Natural abundance of 15N in tropical plants with emphasis on tree legumes

• DOI: 10.1007/bf00013003
• Publication Date: 2004-12-21T08:16:08Z
• Authors: T. Yoneyama; T. Muraoka; T. Murakami; N. Boonkerd
• Keywords: Panicum; Prosopis; Leucaena; Multipurpose tree

Natural abundance of 15N (δ 15N) of leaves harvested from tropical plants in Brazil and Thailand was analyzed. The δ 15N values of non-N2-fixing trees in Brazil were +4.5±1.9‰, which is lower than those of soil nitrogen (+8.0±2.2‰). In contrast, mimosa and kudzu had very low δ 15N values (−1.4≈+0.5‰). The δ 15N values of Panicum maximum and leguminous trees, except Leucaena leucocephala, were similar to those of non-N2-fixing trees, suggesting that the contribution of fixed N in these plants is negligible. The δ 15N values of non-N2-fixing trees in Thailand were +4.9±2.0‰. Leucaena leucocephala, Sesbania grandiflora, Casuarina spp. and Cycas spp. had low δ 15N values, close to the value of atmospheric N2 (0‰), pointing to a major contribution of N2 fixation in these plants. Cassia spp. and Tamarindus indica had high δ 15N values, which confirms that these species are non-nodulating legumes. The δ 15N values of Acacia spp. and Gliricidia sepium and other potentially nodulating tree legumes were, on average, slightly lower than those of non-N2-fixing trees, indicating a small contribution of N2 fixation in these legumes.