The distribution and composition of Arctic vegetation are expected to shift with ongoing climate change. Global models generally predict northward shifts in high‐latitude ecotones, and analysis of remote sensing data shows widespread greening and changes in vegetation structure across the circumpolar Arctic. However, there are still uncertainties related to the timing of these shifts and variation among different plant functional types. In this paper, we investigate disequilibrium dynamics of green alder and white spruce in the Tuktoyaktuk Coastal Plain, NWT. We used high‐resolution air photographs captured in the 1970s and 2000s to quantify changes in the distribution and abundance of alder and spruce near their northern limits. We found increases in alder and spruce stem density over time, but no change in their range limits, indicating that both species are affected by leading‐edge disequilibrium. Low stand density and temperature limitation of reproduction along the northern margin likely contributed to observed disequilibrium in both species. We also observed the greatest change in species occupancy within a burned area, suggesting that the increased frequency of fire will play a significant role in the timing and magnitude of near‐term vegetation change.

中文翻译：

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森林-苔原交错带的al木和云杉种群的前沿不平衡

预计随着气候变化，北极植被的分布和组成将发生变化。全球模型通常预测高纬度过渡带向北移动，对遥感数据的分析表明，整个极地北极地区普遍存在绿化和植被结构变化。但是，仍然存在与不同植物功能类型之间的这些转变和变化的时间有关的不确定性。在本文中，我们研究了西北地区图克托亚克图克沿海平原上的绿色al木和白色云杉的不平衡动态。我们使用了1970年代和2000年代拍摄的高分辨率航空照片来量化of木和云杉在其北边界附近的分布和丰度的变化。我们发现随着时间的推移，stem木和云杉的茎密度会增加，但是它们的射程极限没有变化，表明这两个物种都受到前沿不平衡的影响。较低的林分密度和北缘繁殖的温度限制可能导致了两个物种中观察到的不平衡。我们还观察到了燃烧区域内物种占用的最大变化，这表明着火频率的增加将对近期植被变化的时间和幅度起重要作用。