Snowpack in the western U.S. is critical for water supply and is threatened by wildfires, which are becoming larger and more common. Numerous studies have examined impacts of wildfire on snow water equivalent (SWE), but many of these studies are limited in the number of observation locations, and they have sometimes produced conflicting results. The objective of this study is to distinguish the net effects of wildfires on snowpack from those of climate. We consider 45 burned sites from the Snow Telemetry network. For each burned site, unburned control sites are identified from the same level III ecoregion. Impacts of climate changes on snowpack are analyzed by comparing pre-fire and post-fire snow water equivalent at the unburned sites. Combined climate and wildfire effects are considered by comparing pre-fire and post-fire SWE at the burned sites. Wildfire impacts are then isolated by taking the difference between the burned and unburned sites. The wildfire-induced changes in SWE are also compared to several possible controlling variables including burn severity, leaf-area index change, dominant pre-fire tree genus, years since the fire, and site elevation. On average, wildfires have advanced melt-out dates 9 days and maximum SWE dates 6 days and reduced annual maximum SWE by 10% across the sites considered. On average, the combined effects of climate and wildfire have advanced melt-out and maximum SWE dates approximately 14 and 10 days, respectively, while decreasing annual maximum SWE by approximately 10%.

中文翻译：

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野火对美国西部气候变化中积雪物候的影响

美国西部的积雪对供水至关重要，并受到野火的威胁，野火变得越来越大，越来越普遍。许多研究已经检查了野火对雪水当量 (SWE) 的影响，但其中许多研究的观测地点数量有限，并且有时会产生相互矛盾的结果。本研究的目的是区分野火对积雪的净影响与气候的净影响。我们考虑了来自 Snow Telemetry 网络的 45 个被烧毁的站点。对于每个烧毁的地点，未烧毁的控制地点都来自相同的 III 级生态区。通过比较未燃烧地点的火灾前和火灾后雪水当量，分析了气候变化对积雪的影响。通过比较燃烧地点的火灾前和火灾后 SWE，考虑了气候和野火的综合影响。然后通过区分已燃烧地点和未燃烧地点之间的差异来隔离野火影响。野火引起的 SWE 变化也与几个可能的控制变量进行了比较，包括烧伤严重程度、叶面积指数变化、主要的火灾前树属、火灾后的年份和场地海拔。平均而言，野火的融化日期提前 9 天，最大 SWE 日期提前 6 天，并且在所考虑的地点将年度最大 SWE 降低了 10%。平均而言，气候和野火的综合影响分别使融化和最大 SWE 日期提前约 14 天和 10 天，同时每年最大 SWE 减少约 10%。野火引起的 SWE 变化也与几个可能的控制变量进行了比较，包括烧伤严重程度、叶面积指数变化、主要的火灾前树属、火灾后的年份和场地海拔。平均而言，野火的融化日期提前 9 天，最大 SWE 日期提前 6 天，并且在所考虑的地点将年度最大 SWE 降低了 10%。平均而言，气候和野火的综合影响分别使融化和最大 SWE 日期提前约 14 天和 10 天，同时每年最大 SWE 减少约 10%。野火引起的 SWE 变化也与几个可能的控制变量进行了比较，包括烧伤严重程度、叶面积指数变化、主要的火灾前树属、火灾后的年份和场地海拔。平均而言，野火的融化日期提前 9 天，最大 SWE 日期提前 6 天，并且在所考虑的地点将年度最大 SWE 降低了 10%。平均而言，气候和野火的综合影响分别使融化和最大 SWE 日期提前约 14 天和 10 天，同时每年最大 SWE 减少约 10%。