What limits fire? An examination of drivers of burnt area in Southern Africa
What limits fire? An examination of drivers of burnt area in Southern Africa
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DOI：
10.1111/j.1365-2486.2008.01754.x
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发表时间：
2009-03-01
影响因子：
11.6
通讯作者：
Scholes, Robert J.
中科院分区：
文献类型：
--
作者：
Archibald, Sally;Roy, David P.;Scholes, Robert J.
使用中等分辨率（500 m）卫星生成的烧毁区域地图和有关影响烧毁区域的环境因素的空间数据，对控制赤道以南非洲火灾范围的因素进行了调查。使用随机森林回归树程序来确定每个因素在解释烧毁面积分数方面的相对重要性，并解决与人类和气候对烧毁面积驱动因素影响相关的假设。该模型解释了烧伤面积 68% 的差异。树木覆盖率、前两年的降雨量和降雨季节性是最重要的预测因素。人类活动——以放牧、单位面积道路、人口密度和耕种比例为代表——也被证明会影响烧毁面积，但仅限于非洲大陆具有特定气候条件的部分地区，而且往往与“人类活动越多会导致火灾越多”这一普遍观点相悖。分析发现，没有迹象表明点火限制了非洲大陆的总燃烧面积，大部分空间变化是由于燃料负荷和湿度的变化造成的。回归树的分割条件确定了 (i) 降雨量低的地区，火灾很少发生； (ii) 火灾受到人类控制的地区； (iii) 降雨量较高的地区，其燃烧面积由降雨季节决定。这项研究深入了解了火灾的自然、气候和人类驱动因素及其在整个南部非洲的相对重要性，并代表了烧毁地区预测框架的开始。
The factors controlling the extent of fire in Africa south of the equator were investigated using moderate resolution (500 m) satellite-derived burned area maps and spatial data on the environmental factors thought to affect burnt area. A random forest regression tree procedure was used to determine the relative importance of each factor in explaining the burned area fraction and to address hypotheses concerned with human and climatic influences on the drivers of burnt area. The model explained 68% of the variance in burnt area. Tree cover, rainfall in the previous 2 years, and rainfall seasonality were the most important predictors. Human activities - represented by grazing, roads per unit area, population density, and cultivation fraction - were also shown to affect burnt area, but only in parts of the continent with specific climatic conditions, and often in ways counter to the prevailing wisdom that more human activity leads to more fire. The analysis found no indication that ignitions were limiting total burnt area on the continent, and most of the spatial variation was due to variation in fuel load and moisture. Split conditions from the regression tree identified (i) low rainfall regions, where fire is rare; (ii) regions where fire is under human control; and (iii) higher rainfall regions where burnt area is determined by rainfall seasonality. This study provides insights into the physical, climatic, and human drivers of fire and their relative importance across southern Africa, and represents the beginnings of a predictive framework for burnt area.