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Spatial pattern analysis of encroaching tree species (Vachellia karroo and Vachellia nilotica) after fire suppression in a semi-arid savanna

Published online by Cambridge University Press:  15 December 2017

Justice Muvengwi ,
Hilton G.T. Ndagurwa ,
Tatenda Nyenda ,
Richard Mwembe  and
Monicah Mbiba Open the ORCID record for Monicah Mbiba [Opens in a new window]
Justice Muvengwi
Affiliation:
Department of Natural Resources, Bindura University of Science Education, Private Bag, 1020 Bindura, Zimbabwe School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa
Hilton G.T. Ndagurwa
Affiliation:
Department of Forest Resources & Wildlife Management, Faculty of Applied Science, National University of Science & Technology, P.O. Box AC 939 Ascot, Bulawayo, Zimbabwe Forest Ecology Laboratory, Faculty of Applied Science, National University of Science & Technology, P.O. Box AC 939 Ascot, Bulawayo, Zimbabwe
Tatenda Nyenda
Affiliation:
Department of Natural Resources, Bindura University of Science Education, Private Bag, 1020 Bindura, Zimbabwe
Richard Mwembe
Affiliation:
Matopos Research Station, P Bag K5137, Bulawayo, Zimbabwe
Monicah Mbiba*
Affiliation:
Department of Natural Resources, Bindura University of Science Education, Private Bag, 1020 Bindura, Zimbabwe School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa
*
*Corresponding author. Email: mambiba@gmail.com
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Abstract:

Bush encroachment has serious consequences on ecosystem functioning through alteration of species composition and ecosystem productivity. However, little is known regarding the spatial patterning of invading shrubs in semi-arid savannas. Cartesian coordinates of two invading woody species (Vachellia karroo and V. nilotica), were recorded in a 20 × 20-m plot on a grassland at Matopos research station, south-west Zimbabwe. We recorded a total of 308 plants including both saplings and shrubs from the two study plant species. Second-order spatial statistics was applied in order to understand the spatial pattern of encroaching plants. We predicted that the encroaching plants would be spatially aggregated because of facilitation that occurs in harsh environmental conditions. Consistent with our predictions, the two species were aggregated, with no evidence of inter- and intra specific species competition. This study demonstrates that encroaching trees in semi-arid savanna generally do not show self organization during early growth stages.

Keywords

Bush encroachmentsavannaspatial statisticsVachellia karrooV. niloticaVoronoi
Type
Short Communication
Information
Journal of Tropical Ecology , Volume 33 , Issue 6 , November 2017 , pp. 411 - 414
Copyright
Copyright © Cambridge University Press 2017 

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