Schertzer E, Staver A C, Levin S A
UPMC Univ. Paris 06, Laboratoire de Probabilités et Modèles Aléatoires, CNRS UMR 7599, Paris, France,
J Math Biol. 2015 Jan;70(1-2):329-41. doi: 10.1007/s00285-014-0757-z. Epub 2014 Feb 26.
The role of fire in expanding the global distribution of savanna is well recognized. Empirical observations and modeling suggest that fire spread has a threshold response to fuel-layer continuity, which sets up a positive feedback that maintains savanna-forest bistability. However, modeling has so far failed to examine fire spread as a spatial process that interacts with vegetation. Here, we use simple, well-supported assumptions about fire spread as an infection process and its effects on trees to ask whether spatial dynamics qualitatively change the potential for savanna-forest bistability. We show that the spatial effects of fire spread are the fundamental reason that bistability is possible: because fire spread is an infection process, it exhibits a threshold response to fuel continuity followed by a rapid increase in fire size. Other ecological processes affecting fire spread may also contribute including temporal variability in demography or fire spread. Finally, including the potential for spatial aggregation increases the potential both for savanna-forest bistability and for savanna and forest to coexist in a landscape mosaic.
火灾在扩大稀树草原全球分布范围方面的作用已得到广泛认可。实证观察和模型表明，火灾蔓延对燃料层连续性具有阈值响应，这建立了一个正反馈，维持了稀树草原 - 森林的双稳态。然而，迄今为止，模型尚未将火灾蔓延作为与植被相互作用的空间过程进行研究。在此，我们基于关于火灾蔓延作为一种感染过程及其对树木影响的简单且有充分依据的假设，来探讨空间动态是否会在质上改变稀树草原 - 森林双稳态的可能性。我们表明，火灾蔓延的空间效应是双稳态得以存在的根本原因：由于火灾蔓延是一种感染过程，它对燃料连续性表现出阈值响应，随后火灾规模迅速增大。影响火灾蔓延的其他生态过程也可能起作用，包括种群统计学或火灾蔓延的时间变异性。最后，考虑空间聚集的可能性会增加稀树草原 - 森林双稳态以及稀树草原和森林在景观镶嵌体中共存的可能性。
