Fire drives functional thresholds on the savanna-forest transition
Fire drives functional thresholds on the savanna-forest transition
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DOI：
10.1890/12-1629.1
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发表时间：
2013-11-01
期刊：
影响因子：
4.8
通讯作者：
Pausas, Juli G.
中科院分区：
文献类型：
--
作者：
Dantas, Vinicius de L.;Batalha, Marco A.;Pausas, Juli G.
在热带景观中，树木密度不同的植被斑块呈马赛克状分布。然而，斑块的位置和其中的树木密度不能单独通过气候模型预测。有人提出，植物火灾反馈驱动功能阈值在景观尺度上，从而保持开放（稀树草原）和封闭（森林）社区作为两个不同的稳定状态。然而，几乎没有严格的现场证据，这个阈值模型。在这里，我们的目标是提供支持这样一个模型从外地的角度来看，并分析在巴西热带稀树草原景观（塞拉多）火灾的功能和系统发育的后果。我们假设，在热带景观，稀树草原和森林是两个稳定的状态，维持植物火灾反馈。如果是这样的话，它们的功能和多样性属性应该沿着沿着发生突变。我们设置了98块沿着梯度从开放的稀树草原到封闭的森林在巴西塞拉多和测试的阈值模式在9个功能性状，5个土壤功能，和7个多样性指标。然后，我们测试了阈值模式是否与不同的火灾制度。大多数社区属性提出了一个阈值模式的稀树草原森林过渡重合断点。阈值将两种群落状态分开：（1）开放环境，低多样性群落生长在贫瘠的土壤中，并由对高强度火灾具有高度抵抗力的植物占主导地位;（2）封闭环境，高度多样性植物群落生长在更肥沃的土壤中，并由耐荫物种占主导地位，有效地阻止光线到达林下植物。此外，每个州都与对比鲜明的火灾制度有关。我们的研究结果是一致的假设，即森林和稀树草原是两个共存的稳定状态，具有对比的功能和多样性模式，由火植物反馈调节;我们的研究结果还揭示了驱动每个状态的机制。总的来说，我们的研究结果支持这样的想法，火在调节热带景观中的稀树草原和森林生物群落的分布中起着重要的作用。
In tropical landscapes, vegetation patches with contrasting tree densities are distributed as mosaics. However, the locations of patches and densities of trees within them cannot be predicted by climate models alone. It has been proposed that plant-fire feedbacks drive functional thresholds at a landscape scale, thereby maintaining open (savanna) and closed (forest) communities as two distinct stable states. However, there is little rigorous field evidence for this threshold model. Here we aim to provide support for such a model from a field perspective and to analyze the functional and phylogenetic consequences of fire in a Brazilian savanna landscape (Cerrado). We hypothesize that, in tropical landscapes, savanna and forest are two stable states maintained by plant-fire feedbacks. If so, their functional and diversity attributes should change abruptly along a community closure gradient. We set 98 plots along a gradient from open savanna to closed forest in the Brazilian Cerrado and tested for a threshold pattern in nine functional traits, five soil features, and seven diversity indicators. We then tested whether the threshold pattern was associated with different fire regimes. Most community attributes presented a threshold pattern on the savanna-forest transition with coinciding breakpoints. The thresholds separated two community states: (1) open environments with low-diversity communities growing in poor soils and dominated by plants that are highly resistant to high-intensity fires; and (2) closed environments with highly diverse plant communities growing in more fertile soils and dominated by shade-tolerant species that efficiently prevent light from reaching the understory. In addition, each state was associated with contrasting fire regimes. Our results are consistent with the hypothesis that forests and savannas are two coexisting stable states with contrasting patterns of function and diversity that are regulated by fire-plant feedbacks; our results also shed light on the mechanism driving each state. Overall, our results support the idea that fire plays an important role in regulating the distribution of savanna and forest biomes in tropical landscapes.