Climate drives the coevolution of vegetation and the soil that supports it. Wildfire dramatically affects many key eco‐hydro‐geomorphic processes, but its potential role in coevolution of soil‐forest systems has been largely overlooked. The steep landscapes of southeastern Australia provide an excellent natural laboratory to study the role of fire in the coevolution of soil and forests, as they are characterized by temperate forest types, fire frequencies, and soil depths that vary systematically with aridity. The aims of this study were (i) to test the hypothesis that in Southeastern Australia, fire‐related processes are critical to explain the variations in coevolved soil‐forest system states across an aridity gradient and (ii) to identify the key processes and (iii) feedbacks involved. To achieve these aims, we developed a numerical model that simulates the coevolution of soil‐forest systems which employ eco‐hydro‐geomorphic processes that are typical of the flammable forests of southeastern Australia. A stepwise model evaluation, using measurements and published data, confirms the robustness of the model to simulate eco‐hydro‐geomorphic processes across the aridity gradient. Simulations that included fire replicated patterns of observed soil depth and forest cover across an aridity gradient, supporting our hypothesis. The contribution of fire to coevolution increased in magnitude with aridity, mainly due to the higher fire frequency and lower post‐fire infiltration capacity, increasing the rates of fire‐related surface runoff and erosion. Our results show that critical feedbacks between soil depth, vegetation, and fire frequency dictate the trajectory and pace of the coevolution of flammable temperate forests and soils.

中文翻译：

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火在土壤和温带森林共同进化中的作用

气候驱动着植被和支撑植被的土壤一起进化。野火极大地影响了许多关键的生态-水-地貌过程，但其在土壤-森林系统协同进化中的潜在作用却被大大忽略了。澳大利亚东南部的陡峭景观为研究火在土壤和森林的共同进化中的作用提供了出色的自然实验室，因为它们的特征是温带森林类型，火频和土壤深度随干旱而系统变化。这项研究的目的是（i）检验以下假设：在澳大利亚东南部，与火有关的过程对于解释整个干旱梯度下共同进化的土壤-森林系统状态的变化至关重要;以及（ii）识别关键过程和（ iii）涉及的反馈。为了实现这些目标，我们开发了一个数值模型，用于模拟采用生态水-地貌过程的土壤-森林系统的共同演化，这种过程是澳大利亚东南部易燃森林的典型特征。通过使用测量和公开数据进行的逐步模型评估，确认了该模型在整个干旱梯度上模拟生态水-地貌过程的鲁棒性。模拟包括在干旱梯度上观察到的土壤深度和森林覆盖率的火复制模式，这支持了我们的假设。火灾对协同进化的贡献随着干旱的增加而增加，这主要是由于更高的火灾频率和更低的火灾后渗透能力，增加了与火有关的地表径流和侵蚀的速率。我们的结果表明，土壤深度，植被，