TY - JOUR
T1 - Nitrogen loss from unpolluted South American forests mainly via dissolved organic compounds
AU - Perakis, Steven S.
AU - Hedin, Lars O.
N1 - Funding Information:
We thank A. V. Balatsky, E. Dagotto, M. E. Flatté, S. A. Kivelson, V. Z. Kresin, R. B. Laughlin, J. W. Loram, D.-H. Lee, P. A. Lee, I. Martin, D. K. Morr, S. H. Pan, D. Pines, D. J. Scalapino, Z.-X. Shen, N. Trivedi and S. A. Wolf for discussions and communications. This work was supported by the LDRD program of Lawrence Berkeley National Laboratory, by the ONR, by the CULAR program of Los Alamos National Laboratory, by the Miller Research Foundation (J.C.D.), by IBM (K.M.L.), by Grant-in-Aid for Scientific Research, by a COE grant from the Ministry of Education, and by an International Joint Research Grant from NEDO (Japan).
Funding Information:
We thank S. Nodvin for sharing samples from CO and SF; M. Medina, B. Houlton, J. Armesto, C. Perez, G. Steinhart, J. O'Brien, G. Likens, J. Franklin, O. Sala, G. Lewis, T. Flum, J. Jamison, Corporación Nacional Forestal de Chile and Administración de Parque Nacionales de Argentina for site selection, field assistance and sample collection; M. Brown and K. Lohse for sample analysis; E. Boyer for cartography; and J. Compton, T. Fahey, R. Howarth, K. Lajtha, J. von Fischer, G. Lewis and P. Vitousek for comments on the manuscript. This work is a contribution to the Cordillera Piuchué Ecosystem Study and was supported by the Andrew W. Mellon Foundation, the NASA Earth Systems Science Fellowship Program and the US NSF.
Funding Information:
the Human Frontiers Science Program at Harvard University. C.B. acknowledges support from Jean-Luc Popot and the CNRS-UMR7099, where she carried out the final part of the analysis.
PY - 2002/1/24
Y1 - 2002/1/24
N2 - Conceptual1-4 and numerical5-8 models of nitrogen cycling in temperate forests assume that nitrogen is lost from these ecosystems predominantly by way of inorganic forms, such as nitrate and ammonium ions. Of these, nitrate is thought to be particularly mobile, being responsible for nitrogen loss to deep soil and stream waters. But human activities- such as fossil fuel combustion, fertilizer production and land-use change- have substantially altered the nitrogen cycle over large regions9, making it difficult to separate natural aspects of nitrogen cycling from those induced by human perturbations10. Here we report stream chemistry data from 100 unpolluted primary forests in temperate South America. Although the sites exhibit a broad range of environmental factors that influence ecosystem nutrient cycles11-13 (such as climate, parent material, time of ecosystem development, topography and biotic diversity), we observed a remarkably consistent pattern of nitrogen loss across all forests. In contrast to findings from forests in polluted regions, streamwater nitrate concentrations are exceedingly low, such that nitrate to ammonium ratios were less than unity, and dissolved organic nitrogen is responsible for the majority of nitrogen losses from these forests. We therefore suggest that organic nitrogen losses should be considered in models of forest nutrient cycling, which could help to explain observations of nutrient limitation in temperate forest ecosystems.
AB - Conceptual1-4 and numerical5-8 models of nitrogen cycling in temperate forests assume that nitrogen is lost from these ecosystems predominantly by way of inorganic forms, such as nitrate and ammonium ions. Of these, nitrate is thought to be particularly mobile, being responsible for nitrogen loss to deep soil and stream waters. But human activities- such as fossil fuel combustion, fertilizer production and land-use change- have substantially altered the nitrogen cycle over large regions9, making it difficult to separate natural aspects of nitrogen cycling from those induced by human perturbations10. Here we report stream chemistry data from 100 unpolluted primary forests in temperate South America. Although the sites exhibit a broad range of environmental factors that influence ecosystem nutrient cycles11-13 (such as climate, parent material, time of ecosystem development, topography and biotic diversity), we observed a remarkably consistent pattern of nitrogen loss across all forests. In contrast to findings from forests in polluted regions, streamwater nitrate concentrations are exceedingly low, such that nitrate to ammonium ratios were less than unity, and dissolved organic nitrogen is responsible for the majority of nitrogen losses from these forests. We therefore suggest that organic nitrogen losses should be considered in models of forest nutrient cycling, which could help to explain observations of nutrient limitation in temperate forest ecosystems.
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U2 - 10.1038/415416a
DO - 10.1038/415416a
M3 - Article
C2 - 11807551
AN - SCOPUS:0037165159
SN - 0028-0836
VL - 415
SP - 416
EP - 419
JO - Nature
JF - Nature
IS - 6870
ER -