Datensatz

Zusammenfassung

In a Várzea floodplain forest, nitrogen fixation of legume-rhizobium symbioses was investigated using the ¹⁵N natural abundance method. Mean δ¹⁵N values in soil were positive and ranged from 5.0 to 5.8, average δ¹⁵N value in litter was 3.9 and therefore depleted in ¹⁵N by comparison with soil. Mean δ¹⁵N values in legumes were low by comparison with non-legumes and varied between 0.94 - 4.90. In non-legumes mean δ¹⁵N values were 3.17 - 7.79. Estimation of the proportion of nitrogen derived from atmospheric N₂ resulted in mean values of 60% Ndfa for Zygia inaequalis, 37%Ndfa for Albizia multiflora and 32% Ndfa for Pterocarpus amazonum. Legume trees showed a high inter- and intraspecific variation in their per cent nitrogen derived from atmosphere (%Ndfa), but there was no significant temporal variation of nitrogen fixation by rhizobium-legume symbioses from October 1998 to April 1999. N₂ fixation was an important source of nitrogen for nodulated legume trees and therefore might have been of certain importance for the biomass production of the forest