Consequences of declining snow accumulation for water balance of mid‐latitude dry regions
Consequences of declining snow accumulation for water balance of mid‐latitude dry regions
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DOI：
10.1111/j.1365-2486.2012.02642.x
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发表时间：
2012-06
影响因子：
11.6
通讯作者：
D. Schlaepfer;W. Lauenroth;J. Bradford
中科院分区：
文献类型：
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作者：
D. Schlaepfer;W. Lauenroth;J. Bradford
北半球冬季气温正异常、积雪减少和积雪提前融化的广泛记录引起了人们对该地区水资源和野火后果的担忧。关于积雪减少的一个问题是对生态系统水平衡的影响。水平衡动态的变化在中纬度干旱地区的低海拔地区将特别明显，因为这些地区将首先受到气温上升导致的降雪的影响。作为一个模型系统，我们使用模拟实验来研究大型鼠尾草生态系统，这些生态系统主导了美国西部半干旱地区的很大一部分地区。我们的结果表明，未来生态系统水平衡的影响将沿着从干燥、温暖和贫雪到潮湿、寒冷和多雪的气候梯度增加。超过这个气候梯度的阈值，对植被的预测后果从没有变化转变为蒸腾增加。反应对气候预测中的不确定性很敏感；特别是，降水向较冷季节的转移可以减少未来变暖和降雪减少的影响，这取决于生态系统物候跟踪降水变化的程度。我们的结果表明，大型山艾树和其他类似的半干旱生态系统可能会在干旱到中等地区的生存能力下降或消失，而可能只在积雪最多的地区增加，即高海拔和高纬度。与高海拔或北极的寒冷地区不同，低海拔的生态系统对未来条件的反应是不同的和复杂的，因为越来越多的限水和更长的无雪季节产生了相反的影响。这种非线性相互作用对未来生态系统的结果可能包括植物组成和生产力、水平衡动态和水资源可获得性的变化。
Widespread documentation of positive winter temperature anomalies, declining snowpack and earlier snow melt in the Northern Hemisphere have raised concerns about the consequences for regional water resources as well as wildfire. A topic that has not been addressed with respect to declining snowpack is effects on ecosystem water balance. Changes in water balance dynamics will be particularly pronounced at low elevations of mid‐latitude dry regions because these areas will be the first to be affected by declining snow as a result of rising temperatures. As a model system, we used simulation experiments to investigate big sagebrush ecosystems that dominate a large fraction of the semiarid western United States. Our results suggest that effects on future ecosystem water balance will increase along a climatic gradient from dry, warm and snow‐poor to wet, cold and snow‐rich. Beyond a threshold within this climatic gradient, predicted consequences for vegetation switched from no change to increasing transpiration. Responses were sensitive to uncertainties in climatic prediction; particularly, a shift of precipitation to the colder season could reduce impacts of a warmer and snow‐poorer future, depending on the degree to which ecosystem phenology tracks precipitation changes. Our results suggest that big sagebrush and other similar semiarid ecosystems could decrease in viability or disappear in dry to medium areas and likely increase only in the snow‐richest areas, i.e. higher elevations and higher latitudes. Unlike cold locations at high elevations or in the arctic, ecosystems at low elevations respond in a different and complex way to future conditions because of opposing effects of increasing water‐limitation and a longer snow‐free season. Outcomes of such nonlinear interactions for future ecosystems will likely include changes in plant composition and productivity, dynamics of water balance, and availability of water resources.