Science.gov

Sample records for ecosystem carbon gain

  1. Assessing carbon dynamics in semiarid ecosystems : Balancing potential gains with potential large rapid losses

    SciTech Connect

    Breshears, D. D.; Ebinger, M. H.; Unkefer, P. J.

    2001-01-01

    Photosynthesis and respiration are the largest fluxes into and out of the biosphere (Molles 1999). Consequently, small changes in these fluxes can potentially produce large changes in the storage of carbon in the biosphere. Terrestrial carbon fluxes account for more than half of the carbon transferred between the atmosphere and the earth's surface (about 120 GigaTons/year), and current stores of carbon in terrestrial ecosystem are estimated at 2060 GigaTons. Increasing attention is being focused on the role of managing and sequestering carbon in the terrestrial biosphere as a means for addressing global climate change (IGBP, 1998; U.S. Department of Energy, 1999). Terrestrial ecosystems are widely recognized as a major biological scrubber for atmosphereic CO{sub 2} and their ability to finction as such can be increased significantly over the next 25 years through careful manipulation. The potential for terrestrial carbon gains has been the subject of much attention (Dixon et al., 1994; Masera et al. 1997; Cao and Woodward, 1998; DeLucia et al. 1999). In contrast to other strategies for reducing net carbon emissions, terrestrial sequestration has the potential for rapid implementation. Strategies that focus on soil carbon are likely to be effective because in addition to being a storage pool of carbon, soil carbon also improves site productivity through improving soil quality (e.g., water retention and nutrient availability). The carbon pool in soils is immense and highly dynamic. The flux of carbon into and out of soils is one of the largest uncertainties in the total mass balance of global carbon (NRC, 1999; La1 et al., 1998; Cambardella, 1998). Reducing these uncertainties is key to developing carbon sequestration strategies. Soil carbon pools have been greatly depleted over recent centuries, and there is potential to increase storage of carbon in these soils through effective land management. Whereas carbon in vegetation can be managed directly through land use

  2. Quantifying ecosystem carbon losses and gains following development in New England: A combined field, modeling, and remote sensing approach

    NASA Astrophysics Data System (ADS)

    Raciti, S. M.; Hutyra, L.; Briber, B. M.; Dunn, A. L.; Friedl, M. A.; Woodcock, C.; Zhu, Z.; Olofsson, P.

    2013-12-01

    If current trends continue, the world's urban population may double and urban land area may quadruple over the next 50 years. Despite the rapid expansion of urban areas, the trajectories of carbon losses and gains following development remain poorly quantified. We are using a combination of field measurements, modeling, and remote sensing to advance our ability to measure and monitor trajectories of ecosystem carbon over space and time. To characterize how carbon stocks change across urban-to-rural gradients, we previously established field plots to survey live and dead tree biomass, tree canopy, soil and foliar carbon and nitrogen concentrations, and a range of landscape characteristics (Raciti et al. 2012). In 2013, we extended our field sampling to focus specifically on places that experienced land use and land cover change over the past 35 years. This chronosequence approach was informed by Landsat time series (1982-present) and property records (before 1982). The Landsat time series approach differs from traditional remote-sensing-based land use change detection methods because it leverages the entire Landsat archive of imagery using a Fourier fitting approach (Zhu et al. 2012). The result is a temporally and spatially continuous map of land use and land cover change across the study region. We used these field and remote sensing data to inform a carbon bookkeeping model that estimates changes in past and potential future carbon stocks over time. Here we present preliminary results of this work for eastern Massachusetts.

  3. Response of photosynthetic carbon gain to ecosystem retrogression of vascular plants and mosses in the boreal forest.

    PubMed

    Bansal, Sheel; Nilsson, Marie-Charlotte; Wardle, David A

    2012-07-01

    In the long-term absence of rejuvenating disturbances, forest succession frequently proceeds from a maximal biomass phase to a retrogressive phase characterized by reduced nutrient availability [notably nitrogen (N) and phosphorus (P)] and net primary productivity. Few studies have considered how retrogression induces changes in ecophysiological responses associated with photosynthetic carbon (C) gain, and only for trees. We tested the hypothesis that retrogression would negatively impact photosynthetic C gain of four contrasting species, and that this impact would be greater for vascular plants (i.e., trees and shrubs) than for non-vascular plants (i.e., mosses). We used a 5,000-year-old chronosequence of forested islands in Sweden, where retrogression occurs in the long-term absence of lightning-ignited wildfires. Despite fundamental differences in plant form and ecological niche among species, vascular plants and mosses showed similar ecophysiological responses to retrogression. The most common effects of retrogression were reductions in photosynthesis and respiration per unit foliar N, increases in foliar N, δ(13)C and δ(15)N, and decreases in specific leaf areas. In contrast, photosynthesis per unit mass or area generally did not change along the chronosequence, but did vary many-fold between vascular plants and mosses. The consistent increases in foliar N without corresponding increases in mass- or area-based photosynthesis suggest that other factor(s), such as P co-limitation, light conditions or water availability, may co-regulate C gain in retrogressive boreal forests. Against our predictions, traits of mosses associated with C and N were generally highly responsive to retrogression, which has implications for how mosses influence ecosystem processes in boreal forests.

  4. Photosynthesis, Nitrogen, Their Adjustment and its Effects on Ecosystem Carbon Gain at Elevated CO{sub 2}l. A Comparison of Loblolly and Ponderosa Pines

    SciTech Connect

    Ball, J. Timothy; Eichelmann, Hillar Y.; Tissue, David T.; Lewis, James D.; Picone, Johnn B.; Ross, Peter D.

    1996-12-01

    A functional understanding of terrestrial ecosystem carbon processes is essential for two reasons. First, carbon flow is a most fundamental aspects of ecosystem function as it mediates most of the energy flow in these systems. Second, carbon flow also mediates the majority of energy flow in the global economy and will do for the foreseeable future. The increased atmospheric carbon dioxide and its inevitable flow through global ecosystems will influence ecosystem processes. There is, of course, great interest in the potential of ecosystems to sequester some of the carbon being loaded into the atmosphere by economic activity.

  5. Carbon sequestration in dryland ecosystems.

    PubMed

    Lal, Rattan

    2004-04-01

    Drylands occupy 6.15 billion hectares (Bha) or 47.2% of the world's land area. Of this, 3.5 to 4.0 Bha (57%-65%) are either desertified or prone to desertification. Despite the low soil organic carbon (SOC) concentration, total SOC pool of soils of the drylands is 241 Pg (1 Pg = petagram = 10(15)g = 1 billion metric ton) or 15.5% of the world's total of 1550 Pg to 1-meter depth. Desertification has caused historic C loss of 20 to 30 Pg. Assuming that two-thirds of the historic loss can be resequestered, the total potential of SOC sequestration is 12 to 20 Pg C over a 50-year period. Land use and management practices to sequester SOC include afforestation with appropriate species, soil management on cropland, pasture management on grazing land, and restoration of degraded soils and ecosystems through afforestation and conversion to other restorative land uses. Tree species suitable for afforestation in dryland ecosystems include Mesquite, Acacia, Neem and others. Recommended soil management practices include application of biosolids (e.g., manure, sludge), which enhance activity of soil macrofauna (e.g., termites), use of vegetative mulches, water harvesting, and judicious irrigation systems. Recommended practices of managing grazing lands include controlled grazing at an optimal stocking rate, fire management, and growing improved species. The estimated potential of SOC sequestration is about 1 Pg C/y for the world and 50 Tg C/y for the U.S. This potential of dryland soils is relevant to both the Kyoto Protocol under UNFCCC and the U.S. Farm Bill 2002.

  6. Trophic cascade alters ecosystem carbon exchange

    PubMed Central

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

    2013-01-01

    Trophic cascades—the indirect effects of carnivores on plants mediated by herbivores—are common across ecosystems, but their influence on biogeochemical cycles, particularly the terrestrial carbon cycle, are largely unexplored. Here, using a 13C pulse-chase experiment, we demonstrate how trophic structure influences ecosystem carbon dynamics in a meadow system. By manipulating the presence of herbivores and predators, we show that even without an initial change in total plant or herbivore biomass, the cascading effects of predators in this system begin to affect carbon cycling through enhanced carbon fixation by plants. Prolonged cascading effects on plant biomass lead to slowing of carbon loss via ecosystem respiration and reallocation of carbon among plant aboveground and belowground tissues. Consequently, up to 1.4-fold more carbon is retained in plant biomass when carnivores are present compared with when they are absent, owing primarily to greater carbon storage in grass and belowground plant biomass driven largely by predator nonconsumptive (fear) effects on herbivores. Our data highlight the influence that the mere presence of predators, as opposed to direct consumption of herbivores, can have on carbon uptake, allocation, and retention in terrestrial ecosystems. PMID:23776213

  7. Boreal carbon loss due to poleward shift in low-carbon ecosystems

    NASA Astrophysics Data System (ADS)

    Koven, Charles D.

    2013-06-01

    Climate change can be thought of in terms of geographical shifts in climate properties. Examples include assessments of shifts in habitat distributions, of the movement needed to maintain constant temperature or precipitation, and of the emergence and disappearance of climate zones. Here I track the movement of analogue climates within climate models. From the model simulations, I define a set of vectors that link a historical reference climate for each location to the location in a changed climate whose seasonal temperature and precipitation cycles best match the reference climate. I use these vectors to calculate the change in vegetation carbon storage with climate change due to ecosystems following climate analogues. Comparing the derived carbon content change to direct carbon projections by coupled carbon-climate models reveals two regions of divergence. In the tropical forests, vector projections are fundamentally uncertain because of a lack of close climatic analogues. In the southern boreal forest, carbon losses are projected in the vector perspective because low-carbon ecosystems shift polewards. However, the majority of carbon-climate models--typically without explicit simulation of the disturbance and mortality processes behind such shifts--instead project vegetation carbon gains throughout the boreal region. Southern boreal carbon loss as a result of ecosystem shift is likely to offset carbon gains from northern boreal forest expansion.

  8. Carbon cycling in high-latitude ecosystems

    NASA Technical Reports Server (NTRS)

    Townsend, Alan; Frolking, Stephen; Holland, Elizabeth

    1992-01-01

    The carbon-rich soils and peatlands of high-latitude ecosystems could substantially influence atmospheric concentrations of CO2 and CH4 in a changing climate. Currently, cold, often waterlogged conditions retard decomposition, and release of carbon back to the atmosphere may be further slowed by physical protection of organic matter in permafrost. As a result, many northern ecosystems accumulate carbon over time (Billings et al., 1982; Poole and Miller, 1982), and although such rates of accumulation are low, thousands of years of development have left Arctic ecosystems with an extremely high soil carbon content; Schlesinger's (1984) average value of 20.4 kg C/m(sup 2) leads to a global estimate of 163 x 10(exp 15) g C. All GCM simulations of a doubled CO2 climate predict the greatest warming to occur in the polar regions (Dickinson, 1986; Mitchell, 1989). Given the extensive northern carbon pools and the strong sensitivity of decomposition processes to temperature, even a slight warming of the soil could dramatically alter the carbon balance of Arctic ecosystems. If warming accelerates rates of decomposition more than rates of primary production, a sizeable additional accumulation of CO2 in the atmosphere could occur. Furthermore, CH4 produced in anaerobic soils and peatlands of the Arctic already composes a good percentage of the global efflux (Cicerone and Oremlund, 1988); if northern soils become warmer and wetter as a whole, CH4 emissions could dramatically rise. A robust understanding of the primary controls of carbon fluxes in Arctic ecosystems is critical. As a framework for a systematic examination of these controls, we discussed a conceptual model of regional-scale Arctic carbon turnover, including CH4 production, and based upon the Century soil organic matter model.

  9. Carbon dioxide sequestration in terrestrial ecosystems

    SciTech Connect

    Wisniewski, J.; Dixon, R.K.; Kinsman, J.D.; Sampson, R.N.; Lugo, A.E.

    1993-01-01

    The terrestrial biosphere plays a prominent role in the global carbon (C) cycle. Terrestrial ecosystems are currently accumulating C and it appears feasible to manage existing terrestrial (forest, agronomic, desert) ecosystems to maintain or increase C storage. Forest ecosystems can be managed to sequester and store globally significant amounts of C. Agroecosystems and arid lands could be managed to conserve existing terrestrial C but CO2 sequestration rates by vegetation in these systems is relatively low. Biomass from forest agroecosystems has the potential to be used as an energy source and trees could be used to conserve energy in urban environments. Some ecosystem management practices that result in C sequestration and conservation provide ancillary benefits.

  10. Protected Area Certificates: Gaining Ground for Better Ecosystem Protection?

    NASA Astrophysics Data System (ADS)

    Segerstedt, Anna; Grote, Ulrike

    2015-06-01

    Protected areas are vital to sustain a number of ecosystem services. Yet, many protected areas are underfinanced and lack management effectiveness. Protected area certificates have been suggested as a way to resolve these problems. This instrument would allow land managers to certify an area if it meets certain conservation criteria. The certificates could then be sold on an international market, for example to companies and any consumers that are interested in environmental protection. Some pilot initiatives have been launched, yet little is known about future demand and features of protected area certificates. To fill this knowledge gap, we conduct a choice experiment with close to 400 long-distance tourists from Germany as a potential group of buyers. Our results indicate that the respondents have the highest willingness to pay for certificates that conserve sensitive ecosystems and in addition to this lead to poverty reduction and safeguard water resources. For other attributes such as a greenhouse gas reduction, the preferences are less significant. Overall, the results are rather homogenous irrespective of where the protected areas are located. These insights are important for the future design and marketing of protected area certificates.

  11. Protected area certificates: gaining ground for better ecosystem protection?

    PubMed

    Segerstedt, Anna; Grote, Ulrike

    2015-06-01

    Protected areas are vital to sustain a number of ecosystem services. Yet, many protected areas are underfinanced and lack management effectiveness. Protected area certificates have been suggested as a way to resolve these problems. This instrument would allow land managers to certify an area if it meets certain conservation criteria. The certificates could then be sold on an international market, for example to companies and any consumers that are interested in environmental protection. Some pilot initiatives have been launched, yet little is known about future demand and features of protected area certificates. To fill this knowledge gap, we conduct a choice experiment with close to 400 long-distance tourists from Germany as a potential group of buyers. Our results indicate that the respondents have the highest willingness to pay for certificates that conserve sensitive ecosystems and in addition to this lead to poverty reduction and safeguard water resources. For other attributes such as a greenhouse gas reduction, the preferences are less significant. Overall, the results are rather homogenous irrespective of where the protected areas are located. These insights are important for the future design and marketing of protected area certificates. PMID:25868572

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

    PubMed

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

    2011-05-01

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

  13. Predators help protect carbon stocks in blue carbon ecosystems

    NASA Astrophysics Data System (ADS)

    Atwood, Trisha B.; Connolly, Rod M.; Ritchie, Euan G.; Lovelock, Catherine E.; Heithaus, Michael R.; Hays, Graeme C.; Fourqurean, James W.; Macreadie, Peter I.

    2015-12-01

    Predators continue to be harvested unsustainably throughout most of the Earth's ecosystems. Recent research demonstrates that the functional loss of predators could have far-reaching consequences on carbon cycling and, by implication, our ability to ameliorate climate change impacts. Yet the influence of predators on carbon accumulation and preservation in vegetated coastal habitats (that is, salt marshes, seagrass meadows and mangroves) is poorly understood, despite these being some of the Earth's most vulnerable and carbon-rich ecosystems. Here we discuss potential pathways by which trophic downgrading affects carbon capture, accumulation and preservation in vegetated coastal habitats. We identify an urgent need for further research on the influence of predators on carbon cycling in vegetated coastal habitats, and ultimately the role that these systems play in climate change mitigation. There is, however, sufficient evidence to suggest that intact predator populations are critical to maintaining or growing reserves of 'blue carbon' (carbon stored in coastal or marine ecosystems), and policy and management need to be improved to reflect these realities.

  14. Organic carbon hidden in urban ecosystems.

    PubMed

    Edmondson, Jill L; Davies, Zoe G; McHugh, Nicola; Gaston, Kevin J; Leake, Jonathan R

    2012-01-01

    Urbanization is widely presumed to degrade ecosystem services, but empirical evidence is now challenging these assumptions. We report the first city-wide organic carbon (OC) budget for vegetation and soils, including under impervious surfaces. Urban soil OC storage was significantly greater than in regional agricultural land at equivalent soil depths, however there was no significant difference in storage between soils sampled beneath urban greenspaces and impervious surfaces, at equivalent depths. For a typical U.K. city, total OC storage was 17.6 kg m(-2) across the entire urban area (assuming 0 kg m(-2) under 15% of land covered by buildings). The majority of OC (82%) was held in soils, with 13% found under impervious surfaces, and 18% stored in vegetation. We reveal that assumptions underpinning current national estimates of ecosystem OC stocks, as required by Kyoto Protocol signatories, are not robust and are likely to have seriously underestimated the contributions of urban areas.

  15. BOREAS TE-19 Ecosystem Carbon Balance Model

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Papagno, Andrea (Editor); Frolking, Steve

    2000-01-01

    The BOREAS TE-19 team developed a model called the Spruce and Moss Model (SPAM) designed to simulate the daily carbon balance of a black spruce/moss boreal forest ecosystem. It is driven by daily weather conditions, and consists of four components: (1) soil climate, (2) tree photosynthesis and respiration, (3) moss photosynthesis and respiration, and (4) litter decomposition and associated heterotrophic respiration. The model simulates tree gross and net photosynthesis, wood respiration, live root respiration, moss gross and net photosynthesis, and heterotrophic respiration (decomposition of root litter, young needle and moss litter, and humus). These values can be combined to generate predictions of total site net ecosystem exchange of carbon (NEE), total soil dark respiration (live roots + heterotrophs + live moss), spruce and moss net productivity, and net carbon accumulation in the soil. To date, simulations have been of the BOREAS NSA-OBS and SSA-OBS tower sites, from 1968-95 (except 1990-93). The files include source code and sample input and output files in ASCII format. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Activity Archive Center (DAAC).

  16. Carbon dioxide dynamics in an artificial ecosystem

    NASA Astrophysics Data System (ADS)

    Hu, Enzhu; Hu, Dawei; Tong, Ling; Li, Ming; Fu, Yuming; He, Wenting; Liu, Hong

    An experimental artificial ecosystem was established as a tool to understand the behavior of closed ecosystem and to develop the technology for a future bioregenerative life support system for lunar or planetary exploration. Total effective volume of the system is 0.7 m3 . It consists of a higher plant chamber, an animal chamber and a photo-bioreactor which cultivated lettuce (Lactuca sativa L.), silkworm (Bombyx Mori L.) and microalgae (Chlorella), respectively. For uniform and sustained observations, lettuce and silkworms was cultivated using sequential cultivation method, and microalgae using continuous culture. Four researchers took turns breathing the system air through a tube for brief periods every few hours. A mathematic model, simulating the carbon dioxide dynamics was developed. The main biological parameters concerning photosynthesis of lettuce and microalgae, respiration of silkworms and human were validated by the experimental data. The model described the respiratory relationship between autotrophic and heterotrophic compartments. A control strategy was proposed as a tool for the atmosphere management of the artificial ecosystem.

  17. Net ecosystem production: A comprehensive measure of net carbon accumulation by ecosystems

    USGS Publications Warehouse

    Randerson, J.T.; Chapin, F. S.; Harden, J.W.; Neff, J.C.; Harmon, M.E.

    2002-01-01

    The conceptual framework used by ecologists and biogeochemists must allow for accurate and clearly defined comparisons of carbon fluxes made with disparate techniques across a spectrum of temporal and spatial scales. Consistent with usage over the past four decades, we define "net ecosystem production" (NEP) as the net carbon accumulation by ecosystems. Past use of this term has been ambiguous, because it has been used conceptually as a measure of carbon accumulation by ecosystems, but it has often been calculated considering only the balance between gross primary production (GPP) and ecosystem respiration. This calculation ignores other carbon fluxes from ecosystems (e.g., leaching of dissolved carbon and losses associated with disturbance). To avoid conceptual ambiguities, we argue that NEP be defined, as in the past, as the net carbon accumulation by ecosystems and that it explicitly incorporate all the carbon fluxes from an ecosystem, including autotrophic respiration, heterotrophic respiration, losses associated with disturbance, dissolved and particulate carbon losses, volatile organic compound emissions, and lateral transfers among ecosystems. Net biome productivity (NBP), which has been proposed to account for carbon loss during episodic disturbance, is equivalent to NEP at regional or global scales. The multi-scale conceptual framework we describe provides continuity between flux measurements made at the scale of soil profiles and chambers, forest inventories, eddy covariance towers, aircraft, and inversions of remote atmospheric flask samples, allowing a direct comparison of NEP estimates made at all temporal and spatial scales.

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

    PubMed

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

    2010-03-01

    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.

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

    USGS Publications Warehouse

    Zhao, Shuqing

    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. Organic carbon hidden in urban ecosystems

    PubMed Central

    Edmondson, Jill L.; Davies, Zoe G.; McHugh, Nicola; Gaston, Kevin J.; Leake, Jonathan R.

    2012-01-01

    Urbanization is widely presumed to degrade ecosystem services, but empirical evidence is now challenging these assumptions. We report the first city-wide organic carbon (OC) budget for vegetation and soils, including under impervious surfaces. Urban soil OC storage was significantly greater than in regional agricultural land at equivalent soil depths, however there was no significant difference in storage between soils sampled beneath urban greenspaces and impervious surfaces, at equivalent depths. For a typical U.K. city, total OC storage was 17.6 kg m−2 across the entire urban area (assuming 0 kg m−2 under 15% of land covered by buildings). The majority of OC (82%) was held in soils, with 13% found under impervious surfaces, and 18% stored in vegetation. We reveal that assumptions underpinning current national estimates of ecosystem OC stocks, as required by Kyoto Protocol signatories, are not robust and are likely to have seriously underestimated the contributions of urban areas. PMID:23236585

  1. Soil carbon sequestration in degraded semiarid agro-ecosystems--perils and potentials.

    PubMed

    Olsson, Lennart; Ardö, Jonas

    2002-09-01

    The Kyoto Protocol opens new possibilities for using the biosphere as a carbon sink. Using agro-ecosystems as carbon sinks may be the most appropriate practice from both environmental and socioeconomic points of view. Degraded agro-ecosystems in Africa might benefit significantly from the improved land management that would be part of a carbon sequestration program. There are vast areas of these agro-ecosystems in Africa and their rehabilitation is an urgent matter. We agree with UNEP that there are potentially important synergies to be made between the Convention on Climate Change, the UN Convention to Combat Desertification and the UN Convention on Biodiversity. In this paper, we have investigated the potential for increasing soil carbon content in semiarid agro-ecosystems in the Sudan and found that increasing fallow periods will result in increased soil carbon content and converting marginal agricultural areas to rangeland will restore the carbon levels to 80% of the natural savannah carbon levels in 100 years. The economic gain from a future carbon sequestration program has the potential of a significant contribution to the household economy in these agro-ecosystems.

  2. Estimating ecosystem carbon stocks at Redwood National and State Parks

    USGS Publications Warehouse

    van Mantgem, Phillip J.; Madej, Mary Ann; Seney, Joseph; Deshais, Janelle

    2013-01-01

    Accounting for ecosystem carbon is increasingly important for park managers. In this case study we present our efforts to estimate carbon stocks and the effects of management on carbon stocks for Redwood National and State Parks in northern California. Using currently available information, we estimate that on average these parks’ soils contain approximately 89 tons of carbon per acre (200 Mg C per ha), while vegetation contains about 130 tons C per acre (300 Mg C per ha). estoration activities at the parks (logging-road removal, second-growth forest management) were shown to initially reduce ecosystem carbon, but may provide for enhanced ecosystem carbon storage over the long term. We highlight currently available tools that could be used to estimate ecosystem carbon at other units of the National Park System.

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

    PubMed

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

    2014-06-01

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

  4. Wintertime ecosystem respiration shifts tundra from carbon sink to carbon source at tundra warming experiment

    NASA Astrophysics Data System (ADS)

    Webb, E.; Schuur, E. A.; Natali, S.; Bracho, R.

    2013-12-01

    Northern latitude ecosystems play a significant role in the global carbon (C) budget due to the roughly 1700 Pg of C stored in permafrost soils. As high latitudes warm, previously frozen C is expected to decompose, thereby increasing CO2 fluxes to the atmosphere and potentially creating a positive feedback to climate warming. While warming has been shown to increase plant C uptake during the growing season, these seasonal C gains may be offset on an annual basis by ecosystem respiration (Reco) during the remaining seven months of the year. Here we present research from the Carbon in Permafrost Experimental Heating Research (CiPEHR) project, a tundra ecosystem warming experiment in interior Alaska. We partitioned the non-growing season into three segments: fall (October 1 until first snow), winter (snow-covered period until spring), and spring (snow depth less than 30cm until melt out). During fall, we measured net ecosystem exchange and Reco using a static flux chamber. In winter, we measured Reco using chamber measurements and soda lime. For spring, we modeled fluxes based on known relationships between snow depth and photosynthetic rate of arctic evergreen species. We found that ecosystem warming caused plants to photosynthesize later in fall and increased C uptake during spring but also enhanced respiration during the long winter. We combined these off-season estimates with measurements from growing season auto-chamber data and found that despite the C gained during the growing season, ecosystem warming resulted in net annual C loss for the two years measured. This annual C loss was dependent on the magnitude of wintertime Reco. Our results indicate that snow depth, soil temperature, and day of season are the major determinants of wintertime Reco. Some climate models predict that arctic ecosystems will experience warmer winters with more snow. Thus, despite increased plant productivity during the growing season, we document that increased wintertime temperatures

  5. Ecosystem Carbon Stocks of Intertidal Wetlands in Singapore

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  6. Plant diversity effects on ecosystem evapotranspiration and carbon uptake: a controlled environment (Ecotron) and modeling approach

    NASA Astrophysics Data System (ADS)

    Milcu, Alexandru; Roy, Jacques

    2016-04-01

    Effects of species and functional diversity of plants on ecosystem evapotranspiration and carbon fluxes have been rarely assessed simultaneously. Here we present the results from an experiment that combined a lysimeter setup in a controlled environment facility (Ecotron) with large ecosystem samples/ monoliths originating from a long-term biodiversity experiment ("The Jena Experiment") and a modelling approach. We aimed at (1) quantifying the impact of plant species richness (4 vs. 16 species) on day- and night-time ecosystem water vapor fluxes and carbon uptake, (2) partitioning ecosystem evapotranspiration into evaporation and plant transpiration using the Shuttleworth and Wallace (SW) energy partitioning model, and (3) identifying the most parsimonious predictors of water vapor vapor and CO2 fluxes using plant functional trait-based metrics such as functional diversity and community weighted means. The SW model indicated that at low plant species richness, a higher proportion of the available energy was diverted to evaporation (a non-productive flux), while at higher species richness the proportion of ecosystem transpiration (a production-related water flux) increased. This led to an increased carbon gain per amount of water vapor loss (i.e. increased water use efficiency). While the LAI controlled the carbon and water fluxes, we also found that the diversity of plant functional traits, and in particular of leaf nitrogen concentration are potential important predictors of ecosystem transpiration and carbon uptake and consequently significantly contributed to increase in water use efficiency in communities with higher plant diversity.

  7. Looking skyward to study ecosystem carbon dynamics

    USGS Publications Warehouse

    Dye, Dennis G.

    2012-01-01

    Between May and October 2011 the U.S. Geological Survey (USGS), in cooperation with the U.S. Department of Energy's Atmospheric Radiation Measurement (ARM) program, conducted a field campaign at the ARM Southern Great Plains site in north central Oklahoma to evaluate a new instrument for quantitative image-based monitoring of sky conditions and solar radiation. The High Dynamic Range All-Sky Imaging System (HDR-ASIS) was developed by USGS to support studies of cloud- and aerosol-induced variability in the geometric properties of solar radiation (the sky radiance distribution) and its effects on photosynthesis and uptake of carbon dioxide (CO2) by terrestrial ecosystems. Under a clean, cloudless atmosphere when the Sun is above the horizon, most of the solar radiation reaching an area of the Earth's surface is concentrated in a beam coming directly from the Sun; a relatively small proportion arrives as diffuse radiation from the rest of the sky. Clouds and atmospheric aerosols cause increased scattering of the beam radiation, which increases the proportion of diffuse radiation at the surface.

  8. Using Radiocarbon to Test Models of Ecosystem Carbon Cycling

    NASA Astrophysics Data System (ADS)

    Trumbore, S.; Lin, H.; Randerson, J.

    2007-05-01

    The radiocarbon content of carbon stored in and respired by ecosystems provides a direct measure of ecosystem carbon dynamics that can be directly compared to model predictions. Because carbon cycles through ecosystems on a variety of timescales, the mean age of C in standing biomass and soil organic matter pools is older than the mean age of microbially respired carbon. In turn, each pathway for C transit through ecosystems my respond differently to edaphic conditions; for example, soil organic matter mean age is controlled by factors affecting stabilization of C on very long timescales, such as mineralogy, while a factor like litter quality that effects decomposition rates reflects vegetation and climate characteristics. We compare the radiocarbon signature of heterotrophically respired CO2 across a number of ecosystems with models predicted using the CASA ecosystem model. The major controls of microbially respired CO2 from ecosystems include the residence time of C in living plant pools (i.e. the age of C in litter inputs to soil) and factors that control decomposition rates (litter quality and climate). Major differences between model and measured values at low latitudes are related to how woody debris pools are treated differently in models and measurements. The time lag between photosynthesis and respiration is a key ecosystem property that defines its potential to store or release carbon given variations in annual net primary production. Radiocarbon provides a rare case where models can be directly compared with measurements to provide a test of this parameter.

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

    NASA Astrophysics Data System (ADS)

    Amiro, B. D.; Barr, A. G.; Barr, J. G.; Black, T. A.; Bracho, R.; Brown, M.; Chen, J.; Clark, K. L.; Davis, K. J.; Desai, A. R.; Dore, S.; Engel, V.; Fuentes, J. D.; Goldstein, A. H.; Goulden, M. L.; Kolb, T. E.; Lavigne, M. B.; Law, B. E.; Margolis, H. A.; Martin, T.; McCaughey, J. H.; Misson, L.; Montes-Helu, M.; Noormets, A.; Randerson, J. T.; Starr, G.; Xiao, J.

    2010-12-01

    Disturbances are important for renewal of North American forests. Here we summarize more than 180 site years of eddy covariance measurements of carbon dioxide flux made at forest chronosequences in North America. The disturbances included stand-replacing fire (Alaska, Arizona, Manitoba, and Saskatchewan) and harvest (British Columbia, Florida, New Brunswick, Oregon, Quebec, Saskatchewan, and Wisconsin) events, insect infestations (gypsy moth, forest tent caterpillar, and mountain pine beetle), Hurricane Wilma, and silvicultural thinning (Arizona, California, and New Brunswick). Net ecosystem production (NEP) showed a carbon loss from all ecosystems following a stand-replacing disturbance, becoming a carbon sink by 20 years for all ecosystems and by 10 years for most. Maximum carbon losses following disturbance (g C m-2y-1) ranged from 1270 in Florida to 200 in boreal ecosystems. Similarly, for forests less than 100 years old, maximum uptake (g C m-2y-1) was 1180 in Florida mangroves and 210 in boreal ecosystems. More temperate forests had intermediate fluxes. Boreal ecosystems were relatively time invariant after 20 years, whereas western ecosystems tended to increase in carbon gain over time. This was driven mostly by gross photosynthetic production (GPP) because total ecosystem respiration (ER) and heterotrophic respiration were relatively invariant with age. GPP/ER was as low as 0.2 immediately following stand-replacing disturbance reaching a constant value of 1.2 after 20 years. NEP following insect defoliations and silvicultural thinning showed lesser changes than stand-replacing events, with decreases in the year of disturbance followed by rapid recovery. NEP decreased in a mangrove ecosystem following Hurricane Wilma because of a decrease in GPP and an increase in ER.

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

    NASA Astrophysics Data System (ADS)

    Amiro, B. D.; Barr, A. G.; Barr, J. G.; Black, T. A.; Bracho, R.; Brown, M.; Chen, J.; Clark, K. L.; Davis, K. J.; Desai, A. R.; Dore, S.; Engel, V.; Fuentes, J. D.; Goldstein, A. H.; Goulden, M. L.; Kolb, T. E.; Lavigne, M. B.; Law, B. E.; Margolis, H. A.; Martin, T.; McCaughey, J. H.; Misson, L.; Montes-Helu, M.; Noormets, A.; Randerson, J. T.; Starr, G.; Xiao, J.

    2010-10-01

    Disturbances are important for renewal of North American forests. Here we summarize more than 180 site years of eddy covariance measurements of carbon dioxide flux made at forest chronosequences in North America. The disturbances included stand-replacing fire (Alaska, Arizona, Manitoba, and Saskatchewan) and harvest (British Columbia, Florida, New Brunswick, Oregon, Quebec, Saskatchewan, and Wisconsin) events, insect infestations (gypsy moth, forest tent caterpillar, and mountain pine beetle), Hurricane Wilma, and silvicultural thinning (Arizona, California, and New Brunswick). Net ecosystem production (NEP) showed a carbon loss from all ecosystems following a stand-replacing disturbance, becoming a carbon sink by 20 years for all ecosystems and by 10 years for most. Maximum carbon losses following disturbance (g C m-2y-1) ranged from 1270 in Florida to 200 in boreal ecosystems. Similarly, for forests less than 100 years old, maximum uptake (g C m-2y-1) was 1180 in Florida mangroves and 210 in boreal ecosystems. More temperate forests had intermediate fluxes. Boreal ecosystems were relatively time invariant after 20 years, whereas western ecosystems tended to increase in carbon gain over time. This was driven mostly by gross photosynthetic production (GPP) because total ecosystem respiration (ER) and heterotrophic respiration were relatively invariant with age. GPP/ER was as low as 0.2 immediately following stand-replacing disturbance reaching a constant value of 1.2 after 20 years. NEP following insect defoliations and silvicultural thinning showed lesser changes than stand-replacing events, with decreases in the year of disturbance followed by rapid recovery. NEP decreased in a mangrove ecosystem following Hurricane Wilma because of a decrease in GPP and an increase in ER.

  11. Carbon emissions and sequestration potential of Central African ecosystems.

    PubMed

    Zhang, Q; Justice, C O

    2001-09-01

    Joint Implementation under the Climate Change Convention and Clean Development Mechanism of the Kyoto Protocol require a scientific understanding of current carbon stocks, fluxes, and sequestration potential, especially in tropical ecosystems where there are large carbon reservoirs, significant carbon emissions, and large land areas available for reforestation. Central Africa contains 10% of the world's remaining tropical moist forests and has received little attention in carbon studies. In 1980, above-ground carbon stocks in the central African ecosystem were 28.92 Pg and were reduced to 24.79 Pg by 1990. Improved forest management aimed at increasing biomass density could sequester 18.32 Pg of carbon, and over 500,000 km2 formerly forested land will be available by 2050 for reforestation with a capacity to offset 10 Pg carbon. Understanding the spatial distribution of biomass carbon and sequestration potential will be essential for carbon trading initiatives through Joint Implementation and Clean Development Mechanism.

  12. Measurement of population inversions and gain in carbon fiber plasmas

    SciTech Connect

    Milchberg, H.; Skinner, C.H.; Suckewer, S.; Voorhees, D.

    1985-10-01

    A CO/sub 2/ laser (approx.0.5 kJ energy, 70 nsec pulse width) was focussed onto the end of an axially oriented, thick (35 to 350 ..mu..) carbon fiber with or without a magnetic field present along the laser-fiber axis. We present evidence for axial-to-transverse enhancement of the CVI 182A (n = 3 ..-->.. 2) transition, which is correlated with the appearance of a population inversion between levels n = 3 and 2. For the B = 0 kG, zero field case, the maximum gain-length product of kl approx. =3 (k approx. =6 cm/sup -1/) was measured for a carbon fiber coated with a thin layer of aluminum (for additional radiation cooling). The results are interpreted in terms of fast recombination due mostly to thermal conduction from the plasma to the cold fiber core.

  13. Ecosystem Carbon Storage in Alpine Grassland on the Qinghai Plateau.

    PubMed

    Liu, Shuli; Zhang, Fawei; Du, Yangong; Guo, Xiaowei; Lin, Li; Li, Yikang; Li, Qian; Cao, Guangmin

    2016-01-01

    The alpine grassland ecosystem can sequester a large quantity of carbon, yet its significance remains controversial owing to large uncertainties in the relative contributions of climate factors and grazing intensity. In this study we surveyed 115 sites to measure ecosystem carbon storage (both biomass and soil) in alpine grassland over the Qinghai Plateau during the peak growing season in 2011 and 2012. Our results revealed three key findings. (1) Total biomass carbon density ranged from 0.04 for alpine steppe to 2.80 kg C m-2 for alpine meadow. Median soil organic carbon (SOC) density was estimated to be 16.43 kg C m-2 in alpine grassland. Total ecosystem carbon density varied across sites and grassland types, from 1.95 to 28.56 kg C m-2. (2) Based on the median estimate, the total carbon storage of alpine grassland on the Qinghai Plateau was 5.14 Pg, of which 94% (4.85 Pg) was soil organic carbon. (3) Overall, we found that ecosystem carbon density was affected by both climate and grazing, but to different extents. Temperature and precipitation interaction significantly affected AGB carbon density in winter pasture, BGB carbon density in alpine meadow, and SOC density in alpine steppe. On the other hand, grazing intensity affected AGB carbon density in summer pasture, SOC density in alpine meadow and ecosystem carbon density in alpine grassland. Our results indicate that grazing intensity was the primary contributing factor controlling carbon storage at the sites tested and should be the primary consideration when accurately estimating the carbon storage in alpine grassland. PMID:27494253

  14. Ecosystem Carbon Storage in Alpine Grassland on the Qinghai Plateau

    PubMed Central

    Liu, Shuli; Zhang, Fawei; Du, Yangong; Guo, Xiaowei; Lin, Li; Li, Yikang; Li, Qian; Cao, Guangmin

    2016-01-01

    The alpine grassland ecosystem can sequester a large quantity of carbon, yet its significance remains controversial owing to large uncertainties in the relative contributions of climate factors and grazing intensity. In this study we surveyed 115 sites to measure ecosystem carbon storage (both biomass and soil) in alpine grassland over the Qinghai Plateau during the peak growing season in 2011 and 2012. Our results revealed three key findings. (1) Total biomass carbon density ranged from 0.04 for alpine steppe to 2.80 kg C m-2 for alpine meadow. Median soil organic carbon (SOC) density was estimated to be 16.43 kg C m-2 in alpine grassland. Total ecosystem carbon density varied across sites and grassland types, from 1.95 to 28.56 kg C m-2. (2) Based on the median estimate, the total carbon storage of alpine grassland on the Qinghai Plateau was 5.14 Pg, of which 94% (4.85 Pg) was soil organic carbon. (3) Overall, we found that ecosystem carbon density was affected by both climate and grazing, but to different extents. Temperature and precipitation interaction significantly affected AGB carbon density in winter pasture, BGB carbon density in alpine meadow, and SOC density in alpine steppe. On the other hand, grazing intensity affected AGB carbon density in summer pasture, SOC density in alpine meadow and ecosystem carbon density in alpine grassland. Our results indicate that grazing intensity was the primary contributing factor controlling carbon storage at the sites tested and should be the primary consideration when accurately estimating the carbon storage in alpine grassland. PMID:27494253

  15. Leaf conductance and carbon gain under salt-stressed conditions

    NASA Astrophysics Data System (ADS)

    Volpe, V.; Manzoni, S.; Marani, M.; Katul, G.

    2011-12-01

    Exposure of plants to salt stress is often accompanied by reductions in leaf photosynthesis and in stomatal and mesophyll conductances. To separate the effects of salt stress on these quantities, a model based on the hypothesis that carbon gain is maximized subject to a water loss cost is proposed. The optimization problem of adjusting stomatal aperture for maximizing carbon gain at a given water loss is solved for both a non-linear and a linear biochemical demand function. A key novel theoretical outcome of the optimality hypothesis is an explicit relationship between the stomatal and mesophyll conductances that can be evaluated against published measurements. The approaches here successfully describe gas-exchange measurements reported for olive trees (Olea europea L.) and spinach (Spinacia oleraceaL.) in fresh water and in salt-stressed conditions. Salt stress affected both stomatal and mesophyll conductances and photosynthetic efficiency of both species. The fresh water/salt water comparisons show that the photosynthetic capacity is directly reduced by 30%-40%, indicating that reductions in photosynthetic rates under increased salt stress are not due only to a limitation of CO2diffusion. An increase in salt stress causes an increase in the cost of water parameter (or marginal water use efficiency) exceeding 100%, analogous in magnitude to findings from extreme drought stress studies. The proposed leaf-level approach can be incorporated into physically based models of the soil-plant-atmosphere system to assess how saline conditions and elevated atmospheric CO2 jointly impact transpiration and photosynthesis.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  17. Carbon dynamics and sequestration in urban turfgrass ecosystems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Urbanization is a global trend. Turfgrass covers 1.9% of land in the continental US. Here we review existing literature associated with carbon (C) pools, sequestration, and nitrous oxide emission of urban turfgrass ecosystems. Turfgrasses exhibit significant carbon sequestration (0.34–1.4 Mg ha-1 ye...

  18. The carbon balance of terrestrial ecosystems in China.

    PubMed

    Piao, Shilong; Fang, Jingyun; Ciais, Philippe; Peylin, Philippe; Huang, Yao; Sitch, Stephen; Wang, Tao

    2009-04-23

    Global terrestrial ecosystems absorbed carbon at a rate of 1-4 Pg yr(-1) during the 1980s and 1990s, offsetting 10-60 per cent of the fossil-fuel emissions. The regional patterns and causes of terrestrial carbon sources and sinks, however, remain uncertain. With increasing scientific and political interest in regional aspects of the global carbon cycle, there is a strong impetus to better understand the carbon balance of China. This is not only because China is the world's most populous country and the largest emitter of fossil-fuel CO(2) into the atmosphere, but also because it has experienced regionally distinct land-use histories and climate trends, which together control the carbon budget of its ecosystems. Here we analyse the current terrestrial carbon balance of China and its driving mechanisms during the 1980s and 1990s using three different methods: biomass and soil carbon inventories extrapolated by satellite greenness measurements, ecosystem models and atmospheric inversions. The three methods produce similar estimates of a net carbon sink in the range of 0.19-0.26 Pg carbon (PgC) per year, which is smaller than that in the conterminous United States but comparable to that in geographic Europe. We find that northeast China is a net source of CO(2) to the atmosphere owing to overharvesting and degradation of forests. By contrast, southern China accounts for more than 65 per cent of the carbon sink, which can be attributed to regional climate change, large-scale plantation programmes active since the 1980s and shrub recovery. Shrub recovery is identified as the most uncertain factor contributing to the carbon sink. Our data and model results together indicate that China's terrestrial ecosystems absorbed 28-37 per cent of its cumulated fossil carbon emissions during the 1980s and 1990s.

  19. Observing terrestrial ecosystems and the carbon cycle from space.

    PubMed

    Schimel, David; Pavlick, Ryan; Fisher, Joshua B; Asner, Gregory P; Saatchi, Sassan; Townsend, Philip; Miller, Charles; Frankenberg, Christian; Hibbard, Kathy; Cox, Peter

    2015-05-01

    Terrestrial ecosystem and carbon cycle feedbacks will significantly impact future climate, but their responses are highly uncertain. Models and tipping point analyses suggest the tropics and arctic/boreal zone carbon-climate feedbacks could be disproportionately large. In situ observations in those regions are sparse, resulting in high uncertainties in carbon fluxes and fluxes. Key parameters controlling ecosystem carbon responses, such as plant traits, are also sparsely observed in the tropics, with the most diverse biome on the planet treated as a single type in models. We analyzed the spatial distribution of in situ data for carbon fluxes, stocks and plant traits globally and also evaluated the potential of remote sensing to observe these quantities. New satellite data products go beyond indices of greenness and can address spatial sampling gaps for specific ecosystem properties and parameters. Because environmental conditions and access limit in situ observations in tropical and arctic/boreal environments, use of space-based techniques can reduce sampling bias and uncertainty about tipping point feedbacks to climate. To reliably detect change and develop the understanding of ecosystems needed for prediction, significantly, more data are required in critical regions. This need can best be met with a strategic combination of remote and in situ data, with satellite observations providing the dense sampling in space and time required to characterize the heterogeneity of ecosystem structure and function.

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

    NASA Astrophysics Data System (ADS)

    Cifuentes, M.

    2012-12-01

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

  1. Sustainable carbon uptake - important ecosystem service within sustainable forest management

    NASA Astrophysics Data System (ADS)

    Zorana Ostrogović Sever, Maša; Anić, Mislav; Paladinić, Elvis; Alberti, Giorgio; Marjanović, Hrvoje

    2016-04-01

    Even-aged forest management with natural regeneration under continuous cover (i.e. close to nature management) is considered to be sustainable regarding the yield, biodiversity and stability of forest ecosystems. Recently, in the context of climate change, there is a raising question of sustainable forest management regarding carbon uptake. Aim of this research was to explore whether current close to nature forest management approach in Croatia can be considered sustainable in terms of carbon uptake throughout the life-time of Pedunculate oak forest. In state-owned managed forest a chronosequence experiment was set up and carbon stocks in main ecosystem pools (live biomass, dead wood, litter and mineral soil layer), main carbon fluxes (net primary production, soil respiration (SR), decomposition) and net ecosystem productivity were estimated in eight stands of different age (5, 13, 38, 53, 68, 108, 138 and 168 years) based on field measurements and published data. Air and soil temperature and soil moisture were recorded on 7 automatic mini-meteorological stations and weekly SR measurements were used to parameterize SR model. Carbon balance was estimated at weekly scale for the growing season 2011 (there was no harvesting), as well as throughout the normal rotation period of 140 years (harvesting was included). Carbon stocks in different ecosystem pools change during a stand development. Carbon stocks in forest floor increase with stand age, while carbon stocks in dead wood are highest in young and older stands, and lowest in middle-aged, mature stands. Carbon stocks in mineral soil layer were found to be stable across chronosequence with no statistically significant age-dependent trend. Pedunculate Oak stand, assuming successful regeneration, becomes carbon sink very early in a development phase, between the age of 5 and 13 years, and remains carbon sink even after the age of 160 years. Greatest carbon sink was reached in the stand aged 53 years. Obtained results

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

    SciTech Connect

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

    2000-08-28

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

  3. Influence of the Tussock Growth Form on Arctic Ecosystem Carbon Stocks

    NASA Astrophysics Data System (ADS)

    Curasi, S.; Rocha, A. V.; Sonnentag, O.; Wullschleger, S. D.; Myers-Smith, I. H.; Fetcher, N.; Mack, M. C.; Natali, S.; Loranty, M. M.; Parker, T.

    2015-12-01

    The influence of plant growth forms on ecosystem carbon (C) cycling has been under appreciated. In arctic tundra, environmental factors and plant traits of the sedge Eriophorum vaginatum cause the formation of mounds that are dense amalgamations of belowground C called tussocks. Tussocks have important implications for arctic ecosystem biogeochemistry and C stocks, but the environmental and biological factors controlling their size and distribution across the landscape are poorly understood. In order to better understand how landscape variation in tussock size and density impact ecosystem C stocks, we formed the Carbon in Arctic Tussock Tundra (CATT) network and recruited an international team to sample locations across the arctic. The CATT network provided a latitudinal and longitudinal gradient along which to improve our understanding of tussocks' influence on ecosystem structure and function. CATT data revealed important insights into tussock formation across the arctic. Tussock density generally declined with latitude, and tussock size exhibited substantial variation across sites. The relationship between height and diameter was similar across CATT sites indicating that both biological and environmental factors control tussock formation. At some sites, C in tussocks comprised a substantial percentage of ecosystem C stocks that may be vulnerable to climate change. It is concluded that the loss of this growth form would offset C gains from projected plant functional shifts from graminoid to shrub tundra. This work highlights the role of plant growth forms on the magnitude and retention of ecosystem C stocks.

  4. Observing terrestrial ecosystems and the carbon cycle from space

    SciTech Connect

    Schimel, David; Pavlick, Ryan; Fisher, Joshua B.; Asner, Gregory P.; Saatchi, Sassan; Townsend, Philip; Miller, Charles E.; Frankenberg, Christian; Hibbard, Kathleen A.; Cox, Peter

    2015-02-06

    Modeled terrestrial ecosystem and carbon cycle feedbacks contribute substantial uncertainty to projections of future climate. The limitations of current observing networks contribute to this uncertainty. Here we present a current climatology of global model predictions and observations for photosynthesis, biomass, plant diversity and plant functional diversity. Carbon cycle tipping points occur in terrestrial regions where fluxes or stocks are largest, and where biological variability is highest, the tropics and Arctic/Boreal zones. Global observations are predominately in the mid-latitudes and are sparse in high and low latitude ecosystems. Observing and forecasting ecosystem change requires sustained observations of sufficient density in time and space in critical regions. Using data and theory available now, we can develop a strategy to detect and forecast terrestrial carbon cycle-climate interactions, by combining in situ and remote techniques.

  5. Tracing changes in ecosystem function under elevated carbon dioxide conditions.

    SciTech Connect

    Pataki, D. E.; Ellsworth, D. S.; Evans, R. D.; Gonzalez-Meler, M.; King, J.; Leavitt, S. W.; Lin, G.; Matamala, R.; Pendall, E.; Siegwolf, R.; Van Kessel, C.; Ehleringer, J. F.; Environmental Research; Univ. of Utah; Univ. of Michigan; Washington State Univ.; Univ. of Illinois at Chicago; Michigan Technological Univ.; Univ. of Arizona; Columbia Univ.; Univ. of Wyoming; Paul Scherrer Inst.; Univ. of California, Davis

    2003-09-01

    Responses of ecosystems to elevated levels of atmospheric carbon dioxide (CO{sub 2}) remain a critical uncertainty in global change research. Two key unknown factors are the fate of carbon newly incorporated by photosynthesis into various pools within the ecosystem and the extent to which elevated CO{sub 2} is transferred to and sequestered in pools with long turnover times. The CO{sub 2} used for enrichment in many experiments incorporates a dual isotopic tracer, in the sense that ratios of both the stable carbon-13 ({sup 13}C) and the radioactive carbon-14 ({sup 14}C) isotopes with respect to carbon-12 are different from the corresponding ratios in atmospheric CO{sub 2}. Here we review techniques for using {sup 13}C and {sup 14}C abundances to follow the fate of newly fixed carbon and to further our understanding of the turnover times of ecosystem carbon pools. We also discuss the application of nitrogen, oxygen, and hydrogen isotope analyses for tracing changes in the linkages between carbon, nitrogen, and water cycles under conditions of elevated CO{sub 2}.

  6. Global simulation of the carbon isotope exchange of terrestrial ecosystems

    NASA Astrophysics Data System (ADS)

    Ito, A.; Terao, Y.; Mukai, H.

    2009-12-01

    There remain large uncertainties in our quantification of global carbon cycle, which has close interactions with the climate system and is subject to human-induced global environmental change. Information on carbon isotopes is expected to reduce the uncertainty by providing additional constraints on net atmosphere-ecosystem exchange. This study attempted to simulate the dynamics of carbon isotopes at the global scale, using a process-based terrestrial ecosystem model: Vegetation Integrative SImulator for Trace gases (VISIT). The base-model of carbon cycle (Sim-CYCLE, Ito 2003) has already considered stable carbon isotope composition (13C/12C), and here radioactive carbon isotope (14C) was included. The isotope ratios characterize various aspects of terrestrial carbon cycle, which is difficult to be constrained by sole mass balance. For example, isotopic discrimination by photosynthetic assimilation is closely related with leaf stomatal conductance and composition of C3 and C4 plant in grasslands. Isotopic disequilibrium represents mean residence time of terrestrial carbon pools. In this study, global simulations (spatial resolution 0.5-deg, time-step 1-month) were conducted during the period 1901 to 2100 on the basis of observed and projected atmospheric CO2, climate, and land-use conditions. As anthropogenic CO2 accumulates in the atmosphere, heavier stable carbon isotope (13C) was diluted, while radioactive carbon isotope (14C) is strongly affected by atomic bomb experiments mainly in the 1950s and 1960s. The model simulated the decadal change in carbon isotope compositions. Leaf carbon with shorter mean residence time responded rapidly to the atmospheric change, while plant stems and soil humus showed substantial time-lag, leading to large isotopic disequilibrium. In the future, the isotopic disequilibrium was estimated to augment, due to accelerated rate of anthropogenic CO2 accumulation. Spatial distribution of stable isotope composition (12C/13C, or d13C) was

  7. Soil carbon sensitivity to temperature and carbon use efficiency compared across microbial-ecosystem models of varying complexity

    SciTech Connect

    Li, Jianwei; Wang, Gangsheng; Allison, Steven D.; Mayes, Melanie; Luo, Yiqi

    2014-01-01

    Global ecosystem models may require microbial components to accurately predict feedbacks between climate warming and soil decomposition, but it is unclear what parameters and levels of complexity are ideal for scaling up to the globe. Here we conducted a model comparison using a conventional model with first-order decay and three microbial models of increasing complexity that simulate short- to long-term soil carbon dynamics. We focused on soil carbon responses to microbial carbon use efficiency (CUE) and temperature. Three scenarios were implemented in all models: constant CUE (held at 0.31), varied CUE ( 0.016 C 1), and 50 % acclimated CUE ( 0.008 C 1). Whereas the conventional model always showed soil carbon losses with increasing temperature, the microbial models each predicted a temperature threshold above which warming led to soil carbon gain. The location of this threshold depended on CUE scenario, with higher temperature thresholds under the acclimated and constant scenarios. This result suggests that the temperature sensitivity of CUE and the structure of the soil carbon model together regulate the long-term soil carbon response to warming. Equilibrium soil carbon stocks predicted by the microbial models were much less sensitive to changing inputs compared to the conventional model. Although many soil carbon dynamics were similar across microbial models, the most complex model showed less pronounced oscillations. Thus, adding model complexity (i.e. including enzyme pools) could improve the mechanistic representation of soil carbon dynamics during the transient phase in certain ecosystems. This study suggests that model structure and CUE parameterization should be carefully evaluated when scaling up microbial models to ecosystems and the globe.

  8. Contrasting responses of shrubland carbon gain and soil carbon efflux to drought and warming across a European climate gradient

    NASA Astrophysics Data System (ADS)

    Reinsch, Sabine; Koller, Eva; Sowerby, Alwyn; de Dato, Giovanbattista; Estiarte, Marc; Guidolotti, Gabriele; Kovács-Láng, Edit; Kröel-Dulay, György; Lellei-Kovács, Eszter; Larsen, Klaus S.; Liberati, Dario; Penuelas, Josep; Ransijn, Johannes; Schmidt, Inger K.; Smith, Andrew R.; Tietema, Albert; Dukes, Jeffrey S.; Emmett, Bridget A.

    2016-04-01

    Understanding the relationship between above- and belowground processes is crucial if we are to forecast feedbacks between terrestrial carbon (C) dynamics and future climate. To test if climate-induced changes in annual aboveground net primary productivity (aNPP) will drive changes in C loss by soil respiration (Rs), we integrated data across a European temperature and precipitation gradient. For over a decade, six European shrublands were exposed to repeated drought (-30 % annual rain) during the plants' growth season or year-round night-time warming (+1.5 oC), using an identical experimental approach. As a result, drought reduced ecosystem C gain via aNPP by 0-25 % (compared to an untreated control) with the lowest C gain in warm-dry sites and highest in wet-cold sites (R2=0.078, p-value = 0.544, slope = 14.35 %). In contrast, drought induced C loss via Rs was of a lower magnitude (10-20 %) and was most pronounced in warm-dry sites compared to wet-cold sites (R2=0.687, p-value = 0.131, slope = 7.86 %). This suggests that belowground activity (microbes and roots) is stabilizing ecosystem processes and functions in terms of C storage. However, when the drought treatment permanently altered the soil structure at our hydric site, indicating we had exceeded the resilience of the system, the ecosystem C gain was no longer predictable from current (linear) relationships. Results from the warming treatment were generally of lower magnitude and of opposing direction compared to the drought treatment, indicating different mechanisms were driving ecosystem responses. Overall, our results suggest that aNPP is less sensitive than Rs to climate stresses and soil respiration C fluxes are not predictable from changes in plant productivity. Drought and warming effects on aNPP and Rs did not weaken over decadal timescales at larger, continental scales if no catastrophic threshold is passed. However, indirect effects of climate change on soil properties and/or microbial communities

  9. Energy gains predict the distribution of plains bison across populations and ecosystems.

    PubMed

    Babin, Jean-Sébastien; Fortin, Daniel; Wilmshurst, John F; Fortin, Marie-Eve

    2011-01-01

    Developing tools that help predict animal distribution in the face of environmental change is central to understanding ecosystem function, but it remains a significant ecological challenge. We tested whether a single foraging currency could explain bison (Bison bison) distribution in dissimilar environments: a largely forested environment in Prince Albert National Park (Saskatchewan, Canada) and a prairie environment in Grasslands National Park (Saskatchewan, Canada). We blended extensive behavioral observations, relocations of radio-collared bison, vegetation surveys, and laboratory analyses to spatially link bison distribution in the two parks and expected gains for different nutritional currencies. In Prince Albert National Park, bison were more closely associated with the distribution of plants that maximized their instantaneous energy intake rate (IDE) than their daily intake of digestible energy. This result reflected both bison's intensity of use of individual meadows and their selection of foraging sites within meadows. On this basis, we tested whether IDE could explain the spatial dynamics of bison reintroduced to Grasslands National Park. As predicted, bison distribution in this park best matched spatial patterns of plants offering rapid IDE rather than rapid sodium intake, phosphorus intake, or daily intake of digestible energy. Because the two study areas have very different plant communities, a phenomenological model of resource selection developed in one area could not be used to predict animal distribution in the other. We were able, however, to successfully infer the distribution of bison from their foraging objective. This consistency in foraging currency across ecosystems and populations provides a strong basis for forecasting animal distributions in novel and dynamic environments.

  10. Thermal Acclimation and Adaptation of Net Ecosystem Carbon Exchange (Invited)

    NASA Astrophysics Data System (ADS)

    Luo, Y.; Niu, S.; Fei, S.; Yuan, W.; Zhang, Z.; Schimel, D.; Fluxnet Pis, .

    2010-12-01

    Ecosystem responses to temperature change are collectively determined by its constituents, which are plants, animals, microbes, and their interactions. It has been long documented that all plant, animals, and microbial carbon metabolism (photosynthesis, respiration) can acclimate and respond to changing temperatures, influencing the response of ecosystem carbon fluxes to climate change. Climate change also can induce competition between species with different thermal responses leading to changes in community composition. While a great deal of research has been done on species-level responses to temperature, it is yet to examine thermal acclimation of adaptation of ecosystem carbon processes to temperature change. With the advent of eddy flux measurements, it is possible to directly characterize the ecosystem-scale temperature response of carbon storage. In this study, we quantified the temperature response functions of net ecosystem carbon exchange (NEE), from which the responses of apparent optimal temperatures across broad spatial and temporal scales were examined. While temperature responses are normally parameterized in terms of the physiological variables describing photosynthesis and respiration, we focus on the apparent optimal behavior of NEE. Because the measurement integrated over multiple individuals and species within the footprint of the measurement (100s to 1000s of ha), it is challenging to interpret this measurement in terms of classical physiological variables such as the Q10. Rather we focus on the realized behavior of the ecosystem and its sensitivity to temperature. These empirical response functions can then be used as a benchmark for model evaluation and testing. Our synthesis of 656 site-years of eddy covariance data over the world shows that temperature response curves of NEE are parabolic, with their optima temperature strongly correlated with site growing season temperature across the globe and with annual mean temperature over years at

  11. Scale criticality in estimating ecosystem carbon dynamics.

    PubMed

    Zhao, Shuqing; Liu, Shuguang

    2014-07-01

    Scaling is central to ecology and Earth system sciences. However, the importance of scale (i.e. resolution and extent) for understanding carbon dynamics across scales is poorly understood and quantified. We simulated carbon dynamics under a wide range of combinations of resolution (nine spatial resolutions of 250 m, 500 m, 1 km, 2 km, 5 km, 10 km, 20 km, 50 km, and 100 km) and extent (57 geospatial extents ranging from 108 to 1 247 034 km(2) ) in the southeastern United States to explore the existence of scale dependence of the simulated regional carbon balance. Results clearly show the existence of a critical threshold resolution for estimating carbon sequestration within a given extent and an error limit. Furthermore, an invariant power law scaling relationship was found between the critical resolution and the spatial extent as the critical resolution is proportional to A(n) (n is a constant, and A is the extent). Scale criticality and the power law relationship might be driven by the power law probability distributions of land surface and ecological quantities including disturbances at landscape to regional scales. The current overwhelming practices without considering scale criticality might have largely contributed to difficulties in balancing carbon budgets at regional and global scales. PMID:24323616

  12. The Alaska Land Carbon Assessment: Baseline and Projected Future Carbon Storage and Greenhouse-gas Fluxes in Ecosystems of Alaska

    NASA Astrophysics Data System (ADS)

    McGuire, A. D.; Genet, H.; He, Y.; Stackpoole, S. M.; D'Amore, D. V.; Rupp, S. T.; Wylie, B. K.; Zhou, X.; Zhu, Z.

    2015-12-01

    The Alaska Land Carbon Assessment was conducted to inform mitigation and adaptation policies and land management decisions at sub-regional, regional, and national scales. Ecosystem carbon balance of Alaska was estimated for two time periods, a historical period (1950-2009) and a projected period (2010-2099) by synthesizing results for upland, wetland, and inland aquatic ecosystems. The total area of Alaska considered in this assessment was 1,474,844 km2, which is composed of 84 percent uplands, 12 percent wetlands, and 4 percent inland waters. Between 1950 and 2009 the upland and wetland ecosystems of the state sequestered an average of 4.4 TgC/yr, which is almost 2 percent of net primary production (NPP) by upland and wetland ecosystems. However, this sequestration is spatially variable with the northern boreal sub-region losing C because of fire disturbance and other sub-regions gaining carbon. For inland aquatic ecosystems, there was a net combined carbon flux through various pathways of 41.2 TgC/yr, or about 17 percent of upland and wetland NPP. The greenhouse gas forcing potential of upland and wetland ecosystems of Alaska was approximately neutral during the historical period, but the state as a whole could be a source for greenhouse gas forcing to the climate system from methane emissions from lake ecosystems, which were not considered in the assessment. During the projected period (2010-2099), carbon sequestration of upland and wetland ecosystems of Alaska would increase substantially (18.2 to 34.4 TgC/yr) primarily because of an increase in NPP of 8 to 19 percent associated with responses to rising atmospheric CO2, increased nitrogen cycling, and longer growing seasons. Although C emissions to the atmosphere from wildfire increase substantially for all of the projected climates, the increases in NPP more than compensate for those losses. The analysis indicates that upland and wetland ecosystems would be sinks for greenhouse gases for all scenarios during

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

    NASA Technical Reports Server (NTRS)

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

    2014-01-01

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

  14. Soil carbon sequestration: Quantifying this ecosystem service

    EPA Science Inventory

    Soils have a crucial role in supplying many goods and services that society depends upon on a daily basis. These include food and fiber production, water cleansing and supply, nutrient cycling, waste isolation and degradation. Soils also provide a significant amount of carbon s...

  15. Technical Report: Investigation of Carbon Cycle Processes within a Managed Landscape: An Ecosystem Manipulation and Isotope Tracer Approach

    SciTech Connect

    Griffis, Timothy J; Baker, John M; Billmark, Kaycie

    2009-06-01

    The goal of this research is to provide a better scientific understanding of carbon cycle processes within an agricultural landscape characteristic of the Upper Midwest. This project recognizes the need to study processes at multiple spatial and temporal scales to reduce uncertainty in ecosystem and landscape-scale carbon budgets to provide a sound basis for shaping future policy related to carbon management. Specifically, this project has attempted to answer the following questions: 1. Would the use of cover crops result in a shift from carbon neutral to significant carbon gain in corn-soybean rotation ecosystems of the Upper Midwest? 2. Can stable carbon isotope analyses be used to partition ecosystem respiration into its autotrophic and heterotrophic components? 3. Can this partitioning be used to better understand the fate of crop residues to project changes in the soil carbon reservoir? 4. Are agricultural ecosystems of the Upper Midwest carbon neutral, sinks, or sources? Can the proposed measurement and modeling framework help address landscape-scale carbon budget uncertainties and help guide future carbon management policy?

  16. Plant growth-rate dependence of detrital carbon storage in ecosystems

    SciTech Connect

    Cebrian, J.; Duarte, C.M.

    1995-06-16

    Detrital carbon accumulation accounts for most of an ecosystem`s capacity to store organic carbon because the carbon contained as plant detritus exceeds that stored in living plants by about threefold. A comparative analysis of the mass and turnover of detrital carbon in ecosystems demonstrates that these properties are strongly related to the turnover rate of the dominant primary producers and are poorly related to ecosystem primary production. These results contribute to an understanding of the factors that control carbon storage in ecosystems and the role of carbon storage in the global carbon budget. 24 refs., 3 figs.

  17. Interactions of Carbon Gain and Nitrogen Addition in a Temperate Forest

    NASA Astrophysics Data System (ADS)

    Bazzaz, F. A.

    2001-12-01

    In plants, carbon and nitrogen are intimately related. The plant gains carbon using nitrogen because it is a major constituent of both the light reaction (chlorophyll) and dark reaction (Rubisco and PEP carboxylase). The plant also gains more nitrogen by using carbon to grow roots that can forage for nitrogen, especially the less mobile (NH4+). Rising CO2 and increased nitrogen deposition are important elements of global change, both of which may affect ecosystem structure and function. They may cause a particularly large shift in species composition in systems where contrasting groups of species co-occur, e.g. evergreen coniferous and deciduous broad-leaved tree species. We studied the impact of nitrogen deposition in a mixed forest in central Massachusetts (Harvard Forest). We found that the early-successional broad-leaved species, yellow birch (Betula alleghaniensis) and red maple (Acer rubrum), both showed large increases in biomass, while the late successional species sugar maple (Acer saccharum) and all the coniferous species, hemlock (Tsuga canadensis), red spruce (Picea rubens) and white pine (Pinus strobus), only showed slight increases. As a result, when these species wre grown together, there was a decrease in species diversity. There was a significant correlation between species growth rate and the growth enhancement following nitrogen addition. We used SORTIE, a spatially explicit forest model to speculate about the future of this community. In both hemlock and red oak stands, nitrogen deposition led to shift in forest composition towards further dominance of young forests by yellow birch. We conclude that seedling physiological and demographic responses to increased nitrogen availability will scale up to exaggerate successional dynamics in mixed temperate forests in the future

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  19. Carbon and nitrogen isotope studies in an arctic ecosystem

    SciTech Connect

    Schell, D.M.

    1989-01-01

    This proposal requests funding for the completion of our current ecological studies at the MS-117 research site at Toolik Lake, Alaska. We have been using a mix of stable and radioisotope techniques to assess the fluxes of carbon and nitrogen within the ecosystem and the implications for long-term carbon storage or loss from the tundra. Several tentative conclusions have emerged from our study including: Tundra in the foothills is no longer accumulating carbon. Surficial radiocarbon abundances show little or no accumulation since 1000--2500 yrs BP. Coastal plain tundra is still accumulating carbon, but the rate of accumulation has dropped in the last few thousand years. Carbon export from watersheds in the Kuparuk and Imnavait Creek drainages are in excess of that expected from estimated primary productivity; and Nitrogen isotope abundances vary between species of plants and along hydrologic gradients.

  20. Carbon and nitrogen isotope studies in an arctic ecosystem

    SciTech Connect

    Schell, D.M.

    1989-12-31

    This proposal requests funding for the completion of our current ecological studies at the MS-117 research site at Toolik Lake, Alaska. We have been using a mix of stable and radioisotope techniques to assess the fluxes of carbon and nitrogen within the ecosystem and the implications for long-term carbon storage or loss from the tundra. Several tentative conclusions have emerged from our study including: Tundra in the foothills is no longer accumulating carbon. Surficial radiocarbon abundances show little or no accumulation since 1000--2500 yrs BP. Coastal plain tundra is still accumulating carbon, but the rate of accumulation has dropped in the last few thousand years. Carbon export from watersheds in the Kuparuk and Imnavait Creek drainages are in excess of that expected from estimated primary productivity; and Nitrogen isotope abundances vary between species of plants and along hydrologic gradients.

  1. Convergent Evolution towards High Net Carbon Gain Efficiency Contributes to the Shade Tolerance of Palms (Arecaceae).

    PubMed

    Ma, Ren-Yi; Zhang, Jiao-Lin; Cavaleri, Molly A; Sterck, Frank; Strijk, Joeri S; Cao, Kun-Fang

    2015-01-01

    Most palm species occur in the shaded lower strata of tropical rain forests, but how their traits relate to shade adaptation is poorly understood. We hypothesized that palms are adapted to the shade of their native habitats by convergent evolution towards high net carbon gain efficiency (CGEn), which is given by the maximum photosynthetic rate to dark respiration rate ratio. Leaf mass per area, maximum photosynthetic rate, dark respiration and N and P concentrations were measured in 80 palm species grown in a common garden, and combined with data of 30 palm species growing in their native habitats. Compared to other species from the global leaf economics data, dicotyledonous broad-leaved trees in tropical rainforest or other monocots in the global leaf economics data, palms possessed consistently higher CGEn, achieved by lowered dark respiration and fairly high foliar P concentration. Combined phylogenetic analyses of evolutionary signal and trait evolution revealed convergent evolution towards high CGEn in palms. We conclude that high CGEn is an evolutionary strategy that enables palms to better adapt to shady environments than coexisting dicot tree species, and may convey advantages in competing with them in the tropical forest understory. These findings provide important insights for understanding the evolution and ecology of palms, and for understanding plant shade adaptations of lower rainforest strata. Moreover, given the dominant role of palms in tropical forests, these findings are important for modelling carbon and nutrient cycling in tropical forest ecosystems.

  2. Convergent Evolution towards High Net Carbon Gain Efficiency Contributes to the Shade Tolerance of Palms (Arecaceae)

    PubMed Central

    Ma, Ren-Yi; Zhang, Jiao-Lin; Cavaleri, Molly A.; Sterck, Frank; Strijk, Joeri S.; Cao, Kun-Fang

    2015-01-01

    Most palm species occur in the shaded lower strata of tropical rain forests, but how their traits relate to shade adaptation is poorly understood. We hypothesized that palms are adapted to the shade of their native habitats by convergent evolution towards high net carbon gain efficiency (CGEn), which is given by the maximum photosynthetic rate to dark respiration rate ratio. Leaf mass per area, maximum photosynthetic rate, dark respiration and N and P concentrations were measured in 80 palm species grown in a common garden, and combined with data of 30 palm species growing in their native habitats. Compared to other species from the global leaf economics data, dicotyledonous broad-leaved trees in tropical rainforest or other monocots in the global leaf economics data, palms possessed consistently higher CGEn, achieved by lowered dark respiration and fairly high foliar P concentration. Combined phylogenetic analyses of evolutionary signal and trait evolution revealed convergent evolution towards high CGEn in palms. We conclude that high CGEn is an evolutionary strategy that enables palms to better adapt to shady environments than coexisting dicot tree species, and may convey advantages in competing with them in the tropical forest understory. These findings provide important insights for understanding the evolution and ecology of palms, and for understanding plant shade adaptations of lower rainforest strata. Moreover, given the dominant role of palms in tropical forests, these findings are important for modelling carbon and nutrient cycling in tropical forest ecosystems. PMID:26461108

  3. Convergent Evolution towards High Net Carbon Gain Efficiency Contributes to the Shade Tolerance of Palms (Arecaceae).

    PubMed

    Ma, Ren-Yi; Zhang, Jiao-Lin; Cavaleri, Molly A; Sterck, Frank; Strijk, Joeri S; Cao, Kun-Fang

    2015-01-01

    Most palm species occur in the shaded lower strata of tropical rain forests, but how their traits relate to shade adaptation is poorly understood. We hypothesized that palms are adapted to the shade of their native habitats by convergent evolution towards high net carbon gain efficiency (CGEn), which is given by the maximum photosynthetic rate to dark respiration rate ratio. Leaf mass per area, maximum photosynthetic rate, dark respiration and N and P concentrations were measured in 80 palm species grown in a common garden, and combined with data of 30 palm species growing in their native habitats. Compared to other species from the global leaf economics data, dicotyledonous broad-leaved trees in tropical rainforest or other monocots in the global leaf economics data, palms possessed consistently higher CGEn, achieved by lowered dark respiration and fairly high foliar P concentration. Combined phylogenetic analyses of evolutionary signal and trait evolution revealed convergent evolution towards high CGEn in palms. We conclude that high CGEn is an evolutionary strategy that enables palms to better adapt to shady environments than coexisting dicot tree species, and may convey advantages in competing with them in the tropical forest understory. These findings provide important insights for understanding the evolution and ecology of palms, and for understanding plant shade adaptations of lower rainforest strata. Moreover, given the dominant role of palms in tropical forests, these findings are important for modelling carbon and nutrient cycling in tropical forest ecosystems. PMID:26461108

  4. The microbial carbon pump: from genes to ecosystems.

    PubMed

    Jiao, Nianzhi; Zheng, Qiang

    2011-11-01

    The majority of marine dissolved organic carbon (DOC) is resistant to biological degradation and thus can remain in the water column for thousands of years, constituting carbon sequestration in the ocean. To date the origin of such recalcitrant DOC (RDOC) is unclear. A recently proposed conceptual framework, the microbial carbon pump (MCP), emphasizes the microbial transformation of organic carbon from labile to recalcitrant states. The MCP is concerned with both microbial uptakes and outputs of DOC compounds, covering a wide range from gene to ecosystem levels. In this minireview, the ATP binding cassette (ABC) transporter is used as an example for the microbial processing of DOC at the genetic level. The compositions of the ABC transporter genes of the two major marine bacterial clades Roseobacter and SAR11 demonstrate that they have distinct patterns in DOC utilization: Roseobacter strains have the advantage of taking up carbohydrate DOC, while SAR11 bacteria prefer nitrogen-containing DOC. At the ecosystem level, bacterially derived RDOC based on d-amino acid biomarkers is reported to be responsible for about a quarter of the total marine RDOC pool. Under future global warming scenarios, partitioning of primary production into DOC could be enhanced, and thus the MCP could play an even more important role in carbon sequestration by the ocean. Joint efforts to study the MCP from multiple disciplines are required to obtain a better understanding of ocean carbon cycle and its coupling with global change.

  5. Assessing Effects of Rising Carbon Dioxide Levels on Ocean Ecosystems

    NASA Astrophysics Data System (ADS)

    Lance, Veronica P.

    2009-07-01

    Carbon Productivity Responses to Increased Dissolved Inorganic Carbon Concentrations in Surface Ocean: Exploring the Feasibility of an in Situ Mesoscale Carbon Addition Experiment; Palisades, New York, 23-24 March 2009; To assess the effects of future elevated carbon dioxide (CO2) levels on ocean biogeochemistry and ecosystems, it is desirable to mimic such an environment in nature. A workshop to explore an in situ open ocean mesoscale CO2 perturbation experiment that would simulate the oceanic conditions expected toward the end of this century was held at Lamont-Doherty Earth Observatory at Columbia University (LDEO). The objectives were to evaluate the current understanding of the potential effects on open ocean ecosystems and biogeochemical cycling resulting from carbon chemistry and pH changes in response to increased atmospheric partial pressure of carbon dioxide (pCO2) and to examine the scientific justification and logistical feasibility of an in situ open ocean mesoscale CO2/pH perturbation experiment. The 15 participants represented fields of modeling and physical, geochemical, and biological oceanography.

  6. Organic carbon flow in a swamp-stream ecosystem

    SciTech Connect

    Mulholland, P.J.

    1981-01-01

    An annual organic carbon budget is presented for an 8-km segment of Creeping Swamp, an undisturbed, third-order swamp-stream in the Coastal Plain of North Carolina, USA. Annual input of organic carbon (588 gC/m/sup 2/) was 96% allochthonous and was dominated by leaf litter inputs (36%) and fluvial, dissolved organic carbon (DOC) inputs (31%). Although the swamp-stream was primarily heterotrophic, autochthonous organic carbon input, primarily from filamentous algae, was important during February and March when primary production/ecosystem respiration (P/R) ratios of the flooded portions were near one. Annual output of organic carbon via fluvial processes (214 gC/m/sup 2/), 95% as DOC, was 36% of total annual inputs, indicating that the swamp-stream segment ecosystem was 64% efficient at retaining organic carbon. Organic carbon dynamics in the Creeping Swamp segment were compared to those reported for upland stream segments using indices of organic matter processing suggested by Fisher (1977) and a loading potential index suggested here. Creeping Swamp, while loading at a high rate, retains a much larger portion of its organic carbon inputs than two upland streams. Despite the high degree of retention and oxidation of organic inputs to Creeping Swamp, there is a net annual fluvial export of 21 gC/m/sup 2/, mostly in the dissolved form. Watersheds drained by swamp-streams in the southeastern United States are thought to have large organic carbon exports compared to upland forested drainages, because the stream network covers a much greater proportion of the total watershed area.

  7. Comparison of Current and Historical Rates of Ecosystem Carbon Accumulation in a Northern Alberta Peatland

    NASA Astrophysics Data System (ADS)

    Syed, K. H.; Flanagan, L. B.; Carlson, P. J.; Glenn, A. J.; Ponton, S.

    2005-12-01

    As part of Fluxnet-Canada, we have been investigating the environmental controls on net ecosystem carbon dioxide exchange using the eddy covariance technique in a moderately rich (treed) fen in northern Alberta, Canada. In addition, integrated CO2 fluxes were compared to carbon stock measurements and rates of peat accumulation. The total ecosystem carbon stock was 52,669 g C m-2 with the vast majority (52,129) accumulated in peat over a 2 meter depth. The basal age for the peat was 2210 ± 50 years before present. The above-ground carbon stock in the two tree species was 226 g C m-2. The oldest Picea mariana trees were aged at 135 years, and they showed a rapid increase in basal area increment starting about 65 years ago that peaked at rates of 2 cm2 yr-1 about 40 years ago. The Larix laricina trees became established approximately 45 years ago and currently have a basal area increment of 3 to 4 cm2 yr-1, much higher than the current rates (0.5 cm2 yr-1) observed for Picea mariana. The rates of peat accumulation were determined on 210Pb-dated cores. Over the last 70 years the peat gained an average of 113 ± 12 g C m-2 yr-1. This was similar to net ecosystem production measured by eddy covariance (95 and 210 g C m-2 yr-1) over the last two years. Variation in annual net ecosystem production was associated with shifts in weather and growing season length. Current and recent historical rates of carbon accumulation were quite consistent despite significant variation in tree species growth and successional changes in this peatland over the last 70 years.

  8. Carbon dioxide budget in a temperature grassland ecosystem

    NASA Technical Reports Server (NTRS)

    Kim, Joon; Verma, Shashi B.; Clement, Robert J.

    1992-01-01

    Eddy correlation measurements of CO2 flux made during May-October 1987 and June-August 1989 were employed, in conjunction with simulated data, to examine the net exchange of CO2 in a temperature grassland ecosystem. Simulated estimates of CO2 uptake were used when flux measurements were not available. These estimates were based on daily intercepted photosynthetically active radiation, air temperature, and extractable soil water. Soil CO2 flux and dark respiration of the aerial part of plants were estimated using the relationships developed by Norman et al. (1992) and Polley et al. (1992) at the study site. The results indicate that the CO2 exchange between this ecosystem and the atmosphere is highly variable. The net ecosystem CO2 exchange reached its peak value (12-18 g/sq m d) during the period when the leaf area index was maximum. Drought, a frequent occurrence in this region, can change this ecosystem from a sink to a source for atmospheric CO2. Comparison with data on dry matter indicated that the aboveground biomass accounted for about 45-70 percent of the net carbon uptake, suggesting the importance of the below ground biomass in estimating net primary productivity in this ecosystem.

  9. A decision framework for identifying models to estimate forest ecosystem services gains from restoration

    USGS Publications Warehouse

    Christin, Zachary; Bagstad, Kenneth J.; Verdone, Michael

    2016-01-01

    Restoring degraded forests and agricultural lands has become a global conservation priority. A growing number of tools can quantify ecosystem service tradeoffs associated with forest restoration. This evolving “tools landscape” presents a dilemma: more tools are available, but selecting appropriate tools has become more challenging. We present a Restoration Ecosystem Service Tool Selector (RESTS) framework that describes key characteristics of 13 ecosystem service assessment tools. Analysts enter information about their decision context, services to be analyzed, and desired outputs. Tools are filtered and presented based on five evaluative criteria: scalability, cost, time requirements, handling of uncertainty, and applicability to benefit-cost analysis. RESTS uses a spreadsheet interface but a web-based interface is planned. Given the rapid evolution of ecosystem services science, RESTS provides an adaptable framework to guide forest restoration decision makers toward tools that can help quantify ecosystem services in support of restoration.

  10. Experiences gained from implementing mandatory buffer strips in Denmark: how can we enhance their ecosystem services?

    NASA Astrophysics Data System (ADS)

    Kronvang, Brian; Hoffmann, Carl Christian; Baattrup-Pedersen, Annette; Hille, Sandra; Rubæk, Gitte; Heckrath, Goswin; Gertz, Flemming; Jensen, Henning; Feuerback, Peter; Strand, John; Stutter, Marc

    2015-04-01

    along watercourses from ca. 50,000 ha to ca. 25,000 ha and at the same time they reduced the width of the mandatory BSs from 10 m to 9 m. The aim of this presentation is to share the experience gained in Denmark on establishing mandatory BSs. Furthermore, we will show some preliminary results from two newly initiated research projects (BUFFERTECH and BALTICSEA2020) that studies how to enhance the ecosystem services provided by buffer strips. We will show how intelligently to guide managers when establishing BSs along watercourses at catchment scale utilizing a combined P-index model for soil erosion and a statistical model for P retention in BSs as well as results obtained from new 'Engineered' or 'Constructed' BSs that delays tile drainage flow from field to streams thereby increasing nutrient retention. Acknowledgement The work is supported by the Strategic Research Foundation/Innovation Fund Denmark project 'BUFFERTECH - Optimization of Ecosystem Services Provided by Buffer Strips Using Novel Technological Methods' (Grant No. 1305-00017B) and the BalticSea2020 project 'Integrerade skyddszoner (IBZ)'.

  11. Changes in the Carbon Cycle of Amazon Ecosystems During the 2010 Drought

    NASA Technical Reports Server (NTRS)

    Potter, Christophera; Klooster, Steven; Hiatt, Cyrus; Genovese, Vanessa; Castilla-Rubino, Juan Carlos

    2011-01-01

    Satellite remote sensing was combined with the NASA-CASA carbon cycle simulation model to evaluate the impact of the 2010 drought (July through September) throughout tropical South America. Results indicated that net primary production (NPP) in Amazon forest areas declined by an average of 7% in 2010 compared to 2008. This represented a loss of vegetation CO2 uptake and potential Amazon rainforest growth of nearly 0.5 Pg C in 2010. The largest overall decline in ecosystem carbon gains by land cover type was predicted for closed broadleaf forest areas of the Amazon River basin, including a large fraction of regularly flooded forest areas. Model results support the hypothesis that soil and dead wood carbon decomposition fluxes of CO2 to the atmosphere were elevated during the drought period of 2010 in periodically flooded forest areas, compared to forests outside the main river floodplains.

  12. Global distribution of carbon turnover times in terrestrial ecosystems

    NASA Astrophysics Data System (ADS)

    Carvalhais, Nuno; Forkel, Matthias; Khomik, Myroslava; Bellarby, Jessica; Jung, Martin; Migliavacca, Mirco; Mu, Mingquan; Saatchi, Sassan; Santoro, Maurizio; Thurner, Martin; Weber, Ulrich; Ahrens, Bernhard; Beer, Christian; Cescatti, Alessandro; Randerson, James T.; Reichstein, Markus

    2015-04-01

    The response of the carbon cycle in terrestrial ecosystems to climate variability remains one of the largest uncertainties affecting future projections of climate change. This feedback between the terrestrial carbon cycle and climate is partly determined by the response of carbon uptake and by changes in the residence time of carbon in land ecosystems, which depend on climate, soil, and vegetation type. Thus, it is of foremost importance to quantify the turnover times of carbon in terrestrial ecosystems and its spatial co-variability with climate. Here, we develop a global, spatially explicit and observation-based assessment of whole-ecosystem carbon turnover times (τ) to investigate its co-variation with climate at global scale. Assuming a balance between uptake (gross primary production, GPP) and emission fluxes, τ can be defined as the ratio between the total stock (C_total) and the output or input fluxes (GPP). The estimation of vegetation (C_veg) stocks relies on new remote sensing-based estimates from Saatchi et al (2011) and Thurner et al (2014), while soil carbon stocks (C_soil) are estimated based on state of the art global (Harmonized World Soil Database) and regional (Northern Circumpolar Soil Carbon Database) datasets. The uptake flux estimates are based on global observation-based fields of GPP (Jung et al., 2011). Globally, we find an overall mean global carbon turnover time of 23-4+7 years (95% confidence interval). A strong spatial variability globally is also observed, from shorter residence times in equatorial regions to longer periods at latitudes north of 75°N (mean τ of 15 and 255 years, respectively). The observed latitudinal pattern reflect the clear dependencies on temperature, showing increases from the equator to the poles, which is consistent with our current understanding of temperature controls on ecosystem dynamics. However, long turnover times are also observed in semi-arid and forest-herbaceous transition regions. Furthermore

  13. Ecosystem and Societal Consequences of Ocean versus Atmosphere Carbon Storage

    NASA Astrophysics Data System (ADS)

    Barry, J. P.; Adams, E. E.; Bleck, R.; Caldeira, K.; Carman, K.; Erickson, D.; Kennett, J. P.; Sarmiento, J. L.; Tsouris, C.

    2005-12-01

    Climate stabilization during the next 100 to 200 y will require significant reductions in atmospheric carbon dioxide emissions to avoid large increases in global temperature. While there is only mild disagreement concerning carbon management options such as energy efficiency, alternative energy sources, and even geologic C storage, ocean storage remains controversial, due to its potential impacts for deep-sea ecosystems. A cautionary approach to carbon management might avoid any ocean C storage. However, this approach does not consider the balance between ocean and terrestrial ecosystems, or societal concerns. Using a broader perspective, we might ask whether atmospheric CO2 storage (i.e. the status quo), or deep ocean sequestration is better for Earth's ecosystems and societies? We explored the potential storage capacity of the deep ocean for carbon dioxide, under scenarios producing a 0.2 pH unit reduction, a level similar to observed scale of pH variability in deep ocean basins, which may also represent coarse thresholds for deep-sea ecosystem impacts. Roughly 500 PgC could be stored in the deep ocean to lower pH by 0.2 units, yielding a long term (~250 y) ocean sequestration program of 2 PgCy-1. The mitigation value of such ocean C sequestration for upper ocean and terrestrial systems depends strongly on future emission scenarios. Under a low emission scenario (e.g. SRES scenario A1T, B1; atm CO2 ~575 ppm, global temperature change of ~+2 oC), a 2 PgCy-1 ocean CO2 injection program could mitigate global temperature by ~-0.4 oC (20%) by 2100. This could reduce significantly the number of people at risk of water shortage and tropical diseases, with lesser improvement expected for hunger or coastal flooding. Mitigation for terrestrial and shallow ocean ecosystems is difficult to predict. A 0.4 oC reduction in warming this century is expected to delay the progression of coral reef devastation by roughly 20 y. The mitigation potential of ocean storage under very

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

    PubMed

    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.

  15. Carbon and nitrogen isotope studies in an arctic aquatic ecosystem

    SciTech Connect

    Schell, D.M.

    1989-01-01

    The Phase II studies of the R4D Program on stream and watershed ecology reflect the accomplishments and accumulation of baseline information obtained during the past studies. Although our rough estimates indicate that nitrogen inputs to the watershed ba lance losses, the carbon fluxes suggest that they are not in equilibrium and that there is a net loss of carbon from the tundra ecosystem through respiration and transport out of the watershed via the stream system. Radiocarbon profiles of soil sections coupled with mass transport calculations revealed that peat accumulation has essentially ceased in the R4D watershed and appears to be in ablative loss. Thus the carbon flux measurements provide validation tests for the PLANTGRO and GAS-HYDRO models of the PHASE II studies. These findings are also important in the context of global CO[sub 2] increases from positive feedback mechanisms in peatlands associated with climatic warming in the subarctic regions.

  16. Carbon and nitrogen isotope studies in an arctic aquatic ecosystem

    SciTech Connect

    Schell, D.M.

    1989-12-31

    The Phase II studies of the R4D Program on stream and watershed ecology reflect the accomplishments and accumulation of baseline information obtained during the past studies. Although our rough estimates indicate that nitrogen inputs to the watershed ba lance losses, the carbon fluxes suggest that they are not in equilibrium and that there is a net loss of carbon from the tundra ecosystem through respiration and transport out of the watershed via the stream system. Radiocarbon profiles of soil sections coupled with mass transport calculations revealed that peat accumulation has essentially ceased in the R4D watershed and appears to be in ablative loss. Thus the carbon flux measurements provide validation tests for the PLANTGRO and GAS-HYDRO models of the PHASE II studies. These findings are also important in the context of global CO{sub 2} increases from positive feedback mechanisms in peatlands associated with climatic warming in the subarctic regions.

  17. Whole-ecosystem exposure to elevated carbon dioxide increases total ecosystem carbon and nitrogen in the Mojave Desert

    NASA Astrophysics Data System (ADS)

    Evans, R. D.; Koyama, A.; Sonderegger, D.; Charlet, D.; Newingham, B. A.; Fenstermaker, L.; Ogle, K.; Smith, S. D.; Nowak, R.

    2011-12-01

    Arid ecosystems are predicted to be among the most responsive to global change and their response is globally significant considering their extensive spatial coverage. Although carbon cycling in arid lands is an important component of the global carbon budget, there is substantial uncertainty about the potential impacts of global change drivers, such as elevated CO2, on arid land carbon budgets. Studies suggest that productivity may be stimulated by elevated CO2 directly due to enhanced plant water-use efficiency. The indirect impacts of elevated CO2 on ecosystem productivity may also be constrained by available nitrogen, but little is known about how the importance of the nitrogen constraint or how the nitrogen cycle may be affected by global change drivers. Here we present the carbon and nitrogen mass budgets of a Mojave Desert ecosystem after ten years of exposure to elevated CO2. The Nevada Desert Free-Air Carbon Enrichment Facility (FACE) was established in 1997 to evaluate the response of an intact Mojave Desert ecosystem to elevated CO2. The CO2 concentration of the atmosphere in the elevated treatment was maintained at 513 uL/L until harvest in 2007. At harvest time, all aboveground biomass for 2/3 of each plot was harvested and soils and roots were removed down to 1 m depth and analyzed for total carbon and nitrogen. We observed significantly greater carbon (10,800 versus 9,200 kg C/ha, P=0.004) and nitrogen (1,400 versus 1,100 kg N/ha, P=0.002) in elevated compared to ambient CO2 treatments. Differences between treatments were due solely to greater C and N in soils across all cover types, and no differences were observed in above and belowground plant biomass. Companion research shows that increased soil C was from increased root exudation, microbial residues, and episodic increased litter input under elevated CO2, and these increased C inputs in turn stimulated production of inorganic nitrogen. Results from the Nevada Desert FACE Facility demonstrate

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    More accurate projections of future carbon dioxide concentrations in the atmosphere and associated climate change as well as carbon accounting and climate policy-making depend on improved scientific understanding of the terrestrial carbon cycle. Despite the consensus that U.S. terrestrial ecosystems...

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

    PubMed Central

    2011-01-01

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

  20. [Changes of carbon storage and carbon sequestration in plantation ecosystems on purple soil].

    PubMed

    Yu, Zhanyuan; Yang, Yusheng; Chen, Guangshui

    2004-10-01

    This paper studied the carbon storages and carbon sequestration capacities of degraded plantation ecosystems in purple soil area. Using space-time replacement method, four ecological restoration treatments (I, II, III and IV) were selected on the basis of erosion intensions from high to low in Ninghua, Fujian. Treatment I was not treated with any other measures after afforestation. Treatment II adopted engineering soil and water conservation measure after afforestation. In treatment III, the engineering measure associated biological measure was taken after afforestation. As for treatment IV, enclosure was adopted to protect against anthropogenic disturbances after afforestation. We observed that the carbon sequestration potential was increased with weakening erosion degree, i.e., I < II < III < IV. The carbon storage of 4 treatments was 1.4, 8.5, 25.6 and 37.6 t x hm(-2), and the annual assimilation of CO2 was 712.87, 1458.01, 9718.10 and 11,109.56 kg x hm(-2), respectively. It was suggested that the restored forest ecosystem was one of the important carbon sinks in this area. Engineering soil and water conservation measure associated biological measure would be the main means of restoring degraded ecosystem. But presently, the reasonable strategy was to decrease human's disturbances, and hence, the enclosure for reforestation could be used to transform forest ecosystem into carbon sink.

  1. Biotic Processes Regulating the Carbon Balance of Desert Ecosystems

    SciTech Connect

    R. S. Nowak; J. Arnone; L. Fenstermaker; and S. D. Smith

    2005-07-26

    This project provided the funding to operate and maintain the Nevada Desert FACE Facility. This support funds the CO{sub 2}, system repairs and maintenance, basic physical and biological site information, and personnel that are essential for the experiment to continue. They have continued to assess the effects of elevated CO{sub 2} on three key processes: (1) leaf- to plant-level responses of desert vegetation to elevated atmospheric CO{sub 2}; (2) ecosystem-level responses; and (3) integration of plant and ecosystem processes to understand carbon balance of deserts. The focus is the seminal interactions among atmospheric CO{sub 2}, water, and nitrogen that drive desert responses to elevated CO{sub 2} and explicitly address processes that occur across scales (biological, spatial, and temporal).

  2. Long-term increase in forest water-use efficiency observed across ecosystem carbon flux networks

    NASA Astrophysics Data System (ADS)

    Keenan, Trevor; Bohrer, Gil; Dragoni, Danilo; Hollinger, David; Munger, James W.; Schmid, Hans Peter; Richardson, Andrew

    2014-05-01

    Terrestrial plants remove CO2 from the atmosphere through photo- synthesis, a process that is accompanied by the loss of water vapour from leaves. The ratio of water loss to carbon gain, or water-use efficiency, is a key characteristic of ecosystem function that is central to the global cycles of water, energy and carbon. Here we analyse direct, long-term measurements of whole-ecosystem carbon and water exchange. We find a substantial increase in water-use efficiency in temperate and boreal forests of the Northern Hemisphere over the past two decades. We systematically assess various competing hypotheses to explain this trend, and find that the observed increase is most consistent with a strong CO2 fertilization effect. The results suggest a partial closure of stomata - small pores on the leaf surface that regulate gas exchange - to maintain a near- constant concentration of CO2 inside the leaf even under continually increasing atmospheric CO2 levels. The observed increase in forest water-use efficiency is larger than that predicted by existing theory and 13 terrestrial biosphere models. The increase is associated with trends of increasing ecosystem-level photosynthesis and net carbon uptake, and decreasing evapotranspiration. Our findings demonstrate the utility of maintaining long-term eddy-covariance flux measurement sites. The results suggest a shift in the carbon- and water-based economics of terrestrial vegetation, which may require a reassessment of the role of stomatal control in regulating interactions between forests and climate change, and a re-evaluation of coupled vegetation-climate models.

  3. Quantifying the role of fire in the Earth system - Part 2: Impact on the net carbon balance of global terrestrial ecosystems for the 20th century

    SciTech Connect

    Li, Fang; Bond-Lamberty, Benjamin; Levis, Samuel

    2014-03-07

    Fire is the primary terrestrial ecosystem disturbance agent on a global scale. It affects carbon balance of global terrestrial ecosystems by emitting carbon to atmosphere directly and immediately from biomass burning (i.e., fire direct effect), and by changing net ecosystem productivity and land-use carbon loss in post-fire regions due to biomass burning and fire-induced vegetation mortality (i.e., fire indirect effect). Here, we provide the first quantitative assessment about the impact of fire on the net carbon balance of global terrestrial ecosystems for the 20th century, and investigate the roles of fire direct and indirect effects. This study is done by quantifying the difference between the 20th century fire-on and fire-off simulations with NCAR community land model CLM4.5 as the model platform. Results show that fire decreases net carbon gain of the global terrestrial ecosystems by 1.0 Pg C yr-1 average across the 20th century, as a results of fire direct effect (1.9 Pg C yr-1) partly offset by indirect effect (-0.9 Pg C yr-1). Fire generally decreases the average carbon gains of terrestrial ecosystems in post-fire regions, which are significant over tropical savannas and part of forests in North America and the east of Asia. The general decrease of carbon gains in post-fire regions is because fire direct and indirect effects have similar spatial patterns and the former (to decrease carbon gain) is generally stronger. Moreover, the effect of fire on net carbon balance significantly declines prior to ~1970 with trend of 8 Tg C yr-1 due to increasing fire indirect effect and increases afterward with trend of 18 Tg C yr-1 due to increasing fire direct effect.

  4. Antarctic sea ice losses drive gains in benthic carbon drawdown.

    PubMed

    Barnes, D K A

    2015-09-21

    Climate forcing of sea-ice losses from the Arctic and West Antarctic are blueing the poles. These losses are accelerating, reducing Earth's albedo and increasing heat absorption. Subarctic forest (area expansion and increased growth) and ice-shelf losses (resulting in new phytoplankton blooms which are eaten by benthos) are the only significant described negative feedbacks acting to counteract the effects of increasing CO2 on a warming planet, together accounting for uptake of ∼10(7) tonnes of carbon per year. Most sea-ice loss to date has occurred over polar continental shelves, which are richly, but patchily, colonised by benthic animals. Most polar benthos feeds on microscopic algae (phytoplankton), which has shown increased blooms coincident with sea-ice losses. Here, growth responses of Antarctic shelf benthos to sea-ice losses and phytoplankton increases were investigated. Analysis of two decades of benthic collections showed strong increases in annual production of shelf seabed carbon in West Antarctic bryozoans. These were calculated to have nearly doubled to >2x10(5) tonnes of carbon per year since the 1980s. Annual production of bryozoans is median within wider Antarctic benthos, so upscaling to include other benthos (combined study species typically constitute ∼3% benthic biomass) suggests an increased drawdown of ∼2.9x10(6) tonnes of carbon per year. This drawdown could become sequestration because polar continental shelves are typically deeper than most modern iceberg scouring, bacterial breakdown rates are slow, and benthos is easily buried. To date, most sea-ice losses have been Arctic, so, if hyperboreal benthos shows a similar increase in drawdown, polar continental shelves would represent Earth's largest negative feedback to climate change.

  5. Antarctic sea ice losses drive gains in benthic carbon drawdown.

    PubMed

    Barnes, D K A

    2015-09-21

    Climate forcing of sea-ice losses from the Arctic and West Antarctic are blueing the poles. These losses are accelerating, reducing Earth's albedo and increasing heat absorption. Subarctic forest (area expansion and increased growth) and ice-shelf losses (resulting in new phytoplankton blooms which are eaten by benthos) are the only significant described negative feedbacks acting to counteract the effects of increasing CO2 on a warming planet, together accounting for uptake of ∼10(7) tonnes of carbon per year. Most sea-ice loss to date has occurred over polar continental shelves, which are richly, but patchily, colonised by benthic animals. Most polar benthos feeds on microscopic algae (phytoplankton), which has shown increased blooms coincident with sea-ice losses. Here, growth responses of Antarctic shelf benthos to sea-ice losses and phytoplankton increases were investigated. Analysis of two decades of benthic collections showed strong increases in annual production of shelf seabed carbon in West Antarctic bryozoans. These were calculated to have nearly doubled to >2x10(5) tonnes of carbon per year since the 1980s. Annual production of bryozoans is median within wider Antarctic benthos, so upscaling to include other benthos (combined study species typically constitute ∼3% benthic biomass) suggests an increased drawdown of ∼2.9x10(6) tonnes of carbon per year. This drawdown could become sequestration because polar continental shelves are typically deeper than most modern iceberg scouring, bacterial breakdown rates are slow, and benthos is easily buried. To date, most sea-ice losses have been Arctic, so, if hyperboreal benthos shows a similar increase in drawdown, polar continental shelves would represent Earth's largest negative feedback to climate change. PMID:26394097

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  7. Airborne Measurement of Ecosystem Carbon Dynamics over Heterogeneous Landscapes

    NASA Astrophysics Data System (ADS)

    Wade, T. J.; Hill, T. C.; Clement, R.; Moncrieff, J.; Disney, M.; Nichol, C. J.; Williams, M. D.

    2009-12-01

    Terrestrial carbon sinks are currently believed to account for the removal and storage of approximately 25% of anthropogenic carbon emissions from the atmosphere. The processes involved are numerous and complex and many feedbacks are at play. The ability to study the dynamics of different ecosystems at scales meaningful to climatic forcing is essential for understanding the key processes involved and identifying crucial sensitivities and thresholds. Airborne platforms with the requisite instrumentation offer the opportunity to directly measure biological processes and atmospheric structures at scales that are not achievable by ground measurements alone. The current generation of small research aircraft such as the University of Edinburgh’s Diamond HK36TTC ECO Dimona present excellent platforms for measurement of both the atmosphere and terrestrial surface. In this study we present results from airborne CO2/H2O flux measuring campaigns in contrasting climatic systems to quantify spatial patterns in ecosystem photosynthesis. Several airborne campaigns were undertaken in Arctic Finland, as part of the Arctic Biosphere Atmosphere Coupling at Multiple Scales (ABACUS) project (2008), and mainland UK as part of the UK Population Biology Network (UKPopNet) 2009 project, to explore the variability in surface CO2 flux across spatial scales larger than captured using conventional ground based eddy covariance. We discuss the application of our aircraft platform as a tool to address the challenge of understanding carbon dynamics within landscapes of heterogeneous vegetation class, terrain and hydrology using complementary datasets acquired from airborne eddy covariance and remote sensing.

  8. Comparison of a mass balance and an ecosystem model approach when evaluating the carbon cycling in a lake ecosystem.

    PubMed

    Andersson, Eva; Sobek, Sebastian

    2006-12-01

    Carbon budgets are frequently used in order to understand the pathways of organic matter-in ecosystems, and they also have an important function in the risk assessment of harmful substances. We compared two approaches, mass balance calculations and an ecosystem budget, to describe carbon processing in a shallow, oligotrophic hardwater lake. Both approaches come to the same main conclusion, namely that the lake is a net autotrophic ecosystem, in spite of its high dissolved organic carbon and low total phosphorus concentrations. However, there were several differences between the carbon budgets, e.g. in the rate of sedimentation and the air-water flux of CO2. The largest uncertainty in the mass balance is the contribution of emergent macrophytes to the carbon cycling of the lake, while the ecosystem budget is very sensitive towards the choice of conversion factors and literature values. While the mass balance calculations produced more robust results, the ecosystem budget gave valuable insights into the pathways of organic matter transfer in the ecosystem. We recommend that when using an ecosystem budget for the risk assessment of harmful substances, mass balance calculations should be performed in parallel in order to increase the robustness of the conclusions.

  9. Ecosystem carbon balance and vulnerability of soil carbon in a drained lower coastal plain loblolly pine plantation

    NASA Astrophysics Data System (ADS)

    Noormets, A.; McNulty, S. G.; Gavazzi, M.; Domec, J.; Sun, G.; King, J. S.; Chen, J.

    2008-12-01

    Coastal plain ecosystems comprise only about 5% of total U.S. land area, but the soil carbon density in these ecosystems is about 10-fold higher than in upland ecosystems and they may therefore play a disproportionately large role in ecosystem-climate feedbacks. The role of these ecosystems in continental carbon exchange is largely unclear because they have been underrepresented in flux monitoring networks. We monitored ecosystem carbon fluxes and pools for three years in two lower coastal plain loblolly pine plantations (3 and 17 years of age). The contribution of soil to ecosystem respiration decreased from over 90% immediately following a harvest to about 50% by age 17. The replenishment of soil C through litterfall exceeded heterotrophic respiration (Rh) by 2-9% in two years, but was 30% lower than Rh in the third year, highlighting the vulnerability of soil carbon stocks to interannual climate variability.

  10. Terrestrial Carbon Sinks in the Brazilian Amazon and Cerrado Region Predicted from MODIS Satellite Data and Ecosystem Modeling

    NASA Technical Reports Server (NTRS)

    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.

  11. Terrestrial carbon sinks in the Brazilian Amazon and Cerrado region predicted from MODIS satellite data and ecosystem modeling

    NASA Astrophysics Data System (ADS)

    Potter, C.; Klooster, S.; Huete, A.; Genovese, V.; Bustamante, M.; Guimaraes Ferreira, L.; Cosme de Oliveira Junior, R.; 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 Rondônia and the northern portions of the state of Pará. These areas were not significantly impacted by the 2002-2003 El Niño 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 Maranhão 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.

  12. Terrestrial carbon sinks in the Brazilian Amazon and Cerrado region predicted from MODIS satellite data and ecosystem modeling

    NASA Astrophysics Data System (ADS)

    Potter, C.; Klooster, S.; Huete, A.; Genovese, V.; Bustamante, M.; Guimaraes Ferreira, L.; de Oliveira, R. C., Jr.; Zepp, R.

    2009-06-01

    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 Rondônia and the northern portions of the state of Pará. These areas were not significantly impacted by the 2002-2003 El Niño 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 Maranhão 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.

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

    SciTech Connect

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

    2011-01-01

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

  14. Modeling Root Exudation, Priming and Protection in Soil Carbon Responses to Elevated CO2 from Ecosystem to Global Scales

    NASA Astrophysics Data System (ADS)

    Sulman, B. N.; Phillips, R.; Shevliakova, E.; Oishi, A. C.; Pacala, S. W.

    2014-12-01

    The sensitivity of soil organic carbon (SOC) to changing environmental conditions represents a critical uncertainty in coupled carbon cycle-climate models. Much of this uncertainty arises from our limited understanding of the extent to which plants induce SOC losses (through accelerated decomposition or "priming") or promote SOC gains (via stabilization through physico-chemical protection). We developed a new SOC model, "Carbon, Organisms, Rhizosphere and Protection in the Soil Environment" (CORPSE), to examine the net effect of priming and protection in response to rising atmospheric CO2, and conducted simulations of rhizosphere priming effects at both ecosystem and global scales. At the ecosystem scale, the model successfully captured and explained disparate SOC responses at the Duke and Oak Ridge free-air CO2 enrichment (FACE) experiments. We show that stabilization of "new" carbon in protected SOC pools may equal or exceed microbial priming of "old" SOC in ecosystems with readily decomposable litter (e.g. Oak Ridge). In contrast, carbon losses owing to priming dominate the net SOC response in ecosystems with more resistant litters (e.g. Duke). For global simulations, the model was fully integrated into the Geophysical Fluid Dynamics Laboratory (GFDL) land model LM3. Globally, priming effects driven by enhanced root exudation and expansion of the rhizosphere reduced SOC storage in the majority of terrestrial areas, partially counterbalancing SOC gains from the enhanced ecosystem productivity driven by CO2 fertilization. Collectively, our results suggest that SOC stocks globally depend not only on temperature and moisture, but also on vegetation responses to environmental changes, and that protected C may provide an important constraint on priming effects.

  15. Assessing China's Forest Ecosystem Carbon Accumulation Using China's Forest Carbon Model (CFCM)

    NASA Astrophysics Data System (ADS)

    Huang, M.

    2015-12-01

    China's forests have a great potential in mitigating the rate of global climate change. Carbon sequestration capacity in China's forest ecosystems has been estimated using inventory and modeling methods in the past two decades. However, different methods result in varied magnitudes and large uncertainties exist especially in the soil carbon estimation. In this study, a model named China's forest carbon model (CFCM) has been developed based on over 7000 forest field plots data obtained during 2011-2014 to estimate China's forest ecosystem carbon sequestration capacity. The simulated forest biomass and soil carbon densities correspond well with field observations across China. Our calculation shown China's total forest biomass carbon sink decreased from 210 Tg C a-1 in 2002 to 175 Tg C a-1 in 2010, and total forest soil C sink fluctuated between -10-32Tg C a-1 during 2002-2010. Total forest soil C sink is closely correlated with interannual soil temperature change. Combine biomass and soil C sink, China's forest ecosystem C sink is in the range of 180-231 Tg C a-1, with the maximum value in 2005 and minimum in 2007 during 2001-2010.

  16. Competitive strategies in adult beech and spruce: space-related foliar carbon investment versus carbon gain.

    PubMed

    Reiter, I M; Häberle, K-H; Nunn, A J; Heerdt, C; Reitmayer, H; Grote, R; Matyssek, R

    2005-12-01

    In Central Europe, Fagus sylvatica and Picea abies represent contrasting extremes in foliage type, crown structure and length of growing season. In order to examine the competitive strategies of these two co-occurring species, we tested the following hypotheses: (1) the space occupied by the foliage of sun branches is characterized by greater foliar mass investment compared to shade branches, (2) the carbon (C) gain per unit of occupied space is greater in sun than in shade branches, and (3) annual C and water costs of the foliage for sustaining the occupied space are low, wherever C gain per unit of occupied space is low. These were investigated in a mature forest in Southern Germany. The examination was based on the annual assessment of space-related resource investments and gains of the foliage. The foliated space around branches was regarded as the relevant volume with respect to aboveground resource availability. Occupied crown space per standing foliage mass was higher in shade compared to sun branches of beech, whereas no difference existed in crown volume per foliage mass between sun and shade branches of spruce (hypothesis 1 accepted for beech but rejected for spruce). However, beech occupied more space per foliage mass than spruce. The C gain per occupied crown volume was greater in sun than in shade branches (hypothesis 2 accepted) but did not differ between species. The amount of occupied space per respiratory and transpiratory costs did not differ between species or between sun and shade branches. In beech and spruce, the proportion of foliage investment in the annual C balance of sun and shade branches remained rather stable, whereas respiratory costs distinctly increased in shade foliage. Hence, shade branches were costly structures to occupy space, achieving only low and even negative C balances (rejection of hypothesis 3), which conflicts with the claimed C autonomy of branches. Our findings suggest that competitiveness is determined by the

  17. [Carbon budget of ecosystem in Changbai Mountain Natural Reserve].

    PubMed

    Zhang, Na; Yu, Guirui; Zhao, Shidong; Yu, Zhenliang

    2003-01-01

    The study used EPPML, a biological geochemistry cycle model that was built, to simulate the carbon budget for ecosystems in Changbai Mountain Natural Reserve. The results indicated that the annual net primary productivity [NPP (carbon)] of the natural reserve was 1.332 x 10(6) t.a-1. The annual NPP of mixed broad-leaved and Korean pine forest and spruce-fir forest were maximal, 0.540 x 10(6) t.a-1 and 0.428 x 10(6) t.a-1 respectively. The area and productivity of the two stands were maximal in Changbai Mountain, therefore, the simulating productivity of the two stands most greatly affect carbon cycle and carbon budget of the natural reserve, and the veracity of the former decides the security of the latter. To sum up, not only did the simulations accord with routines in the relative comparisons between different vegetation belts and climate belts in the whole natural reserve, but also was exact in the absolute comparisons with very disperse data from field survey. Vegetations in the natural reserve had evident carbon sink functions, mainly exhibiting in the increasing of carbon, about 1.058 x 10(6) t.a-1. The annual carbon of mixed broad-leaved and Korean pine forest increased greatest (0.452 x 10(6) t.a-1), secondly spruce-fir forest (0.339 x 10(6) t.a-1). The two stands played crucial roles in the carbon sink for Changbai Mountain, others being Changbai larch forest, broad-leaved forest, meadow, shrub, alpine tundra, subalpine Betula ermanii forest and alpine grass. In 1995, the decomposing carbon of soil organic matter was 0.169 x 10(6) t.a-1 higher than the littering carbon in the natural reserve. There was accumulation of organic matter in the meadow soil and shrub soil. The decomposition and accumulation of soil organic matter was in the nearly balancing condition in the alpine tundra soil and alpine grass soil. The decomposition of organic matter was as one and a half time or double as litterfall in the arbor forest soil.

  18. Multiple independent constraints help resolve net ecosystem carbon exchange under nutrient limitation

    NASA Astrophysics Data System (ADS)

    Thornton, P. E.; Metcalfe, D.; Oren, R.; Ricciuto, D. M.

    2014-12-01

    The magnitude, spatial distribution, and variability of land net ecosystem exchange of carbon (NEE) are important determinants of the trajectory of atmospheric carbon dioxide concentration. Independent observational constraints provide important clues regarding NEE and its component fluxes, with information available at multiple spatial scales: from cells, to leaves, to entire organisms and collections of organisms, to complex landscapes and up to continental and global scales. Experimental manipulations, ecosystem observations, and process modeling all suggest that the components of NEE (photosynthetic gains, and respiration and other losses) are controlled in part by the availability of mineral nutrients, and that nutrient limitation is a common condition in many biomes. Experimental and observational constraints at different spatial scales provide a complex and sometimes puzzling picture of the nature and degree of influence of nutrient availability on carbon cycle processes. Photosynthetic rates assessed at the cellular and leaf scales are often higher than the observed accumulation of carbon in plant and soil pools would suggest. We infer that a down-regulation process intervenes between carbon uptake and plant growth under conditions of nutrient limitation, and several down-regulation mechanisms have been hypothesized and tested. A recent evaluation of two alternative hypotheses for down-regulation in the light of whole-plant level flux estimates indicates that some plants take up and store extra carbon, releasing it to the environment again on short time scales. The mechanism of release, either as additional autotrophic respiration or as exudation belowground is unclear, but has important consequences for long-term ecosystem state and response to climate change signals. Global-scale constraints from atmospheric concentration and isotopic composition data help to resolve this question, ultimately focusing attention on land use fluxes as the most uncertain

  19. Carbon Gain and Photosynthetic Response of Chrysanthemum to Photosynthetic Photon Flux Density Cycles 1

    PubMed Central

    Stoop, Johan M. H.; Willits, Dan H.; Peet, Mary M.; Nelson, Paul V.

    1991-01-01

    Most models of carbon gain as a function of photosynthetic irradiance assume an instantaneous response to increases and decreases in irradiance. High- and low-light-grown plants differ, however, in the time required to adjust to increases and decreases in irradiance. In this study the response to a series of increases and decreases in irradiance was observed in Chrysanthemum × morifolium Ramat. “Fiesta” and compared with calculated values assuming an instantaneous response. There were significant differences between high- and low-light-grown plants in their photosynthetic response to four sequential photosynthetic photon flux density (PPFD) cycles consisting of 5-minute exposures to 200 and 400 micromoles per square meter per second (μmol m−2s−1). The CO2 assimilation rate of high-light-grown plants at the cycle peak increased throughout the PPFD sequence, but the rate of increase was similar to the increase in CO2 assimilation rate observed under continuous high-light conditions. Low-light leaves showed more variability in their response to light cycles with no significant increase in CO2 assimilation rate at the cycle peak during sequential cycles. Carbon gain and deviations from actual values (percentage carbon gain over- or underestimation) based on assumptions of instantaneous response were compared under continuous and cyclic light conditions. The percentage carbon gain overestimation depended on the PPFD step size and growth light level of the leaf. When leaves were exposed to a large PPFD increase, the carbon gain was overestimated by 16 to 26%. The photosynthetic response to 100 μmol m−2 s−1 PPFD increases and decreases was rapid, and the small overestimation of the predicted carbon gain, observed during photosynthetic induction, was almost entirely negated by the carbon gain underestimation observed after a decrease. If the PPFD cycle was 200 or 400 μmol m−2 s−1, high- and low-light leaves showed a carbon gain overestimation of 25

  20. Volcanic carbon dioxide vents show ecosystem effects of ocean acidification.

    PubMed

    Hall-Spencer, Jason M; Rodolfo-Metalpa, Riccardo; Martin, Sophie; Ransome, Emma; Fine, Maoz; Turner, Suzanne M; Rowley, Sonia J; Tedesco, Dario; Buia, Maria-Cristina

    2008-07-01

    The atmospheric partial pressure of carbon dioxide (p(CO(2))) will almost certainly be double that of pre-industrial levels by 2100 and will be considerably higher than at any time during the past few million years. The oceans are a principal sink for anthropogenic CO(2) where it is estimated to have caused a 30% increase in the concentration of H(+) in ocean surface waters since the early 1900s and may lead to a drop in seawater pH of up to 0.5 units by 2100 (refs 2, 3). Our understanding of how increased ocean acidity may affect marine ecosystems is at present very limited as almost all studies have been in vitro, short-term, rapid perturbation experiments on isolated elements of the ecosystem. Here we show the effects of acidification on benthic ecosystems at shallow coastal sites where volcanic CO(2) vents lower the pH of the water column. Along gradients of normal pH (8.1-8.2) to lowered pH (mean 7.8-7.9, minimum 7.4-7.5), typical rocky shore communities with abundant calcareous organisms shifted to communities lacking scleractinian corals with significant reductions in sea urchin and coralline algal abundance. To our knowledge, this is the first ecosystem-scale validation of predictions that these important groups of organisms are susceptible to elevated amounts of p(CO(2)). Sea-grass production was highest in an area at mean pH 7.6 (1,827 (mu)atm p(CO(2))) where coralline algal biomass was significantly reduced and gastropod shells were dissolving due to periods of carbonate sub-saturation. The species populating the vent sites comprise a suite of organisms that are resilient to naturally high concentrations of p(CO(2)) and indicate that ocean acidification may benefit highly invasive non-native algal species. Our results provide the first in situ insights into how shallow water marine communities might change when susceptible organisms are removed owing to ocean acidification.

  1. Gaining insight into river ecosystem processes from a large-scale flow experiment

    NASA Astrophysics Data System (ADS)

    Harrison, L.; Pike, A.; Boughton, D. A.

    2015-12-01

    In rivers throughout the world, anthropogenic impacts related to large dams have altered or eliminated the habitat necessary for many aquatic organisms. Flow experiments, both planned and unplanned, provide unique opportunities to evaluate the extent to which alternative dam operations can provide downstream ecological benefits. Here we use an unanticipated, reservoir release on the Santa Ynez River in southern California to investigate how a large flood influenced river ecosystem processes. We directly measured the flood-induced, topographic changes over 80 km of the river and floodplain using two high-resolution field and remote sensing data sets that bracketed the flood event. DEM-differencing of the pre- and post-flood topography was used to calculate shifts in the active channel planform and the net volumetric fluxes in gravel storage along the channel and floodplain. LiDAR and image-based habitat mapping was conducted to quantify the proportion of different habitat units before and after the flood. Large-scale geomorphic changes were observed as a result of the flood, including lateral migration of the river channel, gravel bar formation and the development of off-channel chute habitat. Spatial patterns of gravel storage changed with distance from the dam, with the upper 20 km experiencing a net sediment deficit and the lower 60 km undergoing net deposition. The longitudinal trends in gravel transport and storage reflect differences in the channel gradient, valley confinement and density of floodplain vegetation. We found that the flood nearly doubled the extent of pool habitat, primarily by converting runs to pools and by incising new pools adjacent to valley walls and terraces. The increase in the number of pools was predicted to have positive impacts on steelhead habitat, by providing a broader range of water depths and micro-habitats utilized by different age classes. Results from this study highlight the value of using flow pulses as opportunities to

  2. Using carbon oxidation state and ecosystem oxidative ratio to understand terrestrial ecosystem response to elevated CO2

    NASA Astrophysics Data System (ADS)

    Hockaday, W. C.; Masiello, C. A.; Gallagher, M. E.

    2015-12-01

    Here we show that an easily-measured biogeochemical tracer, carbon oxidation state (Cox) can be used to understand ecosystem response to elevated atmospheric CO2 concentrations. We briefly review the use of Cox in understanding C sink estimates, and its role in understanding the coupled nature of carbon and oxygen cycles, which derives from its relationship with ecosystem oxidative ratio (OR). The Cox of a carbon pool provides an integrated measure of all processes that create and destroy organic matter (e.g. photosynthesis, respiration, fire) and therefore, can be used to estimate the oxidative ratio (O2/CO2) of biosphere-atmosphere exchange. Our preliminary data suggest that the OR of temperate hardwood forest and grassland ecosystems are influenced by atmospheric CO2 concentration. The variation in ecosystem Cox with atmospheric CO2 concentration suggest that OR is not a conservative property of terrestrial ecosystems on annual or decadal timescales. In the grassland ecosystem, the Cox of plant biomass increased by as much as 50% across a CO2 concentration gradient of 190 ppm, but the response was highly dependent upon soil properties. In the temperate forest, the Cox of the soil C pool increased by 40% after 9 seasons of CO2 enrichment (by 175 ppm). We will discuss our interpretation of Cox as a proxy and its potential use in studies of coupled O2 and CO2 cycling.

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

    PubMed

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

    2014-08-01

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

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

    PubMed

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

    2014-08-01

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

  5. Typhoons exert significant but differential impact on net carbon ecosystem exchange of subtropical mangrove ecosystems in China

    NASA Astrophysics Data System (ADS)

    Chen, H.; Lu, W.; Yan, G.; Yang, S.; Lin, G.

    2014-06-01

    Typhoons are very unpredictable natural disturbances to subtropical mangrove forests in Asian countries, but litter information is available on how these disturbances affect ecosystem level carbon dioxide (CO2) exchange of mangrove wetlands. In this study, we examined short-term effect of frequent strong typhoons on defoliation and net ecosystem CO2 exchange (NEE) of subtropical mangroves, and also synthesized 19 typhoons during a 4-year period between 2009 and 2012 to further investigate the regulation mechanisms of typhoons on ecosystem carbon and water fluxes following typhoon disturbances. Strong wind and intensive rainfall caused defoliation and local cooling effect during typhoon season. Daily total NEE values were decreased by 26-50% following some typhoons (e.g. W28-Nockten, W35-Molave and W35-Lio-Fan), but were significantly increased (43-131%) following typhoon W23-Babj and W38-Megi. The magnitudes and trends of daily NEE responses were highly variable following different typhoons, which were determined by the balance between the variances of gross ecosystem production (GEP) and ecosystem respiration (RE). Furthermore, results from our synthesis indicated that the landfall time of typhoon, wind speed and rainfall were the most important factors controlling the CO2 fluxes following typhoon events. These findings not only indicate that mangrove ecosystems have strong resilience to the frequent typhoon disturbances, but also demonstrate the damage of increasing typhoon intensity and frequency on subtropical mangrove ecosystems under future global climate change scenarios.

  6. Ecosystem carbon budgeting and soil carbon sequestration in reclaimed mine soil.

    PubMed

    Shrestha, Raj K; Lal, Rattan

    2006-08-01

    Global warming risks from emissions of green house gases (GHGs) by anthropogenic activities, and possible mitigation strategies of terrestrial carbon (C) sequestration have increased the need for the identification of ecosystems with high C sink capacity. Depleted soil organic C (SOC) pools of reclaimed mine soil (RMS) ecosystems can be restored through conversion to an appropriate land use and adoption of recommended management practices (RMPs). The objectives of this paper are to (1) synthesize available information on carbon dioxide (CO2) emissions from coal mining and combustion activities, (2) understand mechanisms of SOC sequestration and its protection, (3) identify factors affecting C sequestration potential in RMSs, (4) review available methods for the estimation of ecosystem C budget (ECB), and (5) identify knowledge gaps to enhance C sink capacity of RMS ecosystems and prioritize research issues. The drastic perturbations of soil by mining activities can accentuate CO2 emission through mineralization, erosion, leaching, changes in soil moisture and temperature regimes, and reduction in biomass returned to the soil. The reclamation of drastically disturbed soils leads to improvement in soil quality and development of soil pedogenic processes accruing the benefit of SOC sequestration and additional income from trading SOC credits. The SOC sequestration potential in RMS depends on amount of biomass production and return to soil, and mechanisms of C protection. The rate of SOC sequestration ranges from 0.1 to 3.1 Mg ha(-1) yr(-1) and 0.7 to 4 Mg ha(-1) yr(-1) in grass and forest RMS ecosystem, respectively. Proper land restoration alone could off-set 16 Tg CO2 in the U.S. annually. However, the factors affecting C sequestration and protection in RMS leading to increase in microbial activity, nutrient availability, soil aggregation, C build up, and soil profile development must be better understood in order to formulate guidelines for development of an

  7. Ecosystem carbon budgeting and soil carbon sequestration in reclaimed mine soil.

    PubMed

    Shrestha, Raj K; Lal, Rattan

    2006-08-01

    Global warming risks from emissions of green house gases (GHGs) by anthropogenic activities, and possible mitigation strategies of terrestrial carbon (C) sequestration have increased the need for the identification of ecosystems with high C sink capacity. Depleted soil organic C (SOC) pools of reclaimed mine soil (RMS) ecosystems can be restored through conversion to an appropriate land use and adoption of recommended management practices (RMPs). The objectives of this paper are to (1) synthesize available information on carbon dioxide (CO2) emissions from coal mining and combustion activities, (2) understand mechanisms of SOC sequestration and its protection, (3) identify factors affecting C sequestration potential in RMSs, (4) review available methods for the estimation of ecosystem C budget (ECB), and (5) identify knowledge gaps to enhance C sink capacity of RMS ecosystems and prioritize research issues. The drastic perturbations of soil by mining activities can accentuate CO2 emission through mineralization, erosion, leaching, changes in soil moisture and temperature regimes, and reduction in biomass returned to the soil. The reclamation of drastically disturbed soils leads to improvement in soil quality and development of soil pedogenic processes accruing the benefit of SOC sequestration and additional income from trading SOC credits. The SOC sequestration potential in RMS depends on amount of biomass production and return to soil, and mechanisms of C protection. The rate of SOC sequestration ranges from 0.1 to 3.1 Mg ha(-1) yr(-1) and 0.7 to 4 Mg ha(-1) yr(-1) in grass and forest RMS ecosystem, respectively. Proper land restoration alone could off-set 16 Tg CO2 in the U.S. annually. However, the factors affecting C sequestration and protection in RMS leading to increase in microbial activity, nutrient availability, soil aggregation, C build up, and soil profile development must be better understood in order to formulate guidelines for development of an

  8. Global change accelerates carbon assimilation by a wetland ecosystem engineer

    NASA Astrophysics Data System (ADS)

    Caplan, Joshua S.; Hager, Rachel N.; Megonigal, J. Patrick; Mozdzer, Thomas J.

    2015-11-01

    The primary productivity of coastal wetlands is changing dramatically in response to rising atmospheric carbon dioxide (CO2) concentrations, nitrogen (N) enrichment, and invasions by novel species, potentially altering their ecosystem services and resilience to sea level rise. In order to determine how these interacting global change factors will affect coastal wetland productivity, we quantified growing-season carbon assimilation (≈gross primary productivity, or GPP) and carbon retained in living plant biomass (≈net primary productivity, or NPP) of North American mid-Atlantic saltmarshes invaded by Phragmites australis (common reed) under four treatment conditions: two levels of CO2 (ambient and +300 ppm) crossed with two levels of N (0 and 25 g N added m-2 yr-1). For GPP, we combined descriptions of canopy structure and leaf-level photosynthesis in a simulation model, using empirical data from an open-top chamber field study. Under ambient CO2 and low N loading (i.e., the Control), we determined GPP to be 1.66 ± 0.05 kg C m-2 yr-1 at a typical Phragmites stand density. Individually, elevated CO2 and N enrichment increased GPP by 44 and 60%, respectively. Changes under N enrichment came largely from stimulation to carbon assimilation early and late in the growing season, while changes from CO2 came from stimulation during the early and mid-growing season. In combination, elevated CO2 and N enrichment increased GPP by 95% over the Control, yielding 3.24 ± 0.08 kg C m-2 yr-1. We used biomass data to calculate NPP, and determined that it represented 44%-60% of GPP, with global change conditions decreasing carbon retention compared to the Control. Our results indicate that Phragmites invasions in eutrophied saltmarshes are driven, in part, by extended phenology yielding 3.1× greater NPP than native marsh. Further, we can expect elevated CO2 to amplify Phragmites productivity throughout the growing season, with potential implications including accelerated spread

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

    PubMed

    Selmants, Paul C; Litton, Creighton M; Giardina, Christian P; Asner, Gregory P

    2014-09-01

    Theory and experiment agree that climate warming will increase carbon fluxes between terrestrial ecosystems and the atmosphere. The effect of this increased exchange on terrestrial carbon storage is less predictable, with important implications for potential feedbacks to the climate system. We quantified how increased mean annual temperature (MAT) affects ecosystem carbon storage in above- and belowground live biomass and detritus across a well-constrained 5.2 °C MAT gradient in tropical montane wet forests on the Island of Hawaii. This gradient does not systematically vary in biotic or abiotic factors other than MAT (i.e. dominant vegetation, substrate type and age, soil water balance, and disturbance history), allowing us to isolate the impact of MAT on ecosystem carbon storage. Live biomass carbon did not vary predictably as a function of MAT, while detrital carbon declined by ~14 Mg of carbon ha(-1) for each 1 °C rise in temperature - a trend driven entirely by coarse woody debris and litter. The largest detrital pool, soil organic carbon, was the most stable with MAT and averaged 48% of total ecosystem carbon across the MAT gradient. Total ecosystem carbon did not vary significantly with MAT, and the distribution of ecosystem carbon between live biomass and detritus remained relatively constant across the MAT gradient at ~44% and ~56%, respectively. These findings suggest that in the absence of alterations to precipitation or disturbance regimes, the size and distribution of carbon pools in tropical montane wet forests will be less sensitive to rising MAT than predicted by ecosystem models. This article also provides needed detail on how individual carbon pools and ecosystem-level carbon storage will respond to future warming.

  10. Cold ecosystems in a warmer climate: carbon fluxes at the alpine treeline under experimental soil warming

    NASA Astrophysics Data System (ADS)

    Wipf, Sonja; Hagedorn, Frank; Martin, Melissa

    2010-05-01

    The impact of climatic warming on the C balance of terrestrial ecosystems is uncertain because rising temperature increases both C gains through net primary production, but also respiratory C losses. 'Cold' ecosystems such as treeline ecotones will respond particularly sensitive to climatic changes because many processes are limited by temperature and soils store particular large amounts of labile soil organic matter. In our study, we investigate ecosystem responses to 9 years of elevated atmospheric CO2 and to 3 years of experimental soil warming by 4° C. The added CO2 contains another δ13C signature than normal air, which allows the tracing of new carbon through the plant and soil system. This provides new insight into carbon cycling at the treeline and it shows which C flux respond most sensitive to climatic changes. Results showed that soil warming increased soil CO2 effluxes instantaneously and persisted for at least three vegetation periods (+35-45%; +80 to 120 g C m y-1). In contrast, DOC leaching showed a negligible response of less than 5% increase. Annual C uptake of new shoots was not significantly affected by elevated soil temperatures, with a 10 to 20% increase for larch, pine, and dwarf shrubs, respectively, resulting in an overall increase in net C uptake by plants of 20 to 40 g C m-2y-1. The Q10 of 3.0 measured for soil respiration did not change compared to a three-year period before the warming treatment started, suggesting little impact of warming-induced lower soil moisture (-15% relative decrease) or a depletion in labile soil C. The fraction of recent plant-derived C in soil respired CO2 from warmed soils was smaller than that from control soils (25 vs. 40% of total C respired), which implies that the warming-induced increase in soil CO2 efflux resulted mainly from mineralization of older SOM rather than from stimulated root respiration. In summary, the 4 ° C soil warming led to C losses from the studied alpine treeline ecosystem by

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

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Xiao, J.

    2013-12-01

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

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

    PubMed

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

    2015-01-01

    We combine the process-based ecosystem model (Biome-BGC) with climate change-scenarios based on both RegCM3 model outputs and historic observed trends to quantify differential effects of symmetric and asymmetric warming on ecosystem net primary productivity (NPP), heterotrophic respiration (Rh) and net ecosystem productivity (NEP) of six ecosystem types representing different climatic zones of northern China. Analysis of covariance shows that NPP is significant greater at most ecosystems under the various environmental change scenarios once temperature asymmetries are taken into consideration. However, these differences do not lead to significant differences in NEP, which indicates that asymmetry in climate change does not result in significant alterations of the overall carbon balance in the dominating forest or grassland ecosystems. Overall, NPP, Rh and NEP are regulated by highly interrelated effects of increases in temperature and atmospheric CO2 concentrations and precipitation changes, while the magnitude of these effects strongly varies across the six sites. Further studies underpinned by suitable experiments are nonetheless required to further improve the performance of ecosystem models and confirm the validity of these model predictions. This is crucial for a sound understanding of the mechanisms controlling the variability in asymmetric warming effects on ecosystem structure and functioning. PMID:25766381

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

    PubMed

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

    2015-03-13

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  16. Microbial carbon cycling in Lost City hydrothermal chimneys and other serpentinite-hosted ecosystems (Invited)

    NASA Astrophysics Data System (ADS)

    Brazelton, W. J.; Lang, S. Q.; Morrill, P. L.; Twing, K. I.; Crespo-Medina, M.; Morgan-Smith, D.; Früh-Green, G. L.; Schrenk, M. O.

    2013-12-01

    Ultramafic rocks formed in the Earth's mantle and uplifted into the crust represent an immense but poorly described reservoir of carbon. The biological availability of this rock-hosted carbon reservoir is unknown, but the set of geochemical reactions known as serpentinization can mobilize carbon from the subsurface and trigger the growth of dense microbial communities. Serpentinite-hosted ecosystems such as the chimney biofilms of the Lost City hydrothermal field can support dense populations of bacteria and archaea fueled by the copious quantities of H2 and methane (CH4) released by serpentinization (1-5). The metabolic pathways involved, however, remain unknown, and conventional interpretations of genomic and experimental data are complicated by the unusual carbon speciation in these environments. Carbon dioxide is scarce due to the highly reducing, high pH conditions. Instead, the predominant forms of carbon are CH4 and formate (5). Despite its natural abundance, however, direct evidence for CH4-derived biomass is lacking (1,4,5), and the role of formate is potentially significant but largely unexplored (1,5). To gain a more generalized perspective of carbon cycling in serpentinite-hosted ecosystems, we have recently investigated fluids and rocks collected from serpentinizing ophiolites in California, Canada, and Italy. Our results point to potentially H2-utilizing, autotrophic Betaproteobacteria thriving in shallow, oxic-anoxic transition zones and anaerobic Clostridia inhabiting anoxic, subsurface zones (1,6). The carbon sources utilized by the Clostridia are unknown, but preliminary metagenomic evidence is consistent with a fermentation-style metabolic strategy that may be conducive to an oxidant-limited, subsurface environment. Curiously, despite the abundance of H2 and CH4 in these continental springs, none of the geochemical, genomic, or experimental results obtained thus far contain any evidence for biological methanogenesis (1,6). This is in stark

  17. Land Use Effects on Carbon Storage in Thailand Tropical Ecosystems

    NASA Astrophysics Data System (ADS)

    Kai, F.; Tostado, E.; Chidthaisong, A.; Tyler, S. C.

    2004-12-01

    Measurements of stable isotopes of C have proved to be of value in estimating soil organic C turnover times and in partitioning soil organic carbon (SOC) from different sources. Typically, the contrast between sources and estimates of C turnover have been studied in ecosystems where C-3 photosynthetic plants such as hardwoods have been replaced by C-4 photosynthetic plants from agriculture such as corn or sugarcane. Here we report concentrations and stable C isotope ratios of SOC from Thailand coastal mangrove forests and intrusive coastal aquaculture in the form of shrimp and wastewater treatment ponds. There are clear changes in both magnitude and 13C/12C of SOC at former mangrove sites which have been altered to make ponds for shrimp farming and wastewater treatment. For instance, total per cent C from 0-40 cm soil depth (average of four 10 cm layers at 2 sites) was 6.2±2.8% for mature mangrove, while it was only 0.5±0.4% for a 10-year old shrimp pond and 1.3±0.4% for an 8-year old water treatment pond. Previous studies of mangrove organic C balance have indicated that these inter-tidal forest ecosystems are a sink for C and that significant C is vested in both above- and below-ground biomass and stored in sediments. Mangrove forest disturbance by human activities clearly has the potential to affect C storage. Our data indicates that stable C isotope tracing will be of value in tracking changes in coastal forest-aquaecosystems just as it has been for forest-agroecosystems

  18. [A review on carbon and water interactions of forest ecosystem and its impact factors].

    PubMed

    Song, Chun-lin; Sun, Xiang-yang; Wang, Gen-xu

    2015-09-01

    Interaction between carbon and water in forest ecosystem is a coupling process in terrestrial ecosystem, which is an indispensable aspect for the study of forest carbon pool, ecohydrological processes and the responses to global change. In the context of global change, the interaction and coupling of carbon and water in forest ecosystem has attracted much attention among scientists. In this paper, we reviewed the process mechanism of forest carbon and water relationships based on previous studies, which consisted of advance in forest water use efficiency, carbon and water interactions at different scales, scaling, and model simulation. We summed up the factors affecting for- est water and carbon interaction, including water condition, carbon dioxide enrichment, warming, nitrogen deposition, ozone concentration variation, solar radiation, and altitudinal gradients. Finally, we discussed the problems in the previous studies, and prospected the possible future research fields, among which we thought the inherent dynamics mechanism and scaling of forest carbon and water interactions should be enhanced.

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

    USGS Publications Warehouse

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

    1997-01-01

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

  20. Assessing and Monitoring Spatial and Temporal Distributions of Ecosystem Carbon Storage and Changes in the United States

    NASA Astrophysics Data System (ADS)

    Zhu, Z.; Liu, S.; Sleeter, B. M.; Sohl, T. L.; Hawbaker, T. J.; Stackpoole, S. M.

    2011-12-01

    Land changes (land use and ecosystem disturbances) are the primary driver of stability and vulnerability of ecosystem carbon sequestration. Advances in remote sensing and modeling make it possible that carbon storage in relation to land changes can be assessed and monitored at the national and regional scales. Using remote sensing and modeling tools, the U.S. Geological Survey is conducting a national assessment to estimate spatial and temporal distributions of carbon storage in relation to land changes. The assessment covers all major ecosystems: forests, shrub and grasslands, croplands, wetlands, and aquatic systems. Recent land changes (baseline, 1992 to current) are mapped on an annual basis using Landsat imagery; future land changes (current to 2050) are modeled by incorporating IPCC socioeconomic storylines and climate change projections (three storylines and projections used: A1B, A2, and B1, each with multiple GCM runs). Carbon storage in, and transitions between, ecosystems are modeled and estimated annually using biogeochemical models, with the baseline and future potential land use changes and fire disturbances as the primary input. Effects of land changes and management activities are analyzed. A series of regional-scale maps and datasets are produced as deliverables of the assessment. The Great Plains region of the United States is the first region to complete for the assessment. The region encompasses 2.17 million square kilometers from eastern half of Montana south to Texas and east to Minnesota and Iowa. Changes in land use between 1992 and 2050 are pronounced for major ecosystems, including 7-16% gains in agriculture, 8-17% losses of grasslands and 18-19% losses of wetlands under A1B and A2 scenarios. More environmental oriented scenarios such as B1 will see gains in wetlands (15%) while holding areas of other ecosystems stable. For fire disturbances, number, size, and severity of large wildland fires in the region are highly variable, depending on

  1. Ecosystem Carbon Dynamics in Response to Five Winters of Experimental Soil Warming and Permafrost Degradation

    NASA Astrophysics Data System (ADS)

    Mauritz, M.; Schuur, E. A. G.; Bracho, R. G.; Celis, G.; Natali, S.; Hutchings, J. A.; Salmon, V. G.; Webb, E.

    2014-12-01

    Arctic permafrost soils store 1700 Pg carbon (C), almost half the global soil C. For millennia permafrost soil C has been protected from decomposition by cold, waterlogged conditions. Warming temperatures will likely thaw permafrost, however the impact on arctic C balance is uncertain. Nutrient availability is predicted to increase with thaw depth and promote plant growth, potentially creating an ecosystem C sink. However, deeper thaw could also increase microbial respiration and eventually exceed C gains. Using data from a warming experiment in sub-arctic moist acidic tundra, designed to insulate soils in winter and stimulate permafrost degradation, we investigated spatial and temporal drivers of ecosystem C balance. Net ecosystem exchange (NEE) was measured continuously from May-September 2009-2013 using clear automated chambers; ecosystem respiration (Reco) was extrapolated from low light NEE and gross primary productivity (GPP) was derived (GPP = NEE-Reco). Five years of warming led to progressive increases in active layer depth. Active layer depth was positively correlated with cumulative growing season NEE, GPP and Reco. Although warming increased Reco the ecosystem remained a C sink during the growing season because high Reco was offset by increased plant growth and GPP. Eriophorum vaginatum growth accounted for most of the increased plant biomass, and was correlated with cumulative growing season GPP and Reco. NEE, GPP and Reco all peaked mid-season, and the mid-season amplitudes increased annually leading to higher cumulative NEE, GPP and Reco. In the shoulder seasons NEE and GPP were similar among years. In contrast, Reco increased at the end of the growing season each year, and high mid-season GPP was positively correlated with end season Reco. Thus, conditions that promoted plant growth also promoted C loss. These results suggest plant responses to permafrost thaw are an important driver of C dynamics. Reco associated with high biomass may result from

  2. Modeling the above and below ground carbon and nitrogen stocks in northern high latitude terrestrial ecosystems

    NASA Astrophysics Data System (ADS)

    ElMasri, B.; Jain, A. K.

    2012-12-01

    Climate change is expected to cause warming in the northern high latitudes, but it is still uncertain what the respond of the northern high latitudes ecosystem will be to such warming. One of the biggest scientific questions is to determine whether northern high latitude ecosystem are or will act as a terrestrial carbon sink or source. Therefore, it is essential to understand and quantify the biogeochemical cycle of the northern high latitude ecosystems in order to predict their respond to climate change. Using a land surface model, the Integrated Science Assessment Model (ISAM) with its coupled carbon-nitrogen cycle, we provide a detail quantification of the carbon and nitrogen in the vegetation pools and the soil carbon for the northern high latitude ecosystems. We focus on soil carbon and vegetation carbon and nitrogen, though we provide results for gross primary production (GPP), autotrophic respiration (Ra), net primary production (NPP), net ecosystem exchange (NEE), and heterotrophic respiration (Rh). In addition, we examine the effect of nitrogen limitation on the carbon fluxes and soil carbon. We present the results for several flux tower sites representative of the tundra and the boreal ecosystems as well as for the northern high latitude region. Our results provide a comprehensive assessment of below and above ground carbon and nitrogen pools in the northern high latitude and the model calibrated parameters can be used to improve the results of other land surface models.

  3. Effects of carbon percentage, Stelmor cooling rate and laying head temperature on tensile strength gain in low carbon steels

    NASA Astrophysics Data System (ADS)

    Gade, Surya Prakash

    Low carbon steel wire rods are used to produce finished products such as fine wire, coat hangers, staples, and roofing nails. These products are subjected to excessively high work hardening rates during wire drawing process resulting in a variation in wire tensile strength. This research analyzes the effects of carbon percentage, StelmorRTM cooling rate and laying head temperature on the tensile strength gain in wire drawn low carbon steels using design of experiments. The probable reasons for variations in tensile strength gain are analyzed by observing the microstructural changes during experiments. Microstructural analysis was done extensively using optical microscope and Transmission Electron Microscope (TEM) and it was found that the tensile strength gain variation is mainly caused by the increase in the dislocation density in wire rod and wire due to high cooling rate and high laying head temperature, within the range considered. This research concludes that a low carbon wire rod can be produced with minimum tensile strength gain, lower dislocation density and finer ferrite grain size by maintaining a low cooling rate in the StelmorRTM cooling zone and low laying head temperature, which is the temperature at which the wire rod coils are laid on the Stelmor RTM deck. It is also concluded from the results of the present study that: (1) The lowest tensile strength gain is for NS 1006T-3 (0.07 wt.% Carbon) with low cooling rate of 14°F/s and low laying head temperature of 1500°F. (2) The highest tensile strength gain is for NS 1006T-3 with high cooling rate of 26°F/s and high laying head temperature of 1650°F. (3) The effect of StelmorRTM cooling rate and laying head temperature and their interaction are found to be the significant factors causing the variation in wire tensile strength gain. The StelmorRTM cooling rate has the most significant effect on tensile strength gain among the three factors. (4) The effect of carbon percentage on wire tensile strength

  4. Whole-canopy carbon gain as a result of selection on individual performance of ten genotypes of a clonal plant.

    PubMed

    Vermeulen, Peter J; Anten, Niels P R; Stuefer, Josef F; During, Heinjo J

    2013-06-01

    Game theoretical models predict that plant competition for light leads to reduced productivity of vegetation stands through selection for traits that maximize carbon gains of individuals. Using empirical results from a 5-year competition experiment with 10 genotypes of the clonal plant Potentilla reptans, we tested this prediction by analyzing the effects of the existing leaf area values on the carbon gain of the different genotypes and the consequent whole canopy carbon gain. We focused on specific leaf area (SLA) due to its role in the trade-off between light capture area and photosynthetic capacity per unit area. By combining a canopy model based on measured leaf area and light profiles with a game theoretical approach, we analyzed how changes in the SLA affected genotypic and whole-stand carbon gain. This showed that all genotypes contributed to reduced stand productivity. The dominant genotype maximized its share of total carbon gain, resulting in lower than maximal absolute gain. Other genotypes did not maximize their share. Hypothetical mutants of the dominant genotype were not able to achieve a higher carbon gain. Conversely, in other genotypes, some mutations did result in increased carbon gain. Hence, genotypic differences in the ability to maximize performance may determine genotype frequency. It shows how genotypic selection may result in lower carbon gains of the whole vegetation, and of the individual genotypes it consists of, through similar mechanisms as those that lead to the tragedy of the commons. PMID:23114427

  5. Modeling the role of terrestrial ecosystems in the global carbon cycle

    SciTech Connect

    Emanuel, W. R.; Post, W. M.; Shugart, Jr., H. H.

    1980-01-01

    A model for the global biogeochemical cycle of carbon which includes a five-compartment submodel for circulation in terrestrial ecosystems of the world is presented. Although this terrestrial submodel divides carbon into compartments with more functional detail than previous models, the variability in carbon dynamics among ecosystem types and in different climatic zones is not adequately treated. A new model construct which specifically treats this variability by modeling the distribution of ecosystem types as a function of climate on a 0.5/sup 0/ latitude by 0.5/sup 0/ longitude scale of resolution is proposed.

  6. [Ecosystem carbon exchange in Artemisia ordosica shrubland of Ordos Plateau in two different precipitation years].

    PubMed

    Gao, Li; Dong, Ting-Ting; Wang, Yu-Qing; Yan, Zhi-Jian; Baoyin, Tao-ge-tao; Wang, Hui; Dai, Ya-Ting

    2014-08-01

    Characteristics of ecosystem carbon exchange and its impact factors in Artemisia ordosica shrubland in 2011 (low precipitation) and 2012 (high precipitation), Ordos Plateau, were studied using eddy covariance methods. The results showed that the diurnal dynamics of ecosystem carbon exchange could be expressed as single-peak and double-peak curves in the two different precipitation years. In 2011, three carbon absorption peaks and three carbon release peaks of ecosystem carbon exchange presented in the growing season. In 2012, four carbon absorption peaks and one carbon release peak appeared in the growing season. The A. ordosica shrubland was a net carbon sink from June to September and a carbon source in October in 2011. In 2012, A. ordosica shrubland was a net carbon sink in the whole growing season. The amount of carbon fixed by A. ordosica shrubland in the growing season in 2012 was 268.90 mg CO2 x m(-2) x s(-1) higher than that in 2011. The ecosystem carbon exchange of A. ordosica shrubland was controlled by PAR (photosynthetically active radiation) on the day scale, and affected by both abiotic (precipitation and soil water content) and biotic (aboveground net primary, productivity) factors on the growing season scale.

  7. Ontogeny, understorey light interception and simulated carbon gain of juvenile rainforest evergreens differing in shade tolerance

    PubMed Central

    Lusk, Christopher H.; Pérez-Millaqueo, Manuel Matías; Piper, Frida I.; Saldaña, Alfredo

    2011-01-01

    Background and Aims A long-running debate centres on whether shade tolerance of tree seedlings is mainly a function of traits maximizing net carbon gain in low light, or of traits minimizing carbon loss. To test these alternatives, leaf display, light-interception efficiency, and simulated net daily carbon gain of juvenile temperate evergreens of differing shade tolerance were measured, and how these variables are influenced by ontogeny was queried. Methods The biomass distribution of juveniles (17–740 mm tall) of seven temperate rainforest evergreens growing in low (approx. 4 %) light in the understorey of a second-growth stand was quantified. Daytime and night-time gas exchange rates of leaves were also determined, and crown architecture was recorded digitally. YPLANT was used to model light interception and carbon gain. Results An index of species shade tolerance correlated closely with photosynthetic capacities and respiration rates per unit mass of leaves, but only weakly with respiration per unit area. Accumulation of many leaf cohorts by shade-tolerant species meant that their ratios of foliage area to biomass (LAR) decreased more gradually with ontogeny than those of light-demanders, but also increased self-shading; this depressed the foliage silhouette-to-area ratio (STAR), which was used as an index of light-interception efficiency. As a result, displayed leaf area ratio (LARd = LAR × STAR) of large seedlings was not related to species shade tolerance. Self-shading also caused simulated net daily carbon assimilation rates of shade-tolerant species to decrease with ontogeny, leading to a negative correlation of shade tolerance with net daily carbon gain of large (500 mm tall) seedlings in the understorey. Conclusions The results suggest that efficiency of energy capture is not an important correlate of shade tolerance in temperate rainforest evergreens. Ontogenetic increases in self-shading largely nullify the potential carbon gain advantages expected

  8. The Carbon Balance of Semi-Arid Ecosystems: Why Southern Africa Carbon-Climate Dynamics are uniquely different

    NASA Astrophysics Data System (ADS)

    Lawal, S. A.; Fisher, J. B.

    2015-12-01

    Previous studies by Poulter et al (2014) and Alhstrom et al (2015) have shown that the semi-arid ecosystems (e.g. Australia) can dramatically alter the regional and global net carbon sink/source status depending on sporadic precipitation. For example, the unprecedented huge carbon sink which occurred in 2011 was mainly due to the growth semi-arid vegetation over Australia; which was driven by increased precipitation. Thus, we sought to uncover if this was the case with the semi-arid ecosystems in southern Africa. We used 10 models from the "Trends In Net Land-Atmosphere Carbon Exchange - Model Inter comparison Project (TRENDY-MIP)" to evaluate response of southern Africa semi-arid ecosystems to precipitation in the 20th century. Our study revealed that the sensitivities and net carbon source/sink dynamics in these ecosystems are distinctly different from those elsewhere owing to opposite climate anomalies; i.e. the region receives sporadic precipitation drops, rather than spikes which is the case in other semi-arid regions. The implications for this study is explored in an ecosystem services context for future trajectories of the region as the ability of the ecosystems to continually provide such services directly depends on the soaring population rise in the region. Key words: Semi-arid ecosystem, Southern Africa, TRENDY-MIP, Carbon dynamics and climate change.

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

    NASA Astrophysics Data System (ADS)

    Ryals, R.; Silver, W. L.

    2010-12-01

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

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

    PubMed

    Pendleton, Linwood; Donato, Daniel C; Murray, Brian C; Crooks, Stephen; Jenkins, W Aaron; Sifleet, Samantha; Craft, Christopher; Fourqurean, James W; Kauffman, J Boone; Marbà, Núria; Megonigal, Patrick; Pidgeon, Emily; Herr, Dorothee; Gordon, David; Baldera, Alexis

    2012-01-01

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

  11. Tradeoffs between global warming and day length on the start of the carbon uptake period in seasonally cold ecosystems.

    PubMed

    Wohlfahrt, Georg; Cremonese, Edoardo; Hammerle, Albin; Hörtnagl, Lukas; Galvagno, Marta; Gianelle, Damiano; Marcolla, Barbara; di Cella, Umberto Morra

    2013-12-16

    It is well established that warming leads to longer growing seasons in seasonally cold ecosystems. Whether this goes along with an increase in the net ecosystem carbon dioxide (CO2) uptake is much more controversial. We studied the effects of warming on the start of the carbon uptake period (CUP) of three mountain grasslands situated along an elevational gradient in the Alps. To this end we used a simple empirical model of the net ecosystem CO2 exchange, calibrated and forced with multi-year empirical data from each site. We show that reductions in the quantity and duration of daylight associated with earlier snowmelts were responsible for diminishing returns, in terms of carbon gain, from longer growing seasons caused by reductions in daytime photosynthetic uptake and increases in nighttime losses of CO2. This effect was less pronounced at high, compared to low, elevations, where the start of the CUP occurred closer to the summer solstice when changes in day length and incident radiation are minimal.

  12. The impact of early morning elevated CO sub 2 on foliar carbon gain

    SciTech Connect

    Hanson, P.J.; Norby, R.J. )

    1990-05-01

    Predawn concentrations of CO{sub 2} in the boundary layer above vegetated landscapes can be as much as 200 {mu}L{sup {minus}1} higher than typical midday concentrations (330-360 {mu}l L{sup {minus}1}). This period of elevated CO{sub 2} lasts up to 3 hours after sunrise. Estimates of daily carbon gain from models of photosynthesis have often assumed constant CO{sub 2} concentrations. Photosynthesis and stomatal conductance models were coupled and used to assess the importance of a diurnal variation in CO{sub 2} concentration. Daily carbon gain estimates based on a constant CO{sub 2} concentration equal to the afternoon average (1,200 to 1,600 h), were as much as 13% less than estimates based on the more realistic diurnal pattern including elevated CO{sub 2} concentrations in the morning. The largest discrepancies in calculated carbon gain (6-13%) occurred for simulated sunny days, and for foliage having a low carboxylation efficiency.

  13. Exploiting heterogeneous environments: does photosynthetic acclimation optimize carbon gain in fluctuating light?

    PubMed Central

    Retkute, Renata; Smith-Unna, Stephanie E.; Smith, Robert W.; Burgess, Alexandra J.; Jensen, Oliver E.; Johnson, Giles N.; Preston, Simon P.; Murchie, Erik H.

    2015-01-01

    Plants have evolved complex mechanisms to balance the efficient use of absorbed light energy in photosynthesis with the capacity to use that energy in assimilation, so avoiding potential damage from excess light. This is particularly important under natural light, which can vary according to weather, solar movement and canopy movement. Photosynthetic acclimation is the means by which plants alter their leaf composition and structure over time to enhance photosynthetic efficiency and productivity. However there is no empirical or theoretical basis for understanding how leaves track historic light levels to determine acclimation status, or whether they do this accurately. We hypothesized that in fluctuating light (varying in both intensity and frequency), the light-response characteristics of a leaf should adjust (dynamically acclimate) to maximize daily carbon gain. Using a framework of mathematical modelling based on light-response curves, we have analysed carbon-gain dynamics under various light patterns. The objective was to develop new tools to quantify the precision with which photosynthesis acclimates according to the environment in which plants exist and to test this tool on existing data. We found an inverse relationship between the optimal maximum photosynthetic capacity and the frequency of low to high light transitions. Using experimental data from the literature we were able to show that the observed patterns for acclimation were consistent with a strategy towards maximizing daily carbon gain. Refinement of the model will further determine the precision of acclimation. PMID:25788730

  14. Exploiting heterogeneous environments: does photosynthetic acclimation optimize carbon gain in fluctuating light?

    PubMed

    Retkute, Renata; Smith-Unna, Stephanie E; Smith, Robert W; Burgess, Alexandra J; Jensen, Oliver E; Johnson, Giles N; Preston, Simon P; Murchie, Erik H

    2015-05-01

    Plants have evolved complex mechanisms to balance the efficient use of absorbed light energy in photosynthesis with the capacity to use that energy in assimilation, so avoiding potential damage from excess light. This is particularly important under natural light, which can vary according to weather, solar movement and canopy movement. Photosynthetic acclimation is the means by which plants alter their leaf composition and structure over time to enhance photosynthetic efficiency and productivity. However there is no empirical or theoretical basis for understanding how leaves track historic light levels to determine acclimation status, or whether they do this accurately. We hypothesized that in fluctuating light (varying in both intensity and frequency), the light-response characteristics of a leaf should adjust (dynamically acclimate) to maximize daily carbon gain. Using a framework of mathematical modelling based on light-response curves, we have analysed carbon-gain dynamics under various light patterns. The objective was to develop new tools to quantify the precision with which photosynthesis acclimates according to the environment in which plants exist and to test this tool on existing data. We found an inverse relationship between the optimal maximum photosynthetic capacity and the frequency of low to high light transitions. Using experimental data from the literature we were able to show that the observed patterns for acclimation were consistent with a strategy towards maximizing daily carbon gain. Refinement of the model will further determine the precision of acclimation.

  15. [Effects of enhanced UV-B radiation on terrestrial ecosystem carbon cycle: a review].

    PubMed

    Liu, Shu-Rong; Hu, Rong-Gui; Cai, Gao-Chao

    2012-07-01

    As one of the most important phenomena of global climate change, the enhancement of ultraviolet-B radiation (UV-B, 280-320 nm) could have critical impact on the carbon cycle in terrestrial ecosystem. Through the impacts on plant photosynthesis, litter decomposition, and soil respiration, the enhanced UV-B radiation can affect the carbon input, turnover, and output of terrestrial ecosystem. Other climatic factors (ambient CO2 concentration, air temperature, and precipitation) may promote or mitigate the impact of enhanced UV-B radiation on terrestrial ecosystem carbon cycle. This paper introduced the background of UV-B radiation enhancement, reviewed the impacts of enhanced UV-B radiation and its interactions with other climatic factors on terrestrial ecosystem carbon cycle, summarized the existing problems in related researches, and discussed the priorities and directions of future researches.

  16. Ecosystem carbon storage capacity as affected by disturbance regimes: A general theoretical model

    SciTech Connect

    Weng, Ensheng; Luo, Yiqi; Wang, Weile; Wang, Han; Hayes, Daniel J; McGuire, A. David; Hastings, Alan; Schimel, David

    2012-01-01

    Disturbances have been recognized as a key factor shaping terrestrial ecosystem states and dynamics. A general model that quantitatively describes the relationship between carbon storage and disturbance regime is critical for better understanding large scale terrestrial ecosystem carbon dynamics. We developed a model (REGIME) to quantify ecosystem carbon storage capacities (E[x]) under varying disturbance regimes with an analytical solution E[x] = U {center_dot} {tau}{sub E} {center_dot} {lambda}{lambda} + s {tau} 1, where U is ecosystem carbon influx, {tau}{sub E} is ecosystem carbon residence time, and {tau}{sub 1} is the residence time of the carbon pool affected by disturbances (biomass pool in this study). The disturbance regime is characterized by the mean disturbance interval ({lambda}) and the mean disturbance severity (s). It is a Michaelis-Menten-type equation illustrating the saturation of carbon content with mean disturbance interval. This model analytically integrates the deterministic ecosystem carbon processes with stochastic disturbance events to reveal a general pattern of terrestrial carbon dynamics at large scales. The model allows us to get a sense of the sensitivity of ecosystems to future environmental changes just by a few calculations. According to the REGIME model, for example, approximately 1.8 Pg C will be lost in the high-latitude regions of North America (>45{sup o} N) if fire disturbance intensity increases around 5.7 time the current intensity to the end of the twenty-first century, which will require around 12% increases in net primary productivity (NPP) to maintain stable carbon stocks. If the residence time decreased 10% at the same time additional 12.5% increases in NPP are required to keep current C stocks. The REGIME model also lays the foundation for analytically modeling the interactions between deterministic biogeochemical processes and stochastic disturbance events.

  17. Responses of ecosystem carbon cycling to climate change treatments along an elevation gradient

    USGS Publications Warehouse

    Wu, Zhuoting; Koch, George W.; Dijkstra, Paul; Bowker, Matthew A.; Hungate, Bruce A.

    2011-01-01

    Global temperature increases and precipitation changes are both expected to alter ecosystem carbon (C) cycling. We tested responses of ecosystem C cycling to simulated climate change using field manipulations of temperature and precipitation across a range of grass-dominated ecosystems along an elevation gradient in northern Arizona. In 2002, we transplanted intact plant–soil mesocosms to simulate warming and used passive interceptors and collectors to manipulate precipitation. We measured daytime ecosystem respiration (ER) and net ecosystem C exchange throughout the growing season in 2008 and 2009. Warming generally stimulated ER and photosynthesis, but had variable effects on daytime net C exchange. Increased precipitation stimulated ecosystem C cycling only in the driest ecosystem at the lowest elevation, whereas decreased precipitation showed no effects on ecosystem C cycling across all ecosystems. No significant interaction between temperature and precipitation treatments was observed. Structural equation modeling revealed that in the wetter-than-average year of 2008, changes in ecosystem C cycling were more strongly affected by warming-induced reduction in soil moisture than by altered precipitation. In contrast, during the drier year of 2009, warming induced increase in soil temperature rather than changes in soil moisture determined ecosystem C cycling. Our findings suggest that warming exerted the strongest influence on ecosystem C cycling in both years, by modulating soil moisture in the wet year and soil temperature in the dry year.

  18. Effects of temperature, moisture, and permafrost thaw on ecosystem carbon exchange in Alaskan tundra.

    NASA Astrophysics Data System (ADS)

    Natali, S.; Schuur, E. A.; Webb, E.

    2012-12-01

    Carbon has been accumulating in northern high latitude ecosystems for thousands of years because cold and moist conditions have protected soil organic matter from microbial decomposition. Over the past several decades, warming surface air temperatures have been accompanied by thawing of the perennially frozen permafrost layer where much of the accumulated carbon is stored. In addition to its role in carbon storage, permafrost regulates surface hydrology by restricting vertical water flow, thereby maintaining a water table that remains close to the ground surface. In the absence of the permafrost layer, enhanced water drainage will result in increased water table depth and decreased soil moisture. The biological availability of permafrost carbon may increase in a warmer and drier soil environment, as is expected for the region of this study. To determine the effects of warming temperatures and changes in soil moisture on ecosystem carbon exchange, we established a water table drawdown experiment within the footprint of the Carbon in Permafrost Experimental Heating Research (CiPEHR) project, an ecosystem warming experiment in Interior Alaska that warms air and soil temperatures and degrades permafrost. Here we present ecosystem carbon balance results from combined warming and moisture manipulation treatments at the CiPEHR project. Soil warming increased soil temperature by 2-3o C and resulted in a 10% increase in growing season thaw depth. Surprisingly, the additional 2 kg of thawed soil C m-2 in the warmed plots did not increase net growing season CO2 loss from this ecosystem. In contrast, soil warming and permafrost thaw increased growing season CO2 uptake, which was a result of both higher net primary productivity and an inhibition of microbial decomposition by soil saturation at the base of the active layer. The drying treatment (i.e., water table drawdown) decreased soil moisture by 25%, which led to an increase in ecosystem respiration and decrease in net

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

    PubMed Central

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

    2013-01-01

    Restoring disturbed and over-exploited ecosystems is important to mitigate human pressures on natural ecosystems. China has launched an ambitious national ecosystem restoration program called Grain to Green Program (GTGP) over the last decade. By using remote sensing techniques and ecosystem modelling, we quantitatively evaluated the changes in ecosystem carbon sequestration since China's GTGP program during period of 2000–2008. It was found the NPP and NEP in this region had steadily increased after the initiative of the GTGP program, and a total of 96.1 Tg of additional carbon had been sequestered during that period. Changes in soil carbon storage were lagged behind and thus insignificant over the period, but was expected to follow in the coming decades. As a result, the Loess Plateau ecosystem had shifted from a net carbon source in 2000 to a net carbon sink in 2008. The carbon sequestration efficiency was constrained by precipitation, and appropriate choices of restoration types (trees, shrubs, and grasses) in accordance to local climate are critical for achieving the best benefit/cost efficiency. PMID:24088871

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

    USGS Publications Warehouse

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

    1998-01-01

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

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

    PubMed

    Liu, Yuguo; Liu, Changcheng; Wang, Shijie; Guo, Ke; Yang, Jun; Zhang, Xinshi; Li, Guoqing

    2013-01-01

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

  2. Global covariation of carbon turnover times with climate in terrestrial ecosystems.

    PubMed

    Carvalhais, Nuno; Forkel, Matthias; Khomik, Myroslava; Bellarby, Jessica; Jung, Martin; Migliavacca, Mirco; Mu, Mingquan; Saatchi, Sassan; Santoro, Maurizio; Thurner, Martin; Weber, Ulrich; Ahrens, Bernhard; Beer, Christian; Cescatti, Alessandro; Randerson, James T; Reichstein, Markus

    2014-10-01

    The response of the terrestrial carbon cycle to climate change is among the largest uncertainties affecting future climate change projections. The feedback between the terrestrial carbon cycle and climate is partly determined by changes in the turnover time of carbon in land ecosystems, which in turn is an ecosystem property that emerges from the interplay between climate, soil and vegetation type. Here we present a global, spatially explicit and observation-based assessment of whole-ecosystem carbon turnover times that combines new estimates of vegetation and soil organic carbon stocks and fluxes. We find that the overall mean global carbon turnover time is 23(+7)(-4) years (95 per cent confidence interval). On average, carbon resides in the vegetation and soil near the Equator for a shorter time than at latitudes north of 75° north (mean turnover times of 15 and 255 years, respectively). We identify a clear dependence of the turnover time on temperature, as expected from our present understanding of temperature controls on ecosystem dynamics. Surprisingly, our analysis also reveals a similarly strong association between turnover time and precipitation. Moreover, we find that the ecosystem carbon turnover times simulated by state-of-the-art coupled climate/carbon-cycle models vary widely and that numerical simulations, on average, tend to underestimate the global carbon turnover time by 36 per cent. The models show stronger spatial relationships with temperature than do observation-based estimates, but generally do not reproduce the strong relationships with precipitation and predict faster carbon turnover in many semi-arid regions. Our findings suggest that future climate/carbon-cycle feedbacks may depend more strongly on changes in the hydrological cycle than is expected at present and is considered in Earth system models.

  3. Global covariation of carbon turnover times with climate in terrestrial ecosystems.

    PubMed

    Carvalhais, Nuno; Forkel, Matthias; Khomik, Myroslava; Bellarby, Jessica; Jung, Martin; Migliavacca, Mirco; Mu, Mingquan; Saatchi, Sassan; Santoro, Maurizio; Thurner, Martin; Weber, Ulrich; Ahrens, Bernhard; Beer, Christian; Cescatti, Alessandro; Randerson, James T; Reichstein, Markus

    2014-10-01

    The response of the terrestrial carbon cycle to climate change is among the largest uncertainties affecting future climate change projections. The feedback between the terrestrial carbon cycle and climate is partly determined by changes in the turnover time of carbon in land ecosystems, which in turn is an ecosystem property that emerges from the interplay between climate, soil and vegetation type. Here we present a global, spatially explicit and observation-based assessment of whole-ecosystem carbon turnover times that combines new estimates of vegetation and soil organic carbon stocks and fluxes. We find that the overall mean global carbon turnover time is 23(+7)(-4) years (95 per cent confidence interval). On average, carbon resides in the vegetation and soil near the Equator for a shorter time than at latitudes north of 75° north (mean turnover times of 15 and 255 years, respectively). We identify a clear dependence of the turnover time on temperature, as expected from our present understanding of temperature controls on ecosystem dynamics. Surprisingly, our analysis also reveals a similarly strong association between turnover time and precipitation. Moreover, we find that the ecosystem carbon turnover times simulated by state-of-the-art coupled climate/carbon-cycle models vary widely and that numerical simulations, on average, tend to underestimate the global carbon turnover time by 36 per cent. The models show stronger spatial relationships with temperature than do observation-based estimates, but generally do not reproduce the strong relationships with precipitation and predict faster carbon turnover in many semi-arid regions. Our findings suggest that future climate/carbon-cycle feedbacks may depend more strongly on changes in the hydrological cycle than is expected at present and is considered in Earth system models. PMID:25252980

  4. Long-term increase in forest water-use efficiency observed across ecosystem carbon flux networks (Invited)

    NASA Astrophysics Data System (ADS)

    Keenan, T. F.; Hollinger, D. Y.; Bohrer, G.; Dragoni, D.; Munger, J. W.; Schmid, H. E.; Richardson, A. D.

    2013-12-01

    Terrestrial plants remove CO2 from the atmosphere through photo- synthesis, a process that is accompanied by the loss of water vapour from leaves. The ratio of water loss to carbon gain, or water-use efficiency, is a key characteristic of ecosystem function that is central to the global cycles of water, energy and carbon. Here we analyse direct, long-term measurements of whole-ecosystem carbon and water exchange. We find a substantial increase in water-use efficiency in temperate and boreal forests of the Northern Hemisphere over the past two decades. We systematically assess various competing hypotheses to explain this trend, and find that the observed increase is most consistent with a strong CO2 fertilization effect. The results suggest a partial closure of stomata - small pores on the leaf surface that regulate gas exchange - to maintain a near- constant concentration of CO2 inside the leaf even under continually increasing atmospheric CO2 levels. The observed increase in forest water-use efficiency is larger than that predicted by existing theory and 13 terrestrial biosphere models. The increase is associated with trends of increasing ecosystem-level photosynthesis and net carbon uptake, and decreasing evapotranspiration. Our findings demonstrate the utility of maintaining long-term eddy-covariance flux measurement sites. The results suggest a shift in the carbon- and water-based economics of terrestrial vegetation, which may require a reassessment of the role of stomatal control in regulating interactions between forests and climate change, and a re-evaluation of coupled vegetation-climate models.

  5. Whole ecosystem estimates of carbon exchange and storage in a New England salt marsh

    NASA Astrophysics Data System (ADS)

    Forbrich, I.; Giblin, A.

    2013-12-01

    Salt marshes are wetlands situated at the interface of land and ocean. They are among the most productive ecosystems worldwide and store substantial amounts of carbon as peat. Their long-term stability is dependent on sediment accretion and carbon accumulation to avoid submergence when sea level is rising. Currently, estimates of carbon storage in salt marshes are uncertain because our understanding of the coupling between marsh plant productivity and carbon release to the adjacent ocean is limited. To evaluate the capacity to store carbon as well as the resilience of the ecosystem, long-term studies of carbon cycling considering both vertical and lateral fluxes are necessary. To study the net exchange between marsh and atmosphere, we chose the non-intrusive eddy covariance which allows nearly continuous half hourly flux measurements of net ecosystem exchange (NEE) on the ecosystem scale. Since spring 2012, we have been investigating the marsh-atmosphere exchange of carbon dioxide (CO2) at a Spartina patens high marsh at the Plum Island Ecosystems Long-Term Ecological Research site. Seasonal dynamics of CO2 exchange during summer were controlled by the phenology of S. patens. Preliminary estimates for seasonal carbon storage range from 185 to 228 g C m-2 (5/1/2012 to 10/31/2012). During the winter months we observed small fluxes, but carbon uptake still occurred during the day. We attribute this to microalgae productivity. Winter carbon release is estimated to be approximately 130 g C m-2 (12/6/2012 to 4/30/2013), when uptake by microalgae is not taken into account. This emphasizes the relevance of transitional and cold season carbon cycling for the carbon storage capacity of northern salt marshes, since a large proportion of fixed carbon is released during these periods. Direct tidal effects on the marsh-atmosphere carbon exchange are visible especially during monthly spring tides, when both daytime carbon uptake and night time respiration were reduced during

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

    PubMed

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

    2013-03-01

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

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

    PubMed

    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.

  8. Carbon financing of household water treatment: background, operation and recommendations to improve potential for health gains.

    PubMed

    Hodge, James M; Clasen, Thomas F

    2014-11-01

    Household water treatment (HWT) provides a means for vulnerable populations to take charge of their own drinking water quality as they patiently wait for the pipe to finally reach them. In many low-income countries, however, promoters have not succeeded in scaling up the intervention among the target population or securing its consistent and sustained use. Carbon financing can provide the funding for reaching targeted populations with effective HWT solutions and the incentives to ensure their long-term uptake. Nevertheless, programs have been criticized because they do not actually reduce carbon emissions. We summarize the background and operation of carbon financing of HWT interventions, including the controversial construct of "suppressed demand". We agree that these programs have limited potential to reduce greenhouse gas emissions and that their characterization of trading "carbon for water" is misleading. Nevertheless, we show that the Kyoto Protocol expressly encouraged the use of suppressed demand as a means of allowing low-income countries to benefit from carbon financing provided it is used to advance development priorities such as health. We conclude by recommending changes to existing criteria for eligible HWT programs that will help ensure that they meet the conditions of microbiological effectiveness and actual use that will improve their potential for health gains.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2003-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  13. Economic innovation and efficiency gains as the driving force for accelerating carbon dioxide emissions

    NASA Astrophysics Data System (ADS)

    Garrett, T. J.

    2012-12-01

    It is normally assumed that gains in energy efficiency are one of the best routes that society has available to it for stabilizing future carbon dioxide emissions. For a given degree of economic productivity less energy is consumed and a smaller quantity of fossil fuels is required. While certainly this observation is true in the instant, it ignores feedbacks in the economic system such that efficiency gains ultimately lead to greater energy consumption: taken as a global whole, they permit civilization to accelerate its expansion into the energy reserves that sustain it. Here this argument is formalized from a general thermodynamic perspective. The core result is that there exists a fixed, time-independent link between a very general representation of global inflation-adjusted economic wealth (units currency) and civilization's total capacity to consume power (units energy per time). Based on 40 years of available statistics covering more than a tripling of global GDP and a doubling of wealth, this constant has a value of 7.1 +/- 0.01 Watts per one thousand 2005 US dollars. Essentially, wealth is power. Civilization grows by dissipating power in order to sustain all its current activities and to incorporate more raw material into its existing structure. Growth of its structure is related to economic production, so more energy efficient economic production facilitates growth. Growth is into the reserves that sustain civilization, in which case there is a positive feedback in the economic system whereby energy efficiency gains ultimately "backfire" if their intended purpose is to reduce energy consumption and carbon dioxide emissions. The analogy that can be made is to a growing child: a healthy child who efficiently incorporates food into her structure grows quickly and is able to consume more in following years. Economically, an argument is made that, for a range of reasons, there are good reasons to refer to efficiency gains as economic "innovation", both for

  14. An Integrated Functional Genomics Consortium to Increase Carbon Sequestration in Poplars: Optimizing Aboveground Carbon Gain

    SciTech Connect

    Karnosky, David F; Podila, G Krishna; Burton, Andrew J

    2009-02-17

    This project used gene expression patterns from two forest Free-Air CO2 Enrichment (FACE) experiments (Aspen FACE in northern Wisconsin and POPFACE in Italy) to examine ways to increase the aboveground carbon sequestration potential of poplars (Populus). The aim was to use patterns of global gene expression to identify candidate genes for increased carbon sequestration. Gene expression studies were linked to physiological measurements in order to elucidate bottlenecks in carbon acquisition in trees grown in elevated CO2 conditions. Delayed senescence allowing additional carbon uptake late in the growing season, was also examined, and expression of target genes was tested in elite P. deltoides x P. trichocarpa hybrids. In Populus euramericana, gene expression was sensitive to elevated CO2, but the response depended on the developmental age of the leaves. Most differentially expressed genes were upregulated in elevated CO2 in young leaves, while most were downregulated in elevated CO2 in semi-mature leaves. In P. deltoides x P. trichocarpa hybrids, leaf development and leaf quality traits, including leaf area, leaf shape, epidermal cell area, stomatal number, specific leaf area, and canopy senescence were sensitive to elevated CO2. Significant increases under elevated CO2 occurred for both above- and belowground growth in the F-2 generation. Three areas of the genome played a role in determining aboveground growth response to elevated CO2, with three additional areas of the genome important in determining belowground growth responses to elevated CO2. In Populus tremuloides, CO2-responsive genes in leaves were found to differ between two aspen clones that showed different growth responses, despite similarity in many physiological parameters (photosynthesis, stomatal conductance, and leaf area index). The CO2-responsive clone shunted C into pathways associated with active defense/response to stress, carbohydrate/starch biosynthesis and subsequent growth. The CO2

  15. Carbon and nitrogen cycles in European ecosystems respond differently to global warming.

    PubMed

    Beier, C; Emmett, B A; Peñuelas, J; Schmidt, I K; Tietema, A; Estiarte, M; Gundersen, P; Llorens, L; Riis-Nielsen, T; Sowerby, A; Gorissen, A

    2008-12-15

    The global climate is predicted to become significantly warmer over the next century. This will affect ecosystem processes and the functioning of semi natural and natural ecosystems in many parts of the world. However, as various ecosystem processes may be affected to a different extent, balances between different ecosystem processes as well as between different ecosystems may shift and lead to major unpredicted changes. In this study four European shrubland ecosystems along a north-south temperature gradient were experimentally warmed by a novel nighttime warming technique. Biogeochemical cycling of both carbon and nitrogen was affected at the colder sites with increased carbon uptake for plant growth as well as increased carbon loss through soil respiration. Carbon uptake by plant growth was more sensitive to warming than expected from the temperature response across the sites while carbon loss through soil respiration reacted to warming in agreement with the overall Q10 and response functions to temperature across the sites. Opposite to carbon, the nitrogen mineralization was relatively insensitive to the temperature increase and was mainly affected by changes in soil moisture. The results suggest that C and N cycles respond asymmetrically to warming, which may lead to progressive nitrogen limitation and thereby acclimation in plant production. This further suggests that in many temperate zones nitrogen deposition has to be accounted for, not only with respect to the impact on water quality through increased nitrogen leaching where N deposition is high, but also in predictions of carbon sequestration in terrestrial ecosystems under future climatic conditions. Finally the results indicate that on the short term the above-ground processes are more sensitive to temperature changes than the below ground processes. PMID:18930514

  16. Carbon and nitrogen cycles in European ecosystems respond differently to global warming.

    PubMed

    Beier, C; Emmett, B A; Peñuelas, J; Schmidt, I K; Tietema, A; Estiarte, M; Gundersen, P; Llorens, L; Riis-Nielsen, T; Sowerby, A; Gorissen, A

    2008-12-15

    The global climate is predicted to become significantly warmer over the next century. This will affect ecosystem processes and the functioning of semi natural and natural ecosystems in many parts of the world. However, as various ecosystem processes may be affected to a different extent, balances between different ecosystem processes as well as between different ecosystems may shift and lead to major unpredicted changes. In this study four European shrubland ecosystems along a north-south temperature gradient were experimentally warmed by a novel nighttime warming technique. Biogeochemical cycling of both carbon and nitrogen was affected at the colder sites with increased carbon uptake for plant growth as well as increased carbon loss through soil respiration. Carbon uptake by plant growth was more sensitive to warming than expected from the temperature response across the sites while carbon loss through soil respiration reacted to warming in agreement with the overall Q10 and response functions to temperature across the sites. Opposite to carbon, the nitrogen mineralization was relatively insensitive to the temperature increase and was mainly affected by changes in soil moisture. The results suggest that C and N cycles respond asymmetrically to warming, which may lead to progressive nitrogen limitation and thereby acclimation in plant production. This further suggests that in many temperate zones nitrogen deposition has to be accounted for, not only with respect to the impact on water quality through increased nitrogen leaching where N deposition is high, but also in predictions of carbon sequestration in terrestrial ecosystems under future climatic conditions. Finally the results indicate that on the short term the above-ground processes are more sensitive to temperature changes than the below ground processes.

  17. Responses of terrestrial ecosystems and carbon budgets to current and future environmental variability

    PubMed Central

    Medvigy, David; Wofsy, Steven C.; Munger, J. William; Moorcroft, Paul R.

    2010-01-01

    We assess the significance of high-frequency variability of environmental parameters (sunlight, precipitation, temperature) for the structure and function of terrestrial ecosystems under current and future climate. We examine the influence of hourly, daily, and monthly variance using the Ecosystem Demography model version 2 in conjunction with the long-term record of carbon fluxes measured at Harvard Forest. We find that fluctuations of sunlight and precipitation are strongly and nonlinearly coupled to ecosystem function, with effects that accumulate through annual and decadal timescales. Increasing variability in sunlight and precipitation leads to lower rates of carbon sequestration and favors broad-leaved deciduous trees over conifers. Temperature variability has only minor impacts by comparison. We also find that projected changes in sunlight and precipitation variability have important implications for carbon storage and ecosystem structure and composition. Based on Intergovernmental Panel on Climate Change model estimates for changes in high-frequency meteorological variability over the next 100 years, we expect that terrestrial ecosystems will be affected by changes in variability almost as much as by changes in mean climate. We conclude that terrestrial ecosystems are highly sensitive to high-frequency meteorological variability, and that accurate knowledge of the statistics of this variability is essential for realistic predictions of ecosystem structure and functioning. PMID:20404190

  18. Responses of terrestrial ecosystems and carbon budgets to current and future environmental variability.

    PubMed

    Medvigy, David; Wofsy, Steven C; Munger, J William; Moorcroft, Paul R

    2010-05-01

    We assess the significance of high-frequency variability of environmental parameters (sunlight, precipitation, temperature) for the structure and function of terrestrial ecosystems under current and future climate. We examine the influence of hourly, daily, and monthly variance using the Ecosystem Demography model version 2 in conjunction with the long-term record of carbon fluxes measured at Harvard Forest. We find that fluctuations of sunlight and precipitation are strongly and nonlinearly coupled to ecosystem function, with effects that accumulate through annual and decadal timescales. Increasing variability in sunlight and precipitation leads to lower rates of carbon sequestration and favors broad-leaved deciduous trees over conifers. Temperature variability has only minor impacts by comparison. We also find that projected changes in sunlight and precipitation variability have important implications for carbon storage and ecosystem structure and composition. Based on Intergovernmental Panel on Climate Change model estimates for changes in high-frequency meteorological variability over the next 100 years, we expect that terrestrial ecosystems will be affected by changes in variability almost as much as by changes in mean climate. We conclude that terrestrial ecosystems are highly sensitive to high-frequency meteorological variability, and that accurate knowledge of the statistics of this variability is essential for realistic predictions of ecosystem structure and functioning. PMID:20404190

  19. Responses of terrestrial ecosystems and carbon budgets to current and future environmental variability.

    PubMed

    Medvigy, David; Wofsy, Steven C; Munger, J William; Moorcroft, Paul R

    2010-05-01

    We assess the significance of high-frequency variability of environmental parameters (sunlight, precipitation, temperature) for the structure and function of terrestrial ecosystems under current and future climate. We examine the influence of hourly, daily, and monthly variance using the Ecosystem Demography model version 2 in conjunction with the long-term record of carbon fluxes measured at Harvard Forest. We find that fluctuations of sunlight and precipitation are strongly and nonlinearly coupled to ecosystem function, with effects that accumulate through annual and decadal timescales. Increasing variability in sunlight and precipitation leads to lower rates of carbon sequestration and favors broad-leaved deciduous trees over conifers. Temperature variability has only minor impacts by comparison. We also find that projected changes in sunlight and precipitation variability have important implications for carbon storage and ecosystem structure and composition. Based on Intergovernmental Panel on Climate Change model estimates for changes in high-frequency meteorological variability over the next 100 years, we expect that terrestrial ecosystems will be affected by changes in variability almost as much as by changes in mean climate. We conclude that terrestrial ecosystems are highly sensitive to high-frequency meteorological variability, and that accurate knowledge of the statistics of this variability is essential for realistic predictions of ecosystem structure and functioning.

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

    PubMed

    Dubbert, Maren; Piayda, Arndt; Cuntz, Matthias; Correia, Alexandra C; Costa E Silva, Filipe; Pereira, Joao S; Werner, Christiane

    2014-01-01

    Semi-arid ecosystems contribute about 40% to global net primary production (GPP) even though water is a major factor limiting carbon uptake. Evapotranspiration (ET) accounts for up to 95% of the water loss and in addition, vegetation can also mitigate drought effects by altering soil water distribution. Hence, partitioning of carbon and water fluxes between the soil and vegetation components is crucial to gain mechanistic understanding of vegetation effects on carbon and water cycling. However, the possible impact of herbaceous vegetation in savanna type ecosystems is often overlooked. Therefore, we aimed at quantifying understory vegetation effects on the water balance and productivity of a Mediterranean oak savanna. ET and net ecosystem CO2 exchange (NEE) were partitioned based on flux and stable oxygen isotope measurements and also rain infiltration was estimated. The understory vegetation contributed importantly to total ecosystem ET and GPP with a maximum of 43 and 51%, respectively. It reached water-use efficiencies (WUE; ratio of carbon gain by water loss) similar to cork-oak trees. The understory vegetation inhibited soil evaporation (E) and, although E was large during wet periods, it did not diminish WUE during water-limited times. The understory strongly increased soil water infiltration, specifically following major rain events. At the same time, the understory itself was vulnerable to drought, which led to an earlier senescence of the understory growing under trees as compared to open areas, due to competition for water. Thus, beneficial understory effects are dominant and contribute to the resilience of this ecosystem. At the same time the vulnerability of the understory to drought suggests that future climate change scenarios for the Mediterranean basin threaten understory development. This in turn will very likely diminish beneficial understory effects like infiltration and ground water recharge and therefore ecosystem resilience to drought. PMID

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

    PubMed

    Dubbert, Maren; Piayda, Arndt; Cuntz, Matthias; Correia, Alexandra C; Costa E Silva, Filipe; Pereira, Joao S; Werner, Christiane

    2014-01-01

    Semi-arid ecosystems contribute about 40% to global net primary production (GPP) even though water is a major factor limiting carbon uptake. Evapotranspiration (ET) accounts for up to 95% of the water loss and in addition, vegetation can also mitigate drought effects by altering soil water distribution. Hence, partitioning of carbon and water fluxes between the soil and vegetation components is crucial to gain mechanistic understanding of vegetation effects on carbon and water cycling. However, the possible impact of herbaceous vegetation in savanna type ecosystems is often overlooked. Therefore, we aimed at quantifying understory vegetation effects on the water balance and productivity of a Mediterranean oak savanna. ET and net ecosystem CO2 exchange (NEE) were partitioned based on flux and stable oxygen isotope measurements and also rain infiltration was estimated. The understory vegetation contributed importantly to total ecosystem ET and GPP with a maximum of 43 and 51%, respectively. It reached water-use efficiencies (WUE; ratio of carbon gain by water loss) similar to cork-oak trees. The understory vegetation inhibited soil evaporation (E) and, although E was large during wet periods, it did not diminish WUE during water-limited times. The understory strongly increased soil water infiltration, specifically following major rain events. At the same time, the understory itself was vulnerable to drought, which led to an earlier senescence of the understory growing under trees as compared to open areas, due to competition for water. Thus, beneficial understory effects are dominant and contribute to the resilience of this ecosystem. At the same time the vulnerability of the understory to drought suggests that future climate change scenarios for the Mediterranean basin threaten understory development. This in turn will very likely diminish beneficial understory effects like infiltration and ground water recharge and therefore ecosystem resilience to drought.

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

    PubMed Central

    Dubbert, Maren; Piayda, Arndt; Cuntz, Matthias; Correia, Alexandra C.; Costa e Silva, Filipe; Pereira, Joao S.; Werner, Christiane

    2014-01-01

    Semi-arid ecosystems contribute about 40% to global net primary production (GPP) even though water is a major factor limiting carbon uptake. Evapotranspiration (ET) accounts for up to 95% of the water loss and in addition, vegetation can also mitigate drought effects by altering soil water distribution. Hence, partitioning of carbon and water fluxes between the soil and vegetation components is crucial to gain mechanistic understanding of vegetation effects on carbon and water cycling. However, the possible impact of herbaceous vegetation in savanna type ecosystems is often overlooked. Therefore, we aimed at quantifying understory vegetation effects on the water balance and productivity of a Mediterranean oak savanna. ET and net ecosystem CO2 exchange (NEE) were partitioned based on flux and stable oxygen isotope measurements and also rain infiltration was estimated. The understory vegetation contributed importantly to total ecosystem ET and GPP with a maximum of 43 and 51%, respectively. It reached water-use efficiencies (WUE; ratio of carbon gain by water loss) similar to cork-oak trees. The understory vegetation inhibited soil evaporation (E) and, although E was large during wet periods, it did not diminish WUE during water-limited times. The understory strongly increased soil water infiltration, specifically following major rain events. At the same time, the understory itself was vulnerable to drought, which led to an earlier senescence of the understory growing under trees as compared to open areas, due to competition for water. Thus, beneficial understory effects are dominant and contribute to the resilience of this ecosystem. At the same time the vulnerability of the understory to drought suggests that future climate change scenarios for the Mediterranean basin threaten understory development. This in turn will very likely diminish beneficial understory effects like infiltration and ground water recharge and therefore ecosystem resilience to drought. PMID

  3. Extreme events and the terrestrial carbon cycle - mechanisms, processes and impacts on different ecosystem types-

    NASA Astrophysics Data System (ADS)

    Frank, Dorothea; Reichstein, Markus

    2013-04-01

    Severe droughts, heat waves, extreme precipitation or storms can impact the structure, composition, and functioning of terrestrial ecosystems and thus their carbon cycling and carbon sequestration potential. Besides direct impacts on the carbon fluxes of photosynthesis and respiration, extreme events may also trigger further partially lagged phenomena such as heat wave and drought related fires, pest and pathogen outbreaks following heavy storm caused windthrow or drought stress reduced plant health. Extreme events have the potential to cause rapid carbon losses from accumulated stocks, as well as long-lasting impacts on the carbon cycle due to direct and lagged effects on plant growth and mortality, going often beyond the duration of the extreme event itself. Extreme events have the potential to impact the terrestrial ecosystem carbon balance through a single factor or as a combination of factors, and forests, grassland and croplands are differently affected by the various types of extremes.

  4. How does wind-throw disturbance affect the carbon budget of an upland spruce forest ecosystem?

    NASA Astrophysics Data System (ADS)

    Lindauer, Matthias; Schmid, Hans Peter; Grote, Rüdiger; Mauder, Matthias; Wolpert, Benjamin; Steinbrecher, Rainer

    2014-05-01

    Forests, especially in mid-latitudes are generally designated as large carbon sinks. However, stand-replacing disturbance events like fires, insect-infestations, or severe wind-storms can shift an ecosystem from carbon sink to carbon source within short time and keep it as this for a long time. In Addition, extreme weather situations which promote the occurrence of ecosystem disturbances are likely to increase in the future due to climate change. The development and competition of different vegetation types (spruce vs. grass) as well as soil organic matter (SOM), and their contribution to the net ecosystem exchange (NEE), in such disturbed forest ecosystems are largely unknown. In a large wind-throw area (ca. 600 m diameter, due to cyclone Kyrill in January 2007) within a mature upland spruce forest, where dead-wood has not been removed, in the Bavarian Forest National Park (Lackenberg, 1308 m a.s.l., Bavaria, Germany), fluxes of CO2, water vapor and energy have been measured with the Eddy Covariance (EC) method since 2009. Model simulations (MoBiLE) were used to estimate the GPP components from trees and grassland as well as to differentiate between soil and plant respiration, and to get an idea about the long term behavior of the ecosystems carbon exchange. For 2009, 2010, 2011, 2012, and 2013 estimates of annual Net Ecosystem Exchange (NEE) showed that the wind-throw was a marked carbon source. However, the few remaining trees and newly emerging vegetation (grass, sparse young spruce, etc.) lead to an already strong Gross Ecosystem Production (GEP). Model simulations conformed well with the measurements. To our knowledge, we present the worldwide first long-term measurements of NEE within a non-cleared wind-throw-disturbed forest ecosystem.

  5. Ecosystem carbon exchange in response to locust outbreaks in a temperate steppe.

    PubMed

    Song, Jian; Wu, Dandan; Shao, Pengshuai; Hui, Dafeng; Wan, Shiqiang

    2015-06-01

    It is predicted that locust outbreaks will occur more frequently under future climate change scenarios, with consequent effects on ecological goods and services. A field manipulative experiment was conducted to examine the responses of gross ecosystem productivity (GEP), net ecosystem carbon dioxide (CO2) exchange (NEE), ecosystem respiration (ER), and soil respiration (SR) to locust outbreaks in a temperate steppe of northern China from 2010 to 2011. Two processes related to locust outbreaks, natural locust feeding and carcass deposition, were mimicked by clipping 80 % of aboveground biomass and adding locust carcasses, respectively. Ecosystem carbon (C) exchange (i.e., GEP, NEE, ER, and SR) was suppressed by locust feeding in 2010, but stimulated by locust carcass deposition in both years (except SR in 2011). Experimental locust outbreaks (i.e., clipping plus locust carcass addition) decreased GEP and NEE in 2010 whereas they increased GEP, NEE, and ER in 2011, leading to neutral changes in GEP, NEE, and SR across the 2 years. The responses of ecosystem C exchange could have been due to the changes in soil ammonium nitrogen, community cover, and aboveground net primary productivity. Our findings of the transient and neutral changes in ecosystem C cycling under locust outbreaks highlight the importance of resistance, resilience, and stability of the temperate steppe in maintaining reliable ecosystem services, and facilitate the projections of ecosystem functioning in response to natural disturbance and climate change.

  6. Effects of high CO2 levels on dynamic photosynthesis: carbon gain, mechanisms, and environmental interactions.

    PubMed

    Tomimatsu, Hajime; Tang, Yanhong

    2016-05-01

    Understanding the photosynthetic responses of terrestrial plants to environments with high levels of CO2 is essential to address the ecological effects of elevated atmospheric CO2. Most photosynthetic models used for global carbon issues are based on steady-state photosynthesis, whereby photosynthesis is measured under constant environmental conditions; however, terrestrial plant photosynthesis under natural conditions is highly dynamic, and photosynthetic rates change in response to rapid changes in environmental factors. To predict future contributions of photosynthesis to the global carbon cycle, it is necessary to understand the dynamic nature of photosynthesis in relation to high CO2 levels. In this review, we summarize the current body of knowledge on the photosynthetic response to changes in light intensity under experimentally elevated CO2 conditions. We found that short-term exposure to high CO2 enhances photosynthetic rate, reduces photosynthetic induction time, and reduces post-illumination CO2 burst, resulting in increased leaf carbon gain during dynamic photosynthesis. However, long-term exposure to high CO2 during plant growth has varying effects on dynamic photosynthesis. High levels of CO2 increase the carbon gain in photosynthetic induction in some species, but have no significant effects in other species. Some studies have shown that high CO2 levels reduce the biochemical limitation on RuBP regeneration and Rubisco activation during photosynthetic induction, whereas the effects of high levels of CO2 on stomatal conductance differ among species. Few studies have examined the influence of environmental factors on effects of high levels of CO2 on dynamic photosynthesis. We identified several knowledge gaps that should be addressed to aid future predictions of photosynthesis in high-CO2 environments. PMID:27094437

  7. Biomass burning in boreal forests and peatlands: Effects on ecosystem carbon losses and soil carbon stabilization as black carbon

    NASA Astrophysics Data System (ADS)

    Turetsky, M. R.; Kane, E. S.; Benscoter, B.

    2011-12-01

    Climate change has increased both annual area burned and the severity of biomass combustion in some boreal regions. For example, there has been a four-fold increase in late season fires in boreal Alaska over the last decade relative to the previous 50 years. Such changes in the fire regime are expected to stimulate ecosystem carbon losses through fuel combustion, reduced primary production, and increased decomposition. However, biomass burning also will influence the accumulation of black carbon in soils, which could promote long-term soil carbon sequestration. Variations in slope and aspect regulate soil temperatures and drainage conditions, and affect the development of permafrost and thick peat layers. Wet soil conditions in peatlands and permafrost forests often inhibit combustion during wildfires, leading to strong positive correlations between pre- and post- fire organic soil thickness that persist through multiple fire cycles. However, burning can occur in poorly drained ecosystems through smouldering combustion, which has implications for emission ratios of CO2:CH4:CO as well as black carbon formation. Our studies of combustion severity and black carbon concentrations in boreal soils show a negative relationship between concentrations of black carbon and organic carbon in soils post-fire. Relative to well drained stands, poorly drained sites with thick peat layers (such as north-facing stands) had less severe burning and low concentrations of black carbon in mineral soils post-fire. Conversely, drier forests lost a greater proportion of their organic soils during combustion but retained larger black carbon stocks following burning. Overall, we have quantified greater black carbon concentrations in surface mineral soil horizons than in organic soil horizons. This is surprising given that wildfires typically do not consume the entire organic soil layer in boreal forests, and could be indicative of the vulnerability of black carbon formed in organic horizons

  8. Carbon budget estimation of a subarctic catchment using a dynamic ecosystem model at high spatial resolution

    NASA Astrophysics Data System (ADS)

    Tang, J.; Miller, P. A.; Persson, A.; Olefeldt, D.; Pilesjo, P.; Heliasz, M.; Jackowicz-Korczynski, M.; Yang, Z.; Smith, B.; Callaghan, T. V.; Christensen, T. R.

    2015-05-01

    A large amount of organic carbon is stored in high-latitude soils. A substantial proportion of this carbon stock is vulnerable and may decompose rapidly due to temperature increases that are already greater than the global average. It is therefore crucial to quantify and understand carbon exchange between the atmosphere and subarctic/arctic ecosystems. In this paper, we combine an Arctic-enabled version of the process-based dynamic ecosystem model, LPJ-GUESS (version LPJG-WHyMe-TFM) with comprehensive observations of terrestrial and aquatic carbon fluxes to simulate long-term carbon exchange in a subarctic catchment at 50 m resolution. Integrating the observed carbon fluxes from aquatic systems with the modeled terrestrial carbon fluxes across the whole catchment, we estimate that the area is a carbon sink at present and will become an even stronger carbon sink by 2080, which is mainly a result of a projected densification of birch forest and its encroachment into tundra heath. However, the magnitudes of the modeled sinks are very dependent on future atmospheric CO2 concentrations. Furthermore, comparisons of global warming potentials between two simulations with and without CO2 increase since 1960 reveal that the increased methane emission from the peatland could double the warming effects of the whole catchment by 2080 in the absence of CO2 fertilization of the vegetation. This is the first process-based model study of the temporal evolution of a catchment-level carbon budget at high spatial resolution, including both terrestrial and aquatic carbon. Though this study also highlights some limitations in modeling subarctic ecosystem responses to climate change, such as aquatic system flux dynamics, nutrient limitation, herbivory and other disturbances, and peatland expansion, our study provides one process-based approach to resolve the complexity of carbon cycling in subarctic ecosystems while simultaneously pointing out the key model developments for capturing

  9. [Design of dynamic simulation system for carbon cycle in forest ecosystem].

    PubMed

    Zhu, Jian-Gang; Yu, Xin-Xiao; Zhang, Zhen-Ming; Wang, Chen; Gan, Jing; Wang, Xiao-Ping; Li, Jin-Hai

    2009-11-01

    Modeling techniques are indispensable for the researches on the carbon cycle of forest ecosystem. In this paper, a new general simulation system FORCASS (FORest CArbon Simulation System) was designed and developed under Simulink environment, with the objectives of modeling the carbon cycle dynamics of forest ecosystems. A comprehensive analysis on the framework, design solution, and development process showed that the FORCASS was feasible. This simulation system had the characteristics of 1) it divided the carbon storage in forest ecosystem into four compartments, i.e., vegetation, litter, soil, and animal, and took into account the carbon flows between the compartments, possessing high mechanism and easily to be comprehended, 2) it was a process-based system, taking the Richards growth function of vegetation component biomass carbon storage as the input to solve difference equations, and was easily to export the outputs such as net primary productivity (NPP) and net ecosystem productivity (NEP) at different stand ages, and 3) it had the explicit expansibility because it was developed based on a general framework for carbon cycle patterns.

  10. Losses and recovery of organic carbon from a seagrass ecosystem following disturbance.

    PubMed

    Macreadie, Peter I; Trevathan-Tackett, Stacey M; Skilbeck, Charles G; Sanderman, Jonathan; Curlevski, Nathalie; Jacobsen, Geraldine; Seymour, Justin R

    2015-10-22

    Seagrasses are among the Earth's most efficient and long-term carbon sinks, but coastal development threatens this capacity. We report new evidence that disturbance to seagrass ecosystems causes release of ancient carbon. In a seagrass ecosystem that had been disturbed 50 years ago, we found that soil carbon stocks declined by 72%, which, according to radiocarbon dating, had taken hundreds to thousands of years to accumulate. Disturbed soils harboured different benthic bacterial communities (according to 16S rRNA sequence analysis), with higher proportions of aerobic heterotrophs compared with undisturbed. Fingerprinting of the carbon (via stable isotopes) suggested that the contribution of autochthonous carbon (carbon produced through plant primary production) to the soil carbon pool was less in disturbed areas compared with seagrass and recovered areas. Seagrass areas that had recovered from disturbance had slightly lower (35%) carbon levels than undisturbed, but more than twice as much as the disturbed areas, which is encouraging for restoration efforts. Slow rates of seagrass recovery imply the need to transplant seagrass, rather than waiting for recovery via natural processes. This study empirically demonstrates that disturbance to seagrass ecosystems can cause release of ancient carbon, with potentially major global warming consequences. PMID:26490788

  11. Losses and recovery of organic carbon from a seagrass ecosystem following disturbance

    PubMed Central

    Macreadie, Peter I.; Trevathan-Tackett, Stacey M.; Skilbeck, Charles G.; Sanderman, Jonathan; Curlevski, Nathalie; Jacobsen, Geraldine; Seymour, Justin R.

    2015-01-01

    Seagrasses are among the Earth's most efficient and long-term carbon sinks, but coastal development threatens this capacity. We report new evidence that disturbance to seagrass ecosystems causes release of ancient carbon. In a seagrass ecosystem that had been disturbed 50 years ago, we found that soil carbon stocks declined by 72%, which, according to radiocarbon dating, had taken hundreds to thousands of years to accumulate. Disturbed soils harboured different benthic bacterial communities (according to 16S rRNA sequence analysis), with higher proportions of aerobic heterotrophs compared with undisturbed. Fingerprinting of the carbon (via stable isotopes) suggested that the contribution of autochthonous carbon (carbon produced through plant primary production) to the soil carbon pool was less in disturbed areas compared with seagrass and recovered areas. Seagrass areas that had recovered from disturbance had slightly lower (35%) carbon levels than undisturbed, but more than twice as much as the disturbed areas, which is encouraging for restoration efforts. Slow rates of seagrass recovery imply the need to transplant seagrass, rather than waiting for recovery via natural processes. This study empirically demonstrates that disturbance to seagrass ecosystems can cause release of ancient carbon, with potentially major global warming consequences. PMID:26490788

  12. Losses and recovery of organic carbon from a seagrass ecosystem following disturbance.

    PubMed

    Macreadie, Peter I; Trevathan-Tackett, Stacey M; Skilbeck, Charles G; Sanderman, Jonathan; Curlevski, Nathalie; Jacobsen, Geraldine; Seymour, Justin R

    2015-10-22

    Seagrasses are among the Earth's most efficient and long-term carbon sinks, but coastal development threatens this capacity. We report new evidence that disturbance to seagrass ecosystems causes release of ancient carbon. In a seagrass ecosystem that had been disturbed 50 years ago, we found that soil carbon stocks declined by 72%, which, according to radiocarbon dating, had taken hundreds to thousands of years to accumulate. Disturbed soils harboured different benthic bacterial communities (according to 16S rRNA sequence analysis), with higher proportions of aerobic heterotrophs compared with undisturbed. Fingerprinting of the carbon (via stable isotopes) suggested that the contribution of autochthonous carbon (carbon produced through plant primary production) to the soil carbon pool was less in disturbed areas compared with seagrass and recovered areas. Seagrass areas that had recovered from disturbance had slightly lower (35%) carbon levels than undisturbed, but more than twice as much as the disturbed areas, which is encouraging for restoration efforts. Slow rates of seagrass recovery imply the need to transplant seagrass, rather than waiting for recovery via natural processes. This study empirically demonstrates that disturbance to seagrass ecosystems can cause release of ancient carbon, with potentially major global warming consequences.

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

    PubMed Central

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

    2013-01-01

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

  14. Carbon storages in plantation ecosystems in sand source areas of north Beijing, China.

    PubMed

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

    2013-01-01

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

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

    USGS Publications Warehouse

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

    2000-01-01

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

  16. Carbon Offset Forestry: Forecasting Ecosystem Effects (COFFEE) Project Implementation Plan

    EPA Science Inventory

    COFFEE will evaluate the environmental impacts of implementing various COF practices by using the amount of total ecosystem C (TEC) sequestered in forests as the integrative response metric. These evaluations will be done for current-climate and future-climate scenarios and will...

  17. Stomatal limitation to carbon gain in Paphiopedilum sp. (Orchidaceae) and its reversal by blue light

    SciTech Connect

    Zeiger, E.; Grivet, C.; Assmann, S.M.; Dietzer, G.F.; Hannegan, M.W.

    1985-02-01

    Leaves from Paphiopedilum sp. (Orchidaceae) having achlorophyllous stomata, show reduced levels of stomatal conductance when irradiated with red light, as compared with either the related, chlorophyllous genus Phragmipedium or with their response to blue light. These reduced levels of stomatal conductance, and the failure of isolated Paphiopedilum stomata to open under red irradiation indicates that the small stomatal response measured in the intact leaf under red light is indirect. The overall low levels of stomatal conductance observed in Paphiopedilum leaves under most growing conditions and their capacity to increase stomatal conductance in response to blue light suggested that growth and carbon gain in Paphiopedilum could be enhanced in a blue light-enriched environment. To test that hypothesis, plants of Paphiopedilum acmodontum were grown in controlled growth chambers under daylight fluorescent light, with or without blue light supplementation. Blue light enrichment resulted in significantly higher growth rates over a 3 to 4 week growing period, with all evidence indicating that the blue light effect was a stomatal response. Manipulations of stomatal properties aimed at long-term carbon gains could have agronomic applications.

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

    NASA Astrophysics Data System (ADS)

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

    2008-03-01

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

  19. A carbon budget of Arizona: Comparing Natural Ecosystems with Emissions from Human Activities

    NASA Astrophysics Data System (ADS)

    Ford, A. C.; Finley, B. K.; Koch, G. W.; Hungate, B. A.

    2011-12-01

    A carbon budget of Arizona was constructed to examine the potential for carbon uptake by the state's ecosystems to mitigate human-caused emissions of greenhouse gases. The NASA-CASA (Carnegie Ames Stanford Approach) carbon flux model was used to estimate annual ecosystem CO2 exchange and the State's 2006 greenhouse gas inventory provided data on emissions from transportation, industry, waste, agriculture, electricity, industrial, and residential fuel use. The net carbon flux from primary production in the eight major land resource areas in the state averaged -1.56 million metric tons of carbon (MMTC) per year between 2001 and 2004. This net uptake from the atmosphere amounts to only 1.5% of statewide anthropogenic emissions of 99 MMTCE per year. Given this large imbalance and that projected climate trends for the region are likely to reduce C stocks in the state's forest and woodland ecosystems, land management to promote ecosystem carbon uptake is not a realistic solution to mitigate Arizona's anthropogenic greenhouse gas emissions.

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

    PubMed

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

    2004-10-01

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

  1. Pervasive Drought Legacy Effects in Forest Ecosystems and their Carbon Cycle Implications

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    The impacts of climate extremes on terrestrial ecosystems are poorly understood but central 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 basic plant physiological understanding. We examine the recovery of tree stem growth after severe drought at 1,338 forest sites globally comprising 49,339 site-years and compare it to simulated recovery in climate-vegetation models. We find pervasive and substantial "legacy effects" of reduced growth and incomplete recovery for 1-4 years after severe drought, and that legacy effects are most prevalent in dry ecosystems, Pinaceae, and species with low hydraulic safety margins. In contrast, no or limited legacy effects are simulated in current climate-vegetation models after drought. Our results highlight hysteresis in ecosystem carbon cycling and delayed recovery from climate extremes.

  2. FOREST ECOLOGY. Pervasive drought legacies in forest ecosystems and their implications for carbon cycle models.

    PubMed

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

    2015-07-31

    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 stem growth in trees after severe drought at 1338 forest sites across the globe, comprising 49,339 site-years, and compared the results with simulated recovery in climate-vegetation models. We found pervasive and substantial "legacy effects" of reduced growth and incomplete recovery for 1 to 4 years after severe drought. Legacy effects were most prevalent in dry ecosystems, among Pinaceae, and among species with low hydraulic safety margins. In contrast, limited or no legacy effects after drought were simulated by current climate-vegetation models. Our results highlight hysteresis in ecosystem-level carbon cycling and delayed recovery from climate extremes. PMID:26228147

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

    SciTech Connect

    King, A W

    1991-12-31

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

  4. Contribution of semi-arid ecosystems to interannual variability of the global carbon cycle.

    PubMed

    Poulter, Benjamin; Frank, David; Ciais, Philippe; Myneni, Ranga B; Andela, Niels; Bi, Jian; Broquet, Gregoire; Canadell, Josep G; Chevallier, Frederic; Liu, Yi Y; Running, Steven W; Sitch, Stephen; van der Werf, Guido R

    2014-05-29

    The land and ocean act as a sink for fossil-fuel emissions, thereby slowing the rise of atmospheric carbon dioxide concentrations. Although the uptake of carbon by oceanic and terrestrial processes has kept pace with accelerating carbon dioxide emissions until now, atmospheric carbon dioxide concentrations exhibit a large variability on interannual timescales, considered to be driven primarily by terrestrial ecosystem processes dominated by tropical rainforests. We use a terrestrial biogeochemical model, atmospheric carbon dioxide inversion and global carbon budget accounting methods to investigate the evolution of the terrestrial carbon sink over the past 30 years, with a focus on the underlying mechanisms responsible for the exceptionally large land carbon sink reported in 2011 (ref. 2). Here we show that our three terrestrial carbon sink estimates are in good agreement and support the finding of a 2011 record land carbon sink. Surprisingly, we find that the global carbon sink anomaly was driven by growth of semi-arid vegetation in the Southern Hemisphere, with almost 60 per cent of carbon uptake attributed to Australian ecosystems, where prevalent La Niña conditions caused up to six consecutive seasons of increased precipitation. In addition, since 1981, a six per cent expansion of vegetation cover over Australia was associated with a fourfold increase in the sensitivity of continental net carbon uptake to precipitation. Our findings suggest that the higher turnover rates of carbon pools in semi-arid biomes are an increasingly important driver of global carbon cycle inter-annual variability and that tropical rainforests may become less relevant drivers in the future. More research is needed to identify to what extent the carbon stocks accumulated during wet years are vulnerable to rapid decomposition or loss through fire in subsequent years.

  5. Carbon Sequestration in Semi-arid Ecosystems: Potential Benefits of Sagebrush Restoration

    NASA Astrophysics Data System (ADS)

    Austreng, A. C.; Olin, P. H.; Hummer, A.; Pierce, J. L.; deGraaff, M.; Benner, S. G.

    2011-12-01

    The results of our work indicate that sagebrush restoration may have the potential to offset 23% of annual US carbon emissions. Invasion of native sagebrush (Artemisia tridentata) communities by cheatgrass (Bromus tectorum) in semi-arid ecosystems of the Intermountain Northwest is degrading ecosystem structure and function and can significantly decrease soil carbon contents. Remediation of invaded sagebrush-steppe communities may be accomplished by replacing cheatgrass with bunchgrass (Agropyron cristatum) and subsequently reestablishing native sagebrush. To evaluate how this remedial strategy affects soil carbon contents, we have quantified carbon associated with root biomass and soils under adjacent cheatgrass, bunchgrass and sagebrush communities at a site in the central Snake River Plain of southern Idaho. A large soil carbon dataset (n = 850) was generated allowing statistical distinction of belowground carbon pools (biomass and soil C). Our study led to two main results: (1) Soil carbon stores were greatest under sagebrush and lowest under cheatgrass (67 and 35 t C per hectare, respectively). Soil carbon was found to be significantly greater beneath sagebrush compared to cheatgrass (~90% increase) at all depths throughout a 60cm profile. (2) Belowground biomass was greatest under sagebrush and lowest beneath cheatgrass (31 and 14 t per hectare, respectively), which accounted for approximately 20% of the total increase in belowground carbon beneath sagebrush. The results of our work indicate that this stepwise reclamation strategy will produce significant increases in soil carbon storage with conversion of cheatgrass to bunchgrass facilitating carbon storage benefits of ~15 t C per hectare and a bunchgrass to native sagebrush benefit of ~17 t C per hectare. Extending these results to all ~10 million ha of cheatgrass-infested ecosystems in the Great Basin, suggests that sagebrush restoration may have the potential to compensate for 23% of US annual carbon

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

    USGS Publications Warehouse

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

    2013-01-01

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

  7. Growing season and spatial variations of carbon fluxes of Arctic and boreal ecosystems in Alaska (USA).

    PubMed

    Ueyama, Masahito; Iwata, Hiroki; Harazono, Yoshinobu; Euskirchen, Eugénie S; Oechel, Walter C; Zona, Donatella

    2013-12-01

    To better understand the spatial and temporal dynamics of CO2 exchange between Arctic ecosystems and the atmosphere, we synthesized CO2 flux data, measured in eight Arctic tundra and five boreal ecosystems across Alaska (USA) and identified growing season and spatial variations of the fluxes and environmental controlling factors. For the period examined, all of the boreal and seven of the eight Arctic tundra ecosystems acted as CO2 sinks during the growing season. Seasonal patterns of the CO2 fluxes were mostly determined by air temperature, except ecosystem respiration (RE) of tundra. For the tundra ecosystems, the spatial variation of gross primary productivity (GPP) and net CO2 sink strength were explained by growing season length, whereas RE increased with growing degree days. For boreal ecosystems, the spatial variation of net CO2 sink strength was mostly determined by recovery of GPP from fire disturbance. Satellite-derived leaf area index (LAI) was a better index to explain the spatial variations of GPP and NEE of the ecosystems in Alaska than were the normalized difference vegetation index (NDVI) and enhanced vegetation index (EVI). Multiple regression models using growing degree days, growing season length, and satellite-derived LAI explained much of the spatial variation in GPP and net CO2 exchange among the tundra and boreal ecosystems. The high sensitivity of the sink strength to growing season length indicated that the tundra ecosystem could increase CO2 sink strength under expected future warming, whereas ecosystem compositions associated with fire disturbance could play a major role in carbon release from boreal ecosystems.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  9. Protecting terrestrial ecosystems and the climate through a global carbon market.

    PubMed

    Bonnie, Robert; Carey, Melissa; Petsonk, Annie

    2002-08-15

    Protecting terrestrial ecosystems through international environmental laws requires the development of economic mechanisms that value the Earth's natural systems. The major international treaties to address ecosystem protection lack meaningful binding obligations and the requisite financial instruments to affect large-scale conservation. The Kyoto Protocol's emissions-trading framework creates economic incentives for nations to reduce greenhouse-gas (GHG) emissions cost effectively. Incorporating GHG impacts from land-use activities into this system would create a market for an important ecosystem service provided by forests and agricultural lands: sequestration of atmospheric carbon. This would spur conservation efforts while reducing the 20% of anthropogenic CO(2) emissions produced by land-use change, particularly tropical deforestation. The Kyoto negotiations surrounding land-use activities have been hampered by a lack of robust carbon inventory data. Moreover, the Protocol's provisions agreed to in Kyoto made it difficult to incorporate carbon-sequestering land-use activities into the emissions-trading framework without undermining the atmospheric GHG reductions contemplated in the treaty. Subsequent negotiations since 1997 failed to produce a crediting system that provides meaningful incentives for enhanced carbon sequestration. Notably, credit for reducing rates of tropical deforestation was explicitly excluded from the Protocol. Ultimately, an effective GHG emissions-trading framework will require full carbon accounting for all emissions and sequestration from terrestrial ecosystems. Improved inventory systems and capacity building for developing nations will, therefore, be necessary.

  10. Surficial gains and subsoil losses of soil carbon and nitrogen during secondary forest development.

    PubMed

    Mobley, Megan L; Lajtha, Kate; Kramer, Marc G; Bacon, Allan R; Heine, Paul R; Richter, Daniel Deb

    2015-02-01

    Reforestation of formerly cultivated land is widely understood to accumulate above- and belowground detrital organic matter pools, including soil organic matter. However, during 40 years of study of reforestation in the subtropical southeastern USA, repeated observations of above- and belowground carbon documented that significant gains in soil organic matter (SOM) in surface soils (0-7.5 cm) were offset by significant SOM losses in subsoils (35-60 cm). Here, we extended the observation period in this long-term experiment by an additional decade, and used soil fractionation and stable isotopes and radioisotopes to explore changes in soil organic carbon and soil nitrogen that accompanied nearly 50 years of loblolly pine secondary forest development. We observed that accumulations of mineral soil C and N from 0 to 7.5 cm were almost entirely due to accumulations of light-fraction SOM. Meanwhile, losses of soil C and N from mineral soils at 35 to 60 cm were from SOM associated with silt and clay-sized particles. Isotopic signatures showed relatively large accumulations of forest-derived carbon in surface soils, and little to no accumulation of forest-derived carbon in subsoils. We argue that the land use change from old field to secondary forest drove biogeochemical and hydrological changes throughout the soil profile that enhanced microbial activity and SOM decomposition in subsoils. However, when the pine stands aged and began to transition to mixed pines and hardwoods, demands on soil organic matter for nutrients to support aboveground growth eased due to pine mortality, and subsoil organic matter levels stabilized. This study emphasizes the importance of long-term experiments and deep measurements when characterizing soil C and N responses to land use change and the remarkable paucity of such long-term soil data deeper than 30 cm. PMID:25155991

  11. Surficial gains and subsoil losses of soil carbon and nitrogen during secondary forest development.

    PubMed

    Mobley, Megan L; Lajtha, Kate; Kramer, Marc G; Bacon, Allan R; Heine, Paul R; Richter, Daniel Deb

    2015-02-01

    Reforestation of formerly cultivated land is widely understood to accumulate above- and belowground detrital organic matter pools, including soil organic matter. However, during 40 years of study of reforestation in the subtropical southeastern USA, repeated observations of above- and belowground carbon documented that significant gains in soil organic matter (SOM) in surface soils (0-7.5 cm) were offset by significant SOM losses in subsoils (35-60 cm). Here, we extended the observation period in this long-term experiment by an additional decade, and used soil fractionation and stable isotopes and radioisotopes to explore changes in soil organic carbon and soil nitrogen that accompanied nearly 50 years of loblolly pine secondary forest development. We observed that accumulations of mineral soil C and N from 0 to 7.5 cm were almost entirely due to accumulations of light-fraction SOM. Meanwhile, losses of soil C and N from mineral soils at 35 to 60 cm were from SOM associated with silt and clay-sized particles. Isotopic signatures showed relatively large accumulations of forest-derived carbon in surface soils, and little to no accumulation of forest-derived carbon in subsoils. We argue that the land use change from old field to secondary forest drove biogeochemical and hydrological changes throughout the soil profile that enhanced microbial activity and SOM decomposition in subsoils. However, when the pine stands aged and began to transition to mixed pines and hardwoods, demands on soil organic matter for nutrients to support aboveground growth eased due to pine mortality, and subsoil organic matter levels stabilized. This study emphasizes the importance of long-term experiments and deep measurements when characterizing soil C and N responses to land use change and the remarkable paucity of such long-term soil data deeper than 30 cm.

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

    PubMed

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

    2010-05-01

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

  13. Carbon Transformations Following Landscape Fire: Carbon Loss, Mortality, and Ecosystem Recovery Across the Metolius Watershed, Oregon

    NASA Astrophysics Data System (ADS)

    Meigs, G. W.; Law, B. E.

    2008-12-01

    Since 2002, mixed-severity wildfires have burned more than 65,000 ha in the Eastern Cascades of Oregon. This study quantifies changes in aboveground carbon pools and estimates carbon balance and ecosystem recovery 4-5 years following fire. We integrate results from 64 1-ha field plots, forest inventories, and remote sensing data and focus on four fires that burned 35% of the Metolius Watershed (115,000 ha) in 2002 and 2003. We used a stratified random factorial design across three landscape gradients: 1. forest type (ponderosa pine (PP) and mixed-conifer (MC)); 2. burn severity (unburned, low, moderate, and high overstory mortality); 3. prefire biomass (low to high). The fires created a complex mosaic of burn severity and associated overstory and understory responses. Total aboveground mass was 75% greater in MC forests than in PP forests (mean: 10.21 vs. 5.85 kg C m-2, p < 0.001), and trees dominated both live and dead C pools. Across both forest types, mean aboveground dead mass increased twofold in high severity stands compared to low severity stands. Basal area (BA) mortality was an effective ground-based metric of burn severity that validated the remotely-sensed dNBR severity map. BA mortality ranged from 14% in low severity PP stands to 100% in high severity PP stands, with parallel patterns in MC stands. Postfire conifer seedling density was negatively correlated with burn severity (median range: 10,223 seedlings ha-1 in low severity MC to zero seedlings ha-1in high severity PP), while shrub cover and biomass showed the opposite trend. These diverse understory responses demonstrate a wide range of trajectories across the mixed-severity mosaic that, coupled with overstory productivity and decomposition, will drive short- and long-term patterns of C loss and recovery. We used these field estimates of fire effects to: 1. validate a novel Landsat trajectory-based change detection that measures multiple disturbances, partial disturbance, and recovery and 2

  14. Tracing pyrogenic carbon (PyC) beyond terrestrial ecosystems

    NASA Astrophysics Data System (ADS)

    Wiedemeier, Daniel B.; Eglinton, Timothy I.; Hanke, Ulrich M.; Schmidt, Michael W. I.

    2015-04-01

    Combustion-derived, pyrogenic carbon (PyC) is a persistent organic carbon fraction. Due to its aromatic and condensed nature (Wiedemeier et al., 2015), it is relatively resistant against chemical and biological degradation in the environment, leading to a comparatively slow turnover, which would support carbon sequestration. PyC is produced on large scales (hundreds of teragrams) in biomass burning events such as wildfires, and by combustion of fossil fuel in industry and traffic. PyC is an inherently terrestrial product and thus has predominantly been investigated in soils and the atmosphere. Much fewer studies are available about the subsequent transport of PyC to rivers and oceans. Recently, awareness has been rising about the mobility of PyC from terrestrial to marine systems and its fate in coastal and abyssal sediments was recognized (Mitra et al, 2014). It is therefore crucial to extend our knowledge about the PyC cycle by tracing PyC through all environmental compartments. By comparing its biogeochemical behavior and budgets to that of other forms of organic carbon, it will eventually be possible to elucidate PyC's total spatiotemporal contribution to carbon sequestration. In this study, we are using a state-of-the-art PyC molecular marker method (Wiedemeier et al., 2013, Gierga et al., 2014) to trace quantity, quality as well as 13C and 14C signature of PyC in selected major river systems around the globe (Godavari, Yellow, Danube, Fraser, Mackenzie and Yukon river). Different size fractions of particulate suspended sediment are being analyzed and compared across a north-south gradient. Previous studies suggested a distinct relationship between the age of plant-derived suspended carbon and the latitude of the river system, indicating slower cycling of plant biomarkers in higher latitudes. We discuss this pattern with respect to PyC, its isotopic signature and quality and the resulting implications for the global carbon and PyC cycle. Gierga et al., 2014

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

    USGS Publications Warehouse

    Liu, J.; Vogelmann, J.E.; Zhu, Z.; Key, C.H.; Sleeter, B.M.; Price, D.T.; Chen, J.M.; Cochrane, M.A.; Eidenshink, J.C.; Howard, S.M.; Bliss, N.B.; Jiang, H.

    2011-01-01

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

  16. Spatial and temporal patterns of carbon storage in forest ecosystems on Hainan island, southern China.

    PubMed

    Ren, Hai; Li, Linjun; Liu, Qiang; Wang, Xu; Li, Yide; Hui, Dafeng; Jian, Shuguang; Wang, Jun; Yang, Huai; Lu, Hongfang; Zhou, Guoyi; Tang, Xuli; Zhang, Qianmei; Wang, Dong; Yuan, Lianlian; Chen, Xubing

    2014-01-01

    Spatial and temporal patterns of carbon (C) storage in forest ecosystems significantly affect the terrestrial C budget, but such patterns are unclear in the forests in Hainan Province, the largest tropical island in China. Here, we estimated the spatial and temporal patterns of C storage from 1993-2008 in Hainan's forest ecosystems by combining our measured data with four consecutive national forest inventories data. Forest coverage increased from 20.7% in the 1950s to 56.4% in the 2010s. The average C density of 163.7 Mg C/ha in Hainan's forest ecosystems in this study was slightly higher than that of China's mainland forests, but was remarkably lower than that in the tropical forests worldwide. Total forest ecosystem C storage in Hainan increased from 109.51 Tg in 1993 to 279.17 Tg in 2008. Soil C accounted for more than 70% of total forest ecosystem C. The spatial distribution of forest C storage in Hainan was uneven, reflecting differences in land use change and forest management. The potential carbon sequestration of forest ecosystems was 77.3 Tg C if all forested lands were restored to natural tropical forests. To increase the C sequestration potential on Hainan Island, future forest management should focus on the conservation of natural forests, selection of tree species, planting of understory species, and implementation of sustainable practices.

  17. Ecosystem carbon stocks and sequestration potential of federal lands across the conterminous United States

    USGS Publications Warehouse

    Tan, Zhengxi; Liu, Shuguang; Sohl, Terry L.; Wu, Yiping; Young, Claudia J.

    2015-01-01

    Federal lands across the conterminous United States (CONUS) account for 23.5% of the CONUS terrestrial area but have received no systematic studies on their ecosystem carbon (C) dynamics and contribution to the national C budgets. The methodology for US Congress-mandated national biological C sequestration potential assessment was used to evaluate ecosystem C dynamics in CONUS federal lands at present and in the future under three Intergovernmental Panel on Climate Change Special Report on Emission Scenarios (IPCC SRES) A1B, A2, and B1. The total ecosystem C stock was estimated as 11,613 Tg C in 2005 and projected to be 13,965 Tg C in 2050, an average increase of 19.4% from the baseline. The projected annual C sequestration rate (in kilograms of carbon per hectare per year) from 2006 to 2050 would be sinks of 620 and 228 for forests and grasslands, respectively, and C sources of 13 for shrublands. The federal lands’ contribution to the national ecosystem C budget could decrease from 23.3% in 2005 to 20.8% in 2050. The C sequestration potential in the future depends not only on the footprint of individual ecosystems but also on each federal agency’s land use and management. The results presented here update our current knowledge about the baseline ecosystem C stock and sequestration potential of federal lands, which would be useful for federal agencies to decide management practices to achieve the national greenhouse gas (GHG) mitigation goal.

  18. Ecosystem carbon stocks and sequestration potential of federal lands across the conterminous United States

    PubMed Central

    Tan, Zhengxi; Liu, Shuguang; Sohl, Terry L.; Wu, Yiping; Young, Claudia J.

    2015-01-01

    Federal lands across the conterminous United States (CONUS) account for 23.5% of the CONUS terrestrial area but have received no systematic studies on their ecosystem carbon (C) dynamics and contribution to the national C budgets. The methodology for US Congress-mandated national biological C sequestration potential assessment was used to evaluate ecosystem C dynamics in CONUS federal lands at present and in the future under three Intergovernmental Panel on Climate Change Special Report on Emission Scenarios (IPCC SRES) A1B, A2, and B1. The total ecosystem C stock was estimated as 11,613 Tg C in 2005 and projected to be 13,965 Tg C in 2050, an average increase of 19.4% from the baseline. The projected annual C sequestration rate (in kilograms of carbon per hectare per year) from 2006 to 2050 would be sinks of 620 and 228 for forests and grasslands, respectively, and C sources of 13 for shrublands. The federal lands’ contribution to the national ecosystem C budget could decrease from 23.3% in 2005 to 20.8% in 2050. The C sequestration potential in the future depends not only on the footprint of individual ecosystems but also on each federal agency’s land use and management. The results presented here update our current knowledge about the baseline ecosystem C stock and sequestration potential of federal lands, which would be useful for federal agencies to decide management practices to achieve the national greenhouse gas (GHG) mitigation goal. PMID:26417074

  19. Ecosystem carbon stocks and sequestration potential of federal lands across the conterminous United States.

    PubMed

    Tan, Zhengxi; Liu, Shuguang; Sohl, Terry L; Wu, Yiping; Young, Claudia J

    2015-10-13

    Federal lands across the conterminous United States (CONUS) account for 23.5% of the CONUS terrestrial area but have received no systematic studies on their ecosystem carbon (C) dynamics and contribution to the national C budgets. The methodology for US Congress-mandated national biological C sequestration potential assessment was used to evaluate ecosystem C dynamics in CONUS federal lands at present and in the future under three Intergovernmental Panel on Climate Change Special Report on Emission Scenarios (IPCC SRES) A1B, A2, and B1. The total ecosystem C stock was estimated as 11,613 Tg C in 2005 and projected to be 13,965 Tg C in 2050, an average increase of 19.4% from the baseline. The projected annual C sequestration rate (in kilograms of carbon per hectare per year) from 2006 to 2050 would be sinks of 620 and 228 for forests and grasslands, respectively, and C sources of 13 for shrublands. The federal lands' contribution to the national ecosystem C budget could decrease from 23.3% in 2005 to 20.8% in 2050. The C sequestration potential in the future depends not only on the footprint of individual ecosystems but also on each federal agency's land use and management. The results presented here update our current knowledge about the baseline ecosystem C stock and sequestration potential of federal lands, which would be useful for federal agencies to decide management practices to achieve the national greenhouse gas (GHG) mitigation goal. PMID:26417074

  20. Ecosystem carbon stocks and sequestration potential of federal lands across the conterminous United States.

    PubMed

    Tan, Zhengxi; Liu, Shuguang; Sohl, Terry L; Wu, Yiping; Young, Claudia J

    2015-10-13

    Federal lands across the conterminous United States (CONUS) account for 23.5% of the CONUS terrestrial area but have received no systematic studies on their ecosystem carbon (C) dynamics and contribution to the national C budgets. The methodology for US Congress-mandated national biological C sequestration potential assessment was used to evaluate ecosystem C dynamics in CONUS federal lands at present and in the future under three Intergovernmental Panel on Climate Change Special Report on Emission Scenarios (IPCC SRES) A1B, A2, and B1. The total ecosystem C stock was estimated as 11,613 Tg C in 2005 and projected to be 13,965 Tg C in 2050, an average increase of 19.4% from the baseline. The projected annual C sequestration rate (in kilograms of carbon per hectare per year) from 2006 to 2050 would be sinks of 620 and 228 for forests and grasslands, respectively, and C sources of 13 for shrublands. The federal lands' contribution to the national ecosystem C budget could decrease from 23.3% in 2005 to 20.8% in 2050. The C sequestration potential in the future depends not only on the footprint of individual ecosystems but also on each federal agency's land use and management. The results presented here update our current knowledge about the baseline ecosystem C stock and sequestration potential of federal lands, which would be useful for federal agencies to decide management practices to achieve the national greenhouse gas (GHG) mitigation goal.

  1. Spatial and Temporal Patterns of Carbon Storage in Forest Ecosystems on Hainan Island, Southern China

    PubMed Central

    Tang, Xuli; Zhang, Qianmei; Wang, Dong; Yuan, Lianlian; Chen, Xubing

    2014-01-01

    Spatial and temporal patterns of carbon (C) storage in forest ecosystems significantly affect the terrestrial C budget, but such patterns are unclear in the forests in Hainan Province, the largest tropical island in China. Here, we estimated the spatial and temporal patterns of C storage from 1993–2008 in Hainan's forest ecosystems by combining our measured data with four consecutive national forest inventories data. Forest coverage increased from 20.7% in the 1950s to 56.4% in the 2010s. The average C density of 163.7 Mg C/ha in Hainan's forest ecosystems in this study was slightly higher than that of China's mainland forests, but was remarkably lower than that in the tropical forests worldwide. Total forest ecosystem C storage in Hainan increased from 109.51 Tg in 1993 to 279.17 Tg in 2008. Soil C accounted for more than 70% of total forest ecosystem C. The spatial distribution of forest C storage in Hainan was uneven, reflecting differences in land use change and forest management. The potential carbon sequestration of forest ecosystems was 77.3 Tg C if all forested lands were restored to natural tropical forests. To increase the C sequestration potential on Hainan Island, future forest management should focus on the conservation of natural forests, selection of tree species, planting of understory species, and implementation of sustainable practices. PMID:25229628

  2. Use of Remote Sensing Products in a Terrestrial Ecosystems Verified Full Carbon Account: Experiences from Russia

    NASA Astrophysics Data System (ADS)

    Shvidenko, Anatoly; Schepaschenko, Dmitry; McCallum, Ian; Santoro, Maurizio; Schmullius, Christine

    2011-01-01

    The paper considers the specifics, strengths and weaknesses of available remote sensing products within major steps and modules of a verified terrestrial ecosystems full carbon account (FCA) of Russia’s land. The methodology used is based on system integration of all available information sources and major methods of carbon accounting using IIASA’s landscape-ecosystem approach for overall designing of the account. A multi-sensor remote sensing concept is a corner stone of the methodology being substantially used for (1) georeferencing and parametrization of land cover and its change, (2) assessment of important biophysical and ecological parameters of ecosystems and landscapes, and (3) assessment of the impacts of environmental conditions on ecosystem productivity and disturbance regimes. System integration and mutual constraints of remote sensing and ground information allow for substantially decreasing uncertainty of the FCA. In the Russian case-study, the net ecosystem carbon balance of Russia for an individual year (2009) is estimated with uncertainty at 25-30% (CI 0.9), that presumably should satisfy current requirements to the FCA at the national (continental) scale.

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

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

  5. Counterintuitive carbon-to-nutrient coupling in an Arctic pelagic ecosystem.

    PubMed

    Thingstad, T F; Bellerby, R G J; Bratbak, G; Børsheim, K Y; Egge, J K; Heldal, M; Larsen, A; Neill, C; Nejstgaard, J; Norland, S; Sandaa, R-A; Skjoldal, E F; Tanaka, T; Thyrhaug, R; Töpper, B

    2008-09-18

    Predicting the ocean's role in the global carbon cycle requires an understanding of the stoichiometric coupling between carbon and growth-limiting elements in biogeochemical processes. A recent addition to such knowledge is that the carbon/nitrogen ratio of inorganic consumption and release of dissolved organic matter may increase in a high-CO(2) world. This will, however, yield a negative feedback on atmospheric CO(2) only if the extra organic material escapes mineralization within the photic zone. Here we show, in the context of an Arctic pelagic ecosystem, how the fate and effects of added degradable organic carbon depend critically on the state of the microbial food web. When bacterial growth rate was limited by mineral nutrients, extra organic carbon accumulated in the system. When bacteria were limited by organic carbon, however, addition of labile dissolved organic carbon reduced phytoplankton biomass and activity and also the rate at which total organic carbon accumulated, explained as the result of stimulated bacterial competition for mineral nutrients. This counterintuitive 'more organic carbon gives less organic carbon' effect was particularly pronounced in diatom-dominated systems where the carbon/mineral nutrient ratio in phytoplankton production was high. Our results highlight how descriptions of present and future states of the oceanic carbon cycle require detailed understanding of the stoichiometric coupling between carbon and growth-limiting mineral nutrients in both autotrophic and heterotrophic processes.

  6. Fighting carbon loss of degraded peatlands by jump-starting ecosystem functioning with ecological restoration.

    PubMed

    Kareksela, Santtu; Haapalehto, Tuomas; Juutinen, Riikka; Matilainen, Rose; Tahvanainen, Teemu; Kotiaho, Janne S

    2015-12-15

    Degradation of ecosystems is a great concern on the maintenance of biodiversity and ecosystem services. Ecological restoration fights degradation aiming at the recovery of ecosystem functions such as carbon (C) sequestration and ecosystem structures like plant communities responsible for the C sequestration function. We selected 38 pristine, drained and restored boreal peatland sites in Finland and asked i) what is the long-term effect of drainage on the peatland surface layer C storage, ii) can restoration recover ecosystem functioning (surface layer growth) and structure (plant community composition) and iii) is the recovery of the original structure needed for the recovery of ecosystem functions? We found that drainage had resulted in a substantial net loss of C from surface layer of drained sites. Restoration was successful in regaining natural growth rate in the peatland surface layer already within 5 years after restoration. However, the regenerated surface layer sequestered C at a mean rate of 116.3 g m(-2) yr(-1) (SE 12.7), when a comparable short-term rate was 178.2 g m(-2) yr(-1) (SE 13.3) at the pristine sites. The plant community compositions of the restored sites were considerably dissimilar to those of pristine sites still 10 years after restoration. We conclude that ecological restoration can be used to jump-start some key peatland ecosystem functions even without the recovery of original ecosystem structure (plant community composition). However, the re-establishment of other functions like C sequestration may require more profound recovery of conditions and ecosystem structure. We discuss the potential economic value of restored peatland ecosystems from the perspective of their C sequestration function.

  7. TEMPERATURE SENSITIVITY OF SOIL RESPIRATION AND ITS EFFECTS ON ECOSYSTEM CARBON BUDGET: NONLINEARITY BEGETS SURPRISES. (R827676)

    EPA Science Inventory

    Nonlinearity is a salient feature in all complex systems, and it certainly characterizes biogeochemical cycles in ecosystems across a wide range of scales. Soil carbon emission is a major source of uncertainty in estimating the terrestrial carbon budget at the ecosystem level ...

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

    USGS Publications Warehouse

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

    2014-01-01

    Boreal regions store large quantities of carbon but are increasingly vulnerable to carbon loss due to disturbance and climate warming. The boreal region, underlain by discontinuous permafrost, presents a challenging landscape for itemizing current and potential carbon sources and sinks in the boreal soil and vegetation. The roles of fire, forest succession, and the presence (or absence) of permafrost on carbon cycle, vegetation, and hydrologic processes have been the focus of multidisciplinary research in this area for the past 20 years. However, projections of a warming future climate, an increase in fire severity and extent, and the potential degradation of permafrost could lead to major landscape process changes over the next 20 to 50 years. This provides a major challenge for predicting how the interplay between land management activities and impacts of climate warming will affect carbon sources and sinks in Interior Alaska. To assist land managers in adapting and managing for potential changes in the Interior Alaska carbon cycle we developed this review paper incorporating an overview of the climate, ecosystem processes, vegetation types, and soil regimes in Interior Alaska with a focus on ramifications for the carbon cycle. Our objective is to provide a synthesis of the most current carbon storage estimates and measurements to support policy and land management decisions on how to best manage carbon sources and sinks in Interior Alaska. To support this we have surveyed relevant peer reviewed estimates of carbon stocks in aboveground and belowground biomass for Interior Alaska boreal ecosystems. We have also summarized methane and carbon dioxide fluxes from the same ecosystems. These data have been converted into the same units to facilitate comparison across ecosystem compartments. We identify potential changes in the carbon cycle with climate change and human disturbance including how compounding disturbances can affect the boreal system. Finally, we provide

  9. FOREST SOIL CARBON SEQUESTRATION: ACCOUNTING FOR THIS VITAL ECOSYSTEM SERVICE

    EPA Science Inventory

    Forests play a crucial role in supplying many goods and services that society depends upon on a daily basis including water supply, production of oxygen, soil protection, building materials, wildlife habitat and recreation. Forests also provide a significant amount of carbon seq...

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

    PubMed Central

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

    2016-01-01

    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. PMID:27044070

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

    PubMed

    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.

  12. Carbon storage in terrestrial ecosystems: do browsing and grazing herbivores matter?

    PubMed

    Tanentzap, Andrew J; Coomes, David A

    2012-02-01

    Large mammalian herbivores manifest a strong top-down control on ecosystems that can transform entire landscapes, but their impacts have not been reviewed in the context of terrestrial carbon storage. Here, we evaluate the effects of plant biomass consumption by large mammalian herbivores (>10 kg adult biomass), and the responses of ecosystems to these herbivores, on carbon stocks in temperate and tropical regions, and the Arctic. We calculate the difference in carbon stocks resulting from herbivore exclusion using the results of 108 studies from 52 vegetation types. Our estimates suggest that herbivores can reduce terrestrial above- and below-ground carbon stocks across vegetation types but reductions in carbon stocks may approach zero given sufficient periods of time for systems to respond to herbivory (i.e. decades). We estimate that if all large herbivores were removed from the vegetation types sampled in our review, increases in terrestrial carbon stocks would be up to three orders of magnitude less than many of the natural and human-influenced sources of carbon emissions. However, we lack estimates for the effects of herbivores on below-ground biomass and soil carbon levels in many regions, including those with high herbivore densities, and upwards revisions of our estimates may be necessary. Our results provide a starting point for a discussion on the magnitude of the effects of herbivory on the global carbon cycle, particularly given that large herbivores are common in many ecosystems. We suggest that herbivore removal might represent an important strategy towards increasing terrestrial carbon stocks at local and regional scales within specific vegetation types, since humans influence populations of most large mammals.

  13. Baseline and projected future carbon storage and greenhouse-gas fluxes in ecosystems of Alaska

    USGS Publications Warehouse

    Zhu, Zhiliang; McGuire, A. David

    2016-06-01

    This assessment was conducted to fulfill the requirements of section 712 of the Energy Independence and Security Act of 2007 and to contribute to knowledge of the storage, fluxes, and balance of carbon and methane gas in ecosystems of Alaska. The carbon and methane variables were examined for major terrestrial ecosystems (uplands and wetlands) and inland aquatic ecosystems in Alaska in two time periods: baseline (from 1950 through 2009) and future (projections from 2010 through 2099). The assessment used measured and observed data and remote sensing, statistical methods, and simulation models. The national assessment, conducted using the methodology described in SIR 2010-5233, has been completed for the conterminous United States, with results provided in three separate regional reports (PP 1804, PP 1797, and PP 1897).

  14. Baseline and projected future carbon storage and greenhouse-gas fluxes in ecosystems of Alaska

    USGS Publications Warehouse

    2016-01-01

    This assessment was conducted to fulfill the requirements of section 712 of the Energy Independence and Security Act of 2007 and to contribute to knowledge of the storage, fluxes, and balance of carbon and methane gas in ecosystems of Alaska. The carbon and methane variables were examined for major terrestrial ecosystems (uplands and wetlands) and inland aquatic ecosystems in Alaska in two time periods: baseline (from 1950 through 2009) and future (projections from 2010 through 2099). The assessment used measured and observed data and remote sensing, statistical methods, and simulation models. The national assessment, conducted using the methodology described in SIR 2010-5233, has been completed for the conterminous United States, with results provided in three separate regional reports (PP 1804, PP 1797, and PP 1897).

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

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

    NASA Astrophysics Data System (ADS)

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

    2005-12-01

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

  17. Stock assessment and balance of organic carbon in the Eastern European steppe ecosystems tree windbreaks

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Reserves and balance of organic carbon in ecosystems of windbreaks planted in the mid-1950s within the Forest-Steppe of Central Eastern Europe were determined from field sampling. Windbreaks were represented by 5-6-row plantings of Populus nigra and Betula pendula ("Streletskaya Steppe"), Acer negun...

  18. The Effects of Nitrogen Fertilization of a Corn Ecosystem's Oxidative Ratio and Its Carbon Cycle Implications

    NASA Astrophysics Data System (ADS)

    Gallagher, M. E.; Masiello, C. A.; Hockaday, W. C.; McSwiney, C. P.; Robertson, G. P.

    2008-12-01

    One of the most effective ways to estimate the size of carbon sinks in the terrestrial biosphere and oceans is through paired measurements of atmospheric CO2 and O2 concentrations (e.g. (Keeling et al. 1996)). Successful use of this technique requires knowledge of the oxidative ratio (OR) of the terrestrial biosphere (the ratio of moles of O2 released per moles of CO2 consumed in gas fluxes between the terrestrial biosphere and atmosphere.) Historically the terrestrial biosphere's OR has been assumed to be a constant, approximately 1.1 (e.g. Prentice et al. 2001). However, small shifts in the biosphere's OR values can lead to large variations in the calculated sizes of the terrestrial biosphere and ocean carbon sinks (Randerson et al. 2006). We have recently shown that it is possible to measure the OR of biomass to at least +/- 0.01 units (Masiello et al., 2008), and that there is significant natural variability in ecosystem OR. Ecosystem OR is impacted by human activities. In this presentation, we explore the effects of one major form of anthropogenic ecosystem alteration: nitrogen fertilization. We are measuring ecosystem OR in corn agricultural ecosystems under a range of nitrogen fertilization treatments at the Kellogg Biological Station- Long Term Ecological Research Site (KBS-LTER) in Michigan. We measure OR indirectly, through its relationship with organic carbon oxidation state (Cox) (Masiello et al. 2008). Here we present data showing the effects of varying corn ecosystem nitrogen fertilization rates (from 0 to 202 kg N/ha) on ecosystem OR and the implications it will have on apportionment calculations.

  19. Integrated Carbon Observation System (ICOS) ecosystem network: current state and future perspectives

    NASA Astrophysics Data System (ADS)

    Gielen, B.; Op de Beeck, M.; Ceulemans, R.; Janssens, I.; Loustau, D.; Valentini, R.; Papale, D.

    2013-12-01

    Atmospheric concentrations of greenhouse gases (GHG) such as carbon dioxide (CO2) and methane (CH4) are increasing due to emissions related to human activity, affecting the global climate. Natural sinks remove a fraction of the GHG anthropogenic excess at the global level. The characterization of greenhouse gases atmospheric burden and fluxes, both anthropogenic and natural, are needed at the global and regional scale, making use of all available information in an integrated framework. The Integrated Carbon Observation System (ICOS) research infrastructure will address this issue by providing the community with systematic measurements of a suite of atmospheric, terrestrial ecosystem and oceanic measurements. The ecosystem network comprises three station classes, for which variables are collected with different intensity. These stations are well distributed among the major European ecosystem types and cover most climatic zones in Europe. The Ecosystem Thematic Center (ETC) is coordinating the ICOS ecosystem network providing assistance with instruments and methods, testing and developing new measurement techniques and associated processing algorithms; also ensuring a high level of data standardization, uncertainty analysis and database services in coordination with the ICOS carbon portal. The ETC is also coordinating the drafting of the protocols describing in detail how measurements will be collected at all ecosystem stations, in order to guarantee inter comparability. This is done in close collaboration with experts in the field and with the other existing ecological and meteorological networks (NEON, Ameriflux, ICP -forests, MWO, TERN, ...). This presentation will focus on the current state of the ICOS ecosystem network, on the data products and the potential user community.

  20. Association genetics, geography and ecophysiology link stomatal patterning in Populus trichocarpa with carbon gain and disease resistance trade-offs.

    PubMed

    McKown, Athena D; Guy, Robert D; Quamme, Linda; Klápště, Jaroslav; La Mantia, Jonathan; Constabel, C P; El-Kassaby, Yousry A; Hamelin, Richard C; Zifkin, Michael; Azam, M S

    2014-12-01

    Stomata are essential for diffusive entry of gases to support photosynthesis, but may also expose internal leaf tissues to pathogens. To uncover trade-offs in range-wide adaptation relating to stomata, we investigated the underlying genetics of stomatal traits and linked variability in these traits with geoclimate, ecophysiology, condensed foliar tannins and pathogen susceptibility in black cottonwood (Populus trichocarpa). Upper (adaxial) and lower (abaxial) leaf stomatal traits were measured from 454 accessions collected throughout much of the species range. We calculated broad-sense heritability (H(2) ) of stomatal traits and, using SNP data from a 34K Populus SNP array, performed a genome-wide association studies (GWAS) to uncover genes underlying stomatal trait variation. H(2) values for stomatal traits were moderate (average H(2) = 0.33). GWAS identified genes associated primarily with adaxial stomata, including polarity genes (PHABULOSA), stomatal development genes (BRASSINOSTEROID-INSENSITIVE 2) and disease/wound-response genes (GLUTAMATE-CYSTEINE LIGASE). Stomatal traits correlated with latitude, gas exchange, condensed tannins and leaf rust (Melampsora) infection. Latitudinal trends of greater adaxial stomata numbers and guard cell pore size corresponded with higher stomatal conductance (gs ) and photosynthesis (Amax ), faster shoot elongation, lower foliar tannins and greater Melampsora susceptibility. This suggests an evolutionary trade-off related to differing selection pressures across the species range. In northern environments, more adaxial stomata and larger pore sizes reflect selection for rapid carbon gain and growth. By contrast, southern genotypes have fewer adaxial stomata, smaller pore sizes and higher levels of condensed tannins, possibly linked to greater pressure from natural leaf pathogens, which are less significant in northern ecosystems.

  1. Effects of Fire on Ecosystem Carbon Exchange in Siberian Larch Forest

    NASA Astrophysics Data System (ADS)

    Natali, S.; Alexander, H. D.; Davydov, S. P.; Loranty, M. M.; Mack, M. C.; Zimov, N.

    2014-12-01

    Fire frequency and severity have been increasing across the Arctic, and fires are expected to intensify as the climate becomes warmer and dryer. Fire plays a prominent role in global carbon cycling through direct emissions of greenhouse gases from organic matter combustion as well as through indirect effects of vegetation changes and permafrost thaw, both of which can impact ecosystem carbon exchange over timescales ranging from years to centuries. We examined the indirect effects of fire (i.e., years to decades timescales) on ecosystem carbon exchange in Siberian larch (Larix cajanderi) forests underlain by continuous permafrost and carbon-rich yedoma deposits. We measured understory net ecosystem exchange (NEE) and ecosystem respiration (Reco) from experimental burns, and from larch stands of varying stand densities occurring within a 75-yr burn scar in the vicinity of Cherskiy, Russia. The plot-level (4 m2) experimental burns were conducted in 2012 and comprise four burn treatments based on residual soil organic layer (SOL) depths: control, low severity (> 8 cm), moderate severity (5-8 cm), and high severity (2-5 cm). After three growing seasons, thaw depth was 6%, 11% and 30% deeper in the low, mid, and high severity burn plots compared to control. Immediately following the burns, Reco declined and was related to burn severity; Reco in the mid and high severity plots was fourfold lower than in low severity and control. In the second and third growing seasons, understory Reco continued to be lower in the burn plots relative to control, but effects of burn severity varied across measurement years. While Reco declined as a result of fire, there was a greater net release of CO2 (i.e., NEE) from the burn plots compared to control because there was limited carbon uptake by the regenerating plant community. In the 75-yr burn, we found that variation in stand density, which was likely related to fire severity, significantly impacted understory CO2 exchange through

  2. Carbon dioxide exchange in a temperate grassland ecosystem

    NASA Technical Reports Server (NTRS)

    Kim, Joon; Verma, Shashi B.

    1990-01-01

    Carbon dioxide exchange was measured, using the eddy correlation technique, over a tallgrass prairie in northeastern Kansas, U.S.A., during a six-month period in 1987. The diurnal patterns of daytime and nocturnal CO2 fluxes are presented on eight selected days. These days were distributed throughout most of the growing season and covered a wide range of meteorological and soil water conditions. The midday CO2 flux reached a maximum of 1.3 mg/sq m (ground area)/s during early July and was near zero during the dry period in late July. The dependence of the daytime carbon dioxide exchange on pertinent controlling variables, particularly photosynthetically active radiation, vapor pressure deficit, and soil water content is discussed. The nocturnal CO2 flux (soil plus plant respiration) averaged -0.4 m sq m (ground area)/s during early July and was about -0.2 mg sq/m during the dry period.

  3. Can leaf net carbon gain acclimate to keep up with global warming?

    NASA Astrophysics Data System (ADS)

    Vico, Giulia; Manzoni, Stefano; Way, Danielle; Hurry, Vaughan

    2016-04-01

    Plants are able to adjust their physiological activity to fluctuations and long-term changes in their growing environment. Nevertheless, projected increases in temperature will occur with unprecedented speed. Will global warming exceed the thermal acclimation capacity of leaves, thus reducing net CO2 assimilation? Such a reduction in net CO2 assimilation rate (Anet) in response to warming may deplete ecosystems' net primary productivity, with global impacts on the carbon cycling. Here we combine data on net photosynthetic thermal acclimation to changes in temperature with a probabilistic description of leaf temperature variability. We analytically obtain the probability distribution of the net CO2 assimilation rate as a function of species-specific leaf traits and growing conditions. Using this approach, we study the effects of mean leaf temperature and its variability on average Anet and the frequency of occurrence of sub-optimal thermal conditions. To maximize the net CO2 assimilation in warmer conditions, the thermal optimum for Anet (Topt) must track the growing temperature. Observations suggest that plants' thermal acclimation capacity is limited, so that growing temperatures cannot be tracked by the Topt. It is thus likely that net CO2 assimilation rates will decline in the future. Furthermore, for set leaf traits, large fluctuations in leaf temperature reduce average Anet and increase the frequency of occurrence of sub-optimal conditions for net CO2 assimilation.

  4. Improved determination of daytime net ecosystem exchange of carbon dioxide at croplands

    NASA Astrophysics Data System (ADS)

    Zhao, P.; Lüers, J.

    2012-03-01

    The eddy-covariance technique is applied worldwide to acquire information about carbon exchange between a variety of ecosystems and atmosphere, but the data acquisition only covers, on average, two-thirds of the whole year due to system failures and data rejection. Therefore, data must be corrected and data gaps must be filled to provide seasonal or annual budgets. The gap-filing strategies, however, are still under discussion within the research community. Presently the major gap-filling methods work quite well for long-time running sites over slow-developing biosphere surfaces such as long-living evergreen forests, but difficulties appear for short-living and fast-growing croplands. In this study we developed a new Multi-Step Error Filter procedure to gain good-quality data as input for different parameterizations of the light response function of plants for two cropland sites (rice and potatoes), and we could prove that the conventional temperature binning approach is inadequate. The presented time-window scheme showed best results with a four-day time window for the potato field and an eight-day time window for the rice field. The influence of vapor pressure deficit was tested as well, but in our case it plays a minor role at both the potato and the rice fields with the exception of the early growing stage of the potatoes. Completing our research, we suggest an innovative method by introducing a Leaf Area Index factor to capture the seasonal vegetation development. With this method we are now able to fill the large gaps between observation periods when conventional methods are invalid.

  5. Partitioning of catchment water budget and its implications for ecosystem carbon exchange

    NASA Astrophysics Data System (ADS)

    Lee, D.; Kim, J.; Lee, K.-S.; Kim, S.

    2010-06-01

    Spatially averaged annual carbon budget is one of the key information needed to understand ecosystem response and feedback to climate change. Water availability is a primary constraint of carbon uptake in many ecosystems and therefore the estimation of ecosystem water use may serve as an alternative to quantify Gross Primary Productivity (GPP). To examine this concept, we estimated a long-term steady state water budget for the Han River basin (~26 000 km2) in Korea and examined its application for catchment scale carbon exchange. For this, the catchment scale evapotranspiration (ET) was derived from the long term precipitation (P) and discharge (Q) data. Then, using stable isotope data of P and Q along with other hydrometeorological information, ET was partitioned into evaporation from soil and water surfaces (ES), evaporation from intercepted rainfall (EI, and transpiration (T). ES was identified as a minor component of ET in the study areas regardless of the catchment scales. The annual T, estimated from ET after accounting for EI and ES for the Han River basin from 1966 to 2007, was 22~31% of annual P and the proportion decreased with increasing P. Assuming that T further constrains the catchment scale GPP in terms of water use efficiency (WUE), we examined the possibility of using T as a relative measure for the strength and temporal changes of carbon uptake capacity. The proposed relationship would provide a simple and practical way to assess the spatial distribution of ecosystem GPP, provided the WUE estimates in terms of GPP/T at ecosystem scale could be obtained. For carbon and water tracking toward a sustainable Asia, ascertaining such a spatiotemporally representative WUE and their variability is a requisite facing the flux measurement and modeling communities.

  6. Spatial and temporal variability of carbon fluxes in African ecosystems - a CarboAfrica synthesis study

    NASA Astrophysics Data System (ADS)

    Kutsch, Werner Leo; Merbold, Lutz; Scholes, Bob

    2010-05-01

    This study reports carbon and water fluxes between the land surface and atmosphere in eleven different ecosystems in Sub-Saharan Africa, as measured using eddy covariance (EC) technology. The ecosystems for which data were available ranged in mean annual rainfall from 320mm (Sudan) to 1150mm (Republic of Congo) and include a spectrum of land cover types (savannas, woodlands, croplands and grasslands). Data were analysed across the network, in order to understand the driving factors for ecosystem respiration and carbon assimilation, and to reveal the different water use strategies in these highly seasonal environments. In addition to the spatial pattern, the temporal pattern that connects carbon fluxes with water relations in savanna ecosystems were studied in detail in a savanna ecosystem at Kruger National Park, South Africa and a miombo woodland in Western Zambia. Temporal variability: The regulation of canopy conductance was temporally changing in two ways: changes due to phenology during the course of the growing season and short-term (hours to days) acclimation to soil water conditions. The most constant parameter was water use efficiency. It was influenced by humidity (VPD) during the day, but the VPD response curve of water usage only changed slightly during the course of the growing season, and decreased by about 30% during the transition from wet to dry season. The regulation of canopy conductance and photosynthetic capacity were closely related. This observation meets recent leaf-level findings that stomatal closure triggers down-regulation of photosynthesis during drought. Our results may show the effects of these processes on the ecosystem scale. Spatial variability: The same pattern was found at large spatial scales. Maximum carbon assimilation rates were highly correlated with mean annual rainfall (r2=0.74) and were also positively correlated with satellite-derived fAPAR. Ecosystem respiration was dependent on temperature at all sites, and was

  7. Carbon Sequestration and Energy Balance of Turf in the Denver Urban Ecosystem and Adjacent Tallgrass Prairie

    NASA Astrophysics Data System (ADS)

    Thienelt, T.; Anderson, D. E.; Powell, K. M.

    2012-12-01

    Urban ecosystems are currently characterized by rapid growth and are expected to continually expand. They represent an important driver of land use change. A significant component of urban ecosystems is lawns, potentially the single largest irrigated "crop" in the U.S. Between March and October of 2011 and 2012, eddy covariance measurements of net carbon dioxide exchange and evapotranspiration along with energy balance fluxes were conducted for an irrigated, fertilized lawn (rye-bluegrass-mix) in metropolitan Denver and for a nearby tallgrass prairie (big bluestem, switchgrass, cheatgrass, blue grama). Due to the semi-arid climate conditions of the Denver region, differences in management (i.e., irrigation and fertilization) are expected to have a discernible impact on ecosystem productivity and thus on carbon sequestration rates, evapotranspiration, and the partitioning of sensible and latent heat. Data for the 2011 season showed that cumulative evapotranspiration was approximately 600 mm for the urban lawn and 305 mm for the tallgrass prairie; cumulative carbon sequestration was calculated to be 172 and 85 g C/m2, respectively. Also, patterns of carbon exchange differed between the grasslands. In 2011, both sites showed daily net uptake of carbon starting in late May, but the urban lawn displayed greater diurnal variability as well as greater uptake rates in general, especially following fertilization in mid-June. In contrast, the trend of carbon uptake at the prairie site was occasionally reversed following strong convective precipitation events, resulting in a temporary net release of carbon. Preliminary data for the 2012 season (up to early July) indicated an earlier start of net carbon uptake and higher cumulative evapotranspiration for both locations, likely due to a warm spring. The continuing acquisition of data and investigation of these relations will help assess the potential impact of urban growth on regional carbon sequestration.

  8. The impact of Indonesian peatland degradation on downstream marine ecosystems and the global carbon cycle.

    PubMed

    Abrams, Jesse F; Hohn, Sönke; Rixen, Tim; Baum, Antje; Merico, Agostino

    2016-01-01

    Tropical peatlands are among the most space-efficient stores of carbon on Earth containing approximately 89 Gt C. Of this, 57 Gt (65%) are stored in Indonesian peatlands. Large-scale exploitation of land, including deforestation and drainage for the establishment of oil palm plantations, is changing the carbon balance of Indonesian peatlands, turning them from a natural sink to a source via outgassing of CO2 to the atmosphere and leakage of dissolved organic carbon (DOC) into the coastal ocean. The impacts of this perturbation to the coastal environment and at the global scale are largely unknown. Here, we evaluate the downstream effects of released Indonesian peat carbon on coastal ecosystems and on the global carbon cycle. We use a biogeochemical box model in combination with novel and literature observations to investigate the impact of different carbon emission scenarios on the combined ocean-atmosphere system. The release of all carbon stored in the Indonesian peat pool, considered as a worst-case scenario, will increase atmospheric pCO2 by 8 ppm to 15 ppm within the next 200 years. The expected impact on the Java Sea ecosystems is most significant on the short term (over a few hundred years) and is characterized by an increase of 3.3% in phytoplankton, 32% in seagrass biomass, and 5% decrease in coral biomass. On the long term, however, the coastal ecosystems will recover to reach near pre-excursion conditions. Our results suggest that the ultimate fate of the peat carbon is in the deep ocean with 69% of it landing in the deep DIC pool after 1000 years, but the effects on the global ocean carbonate chemistry will be marginal. PMID:26416553

  9. The impact of Indonesian peatland degradation on downstream marine ecosystems and the global carbon cycle.

    PubMed

    Abrams, Jesse F; Hohn, Sönke; Rixen, Tim; Baum, Antje; Merico, Agostino

    2016-01-01

    Tropical peatlands are among the most space-efficient stores of carbon on Earth containing approximately 89 Gt C. Of this, 57 Gt (65%) are stored in Indonesian peatlands. Large-scale exploitation of land, including deforestation and drainage for the establishment of oil palm plantations, is changing the carbon balance of Indonesian peatlands, turning them from a natural sink to a source via outgassing of CO2 to the atmosphere and leakage of dissolved organic carbon (DOC) into the coastal ocean. The impacts of this perturbation to the coastal environment and at the global scale are largely unknown. Here, we evaluate the downstream effects of released Indonesian peat carbon on coastal ecosystems and on the global carbon cycle. We use a biogeochemical box model in combination with novel and literature observations to investigate the impact of different carbon emission scenarios on the combined ocean-atmosphere system. The release of all carbon stored in the Indonesian peat pool, considered as a worst-case scenario, will increase atmospheric pCO2 by 8 ppm to 15 ppm within the next 200 years. The expected impact on the Java Sea ecosystems is most significant on the short term (over a few hundred years) and is characterized by an increase of 3.3% in phytoplankton, 32% in seagrass biomass, and 5% decrease in coral biomass. On the long term, however, the coastal ecosystems will recover to reach near pre-excursion conditions. Our results suggest that the ultimate fate of the peat carbon is in the deep ocean with 69% of it landing in the deep DIC pool after 1000 years, but the effects on the global ocean carbonate chemistry will be marginal.

  10. The carbon balance pivot point of southwestern U.S. semiarid ecosystems: Insights from the 21st century drought

    NASA Astrophysics Data System (ADS)

    Scott, Russell L.; Biederman, Joel A.; Hamerlynck, Erik P.; Barron-Gafford, Greg A.

    2015-12-01

    Global-scale studies indicate that semiarid regions strongly regulate the terrestrial carbon sink. However, we lack understanding of how climatic shifts, such as decadal drought, impact carbon sequestration across the wide range of structural diversity in semiarid ecosystems. Therefore, we used eddy covariance measurements to quantify how net ecosystem production of carbon dioxide (NEP) differed with relative grass and woody plant abundance over the last decade of drought in four Southwest U.S. ecosystems. We identified a precipitation "pivot point" in the carbon balance for each ecosystem where annual NEP switched from negative to positive. Ecosystems with grass had pivot points closer to the drought period precipitation than the predrought average, making them more likely to be carbon sinks (and a grass-free shrubland, a carbon source) during the current drought. One reason for this is that the grassland located closest to the shrubland supported higher leaf area and photosynthesis at the same water availability. Higher leaf area was associated with a greater proportion of evapotranspiration being transpiration (T/ET), and therefore with higher ecosystem water use efficiency (gross ecosystem photosynthesis/ET). Our findings strongly show that water availability is a primary driver of both gross and net semiarid productivity and illustrate that structural differences may contribute to the speed at which ecosystem carbon cycling adjusts to climatic shifts.

  11. Neighborhood structure influences the convergence in light capture efficiency and carbon gain: an architectural approach for cloud forest shrubs.

    PubMed

    Guzmán Q, J Antonio; Cordero S, Roberto A

    2016-06-01

    Although plant competition is recognized as a fundamental factor that limits survival and species coexistence, its relative importance on light capture efficiency and carbon gain is not well understood. Here, we propose a new framework to explain the effects of neighborhood structures and light availability on plant attributes and their effect on plant performance in two understory shade-tolerant species (Palicourea padifolia (Roem. & Schult.) C.M. Taylor & Lorence and Psychotria elata (Swartz)) within two successional stages of a cloud forest in Costa Rica. Features of plant neighborhood physical structure and light availability, estimated by hemispherical photographs, were used to characterize the plant competition. Plant architecture, leaf attributes and gas exchange parameters extracted from the light-response curve were used as functional plant attributes, while an index of light capture efficiency (silhouette to total area ratio, averaged over all viewing angles, STAR) and carbon gain were used as indicators of plant performance. This framework is based in a partial least square Path model, which suggests that changes in plant performance in both species were affected in two ways: (i) increasing size and decreasing distance of neighbors cause changes in plant architecture (higher crown density and greater leaf dispersion), which contribute to lower STAR and subsequently lower carbon gain; and (ii) reductions in light availability caused by the neighbors also decrease plant carbon gain. The effect of neighbors on STAR and carbon gain were similar for the two forests sites, which were at different stages of succession, suggesting that the architectural changes of the two understory species reflect functional convergence in response to plant competition. Because STAR and carbon gain are variables that depend on multiple plant attributes and environmental characteristics, we suggest that changes in these features can be used as a whole-plant response approach to

  12. Extended leaf senescence promotes carbon gain and nutrient resorption: importance of maintaining winter photosynthesis in subtropical forests.

    PubMed

    Zhang, Yong-Jiang; Yang, Qiu-Yun; Lee, David W; Goldstein, Guillermo; Cao, Kun-Fang

    2013-11-01

    The relative advantages of being deciduous or evergreen in subtropical forests and the relationship between leaf phenology and nutrient resorption efficiency are not well understood. The most successful deciduous species (Lyonia ovalifolia) in an evergreen-dominated subtropical montane cloud forest in southwest (SW) China maintains red senescing leaves throughout much of the winter. The aim of this study was to investigate whether red senescing leaves of this species were able to assimilate carbon in winter, to infer the importance of maintaining a positive winter carbon balance in subtropical forests, and to test whether an extended leaf life span is associated with enhanced nutrient resorption and yearly carbon gain. The red senescing leaves of L. ovalifolia assimilated considerable carbon during part of the winter, resulting in a higher yearly carbon gain than co-occurring deciduous species. Its leaf N and P resorption efficiency was higher than for co-occurring non-anthocyanic deciduous species that dropped leaves in autumn, supporting the hypothesis that anthocyanin accumulation and/or extended leaf senescence help in nutrient resorption. Substantial winter carbon gain and efficient nutrient resorption may partially explain the success of L. ovalifolia versus that of the other deciduous species in this subtropical forest. The importance of maintaining a positive carbon balance for ecological success in this forest also provides indirect evidence for the dominance of evergreen species in the subtropical forests of SW China.

  13. Extended leaf senescence promotes carbon gain and nutrient resorption: importance of maintaining winter photosynthesis in subtropical forests.

    PubMed

    Zhang, Yong-Jiang; Yang, Qiu-Yun; Lee, David W; Goldstein, Guillermo; Cao, Kun-Fang

    2013-11-01

    The relative advantages of being deciduous or evergreen in subtropical forests and the relationship between leaf phenology and nutrient resorption efficiency are not well understood. The most successful deciduous species (Lyonia ovalifolia) in an evergreen-dominated subtropical montane cloud forest in southwest (SW) China maintains red senescing leaves throughout much of the winter. The aim of this study was to investigate whether red senescing leaves of this species were able to assimilate carbon in winter, to infer the importance of maintaining a positive winter carbon balance in subtropical forests, and to test whether an extended leaf life span is associated with enhanced nutrient resorption and yearly carbon gain. The red senescing leaves of L. ovalifolia assimilated considerable carbon during part of the winter, resulting in a higher yearly carbon gain than co-occurring deciduous species. Its leaf N and P resorption efficiency was higher than for co-occurring non-anthocyanic deciduous species that dropped leaves in autumn, supporting the hypothesis that anthocyanin accumulation and/or extended leaf senescence help in nutrient resorption. Substantial winter carbon gain and efficient nutrient resorption may partially explain the success of L. ovalifolia versus that of the other deciduous species in this subtropical forest. The importance of maintaining a positive carbon balance for ecological success in this forest also provides indirect evidence for the dominance of evergreen species in the subtropical forests of SW China. PMID:23636462

  14. Responses of ecosystem carbon cycle to experimental warming: a meta-analysis.

    PubMed

    Lu, Meng; Zhou, Xuhui; Yang, Qiang; Li, Hui; Luo, Yiqi; Fang, Changming; Chen, Jiakuan; Yang, Xin; Li, Bo

    2013-03-01

    Global warming potentially alters the terrestrial carbon (C) cycle, likely feeding back to further climate warming. However, how the ecosystem C cycle responds and feeds back to warming remains unclear. Here we used a meta-analysis approach to quantify the response ratios of 18 variables of the ecosystem C cycle to experimental warming and evaluated ecosystem C-cycle feedback to climate warming. Our results showed that warming stimulated gross ecosystem photosynthesis (GEP) by 15.7%, net primary production (NPP) by 4.4%, and plant C pools from above- and belowground parts by 6.8% and 7.0%, respectively. Experimental warming accelerated litter mass loss by 6.8%, soil respiration by 9.0%, and dissolved organic C leaching by 12.1%. In addition, the responses of some of those variables to experimental warming differed among the ecosystem types. Our results demonstrated that the stimulation of plant-derived C influx basically offset the increase in warming-induced efflux and resulted in insignificant changes in litter and soil C content, indicating that climate warming may not trigger strong positive C-climate feedback from terrestrial ecosystems. Moreover, the increase in plant C storage together with the slight but not statistically significant decrease of net ecosystem exchange (NEE) across ecosystems suggests that terrestrial ecosystems might be a weak C sink rather than a C source under global climate warming. Our results are also potentially useful for parameterizing and benchmarking land surface models in terms of C cycle responses to climate warming.

  15. Photosynthetic properties of boreal bog plant species and their contribution to ecosystem level carbon sink

    NASA Astrophysics Data System (ADS)

    Korrensalo, Aino; Hájek, Tomas; Alekseychik, Pavel; Rinne, Janne; Vesala, Timo; Mehtätalo, Lauri; Mammarella, Ivan; Tuittila, Eeva-Stiina

    2016-04-01

    Boreal bogs have a low number of plant species, but a large diversity of growth forms. This heterogeneity might explain the seasonally less varying photosynthetic productivity of these ecosystems compared to peatlands with vegetation consisting of fewer growth forms. The differences in photosynthetic properties within bog species and phases of growing season has not been comprehensively studied. Also the role of different plant species for the ecosystem level carbon (C) sink function is insufficiently known. We quantified the seasonal variation of photosynthetic properties in bog plant species and assessed how this variation accounts for the temporal variation in the ecosystem C sink. Photosynthetic light response of 11 vascular plant and 8 Sphagnum moss species was measured monthly over the growing season of 2013. Based on the species' light response parameters, leaf area development and areal coverage, we estimated the ecosystem level gross photosynthesis rate (PG) over the growing season. The level of upscaled PG was verified by comparing it to the ecosystem gross primary production (GPP) estimate calculated based on eddy covariance (EC) measurements. Although photosynthetic parameters differed within plant species and months, these differences were of less importance than expected for the variation in ecosystem level C sink. The most productive plant species at the ecosystem scale were not those with the highest maximum potential photosynthesis per unit of leaf area (Pmax), but those having the largest areal coverage. Sphagnum mosses had 35% smaller Pmax than vascular plants, but had higher photosynthesis at the ecosystem scale throughout the growing season. The contribution of the bog plant species to the ecosystem level PG differed over the growing season. The seasonal variation in ecosystem C sink was mainly controlled by phenology. Sedge PG had a sharp mid-summer peak, but the PG of evergreen shrubs and Sphagna remained rather stable over the growing season

  16. Modeling forest ecosystem responses to elevated carbon dioxide and ozone using artificial neural networks.

    PubMed

    Larsen, Peter E; Cseke, Leland J; Miller, R Michael; Collart, Frank R

    2014-10-21

    Rising atmospheric levels of carbon dioxide and ozone will impact productivity and carbon sequestration in forest ecosystems. The scale of this process and the potential economic consequences provide an incentive for the development of models to predict the types and rates of ecosystem responses and feedbacks that result from and influence of climate change. In this paper, we use phenotypic and molecular data derived from the Aspen Free Air CO2 Enrichment site (Aspen-FACE) to evaluate modeling approaches for ecosystem responses to changing conditions. At FACE, it was observed that different aspen clones exhibit clone-specific responses to elevated atmospheric levels of carbon dioxide and ozone. To identify the molecular basis for these observations, we used artificial neural networks (ANN) to examine above and below-ground community phenotype responses to elevated carbon dioxide, elevated ozone and gene expression profiles. The aspen community models generated using this approach identified specific genes and subnetworks of genes associated with variable sensitivities for aspen clones. The ANN model also predicts specific co-regulated gene clusters associated with differential sensitivity to elevated carbon dioxide and ozone in aspen species. The results suggest ANN is an effective approach to predict relevant gene expression changes resulting from environmental perturbation and provides useful information for the rational design of future biological experiments.

  17. Process contributions of Australian ecosystems to interannual variations in the carbon cycle

    NASA Astrophysics Data System (ADS)

    Haverd, Vanessa; Smith, Benjamin; Trudinger, Cathy

    2016-05-01

    New evidence is emerging that semi-arid ecosystems dominate interannual variability (IAV) of the global carbon cycle, largely via fluctuating water availability associated with El Niño/Southern Oscillation. Recent evidence from global terrestrial biosphere modelling and satellite-based inversion of atmospheric CO2 point to a large role of Australian ecosystems in global carbon cycle variability, including a large contribution from Australia to the record land sink of 2011. However the specific mechanisms governing this variability, and their bioclimatic distribution within Australia, have not been identified. Here we provide a regional assessment, based on best available observational data, of IAV in the Australian terrestrial carbon cycle and the role of Australia in the record land sink anomaly of 2011. We find that IAV in Australian net carbon uptake is dominated by semi-arid ecosystems in the east of the continent, whereas the 2011 anomaly was more uniformly spread across most of the continent. Further, and in contrast to global modelling results suggesting that IAV in Australian net carbon uptake is amplified by lags between production and decomposition, we find that, at continental scale, annual variations in production are dampened by annual variations in decomposition, with both fluxes responding positively to precipitation anomalies.

  18. The Effect of Mitochondrial Respiration During Photosynthesis on the Carbon Gain of Betula nana

    NASA Astrophysics Data System (ADS)

    Griffin, K. L.; Stieglitz, M.; Boelman, N. T.; Shaver, G. R.

    2001-12-01

    the absence of light in the elevated temperature plants but 9% lower in control plants. Taken together these results suggest that existing estimates of both the rate of respiration, and the temperature response of respiration could be significant underestimates. Our overall aim in this research is to quantify the components of the carbon balance in the woody component of this important ecosystem and identify the environmental variables that limit carbon uptake.

  19. Artificial drainage and associated carbon fluxes (CO2/CH4) in a tundra ecosystem

    NASA Astrophysics Data System (ADS)

    Merbold, Lutz; Kutsch, Werner Leo; Corradi, Chiara; Kolle, Olaf; Rebmann, Corinna; Stoy, Paul C.; Zimov, Sergej A.; Schulze, Ernst-Detlef

    2010-05-01

    Ecosystem flux measurements using the eddy covariance (EC) technique were undertaken in 4 subsequent years during summer for a total of 562 days in an arctic wet tundra ecosystem, located near Cherskii, Far-Eastern Federal District, Russia. Methane (CH4) emissions were measured using permanent chambers. The experimental field is characterized by late thawing of permafrost soils in June and periodic spring floods. A stagnant water table below the grass canopy is fed by melting of the active layer of permafrost and by flood water. Following 3 years of EC measurements, the site was drained by building a 3m wide drainage channel surrounding the EC tower to examine possible future effects of global change on the tundra tussock ecosystem. Cumulative summertime net carbon fluxes before experimental alteration were estimated to be about +115 gCm-2 (i.e. an ecosystem C loss) and +18 gCm-2 after draining the study site. When taking CH4 as another important greenhouse gas into account and considering the global warming potential (GWP) of CH4 vs. CO2, the ecosystem had a positive GWP during all summers. However CH4 emissions after drainage decreased significantly and therefore the carbon related greenhouse gas flux was much smaller than beforehand (475 ± 253 gC-CO2-em-2 before drainage in 2003 vs. 23 ± 26 g C-CO2-em-2 after drainage in 2005).

  20. Response of carbon fluxes to water relations in a savanna ecosystem in South Africa

    NASA Astrophysics Data System (ADS)

    Kutsch, W. L.; Hanan, N.; Scholes, R. J.; McHugh, I.; Kubheka, W.; Eckhardt, H.; Williams, C.

    2008-05-01

    The principal mechanisms that connect carbon fluxes with water relations in savanna ecosystems were studied by using eddy covariance in a savanna ecosystem at Kruger National Park, South Africa. Since the annual drought and rewetting cycle is a major factor influencing the function of savanna ecosystems, this work focused on the close inter-connection between water relations and carbon fluxes. Data from a nine-month measuring campaign lasting from the early wet season to the late dry season were used. Total ecosystem respiration showed highest values at the onset of the growing season, a slightly lower plateau during the main part of the growing season and a continuous decrease during the transition towards the dry season. The regulation of canopy conductance was changed in two ways: changes due to phenology during the course of the growing season and short-term acclimation to soil water conditions. The most constant parameter was water use efficiency that was influenced by VPD during the day but the VPD response curve of water usage did change only slightly during the course of the growing season and decreased by about 30% during the transition from wet to dry season. The regulation of canopy conductance and photosynthetic capacity were closely related. This observation meets recent leaf-level findings that stomatal closure triggers down-regulation of Rubisco during drought. Our results may show the effects of these processes on the ecosystem scale.

  1. Response of carbon fluxes to water relations in a savanna ecosystem in South Africa

    NASA Astrophysics Data System (ADS)

    Kutsch, W. L.; Hanan, N.; Scholes, B.; McHugh, I.; Kubheka, W.; Eckhardt, H.; Williams, C.

    2008-12-01

    The principal mechanisms that connect carbon fluxes with water relations in savanna ecosystems were studied by using eddy covariance method in a savanna ecosystem at Kruger National Park, South Africa. Since the annual drought and rewetting cycle is a major factor influencing the function of savanna ecosystems, this work focused on the close inter-connection between water relations and carbon fluxes. Data from a nine-month measuring campaign lasting from the early wet season to the late dry season were used. Total ecosystem respiration showed highest values at the onset of the growing season, a slightly lower plateau during the main part of the growing season and a continuous decrease during the transition towards the dry season. The regulation of canopy conductance was changed in two ways: changes due to phenology during the course of the growing season and short-term acclimation to soil water conditions. The most constant parameter was water use efficiency that was influenced by VPD during the day but the VPD response curve of water usage did change only slightly during the course of the growing season and decreased by about 30% during the transition from wet to dry season. The regulation of canopy conductance and photosynthetic capacity were closely related. This observation meets recent leaf-level findings that stomatal closure triggers down-regulation of Rubisco during drought. Our results may show the effects of these processes on the ecosystem scale.

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

    PubMed

    Yan, Wei; Hu, Zhongmin; Zhao, Yuping; Zhang, Xianzhou; Fan, Yuzhi; Shi, Peili; He, Yongtao; Yu, Guirui; Li, Yingnian

    2015-01-01

    Estimate of net ecosystem carbon exchange (NEE) between the atmosphere and terrestrial ecosystems, the balance of gross primary productivity (GPP) and ecosystem respiration (Reco) has significant importance for studying the regional and global carbon cycles. Using models driven by satellite data and climatic data is a promising approach to estimate NEE at regional scales. For this purpose, we proposed a semi-empirical model to estimate NEE in this study. In our model, the component GPP was estimated with a light response curve of a rectangular hyperbola. The component Reco was estimated with an exponential function of soil temperature. To test the feasibility of applying our model at regional scales, the temporal variations in the model parameters derived from NEE observations in an alpine grassland ecosystem on Tibetan Plateau were investigated. The results indicated that all the inverted parameters exhibit apparent seasonality, which is in accordance with air temperature and canopy phenology. In addition, all the parameters have significant correlations with the remote sensed vegetation indexes or environment temperature. With parameters estimated with these correlations, the model illustrated fair accuracy both in the validation years and at another alpine grassland ecosystem on Tibetan Plateau. Our results also indicated that the model prediction was less accurate in drought years, implying that soil moisture is an important factor affecting the model performance. Incorporating soil water content into the model would be a critical step for the improvement of the model. PMID:25849325

  3. Modeling Net Ecosystem Carbon Exchange of Alpine Grasslands with a Satellite-Driven Model

    PubMed Central

    Zhao, Yuping; Zhang, Xianzhou; Fan, Yuzhi; Shi, Peili; He, Yongtao; Yu, Guirui; Li, Yingnian

    2015-01-01

    Estimate of net ecosystem carbon exchange (NEE) between the atmosphere and terrestrial ecosystems, the balance of gross primary productivity (GPP) and ecosystem respiration (Reco) has significant importance for studying the regional and global carbon cycles. Using models driven by satellite data and climatic data is a promising approach to estimate NEE at regional scales. For this purpose, we proposed a semi-empirical model to estimate NEE in this study. In our model, the component GPP was estimated with a light response curve of a rectangular hyperbola. The component Reco was estimated with an exponential function of soil temperature. To test the feasibility of applying our model at regional scales, the temporal variations in the model parameters derived from NEE observations in an alpine grassland ecosystem on Tibetan Plateau were investigated. The results indicated that all the inverted parameters exhibit apparent seasonality, which is in accordance with air temperature and canopy phenology. In addition, all the parameters have significant correlations with the remote sensed vegetation indexes or environment temperature. With parameters estimated with these correlations, the model illustrated fair accuracy both in the validation years and at another alpine grassland ecosystem on Tibetan Plateau. Our results also indicated that the model prediction was less accurate in drought years, implying that soil moisture is an important factor affecting the model performance. Incorporating soil water content into the model would be a critical step for the improvement of the model. PMID:25849325

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

    PubMed

    Yan, Wei; Hu, Zhongmin; Zhao, Yuping; Zhang, Xianzhou; Fan, Yuzhi; Shi, Peili; He, Yongtao; Yu, Guirui; Li, Yingnian

    2015-01-01

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

  5. Turning sunlight into stone: the oxalate-carbonate pathway in a tropical tree ecosystem

    NASA Astrophysics Data System (ADS)

    Cailleau, G.; Braissant, O.; Verrecchia, E. P.

    2011-02-01

    roots, leading to carbonate precipitation. The main pools of carbon are clearly identified as the organic matter (the tree and its organic products), the oxalate crystals, and the various carbonate features. A functional model based on field observations and diagenetic investigations with δ13C signatures of the various compartments involved in the local carbon cycle is proposed. It suggests that the iroko ecosystem can act as a long-term carbon sink, as long as the calcium source is related to non-carbonate rocks. Consequently, this carbon sink, driven by the oxalate carbonate pathway around an iroko tree, constitutes a true carbon trapping ecosystem as define by the ecological theory.

  6. Turning sunlight into stone: the oxalate-carbonate pathway in a tropical tree ecosystem

    NASA Astrophysics Data System (ADS)

    Cailleau, G.; Braissant, O.; Verrecchia, E. P.

    2011-07-01

    pumped through the roots, leading to carbonate precipitation. The main pools of carbon are clearly identified as the organic matter (the tree and its organic products), the oxalate crystals, and the various carbonate features. A functional model based on field observations and diagenetic investigations with δ13C signatures of the various compartments involved in the local carbon cycle is proposed. It suggests that the iroko ecosystem can act as a long-term carbon sink, as long as the calcium source is related to non-carbonate rocks. Consequently, this carbon sink, driven by the oxalate carbonate pathway around an iroko tree, constitutes a true carbon trapping ecosystem as defined by ecological theory.

  7. Detecting Disturbance and its Impact on Ecosystem Carbon Balance from Global to Regional Scales

    NASA Astrophysics Data System (ADS)

    Ballantyne, A.; Jacobson, A. R.; Anderegg, W.; Poulter, B.; Cooper, L. A.; Smith, W. K.; Miller, J. B.

    2015-12-01

    One of the most vital ecosystem services currently provided by the terrestrial biosphere is the removal of approximately one quarter of the anthropogenic CO2 emitted to the atmosphere. However, as patterns of temperature and precipitation change so is the frequency and intensity of ecosystem disturbance. Despite evidence that ecosystem disturbance regimes have shifted leading to widespread forest mortality, the net effect of disturbance on the carbon (C) balance of forest ecosystems remains uncertain. We will use satellite and atmospheric observations to deconvolve net carbon exchange (NEE) into its component fluxes of gross primary productivity and total respiration (e.g. NEE= GPP - R) at global to regional scales. At the global scale we find that NEE has increased over the last 50 years and appears to have accelerated as a result of diminished R over the last 15 years. However the variance in global NEE has also increased perhaps due to inter-annual variability in R, especially within semi-arid ecosystems. These global trends are not necessarily consistent with regional patterns in the net carbon balance, especially across the western US. Atmospheric mass balance suggests that ecosystems of North America have shifted from a net C sink to a net C source. While prolonged drought across the Western US has likely caused this shift in continental scale NEE, attributing this shift in the net C balance to any one mechanism of disturbance (e.g. drought, insect infestation, and fire) or their interactions is challenging. Lastly, we will evaluate existing observing networks, such as NOAA/ESRL and Ameriflux, and how they can be combined with nascent networks, such as NEON, EarthNetworks, and OCO-2, to identify regional disturbance processes that may be causing increasing variance in the global C cycle.

  8. Increased forest ecosystem carbon and nitrogen storage from nitrogen rich bedrock.

    PubMed

    Morford, Scott L; Houlton, Benjamin Z; Dahlgren, Randy A

    2011-09-01

    Nitrogen (N) limits the productivity of many ecosystems worldwide, thereby restricting the ability of terrestrial ecosystems to offset the effects of rising atmospheric CO(2) emissions naturally. Understanding input pathways of bioavailable N is therefore paramount for predicting carbon (C) storage on land, particularly in temperate and boreal forests. Paradigms of nutrient cycling and limitation posit that new N enters terrestrial ecosystems solely from the atmosphere. Here we show that bedrock comprises a hitherto overlooked source of ecologically available N to forests. We report that the N content of soils and forest foliage on N-rich metasedimentary rocks (350-950 mg N kg(-1)) is elevated by more than 50% compared with similar temperate forest sites underlain by N-poor igneous parent material (30-70 mg N kg(-1)). Natural abundance N isotopes attribute this difference to rock-derived N: (15)N/(14)N values for rock, soils and plants are indistinguishable in sites underlain by N-rich lithology, in marked contrast to sites on N-poor substrates. Furthermore, forests associated with N-rich parent material contain on average 42% more carbon in above-ground tree biomass and 60% more carbon in the upper 30 cm of the soil than similar sites underlain by N-poor rocks. Our results raise the possibility that bedrock N input may represent an important and overlooked component of ecosystem N and C cycling elsewhere. PMID:21886160

  9. Increased forest ecosystem carbon and nitrogen storage from nitrogen rich bedrock.

    PubMed

    Morford, Scott L; Houlton, Benjamin Z; Dahlgren, Randy A

    2011-08-31

    Nitrogen (N) limits the productivity of many ecosystems worldwide, thereby restricting the ability of terrestrial ecosystems to offset the effects of rising atmospheric CO(2) emissions naturally. Understanding input pathways of bioavailable N is therefore paramount for predicting carbon (C) storage on land, particularly in temperate and boreal forests. Paradigms of nutrient cycling and limitation posit that new N enters terrestrial ecosystems solely from the atmosphere. Here we show that bedrock comprises a hitherto overlooked source of ecologically available N to forests. We report that the N content of soils and forest foliage on N-rich metasedimentary rocks (350-950 mg N kg(-1)) is elevated by more than 50% compared with similar temperate forest sites underlain by N-poor igneous parent material (30-70 mg N kg(-1)). Natural abundance N isotopes attribute this difference to rock-derived N: (15)N/(14)N values for rock, soils and plants are indistinguishable in sites underlain by N-rich lithology, in marked contrast to sites on N-poor substrates. Furthermore, forests associated with N-rich parent material contain on average 42% more carbon in above-ground tree biomass and 60% more carbon in the upper 30 cm of the soil than similar sites underlain by N-poor rocks. Our results raise the possibility that bedrock N input may represent an important and overlooked component of ecosystem N and C cycling elsewhere.

  10. [Carbon cycle in ten kinds of forest ecosystem in Guangzhou City].

    PubMed

    Kang, Wen-xing; Tian, Zheng; He, Jie-nan; Cui, Sha-sha

    2009-12-01

    Based on an extensive collection of information and experimental data, this paper studied the carbon cycle in ten kinds of forest ecosystem in Guangzhou, China, aimed to explore the carbon cycling patterns in, southern subtropical forest ecosystems. For the test ecosystems, their carbon density ranged from 108.35 to 151.85 t C x hm(-2), with 10. 85-48.86 t C x hm(-2) in tree layer and 87.74-99.01 t C x hm(-2) in soil layer (0-60 cm), being lower than the national average. There were 4. 41-9. 15 t C x hm(-2) x a(-1) flowed from atmosphere to vegetation stratum, 0. 74-2.06 t C x hm(-2) x a(-1) from vegetation stratum to soil, and 3.94-5.42 t C x hm(-2) x a(-1) from soil to atmosphere, i.e., the forest systems absorbed 0.47-4.97 t C x hm(-2) x a(-1) from atmosphere. The net ecosystem production (NEP) varied with forest stand, being higher for broadleaved forest than coniferous forest, mixed forest than pure forest, and natural secondary forest than artificial forest.

  11. Carbon budget estimation of a subarctic catchment using a dynamic ecosystem model at high spatial resolution

    NASA Astrophysics Data System (ADS)

    Tang, J.; Miller, P. A.; Persson, A.; Olefeldt, D.; Pilesjö, P.; Heliasz, M.; Jackowicz-Korczynski, M.; Yang, Z.; Smith, B.; Callaghan, T. V.; Christensen, T. R.

    2015-01-01

    Large amount of organic carbon is stored in high latitude soils. A substantial proportion of this carbon stock is vulnerable and may decompose rapidly due to temperature increases that are already greater than the global average. It is therefore crucial to quantify and understand carbon exchange between the atmosphere and subarctic/arctic ecosystems. In this paper, we combine an arctic-enabled version of the process-based dynamic ecosystem model, LPJ-GUESS (version LPJG-WHyMe-TFM) with comprehensive observations of terrestrial and aquatic carbon fluxes to simulate long-term carbon exchange in a subarctic catchment comprising both mineral and peatland soils. The model is applied at 50 m resolution and is shown to be able to capture the seasonality and magnitudes of observed fluxes at this fine scale. The modelled magnitudes of CO2 uptake generally follow the descending sequence: birch forest, non-permafrost Eriophorum, Sphagnum and then tundra heath during the observation periods. The catchment-level carbon fluxes from aquatic systems are dominated by CO2 emissions from streams. Integrated across the whole catchment, we estimate that the area is a carbon sink at present, and will become an even stronger carbon sink by 2080, which is mainly a result of a projected densification of birch forest and its encroachment into tundra heath. However, the magnitudes of the modelled sinks are very dependent on future atmospheric CO2 concentrations. Furthermore, comparisons of global warming potentials between two simulations with and without CO2 increase since 1960 reveal that the increased methane emission from the peatland could double the warming effects of the whole catchment by 2080 in the absence of CO2 fertilization of the vegetation. This is the first process-based model study of the temporal evolution of a catchment-level carbon budget at high spatial resolution, integrating comprehensive and diverse fluxes including both terrestrial and aquatic carbon. Though this

  12. Response of a tundra ecosystem to elevated atmospheric carbon dioxide and CO{sub 2}-induced climate change. [Annual report

    SciTech Connect

    Oechel, W.C.

    1989-12-31

    Predicting the response of northern ecosystems to increases in atmospheric CO{sub 2} and associated climatic change is important for several reasons, including the fact that northern ecosystems contain large stores of carbon, most of which is below ground and because northern ecosystems could conceivably be either sources or sinks for CO{sub 2} under future climatic and atmospheric CO{sub 2} concentrations. The carbon in northern ecosystems is equal to about 20% of the world`s terrestrial carbon and about 70% of the carbon currently in the atmosphere. Eighty-three percent of this carbon is below ground in the seasonally-thawed upper soil layers and in the permanently frozen zone, the permafrost. Because of bogs and permafrost, northern ecosystems are unusual in that they can potentially store significant amounts of carbon over long time periods. Most other mature ecosystems have little capacity for long- term carbon storage. Given the right conditions, northern ecosystems can also release a significant amount of carbon. A substantial amount of the carbon stored in northern ecosystems, and much of the future storage potential, is in the tundra regions. These systems could conceivably act as sources or sinks depending on developing climatic and atmospheric conditions. Our recent work indicates that elevated CO{sub 2} alone will have little effect on carbon storage in the tundra. However, the combination of elevated atmospheric CO{sub 2} (+ 340 ppm) and air temperature (+4{degrees}C) in the absence of any change in soil water table or soil moisture content, should result in significant increases in carbon sequestering in the tundra. However, if changing climate results in a decrease in the water table and soil moisture levels, this may lead to sizeable losses of carbon from the tundra soils.

  13. Biotic Processes Regulating the Carbon Balance of Desert Ecosystems - Final Report

    SciTech Connect

    Nowak, Robert S; Smith, Stanley D; Evans, Dave; Ogle, Kiona; Fenstermaker, Lynn

    2012-12-13

    Our results from the 10-year elevated atmospheric CO{sub 2} concentration study at the Nevada Desert FACE (Free-air CO{sub 2} Enrichment) Facility (NDFF) indicate that the Mojave Desert is a dynamic ecosystem with the capacity to respond quickly to environmental changes. The Mojave Desert ecosystem is accumulating carbon (C), and over the 10-year experiment, C accumulation was significantly greater under elevated [CO{sub 2}] than under ambient, despite great fluctuations in C inputs from year to year and even apparent reversals in which [CO{sub 2}] treatment had greater C accumulations.

  14. Comparing carbon storage of Siberian tundra and taiga permafrost ecosystems at very high spatial resolution

    NASA Astrophysics Data System (ADS)

    Siewert, Matthias B.; Hanisch, Jessica; Weiss, Niels; Kuhry, Peter; Maximov, Trofim C.; Hugelius, Gustaf

    2015-10-01

    Permafrost-affected ecosystems are important components in the global carbon (C) cycle that, despite being vulnerable to disturbances under climate change, remain poorly understood. This study investigates ecosystem carbon storage in two contrasting continuous permafrost areas of NE and East Siberia. Detailed partitioning of soil organic carbon (SOC) and phytomass carbon (PC) is analyzed for one tundra (Kytalyk) and one taiga (Spasskaya Pad/Neleger) study area. In total, 57 individual field sites (24 and 33 in the respective areas) have been sampled for PC and SOC, including the upper permafrost. Landscape partitioning of ecosystem C storage was derived from thematic upscaling of field observations using a land cover classification from very high resolution (2 × 2 m) satellite imagery. Nonmetric multidimensional scaling was used to explore patterns in C distribution. In both environments the ecosystem C is mostly stored in the soil (≥86%). At the landscape scale C stocks are primarily controlled by the presence of thermokarst depressions (alases). In the tundra landscape, site-scale variability of C is controlled by periglacial geomorphological features, while in the taiga, local differences in catenary position, soil texture, and forest successions are more important. Very high resolution remote sensing is highly beneficial to the quantification of C storage. Detailed knowledge of ecosystem C storage and ground ice distribution is needed to predict permafrost landscape vulnerability to projected climatic changes. We argue that vegetation dynamics are unlikely to offset mineralization of thawed permafrost C and that landscape-scale reworking of SOC represents the largest potential changes to C cycling.

  15. Ecosystem Model Performance at Wetlands: Results from the North American Carbon Program Site Synthesis

    NASA Astrophysics Data System (ADS)

    Sulman, B. N.; Desai, A. R.; Schroeder, N. M.; NACP Site Synthesis Participants

    2011-12-01

    Northern peatlands contain a significant fraction of the global carbon pool, and their responses to hydrological change are likely to be important factors in future carbon cycle-climate feedbacks. Global-scale carbon cycle modeling studies typically use general ecosystem models with coarse spatial resolution, often without peatland-specific processes. Here, seven ecosystem models were used to simulate CO2 fluxes at three field sites in Canada and the northern United States, including two nutrient-rich fens and one nutrient-poor, sphagnum-dominated bog, from 2002-2006. Flux residuals (simulated - observed) were positively correlated with measured water table for both gross ecosystem productivity (GEP) and ecosystem respiration (ER) at the two fen sites for all models, and were positively correlated with water table at the bog site for the majority of models. Modeled diurnal cycles at fen sites agreed well with eddy covariance measurements overall. Eddy covariance GEP and ER were higher during dry periods than during wet periods, while model results predicted either the opposite relationship or no significant difference. At the bog site, eddy covariance GEP had no significant dependence on water table, while models predicted higher GEP during wet periods. All models significantly over-estimated GEP at the bog site, and all but one over-estimated ER at the bog site. Carbon cycle models in peatland-rich regions could be improved by incorporating better models or measurements of hydrology and by inhibiting GEP and ER rates under saturated conditions. Bogs and fens likely require distinct treatments in ecosystem models due to differences in nutrients, peat properties, and plant communities.

  16. Using Targeted Active-Learning Exercises and Diagnostic Question Clusters to Improve Students' Understanding of Carbon Cycling in Ecosystems

    PubMed Central

    Maskiewicz, April Cordero; Griscom, Heather Peckham; Welch, Nicole Turrill

    2012-01-01

    In this study, we used targeted active-learning activities to help students improve their ways of reasoning about carbon flow in ecosystems. The results of a validated ecology conceptual inventory (diagnostic question clusters [DQCs]) provided us with information about students' understanding of and reasoning about transformation of inorganic and organic carbon-containing compounds in biological systems. These results helped us identify specific active-learning exercises that would be responsive to students' existing knowledge. The effects of the active-learning interventions were then examined through analysis of students' pre- and postinstruction responses on the DQCs. The biology and non–biology majors participating in this study attended a range of institutions and the instructors varied in their use of active learning; one lecture-only comparison class was included. Changes in pre- to postinstruction scores on the DQCs showed that an instructor's teaching method had a highly significant effect on student reasoning following course instruction, especially for questions pertaining to cellular-level, carbon-transforming processes. We conclude that using targeted in-class activities had a beneficial effect on student learning regardless of major or class size, and argue that using diagnostic questions to identify effective learning activities is a valuable strategy for promoting learning, as gains from lecture-only classes were minimal. PMID:22383618

  17. Carbon and nitrogen gain during the growth of orchid seedlings in nature.

    PubMed

    Stöckel, Marcus; Těšitelová, Tamara; Jersáková, Jana; Bidartondo, Martin I; Gebauer, Gerhard

    2014-04-01

    For germination and establishment, orchids depend on carbon (C) and nutrients supplied by mycorrhizal fungi. As adults, the majority of orchids then appear to become autotrophic. To compare the proportional C and nitrogen (N) gain from fungi in mycoheterotrophic seedlings and in adults, here we examined in the field C and N stable isotope compositions in seedlings and adults of orchids associated with ectomycorrhizal and saprotrophic fungi. Using a new highly sensitive approach, we measured the isotope compositions of seedlings and adults of four orchid species belonging to different functional groups: fully and partially mycoheterotrophic orchids associated with narrow or broad sets of ectomycorrhizal fungi, and two adult putatively autotrophic orchids associated exclusively with saprotrophic fungi. Seedlings of orchids associated with ectomycorrhizal fungi were enriched in (13) C and (15) N similarly to fully mycoheterotrophic adults. Seedlings of saprotroph-associated orchids were also enriched in (13) C and (15) N, but unexpectedly their enrichment was significantly lower, making them hardly distinguishable from their respective adult stages and neighbouring autotrophic plants. We conclude that partial mycoheterotrophy among saprotroph-associated orchids cannot be identified unequivocally based on C and N isotope compositions alone. Thus, partial mycoheterotrophy may be much more widely distributed among orchids than hitherto assumed. PMID:24444001

  18. Carbon and nitrogen gain during the growth of orchid seedlings in nature.

    PubMed

    Stöckel, Marcus; Těšitelová, Tamara; Jersáková, Jana; Bidartondo, Martin I; Gebauer, Gerhard

    2014-04-01

    For germination and establishment, orchids depend on carbon (C) and nutrients supplied by mycorrhizal fungi. As adults, the majority of orchids then appear to become autotrophic. To compare the proportional C and nitrogen (N) gain from fungi in mycoheterotrophic seedlings and in adults, here we examined in the field C and N stable isotope compositions in seedlings and adults of orchids associated with ectomycorrhizal and saprotrophic fungi. Using a new highly sensitive approach, we measured the isotope compositions of seedlings and adults of four orchid species belonging to different functional groups: fully and partially mycoheterotrophic orchids associated with narrow or broad sets of ectomycorrhizal fungi, and two adult putatively autotrophic orchids associated exclusively with saprotrophic fungi. Seedlings of orchids associated with ectomycorrhizal fungi were enriched in (13) C and (15) N similarly to fully mycoheterotrophic adults. Seedlings of saprotroph-associated orchids were also enriched in (13) C and (15) N, but unexpectedly their enrichment was significantly lower, making them hardly distinguishable from their respective adult stages and neighbouring autotrophic plants. We conclude that partial mycoheterotrophy among saprotroph-associated orchids cannot be identified unequivocally based on C and N isotope compositions alone. Thus, partial mycoheterotrophy may be much more widely distributed among orchids than hitherto assumed.

  19. An eddy covariance derived annual carbon budget for an arctic terrestrial ecosystem (Disko, Greenland)

    NASA Astrophysics Data System (ADS)

    McConnell, Alistair; Lund, Magnus; Friborg, Thomas

    2016-04-01

    Ecosystems with underlying permafrost cover nearly 25% of the ice-free land area in the northern hemisphere and store almost half of the global soil carbon. Future climate changes are predicted to have the most pronounced effect in northern latitudes. These Arctic ecosystems are therefore subject to dramatic changes following thawing of permafrost, glacial retreat, and coastal erosion. The most dramatic effect of permafrost thawing is the accelerated decomposition and potential mobilization of organic matter stored in the permafrost. This will impact global climate through the mobilization of carbon and nitrogen accompanied by release of greenhouses gases, including carbon dioxide. This study presents the initial findings and first full annual carbon (CO2) budget, derived from eddy covariance measurements, for an Arctic landscape in West Greenland. The study site, a terrestrial Arctic maritime climate, is located at Østerlien, near Qeqertarsuaq, on the southern coast of Disko Island in central West Greenland (69° 15' N, 53° 34' W) within the transition zone from continuous to discontinuous permafrost. The mean annual air temperature is -5 C and the annual precipitation as rain is 150-200 mm. Arctic ecosystem feedback mechanisms and processes interact on micro, local and regional scales. This is further complicated by several potential feedback mechanisms likely to occur in permafrost-affected ecosystems, involving the interactions of microorganisms, vegetation and soil. The eddy covariance method allows us to interrogate the processes and drivers of land-atmosphere carbon exchange at extremely high temporary frequency (10 Hz), providing landscape-scale measurements of CO2, H2O and heat fluxes for the site, which are processed to derive daily, monthly and now, annual carbon fluxes. We discuss the scientific methodology, challenges, and analysis, as well as the practical and logistic challenges of working in the Arctic, and present an annual carbon budget

  20. How is climate warming altering the carbon cycle of a tundra ecosystem in the Siberian Arctic?

    NASA Astrophysics Data System (ADS)

    Belelli Marchesini, Luca; (Ko) van Huissteden, Jacobus; van der Molen, Michiel; Parmentier, Frans-Jan W.; Maximov, Trofim; Budishchev, Artem; Gallagher, Angela; (Han) Dolman, Albertus J.

    2015-04-01

    Climate has been warming over the the Arctic region with the strongest anomalies taking place in autumn and winter for the period 2000-2010, particularly in northern Eurasia. The quantification of the impact on climate warming on the degradation of permafrost and the associated potential release to the atmosphere of carbon stocked in the soil under the form of greenhouse gases, thus further increasing the radiative forcing of the atmosphere, is currently a matter of scientific debate. The positive trend in primary productivity in the last decades inferred by vegetation indexes (NDVI) and confirmed by observations on the enhanced growth of shrub vegetation represents indeed a contrasting process that, if prevalent could offset GHG emissions or even strengthen the carbon sink over the Arctic tundra. At the site of Kytalyk, in north-eastern Siberia, net fluxes of CO2 at ecosystem scale (NEE) have been monitored by eddy covariance technique since 2003. While presenting the results of the seasonal (snow free period) and inter-annual variability of NEE, conceived as the interplay between meteorological drivers and ecosystem responses, we test the role of climate as the main source of NEE variability in the last decade using a data oriented statistical approach. The impact of the timing and duration of the snow free period on the seasonal carbon budget is also considered. Finally, by including the results of continuous micrometeorological observations of methane fluxes taken during summer 2012, corroborated with seasonal CH4 budgets from two previous shorter campaigns (2008, 2009), as well as an experimentally determined estimate of dissolved organic carbon (DOC) flux, we provide an assessment of the carbon budget and its stability over time. The examined tundra ecosystem was found to sequester CO2 during the snow free season with relatively small inter-annual variability (-97.9±12.1gC m-2) during the last decade and without any evident trend despite the carbon uptake

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  2. Functional Diversity of Boreal Bog Plant Species Decreases Seasonal Variation of Ecosystem Carbon Sink Function

    NASA Astrophysics Data System (ADS)

    Korrensalo, A.

    2015-12-01

    Species diversity has been found to decrease the temporal variance of productivity of a plant community, and diversity in species responses to environmental factors seems to make a plant community more stable in changing conditions. Boreal bogs are nutrient poor peatland ecosystems where the number of plant species is low but the species differ greatly in their growth form. In here we aim to assess the role of the variation in photosynthesis between species for the temporal variation in ecosystem carbon sink function. To quantify the photosynthetic properties and their seasonal variation for different bog plant species we measured photosynthetic parameters and stress-inducing chlorophyll fluorescence of vascular plant and Sphagnum moss species in a boreal bog over a growing season. We estimated monthly gross photosynthesis (PG) of the whole study site based on species level light response curves and leaf area development. The estimated PG was further compared with a gross primary production (GPP) estimate measured by eddy covariance (EC) technique. The sum of upscaled PG estimates agreed well with the GPP estimate measured by the EC technique. The contributions of the species and species groups to the ecosystem level PG changed over the growing season. The sharp mid-summer peak in sedge PG was balanced by more stable PG of evergreen shrubs and Sphagna. Species abundance rather than differences in photosynthetic properties between species and growth forms determined the most productive plants on the ecosystem scale. Sphagna had lower photosynthesis and clorophyll fluorescence than vascular plants but were more productive on the ecosystem scale throughout the growing season due to their high areal coverage. These results show that the diversity of growth forms stabilizes the seasonal variation of the ecosystem level PG in an ombrotrophic bog ecosystem. This may increase the resilience of the ecosystem to changing environmental conditions.

  3. Effects of invasive species on ecosystem carbon dynamics in a restored tallgrass prairie

    NASA Astrophysics Data System (ADS)

    Matamala, R.; Graham, S. L.; Cook, D. R.; Gonzalez-Meler, M. A.

    2007-12-01

    Land cover is an important determinant of soil C storage and dynamics. Restoration of degraded ecosystems and soils represents a target sink for offsetting rising atmospheric CO2 levels by increasing carbon sequestration in soils. The Conservation Reserve Program (CRP) and other initiatives to halt land degradation after cessation of cultivation present opportunities to assess the C sequestration potential of restoration practices. Our aim is to study what key ecosystem and climatic components exert the largest leverage for these lands to be sustainable C sinks. When considering controls on ecosystem C cycling, biodiversity has the potential to be a strong biotic influence. Invasive species can disrupt ecosystem processes by exhibiting functional characteristics which are distinct from their native counterparts. Invasive species, while affecting nearly all ecosystems, may pose a particular threat to restorations and impact rates of C accrual. We measured net ecosystem production (NEP) at a 18 years-old restored tallgrass prairie using the eddy covariance technique coupled to biometric estimates of biomass and soil C in a two year study where climatic conditions and plant species dominance varied. In 2005, the prairie restoration was a strong C sink with a NEP 438 gCm-2, despite a pronounced spring drought. In 2006, with above normal precipitation, a Melilotus alba dominance dramatically reduced NEP when compared to 2005. The loss of ecosystem functional diversity that resulted from the dominance of the invasive M. alba led to a 42% reduction in the length of the photosynthetically active season, as compared to the previous year. These results suggest that understudied biotic limitations to NEP may outweigh the effects of more commonly studied abiotic limitations. Ecosystem models and management strategies should consider biotic limitations to NEP in grasslands in order to maximize long term C sequestration of restorations and CRP management practices.

  4. Modeled Climate and Disturbance Impacts to Carbon Sequestration of Recent Interior Boreal Alaska Ecosystem Productivity Declines

    NASA Astrophysics Data System (ADS)

    Neigh, C. S.; Carvalhais, N.; Collatz, G. J.; Tucker, C. J.

    2010-12-01

    Terrestrial Higher Northern Latitude Boreal ecosystems over the past half century have and are expected to incur substantial future climate warming altering long-term biophysical processes that mediate carbon sink status. Boreal ecosystems are one of the primary terrestrial pools with high organic and mineral soil carbon concentrations due to reduced decomposition from extended periods below freezing. Direct impacts of changing local to regional climate have altered Interior Alaska disturbance regimes shifting patterns of net primary production (NPP), soil heterotrophic respiration (Rh), net ecosystem production (NEP = NPP - Rh) and net biome production (NBP = NEP - De) which includes disturbance events (De). We investigated ecosystem dynamics with a satellite remote sensing driven model accounting for fine-scale heterogeneous events observed from multi temporal-spectral index vectors derived from Landsat. Our intent was to elucidate local to regional processes which have resulted in negative trends observed from the NOAA series of Advanced Very High Resolution Radiometers (AVHRR) over the past decade. The Carnegie-Ames-Stanford approach (CASA) model was run with changing fractional burned area to simulate bi-monthly patterns of net plant carbon fixation, biomass and nutrient allocation, litterfall, soil nitrogen mineralization, combustion emissions, and microbial CO2 production. Carbon reallocation was based on fire disturbances identified with remote sensing data (Landsat, IKONOS, and aerial photography) and disturbance perimeter maps from land management agencies. Warming coupled with insect and fire disturbance emissions reduced interior Boreal forest recalcitrant carbon pools for which losses greatly exceed the North Slope Tundra sink. Our multi spatial-temporal approach confirms substantial forested NPP declines in Landsat and AVHRR while distinguishing abiotic and biophysical disturbance frequency impacts upon NBP.

  5. Ecosystem scale controls on the vascular plant component of dissolved organic carbon across a freshwater delta

    NASA Astrophysics Data System (ADS)

    Eckard, R.; Hernes, P.; Bergamaschi, B.

    2006-12-01

    In the context of global carbon cycling, rivers are typically modeled as spatial integrators of all sources and processes within the watershed. However, substantial evidence in many scientific fields, including soils science, ecology, and hydrology, indicate that spatial variation is significant at sub-watershed scales. Thus it is reasonable to assume that spatial heterogeneity also occurs with respect to carbon sources and dynamics, and that not all features within a watershed are equally important toward determining riverine carbon concentration and composition. Presented are the results of a fine scale investigation of lignin and DOC dynamics within the Sacramento-San Joaquin River Delta. Specifically, DOC concentration ranged from 1.3 to 39.9 mg/L (median 3.0 mg/L), with significant differences in concentration among ecosystems and sampling stations. Lignin concentration ranged from 3.0 to 110 μg/L (median 11.6 μg/L), with significant differences among ecosystems and sampling stations. Lignin carbon normalized yields ranged from 0.07 to 0.84 mg/100 mg OC (median 0.36 mg 100/mg OC), with significant differences among ecosystems. A simple mass balance model utilized lignin phenol ratio parameters to determine the ecosystem scale sources of lignin at the intake to the California State Water Project pumps. Results indicated temporal variation in source, with riverine source signatures predominating from early spring through early autumn, and wetland signatures predominating through the remainder of the year. Finally, Delta-derived sources of DOC appear to overwhelm upstream source signatures, potentially significantly influencing carbon export across the estuary.

  6. Estimating Ecosystem Carbon Stock Change in the Conterminous United States from 1971 to 2010

    NASA Astrophysics Data System (ADS)

    Liu, J.; Sleeter, B. M.; Zhu, Z.; Loveland, T. R.; Sohl, T.; Howard, S. M.; Hawbaker, T. J.; Liu, S.; Heath, L. S.; Cochrane, M. A.; Key, C. H.; Jiang, H.; Price, D. T.; Chen, J. M.

    2015-12-01

    There is significant geographic variability in U.S. ecosystem carbon sequestration due to natural and human environmental conditions. Climate change, natural disturbance and human land use are the major driving forces that can alter local and regional carbon sequestration rates. In this study, a comprehensive environmental input dataset (1-km resolution) was developed and used in the process-based Integrated Biosphere Simulator (IBIS) to quantify the U.S. carbon stock changes from 1971-2010, which potentially forms a baseline for future U.S. carbon scenarios. The key environmental data sources include land cover change information from more than 2,600 sample blocks across U.S. (10-km by 10-km in size, 60-m resolution, 1973-2000), wildland fire scar and burn severity information (30-m resolution, 1984-2010), vegetation canopy percentage and live biomass level (30-m resolution, ~2000), spatially heterogeneous atmospheric carbon dioxide and nitrogen deposition (~50-km resolution, 2003-2009), and newly available climate (4-km resolution, 1895-2010) and soil variables (1-km resolution, ~2000). The IBIS simulated the effects of atmospheric CO2 fertilization, nitrogen deposition, climate change, fire, logging, and deforestation/devegetation on ecosystem carbon changes. Multiple comparable simulations were implemented to quantify the contributions of key environmental drivers.

  7. Determining the Carbon Transport Rate of an Enclosed Tropical Rainforest Ecosystem in Biosphere 2

    NASA Astrophysics Data System (ADS)

    Takagi, Y. A.; Van Haren, J. L.

    2013-12-01

    Determining how carbon moves through a tropical rainforest ecosystem is an important step towards understanding its role as a carbon sink system in the global carbon cycle. The paths by which carbon moves through forest ecosystems are reasonably well known. However, very little is known about how quickly this happens. We will present data from experiments where we isotopically pulse label the atmospheric carbon dioxide within the Biosphere 2 tropical rainforest biome with natural gas derived CO2 (∂13C ~ -40‰ vs. ~ -8.5‰ for ambient air). We are continually monitoring the CO2 concentration and isotope composition of the ambient air along a vertical profile to measure ecosystem gas exchange, and that of six branch-bag and five soil-chamber locations within the Biosphere 2 tropical rainforest, with an Aerodyne Quantum Cascade Laser to trace the labeled carbon (precision for ∂13C = 0.02‰ and CO2 = 0.07ppm, calibrated to NOAA air standards). Environmental parameters such as light, relative humidity, soil moisture, and temperature are monitored at fifteen-minute intervals. We have selected one vine species and three different tree species for branch bag enclosures at two canopy heights that we expect represent the bulk photosynthetic biomass of the rainforest. The soil chambers are distributed randomly. By treating the Biosphere 2 tropical rainforest biome, a glass enclosed ecosystem with 1900m2 of ground, 26700m3 of air, and 92 different plant species, as a model ecosystem, we anticipate to determine carbon transport rates that would otherwise be practically impossible to determine in the real world due to the difficulty of isotopically labeling and monitoring entire canopies or even individual trees, which can reach heights over 60m. The data we have collected thus far will provide a baseline comparison for the labeling data. Comparing the branch bag data with the ecosystem data has helped us determine how well small branches represent the canopy and whole

  8. Control of Growth Efficiency in Young Plantation Loblolly Pine and Sweetgum through Irrigation and Fertigation Enhancement of Leaf Carbon Gain

    SciTech Connect

    L. Samuelson

    1999-07-07

    The overall objective of this study was to determine if growth efficiency of young plantation loblolly pine and sweetgum can be maintained by intensive forest management and whether increased carbon gain is the mechanism controlling growth efficiency response to resource augmentation. Key leaf physiological processes were examined over two growing seasons in response to irrigation, fertigation (irrigation with a fertilizer solution), and fertigation plus pest control (pine only). Although irrigation improved leaf net photosynthesis in pine and decreased stomatal sensitivity to vapor pressure deficit in sweetgum, no consistent physiological responses to fertigation were detected in either species. After 4 years of treatment, a 3-fold increase in woody net primary productivity was observed in both species in response to fertigation. Trees supplemented with fertigation and fertigation plus pest control exhibited the largest increases in growth and biomass. Furthermore, growth efficiency was maintained by fertigation and fertigation plus pest control, despite large increases in crown development and self-shading. Greater growth in response to intensive culture was facilitated by significant gains in leaf mass and whole tree carbon gain rather than detectable increases in leaf level processes. Growth efficiency was not maintained by significant increases in leaf level carbon gain but was possibly influenced by changes in carbon allocation to root versus shoot processes.

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

    NASA Astrophysics Data System (ADS)

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

    2001-12-01

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

  10. Unmasking the effect of a precipitation pulse on the biological processes composing Net Ecosystem Carbon Exchange

    NASA Astrophysics Data System (ADS)

    Lopez-Ballesteros, Ana; Sanchez-Cañete, Enrique P.; Serrano-Ortiz, Penelope; Oyonarte, Cecilio; Kowalski, Andrew S.; Perez-Priego, Oscar; Domingo, Francisco

    2015-04-01

    Drylands occupy 47.2% of the global terrestrial area and are key ecosystems that significantly determine the inter-annual variability of the global carbon balance. However, it is still necessary to delve into the functional behavior of arid and semiarid ecosystems due to the complexity of drivers and interactions between underpinning processes (whether biological or abiotic) that modulate net ecosystem CO2 exchange (NEE). In this context, water inputs are crucial to biological organisms survival in arid ecosystems and frequently arrive via rain events that are commonly stochastic and unpredictable (i.e. precipitation pulses) and strongly control arid land ecosystem structure and function. The eddy covariance technique can be used to investigate the effect of precipitation pulses on NEE, but provide limited understanding of what exactly happens after a rain event. The chief reasons are that, firstly, we cannot measure separately autotrophic and heterotrophic components, and secondly, the partitioning techniques widely utilized to separate Gross Primary Production and Total Ecosystem Respiration, do not work properly in these water-limited ecosystems, resulting in biased estimations of plant and soil processes. Consequently, it is essential to combine eddy covariance measurements with other techniques to disentangle the different biological processes composing NEE that are activated by a precipitation pulse. Accordingly, the main objectives of this work were: (i) to quantify the contribution of precipitation pulse events to annual NEE using the eddy covariance technique in a semiarid steppe located in Almería (Spain), and (ii) to simulate a realistic precipitation pulse in order to understand its effect on the ecosystem, soil and plant CO2 exchanges by using a transitory-state closed canopy chamber, soil respiration chambers and continuous monitoring CO2 sensors inserted in the subsoil. Preliminary results showed, as expected, a delay between soil and plant

  11. Detecting a Terrestrial Biosphere Sink for Carbon Dioxide: Interannual Ecosystem Modeling for the Mid-1980s

    NASA Technical Reports Server (NTRS)

    Potter, Christopher S.; Klooster, Steven A.; Brooks, Vanessa; Gore, Warren J. (Technical Monitor)

    1998-01-01

    There is considerable uncertainty as to whether interannual variability in climate and terrestrial ecosystem production is sufficient to explain observed variation in atmospheric carbon content over the past 20-30 years. In this paper, we investigated the response of net CO2 exchange in terrestrial ecosystems to interannual climate variability (1983 to 1988) using global satellite observations as drivers for the NASA-CASA (Carnegie-Ames-Stanford Approach) simulation model. This computer model of net ecosystem production (NEP) is calibrated for interannual simulations driven by monthly satellite vegetation index data (NDVI) from the NOAA Advanced Very High Resolution Radiometer (AVHRR) at 1 degree spatial resolution. Major results from NASA-CASA simulations suggest that from 1985 to 1988, the northern middle-latitude zone (between 30 and 60 degrees N) was the principal region driving progressive annual increases in global net primary production (NPP; i.e., the terrestrial biosphere sink for carbon). The average annual increase in NPP over this predominantly northern forest zone was on the order of +0.4 Pg (10 (exp 15) g) C per year. This increase resulted mainly from notable expansion of the growing season for plant carbon fixation toward the zonal latitude extremes, a pattern uniquely demonstrated in our regional visualization results. A net biosphere source flux of CO2 in 1983-1984, coinciding with an El Nino event, was followed by a major recovery of global NEP in 1985 which lasted through 1987 as a net carbon sink of between 0.4 and 2.6 Avg C per year. Analysis of model controls on NPP and soil heterotrophic CO2 fluxes (Rh) suggests that regional warming in northern forests can enhance ecosystem production significantly. In seasonally dry tropical zones, periodic drought and temperature drying effects may carry over with at least a two-year lag time to adversely impact ecosystem production. These yearly patterns in our model-predicted NEP are consistent in

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

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

    PubMed

    Yang, Qichun; Zhang, Xuesong

    2016-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

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

    NASA Astrophysics Data System (ADS)

    Rastogi, B.; Still, C. J.; Noone, D. C.; Berkelhammer, M. B.; Whelan, M.; Lai, C. T.; Hollinger, D. Y.; Gupta, M.; Leen, J. B.; Huang, Y. W.

    2015-12-01

    Understanding the processes that control the terrestrial exchange of carbon and water are critical for examining the role of forested ecosystems in changing climates. A small but increasing number of studies have identified Carbonyl Sulfide (OCS) as a potential tracer for photosynthesis. OCS is hydrolyzed by an irreversible reaction in leaf mesophyll cells that is catalyzed by the enzyme, carbonic anhydrase. Leaf- level field and greenhouse studies indicate that OCS uptake is controlled by stomatal activity and that the ratio of OCS and CO2 uptake is reasonably constant. Existing studies on ecosystem OCS exchange have been based on laboratory measurements or short field campaigns and therefore little information on OCS exchange in a natural ecosystem over longer timescales is available. The objective of this study is to further assess the stability of OCS as a tracer for canopy photosynthesis in an active forested ecosystem and also to assess its utility for constraining transpiration, since both fluxes are mediated by canopy stomatal conductance. An off-axis integrated cavity output spectroscopy analyzer (Los Gatos Research Inc.) was deployed at the Wind River Experimental Forest in Washington (45.8205°N, 121.9519°W). Canopy air was sampled from four heights as well as the soil to measure vertical gradients of OCS within the canopy, and OCS exchange between the forest and the atmosphere for the growing season. Here we take advantage of simultaneous measurements of the stable isotopologues of H2O and CO2 at corresponding heights as well as NEE (Net Ecosystem Exchange) from eddy covariance measurements to compare GPP (Gross Primary Production) and transpiration estimates from a variety of independent techniques. Our findings also seek to allow assessment of the environmental and ecophysicological controls on evapotranspiration rates, which are projected to change in coming decades, and are otherwise poorly constrained.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  17. Carbon account of forest ecosystems as a fuzzy system: a case study for Northern Eurasia

    NASA Astrophysics Data System (ADS)

    Shvidenko, A.; Shchepashchenko, D.; Kraxner, F.; Maksyutov, S. S.

    2015-12-01

    We consider practicality of a verified account of Net Ecosystem Carbon Budget for forest ecosystems (FCA) that supposes reliable assessment of uncertainties, i.e. understanding "uncertainty of uncertainties". The FCA is a fuzzy (underspecified) system, of which membership function is inherently stochastic. Thus, any individually used method of FCA is not able to estimate structural uncertainties and usually reported "within method" uncertainties are inevitably partial. Attempting at estimation of "full uncertainties" of the studied system we follow the requirements of applied systems analysis integrating the major methods of terrestrial ecosystems carbon account, assessing the uncertainties "within method" for intermediate and final indicators of FCA with their following mutual constrains. Landscape-ecosystem approach (LEA) 1) serves for strict systems designing the account, 2) contains all relevant spatially distributed empirical and semi-empirical data and models, and 3) is presented in form of an Integrated Land Information System (ILIS). By-pixel parametrization of forest cover is provided by utilizing multi-sensor remote sensing data (12 RS products used) within GEO-wiki platform and other relevant information based on special optimization algorithms. Major carbon fluxes within the LEA (NPP, HR, disturbances etc.) are estimated based on fusion of empirical data with process-based elements by sets of regionally distributed models. Uncertainties within LEA are assessed for each module and at each step of the account. "Within method" results and uncertainties (including LEA, process-based models, eddy covariance, and inverse modelling) are harmonized based on the Bayesian approach. The above methodology have been applied to carbon account of Russian forests for 2000-2010; uncertainties of the FCA for individual years were estimated in limits of 25%. We discussed strengths and weaknesses of the approach, system requirements to different methods of FCA, information

  18. Can We Make Use of Abandoned Land for Carbon Management and Ecosystem Restoration?

    NASA Astrophysics Data System (ADS)

    Yamagata, Y.; Shoyama, K.

    2014-12-01

    Potential conflicts between biodiversity conservation and climate-change mitigation can result in trade-offs in multiple-use land management. This study aimed to detect possible changes in land-use patterns in response to biodiversity conservation and climate-change mitigation measures and the effects on ecosystem services across a watershed. For that purpose, we have developed a new method to combine land-use change scenarios and ecosystem service assessments. We analyzed land-cover change based on past and future scenarios in the rural Kushiro watershed in northern Japan. The analysis showed that if no conservation measures were implemented and the timber and agricultural industry remained small until 2060, supporting and provisioning services would decline due to less land management. Although biodiversity conservation measures are predicted to improve three of the ecosystem services that we studied, carbon sequestration and timber production would be improved to a greater degree by climate-change mitigation measures. The greatest land-cover changes are likely to occur in the unprotected area around the middle reaches of the Kushiro River, and such changes could affect the provision of ecosystem services throughout the entire watershed. Thus, our findings indicate that land-use decisions for the middle reaches of the watershed are particularly important for managing the integrated ecosystem services of the entire watershed for the future.

  19. Biophysical regulation of carbon fluxes over an alpine meadow ecosystem in the eastern Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Wang, Shaoying; Zhang, Yu; Lü, Shihua; Su, Peixi; Shang, Lunyu; Li, Zhaoguo

    2016-06-01

    The eddy covariance method was used to measure net ecosystem CO2 exchange (NEE) between atmosphere and an alpine meadow ecosystem in the eastern Tibetan Plateau of China in 2010. Our results show that photosynthesis was reduced under low air temperature ( T a), high vapor pressure deficit (VPD), and medium soil water content (SWC) conditions, when compared to that under other T a (i.e., medium and high), VPD (i.e., low and medium), and SWC (i.e., low and high) conditions. The apparent temperature sensitivity of ecosystem respiration ( Q 10) declined with progressing phenology during the growing season and decreased with an increase of soil temperature ( T s) during the non-growing season. Increased ecosystem respiration ( R eco) was measured during spring soil thawing. By the path analysis, T a, T s, and VPD were the main control factors of CO2 exchange at 30-min scale in this alpine meadow. Integrated NEE, gross primary production (GPP), and R eco over the measured year were -156.4, 1164.3, and 1007.9 g C m-2, respectively. Zoige alpine meadow was a medium carbon sink based on published data for grassland ecosystems.

  20. An inventory-based carbon budget for forest and woodland ecosystems of Turkey.

    PubMed

    Evrendilek, Fatih

    2004-01-01

    Environmental monitoring of national-level comparisons of CO(2) emissions is needed to quantify sources and sinks of carbon (C) in national ecosystems. In this study, a national forest inventory database was used to estimate the past and current pools and fluxes of C in deciduous and coniferous forest and woodland ecosystems (20.7 x 10(6) ha) of Turkey. Growing C stock was 12.63 t C ha(-1) in 1960 and 16.55 t C ha(-1) in 1995. Total C store in the whole live woody biomass was estimated at 22.77 t C ha(-1) in 1996. The total flux of C from the atmosphere into the forest and woodland ecosystems driven by primary productivity was about 1.46 t C ha(-1)(or 30.2 Mt C) in 1996. The estimated net release of C from the forest and woodland ecosystems of Turkey to the atmosphere was about 1.34 t C ha(-1)(or 21.5 Mt C) in 1996. When C released was taken into account, net ecosystem sequestration (NES) resulted in 0.12 t C ha(-1) per year. Such analytical tools as national forest C budgets are needed to improve our preventive and mitigative strategies for dealing with global climate change.

  1. Irrigation and Fertilization Controls on Critical Zone Carbon and Nitrogen cycles in Harvested Ecosystems

    NASA Astrophysics Data System (ADS)

    Parolari, A.; Katul, G. G.; Porporato, A. M.

    2014-12-01

    Feedbacks between hydrology, soil biogeochemistry, and primary productivity raise questions regarding the broader impact of human modifications to one or more of these critical zone processes. In particular, irrigation and nitrogen fertilization are used simultaneously to stimulate agricultural productivity and biomass export; however, together they may lead to unintended downstream consequences such as increased nitrogen leaching or greenhouse gas release. To quantify such trade-offs among ecosystem services and to identify optimal agricultural management practices, an ecosystem model coupling the water, carbon, and nitrogen cycles is studied. The model is forced by stochastic climate and periodic management interventions that include irrigation, fertilization, and harvest. Steady-state solutions of ecosystems under rotational harvest are developed, demonstrating that these ecosystems operate in a limit-cycle. Under constant fertilization and soil moisture conditions, the model predicts an optimal rotation length associated with maximum yield and maximum ecosystem nitrogen use efficiency. Through plant-soil feedbacks mediated by the harvest, intermediate rotation lengths promote short periods of immobilization, which stimulates mineral nitrogen retention. In these systems, increased soil moisture increases non-productive nitrogen losses, especially under long rotations, where mineral nitrogen availability is greatest. Time-variable water and nitrogen input scenarios are also considered and suggest the possibility of an optimal irrigation-fertilization strategy that balances productivity, which provides an economic benefit, and leaching, which may have consequences for aquatic ecosystems in receiving waters. These results highlight several soil C-N cycle responses to management practices that influence the provision of and trade-off between ecosystem services, namely primary productivity and mineral nitrogen export.

  2. A Source of Terrestrial Organic Carbon to Investigate the Browning of Aquatic Ecosystems

    PubMed Central

    Lennon, Jay T.; Hamilton, Stephen K.; Muscarella, Mario E.; Grandy, A. Stuart; Wickings, Kyle; Jones, Stuart E.

    2013-01-01

    There is growing evidence that terrestrial ecosystems are exporting more dissolved organic carbon (DOC) to aquatic ecosystems than they did just a few decades ago. This “browning” phenomenon will alter the chemistry, physics, and biology of inland water bodies in complex and difficult-to-predict ways. Experiments provide an opportunity to elucidate how browning will affect the stability and functioning of aquatic ecosystems. However, it is challenging to obtain sources of DOC that can be used for manipulations at ecologically relevant scales. In this study, we evaluated a commercially available source of humic substances (“Super Hume”) as an analog for natural sources of terrestrial DOC. Based on chemical characterizations, comparative surveys, and whole-ecosystem manipulations, we found that the physical and chemical properties of Super Hume are similar to those of natural DOC in aquatic and terrestrial ecosystems. For example, Super Hume attenuated solar radiation in ways that will not only influence the physiology of aquatic taxa but also the metabolism of entire ecosystems. Based on its chemical properties (high lignin content, high quinone content, and low C:N and C:P ratios), Super Hume is a fairly recalcitrant, low-quality resource for aquatic consumers. Nevertheless, we demonstrate that Super Hume can subsidize aquatic food webs through 1) the uptake of dissolved organic constituents by microorganisms, and 2) the consumption of particulate fractions by larger organisms (i.e., Daphnia). After discussing some of the caveats of Super Hume, we conclude that commercial sources of humic substances can be used to help address pressing ecological questions concerning the increased export of terrestrial DOC to aquatic ecosystems. PMID:24124511

  3. Land Use and Ecosystems Data from the Carbon Dioxide Information Analysis Center (CDIAC)

    DOE Data Explorer

    CDIAC products are indexed and searchable through a customized interface powered by ORNL's Mercury search engine. Products include numeric data packages, publications, trend data, atlases, models, etc. and can be searched for by subject area, keywords, authors, product numbers, time periods, collection sites, spatial references, etc. Some of the collections may also be included in the CDIAC publication titled Trends Online: A Compendium of Global Change Data. Most data sets, many with numerous data files, are free to download from CDIAC's ftp area. Land Use and Ecosystems information includes Terrestrial Carbon Sequestration Data Sets, data sets from Africa and Asia, the Worldwide Organic Soil Carbon and Nitrogen Dataset, and much more.

  4. Contribution of increasing CO2 and climate to carbon storage by ecosystems in the United States

    USGS Publications Warehouse

    Schimel, D.; Melillo, J.; Tian, H.; McGuire, A.D.; Kicklighter, D.; Kittel, T.; Rosenbloom, N.; Running, S.; Thornton, P.; Ojima, D.; Parton, W.; Kelly, R.; Sykes, M.; Neilson, R.; Rizzo, B.

    2000-01-01

    The effects of increasing carbon dioxide (CO2) and climate on net carbon storage in terrestrial ecosystems of the conterminous United States for the period 1895-1993 were modeled with new, detailed historical climate information. For the period 1980-1993, results from an ensemble of three models agree within 25%, simulating a land carbon sink from CO2 and climate effects of 0.08 gigaton of carbon per year. The best estimates of the total sink from inventory data are about three times larger, suggesting that processes such as regrowth on abandoned agricultural land or in forests harvested before 1980 have effects as large as or larger than the direct effects of CO2 and climate. The modeled sink varies by about 100% from year to year as a result of climate variability.

  5. Subsurface Intertidal Microbes: A Cryptic Source Of Organic Carbon For Beach Ecosystems

    NASA Technical Reports Server (NTRS)

    Rothschild, Lynn J.; Giver, Lorraine J.; Alvarez, Teresa (Technical Monitor)

    1994-01-01

    Some freshwater, marine or hotspring beaches have no visible source of primary production, yet beneath the surface is an interstitial photosynthetic microbial community. To assess the significance of this source of organic carbon, we measured in situ carbon fixation rates in an intertidal marine beach through a diurnal cycle. Gross fixation for a transect (99 x 1 m) perpendicular to the shore was approx. 4041 mg C fixed/ day, or approx. 41 mg C fixed/ sq m day. In contrast, an adjacent well-established cyanobacterial (Lyngbya) mat was approx. 12 x as productive (approx. 490 mg C fixed/sq m day). Thus, subsurface sand mats may be an overlooked, yet important, endogenous source of organic carbon for intertidal ecosystems, as well as a sink in the global carbon cycle.

  6. Herbivory makes major contributions to ecosystem carbon and nutrient cycling in tropical forests.

    PubMed

    Metcalfe, Daniel B; Asner, Gregory P; Martin, Roberta E; Silva Espejo, Javier E; Huasco, Walter Huaraca; Farfán Amézquita, Felix F; Carranza-Jimenez, Loreli; Galiano Cabrera, Darcy F; Baca, Liliana Durand; Sinca, Felipe; Huaraca Quispe, Lidia P; Taype, Ivonne Alzamora; Mora, Luzmila Eguiluz; Dávila, Angela Rozas; Solórzano, Marlene Mamani; Puma Vilca, Beisit L; Laupa Román, Judith M; Guerra Bustios, Patricia C; Revilla, Norma Salinas; Tupayachi, Raul; Girardin, Cécile A J; Doughty, Christopher E; Malhi, Yadvinder

    2014-03-01

    The functional role of herbivores in tropical rainforests remains poorly understood. We quantified the magnitude of, and underlying controls on, carbon, nitrogen and phosphorus cycled by invertebrate herbivory along a 2800 m elevational gradient in the tropical Andes spanning 12°C mean annual temperature. We find, firstly, that leaf area loss is greater at warmer sites with lower foliar phosphorus, and secondly, that the estimated herbivore-mediated flux of foliar nitrogen and phosphorus from plants to soil via leaf area loss is similar to, or greater than, other major sources of these nutrients in tropical forests. Finally, we estimate that herbivores consume a significant portion of plant carbon, potentially causing major shifts in the pattern of plant and soil carbon cycling. We conclude that future shifts in herbivore abundance and activity as a result of environmental change could have major impacts on soil fertility and ecosystem carbon sequestration in tropical forests. PMID:24372865

  7. Carbon cycle. The dominant role of semi-arid ecosystems in the trend and variability of the land CO₂ sink.

    PubMed

    Ahlström, Anders; Raupach, Michael R; Schurgers, Guy; Smith, Benjamin; Arneth, Almut; Jung, Martin; Reichstein, Markus; Canadell, Josep G; Friedlingstein, Pierre; Jain, Atul K; Kato, Etsushi; Poulter, Benjamin; Sitch, Stephen; Stocker, Benjamin D; Viovy, Nicolas; Wang, Ying Ping; Wiltshire, Andy; Zaehle, Sönke; Zeng, Ning

    2015-05-22

    The growth rate of atmospheric carbon dioxide (CO2) concentrations since industrialization is characterized by large interannual variability, mostly resulting from variability in CO2 uptake by terrestrial ecosystems (typically termed carbon sink). However, the contributions of regional ecosystems to that variability are not well known. Using an ensemble of ecosystem and land-surface models and an empirical observation-based product of global gross primary production, we show that the mean sink, trend, and interannual variability in CO2 uptake by terrestrial ecosystems are dominated by distinct biogeographic regions. Whereas the mean sink is dominated by highly productive lands (mainly tropical forests), the trend and interannual variability of the sink are dominated by semi-arid ecosystems whose carbon balance is strongly associated with circulation-driven variations in both precipitation and temperature.

  8. Carbon cycle. The dominant role of semi-arid ecosystems in the trend and variability of the land CO₂ sink.

    PubMed

    Ahlström, Anders; Raupach, Michael R; Schurgers, Guy; Smith, Benjamin; Arneth, Almut; Jung, Martin; Reichstein, Markus; Canadell, Josep G; Friedlingstein, Pierre; Jain, Atul K; Kato, Etsushi; Poulter, Benjamin; Sitch, Stephen; Stocker, Benjamin D; Viovy, Nicolas; Wang, Ying Ping; Wiltshire, Andy; Zaehle, Sönke; Zeng, Ning

    2015-05-22

    The growth rate of atmospheric carbon dioxide (CO2) concentrations since industrialization is characterized by large interannual variability, mostly resulting from variability in CO2 uptake by terrestrial ecosystems (typically termed carbon sink). However, the contributions of regional ecosystems to that variability are not well known. Using an ensemble of ecosystem and land-surface models and an empirical observation-based product of global gross primary production, we show that the mean sink, trend, and interannual variability in CO2 uptake by terrestrial ecosystems are dominated by distinct biogeographic regions. Whereas the mean sink is dominated by highly productive lands (mainly tropical forests), the trend and interannual variability of the sink are dominated by semi-arid ecosystems whose carbon balance is strongly associated with circulation-driven variations in both precipitation and temperature. PMID:25999504

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  10. Elevated carbon dioxide alters impacts of precipitation pulses on ecosystem photosynthesis and respiration in a semi-arid grassland

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Predicting net carbon (C) balance under future global change scenarios requires a comprehensive understanding of photosynthetic (GPP) and ecosystem respiration (Re) responses to atmospheric CO2 concentration and water availability. We measured net ecosystem exchange of CO2 (NEE), GPP and Re prior to...

  11. Soil Carbon Storage in Christmas Tree Farms: Maximizing Ecosystem Management and Sustainability for Carbon Sequestration

    NASA Astrophysics Data System (ADS)

    Chapman, S. K.; Shaw, R.; Langley, A.

    2008-12-01

    Management of agroecosystems for the purpose of manipulating soil carbon stocks could be a viable approach for countering rising atmospheric carbon dioxide concentrations, while maximizing sustainability of the agroforestry industry. We investigated the carbon storage potential of Christmas tree farms in the southern Appalachian mountains as a potential model for the impacts of land management on soil carbon. We quantified soil carbon stocks across a gradient of cultivation duration and herbicide management. We compared soil carbon in farms to that in adjacent pastures and native forests that represent a control group to account for variability in other soil-forming factors. We partitioned tree farm soil carbon into fractions delineated by stability, an important determinant of long-term sequestration potential. Soil carbon stocks in the intermediate pool are significantly greater in the tree farms under cultivation for longer periods of time than in the younger tree farms. This pool can be quite large, yet has the ability to repond to biological environmental changes on the centennial time scale. Pasture soil carbon was significantly greater than both forest and tree farm soil carbon, which were not different from each other. These data can help inform land management and soil carbon sequestration strategies.

  12. Nitrogen feedbacks increase future terrestrial ecosystem carbon uptake in an individual-based dynamic vegetation model

    NASA Astrophysics Data System (ADS)

    Wårlind, D.; Smith, B.; Hickler, T.; Arneth, A.

    2014-11-01

    Recently a considerable amount of effort has been put into quantifying how interactions of the carbon and nitrogen cycle affect future terrestrial carbon sinks. Dynamic vegetation models, representing the nitrogen cycle with varying degree of complexity, have shown diverging constraints of nitrogen dynamics on future carbon sequestration. In this study, we use LPJ-GUESS, a dynamic vegetation model employing a detailed individual- and patch-based representation of vegetation dynamics, to evaluate how population dynamics and resource competition between plant functional types, combined with nitrogen dynamics, have influenced the terrestrial carbon storage in the past and to investigate how terrestrial carbon and nitrogen dynamics might change in the future (1850 to 2100; one representative "business-as-usual" climate scenario). Single-factor model experiments of CO2 fertilisation and climate change show generally similar directions of the responses of C-N interactions, compared to the C-only version of the model as documented in previous studies using other global models. Under an RCP 8.5 scenario, nitrogen limitation suppresses potential CO2 fertilisation, reducing the cumulative net ecosystem carbon uptake between 1850 and 2100 by 61%, and soil warming-induced increase in nitrogen mineralisation reduces terrestrial carbon loss by 31%. When environmental changes are considered conjointly, carbon sequestration is limited by nitrogen dynamics up to the present. However, during the 21st century, nitrogen dynamics induce a net increase in carbon sequestration, resulting in an overall larger carbon uptake of 17% over the full period. This contrasts with previous results with other global models that have shown an 8 to 37% decrease in carbon uptake relative to modern baseline conditions. Implications for the plausibility of earlier projections of future terrestrial C dynamics based on C-only models are discussed.

  13. Nitrogen feedbacks increase future terrestrial ecosystem carbon uptake in an individual-based dynamic vegetation model

    NASA Astrophysics Data System (ADS)

    Wårlind, D.; Smith, B.; Hickler, T.; Arneth, A.

    2014-01-01

    Recently a considerable amount of effort has been put into quantifying how interactions of the carbon and nitrogen cycle affect future terrestrial carbon sinks. Dynamic vegetation models, representing the nitrogen cycle with varying degree of complexity, have shown diverging constraints of nitrogen dynamics on future carbon sequestration. In this study, we use the dynamic vegetation model LPJ-GUESS to evaluate how population dynamics and resource competition between plant functional types, combined with nitrogen dynamics, have influenced the terrestrial carbon storage in the past and to investigate how terrestrial carbon and nitrogen dynamics might change in the future (1850 to 2100; one exemplary "business-as-usual" climate scenario). Single factor model experiments of CO2 fertilisation and climate change show generally similar directions of the responses of C-N interactions, compared to the C-only version of the model, as documented in previous studies. Under a RCP 8.5 scenario, nitrogen limitation suppresses potential CO2 fertilisation, reducing the cumulative net ecosystem carbon uptake between 1850 and 2100 by 61%, and soil warming-induced increase in nitrogen mineralisation reduces terrestrial carbon loss by 31%. When environmental changes are considered conjointly, carbon sequestration is limited by nitrogen dynamics until present. However, during the 21st century nitrogen dynamics induce a net increase in carbon sequestration, resulting in an overall larger carbon uptake of 17% over the full period. This contradicts earlier model results that showed an 8 to 37% decrease in carbon uptake, questioning the often stated assumption that projections of future terrestrial C dynamics from C-only models are too optimistic.

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

    NASA Astrophysics Data System (ADS)

    Rastogi, B.; Kim, Y.; Berkelhammer, M. B.; Noone, D. C.; Lai, C. T.; Hollinger, D. Y.; Bible, K.; Leen, J. B.; Gupta, M.; Still, C. J.

    2014-12-01

    Understanding the processes that control the terrestrial exchange of carbon and water are critical for examining the role of forested ecosystems in changing climates. A small but increasing number of studies have identified Carbonyl Sulfide (OCS) as a potential tracer for photosynthesis. OCS is hydrolyzed by an irreversible reaction in leaf mesophyll cells that is catalyzed by the enzyme, carbonic anhydrase. Leaf-level field and greenhouse studies indicate that OCS uptake is controlled by stomatal activity and that the ratio of OCS and CO2 uptake is reasonably constant. Existing studies on ecosystem OCS exchange have been based on laboratory measurements or short field campaigns and therefore little information on OCS exchange in a natural ecosystem over longer timescales is available. The objective of this study is to further assess the stability of OCS as a tracer for canopy photosynthesis in an active forested ecosystem and also to assess its utility for constraining transpiration, since both fluxes are mediated by canopy stomatal conductance. An off-axis integrated cavity output spectroscopy analyzer (Los Gatos Research Inc.) was deployed at the Wind River Experimental Forest in Washington (45.8205°N, 121.9519°W). Canopy air was sampled from three heights to measure vertical gradients of OCS within the canopy, and OCS exchange between the forest and the atmosphere. Here we take advantage of simultaneous measurements of the stable isotopologues of H2O and CO2 at corresponding heights as well as NEE (Net Ecosystem Exchange) from eddy covariance measurements to compare GPP (Gross Primary Production) and transpiration estimates from a variety of independent techniques. Our findings seek to allow assessment of the environmental and ecophysicological controls on evapotranspiration rates, which are projected to change in coming decades, and are otherwise poorly constrained.

  15. Impact of climate change on the northwestern Mediterranean Sea pelagic planktonic ecosystem and associated carbon cycle

    NASA Astrophysics Data System (ADS)

    Herrmann, Marine; Estournel, Claude; Adloff, Fanny; Diaz, Frédéric

    2014-09-01

    The northwestern Mediterranean Sea (NWMS) is biologically one of the most productive Mediterranean regions. NWMS pelagic planktonic ecosystem is strongly influenced by hydrodynamics, in particular by deep convection that could significantly weaken under the influence of climate change. Here we investigate the response of this ecosystem and associated carbon cycle to the long-term evolution of oceanic and atmospheric circulations. For that we developed a tridimensional coupled physical-biogeochemical model and performed two groups of annual simulations under the climate conditions of respectively the 20th and the end of 21st centuries. Our results suggest that the evolution of oceanic and atmospheric circulations does not modify the NWMS pelagic planktonic ecosystem and associated carbon cycle at a first order. However, differences mainly induced by the deep convection weakening and the surface warming are obtained at a second order. The spring bloom occurs 1 month earlier. Resulting from the decrease in nutrients availability, the bottom up control of phytoplankton development and bacteria growth by the nitrogen and phosphorus availability strengthens and the microbial loop intensifies as the small-sized plankton biomass increases. Carbon net fixation and deep export do not change significantly. The choice of the biogeochemical initial and boundary conditions does not change the representation of the ecosystem seasonal cycle, but the associated uncertainty range can be one order of magnitude larger than the predicted interannual and long-term variabilities. The uncertainty range of long-term trends associated with the physical forcing (hydrological, atmospheric, hydrodynamical, and socioeconomic) is much smaller (<10%).

  16. The combination of different carbon sources enhances bacterial growth efficiency in aquatic ecosystems.

    PubMed

    Fonte, Ellen S; Amado, André M; Meirelles-Pereira, Frederico; Esteves, Francisco A; Rosado, Alexandre S; Farjalla, Vinicius F

    2013-11-01

    The dissolved organic carbon (DOC) pool is composed of several organic carbon compounds from different carbon sources. Each of these sources may support different bacterial growth rates, but few studies have specifically analyzed the effects of the combination of different carbon sources on bacterial metabolism. In this study, we evaluated the response of several metabolic parameters, including bacterial biomass production (BP), bacterial respiration (BR), bacterial growth efficiency (BGE), and bacterial community structure, on the presence of three DOC sources alone and in combination. We hypothesized that the mixture of different DOC sources would increase the efficiency of carbon use by bacteria (BGE). We established a full-factorial substitutive design (seven treatments) in which the effects of the number and identity of DOC sources on bacterial metabolism were evaluated. We calculated the expected metabolic rates of the combined DOC treatments based on the single-DOC treatments and observed a positive interaction on BP, a negative interaction on BR, and, consequently, a positive interaction on BGE for the combinations. The bacterial community composition appeared to have a minor impact on differences in bacterial metabolism among the treatments. Our data indicate that mixtures of DOC sources result in a more efficient biological use of carbon. This study provides strong evidence that the mixture of different DOC sources is a key factor affecting the role of bacteria in the carbon flux of aquatic ecosystems. PMID:23963223

  17. Spatial Simulation of Land Use based on Terrestrial Ecosystem Carbon Storage in Coastal Jiangsu, China

    PubMed Central

    Chuai, Xiaowei; Huang, Xianjin; Wang, Wanjing; Wu, Changyan; Zhao, Rongqin

    2014-01-01

    This paper optimises projected land-use structure in 2020 with the goal of increasing terrestrial ecosystem carbon storage and simulates its spatial distribution using the CLUE-S model. We found the following: The total carbon densities of different land use types were woodland > water area > cultivated land > built-up land > grassland > shallows. Under the optimised land-use structure projected for 2020, coastal Jiangsu showed the potential to increase carbon storage, and our method was effective even when only considering vegetation carbon storage. The total area will increase by reclamation and the original shallows will be exploited, which will greatly increase carbon storage. For built-up land, rural land consolidation caused the second-largest carbon storage increase, which might contribute the most as the rural population will continue to decrease in the future, while the decrease of cultivated land will contribute the most to carbon loss. The area near the coastline has the greatest possibility for land-use change and is where land management should be especially strengthened. PMID:25011476

  18. How Argonne's Intense Pulsed Neutron Source came to life and gained its niche : the view from an ecosystem perspective.

    SciTech Connect

    Westfall, C.; Office of The Director

    2008-02-25

    of money to produce science and technology at multipurpose laboratories like Argonne. For example, in the mid-1990s, about the time the IPNS's fortunes were secured, DOE spent more than $6 billion a year to fund nine such facilities, with Argonne's share totaling $500 million. And an important justification for funding these expensive laboratories is that they operate expensive but powerful scientific tools like the IPNS, generally considered too large to be built and managed by universities. Clearly, 'life and death' decision making has a lot to tell us about how the considerable U.S. federal investment in science and technology at national laboratories is actually transacted and, indeed, how a path is cleared or blocked for good science to be produced. Because forces within Argonne, DOE, and the materials science community obviously dictated the changing fortunes of the IPNS, it makes sense to probe the interactions binding these three environments for an understanding of how the IPNS was threatened and how it survived. In other words, sorting out what happened requires analyzing the system that includes all three environments. In an attempt to find a better way to understand its twists and turns, I will view the life-and-death IPNS story through the lens of an ecological metaphor. Employing the ideas and terms that ecologists use to describe what happens in a system of shared resources, that is, an ecosystem, I will describe the IPNS as an organism that vied with competitors for resources to find a niche in the interrelated environments of Argonne, DOE, and the materials science community. I will start with an explanation of the Argonne 'ecosystem' before the advent of the IPNS and then describe how the project struggled to emerge in the 1970s, how it scratched its way to a fragile niche in the early 1980s, and how it adapted and matured through the turn of the 21st century. The paper will conclude with a summary of what the ecosystem perspective shows about the

  19. Epiphyte dynamics and carbon metabolism in a nutrient enriched Mediterranean seagrass ( Posidonia oceanica ) ecosystem

    NASA Astrophysics Data System (ADS)

    Apostolaki, Eugenia T.; Holmer, Marianne; Marbà, Núria; Karakassis, Ioannis

    2011-08-01

    The study aimed at examining the relationship between epiphyte dynamics and carbon metabolism in seagrass ecosystems under nutrient enrichment. Temporal variability of epiphytes and factors controlling their dynamics (i.e. environmental conditions, substratum availability, substratum stability and herbivore pressure) were assessed in a fish farm impacted and an unaffected Mediterranean seagrass ( Posidonia oceanica) meadow in the Aegean Sea (Greece). The factors controlling epiphyte dynamics responded differently to nutrient enrichment and partly interacted, rendering their cumulative effect on epiphyte load difficult to elucidate. Yet epiphytes accumulated on seagrass leaves near to the fish farm throughout the year, contributing 2 times more in above-ground biomass at cages than the control station. Reduction in substratum availability (i.e. decrease in leaf biomass) and increase in herbivore pressure affected epiphyte load, albeit their effects were not strong enough to counterbalance the effect of nutrient input from fish farm effluents. Moderate yet continuous nutrient input possibly stimulated epiphyte growth in excess of herbivory, shifting the control of epiphytes from top-down to bottom-up. Epiphyte accumulation affected carbon metabolism in the seagrass ecosystem by contributing to enhanced dissolved organic carbon (DOC) release, but seagrass loss was so acute that increased epiphyte cover could not counterbalance the decrease in community carbon production which was mainly driven by seagrass decline.

  20. Carbon sequestration through urban ecosystem services: A case study from Finland.

    PubMed

    Kuittinen, Matti; Moinel, Caroline; Adalgeirsdottir, Kristjana

    2016-09-01

    Plants and soil are natural regulators of atmospheric CO2. Whereas plants sequester atmospheric carbon, soils deposit it for decades. As cities become increasingly more densely built, the available land area for such ecosystem services may decrease. We studied seven different housing areas in the Finnish city of Espoo to ascertain the extent to which site efficiency affects to the ecosystem services if the full life-cycle GHG emissions of these areas are taken into account. The results show that the impact of CO2 uptake through carbon sinks in growing plants and the uptake of soil organic carbon vary greatly. Its share of all emissions varied from a marginal value of 1.2% to a more considerable value of 11.9%. The highest potential was calculated for a detached house located on a large site, while the weakest was calculated for compact apartment blocks. The study revealed that in order to quantify this potential more accurately, several knowledge gaps must first be addressed. These include impartial growth algorithms for Nordic wood species, missing accumulation factors for soil organic carbon in cold climates and statistical maintenance scenarios for gardens. PMID:27213698

  1. Linking Rainfall Variability and Carbon Cycling in a Green Roof Ecosystem

    NASA Astrophysics Data System (ADS)

    Potts, D. L.; Warren, R. J., II; Ivancic, T. A.

    2015-12-01

    Whereas green roof hydrology is well-studied, these systems present a novel opportunity to examine plant-mediated linkages between rainfall and carbon cycling. For example, green roofs experience dramatic fluctuations in soil moisture because they have limited soil water holding capacity and high rates of evaporation. Stonecrop (Sedum spp.) is widely planted in green roofs and its traits reflect an overall strategy of water conservation. In addition to succulent leaves and a slow growth rate, several stonecrop species possess inducible CAM photosynthesis. We made continuous measurements of ecosystem CO2 exchange, soil temperature (T), and volumetric soil moisture (θ) using a chamber-based automated monitoring system installed on a 3-year old green roof located in Buffalo, New York. Concurrent measurements of net ecosystem CO2 exchange (NEE) and ecosystem respiration (Re) allowed us to estimate gross ecosystem CO2 exchange (GEE). We predicted that CAM photosynthesis by stonecrop would be induced by high T and low θ and would manifest at the ecosystem scale by a reductions in both reduced midday CO2 uptake associated with stomatal closure and nighttime net CO2 efflux as CAM-driven assimilation offset respiratory losses. Not surprisingly, increased T and decreased θ negatively influenced GEE while Re increased in response to increased T and θ. During a period of unusually hot, dry conditions the responses of GEE and Re were reflected in a decline in daytime NEE. However, this decline in NEE was not associated with a similar reduction in nighttime Re suggesting that these conditions were insufficient to induce CAM photosynthesis. Future ecohydrological investigations of green roofs may provide new insights into how rainfall variability interacts with plant traits, community diversity, and edaphic factors to shape ecosystem function.

  2. Biophysical Regulation of Carbon Fluxes over an Alpine Meadow Ecosystem in the Eastern Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Wang, Shaoying; Zhang, Yu; Lü, Shihua; Shang, Lunyu

    2014-05-01

    We used the eddy covariance method to measure the CO2 exchange between the atmosphere and an alpine meadow ecosystem in the eastern Tibetan Plateau, China in 2010. The photosynthesis was depressed under low air temperature (Ta), high vapor pressure deficit (VPD) and medium soil water content (SWC) conditions. Temperature was the most dominant factor controlling ecosystem photosynthesis in this alpine meadow. Regardless of photosynthetically active radiation (PAR), the relationship between net ecosystem CO2 exchange (NEE) and Ta (VPD) showed positive correlation when Ta (VPD) lower than optimal value 16.5 ° (0.55 kPa), whereas negative correlation when Ta (VPD) higher than this value. The responses of NEE and ecosystem respiration (Reco) to SWC can be described as a quadratic polynomial when SWC lower than the threshold value 32.5%, however, both NEE and Reco were increased linearly when SWC higher than this value. The optimal SWC for maximum NEE and Reco was 24.6 % when SWC lower than 32.5%. The apparent temperature sensitivity of ecosystem respiration (Q10) declined with the phenology progressed during the growing season, and decreased with the increase in soil temperature (Ts) during the non-growing. Peak daily sums of NEE, gross primary production (GPP), and Reco were -5.27, 13.33, and 10.24 g C m-2 d-1, respectively. Integrated NEE, GPP, and Reco over measured year were -156.4, 1164.3 and 1007.9 g C m-2, respectively. The Zoige alpine meadow was a medium carbon sink in grassland ecosystems.

  3. Response of tundra ecosystems to elevated atmospheric carbon dioxide. [Annual report

    SciTech Connect

    Oechel, W.C.; Grulke, N.E.

    1988-12-31

    Our past research shows that arctic tussock tundra responds to elevated atmospheric CO{sub 2} with marked increases in net ecosystem carbon flux and photosynthetic rates. However, at ambient temperatures and nutrient availabilities, homeostatic adjustments result in net ecosystem flux rates dropping to those found a contemporary CO{sub 2} levels within three years. Evidence for ecosystem-level acclimation in the first season of elevated CO{sub 2} exposure was found in 1987. Photosynthetic rates of Eriophorum vaginatum, the dominant species, adjusts to elevated CO{sub 2} within three weeks. Past research also indicates other changes potentially important to ecosystem structure and function. Elevated CO{sub 2} treatment apparently delays senescence and increases the period of positive photosynthetic activity. Recent results from the 1987 field season verify the results obtained in the 1983--1986 field seasons: Elevated CO{sub 2} resulted in increased ecosystem-level flux rates. Regressions fitted to the seasonal flux rates indicate an apparent 10 d extension of positive CO{sub 2} uptake reflecting a delay of the onset of plant dormancy. This delay in senescence could increase the frost sensitivity of the system. Major end points proposed for this research include the effects of elevated CO{sub 2} and the interaction of elevated atmospheric CO{sub 2} with elevated soil temperature and increased nutrient availability on: (1) Net ecosystem CO{sub 2} flux; (2) Net photosynthetic rates; (3) Patterns and resource controls on homeostatic adjustment in the above processes to elevated CO{sub 2}; (4) Plant-nutrient status, litter quality, and forage quality; (5) Soil-nutrient status; (6) Plant-growth pattern and shoot demography.

  4. Monitoring Ecosystem Carbon and Water Variations During a Severe Drought in the Southwest With AVIRIS and MODIS Sensor Data.

    NASA Astrophysics Data System (ADS)

    Kim, Y.; Huete, A. R.; Didan, K.; Cobb, N.; Koch, G.

    2004-12-01

    We investigated the spatial and temporal variations in vegetation biologic activity across a wide range of ecosystems (desert shrub to conifer forest) in northern Arizona with carbon and water indices derived from fine resolution AVIRIS data and moderate resolution MODIS observations. Leaf level and canopy level surface moisture indices were computed over the range of ecosystems and drought-induced mortality sites with hyperspectral AVIRIS data in the 1240nm and 2100nm water absorption regions. The land surface moisture indices were combined with the vegetation index, carbon measures to map spatial and temporal patterns of above-ground net productivity and analyze ecosystem sensitivity to water availability and precipitation. The coupled water and carbon indices were scaled up to MODIS data for spatial extension and time series analysis over the past 5 years. Land surface moisture and carbon patterns behaved differently across the range of ecosystems and within drought impact sites. Drought impacts were observed in all ecosystems, particularly in tree mortality areas and the grassland and desert areas. Our results show that combined water and carbon indices offer improved sensitivity to ecosystem health assessment and drought detection and analysis. Remotely-sensed land surface water indices combined with the carbon products yielded important information useful in the prediction of vegetation health response to climate change and human land cover modifications.

  5. Soil Organic Carbon and Total Nitrogen Gains in an Old Growth Deciduous Forest in Germany

    PubMed Central

    Schrumpf, Marion; Kaiser, Klaus; Schulze, Ernst-Detlef

    2014-01-01

    Temperate forests are assumed to be organic carbon (OC) sinks, either because of biomass increases upon elevated CO2 in the atmosphere and large nitrogen deposition, or due to their age structure. Respective changes in soil OC and total nitrogen (TN) storage have rarely been proven. We analysed OC, TN, and bulk densities of 100 soil cores sampled along a regular grid in an old-growth deciduous forest at the Hainich National Park, Germany, in 2004 and again in 2009. Concentrations of OC and TN increased significantly from 2004 to 2009, mostly in the upper 0–20 cm of the mineral soil. Changes in the fine earth masses per soil volume impeded the detection of OC changes based on fixed soil volumes. When calculated on average fine earth masses, OC stocks increased by 323±146 g m−2 and TN stocks by 39±10 g m−2 at 0–20 cm soil depth from 2004 to 2009, giving average annual accumulation rates of 65±29 g OC m−2 yr−1 and 7.8±2 g N m−2 yr−1. Accumulation rates were largest in the upper part of the B horizon. Regional increases in forest biomass, either due to recovery of forest biomass from previous forest management or to fertilization by elevated CO2 and N deposition, are likely causes for the gains in soil OC and TN. As TN increased stronger (1.3% yr−1 of existing stocks) than OC (0.9% yr−1), the OC-to-TN ratios declined significantly. Results of regression analyses between changes in OC and TN stocks suggest that at no change in OC, still 3.8 g TN m−2 yr−1 accumulated. Potential causes for the increase in TN in excess to OC are fixation of inorganic N by the clay-rich soil or changes in microbial communities. The increase in soil OC corresponded on average to 6–13% of the estimated increase in net biome productivity. PMID:24586720

  6. Soil organic carbon and total nitrogen gains in an old growth deciduous forest in Germany.

    PubMed

    Schrumpf, Marion; Kaiser, Klaus; Schulze, Ernst-Detlef

    2014-01-01

    Temperate forests are assumed to be organic carbon (OC) sinks, either because of biomass increases upon elevated CO2 in the atmosphere and large nitrogen deposition, or due to their age structure. Respective changes in soil OC and total nitrogen (TN) storage have rarely been proven. We analysed OC, TN, and bulk densities of 100 soil cores sampled along a regular grid in an old-growth deciduous forest at the Hainich National Park, Germany, in 2004 and again in 2009. Concentrations of OC and TN increased significantly from 2004 to 2009, mostly in the upper 0-20 cm of the mineral soil. Changes in the fine earth masses per soil volume impeded the detection of OC changes based on fixed soil volumes. When calculated on average fine earth masses, OC stocks increased by 323 ± 146 g m(-2) and TN stocks by 39 ± 10 g m(-2) at 0-20 cm soil depth from 2004 to 2009, giving average annual accumulation rates of 65 ± 29 g OC m(-2) yr(-1) and 7.8 ± 2 g N m(-2) yr(-1). Accumulation rates were largest in the upper part of the B horizon. Regional increases in forest biomass, either due to recovery of forest biomass from previous forest management or to fertilization by elevated CO2 and N deposition, are likely causes for the gains in soil OC and TN. As TN increased stronger (1.3% yr(-1) of existing stocks) than OC (0.9% yr(-1)), the OC-to-TN ratios declined significantly. Results of regression analyses between changes in OC and TN stocks suggest that at no change in OC, still 3.8 g TN m(-2) yr(-1) accumulated. Potential causes for the increase in TN in excess to OC are fixation of inorganic N by the clay-rich soil or changes in microbial communities. The increase in soil OC corresponded on average to 6-13% of the estimated increase in net biome productivity. PMID:24586720

  7. Soil organic carbon and total nitrogen gains in an old growth deciduous forest in Germany.

    PubMed

    Schrumpf, Marion; Kaiser, Klaus; Schulze, Ernst-Detlef

    2014-01-01

    Temperate forests are assumed to be organic carbon (OC) sinks, either because of biomass increases upon elevated CO2 in the atmosphere and large nitrogen deposition, or due to their age structure. Respective changes in soil OC and total nitrogen (TN) storage have rarely been proven. We analysed OC, TN, and bulk densities of 100 soil cores sampled along a regular grid in an old-growth deciduous forest at the Hainich National Park, Germany, in 2004 and again in 2009. Concentrations of OC and TN increased significantly from 2004 to 2009, mostly in the upper 0-20 cm of the mineral soil. Changes in the fine earth masses per soil volume impeded the detection of OC changes based on fixed soil volumes. When calculated on average fine earth masses, OC stocks increased by 323 ± 146 g m(-2) and TN stocks by 39 ± 10 g m(-2) at 0-20 cm soil depth from 2004 to 2009, giving average annual accumulation rates of 65 ± 29 g OC m(-2) yr(-1) and 7.8 ± 2 g N m(-2) yr(-1). Accumulation rates were largest in the upper part of the B horizon. Regional increases in forest biomass, either due to recovery of forest biomass from previous forest management or to fertilization by elevated CO2 and N deposition, are likely causes for the gains in soil OC and TN. As TN increased stronger (1.3% yr(-1) of existing stocks) than OC (0.9% yr(-1)), the OC-to-TN ratios declined significantly. Results of regression analyses between changes in OC and TN stocks suggest that at no change in OC, still 3.8 g TN m(-2) yr(-1) accumulated. Potential causes for the increase in TN in excess to OC are fixation of inorganic N by the clay-rich soil or changes in microbial communities. The increase in soil OC corresponded on average to 6-13% of the estimated increase in net biome productivity.

  8. Cascading effects of fishing can alter carbon flow through a temperate coastal ecosystem.

    PubMed

    Salomon, Anne K; Shears, Nick T; Langlois, Timothy J; Babcock, Russell C

    2008-12-01

    Mounting evidence suggests that fishing can trigger trophic cascades and alter food web dynamics, yet its effects on ecosystem function remain largely unknown. We used the large-scale experimental framework of four marine reserves, spanning an oceanographic gradient in northeastern New Zealand, to test the extent to which the exploitation of reef predators can alter kelp carbon flux and secondary production. We provide evidence that the reduction of predatory snapper (Pagrus auratus) and lobster (Jasus edwardsii) can lead to an increase in sea urchins (Evechinus chloroticus) and indirect declines in kelp biomass in some locations but not others. Stable carbon isotope ratios (delta13C) of oysters (Crassostrea gigas) and mussels (Perna canaliculus) transplanted in reserve and fished sites within four locations revealed that fishing indirectly reduced the proportion of kelp-derived organic carbon assimilated by filter feeders in two locations where densities of actively grazing sea urchins were 23.7 and 8.3 times higher and kelp biomass was an order of magnitude lower than in non-fished reserve sites. In contrast, in the two locations where fishing had no effect on urchin density or kelp biomass, we detected no effect of fishing on the carbon signature of filter feeders. We show that the effects of fishing on nearshore trophic structure and carbon flux are context-dependent and hinge on large-scale, regional oceanographic factors. Where cascading effects of fishing on kelp biomass were documented, enhanced assimilation of kelp carbon did not result in the magnification of secondary production. Instead, a strong regional gradient in filter feeder growth emerged, best predicted by chlorophyll a. Estimates of kelp contribution to the diet of transplanted consumers averaged 56.9% +/- 6.2% (mean +/- SE) for mussels and 33.8% +/- 7.3% for oysters, suggesting that organic carbon fixed by kelp is an important food source fueling northeastern New Zealand's nearshore food webs

  9. Cascading effects of fishing can alter carbon flow through a temperate coastal ecosystem.

    PubMed

    Salomon, Anne K; Shears, Nick T; Langlois, Timothy J; Babcock, Russell C

    2008-12-01

    Mounting evidence suggests that fishing can trigger trophic cascades and alter food web dynamics, yet its effects on ecosystem function remain largely unknown. We used the large-scale experimental framework of four marine reserves, spanning an oceanographic gradient in northeastern New Zealand, to test the extent to which the exploitation of reef predators can alter kelp carbon flux and secondary production. We provide evidence that the reduction of predatory snapper (Pagrus auratus) and lobster (Jasus edwardsii) can lead to an increase in sea urchins (Evechinus chloroticus) and indirect declines in kelp biomass in some locations but not others. Stable carbon isotope ratios (delta13C) of oysters (Crassostrea gigas) and mussels (Perna canaliculus) transplanted in reserve and fished sites within four locations revealed that fishing indirectly reduced the proportion of kelp-derived organic carbon assimilated by filter feeders in two locations where densities of actively grazing sea urchins were 23.7 and 8.3 times higher and kelp biomass was an order of magnitude lower than in non-fished reserve sites. In contrast, in the two locations where fishing had no effect on urchin density or kelp biomass, we detected no effect of fishing on the carbon signature of filter feeders. We show that the effects of fishing on nearshore trophic structure and carbon flux are context-dependent and hinge on large-scale, regional oceanographic factors. Where cascading effects of fishing on kelp biomass were documented, enhanced assimilation of kelp carbon did not result in the magnification of secondary production. Instead, a strong regional gradient in filter feeder growth emerged, best predicted by chlorophyll a. Estimates of kelp contribution to the diet of transplanted consumers averaged 56.9% +/- 6.2% (mean +/- SE) for mussels and 33.8% +/- 7.3% for oysters, suggesting that organic carbon fixed by kelp is an important food source fueling northeastern New Zealand's nearshore food webs

  10. Impact of extreme inter-annual climatic events on the net ecosystem carbon dioxide exchange of a Sitka spruce forest

    NASA Astrophysics Data System (ADS)

    Saunders, M.; Tobin, B.; Gioria, M.; Cacciotti, E.; Benanti, G.; Osborne, B. A.

    2013-12-01

    0.2 to 0.3 g C m-2 d-1 per degree increase in air temperature. At temperatures below ~0oC the forest was a carbon source, whilst there was a progressive increase in sink capacity as temperatures increased up to ~20 degrees C. The observed decrease in NEE was dependent on both the duration of exposure and the extent to which the temperature was reduced below zero. This information indicates that while temperature remains the key driver of NEE in this forest ecosystem, the observed reduction in NEE during periods of high water availability in 2009 suggests that under future climatic scenarios the magnitude and timing of extreme precipitation events may also have a significant impact on annual carbon gain.

  11. [Distribution of soil organic carbon storage and carbon density in Gahai Wetland ecosystem].

    PubMed

    Ma, Wei-Wei; Wang, Hui; Huang, Rong; Li, Jun-Zhen; Li, De-Yu

    2014-03-01

    The profile distribution and accumulation characteristics of organic carbon of four typical marshes (herbaceous peat, marsh wetland, mountain wetland, subalpine meadow) were studied in Gahai Wetlands of Gannan in July 2011. The results showed that the soil bulk densities of the four typical marshes ranged from 0.22 to 1.29 g x cm(-3). The content of soil organic carbon in the herbaceous peat was higher than in other types, with its average content of organic carbon (286. 80 g x kg(-1)) being about 2.91, 4.99, 7.31 times as much as that of the marsh wetland, mountain wetland and subalpine meadow, respectively. The average organic carbon densities were in order of herbaceous peat > subalpine meadow > marsh wetland > mountain wetland, with the highest in the 0-10 cm layer. The change of organic carbon density along the soil profile was basically in accordance with the organic carbon content in the four typical marshes, but fluctuated with soil depth. There were obviously two carbon storage layers (0-10 and 20-40 cm, respectively) in the four typical marshes. The amounts of organic carbon stored in the 0-60 cm layer of the four typical marshes were 369.46, 278.83, 276.16, 292.23 t x hm(-2), respectively. The total amount of organic carbon stored in the 0-60 cm of the four typical marshes was about 9.50 x 10(6) t.

  12. Carbon-sequestration and ecosystem services in the boreal ecoregion of Alaska

    NASA Astrophysics Data System (ADS)

    Wang, B.; Manies, K.; Labay, K.; Johnson, W. N.; Harden, J. W.

    2011-12-01

    Managing public lands for carbon (C) sequestration is increasingly discussed as a component of national carbon policies. However, management of public land to facilitate carbon sequestration must be considered in the context of other management mandates and the effects on other ecosystem services. Of the United States Fish and Wildlife Service's (USFWS) National Wildlife Refuge lands in Alaska, about 35% are in the boreal ecoregion; primarily in the Intermountain and the Alaska Range Transition ecoregions. These refuges were established to conserve wildlife habitat, fulfill treaty obligations, provide for continued subsistence uses, and ensure necessary water quality and quantity. One of the major factors in determining ecosystem distribution in the boreal ecoregion is disturbance. Fire is the dominant disturbance for Alaska's boreal region. Most USFWS refuge lands are managed with "limited" suppression, where fires burn naturally and are monitored to assure the protection of human life, property, and site specific values (such as historical or religious). However, there is increasing interest in biomass harvest and combustion for local energy production. Harvest and fire can have differing effects on both the spatial and temporal aspects of carbon storage. The current biomass harvest for energy production proposals are considered to be C neutral because they focus on "hazardous" biomass which would burn naturally or in a prescribed burn. The goal of this effort is to explore the relation between C storage and other public land management priorities, as well as, to explore how disturbance type (fire and harvest) affect C storage and boreal ecosystem distribution in the context of wildlife habitat and subsistence use management priorities. We present a conceptual model that defines the linkages among these management priorities, a data gap analysis, and scenarios to be evaluated.

  13. Ecosystem Function in Amazon Floodplain Wetlands: Climate Variability, Landscape Dynamics and Carbon Biogeochemistry.

    NASA Astrophysics Data System (ADS)

    Silva, T. S. F.; Melack, J. M.; Sousa, R. N. D.; Ferreira-Ferreira, J.; Streher, A. S.; Fragal, E. H.; Furtado, L. F.; Resende, A. F. D.; Luize, B. G.; Rudorff, C.; Queiroz, H. L.; Schongart, J.; Novo, E. M.

    2015-12-01

    Wetlands comprise 14% of the Amazon basin, and are a major component of the hydrological and biogeochemical cycles. Most of these areas correspond to floodplain ecosystems along the Amazon River and its major tributaries, hosting unique vegetation types that are strongly controlled by annual hydrological fluctuations. The combination of strong environmental filtering and active fluvial dynamics results in a highly heterogeneous landscape, and in physiological linkages between climate variability and ecosystem processes. We will show several years of results obtained within the framework of the LBA program, discussing the interplay between hydroclimatic variability, landscape dynamics, ecosystem functioning and carbon biogeochemistry in the Amazon floodplains. Using optical and microwave remote sensing, we assessed the distribution of major vegetation types and flooding regimes at several locations across the floodplain. Strong variability in vegetation distribution can be observed, with high and low várzea forests ranging from 30% and 34%, respectively, at the upper Solimões River, to 6% and 25% at the lower Solimões, while non-forested habitats and lakes increase from a percent cover of 8% and 10% to 28% and 27%, respectively. Strong variability in local flood regimes was also determined for each vegetation type, revealing a gradient of habitats within each floodplain. As tree growth, diversity and phenology are affected by flood duration, we expect local conditions to strongly impact carbon stocks and cycling at the landscape scale. Fluvial processes also disturb forest patches, ensuring a mixture of age distributions in the landscape, with varying species composition, carbon stocks, and carbon uptake rates. Herbaceous vegetation growth responds very rapidly to changes in hydrological conditions, and modeling based on microwave imagery and in situ observations showed expected changes of up to 50% in annual net primary production between regular and extreme

  14. Understanding ecosystems' sub-daily water and carbon flux changes during dry-down events

    NASA Astrophysics Data System (ADS)

    Nelson, Jacob; Jung, Martin; Carvalhais, Nuno; Migliavacca, Mirco; Reichstein, Markus

    2016-04-01

    Sub-daily water and carbon flux patterns give important and sometimes overlooked information about ecosystem processes and land-atmosphere feedbacks. While models often perform well down to daily timescales, they can be uncertain with respect to the diurnal courses, especially during dry-down events where the fraction of T to ET is shifting. We analyzed events from multiple locations for unique pattern changes that were robust across sites. Of particular interest were the divergence of water and carbon fluxes during high radiation periods, which indicates changes in water use efficiency as drought conditions intensified. The validity of attributing the signatures to ecosystem transitions such as changes in phenology, switches in soil evaporation vs transpiration dominance, and physiological stress were evaluated by comparing to site specific sap flow, soil moisture, and remote sensing data. Going forward, these findings can be used to further understand ecosystem physiology under drought conditions, and can also be used to partition of water fluxes and better constrain future models.

  15. Evaluating two experimental approaches for measuring ecosystem carbon oxidation state and oxidative ratio

    NASA Astrophysics Data System (ADS)

    Masiello, C. A.; Gallagher, M. E.; Randerson, J. T.; Deco, R. M.; Chadwick, O. A.

    2008-09-01

    Degree of oxidation of organic carbon (Cox) is a fundamental property of the carbon cycle, reflecting the synthesis and decomposition of natural organic matter. Cox is also related to ecosystem oxidative ratio (OR), the molar ratio of O2 to CO2 fluxes associated with net ecosystem exchange (NEE). Here we compare two methods for measuring Cox and OR: (1) %C, %H, %N, and %O elemental analysis, and (2) heat of combustion (ΔHc) measured by means of bomb calorimetry coupled with %C elemental analysis (hereafter referred to as calorimetry). Compared with %C, %N, %H, and %O elemental analysis, calorimetry generates Cox and OR data more rapidly and cheaply. However, calorimetric measurements yield less accurate Cox and OR data. We additionally report Cox and OR data for a pair of biomass standards and a suite of biomass samples. The OR values we measured in these samples were less variable than OR data reported in the literature (generated by simultaneous measurement of ecosystem O2 and CO2 gas mixing ratios). Our biomass OR values had a mean of 1.03 and range of 0.99-1.06. These estimates are lower than the OR value of 1.10 that is often used to partition uptake of fossil fuel CO2 between the ocean and the terrestrial biosphere.

  16. Integrating remotely sensed land cover observations and a biogeochemical model for estimating forest ecosystem carbon dynamics

    USGS Publications Warehouse

    Liu, J.; Liu, S.; Loveland, T.R.; Tieszen, L.L.

    2008-01-01

    Land cover change is one of the key driving forces for ecosystem carbon (C) dynamics. We present an approach for using sequential remotely sensed land cover observations and a biogeochemical model to estimate contemporary and future ecosystem carbon trends. We applied the General Ensemble Biogeochemical Modelling System (GEMS) for the Laurentian Plains and Hills ecoregion in the northeastern United States for the period of 1975-2025. The land cover changes, especially forest stand-replacing events, were detected on 30 randomly located 10-km by 10-km sample blocks, and were assimilated by GEMS for biogeochemical simulations. In GEMS, each unique combination of major controlling variables (including land cover change history) forms a geo-referenced simulation unit. For a forest simulation unit, a Monte Carlo process is used to determine forest type, forest age, forest biomass, and soil C, based on the Forest Inventory and Analysis (FIA) data and the U.S. General Soil Map (STATSGO) data. Ensemble simulations are performed for each simulation unit to incorporate input data uncertainty. Results show that on average forests of the Laurentian Plains and Hills ecoregion have been sequestrating 4.2 Tg C (1 teragram = 1012 gram) per year, including 1.9 Tg C removed from the ecosystem as the consequences of land cover change. ?? 2008 Elsevier B.V.

  17. Analysis of trophic networks and carbon flows in south-eastern Baltic coastal ecosystems

    NASA Astrophysics Data System (ADS)

    Tomczak, Maciej T.; Müller-Karulis, Bärbel; Järv, Leili; Kotta, Jonne; Martin, Georg; Minde, Atis; Põllumäe, Arno; Razinkovas, Arturas; Strake, Solvita; Bucas, Martynas; Blenckner, Thorsten

    2009-04-01

    Carbon flows in five south-eastern Baltic coastal ecosystems (Puck Bay, Curonian Lagoon, Lithuanian coast, Gulf of Riga coast and Pärnu Bay) were compared on the basis of ECOPATH models using 12 common functional groups. The studied systems ranged from the hypertrophic Curonian Lagoon to the mesotrophic Gulf of Riga coast. Interestingly, we found that macrophytes were not consumed by grazers, but rather channelled into the detritus food chain. In all ecosystems fisheries had far reaching impacts on their target species and on the food-web in general. In particular, benthic food-webs were partly affected by indirect fisheries effects. For example, fisheries tend to change the biomass of piscivorous fish, causing a cascading effect on benthivorous fish and macrozoobenthos. These cascades are ecosystem specific and need to be considered when using benthic invertebrates as productivity and eutrophication indicators. Odum’s maturity attributes allowed a ranking of costal ecosystems according to their maturity. Namely, the community development decreased in the following order: Pärnu Bay > Gulf of Riga coast > Lithuanian coast > Puck Bay > Curonian Lagoon.

  18. Structural equation modelling reveals plant-community drivers of carbon storage in boreal forest ecosystems.

    PubMed

    Jonsson, Micael; Wardle, David A

    2010-02-23

    Boreal forest ecosystems are important drivers of the global carbon (C) cycle by acting as both sinks and sources of atmospheric CO(2). While several factors have been proposed as determining the ability of boreal forest to function as C sinks, little is known about their relative importance. In this study, we applied structural equation modelling to a previously published dataset involving 30 boreal-forested islands that vary greatly in their historic fire regime, in order to explore the simultaneous influence of several factors believed to be important in influencing above-ground, below-ground and total ecosystem C accumulation. We found that wildfire was a major driver of ecosystem C sequestration, and exerted direct effects on below-ground C storage (presumably through humus combustion) and indirect effects on both above-ground and below-ground C storage through altering plant-community composition. By contrast, plant diversity influenced only below-ground C storage (and even then only weakly), while net primary productivity and decomposition had no detectable effect. Our results suggest that while boreal forests have great potential for storing significant amounts of C, traits of dominant plant species that promote below-ground C accumulation and the absence of wildfire are the most important drivers of C sequestration in these ecosystems. PMID:19755530

  19. Photosynthetic carbon isotope discrimination and its relationship to the carbon isotope signals of stem, soil and ecosystem respiration (Invited)

    NASA Astrophysics Data System (ADS)

    Wingate, L.; Ogée, J.; Burlett, R.; Bosc, A.; Devaux, M.; Grace, J.; Loustau, D.; Gessler, A.

    2010-12-01

    Photosynthetic carbon (C) isotope discrimination labels photosynthates (δA) and atmospheric CO2 (δa) with variable C isotope compositions during fluctuating environmental conditions. In this context, the C isotope composition of respired CO2 within ecosystems is often hypothesized to vary temporally with photosynthetic discrimination. We investigated the relationship between photosynthetic discrimination and the C isotope signals from stem (δW), soil (δS) and ecosystem (δE) respired CO2 to environmental fluctuations, using novel tuneable diode laser absorption spectrometer instrumentation in a mature maritime pine forest. Broad seasonal changes in photosynthetic discrimination were reflected in δW, δS and δE. However, respired CO2 signals had smaller short-term variations than photosynthetic discrimination and were offset and delayed by 2-10 d, indicating fractionation and isotopic mixing in a large C pool. Variations in δS did not follow photosynthetic discrimination at all times, especially during rainy periods and when there is a strong demand for C allocation above ground. It is likely that future isotope-enabled vegetation models will need to develop transfer functions that can account for these phenomena in order to interpret and predict the isotopic impact of biosphere gas exchange on the C isotope composition of atmospheric CO2. L. Wingate, J. Ogée, R. Burlett, A. Bosc, M. Devaux, J. Grace, D. Loustau and A. Gessler. Photosynthetic carbon isotope discrimination and its relationship to the carbon isotope signals of stem, soil and ecosystem respiration. New Phytologist, doi: 10.1111/j.1469-8137.2010.03384.x

  20. The Influence of Landscape Drainage on Biogeochemical Cycling of Carbon in Agricultural Ecosystems

    NASA Astrophysics Data System (ADS)

    Dalzell, B. J.; King, J. Y.; Mulla, D. J.; Finlay, J. C.; Sands, G. R.

    2008-12-01

    The movement of water through agricultural ecosystems is often modified by the presence of open ditches and subsurface tile drainage systems. Despite the common occurrence of these practices, particularly in the corn- and soybean-producing regions of the midwestern United States, much remains unknown about how altered drainage patterns may influence carbon export from agricultural landscapes. In this study, we examined the role of subsurface drainage systems on the quantity and quality of dissolved carbon export from experimental agricultural fields located in south-central Minnesota. Results from two years of observations show that fields with more intense drainage designs (e.g., greater density of subsurface drain lines) have dissolved organic carbon (DOC) concentrations that are similar to conventionally drained fields. However, fields with more intense drainage exhibit greater annual DOC loads due to higher water yields resulting from more intense drainage. In contrast, dissolved inorganic carbon (DIC) concentrations were consistently greater in fields with more intense drainage practices across all flow conditions. Our ongoing work is focused on determining if these differences in DIC concentrations are the result of either increased weathering or increased soil/plant root respiration resulting in increased soil CO2 concentrations. Molecular weight characterization of samples from our experimental fields shows that DOC from subsurface tile drainage is generally comprised of low molecular weight compounds. This low molecular weight signal is less apparent in samples from downstream ditch and river sites which are dominated by higher molecular weight compounds; suggesting that differences in organic matter source and/or processing are apparent over spatial scales transitioning from the field to small watershed. Overall, these results show that subsurface drainage practices fundamentally alter annual DOC and DIC carbon export from agricultural ecosystems as well

  1. Coordination of crown structure, leaf plasticity and carbon gain within the crowns of three winter-deciduous mature trees.

    PubMed

    Uemura, Akira; Harayama, Hisanori; Koike, Nobuya; Ishida, Atsushi

    2006-05-01

    We examined the vertical profiles of leaf characteristics within the crowns of two late-successional (Fagus crenata Blume and Fagus japonica Maxim.) and one early-successional tree species (Betula grossa Sieb. et Zucc.) in a Japanese forest. We also assessed the contributions of the leaves in each crown layer to whole-crown instantaneous carbon gain at midday. Carbon gain was estimated from the relationship between electron transport and photosynthetic rates. We hypothesized that more irradiance can penetrate into the middle of the crown if the upper crown layers have steep leaf inclination angles. We found that such a crown has a high whole-crown carbon gain, even if leaf traits do not change greatly with decreasing crown height. Leaf area indices (LAIs) of the two Fagus trees (5.26-5.52) were higher than the LAI of the B. grossa tree (4.50) and the leaves of the F. crenata tree were more concentrated in the top crown layers than were leaves of the other trees. Whole-crown carbon gain per unit ground area (micromol m(-2) ground s(-1)) at midday on fine days in summer was 16.3 for F. crenata, 11.0 for F. japonica, and 20.4 for B. grossa. In all study trees, leaf dry mass (LMA) and leaf nitrogen content (N) per unit area decreased with decreasing height in the crown, but leaf N per unit mass increased. Variations (plasticity) between the uppermost and lowermost crown layers in LMA, leaf N, the ratio of chlorophyll to N and the ratio of chlorophyll a to b were smaller for F. japonica and B. grossa than for F. crenata. The light extinction coefficients in the crowns were lower for the F. japonica and B. grossa trees than for the F. crenata tree. The leaf carbon isotope ratio (delta(13)C) was higher for F. japonica and B. grossa than for F. crenata, especially in the mid-crown. These results suggest that, in crowns with low leaf plasticity but steep leaf inclination angles, such as those of F. japonica and B. grossa trees, irradiance can penetrate into the middle of

  2. Historical and projected carbon balance of mature black spruce ecosystems across north america: The role of carbon-nitrogen interactions

    USGS Publications Warehouse

    Clein, J.S.; McGuire, A.D.; Zhang, X.; Kicklighter, D.W.; Melillo, J.M.; Wofsy, S.C.; Jarvis, P.G.; Massheder, J.M.

    2002-01-01

    The role of carbon (C) and nitrogen (N) interactions on sequestration of atmospheric CO2 in black spruce ecosystems across North America was evaluated with the Terrestrial Ecosystem Model (TEM) by applying parameterizations of the model in which C-N dynamics were either coupled or uncoupled. First, the performance of the parameterizations, which were developed for the dynamics of black spruce ecosystems at the Bonanza Creek Long-Term Ecological Research site in Alaska, were evaluated by simulating C dynamics at eddy correlation tower sites in the Boreal Ecosystem Atmosphere Study (BOREAS) for black spruce ecosystems in the northern study area (northern site) and the southern study area (southern site) with local climate data. We compared simulated monthly growing season (May to September) estimates of gross primary production (GPP), total ecosystem respiration (RESP), and net ecosystem production (NEP) from 1994 to 1997 to available field-based estimates at both sites. At the northern site, monthly growing season estimates of GPP and RESP for the coupled and uncoupled simulations were highly correlated with the field-based estimates (coupled: R2= 0.77, 0.88 for GPP and RESP; uncoupled: R2 = 0.67, 0.92 for GPP and RESP). Although the simulated seasonal pattern of NEP generally matched the field-based data, the correlations between field-based and simulated monthly growing season NEP were lower (R2 = 0.40, 0.00 for coupled and uncoupled simulations, respectively) in comparison to the correlations between field-based and simulated GPP and RESP. The annual NEP simulated by the coupled parameterization fell within the uncertainty of field-based estimates in two of three years. On the other hand, annual NEP simulated by the uncoupled parameterization only fell within the field-based uncertainty in one of three years. At the southern site, simulated NEP generally matched field-based NEP estimates, and the correlation between monthly growing season field-based and

  3. Carbon Isotopic Studies of Assimilated and Ecosystem Respired CO2 in a Southeastern Pine Forest. Final Report and Conference Proceedings

    SciTech Connect

    Conte, Maureen H

    2008-04-10

    Carbon dioxide is the major “greenhouse” gas responsible for global warming. Southeastern pine forests appear to be among the largest terrestrial sinks of carbon dioxide in the US. This collaborative study specifically addressed the isotopic signatures of the large fluxes of carbon taken up by photosynthesis and given off by respiration in this ecosystem. By measuring these isotopic signatures at the ecosystem level, we have provided data that will help to more accurately quantify the magnitude of carbon fluxes on the regional scale and how these fluxes vary in response to climatic parameters such as rainfall and air temperature. The focus of the MBL subcontract was to evaluate how processes operating at the physiological and ecosystem scales affects the resultant isotopic signature of plant waxes that are emitted as aerosols into the convective boundary layer. These wax aerosols provide a large-spatial scale integrative signal of isotopic discrimination of atmospheric carbon dioxide by terrestrial photosynthesis (Conte and Weber 2002). The ecosystem studies have greatly expanded of knowledge of wax biosynthetic controls on their isootpic signature The wax aerosol data products produced under this grant are directly applicable as input for global carbon modeling studies that use variations in the concentration and carbon isotopic composition of atmospheric carbon dioxide to quantify the magnitude and spatial and temporal patterns of carbon uptake on the global scale.

  4. Autotrophic and Heterotrophic Controls over Winter Soil Carbon Cycling in a Subalpine Forest Ecosystem

    NASA Astrophysics Data System (ADS)

    Monson, R. K.; Scott-Denton, L. E.; Lipson, D. A.; Weintrub, M. N.; Rosenstiel, T. N.; Schmidt, S. K.; Williams, M. W.; Burns, S. P.; Delany, A. E.; Turnipseed, A. A.

    2005-12-01

    Studies were conducted at the Niwot Ridge Ameriflux site to understand wintertime soil carbon cycling and its control over ecosystem respiration. Wintertime respiration in this ecosystem results in the loss of 60-90% of the carbon assimilated the previous growing season. Thus, an understanding of the controls over winter carbon cycling is required to understand controls over the annual carbon budget. Trees were girdled to prevent the transport of photosynthates to the rhizosphere. In plots with non-girdled trees a large mid-winter pulse of sucrose was observed to enter the soil. In plots with girdled trees, no sucrose pulse was observed. Trees of this ecosystem are not photosynthetically active during the winter, leading us to conclude that the sucrose pulse is due to the death of fine roots that had accumulated sucrose the previous autumn. The sucrose pulse is potentially utilized by a novel winter community of microbes. Using DNA fingerprinting we discovered that the dominant isolates from the winter soils were from Jathinobacter, whereas the summer isolates were from Burkholderia. The winter community was capable of high rates of respiration and exponential growth at low temperatures, whereas the summer community was not. Our winter observations also indicated high activity of N-acetyl-C-glucosaminidase, one of the principal enzymes involved in chitin degradation. The presence of such high chitinase activities implicates decomposing fungal biomass as a principle source of CO2 beneath the snow pack. Using a novel in situ, beneath-snow CO2 measurement system, we observed unprecedented Q10 values for winter respiration, being 98 and 8.44 x 104 for the soil next to tree boles or within the open spaces between trees, respectively. These high Q10 values are likely the result of fractional changes in the availability of liquid water below 0°C and responses of microbial biomass to changes in the liquid water fraction. Using six-years of eddy covariance data, we showed

  5. Getting a Helping Hand From 'Dead Man's Fingers': The Role of Pneumatophore Photosynthesis in Black Mangrove Ecosystem Carbon Fluxes

    NASA Astrophysics Data System (ADS)

    Bovard, B. D.; Hartley, J. G.; Cartwright, F. B.

    2011-12-01

    Getting a Helping Hand From "Dead Man's Fingers": The Role of Pneumatophore Photosynthesis in Black Mangrove Ecosystem Carbon Fluxes B. D Bovard, J.G Hartley and F. B. Cartwright. Mangrove wetlands are thought to be an important carbon sink in the context of global carbon budgets, but many components of their carbon cycle have been unmeasured or understudied. Little is known regarding the role of pneumatophores in ecosystem carbon fluxes, but some species of Avicennia have been shown to possess photosynthetic activity. In this study, the carbon dioxide gas exchange of Avicennia germinans (Black Mangroves) pneumatophores was measured in situ to assess the impact of their photosynthetic activity on ecosystem carbon dynamics in southwest Florida's mangrove ecosystems. Our study site was a stand of Avicennia germinans located on Sanibel Island within the Ding Darling National Wildlife Refuge and was part of a larger study on mangrove ecosystem carbon storage. The density of pneumatophores at this site was 368.4 pneumatophores m-2- with an aboveground pneumatophore biomass of 788.4 g m-2. Pneumatophore dark respiration rates averaged 0.20 ± 0.02 μmol CO2 g-1 s-1, while their fluxes under ambient light conditions were 0.19 ± 0.03 μmol CO2 g-1 s-1, but these fluxes were not statistically different from one another (p<0.21). Although not statistically significant, pneumatophores exposed to light consistently respired less as hypothesized, suggesting their photosynthetic activity is small but not negligible. Combined with pneumatophore density and biomass data, ecosystem carbon fluxes from Avicennia germinans pneumatophores were estimated to be 157.4 μmol CO2 m-2 s-1 in the dark, and 150.3 μmol CO2 m-2 s-1 under ambient light levels, an approximate 5% reduction in pneumatophore carbon losses as a result of pneumatophore photosynthetic activity.

  6. Soil Water Cycling Links to Carbon Content between Ecosystems in the Colorado Front Range

    NASA Astrophysics Data System (ADS)

    Powell, K. M.; Anderson, D. E.; Stannard, D. I.; Mladinich, C. S.; Thienelt, T. S.; Blanken, P.

    2011-12-01

    Near surface soil-water content is crucial to the sustainability of an ecosystem. Additionally, the feedbacks between soil water and soil carbon improve the ability to predict carbon sequestration rates. Organic-carbon content in surface soils influences soil texture and, subsequently, water holding capacity. Preliminary research for two growing seasons (2010 and 2011) compares soil water, temperature, heat flux, and evapotranspiration (ET) with soil organic carbon content at several sites in the Colorado Front Range. Continuous measurements of precipitation, soil moisture and temperature, and energy fluxes were conducted from eddy covariance flux towers at three sites around metropolitan Denver: one urban site and two adjacent sites, a montane forest (Flying J Ranch Open Space), and a native tallgrass prairie (Rocky Flats National Wildlife Refuge (NWR)). Irrigation data were obtained for the Denver urban site and added to its precipitation to obtain total water inputs. Soil samples (0-5cm) were collected at each tower site and analyzed for bulk density, volumetric water content, and organic carbon content. Soil water inputs and losses (as ET) were analyzed for each site and compared to soil organic carbon content. Rocky Flats NWR soils contained the highest organic carbon content (20-30 percent), while the urban site and Flying J Ranch soils contained between 10-15 percent. Comparing grassland sites, the urban soil received 5 times higher water input (600mm, more than half from irrigation) in 2010 than those of Rocky Flats. Despite less water input, the Rocky Flats site developed more soil organic carbon, possibly due to large amounts of grassland biomass mineralization and moderate soil moisture conditions through the season. The Denver urban site demonstrated less soil moisture variability in response to surface-water inputs from precipitation compared to soils at the native grassland and montane sites, perhaps limiting the conditions under which soil carbon

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

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

    PubMed

    Zhang, Lei; Sun, Rui; Xu, Ziwei; Qiao, Chen; Jiang, Guoqing

    2015-01-01

    Quantifying carbon dioxide exchange and understanding the response of key environmental factors in various ecosystems are critical to understanding regional carbon budgets and ecosystem behaviors. For this study, CO2 fluxes were measured in a variety of ecosystems with an eddy covariance observation matrix between June 2012 and September 2012 in the Zhangye oasis area of Northwest China. The results show distinct diurnal variations in the CO2 fluxes in vegetable field, orchard, wetland, and maize cropland. Diurnal variations of CO2 fluxes were not obvious, and their values approached zero in the sandy desert, desert steppe, and Gobi ecosystems. Additionally, daily variations in the Gross Primary Production (GPP), Ecosystem Respiration (Reco) and Net Ecosystem Exchange (NEE) were not obvious in the sandy desert, desert steppe, and Gobi ecosystems. In contrast, the distributions of the GPP, Reco, and NEE show significant daily variations, that are closely related to the development of vegetation in the maize, wetland, orchard, and vegetable field ecosystems. All of the ecosystems are characterized by their carbon absorption during the observation period. The ability to absorb CO2 differed significantly among the tested ecosystems. We also used the Michaelis-Menten equation and exponential curve fitting methods to analyze the impact of Photosynthetically Active Radiation (PAR) on the daytime CO2 flux and impact of air temperature on Reco at night. The results show that PAR is the dominant factor in controlling photosynthesis with limited solar radiation, and daytime CO2 assimilation increases rapidly with PAR. Additionally, the carbon assimilation rate was found to increase slowly with high solar radiation. The light response parameters changed with each growth stage for all of the vegetation types, and higher light response values were observed during months or stages when the plants grew quickly. Light saturation points are different for different species. Nighttime

  10. Contemporary mire net ecosystem carbon balance - controls and susceptibility to change (Invited)

    NASA Astrophysics Data System (ADS)

    Nilsson, M. B.

    2013-12-01

    In this presentation I will address three main issues: 1 - The relative importance of the component carbon (C) fluxes for the annual mire Net Ecosystem Carbon Balance (NECB); 2 - The importance of gross primary production (GPP) versus ecosystem respiration (Reco) for the annual Net Ecosystem Exchange (NEE) and finally; 3) the degree of consistency or inconsistency in how controlling factors affects NEE of different mire types. The annual mire NECB is made up principally by the biosphere-atmosphere exchange of CO2 (NEE) and CH4 and the runoff C-export. One important research issue is to further understand what controls the relative contribution from the component fluxes to the annual mire NECB. A second important major research issue is to reveal the relative importance of gross photosynthesis (GPP) and ecosystem respiration (Reco) respectively for the annual mire NEE. The relative importance of GPP and Reco respectively for the NECB also encounters the effect of changes in the lengths of the growing season and non-growing season respectively. The general understanding is that the low rate of decomposition constitutes the major control on peat accumulation. There is though growing evidences from estimates of contemporary annual as well as growing season NEE and peat core based estimates of long-term C accumulation that GPP is at least as important for the annual NEE. Finally, I will address the question to what extent different mire types respond differently to controlling e.g. if bogs and fens respond differently. Recent empirical as well as modeling studies indicate that e.g. changes in water table level causes contrasting response in NEE between bogs and fens.

  11. Nitrogen controls on ecosystem carbon sequestration: A model implementation and application to Saskatchewan, Canada

    USGS Publications Warehouse

    Liu, J.; Price, D.T.; Chen, J.M.

    2005-01-01

    A plant-soil nitrogen (N) cycling model was developed and incorporated into the Integrated BIosphere Simulator (IBIS) of Foley et al. [Foley, J.A., Prentice, I.C., Ramankutty, N., Levis, S., Pollard, D., Sitch, S., Haxeltine, A., 1996. An integrated biosphere model of land surface process, terrestrial carbon balance and vegetation dynamics. Global Biogeochem. Cycles 10, 603-628]. In the N-model, soil mineral N regulates ecosystem carbon (C) fluxes and ecosystem C:N ratios. Net primary productivity (NPP) is controlled by feedbacks from both leaf C:N and soil mineral N. Leaf C:N determines the foliar and canopy photosynthesis rates, while soil mineral N determines the N availability for plant growth and the efficiency of biomass construction. Nitrogen controls on the decomposition of soil organic matter (SOM) are implemented through N immobilization and mineralization separately. The model allows greater SOM mineralization at lower mineral N, and conversely, allows greater N immobilization at higher mineral N. The model's seasonal and inter-annual behaviours are demonstrated. A regional simulation for Saskatchewan, Canada, was performed for the period 1851-2000 at a 10 km x 10 km resolution. Simulated NPP was compared with high-resolution (1 km x 1 km) NPP estimated from remote sensing data using the boreal ecosystem productivity simulator (BEPS) [Liu, J., Chen, J.M., Cihlar, J., Park, W.M., 1997. A process-based boreal ecosystem productivity simulator using remote sensing inputs. Remote Sens. Environ. 44, 81-87]. The agreement between IBIS and BEPS, particularly in NPP spatial variation, was considerably improved when the N controls were introduced into IBIS. ?? 2005 Elsevier B.V. All rights reserved.

  12. Carbon Biogeochemistry: A Stable Isotope Approach to Trophic Dynamics in an Indian Coastal Ecosystem

    NASA Astrophysics Data System (ADS)

    Mathukumalli, B.; Alagappan, R.

    2005-12-01

    Stable isotope(δ13C & δ15N) approach was applied to understand carbon biogeochemistry and trophic dynamics in an Indian coastal mangrove wetland. The δ13C and δ15N values of potential nutrient sources (mangrove plant leaves, lichen, sediment and suspended material) and in seven species of consumers (invertebrates) were measured. The value of δ13C and δ15N isotopes of different potential nutrient sources and the consumers determine the sources of nutrients for the invertebrate consumer community of the mangrove. There is a significant variation in the stable carbon in the nutrient sources; however, δ15N signatures were not significantly different among the different potential nutrient sources. Organic matter in the sediments under the mangrove vegetation was characterized by relatively negatively fractionated and moderately high C:N ratios, indicating that mangrove derived organic matter was the principal diet source for the invertebrate consumer communities in the mangrove ecosystem. Invertebrates in the mangrove showed a wide range of δ13C signatures and are enriched relative to the mangrove leaf stable isotope values. Micro-environmental differences certainly drive the variability in the nutrient sources and consumable nature among the different regions of the ecosystem. Therefore, further research is needed to determine whether carbon assimilation is different from one zone to another.

  13. Tundra ecosystems observed to be CO2 sources due to differential amplification of the carbon cycle.

    PubMed

    Belshe, E F; Schuur, E A G; Bolker, B M

    2013-10-01

    Are tundra ecosystems currently a carbon source or sink? What is the future trajectory of tundra carbon fluxes in response to climate change? These questions are of global importance because of the vast quantities of organic carbon stored in permafrost soils. In this meta-analysis, we compile 40 years of CO2 flux observations from 54 studies spanning 32 sites across northern high latitudes. Using time-series analysis, we investigated if seasonal or annual CO2 fluxes have changed over time, and whether spatial differences in mean annual temperature could help explain temporal changes in CO2 flux. Growing season net CO2 uptake has definitely increased since the 1990s; the data also suggest (albeit less definitively) an increase in winter CO2 emissions, especially in the last decade. In spite of the uncertainty in the winter trend, we estimate that tundra sites were annual CO2 sources from the mid-1980s until the 2000s, and data from the last 7 years show that tundra continue to emit CO2 annually. CO2 emissions exceed CO2 uptake across the range of temperatures that occur in the tundra biome. Taken together, these data suggest that despite increases in growing season uptake, tundra ecosystems are currently CO2 sources on an annual basis.

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

    PubMed Central

    2013-01-01

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

  15. Dynamical prediction of terrestrial ecosystems and the global carbon cycle: A 25-year hindcast experiment

    NASA Astrophysics Data System (ADS)

    Zeng, Ning; Yoon, Jin-Ho; Vintzileos, Augustin; Collatz, G. James; Kalnay, Eugenia; Mariotti, Annarita; Kumar, Arun; Busalacchi, Antonio; Lord, Stephen

    2008-12-01

    Using a 25-year hindcast experiment, we explore the possibility of seasonal-interannual prediction of terrestrial ecosystems and the global carbon cycle. This has been achieved using a prototype forecasting system in which the dynamic vegetation and terrestrial carbon cycle model VEGAS was forced with 15-member ensemble climate predictions generated by the NOAA/NCEP coupled climate forecasting system (CFS) for the period 1981-2005, with lead times up to 9 months. The results show that the predictability is dominated by the ENSO signal with its major influence on the tropical and subtropical regions, including South America, Indonesia, southern Africa, eastern Australia, western United States, and central Asia. There is also important non-ENSO related predictability such as that associated with midlatitude drought. Comparison of the dynamical prediction results with benchmark statistical prediction methods such as anomaly persistence and damping show that the dynamical method performs significantly better. The hindcasted ecosystem variables and carbon flux show significantly slower decrease in skill at longer lead time compared to the climate forcing variables, partly because of the memories in land and vegetation processes that filter out the higher-frequency noise and sustain the signal.

  16. The Carbon Balance Pivot Point of Southwestern U.S. Semiarid Ecosystems: Insights From the 21st Century Drought

    NASA Astrophysics Data System (ADS)

    Scott, R. L.; Biederman, J.; Barron-Gafford, G.; Hamerlynck, E. P.

    2015-12-01

    Global-scale studies indicate that semiarid ecosystems strongly regulate the long-term trend and interannual variability of the terrestrial carbon sink, possibly due to changes in vegetation and an inherent sensitivity to changes in water availability. However, we lack understanding of how climate shifts, such as the ongoing decadal-scale drought in the Southwest US, impact carbon sink functioning in semiarid ecosystems with differing structure. Therefore, we investigated the response of net ecosystem production of carbon dioxide (NEP) to changes in annual water availability in four Southwest US ecosystems varying in relative shrub, tree and grass abundance. Using eddy covariance carbon dioxide and water vapor flux measurements collected over the last drought-impacted decade, we identified a precipitation "pivot point" in the annual carbon balance for each ecosystem type where annual NEP switched from negative to positive. At the three sites with larger amounts of grass, rather than woody plant, cover, pivot points were closer to the drought-period mean annual precipitation (MAP) than MAP over the preceding 30 years, suggesting the carbon pools of these grassier ecosystems have more quickly adjusted to the decadal-scale drought. Current-year water availability, as quantified by evapotranspiration (ET) overwhelmingly drove the response of gross ecosystem photosynthesis (GEP) and respiration (Reco) fluxes. Ecosystem water use efficiency (GEP/ET) increased with water availability and leaf area index, resulting in a more efficient photosynthetic use of water in wetter years and at wetter sites. Grasslands supported a higher leaf area than shrublands at a given water availability, and thus had higher GEP/ET. Differences in GEP/ET were also related to the relative proportion of abiotic evaporation, estimated from the ET intercept in a linear regression of ET and GEP, to total ET at a site, highlighting the importance of ET partitioning for understanding how semiarid

  17. Quantifying carbon dioxide fluxes from photodegrading plant litter in arid ecosystems

    NASA Astrophysics Data System (ADS)

    Brandt, L. A.; Bohnet, C.; King, J. Y.

    2007-12-01

    Biogeochemical models fail to fully explain patterns of litter decomposition in arid ecosystems. Previous research in arid ecosystems has demonstrated that photodegradation, the break-down of chemical compounds by solar radiation, can account for a significant proportion of surface litter mass loss in these ecosystems. However, little is known about the mechanisms of this mass loss. We investigated the potential for solar radiation to lead to direct mineralization to carbon dioxide (CO2) in 5 litter species native to both arid and mesic ecosystems that receive high levels of solar radiation. In one experiment, we exposed litter to a factorial design of ultraviolet (UV) radiation (UV+, UV-), and sterilization (sterile, non-sterile) over a 10 week period in the lab under dry conditions. Over the ten week period, the only significant effect on CO2 emissions was due to UV exposure, with UV+ treatments producing 6 times the amount of CO2 produced under the UV- treatments. CO2 production rates remained constant over the 10 week period, following a zero order decay model. In a second experiment, we exposed litter of one species to natural solar radiation outdoors on clear, sunny days close to the summer solstice in Minnesota. Our emission rates were seven times higher under natural radiation than under lamps in the lab, possibly due to increased temperature and higher radiation intensity. We found that UV radiation accounted for the largest proportion (47%) of photochemically-induced CO2 emissions, while shortwave visible radiation (<500 nm) accounted for 38% of CO2 emissions. A small percentage (15%) was due to wavelengths longer than 500 nm. Production of CO2 under natural radiation averaged 13 mg C m-2 d-1 on clear sunny days. Assuming a linear relationship between total solar irradiance and CO2 production, we estimate that CO2 production via photodegradation is between 3.5 and 7 g C m-2 y- 1 in arid ecosystems in the southwestern USA. Taken together with low levels of

  18. Temporal-Spatial Pattern of Carbon Stocks in Forest Ecosystems in Shaanxi, Northwest China.

    PubMed

    Cui, Gaoyang; Chen, Yunming; Cao, Yang

    2015-01-01

    The precise and accurate quantitative evaluation of the temporal and spatial pattern of carbon (C) storage in forest ecosystems is critical for understanding the role of forests in the global terrestrial C cycle and is essential for formulating forest management policies to combat climate change. In this study, we examined the C dynamics of forest ecosystems in Shaanxi, northwest China, based on four forest inventories (1989-1993, 1994-1998, 1999-2003, and 2004-2008) and field-sampling measurements (2012). The results indicate that the total C storage of forest ecosystems in Shaanxi increased by approximately 29.3%, from 611.72 Tg in 1993 to 790.75 Tg in 2008, partially as a result of ecological restoration projects. The spatial pattern of C storage in forest ecosystems mainly exhibited a latitude-zonal distribution across the province, increasing from north (high latitude) to south (low latitude) generally, which signifies the effect of environmental conditions, chiefly water and heat related factors, on forest growth and C sequestration. In addition, different data sources and estimation methods had a significant effect on the results obtained, with the C stocks in 2008 being considerably overestimated (864.55 Tg) and slightly underestimated (778.07 Tg) when measured using the mean C density method and integrated method, respectively. Overall, our results demonstrated that the forest ecosystem in Shaanxi acted as a C sink over the last few decades. However, further studies should be carried out with a focus on adaption of plants to environmental factors along with forest management for vegetation restoration to maximize the C sequestration potential and to better cope with climate change. PMID:26353011

  19. Tree Species Linked to Large Differences in Ecosystem Carbon Distribution in the Boreal Forest of Alaska

    NASA Astrophysics Data System (ADS)

    Melvin, A. M.; Mack, M. C.; Johnstone, J. F.; Schuur, E. A. G.; Genet, H.; McGuire, A. D.

    2014-12-01

    In the boreal forest of Alaska, increased fire severity associated with climate change is altering plant-soil-microbial feedbacks and ecosystem carbon (C) dynamics. The boreal landscape has historically been dominated by black spruce (Picea mariana), a tree species associated with slow C turnover and large soil organic matter (SOM) accumulation. Historically, low severity fires have led to black spruce regeneration post-fire, thereby maintaining slow C cycling rates and large SOM pools. In recent decades however, an increase in high severity fires has led to greater consumption of the soil organic layer (SOL) during fire and subsequent establishment of deciduous tree species in areas previously dominated by black spruce. This shift to a more deciduous dominated landscape has many implications for ecosystem structure and function, as well as feedbacks to global C cycling. To improve our understanding of how boreal tree species affect C cycling, we quantified above- and belowground C stocks and fluxes in adjacent, mid-successional stands of black spruce and Alaska paper birch (Betula neoalaskana) that established following a 1958 fire near Fairbanks, Alaska. Although total ecosystem C pools (aboveground live tree biomass + dead wood + SOL + top 10 cm of mineral soil) were similar for the two stand types, the distribution of C among pools was markedly different. In black spruce, 78% of measured C was found in soil pools, primarily in the SOL, where spruce contained twice the C stored in paper birch (4.8 ± 0.3 vs. 2.4 ± 0.1 kg C m-2). In contrast, aboveground biomass dominated ecosystem C pools in birch forest (6.0 ± 0.3 vs. 2.5 ± 0.2 kg C m-2 in birch and spruce, respectively). Our findings suggest that tree species exert a strong influence over plant-soil-microbial feedbacks and may have long-term effects on ecosystem C sequestration and storage that feedback to the climate system.

  20. Sustainability of Carbon Sequestration in Terrestrial Ecosystems: Theoretical Framework and a Case Study

    NASA Astrophysics Data System (ADS)

    Luo, Y.

    2002-12-01

    A sound understanding of the sustainability of terrestrial carbon (C) sequestration is critical for the success of any policies geared to stabilize atmospheric greenhouse concentrations. This includes the controversial Kyoto Protocol and/or other greenhouse strategies by individual countries. However, the sustainability of C sinks and pools has not been carefully studied with either empirical or theoretical approaches. This study establishes a theoretical framework to define the sustainability based on C influx and residence time (t). Ecosystem C influx is determined by canopy photosynthetic capacity, which is regulated by leaf photosynthetic capacity and leaf area index. The residence time represents the capacity of an ecosystem to store C in plant and soil pools (i.e., the C-storage capacity). The C-sequestration capacity in an ecosystem is jointly determined by the canopy photosynthetic capacity and the C-storage capacity. The C-sequestration capacity is maintained in a future global change scenario only if neither the canopy photosynthetic capacity nor the C-storage capacity is up-or down-regulated. In that case, the future rate of terrestrial C sequestration is primarily determined by environmental forcing functions. The forcing functions could be the rising of atmospheric CO2 concentration, forest regrowth, woody plant encroachment, and nitrogen deposition. We applied this framework to the Free-Air CO2 Enrichment (FACE) experiment in Duke Forest, North Carolina, USA. We estimated C influx with a mechanistic canopy model and residence time via inverse analysis of multiple data sets. Our results indicated that neither canopy photosynthetic capacity nor the C-storage capacity was altered by elevated CO2 at this forest site Thus, the current evidence from both experimental observations and inverse analysis suggests that C sequestration in the ecosystem will increase gradually as Ca gradually increases. Nonetheless, the increased C sequestration in terrestrial

  1. Temporal-Spatial Pattern of Carbon Stocks in Forest Ecosystems in Shaanxi, Northwest China

    PubMed Central

    Cui, Gaoyang; Chen, Yunming; Cao, Yang

    2015-01-01

    The precise and accurate quantitative evaluation of the temporal and spatial pattern of carbon (C) storage in forest ecosystems is critical for understanding the role of forests in the global terrestrial C cycle and is essential for formulating forest management policies to combat climate change. In this study, we examined the C dynamics of forest ecosystems in Shaanxi, northwest China, based on four forest inventories (1989–1993, 1994–1998, 1999–2003, and 2004–2008) and field-sampling measurements (2012). The results indicate that the total C storage of forest ecosystems in Shaanxi increased by approximately 29.3%, from 611.72 Tg in 1993 to 790.75 Tg in 2008, partially as a result of ecological restoration projects. The spatial pattern of C storage in forest ecosystems mainly exhibited a latitude-zonal distribution across the province, increasing from north (high latitude) to south (low latitude) generally, which signifies the effect of environmental conditions, chiefly water and heat related factors, on forest growth and C sequestration. In addition, different data sources and estimation methods had a significant effect on the results obtained, with the C stocks in 2008 being considerably overestimated (864.55 Tg) and slightly underestimated (778.07 Tg) when measured using the mean C density method and integrated method, respectively. Overall, our results demonstrated that the forest ecosystem in Shaanxi acted as a C sink over the last few decades. However, further studies should be carried out with a focus on adaption of plants to environmental factors along with forest management for vegetation restoration to maximize the C sequestration potential and to better cope with climate change. PMID:26353011

  2. Wildfire, thermokarst and vegetation change: integrating diverse controls over carbon cycling in arctic and boreal ecosystems

    NASA Astrophysics Data System (ADS)

    Mack, M. C.; Alexander, H. D.; DeMarco, J.; Melvin, A.

    2012-12-01

    Climate is warming more rapidly in the tundra and forests of high northern latitudes than any other place on earth. Large, globally-important stocks of carbon (C) reside in these ecosystems. Characterized by cold, moist climate and frozen soils, these ecosystems have historically acted as a net sink for atmospheric C: they remove more C from the atmosphere on an annual basis than they release, resulting in the accumulation of large stocks in soils and plants. With warming climate comes the potential for fundamental changes in ecological controls over C cycling. Plant growth is limited by both low temperature and the slow regeneration of nutrients such as nitrogen (N). If warming stimulates plant growth by alleviating these limitations, than C uptake may increase. Indeed, satellite indices of greening as well as observations of shrub expansion and northern migration of the arctic treeline point towards increased plant productivity concurrent with climate warming. But as soils warm, microbial decomposition and release of C to the atmosphere, as well as disturbances such as wildfire or thermal erosion (thermokarst), are likely to increase, and it is unclear whether increased C loss may balance or even outweigh increased production, at least on the time-scale of decades to centuries. Understanding the net outcome of these two processes is important because it determines the sign of the feedback between the arctic/boreal C cycle and climate. A positive feedback, where warming increases C losses more than uptake, would amplify anthropogenic changes in climate, accelerating warming and destabilizing feedbacks between ecosystems and the atmosphere. A negative feedback, by contrast, where warming increases C uptake more than losses, would dampen the anthropogenic signal and stabilize climate. This presentation will focus on three general areas of ecological control over net ecosystem C balance in arctic and boreal ecosystems: nutrient availability, changing disturbance

  3. How have past fire disturbances contributed to the current carbon balance of boreal ecosystems?

    NASA Astrophysics Data System (ADS)

    Yue, C.; Ciais, P.; Zhu, D.; Wang, T.; Peng, S. S.; Piao, S. L.

    2016-02-01

    Boreal fires have immediate effects on regional carbon budgets by emitting CO2 into the atmosphere at the time of burning, but they also have legacy effects by initiating a long-term carbon sink during post-fire vegetation recovery. Quantifying these different effects on the current-day pan-boreal (44-84° N) carbon balance and quantifying relative contributions of legacy sinks by past fires is important for understanding and predicting the carbon dynamics in this region. Here we used the global dynamic vegetation model ORCHIDEE-SPITFIRE (Organising Carbon and Hydrology In Dynamic Ecosystems - SPread and InTensity of FIRE) to attribute the contributions by fires in different decades between 1850 and 2009 to the carbon balance of 2000-2009, taking into account the atmospheric CO2 change and climate change since 1850. The fire module of ORCHIDEE-SPITFIRE was turned off for each decade in turn and was also turned off before and after the decade in question in order to model the legacy carbon trajectory by fires in each past decade. We found that, unsurprisingly, fires that occurred in 2000-2009 are a carbon source (-0.17 Pg C yr-1) for the carbon balance of 2000-2009, whereas fires in all decades before 2000 contribute carbon sinks with a collective contribution of 0.23 Pg C yr-1. This leaves a net fire sink effect of 0.06 Pg C yr-1, or 6.3 % of the simulated regional carbon sink (0.95 Pg C yr-1). Further, fires with an age of 10-40 years (i.e., those that occurred during 1960-1999) contribute more than half of the total sink effect of fires. The small net sink effect of fires indicates that current-day fire emissions are roughly balanced out by legacy sinks. The future role of fires in the regional carbon balance remains uncertain and will depend on whether changes in fires and associated carbon emissions will exceed the enhanced sink effects of previous fires, both being strongly affected by global change.

  4. Climate sensitivity of global terrestrial ecosystems' subdaily carbon, water, and energy dynamics.

    NASA Astrophysics Data System (ADS)

    Yu, R.; Ruddell, B. L.; Childers, D. L.; Kang, M.

    2015-12-01

    Abstract: Under the context of global climate change, it is important to understand the direction and magnitude of different ecosystems respond to climate at the global level. In this study, we applied dynamical process network (DPN) approach combined with eco-climate system sensitivity model and used the global FLUXNET eddy covariance measurements (subdaily net ecosystem exchange of CO2, air temperature, and precipitation) to access eco-climate system sensitivity to climate and biophysical factors at the flux site level. For the first time, eco-climate system sensitivity was estimated at the global flux sites and extrapolated to all possible land covers by employing artificial neural network approach and using the MODIS phenology and land cover products, the long-term climate GLDAS-2 product, and the GMTED2010 Global Grid elevation dataset. We produced the seasonal eco-climate system DPN maps, which revealed how global carbon dynamics driven by temperature and precipitation. We also found that the eco-climate system dynamical process structures are more sensitive to temperature, whether directly or indirectly via phenology. Interestingly, if temperature continues rising, the temperature-NEE coupling may increase in tropical rain forest areas while decrease in tropical desert or Savanna areas, which means that rising temperature in the future could lead to more carbon sequestration in tropical forests whereas less carbon sequestration in tropical drylands. At the same time, phenology showed a positive effect on the temperature-NEE coupling at all pixels, which suggests increased greenness may increase temperature driven carbon dynamics and consequently carbon sequestration globally. Precipitation showed relatively strong influence on the precipitation-NEE coupling, especially indirectly via phenology. This study has the potential to conduct eco-climate system short-term and long-term forecasting.

  5. The carbon balance pivot point of southwestern U.S. semiarid ecosystems: Insights from the 21st century drought

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Global-scale studies indicate that semiarid regions strongly regulate the terrestrial carbon sink. However, we lack understanding of how climatic shifts, such as decadal drought, impact carbon sequestration across the wide-range of structural diversity in semiarid ecosystems. Therefore, we used edd...

  6. [Stability and organic carbon characteristics of soil aggregates under different ecosystems in karst canyon region].

    PubMed

    Tan, Qiu-Jin; Song, Tong-Qing; Peng, Wan-Xi; Zeng, Fu-Ping; Du, Hu; Yang, Gai-Ren; Fan, Fu-Jing

    2014-03-01

    Soil aggregates and their organic carbon distributions were studied under six ecosystems, i. e., farmland (short for ST), dry land (HD), grassland (CD), shrubbery (GC), plantation (RGL) and secondary forest (CSL), in a karst canyon region of China by a combination of field investigation and laboratory analysis. The result showed that, soil aggregates were dominated by particles with sizes>8 mm in the ecosystems except HD under dry sieving, and basically presented a trend of decreasing firstly, then increasing and finally decreasing along with particle sizes decreasing; while soil aggregates were dominated by particles with sizes > 5 mm in the ecosystems except HD under wet sieving and decreased with decreasing of particle sizes. The mean mass diameter (MMD) was in the order of ST>CD>RGL>CSL>GC>HD and the geometric mean diameter (GMD) was ST>CD>RGL>CSL>HD>GC by dry sieving, and MMD was RGL>CSL>GC>CD>ST>HD and GMD was CSL>RGL>GC>CD>ST>HD by wet sieving. Therefore, MMD and especially GMD of wet sieving were more accurate than that of dry sieving to evaluate soil aggregates quality in the karst cannon region. The fractal dimension (D) of mechanical stability in soil aggregates followed the order of CD>HD>ST>RGL>CSL>GC and the water stability was in the order of GC>CSL>RGL>HD> CD>ST. The higher the SOC content was, the larger values of D, MMD, GMD became, and the more sense the soil structure made. Soil organic carbon content was highest in the aggregate particles with sizes ranging from 0.25 to 0.053 mm, and the content in some particles with sizes > 5 mm was lowest. However, the contribution rate of particles with sizes > 5 mm was largest to soil organic carbon, which gradually decreased with the decrease of particle size.

  7. The influence of ecosystem nitrogen status on carbon cycling in forests

    NASA Astrophysics Data System (ADS)

    Ollinger, S. V.; Smith, M.; Richardson, A.; Hollinger, D. Y.; Martin, M.; Jenkins, J.

    2006-12-01

    The carbon and nitrogen cycles in terrestrial ecosystems are tightly coupled through a shared set of biological processes. The N status of plant canopies exerts a direct influence on carbon assimilation through its well-known effect on net photosynthesis. In soils, both the accumulation of N and the decay of organic matter are often related to the initial C/N ratio of litterfall. Similarly, respiration rates in both roots and foliage have been shown to be positively correlated with tissue N concentrations. These linkages suggest that the N status of ecosystems may provide a useful indicator of their overall C metabolism. Further, evidence from both CO2 and N enrichment experiments indicates that alteration of one cycle can have important implications for the other. This is significant in that global cycles of both C and N have been greatly perturbed by humans. Despite the well-known influence of nitrogen availability on fluxes of carbon, few studies have explicitly examined the role of nitrogen as it pertains to spatial and temporal variation in carbon cycling. This is due, in part, to limited crossover between different scientific communities, but also stems from some very real methodological limitations that make regional-scale assessment of N status difficult. Here, we report on an NACP investigation that examines the degree to which rates of carbon assimilation and growth in forests can be related to both local and regional variation in ecosystem N status. Field measurements from a series of forested research sites within the AmeriFlux network have been combined with hyperspectral remote sensing data from the AVIRIS and Hyperion instruments. Results from a cross-site synthesis indicate a positive relationship between canopy N and the maximum rate of carbon assimilation, as measured by flux towers. Because existing methods of canopy N detection are restricted to small landscapes, a parallel investigation involves developing generalizeable canopy N detection

  8. Quantification of terrestrial ecosystem carbon dynamics in the conterminous United States combining a process-based biogeochemical model and MODIS and AmeriFlux data

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Satellite remote sensing provides continuous temporal and spatial information of terrestrial ecosystems. Using these remote sensing data and eddy flux measurements and biogeochemical models, such as the Terrestrial Ecosystem Model (TEM), should provide a more adequate quantification of carbon dynami...

  9. Quantifying thermal constraints on carbon and water fluxes in a mixed-conifer sky island ecosystem

    NASA Astrophysics Data System (ADS)

    Braun, Z.; Minor, R. L.; Potts, D. L.; Barron-Gafford, G. A.

    2012-12-01

    Western North American forests represent a potential, yet uncertain, sink for atmospheric carbon. Revealing how predicted climatic conditions of warmer temperatures and longer inter-storm periods of moisture stress might influence the carbon status of these forests requires a fuller understanding of plant functional responses to abiotic stress. While data related to snow dominated montane ecosystems has become more readily available to parameterize ecosystem function models, there is a paucity of data available for Madrean sky island mixed-conifer forests, which receive about one third of their precipitation from the North American Monsoon. Thus, we quantified ecophysiological responses to moisture and temperature stress in a Madrean mixed-conifer forest near Tucson, Arizona, within the footprint of the Mt. Bigelow Eddy Covariance Tower. In measuring a series of key parameters indicative of carbon and water fluxes within the dominant species across pre-monsoon and monsoon conditions, we were able to develop a broader understanding of what abiotic drivers are most restrictive to plant performance in this ecosystem. Within Pinus ponderosa (Ponderosa Pine), Pseudotsuga menziesii (Douglas Fir), and Pinus strobiformis (Southwestern White Pine) we quantified: (i) the optimal temperature (Topt) for maximum photosynthesis (Amax), (ii) the range of temperatures over which photosynthesis was at least 50% of Amax (Ω50), and (iii) each conifer's water use efficiency (WUE) to relate to the balance between carbon uptake and water loss in this high elevation semiarid ecosystem. Our findings support the prediction that photosynthesis decreases under high temperatures (>30°C) among the three species we measured, regardless of soil moisture status. However, monsoon moisture reduced sensitivity to temperature extremes and fluctuations (Ω50), which substantially magnified total photosynthetic productivity. In particular, wet conditions enhanced Amax the most dramatically for P

  10. Integration of ecosystem services into the carbon footprint of milk of South German dairy farms.

    PubMed

    Robert Kiefer, Lukas; Menzel, Friederike; Bahrs, Enno

    2015-04-01

    Allocation of greenhouse gas emissions (GHG) in Life Cycle Assessments (LCA) is challenging especially when multi-functionality of dairy farms, which do not only produce milk but also meat is considered. Moreover, some farms fulfill a wide range of additional services for society such as management of renewable natural resources as well as preservation of biodiversity and cultural landscapes. Due to the increasing degradation of ecosystems many industrialized as well as developing countries designed payment systems for environmental services. This study examines different allocation methods of GHG for a comparatively large convenience sample of 113 dairy farms located in grassland-based areas of southern Germany. Results are carbon footprints of 1.99 kg CO2eq/kg of fat and protein corrected milk (FPCM) on average if "no allocation" for coupled products is performed. "Physical allocation" results in 1.53 kg CO2eq/kg FPCM and "conventional economic allocation" in 1.66 kg CO2eq/kg FPCM on average if emissions are apportioned between milk and meat. Economic allocation which includes ecosystem services for society based on the farm net income as a new aspect in this study results in a carbon footprint of 1.5 kg CO2eq/kg FPCM on average. System expansion that puts greater emphasis on coupled beef production accounts for a carbon footprint of 0.68 kg CO2eq/kg FPCM on average. Intense milk production systems with higher milk yields show better results based on "no allocation", "physical allocation" and "conventional economic allocation". By contrast, economic allocation, which takes into account ecosystem services favors extensive systems, especially in less favored areas. This shows that carbon footprints of dairy farms should not be examined one-dimensionally based on the amount of milk and meat that is produced on the farm. Rather, a broader perspective is necessary that takes into account the multi-functionality of dairy farms especially in countries where a wide

  11. Integration of ecosystem services into the carbon footprint of milk of South German dairy farms.

    PubMed

    Robert Kiefer, Lukas; Menzel, Friederike; Bahrs, Enno

    2015-04-01

    Allocation of greenhouse gas emissions (GHG) in Life Cycle Assessments (LCA) is challenging especially when multi-functionality of dairy farms, which do not only produce milk but also meat is considered. Moreover, some farms fulfill a wide range of additional services for society such as management of renewable natural resources as well as preservation of biodiversity and cultural landscapes. Due to the increasing degradation of ecosystems many industrialized as well as developing countries designed payment systems for environmental services. This study examines different allocation methods of GHG for a comparatively large convenience sample of 113 dairy farms located in grassland-based areas of southern Germany. Results are carbon footprints of 1.99 kg CO2eq/kg of fat and protein corrected milk (FPCM) on average if "no allocation" for coupled products is performed. "Physical allocation" results in 1.53 kg CO2eq/kg FPCM and "conventional economic allocation" in 1.66 kg CO2eq/kg FPCM on average if emissions are apportioned between milk and meat. Economic allocation which includes ecosystem services for society based on the farm net income as a new aspect in this study results in a carbon footprint of 1.5 kg CO2eq/kg FPCM on average. System expansion that puts greater emphasis on coupled beef production accounts for a carbon footprint of 0.68 kg CO2eq/kg FPCM on average. Intense milk production systems with higher milk yields show better results based on "no allocation", "physical allocation" and "conventional economic allocation". By contrast, economic allocation, which takes into account ecosystem services favors extensive systems, especially in less favored areas. This shows that carbon footprints of dairy farms should not be examined one-dimensionally based on the amount of milk and meat that is produced on the farm. Rather, a broader perspective is necessary that takes into account the multi-functionality of dairy farms especially in countries where a wide

  12. A dynamical systems analysis of the data assimilation linked ecosystem carbon (DALEC) models.

    PubMed

    Chuter, Anna M; Aston, Philip J; Skeldon, Anne C; Roulstone, Ian

    2015-03-01

    Changes in our climate and environment make it ever more important to understand the processes involved in Earth systems, such as the carbon cycle. There are many models that attempt to describe and predict the behaviour of carbon stocks and stores but, despite their complexity, significant uncertainties remain. We consider the qualitative behaviour of one of the simplest carbon cycle models, the Data Assimilation Linked Ecosystem Carbon (DALEC) model, which is a simple vegetation model of processes involved in the carbon cycle of forests, and consider in detail the dynamical structure of the model. Our analysis shows that the dynamics of both evergreen and deciduous forests in DALEC are dependent on a few key parameters and it is possible to find a limit point where there is stable sustainable behaviour on one side but unsustainable conditions on the other side. The fact that typical parameter values reside close to this limit point highlights the difficulty of predicting even the correct trend without sufficient data and has implications for the use of data assimilation methods.

  13. The transfer of modern organic carbon by landslide activity in tropical montane ecosystems

    NASA Astrophysics Data System (ADS)

    Ramos Scharrón, Carlos E.; Castellanos, Edwin J.; Restrepo, Carla

    2012-09-01

    Geomorphic processes play an important role in the transfer and storage of carbon within steep mountainous terrain. Among these, mass wasting stands out because of its impact on above- and below-ground carbon pools and its potential for releasing or sequestering carbon. A combined remote-sensing and GIS modeling approach was used to quantify the amount and spatial redistribution of modern organic carbon mobilized by mass wasting activity in a tropical mountain setting. The study focused on a population of hundreds of shallow, translational landslides triggered by Hurricane Mitch (1998) on seven watersheds draining the southern flank of the Sierra de Las Minas mountain range (SLM) in central-eastern Guatemala. Results illustrate that mass wasting contributed to the transfer of 43 × 104MgC, or 3%, of the pre-event C in above-ground vegetation and soils for an equivalent carbon flux rate of 0.08-0.33 MgC ha-1 y-1, depending on whether we consider Hurricane Mitch to be a landslide-triggering event with a 20-year or an 80-year recurrence interval. While 30% of this carbon was delivered to hillslopes or first-order streams with a presumed high potential for long-term sequestration, the remaining 70% was delivered to higher-order streams with unknown carbon retention capabilities. Therefore, the ultimate fate of the carbon released by landsliding is very uncertain, but depending on the proportion sequestered by colluvial deposits, the recurrence interval of landslide-triggering events, and the rate of ecosystem recuperation at the landslide failure sites, mass wasting could be either a net source or sink of carbon. In a simulated setting based on the SLM study results in which all carbon transferred by landslides from all tropical mountains of the globe is released to the atmosphere, it would represent an amount equivalent to 1%-11% of the global carbon currently being released by the burning of fossil fuels. Meanwhile, in a projected scenario where a significant

  14. High Resolution Ecosystem Modeling as Part of a Robust Carbon Monitoring System

    NASA Astrophysics Data System (ADS)

    Armstrong, A. H.; Hurtt, G. C.; Dubayah, R.; Fisk, J. P.; Pinto, N.; Franks, S.; Suarez, J.; Rourke, O.; Flanagan, S.

    2011-12-01

    The ability to accurately assess aboveground biomass and associated carbon stocks across large heterogeneous landscapes is a topic at the forefront of current scientific investigation and methodological refinement. Of key importance in the advancement of carbon assessment and monitoring systems is the development of high-resolution ecosystem models that have the ability to incorporate fine-scale in situ vegetation measurements as well as high-resolution satellite imagery, such as LIDAR, to improve larger-scale estimates of carbon and reduce uncertainties in our overall understanding of global carbon cycle dynamics. The aim of this study was to develop and test a high-resolution version of the Ecosystem Demography (ED) Model, as well as develop a framework with the capability to model vegetation dynamics at 90m resolution over large geographic areas. This unprecedented combination of high resolution and large domain size, constrained with multiple sources of remote sensing and field data, provides the basis for a robust carbon monitoring system. The application of this system will monitor changes in carbon stocks over large continental areas through time and will introduce predictive capability for future planning and management purposes at a more human-relevant scale than has been previously achieved. Our experimental approach was designed to quantify the individual effect of each input dataset by running multi-scale model tests using combinations of biotic and abiotic input data. Through this methodology we sought to answer the following: 1) What are the high resolution carbon stocks and fluxes (past, present, future) over the domain and 2) How do different input datasets improve and/or constrain model estimates? Aboveground biomass results of model runs compared favorably to LIDAR and field-derived estimates over the study area. From model results, we developed aboveground biomass and flux maps for Anne Arundel and Howard Counties in Maryland, that in conjunction

  15. Rock Outcrops Redistribute Organic Carbon and Nutrients to Nearby Soil Patches in Three Karst Ecosystems in SW China.

    PubMed

    Wang, Dianjie; Shen, Youxin; Li, Yuhui; Huang, Jin

    2016-01-01

    Emergent rock outcrops are common in terrestrial ecosystems. However, little research has been conducted regarding their surface function in redistributing organic carbon and nutrient fluxes to soils nearby. Water that fell on and ran off 10 individual rock outcrops was collected in three 100 × 100 m plots within a rock desertification ecosystem, an anthropogenic forest ecosystem, and a secondary forest ecosystem between June 2013 and June 2014 in Shilin, SW China. The concentrations of total organic carbon (TOC), total nitrogen (N), total phosphorus (P), and potassium (K) in the water samples were determined during three seasons, and the total amounts received by and flowing out from the outcrops were calculated. In all three ecosystems, TOC and N, P, and K were found throughout the year in both the water received by and delivered to nearby soil patches. Their concentrations and amounts were generally greater in forested ecosystems than in the rock desertification ecosystem. When rock outcrops constituted a high percentage (≥ 30%) of the ground surface, the annual export of rock outcrop runoff contributed a large amount of organic carbon and N, P, and K nutrients to soil patches nearby by comparison to the amount soil patches received via atmospheric deposition. These contributions may increase the spatial heterogeneity of soil fertility within patches, as rock outcrops of different sizes, morphologies, and emergence ratios may surround each soil patch.

  16. Rock Outcrops Redistribute Organic Carbon and Nutrients to Nearby Soil Patches in Three Karst Ecosystems in SW China

    PubMed Central

    Wang, Dianjie; Shen, Youxin; Li, Yuhui; Huang, Jin

    2016-01-01

    Emergent rock outcrops are common in terrestrial ecosystems. However, little research has been conducted regarding their surface function in redistributing organic carbon and nutrient fluxes to soils nearby. Water that fell on and ran off 10 individual rock outcrops was collected in three 100 × 100 m plots within a rock desertification ecosystem, an anthropogenic forest ecosystem, and a secondary forest ecosystem between June 2013 and June 2014 in Shilin, SW China. The concentrations of total organic carbon (TOC), total nitrogen (N), total phosphorus (P), and potassium (K) in the water samples were determined during three seasons, and the total amounts received by and flowing out from the outcrops were calculated. In all three ecosystems, TOC and N, P, and K were found throughout the year in both the water received by and delivered to nearby soil patches. Their concentrations and amounts were generally greater in forested ecosystems than in the rock desertification ecosystem. When rock outcrops constituted a high percentage (≥ 30%) of the ground surface, the annual export of rock outcrop runoff contributed a large amount of organic carbon and N, P, and K nutrients to soil patches nearby by comparison to the amount soil patches received via atmospheric deposition. These contributions may increase the spatial heterogeneity of soil fertility within patches, as rock outcrops of different sizes, morphologies, and emergence ratios may surround each soil patch. PMID:27509199

  17. Rock Outcrops Redistribute Organic Carbon and Nutrients to Nearby Soil Patches in Three Karst Ecosystems in SW China.

    PubMed

    Wang, Dianjie; Shen, Youxin; Li, Yuhui; Huang, Jin

    2016-01-01

    Emergent rock outcrops are common in terrestrial ecosystems. However, little research has been conducted regarding their surface function in redistributing organic carbon and nutrient fluxes to soils nearby. Water that fell on and ran off 10 individual rock outcrops was collected in three 100 × 100 m plots within a rock desertification ecosystem, an anthropogenic forest ecosystem, and a secondary forest ecosystem between June 2013 and June 2014 in Shilin, SW China. The concentrations of total organic carbon (TOC), total nitrogen (N), total phosphorus (P), and potassium (K) in the water samples were determined during three seasons, and the total amounts received by and flowing out from the outcrops were calculated. In all three ecosystems, TOC and N, P, and K were found throughout the year in both the water received by and delivered to nearby soil patches. Their concentrations and amounts were generally greater in forested ecosystems than in the rock desertification ecosystem. When rock outcrops constituted a high percentage (≥ 30%) of the ground surface, the annual export of rock outcrop runoff contributed a large amount of organic carbon and N, P, and K nutrients to soil patches nearby by comparison to the amount soil patches received via atmospheric deposition. These contributions may increase the spatial heterogeneity of soil fertility within patches, as rock outcrops of different sizes, morphologies, and emergence ratios may surround each soil patch. PMID:27509199

  18. Conservation of soil organic carbon, biodiversity and the provision of other ecosystem services along climatic gradients in West Africa

    NASA Astrophysics Data System (ADS)

    Marks, E.; Aflakpui, G. K. S.; Nkem, J.; Poch, R. M.; Khouma, M.; Kokou, K.; Sagoe, R.; Sebastiã, M.-T.

    2009-08-01

    Terrestrial carbon resources are major drivers of development in West Africa. The distribution of these resources co-varies with ecosystem type and rainfall along a strong Northeast-Southwest climatic gradient. Soil organic carbon, a strong indicator of soil quality, has been severely depleted in some areas by human activities, which leads to issues of soil erosion and desertification, but this trend can be altered with appropriate management. There is significant potential to enhance existing soil carbon stores in West Africa, with benefits at the global and local scale, for atmospheric CO2 mitigation as well as supporting and provisioning ecosystem services. Three key factors impacting carbon stocks are addressed in this review: climate, biotic factors, and human activities. Climate risks must be considered in a framework of global change, especially in West Africa, where landscape managers have few resources available to adapt to climatic perturbations. Among biotic factors, biodiversity conservation paired with carbon conservation may provide a pathway to sustainable development, and biodiversity conservation is also a global priority with local benefits for ecosystem resilience, biomass productivity, and provisioning services such as foodstuffs. Finally, human management has largely been responsible for reduced carbon stocks, but this trend can be reversed through the implementation of appropriate carbon conservation strategies in the agricultural sector, as shown by multiple studies. Owing to the strong regional climatic gradient, country-level initiatives will need to consider carbon sequestration approaches for multiple ecosystem types. Given the diversity of environments, global policies must be adapted and strategies developed at the national or sub-national levels to improve carbon storage above and belowground. Initiatives of this sort must act locally at farmer scale, and focus on ecosystem services rather than on carbon sequestration solely.

  19. Partitioning of organic carbon in European Russian tundra and taiga ecosystems

    NASA Astrophysics Data System (ADS)

    Oosterwoud, M. R.; Temminghoff, E. J. M.; van der Zee, S. E. A. T. M.

    2009-04-01

    Sorption of dissolved organic carbon (DOC) on mineral phases is an important process for carbon preservation and element cycling in soils. Sorption of DOC to active minerals results in its fractionation because hydrophobic compounds (humic and fulvic acids) will be preferentially sorbed. Binding of cations (Ca2+, Mg2+, Al3+, Fe3+) by the DOC reduces the negative charge and thus its water solubility. At low pH and high cation concentrations, cations may cause coagulation of DOC. The sorption and/or coagulation are important factors in relation to DOC transport. Little is known about DOC partitioning between the soil solid and solution phases of arctic ecosystems. As a consequence of future warming arctic ecosystem will shift from surface water dominated to groundwater dominated systems. In general, permafrost affected soils with shallow active layers, having lateral flow towards the stream with only short contact time to mineral layers, lead to higher hydrophobic (humic and fulvic acid) DOC concentrations in streams compared to permafrost free soils where a larger share of hydrophilic DOC is expected to be discharged into streams. Changes in the delivery of DOC, nutrients and major ions to arctic rivers may have important consequences for primary production and carbon cycling. The partitioning of DOC is a fundamental process needed for modelling current and future stream water quality and solute transport. Therefore, the objective of this study is to determine the sorption and consequent fractionation of DOC in arctic ecosystems. During fieldwork carried out in the summer of 2007 and 2008 in the Russian Komi Republic, we collected soil, soil solution and surface water samples in both a forested taiga and a permafrost affected tundra catchment. The liquid samples were analysed for total organic carbon and inorganic cations. A rapid batch procedure was used for determining the humic-, fulvic- and hydrophilic acid fractions. Using the chemical speciation model

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    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.

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

    PubMed

    Aslan-Sungur, Guler; Lee, Xuhui; Evrendilek, Fatih; Karakaya, Nusret

    2016-06-01

    Peatland ecosystems play an important role in the global carbon (C) cycle as significant C sinks. However, human-induced disturbances can turn these sinks into sources of atmospheric CO2. Long-term measurements are needed to understand seasonal and interannual variability of net ecosystem CO2 exchange (NEE) and effects of hydrological conditions and their disturbances on C fluxes. Continuous eddy-covariance measurements of NEE were conducted between August 2010 and April 2014 at Yenicaga temperate peatland (Turkey), which was drained for agricultural usage and for peat mining until 2009. Annual NEE during the three full years of measurement indicated that the peatland acted as a CO2 source with large interannual variability, at rates of 246, 244 and 663 g Cm(-2)yr(-1) for 2011, 2012, and 2013 respectively, except for June 2011, and May to July 2012. The emission strengths were comparable to those found for severely disturbed tropical peatlands. The peak CO2 emissions occurred in the dry summer of 2013 when water table level (WTL) was below a threshold value of -60 cm and soil water content (SCW) below a threshold value of 70% by volume. Water availability index was found to have a stronger explanatory power for variations in monthly ecosystem respiration (ER) than the traditional water status indicators (SCW and WTL). Air temperature, evapotranspiration and vapor pressure deficient were the most significant variables strongly correlated with NEE and its component fluxes of gross primary production and ER. PMID:26950633

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

    PubMed Central

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

    2016-01-01

    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. PMID:26813078

  3. Factors controlling the temporal variability of ecosystem respiration and its carbon isotope composition

    NASA Astrophysics Data System (ADS)

    Fassbinder, J.; Griffis, T. J.; Baker, J. M.; Erickson, M.; Billmark, K.; Smith, J.

    2009-12-01

    Ecosystem respiration (FR ) is the major pathway for carbon loss from terrestrial ecosystems. Stable carbon isotope analyses have been used to improve our understanding of the processes controlling ecosystem respiration. In particular, 13CO2 has been used to partition the autotrophic (Fa) and heterotrophic (Fh) contributions to FR. Further, there has been some concern in the literature regarding the temporal variability of the isotopic composition of ecosystem respiration (δR) and its potential influence on ecosystem flux partitioning based on isotope methods. In this study, we used an automated chamber and tunable diode laser system to measure soil respiration (FRs) and its isotopic composition (δRs) in an agricultural ecosystem under a C3/C4 crop rotation. Further, we used the same chamber-TDL system in a climate controlled greenhouse facility with C3/C4 treatments to examine the main factors causing variability in δRs and δR. The chamber data revealed strong diurnal patterns in the isotopic composition of Fh in the agricultural soil plots before crop emergence and in the greenhouse experiments involving bare soils. The diurnal pattern consisted of a sharp enrichment of up to 6‰ from 0700 to 1200 hr followed by a gradual depletion throughout the afternoon and evening. The diurnal signals of FR and soil temperature closely resembled the diurnal signal of δh, but consistently lagged δh by 3 to 4 hours. During peak corn growth, diurnal variation in δRs was strongly influenced by the isotopic composition of root respiration (δas), which enriched nighttime δRs by as much as 7‰ and daytime δRs by as much as 3‰. Chamber and flux-gradient data also indicated considerable seasonal variation in δR during corn growing seasons, ranging from -25‰ at the time of planting to -11‰ during peak growth. Less variation in δR was observed during soybean seasons, with values ranging from -26 to -21‰. Major shifts in δR during corn seasons were consistently

  4. Natural ecosystems

    USGS Publications Warehouse

    Fleishman, Erica; Belnap, Jayne; Cobb, Neil; Enquist, Carolyn A.F.; Ford, Karl; MacDonald, Glen; Pellant, Mike; Schoennagel, Tania; Schmit, Lara M.; Schwartz, Mark; van Drunick, Suzanne; Westerling, Anthony LeRoy; Keyser, Alisa; Lucas, Ryan

    2013-01-01

    Natural Ecosystems analyzes the association of observed changes in climate with changes in the geographic distributions and phenology (the timing of blossoms or migrations of birds) for Southwestern ecosystems and their species, portraying ecosystem disturbances—such as wildfires and outbreaks of forest pathogens—and carbon storage and release, in relation to climate change.

  5. Carbon fluxes in the pelagic ecosystem of the Gulf of Trieste (Northern Adriatic Sea)

    NASA Astrophysics Data System (ADS)

    Umani, Serena Fonda; Malfatti, Francesca; Del Negro, Paola

    2012-12-01

    By measuring a broad suite of physical, chemical, and biological parameters coupled with experiments on grazing efficiency of mesozoo-, microzoo- and heteronano-plankton we were able to depict the seasonal trophic status of the pelagic system in the Gulf of Trieste over a period of 8 years from 1998 to 2005. In winter and spring, primary production exceeded respiration, the autotrophic fraction biomass was higher than the heterotrophic biomass. Moreover, predation on microphytoplankton and autotrophic nanoplankton largely structured the ecosystem and bacterial carbon production accounted for <50% of primary production. The ratio of primary production/respiration was higher than 1 in winter and spring suggesting that pelagic ecosystem was autotrophic whereas in summer and in autumn the ratio was lower than 1 suggesting a shift towards net heterotrophic status. Carbon export was possible in winter and in autumn, and the few data from the sediment trap supported the theoretical rates. Thus since spring most of the C fixed by photosynthesis remained segregated in the surface layer and possibly it was exported to the bottom through grazer fecal pellets. In summer the system was dominated by heterotrophic picoplankton, which showed the highest production rate. In this scenario we hypothesize that the DOC produced during the winter-spring period can sustain a high and active bacterial biomass that is the primary energy source for the whole system. Picoplankton communities were heavily grazed by microzooplankton and heteronano-plankton, moreover predation rates of mesozooplankton on microzooplankton were particularly high in summer. Despite the high variability typical of the coastal areas, the pelagic ecosystem during these 8 years has shifted seasonally from a nutrient-excited state (winter-spring) to a background state (summer-autumn) as it has been observed from open-ocean ecosystem. Understanding the dynamic and the magnitude of this variability-shift is rather

  6. High elastic polyurethane/carbon nanotube composite laminate for structure health monitoring by gain shifting of antenna sensing element

    NASA Astrophysics Data System (ADS)

    Olejnik, Robert; Slobodian, Petr; Matyas, Jiri; Gorakh Babar, Dipak

    2016-03-01

    The composite of carbon nanotubes and polyurethane (PU) was prepared by simple filtration technique. The PU nonwoven filtration membrane was prepared by electrospinning. A layer of carbon nanotubes was prepared by vacuum filtration on the surface of PU membrane. The resulting composite was subsequently placed on highly elastic polyurethane substrate. The contribution shows an efficient method of preparing the sensing element for monitoring the state of strain of loaded structures by using highly elastic polyurethane / carbon nanotubes composite. This sensor has been involved as passive antenna with stable resonance frequency of 650 MHz. When it is get deformed in the range from 0 to 3.5% the sensor gain was changing from -39 dB to - 19.45 dB. But if it is get deformed by 15% and again measured strain from 0 to 3.5%, sensor gain was changing from -33 dB to -12.3 dB, which clearly indicates the damage of structure.

  7. Relationship between carbon and nitrogen isotope ratios for lower trophic ecosystem in marine environments

    NASA Astrophysics Data System (ADS)

    Aita, M. N.; Ishii, R.; Tadokoro, K.; Smith, S. L.; Wada, E.

    2012-12-01

    To examine the relationship between carbon and nitrogen stable isotope ratios (δ13C and δ15N) along food chains, we analyzed using the data from the Oyashio waters at the western North Pacific (samples collected from March to October 2009), the warm-core ring 86-B derived from the Kuroshio extension region (preserved samples), and previously published data from the Gulf of Alaska and Antarctic Ocean. The statistical analysis suggested a common slope of δ15N versus δ13C (Δδ15N/Δδ13C) among regions. We attribute this similarity to common physiological aspects of feeding processes (e.g., kinetic isotope effects inherent in the processes of amino acid synthesis). We also compared seasonal differences seasonal in Δδ15N/Δδ13C for the euphotic layers of the Oyashio waters. The Δδ15N/Δδ13C slope of the food chain during the spring bloom differs from its common value in other seasons. If we could better understand both carbon and nitrogen trophic fractionation within ecosystems, the stable isotope ratios may help to elucidate migratory behavior of higher trophic levels such as fishes in marine ecosystems as well as frame work of biogeochemical cycles in question.

  8. Conservation of soil organic carbon, biodiversity and the provision of other ecosystem services along climatic gradients in West Africa

    NASA Astrophysics Data System (ADS)

    Marks, E.; Aflakpui, G. K. S.; Nkem, J.; Poch, R. M.; Khouma, M.; Kokou, K.; Sagoe, R.; Sebastiã, M.-T.

    2008-11-01

    Terrestrial carbon resources are major drivers of development in West Africa. The distribution of these resources co-varies with ecosystem type and rainfall along a strong Northeast-Southwest climatic gradient. Soil organic carbon, a strong indicator of soil quality, has been severely depleted in some areas by human activities, which leads to issues of soil erosion and desertification, but this trend can be altered via appropriate management. There is significant potential to enhance existing soil carbon stores in West Africa, with benefits at the global and local scales, for atmospheric CO2 mitigation and supporting, and provisioning ecosystem services, respectively. Three key factors impacting carbon stocks are addressed in this review: climate, biotic factors, and human activities. Climate risks must be considered in a framework of global change, especially in West Africa, where landscape managers have few resources available to adapt to climatic perturbations. Among biotic factors, biodiversity conservation paired with carbon conservation may provide a pathway to sustainable development, as evidence suggests that both may be inter-linked, and biodiversity conservation is also a global priority with local benefits for ecosystem resilience, biomass productivity, and provisioning services such as foodstuffs. Finally, human management has largely been responsible for reduced carbon stocks, but this trend can be reversed through the implementation of appropriate carbon conservation strategies in the agricultural sector, as shown by multiple studies. Owing to the strong regional climatic gradient, country-level initiatives will need to consider carbon sequestration approaches for multiple ecosystem types. Given the diversity of environments, global policies must be adapted and strategised at the national or sub-national levels to improve C storage above and belowground. Initiatives of this sort must act locally at farmer scale, and focus on ecosystem services rather

  9. The loss of Scottish peatlands: Implications for long-term net gains in coastal Blue Carbon stocks.

    NASA Astrophysics Data System (ADS)

    Austin, William; Smeaton, Craig; Winterton, Cathy; Clarke, Jessica; Smith, Laura; Ward, Hannah; Bennett, Keith

    2016-04-01

    Nearly 66% of Scotland is covered by peat and organic soils, representing over 50% of the UK's soil carbon stocks. Peatland erosion, while partly a natural process, is also accelerated by human activities, such as land management and potentially by the impacts of climate change. We present evidence from the voes (sea lochs or fjords) of Shetland's west coast to suggest that this process may have accelerated since Medieval times. Our work is supported by the analyses of short sediment (Craib) cores (triplicate coring) recovered from 17 sites. We present preliminary chronologies supported by radiocarbon dating and sediment characteristics that highlight both changes in the rate of accumulation and source of sedimentary organic carbon to the west Shetland voes during the late Holocene. Scottish coastal sediments contain a significant Blue Carbon stock, a significant proportion of which derives directly from terrestrial sources. The loss of peatland carbon represents a potentially important contribution (i.e. net gain) in refractory carbon within the marine environment and we present preliminary estimates to assess the significance of these large-scale transfers to the coastal ocean.

  10. [Simulation of carbon cycle in Qianyanzhou artificial masson pine forest ecosystem and sensitivity analysis of model parameters].

    PubMed

    Wang, Yuan; Zhang, Na; Yu, Gui-rui

    2010-07-01

    By using modified carbon-water cycle model EPPML (ecosystem productivity process model for landscape), the carbon absorption and respiration in Qianyanzhou artificial masson pine forest ecosystem in 2003 and 2004 were simulated, and the sensitivity of the model parameters was analyzed. The results showed that EPPML could effectively simulate the carbon cycle process of this ecosystem. The simulated annual values and the seasonal variations of gross primary productivity (GPP), net ecosystem productivity (NEP), and ecosystem respiration (Re) not only fitted well with the measured data, but also reflected the major impacts of extreme weather on carbon flows. The artificial masson pine forest ecosystem in Qianyanzhou was a strong carbon sink in both 2003 and 2004. Due to the coupling of high temperature and severe drought in the growth season in 2003, the carbon absorption in 2003 was lower than that in 2004. The annual NEP in 2003 and 2004 was 481.8 and 516.6 g C x m(-2) x a(-1), respectively. The key climatic factors giving important impacts on the seasonal variations of carbon cycle were solar radiation during early growth season, drought during peak growth season, and precipitation during post-peak growth season. Autotrophic respiration (Ra) and net primary productivity (NPP) had the similar seasonal variations. Soil heterotrophic respiration (Rh) was mainly affected by soil temperature at yearly scale, and by soil water content at monthly scale. During wet growth season, the higher the soil water content, the lower the Rh was; during dry growth season, the higher the precipitation during the earlier two months, the higher the Rh was. The maximum RuBP carboxylation rate at 25 degrees C (Vm25), specific leaf area (SLA), maximum leaf nitrogen content (LNm), average leaf nitrogen content (LN), and conversion coefficient of biomass to carbon (C/B) had the greatest influence on annual NEP. Different carbon cycle process could have different responses to sensitive

  11. [Simulation of carbon cycle in Qianyanzhou artificial masson pine forest ecosystem and sensitivity analysis of model parameters].

    PubMed

    Wang, Yuan; Zhang, Na; Yu, Gui-rui

    2010-07-01

    By using modified carbon-water cycle model EPPML (ecosystem productivity process model for landscape), the carbon absorption and respiration in Qianyanzhou artificial masson pine forest ecosystem in 2003 and 2004 were simulated, and the sensitivity of the model parameters was analyzed. The results showed that EPPML could effectively simulate the carbon cycle process of this ecosystem. The simulated annual values and the seasonal variations of gross primary productivity (GPP), net ecosystem productivity (NEP), and ecosystem respiration (Re) not only fitted well with the measured data, but also reflected the major impacts of extreme weather on carbon flows. The artificial masson pine forest ecosystem in Qianyanzhou was a strong carbon sink in both 2003 and 2004. Due to the coupling of high temperature and severe drought in the growth season in 2003, the carbon absorption in 2003 was lower than that in 2004. The annual NEP in 2003 and 2004 was 481.8 and 516.6 g C x m(-2) x a(-1), respectively. The key climatic factors giving important impacts on the seasonal variations of carbon cycle were solar radiation during early growth season, drought during peak growth season, and precipitation during post-peak growth season. Autotrophic respiration (Ra) and net primary productivity (NPP) had the similar seasonal variations. Soil heterotrophic respiration (Rh) was mainly affected by soil temperature at yearly scale, and by soil water content at monthly scale. During wet growth season, the higher the soil water content, the lower the Rh was; during dry growth season, the higher the precipitation during the earlier two months, the higher the Rh was. The maximum RuBP carboxylation rate at 25 degrees C (Vm25), specific leaf area (SLA), maximum leaf nitrogen content (LNm), average leaf nitrogen content (LN), and conversion coefficient of biomass to carbon (C/B) had the greatest influence on annual NEP. Different carbon cycle process could have different responses to sensitive

  12. Mineral carbonation: energy costs of pretreatment options and insights gained from flow loop reaction studies

    SciTech Connect

    Penner, Larry R.; O'Connor, William K.; Dahlin, David C.; Gerdemann, Stephen J.; Rush, Gilbert E.

    2004-01-01

    Sequestration of carbon as a stable mineral carbonate has been proposed to mitigate environmental concerns that carbon dioxide may with time escape from its sequestered matrix using alternative sequestration technologies. A method has been developed to prepare stable carbonate products by reacting CO2 with magnesium silicate minerals in aqueous bicarbonate/chloride media at high temperature and pressure. Because this approach is inherently expensive due to slow reaction rates and high capital costs, studies were conducted to improve the reaction rates through mineral pretreatment steps and to cut expenses through improved reactor technology. An overview is given for the estimated cost of the process including sensitivity to grinding and heating as pretreatment options for several mineral feedstocks. The energy costs are evaluated for each pretreatment in terms of net carbon avoided. New studies with a high-temperature, high-pressure flow-loop reactor have yielded information on overcoming kinetic barriers experienced with processing in stirred autoclave reactors. Repeated tests with the flow-loop reactor have yielded insights on wear and failure of system components, on challenges to maintain and measure flow, and for better understanding of the reaction mechanism.

  13. Erosion and vegetation restoration impacts on ecosystem carbon dynamics in South China

    USGS Publications Warehouse

    Tang, X.; Liu, S.; Zhou, G.

    2010-01-01

    To quantify the consequences of erosion and vegetation restoration on ecosystem C dynamics (a key element in understanding the terrestrial C cycle), field measurements were collected since 1959 at two experimental sites set up on highly disturbed barren land in South China. One site had received vegetation restoration (the restored site) while the other received no planting and remained barren (the barren site). The Erosion-Deposition Carbon Model (EDCM) was used to simulate the ecosystem C dynamics at both sites. The on-site observations in 2007 showed that soil organic C (SOC) storage in the top 80-cm soil layer at the barren site was 50.3 ?? 3.5 Mg C ha-1, half that of the restored site. The SOC and surface soil loss by erosion at the restored site from 1959 to 2007 was 3.7 MgC ha-1 and 2.2 cm, respectively-one-third and one-eighth that of the barren site. The on-site C sequestration in SOC and vegetation at the restored site was 0.67 and 2.5 Mg C ha-1 yr-1, respectively, from 1959 to 2007, driven largely by tree growth and high atmospheric N deposition in the study area. Simulated findings suggested that higher N deposition resulted in higher on-site SOC storage in the soil profile (with SOC in the top 20-cm layer increasing more significantly), and higher on-site ecosystem C sequestration as long as N saturation was not reached. Lacking human-induced vegetation recovery, the barren site remained as barren land from 1959 to 2007 and the on-site C decrease was 0.28 Mg C ha-1 yr-1. Our study clearly indicated that vegetation restoration and burial by soil erosion provide a large potential C sink in terrestrial ecosystems. ?? Soil Science Society of America.

  14. Shifts in Timing and Magnitude of Precipitation Modulate Soil Carbon Pools in Semi-Arid Ecosystems

    NASA Astrophysics Data System (ADS)

    Joy, S.; Huber, D. P.; Lohse, K. A.; Germino, M. J.; De Graaff, M.; Feris, K. P.

    2012-12-01

    Semi-arid ecosystems cover a large part of continental land area and are predicted to be strongly influenced by climate change. Shifts in the seasonal timing and magnitude of precipitation are predicted to alter ecosystem function in semi-arid rangelands, which are especially sensitive to seasonal changes in precipitation. Of particular interest is how changing climate will impact carbon cycling and the flux of carbon between the land and atmosphere. In semi-arid regions, carbon fluxes are often dynamic, varying orders of magnitude both spatially and temporally; whether long-term changes in climate will diminish or exaggerate these processes is not well studied in cold desert systems. Utilizing a long-term eco-hydrologic site (est. 1993) located in southeastern Idaho, we attempt to study the modulation of soil carbon pools in a cold desert ecosystem containing native and exotic plant species subjected to precipitation treatments varying both magnitude and seasonality of rainfall. The site consist of native sagebrush (Artemisia tridentata spp. tridentata) and exotic crested wheatgrass (Agropyron cristatum) plots, each with three seasonal precipitation treatments (ambient control, 2x ambient added in the winter and 2 x ambient added in the summer). We expect increases in both above and below-ground productivity as precipitation increases, as well as increased heterotrophic activity in the soils; we hypothesized that changes in the timing and magnitude of precipitation provide a mechanism in semi-arid regions for reallocation of soil carbon pools from soil organic matter to precipitated inorganic carbon (IC). Specifically, additional precipitation during the summer season will lead to the greatest increased production of inorganic carbon. Results show summer plots with significantly more IC content (P=0.0091) than winter plots irrespective of vegetation type (14.57 + 0.42 kg IC/m2 and 12.79+ 0.39 kg IC/m2 respectively). Although not significant, summer plots also show

  15. Viral Regulation of Prokaryotic Carbon Metabolism in a Hypereutrophic Freshwater Reservoir Ecosystem (Villerest, France).

    PubMed

    Pradeep Ram, Angia Sriram; Colombet, Jonathan; Perriere, Fanny; Thouvenot, Antoine; Sime-Ngando, Télesphore

    2016-01-01

    The current consensus concerning the viral regulation of prokaryotic carbon metabolism is less well-studied, compared to substrate availability. We explored the seasonal and vertical distribution of viruses and its relative influence on prokaryotic carbon metabolism in a hypereutrophic reservoir, Lake Villerest (France). Flow cytometry and transmission electron microscopy (TEM) analyses to determine viral abundance (VA; range = 6.1-63.5 × 10(7) ml(-1)) and viral infection rates of prokaryotes (range = 5.3-32%) respectively suggested that both the parameters varied more significantly with depths than with seasons. Prokaryotic growth efficiency (PGE, considered as a proxy of prokaryotic carbon metabolism) calculated from prokaryotic production and respiration measurements (PGE = prokaryotic production/[prokaryotic production + prokaryotic respiration] × 100) varied from 14 to 80% across seasons and depths. Viruses through selective lyses had antagonistic impacts on PGE by regulating key prokaryotic metabolic processes (i.e., production and respiration). Higher viral lysis accompanied by higher respiration rates and lower PGE in the summer (mean = 22.9 ± 10.3%) than other seasons (mean = 59.1 ± 18.6%), led to significant loss of carbon through bacterial-viral loop and shifted the reservoir system to net heterotrophy. Our data therefore suggests that the putative adverse impact of viruses on the growth efficiency of the prokaryotic community can have strong implications on nutrient flux patterns and on the overall ecosystem metabolism in anthropogenic dominated aquatic systems such as Lake Villerest. PMID:26903963

  16. High carbon dioxide uptake by subtropical forest ecosystems in the East Asian monsoon region

    PubMed Central

    Yu, Guirui; Chen, Zhi; Piao, Shilong; Peng, Changhui; Ciais, Philippe; Wang, Qiufeng; Li, Xuanran; Zhu, Xianjin

    2014-01-01

    Temperate- and high-latitude forests have been shown to contribute a carbon sink in the Northern Hemisphere, but fewer studies have addressed the carbon balance of the subtropical forests. In the present study, we integrated eddy covariance observations established in the 1990s and 2000s to show that East Asian monsoon subtropical forests between 20°N and 40°N represent an average net ecosystem productivity (NEP) of 362 ± 39 g C m−2 yr−1 (mean ± 1 SE). This average forest NEP value is higher than that of Asian tropical and temperate forests and is also higher than that of forests at the same latitudes in Europe–Africa and North America. East Asian monsoon subtropical forests have comparable NEP to that of subtropical forests of the southeastern United States and intensively managed Western European forests. The total NEP of East Asian monsoon subtropical forests was estimated to be 0.72 ± 0.08 Pg C yr−1, which accounts for 8% of the global forest NEP. This result indicates that the role of subtropical forests in the current global carbon cycle cannot be ignored and that the regional distributions of the Northern Hemisphere's terrestrial carbon sinks are needed to be reevaluated. The young stand ages and high nitrogen deposition, coupled with sufficient and synchronous water and heat availability, may be the primary reasons for the high NEP of this region, and further studies are needed to quantify the contribution of each underlying factor. PMID:24639529

  17. Viral Regulation of Prokaryotic Carbon Metabolism in a Hypereutrophic Freshwater Reservoir Ecosystem (Villerest, France)

    PubMed Central

    Pradeep Ram, Angia Sriram; Colombet, Jonathan; Perriere, Fanny; Thouvenot, Antoine; Sime-Ngando, Télesphore

    2016-01-01

    The current consensus concerning the viral regulation of prokaryotic carbon metabolism is less well-studied, compared to substrate availability. We explored the seasonal and vertical distribution of viruses and its relative influence on prokaryotic carbon metabolism in a hypereutrophic reservoir, Lake Villerest (France). Flow cytometry and transmission electron microscopy (TEM) analyses to determine viral abundance (VA; range = 6.1–63.5 × 107 ml-1) and viral infection rates of prokaryotes (range = 5.3–32%) respectively suggested that both the parameters varied more significantly with depths than with seasons. Prokaryotic growth efficiency (PGE, considered as a proxy of prokaryotic carbon metabolism) calculated from prokaryotic production and respiration measurements (PGE = prokaryotic production/[prokaryotic production + prokaryotic respiration] × 100) varied from 14 to 80% across seasons and depths. Viruses through selective lyses had antagonistic impacts on PGE by regulating key prokaryotic metabolic processes (i.e., production and respiration). Higher viral lysis accompanied by higher respiration rates and lower PGE in the summer (mean = 22.9 ± 10.3%) than other seasons (mean = 59.1 ± 18.6%), led to significant loss of carbon through bacterial-viral loop and shifted the reservoir system to net heterotrophy. Our data therefore suggests that the putative adverse impact of viruses on the growth efficiency of the prokaryotic community can have strong implications on nutrient flux patterns and on the overall ecosystem metabolism in anthropogenic dominated aquatic systems such as Lake Villerest. PMID:26903963

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

    USGS Publications Warehouse

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

    2010-01-01

    The Energy Independence and Security Act of 2007 (EISA), Section 712, authorizes the U.S. Department of the Interior to develop a methodology and conduct an assessment of the Nation's ecosystems focusing on carbon stocks, carbon sequestration, and emissions of three greenhouse gases (GHGs): carbon dioxide, methane, and nitrous oxide. The major requirements include (1) an assessment of all ecosystems (terrestrial systems, such as forests, croplands, wetlands, shrub and grasslands; and aquatic ecosystems, such as rivers, lakes, and estuaries), (2) an estimation of annual potential capacities of ecosystems to increase carbon sequestration and reduce net GHG emissions in the context of mitigation strategies (including management and restoration activities), and (3) an evaluation of the effects of controlling processes, such as climate change, land use and land cover, and wildlfires. The purpose of this draft methodology for public review is to propose a technical plan to conduct the assessment. Within the methodology, the concepts of ecosystems, carbon pools, and GHG fluxes used for the assessment follow conventional definitions in use by major national and international assessment or inventory efforts. In order to estimate current ecosystem carbon stocks and GHG fluxes and to understand the potential capacity and effects of mitigation strategies, the method will use two time periods for the assessment: 2001 through 2010, which establishes a current ecosystem GHG baseline and will be used to validate the models; and 2011 through 2050, which will be used to assess future potential conditions based on a set of projected scenarios. The scenario framework is constructed using storylines of the Intergovernmental Panel on Climate Change (IPCC) Special Report Emission Scenarios (SRES), along with initial reference land-use and land-cover (LULC) and land-management scenarios. An additional three LULC and land-management mitigation scenarios will be constructed for each

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  20. Stress differentially impacts reserve pools and root exudation: implications for ecosystem functioning and carbon balance

    NASA Astrophysics Data System (ADS)

    Landhäusser, Simon; Karst, Justine; Wiley, Erin; Gaster, Jacob

    2016-04-01

    Environmental stress can influence carbon assimilation and the accumulation and distribution of carbon between growth, reserves, and exudation; however, it is unclear how these processes vary by different stress types. Partitioning of carbon to growth and reserves in plants might also vary between different organs. Roots reserves are of particular interest as they link the plant with the soil carbon cycle through exudation. Simple models of diffusion across concentration gradients predict the more C reserves in roots, the more C should be exuded from roots. However, the mechanisms underlying the accumulation and loss of C from roots may differ depending on the stress experienced by the plants. In a controlled study we tested whether different types of stresses (shade, cold soil, and drought) have differential effects on the distribution, abundance, and form (sugar vs. starch) of carbohydrates in seedlings, and whether these changes alone could explain differences in root exudation between stress types. Non-structural carbohydrate (NSC) concentration and pool sizes varied by stress type and between organs. Mass-specific C exudation increased with fine root sugar concentration; however, stress type affected exudation independently of reserve concentration. Seedlings exposed to cold soils exuded the most C on a per root mass basis followed by shade and drought. Through 13C labeling, we also found that depending on the stress type, aspen seedlings may be less able to control the loss of C to the soil compared with unstressed seedlings, resulting in more C leaked to the rhizosphere. The loss of C beyond that predicted by simple concentration gradients might have important implications for ecosystem functioning and carbon balance. If stressed plants lose proportionally more carbon to the soil, existing interactions between plants and soils may decouple under stress, and may include unexpected C fluxes between trees, soils and the atmosphere with a changing climate.

  1. Effects of Conversion from Boreal Forest to Arctic Steppe on Soil Communities and Ecosystem Carbon Pools

    NASA Astrophysics Data System (ADS)

    Han, P. D.; Natali, S.; Schade, J. D.; Zimov, N.; Zimov, S. A.

    2014-12-01

    The end of the Pleistocene marked the extinction of a great variety of arctic megafauna, which, in part, led to the conversion of arctic grasslands to modern Siberian larch forest. This shift may have increased the vulnerability of permafrost to thawing because of changes driven by the vegetation shift; the higher albedo of grassland and low insulation of snow trampled by animals may have decreased soil temperatures and reduced ground thaw in the grassland ecosystem, resulting in protection of organic carbon in thawed soil and permafrost. To test these hypothesized impacts of arctic megafauna, we examined an experimental reintroduction of large mammals in northeast Siberia, initiated in 1988. Pleistocene Park now contains 23 horses, three musk ox, one bison, and several moose in addition to the native fauna. The park is 16 square km with a smaller enclosure (< 1 km) where animals spend most of their time and our study was focused. We measured carbon-pools in forested sites (where scat surveys showed low animal use), and grassy sites (which showed higher use), within the park boundaries. We also measured thaw depth and documented the soil invertebrate communities in each ecosystem. There was a substantial difference in number of invertebrates per kg of organic soil between the forest (600 ± 250) and grassland (300 ± 250), though these differences were not statistically significant they suggest faster nutrient turnover in the forest or a greater proportion of decomposition by invertebrates than other decomposers. While thaw depth was deeper in the grassland (60 ± 4 cm) than in the forest (40 ± 6 cm), we did not detect differences in organic layer depth or percent organic matter between grassland and forest. However, soil in the grassland had higher bulk density, and higher carbon stocks in the organic and mineral soil layers. Although deeper thaw depth in the grassland suggests that more carbon is available to microbial decomposers, ongoing temperature monitoring

  2. [Global climate change and carbon balance in forest ecosystems of boreal zones: imitating modeling as a forecast tool].

    PubMed

    Shanin, V N; Mikhaĭlov, A V; Bykhovets, S S; Komarov, A S

    2010-01-01

    The individually oriented system of the EFIMOD models simulating carbon and nitrogen flows in forest ecosystems has been used for forecasting the response of forest ecosystems to various forest exploitation regimes with climate change. As input data the forest management materials for the Manturovskii forestry of the Kostroma region were used. It has been shown that increase of mid-annual temperatures and rainfall influence the redistribution of carbon and nitrogen supply in organic form: supply increase of these elements in phytomass simultaneously with depletion of them in soil occurred. The most carbon and nitrogen accumulation in forest ecosystems occurs in the scenario without felling. In addition, in this scenario only the ecosystems of the modeling territory function as a carbon drain; in the other two scenarios (with selective and total felling) they function as a source of carbon. Climate changes greatly influence the decomposition rate of organic matter in soil, which leads to increased emission of carbonic acid. The second consequence of the increase in the destruction rate is nitrogen increase in the soil in a form available for plants that entails production increase of plantations. PMID:21268870

  3. Spatial variation in vegetation productivity trends, fire disturbance, and soil carbon across arctic-boreal permafrost ecosystems

    NASA Astrophysics Data System (ADS)

    Loranty, Michael M.; Liberman-Cribbin, Wil; Berner, Logan T.; Natali, Susan M.; Goetz, Scott J.; Alexander, Heather D.; Kholodov, Alexander L.

    2016-09-01

    In arctic tundra and boreal forest ecosystems vegetation structural and functional influences on the surface energy balance can strongly influence permafrost soil temperatures. As such, vegetation changes will likely play an important role in permafrost soil carbon dynamics and associated climate feedbacks. Processes that lead to changes in vegetation, such as wildfire or ecosystem responses to rising temperatures, are of critical importance to understanding the impacts of arctic and boreal ecosystems on future climate. Yet these processes vary within and between ecosystems and this variability has not been systematically characterized across the arctic-boreal region. Here we quantify the distribution of vegetation productivity trends, wildfire, and near-surface soil carbon, by vegetation type, across the zones of continuous and discontinuous permafrost. Siberian larch forests contain more than one quarter of permafrost soil carbon in areas of continuous permafrost. We observe pervasive positive trends in vegetation productivity in areas of continuous permafrost, whereas areas underlain by discontinuous permafrost have proportionally less positive productivity trends and an increase in areas exhibiting negative productivity trends. Fire affects a much smaller proportion of the total area and thus a smaller amount of permafrost soil carbon, with the vast majority occurring in deciduous needleleaf forests. Our results indicate that vegetation productivity trends may be linked to permafrost distribution, fire affects a relatively small proportion of permafrost soil carbon, and Siberian larch forests will play a crucial role in the strength of the permafrost carbon climate feedback.

  4. Evaluating Ecological and Economic Benefits of a Low-Carbon Industrial Park Based on Millennium Ecosystem Assessment Framework

    PubMed Central

    Chen, Bin; He, Guoxuan; Yang, Jin; Zhang, Jieru; Su, Meirong; Qi, Jing

    2012-01-01

    The Millennium Ecosystem Assessment (MA) framework was modified with a special focus on ecosystem service values. A case study of a typical low-carbon industrial park in Beijing was conducted to assess the ecological and economic benefits. The total economic value of this industrial park per year is estimated to be 1.37 × 108 RMB yuan, where the accommodating and social cultural services are the largest two contributors. Due to the construction of small grasslands or green roofs, considerable environmental regulation services are also provided by the park. However, compared with an ecoindustrial park, carbon mitigation is the most prominent service for the low-carbon industrial park. It can be concluded that low-carbon industrial park construction is an efficacious way to achieve coordinated development of society, economy, and environment, and a promising approach to achieving energy saving and carbon reduction. PMID:23365537

  5. Baseline and projected future carbon storage and greenhouse-gas fluxes in ecosystems of the Western United States

    USGS Publications Warehouse

    Zhu, Zhi-Liang; Reed, Bradley C.

    2012-01-01

    This assessment was conducted to fulfill the requirements of section 712 of the Energy Independence and Security Act (EISA) of 2007 and to improve understanding of carbon and greenhouse gas (GHG) fluxes in ecosystems of the Western United States. The assessment examined carbon storage, carbon fluxes, and other GHG fluxes (methane and nitrous oxide) in all major terrestrial ecosystems (forests, grasslands/shrublands, agricultural lands, and wetlands) and aquatic ecosystems (rivers, streams, lakes, reservoirs, and coastal waters) in two time periods: baseline (generally in the first half of the 2010s) and future (projections from baseline to 2050). The assessment was based on measured and observed data collected by the U.S. Geological Survey (USGS) and many other agencies and organizations and used remote sensing, statistical methods, and simulation models.

  6. PISCES-v2: an ocean biogeochemical model for carbon and ecosystem studies

    NASA Astrophysics Data System (ADS)

    Aumont, O.; Ethé, C.; Tagliabue, A.; Bopp, L.; Gehlen, M.

    2015-08-01

    PISCES-v2 (Pelagic Interactions Scheme for Carbon and Ecosystem Studies volume 2) is a biogeochemical model which simulates the lower trophic levels of marine ecosystems (phytoplankton, microzooplankton and mesozooplankton) and the biogeochemical cycles of carbon and of the main nutrients (P, N, Fe, and Si). The model is intended to be used for both regional and global configurations at high or low spatial resolutions as well as for short-term (seasonal, interannual) and long-term (climate change, paleoceanography) analyses. There are 24 prognostic variables (tracers) including two phytoplankton compartments (diatoms and nanophytoplankton), two zooplankton size classes (microzooplankton and mesozooplankton) and a description of the carbonate chemistry. Formulations in PISCES-v2 are based on a mixed Monod-quota formalism. On the one hand, stoichiometry of C / N / P is fixed and growth rate of phytoplankton is limited by the external availability in N, P and Si. On the other hand, the iron and silicon quotas are variable and the growth rate of phytoplankton is limited by the internal availability in Fe. Various parameterizations can be activated in PISCES-v2, setting, for instance, the complexity of iron chemistry or the description of particulate organic materials. So far, PISCES-v2 has been coupled to the Nucleus for European Modelling of the Ocean (NEMO) and Regional Ocean Modeling System (ROMS) systems. A full description of PISCES-v2 and of its optional functionalities is provided here. The results of a quasi-steady-state simulation are presented and evaluated against diverse observational and satellite-derived data. Finally, some of the new functionalities of PISCES-v2 are tested in a series of sensitivity experiments.

  7. Winter Insulation By Snow Accumulation in a Subarctic Treeline Ecosystem Increases Summer Carbon Cycling Rates

    NASA Astrophysics Data System (ADS)

    Parker, T.; Subke, J. A.; Wookey, P. A.

    2014-12-01

    The effect of snow accumulation on soil carbon and nutrient cycling is attracting substantial attention from researchers. We know that deeper snow accumulation caused by high stature vegetation increases winter microbial activity and therefore carbon and nitrogen flux rates. However, until now the effect of snow accumulation, by buffering winter soil temperature, on subsequent summer soil processes, has scarcely been considered. We carried out an experiment at an alpine treeline in subarctic Sweden in which soil monoliths, contained within PVC collars, were transplanted between forest (deep winter snow) and tundra heath (shallow winter snow). We measured soil CO2efflux over two growing seasons and quantified soil microbial biomass after the second winter. We showed that respiration rates of transplanted forest soil were significantly reduced compared with control collars (remaining in the forest) as a consequence of colder, but more variable, winter temperatures. We hypothesised that microbial biomass would be reduced in transplanted forests soils but found there was no difference compared to control. We therefore further hypothesised that the similarly sized microbial pool in the control is assembled differently to the transplant. We believe that the warmer winters in forests foster more active consortia of decomposer microbes as a result of different abiotic selection pressures. Using an ecosystem scale experimental approach, we have identified a mechanism that influences summer carbon cycling rates based solely on the amount of snow that accumulates the previous winter. We conclude that modification of snow depth as a consequence of changes in vegetation structure is an important mechanism influencing soil C stocks in ecosystems where snow persists for a major fraction of the year.

  8. Carbon storage, timber production, and biodiversity: comparing ecosystem services with multi-criteria decision analysis.

    PubMed

    Schwenk, W Scott; Donovan, Therese M; Keeton, William S; Nunery, Jared S

    2012-07-01

    Increasingly, land managers seek ways to manage forests for multiple ecosystem services and functions, yet considerable challenges exist in comparing disparate services and balancing trade-offs among them. We applied multi-criteria decision analysis (MCDA) and forest simulation models to simultaneously consider three objectives: (1) storing carbon, (2) producing timber and wood products, and (3) sustaining biodiversity. We used the Forest Vegetation Simulator (FVS) applied to 42 northern hardwood sites to simulate forest development over 100 years and to estimate carbon storage and timber production. We estimated biodiversity implications with occupancy models for 51 terrestrial bird species that were linked to FVS outputs. We simulated four alternative management prescriptions that spanned a range of harvesting intensities and forest structure retention. We found that silvicultural approaches emphasizing less frequent harvesting and greater structural retention could be expected to achieve the greatest net carbon storage but also produce less timber. More intensive prescriptions would enhance biodiversity because positive responses of early successional species exceeded negative responses of late successional species within the heavily forested study area. The combinations of weights assigned to objectives had a large influence on which prescriptions were scored as optimal. Overall, we found that a diversity of silvicultural approaches is likely to be preferable to any single approach, emphasizing the need for landscape-scale management to provide a full range of ecosystem goods and services. Our analytical framework that combined MCDA with forest simulation modeling was a powerful tool in understanding trade-offs among management objectives and how they can be simultaneously accommodated. PMID:22908717

  9. Holocene Carbon Fluxes and Palaeoproductivity in Aquatic Ecosystems: a Multiproxy, Palaeolimnological Approach

    NASA Astrophysics Data System (ADS)

    Mackay, A. W.; Leng, M. J.; Morley, D. W.; Piotrowska, N.; Rioual, P.; Swann, G. E. A.

    2014-12-01

    Inland waters act as an important control on the global carbon cycle. Deep tectonic lakes may provide a key link between short-term and long-term carbon cycles as buried carbon is essentially locked away from the atmosphere over geological timescales. Here we investigate Holocene carbon dynamics in one of the worlds most important lake ecosystems, Lake Baikal, Siberia. We test the hypothesis that multiple factors play a significant role in determining long-term carbon dynamics in central Asia, and that these factors change in importance over time. Carbon isotopes (δ13C), percentage total organic carbon (%TOC) were analysed during combustion in a Carlo Erba 1500 on-line to a VG Triple Trap and dual-inlet mass spectrometer. A multi-decadal organic geochemistry record (%TOC; δ13C, C/N ratios) was determined on Holocene sediments extracted from a slope terrace c. 600 m deep. Age-depth modelling on radiocarbon-dated pollen extracts was undertaken using 'Bacon', which takes into account variable sediment accumulation rates. Carbon mass accumulation rates (CMAR; g cm-2 yr-1) were estimated at a centennial scale resolution. δ13C values were routinely higher during cool glacial periods (-26 ‰) than during warmer climates (-28 ‰) linked to changes in carbon sources. Diatom productivity & boreal forest expansion were strongly associated with δ13C variability during the early Holocene, but after 8 kyr BP, no relationships are apparent. CMAR were highest during the early Holocene (11.7 - 8 kyr BP) although rates fluctuated considerably. Peak values of 12.5 g cm-2 yr-1 were observed at 10.35 kyr BP before a rapid decline to c. 5.2 g cm-2 yr-1 at 10.05 kyr BP. CMAR declined to lowest Holocene values of 3.5 g cm-2 yr-1 by 3.9 kyr BP at the same time as maximum δ13C values (-27.0 ‰), indicative of low palaeoproductivity. Our data show that measures of palaeoproductivity in Lake Baikal are complex, and during the early Holocene are strongly associated with allochthonous

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    Temperate grasslands constitute over 30% of the Earth's naturally-occurring biomes and make an important contribution towards the partial mitigation of anthropogenic greenhouse gas emissions by terrestrial ecosystems. Accumulation of carbon (C) in grassland systems predominantly takes place in below-ground repositories, enhanced by the presence of a stable soil environment with low carbon turnover rates, active rhizodeposition and high levels of residue and organic inputs. Predicted future warming is expected to increase productivity in temperate zones, thereby enhancing rates of terrestrial carbon sequestration. However, the susceptibility of many ecosystems, including grasslands, to extreme climatic events and inter-annual variability has been demonstrated previously. Temperature anomalies as well as modifications in the temporal pattern and quantity of precipitation alter the balance between carbon uptake and release processes and a mechanistic understanding of ecosystem response to such changes is still lacking. In the present study, the impact of extreme inter-annual variability in summer rainfall and temperature on carbon dynamics in two rotationally-grazed grasslands in Ireland was examined. The sites experience similar temperate climatic regimes but differ in soil drainage characteristics. Eddy covariance measurements of net ecosystem exchange of carbon were complemented by regular assessment of standing biomass, leaf cover, harvest exports and organic amendment inputs. The summers of 2012 and 2013 showed contrasting climatic conditions, with summer precipitation 93% higher and 25% lower respectively than long-term means. In addition, soil temperatures were 7% lower and 11% higher than expected. Cool, wet conditions in 2012 facilitated net carbon uptake for more than ten months of the year at the poorly-drained site, however the ecosystem switched to a net source of carbon in 2013 during months with significantly reduced rainfall. In contrast, net C

  11. Cyclic Occurrence of Fire and Its Role in Carbon Dynamics along an Edaphic Moisture Gradient in Longleaf Pine Ecosystems

    PubMed Central

    Whelan, Andrew; Mitchell, Robert; Staudhammer, Christina; Starr, Gregory

    2013-01-01

    Fire regulates the structure and function of savanna ecosystems, yet we lack understanding of how cyclic fire affects savanna carbon dynamics. Furthermore, it is largely unknown how predicted changes in climate may impact the interaction between fire and carbon cycling in these ecosystems. This study utilizes a novel combination of prescribed fire, eddy covariance (EC) and statistical techniques to investigate carbon dynamics in frequently burned longleaf pine savannas along a gradient of soil moisture availability (mesic, intermediate and xeric). This research approach allowed us to investigate the complex interactions between carbon exchange and cyclic fire along the ecological amplitude of longleaf pine. Over three years of EC measurement of net ecosystem exchange (NEE) show that the mesic site was a net carbon sink (NEE = −2.48 tonnes C ha−1), while intermediate and xeric sites were net carbon sources (NEE = 1.57 and 1.46 tonnes C ha−1, respectively), but when carbon losses due to fuel consumption were taken into account, all three sites were carbon sources (10.78, 7.95 and 9.69 tonnes C ha−1 at the mesic, intermediate and xeric sites, respectively). Nonetheless, rates of NEE returned to pre-fire levels 1–2 months following fire. Consumption of leaf area by prescribed fire was associated with reduction in NEE post-fire, and the system quickly recovered its carbon uptake capacity 30–60 days post fire. While losses due to fire affected carbon balances on short time scales (instantaneous to a few months), drought conditions over the final two years of the study were a more important driver of net carbon loss on yearly to multi-year time scales. However, longer-term observations over greater environmental variability and additional fire cycles would help to more precisely examine interactions between fire and climate and make future predictions about carbon dynamics in these systems. PMID:23335986

  12. Carbon balance of grazed savanna grassland ecosystem in Welgegund, South Africa

    NASA Astrophysics Data System (ADS)

    Räsänen, Matti; Aurela, Mika; Vakkari, Ville; Beukes, Paul; Van Zyl, Pieter; Josipovic, Micky; Venter, Andrew; Jaars, Kerneels; Siebert, Stefan; Laurila, Tuomas; Tuovinen, Juha-Pekka; Rinne, Janne; Laakso, Lauri

    2016-04-01

    Tropical savannas and grasslands are estimated to contribute significantly to the global primary production of all terrestrial vegetation. It is suggested that semi-arid ecosystems dominate the inter-annual variation of the global land carbon sink. Most of the previous carbon flux measurements of African savannas have focused on the areas around national parks or nature reserves. However, large parts of African savannas and grasslands are used for agriculture or cattle grazing and there is a lack of measurements from these areas. In this study, we present carbon dioxide fluxes measured with the eddy covariance method for three years at a grazed savanna grassland in South Africa. The tree cover around the Welgegund measurement site (26°34'10"S, 26°56'21"E, 1480 m.a.s.l.; www.welgegund.org) was around 15% and it was grazed by cattle and sheep. Weekly monitoring of the measurements produced high quality flux measurements and only 33% of the measured flux values were missing or discarded due to e.g. too small turbulence. The inter-annual variation of yearly carbon balance was high. The carbon balance for the years 2010, 2011 and 2012 were -73, 82 and 167 gC m-2 y-1, respectively. The yearly variation in GPP and respiration followed the changes in precipitation, whereas the yearly variation in NEE was not explained by the changes in annual precipitation, the length of rainy season or peak NDVI. However, the number of days when soil was wet, seems to relate to the annual sum of NEE.

  13. Simulated Net Ecosystem Carbon Balance of Western US Forests Under Contemporary Climate and Management

    NASA Astrophysics Data System (ADS)

    Yang, Z.; Law, B. E.; Jones, M. O.

    2015-12-01

    Previous projections of the contemporary forest carbon balance in the western US showed uncertainties associated with impacts of climate extremes and a coarse spatio-temporal resolution implemented over heterogeneous mountain regions. We modified the Community Land Model (CLM) 4.5 to produce 4km resolution forest carbon changes with drought, fire and management in the western US. We parameterized the model with species data using local plant trait observations for 30 species. To quantify uncertainty, we evaluated the model with data from flux sites, inventories and ancillary data in the region. Simulated GPP was lower than the measurements at our AmeriFlux sites by 17-22%. Simulated burned area was generally higher than Landsat observations, suggesting the model overestimates fire emissions with the new fire model. Landsat MTBS data show high severity fire represents only a small portion of the total burnt area (12-14%), and no increasing trend from 1984 to 2011. Moderate severity fire increased ~0.23%/year due to fires in the Sierra Nevada (Law & Waring 2014). Oregon, California, and Washington were a net carbon sink, and net ecosystem carbon balance (NECB) declined in California over the past 15 years, partly due to drought impacts. Fire emissions were a small portion of the regional carbon budget compared with the effect of harvest removals. Fossil fuel emissions in CA are more than 3x that of OR and WA combined, but are lower per capita. We also identified forest regions that are most vulnerable to climate-driven transformations and to evaluate the effects of management strategies on forest NECB. Differences in forest NECB among states are strongly influenced by the extent of drought (drier longer in the SW) and management intensity (higher in the PNW).

  14. Fire alters ecosystem carbon and nutrients but not plant nutrient stoichiometry or composition in tropical savanna.

    PubMed

    Pellegrini, Adam F A; Hedin, Lars O; Staver, A Carla; Govender, Navashni

    2015-05-01

    Fire and nutrients interact to influence the global distribution and dynamics of the savanna biome, but the results of these interactions are both complex and poorly known. A critical but unresolved question is whether short-term losses of carbon and nutrients caused by fire can trigger long-term and potentially compensatory responses in the nutrient stoichiometry of plants, or in the abundance of dinitrogen-fixing trees. There is disagreement in the literature about the potential role of fire on savanna nutrients, and, in turn, on plant stoichiometry and composition. A major limitation has been the lack of fire manipulations over time scales sufficiently long for these interactions to emerge. We use a 58-year, replicated, large-scale, fire manipulation experiment in Kruger National Park (South Africa) in savanna to quantify the effect of fire on (1) distributions of carbon, nitrogen, and phosphorus at the ecosystem scale; (2) carbon: nitrogen: phosphorus stoichiometry of above- and belowground tissues of plant species; and (3) abundance of plant functional groups including nitrogen fixers. Our results show dramatic effects of fire on the relative distribution of nutrients in soils, but that individual plant stoichiometry and plant community composition remained unexpectedly resilient. Moreover, measures of nutrients and carbon stable isotopes allowed us to discount the role of tree cover change in favor of the turnover of herbaceous biomass as the primary mechanism that mediates a transition from low to high 'soil carbon and nutrients in the absence of fire. We conclude that, in contrast to extra-tropical grasslands or closed-canopy forests, vegetation in the savanna biome may be uniquely adapted to nutrient losses caused by recurring fire.

  15. Carbon Cycling Studies in Forest and Rangeland Ecosystems of Northern and Central Coastal California

    NASA Astrophysics Data System (ADS)

    Potter, C.; Klooster, S.; Gross, P.; Hiatt, S.; Genovese, V.

    2008-12-01

    The varied topography and micro-climates of northern and central coastal California result in high biodiversity and many different levels of primary production driving regional carbon cycles. Coastal mountains trap moisture from low clouds and fog in summer to supplement rainfall in winter. This creates a favorable micro-environment for coniferous forests, including the southernmost habitat of the coast redwood (Sequoia sempervirens), which grows mainly on lower north-facing slopes in Big Sur. In rain shadows, forests transition to open oak woodland, and then into the more fire-tolerant chaparral and coast scrub. Field sites for our on-going climate change studies on the California northern and central coasts currently include the University of California Santa Cruz Campus Natural Reserve, the US Forest Service Brazil Ranch, and the University of California Big Creek Reserve. We are conducting research at each of these sites to better understand possible impacts of climate change, including: (1) biological and physical capacity of soils to capture carbon and retain plant-essential nutrients; (2) rates of plant-soil water and carbon cycling and energy flow; and (3) recovery mechanisms for disturbances such as invasive weed species, grazing, and wildfire. The NASA-CASA simulation model based on satellite observations of monthly vegetation cover from the Moderate Resolution Imaging Spectroradiometer (MODIS) was used to estimate carbon cycling for much of the central coast as far north as Mendocino County. Net primary production (NPP) of all vegetation cover was mapped at 30-meter resolution for selected years by combining MODIS and Landsat images across the region. Results show annual NPP predictions of between 200-400 grams C per square meter for coastal scrub and 800-1200 grams C per square meter for coastal evergreen forests, Net ecosystem fluxes of carbon will be presented for the region based on NASA-CASA modeling and field measurements of soil respiration fluxes.

  16. Hydrology-driven ecosystem respiration determines the carbon balance of a boreal peatland.

    PubMed

    Gažovič, Michal; Forbrich, Inke; Jager, Daniel F; Kutzbach, Lars; Wille, Christian; Wilmking, Martin

    2013-10-01

    The carbon (C) balance of boreal peatlands is mainly the sum of three different C fluxes: carbon dioxide (CO2), methane (CH4) and dissolved organic carbon (DOC). Intra- and inter-annual dynamics of these fluxes are differentially controlled by similar factors, such as temperature and water-table. Different climatic conditions within and between years might thus result in varying absolute and relative contributions of each flux to net ecosystem productivity (NEP). In this study CO2 fluxes were measured at a boreal peatland in eastern Finland during a dry year (2006) and a wet year (2007) and combined with DOC and CH4 fluxes from the same site. CO2 uptake in the wet year was 65% higher than in the dry year, caused by higher water table (WT) and subsequently reduced rates of soil respiration. Two to three-fold increases in DOC and CH4 fluxes in the wet year did not completely offset the higher CO2 uptake in that year, resulting in NEP of -83.7±14 g C m(-2) in the dry and -134.5±21 g C m(-2) in the wet year. Thus, in our study, WT was identified as the most important factor responsible for variations in the C balance between the observed years.

  17. [Microbial community abundance and diversity in typical karst ecosystem to indicate soil carbon cycle].

    PubMed

    Jin, Zhen-Jiang; Tang, Hua-Feng; Li, Min; Huang, Bing-Fu; Li, Qiang; Zhang, Jia-Yu; Li, Gui-Wen

    2014-11-01

    The soil microbial characteristics were detected to clarify their indications in organic carbon cycle in karst system. Soil samples from three karst types (saddle, depression and slop) at 0-10 cm, 10-20 cm and 20-30 cm layers were collected in the Yaji Karst Experimental Site, a typical karst ecosystem. The microbial diversity and abundance were assayed using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and fluorescence quantitative PCR. The data showed that the highest abundance of 16S rRNA and 18S rRNA were in depression with 1.32 x 10(11) copies x g(-1) and in saddle with 1.12 x 10(10) copies x g(-1), respectively. The abundance of 16S rRNA in saddle and depression decreased from top to bottom, while that of 18S rRNA in three karst forms decreased, which showed that the abundance changed consistently with soil organic carbon (SOC). The 3 diversity indices of 16S rRNA and 6 diversity indices of 18S rRNA increased from top to bottom in soil profiles of three karst forms. These results showed that microbial diversity changed conversely with the abundance and SOC in soil profile. It can be concluded that the abundance was more important than the diversity index for soil carbon cycle in karst system.

  18. Final Report on "Rising CO2 and Long-term Carbon Storage in Terrestrial Ecosystems: An Empirical Carbon Budget Validation"

    SciTech Connect

    J. Patrick Megonigal; Bert G. Drake

    2010-08-27

    The primary goal of this report is to report the results of Grant DE-FG02-97ER62458, which began in 1997 as Grant DOE-98-59-MP-4 funded through the TECO program. However, this project has a longer history because DOE also funded this study from its inception in 1985 through 1997. The original grant was focused on plant responses to elevated CO2 in an intact ecosystem, while the latter grant was focused on belowground responses. Here we summarize the major findings across the 25 years this study has operated, and note that the experiment will continue to run through 2020 with NSF support. The major conclusions of the study to date are: (1 Elevated CO2 stimulated plant productivity in the C3 plant community by ~30% during the 25 year study. The magnitude of the increase in productivity varied interannually and was sometime absent altogether. There is some evidence of down-regulation at the ecosystem level across the 25 year record that may be due to interactions with other factors such as sea-level rise or long-term changes in N supply; (2) Elevated CO2 stimulated C4 productivity by <10%, perhaps due to more efficient water use, but C3 plants at elevated CO2 did not displace C4 plants as predicted; (3) Increased primary production caused a general stimulation of microbial processes, but there were both increases and decreases in activity depending on the specific organisms considered. An increase in methanogenesis and methane emissions implies elevated CO2 may amplify radiative forcing in the case of wetland ecosystems; (4) Elevated CO2 stimulated soil carbon sequestration in the form of an increase in elevation. The increase in elevation is 50-100% of the increase in net ecosystem production caused by elevated CO2 (still under analysis). The increase in soil elevation suggests the elevated CO2 may have a positive outcome for the ability of coastal wetlands to persist despite accelerated sea level rise; (5) Crossing elevated CO2 with elevated N causes the elevated CO

  19. An Ecosystem Assessment of Carbon Storage and Fluxes Over Space and Time in the Conterminous United States

    NASA Astrophysics Data System (ADS)

    Zhu, Z.; Bergamaschi, B. A.; Hawbaker, T.; Liu, S.; Reed, B.; Sleeter, B. M.; Sohl, T.; Stackpoole, S. M.

    2013-12-01

    Ecosystem carbon stock, sequestration, and greenhouse gasl (GHG) flux were estimated for the conterminous United States (CONUS) in two time periods: baseline (annual average of 2001-2005) and future projection (annual average of 2006-2050). Major input data for baseline estimates included national resource inventories (such as forest and agricultural inventories and data from a national stream gage network), land use and land cover (LULC) map and soil carbon from national soil databases. The assessment covered 7,88 million km2 in land and water areas. Major input data for projected carbon estimates included future LULC scenarios developed in a framework consistent with the Intergovernmental Panel on Climate Change's future climate projections, and the future climate projection data. Estimated carbon stock and net ecosystem carbon balance for all major pools (live biomass, dead biomass, and soil organic matter) and terrestrial ecosystems (forests, agrcilture, wetlands, and grasslands) were produced using ecosystem models (Table 1). Emission from wildfires of the CONUS was evaluated based on remote sensing methods and fire behavior modeling. Emission fom inland water bodies (including rivers, lakes, and reservoirs), carbon transport by riverine systems, and carbon burial in sediments of lakes and reservoirs in the CONUS were estimated using input data from available aquatic measurements in a national water information system, water areas, and empirial methods (Table 2). Details of the methods used, and effects of drivers (both natural and anthropogenic processes) will be presented in the poster. Uncertainties from the assessment remained high as indicated by the major results shown above. Sources of uncertainties included scarcity of input data, structure differences of methods and models used, and parameterization and assumptions made in the modeling process.Table 1. Estimated carbon stock and net ecosystem carbon balance (NECB) of the major ecosystems by two time

  20. Long-Term Influence of the BOREAS Field Experiment on Carbon Cycle and Ecosystem Research in Canada

    NASA Astrophysics Data System (ADS)

    Margolis, H. A.

    2015-12-01

    The NASA-led Boreal Ecosystem-Atmosphere Study (BOREAS) field experiment brought together an interdisciplinary team of scientists during the mid-1990's to study biosphere-atmosphere interactions of the boreal forest biome in Saskatchewan and Manitoba, Canada. It represented the beginning of coordinated, long-term eddy covariance flux tower measurements of the exchanges of carbon dioxide, water, and energy at the ecosystem scale in Canada and initiated research on how to upscale these processes to larger spatial domains using remote sensing. The focus of this presentation will be on the long-term impacts of BOREAS on carbon cycle and ecosystems research in Canada. The BOREAS flux tower effort was expanded to the national level in Canada through the Fluxnet-Canada and Canadian Carbon Program research networks (2002-2011). Within these two research networks, many of the Canadian scientists brought together during BOREAS continued their close scientific collaborations and maintained their links to related programs in the US such as the North American Carbon Program. These Canadian efforts allowed us to improve greatly our understanding of the impacts of inter-annual climate variability and ecological disturbance on carbon, water and energy dynamics of northern forests and allowed us to use these flux data for calibration and validation of a wide-range of ecosystem modelling and analysis efforts. Many of the flux tower measurements continue to this day and they assure the long-term legacy of the NASA Terrestrial Ecology Program's initial investment in the BOREAS field campaign.

  1. Nitrogen-addition effects on leaf traits and photosynthetic carbon gain of boreal forest understory shrubs.

    PubMed

    Palmroth, Sari; Bach, Lisbet Holm; Nordin, Annika; Palmqvist, Kristin

    2014-06-01

    Boreal coniferous forests are characterized by fairly open canopies where understory vegetation is an important component of ecosystem C and N cycling. We used an ecophysiological approach to study the effects of N additions on uptake and partitioning of C and N in two dominant understory shrubs: deciduous Vaccinium myrtillus in a Picea abies stand and evergreen Vaccinium vitis-idaea in a Pinus sylvestris stand in northern Sweden. N was added to these stands for 16 and 8 years, respectively, at rates of 0, 12.5, and 50 kg N ha(-1) year(-1). N addition at the highest rate increased foliar N and chlorophyll concentrations in both understory species. Canopy cover of P. abies also increased, decreasing light availability and leaf mass per area of V. myrtillus. Among leaves of either shrub, foliar N content did not explain variation in light-saturated CO2 exchange rates. Instead photosynthetic capacity varied with stomatal conductance possibly reflecting plant hydraulic properties and within-site variation in water availability. Moreover, likely due to increased shading under P. abies and due to water limitations in the sandy soil under P. sylvestris, individuals of the two shrubs did not increase their biomass or shift their allocation between above- and belowground parts in response to N additions. Altogether, our results indicate that the understory shrubs in these systems show little response to N additions in terms of photosynthetic physiology or growth and that changes in their performance are mostly associated with responses of the tree canopy.

  2. Soil Organic Carbon for Global Benefits - assessing potential SOC increase under SLM technologies worldwide and evaluating tradeoffs and gains of upscaling SLM technologies

    NASA Astrophysics Data System (ADS)

    Wolfgramm, Bettina; Hurni, Hans; Liniger, Hanspeter; Ruppen, Sebastian; Milne, Eleanor; Bader, Hans-Peter; Scheidegger, Ruth; Amare, Tadele; Yitaferu, Birru; Nazarmavloev, Farrukh; Conder, Malgorzata; Ebneter, Laura; Qadamov, Aslam; Shokirov, Qobiljon; Hergarten, Christian; Schwilch, Gudrun

    2013-04-01

    There is a fundamental mutual interest between enhancing soil organic carbon (SOC) in the world's soils and the objectives of the major global environmental conventions (UNFCCC, UNCBD, UNCCD). While there is evidence at the case study level that sustainable land management (SLM) technologies increase SOC stocks and SOC related benefits, there is no quantitative data available on the potential for increasing SOC benefits from different SLM technologies and especially from case studies in the developing countries, and a clear understanding of the trade-offs related to SLM up-scaling is missing. This study aims at assessing the potential increase of SOC under SLM technologies worldwide, evaluating tradeoffs and gains in up-scaling SLM for case studies in Tajikistan, Ethiopia and Switzerland. It makes use of the SLM technologies documented in the online database of the World Overview of Conservation Approaches and Technologies (WOCAT). The study consists of three components: 1) Identifying SOC benefits contributing to the major global environmental issues for SLM technologies worldwide as documented in the WOCAT global database 2) Validation of SOC storage potentials and SOC benefit predictions for SLM technologies from the WOCAT database using results from existing comparative case studies at the plot level, using soil spectral libraries and standardized documentations of ecosystem service from the WOCAT database. 3) Understanding trade-offs and win-win scenarios of up-scaling SLM technologies from the plot to the household and landscape level using material flow analysis. This study builds on the premise that the most promising way to increase benefits from land management is to consider already existing sustainable strategies. Such SLM technologies from all over the world documented are accessible in a standardized way in the WOCAT online database. The study thus evaluates SLM technologies from the WOCAT database by calculating the potential SOC storage increase and

  3. Importance of soil thermal regime in terrestrial ecosystem carbon dynamics in the circumpolar north

    NASA Astrophysics Data System (ADS)

    Jiang, Yueyang; Zhuang, Qianlai; Sitch, Stephen; O'Donnell, Jonathan A.; Kicklighter, David; Sokolov, Andrei; Melillo, Jerry

    2016-07-01

    In the circumpolar north (45-90°N), permafrost plays an important role in vegetation and carbon (C) dynamics. Permafrost thawing has been accelerated by the warming climate and exerts a positive feedback to climate through increasing soil C release to the atmosphere. To evaluate the influence of permafrost on C dynamics, changes in soil temperature profiles should be considered in global C models. This study incorporates a sophisticated soil thermal model (STM) into a dynamic global vegetation model (LPJ-DGVM) to improve simulations of changes in soil temperature profiles from the ground surface to 3 m depth, and its impacts on C pools and fluxes during the 20th and 21st centuries. With cooler simulated soil temperatures during the summer, LPJ-STM estimates ~ 0.4 Pg C yr- 1 lower present-day heterotrophic respiration but ~ 0.5 Pg C yr- 1 higher net primary production than the original LPJ model resulting in an additional 0.8 to 1.0 Pg C yr- 1 being sequestered in circumpolar ecosystems. Under a suite of projected warming scenarios, we show that the increasing active layer thickness results in the mobilization of permafrost C, which contributes to a more rapid increase in heterotrophic respiration in LPJ-STM compared to the stand-alone LPJ model. Except under the extreme warming conditions, increases in plant production due to warming and rising CO2, overwhelm the e nhanced ecosystem respiration so that both boreal forest and arctic tundra ecosystems remain a net C sink over the 21st century. This study highlights the importance of considering changes in the soil thermal regime when quantifying the C budget in the circumpolar north.

  4. Perspectives on the microbial carbon pump with special reference to microbial respiration and ecosystem efficiency in large estuarine systems

    NASA Astrophysics Data System (ADS)

    Dang, H.; Jiao, N.

    2014-07-01

    Although respiration-based oxidation of reduced carbon releases CO2 into the environment, it provides an ecosystem with the metabolic energy for essential biogeochemical processes, including the newly proposed microbial carbon pump (MCP). The efficiency of MCP in heterotrophic microorganisms is related to the mechanisms of energy transduction employed and hence is related to the form of respiration utilized. Anaerobic organisms typically have lower efficiencies of energy transduction and hence lower efficiencies of energy-dependent carbon transformation. This leads to a lower MCP efficiency on a per-cell basis. Substantial input of terrigenous nutrients and organic matter into estuarine ecosystems typically results in elevated heterotrophic respiration that rapidly consumes dissolved oxygen, potentially producing hypoxic and anoxic zones in the water column. The lowered availability of dissolved oxygen and the excessive supply of nutrients such as nitrate from river discharge lead to enhanced anaerobic respiration processes such as denitrification and dissimilatory nitrate reduction to ammonium. Thus, some nutrients may be consumed through anaerobic heterotrophs, instead of being utilized by phytoplankton for autotrophic carbon fixation. In this manner, eutrophied estuarine ecosystems become largely fueled by anaerobic respiratory pathways and their efficiency is less due to lowered ecosystem productivity when compared to healthy and balanced estuarine ecosystems. This situation may have a negative impact on the ecological function and efficiency of the MCP which depends on the supply of both organic carbon and metabolic energy. This review presents our current understanding of the MCP mechanisms from the view point of ecosystem energy transduction efficiency, which has not been discussed in previous literature.

  5. Near-neutral carbon dioxide balance at a seminatural, temperate bog ecosystem

    NASA Astrophysics Data System (ADS)

    Hurkuck, Miriam; Brümmer, Christian; Kutsch, Werner L.

    2016-02-01

    The majority of peatlands in the temperate zone is subjected to drainage and agricultural land use and have been found to be anthropogenic emission hot spots for greenhouse gases. At the same time, many peatlands receive increased atmospheric nitrogen (N) deposition by intensive agricultural practices. Here we provide eddy covariance measurements determining net ecosystem carbon dioxide (CO2) exchange at a protected but moderately drained ombrotrophic bog in Northwestern Germany over three consecutive years. The region is dominated by intensive agricultural land use with total (wet and dry) atmospheric N deposition being about 25 kg N ha-1 yr-1. The investigated peat bog was a small net CO2 sink during all three years ranging from -9 to -73 g C m-2 yr-1. We found temperature- and light-dependent ecosystem respiration (Reco) and gross primary production, respectively, but only weak correlations to water table depths despite large interannual and seasonal variability. Significant short-term effects of atmospheric N deposition on CO2 flux components could not be observed, as the primary controlling factors for N deposition and C sequestration, i.e., fertilization of adjacent fields as well as temperature and light availability, respectively, exceeded potential interactions between the two.

  6. Carbon Monoxide Based Metabolism and CO Cycling in Anaerobic Microbial Ecosystems

    NASA Astrophysics Data System (ADS)

    Colman, A. S.; Techtmann, S. M.; He, B.; Anderson, M. R.; Robb, F. T.

    2011-12-01

    Carbon monoxide binds tightly to many hemes and other porphyrins, proving toxic to humans and microbes. Nevertheless, CO is an attractive fuel for anaerobic chemolithotrophy for those microbes not impaired by CO's toxicity. CO can be oxidized to CO2 anaerobically through the water-gas-shift reaction by hydrogenogenic carboxydotrophs. CO can also be used by certain homoacetogens in the production of acetate and by certain methanogens in the production of methane, acetate, and formate. CO is not only consumed by microbes, but a diverse range of evidence points towards biogenic production of CO. We present measurements of CO concentrations in dissolved and free phase gases in hot springs in Kamchatka, Russia, and Lassen Volcanic National Park, CA. These measurements implicate microbial CO production as a dominant source of CO in these anaerobic ecosystems. There are few in situ measurements of dissolved CO in microbial mats and sediment pore waters. However, the concentration dependent biochemical and transcriptional responses of carboxydotrophs to CO offer strong evidence for the growth conditions to which these microbes have adapted. CooA is a CO-sensing transcriptional activator found in most anaerobic carboxydotrophs. We interpret the CO-binding properties of CooA in Carboxydothermus hydrogenoformans and Rhodospirillum rubrum as evidence for the ranges of environmental CO concentrations that are frequently encountered in anaerobic ecosystems.

  7. Organic nutrient uptake by mycorrhizal fungi enhances ecosystem carbon storage: a model-based assessment.

    PubMed

    Orwin, Kate H; Kirschbaum, Miko U F; St John, Mark G; Dickie, Ian A

    2011-05-01

    Understanding the factors that drive soil carbon (C) accumulation is of fundamental importance given their potential to mitigate climate change. Much research has focused on the relationship between plant traits and C sequestration, but no studies to date have quantitatively considered traits of their mycorrhizal symbionts. Here, we use a modelling approach to assess the contribution of an important mycorrhizal fungal trait, organic nutrient uptake, to soil C accumulation. We show that organic nutrient uptake can significantly increase soil C storage, and that it has a greater effect under nutrient-limited conditions. The main mechanism behind this was an increase in plant C fixation and subsequent increased C inputs to soil through mycorrhizal fungi. Reduced decomposition due to increased nutrient limitation of saprotrophs also played a role. Our results indicate that direct uptake of nutrients from organic pools by mycorrhizal fungi could have a significant effect on ecosystem C cycling and storage. PMID:21395963

  8. Soil Carbon Stocks in a Shifting Ecosystem; Climate Induced Migration of Mangroves into Salt Marsh

    NASA Astrophysics Data System (ADS)

    Simpson, L.; Osborne, T.; Feller, I. C.

    2015-12-01

    Across the globe, coastal wetland vegetation distributions are changing in response to climate change. The increase in global average surface temperature has already caused shifts in the structure and distribution of many ecological communities. In parts of the southeastern United States, increased winter temperatures have resulted in the poleward range expansion of mangroves at the expense of salt marsh habitat. Our work aims to document carbon storage in the salt marsh - mangrove ecotone and any potential changes in this reservoir that may ensue due to the shifting range of this habitat. Differences in SOM and C stocks along a latitudinal gradient on the east coast of Florida will be presented. The gradient studied spans 342 km and includes pure mangrove habitat, the salt marsh - mangrove ecotone, and pure salt marsh habitat.This latitudinal gradient gives us an exceptional opportunity to document and investigate ecosystem soil C modifications as mangroves transgress into salt marsh habitat due to climatic change.

  9. Modeled effect of warming on ecosystem carbon and water dynamics within grassland/old-field ecosystems along a moisture gradient

    Technology Transfer Automated Retrieval System (TEKTRAN)

    As a consequence of steadily increasing concentrations of greenhouse gases in Earth’s atmosphere, average world-wide surface temperature is expected to increase 1.5-6.4°C by the end of the 21st Century. Results from manipulative field experiments and ecosystem modeling indicate that plants and soil...

  10. Tunable Diode Laser Measurements of Leaf-scale Carbon Isotope Discrimination and Ecosystem Respired Carbon and Oxygen Isotope Ratios in a Semi-arid Woodland

    NASA Astrophysics Data System (ADS)

    McDowell, N.; Chris, B.; Hanson, D.; Kern, S.; Meyer, C.; Pockman, W.; Powers, H.

    2005-12-01

    We present results and speculative interpretation of leaf-level carbon isotope discrimination and ecosystem respired carbon and oxygen isotope ratios from a semi-arid, C3/C4 woodland located in northern New Mexico, USA. Overstory leaf area index (LAI) is dominated by live juniper (Juniperus monosperma) trees with an LAI value of approximately 1.0 m2 per m2 ground area, and has a seasonally dynamic understory of mixed C3 forbs and C4 grasses and cacti, with a maximum LAI of 0.30 m2 per m2 ground area. Ecosystem respired carbon isotope ratios showed values characteristic of C3 dominated photosynthesis (Keeling plot intercepts of -35 to -22 per mil). Seasonal variation was typical of that found in wetter, C3 dominated forests, as was the dependence on climate (e.g. relationships with vapor pressure deficit, soil water content, and canopy conductance). Leaf-level carbon isotope discrimination of the junipers, measured by coupling a Li-Cor 6400 photosynthesis system to the TDL, provided discrimination-Ci and discrimination-vpd relationships consistent with measured ecosystem respired carbon isotope ratios. The oxygen isotope ratio of ecosystem respiration was dependent on rain water isotope composition, but was correlated with soil water content during rain-free periods. The cumulative effect of vapor pressure deficit after a rain event was tightly correlated with the oxygen isotope ratio of ecosystem respiration, suggesting the primary drivers are evaporative enrichment of soil water and perhaps nocturnal leaf enrichment. Instrument precision for carbon and oxygen isotope ratios of carbon dioxide is 0.06 to 0.18 per mil; however, overall precision is somewhat lower due to pressure and sampling effects.

  11. After the Storm: Assessing the carbon and nitrogen leaching potential from sediments deposited in aquatic ecosystems

    NASA Astrophysics Data System (ADS)

    Johnson, E. R.; Krieg, C.; Canning, C.; Inamdar, S. P.; Rowland, R. D.

    2015-12-01

    The erosive energy of large storms can mobilize, and subsequently deposit large amounts of sediment in receiving aquatic ecosystems. Depending on the character of the sediments there is potential for leaching or sequestration of carbon (C) and nitrogen (N) from the sediments. This could have significant implications for water quality, aquatic metabolism, and global cycling of C and N. This study examines the fate of these sediments by: (1) determining the amount and quality of organic matter that can be leached into the surrounding water from coarse, medium and fine particle classes (2) assessing the C and N contents of various particles classes and the sources of the sediment through isotopic composition. Bed sediment samples were collected along a 1-2nd order stream (eight locations) in a forested catchment in the Piedmont region of Maryland following a large storm event. Samples were sieved into three particle classes - coarse (2mm-1mm), medium (1mm-250µm) and fine (<250µm). Extractions were performed for each of three particle class sizes by leaching with DI water. Organic matter composition for the extracts was characterized using fluorescence. Stable isotopes of 13C and 15N were determined for bed sediment classes and upland source sediments to identify the origins of the eroded sediments. Extracts with low C:N ratios that also exhibit a higher percent protein and lower percent humic carbon content are considered most labile. Within the bed sediment deposits, differences were found in the distribution of labile compounds between each particle class size. Generally, course particle size exhibited the most labile characteristics, closely followed by medium particle size. Fine particle size exhibited the most refractory characteristics in all locations. These results are critical since climate-change predictions reveal more intense and large storms for the northeast US, with potentially greater impacts on aquatic ecosystems from eroded upland sediments.

  12. Degradation State and Sequestration Potential of Carbon in Coastal Wetlands of Texas: Mangrove Vs. Saltmarsh Ecosystems

    NASA Astrophysics Data System (ADS)

    Sterne, A. M. E.; Kaiser, K.; Louchouarn, P.; Norwood, M. J.

    2015-12-01

    The estimated magnitude of the organic carbon (OC) stocks contained in the first meter of US coastal wetland soils represents ~10% of the entire OC stock in US soils (4 vs. 52 Pg, respectively). Because this stock extends to several meters below the surface for many coastal wetlands, it becomes paramount to understand the fate of OC under ecosystem shifts, varying natural environmental constraints, and changing land use. In this project we analyze the major classes of biochemicals including total hydrolysable neutral carbohydrates, enantiomeric amino acids, phenols, and cutins/suberins at two study sites located on the Texas coastline to investigate chemical composition and its controls on organic carbon preservation in mangrove (Avicennia germinans) and saltmarsh grass (Spartina alterniflora) dominated wetlands. Results show neutral carbohydrates and lignin contribute 30-70% and 10-40% of total OC, respectively, in plant litter and surface sediments at both sites. Sharp declines of carbohydrate yields with depth occur parallel to increasing Ac/AlS,V ratios indicating substantial decomposition of both the polysaccharide and lignin components of litter detritus. Contrasts in the compositions and relative abundances of all previously mentioned compound classes are further discussed to examine the role of litter biochemistry in OC preservation. For example, the selective preservation of cellulose over hemicellulose in sediments indicates macromolecular structure plays a key role in preservation between plant types. It is concluded that the chemical composition of litter material controls the composition and magnitude of OC stored in sediments. Ultimately, as these ecosystems transition from one dominant plant type to another, as is currently observed along the Texas coastline, there is the potential for OC sequestration efficiency to shift due to the changing composition of OC input to sediments.

  13. Black (Pyrogenic) Carbon as a Component of Carbon Cycling and Ecosystem Function in Boreal Regions

    NASA Astrophysics Data System (ADS)

    Preston, C. M.; Schmidt, M. W.

    2005-12-01

    The carbon (C) cycle in boreal regions is strongly influenced by fire, which converts a small fraction (1-7% of mass) to pyrogenic C (PyC). PyC is mainly produced as solid charred residues including a black carbon (BC) fraction chemically defined by its oxidation resistance, plus much lower proportions of volatile soot and polycyclic aromatic hydrocarbons (PAHs). All PyC is characterized by fused aromatic rings, but varying in cluster sizes and degree of ordering, and presence of other elements (N, O) and functional groups. Char PyC is expected to be highly resistant to decomposition, and therefore to contribute to very stable C pools in soils and sediments. It also appears to influence soil processes, mainly through its sorption properties and contribution to cation exchange capacity. By contrast, soot aerosols absorb solar radiation, and may contribute to global warming. However, information is lacking to integrate PyC into C cycle and atmospheric models for boreal regions. Analytical methods are still under development and individual methods, which are mainly based on various measures of oxidation resistance, capture different fractions of the PyC ``continuum''. Short- term incubations indicate a small initial breakdown of solid PyC, leveling off after 1-2 years. Quantitative long-term field studies on PyC longevity are missing, but circumstantial evidence suggests turnover on a millennium timescale (5,000-10,000 y), depending on environmental conditions and PyC properties. Degraded, functionalized PyC becomes water soluble and has been detected in river water and sediments. We have synthesized the limited information available on production, stocks, characteristics, and loss proce