Skip to content
Home
About Us
Resources
Profiles Metrics
Authors Directory
Institutions Directory
Top Authors
Top Institutions
Top Sponsors
AI Digest
Contact Us
Menu
Home
About Us
Resources
Profiles Metrics
Authors Directory
Institutions Directory
Top Authors
Top Institutions
Top Sponsors
AI Digest
Contact Us
Home
About Us
Resources
Profiles Metrics
Authors Directory
Institutions Directory
Top Authors
Top Institutions
Top Sponsors
AI Digest
Contact Us
Menu
Home
About Us
Resources
Profiles Metrics
Authors Directory
Institutions Directory
Top Authors
Top Institutions
Top Sponsors
AI Digest
Contact Us
Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
agricultural and biological sciences
A patch-dynamics approach to savanna dynamics and woody plant encroachment - Insights from an arid savanna
Perspectives in Plant Ecology, Evolution and Systematics, Volume 7, No. 4, Year 2006
Notification
URL copied to clipboard!
Description
The coexistence of woody and grassy plants in savannas has often been attributed to a rooting-niche separation (two-layer hypothesis). Water was assumed to be the limiting resource for both growth forms and grasses were assumed to extract water from the upper soil layer and trees and bushes from the lower layers. Woody plant encroachment (i.e. an increase in density of woody plants often unpalatable to domestic livestock) is a serious problem in many savannas and is believed to be the result of overgrazing in 'two-layer systems'. Recent research has questioned the universality of both the two-layer hypothesis and the hypothesis that overgrazing is the cause of woody plant encroachment. We present an alternative hypothesis explaining both tree-grass coexistence and woody plant encroachment in arid savannas. We propose that woody plant encroachment is part of a cyclical succession between open savanna and woody dominance and is driven by two factors: rainfall that is highly variable in space and time, and inter-tree competition. In this case, savanna landscapes are composed of many patches (a few hectares in size) in different states of transition between grassy and woody dominance, i.e. we hypothesize that arid savannas are patch-dynamic systems. We summarize patterns of tree distribution observed in an arid savanna in Namibia and show that these patterns are in agreement with the patch-dynamic savanna hypothesis. We discuss the applicability of this hypothesis to fire-dominated savannas, in which rainfall variability is low and fire drives spatial heterogeneity. We conclude that field studies are more likely to contribute to a general understanding of tree-grass coexistence and woody plant encroachment if they consider both primary (rain and nutrients) and secondary (fire and grazing) determinants of patch properties across different savannas. © 2005 Rübel Foundation, ETH Zürich. Published by Elsevier GmbH. All rights reserved.
Authors & Co-Authors
Wiegand, Kerstin
United States, Princeton
Princeton University
Israel, Beer-sheva
Ben-gurion University of the Negev
Germany, Jena
Friedrich-schiller-universität Jena
Saltz, David
Israel, Beer-sheva
Ben-gurion University of the Negev
Israel, Jerusalem
Israel Nature and Parks Authority
Ward, David
Israel, Beer-sheva
Ben-gurion University of the Negev
South Africa, Durban
University of Kwazulu-natal
Statistics
Citations: 263
Authors: 3
Affiliations: 5
Identifiers
Doi:
10.1016/j.ppees.2005.10.001
ISSN:
14338319
e-ISSN:
16180437
Research Areas
Environmental
Genetics And Genomics
Study Locations
Namibia