Ecosystems Center
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The Ecosystems Center carries out research in ecosystems that range from the Arctic to the Antarctic, from Brazil to Martha’s Vineyard. In the Alaskan Arctic, scientists study the effect of warmer temperatures on tundra, stream and lake ecosystems. On the Arctic rivers of Eurasia, they measure how freshwater discharge is changing as the climate warms. On the western Antarctic peninsula, research focuses on the responses of the marine coastal ecosystem to rapid climate warming. In the western Amazon in Brazil, researchers assess how much the clearing of tropical forests will change the amount of greenhouse gas released into the atmosphere, while on the island of Martha’s Vineyard, scientists used controlled burns to restore coastal ecosystems. In central Massachusetts and in Abisko, Sweden, soil warming experiments are conducted to assess the forest’s response to climate warming. In northeastern Massachusetts, scientists study how changes in rural land use and urban development affect the flow of nutrients and organic matter into New England estuaries. In Boston Harbor, they measure the transfer of nitrogen from sediments to the water column as the harbor recovers from decades of sewage addition.
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Browsing Ecosystems Center by Subject "Carbon sequestration"
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PreprintImportance of recent shifts in soil thermal dynamics on growing season length, productivity, and carbon sequestration in terrestrial high-latitude ecosystems( 2005-10-07) Euskirchen, Eugenie ; McGuire, A. David ; Kicklighter, David W. ; Zhuang, Qianlai ; Clein, Joy S. ; Dargaville, R. J. ; Dye, D. G. ; Kimball, John S. ; McDonald, Kyle C. ; Melillo, Jerry M. ; Romanovsky, Vladimir ; Smith, N. V.In terrestrial high-latitude regions, observations indicate recent changes in snow cover, permafrost, and soil freeze-thaw transitions due to climate change. These modifications may result in temporal shifts in the growing season and the associated rates of terrestrial productivity. Changes in productivity will influence the ability of these ecosystems to sequester atmospheric CO2. We use the Terrestrial Ecosystem Model (TEM), which simulates the soil thermal regime, in addition to terrestrial carbon, nitrogen and water dynamics, to explore these issues over the years 1960-2100 in extratropical regions (30°-90°N). Our model simulations show decreases in snow cover and permafrost stability from 1960 to 2100. Decreases in snow cover agree well with NOAA satellite observations collected between the years 1972-2000, with Pearson rank correlation coefficients between 0.58-0.65. Model analyses also indicate a trend towards an earlier thaw date of frozen soils and the onset of the growing season in the spring by approximately 2-4 days from 1988-2000. Between 1988 and 2000, satellite records yield a slightly stronger trend in thaw and the onset of the growing season, averaging between 5-8 days earlier. In both the TEM simulations and satellite records, trends in day of freeze in the autumn are weaker, such that overall increases in growing season length are due primarily to earlier thaw. Although regions with the longest snow cover duration displayed the greatest increase in growing season length, these regions maintained smaller increases in productivity and heterotrophic respiration than those regions with shorter duration of snow cover and less of an increase in growing season length. Concurrent with increases in growing season length, we found a reduction in soil carbon and increases in vegetation carbon, with greatest losses of soil carbon occurring in those areas with more vegetation, but simulations also suggest that this trend could reverse in the future. Our results reveal noteworthy changes in snow, permafrost, growing season length, productivity, and net carbon uptake, indicating that prediction of terrestrial carbon dynamics from one decade to the next will require that large-scale models adequately take into account the corresponding changes in soil thermal regimes.
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ArticleN and P constrain C in ecosystems under climate change: role of nutrient redistribution, accumulation, and stoichiometry(Ecological Society of America, 2022-05-28) Rastetter, Edward B. ; Kwiatkowski, Bonnie L. ; Kicklighter, David W. ; Barker Plotkin, Audrey ; Genet, Helene ; Nippert, Jesse B. ; O'Keefe, Kimberly ; Perakis, Steven S. ; Porder, Stephen ; Roley, Sarah S. ; Ruess, Roger W. ; Thompson, Jonathan R. ; Wieder, William R. ; Wilcox, Kevin R. ; Yanai, Ruth D.We use the Multiple Element Limitation (MEL) model to examine responses of 12 ecosystems to elevated carbon dioxide (CO2), warming, and 20% decreases or increases in precipitation. Ecosystems respond synergistically to elevated CO2, warming, and decreased precipitation combined because higher water-use efficiency with elevated CO2 and higher fertility with warming compensate for responses to drought. Response to elevated CO2, warming, and increased precipitation combined is additive. We analyze changes in ecosystem carbon (C) based on four nitrogen (N) and four phosphorus (P) attribution factors: (1) changes in total ecosystem N and P, (2) changes in N and P distribution between vegetation and soil, (3) changes in vegetation C:N and C:P ratios, and (4) changes in soil C:N and C:P ratios. In the combined CO2 and climate change simulations, all ecosystems gain C. The contributions of these four attribution factors to changes in ecosystem C storage varies among ecosystems because of differences in the initial distributions of N and P between vegetation and soil and the openness of the ecosystem N and P cycles. The net transfer of N and P from soil to vegetation dominates the C response of forests. For tundra and grasslands, the C gain is also associated with increased soil C:N and C:P. In ecosystems with symbiotic N fixation, C gains resulted from N accumulation. Because of differences in N versus P cycle openness and the distribution of organic matter between vegetation and soil, changes in the N and P attribution factors do not always parallel one another. Differences among ecosystems in C-nutrient interactions and the amount of woody biomass interact to shape ecosystem C sequestration under simulated global change. We suggest that future studies quantify the openness of the N and P cycles and changes in the distribution of C, N, and P among ecosystem components, which currently limit understanding of nutrient effects on C sequestration and responses to elevated CO2 and climate change.
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PreprintTerrestrial C sequestration at elevated CO2 and temperature : the role of dissolved organic N loss( 2004-06-07) Rastetter, Edward B. ; Perakis, Steven S. ; Shaver, Gaius R. ; Agren, Goran I.We used a simple model of carbon–nitrogen (C–N) interactions in terrestrial ecosystems to examine the responses to elevated CO2 and to elevated CO2 plus warming in ecosystems that had the same total nitrogen loss but that differed in the ratio of dissolved organic nitrogen (DON) to dissolved inorganic nitrogen (DIN) loss. We postulate that DIN losses can be curtailed by higher N demand in response to elevated CO2, but that DON losses cannot. We also examined simulations in which DON losses were held constant, were proportional to the amount of soil organic matter, were proportional to the soil C:N ratio, or were proportional to the rate of decomposition. We found that the mode of N loss made little difference to the short-term (<60 years) rate of carbon sequestration by the ecosystem, but high DON losses resulted in much lower carbon sequestration in the long term than did low DON losses. In the short term, C sequestration was fueled by an internal redistribution of N from soils to vegetation and by increases in the C:N ratio of soils and vegetation. This sequestration was about three times larger with elevated CO2 and warming than with elevated CO2 alone. After year 60, C sequestration was fueled by a net accumulation of N in the ecosystem, and the rate of sequestration was about the same with elevated CO2 and warming as with elevated CO2 alone. With high DON losses, the ecosystem either sequestered C slowly after year 60 (when DON losses were constant or proportional to soil organic matter) or lost C (when DON losses were proportional to the soil C:N ratio or to decomposition). We conclude that changes in long-term C sequestration depend not only on the magnitude of N losses, but also on the form of those losses.