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Post-fire succession on savanna habitats in the Okavango Delta wetland, Botswana

Published online by Cambridge University Press:  29 October 2007

Michael Heinl
Affiliation:
Institute of Ecology, University of Innsbruck, Sternwartestr. 15, A-6020 Innsbruck, Austria Chair of Vegetation Ecology, Munich University of Technology (TUM), D-85350 Freising-Weihenstephan, Germany
Jan Sliva
Affiliation:
Chair of Vegetation Ecology, Munich University of Technology (TUM), D-85350 Freising-Weihenstephan, Germany
Michael Murray-Hudson
Affiliation:
Harry Oppenheimer Okavango Research Center (HOORC), University of Botswana, Maun, Botswana
Budzanani Tacheba
Affiliation:
Harry Oppenheimer Okavango Research Center (HOORC), University of Botswana, Maun, Botswana

Abstract

Drying floodplains that were not inundated for more than 10 y were investigated to relate plant species and vegetation structure to time-since-fire for the southern Okavango Delta wetland in Botswana. The aims of the research were to study post-fire succession on savanna habitats in the Okavango Delta and to investigate the mechanisms behind vegetation changes with time-since-fire. We hypothesize that vegetation structure rather than species occurrence is affected by the fire event and that the driving forces of post-fire succession change from fire-driven to competition-driven with increasing time-since-fire. A total number of 153 study sites were investigated, representing areas of 2–12 y without a fire. Both woody and herbaceous plant species were recorded and cover/abundance values were measured. The vegetation changes with time-since-fire could be assigned to three different successional stages: (1) the post-fire conditions shortly after fire, supporting high species numbers due to open space and little competition; (2) the dominance of competitive perennial grass species (e.g. Urochloa mosambicensis) after 6–8 y; and (3) the enhanced establishment of woody species after about 10 y, creating new habitats in their vicinity. High species numbers were found after short and long fire-free periods, and different species occurred shortly after the fire event and at late stages of the post-fire succession. A variety of different inter-fire intervals is therefore expected to be responsible for sustaining plant species richness and habitat diversity in the study area. Post-fire succession could be described as not only being driven by the life history of the species, but also by seedbank dynamics and plant mobility in early successional stages and by competition and niche differentiation in late-successional stages.

Type
Research Article
Copyright
2007 Cambridge University Press

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