Changes are projected for the boreal biome with complex and variable effects on forest vegetation including drought-induced tree mortality and forest loss. With soil and atmospheric conditions governing drought intensity, specific drivers of trees water stress can be difficult to disentangle across temporal scales. We used wavelet analysis and causality detection to identify potential environmental controls (evapotranspiration, soil moisture, rainfall, vapor pressure deficit, air temperature and photosynthetically active radiation) on daily tree water deficit and on longer periods of tree dehydration in black spruce and tamarack. Daily tree water deficit was controlled by photosynthetically active radiation, vapor pressure deficit, and air temperature, causing greater stand evapotranspiration. Prolonged periods of tree water deficit (multi-day) were regulated by photosynthetically active radiation and soil moisture. We provide empirical evidence that continued warming and drying will cause short-term increases in black spruce and tamarack transpiration, but greater drought stress with reduced soil water availability.

中文翻译：

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辐射、气温和土壤水可用性导致加拿大西部北方森林在不同时间尺度上出现树木缺水

预计北方生物群落将发生变化，对森林植被产生复杂多变的影响，包括干旱引起的树木死亡和森林丧失。由于土壤和大气条件决定干旱强度，树木水分胁迫的具体驱动因素可能很难在时间尺度上理清。我们使用小波分析和因果关系检测来确定对黑云杉和落叶松的日常树木缺水和较长时间的树木脱水的潜在环境控制（蒸散量、土壤湿度、降雨、蒸气压不足、气温和光合有效辐射）。每日树木水分亏缺受到光合有效辐射、蒸气压亏缺和气温的控制，导致更大的林分蒸散量。树木长期缺水（多天）受到光合有效辐射和土壤湿度的调节。我们提供的经验证据表明，持续变暖和干燥将导致黑云杉和落叶松蒸腾量的短期增加，但随着土壤可用水量的减少，干旱胁迫会更大。