ABSTRACT To investigate drought influences on mixed-severity fire regimes in montane forests of southeastern British Columbia, we developed a Douglas-fir latewood-width chronology and tested its associations with drought records across the fire season. Associations were strong between drought and latewood-widths particularly for June–August. Based on the chronology, we reconstructed the summer Drought Code, an index of moisture content in slow-drying deep compact organics in the soil and coarse woody fuels. Using the summer Drought Code and an existing reconstruction of the summer Palmer Drought Severity Index, representing moisture content in the quick-drying duff layer, we tested fire–drought associations using fire-scar records. Subtle differences in fire–drought associations reflect distinct drying rates and overwintering capacity among forest fuels represented by each summer drought reconstruction. Variable moisture conditions across fuels influence fire occurrence; in particular when the summer Drought Code exceeds 344 and the summer Palmer Drought Severity Index is below 0.08, fire occurrence is more likely. The application of these thresholds with climate change scenarios may provide insights on how mixed-severity fire regimes could be impacted in montane forests of southeastern British Columbia.

中文翻译：

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使用补充干旱代理改善山地森林火灾历史的解释

摘要 为了研究干旱对不列颠哥伦比亚省东南部山地森林混合严重程度火灾状况的影响，我们开发了花旗松晚材宽度年表，并测试了其与整个火灾季节干旱记录的关联。干旱和晚材宽度之间的关联性很强，尤其是在 6 月至 8 月期间。根据年表，我们重建了夏季干旱代码，这是土壤中慢干深层致密有机物和粗木本燃料的含水量指数。使用夏季干旱代码和夏季帕尔默干旱严重程度指数的现有重建，代表快干尘埃层中的水分含量，我们使用火痕记录测试了火灾-干旱的关联。火灾-干旱关联的细微差异反映了以夏季干旱重建为代表的森林燃料之间不同的干燥速率和越冬能力。燃料中不同的水分条件会影响火灾的发生；特别是夏季干旱代码超过344，夏季帕尔默干旱指数低于0.08时，更容易发生火灾。这些阈值在气候变化情景中的应用可能会为不列颠哥伦比亚省东南部山地森林中混合严重程度的火灾制度如何受到影响提供见解。