Buffering the savanna: fire regimes and disequilibrium ecology in West Africa
Buffering the savanna: fire regimes and disequilibrium ecology in West Africa
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DOI：
10.1007/s11258-016-0602-0
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发表时间：
2016-05-01
期刊：
影响因子：
1.7
通讯作者：
Wechsler, S.
中科院分区：
文献类型：
--
作者：
Laris, P.;Dadashi, S.;Wechsler, S.
根据当代生态学理论，控制稀树草原树木覆盖的机制随降水水平而变化。在降雨量中等的热带地区，稀树草原是不稳定的系统，其中的干扰，如火灾，决定了树与草的比例。这些所谓的“扰动驱动的稀树草原”的降水足以支持森林，但频繁的扰动阻碍了向封闭冠层状态的过渡。在稀树草原缓冲模型的基础上，我们认为需要一个一致的火灾制度来维持mesic地区的稀树草原。我们假设这些地区的火灾时空格局是高度规则和稳定的。此外，由于热带稀树草原的树木生长速率是降水的函数，我们假设降雨量最高的热带稀树草原将具有最一致的火灾模式和最强烈的火灾-因此具有最强的缓冲机制。研究人员利用中分辨率成像光谱辐射计活火产品，分析了西非热带稀树草原11年来大部分地区的燃烧时空格局，记录了三个不同降水水平的热带稀树草原带的火灾状况。我们使用LISA分析来量化火灾的时空格局，使用方差系数来量化火灾高峰日期的差异，并使用中心或重力路径来表征每个地区的火灾时空格局。我们的分析证实，在降水较少的地区和降水较多的地区，火灾状况的时空规律性更强。
According to contemporary ecological theory, the mechanisms governing tree cover in savannas vary by precipitation level. In tropical areas with mesic rainfall levels, savannas are unstable systems in which disturbances, such as fire, determine the ratio of trees to grasses. Precipitation in these so-called "disturbance-driven savannas" is sufficient to support forest but frequent disturbances prevent transition to a closed canopy state. Building on a savanna buffering model we argue that a consistent fire regime is required to maintain savannas in mesic areas. We hypothesize that the spatiotemporal pattern of fires is highly regular and stable in these areas. Furthermore, because tree growth rates in savannas are a function of precipitation, we hypothesize that savannas with the highest rainfall levels will have the most consistent fire pattern and the most intense fires-thus the strongest buffering mechanisms. We analyzed the spatiotemporal pattern of burning over 11 years for a large subset of the West African savanna using a moderate resolution imaging spectroradiometer active fire product to document the fire regime for three savanna belts with different precipitation levels. We used LISA analysis to quantify the spatiotemporal patterns of fires, coefficient of variance to quantify differences in peak fire dates, and center or gravity pathways to characterize the spatiotemporal patterns of the fires for each area. Our analysis confirms that spatiotemporal regularity of the fire regime is greater for mesic areas that for areas where precipitation is lower and that areas with more precipitation have more regular fire regimes.