Department of Earth and Environment, Boston University, Boston, MA, USA.
Département de Géographie, Université de Montréal, Montréal, QC, Canada.
Glob Chang Biol. 2020 Feb;26(2):807-822. doi: 10.1111/gcb.14804. Epub 2019 Sep 17.
A multitude of disturbance agents, such as wildfires, land use, and climate-driven expansion of woody shrubs, is transforming the distribution of plant functional types across Arctic-Boreal ecosystems, which has significant implications for interactions and feedbacks between terrestrial ecosystems and climate in the northern high-latitude. However, because the spatial resolution of existing land cover datasets is too coarse, large-scale land cover changes in the Arctic-Boreal region (ABR) have been poorly characterized. Here, we use 31 years (1984-2014) of moderate spatial resolution (30 m) satellite imagery over a region spanning 4.7 × 10 km in Alaska and northwestern Canada to characterize regional-scale ABR land cover changes. We find that 13.6 ± 1.3% of the domain has changed, primarily via two major modes of transformation: (a) simultaneous disturbance-driven decreases in Evergreen Forest area (-14.7 ± 3.0% relative to 1984) and increases in Deciduous Forest area (+14.8 ± 5.2%) in the Boreal biome; and (b) climate-driven expansion of Herbaceous and Shrub vegetation (+7.4 ± 2.0%) in the Arctic biome. By using time series of 30 m imagery, we characterize dynamics in forest and shrub cover occurring at relatively short spatial scales (hundreds of meters) due to fires, harvest, and climate-induced growth that are not observable in coarse spatial resolution (e.g., 500 m or greater pixel size) imagery. Wildfires caused most of Evergreen Forest Loss and Evergreen Forest Gain and substantial areas of Deciduous Forest Gain. Extensive shifts in the distribution of plant functional types at multiple spatial scales are consistent with observations of increased atmospheric CO seasonality and ecosystem productivity at northern high-latitudes and signal continental-scale shifts in the structure and function of northern high-latitude ecosystems in response to climate change.
大量的干扰因素，如野火、土地利用以及受气候驱动的木本灌木扩张，正在改变北极-北方生态系统中植物功能类型的分布，这对高纬度北方陆地生态系统与气候之间的相互作用和反馈具有重大意义。然而，由于现有土地覆盖数据集的空间分辨率太粗，北极-北方地区（ABR）的大规模土地覆盖变化特征描述不足。在这里，我们使用 31 年（1984-2014 年）中等空间分辨率（30m）的卫星图像来描述阿拉斯加和加拿大西北部跨越 4.7×10 平方公里区域的北极-北方地区的土地覆盖变化。我们发现，该区域有 13.6±1.3%发生了变化，主要通过两种主要的转化模式：（a）北方生物群落中常绿林面积的同时减少（与 1984 年相比减少了-14.7±3.0%）和落叶林面积的增加（增加了 14.8±5.2%）；（b）北极生物群落中草本和灌木植被的气候驱动扩张（增加了 7.4±2.0%）。通过使用 30m 图像的时间序列，我们可以描述由于火灾、收获和气候诱导生长而在相对较短的空间尺度（数百米）发生的森林和灌木覆盖的动态变化，这些变化在粗空间分辨率（例如，500m 或更大的像素大小）图像中是不可见的。野火导致了大部分常绿林的损失和常绿林的增加，以及大量落叶林的增加。在多个空间尺度上植物功能类型的广泛分布变化与在高纬度北方地区观测到的大气 CO 季节性增加和生态系统生产力增加一致，并表明北方高纬度生态系统的结构和功能在应对气候变化方面发生了大陆尺度的变化。
