Contribution of transpiration to forest ambient vapour based on isotopic measurements |
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| Authors: | MARCELO MOREIRA LEONEL STERNBERG LUIZ MARTINELLI REYNALDO VICTORIA EDELCILIO BARBOSA LUIZ BONATES & DANIEL NEPSTAD |
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| Institution: | Department of Biology, University of Miami, PO Box 249118, Coral Gables, Florida 33124, USA,;Centro de Energia Nuclear na Agricultura, University of São Paulo, CP 96, 13416–000, Piracicaba, SP, Brazil,;Coordenação de Pesquisas em Botânica, Instituto Nacional de Pesquisa da Amazônia, CP 478, 69083–000, Manaus, AM, Brazil,;Woods Hole Research Centre, Woods Hole, Massachusetts, 02543, USA |
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| Abstract: | Using a simple isotope mixing model, we evaluated the relative proportion of water vapour generated by plant transpiration and by soil evaporation at two sites in the Amazon basin. Sampling was carried out at two different soil covers (forest and pasture), in a seasonal tropical rainforest at eastern Amazon where major deforestation is the result of land-use change, and compared to a less seasonal central Amazon forest. In both forests, vapour from transpiration was responsible for most, if not all, of the water vapour generated in the forest, while it could not be detected above the grassy pastures. Thus the canopy transpiration may be a major source of water vapour to the forest and perhaps to the atmosphere during the dry season. The results are discussed in relation to predictive models based on net radiation that usually are not able to distinguish between transpiration and evaporation. |
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