Stinger Ghaffarian Technologies, Inc. (contractor to the U.S. Geological Survey), Sioux Falls, South Dakota.
Department of Forest Resources, University of Minnesota, St. Paul, Minnesota.
Glob Chang Biol. 2019 Mar;25(3):1171-1189. doi: 10.1111/gcb.14279. Epub 2018 May 28.
Contemporary climate change in Alaska has resulted in amplified rates of press and pulse disturbances that drive ecosystem change with significant consequences for socio-environmental systems. Despite the vulnerability of Arctic and boreal landscapes to change, little has been done to characterize landscape change and associated drivers across northern high-latitude ecosystems. Here we characterize the historical sensitivity of Alaska's ecosystems to environmental change and anthropogenic disturbances using expert knowledge, remote sensing data, and spatiotemporal analyses and modeling. Time-series analysis of moderate-and high-resolution imagery was used to characterize land- and water-surface dynamics across Alaska. Some 430,000 interpretations of ecological and geomorphological change were made using historical air photos and satellite imagery, and corroborate land-surface greening, browning, and wetness/moisture trend parameters derived from peak-growing season Landsat imagery acquired from 1984 to 2015. The time series of change metrics, together with climatic data and maps of landscape characteristics, were incorporated into a modeling framework for mapping and understanding of drivers of change throughout Alaska. According to our analysis, approximately 13% (~174,000 ± 8700 km ) of Alaska has experienced directional change in the last 32 years (±95% confidence intervals). At the ecoregions level, substantial increases in remotely sensed vegetation productivity were most pronounced in western and northern foothills of Alaska, which is explained by vegetation growth associated with increasing air temperatures. Significant browning trends were largely the result of recent wildfires in interior Alaska, but browning trends are also driven by increases in evaporative demand and surface-water gains that have predominately occurred over warming permafrost landscapes. Increased rates of photosynthetic activity are associated with stabilization and recovery processes following wildfire, timber harvesting, insect damage, thermokarst, glacial retreat, and lake infilling and drainage events. Our results fill a critical gap in the understanding of historical and potential future trajectories of change in northern high-latitude regions.
阿拉斯加当代气候变化导致压力和脉冲干扰放大,从而推动生态系统变化,对社会-环境系统产生重大影响。尽管北极和北方森林景观容易受到变化的影响,但人们在描述北方高纬度生态系统的景观变化及其相关驱动因素方面做得很少。在这里,我们利用专业知识、遥感数据以及时空分析和建模,来描述阿拉斯加生态系统对环境变化和人为干扰的历史敏感性。利用中高分辨率图像的时间序列分析,描述了阿拉斯加各地的土地和水面动态。通过历史航空照片和卫星图像,对约 43 万次生态和地貌变化的解释进行了分析,这些解释与从 1984 年到 2015 年获取的峰值生长季节陆地卫星图像得出的土地表面变绿、变褐以及变湿/湿润趋势参数相吻合。变化度量的时间序列,加上气候数据和景观特征图,被纳入一个建模框架,用于绘制和理解阿拉斯加各地的变化驱动因素。根据我们的分析,在过去的 32 年中(置信区间为 95%),阿拉斯加约有 13%(~174,000 ± 8700km)经历了方向变化。在生态区层面,阿拉斯加西部和北部山麓的遥感植被生产力显著增加,这是由于与气温升高相关的植被生长所致。显著的变褐趋势主要是由于阿拉斯加内陆最近的野火,但变褐趋势也受到增加的蒸发需求和表面水增加的驱动,这些主要发生在变暖的永久冻土景观上。光合作用活性的增加与野火、木材采伐、虫害、热喀斯特、冰川退缩以及湖泊填充和排水事件后的稳定和恢复过程有关。我们的研究结果填补了对北方高纬度地区历史和潜在未来变化轨迹的理解的关键空白。