In fire-adapted ecosystems of the western USA, prescribed fire is an essential restoration and fuel reduction tool. There is general concern that, as the fire season lengthens, the window for conducting prescribed burns will contract unless management changes are made. This could occur because a number of conditions must be met before prescribed fire can be used in the field, and those are most common during the spring and autumn when the need for fire suppression response has been historically less. To assess patterns of potential prescribed burning feasibility, this study evaluated three conditions: (1) permission to burn as granted by air quality regulators; (2) weather within burn plan prescription; and (3) availability of operational and contingency resources. Our 21-year analysis (1999 to 2019) combines three independent datasets for a daily comparison of when prescribed fires could have been implemented (henceforth, burn windows) in the Lake Tahoe Basin (LTB) and analyzes seasonality, interannual variability, and trends. Burn windows were most frequent during spring, followed by autumn, with the fewest burn windows during the summer and winter. Burn windows lasting multiple days occurred infrequently. Two- to three-day burn windows did not often occur more than twice per month over the study period, and longer burn windows were very rare. Interannual variation was considerable. Finally, an abrupt increase in burn windows was detected in 2008. This was determined to be related to a methodological change by air quality regulators and not to any changes in climate or resource availability. While this case study focuses on the LTB, the analysis was performed with readily available data and could be applied easily to other land management units, demonstrating a valuable method for planning and prioritizing fire and fuels management activities. This type of tool can also identify areas for research. For example, if there were unused burn windows during the winter and early spring—or they were projected to increase—research into the ecological impacts of winter and spring burning may allow managers to more confidently adapt to changing climate. Moreover, this analysis demonstrated that modest and reasonable regulatory changes can increase opportunities for prescribed burning.

中文翻译：

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火灾和燃料管理用燃烧窗的回顾性分析：以美国加利福尼亚州塔霍湖盆地为例

在美国西部适应火灾的生态系统中，规定的火灾是必不可少的恢复和减少燃料的工具。人们普遍担心，随着火灾季节的延长，除非进行管理上的更改，否则进行规定燃烧的窗口会收缩。之所以会发生这种情况，是因为在野外使用规定的火种之前必须满足许多条件，而在春季和秋季，这种情况最普遍，因为过去对灭火的需求已经很少。为了评估潜在的规定燃烧可能性的模式，本研究评估了以下三个条件：（1）空气质量监管机构授予的燃烧许可；（2）燃烧计划规定范围内的天气；（3）运营和应急资源的可用性。我们为期21年的分析（1999年至2019年）结合了三个独立的数据集，用于每日比较塔霍湖盆地（LTB）何时可能发生规定的大火（以下简称``大火''），并分析季节性，年际变化和趋势。春季的烧窗最频繁，其次是秋天，夏季和冬季的烧窗最少。持续数天的刻录窗口很少发生。在研究期间，每个月两到三天的烧伤窗户通常不会发生两次以上，而且很少有更长的烧伤窗户。年际变化很大。最终，在2008年发现燃烧窗口突然增加。这与空气质量监管机构确定的方法变化有关，与气候或资源可用性的任何变化均无关。尽管此案例研究的重点是LTB，但该分析是利用易于获得的数据进行的，并且可以轻松地应用于其他土地管理部门，这说明了规划和确定火灾和燃料管理活动优先级的有价值的方法。这种工具也可以确定研究领域。例如，如果在冬季和初春期间没有使用过的燃烧窗（或预计会增加），那么对冬季和春季燃烧对生态的影响的研究可以使管理人员更自信地适应气候变化。此外，该分析表明，适度而合理的法规变更可以增加规定燃烧的机会。展示了一种有价值的方法，可用于计划和确定火灾和燃料管理活动的优先级。这种工具也可以确定研究领域。例如，如果冬季和初春期间没有使用过的燃烧窗（或预计会增加），则对冬季和春季燃烧对生态的影响进行的研究可能使管理人员更自信地适应气候变化。此外，该分析表明，适度而合理的法规变更可以增加规定燃烧的机会。展示了一种有价值的方法，可用于计划和确定火灾和燃料管理活动的优先级。这种工具也可以确定研究领域。例如，如果在冬季和初春期间没有使用过的燃烧窗（或预计会增加），那么对冬季和春季燃烧对生态的影响的研究可以使管理人员更自信地适应气候变化。此外，该分析表明，适度而合理的法规变更可以增加规定燃烧的机会。如果冬季和初春期间没有使用过的燃烧窗（或预计会增加），则对冬季和春季燃烧对生态的影响进行的研究可能使管理人员更自信地适应气候变化。此外，该分析表明，适度而合理的法规变更可以增加规定燃烧的机会。如果冬季和初春期间没有使用过的燃烧窗（或预计会增加），则对冬季和春季燃烧对生态的影响进行的研究可能使管理人员更自信地适应气候变化。此外，该分析表明，适度而合理的法规变更可以增加规定燃烧的机会。