Humans and elephants as treefall drivers in African savannas

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dc.contributor.author Mograbi, Penelope J.
dc.contributor.author Asner, Gregory P.
dc.contributor.author Witkowski, Ed T.F.
dc.contributor.author Erasmus, Barend F.N.
dc.contributor.author Wessels, K.J. (Konrad)
dc.contributor.author Mathieu, Renaud
dc.contributor.author Vaughn, Nicholas R.
dc.date.accessioned 2017-11-15T07:43:35Z
dc.date.issued 2017-11
dc.description.abstract Humans have played a major role in altering savanna structure and function, and growing land-use pressure will only increase their influence on woody cover. Yet humans are often overlooked as ecological components. Both humans and the African elephant Loxodonta africana alter woody vegetation in savannas through removal of large trees and activities that may increase shrub cover. Interactive effects of both humans and elephants with fire may also alter vegetation structure and composition. Here we capitalize on a macroscale experimental opportunity – brought about by the juxtaposition of an elephant-mediated landscape, human-utilized communal harvesting lands and a nature reserve fenced off from both humans and elephants – to investigate the influence of humans and elephants on height-specific treefall dynamics. We surveyed 6812 ha using repeat, airborne high resolution Light Detection and Ranging (LiDAR) to track the fate of 453 685 tree canopies over two years. Human-mediated biennial treefall rates were 2–3.5 fold higher than the background treefall rate of 1.5% treefall ha–1, while elephant-mediated treefall rates were 5 times higher at 7.6% treefall ha–1 than the control site. Model predictors of treefall revealed that human or elephant presence was the most important variable, followed by the interaction between geology and fire frequency. Treefall patterns were spatially heterogeneous with elephant-driven treefall associated with geology and surface water, while human patterns were related to perceived ease of access to wood harvesting areas and settlement expansion. Our results show humans and elephants utilize all height classes of woody vegetation, and that large tree shortages in a heavily utilized communal land has transferred treefall occurrence to shorter vegetation. Elephant- and human-dominated landscapes are tied to interactive effects that may hinder tree seedling survival which, combined with tree loss in the landscape, may compromise woodland sustainability. en_ZA
dc.description.department Geography, Geoinformatics and Meteorology en_ZA
dc.description.embargo 2018-11-30
dc.description.librarian hj2017 en_ZA
dc.description.sponsorship Andrew Mellon Foundation; Council for Scientific and Industrial Research (CSIR) Strategic Research Panel; Dept of Science and Technology (DST); Avatar Alliance Foundation; Margaret A. Cargill Foundation; David and Lucile Packard Foundation; Gordon and Betty Moore Foundation; Grantham Foundation for the Protection of the Environment; W. M. Keck Foundation; John D. and Catherine T. MacArthur Foundation; Exxaro Chairman's Fund; Applied Centre for Climate and Earth System Science; DST/NRF Centre of Excellence in Tree Health Biotechnology; NRF Innovation Scholarship [UID: 95030]. en_ZA
dc.description.uri http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1600-0587 en_ZA
dc.identifier.citation Mograbi, P.J., Asner, G.P., Witkowski, E.T.F. ... et al. 2017, 'Humans and elephants as treefall drivers in African savannas', Ecography, vol. 40, no. 11, pp. 1274-1284. en_ZA
dc.identifier.issn 0906-7590 (print)
dc.identifier.issn 1600-0587 (online)
dc.identifier.other 10.1111/ecog.02549
dc.identifier.uri http://hdl.handle.net/2263/63164
dc.language.iso en en_ZA
dc.publisher Wiley en_ZA
dc.rights © 2016 University of the Witwatersrand. Ecography © 2016 Nordic Society Oikos. This is the pre-peer reviewed version of the following article : (name of article), Journal name, vol. 40, no. 11, pp. 1274-1284, 2017, doi : 10.1111/ecog.02549 . The definite version is available at : http://onlinelibrary.wiley.comjournal/10.1111/(ISSN)1600-0587. en_ZA
dc.subject Kruger National Park (KNP) en_ZA
dc.subject Kruger National Park (South Africa) en_ZA
dc.subject Woody vegetation en_ZA
dc.subject South Africa (SA) en_ZA
dc.subject Savannah en_ZA
dc.subject Spatial pattern en_ZA
dc.subject Fire regimes en_ZA
dc.subject Large trees en_ZA
dc.subject Population en_ZA
dc.subject Land use en_ZA
dc.subject African elephant (Loxodonta africana) en_ZA
dc.subject Humans en_ZA
dc.subject Treefall drivers en_ZA
dc.subject African savannas en_ZA
dc.title Humans and elephants as treefall drivers in African savannas en_ZA
dc.type Postprint Article en_ZA


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