边缘火灾驱动热带森林的形状和稳定性
Edge fires drive the shape and stability of tropical forests
摘要：
在热带地区，火灾在草原上很容易蔓延，但通常只会消耗森林斑块的边缘。因此，森林斑块由于树木繁殖而增长，并因周围草原的火灾而缩小。这些相互竞争的边缘效应之间的相互作用是未知的，但在确定单个森林斑块的形状和稳定性，以及森林的空间分布和稳定性的关键。我们分析了高分辨率的遥感数据，从保护区的巴西塞拉多，发现森林形状服从一个强大的周长面积缩放关系，跨气候带。我们解释这种缩放通过引入一个异质火传播模型的热带森林草原交错带。从这种周长面积关系的偏差确定了稳定的个别森林斑块。在更大的尺度上，我们的模型预测，树木生长的相对速度，由于传播扩张和长距离的种子传播确定区域尺度的树木覆盖的崩溃是连续的或不连续的火灾频率的变化。
英文摘要：
In tropical regions, fires propagate readily in grasslands but typically consume only edges of forest patches. Thus forest patches grow due to tree propagation and shrink by fires in surrounding grasslands. The interplay between these competing edge effects is unknown, but critical in determining the shape and stability of individual forest patches, as well the landscape-level spatial distribution and stability of forests. We analyze high-resolution remote-sensing data from protected areas of the Brazilian Cerrado and find that forest shapes obey a robust perimeter-area scaling relation across climatic zones. We explain this scaling by introducing a heterogeneous fire propagation model of tropical forest-grassland ecotones. Deviations from this perimeter-area relation determine the stability of individual forest patches. At a larger scale, our model predicts that the relative rates of tree growth due to propagative expansion and long-distance seed dispersal determine whether collapse of regional-scale tree cover is continuous or discontinuous as fire frequency changes.
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