caa a22 4500 605517274 CHVBK 20210128100718.0 cr unu---uuuuu 210128e20150301xx s 000 0 eng 10.1007/s10533-015-0069-4 doi (NATIONALLICENCE)springer-10.1007/s10533-015-0069-4 Acacia tree density strongly affects N and P fluxes in savanna [Elektronische Daten] [Judith Sitters, Peter Edwards, Werner Suter, Harry Olde Venterink] Studies of nutrient cycling in savanna ecosystems rarely consider how fluxes are affected by local variations in tree density and nutrient redistribution by herbivores. We studied how the density of Acacia zanzibarica trees in a humid savanna ecosystem affected the input of nitrogen (N) through N2-fixation and N and phosphorus (P) outputs through fire and also internal pathways of N and P return through herbivores. We found that N inputs and P outputs both increased with increasing density of N2-fixing trees, the N effect being due to tree density rather than to differences in the rate of N2-fixation. However, total N outputs due to fire did not vary with tree density because losses from the herb layer decreased as losses from the tree layer increased. In contrast, total P outputs did increase with tree density because P losses from the tree layer exceeded those from the herb layer. We suggest that variation in the density of N2-fixing trees coupled with the effects of fire can cause substantial differences in the local N and P balances in savanna vegetation. To some extent, these differences may be evened out by the tendency for browsing herbivores to transfer nutrients from Acacia- to grass-dominated areas. We conclude that encroachment by N2-fixing trees and shrubs has important consequences for ecosystem properties such as N and P dynamics. Springer International Publishing Switzerland, 2015 Fire nationallicence Herbivore dung nationallicence Nitrogen fixation nationallicence Nutrient balances nationallicence Phosphorus nationallicence Woody encroachment nationallicence Sitters Judith Institute of Integrative Biology, ETH Zurich, Universitätsstrasse 16, 8092, Zurich, Switzerland aut Edwards Peter Institute of Integrative Biology, ETH Zurich, Universitätsstrasse 16, 8092, Zurich, Switzerland aut Suter Werner Swiss Federal Research Institute WSL, Zürcherstrasse 111, 8903, Birmensdorf, Switzerland aut Olde Venterink Harry Institute of Integrative Biology, ETH Zurich, Universitätsstrasse 16, 8092, Zurich, Switzerland aut Biogeochemistry Springer International Publishing 123/1-2(2015-03-01), 285-297 0168-2563 123:1-2<285 2015 123 10533 https://doi.org/10.1007/s10533-015-0069-4 text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 research-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s10533-015-0069-4 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Sitters Judith Institute of Integrative Biology, ETH Zurich, Universitätsstrasse 16, 8092, Zurich, Switzerland aut NATIONALLICENCE 700 1- Edwards Peter Institute of Integrative Biology, ETH Zurich, Universitätsstrasse 16, 8092, Zurich, Switzerland aut NATIONALLICENCE 700 1- Suter Werner Swiss Federal Research Institute WSL, Zürcherstrasse 111, 8903, Birmensdorf, Switzerland aut NATIONALLICENCE 700 1- Olde Venterink Harry Institute of Integrative Biology, ETH Zurich, Universitätsstrasse 16, 8092, Zurich, Switzerland aut NATIONALLICENCE 773 0- Biogeochemistry Springer International Publishing 123/1-2(2015-03-01), 285-297 0168-2563 123:1-2<285 2015 123 10533