Abstract
Several Prosopis species were introduced into South Africa in the last century. Since then two species, Prosopis glandulosa var. torreyana and Prosopis velutina have invaded large parts of arid southern Africa. Here, we examine the extent to which increased mortality of Acacia erioloba, a keystone species in the Kalahari Desert, can be attributed to competition for water with Prosopis. We do this for A. erioloba and Prosopis sp. at invaded, as well as cleared sites through a determination of species abundance, canopy vitality, plant water stress and plant water source. Our stable isotope results show that in the riparian zone both A. erioloba and Prosopis are using the same water source. Our results also show that there is a 50 % increase in canopy dieback of A. erioloba in the invaded river plots relative to the cleared river plots. This dieback cannot be related to changes in rainfall and temperature as there were no adverse fluctuations (drought) in the weather in the 10 years preceding our study. We speculate that because A. erioloba is more water stressed in the invaded river plot this increase in mortality and dieback is related to plant moisture stress that is not related to climate but to competition for water with Prosopis. Our study gives strong support for the eradication of Prosopis from rivers in arid parts of Southern Africa.
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Acknowledgments
We would like to thank the National Research Foundation of South Africa for partial funding of this project. S. Davids and E. Zitha provided laboratory assistance. Prof. T. Clutton Brock’s team (especially T. Flower and A. Ross-Gillesby) of the Meerkat Project for access to the study site and their assistance in data collection. Mr. Masela of van Zylsrus gave us access to a borehole.
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Schachtschneider, K., February, E.C. Impact of Prosopis invasion on a keystone tree species in the Kalahari Desert. Plant Ecol 214, 597–605 (2013). https://doi.org/10.1007/s11258-013-0192-z
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DOI: https://doi.org/10.1007/s11258-013-0192-z