Department of Biology, Western University, 1151 Richmond St., London, ON, N6A 5B7, Canada.
Glob Chang Biol. 2014 Oct;20(10):3191-208. doi: 10.1111/gcb.12615. Epub 2014 Jun 14.
Climate warming is projected to affect forest water yields but the effects are expected to vary. We investigated how forest type and age affect water yield resilience to climate warming. To answer this question, we examined the variability in historical water yields at long-term experimental catchments across Canada and the United States over 5-year cool and warm periods. Using the theoretical framework of the Budyko curve, we calculated the effects of climate warming on the annual partitioning of precipitation (P) into evapotranspiration (ET) and water yield. Deviation (d) was defined as a catchment's change in actual ET divided by P [AET/P; evaporative index (EI)] coincident with a shift from a cool to a warm period - a positive d indicates an upward shift in EI and smaller than expected water yields, and a negative d indicates a downward shift in EI and larger than expected water yields. Elasticity was defined as the ratio of interannual variation in potential ET divided by P (PET/P; dryness index) to interannual variation in the EI - high elasticity indicates low d despite large range in drying index (i.e., resilient water yields), low elasticity indicates high d despite small range in drying index (i.e., nonresilient water yields). Although the data needed to fully evaluate ecosystems based on these metrics are limited, we were able to identify some characteristics of response among forest types. Alpine sites showed the greatest sensitivity to climate warming with any warming leading to increased water yields. Conifer forests included catchments with lowest elasticity and stable to larger water yields. Deciduous forests included catchments with intermediate elasticity and stable to smaller water yields. Mixed coniferous/deciduous forests included catchments with highest elasticity and stable water yields. Forest type appeared to influence the resilience of catchment water yields to climate warming, with conifer and deciduous catchments more susceptible to climate warming than the more diverse mixed forest catchments.
气候变暖预计会影响森林的水分产量，但这种影响预计会有所不同。我们研究了森林类型和年龄如何影响水分产量对气候变暖的恢复力。为了回答这个问题，我们研究了加拿大和美国长期实验流域历史上水分产量的变异性，在 5 年的凉爽和温暖时期。我们利用 Budyko 曲线的理论框架，计算了气候变暖对降水（P）分配为蒸散（ET）和水分产量的影响。偏差（d）定义为流域实际 ET 的变化除以 P [AET/P; 蒸发指数（EI）]，与从凉爽期到温暖期的转变相一致——正的 d 表示 EI 的上升和低于预期的水分产量，负的 d 表示 EI 的下降和高于预期的水分产量。弹性定义为潜在 ET 的年际变化除以 P（PET/P；干燥指数）与 EI 的年际变化之比——高弹性表示尽管干燥指数范围较大，但 d 较小（即水分产量具有弹性），低弹性表示尽管干燥指数范围较小，但 d 较大（即水分产量无弹性）。尽管基于这些指标全面评估生态系统所需的数据有限，但我们能够确定不同森林类型之间的一些响应特征。高山地区对气候变暖最为敏感，任何变暖都会导致水分产量增加。针叶林包括具有最低弹性和稳定到更大水分产量的流域。落叶林包括具有中等弹性和稳定到较小水分产量的流域。混交林包括具有最高弹性和稳定水分产量的流域。森林类型似乎影响流域水分产量对气候变暖的恢复力，与更具多样性的混交林流域相比，针叶林和阔叶林流域更容易受到气候变暖的影响。
