Trends in fire patterns in a southern African savanna under alternative land use practices |
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| Institution: | 1. USFS Rocky Mountain Research Station, 1221 S. Main St., Moscow, ID 83843, USA;2. Percy Fitzpatrick Institute, University of Cape Town, Rondebosch 7701, South Africa;3. North West Parks and Tourism Board, P.O. Box 1201, Mogwase 0314, South Africa;1. Institute of Systems Science, Durban University of Technology, Durban 4000, South Africa;2. School of Mathematics, Statistics and Computer Science, University of KwaZulu-Natal, Durban 4000, South Africa;1. Department of Intensive Care, Erasme University Hospital, Université Libre de Bruxelles, 1070 Brussels, Belgium;1. Scientific Services, South African National Parks, Private Bag X402, Skukuza 1350, South Africa;2. Centre for African Ecology, School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Private Bag 3, WITS, 2050, Johannesburg, South Africa;3. Centre for African Conservation Ecology, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031, South Africa;4. Department of Botany, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031, South Africa;5. Scientific Services, South African National Parks, PO Box 3542, Knysna 6570, South Africa;1. DREAM Italia, via dei Guazzi 31, I-52013 Poppi, AR, Italy;2. Or.Me., Via Saponaro 7, 73100 Lecce, LE, Italy;3. Parco Nazionale dell’Alta Murgia, Via Firenze, 10, Gravina in Puglia, BA, Italy |
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| Abstract: | Climate, topography, vegetation and land use interact to influence fire regimes. Variable fire regimes may promote landscape heterogeneity, diversification in vegetation pattern and biotic diversity. The objective was to compare effects of alternative land use practices on landscape heterogeneity. Patch characteristics of fire scars were measured from 21 annual burn maps produced from 1972 to 2001 Landsat imagery. Trends in fire patterns under alternative land use practices were compared across a 250,000 ha savanna in southern Africa partitioned into three land use zones. Zone 1, Madikwe Game Reserve (MGR), has had mostly prescribed fires since 1993. Zone 2, cattle farms near MGR in South Africa (SAF), has experienced occasional fires. Zone 3, communal grazing lands in neighboring Botswana (BOT), has had the fewest fires. Cattle ranching was the predominant land use throughout the study area until 1992, when land use switched to conservation and eco-tourism in MGR. Sixteen landscape metrics were applied to this data set to uncover trends in the patch characteristics of the fire scars. A principal components analysis (PCA) reduced the dimensionality of the results so trends in the 10 most important size, shape, and proximity metrics could be better interpreted. The PCA results showed that more burning over time in MGR, and to a lesser extent in SAF, increased patch size, size variability, shape complexity and proximity, while fire exclusion in BOT produced no change or decreasing trends. We tested for significant differences in these metrics between the three land use zones and between two periods, 1972–1992 and 1993–2001. Most patch characteristics in MGR and SAF differed significantly from those in BOT, especially during the latter period, while between MGR and SAF they did not. Patch area, shape complexity and core area increased significantly between periods in MGR, while patch size, size variability and core area increased significantly between periods in SAF. In BOT, no patch characteristics changed significantly between periods. Within the time span analyzed for the study area, we conclude that increased fire occurrence promoted landscape heterogeneity while fire exclusion did not. |
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