Nitrogen stable isotopic composition of leaves and soil: Tropical versus temperate forests |
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Authors: | L.A. Martinelli M.C. Piccolo A.R. Townsend P.M. Vitousek E. Cuevas W. McDowell G.P. Robertson O.C. Santos K. Treseder |
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Affiliation: | (1) Cena-Av. Centenário 303, 13416-000 Piracicaba-SP., Brazil;(2) INSTAAR and Department of EPO-Biology, University of Colorado, Campus Box 450, 80309 Boulder, CO, USA;(3) Department of Biological Sciences, Stanford University, 94305-5020 Stanford, CA, USA;(4) IVIC, BAMCO CCS-199-00, PO Box 025322, 33102-5322 Miami, Fl, USA;(5) Department of Natural Resources, University of New Hampshire, 03824 Durham, NH, USA;(6) W.K. Kellogg Biological Station, Michigan State University, 9060-9516 Hickory Corners, MI, USA;(7) Meteorological Institute, Ministry of Science Technology and Environment, Aptdo, 17032, Habana 17, CP 11700 Havana, Cuba |
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Abstract: | Several lines of evidence suggest that nitrogen in most tropical forests is relatively more available than N in most temperate forests, and even that it may function as an excess nutrient in many tropical forests. If this is correct, tropical forests should have more open N cycles than temperate forests, with both inputs and outputs of N large relative to N cycling within systems. Consequent differences in both the magnitude and the pathways of N loss imply that tropical forests should in general be more15N enriched than are most temperate forests. In order to test this hypothesis, we compared the nitrogen stable isotopic composition of tree leaves and soils from a variety of tropical and temperate forests. Foliar 15N values from tropical forests averaged 6.5 higher than from temperate forests. Within the tropics, ecosystems with relatively low N availability (montane forests, forests on sandy soils) were significantly more depleted in15N than other tropical forests. The average 15N values for tropical forest soils, either for surface or for depth samples, were almost 8 higher than temperate forest soils. These results provide another line of evidence that N is relatively abundant in many tropical forest ecosystems. |
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Keywords: | N15 nitrogen nutrient cycling plants stable isotopes soil temperate forest tropical forest |
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