Now showing items 158-177 of 262

  • A new US polar research vessel for the twenty-first century 

    Dunbar, Robert B.; Alberts, Jon; Ashjian, Carin J.; Asper, Vernon L.; Chayes, Dale; Domack, Eugene; Ducklow, Hugh W.; Huber, Bruce; Lawver, Lawrence; Oliver, Daniel; Russell, Doug; Smith, Craig R.; Vernet, Maria (The Oceanography Society, 2012-09)
    Scientific and political interests at the poles are significant and rapidly increasing, driven in part by the effects of climate change and emerging geopolitical realities. The polar regions provide important services to ...
  • Nitrogen attenuation of terrestrial carbon cycle response to global environmental factors 

    Jain, Atul K.; Yang, Xiaojuan; Kheshgi, Haroon; McGuire, A. David; Post, Wilfred; Kicklighter, David W. (American Geophysical Union, 2009-12-30)
    Nitrogen cycle dynamics have the capacity to attenuate the magnitude of global terrestrial carbon sinks and sources driven by CO2 fertilization and changes in climate. In this study, two versions of the terrestrial carbon ...
  • Nitrogen dynamics in a small arctic watershed: retention and downhill movement of 15N 

    Yano, Yuriko; Shaver, Gaius R.; Giblin, Anne E.; Rastetter, Edward B.; Nadelhoffer, Knute J. (2009-06-12)
    We examined short- and long-term nitrogen (N) dynamics and availability along an arctic hillslope in Alaska, USA, using stable isotope of nitrogen (15N), as a tracer. Tracer levels of 15NH4+ were sprayed once onto the ...
  • Nitrogen dynamics in arctic tundra soils of varying age : differential responses to fertilization and warming 

    Yano, Yuriko; Shaver, Gaius R.; Rastetter, Edward B.; Giblin, Anne E.; Laundre, James A. (2013-03)
    In the northern foothills of the Brooks Range, Alaska, a series of glacial retreats has created a landscape that varies widely in time since deglaciation (= soil age), from ~10k years to more than 2M years. Productivity ...
  • Nitrogen effect on carbon-water coupling in forests, grasslands, and shrublands in the arid western United States 

    Felzer, Benjamin S.; Cronin, Timothy W.; Melillo, Jerry M.; Kicklighter, David W.; Schlosser, C. Adam; Dangal, Shree R. S. (American Geophysical Union, 2011-08-25)
    As greenhouse gases, including CO2, accumulate in the atmosphere, the western United States is predicted to undergo large-scale climate warming and reduced summer precipitation in the coming decades. In this study we explore ...
  • Nitrogen interception and export by experimental salt marsh plots exposed to chronic nutrient addition 

    Brin, Lindsay D.; Valiela, Ivan; Goehringer, Dale; Howes, Brian L. (Inter-Research, 2010-02-11)
    Mass balance studies conducted in the 1970s in Great Sippewissett Salt Marsh, New England, showed that fertilized plots intercepted 60 to 80% of the nitrogen (N) applied at several treatment levels every year from April ...
  • Nitrogen stable isotopes in the shell of Mercenaria mercenaria trace wastewater inputs from watersheds to estuarine ecosystems 

    Carmichael, Ruth H.; Hattenrath, Theresa K.; Valiela, Ivan; Michener, Robert H. (Inter-Research, 2008-11-25)
    We tested the usefulness of δ15N values in the organic matrix of whole shells from Mercenaria mercenaria as tracers of anthropogenic nitrogen inputs to coastal ecosystems. Low and high stringency acidification methods were ...
  • Nitrous oxide nitrification and denitrification 15N enrichment factors from Amazon forest soils 

    Perez, Tibisay; Garcia-Montiel, Diana; Trumbore, Susan E.; Tyler, Stanley; de Camargo, Plinio; Moreira, Marcelo; Piccolo, Marisa C.; Cerri, Carlos C. (Ecological Society of America, 2006-12)
    The isotopic signatures of 15N and 18O in N2O emitted from tropical soils vary both spatially and temporally, leading to large uncertainty in the overall tropical source signature and thereby limiting the utility of isotopes ...
  • NLOAD : an interactive, web-based modeling tool for nitrogen management in estuaries 

    Bowen, Jennifer L.; Ramstack, Joy M.; Mazzilli, S.; Valiela, Ivan (Ecological Society of America, 2007-07)
    Eutrophication of estuaries is an increasing global concern that requires development of new tools to identify causes, quantify conditions, and propose management options that address this environmental problem. Since ...
  • Nutrient gradients in Panamanian estuaries : effects of watershed deforestation, rainfall, upwelling, and within-estuary transformations 

    Valiela, Ivan; Giblin, Anne E.; Barth-Jensen, Coralie; Harris, Carolynn; Stone, Thomas A.; Fox, Sophia E.; Crusius, John (Inter-Research, 2013-05-22)
    To test whether deforestation of tropical forests alters coupling of watersheds, estuaries, and coastal waters, we measured nutrients in 8 watershed-estuarine systems on the Pacific coast of Panama where watershed forest ...
  • Objective indicators of pasture degradation from spectral mixture analysis of Landsat imagery 

    Davidson, Eric A.; Asner, Gregory P.; Stone, Thomas A.; Neill, Christopher; Figueiredo, Ricardo O. (American Geophysical Union, 2008-07-23)
    Degradation of cattle pastures is a management concern that influences future land use in Amazonia. However, “degradation” is poorly defined and has different meanings for ranchers, ecologists, and policy makers. Here we ...
  • Oceanic heterotrophic bacterial nutrition by semilabile DOM as revealed by data assimilative modeling 

    Luo, Ya-Wei; Friedrichs, Marjorie A. M.; Doney, Scott C.; Church, Matthew J.; Ducklow, Hugh W. (Inter-Research, 2010-08-03)
    Previous studies have focused on the role of labile dissolved organic matter (DOM) (defined as turnover time of ~1 d) in supporting heterotrophic bacterial production, but have mostly neglected semilabile DOM (defined as ...
  • Optical instruments for measuring leaf area index in low vegetation : application in Arctic ecosystems 

    van Wijk, Mark T.; Williams, Mathew (Ecological Society of America, 2005-08)
    Leaf area index (LAI) is a powerful diagnostic of plant productivity. Despite the fact that many methods have been developed to quantify LAI, both directly and indirectly, leaf area index remains difficult to quantify ...
  • A pan-arctic evaluation of changes in river discharge during the latter half of the 20th century 

    McClelland, James W.; Dery, Stephen J.; Peterson, Bruce J.; Holmes, Robert M.; Wood, Eric F. (American Geophysical Union, 2006-03-30)
    Several recent publications have documented changes in river discharge from arctic and subarctic watersheds. Comparison of these findings, however, has been hampered by differences in time periods and methods of analysis. ...
  • Particle export from the upper ocean over the continental shelf of the west Antarctic Peninsula: A long-term record, 1992–2007 

    Ducklow, Hugh W.; Erickson, Matthew; Kelly, Joann; Montes-Hugo, Martin; Ribic, Christine A.; Smith, Raymond C.; Stammerjohn, Sharon E.; Karl, David M. (2008-03)
    We report on results of a long-term (1993-2007) time series sediment trap moored at 170 m to the west of the Antarctic Peninsula in the mid-continental shelf region (350 m depth; 64º30’ S, 66º00’ W). This is a region ...
  • Particle Flux in the deep Sargasso Sea : the 35-Year Oceanic Flux Program time series 

    Conte, Maureen H.; Weber, John C. (The Oceanography Society, 2014-03)
    The Oceanic Flux Program (OFP) sediment trap time series, the longest running time series of its kind, has continuously measured particle fluxes in the deep Sargasso Sea since 1978. OFP results provided the first direct ...
  • Past, present, and future roles of long-term experiments in the LTER Network 

    Knapp, Alan K.; Smith, Melinda D.; Hobbie, Sarah E.; Collins, Scott L.; Fahey, Timothy J.; Hansen, Gretchen J. A.; Landis, Douglas A.; La Pierre, Kimberly J.; Melillo, Jerry M.; Seastedt, Timothy R.; Shaver, Gaius R.; Webster, Jackson R. (American Institute of Biological Sciences, 2012-04)
    The US National Science Foundation—funded Long Term Ecological Research (LTER) Network supports a large (around 240) and diverse portfolio of long-term ecological experiments. Collectively, these long-term experiments have ...
  • Pattern and variation of C:N:P ratios in China’s soils : a synthesis of observational data 

    Tian, Hanqin; Chen, Guangsheng; Zhang, Chi; Melillo, Jerry M.; Hall, Charles A. S. (2009-09-01)
    Inspired by previous studies that have indicated consistent or even well-constrained relationships among carbon (C), nitrogen (N) and phosphorus (P) in soils, we have endeavored to explore general soil C:N:P ratios in ...
  • Permafrost degradation and methane : low risk of biogeochemical climate-warming feedback 

    Gao, Xiang; Schlosser, C. Adam; Sokolov, Andrei P.; Walter Anthony, Katey M.; Zhuang, Qianlai; Kicklighter, David W. (IOP Publishing, 2013-07-10)
    Climate change and permafrost thaw have been suggested to increase high latitude methane emissions that could potentially represent a strong feedback to the climate system. Using an integrated earth-system model framework, ...
  • Plant community responses to experimental warming across the tundra biome 

    Walker, Marilyn D.; Wahren, C. Henrik; Hollister, Robert D.; Henry, Greg H. R.; Ahlquist, Lorraine E.; Alatalo, Juha M.; Bret-Harte, M. Syndonia; Calef, Monika P.; Callaghan, Terry V.; Carroll, Amy B.; Epstein, Howard E.; Jonsdottir, Ingibjorg S.; Klein, Julia A.; Magnusson, Borgbor; Molau, Ulf; Oberbauer, Steven F.; Rewa, Steven P.; Robinson, Clare H.; Shaver, Gaius R.; Suding, Katharine N.; Thompson, Catharine C.; Tolvanen, Anne; Totland, Orjan; Turner, P. Lee; Tweedie, Craig E.; Webber, Patrick J.; Wookey, Philip A. (National Academy of Sciences of the USA, 2006-01-20)
    Recent observations of changes in some tundra ecosystems appear to be responses to a warming climate. Several experimental studies have shown that tundra plants and ecosystems can respond strongly to environmental change, ...