Transferts d'azote minéral dans les sols froids: Essai de traçage isotopique in situ |
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| Authors: | L Labroue W Vidal JC Tosca Ph Berge |
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| Institution: | 1. Laboratoire d''Ecologie Végétale, Université Paul Sabatier, 31062 Toulouse Cedex, France;1. Laboratoire de Géologie Chronologique, Université Paul Sabatier, 31062 Toulouse Cedex, France |
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| Abstract: | In situ analysis of mineral nitrogen dynamics by means of the isotopic tracer method was conducted in a subalpine meadow of the Pyrenees during summer. The observed isotope dilution curves were interpreted by both compartment and stochastic analysis. Only stochastic analysis gave reliable results although the net mean output of ammonium was high (124 mg NH+4-N m?2day?1). This high mineralization rate is accounted for by the great size of the labile fraction of organic matter present in the top layer. The released ammonium is quickly taken up by vascular plants, thus reducing nitrogen loss from the ecosystem. Unfortunately, direct foliar labelling during tracer injection does not allow the exploitation of the isotope dilution curve of the plant compartment. This considerably reduces the data supplied by this type of experiment. |
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