15N natural abundance of non-fixing woody species in the Brazilian dry forest (caatinga) |
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| Authors: | Ana Dolores Santiago de Freitas Everardo Valadares de Sá Barretto Sampaio Rômulo Simões Cezar Menezes Holm Tiessen |
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| Institution: | 1. Departamento de Agronomia , Universidade Federal Rural de Pernambuco (UFRPE) , Recife, Brazil ana.freitas@depa.ufrpe.br;3. Departamento de Energia Nuclear , Universidade Federal de Pernambuco (UFPE) , Recife, Brazil;4. Inter-American Institute for Global Changes (IAI) , S?o José dos Campos, Brazil |
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| Abstract: | Foliar δ15N values are useful to calculate N2 fixation and N losses from ecosystems. However, a definite pattern among vegetation types is not recognised and few data are available for semi-arid areas. We sampled four sites in the Brazilian caatinga, along a water availability gradient. Sites with lower annual rainfall (700 mm) but more uniform distribution (six months) had δ15N values of 9.4 and 10.1 ‰, among the highest already reported, and significantly greater than those (6.5 and 6.3 ‰) of sites with higher rainfall (800 mm) but less uniform distribution (three months). There were no significant differences at each site among species or between non-fixing legume and non-legume species, in spite of the higher N content of the first group. Therefore, they constitute ideal reference plants in estimations of legume N2 fixation. The higher values could result from higher losses of 15N depleted gases or lower losses of enriched 15N material. |
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| Keywords: | Brazil forest isotope ecology legumes nitrogen-15 nitrogen cycle rainfall tropical vegetation |
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