Effects of forest disturbance on snow mass and energy balance in headwater regions

由于干旱、虫害、野火和疾病，北美西部的森林正在死亡。由此产生的水文影响在以积雪融化为主的源头流域尤为显著，那里的森林协调雪与大气的相互作用。这些流域的径流可以为下游农业、居民和工业用户提供80%以上的供水。积雪融化在半干旱地区尤其关键，如艾伯塔省西南部和美国西南部，那里储存的春季融化水在干燥的夏季增加了供水。干扰后森林结构的变化会影响积雪和消融，并对下游水文产生级联效应。 拟议的研究重点是提高我们管理森林山区供水的能力。 考虑到森林覆盖变化对积雪质量和能量平衡的影响，全球变暖将影响到积雪的质量和能量平衡。虽然我们部分了解森林干扰对林分尺度雪水文学的影响，但我们的知识仍然局限于能量平衡的特定部分(例如短波辐射)和特定尺度(森林林分尺度)。需要研究以量化扰动对能量平衡的长波和湍流通量分量的影响。这些信息可以用于数值模型，以更好地了解积雪能量变化对流域径流的影响。这是首次专门研究：(1)森林干扰对林分尺度积雪变率的影响；(2)枯树对能量平衡长波分量的影响；(3)冬季Chinook事件对冠层以下雪面湍流通量的影响；(4)干扰后积雪和融化的空间格局。对不同规模的这些进程进行审查，将使结果能够用于改进诸如水文模型等森林水管理工具。然后，森林和水资源管理人员可以利用改进的模型产出，就维护非木材水文价值和地表水资源分配作出基于科学的管理决策。

Forests across western North America are dying as a result of drought, insect infestation, wildfire and disease. The resulting hydrologic impacts are particularly significant in snowmelt dominated headwater basins, where forests mediate snow-atmosphere interactions. Runoff from these watersheds can provide more than 80% of water supply for downstream agricultural, residential and industrial users. Snowmelt is particularly critical in semi-arid regions, such as southwestern Alberta and the southwestern US, where stored spring meltwater augments water supply during the dry summer season. Changing forest structure following disturbance affects snow accumulation and ablation, with cascading effects on downstream hydrology. The proposed research focuses on enhancing our ability to manage water supply from forested mountain headwaters given the effects of changing forest cover on snowpack mass and energy balance. While we partially understand the effects of forest disturbance on stand-scale snow hydrology, our knowledge remains limited to specific portions of the energy balance (e.g., shortwave radiation) and to specific scales (forest stand scale). Research is required to quantify the effects of disturbance on the longwave and turbulent flux components of the energy balance. This information can then be used in numerical models to better understand the effect of changing snowpack energetics on basin-scale runoff. This is the first research to focus specifically on: (1) the effects of forest disturbance on stand-scale snow accumulation variability; (2) the effects of dead trees on the longwave component of the energy balance; (3) the impacts of winter chinook events on turbulent fluxes at the below canopy snow surface; and (4) spatial patterns of snow accumulation and melt following disturbance. Examination of these processes across scales will allow results to be used to improve forest-water management tools such as hydrologic models. Improved model output can then be used by forest and water resource managers to make scientifically-based management decisions regarding maintenance of non-timber hydrologic values, and surface water resource allocations.