10 Ma, then the carbon content of the mantle lithosphere + crust + ocean + atmosphere must be increasing. Such an increase is consistent with inferences from noble gas data. Carbon in diamonds, which may have been recycled into the convecting mantle, is a small fraction of the global carbon inventory. PMID:26048906

  10. Reevaluating carbon fluxes in subduction zones, what goes down, mostly comes up

    NASA Astrophysics Data System (ADS)

    Kelemen, Peter B.; Manning, Craig E.

    2015-07-01

    Carbon fluxes in subduction zones can be better constrained by including new estimates of carbon concentration in subducting mantle peridotites, consideration of carbonate solubility in aqueous fluid along subduction geotherms, and diapirism of carbon-bearing metasediments. Whereas previous studies concluded that about half the subducting carbon is returned to the convecting mantle, we find that relatively little carbon may be recycled. If so, input from subduction zones into the overlying plate is larger than output from arc volcanoes plus diffuse venting, and substantial quantities of carbon are stored in the mantle lithosphere and crust. Also, if the subduction zone carbon cycle is nearly closed on time scales of 5-10 Ma, then the carbon content of the mantle lithosphere + crust + ocean + atmosphere must be increasing. Such an increase is consistent with inferences from noble gas data. Carbon in diamonds, which may have been recycled into the convecting mantle, is a small fraction of the global carbon inventory.

  11. Reevaluating carbon fluxes in subduction zones, what goes down, mostly comes up

    PubMed Central

    Kelemen, Peter B.; Manning, Craig E.

    2015-01-01

    Carbon fluxes in subduction zones can be better constrained by including new estimates of carbon concentration in subducting mantle peridotites, consideration of carbonate solubility in aqueous fluid along subduction geotherms, and diapirism of carbon-bearing metasediments. Whereas previous studies concluded that about half the subducting carbon is returned to the convecting mantle, we find that relatively little carbon may be recycled. If so, input from subduction zones into the overlying plate is larger than output from arc volcanoes plus diffuse venting, and substantial quantities of carbon are stored in the mantle lithosphere and crust. Also, if the subduction zone carbon cycle is nearly closed on time scales of 5–10 Ma, then the carbon content of the mantle lithosphere + crust + ocean + atmosphere must be increasing. Such an increase is consistent with inferences from noble gas data. Carbon in diamonds, which may have been recycled into the convecting mantle, is a small fraction of the global carbon inventory. PMID:26048906

  12. Reevaluating carbon fluxes in subduction zones, what goes down, mostly comes up.

    PubMed

    Kelemen, Peter B; Manning, Craig E

    2015-07-28

    Carbon fluxes in subduction zones can be better constrained by including new estimates of carbon concentration in subducting mantle peridotites, consideration of carbonate solubility in aqueous fluid along subduction geotherms, and diapirism of carbon-bearing metasediments. Whereas previous studies concluded that about half the subducting carbon is returned to the convecting mantle, we find that relatively little carbon may be recycled. If so, input from subduction zones into the overlying plate is larger than output from arc volcanoes plus diffuse venting, and substantial quantities of carbon are stored in the mantle lithosphere and crust. Also, if the subduction zone carbon cycle is nearly closed on time scales of 5-10 Ma, then the carbon content of the mantle lithosphere + crust + ocean + atmosphere must be increasing. Such an increase is consistent with inferences from noble gas data. Carbon in diamonds, which may have been recycled into the convecting mantle, is a small fraction of the global carbon inventory.

  13. Carbon Management In the Post-Cap-and-Trade Carbon Economy: An Economic Model for Limiting Climate Change by Managing Anthropogenic Carbon Flux

    NASA Astrophysics Data System (ADS)

    DeGroff, F. A.

    2013-05-01

    In this paper, we discuss an economic model for comprehensive carbon management that focuses on changes in carbon flux in the biosphere due to anthropogenic activity. The two unique features of the model include: 1. A shift in emphasis from primarily carbon emissions, toward changes in carbon flux, mainly carbon extraction, and 2. A carbon price vector (CPV) to express the value of changes in carbon flux, measured in changes in carbon sequestration, or carbon residence time. The key focus with the economic model is the degree to which carbon flux changes due to anthropogenic activity. The economic model has three steps: 1. The CPV metric is used to value all forms of carbon associated with any anthropogenic activity. In this paper, the CPV used is a logarithmic chronological scale to gauge expected carbon residence (or sequestration) time. In future economic models, the CPV may be expanded to include other factors to value carbon. 2. Whenever carbon changes form (and CPV) due to anthropogenic activity, a carbon toll is assessed as determined by the change in the CPV. The standard monetary unit for carbon tolls are carbon toll units, or CTUs. The CTUs multiplied by the quantity of carbon converted (QCC) provides the total carbon toll, or CT. For example, CT = (CTU /mole carbon) x (QCC moles carbon). 3. Whenever embodied carbon (EC) attributable to a good or service moves via trade to a jurisdiction with a different CPV metric, a carbon toll (CT) is assessed representing the CPV difference between the two jurisdictions. This economic model has three clear advantages. First, the carbon pricing and cost scheme use existing and generally accepted accounting methodologies to ensure the veracity and verifiability of carbon management efforts with minimal effort and expense using standard, existing auditing protocols. Implementing this economic model will not require any new, special, unique, or additional training, tools, or systems for any entity to achieve their minimum

  14. Fluxes of Soot Carbon to South Atlantic Sediments

    EPA Science Inventory

    Deep sea sediment samples from the South Atlantic Ocean were analyzed for soot black carbon (BC), total organic carbon (TOC), stable carbon isotope ratios (δ 13C), and polycyclic aromatic hydrocarbons (PAHs). Soot BC was present at low concentrations (0.04–0.17% dry weight), but ...

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

    NASA Technical Reports Server (NTRS)

    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.

  16. Adaptive data-driven models for estimating carbon fluxes in the Northern Great Plains

    USGS Publications Warehouse

    Wylie, B.K.; Fosnight, E.A.; Gilmanov, T.G.; Frank, A.B.; Morgan, J.A.; Haferkamp, Marshall R.; Meyers, T.P.

    2007-01-01

    Rangeland carbon fluxes are highly variable in both space and time. Given the expansive areas of rangelands, how rangelands respond to climatic variation, management, and soil potential is important to understanding carbon dynamics. Rangeland carbon fluxes associated with Net Ecosystem Exchange (NEE) were measured from multiple year data sets at five flux tower locations in the Northern Great Plains. These flux tower measurements were combined with 1-km2 spatial data sets of Photosynthetically Active Radiation (PAR), Normalized Difference Vegetation Index (NDVI), temperature, precipitation, seasonal NDVI metrics, and soil characteristics. Flux tower measurements were used to train and select variables for a rule-based piece-wise regression model. The accuracy and stability of the model were assessed through random cross-validation and cross-validation by site and year. Estimates of NEE were produced for each 10-day period during each growing season from 1998 to 2001. Growing season carbon flux estimates were combined with winter flux estimates to derive and map annual estimates of NEE. The rule-based piece-wise regression model is a dynamic, adaptive model that captures the relationships of the spatial data to NEE as conditions evolve throughout the growing season. The carbon dynamics in the Northern Great Plains proved to be in near equilibrium, serving as a small carbon sink in 1999 and as a small carbon source in 1998, 2000, and 2001. Patterns of carbon sinks and sources are very complex, with the carbon dynamics tilting toward sources in the drier west and toward sinks in the east and near the mountains in the extreme west. Significant local variability exists, which initial investigations suggest are likely related to local climate variability, soil properties, and management.

  17. Evaluation of the Community Land Model simulated carbon and water fluxes against observations over ChinaFLUX sites

    NASA Astrophysics Data System (ADS)

    Zhang, L.; Mao, J.; Shi, X.; Ricciuto, D. M.; He, H.; Thornton, P. E.; Yu, G.; Han, S.; Li, Y.; Yan, J.; Hao, Y.; Wang, H.

    2014-12-01

    The Community Land Model (CLM) is an advanced process-based land surface model that simulates the complicated carbon, water vapor and energy exchanges between the terrestrial ecosystem and the atmosphere at various spatial-temporal scales. We for the first time use eddy-covariance observations of CO2 and water vapor exchange and soil respiration measurements at five representative Chinese Terrestrial Ecosystem Flux Observational Network (ChinaFLUX) tower sites to systematically evaluate the latest versions of CLM, the CLM4.0 and CLM4.5, and comprehensively examine the similarities and differences between the observational and simulated results. The CLM4.5 underestimates annual carbon sink at three forest sites and one alpine grassland site but overestimates the carbon sink at a semi-arid grassland site. The underestimation in annual carbon sink at a deciduous dominated forest site is resulted from underestimated daytime carbon sequestration in summer and overestimated nighttime carbon emission in spring and autumn. Compared with the CLM4.0, the bias of annual Gross Primary Production (GPP) is reduced by 24% and 28% in CLM4.5 at two subtropical forest sites. However, CLM4.5 still has a large positive bias in annual GPP. The improvement in NEE is limited, although the bias of soil respiration decreases by 16%-43% at three forest sites. The CLM4.5 has lower soil water content in dry season than this simulated by the CLM4.0 at two grassland sites. These lead to the significant drop in leaf area index and GPP, and the increase in respiration for the CLM4.5. The new fire parameterization in CLM4.5 causes incorrect fire estimation at Changbaishan forest site, which results in unexpected underestimation of NEE, vegetation carbon, and soil organic carbon by 46%, 95%, and 87%, respectively. Our study with the ChinaFLUX sites indicates a significant improvement of the CLM4.5 than the CLM4, and suggests further developments on the parameterization of seasonal GPP and

  18. Factors affecting expired waveform for carbon monoxide

    SciTech Connect

    Rubin, D.Z.; Lewis, S.M.; Mittman, C.

    1984-01-01

    The authors previously presented a method based on a computer lung model for determining the distribution of both specific ventilation and specific diffusing capacity. These argon and carbon monoxide (CO) washin and washout studies were obtained in 12 normal subjects and 24 patients with varying degrees of obstructive lung disease. In addition to end-tidal and mixed expired gas concentrations, the expired waveform for both gases was sampled. In patients we found that this method failed to adequately describe CO dynamics during the early part of expiration; predicted concentrations were higher than actual data. Modifications of the original model that satisfy all data are presented. This new model suggests that CO uptake occurs in spaces with ventilatory properties of dead space. The accuracy and reliability of these observations were established by computer simulation studies as well as by repeated testing in one subject. These proved to be highly reproducible over a period of 5 mo. Standard parameter sensitivity tests showed parameters to vary by less than 10% and to be stable even when realistic levels of noise were added to the data. We conclude that studies involving ventilation of insoluble gases are insufficient to describe gas exchange in the lung. The addition of an exchangeable gas adds significant understanding of lung function, particularly in disease.

  19. Observed and modeled carbon and energy fluxes for agricultural sites under North American Carbon Program site-level interim synthesis

    NASA Astrophysics Data System (ADS)

    Lokupitiya, E. Y.; Denning, A.

    2010-12-01

    Croplands are unique, man-made ecosystems with dynamics mostly dependent on human decisions. Crops uptake a significant amount of Carbon dioxide (CO2) during their short growing seasons. Reliability of the available models to predict the carbon exchanges by croplands is important in estimating the cropland contribution towards overall land-atmosphere carbon exchange and global carbon cycle. The energy exchanges from croplands include both sensible and latent heat fluxes. This study focuses on analyzing the performance of 19 land surface models across five agricultural sites under the site-level interim synthesis of North American Carbon Program (NACP). Model simulations were performed using a common simulation protocol and input data, including gap-filled meteorological data corresponding to each site. The net carbon fluxes (i.e. net ecosystem exchange; NEE) and energy fluxes (sensible and latent heat) predicted by 12 models with sub-hourly/hourly temporal resolution and 7 models with daily temporal resolution were compared against the site-specific gap-filled observed flux tower data. Comparisons were made by site and crop type (i.e. maize, soybean, and wheat), mainly focusing on the coefficient of determination, correlation, root mean square error, and standard deviation. Analyses also compared the diurnal, seasonal, and inter-annual variability of the modeled fluxes against the observed data and the mean modeled data.

  20. Upscaling carbon fluxes over the Great Plains grasslands: Sinks and sources

    USGS Publications Warehouse

    Zhang, Li; Wylie, Bruce K.; Ji, Lei; Gilmanov, Tagir G.; Tieszen, Larry L.; Howar, Daniel M.

    2011-01-01

    Previous studies suggested that the grasslands may be carbon sinks or near equilibrium, and they often shift between carbon sources in drought years and carbon sinks in other years. It is important to understand the responses of net ecosystem production (NEP) to various climatic conditions across the U.S. Great Plains grasslands. Based on 15 grassland flux towers, we developed a piecewise regression model and mapped the grassland NEP at 250 m spatial resolution over the Great Plains from 2000 to 2008. The results showed that the Great Plains was a net sink with an averaged annual NEP of 24 ± 14 g C m−2 yr−1, ranging from a low value of 0.3 g C m−2 yr−1 in 2002 to a high value of 47.7 g C m−2 yr−1 in 2005. The regional averaged NEP for the entire Great Plains grasslands was estimated to be 336 Tg C yr−1 from 2000 to 2008. In the 9 year period including 4 dry years, the annual NEP was very variable in both space and time. It appeared that the carbon gains for the Great Plains were more sensitive to droughts in the west than the east. The droughts in 2000, 2002, 2006, and 2008 resulted in increased carbon losses over drought-affected areas, and the Great Plains grasslands turned into a relatively low sink with NEP values of 15.8, 0.3, 20.1, and 10.2 g C m−2 yr−1 for the 4 years, respectively.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    Brüggemann, N.; Gessler, A.; Kayler, Z.; Keel, S. G.; Badeck, F.; Barthel, M.; Boeckx, P.; Buchmann, N.; Brugnoli, E.; Esperschütz, J.; Gavrichkova, O.; Ghashghaie, J.; Gomez-Casanovas, N.; Keitel, C.; Knohl, A.; Kuptz, D.; Palacio, S.; Salmon, Y.; Uchida, Y.; Bahn, M.

    2011-11-01

    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 CO2 diffusion and dissolution processes within the

  3. Calculations of automatic chamber flux measurements of methane and carbon dioxide using short time series of concentrations

    NASA Astrophysics Data System (ADS)

    Pirk, N.; Mastepanov, M.; Parmentier, F.-J. W.; Lund, M.; Crill, P.; Christensen, T. R.

    2015-09-01

    The closed chamber technique is widely used to measure the exchange of methane (CH4) and carbon dioxide (CO2) from terrestrial ecosystems. There is, however, large uncertainty about which model should be used to calculate the gas flux from the measured gas concentrations. Due to experimental uncertainties the robust linear regression model (first order polynomial) is often applied, even though theoretical considerations of the technique suggest the application of other, curvilinear models. High-resolution automatic chamber systems which sample gas concentrations several hundred times per flux measurement make it possible to resolve the curvilinear behavior and study the information imposed by the natural variability of the temporal concentration changes. We used more than 50 000 such flux measurements of CH4 and CO2 from five field sites located in peat forming wetlands to calculate fluxes with different models. The flux differences from independent linear estimates are generally found to be smaller than the local flux variability on the plot scale. The curvilinear behavior of the gas concentrations within the chamber is strongly influenced by wind driven chamber leakage, and less so by changing gas concentration gradients in the soil during chamber closure. Such physical processes affect both gas species equally, which makes it possible to isolate biochemical processes affecting the gases differently, such as photosynthesis limitation by chamber headspace CO2 concentrations under high levels of incoming solar radiation. We assess the possibility to exploit this effect for a partitioning of the net CO2 flux into photosynthesis and ecosystem respiration and argue that high-resolution automatic chamber measurements could be used for purposes beyond the estimation of the net gas flux.

  4. Local to regional emission sources affecting mercury fluxes to New York lakes

    NASA Astrophysics Data System (ADS)

    Bookman, Revital; Driscoll, Charles T.; Engstrom, Daniel R.; Effler, Steven W.

    Lake-sediment records across the Northern Hemisphere show increases in atmospheric deposition of anthropogenic mercury (Hg) over the last 150 years. Most of the previous studies have examined remote lakes affected by the global atmospheric Hg reservoir. In this study, we present Hg flux records from lakes in an urban/suburban setting of central New York affected also by local and regional emissions. Sediment cores were collected from the Otisco and Skaneateles lakes from the Finger Lakes region, Cross Lake, a hypereutrophic lake on the Seneca River, and Glacial Lake, a small seepage lake with a watershed that corresponds with the lake area. Sediment accumulation rates and dates were established by 210Pb. The pre-anthropogenic regional atmospheric Hg flux was estimated to be 3.0 μg m -2 yr -1 from Glacial Lake, which receives exclusively direct atmospheric deposition. Mercury fluxes peaked during 1971-2001, and were 3 to more than 30 times greater than pre-industrial deposition. Land use change and urbanization in the Otisco and Cross watersheds during the last century likely enhanced sediment loads and Hg fluxes to the lakes. Skaneateles and Glacial lakes have low sediment accumulation rates, and thus are excellent indicators for atmospheric Hg deposition. In these lakes, we found strong correlations with emission records for the Great Lakes region that markedly increased in the early 1900s, and peaked during WWII and in the early 1970s. Declines in modern Hg fluxes are generally evident in the core records. However, the decrease in sediment Hg flux at Glacial Lake was interrupted and has increased since the early 1990s probably due to the operation of new local emission sources. Assuming the global Hg reservoir tripled since the pre-industrial period, the contribution of local and regional emission sources to central New York lakes was estimated to about 80% of the total atmospheric Hg deposition.

  5. Canopy structure of sagebrush ecosystems leading to differences in carbon and water fluxes

    NASA Astrophysics Data System (ADS)

    Reed, D. E.; Ewers, B. E.; Peckham, S. D.; Pendall, E. G.; Kelly, R. D.

    2013-12-01

    The sagebrush steppe ecosystem covers nearly 15% of Western North America, and its productivity is sensitive to warming and increasingly variable precipitation. Previous work has shown that interannual variability of precipitation is the largest factor in carbon and water cycling in these semi-arid ecosystems and that the relationship of traditional drivers of fluxes (VPD, net radiation, soil temperature) to carbon and water fluxes as well as ecosystem water use efficiency does not change along an elevation gradient. We seek to expand on that work by using multiple site-years from eddy covariance data near the upper (2469m) and lower (2069m) elevation range of sagebrush to answer the question 'How does canopy structure and canopy leaf area index combine to control the ecosystem carbon and water fluxes from rocky mountain sagebrush ecosystems'. We are answering this question by quantifying ecosystem scale carbon and water using eddy covariance measurements and a standard suite of atmospheric, soil and vegetation monitoring instruments. This data will be used with the Terrestrial Regional Ecosystem Exchange Simulator (TREES) Bayesian framework model that utilizes a coupled plant hydraulic and carbon uptake. For this work we use the TREES model to simulate canopy structure and leaf area based on seven years of eddy covariance data from the two different locations. This canopy information will be compared with canopy structure ground measurements within the eddy covariance footprint, and then we will compare the relationship between canopy structure and ecosystem fluxes. During well watered growing season time periods, the high elevation site has average water flux of 1.06 mmol m-2 s-1 and carbon flux of 1.54 μmol m-2 s-1 of uptake. Average water and carbon fluxes at the lower elevation site were 0.84 mmol m-2 s-1 and 1.09 μmol m-2 s-1 of uptake respectively. This is a reduction of 20% for water flux and 30% and carbon flux down the elevation gradient. With the

  6. Carbon dioxide fluxes from Tifway bermudagrass: early results

    NASA Astrophysics Data System (ADS)

    Cotten, David L.; Zhang, G.; Leclerc, M. Y.; Raymer, P.; Steketee, C. J.

    2016-06-01

    This paper reports for the first time preliminary data on carbon uptake of warm-season turfgrass at a well-managed sod farm in south central Georgia. It examines the changes in carbon uptake from one of the most widely used warm-season turfgrass cultivars in the world, Tifway Bermudagrass. It elucidates the role of canopy density and light avalaibility on the net carbon uptake using the eddy-covariance technique. Preliminary evidence suggests that turfgrass is effective at sequestering carbon dioxide during the summer months even when the canopy is being reestablished following a grass harvest.

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

    SciTech Connect

    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.

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

    PubMed

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

    2007-07-17

    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 (approximately 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 approximately 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/m2/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

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

    NASA Astrophysics Data System (ADS)

    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

  10. A Satellite Based Modeling Framework for Estimating Seasonal Carbon Fluxes Over Agricultural Lands

    NASA Astrophysics Data System (ADS)

    Bandaru, V.; Houborg, R.; Izaurralde, R. C.

    2014-12-01

    Croplands are typically characterized by fine-scale heterogeneity, which makes it difficult to accurately estimate cropland carbon fluxes over large regions given the fairly coarse spatial resolution of high-frequency satellite observations. It is, however, important that we improve our ability to estimate spatially and temporally resolved carbon fluxes because croplands constitute a large land area and have a large impact on global carbon cycle. A Satellite based Dynamic Cropland Carbon (SDCC) modeling framework was developed to estimate spatially resolved crop specific daily carbon fluxes over large regions. This modeling framework uses the REGularized canopy reFLECtance (REGFLEC) model to estimate crop specific leaf area index (LAI) using downscaled MODIS reflectance data, and subsequently LAI estimates are integrated into the Environmental Policy Integrated Model (EPIC) model to determine daily net primary productivity (NPP) and net ecosystem productivity (NEP). Firstly, we evaluate the performance of this modeling framework over three eddy covariance flux tower sites (Bondville, IL; Fermi Agricultural Site, IL; and Rosemount site, MN). Daily NPP and NEP of corn and soybean crops are estimated (based on REGFLEC LAI) for year 2007 and 2008 over the flux tower sites and compared against flux tower observations and model estimates based on in-situ LAI. Secondly, we apply the SDCC framework for estimating regional NPP and NEP for corn, soybean and sorghum crops in Nebraska during year 2007 and 2008. The methods and results will be presented.

  11. A Satellite Based Modeling Framework for Estimating Seasonal Carbon Fluxes Over Agricultural Lands

    NASA Astrophysics Data System (ADS)

    Bandaru, V.; Izaurralde, R. C.; Sahajpal, R.; Houborg, R.; Milla, Z.

    2013-12-01

    Croplands are typically characterized by fine-scale heterogeneity, which makes it difficult to accurately estimate cropland carbon fluxes over large regions given the fairly coarse spatial resolution of high-frequency satellite observations. It is, however, important that we improve our ability to estimate spatially and temporally resolved carbon fluxes because croplands constitute a large land area and have a large impact on global carbon cycle. A Satellite based Dynamic Cropland Carbon (SDCC) modeling framework was developed to estimate spatially resolved crop specific daily carbon fluxes over large regions. This modeling framework uses the REGularized canopy reFLECtance (REGFLEC) model to estimate crop specific leaf area index (LAI) using downscaled MODIS reflectance data, and subsequently LAI estimates are integrated into the Environmental Policy Integrated Model (EPIC) model to determine daily net primary productivity (NPP) and net ecosystem productivity (NEP). Firstly, we evaluate the performance of this modeling framework over three eddy covariance flux tower sites (Bondville, IL; Fermi Agricultural Site, IL; and Rosemount site, MN). Daily NPP and NEP of corn and soybean crops are estimated (based on REGFLEC LAI) for year 2007 and 2008 over the flux tower sites and compared against flux tower observations and model estimates based on in-situ LAI. Secondly, we apply the SDCC framework for estimating regional NPP and NEP for corn, soybean and sorghum crops in Nebraska during year 2007 and 2008. The methods and results will be presented.

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

    NASA Astrophysics Data System (ADS)

    Hansis, Eberhard; Davis, Steven J.; Pongratz, Julia

    2015-08-01

    Accounting for carbon fluxes from land use and land cover change (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 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 2008-2012 as an 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.

  13. [Research progress on urban carbon fluxes based on eddy covariance technique].

    PubMed

    Liu, Min; Fu, Yu-Ling; Yang, Fang

    2014-02-01

    Land use change and fossil fuel consumption due to urbanization have made significant effect on global carbon cycle and climate change. Accurate estimating and understanding of the carbon budget and its characteristics are the premises for studying carbon cycle and its driving mechanisms in urban system. Based on the theory of eddy covariance (EC) technique, the characteristics atmospheric boundary layer and carbon cycle in urban area, this study systematically reviewed the principles of CO2 flux monitoring in urban system with EC technique, and then summarized the problems faced in urban CO2 flux monitoring and the method for data processing and further assessment. The main research processes on urban carbon fluxes with EC technique were also illustrated. The results showed that the urban surface was mostly acting as net carbon source. The CO2 exchange between urban surface and atmosphere showed obvious diurnal, weekly and seasonal variation resulted from the vehicle exhaust, domestic heating and vegetation respiration. However, there still exist great uncertainties in urban flux measurement and its explanation due to high spatial heterogeneity and complex distributions of carbon source/sink in urban environments. In the end, we suggested that further researches on EC technique and data assessment in complex urban area should be strengthened. It was also requisite to develop models of urban carbon cycle on the basis of the system principle, to investigate the influencing mechanism and variability of urban cycle at regional scale with spatial analysis technique. PMID:24830264

  14. [Research progress on urban carbon fluxes based on eddy covariance technique].

    PubMed

    Liu, Min; Fu, Yu-Ling; Yang, Fang

    2014-02-01

    Land use change and fossil fuel consumption due to urbanization have made significant effect on global carbon cycle and climate change. Accurate estimating and understanding of the carbon budget and its characteristics are the premises for studying carbon cycle and its driving mechanisms in urban system. Based on the theory of eddy covariance (EC) technique, the characteristics atmospheric boundary layer and carbon cycle in urban area, this study systematically reviewed the principles of CO2 flux monitoring in urban system with EC technique, and then summarized the problems faced in urban CO2 flux monitoring and the method for data processing and further assessment. The main research processes on urban carbon fluxes with EC technique were also illustrated. The results showed that the urban surface was mostly acting as net carbon source. The CO2 exchange between urban surface and atmosphere showed obvious diurnal, weekly and seasonal variation resulted from the vehicle exhaust, domestic heating and vegetation respiration. However, there still exist great uncertainties in urban flux measurement and its explanation due to high spatial heterogeneity and complex distributions of carbon source/sink in urban environments. In the end, we suggested that further researches on EC technique and data assessment in complex urban area should be strengthened. It was also requisite to develop models of urban carbon cycle on the basis of the system principle, to investigate the influencing mechanism and variability of urban cycle at regional scale with spatial analysis technique.

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

    NASA Astrophysics Data System (ADS)

    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

  16. Distribution and air-sea fluxes of carbon dioxide on the Chukchi Sea shelf

    NASA Astrophysics Data System (ADS)

    Pipko, I. I.; Pugach, S. P.; Repina, I. A.; Dudarev, O. V.; Charkin, A. N.; Semiletov, I. P.

    2015-12-01

    This article presents the results of long-term studies of the dynamics of carbonate parameters and air-sea carbon dioxide fluxes on the Chukchi Sea shelf during the summer. As a result of the interaction of physical and biological factors, the surface waters on the west of Chukchi Sea were undersaturated with carbon dioxide when compared with atmospheric air; the partial pressure of CO2 varied in the range from 134 to 359 μatm. The average value of CO2 flux in the Chukchi Sea per unit area varied in the range from-2.4 to-22.0 mmol /(m2 day), which is significantly higher than the average value of CO2 flux in the World Ocean. It has been estimated that the minimal mass of C absorbed by the surface of Chukchi Sea from the atmosphere during ice-free season is 13 × 1012 g; a great part of this carbon is transported to the deeper layers of sea and isolated from the atmosphere for a long period of time. The studies of the carbonate system of the Chukchi Sea, especially of its western part, will provide some new data on the fluxes of carbon dioxide in the Arctic Ocean and their changes. Our analysis can be used for an interpretation of the satellite assessment of CO2 fluxes and dissolved CO2 distribution in the upper layers of the ocean.

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

    SciTech Connect

    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.

  18. Hydrologic Carbon Fluxes from the Dryland Grain Producing Region of the Inland Pacific Northwest: Measurements and Modeling

    NASA Astrophysics Data System (ADS)

    Boylan, R. D.; Brooks, E. S.; Johnson-Maynard, J.; Huggins, D.

    2013-12-01

    Mitigation strategies to minimize the loss of soil carbon require a fundamental understanding of the dominant hydrologic flow paths, which drive runoff generation, soil erosion, and ultimately the quantity and quality of carbon exported from a landscape. The variation in climate across the Inland Pacific Northwest has resulted in unique agroecosystems which in turn has affected the long term carbon storage and transport. This study assess the ability of the Water Erosion Prediction Project (WEPP) model to simulate runoff, sediment yield and soil carbon export from two ~10 ha field catchments managed under no-till and conventional tillage practices, respectively. End of winter observed erosion maps and soil carbon measurements are compared to simulated erosion and deposition patterns within the conventionally tilled catchment. The effect of scale and climate on hydrologic carbon fluxes will be compared at three watershed scales (~10 ha, ~5,000 ha and ~900,000 ha) as well as from 9 third order streams in the low moderate and high precipitation zones across the Palouse. Samples were collected on an event basis for water years 2012 and 2013 using automated ISCO samplers at the watershed scale and grab samples were taken at the nine locations during high flows. Samples were analyzed for dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), particulate organic carbon (POC), total nitrogen (TN), and Suspended sediment concentrations (SSC). Preliminary results indicate that (DOC) do not significantly vary with discharge at all sampling locations but there were significant differences in DOC concentrations and POC loads from the conventional and no-till catchments. The mass of inorganic carbon found in the water samples is greater in the drier climates than the eastern wetter climates reflecting the changes in soil type and hydrology across the region. Understanding the variability in hydrology as well as the trends in carbon export is an essential first step in

  19. Spatial and temporal patterns of carbon and water fluxes in East Asia

    NASA Astrophysics Data System (ADS)

    Ryu, Y.; Jiang, C.

    2014-12-01

    East Asia accounts for 20% of global population, is responsible for 30% of global GHG emissions, and experiences rapid land use changes. These facts are likely to substantially alter terrestrial water and carbon cycles; however, little is known about spatial and temporal patterns of carbon and water fluxes in East Asia. In this study, we use the Breathing Earth System Simulator (BESS) which computes gross primary productivity and evaporation between 2001 and 2013 using a series of MODIS Atmosphere and Land products. We have improved BESS by incorporating chlorophyll fluorescence module, updated module of Ci:Ca, and atmospheric stability. We prepare independent data such as NDVI, EVI, and GOSAT-derived fluorescence to cross-check our spatial and temporal patterns of carbon and water flux maps. We investigate how water and carbon fluxes respond to extreme weather events and land use changes in East Asia.

  20. Carbon fluxes resulting from land-use changes in the Tamaulipan thornscrub of northeastern Mexico

    PubMed Central

    Návar-Chaidez, Jose de Jesus

    2008-01-01

    Information on carbon stock and flux resulting from land-use changes in subtropical, semi-arid ecosystems are important to understand global carbon flux, yet little data is available. In the Tamaulipan thornscrub forests of northeastern Mexico, biomass components of standing vegetation were estimated from 56 quadrats (200 m2 each). Regional land-use changes and present forest cover, as well as estimates of soil organic carbon from chronosequences, were used to predict carbon stocks and fluxes in this ecosystem. For the period of 1980–1996, the Tamaulipan thornscrub is presenting an annual deforestation rate of 2.27% indicating that approximately 600 km2 of this plant community are lost every year and that 60% of the original Mexican Tamaulipan thornscrub vegetation has been lost since the 1950's. On the other hand, intensive agriculture, including introduced grasslands increased (4,000 km2) from 32 to 42% of the total studied area, largely at the expense of the Tamaulipan thornscrub forests. Land-use changes from Tamaulipan thornscrub forest to agriculture contribute 2.2 Tg to current annual carbon emissions and standing biomass averages 0.24 ± 0.06 Tg, root biomass averages 0.17 ± 0.03 Tg, and soil organic carbon averages 1.80 ± 0.27 Tg. Land-use changes from 1950 to 2000 accounted for Carbon emissions of the order of 180.1 Tg. Projected land-use changes will likely contribute to an additional carbon flux of 98.0 Tg by the year 2100. Practices to conserve sequester, and transfer carbon stocks in semi-arid ecosystems are discussed as a means to reduce carbon flux from deforestation practices. PMID:18826617

  1. Impacts of ontogenetically migrating copepods on downward carbon flux in the western subarctic Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Kobari, Toru; Steinberg, Deborah K.; Ueda, Ai; Tsuda, Atsushi; Silver, Mary W.; Kitamura, Minoru

    2008-07-01

    To evaluate the impacts of ontogenetically (seasonally) migrating copepods on carbon transport to the mesopelagic zone, we investigated depth distribution, population structure, and feeding activity of the ontogentic copepod community in the western subarctic Pacific Ocean from day-night pairs of zooplankton samples down to 1000 m during the VERtical Transport In the Global Ocean (VERTIGO) program. Over the 31 July-16 August 2005 study period, the biomass of Neocalanus cristatus and Neocalanus plumchrus predominated in the near surface waters, while Neocalanus flemingeri was already dormant at depth. We observed a strong diel migration for Metridia pacifica, and a seasonal downward migration for Eucalanus bungii. Based on gut pigment analysis, ingestion rate of the copepod community was 214-375 mg C m -2 day -1, which was equal to 26-37% of the concurrent primary production. However, comparison of grazing estimated from gut pigments to calculated carbon demand of the copepod community indicates that phytoplankton comprised 37-59% of the ingested carbon. Thus, the copepod community appears to have also relied on detritus and microzooplankton for their nutrition, likely because primary production during this time was dominated by picophytoplankton too small to be grazed by these large copepods. Fecal pellet flux by the copepod community was estimated to account for 141-223% of the sedimentary particulate organic carbon (POC) flux at 150 m, suggesting considerable fragmentation and consumption of pellets in the upper layers. Fecal pellets alone were adequate to meet copepod carbon demand in the surface 0-150 m layer. Active carbon flux by diel migration of M. pacifica (respiration, egestion, and mortality) was 4-17 mg C m -2 day -1, equal to 6-44% of sedimentary POC flux at 150 m. Active carbon flux by N. flemingeri ontogenetic migration (i.e., respiration and mortality at depth) contributed 246 mg C m -2 year -1, equal to 9% of sedimentary POC flux at 1000 m. The

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

    NASA Astrophysics Data System (ADS)

    Brüggemann, N.; Gessler, A.; Kayler, Z.; Keel, S. G.; Badeck, F.; Barthel, M.; Boeckx, P.; Buchmann, N.; Brugnoli, E.; Esperschütz, J.; Gavrichkova, O.; Ghashghaie, J.; Gomez-Casanovas, N.; Keitel, C.; Knohl, A.; Kuptz, D.; Palacio, S.; Salmon, Y.; Uchida, Y.; Bahn, M.

    2011-04-01

    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. The last part of the paper is dedicated to physical interactions between soil CO2 and the soil matrix, such as CO2 diffusion and dissolution processes within the

  3. The effect of management on forest carbon fluxes

    NASA Astrophysics Data System (ADS)

    Noormets, A.; McNulty, D.; Sun, G.; domec, J.; Gavazi, M.; King, J. S.

    2013-12-01

    Intensification of land use is often considered a primary factor leading to accelerated mineralization of soil carbon. This is particularly evident in agricultural lands, but is also suggested under less intensive management practices, including commercial forestry. If true, such an effect would offset efforts to manage ecosystems for carbon sequestration and climate change mitigation. Yet, recent studies of carbon cycling in managed forests have not found unequivocal evidence of greater respiratory activity compared to unmanaged ones, which is a major process determining carbon balance of ecosystems. In the current study, we evaluated both direct and indirect effects of management on respiratory carbon emissions. The preliminary results indicate minimal systematic effect on respiration rates, whereas the increased frequency of harvest disturbances resulting in more frequent post-disturbance spikes in heterotrophic respiration leads to greater net loss of soil C over time. In contrast, the higher productivity of managed forests results in greater mean net carbon uptake, which partially offsets the respiration losses. The cumulative long-term effect of forest management on ecosystem carbon balance depends on the net balance between productivity and respiration processes, and likely will be more responsive to the fate of harvested biomass than the direct and indirect effects on respiratory dynamics.

  4. Impact of hydrology on methane flux patterns in a permafrost-affected floodplain in Northeast Siberia

    NASA Astrophysics Data System (ADS)

    Kwon, Min Jung; Beulig, Felix; Kuesel, Kirsten; Wildner, Marcus; Heimann, Martin; Zimov, Nikita; Zimov, Sergei; Goeckede, Mathias

    2015-04-01

    A large fraction of organic carbon stored in Arctic permafrost soil is at risk to be decomposed and released to the atmosphere under climate change. Thawing of ice-rich permafrost will re-structure the surface topography, with potentially significant effects on hydrology: water table depth (WTD) of depressed areas will increase, while that of the surrounding area will decrease. Changes in hydrology will trigger modifications in soil and vegetation, e.g. soil temperature, vegetation and microbial community structure. All of these secondary effects will alter carbon cycle processes, with the magnitude and even sign of the net effect yet unknown. The objective of this study is to investigate effects of drainage on methane fluxes in a floodplain of the Kolyma River near Cherskii, Northeast Siberia. The study site is separated into two areas, one that has been drained since 2004, and a nearby reference site. Methane flux was measured for ~16 weeks during summer and early winter of 2013, and summer of 2014. In addition, to separate different methane emission pathways, plant-mediated methane transport (through aerenchyma) as well as the proportion of ebullition were measured in 2014. Vegetation and microbial community structures were investigated and compared. After a decade of drainage history that lowered WTD by about 20cm in the drained area, Eriophorum (cotton grass) that previously dominated have to a large part been replaced by Carex (tussock-forming sedge) and shrub species. While WTD primarily influenced the methane flux rate, this vegetation change indirectly altered the flux as well in a way that sites with Eriophorum emitted more methane. Concerning the microbial community structure, the relative abundance of methanogen and ratio of methanotrophs to methanogens were well correlated with methane flux rates, implying that the methane flux is highly influenced by microorganisms. As a consequence of these changes, in the drained area less amount of methane was

  5. Effects of Environmental Change on Carbon and Nitrogen Fluxes from a Midwestern Agricultural Watershed

    NASA Astrophysics Data System (ADS)

    Riha, K. M.; Michalski, G.; Filley, T. R.; Dalzell, B. J.

    2009-12-01

    Climate change is expected to change precipitation patterns, which would alter the runoff of excess carbon and nitrogen into the surrounding waterways. If agricultural areas experience an increase in precipitation, then coastal areas downstream from these areas could expect to develop hypoxic conditions that are more widespread, continual, and severe causing loss of biodiversity in the ocean and economical loss to fishing industries. In the Midwest, these waterways feed into local drinking water reservoirs increasing the nitrate concentration and could easily surpass the EPA maximum nitrate concentration of 10ppm. In order to evaluate the damage to the environment due to excess nitrogen, and the possible gains by its mitigation, requires a thorough assessment of the environmental controls on nitrogen and carbon fluxes. To understand the extent of nitrogen and carbon runoff from agricultural ecosystems we are studying an 850 km2 Midwestern United States agricultural watershed located in west central Indiana. Previous studies by Dalzell et. al. examined organic carbon export from this watershed as a function of stream flow and precipitation events and observed shifts in the amount and type of carbon with season. We are interested in the nitrate concentration and how it couples with the carbon fluxes. Anions (Cl-, NO3-, and SO42-) were analyzed for the samples that were collected in 2002 and 2003. A correlation was seen between storm events, fertilizer application, and the nitrate runoff; with the highest nitrate concentration seen in April 2002 with a storm event. Recent fertilizer application is believed to be the cause. Cations were analyzed (Ca2+, Na+, K+, Fe2+, Mn2+ and Mg2+) to qualitatively determine a relationship between DOC and nitrate and determine possible flowpaths. Relationships were seen with storm events and cation fluxes, with highest concentrations seen in April 2002 during a storm event and a dilution peak seen in May 2002 which is characteristic of

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

    PubMed

    Zeri, Marcelo; Sá, Leonardo D A; Manzi, Antônio O; Araújo, Alessandro C; Aguiar, Renata G; von Randow, Celso; Sampaio, Gilvan; Cardoso, Fernando L; Nobre, Carlos A

    2014-01-01

    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. PMID:24558378

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

    PubMed

    Zeri, Marcelo; Sá, Leonardo D A; Manzi, Antônio O; Araújo, Alessandro C; Aguiar, Renata G; von Randow, Celso; Sampaio, Gilvan; Cardoso, Fernando L; Nobre, Carlos A

    2014-01-01

    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.

  8. Variability of Carbon and Water Fluxes Following Climate Extremes over a Tropical Forest in Southwestern Amazonia

    PubMed Central

    Zeri, Marcelo; Sá, Leonardo D. A.; Manzi, Antônio O.; Araújo, Alessandro C.; Aguiar, Renata G.; von Randow, Celso; Sampaio, Gilvan; Cardoso, Fernando L.; Nobre, Carlos A.

    2014-01-01

    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. PMID:24558378

  9. Are long-term trends in lake carbon dioxide flux responsive to climaticvariability and change?

    NASA Astrophysics Data System (ADS)

    Golub, M.; Desai, A. R.

    2012-12-01

    Inland water bodies are major but understudied conduits of carbon in within the global land-ocean-atmosphere carbon cycle. While many researchers have shown significant 20th century trends in physical and biological lake processes driven by climatic change, there is less research on how these influence lake-atmosphere carbon dioxide flux. We investigated the effects of climatic drivers on physical features and CO2 flux in lakes. We estimated the long-term trends in ice phenology, thermal structure, and amount of carbon exchanged, using 15-25-year time series of measurements of temperature, alkalinity, pH for eleven lakes monitored by the North Temperate Lakes Long-Term Ecological Research (NTL-LTER) program. Lakes coherently responded to regional climatic warming, showing declining ice cover duration, prolonged growing season, and increasingly warmer waters. Long-term trends of CO2 trends varied among lakes, however, with the majority of lakes showing a weakening source of CO2 to atmosphere. We further compared the sensitivity of CO2 flux to climate forcing in lakes as a function of trophic states, dissolved organic carbon concentrations, and morphometric features. These results provide new insights into our understanding about the role of lakes in regional and global carbon balances, on the sensitivity of CO2 flux to climatic variability, and in improving prediction of future carbon-climate change feedbacks.

  10. The response of ecosystem carbon fluxes to LAI and environmental drivers in a maize crop grown in two contrasting seasons

    NASA Astrophysics Data System (ADS)

    Vitale, Luca; Di Tommasi, Paul; D'Urso, Guido; Magliulo, Vincenzo

    2016-03-01

    The eddy correlation technique was used to investigate the influence of biophysical variables and crop phenological phases on the behaviour of ecosystem carbon fluxes of a maize crop, in two contrasting growing seasons. In 2009, the reduced water supply during the early growing stage limited leaf area expansion, thus negatively affecting canopy photosynthesis. The variability of gross primary production (GPP) and ecosystem respiration ( R eco) was mainly explained by seasonal variation of leaf area index (LAI). The seasonal variation of R eco was positively influenced by soil temperatures ( T soil) in 2008 but not in 2009. In 2008, a contribution of both autotrophic and heterotrophic components to total R eco could be hypothesized, while during 2009, autotrophic respiration is supposed to be the most important component. Crop phenological phases affected the response of ecosystem fluxes to biophysical drivers.

  11. Resource quality affects carbon cycling in deep-sea sediments

    PubMed Central

    Mayor, Daniel J; Thornton, Barry; Hay, Steve; Zuur, Alain F; Nicol, Graeme W; McWilliam, Jenna M; Witte, Ursula F M

    2012-01-01

    Deep-sea sediments cover ∼70% of Earth's surface and represent the largest interface between the biological and geological cycles of carbon. Diatoms and zooplankton faecal pellets naturally transport organic material from the upper ocean down to the deep seabed, but how these qualitatively different substrates affect the fate of carbon in this permanently cold environment remains unknown. We added equal quantities of 13C-labelled diatoms and faecal pellets to a cold water (−0.7 °C) sediment community retrieved from 1080 m in the Faroe-Shetland Channel, Northeast Atlantic, and quantified carbon mineralization and uptake by the resident bacteria and macrofauna over a 6-day period. High-quality, diatom-derived carbon was mineralized >300% faster than that from low-quality faecal pellets, demonstrating that qualitative differences in organic matter drive major changes in the residence time of carbon at the deep seabed. Benthic bacteria dominated biological carbon processing in our experiments, yet showed no evidence of resource quality-limited growth; they displayed lower growth efficiencies when respiring diatoms. These effects were consistent in contrasting months. We contend that respiration and growth in the resident sediment microbial communities were substrate and temperature limited, respectively. Our study has important implications for how future changes in the biochemical makeup of exported organic matter will affect the balance between mineralization and sequestration of organic carbon in the largest ecosystem on Earth. PMID:22378534

  12. Resource quality affects carbon cycling in deep-sea sediments.

    PubMed

    Mayor, Daniel J; Thornton, Barry; Hay, Steve; Zuur, Alain F; Nicol, Graeme W; McWilliam, Jenna M; Witte, Ursula F M

    2012-09-01

    Deep-sea sediments cover ~70% of Earth's surface and represent the largest interface between the biological and geological cycles of carbon. Diatoms and zooplankton faecal pellets naturally transport organic material from the upper ocean down to the deep seabed, but how these qualitatively different substrates affect the fate of carbon in this permanently cold environment remains unknown. We added equal quantities of (13)C-labelled diatoms and faecal pellets to a cold water (-0.7 °C) sediment community retrieved from 1080 m in the Faroe-Shetland Channel, Northeast Atlantic, and quantified carbon mineralization and uptake by the resident bacteria and macrofauna over a 6-day period. High-quality, diatom-derived carbon was mineralized >300% faster than that from low-quality faecal pellets, demonstrating that qualitative differences in organic matter drive major changes in the residence time of carbon at the deep seabed. Benthic bacteria dominated biological carbon processing in our experiments, yet showed no evidence of resource quality-limited growth; they displayed lower growth efficiencies when respiring diatoms. These effects were consistent in contrasting months. We contend that respiration and growth in the resident sediment microbial communities were substrate and temperature limited, respectively. Our study has important implications for how future changes in the biochemical makeup of exported organic matter will affect the balance between mineralization and sequestration of organic carbon in the largest ecosystem on Earth. PMID:22378534

  13. Natural and anthropogenic factors controlling the dissolved organic carbon concentrations and fluxes in a large tropical river, India.

    PubMed

    Balakrishna, K; Kumar, Itta Arun; Srinikethan, G; Mugeraya, Gopal

    2006-11-01

    Carbon studies in tropical rivers have gained significance since it was realized that a significant chunk of anthropogenic CO(2) emitted into the atmosphere returns to the biosphere, that is eventually transported by the river and locked up in coastal sediments for a few thousand years. Carbon studies are also significant because dissolved organic carbon (DOC) is known to complex the toxic trace metals in the river and carry them in the dissolved form. For the first time, this work has made an attempt to study the variations in DOC concentrations in space and time for a period of 19 months, and estimate their fluxes in the largest peninsular Indian river, the Godavari at Rajahmundry. Anthropogenic influence on DOC concentrations possibly from the number of bathing ghats along the banks and domestic sewage discharge into the river are evident during the pre-monsoon of 2004 and 2005. The rise in DOC concentrations at the onset of monsoon could be due to the contributions from flood plains and soils from the river catchment. Spatial variations highlighted that the DOC concentrations in the river are affected more by the anthropogenic discharges in the downstream than in the upstream. The discharge weighted DOC concentrations in the Godavari river is 3-12 times lower than Ganga-Brahmaputra, Indus and major Chinese rivers. The total carbon fluxes from the Godavari into the Bay of Bengal is insignificant (0.5%) compared to the total carbon discharges by major rivers of the world into oceans.

  14. Natural and anthropogenic factors controlling the dissolved organic carbon concentrations and fluxes in a large tropical river, India.

    PubMed

    Balakrishna, K; Kumar, Itta Arun; Srinikethan, G; Mugeraya, Gopal

    2006-11-01

    Carbon studies in tropical rivers have gained significance since it was realized that a significant chunk of anthropogenic CO(2) emitted into the atmosphere returns to the biosphere, that is eventually transported by the river and locked up in coastal sediments for a few thousand years. Carbon studies are also significant because dissolved organic carbon (DOC) is known to complex the toxic trace metals in the river and carry them in the dissolved form. For the first time, this work has made an attempt to study the variations in DOC concentrations in space and time for a period of 19 months, and estimate their fluxes in the largest peninsular Indian river, the Godavari at Rajahmundry. Anthropogenic influence on DOC concentrations possibly from the number of bathing ghats along the banks and domestic sewage discharge into the river are evident during the pre-monsoon of 2004 and 2005. The rise in DOC concentrations at the onset of monsoon could be due to the contributions from flood plains and soils from the river catchment. Spatial variations highlighted that the DOC concentrations in the river are affected more by the anthropogenic discharges in the downstream than in the upstream. The discharge weighted DOC concentrations in the Godavari river is 3-12 times lower than Ganga-Brahmaputra, Indus and major Chinese rivers. The total carbon fluxes from the Godavari into the Bay of Bengal is insignificant (0.5%) compared to the total carbon discharges by major rivers of the world into oceans. PMID:16738757

  15. Physical and biogeochemical processes controlling particle fluxes variability and carbon export in the Southern Adriatic

    NASA Astrophysics Data System (ADS)

    Turchetto, M.; Boldrin, A.; Langone, L.; Miserocchi, S.

    2012-08-01

    In the framework of the Vector Project downward particle fluxes have been measured in a station located in the centre of the South Adriatic Pit from November 2006 to August 2008. Sediment trap samples were collected at two different depths, below the photic layer (168 m) and near the bottom (1174 m), and analysed for total mass flux, for total and organic carbon, total nitrogen, carbonate, stable isotope of organic carbon (δ13Corg) and biogenic silica contents. The results have been integrated and compared with data obtained from previous research projects, carried out in the Southern Adriatic area in 1994-1995 and 1997-1998. Fluxes of particulate matter showed high seasonal and interannual variability, with maximum values in late winter-spring season. The organic carbon flux, followed the same seasonal trend, with higher values below the photic zone, and peaks in spring, related to blooms of silica and/or carbonates phytoplankton organisms (e.g., diatoms, coccolithophorids). The organic carbon export from the photic layer was of 5.2 and 2.1 g C m-2 y-1 reached the bottom. Climatological cycles and, in particular, the maximum depth of the convective vertical mixing determined the high fluxes measured in 1998 and in 2008 springs. Total mass fluxes measured at the bottom trap were twofold those measured below the photic layer, and showed a high lithogenic fraction, highlighting the presence of advective processes that appear particularly active in the area. These processes can be correlated with the spreading of dense waters coming from the north and central Adriatic, generally observed in spring. The elemental and isotopic composition of bottom trap samples, resulted similar to that of samples collected in the south-western Adriatic slope, corroborating the assumption that lateral advection other than vertical input were contributing to bottom particle fluxes.

  16. Assessing the influence of historic net and gross land changes on the carbon fluxes of Europe.

    PubMed

    Fuchs, Richard; Schulp, Catharina J E; Hengeveld, Geerten M; Verburg, Peter H; Clevers, Jan G P W; Schelhaas, Mart-Jan; Herold, Martin

    2016-07-01

    Legacy effects of land cover/use on carbon fluxes require considering both present and past land cover/use change dynamics. To assess past land use dynamics, model-based reconstructions of historic land cover/use are needed. Most historic reconstructions consider only the net area difference between two time steps (net changes) instead of accounting for all area gains and losses (gross changes). Studies about the impact of gross and net land change accounting methods on the carbon balance are still lacking. In this study, we assessed historic changes in carbon in soils for five land cover/use types and of carbon in above-ground biomass of forests. The assessment focused on Europe for the period 1950 to 2010 with decadal time steps at 1-km spatial resolution using a bookkeeping approach. To assess the implications of gross land change data, we also used net land changes for comparison. Main contributors to carbon sequestration between 1950 and 2010 were afforestation and cropland abandonment leading to 14.6 PgC sequestered carbon (of which 7.6 PgC was in forest biomass). Sequestration was highest for old-growth forest areas. A sequestration dip was reached during the 1970s due to changes in forest management practices. Main contributors to carbon emissions were deforestation (1.7 PgC) and stable cropland areas on peaty soils (0.8 PgC). In total, net fluxes summed up to 203 TgC yr(-1) (98 TgC yr(-1) in forest biomass and 105 TgC yr(-1) in soils). For areas that were subject to land changes in both reconstructions (35% of total area), the differences in carbon fluxes were about 68%. Overall for Europe the difference between accounting for either gross or net land changes led to 7% difference (up to 11% per decade) in carbon fluxes with systematically higher fluxes for gross land change data.

  17. Benthic foraminiferal stable isotope record of organic carbon fluxes during deposition of Mediterranean sapropel S1

    NASA Astrophysics Data System (ADS)

    Theodor, Marc; Schmiedl, Gerhard; Mackensen, Andreas

    2016-04-01

    We integrated Late Glacial to Holocene stable isotope records for different epi- and endobenthic foraminifera from the Mediterranean Sea in order to document the sequence of environmental changes across formation of the most recent sapropel S1. The stable carbon isotope record of epibenthic taxa corroborates results from model experiments indicating a Late Glacial onset of deep-water stagnation with short-term reventilation events during cold intervals of the Heinrich event 1, the Younger Dryas, and the 8.2 event. The stable carbon isotope difference between epi- and shallow endobenthic foraminifera exhibits marked temporal fluctuations linked to microhabitat shifts and changes in organic matter fluxes. We generated a transfer function for organic carbon fluxes based on a correlation between the stable carbon isotope signature of modern benthic foraminifera and observed organic carbon flux rates from different Mediterranean basins. Application of this transfer function to the down-core data reveals generally elevated organic matter fluxes during the Last Glacial Maximum and the Younger Dryas, while values drop significantly during the Bølling-Allerød interstadial and with onset of the Holocene. Our results support a scenario where average organic matter fluxes in the eastern Mediterranean Sea were not significantly enhanced during formation of sapropel S1. Instead, our data corroborate earlier results from benthic foraminiferal faunal successions and model experiments suggesting that sufficient amounts of organic matter are buried under oligotrophic conditions in an intermittently hypoxic water column.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  19. Stream restoration and sewers impact sources and fluxes of water,carbon, and nutrients in urban watersheds

    EPA Science Inventory

    An improved understanding of sources and timing of water and nutrient fluxes associated with urban stream restoration is critical for guiding effective watershed management. We investigated how sources, fluxes, and flowpaths of water, carbon (C), nitrogen (N), and phosphorus (P)...

  20. Dissolved Organic Carbon Fluxes in Rivers of the Conterminous United States: Influence of Terrestrial - Aquatic Linkages

    NASA Astrophysics Data System (ADS)

    Stackpoole, S. M.; Butman, D. E.; Stets, E.; Striegl, R. G.; Bachelet, D. M.; Zhu, Z.; Liu, S.

    2015-12-01

    Management of terrestrial carbon stocks in natural ecosystems has been proposed as a sustainable approach to counteracting the anthropogenic contribution of carbon dioxide to the atmosphere. One factor of uncertainty in carbon accounting is that a portion of carbon assumed to be sequestered in soils may in fact be transported to river networks. The primary objectives of this study are to: 1) determine if the magnitude of empirical estimates of dissolved organic carbon (DOC) export in rivers correlates with simulated soil DOC leachate values from terrestrial carbon models, and 2) quantify terrestrial loading of DOC to river networks across the conterminous US. We evaluated the magnitude of riverine DOC fluxes relative to carbon storage in terrestrial biomass and soils using the aggregated results from the terrestrial carbon models included in the LandCarbon and Multi-scale Synthesis and Terrestrial Model Intercomparison Projects. We also compared gridded terrestrial DOC leaching values to downstream DOC fluxes in rivers estimated by the USGS LOADEST model. Quantification of terrestrial-aquatic linkages is necessary to better evaluate ecosystem carbon sequestration as a potential tool for mitigating anthropogenic perturbance to the global carbon cycle.

  1. Bioturbation and dissolved organic matter enhance contaminant fluxes from sediment treated with powdered and granular activated carbon.

    PubMed

    Kupryianchyk, D; Noori, A; Rakowska, M I; Grotenhuis, J T C; Koelmans, A A

    2013-05-21

    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 report polychlorobiphenyl (PCB) pore water concentrations, fluxes, mass transfer coefficients, and survival data of two benthic species, for four treatments: no AC addition (control), powdered AC addition, granular AC addition and addition and subsequent removal of GAC (sediment stripping). AC addition decreased mass fluxes but increased apparent mass transfer coefficients because of dissolved organic carbon (DOC) facilitated transport across the benthic boundary layer (BBL). In turn, DOC concentrations depended on bioturbator activity which was high for the PAC tolerant species Asellus aquaticus and low for AC sensitive species Lumbriculus variegatus. A dual BBL resistance model combining AC effects on gradients, DOC facilitated transport and biodiffusion was evaluated against the data and showed how the type of resistance differs with treatment and chemical hydrophobicity. Data and simulations illustrate the complex interplay between AC and contaminant toxicity to benthic organisms and how differences in species tolerance affect mass fluxes from sediment to the water column. PMID:23590290

  2. Carbon fluxes in an acid rain impacted boreal headwater catchment

    NASA Astrophysics Data System (ADS)

    Marx, Anne; Hintze, Simone; Jankovec, Jakub; Sanda, Martin; Dusek, Jaromir; Vogel, Tomas; van Geldern, Robert; Barth, Johannes A. C.

    2016-04-01

    Terrestrial carbon export via inland aquatic systems is a key process in the budget of the global carbon cycle. This includes loss of carbon to the atmosphere via gas evasion from rivers or reservoirs as well as carbon fixation in freshwater sediments. Headwater streams are the first endmembers of the transition of carbon between soils, groundwater and surface waters and the atmosphere. In order to quantify these processes the experimental catchment Uhlirska (1.78 km2) located in the northern Czech Republic was studied. Dissolved inorganic, dissolved organic and particulate organic carbon (DIC, DOC, POC) concentrations and isotopes were analyzed in ground-, soil -and stream waters between 2014 and 2015. In addition, carbon dioxide degassing was quantified via a stable isotope modelling approach. Results show a discharge-weighted total carbon export of 31.99 g C m-2 yr-1 of which CO2 degassing accounts 79 %. Carbon isotope ratios (δ13C) of DIC, DOC, and POC (in ‰ VPDB) ranged from -26.6 to -12.4 ‰ from -29.4 to -22.7 ‰ and from -30.6 to -26.6 ‰ respectively. The mean values for DIC are -21.8 ±3.8 ‰ -23.6 ±0.9 ‰ and -19.5 ±3.0 ‰ for soil, shallow ground and surface water compartments. For DOC, these compartments have mean values of -27.1 ±0.3 ‰ -27.0 ±0.8 ‰ and -27.4 ±0.7 ‰Ṁean POC value of shallow groundwaters and surface waters are -28.8 ±0.8 ‰ and -29.3 ±0.5 ‰ respectively. These isotope ranges indicate little turnover of organic material and predominant silicate weathering. The degassing of CO2 caused an enrichment of the δ13C-DIC values of up to 6.8 ‰ between a catchment gauge and the catchment outlet over a distance of 866 m. In addition, the Uhlirska catchment has only negligible natural sources of sulphate, yet SO42- accounts for 21 % of major stream water ions. This is most likely a remainder from acid rain impacts in the area.

  3. Carbon fluxes in an acid rain impacted boreal headwater catchment

    NASA Astrophysics Data System (ADS)

    Marx, Anne; Hintze, Simone; Jankovec, Jakub; Sanda, Martin; Dusek, Jaromir; Vogel, Tomas; van Geldern, Robert; Barth, Johannes A. C.

    2016-04-01

    Terrestrial carbon export via inland aquatic systems is a key process in the budget of the global carbon cycle. This includes loss of carbon to the atmosphere via gas evasion from rivers or reservoirs as well as carbon fixation in freshwater sediments. Headwater streams are the first endmembers of the transition of carbon between soils, groundwater and surface waters and the atmosphere. In order to quantify these processes the experimental catchment Uhlirska (1.78 km2) located in the northern Czech Republic was studied. Dissolved inorganic, dissolved organic and particulate organic carbon (DIC, DOC, POC) concentrations and isotopes were analyzed in ground-, soil -and stream waters between 2014 and 2015. In addition, carbon dioxide degassing was quantified via a stable isotope modelling approach. Results show a discharge-weighted total carbon export of 31.99 g C m‑2 yr‑1 of which CO2 degassing accounts 79 %. Carbon isotope ratios (δ13C) of DIC, DOC, and POC (in ‰ VPDB) ranged from -26.6 to -12.4 ‰ from -29.4 to -22.7 ‰ and from -30.6 to -26.6 ‰ respectively. The mean values for DIC are -21.8 ±3.8 ‰ -23.6 ±0.9 ‰ and -19.5 ±3.0 ‰ for soil, shallow ground and surface water compartments. For DOC, these compartments have mean values of -27.1 ±0.3 ‰ -27.0 ±0.8 ‰ and -27.4 ±0.7 ‰Ṁean POC value of shallow groundwaters and surface waters are -28.8 ±0.8 ‰ and -29.3 ±0.5 ‰ respectively. These isotope ranges indicate little turnover of organic material and predominant silicate weathering. The degassing of CO2 caused an enrichment of the δ13C-DIC values of up to 6.8 ‰ between a catchment gauge and the catchment outlet over a distance of 866 m. In addition, the Uhlirska catchment has only negligible natural sources of sulphate, yet SO42‑ accounts for 21 % of major stream water ions. This is most likely a remainder from acid rain impacts in the area.

  4. Assessing and Synthesizing the Last Decade of Research on the Major Pools and Fluxes of the Carbon Cycle in the US and North America: An Interagency Governmental Perspective

    NASA Astrophysics Data System (ADS)

    Cavallaro, N.; Shrestha, G.; Stover, D. B.; Zhu, Z.; Ombres, E. H.; Deangelo, B.

    2015-12-01

    The 2nd State of the Carbon Cycle Report (SOCCR-2) is focused on US and North American carbon stocks and fluxes in managed and unmanaged systems, including relevant carbon management science perspectives and tools for supporting and informing decisions. SOCCR-2 is inspired by the US Carbon Cycle Science Plan (2011) which emphasizes global scale research on long-lived, carbon-based greenhouse gases, carbon dioxide and methane, and the major pools and fluxes of the global carbon cycle. Accordingly, the questions framing the Plan inform this report's topical roadmap, with a focus on US and North America in the global context: 1) How have natural processes and human actions affected the global carbon cycle on land, in the atmosphere, in the oceans and in the ecosystem interfaces (e.g. coastal, wetlands, urban-rural)? 2) How have socio-economic trends affected the levels of the primary carbon-containing gases, carbon dioxide and methane, in the atmosphere? 3) How have species, ecosystems, natural resources and human systems been impacted by increasing greenhouse gas concentrations, the associated changes in climate, and by carbon management decisions and practices? To address these aspects, SOCCR-2 will encompass the following broad assessment framework: 1) Carbon Cycle at Scales (Global Perspective, North American Perspective, US Perspective, Regional Perspective); 2) Role of carbon in systems (Soils; Water, Oceans, Vegetation; Terrestrial-aquatic Interfaces); 3) Interactions/Disturbance/Impacts from/on the carbon cycle. 4) Carbon Management Science Perspective and Decision Support (measurements, observations and monitoring for research and policy relevant decision-support etc.). In this presentation, the Carbon Cycle Interagency Working Group and the U.S. Global Change Research Program's U.S. Carbon Cycle Science Program Office will highlight the scientific context, strategy, structure, team and production process of the report, which is part of the USGCRP's Sustained

  5. Sensitivities of marine carbon fluxes to ocean change

    PubMed Central

    Riebesell, Ulf; Körtzinger, Arne; Oschlies, Andreas

    2009-01-01

    Throughout Earth's history, the oceans have played a dominant role in the climate system through the storage and transport of heat and the exchange of water and climate-relevant gases with the atmosphere. The ocean's heat capacity is ≈1,000 times larger than that of the atmosphere, its content of reactive carbon more than 60 times larger. Through a variety of physical, chemical, and biological processes, the ocean acts as a driver of climate variability on time scales ranging from seasonal to interannual to decadal to glacial–interglacial. The same processes will also be involved in future responses of the ocean to global change. Here we assess the responses of the seawater carbonate system and of the ocean's physical and biological carbon pumps to (i) ocean warming and the associated changes in vertical mixing and overturning circulation, and (ii) ocean acidification and carbonation. Our analysis underscores that many of these responses have the potential for significant feedback to the climate system. Because several of the underlying processes are interlinked and nonlinear, the sign and magnitude of the ocean's carbon cycle feedback to climate change is yet unknown. Understanding these processes and their sensitivities to global change will be crucial to our ability to project future climate change. PMID:19995981

  6. Biogenic carbon fluxes from global agricultural production and consumption: Gridded, annual estimates of net ecosystem carbon exchange

    NASA Astrophysics Data System (ADS)

    Wolf, J.; West, T. O.; le Page, Y.; Thomson, A. M.

    2014-12-01

    Quantification of biogenic carbon fluxes from agricultural lands is needed to generate globally consistent bottom-up estimates for carbon monitoring and model input. We quantify agricultural carbon fluxes associated with annual (starting in 1961) crop net primary productivity (NPP), harvested biomass, and human and livestock consumption and emissions, with estimates of uncertainty, by applying region- and species-specific carbon parameters to annual crop, livestock, food and trade inventory data, and generate downscaled, gridded (0.05 degree resolution) representations of these fluxes. In 2011, global crop NPP was 5.25 ± 0.46 Pg carbon (excluding root exudates), of which 2.05 ± 0.051 Pg carbon was harvested as primary crops; an additional 0.54 Pg of crop residue carbon was collected for livestock fodder. In 2011, total livestock feed intake was 2.42 ± 0.21 Pg carbon, of which 2.31 ± 0.21 Pg carbon was emitted as carbon dioxide and 0.072 ± 0.005 Pg carbon was emitted as methane. We estimate that livestock grazed 1.18 Pg carbon from non-crop lands in 2011, representing 48.5 % of global total feed intake. In 2009, the latest available data year, we estimate global human food intake (excluding seafood and orchard fruits and nuts) at 0.52 ± 0.03 Pg carbon, with an additional 0.24 ± 0.01 Pg carbon of food supply chain losses. Trends in production and consumption of agricultural carbon between 1961 and recent years, such as increasing dominance of oilcrops and decreasing percent contribution of pasturage to total livestock feed intake, are discussed, and accounting of all agricultural carbon was done for the years 2005 and 2009. Gridded at 0.05 degree resolution, these quantities represent local uptake and release of agricultural biogenic carbon (e.g. biomass production and removal, residue and manure inputs to soils) and may be used with other gridded data to help estimate current and future changes in soil organic carbon.

  7. The effect of induced anoxia and reoxygenation on benthic fluxes of organic carbon, phosphate, iron, and manganese.

    PubMed

    Skoog, Annelie C; Arias-Esquivel, Victor A

    2009-11-15

    Eutrophication causes seasonally anoxic bottom waters in coastal environments, but we lack information on effects of onset of anoxia and subsequent reoxygenation on benthic fluxes of redox-sensitive minerals and associated organic carbon (OC). As the first study, we determined the effect of inducing anoxia and subsequently restoring oxic conditions in mesocosms with surface sediment and water from a coastal environment. These concentration changes were compared with those in an oxygenated control. We determined water column concentrations of dissolved organic carbon (DOC), particulate organic carbon (POC), iron, manganese, and phosphate. Benthic fluxes of DOC, POC, and iron increased at the onset of anoxia in oxygen-depleted treatments. DOC and iron concentrations increased concomitantly towards maxima, which may have indicated reductive dissolution of FeOOH and release of associated OC. The subsequent concomitant concentration decreases may have been the result of coprecipitation of OC with iron-containing minerals. In contrast, the phosphate-concentration increase occurred several days after the onset of anoxia and the manganese concentration was not affected by the onset of anoxia. Restoring oxic conditions resulted in a decrease in DOC, POC, and phosphate concentrations, which may indicate coprecipitation of OC with phosphate-containing minerals. The high DOC fluxes at the onset of anoxia indicate that redox oscillations may be important in OC degradation. Further, our results indicate a close coupling between OC cycling and dissolution/precipitation of iron-containing minerals in intermittently anoxic sediments.

  8. Diurnal and seasonal variation of various carbon fluxes from an urban tower platform in Houston, TX

    NASA Astrophysics Data System (ADS)

    Schade, G. W.; Werner, N.; Hale, M. C.

    2013-12-01

    We measured carbon fluxes (CO2, CO, VOCs) from a tall lattice tower in Houston between 2007 and 2009, and 2011-2013. We present results from various analyses of (i) anthropogenic and biogenic CO2 fluxes using a quadrant segregation technique, (ii) seasonal and multi-year changes of CO fluxes as related to car traffic and industrial sources, and (iii) the accuracy of, and usefulness of a bulk flux footprint model to quantify pentane emissions form a distant source in comparison to permitted emission levels. Segregated and net anthropogenic CO2 fluxes were dominated by car traffic but industrial sources were identified as well. Emissions sank to minimal levels after hurricane Ike had passed over Houston, causing a traffic shutdown and lower population density. Segregated biogenic fluxes showed a clear seasonal variation with photosynthetic activity between April and November, and large effects of the 2011 Texas drought due to negligible irrigation in the study area. Carbon monoxide fluxes, measured via a flux gradient technique, are even stronger dominated by car traffic than CO2 fluxes and serve as a traffic tracer. Our data show a continued drop in emissions over time, seasonal changes with higher emissions during winter, and local influences due to industrial emissions. Lastly, we present the results of a tracer release study and a single point source quantification to test a bulk footprint model in this complex urban area. Known releases of volatile acetone and MEK were compered to measured fluxes using a REA-GC-FID system, and permit emissions of pentane from a foam plastics manufacturing facility were compared to measured pentane fluxes. Both comparisons reveal a surprisingly accurate performance of the footprint model within a factor of 2.

  9. Does consideration of water routing affect simulated water and carbon dynamics in terrestrial ecosystems?

    NASA Astrophysics Data System (ADS)

    Tang, G.; Schneiderman, E. M.; Band, L. E.; Hwang, T.; Pierson, D. C.; Pradhanang, S. M.; Zion, M. S.

    2013-10-01

    The cycling of carbon in terrestrial ecosystems is closely coupled with the cycling of water. An important mechanism connecting ecological and hydrological processes in terrestrial ecosystems is lateral flow of water along landscapes. Few studies, however, have examined explicitly how consideration of water routing affects simulated water and carbon dynamics in terrestrial ecosystems. The objective of this study is to explore how consideration of water routing in a process-based hydroecological model affects simulated water and carbon dynamics. To achieve that end, we rasterized the regional hydroecological simulation systems (RHESSys) and employed the rasterized RHESSys (R-RHESSys) in a forested watershed. We performed and compared two contrasting simulations, one with and another without water routing. We found that R-RHESSys is able to correctly simulate major hydrological and ecological variables regardless of whether water routing is considered. When water routing was neglected, however, soil water table depth and saturation deficit were simulated to be smaller and spatially more homogeneous. As a result, evaporation, forest productivity and soil heterotrophic respiration also were simulated to be spatially more homogeneous compared to simulation with water routing. When averaged for the entire watershed, however, differences in simulated water and carbon fluxes are not significant between the two simulations. Overall, the study demonstrated that consideration of water routing enabled R-RHESSys to better capture our preconception of the spatial patterns of water table depth and saturation deficit across the watershed. Because the spatial pattern of soil moisture is fundamental to water efflux from land to the atmosphere, forest productivity and soil microbial activity, ecosystem and carbon cycle models, therefore, need to explicitly represent water routing in order to accurately quantify the magnitudes and patterns of water and carbon fluxes in terrestrial

  10. Multi-decadal increases in dissolved organic carbon and alkalinity flux from the Mackenzie drainage basin to the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Tank, Suzanne E.; Striegl, Robert G.; McClelland, James W.; Kokelj, Steven V.

    2016-05-01

    Riverine exports of organic and inorganic carbon (OC, IC) to oceans are intricately linked to processes occurring on land. Across high latitudes, thawing permafrost, alteration of hydrologic flow paths, and changes in vegetation may all affect this flux, with subsequent implications for regional and global carbon (C) budgets. Using a unique, multi-decadal dataset of continuous discharge coupled with water chemistry measurements for the Mackenzie River, we show major increases in dissolved OC (DOC) and IC (as alkalinity) fluxes since the early 1970s, for a watershed that covers 1.8 M km2 of northwestern Canada, and provides substantial inputs of freshwater and biogeochemical constituents to the Arctic Ocean. Over a 39-year period of record, DOC flux at the Mackenzie mouth increased by 39.3% (44.5 ± 22.6 Gmol), while alkalinity flux increased by 12.5% (61.5 ± 60.1 Gmol). Isotopic analyses and substantial increases in sulfate flux indicate that increases in alkalinity are driven by accelerating sulfide oxidation, a process that liberates IC from rock and soils in the absence of CO2 consumption. Seasonal and sub-catchment trends suggest that permafrost thaw plays an important role in the observed increases in DOC and alkalinity: sub-catchment increases for all constituents are confined to northern, permafrost-affected regions, while observed increases in autumn to winter are consistent with documented landscape-scale changes that have resulted from changing thaw dynamics. This increase in DOC and sulfide-derived alkalinity represents a substantial intensification of land-to-ocean C mobilization, at a level that is significant within the regional C budget. The change we observe, for example, is similar to current and projected future rates of CO2 consumption by weathering in the Mackenzie basin.

  11. Plant species diversity affects soil-atmosphere fluxes of methane and nitrous oxide.

    PubMed

    Niklaus, Pascal A; Le Roux, Xavier; Poly, Franck; Buchmann, Nina; Scherer-Lorenzen, Michael; Weigelt, Alexandra; Barnard, Romain L

    2016-07-01

    Plant diversity effects on ecosystem functioning can potentially interact with global climate by altering fluxes of the radiatively active trace gases nitrous oxide (N2O) and methane (CH4). We studied the effects of grassland species richness (1-16) in combination with application of fertilizer (nitrogen:phosphorus:potassium = 100:43.6:83 kg ha(-1) a(-1)) on N2O and CH4 fluxes in a long-term field experiment. Soil N2O emissions, measured over 2 years using static chambers, decreased with species richness unless fertilizer was added. N2O emissions increased with fertilization and the fraction of legumes in plant communities. Soil CH4 uptake, a process driven by methanotrophic bacteria, decreased with plant species numbers, irrespective of fertilization. Using structural equation models, we related trace gas fluxes to soil moisture, soil inorganic N concentrations, nitrifying and denitrifying enzyme activity, and the abundance of ammonia oxidizers, nitrite oxidizers, and denitrifiers (quantified by real-time PCR of gene fragments amplified from microbial DNA in soil). These analyses indicated that plant species richness increased soil moisture, which in turn increased N cycling-related activities. Enhanced N cycling increased N2O emission and soil CH4 uptake, with the latter possibly caused by removal of inhibitory ammonium by nitrification. The moisture-related indirect effects were surpassed by direct, moisture-independent effects opposite in direction. Microbial gene abundances responded positively to fertilizer but not to plant species richness. The response patterns we found were statistically robust and highlight the potential of plant biodiversity to interact with climatic change through mechanisms unrelated to carbon storage and associated carbon dioxide removal. PMID:27038993

  12. Carbon and Nitrogen Provisions Alter the Metabolic Flux in Developing Soybean Embryos1[W][OA

    PubMed Central

    Allen, Doug K.; Young, Jamey D.

    2013-01-01

    Soybean (Glycine max) seeds store significant amounts of their biomass as protein, levels of which reflect the carbon and nitrogen received by the developing embryo. The relationship between carbon and nitrogen supply during filling and seed composition was examined through a series of embryo-culturing experiments. Three distinct ratios of carbon to nitrogen supply were further explored through metabolic flux analysis. Labeling experiments utilizing [U-13C5]glutamine, [U-13C4]asparagine, and [1,2-13C2]glucose were performed to assess embryo metabolism under altered feeding conditions and to create corresponding flux maps. Additionally, [U-14C12]sucrose, [U-14C6]glucose, [U-14C5]glutamine, and [U-14C4]asparagine were used to monitor differences in carbon allocation. The analyses revealed that: (1) protein concentration as a percentage of total soybean embryo biomass coincided with the carbon-to-nitrogen ratio; (2) altered nitrogen supply did not dramatically impact relative amino acid or storage protein subunit profiles; and (3) glutamine supply contributed 10% to 23% of the carbon for biomass production, including 9% to 19% of carbon to fatty acid biosynthesis and 32% to 46% of carbon to amino acids. Seed metabolism accommodated different levels of protein biosynthesis while maintaining a consistent rate of dry weight accumulation. Flux through ATP-citrate lyase, combined with malic enzyme activity, contributed significantly to acetyl-coenzyme A production. These fluxes changed with plastidic pyruvate kinase to maintain a supply of pyruvate for amino and fatty acids. The flux maps were independently validated by nitrogen balancing and highlight the robustness of primary metabolism. PMID:23314943

  13. Carbon Explorer Assessment of Carbon Biomass Variability and Carbon Flux Systematics in the Upper Ocean During SOFEX

    NASA Astrophysics Data System (ADS)

    Bishop, J. K.; Wood, T. J.; Sherman, J. T.

    2002-12-01

    Three autonomous Carbon Explorers built on SIO's Orbcomm/GPS enhanced Sounding Oceanographic Lagrangian Observer were launched near 55S 172W in the "North" SOFEX experiment area in early January 2002. All Explorers at 55S were programmed to perform profiles from 1000, 300, and 300 m with surfacings, GPS position, and telemetry of profile data initiating at local 0600, 1200, and 1800 hours. The floats were programmed to 'sleep' at 100 m depth between profiles to maximize tracking of the surface layer. Each Explorer carried SeaBird T and S sensors and was additionally fitted with a WETLabs transmissometer based "POC" sensor and a Seapoint scattering meter to assess particulate matter variability. A carbon flux "index" obtained during the 100 m sleep periods was also derived from the POC sensor readings. Explorer 1177 was deployed as a control outside of Fe treated waters on Jan 11 2002 (UTC) and drifted initially to the North East at 10 cm/sec. Explorer 2104, deployed on Jan 19 2002 after the 3rd Fe infusion, advected with the patch to the NE on a course that closely paralleled that of the "control". By Feb 8 2002, the two floats had drifted with the circumpolar current nearly 200 km; Explorer 2104 had recorded a 4-fold build-up of of particles in the upper 60 m whereas records from the nearby control Explorer 1177 showed little change. Ship survey data (Revelle) indicated that Explorer 2104 was near but "in" the trailing edge of the patch. Beginning Feb 14 (several days after the 4th infusion of Fe) and ending on Feb 24 2002, Explorer 2104 data showed isolines of POC concentration beginning to deepen in waters below 60 m and a coincident loss of POC from above; the POC flux index also began to show clearly different and enhanced 'spikes' compared to that recorded by the control. The spikes either reflected temporal variability of particle export from the patch or the intermingled sampling of the "in patch" settling plume of particles and "out-of-patch" background

  14. Warmer Boreal Forest Organic Soil Horizons are Associated with Larger Fluxes of Dissolved Organic Carbon than their Cooler Climate Counterparts.

    NASA Astrophysics Data System (ADS)

    Bowering, K.; Edwards, K. A.; Ziegler, S. E.

    2015-12-01

    Boreal forest soils are characterized by large stocks of carbon associated with relatively slow decomposition and deep organic horizons. Dissolved organic carbon (DOC) loss from organic soil horizons occurs through hydrologically-mediated leaching processes, and contributes to downstream carbon both in deeper mineral soils and also in connected aquatic systems. However, the amount of DOC that leaves organic horizons and the environmental controls on this flux are poorly understood and are likely to be affected by climate changes. We sampled zero-tension lysimeters along 3 forested sites of a boreal climate transect to estimate DOC export from organic soil horizons of mesic boreal podzols (spodosols), and to investigate the climatic drivers of this flux. The sites are part of the Newfoundland and Labrador Boreal Ecosystems Latitudinal Transect (NL-BELT) and span approximately 5°C in mean annual temperature. Lysimeters were sampled over 4 years and DOC flux was calculated for each seasonal period (summer, fall, and winter) of each year. DOC flux was greatest in the warmest site (114 mg C day-1 m-2), with the two cooler sites having lower flux rates (40 and 36 mg C day-1 m-2 in the intermediate and coolest sites respectively). Seasonal variation was most pronounced in the warmest site where more DOC exited the organic soil horizons during fall than during summer or winter. DOC flux was correlated with the volume of soil solution collected in the lysimeters (R2 = .46), however the larger sample volumes collected in the warmest climate do not reflect greater overall precipitation. During the 4-year period of this study, similar amounts of precipitation were recorded in all regions, and the number of days with >10mm precipitation did not differ. The greater DOC flux in the warmer climate site may be due to higher rates of both litterfall and decomposition, contributing to increased labile DOC sources in the warmer climate. Analyses of the carbon quality of these samples

  15. Benthic Primary Production in a Saltmarsh Pond: Insights from Fluxes of Dissolved Inorganic Carbon and Oxygen

    NASA Astrophysics Data System (ADS)

    Karolewski, J. S.; Stanley, R. H.; Howard, E. M.; Spivak, A. C.

    2014-12-01

    Salt marshes are important carbon sinks that exist at continental margins and act as mediators in the exchange of nutrients and carbon between terrestrial and marine environments. Within salt marshes, 10-20% of total surface area is covered by marshtop ponds. The fractional area of marshtop ponds is predicted to increase as sea level rises. Despite their potential importance, the balance between autotrophic and heterotrophic processes within such ponds remain poorly understood. To quantify the balance of metabolic fluxes within salt marsh ponds, chemical fluxes of dissolved inorganic carbon (DIC) and dissolved oxygen (DO) were measured in July, 2014 in benthic flux chambers inserted into a salt marsh pond in the Plum Island Estuary Long-Term Ecosystem Research (PIE-LTER) site. Light and dark chambers were used to enable separation of rates of photosynthesis and respiration. Separate chambers were used to enclose sediment covered by primarily benthic microalgae and primarily benthic macroalgae. Net ecosystem metabolism in the microalgae was ~10 and in the macroalgae ~15 mmol C/m2/hour. Respiration rates were ~10 mmol C/m2/ hour for both microalgae and macroalgae. The resulting fluxes of net ecosystem production in the ponds will be compared with overall marsh net ecosystem flux as measured by an eddy flux tower that was located 100 meters from the pond. Additionally, concurrent measurements of DIC and DO allow quantification of the C:O ratio during respiration (i.e. respiratory quotient) in this system.

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

    PubMed Central

    2013-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Thaysen, E. M.; Jacques, D.; Jessen, S.; Andersen, C. E.; Laloy, E.; Ambus, P.; Postma, D.; Jakobsen, I.

    2014-03-01

    The efflux of carbon dioxide (CO2) from soils influences atmospheric CO2 concentrations and thereby climate change. The partitioning of inorganic carbon fluxes in the vadose zone between emission to the atmosphere and to the groundwater was investigated. Carbon dioxide partial pressure in the soil gas (pCO2), 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 pCO2, alkalinity and the water flux at the mesocosm bottom. Carbon dioxide exchange between the soil surface and the atmosphere was measured at regular intervals. The soil diffusivity was determined from soil radon-222 (222Rn) emanation rates and soil air Rn concentration profiles, and was used in conjunction with measured pCO2 gradients to calculate the soil CO2 production. Carbon dioxide fluxes were modelled 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 μmol carbon (C) m-2 s-1, respectively, and largely exceeded the corresponding DIC percolation fluxes of 0.01 ± 0.004 and 0.06 ± 0.03 μmol C m-2 s-1. Post-harvest soil respiration (Rs) was only 10% of the Rs during plant growth, while the post-harvest DIC percolation flux was more than one third of the flux during growth. The Rs was controlled by production and diffusivity of CO2 in the soil. The DIC percolation flux was largely controlled by the pCO2 and the drainage flux due to low solution pH. Plant biomass and soil pCO2 were high in the mesocosms as compared to a standard field situation. Our results indicate no change of the cropland C balance under elevated atmospheric CO2 in a warmer future climate, in which plant biomass and soil pCO2 are expected to increase.

  18. A comparison of six methods for measuring soil-surface carbon dioxide fluxes

    USGS Publications Warehouse

    Norman, J.M.; Kucharik, C.J.; Gower, S.T.; Baldocchi, D.D.; Crill, P.M.; Rayment, M.; Savage, K.; Striegl, R.G.

    1997-01-01

    Measurements of soil-surface CO2 fluxes are important for characterizing the carbon budget of boreal forests because these fluxes can be the second largest component of the budget. Several methods for measuring soil-surface CO2 fluxes are available: (1) closed-dynamic-chamber systems, (2) closed-static-chamber systems, (3) open-chamber systems, and (4) eddy covariance systems. This paper presents a field comparison of six individual systems for measuring soil-surface CO2 fluxes with each of the four basic system types represented. A single system is used as a reference and compared to each of the other systems individually in black spruce (Picea mariana), jack pine (Pinus banksiana), or aspen (Populus tremuloides) forests. Fluxes vary from 1 to 10 ??mol CO2 m-2 s-1. Adjustment factors to bring all of the systems into agreement vary from 0.93 to 1.45 with an uncertainty of about 10-15%.

  19. Aspects of spatial and temporal aggregation in estimating regional carbon dioxide fluxes from temperate forest soils

    NASA Technical Reports Server (NTRS)

    Kicklighter, David W.; Melillo, Jerry M.; Peterjohn, William T.; Rastetter, Edward B.; Mcguire, A. David; Steudler, Paul A.; Aber, John D.

    1994-01-01

    We examine the influence of aggregation errors on developing estimates of regional soil-CO2 flux from temperate forests. We find daily soil-CO2 fluxes to be more sensitive to changes in soil temperatures (Q(sub 10) = 3.08) than air temperatures (Q(sub 10) = 1.99). The direct use of mean monthly air temperatures with a daily flux model underestimates regional fluxes by approximately 4%. Temporal aggregation error varies with spatial resolution. Overall, our calibrated modeling approach reduces spatial aggregation error by 9.3% and temporal aggregation error by 15.5%. After minimizing spatial and temporal aggregation errors, mature temperate forest soils are estimated to contribute 12.9 Pg C/yr to the atmosphere as carbon dioxide. Georeferenced model estimates agree well with annual soil-CO2 fluxes measured during chamber studies in mature temperate forest stands around the globe.

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

    USGS Publications Warehouse

    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.

  1. Carbon Fluxes Between the Atmosphere, Terrestrial, and River Systems Across a Glacier-Dominated Landscape in Southcentral Alaska

    NASA Astrophysics Data System (ADS)

    Zulueta, R. C.; Welker, J. M.; Tomco, P. L.

    2011-12-01

    The coastal Gulf of Alaska region is experiencing rapid and accelerating changes due to local and regional warming. Predicted high latitude warming may result in rapid recession of glaciers with subsequent changes in river discharge, nutrient fluxes into the rivers, shifts in landscape vegetation cover, and altered CO2 fluxes affecting the regional carbon balance. As glaciers recede an increase in glacier-dominated river discharge and a change in seasonality of the river discharge are expected. Recently deglaciated landscapes will, over time, be occupied by a succession of vegetation cover that are likely to alter the fluxes of carbon both between the atmosphere and terrestrial ecosystems, and between terrestrial ecosystems and stream and river systems. As the landscape evolves from deglaciated forelands it is expected that there is low to no CO2 fluxes between the atmosphere and the recently deglaciated landscape, as well as dissolved organic and inorganic carbon inputs into rivers and streams. These recently deglaciated landscapes will transition to early successional plant species and on towards mature spruce forests. Each transitional terrestrial ecosystem will have different carbon cycling between the atmosphere, terrestrial, and aquatic systems until the mature spruce forests which is expected to have high carbon uptake and sequestration as well as increased inputs of dissolved organic and inorganic carbon into the rivers and streams. A new research project was initiated in the summer of 2011 focusing on glacier-dominated landscapes within the Wrangell-St. Elias National Park and Preserve in southcentral Alaska with the objective to quantify how the transition from deglaciated forelands to mature spruce forests (a successional sequence) alters the patterns and magnitudes of CO2 exchange, the dissolved carbon inputs from terrestrial to aquatic systems and the extent to which these are manifested due to changes in glacier coverage. We seek to examine present

  2. Optimizing Large Scale Carbon Fluxes for North America

    NASA Astrophysics Data System (ADS)

    Schuh, A. E.; Denning, A. S.; Corbin, K. D.; Ulliasz, M.; Parazoo, N. C.

    2008-12-01

    We combine the SiB3 biosphere model with the RAMS mesoscale meteorology model and associated Lagrangian particle dispersion model (LPDM) and use CO2 observations from a 8-tower network in 2004 to correct a priori ecosystem respiration (ER) and gross primary productivity (GPP) fluxes for a domain consisting of most of North America. Results are presented as weekly corrections to ER and GPP for 2004. A sink is recovered from the inversion but is smaller than expected due to the limited constraint imposed by the sampling footprint of the 8-tower observing network. The sensitivities of the inversion to independently derived boundary conditions, different fossil fuel sources, and various parameters in the inversion are analyzed and discussed.

  3. Performance of beryllium, carbon, and tungsten under intense thermal fluxes

    NASA Astrophysics Data System (ADS)

    Linke, J.; Akiba, M.; Bolt, H.; Breitbach, G.; Duwe, R.; Makhankov, A.; Ovchinnikov, I.; Rödig, M.; Wallura, E.

    1997-02-01

    Transient heat loads on a millisecond timescale with deposited energy densities beyond 1 MJ m -2 have been simulated in a plasma accelerator facility (VIKA) and in two high power electron beam teststands (JUDITH, JEBIS). Main objective of these experiments was to study and to compare the behaviour of different plasma facing materials (Be, CFC, W) under heat loads which occur during disruptions in future thermonuclear fusion reactors such as ITER. In these tests special attention was paid to the thermal shock resistance, the processes during melt layer formation, and the resulting material erosion. To perform these tests specific loading techniques and diagnostics have been developed and applied. Among these are high heat flux loading experiments at elevated temperatures ( T > DBTT) of the test coupons, fast surface pyrometry, and reliable techniques for the quantification of the absorbed energy.

  4. Quantifying legacies of clearcut on carbon fluxes and biomass carbon stock in northern temperate forests

    NASA Astrophysics Data System (ADS)

    Wang, W.; Xiao, J.; Ollinger, S. V.; Desai, A. R.; Chen, J.; Noormets, A.

    2014-06-01

    Stand-replacing disturbances including harvests have substantial impacts on forest carbon (C) fluxes and stocks. The quantification and simulation of these effects is essential for better understanding forest C dynamics and informing forest management in the context of global change. We evaluated the process-based forest ecosystem model, PnET-CN, for how well and by what mechanisms changes of ecosystem C fluxes, aboveground C stocks (AGC), and leaf area index (LAI) arise after clearcuts. We compared the effects of stand-replacing harvesting on C fluxes and stocks using two chronosequences of eddy covariance flux sites for deciduous broadleaf forests (DBF) and evergreen needleleaf forests (ENF) in the Upper Midwest region of northern Wisconsin and Michigan, USA. The average values of normalized root mean square error (NRMSE) and the Willmott index of agreement (d) between simulated and inferred from observation variables including gross primary productivity (GPP), ecosystem respiration (ER), net ecosystem productivity (NEP), LAI, and AGC in the two chronosequences were 20% and 0.90, respectively. Simulated GPP increased with stand age, reaching a maximum (∼1200-1500 g C m-2 yr-1) at 11-30 years of age, and leveled off thereafter (∼900-1000 g C m-2 yr-1). Simulated ER for both forest types was initially as high as ∼700-1000 g C m-2 yr-1 in the first or second year after clearcuts, decreased with age (∼400-800 g C m-2 yr-1) before canopy closure at 10-25 years of age, and increased to ∼800-900 g C m-2 yr-1 with stand development after canopy recovery. Simulated NEP for both forest types was initially negative with the net C losses of ∼400-700 g C m-2 yr-1 for 6-17 years after harvesting, reached the peak values of ∼400-600 g C m-2 yr-1 at 14-29 years of age, and became stable and a weak C sink (∼100-200 g C m-2 yr-1) in mature forests (>60 years old). The decline of NEP with age was caused by the relative flatting of GPP and gradual

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

    NASA Astrophysics Data System (ADS)

    Thaysen, E. M.; Jacques, D.; Jessen, S.; Andersen, C. E.; Laloy, E.; Ambus, P.; Postma, D.; Jakobsen, I.

    2014-12-01

    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 (pCO2), 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 pCO2, alkalinity and the water flux at the mesocosm bottom. Carbon dioxide exchange between the soil surface and the atmosphere was measured at regular intervals. The soil diffusivity was determined from soil radon-222 (222Rn) emanation rates and soil air Rn concentration profiles and was used in conjunction with measured pCO2 gradients 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 μmol C m-2 s-1, respectively, and grossly exceeded the corresponding DIC percolation fluxes of 0.01 ± 0.004 and 0.06 ± 0.03 μmol C m-2 s-1. Plant biomass was high in the mesocosms as compared to a standard field situation. Post-harvest soil respiration (Rs) was only 10% of the Rs during plant growth, while the post-harvest DIC percolation flux was more than one-third of the flux during growth. The Rs was controlled by production and diffusivity of CO2 in the soil. The DIC percolation flux was largely controlled by the pCO2 and the drainage flux due to low solution pH. Modeling suggested that increasing soil alkalinity during plant growth was due to nutrient buffering during root nitrate uptake.

  6. Methane and Carbon Dioxide Fluxes from Stems, Soils, and Coarse Woody Debris in a Temperate Forest

    NASA Astrophysics Data System (ADS)

    Warner, D. L.; Villarreal, S.; McWilliams, K.; Inamdar, S. P.; Vargas, R.

    2015-12-01

    Quantifying the magnitude and variability of greenhouse gas fluxes from different terrestrial carbon pools is necessary for enhancing understanding of terrestrial carbon cycling. While much more is known about variability CO2 fluxes, we have little information on how CH4 fluxes vary across multiple carbon pools within terrestrial ecosystems. We measured fluxes of CH4 and CO2 from living tree stems, soils, and coarse woody debris within a temperate forested watershed during the growing season (May-November). Fluxes of both CH4 and CO2 were significantly different among carbon pools. Living tree stems were weak sources of both CH4 and CO2 with seasonal means (± 1 SD) of 0.08 ± 0.19 nmol CH4 m-2 s-1 and 1.16 ± 1.21 μmol CO2 m-2 s-1. Soils were sinks of CH4 and sources of CO2 with seasonal means (± 1 SD) of -2.00 ± 1.41 nmol CH4 m-2 s-1 and 3.07 ± 2.10 μmol CO2 m-2 s-1. Fluxes of CH4 and CO2 from coarse woody debris were largely variable relative to the other pools with seasonal means (± 1 SD) of -0.21 ± 0.76 nmol CH4 m-2 s-1 and 2.61 ± 2.50 μmol CO2m-2 s-1. Gas fluxes varied significantly (p < 0.05) between sampling sites for both living stems and coarse woody debris, but not for soils. For living stems, this variability was explained by differences in tree species, where N. sylvatica had largest seasonal mean flux of CH4 and L. tulipifera had the largest seasonal mean flux of CO2. For woody debris sites, the variability was explained wood density, with dense, fresh wood acting as CH4 sources, and less dense, decayed wood acting as CH4 sinks. Our results show homogeneity in soil CH4 and CO2 fluxes, but a large heterogeneity in fluxes from tree stems and coarse woody debris. These results provide insights on how forest management strategies could influence greenhouse gas emissions from forested watersheds.

  7. Linking water and carbon fluxes in a Mediterranean oak woodland using a combined flux and ?18O partitioning approach

    NASA Astrophysics Data System (ADS)

    Dubbert, M.; Piayda, A.; Costa e Silva, F.; Correia, A.; Pereira, J. S.; Cuntz, M.; Werner, C.

    2013-12-01

    Water is one of the key factors driving ecosystem productivity, especially in water-limited ecosystems, where global climate change is expected to intensify drought and alter precipitation patterns. One such ecosystem is the ';Montado', where two vegetation layers respond differently to drought: oak trees avoid drought due to their access to deeper soil layers and ground water while herbaceous plants, surviving the summer in the form of seeds. We aimed at 1) quantifying the impact of the understory herbaceous vegetation on ecosystem carbon and water fluxes throughout the year, 2) determining the driving environmental factors for evapotranspiration (ET) and net ecosystem exchange (NEE) and 3) disentangling how ET components of the ecosystem relate to carbon dioxide exchange. We present one year data set comparing modeled and measured stable oxygen isotope signatures (δ18O) of soil evaporation, confirming that the Craig and Gordon equation leads to good agreement with measured δ18O of evaporation (Dubbert et al. 2013). Partitioning ecosystem ET and NEE into its three sources revealed a strong contribution of soil evaporation (E) and herbaceous transpiration (T) to ecosystem ET during spring and fall. In contrast, soil respiration (R) and herbaceous net carbon gain contributed to a lesser amount to ecosystem NEE during spring and fall, leading to consistently smaller water use efficiencies (WUE) of the herbaceous understory compared to the cork-oaks. Here, we demonstrate that the ability to assess ET, NEE and WUE independent of soil evaporation dynamics enables the understanding of the mechanisms of the coupling between water and carbon fluxes and their responses to drought. Dubbert, M., Cuntz, M., Piayda, A., Maguas, C., Werner, C., 2013: Partitioning evapotranspiration - Testing the Craig and Gordon model with field measurements of oxygen isotope ratios of evaporative fluxes. J Hydrol. a) Oxygen isotope signatures of soil evaporation on bare soil plots calculated

  8. Can We Estimate Surface Carbon Fluxes With a 6-hour Data Assimilation System?

    NASA Astrophysics Data System (ADS)

    Kalnay, E.; Kang, J.; Liu, J.; Fung, I.

    2011-12-01

    The estimation of surface carbon fluxes from atmospheric measurements of CO2 is an ill-posed problem (Enting, 2002). In the real atmosphere emissions are transported and mixed, losing information; measuring atmospheric concentrations introduces further errors; and the calculation of transports with imperfect models amplifies the errors in estimating surface sources and sinks. Because of this ill-posedness, prior information on carbon surface fluxes is essential for inverse estimations (e.g., Gurney et al., 2004, Baker et al., 2006, Roedenbeck et al., 2003). Peters et al. (2007) have used instead an Ensemble Kalman Filter (EnKF) data assimilation approach where the winds are given (e.g., from ECMWF). They use a Kalman smoother with a 5-week smoother, producing the operational "Carbon Tracker" estimation of surface fluxes at NOAA. We address the ill-posedness by assimilating simultaneously every 6 hours both carbon concentrations and meteorological variables, since within this time scale changes in atmospheric CO2 concentrations should be dominated by surface fluxes rather than transport and mixing. A simulation system using the Local Ensemble Transform Kalman Filter (LETKF) to assimilate CO2 from a realistic observing system including GOSAT, AIRS and surface observations, and is able to estimate in detail the seasonal evolution of "true" surface fluxes (including fossil fuel emissions) even in the absence of prior information. These promising results (albeit simulated) suggest that with more advanced models and accurate column observations such as those expected from OCO-2 it may be possible to estimate surface carbon fluxes if the LETKF is optimized (Kang et al., 2011).

  9. Carbon, Water Vapor, and Energy Fluxes of Grazed and Ungrazed Tallgrass Prairie

    NASA Astrophysics Data System (ADS)

    Owensby, C. E.; Ham, J. M.; Auen, L. M.

    2004-12-01

    To determine the impact of seasonal steer grazing on annual CO2 fluxes of annually-burned native tallgrass prairie, we used conditional sampling (relaxed eddy accumulation) on adjacent pastures of grazed (GR) and ungrazed (UG) tallgrass prairie from 1998 to 2001 and eddy correlation from 2002 to 2004. Fluxes of CO2 were measured almost continuously (24 hr) from immediately following burning through the burn date the following year (365 d). Aboveground biomass and leaf area were determined by clipping biweekly during the growing season. Carbon lost due to burning was estimated by clipping immediately prior to burning and collecting residual surface carbon after the burn. Soil CO2 flux was measured biweekly at midday each year using portable chambers from 1998 to 2002 and diurnally by large autochambers from 2002 to 2004. Steers were stocked at twice the normal season-long stocking rate (0.81 ha steer-1) for the first half of the grazing season (~May 1 to July 15) and the area left ungrazed the remainder of the year. That system of grazing is termed "intensive early stocking" and is commonly used throughout the Kansas Flint Hills. During the early growing season, grazing reduced net carbon exchange relative to the reduction in green leaf area, but as the growing season progressed on the grazed area, regrowth produced younger leaves that had an apparent higher photosynthetic efficiency. Despite a substantially greater green leaf area on the ungrazed area, greater positive net carbon flux occurred on the grazed area during the late season. Nighttime carbon losses were greater on the ungrazed area in the early season, but were greater on the grazed area late in the season. During the peak growth period, an amount equivalent to ~80% of the carbon fixed on a clear day was lost each day through soil CO2 flux and plant respiration. Soil CO2 flux followed a definite diurnal pattern during the growing season with daytime fluxes twice that of nighttime. During the dormant

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

    USGS Publications Warehouse

    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.

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

    NASA Astrophysics Data System (ADS)

    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

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

    NASA Astrophysics Data System (ADS)

    Ryals, R.; Silver, W. L.

    2010-12-01

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

  13. Drought impact on forest carbon dynamics and fluxes in Amazonia.

    PubMed

    Doughty, Christopher E; Metcalfe, D B; Girardin, C A J; Amézquita, F Farfán; Cabrera, D Galiano; Huasco, W Huaraca; Silva-Espejo, J E; Araujo-Murakami, A; da Costa, M C; Rocha, W; Feldpausch, T R; Mendoza, A L M; da Costa, A C L; Meir, P; Phillips, O L; Malhi, Y

    2015-03-01

    In 2005 and 2010 the Amazon basin experienced two strong droughts, driven by shifts in the tropical hydrological regime possibly associated with global climate change, as predicted by some global models. Tree mortality increased after the 2005 drought, and regional atmospheric inversion modelling showed basin-wide decreases in CO2 uptake in 2010 compared with 2011 (ref. 5). But the response of tropical forest carbon cycling to these droughts is not fully understood and there has been no detailed multi-site investigation in situ. Here we use several years of data from a network of thirteen 1-ha forest plots spread throughout South America, where each component of net primary production (NPP), autotrophic respiration and heterotrophic respiration is measured separately, to develop a better mechanistic understanding of the impact of the 2010 drought on the Amazon forest. We find that total NPP remained constant throughout the drought. However, towards the end of the drought, autotrophic respiration, especially in roots and stems, declined significantly compared with measurements in 2009 made in the absence of drought, with extended decreases in autotrophic respiration in the three driest plots. In the year after the drought, total NPP remained constant but the allocation of carbon shifted towards canopy NPP and away from fine-root NPP. Both leaf-level and plot-level measurements indicate that severe drought suppresses photosynthesis. Scaling these measurements to the entire Amazon basin with rainfall data, we estimate that drought suppressed Amazon-wide photosynthesis in 2010 by 0.38 petagrams of carbon (0.23-0.53 petagrams of carbon). Overall, we find that during this drought, instead of reducing total NPP, trees prioritized growth by reducing autotrophic respiration that was unrelated to growth. This suggests that trees decrease investment in tissue maintenance and defence, in line with eco-evolutionary theories that trees are competitively disadvantaged in the

  14. Drought impact on forest carbon dynamics and fluxes in Amazonia

    NASA Astrophysics Data System (ADS)

    Doughty, C.

    2015-12-01

    In 2005 and 2010 the Amazon basin experienced two strong droughts1, driven by shifts in the tropical hydrological regime2 possibly associated with global climate change3, as predicted by some global models3. Tree mortality increased after the 2005 drought4, and regional atmospheric inversion modelling showed basin-wide decreases in CO2 uptake in 2010 compared with 2011 (ref. 5). But the response of tropical forest carbon cycling to these droughts is not fully understood and there has been no detailed multi-site investigation in situ. Here we use several years of data from a network of thirteen 1-ha forest plots spread throughout South America, where each component of net primary production (NPP), autotrophic respiration and heterotrophic respiration is measured separately, to develop a better mechanistic understanding of the impact of the 2010 drought on the Amazon forest. We find that total NPP remained constant throughout the drought. However, towards the end of the drought, autotrophic respiration, especially in roots and stems, declined significantly compared with measurements in 2009 made in the absence of drought, with extended decreases in autotrophic respiration in the three driest plots. In the year after the drought, total NPP remained constant but the allocation of carbon shifted towards canopy NPP and away from fine-root NPP. Both leaf-level and plot-level measurements indicate that severe drought suppresses photosynthesis. Scaling these measurements to the entire Amazon basin with rainfall data, we estimate that drought suppressed Amazon-wide photosynthesis in 2010 by 0.38 petagrams of carbon (0.23-0.53 petagrams of carbon). Overall, we find that during this drought, instead of reducing total NPP, trees prioritized growth by reducing autotrophic respiration that was unrelated to growth. This suggests that trees decrease investment in tissue maintenance and defence, in line with eco-evolutionary theories that trees are competitively disadvantaged in the

  15. Drought impact on forest carbon dynamics and fluxes in Amazonia.

    PubMed

    Doughty, Christopher E; Metcalfe, D B; Girardin, C A J; Amézquita, F Farfán; Cabrera, D Galiano; Huasco, W Huaraca; Silva-Espejo, J E; Araujo-Murakami, A; da Costa, M C; Rocha, W; Feldpausch, T R; Mendoza, A L M; da Costa, A C L; Meir, P; Phillips, O L; Malhi, Y

    2015-03-01

    In 2005 and 2010 the Amazon basin experienced two strong droughts, driven by shifts in the tropical hydrological regime possibly associated with global climate change, as predicted by some global models. Tree mortality increased after the 2005 drought, and regional atmospheric inversion modelling showed basin-wide decreases in CO2 uptake in 2010 compared with 2011 (ref. 5). But the response of tropical forest carbon cycling to these droughts is not fully understood and there has been no detailed multi-site investigation in situ. Here we use several years of data from a network of thirteen 1-ha forest plots spread throughout South America, where each component of net primary production (NPP), autotrophic respiration and heterotrophic respiration is measured separately, to develop a better mechanistic understanding of the impact of the 2010 drought on the Amazon forest. We find that total NPP remained constant throughout the drought. However, towards the end of the drought, autotrophic respiration, especially in roots and stems, declined significantly compared with measurements in 2009 made in the absence of drought, with extended decreases in autotrophic respiration in the three driest plots. In the year after the drought, total NPP remained constant but the allocation of carbon shifted towards canopy NPP and away from fine-root NPP. Both leaf-level and plot-level measurements indicate that severe drought suppresses photosynthesis. Scaling these measurements to the entire Amazon basin with rainfall data, we estimate that drought suppressed Amazon-wide photosynthesis in 2010 by 0.38 petagrams of carbon (0.23-0.53 petagrams of carbon). Overall, we find that during this drought, instead of reducing total NPP, trees prioritized growth by reducing autotrophic respiration that was unrelated to growth. This suggests that trees decrease investment in tissue maintenance and defence, in line with eco-evolutionary theories that trees are competitively disadvantaged in the

  16. Calculations of automatic chamber flux measurements of methane and carbon dioxide using short time series of concentrations

    NASA Astrophysics Data System (ADS)

    Pirk, Norbert; Mastepanov, Mikhail; Parmentier, Frans-Jan W.; Lund, Magnus; Crill, Patrick; Christensen, Torben R.

    2016-02-01

    The closed chamber technique is widely used to measure the exchange of methane (CH4) and carbon dioxide (CO2) from terrestrial ecosystems. There is, however, large uncertainty about which model should be used to calculate the gas flux from the measured gas concentrations. Due to experimental uncertainties the simple linear regression model (first-order polynomial) is often applied, even though theoretical considerations of the technique suggest the application of other, curvilinear models. High-resolution automatic chamber systems which sample gas concentrations several hundred times per flux measurement make it possible to resolve the curvilinear behavior and study the information imposed by the natural variability of the temporal concentration changes. We used more than 50 000 such flux measurements of CH4 and CO2 from five field sites located in peat-forming wetlands ranging from 56 to 78° N to quantify the typical differences between flux estimates of different models. In addition, we aimed to assess the curvilinearity of the concentration time series and test the general applicability of curvilinear models. Despite significant episodic differences between the calculated flux estimates, the overall differences are generally found to be smaller than the local flux variability on the plot scale. The curvilinear behavior of the gas concentrations within the chamber is strongly influenced by wind-driven chamber leakage, and less so by changing gas concentration gradients in the soil during chamber closure. Such physical processes affect both gas species equally, which makes it possible to isolate biochemical processes affecting the gases differently, such as photosynthesis limitation by chamber headspace CO2 concentrations under high levels of incoming solar radiation. We assess the possibility to exploit this effect for a partitioning of the net CO2 flux into photosynthesis and ecosystem respiration as an example of how high-resolution automatic chamber

  17. Regional carbon dioxide fluxes from mixing ratio data

    NASA Astrophysics Data System (ADS)

    Bakwin, P. S.; Davis, K. J.; Yi, C.; Wofsy, S. C.; Munger, J. W.; Haszpra, L.; Barcza, Z.

    2004-09-01

    We examine the atmospheric budget of CO2 at temperate continental sites in the Northern Hemisphere. On a monthly time scale both surface exchange and atmospheric transport are important in determining the rate of change of CO2 mixing ratio at these sites. Vertical differences between the atmospheric boundary layer and free troposphere over the continent are generally greater than large-scale zonal gradients such as the difference between the free troposphere over the continent and the marine boundary layer. Therefore, as a first approximation we parametrize atmospheric transport as a vertical exchange term related to the vertical gradient of CO2 and the mean vertical velocity from the NCEP Reanalysis model. Horizontal advection is assumed to be negligible in our simple analysis. We then calculate the net surface exchange of CO2 from CO2 mixing ratio measurements at four tower sites. The results provide estimates of the surface exchange that are representative of a regional scale (i.e. ~106 km2). Comparison with direct, local-scale (eddy covariance) measurements of net exchange with the ecosystems around the towers are reasonable after accounting for anthropogenic CO2 emissions within the larger area represented by the mixing ratio data. A network of tower sites and frequent aircraft vertical profiles, separated by several hundred kilometres, where CO2 is accurately measured would provide data to estimate horizontal and vertical advection and hence provide a means to derive net CO2 fluxes on a regional scale. At present CO2 mixing ratios are measured with sufficient accuracy relative to global reference gas standards at only a few continental sites. The results also confirm that flux measurements from carefully sited towers capture seasonal variations representative of large regions, and that the midday CO2 mixing ratios sampled in the atmospheric surface layer

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

    USGS Publications Warehouse

    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.

  19. Significance of erosion-induced carbon fluxes in the carbon balance of a Mediterranean catchment

    NASA Astrophysics Data System (ADS)

    Nadeu, Elisabet; de Vente, Joris; Boix-Fayos, Carolina

    2014-05-01

    Large uncertainties surround our knowledge of the processes through which carbon (C) sequestration takes place in terrestrial ecosystems. Nevertheless, terrestrial ecosystems could be capturing up to one fourth of the CO2 that is emitted annually to the atmosphere from the burning of fossil fuels and land use changes. Soils are the third largest C reservoir in the C cycle, storing around 1500 Gt of C. Over the last decades, geomorphologists and soil scientists have claimed the role of soil erosion within the C cycle and its potential contribution to the terrestrial C sink. In order to assess the impact of soil erosion on the C cycle, however, an understanding and quantification of the impact of soil erosion on soil C stocks is needed. This implies quantifying lateral and vertical C fluxes associated to detachment, transport and deposition of soil and sediment at different spatial scales. As an example, we present a C budget for a mountainous catchment in south-eastern Spain for a 28 year study period during which the catchment underwent significant land use changes and hydrological correction works (i.e. check-dam construction and reforestations). We quantified lateral C fluxes induced by soil erosion processes and closed a soil/sediment C budget by combining field measurements and numerical modeling. In addition, correlation analysis was conducted between catchment properties (topographic, land use, lithology) and measured C deposition rates to understand the controlling factors on C yield (export) and C concentration in sediments. The results showed that the highest C yields (associated to high sediment yields) were found in subcatchments dominated by soft lithologies and high drainage densities. On the other hand, C concentration in deposited sediments was higher in areas dominated by forest cover, and presented high variability in those parts of the catchment with smoother slopes. Overall, we estimated that around 4000 Mg of C were mobilized from the catchment

  20. Influence of Different Environmental Variables on Energy and Carbon Fluxes in a Mediterranean Maquis Site

    NASA Astrophysics Data System (ADS)

    Bellucco, V.; Marras, S.; Sirca, C.; Duce, P.; Spano, D.

    2015-12-01

    Recent studies show that, in the Mediterranean area, global climate changes are likely causing an increase in frequency and intensity of drought periods as well as in the number of warmer days and nights. Mediterranean maquis (schlerophyll species) is a typical evergreen ecosystem consisting of short shrubs with leathery leaves sparsely distributed. It is adapted to live in a semi-arid climate as that of Mediterranean coasts and can survive to these environmental stress condition, being able to recover after autumn rainfall. However, increased environmental stress condition may determine changes in vegetation behavior in the long period. The aim of this study is to show the seasonal variability of sensible and latent heat, and CO2 exchanges measured, with the Eddy Covariance (EC) technique, over a Mediterranean Maquis site. It is located, about 600 m far from the sea, in the Capo Caccia peninsula (municipal district of Alghero (SS), Italy) within a natural reserve called "Le Prigionette", also known as Arca di Noé, in the North-West Sardinia coast (40.61° N, 8.15° E, 74 m asl). Due to this proximity of the EC tower to the sea, the ecosystem vertical exchanges and their footprint may be differently affected by sea and land breeze during days and nights, respectively. A four-component net radiometer, a quantum sensor, and a meteorological station were also set up for ancillary measurements as well as four heat plates in four different positions to account for under canopy and bare soil conditions in the Maquis ecosystem. Therefore, the influence of different environmental variables, such as soil/air temperature, atmospheric conditions and soil moisture content, on energy and carbon fluxes will be investigated and their effect on the seasonal and inter-annual variability of surface fluxes will be analyzed.

  1. Dissolved and particulate organic carbon fluxes from an agricultural watershed during consecutive tropical storms

    NASA Astrophysics Data System (ADS)

    Caverly, Emma; Kaste, James M.; Hancock, Gregory S.; Chambers, Randolph M.

    2013-10-01

    Low-frequency high-magnitude hydrologic events mobilize a disproportionate amount of dissolved organic carbon (DOC) from watersheds, but few studies measure the role of extreme storms in exporting organic carbon from croplands. We use high-resolution measurements of storm runoff to quantify DOC and particulate organic carbon (POC) fluxes from an agricultural field during consecutive tropical storms that delivered 41 cm of rainfall to the Virginia Coastal Plain. Over a 2 week period, we measured exports of 22 kg DOC ha-1 and 11.3 kg POC ha-1. Ultraviolet absorbance measurements indicate that the aromatic DOC fraction systematically increased as plant-derived aliphatic carbon was depleted during the initial event. Croplands can have event-scale carbon losses that equal or exceed published estimates of annual export for perennial streams draining forested and mixed land use watersheds. We quantify aromatic DOC fractions approaching 50%, indicating that agricultural stormflow can produce a significant load of relatively photoreactive carbon.

  2. Using rare earth elements to constrain particulate organic carbon flux in the East China Sea

    PubMed Central

    Hung, Chin-Chang; Chen, Ya-Feng; Hsu, Shih-Chieh; Wang, Kui; Chen, Jian Feng; Burdige, David J.

    2016-01-01

    Fluxes of particulate organic carbon (POC) in the East China Sea (ECS) have been reported to decrease from the inner continental shelf towards the outer continental shelf. Recent research has shown that POC fluxes in the ECS may be overestimated due to active sediment resuspension. To better characterize the effect of sediment resuspension on particle fluxes in the ECS, rare earth elements (REEs) and organic carbon (OC) were used in separate two-member mixing models to evaluate trap-collected POC fluxes. The ratio of resuspended particles from sediments to total trap-collected particles in the ECS ranged from 82–94% using the OC mixing model, and 30–80% using the REEs mixing model, respectively. These results suggest that REEs may be better proxies for sediment resuspension than OC in high turbidity marginal seas because REEs do not appear to undergo degradation during particle sinking as compared to organic carbon. Our results suggest that REEs can be used as tracers to provide quantitative estimates of POC fluxes in marginal seas. PMID:27670426

  3. Using rare earth elements to constrain particulate organic carbon flux in the East China Sea

    NASA Astrophysics Data System (ADS)

    Hung, Chin-Chang; Chen, Ya-Feng; Hsu, Shih-Chieh; Wang, Kui; Chen, Jian Feng; Burdige, David J.

    2016-09-01

    Fluxes of particulate organic carbon (POC) in the East China Sea (ECS) have been reported to decrease from the inner continental shelf towards the outer continental shelf. Recent research has shown that POC fluxes in the ECS may be overestimated due to active sediment resuspension. To better characterize the effect of sediment resuspension on particle fluxes in the ECS, rare earth elements (REEs) and organic carbon (OC) were used in separate two-member mixing models to evaluate trap-collected POC fluxes. The ratio of resuspended particles from sediments to total trap-collected particles in the ECS ranged from 82–94% using the OC mixing model, and 30–80% using the REEs mixing model, respectively. These results suggest that REEs may be better proxies for sediment resuspension than OC in high turbidity marginal seas because REEs do not appear to undergo degradation during particle sinking as compared to organic carbon. Our results suggest that REEs can be used as tracers to provide quantitative estimates of POC fluxes in marginal seas.

  4. Molar tooth carbonates and benthic methane fluxes in Proterozoic oceans.

    PubMed

    Shen, Bing; Dong, Lin; Xiao, Shuhai; Lang, Xianguo; Huang, Kangjun; Peng, Yongbo; Zhou, Chuanming; Ke, Shan; Liu, Pengju

    2016-01-01

    Molar tooth structures are ptygmatically folded and microspar-filled structures common in early- and mid-Proterozoic (∼2,500-750 million years ago, Ma) subtidal successions, but extremely rare in rocks <750 Ma. Here, on the basis of Mg and S isotopes, we show that molar tooth structures may have formed within sediments where microbial sulphate reduction and methanogenesis converged. The convergence was driven by the abundant production of methyl sulphides (dimethyl sulphide and methanethiol) in euxinic or H2S-rich seawaters that were widespread in Proterozoic continental margins. In this convergence zone, methyl sulphides served as a non-competitive substrate supporting methane generation and methanethiol inhibited anaerobic oxidation of methane, resulting in the buildup of CH4, formation of degassing cracks in sediments and an increase in the benthic methane flux from sediments. Precipitation of crack-filling microspar was driven by methanogenesis-related alkalinity accumulation. Deep ocean ventilation and oxygenation around 750 Ma brought molar tooth structures to an end. PMID:26739600

  5. Molar tooth carbonates and benthic methane fluxes in Proterozoic oceans

    NASA Astrophysics Data System (ADS)

    Shen, Bing; Dong, Lin; Xiao, Shuhai; Lang, Xianguo; Huang, Kangjun; Peng, Yongbo; Zhou, Chuanming; Ke, Shan; Liu, Pengju

    2016-01-01

    Molar tooth structures are ptygmatically folded and microspar-filled structures common in early- and mid-Proterozoic (~2,500-750 million years ago, Ma) subtidal successions, but extremely rare in rocks <750 Ma. Here, on the basis of Mg and S isotopes, we show that molar tooth structures may have formed within sediments where microbial sulphate reduction and methanogenesis converged. The convergence was driven by the abundant production of methyl sulphides (dimethyl sulphide and methanethiol) in euxinic or H2S-rich seawaters that were widespread in Proterozoic continental margins. In this convergence zone, methyl sulphides served as a non-competitive substrate supporting methane generation and methanethiol inhibited anaerobic oxidation of methane, resulting in the buildup of CH4, formation of degassing cracks in sediments and an increase in the benthic methane flux from sediments. Precipitation of crack-filling microspar was driven by methanogenesis-related alkalinity accumulation. Deep ocean ventilation and oxygenation around 750 Ma brought molar tooth structures to an end.

  6. Molar tooth carbonates and benthic methane fluxes in Proterozoic oceans

    PubMed Central

    Shen, Bing; Dong, Lin; Xiao, Shuhai; Lang, Xianguo; Huang, Kangjun; Peng, Yongbo; Zhou, Chuanming; Ke, Shan; Liu, Pengju

    2016-01-01

    Molar tooth structures are ptygmatically folded and microspar-filled structures common in early- and mid-Proterozoic (∼2,500–750 million years ago, Ma) subtidal successions, but extremely rare in rocks <750 Ma. Here, on the basis of Mg and S isotopes, we show that molar tooth structures may have formed within sediments where microbial sulphate reduction and methanogenesis converged. The convergence was driven by the abundant production of methyl sulphides (dimethyl sulphide and methanethiol) in euxinic or H2S-rich seawaters that were widespread in Proterozoic continental margins. In this convergence zone, methyl sulphides served as a non-competitive substrate supporting methane generation and methanethiol inhibited anaerobic oxidation of methane, resulting in the buildup of CH4, formation of degassing cracks in sediments and an increase in the benthic methane flux from sediments. Precipitation of crack-filling microspar was driven by methanogenesis-related alkalinity accumulation. Deep ocean ventilation and oxygenation around 750 Ma brought molar tooth structures to an end. PMID:26739600

  7. Comparing simulated carbon budget of a Lei bamboo forest with flux tower data

    USGS Publications Warehouse

    Li, Xuehe; Jiang, Hong; Liu, Jinxun; Sun, Cheng; Wang, Ying; Jin, Jiaxin

    2014-01-01

    Bamboo forest ecosystem is the part of the forest ecosystem. The distribution area of bamboo forest is limited, but in somewhere, like south China, it has been cultivate for a long time with human management. As the climate change has been take great effect on forest carbon budget, many researchers pay attention to the carbon budget in bamboo forest. Moreover cultivative management had a significant impact on the bamboo forest carbon budget. In this study, we modified a terrestrial ecosystem model named Integrated Biosphere Simulator (IBIS) according the management of Lei bamboo forest. Some management, like fertilization, shoots harvesting and organic mulching in winter, had been incorporated into model. Then we had compared model results with the observation data from a Lei bamboo flux tower. The simulated and observed results had achieved good consistency. Our simulated Lei bamboo forest yearly net ecosystem productivity (NEP) was 0.41 kgC a-1 of carbon, which is very close to the observation data 0.45 kgC a-1 of carbon. And the monthly simulated results can take the change of carbon budget in each month, similar to the data we got from flux tower. It reflects that the modified IBIS model can characterize the growth of bamboo forest and perform the simulation well. And then two groups of simulations were set to evaluate effects of cultivative managements on Lei bamboo forests carbon budget. And results showed that both fertilization and organic mulching had taken positive effects on Lei bamboo forests carbon sequestration.

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  9. Fluxes of carbon and nutrients to the Iceland Sea surface waters and inferred primary productivity and stoichiometry

    NASA Astrophysics Data System (ADS)

    Jeansson, Emil; Bellerby, Richard; Frigstad, Helene; Ólafsdóttir, Sólveig R.; Olafsson, Jón; Skjelvan, Ingunn

    2014-05-01

    Fluxes of carbon and nutrients to the upper 100 m of the Iceland Sea are evaluated. The study utilises hydro-chemical data from the quarterly sampled Iceland Sea time-series station (68.00 ° N, 12.67 ° W), for the years between 1993 and 2006. By comparing data of dissolved inorganic carbon (DIC) and nutrients in the surface layer (upper 100 m), and a sub-surface layer (100-200 m), we calculate monthly deficits in the surface, and use this to deduce the fluxes into and out of the surface layer that affect the deficit: vertical mixing, horizontal advection, air-sea exchange, and biological activity. The deficits show a clear seasonality with a minimum in winter, when the mixed layer is at the deepest, and a maximum in September, when biological uptake has removed much of the nutrients. The annual vertical fluxes of DIC and nitrate amounts to 2.3 and 0.41 mol m-2 yr-1, respectively, the annual air-sea uptake of atmospheric CO2 is 4.4 mol m-2 yr-1, and the net annual flux due to biological activity is calculated to 5.5 mol C m-2 yr-1, and 0.37 mol N m-2 yr-1. We also deduce seasonal NCP by summing up the months with a positive drawdown of DIC, and similar for new production by summing up the months with positive nitrate drawdown. We quantify these to 5.6 mol C m-2 yr-1, and 0.51 mol N m-2 yr-1, which gives a ratio markedly higher than Redfield. Results for phosphate and silicate are also shown and discussed, as are the stoichiometry of the all deduced fluxes.

  10. Carbon amendment and soil depth affect the distribution and abundance of denitrifiers in agricultural soils.

    PubMed

    Barrett, M; Khalil, M I; Jahangir, M M R; Lee, C; Cardenas, L M; Collins, G; Richards, K G; O'Flaherty, V

    2016-04-01

    The nitrite reductase (nirS and nirK) and nitrous oxide reductase-encoding (nosZ) genes of denitrifying populations present in an agricultural grassland soil were quantified using real-time polymerase chain reaction (PCR) assays. Samples from three separate pedological depths at the chosen site were investigated: horizon A (0-10 cm), horizon B (45-55 cm), and horizon C (120-130 cm). The effect of carbon addition (treatment 1, control; treatment 2, glucose-C; treatment 3, dissolved organic carbon (DOC)) on denitrifier gene abundance and N2O and N2 fluxes was determined. In general, denitrifier abundance correlated well with flux measurements; nirS was positively correlated with N2O, and nosZ was positively correlated with N2 (P < 0.03). Denitrifier gene copy concentrations per gram of soil (GCC) varied in response to carbon type amendment (P < 0.01). Denitrifier GCCs were high (ca. 10(7)) and the bac:nirK, bac:nirS, bac:nir (T) , and bac:nosZ ratios were low (ca. 10(-1)/10) in horizon A in all three respective treatments. Glucose-C amendment favored partial denitrification, resulting in higher nir abundance and higher N2O fluxes compared to the control. DOC amendment, by contrast, resulted in relatively higher nosZ abundance and N2 emissions, thus favoring complete denitrification. We also noted soil depth directly affected bacterial, archaeal, and denitrifier abundance, possibly due to changes in soil carbon availability with depth.

  11. How life affects the geochemical cycle of carbon

    NASA Technical Reports Server (NTRS)

    Walker, James C. G.

    1992-01-01

    Developing a quantitative understanding of the biogeochemical cycles of carbon as they have worked throughout Earth history on various time scales, how they have been affected by biological evolution, and how changes in the carbon content of ocean and atmosphere may have affected climate and the evolution of life are the goals of the research. Theoretical simulations were developed that can be tuned to reproduce such data as exist and, once tuned, can be used to predict properties that have not yet been observed. This is an ongoing process, in which models and results are refined as new data and interpretations become available and as understanding of the global system improves. Results of the research are described in several papers which were published or submitted for publication. These papers are summarized. Future research plans are presented.

  12. Hydrologic Treatments Affect Gaseous Carbon Loss From Organic Soils, Twitchell Island, California, October 1995-December 1997

    USGS Publications Warehouse

    Miller, Robin L.; Hastings, Lauren; Fujii, Roger

    2000-01-01

    Subsidence of organic soils in the Sacramento-San Joaquin Delta, California, has increased the potential for levee failure and flooding in the region. Because oxidation of the peat soils is a primary cause of subsidence, reversion of affected lands to wetlands has been proposed as a mitigation tool. To test this hypothesis, three 10 x 10 meter enclosures were built on Twitchell Island in the Delta and managed as different wetland habitats. Emissions of carbon dioxide and methane were measured in situ from October 1995 through December 1997, from the systems that developed under the different water-management treatments. Treatments included a seasonal control (SC) under current island management conditions; reverse flooding (RF), where the land is intentionally flooded from early dry season until midsummer; permanent shallow flooding (F); and a more deeply flooded, open-water (OW) treatment. Hydrologic treatments affected microbial processes, plant community and temperature dynamics which, in turn, affected carbon cycling. Water-management treatments with a period of flooding significantly decreased gaseous carbon emissions compared to the seasonal control. Permanent flooding treatments showed significantly higher methane fluxes than treatments with some period of aerobic conditions. Shallow flooding treatments created conditions that support cattail [Typha species (spp.)] marshes, while deep flooding precluded emergent vegetation. Carbon inputs to the permanent shallow flooding treatment tended to be greater than the measured losses. This suggests that permanent shallow flooding has the greatest potential for managing subsidence of these soils by generating organic substrate more rapidly than is lost through decomposition. Carbon input estimates of plant biomass compared to measurements of gaseous carbon losses indicate the potential for mitigation of subsidence through hydrologic management of the organic soils in the area.

  13. Investigating Alaskan methane and carbon dioxide fluxes using measurements from the CARVE tower

    NASA Astrophysics Data System (ADS)

    Karion, Anna; Sweeney, Colm; Miller, John B.; Andrews, Arlyn E.; Commane, Roisin; Dinardo, Steven; Henderson, John M.; Lindaas, Jacob; Lin, John C.; Luus, Kristina A.; Newberger, Tim; Tans, Pieter; Wofsy, Steven C.; Wolter, Sonja; Miller, Charles E.

    2016-04-01

    Northern high-latitude carbon sources and sinks, including those resulting from degrading permafrost, are thought to be sensitive to the rapidly warming climate. Because the near-surface atmosphere integrates surface fluxes over large ( ˜ 500-1000 km) scales, atmospheric monitoring of carbon dioxide (CO2) and methane (CH4) mole fractions in the daytime mixed layer is a promising method for detecting change in the carbon cycle throughout boreal Alaska. Here we use CO2 and CH4 measurements from a NOAA tower 17 km north of Fairbanks, AK, established as part of NASA's Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE), to investigate regional fluxes of CO2 and CH4 for 2012-2014. CARVE was designed to use aircraft and surface observations to better understand and quantify the sensitivity of Alaskan carbon fluxes to climate variability. We use high-resolution meteorological fields from the Polar Weather Research and Forecasting (WRF) model coupled with the Stochastic Time-Inverted Lagrangian Transport model (hereafter, WRF-STILT), along with the Polar Vegetation Photosynthesis and Respiration Model (PolarVPRM), to investigate fluxes of CO2 in boreal Alaska using the tower observations, which are sensitive to large areas of central Alaska. We show that simulated PolarVPRM-WRF-STILT CO2 mole fractions show remarkably good agreement with tower observations, suggesting that the WRF-STILT model represents the meteorology of the region quite well, and that the PolarVPRM flux magnitudes and spatial distribution are generally consistent with CO2 mole fractions observed at the CARVE tower. One exception to this good agreement is that during the fall of all 3 years, PolarVPRM cannot reproduce the observed CO2 respiration. Using the WRF-STILT model, we find that average CH4 fluxes in boreal Alaska are somewhat lower than flux estimates by Chang et al. (2014) over all of Alaska for May-September 2012; we also find that enhancements appear to persist during some wintertime

  14. Investigating Alaskan methane and carbon dioxide fluxes using measurements from the CARVE tower

    NASA Astrophysics Data System (ADS)

    Karion, A.; Sweeney, C.; Miller, J. B.; Andrews, A. E.; Commane, R.; Dinardo, S.; Henderson, J. M.; Lindaas, J.; Lin, J. C.; Luus, K. A.; Newberger, T.; Tans, P.; Wofsy, S. C.; Wolter, S.; Miller, C. E.

    2015-12-01

    Northern high-latitude carbon sources and sinks, including those resulting from degrading permafrost, are thought to be sensitive to the rapidly warming climate. Because the near-surface atmosphere integrates surface fluxes over large (~ 500-1000 km) scales, atmospheric monitoring of carbon dioxide (CO2) and methane (CH4) mole fractions in the daytime mixed layer is a promising method for detecting change in the carbon cycle throughout boreal Alaska. Here we use CO2 and CH4 measurements from a NOAA tower 17 km north of Fairbanks AK, established as part of NASA's Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE), to investigate regional fluxes of CO2 and CH4 for 2012-2014. CARVE was designed to use aircraft and surface observations to better understand and quantify the sensitivity of Alaskan carbon fluxes to climate variability. We use high-resolution meteorological fields from the Polar Weather Research and Forecasting (WRF) model coupled with the Stochastic Time-Inverted Lagrangian Transport model (hereafter, WRF-STILT), along with the Polar Vegetation Photosynthesis and Respiration Model (PolarVPRM), to investigate fluxes of CO2 in boreal Alaska using the tower observations, which are sensitive to large areas of central Alaska. We show that simulated PolarVPRM/WRF-STILT CO2 mole fractions show remarkably good agreement with tower observations, suggesting that the WRF-STILT model represents the meteorology of the region quite well, and that the PolarVPRM flux magnitudes and spatial distribution are consistent with CO2 mole fractions observed at the CARVE tower. CO2 signals at the tower are larger than predicted, with significant respiration occurring in the fall that is not captured by PolarVPRM. Using the WRF-STILT model, we find that average CH4 fluxes in boreal Alaska are somewhat lower than flux estimates by Chang et al. (2014) over all of Alaska for May-September 2012; we also find emissions persist during some wintertime periods, augmenting those

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

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

    EPA Science Inventory

    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...

  17. Carbon, water, and heat flux responses to experimental burning and drought in a tallgrass prairie

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Both natural fire and prescribed burns are disturbances to biogeochemical cycles of grassland ecosystems in the southern Great Plains. This study examined eddy covariance whole ecosystem-atmosphere flux in carbon (C) exchange in response to a prescribed burn. Two, paired 34 ha paddocks in central Ok...

  18. CARBON MONOXIDE FLUXES OF DIFFERENT SOIL LAYERS IN UPLAND CANADIAN BOREAL FORESTS

    EPA Science Inventory

    Dark or low-light carbon monoxide fluxes at upland Canadian boreal forest sites were measured on-site with static chambers and with a laboratory incubation technique using cores from different depths at the same sites. Three different upland black spruce sites, burned in 1987,199...

  19. Mapping land-surface fluxes of carbon, water and energy from field to regional scales

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A framework for routine mapping of land-surface fluxes of carbon, water, and energy at the field to regional scales has been established for drought monitoring, water resource management, yield forecasting and crop-growth monitoring. The framework uses the ALEXI/DisALEXI suite of land-surface model...

  20. Assessing the nonconservative fluvial fluxes of dissolved organic carbon in North America

    NASA Astrophysics Data System (ADS)

    Lauerwald, Ronny; Hartmann, Jens; Ludwig, Wolfgang; Moosdorf, Nils

    2012-03-01

    Fluvial transport of dissolved organic carbon (DOC) is an important link in the global carbon cycle. Previous studies largely increased our knowledge of fluvial exports of carbon to the marine system, but considerable uncertainty remains about in-stream/in-river losses of organic carbon. This study presents an empirical method to assess the nonconservative behavior of fluvial DOC at continental scale. An empirical DOC flux model was trained on two different subsets of training catchments, one with catchments smaller than 2,000 km2 (n = 246, avg. 494 km2) and one with catchments larger than 2,000 km2 (n = 207, avg. 26,525 km2). A variety of potential predictors and controlling factors of fluvial DOC fluxes is discussed. The predictors retained for the final DOC flux models are runoff, slope gradient, land cover, and areal proportions of wetlands. According to the spatially explicit extrapolation of the models, in North America south of 60°N, the total fluvial DOC flux from small catchments (25.8 Mt C a-1, std. err.: 12%) is higher than that from large catchments (19.9 Mt C a-1, std. err.: 10%), giving a total DOC loss of 5.9 Mt C a-1 (std. err.: 78%). As DOC losses in headwaters are not represented in this budget, the estimated DOC loss is rather a minimum value for the total DOC loss within the fluvial network.

  1. Evaluate the seasonal cycle and interannual variability of carbon fluxes and the associated uncertainties using modeled and observed data

    NASA Astrophysics Data System (ADS)

    Zeng, F.; Collatz, G. J.; Ivanoff, A.

    2013-12-01

    We assessed the performance of the Carnegie-Ames-Stanford Approach - Global Fire Emissions Database (CASA-GFED3) terrestrial carbon cycle model in simulating seasonal cycle and interannual variability (IAV) of global and regional carbon fluxes and uncertainties associated with model parameterization. Key model parameters were identified from sensitivity analyses and their uncertainties were propagated through model processes using the Monte Carlo approach to estimate the uncertainties in carbon fluxes and pool sizes. Three independent flux data sets, the global gross primary productivity (GPP) upscaled from eddy covariance flux measurements by Jung et al. (2011), the net ecosystem exchange (NEE) estimated by CarbonTracker, and the eddy covariance flux observations, were used to evaluate modeled fluxes and the uncertainties. Modeled fluxes agree well with both Jung's GPP and CarbonTracker NEE in the amplitude and phase of seasonal cycle, except in the case of GPP in tropical regions where Jung et al. (2011) showed larger fluxes and seasonal amplitude. Modeled GPP IAV is positively correlated (p < 0.1) with Jung's GPP IAV except in the tropics and temperate South America. The correlations between modeled NEE IAV and CarbonTracker NEE IAV are weak at regional to continental scales but stronger when fluxes are aggregated to >40°N latitude. At regional to continental scales flux uncertainties were larger than the IAV in the fluxes for both Jung's GPP and CarbonTracker NEE. Comparisons with eddy covariance flux observations are focused on sites within regions and years of recorded large-scale climate anomalies. We also evaluated modeled biomass using other independent continental biomass estimates and found good agreement. From the comparisons we identify the strengths and weaknesses of the model to capture the seasonal cycle and IAV of carbon fluxes and highlight ways to improve model performance.

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

    PubMed

    Yang, Qichun; Zhang, Xuesong

    2016-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

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

    NASA Astrophysics Data System (ADS)

    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

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

    PubMed

    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. PMID:25597686

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

    PubMed

    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.

  7. Roles of Climate, Vegetation and Soil in Regulating the Spatial Variations in Ecosystem Carbon Dioxide Fluxes in the Northern Hemisphere

    PubMed Central

    Chen, Zhi; Yu, Guirui; Ge, Jianping; Wang, Qiufeng; Zhu, Xianjin; Xu, Zhiwei

    2015-01-01

    Climate, vegetation, and soil characteristics play important roles in regulating the spatial variation in carbon dioxide fluxes, but their relative influence is still uncertain. In this study, we compiled data from 241 eddy covariance flux sites in the Northern Hemisphere and used Classification and Regression Trees and Redundancy Analysis to assess how climate, vegetation, and soil affect the spatial variations in three carbon dioxide fluxes (annual gross primary production (AGPP), annual ecosystem respiration (ARE), and annual net ecosystem production (ANEP)). Our results showed that the spatial variations in AGPP, ARE, and ANEP were significantly related to the climate and vegetation factors (correlation coefficients, R = 0.22 to 0.69, P < 0.01) while they were not related to the soil factors (R = -0.11 to 0.14, P > 0.05) in the Northern Hemisphere. The climate and vegetation together explained 60 % and 58 % of the spatial variations in AGPP and ARE, respectively. Climate factors (mean annual temperature and precipitation) could account for 45 - 47 % of the spatial variations in AGPP and ARE, but the climate constraint on the vegetation index explained approximately 75 %. Our findings suggest that climate factors affect the spatial variations in AGPP and ARE mainly by regulating vegetation properties, while soil factors exert a minor effect. To more accurately assess global carbon balance and predict ecosystem responses to climate change, these discrepant roles of climate, vegetation, and soil are required to be fully considered in the future land surface models. Moreover, our results showed that climate and vegetation factors failed to capture the spatial variation in ANEP and suggest that to reveal the underlying mechanism for variation in ANEP, taking into account the effects of other factors (such as climate change and disturbances) is necessary. PMID:25928452

  8. Roles of climate, vegetation and soil in regulating the spatial variations in ecosystem carbon dioxide fluxes in the Northern Hemisphere.

    PubMed

    Chen, Zhi; Yu, Guirui; Ge, Jianping; Wang, Qiufeng; Zhu, Xianjin; Xu, Zhiwei

    2015-01-01

    Climate, vegetation, and soil characteristics play important roles in regulating the spatial variation in carbon dioxide fluxes, but their relative influence is still uncertain. In this study, we compiled data from 241 eddy covariance flux sites in the Northern Hemisphere and used Classification and Regression Trees and Redundancy Analysis to assess how climate, vegetation, and soil affect the spatial variations in three carbon dioxide fluxes (annual gross primary production (AGPP), annual ecosystem respiration (ARE), and annual net ecosystem production (ANEP)). Our results showed that the spatial variations in AGPP, ARE, and ANEP were significantly related to the climate and vegetation factors (correlation coefficients, R = 0.22 to 0.69, P < 0.01) while they were not related to the soil factors (R = -0.11 to 0.14, P > 0.05) in the Northern Hemisphere. The climate and vegetation together explained 60% and 58% of the spatial variations in AGPP and ARE, respectively. Climate factors (mean annual temperature and precipitation) could account for 45-47% of the spatial variations in AGPP and ARE, but the climate constraint on the vegetation index explained approximately 75%. Our findings suggest that climate factors affect the spatial variations in AGPP and ARE mainly by regulating vegetation properties, while soil factors exert a minor effect. To more accurately assess global carbon balance and predict ecosystem responses to climate change, these discrepant roles of climate, vegetation, and soil are required to be fully considered in the future land surface models. Moreover, our results showed that climate and vegetation factors failed to capture the spatial variation in ANEP and suggest that to reveal the underlying mechanism for variation in ANEP, taking into account the effects of other factors (such as climate change and disturbances) is necessary.

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

    NASA Astrophysics Data System (ADS)

    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

  10. Decadal and annual changes in biogenic opal and carbonate fluxes to the deep Sargasso Sea

    USGS Publications Warehouse

    Deuser, W.G.; Jickells, T.D.; Commeau, Judith A.

    1995-01-01

    Analyses of samples from a 14-year series of sediment-trap deployments in the deep Sargasso Sea reveal a significant trend in the ratio of the sinking fluxes of biogenic calcium carbonate and silica. Although there are pronounced seasonal cycles for both flux components, the overall opal/CaCO3 ratio changed by 50% from 1978 to 1991 (largely due to a decrease of opal flux), while total flux had no significant trend. These results suggest that plankton communities respond rapidly to subtle climate change, such as is evident in regional variations of wind speed, precipitation, wintertime ventilation and midwater temperatures. If the trends we observe in the makeup of sinking particulate matter occur on a large scale, they may in turn modify climate by modulating ocean-atmosphere CO2 exchange and albedo over the ocean.

  11. Direct measurement of the oceanic carbon monoxide flux by eddy correlation

    NASA Astrophysics Data System (ADS)

    Blomquist, B. W.; Fairall, C. W.; Huebert, B. J.; Wilson, S. T.

    2012-12-01

    This report presents results from a field trial of ship-based air-sea flux measurements of carbon monoxide (CO) by direct eddy correlation with an infrared-laser trace gas analyzer. The analyzer utilizes Off-Axis Integrated-Cavity-Output Spectroscopy (OA-ICOS) to achieve high selectivity for CO, rapid response (~2 Hz) and low noise. Over a two-day sea trial, peak daytime seawater CO concentrations were ~1.5 nM and wind speeds were consistently 10-12 m s-1. A clear diel cycle in CO flux with an early afternoon maximum was observed. An analysis of flux error suggests the effects of non-stationarity are important, and air-sea CO flux measurements are best performed in regions remote from continental pollution sources.

  12. Direct measurement of the oceanic carbon monoxide flux by eddy correlation

    NASA Astrophysics Data System (ADS)

    Blomquist, B. W.; Fairall, C. W.; Huebert, B. J.; Wilson, S. T.

    2012-07-01

    This report presents results from a field trial of ship-based air-sea flux measurements of carbon monoxide (CO) by direct eddy correlation using an infrared-laser trace gas analyzer. The analyzer utilizes Off-Axis Integrated-Cavity-Output Spectroscopy (OA-ICOS) to achieve high selectivity for CO, rapid response (10 Hz) and low noise. Over a two-day sea trial, peak daytime seawater CO concentrations were ~ 1.5 nM and wind speeds were consistently 10-12 m s-1. A clear diel cycle in CO flux with an early afternoon maximum was observed. An analysis of flux error sources suggests air-sea CO flux measurements are best performed in regions remote from continental pollution sources.

  13. Analysis of field measurements of carbon dioxide and water vapor fluxes

    NASA Technical Reports Server (NTRS)

    Verma, Shashi B.

    1991-01-01

    Analysis of the field measurements of carbon dioxide and water vapor fluxes is discussed. These data were examined in conjunction with reflectance obtained from helicopter mounted Modular Multiband Radiometer. These measurements are representative of the canopy scale (10 to 100 m)(exp 2) and provide a good basis for investigating the hypotheses/relationship potentially useful in remote sensing applications. All the micrometeorological data collected during FIFE-89 were processed and fluxes of CO2, water vapor, and sensible heat were calculated. Soil CO2 fluxes were also estimated. Employing these soil CO2 flux values, in conjunction with micrometeorological measurements, canopy photosynthesis is being estimated. A biochemical model of leaf photosynthesis was adapted to the prairie vegetation. The modeled leaf photosynthesis rates were scaled up to the canopy level. This model and a multiplicative stomatal conductance model are also used to calculate canopy conductance.

  14. Variation of energy and carbon fluxes from a restored temperate freshwater wetland and implications for carbon market verification protocols

    USGS Publications Warehouse

    Anderson, Frank; Bergamaschi, Brian; Sturtevant, Cove; Knox, Sarah; Hastings, Lauren; Windham-Myers, Lisamarie; Detto, Matteo; Hestir, Erin L.; Drexler, Judith; Miller, Robin L.; Matthes, Jaclyn; Verfaillie, Joseph; Baldocchi, Dennis; Snyder, Richard L.; Fujii, Roger

    2016-01-01

    Temperate freshwater wetlands are among the most productive terrestrial ecosystems, stimulating interest in using restored wetlands as biological carbon sequestration projects for greenhouse gas reduction programs. In this study, we used the eddy covariance technique to measure surface energy carbon fluxes from a constructed, impounded freshwater wetland during two annual periods that were 8 years apart: 2002–2003 and 2010–2011. During 2010–2011, we measured methane (CH4) fluxes to quantify the annual atmospheric carbon mass balance and its concomitant influence on global warming potential (GWP). Peak growing season fluxes of latent heat and carbon dioxide (CO2) were greater in 2002–2003 compared to 2010–2011. In 2002, the daily net ecosystem exchange reached as low as −10.6 g C m−2 d−1, which was greater than 3 times the magnitude observed in 2010 (−2.9 g C m−2 d−1). CH4 fluxes during 2010–2011 were positive throughout the year and followed a strong seasonal pattern, ranging from 38.1 mg C m−2 d−1 in the winter to 375.9 mg C m−2 d−1 during the summer. The results of this study suggest that the wetland had reduced gross ecosystem productivity in 2010–2011, likely due to the increase in dead plant biomass (standing litter) that inhibited the generation of new vegetation growth. In 2010–2011, there was a net positive GWP (675.3 g C m−2 yr−1), and when these values are evaluated as a sustained flux, the wetland will not reach radiative balance even after 500 years.

  15. Variation of energy and carbon fluxes from a restored temperate freshwater wetland and implications for carbon market verification protocols

    NASA Astrophysics Data System (ADS)

    Anderson, Frank E.; Bergamaschi, Brian; Sturtevant, Cove; Knox, Sara; Hastings, Lauren; Windham-Myers, Lisamarie; Detto, Matteo; Hestir, Erin L.; Drexler, Judith; Miller, Robin L.; Matthes, Jaclyn Hatala; Verfaillie, Joseph; Baldocchi, Dennis; Snyder, Richard L.; Fujii, Roger

    2016-03-01

    Temperate freshwater wetlands are among the most productive terrestrial ecosystems, stimulating interest in using restored wetlands as biological carbon sequestration projects for greenhouse gas reduction programs. In this study, we used the eddy covariance technique to measure surface energy carbon fluxes from a constructed, impounded freshwater wetland during two annual periods that were 8 years apart: 2002-2003 and 2010-2011. During 2010-2011, we measured methane (CH4) fluxes to quantify the annual atmospheric carbon mass balance and its concomitant influence on global warming potential (GWP). Peak growing season fluxes of latent heat and carbon dioxide (CO2) were greater in 2002-2003 compared to 2010-2011. In 2002, the daily net ecosystem exchange reached as low as -10.6 g C m-2 d-1, which was greater than 3 times the magnitude observed in 2010 (-2.9 g C m-2 d-1). CH4 fluxes during 2010-2011 were positive throughout the year and followed a strong seasonal pattern, ranging from 38.1 mg C m-2 d-1 in the winter to 375.9 mg C m-2 d-1 during the summer. The results of this study suggest that the wetland had reduced gross ecosystem productivity in 2010-2011, likely due to the increase in dead plant biomass (standing litter) that inhibited the generation of new vegetation growth. In 2010-2011, there was a net positive GWP (675.3 g C m-2 yr-1), and when these values are evaluated as a sustained flux, the wetland will not reach radiative balance even after 500 years.

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  17. The influence of drought-heat stress on long term carbon fluxes of bioenergy crops grown in the Midwestern US

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Perennial grasses are promising feedstocks for bioenergy production in the Midwestern US. Few experiments have addressed how drought influences their carbon fluxes and storage. This study provides a direct comparison of ecosystem-scale measurements of carbon fluxes associated with miscanthus (Miscan...

  18. Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico, St. Petersburg, FL

    NASA Technical Reports Server (NTRS)

    Robbins, L. L.; Coble, P. G.; Clayton, T. D.; Cai, W. J.

    2008-01-01

    Despite their relatively small surface area, ocean margins may have a significant impact on global biogeochemical cycles and, potentially, the global air-sea fluxes of carbon dioxide. Margins are characterized by intense geochemical and biological processing of carbon and other elements and exchange large amounts of matter and energy with the open ocean. The area-specific rates of productivity, biogeochemical cycling, and organic/inorganic matter sequestration are high in coastal margins, with as much as half of the global integrated new production occurring over the continental shelves and slopes (Walsh, 1991; Doney and Hood, 2002; Jahnke, in press). However, the current lack of knowledge and understanding of biogeochemical processes occurring at the ocean margins has left them largely ignored in most of the previous global assessments of the oceanic carbon cycle (Doney and Hood, 2002). A major source of North American and global uncertainty is the Gulf of Mexico, a large semi-enclosed subtropical basin bordered by the United States, Mexico, and Cuba. Like many of the marginal oceans worldwide, the Gulf of Mexico remains largely unsampled and poorly characterized in terms of its air-sea exchange of carbon dioxide and other carbon fluxes. The goal of the workshop was to bring together researchers from multiple disciplines studying terrestrial, aquatic, and marine ecosystems to discuss the state of knowledge in carbon fluxes in the Gulf of Mexico, data gaps, and overarching questions in the Gulf of Mexico system. The discussions at the workshop were intended to stimulate integrated studies of marine and terrestrial biogeochemical cycles and associated ecosystems that will help to establish the role of the Gulf of Mexico in the carbon cycle and how it might evolve in the face of environmental change.

  19. Quantifying the Observability of CO2 Flux Uncertainty in Atmospheric CO2 Records Using Products from Nasa's Carbon Monitoring Flux Pilot Project

    NASA Technical Reports Server (NTRS)

    Ott, Lesley; Pawson, Steven; Collatz, Jim; Watson, Gregg; Menemenlis, Dimitris; Brix, Holger; Rousseaux, Cecile; Bowman, Kevin; Bowman, Kevin; Liu, Junjie; Eldering, Annmarie; Gunson, Michael; Kawa, Stephan R.

    2014-01-01

    NASAs Carbon Monitoring System (CMS) Flux Pilot Project (FPP) was designed to better understand contemporary carbon fluxes by bringing together state-of-the art models with remote sensing datasets. Here we report on simulations using NASAs Goddard Earth Observing System Model, version 5 (GEOS-5) which was used to evaluate the consistency of two different sets of observationally constrained land and ocean fluxes with atmospheric CO2 records. Despite the strong data constraint, the average difference in annual terrestrial biosphere flux between the two land (NASA Ames CASA and CASA-GFED) models is 1.7 Pg C for 2009-2010. Ocean models (NOBM and ECCO2-Darwin) differ by 35 in their global estimates of carbon flux with particularly strong disagreement in high latitudes. Based upon combinations of terrestrial and ocean fluxes, GEOS-5 reasonably simulated the seasonal cycle observed at northern hemisphere surface sites and by the Greenhouse gases Observing SATellite (GOSAT) while the model struggled to simulate the seasonal cycle at southern hemisphere surface locations. Though GEOS-5 was able to reasonably reproduce the patterns of XCO2 observed by GOSAT, it struggled to reproduce these aspects of AIRS observations. Despite large differences between land and ocean flux estimates, resulting differences in atmospheric mixing ratio were small, typically less than 5 ppmv at the surface and 3 ppmv in the XCO2 column. A statistical analysis based on the variability of observations shows that flux differences of these magnitudes are difficult to distinguish from natural variability, regardless of measurement platform.

  20. The imprint of surface fluxes and transport on variations in total column carbon dioxide

    SciTech Connect

    Keppel-Aleks, G; Wennberg, PO; Washenfelder, RA; Wunch, D; Schneider, T; Toon, GC; Andres, Robert Joseph; Blavier, J-F; Connor, B; Davis, K. J.; Desai, Desai Ankur R.; Messerschmidt, J; Notholt, J; Roehl, CM; Sherlock, V; Stephens, BB; Vay, SA; Wofsy, Steve

    2012-01-01

    New observations of the vertically integrated CO{sub 2} mixing ratio, , from ground-based remote sensing show that variations in are primarily determined by large-scale flux patterns. They therefore provide fundamentally different information than observations made within the boundary layer, which reflect the combined influence of large-scale and local fluxes. Observations of both and CO{sub 2} concentrations in the free troposphere show that large-scale spatial gradients induce synoptic-scale temporal variations in in the Northern Hemisphere midlatitudes through horizontal advection. Rather than obscure the signature of surface fluxes on atmospheric CO{sub 2}, these synoptic-scale variations provide useful information that can be used to reveal the meridional flux distribution. We estimate the meridional gradient in from covariations in and potential temperature, {theta}, a dynamical tracer, on synoptic timescales to evaluate surface flux estimates commonly used in carbon cycle models. We find that simulations using Carnegie Ames Stanford Approach (CASA) biospheric fluxes underestimate both the seasonal cycle amplitude throughout the Northern Hemisphere midlatitudes and the meridional gradient during the growing season. Simulations using CASA net ecosystem exchange (NEE) with increased and phase-shifted boreal fluxes better fit the observations. Our simulations suggest that climatological mean CASA fluxes underestimate boreal growing season NEE (between 45-65{sup o} N) by {approx}40%. We describe the implications for this large seasonal exchange on inference of the net Northern Hemisphere terrestrial carbon sink.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  2. Soil organic carbon stocks and fluxes due to land use conversions at the European scale

    NASA Astrophysics Data System (ADS)

    Gobin, A.; Campling, P.

    2012-04-01

    European soils store around 73 to 79 billion tonnes of carbon, which is about 50 times the total CO2-equivalent emissions of the 27 Member States of the European Union in 2009 (4.6 billion tones; EEA, 2010). More than twice as much carbon is held in soils as compared to the storage in vegetation or the atmosphere. Soil organic carbon (SOC) stocks are dynamic and changes in land use, land management and climate may result in instant losses, whereas gains accumulate more slowly over several decades. The soil organic carbon cycle is based on continually supplying carbon in the form of organic matter as a food source for microorganisms, the loss of some carbon as carbon dioxide, and the assimilation of stable carbon in the soil. The organic carbon stocks and fluxes to and from the soil across the EU were quantified for agriculture, forestry and peatlands under different land use change and management scenarios taking into account climate change and using a coupled regional balance and multi-compartment soil organic matter model (Roth-C). Abolishing permanent grassland restrictions would have a negative effect on SOC stocks, which at the EU level can be quantified in a loss 30% higher than in the case of maintaining the current permanent grassland restrictions. Promoting the afforestation of 10% and 25% former set-aside land in the EU-15 would reduce the loss of SOC stock by 2030 by 19% and 65% respectively compared to conversions to arable land. An increase of the current afforestation rates by 2% would result in a 10% increase in carbon stock levels by 2030. The combined effect of the land use conversions to and from agricultural land use demonstrate an EU-27 average -9.7 tonnes/ha SOC stock loss for the worst option and a +5.0 tonnes/ha SOC stock gain for C-Rich option. Larger variations between Member States than between scenario options stem from regional differences in bio-geography, soil types and climatic regimes. The amount of stable or humified organic carbon

  3. A High-Flux, Flexible Membrane with Parylene-encapsulated Carbon Nanotubes

    SciTech Connect

    Park, H G; In, J; Kim, S; Fornasiero, F; Holt, J K; Grigoropoulos, C P; Noy, A; Bakajin, O

    2008-03-14

    We present fabrication and characterization of a membrane based on carbon nanotubes (CNTs) and parylene. Carbon nanotubes have shown orders of magnitude enhancement in gas and water permeability compared to estimates generated by conventional theories [1, 2]. Large area membranes that exhibit flux enhancement characteristics of carbon nanotubes may provide an economical solution to a variety of technologies including water desalination [3] and gas sequestration [4]. We report a novel method of making carbon nanotube-based, robust membranes with large areas. A vertically aligned dense carbon nanotube array is infiltrated with parylene. Parylene polymer creates a pinhole free transparent film by exhibiting high surface conformity and excellent crevice penetration. Using this moisture-, chemical- and solvent-resistant polymer creates carbon nanotube membranes that promise to exhibit high stability and biocompatibility. CNT membranes are formed by releasing a free-standing film that consists of parylene-infiltrated CNTs, followed by CNT uncapping on both sides of the composite material. Thus fabricated membranes show flexibility and ductility due to the parylene matrix material, as well as high permeability attributed to embedded carbon nanotubes. These membranes have a potential for applications that may require high flux, flexibility and durability.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  5. Assessing the influence of historic net and gross land changes on the carbon fluxes of Europe.

    PubMed

    Fuchs, Richard; Schulp, Catharina J E; Hengeveld, Geerten M; Verburg, Peter H; Clevers, Jan G P W; Schelhaas, Mart-Jan; Herold, Martin

    2016-07-01

    Legacy effects of land cover/use on carbon fluxes require considering both present and past land cover/use change dynamics. To assess past land use dynamics, model-based reconstructions of historic land cover/use are needed. Most historic reconstructions consider only the net area difference between two time steps (net changes) instead of accounting for all area gains and losses (gross changes). Studies about the impact of gross and net land change accounting methods on the carbon balance are still lacking. In this study, we assessed historic changes in carbon in soils for five land cover/use types and of carbon in above-ground biomass of forests. The assessment focused on Europe for the period 1950 to 2010 with decadal time steps at 1-km spatial resolution using a bookkeeping approach. To assess the implications of gross land change data, we also used net land changes for comparison. Main contributors to carbon sequestration between 1950 and 2010 were afforestation and cropland abandonment leading to 14.6 PgC sequestered carbon (of which 7.6 PgC was in forest biomass). Sequestration was highest for old-growth forest areas. A sequestration dip was reached during the 1970s due to changes in forest management practices. Main contributors to carbon emissions were deforestation (1.7 PgC) and stable cropland areas on peaty soils (0.8 PgC). In total, net fluxes summed up to 203 TgC yr(-1) (98 TgC yr(-1) in forest biomass and 105 TgC yr(-1) in soils). For areas that were subject to land changes in both reconstructions (35% of total area), the differences in carbon fluxes were about 68%. Overall for Europe the difference between accounting for either gross or net land changes led to 7% difference (up to 11% per decade) in carbon fluxes with systematically higher fluxes for gross land change data. PMID:26668087

  6. The global ocean flux by particulate organic carbon: Areal distribution and magnitude

    SciTech Connect

    Jahnke, R.A.

    1996-03-01

    The magnitude and distribution of the particulate organic carbon (POC) rain rate to the seafloor in the Atlantic, Pacific and Indian Ocean basins between 61{degrees}N and 61{degrees}S has been estimated from benthic oxygen flux estimates (for water depths {ge} 1000 m). The calculation uses extensive data sets of sedimentary organic carbon and accumulation rate to extrapolate between individual benthic flux measurement sites using an empirically-derived correlation between the seafloor oxygen flux and these parameters. The POC flux through the 1000 m depth horizon was estimated from published correlations between sediment trap-determined fluxes and water depth. Total oxygen utilization in the deep ocean is estimated to be 1.2x10{sup 14} mol O{sub 2} yr{sup -1}, which agrees well with previous estimates and with deep water respiration rates. Based on the derived global ocean flux distribution, it is concluded that (1) dissolved organic carbon (DOC) inputs are not required to account for estimated deep water respiration rates; (2) the majority of the POC input to the deep ocean occurs within 30{degrees} of the equator; (3) the proportion of primary production that reaches the deep sea does not vary greatly with latitude; (4) gyre and continental margin regions contribute roughly equally to the deep POC flux with a relatively minor contribution from the equatorial divergence region; (5) of the estimated 7.2x10{sup 13} mol C yr{sup -1} of POC that sinks below the 1000 m depth horizon, 45% (3.3x10{sup 13} mol C yr{sup -1}) reaches the seafloor where it is oxidized; (6) when normalized to basin area, average deep flux rates in the Atlantic and Pacific are similar while highest rates are observed in the Indian Ocean; and (7) the results can be fully reconciled only if the benthic flux of DOC is significantly less than the benthic O{sub 2} flux. 51 refs., 5 figs., 3 tabs.

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

    NASA Astrophysics Data System (ADS)

    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

  8. Biospheric and petrogenic organic carbon flux along southeast Alaska

    NASA Astrophysics Data System (ADS)

    Cui, Xingqian; Bianchi, Thomas S.; Jaeger, John M.; Smith, Richard W.

    2016-10-01

    Holocene fjords store ca. 11-12% of the total organic carbon (OC) buried in marine sediments with fjords along southeast (SE) Alaska possibly storing half of this OC (Smith et al., 2015). However, the respective burial of biospheric (OCbio) and petrogenic OC (OCpetro) remains poorly constrained, particularly across glaciated versus non-glaciated systems. Here, we use surface sediment samples to quantify the sources and burial of sedimentary OC along SE Alaska fjord-coastal systems, and conduct a latitudinal comparison across a suite of fjords and river-coastal systems with distinctive OC sources. Our results for SE Alaska show that surface sediments in northern fjords (north of Icy Strait) with headwater glaciers are dominated by OCpetro, in contrast to marine and terrestrially-derived fresh OC in non-glaciated southern fjords. Along the continental shelf of the Gulf of Alaska, terrestrial OC is exported from rivers. Using end-member mixing models, we determine that glaciated fjords have significantly higher burial rates of OCpetro (∼ 1.1 ×103 gOC m-2yr-1) than non-glaciated fjords and other coastal systems, making SE Alaska potentially the largest sink of OCpetro in North America. In contrast, non-glaciated fjords in SE Alaska are effective in burying marine OC (OCbio-mari) (13-82 g OC m-2yr-1). Globally, OC in fjord sediments are comprised of a mixture of OCpetro and fresh OCbio, in contrast to the pre-aged OC from floodplain river-coastal systems. We find that there may be a general latitudinal trend in the role of fjords in processing OC, where high-latitude temperate glacial fjords (e.g., Yakutat Bay, SE Alaska) rebury OCpetro and non-glacial mid-latitude fjords (e.g., Doubtful Sound, Fiordland) sequester CO2 from phytoplankton and/or temperate forests. Overall, we propose that fjords are effective in sequestering OCbio and re-burying OCpetro. Based on our study, we hypothesize that climate change will have a semi-predictable impact on fjords' OC cycling in

  9. Impacts of a decadal drainage disturbance on surface-atmosphere fluxes of carbon dioxide in a permafrost ecosystem

    NASA Astrophysics Data System (ADS)

    Kittler, Fanny; Burjack, Ina; Corradi, Chiara A. R.; Heimann, Martin; Kolle, Olaf; Merbold, Lutz; Zimov, Nikita; Zimov, Sergey; Göckede, Mathias

    2016-09-01

    Hydrologic conditions are a major controlling factor for carbon exchange processes in high-latitude ecosystems. The presence or absence of water-logged conditions can lead to significant shifts in ecosystem structure and carbon cycle processes. In this study, we compared growing season CO2 fluxes of a wet tussock tundra ecosystem from an area affected by decadal drainage to an undisturbed area on the Kolyma floodplain in northeastern Siberia. For this comparison we found the sink strength for CO2 in recent years (2013-2015) to be systematically reduced within the drained area, with a minor increase in photosynthetic uptake due to a higher abundance of shrubs outweighed by a more pronounced increase in respiration due to warmer near-surface soil layers. Still, in comparison to the strong reduction of fluxes immediately following the drainage disturbance in 2005, recent CO2 exchange with the atmosphere over this disturbed part of the tundra indicate a higher carbon turnover, and a seasonal amplitude that is comparable again to that within the control section. This indicates that the local permafrost ecosystem is capable of adapting to significantly different hydrologic conditions without losing its capacity to act as a net sink for CO2 over the growing season. The comparison of undisturbed CO2 flux rates from 2013-2015 to the period of 2002-2004 indicates that CO2 exchange with the atmosphere was intensified, with increased component fluxes (ecosystem respiration and gross primary production) over the past decade. Net changes in CO2 fluxes are dominated by a major increase in photosynthetic uptake, resulting in a stronger CO2 sink in 2013-2015. Application of a MODIS-based classification scheme to separate the growing season into four sub-seasons improved the interpretation of interannual variability by illustrating the systematic shifts in CO2 uptake patterns that have occurred in this ecosystem over the past 10 years and highlighting the important role of the late

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  11. Assessment of metabolic flux distribution in the thermophilic hydrogen producer Caloramator celer as affected by external pH and hydrogen partial pressure

    PubMed Central

    2014-01-01

    Background Caloramator celer is a strict anaerobic, alkalitolerant, thermophilic bacterium capable of converting glucose to hydrogen (H2), carbon dioxide, acetate, ethanol and formate by a mixed acid fermentation. Depending on the growth conditions C. celer can produce H2 at high yields. For a biotechnological exploitation of this bacterium for H2 production it is crucial to understand the factors that regulate carbon and electron fluxes and therefore the final distribution of metabolites to channel the metabolic flux towards the desired product. Results Combining experimental results from batch fermentations with genome analysis, reconstruction of central carbon metabolism and metabolic flux analysis (MFA), this study shed light on glucose catabolism of the thermophilic alkalitolerant bacterium C. celer. Two innate factors pertaining to culture conditions have been identified to significantly affect the metabolic flux distribution: culture pH and partial pressures of H2 (PH2). Overall, at alkaline to neutral pH the rate of biomass synthesis was maximized, whereas at acidic pH the lower growth rate and the less efficient biomass formation are accompanied with more efficient energy recovery from the substrate indicating high cell maintenance possibly to sustain intracellular pH homeostasis. Higher H2 yields were associated with fermentation at acidic pH as a consequence of the lower synthesis of other reduced by-products such as formate and ethanol. In contrast, PH2 did not affect the growth of C. celer on glucose. At high PH2 the cellular redox state was balanced by rerouting the flow of carbon and electrons to ethanol and formate production allowing unaltered glycolytic flux and growth rate, but resulting in a decreased H2 synthesis. Conclusion C. celer possesses a flexible fermentative metabolism that allows redistribution of fluxes at key metabolic nodes to simultaneously control redox state and efficiently harvest energy from substrate even under unfavorable

  12. Predicting carbon dioxide and energy fluxes across global FLUXNET sites with regression algorithms

    NASA Astrophysics Data System (ADS)

    Tramontana, Gianluca; Jung, Martin; Schwalm, Christopher R.; Ichii, Kazuhito; Camps-Valls, Gustau; Ráduly, Botond; Reichstein, Markus; Altaf Arain, M.; Cescatti, Alessandro; Kiely, Gerard; Merbold, Lutz; Serrano-Ortiz, Penelope; Sickert, Sven; Wolf, Sebastian; Papale, Dario

    2016-07-01

    Spatio-temporal fields of land-atmosphere fluxes derived from data-driven models can complement simulations by process-based land surface models. While a number of strategies for empirical models with eddy-covariance flux data have been applied, a systematic intercomparison of these methods has been missing so far. In this study, we performed a cross-validation experiment for predicting carbon dioxide, latent heat, sensible heat and net radiation fluxes across different ecosystem types with 11 machine learning (ML) methods from four different classes (kernel methods, neural networks, tree methods, and regression splines). We applied two complementary setups: (1) 8-day average fluxes based on remotely sensed data and (2) daily mean fluxes based on meteorological data and a mean seasonal cycle of remotely sensed variables. The patterns of predictions from different ML and experimental setups were highly consistent. There were systematic differences in performance among the fluxes, with the following ascending order: net ecosystem exchange (R2 < 0.5), ecosystem respiration (R2 > 0.6), gross primary production (R2> 0.7), latent heat (R2 > 0.7), sensible heat (R2 > 0.7), and net radiation (R2 > 0.8). The ML methods predicted the across-site variability and the mean seasonal cycle of the observed fluxes very well (R2 > 0.7), while the 8-day deviations from the mean seasonal cycle were not well predicted (R2 < 0.5). Fluxes were better predicted at forested and temperate climate sites than at sites in extreme climates or less represented by training data (e.g., the tropics). The evaluated large ensemble of ML-based models will be the basis of new global flux products.

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

    NASA Astrophysics Data System (ADS)

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

    NASA Astrophysics Data System (ADS)

    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.

  15. Understanding the representativeness of FLUXNET for upscaling carbon flux from eddy covariance measurements

    DOE PAGES

    Kumar, Jitendra; Hoffman, Forrest M.; Hargrove, William W.; Collier, Nathan

    2016-08-23

    Eddy covariance data from regional flux networks are direct in situ measurement of carbon, water, and energy fluxes and are of vital importance for understanding the spatio-temporal dynamics of the the global carbon cycle. FLUXNET links regional networks of eddy covariance sites across the globe to quantify the spatial and temporal variability of fluxes at regional to global scales and to detect emergent ecosystem properties. This study presents an assessment of the representativeness of FLUXNET based on the recently released FLUXNET2015 data set. We present a detailed high resolution analysis of the evolving representativeness of FLUXNET through time. Results providemore » quantitative insights into the extent that various biomes are sampled by the network of networks, the role of the spatial distribution of the sites on the network scale representativeness at any given time, and how that representativeness has changed through time due to changing operational status and data availability at sites in the network. To realize the full potential of FLUXNET observations for understanding emergent ecosystem properties at regional and global scales, we present an approach for upscaling eddy covariance measurements. Informed by the representativeness of observations at the flux sites in the network, the upscaled data reflects the spatio-temporal dynamics of the carbon cycle captured by the in situ measurements. In conclusion, this study presents a method for optimal use of the rich point measurements from FLUXNET to derive an understanding of upscaled carbon fluxes, which can be routinely updated as new data become available, and direct network expansion by identifying regions poorly sampled by the current network.« less

  16. Regional Mapping of Coupled Fluxes of Carbon and Water Using Multi-Sensor Fusion Techniques

    NASA Astrophysics Data System (ADS)

    Schull, M. A.; Anderson, M. C.; Semmens, K. A.; Yang, Y.; Gao, F.; Hain, C.; Houborg, R.

    2014-12-01

    In an ever-changing climate there is an increasing need to measure the fluxes of water, energy and carbon for decision makers to implement policies that will help mitigate the effects of climate change. In an effort to improve drought monitoring, water resource management and agriculture assessment capabilities, a multi-scale and multi-sensor framework for routine mapping of land-surface fluxes of water and energy at field to regional scales has been established. The framework uses the ALEXI (Atmosphere Land Exchange Inverse)/DisALEXI (Disaggregated ALEXI) suite of land-surface models forced by remotely sensed data from Landsat, MODIS (MODerate resolution Imaging Spectroradiometer), and GOES (Geostationary Operational Environmental Satellite). Land-surface temperature (LST) can be an effective substitute for in-situ surface moisture observations and a valuable metric for constraining land-surface fluxes at sub-field scales. The adopted multi-scale thermal-based land surface modeling framework facilitates regional to local downscaling of water and energy fluxes by using a combination of shortwave reflective and thermal infrared (TIR) imagery from GOES (4-10 km; hourly), MODIS (1 km; daily), and Landsat (30-100 m; bi-weekly). In this research the ALEXI/DisALEXI modeling suite is modified to incorporate carbon fluxes using a stomatal resistance module, which replaces the Priestley-Taylor latent heat approximation. In the module, canopy level nominal light-use-efficiency (βn) is the parameter that modulates the flux of water and carbon in and out of the canopy. Leaf chlorophyll (Chl) is a key parameter for quantifying variability in photosynthetic efficiency to facilitate the spatial distribution of coupled carbon and water retrievals. Spatial distribution of Chl are retrieved from Landsat (30 m) using a surface reflectance dataset as input to the REGularized canopy reFLECtance (REGFLEC) tool. The modified ALEXI/DisALEXI suite is applied to regions of rain fed and

  17. Carbon fluxes and export in the northern and middle Atlantic Sea measured with drifting sediment traps

    SciTech Connect

    Miquel, J-C; Fowler, S; Hamilton, T; Heilmann, J P; LaRosa, J; Carroll, M

    2000-07-26

    In July 1993 and June 1995 drifting sediment traps were deployed near the Po outflow, in the coastal zone and in the Jabuka Pit in order to obtain quantitative information on the vertical flux of particulate material and export of organic carbon in the Northern and Middle Adriatic Sea. During these periods and in July 1994, the standing stock of carbon and nitrogen in the water column were also estimated. Carbon and nitrogen concentrations were higher in the north with a mean of 266 {micro}g C l{sup -1} in surface waters as compared to 92 {micro}g C l{sup -1} in Middle Adriatic; maximum concentrations were associated to the less-saline surface-subsurface waters in the north and to the chlorophyll a maximum in the Middle Adriatic. Organic carbon flux was roughly five times higher near the Po than in the more oligotrophic waters of the central region, with overall values (0.8 to 11.5 mg m{sup -2} d{sup -1}) being low compared to the open Northwestern Mediterranean. Comparison with primary production measurements yielded estimates of carbon export (f-ratio) of 4.7 and 3.4% in the Po and Pit stations, respectively, in 1993 and of 1.6 and 3.6% in the central part of the Adriatic in 1995. These consistently low values suggest enhanced carbon recycling in the upper water column, even in regions characterized by different production and organic flux regimes. Zooplankton fecal pellets were important conveyors of organic carbon in this region; particularly those produced by fishes in the North and coastal sites.

  18. Metabolic carbon fluxes and biosynthesis of polyhydroxyalkanoates in Ralstonia eutropha on short chain fatty acids.

    PubMed

    Yu, Jian; Si, Yingtao

    2004-01-01

    Short chain fatty acids such as acetic, propionic, and butyric acids can be synthesized into polyhydroxyalkanoates (PHAs) by Ralstonia eutropha. Metabolic carbon fluxes of the acids in living cells have significant effect on the yield, composition, and thermomechanical properties of PHA bioplastics. Based on the general knowledge of central metabolism pathways and the unusual metabolic pathways in R. eutropha, a metabolic network of 41 bioreactions is constructed to analyze the carbon fluxes on utilization of the short chain fatty acids. In fed-batch cultures with constant feeding of acid media, carbon metabolism and distribution in R. eutropha were measured involving CO2, PHA biopolymers, and residual cell mass. As the cells underwent unsteady state metabolism and PHA biosynthesis under nitrogen-limited conditions, accumulative carbon balance was applied for pseudo-steady-state analysis of the metabolic carbon fluxes. Cofactor NADP/NADPH balanced between PHA synthesis and the C3/C4 pathway provided an independent constraint for solution of the underdetermined metabolic network. A major portion of propionyl-CoA was directed to pyruvate via the 2-methylcitrate cycle and further decarboxylated to acetyl-CoA. Only a small amount of propionate carbon (<15% carbon) was directly condensed with acetyl-CoA for 3-hydroxyvalerate. The ratio of glyoxylate shunt to TCA cycle varies from 0 to 0.25, depending on the intracellular acetyl-CoA level and acetic acid in the medium. Malate is the node of the C3/C4 pathway and TCA cycle and its decarboxylation to dehydrogenation ranges from 0.33 to 1.28 in response to the demands on NADPH and oxaloacetate for short chain fatty acids utilization. PMID:15296425

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

    NASA Technical Reports Server (NTRS)

    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.

  20. Fluxnet and Satellite data to optimize carbon and water fluxes simulated by ORCHIDEE biosphere model

    NASA Astrophysics Data System (ADS)

    Santaren, D.; Peylin, P.; Kuppel, S.; Bacour, C.; Granier, A.; Rayner, P. J.; Ciais, P.

    2010-12-01

    Terrestrial ecosystem models are used to predict the response of energy water and carbon balances of Earth's ecosystems to environmental changes. However, the estimated fluxes remain subject to large uncertainties, partly because of unknown or poorly calibrated parameters. Assimilation of in situ data should help constraining these parameter to improve simulations of the carbon balance and climate predictions. Using a state of the art mechanistic vegetation model ORCHIDEE, involved in the next AR5-IPCC report, we investigated the benefit of Fluxnet data (net CO2 flux (NEE) and latent heat flux (LE)) as well as remotely sensed fAPAR (fraction of absorbed photosynthetically active radiation) to improve the model. ORCHIDEE computes the energy, carbon and water balances on a half-hourly basis, depending on the meteorological forcing and the biome composition of the ecosystem. The phenology of the model is also fully prognostic allowing the derivation of leaf area index time course. A four dimensional variational data (4D-var) assimilation system has been developed, using the tangent linear model, to assimilate synergistically different observations (daily means) and optimize critical parameters of the model (on the order of 20). The study makes uses of available data from few sites in Europe and investigates three major points. We first analyze the ability of the model to capture the fluxes during particular extreme climate conditions (i.e. summer 2003 in Europe) using parameters optimized during “normal weather” conditions at a beach forest in France (Hesse site). The model-data fit for NEE and LE is analyzed in terms of annual mean, seasonal cycles and synoptic variations. We then performed an optimization using multiple sites of the same Plant Functional Type (PFT) at the same time. This optimization allows assessing the potential of the model to simulate with a mean set of parameters the carbon and water fluxes of several sites under different climate regimes

  1. Precipitation pulses and carbon fluxes in semiarid and arid ecosystems.

    PubMed

    Huxman, Travis E; Snyder, Keirith A; Tissue, David; Leffler, A Joshua; Ogle, Kiona; Pockman, William T; Sandquist, Darren R; Potts, Daniel L; Schwinning, Susan

    2004-10-01

    In the arid and semiarid regions of North America, discrete precipitation pulses are important triggers for biological activity. The timing and magnitude of these pulses may differentially affect the activity of plants and microbes, combining to influence the C balance of desert ecosystems. Here, we evaluate how a "pulse" of water influences physiological activity in plants, soils and ecosystems, and how characteristics, such as precipitation pulse size and frequency are important controllers of biological and physical processes in arid land ecosystems. We show that pulse size regulates C balance by determining the temporal duration of activity for different components of the biota. Microbial respiration responds to very small events, but the relationship between pulse size and duration of activity likely saturates at moderate event sizes. Photosynthetic activity of vascular plants generally increases following relatively larger pulses or a series of small pulses. In this case, the duration of physiological activity is an increasing function of pulse size up to events that are infrequent in these hydroclimatological regions. This differential responsiveness of photosynthesis and respiration results in arid ecosystems acting as immediate C sources to the atmosphere following rainfall, with subsequent periods of C accumulation should pulse size be sufficient to initiate vascular plant activity. Using the average pulse size distributions in the North American deserts, a simple modeling exercise shows that net ecosystem exchange of CO2 is sensitive to changes in the event size distribution representative of wet and dry years. An important regulator of the pulse response is initial soil and canopy conditions and the physical structuring of bare soil and beneath canopy patches on the landscape. Initial condition influences responses to pulses of varying magnitude, while bare soil/beneath canopy patches interact to introduce nonlinearity in the relationship between pulse

  2. Sensitivity of Simulated Global Ocean Carbon Flux Estimates to Forcing by Reanalysis Products

    NASA Technical Reports Server (NTRS)

    Gregg, Watson W.; Casey, Nancy W.; Rousseaux, Cecile S.

    2015-01-01

    Reanalysis products from MERRA, NCEP2, NCEP1, and ECMWF were used to force an established ocean biogeochemical model to estimate air-sea carbon fluxes (FCO2) and partial pressure of carbon dioxide (pCO2) in the global oceans. Global air-sea carbon fluxes and pCO2 were relatively insensitive to the choice of forcing reanalysis. All global FCO2 estimates from the model forced by the four different reanalyses were within 20% of in situ estimates (MERRA and NCEP1 were within 7%), and all models exhibited statistically significant positive correlations with in situ estimates across the 12 major oceanographic basins. Global pCO2 estimates were within 1% of in situ estimates with ECMWF being the outlier at 0.6%. Basin correlations were similar to FCO2. There were, however, substantial departures among basin estimates from the different reanalysis forcings. The high latitudes and tropics had the largest ranges in estimated fluxes among the reanalyses. Regional pCO2 differences among the reanalysis forcings were muted relative to the FCO2 results. No individual reanalysis was uniformly better or worse in the major oceanographic basins. The results provide information on the characterization of uncertainty in ocean carbon models due to choice of reanalysis forcing.

  3. [Net CO2 exchange and carbon isotope flux in Acacia mangium plantation].

    PubMed

    Zou, Lu-Liu; Sun, Gu-Chou; Zhao, Ping; Cai, Xi-An; Zeng, Xiao-Ping; Wang, Quan

    2009-11-01

    By using stable carbon isotope technique, the leaf-level 13C discrimination was integrated to canopy-scale photosynthetic discrimination (Deltacanopy) through weighted the net CO2 assimilation (Anet) of sunlit and shaded leaves and the stand leaf area index (L) in an A. mangium plantation, and the carbon isotope fluxes from photosynthesis and respiration as well as their net exchange flux were obtained. There was an obvious diurnal variation in Deltacanopy, being lower at dawn and at noon time (18.47 per thousand and 19.87 per thousand, respectively) and the highest (21.21 per thousand) at dusk. From the end of November to next May, the Deltacanopy had an increasing trend, with an annual average of (20.37 +/- 0.29) per thousand. The carbon isotope ratios of CO2 from autotrophic respiration (excluding daytime foliar respiration) and heterotrophic respiration were respectively (- 28.70 +/- 0.75) per thousand and (- 26.75 +/- 1.3) per thousand in average. The delta13 C of nighttime ecosystem-respired CO2 in May was the lowest (-30.14 per thousand), while that in November was the highest (-28.01 per thousand). The carbon isotope flux of CO2 between A. mangium forest and atmosphere showed a midday peak of 178.5 and 217 micromol x m(-2) x s(-1) x per thousand in May and July, with the daily average of 638.4 and 873.2 micromol x m(-2) x s(-1) x per thousand, respectively. The carbon isotope flux of CO2 absorbed by canopy leaves was 1.6-2.5 times higher than that of CO2 emitted from respiration, suggesting that a large sum of CO2 was absorbed by A. mangium, which decreased the atmospheric CO2 concentration and improved the environment.

  4. Downward particle flux and carbon export in the Beaufort Sea, Arctic Ocean; the role of zooplankton

    NASA Astrophysics Data System (ADS)

    Miquel, J.-C.; Gasser, B.; Martín, J.; Marec, C.; Babin, M.; Fortier, L.; Forest, A.

    2015-08-01

    As part of the international, multidisciplinary project Malina, downward particle fluxes were investigated by means of a drifting multi-sediment trap mooring deployed at three sites in the Canadian Beaufort Sea in late summer 2009. Mooring deployments lasted between 28 and 50 h and targeted the shelf-break and the slope along the Beaufort-Mackenzie continental margin, as well as the edge between the Mackenzie Shelf and the Amundsen Gulf. Besides analyses of C and N, the collected material was investigated for pigments, phyto- and microzooplankton, faecal pellets and swimmers. The measured fluxes were relatively low, in the range of 11-54 mg m-2 d-1 for the total mass, 1-15 mg C m-2 d-1 for organic carbon and 0.2-2.5 mg N m-2 d-1 for nitrogen. Comparison with a long-term trap data set from the same sampling area showed that the short-term measurements were at the lower end of the high variability characterizing a rather high flux regime during the study period. The sinking material consisted of aggregates and particles that were characterized by the presence of hetero- and autotrophic microzooplankters and diatoms and by the corresponding pigment signatures. Faecal pellets contribution to sinking carbon flux was important, especially at depths below 100 m, where they represented up to 25 % of the total carbon flux. The vertical distribution of different morphotypes of pellets showed a marked pattern with cylindrical faeces (produced by calanoid copepods) present mainly within the euphotic zone, whereas elliptical pellets (produced mainly by smaller copepods) were more abundant at mesopelagic depths. These features, together with the density of matter within the pellets, highlighted the role of the zooplankton community in the transformation of carbon issued from the primary production and the transition of that carbon from the productive surface zone to the Arctic Ocean's interior. Our data indicate that sinking carbon flux in this late summer period is primarily

  5. Downward particle flux and carbon export in the Beaufort Sea, Arctic Ocean; the Malina experiment

    NASA Astrophysics Data System (ADS)

    Miquel, J.-C.; Gasser, B.; Martín, J.; Marec, C.; Babin, M.; Fortier, L.; Forest, A.

    2015-01-01

    As part of the international, multidisciplinary project Malina, downward particle fluxes were investigated by means of a drifting multi-sediment trap mooring deployed at three sites in the Canadian Beaufort Sea in late summer 2009. Mooring deployments lasted for 28-50 h and targeted the shelf-break and the slope along the Beaufort-Mackenzie continental margin, as well as the edge between the Mackenzie Shelf and the Amundsen Gulf. Besides analyses of C and N, the collected material was investigated for pigments, phyto- and microzooplankton, faecal pellets and swimmers. The measured fluxes were relatively low, in the range of 11-54 mg m-2 d-1 for the total mass, 1-15 mg C m-2 d-1 for organic carbon and 0.2-2.5 mg N m-2 d-1 for nitrogen. Comparison with a long-term trap dataset from the same sampling area showed that the short-term measurements were at the lower end of the high variability characterizing a rather high flux regime during the study period. The sinking material consisted of aggregates and particles that were characterized by the presence of hetero- and autotrophic microzooplankters and diatoms and by the corresponding pigment signatures. Faecal pellets contribution to sinking carbon flux was important, especially at depth where they represented up to 25% of the total carbon flux. The vertical distribution of different morphotypes of pellets showed a marked pattern with cylindrical faeces (produced by calanoid copepods) present mainly within the euphotic zone, whereas elliptical pellets (produced mainly by smaller copepods) were more abundant at mesopelagic depths. These features, together with the density of matter within the pellets, highlighted the role of the zooplankton community in the transformation of carbon issued from the primary production and the transition of that carbon from the productive surface zone to the Arctic Ocean's interior. Our data indicate that sinking carbon flux in this late summer period is primarily the result of a

  6. Reactive transport modeling of the impact of ocean acidification on global carbon fluxes in coastal marine sediments

    NASA Astrophysics Data System (ADS)

    Krumins, Valdis; van Cappellen, Philippe; Regnier, Pierre

    2010-05-01

    Because of relatively high productivity of both calcifying and non-calcifying phytoplankton in coastal zones, coastal sediments can act as a significant carbon sink. Ocean acidification is likely to impact productivity of these groups differently, raising the question of the overall effect of ocean acidification on carbon burial in coastal sediments. We modeled the effect of varying depositional fluxes of particulate organic carbon (POC) and particulate inorganic carbon (PIC) on carbon cycling in coastal marine sediments using a one-dimensional reactive transport model. Transport processes include sediment burial, advection, diffusion, bioturbation and bioirrigation. The model incorporates the hydrolysis of macromolecular organic matter, the redox pathways of POC oxidation, re-oxidation reactions of the reduced compounds produced during POC decomposition, the acid-base chemical equilibria, and the dissolution of PIC (calcite, aragonite, and Mg-calcite) in the upper 50 cm of sediment. The following processes are also included: precipitation of iron sulfide and iron carbonate, sorption of Fe(II), ammonium and phosphate, sulfidization of organic matter, and pyritization. The global return fluxes of dissolved inorganic carbon (DIC) and alkalinity are estimated by modeling sediments at 25 m, 75 m, and 150 m depths, and multiplying by the global area of seafloor depths 0-50 m, 50-100 m, and 100-200 m, respectively. We determined the sensitivity of carbon and nutrient return fluxes to changes in pH, PIC and POC fluxes, as well as to poorly constrained Fe(III) deposition fluxes. Inorganic carbon return fluxes are influenced most by the particulate organic and inorganic carbon depositional fluxes; the seawater pH has a limited effect. Modeled sediment pH profiles and PIC dissolution are also sensitive to the iron deposition flux. The overreaching goal of the research is to forecast the global response of coastal sediment return fluxes as a result of anthropogenic ocean

  7. Soil Surface Carbon Dioxide Fluxes and Carbon Dioxide Concentrations in Soil Air

    NASA Astrophysics Data System (ADS)

    Arkebauer, T. J.; Billesbach, D.

    2006-12-01

    We have been monitoring soil surface CO2 fluxes at three AmeriFlux sites in eastern Nebraska for several years. Recently, we have installed soil CO2 sensors at the rainfed soybean site in order to obtain profiles of CO2 concentrations in soil air (to 0.8 m depth). Supporting data include profiles of soil water content and soil temperature, aboveground biomass, leaf area index and precipitation. Soil surface fluxes had been rather small for much of the 2006 growing season (e.g., midday values of about 5 umol/m2/s) due, in large part, to the very dry conditions in eastern Nebraska and the consequent low soil water contents. However, copious rainfall in August raised soil water contents to field capacity throughout the profile. Soil air CO2 concentrations during this period also increased and reached peaks near 10% (at 0.4 and 0.8 m depth). Through analyses of relationships between surface CO2 flux and profiles of soil parameters we seek to identify biophysical factors responsible for controlling surface fluxes as well as to begin to quantify sources and sinks of CO2 within the soil profile (e.g., plant-related production of CO2 due to root exudation and respiration). The influence of precipitation events on CO2 profiles and fluxes is of particular interest.

  8. Gas flux and carbonate occurrence at a shallow seep of thermogenic natural gas

    NASA Astrophysics Data System (ADS)

    Kinnaman, Franklin S.; Kimball, Justine B.; Busso, Luis; Birgel, Daniel; Ding, Haibing; Hinrichs, Kai-Uwe; Valentine, David L.

    2010-06-01

    The Coal Oil Point seep field located offshore Santa Barbara, CA, consists of dozens of named seeps, including a peripheral ˜200 m2 area known as Brian Seep, located in 10 m water depth. A single comprehensive survey of gas flux at Brian Seep yielded a methane release rate of ˜450 moles of CH4 per day, originating from 68 persistent gas vents and 23 intermittent vents, with gas flux among persistent vents displaying a log normal frequency distribution. A subsequent series of 33 repeat surveys conducted over a period of 6 months tracked eight persistent vents, and revealed substantial temporal variability in gas venting, with flux from each individual vent varying by more than a factor of 4. During wintertime surveys sediment was largely absent from the site, and carbonate concretions were exposed at the seafloor. The presence of the carbonates was unexpected, as the thermogenic seep gas contains 6.7% CO2, which should act to dissolve carbonates. The average δ13C of the carbonates was -29.2 ± 2.8‰ VPDB, compared to a range of -1.0 to +7.8‰ for CO2 in the seep gas, indicating that CO2 from the seep gas is quantitatively not as important as 13C-depleted bicarbonate derived from methane oxidation. Methane, with a δ13C of approximately -43‰, is oxidized and the resulting inorganic carbon precipitates as high-magnesium calcite and other carbonate minerals. This finding is supported by 13C-depleted biomarkers typically associated with anaerobic methanotrophic archaea and their bacterial syntrophic partners in the carbonates (lipid biomarker δ13C ranged from -84 to -25‰). The inconsistency in δ13C between the carbonates and the seeping CO2 was resolved by discovering pockets of gas trapped near the base of the sediment column with δ13C-CO2 values ranging from -26.9 to -11.6‰. A mechanism of carbonate formation is proposed in which carbonates form near the sediment-bedrock interface during times of sufficient sediment coverage, in which anaerobic oxidation

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

    NASA Astrophysics Data System (ADS)

    Sus, O.; Heuer, M. W.; Meyers, T. P.; Williams, M.

    2012-08-01

    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 a 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 variationally (for sowing date estimation) and sequentially (for improved model state estimation, using the Ensemble Kalman Filter) into a crop carbon mass balance model (SPAc). In doing so, we are able to accurately 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) From Bondville site results we deduce that MODIS-derived sowing dates allow for accurate simulations of growing season carbon cycling at locations for which such 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, observing carbon cycling at one single field with its individual sowing pattern is not

  10. Developing an Understanding of Vegetation Change and Fluvial Carbon Fluxes in Semi-Arid Environments

    NASA Astrophysics Data System (ADS)

    Puttock, A.; Brazier, R. E.; Dungait, J. A. J.; Bol, R.; Macleod, C. J. A.

    2012-04-01

    Dryland environments are estimated to cover around 40% of the global land surface (Okin et al, 2009) and are home to approximately 2.5 billion people (Reynolds et al. 2007). Many of these areas have recently experienced extensive land degradation. One such area and the focus of this project is the semi-arid US Southwest, where degradation over the past 150 years has been characterised by the invasion of woody vegetation into grasslands. Transition from grass to woody vegetation results in a change in ecosystem structure and function (Turnbull et al, 2008). Structural change is typically characterised by an increased heterogeneity of soil and vegetation resources, associated with reduced vegetation coverage and an increased vulnerability to soil erosion and the potential loss of key nutrients to adjacent fluvial systems. Such loss of resources may impact heavily upon the amount of carbon that is sequestered by these environments and the amount of carbon that is lost as the land becomes more degraded. Therefore, understanding these vegetation transitions is significant for sustainable land use and global biogeochemical cycling. This project uses an ecohydrological approach, monitoring natural rainfall-runoff events over six bounded plots with different vegetation coverage. The experiment takes advantage of a natural abundance stable 13C isotope shift from C3 piñon-juniper (Pinus edulis-Juniperus monosperma) mixed stand through a C4 pure-grass (Bouteloua eriopoda) to C3 shrub (Larrea tridentata). Data collected quantify fluvial fluxes of sediment and associated soil organic matter and carbon that is lost from across the grass-to-shrub and grass-to-woodland transition (where change in space is taken to indicate a similar change through time). Results collected during the 2010 and 2011 monsoon seasons will be presented, illustrating that soil and carbon losses are greater as the ecosystem becomes more dominated by woody plants. Additionally this project utilises novel

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

    USGS Publications Warehouse

    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.

  12. Oregon-California Regional Carbon Budget Approach Using Model-Data Fusion to Estimate Gross Carbon Fluxes: Component of ORCA

    NASA Astrophysics Data System (ADS)

    Styles, J.; Goeckede, M.; Law, B.; Turner, D.; Cohen, W.

    2005-12-01

    This study presents preliminary results from the model-data fusion component of the ORCA project, which aims to quantify carbon stocks and fluxes across the whole of Oregon and north California (see Law et al., this meeting). Process models for gross primary production (GPP), autotrophic respiration (RA) and heterotrophic respiration (RH) are formulated that incorporate effects of disturbance (forest stand age) on growth and respiration. The model-data fusion approach utilizes both eddy covariance and atmospheric CO2 concentration measurements for parameter estimation, and is applied initially at three flux tower sites covering different age classes of ponderosa pine forest. Concentration data are interpreted within a one-dimensional atmospheric boundary layer model to infer daytime CO2 flux. These flux estimates cover a larger region than the eddy covariance measurements and footprint modeling allows partitioning among surrounding land cover types and age classes (see Goeckede et al., this meeting). The simple process models for GPP, RA and RH are formulated with a base rate for each flux component (this rate being the light-use-efficiency in the case of GPP), and modulation with climate variables, forest structure and stand age. The simplicity of the functions make them easy to parameterize and employ across large spatial regions, driven by distributed climate data and satellite observations, while encompassing sufficient mechanistic linkages between vegetation fluxes and climate and physiological drivers to reproduce the observations effectively. The parameter optimization procedure is used to determine the dominant parameters driving diurnal and seasonal variation in flux components, and parameter uncertainties and correlations are investigated. The influences of factors such as drought, diffuse light fraction and stand age on production and/or respiration and the link between production and respiration are discussed.

  13. Aircraft- and tower-based fluxes of carbon dioxide, latent, and sensible heat

    NASA Technical Reports Server (NTRS)

    Desjardins, R. L.; Hart, R. L.; Macpherson, J. I.; Schuepp, P. H.; Verma, S. B.

    1992-01-01

    Fluxes of carbon dioxide, water vapor, and sensible heat obtained over a grassland ecosystem, during the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE), using an aircraft- and two tower-based systems are compared for several days in 1987 and in 1989. The tower-based cospectral estimates of CO2, sensible heat, water vapor, and momentum, expressed as a function of wavenumber K times sampling height z, are relatively similar to the aircraft-based estimates for K x z greater than 0.1. A measurable contribution to the fluxes is observed by tower-based systems at K x z less than 0.01 but not by the aircraft-based system operating at an altitude of approximately 100 m over a 15 x 15 km area. Using all available simultaneous aircraft and tower data, flux estimates by both systems were shown to be highly correlated. As expected from the spatial variations of the greenness index, surface extrapolation of airborne flux estimates tended to lie between those of the two tower sites. The average fluxes obtained, on July 11, 1987, and August 4, 1989, by flying a grid pattern over the FIFE site agreed with the two tower data sets for CO2, but sensible and latent heat were smaller than those obtained by the tower-based systems. However, in general, except for a small underestimation due to the long wavelength contributions and due to flux divergence with height, the differences between the aircraft- and tower-based surface estimates of fluxes appear to be mainly attributable to differences in footprint, that is, differences in the area contributing to the surface flux estimates.

  14. Aircraft- and tower-based fluxes of carbon dioxide, latent, and sensible heat

    SciTech Connect

    Desjardins, R.L.; Hart, R.L.; Macpherson, J.I.; Schuepp, P.H.; Verma, S.B. Argonne National Lab., IL National Research Council of Canada, Flight Research Lab., Ottawa McGill Univ., Sainte-Anne-de-Bellevue Nebraska Univ., Lincoln )

    1992-11-01

    Fluxes of carbon dioxide, water vapor, and sensible heat obtained over a grassland ecosystem, during the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE), using an aircraft- and two tower-based systems are compared for several days in 1987 and in 1989. The tower-based cospectral estimates of CO2, sensible heat, water vapor, and momentum, expressed as a function of wavenumber K times sampling height z, are relatively similar to the aircraft-based estimates for K x z greater than 0.1. A measurable contribution to the fluxes is observed by tower-based systems at K x z less than 0.01 but not by the aircraft-based system operating at an altitude of approximately 100 m over a 15 x 15 km area. Using all available simultaneous aircraft and tower data, flux estimates by both systems were shown to be highly correlated. As expected from the spatial variations of the greenness index, surface extrapolation of airborne flux estimates tended to lie between those of the two tower sites. The average fluxes obtained, on July 11, 1987, and August 4, 1989, by flying a grid pattern over the FIFE site agreed with the two tower data sets for CO2, but sensible and latent heat were smaller than those obtained by the tower-based systems. However, in general, except for a small underestimation due to the long wavelength contributions and due to flux divergence with height, the differences between the aircraft- and tower-based surface estimates of fluxes appear to be mainly attributable to differences in footprint, that is, differences in the area contributing to the surface flux estimates. 21 refs.

  15. Regulation of CO2 and N2O fluxes by coupled carbon and nitrogen availability

    NASA Astrophysics Data System (ADS)

    Liang, L. L.; Eberwein, J. R.; Allsman, L. A.; Grantz, D. A.; Jenerette, G. D.

    2015-03-01

    Carbon (C) and nitrogen (N) interactions contribute to uncertainty in current biogeochemical models that aim to estimate greenhouse gas (GHG, including CO2 and N2O) emissions from soil to atmosphere. In this study, we quantified CO2 and N2O flux patterns and their relationship along with increasing C additions only, N additions only, a C gradient combined with excess N, and an N gradient with excess C via laboratory incubations. Conventional trends, where labile C or N addition results in higher CO2 or N2O fluxes, were observed. However, at low levels of C availability, saturating N amendments reduced soil CO2 flux while with high C availability N amendments enhanced it. At saturating C conditions increasing N amendments first reduced and then increased CO2 fluxes. Similarly, N2O fluxes were initially reduced by adding labile C under N limited conditions, but additional C enhanced N2O fluxes by more than two orders of magnitude in the saturating N environment. Changes in C or N use efficiency could explain the altered gas flux patterns and imply a critical level in the interactions between N and C availability that regulate soil trace gas emissions and biogeochemical cycling. Compared to either N or C amendment alone, the interaction of N and C caused ∼60 and ∼5 times the total GHG emission, respectively. Our findings suggested that the response of CO2 and N2O fluxes along stoichiometric gradients in C and N availability should be accounted for interpreting or modeling the biogeochemistry of GHG emissions.

  16. Regional carbon fluxes from land use and land cover change in Asia, 1980-2009

    NASA Astrophysics Data System (ADS)

    Calle, Leonardo; Canadell, Josep G.; Patra, Prabir; Ciais, Philippe; Ichii, Kazuhito; Tian, Hanqin; Kondo, Masayuki; Piao, Shilong; Arneth, Almut; Harper, Anna B.; Ito, Akihiko; Kato, Etsushi; Koven, Charlie; Sitch, Stephen; Stocker, Benjamin D.; Vivoy, Nicolas; Wiltshire, Andy; Zaehle, Sönke; Poulter, Benjamin

    2016-07-01

    We present a synthesis of the land-atmosphere carbon flux from land use and land cover change (LULCC) in Asia using multiple data sources and paying particular attention to deforestation and forest regrowth fluxes. The data sources are quasi-independent and include the U.N. Food and Agriculture Organization-Forest Resource Assessment (FAO-FRA 2015; country-level inventory estimates), the Emission Database for Global Atmospheric Research (EDGARv4.3), the ‘Houghton’ bookkeeping model that incorporates FAO-FRA data, an ensemble of 8 state-of-the-art Dynamic Global Vegetation Models (DGVM), and 2 recently published independent studies using primarily remote sensing techniques. The estimates are aggregated spatially to Southeast, East, and South Asia and temporally for three decades, 1980-1989, 1990-1999 and 2000-2009. Since 1980, net carbon emissions from LULCC in Asia were responsible for 20%-40% of global LULCC emissions, with emissions from Southeast Asia alone accounting for 15%-25% of global LULCC emissions during the same period. In the 2000s and for all Asia, three estimates (FAO-FRA, DGVM, Houghton) were in agreement of a net source of carbon to the atmosphere, with mean estimates ranging between 0.24 to 0.41 Pg C yr-1, whereas EDGARv4.3 suggested a net carbon sink of -0.17 Pg C yr-1. Three of 4 estimates suggest that LULCC carbon emissions declined by at least 34% in the preceding decade (1990-2000). Spread in the estimates is due to the inclusion of different flux components and their treatments, showing the importance to include emissions from carbon rich peatlands and land management, such as shifting cultivation and wood harvesting, which appear to be consistently underreported.

  17. Simulating crop phenology in the Community Land Model and its impact on energy and carbon fluxes

    NASA Astrophysics Data System (ADS)

    Chen, Ming; Griffis, Tim J.; Baker, John; Wood, Jeffrey D.; Xiao, Ke

    2015-02-01

    A reasonable representation of crop phenology and biophysical processes in land surface models is necessary to accurately simulate energy, water, and carbon budgets at the field, regional, and global scales. However, the evaluation of crop models that can be coupled to Earth system models is relatively rare. Here we evaluated two such models (CLM4-Crop and CLM3.5-CornSoy), both implemented within the Community Land Model (CLM) framework, at two AmeriFlux corn-soybean sites to assess their ability to simulate phenology, energy, and carbon fluxes. Our results indicated that the accuracy of net ecosystem exchange and gross primary production simulations was intimately connected to the phenology simulations. The CLM4-Crop model consistently overestimated early growing season leaf area index, causing an overestimation of gross primary production, to such an extent that the model simulated a carbon sink instead of the measured carbon source for corn. The CLM3.5-CornSoy-simulated leaf area index (LAI), energy, and carbon fluxes showed stronger correlations with observations compared to CLM4-Crop. Net radiation was biased high in both models and was especially pronounced for soybeans. This was primarily caused by the positive LAI bias, which led to a positive net long-wave radiation bias. CLM4-Crop underestimated soil water content during midgrowing season in all soil layers at the two sites, which caused unrealistic water stress, especially for soybean. Future work regarding the mechanisms that drive early growing season phenology and soil water dynamics is needed to better represent crops including their net radiation balance, energy partitioning, and carbon cycle processes.

  18. Regional carbon fluxes from land use and land cover change in Asia, 1980–2009

    NASA Astrophysics Data System (ADS)

    Calle, Leonardo; Canadell, Josep G.; Patra, Prabir; Ciais, Philippe; Ichii, Kazuhito; Tian, Hanqin; Kondo, Masayuki; Piao, Shilong; Arneth, Almut; Harper, Anna B.; Ito, Akihiko; Kato, Etsushi; Koven, Charlie; Sitch, Stephen; Stocker, Benjamin D.; Vivoy, Nicolas; Wiltshire, Andy; Zaehle, Sönke; Poulter, Benjamin

    2016-07-01

    We present a synthesis of the land-atmosphere carbon flux from land use and land cover change (LULCC) in Asia using multiple data sources and paying particular attention to deforestation and forest regrowth fluxes. The data sources are quasi-independent and include the U.N. Food and Agriculture Organization-Forest Resource Assessment (FAO-FRA 2015; country-level inventory estimates), the Emission Database for Global Atmospheric Research (EDGARv4.3), the ‘Houghton’ bookkeeping model that incorporates FAO-FRA data, an ensemble of 8 state-of-the-art Dynamic Global Vegetation Models (DGVM), and 2 recently published independent studies using primarily remote sensing techniques. The estimates are aggregated spatially to Southeast, East, and South Asia and temporally for three decades, 1980–1989, 1990–1999 and 2000–2009. Since 1980, net carbon emissions from LULCC in Asia were responsible for 20%–40% of global LULCC emissions, with emissions from Southeast Asia alone accounting for 15%–25% of global LULCC emissions during the same period. In the 2000s and for all Asia, three estimates (FAO-FRA, DGVM, Houghton) were in agreement of a net source of carbon to the atmosphere, with mean estimates ranging between 0.24 to 0.41 Pg C yr‑1, whereas EDGARv4.3 suggested a net carbon sink of ‑0.17 Pg C yr‑1. Three of 4 estimates suggest that LULCC carbon emissions declined by at least 34% in the preceding decade (1990–2000). Spread in the estimates is due to the inclusion of different flux components and their treatments, showing the importance to include emissions from carbon rich peatlands and land management, such as shifting cultivation and wood harvesting, which appear to be consistently underreported.

  19. Carbon flux and growth in mature deciduous forest trees exposed to elevated CO2.

    PubMed

    Körner, Christian; Asshoff, Roman; Bignucolo, Olivier; Hättenschwiler, Stephan; Keel, Sonja G; Peláez-Riedl, Susanna; Pepin, Steeve; Siegwolf, Rolf T W; Zotz, Gerhard

    2005-08-26

    Whether rising atmospheric carbon dioxide (CO2) concentrations will cause forests to grow faster and store more carbon is an open question. Using free air CO2 release in combination with a canopy crane, we found an immediate and sustained enhancement of carbon flux through 35-meter-tall temperate forest trees when exposed to elevated CO2. However, there was no overall stimulation in stem growth and leaf litter production after 4 years. Photosynthetic capacity was not reduced, leaf chemistry changes were minor, and tree species differed in their responses. Although growing vigorously, these trees did not accrete more biomass carbon in stems in response to elevated CO2, thus challenging projections of growth responses derived from tests with smaller trees.

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

    PubMed Central

    2011-01-01

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

  1. Technical note: mesocosm approach to quantification of carbon dioxide fluxes across the vadose zone

    NASA Astrophysics Data System (ADS)

    Thaysen, E. M.; Jessen, S.; Ambus, P.; Beier, C.; Postma, D.; Jakobsen, I.

    2013-06-01

    Carbon dioxide (CO2) fluxes in the vadose zone are influenced by a complex interplay of biological, chemical and physical factors. A soil mesocosm system was designed to assess the effect of agricultural practices on carbon fluxes within and out of the vadose zone at controlled environmental conditions. Carbon dioxide partial pressure (pCO2), 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 pCO2 varied between 0.2-1.1% and alkalinity was 0.1-0.6 meq L-1. The measured effluent DIC flux was 185-196 mg L-1 m-2 and in the same range as estimates derived from pCO2 and alkalinity in samples extracted from the side of the mesocosm column, and the water flux. The relatively small variation provides confidence that the mesocosm system is a promising tool for studying a~range of processes in unsaturated environments. Meanwhile, high suction at the mesocosm bottom applied to reduce water ponding during intensive irrigation caused degassing of dissolved CO2 from the water phase just below the outlet, leading to diffusion of dissolved CO2 across the lower boundary. Though not influencing DIC flux measurements to the groundwater, this lead to a lowering of the pCO2 in the stagnant water at the mesocosm bottom. A free-drainage boundary is suggested in order to avoid this effect.

  2. Measurement of Boron and Carbon Fluxes in Cosmic Rays with the PAMELA Experiment

    NASA Astrophysics Data System (ADS)

    Adriani, O.; Barbarino, G. C.; Bazilevskaya, G. A.; Bellotti, R.; Boezio, M.; Bogomolov, E. A.; Bongi, M.; Bonvicini, V.; Bottai, S.; Bruno, A.; Cafagna, F.; Campana, D.; Carbone, R.; Carlson, P.; Casolino, M.; Castellini, G.; Danilchenko, I. A.; De Donato, C.; De Santis, C.; De Simone, N.; Di Felice, V.; Formato, V.; Galper, A. M.; Karelin, A. V.; Koldashov, S. V.; Koldobskiy, S.; Krutkov, S. Y.; Kvashnin, A. N.; Leonov, A.; Malakhov, V.; Marcelli, L.; Martucci, M.; Mayorov, A. G.; Menn, W.; Mergé, M.; Mikhailov, V. V.; Mocchiutti, E.; Monaco, A.; Mori, N.; Munini, R.; Osteria, G.; Palma, F.; Panico, B.; Papini, P.; Pearce, M.; Picozza, P.; Pizzolotto, C.; Ricci, M.; Ricciarini, S. B.; Rossetto, L.; Sarkar, R.; Scotti, V.; Simon, M.; Sparvoli, R.; Spillantini, P.; Stozhkov, Y. I.; Vacchi, A.; Vannuccini, E.; Vasilyev, G. I.; Voronov, S. A.; Yurkin, Y. T.; Zampa, G.; Zampa, N.; Zverev, V. G.

    2014-08-01

    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.

  3. Impact of vegetation cover variability on surface energy and carbon fluxes

    NASA Astrophysics Data System (ADS)

    Boussetta, Souhail; Balsamo, Gianpaolo; Dutra, Emanuel; Beljaars, Anton; Albergel, Clement; De Rosnay, Patricia; Munoz-Sabater, Joaquin

    2015-04-01

    The effects of vegetation coverage distributions on surface energy and carbon fluxes predictions from the land surface model are investigated. The model is applied at global scale and a comparison between two vegetation cover configurations is performed. In the first configuration, the vegetation cover is based on a fixed prescribed map, in the second the vegetation cover varies based on satellite observation of Leaf Area Index according to a modified Beer-Lamber law which includes vegetation clumping. The impact of consideration of vegetation cover variability on surface fluxes derived from offline runs of the ECMWF land surface scheme is studied. The near-surface air temperature and humidity derived from coupled runs using the ECMWF Integrated Forecasting system (IFS) and the carbon dioxide will be shown to respond to vegetation changes.

  4. Vertical flux of biogenic carbon in the ocean: Is there food web control?

    SciTech Connect

    Rivkin, R.B.; Legendre, L.; Deibel, D.

    1996-05-24

    Models of biogenic carbon (BC) flux assume that short herbivorous food chains lead to high export, whereas complex microbial or omnivorous food webs lead to recycling and low export, and that export of BC from the euphotic zone equals new production (NP). In the Gulf of St. Lawrence, particulate organic carbon fluxes were similar during the spring phytoplankton bloom, when herbivory dominated, and during nonbloom conditions, when microbial and omnivorous food webs dominated. In contrast, NP was 1.2 to 161 times greater during the bloom than after it. Thus, neither food web structure nor NP can predict the magnitude or patterns of BC export, particularly on time scales over which the ocean is in nonequilibrium conditions. 29 refs., 3 figs., 1 tab.

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

    SciTech Connect

    Adriani, O.; Bongi, M.; Barbarino, G. C.; Bazilevskaya, G. A.; Bellotti, R.; Bruno, A.; Boezio, M.; Bonvicini, V.; Carbone, R.; Bogomolov, E. A.; Bottai, S.; Cafagna, F.; Campana, D.; Carlson, P.; Casolino, M.; De Donato, C.; De Santis, C.; De Simone, N.; Castellini, G.; Danilchenko, I. A.; 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.

  6. Hotspots in ground and surface water carbon fluxes through a freshwater to marine (mangrove) transition zone

    NASA Astrophysics Data System (ADS)

    Larsen, J.; Welti, N.; Hayes, M.; Lockington, D. A.

    2014-12-01

    The transfer of carbon and water from coastal freshwater wetlands to intertidal and marine zones is significant for sustaining ecosystem processes, particularly within mangroves environments. Large increases in carbon and nutrient fluxes within spatially confined zones (hotspots) are significant as drivers for broader cycling. How these processes relate to the transfers between surface and groundwater systems, as well as the transition from freshwater to marine environments, remains poorly understood. We investigated the flux of carbon and water from a freshwater wetland, to a saltmarsh and then mangroves, both within the main surface channel and within a comprehensive shallow groundwater bore network. We were able to characterise the main spatial trends in water gradients and mixing (using salinity, hydraulic gradients, stable water isotopes, and temperature) over seasonal cycles. In addition, at the same time we investigated the changes in dissolved organic carbon concentration and quality (fluorescence, UV), as well as nutrients (NO3, NH4). This revealed the river and tidal channel to be a significant export pathway for organic carbon, which was generally highly aromatic and recalcitrant. However, we also found that isolated sections of the brackish groundwater mixing zone between freshwater and marine provided a consistently high DOC 'hotspot' of very high quality carbon. This hotspot has high lateral groundwater gradients and therefore likely transports this carbon to the rest of the mangrove subsurface, where it is rapidly assimilated. These results imply large spatial heterogeneity in the carbon cycling between freshwater and marine environments, and have significant implications for the processing of the organic matter, and therefore also the respiration of greenhouse gases such as CO2 and CH4.

  7. Seasonal Changes in Plankton Food Web Structure and Carbon Dioxide Flux from Southern California Reservoirs.

    PubMed

    Adamczyk, Emily M; Shurin, Jonathan B

    2015-01-01

    Reservoirs around the world contribute to cycling of carbon dioxide (CO2) with the atmosphere, but there is little information on how ecosystem processes determine the absorption or emission of CO2. Reservoirs are the most prevalent freshwater systems in the arid southwest of North America, yet it is unclear whether they sequester or release CO2 and therefore how water impoundment impacts global carbon cycling. We sampled three reservoirs in San Diego, California, weekly for one year. We measured seasonal variation in the abundances of bacteria, phytoplankton, and zooplankton, as well as water chemistry (pH, nutrients, ions, dissolved organic carbon [DOC]), which were used to estimate partial pressure of CO2 (pCO2), and CO2 flux. We found that San Diego reservoirs are most often undersaturated with CO2 with respect to the atmosphere and are estimated to absorb on average 3.22 mmol C m(-2) day(-1). pCO2 was highest in the winter and lower in the summer, indicating seasonal shifts in the magnitudes of photosynthesis and respiration associated with day length, temperature and water inputs. Abundances of microbes (bacteria) peaked in the winter along with pCO2, while phytoplankton, nutrients, zooplankton and DOC were all unrelated to pCO2. Our data indicate that reservoirs of semi-arid environments may primarily function as carbon sinks, and that carbon flux varies seasonally but is unrelated to nutrient or DOC availability, or the abundances of phytoplankton or zooplankton. PMID:26473601

  8. Seasonal Changes in Plankton Food Web Structure and Carbon Dioxide Flux from Southern California Reservoirs

    PubMed Central

    Adamczyk, Emily M.; Shurin, Jonathan B.

    2015-01-01

    Reservoirs around the world contribute to cycling of carbon dioxide (CO2) with the atmosphere, but there is little information on how ecosystem processes determine the absorption or emission of CO2. Reservoirs are the most prevalent freshwater systems in the arid southwest of North America, yet it is unclear whether they sequester or release CO2 and therefore how water impoundment impacts global carbon cycling. We sampled three reservoirs in San Diego, California, weekly for one year. We measured seasonal variation in the abundances of bacteria, phytoplankton, and zooplankton, as well as water chemistry (pH, nutrients, ions, dissolved organic carbon [DOC]), which were used to estimate partial pressure of CO2 (pCO2), and CO2 flux. We found that San Diego reservoirs are most often undersaturated with CO2 with respect to the atmosphere and are estimated to absorb on average 3.22 mmol C m-2 day-1. pCO2 was highest in the winter and lower in the summer, indicating seasonal shifts in the magnitudes of photosynthesis and respiration associated with day length, temperature and water inputs. Abundances of microbes (bacteria) peaked in the winter along with pCO2, while phytoplankton, nutrients, zooplankton and DOC were all unrelated to pCO2. Our data indicate that reservoirs of semi-arid environments may primarily function as carbon sinks, and that carbon flux varies seasonally but is unrelated to nutrient or DOC availability, or the abundances of phytoplankton or zooplankton. PMID:26473601

  9. Seasonal Changes in Plankton Food Web Structure and Carbon Dioxide Flux from Southern California Reservoirs.

    PubMed

    Adamczyk, Emily M; Shurin, Jonathan B

    2015-01-01

    Reservoirs around the world contribute to cycling of carbon dioxide (CO2) with the atmosphere, but there is little information on how ecosystem processes determine the absorption or emission of CO2. Reservoirs are the most prevalent freshwater systems in the arid southwest of North America, yet it is unclear whether they sequester or release CO2 and therefore how water impoundment impacts global carbon cycling. We sampled three reservoirs in San Diego, California, weekly for one year. We measured seasonal variation in the abundances of bacteria, phytoplankton, and zooplankton, as well as water chemistry (pH, nutrients, ions, dissolved organic carbon [DOC]), which were used to estimate partial pressure of CO2 (pCO2), and CO2 flux. We found that San Diego reservoirs are most often undersaturated with CO2 with respect to the atmosphere and are estimated to absorb on average 3.22 mmol C m(-2) day(-1). pCO2 was highest in the winter and lower in the summer, indicating seasonal shifts in the magnitudes of photosynthesis and respiration associated with day length, temperature and water inputs. Abundances of microbes (bacteria) peaked in the winter along with pCO2, while phytoplankton, nutrients, zooplankton and DOC were all unrelated to pCO2. Our data indicate that reservoirs of semi-arid environments may primarily function as carbon sinks, and that carbon flux varies seasonally but is unrelated to nutrient or DOC availability, or the abundances of phytoplankton or zooplankton.

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    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 CO2 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 CO2 uptake to water vapor loss) did not change. Between 2009 and 2011, canopy water conductance increased from 98.6 to 151.7 mmol H2O 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 CO2 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 CO2 exchange. These results agree with an emerging consensus in the literature demonstrating CO2 and H2O dynamics following large

  11. Metabolic Flux Ratio Analysis of Genetic and Environmental Modulations of Escherichia coli Central Carbon Metabolism

    PubMed Central

    Sauer, Uwe; Lasko, Daniel R.; Fiaux, Jocelyne; Hochuli, Michel; Glaser, Ralf; Szyperski, Thomas; Wüthrich, Kurt; Bailey, James E.

    1999-01-01

    The response of Escherichia coli central carbon metabolism to genetic and environmental manipulation has been studied by use of a recently developed methodology for metabolic flux ratio (METAFoR) analysis; this methodology can also directly reveal active metabolic pathways. Generation of fluxome data arrays by use of the METAFoR approach is based on two-dimensional 13C-1H correlation nuclear magnetic resonance spectroscopy with fractionally labeled biomass and, in contrast to metabolic flux analysis, does not require measurements of extracellular substrate and metabolite concentrations. METAFoR analyses of E. coli strains that moderately overexpress phosphofructokinase, pyruvate kinase, pyruvate decarboxylase, or alcohol dehydrogenase revealed that only a few flux ratios change in concert with the overexpression of these enzymes. Disruption of both pyruvate kinase isoenzymes resulted in altered flux ratios for reactions connecting the phosphoenolpyruvate (PEP) and pyruvate pools but did not significantly alter central metabolism. These data indicate remarkable robustness and rigidity in central carbon metabolism in the presence of genetic variation. More significant physiological changes and flux ratio differences were seen in response to altered environmental conditions. For example, in ammonia-limited chemostat cultures, compared to glucose-limited chemostat cultures, a reduced fraction of PEP molecules was derived through at least one transketolase reaction, and there was a higher relative contribution of anaplerotic PEP carboxylation than of the tricarboxylic acid (TCA) cycle for oxaloacetate synthesis. These two parameters also showed significant variation between aerobic and anaerobic batch cultures. Finally, two reactions catalyzed by PEP carboxykinase and malic enzyme were identified by METAFoR analysis; these had previously been considered absent in E. coli cells grown in glucose-containing media. Backward flux from the TCA cycle to glycolysis, as

  12. Explaining the redistribution of carbon dioxide fluxes seen in satellite-based inversions

    NASA Astrophysics Data System (ADS)

    Marshall, Julia; Rödenbeck, Christian; Reum, Friedemann; Nuñez Ramirez, Tonatiuh; Butz, Andre; Hasekamp, Otto; Heimann, Martin

    2015-04-01

    Flux inversions using GOSAT total column carbon dioxide measurements have shown significantly different patterns than those using the surface-based measurement network, with a substantially larger temperate northern hemisphere sink and a larger carbon source from tropical land. In particular the large sink found in Europe is difficult to reconcile with inventories and process models. These differences are quite consistent across inversion models and retrievals. At times the discrepancy between the two flux estimates has been discounted as an artefact due to undiagnosed systematic errors, poorly resolved transport, or sampling biases in the satellite measurements. None of these hypotheses has yet been proven convincingly, however, and the generally good agreement between the satellite retrievals and ground-based FTIR measurements from TCCON suggest that systematic errors are not to blame. This study presents evidence suggesting that the problem may instead lie with a sampling bias in the comparatively sparse surface network which, while constant in time, leaves large portions of the earth completely unsampled. This study presents simulations where satellite measurements were spatially filtered to include only those near the surface stations, and the resultant fluxes are found to converge to those based on surface measurements alone when increasingly tight spatial constraints are applied. This suggests that the location of the stations, even within a given region, has a significant impact on the flux pattern inferred. This study suggests that the information from the two data streams is in fact consistent, but that the surface network alone, while critical for the determination of interannual variability, particularly over longer time scales, is not sufficient to constrain the regional distribution of fluxes. These results support the robustness of the flux redistribution seen in satellite inversions. This raises further questions regarding how to harmonize these

  13. Landscape-level controls on dissolved carbon flux from diverse catchments of the circumboreal

    USGS Publications Warehouse

    Tank, Suzanne; Frey, Karen E.; Striegl, Robert G.; Raymond, Peter A.; Holmes, R. Max; McClelland, James W.; Peterson, Bruce J.

    2012-01-01

    While much of the dissolved organic carbon (DOC) within rivers is destined for mineralization to CO2, a substantial fraction of riverine bicarbonate (HCO3-) flux represents a CO2 sink, as a result of weathering processes that sequester CO2 as HCO3-. We explored landscape-level controls on DOC and HCO3- flux in subcatchments of the boreal, with a specific focus on the effect of permafrost on riverine dissolved C flux. To do this, we undertook a multivariate analysis that partitioned the variance attributable to known, key regulators of dissolved C flux (runoff, lithology, and vegetation) prior to examining the effect of permafrost, using riverine biogeochemistry data from a suite of subcatchments drawn from the Mackenzie, Yukon, East, and West Siberian regions of the circumboreal. Across the diverse catchments that we study, controls on HCO3- flux were near-universal: runoff and an increased carbonate rock contribution to weathering (assessed as riverwater Ca:Na) increased HCO3- yields, while increasing permafrost extent was associated with decreases in HCO3-. In contrast, permafrost had contrasting and region-specific effects on DOC yield, even after the variation caused by other key drivers of its flux had been accounted for. We used ionic ratios and SO4 yields to calculate the potential range of CO2 sequestered via weathering across these boreal subcatchments, and show that decreasing permafrost extent is associated with increases in weathering-mediated CO2 fixation across broad spatial scales, an effect that could counterbalance some of the organic C mineralization that is predicted with declining permafrost.

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

    NASA Astrophysics Data System (ADS)

    Sus, O.; Heuer, M. W.; Meyers, T. P.; Williams, M.

    2013-04-01

    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, observing carbon

  15. African tropical rainforest net carbon dioxide fluxes in the twentieth century.

    PubMed

    Fisher, Joshua B; Sikka, Munish; Sitch, Stephen; Ciais, Philippe; Poulter, Benjamin; Galbraith, David; Lee, Jung-Eun; Huntingford, Chris; Viovy, Nicolas; Zeng, Ning; Ahlström, Anders; Lomas, Mark R; Levy, Peter E; Frankenberg, Christian; Saatchi, Sassan; Malhi, Yadvinder

    2013-01-01

    The African humid tropical biome constitutes the second largest rainforest region, significantly impacts global carbon cycling and climate, and has undergone major changes in functioning owing to climate and land-use change over the past century. We assess changes and trends in CO₂ fluxes from 1901 to 2010 using nine land surface models forced with common driving data, and depict the inter-model variability as the uncertainty in fluxes. The biome is estimated to be a natural (no disturbance) net carbon sink (-0.02 kg C m⁻² yr⁻¹ or -0.04 Pg C yr⁻¹, p < 0.05) with increasing strength fourfold in the second half of the century. The models were in close agreement on net CO₂ flux at the beginning of the century (σ1901 = 0.02 kg C m⁻² yr⁻¹), but diverged exponentially throughout the century (σ2010 = 0.03 kg C m⁻² yr⁻¹). The increasing uncertainty is due to differences in sensitivity to increasing atmospheric CO₂, but not increasing water stress, despite a decrease in precipitation and increase in air temperature. However, the largest uncertainties were associated with the most extreme drought events of the century. These results highlight the need to constrain modelled CO₂ fluxes with increasing atmospheric CO₂ concentrations and extreme climatic events, as the uncertainties will only amplify in the next century. PMID:23878340

  16. African tropical rainforest net carbon dioxide fluxes in the twentieth century

    PubMed Central

    Fisher, Joshua B.; Sikka, Munish; Sitch, Stephen; Ciais, Philippe; Poulter, Benjamin; Galbraith, David; Lee, Jung-Eun; Huntingford, Chris; Viovy, Nicolas; Zeng, Ning; Ahlström, Anders; Lomas, Mark R.; Levy, Peter E.; Frankenberg, Christian; Saatchi, Sassan; Malhi, Yadvinder

    2013-01-01

    The African humid tropical biome constitutes the second largest rainforest region, significantly impacts global carbon cycling and climate, and has undergone major changes in functioning owing to climate and land-use change over the past century. We assess changes and trends in CO2 fluxes from 1901 to 2010 using nine land surface models forced with common driving data, and depict the inter-model variability as the uncertainty in fluxes. The biome is estimated to be a natural (no disturbance) net carbon sink (−0.02 kg C m−2 yr−1 or −0.04 Pg C yr−1, p < 0.05) with increasing strength fourfold in the second half of the century. The models were in close agreement on net CO2 flux at the beginning of the century (σ1901 = 0.02 kg C m−2 yr−1), but diverged exponentially throughout the century (σ2010 = 0.03 kg C m−2 yr−1). The increasing uncertainty is due to differences in sensitivity to increasing atmospheric CO2, but not increasing water stress, despite a decrease in precipitation and increase in air temperature. However, the largest uncertainties were associated with the most extreme drought events of the century. These results highlight the need to constrain modelled CO2 fluxes with increasing atmospheric CO2 concentrations and extreme climatic events, as the uncertainties will only amplify in the next century. PMID:23878340

  17. African tropical rainforest net carbon dioxide fluxes in the twentieth century.

    PubMed

    Fisher, Joshua B; Sikka, Munish; Sitch, Stephen; Ciais, Philippe; Poulter, Benjamin; Galbraith, David; Lee, Jung-Eun; Huntingford, Chris; Viovy, Nicolas; Zeng, Ning; Ahlström, Anders; Lomas, Mark R; Levy, Peter E; Frankenberg, Christian; Saatchi, Sassan; Malhi, Yadvinder

    2013-01-01

    The African humid tropical biome constitutes the second largest rainforest region, significantly impacts global carbon cycling and climate, and has undergone major changes in functioning owing to climate and land-use change over the past century. We assess changes and trends in CO₂ fluxes from 1901 to 2010 using nine land surface models forced with common driving data, and depict the inter-model variability as the uncertainty in fluxes. The biome is estimated to be a natural (no disturbance) net carbon sink (-0.02 kg C m⁻² yr⁻¹ or -0.04 Pg C yr⁻¹, p < 0.05) with increasing strength fourfold in the second half of the century. The models were in close agreement on net CO₂ flux at the beginning of the century (σ1901 = 0.02 kg C m⁻² yr⁻¹), but diverged exponentially throughout the century (σ2010 = 0.03 kg C m⁻² yr⁻¹). The increasing uncertainty is due to differences in sensitivity to increasing atmospheric CO₂, but not increasing water stress, despite a decrease in precipitation and increase in air temperature. However, the largest uncertainties were associated with the most extreme drought events of the century. These results highlight the need to constrain modelled CO₂ fluxes with increasing atmospheric CO₂ concentrations and extreme climatic events, as the uncertainties will only amplify in the next century.

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

    PubMed Central

    Li, Siyue; Bush, Richard T.

    2015-01-01

    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 SO42−, Cl− and Na+. The estimated fluxes of solutes from the Mekong decrease as follows (Mt/y): TDS (40.4) > HCO3− (23.4) > Ca2+ (6.4) > SO42− (3.8) > Cl− (1.74)~Na+ (1.7) ~ Si (1.67) > Mg2+ (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 34014 × 109 mol/y (0.41 Pg C/y), 3915 Mt/y for solute load, including HCO3−, and 13553 Mt/y for TSS. Thereby this study illustrates the importance of riverine solute delivery in global carbon cycling. PMID:26522820

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

    PubMed

    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.

  20. Determination of the carbon budget of a pasture: effect of system boundaries and flux uncertainties

    NASA Astrophysics Data System (ADS)

    Felber, Raphael; Bretscher, Daniel; Münger, Andreas; Neftel, Albrecht; Ammann, Christof

    2016-05-01

    Carbon (C) sequestration in the soil is considered as a potential important mechanism to mitigate greenhouse gas (GHG) emissions of the agricultural sector. It can be quantified by the net ecosystem carbon budget (NECB) describing the change of soil C as the sum of all relevant import and export fluxes. NECB was investigated here in detail for an intensively grazed dairy pasture in Switzerland. Two budget approaches with different system boundaries were applied: NECBtot for system boundaries including the grazing cows and NECBpast for system boundaries excluding the cows. CO2 and CH4 exchange induced by soil/vegetation processes as well as direct emissions by the animals were derived from eddy covariance measurements. Other C fluxes were either measured (milk yield, concentrate feeding) or derived based on animal performance data (intake, excreta). For the investigated year, both approaches resulted in a small near-neutral C budget: NECBtot -27 ± 62 and NECBpast 23 ± 76 g C m-2 yr-1. The considerable uncertainties, depending on the approach, were mainly due to errors in the CO2 exchange or in the animal-related fluxes. The comparison of the NECB results with the annual exchange of other GHG revealed CH4 emissions from the cows to be the major contributor in terms of CO2 equivalents, but with much lower uncertainty compared to NECB. Although only 1 year of data limit the representativeness of the carbon budget results, they demonstrate the important contribution of the non-CO2 fluxes depending on the chosen system boundaries and the effect of their propagated uncertainty in an exemplary way. The simultaneous application and comparison of both NECB approaches provides a useful consistency check for the carbon budget determination and can help to identify and eliminate systematic errors.

  1. Determination of the carbon budget of a pasture: effect of system boundaries and flux uncertainties

    NASA Astrophysics Data System (ADS)

    Felber, R.; Bretscher, D.; Münger, A.; Neftel, A.; Ammann, C.

    2015-12-01

    Carbon (C) sequestration in the soil is considered as a potential important mechanism to mitigate greenhouse gas (GHG) emissions of the agricultural sector. It can be quantified by the net ecosystem carbon budget (NECB) describing the change of soil C as the sum of all relevant import and export fluxes. NECB was investigated here in detail for an intensively grazed dairy pasture in Switzerland. Two budget approaches with different system boundaries were applied: NECBtot for system boundaries including the grazing cows and NECBpast for system boundaries excluding the cows. CO2 and CH4 exchange induced by soil/vegetation processes as well as direct emissions by the animals were derived from eddy covariance measurements. Other C fluxes were either measured (milk yield, concentrate feeding) or derived based on animal performance data (intake, excreta). For the investigated year, both approaches resulted in a small non-significant C loss: NECBtot - 13 ± 61 g C m-2 yr-1 and NECBpast - 17 ± 81 g C m-2 yr-1. The considerable uncertainties, depending on the approach, were mainly due to errors in the CO2 exchange or in the animal related fluxes. The associated GHG budget revealed CH4 emissions from the cows to be the major contributor, but with much lower uncertainty compared to NECB. Although only one year of data limit the representativeness of the carbon budget results, they demonstrated the important contribution of the non-CO2 fluxes depending on the chosen system boundaries and the effect of their propagated uncertainty in an exemplary way. The simultaneous application and comparison of both NECB approaches provides a useful consistency check for the carbon budget determination and can help to identify and eliminate systematic errors.

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

    NASA Astrophysics Data System (ADS)

    Czerny, J.; Schulz, K. G.; Boxhammer, T.; Bellerby, R. G. J.; Büdenbender, J.; Engel, A.; Krug, S. A.; Ludwig, A.; Nachtigall, K.; Nondal, G.; Niehoff, B.; Silyakova, A.; Riebesell, U.

    2013-05-01

    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 uptake in two of

  3. Estimating carbon fluxes in a Posidonia oceanica system: Paradox of the bacterial carbon demand

    NASA Astrophysics Data System (ADS)

    Velimirov, B.; Lejeune, P.; Kirschner, A.; Jousseaume, M.; Abadie, A.; Pête, D.; Dauby, P.; Richir, J.; Gobert, S.

    2016-03-01

    A mass balance ecosystemic approach, based on bacterial carbon demands and primary production data, was used to investigate if the bacterial community (freewater bacterioplankton and benthic bacteria of the oxygenated sediment layer) could be sustained by the main primary producers (Posidonia oceanica and its epiphytes, adjacent macroalgae and phytoplankton communities; hereafter called the P. oceanica system) of a non-eutrophic Mediterranean bay. Unexpectedly, the findings of this study differed from previous works that used benthic incubation chamber and O2 optode methods. In this study, data were grouped in two categories, corresponding to two time periods, according to the seawater temperature regime (<18 °C or >18 °C): from May to October and from November to April. Between May and October, the produced benthic macrophyte tissues could not provide the carbon required by the bacteria of the oxygenated sediment layer, showing that the balance production of the investigated bay was clearly heterotrophic (i.e. negative) during this time period. In contrast, between November and April, benthic bacteria respiration nearly equated to carbon production. When integrating the open water carbon dynamics above the meadow in the model, a negative carbon balance was still observed between May and October, while a slight carbon excess was noticed between November and April. In the light of these findings, the carbon balance being negative on an annual basis, alternative carbon sources are required for the maintenance of the bacterial carbon production.

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

    NASA Astrophysics Data System (ADS)

    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.

  5. Attenuation of sinking particulate organic carbon flux through the mesopelagic ocean.

    PubMed

    Marsay, Chris M; Sanders, Richard J; Henson, Stephanie A; Pabortsava, Katsiaryna; Achterberg, Eric P; Lampitt, Richard S

    2015-01-27

    The biological carbon pump, which transports particulate organic carbon (POC) from the surface to the deep ocean, plays an important role in regulating atmospheric carbon dioxide (CO2) concentrations. We know very little about geographical variability in the remineralization depth of this sinking material and less about what controls such variability. Here we present previously unpublished profiles of mesopelagic POC flux derived from neutrally buoyant sediment traps deployed in the North Atlantic, from which we calculate the remineralization length scale for each site. Combining these results with corresponding data from the North Pacific, we show that the observed variability in attenuation of vertical POC flux can largely be explained by temperature, with shallower remineralization occurring in warmer waters. This is seemingly inconsistent with conclusions drawn from earlier analyses of deep-sea sediment trap and export flux data, which suggest lowest transfer efficiency at high latitudes. However, the two patterns can be reconciled by considering relatively intense remineralization of a labile fraction of material in warm waters, followed by efficient downward transfer of the remaining refractory fraction, while in cold environments, a larger labile fraction undergoes slower remineralization that continues over a longer length scale. Based on the observed relationship, future increases in ocean temperature will likely lead to shallower remineralization of POC and hence reduced storage of CO2 by the ocean.

  6. Attenuation of sinking particulate organic carbon flux through the mesopelagic ocean

    PubMed Central

    Marsay, Chris M.; Sanders, Richard J.; Henson, Stephanie A.; Pabortsava, Katsiaryna; Achterberg, Eric P.; Lampitt, Richard S.

    2015-01-01

    The biological carbon pump, which transports particulate organic carbon (POC) from the surface to the deep ocean, plays an important role in regulating atmospheric carbon dioxide (CO2) concentrations. We know very little about geographical variability in the remineralization depth of this sinking material and less about what controls such variability. Here we present previously unpublished profiles of mesopelagic POC flux derived from neutrally buoyant sediment traps deployed in the North Atlantic, from which we calculate the remineralization length scale for each site. Combining these results with corresponding data from the North Pacific, we show that the observed variability in attenuation of vertical POC flux can largely be explained by temperature, with shallower remineralization occurring in warmer waters. This is seemingly inconsistent with conclusions drawn from earlier analyses of deep-sea sediment trap and export flux data, which suggest lowest transfer efficiency at high latitudes. However, the two patterns can be reconciled by considering relatively intense remineralization of a labile fraction of material in warm waters, followed by efficient downward transfer of the remaining refractory fraction, while in cold environments, a larger labile fraction undergoes slower remineralization that continues over a longer length scale. Based on the observed relationship, future increases in ocean temperature will likely lead to shallower remineralization of POC and hence reduced storage of CO2 by the ocean. PMID:25561526

  7. On the nature of the excess 100 micron flux associated with carbon stars

    NASA Technical Reports Server (NTRS)

    Egan, Michael P.; Leung, Chun M.

    1991-01-01

    The emission from carbon stars with circumstellar dust shells of different structure, composition, opacity, and age was modeled with the purpose of determining the origin of the excess flux in the FIR and testing the detached shell hypotheses of Willems (1987) and Olofsson et al. (1990). Three possible sources for the excess flux were identified: (1) cool dust in a single extended shell; (2) emission from dust in the intervening interstellar medium; or (3) emission from a two-shell system in which the additional shell is a remnant from an earlier mass-loss episode. It was found that only the two-shell model with a remnant shell which is at least 1 pc thick could explain the 60- and 100-micron flux excesses seen in carbon stars with dust shells of a given opacity. Calculations of time scales for the production of the detached shells and of the carbon star lifetime were found to be consistent with the evolutionary scenario proposed by Willems.

  8. Pools and fluxes of biogenic carbon in the former Soviet Union

    SciTech Connect

    Vinson, T.S.; Kolchugina, T.P.

    1993-01-01

    The former Soviet Union (FSU) was the largest country in the world. It occupied one-sixth of the land surface of the Earth. An understanding of the pools and fluxes of biogenic carbon in the FSU is essential to the development of international strategies aimed at mitigation of the negative impacts of global climate change. The vegetation of the FSU includes the following principal types: forest, woodland, shrubland, grassland, tundra, desert, peatlands, and cultivated land. Arctic deserts and tundra formations are found in the northern part; deserts and semi-deserts are found in the southern part. The territory is represented by a variety of climate conditions. The major part of the FSU territory is in the temperate climatic zone which changes from arctic and subarctic in the North to subtropical and desert in the South. The carbon pools and fluxes for all the ecoregions were summed to arrive at an initial estimate of the pools and fluxes of biogenic carbon for 95% of the FSU. (Copyright (c) 1993 Kluwer Academic Publishers.)

  9. [Factors affecting benzene diffusion from contaminated soils to the atmosphere and flux characteristics].

    PubMed

    Du, Ping; Wang, Shi-Jie; Zhao, Huan-Huan; Wu, Bin; Han, Chun-Mei; Fang, Ji-Dun; Li, Hui-Ying; Hosomi, Masaaki; Li, Fa-Sheng

    2013-12-01

    The influencing factors of benzene diffusion fluxes from sand and black soil to atmosphere were investigated using a flux chamber (30.0 cm x 17.5 cm x 29.0 cm). In this study, the benzene diffusion fluxes were estimated by measuring the benzene concentrations both in the headspace of the chamber and in the soils of different layers. The results indicated that the soil water content played an important role in benzene diffusion fluxes. The diffusion flux showed positive correlation with the initial benzene concentration and the benzene dissolution concentration for both soil types. The changes of air flow rate from 300 to 900 mL x min(-1) and temperature from 20 degrees C to 40 degrees C resulted in increases of the benzene diffusion flux. Our study of benzene diffusion fluxes from contaminated soils will be beneficial for the predicting model, and emergency management and precautions.

  10. Carbon fluxes acclimate more strongly to elevated growth temperatures than to elevated CO2 concentrations in a northern conifer.

    PubMed

    Kroner, Yulia; Way, Danielle A

    2016-08-01

    Increasing temperatures and atmospheric CO2 concentrations will affect tree carbon fluxes, generating potential feedbacks between forests and the global climate system. We studied how elevated temperatures and CO2 impacted leaf carbon dynamics in Norway spruce (Picea abies), a dominant northern forest species, to improve predictions of future photosynthetic and respiratory fluxes from high-latitude conifers. Seedlings were grown under ambient (AC, c. 435 μmol mol(-1) ) or elevated (EC, 750 μmol mol(-1) ) CO2 concentrations at ambient, +4 °C, or +8 °C growing temperatures. Photosynthetic rates (Asat ) were high in +4 °C/EC seedlings and lowest in +8 °C spruce, implying that moderate, but not extreme, climate change may stimulate carbon uptake. Asat , dark respiration (Rdark ), and light respiration (Rlight ) rates acclimated to temperature, but not CO2 : the thermal optimum of Asat increased, and Rdark and Rlight were suppressed under warming. In all treatments, the Q10 of Rlight (the relative increase in respiration for a 10 °C increase in leaf temperature) was 35% higher than the Q10 of Rdark , so the ratio of Rlight to Rdark increased with rising leaf temperature. However, across all treatments and a range of 10-40 °C leaf temperatures, a consistent relationship between Rlight and Rdark was found, which could be used to model Rlight in future climates. Acclimation reduced daily modeled respiratory losses from warm-grown seedlings by 22-56%. When Rlight was modeled as a constant fraction of Rdark , modeled daily respiratory losses were 11-65% greater than when using measured values of Rlight . Our findings highlight the impact of acclimation to future climates on predictions of carbon uptake and losses in northern trees, in particular the need to model daytime respiratory losses from direct measurements of Rlight or appropriate relationships with Rdark .

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

    SciTech Connect

    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.

  12. Increased water flux induced by an aquaporin-1/carbonic anhydrase II interaction

    PubMed Central

    Vilas, Gonzalo; Krishnan, Devishree; Loganathan, Sampath Kumar; Malhotra, Darpan; Liu, Lei; Beggs, Megan Rachele; Gena, Patrizia; Calamita, Giuseppe; Jung, Martin; Zimmermann, Richard; Tamma, Grazia; Casey, Joseph Roman; Alexander, Robert Todd

    2015-01-01

    Aquaporin-1 (AQP1) enables greatly enhanced water flux across plasma membranes. The cytosolic carboxy terminus of AQP1 has two acidic motifs homologous to known carbonic anhydrase II (CAII) binding sequences. CAII colocalizes with AQP1 in the renal proximal tubule. Expression of AQP1 with CAII in Xenopus oocytes or mammalian cells increased water flux relative to AQP1 expression alone. This required the amino-terminal sequence of CAII, a region that binds other transport proteins. Expression of catalytically inactive CAII failed to increase water flux through AQP1. Proximity ligation assays revealed close association of CAII and AQP1, an effect requiring the second acidic cluster of AQP1. This motif was also necessary for CAII to increase AQP1-mediated water flux. Red blood cell ghosts resealed with CAII demonstrated increased osmotic water permeability compared with ghosts resealed with albumin. Water flux across renal cortical membrane vesicles, measured by stopped-flow light scattering, was reduced in CAII-deficient mice compared with wild-type mice. These data are consistent with CAII increasing water conductance through AQP1 by a physical interaction between the two proteins. PMID:25609088

  13. Aspects of spatial and temporal aggregation in estimating regional carbon dioxide fluxes from temperate forest soils

    SciTech Connect

    Kicklighter, D.W.; Melillo, J.M.; Peterjohn, W.T.; Rastetter, E.B.; McGuire, A.D.; Steudler, P.A.; Aber, J.D.

    1994-01-20

    We examine the influence of aggregation errors on developing estimates of regional soil-CO{sub 2} flux from temperate forests. We find daily soil-CO{sub 2} fluxes to be more sensitive to changes in soil temperatures (Q{sub 10} = 3.08) than air temperatures (Q{sub 10} = 1.99). The direct use of mean monthly air temperatures with a daily flux model underestimates regional fluxes by approximately 4%. Temporal aggregation error varies with spatial resolution. Overall, our calibrated modeling approach reduces spatial aggregation error by 9.3% and temporal aggregation error by 15.5%. After minimizing spatial and temporal aggregation errors, mature temperate forest soils are estimated to contribute 12.9 Pg C yr{sup {minus}1} to the atmosphere as carbon dioxide. Georeferenced model estimates agree well with annual soil-CO{sub 2} fluxes measured during chamber studies in mature temperate forest stands around the globe. 75 refs., 8 figs., 5 tabs.

  14. Altered Seasonality and Magnitude of Rainfall Affects Soil Respiration and Nitrous Oxide Fluxes in California Annual Grassland

    NASA Astrophysics Data System (ADS)

    Chou, W. W.; Silver, W. L.; Jackson, R. D.; Allen-Diaz, B.

    2004-12-01

    Currently, climate models do not agree on how rising concentrations of CO2 and other greenhouse gases will affect rainfall in California. Changes in moisture regime will likely alter rates of carbon (C) loss via soil respiration, as well as fluxes of N2O. Moisture availability can also affect plant productivity in highly seasonal environments. We examined the consequences of wetter conditions in an annual grassland in the Sierra foothills of northern California by extending the duration of the wet season by about 5 weeks and augmenting total annual rainfall by approximately 50 %. Discrete wet-up events took place prior to the onset of natural rains (early October 2003) and early in the drought period (May 2004). Soil respiration, N2O and CH4 effluxes, N mineralization, and above- and belowground plant production were measured in treatment and control plots over a one-year period. Soil CO2 fluxes for the first treatment year, though large, were not statistically different between wet and control plots (1078 \\pm148 g C m-2 and 1006 \\pm138 g C m-2, respectively). The combined wet-up events comprised 17 % of the soil respiration over the 12-month period in treated plots, about twice as much C released by control plots during the same time interval. Aboveground biomass was similar between wetted and control plots (415 \\pm45 g m-2 y-1 and 374 \\pm36 g m-2 y-1, respectively), while root biomass increased significantly with wetting during the first year of treatment (179 \\pm23 g m-2 y-1 and 111 \\pm13 g m-2 y-1 for treatment and control plots, respectively). The additional biomass C gained in treatment plots (53 g C m-2) partly offset the greater losses from respired C observed in treatment plots (72 g C m-2). Nitrous oxide emissions were low to negligible during the year with the exception of the time directly following wet-up, when N2O emissions averaged over 78\\pm13 ng N cm-2 h-1. Our first year of water manipulation in annual grasslands suggests that increased

  15. Headwater management alters sources, flowpaths, and fluxes of water, carbon, and nitrogen in urban watersheds

    NASA Astrophysics Data System (ADS)

    Pennino, M. J.; Kaushal, S.; Mayer, P. M.; Welty, C.; Miller, A. J.

    2012-12-01

    Increased urbanization has altered watershed hydrology and increased nutrient pollution, leading to eutrophication and hypoxia in downstream coastal ecosystems. Due to urban stream degradation, there have been efforts to restore streams and reduce peak-flow discharges and contaminant export through stormwater management and stream restoration. However, there have been relatively few studies comparing watershed scale impacts of contrasting headwater management practices on sources and fluxes of water, carbon, and nutrients across space and time. In this study we compared sources and fluxes of water, carbon (C), and nitrogen (N) along 4 watersheds of contrasting headwater management: 2 urban degraded watersheds with minimal or no stormwater management and 2 managed urban watersheds with stormwater controls and stream restoration. Surface water samples were collected biweekly at USGS gauging stations located within each watershed over 2 years. Spatially, watersheds were sampled longitudinally during 4 seasons. Sources of water, nitrate, and carbon were investigated using isotopic and spectroscopic tracer techniques. Indicator anions (F-, Cl-, I-, SO42-) were also used to trace anthropogenic vs. natural water sources. Hydrologic flowpaths (groundwater vs. overland flow) were assessed with longitudinal synoptic surveys using stable water isotopes of H and O. Annual fluxes of water, C, and N, were estimated using the USGS program LOADEST. H and O isotope data showed that the source of stream water is primarily groundwater during summer months, with greater contributions from stormflow during winter months for all 4 watersheds. Elevated levels of indicator anions (F-, Cl-, I-, SO42-) as well as greater "pulses" of C and N over time in the degraded vs. managed watersheds indicate potential sewage sources due to leaky sanitary sewers and greater stormdrain inputs. Unlike the managed watersheds where hydrologic flowpaths were from groundwater in headwaters, the longitudinal

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

    NASA Astrophysics Data System (ADS)

    Helfter, Carole; Tremper, Anja H.; Halios, Christoforos H.; Kotthaus, Simone; Bjorkegren, Alex; Grimmond, C. Sue B.; Barlow, Janet F.; Nemitz, Eiko

    2016-08-01

    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 London. This is however not the case for CH4 emissions which are

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

    NASA Astrophysics Data System (ADS)

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

    2009-11-01

    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. Previous papers have utilized inversion regions formed by collapsing biome-similar grid cells into large aggregated regions. The effect of this is that the NEE correction 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. We perform the inversion with two independently derived boundary inflow conditions and calculate jackknife-based statistics to test

  18. Optimal recovery of regional carbon dioxide surface fluxes by data assimilation of anthropogenic and biogenic tracers

    NASA Astrophysics Data System (ADS)

    Campbell, Elliott

    Measurements of atmospheric carbon dioxide (CO2) have led to an understanding of the past and present CO2 trends at global scales. However, many of the processes that underlie the CO 2 fluxes are highly uncertain, especially at smaller spatial scales in the terrestrial biosphere. Our abilities to forecast climate change and manage the carbon cycle are reliant on an understanding of these underlying processes. In this dissertation, new steps were taken to understand the biogenic and anthropogenic processes based on analysis with an atmospheric transport model and simultaneous measurements of CO2 and other trace gases. The biogenic processes were addressed by developing an approach for quantifying photosynthesis and respiration surface fluxes using observations of CO 2 and carbonyl sulfide (COS). There is currently no reliable method for separating the influence of these gross biosphere fluxes on atmospheric CO2 concentrations. First, the plant sink for COS was quantified as a function of the CO2 photosynthesis uptake using the STEM transport model and measurements of COS and CO2 from the INTEX-NA campaign. Next, the STEM inversion model was modified for the simultaneous optimization of fluxes using COS and CO2 measurements and using only CO 2 measurements. The CO2-only inversion was found to be process blind, while the simultaneous COS/CO2 inversion was found to provide a unique estimate of the respiration and photosynthesis component fluxes. Further validation should be pursued with independent observations. The approach presented here is the first application of COS measurements for inferring information about the carbon cycle. Anthropogenic emissions were addressed by improving the estimate of the fossil fuel component of observed CO2 by using observed carbon monoxide (CO). Recent applications of the CO approach were based on simple approximations of non-fossil fuel influences on the measured CO such as sources from oxidation of volatile organic carbon species

  19. Cold ecosystems in a warmer climate: carbon fluxes at the alpine treeline under experimental soil warming

    NASA Astrophysics Data System (ADS)

    Wipf, Sonja; Hagedorn, Frank; Martin, Melissa

    2010-05-01

    The impact of climatic warming on the C balance of terrestrial ecosystems is uncertain because rising temperature increases both C gains through net primary production, but also respiratory C losses. 'Cold' ecosystems such as treeline ecotones will respond particularly sensitive to climatic changes because many processes are limited by temperature and soils store particular large amounts of labile soil organic matter. In our study, we investigate ecosystem responses to 9 years of elevated atmospheric CO2 and to 3 years of experimental soil warming by 4° C. The added CO2 contains another δ13C signature than normal air, which allows the tracing of new carbon through the plant and soil system. This provides new insight into carbon cycling at the treeline and it shows which C flux respond most sensitive to climatic changes. Results showed that soil warming increased soil CO2 effluxes instantaneously and persisted for at least three vegetation periods (+35-45%; +80 to 120 g C m y-1). In contrast, DOC leaching showed a negligible response of less than 5% increase. Annual C uptake of new shoots was not significantly affected by elevated soil temperatures, with a 10 to 20% increase for larch, pine, and dwarf shrubs, respectively, resulting in an overall increase in net C uptake by plants of 20 to 40 g C m-2y-1. The Q10 of 3.0 measured for soil respiration did not change compared to a three-year period before the warming treatment started, suggesting little impact of warming-induced lower soil moisture (-15% relative decrease) or a depletion in labile soil C. The fraction of recent plant-derived C in soil respired CO2 from warmed soils was smaller than that from control soils (25 vs. 40% of total C respired), which implies that the warming-induced increase in soil CO2 efflux resulted mainly from mineralization of older SOM rather than from stimulated root respiration. In summary, the 4 ° C soil warming led to C losses from the studied alpine treeline ecosystem by

  20. Water- and Plant-Mediated Responses of Ecosystem Carbon Fluxes to Warming and Nitrogen Addition on the Songnen Grassland in Northeast China

    PubMed Central

    Jiang, Li; Guo, Rui; Zhu, Tingcheng; Niu, Xuedun; Guo, Jixun; Sun, Wei

    2012-01-01

    Background Understanding how grasslands are affected by a long-term increase in temperature is crucial to predict the future impact of global climate change on terrestrial ecosystems. Additionally, it is not clear how the effects of global warming on grassland productivity are going to be altered by increased N deposition and N addition. Methodology/Principal Findings In-situ canopy CO2 exchange rates were measured in a meadow steppe subjected to 4-year warming and nitrogen addition treatments. Warming treatment reduced net ecosystem CO2 exchange (NEE) and increased ecosystem respiration (ER); but had no significant impacts on gross ecosystem productivity (GEP). N addition increased NEE, ER and GEP. However, there were no significant interactions between N addition and warming. The variation of NEE during the four experimental years was correlated with soil water content, particularly during early spring, suggesting that water availability is a primary driver of carbon fluxes in the studied semi-arid grassland. Conclusion/Significance Ecosystem carbon fluxes in grassland ecosystems are sensitive to warming and N addition. In the studied water-limited grassland, both warming and N addition influence ecosystem carbon fluxes by affecting water availability, which is the primary driver in many arid and semiarid ecosystems. It remains unknown to what extent the long-term N addition would affect the turn-over of soil organic matter and the C sink size of this grassland. PMID:23028848

  1. Carbon fluxes forced by anticyclonic mesoscale eddies generated by islands at the subtropical NE Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Lasternas, S.; Piedeleu, M.; Sangrà, P.; Duarte, C. M.; Agustí, S.

    2012-08-01

    The carbon fluxes mediated by planktonic communities in two cyclonic eddies (CEs) and two anticyclonic eddies (AEs) at the Canary Eddy Corridor were studied and compared with the dynamics in two far-field (FF) stations located outside the eddies. We observed favorable conditions and signs for upwelling at the center of CEs and for downwelling and mixing at the centers of AEs. CEs were characterized by higher nutrients concentration and highest chlorophyll a concentration, associated with highest microphytoplankton and diatoms abundance. AEs displayed similar chlorophyll a values and nutrients concentration (except highest ammonium concentration) to those of the FF stations and were characterized by increasing abundance of picophytoplankton and heterotrophic bacteria. While primary production was similar between the systems, the production of dissolved organic carbon (PDOC) was significantly higher at AEs. Phytoplankton cell mortality was lowest in CEs and we found higher cell mortality in AE than FF, despite similar chl a concentration. Environmental changes at the AEs presented significant prejudicial effects on the phytoplankton health as indicated by higher phytoplankton mortality (e.g. 60% of dead diatoms cells) and higher cell lysis rates observed at AEs than at two other systems. The adverse conditions associated to the early-stage anticyclonic systems, mainly triggered by active downwelling, resulted in higher consequent PDOC production, corresponding to forcing of the carbon flux to the dissolved pool and a weakness of the carbon pump.

  2. Assessing the magnitude of CO2 flux uncertainty in atmospheric CO2 records using products from NASA's Carbon Monitoring Flux Pilot Project

    NASA Astrophysics Data System (ADS)

    Ott, Lesley E.; Pawson, Steven; Collatz, George J.; Gregg, Watson W.; Menemenlis, Dimitris; Brix, Holger; Rousseaux, Cecile S.; Bowman, Kevin W.; Liu, Junjie; Eldering, Annmarie; Gunson, Michael R.; Kawa, Stephan R.

    2015-01-01

    Carbon Monitoring System Flux Pilot Project (FPP) was designed to better understand contemporary carbon fluxes by bringing together state-of-the art models with remote sensing data sets. Here we report on simulations using NASA's Goddard Earth Observing System Model, version 5 (GEOS-5) which was used to evaluate the consistency of two different sets of observationally informed land and ocean fluxes with atmospheric CO2 records. Despite the observation inputs, the average difference in annual terrestrial biosphere flux between the two land (NASA Ames Carnegie-Ames-Stanford-Approach (CASA) and CASA-Global Fire Emissions Database version 3 (GFED)) models is 1.7 Pg C for 2009-2010. Ocean models (NASA's Ocean Biogeochemical Model (NOBM) and Estimating the Circulation and Climate of the Ocean Phase II (ECCO2)-Darwin) differ by 35% in their global estimates of carbon flux with particularly strong disagreement in high latitudes. Based upon combinations of terrestrial and ocean fluxes, GEOS-5 reasonably simulated the seasonal cycle observed at Northern Hemisphere surface sites and by the Greenhouse gases Observing SATellite (GOSAT) while the model struggled to simulate the seasonal cycle at Southern Hemisphere surface locations. Though GEOS-5 was able to reasonably reproduce the patterns of XCO2 observed by GOSAT, it struggled to reproduce these aspects of Atmospheric Infrared Sounder observations. Despite large differences between land and ocean flux estimates, resulting differences in atmospheric mixing ratio were small, typically less than 5 ppm at the surface and 3 ppm in the XCO2 column. A statistical analysis based on the variability of observations shows that flux differences of these magnitudes are difficult to distinguish from inherent measurement variability, regardless of the measurement platform.

  3. EFFECTS OF CO2 AND O3 ON CARBON FLUX FOR PONDEROSA PINE PLANT/LITTER/SOIL SYSTEM

    EPA Science Inventory

    Carbon dioxide (CO2), a main contributor to global climate change, also adds carbon to forests. In contrast, tropospheric ozone (O3) can reduce carbon uptake and increase carbon loss by forests. Thus, the net balance of carbon uptake and loss for forests can be affected by concu...

  4. Small-scale variability in the coupling/uncoupling of bacteria, phytoplankton and organic carbon fluxes along the continental margin of the Gulf of Lions, Northwestern Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Van Wambeke, F.; Heussner, S.; Diaz, F.; Raimbault, P.; Conan, P.

    2002-06-01

    A High Frequency Flux (HFF) experiment was conducted during spring 1997 on the continental slope of the Gulf of Lions (Northwestern Mediterranean Sea) with the aim of examining the dynamical and biological processes controlling particle transfer in this margin environment. Within this general framework, a special attention was paid to short temporal and small spatial variations of phytoplankton and bacterial production through six hydrological and biological surveys performed during a 7-week period at nine sampling stations located on a 10×20-mile grid. Downward fluxes of particulate organic carbon at each station were measured by traps deployed at 240 m depth. The f-ratio and the ratio of integrated bacterial to primary production (IBP/IPP ratio), computed as indexes of biological export for each survey and station, did not provide a clear, unambiguous understanding of the importance of biological processes in the cycling of carbon in the upper water column. However, the data collected allowed to draw up carbon budgets for the different phases of the experiment. The comparison of primary production with measured and estimated organic carbon removal terms (sinking, cycling through the microbial food web, grazing by ciliates and metazoans) showed that a balance was never reached between fluxes of production and removal of organic carbon during the course of the experiment. The system shifted from an initial situation of 'missing' carbon (removal>production) to one of 'excess' carbon (removalcarbon into and out of the experimental area and accumulation of dissolved organic carbon (dissolved biological pump) are invoked to explain the observed imbalances. A sensitivity test of the budget to the variations of the different parameters involved showed that bacterial growth efficiency was the most important factor affecting the budget.

  5. Fluxes of nitrous oxide and carbon dioxide over four potential biofuel crops in Central Illinois

    NASA Astrophysics Data System (ADS)

    Zeri, M.; Hickman, G. C.; Bernacchi, C.

    2009-12-01

    Nitrous oxide (N2O) and carbon dioxide (CO2) are important greenhouse gases that contribute to global climate change. Agriculture is a significant source of N2O to the atmosphere due to the use of nitrogen-based fertilizers. Fluxes of N2O and CO2 are measured using the flux-gradient technique over four different crops at the Energy Farm, a University of Illinois research facility in Urbana, Illinois. Measurements started in June of 2009 and are part of a project that aims to assess the impacts of potential biofuel crops on the carbon, water and nitrogen cycles. The species chosen are Maize (Zea mays), Miscanthus (Miscanthus x giganteus), Switchgrass (Panicum virgatum) and Prairie (a mix of several native species). The choice of species was based on their potential for the production of second-generation biofuels, i.e., fuels derived from the decomposition of the cellulosic material in the plant biomass. The use of corn residue for cellulosic biofuels might impact the carbon cycle through the reduction of soil organic content. Miscanthus is a perennial grass with great potential for biomass production. However, the total water used during the growing season and its water use efficiency might impose limits on the regions where this biofuel crop can be sustainably planted on a large scale. Switchgrass and the prairie species are less productive but might be suited for being well adapted and easy to establish. This study is the first side-by-side comparison of fluxes of N2O for these agro-ecosystems. The measurements are performed at micrometeorological towers placed at the center of 4 ha plots. The air is sampled at two heights over the vegetation and is analyzed in a tunable diode laser (TDL) installed nearby. A valve system cycles the TDL measurements trough all the intakes in the plots. The fluxes are calculated using the flux-gradient method, which requires the knowledge of the scalar vertical gradient as well as of the friction velocity (u*) and the Monin

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

    PubMed

    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.

  7. Carbon dioxide and energy fluxes over a small boreal lake in Southern Finland

    NASA Astrophysics Data System (ADS)

    Mammarella, Ivan; Nordbo, Annika; Rannik, Üllar; Haapanala, Sami; Levula, Janne; Laakso, Heikki; Ojala, Anne; Peltola, Olli; Heiskanen, Jouni; Pumpanen, Jukka; Vesala, Timo

    2015-07-01

    Dynamics of carbon dioxide and energy exchange over a small boreal lake were investigated. Flux measurements have been carried out by the eddy covariance technique during two open-water periods (June-October) at Lake Kuivajärvi in Finland. Sensible heat (H) flux peaked in the early morning, and upward sensible heat flux at night results in unstable stratification over the lake. Minimum H was measured in the late afternoon, often resulting in adiabatic conditions or slightly stable stratification over the lake. The latent heat flux (LE) showed a different pattern, peaking in the afternoon and having a minimum at night. High correlation (r2 = 0.75) between H and water-air temperature difference multiplied by wind speed (U) was found, while LE strongly correlated with the water vapor pressure deficit multiplied by U (r2 = 0.78). Monthly average values of energy balance closure ranged between 70 and 99%. The lake acted as net source of carbon dioxide, and the measured flux (FCO2) averaged over the two open-water periods (0.7 µmol m-2 s-1) was up to 3 times higher than those reported in other studies. Furthermore, it was found that during period of high wind speed (>3 m s-1) shear-induced water turbulence controls the water-air gas transfer efficiency. However, under calm nighttime conditions, FCO2 was poorly correlated with the difference between the water and the equilibrium CO2 concentrations multiplied by U. Nighttime cooling of surface water enhances the gas transfer efficiency through buoyancy-driven turbulent mixing, and simple wind speed-based transfer velocity models strongly underestimate FCO2.

  8. Trends in long-term carbon and water fluxes - a case study from a temperate Norway spruce site

    NASA Astrophysics Data System (ADS)

    Babel, Wolfgang; Lüers, Johannes; Hübner, Jörg; Serafimovich, Andrei; Thomas, Christoph; Foken, Thomas

    2016-04-01

    In this study we analyse eddy-covariance flux measurements of carbon dioxide and water vapour from 18 years at Waldstein-Weidenbrunnen (DE-Bay), a Norway spruce forest site in the Fichtelgebirge, Germany. Standard flux partitioning algorithms have been applied for separation of net ecosystem exchange NEE into gross ecosystem uptake GEE and ecosystem respiration Reco, and gap-filling. The annual NEE shows a positive trend, which is related to a strong increase in GEE, while Reco enhances slightly. Annual evapotranspiration increases as well, while atmospheric demand, i.e. potential evapotranspiration, shows inter-annual variability, but no trend. Comparisons with studies from other warm temperate needle-leaved forests show, that NEE is at the upper range of the distribution, and evapotranspiration in Budyko space is in a similar range, but with a large inter-annual variability. While this trends are generally in agreement with findings from other locations and expectations to climate change, the specific history at this site clearly has a large impact on the results: The forest was in the first years very much affected due to forest decline and convalesced after a liming. In the last ten years the site was much affected by beetles and windthrow. Thus the more recent positive trends may be related to increased heterogeneity at the site. As FLUXNET stations, built 10-20 years ago, often started with "ideal forest sites", increasing heterogeneity might be a more general problem for trend analysis of long-term data sets.

  9. The Yeast Cyclin-Dependent Kinase Routes Carbon Fluxes to Fuel Cell Cycle Progression.

    PubMed

    Ewald, Jennifer C; Kuehne, Andreas; Zamboni, Nicola; Skotheim, Jan M

    2016-05-19

    Cell division entails a sequence of processes whose specific demands for biosynthetic precursors and energy place dynamic requirements on metabolism. However, little is known about how metabolic fluxes are coordinated with the cell division cycle. Here, we examine budding yeast to show that more than half of all measured metabolites change significantly through the cell division cycle. Cell cycle-dependent changes in central carbon metabolism are controlled by the cyclin-dependent kinase (Cdk1), a major cell cycle regulator, and the metabolic regulator protein kinase A. At the G1/S transition, Cdk1 phosphorylates and activates the enzyme Nth1, which funnels the storage carbohydrate trehalose into central carbon metabolism. Trehalose utilization fuels anabolic processes required to reliably complete cell division. Thus, the cell cycle entrains carbon metabolism to fuel biosynthesis. Because the oscillation of Cdk activity is a conserved feature of the eukaryotic cell cycle, we anticipate its frequent use in dynamically regulating metabolism for efficient proliferation.

  10. Grain boundary mobility of carbon in Earth's mantle: a possible carbon flux from the core.

    PubMed

    Hayden, Leslie A; Watson, E Bruce

    2008-06-24

    The importance of carbon in Earth's mantle greatly exceeds its modest abundance of approximately 1,000-4,000 ppm. Carbon is a constituent of key terrestrial volatiles (CO, CO(2), CH(4)), it forms diamonds, and it may also contribute to the bulk electrical properties of the silicate Earth. In contrast to that of the mantle, the carbon content of Earth's metallic core may be quite high ( approximately 5 wt %), raising the possibility that the core has supplied carbon to the mantle over geologic time. The plausibility of this process depends in part upon the mobility of carbon atoms in the solid mantle. Grain boundaries of mantle minerals could represent fast pathways for transport as well as localized sites for enrichment and storage of carbon. Here, we report the results of an experimental study of grain-boundary diffusion of carbon through polycrystalline periclase (MgO) and olivine ([Mg,Fe](2)SiO(4)) that were obtained by determining the extent of solid solution formation between a graphite source and a metal sink (Ni or Fe) separated by the polycrystalline materials. Experimental materials were annealed at 1,373-1,773 K and 1.5-2.5 GPa pressure. Calculated diffusivities, which range up to 10(-11) m(2).s(-1), are fast enough to allow transport over geologically significant length scales ( approximately 10 km) over the age of the Earth. Mobility and enrichment of carbon on grain boundaries may also explain the high electrical conductivity of upper mantle rocks, and could result in the formation of C-H-O volatiles through interactions of core-derived C with recycled H(2)O in subduction zones.

  11. Grain boundary mobility of carbon in Earth's mantle: A possible carbon flux from the core

    PubMed Central

    Hayden, Leslie A.; Watson, E. Bruce

    2008-01-01

    The importance of carbon in Earth's mantle greatly exceeds its modest abundance of ≈1,000–4,000 ppm. Carbon is a constituent of key terrestrial volatiles (CO, CO2, CH4), it forms diamonds, and it may also contribute to the bulk electrical properties of the silicate Earth. In contrast to that of the mantle, the carbon content of Earth's metallic core may be quite high (≈5 wt %), raising the possibility that the core has supplied carbon to the mantle over geologic time. The plausibility of this process depends in part upon the mobility of carbon atoms in the solid mantle. Grain boundaries of mantle minerals could represent fast pathways for transport as well as localized sites for enrichment and storage of carbon. Here, we report the results of an experimental study of grain-boundary diffusion of carbon through polycrystalline periclase (MgO) and olivine ([Mg,Fe]2SiO4) that were obtained by determining the extent of solid solution formation between a graphite source and a metal sink (Ni or Fe) separated by the polycrystalline materials. Experimental materials were annealed at 1,373–1,773 K and 1.5–2.5 GPa pressure. Calculated diffusivities, which range up to 10−11 m2·s−1, are fast enough to allow transport over geologically significant length scales (≈10 km) over the age of the Earth. Mobility and enrichment of carbon on grain boundaries may also explain the high electrical conductivity of upper mantle rocks, and could result in the formation of C-H-O volatiles through interactions of core-derived C with recycled H2O in subduction zones. PMID:18559860

  12. Grazing alters the biophysical regulation of carbon fluxes in a desert steppe

    NASA Astrophysics Data System (ADS)

    Shao, Changliang; Chen, Jiquan; Li, Linghao

    2013-06-01

    To determine the role of grazing on CO2 fluxes in a desert steppe, we used paired eddy-covariance systems to measure the net ecosystem exchange (NEE) and microclimate on adjacent pastures of grazed (GS) and ungrazed (FS) steppes on the Mongolian Plateau from 2010 to 2011. The first year was an average precipitation year, while the second year was a dry year. In 2010, there was 91% greater growing seasonal gross ecosystem production (GEP) and 55% greater ecosystem respiration (Re) in the GS than in the FS. As a result, the GS acted as a net carbon uptake of -20 g C m-2 while the FS was a small net carbon release of 10 g C m-2. The greater GEP was mainly caused by the greater photosynthetic capacity due to the suitable environmental conditions and longer growing time in a day and in the growing period accompanied by the enhanced Re that seemed to be responsible for the increased NEE, which compensated for the lower leaf area in the GS. However, an inverse trend was detected in 2011. The seasonal cumulative GEP, Re and NEE were characterized with 92% greater GEP and similar Re in the FS compared with the GS. As a result, the FS acted as a small net carbon uptake of -5 g C m-2, while the GS was a net carbon release of 59 g C m-2. Although the GS had greater carbon uptake in 2010, the variation of daily NEE from both years was lower in the FS, suggesting that the FS has a greater resistance to the changing climate. This also means that future modeling effort should consider year-to-year differences in the carbon balance because relationships between fluxes and climatic regulators change annually in different land use change scenarios.

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

    NASA Astrophysics Data System (ADS)

    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

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

    PubMed

    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.

  15. Large Carbon Dioxide Fluxes from Headwater Boreal and Sub-Boreal Streams

    PubMed Central

    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. PMID:25058488

  16. Impact of vegetation cover and stand age on scaling carbon fluxes in the upper Midwest: a multiple eddy flux site study

    NASA Astrophysics Data System (ADS)

    Desai, A. R.; Normeets, A.; Bolstad, P. V.; Chen, J.; Cook, B. D.; Curtis, P. S.; Davis, K. J.; Euskirchen, E.; Gough, C.; Martin, J.; Ricciuto, D. M.; Schmid, H. P.; Tang, J.; Su, H.; Vogel, C.; Wang, W.

    2004-12-01

    Eight permanent and three roving eddy flux towers were used to observe the exchange of carbon dioxide between the ecosystem and atmosphere at fourteen different sites in northern Wisconsin and Michigan (USA) during the growing seasons (May-Sept) of 2002 and 2003. These towers were part of the Chequamegon Ecosystem-Atmosphere Study (ChEAS), the University of Michigan Biological Station (UMBS), and the Michigan Technical University. The sites spanned a range of vegetation types typical of the region (northern hardwood, hemlock-hardwood, mixed forest, red pine, jack pine, pine barrens and shrub wetland). The hardwood and red pine sites also spanned a range of forest stand age (young, intermediate, mature and old). All sites experienced roughly similar climate; thus, comparisons among the sites allow for an examination of the impact of heterogeneous vegetation cover and stand age across a regional landscape. Carbon fluxes at different sites generally reacted similarly in response to variability in climate. Results suggest that both cover type and stand age are important variables for modeling and predicting fluxes in this region. These results have implications for developing methods of scaling carbon dioxide fluxes from sites to regions. These results will be contrasted to a flux decomposition at the WLEF tall tower.

  17. Fluxes of Dissolved Organic Carbon within Soils across a Boreal Forest Ecosystem Latitudinal Transect

    NASA Astrophysics Data System (ADS)

    Bowering, K.; Edwards, K.; Billings, S. A.; Skinner, A.; Warren, J.; Ziegler, S. E.

    2013-12-01

    The movement of dissolved organic carbon (DOC) can represent a significant flux of C within soils, and may be a critical flux of C from the terrestrial into the aquatic environment. Further, these fluxes can represent an important source of C to deeper mineral horizons where stabilization mechanisms may exist. However the quantity and quality of this C flux is largely unknown, and regulating factors that are influenced by climate and land-use change are poorly understood. This movement of C is of particular interest in the boreal forest, where large soil C stocks are vulnerable to the impacts of climate change. Laboratory experiments have demonstrated that warming, in the absence of moisture limitation, can increase the rate of production of DOC in soils directly through increased decomposition rates; however, this has been difficult to test under field conditions where seasonality, intact soil, and hydrological systems influence DOC production and movement. To assess the impact of climate warming on DOC fluxes occurring through the organic soil layer of the eastern North American boreal forest, we sampled passive lysimeters installed at 3 sites along a latitudinal transect in Newfoundland and Labrador, Canada. Separated by just over 5° latitude, mean annual temperature at these sites were 4°C, 2.1°C, and -0.5°C from lowest to highest latitude. Six lysimeters were sampled from each site and collections were made at least three times annually for two consecutive years (2011-2013). Soils tend to freeze over-winter in the high-latitude site whereas they rarely freeze in the low-latitude site. The low-latitude site also experiences more variable precipitation, with a longer snow-free season and more precipitation falling during single events. Rates of DOC flux increased with decreasing latitude, indicating greater DOC transport through soils in forests experiencing a warmer climate. DOC fluxes calculated over different seasonal time periods ranged from 4.6 to 20

  18. Plant phenology and composition controls of carbon fluxes in a boreal peatland

    NASA Astrophysics Data System (ADS)

    Peichl, Matthias; Gažovič, Michal; Vermeij, Ilse; De Goede, Eefje; Sonnentag, Oliver; Limpens, Juul; Nilsson, Mats B.

    2016-04-01

    Vegetation drives the peatland carbon (C) cycle via the processes of photosynthesis, plant respiration and decomposition as well as by providing substrate for methane (CH4) and dissolved organic carbon production. However, due to the lack of comprehensive vegetation data, variations in the peatland C fluxes are commonly related to temperature and other more easily measured abiotic (i.e. weather and soil) variables. Due to the temporal co-linearity between plant development and abiotic variables, these relationships may describe the variations in C fluxes reasonably well, however, without representing the true mechanistic processes driving the peatland C cycle. As a consequence, current process-based models are poorly parameterized and unable to adequately predict the responses of the peatland C cycle to climate change, extreme events and anthropogenic impacts. To fill this knowledge gap, we explored vegetation phenology and composition effects on the peatland C cycle at the Degerö peatland located in northern Sweden. We used a greenness index derived from digital repeat photography to quantitatively describe plant canopy development with high temporal (i.e. daily) and spatial (plot to ecosystem) resolution. In addition, eddy covariance and static chamber measurements of carbon dioxide (CO2) and CH4 fluxes over an array of vegetation manipulation plots were conducted over multiple years. Our results suggest that vascular plant phenology controls the onset and pattern of eddy covariance-derived gross primary production (GPP) during the spring period, while abiotic conditions modify GPP during the summer period when plant canopy cover is fully developed. Inter-annual variations in the spring onset and patterns of plant canopy development were best explained by differences in the preceding growing degree day sum. We also observed strong correlations of canopy greenness with the net ecosystem CO2 exchange and ecosystem respiration. On average, vascular plant and moss

  19. Wildfires in a warmer climate: Emission fluxes, emission heights, and black carbon concentrations in 2090-2099

    NASA Astrophysics Data System (ADS)

    Veira, A.; Lasslop, G.; Kloster, S.

    2016-04-01

    Global warming is expected to considerably impact wildfire activity and aerosol emission release in the future. Due to their complexity, the future interactions between climate change, wildfire activity, emission release, and atmospheric aerosol processes are still uncertain. Here we use the process-based fire model SPITFIRE within the global vegetation model JSBACH to simulate wildfire activity for present-day climate conditions and future Representative Concentration Pathways (RCPs). The modeled fire emission fluxes and fire radiative power serve as input for the aerosol-climate model ECHAM6-HAM2, which has been extended by a semiempirical plume height parametrization. Our results indicate a general increase in extratropical and a decrease in tropical wildfire activity at the end of the 21st century. Changes in emission fluxes are most pronounced for the strongest warming scenario RCP8.5 (+49% in the extratropics, -37% in the tropics). Tropospheric black carbon (BC) concentrations are similarly affected by changes in emission fluxes and changes in climate conditions with regional variations of up to -50% to +100%. In the Northern Hemispheric extratropics, we attribute a mean increase in aerosol optical thickness of +0.031±0.002 to changes in wildfire emissions. Due to the compensating effects of fire intensification and more stable atmospheric conditions, global mean emission heights change by at most 0.3 km with only minor influence on BC long-range transport. The changes in wildfire emission fluxes for the RCP8.5 scenario, however, may largely compensate the projected reduction in anthropogenic BC emissions by the end of the 21st century.

  20. Effects of sinking velocities and microbial respiration rates on the attenuation of particulate carbon fluxes through the mesopelagic zone

    NASA Astrophysics Data System (ADS)

    McDonnell, A. M. P.; Boyd, P. W.; Buesseler, K. O.

    2015-02-01

    The attenuation of sinking particle fluxes through the mesopelagic zone is an important process that controls the sequestration of carbon and the distribution of other elements throughout the oceans. Case studies at two contrasting sites, the oligotrophic regime of the Bermuda Atlantic Time-series Study (BATS) and the mesotrophic waters of the west Antarctic Peninsula (WAP) sector of the Southern Ocean, revealed large differences in the rates of particle-attached microbial respiration and the average sinking velocities of marine particles, two parameters that affect the transfer efficiency of particulate matter from the base of the euphotic zone into the deep ocean. Rapid average sinking velocities of 270 ± 150 m d-1 were observed along the WAP, whereas the average velocity was 49 ± 25 m d-1 at the BATS site. Respiration rates of particle-attached microbes were measured using novel RESPIRE (REspiration of Sinking Particles In the subsuRface ocEan) sediment traps that first intercepts sinking particles then incubates them in situ. RESPIRE experiments yielded flux-normalized respiration rates of 0.4 ± 0.1 day-1 at BATS when excluding an outlier of 1.52 day-1, while these rates were undetectable along the WAP (0.01 ± 0.02 day-1). At BATS, flux-normalized respiration rates decreased exponentially with respect to depth below the euphotic zone with a 75% reduction between the 150 and 500 m depths. These findings provide quantitative and mechanistic insights into the processes that control the transfer efficiency of particle flux through the mesopelagic and its variability throughout the global oceans.

  1. Environmental correlates of peatland carbon fluxes in a thawing landscape: do transitional thaw stages matter?

    NASA Astrophysics Data System (ADS)

    Malhotra, A.; Roulet, N. T.

    2015-01-01

    Peatlands in discontinuous permafrost regions occur as a mosaic of wetland types, each with variable sensitivity to climate change. Permafrost thaw further increases the spatial heterogeneity in ecosystem structure and function in peatlands. Carbon (C) fluxes are well characterized in end-member thaw stages such as fully intact or fully thawed permafrost but remain unconstrained for transitional stages that cover a significant area of thawing peatlands. Furthermore, changes in the environmental correlates of C fluxes, due to thaw are not well described: a requirement for modeling future changes to C storage of permafrost peatlands. We investigated C fluxes and their correlates in end-member and a number of transitional thaw stages in a sub-arctic peatland. Across peatland lumped CH4 and CO2 flux data had significant correlations with expected correlates such as water table depth, thaw depth, temperature, photosynthetically active radiation and vascular green area. Within individual thaw states, bivariate correlations as well as multiple regressions between C flux and environmental factors changed variably with increasing thaw. The variability in directions and magnitudes of correlates reflects the range of structural conditions that could be present along a thaw gradient. These structural changes correspond to changes in C flux controls, such as temperature and moisture, and their interactions. Temperature sensitivity of CH4 increased with increasing thaw in bivariate analyses, but lack of this trend in multiple regression analyses suggested cofounding effects of substrate or water limitation on the apparent temperature sensitivity. Our results emphasize the importance of incorporating transitional stages of thaw in landscape level C budgets and highlight that end-member or adjacent thaw stages do not adequately describe the variability in structure-function relationships present along a thaw gradient.

  2. Environmental correlates of peatland carbon fluxes in a thawing landscape: do transitional thaw stages matter?

    NASA Astrophysics Data System (ADS)

    Malhotra, A.; Roulet, N. T.

    2015-05-01

    Peatlands in discontinuous permafrost regions occur as a mosaic of wetland types, each with variable sensitivity to climate change. Permafrost thaw further increases the spatial heterogeneity in ecosystem structure and function in peatlands. Carbon (C) fluxes are well characterized in end-member thaw stages such as fully intact or fully thawed permafrost but remain unconstrained for transitional stages that cover a significant area of thawing peatlands. Furthermore, changes in the environmental correlates of C fluxes, due to thaw, are not well described - a requirement for modeling future changes to C storage of permafrost peatlands. We investigated C fluxes and their correlates in end-member and a number of transitional thaw stages in a sub-arctic peatland. Across peatland-lumped CH4 and CO2 flux data had significant correlations with expected correlates such as water table depth, thaw depth, temperature, photosynthetically active radiation and vascular green area. Within individual thaw states, bivariate correlations as well as multiple regressions between C flux and environmental factors changed variably with increasing thaw. The variability in directions and magnitudes of correlates reflects the range of structural conditions that could be present along a thaw gradient. These structural changes correspond to changes in C flux controls, such as temperature and moisture, and their interactions. Temperature sensitivity of CH4 increased with increasing thaw in bivariate analyses, but lack of this trend in multiple regression analyses suggested cofounding effects of substrate or water limitation on the apparent temperature sensitivity. Our results emphasize the importance of incorporating transitional stages of thaw in landscape level C budgets and highlight that end-member or adjacent thaw stages do not adequately describe the variability in structure-function relationships present along a thaw gradient.

  3. Eddy covariance based carbon fluxes from differently grazed grassland in Inner Mongolia, China

    NASA Astrophysics Data System (ADS)

    Vetter, Sylvia; Ketzer, Bettina; Bernhofer, Christian

    2010-05-01

    Grasslands are one of the dominating vegetation types in the world. In China grasslands capture 400 Mha. This huge area has great influence on water and carbon stocks and fluxes. Water and carbon exchange influence the local concentration of greenhouse gases. In the steppe of Inner Mongolia (China) problems exist of overgrazing, erosion and ongoing desertification. Through these processes the seasonal patterns of the carbon cycles are changed. Within the project MAGIM (Matter fluxes in grasslands of Inner Mongolia as influenced by stocking rate), which is a multidisciplinary project bringing together German and Chinese expertise, fluxes of CO2 and H2O were measured by the eddy covariance (EC) method. The study site is in the Xilin River catchment in the Northeast of Inner Mongolia Autonomous Region, China. The region is a continental temperate semiarid zone with cold dry winters and warm humid summers. The annual mean temperature is about 2 °C and the annual precipitation is 350 mm. The EC measurements at Leymus chinensis steppe include various grazing intensities (heavily grazed, continuously grazed, winter grazed, ungrazed since 1979) by one permanent and one roving tower. From 2004 to 2006, there were continuous measurements at the ungrazed site (Leymus chinensis). The roving tower was used in the vegetation period at the grazed sites. In general, carbon fluxes are small in Inner Mongolia: At the ungrazed site an average negative net ecosystem exchange NEE was observed of -0.13 g C m-2 d-1 (C sink) over all observations from 2004 to 2006. During roving periods only, ungrazed was C neutral, but the heavily grazed site showed a positive NEE of 0.48 g C m-2 s-1 (C source). The intermediately grazed sites switched from CO2 sink to source. Lack of precipitation reduced the CO2 sink or increased the CO2 source. So, precipitation and its seasonal pattern are the major drivers controlling the atmospheric fluxes. Temperature and soil moisture, as drivers of respiration

  4. A paired flux approach to study the carbon balance of a corn/soybean rotation

    NASA Astrophysics Data System (ADS)

    Baker, J.; Griffis, T.

    2003-04-01

    There is intense interest in finding ways to damp projected increases in atmospheric CO_2 by adopting strategies that alter local rates of surface/atmosphere carbon exchange in ways that favor increased surface storage. It is generally accepted that row crop agriculture has historically been a contributor to the debit side of the terrestrial carbon ledger. However, changes in farming practice, primarily reduction of tillage, appear to have arrested this decline. The very fact that so much soil carbon was lost is now viewed positively, in the sense that it may represent a reservoir that can be refilled through the adoption of appropriate farming practices, but verification of carbon gain is a difficult problem. Soil sampling is the accepted standard, but it has a low signal to noise ratio and poor temporal resolution so it offers little insight into causes and effects or underlying processes. Micrometeorological methods address these shortcomings, replacing them with a new set of problems. Temporal resolution is superb, but determination of net carbon gain or loss requires integration of short-term (e.g. half-hourly) flux measurements over at least one full cycle of the system under test -- typically a year or more. Unfortunately, data are missed due to instrument failures and power outages, and other data must be discarded because theoretical assumptions of turbulent transport are not met. As a consequence, the end sum of net carbon exchange from these sites depends substantially on the gap-filling strategies that are used. Nonetheless, valuable information can be obtained by measuring differentially, i.e. making simultaneous flux measurements in two adjacent fields that are subjected to the same weather conditions, but with specific differences in farming practice. Insights into the differences in carbon balance between the systems, even in the face of the inevitable data gaps, can be obtained by considering only those time periods in which both fields are

  5. Sap flux in pure aspen and mixed aspen-birch forests exposed to elevated concentrations of carbon dioxide and ozone.

    PubMed

    Uddling, Johan; Teclaw, Ronald M; Kubiske, Mark E; Pregitzer, Kurt S; Ellsworth, David S

    2008-08-01

    Elevated concentrations of atmospheric carbon dioxide ([CO2]) and tropospheric ozone ([O3]) have the potential to affect tree physiology and structure and hence forest water use, which has implications for climate feedbacks. We investigated how a 40% increase above ambient values in [CO2] and [O3], alone and in combination, affect tree water use of pure aspen and mixed aspen-birch forests in the free air CO2-O3 enrichment experiment near Rhinelander, Wisconsin (Aspen FACE). Measurements of sap flux and canopy leaf area index (L) were made during two growing seasons, when steady-state L had been reached after more than 6 years of exposure to elevated [CO2] and [O3]. Maximum stand-level sap flux was not significantly affected by elevated [O3], but was increased by 18% by elevated [CO2] averaged across years, communities and O(3) regimes. Treatment effects were similar in pure aspen and mixed aspen-birch communities. Increased tree water use in response to elevated [CO2] was related to positive CO2 treatment effects on tree size and L (+40%). Tree water use was not reduced by elevated [O3] despite strong negative O3 treatment effects on tree size and L (-22%). Elevated [O3] predisposed pure aspen stands to drought-induced sap flux reductions, whereas increased tree water use in response to elevated [CO2] did not result in lower soil water content in the upper soil or decreasing sap flux relative to control values during dry periods. Maintenance of soil water content in the upper soil in the elevated [CO2] treatment was at least partly a function of enhanced soil water-holding capacity, probably a result of increased organic matter content from increased litter inputs. Our findings that larger trees growing in elevated [CO2] used more water and that tree size, but not maximal water use, was negatively affected by elevated [O3] suggest that the long-term cumulative effects on stand structure may be more important than the expected primary stomatal closure responses to

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  7. Artificial drainage and associated carbon fluxes (CO2/CH4) in a tundra ecosystem

    NASA Astrophysics Data System (ADS)

    Merbold, Lutz; Kutsch, Werner Leo; Corradi, Chiara; Kolle, Olaf; Rebmann, Corinna; Stoy, Paul C.; Zimov, Sergej A.; Schulze, Ernst-Detlef

    2010-05-01

    Ecosystem flux measurements using the eddy covariance (EC) technique were undertaken in 4 subsequent years during summer for a total of 562 days in an arctic wet tundra ecosystem, located near Cherskii, Far-Eastern Federal District, Russia. Methane (CH4) emissions were measured using permanent chambers. The experimental field is characterized by late thawing of permafrost soils in June and periodic spring floods. A stagnant water table below the grass canopy is fed by melting of the active layer of permafrost and by flood water. Following 3 years of EC measurements, the site was drained by building a 3m wide drainage channel surrounding the EC tower to examine possible future effects of global change on the tundra tussock ecosystem. Cumulative summertime net carbon fluxes before experimental alteration were estimated to be about +115 gCm-2 (i.e. an ecosystem C loss) and +18 gCm-2 after draining the study site. When taking CH4 as another important greenhouse gas into account and considering the global warming potential (GWP) of CH4 vs. CO2, the ecosystem had a positive GWP during all summers. However CH4 emissions after drainage decreased significantly and therefore the carbon related greenhouse gas flux was much smaller than beforehand (475 ± 253 gC-CO2-em-2 before drainage in 2003 vs. 23 ± 26 g C-CO2-em-2 after drainage in 2005).

  8. Effects of Complexity in Floor Reflectance on Carbon and Water Fluxes in an Urban Park

    NASA Astrophysics Data System (ADS)

    Kimm, H.; Ryu, Y.; Kobayashi, H.; Lee, K.; Hong, J. W.

    2014-12-01

    Urban parks account for great portion of urban vegetation that could partially contribute to carbon uptake. However, the complex land surface reflectance have limited our understanding on canopy photosynthesis in urban parks. In this study, a 3-D canopy radiative transfer model, Forest Light Environment Simulator (FLiES), is coupled with a 1-D biophysical model, CANOAK, to investigate effect of floor reflectance on canopy-scale photosynthesis and evapotranspiration in an urban park, Seoul Forest Park (Seoul, the Republic of Korea). Through a series of intensive field works, we prepared model input data such as tree positions, crown shapes, leaf area index, photosynthetic parameters such as Vcmax and Jmax. Meteorological data were derived from flux tower observations. We first evaluate the modelled net ecosystem exchange and latent heat flux against flux measurements from the eddy covariance system in the park. Then, we test the effects of floor reflectance on canopy photosynthesis and evapotranspiration using the model with different scenarios. Finally, we propose several design guidelines for urban park to increase carbon uptake by plants. The model simulation uncertainties are also discussed. We expect the usage of 3-D RTM would give better understanding of ecological processes in a complex space.

  9. CARBON DIOXIDE FLUXES IN A CENTRAL HARDWOODS OAK-HICKORY FOREST ECOSYSTEM

    SciTech Connect

    Pallardy, Stephen G.; Gu, Lianhong; Hanson, Paul J; Meyers, T. P.; Wullschleger, Stan D; Yang, Bai; Hosman, K. P.

    2007-01-01

    A long-term experiment to measure carbon and water fluxes was initiated in 2004 as part of the Ameriflux network in a second-growth oak-hickory forest in central Missouri. Ecosystem-scale (~ 1 km2) canopy gas exchange (measured by eddy-covariance methods), vertical CO2 profile sampling and soil respiration along with meteorological parameters were monitored continuously. Early results from this forest located on the western margin of the Eastern Deciduous Forest indicated high peak rates of canopy CO2 uptake (35-40 ?mol m-2 s-1) during the growing season. Canopy CO2 profile measurements indicated substantial accumulation of CO2 (~500 ppm) near the surface in still air at night, venting of this buildup in the morning hours under radiation-induced turbulent air flow, and small vertical gradients of CO2 during most of the subsequent light period with minimum CO2 concentrations in the canopy. Flux of CO2 from the soil ranged from 2 to 8 ?mol m-2 s-1 and increased with temperature. Data from this site and others in the network will also allow characterization of regional spatial variation in carbon fluxes as well as inter-annual differences attributable to climatic events such as droughts.

  10. Crustal solute fluxes and transient carbon dioxide drawdown in the Scottbreen Basin, Svalbard in 2002

    NASA Astrophysics Data System (ADS)

    Krawczyk, Wiesława Ewa; Bartoszewski, Stefan A.

    2008-12-01

    SummarySolute fluxes and transient carbon dioxide drawdown in a small glacierized basin investigated on Svalbard in 2002 are presented. It was a sample year within a period of significant climate warming in the Arctic. Discharge was recorded in the Scottbreen Basin (10.1 km 2), Bellsund Fjord, between July 8 and September 10, 2002. Specific runoff for this period was 0.784 m, 22% more than the mean for 1986-2001. The runoff for all of 2002 (i.e. the hydrologic year) was estimated by comparison with Bayelva, the only glacial river with longer records on Svalbard. The specific runoff for 2002 was ˜1.228 m, yielding crustal solute fluxes of 69.4 t km -2 yr -1 (25.8 m 3 km -2 yr -1). This rate is the highest chemical denudation rate reported from glacierized basins on Svalbard, and it may be underestimated because higher solute fluxes at the beginning of the melt season were not taken into account. Crustal fluxes in the fall may also have been higher because it is probable that crustal ion concentrations were increasing after recording stopped in September. The cation denudation rate was 1213 ∑ meq + m -2 yr -1 and the mean annual crustal ion concentration derived from it amounted to 981 μeq L -1. Transient CO 2 drawdown in 2002 was 5242 kg C km -2 yr -1. Most of the carbon dioxide was removed in the summer ablation waters, estimated CO 2 drawdown in the fall being only 13% of the total. Comparison with crustal solute fluxes (CSF) computed from specific conductivity in the 1980s and 1990s suggests that earlier fluxes may have been overestimated by around 19%. Comparing earlier data with the 2002 rates may confirm the influence of climate warming on increasing chemical denudation rates. It was also found that a globally derived equation relating specific conductivity to concentrations of dissolved limestone in water gave estimates of the crustal solute fluxes that were only 1.1% less than those obtained via comprehensive chemical analyses of waters and ion

  11. Constraining terrestrial ecosystem CO2 fluxes by integrating models of biogeochemistry and atmospheric transport and data of surface carbon fluxes and atmospheric CO2 concentrations

    NASA Astrophysics Data System (ADS)

    Zhu, Q.; Zhuang, Q.; Henze, D.; Bowman, K.; Chen, M.; Liu, Y.; He, Y.; Matsueda, H.; Machida, T.; Sawa, Y.; Oechel, W.

    2014-09-01

    Regional net carbon fluxes of terrestrial ecosystems could be estimated with either biogeochemistry models by assimilating surface carbon flux measurements or atmospheric CO2 inversions by assimilating observations of atmospheric CO2 concentrations. Here we combine the ecosystem biogeochemistry modeling and atmospheric CO2 inverse modeling to investigate the magnitude and spatial distribution of the terrestrial ecosystem CO2 sources and sinks. First, we constrain a terrestrial ecosystem model (TEM) at site level by assimilating the observed net ecosystem production (NEP) for various plant functional types. We find that the uncertainties of model parameters are reduced up to 90% and model predictability is greatly improved for all the plant functional types (coefficients of determination are enhanced up to 0.73). We then extrapolate the model to a global scale at a 0.5° × 0.5° resolution to estimate the large-scale terrestrial ecosystem CO2 fluxes, which serve as prior for atmospheric CO2 inversion. Second, we constrain the large-scale terrestrial CO2 fluxes by assimilating the GLOBALVIEW-CO2 and mid-tropospheric CO2 retrievals from the Atmospheric Infrared Sounder (AIRS) into an atmospheric transport model (GEOS-Chem). The transport inversion estimates that: (1) the annual terrestrial ecosystem carbon sink in 2003 is -2.47 Pg C yr-1, which agrees reasonably well with the most recent inter-comparison studies of CO2 inversions (-2.82 Pg C yr-1); (2) North America temperate, Europe and Eurasia temperate regions act as major terrestrial carbon sinks; and (3) The posterior transport model is able to reasonably reproduce the atmospheric CO2 concentrations, which are validated against Comprehensive Observation Network for TRace gases by AIrLiner (CONTRAIL) CO2 concentration data. This study indicates that biogeochemistry modeling or atmospheric transport and inverse modeling alone might not be able to well quantify regional terrestrial carbon fluxes. However, combining

  12. Stream restoration and sewers impact sources and fluxes of water, carbon, and nutrients in urban watersheds

    NASA Astrophysics Data System (ADS)

    Pennino, Michael J.; Kaushal, Sujay S.; Mayer, Paul M.; Utz, Ryan M.; Cooper, Curtis A.

    2016-08-01

    An improved understanding of sources and timing of water, carbon, and nutrient fluxes associated with urban infrastructure and stream restoration is critical for guiding effective watershed management globally. We investigated how sources, fluxes, and flowpaths of water, carbon (C), nitrogen (N), and phosphorus (P) shift in response to differences in urban stream restoration and sewer infrastructure. We compared an urban restored stream with two urban degraded streams draining varying levels of urban development and one stream with upland stormwater management systems over a 3-year period. We found that there was significantly decreased peak discharge in response to precipitation events following stream restoration. Similarly, we found that the restored stream showed significantly lower (p < 0.05) monthly peak runoff (9.4 ± 1.0 mm day-1) compared with two urban degraded streams (ranging from 44.9 ± 4.5 to 55.4 ± 5.8 mm day-1) draining higher impervious surface cover, and the stream-draining stormwater management systems and less impervious surface cover in its watershed (13.2 ± 1.9 mm day-1). The restored stream exported most carbon, nitrogen, and phosphorus at relatively lower streamflow than the two more urban catchments, which exported most carbon and nutrients at higher streamflow. Annual exports of total carbon (6.6 ± 0.5 kg ha-1 yr-1), total nitrogen (4.5 ± 0.3 kg ha-1 yr-1), and total phosphorus (161 ± 15 kg ha-1 yr-1) were significantly lower in the restored stream compared to both urban degraded streams (p < 0.05), but statistically similar to the stream draining stormwater management systems, for N exports. However, nitrate isotope data suggested that 55 ± 1 % of the nitrate in the urban restored stream was derived from leaky sanitary sewers (during baseflow), statistically similar to the urban degraded streams. These isotopic results as well as additional tracers, including fluoride (added to drinking water) and iodide (contained in dietary salt

  13. Benthic fluxes of dissolved organic carbon from gas hydrate sediments in the northern South China Sea

    PubMed Central

    Hung, Chia-Wei; Huang, Kuo-Hao; Shih, Yung-Yen; Lin, Yu-Shih; Chen, Hsin-Hung; Wang, Chau-Chang; Ho, Chuang-Yi; Hung, Chin-Chang; Burdige, David J.

    2016-01-01

    Hydrocarbon vents have recently been reported to contribute considerable amounts of dissolved organic carbon (DOC) to the oceans. Many such hydrocarbon vents widely exist in the northern South China Sea (NSCS). To investigate if these hydrocarbon vent sites release DOC, we used a real-time video multiple-corer to collect bottom seawater and surface sediments at vent sites. We analyzed concentrations of DOC in these samples and estimated DOC fluxes. Elevated DOC concentrations in the porewaters were found at some sites suggesting that DOC may come from these hydrocarbon vents. Benthic fluxes of DOC from these sediments were 28 to 1264 μmol m−2 d−1 (on average ~321 μmol m−2 d−1) which are several times higher than most DOC fluxes in coastal and continental margin sediments. The results demonstrate that the real-time video multiple-corer can precisely collect samples at vent sites. The estimated benthic DOC flux from the methane venting sites (8.6 × 106 mol y−1), is 24% of the DOC discharge from the Pearl River to the South China Sea, indicating that these sediments make an important contribution to the DOC in deep waters. PMID:27432631

  14. Benthic fluxes of dissolved organic carbon from gas hydrate sediments in the northern South China Sea

    NASA Astrophysics Data System (ADS)

    Hung, Chia-Wei; Huang, Kuo-Hao; Shih, Yung-Yen; Lin, Yu-Shih; Chen, Hsin-Hung; Wang, Chau-Chang; Ho, Chuang-Yi; Hung, Chin-Chang; Burdige, David J.

    2016-07-01

    Hydrocarbon vents have recently been reported to contribute considerable amounts of dissolved organic carbon (DOC) to the oceans. Many such hydrocarbon vents widely exist in the northern South China Sea (NSCS). To investigate if these hydrocarbon vent sites release DOC, we used a real-time video multiple-corer to collect bottom seawater and surface sediments at vent sites. We analyzed concentrations of DOC in these samples and estimated DOC fluxes. Elevated DOC concentrations in the porewaters were found at some sites suggesting that DOC may come from these hydrocarbon vents. Benthic fluxes of DOC from these sediments were 28 to 1264 μmol m‑2 d‑1 (on average ~321 μmol m‑2 d‑1) which are several times higher than most DOC fluxes in coastal and continental margin sediments. The results demonstrate that the real-time video multiple-corer can precisely collect samples at vent sites. The estimated benthic DOC flux from the methane venting sites (8.6 × 106 mol y‑1), is 24% of the DOC discharge from the Pearl River to the South China Sea, indicating that these sediments make an important contribution to the DOC in deep waters.

  15. Benthic fluxes of dissolved organic carbon from gas hydrate sediments in the northern South China Sea.

    PubMed

    Hung, Chia-Wei; Huang, Kuo-Hao; Shih, Yung-Yen; Lin, Yu-Shih; Chen, Hsin-Hung; Wang, Chau-Chang; Ho, Chuang-Yi; Hung, Chin-Chang; Burdige, David J

    2016-01-01

    Hydrocarbon vents have recently been reported to contribute considerable amounts of dissolved organic carbon (DOC) to the oceans. Many such hydrocarbon vents widely exist in the northern South China Sea (NSCS). To investigate if these hydrocarbon vent sites release DOC, we used a real-time video multiple-corer to collect bottom seawater and surface sediments at vent sites. We analyzed concentrations of DOC in these samples and estimated DOC fluxes. Elevated DOC concentrations in the porewaters were found at some sites suggesting that DOC may come from these hydrocarbon vents. Benthic fluxes of DOC from these sediments were 28 to 1264 μmol m(-2 )d(-1) (on average ~321 μmol m(-2 )d(-1)) which are several times higher than most DOC fluxes in coastal and continental margin sediments. The results demonstrate that the real-time video multiple-corer can precisely collect samples at vent sites. The estimated benthic DOC flux from the methane venting sites (8.6 × 10(6 )mol y(-1)), is 24% of the DOC discharge from the Pearl River to the South China Sea, indicating that these sediments make an important contribution to the DOC in deep waters. PMID:27432631

  16. Benthic fluxes of dissolved organic carbon from gas hydrate sediments in the northern South China Sea.

    PubMed

    Hung, Chia-Wei; Huang, Kuo-Hao; Shih, Yung-Yen; Lin, Yu-Shih; Chen, Hsin-Hung; Wang, Chau-Chang; Ho, Chuang-Yi; Hung, Chin-Chang; Burdige, David J

    2016-01-01

    Hydrocarbon vents have recently been reported to contribute considerable amounts of dissolved organic carbon (DOC) to the oceans. Many such hydrocarbon vents widely exist in the northern South China Sea (NSCS). To investigate if these hydrocarbon vent sites release DOC, we used a real-time video multiple-corer to collect bottom seawater and surface sediments at vent sites. We analyzed concentrations of DOC in these samples and estimated DOC fluxes. Elevated DOC concentrations in the porewaters were found at some sites suggesting that DOC may come from these hydrocarbon vents. Benthic fluxes of DOC from these sediments were 28 to 1264 μmol m(-2 )d(-1) (on average ~321 μmol m(-2 )d(-1)) which are several times higher than most DOC fluxes in coastal and continental margin sediments. The results demonstrate that the real-time video multiple-corer can precisely collect samples at vent sites. The estimated benthic DOC flux from the methane venting sites (8.6 × 10(6 )mol y(-1)), is 24% of the DOC discharge from the Pearl River to the South China Sea, indicating that these sediments make an important contribution to the DOC in deep waters.

  17. Interactions of bluff-body obstacles with turbulent airflows affecting evaporative fluxes from porous surfaces

    NASA Astrophysics Data System (ADS)

    Haghighi, Erfan; Or, Dani

    2015-11-01

    Bluff-body obstacles interacting with turbulent airflows are common in many natural and engineering applications (from desert pavement and shrubs over natural surfaces to cylindrical elements in compact heat exchangers). Even with obstacles of simple geometry, their interactions within turbulent airflows result in a complex and unsteady flow field that affects surface drag partitioning and transport of scalars from adjacent evaporating surfaces. Observations of spatio-temporal thermal patterns on evaporating porous surfaces adjacent to bluff-body obstacles depict well-defined and persistent zonation of evaporation rates that were used to construct a simple mechanistic model for surface-turbulence interactions. Results from evaporative drying of sand surfaces with isolated cylindrical elements (bluff bodies) subjected to constant turbulent airflows were in good agreement with model predictions for localized exchange rates. Experimental and theoretical results show persistent enhancement of evaporative fluxes from bluff-rough surfaces relative to smooth flat surfaces under similar conditions. The enhancement is attributed to formation of vortices that induce a thinner boundary layer over part of the interacting surface footprint. For a practical range of air velocities (0.5-4.0 m/s), low-aspect ratio cylindrical bluff elements placed on evaporating sand surfaces enhanced evaporative mass losses (relative to a flat surface) by up to 300% for high density of elements and high wind velocity, similar to observations reported in the literature. Concepts from drag partitioning were used to generalize the model and upscale predictions to evaporation from surfaces with multiple obstacles for potential applications to natural bluff-rough surfaces.

  18. Impact of uncertainty in attributing modeled North American terrestrial carbon fluxes to anthropogenic forcings

    NASA Astrophysics Data System (ADS)

    Ricciuto, D. M.

    2015-12-01

    Although much progress has been made in the past decade in constraining the net North American terrestrial carbon flux, considerable uncertainty remains in the sink magnitude and trend. Terrestrial carbon cycle models are increasing in spatial resolution, complexity and predictive skill, allowing for increased process-level understanding and attribution of net carbon fluxes to specific causes. Here we examine the various sources of uncertainty, including driver uncertainty, model parameter uncertainty, and structural uncertainty, and the contribution of each type uncertainty to the net sink, and the attribution of this sink to anthropogenic causes: Increasing CO2 concentrations, nitrogen deposition, land use change, and changing climate. To examine driver and parameter uncertainty, model simulations are performed using the Community Land Model version 4.5 (CLM4.5) with literature-based parameter ranges and three different reanalysis meteorological forcing datasets. We also examine structural uncertainty thorough analysis of the Multiscale Terrestrial Model Intercomparison (MsTMIP). Identififying major sources of uncertainty can help to guide future observations, experiments, and model development activities.

  19. Flux-Dependent Growth Kinetics and Diameter Selectivity in Single-Wall Carbon Nanotube Arrays

    SciTech Connect

    Geohegan, David B; Puretzky, Alexander A; Jackson, Jeremy Joseph; Rouleau, Christopher M; Eres, Gyula; More, Karren Leslie

    2011-01-01

    The nucleation and growth kinetics of single-wall carbon nanotubes in aligned arrays have been measured using fast pulses of acetylene and in situ optical diagnostics in conjunction with low pressure chemical vapor deposition (CVD). Increasing the acetylene partial pressure is shown to decrease nucleation times by three orders of magnitude, permitting aligned nanotube arrays to nucleate and grow to microns lengths within single gas pulses at high (up to 7 micron/s) peak growth rates and short ~ 0.5 s times.Low-frequency Raman scattering (> 10 cm-1) and transmission electron microscopy measurements show that increasing the feedstock flux in both continuous-CVD and pulsed-CVD shifts the product distribution to large single-wall carbon nanotube diameters > 2.5 nm. Sufficiently high acetylene partial pressures in pulsed-CVD appear to temporarily terminate the growth of the fastest- growing, small-diameter nanotubes by overcoating the more catalytically-active, smaller catalyst nanoparticles within the ensemble with non-nanotube carbon in agreement with a growth model. The results indicate that subsets of catalyst nanoparticle ensembles nucleate, grow, and terminate growth within different flux ranges according to their catalytic activity.

  20. Improve carbon metabolic flux in Saccharomyces cerevisiae at high temperature by overexpressed TSL1 gene.

    PubMed

    Ge, Xiang-Yang; Xu, Yan; Chen, Xiang

    2013-04-01

    This study describes a novel strategy to improve the glycolysis flux of Saccharomyces cerevisiae at high temperature. The TSL1 gene-encoding regulatory subunit of the trehalose synthase complex was overexpressed in S. cerevisiae Z-06, which increased levels of trehalose synthase activity in extracts, enhanced stress tolerance and glucose consuming rate of the yeast cells. As a consequence, the final ethanol concentration of 185.5 g/L was obtained at 38 °C for 36 h (with productivity up to 5.2 g/L/h) in 7-L fermentor, and the ethanol productivity was 92.7 % higher than that of the parent strain. The results presented here provide a novel way to enhance the carbon metabolic flux at high temperature, which will be available for the purposes of producing other primary metabolites of commercial interest using S. cerevisiae as a host.

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-10-01

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

  3. Quantification of Lateral Carbon Flux in a Chaparral Ecosystem in Southern California Alessandra Rossi, Walter Oechel, Patrick Murphy

    NASA Astrophysics Data System (ADS)

    Rossi, A.; Oechel, W. C.; Murphy, P.

    2013-12-01

    The lateral transport of carbon is a horizontal transfer of carbon away from the area it was withdrawn from the atmosphere (Ciais et al. 2006). Research regarding horizontal C transport has received much less attention in arid and semi-arid regions compared to other types of ecosystems. Drylands represent around 47.2% (Lal 2004) of the global terrestrial area and despite characterized by relatively low carbon flux, drylands comprise approximately 15.5% of the world's total soil organic carbon (SOC) (Eswaran et al. 2000, Schlesinger, 1991). Moreover, these dry areas contain at least as much soil inorganic carbon (SIC) as SOC (Eswaran et al. 2000). Therefore, these areas potentially have a large contribution to the global carbon budget and they deserve attention. A long-term observation of CO2 flux with the eddy covariance technique has been conducted since 1997 at Sky Oaks Field Station in Southern California, an area of Mediterranean climate at the climatic transition between semiarid area and desert. The long term record of CO2 flux showed the area has been a sink of CO2 of over -0.2 kgCm-2yr-1. In addition to evaluating vertical carbon fluxes, we initiated a project to evaluate lateral carbon transports using litter traps, sediment fences and two small weirs adjacent to the eddy covariance site. Preliminary results indicate that the lateral transfer of C in the area may offset the vertical influx to this shrub ecosystem. However, it is still necessary to develop the methodology to compare vertical carbon flux and the lateral carbon fluxes more accurately.

  4. The Mountain Pine Beetle epidemic contributes to increased spatial and temporal variability and decoupling of carbon and water fluxes from lodgepole pine ecosystems

    NASA Astrophysics Data System (ADS)

    Reed, D. E.; Kelly, R. D.; Ewers, B. E.; Pendall, E.

    2010-12-01

    Perturbations of ecosystems provide opportunities to test our predictive understanding of carbon and water cycles. An ongoing mountain pine beetle (MPB) and associated xylem-blocking blue-stain fungi epidemic is causing widespread, yet spatially heterogeneous mortality of mature trees in conifer forests across the mountains of western North America. We seek to answer the question “How does spatial heterogeneity in tree mortality affect the response to drivers and temporal variability in ecosystem fluxes of carbon and water.” We are answering this question by quantifying ecosystem-scale carbon and water cycling using eddy covariance (EC) measurements and a standard suite of atmospheric, soil and vegetation monitoring instruments. The study site had a first wave of MPB during the summer of 2007. EC measurements began in early 2009. A spatial grid 800 by 450 m with 135 plots approximating 80% of the flux footprint showed that tree mortality varied from a plot average of less than 1% to 60%. Using an un-biased statistical friction velocity filter, there was a clear difference found between the growing season and the winter season. The growing season night data was filtered at a friction velocity below 0.09 m/s and the winter season data did not need filtering. The average friction velocity for the entire site is 0.64 m/s over the entire year, making it the second most turbulent site in the AmeriFlux Network, but during the growing season the fluxes only pass the un-bias filter under much higher turbulence conditions than any other flux tower site. We speculate this is due to the heterogeneous footprint pattern and the high amount of mixing needed to discern the signal from noise. Due to the nearer portions of the footprint having less mortality, there was no clear decline in ecosystem level water vapor fluxes over the growing season period after accounting for changes in the seasonal drivers of vapor pressure deficit, net radiation and soil moisture. Carbon flux

  5. The Ecohydrological Consequences of Woody Plant Encroachment: How Accessibility to Deep Soil Water Resources Affects Ecosystem Carbon and Water Exchange

    NASA Astrophysics Data System (ADS)

    Scott, R. L.; Huxman, T. E.; Barron-Gafford, G.; Jenerette, D.; Young, J. M.

    2013-12-01

    Woody plant encroachment into grassland systems, a process that has increased rapidly over the last century, has potentially broad ecohydrological consequences by affecting the way ecosystems use water and cycle carbon. This study examines the influence of precipitation- and groundwater-derived water availability by comparing eddy covariance measurements of water vapor and carbon dioxide fluxes over a riparian grassland, shrubland, and woodland, and an upland grassland site in southeastern Arizona USA. Compared to the upland grassland, the riparian sites exhibited greater net carbon uptake (NEP) and higher evapotranspiration (ET) across a longer portion of the year. Among the riparian sites, however, the grassland was less able to take advantage of the stable groundwater supply. Increasing woody plant density facilitated greater water and carbon exchange that became increasingly decoupled from incident precipitation (P). How groundwater accessibility affected NEP was more complex than ET. Respiration (Reco) costs were higher for the riparian grassland so, while it had a similar ET and gross carbon uptake (GEP) to the shrubland, its NEP was substantially less. Also, riparian grassland fluxes were much more variable due to flooding that occurred at the site, which could stimulate or inhibit NEP. Woodland NEP was largest but surprisingly similar to the less mature and dense shrubland even while having much greater GEP. Woodland NEP responded negatively to P, due to the stimulation of Reco likely due to greater amounts of aboveground and soil carbon. With many areas of the world experiencing woody plants encroachment, encroachment into areas where there are additional deep soil water sources, such as in riparian settings or in areas of deep soil moisture recharge, will likely increase carbon sequestration but at the expense of higher water use.

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

    NASA Astrophysics Data System (ADS)

    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

  7. Evaluations of carbon fluxes in tropical regions estimated by top-down and bottom-up approaches

    NASA Astrophysics Data System (ADS)

    Murakami, Kazutaka; Sasai, Takahiro; Matsunaga, Tsuneo; Saito, Makoto; Maksyutov, Shamil; Yokota, Tatsuya

    2015-04-01

    Many researchers have been trying to reveal distribution of carbon flux for understanding global carbon cycle dynamics. There are two approaches of estimating carbon fluxes using satellite observation data, and these are generally referred to as top-down and bottom-up approaches. These approaches are different in that the top-down approach estimates the carbon flux by using the distributions of CO2 concentration and an atmospheric transport model, on the other hand, the bottom-up approach estimates the flux by using the ground surface information (e.g. leaf area, surface temperature) from the satellite data and a biosphere model. However, many uncertainties are still remain in carbon flux estimations, because the true values of carbon flux are still unclear and the estimations vary with the type of the model (e.g. a transport model, a terrestrial biosphere model) and input data (e.g. satellite data, climate data). But the satellite-based carbon flux estimations with reduced uncertainty will be very efficient for identifications of large emission area and terrestrial carbon stock regions. In this study, we evaluated the carbon flux estimations in tropical regions from two approaches. We used GOSAT L4A CO2 flux data as top-down approach estimations, CarbonTracker (CT2013) flux data as top-down approach estimations (used no satellite data, only ground observations), and net ecosystem productions (NEP) estimated by the diagnostic type biosphere model BEAMS as bottom-up approach estimations. GOSAT (Greenhouse gases Observing SATellite) launched on January 2009 is first satellite to measure the concentrations of GHGs (CO2, CH4) from space. GOSAT have two sensors that TANSO-FTS (Thermal And Near infrared Sensor for carbon Observation - Fourier Transform Spectrometer) is measuring CO2 and CH4 column amount, and TANSO-CAI (Thermal And Near infrared Sensor for carbon Observation - Cloud and Aerosol Imager) is imaging the states of atmosphere and land surface and return to

  8. Carbon material distribution and flux analysis under varying glucose concentrations in hydrogen-producing Clostridium tyrobutyricum JM1.

    PubMed

    Jo, Ji Hye; Kim, Woong

    2016-06-20

    Anaerobic glucose metabolism in hydrogen-producing Clostridium tyrobutyricum was investigated in batch culture with varying initial glucose concentrations (27.8-333.6mM). To understand the regulation of metabolism, the carbon material and reduction balances were applied to estimate the carbon flux distribution for the first time, and metabolic flux analysis (MFA) was used to provide qualitative information and guidance for effective metabolic design. The overall flux distribution suggested that C. tyrobutyricum metabolism has a high capacity for the production of butyrate and hydrogen at an initial glucose concentration of 222.4mM, with balanced activities of NADH and ATP.

  9. Trace gas fluxes along soil carbon and drainage gradients at a peaty grassland

    NASA Astrophysics Data System (ADS)

    Leiber-Sauheitl, Katharina; Fuß, Roland; Freibauer, Annette

    2013-04-01

    The importance of organic soils for the greenhouse gas (GHG) balance and the beneficial effect of CO2 uptake by undisturbed peatlands are widely accepted. In contrast, it is known that after drainage peatlands become a large source of GHGs due to mineralization of organic material. Emissions decrease only when easily degradable substances are depleted and more stable substances accumulate. Therefore, subsequent to the first mineralization peak degraded peatlands are assumed to be a small source of GHGs. Based on GHG flux measurements along small-scale soil organic carbon and groundwater level gradients, we show that this assumption cannot be generalized. The study area "Grosses Moor" (Gifhorn, Germany) is located within a former peat bog, which has been altered by drainage and peat cutting and is currently grassland under extensive agricultural use. The peat is amorphous and highly degraded. The focus of our study is on the acquisition of CO2, CH4 and N2O fluxes at six measurement sites via manual closed chambers. The effects of small-scale soil organic carbon and groundwater level gradients on the GHG fluxes (CO2, CH4, and N2O) are quantified. In order to calculate the annual CO2 exchange rate, values are modeled on a 0.5 hour scale between measurement campaigns. The model is based on meteorological parameters, such as the photosynthetic active radiation and soil temperature. During the 2011/2012 campaign, CO2 was the most important greenhouse gas. Emissions were dependent on water table level but not on soil carbon content. Positive annual balances occurred on all sites demonstrating that even highly degraded peaty soils are an important source of greenhouse gases. This study gives valuable information on the GHG source function of degraded peaty soils. Thus, our study improves predictions of the reaction of peatland soils to changes of soil and climate conditions with respect to their GHG emissions.

  10. Impact of 40 years poplar cultivation on soil carbon stocks and greenhouse gas fluxes

    NASA Astrophysics Data System (ADS)

    Ferré, C.; Leip, A.; Matteucci, G.; Previtali, F.; Seufert, G.

    2005-08-01

    Within the JRC Kyoto Experiment in the Regional Park and UN-Biosphere Reserve "Parco Ticino" (North-Italy, near Pavia), the soil carbon stocks and fluxes of CO2, N2O, and CH4 were measured in a poplar plantation in comparison with a natural mesohygrophilous deciduous forest nearby, which represents the pristine land cover of the area. Soil fluxes were measured using the static and dynamic closed chamber techniques for CH4 N2O, and CO2, respectively. We made further a pedological study to relate the spatial variability found with soil parameters.

    Annual emission fluxes of N2O and CO2 and deposition fluxes of CH4 were calculated for the year 2003 for the poplar plantation and compared to those measured at the natural forest site. N2O emissions at the poplar plantation were 0.15plusmn;0.1 g N2O m-2 y-1 and the difference to the emissions at the natural forest of 0.07±0.06 g N2O m-2 y-1 are partly due to a period of high emissions after the flooding of the site at the end of 2002. CH4 consumption at the natural forest was twice as large as at the poplar plantation. In comparison to the relict forest, carbon stocks in the soil under the poplar plantation were depleted by 61% of surface (10 cm) carbon and by 25% down the profile under tillage (45 cm). Soil respiration rates were not significant different at both sites with 1608±1053 and 2200±791 g CO2 m-2 y-1 at the poplar plantation and natural forest, respectively, indicating that soil organic carbon is much more stable in the natural forest. In terms of the greenhouse gas budget, the non-CO2 gases contributed minor to the overall soil balance with only 0.9% (N2O) and -0.3% (CH4 of CO2-eq emissions in the natural forest, and 2.7% (N2O) and -0.2% of CO2-eq. emissions in the poplar plantation.

    The very high spatial variability of soil fluxes within the two sites was related to the morphology of the floodplain area, which was formed by the historic course of

  11. Developing an Understanding of Vegetation Change and Fluvial Carbon Fluxes in Semi-Arid Environments

    NASA Astrophysics Data System (ADS)

    Puttock, A. K.; Dungait, J.; Bol, R.; MacLeod, C. J.; Brazier, R.

    2011-12-01

    Dryland environments are estimated to cover around 40% of the global land surface (Okin et al, 2009) and are home to approximately 2.5 billion people (Reynolds et al. 2007). Many of these areas have recently experienced extensive land degradation. One such area and the focus of this project is the semi-arid US Southwest, where degradation over the past 150 years has been characterized by the invasion of woody vegetation into grasslands. Transition from grass to woody vegetation results in a change in ecosystem structure and function (Turnbull et al, 2008). Structural change is typically characterised by an increased heterogeneity of soil and vegetation resources, associated with reduced vegetation coverage and an increased vulnerability to soil erosion and the potential loss of key nutrients to adjacent fluvial systems. Such loss of resources may impact heavily upon the amount of carbon that is sequestered by these environments and the amount of carbon that is lost as the land becomes more degraded. Therefore, understanding these vegetation transitions is significant for sustainable land use and global biogeochemical cycling. This project uses an ecohydrological approach, monitoring natural rainfall-runoff events over six bounded plots with different vegetation coverage. The experiment takes advantage of a natural abundance stable 13C isotope shift from C3 piñon-juniper (Pinus edulis-Juniperus monosperma) mixed stand through a C4 pure-grass (Bouteloua eriopoda) to C3 shrub (Larrea tridentate). Data collected quantify fluvial fluxes of sediment and associated soil organic matter and carbon that is lost from across the grass-to-shrub and grass-to-woodland transition (where change in space is taken to indicate a similar change through time). Results collected during the 2010 and 2011 monsoon seasons will be presented, illustrating that soil and carbon losses are greater as the ecosystem becomes more dominated by woody plants. Additionally this project utilises novel

  12. HyFlux - Part II: Subsurface sequestration of methane-derived carbon in gas-hydrate- bearing marine sediments

    NASA Astrophysics Data System (ADS)

    Naehr, T. H.; Asper, V. L.; Garcia, O.; Kastner, M.; Leifer, I.; MacDonald, I. R.; Solomon, E. A.; Yvon-Lewis, S.; Zimmer, B.

    2008-12-01

    The recently funded DOE/NETL study "HyFlux: Remote sensing and sea-truth measurements of methane flux to the atmosphere" (see MacDonald et al.: HyFlux - Part I) will combine sea surface, water column and shallow subsurface observations to improve our estimates of methane flux from submarine seeps and associated gas hydrate deposits to the water column and atmosphere along the Gulf of Mexico continental margin and other selected areas world-wide. As methane-rich fluids rise towards the sediment-water interface, they will interact with sulfate-rich pore fluids derived from overlying bottom water, which results in the formation of an important biogeochemical redox boundary, the so-called sulfate-methane interface, or SMI. Both methane and sulfate are consumed within the SMI and dissolved inorganic carbon, mostly bicarbonate (HCO3-) and hydrogen sulfide are produced, stimulating authigenic carbonate precipitation at and immediately below the SMI. Accordingly, the formation of authigenic carbonates in methane- and gas-hydrate-rich sediments will sequester a portion of the methane-derived carbon. To date, however, little is known about the quantitative aspects of these reactions. Rates of DIC production are not well constrained, but recent biogeochemical models indicate that CaCO3 precipitation rates may be as high as 120 μmol cm-2a-1. Therefore, AOM-driven carbonate precipitation must be considered when assessing the impact of gas-hydrate-derived methane on the global carbon cycle. As part of HyFlux, we will conduct pore water analyses (DOC, DIC, CH4, δ13CDIC, δ13CDOC, δ13CCH4, δ18O, and δD isotope ratios) to evaluate the importance of authigenic carbonate precipitation as a sequestration mechanism for methane- derived carbon. In addition, sediment and seafloor carbonate samples will be analyzed for bulk sedimentary carbonate (δ13C and δ18O) and bulk sedimentary organic matter (δ13C and δ15N), as well as sulfur, bulk mineralogy, texture and morphological

  13. Carbon Fluxes And Yield Of Bioenergy Sorghum In An Extreme Desert Production Environment

    NASA Astrophysics Data System (ADS)

    Grantz, D. A.; Oikawa, P. Y.; Jenerette, D.

    2012-12-01

    Carbon accumulation and agronomic yield of tropical C4 grasses are high under irrigated conditions in low desert, western U.S. production areas. These are candidate production systems for purpose-grown biofuel feedstocks. Here we report fluxes of carbon at leaf and canopy scales, along with above-ground biomass yield, in an irrigated, fertilized field (5.26 ha) in the low desert (Imperial Valley) of California. This is an uncommonly productive but environmentally extreme growth environment with typical Tsoil > 55 C and Tair > 42 C during the growing season. We monitored a single field under fallow conditions, followed by planting, growth, harvest, and re-growth from stubble of Sorghum bicolor. Carbon accumulation is one aspect of our developing sustainability metric that characterizes land use conversion to biofuel produ