Central Seward Peninsula Deciduous Tall Shrub Map (1950-2018) and Suitable Habitat Model

Tall deciduous shrubs are critically important to carbon and nutrient cycling in high-latitude ecosystems. As Arctic regions warm, shrubs expand heterogeneously across their ranges, including within unburned terrain experiencing isometric gradients of warming. To constrain the effects of widespread shrub expansion in terrestrial and Earth System Models, improved knowledge of local to regional-scale patterns, rates, and controls on decadal shrub expansion is required. Here we map tall deciduous shrub canopies in the central Seward Peninsula of Alaska in 1950 using ~1 meter (m)-resolution aerial photographs from US Navy missions in three subsites (1950ShrubClass.tif and 1950AlderClass.tif) and in 2018 using 3m-resolution PlanetScope satellite imagery for the entire study region (SummerShrubExtent.tif and AlderExtent2017.tif). The timing of alder shrub senescence allowed us to separate the classification into alder and non-alder categories. We computed two change maps: one exclusively for alder and one including all deciduous tall shrubs. The change maps were modeled against a suite of environmental factors and the shrub change model was extended across the study region (SewardShrub.tif). The model was rerun for future scenarios with 10 (SewardMinus10PF.tif) and 30 (SewardMinus30PF.tif) percent reductions in permafrost probability to determine the likely effects of permafrost degradation on shrub extent.

高纬度生态系统中，高大落叶灌木对碳循环与养分循环至关重要。随着北极地区升温，灌木在其分布范围内呈现异质性扩张，涵盖未受火烧且存在等距升温梯度的区域。为约束陆地系统与地球系统模型中广泛灌木扩张的效应，亟需深化对十年尺度灌木扩张的局地至区域格局、速率及其调控因子的认知。本研究利用美国海军任务获取的约1米分辨率航空影像，完成了阿拉斯加苏厄德半岛中部1950年高大落叶灌木冠层的制图，覆盖三个子研究区（对应文件：1950ShrubClass.tif与1950AlderClass.tif）；并利用覆盖全研究区的3米分辨率PlanetScope卫星影像，完成了2018年的灌木冠层制图（对应文件：SummerShrubExtent.tif与AlderExtent2017.tif）。桤木灌木的物候衰老时序使得我们能够将分类结果划分为桤木与非桤木两类。我们生成了两幅变化图：一幅仅针对桤木灌木，另一幅涵盖所有高大落叶灌木。将上述变化图与一系列环境因子进行建模，并将灌木变化模型拓展至全研究区（对应文件：SewardShrub.tif）。为探究永久冻土退化对灌木分布范围的潜在影响，我们针对两种未来情景重新运行了模型：永久冻土概率分别降低10%（对应文件：SewardMinus10PF.tif）与30%（对应文件：SewardMinus30PF.tif）。