Estimates of nitrogen fixation by trees on an aridity gradient in Namibia |
| |
Authors: | E.-D. Schulze G. Gebauer H. Ziegler O. L. Lange |
| |
Affiliation: | (1) Lehrstuhl Pflanzenökologie, Universität Bayreuth, Box 101251, W-8580 Bayreuth, Federal Republic of Germany;(2) Institut für Botanik und Mikrobiologie, TU München, Arcisstrasse 21, W-8000 München, Federal Republic of Germany;(3) Lehrstuhl Botanik II, Universität Würzburg, Mittlerer Dallenbergweg 64, W-8700 Würzburg, Federal Republic of Germany |
| |
Abstract: | Summary Nitrogen (N2) fixation was estimated along an aridity gradient in Namibia from the natural abundance of 15N (15N value) in 11 woody species of the Mimosacease which were compared with the 15N values in 11 woody non-Mimosaceae. Averaging all species and habitats the calculated contribution of N2 fixation (Nf) to leaf nitrogen (N) concentration of Mimosaceae averaged about 30%, with large variation between and within species. While in Acacia albida Nf was only 2%, it was 49% in Acacia hereroensis and Dichrostachys cinerea, and reached 71% in Acacia melifera. In the majority of species Nf was 10–30%. There was a marked variation in background 15N values along the aridity gradient, with the highest 15N values in the lowland savanna. The difference between 15N values of Mimosaceae and non-Mimosaceae, which is assumed to result mainly from N2 fixation, was also largest in the lowland savanna. Variations in 15N of Mimosaceae did not affect N concentrations, but higher 15N-values of Mimosaeae are associated with lower carbon isotope ratios (13C value). N2 fixation was associated with reduced intrinsic water use efficiency. The opposite trends were found in non-Mimosaceae, in which N-concentration increased with 15N, but 13C was unaffected. The large variation among species and sites is discussed.This paper is prepared in memory of J. Visser, who took part in the collection of species, but died in 1990 |
| |
Keywords: | Nitrogen fixation Carbon isotope ratio Nitrogen isotope ratio Acacia Namibia |
本文献已被 SpringerLink 等数据库收录! |
|