High latitude regions are warming rapidly with important ecological and societal consequences. Utilizing two landscape‐scale data sets from interior Alaska, we compared patterns in forest structure in two regions with differing fire disturbance, topography, and summer climate norms. Our goal was to evaluate a set of hypotheses concerning possible warming‐driven changes in forest structure suggested by recent literature. We found essentially consistent habitat associations for the tree flora across two disparate study areas concomitant with considerable differences in observed patterns of forest structure and composition. Our results confirmed expected increases in broadleaved species occupancy and abundance in the warmer, more fire‐affected study region along with considerably higher tree occupancy and abundance in high elevation areas there. However, contrary to our predictions, we found no evidence of expected reductions in conifer occupancy or increases in non‐fire related tree mortality. Instead, both individual and combined tree species occupancy, density, abundance, and richness were considerably higher in the warmer, more fire‐influenced region, except in the warmest, driest areas (steep and south‐facing slopes at low elevation). Our comparison of two landscape‐scale data sets suggests that changes in tree distribution and forest structure in interior Alaska will proceed unevenly, governed by a mosaic of site‐dependent influences wherein forest community composition and species dominance will shift along different trajectories and at different rates according to variation in underlying landscape attributes. Although there were clear differences in forest structure between the two areas that were likely attributable to differences in growing season warmth and fire disturbance, we found scant support for the concept of an incipient, ongoing biome shift in interior Alaska resulting from impending diminution of boreal forest cover over the short to medium term. Indeed, we suggest that (depending on severity of disturbance dynamics and the rapidity of future warming) cooler areas of interior Alaska's forest may reasonably be expected to sustain marginal increases in forest cover with additional warming, at least in certain topographic positions (such as poorly drained basins and cool treeline sites) and/or geographic regions, prior to any landscape‐scale diminution of forest cover due to warming.

中文翻译：

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火灾，地形和气候驱动阿拉斯加北部北方森林的区域变化

高纬度地区正在迅速升温，对生态和社会产生重要影响。利用来自阿拉斯加内部的两个景观数据集，我们比较了火灾干扰，地形和夏季气候规范不同的两个地区的森林结构模式。我们的目标是评估一组有关最近文献提出的可能由变暖驱动的森林结构变化的假说。我们发现，在两个不同的研究区域中，树木植物群的栖息地关联基本一致，同时在观察到的森林结构和组成模式上也有相当大的差异。我们的结果证实，在温暖，受火灾影响更大的研究区域中，阔叶树种的占有率和丰度有望增加，而高海拔地区的树木占有率和丰度则要高得多。但是，与我们的预测相反，我们没有发现任何证据表明针叶树占用量会减少或与非火灾相关的树木死亡率会增加。取而代之的是，除了最温暖，最干燥的地区（低海拔的陡坡和南坡）之外，在较温暖，受火灾影响较大的地区，个体和混合树种的占有率，密度，丰度和丰富度都高得多。我们对两个景观规模数据集的比较表明，阿拉斯加内部树木分布和森林结构的变化将不均匀地进行，这取决于地点相关影响的镶嵌，其中森林群落组成和物种优势将沿着不同的轨迹和不同的速率发生变化。根据基础景观属性的变化。尽管这两个地区之间的森林结构存在明显差异，这很可能是由于生长季节温暖和火灾干扰的差异所致，但我们发现阿拉斯加内部因北方森林的减少而导致的生物群落发生初期，持续的生物群落转移这一概念很少得到支持。涵盖短期到中期。实际上，我们建议（取决于扰动的严重程度和未来变暖的速度），可以合理地预期阿拉斯加内部森林的较凉爽区域至少会在某些地形位置（例如较差），伴随着额外变暖而维持森林覆盖率的小幅增长。流域和凉爽的林木地带）和/或地理区域，然后再因变暖而导致景观覆盖面积减少。