WorldWideScience

Sample records for terrestrial carbon cycles

  1. The decadal state of the terrestrial carbon cycle

    NARCIS (Netherlands)

    Velde, van der I.R.; Bloom, J.; Exbrayat, J.; Feng, L.; Williams, M.

    2016-01-01

    The terrestrial carbon cycle is currently the least constrained component of the global carbon budget. Large uncertainties stem from a poor understanding of plant carbon allocation, stocks, residence times, and carbon use efficiency. Imposing observational constraints on the terrestrial carbon cycle

  2. The decadal state of the terrestrial carbon cycle : Global retrievals of terrestrial carbon allocation, pools, and residence times

    NARCIS (Netherlands)

    Bloom, A Anthony; Exbrayat, Jean-François; van der Velde, Ivar R; Feng, Liang; Williams, Mathew

    2016-01-01

    The terrestrial carbon cycle is currently the least constrained component of the global carbon budget. Large uncertainties stem from a poor understanding of plant carbon allocation, stocks, residence times, and carbon use efficiency. Imposing observational constraints on the terrestrial carbon cycle

  3. Terrestrial nitrogen-carbon cycle interactions at the global scale.

    Science.gov (United States)

    Zaehle, S

    2013-07-05

    Interactions between the terrestrial nitrogen (N) and carbon (C) cycles shape the response of ecosystems to global change. However, the global distribution of nitrogen availability and its importance in global biogeochemistry and biogeochemical interactions with the climate system remain uncertain. Based on projections of a terrestrial biosphere model scaling ecological understanding of nitrogen-carbon cycle interactions to global scales, anthropogenic nitrogen additions since 1860 are estimated to have enriched the terrestrial biosphere by 1.3 Pg N, supporting the sequestration of 11.2 Pg C. Over the same time period, CO2 fertilization has increased terrestrial carbon storage by 134.0 Pg C, increasing the terrestrial nitrogen stock by 1.2 Pg N. In 2001-2010, terrestrial ecosystems sequestered an estimated total of 27 Tg N yr(-1) (1.9 Pg C yr(-1)), of which 10 Tg N yr(-1) (0.2 Pg C yr(-1)) are due to anthropogenic nitrogen deposition. Nitrogen availability already limits terrestrial carbon sequestration in the boreal and temperate zone, and will constrain future carbon sequestration in response to CO2 fertilization (regionally by up to 70% compared with an estimate without considering nitrogen-carbon interactions). This reduced terrestrial carbon uptake will probably dominate the role of the terrestrial nitrogen cycle in the climate system, as it accelerates the accumulation of anthropogenic CO2 in the atmosphere. However, increases of N2O emissions owing to anthropogenic nitrogen and climate change (at a rate of approx. 0.5 Tg N yr(-1) per 1°C degree climate warming) will add an important long-term climate forcing.

  4. Nonautonomous linear system of the terrestrial carbon cycle

    Science.gov (United States)

    Luo, Y.

    2012-12-01

    Carbon cycle has been studied by uses of observation through various networks, field and laboratory experiments, and simulation models. Much less has been done on theoretical thinking and analysis to understand fundament properties of carbon cycle and then guide observatory, experimental, and modeling research. This presentation is to explore what would be the theoretical properties of terrestrial carbon cycle and how those properties can be used to make observatory, experimental, and modeling research more effective. Thousands of published data sets from litter decomposition and soil incubation studies almost all indicate that decay processes of litter and soil organic carbon can be well described by first order differential equations with one or more pools. Carbon pool dynamics in plants and soil after disturbances (e.g., wildfire, clear-cut of forests, and plows of soil for cropping) and during natural recovery or ecosystem restoration also exhibit characteristics of first-order linear systems. Thus, numerous lines of empirical evidence indicate that the terrestrial carbon cycle can be adequately described as a nonautonomous linear system. The linearity reflects the nature of the carbon cycle that carbon, once fixed by photosynthesis, is linearly transferred among pools within an ecosystem. The linear carbon transfer, however, is modified by nonlinear functions of external forcing variables. In addition, photosynthetic carbon influx is also nonlinearly influenced by external variables. This nonautonomous linear system can be mathematically expressed by a first-order linear ordinary matrix equation. We have recently used this theoretical property of terrestrial carbon cycle to develop a semi-analytic solution of spinup. The new methods have been applied to five global land models, including NCAR's CLM and CABLE models and can computationally accelerate spinup by two orders of magnitude. We also use this theoretical property to develop an analytic framework to

  5. A tree-ring perspective on the terrestrial carbon cycle

    International Nuclear Information System (INIS)

    Babst, F.; Alexander, M.R.; Szejner, P.; Trouet, V.; Alexander, M.R.; Moore, D.J.P.; Bouriaud, O.; Klesse, S.; Frank, D.; Roden, J.; Ciais, P.; Poulter, B.

    2014-01-01

    Tree-ring records can provide valuable information to advance our understanding of contemporary terrestrial carbon cycling and to reconstruct key metrics in the decades preceding monitoring data. The growing use of tree rings in carbon-cycle research is being facilitated by increasing recognition of reciprocal benefits among research communities. Yet, basic questions persist regarding what tree rings represent at the ecosystem level, how to optimally integrate them with other data streams, and what related challenges need to be overcome. It is also apparent that considerable unexplored potential exists for tree rings to refine assessments of terrestrial carbon cycling across a range of temporal and spatial domains. Here, we summarize recent advances and highlight promising paths of investigation with respect to (1) growth phenology, (2) forest productivity trends and variability, (3) CO 2 fertilization and water-use efficiency, (4) forest disturbances, and (5) comparisons between observational and computational forest productivity estimates. We encourage the integration of tree-ring data: with eddy-covariance measurements to investigate carbon allocation patterns and water-use efficiency; with remotely sensed observations to distinguish the timing of cambial growth and leaf phenology; and with forest inventories to develop continuous, annually resolved and long-term carbon budgets. In addition, we note the potential of tree-ring records and derivatives thereof to help evaluate the performance of earth system models regarding the simulated magnitude and dynamics of forest carbon uptake, and inform these models about growth responses to (non-)climatic drivers. Such efforts are expected to improve our understanding of forest carbon cycling and place current developments into a long-term perspective. (authors)

  6. Terrestrial Carbon Cycle Variability [version 1; referees: 2 approved

    Directory of Open Access Journals (Sweden)

    Dennis Baldocchi

    2016-09-01

    Full Text Available A growing literature is reporting on how the terrestrial carbon cycle is experiencing year-to-year variability because of climate anomalies and trends caused by global change. As CO2 concentration records in the atmosphere exceed 50 years and as satellite records reach over 30 years in length, we are becoming better able to address carbon cycle variability and trends. Here we review how variable the carbon cycle is, how large the trends in its gross and net fluxes are, and how well the signal can be separated from noise. We explore mechanisms that explain year-to-year variability and trends by deconstructing the global carbon budget. The CO2 concentration record is detecting a significant increase in the seasonal amplitude between 1958 and now. Inferential methods provide a variety of explanations for this result, but a conclusive attribution remains elusive. Scientists have reported that this trend is a consequence of the greening of the biosphere, stronger northern latitude photosynthesis, more photosynthesis by semi-arid ecosystems, agriculture and the green revolution, tropical temperature anomalies, or increased winter respiration. At the global scale, variability in the terrestrial carbon cycle can be due to changes in constituent fluxes, gross primary productivity, plant respiration and heterotrophic (microbial respiration, and losses due to fire, land use change, soil erosion, or harvesting. It remains controversial whether or not there is a significant trend in global primary productivity (due to rising CO2, temperature, nitrogen deposition, changing land use, and preponderance of wet and dry regions. The degree to which year-to-year variability in temperature and precipitation anomalies affect global primary productivity also remains uncertain. For perspective, interannual variability in global gross primary productivity is relatively small (on the order of 2 Pg-C y-1 with respect to a large and uncertain background (123 +/- 4 Pg-C y-1

  7. Terrestrial carbon cycle affected by non-uniform climate warming

    International Nuclear Information System (INIS)

    Jianyang Xia; Yiqi Luo; Jiquan Chen; Shilong Piao; Ciais, Philippe; Shiqiang Wan

    2014-01-01

    Feedbacks between the terrestrial carbon cycle and climate change could affect many ecosystem functions and services, such as food production, carbon sequestration and climate regulation. The rate of climate warming varies on diurnal and seasonal timescales. A synthesis of global air temperature data reveals a greater rate of warming in winter than in summer in northern mid and high latitudes, and the inverse pattern in some tropical regions. The data also reveal a decline in the diurnal temperature range over 51% of the global land area and an increase over only 13%, because night-time temperatures in most locations have risen faster than daytime temperatures. Analyses of satellite data, model simulations and in situ observations suggest that the impact of seasonal warming varies between regions. For example, spring warming has largely stimulated ecosystem productivity at latitudes between 30 degrees and 90 degrees N, but suppressed productivity in other regions. Contrasting impacts of day- and night-time warming on plant carbon gain and loss are apparent in many regions. We argue that ascertaining the effects of non-uniform climate warming on terrestrial ecosystems is a key challenge in carbon cycle research. (authors)

  8. The terrestrial carbon cycle on the regional and global scale : modeling, uncertainties and policy relevance

    NARCIS (Netherlands)

    Minnen, van J.G.

    2008-01-01

    Contains the chapters: The importance of three centuries of climate and land-use change for the global and regional terrestrial carbon cycle; and The terrestrial C cycle and its role in the climate change policy

  9. Importance of vegetation dynamics for future terrestrial carbon cycling

    International Nuclear Information System (INIS)

    Ahlström, Anders; Smith, Benjamin; Xia, Jianyang; Luo, Yiqi; Arneth, Almut

    2015-01-01

    Terrestrial ecosystems currently sequester about one third of anthropogenic CO 2 emissions each year, an important ecosystem service that dampens climate change. The future fate of this net uptake of CO 2 by land based ecosystems is highly uncertain. Most ecosystem models used to predict the future terrestrial carbon cycle share a common architecture, whereby carbon that enters the system as net primary production (NPP) is distributed to plant compartments, transferred to litter and soil through vegetation turnover and then re-emitted to the atmosphere in conjunction with soil decomposition. However, while all models represent the processes of NPP and soil decomposition, they vary greatly in their representations of vegetation turnover and the associated processes governing mortality, disturbance and biome shifts. Here we used a detailed second generation dynamic global vegetation model with advanced representation of vegetation growth and mortality, and the associated turnover. We apply an emulator that describes the carbon flows and pools exactly as in simulations with the full model. The emulator simulates ecosystem dynamics in response to 13 different climate or Earth system model simulations from the Coupled Model Intercomparison Project Phase 5 ensemble under RCP8.5 radiative forcing. By exchanging carbon cycle processes between these 13 simulations we quantified the relative roles of three main driving processes of the carbon cycle; (I) NPP, (II) vegetation dynamics and turnover and (III) soil decomposition, in terms of their contribution to future carbon (C) uptake uncertainties among the ensemble of climate change scenarios. We found that NPP, vegetation turnover (including structural shifts, wild fires and mortality) and soil decomposition rates explained 49%, 17% and 33%, respectively, of uncertainties in modelled global C-uptake. Uncertainty due to vegetation turnover was further partitioned into stand-clearing disturbances (16%), wild fires (0%), stand

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

    Science.gov (United States)

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

    2012-05-01

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

  11. Nitrogen attenuation of terrestrial carbon cycle response to global environmental factors

    Science.gov (United States)

    Atul Jain; Xiaojuan Yang; Haroon Kheshgi; A. David McGuire; Wilfred Post; David. Kicklighter

    2009-01-01

    Nitrogen cycle dynamics have the capacity to attenuate the magnitude of global terrestrial carbon sinks and sources driven by CO2 fertilization and changes in climate. In this study, two versions of the terrestrial carbon and nitrogen cycle components of the Integrated Science Assessment Model (ISAM) are used to evaluate how variation in nitrogen...

  12. Multiple Observation Types Jointly Constrain Terrestrial Carbon and Water Cycles

    Science.gov (United States)

    Raupach, M. R.; Haverd, V.; Briggs, P. R.; Canadell, J.; Davis, S. J.; Isaac, P. R.; Law, R.; Meyer, M.; Peters, G. P.; Pickett Heaps, C.; Roxburgh, S. H.; Sherman, B.; van Gorsel, E.; Viscarra Rossel, R.; Wang, Z.

    2012-12-01

    Information about the carbon cycle potentially constrains the water cycle, and vice versa. This paper explores the utility of multiple observation sets to constrain carbon and water fluxes and stores in a land surface model, and a resulting determination of the Australian terrestrial carbon budget. Observations include streamflow from 416 gauged catchments, measurements of evapotranspiration (ET) and net ecosystem production (NEP) from 12 eddy-flux sites, litterfall data, and data on carbon pools. The model is a version of CABLE (the Community Atmosphere-Biosphere-Land Exchange model), coupled with CASAcnp (a biogeochemical model) and SLI (Soil-Litter-Iso, a soil hydrology model including liquid and vapour water fluxes and the effects of litter). By projecting observation-prediction residuals onto model uncertainty, we find that eddy flux measurements provide a significantly tighter constraint on Australian continental net primary production (NPP) than the other data types. However, simultaneous constraint by multiple data types is important for mitigating bias from any single type. Results emerging from the multiply-constrained model are as follows (with all values applying over 1990-2011 and all ranges denoting ±1 standard error): (1) on the Australian continent, a predominantly semi-arid region, over half (0.64±0.05) of the water loss through ET occurs through soil evaporation and bypasses plants entirely; (2) mean Australian NPP is 2200±400 TgC/y, making the NPP/precipitation ratio about the same for Australia as the global land average; (3) annually cyclic ("grassy") vegetation and persistent ("woody") vegetation respectively account for 0.56±0.14 and 0.43±0.14 of NPP across Australia; (4) the average interannual variability of Australia's NEP (±180 TgC/y) is larger than Australia's total anthropogenic greenhouse gas emissions in 2011 (149 TgCeq/y), and is dominated by variability in desert and savannah regions. The mean carbon budget over 1990

  13. Terrestrial carbon turnover time constraints on future carbon cycle-climate feedback

    Science.gov (United States)

    Fan, N.; Carvalhais, N.; Reichstein, M.

    2017-12-01

    Understanding the terrestrial carbon cycle-climate feedback is essential to reduce the uncertainties resulting from the between model spread in prognostic simulations (Friedlingstein et al., 2006). One perspective is to investigate which factors control the variability of the mean residence times of carbon in the land surface, and how these may change in the future, consequently affecting the response of the terrestrial ecosystems to changes in climate as well as other environmental conditions. Carbon turnover time of the whole ecosystem is a dynamic parameter that represents how fast the carbon cycle circulates. Turnover time τ is an essential property for understanding the carbon exchange between the land and the atmosphere. Although current Earth System Models (ESMs), supported by GVMs for the description of the land surface, show a strong convergence in GPP estimates, but tend to show a wide range of simulated turnover times (Carvalhais, 2014). Thus, there is an emergent need of constraints on the projected response of the balance between terrestrial carbon fluxes and carbon stock which will give us more certainty in response of carbon cycle to climate change. However, the difficulty of obtaining such a constraint is partly due to lack of observational data on temporal change of terrestrial carbon stock. Since more new datasets of carbon stocks such as SoilGrid (Hengl, et al., 2017) and fluxes such as GPP (Jung, et al., 2017) are available, improvement in estimating turnover time can be achieved. In addition, previous study ignored certain aspects such as the relationship between τ and nutrients, fires, etc. We would like to investigate τ and its role in carbon cycle by combining observatinoal derived datasets and state-of-the-art model simulations.

  14. A synthesis of the arctic terrestrial and marine carbon cycles under pressure from a dwindling cryosphere

    DEFF Research Database (Denmark)

    Parmentier, Frans-Jan W; Christensen, Torben R; Rysgaard, Søren

    2017-01-01

    The current downturn of the arctic cryosphere, such as the strong loss of sea ice, melting of ice sheets and glaciers, and permafrost thaw, affects the marine and terrestrial carbon cycles in numerous interconnected ways. Nonetheless, processes in the ocean and on land have been too often...

  15. Reviews and syntheses: Systematic Earth observations for use in terrestrial carbon cycle data assimilation systems

    Science.gov (United States)

    Scholze, Marko; Buchwitz, Michael; Dorigo, Wouter; Guanter, Luis; Quegan, Shaun

    2017-07-01

    The global carbon cycle is an important component of the Earth system and it interacts with the hydrology, energy and nutrient cycles as well as ecosystem dynamics. A better understanding of the global carbon cycle is required for improved projections of climate change including corresponding changes in water and food resources and for the verification of measures to reduce anthropogenic greenhouse gas emissions. An improved understanding of the carbon cycle can be achieved by data assimilation systems, which integrate observations relevant to the carbon cycle into coupled carbon, water, energy and nutrient models. Hence, the ingredients for such systems are a carbon cycle model, an algorithm for the assimilation and systematic and well error-characterised observations relevant to the carbon cycle. Relevant observations for assimilation include various in situ measurements in the atmosphere (e.g. concentrations of CO2 and other gases) and on land (e.g. fluxes of carbon water and energy, carbon stocks) as well as remote sensing observations (e.g. atmospheric composition, vegetation and surface properties).We briefly review the different existing data assimilation techniques and contrast them to model benchmarking and evaluation efforts (which also rely on observations). A common requirement for all assimilation techniques is a full description of the observational data properties. Uncertainty estimates of the observations are as important as the observations themselves because they similarly determine the outcome of such assimilation systems. Hence, this article reviews the requirements of data assimilation systems on observations and provides a non-exhaustive overview of current observations and their uncertainties for use in terrestrial carbon cycle data assimilation. We report on progress since the review of model-data synthesis in terrestrial carbon observations by Raupach et al.(2005), emphasising the rapid advance in relevant space-based observations.

  16. Aquatic carbon cycling in the conterminous United States and implications for terrestrial carbon accounting.

    Science.gov (United States)

    Butman, David; Stackpoole, Sarah; Stets, Edward; McDonald, Cory P; Clow, David W; Striegl, Robert G

    2016-01-05

    Inland water ecosystems dynamically process, transport, and sequester carbon. However, the transport of carbon through aquatic environments has not been quantitatively integrated in the context of terrestrial ecosystems. Here, we present the first integrated assessment, to our knowledge, of freshwater carbon fluxes for the conterminous United States, where 106 (range: 71-149) teragrams of carbon per year (TgC⋅y(-1)) is exported downstream or emitted to the atmosphere and sedimentation stores 21 (range: 9-65) TgC⋅y(-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 flux at 69 (range: 36-110) TgC⋅y(-1) or 65% of the total aquatic carbon flux for the conterminous United States. Comparing our results with the output of a suite of terrestrial biosphere models (TBMs), we suggest that within the current modeling framework, calculations of net ecosystem production (NEP) defined as terrestrial only may be overestimated by as much as 27%. However, the internal production and mineralization of carbon in freshwaters remain to be quantified and would reduce the effect of including aquatic carbon fluxes within calculations of terrestrial NEP. Reconciliation of carbon mass-flux interactions between terrestrial and aquatic carbon sources and sinks will require significant additional research and modeling capacity.

  17. Aquatic carbon cycling in the conterminous United States and implications for terrestrial carbon accounting

    Science.gov (United States)

    Butman, David; Stackpoole, Sarah; Stets, Edward; McDonald, Cory P.; Clow, David W.; Striegl, Robert G.

    2016-01-01

    Inland water ecosystems dynamically process, transport, and sequester carbon. However, the transport of carbon through aquatic environments has not been quantitatively integrated in the context of terrestrial ecosystems. Here, we present the first integrated assessment, to our knowledge, of freshwater carbon fluxes for the conterminous United States, where 106 (range: 71–149) teragrams of carbon per year (TgC⋅y−1) is exported downstream or emitted to the atmosphere and sedimentation stores 21 (range: 9–65) TgC⋅y−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 flux at 69 (range: 36–110) TgC⋅y−1 or 65% of the total aquatic carbon flux for the conterminous United States. Comparing our results with the output of a suite of terrestrial biosphere models (TBMs), we suggest that within the current modeling framework, calculations of net ecosystem production (NEP) defined as terrestrial only may be overestimated by as much as 27%. However, the internal production and mineralization of carbon in freshwaters remain to be quantified and would reduce the effect of including aquatic carbon fluxes within calculations of terrestrial NEP. Reconciliation of carbon mass–flux interactions between terrestrial and aquatic carbon sources and sinks will require significant additional research and modeling capacity. PMID:26699473

  18. A terrestrial Eocene stack: tying terrestrial lake ecology to marine carbon cycling through the Early Eocene Climatic Optimum

    Science.gov (United States)

    Grogan, D. S.; Whiteside, J. H.; Musher, D.; Rosengard, S. Z.; Vankeuren, M. A.; Pancost, R. D.

    2010-12-01

    The lacustrine Green River Formation is known to span ≥15 million years through the early-middle Eocene, and recent work on radioisotopic dating has provided a framework on which to build ties to the orbitally-tuned marine Eocene record. Here we present a spliced stack of Fischer assay data from drilled cores of the Green River Formation that span both an East-West and a North-South transect of the Uinta Basin of Utah. Detailed work on two cores demonstrate that Fischer assay measurements covary with total organic carbon and bulk carbon isotopes, allowing us to use Fisher assay results as a representative carbon cycling proxy throughout the stack. We provide an age model for this core record by combining radioisotopic dates of tuff layers with frequency analysis of Fischer assay measurements. Identification of orbital frequencies tied directly to magnetochrons through radioisotopic dates allows for a direct comparison of the terrestrial to the marine Eocene record. Our analysis indicates that the marker beds used to correlate the stack cores represent periods of enhanced lake productivity and extreme carbon burial; however, unlike the hyperthermal events that are clearly marked in the marine Eocene record, the hydrocarbon-rich "Mahogany Bed" period of burial does not correspond to a clear carbon isotope excursion. This suggests that the terrestrial realm may have experienced extreme ecological responses to relatively small perturbations in the carbon cycle during the Early Eocene Climatic Optimum. To investigate the ecological responses to carbon cycle perturbations through the hydrocarbon rich beds, we analyzed a suite of microbial biomarkers, finding evidence for cyanobacteria, dinoflagellates, and potentially green sulfur bacteria. These taxa indicate fluctuating oxic/anoxic conditions in the lake during abrupt intervals of carbon burial, suggesting a lake biogeochemical regime with no modern analogues.

  19. Exploring global carbon turnover and radiocarbon cycling in terrestrial biosphere models

    Science.gov (United States)

    Graven, H. D.; Warren, H.

    2017-12-01

    The uptake of carbon into terrestrial ecosystems through net primary productivity (NPP) and the turnover of that carbon through various pathways are the fundamental drivers of changing carbon stocks on land, in addition to human-induced and natural disturbances. Terrestrial biosphere models use different formulations for carbon uptake and release, resulting in a range of values in NPP of 40-70 PgC/yr and biomass turnover times of about 25-40 years for the preindustrial period in current-generation models from CMIP5. Biases in carbon uptake and turnover impact simulated carbon uptake and storage in the historical period and later in the century under changing climate and CO2 concentration, however evaluating global-scale NPP and carbon turnover is challenging. Scaling up of plot-scale measurements involves uncertainty due to the large heterogeneity across ecosystems and biomass types, some of which are not well-observed. We are developing the modelling of radiocarbon in terrestrial biosphere models, with a particular focus on decadal 14C dynamics after the nuclear weapons testing in the 1950s-60s, including the impact of carbon flux trends and variability on 14C cycling. We use an estimate of the total inventory of excess 14C in the biosphere constructed by Naegler and Levin (2009) using a 14C budget approach incorporating estimates of total 14C produced by the weapons tests and atmospheric and oceanic 14C observations. By simulating radiocarbon in simple biosphere box models using carbon fluxes from the CMIP5 models, we find that carbon turnover is too rapid in many of the simple models - the models appear to take up too much 14C and release it too quickly. Therefore many CMIP5 models may also simulate carbon turnover that is too rapid. A caveat is that the simple box models we use may not adequately represent carbon dynamics in the full-scale models. Explicit simulation of radiocarbon in terrestrial biosphere models would allow more robust evaluation of biosphere

  20. Effects of climate extremes on the terrestrial carbon cycle: concepts, processes and potential future impacts

    Science.gov (United States)

    Frank, Dorothea; Reichstein, Markus; Bahn, Michael; Thonicke, Kirsten; Frank, David; Mahecha, Miguel D; Smith, Pete; van der Velde, Marijn; Vicca, Sara; Babst, Flurin; Beer, Christian; Buchmann, Nina; Canadell, Josep G; Ciais, Philippe; Cramer, Wolfgang; Ibrom, Andreas; Miglietta, Franco; Poulter, Ben; Rammig, Anja; Seneviratne, Sonia I; Walz, Ariane; Wattenbach, Martin; Zavala, Miguel A; Zscheischler, Jakob

    2015-01-01

    Extreme droughts, heat waves, frosts, precipitation, wind storms and other climate extremes may impact the structure, composition and functioning of terrestrial ecosystems, and thus carbon cycling and its feedbacks to the climate system. Yet, the interconnected avenues through which climate extremes drive ecological and physiological processes and alter the carbon balance are poorly understood. Here, we review the literature on carbon cycle relevant responses of ecosystems to extreme climatic events. Given that impacts of climate extremes are considered disturbances, we assume the respective general disturbance-induced mechanisms and processes to also operate in an extreme context. The paucity of well-defined studies currently renders a quantitative meta-analysis impossible, but permits us to develop a deductive framework for identifying the main mechanisms (and coupling thereof) through which climate extremes may act on the carbon cycle. We find that ecosystem responses can exceed the duration of the climate impacts via lagged effects on the carbon cycle. The expected regional impacts of future climate extremes will depend on changes in the probability and severity of their occurrence, on the compound effects and timing of different climate extremes, and on the vulnerability of each land-cover type modulated by management. Although processes and sensitivities differ among biomes, based on expert opinion, we expect forests to exhibit the largest net effect of extremes due to their large carbon pools and fluxes, potentially large indirect and lagged impacts, and long recovery time to regain previous stocks. At the global scale, we presume that droughts have the strongest and most widespread effects on terrestrial carbon cycling. Comparing impacts of climate extremes identified via remote sensing vs. ground-based observational case studies reveals that many regions in the (sub-)tropics are understudied. Hence, regional investigations are needed to allow a global

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

    DEFF Research Database (Denmark)

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

    2015-01-01

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

  2. Evaluation of Terrestrial Carbon Cycle with the Land Use Harmonization Dataset

    Science.gov (United States)

    Sasai, T.; Nemani, R. R.

    2017-12-01

    CO2 emission by land use and land use change (LULUC) has still had a large uncertainty (±50%). We need to more accurately reveal a role of each LULUC process on terrestrial carbon cycle, and to develop more complicated land cover change model, leading to improve our understanding of the mechanism of global warming. The existing biosphere model studies do not necessarily have enough major LULUC process in the model description (e.g., clear cutting and residual soil carbon). The issue has the potential for causing an underestimation of the effect of LULUC on the global carbon exchange. In this study, the terrestrial biosphere model was modified with several LULUC processes according to the land use harmonization data set. The global mean LULUC emission from the year 1850 to 2000 was 137.2 (PgC 151year-1), and we found the noticeable trend in tropical region. As with the case of primary production in the existing studies, our results emphasized the role of tropical forest on wood productization and residual soil organic carbon by cutting. Global mean NEP was decreased by LULUC. NEP is largely affected by decreasing leaf biomass (photosynthesis) by deforestation process and increasing plant growth rate by regrowth process. We suggested that the model description related to deforestation, residual soil decomposition, wood productization and plant regrowth is important to develop a biosphere model for estimating long-term global carbon cycle.

  3. Comparing Terrestrial Organic Carbon Cycle Dynamics in Interglacial and Glacial Climates in the South American Tropics

    Science.gov (United States)

    Fornace, K. L.; Galy, V.; Hughen, K. A.

    2014-12-01

    The application of compound-specific radiocarbon dating to molecular biomarkers has allowed for tracking of specific organic carbon pools as they move through the environment, providing insight into complex processes within the global carbon cycle. Here we use this technique to investigate links between glacial-interglacial climate change and terrestrial organic carbon cycling in the catchments of Cariaco Basin and Lake Titicaca, two tropical South American sites with well-characterized climate histories since the last glacial period. By comparing radiocarbon ages of terrestrial biomarkers (leaf wax compounds) with deposition ages in late glacial and Holocene sediments, we are able to gauge the storage time of these compounds in the catchments in soils, floodplains, etc. before transport to marine or lacustrine sediments. We are also able to probe the effects of temperature and hydrologic change individually by taking advantage of opposite hydrologic trends at the two sites: while both were colder during the last glacial period, precipitation at Titicaca decreased from the last glacial period to the Holocene, but the late glacial was marked by drier conditions at Cariaco. Preliminary data from both sites show a wide range of apparent ages of long-chain n-fatty acids (within error of 0 to >10,000 years older than sediment), with the majority showing ages on the order of several millennia at time of deposition and age generally increasing with chain length. While late glacial leaf waxes appear to be older relative to sediment than those deposited in the Holocene at both sites, at Cariaco we find a ~2-3 times larger glacial-interglacial age difference than at Titicaca. We hypothesize that at Titicaca the competing influences of wetter and colder conditions during the last glacial period, which respectively tend to increase and decrease the rate of organic carbon turnover on land, served to minimize the contrast between glacial and interglacial leaf wax storage time

  4. Asia-MIP: Multi Model-data Synthesis of Terrestrial Carbon Cycles in Asia

    Science.gov (United States)

    Ichii, K.; Kondo, M.; Ito, A.; Kang, M.; Sasai, T.; SATO, H.; Ueyama, M.; Kobayashi, H.; Saigusa, N.; Kim, J.

    2013-12-01

    Asia, which is characterized by monsoon climate and intense human activities, is one of the prominent understudied regions in terms of terrestrial carbon budgets and mechanisms of carbon exchange. To better understand terrestrial carbon cycle in Asia, we initiated multi-model and data intercomparison project in Asia (Asia-MIP). We analyzed outputs from multiple approaches: satellite-based observations (AVHRR and MODIS) and related products, empirically upscaled estimations (Support Vector Regression) using eddy-covariance observation network in Asia (AsiaFlux, CarboEastAsia, FLUXNET), ~10 terrestrial biosphere models (e.g. BEAMS, Biome-BGC, LPJ, SEIB-DGVM, TRIFFID, VISIT models), and atmospheric inversion analysis (e.g. TransCom models). We focused on the two difference temporal coverage: long-term (30 years; 1982-2011) and decadal (10 years; 2001-2010; data intensive period) scales. The regions of covering Siberia, Far East Asia, East Asia, Southeast Asia and South Asia (60-80E, 10S-80N), was analyzed in this study for assessing the magnitudes, interannual variability, and key driving factors of carbon cycles. We will report the progress of synthesis effort to quantify terrestrial carbon budget in Asia. First, we analyzed the recent trends in Gross Primary Productivities (GPP) using satellite-based observation (AVHRR) and multiple terrestrial biosphere models. We found both model outputs and satellite-based observation consistently show an increasing trend in GPP in most of the regions in Asia. Mechanisms of the GPP increase were analyzed using models, and changes in temperature and precipitation play dominant roles in GPP increase in boreal and temperate regions, whereas changes in atmospheric CO2 and precipitation are important in tropical regions. However, their relative contributions were different. Second, in the decadal analysis (2001-2010), we found that the negative GPP and carbon uptake anomalies in 2003 summer in Far East Asia is one of the largest

  5. A global model of carbon, nitrogen and phosphorus cycles for the terrestrial biosphere

    Directory of Open Access Journals (Sweden)

    Y. P. Wang

    2010-07-01

    Full Text Available Carbon storage by many terrestrial ecosystems can be limited by nutrients, predominantly nitrogen (N and phosphorus (P, in addition to other environmental constraints, water, light and temperature. However the spatial distribution and the extent of both N and P limitation at the global scale have not been quantified. Here we have developed a global model of carbon (C, nitrogen (N and phosphorus (P cycles for the terrestrial biosphere. Model estimates of steady state C and N pool sizes and major fluxes between plant, litter and soil pools, under present climate conditions, agree well with various independent estimates. The total amount of C in the terrestrial biosphere is 2767 Gt C, and the C fractions in plant, litter and soil organic matter are 19%, 4% and 77%. The total amount of N is 135 Gt N, with about 94% stored in the soil, 5% in the plant live biomass, and 1% in litter. We found that the estimates of total soil P and its partitioning into different pools in soil are quite sensitive to biochemical P mineralization. The total amount of P (plant biomass, litter and soil excluding occluded P in soil is 17 Gt P in the terrestrial biosphere, 33% of which is stored in the soil organic matter if biochemical P mineralization is modelled, or 31 Gt P with 67% in soil organic matter otherwise.

    This model was used to derive the global distribution and uncertainty of N or P limitation on the productivity of terrestrial ecosystems at steady state under present conditions. Our model estimates that the net primary productivity of most tropical evergreen broadleaf forests and tropical savannahs is reduced by about 20% on average by P limitation, and most of the remaining biomes are N limited; N limitation is strongest in high latitude deciduous needle leaf forests, and reduces its net primary productivity by up to 40% under present conditions.

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

    Science.gov (United States)

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

    2010-12-01

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

  7. Impacts of large-scale climatic disturbances on the terrestrial carbon cycle

    Directory of Open Access Journals (Sweden)

    Lucht Wolfgang

    2006-07-01

    Full Text Available Abstract Background The amount of carbon dioxide in the atmosphere steadily increases as a consequence of anthropogenic emissions but with large interannual variability caused by the terrestrial biosphere. These variations in the CO2 growth rate are caused by large-scale climate anomalies but the relative contributions of vegetation growth and soil decomposition is uncertain. We use a biogeochemical model of the terrestrial biosphere to differentiate the effects of temperature and precipitation on net primary production (NPP and heterotrophic respiration (Rh during the two largest anomalies in atmospheric CO2 increase during the last 25 years. One of these, the smallest atmospheric year-to-year increase (largest land carbon uptake in that period, was caused by global cooling in 1992/93 after the Pinatubo volcanic eruption. The other, the largest atmospheric increase on record (largest land carbon release, was caused by the strong El Niño event of 1997/98. Results We find that the LPJ model correctly simulates the magnitude of terrestrial modulation of atmospheric carbon anomalies for these two extreme disturbances. The response of soil respiration to changes in temperature and precipitation explains most of the modelled anomalous CO2 flux. Conclusion Observed and modelled NEE anomalies are in good agreement, therefore we suggest that the temporal variability of heterotrophic respiration produced by our model is reasonably realistic. We therefore conclude that during the last 25 years the two largest disturbances of the global carbon cycle were strongly controlled by soil processes rather then the response of vegetation to these large-scale climatic events.

  8. Effects of nitrogen deposition on carbon cycle in terrestrial ecosystems of China: A meta-analysis

    International Nuclear Information System (INIS)

    Chen, Hao; Li, Dejun; Gurmesa, Geshere A.; Yu, Guirui; Li, Linghao; Zhang, Wei; Fang, Huajun; Mo, Jiangming

    2015-01-01

    Nitrogen (N) deposition in China has increased greatly, but the general impact of elevated N deposition on carbon (C) dynamics in Chinese terrestrial ecosystems is not well documented. In this study we used a meta-analysis method to compile 88 studies on the effects of N deposition C cycling on Chinese terrestrial ecosystems. Our results showed that N addition did not change soil C pools but increased above-ground plant C pool. A large decrease in below-ground plant C pool was observed. Our result also showed that the impacts of N addition on ecosystem C dynamics depend on ecosystem type and rate of N addition. Overall, our findings suggest that 1) decreased below-ground plant C pool may limit long-term soil C sequestration; and 2) it is better to treat N-rich and N-limited ecosystems differently in modeling effects of N deposition on ecosystem C cycle. - Highlights: • Meta-analysis was used to address the effects of N addition on C cycle. • N addition caused an large decease in belowground plant C pool. • N-rich and N-limited ecosystems had different responses to N addition. - N addition caused a large decrease in below-ground plant C pool.

  9. Multi model and data analysis of terrestrial carbon cycle in Asia: From 2001 to 2006

    Science.gov (United States)

    Ichii, K.; Takahashi, K.; Suzuki, T.; Ueyama, M.; Sasai, T.; Hirata, R.; Saigusa, N.

    2009-12-01

    Accurate monitoring and modeling of the current status and their causes of interannual variations in terrestrial carbon cycle are important. Recently, many studies analyze using multiple methods (e.g. satellite data and ecosystem models) to clarify the underlain mechanisms and recent trend since each single methodology contains its own biases. The multi-model and data ensemble approach is a powerful method to clarify the current status and their underlain mechanisms. So far, many studies using multiple sources of data and models are conducted in North America, Europe, Africa, Amazon, and Japan, however, studies in monsoon Asia are lacking. In this study, we analyzed interannual variations in terrestrial carbon cycles in monsoon Asia, and evaluated current capability of remote sensing and ecosystem model to capture them based on multiple model and data sources; flux observations, remote sensing (e.g. MODIS, AVHRR, and VGT), and ecosystem models (e.g. SVM, BEAMS, CASA, Biome-BGC, LPJ, and TRIFFID). The satellite observation and ecosystem models show clear characteristics in interannual variabilities in satellite-based NDVI and model-based GPP. These are characterized by (1) spring NDVI and modeled GPP anomalies related to temperature anomaly in mid and high latitudinal areas (positive anomalies in 2002 and 2005 and negative one in 2006), (2) NDVI and GPP anomalies in southeastern and central Asia related to precipitation (e.g. India from 2003-2006), and (3) summer NDVI and GPP anomalies in 2003 related to strong anomalies in solar radiations. NDVI anomalies related to radiation ones (2003 summer) were not accurately captured by terrestrial ecosystem models. For example, LPJ model rather shows GPP positive anomalies in Far East Asia regions probably caused by positive precipitation anomalies. Further analysis requires improvement of models to reproduce more consistent spatial patterns in NDVI anomaly, and longer term analysis (e.g. after 1982).

  10. Plumbing the global carbon cycle: Integrating inland waters into the terrestrial carbon budget

    NARCIS (Netherlands)

    Cole, J.; Prairie, Y.T.; Caraco, N.; McDowell, W.H.; Tranvil, L.; Striegl, R.G.; Duarte, C.M.; Kortelainen, P.; Downing, J.A.; Middelburg, J.J.; Melack, J.

    2007-01-01

    Because freshwater covers such a small fraction of the Earth’s surface area, inland freshwater ecosystems (particularly lakes, rivers, and reservoirs) have rarely been considered as potentially important quantitative components of the carbon cycle at either global or regional scales. By taking

  11. Effects of nitrogen deposition on carbon cycle in terrestrial ecosystems of China: A meta-analysis.

    Science.gov (United States)

    Chen, Hao; Li, Dejun; Gurmesa, Geshere A; Yu, Guirui; Li, Linghao; Zhang, Wei; Fang, Huajun; Mo, Jiangming

    2015-11-01

    Nitrogen (N) deposition in China has increased greatly, but the general impact of elevated N deposition on carbon (C) dynamics in Chinese terrestrial ecosystems is not well documented. In this study we used a meta-analysis method to compile 88 studies on the effects of N deposition C cycling on Chinese terrestrial ecosystems. Our results showed that N addition did not change soil C pools but increased above-ground plant C pool. A large decrease in below-ground plant C pool was observed. Our result also showed that the impacts of N addition on ecosystem C dynamics depend on ecosystem type and rate of N addition. Overall, our findings suggest that 1) decreased below-ground plant C pool may limit long-term soil C sequestration; and 2) it is better to treat N-rich and N-limited ecosystems differently in modeling effects of N deposition on ecosystem C cycle. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. The carbonate-silicate cycle and CO2/climate feedbacks on tidally locked terrestrial planets.

    Science.gov (United States)

    Edson, Adam R; Kasting, James F; Pollard, David; Lee, Sukyoung; Bannon, Peter R

    2012-06-01

    Atmospheric gaseous constituents play an important role in determining the surface temperatures and habitability of a planet. Using a global climate model and a parameterization of the carbonate-silicate cycle, we explored the effect of the location of the substellar point on the atmospheric CO(2) concentration and temperatures of a tidally locked terrestrial planet, using the present Earth continental distribution as an example. We found that the substellar point's location relative to the continents is an important factor in determining weathering and the equilibrium atmospheric CO(2) level. Placing the substellar point over the Atlantic Ocean results in an atmospheric CO(2) concentration of 7 ppmv and a global mean surface air temperature of 247 K, making ∼30% of the planet's surface habitable, whereas placing it over the Pacific Ocean results in a CO(2) concentration of 60,311 ppmv and a global temperature of 282 K, making ∼55% of the surface habitable.

  13. Earth system model simulations show different feedback strengths of the terrestrial carbon cycle under glacial and interglacial conditions

    Science.gov (United States)

    Adloff, Markus; Reick, Christian H.; Claussen, Martin

    2018-04-01

    In simulations with the MPI Earth System Model, we study the feedback between the terrestrial carbon cycle and atmospheric CO2 concentrations under ice age and interglacial conditions. We find different sensitivities of terrestrial carbon storage to rising CO2 concentrations in the two settings. This result is obtained by comparing the transient response of the terrestrial carbon cycle to a fast and strong atmospheric CO2 concentration increase (roughly 900 ppm) in Coupled Climate Carbon Cycle Model Intercomparison Project (C4MIP)-type simulations starting from climates representing the Last Glacial Maximum (LGM) and pre-industrial times (PI). In this set-up we disentangle terrestrial contributions to the feedback from the carbon-concentration effect, acting biogeochemically via enhanced photosynthetic productivity when CO2 concentrations increase, and the carbon-climate effect, which affects the carbon cycle via greenhouse warming. We find that the carbon-concentration effect is larger under LGM than PI conditions because photosynthetic productivity is more sensitive when starting from the lower, glacial CO2 concentration and CO2 fertilization saturates later. This leads to a larger productivity increase in the LGM experiment. Concerning the carbon-climate effect, it is the PI experiment in which land carbon responds more sensitively to the warming under rising CO2 because at the already initially higher temperatures, tropical plant productivity deteriorates more strongly and extratropical carbon is respired more effectively. Consequently, land carbon losses increase faster in the PI than in the LGM case. Separating the carbon-climate and carbon-concentration effects, we find that they are almost additive for our model set-up; i.e. their synergy is small in the global sum of carbon changes. Together, the two effects result in an overall strength of the terrestrial carbon cycle feedback that is almost twice as large in the LGM experiment as in the PI experiment

  14. A New Global LAI Product and Its Use for Terrestrial Carbon Cycle Estimation

    Science.gov (United States)

    Chen, J. M.; Liu, R.; Ju, W.; Liu, Y.

    2014-12-01

    For improving the estimation of the spatio-temporal dynamics of the terrestrial carbon cycle, a new time series of the leaf area index (LAI) is generated for the global land surface at 8 km resolution from 1981 to 2012 by combining AVHRR and MODIS satellite data. This product differs from existing LAI products in the following two aspects: (1) the non-random spatial distribution of leaves with the canopy is considered, and (2) the seasonal variation of the vegetation background is included. The non-randomness of the leaf spatial distribution in the canopy is considered using the second vegetation structural parameter named clumping index (CI), which quantifies the deviation of the leaf spatial distribution from the random case. Using the MODIS Bidirectional Reflectance Distribution Function product, a global map of CI is produced at 500 m resolution. In our LAI algorithm, CI is used to convert the effective LAI obtained from mono-angle remote sensing into the true LAI, otherwise LAI would be considerably underestimated. The vegetation background is soil in crop, grass and shrub but includes soil, grass, moss, and litter in forests. Through processing a large volume of MISR data from 2000 to 2010, monthly red and near-infrared reflectances of the vegetation background is mapped globally at 1 km resolution. This new LAI product has been validated extensively using ground-based LAI measurements distributed globally. In carbon cycle modeling, the use of CI in addition to LAI allows for accurate separation of sunlit and shaded leaves as an important step in terrestrial photosynthesis and respiration modeling. Carbon flux measurements over 100 sites over the globe are used to validate an ecosystem model named Boreal Ecosystem Productivity Simulator (BEPS). The validated model is run globally at 8 km resolution for the period from 1981 to 2012 using the LAI product and other spatial datasets. The modeled results suggest that changes in vegetation structure as quantified

  15. A comparison of simulation results from two terrestrial carbon cycle models using three climate data sets

    International Nuclear Information System (INIS)

    Ito, Akihiko; Sasai, Takahiro

    2006-01-01

    This study addressed how different climate data sets influence simulations of the global terrestrial carbon cycle. For the period 1982-2001, we compared the results of simulations based on three climate data sets (NCEP/NCAR, NCEP/DOE AMIP-II and ERA40) employed in meteorological, ecological and biogeochemical studies and two different models (BEAMS and Sim-CYCLE). The models differed in their parameterizations of photosynthetic and phenological processes but used the same surface climate (e.g. shortwave radiation, temperature and precipitation), vegetation, soil and topography data. The three data sets give different climatic conditions, especially for shortwave radiation, in terms of long-term means, linear trends and interannual variability. Consequently, the simulation results for global net primary productivity varied by 16%-43% only from differences in the climate data sets, especially in these regions where the shortwave radiation data differed markedly: differences in the climate data set can strongly influence simulation results. The differences among the climate data set and between the two models resulted in slightly different spatial distribution and interannual variability in the net ecosystem carbon budget. To minimize uncertainty, we should pay attention to the specific climate data used. We recommend developing an accurate standard climate data set for simulation studies

  16. Insights into deep-time terrestrial carbon cycle processes from modern plant isotope ecology

    Science.gov (United States)

    Sheldon, N. D.; Smith, S. Y.

    2012-12-01

    While the terrestrial biosphere and soils contain much of the readily exchangeable carbon on Earth, how those reservoirs function on long time scales and at times of higher atmospheric CO2 and higher temperatures is poorly understood, which limits our ability to make accurate future predictions of their response to anthropogenic change. Recent data compilation efforts have outlined the response of plant carbon isotope compositions to a variety of environmental factors including precipitation amount and timing, elevation, and latitude. The compilations involve numerous types of plants, typically only found at a limited number of climatic conditions. Here, we expand on those efforts by examining the isotopic response of specific plant groups found both globally and across environmental gradients including: 1) ginkgo, 2) conifers, and 3) C4 grasses. Ginkgo is presently widely distributed as a cultivated plant and the ginkgoalean fossil record spans from the Permian to the present, making it an ideal model organism to understand climatic influence on carbon cycling both in modern and ancient settings. Ginkgo leaves have been obtained from a range of precipitation conditions (400-2200 mm yr-1), including dense sampling from individuals and populations in both Mediterranean and temperate climate areas and samples of different organs and developmental stages. Ginkgo carbon isotope results plot on the global C3 plant array, are consistent among trees at single sites, among plant organs, and among development stages, making ginkgo a robust recorder of both climatic conditions and atmospheric δ13C. In contrast, a climate-carbon isotope transect in Arizona highlights that conifers (specifically, pine and juniper) record large variability between organs and have a very different δ13C slope as a function of climate than the global C3 plant array, while C4 plants have a slope with the opposite sign as a function of climate. This has a number of implications for paleo

  17. Earth system model simulations show different feedback strengths of the terrestrial carbon cycle under glacial and interglacial conditions

    Directory of Open Access Journals (Sweden)

    M. Adloff

    2018-04-01

    Full Text Available In simulations with the MPI Earth System Model, we study the feedback between the terrestrial carbon cycle and atmospheric CO2 concentrations under ice age and interglacial conditions. We find different sensitivities of terrestrial carbon storage to rising CO2 concentrations in the two settings. This result is obtained by comparing the transient response of the terrestrial carbon cycle to a fast and strong atmospheric CO2 concentration increase (roughly 900 ppm in Coupled Climate Carbon Cycle Model Intercomparison Project (C4MIP-type simulations starting from climates representing the Last Glacial Maximum (LGM and pre-industrial times (PI. In this set-up we disentangle terrestrial contributions to the feedback from the carbon-concentration effect, acting biogeochemically via enhanced photosynthetic productivity when CO2 concentrations increase, and the carbon–climate effect, which affects the carbon cycle via greenhouse warming. We find that the carbon-concentration effect is larger under LGM than PI conditions because photosynthetic productivity is more sensitive when starting from the lower, glacial CO2 concentration and CO2 fertilization saturates later. This leads to a larger productivity increase in the LGM experiment. Concerning the carbon–climate effect, it is the PI experiment in which land carbon responds more sensitively to the warming under rising CO2 because at the already initially higher temperatures, tropical plant productivity deteriorates more strongly and extratropical carbon is respired more effectively. Consequently, land carbon losses increase faster in the PI than in the LGM case. Separating the carbon–climate and carbon-concentration effects, we find that they are almost additive for our model set-up; i.e. their synergy is small in the global sum of carbon changes. Together, the two effects result in an overall strength of the terrestrial carbon cycle feedback that is almost twice as large in the LGM experiment

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

    Science.gov (United States)

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

    2009-08-01

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

  19. Multiple Observation Types Jointly Constrain Australian Terrestrial Carbon and Water Cycles

    Science.gov (United States)

    Haverd, Vanessa; Raupach, Michael; Briggs, Peter; Canadell, Pep; Davis, Steven; Isaac, Peter; Law, Rachel; Meyer, Mick; Peters, Glenn; Pickett-Heaps, Christopher; Roxburgh, Stephen; Sherman, Bradford; van Gorsel, Eva; Viscarra Rossel, Raphael; Wang, Ziyuan

    2013-04-01

    Information about the carbon cycle potentially constrains the water cycle, and vice versa. This paper explores the utility of multiple observation sets to constrain carbon and water fluxes and stores in a land surface model, and a resulting determination of the Australian terrestrial carbon budget. Observations include streamflow from 416 gauged catchments, measurements of evapotranspiration (ET) and net ecosystem production (NEP) from 12 eddy-flux sites, litterfall data, and data on carbon pools. The model is a version of CABLE (the Community Atmosphere-Biosphere-Land Exchange model), coupled with CASAcnp (a biogeochemical model) and SLI (Soil-Litter-Iso, a soil hydrology model including liquid and vapour water fluxes and the effects of litter). By projecting observation-prediction residuals onto model uncertainty, we find that eddy flux measurements provide a significantly tighter constraint on Australian continental net primary production (NPP) than the other data types. However, simultaneous constraint by multiple data types is important for mitigating bias from any single type. Results emerging from the multiply-constrained model are as follows (with all values applying over 1990-2011 and all ranges denoting ±1 standard error): (1) on the Australian continent, a predominantly semi-arid region, over half (0.64±0.05) of the water loss through ET occurs through soil evaporation and bypasses plants entirely; (2) mean Australian NPP is 2200±400 TgC/y, making the NPP/precipitation ratio about the same for Australia as the global land average; (3) annually cyclic ("grassy") vegetation and persistent ("woody") vegetation respectively account for 0.56±0.14 and 0.43±0.14 of NPP across Australia; (4) the average interannual variability of Australia's NEP (±180 TgC/y) is larger than Australia's total anthropogenic greenhouse gas emissions in 2011 (149 TgCeq/y), and is dominated by variability in desert and savannah regions. The mean carbon budget over 1990

  20. Studies of the terrestrial O2 and carbon cycles in sand dune gases and in biosphere 2

    Energy Technology Data Exchange (ETDEWEB)

    Severinghaus, Jeffrey Peck [Columbia Univ., New York, NY (United States)

    1995-01-01

    Molecular oxygen in the atmosphere is coupled tightly to the terrestrial carbon cycle by the processes of photosynthesis, respiration, and burning. This dissertation examines different aspects of this coupling in four chapters. Chapter 1 explores the feasibility of using air from sand dunes to reconstruct atmospheric O2 composition centuries ago. Such a record would reveal changes in the mass of the terrestrial biosphere, after correction for known fossil fuel combustion, and constrain the fate of anthropogenic CO2.

  1. How does soil erosion influence the terrestrial carbon cycle and the impacts of land use and land cover change?

    Science.gov (United States)

    Naipal, V.; Wang, Y.; Ciais, P.; Guenet, B.; Lauerwald, R.

    2017-12-01

    The onset of agriculture has accelerated soil erosion rates significantly, mobilizing vast quantities of soil organic carbon (SOC) globally. Studies show that at timescales of decennia to millennia this mobilized SOC can significantly alter previously estimated carbon emissions from land use and land cover change (LULCC). However, a full understanding of the impact of soil erosion on land-atmosphere carbon exchange is still missing. The aim of our study is to better constrain the terrestrial carbon fluxes by developing methods, which are compatible with earth system models (ESMs), and explicitly represent the links between soil erosion and carbon dynamics. For this we use an emulator that represents the carbon cycle of ORCHIDEE, which is the land component of the IPSL ESM, in combination with an adjusted version of the Revised Universal Soil Loss Equation (RUSLE) model. We applied this modeling framework at the global scale to evaluate how soil erosion influenced the terrestrial carbon cycle in the presence of elevated CO2, regional climate change and land use change. Here, we focus on the effects of soil detachment by erosion only and do not consider sediment transport and deposition. We found that including soil erosion in the SOC dynamics-scheme resulted in two times more SOC being lost during the historical period (1850-2005 AD). LULCC is the main contributor to this SOC loss, whose impact on the SOC stocks is significantly amplified by erosion. Regionally, the influence of soil erosion varies significantly, depending on the magnitude of the perturbations to the carbon cycle and the effects of LULCC and climate change on soil erosion rates. We conclude that it is necessary to include soil erosion in assessments of LULCC, and to explicitly consider the effects of elevated CO2 and climate change on the carbon cycle and on soil erosion, for better quantification of past, present, and future LULCC carbon emissions.

  2. Potential strong contribution of future anthropogenic land-use and land-cover change to the terrestrial carbon cycle

    Science.gov (United States)

    Quesada, Benjamin; Arneth, Almut; Robertson, Eddy; de Noblet-Ducoudré, Nathalie

    2018-06-01

    Anthropogenic land-use and land cover changes (LULCC) affect global climate and global terrestrial carbon (C) cycle. However, relatively few studies have quantified the impacts of future LULCC on terrestrial carbon cycle. Here, using Earth system model simulations performed with and without future LULCC, under the RCP8.5 scenario, we find that in response to future LULCC, the carbon cycle is substantially weakened: browning, lower ecosystem C stocks, higher C loss by disturbances and higher C turnover rates are simulated. Projected global greening and land C storage are dampened, in all models, by 22% and 24% on average and projected C loss by disturbances enhanced by ~49% when LULCC are taken into account. By contrast, global net primary productivity is found to be only slightly affected by LULCC (robust +4% relative enhancement compared to all forcings, on average). LULCC is projected to be a predominant driver of future C changes in regions like South America and the southern part of Africa. LULCC even cause some regional reversals of projected increased C sinks and greening, particularly at the edges of the Amazon and African rainforests. Finally, in most carbon cycle responses, direct removal of C dominates over the indirect CO2 fertilization due to LULCC. In consequence, projections of land C sequestration potential and Earth’s greening could be substantially overestimated just because of not fully accounting for LULCC.

  3. Multi-model analysis of terrestrial carbon cycles in Japan: limitations and implications of model calibration using eddy flux observations

    Directory of Open Access Journals (Sweden)

    K. Ichii

    2010-07-01

    Full Text Available Terrestrial biosphere models show large differences when simulating carbon and water cycles, and reducing these differences is a priority for developing more accurate estimates of the condition of terrestrial ecosystems and future climate change. To reduce uncertainties and improve the understanding of their carbon budgets, we investigated the utility of the eddy flux datasets to improve model simulations and reduce variabilities among multi-model outputs of terrestrial biosphere models in Japan. Using 9 terrestrial biosphere models (Support Vector Machine – based regressions, TOPS, CASA, VISIT, Biome-BGC, DAYCENT, SEIB, LPJ, and TRIFFID, we conducted two simulations: (1 point simulations at four eddy flux sites in Japan and (2 spatial simulations for Japan with a default model (based on original settings and a modified model (based on model parameter tuning using eddy flux data. Generally, models using default model settings showed large deviations in model outputs from observation with large model-by-model variability. However, after we calibrated the model parameters using eddy flux data (GPP, RE and NEP, most models successfully simulated seasonal variations in the carbon cycle, with less variability among models. We also found that interannual variations in the carbon cycle are mostly consistent among models and observations. Spatial analysis also showed a large reduction in the variability among model outputs. This study demonstrated that careful validation and calibration of models with available eddy flux data reduced model-by-model differences. Yet, site history, analysis of model structure changes, and more objective procedure of model calibration should be included in the further analysis.

  4. Multi-model analysis of terrestrial carbon cycles in Japan: limitations and implications of model calibration using eddy flux observations

    Science.gov (United States)

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

    2010-07-01

    Terrestrial biosphere models show large differences when simulating carbon and water cycles, and reducing these differences is a priority for developing more accurate estimates of the condition of terrestrial ecosystems and future climate change. To reduce uncertainties and improve the understanding of their carbon budgets, we investigated the utility of the eddy flux datasets to improve model simulations and reduce variabilities among multi-model outputs of terrestrial biosphere models in Japan. Using 9 terrestrial biosphere models (Support Vector Machine - based regressions, TOPS, CASA, VISIT, Biome-BGC, DAYCENT, SEIB, LPJ, and TRIFFID), we conducted two simulations: (1) point simulations at four eddy flux sites in Japan and (2) spatial simulations for Japan with a default model (based on original settings) and a modified model (based on model parameter tuning using eddy flux data). Generally, models using default model settings showed large deviations in model outputs from observation with large model-by-model variability. However, after we calibrated the model parameters using eddy flux data (GPP, RE and NEP), most models successfully simulated seasonal variations in the carbon cycle, with less variability among models. We also found that interannual variations in the carbon cycle are mostly consistent among models and observations. Spatial analysis also showed a large reduction in the variability among model outputs. This study demonstrated that careful validation and calibration of models with available eddy flux data reduced model-by-model differences. Yet, site history, analysis of model structure changes, and more objective procedure of model calibration should be included in the further analysis.

  5. Top-down constraints on disturbance dynamics in the terrestrial carbon cycle: effects at global and regional scales

    Science.gov (United States)

    Bloom, A. A.; Exbrayat, J. F.; van der Velde, I.; Peters, W.; Williams, M.

    2014-12-01

    Large uncertainties preside over terrestrial carbon flux estimates on a global scale. In particular, the strongly coupled dynamics between net ecosystem productivity and disturbance C losses are poorly constrained. To gain an improved understanding of ecosystem C dynamics from regional to global scale, we apply a Markov Chain Monte Carlo based model-data-fusion approach into the CArbon DAta-MOdel fraMework (CARDAMOM). We assimilate MODIS LAI and burned area, plant-trait data, and use the Harmonized World Soil Database (HWSD) and maps of above ground biomass as prior knowledge for initial conditions. We optimize model parameters based on (a) globally spanning observations and (b) ecological and dynamic constraints that force single parameter values and parameter inter-dependencies to be representative of real world processes. We determine the spatial and temporal dynamics of major terrestrial C fluxes and model parameter values on a global scale (GPP = 123 +/- 8 Pg C yr-1 & NEE = -1.8 +/- 2.7 Pg C yr-1). We further show that the incorporation of disturbance fluxes, and accounting for their instantaneous or delayed effect, is of critical importance in constraining global C cycle dynamics, particularly in the tropics. In a higher resolution case study centred on the Amazon Basin we show how fires not only trigger large instantaneous emissions of burned matter, but also how they are responsible for a sustained reduction of up to 50% in plant uptake following the depletion of biomass stocks. The combination of these two fire-induced effects leads to a 1 g C m-2 d-1reduction in the strength of the net terrestrial carbon sink. Through our simulations at regional and global scale, we advocate the need to assimilate disturbance metrics in global terrestrial carbon cycle models to bridge the gap between globally spanning terrestrial carbon cycle data and the full dynamics of the ecosystem C cycle. Disturbances are especially important because their quick occurrence may have

  6. Fingerprints of changes in the terrestrial carbon cycle in response to large reorganizations in ocean circulation

    Directory of Open Access Journals (Sweden)

    A. Bozbiyik

    2011-03-01

    Full Text Available CO2 and carbon cycle changes in the land, ocean and atmosphere are investigated using the comprehensive carbon cycle-climate model NCAR CSM1.4-carbon. Ensemble simulations are forced with freshwater perturbations applied at the North Atlantic and Southern Ocean deep water formation sites under pre-industrial climate conditions. As a result, the Atlantic Meridional Overturning Circulation reduces in each experiment to varying degrees. The physical climate fields show changes qualitatively in agreement with results documented in the literature, but there is a clear distinction between northern and southern perturbations. Changes in the physical variables, in turn, affect the land and ocean biogeochemical cycles and cause a reduction, or an increase, in the atmospheric CO2 concentration by up to 20 ppmv, depending on the location of the perturbation. In the case of a North Atlantic perturbation, the land biosphere reacts with a strong reduction in carbon stocks in some tropical locations and in high northern latitudes. In contrast, land carbon stocks tend to increase in response to a southern perturbation. The ocean is generally a sink of carbon although large reorganizations occur throughout various basins. The response of the land biosphere is strongest in the tropical regions due to a shift of the Intertropical Convergence Zone. The carbon fingerprints of this shift, either to the south or to the north depending on where the freshwater is applied, can be found most clearly in South America. For this reason, a compilation of various paleoclimate proxy records of Younger Dryas precipitation changes are compared with our model results. The proxy records, in general, show good agreement with the model's response to a North Atlantic freshwater perturbation.

  7. New era of satellite chlorophyll fluorescence and soil moisture observations leads to advances in the predictive understanding of global terrestrial coupled carbon-water cycles

    Science.gov (United States)

    Qiu, B.; Xue, Y.; Fisher, J.; Guo, W.

    2017-12-01

    The terrestrial carbon cycle and water cycle are coupled through a multitude of connected processes among soil, roots, leaves, and the atmosphere. The strength and sensitivity of these couplings are not yet well known at the global scale, which contributes to uncertainty in predicting the terrestrial water and carbon budgets. For the first time, we now have synchronous, high fidelity, global-scale satellite observations of critical terrestrial carbon and water cycle components: sun-induced chlorophyll fluorescence (SIF) and soil moisture. We used these observations within the framework of a well-established global terrestrial biosphere model (Simplified Simple Biosphere Model version 2.0, SSiB2) to investigate carbon-water coupling processes. We updated SSiB2 to include a mechanistic representation of SIF and tested the sensitivity of model parameters to improve the simulation of both SIF and soil moisture with the ultimate objective of improving the first-order terrestrial carbon component, gross primary production (GPP). Although several vegetation parameters, such as leaf area index (LAI) and green leaf fraction, improved the simulated SIF, and several soil parameters, such as hydraulic conductivity, improved simulated soil moisture, their effects were mainly limited to their respective cycles. One parameter emerged as the key coupler between the carbon and water cycles: the wilting point. Updates to the wilting point significantly improved the simulations for both soil moisture and SIF, as well as GPP. This study demonstrates the value of synchronous global measurements of the terrestrial carbon and water cycles in improving the understanding of coupled carbon-water cycles.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-03-15

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

  9. A Study of the Abundance and 13C/12C Ratio of Atmospheric Carbon Dioxide to Advance the Scientific Understanding of Terrestrial Processes Regulating the Global Carbon Cycle

    Energy Technology Data Exchange (ETDEWEB)

    Stephen C. Piper

    2005-10-15

    The primary goal of our research program, consistent with the goals of the U.S. Climate Change Science Program and funded by the terrestrial carbon processes (TCP) program of DOE, has been to improve understanding of changes in the distribution and cycling of carbon among the active land, ocean and atmosphere reservoirs, with particular emphasis on terrestrial ecosystems. Our approach is to systematically measure atmospheric CO2 to produce time series data essential to reveal temporal and spatial patterns. Additional measurements of the 13C/12C isotopic ratio of CO2 provide a basis for distinguishing organic and inorganic processes. To pursue the significance of these patterns further, our research also involved interpretations of the observations by models, measurements of inorganic carbon in sea water, and of CO2 in air near growing land plants.

  10. Diagnosing phosphorus limitations in natural terrestrial ecosystems in carbon cycle models

    Science.gov (United States)

    Sun, Yan; Peng, Shushi; Goll, Daniel S.; Ciais, Philippe; Guenet, Bertrand; Guimberteau, Matthieu; Hinsinger, Philippe; Janssens, Ivan A.; Peñuelas, Josep; Piao, Shilong; Poulter, Benjamin; Violette, Aurélie; Yang, Xiaojuan; Yin, Yi; Zeng, Hui

    2017-07-01

    Most of the Earth System Models (ESMs) project increases in net primary productivity (NPP) and terrestrial carbon (C) storage during the 21st century. Despite empirical evidence that limited availability of phosphorus (P) may limit the response of NPP to increasing atmospheric CO2, none of the ESMs used in the previous Intergovernmental Panel on Climate Change assessment accounted for P limitation. We diagnosed from ESM simulations the amount of P need to support increases in carbon uptake by natural ecosystems using two approaches: the demand derived from (1) changes in C stocks and (2) changes in NPP. The C stock-based additional P demand was estimated to range between -31 and 193 Tg P and between -89 and 262 Tg P for Representative Concentration Pathway (RCP) 2.6 and RCP8.5, respectively, with negative values indicating a P surplus. The NPP-based demand, which takes ecosystem P recycling into account, results in a significantly higher P demand of 648-1606 Tg P for RCP2.6 and 924-2110 Tg P for RCP8.5. We found that the P demand is sensitive to the turnover of P in decomposing plant material, explaining the large differences between the NPP-based demand and C stock-based demand. The discrepancy between diagnosed P demand and actual P availability (potential P deficit) depends mainly on the assumptions about availability of the different soil P forms. Overall, future P limitation strongly depends on both soil P availability and P recycling on ecosystem scale.

  11. Aspects of the carbon cycle in terrestrial ecosystems of Northeastern Smaaland

    Energy Technology Data Exchange (ETDEWEB)

    Tagesson, Torbern [Lund Univ., Geobiosphere Science Centre (Sweden). Physical Geography and Ecosystems Analysis

    2006-02-15

    Boreal and temperate ecosystems of the northern hemisphere are important for the future development of global climate. In this study, the carbon cycle has been studied in a pine forest, a meadow, a spruce forest and two deciduous forests in the Simpevarp investigation area in southern Sweden (57 deg 5 min N, 34 deg 55 min E). Ground respiration and ground Gross Primary Production (GPP) has been measured three times during spring 2004 with the closed chamber technique. Soil temperature, soil moisture and Photosynthetically Active Radiation (PAR) were also measured. An exponential regression with ground respiration against soil temperature was used to extrapolate respiration over spring 2004. A logarithmic regression with ground GPP against PAR was used to extrapolate GPP in meadow over spring 2004. Ground respiration is affected by soil temperature in all ecosystems but pine, but still it only explains a small part of the variation in respiration and this indicates that other abiotic factors also have an influence. Soil moisture affects respiration in spruce and one of the deciduous ecosystems. A comparison between measured and extrapolated ground respiration indicated that soil temperature could be used to extrapolate ground respiration. PAR is the main factor influencing GPP in all ecosystems but pine, still it could not be used to extrapolate GPP in meadow since too few measurements were done and they were from different periods of spring. Soil moisture did not have any significant effect on GPP. A Dynamic Global Vegetation Model, a DGVM called LPJ-GUESS, was downscaled to the Simpevarp investigation area. The downscaled DGVM was evaluated against measured respiration and soil organic acids for all five ecosystems. In meadow, it was evaluated against Net Primary Production, NPP. For the forest ecosystems, it was evaluated against tree layer carbon pools. The evaluation indicated that the DGVM is reasonably well downscaled to the Simpevarp investigation area and

  12. Aspects of the carbon cycle in terrestrial ecosystems of Northeastern Smaaland

    International Nuclear Information System (INIS)

    Tagesson, Torbern

    2006-02-01

    Boreal and temperate ecosystems of the northern hemisphere are important for the future development of global climate. In this study, the carbon cycle has been studied in a pine forest, a meadow, a spruce forest and two deciduous forests in the Simpevarp investigation area in southern Sweden (57 deg 5 min N, 34 deg 55 min E). Ground respiration and ground Gross Primary Production (GPP) has been measured three times during spring 2004 with the closed chamber technique. Soil temperature, soil moisture and Photosynthetically Active Radiation (PAR) were also measured. An exponential regression with ground respiration against soil temperature was used to extrapolate respiration over spring 2004. A logarithmic regression with ground GPP against PAR was used to extrapolate GPP in meadow over spring 2004. Ground respiration is affected by soil temperature in all ecosystems but pine, but still it only explains a small part of the variation in respiration and this indicates that other abiotic factors also have an influence. Soil moisture affects respiration in spruce and one of the deciduous ecosystems. A comparison between measured and extrapolated ground respiration indicated that soil temperature could be used to extrapolate ground respiration. PAR is the main factor influencing GPP in all ecosystems but pine, still it could not be used to extrapolate GPP in meadow since too few measurements were done and they were from different periods of spring. Soil moisture did not have any significant effect on GPP. A Dynamic Global Vegetation Model, a DGVM called LPJ-GUESS, was downscaled to the Simpevarp investigation area. The downscaled DGVM was evaluated against measured respiration and soil organic acids for all five ecosystems. In meadow, it was evaluated against Net Primary Production, NPP. For the forest ecosystems, it was evaluated against tree layer carbon pools. The evaluation indicated that the DGVM is reasonably well downscaled to the Simpevarp investigation area and

  13. Diagnosing and Assessing Uncertainties of the Carbon Cycle in Terrestrial Ecosystem Models from a Multi-Model Ensemble Experiment

    Science.gov (United States)

    Wang, W.; Dungan, J. L.; Hashimoto, H.; Michaelis, A.; Milesi, C.; Ichii, K.; Nemani, R. R.

    2009-12-01

    We are conducting an ensemble modeling exercise using the Terrestrial Observation and Prediction System (TOPS) to characterize structural uncertainty in carbon fluxes and stocks estimates from different ecosystem models. The experiment uses public-domain versions of Biome-BGC, LPJ, TOPS-BGC, and CASA, driven by a consistent set of climate fields for North America at 8km resolution and daily/monthly time steps over the period of 1982-2006. A set of diagnostics is developed to characterize the behavior of the models in the climate (temperature-precipitation) space, and to evaluate the simulated carbon cycle in an integrated way. The key findings of this study include that: (relative) optimal primary production is generally found in climate regions where the relationship between annual temperature (T, oC) and precipitation (P, mm) is defined by P = 50*T+500; the ratios between NPP and GPP are close to 50% on average, yet can vary between models and in different climate regions; the allocation of carbon to leaf growth represents a positive feedback to the primary production, and different approaches to constrain this process have significant impacts on the simulated carbon cycle; substantial differences in biomass stocks may be induced by small differences in the tissue turnover rate and the plant mortality; the mean residence time of soil carbon pools is strongly influenced by schemes of temperature regulations; non-respiratory disturbances (e.g., fires) are the main driver for NEP, yet its magnitudes vary between models. Overall, these findings indicate that although the structures of the models are similar, the uncertainties among them can be large, highlighting the problem inherent in relying on only one modeling approach to map surface carbon fluxes or to assess vegetation-climate interactions.

  14. The global carbon cycle

    International Nuclear Information System (INIS)

    Maier-Reimer, E.

    1991-01-01

    Basic concepts of the global carbon cycle on earth are described; by careful analyses of isotopic ratios, emission history and oceanic ventilation rates are derived, which provide crucial tests for constraining and calibrating models. Effects of deforestation, fertilizing, fossil fuel burning, soil erosion, etc. are quantified and compared, and the oceanic carbon process is evaluated. Oceanic and terrestrial biosphere modifications are discussed and a carbon cycle model is proposed

  15. The value of soil respiration measurements for interpreting and modeling terrestrial carbon cycling

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, Claire L.; Bond-Lamberty, Ben; Desai, Ankur R.; Lavoie, Martin; Risk, Dave; Tang, Jianwu; Todd-Brown, Katherine; Vargas, Rodrigo

    2016-11-16

    A recent acceleration of model-data synthesis activities has leveraged many terrestrial carbon (C) datasets, but utilization of soil respiration (RS) data has not kept pace with other types such as eddy covariance (EC) fluxes and soil C stocks. Here we argue that RS data, including non-continuous measurements from survey sampling campaigns, have unrealized value and should be utilized more extensively and creatively in data synthesis and modeling activities. We identify three major challenges in interpreting RS data, and discuss opportunities to address them. The first challenge is that when RS is compared to ecosystem respiration (RECO) measured from EC towers, it is not uncommon to find substantial mismatch, indicating one or both flux methodologies are unreliable. We argue the most likely cause of mismatch is unreliable EC data, and there is an unrecognized opportunity to utilize RS for EC quality control. The second challenge is that RS integrates belowground heterotrophic (RH) and autotrophic (RA) activity, whereas modelers generally prefer partitioned fluxes, and few models include an explicit RS output. Opportunities exist to use the total RS flux for data assimilation and model benchmarking methods rather than less-certain partitioned fluxes. Pushing for more experiments that not only partition RS but also monitor the age of RA and RH, as well as for the development of belowground RA components in models, would allow for more direct comparison between measured and modeled values. The third challenge is that soil respiration is generally measured at a very different resolution than that needed for comparison to EC or ecosystem- to global-scale models. Measuring soil fluxes with finer spatial resolution and more extensive coverage, and downscaling EC fluxes to match the scale of RS, will improve chamber and tower comparisons. Opportunities also exist to estimate RH at regional scales by implementing decomposition functional types, akin to plant functional

  16. FeedbackBetweenHumanActivitiesAndTerrestrialCarbonCyclesInSystemsOfShadeCoffeePro ductionInMexico

    Science.gov (United States)

    Pena Del Valle, A. E.; Perez-Samayoa, I. A.

    2007-12-01

    Coffee production in Mexico is carried out within a strong natural context. Coffee is grown under a canopy of several native and introduced tree species. This fact ensures a greater diversity of natural resources and environmental services available for local inhabitants to sustain their livelihoods. However, the lack of opportunities for coffee farmers is increasing the demand over the remaining forest areas by exacerbating non- sustainable timber extraction practices and promoting conversion of forests to pasture lands. This situation hampers the landscapes equilibrium and threatens the wellbeing of rural livelihoods. To understand the interactions between human activities and ecological functions associated with shaded coffee systems, this research has explored the extent to which socio-economic and cultural factors have influenced the use and management of natural resources sustaining coffee livelihoods. At the same time, it examines how customary patterns of resource use have induced changes in the terrestrial carbon cycle at the local level. The empirical study was carried out in a coffee-growing region in Mexico. It involved substantial fieldwork, use of satellite imagery, and participatory research methods in order to gauge a variety of biophysical and socio- economic factors, including forest cover, land use, and carbon balances, as well as, farming practices and off- farming strategies. In addition, a livelihood perspective was applied to approach the linkages between the management of natural resources, the environmental goods and services, and the socio-economic conditions in the coffee-growing region. The empirical evidence from the research marks out shade coffee systems as important supporters for broader natural systems as suppliers of environmental services. However, it also suggests that non-climatic factors might have significant impacts on the local environment and therefore on the terrestrial carbon cycle. According to the research estimations

  17. Detecting robust signals of interannual variability of gross primary productivity in Asia from multiple terrestrial carbon cycle models and long-term satellite-based vegetation data

    Science.gov (United States)

    Ichii, K.; Kondo, M.; Ueyama, M.; Kato, T.; Ito, A.; Sasai, T.; Sato, H.; Kobayashi, H.; Saigusa, N.

    2014-12-01

    Long term record of satellite-based terrestrial vegetation are important to evaluate terrestrial carbon cycle models. In this study, we demonstrate how multiple satellite observation can be used for evaluating past changes in gross primary productivity (GPP) and detecting robust anomalies in terrestrial carbon cycle in Asia through our model-data synthesis analysis, Asia-MIP. We focused on the two different temporal coverages: long-term (30 years; 1982-2011) and decadal (10 years; 2001-2011; data intensive period) scales. We used a NOAA/AVHRR NDVI record for long-term analysis and multiple satellite data and products (e.g. Terra-MODIS, SPOT-VEGETATION) as historical satellite data, and multiple terrestrial carbon cycle models (e.g. BEAMS, Biome-BGC, ORCHIDEE, SEIB-DGVM, and VISIT). As a results of long-term (30 years) trend analysis, satellite-based time-series data showed that approximately 40% of the area has experienced a significant increase in the NDVI, while only a few areas have experienced a significant decreasing trend over the last 30 years. The increases in the NDVI were dominant in the sub-continental regions of Siberia, East Asia, and India. Simulations using the terrestrial biosphere models also showed significant increases in GPP, similar to the results for the NDVI, in boreal and temperate regions. A modeled sensitivity analysis showed that the increases in GPP are explained by increased temperature and precipitation in Siberia. Precipitation, solar radiation, CO2fertilization and land cover changes are important factors in the tropical regions. However, the relative contributions of each factor to GPP changes are different among the models. Year-to-year variations of terrestrial GPP were overall consistently captured by the satellite data and terrestrial carbon cycle models if the anomalies are large (e.g. 2003 summer GPP anomalies in East Asia and 2002 spring GPP anomalies in mid to high latitudes). The behind mechanisms can be consistently

  18. Equilibration of the terrestrial water, nitrogen, and carbon cycles

    OpenAIRE

    Schimel, David S.; Braswell, B. H.; Parton, W. J.

    1997-01-01

    Recent advances in biologically based ecosystem models of the coupled terrestrial, hydrological, carbon, and nutrient cycles have provided new perspectives on the terrestrial biosphere’s behavior globally, over a range of time scales. We used the terrestrial ecosystem model Century to examine relationships between carbon, nitrogen, and water dynamics. The model, run to a quasi-steady-state, shows strong correlations between carbon, water, and nitrogen fluxes that l...

  19. Top-down constraints on disturbance dynamics in the terrestrial carbon cycle: effects at global and regional scales

    NARCIS (Netherlands)

    Bloom, A. A.; Exbrayat, J. F.; van der Velde, I.; Peters, W.; Williams, M.

    2014-01-01

    Large uncertainties preside over terrestrial carbon flux estimates on a global scale. In particular, the strongly coupled dynamics between net ecosystem productivity and disturbance C losses are poorly constrained. To gain an improved understanding of ecosystem C dynamics from regional to global

  20. The SMAP Level-4 ECO Project: Linking the Terrestrial Water and Carbon Cycles

    Science.gov (United States)

    Kolassa, J.; Reichle, R. H.; Liu, Qing; Koster, Randal D.

    2017-01-01

    The SMAP (Soil Moisture Active Passive) Level-4 projects aims to develop a fully coupled hydrology-vegetation data assimilation algorithm to generate improved estimates of modeled hydrological fields and carbon fluxes. This includes using the new NASA Catchment-CN (Catchment-Carbon-Nitrogen) model, which combines the Catchment land surface hydrology model with dynamic vegetation components from the Community Land Model version 4 (CLM4). As such, Catchment-CN allows a more realistic, fully coupled feedback between the land hydrology and the biosphere. The L4 ECO project further aims to inform the model through the assimilation of Soil Moisture Active Passive (SMAP) brightness temperature observations as well as observations of Moderate Resolution Imaging Spectroradiometer (MODIS) fraction of absorbed photosynthetically active radiation (FPAR). Preliminary results show that the assimilation of SMAP observations leads to consistent improvements in the model soil moisture skill. An evaluation of the Catchment-CN modeled vegetation characteristics showed that a calibration of the model's vegetation parameters is required before an assimilation of MODIS FPAR observations is feasible.

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

    DEFF Research Database (Denmark)

    Yi, Chuixiang; Ricciuto, Daniel; Li, Runze

    2010-01-01

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

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

    NARCIS (Netherlands)

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

    2010-01-01

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

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

    NARCIS (Netherlands)

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

    2010-01-01

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

  4. Nitrogen Availability Dampens the Positive Impacts of CO2 Fertilization on Terrestrial Ecosystem Carbon and Water Cycles

    Science.gov (United States)

    He, Liming; Chen, Jing M.; Croft, Holly; Gonsamo, Alemu; Luo, Xiangzhong; Liu, Jane; Zheng, Ting; Liu, Ronggao; Liu, Yang

    2017-11-01

    The magnitude and variability of the terrestrial CO2 sink remain uncertain, partly due to limited global information on ecosystem nitrogen (N) and its cycle. Without N constraint in ecosystem models, the simulated benefits from CO2 fertilization and CO2-induced increases in water use efficiency (WUE) may be overestimated. In this study, satellite observations of a relative measure of chlorophyll content are used as a proxy for leaf photosynthetic N content globally for 2003-2011. Global gross primary productivity (GPP) and evapotranspiration are estimated under elevated CO2 and N-constrained model scenarios. Results suggest that the rate of global GPP increase is overestimated by 85% during 2000-2015 without N limitation. This limitation is found to occur in many tropical and boreal forests, where a negative leaf N trend indicates a reduction in photosynthetic capacity, thereby suppressing the positive vegetation response to enhanced CO2 fertilization. Based on our carbon-water coupled simulations, enhanced CO2 concentration decreased stomatal conductance and hence increased WUE by 10% globally over the 1982 to 2015 time frame. Due to increased anthropogenic N application, GPP in croplands continues to grow and offset the weak negative trend in forests due to N limitation. Our results also show that the improved WUE is unlikely to ease regional droughts in croplands because of increases in evapotranspiration, which are associated with the enhanced GPP. Although the N limitation on GPP increase is large, its associated confidence interval is still wide, suggesting an urgent need for better understanding and quantification of N limitation from satellite observations.

  5. Ancient Terrestrial Carbon: Lost and Found

    Science.gov (United States)

    Freeman, K. H.

    2017-12-01

    Carbon fluxes in terrestrial environments dominate the global carbon cycle. The fluxes of terrestrial carbon are strongly tied to regional climate due to the influences of temperature, water, and nutrient dynamics on plant productivity. However, climate also influences the destruction of terrestrial organic matter, through weathering, erosion, and biomass loss via fire and oxidative microbial processes. Organic geochemical methods enable us to interrogate past terrestrial carbon dynamics and learn how continental processes might accelerate, or mitigate carbon transfer to the atmosphere, and the associated greenhouse warming. Terrestrial soil systems represent the weathering rind of the continents, and are inherently non-depositional and erosive. The production, transport, and depositional processes affecting organics in continental settings each impart their own biases on the amount and characteristics of preserved carbon. Typically, the best archives for biomarker records are sediments in ancient lakes or subaqueous fans, which represents a preservation bias that tends to favor wetter environments. Paleosols, or ancient soils, formed under depositional conditions that, for one reason or another, truncated soil ablation, erosion, or other loss processes. In modern soils, widely ranging organic carbon abundances are almost always substantially greater than the trace amounts of carbon left behind in ancient soils. Even so, measureable amounts of organic biomarkers persist in paleosols. We have been investigating processes that preserve soil organic carbon on geologic timescales, and how these mechanisms may be sensitive to past climate change. Climate-linked changes in temperature, moisture, pH, and weathering processes can impact carbon preservation via organo-mineral sorption, soil biogeochemistry, and stability based on the physical and chemical properties of organic compounds. These will be discussed and illustrated with examples from our studies of Cenozoic

  6. Study of the Role of Terrestrial Processes in the Carbon Cycle Based on Measurements of the Abundance and Isotopic Composition of Atmospheric CO2

    Energy Technology Data Exchange (ETDEWEB)

    Piper, Stephen C; Keeling, Ralph F

    2012-01-03

    The main objective of this project was to continue research to develop carbon cycle relationships related to the land biosphere based on remote measurements of atmospheric CO2 concentration and its isotopic ratios 13C/12C, 18O/16O, and 14C/12C. The project continued time-series observations of atmospheric carbon dioxide and isotopic composition begun by Charles D. Keeling at remote sites, including Mauna Loa, the South Pole, and eight other sites. Using models of varying complexity, the concentration and isotopic measurements were used to study long-term change in the interhemispheric gradients in CO2 and 13C/12C to assess the magnitude and evolution of the northern terrestrial carbon sink, to study the increase in amplitude of the seasonal cycle of CO2, to use isotopic data to refine constraints on large scale changes in isotopic fractionation which may be related to changes in stomatal conductance, and to motivate improvements in terrestrial carbon cycle models. The original proposal called for a continuation of the new time series of 14C measurements but subsequent descoping to meet budgetary constraints required termination of measurements in 2007.

  7. Changing global carbon cycle

    International Nuclear Information System (INIS)

    Canadell, Pep

    2007-01-01

    Full text: The increase in atmospheric carbon dioxide (C02) is the single largest human perturbation on the earth's radiative balance contributing to climate change. Its rate of change reflects the balance between anthropogenic carbon emissions and the dynamics of a number of terrestrial and ocean processes that remove or emit C02. It is the long term evolution of this balance that will determine to large extent the speed and magnitude of the human induced climate change and the mitigation requirements to stabilise atmospheric C02 concentrations at any given level. In this talk, we show new trends in global carbon sources and sinks, with particularly focus on major shifts occurring since 2000 when the growth rate of atmospheric C02 has reached its highest level on record. The acceleration in the C02 growth results from the combination of several changes in properties of the carbon cycle, including: acceleration of anthropogenic carbon emissions; increased carbon intensity of the global economy, and decreased efficiency of natural carbon sinks. We discuss in more detail some of the possible causes of the reduced efficiency of natural carbon sinks on land and oceans, such as the decreased net sink in the Southern Ocean and on terrestrial mid-latitudes due to world-wide occurrence of drought. All these changes reported here characterise a carbon cycle that is generating stronger than expected climate forcing, and sooner than expected

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

    Science.gov (United States)

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

    2010-01-01

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

  9. Nitrogen, organic carbon and sulphur cycling in terrestrial ecosystems: linking nitrogen saturation to carbon limitation of soil microbial processes

    Czech Academy of Sciences Publication Activity Database

    Kopáček, Jiří; Cosby, B. J.; Evans, C. D.; Hruška, J.; Moldan, F.; Oulehle, F.; Šantrůčková, H.; Tahovská, K.; Wright, R. F.

    2013-01-01

    Roč. 115, 1-3 (2013), s. 33-51 ISSN 0168-2563. [BIOGEOMON : international symposium on ecosystem behavior /7./. Northport, 15.07.2012-20.07.2012] R&D Projects: GA ČR(CZ) GAP504/12/1218 Institutional support: RVO:60077344 Keywords : nitrogen * carbon * sulphur * acidification * forest soil * modelling Subject RIV: DJ - Water Pollution ; Quality Impact factor: 3.730, year: 2013

  10. Carbon cycle

    Energy Technology Data Exchange (ETDEWEB)

    Jaeger, J; Halbritter, G; Neumann-Hauf, G

    1982-05-01

    This report contains a review of literature on the subjects of the carbon cycle, the increase of the atmospheric CO/sub 2/ concentration and the possible impacts of an increased CO/sub 2/ concentration on the climate. In addition to this survey, the report discusses the questions that are still open and the resulting research needs. During the last twenty years a continual increase of the atmospheric carbon dioxide concentration by about 1-2 ppm per years has been observed. In 1958 the concentration was 315 ppm and this increased to 336 ppm in 1978. A rough estimate shows that the increase of the atmospheric carbon dioxide concentration is about half of the amount of carbon dioxide added to the atmosphere by the combustion of fossil fuels. Two possible sinks for the CO/sub 2/ released into the atmosphere are known: the ocean and the biota. The role of the biota is, however, unclear, since it can act both as a sink and as a source. Most models of the carbon cycle are one-dimensional and cannot be used for accurate predictions. Calculations with climate models have shown that an increased atmospheric CO/sub 2/ concentration leads to a warming of the earth's surface and lower atmosphere. Calculations show that a doubling of the atmospheric CO/sub 2/-concentration would lead to a net heating of the lower atmosphere and earth's surface by a global average of about 4 W m/sup -2/. Greater uncertainties arise in estimating the change in surface temperature resulting from this change in heating rate. It is estimated that the global average annual surface temperature would change between 1.5 and 4.5 K. There are, however, latitudinal and seasonal variations of the impact of increased CO/sub 2/ concentration. Other meteorological variables (e.g. precipitation, wind speed etc.) would also be changed. It appears that the impacts of the other products of fossil fuel combustion are unlikely to counteract the impacts of CO/sub 2/ on the climate.

  11. Parallel Computing for Terrestrial Ecosystem Carbon Modeling

    International Nuclear Information System (INIS)

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

    2011-01-01

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

  12. The Contemporary Carbon Cycle

    Science.gov (United States)

    Houghton, R. A.

    2003-12-01

    C). Additions of greenhouse gases to the atmosphere from industrial activity, however, are increasing the concentrations of these gases, enhancing the greenhouse effect, and starting to warm the Earth.The rate and extent of the warming depend, in part, on the global carbon cycle. If the rate at which the oceans remove CO2 from the atmosphere were faster, e.g., concentrations of CO2 would have increased less over the last century. If the processes removing carbon from the atmosphere and storing it on land were to diminish, concentrations of CO2 would increase more rapidly than projected on the basis of recent history. The processes responsible for adding carbon to, and withdrawing it from, the atmosphere are not well enough understood to predict future levels of CO2 with great accuracy. These processes are a part of the global carbon cycle.Some of the processes that add carbon to the atmosphere or remove it, such as the combustion of fossil fuels and the establishment of tree plantations, are under direct human control. Others, such as the accumulation of carbon in the oceans or on land as a result of changes in global climate (i.e., feedbacks between the global carbon cycle and climate), are not under direct human control except through controlling rates of greenhouse gas emissions and, hence, climatic change. Because CO2 has been more important than all of the other greenhouse gases under human control, combined, and is expected to continue so in the future, understanding the global carbon cycle is a vital part of managing global climate.This chapter addresses, first, the reservoirs and natural flows of carbon on the earth. It then addresses the sources of carbon to the atmosphere from human uses of land and energy and the sinks of carbon on land and in the oceans that have kept the atmospheric accumulation of CO2 lower than it would otherwise have been. The chapter describes changes in the distribution of carbon among the atmosphere, oceans, and terrestrial ecosystems over

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

    Science.gov (United States)

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

    2016-12-01

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

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

    Czech Academy of Sciences Publication Activity Database

    Yi, C.; Ricciuto, D.; Marek, Michal V.

    2010-01-01

    Roč. 5, č. 3 (2010), s. 034007 ISSN 1748-9326 Institutional research plan: CEZ:AV0Z60870520 Keywords : NEE * climate control * terrestrial carbon sequestration * temperature * dryness * eddy flux * biomes * photosynthesis * respiration * global carbon cycle Subject RIV: EH - Ecology, Behaviour Impact factor: 3.049, year: 2010

  15. Contrasting terrestrial carbon cycle responses to the 1997/98 and 2015/16 extreme El Niño events

    Science.gov (United States)

    Wang, Jun; Zeng, Ning; Wang, Meirong; Jiang, Fei; Wang, Hengmao; Jiang, Ziqiang

    2018-01-01

    Large interannual atmospheric CO2 variability is dominated by the response of the terrestrial biosphere to El Niño-Southern Oscillation (ENSO). However, the behavior of terrestrial ecosystems differs during different El Niños in terms of patterns and biological processes. Here, we comprehensively compare two extreme El Niños (2015/16 and 1997/98) in the context of a multi-event composite El Niño. We find large differences in the terrestrial carbon cycle responses, even though the two events were of similar magnitude.More specifically, we find that the global-scale land-atmosphere carbon flux (FTA) anomaly during the 1997/98 El Niño was 1.64 Pg C yr-1, but half that quantity during the 2015/16 El Niño (at 0.73 Pg C yr-1). Moreover, FTA showed no obvious lagged response during the 2015/16 El Niño, in contrast to that during 1997/98. Separating the global flux by geographical regions, we find that the fluxes in the tropics and extratropical Northern Hemisphere were 1.70 and -0.05 Pg C yr-1 during 1997/98, respectively. During 2015/16, they were 1.12 and -0.52 Pg C yr-1, respectively. Analysis of the mechanism shows that, in the tropics, the widespread drier and warmer conditions caused a decrease in gross primary productivity (GPP; -0.73 Pg C yr-1) and an increase in terrestrial ecosystem respiration (TER; 0.62 Pg C yr-1) during the 1997/98 El Niño. In contrast, anomalously wet conditions occurred in the Sahel and East Africa during 2015/16, which caused an increase in GPP, compensating for its reduction in other tropical regions. As a result, the total 2015/16 tropical GPP and TER anomalies were -0.03 and 0.95 Pg C yr-1. GPP dominance during 1997/98 and TER dominance during 2015/16 accounted for the phase difference in their FTA. In the extratropical Northern Hemisphere, the large difference occurred because temperatures over Eurasia were warmer during the 2015/16, as compared with the cooling seen during the 1997/98 and the composite El Niño. These warmer

  16. The Australian terrestrial carbon budget

    Directory of Open Access Journals (Sweden)

    V. Haverd

    2013-02-01

    Full Text Available This paper reports a study of the full carbon (C-CO2 budget of the Australian continent, focussing on 1990–2011 in the context of estimates over two centuries. The work is a contribution to the RECCAP (REgional Carbon Cycle Assessment and Processes project, as one of numerous regional studies. In constructing the budget, we estimate the following component carbon fluxes: net primary production (NPP; net ecosystem production (NEP; fire; land use change (LUC; riverine export; dust export; harvest (wood, crop and livestock and fossil fuel emissions (both territorial and non-territorial. Major biospheric fluxes were derived using BIOS2 (Haverd et al., 2012, a fine-spatial-resolution (0.05° offline modelling environment in which predictions of CABLE (Wang et al., 2011, a sophisticated land surface model with carbon cycle, are constrained by multiple observation types. The mean NEP reveals that climate variability and rising CO2 contributed 12 ± 24 (1σ error on mean and 68 ± 15 TgC yr−1, respectively. However these gains were partially offset by fire and LUC (along with other minor fluxes, which caused net losses of 26 ± 4 TgC yr−1 and 18 ± 7 TgC yr−1, respectively. The resultant net biome production (NBP is 36 ± 29 TgC yr−1, in which the largest contributions to uncertainty are NEP, fire and LUC. This NBP offset fossil fuel emissions (95 ± 6 TgC yr−1 by 38 ± 30%. The interannual variability (IAV in the Australian carbon budget exceeds Australia's total carbon emissions by fossil fuel combustion and is dominated by IAV in NEP. Territorial fossil fuel emissions are significantly smaller than the rapidly growing fossil fuel exports: in 2009–2010, Australia exported 2.5 times more carbon in fossil fuels than it emitted by burning fossil fuels.

  17. Evaluation of 11 terrestrial carbon-nitrogen cycle models against observations from two temperate Free-Air CO2 Enrichment studies.

    Science.gov (United States)

    Zaehle, Sönke; Medlyn, Belinda E; De Kauwe, Martin G; Walker, Anthony P; Dietze, Michael C; Hickler, Thomas; Luo, Yiqi; Wang, Ying-Ping; El-Masri, Bassil; Thornton, Peter; Jain, Atul; Wang, Shusen; Warlind, David; Weng, Ensheng; Parton, William; Iversen, Colleen M; Gallet-Budynek, Anne; McCarthy, Heather; Finzi, Adrien; Hanson, Paul J; Prentice, I Colin; Oren, Ram; Norby, Richard J

    2014-05-01

    We analysed the responses of 11 ecosystem models to elevated atmospheric [CO2 ] (eCO2 ) at two temperate forest ecosystems (Duke and Oak Ridge National Laboratory (ORNL) Free-Air CO2 Enrichment (FACE) experiments) to test alternative representations of carbon (C)-nitrogen (N) cycle processes. We decomposed the model responses into component processes affecting the response to eCO2 and confronted these with observations from the FACE experiments. Most of the models reproduced the observed initial enhancement of net primary production (NPP) at both sites, but none was able to simulate both the sustained 10-yr enhancement at Duke and the declining response at ORNL: models generally showed signs of progressive N limitation as a result of lower than observed plant N uptake. Nonetheless, many models showed qualitative agreement with observed component processes. The results suggest that improved representation of above-ground-below-ground interactions and better constraints on plant stoichiometry are important for a predictive understanding of eCO2 effects. Improved accuracy of soil organic matter inventories is pivotal to reduce uncertainty in the observed C-N budgets. The two FACE experiments are insufficient to fully constrain terrestrial responses to eCO2 , given the complexity of factors leading to the observed diverging trends, and the consequential inability of the models to explain these trends. Nevertheless, the ecosystem models were able to capture important features of the experiments, lending some support to their projections. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

  18. Description, calibration and sensitivity analysis of the local ecosystem submodel of a global model of carbon and nitrogen cycling and the water balance in the terrestrial biosphere

    Energy Technology Data Exchange (ETDEWEB)

    Kercher, J.R. [Lawrence Livermore National Lab., CA (United States); Chambers, J.Q. [Lawrence Livermore National Lab., CA (United States)]|[California Univ., Santa Barbara, CA (United States). Dept. of Biological Sciences

    1995-10-01

    We have developed a geographically-distributed ecosystem model for the carbon, nitrogen, and water dynamics of the terrestrial biosphere TERRA. The local ecosystem model of TERRA consists of coupled, modified versions of TEM and DAYTRANS. The ecosystem model in each grid cell calculates water fluxes of evaporation, transpiration, and runoff; carbon fluxes of gross primary productivity, litterfall, and plant and soil respiration; and nitrogen fluxes of vegetation uptake, litterfall, mineralization, immobilization, and system loss. The state variables are soil water content; carbon in live vegetation; carbon in soil; nitrogen in live vegetation; organic nitrogen in soil and fitter; available inorganic nitrogen aggregating nitrites, nitrates, and ammonia; and a variable for allocation. Carbon and nitrogen dynamics are calibrated to specific sites in 17 vegetation types. Eight parameters are determined during calibration for each of the 17 vegetation types. At calibration, the annual average values of carbon in vegetation C, show site differences that derive from the vegetation-type specific parameters and intersite variation in climate and soils. From calibration, we recover the average C{sub v} of forests, woodlands, savannas, grasslands, shrublands, and tundra that were used to develop the model initially. The timing of the phases of the annual variation is driven by temperature and light in the high latitude and moist temperate zones. The dry temperate zones are driven by temperature, precipitation, and light. In the tropics, precipitation is the key variable in annual variation. The seasonal responses are even more clearly demonstrated in net primary production and show the same controlling factors.

  19. Carbon cycle makeover

    DEFF Research Database (Denmark)

    Canfield, Donald Eugene; Kump, Lee R.

    2013-01-01

    remaining in sediments after respiration leave a residual of oxygen in the atmosphere. The source of oxygen to the atmosphere represented by organic matter burial is balanced by oxygen sinks associated with rock weathering and chemical reaction with volcanic gases. This is the long-term carbon and oxygen...... geochemical cycle. But Earth is an old planet, and oxygen levels have changed through time (2). On page 540 of this issue, Schrag et al. (3) challenge the most commonly used geochemical approach to assess long-term changes in the coupled oxygen and carbon cycles....

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

    Science.gov (United States)

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

    2017-12-01

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

  1. Terrestrial nitrogen cycling in Earth system models revisited

    Science.gov (United States)

    Stocker, Benjamin D; Prentice, I. Colin; Cornell, Sarah; Davies-Barnard, T; Finzi, Adrien; Franklin, Oskar; Janssens, Ivan; Larmola, Tuula; Manzoni, Stefano; Näsholm, Torgny; Raven, John; Rebel, Karin; Reed, Sasha C.; Vicca, Sara; Wiltshire, Andy; Zaehle, Sönke

    2016-01-01

    Understanding the degree to which nitrogen (N) availability limits land carbon (C) uptake under global environmental change represents an unresolved challenge. First-generation ‘C-only’vegetation models, lacking explicit representations of N cycling,projected a substantial and increasing land C sink under rising atmospheric CO2 concentrations. This prediction was questioned for not taking into account the potentially limiting effect of N availability, which is necessary for plant growth (Hungate et al.,2003). More recent global models include coupled C and N cycles in land ecosystems (C–N models) and are widely assumed to be more realistic. However, inclusion of more processes has not consistently improved their performance in capturing observed responses of the global C cycle (e.g. Wenzel et al., 2014). With the advent of a new generation of global models, including coupled C, N, and phosphorus (P) cycling, model complexity is sure to increase; but model reliability may not, unless greater attention is paid to the correspondence of model process representations ande mpirical evidence. It was in this context that the ‘Nitrogen Cycle Workshop’ at Dartington Hall, Devon, UK was held on 1–5 February 2016. Organized by I. Colin Prentice and Benjamin D. Stocker (Imperial College London, UK), the workshop was funded by the European Research Council,project ‘Earth system Model Bias Reduction and assessing Abrupt Climate change’ (EMBRACE). We gathered empirical ecologists and ecosystem modellers to identify key uncertainties in terrestrial C–N cycling, and to discuss processes that are missing or poorly represented in current models.

  2. 1km Global Terrestrial Carbon Flux: Estimations and Evaluations

    Science.gov (United States)

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

    2017-12-01

    very high correlations, and slight variations were showed in precipitation data. LAI data that was another large driving factor of terrestrial carbon cycle was not included in FLUXNET2015 datasets and it could not be evaluated.

  3. Carbon Fluxes and Transport Along the Terrestrial Aquatic Continuum

    Science.gov (United States)

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

    2017-12-01

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

  4. Biological control of the terrestrial carbon sink

    Science.gov (United States)

    Schulze, E.-D.

    2006-03-01

    This lecture reviews the past (since 1964 when the International Biological Program began) and the future of our understanding of terrestrial carbon fluxes with focus on photosynthesis, respiration, primary-, ecosystem-, and biome-productivity. Photosynthetic capacity is related to the nitrogen concentration of leaves, but the capacity is only rarely reached under field conditions. Average rates of photosynthesis and stomatal conductance are closely correlated and operate near 50% of their maximal rate, with light being the limiting factor in humid regions and air humidity and soil water the limiting factor in arid climates. Leaf area is the main factor to extrapolate from leaves to canopies, with maximum surface conductance being dependent on leaf level stomatal conductance. Additionally, gas exchange depends also on rooting depth which determines the water and nutrient availability and on mycorrhizae which regulate the nutrient status. An important anthropogenic disturbance is the nitrogen uptake from air pollutants, which is not balanced by cation uptake from roots and this may lead to damage and breakdown of the plant cover. Photosynthesis is the main carbon input into ecosystems, but it alone does not represent the ecosystem carbon balance, which is determined by respiration of various kinds. Plant respiration and photosynthesis determine growth (net primary production) and microbial respiration balances the net ecosystem flux. In a spruce forest, 30% of the assimilatory carbon gain is used for respiration of needles, 20% is used for respiration in stems. Soil respiration is about 50% the carbon gain, half of which is root respiration, half is microbial respiration. In addition, disturbances lead to carbon losses, where fire, harvest and grazing bypass the chain of respiration. In total, the carbon balance at the biome level is only about 1% of the photosynthetic carbon input, or may indeed become negative. The recent observed increase in plant growth has

  5. Biological control of the terrestrial carbon sink

    Directory of Open Access Journals (Sweden)

    E.-D. Schulze

    2006-01-01

    Full Text Available This lecture reviews the past (since 1964 when the International Biological Program began and the future of our understanding of terrestrial carbon fluxes with focus on photosynthesis, respiration, primary-, ecosystem-, and biome-productivity. Photosynthetic capacity is related to the nitrogen concentration of leaves, but the capacity is only rarely reached under field conditions. Average rates of photosynthesis and stomatal conductance are closely correlated and operate near 50% of their maximal rate, with light being the limiting factor in humid regions and air humidity and soil water the limiting factor in arid climates. Leaf area is the main factor to extrapolate from leaves to canopies, with maximum surface conductance being dependent on leaf level stomatal conductance. Additionally, gas exchange depends also on rooting depth which determines the water and nutrient availability and on mycorrhizae which regulate the nutrient status. An important anthropogenic disturbance is the nitrogen uptake from air pollutants, which is not balanced by cation uptake from roots and this may lead to damage and breakdown of the plant cover. Photosynthesis is the main carbon input into ecosystems, but it alone does not represent the ecosystem carbon balance, which is determined by respiration of various kinds. Plant respiration and photosynthesis determine growth (net primary production and microbial respiration balances the net ecosystem flux. In a spruce forest, 30% of the assimilatory carbon gain is used for respiration of needles, 20% is used for respiration in stems. Soil respiration is about 50% the carbon gain, half of which is root respiration, half is microbial respiration. In addition, disturbances lead to carbon losses, where fire, harvest and grazing bypass the chain of respiration. In total, the carbon balance at the biome level is only about 1% of the photosynthetic carbon input, or may indeed become negative. The recent observed increase in

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2010-07-15

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

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

    International Nuclear Information System (INIS)

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

    2010-01-01

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

  8. Terrestrial nitrogen cycles: Some unanswered questions

    Science.gov (United States)

    Vitousek, P.

    1984-01-01

    Nitrogen is generally considered to be the element which most often limits the growth of plants in both natural and agricultural ecosystems. It regulates plant growth because photosynthetic rates are strongly dependent on the concentration of nitrogen in leaves, and because relatively large mounts of protein are required for cell division and growth. Yet nitrogen is abundant in the biosphere - the well-mixed pool in the atmosphere is considered inexhaustible compared to biotic demand, and the amount of already fixed organic nitrogen in soils far exceeds annual plant uptake in terrestrial ecosystems. In regions where natural vegetation is not nitrogen limited, continuous cultivation induces nitrogen deficiency. Nitrogen loss from cultivated lands is more rapid than that of other elements, and nitrogen fertilization is generally required to maintain crop yield under any continuous system. The pervasiveness of nitrogen deficiency in many natural and most managed sites is discussed.

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

    Science.gov (United States)

    Kondo, M.; Ichii, K.

    2012-12-01

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

  10. Quantifying the effect of nighttime interactions between roots and canopy physiology and their control of water and carbon cycling on feedbacks between soil moisture and terrestrial climatology under variable environmental conditions

    Energy Technology Data Exchange (ETDEWEB)

    Domec, Jean-Christophe [North Carolina State Univ., Raleigh, NC (United States); Palmroth, Sari [Duke Univ., Durham, NC (United States); Oren, Ram [Duke Univ., Durham, NC (United States); Swenson, Jennifer [Duke Univ., Durham, NC (United States); King, John S. [North Carolina State Univ., Raleigh, NC (United States); Noormets, Asko [North Carolina State Univ., Raleigh, NC (United States)

    2016-04-01

    The primary objective of this project is to characterize and quantify how the temporal variability of hydraulic redistribution (HR) and its physiological regulation in unmanaged and complex forests is affecting current water and carbon exchange and predict how future climate scenarios will affect these relationships and potentially feed back to the climate. Specifically, a detailed study of ecosystem water uptake and carbon exchange in relation to root functioning was proposed in order to quantify the mechanisms controlling temporal variability of soil moisture dynamic and HR in three active AmeriFlux sites, and to use published data of two other inactive AmeriFlux sites. Furthermore, data collected by our research group at the Duke Free Air CO2 enrichment (FACE) site was also being utilized to further improve our ability to forecast future environmental impacts of elevated CO2 concentration on soil moisture dynamic and its effect on carbon sequestration and terrestrial climatology. The overarching objective being to forecast, using a soil:plant:atmosphere model coupled with a biosphere:atmosphere model, the impact of root functioning on land surface climatology. By comparing unmanaged sites to plantations, we also proposed to determine the effect of land use change on terrestrial carbon sequestration and climatology through its effect on soil moisture dynamic and HR. Our simulations of HR by roots indicated that in some systems HR is an important mechanism that buffers soil water deficit, affects energy and carbon cycling; thus having significant implications for seasonal climate. HR maintained roots alive and below 70% loss of conductivity and our simulations also showed that the increased vapor pressure deficit at night under future conditions was sufficient to drive significant nighttime transpiration at all sites, which reduced HR. This predicted reduction in HR under future climate conditions played an important regulatory role in land atmosphere interactions

  11. The changing global carbon cycle: Linking plant-soil carbon dynamics to global consequences

    Science.gov (United States)

    Chapin, F. S.; McFarland, J.; McGuire, David A.; Euskirchen, E.S.; Ruess, Roger W.; Kielland, K.

    2009-01-01

    Most current climate-carbon cycle models that include the terrestrial carbon (C) cycle are based on a model developed 40 years ago by Woodwell & Whittaker (1968) and omit advances in biogeochemical understanding since that time. Their model treats net C emissions from ecosystems as the balance between net primary production (NPP) and heterotrophic respiration (HR, i.e. primarily decomposition).

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

    Science.gov (United States)

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

    2015-12-01

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

  13. What Drives Carbon Isotope Fractionation by the Terrestrial Biosphere?

    Science.gov (United States)

    Still, Christopher; Rastogi, Bharat

    2017-11-01

    During photosynthesis, terrestrial plants preferentially assimilate the lighter and much more abundant form of carbon, 12C, which accounts for roughly 99% of naturally occurring forms of this element. This photosynthetic preference for lighter carbon is driven principally by differences in molecular diffusion of carbon dioxide with differing 13C/12C across stomatal pores on leaves, followed by differences in carboxylation rates by the Rubisco enzyme that is central to the process of photosynthesis. As a result of these slight preferences, which work out to about a 2% difference in the fixation rates of 12CO2 versus 13CO2 by C3 vegetation, plant tissues are depleted in the heavier form of carbon (13C) relative to atmospheric CO2. This difference has been exploited in a wide range of scientific applications, as the photosynthetic isotope signature is passed to ecosystem carbon pools and through ecological food webs. What is less appreciated is the signature that terrestrial carbon exchanges leave on atmospheric CO2, as the net uptake of carbon by land plants during their growing season not only draws down the local CO2 concentration, it also leaves behind relatively more CO2 molecules containing 13C. The converse happens outside the growing season, when autotrophic and heterotrophic respiration predominate. During these periods, atmospheric CO2 concentration increases and its corresponding carbon isotope composition becomes relatively depleted in 13C as the products of photosynthesis are respired, along with some small isotope fractionation that happen downstream of the initial photosynthetic assimilation. Similar phenomena were first observed at shorter time scales by the eminent carbon cycle scientist, Charles (Dave) Keeling. Keeling collected samples of air in glass flasks from sites along the Big Sur coast that he later measured for CO2 concentration and carbon isotope composition (δ13C) in his lab (Keeling, 1998). From these samples, Keeling observed increasing

  14. Global variation of carbon use efficiency in terrestrial ecosystems

    Science.gov (United States)

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

    2017-04-01

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

  15. Observing the continental-scale carbon balance: assessment of sampling complementarity and redundancy in a terrestrial assimilation system by means of quantitative network design

    OpenAIRE

    Kaminski, T.; Rayner, P. J.; Vossbeck, M.; Scholze, M.; Koffi, E.

    2012-01-01

    This paper investigates the relationship between the heterogeneity of the terrestrial carbon cycle and the optimal design of observing networks to constrain it. We combine the methods of quantitative network design and carbon-cycle data assimilation to a hierarchy of increasingly heterogeneous descriptions of the European terrestrial biosphere as indicated by increasing diversity of plant functional types. We employ three types of observat...

  16. Soil erosion, sedimentation and the carbon cycle

    Science.gov (United States)

    Cammeraat, L. H.; Kirkels, F.; Kuhn, N. J.

    2012-04-01

    Historically soil erosion focused on the effects of on-site soil quality loss and consequently reduced crop yields, and off-site effects related to deposition of material and water quality issues such as increased sediment loads of rivers. In agricultural landscapes geomorphological processes reallocate considerable amounts of soil and soil organic carbon (SOC). The destiny of SOC is of importance because it constitutes the largest C pool of the fast carbon cycle, and which cannot only be understood by looking at the vertical transfer of C from soil to atmosphere. Therefore studies have been carried out to quantify this possible influence of soil erosion and soil deposition and which was summarized by Quinton et al. (2010) by "We need to consider soils as mobile systems to make accurate predictions about the consequences of global change for terrestrial biogeochemical cycles and climate feedbacks". Currently a debate exists on the actual fate of SOC in relation to the global carbon cycle, represented in a controversy between researchers claiming that erosion is a sink, and those who claim the opposite. This controversy is still continuing as it is not easy to quantify and model the dominating sink and source processes at the landscape scale. Getting insight into the balance of the carbon budget requires a comprehensive research of all relevant processes at broad spatio-temporal scales, from catchment to regional scales and covering the present to the late Holocene. Emphasising the economic and societal benefits, the merits for scientific knowledge of the carbon cycle and the potential to sequester carbon and consequently offset increasing atmospheric CO2 concentrations, make the fate of SOC in agricultural landscapes a high-priority research area. Quinton, J.N., Govers, G., Van Oost, K., Bardgett, R.D., 2010. The impact of agricultural soil erosion on biogeochemical cycling. Nature Geosci, 3, 311-314.

  17. Watch: Current knowledge of the terrestrial Global Water Cycle"

    NARCIS (Netherlands)

    Harding, R.; Best, M.; Hagemann, S.; Kabat, P.; Tallaksen, L.M.; Warnaars, T.; Wiberg, D.; Weedon, G.P.; Lanen, van H.A.J.; Ludwig, F.; Haddeland, I.

    2011-01-01

    Water-related impacts are among the most important consequences of increasing greenhouse gas concentrations. Changes in the global water cycle will also impact the carbon and nutrient cycles and vegetation patterns. There is already some evidence of increasing severity of floods and droughts and

  18. Arctic carbon cycling

    NARCIS (Netherlands)

    Christensen, Torben R; Rysgaard, SØREN; Bendtsen, JØRGEN; Else, Brent; Glud, Ronnie N; van Huissteden, J.; Parmentier, F.J.W.; Sachs, Torsten; Vonk, J.E.

    2017-01-01

    The marine Arctic is considered a net carbon sink, with large regional differences in uptake rates. More regional modelling and observational studies are required to reduce the uncertainty among current estimates. Robust projections for how the Arctic Ocean carbon sink may evolve in the future are

  19. Traceable components of terrestrial carbon storage capacity in biogeochemical models.

    Science.gov (United States)

    Xia, Jianyang; Luo, Yiqi; Wang, Ying-Ping; Hararuk, Oleksandra

    2013-07-01

    Biogeochemical models have been developed to account for more and more processes, making their complex structures difficult to be understood and evaluated. Here, we introduce a framework to decompose a complex land model into traceable components based on mutually independent properties of modeled biogeochemical processes. The framework traces modeled ecosystem carbon storage capacity (Xss ) to (i) a product of net primary productivity (NPP) and ecosystem residence time (τE ). The latter τE can be further traced to (ii) baseline carbon residence times (τ'E ), which are usually preset in a model according to vegetation characteristics and soil types, (iii) environmental scalars (ξ), including temperature and water scalars, and (iv) environmental forcings. We applied the framework to the Australian Community Atmosphere Biosphere Land Exchange (CABLE) model to help understand differences in modeled carbon processes among biomes and as influenced by nitrogen processes. With the climate forcings of 1990, modeled evergreen broadleaf forest had the highest NPP among the nine biomes and moderate residence times, leading to a relatively high carbon storage capacity (31.5 kg cm(-2) ). Deciduous needle leaf forest had the longest residence time (163.3 years) and low NPP, leading to moderate carbon storage (18.3 kg cm(-2) ). The longest τE in deciduous needle leaf forest was ascribed to its longest τ'E (43.6 years) and small ξ (0.14 on litter/soil carbon decay rates). Incorporation of nitrogen processes into the CABLE model decreased Xss in all biomes via reduced NPP (e.g., -12.1% in shrub land) or decreased τE or both. The decreases in τE resulted from nitrogen-induced changes in τ'E (e.g., -26.7% in C3 grassland) through carbon allocation among plant pools and transfers from plant to litter and soil pools. Our framework can be used to facilitate data model comparisons and model intercomparisons via tracking a few traceable components for all terrestrial carbon

  20. Terrestrial carbon storage dynamics: Chasing a moving target

    Science.gov (United States)

    Luo, Y.; Shi, Z.; Jiang, L.; Xia, J.; Wang, Y.; Kc, M.; Liang, J.; Lu, X.; Niu, S.; Ahlström, A.; Hararuk, O.; Hastings, A.; Hoffman, F. M.; Medlyn, B. E.; Rasmussen, M.; Smith, M. J.; Todd-Brown, K. E.; Wang, Y.

    2015-12-01

    Terrestrial ecosystems have been estimated to absorb roughly 30% of anthropogenic CO2 emissions. Past studies have identified myriad drivers of terrestrial carbon storage changes, such as fire, climate change, and land use changes. Those drivers influence the carbon storage change via diverse mechanisms, which have not been unified into a general theory so as to identify what control the direction and rate of terrestrial carbon storage dynamics. Here we propose a theoretical framework to quantitatively determine the response of terrestrial carbon storage to different exogenous drivers. With a combination of conceptual reasoning, mathematical analysis, and numeric experiments, we demonstrated that the maximal capacity of an ecosystem to store carbon is time-dependent and equals carbon input (i.e., net primary production, NPP) multiplying by residence time. The capacity is a moving target toward which carbon storage approaches (i.e., the direction of carbon storage change) but usually does not attain. The difference between the capacity and the carbon storage at a given time t is the unrealized carbon storage potential. The rate of the storage change is proportional to the magnitude of the unrealized potential. We also demonstrated that a parameter space of NPP, residence time, and carbon storage potential can well characterize carbon storage dynamics quantified at six sites ranging from tropical forests to tundra and simulated by two versions (carbon-only and coupled carbon-nitrogen) of the Australian Community Atmosphere-Biosphere Land Ecosystem (CABLE) Model under three climate change scenarios (CO2 rising only, climate warming only, and RCP8.5). Overall this study reveals the unified mechanism unerlying terrestrial carbon storage dynamics to guide transient traceability analysis of global land models and synthesis of empirical studies.

  1. Using satellite-derived optical thickness to assess the influence of clouds on terrestrial carbon uptake

    Science.gov (United States)

    S.J. Cheng; A.L. Steiner; D.Y. Hollinger; G. Bohrer; K.J. Nadelhoffer

    2016-01-01

    Clouds scatter direct solar radiation, generating diffuse radiation and altering the ratio of direct to diffuse light. If diffuse light increases plant canopy CO2 uptake, clouds may indirectly influence climate by altering the terrestrial carbon cycle. However, past research primarily uses proxies or qualitative categories of clouds to connect...

  2. Drought and ecosystem carbon cycling

    NARCIS (Netherlands)

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

    2011-01-01

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

  3. Increase of carbon cycle feedback with climate sensitivity: results from a coupled climate and carbon cycle model

    International Nuclear Information System (INIS)

    Govindasamy, B.; Thompson, S.; Mirin, A.; Wickett, M.; Caldeira, K.; Delire, C.

    2005-01-01

    Coupled climate and carbon cycle modelling studies have shown that the feedback between global warming and the carbon cycle, in particular the terrestrial carbon cycle, could accelerate climate change and result in greater warming. In this paper we investigate the sensitivity of this feedback for year 2100 global warming in the range of 0 to 8 K. Differing climate sensitivities to increased CO 2 content are imposed on the carbon cycle models for the same emissions. Emissions from the SRES A2 scenario are used. We use a fully coupled climate and carbon cycle model, the INtegrated Climate and CArbon model (INCCA), the NCAR/DOE Parallel Climate Model coupled to the IBIS terrestrial biosphere model and a modified OCMIP ocean biogeochemistry model. In our integrated model, for scenarios with year 2100 global warming increasing from 0 to 8 K, land uptake decreases from 47% to 29% of total CO 2 emissions. Due to competing effects, ocean uptake (16%) shows almost no change at all. Atmospheric CO 2 concentration increases are 48% higher in the run with 8 K global climate warming than in the case with no warming. Our results indicate that carbon cycle amplification of climate warming will be greater if there is higher climate sensitivity to increased atmospheric CO 2 content; the carbon cycle feedback factor increases from 1.13 to 1.48 when global warming increases from 3.2 to 8 K

  4. Ignoring detailed fast-changing dynamics of land use overestimates regional terrestrial carbon sequestration

    Directory of Open Access Journals (Sweden)

    S. Q. Zhao

    2009-08-01

    Full Text Available Land use change is critical in determining the distribution, magnitude and mechanisms of terrestrial carbon budgets at the local to global scales. To date, almost all regional to global carbon cycle studies are driven by a static land use map or land use change statistics with decadal time intervals. The biases in quantifying carbon exchange between the terrestrial ecosystems and the atmosphere caused by using such land use change information have not been investigated. Here, we used the General Ensemble biogeochemical Modeling System (GEMS, along with consistent and spatially explicit land use change scenarios with different intervals (1 yr, 5 yrs, 10 yrs and static, respectively, to evaluate the impacts of land use change data frequency on estimating regional carbon sequestration in the southeastern United States. Our results indicate that ignoring the detailed fast-changing dynamics of land use can lead to a significant overestimation of carbon uptake by the terrestrial ecosystem. Regional carbon sequestration increased from 0.27 to 0.69, 0.80 and 0.97 Mg C ha−1 yr−1 when land use change data frequency shifting from 1 year to 5 years, 10 years interval and static land use information, respectively. Carbon removal by forest harvesting and prolonged cumulative impacts of historical land use change on carbon cycle accounted for the differences in carbon sequestration between static and dynamic land use change scenarios. The results suggest that it is critical to incorporate the detailed dynamics of land use change into local to global carbon cycle studies. Otherwise, it is impossible to accurately quantify the geographic distributions, magnitudes, and mechanisms of terrestrial carbon sequestration at the local to global scales.

  5. Influence of multiple global change drivers on terrestrial carbon storage

    DEFF Research Database (Denmark)

    Yue, Kai; Fornara, Dario A; Yang, Wanqin

    2017-01-01

    The interactive effects of multiple global change drivers on terrestrial carbon (C) storage remain poorly understood. Here, we synthesise data from 633 published studies to show how the interactive effects of multiple drivers are generally additive (i.e. not differing from the sum of their indivi......The interactive effects of multiple global change drivers on terrestrial carbon (C) storage remain poorly understood. Here, we synthesise data from 633 published studies to show how the interactive effects of multiple drivers are generally additive (i.e. not differing from the sum...... additive effects of multiple global change drivers into future assessments of the C storage ability of terrestrial ecosystems....

  6. Carbon Cycling in Wetland Forest Soils

    Science.gov (United States)

    Carl C. Trettin; Martin F. Jurgensen

    2003-01-01

    Wetlands comprise a small proportion (i.e., 2 to 3%) of earth's terrestrial surface, yet they contain a significant proportion of the terrestrial carbon (C) pool. Soils comprise the largest terrestrial C pool (ca. 1550 Pg C in upper 100 cm; Eswaran et al., 1993; Batjes, 1996), and wetlands contain the single largest component, with estimates ranging between 18...

  7. Carbon dioxide efficiency of terrestrial enhanced weathering

    OpenAIRE

    Moosdorf, Nils; Renforth, Philip; Hartmann, Jens

    2014-01-01

    Terrestrial enhanced weathering, the spreading of ultramafic silicate rock flour to enhance natural weathering rates, has been suggested as part of a strategy to reduce global atmospheric CO2 levels. We budget potential CO2 sequestration against associated CO2 emissions to assess the net CO2 removal of terrestrial enhanced weathering. We combine global spatial data sets of potential source rocks, transport networks, and application areas with associated CO2 emissions in optimistic and pessimi...

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

    Science.gov (United States)

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

    2015-12-01

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

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

    Science.gov (United States)

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

    2011-12-01

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

  10. Closing carbon cycles

    NARCIS (Netherlands)

    Patel, Martin

    1999-01-01

    Fossil fuels are used as raw materials for the manufacture of synthetic organic materials, e.g. plastics, fibres, synthetic rubber, paints, solvents, fertilisers, surfactants, lubricants and bitumen. Since fossil carbon is embodied in these products they may be particularly relevant to climate

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-01-01

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

  12. Terrestrial biological carbon sequestration: science for enhancement and implementation

    Science.gov (United States)

    Wilfred M. Post; James E. Amonette; Richard Birdsey; Charles T. Jr. Garten; R. Cesar Izaurralde; Philip Jardine; Julie Jastrow; Rattan Lal; Gregg. Marland

    2009-01-01

    The purpose of this chapter is to review terrestrial biological carbon sequestration and evaluate the potential carbon storage capacity if present and new techniques are more aggressively utilized. Photosynthetic CO2 capture from the atmosphere and storage of the C in aboveground and belowground biomass and in soil organic and inorganic forms can...

  13. Carbon cycle changes during the Triassic-Jurassic transition

    NARCIS (Netherlands)

    Ruhl, M.|info:eu-repo/dai/nl/304838357

    2010-01-01

    The end-Triassic is regarded as one of the five major mass extinction events of the Phanerozoic. This time interval is marked by up to 50% of marine biodiversity loss and major changes in terrestrial ecosystems. Mass extinction events are often marked by changes in the global carbon cycle. The

  14. Accelerator mass analyses of meteorites - carbon-14 terrestrial ages

    International Nuclear Information System (INIS)

    Miura, Y.; Rucklidge, J.; Beukens, R.; Fireman, E.

    1988-01-01

    Carbon-14 terrestrial ages of ten Antarctic meteorites have been measured by the IsoTrace accelerator mass spectrometry (AMS). The 14 C terrestrial age of 1 gram sample was determined from 14 C concentrations collected at melt and re-melt temperatures, compared with the 14 C concentration of the known Bruderheim chondrite. Yamato-790448 (LL3) chondrite was found to be the oldest terrestrial age of 3x10 4 years in the nine Yamato chondrites, whereas Yamato-791630 (L4) chondrite is considered to be the youngest chondrites less than thousand years. Allan Hills chondrite of ALH-77231 (L6) shows older terrestrial age than the nine Yamato chondrites. New accelerator data of the terrestrial age show higher accuracy with smaller sample than the previous counting method. (author)

  15. Peatland geoengineering: an alternative approach to terrestrial carbon sequestration.

    Science.gov (United States)

    Freeman, Christopher; Fenner, Nathalie; Shirsat, Anil H

    2012-09-13

    Terrestrial and oceanic ecosystems contribute almost equally to the sequestration of ca 50 per cent of anthropogenic CO(2) emissions, and already play a role in minimizing our impact on Earth's climate. On land, the majority of the sequestered carbon enters soil carbon stores. Almost one-third of that soil carbon can be found in peatlands, an area covering just 2-3% of the Earth's landmass. Peatlands are thus well established as powerful agents of carbon capture and storage; the preservation of archaeological artefacts, such as ancient bog bodies, further attest to their exceptional preservative properties. Peatlands have higher carbon storage densities per unit ecosystem area than either the oceans or dry terrestrial systems. However, despite attempts over a number of years at enhancing carbon capture in the oceans or in land-based afforestation schemes, no attempt has yet been made to optimize peatland carbon storage capacity or even to harness peatlands to store externally captured carbon. Recent studies suggest that peatland carbon sequestration is due to the inhibitory effects of phenolic compounds that create an 'enzymic latch' on decomposition. Here, we propose to harness that mechanism in a series of peatland geoengineering strategies whereby molecular, biogeochemical, agronomical and afforestation approaches increase carbon capture and long-term sequestration in peat-forming terrestrial ecosystems.

  16. Terrestrial N Cycling And C Storage: Some Insights From A Process-based Land Surface Model

    Science.gov (United States)

    Zaehle, S.; Friend, A. D.; Friedlingstein, P.

    2008-12-01

    We present results of a new land surface model, O-CN, which includes a process-based coupling between the terrestrial cycling of energy, water, carbon, and nitrogen. The model represents the controls of the terrestrial nitrogen (N) cycling on carbon (C) pools and fluxes through photosynthesis, respiration, changes in allocation, and soil organic matter decomposition, and explicitly accounts for N leaching and gaseous losses. O-CN has been shown to give realistic results in comparison to observations at a wide range of scales, including in situ flux measurements, productivity databases, and atmospheric CO2 concentration data. O-CN is run for three free air carbon dioxide enrichment (FACE) sites (Duke, Oak Ridge, Aspen), and reproduces observed magnitudes of changes in net primary productivity, foliage area and foliage N content. Several alternative hypotheses concerning the control of N on vegetation growth and decomposition, including effects of diluting foliage N concentrations, down-regulation of photosynthesis and respiration, acclimation of C allocation patterns and biological N fixation, are tested with respect to their effect on long- term C sequestration estimate. Differences in initial N availability, small transient changes in N inputs and the assumed plasticity of C:N stoichiometry can lead to substantial differences in the simulated long-term changes in productivity and C sequestration. We discuss the capacity of observations obtained at FACE sites to evaluate these alternative hypotheses, and investigate implications of a transient versus instantaneous increase in atmospheric carbon dioxide for the magnitude of the simulated limiting effect of N on C cycling. Finally, we re-examine earlier model-based assessments of the terrestrial C sequestration potential using a global transient O-CN simulation driven by increases in atmospheric CO2, N deposition and climatic changes over the 21st century.

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

    Science.gov (United States)

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

    2016-04-19

    A mechanistic understanding of the controls on carbon storage and losses is essential for our capacity to predict and mitigate human impacts on the global carbon cycle. Plant litter decomposition is an important first step for carbon and nutrient turnover, and litter inputs and losses are essential in determining soil organic matter pools and the carbon balance in terrestrial ecosystems. Photodegradation, the photochemical mineralization of organic matter, has been recently identified as a mechanism for previously unexplained high rates of litter mass loss in arid lands; however, the global significance of this process as a control on carbon cycling in terrestrial ecosystems is not known. Here we show that, across a wide range of plant species, photodegradation enhanced subsequent biotic degradation of leaf litter. Moreover, we demonstrate that the mechanism for this enhancement involves increased accessibility to plant litter carbohydrates for microbial enzymes. Photodegradation of plant litter, driven by UV radiation, and especially visible (blue-green) light, reduced the structural and chemical bottleneck imposed by lignin in secondary cell walls. In leaf litter from woody species, specific interactions with UV radiation obscured facilitative effects of solar radiation on biotic decomposition. The generalized effect of sunlight exposure on subsequent microbial activity, mediated by increased accessibility to cell wall polysaccharides, suggests that photodegradation is quantitatively important in determining rates of mass loss, nutrient release, and the carbon balance in a broad range of terrestrial ecosystems.

  18. Do ENSO and Coastal Development Enhance Coastal Burial of Terrestrial Carbon?

    Science.gov (United States)

    Macreadie, Peter I; Rolph, Timothy C; Boyd, Ron; Schröder-Adams, Claudia J; Skilbeck, Charles G

    2015-01-01

    Carbon cycling on the east coast of Australia has the potential to be strongly affected by El Niño-Southern Oscillation (ENSO) intensification and coastal development (industrialization and urbanization). We performed paleoreconstructions of estuarine sediments from a seagrass-dominated estuary on the east coast of Australia (Tuggerah Lake, New South Wales) to test the hypothesis that millennial-scale ENSO intensification and European settlement in Australia have increased the transfer of organic carbon from land into coastal waters. Our data show that carbon accumulation rates within coastal sediments increased significantly during periods of maximum millennial-scale ENSO intensity ("super-ENSO") and coastal development. We suggest that ENSO and coastal development destabilize and liberate terrestrial soil carbon, which, during rainfall events (e.g., La Niña), washes into estuaries and becomes trapped and buried by coastal vegetation (seagrass in this case). Indeed, periods of high carbon burial were generally characterized as having rapid sedimentation rates, higher content of fine-grained sediments, and increased content of wood and charcoal fragments. These results, though preliminary, suggest that coastal development and ENSO intensification--both of which are predicted to increase over the coming century--can enhance capture and burial of terrestrial carbon by coastal ecosystems. These findings have important relevance for current efforts to build an understanding of terrestrial-marine carbon connectivity into global carbon budgets.

  19. Carbon dioxide efficiency of terrestrial enhanced weathering.

    Science.gov (United States)

    Moosdorf, Nils; Renforth, Phil; Hartmann, Jens

    2014-05-06

    Terrestrial enhanced weathering, the spreading of ultramafic silicate rock flour to enhance natural weathering rates, has been suggested as part of a strategy to reduce global atmospheric CO2 levels. We budget potential CO2 sequestration against associated CO2 emissions to assess the net CO2 removal of terrestrial enhanced weathering. We combine global spatial data sets of potential source rocks, transport networks, and application areas with associated CO2 emissions in optimistic and pessimistic scenarios. The results show that the choice of source rocks and material comminution technique dominate the CO2 efficiency of enhanced weathering. CO2 emissions from transport amount to on average 0.5-3% of potentially sequestered CO2. The emissions of material mining and application are negligible. After accounting for all emissions, 0.5-1.0 t CO2 can be sequestered on average per tonne of rock, translating into a unit cost from 1.6 to 9.9 GJ per tonne CO2 sequestered by enhanced weathering. However, to control or reduce atmospheric CO2 concentrations substantially with enhanced weathering would require very large amounts of rock. Before enhanced weathering could be applied on large scales, more research is needed to assess weathering rates, potential side effects, social acceptability, and mechanisms of governance.

  20. The carbon balance of terrestrial ecosystems of China

    Directory of Open Access Journals (Sweden)

    Pilli R

    2009-05-01

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

  1. Carbon Cycling with Nuclear Power

    Science.gov (United States)

    Lackner, Klaus S.

    2011-11-01

    Liquid hydrocarbon fuels like gasoline, diesel or jet fuel are the most efficient ways of delivering energy to the transportation sector, in particular cars, ships and airplanes. Unfortunately, their use nearly unavoidably leads to the emission of carbon dioxide into the atmosphere. Unless an equivalent amount is removed from the air, the carbon dioxide will accumulate and significantly contribute to the man-made greenhouse effect. If fuels are made from biomass, the capture of carbon dioxide is a natural part of the cycle. Here, we discuss technical options for capturing carbon dioxide at much faster rates. We outline the basic concepts, discuss how such capture technologies could be made affordable and show how they could be integrated into a larger system approach. In the short term, the likely source of the hydrocarbon fuels is oil or gas; in the longer term, technologies that can provide energy to remove oxygen from carbon dioxide and water molecules and combine the remaining components into liquid fuels make it possible to recycle carbon between fuels and carbon dioxide in an entirely abiotic process. Here we focus on renewable and nuclear energy options for producing liquid fuels and show how air capture combined with fuel synthesis could be more economic than a transition to electric cars or hydrogen-fueled cars.

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

    Science.gov (United States)

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

  3. Status and potential of terrestrial carbon sequestration in West Virginia

    Science.gov (United States)

    Benktesh D. Sharma; Jingxin. Wang

    2011-01-01

    Terrestrial ecosystem management offers cost-effective ways to enhance carbon (C) sequestration. This study utilized C stock and C sequestration in forest and agricultural lands, abandoned mine lands, and harvested wood products to estimate the net current annual C sequestration in West Virginia. Several management options within these components were simulated using a...

  4. Multi-factor controls on terrestrial carbon dynamics in urbanized areas

    Science.gov (United States)

    Zhang, C.; Tian, H.; Pan, S.; Lockaby, G.; Chappelka, A.

    2014-12-01

    As urban land expands rapidly across the globe, much concern has been raised that urbanization may alter the terrestrial carbon cycle. Urbanization involves complex changes in land structure and multiple environmental factors. Little is known about the relative contribution of these individual factors and their interactions to the terrestrial carbon dynamics, however, which is essential for assessing the effectiveness of carbon sequestration policies focusing on urban development. This study developed a comprehensive analysis framework for quantifying relative contribution of individual factors (and their interactions) to terrestrial carbon dynamics in urbanized areas. We identified 15 factors belonging to five categories, and we applied a newly developed factorial analysis scheme to the southern United States (SUS), a rapidly urbanizing region. In all, 24 numeric experiments were designed to systematically isolate and quantify the relative contribution of individual factors. We found that the impact of land conversion was far larger than other factors. Urban managements and the overall interactive effects among major factors, however, created a carbon sink that compensated for 42% of the carbon loss in land conversion. Our findings provide valuable information for regional carbon management in the SUS: (1) it is preferable to preserve pre-urban carbon pools than to rely on the carbon sinks in urban ecosystems to compensate for the carbon loss in land conversion. (2) In forested areas, it is recommendable to improve landscape design (e.g., by arranging green spaces close to the city center) to maximize the urbanization-induced environmental change effect on carbon sequestration. Urbanization-induced environmental change will be less effective in shrubland regions. (3) Urban carbon sequestration can be significantly improved through changes in management practices, such as increased irrigation and fertilizer and targeted use of vehicles and machinery with least

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

    Science.gov (United States)

    Kondo, M.; Ichii, K.

    2011-12-01

    optimization procedure as the point analysis, and found that these spatial data help to improve the model's overall reproducibility. The GOSAT product is expected to have higher accuracy since it uses global CO2 observations. Therefore, with the application of GOSAT data, a better estimation of terrestrial carbon cycle can be achieved with optimization. It is anticipated to carry out more detailed analysis upon the arrival of GOSAT product and to verify the reduction in the uncertainty in the future carbon budget and the climate change with the calibrated models, which is the major contribution can be achieved from GOSAT.

  6. Environmental forcing of terrestrial carbon isotope excursion amplification across five Eocene hyperthermals

    Science.gov (United States)

    Bowen, G. J.; Abels, H.

    2015-12-01

    Abrupt changes in the isotope composition of exogenic carbon pools accompany many major episodes of global change in the geologic record. The global expression of this change in substrates that reflect multiple carbon pools provides important evidence that many events reflect persistent, global redistribution of carbon between reduced and oxidized stocks. As the diversity of records documenting any event grows, however, discrepancies in the expression of carbon isotope change among substrates are almost always revealed. These differences in magnitude, pace, and pattern of change can complicate interpretations of global carbon redistribution, but under ideal circumstances can also provide additional information on changes in specific environmental and biogeochemical systems that accompanied the global events. Here we evaluate possible environmental influences on new terrestrial records of the negative carbon isotope excursions (CIEs) associated with multiple hyperthermals of the Early Eocene, which show a common pattern of amplified carbon isotope change in terrestrial paleosol carbonate records relative to that recorded in marine substrates. Scaling relationships between climate and carbon-cycle proxies suggest that that the climatic (temperature) impact of each event scaled proportionally with the magnitude of its marine CIE, likely implying that all events involved release of reduced carbon with a similar isotopic composition. Amplification of the terrestrial CIEs, however, does not scale with event magnitude, being proportionally less for the first, largest event (the PETM). We conduct a sensitivity test of a coupled plant-soil carbon isotope model to identify conditions that could account for the observed CIE scaling. At least two possibilities consistent with independent lines of evidence emerge: first, varying effects of pCO2 change on photosynthetic carbon isotope discrimination under changing background pCO2, and second, contrasting changes in regional

  7. Deposition and Burial Efficiency of Terrestrial Organic Carbon Exported from Small Mountainous Rivers to the Continental Margin, Southwest of Taiwan

    Science.gov (United States)

    Hsu, F.; Lin, S.; Wang, C.; Huh, C.

    2007-12-01

    Terrestrial organic carbon exported from small mountainous river to the continental margin may play an important role in global carbon cycle and it?|s biogeochemical process. A huge amount of suspended materials from small rivers in southwestern Taiwan (104 million tons per year) could serve as major carbon source to the adjacent ocean. However, little is know concerning fate of this terrigenous organic carbon. The purpose of this study is to calculate flux of terrigenous organic carbon deposited in the continental margin, offshore southwestern Taiwan through investigating spatial variation of organic carbon content, organic carbon isotopic compositions, organic carbon deposition rate and burial efficiency. Results show that organic carbon compositions in sediment are strongly influenced by terrestrial material exported from small rivers in the region, Kaoping River, Tseng-wen River and Er-jan Rver. In addition, a major part of the terrestrial materials exported from the Kaoping River may bypass shelf region and transport directly into the deep sea (South China Sea) through the Kaoping Canyon. Organic carbon isotopic compositions with lighter carbon isotopic values are found near the Kaoping River and Tseng-wen River mouth and rapidly change from heavier to lighter values through shelf to slope. Patches of lighter organic carbon isotopic compositions with high organic carbon content are also found in areas west of Kaoping River mouth, near the Kaoshiung city. Furthermore, terrigenous organic carbons with lighter isotopic values are found in the Kaoping canyon. A total of 0.028 Mt/yr of terrestrial organic carbon was found in the study area, which represented only about 10 percent of all terrestrial organic carbon deposited in the study area. Majority (~90 percent) of the organic carbon exported from the Kaoping River maybe directly transported into the deep sea (South China Sea) and become a major source of organic carbon in the deep sea.

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

    Science.gov (United States)

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

    2015-01-01

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

  9. The Importance of Uncertainty and Sensitivity Analysis in Process-based Models of Carbon and Nitrogen Cycling in Terrestrial Ecosystems with Particular Emphasis on Forest Ecosystems — Selected Papers from a Workshop Organized by the International Society for Ecological Modelling (ISEM) at the Third Biennal Meeting of the International Environmental Modelling and Software Society (IEMSS) in Burlington, Vermont, USA, August 9-13, 2006

    Science.gov (United States)

    Larocque, Guy R.; Bhatti, Jagtar S.; Liu, Jinxun; Ascough, James C.; Gordon, Andrew M.

    2008-01-01

    Many process-based models of carbon (C) and nitrogen (N) cycles have been developed for terrestrial ecosystems, including forest ecosystems. They address many basic issues of ecosystems structure and functioning, such as the role of internal feedback in ecosystem dynamics. The critical factor in these phenomena is scale, as these processes operate at scales from the minute (e.g. particulate pollution impacts on trees and other organisms) to the global (e.g. climate change). Research efforts remain important to improve the capability of such models to better represent the dynamics of terrestrial ecosystems, including the C, nutrient, (e.g. N) and water cycles. Existing models are sufficiently well advanced to help decision makers develop sustainable management policies and planning of terrestrial ecosystems, as they make realistic predictions when used appropriately. However, decision makers must be aware of their limitations by having the opportunity to evaluate the uncertainty associated with process-based models (Smith and Heath, 2001 and Allen et al., 2004). The variation in scale of issues currently being addressed by modelling efforts makes the evaluation of uncertainty a daunting task.

  10. The Hamburg oceanic carbon cycle circulation model. Cycle 1

    International Nuclear Information System (INIS)

    Maier-Reimer, E.; Heinze, C.

    1992-02-01

    The carbon cycle model calculates the prognostic fields of oceanic geochemical carbon cycle tracers making use of a 'frozen' velocity field provided by a run of the LSG oceanic circulation model (see the corresponding manual, LSG=Large Scale Geostrophic). The carbon cycle model includes a crude approximation of interactions between sediment and bottom layer water. A simple (meridionally diffusive) one layer atmosphere model allows to calculate the CO 2 airborne fraction resulting from the oceanic biogeochemical interactions. (orig.)

  11. Climate and the Carbon Cycle

    Science.gov (United States)

    Manley, Jim

    2017-04-01

    Climate and the Carbon Cycle EOS3a Science in tomorrow's classroom Students, like too much of the American public, are largely unaware or apathetic to the changes in world climate and the impact that these changes have for life on Earth. A study conducted by Michigan State University and published in 2011 by Science Daily titled 'What carbon cycle? College students lack scientific literacy, study finds'. This study relates how 'most college students in the United States do not grasp the scientific basis of the carbon cycle - an essential skill in understanding the causes and consequences of climate change.' The study authors call for a new approach to teaching about climate. What if teachers better understood vital components of Earth's climate system and were able to impart his understanding to their students? What if students based their responses to the information taught not on emotion, but on a deeper understanding of the forces driving climate change, their analysis of the scientific evidence and in the context of earth system science? As a Middle School science teacher, I have been given the opportunity to use a new curriculum within TERC's EarthLabs collection, Climate and the Carbon Cycle, to awaken those brains and assist my students in making personal lifestyle choices based on what they had learned. In addition, with support from TERC and The University of Texas Institute for Geophysics I joined others to begin training other teachers on how to implement this curriculum in their classrooms to expose their students to our changing climate. Through my poster, I will give you (1) a glimpse into the challenges faced by today's science teachers in communicating the complicated, but ever-deepening understanding of the linkages between natural and human-driven factors on climate; (2) introduce you to a new module in the EarthLabs curriculum designed to expose teachers and students to global scientific climate data and instrumentation; and (3) illustrate how

  12. The importance of terrestrial carbon in supporting molluscs in the wetlands of Poyang Lake

    Science.gov (United States)

    Zhang, Huan; Yu, Xiubo; Wang, Yuyu; Xu, Jun

    2017-07-01

    Allochthonous organic matter plays an important role in nutrient cycling and energy mobilization in freshwater ecosystems. However, the subsidies of this carbon source in floodplain ecosystems have not yet well understood. We used a Bayesian mixing model and stable isotopes (δ13C and δ15N) of primary food resources and dominant molluscs species, to estimate the relative importance of allochthonous carbon sources for consumers in a representative sub-lake of Poyang Lake during a prolonged dry season. Our study inferred that terrestrial-derived carbon from Carex spp. could be the primary contributor to snails and mussels in Dahuchi Lake. The mean percentage of allochthonous food resources accounted for 35%-50% of the C incorporated by these consumers. Seston was another important energy sources for benthic consumers. However, during the winter and low water-level period, benthic algae and submerged vegetation contributed less carbon to benthic consumers. Our data highlighted the importance of terrestrial organic carbon to benthic consumers in the wetlands of Poyang Lake during the prolonged dry period. Further, our results provided a perspective that linkages between terrestrial and aquatic ecosystems might be facilitated by wintering geese via their droppings.

  13. The economic implications of carbon cycle uncertainty

    International Nuclear Information System (INIS)

    Smith, Steven J.; Edmonds, James A.

    2006-01-01

    This paper examines the implications of uncertainty in the carbon cycle for the cost of stabilizing carbon dioxide concentrations. Using a state of the art integrated assessment model, we find that uncertainty in our understanding of the carbon cycle has significant implications for the costs of a climate stabilization policy, with cost differences denominated in trillions of dollars. Uncertainty in the carbon cycle is equivalent to a change in concentration target of up to 100 ppmv. The impact of carbon cycle uncertainties are smaller than those for climate sensitivity, and broadly comparable to the effect of uncertainty in technology availability

  14. Bioenergy, the Carbon Cycle, and Carbon Policy

    Science.gov (United States)

    Kammen, D. M.

    2003-12-01

    The evolving energy and land-use policies across North America and Africa provide critical case studies in the relationship between regional development, the management of natural resources, and the carbon cycle. Over 50 EJ of the roughly 430 EJ total global anthropogenic energy budget is currently utilized in the form of direct biomass combustion. In North America 3 - 4 percent of total energy is derived from biomass, largely in combined heat and power (CHP) combustion applications. By contrast Africa, which is a major consumer of 'traditional' forms of biomass, uses far more total bioenergy products, but largely in smaller batches, with quantities of 0.5 - 2 tons/capita at the household level. Several African nations rely on biomass for well over 90 percent of household energy, and in some nations major portions of the industrial energy supply is also derived from biomass. In much of sub-Saharan Africa the direct combustion of biomass in rural areas is exceeded by the conversion of wood to charcoal for transport to the cities for household use there. There are major health, and environmental repercussions of these energy flows. The African, as well as Latin American and Asian charcoal trade has a noticeable signature on the global greenhouse gas cycles. In North America, and notably Scandinavia and India as well, biomass energy and emerging conversion technologies are being actively researched, and provide tremendous opportunities for the evolution of a sustainable, locally based, energy economy for many nations. This talk will examine aspects of these current energy and carbon flows, and the potential that gassification and new silvicultural practices hold for clean energy systems in the 21st century. North America and Africa will be examined in particular as both sources of innovation in this field, and areas with specific promise for application of these energy technologies and biomass/land use practices to further energy and global climate management.

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

    Science.gov (United States)

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

    2017-04-01

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

  16. State of the Carbon Cycle of North America: Overarching Findings

    Science.gov (United States)

    Mayes, M. A.; Reed, S.; Najjar, R.; Romero-Lankao, P.; Birdsey, R.

    2016-12-01

    This presentation will provide an overarching summary of the second "State of the Carbon Cycle of North America Report" (SOCCR2) from the perspective of the five editorial lead authors. The chapters of SOCCR2 represent a major update and much new material since the original report published a decade ago. The new report includes an overview of the North American carbon budget and future projections, the consequences of changes to the carbon budget, details of the carbon budget in major terrestrial and aquatic ecosystems and anthropogenic drivers, and implications for carbon management. The chapters focus on advances since the 2007 report, but also include new focus areas such as soil carbon, tribal lands, as well as greater emphasis on aquatic systems and the role of societal drivers and decision making on the carbon cycle. In addition, methane and the role of nitrogen will be considered to a greater extent than before. Each chapter also contains a section focusing on national and regional accounting to complement the overarching North American framework. In conclusion, SOCCR2 is expected to provide an updated assessment and a unique perspective on the carbon cycle, which will contribute to the next U.S. National Climate Assessment.

  17. The GLOBE Carbon Project: Integrating the Science of Carbon Cycling and Climate Change into K-12 Classrooms.

    Science.gov (United States)

    Ollinger, S. V.; Silverberg, S.; Albrechtova, J.; Freuder, R.; Gengarelly, L.; Martin, M.; Randolph, G.; Schloss, A.

    2007-12-01

    The global carbon cycle is a key regulator of the Earth's climate and is central to the normal function of ecological systems. Because rising atmospheric CO2 is the principal cause of climate change, understanding how ecosystems cycle and store carbon has become an extremely important issue. In recent years, the growing importance of the carbon cycle has brought it to the forefront of both science and environmental policy. The need for better scientific understanding has led to establishment of numerous research programs, such as the North American Carbon Program (NACP), which seeks to understand controls on carbon cycling under present and future conditions. Parallel efforts are greatly needed to integrate state-of-the-art science on the carbon cycle and its importance to climate with education and outreach efforts that help prepare society to make sound decisions on energy use, carbon management and climate change adaptation. Here, we present a new effort that joins carbon cycle scientists with the International GLOBE Education program to develop carbon cycle activities for K-12 classrooms. The GLOBE Carbon Cycle project is focused on bringing cutting edge research and research techniques in the field of terrestrial ecosystem carbon cycling into the classroom. Students will collect data about their school field site through existing protocols of phenology, land cover and soils as well as new protocols focused on leaf traits, and ecosystem growth and change. They will also participate in classroom activities to understand carbon cycling in terrestrial ecosystems, these will include plant- a-plant experiments, hands-on demonstrations of various concepts, and analysis of collected data. In addition to the traditional GLOBE experience, students will have the opportunity to integrate their data with emerging and expanding technologies including global and local carbon cycle models and remote sensing toolkits. This program design will allow students to explore research

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

    Directory of Open Access Journals (Sweden)

    Melissa R. A. Pingree

    2017-08-01

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

  19. Terrestrial carbon losses from mountaintop coal mining offset regional forest carbon sequestration in the 21st century

    International Nuclear Information System (INIS)

    Elliott Campbell, J; Fox, James F; Acton, Peter M

    2012-01-01

    Studies that quantify the spatial and temporal variability of carbon sources and sinks provide process-level information for the prediction of future levels of atmospheric carbon dioxide as well as verification of current emission agreements. Assessments of carbon sources and sinks for North America that compare top-down atmospheric constraints with bottom-up inventories find particularly large carbon sinks in the southeastern US. However, this southeastern US sink may be impacted by extreme land-use disturbance events due to mountaintop coal mining (MCM). Here we apply ecosystem modeling and field experiment data to quantify the potential impact of future mountaintop coal mining on the carbon budget of the southern Appalachian forest region. For projections based on historical mining rates, grassland reclamation, and the continued regrowth of un-mined forests, we find that the southern Appalachian forests switch from a net carbon sink to a net carbon source by year 2025–33 with a 30%–35% loss in terrestrial carbon stocks relative to a scenario with no future mining by the year 2100. Alternatively, scenarios of forest sequestration due to the effect of CO 2 fertilization result in a 15%–24% loss in terrestrial carbon stocks by the year 2100 for mining scenarios relative to scenarios with no future mining. These results suggest that while power plant stack emissions are the dominant life-cycle stage in coal-fired electricity, accounting for mountaintop coal mining in bottom-up inventories may be a critical component of regional carbon budgets. (letter)

  20. Simulation of carbon isotope discrimination of the terrestrial biosphere

    Science.gov (United States)

    Suits, N. S.; Denning, A. S.; Berry, J. A.; Still, C. J.; Kaduk, J.; Miller, J. B.; Baker, I. T.

    2005-03-01

    We introduce a multistage model of carbon isotope discrimination during C3 photosynthesis and global maps of C3/C4 plant ratios to an ecophysiological model of the terrestrial biosphere (SiB2) in order to predict the carbon isotope ratios of terrestrial plant carbon globally at a 1° resolution. The model is driven by observed meteorology from the European Centre for Medium-Range Weather Forecasts (ECMWF), constrained by satellite-derived Normalized Difference Vegetation Index (NDVI) and run for the years 1983-1993. Modeled mean annual C3 discrimination during this period is 19.2‰; total mean annual discrimination by the terrestrial biosphere (C3 and C4 plants) is 15.9‰. We test simulation results in three ways. First, we compare the modeled response of C3 discrimination to changes in physiological stress, including daily variations in vapor pressure deficit (vpd) and monthly variations in precipitation, to observed changes in discrimination inferred from Keeling plot intercepts. Second, we compare mean δ13C ratios from selected biomes (Broadleaf, Temperate Broadleaf, Temperate Conifer, and Boreal) to the observed values from Keeling plots at these biomes. Third, we compare simulated zonal δ13C ratios in the Northern Hemisphere (20°N to 60°N) to values predicted from high-frequency variations in measured atmospheric CO2 and δ13C from terrestrially dominated sites within the NOAA-Globalview flask network. The modeled response to changes in vapor pressure deficit compares favorably to observations. Simulated discrimination in tropical forests of the Amazon basin is less sensitive to changes in monthly precipitation than is suggested by some observations. Mean model δ13C ratios for Broadleaf, Temperate Broadleaf, Temperate Conifer, and Boreal biomes compare well with the few measurements available; however, there is more variability in observations than in the simulation, and modeled δ13C values for tropical forests are heavy relative to observations

  1. Inland Waters and the North American Carbon Cycle

    Science.gov (United States)

    Butman, D. E.; Striegl, R. G.; Stackpoole, S. M.; del Giorgio, P.; Prairie, Y.; Pilcher, D.; Raymond, P. A.; Alcocer, J.; Paz, F.

    2016-12-01

    Inland aquatic ecosystems process, store, and release carbon to the atmosphere and coastal margins. The form of this carbon is a function of terrestrial and aquatic primary and secondary production, the weathering of materials in soils and subsurface environments, the hydrologic controls on the movement of carbon from land to inland waters, and the connectivity between streams, rivers, lakes, reservoirs and groundwater. The 2007 1st State of the Carbon Cycle reported fluxes for the continental United States (CONUS) only. Streams and rivers exported 30-40 Tg C yr-1 to coastal environments, and 17-25 Tg C yr-1 were buried in lake and reservoir sediments. Remarkably, the 2007 report did not quantify gas emissions, which represent over half of the total carbon fluxes through inland water in the US. Current research has shown that 71-149 Tg C yr-1 exits freshwater systems either through atmospheric emissions of carbon dioxide or as inorganic and organic carbon fluxes to the coast from the CONUS. These estimates did not include the Laurentian Great Lakes. Variation in the magnitude of these fluxes across regions of the CONUS has been linked to differences in precipitation and terrestrial net ecosystem production. Similar comprehensive assessments have not been done for Canada or Mexico. Here we provide, as part of the 2nd State of the Carbon Cycle report, estimates for the river coastal export and vertical emissions of carbon from inland waters of North America, and report major data gaps, and weaknesses in methodologies. These findings stress that strong international partnerships are needed to improve assessment, monitoring, and modeling of human impacts on the magnitude and timing of aquatic fluxes in the future.

  2. A reappraisal of the terrestrial nitrogen cycle: what can we learn by extracting concepts from Gaia theory?

    Science.gov (United States)

    Cresser, Malcolm S; Aitkenhead, Matthew J; Mian, Ishaq A

    2008-08-01

    Although soil scientists and most environmental scientists are acutely aware of the interactions between the cycling of carbon and nitrogen, for conceptual convenience when portraying the nitrogen cycle in text books the N cycle tends to be considered in isolation from its interactions with the cycling of other elements and water, usually as a snap shot at the current time; the origins of dinitrogen are rarely considered, for example. The authors suggest that Lovelock's Gaia hypothesis provides a useful and stimulating framework for consideration of the terrestrial nitrogen cycle. If it is used, it suggests that urbanization and management of sewage, and intensive animal rearing are probably bigger global issues than nitrogen deposition from fossil fuel combustion, and that plant evolution may be driven by the requirement of locally sustainable and near optimal soil mineral N supply dynamics. This may, in turn, be partially regulating global carbon and oxygen cycles. It is suggested that pollutant N deposition may disrupt this essential natural plant and terrestrial ecosystem evolutionary process, causing biodiversity change. Interactions between the Earth and other bodies in the solar system, and possibly beyond, also need to be considered in the context of the global N cycle over geological time scales. This is because of direct potential impacts on the nitrogen content of the atmosphere, potential long-term impacts of past boloid collisions on plate tectonics and thus on global N cycling via subduction and volcanic emissions, and indirect effects upon C, O and water cycling that all may impact upon the N cycle in the long term.

  3. Stimulation of terrestrial ecosystem carbon storage by nitrogen addition: a meta-analysis.

    Science.gov (United States)

    Yue, Kai; Peng, Yan; Peng, Changhui; Yang, Wanqin; Peng, Xin; Wu, Fuzhong

    2016-01-27

    Elevated nitrogen (N) deposition alters the terrestrial carbon (C) cycle, which is likely to feed back to further climate change. However, how the overall terrestrial ecosystem C pools and fluxes respond to N addition remains unclear. By synthesizing data from multiple terrestrial ecosystems, we quantified the response of C pools and fluxes to experimental N addition using a comprehensive meta-analysis method. Our results showed that N addition significantly stimulated soil total C storage by 5.82% ([2.47%, 9.27%], 95% CI, the same below) and increased the C contents of the above- and below-ground parts of plants by 25.65% [11.07%, 42.12%] and 15.93% [6.80%, 25.85%], respectively. Furthermore, N addition significantly increased aboveground net primary production by 52.38% [40.58%, 65.19%] and litterfall by 14.67% [9.24%, 20.38%] at a global scale. However, the C influx from the plant litter to the soil through litter decomposition and the efflux from the soil due to microbial respiration and soil respiration showed insignificant responses to N addition. Overall, our meta-analysis suggested that N addition will increase soil C storage and plant C in both above- and below-ground parts, indicating that terrestrial ecosystems might act to strengthen as a C sink under increasing N deposition.

  4. Comparative carbon cycle dynamics of the present and last interglacial

    Science.gov (United States)

    Brovkin, Victor; Brücher, Tim; Kleinen, Thomas; Zaehle, Sönke; Joos, Fortunat; Roth, Raphael; Spahni, Renato; Schmitt, Jochen; Fischer, Hubertus; Leuenberger, Markus; Stone, Emma J.; Ridgwell, Andy; Chappellaz, Jérôme; Kehrwald, Natalie; Barbante, Carlo; Blunier, Thomas; Dahl Jensen, Dorthe

    2016-04-01

    Changes in temperature and carbon dioxide during glacial cycles recorded in Antarctic ice cores are tightly coupled. However, this relationship does not hold for interglacials. While climate cooled towards the end of both the last (Eemian) and present (Holocene) interglacials, CO2 remained stable during the Eemian while rising in the Holocene. We identify and review twelve biogeochemical mechanisms of terrestrial (vegetation dynamics and CO2 fertilization, land use, wildfire, accumulation of peat, changes in permafrost carbon, subaerial volcanic outgassing) and marine origin (changes in sea surface temperature, carbonate compensation to deglaciation and terrestrial biosphere regrowth, shallow-water carbonate sedimentation, changes in the soft tissue pump, and methane hydrates), which potentially may have contributed to the CO2 dynamics during interglacials but which remain not well quantified. We use three Earth System Models (ESMs) of intermediate complexity to compare effects of selected mechanisms on the interglacial CO2 and δ13CO2 changes, focusing on those with substantial potential impacts: namely carbonate sedimentation in shallow waters, peat growth, and (in the case of the Holocene) human land use. A set of specified carbon cycle forcings could qualitatively explain atmospheric CO2 dynamics from 8 ka BP to the pre-industrial. However, when applied to Eemian boundary conditions from 126 to 115 ka BP, the same set of forcings led to disagreement with the observed direction of CO2 changes after 122 ka BP. This failure to simulate late-Eemian CO2 dynamics could be a result of the imposed forcings such as prescribed CaCO3 accumulation and/or an incorrect response of simulated terrestrial carbon to the surface cooling at the end of the interglacial. These experiments also reveal that key natural processes of interglacial CO2 dynamics - shallow water CaCO3 accumulation, peat and permafrost carbon dynamics - are not well represented in the current ESMs. Global

  5. Terrestrial biosphere carbon storage under alternative climate projections

    Energy Technology Data Exchange (ETDEWEB)

    Schaphoff, S.; Lucht, W.; Gerten, D.; Sitch, S.; Cramer, W. [Potsdam Institute for Climate Impact Research, P.O. Box 601203, D-14412 Potsdam (Germany); Prentice, I.C. [QUEST, Department of Earth Sciences, University of Bristol, Wills Memorial Building, Bristol, BS8 1RJ (United Kingdom)

    2006-01-15

    This study investigates commonalities and differences in projected land biosphere carbon storage among climate change projections derived from one emission scenario by five different general circulation models (GCMs). Carbon storage is studied using a global biogeochemical process model of vegetation and soil that includes dynamic treatment of changes in vegetation composition, a recently enhanced version of the Lund-Potsdam-Jena Dynamic Global Vegetation Model (LPJ-DGVM). Uncertainty in future terrestrial carbon storage due to differences in the climate projections is large. Changes by the end of the century range from -106 to +201 PgC, thus, even the sign of the response whether source or sink, is uncertain. Three out of five climate projections produce a land carbon source by the year 2100, one is approximately neutral and one a sink. A regional breakdown shows some robust qualitative features. Large areas of the boreal forest are shown as a future CO2 source, while a sink appears in the arctic. The sign of the response in tropical and sub-tropical ecosystems differs among models, due to the large variations in simulated precipitation patterns. The largest uncertainty is in the response of tropical rainforests of South America and Central Africa.

  6. Terrestrial biosphere carbon storage under alternative climate projections

    International Nuclear Information System (INIS)

    Schaphoff, S.; Lucht, W.; Gerten, D.; Sitch, S.; Cramer, W.; Prentice, I.C.

    2006-01-01

    This study investigates commonalities and differences in projected land biosphere carbon storage among climate change projections derived from one emission scenario by five different general circulation models (GCMs). Carbon storage is studied using a global biogeochemical process model of vegetation and soil that includes dynamic treatment of changes in vegetation composition, a recently enhanced version of the Lund-Potsdam-Jena Dynamic Global Vegetation Model (LPJ-DGVM). Uncertainty in future terrestrial carbon storage due to differences in the climate projections is large. Changes by the end of the century range from -106 to +201 PgC, thus, even the sign of the response whether source or sink, is uncertain. Three out of five climate projections produce a land carbon source by the year 2100, one is approximately neutral and one a sink. A regional breakdown shows some robust qualitative features. Large areas of the boreal forest are shown as a future CO2 source, while a sink appears in the arctic. The sign of the response in tropical and sub-tropical ecosystems differs among models, due to the large variations in simulated precipitation patterns. The largest uncertainty is in the response of tropical rainforests of South America and Central Africa

  7. [Effects and mechanism of freeze-thawing cycles on key processes of nitrogen cycle in terrestrial ecosystem].

    Science.gov (United States)

    Wang, Li-qin; Qi, Yu-chun; Dong, Yun-she; Peng, Qin; Guo, Shu-fang; He, Yun-long; Yan, Zhong-qing

    2015-11-01

    As a widespread natural phenomenon in the soil of middle and high latitude as well as high altitude, freeze-thawing cycles have a great influence on the nitrogen cycle of terrestrial ecosystem in non-growing season. Freeze-thawing cycles can alter the physicochemical and biological properties of the soil, which thereby affect the migration and transformation of soil nitrogen. The impacts of freeze-thawing cycles on key processes of nitrogen cycle in terrestrial ecosystem found in available studies remain inconsistent, the mechanism is still not clear, and the research methods also need to be further explored and innovated. So it is necessary to sum up and analyze the existing achievements in order to better understand the processes of soil nitrogen cycle subjected to freeze-thawing cycles. This paper reviewed the research progress in China and abroad about the effects and mechanisms of freeze-thawing cycles on key processes of nitrogen cycle in terrestrial ecosystem, including mineralization, immobilization, nitrification and denitrification, N leakage and gaseous loss, and analyzed the deficiencies of extant research. The possible key research topics that should be urgently paid more attention to in the future were also discussed.

  8. Role of volcanic forcing on future global carbon cycle

    Directory of Open Access Journals (Sweden)

    J. F. Tjiputra

    2011-06-01

    Full Text Available Using a fully coupled global climate-carbon cycle model, we assess the potential role of volcanic eruptions on future projection of climate change and its associated carbon cycle feedback. The volcanic-like forcings are applied together with a business-as-usual IPCC-A2 carbon emissions scenario. We show that very large volcanic eruptions similar to Tambora lead to short-term substantial global cooling. However, over a long period, smaller eruptions similar to Pinatubo in amplitude, but set to occur frequently, would have a stronger impact on future climate change. In a scenario where the volcanic external forcings are prescribed with a five-year frequency, the induced cooling immediately lower the global temperature by more than one degree before it returns to the warming trend. Therefore, the climate change is approximately delayed by several decades, and by the end of the 21st century, the warming is still below two degrees when compared to the present day period. Our climate-carbon feedback analysis shows that future volcanic eruptions induce positive feedbacks (i.e., more carbon sink on both the terrestrial and oceanic carbon cycle. The feedback signal on the ocean is consistently smaller than the terrestrial counterpart and the feedback strength is proportionally related to the frequency of the volcanic eruption events. The cooler climate reduces the terrestrial heterotrophic respiration in the northern high latitude and increases net primary production in the tropics, which contributes to more than 45 % increase in accumulated carbon uptake over land. The increased solubility of CO2 gas in seawater associated with cooler SST is offset by a reduced CO2 partial pressure gradient between the ocean and the atmosphere, which results in small changes in net ocean carbon uptake. Similarly, there is nearly no change in the seawater buffer capacity simulated between the different volcanic scenarios. Our study shows that even

  9. Soil carbon and nitrogen erosion in forested catchments: implications for erosion-induced terrestrial carbon sequestration

    Science.gov (United States)

    E. M. Stacy; S. C. Hart; C. T. Hunsaker; D. W. Johnson; A. A. Berhe

    2015-01-01

    Lateral movement of organic matter (OM) due to erosion is now considered an important flux term in terrestrial carbon (C) and nitrogen (N) budgets, yet most published studies on the role of erosion focus on agricultural or grassland ecosystems. To date, little information is available on the rate and nature of OM eroded from forest ecosystems. We present annual...

  10. Scale-dependent performances of CMIP5 earth system models in simulating terrestrial vegetation carbon

    Science.gov (United States)

    Jiang, L.; Luo, Y.; Yan, Y.; Hararuk, O.

    2013-12-01

    Mitigation of global changes will depend on reliable projection for the future situation. As the major tools to predict future climate, Earth System Models (ESMs) used in Coupled Model Intercomparison Project Phase 5 (CMIP5) for the IPCC Fifth Assessment Report have incorporated carbon cycle components, which account for the important fluxes of carbon between the ocean, atmosphere, and terrestrial biosphere carbon reservoirs; and therefore are expected to provide more detailed and more certain projections. However, ESMs are never perfect; and evaluating the ESMs can help us to identify uncertainties in prediction and give the priorities for model development. In this study, we benchmarked carbon in live vegetation in the terrestrial ecosystems simulated by 19 ESMs models from CMIP5 with an observationally estimated data set of global carbon vegetation pool 'Olson's Major World Ecosystem Complexes Ranked by Carbon in Live Vegetation: An Updated Database Using the GLC2000 Land Cover Product' by Gibbs (2006). Our aim is to evaluate the ability of ESMs to reproduce the global vegetation carbon pool at different scales and what are the possible causes for the bias. We found that the performance CMIP5 ESMs is very scale-dependent. While CESM1-BGC, CESM1-CAM5, CESM1-FASTCHEM and CESM1-WACCM, and NorESM1-M and NorESM1-ME (they share the same model structure) have very similar global sums with the observation data but they usually perform poorly at grid cell and biome scale. In contrast, MIROC-ESM and MIROC-ESM-CHEM simulate the best on at grid cell and biome scale but have larger differences in global sums than others. Our results will help improve CMIP5 ESMs for more reliable prediction.

  11. Global Carbon Cycle of the Precambrian Earth

    DEFF Research Database (Denmark)

    Wiewióra, Justyna

    The carbon isotopic composition of distinct Archaean geological records provides information about the global carbon cycle and emergence of life on early Earth. We utilized carbon isotopic records of Greenlandic carbonatites, diamonds, graphites, marbles, metacarbonates and ultramafic rocks...... in the surface environment and recycled back into the mantle In the third manuscript we investigate the carbon cycle components, which have maintained the carbon isotope composition of the mantle constant through time. Assuming constant organic ratio of the total carbon burial (f), we show that increased.......1‰) and metacarbonate ( -6.1 ± 0.1‰ to +1.5 ± 0.0‰) rocks from the ~3.8 Ga Isua Supracrustal Belt as resulting from the Rayleigh distillation process, which affected the ultramafic reservoir with initial δ13C between -2‰ and 0‰. Due to its high primary δ13C signature, carbon in the Isuan magnesite was most likely...

  12. Current and future impacts of ultraviolet radiation on the terrestrial carbon balance

    Institute of Scientific and Technical Information of China (English)

    W. Kolby SMITH; Wei GAO; Heidi STELTZER

    2009-01-01

    One of the most documented effects of human activity on our environment is the reduction of stratospheric ozone resulting in an increase of biologically harmful ultraviolet (UV) radiation. In a less predictable manner, UV radiation incident at the surface of the earth is expected to be further modified in the future as a result of altered cloud condition, atmospheric aerosol concentration, and snow cover. Although UV radiation comprises only a small fraction of the total solar radiation that is incident at the earth's surface, it has the greatest energy per unit wavelength and, thus, the greatest potential to damage the biosphere. Recent investigations have highlighted numerous ways that UV radiation could potentially affect a variety of ecological processes, including nutrient cycling and the terrestrial carbon cycle. The objectives of the following literature review are to summarize and synthesize the available information relevant to the effects of UV radiation and other climate change factors on the terrestrial carbon balance in an effort to highlight current gaps in knowledge and future research directions for UV radiation research.

  13. Africa and the global carbon cycle

    CSIR Research Space (South Africa)

    Williams, CA

    2007-03-01

    Full Text Available The African continent has a large and growing role in the global carbon cycle, with potentially important climate change implications. However, the sparse observation network in and around the African continent means that Africa is one...

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

    Science.gov (United States)

    Chen, Min

    period of 2003-2010. Ecosystem heterotrophic respiration (RH) was negatively affected by the aerosol loading. These results support previous conclusions of the advantage of aerosol light scattering effect on plant productions in other studies but suggest there is strong spatial variation. This study finds indirect aerosol effects on terrestrial ecosystem carbon dynamics through affecting plant phenology, thermal and hydrological environments. All these evidences suggested that the aerosol direct radiative effect on global terrestrial ecosystem carbon dynamics should be considered to better understand the global carbon cycle and climate change. An ozone sub-model is developed in this dissertation and fully coupled with iTem. The coupled model, named iTemO3 considers the processes of ozone stomatal deposition, plant defense to ozone influx, ozone damage and plant repairing mechanism. By using a global atmospheric chemical transport model (GACTM) estimated ground-level ozone concentration data, the model estimated global annual stomatal ozone deposition is 234.0 Tg O3 yr-1 and indicates which regions have high ozone damage risk. Different plant functional types, sunlit and shaded leaves are shown to have different responses to ozone. The model predictions suggest that ozone has caused considerable change on global terrestrial ecosystem carbon storage and carbon exchanges over the study period 2004-2008. The study suggests that uncertainty of the key parameters in iTemO3 could result in large errors in model predictions. Thus more experimental data for better model parameterization is highly needed.

  15. Data-driven diagnostics of terrestrial carbon dynamics over North America

    Science.gov (United States)

    Jingfeng Xiao; Scott V. Ollinger; Steve Frolking; George C. Hurtt; David Y. Hollinger; Kenneth J. Davis; Yude Pan; Xiaoyang Zhang; Feng Deng; Jiquan Chen; Dennis D. Baldocchi; Bevery E. Law; M. Altaf Arain; Ankur R. Desai; Andrew D. Richardson; Ge Sun; Brian Amiro; Hank Margolis; Lianhong Gu; Russell L. Scott; Peter D. Blanken; Andrew E. Suyker

    2014-01-01

    The exchange of carbon dioxide is a key measure of ecosystem metabolism and a critical intersection between the terrestrial biosphere and the Earth's climate. Despite the general agreement that the terrestrial ecosystems in North America provide a sizeable carbon sink, the size and distribution of the sink remain uncertain. We use a data-driven approach to upscale...

  16. Contributions of secondary forest and nitrogen dynamics to terrestrial carbon uptake

    Directory of Open Access Journals (Sweden)

    X. Yang

    2010-10-01

    Full Text Available We use a terrestrial carbon-nitrogen cycle component of the Integrated Science Assessment Model (ISAM to investigate the impacts of nitrogen dynamics on regrowing secondary forests over the 20th century. We further examine what the impacts of nitrogen deposition and land use change history are on terrestrial carbon uptake since preindustrial time. Our results suggest that global total net land use emissions for the 1990s associated with changes in cropland, pastureland, and wood harvest are 1.22 GtC/yr. Without considering the secondary forest regrowth, the estimated net global total land use emissions are 1.58 GtC/yr or about 0.36 GtC/yr higher than if secondary forest regrowth is considered. Results also show that without considering the nitrogen dynamics and deposition, the estimated global total secondary forest sink for the 1990s is 0.90 GtC/yr or about 0.54 GtC/yr higher than estimates that include the impacts of nitrogen dynamics and deposition. Nitrogen deposition alone is responsible for about 0.13 GtC/yr of the total secondary forest sink. While nitrogen is not a limiting nutrient in the intact primary forests in tropical regions, our study suggests that nitrogen becomes a limiting nutrient for regrowing secondary forests of the tropical regions, in particular Latin America and Tropical Africa. This is because land use change activities, especially wood harvest, removes large amounts of nitrogen from the system when slash is burnt or wood is removed for harvest. However, our model results show that carbon uptake is enhanced in the tropical secondary forests of the Indian region. We argue that this may be due to enhanced nitrogen mineralization and increased nitrogen availability following land use change in the Indian tropical forest ecosystems. Results also demonstrate that there is a significant amount of carbon accumulating in the Northern Hemisphere where most land use changes and forest regrowth has occurred in recent decades

  17. Regional carbon cycle responses to 25 years of variation in climate and disturbance in the US Pacific Northwest

    Science.gov (United States)

    David P. Turner; William D. Ritts; Robert E. Kennedy; Andrew N. Gray; Zhiqiang Yang

    2016-01-01

    Variation in climate, disturbance regime, and forest management strongly influence terrestrial carbon sources and sinks. Spatially distributed, process-based, carbon cycle simulation models provide a means to integrate information on these various influences to estimate carbon pools and flux over large domains. Here we apply the Biome-BGC model over the four-state...

  18. The origin of methane and biomolecules from a CO2 cycle on terrestrial planets

    Science.gov (United States)

    Civiš, Svatopluk; Knížek, Antonín; Ivanek, Ondřej; Kubelík, Petr; Zukalová, Markéta; Kavan, Ladislav; Ferus, Martin

    2017-10-01

    Understanding the chemical evolution of newly formed terrestrial planets involves uncertainties in atmospheric chemical composition and assessing the plausibility of biomolecule synthesis. In this study, an original scenario for the origin of methane on Mars and terrestrial planets is suggested. Carbon dioxide in Martian and other planetary atmospheres can be abiotically converted into a mixture of methane and carbon monoxide by `methanogenesis' on porous mineral photoactive surfaces under soft ultraviolet irradiation. On young planets exposed to heavy bombardment by interplanetary matter, this process can be followed by biomolecule synthesis through the reprocessing of reactive reducing atmospheres by impact-induced shock waves. The proposed mechanism of methanogenesis may help to answer the question concerning the formation of methane and carbon monoxide by photochemical processes, the formation of biomolecules on early Earth and other terrestrial planets, and the source and seasonal variation of methane concentrations on Mars.

  19. Recuperative supercritical carbon dioxide cycle

    Science.gov (United States)

    Sonwane, Chandrashekhar; Sprouse, Kenneth M; Subbaraman, Ganesan; O'Connor, George M; Johnson, Gregory A

    2014-11-18

    A power plant includes a closed loop, supercritical carbon dioxide system (CLS-CO.sub.2 system). The CLS-CO.sub.2 system includes a turbine-generator and a high temperature recuperator (HTR) that is arranged to receive expanded carbon dioxide from the turbine-generator. The HTR includes a plurality of heat exchangers that define respective heat exchange areas. At least two of the heat exchangers have different heat exchange areas.

  20. Testing the ``Wildfire Hypothesis:'' Terrestrial Organic Carbon Burning as the Cause of the Paleocene-Eocene Boundary Carbon Isotope Excursion

    Science.gov (United States)

    Moore, E. A.; Kurtz, A. C.

    2005-12-01

    The 3‰ negative carbon isotope excursion (CIE) at the Paleocene-Eocene boundary has generally been attributed to dissociation of seafloor methane hydrates. We are testing the alternative hypothesis that the carbon cycle perturbation resulted from wildfires affecting the extensive peatlands and coal swamps formed in the Paleocene. Accounting for the CIE with terrestrial organic carbon rather than methane requires a significantly larger net release of fossil carbon to the ocean-atmosphere, which may be more consistent with the extreme global warming and ocean acidification characteristic of the Paleocene-Eocene Thermal Maximum (PETM). While other researchers have noted evidence of fires at the Paleocene-Eocene boundary in individual locations, the research presented here is designed to test the "wildfire hypothesis" for the Paleocene-Eocene boundary by examining marine sediments for evidence of a global increase in wildfire activity. Such fires would produce massive amounts of soot, widely distributed by wind and well preserved in marine sediments as refractory black carbon. We expect that global wildfires occurring at the Paleocene-Eocene boundary would produce a peak in black carbon abundance at the PETM horizon. We are using the method of Gelinas et al. (2001) to produce high-resolution concentration profiles of black carbon across the Paleocene-Eocene boundary using seafloor sediments from ODP cores, beginning with the Bass River core from ODP leg 174AX and site 1209 from ODP leg 198. This method involves the chemical and thermal extraction of non-refractory carbon followed by combustion of the residual black carbon and measurement as CO2. Measurement of the δ 13C of the black carbon will put additional constraints on the source of the organic material combusted, and will allow us to determine if this organic material was formed prior to or during the CIE.

  1. Decadal trends in the seasonal-cycle amplitude of terrestrial CO2 exchange resulting from the ensemble of terrestrial biosphere models

    Directory of Open Access Journals (Sweden)

    Akihiko Ito

    2016-05-01

    Full Text Available The seasonal-cycle amplitude (SCA of the atmosphere–ecosystem carbon dioxide (CO2 exchange rate is a useful metric of the responsiveness of the terrestrial biosphere to environmental variations. It is unclear, however, what underlying mechanisms are responsible for the observed increasing trend of SCA in atmospheric CO2 concentration. Using output data from the Multi-scale Terrestrial Model Intercomparison Project (MsTMIP, we investigated how well the SCA of atmosphere–ecosystem CO2 exchange was simulated with 15 contemporary terrestrial ecosystem models during the period 1901–2010. Also, we made attempt to evaluate the contributions of potential mechanisms such as atmospheric CO2, climate, land-use, and nitrogen deposition, through factorial experiments using different combinations of forcing data. Under contemporary conditions, the simulated global-scale SCA of the cumulative net ecosystem carbon flux of most models was comparable in magnitude with the SCA of atmospheric CO2 concentrations. Results from factorial simulation experiments showed that elevated atmospheric CO2 exerted a strong influence on the seasonality amplification. When the model considered not only climate change but also land-use and atmospheric CO2 changes, the majority of the models showed amplification trends of the SCAs of photosynthesis, respiration, and net ecosystem production (+0.19 % to +0.50 % yr−1. In the case of land-use change, it was difficult to separate the contribution of agricultural management to SCA because of inadequacies in both the data and models. The simulated amplification of SCA was approximately consistent with the observational evidence of the SCA in atmospheric CO2 concentrations. Large inter-model differences remained, however, in the simulated global tendencies and spatial patterns of CO2 exchanges. Further studies are required to identify a consistent explanation for the simulated and observed amplification trends, including their

  2. Uncertainty in climate-carbon-cycle projections associated with the sensitivity of soil respiration to temperature

    International Nuclear Information System (INIS)

    Jones, Chris D.; Cox, Peter; Huntingford, Chris

    2003-01-01

    Carbon-cycle feedbacks have been shown to be very important in predicting climate change over the next century, with a potentially large positive feedback coming from the release of carbon from soils as global temperatures increase. The magnitude of this feedback and whether or not it drives the terrestrial carbon cycle to become a net source of carbon dioxide during the next century depends particularly on the response of soil respiration to temperature. Observed global atmospheric CO 2 concentration, and its response to naturally occurring climate anomalies, is used to constrain the behaviour of soil respiration in our coupled climate-carbon-cycle GCM. This constraint is used to quantify some of the uncertainties in predictions of future CO 2 levels. The uncertainty is large, emphasizing the importance of carbon-cycle research with respect to future climate change predictions

  3. Microbial contributions to climate change through carbon cycle feedbacks.

    Science.gov (United States)

    Bardgett, Richard D; Freeman, Chris; Ostle, Nicholas J

    2008-08-01

    There is considerable interest in understanding the biological mechanisms that regulate carbon exchanges between the land and atmosphere, and how these exchanges respond to climate change. An understanding of soil microbial ecology is central to our ability to assess terrestrial carbon cycle-climate feedbacks, but the complexity of the soil microbial community and the many ways that it can be affected by climate and other global changes hampers our ability to draw firm conclusions on this topic. In this paper, we argue that to understand the potential negative and positive contributions of soil microbes to land-atmosphere carbon exchange and global warming requires explicit consideration of both direct and indirect impacts of climate change on microorganisms. Moreover, we argue that this requires consideration of complex interactions and feedbacks that occur between microbes, plants and their physical environment in the context of climate change, and the influence of other global changes which have the capacity to amplify climate-driven effects on soil microbes. Overall, we emphasize the urgent need for greater understanding of how soil microbial ecology contributes to land-atmosphere carbon exchange in the context of climate change, and identify some challenges for the future. In particular, we highlight the need for a multifactor experimental approach to understand how soil microbes and their activities respond to climate change and consequences for carbon cycle feedbacks.

  4. Atmospheric carbon dioxide and the global carbon cycle

    Energy Technology Data Exchange (ETDEWEB)

    Trabalka, J R [ed.

    1985-12-01

    This state-of-the-art volume presents discussions on the global cycle of carbon, the dynamic balance among global atmospheric CO2 sources and sinks. Separate abstracts have been prepared for the individual papers. (ACR)

  5. Chemical Oceanography and the Marine Carbon Cycle

    Science.gov (United States)

    Emerson, Steven; Hedges, John

    The principles of chemical oceanography provide insight into the processes regulating the marine carbon cycle. The text offers a background in chemical oceanography and a description of how chemical elements in seawater and ocean sediments are used as tracers of physical, biological, chemical and geological processes in the ocean. The first seven chapters present basic topics of thermodynamics, isotope systematics and carbonate chemistry, and explain the influence of life on ocean chemistry and how it has evolved in the recent (glacial-interglacial) past. This is followed by topics essential to understanding the carbon cycle, including organic geochemistry, air-sea gas exchange, diffusion and reaction kinetics, the marine and atmosphere carbon cycle and diagenesis in marine sediments. Figures are available to download from www.cambridge.org/9780521833134. Ideal as a textbook for upper-level undergraduates and graduates in oceanography, environmental chemistry, geochemistry and earth science and a valuable reference for researchers in oceanography.

  6. Terrestrial Carbon [Environmental Pollution: Part I, Special Issue, March 2002; Part II, Special Issue Supplement to 116/3, 2002

    Energy Technology Data Exchange (ETDEWEB)

    Mickler, Robert (ed.); McNulty, Steven (ed.)

    2002-03-01

    These issues contain a total of forty-four peer reviewed science papers on terrestrial carbon presented at the Advances in Terrestrial Ecosystem Carbon Inventory, Measurements, and Monitoring Conference held in Raleigh, N.C., in October 2000.

  7. The fate of eroded soil organic carbon along a European transect – controls after deposition in terrestrial and aquatic systems

    DEFF Research Database (Denmark)

    Kirkels, Frédérique; Cammeraat, Erik; Kalbitz, Karsten

    that the turnover of deposited C is significantly affected by soil and organic matter properties, and whether deposition occurs in terrestrial or aquatic environments. We sampled topsoils from 10 agricultural sites along a European transect, spanning a wide range of SOC and soil characteristics (e.g. texture......The potential fate of eroded soil organic carbon (SOC) after deposition is key to understand carbon cycling in eroding landscapes. Globally, large quantities of sediments and SOC are redistributed by soil erosion on agricul-tural land, particularly after heavy precipitation events. Deposition......, aggregation, C content, etc.). Turnover of SOC was determined for terrestrial and aquatic depositional conditions in a 10-week incubation study. Moreover, we studied the impact of labile carbon inputs (‘priming’) on SOC stability using 13C labelled cellulose. We evaluated potentially important controls...

  8. Organic carbon burial in fjords: Terrestrial versus marine inputs

    Science.gov (United States)

    Cui, Xingqian; Bianchi, Thomas S.; Savage, Candida; Smith, Richard W.

    2016-10-01

    Fjords have been identified as sites of enhanced organic carbon (OC) burial and may play an important role in regulating climate change on glacial-interglacial timescales. Understanding sediment processes and sources of sedimentary OC are necessary to better constrain OC burial in fjords. In this study, we use Fiordland, New Zealand, as a case study and present data on surface sediments, sediment down-cores and terrestrial end-members to examine dynamics of sediments and the sources of OC in fjord sediments. Sediment cores showed evidence of multiple particle sources, frequent bioturbation and mass-wasting events. A multi-proxy approach (stable isotopes, lignin-phenols and fatty acids) allowed for separation of marine, soil and vascular plant OC in surface sediments. The relationship between mass accumulation rate (MAR) and OC contents in fjord surface sediments suggested that mineral dilution is important in controlling OC content on a global scale, but is less important for specific regions (e.g., New Zealand). The inconsistency of OC budgets calculated by using MAR weighted %OC and OC accumulation rates (AR; 6 vs 21-31 Tg OC yr-1) suggested that sediment flux in fjords was likely underestimated. By using end-member models, we propose that 55% to 62% of total OC buried in fjords is terrestrially derived, and accounts for 17 ± 12% of the OCterr buried in all marine sediments. The strong correlation between MAR and OC AR indicated that OC flux will likely decrease in fjords in the future with global warming due to decrease in sediment flux caused by glacier denudation.

  9. The carbon cycle and global warming

    International Nuclear Information System (INIS)

    Anon.

    1991-01-01

    Five land-use-based approaches can be used to slow the buildup of CO 2 in the atmosphere: slowing or stopping the loss of existing forests, thus preserving current carbon reservoirs; adding to the planet's vegetative cover through reforestation or other means, thus enlarging living terrestrial carbon reservoirs; increasing the carbon stored in nonliving carbon reservoirs such as agricultural soils; increasing the carbon stored in artificial reservoirs, including timber products; and substituting sustainable biomass energy sources for fossil fuel consumption, thus reducing energy-related carbon emissions. These approaches are all based on the same basic premise: adding to the planet's net carbon stores in vegetative cover or soil, or preventing any net loss, will help moderate global warming by keeping atmospheric CO 2 levels lower than they would otherwise be. Because biotic policy options appear capable of contributing significantly to the mitigation of global warming while also furthering many other public policy objectives, their role deserves careful consideration on a country-by-country basis

  10. The Second State of the Carbon Cycle Report: A Scientific Basis for Policy and Management Decisions

    Science.gov (United States)

    Birdsey, R.; Mayes, M. A.; Reed, S.; Najjar, R.; Romero-Lankao, P.

    2017-12-01

    The second "State of the Carbon Cycle of North America Report" (SOCCR-2) includes an overview of the North American carbon budget and future projections, the consequences of changes to the carbon budget, details of the carbon budget in major terrestrial and aquatic ecosystems (including coastal ocean waters), information about anthropogenic drivers, and implications for policy and carbon management. SOCCR-2 includes new focus areas such as soil carbon, arctic and boreal ecosystems, tribal lands, and greater emphasis on aquatic systems and the role of societal drivers and decision making on the carbon cycle. In addition, methane is considered to a greater extent than before. SOCCR-2 will contribute to the next U.S. National Climate Assessment, as well as providing information to support science-based management decisions and policies that include climate change mitigation and adaptation in Canada, the United States, and Mexico. Although the Report is still in the review process, preliminary findings indicate that North America is a net emitter of carbon dioxide and methane to the atmosphere, and that natural sinks offset about 25% of emitted carbon dioxide. Combustion of fossil fuels represents the largest source of emissions, but show a decreasing trend over the last decade and a lower share (20%) of the global total compared with the previous decade. Forests, soils, grasslands, and coastal oceans comprise the largest carbon sinks, while emissions from inland waters are a significant source of carbon dioxide. The Report also documents the lateral transfers of carbon among terrestrial ecosystems and from terrestrial to near-coastal ecosystems, to complete the carbon cycle accounting. Further, the Report explores the consequences of rising atmospheric carbon dioxide on terrestrial and oceanic systems, and the capacity of these systems to continue to act as carbon sinks based on the drivers of future carbon cycle changes, including carbon-climate feedbacks

  11. Soil organic matter dynamics and the global carbon cycle

    International Nuclear Information System (INIS)

    Post, W.M.; Emanuel, W.R.; King, A.W.

    1992-01-01

    The large size and potentially long residence time of the soil organic matter pool make it an important component of the global carbon cycle. Net terrestrial primary production of about 60 Pg C·yr -1 is, over a several-year period of time, balanced by an equivalent flux of litter production and subsequent decomposition of detritus and soil organic matter. We will review many of the major factors that influence soil organic matter dynamics that need to be explicitly considered in development of global estimates of carbon turnover in the world's soils. We will also discuss current decomposition models that are general enough to be used to develop a representation of global soil organic matter dynamics

  12. Altered belowground carbon cycling following land use change to perennial bioenergy crops

    Science.gov (United States)

    Belowground carbon (C) dynamics of terrestrial ecosystems play an important role in the global C cycle and thereby in climate regulation, yet remain poorly understood. Globally, land use change is a major driver of changes in belowground C storage; in general, land clearing and tillage for agricult...

  13. Patterns and controls of inter-annual variability in the terrestrial carbon budget

    Directory of Open Access Journals (Sweden)

    B. Marcolla

    2017-08-01

    Full Text Available The terrestrial carbon fluxes show the largest variability among the components of the global carbon cycle and drive most of the temporal variations in the growth rate of atmospheric CO2. Understanding the environmental controls and trends of the terrestrial carbon budget is therefore essential to predict the future trajectories of the CO2 airborne fraction and atmospheric concentrations. In the present work, patterns and controls of the inter-annual variability (IAV of carbon net ecosystem exchange (NEE have been analysed using three different data streams: ecosystem-level observations from the FLUXNET database (La Thuile and 2015 releases, the MPI-MTE (model tree ensemble bottom–up product resulting from the global upscaling of site-level fluxes, and the Jena CarboScope Inversion, a top–down estimate of surface fluxes obtained from observed CO2 concentrations and an atmospheric transport model. Consistencies and discrepancies in the temporal and spatial patterns and in the climatic and physiological controls of IAV were investigated between the three data sources. Results show that the global average of IAV at FLUXNET sites, quantified as the standard deviation of annual NEE, peaks in arid ecosystems and amounts to  ∼  120 gC m−2 y−1, almost 6 times more than the values calculated from the two global products (15 and 20 gC m−2 y−1 for MPI-MTE and the Jena Inversion, respectively. Most of the temporal variability observed in the last three decades of the MPI-MTE and Jena Inversion products is due to yearly anomalies, whereas the temporal trends explain only about 15 and 20 % of the variability, respectively. Both at the site level and on a global scale, the IAV of NEE is driven by the gross primary productivity and in particular by the cumulative carbon flux during the months when land acts as a sink. Altogether these results offer a broad view on the magnitude, spatial patterns and environmental drivers of IAV

  14. Patterns and controls of inter-annual variability in the terrestrial carbon budget

    Science.gov (United States)

    Marcolla, Barbara; Rödenbeck, Christian; Cescatti, Alessandro

    2017-08-01

    The terrestrial carbon fluxes show the largest variability among the components of the global carbon cycle and drive most of the temporal variations in the growth rate of atmospheric CO2. Understanding the environmental controls and trends of the terrestrial carbon budget is therefore essential to predict the future trajectories of the CO2 airborne fraction and atmospheric concentrations. In the present work, patterns and controls of the inter-annual variability (IAV) of carbon net ecosystem exchange (NEE) have been analysed using three different data streams: ecosystem-level observations from the FLUXNET database (La Thuile and 2015 releases), the MPI-MTE (model tree ensemble) bottom-up product resulting from the global upscaling of site-level fluxes, and the Jena CarboScope Inversion, a top-down estimate of surface fluxes obtained from observed CO2 concentrations and an atmospheric transport model. Consistencies and discrepancies in the temporal and spatial patterns and in the climatic and physiological controls of IAV were investigated between the three data sources. Results show that the global average of IAV at FLUXNET sites, quantified as the standard deviation of annual NEE, peaks in arid ecosystems and amounts to ˜ 120 gC m-2 y-1, almost 6 times more than the values calculated from the two global products (15 and 20 gC m-2 y-1 for MPI-MTE and the Jena Inversion, respectively). Most of the temporal variability observed in the last three decades of the MPI-MTE and Jena Inversion products is due to yearly anomalies, whereas the temporal trends explain only about 15 and 20 % of the variability, respectively. Both at the site level and on a global scale, the IAV of NEE is driven by the gross primary productivity and in particular by the cumulative carbon flux during the months when land acts as a sink. Altogether these results offer a broad view on the magnitude, spatial patterns and environmental drivers of IAV from a variety of data sources that can be

  15. The Development of Terrestrial Water Cycle Applications for SMAP Soil Moisture Data Products

    Science.gov (United States)

    Soil moisture storage sits at the locus of the terrestrial water cycle and governs the relative partitioning of precipitation into various land surface flux components. Consequently, improved observational constraint of soil moisture variations should improve our ability to globally monitor the te...

  16. The nuclear fuel cycle versus the carbon cycle

    International Nuclear Information System (INIS)

    Ewing, R.C.

    2005-01-01

    Nuclear power provides approximately 17% of the world's electricity, which is equivalent to a reduction in carbon emissions of ∼0.5 gigatonnes (Gt) of C/yr. This is a modest reduction as compared with global emissions of carbon, ∼7 Gt C/yr. Most analyses suggest that in order to have a significant and timely impact on carbon emissions, carbon-free sources, such as nuclear power, would have to expand total production of energy by factors of three to ten by 2050. A three-fold increase in nuclear power capacity would result in a projected reduction in carbon emissions of 1 to 2 Gt C/yr, depending on the type of carbon-based energy source that is displaced. This three-fold increase utilizing present nuclear technologies would result in 25,000 metric tonnes (t) of spent nuclear fuel (SNF) per year, containing over 200 t of plutonium. This is compared to a present global inventory of approximately 280,000 t of SNF and >1,700 t of Pu. A nuclear weapon can be fashioned from as little as 5 kg of 239 Pu. However, there is considerable technological flexibility in the nuclear fuel cycle. There are three types of nuclear fuel cycles that might be utilized for the increased production of energy: open, closed, or a symbiotic combination of different types of reactor (such as, thermal and fast neutron reactors). The neutron energy spectrum has a significant effect on the fission product yield, and the consumption of long-lived actinides, by fission, is best achieved by fast neutrons. Within each cycle, the volume and composition of the high-level nuclear waste and fissile material depend on the type of nuclear fuel, the amount of burn-up, the extent of radionuclide separation during reprocessing, and the types of materials used to immobilize different radionuclides. As an example, a 232 Th-based fuel cycle can be used to breed fissile 233 U with minimum production of Pu. In this paper, I will contrast the production of excess carbon in the form of CO 2 from fossil fuels with

  17. Formulating Energy Policies Related to Fossil Fuel Use: Critical Uncertainties in the Global Carbon Cycle

    Science.gov (United States)

    Post, W. M.; Dale, V. H.; DeAngelis, D. L.; Mann, L. K.; Mulholland, P. J.; O`Neill, R. V.; Peng, T. -H.; Farrell, M. P.

    1990-02-01

    The global carbon cycle is the dynamic interaction among the earth's carbon sources and sinks. Four reservoirs can be identified, including the atmosphere, terrestrial biosphere, oceans, and sediments. Atmospheric CO{sub 2} concentration is determined by characteristics of carbon fluxes among major reservoirs of the global carbon cycle. The objective of this paper is to document the knowns, and unknowns and uncertainties associated with key questions that if answered will increase the understanding of the portion of past, present, and future atmospheric CO{sub 2} attributable to fossil fuel burning. Documented atmospheric increases in CO{sub 2} levels are thought to result primarily from fossil fuel use and, perhaps, deforestation. However, the observed atmospheric CO{sub 2} increase is less than expected from current understanding of the global carbon cycle because of poorly understood interactions among the major carbon reservoirs.

  18. Biogeochemical cycling in terrestrial ecosystems of the Caatinga Biome.

    Science.gov (United States)

    Menezes, R S C; Sampaio, E V S B; Giongo, V; Pérez-Marin, A M

    2012-08-01

    The biogeochemical cycles of C, N, P and water, the impacts of land use in the stocks and flows of these elements and how they can affect the structure and functioning of Caatinga were reviewed. About half of this biome is still covered by native secondary vegetation. Soils are deficient in nutrients, especially N and P. Average concentrations of total soil P and C in the top layer (0-20 cm) are 196 mg kg(-1) and 9.3 g kg(-1), corresponding to C stocks around 23 Mg ha(-1). Aboveground biomass of native vegetation varies from 30 to 50 Mg ha(-1), and average root biomass from 3 to 12 Mg ha(-1). Average annual productivities and biomass accumulation in different land use systems vary from 1 to 7 Mg ha(-1) year(-1). Biological atmospheric N2 fixation is estimated to vary from 3 to 11 kg N ha(-1) year-1 and 21 to 26 kg N ha(-1) year(-1) in mature and secondary Caatinga, respectively. The main processes responsible for nutrient and water losses are fire, soil erosion, runoff and harvest of crops and animal products. Projected climate changes in the future point to higher temperatures and rainfall decreases. In face of the high intrinsic variability, actions to increase sustainability should improve resilience and stability of the ecosystems. Land use systems based on perennial species, as opposed to annual species, may be more stable and resilient, thus more adequate to face future potential increases in climate variability. Long-term studies to investigate the potential of the native biodiversity or adapted exotic species to design sustainable land use systems should be encouraged.

  19. Monitoring terrestrial dissolved organic carbon export at land-water interfaces using remote sensing

    Science.gov (United States)

    Yu, Q.; Li, J.; Tian, Y. Q.

    2017-12-01

    Carbon flux from land to oceans and lakes is a crucial component of carbon cycling. However, this lateral carbon flow at land-water interface is often neglected in the terrestrial carbon cycle budget, mainly because observations of the carbon dynamics are very limited. Monitoring CDOM/DOC dynamics using remote sensing and assessing DOC export from land to water remains a challenge. Current CDOM retrieval algorithms in the field of ocean color are not simply applicable to inland aquatic ecosystems since they were developed for coarse resolution ocean-viewing imagery and less complex water types in open-sea. We developed a new semi-analytical algorithm, called SBOP (Shallow water Bio-Optical Properties algorithm) to adapt to shallow inland waters. SBOP was first developed and calibrated based on in situ hyperspectral radiometer data. Then we applied it to the Landsat-8 OLI images and evaluated the effectiveness of the multispectral images on inversion of CDOM absorption based on our field sampling at the Saginaw Bay in the Lake Huron. The algorithm performances (RMSE = 0.17 and R2 = 0.87 in the Saginaw Bay; R2 = 0.80 in the northeastern US lakes) is promising and we conclude the CDOM absorption can be derived from Landsat-8 OLI image in both optically deep and optically shallow waters with high accuracy. Our method addressed challenges on employing appropriate atmospheric correction, determining bottom reflectance influence for shallow waters, and improving for bio-optical properties retrieval, as well as adapting to both hyperspectral and the multispectral remote sensing imagery. Over 100 Landsat-8 images in Lake Huron, northeastern US lakes, and the Arctic major rivers were processed to understand the CDOM spatio-temporal dynamics and its associated driving factors.

  20. Climate-carbon cycle feedbacks under stabilization: uncertainty and observational constraints

    International Nuclear Information System (INIS)

    Jones, Chris D.; Cox, Peter M.; Huntingford, Chris

    2006-01-01

    Avoiding 'dangerous climate change' by stabilization of atmospheric CO 2 concentrations at a desired level requires reducing the rate of anthropogenic carbon emissions so that they are balanced by uptake of carbon by the natural terrestrial and oceanic carbon cycles. Previous calculations of profiles of emissions which lead to stabilized CO 2 levels have assumed no impact of climate change on this natural carbon uptake. However, future climate change effects on the land carbon cycle are predicted to reduce its ability to act as a sink for anthropogenic carbon emissions and so quantification of this feedback is required to determine future permissible emissions. Here, we assess the impact of the climate-carbon cycle feedback and attempt to quantify its uncertainty due to both within-model parameter uncertainty and between-model structural uncertainty. We assess the use of observational constraints to reduce uncertainty in the future permissible emissions for climate stabilization and find that all realistic carbon cycle feedbacks consistent with the observational record give permissible emissions significantly less than previously assumed. However, the observational record proves to be insufficient to tightly constrain carbon cycle processes or future feedback strength with implications for climate-carbon cycle model evaluation

  1. Africa and the global carbon cycle

    Directory of Open Access Journals (Sweden)

    Denning A Scott

    2007-03-01

    Full Text Available Abstract The African continent has a large and growing role in the global carbon cycle, with potentially important climate change implications. However, the sparse observation network in and around the African continent means that Africa is one of the weakest links in our understanding of the global carbon cycle. Here, we combine data from regional and global inventories as well as forward and inverse model analyses to appraise what is known about Africa's continental-scale carbon dynamics. With low fossil emissions and productivity that largely compensates respiration, land conversion is Africa's primary net carbon release, much of it through burning of forests. Savanna fire emissions, though large, represent a short-term source that is offset by ensuing regrowth. While current data suggest a near zero decadal-scale carbon balance, interannual climate fluctuations (especially drought induce sizeable variability in net ecosystem productivity and savanna fire emissions such that Africa is a major source of interannual variability in global atmospheric CO2. Considering the continent's sizeable carbon stocks, their seemingly high vulnerability to anticipated climate and land use change, as well as growing populations and industrialization, Africa's carbon emissions and their interannual variability are likely to undergo substantial increases through the 21st century.

  2. Estimating Terrestrial Wood Biomass from Observed Concentrations of Atmospheric Carbon Dioxide

    NARCIS (Netherlands)

    Schaefer, K. M.; Peters, W.; Carvalhais, N.; van der Werf, G.; Miller, J.

    2008-01-01

    We estimate terrestrial disequilibrium state and wood biomass from observed concentrations of atmospheric CO2 using the CarbonTracker system coupled to the SiBCASA biophysical model. Starting with a priori estimates of carbon flux from the land, ocean, and fossil fuels, CarbonTracker estimates net

  3. Sub-grid scale representation of vegetation in global land surface schemes: implications for estimation of the terrestrial carbon sink

    Directory of Open Access Journals (Sweden)

    J. R. Melton

    2014-02-01

    Full Text Available Terrestrial ecosystem models commonly represent vegetation in terms of plant functional types (PFTs and use their vegetation attributes in calculations of the energy and water balance as well as to investigate the terrestrial carbon cycle. Sub-grid scale variability of PFTs in these models is represented using different approaches with the "composite" and "mosaic" approaches being the two end-members. The impact of these two approaches on the global carbon balance has been investigated with the Canadian Terrestrial Ecosystem Model (CTEM v 1.2 coupled to the Canadian Land Surface Scheme (CLASS v 3.6. In the composite (single-tile approach, the vegetation attributes of different PFTs present in a grid cell are aggregated and used in calculations to determine the resulting physical environmental conditions (soil moisture, soil temperature, etc. that are common to all PFTs. In the mosaic (multi-tile approach, energy and water balance calculations are performed separately for each PFT tile and each tile's physical land surface environmental conditions evolve independently. Pre-industrial equilibrium CLASS-CTEM simulations yield global totals of vegetation biomass, net primary productivity, and soil carbon that compare reasonably well with observation-based estimates and differ by less than 5% between the mosaic and composite configurations. However, on a regional scale the two approaches can differ by > 30%, especially in areas with high heterogeneity in land cover. Simulations over the historical period (1959–2005 show different responses to evolving climate and carbon dioxide concentrations from the two approaches. The cumulative global terrestrial carbon sink estimated over the 1959–2005 period (excluding land use change (LUC effects differs by around 5% between the two approaches (96.3 and 101.3 Pg, for the mosaic and composite approaches, respectively and compares well with the observation-based estimate of 82.2 ± 35 Pg C over the same

  4. Acceleration of global warming due to carbon-cycle feedbacks in a coupled climate model

    International Nuclear Information System (INIS)

    Cox, P.M.; Betts, R.A.; Jones, C.D.; Spall, S.A.; Totterdell, I.J.

    2000-01-01

    The continued increase in the atmospheric concentration of carbon dioxide due to anthropogenic emissions is predicted to lead to significant changes in climate. About half of the current emissions are being absorbed by the ocean and by land ecosystems, but this absorption is sensitive to climate as well as to atmospheric carbon dioxide concentrations, creating a feedback loop. General circulation models have generally excluded the feedback between climate and the biosphere, using static vegetation distributions and CO 2 concentrations from simple carbon-cycle models that do not include climate change. Here we present results from a fully coupled, three-dimensional carbon-climate model, indicating that carbon-cycle feedbacks could significantly accelerate climate change over the twenty-first century. We find that under a 'business as usual' scenario, the terrestrial biosphere acts as an overall carbon sink until about 2050, but turns into a source thereafter. By 2100, the ocean uptake rate of 5 Gt C yr -1 is balanced by the terrestrial carbon source, and atmospheric CO 2 concentrations are 250 p.p.m.v. higher in our fully coupled simulation than in uncoupled carbon models, resulting in a global-mean warming of 5.5 K, as compared to 4 K without the carbon-cycle feedback. (author)

  5. Hydrological effects on carbon cycles of Canada's forests and wetlands

    International Nuclear Information System (INIS)

    Ju, Weimin; Chen, Jing M.; Black, T. Andrew; Barr, Alan G.; Mccaughey, Harry; Roulet, Nigel T.

    2006-01-01

    The hydrological cycle has significant effects on the terrestrial carbon (C) balance through its controls on photosynthesis and C decomposition. A detailed representation of the water cycle in terrestrial C cycle models is essential for reliable estimates of C budgets. However, it is challenging to accurately describe the spatial and temporal variations of soil water, especially for regional and global applications. Vertical and horizontal movements of soil water should be included. To constrain the hydrology-related uncertainty in modelling the regional C balance, a three-dimensional hydrological module was incorporated into the Integrated Terrestrial Ecosystem Carbon-budget model (InTEC V3.0). We also added an explicit parameterization of wetlands. The inclusion of the hydrological module considerably improved the model's ability to simulate C content and balances in different ecosystems. Compared with measurements at five flux-tower sites, the model captured 85% and 82% of the variations in volumetric soil moisture content in the 0-10 cm and 10-30 cm depths during the growing season and 84% of the interannual variability in the measured C balance. The simulations showed that lateral subsurface water redistribution is a necessary mechanism for simulating water table depth for both poorly drained forest and peatland sites. Nationally, soil C content and their spatial variability are significantly related to drainage class. Poorly drained areas are important C sinks at the regional scale, however, their soil C content and balances are difficult to model and may have been inadequately represented in previous C cycle models. The InTEC V3.0 model predicted an annual net C uptake by Canada's forests and wetlands for the period 1901-1998 of 111.9 Tg C/yr, which is 41.4 Tg C/yr larger than our previous estimate (InTEC V2.0). The increase in the net C uptake occurred mainly in poorly drained regions and resulted from the inclusion of a separate wetland parameterization

  6. Soil Carbon and Nitrogen Cycle Modeling

    Science.gov (United States)

    Woo, D.; Chaoka, S.; Kumar, P.; Quijano, J. C.

    2012-12-01

    Second generation bioenergy crops, such as miscanthus (Miscantus × giganteus) and switchgrass (Panicum virgatum), are regarded as clean energy sources, and are an attractive option to mitigate the human-induced climate change. However, the global climate change and the expansion of perennial grass bioenergy crops have the power to alter the biogeochemical cycles in soil, especially, soil carbon storages, over long time scales. In order to develop a predictive understanding, this study develops a coupled hydrological-soil nutrient model to simulate soil carbon responses under different climate scenarios such as: (i) current weather condition, (ii) decreased precipitation by -15%, and (iii) increased temperature up to +3C for four different crops, namely miscanthus, switchgrass, maize, and natural prairie. We use Precision Agricultural Landscape Modeling System (PALMS), version 5.4.0, to capture biophysical and hydrological components coupled with a multilayer carbon and ¬nitrogen cycle model. We apply the model at daily time scale to the Energy Biosciences Institute study site, located in the University of Illinois Research Farms, in Urbana, Illinois. The atmospheric forcing used to run the model was generated stochastically from parameters obtained using available data recorded in Bondville Ameriflux Site. The model simulations are validated with observations of drainage and nitrate and ammonium concentrations recorded in drain tiles during 2011. The results of this study show (1) total soil carbon storage of miscanthus accumulates most noticeably due to the significant amount of aboveground plant carbon, and a relatively high carbon to nitrogen ratio and lignin content, which reduce the litter decomposition rate. Also, (2) the decreased precipitation contributes to the enhancement of total soil carbon storage and soil nitrogen concentration because of the reduced microbial biomass pool. However, (3) an opposite effect on the cycle is introduced by the increased

  7. Nitrogen and carbon isotopic composition of bone collagen from marine and terrestrial animals

    International Nuclear Information System (INIS)

    Schoeninger, M.J.; DeNiro, M.J.

    1984-01-01

    The stable nitrogen and carbon isotope ratios of bone collagen prepared from more than 100 animals representing 66 species of birds, fish, and mammals are presented. The delta 15 N values of bone collagen from animals that fed exclusively in the marine environment are, on average, 9 per mille more positive than those from animals that fed exclusively in the terrestrial environment: ranges for the two groups overlap by less than 1 per mille. Bone collagen delta 15 N values also serve to separate marine fish from the small number of freshwater fish we analyzed. The bone collagen delta 15 N values of birds and fish that spent part of their life cycles feeding in the marine environment and part in the freshwater environment are intermediate between those of animals that fed exclusively in one or the other system. Further, animals that fed at successive trophic levels in the marine and terrestrial environment are separated, on average, by a 3 per mille difference in the delta 15 N values of their bone collagen. Results are given and discussed. (author)

  8. Climate Change Impacts on the Organic Carbon Cycle at the Land-Ocean Interface

    Science.gov (United States)

    Canuel, Elizabeth A.; Cammer, Sarah S.; McIntosh, Hadley A.; Pondell, Christina R.

    2012-05-01

    Estuaries are among the most altered and vulnerable marine ecosystems. These ecosystems will likely continue to deteriorate owing to increased population growth in coastal regions, expected temperature and precipitation changes associated with climate change, and their interaction with each other, leading to serious consequences for the ecological and societal services they provide. A key function of estuaries is the transfer, transformation, and burial of carbon and other biogenic elements exchanged between the land and ocean systems. Climate change has the potential to influence the carbon cycle through anticipated changes to organic matter production in estuaries and through the alteration of carbon transformation and export processes. This review discusses the effects of climate change on processes influencing the cycling of organic carbon in estuaries, including examples from three temperate estuaries in North America. Our goal is to evaluate the impact of climate change on the connectivity of terrestrial, estuarine, and coastal ocean carbon cycles.

  9. Seasonal carbon cycling in a Greenlandic fjord

    DEFF Research Database (Denmark)

    Sørensen, Heidi L.; Meire, Lorenz; Juul-Pedersen, Thomas

    2015-01-01

    Climate change is expected to have a pronounced effect on biogeochemical cycling in Arctic fjords, but current insight on the biogeochemical functioning of these systems is limited. Here, we present seasonal data on primary production, export of particulate organic carbon (POC), and the coupling...... carbon amounted to 3.2 and 5.3 mol C m−2 yr−1, respectively. Sulfate reduction was the most prominent mineralization pathway, accounting for 69% of the benthic mineralization, while denitrification accounted for 2%. Overall, the carbon mineralization and burial in Kobbefjord were significantly higher...... in ice coverage in higher Arctic Greenlandic fjords will, as a first approximation, entail proportional increases in productivity, mineralization, and burial of organic carbon in the fjords, which will thus become similar to present-day southerly systems....

  10. Climate implications of including albedo effects in terrestrial carbon policy

    Science.gov (United States)

    Jones, A. D.; Collins, W.; Torn, M. S.; Calvin, K. V.

    2012-12-01

    Proposed strategies for managing terrestrial carbon in order to mitigate anthropogenic climate change, such as financial incentives for afforestation, soil carbon sequestration, or biofuel production, largely ignore the direct effects of land use change on climate via biophysical processes that alter surface energy and water budgets. Subsequent influences on temperature, hydrology, and atmospheric circulation at regional and global scales could potentially help or hinder climate stabilization efforts. Because these policies often rely on payments or credits expressed in units of CO2-equivalents, accounting for biophysical effects would require a metric for comparing the strength of biophysical climate perturbation from land use change to that of emitting CO2. One such candidate metric that has been suggested in the literature on land use impacts is radiative forcing, which underlies the global warming potential metric used to compare the climate effects of various greenhouse gases with one another. Expressing land use change in units of radiative forcing is possible because albedo change results in a net top-of-atmosphere radiative flux change. However, this approach has also been critiqued on theoretical grounds because not all climatic changes associated with land use change are principally radiative in nature, e.g. changes in hydrology or the vertical distribution of heat within the atmosphere, and because the spatial scale of land use change forcing differs from that of well-mixed greenhouse gases. To explore the potential magnitude of this discrepancy in the context of plausible scenarios of future land use change, we conduct three simulations with the Community Climate System Model 4 (CCSM4) utilizing a slab ocean model. Each simulation examines the effect of a stepwise change in forcing relative to a pre-industrial control simulation: 1) widespread conversion of forest land to crops resulting in approximately 1 W/m2 global-mean radiative forcing from albedo

  11. Implications of Deep Decarbonization for Carbon Cycle Science

    Science.gov (United States)

    Jones, A. D.; Williams, J.; Torn, M. S.

    2016-12-01

    The energy-system transformations required to achieve deep decarbonization in the United States, defined as a reduction of greenhouse gas emissions of 80% or more below 1990 levels by 2050, have profound implications for carbon cycle science, particularly with respect to 4 key objectives: understanding and enhancing the terrestrial carbon sink, using bioenergy sustainably, controlling non-CO2 GHGs, and emissions monitoring and verification. (1) As a source of mitigation, the terrestrial carbon sink is pivotal but uncertain, and changes in the expected sink may significantly affect the overall cost of mitigation. Yet the dynamics of the sink under changing climatic conditions, and the potential to protect and enhance the sink through land management, are poorly understood. Policy urgently requires an integrative research program that links basic science knowledge to land management practices. (2) Biomass resources can fill critical energy needs in a deeply decarbonized system, but current understanding of sustainability and lifecycle carbon aspects is limited. Mitigation policy needs better understanding of the sustainable amount, types, and cost of bioenergy feedstocks, their interactions with other land uses, and more efficient and reliable monitoring of embedded carbon. (3) As CO2 emissions from energy decrease under deep decarbonization, the relative share of non-CO2 GHGs grows larger and their mitigation more important. Because the sources tend to be distributed, variable, and uncertain, they have been under-researched. Policy needs a better understanding of mitigation priorities and costs, informed by deeper research in key areas such as fugitive CH4, fertilizer-derived N2O, and industrial F-gases. (4) The M&V challenge under deep decarbonization changes with a steep decrease in the combustion CO2 sources due to widespread electrification, while a greater share of CO2 releases is net-carbon-neutral. Similarly, gas pipelines may carry an increasing share of

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

    International Nuclear Information System (INIS)

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

    2003-01-01

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

  13. The Global Carbon Cycle: It's a Small World

    Science.gov (United States)

    Ineson, Philip; Milcu, Alexander; Subke, Jens-Arne; Wildman, Dennis; Anderson, Robert; Manning, Peter; Heinemeyer, Andreas

    2010-05-01

    Predicting future atmospheric concentrations of carbon dioxide (CO2), together with the impacts of these changes on global climate, are some of the most urgent and important challenges facing mankind. Modelling is the only way in which such predictions can be made, leading to the current generation of increasingly complex computer simulations, with associated concerns about embedded assumptions and conflicting model outputs. Alongside analysis of past climates, the GCMs currently represent our only hope of establishing the importance of potential runaway positive feedbacks linking climate change and atmospheric greenhouse gases yet the incorporation of necessary biospheric responses into GCMs markedly increases the uncertainty of predictions. Analysis of the importance of the major components of the global carbon (C) cycle reveals that an understanding of the conditions under which the terrestrial biosphere could switch from an overall carbon (C) sink to a source is critical to our ability to make future climate predictions. Here we present an alternative approach to assessing the short term biotic (plant and soil) sensitivities to elevated temperature and atmospheric CO2 through the use of a purely physical analogue. Centred on the concept of materially-closed systems containing scaled-down ratios of the global C stocks for the atmosphere, vegetation and soil we show that, in these model systems, the terrestrial biosphere is able to buffer a rise of 3oC even when coupled to very strong CO2-temperature positive feedbacks. The system respiratory response appears to be extremely well linked to temperature and is critical in deciding atmospheric concentrations of CO2. Simulated anthropogenic emissions of CO2 into the model systems showed an initial corresponding increase in atmospheric CO2 but, somewhat surprisingly, CO2 concentrations levelled off at ca. 480 p.p.m.v., despite continuing additions of CO2. Experiments were performed in which reversion of atmospheric

  14. Future Projections and Consequences of the Changing North American Carbon Cycle

    Science.gov (United States)

    Huntzinger, D. N.; Cooley, S. R.; Moore, D. J.

    2017-12-01

    The rise of atmospheric carbon dioxide (CO2), primarily due to human-caused fossil fuel emissions and land-use change, has been dampened by carbon uptake by the oceans and terrestrial biosphere. Nevertheless, today's atmospheric CO2 levels are higher than at any time in the past 800,000 years. Over the past decade, there has been considerable effort to understand how carbon cycle changes interact with, and influence, atmospheric CO2 concentrations and thus climate. Here, we summarize the key findings related to projected changes to the North American carbon cycle and the consequences of these changes as reported in Chapters 17 and 19 of the 2nd State of the Carbon Cycle Report (SOCCR-2). In terrestrial ecosystems, increased atmospheric CO2 causes enhanced photosynthesis, plant growth, and water-use efficiency. Together, these may lead to changes in vegetation composition, carbon storage, hydrology and biogeochemical cycling. In the ocean, increased uptake of atmospheric CO2 causes ocean acidification, which leads to changes in reproduction, survival, and growth of many marine species. These direct physiological responses to acidification are likely to have indirect ecosystem-scale consequences that we are just beginning to understand. In all environments, the effects of rising CO2 also interact with other global changes. For example, nutrient availability can set limits on growth and a warming climate alters carbon uptake depending on a number of other factors. As a result, there is low confidence in the future evolution of the North American carbon cycle. For example, models project that terrestrial ecosystems could continue to be a net sink (of up to 1.19 PgC yr-1) or switch to a net source of carbon to the atmosphere (of up to 0.60 PgC yr-1) by the end of the century under business-as-usual emission scenarios. And, while North American coastal areas have historically been a sink of carbon (e.g., 2.6 to 3.5 PgC since 1995) and are projected to continue to take up

  15. Toward explaining the Holocene carbon dioxide and carbon isotope records: Results from transient ocean carbon cycle-climate simulations

    Science.gov (United States)

    Menviel, L.; Joos, F.

    2012-03-01

    The Bern3D model was applied to quantify the mechanisms of carbon cycle changes during the Holocene (last 11,000 years). We rely on scenarios from the literature to prescribe the evolution of shallow water carbonate deposition and of land carbon inventory changes over the glacial termination (18,000 to 11,000 years ago) and the Holocene and modify these scenarios within uncertainties. Model results are consistent with Holocene records of atmospheric CO2 and δ13C as well as the spatiotemporal evolution of δ13C and carbonate ion concentration in the deep sea. Deposition of shallow water carbonate, carbonate compensation of land uptake during the glacial termination, land carbon uptake and release during the Holocene, and the response of the ocean-sediment system to marine changes during the termination contribute roughly equally to the reconstructed late Holocene pCO2 rise of 20 ppmv. The 5 ppmv early Holocene pCO2 decrease reflects terrestrial uptake largely compensated by carbonate deposition and ocean sediment responses. Additional small contributions arise from Holocene changes in sea surface temperature, ocean circulation, and export productivity. The Holocene pCO2 variations result from the subtle balance of forcings and processes acting on different timescales and partly in opposite direction as well as from memory effects associated with changes occurring during the termination. Different interglacial periods with different forcing histories are thus expected to yield different pCO2 evolutions as documented by ice cores.

  16. The role of tectonic uplift, climate, and vegetation in the long-term terrestrial phosphorous cycle

    Directory of Open Access Journals (Sweden)

    C. Buendía

    2010-06-01

    Full Text Available Phosphorus (P is a crucial element for life and therefore for maintaining ecosystem productivity. Its local availability to the terrestrial biosphere results from the interaction between climate, tectonic uplift, atmospheric transport, and biotic cycling. Here we present a mathematical model that describes the terrestrial P-cycle in a simple but comprehensive way. The resulting dynamical system can be solved analytically for steady-state conditions, allowing us to test the sensitivity of the P-availability to the key parameters and processes. Given constant inputs, we find that humid ecosystems exhibit lower P availability due to higher runoff and losses, and that tectonic uplift is a fundamental constraint. In particular, we find that in humid ecosystems the biotic cycling seem essential to maintain long-term P-availability. The time-dependent P dynamics for the Franz Josef and Hawaii chronosequences show how tectonic uplift is an important constraint on ecosystem productivity, while hydroclimatic conditions control the P-losses and speed towards steady-state. The model also helps describe how, with limited uplift and atmospheric input, as in the case of the Amazon Basin, ecosystems must rely on mechanisms that enhance P-availability and retention. Our novel model has a limited number of parameters and can be easily integrated into global climate models to provide a representation of the response of the terrestrial biosphere to global change.

  17. Climate impacts of bioenergy: Inclusion of carbon cycle and albedo dynamics in life cycle impact assessment

    International Nuclear Information System (INIS)

    Bright, Ryan M.; Cherubini, Francesco; Strømman, Anders H.

    2012-01-01

    Life cycle assessment (LCA) can be an invaluable tool for the structured environmental impact assessment of bioenergy product systems. However, the methodology's static temporal and spatial scope combined with its restriction to emission-based metrics in life cycle impact assessment (LCIA) inhibits its effectiveness at assessing climate change impacts that stem from dynamic land surface–atmosphere interactions inherent to all biomass-based product systems. In this paper, we focus on two dynamic issues related to anthropogenic land use that can significantly influence the climate impacts of bioenergy systems: i) temporary changes to the terrestrial carbon cycle; and ii) temporary changes in land surface albedo—and illustrate how they can be integrated within the LCA framework. In the context of active land use management for bioenergy, we discuss these dynamics and their relevancy and outline the methodological steps that would be required to derive case-specific biogenic CO 2 and albedo change characterization factors for inclusion in LCIA. We demonstrate our concepts and metrics with application to a case study of transportation biofuel sourced from managed boreal forest biomass in northern Europe. We derive GWP indices for three land management cases of varying site productivities to illustrate the importance and need to consider case- or region-specific characterization factors for bioenergy product systems. Uncertainties and limitations of the proposed metrics are discussed. - Highlights: ► A method for including temporary surface albedo and carbon cycle changes in Life Cycle Impact Assessment (LCIA) is elaborated. ► Concepts are applied to a single bioenergy case whereby a range of feedstock productivities are shown to influence results. ► Results imply that case- and site-specific characterization factors can be essential for a more informed impact assessment. ► Uncertainties and limitations of the proposed methodologies are elaborated.

  18. How positive is the feedback between climate change and the carbon cycle?

    International Nuclear Information System (INIS)

    Friedlingstein, P.; Rayner, P.

    2003-01-01

    Future climate change induced by atmospheric emissions of greenhouse gases is believed to have a large impact on the global carbon cycle. Several offline studies focusing either on the marine or on the terrestrial carbon cycle highlighted such potential effects. Two recent online studies, using ocean-atmosphere general circulation models coupled to land and ocean carbon cycle models, investigated in a consistent way the feedback between the climate change and the carbon cycle. These two studies used observed anthropogenic CO 2 emissions for the 1860-1995 period and IPCC scenarios for the 1995-2100 period to force the climate - carbon cycle models. The study from the Hadley Centre group showed a very large positive feedback, atmospheric CO 2 reaching 980 ppmv by 2100 if future climate impacts on the carbon cycle, but only about 700 ppmv if the carbon cycle is included but assumed to be insensitive to the climate change. The IPSL coupled climate - carbon cycle model simulated a much smaller positive feedback: climate impact on the carbon cycle leads by 2100 to an addition of less than 100 ppmv in the atmosphere. Here we perform a detailed feedback analysis to show that such differences are due to two key processes that are still poorly constrained in these coupled models: first Southern Ocean circulation, which primarily controls the geochemical uptake of CO 2 , and second vegetation and soil carbon response to global warming. Our analytical analysis reproduces remarkably the results obtained by the fully coupled models. Also it allows us to identify that, amongst the two processes mentioned above, the latter (the land response to global warming) is the one that essentially explains the differences between the IPSL and the Hadley results

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

    Science.gov (United States)

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

    2010-01-01

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

  20. Impact of atmospheric and terrestrial CO2 feedbacks on fertilization-induced marine carbon uptake

    Science.gov (United States)

    Oschlies, A.

    2009-08-01

    The sensitivity of oceanic CO2 uptake to alterations in the marine biological carbon pump, such as brought about by natural or purposeful ocean fertilization, has repeatedly been investigated by studies employing numerical biogeochemical ocean models. It is shown here that the results of such ocean-centered studies are very sensitive to the assumption made about the response of the carbon reservoirs on the atmospheric side of the sea surface. Assumptions made include prescribed atmospheric pCO2, an interactive atmospheric CO2 pool exchanging carbon with the ocean but not with the terrestrial biosphere, and an interactive atmosphere that exchanges carbon with both oceanic and terrestrial carbon pools. The impact of these assumptions on simulated annual to millennial oceanic carbon uptake is investigated for a hypothetical increase in the C:N ratio of the biological pump and for an idealized enhancement of phytoplankton growth. Compared to simulations with interactive atmosphere, using prescribed atmospheric pCO2 overestimates the sensitivity of the oceanic CO2 uptake to changes in the biological pump, by about 2%, 25%, 100%, and >500% on annual, decadal, centennial, and millennial timescales, respectively. The smaller efficiency of the oceanic carbon uptake under an interactive atmosphere is due to the back flux of CO2 that occurs when atmospheric CO2 is reduced. Adding an interactive terrestrial carbon pool to the atmosphere-ocean model system has a small effect on annual timescales, but increases the simulated fertilization-induced oceanic carbon uptake by about 4%, 50%, and 100% on decadal, centennial, and millennial timescales, respectively, for pCO2 sensitivities of the terrestrial carbon storage in the middle range of the C4MIP models (Friedlingstein et al., 2006). For such sensitivities, a substantial fraction of oceanic carbon uptake induced by natural or purposeful ocean fertilization originates, on timescales longer than decades, not from the atmosphere

  1. Development of new historical global Nitrogen fertilizer map and the evaluation of their impacts on terrestrial N cycling and the evaluation of their impacts on terrestrial N cycling

    Science.gov (United States)

    Nishina, K.; Ito, A.; Hayashi, S.

    2015-12-01

    The use of synthetic nitrogen fertilizer was rapidly growing up after the birth of Haber-Bosch process in the early 20th century. The recent N loading derived from these sources on terrestrial ecosystems was estimated 2 times higher than biogenic N fixation in terrestrial ecosystems (Gruber et al., 2009). However, there are still large uncertainties in cumulative N impacts on terrestrial impact at global scale. In this study, to assess historical N impacts at global scale, we made a new global N fertilizer input map, which was a spatial-temporal explicit map (during 1960-2010) and considered the fraction of NH4+ and NO3- in the N fertilizer inputs. With the developed N fertilizer map, we evaluated historical N20 cycling changes by land-use changes and N depositions in N cycling using ecosystem model 'VISIT'. Prior to the downscaling processes for global N fertilizer map, we applied the statistical data imputation to FAOSTAT data due to there existing many missing data especially in developing countries. For the data imputation, we used multiple data imputation method proposed by Honaker & King (2010). The statistics of various types of synthetic fertilizer consumption are available in FAOSTAT, which can be sorted by the content of NH4+ and NO3-, respectively. To downscaling the country by country N fertilizer consumptions data to the 0.5˚x 0.5˚ grid-based map, we used historical land-use map in Earthstat (Rumankutty et al., 1999). Before the assignment of N fertilizer in each grid, we weighted the double cropping regions to be more N fertilizer input on to these regions. Using M3-Crops Data (Monfreda et al., 2008), we picked up the dominant cropping species in each grid cell. After that, we used Crop Calendar in SAGE dataset (Sacks et al., 2010) and determined schedule of N fertilizer input in each grid cell using dominant crop calendar. Base fertilizer was set to be 7 days before transplanting and second fertilizer to be 30 days after base fertilizer application

  2. Carbon footprint estimation of municipal water cycle

    Science.gov (United States)

    Bakhshi, Ali A.

    2009-11-01

    This research investigates the embodied energy associated with water use. A geographic information system (GIS) was tested using data from Loudoun County, Virginia. The objective of this study is to estimate the embodied energy and carbon emission levels associated with water service at a geographical location and to improve for sustainability planning. Factors that affect the carbon footprint were investigated and the use of a GIS based model as a sustainability planning framework was evaluated. The carbon footprint metric is a useful tool for prediction and measurement of a system's sustainable performance over its expected life cycle. Two metrics were calculated: tons of carbon dioxide per year to represent the contribution to global warming and watt-hrs per gallon to show the embodied energy associated with water consumption. The water delivery to the building, removal of wastewater from the building and associated treatment of water and wastewater create a sizable carbon footprint; often the energy attributed to this water service is the greatest end use of electrical energy. The embodied energy in water depends on topographical characteristics of the area's local water supply, the efficiency of the treatment systems, and the efficiency of the pumping stations. The questions answered by this research are: What is the impact of demand side sustainable water practices on the embodied energy as represented by a comprehensive carbon footprint? What are the major energy consuming elements attributed to the system? What is a viable and visually identifiable tool to estimate the carbon footprint attributed to those Greenhouse Gas (GHG) producing elements? What is the embodied energy and emission associated with water use delivered to a building? Benefits to be derived from a standardized GIS applied carbon footprint estimation approach include: (1) Improved environmental and economic information for the developers, water and wastewater processing and municipal

  3. Sources and characteristics of terrestrial carbon in Holocene-scale sediments of the East Siberian Sea

    Science.gov (United States)

    Keskitalo, Kirsi; Tesi, Tommaso; Bröder, Lisa; Andersson, August; Pearce, Christof; Sköld, Martin; Semiletov, Igor P.; Dudarev, Oleg V.; Gustafsson, Örjan

    2017-09-01

    Thawing of permafrost carbon (PF-C) due to climate warming can remobilise considerable amounts of terrestrial carbon from its long-term storage to the marine environment. PF-C can be then be buried in sediments or remineralised to CO2 with implications for the carbon-climate feedback. Studying historical sediment records during past natural climate changes can help us to understand the response of permafrost to current climate warming. In this study, two sediment cores collected from the East Siberian Sea were used to study terrestrial organic carbon sources, composition and degradation during the past ˜ 9500 cal yrs BP. CuO-derived lignin and cutin products (i.e., compounds solely biosynthesised in terrestrial plants) combined with δ13C suggest that there was a higher input of terrestrial organic carbon to the East Siberian Sea between ˜ 9500 and 8200 cal yrs BP than in all later periods. This high input was likely caused by marine transgression and permafrost destabilisation in the early Holocene climatic optimum. Based on source apportionment modelling using dual-carbon isotope (Δ14C, δ13C) data, coastal erosion releasing old Pleistocene permafrost carbon was identified as a significant source of organic matter translocated to the East Siberian Sea during the Holocene.

  4. Solar cycle variations in mesospheric carbon monoxide

    Science.gov (United States)

    Lee, Jae N.; Wu, Dong L.; Ruzmaikin, Alexander; Fontenla, Juan

    2018-05-01

    As an extension of Lee et al. (2013), solar cycle variation of carbon monoxide (CO) is analyzed with MLS observation, which covers more than thirteen years (2004-2017) including maximum of solar cycle 24. Being produced primarily by the carbon dioxide (CO2) photolysis in the lower thermosphere, the variations of the mesospheric CO concentration are largely driven by the solar cycle modulated ultraviolet (UV) variation. This solar signal extends down to the lower altitudes by the dynamical descent in the winter polar vortex, showing a time lag that is consistent with the average descent velocity. To characterize a global distribution of the solar impact, MLS CO is correlated with the SORCE measured total solar irradiance (TSI) and UV. As high as 0.8 in most of the polar mesosphere, the linear correlation coefficients between CO and UV/TSI are more robust than those found in the previous work. The photochemical contribution explains most (68%) of the total variance of CO while the dynamical contribution accounts for 21% of the total variance at upper mesosphere. The photochemistry driven CO anomaly signal is extended in the tropics by vertical mixing. The solar cycle signal in CO is further examined with the Whole Atmosphere Community Climate Model (WACCM) 3.5 simulation by implementing two different modeled Spectral Solar Irradiances (SSIs): SRPM 2012 and NRLSSI. The model simulations underestimate the mean CO amount and solar cycle variations of CO, by a factor of 3, compared to those obtained from MLS observation. Different inputs of the solar spectrum have small impacts on CO variation.

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

    Science.gov (United States)

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

    2012-01-01

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

  6. Solar cycle distribution of strong solar proton events and the related solar-terrestrial phenomena

    Science.gov (United States)

    Le, Guiming; Yang, Xingxing; Ding, Liuguang; Liu, Yonghua; Lu, Yangping; Chen, Minhao

    2014-08-01

    We investigated the solar cycle distribution of strong solar proton events (SPEs, peak flux ≥1000 pfu) and the solar-terrestrial phenomena associated with the strong SPEs during solar cycles 21-23. The results show that 37 strong SPEs were registered over this period of time, where 20 strong SPEs were originated from the super active regions (SARs) and 28 strong SPEs were accompanied by the X-class flares. Most strong SPEs were not associated with the ground level enhancement (GLE) event. Most strong SPEs occurred in the descending phases of the solar cycles. The weaker the solar cycle, the higher the proportion of strong SPES occurred in the descending phase of the cycle. The number of the strong SPEs that occurred within a solar cycle is poorly associated with the solar cycle size. The intensity of the SPEs is highly dependent of the location of their source regions, with the super SPEs (≥20000 pfu) distributed around solar disk center. A super SPE was always accompanied by a fast shock driven by the associated coronal mass ejection and a great geomagnetic storm. The source location of strongest GLE event is distributed in the well-connected region. The SPEs associated with super GLE events (peak increase rate ≥100%) which have their peak flux much lower than 10000 pfu were not accompanied by an intense geomagnetic storm.

  7. Carbonate-silicate cycle models of the long-term carbon cycle, carbonate accumulation in the oceans, and climate

    International Nuclear Information System (INIS)

    Caldeira, K.G.

    1991-01-01

    Several models of the long-term carbon cycle, incorporating models of the carbonate-silicate cycle, were developed and utilized to investigate issues relating to global climate and the causes and consequences of changes in calcium carbonate accumulation in the oceans. Model results indicate that the marked mid-Cretaceous (120 Ma) global warming could be explained by increased rates of release of carbon dioxide from subduction-zone metamorphism and mid-ocean-ridges, in conjunction with paleogeographic factors. Since the mid-Cretaceous, the primary setting for calcium carbonate accumulation in the oceans has shifted from shallow-water to deep-water environments. Model results suggest that this shift could have major consequences for the carbonate-silicate cycle and climate, and lead to significant increases in the flux of metamorphic carbon dioxide to the atmosphere. Increases in pelagic carbonate productivity, and decreases in tropical shallow-water area available for neritic carbonate accumulation, have both been proposed as the primary cause of this shift. Two lines of evidence developed here (one involving a statistical analysis of Tertiary carbonate-accumulation and oxygen-isotope data, and another based on modeling the carbonate-silicate cycle and ocean chemistry) suggest that a decrease in tropical shallow-water area was more important than increased pelagic productivity in explaining this shift. Model investigations of changes in ocean chemistry at the Cretaceous/Tertiary (K/T) boundary (66 Ma) indicate that variations in deep-water carbonate productivity may affect shallow-water carbonate accumulation rates through a mechanism involving surface-water carbonate-ion concentration. In the aftermath of the K/T boundary event, deep-water carbonate production and accumulation were significantly reduced as a result of the extinction of calcareous plankton

  8. Is litter decomposition 'primed' by primary producer-release of labile carbon in terrestrial and aquatic experimental systems?

    Science.gov (United States)

    Soares, A. Margarida P. M.; Kritzberg, Emma S.; Rousk, Johannes

    2015-04-01

    It is possible that recalcitrant organic matter (ROM) can be 'activated' by inputs of labile organic matter (LOM) through the priming effect (PE). Investigating the PE is of major importance to fully understand the microbial use of ROM and its role on carbon (C) and nutrient cycling in both aquatic and terrestrial ecosystems. In aquatic ecosystems it is thought that the PE is triggered by periphytic algae release of LOM. Analogously, in terrestrial systems it is hypothesized that the LOM released in plant rhizospheres, or from the green crusts on the surface of agricultural soils, stimulate the activity and growth of ROM decomposers. Most previous studies on PE have utilised pulse additions of single substrates at high concentrations. However, to achieve an assessment of the true importance of the PE, it is important to simulate a realistic delivery of LOM. We investigated, in a series of 2-week laboratory experiments, how primary producer (PP)-release of LOM influence litter degradation in terrestrial and aquatic experimental systems. We used soil (terrestrial) and pond water (aquatic) microbial communities to which litter was added under light and dark conditions. In addition, glucose was added at PP delivery rates in dark treatments to test if the putative PE in light systems could be reproduced. We observed an initial peak of bacterial growth rate followed by an overall decrease over time with no treatment differences. In light treatments, periphytic algae growth and increased fungal production was stimulated when bacterial growth declined. In contrast, both fungal growth and algal production were negligible in dark treatments. This reveals a direct positive influence of photosynthesis on fungal growth. To investigate if PP LOM supplements, and the associated fungal growth, translate into a modulated litter decomposition, we are using stable isotopes to track the use of litter and algal-derived carbon by determining the δ13C in produced CO2. Fungi and bacteria

  9. Use of Landsat-based monitoring of forest change to sample and assess the role of disturbance and regrowth in the carbon cycle at continental scales

    Science.gov (United States)

    Warren B. Cohen; Sean P. Healey; Samuel Goward; Gretchen G. Moisen; Jeffrey G. Masek; Robert E. Kennedy; Scott L. Powell; Chengquan Huang; Nancy Thomas; Karen Schleeweis; Michael A. Wulder

    2007-01-01

    The exchange of carbon between forests and the atmosphere is a function of forest type, climate, and disturbance history, with previous studies illustrating that forests play a key role in the terrestrial carbon cycle. The North American Carbon Program (NACP) has supported the acquisition of biennial Landsat image time-series for sample locations throughout much of...

  10. Nitrogen inputs accelerate phosphorus cycling rates across a wide variety of terrestrial ecosystems.

    Science.gov (United States)

    Marklein, Alison R; Houlton, Benjamin Z

    2012-02-01

    • Biologically essential elements--especially nitrogen (N) and phosphorus (P)--constrain plant growth and microbial functioning; however, human activities are drastically altering the magnitude and pattern of such nutrient limitations on land. Here we examine interactions between N and P cycles of P mineralizing enzyme activities (phosphatase enzymes) across a wide variety of terrestrial biomes. • We synthesized results from 34 separate studies and used meta-analysis to evaluate phosphatase activity with N, P, or N×P fertilization. • Our results show that N fertilization enhances phosphatase activity, from the tropics to the extra-tropics, both on plant roots and in bulk soils. By contrast, P fertilization strongly suppresses rates of phosphatase activity. • These results imply that phosphatase enzymes are strongly responsive to changes in local nutrient cycle conditions. We also show that plant phosphatases respond more strongly to fertilization than soil phosphatases. The tight coupling between N and P provides a mechanism for recent observations of N and P co-limitation on land. Moreover, our results suggest that terrestrial plants and microbes can allocate excess N to phosphatase enzymes, thus delaying the onset of single P limitation to plant productivity as can occur via human modifications to the global N cycle. © 2011 The Authors. New Phytologist © 2011 New Phytologist Trust.

  11. Coupling between the continental carbon and water cycles

    Science.gov (United States)

    Gentine, P.; Lemordant, L. A.; Green, J. K.

    2017-12-01

    The continental carbon adn water cycles are fundamentally coupled through leaf gas exchange at the stomata level. IN this presnetation we will emphasize the importance of this coupling for the future of the water cycle (runoff, evaporation, soil moisture) and in turn the implications for the carbon cycle and the capacity of continents to act as a carbon dioxyde sink in the future. Opprtunites from coupled carbon-water monitoring platforms will be then emphasized.

  12. How does global biogeochemical cycle become complicated by terrestrial-aquatic interactions ?

    Science.gov (United States)

    Nakayama, Tadanobu; Maksyutov, Shamil

    2015-04-01

    Inland water such as river and lake are now known to be important and active components of global carbon cycle though its contribution has remained uncertain due to data scarcity (Battin et al., 2009; Aufdenkampe et al., 2011). The author has developed process-based National Integrated Catchment-based Eco-hydrology (NICE) model (Nakayama, 2008a-b, 2010, 2011a-b, 2012a-c, 2013; Nakayama and Fujita, 2010; Nakayama and Hashimoto, 2011; Nakayama and Shankman, 2013a-b; Nakayama and Watanabe, 2004, 2006, 2008a-b; Nakayama et al., 2006, 2007, 2010, 2012), which incorporates surface-groundwater interactions, includes up- and down-scaling processes between local-global scales, and can simulate iteratively nonlinear feedback between hydrologic, geomorphic, and ecological processes. In this study, NICE was coupled with various biogeochemical models to incorporate biogeochemical cycle including reaction between inorganic and organic carbons (DOC, POC, DIC, pCO2, etc.) in terrestrial and aquatic ecosystems including surface water and groundwater. The coupled model simulated CO2 evasion from inland water in global scale, was relatively in good agreement in that estimated by empirical regression model (Raymond et al., 2013). In particular, the simulated result implied importance of connectivity between terrestrial and aquatic ecosystems in addition to surface and groundwater, and hillslopes and stream channels, etc. The model further improved the accuracy of CH4 flux in wetland which is sensitive to fluctuations of shallow groundwater because the original NICE incorporates 3-D groundwater sub-model and simulates lateral subsurface flow more reasonably. This simulation system would play important role in integration of greenhouse gas budget of the biosphere, quantification of hot spots in boundless biogeochemical cycle, and bridging gap between top-down and bottom-up approaches (Cole et al., 2007; Frei et al., 2012; Kiel and Cardenas, 2014). References; Aufdenkampe, A.K., et al

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

    Science.gov (United States)

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

    2017-12-01

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

  14. Carbon Cycle Extremes in the 22nd and 23rd Century and Attribution to Climate Drivers

    Science.gov (United States)

    Sharma, B.; Hoffman, F. M.; Kumar, J.; Ganguly, A. R.

    2017-12-01

    Terrestrial ecosystems are affected by climate extremes such as droughts and heatwaves which have a potential to modify carbon budgets. Previous studies have found the impact of negative extremes in gross primary production (GPP) and net ecosystem production (NEP) to be diminishing towards the end of the 21st century relative to the overall increase in global carbon uptake. A few studies have estimated that the land use changes (e.g. from forest to croplands) would cause more cumulative carbon loss between 1850 and 2300 than due to climate change caused by anthropogenic forcing over the same interval. However, not many studies have looked at the impact of carbon cycle extremes beyond 21st century especially under with and without LULCC scenarios. This study aims to analyze spatiotemporal extreme events in GPP and NEP using the model CESM1-BGC and understand the climate drivers they can be attributed to. Using the Community Earth System Model (CESM1-BGC), we investigated the impact of climate extremes on the terrestrial ecosystem using simulations forced by Representative Concentration Pathway 8.5 with and without land-use and land-cover change (LULCC). To capture non-linear feedbacks in the global carbon cycle, both these simulations were extended to the year 2300. It is important to understand the impacts of climate extremes on the carbon cycle for quantifying carbon-cycle climate feedback and estimating future atmospheric CO2 levels and temperature increases. The results of this study would help improve our understanding of carbon cycle extremes and inform future mitigation policy.

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

    International Nuclear Information System (INIS)

    Nikolov, Ned; Zeller, Karl F.

    2003-01-01

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

  16. Global patterns and substrate-based mechanisms of the terrestrial nitrogen cycle

    DEFF Research Database (Denmark)

    Niu, Shuli; Classen, Aimee Taylor; Dukes, Jeffrey S.

    2016-01-01

    availability but increase exponentially and become the dominant fate of N at high loading rates. The original N saturation hypothesis emphasises sequential N saturation from plant uptake to soil retention before N losses occur. However, biogeochemical models that simulate simultaneous competition for soil N...... substrates by multiple processes match the observed patterns of N losses better than models based on sequential competition. To enable better prediction of terrestrial N cycle responses to N loading, we recommend that future research identifies the response functions of different N processes to substrate...

  17. The origin of methane and biomolecules from a CO2 cycle on terrestrial planets

    Czech Academy of Sciences Publication Activity Database

    Civiš, Svatopluk; Knížek, Antonín; Ivanek, Ondřej; Kubelík, Petr; Zukalová, Markéta; Kavan, Ladislav; Ferus, Martin

    2017-01-01

    Roč. 1, č. 10 (2017), s. 721-726 E-ISSN 2397-3366 R&D Projects: GA ČR GA17-05076S; GA ČR GA13-07724S Grant - others:Akademie věd - GA AV ČR(CZ) R200401721; Akademie věd - GA AV ČR(CZ) R200401521 Institutional support: RVO:61388955 Keywords : biomolecules * CO2 cycle on terrestrial planets * Mars Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry

  18. Sources and Reactivity of Terrestrial Organic Carbon to the Colville River Delta, Beaufort Sea, Alaska

    Science.gov (United States)

    Schreiner, K. M.; Bianchi, T. S.; Rosenheim, B. E.

    2014-12-01

    Terrestrial particulate organic carbon (tPOC) delivery to nearshore deltaic regions is an important mechanism of OC storage and burial, and continental margins worldwide account for approximately 90% of the carbon burial in the ocean. Increasing warming in the Arctic is leading to an acceleration of the hydrologic cycle, warming of permafrost, and broad shifts in vegetation. All of these changes are likely to affect the delivery, reactivity, and burial of tPOC in nearshore Arctic regions, making the Arctic an ideal place to study the effects of climate change on tPOC delivery. However, to date, most studies of tPOC delivery from North America to the Arctic Ocean have focused on large Arctic rivers like the Mackenzie and Yukon, and a significant portion of those watersheds lie in sub-Arctic latitudes, meaning that their tPOC delivery is likely not uniquely representative of the high Arctic tundra. Here, we focus on tPOC delivery by the Colville River, the largest North American river with a watershed that does not include sub-Arctic latitudes. Sediment samples from the river delta and nearby Simpson's Lagoon were taken in August of 2010 and subsequently fractionated by density, in order to study the delivery of both discrete and sediment-sorbed tPOC. Samples were analyzed for stable carbon isotopes, bulk radiocarbon, terrestrial biomarkers (including lignin-phenols, and other CuO reaction products), and aquatic biomarkers (algal pigments), and additionally a subset of the samples were analyzed by ramped pyrolysis-14C. Results show that tPOC delivery near the river mouth is sourced from coastal plain tundra, with additional delivery of tPOC from peat released into the lagoon from the seaward limit of the tundra by coastal erosion. Ramped pyrolysis-14C analysis also shows a clear differentiation between tPOC delivered by the river and tPOC delivered by coastal retreat in the lagoon. Additionally, a significant portion of the OC released by the Colville River is

  19. An isopycnic ocean carbon cycle model

    Directory of Open Access Journals (Sweden)

    K. M. Assmann

    2010-02-01

    Full Text Available The carbon cycle is a major forcing component in the global climate system. Modelling studies, aiming to explain recent and past climatic changes and to project future ones, increasingly include the interaction between the physical and biogeochemical systems. Their ocean components are generally z-coordinate models that are conceptually easy to use but that employ a vertical coordinate that is alien to the real ocean structure. Here, we present first results from a newly-developed isopycnic carbon cycle model and demonstrate the viability of using an isopycnic physical component for this purpose. As expected, the model represents well the interior ocean transport of biogeochemical tracers and produces realistic tracer distributions. Difficulties in employing a purely isopycnic coordinate lie mainly in the treatment of the surface boundary layer which is often represented by a bulk mixed layer. The most significant adjustments of the ocean biogeochemistry model HAMOCC, for use with an isopycnic coordinate, were in the representation of upper ocean biological production. We present a series of sensitivity studies exploring the effect of changes in biogeochemical and physical processes on export production and nutrient distribution. Apart from giving us pointers for further model development, they highlight the importance of preformed nutrient distributions in the Southern Ocean for global nutrient distributions. The sensitivity studies show that iron limitation for biological particle production, the treatment of light penetration for biological production, and the role of diapycnal mixing result in significant changes of nutrient distributions and liniting factors of biological production.

  20. State of the Carbon Cycle - Consequences of Rising Atmospheric CO2

    Science.gov (United States)

    Moore, D. J.; Cooley, S. R.; Alin, S. R.; Brown, M. E.; Butman, D. E.; French, N. H. F.; Johnson, Z. I.; Keppel-Aleks, G.; Lohrenz, S. E.; Ocko, I.; Shadwick, E. H.; Sutton, A. J.; Potter, C. S.; Yu, R. M. S.

    2016-12-01

    The rise of atmospheric CO2, largely attributable to human activity through fossil fuel emissions and land-use change, has been dampened by carbon uptake by the ocean and terrestrial biosphere. We outline the consequences of this carbon uptake as direct and indirect effects on terrestrial and oceanic systems and processes for different regions of North America and the globe. We assess the capacity of these systems to continue to act as carbon sinks. Rising CO2 has decreased seawater pH; this process of ocean acidification has impacted some marine species and altered fundamental ecosystem processes with further effects likely. In terrestrial ecosystems, increased atmospheric CO2 causes enhanced photosynthesis, net primary production, and increased water-use efficiency. Rising CO2 may change vegetation composition and carbon storage, and widespread increases in water use efficiency likely influence terrestrial hydrology and biogeochemical cycling. Consequences for human populations include changes to ecosystem services including cultural activities surrounding land use, agricultural or harvesting practices. Commercial fish stocks have been impacted and crop production yields have been changed as a result of rising CO2. Ocean and terrestrial effects are contingent on, and feedback to, global climate change. Warming and modified precipitation regimes impact a variety of ecosystem processes, and the combination of climate change and rising CO2 contributes considerable uncertainty to forecasting carbon sink capacity in the ocean and on land. Disturbance regime (fire and insects) are modified with increased temperatures. Fire frequency and intensity increase, and insect lifecycles are disrupted as temperatures move out of historical norms. Changes in disturbance patterns modulate the effects of rising CO2 depending on ecosystem type, disturbance frequency, and magnitude of events. We discuss management strategies designed to limit the rise of atmospheric CO2 and reduce

  1. State of the Carbon Cycle - Consequences of Rising Atmospheric CO2

    Science.gov (United States)

    Moore, David J.; Cooley, Sarah R.; Alin, Simone R.; Brown, Molly; Butman, David E.; French, Nancy H. F.; Johnson, Zackary I.; Keppel-Aleks; Lohrenz, Steven E.; Ocko, Ilissa; hide

    2016-01-01

    The rise of atmospheric CO2, largely attributable to human activity through fossil fuel emissions and land-use change, has been dampened by carbon uptake by the ocean and terrestrial biosphere. We outline the consequences of this carbon uptake as direct and indirect effects on terrestrial and oceanic systems and processes for different regions of North America and the globe. We assess the capacity of these systems to continue to act as carbon sinks. Rising CO2 has decreased seawater pH; this process of ocean acidification has impacted some marine species and altered fundamental ecosystem processes with further effects likely. In terrestrial ecosystems, increased atmospheric CO2 causes enhanced photosynthesis, net primary production, and increased water-use efficiency. Rising CO2 may change vegetation composition and carbon storage, and widespread increases in water use efficiency likely influence terrestrial hydrology and biogeochemical cycling. Consequences for human populations include changes to ecosystem services including cultural activities surrounding land use, agricultural or harvesting practices. Commercial fish stocks have been impacted and crop production yields have been changed as a result of rising CO2. Ocean and terrestrial effects are contingent on, and feedback to, global climate change. Warming and modified precipitation regimes impact a variety of ecosystem processes, and the combination of climate change and rising CO2 contributes considerable uncertainty to forecasting carbon sink capacity in the ocean and on land. Disturbance regime (fire and insects) are modified with increased temperatures. Fire frequency and intensity increase, and insect lifecycles are disrupted as temperatures move out of historical norms. Changes in disturbance patterns modulate the effects of rising CO2 depending on ecosystem type, disturbance frequency, and magnitude of events. We discuss management strategies designed to limit the rise of atmospheric CO2 and reduce

  2. How interactions between top-down and bottom-up controls on carbon cycling affect fluxes within and from lakes

    Science.gov (United States)

    Sadro, S.; Piovia-Scott, J.; Nelson, C.; Sickman, J. O.; Knapp, R.

    2017-12-01

    While the role of inland waters in global carbon cycling has grown clearer in recent decades, the extent to which top-down and bottom-up mechanisms interact to regulate dynamics at the catchment scale is not well understood. The degree to which lakes process, export, or store terrestrial carbon is influenced by hydrological variability, variation in the magnitude of terrestrial organic matter (t-OM) entering a system, the efficiency with which such material is metabolized by bacterioplankton, the extent to which it is incorporated into secondary consumer biomass, and by the effects of food-web structure, such as the presence or absence of top predators. However, how these processes interact to mediate carbon fluxes between terrestrial, aquatic, and atmospheric reservoirs remains unclear. We develop a conceptual model that explores how interactions among these factors ultimately affects carbon dynamics using data from lakes located in the Sierra Nevada mountains of California. The Sierra are an excellent system for studies of carbon cycling because elevation-induced landscape gradients in soil development and vegetation cover provide large natural variation in terrestrial inputs to lakes, while variation in confounding factors such as lake morphometry or trophic state is comparatively small. Dissolved organic carbon concentrations increase 100 fold in lakes spanning the alpine to montane elevation gradient found in the Sierra, and fluorescence characteristics reflect an increasingly terrestrial signature with decreasing elevation. Bacterioplankton make up a large proportion of total ecosystem metabolism in these systems, and their metabolic efficiency is tightly coupled to the composition of dissolved organic matter. Stable isotope food web data (δ13C, Δ14C, and δ2H) and measurements of pCO2 from lakes indicate the magnitude of allochthony, rates if carbon cycling, and ecosystem heterotrophy all increase with the increasingly terrestrial signature of dissolved

  3. Towards a quantitative understanding of the late Neoproterozoic carbon cycle

    DEFF Research Database (Denmark)

    Bjerrum, Christian J.; Canfield, Donald Eugene

    2011-01-01

    Neoproterozoic Eon, the time when animals first evolved, experienced wild isotope fluctuations which do not conform to our normal understanding of the carbon cycle and carbon-oxygen coupling. We interpret these fluctuations with a new carbon cycle model and demonstrate that all of the main features...

  4. Climate and landscape influence on indicators of lake carbon cycling through spatial patterns in dissolved organic carbon.

    Science.gov (United States)

    Lapierre, Jean-Francois; Seekell, David A; Del Giorgio, Paul A

    2015-12-01

    Freshwater ecosystems are strongly influenced by both climate and the surrounding landscape, yet the specific pathways connecting climatic and landscape drivers to the functioning of lake ecosystems are poorly understood. Here, we hypothesize that the links that exist between spatial patterns in climate and landscape properties and the spatial variation in lake carbon (C) cycling at regional scales are at least partly mediated by the movement of terrestrial dissolved organic carbon (DOC) in the aquatic component of the landscape. We assembled a set of indicators of lake C cycling (bacterial respiration and production, chlorophyll a, production to respiration ratio, and partial pressure of CO2 ), DOC concentration and composition, and landscape and climate characteristics for 239 temperate and boreal lakes spanning large environmental and geographic gradients across seven regions. There were various degrees of spatial structure in climate and landscape features that were coherent with the regionally structured patterns observed in lake DOC and indicators of C cycling. These different regions aligned well, albeit nonlinearly along a mean annual temperature gradient; whereas there was a considerable statistical effect of climate and landscape properties on lake C cycling, the direct effect was small and the overall effect was almost entirely overlapping with that of DOC concentration and composition. Our results suggest that key climatic and landscape signals are conveyed to lakes in part via the movement of terrestrial DOC to lakes and that DOC acts both as a driver of lake C cycling and as a proxy for other external signals. © 2015 John Wiley & Sons Ltd.

  5. Nested atmospheric inversion for the terrestrial carbon sources and sinks in China

    Directory of Open Access Journals (Sweden)

    F. Jiang

    2013-08-01

    Full Text Available In this study, we establish a nested atmospheric inversion system with a focus on China using the Bayesian method. The global surface is separated into 43 regions based on the 22 TransCom large regions, with 13 small regions in China. Monthly CO2 concentrations from 130 GlobalView sites and 3 additional China sites are used in this system. The core component of this system is an atmospheric transport matrix, which is created using the TM5 model with a horizontal resolution of 3° × 2°. The net carbon fluxes over the 43 global land and ocean regions are inverted for the period from 2002 to 2008. The inverted global terrestrial carbon sinks mainly occur in boreal Asia, South and Southeast Asia, eastern America and southern South America. Most China areas appear to be carbon sinks, with strongest carbon sinks located in Northeast China. From 2002 to 2008, the global terrestrial carbon sink has an increasing trend, with the lowest carbon sink in 2002. The inter-annual variation (IAV of the land sinks shows remarkable correlation with the El Niño Southern Oscillation (ENSO. The terrestrial carbon sinks in China also show an increasing trend. However, the IAV in China is not the same as that of the globe. There is relatively stronger land sink in 2002, lowest sink in 2006, and strongest sink in 2007 in China. This IAV could be reasonably explained with the IAVs of temperature and precipitation in China. The mean global and China terrestrial carbon sinks over the period 2002–2008 are −3.20 ± 0.63 and −0.28 ± 0.18 PgC yr−1, respectively. Considering the carbon emissions in the form of reactive biogenic volatile organic compounds (BVOCs and from the import of wood and food, we further estimate that China's land sink is about −0.31 PgC yr−1.

  6. Bacterial carbon cycling in a subarctic fjord

    DEFF Research Database (Denmark)

    Middelboe, Mathias; Glud, Ronnie Nøhr; Sejr, M.K.

    2012-01-01

    of viruses on bacterial mortality (4–36% of cell production) and carbon cycling. Heterotrophic bacterial consumption was closely coupled with autochthonous BDOC production, and the majority of the primary production was consumed by pelagic bacteria at all seasons. The relatively low measured BGE emphasized......In this seasonal study, we examined the environmental controls and quantitative importance of bacterial carbon consumption in the water column and the sediment in the subarctic Kobbefjord, Greenland. Depth-integrated bacterial production in the photic zone varied from 5.0 ± 2.7 mg C m−2 d−1...... in February to 42 ± 28 mg C m−2 d−1 in May and 34 ± 7 mg C m−2 d−1 in September, corresponding to a bacterial production to primary production ratio of 0.34 ± 0.14, 0.07 ± 0.04, and 0.08 ± 0.06, respectively. Based on measured bacterial growth efficiencies (BGEs) of 0.09–0.10, pelagic bacterial carbon...

  7. Society and the Carbon Cycle: A Social Science Perspective

    Science.gov (United States)

    Romero-Lankao, P.

    2017-12-01

    Societal activities, actions, and practices affect the carbon cycle and the climate of North America in complex ways. Carbon is a key component for the functioning of croplands, grasslands, forests. Carbon fuels our industry, transportation (vehicles and roadways), buildings, and other structures. Drawing on results from the SOCCR-2, this presentation uses a social science perspective to address three scientific questions. How do human actions and activities affect the carbon cycle? How human systems such as cities, agricultural field and forests are affected by changes in the carbon cycle? How is carbon management enabled and constraint by socio-political dynamics?

  8. Three-Dimensional Water and Carbon Cycle Modeling at High Spatial-Temporal Resolutions

    Science.gov (United States)

    Liao, C.; Zhuang, Q.

    2017-12-01

    Terrestrial ecosystems in cryosphere are very sensitive to the global climate change due to the presence of snow covers, mountain glaciers and permafrost, especially when the increase in near surface air temperature is almost twice as large as the global average. However, few studies have investigated the water and carbon cycle dynamics using process-based hydrological and biogeochemistry modeling approach. In this study, we used three-dimensional modeling approach at high spatial-temporal resolutions to investigate the water and carbon cycle dynamics for the Tanana Flats Basin in interior Alaska with emphases on dissolved organic carbon (DOC) dynamics. The results have shown that: (1) lateral flow plays an important role in water and carbon cycle, especially in dissolved organic carbon (DOC) dynamics. (2) approximately 2.0 × 104 kg C yr-1 DOC is exported to the hydrological networks and it compromises 1% and 0.01% of total annual gross primary production (GPP) and total organic carbon stored in soil, respectively. This study has established an operational and flexible framework to investigate and predict the water and carbon cycle dynamics under the changing climate.

  9. Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico, St. Petersburg, FL, May 6-8, 2008

    Science.gov (United States)

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

    2009-01-01

    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. In May 2008, the Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico was held in St. Petersburg, FL, to address the information gaps of carbon fluxes associated with the Gulf of Mexico and to offer recommendations to guide future research. The meeting was attended by over 90 participants from over 50 U.S. and Mexican institutions and agencies. The Ocean Carbon and Biogeochemistry program (OCB; http://www.us-ocb.org/) sponsored this workshop with support from the National Science Foundation, the National Oceanic and Atmospheric Administration, the National Aeronautics and Space Administration, the U.S. Geological Survey, and the University of South Florida. The goal of

  10. The limits to global-warming mitigation by terrestrial carbon removal

    OpenAIRE

    Boysen, L.; Lucht, W.; Gerten, D.; Heck, V.; Lenton, T.; Schellnhuber, H.

    2017-01-01

    Massive near-term greenhouse gas emissions reduction is a precondition for staying "well below 2°C" global warming as envisaged by the Paris Agreement. Furthermore, extensive terrestrial carbon dioxide removal (tCDR) through managed biomass growth and subsequent carbon capture and storage is required to avoid temperature "overshoot" in most pertinent scenarios. Here, we address two major issues: First, we calculate the extent of tCDR required to "repair" delayed or insufficient emissions redu...

  11. Terrestrial gross carbon dioxide uptake : Global distribution and covariation with climate

    NARCIS (Netherlands)

    Beer, Christian; Reichstein, Markus; Tomelleri, Enrico; Ciais, Philippe; Jung, Martin; Carvalhais, Nuno; Rödenbeck, Christian; Arain, M. Altaf; Baldocchi, Dennis D.; Bonan, Gordon B.; Bondeau, Alberte; Cescatti, Alessandro; Lasslop, Gitta; Lindroth, Anders; Lomas, Mark; Luyssaert, Sebastiaan; Margolis, Hank; Oleson, Keith W.; Roupsard, Olivier; Veenendaal, Elmar; Viovy, Nicolas; Williams, Christopher M.; Woodward, F. Ian; Papale, Dario

    2010-01-01

    Terrestrial gross primary production (GPP) is the largest global CO 2 flux driving several ecosystem functions. We provide an observation-based estimate of this flux at 123 ± 8 petagrams of carbon per year (Pg C year-1) using eddy covariance flux data and various diagnostic models. Tropical forests

  12. Carbon Sequestration in Terrestrial Ecosystems: A Status Report on R and D Progress

    International Nuclear Information System (INIS)

    Jacobs, G.K.

    2001-01-01

    Sequestration of carbon in terrestrial ecosystems is a low-cost option that may be available in the near-term to mitigate increasing atmospheric CO(sub 2) concentrations, while providing additional benefits. Storing carbon in terrestrial ecosystems can be achieved through maintenance of standing aboveground biomass, utilization of aboveground biomass in long-lived products, or protection of carbon (organic and inorganic) compounds present in soils. There are potential co-benefits from efforts to sequester carbon in terrestrial ecosystems. For example, long-lived valuable products (wood) are produced, erosion would be reduced, soil productivity could be improved through increased capacity to retain water and nutrients, and marginal lands could be improved and riparian ecosystems restored. Another unique feature of the terrestrial sequestration option is that it is the only option that is ''reversible'' should it become desirable or permissible. For example, forests that are created are thus investments which could be harvested should CO(sub 2) emissions be reduced in other ways to acceptable levels 50-100 years from now

  13. European-wide simulations of present cropland phenology, productivity and carbon fluxes using an improved terrestrial biosphere model

    Science.gov (United States)

    Smith, P. C.; Ciais, P.; de Noblet, N.; Peylin, P.; Viovy, N.; Bondeau, A.

    2009-04-01

    Aiming at producing improved estimates of carbon source/sink spatial and interannual patterns across Europe (35% croplands), this work combines the terrestrial biosphere model ORCHIDEE (for vegetation productivity, water balance, soil carbon dynamics) and the generic crop model STICS (for phenology, irrigation, nitrogen balance, harvest). The ORCHIDEE-STICS model, relying on three plant functional types for the representation of temperate agriculture, is evaluated over the last few decades at various spatial and temporal resolutions. The simulated Leaf Area Index seasonal cycle is largely improved relative to the original ORCHIDEE simulating grasslands, and compares favourably with remote-sensing observations (the Figure of Merit in Time doubles over Europe). Crop yield is derived from annual Net Primary Productivity and compared with wheat and grain maize harvest data for five European countries. Discrepancies between 30-year mean simulated and reported yields remain large in Mediterranean countries. Interannual variability amplitude expressed relative to the mean is reduced towards the observed variability (~10%) when using ORCHIDEE-STICS. The simulated 2003 anomalous carbon source from European ecosystems to the atmosphere due to the 2003 summer heat wave is in good agreement with atmospheric inversions (~0.2 GtC, from May to October). The anomaly is twice as large in the ORCHIDEE alone simulation, owing to the unrealistically high exposure of herbaceous plants to the extreme summer conditions. Overall, this study highlights the importance of accounting for the specific phonologies of crops sown both in winter and in spring and for irrigation applied to summer crops in regional/global models of the terrestrial carbon cycle. Limitations suggest accounting for temporal and spatial variability in agricultural practices for further simulation improvement.

  14. Terrestrial Carbon Sequestration: Analysis of Terrestrial Carbon Sequestration at Three Contaminated Sites Remediated and Revitalized with Soil Amendments

    Science.gov (United States)

    This paper provides EPA's analysis of the data to determine carbon sequestration rates at three diverse sites that differ in geography/location, weather, soil properties, type of contamination, and age.

  15. Terrestrial cycling of 13CO2 by photosynthesis, respiration, and biomass burning in SiBCASA

    Science.gov (United States)

    van der Velde, I. R.; Miller, J. B.; Schaefer, K.; van der Werf, G. R.; Krol, M. C.; Peters, W.

    2014-12-01

    We present an enhanced version of the SiBCASA terrestrial biosphere model that is extended with (a) biomass burning emissions from the SiBCASA carbon pools using remotely sensed burned area from the Global Fire Emissions Database (GFED), (b) an isotopic discrimination scheme that calculates 13C signatures of photosynthesis and autotrophic respiration, and (c) a separate set of 13C pools to carry isotope ratios into heterotrophic respiration. We quantify in this study the terrestrial exchange of CO2 and 13CO2 as a function of environmental changes in humidity and biomass burning. The implementation of biomass burning yields similar fluxes as CASA-GFED both in magnitude and spatial patterns. The implementation of isotope exchange gives a global mean discrimination value of 15.2‰, ranges between 4 and 20‰ depending on the photosynthetic pathway in the plant, and compares favorably (annually and seasonally) with other published values. Similarly, the isotopic disequilibrium is similar to other studies that include a small effect of biomass burning as it shortens the turnover of carbon. In comparison to measurements, a newly modified starch/sugar storage pool propagates the isotopic discrimination anomalies to respiration much better. In addition, the amplitude of the drought response by SiBCASA is lower than suggested by the measured isotope ratios. We show that a slight increase in the stomatal closure for large vapor pressure deficit would amplify the respired isotope ratio variability. Our study highlights the importance of isotope ratio observations of 13C to assess and improve biochemical models like SiBCASA, especially with regard to the allocation and turnover of carbon and the responses to drought.

  16. Regional pattern and interannual variations in global terrestrial carbon uptake in response to changes in climate and atmospheric CO2

    International Nuclear Information System (INIS)

    Cao, Mingkui; Tao, B.; Li, Kerang; Prince, Stephen D.; Small, J.

    2005-01-01

    Atmospheric measurements indicate that the terrestrial carbon sink increased substantially from the 1980s to the 1990s, but which factors and regions were responsible for the increase are not well identified yet. Using process- and remote sensing-based ecosystem models, we show that changes in climate and atmospheric CO 2 in the period 1981-2000 enhanced net ecosystem production (NEP) and caused major geographical changes in the global distribution of NEP. In the 1980s the Americas accounted for almost all of the global NEP, but in the 1990s NEP in Eurasia and Africa became higher than that of the Americas. The year-to-year variation in global NEP was up to 2.5 Pg C (1 Pg = 10 15 g), in which 1.4 Pg C was attributable to the El Nino Southern Oscillation cycle (ENSO). NEP clearly decreased in El Nino and increased in La Nina in South America and Africa, but the response in North America and Eurasia was mixed. The estimated NEP increases accounted for only 30% of the global terrestrial carbon sink but can explain almost all of the increase from the 1980s to the 1990s. Because a large part of the increase in NEP was driven by the long-term trend of climate and atmospheric CO 2 , the increase in the global terrestrial carbon sink from the 1980s to the 1990s was a continuation of the trend since the middle of the twentieth century, rather than merely a consequence of short-time climate variability

  17. Carbonate biomineralization in terrestrial gastropods: environmental vs. physiological constraints

    Science.gov (United States)

    Mierzwa, D.; Stolarski, J.

    2009-04-01

    Preservational potential of shells of terrestrial gastropods allows to use them as valuable (paleo)climatic proxies. Despite of the fact, that the elements incorporated in their skeleton derive almost entirely from their diet, details of the ion uptake routes have not been studied in details. This work is a first step in the investigations of element uptake and biomineralization processes in pulmonate gastropod Cepaea vindobonensis (Férussac, 1821). Although phenotypic plasticity in the shell characters of the species appears to be mainly genetic in nature, some differences seem to correlate with availability of ions used in biomineralization. For example, shells of individuals living in marginal parts of flood plains (environment extreme for the species and generally depleted in calcium) have weakened structure and faded color pattern, whereas individuals from the lime substrata form typically developed, pigmented shells with several cross-lamellar layers. Micro- and nanostructural characteristics of shells from different environments are visualized by SEM and AFM imaging techniques and some biogeochemical properties are characterized by spectroscopic and fluorescence methods. Further experiments are required to elucidate the ion/trace elements transfer between the substratum, nutrients, organism, and the shell.

  18. Towards a quantitative understanding of the late Neoproterozoic carbon cycle

    DEFF Research Database (Denmark)

    Bjerrum, Christian Jannik; Canfield, Donald Eugene

    2011-01-01

    The cycles of carbon and oxygen at the Earth surface are intimately linked, where the burial of organic carbon into sediments represents a source of oxygen to the surface environment. This coupling is typically quantified through the isotope records of organic and inorganic carbon. Yet, the late...... Neoproterozoic Eon, the time when animals first evolved, experienced wild isotope fluctuations which do not conform to our normal understanding of the carbon cycle and carbon-oxygen coupling. We interpret these fluctuations with a new carbon cycle model and demonstrate that all of the main features...... of the carbonate and organic carbon isotope record can be explained by the release of methane hydrates from an anoxic dissolved organic carbon-rich ocean into an atmosphere containing oxygen levels considerably less than today....

  19. Aspects of studies on carbon cycle at ground surface

    International Nuclear Information System (INIS)

    Yamazawa, Hiromi; Kawai, Shintaro; Moriizumi, Jun; Iida, Takao

    2008-01-01

    Radiocarbon released from nuclear facilities into the atmosphere is readily involved in a ground surface carbon cycle, which has very large spatial and temporal variability. Most of the recent studies on the carbon cycle at the ground surface are concerned with global warming, to which the ground surface plays a crucial role as a sink and/or source of atmospheric carbon dioxide. In these studies, carbon isotopes are used as tracers to quantitatively evaluate behavior of carbon. From a view point of environmental safety of nuclear facilities, radiocarbon released from a facility should be traced in a specific spatial and temporal situation because carbon cycle is driven by biological activities which are spatially and temporally heterogeneous. With this background, this paper discusses aspects of carbon cycle studies by exemplifying an experimental study on carbon cycle in a forest and a numerical study on soil organic carbon formation. The first example is a typical global warming-related observational study in which radiocarbon is used as a tracer to illustrate how carbon behaves in diurnal to seasonal time scales. The second example is on behavior of bomb carbon incorporated in soil organic matter in a long-term period of decades. The discussion will cover conceptual modelling of carbon cycle from different aspects and importance of specifying time scales of interest. (author)

  20. Terrestrial Carbon[Environmental Pollution: Part I, Special Issue, March 2002, Part II, Special Issue Supplement to 116/3, 2002

    International Nuclear Information System (INIS)

    Mickler, Robert; McNulty, Steven

    2002-01-01

    These issues contain a total of forty-four peer reviewed science papers on terrestrial carbon presented at the Advances in Terrestrial Ecosystem Carbon Inventory, Measurements, and Monitoring Conference held in Raleigh, N.C., in October 2000

  1. Investigating the Early Carbon Cycle Using Carbonaceous Inclusions and Dissolved Carbon in Detrital Zircon

    Science.gov (United States)

    Bell, E. A.; Boehnke, P.; Harrison, M.; Mao, W. L.

    2015-12-01

    Because the terrestrial rock record extends only to ~4 Ga and older materials thus far identified are limited to detrital zircons, information about volatile abundances and cycles on early Earth is limited. Carbon, for instance, plays an important role not only in the modern biosphere but also in deep recycling of materials between the crust and mantle. We are investigating the record of carbon abundance and origin in Hadean zircons from Jack Hills (W. Australia) using two main approaches. First, carbon may partition into the zircon structure at trace levels during crystallization from a magma, and better understanding of this partitioning behavior will allow for zircon's use as a monitor of magmatic carbon contents. We have measured carbon abundances in zircon from a variety of igneous rocks (gabbro; I-, A-, and S-type granitoids) via SIMS and found that although abundances are typically low (average raw 12C/30Si ~ 1x10-6), S-type granite zircons can reach a factor of 1000 over this background. Around 10% of Hadean zircons investigated show similar enrichments, consistent with other evidence for the derivation of many Jack Hills zircons from S-type granitoids and with the establishment of modern-level carbon abundances in the crust by ca. 4.2 Ga. Diamond and graphite inclusions reported in the Jack Hills zircons by previous studies proved to be contamination by polishing debris, leaving the true abundance of these materials in the population uncertain. On a second front, we have identified and investigated primary carbonaceous inclusions in these zircons. From a population of over 10,000 Jack Hills zircons, we identified one concordant 4.10±0.01 Ga zircon that contains primary graphite inclusions (so interpreted due to their enclosure in a crack-free zircon host as shown by transmission X-ray microscopy and their crystal habit). Their δ13CPDB of -24±5‰ is consistent with a biogenic origin and, in the absence of a likely inorganic mechanism to produce such a

  2. The Global Influence of Cloud Optical Thickness on Terrestrial Carbon Uptake

    Science.gov (United States)

    Zhu, P.; Cheng, S. J.; Keppel-Aleks, G.; Butterfield, Z.; Steiner, A. L.

    2016-12-01

    Clouds play a critical role in regulating Earth's climate. One important way is by changing the type and intensity of solar radiation reaching the Earth's surface, which impacts plant photosynthesis. Specifically, the presence of clouds modifies photosynthesis rates by influencing the amount of diffuse radiation as well as the spectral distribution of solar radiation. Satellite-derived cloud optical thickness (COT) may provide the observational constraint necessary to assess the role of clouds on ecosystems and terrestrial carbon uptake across the globe. Previous studies using ground-based observations at individual sites suggest that below a COT of 7, there is a greater increase in light use efficiency than at higher COT values, providing evidence for higher carbon uptake rates than expected given the reduction in radiation by clouds. However, the strength of the COT-terrestrial carbon uptake correlation across the globe remains unknown. In this study, we investigate the influence of COT on terrestrial carbon uptake on a global scale, which may provide insights into cloud conditions favorable for plant photosynthesis and improve our estimates of the land carbon sink. Global satellite-derived MODIS data show that tropical and subtropical regions tend to have COT values around or below the threshold during growing seasons. We find weak correlations between COT and GPP with Fluxnet MTE global GPP data, which may be due to the uncertainty of upscaling GPP from individual site measurements. Analysis with solar-induced fluorescence (SIF) as a proxy for GPP is also evaluated. Overall, this work constructs a global picture of the role of COT on terrestrial carbon uptake, including its temporal and spatial variations.

  3. Global patterns and substrate-based mechanisms of the terrestrial nitrogen cycle.

    Science.gov (United States)

    Niu, Shuli; Classen, Aimée T; Dukes, Jeffrey S; Kardol, Paul; Liu, Lingli; Luo, Yiqi; Rustad, Lindsey; Sun, Jian; Tang, Jianwu; Templer, Pamela H; Thomas, R Quinn; Tian, Dashuan; Vicca, Sara; Wang, Ying-Ping; Xia, Jianyang; Zaehle, Sönke

    2016-06-01

    Nitrogen (N) deposition is impacting the services that ecosystems provide to humanity. However, the mechanisms determining impacts on the N cycle are not fully understood. To explore the mechanistic underpinnings of N impacts on N cycle processes, we reviewed and synthesised recent progress in ecosystem N research through empirical studies, conceptual analysis and model simulations. Experimental and observational studies have revealed that the stimulation of plant N uptake and soil retention generally diminishes as N loading increases, while dissolved and gaseous losses of N occur at low N availability but increase exponentially and become the dominant fate of N at high loading rates. The original N saturation hypothesis emphasises sequential N saturation from plant uptake to soil retention before N losses occur. However, biogeochemical models that simulate simultaneous competition for soil N substrates by multiple processes match the observed patterns of N losses better than models based on sequential competition. To enable better prediction of terrestrial N cycle responses to N loading, we recommend that future research identifies the response functions of different N processes to substrate availability using manipulative experiments, and incorporates the measured N saturation response functions into conceptual, theoretical and quantitative analyses. © 2016 John Wiley & Sons Ltd/CNRS.

  4. Belowground Carbon Cycling Processes at the Molecular Scale: An EMSL Science Theme Advisory Panel Workshop

    Energy Technology Data Exchange (ETDEWEB)

    Hess, Nancy J.; Brown, Gordon E.; Plata, Charity

    2014-02-21

    As part of the Belowground Carbon Cycling Processes at the Molecular Scale workshop, an EMSL Science Theme Advisory Panel meeting held in February 2013, attendees discussed critical biogeochemical processes that regulate carbon cycling in soil. The meeting attendees determined that as a national scientific user facility, EMSL can provide the tools and expertise needed to elucidate the molecular foundation that underlies mechanistic descriptions of biogeochemical processes that control carbon allocation and fluxes at the terrestrial/atmospheric interface in landscape and regional climate models. Consequently, the workshop's goal was to identify the science gaps that hinder either development of mechanistic description of critical processes or their accurate representation in climate models. In part, this report offers recommendations for future EMSL activities in this research area. The workshop was co-chaired by Dr. Nancy Hess (EMSL) and Dr. Gordon Brown (Stanford University).

  5. Recent Acceleration of the Terrestrial Hydrologic Cycle in the U.S. Midwest

    Science.gov (United States)

    Yeh, Pat J.-F.; Wu, Chuanhao

    2018-03-01

    Most hydroclimatic trend studies considered only a subset of water budget variables; hence, the trend consistency and a holistic assessment of hydrologic changes across the entire water cycle cannot be evaluated. Here we use a unique 31 year (1983-2013) observed data set in Illinois (a representative region of the U.S. Midwest), including temperature (T), precipitation (P), evaporation (E), streamflow (R), soil moisture, and groundwater level (GWL), to estimate the trends and their sensitivity to different data periods and lengths. Both the Mann-Kendall trend test and the least squares linear method identify trends in close agreement. Despite no clear trends during 1983-2013, increasing trends are found in P (8.73-9.05 mm/year), E (6.87-7.47 mm/year), and R (1.57-3.54 mm/year) during 1992-2013, concurrently with a pronounced warming trend of 0.029-0.037 °C/year. However, terrestrial water storageis decreased by -2.0 mm/year (mainly due to declining GWL), suggesting that the increased R is caused by increased surface runoff rather than baseflow. Monthly analyses identify warming trends for all months except winter. In summer, P (E) exhibits an increasing (decreasing) trend, leading to increasing R, soil moisture, GWL, and terrestrial water storage. Most trends estimated for different subperiods are found to be sensitive to data lengths and periods. Overall, this study provides an internally consistent observed evidence on the intensification of the hydrologic cycle in response to recent climate warming in U.S. Midwest, in agreement with and well supported by several recent studies consistently reporting the increased P, R and E over the Midwest and Mississippi River basin.

  6. Active sulfur cycling by diverse mesophilic and thermophilic microorganisms in terrestrial mud volcanoes of Azerbaijan.

    Science.gov (United States)

    Green-Saxena, A; Feyzullayev, A; Hubert, C R J; Kallmeyer, J; Krueger, M; Sauer, P; Schulz, H-M; Orphan, V J

    2012-12-01

    Terrestrial mud volcanoes (TMVs) represent geochemically diverse habitats with varying sulfur sources and yet sulfur cycling in these environments remains largely unexplored. Here we characterized the sulfur-metabolizing microorganisms and activity in four TMVs in Azerbaijan. A combination of geochemical analyses, biological rate measurements and molecular diversity surveys (targeting metabolic genes aprA and dsrA and SSU ribosomal RNA) supported the presence of active sulfur-oxidizing and sulfate-reducing guilds in all four TMVs across a range of physiochemical conditions, with diversity of these guilds being unique to each TMV. The TMVs varied in potential sulfate reduction rates (SRR) by up to four orders of magnitude with highest SRR observed in sediments where in situ sulfate concentrations were highest. Maximum temperatures at which SRR were measured was 60°C in two TMVs. Corresponding with these trends in SRR, members of the potentially thermophilic, spore-forming, Desulfotomaculum were detected in these TMVs by targeted 16S rRNA analysis. Additional sulfate-reducing bacterial lineages included members of the Desulfobacteraceae and Desulfobulbaceae detected by aprA and dsrA analyses and likely contributing to the mesophilic SRR measured. Phylotypes affiliated with sulfide-oxidizing Gamma- and Betaproteobacteria were abundant in aprA libraries from low sulfate TMVs, while the highest sulfate TMV harboured 16S rRNA phylotypes associated with sulfur-oxidizing Epsilonproteobacteria. Altogether, the biogeochemical and microbiological data indicate these unique terrestrial habitats support diverse active sulfur-cycling microorganisms reflecting the in situ geochemical environment. © 2012 Society for Applied Microbiology and Blackwell Publishing Ltd.

  7. Carbon Nanotube Based Chemical Sensors for Space and Terrestrial Applications

    Science.gov (United States)

    Li, Jing; Lu, Yijiang

    2009-01-01

    A nanosensor technology has been developed using nanostructures, such as single walled carbon nanotubes (SWNTs), on a pair of interdigitated electrodes (IDE) processed with a silicon-based microfabrication and micromachining technique. The IDE fingers were fabricated using photolithography and thin film metallization techniques. Both in-situ growth of nanostructure materials and casting of the nanostructure dispersions were used to make chemical sensing devices. These sensors have been exposed to nitrogen dioxide, acetone, benzene, nitrotoluene, chlorine, and ammonia in the concentration range of ppm to ppb at room temperature. The electronic molecular sensing of carbon nanotubes in our sensor platform can be understood by intra- and inter-tube electron modulation in terms of charge transfer mechanisms. As a result of the charge transfer, the conductance of p-type or hole-richer SWNTs in air will change. Due to the large surface area, low surface energy barrier and high thermal and mechanical stability, nanostructured chemical sensors potentially can offer higher sensitivity, lower power consumption and better robustness than the state-of-the-art systems, which make them more attractive for defense and space applications. Combined with MEMS technology, light weight and compact size sensors can be made in wafer scale with low cost. Additionally, a wireless capability of such a sensor chip can be used for networked mobile and fixed-site detection and warning systems for military bases, facilities and battlefield areas.

  8. Tracing Carbon Cycling in the Atmosphere and Oceans During the Cretaceous Ocean Anoxic Event 2 (OAE2, 94Ma)

    Science.gov (United States)

    Moran, S. A. M.; Boudinot, F. G.; Dildar, N.; Sepúlveda, J.

    2017-12-01

    We present a high-resolution record of compound-specific stable carbon isotope data from short-chain—aquatic algae—and long-chain n-alkanes—terrestrial plants—preserved in sedimentary sequences from the Smokey Hollow #1 (SH1) core in the Grand Staircase Escalante National Monument in southern Utah. The study area covered by SH1 core was situated at the western margin of the Western Interior Seaway during the Cretaceous Ocean Anoxic Event (OAE2, 94Ma.), and was characterized by high sedimentation rates and enhanced preservation of both marine and terrestrial organic matter. Short- and long-chain n-alkanes were isolated and purified from branched and cyclic aliphatic hydrocarbons using an optimized urea adduction protocol, and δ13Cn-alkane was measured using a Thermo MAT253 GC-C-IR-MS. We use the δ13Cn-alkane from aquatic and terrestrial sources to better understand carbon cycle interactions in the oceanic and atmospheric carbon pools across this event. Our results indicate that the δ13C of terrestrial plants experienced a faster and more pronounced positive carbon isotope excursion compared to marine sources. We will discuss how these results can inform models of carbon cycle interactions between the ocean and the atmosphere during greenhouse climates, and how they can be used to trace possible sources of CO2.

  9. Cycling of modern autochthonous organic matter dominates carbon flow in lakes of north central Alaska

    Science.gov (United States)

    Bogard, M.; Striegl, R. G.; Holtgrieve, G. W.; Kuhn, C.; Dornblaser, M.; Butman, D. E.

    2017-12-01

    Boreal and subarctic regions of the world are warming faster than anywhere else on earth, and undergoing rapid climatic and hydrologic changes. Much of this landscape is underlain by organic carbon (OC)-rich permafrost, and it is hypothesized that climate-induced environmental changes could positively reinforce climatic shifts via an increased delivery of terrestrial OC to aquatic networks. Increased OC terrestrial OC export could potentially result in greater aquatic OC mineralization and greenhouse gas production. Currently, a lack of ecosystem-level data precludes our understanding of aquatic OC processing for the vast majority of this remote northern area. To address this knowledge gap, we quantified whole-lake metabolism, limnological-, and hydrological characteristics across multiple seasons in a diverse set of lakes in the Yukon River Basin (YRB), Alaska. Intense gross primary production (GPP) and autotrophic net ecosystem production (NEP = GPP - respiration [R]) was common across lakes in spring, followed by a spatially synchronous shift toward heterotrophy (NEP origin, suggesting shifts in NEP were fueled by the recently fixed, lake OC. By scaling our metabolic estimates to the entire YRB, we found mineralization of terrestrial OC in lakes likely accounts for < 1% of terrestrial net primary production on an annual scale. We conclude that flows of autochthonous OC drive C cycling in most YRB lakes, that ancient permafrost-OC currently contributes little to heterotrophic processes in YRB lakes, and that the lakes play little role in remineralizing terrestrial organic material at the whole-catchment scale.

  10. Global Carbon Budget 2017

    NARCIS (Netherlands)

    Le Quere, Corinne; Andrew, Robbie M.; Friedlingstein, Pierre; Sitch, Stephen; Pongratz, Julia; Manning, Andrew C.; Korsbakken, Jan Ivar; Peters, Glen P.; Canadell, Josep G.; Jackson, Robert B.; Boden, Thomas A.; Tans, Pieter P.; Andrews, Oliver D.; Arora, Vivek K.; Bakker, Dorothee C. E.; Barbero, Leticia; Becker, Meike; Betts, Richard A.; Bopp, Laurent; Chevallier, Frederic; Chini, Louise P.; Ciais, Philippe; Cosca, Catherine E.; Cross, Jessica; Currie, Kim; Gasser, Thomas; Harris, Ian; Hauck, Judith; Haverd, Vanessa; Houghton, Richard A.; Hunt, Christopher W.; Hurtt, George; Ilyina, Tatiana; Jain, Atul K.; Kato, Etsushi; Kautz, Markus; Keeling, Ralph F.; Goldewijk, Kees Klein; Koertzinger, Arne; Landschuetzer, Peter; Lefevre, Nathalie; Lenton, Andrew; Lienert, Sebastian; Lima, Ivan; Lombardozzi, Danica; Metzl, Nicolas; Millero, Frank; Monteiro, Pedro M. S.; Munro, David R.; Nabel, Julia E. M. S.; Nakaoka, Shin-ichiro; Nojiri, Yukihiro; Padin, X. Antonio; Peregon, Anna; Pfeil, Benjamin; Pierrot, Denis; Poulter, Benjamin; Rehder, Gregor; Reimer, Janet; Roedenbeck, Christian; Schwinger, Jorg; Seferian, Roland; Skjelvan, Ingunn; Stocker, Benjamin D.; Tian, Hanqin; Tilbrook, Bronte; Tubiello, Francesco N.; van der Laan-Luijkx, Ingrid T.; van der Werf, Guido R.; van Heuven, Steven; Viovy, Nicolas; Vuichard, Nicolas; Walker, Anthony P.; Watson, Andrew J.; Wiltshire, Andrew J.; Zaehle, Soenke; Zhu, Dan

    2018-01-01

    Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere - the "global carbon budget" - is important to better understand the global carbon cycle, support the development of climate policies, and project

  11. Iron cycling at corroding carbon steel surfaces

    Science.gov (United States)

    Lee, Jason S.; McBeth, Joyce M.; Ray, Richard I.; Little, Brenda J.; Emerson, David

    2013-01-01

    Surfaces of carbon steel (CS) exposed to mixed cultures of iron-oxidizing bacteria (FeOB) and dissimilatory iron-reducing bacteria (FeRB) in seawater media under aerobic conditions were rougher than surfaces of CS exposed to pure cultures of either type of microorganism. The roughened surface, demonstrated by profilometry, is an indication of loss of metal from the surface. In the presence of CS, aerobically grown FeOB produced tight, twisted helical stalks encrusted with iron oxides. When CS was exposed anaerobically in the presence of FeRB, some surface oxides were removed. However, when the same FeOB and FeRB were grown together in an aerobic medium, FeOB stalks were less encrusted with iron oxides and appeared less tightly coiled. These observations suggest that iron oxides on the stalks were reduced and solubilized by the FeRB. Roughened surfaces of CS and denuded stalks were replicated with three culture combinations of different species of FeOB and FeRB under three experimental conditions. Measurements of electrochemical polarization resistance established different rates of corrosion of CS in aerobic and anaerobic media, but could not differentiate rate differences between sterile controls and inoculated exposures for a given bulk concentration of dissolved oxygen. Similarly, total iron in the electrolyte could not be used to differentiate treatments. The experiments demonstrate the potential for iron cycling (oxidation and reduction) on corroding CS in aerobic seawater media. PMID:24093730

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

    International Nuclear Information System (INIS)

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

    2006-01-01

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

  13. Shifts in nitrogen acquisition strategies enable enhanced terrestrial carbon storage under elevated CO2 in a global model

    Science.gov (United States)

    Sulman, B. N.; Brzostek, E. R.; Menge, D.; Malyshev, S.; Shevliakova, E.

    2017-12-01

    Earth System Model (ESM) projections of terrestrial carbon (C) uptake are critical to understanding the future of the global C cycle. Current ESMs include intricate representations of photosynthetic C fixation in plants, allowing them to simulate the stimulatory effect of increasing atmospheric CO2 levels on photosynthesis. However, they lack sophisticated representations of plant nutrient acquisition, calling into question their ability to project the future land C sink. We conducted simulations using a new model of terrestrial C and nitrogen (N) cycling within the Geophysical Fluid Dynamics Laboratory (GFDL) global land model LM4 that uses a return on investment framework to simulate global patterns of N acquisition via fixation of N2 from the atmosphere, scavenging of inorganic N from soil solution, and mining of organic N from soil organic matter (SOM). We show that these strategies drive divergent C cycle responses to elevated CO2 at the ecosystem scale, with the scavenging strategy leading to N limitation of plant growth and the mining strategy facilitating stimulation of plant biomass accumulation over decadal time scales. In global simulations, shifts in N acquisition from inorganic N scavenging to organic N mining along with increases in N fixation supported long-term acceleration of C uptake under elevated CO2. Our results indicate that the ability of the land C sink to mitigate atmospheric CO2 levels is tightly coupled to the functional diversity of ecosystems and their capacity to change their N acquisition strategies over time. Incorporation of these mechanisms into ESMs is necessary to improve confidence in model projections of the global C cycle.

  14. A lake classification concept for a more accurate global estimate of the dissolved inorganic carbon export from terrestrial ecosystems to inland waters

    Science.gov (United States)

    Engel, Fabian; Farrell, Kaitlin J.; McCullough, Ian M.; Scordo, Facundo; Denfeld, Blaize A.; Dugan, Hilary A.; de Eyto, Elvira; Hanson, Paul C.; McClure, Ryan P.; Nõges, Peeter; Nõges, Tiina; Ryder, Elizabeth; Weathers, Kathleen C.; Weyhenmeyer, Gesa A.

    2018-04-01

    The magnitude of lateral dissolved inorganic carbon (DIC) export from terrestrial ecosystems to inland waters strongly influences the estimate of the global terrestrial carbon dioxide (CO2) sink. At present, no reliable number of this export is available, and the few studies estimating the lateral DIC export assume that all lakes on Earth function similarly. However, lakes can function along a continuum from passive carbon transporters (passive open channels) to highly active carbon transformers with efficient in-lake CO2 production and loss. We developed and applied a conceptual model to demonstrate how the assumed function of lakes in carbon cycling can affect calculations of the global lateral DIC export from terrestrial ecosystems to inland waters. Using global data on in-lake CO2 production by mineralization as well as CO2 loss by emission, primary production, and carbonate precipitation in lakes, we estimated that the global lateral DIC export can lie within the range of {0.70}_{-0.31}^{+0.27} to {1.52}_{-0.90}^{+1.09} Pg C yr-1 depending on the assumed function of lakes. Thus, the considered lake function has a large effect on the calculated lateral DIC export from terrestrial ecosystems to inland waters. We conclude that more robust estimates of CO2 sinks and sources will require the classification of lakes into their predominant function. This functional lake classification concept becomes particularly important for the estimation of future CO2 sinks and sources, since in-lake carbon transformation is predicted to be altered with climate change.

  15. Nuclear reactor closed Brayton cycle power conversion system optimization trends for extra-terrestrial applications

    International Nuclear Information System (INIS)

    Ashe, T.L.; Baggenstoss, W.G.; Bons, R.

    1990-01-01

    Extra-terrestrial exploration and development missions of the next century will require reliable, low-mass power generation modules of 100 kW e and more. These modules will be required to support both fixed-base and manned rover/explorer power needs. Low insolation levels at and beyond Mars and long periods of darkness on the moon make solar conversion less desirable for surface missions. For these missions, a closed Brayton cycle energy conversion system coupled with a reactor heat source is a very attractive approach. The authors conducted parametric studies to assess optimized system design trends for nuclear-Brayton systems as a function of operating environment and user requirements. The inherent design flexibility of the closed Brayton cycle energy conversion system permits ready adaptation of the system to future design constraints. This paper describes a dramatic contrast between system designs requiring man-rated shielding. The paper also considers the ramification of using indigenous materials to provide reactor shielding for a fixed-base power source

  16. Trailblazing the Carbon Cycle of Tropical Forests from Puerto Rico

    Science.gov (United States)

    Sandra Brown; Ariel Lugo

    2017-01-01

    We review the literature that led to clarifying the role of tropical forests in the global carbon cycle from a time when they were considered sources of atmospheric carbon to the time when they were found to be atmospheric carbon sinks. This literature originates from work conducted by US Forest Service scientists in Puerto Rico and their collaborators. It involves the...

  17. Terrestrial Carbon Sequestration in National Parks: Values for the Conterminous United States

    Science.gov (United States)

    Richardson, Leslie A.; Huber, Christopher; Zhu, Zhi-Liang; Koontz, Lynne

    2015-01-01

    Lands managed by the National Park Service (NPS) provide a wide range of beneficial services to the American public. This study quantifies the ecosystem service value of carbon sequestration in terrestrial ecosystems within NPS units in the conterminous United States for which data were available. Combining annual net carbon balance data with spatially explicit NPS land unit boundaries and social cost of carbon estimates, this study calculates the net metric tons of carbon dioxide sequestered annually by park unit under baseline conditions, as well as the associated economic value to society. Results show that, in aggregate, NPS lands in the conterminous United States are a net carbon sink, sequestering more than 14.8 million metric tons of carbon dioxide annually. The associated societal value of this service is estimated at approximately $582.5 million per year. While this analysis provides a broad overview of the annual value of carbon sequestration on NPS lands averaged over a five year baseline period, it should be noted that carbon fluxes fluctuate from year to year, and there can be considerable variation in net carbon balance and its associated value within a given park unit. Future research could look in-depth at the spatial heterogeneity of carbon flux within specific NPS land units.

  18. Atmospheric Carbon Dioxide and the Global Carbon Cycle: The Key Uncertainties

    Science.gov (United States)

    Peng, T. H.; Post, W. M.; DeAngelis, D. L.; Dale, V. H.; Farrell, M. P.

    1987-12-01

    The biogeochemical cycling of carbon between its sources and sinks determines the rate of increase in atmospheric CO{sub 2} concentrations. The observed increase in atmospheric CO{sub 2} content is less than the estimated release from fossil fuel consumption and deforestation. This discrepancy can be explained by interactions between the atmosphere and other global carbon reservoirs such as the oceans, and the terrestrial biosphere including soils. Undoubtedly, the oceans have been the most important sinks for CO{sub 2} produced by man. But, the physical, chemical, and biological processes of oceans are complex and, therefore, credible estimates of CO{sub 2} uptake can probably only come from mathematical models. Unfortunately, one- and two-dimensional ocean models do not allow for enough CO{sub 2} uptake to accurately account for known releases. Thus, they produce higher concentrations of atmospheric CO{sub 2} than was historically the case. More complex three-dimensional models, while currently being developed, may make better use of existing tracer data than do one- and two-dimensional models and will also incorporate climate feedback effects to provide a more realistic view of ocean dynamics and CO{sub 2} fluxes. The instability of current models to estimate accurately oceanic uptake of CO{sub 2} creates one of the key uncertainties in predictions of atmospheric CO{sub 2} increases and climate responses over the next 100 to 200 years.

  19. Terrestrial cycling of (CO2)-C-13 by photosynthesis, respiration, and biomass burning in SiBCASA

    NARCIS (Netherlands)

    Velde, van der I.R.; Miller, J.B.; Schaefer, K.; Werf, van der G.R.; Krol, M.C.; Peters, W.

    2014-01-01

    We present an enhanced version of the SiBCASA terrestrial biosphere model that is extended with (a) biomass burning emissions from the SiBCASA carbon pools using remotely sensed burned area from the Global Fire Emissions Database (GFED), (b) an isotopic discrimination scheme that calculates 13C

  20. Tracing carbon sources through aquatic and terrestrial food webs using amino acid stable isotope fingerprinting.

    Directory of Open Access Journals (Sweden)

    Thomas Larsen

    Full Text Available Tracing the origin of nutrients is a fundamental goal of food web research but methodological issues associated with current research techniques such as using stable isotope ratios of bulk tissue can lead to confounding results. We investigated whether naturally occurring δ(13C patterns among amino acids (δ(13CAA could distinguish between multiple aquatic and terrestrial primary production sources. We found that δ(13CAA patterns in contrast to bulk δ(13C values distinguished between carbon derived from algae, seagrass, terrestrial plants, bacteria and fungi. Furthermore, we showed for two aquatic producers that their δ(13CAA patterns were largely unaffected by different environmental conditions despite substantial shifts in bulk δ(13C values. The potential of assessing the major carbon sources at the base of the food web was demonstrated for freshwater, pelagic, and estuarine consumers; consumer δ(13C patterns of essential amino acids largely matched those of the dominant primary producers in each system. Since amino acids make up about half of organismal carbon, source diagnostic isotope fingerprints can be used as a new complementary approach to overcome some of the limitations of variable source bulk isotope values commonly encountered in estuarine areas and other complex environments with mixed aquatic and terrestrial inputs.

  1. Tracing carbon sources through aquatic and terrestrial food webs using amino acid stable isotope fingerprinting.

    Science.gov (United States)

    Larsen, Thomas; Ventura, Marc; Andersen, Nils; O'Brien, Diane M; Piatkowski, Uwe; McCarthy, Matthew D

    2013-01-01

    Tracing the origin of nutrients is a fundamental goal of food web research but methodological issues associated with current research techniques such as using stable isotope ratios of bulk tissue can lead to confounding results. We investigated whether naturally occurring δ(13)C patterns among amino acids (δ(13)CAA) could distinguish between multiple aquatic and terrestrial primary production sources. We found that δ(13)CAA patterns in contrast to bulk δ(13)C values distinguished between carbon derived from algae, seagrass, terrestrial plants, bacteria and fungi. Furthermore, we showed for two aquatic producers that their δ(13)CAA patterns were largely unaffected by different environmental conditions despite substantial shifts in bulk δ(13)C values. The potential of assessing the major carbon sources at the base of the food web was demonstrated for freshwater, pelagic, and estuarine consumers; consumer δ(13)C patterns of essential amino acids largely matched those of the dominant primary producers in each system. Since amino acids make up about half of organismal carbon, source diagnostic isotope fingerprints can be used as a new complementary approach to overcome some of the limitations of variable source bulk isotope values commonly encountered in estuarine areas and other complex environments with mixed aquatic and terrestrial inputs.

  2. The oceanic response to carbon emissions over the next century: investigation using three ocean carbon cycle models

    International Nuclear Information System (INIS)

    Chuck, A.; Tyrrell, T.; Holligan, P.M.; Totterdell, I.J.

    2005-01-01

    A recent study of coupled atmospheric carbon dioxide and the biosphere found alarming sensitivity of next-century atmospheric pCO 2 (and hence planetary temperature) to uncertainties in terrestrial processes. Here we investigate whether there is similar sensitivity associated with uncertainties in the behaviour of the ocean carbon cycle. We investigate this important question using three models of the ocean carbon cycle of varying complexity: (1) a new three-box oceanic carbon cycle model; (2) the HILDA multibox model with high vertical resolution at low latitudes; (3) the Hadley Centre ocean general circulation model (HadOCC). These models were used in combination to assess the quantitative significance (to year 2100 pCO 2 ) of potential changes to the ocean stimulated by global warming and other anthropogenic activities over the period 2000-2100. It was found that an increase in sea surface temperature and a decrease in the mixing rate due to stratification give rise to the greatest relative changes in pCO 2 , both being positive feedbacks. We failed to find any comparable large sensitivity due to the ocean

  3. Carbon cycling and calcification in hypersaline microbial mats

    OpenAIRE

    Ludwig, Rebecca

    2004-01-01

    Phototrophic microbial mats are laminated aggregations of microorganisms that thrive in extreme and oligotrophic environments. Primary production rates by oxygenic phototrophs are extremely high. Primary producers supply heterotrophic mat members with organic carbon, which in turn regenerate CO2 needed for autotrophic carbon fixation. Another potential source of CO2 is calcification, which is known to shift the carbonate equilibrium towards CO2. This thesis investigated the carbon cycle of mi...

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

    International Nuclear Information System (INIS)

    Vukicevic, Tomislava; Schimel, David

    2001-01-01

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

  5. Modeling of the global carbon cycle - isotopic data requirements

    International Nuclear Information System (INIS)

    Ciais, P.

    1994-01-01

    Isotopes are powerful tools to constrain carbon cycle models. For example, the combinations of the CO 2 and the 13 C budget allows to calculate the net-carbon fluxes between atmosphere, ocean, and biosphere. Observations of natural and bomb-produced radiocarbon allow to estimate gross carbon exchange fluxes between different reservoirs and to deduce time scales of carbon overturning in important reservoirs. 18 O in CO 2 is potentially a tool to make the deconvolution of C fluxes within the land biosphere (assimilation vs respirations). The scope of this article is to identify gaps in our present knowledge about isotopes in the light of their use as constraint for the global carbon cycle. In the following we will present a list of some future data requirements for carbon cycle models. (authors)

  6. CO/sub 2/ carbon cycle and climate interactions

    Energy Technology Data Exchange (ETDEWEB)

    Grassl, H; Maier-Reimer, E; Degens, E T; Kempe, S; Spitzy, A

    1984-03-01

    Past and expected emissions of anthropogenic CO/sub 2/ stimulate carbon cycle and climate research. Prognoses of future CO/sub 2/ levels depend on energy scenarios and on the reaction of the biosphere and hydrosphere to elevated atmospheric CO/sub 2/ concentrations. The reaction of the reservoirs vegetation, freshwater and oceans to disturbances of the carbon cycle is reviewed. For the oceans first results of a simple carbon cycle model implanted in a three-dimensional general circulation model are presented. This model allows experiments not possible with previous box models.

  7. Sedimentary evidence for enhanced hydrological cycling in response to rapid carbon release during the early Toarcian oceanic anoxic event

    Science.gov (United States)

    Izumi, Kentaro; Kemp, David B.; Itamiya, Shoma; Inui, Mutsuko

    2018-01-01

    A pronounced excursion in the carbon-isotope composition of biospheric carbon and coeval seawater warming during the early Toarcian (∼183 Ma) has been linked to the large-scale transfer of 12C-enriched carbon to the oceans and atmosphere. A European bias in the distribution of available data means that the precise pattern, tempo and global expression of this carbon cycle perturbation, and the associated environmental responses, remain uncertain. Here, we present a new cm-scale terrestrial-dominated carbon-isotope record through an expanded lower Toarcian section from Japan that displays a negative excursion pattern similar to marine and terrestrial carbon-isotope records documented from Europe. These new data suggest that 12C-enriched carbon was added to the biosphere in at least one rapid, millennial-scale pulse. Sedimentological analysis indicates a close association between the carbon-isotope excursion and high-energy sediment transport and enhanced fluvial discharge. Together, these data support the hypothesis that a sudden strengthening of the global hydrological cycle occurred in direct and immediate response to rapid carbon release and atmospheric warming.

  8. Ages and transit times as important diagnostics of model performance for predicting carbon dynamics in terrestrial vegetation models

    Science.gov (United States)

    Ceballos-Núñez, Verónika; Richardson, Andrew D.; Sierra, Carlos A.

    2018-03-01

    The global carbon cycle is strongly controlled by the source/sink strength of vegetation as well as the capacity of terrestrial ecosystems to retain this carbon. These dynamics, as well as processes such as the mixing of old and newly fixed carbon, have been studied using ecosystem models, but different assumptions regarding the carbon allocation strategies and other model structures may result in highly divergent model predictions. We assessed the influence of three different carbon allocation schemes on the C cycling in vegetation. First, we described each model with a set of ordinary differential equations. Second, we used published measurements of ecosystem C compartments from the Harvard Forest Environmental Measurement Site to find suitable parameters for the different model structures. And third, we calculated C stocks, release fluxes, radiocarbon values (based on the bomb spike), ages, and transit times. We obtained model simulations in accordance with the available data, but the time series of C in foliage and wood need to be complemented with other ecosystem compartments in order to reduce the high parameter collinearity that we observed, and reduce model equifinality. Although the simulated C stocks in ecosystem compartments were similar, the different model structures resulted in very different predictions of age and transit time distributions. In particular, the inclusion of two storage compartments resulted in the prediction of a system mean age that was 12-20 years older than in the models with one or no storage compartments. The age of carbon in the wood compartment of this model was also distributed towards older ages, whereas fast cycling compartments had an age distribution that did not exceed 5 years. As expected, models with C distributed towards older ages also had longer transit times. These results suggest that ages and transit times, which can be indirectly measured using isotope tracers, serve as important diagnostics of model structure

  9. The role of urbanization in the global carbon cycle

    Directory of Open Access Journals (Sweden)

    Galina eChurkina

    2016-01-01

    Full Text Available Urban areas account for more than 70% of CO2 emissions from burning fossil fuels. Urban expansion in tropics is responsible for 5% of the annual emissions from land use change. Here I show that the effect of urbanization on the global carbon cycle extends beyond these emissions. I quantify the contribution of urbanization to the major carbon fluxes and pools globally and identify gaps crucial for predicting the evolution of the carbon cycle in the future. Urban residents currently control ~22 (12-40 % of the land carbon uptake (112 PgC/yr and ~24 (15-39 % of the carbon emissions (117 PgC/yr from land globally. Urbanization resulted in the creation of new carbon pools on land such as buildings (~6.7 PgC and landfills (~30 PgC. Together these pools store 1.6 (±0.3 % of the total vegetation and soil carbon pools globally. The creation and maintenance of these new pools has been associated with high emissions of CO2, which are currently better understood than the processes associated with the dynamics of these pools and accompanying uptake of carbon. Predictions of the future trajectories of the global carbon cycle will require a much better understanding of how urban development affects the carbon cycle over the long term.

  10. Viral impacts on microbial carbon cycling in thawing permafrost soils

    Science.gov (United States)

    Trubl, G. G.; Roux, S.; Bolduc, B.; Jang, H. B.; Emerson, J. B.; Solonenko, N.; Li, F.; Solden, L. M.; Vik, D. R.; Wrighton, K. C.; Saleska, S. R.; Sullivan, M. B.; Rich, V. I.

    2017-12-01

    Permafrost contains 30-50% of global soil carbon (C) and is rapidly thawing. While the fate of this C is unknown, it will be shaped in part by microbes and their associated viruses, which modulate host activities via mortality and metabolic control. To date, viral research in soils has been outpaced by that in aquatic environments, due to the technical challenges of accessing viruses as well as the dramatic physicochemical heterogeneity in soils. Here, we describe advances in soil viromics from our research on permafrost-associated soils, and their implications for associated terrestrial C cycling. First, we optimized viral resuspension-DNA extraction methods for a range of soil types. Second, we applied cutting-edge viral-specific informatics methods to recover viral populations, define their gene content, connect them to potential hosts, and analyze their relationships to environmental parameters. A total of 781 viral populations were recovered from size-fractionated virus samples of three soils along a permafrost thaw gradient. Ecological analyses revealed endemism as recovered viral populations were largely unique to each habitat and unlike those in aquatic communities. Genome- and network-based classification assigned these viruses into 226 viral clusters (VCs; genus-level taxonomy), 55% of which were novel. This increases the number of VCs by a third and triples the number of soil viral populations in the RefSeq database (currently contains 256 VCs and 316 soil viral populations). Genomic analyses revealed 85% of the genes were functionally unknown, though 5% of the annotatable genes contained C-related auxiliary metabolic genes (AMGs; e.g. glycoside hydrolases). Using sequence-based features and microbial population genomes, we were able to in silico predict hosts for 30% of the viral populations. The identified hosts spanned 3 phyla and 6 genera but suggested these viruses have species-specific host ranges as >80% of hosts for a given virus were in the same

  11. Temperature and rainfall interact to control carbon cycling in tropical forests.

    Science.gov (United States)

    Taylor, Philip G; Cleveland, Cory C; Wieder, William R; Sullivan, Benjamin W; Doughty, Christopher E; Dobrowski, Solomon Z; Townsend, Alan R

    2017-06-01

    Tropical forests dominate global terrestrial carbon (C) exchange, and recent droughts in the Amazon Basin have contributed to short-term declines in terrestrial carbon dioxide uptake and storage. However, the effects of longer-term climate variability on tropical forest carbon dynamics are still not well understood. We synthesised field data from more than 150 tropical forest sites to explore how climate regulates tropical forest aboveground net primary productivity (ANPP) and organic matter decomposition, and combined those data with two existing databases to explore climate - C relationships globally. While previous analyses have focused on the effects of either temperature or rainfall on ANPP, our results highlight the importance of interactions between temperature and rainfall on the C cycle. In cool forests (forests (> 20 °C) it consistently enhanced both ANPP and decomposition. At the global scale, our analysis showed an increase in ANPP with rainfall in relatively warm sites, inconsistent with declines in ANPP with rainfall reported previously. Overall, our results alter our understanding of climate - C cycle relationships, with high precipitation accelerating rates of C exchange with the atmosphere in the most productive biome on earth. © 2017 John Wiley & Sons Ltd/CNRS.

  12. Modeling the grazing effect on dry grassland carbon cycling with modified Biome-BGC grazing model

    Science.gov (United States)

    Luo, Geping; Han, Qifei; Li, Chaofan; Yang, Liao

    2014-05-01

    Identifying the factors that determine the carbon source/sink strength of ecosystems is important for reducing uncertainty in the global carbon cycle. Arid grassland ecosystems are a widely distributed biome type in Xinjiang, Northwest China, covering approximately one-fourth the country's land surface. These grasslands are the habitat for many endemic and rare plant and animal species and are also used as pastoral land for livestock. Using the modified Biome-BGC grazing model, we modeled carbon dynamics in Xinjiang for grasslands that varied in grazing intensity. In general, this regional simulation estimated that the grassland ecosystems in Xinjiang acted as a net carbon source, with a value of 0.38 Pg C over the period 1979-2007. There were significant effects of grazing on carbon dynamics. An over-compensatory effect in net primary productivity (NPP) and vegetation carbon (C) stock was observed when grazing intensity was lower than 0.40 head/ha. Grazing resulted in a net carbon source of 23.45 g C m-2 yr-1, which equaled 0.37 Pg in Xinjiang in the last 29 years. In general, grazing decreased vegetation C stock, while an increasing trend was observed with low grazing intensity. The soil C increased significantly (17%) with long-term grazing, while the soil C stock exhibited a steady trend without grazing. These findings have implications for grassland ecosystem management as it relates to carbon sequestration and climate change mitigation, e.g., removal of grazing should be considered in strategies that aim to increase terrestrial carbon sequestrations at local and regional scales. One of the greatest limitations in quantifying the effects of herbivores on carbon cycling is identifying the grazing systems and intensities within a given region. We hope our study emphasizes the need for large-scale assessments of how grazing impacts carbon cycling. Most terrestrial ecosystems in Xinjiang have been affected by disturbances to a greater or lesser extent in the past

  13. Understanding of Coupled Terrestrial Carbon, Nitrogen and Water Dynamics—An Overview

    Directory of Open Access Journals (Sweden)

    Nicholas C. Coops

    2009-10-01

    Full Text Available Coupled terrestrial carbon (C, nitrogen (N and hydrological processes play a crucial role in the climate system, providing both positive and negative feedbacks to climate change. In this review we summarize published research results to gain an increased understanding of the dynamics between vegetation and atmosphere processes. A variety of methods, including monitoring (e.g., eddy covariance flux tower, remote sensing, etc. and modeling (i.e., ecosystem, hydrology and atmospheric inversion modeling the terrestrial carbon and water budgeting, are evaluated and compared. We highlight two major research areas where additional research could be focused: (i Conceptually, the hydrological and biogeochemical processes are closely linked, however, the coupling processes between terrestrial C, N and hydrological processes are far from well understood; and (ii there are significant uncertainties in estimates of the components of the C balance, especially at landscape and regional scales. To address these two questions, a synthetic research framework is needed which includes both bottom-up and top-down approaches integrating scalable (footprint and ecosystem models and a spatially nested hierarchy of observations which include multispectral remote sensing, inventories, existing regional clusters of eddy-covariance flux towers and CO2 mixing ratio towers and chambers.

  14. Understanding of coupled terrestrial carbon, nitrogen and water dynamics-an overview.

    Science.gov (United States)

    Chen, Baozhang; Coops, Nicholas C

    2009-01-01

    Coupled terrestrial carbon (C), nitrogen (N) and hydrological processes play a crucial role in the climate system, providing both positive and negative feedbacks to climate change. In this review we summarize published research results to gain an increased understanding of the dynamics between vegetation and atmosphere processes. A variety of methods, including monitoring (e.g., eddy covariance flux tower, remote sensing, etc.) and modeling (i.e., ecosystem, hydrology and atmospheric inversion modeling) the terrestrial carbon and water budgeting, are evaluated and compared. We highlight two major research areas where additional research could be focused: (i) Conceptually, the hydrological and biogeochemical processes are closely linked, however, the coupling processes between terrestrial C, N and hydrological processes are far from well understood; and (ii) there are significant uncertainties in estimates of the components of the C balance, especially at landscape and regional scales. To address these two questions, a synthetic research framework is needed which includes both bottom-up and top-down approaches integrating scalable (footprint and ecosystem) models and a spatially nested hierarchy of observations which include multispectral remote sensing, inventories, existing regional clusters of eddy-covariance flux towers and CO(2) mixing ratio towers and chambers.

  15. Influence of dynamic vegetation on climate change and terrestrial carbon storage in the Last Glacial Maximum

    Science.gov (United States)

    O'ishi, R.; Abe-Ouchi, A.

    2013-07-01

    When the climate is reconstructed from paleoevidence, it shows that the Last Glacial Maximum (LGM, ca. 21 000 yr ago) is cold and dry compared to the present-day. Reconstruction also shows that compared to today, the vegetation of the LGM is less active and the distribution of vegetation was drastically different, due to cold temperature, dryness, and a lower level of atmospheric CO2 concentration (185 ppm compared to a preindustrial level of 285 ppm). In the present paper, we investigate the influence of vegetation change on the climate of the LGM by using a coupled atmosphere-ocean-vegetation general circulation model (AOVGCM, the MIROC-LPJ). The MIROC-LPJ is different from earlier studies in the introduction of a bias correction method in individual running GCM experiments. We examined four GCM experiments (LGM and preindustrial, with and without vegetation feedback) and quantified the strength of the vegetation feedback during the LGM. The result shows that global-averaged cooling during the LGM is amplified by +13.5 % due to the introduction of vegetation feedback. This is mainly caused by the increase of land surface albedo due to the expansion of tundra in northern high latitudes and the desertification in northern middle latitudes around 30° N to 60° N. We also investigated how this change in climate affected the total terrestrial carbon storage by using offline Lund-Potsdam-Jena dynamic global vegetation model (LPJ-DGVM). Our result shows that the total terrestrial carbon storage was reduced by 597 PgC during the LGM, which corresponds to the emission of 282 ppm atmospheric CO2. In the LGM experiments, the global carbon distribution is generally the same whether the vegetation feedback to the atmosphere is included or not. However, the inclusion of vegetation feedback causes substantial terrestrial carbon storage change, especially in explaining the lowering of atmospheric CO2 during the LGM.

  16. Influence of dynamic vegetation on climate change and terrestrial carbon storage in the Last Glacial Maximum

    Directory of Open Access Journals (Sweden)

    R. O'ishi

    2013-07-01

    Full Text Available When the climate is reconstructed from paleoevidence, it shows that the Last Glacial Maximum (LGM, ca. 21 000 yr ago is cold and dry compared to the present-day. Reconstruction also shows that compared to today, the vegetation of the LGM is less active and the distribution of vegetation was drastically different, due to cold temperature, dryness, and a lower level of atmospheric CO2 concentration (185 ppm compared to a preindustrial level of 285 ppm. In the present paper, we investigate the influence of vegetation change on the climate of the LGM by using a coupled atmosphere-ocean-vegetation general circulation model (AOVGCM, the MIROC-LPJ. The MIROC-LPJ is different from earlier studies in the introduction of a bias correction method in individual running GCM experiments. We examined four GCM experiments (LGM and preindustrial, with and without vegetation feedback and quantified the strength of the vegetation feedback during the LGM. The result shows that global-averaged cooling during the LGM is amplified by +13.5 % due to the introduction of vegetation feedback. This is mainly caused by the increase of land surface albedo due to the expansion of tundra in northern high latitudes and the desertification in northern middle latitudes around 30° N to 60° N. We also investigated how this change in climate affected the total terrestrial carbon storage by using offline Lund-Potsdam-Jena dynamic global vegetation model (LPJ-DGVM. Our result shows that the total terrestrial carbon storage was reduced by 597 PgC during the LGM, which corresponds to the emission of 282 ppm atmospheric CO2. In the LGM experiments, the global carbon distribution is generally the same whether the vegetation feedback to the atmosphere is included or not. However, the inclusion of vegetation feedback causes substantial terrestrial carbon storage change, especially in explaining the lowering of atmospheric CO2 during the LGM.

  17. Mixed-layer carbon cycling at the Kuroshio Extension Observatory

    Science.gov (United States)

    Fassbender, Andrea J.; Sabine, Christopher L.; Cronin, Meghan F.; Sutton, Adrienne J.

    2017-02-01

    Seven years of data from the NOAA Kuroshio Extension Observatory (KEO) surface mooring, located in the North Pacific Ocean carbon sink region, were used to evaluate drivers of mixed-layer carbon cycling. A time-dependent mass balance approach relying on two carbon tracers was used to diagnostically evaluate how surface ocean processes influence mixed-layer carbon concentrations over the annual cycle. Results indicate that the annual physical carbon input is predominantly balanced by biological carbon uptake during the intense spring bloom. Net annual gas exchange that adds carbon to the mixed layer and the opposing influence of net precipitation that dilutes carbon concentrations make up smaller contributions to the annual mixed-layer carbon budget. Decomposing the biological term into annual net community production (aNCP) and calcium carbonate production (aCaCO3) yields 7 ± 3 mol C m-2 yr-1 aNCP and 0.5 ± 0.3 mol C m-2 yr-1 aCaCO3, giving an annually integrated particulate inorganic carbon to particulate organic carbon production ratio of 0.07 ± 0.05, as a lower limit. Although we find that vertical physical processes dominate carbon input to the mixed layer at KEO, it remains unclear how horizontal features, such as eddies, influence carbon production and export by altering nutrient supply as well as the depth of winter ventilation. Further research evaluating linkages between Kuroshio Extension jet instabilities, eddy activity, and nutrient supply mechanisms is needed to adequately characterize the drivers and sensitivities of carbon cycling near KEO.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-11-17

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

  19. Reservoirs as hotspots of fluvial carbon cycling in peatland catchments.

    Science.gov (United States)

    Stimson, A G; Allott, T E H; Boult, S; Evans, M G

    2017-02-15

    Inland water bodies are recognised as dynamic sites of carbon processing, and lakes and reservoirs draining peatland soils are particularly important, due to the potential for high carbon inputs combined with long water residence times. A carbon budget is presented here for a water supply reservoir (catchment area~9km 2 ) draining an area of heavily eroded upland peat in the South Pennines, UK. It encompasses a two year dataset and quantifies reservoir dissolved organic carbon (DOC), particulate organic carbon (POC) and aqueous carbon dioxide (CO 2 (aq)) inputs and outputs. The budget shows the reservoir to be a hotspot of fluvial carbon cycling, as with high levels of POC influx it acts as a net sink of fluvial carbon and has the potential for significant gaseous carbon export. The reservoir alternates between acting as a producer and consumer of DOC (a pattern linked to rainfall and temperature) which provides evidence for transformations between different carbon species. In particular, the budget data accompanied by 14 C (radiocarbon) analyses provide evidence that POC-DOC transformations are a key process, occurring at rates which could represent at least ~10% of the fluvial carbon sink. To enable informed catchment management further research is needed to produce carbon cycle models more applicable to these environments, and on the implications of high POC levels for DOC composition. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. 2500 high-quality genomes reveal that the biogeochemical cycles of C, N, S and H are cross-linked by metabolic handoffs in the terrestrial subsurface

    Science.gov (United States)

    Anantharaman, K.; Brown, C. T.; Hug, L. A.; Sharon, I.; Castelle, C. J.; Shelton, A.; Bonet, B.; Probst, A. J.; Thomas, B. C.; Singh, A.; Wilkins, M.; Williams, K. H.; Tringe, S. G.; Beller, H. R.; Brodie, E.; Hubbard, S. S.; Banfield, J. F.

    2015-12-01

    Microorganisms drive the transformations of carbon compounds in the terrestrial subsurface, a key reservoir of carbon on earth, and impact other linked biogeochemical cycles. Our current knowledge of the microbial ecology in this environment is primarily based on 16S rRNA gene sequences that paint a biased picture of microbial community composition and provide no reliable information on microbial metabolism. Consequently, little is known about the identity and metabolic roles of the uncultivated microbial majority in the subsurface. In turn, this lack of understanding of the microbial processes that impact the turnover of carbon in the subsurface has restricted the scope and ability of biogeochemical models to capture key aspects of the carbon cycle. In this study, we used a culture-independent, genome-resolved metagenomic approach to decipher the metabolic capabilities of microorganisms in an aquifer adjacent to the Colorado River, near Rifle, CO, USA. We sequenced groundwater and sediment samples collected across fifteen different geochemical regimes. Sequence assembly, binning and manual curation resulted in the recovery of 2,542 high-quality genomes, 27 of which are complete. These genomes represent 1,300 non-redundant organisms comprising both abundant and rare community members. Phylogenetic analyses involving ribosomal proteins and 16S rRNA genes revealed the presence of up to 34 new phyla that were hitherto unknown. Less than 11% of all genomes belonged to the 4 most commonly represented phyla that constitute 93% of all currently available genomes. Genome-specific analyses of metabolic potential revealed the co-occurrence of important functional traits such as carbon fixation, nitrogen fixation and use of electron donors and electron acceptors. Finally, we predict that multiple organisms are often required to complete redox pathways through a complex network of metabolic handoffs that extensively cross-link subsurface biogeochemical cycles.

  1. Glassy carbon supercapacitor: 100,000 cycles demonstrated

    Energy Technology Data Exchange (ETDEWEB)

    Baertsch, M; Braun, A; Schnyder, B; Koetz, R [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1999-08-01

    A 5 V glassy carbon capacitor stack was built consisting of four bipolar and two end-plate electrodes. More than 100,000 charging/discharging cycles were applied to test the stability of the double-layer capacitor. Low and high frequency resistances were measured as a function of the number of cycles. (author) 2 figs., 1 ref.

  2. The impact of carbon prices on generation-cycling costs

    International Nuclear Information System (INIS)

    Denny, Eleanor; O'Malley, Mark

    2009-01-01

    The introduction of mechanisms aimed at reducing greenhouse gas emissions can have a serious impact on electricity system costs. A carbon mechanism that forces generators to internalise their emissions costs may alter the merit order in which generators are dispatched in the market. Heavy carbon dioxide polluters may switch from operating continuously to having to operate on the margin more often. This results in these units being required to switch on and off and vary their output more frequently, which has a significant impact on their costs. In this paper, the impact of carbon prices on the operating profiles of generators in a real electricity system is investigated. A large number of potential scenarios are considered and it is found that carbon prices significantly increase the cycling costs. These increased cycling costs significantly offset the carbon dioxide reduction benefits of the carbon price

  3. Investigators share improved understanding of the North American carbon cycle

    Science.gov (United States)

    Richard A. Birdsey; Robert Cook; Scott Denning; Peter Griffith; Beverly Law; Jeffrey Masek; Anna Michalak; Stephen Ogle; Dennis Ojima; Yude Pan; Christopher Sabine; Edwin Sheffner; Eric Sundquist

    2007-01-01

    The U.S. North American Carbon Program (NACP) sponsored an "all-scientist" meeting to review progress in understanding the dynamics of the carbon cycle of North American and adjacent oceans, and to chart a course for improved integration across scientifi c disciplines, scales, and Earth system boundaries. The meeting participants also addressed the need for...

  4. Carbon cycle observations: gaps threaten climate mitigation policies

    Science.gov (United States)

    Richard Birdsey; Nick Bates; MIke Behrenfeld; Kenneth Davis; Scott C. Doney; Richard Feely; Dennis Hansell; Linda Heath; et al.

    2009-01-01

    Successful management of carbon dioxide (CO2) requires robust and sustained carbon cycle observations. Yet key elements of a national observation network are lacking or at risk. A U.S. National Research Council review of the U.S. Climate Change Science Program earlier this year highlighted the critical need for a U.S. climate observing system to...

  5. Implications of land use change on the national terrestrial carbon budget of Georgia

    Directory of Open Access Journals (Sweden)

    Olofsson Pontus

    2010-09-01

    Full Text Available Abstract Background Globally, the loss of forests now contributes almost 20% of carbon dioxide emissions to the atmosphere. There is an immediate need to reduce the current rates of forest loss, and the associated release of carbon dioxide, but for many areas of the world these rates are largely unknown. The Soviet Union contained a substantial part of the world's forests and the fate of those forests and their effect on carbon dynamics remain unknown for many areas of the former Eastern Bloc. For Georgia, the political and economic transitions following independence in 1991 have been dramatic. In this paper we quantify rates of land use changes and their effect on the terrestrial carbon budget for Georgia. A carbon book-keeping model traces changes in carbon stocks using historical and current rates of land use change. Landsat satellite images acquired circa 1990 and 2000 were analyzed to detect changes in forest cover since 1990. Results The remote sensing analysis showed that a modest forest loss occurred, with approximately 0.8% of the forest cover having disappeared after 1990. Nevertheless, growth of Georgian forests still contribute a current national sink of about 0.3 Tg of carbon per year, which corresponds to 31% of the country anthropogenic carbon emissions. Conclusions We assume that the observed forest loss is mainly a result of illegal logging, but we have not found any evidence of large-scale clear-cutting. Instead local harvesting of timber for household use is likely to be the underlying driver of the observed logging. The Georgian forests are a currently a carbon sink and will remain as such until about 2040 if the current rate of deforestation persists. Forest protection efforts, combined with economic growth, are essential for reducing the rate of deforestation and protecting the carbon sink provided by Georgian forests.

  6. Implications of land use change on the national terrestrial carbon budget of Georgia.

    Science.gov (United States)

    Olofsson, Pontus; Torchinava, Paata; Woodcock, Curtis E; Baccini, Alessandro; Houghton, Richard A; Ozdogan, Mutlu; Zhao, Feng; Yang, Xiaoyuan

    2010-09-13

    Globally, the loss of forests now contributes almost 20% of carbon dioxide emissions to the atmosphere. There is an immediate need to reduce the current rates of forest loss, and the associated release of carbon dioxide, but for many areas of the world these rates are largely unknown. The Soviet Union contained a substantial part of the world's forests and the fate of those forests and their effect on carbon dynamics remain unknown for many areas of the former Eastern Bloc. For Georgia, the political and economic transitions following independence in 1991 have been dramatic. In this paper we quantify rates of land use changes and their effect on the terrestrial carbon budget for Georgia. A carbon book-keeping model traces changes in carbon stocks using historical and current rates of land use change. Landsat satellite images acquired circa 1990 and 2000 were analyzed to detect changes in forest cover since 1990. The remote sensing analysis showed that a modest forest loss occurred, with approximately 0.8% of the forest cover having disappeared after 1990. Nevertheless, growth of Georgian forests still contribute a current national sink of about 0.3 Tg of carbon per year, which corresponds to 31% of the country anthropogenic carbon emissions. We assume that the observed forest loss is mainly a result of illegal logging, but we have not found any evidence of large-scale clear-cutting. Instead local harvesting of timber for household use is likely to be the underlying driver of the observed logging. The Georgian forests are a currently a carbon sink and will remain as such until about 2040 if the current rate of deforestation persists. Forest protection efforts, combined with economic growth, are essential for reducing the rate of deforestation and protecting the carbon sink provided by Georgian forests.

  7. The Phanerozoic diversification of silica-cycling testate amoebae and its possible links to changes in terrestrial ecosystems

    Science.gov (United States)

    Bosak, Tanja; Lara, Enrique; Mitchell, Edward A.D.

    2015-01-01

    The terrestrial cycling of Si is thought to have a large influence on the terrestrial and marine primary production, as well as the coupled biogeochemical cycles of Si and C. Biomineralization of silica is widespread among terrestrial eukaryotes such as plants, soil diatoms, freshwater sponges, silicifying flagellates and testate amoebae. Two major groups of testate (shelled) amoebae, arcellinids and euglyphids, produce their own silica particles to construct shells. The two are unrelated phylogenetically and acquired biomineralizing capabilities independently. Hyalosphenids, a group within arcellinids, are predators of euglyphids. We demonstrate that hyalosphenids can construct shells using silica scales mineralized by the euglyphids. Parsimony analyses of the current hyalosphenid phylogeny indicate that the ability to “steal” euglyphid scales is most likely ancestral in hyalosphenids, implying that euglyphids should be older than hyalosphenids. However, exactly when euglyphids arose is uncertain. Current fossil record contains unambiguous euglyphid fossils that are as old as 50 million years, but older fossils are scarce and difficult to interpret. Poor taxon sampling of euglyphids has also prevented the development of molecular clocks. Here, we present a novel molecular clock reconstruction for arcellinids and consider the uncertainties due to various previously used calibration points. The new molecular clock puts the origin of hyalosphenids in the early Carboniferous (∼370 mya). Notably, this estimate coincides with the widespread colonization of land by Si-accumulating plants, suggesting possible links between the evolution of Arcellinid testate amoebae and the expansion of terrestrial habitats rich in organic matter and bioavailable Si. PMID:26734499

  8. Multimolecular tracers of terrestrial carbon transfer across the pan-Arctic: 14C characteristics of sedimentary carbon components and their environmental controls

    Science.gov (United States)

    Feng, Xiaojuan; Gustafsson, Örjan; Holmes, R. Max; Vonk, Jorien E.; van Dongen, Bart E.; Semiletov, Igor P.; Dudarev, Oleg V.; Yunker, Mark B.; Macdonald, Robie W.; Wacker, Lukas; Montluçon, Daniel B.; Eglinton, Timothy I.

    2015-11-01

    Distinguishing the sources, ages, and fate of various terrestrial organic carbon (OC) pools mobilized from heterogeneous Arctic landscapes is key to assessing climatic impacts on the fluvial release of carbon from permafrost. Through molecular 14C measurements, including novel analyses of suberin- and/or cutin-derived diacids (DAs) and hydroxy fatty acids (FAs), we compared the radiocarbon characteristics of a comprehensive suite of terrestrial markers (including plant wax lipids, cutin, suberin, lignin, and hydroxy phenols) in the sedimentary particles from nine major arctic and subarctic rivers in order to establish a benchmark assessment of the mobilization patterns of terrestrial OC pools across the pan-Arctic. Terrestrial lipids, including suberin-derived longer-chain DAs (C24,26,28), plant wax FAs (C24,26,28), and n-alkanes (C27,29,31), incorporated significant inputs of aged carbon, presumably from deeper soil horizons. Mobilization and translocation of these "old" terrestrial carbon components was dependent on nonlinear processes associated with permafrost distributions. By contrast, shorter-chain (C16,18) DAs and lignin phenols (as well as hydroxy phenols in rivers outside eastern Eurasian Arctic) were much more enriched in 14C, suggesting incorporation of relatively young carbon supplied by runoff processes from recent vegetation debris and surface layers. Furthermore, the radiocarbon content of terrestrial markers is heavily influenced by specific OC sources and degradation status. Overall, multitracer molecular 14C analysis sheds new light on the mobilization of terrestrial OC from arctic watersheds. Our findings of distinct ages for various terrestrial carbon components may aid in elucidating fate of different terrestrial OC pools in the face of increasing arctic permafrost thaw.

  9. Delayed recovery of non-marine tetrapods after the end-Permian mass extinction tracks global carbon cycle

    OpenAIRE

    Irmis, Randall B.; Whiteside, Jessica H.

    2011-01-01

    During the end-Permian mass extinction, marine ecosystems suffered a major drop in diversity, which was maintained throughout the Early Triassic until delayed recovery during the Middle Triassic. This depressed diversity in the Early Triassic correlates with multiple major perturbations to the global carbon cycle, interpreted as either intrinsic ecosystem or external palaeoenvironmental effects. In contrast, the terrestrial record of extinction and recovery is less clear; the effects and magn...

  10. Trailblazing the Carbon Cycle of Tropical Forests from Puerto Rico

    Directory of Open Access Journals (Sweden)

    Sandra Brown

    2017-03-01

    Full Text Available We review the literature that led to clarifying the role of tropical forests in the global carbon cycle from a time when they were considered sources of atmospheric carbon to the time when they were found to be atmospheric carbon sinks. This literature originates from work conducted by US Forest Service scientists in Puerto Rico and their collaborators. It involves the classification of forests by life zones, estimation of carbon density by forest type, assessing carbon storage changes with ecological succession and land use/land cover type, describing the details of the carbon cycle of forests at stand and landscape levels, assessing global land cover by forest type and the complexity of land use change in tropical regions, and assessing the ecological fluxes and storages that contribute to net carbon accumulation in tropical forests. We also review recent work that couples field inventory data, remote sensing technology such as LIDAR, and GIS analysis in order to more accurately determine the role of tropical forests in the global carbon cycle and point out new avenues of carbon research that address the responses of tropical forests to environmental change.

  11. An Analysis of Terrestrial and Aquatic Environmental Controls of Riverine Dissolved Organic Carbon in the Conterminous United States

    Directory of Open Access Journals (Sweden)

    Qichun Yang

    2017-05-01

    Full Text Available Analyses of environmental controls on riverine carbon fluxes are critical for improved understanding of the mechanisms regulating carbon cycling along the terrestrial-aquatic continuum. Here, we compile and analyze riverine dissolved organic carbon (DOC concentration data from 1402 United States Geological Survey (USGS gauge stations to examine the spatial variability and environmental controls of DOC concentrations in the United States (U.S. surface waters. DOC concentrations exhibit high spatial variability in the U.S., with an average of 6.42 ± 6.47 mg C/L (Mean ± Standard Deviation. High DOC concentrations occur in the Upper Mississippi River basin and the southeastern U.S., while low concentrations are mainly distributed in the western U.S. Soil properties such as soil organic matter, soil water content, and soil sand content mainly show positive correlations with DOC concentrations; forest and shrub land have positive correlations with DOC concentrations, but urban area and cropland demonstrate negative impacts; and total instream phosphorus and dam density correlate positively with DOC concentrations. Notably, the relative importance of these environmental controls varies substantially across major U.S. water resource regions. In addition, DOC concentrations and environmental controls also show significant variability from small streams to large rivers. In sum, our results reveal that general multi-linear regression of twenty environmental factors can partially explain (56% the DOC concentration variability. This study also highlights the complexity of the interactions among these environmental factors in determining DOC concentrations, thus calls for processes-based, non-linear methodologies to constrain uncertainties in riverine DOC cycling.

  12. Vulnerability of permafrost carbon to climate change: implications for the global carbon cycle

    Science.gov (United States)

    Edward A.G. Schuur; James Bockheim; Josep G. Canadell; Eugenie Euskirchen; Christopher B. Field; Sergey V. Goryachkin; Stefan Hagemann; Peter Kuhry; Peter M. Lafleur; Hanna Lee; Galina Mazhitova; Frederick E. Nelson; Annette Rinke; Vladimir E. Romanovsky; Nikolay Shiklomanov; Charles Tarnocai; Sergey Venevsky; Jason G. Vogel; Sergei A. Zimov

    2008-01-01

    Thawing permafrost and the resulting microbial decomposition of previously frozen organic carbon (C) is one of the most significant potential feedbacks from terrestrial ecosystems to the atmosphere in a changing climate. In this article we present an overview of the global permafrost C pool and of the processes that might transfer this C into the atmosphere, as well as...

  13. River under anthropogenic stress: An isotope study of carbon cycling in the Vistula, Poland

    International Nuclear Information System (INIS)

    Wachniew, P.; Rozanski, K.

    2002-01-01

    Rivers play an important role in global carbon cycling as they transform and transport substantial amounts of carbon derived from the terrestrial systems to the oceans. Riverine carbon cycling is affected by anthropogenic influences on hydrology, chemistry and biology of the river and its catchment. The Vistula, one of the most mineralized rivers of the world, drains industrialized and agriculturally-used areas populated by almost 23 million inhabitants. Moreover, much of the industrial and domestic wastewaters discharged into the Vistula river are untreated or insufficiently treated. High levels of pollution have serious environmental and economical consequences. For example, they limit use of Vistula waters as a source of drinking water and for industrial purposes. Pollutants transported by the Vistula river significantly influence water quality far into the open Baltic Sea. The aim of the paper is to show how stable isotope techniques can be used to assess human impact on sources, fluxes and fate of dissolved inorganic carbon (DIC) and other pollutants in rivers, taking the Vistula river as an example. Vistula waters were sampled over a one-year period at Krakow (upper reaches), where the anthropogenic influences are at the extreme, and at the river mouth. Two campaigns were undertaken to sample the Vistula river along its course in summer and in autumn. Analyses of river water included temperature, pH, alkalinity, conductivity, dissolved oxygen, δ 13 C of dissolved inorganic carbon and stable isotope composition of water (δ 18 O and δ 2 H)

  14. Ectomycorrhizal fungi slow soil carbon cycling.

    Science.gov (United States)

    Averill, Colin; Hawkes, Christine V

    2016-08-01

    Respiration of soil organic carbon is one of the largest fluxes of CO2 on earth. Understanding the processes that regulate soil respiration is critical for predicting future climate. Recent work has suggested that soil carbon respiration may be reduced by competition for nitrogen between symbiotic ectomycorrhizal fungi that associate with plant roots and free-living microbial decomposers, which is consistent with increased soil carbon storage in ectomycorrhizal ecosystems globally. However, experimental tests of the mycorrhizal competition hypothesis are lacking. Here we show that ectomycorrhizal roots and hyphae decrease soil carbon respiration rates by up to 67% under field conditions in two separate field exclusion experiments, and this likely occurs via competition for soil nitrogen, an effect larger than 2 °C soil warming. These findings support mycorrhizal competition for nitrogen as an independent driver of soil carbon balance and demonstrate the need to understand microbial community interactions to predict ecosystem feedbacks to global climate. © 2016 John Wiley & Sons Ltd/CNRS.

  15. Effect of antecedent terrestrial land-use on C and N cycling in created wetlands

    Science.gov (United States)

    McCalley, C. K.; Al Graiti, T.; Williams, T.; Huang, S.; McGowan, M. B.; Eddingsaas, N. C.; Tyler, A. C.

    2017-12-01

    Land-use legacies and their interaction with both management actions and climate variability has a poorly characterized impact on the development of ecosystem functions and the trajectory of climate-carbon feedbacks. The complex structure-function relationships in wetlands foster delivery of valuable, climate sensitive, ecosystem services (carbon sequestration, nutrient removal, flood control, etc.) but also make them susceptible to colonization by invasive plants and lead to emission of key greenhouse gases. This project uses created wetland ecosystems as a model to understand how heterogeneity in antecedent conditions interacts with management options to create unique structure-function scenarios and a range of climate feedback outcomes. We utilized ongoing experiments in created wetlands that differ in antecedent conditions (crop agriculture, livestock grazing) and investigated how management options (invasive species removal, organic matter addition) interact with legacy impacts to promote key ecosystem functions, including greenhouse gas emissions, carbon sequestration, denitrification and plant biodiversity. The effects of antecedent land-use on soil chemistry, coupled with hydrologic patterns resulted in wetlands with divergent C and N dynamics despite their similar creation history. Additionally, the occurrence of extreme weather events (drought and excessive flooding) during the study period highlighted the overarching role that increased climate variability will play in determining key ecosystem processes in wetlands. Responses to management were linked to hydro-period: while organic matter addition successfully increased soil organic matter to more closely replicate natural systems at all sites, it had the largest impact on C and N cycling when soils were saturated. Overall, environmental conditions that promoted saturated soils, both those shaped by human activities or climate extremes, enhanced primary productivity, nutrient removal and greenhouse gas

  16. Role of the seasonal cycle in coupling climate and carbon cycling in subanartic zone

    CSIR Research Space (South Africa)

    Monteiro, PMS

    2010-08-01

    Full Text Available There is increasing evidence in the Southern Ocean that mesoscales and seasonal scales play an important role in the coupling of ocean carbon cycling and climate. The seasonal cycle is one of the strongest modes of variability in different...

  17. Carbon Cycling and Biosequestration Integrating Biology and Climate Through Systems Science Report from the March 2008 Workshop

    Energy Technology Data Exchange (ETDEWEB)

    Graber, J.; Amthor, J.; Dahlman, R.; Drell, D.; Weatherwax, S.

    2008-12-01

    One of the most daunting challenges facing science in the 21st Century is to predict how Earth's ecosystems will respond to global climate change. The global carbon cycle plays a central role in regulating atmospheric carbon dioxide (CO{sub 2}) levels and thus Earth's climate, but our basic understanding of the myriad of tightly interlinked biological processes that drive the global carbon cycle remains limited at best. Whether terrestrial and ocean ecosystems will capture, store, or release carbon is highly dependent on how changing climate conditions affect processes performed by the organisms that form Earth's biosphere. Advancing our knowledge of biological components of the global carbon cycle is thus crucial to predicting potential climate change impacts, assessing the viability of climate change adaptation and mitigation strategies, and informing relevant policy decisions. Global carbon cycling is dominated by the paired biological processes of photosynthesis and respiration. Photosynthetic plants and microbes of Earth's land-masses and oceans use solar energy to transform atmospheric CO{sub 2} into organic carbon. The majority of this organic carbon is rapidly consumed by plants or microbial decomposers for respiration and returned to the atmosphere as CO{sub 2}. Coupling between the two processes results in a near equilibrium between photosynthesis and respiration at the global scale, but some fraction of organic carbon also remains in stabilized forms such as biomass, soil, and deep ocean sediments. This process, known as carbon biosequestration, temporarily removes carbon from active cycling and has thus far absorbed a substantial fraction of anthropogenic carbon emissions.

  18. Simulated Carbon Cycling in a Model Microbial Mat.

    Science.gov (United States)

    Decker, K. L.; Potter, C. S.

    2006-12-01

    We present here the novel addition of detailed organic carbon cycling to our model of a hypersaline microbial mat ecosystem. This ecosystem model, MBGC (Microbial BioGeoChemistry), simulates carbon fixation through oxygenic and anoxygenic photosynthesis, and the release of C and electrons for microbial heterotrophs via cyanobacterial exudates and also via a pool of dead cells. Previously in MBGC, the organic portion of the carbon cycle was simplified into a black-box rate of accumulation of simple and complex organic compounds based on photosynthesis and mortality rates. We will discuss the novel inclusion of fermentation as a source of carbon and electrons for use in methanogenesis and sulfate reduction, and the influence of photorespiration on labile carbon exudation rates in cyanobacteria. We will also discuss the modeling of decomposition of dead cells and the ultimate release of inorganic carbon. The detailed modeling of organic carbon cycling is important to the accurate representation of inorganic carbon flux through the mat, as well as to accurate representation of growth models of the heterotrophs under different environmental conditions. Because the model ecosystem is an analog of ancient microbial mats that had huge impacts on the atmosphere of early earth, this MBGC can be useful as a biological component to either early earth models or models of other planets that potentially harbor life.

  19. Contribution of fish to the marine inorganic carbon cycle.

    Science.gov (United States)

    Wilson, R W; Millero, F J; Taylor, J R; Walsh, P J; Christensen, V; Jennings, S; Grosell, M

    2009-01-16

    Oceanic production of calcium carbonate is conventionally attributed to marine plankton (coccolithophores and foraminifera). Here we report that marine fish produce precipitated carbonates within their intestines and excrete these at high rates. When combined with estimates of global fish biomass, this suggests that marine fish contribute 3 to 15% of total oceanic carbonate production. Fish carbonates have a higher magnesium content and solubility than traditional sources, yielding faster dissolution with depth. This may explain up to a quarter of the increase in titratable alkalinity within 1000 meters of the ocean surface, a controversial phenomenon that has puzzled oceanographers for decades. We also predict that fish carbonate production may rise in response to future environmental changes in carbon dioxide, and thus become an increasingly important component of the inorganic carbon cycle.

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

    Science.gov (United States)

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

    2014-05-01

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

  1. Optimization of Terrestrial Ecosystem Model Parameters Using Atmospheric CO2 Concentration Data With the Global Carbon Assimilation System (GCAS)

    Science.gov (United States)

    Chen, Zhuoqi; Chen, Jing M.; Zhang, Shupeng; Zheng, Xiaogu; Ju, Weiming; Mo, Gang; Lu, Xiaoliang

    2017-12-01

    The Global Carbon Assimilation System that assimilates ground-based atmospheric CO2 data is used to estimate several key parameters in a terrestrial ecosystem model for the purpose of improving carbon cycle simulation. The optimized parameters are the leaf maximum carboxylation rate at 25°C (Vmax25), the temperature sensitivity of ecosystem respiration (Q10), and the soil carbon pool size. The optimization is performed at the global scale at 1° resolution for the period from 2002 to 2008. The results indicate that vegetation from tropical zones has lower Vmax25 values than vegetation in temperate regions. Relatively high values of Q10 are derived over high/midlatitude regions. Both Vmax25 and Q10 exhibit pronounced seasonal variations at middle-high latitudes. The maxima in Vmax25 occur during growing seasons, while the minima appear during nongrowing seasons. Q10 values decrease with increasing temperature. The seasonal variabilities of Vmax25 and Q10 are larger at higher latitudes. Optimized Vmax25 and Q10 show little seasonal variabilities at tropical regions. The seasonal variabilities of Vmax25 are consistent with the variabilities of LAI for evergreen conifers and broadleaf evergreen forests. Variations in leaf nitrogen and leaf chlorophyll contents may partly explain the variations in Vmax25. The spatial distribution of the total soil carbon pool size after optimization is compared favorably with the gridded Global Soil Data Set for Earth System. The results also suggest that atmospheric CO2 data are a source of information that can be tapped to gain spatially and temporally meaningful information for key ecosystem parameters that are representative at the regional and global scales.

  2. Carbon-isotope stratigraphy from terrestrial organic matter through the Monterey event, Miocene, New Jersey margin (IODP Expedition 313)

    DEFF Research Database (Denmark)

    Fang, Linhao; Bjerrum, Christian J.; Hesselbo, Stephen P.

    2013-01-01

    documented from oceanic settings (i.e., lack of positive excursion of carbon-isotope values in terrestrial organic matter through the Langhian Stage). Factors that may potentially bias local terrestrial carbon-isotope records include reworking from older deposits, degradation and diagenesis, as well....../or reworking of older woody phytoclasts, but where such processes have occurred they do not readily explain the observed carbon-isotope values. It is concluded that the overall carbon-isotope signature for the exchangeable carbon reservoir is distorted, to the extent that the Monterey event excursion...... is not easily identifiable. The most likely explanation is that phytoclast reworking has indeed occurred in clinoform toe-of-slope facies, but the reason for the resulting relatively heavy carbon-isotope values in the Burdigalian remains obscure....

  3. 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

    Science.gov (United States)

    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

  4. Deciphering Complex Carbon Cycle Changes Across the K-Pg Boundary Using Compound-Specific Carbon Isotopic Analyses

    Science.gov (United States)

    Pancost, R. D.; Taylor, K. W.; Hollis, C. J.; Crouch, E. M.

    2014-12-01

    The consequences of the Cretaceous-Paleogene (K/Pg) boundary event on the Earth system have been the subject of much scrutiny. Postulated climate events include a brief (10 - 2000 yr) period of global cooling induced by sulphate aerosols (the so-called 'impact winter'), an interval of warming caused by impact-induced CO2release, as well as longer-term climatic oscillations during the subsequent 1 to 3Myr. Associated with these were putative changes in the biogeochemical cycle, manifested as carbon isotope excursions on both short- and long-term timescales. In this study we develop new biomarker-based climate and biogeochemical records for the mid-Waipara River and Branch Stream sections, NZ. At Branch Stream, a pronounced negative (ca 6 to 8 permil) carbon isotope excursion occurs at the K/Pg; the excursion is recorded by higher plant biomarkers, consistent with some terrestrial records and suggesting that the immediate aftermath of the K/Pg boundary event was characterised by the massive release of 13C-depleted reduced carbon into the ocean-atmosphere reservoir. Mixing across the K/Pg boundary at the Waipara section precludes a similar high-resolution investigation. Lower-resolution, longer-term records, however, also reveal a negative carbon istope excursion documented by both algal and higher plant biomarkers. This event appears to be distinct from that recorded at Branch Stream, being of lower magnitude and longer duration. It coincided with a transient terrestrial and marine warming and appears to have lasted at least 100 kyr and perhaps longer. We argue that this protracted negative CIE reflects a secondary and longer-term consequence of the K/Pg on the global carbon cycle. There is little evidence for an algal extinction as a range of C27 to C30 sterols continued to be deposited throughout the entire section, but changes in GDGT distributions do suggest a change in carbon export dynamics which could have impacted burial of 13C-depleted marine organic matter

  5. Final Technical Report: Fundamental Research on the Fractionation of Carbon Isotopes during Photosynthesis, New Interpretations of Terrestrial Organic Carbon within Geologic Substrates

    Energy Technology Data Exchange (ETDEWEB)

    Schubert, Brian [Univ. of Louisiana, Lafayette (United States); Jahren, A. Hope [Univ. of Louisiana, Lafayette (United States)

    2017-11-30

    The goal for the current grant period (2013 – 2016) was to quantify the effect of changing atmospheric carbon dioxide concentration (pCO2) on published terrestrial carbon isotope excursion events. This work supported four scientists across multiple career stages, and resulted in 5 published papers.

  6. Final Report: Fundamental Research on the Fractionation of Carbon Isotopes during Photosynthesis, New Interpretations of Terrestrial Organic Carbon within Geologic Substrates

    Energy Technology Data Exchange (ETDEWEB)

    Jahren, A. Hope [Univ. of Hawaii, Honolulu, HI (United States); Schubert, Brian A. [Univ. of Louisiana, Lafayette, LA (United States)

    2017-08-02

    The goal for the current grant period (2013 – 2016) was to quantify the effect of changing atmospheric carbon dioxide concentration (pCO2) on published terrestrial carbon isotope excursion events. This work supported four scientists across multiple career stages, and resulted in 5 published papers.

  7. Advanced Supercritical Carbon Dioxide Brayton Cycle Development

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Mark [Univ. of Wisconsin, Madison, WI (United States); Sienicki, James [Argonne National Lab. (ANL), Argonne, IL (United States); Moisseytsev, Anton [Argonne National Lab. (ANL), Argonne, IL (United States); Nellis, Gregory [Univ. of Wisconsin, Madison, WI (United States); Klein, Sanford [Univ. of Wisconsin, Madison, WI (United States)

    2015-10-21

    Fluids operating in the supercritical state have promising characteristics for future high efficiency power cycles. In order to develop power cycles using supercritical fluids, it is necessary to understand the flow characteristics of fluids under both supercritical and two-phase conditions. In this study, a Computational Fluid Dynamic (CFD) methodology was developed for supercritical fluids flowing through complex geometries. A real fluid property module was implemented to provide properties for different supercritical fluids. However, in each simulation case, there is only one species of fluid. As a result, the fluid property module provides properties for either supercritical CO2 (S-CO2) or supercritical water (SCW). The Homogeneous Equilibrium Model (HEM) was employed to model the two-phase flow. HEM assumes two phases have same velocity, pressure, and temperature, making it only applicable for the dilute dispersed two-phase flow situation. Three example geometries, including orifices, labyrinth seals, and valves, were used to validate this methodology with experimental data. For the first geometry, S-CO2 and SCW flowing through orifices were simulated and compared with experimental data. The maximum difference between the mass flow rate predictions and experimental measurements is less than 5%. This is a significant improvement as previous works can only guarantee 10% error. In this research, several efforts were made to help this improvement. First, an accurate real fluid module was used to provide properties. Second, the upstream condition was determined by pressure and density, which determines supercritical states more precise than using pressure and temperature. For the second geometry, the flow through labyrinth seals was studied. After a successful validation, parametric studies were performed to study geometric effects on the leakage rate. Based on these parametric studies, an optimum design strategy for the see

  8. Distinguishing Terrestrial Organic Carbon in Marginal Sediments of East China Sea and Northern South China Sea

    Science.gov (United States)

    Kandasamy, Selvaraj; Lin, Baozhi; Wang, Huawei; Liu, Qianqian; Liu, Zhifei; Lou, Jiann-Yuh; Chen, Chen-Tung Arthur; Mayer, Lawrence M.

    2016-04-01

    Knowledge about the sources, transport pathways and behavior of terrestrial organic carbon in continental margins adjoining to large rivers has improved in recent decades, but uncertainties and complications still exist with human-influenced coastal regions in densely populated wet tropics and subtropics. In these regions, the monsoon and other episodic weather events exert strong climatic control on mineral and particulate organic matter delivery to the marginal seas. Here we investigate elemental (TOC, TN and bromine-Br) and stable carbon isotopic (δ13C) compositions of organic matter (OM) in surface sediments and short cores collected from active (SW Taiwan) and passive margin (East China Sea) settings to understand the sources of OM that buried in these settings. We used sedimentary bromine to total organic carbon (Br/TOC) ratios to apportion terrigenous from marine organic matter, and find that Br/TOC may serve as an additional, reliable proxy for sedimentary provenance in both settings. Variations in Br/TOC are consistent with other provenance indicators in responding to short-lived terrigenous inputs. Because diagenetic alteration of Br is insignificant on shorter time scales, applying Br/TOC ratios as a proxy to identify organic matter source along with carbon isotope mixing models may provide additional constraints on the quantity and transformation of terrigenous organics in continental margins. We apply this combination of approaches to land-derived organic matter in different depositional environments of East Asian marginal seas.

  9. Carbon cycling and gas exchange in soils

    International Nuclear Information System (INIS)

    Trumbore, S.E.

    1989-01-01

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

  10. The sensitivity of terrestrial carbon storage to historical climate variability and atmospheric CO2 in the United States

    Science.gov (United States)

    Tian, H.; Melillo, J. M.; Kicklighter, D. W.; McGuire, A. D.; Helfrich, J.

    1999-04-01

    We use the Terrestrial Ecosystem Model (TEM, Version 4.1) and the land cover data set of the international geosphere biosphere program to investigate how increasing atmospheric CO2 concentration and climate variability during 1900 1994 affect the carbon storage of terrestrial ecosystems in the conterminous USA, and how carbon storage has been affected by land-use change. The estimates of TEM indicate that over the past 95years a combination of increasing atmospheric CO2 with historical temperature and precipitation variability causes a 4.2% (4.3Pg C) decrease in total carbon storage of potential vegetation in the conterminous US, with vegetation carbon decreasing by 7.2% (3.2Pg C) and soil organic carbon decreasing by 1.9% (1.1Pg C). Several dry periods including the 1930s and 1950s are responsible for the loss of carbon storage. Our factorial experiments indicate that precipitation variability alone decreases total carbon storage by 9.5%. Temperature variability alone does not significantly affect carbon storage. The effect of CO2 fertilization alone increases total carbon storage by 4.4%. The effects of increasing atmospheric CO2 and climate variability are not additive. Interactions among CO2, temperature and precipitation increase total carbon storage by 1.1%. Our study also shows substantial year-to-year variations in net carbon exchange between the atmosphere and terrestrial ecosystems due to climate variability. Since the 1960s, we estimate these terrestrial ecosystems have acted primarily as a sink of atmospheric CO2 as a result of wetter weather and higher atmospheric CO2 concentrations. For the 1980s, we estimate the natural terrestrial ecosystems, excluding cropland and urban areas, of the conterminous US have accumulated 78.2 Tg C yr1 because of the combined effect of increasing atmospheric CO2 and climate variability. For the conterminous US, we estimate that the conversion of natural ecosystems to cropland and urban areas has caused a 18.2% (17.7Pg C

  11. On the linkages between the global carbon-nitrogen-phosphorus cycles

    Science.gov (United States)

    Tanaka, Katsumasa; Mackenzie, Fred; Bouchez, Julien; Knutti, Reto

    2013-04-01

    State-of-the-art earth system models used for long-term climate projections are becoming ever more complex in terms of not only spatial resolution but also the number of processes. Biogeochemical processes are beginning to be incorporated into these models. The motivation of this study is to quantify how climate projections are influenced by biogeochemical feedbacks. In the climate modeling community, it is virtually accepted that climate-Carbon (C) cycle feedbacks accelerate the future warming (Cox et al. 2000; Friedlingstein et al. 2006). It has been demonstrated that the Nitrogen (N) cycle suppresses climate-C cycle feedbacks (Thornton et al. 2009). On the contrary, biogeochemical studies show that the coupled C-N-Phosphorus (P) cycles are intimately interlinked via biosphere and the N-P cycles amplify C cycle feedbacks (Ver et al. 1999). The question as to whether the N-P cycles enhance or attenuate C cycle feedbacks is debated and has a significant implication for projections of future climate. We delve into this problem by using the Terrestrial-Ocean-aTmosphere Ecosystem Model 3 (TOTEM3), a globally-aggregated C-N-P cycle box model. TOTEM3 is a process-based model that describes the biogeochemical reactions and physical transports involving these elements in the four domains of the Earth system: land, atmosphere, coastal ocean, and open ocean. TOTEM3 is a successor of earlier TOTEM models (Ver et al. 1999; Mackenzie et al. 2011). In our presentation, we provide an overview of fundamental features and behaviors of TOTEM3 such as the mass balance at the steady state and the relaxation time scales to various types of perturbation. We also show preliminary results to investigate how the N-P cycles influence the behavior of the C cycle. References Cox PM, Betts RA, Jones CD, Spall SA, Totterdell IJ (2000) Acceleration of global warming due to carbon-cycle feedbacks in a coupled climate model. Nature, 408, 184-187. Friedlingstein P, Cox P, Betts R, Bopp L, von Bloh

  12. Past and present of sediment and carbon biogeochemical cycling models

    Directory of Open Access Journals (Sweden)

    F. T. Mackenzie

    2004-01-01

    Full Text Available The global carbon cycle is part of the much more extensive sedimentary cycle that involves large masses of carbon in the Earth's inner and outer spheres. Studies of the carbon cycle generally followed a progression in knowledge of the natural biological, then chemical, and finally geological processes involved, culminating in a more or less integrated picture of the biogeochemical carbon cycle by the 1920s. However, knowledge of the ocean's carbon cycle behavior has only within the last few decades progressed to a stage where meaningful discussion of carbon processes on an annual to millennial time scale can take place. In geologically older and pre-industrial time, the ocean was generally a net source of CO2 emissions to the atmosphere owing to the mineralization of land-derived organic matter in addition to that produced in situ and to the process of CaCO3 precipitation. Due to rising atmospheric CO2 concentrations because of fossil fuel combustion and land use changes, the direction of the air-sea CO2 flux has reversed, leading to the ocean as a whole being a net sink of anthropogenic CO2. The present thickness of the surface ocean layer, where part of the anthropogenic CO2 emissions are stored, is estimated as of the order of a few hundred meters. The oceanic coastal zone net air-sea CO2 exchange flux has also probably changed during industrial time. Model projections indicate that in pre-industrial times, the coastal zone may have been net heterotrophic, releasing CO2 to the atmosphere from the imbalance between gross photosynthesis and total respiration. This, coupled with extensive CaCO3 precipitation in coastal zone environments, led to a net flux of CO2 out of the system. During industrial time the coastal zone ocean has tended to reverse its trophic status toward a non-steady state situation of net autotrophy, resulting in net uptake of anthropogenic CO2 and storage of carbon in the coastal ocean, despite the significant calcification

  13. Opportunities and Challenges for Terrestrial Carbon Offsetting and Marketing, with Some Implications for Forestry in the UK

    Directory of Open Access Journals (Sweden)

    Maria Nijnik

    2010-12-01

    Full Text Available Background and Purpose: Climate change and its mitigation have become increasingly high profile issues since the late 1990s, with the potential of forestry in carbon sequestration a particular focus. The purpose of this paper is to outline the importance of socio-economic considerations in this area. Opportunities for forestry to sequester carbon and the role of terrestrial carbon uptake credits in climate change negotiations are addressed, together with the feasibility of bringing terrestrial carbon offsets into the regulatory emission trading scheme. The paper discusses whether or not significant carbon offsetting and trading will occur on a large scale in the UK or internationally. Material and Methods: The paper reviews the literature on the socio-economic aspects of climate change mitigation via forestry (including the authors’ research on this topic to assess the potential for carbon offsetting and trading, and the likely scale of action. Results and Conclusion: We conclude that the development of appropriate socio-economic framework conditions (e.g. policies, tenure rights, including forest carbon ownership, and markets and incentives for creating and trading terrestrial carbon credits are important in mitigating climate change through forestry projects, and we make suggestions for future research that would be required to support such developments.

  14. A model using marginal efficiency of investment to analyse carbon and nitrogen interactions in terrestrial ecosystems (ACONITE Version 1)

    Science.gov (United States)

    Thomas, R. Q.; Williams, M.

    2014-04-01

    Carbon (C) and nitrogen (N) cycles are coupled in terrestrial ecosystems through multiple processes including photosynthesis, tissue allocation, respiration, N fixation, N uptake, and decomposition of litter and soil organic matter. Capturing the constraint of N on terrestrial C uptake and storage has been a focus of the Earth System modelling community. However there is little understanding of the trade-offs and sensitivities of allocating C and N to different tissues in order to optimize the productivity of plants. Here we describe a new, simple model of ecosystem C-N cycling and interactions (ACONITE), that builds on theory related to plant economics in order to predict key ecosystem properties (leaf area index, leaf C : N, N fixation, and plant C use efficiency) using emergent constraints provided by marginal returns on investment for C and/or N allocation. We simulated and evaluated steady-state ecosystem stocks and fluxes in three different forest ecosystems types (tropical evergreen, temperate deciduous, and temperate evergreen). Leaf C : N differed among the three ecosystem types (temperate deciduous database describing plant traits. Gross primary productivity (GPP) and net primary productivity (NPP) estimates compared well to observed fluxes at the simulation sites. Simulated N fixation at steady-state, calculated based on relative demand for N and the marginal return on C investment to acquire N, was an order of magnitude higher in the tropical forest than in the temperate forest, consistent with observations. A sensitivity analysis revealed that parameterization of the relationship between leaf N and leaf respiration had the largest influence on leaf area index and leaf C : N. Also, a widely used linear leaf N-respiration relationship did not yield a realistic leaf C : N, while a more recently reported non-linear relationship performed better. A parameter governing how photosynthesis scales with day length had the largest influence on total vegetation C

  15. A model using marginal efficiency of investment to analyze carbon and nitrogen interactions in terrestrial ecosystems (ACONITE Version 1)

    Science.gov (United States)

    Thomas, R. Q.; Williams, M.

    2014-09-01

    Carbon (C) and nitrogen (N) cycles are coupled in terrestrial ecosystems through multiple processes including photosynthesis, tissue allocation, respiration, N fixation, N uptake, and decomposition of litter and soil organic matter. Capturing the constraint of N on terrestrial C uptake and storage has been a focus of the Earth System Modeling community. However, there is little understanding of the trade-offs and sensitivities of allocating C and N to different tissues in order to optimize the productivity of plants. Here we describe a new, simple model of ecosystem C-N cycling and interactions (ACONITE), that builds on theory related to plant economics in order to predict key ecosystem properties (leaf area index, leaf C : N, N fixation, and plant C use efficiency) based on the outcome of assessments of the marginal change in net C or N uptake associated with a change in allocation of C or N to plant tissues. We simulated and evaluated steady-state ecosystem stocks and fluxes in three different forest ecosystems types (tropical evergreen, temperate deciduous, and temperate evergreen). Leaf C : N differed among the three ecosystem types (temperate deciduous database describing plant traits. Gross primary productivity (GPP) and net primary productivity (NPP) estimates compared well to observed fluxes at the simulation sites. Simulated N fixation at steady-state, calculated based on relative demand for N and the marginal return on C investment to acquire N, was an order of magnitude higher in the tropical forest than in the temperate forest, consistent with observations. A sensitivity analysis revealed that parameterization of the relationship between leaf N and leaf respiration had the largest influence on leaf area index and leaf C : N. A parameter governing how photosynthesis scales with day length had the largest influence on total vegetation C, GPP, and NPP. Multiple parameters associated with photosynthesis, respiration, and N uptake influenced the rate of N

  16. Sources and mobility of carbonate melts beneath cratons, with implications for deep carbon cycling, metasomatism and rift initiation

    Science.gov (United States)

    Tappe, Sebastian; Romer, Rolf L.; Stracke, Andreas; Steenfelt, Agnete; Smart, Katie A.; Muehlenbachs, Karlis; Torsvik, Trond H.

    2017-05-01

    Kimberlite and carbonatite magmas that intrude cratonic lithosphere are among the deepest probes of the terrestrial carbon cycle. Their co-existence on thick continental shields is commonly attributed to continuous partial melting sequences of carbonated peridotite at >150 km depths, possibly as deep as the mantle transition zone. At Tikiusaaq on the North Atlantic craton in West Greenland, approximately 160 Ma old ultrafresh kimberlite dykes and carbonatite sheets provide a rare opportunity to study the origin and evolution of carbonate-rich melts beneath cratons. Although their Sr-Nd-Hf-Pb-Li isotopic compositions suggest a common convecting upper mantle source that includes depleted and recycled oceanic crust components (e.g., negative ΔεHf coupled with > + 5 ‰ δ7Li), incompatible trace element modelling identifies only the kimberlites as near-primary low-degree partial melts (0.05-3%) of carbonated peridotite. In contrast, the trace element systematics of the carbonatites are difficult to reproduce by partial melting of carbonated peridotite, and the heavy carbon isotopic signatures (-3.6 to - 2.4 ‰ δ13C for carbonatites versus -5.7 to - 3.6 ‰ δ13C for kimberlites) require open-system fractionation at magmatic temperatures. Given that the oxidation state of Earth's mantle at >150 km depth is too reduced to enable larger volumes of 'pure' carbonate melt to migrate, it is reasonable to speculate that percolating near-solidus melts of carbonated peridotite must be silicate-dominated with only dilute carbonate contents, similar to the Tikiusaaq kimberlite compositions (e.g., 16-33 wt.% SiO2). This concept is supported by our findings from the North Atlantic craton where kimberlite and other deeply derived carbonated silicate melts, such as aillikites, exsolve their carbonate components within the shallow lithosphere en route to the Earth's surface, thereby producing carbonatite magmas. The relative abundances of trace elements of such highly

  17. Nutrient limitation reduces land carbon uptake in simulations with a model of combined carbon, nitrogen and phosphorus cycling

    Directory of Open Access Journals (Sweden)

    D. S. Goll

    2012-09-01

    Full Text Available Terrestrial carbon (C cycle models applied for climate projections simulate a strong increase in net primary productivity (NPP due to elevated atmospheric CO2 concentration during the 21st century. These models usually neglect the limited availability of nitrogen (N and phosphorus (P, nutrients that commonly limit plant growth and soil carbon turnover. To investigate how the projected C sequestration is altered when stoichiometric constraints on C cycling are considered, we incorporated a P cycle into the land surface model JSBACH (Jena Scheme for Biosphere–Atmosphere Coupling in Hamburg, which already includes representations of coupled C and N cycles.

    The model reveals a distinct geographic pattern of P and N limitation. Under the SRES (Special Report on Emissions Scenarios A1B scenario, the accumulated land C uptake between 1860 and 2100 is 13% (particularly at high latitudes and 16% (particularly at low latitudes lower in simulations with N and P cycling, respectively, than in simulations without nutrient cycles. The combined effect of both nutrients reduces land C uptake by 25% compared to simulations without N or P cycling. Nutrient limitation in general may be biased by the model simplicity, but the ranking of limitations is robust against the parameterization and the inflexibility of stoichiometry. After 2100, increased temperature and high CO2 concentration cause a shift from N to P limitation at high latitudes, while nutrient limitation in the tropics declines. The increase in P limitation at high-latitudes is induced by a strong increase in NPP and the low P sorption capacity of soils, while a decline in tropical NPP due to high autotrophic respiration rates alleviates N and P limitations. The quantification of P limitation remains challenging. The poorly constrained processes of soil P sorption and biochemical mineralization are identified as the main uncertainties in the strength of P limitation

  18. Continental Scale research of the coupled carbon and water cycles in Australia

    Science.gov (United States)

    Cleugh, Helen; van Gorsel, Eva; Held, Alex; Huete, Alfredo; Karan, Mirko; Liddell, Michael; Phinn, Stuart; Prentice, Colin

    2013-04-01

    It is essential to understand the drivers and processes that regulate uptake and release of carbon and water by the terrestrial biosphere to quantify the sink and source strengths under current climatic conditions. In addition, understanding the consequences of a changing climate on the capacity of the biosphere to sequester carbon by using a certain amount of water and the impacts of disturbances on resilience and thresholds of the terrestrial biosphere is critical. Recently there has been increasing general interest in how human activities may be affecting Australia's natural carbon cycles. Quantification of carbon and water exchanges requires process understanding over long temporal and large spatial scales, but at fine levels of detail. This requires integration of long term, high frequency observations, models and information from process studies and can only be achieved through research infrastructure that can provide easy access to meta-data and data that have been collected in a systematic and standardized way. The Australian Terrestrial Ecosystem Research Network (TERN) provides such nationally networked infrastructure, along with multi-disciplinary capabilities and end-user-focused products to deliver better ways of measuring and estimating Australia's current and future environmental carbon stocks and flows. Multiple Facilities in TERN are studying carbon and water dynamics across a range of distance and time scales. OzFlux, the Australasian arm of the global initiative Fluxnet, is the most obvious deployment of field hardware in TERN with close to 30 flux towers and their associated micrometeorological instrumentation in place around the country, from Central Australia to the Alps, covering ecosystems ranging from rainforest to alpine grasslands to mulga. Intensive monitoring is carried out at the 10 TERN Supersites which carry a suite of environmental instrumentation and perform standardised vegetation, faunal, soil and water monitoring.TERN Aus

  19. Soil Functional Mapping: A Geospatial Framework for Scaling Soil Carbon Cycling

    Science.gov (United States)

    Lawrence, C. R.

    2017-12-01

    Climate change is dramatically altering biogeochemical cycles in most terrestrial ecosystems, particularly the cycles of water and carbon (C). These changes will affect myriad ecosystem processes of importance, including plant productivity, C exports to aquatic systems, and terrestrial C storage. Soil C storage represents a critical feedback to climate change as soils store more C than the atmosphere and aboveground plant biomass combined. While we know plant and soil C cycling are strongly coupled with soil moisture, substantial unknowns remain regarding how these relationships can be scaled up from soil profiles to ecosystems. This greatly limits our ability to build a process-based understanding of the controls on and consequences of climate change at regional scales. In an effort to address this limitation we: (1) describe an approach to classifying soils that is based on underlying differences in soil functional characteristics and (2) examine the utility of this approach as a scaling tool that honors the underlying soil processes. First, geospatial datasets are analyzed in the context of our current understanding of soil C and water cycling in order to predict soil functional units that can be mapped at the scale of ecosystems or watersheds. Next, the integrity of each soil functional unit is evaluated using available soil C data and mapping units are refined as needed. Finally, targeted sampling is conducted to further differentiate functional units or fill in any data gaps that are identified. Completion of this workflow provides new geospatial datasets that are based on specific soil functions, in this case the coupling of soil C and water cycling, and are well suited for integration with regional-scale soil models. Preliminary results from this effort highlight the advantages of a scaling approach that balances theory, measurement, and modeling.

  20. SONNE: Solar-Based Man-Made Carbon Cycle and the Carbon Dioxide Economy

    Energy Technology Data Exchange (ETDEWEB)

    Moeller, Detlev [Brandenburg Technical Univ., Berlin (Germany)], e-mail: moe@btu-lc.fta-berlin.de

    2012-06-15

    Humans became a global force in the chemical evolution with respect to climate change by interrupting naturally evolved biogeochemical cycles. However, humans also have all the facilities to turn the 'chemical revolution' into a sustainable chemical evolution. I define a sustainable society as one able to balance the environment, other life forms, and human interactions over an indefinite time period. There is much discussion on 'sustainable chemistry' (often called green chemistry), but, in my understanding, the basic principle, is to transfer matter for energetic and material use only within global cycles, without changing reservoir concentrations above a critical level. With respect to atmospheric pollution, the last unsolved issues (remaining pollutants) are 'greenhouse' gases, namely CO{sub 2}, which contributes to about 70 % of anthropogenically caused global warming (other important gases such as CH{sub 4} and N{sub 2}O contribute to roughly 25 % of warming; these gases are associated mainly with agricultural activities). The dilemma is given simply by time scales: limits of the 2 deg threshold by 2050 and drastic reduction in global CO{sub 2} emission; that is, the cumulative CO{sub 2} emissions determine atmospheric (and oceanic) CO{sub 2} levels. Because of the large CO{sub 2} residence time in natural reservoirs, in the order of 1000 years in the atmosphere and about 200 000 years for dissolved inorganic carbon-DIC in surface seawater, humans now determine the still unknown relationships of possible climate recovery, irreversible climate change, and future abatement strategies. (Solomon et al. 2009). The percentage not accumulated in the atmosphere must have been taken up by the ocean and terrestrial biosphere as well. Mining and the combustion of fossils fuels now results in the geological reservoir redistribution of carbon close to (or even surpassing) the 'tipping point'. It is assumed that in the near future

  1. Exploring diurnal and seasonal characteristics of global carbon cycle with GISS Model E2 GCM

    Science.gov (United States)

    Aleinov, I. D.; Kiang, N. Y.; Romanou, A.

    2017-12-01

    The ability to properly model surface carbon fluxes on the diurnal and seasonal time scale is a necessary requirement for understanding of the global carbon cycle. It is also one of the most challenging tasks faced by modern General Circulation Models (GCMs) due to complexity of the algorithms and variety of relevant spatial and temporal scales. The observational data, though abundant, is difficult to interpret at the global scale, because flux tower observations are very sparse for large impact areas (such as Amazon and African rainforest and most of Siberia) and satellite missions often struggle to produce sufficiently high confidence data over the land and may be missing CO2 amounts near the surface due to the nature of the method. In this work we use the GISS Model E2 GCM to perform a subset of experiments proposed by the Coupled Climate-Carbon Cycle Model Intercomparison Project (C4MIP) and relate the results to available observations.The GISS Model E2 GCM is currently equipped with a complete global carbon cycle algorithm. Its surface carbon fluxes are computed by the Ent Terrestrial Biosphere Model (Ent TBM) over the land with observed leaf area index of the Moderate Resolution Imaging Spectrometer (MODIS) and by the NASA Ocean Biogeochemistry Model (NOBM) over the ocean. The propagation of atmospheric CO2 is performed by a generic Model E2 tracer algorithm, which is based on a quadratic upstream method (Prather 1986). We perform a series spin-up experiments for preindustrial climate conditions and fixed preindustrial atmospheric CO2 concentration. First, we perform separate spin-up simulations each for terrestrial and ocean carbon. We then combine the spun-up states and perform a coupled spin-up simulation until the model reaches a sufficient equilibrium. We then release restrictions on CO2 concentration and allow it evolve freely, driven only by simulated surface fluxes. We then study the results of the unforced run, comparing the amplitude and the phase

  2. The Martian atmospheric water cycle as viewed from a terrestrial perspective

    Science.gov (United States)

    Zurek, Richard W.

    1988-01-01

    It is noted that the conditions of temperature and pressure that characterize the atmosphere of Mars are similar to those found in the Earth's stratosphere. Of particular significance is the fact that liquid water is unstable in both environments. Thus, it is expected that terrestrial studies of the dynamical behavior of stratospheric water should benefit the understanding of water transport on Mars as well.

  3. The Natural Terrestrial Carbon Sequestration Potential of Rocky Mountain Soils Derived From Volcanic Bedrock

    Science.gov (United States)

    Yager, D. B.; Burchell, A.; Johnson, R. H.

    2008-12-01

    The possible economic and environmental ramifications of climate change have stimulated a range of atmospheric carbon mitigation actions, as well as, studies to understand and quantify potential carbon sinks. However, current carbon management strategies for reducing atmospheric emissions underestimate a critical component. Soils represent between 18 - 30% of the terrestrial carbon sink needed to prevent atmospheric doubling of CO2 by 2050 and a crucial element in mitigating climate change, natural terrestrial sequestration (NTS), is required. NTS includes all naturally occurring, cumulative, biologic and geologic processes that either remove CO2 from the atmosphere or prevent net CO2 emissions through photosynthesis and microbial fixation, soil formation, weathering and adsorption or chemical reactions involving principally alumino- ferromagnesium minerals, volcanic glass and clays. Additionally, NTS supports ecosystem services by improving soil productivity, moisture retention, water purification and reducing erosion. Thus, 'global climate triage' must include the protection of high NTS areas, purposeful enhancement of NTS processes and reclamation of disturbed and mined lands. To better understand NTS, we analyzed soil-cores from Colorado, Rocky Mountain Cordillera sites. North-facing, high-plains to alpine sites in non-wetland environments were selected to represent temperate soils that may be less susceptible to carbon pool declines due to global warming than soils in warmer regions. Undisturbed soils sampled have 2 to 6 times greater total organic soil carbon (TOSC) than global TOSC averages (4 - 5 Wt. %). Forest soils derived from weathering of intermediate to mafic volcanic bedrock have the highest C (34.15 Wt. %), C:N (43) and arylsulfatase (ave. 278, high 461 μg p-nitrophenol/g/h). Intermediate TOSC was identified in soils derived from Cretaceous shale (7.2 Wt. %) and Precambrian, felsic gneiss (6.2 Wt. %). Unreclaimed mine-sites have the lowest C (0

  4. Factoring out natural and indirect human effects on terrestrial carbon sources and sinks

    Energy Technology Data Exchange (ETDEWEB)

    Canadell, J.G. [Global Carbon Project, CSIRO Marine and Atmospheric Research, GPO Box 3023, Canberra, ACT 2601 (Australia); Kirschbaum, M.U.F. [Environmental Biology Group, RSBS, Australian National University, GPO Box 475, Canberra, ACT 2601 (Australia); Kurz, W.A. [Natural Resources Canada, Canadian Forest Service, 506 West Burnside Road, Victoria, BC V8Z 1M5 (Canada); Sanz, M.J. [Fundacion CEAM, Parque Tecnologico, Charles H. Darwin 14, 46980 Paterna, Valencia (Spain); Schlamadinger, B. [Joanneum Research, Elisabethstrasse 11, Graz A-8010 (Austria); Yamagata, Y. [Center for Global Environmental Research, National Institute of Environmental Studies, 16-2 Onogawa, Tsukuba 305-8506 (Japan)

    2007-06-15

    The capacity to partition natural, indirect, and direct human-induced effects on terrestrial carbon (C) sources and sinks is necessary to be able to predict future terrestrial C dynamics and thus their influence on atmospheric CO2 growth. However, it will take a number of years before we can better attribute quantitative estimates of the contribution of various C processes to the net C balance. In a policy context, factoring out natural and indirect human-induced effects on C sources and sinks from the direct human-induced influences, is seen as a requirement of a C accounting approach that establishes a clear and unambiguous connection between human activities and the assignment of C credits and debits. We present options for factoring out various groups of influences including climate variability, CO2 and N fertilization, and legacies from forest management. These are: (1) selecting longer accounting or measurement periods to reduce the effects of inter-annual variability; (2) correction of national inventories for inter-annual variability; (3) use of activity-based accounting and C response curves; (4) use of baseline scenarios or benchmarks at the national level; (5) stratification of the landscape into units with distinct average C stocks. Other, more sophisticated modeling approaches (e.g., demographic models in combination with forest inventories; process-based models) are possible options for future C accounting systems but their complexity and data requirements make their present adoption more difficult in an inclusive international C accounting system.

  5. Simulated responses of terrestrial aridity to black carbon and sulfate aerosols

    Science.gov (United States)

    Lin, L.; Gettelman, A.; Xu, Y.; Fu, Q.

    2016-01-01

    Aridity index (AI), defined as the ratio of precipitation to potential evapotranspiration (PET), is a measure of the dryness of terrestrial climate. Global climate models generally project future decreases of AI (drying) associated with global warming scenarios driven by increasing greenhouse gas and declining aerosols. Given their different effects in the climate system, scattering and absorbing aerosols may affect AI differently. Here we explore the terrestrial aridity responses to anthropogenic black carbon (BC) and sulfate (SO4) aerosols with Community Earth System Model simulations. Positive BC radiative forcing decreases precipitation averaged over global land at a rate of 0.9%/°C of global mean surface temperature increase (moderate drying), while BC radiative forcing increases PET by 1.0%/°C (also drying). BC leads to a global decrease of 1.9%/°C in AI (drying). SO4 forcing is negative and causes precipitation a decrease at a rate of 6.7%/°C cooling (strong drying). PET also decreases in response to SO4 aerosol cooling by 6.3%/°C cooling (contributing to moistening). Thus, SO4 cooling leads to a small decrease in AI (drying) by 0.4%/°C cooling. Despite the opposite effects on global mean temperature, BC and SO4 both contribute to the twentieth century drying (AI decrease). Sensitivity test indicates that surface temperature and surface available energy changes dominate BC- and SO4-induced PET changes.

  6. Factoring out natural and indirect human effects on terrestrial carbon sources and sinks

    International Nuclear Information System (INIS)

    Canadell, J.G.; Kirschbaum, M.U.F.; Kurz, W.A.; Sanz, M.J.; Schlamadinger, B.; Yamagata, Y.

    2007-01-01

    The capacity to partition natural, indirect, and direct human-induced effects on terrestrial carbon (C) sources and sinks is necessary to be able to predict future terrestrial C dynamics and thus their influence on atmospheric CO2 growth. However, it will take a number of years before we can better attribute quantitative estimates of the contribution of various C processes to the net C balance. In a policy context, factoring out natural and indirect human-induced effects on C sources and sinks from the direct human-induced influences, is seen as a requirement of a C accounting approach that establishes a clear and unambiguous connection between human activities and the assignment of C credits and debits. We present options for factoring out various groups of influences including climate variability, CO2 and N fertilization, and legacies from forest management. These are: (1) selecting longer accounting or measurement periods to reduce the effects of inter-annual variability; (2) correction of national inventories for inter-annual variability; (3) use of activity-based accounting and C response curves; (4) use of baseline scenarios or benchmarks at the national level; (5) stratification of the landscape into units with distinct average C stocks. Other, more sophisticated modeling approaches (e.g., demographic models in combination with forest inventories; process-based models) are possible options for future C accounting systems but their complexity and data requirements make their present adoption more difficult in an inclusive international C accounting system

  7. Enhanced transfer of terrestrially derived carbon to the atmosphere in a flooding event

    Science.gov (United States)

    Bianchi, Thomas S.; Garcia-Tigreros, Fenix; Yvon-Lewis, Shari A.; Shields, Michael; Mills, Heath J.; Butman, David; Osburn, Christopher; Raymond, Peter A.; Shank, G. Christopher; DiMarco, Steven F.; Walker, Nan; Kiel Reese, Brandi; Mullins-Perry, Ruth; Quigg, Antonietta; Aiken, George R.; Grossman, Ethan L.

    2013-01-01

    Rising CO2 concentration in the atmosphere, global climate change, and the sustainability of the Earth's biosphere are great societal concerns for the 21st century. Global climate change has, in part, resulted in a higher frequency of flooding events, which allow for greater exchange between soil/plant litter and aquatic carbon pools. Here we demonstrate that the summer 2011 flood in the Mississippi River basin, caused by extreme precipitation events, resulted in a “flushing” of terrestrially derived dissolved organic carbon (TDOC) to the northern Gulf of Mexico. Data from the lower Atchafalaya and Mississippi rivers showed that the DOC flux to the northern Gulf of Mexico during this flood was significantly higher than in previous years. We also show that consumption of radiocarbon-modern TDOC by bacteria in floodwaters in the lower Atchafalaya River and along the adjacent shelf contributed to northern Gulf shelf waters changing from a net sink to a net source of CO2 to the atmosphere in June and August 2011. This work shows that enhanced flooding, which may or may not be caused by climate change, can result in rapid losses of stored carbon in soils to the atmosphere via processes in aquatic ecosystems.

  8. The Carbon Cycle: Teaching Youth about Natural Resource Sustainability

    Science.gov (United States)

    Warren, William A.

    2015-01-01

    The carbon cycle was used as a conceptual construct for organizing the curriculum for a youth summer camp on natural resource use and sustainability. Several studies have indicated the importance of non-traditional youth education settings for science education and understanding responsible natural resource use. The Sixth Grade Forestry Tour, a…

  9. A Carbon Cycle Science Update Since IPCC AR-4

    NARCIS (Netherlands)

    Dolman, A.J.; Werf, van der G.R.; Molen, van der M.K.; Ganssen, G.; Erisman, J.W.; Strengers, B.

    2010-01-01

    We review important advances in our understanding of the global carbon cycle since the publication of the IPCC AR4. We conclude that: the anthropogenic emissions of CO2 due to fossil fuel burning have increased up through 2008 at a rate near to the high end of the IPCC emission scenarios; there are

  10. Nuclear weapons data for use in carbon cycle modelling

    International Nuclear Information System (INIS)

    Enting, I.G.

    1982-01-01

    This report contains tables of atmospheric explosions for use in carbon cycle modelling studies. Descriptions of the sources of the data and the manner in which it can be used are given. The essential requirement is for a specification of the amount of 14 C injected into the atmosphere as a function of time, height, latitude and longitude

  11. Autonomous observing strategies for the ocean carbon cycle

    Energy Technology Data Exchange (ETDEWEB)

    Bishop, James K.; Davis, Russ E.

    2000-07-26

    Understanding the exchanges of carbon between the atmosphere and ocean and the fate of carbon delivered to the deep sea is fundamental to the evaluation of ocean carbon sequestration options. An additional key requirement is that sequestration must be verifiable and that environmental effects be monitored and minimized. These needs can be addressed by carbon system observations made from low-cost autonomous ocean-profiling floats and gliders. We have developed a prototype ocean carbon system profiler based on the Sounding Oceanographic Lagrangian Observer (SOLO; Davis et al., 1999). The SOLO/ carbon profiler will measure the two biomass components of the carbon system and their relationship to physical variables, such as upper ocean stratification and mixing. The autonomous observations within the upper 1500 m will be made on daily time scales for periods of months to seasons and will be carried out in biologically dynamic locations in the world's oceans that are difficult to access with ships (due to weather) or observe using remote sensing satellites (due to cloud cover). Such an observational capability not only will serve an important role in carbon sequestration research but will provide key observations of the global ocean's natural carbon cycle.

  12. Turnover of eroded soil organic carbon after deposition in terrestrial and aquatic environments

    DEFF Research Database (Denmark)

    Kirkels, Frédérique; Cammeraat, Erik; Kalbitz, Karsten

    cycling. However, the net effect on C fluxes between soils, inland waters and atmosphere remains uncertain. In this study, we determined SOC turnover in terrestrial and aquatic environments and indentified its major controls. A European gradient of agricultural sites was sampled, spanning a wide range...... soil properties (e.g. texture, aggregation, etc.), SOC quantity and quality. In a 16-week incubation experiment, SOC turnover was determined for conditions reflecting downslope soils or inland waters. Moreover, we studied the impact of labile C inputs (‘priming’) on SOC stability using 13C labeled...... cellulose. Physical and chemical soil properties and SOC molecular composition were assessed as potential controls on C turnover. SOC deposition in aquatic environments resulted in upto 3.5 times higher C turnover than deposition on downslope soils. Labile C inputs enlarged total CO2 emissions...

  13. Impact of volcanic eruptions on the marine carbon cycle

    Science.gov (United States)

    Segschneider, Joachim; Ulrike, Niemeier; Martin, Wiesner; Claudia, Timmreck

    2010-05-01

    The impact of volcanic eruptions on the marine carbon cycle is investigated for the example of the Pinatubo eruption with model simulations of the distribution of the ash cloud and deposition on the ocean surface and the impact of the nutrient addition from ash leachates on the oceanic biological production and hence biological carbon pump. Natural variations of aerosols, especially due to large-magnitude volcanic eruptions, are recognized as a significant climate forcing, altering the Earth's radiation balance and thus tending to cause global temperature changes. While the impact of such events on climate and the terrestrial biosphere is relatively well documented, scientific knowledge of their effects on marine ecosystems and consequent feedbacks to the atmosphere is still very limited. In the deep sea, subaerial eruptive events of global significance are commonly recorded as widespread ash layers, which were often found to be associated with increased abundances of planktic organisms. This has led to the hypothesis that the influx of volcanic ash may provide an external nutrient source for primary production (in particular through iron fertilization) in ocean surface waters. Recent laboratory experiments have demonstrated that pristine volcanic ash indeed releases significant amounts of macronutrients and bioactive trace metals (including phosphate, iron and silica) adsorbed to the surface of the ash particles. The release of these components most likely has its largest impact in ocean regions where their availability is crucial for the growth of oceanic biomass, which are the high-nutrient but low-productivity (low-iron) areas in the Pacific and the Southern Ocean. These in turn are neighbored by most of those subaerially active volcanoes that are capable of ejecting huge amounts of aerosols into the high-velocity stratospheric wind fields. The dispersal and fallout of ash thus has a high potential to induce globally significant, transient net CO2 removal from

  14. Urbanization and the Carbon Cycle: Synthesis of Ongoing Research

    Science.gov (United States)

    Gurney, K. R.; Duren, R. M.; Hutyra, L.; Ehleringer, J. R.; Patarasuk, R.; Song, Y.; Huang, J.; Davis, K.; Kort, E. A.; Shepson, P. B.; Turnbull, J. C.; Lauvaux, T.; Rao, P.; Eldering, A.; Miller, C. E.; Wofsy, S.; McKain, K.; Mendoza, D. L.; Lin, J. C.; Sweeney, C.; Miles, N. L.; Richardson, S.; Cambaliza, M. O. L.

    2015-12-01

    Given the explosive growth in urbanization and its dominant role in current and future global greenhouse gas emissions, urban areas have received increasing research attention from the carbon cycle science community. The emerging focus is driven by the increasingly dense atmospheric observing capabilities - ground and space-based - in addition to the rising profile of cities within international climate change policymaking. Dominated by anthropogenic emissions, urban carbon cycle research requires a cross-disciplinary perspective with contributions from disciplines such as engineering, economics, social theory, and atmospheric science. We review the recent results from a sample of the active urban carbon research efforts including the INFLUX experiment (Indianapolis), the Megacity carbon project (Los Angeles), Salt Lake City, and Boston. Each of these efforts represent unique approaches in pursuit of different scientific and policy questions and assist in setting priorities for future research. From top-down atmospheric measurement systems to bottom-up estimation, these research efforts offer a view of the challenges and opportunities in urban carbon cycle research.

  15. Self-rewetting carbon nanofluid as working fluid for space and terrestrial heat pipes

    International Nuclear Information System (INIS)

    Di Paola, R.; Savino, R.; Mirabile Gattia, D.; Marazzi, R.; Vittori Antisari, M.

    2011-01-01

    Thermal management is very important in modern electronic systems. Recent researches have been dedicated to the study of the heat transfer performances of binary heat transfer fluids with peculiar surface tension properties and in particular to that of “self-rewetting fluids”, i.e., liquids with a surface tension increasing with temperature and concentration. Since in the course of liquid/vapor-phase change, self-rewetting fluids behavior induces a rather strong liquid inflow (caused by both temperature and concentration gradients) from the cold region (where liquid condensates) to the hot evaporator region, this fluids have been proposed and investigated as new heat transfer fluids for advanced heat transfer devices, e.g., heat pipes or heat spreaders for terrestrial and space applications (Savino et al. in Space Technol 25(1):59–61, 2009). The present work is dedicated to the study of the thermophysical properties of a new class of heat transfer fluids based on water/alcohol solutions with suspended carbon nanostructures, in particular single-wall carbon nanohorns (SWNH), synthesized by a homemade apparatus with an AC arc discharge in open air (Mirabile Gattia et al. in Nanotechnology 18:255604, 2007). SWNHs are cone-shaped nanoparticles with diameters between 1 and 5 nm and lengths in the range of 20–100 nm. SWNHs could be found in the form of quite-spherical aggregates with diameters ranging from 20 to 100 nm. The paper also discusses the results of these investigations and laboratory characterization tests of different heat pipes, including reference ordinary heat pipes and innovative pipes filled with self-rewetting fluids and self-rewetting nanofluids. The potential interest of the proposed studies stems from the large number of possible industrial applications, including space technologies and terrestrial applications, such as cooling of electronic components.

  16. Self-rewetting carbon nanofluid as working fluid for space and terrestrial heat pipes

    Science.gov (United States)

    Di Paola, R.; Savino, R.; Mirabile Gattia, D.; Marazzi, R.; Vittori Antisari, M.

    2011-11-01

    Thermal management is very important in modern electronic systems. Recent researches have been dedicated to the study of the heat transfer performances of binary heat transfer fluids with peculiar surface tension properties and in particular to that of "self-rewetting fluids", i.e., liquids with a surface tension increasing with temperature and concentration. Since in the course of liquid/vapor-phase change, self-rewetting fluids behavior induces a rather strong liquid inflow (caused by both temperature and concentration gradients) from the cold region (where liquid condensates) to the hot evaporator region, this fluids have been proposed and investigated as new heat transfer fluids for advanced heat transfer devices, e.g., heat pipes or heat spreaders for terrestrial and space applications (Savino et al. in Space Technol 25(1):59-61, 2009). The present work is dedicated to the study of the thermophysical properties of a new class of heat transfer fluids based on water/alcohol solutions with suspended carbon nanostructures, in particular single-wall carbon nanohorns (SWNH), synthesized by a homemade apparatus with an AC arc discharge in open air (Mirabile Gattia et al. in Nanotechnology 18:255604, 2007). SWNHs are cone-shaped nanoparticles with diameters between 1 and 5 nm and lengths in the range of 20-100 nm. SWNHs could be found in the form of quite-spherical aggregates with diameters ranging from 20 to 100 nm. The paper also discusses the results of these investigations and laboratory characterization tests of different heat pipes, including reference ordinary heat pipes and innovative pipes filled with self-rewetting fluids and self-rewetting nanofluids. The potential interest of the proposed studies stems from the large number of possible industrial applications, including space technologies and terrestrial applications, such as cooling of electronic components.

  17. Soils and Global Change in the Carbon Cycle over Geological Time

    Science.gov (United States)

    Retallack, G. J.

    2003-12-01

    sedimentary rocks; organic matter burial is an important long-term control on CO2 levels in the atmosphere (Berner and Kothavala, 2001). The magnitudes of carbon pools and fluxes involved provide a perspective on the importance of soils compared with other carbon reservoirs ( Figure 1). (6K)Figure 1. Pools and fluxes of reduced carbon (bold) and oxidized carbon (regular) in Gt in the pre-industrial carbon cycle (sources Schidlowski and Aharon, 1992; Siegenthaler and Sarmiento, 1993; Stallard, 1998). Before industrialization, there was only 600 Gt (1 Gt=1015g) of carbon in CO2 and methane in the atmosphere, which is about the same amount as in all terrestrial biomass, but less than half of the reservoir of soil organic carbon. The ocean contained only ˜3 Gt of biomass carbon. The deep ocean and sediments comprised the largest reservoir of bicarbonate and organic matter, but that carbon has been kept out of circulation from the atmosphere for geologically significant periods of time (Schidlowski and Aharon, 1992). Humans have tapped underground reservoirs of fossil fuels, and our other perturbations of the carbon cycle have also been significant ( Vitousek et al., 1997b; see Chapter 8.10).Atmospheric increase of carbon in CO2 to 750 Gt C by deforestation and fossil fuel burning has driven ongoing global warming, but is not quite balanced by changes in the other carbon reservoirs leading to search for a "missing sink" of some 1.8±1.3 GtC, probably in terrestrial organisms, soils, and sediments of the northern hemisphere (Keeling et al., 1982; Siegenthaler and Sarmiento, 1993; Stallard, 1998). Soil organic matter is a big, rapidly cycling reservoir, likely to include much of this missing sink.During the geological past, the sizes of, and fluxes between, these reservoirs have varied enormously as the world has alternated between greenhouse times of high carbon content of the atmosphere, and icehouse times of low carbon content of the atmosphere. Oscillations in the atmospheric

  18. ENHANCEMENT OF TERRESTRIAL CARBON SINKS THROUGH RECLAMATION OF ABANDONED MINE LANDS IN THE APPALACHIAN REGION

    Energy Technology Data Exchange (ETDEWEB)

    Gary D. Kronrad

    2002-12-01

    The U.S.D.I. Office of Surface Mining (OSM) estimates that there are approximately 1 million acres of abandoned mine land (AML) in the Appalachian region. AML lands are classified as areas that were inadequately reclaimed or were left unreclaimed prior to the passage of the 1977 Surface Mining Control and Reclamation Act, and where no federal or state laws require any further reclamation responsibility to any company or individual. Reclamation and afforestation of these sites have the potential to provide landowners with cyclical timber revenues, generate environmental benefits to surrounding communities, and sequester carbon in the terrestrial ecosystem. Through a memorandum of understanding, the OSM and the U.S. Department of Energy (DOE) have decided to investigate reclaiming and afforesting these lands for the purpose of mitigating the negative effects of anthropogenic carbon dioxide in the atmosphere. This study determined the carbon sequestration potential of northern red oak (Quercus rubra L.), one of the major reclamation as well as commercial species, planted on West Virginia AML sites. Analyses were conducted to (1) calculate the total number of tons that can be stored, (2) determine the cost per ton to store carbon, and (3) calculate the profitability of managing these forests for timber production alone and for timber production and carbon storage together. The Forest Management Optimizer (FORMOP) was used to simulate growth data on diameter, height, and volume for northern red oak. Variables used in this study included site indices ranging from 40 to 80 (base age 50), thinning frequencies of 0, 1, and 2, thinning percentages of 20, 25, 30, 35, and 40, and a maximum rotation length of 100 years. Real alternative rates of return (ARR) ranging from 0.5% to 12.5% were chosen for the economic analyses. A total of 769,248 thinning and harvesting combinations, net present worths, and soil expectation values were calculated in this study. Results indicate that

  19. Carbon dioxide effects research and assessment program. Measurement of changes in terrestrial carbon using remote sensing

    Energy Technology Data Exchange (ETDEWEB)

    Woodwell, G M [ed.

    1980-09-01

    Changes in the area of forests as well as changes in the storage of carbon within forest stands have large potential effects on atmospheric CO/sub 2/. This conference addressed the challenge of measuring changes in the area of forests globally through use of satellite remote sensing. The conclusion of the approximately seventy participants from around the world was that a program based on LANDSAT imagery supplemented by aerial photography is both possible and appropriate.

  20. Projected changes in terrestrial carbon storage in Europe under climate and land-use change, 1990-2100

    International Nuclear Information System (INIS)

    Zaehle, S.; Bondeau, A.; Cramer, W.; Erhard, M.; Sitch, S.; Smith, P.C.; Zaehle, S.; Smith, P.C.; Carter, T.R.; Erhard, M.; Prentice, C.; Prentice, C.; Reginster, I.; Rounsevell, M.D.A.; Sitch, S.; Smith, B.; Sykes, M

    2007-01-01

    Changes in climate and land use, caused by socio-economic changes, greenhouse gas emissions, agricultural policies and other factors, are known to affect both natural and managed ecosystems, and will likely impact on the European terrestrial carbon balance during the coming decades. This study presents a comprehensive European Union wide (EU15 plus Norway and Switzerland, EU*) assessment of potential future changes in terrestrial carbon storage considering these effects based on four illustrative IPCC-SRES story-lines (A1FI, A2, B1, B2). A process-based land vegetation model (LPJ-DGVM), adapted to include a generic representation of managed ecosystems, is forced with changing fields of land-use patterns from 1901 to 2100 to assess the effect of land-use and cover changes on the terrestrial carbon balance of Europe. The uncertainty in the future carbon balance associated with the choice of a climate change scenario is assessed by forcing LPJ-DGVM with output from four different climate models (GCMs: CGCM2, CSIRO2, HadCM3, PCM2) for the same SRES story-line. Decrease in agricultural areas and afforestation leads to simulated carbon sequestration for all land-use change scenarios with an average net uptake of 17-38 Tg C/year between 1990 and 2100, corresponding to 1.9-2.9% of the EU*s CO 2 emissions over the same period. Soil carbon losses resulting from climate warming reduce or even offset carbon sequestration resulting from growth enhancement induced by climate change and increasing atmospheric CO 2 concentrations in the second half of the twenty-first century. Differences in future climate change projections among GCMs are the main cause for uncertainty in the cumulative European terrestrial carbon uptake of 4.4-10.1 Pg C between 1990 and 2100. (authors)

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

    Science.gov (United States)

    A simulation model based on satellite observations of monthly vegetation cover from the Moderate Resolution Imaging Spectroradiometer (MODIS) was used to estimate monthly carbon fluxes in terrestrial ecosystems of Brazilian Amazon and Cerrado regions over the period 2000-2004. Pr...

  2. Carbon Dioxide Effects Research and Assessment Program. The role of tropical forests on the world carbon cycle

    Energy Technology Data Exchange (ETDEWEB)

    Brown, S.; Lugo, A. E.; Liegel, B. [eds.

    1980-08-01

    Tropical forests constitute about half of the world's forest and are characterized by rapid rates of organic matter turnover and high storages of organic matter. Tropical forests are considered to be one of the most significant terrestrial elements in the equation that balances the carbon cycle of the world. As discussed in the paper by Tosi, tropical and subtropical latitudes are more complex in terms of climate and vegetation composition than temperate and boreal latitudes. The implications of the complexity of the tropics and the disregard of this complexity by many scientists is made evident in the paper by Brown and Lugo which shows that biomass estimates for tropical ecosystems have been overestimated by at least 100%. The paper by Brown shows that that rates of succession in the tropics are extremely rapid in terms of the ability of moist and wet forests to accumulate organic matter. Yet, in arid tropical Life Zones succession is slow. This leads to the idea that the question of whether tropical forests are sinks or sources of carbon must be analyzed in relation to Life Zones and to intensities of human activity in these Zones. The paper by Lugo presents conceptual models to illustrate this point and the paper by Tosi shows how land uses in the tropics also correspond to Life Zone characteristics. The ultimate significance of land use to the question of the carbon balance in a large region is addressed in the paper by Detwiler and Hall.

  3. Modelling the soil carbon cycle of pine ecosystems

    International Nuclear Information System (INIS)

    Nakane, K.

    1994-01-01

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

  4. Initializing carbon cycle predictions from the Community Land Model by assimilating global biomass observations

    Science.gov (United States)

    Fox, A. M.; Hoar, T. J.; Smith, W. K.; Moore, D. J.

    2017-12-01

    The locations and longevity of terrestrial carbon sinks remain uncertain, however it is clear that in order to predict long-term climate changes the role of the biosphere in surface energy and carbon balance must be understood and incorporated into earth system models (ESMs). Aboveground biomass, the amount of carbon stored in vegetation, is a key component of the terrestrial carbon cycle, representing the balance of uptake through gross primary productivity (GPP), losses from respiration, senescence and mortality over hundreds of years. The best predictions of current and future land-atmosphere fluxes are likely from the integration of process-based knowledge contained in models and information from observations of changes in carbon stocks using data assimilation (DA). By exploiting long times series, it is possible to accurately detect variability and change in carbon cycle dynamics through monitoring ecosystem states, for example biomass derived from vegetation optical depth (VOD), and use this information to initialize models before making predictions. To make maximum use of information about the current state of global ecosystems when using models we have developed a system that combines the Community Land Model (CLM) with the Data Assimilation Research Testbed (DART), a community tool for ensemble DA. This DA system is highly innovative in its complexity, completeness and capabilities. Here we described a series of activities, using both Observation System Simulation Experiments (OSSEs) and real observations, that have allowed us to quantify the potential impact of assimilating VOD data into CLM-DART on future land-atmosphere fluxes. VOD data are particularly suitable to use in this activity due to their long temporal coverage and appropriate scale when combined with CLM, but their absolute values rely on many assumptions. Therefore, we have had to assess the implications of the VOD retrieval algorithms, with an emphasis on detecting uncertainty due to

  5. Elevated temperature alters carbon cycling in a model microbial community

    Science.gov (United States)

    Mosier, A.; Li, Z.; Thomas, B. C.; Hettich, R. L.; Pan, C.; Banfield, J. F.

    2013-12-01

    Earth's climate is regulated by biogeochemical carbon exchanges between the land, oceans and atmosphere that are chiefly driven by microorganisms. Microbial communities are therefore indispensible to the study of carbon cycling and its impacts on the global climate system. In spite of the critical role of microbial communities in carbon cycling processes, microbial activity is currently minimally represented or altogether absent from most Earth System Models. Method development and hypothesis-driven experimentation on tractable model ecosystems of reduced complexity, as presented here, are essential for building molecularly resolved, benchmarked carbon-climate models. Here, we use chemoautotropic acid mine drainage biofilms as a model community to determine how elevated temperature, a key parameter of global climate change, regulates the flow of carbon through microbial-based ecosystems. This study represents the first community proteomics analysis using tandem mass tags (TMT), which enable accurate, precise, and reproducible quantification of proteins. We compare protein expression levels of biofilms growing over a narrow temperature range expected to occur with predicted climate changes. We show that elevated temperature leads to up-regulation of proteins involved in amino acid metabolism and protein modification, and down-regulation of proteins involved in growth and reproduction. Closely related bacterial genotypes differ in their response to temperature: Elevated temperature represses carbon fixation by two Leptospirillum genotypes, whereas carbon fixation is significantly up-regulated at higher temperature by a third closely related genotypic group. Leptospirillum group III bacteria are more susceptible to viral stress at elevated temperature, which may lead to greater carbon turnover in the microbial food web through the release of viral lysate. Overall, this proteogenomics approach revealed the effects of climate change on carbon cycling pathways and other

  6. Hidden cycle of dissolved organic carbon in the deep ocean.

    Science.gov (United States)

    Follett, Christopher L; Repeta, Daniel J; Rothman, Daniel H; Xu, Li; Santinelli, Chiara

    2014-11-25

    Marine dissolved organic carbon (DOC) is a large (660 Pg C) reactive carbon reservoir that mediates the oceanic microbial food web and interacts with climate on both short and long timescales. Carbon isotopic content provides information on the DOC source via δ(13)C and age via Δ(14)C. Bulk isotope measurements suggest a microbially sourced DOC reservoir with two distinct components of differing radiocarbon age. However, such measurements cannot determine internal dynamics and fluxes. Here we analyze serial oxidation experiments to quantify the isotopic diversity of DOC at an oligotrophic site in the central Pacific Ocean. Our results show diversity in both stable and radio isotopes at all depths, confirming DOC cycling hidden within bulk analyses. We confirm the presence of isotopically enriched, modern DOC cocycling with an isotopically depleted older fraction in the upper ocean. However, our results show that up to 30% of the deep DOC reservoir is modern and supported by a 1 Pg/y carbon flux, which is 10 times higher than inferred from bulk isotope measurements. Isotopically depleted material turns over at an apparent time scale of 30,000 y, which is far slower than indicated by bulk isotope measurements. These results are consistent with global DOC measurements and explain both the fluctuations in deep DOC concentration and the anomalous radiocarbon values of DOC in the Southern Ocean. Collectively these results provide an unprecedented view of the ways in which DOC moves through the marine carbon cycle.

  7. In-Lake Processes Offset Increased Terrestrial Inputs of Dissolved Organic Carbon and Color to Lakes

    Science.gov (United States)

    Köhler, Stephan J.; Kothawala, Dolly; Futter, Martyn N.; Liungman, Olof; Tranvik, Lars

    2013-01-01

    Increased color in surface waters, or browning, can alter lake ecological function, lake thermal stratification and pose difficulties for drinking water treatment. Mechanisms suggested to cause browning include increased dissolved organic carbon (DOC) and iron concentrations, as well as a shift to more colored DOC. While browning of surface waters is widespread and well documented, little is known about why some lakes resist it. Here, we present a comprehensive study of Mälaren, the third largest lake in Sweden. In Mälaren, the vast majority of water and DOC enters a western lake basin, and after approximately 2.8 years, drains from an eastern basin. Despite 40 years of increased terrestrial inputs of colored substances to western lake basins, the eastern basin has resisted browning over this time period. Here we find the half-life of iron was far shorter (0.6 years) than colored organic matter (A420 ; 1.7 years) and DOC as a whole (6.1 years). We found changes in filtered iron concentrations relate strongly to the observed loss of color in the western basins. In addition, we observed a substantial shift from colored DOC of terrestrial origin, to less colored autochthonous sources, with a substantial decrease in aromaticity (-17%) across the lake. We suggest that rapid losses of iron and colored DOC caused the limited browning observed in eastern lake basins. Across a wider dataset of 69 Swedish lakes, we observed greatest browning in acidic lakes with shorter retention times (< 1.5 years). These findings suggest that water residence time, along with iron, pH and colored DOC may be of central importance when modeling and projecting changes in brownification on broader spatial scales. PMID:23976946

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

    Science.gov (United States)

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

    2009-01-01

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

  9. The limits to global-warming mitigation by terrestrial carbon removal

    Science.gov (United States)

    Boysen, Lena R.; Lucht, Wolfgang; Gerten, Dieter; Heck, Vera; Lenton, Timothy M.; Schellnhuber, Hans Joachim

    2017-05-01

    Massive near-term greenhouse gas emissions reduction is a precondition for staying "well below 2°C" global warming as envisaged by the Paris Agreement. Furthermore, extensive terrestrial carbon dioxide removal (tCDR) through managed biomass growth and subsequent carbon capture and storage is required to avoid temperature "overshoot" in most pertinent scenarios. Here, we address two major issues: First, we calculate the extent of tCDR required to "repair" delayed or insufficient emissions reduction policies unable to prevent global mean temperature rise of 2.5°C or even 4.5°C above pre-industrial level. Our results show that those tCDR measures are unable to counteract "business-as-usual" emissions without eliminating virtually all natural ecosystems. Even if considerable (Representative Concentration Pathway 4.5 [RCP4.5]) emissions reductions are assumed, tCDR with 50% storage efficiency requires >1.1 Gha of the most productive agricultural areas or the elimination of >50% of natural forests. In addition, >100 MtN/yr fertilizers would be needed to remove the roughly 320 GtC foreseen in these scenarios. Such interventions would severely compromise food production and/or biosphere functioning. Second, we reanalyze the requirements for achieving the 160-190 GtC tCDR that would complement strong mitigation action (RCP2.6) in order to avoid 2°C overshoot anytime. We find that a combination of high irrigation water input and/or more efficient conversion to stored carbon is necessary. In the face of severe trade-offs with society and the biosphere, we conclude that large-scale tCDR is not a viable alternative to aggressive emissions reduction. However, we argue that tCDR might serve as a valuable "supporting actor" for strong mitigation if sustainable schemes are established immediately.

  10. Multi-Model Assessment of Trends and Variability in Terrestrial Carbon Uptake in India

    Science.gov (United States)

    Rao, A. S.; Bala, G.; Ravindranath, N. H.

    2015-12-01

    Indian terrestrial ecosystem exhibits large temporal and spatial variability in carbon sources and sinks due to its monsoon based climate system, diverse land use and land cover distribution and cultural practices. In this study, a multi-model based assessment is made to study the trends and variability in the land carbon uptake for India over the 20th century. Data from nine models which are a part of a recent land surface model intercomparison project called TRENDY is used for the study. These models are driven with common forcing data over the period of 1901-2010. Model output variables assessed include: gross primary production (GPP), heterotrophic respiration (Rh), autotrophic respiration (Ra) and net primary production (NPP). The net ecosystem productivity (NEP) for the Indian region was calculated as a difference of NPP and Rh and it was found that NEP for the region indicates an estimated increase in uptake over the century by -0.6 TgC/year per year. NPP for India also shows an increasing trend of 2.03% per decade from 1901-2010. Seasonal variation in the multimodel mean NPP is maximum during the southwest monsoon period (JJA) followed by the post monsoon period (SON) and is attributed to the maximum in rainfall for the region during the months of JJA. To attribute the changes seen in the land carbon variables, influence of climatic drivers such as precipitation, temperature and remote influences of large scale phenomenon such as ENSO on the land carbon of the region are also estimated in the study. It is found that although changes in precipitation shows a good correlation to the changes seen in NEP, remote drivers like ENSO do not have much effect on them. The Net Ecosystem Exchange is calculated with the inclusion of the land use change flux and fire flux from the models. NEE suggests that the region behaves as a small sink for carbon with an net uptake of 5 GtC over the past hundred years.

  11. Modeling Carbon Exchange

    Science.gov (United States)

    Sellers, Piers

    2012-01-01

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

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

    Science.gov (United States)

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

    2009-11-17

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

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

    International Nuclear Information System (INIS)

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

    2011-01-01

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

  14. Double polymer sheathed carbon nanotube supercapacitors show enhanced cycling stability

    Science.gov (United States)

    Zhao, Wenqi; Wang, Shanshan; Wang, Chunhui; Wu, Shiting; Xu, Wenjing; Zou, Mingchu; Ouyang, An; Cao, Anyuan; Li, Yibin

    2015-12-01

    Pseudo-materials are effective in boosting the specific capacitance of supercapacitors, but during service their degradation may also be very strong, causing reduced cycling stability. Here, we show that a carbon nanotube sponge grafted by two conventional pseudo-polymer layers in sequence can serve as a porous supercapacitor electrode with significantly enhanced cycling stability compared with single polymer grafting. Creating conformal polymer coatings on the nanotube surface and the resulting double-sheath configuration are important structural factors leading to the enhanced performance. Combining different polymers as double sheaths as reported here might be a potential route to circumvent the dilemma of pseudo-materials, and to simultaneously improve the capacitance and stability for various energy storage devices.Pseudo-materials are effective in boosting the specific capacitance of supercapacitors, but during service their degradation may also be very strong, causing reduced cycling stability. Here, we show that a carbon nanotube sponge grafted by two conventional pseudo-polymer layers in sequence can serve as a porous supercapacitor electrode with significantly enhanced cycling stability compared with single polymer grafting. Creating conformal polymer coatings on the nanotube surface and the resulting double-sheath configuration are important structural factors leading to the enhanced performance. Combining different polymers as double sheaths as reported here might be a potential route to circumvent the dilemma of pseudo-materials, and to simultaneously improve the capacitance and stability for various energy storage devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr05978j

  15. Integrating terrestrial through aquatic processing of water, carbon and nitrogen over hot, cold and lukewarm moments in mixed land use catchments

    Science.gov (United States)

    Band, L. E.; Lin, L.; Duncan, J. M.

    2017-12-01

    A major challenge in understanding and managing freshwater volumes and quality in mixed land use catchments is the detailed heterogeneity of topography, soils, canopy, and inputs of water and biogeochemicals. The short space and time scale dynamics of sources, transport and processing of water, carbon and nitrogen in natural and built environments can have a strong influence on the timing and magnitude of watershed runoff and nutrient production, ecosystem cycling and export. Hydroclimate variability induces a functional interchange of terrestrial and aquatic environments across their transition zone with the temporal and spatial expansion and contraction of soil wetness, standing and flowing water over seasonal, diurnal and storm event time scales. Variation in sources and retention of nutrients at these scales need to be understood and represented to design optimal mitigation strategies. This paper discusses the conceptual framework used to design both simulation and measurement approaches, and explores these dynamics using an integrated terrestrial-aquatic watershed model of coupled water-carbon-nitrogen processes at resolutions necessary to resolve "hot spot/hot moment" phenomena in two well studied catchments in Long Term Ecological Research sites. The potential utility of this approach for design and assessment of urban green infrastructure and stream restoration strategies is illustrated.

  16. Inter-annual variability of the atmospheric carbon dioxide concentrations as simulated with global terrestrial biosphere models and an atmospheric transport model

    Energy Technology Data Exchange (ETDEWEB)

    Fujita, Daisuke; Saeki, Tazu; Nakazawa, Takakiyo [Tohoku Univ., Sendai (Japan). Center for Atmospheric and Oceanic Studies; Ishizawa, Misa; Maksyutov, Shamil [Inst. for Global Change Research, Yokohama (Japan). Frontier Research System for Global Change; Thornton, Peter E. [National Center for Atmospheric Research, Boulder, CO (United States). Climate and Global Dynamics Div.

    2003-04-01

    Seasonal and inter-annual variations of atmospheric CO{sub 2} for the period from 1961 to 1997 have been simulated using a global tracer transport model driven by a new version of the Biome BioGeochemical Cycle model (Biome-BGC). Biome-BGC was forced by daily temperature and precipitation from the NCEP reanalysis dataset, and the calculated monthly-averaged CO{sub 2} fluxes were used as input to the global transport model. Results from an inter-comparison with the Carnegie-Ames-Stanford Approach model (CASA) and the Simulation model of Carbon CYCLE in Land Ecosystems (Sim-CYCLE) model are also reported. The phase of the seasonal cycle in the Northern Hemisphere was reproduced generally well by Biome-BGC, although the amplitude was smaller compared to the observations and to the other biosphere models. The CO{sub 2} time series simulated by Biome-BGC were compared to the global CO{sub 2} concentration anomalies from the observations at Mauna Loa and the South Pole. The modeled concentration anomalies matched the phase of the inter-annual variations in the atmospheric CO{sub 2} observations; however, the modeled amplitude was lower than the observed value in several cases. The result suggests that a significant part of the inter-annual variability in the global carbon cycle can be accounted for by the terrestrial biosphere models. Simulations performed with another climate-based model, Sim-CYCLE, produced a larger amplitude of inter-annual variability in atmospheric CO{sub 2}, making the amplitude closer to the observed range, but with a more visible phase mismatch in a number of time periods. This may indicate the need to increase the Biome-BGC model sensitivity to seasonal and inter-annual changes in temperature and precipitation.

  17. Inter-annual variability of the atmospheric carbon dioxide concentrations as simulated with global terrestrial biosphere models and an atmospheric transport model

    International Nuclear Information System (INIS)

    Fujita, Daisuke; Saeki, Tazu; Nakazawa, Takakiyo; Ishizawa, Misa; Maksyutov, Shamil; Thornton, Peter E.

    2003-01-01

    Seasonal and inter-annual variations of atmospheric CO 2 for the period from 1961 to 1997 have been simulated using a global tracer transport model driven by a new version of the Biome BioGeochemical Cycle model (Biome-BGC). Biome-BGC was forced by daily temperature and precipitation from the NCEP reanalysis dataset, and the calculated monthly-averaged CO 2 fluxes were used as input to the global transport model. Results from an inter-comparison with the Carnegie-Ames-Stanford Approach model (CASA) and the Simulation model of Carbon CYCLE in Land Ecosystems (Sim-CYCLE) model are also reported. The phase of the seasonal cycle in the Northern Hemisphere was reproduced generally well by Biome-BGC, although the amplitude was smaller compared to the observations and to the other biosphere models. The CO 2 time series simulated by Biome-BGC were compared to the global CO 2 concentration anomalies from the observations at Mauna Loa and the South Pole. The modeled concentration anomalies matched the phase of the inter-annual variations in the atmospheric CO 2 observations; however, the modeled amplitude was lower than the observed value in several cases. The result suggests that a significant part of the inter-annual variability in the global carbon cycle can be accounted for by the terrestrial biosphere models. Simulations performed with another climate-based model, Sim-CYCLE, produced a larger amplitude of inter-annual variability in atmospheric CO 2 , making the amplitude closer to the observed range, but with a more visible phase mismatch in a number of time periods. This may indicate the need to increase the Biome-BGC model sensitivity to seasonal and inter-annual changes in temperature and precipitation

  18. Soil carbon model alternatives for ECHAM5/JSBACH climate model: Evaluation and impacts on global carbon cycle estimates

    DEFF Research Database (Denmark)

    Thum, T.; Raisanen, P.; Sevanto, S.

    2011-01-01

    The response of soil organic carbon to climate change might lead to significant feedbacks affecting global warming. This response can be studied by coupled climate-carbon cycle models but so far the description of soil organic carbon cycle in these models has been quite simple. In this work we used...... the coupled climate-carbon cycle model ECHAM5/JSBACH (European Center/Hamburg Model 5/Jena Scheme for Biosphere-Atmosphere Coupling in Hamburg) with two different soil carbon modules, namely (1) the original soil carbon model of JSBACH called CBALANCE and (2) a new soil carbon model Yasso07, to study...... the interaction between climate variability and soil organic carbon. Equivalent ECHAM5/JSBACH simulations were conducted using both soil carbon models, with freely varying atmospheric CO2 for the last 30 years (1977-2006). In this study, anthropogenic CO2 emissions and ocean carbon cycle were excluded. The new...

  19. Dissolved Organic Carbon and Natural Terrestrial Sequestration Potential in Volcanic Terrain, San Juan Mountains, Colorado

    Science.gov (United States)

    Yager, D. B.; Burchell, A.; Johnson, R. H.; Kugel, M.; Aiken, G.; Dick, R.

    2009-12-01

    The need to reduce atmospheric CO2 levels has stimulated studies to understand and quantify carbon sinks and sources. Soils represent a potentially significant natural terrestrial carbon sequestration (NTS) reservoir. This project is part of a collaborative effort to characterize carbon (C) stability in temperate soils. To examine the potential for dissolved organic carbon (DOC) values as a qualitative indicator of C-stability, peak-flow (1500 ft3/s) and low-flow (200 ft3/s) samples from surface and ground waters were measured for DOC. DOC concentrations are generally low. Median peak-flow values from all sample sites (mg/L) were: streams (0.9); seeps (1.2); wells (0.45). Median low-flow values were: streams (0.7); seeps (0.75); wells (0.5). Median DOC values decrease between June and September 0.45 mg/L for seeps, and 0.2 mg/L for streams. Elevated DOC in some ground waters as compared to surface waters indicates increased contact time with soil organic matter. Elevated peak-flow DOC in areas with propylitically-altered bedrocks, composed of a secondary acid neutralizing assemblage of calcite-chlorite-epidote, reflects increased microbial and vegetation activity as compared to reduced organic matter accumulation in highly-altered terrain composed of an acid generating assemblage with abundant pyrite. Waters sampled in propylitically-altered bedrock terrain exhibit the lowest values during low-flow and suggest bedrock alteration type may influence DOC. Previous studies revealed undisturbed soils sampled have 2 to 6 times greater total organic soil carbon (TOSC) than global averages. Forest soils underlain by intermediate to mafic volcanic bedrock have the highest C (34.15 wt%), C: N (43) and arylsulfatase enzyme activity (ave. 278, high 461 µg p-nitrophenol/g/h). Unreclaimed mine sites have the lowest C (0 to 0.78 wt%), and arylsulfatase enzyme activity (0 to 41). Radiocarbon dates on charcoal collected from paleo-burn horizons illustrate Rocky Mountain soils may

  20. Tropical rainforests dominate multi-decadal variability of the global carbon cycle

    Science.gov (United States)

    Zhang, X.; Wang, Y. P.; Peng, S.; Rayner, P. J.; Silver, J.; Ciais, P.; Piao, S.; Zhu, Z.; Lu, X.; Zheng, X.

    2017-12-01

    Recent studies find that inter-annual variability of global atmosphere-to-land CO2 uptake (NBP) is dominated by semi-arid ecosystems. However, the NBP variations at decadal to multi-decadal timescales are still not known. By developing a basic theory for the role of net primary production (NPP) and heterotrophic respiration (Rh) on NBP and applying it to 100-year simulations of terrestrial ecosystem models forced by observational climate, we find that tropical rainforests dominate the multi-decadal variability of global NBP (48%) rather than the semi-arid lands (35%). The NBP variation at inter-annual timescales is almost 90% contributed by NPP, but across longer timescales is progressively controlled by Rh that constitutes the response from the NPP-derived soil carbon input (40%) and the response of soil carbon turnover rates to climate variability (60%). The NBP variations of tropical rainforests is modulated by the ENSO and the PDO through their significant influences on temperature and precipitation at timescales of 2.5-7 and 25-50 years, respectively. This study highlights the importance of tropical rainforests on the multi-decadal variability of global carbon cycle, suggesting that we need to carefully differentiate the effect of NBP long-term fluctuations associated with ocean-related climate modes on the long-term trend in land sink.

  1. Enhanced terrestrial carbon preservation promoted by reactive iron in deltaic sediments

    Science.gov (United States)

    Shields, Michael R.; Bianchi, Thomas S.; Gélinas, Yves; Allison, Mead A.; Twilley, Robert R.

    2016-02-01

    We examined the role of reactive iron (FeR) in preserving organic carbon (OC) across a subaerial chronosequence of the Wax Lake Delta, a prograding delta within the Mississippi River Delta complex. We found that ~15.0% of the OC was bound to FeR, and the dominant binding mechanisms varied from adsorption in the youngest subaerial region to coprecipitation at the older, vegetated sites. The δ13C of the iron-associated OC was more negative than the total OC (mean = -2.6‰), indicating greater preference for terrestrial material and/or compounds with more negative δ13C values. However, only the adsorbed OC displayed preferential binding of lignin phenols. We estimate that ~8% of the OC initially deposited in deltaic systems is bound to FeR (equivalent to 6 × 1012 gC yr-1), and this percentage increases postdepositionally, as coprecipitation of FeR and OC allows for an even greater amount of OC to be bound to FeR.

  2. Diet induced differences in carbon isotope fractionation between sirenians and terrestrial ungulates

    Science.gov (United States)

    Clementz, M.T.; Koch, P.L.; Beck, C.A.

    2007-01-01

    Carbon isotope differences (??13C) between bioapatite and diet, collagen and diet, and bioapatite and collagen were calculated for four species of sirenians, Dugong dugon (Mu??ller), Trichechus manatus (Linnaeus), Trichechus inunguis (Natterer), and the extinct Hydrodamalis gigas (Zimmerman). Bone and tooth samples were taken from archived materials collected from populations during the mid eighteenth century (H. gigas), between 1978 and 1984 (T. manatus, T. inunguis), and between 1997 and 1999 (D. dugon). Mean ??13C values were compared with those for terrestrial ungulates, carnivores, and six species of carnivorous marine mammals (cetaceans = 1; pinnipeds = 4; mustelids = 1). Significant differences in mean ??13C values among species for all tissue types were detected that separated species or populations foraging on freshwater plants or attached marine macroalgae (??13C values -4???; ??13Cbioapatite-diet ???11???). Likewise, ??13Cbioapatite-collagen values for freshwater and algal-foraging species (???7???) were greater than those for seagrass-foraging species (???5???). Variation in ??13C values calculated between tissues and between tissues and diet among species may relate to the nutritional composition of a species' diet and the extent and type of microbial fermentation that occurs during digestion of different types of plants. These results highlight the complications that can arise when making dietary interpretations without having first determined species-specific ??13Ctissue-diet values. ?? 2007 Springer-Verlag.

  3. Current views on the regulation of autotrophic carbon dioxide fixation via the Calvin cycle in bacteria

    NARCIS (Netherlands)

    Dijkhuizen, L.; Harder, W.

    1984-01-01

    The Calvin cycle of carbon dioxide fixation constitutes a biosynthetic pathway for the generation of (multi-carbon) intermediates of central metabolism from the one-carbon compound carbon dioxide. The product of this cycle can be used as a precursor for the synthesis of all components of cell

  4. Floodplain Impact on Riverine Dissolved Carbon Cycling in the Mississippi-Atchafalaya River System

    Science.gov (United States)

    DelDuco, E.; Xu, Y. J.

    2017-12-01

    Studies have shown substantial increases in the export of terrestrial carbon by rivers over the past several decades, and have linked these increases to human activity such as changes in land use, urbanization, and intensive agriculture. The Mississippi River (MR) is the largest river in North America, and is among the largest in the world, making its carbon export globally significant. The Atchafalaya River (AR) receives 25% of the Mississippi River's flow before traveling 189 kilometers through the largest bottomland swamp in North America, providing a unique opportunity to study floodplain impacts on dissolved carbon in a large river. The aim of this study was to determine how dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) in the AR change spatially and seasonally, and to elucidate which processes control carbon cycling in this intricate swamp river system. From May 2015 -May 2016, we conducted monthly river sampling from the river's inflow to its outflow, analyzing samples for DOC and DIC concentrations and δ 13C stable isotope composition. During the study period, the river discharged a total of 5.35 Tg DIC and a total of 2.34 Tg DOC into the Gulf of Mexico. Based on the mass inflow-outflow balance, approximately 0.53 Tg ( 10%) of the total DIC exported was produced within the floodplain, while 0.24 Tg ( 10%) of DOC entering the basin was removed. The AR was consistently saturated with pCO2 above atmospheric pressure, indicating that this swamp-river system acts a large source of DIC to the atmosphere as well as to coastal margins. Largest changes in carbon constituents occurred during periods of greatest inundation of the basin, and corresponded with shifts in isotopic composition that indicated large inputs of DIC from floodplains. This effect was particularly pronounced during initial flood stages. This study demonstrates that a major river with extensive floodplains in its coastal margin can act as an important source of DIC as well

  5. Mechanistic controls on diverse fates of terrestrial organic components in the East China Sea

    NARCIS (Netherlands)

    Zhu, C.; Wagner, T.; Talbot, H.M.; Weijers, J.W.H.; Pan, J.-M.; Pancost, R.D.

    2013-01-01

    Terrestrial carbon transferred from the land to sea is a critical component of the global carbon cycle. A range of geochemical proxies has been developed to fingerprint the fate of terrestrial organic matter (TOM) in marine sediments. However, discrepancies among different proxies limit our ability

  6. Annual Cycles of Two Cyanobacterial Mat Communities in Hydro-Terrestrial Habitats of the High Arctic

    Czech Academy of Sciences Publication Activity Database

    Tashyreva, D.; Elster, Josef

    2016-01-01

    Roč. 71, č. 4 (2016), s. 887-900 ISSN 0095-3628 R&D Projects: GA MŠk ME 934; GA MŠk LA341 Institutional support: RVO:67985939 Keywords : Phormidium * Life cycle * Polar Regions Subject RIV: EH - Ecology , Behaviour Impact factor: 3.630, year: 2016

  7. Testing Urey's carbonate-silicate cycle using the calcium isotopic composition of sedimentary carbonates

    Science.gov (United States)

    Blättler, Clara L.; Higgins, John A.

    2017-12-01

    Carbonate minerals constitute a major component of the sedimentary geological record and an archive of a fraction of the carbon and calcium cycled through the Earth's surface reservoirs for over three billion years. For calcium, carbonate minerals constitute the ultimate sink for almost all calcium liberated during continental and submarine weathering of silicate minerals. This study presents >500 stable isotope ratios of calcium in Precambrian carbonate sediments, both limestones and dolomites, in an attempt to characterize the isotope mass balance of the sedimentary carbonate reservoir through time. The mean of the dataset is indistinguishable from estimates of the calcium isotope ratio of bulk silicate Earth, consistent with the Urey cycle being the dominant mechanism exchanging calcium among surface reservoirs. The variability in bulk sediment calcium isotope ratios within each geological unit does not reflect changes in the global calcium cycle, but rather highlights the importance of local mineralogical and/or diagenetic effects in the carbonate record. This dataset demonstrates the potential for calcium isotope ratios to help assess these local effects, such as the former presence of aragonite, even in rocks with a history of neomorphism and recrystallization. Additionally, 29 calcium isotope measurements are presented from ODP (Ocean Drilling Program) Site 801 that contribute to the characterization of altered oceanic crust as an additional sink for calcium, and whose distinct isotopic signature places a limit on the importance of this subduction flux over Earth history.

  8. Temperature acclimation of photosynthesis and respiration: A key uncertainty in the carbon cycle-climate feedback

    Science.gov (United States)

    Lombardozzi, Danica L.; Bonan, Gordon B.; Smith, Nicholas G.; Dukes, Jeffrey S.; Fisher, Rosie A.

    2015-10-01

    Earth System Models typically use static responses to temperature to calculate photosynthesis and respiration, but experimental evidence suggests that many plants acclimate to prevailing temperatures. We incorporated representations of photosynthetic and leaf respiratory temperature acclimation into the Community Land Model, the terrestrial component of the Community Earth System Model. These processes increased terrestrial carbon pools by 20 Pg C (22%) at the end of the 21st century under a business-as-usual (Representative Concentration Pathway 8.5) climate scenario. Including the less certain estimates of stem and root respiration acclimation increased terrestrial carbon pools by an additional 17 Pg C (~40% overall increase). High latitudes gained the most carbon with acclimation, and tropical carbon pools increased least. However, results from both of these regions remain uncertain; few relevant data exist for tropical and boreal plants or for extreme temperatures. Constraining these uncertainties will produce more realistic estimates of land carbon feedbacks throughout the 21st century.

  9. Slow growth rates of Amazonian trees: Consequences for carbon cycling

    Science.gov (United States)

    Vieira, Simone; Trumbore, Susan; Camargo, Plinio B.; Selhorst, Diogo; Chambers, Jeffrey Q.; Higuchi, Niro; Martinelli, Luiz Antonio

    2005-01-01

    Quantifying age structure and tree growth rate of Amazonian forests is essential for understanding their role in the carbon cycle. Here, we use radiocarbon dating and direct measurement of diameter increment to document unexpectedly slow growth rates for trees from three locations spanning the Brazilian Amazon basin. Central Amazon trees, averaging only ≈1mm/year diameter increment, grow half as fast as those from areas with more seasonal rainfall to the east and west. Slow growth rates mean that trees can attain great ages; across our sites we estimate 17-50% of trees with diameter >10 cm have ages exceeding 300 years. Whereas a few emergent trees that make up a large portion of the biomass grow faster, small trees that are more abundant grow slowly and attain ages of hundreds of years. The mean age of carbon in living trees (60-110 years) is within the range of or slightly longer than the mean residence time calculated from C inventory divided by annual C allocation to wood growth (40-100 years). Faster C turnover is observed in stands with overall higher rates of diameter increment and a larger fraction of the biomass in large, fast-growing trees. As a consequence, forests can recover biomass relatively quickly after disturbance, whereas recovering species composition may take many centuries. Carbon cycle models that apply a single turnover time for carbon in forest biomass do not account for variations in life strategy and therefore may overestimate the carbon sequestration potential of Amazon forests. PMID:16339903

  10. North America's net terrestrial CO2 exchange with the atmosphere 1990-2009

    Science.gov (United States)

    A.W. King; R.J. Andres; K J. Davis; M. Hafer; D.J. Hayes; D.N. Huntzinger; B. de Jong; W.A. Kurz; A.D. McGuire; R. Vargas; Y. Wei; T.O. West; C.W. Woodall

    2015-01-01

    Scientific understanding of the global carbon cycle is required for developing national and international policy to mitigate fossil fuel CO2 emissions by managing terrestrial carbon uptake. Toward that understanding and as a contribution to the REgional Carbon Cycle Assessment and Processes (RECCAP) project, this paper provides a synthesis of net...

  11. A carbon cycle science update since IPCC AR-4.

    Science.gov (United States)

    Dolman, A J; van der Werf, G R; van der Molen, M K; Ganssen, G; Erisman, J-W; Strengers, B

    2010-01-01

    We review important advances in our understanding of the global carbon cycle since the publication of the IPCC AR4. We conclude that: the anthropogenic emissions of CO2 due to fossil fuel burning have increased up through 2008 at a rate near to the high end of the IPCC emission scenarios; there are contradictory analyses whether an increase in atmospheric fraction, that might indicate a declining sink strength of ocean and/or land, exists; methane emissions are increasing, possibly through enhanced natural emission from northern wetland, methane emissions from dry plants are negligible; old-growth forest take up more carbon than expected from ecological equilibrium reasoning; tropical forest also take up more carbon than previously thought, however, for the global budget to balance, this would imply a smaller uptake in the northern forest; the exchange fluxes between the atmosphere and ocean are increasingly better understood and bottom up and observation-based top down estimates are getting closer to each other; the North Atlantic and Southern ocean take up less CO2, but it is unclear whether this is part of the 'natural' decadal scale variability; large-scale fires and droughts, for instance in Amazonia, but also at Northern latitudes, have lead to significant decreases in carbon uptake on annual timescales; the extra uptake of CO2 stimulated by increased N-deposition is, from a greenhouse gas forcing perspective, counterbalanced by the related additional N2O emissions; the amount of carbon stored in permafrost areas appears much (two times) larger than previously thought; preservation of existing marine ecosystems could require a CO2 stabilization as low as 450 ppm; Dynamic Vegetation Models show a wide divergence for future carbon trajectories, uncertainty in the process description, lack of understanding of the CO2 fertilization effect and nitrogen-carbon interaction are major uncertainties.

  12. Forecasting Responses of a Northern Peatland Carbon Cycle to Elevated CO2 and a Gradient of Experimental Warming

    Science.gov (United States)

    Jiang, Jiang; Huang, Yuanyuan; Ma, Shuang; Stacy, Mark; Shi, Zheng; Ricciuto, Daniel M.; Hanson, Paul J.; Luo, Yiqi

    2018-03-01

    The ability to forecast ecological carbon cycling is imperative to land management in a world where past carbon fluxes are no longer a clear guide in the Anthropocene. However, carbon-flux forecasting has not been practiced routinely like numerical weather prediction. This study explored (1) the relative contributions of model forcing data and parameters to uncertainty in forecasting flux- versus pool-based carbon cycle variables and (2) the time points when temperature and CO2 treatments may cause statistically detectable differences in those variables. We developed an online forecasting workflow (Ecological Platform for Assimilation of Data (EcoPAD)), which facilitates iterative data-model integration. EcoPAD automates data transfer from sensor networks, data assimilation, and ecological forecasting. We used the Spruce and Peatland Responses Under Changing Experiments data collected from 2011 to 2014 to constrain the parameters in the Terrestrial Ecosystem Model, forecast carbon cycle responses to elevated CO2 and a gradient of warming from 2015 to 2024, and specify uncertainties in the model output. Our results showed that data assimilation substantially reduces forecasting uncertainties. Interestingly, we found that the stochasticity of future external forcing contributed more to the uncertainty of forecasting future dynamics of C flux-related variables than model parameters. However, the parameter uncertainty primarily contributes to the uncertainty in forecasting C pool-related response variables. Given the uncertainties in forecasting carbon fluxes and pools, our analysis showed that statistically different responses of fast-turnover pools to various CO2 and warming treatments were observed sooner than slow-turnover pools. Our study has identified the sources of uncertainties in model prediction and thus leads to improve ecological carbon cycling forecasts in the future.

  13. What Have We Learned About Arctic Carbon Since The First State of the Carbon Cycle Report?

    Science.gov (United States)

    Schuur, E.

    2015-12-01

    Large pools of organic carbon were reported in The First State of the Carbon Cycle Report, but measurements from high latitude ecosystems, in particular for deeper soils >1m depth, remained scarce. A newly enlarged soil carbon database with an order of magnitude more numerous deep sampling sites has verified the widespread pattern of large quantities of carbon accumulated deep in permafrost (perennially frozen) soils. The known pool of permafrost carbon across the northern circumpolar permafrost zone is now estimated to be 1330-1580 Pg C, with the potential for an additional ~400 Pg C in deep permafrost sediments. In addition, an uncertainty estimate of plus/minus 15% has now been calculated for the soil carbon pool in the surface 0-3m. Laboratory incubations of these permafrost soils reveal that a significant fraction can be mineralized by microbes upon thaw and converted to carbon dioxide and methane on time scales of years to decades, with decade-long average losses from aerobic incubations ranging from 6-34% of initial carbon. Carbon emissions from the same soils incubated in an anaerobic environment are, on average, 78-85% lower than aerobic soils. But, the more potent greenhouse gas methane released under anaerobic conditions in part increases the climate impact of these emissions. While mean quantities of methane are only 3% to 7% that of carbon dioxide emitted from anaerobic incubations (by weight of C), these mean methane values represent 25% to 45% of the overall potential impact on climate when accounting for the higher global warming potential of methane. Taken together though, in spite of the more potent greenhouse gas methane, a unit of newly thawed permafrost carbon could have a greater impact on climate over a century if it thaws and decomposes within a drier, aerobic soil as compared to an equivalent amount of carbon within a waterlogged soil or sediment. Model projections tend to estimate losses of carbon in line with empirical measurements, but

  14. Watershed-scale changes in terrestrial nitrogen cycling during a period of decreased atmospheric nitrate and sulfur deposition

    Science.gov (United States)

    Sabo, Robert D.; Scanga, Sara E.; Lawrence, Gregory B.; Nelson, David M.; Eshleman, Keith N.; Zabala, Gabriel A.; Alinea, Alexandria A.; Schirmer, Charles D.

    2016-01-01

    Recent reports suggest that decreases in atmospheric nitrogen (N) deposition throughout Europe and North America may have resulted in declining nitrate export in surface waters in recent decades, yet it is unknown if and how terrestrial N cycling was affected. During a period of decreased atmospheric N deposition, we assessed changes in forest N cycling by evaluating trends in tree-ring δ15N values (between 1980 and 2010; n = 20 trees per watershed), stream nitrate yields (between 2000 and 2011), and retention of atmospherically-deposited N (between 2000 and 2011) in the North and South Tributaries (North and South, respectively) of Buck Creek in the Adirondack Mountains, USA. We hypothesized that tree-ring δ15N values would decline following decreases in atmospheric N deposition (after approximately 1995), and that trends in stream nitrate export and retention of atmospherically deposited N would mirror changes in tree-ring δ15N values. Three of the six sampled tree species and the majority of individual trees showed declining linear trends in δ15N for the period 1980–2010; only two individual trees showed increasing trends in δ15N values. From 1980 to 2010, trees in the watersheds of both tributaries displayed long-term declines in tree-ring δ15N values at the watershed scale (R = −0.35 and p = 0.001 in the North and R = −0.37 and p <0.001 in the South). The decreasing δ15N trend in the North was associated with declining stream nitrate concentrations (−0.009 mg N L−1 yr−1, p = 0.02), but no change in the retention of atmospherically deposited N was observed. In contrast, nitrate yields in the South did not exhibit a trend, and the watershed became less retentive of atmospherically deposited N (−7.3% yr−1, p < 0.001). Our δ15N results indicate a change in terrestrial N availability in both watersheds prior to decreases in atmospheric N deposition, suggesting that decreased atmospheric N deposition was not the sole driver of

  15. Cycling of beryllium and carbon through hillslope soils in Iowa

    Science.gov (United States)

    Harden, J.W.; Fries, T.L.; Pavich, M.J.

    2002-01-01

    Isotopes of Be and C were used to reconstruct loess accumulation, hillslope evolution, and agricultural modification in soils of western Iowa. While both elements are derived from additions by the atmosphere (via plants in the case of carbon), the differences in element cycling allow erosional and depositional processes to be separated from biochemical processing. Based on 10Be, loess accumulation likely occurred simultaneously with hillslope degradation. Rates of loess accumulation declined five-fold between early stages (late Pleistocene and early Holocene) and later stages (late Holocene) of accumulation, but the absolute timing of accumulation requires independent dating methods. Based on 14C measurements, plant inputs and decomposition are significant near the surface, but below 1-1.5 m carbon inputs are minimal and decomposition is nearly arrested. The amount of carbon below 1.5 m is constant (0.1%) and is composed of soil organic matter that was buried by loess. Agricultural modification results in a dramatic redistribution of 10Be through soil erosion and deposition. By contrast, the redistribution of soil organic matter is masked by the rapid cycling of C through the topsoil as it continually decomposes and is replaced by plant inputs.

  16. Microbial diversity and carbon cycling in San Francisco Bay wetlands

    Energy Technology Data Exchange (ETDEWEB)

    Theroux, Susanna [Lawrence Berkeley National Lab. (LBNL), Walnut Creek, CA (United States). Dept. of Energy Joint Genome Inst.; Hartman, Wyatt [Lawrence Berkeley National Lab. (LBNL), Walnut Creek, CA (United States). Dept. of Energy Joint Genome Inst.; He, Shaomei [Lawrence Berkeley National Lab. (LBNL), Walnut Creek, CA (United States). Dept. of Energy Joint Genome Inst.; Univ. of Wisconsin, Madison, WI (United States); Tringe, Susannah [Lawrence Berkeley National Lab. (LBNL), Walnut Creek, CA (United States). Dept. of Energy Joint Genome Inst.

    2014-03-21

    Wetland restoration efforts in San Francisco Bay aim to rebuild habitat for endangered species and provide an effective carbon storage solution, reversing land subsidence caused by a century of industrial and agricultural development. However, the benefits of carbon sequestration may be negated by increased methane production in newly constructed wetlands, making these wetlands net greenhouse gas (GHG) sources to the atmosphere. We investigated the effects of wetland restoration on below-ground microbial communities responsible for GHG cycling in a suite of historic and restored wetlands in SF Bay. Using DNA and RNA sequencing, coupled with real-time GHG monitoring, we profiled the diversity and metabolic potential of wetland soil microbial communities. The wetland soils harbor diverse communities of bacteria and archaea whose membership varies with sampling location, proximity to plant roots and sampling depth. Our results also highlight the dramatic differences in GHG production between historic and restored wetlands and allow us to link microbial community composition and GHG cycling with key environmental variables including salinity, soil carbon and plant species.

  17. Bacteria in the greenhouse: Modeling the role of oceanic plankton in the global carbon cycle

    International Nuclear Information System (INIS)

    Ducklow, H.W.; Fasham, M.J.R.

    1992-01-01

    To plan effectively to deal with the greenhouse effect, a fundamental understanding is needed of the biogeochemical and physical machinery that cycles carbon in the global system; in addition, models are needed of the carbon cycle to project the effects of increasing carbon dioxide. In this chapter, a description is given of efforts to simulate the cycling of carbon and nitrogen in the upper ocean, concentrating on the model's treatment of marine phytoplankton, and what it reveals of their role in the biogeochemical cycling of carbon between the ocean and atmosphere. The focus is on the upper ocean because oceanic uptake appears to regulate the level of carbon dioxide in the atmosphere

  18. Longevity of terrestrial Carbon sinks: effects of soil degradation on greenhouse gas emissions

    Science.gov (United States)

    Kuhn, Nikolaus J.; Berger, Samuel; Kuonen, Samuel

    2013-04-01

    productivity associated with erosion. Areas with high erosion rates and already erosion-induced damages to soil productivity were considered to be closing or closed landscape carbon sinks. The final global assessment indicates that severe soil degradation in Africa, the Americas and Asia carries the risk of closing terrestrial Carbon sinks that currently contribute to an unintended mitigation of greenhouse gas emissions.

  19. Dynamic of biogeochemical selenium cycle in terrestrial ecosystems: retention and reactivity in soil; role of vegetation

    International Nuclear Information System (INIS)

    Di Tullo, Pamela

    2015-01-01

    This work was performed in the frame of the safety assessment program prior to the possible construction of an underground repository for nuclear waste (HAVL). To consolidate risk assessment models associated to a potential 79 Se biosphere contamination, biogeochemistry of stable selenium was investigated, aiming firstly to highlight the dynamics of Se cycling in a forest ecosystem, in terms of inventories and annual fluxes. Consequently to these first results, which suggest a clay role of soil and its organic pool in the global Se cycle, two studies based on the use of isotopically enriched tracers were further carried out in order to clarify the processes involved in (i) Se retention and reactivity in soils and (ii) incorporation of inorganic Se within organic pool of vegetal biomass. (author) [fr

  20. Exploring Viral Mediated Carbon Cycling in Thawing Permafrost Microbial Communities

    Science.gov (United States)

    Trubl, G. G.; Solonenko, N.; Moreno, M.; Sullivan, M. B.; Rich, V. I.

    2014-12-01

    Viruses are the most abundant biological entities on Earth and their impact on carbon cycling in permafrost habitats is poorly understood. Arctic C cycling is particularly important to interpret due to the rapid climate change occurring and the large amount of C stockpiled there (~1/3 of global soil C is stored in permafrost). Viruses of microbes (i.e. phages) play central roles in C cycling in the oceans, through cellular lysis (phage drive the largest ocean C flux about 150 Gt yr-1, dwarfing all others by >5-fold), production of associated DOC, as well as transport and expression during infection (1029 transduction events day-1). C cycling in thawing permafrost systems is critical in understanding the climate trajectory and phages may be as important for C cycling here as they are in the ocean. The thawed C may become a food source for microbes, producing CO2 and potentially CH4, both potent greenhouse gases. To address the potential role of phage in C cycling in these dynamic systems, we are examining phage from an arctic permafrost thaw gradient in northern Sweden. We have developed a protocol for successfully extracting phage from peat soils and are quantifying phage in 15 peat and 2 lake sediment cores, with the goal of sequencing viromes. Preliminary data suggest that phage are present at 109 g-1 across the permafrost thaw gradient (compared to the typical marine count ~105 ml-1), implying a potentially robust phage-host interaction web in these changing environments. We are examining phage from 11 depth intervals (covering the active and permafrost layer) in the cores to assess phage-host community dynamics. Phage morphology and abundance for each layer and environment are being determined using qTEM and EFM. Understanding the phage that infect bacteria and archaea in these rapidly changing habitats will provide insight into the controls on current and future CH4 and CO2 emissions in permafrost habitats.

  1. Marine geochemistry ocean circulation, carbon cycle and climate change

    CERN Document Server

    Roy-Barman, Matthieu

    2016-01-01

    Marine geochemistry uses chemical elements and their isotopes to study how the ocean works. It brings quantitative answers to questions such as: What is the deep ocean mixing rate? How much atmospheric CO2 is pumped by the ocean? How fast are pollutants removed from the ocean? How do ecosystems react to the anthropogenic pressure? The book provides a simple introduction to the concepts (environmental chemistry, isotopes), the methods (field approach, remote sensing, modeling) and the applications (ocean circulation, carbon cycle, climate change) of marine geochemistry with a particular emphasis on isotopic tracers. Marine geochemistry is not an isolated discipline: numerous openings on physical oceanography, marine biology, climatology, geology, pollutions and ecology are proposed and provide a global vision of the ocean. It includes new topics based on ongoing research programs such as GEOTRACES, Global Carbon Project, Tara Ocean. It provides a complete outline for a course in marine geochemistry. To favor a...

  2. Superior flexibility of a wrinkled carbon shell under electrochemical cycling

    KAUST Repository

    Li, Qianqian; Wang, Peng; Feng, Qiong; Mao, Minmin; Liu, Jiabin; Wang, Hongtao; Mao, Scott; Zhang, Xixiang

    2014-01-01

    Nanocarbon composites have been extensively employed in engineering alloy-type anodes in order to improve the poor cyclability caused by the enormous volume changes during lithium (Li+) insertion/extraction. The chemical vapor deposited wrinkled carbon shell (WCS) shows high electrical conductivity, excellent thermal stability and remarkable mechanical robustness, which help in retaining the structural integrity around the tin (Sn) anode core despite ∼250% variation in volume during repetitive lithiation and delithiation. In situ transmission electron microscopy reveals no embrittlement in the lithiated WCS, which fully recovers its original shape after severe mechanical deformation with no obvious structural change. Further analysis indicates that the capacity to accommodate large strains is closely related to the construction of the carbon shell, that is, the stacking of wrinkled few-layer graphenes. Both the pre-existing wrinkles and the few-layer thickness render the carbon shell superior flexibility and good elasticity under bending or expansion of the interior volume. Moreover, the WCS possesses fast lithium ion diffusion channels, which have lower activation barriers (∼0.1 eV) than that on a smooth graphene (∼0.3 eV). The results provide an insight into the improvement in cycle performance that can be achieved through carbon coating of anodes of lithium ion batteries. © 2014 The Royal Society of Chemistry.

  3. Warm ocean processes and carbon cycling in the Eocene.

    Science.gov (United States)

    John, Eleanor H; Pearson, Paul N; Coxall, Helen K; Birch, Heather; Wade, Bridget S; Foster, Gavin L

    2013-10-28

    Sea surface and subsurface temperatures over large parts of the ocean during the Eocene epoch (55.5-33.7 Ma) exceeded modern values by several degrees, which must have affected a number of oceanic processes. Here, we focus on the effect of elevated water column temperatures on the efficiency of the biological pump, particularly in relation to carbon and nutrient cycling. We use stable isotope values from exceptionally well-preserved planktonic foraminiferal calcite from Tanzania and Mexico to reconstruct vertical carbon isotope gradients in the upper water column, exploiting the fact that individual species lived and calcified at different depths. The oxygen isotope ratios of different species' tests are used to estimate the temperature of calcification, which we converted to absolute depths using Eocene temperature profiles generated by general circulation models. This approach, along with potential pitfalls, is illustrated using data from modern core-top assemblages from the same area. Our results indicate that, during the Early and Middle Eocene, carbon isotope gradients were steeper (and larger) through the upper thermocline than in the modern ocean. This is consistent with a shallower average depth of organic matter remineralization and supports previously proposed hypotheses that invoke high metabolic rates in a warm Eocene ocean, leading to more efficient recycling of organic matter and reduced burial rates of organic carbon.

  4. A new indicator framework for quantifying the intensity of the terrestrial water cycle

    Science.gov (United States)

    Huntington, Thomas G.; Weiskel, Peter K.; Wolock, David M.; McCabe, Gregory J.

    2018-04-01

    A quantitative framework for characterizing the intensity of the water cycle over land is presented, and illustrated using a spatially distributed water-balance model of the conterminous United States (CONUS). We approach water cycle intensity (WCI) from a landscape perspective; WCI is defined as the sum of precipitation (P) and actual evapotranspiration (AET) over a spatially explicit landscape unit of interest, averaged over a specified time period (step) of interest. The time step may be of any length for which data or simulation results are available (e.g., sub-daily to multi-decadal). We define the storage-adjusted runoff (Q‧) as the sum of actual runoff (Q) and the rate of change in soil moisture storage (ΔS/Δt, positive or negative) during the time step of interest. The Q‧ indicator is demonstrated to be mathematically complementary to WCI, in a manner that allows graphical interpretation of their relationship. For the purposes of this study, the indicators were demonstrated using long-term, spatially distributed model simulations with an annual time step. WCI was found to increase over most of the CONUS between the 1945 to 1974 and 1985 to 2014 periods, driven primarily by increases in P. In portions of the western and southeastern CONUS, Q‧ decreased because of decreases in Q and soil moisture storage. Analysis of WCI and Q‧ at temporal scales ranging from sub-daily to multi-decadal could improve understanding of the wide spectrum of hydrologic responses that have been attributed to water cycle intensification, as well as trends in those responses.

  5. Evaluation of 11 terrestrial carbon–nitrogen cycle models against observations from two temperate Free-Air CO2 Enrichment studies

    Science.gov (United States)

    Zaehle, Sönke; Medlyn, Belinda E; De Kauwe, Martin G; Walker, Anthony P; Dietze, Michael C; Hickler, Thomas; Luo, Yiqi; Wang, Ying-Ping; El-Masri, Bassil; Thornton, Peter; Jain, Atul; Wang, Shusen; Warlind, David; Weng, Ensheng; Parton, William; Iversen, Colleen M; Gallet-Budynek, Anne; McCarthy, Heather; Finzi, Adrien; Hanson, Paul J; Prentice, I Colin; Oren, Ram; Norby, Richard J

    2014-01-01

    We analysed the responses of 11 ecosystem models to elevated atmospheric [CO2] (eCO2) at two temperate forest ecosystems (Duke and Oak Ridge National Laboratory (ORNL) Free-Air CO2 Enrichment (FACE) experiments) to test alternative representations of carbon (C)–nitrogen (N) cycle processes. We decomposed the model responses into component processes affecting the response to eCO2 and confronted these with observations from the FACE experiments. Most of the models reproduced the observed initial enhancement of net primary production (NPP) at both sites, but none was able to simulate both the sustained 10-yr enhancement at Duke and the declining response at ORNL: models generally showed signs of progressive N limitation as a result of lower than observed plant N uptake. Nonetheless, many models showed qualitative agreement with observed component processes. The results suggest that improved representation of above-ground–below-ground interactions and better constraints on plant stoichiometry are important for a predictive understanding of eCO2 effects. Improved accuracy of soil organic matter inventories is pivotal to reduce uncertainty in the observed C–N budgets. The two FACE experiments are insufficient to fully constrain terrestrial responses to eCO2, given the complexity of factors leading to the observed diverging trends, and the consequential inability of the models to explain these trends. Nevertheless, the ecosystem models were able to capture important features of the experiments, lending some support to their projections. PMID:24467623

  6. Accelerating Net Terrestrial Carbon Uptake During the Warming Hiatus Due to Reduced Respiration

    Science.gov (United States)

    Ballantyne, Ashley; Smith, William; Anderegg, William; Kauppi, Pekka; Sarmiento, Jorge; Tans, Pieter; Shevliakova, Elena; Pan, Yude; Poulter, Benjamin; Anav, Alessandro; hide

    2017-01-01

    The recent warming hiatus presents an excellent opportunity to investigate climate sensitivity of carbon cycle processes. Here we combine satellite and atmospheric observations to show that the rate of net biome productivity (NBP) has significantly accelerated from - 0.007 +/- 0.065 PgC yr(exp -2) over the warming period (1982 to 1998) to 0.119 +/- 0.071 PgC yr(exp -2) over the warming hiatus (19982012). This acceleration in NBP is not due to increased primary productivity, but rather reduced respiration that is correlated (r = 0.58; P = 0.0007) and sensitive ( y = 4.05 to 9.40 PgC yr(exp -1) per C) to land temperatures. Global land models do not fully capture this apparent reduced respiration over the warming hiatus; however, an empirical model including soil temperature and moisture observations better captures the reduced respiration.

  7. Multi-factor controls on terrestrial carbon dynamics in urbanised areas

    Science.gov (United States)

    Zhang, C.; Tian, H.; Pan, S.; Lockaby, G.; Chappelka, A.

    2013-11-01

    As urban land cover and populations continue rapidly increasing across the globe, much concern has been raised that urbanization may significantly alter terrestrial carbon dynamics that affects atmospheric CO2 concentration and climate. Urbanization involves complex changes in land structure and multiple environmental factors. Relative contribution of these and their interactive effects need be quantified to better understand urbanization effects on regional C dynamics as well as assess the effectiveness of C sequestration policies focusing on urban green space development. In this study, we analyzed the factors that may control the urbanization effect on ecosystem C dynamics, and proposed a numeric experimental scheme, i.e. scenarios design, to conduct factorial analysis on the effects of different factors. Then as a case study, a dynamic land ecosystem model (DLEM) was applied to quantify the urbanization effect on the C dynamics of the Southern US (SUS) from 1945-2007, and to analyze the relative contributions from each environmental factor and their interactive effects. We found the effect of urban land conversion dominated the C dynamics in the SUS, resulting in about 0.37 Pg C lost from 1945-2007. However, urban ecosystem management and urban-induced environmental changes enhanced C sequestration by 0.12 Pg and 0.03 Pg, respectively. Their C sequestration effects, which amounted to 40% of the magnitude of land conversion effect, partially compensated for the C loss during urbanization. Numeric experiments and factorial analyses indicated complex interactive effects among different factors and between various land covers and environmental controls, findings need to be further confirmed by field studies. The proposed numeric experimental scheme provides a quantitative approach for understanding the complex mechanisms controlling C dynamics, and defining best development practices in urbanised areas.

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

    Directory of Open Access Journals (Sweden)

    Zhenggang Du

    2015-03-01

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

  9. Current systematic carbon-cycle observations and the need for implementing a policy-relevant carbon observing system

    Science.gov (United States)

    P. Ciais; A. J. Dolman; A. Bombelli; R. Duren; A. Peregon; P. J. Rayner; C. Miller; N. Gobron; G. Kinderman; G. Marland; N. Gruber; F. Chevallier; R. J. Andres; G. Balsamo; L. Bopp; F.-M. Bréon; G. Broquet; R. Dargaville; T. J. Battin; A. Borges; H. Bovensmann; M. Buchwitz; J. Butler; J. G. Canadell; R. B. Cook; R. DeFries; R. Engelen; K. R. Gurney; C. Heinze; M. Heimann; A. Held; M. Henry; B. Law; S. Luyssaert; J. Miller; T. Moriyama; C. Moulin; R. B. Myneni; C. Nussli; M. Obersteiner; D. Ojima; Y. Pan; J.-D. Paris; S. L. Piao; B. Poulter; S. Plummer; S. Quegan; P. Raymond; M. Reichstein; L. Rivier; C. Sabine; D. Schimel; O. Tarasova; R. Valentini; R. Wang; G. van der Werf; D. Wickland; M. Williams; C. Zehner

    2014-01-01

    A globally integrated carbon observation and analysis system is needed to improve the fundamental understanding of the global carbon cycle, to improve our ability to project future changes, and to verify the effectiveness of policies aiming to reduce greenhouse gas emissions and increase carbon sequestration. Building an integrated carbon observation system requires...

  10. The 2015-2016 El Niño and the response of the carbon cycle: Findings from the Orbiting Carbon Observatory-2 (OCO-2) mission

    Science.gov (United States)

    Chatterjee, A.; Schimel, D.; Stephens, B. B.; Crisp, D.; Eldering, A.; Gunson, M. R.; Feely, R. A.; Gierach, M. M.; Keeling, R. F.; Sutton, A. J.; Weir, B.

    2017-12-01

    The El Nino Southern Oscillation (ENSO) is the most important mode of tropical climate variability on interannual to decadal time scales. Correlations between atmospheric CO2 growth rate and ENSO activity are relatively well known but the magnitude of this correlation, the contribution from tropical marine vs. terrestrial flux components, and the causal mechanisms, are poorly constrained in space and time. The launch of NASA's Orbiting Carbon Observatory-2 (OCO-2) mission in July 2014 was rather timely given the development of strong ENSO conditions over the tropical Pacific Ocean in 2015-2016. In this presentation, we will discuss how the high-density observations from OCO-2 provided us with a novel dataset to resolve the linkages between El Niño and atmospheric CO2. Along with information from in situ observations of ΔpCO2 from NOAA's Tropical Atmosphere Ocean (TAO) project and atmospheric CO2 from the Scripps CO2 Program, and other remote-sensing missions, we are able to piece together the time dependent response of atmospheric CO2 concentrations over the Tropics. Our findings confirm the hypothesis from studies following the 1997-1998 El Niño event that an early reduction in CO2 outgassing from the tropical Pacific Ocean is later reversed by enhanced net CO2 emissions from the terrestrial biosphere. This implies that a component of the interannual variability (IAV) in the growth rate of atmospheric CO2, which has typically been used to constrain the climate sensitivity of tropical land carbon fluxes, is strongly influenced and modified by ocean fluxes during the early phase of the ENSO event. Our analyses shed further light on the understanding of the marine vs. terrestrial partitioning of tropical carbon fluxes during El Niño events, their relative contributions to the global atmospheric CO2 growth rate, and provide clues about the sensitivity of the carbon cycle to climate forcing on interannual time scales.

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

    Science.gov (United States)

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

    2014-12-01

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

  12. Amazon River carbon dioxide outgassing fuelled by wetlands

    NARCIS (Netherlands)

    Abril, G.; Martinez, J.M.; Artigas, L.F.; Moreira-Turcq, P.; Benedetti, M.F.; Vidal, L.; Meziane, T.; Kim, J.-H.; Bernardes, M.C.; Savoye, N.; Deborde, J.; Souza, E.L.; Alberic, P.; de Souza, M.F.L.; Roland, F.

    2014-01-01

    River systems connect the terrestrial biosphere, the atmosphere and the ocean in the global carbon cycle(1). A recent estimate suggests that up to 3 petagrams of carbon per year could be emitted as carbon dioxide (CO2) from global inland waters, offsetting the carbon uptake by terrestrial

  13. Ring-testing and field-validation of a terrestrial model ecosystem - An instrument for testing potentially harmful substances: effects of carbendazim on nutrient cycling.

    NARCIS (Netherlands)

    van Gestel, C.A.M.; Koolhaas, J.E.; Schallnass, H.-J.; Rodrigues, J.M.L.; Jones, S.E.

    2004-01-01

    The effect of the fungicide carbendazim (applied in the formulation Derosal®) on nutrient cycling in soil was determined in Terrestrial Model Ecosystem (TME) tests and corresponding field-validation studies, which were performed in four different countries (United Kingdom, Germany, Portugal, and The

  14. Modeling the Pan-Arctic terrestrial and atmospheric water cycle. Final report; FINAL

    International Nuclear Information System (INIS)

    Gutowski, W.J. Jr.

    2001-01-01

    This report describes results of DOE grant DE-FG02-96ER61473 to Iowa State University (ISU). Work on this grant was performed at Iowa State University and at the University of New Hampshire in collaboration with Dr. Charles Vorosmarty and fellow scientists at the University of New Hampshire's (UNH's) Institute for the Study of the Earth, Oceans, and Space, a subcontractor to the project. Research performed for the project included development, calibration and validation of a regional climate model for the pan-Arctic, modeling river networks, extensive hydrologic database development, and analyses of the water cycle, based in part on the assembled databases and models. Details appear in publications produced from the grant

  15. Assessment of the Effects of Urban Expansion on Terrestrial Carbon Storage: A Case Study in Xuzhou City, China

    Directory of Open Access Journals (Sweden)

    Cheng Li

    2018-02-01

    Full Text Available Carbon storage is closely connected to the productivities and climate regulation capacities of ecosystems. Assessing the effects of urban expansion on carbon storage has become increasingly important for achieving urban sustainability. This study analyzed the effects of urban expansion on terrestrial carbon storage in Xuzhou City, China during 2000–2025. The cellular automata (CA model was developed to simulate future urban expansion under three scenarios, namely, the business as usual (BAU, ecological protection (ECO, and planning strengthened (PLS scenarios. The Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST model was further applied to explore the consequences of urban expansion on carbon storage. The results show that urban expansion resulted in 6.099 Tg of carbon storage loss from 2000–2015. Moreover, significant differences in the effects of the urban expansion scenarios on carbon storage were identified in terms of both magnitude and spatial pattern from 2015–2025. Compared with the other scenarios, the PLS scenario could be considered as a good option that would allow future development to achieve the objectives of the lowest carbon storage losses. The findings improve the understanding of the effects of urban expansion on carbon storage and may be used to support urban planning and management.

  16. Carbon-14 discharges from the nuclear fuel cycle: Pt. 1

    International Nuclear Information System (INIS)

    McCartney, M.; Baxter, M.S.; Scott, E.M.

    1988-01-01

    The radiological impact of 14 C produced by the nuclear fuel cycle is assessed using an advanced 25-box model of the carbon cycle coupled with a range of feasible energy-use scenarios. In particular, this study estimates both the short- and long-term dose implications to the global population. In the former context, it is predicted that the atmospheric 14 C specific activity in the year 2050 will be 234 Bq kg -1 (carbon), corresponding to delivery of an individual effective dose equivalent rate of 15 μSv year -1 . The contribution of reactor-derived 14 C to the individual dose rate increases steadily throughout this period, reaching 1.8 μSv year -1 in 2050, well within ICRP limits. In the longer term, however, the collective effective dose equivalent commitment is conservatively estimated at 141 man Sv TBq -1 , corresponding to 480 man Sv (GW(e) year) -1 . These figures indicate that 14 C could generate one of the largest contributions to the total dose to man from nuclear power production. (author)

  17. Effects of Litter and Nutrient Additions on Soil Carbon Cycling in a Tropical Forest

    Science.gov (United States)

    Cusack, D. F.; Halterman, S.; Turner, B. L.; Tanner, E.; Wright, S. J.

    2014-12-01

    Soil carbon (C) dynamics present one of the largest sources of uncertainty in global C cycle models, with tropical forest soils containing some of the largest terrestrial C stocks. Drastic changes in soil C storage and loss are likely to occur if global change alters plant net primary production (NPP) and/or nutrient availability in these ecosystems. We assessed the effects of litter removal and addition, as well as fertilization with nitrogen (N), phosphorus (P), and/or potassium (K), on soil C stocks in a tropical seasonal forest in Panama after ten and sixteen years, respectively. We used a density fractionation scheme to assess manipulation effects on rapidly and slowly cycling pools of C. Soil samples were collected in the wet and dry seasons from 0-5 cm and 5-10 cm depths in 15- 45x45 m plots with litter removal, 2x litter addition, and control (n=5), and from 32- 40x40 m fertilization plots with factorial additions of N, P, and K. We hypothesized that litter addition would increase all soil C fractions, but that the magnitude of the effect on rapidly-cycling C would be dampened by a fertilization effect. Results for the dry season show that the "free light" C fraction, or rapidly cycling soil C pool, was significantly different among the three litter treatments, comprising 5.1 ± 0.9 % of total soil mass in the litter addition plots, 2.7 ± 0.3 % in control plots, and 1.0 ± 0.1 % in litter removal plots at the 0-5cm depth (means ± one standard error, p < 0.05). Bulk soil C results are similar to observed changes in the rapidly cycling C pool for the litter addition and removal. Fertilization treatments on average diminished this C pool size relative to control plots, although there was substantial variability among fertilization treatments. In particular, addition of N and P together did not significantly alter rapidly cycling C pool sizes (4.1 ± 1.2 % of total soil mass) relative to controls (3.5 ± 0.4 %), whereas addition of P alone resulted in

  18. The biomass burning contribution to climate–carbon-cycle feedback

    Directory of Open Access Journals (Sweden)

    S. P. Harrison

    2018-05-01

    Full Text Available Temperature exerts strong controls on the incidence and severity of fire. All else equal, warming is expected to increase fire-related carbon emissions, and thereby atmospheric CO2. But the magnitude of this feedback is very poorly known. We use a single-box model of the land biosphere to quantify this positive feedback from satellite-based estimates of biomass burning emissions for 2000–2014 CE and from sedimentary charcoal records for the millennium before the industrial period. We derive an estimate of the centennial-scale feedback strength of 6.5 ± 3.4 ppm CO2 per degree of land temperature increase, based on the satellite data. However, this estimate is poorly constrained, and is largely driven by the well-documented dependence of tropical deforestation and peat fires (primarily anthropogenic on climate variability patterns linked to the El Niño–Southern Oscillation. Palaeo-data from pre-industrial times provide the opportunity to assess the fire-related climate–carbon-cycle feedback over a longer period, with less pervasive human impacts. Past biomass burning can be quantified based on variations in either the concentration and isotopic composition of methane in ice cores (with assumptions about the isotopic signatures of different methane sources or the abundances of charcoal preserved in sediments, which reflect landscape-scale changes in burnt biomass. These two data sources are shown here to be coherent with one another. The more numerous data from sedimentary charcoal, expressed as normalized anomalies (fractional deviations from the long-term mean, are then used – together with an estimate of mean biomass burning derived from methane isotope data – to infer a feedback strength of 5.6 ± 3.2 ppm CO2 per degree of land temperature and (for a climate sensitivity of 2.8 K a gain of 0.09 ± 0.05. This finding indicates that the positive carbon cycle feedback from increased fire provides a substantial

  19. Monitoring the Carbon Cycle: Improving Our Ability to Proved Policy Relevant Information

    Science.gov (United States)

    Bruhwiler, L.

    2017-12-01

    Humans have altered the energy balance of the climate system mainly by producing and consuming fossil fuels, but also by emissions from food production. Manufacture and use of halocarbons, many of which are also strong greenhouse gases (GHGs) have added to anthropogenic radiative forcing. In response, the global atmosphere has warmed over the last half century at a rate of 0.17°C. The largest contribution to radiative forcing is due to CO2, and at present, about half of all anthropogenic CO2 emissions have been taken up by the oceans and terrestrial biosphere. The size of this "carbon emission discount" may change in the future as more carbon accumulates in the oceans, as human alter landscapes, and as climate changes. Efforts to limit global average temperature increases to 2°C and avoid the most catastrophic consequences of climate change depend on keeping track of both human emissions of greenhouse gases and changes in natural fluxes of carbon and nitrogen that occur in response to human activities and changing climate. Global in situ network observations provide information about changes in global GHG abundances over recent decades, as well as changing distributions between hemispheres. This information gives insight into changes in global and hemispheric sources and sinks of GHGs. It is, however, currently difficult to obtain robust information about regional sources and to discriminate between natural and anthropogenic fluxes. Information about regional sources is needed for GHG policymaking, while discrimination of natural sources is necessary for detection of trends in GHG fluxes and evaluation of coupled carbon cycle climate models. Although column average GHG abundances from space-based remote sensing data could provide considerable constraints on GHG budgets, there are still technical challenges to be overcome. Possible strategies for making progress involve greater increased observational coverage and more international collaboration, as well as

  20. The carbon cycle in a land surface model: modelling, validation and implementation at a global scale; Cycle du carbone dans un modele de surface continentale: modelisation, validation et mise en oeuvre a l'echelle globale

    Energy Technology Data Exchange (ETDEWEB)

    Gibelin, A.L

    2007-05-15

    ISBA-A-gs is an option of the CNRM land surface model ISBA which allows for the simulation of carbon exchanges between the terrestrial biosphere and the atmosphere. The model was implemented for the first time at the global scale as a stand-alone model. Several global simulations were performed to assess the sensitivity of the turbulent fluxes and Leaf Area Index to a doubling of the CO{sub 2} atmospheric concentration, and to the climate change simulated by the end of the 21. century. In addition, a new option of ISBA, referred to as ISBA-CC, was developed in order to simulate a more detailed ecosystem respiration by separating the autotrophic respiration and the heterotrophic respiration. The vegetation dynamics and the carbon fluxes were validated at a global scale using satellite datasets, and at a local scale using data from 26 sites of the FLUXNET network. All these results show that the model is sufficiently realistic to be coupled with a general circulation model, in order to account for interactions between the terrestrial biosphere, the atmosphere and the carbon cycle. (author)

  1. The carbon cycle in a land surface model: modelling, validation and implementation at a global scale; Cycle du carbone dans un modele de surface continentale: modelisation, validation et mise en oeuvre a l'echelle globale

    Energy Technology Data Exchange (ETDEWEB)

    Gibelin, A L

    2007-05-15

    ISBA-A-gs is an option of the CNRM land surface model ISBA which allows for the simulation of carbon exchanges between the terrestrial biosphere and the atmosphere. The model was implemented for the first time at the global scale as a stand-alone model. Several global simulations were performed to assess the sensitivity of the turbulent fluxes and Leaf Area Index to a doubling of the CO{sub 2} atmospheric concentration, and to the climate change simulated by the end of the 21. century. In addition, a new option of ISBA, referred to as ISBA-CC, was developed in order to simulate a more detailed ecosystem respiration by separating the autotrophic respiration and the heterotrophic respiration. The vegetation dynamics and the carbon fluxes were validated at a global scale using satellite datasets, and at a local scale using data from 26 sites of the FLUXNET network. All these results show that the model is sufficiently realistic to be coupled with a general circulation model, in order to account for interactions between the terrestrial biosphere, the atmosphere and the carbon cycle. (author)

  2. Microbial potential for carbon and nutrient cycling in a geogenic supercritical carbon dioxide reservoir.

    Science.gov (United States)

    Freedman, Adam J E; Tan, BoonFei; Thompson, Janelle R

    2017-06-01

    Microorganisms catalyze carbon cycling and biogeochemical reactions in the deep subsurface and thus may be expected to influence the fate of injected supercritical (sc) CO 2 following geological carbon sequestration (GCS). We hypothesized that natural subsurface scCO 2 reservoirs, which serve as analogs for the long-term fate of sequestered scCO 2 , harbor a 'deep carbonated biosphere' with carbon cycling potential. We sampled subsurface fluids from scCO 2 -water separators at a natural scCO 2 reservoir at McElmo Dome, Colorado for analysis of 16S rRNA gene diversity and metagenome content. Sequence annotations indicated dominance of Sulfurospirillum, Rhizobium, Desulfovibrio and four members of the Clostridiales family. Genomes extracted from metagenomes using homology and compositional approaches revealed diverse mechanisms for growth and nutrient cycling, including pathways for CO 2 and N 2 fixation, anaerobic respiration, sulfur oxidation, fermentation and potential for metabolic syntrophy. Differences in biogeochemical potential between two production well communities were consistent with differences in fluid chemical profiles, suggesting a potential link between microbial activity and geochemistry. The existence of a microbial ecosystem associated with the McElmo Dome scCO 2 reservoir indicates that potential impacts of the deep biosphere on CO 2 fate and transport should be taken into consideration as a component of GCS planning and modelling. © 2017 The Authors. Environmental Microbiology published by Society for Applied Microbiology and John Wiley & Sons Ltd.

  3. Evaluating the effects of terrestrial ecosystems, climate and carbon dioxide on weathering over geological time: a global-scale process-based approach

    Science.gov (United States)

    Taylor, Lyla L.; Banwart, Steve A.; Valdes, Paul J.; Leake, Jonathan R.; Beerling, David J.

    2012-01-01

    Global weathering of calcium and magnesium silicate rocks provides the long-term sink for atmospheric carbon dioxide (CO2) on a timescale of millions of years by causing precipitation of calcium carbonates on the seafloor. Catchment-scale field studies consistently indicate that vegetation increases silicate rock weathering, but incorporating the effects of trees and fungal symbionts into geochemical carbon cycle models has relied upon simple empirical scaling functions. Here, we describe the development and application of a process-based approach to deriving quantitative estimates of weathering by plant roots, associated symbiotic mycorrhizal fungi and climate. Our approach accounts for the influence of terrestrial primary productivity via nutrient uptake on soil chemistry and mineral weathering, driven by simulations using a dynamic global vegetation model coupled to an ocean–atmosphere general circulation model of the Earth's climate. The strategy is successfully validated against observations of weathering in watersheds around the world, indicating that it may have some utility when extrapolated into the past. When applied to a suite of six global simulations from 215 to 50 Ma, we find significantly larger effects over the past 220 Myr relative to the present day. Vegetation and mycorrhizal fungi enhanced climate-driven weathering by a factor of up to 2. Overall, we demonstrate a more realistic process-based treatment of plant fungal–geosphere interactions at the global scale, which constitutes a first step towards developing ‘next-generation’ geochemical models. PMID:22232768

  4. Toward a Mexican eddy covariance network for carbon cycle science

    Science.gov (United States)

    Vargas, Rodrigo; Yépez, Enrico A.

    2011-09-01

    First Annual MexFlux Principal Investigators Meeting; Hermosillo, Sonora, Mexico, 4-8 May 2011; The carbon cycle science community has organized a global network, called FLUXNET, to measure the exchange of energy, water, and carbon dioxide (CO2) between the ecosystems and the atmosphere using the eddy covariance technique. This network has provided unprecedented information for carbon cycle science and global climate change but is mostly represented by study sites in the United States and Europe. Thus, there is an important gap in measurements and understanding of ecosystem dynamics in other regions of the world that are seeing a rapid change in land use. Researchers met under the sponsorship of Red Temática de Ecosistemas and Consejo Nacional de Ciencia y Tecnologia (CONACYT) to discuss strategies to establish a Mexican eddy covariance network (MexFlux) by identifying researchers, study sites, and scientific goals. During the meeting, attendees noted that 10 study sites have been established in Mexico with more than 30 combined years of information. Study sites span from new sites installed during 2011 to others with 9 to 6 years of measurements. Sites with the longest span measurements are located in Baja California Sur (established by Walter Oechel in 2002) and Sonora (established by Christopher Watts in 2005); both are semiarid ecosystems. MexFlux sites represent a variety of ecosystem types, including Mediterranean and sarcocaulescent shrublands in Baja California; oak woodland, subtropical shrubland, tropical dry forest, and a grassland in Sonora; tropical dry forests in Jalisco and Yucatan; a managed grassland in San Luis Potosi; and a managed pine forest in Hidalgo. Sites are maintained with an individual researcher's funds from Mexican government agencies (e.g., CONACYT) and international collaborations, but no coordinated funding exists for a long-term program.

  5. Including an ocean carbon cycle model into iLOVECLIM (v1.0)

    NARCIS (Netherlands)

    Bouttes, N.; Roche, D.M.V.A.P.; Mariotti, V.; Bopp, L.

    2015-01-01

    The atmospheric carbon dioxide concentration plays a crucial role in the radiative balance and as such has a strong influence on the evolution of climate. Because of the numerous interactions between climate and the carbon cycle, it is necessary to include a model of the carbon cycle within a

  6. Assessing Students' Disciplinary and Interdisciplinary Understanding of Global Carbon Cycling

    Science.gov (United States)

    You, Hye Sun; Marshall, Jill A.; Delgado, Cesar

    2018-01-01

    Global carbon cycling describes the movement of carbon through atmosphere, biosphere, geosphere, and hydrosphere; it lies at the heart of climate change and sustainability. To understand the global carbon cycle, students will require "interdisciplinary knowledge." While standards documents in science education have long promoted…

  7. Global patterns and controls of soil organic carbon dynamics as simulated by multiple terrestrial biosphere models: Current status and future directions.

    Science.gov (United States)

    Tian, Hanqin; Lu, Chaoqun; Yang, Jia; Banger, Kamaljit; Huntzinger, Deborah N; Schwalm, Christopher R; Michalak, Anna M; Cook, Robert; Ciais, Philippe; Hayes, Daniel; Huang, Maoyi; Ito, Akihiko; Jain, Atul K; Lei, Huimin; Mao, Jiafu; Pan, Shufen; Post, Wilfred M; Peng, Shushi; Poulter, Benjamin; Ren, Wei; Ricciuto, Daniel; Schaefer, Kevin; Shi, Xiaoying; Tao, Bo; Wang, Weile; Wei, Yaxing; Yang, Qichun; Zhang, Bowen; Zeng, Ning

    2015-06-01

    Soil is the largest organic carbon (C) pool of terrestrial ecosystems, and C loss from soil accounts for a large proportion of land-atmosphere C exchange. Therefore, a small change in soil organic C (SOC) can affect atmospheric carbon dioxide (CO 2 ) concentration and climate change. In the past decades, a wide variety of studies have been conducted to quantify global SOC stocks and soil C exchange with the atmosphere through site measurements, inventories, and empirical/process-based modeling. However, these estimates are highly uncertain, and identifying major driving forces controlling soil C dynamics remains a key research challenge. This study has compiled century-long (1901-2010) estimates of SOC storage and heterotrophic respiration (Rh) from 10 terrestrial biosphere models (TBMs) in the Multi-scale Synthesis and Terrestrial Model Intercomparison Project and two observation-based data sets. The 10 TBM ensemble shows that global SOC estimate ranges from 425 to 2111 Pg C (1 Pg = 10 15  g) with a median value of 1158 Pg C in 2010. The models estimate a broad range of Rh from 35 to 69 Pg C yr -1 with a median value of 51 Pg C yr -1 during 2001-2010. The largest uncertainty in SOC stocks exists in the 40-65°N latitude whereas the largest cross-model divergence in Rh are in the tropics. The modeled SOC change during 1901-2010 ranges from -70 Pg C to 86 Pg C, but in some models the SOC change has a different sign from the change of total C stock, implying very different contribution of vegetation and soil pools in determining the terrestrial C budget among models. The model ensemble-estimated mean residence time of SOC shows a reduction of 3.4 years over the past century, which accelerate C cycling through the land biosphere. All the models agreed that climate and land use changes decreased SOC stocks, while elevated atmospheric CO 2 and nitrogen deposition over intact ecosystems increased SOC stocks-even though the responses varied

  8. Global carbon cycle and possible disturbances due to man's interventions

    Energy Technology Data Exchange (ETDEWEB)

    Pankrath, J

    1979-01-01

    Global atmospheric CO/sub 2/ concentration has increased since the beginning of reliable monitoring in 1958 at a mean rate of about 0.9 ppM CO/sub 2//y. Now, atmospheric, CO/sub 2/ concentration is at 330 ppM. From about 1860 up to 1974, man's intervention in the global carbon cycle caused a likely increase of 76.6 x 10/sup 15/ g C, corresponding to 36 ppM CO/sub 2/ in the atmosphere, if a preindustrial content of 294 ppM CO/sub 2/ or 625.3 x 10/sup 15/ g C is adopted to be valid. A further rise of atmospheric CO/sub 2/ seems to be inevitable and probably will be responsible for a climatic warming in the next several decades; therefore, a global examination of carbon reservoirs and carbon fluxes has been undertaken to determine their storage capacity for excess carbon which originated mainly from burning of fossil fuels and from land clearing. During 1860 to 1974 about 136 x 10/sup 15/ g C have been emitted into the atmosphere by fossil fuel combustion and cement production. At present, the emission rate is about 5 x 10/sup 15/ g C/y. The worldwide examination of carbon release, primarily by deforestation and soil cultivation since 1860, is estimated to be about 120 x 10/sup 15/ g C. The net transfer of carbon to the atmosphere owing to man's interference with the biosphere is now believed to be about 2.4 x 10/sup 15/ g C/y. An oceanic uptake of rougly 179 x 10/sup 15/ g C since 1860 is open to discussion. According to the chemical buffering of sea surface water only about 35.5 x 10/sup 15/ g C could have been absorbed. It is argued, however, that oceanic circulations might have been more effective in removing atmospheric excess carbon of anthropogenic origin.

  9. Evaluation of carbon-14 life cycle in reactors VVER-1000

    International Nuclear Information System (INIS)

    Lysakova, Katerina; Neumann, Jan; Vonkova, Katerina

    2012-09-01

    This work is aimed at the evaluation of carbon-14 life cycle in light water reactors VVER-1000. Carbon-14 is generated as a side product in different systems of nuclear reactors and has been an issue not only in radioactive waste management but mainly in release into the environment in the form of gaseous effluents. The principal sources of this radionuclide are in primary cooling water and fuel. Considerable amount of C-14 is generated by neutron reactions with oxygen 17 O and nitrogen 14 N present in water coolant and fuel. The reaction likelihood and consequently volume of generated radioisotope depends on several factors, especially on the effective cross-section, concentrations of parent elements and conditions of power plant operating strategies. Due to its long half-life and high capability of integration into the environment and thus into the living species, it is very important to monitor the movement of carbon-14 in all systems of nuclear power plant and to manage its release out of NPP. The dominant forms of radioactive carbon-14 are the hydrocarbons owing to the combinations with hydrogen used for absorption of radiolytic oxygen. These organic compounds, such as formaldehyde, methyl alcohol, ethyl alcohol and formic acid can be mostly retained on ion exchange resins used in the system for purifying primary cooling water. The gaseous carbon compounds (CH 4 and CO 2 ) are released into the atmosphere via the ventilation systems of NPP. Based on the information and data obtained from different sources, it has been designed a balance model of possible carbon-14 pathways throughout the whole NPP. This model includes also mass balance model equations for each important node in system and available sampling points which will be the background for further calculations. This document is specifically not to intended to describe the best monitoring program attributes or technologies but rather to provide evaluation of obtained data and find the optimal way to

  10. Effects of Climate and Ecosystem Disturbances on Biogeochemical Cycling in a Semi-Natural Terrestrial Ecosystem

    International Nuclear Information System (INIS)

    Beier, Claus; Schmidt, Inger Kappel; Kristensen, Hanne Lakkenborg

    2004-01-01

    The effects of increased temperature and potential ecosystem disturbances on biogeochemical cycling were investigated by manipulation of temperature in a mixed Calluna/grass heathland in Denmark. A reflective curtain covered the vegetation during the night to reduce the heat loss of IR radiation from the ecosystem to the atmosphere. This 'night time warming' was done for 3 years and warmed the air and soil by 1.1 deg. C. Warming was combined with ecosystem disturbances, including infestation by Calluna heather beetles (Lochmaea suturalis Thompson) causing complete defoliation of Calluna leaves during the summer 2000, and subsequent harvesting of all aboveground biomass during the autumn. Small increases in mineralisation rates were induced by warming and resulted in increased leaching of nitrogen from the organic soil layer. The increased nitrogen leaching from the organic soil layer was re-immobilised in the mineral soil layer as warming stimulated plant growth and thereby increased nitrogen immobilisation. Contradictory to the generally moderate effects of warming, the heather beetle infestation had very strong effects on mineralisation rates and the plant community. The grasses completely out-competed the Calluna plants which had not re-established two years after the infestation, probably due to combined effects of increased nutrient availability and the defoliation of Calluna. On the short term, ecosystem disturbances may have very strong effects on internal ecosystem processes and plant community structure compared to the more long-term effects of climate change

  11. Current systematic carbon-cycle observations and the need for implementing a policy-relevant carbon observing system

    International Nuclear Information System (INIS)

    Ciais, P.; Peregon, A.; Chevallier, F.; Bopp, L.; Breon, F.M.; Broquet, G.; Luyssaert, S.; Moulin, C.; Paris, J.D.; Poulter, B.; Rivier, L.; Wang, R.

    2014-01-01

    A globally integrated carbon observation and analysis system is needed to improve the fundamental understanding of the global carbon cycle, to improve our ability to project future changes, and to verify the effectiveness of policies aiming to reduce greenhouse gas emissions and increase carbon sequestration. Building an integrated carbon observation system requires transformational advances from the existing sparse, exploratory framework towards a dense, robust, and sustained system in all components: anthropogenic emissions, the atmosphere, the ocean, and the terrestrial biosphere. The paper is addressed to scientists, policy makers, and funding agencies who need to have a global picture of the current state of the (diverse) carbon observations. We identify the current state of carbon observations, and the needs and notional requirements for a global integrated carbon observation system that can be built in the next decade. A key conclusion is the substantial expansion of the ground-based observation networks required to reach the high spatial resolution for CO 2 and CH 4 fluxes, and for carbon stocks for addressing policy-relevant objectives, and attributing flux changes to underlying processes in each region. In order to establish flux and stock diagnostics over areas such as the southern oceans, tropical forests, and the Arctic, in situ observations will have to be complemented with remote-sensing measurements. Remote sensing offers the advantage of dense spatial coverage and frequent revisit. A key challenge is to bring remote-sensing measurements to a level of long-term consistency and accuracy so that they can be efficiently combined in models to reduce uncertainties, in synergy with ground based data. Bringing tight observational constraints on fossil fuel and land use change emissions will be the biggest challenge for deployment of a policy-relevant integrated carbon observation system. This will require in situ and remotely sensed data at much higher

  12. Building carbon-carbon bonds using a biocatalytic methanol condensation cycle.

    Science.gov (United States)

    Bogorad, Igor W; Chen, Chang-Ting; Theisen, Matthew K; Wu, Tung-Yun; Schlenz, Alicia R; Lam, Albert T; Liao, James C

    2014-11-11

    Methanol is an important intermediate in the utilization of natural gas for synthesizing other feedstock chemicals. Typically, chemical approaches for building C-C bonds from methanol require high temperature and pressure. Biological conversion of methanol to longer carbon chain compounds is feasible; however, the natural biological pathways for methanol utilization involve carbon dioxide loss or ATP expenditure. Here we demonstrated a biocatalytic pathway, termed the methanol condensation cycle (MCC), by combining the nonoxidative glycolysis with the ribulose monophosphate pathway to convert methanol to higher-chain alcohols or other acetyl-CoA derivatives using enzymatic reactions in a carbon-conserved and ATP-independent system. We investigated the robustness of MCC and identified operational regions. We confirmed that the pathway forms a catalytic cycle through (13)C-carbon labeling. With a cell-free system, we demonstrated the conversion of methanol to ethanol or n-butanol. The high carbon efficiency and low operating temperature are attractive for transforming natural gas-derived methanol to longer-chain liquid fuels and other chemical derivatives.

  13. Chemistry of organic carbon in soil with relationship to the global carbon cycle

    International Nuclear Information System (INIS)

    Post, W.M. III.

    1988-01-01

    Various ecosystem disturbances alter the balances between production of organic matter and its decomposition and therefore change the amount of carbon in soil. The most severe perturbation is conversion of natural vegetation to cultivated crops. Conversion of natural vegetation to cultivated crops results in a lowered input of slowly decomposing material which causes a reduction in overall carbon levels. Disruption of soil matrix structure by cultivation leads to lowered physical protection of organic matter resulting in an increased net mineralization rate of soil carbon. Climate change is another perturbation that affects the amount and composition of plant production, litter inputs, and decomposition regimes but does not affect soil structure directly. Nevertheless, large changes in soil carbon storage are probable with anticipated CO 2 induced climate change, particularly in northern latitudes where anticipated climate change will be greatest (MacCracken and Luther 1985) and large amounts of soil organic matter are found. It is impossible, given the current state of knowledge of soil organic matter processes and transformations to develop detailed process models of soil carbon dynamics. Largely phenomenological models appear to be developing into predictive tools for understanding the role of soil organic matter in the global carbon cycle. In particular, these models will be useful in quantifying soil carbon changes due to human land-use and to anticipated global climate and vegetation changes. 47 refs., 7 figs., 2 tabs

  14. The effects of land cover and land use change on the contemporary carbon balance of the arctic and boreal terrestrial ecosystems of northern Eurasia

    Science.gov (United States)

    Hayes, Daniel J.; McGuire, A. David; Kicklighter, David W.; Burnside , Todd J.; Melillo, Jerry M.

    2010-01-01

    Recent changes in climate, disturbance regimes and land use and management systems in Northern Eurasia have the potential to disrupt the terrestrial sink of atmospheric CO2 in a way that accelerates global climate change. To determine the recent trends in the carbon balance of the arctic and boreal ecosystems of this region, we performed a retrospective analysis of terrestrial carbon dynamics across northern Eurasia over a recent 10-year period using a terrestrial biogeochemical process model. The results of the simulations suggest a shift in direction of the net flux from the terrestrial sink of earlier decades to a net source on the order of 45 Tg C year−1between 1997 and 2006. The simulation framework and subsequent analyses presented in this study attribute this shift to a large loss of carbon from boreal forest ecosystems, which experienced a trend of decreasing precipitation and a large area burned during this time period.

  15. The Carbonate-Silicate Cycle on Earth-like Planets Near The End Of Their Habitable Lifetimes

    Science.gov (United States)

    Rushby, A. J.; Mills, B.; Johnson, M.; Claire, M.

    2016-12-01

    The terrestrial cycle of silicate weathering and metamorphic outgassing buffers atmospheric CO2 and global climate over geological time on Earth. To first order, the operation of this cycle is assumed to occur on Earth-like planets in the orbit of other main-sequence stars in the galaxy that exhibit similar continent/ocean configurations. This has important implications for studies of planetary habitability, atmospheric and climatic evolution, and our understanding of the potential distribution of life in the Universe. We present results from a simple biogeochemical carbon cycle model developed to investigate the operation of the carbonate-silicate cycle under conditions of differing planet mass and position within the radiative habitable zone. An active carbonate-silicate cycle does extend the length of a planet's habitable period through the regulation of the CO2 greenhouse. However, the breakdown of the negative feedback between temperature, pCO2, and weathering rates towards the end of a planet's habitable lifespan results in a transitory regime of `carbon starvation' that would inhibit the ability of oxygenic photoautotrophs to metabolize, and result in the collapse of any putative biosphere supported by these organisms, suggesting an earlier limit for the initiation of inhabitable conditions than when considering temperature alone. This conclusion stresses the importance of considering the full suite of planetary properties when determining potential habitability. A small sample of exoplanets was tested using this model, and the length of their habitable periods were found to be significantly longer than that of the Earth, primarily as a function of the differential rates of stellar evolution expected from their host stars. Furthermore, we carried out statistical analysis of a series of model input parameters, determining that both the mass of the planet and the sensitivity of seafloor weathering processes to dissolved CO2 exhibit significant controls on the

  16. Water extraction of coals - potential for estimating low molecular weight organic acids as carbon feedstock for the deep terrestrial biosphere

    Energy Technology Data Exchange (ETDEWEB)

    Vieth, A.; Mangelsdorf, K.; Sykes, R.; Horsfield, B. [Geoforschungszentrum Potsdam, Potsdam (Germany)

    2008-08-15

    With the recent increasing interest in the deep biosphere, the question arises as to where the carbon sources that support deep microbial communities are derived from. Our research was focussed on the water-soluble, low molecular weight (LMW) organic acids that are potentially available from different sedimentary lithologies to serve as a carbon source to feed the deep biosphere. A series of Eocene-Pleistocene coals, mudstones and sandstones of varying rank (maturity) and total organic carbon (TOC) content from the Waikato Basin, New Zealand, has been Soxhlet-extracted using water. The combined concentration of recovered formate, acetate and oxalate range from 366 to 2499 {mu} g/g sediment and appear to be dependent on rank, organofacies and TOC. The yields indicate the potential of carbonaceous sediments to feed the local deep terrestrial biosphere over geological periods of time. The existence of living microbial organisms in the mudstones and sandstones was proved by the identification of intact phospholipids (PLs).

  17. Simulation and Assessment of Whole Life-Cycle Carbon Emission Flows from Different Residential Structures

    Directory of Open Access Journals (Sweden)

    Rikun Wen

    2016-08-01

    Full Text Available To explore the differences in carbon emissions over the whole life-cycle of different building structures, the published calculated carbon emissions from residential buildings in China and abroad were normalized. Embodied carbon emission flows, operations stage carbon emission flows, demolition and reclamation stage carbon emission flows and total life-cycle carbon emission flows from concrete, steel, and wood structures were obtained. This study is based on the theory of the social cost of carbon, with an adequately demonstrated social cost of carbon and social discount rate. Taking into consideration both static and dynamic situations and using a social discount rate of 3.5%, the total life-cycle carbon emission flows, absolute carbon emission and building carbon costs were calculated and assessed. The results indicated that concrete structures had the highest embodied carbon emission flows and negative carbon emission flows in the waste and reclamation stage. Wood structures that started the life-cycle with stored carbon had the lowest carbon emission flows in the operations stage and relatively high negative carbon emission flows in the reclamation stage. Wood structures present the smallest carbon footprints for residential buildings.

  18. Impacts of peatland and permafrost changes on the terrestrial carbon storage over the last 21 ka

    Science.gov (United States)

    Spahni, Renato; Stocker, Benjamin D.; Joos, Fortunat

    2014-05-01

    Paleoclimate records and global climate-carbon cycle models suggest a net increase in land carbon (C) storage between 300 and 700 Pg C (1 Pg C = 1015 g C) during the transition from the last glacial maximum (LGM), the Holocene up to the preindustrial period. Peat accumulation rate records imply an increase in peatland C of ~600 Pg C over the course of the Holocene. In high northern latitudes mineral and organic soils are subject to permafrost formation, which is believed to have been more extensive during glacial compared to interglacial periods. Soil C in permafrost regions represents the largest inert C pool on land at present. The spatio-temporal evolution, however, of C stocks in soils and vegetation remains poorly quantified and is uncertain. Here, the Land surface Processes and eXchanges (LPX-Bern) Dynamic Global Vegetation Model is applied in transient simulations to explore the evolution of permafrost, peatland and vegetation C over the last 21'000 years. The model is forced with temperature and precipitation output from the Trace-21ka climate simulation, and dynamically simulates the formation and disappearance of peatlands and permafrost soils, vegetation distribution and C stocks. Results indicate that peatlands and permfrost areas existed further south in the LGM, in agreement with available proxy information, and that their associated C was lost during the transition into the Holocene. The simulated loss of inert C is over-compensated by vegetation regrowth. The timing of the C relocation on land is compared to observational evidence from paleoclimate archives and estimates from ocean C inventory changes.

  19. Phylogeny and phylogeography of functional genes shared among seven terrestrial subsurface metagenomes reveal N-cycling and microbial evolutionary relationships

    Directory of Open Access Journals (Sweden)

    Maggie CY Lau

    2014-10-01

    Full Text Available Comparative studies on community phylogenetics and phylogeography of microorganisms living in extreme environments are rare. Terrestrial subsurface habitats are valuable for studying microbial biogeographical patterns due to their isolation and the restricted dispersal mechanisms. Since the taxonomic identity of a microorganism does not always correspond well with its functional role in a particular community, the use of taxonomic assignments or patterns may give limited inference on how microbial functions are affected by historical, geographical and environmental factors. With seven metagenomic libraries generated from fracture water samples collected from five South African mines, this study was carried out to (1 screen for ubiquitous functions or pathways of biogeochemical cycling of CH4, S and N; (2 to characterize the biodiversity represented by the common functional genes; (3 to investigate the subsurface biogeography as revealed by this subset of genes; and (4 to explore the possibility of using metagenomic data for evolutionary study. The ubiquitous functional genes are NarV, NPD, PAP reductase, NifH, NifD, NifK, NifE and NifN genes. Although these 8 common functional genes were taxonomically and phylogenetically diverse and distinct from each other, the dissimilarity between samples did not correlate strongly with either geographical, environmental or residence time of the water. Por genes homologous to those of Thermodesulfovibrio yellowstonii detected in all metagenomes were deep lineages of Nitrospirae, suggesting that subsurface habitats have preserved ancestral genetic signatures that inform the study of the origin and evolution of prokaryotes.

  20. The geological carbon cycle and the global warming / climate debate

    International Nuclear Information System (INIS)

    Frank, F.

    2013-01-01

    The extensively cited seasonal carbon cycle describes the size and the annual fluxes between the temporary reservoirs (ocean, atmosphere, biosphere and soils). Compared with these large annual fluxes (approx. 200 GtC/y) the human contribution seems to be of minor amount and is currently (2011) in the range of 4-5%. However, in the geological carbon cycle, which describes the nearly equal amounts of input (volcanoes etc.) and output (sediments) into and from the temporary reservoirs, the human contribution has now reached 30-50 times the average natural level (9.5 Gt C/y versus ca. 0.2-0.3Gt C/y). In the long-term range (1-10x106y), the variable, but much smaller net imbalance between these geological sources und sinks was responsible for the atmospheric CO2-level in the last 400 My (since then comparable temporary reservoirs exist) and influenced via the various feedbacks the climate on earth. In nearly 95% of this long time the climate system was in (nearly) equilibrium conditions and changes occurred extremely slow. Whenever a certain range of higher rate of change of these driving forces were reached, it had - together with other effects - severe influence on the evolution of life, causing 5 large and many minor 'geological accidents'. Based on isotope geochemistry and a fairly good time resolution by orbitally tuned cyclostratigraphy (astrochronology) in the sedimentary record, we are able to quantify these rates of change with reasonable errors. It turns out that the present rate of change - caused by the C-based fossil energy use - is one to two orders of magnitude more rapid than these severe events (impacts excluded) in the earth system. A vast amount of data is available from the ice age cycles. Climate geology (e.g. the group of M. Sarnthein) made considerable progress in understanding the related geological/oceanic processes and proposed a reasonably constrained mass balance of CO2 during the last cycle, which could help us to understand the future

  1. Remote sensing of annual terrestrial gross primary productivity from MODIS: an assessment using the FLUXNET La Thuile data set

    NARCIS (Netherlands)

    Verma, M.; Friedl, M.A.; Richardson, A.D.; Kiely, G.; Cescatti, A.; Law, B.E.; Wohlfahrt, G.; Gielen, G.; Roupsard, O.; Moors, E.J.

    2014-01-01

    Gross primary productivity (GPP) is the largest and most variable component of the global terrestrial carbon cycle. Repeatable and accurate monitoring of terrestrial GPP is therefore critical for quantifying dynamics in regional-to-global carbon budgets. Remote sensing provides high frequency

  2. Soil mineralogy and microbes determine forest life history strategy and carbon cycling in humid tropical forests

    Science.gov (United States)

    Soong, J.; Verbruggen, E.; Peñuelas, J.; Janssens, I. A.; Grau, O.

    2017-12-01

    Tropical forests account for over one third of global terrestrial gross primary productivity and cycle more C than any other ecosystem on Earth. However, we still lack a mechanistic understanding of how such high productivity is maintained on the old, highly weathered and phosphorus depleted soils in the tropics. We hypothesized that heterogeneity in soil texture, mineralogy and microbial community composition may be the major drivers of differences in soil C storage and P limitation across tropical forests. We sampled 12 forest sites across a 200 km transect in the humid neo-tropics of French Guiana that varied in soil texture, precipitation and mineralogy. We found that soil texture was a major driver of soil carbon stocks and forest life history strategy, where sandy forests have lower soil C stocks, slower turnover and decomposition and a more closed nutrient cycle while clayey forests have higher soil C stocks, faster turnover and a more leaky nutrient cycle (using natural abundance stable isotope evidence). We found that although the presence of Al and Fe oxides in the clayey soils occludes soil organic matter and P, a greater abundance of arbuscular mycorrhizal fungi help forests to access occluded P in clayey soils fueling higher turnover and faster decomposition rates. Evidence from a laboratory incubation of tropical soils with nutrient additions further demonstrates the de-coupling of microbial P demands from C:N limitations providing further evidence for the need to examine microbial stoichiometry to explain C cycling in the P-limited tropics. We argue that microbial community composition and physiological demands, constrained within the limitations of soil mineralogical reactivity, largely controls nutrient and C cycling in tropical forest soils. Together our observational field study and laboratory incubation provide a unique dataset to shed light on the mineralogical and microbial controls on C and nutrient cycling in tropical soils. By integrating

  3. Carbon cycling in the deep eastern North Pacific benthic food web: Investigating the effect of organic carbon input

    NARCIS (Netherlands)

    Dunlop, K.M.; Van Oevelen, D.; Ruhl, H.A.; Huffard, C.L.; Kuhnz, L.A.; Smith, K.L.

    2016-01-01

    The deep ocean benthic environment plays a role in long-term carbon sequestration. Understanding carbon cycling in the deep ocean floor is critical to evaluate the impact of changing climate on the oceanic systems. Linear inverse modeling was used to quantify carbon transfer between compartments in

  4. Sink- or Source-driven Phanerozoic carbon cycle?

    Science.gov (United States)

    Godderis, Y.; Donnadieu, Y.; Maffre, P.; Carretier, S.

    2017-12-01

    The Phanerozoic evolution of the atmospheric CO2 level is controlled by the fluxes entering or leaving the exospheric system. Those fluxes (including continental weathering, magmatic degassing, organic carbon burial, oxidation of sedimentary organic carbon) are intertwined, and their relative importance in driving the global carbon cycle evolution may have fluctuated through time. Deciphering the causes of the Phanerozoic climate evolution thus requires a holistic and quantitative approach. Here we focus on the role played by the paleogeographic configuration on the efficiency of the CO2 sink by continental silicate weathering, and on the impact of the magmatic degassing of CO2. We use the spatially resolved numerical model GEOCLIM (geoclimmodel.worpress.com) to compute the response of the silicate weathering and atmospheric CO2 to continental drift for 22 time slices of the Phanerozoic. Regarding the CO2 released by the magmatic activity, we reconstruct several Phanerozoic histories of this flux, based on published indexes. We calculate the CO2 evolution for each degassing scenario, and accounting for the paleogeographic setting. We show that the paleogeographic setting is a main driver of the climate from 540 Ma to about the beginning of the Jurassic. Regarding the role of the magmatic degassing, the various reconstructions do not converge towards a single signal, and thus introduce large uncertainties in the calculated CO2 level over time. Nevertheless, the continental dispersion, which prevails since the Jurassic, promotes the CO2 consumption by weathering and forces atmospheric CO2 to stay low. Warm climates of the "middle" Cretaceous and early Cenozoic require enhanced CO2 degassing by magmatic activity. In summary, the Phanerozoic climate evolution can be hardly assigned to a single process, but is the result of complex and intertwined processes.

  5. Contributions of Ectomycorrhizal Fungal Mats to Forest Soil Carbon Cycles

    Science.gov (United States)

    Kluber, L. A.; Phillips, C. L.; Myrold, D. D.; Bond, B. J.

    2008-12-01

    Ectomycorrhizal (EM) fungi are a prominent and ubiquitous feature of forest soils, forming symbioses with most tree species, yet little is known about the magnitude of their impact on forest carbon cycles. A subset of EM fungi form dense, perennial aggregations of hyphae, which have elevated respiration rates compared with neighboring non-mat soils. These mats are a foci of EM activity and thereby a natural laboratory for examining how EM fungi impact forest soils. In order to constrain the contributions of EM fungi to forest soil respiration, we quantified the proportion of respiration derived from EM mat soils in an old-growth Douglas-fir stand in western Oregon. One dominant genus of mat-forming fungi, Piloderma, covered 56% of the soil surface area. Piloderma mats were monitored for respiration rates over 15 months and found to have on average 10% higher respiration than non-mat soil. At the stand level, this amounts to roughly 6% of soil respiration due to the presence of Piloderma mats. We calculate that these mats may constitute 27% of autotrophic respiration, based on respiration rates from trenched plots in a neighboring forest stand. Furthermore, enzyme activity and microbial community profiles in mat and non-mat soil provide evidence that specialized communities utilizing chitin contribute to this increased efflux. With 60% higher chitinase activity in mats, the breakdown of chitin is likely an important carbon flux while providing carbon and nitrogen to the microbial communities associated with mats. Quantitative PCR showed similar populations of fungi and bacteria in mat and non-mat soils; however, community analysis revealed distinct fungal and bacterial communities in the two soil types. The higher respiration associated with EM mats does not appear to be due only to a proliferation of EM fungi, but to a shift in overall community composition to organisms that efficiently utilize the unique resources available within the mat, including plant and

  6. The role of hydrology in annual organic carbon loads and terrestrial organic matter export from a midwestern agricultural watershed

    Science.gov (United States)

    Dalzell, Brent J.; Filley, Timothy R.; Harbor, Jon M.

    2007-03-01

    Defining the control that hydrology exerts on organic carbon (OC) export at the watershed scale is important for understanding how the source and quantity of OC in streams and rivers is influenced by climate change or by landscape drainage. To this end, molecular (lignin phenol), stable carbon isotope, and dissolved organic carbon (DOC) data were collected over a range of flow conditions to examine the influence of hydrology on annual OC export from an 850 km 2 Midwestern United States agricultural watershed located in west central Indiana. In years 2002 and 2003, modeled annual DOC loads were 19.5 and 14.1 kg ha -1yr -1, while 71% and 85%, respectively, of the total annual OC was exported in flow events occurring during less than 20% of that time. These results highlight the importance of short-duration, high-discharge events (common in smaller watersheds) in controlling annual OC export. Based on reported increases in annual stream discharge coupled with current estimates of DOC export, annual DOC loads in this watershed may have increased by up to 40% over the past 50 years. Molecular (lignin phenol) characterization of quantity and relative degradation state of terrestrial OC shows as much temporal variability of lignin parameters (in high molecular weight dissolved organic carbon) in this one watershed as that demonstrated in previously published studies of dissolved organic matter in the Mississippi and Amazon Rivers. These results suggest that hydrologic variability is at least as important in determining the nature and extent of OC export as geographic variability. Moreover, molecular and bulk stable carbon isotope data from high molecular weight dissolved organic carbon and colloidal organic carbon showed that increased stream flow from the study watershed was responsible for increased export of agriculturally derived OC. When considered in the context of results from other studies that show the importance of flood events and in-stream processing of

  7. One carbon cycle: Impacts of model integration, ecosystem process detail, model resolution, and initialization data, on projections of future climate mitigation strategies

    Science.gov (United States)

    Fisk, J.; Hurtt, G. C.; le page, Y.; Patel, P. L.; Chini, L. P.; Sahajpal, R.; Dubayah, R.; Thomson, A. M.; Edmonds, J.; Janetos, A. C.

    2013-12-01

    Integrated assessment models (IAMs) simulate the interactions between human and natural systems at a global scale, representing a broad suite of phenomena across the global economy, energy system, land-use, and carbon cycling. Most proposed climate mitigation strategies rely on maintaining or enhancing the terrestrial carbon sink as a substantial contribution to restrain the concentration of greenhouse gases in the atmosphere, however most IAMs rely on simplified regional representations of terrestrial carbon dynamics. Our research aims to reduce uncertainties associated with forest modeling within integrated assessments, and to quantify the impacts of climate change on forest growth and productivity for integrated assessments of terrestrial carbon management. We developed the new Integrated Ecosystem Demography (iED) to increase terrestrial ecosystem process detail, resolution, and the utilization of remote sensing in integrated assessments. iED brings together state-of-the-art models of human society (GCAM), spatial land-use patterns (GLM) and terrestrial ecosystems (ED) in a fully coupled framework. The major innovative feature of iED is a consistent, process-based representation of ecosystem dynamics and carbon cycle throughout the human, terrestrial, land-use, and atmospheric components. One of the most challenging aspects of ecosystem modeling is to provide accurate initialization of land surface conditions to reflect non-equilibrium conditions, i.e., the actual successional state of the forest. As all plants in ED have an explicit height, it is one of the few ecosystem models that can be initialized directly with vegetation height data. Previous work has demonstrated that ecosystem model resolution and initialization data quality have a large effect on flux predictions at continental scales. Here we use a factorial modeling experiment to quantify the impacts of model integration, process detail, model resolution, and initialization data on projections of

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

    NARCIS (Netherlands)

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

    2010-01-01

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

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

    NARCIS (Netherlands)

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

    2010-01-01

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

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

    NARCIS (Netherlands)

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

    We present an estimate of net ecosystem exchange (NEE) of CO(2) in Europe for the years 2001-2007. It is derived with a data assimilation that uses a large set of atmospheric CO(2) mole fraction observations (similar to 70 000) to guide relatively simple descriptions of terrestrial and oceanic net

  11. Field Investigation and Modeling Development for Hydrological and Carbon Cycles in Southwest Karst Region of China

    Science.gov (United States)

    Hu, X. B.

    2017-12-01

    It is required to understanding water cycle and carbon cycle processes for water resource management and pollution prevention and global warming influence in southwest karst region of China. Lijiang river basin is selected as our study region. Interdisciplinary field and laboratory experiments with various technologies are conducted to characterize the karst aquifers in detail. Key processes in the karst water cycle and carbon cycle are determined. Based on the MODFLOW-CFP model, new watershed flow and carbon cycle models are developed coupled subsurface and surface water flow models. Our study focus on the karst springshed in Mao village, the mechanisms coupling carbon cycle and water cycle are explored. This study provides basic theory and simulation method for water resource management and groundwater pollution prevention in China karst region.

  12. Features of supercritical carbon dioxide Brayton cycle coupled with reactor

    International Nuclear Information System (INIS)

    Duan Chengjie; Wang Jie; Yang Xiaoyong

    2010-01-01

    In order to obtain acceptable cycle efficiency, current helium gas turbine power cycle technology needs high cycle temperature which means that the cycle needs high core-out temperature. The technology has high requirements on reactor structure and fuel elements materials, and also on turbine manufacture. While utilizing CO 2 as cycle working fluid, it can guarantee to lower the cycle temperature and turbo machine Janume but achieve the same cycle efficiency, so as to enhance the safety and economy of reactor. According to the laws of thermodynamics, a calculation model of supercritical CO 2 power cycle was established to analyze the feature, and the decisive parameters of the cycle and also investigate the effect of each parameter on the cycle efficiency in detail were obtained. The results show that supercritical CO 2 power cycle can achieve quite satisfied efficiency at a lower cycle highest temperature than helium cycle, and CO 2 is a promising working fluid. (authors)

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

    International Nuclear Information System (INIS)

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

    2012-01-01

    Using a process-based Dynamic Land Ecosystem Model, we assessed carbon dynamics of urbanized/developed lands in the Southern United States during 1945–2007. The results indicated that approximately 1.72 (1.69–1.77) Pg (1P = 10 15 ) carbon was stored in urban/developed lands, comparable to the storage of shrubland or cropland in the region. Urbanization resulted in a release of 0.21 Pg carbon to the atmosphere during 1945–2007. Pre-urbanization vegetation type and time since land conversion were two primary factors dete