Department of Civil and Environmental Engineering, Syracuse University, Syracuse, NY, 13244, USA.
US Forest Service, Northern Research Station, Durham, NH, 03824, USA.
Glob Chang Biol. 2017 Feb;23(2):840-856. doi: 10.1111/gcb.13444. Epub 2016 Aug 25.
A cross-site analysis was conducted on seven diverse, forested watersheds in the northeastern United States to evaluate hydrological responses (evapotranspiration, soil moisture, seasonal and annual streamflow, and water stress) to projections of future climate. We used output from four atmosphere-ocean general circulation models (AOGCMs; CCSM4, HadGEM2-CC, MIROC5, and MRI-CGCM3) included in Phase 5 of the Coupled Model Intercomparison Project, coupled with two Representative Concentration Pathways (RCP 8.5 and 4.5). The coarse resolution AOGCMs outputs were statistically downscaled using an asynchronous regional regression model to provide finer resolution future climate projections as inputs to the deterministic dynamic ecosystem model PnET-BGC. Simulation results indicated that projected warmer temperatures and longer growing seasons in the northeastern United States are anticipated to increase evapotranspiration across all sites, although invoking CO effects on vegetation (growth enhancement and increases in water use efficiency (WUE)) diminish this response. The model showed enhanced evapotranspiration resulted in drier growing season conditions across all sites and all scenarios in the future. Spruce-fir conifer forests have a lower optimum temperature for photosynthesis, making them more susceptible to temperature stress than more tolerant hardwood species, potentially giving hardwoods a competitive advantage in the future. However, some hardwood forests are projected to experience seasonal water stress, despite anticipated increases in precipitation, due to the higher temperatures, earlier loss of snow packs, longer growing seasons, and associated water deficits. Considering future CO effects on WUE in the model alleviated water stress across all sites. Modeled streamflow responses were highly variable, with some sites showing significant increases in annual water yield, while others showed decreases. This variability in streamflow responses poses a challenge to water resource management in the northeastern United States. Our analyses suggest that dominant vegetation type and soil type are important attributes in determining future hydrological responses to climate change.
在美国东北部的七个不同的森林流域进行了跨站点分析，以评估水文响应（蒸散、土壤水分、季节性和年际径流量以及水分胁迫）对未来气候的预测。我们使用了耦合模式比较计划第五阶段（CMIP5）中包含的四个大气海洋通用循环模型（AOGCMs；CCSM4、HadGEM2-CC、MIROC5 和 MRI-CGCM3）的输出，以及两个代表性浓度路径（RCP 8.5 和 4.5）。粗分辨率的 AOGCM 输出使用异步区域回归模型进行了统计降尺度处理，以提供更精细分辨率的未来气候预测作为确定性动态生态系统模型 PnET-BGC 的输入。模拟结果表明，预计美国东北部地区的气温升高和生长季延长将增加所有站点的蒸散量，尽管植被对 CO 的影响（生长增强和水分利用效率（WUE）提高）会减弱这种响应。该模型表明，增强的蒸散作用导致未来所有站点和所有情景的生长季条件更加干燥。云杉-冷杉针叶林的光合作用最适温度较低，因此比更能耐受的硬木物种更容易受到温度胁迫，这可能使硬木在未来具有竞争优势。然而，一些硬木林预计会经历季节性水分胁迫，尽管预计降水会增加，但由于气温升高、积雪更早融化、生长季延长以及相关的水分亏缺，仍会出现这种情况。考虑到模型中未来 CO 对 WUE 的影响，缓解了所有站点的水分胁迫。模型化的径流量响应高度可变，一些站点的年径流量显著增加，而其他站点则减少。这种径流量响应的变异性给美国东北部的水资源管理带来了挑战。我们的分析表明，主要植被类型和土壤类型是确定未来水文对气候变化响应的重要属性。
