, Volume 54, Issue 1, pp 1–39

Physical and biogeochemical controls over terrestrial ecosystem responses to nitrogen deposition


  • Gregory P. Asner
    • Department of Geological Sciences and Environmental Studies ProgramUniversity of Colorado
  • Alan R. Townsend
    • Department of EPO Biology and INSTAARUniversity of Colorado
  • William J. Riley
    • Department of Civil and Environmental EngineeringUniversity of California
  • Pamela A. Matson
    • Department of Geological and Environmental SciencesStanford University
  • Jason C. Neff
    • Natural Resource Ecology LaboratoryColorado State University
  • Cory C. Cleveland
    • Department of EPO Biology and INSTAARUniversity of Colorado

DOI: 10.1023/A:1010653913530

Cite this article as:
Asner, G.P., Townsend, A.R., Riley, W.J. et al. Biogeochemistry (2001) 54: 1. doi:10.1023/A:1010653913530


Anthropogenic perturbations to the global nitrogen (N) cycle nowexceed those to any other major biogeochemical cycle on Earth, yet ourability to predict how ecosystems will respond to the rapidly changing Ncycle is still poor. While northern temperate forest ecosystems haveseen the greatest changes in N inputs from the atmosphere, other biomes,notably semi-arid and tropical regions of the globe, are nowexperiencing increases in N deposition. These systems are even less wellunderstood than temperate forests, and are likely to respond to excess Nin markedly different ways. Here, we present a new integratedterrestrial biophysics-biogeochemical process model, TerraFlux, and usethis model to test the relative importance of factors that may stronglyinfluence the productivity response of both humid tropical and semi-aridsystems to anthropogenic N deposition. These include hydrological lossesof dissolved inorganic and organic N, as well as multiple nutrientinteractions with deposited inorganic N along the hydrological pathway.Our results suggest that N-rich tropical forests may have reducedproductivity following excess N deposition. Our simulations of semi-aridsystems show increases in productivity following N inputs if wateravailability is sufficient and water losses are moderate. The mostimportant model controls over the carbon cycle response in eachsimulation were interactions that are not represented in the most commonterrestrial ecosystem models. These include parameters that control soilsolute transport and nutrient resorption by plants. Rather than attemptprognostic simulations, we use TerraFlux to highlight a variety ofecological and biogeochemical processes that are poorly understood butwhich appear central to understanding ecosystem response to excessN.

calciumcationsnitratenitrogen depositionnitrogen leachingsavannasolute transporttropical forest
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© Kluwer Academic Publishers 2001