Methods to determine the impact of rainfall on fuels and burned area in southern African savannas
S. Archibald A B D , A. Nickless A , R. J. Scholes A B and R. Schulze CA Natural Resources and the Environment, Council for Scientific and Industrial Research (CSIR), PO Box 395, Pretoria 0001, South Africa.
B Animal Plant and Environmental Sciences, University of the Witwatersrand, Private Bag 3, Johannesburg 2050, South Africa.
C School of Bioresources Engineering and Environmental Hydrology, University of KwaZulu-Natal, Private Bag X01, Scottsville 3209, South Africa.
D Corresponding author. Email: sarchibald@csir.co.za
International Journal of Wildland Fire 19(6) 774-782 https://doi.org/10.1071/WF08207
Submitted: 19 December 2008 Accepted: 17 April 2010 Published: 17 September 2010
Abstract
In southern African savannas, grass production, and therefore the annual extent of fire, is highly dependent on rainfall. This response has repeatedly been noted in the literature but authors used different input variables and modelling approaches and the results are not comparable. Using long-term fire occurrence data from six protected areas in southern Africa we tested various methods for determining the relationship between antecedent rainfall and burned area. The types of regression model, the most appropriate index of accumulated rainfall, and the period over which to calculate annual burned area were all investigated. The importance of accumulating rainfall over more than one growing season was verified in all parks – improving the accuracy of the models by up to 30% compared with indices that only used the previous year’s rainfall. Up to 56% of the variance in burned area between years could be explained by an 18-month accumulated rainfall index. Linear models and probit models performed equally well. The method suggested in this paper can be applied across southern Africa. This will improve our understanding of the drivers of interannual variation in burned area in this globally important fire region.
Additional keywords: carry-over, fire, grass fuel, interannual variation.
Acknowledgements
The authors thank all researchers and park managers who contributed fire and rainfall data to this analysis: Navashni Govender and Sanparks for the Kruger National Park data; Ezemvelo Kwa-Zulu Natal Wildlife for the Hluhluwe iMfolozi Park and Mkuze Game Reserve data – in particular Sue Van Rensberg and Craig Mulqueeney; Bruce Brocket and North-West Parks Board for Pilanesberg Game Reserve data; Peter Frost and Simon Chamaille for the Hwange fire and rainfall data; and Johan Le Roux and the Etosha Ecological Institute for the Etosha data. Thanks to Brian van Wilgen, whose original research inspired most of this work.
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