Climate and wildfire are closely linked. Climate regulates wildfire directly over short timescales through its effect on fuel aridity and indirectly over long timescales through vegetation productivity and the structure and abundance of fuels. Prediction of future wildfire regimes in a changing climate often uses empirical studies that presume current relationships between short-term climate variables and wildfire activity will be stationary in the future. This is problematic because landscape-scale wildfire dynamics exhibit non-stationarity, with both positive and negative feedback loops that operate at different temporal and spatial scales. This requires that such feedbacks are accommodated in a model framework from which wildfire dynamics are emergent rather than pre-specified. We use a new model, RHESSys-WMFire, that integrates ecohydrology with fire spread and effects to simulate a 60-yr time series of vegetation, fuel development, and wildfire in a 6572-ha watershed in the Southern Sierra Nevada, USA, with a factorial design of increased temperature and severe drought. All climate scenarios had an initial pulse of elevated area burned associated with high temperature, low precipitation, and high fine fuel loading. There were positive correlations between annual area burned and mean annual maximum temperature and negative correlations with annual precipitation, consistent with understood direct effects of climate on wildfire in this system. Decreased vegetation productivity and increased fine fuel decomposition were predicted with increased temperature, resulting in long-term reduced fine fuels and area burned relative to baseline. Repeated extreme drought increased area burned relative to baseline and over the long-term had substantially reduced overstory biomass. Overstory biomass was resilient to repeat wildfire under baseline climate. The model system predicts that the short-term direct effects of climate on wildfire can differ from long-term indirect effects such that the simple maxim hotter/drier equals more wildfire can be both true and false, depending on scale.

中文翻译：

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炎热和干燥是否等于更多的野火？对比加利福尼亚州内华达山脉火灾的短期和长期气候影响

气候和野火密切相关。气候通过其对燃料干旱的影响在短期内直接调节野火，并通过植被生产力和燃料的结构和丰度在长期内间接调节野火。在不断变化的气候中预测未来的野火状况通常使用实证研究，这些研究假设短期气候变量与野火活动之间的当前关系在未来将是稳定的。这是有问题的，因为景观尺度的野火动态表现出非平稳性，正负反馈循环在不同的时间和空间尺度上运行。这要求将此类反馈容纳在一个模型框架中，从该模型框架中可以出现野火动态，而不是预先指定。我们使用一个新模型，RHESSys-WMFire，将生态水文学与火势蔓延和影响相结合，以模拟美国内华达山脉南部 6572 公顷流域的 60 年时间序列植被、燃料开发和野火，并采用温度升高和严重干旱的因子设计。所有气候情景都有一个初始脉冲，即与高温、低降水和高精细燃料负载相关的升高区域燃烧。年燃烧面积与年平均最高温度呈正相关，与年降水量呈负相关，这与该系统中气候对野火的直接影响一致。随着温度升高，植被生产力下降和精细燃料分解增加，导致精细燃料和燃烧面积相对于基线长期减少。与基线相比，反复发生的极端干旱增加了燃烧面积，并且从长期来看，上层生物量显着减少。在基线气候下，上层生物量对重复野火具有弹性。该模型系统预测，气候对野火的短期直接影响可能与长期间接影响不同，因此根据规模的不同，更热/更干燥等于更多野火的简单格言既可以是真的，也可以是假的。