Alpine plant communities and current topographic microrefugia vary with regional climates

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Topographic microrefugia on slopes are assumed to be critical for the persistence of alpine plant species and the maintenance of alpine plant community diversity in a warming climate. They create microclimates, some of which are cooler and/or wetter than others, which may buffer continuing climate change. However, the current relationship of plant communities to microtopography at individual slope scale could differ among regional climates, and if so resilience in new climates would also differ.Vegetation cover and topographic site characteristics at a fine scale were recorded in the field in three alpine regions of the Rocky Mountains, USA: Glacier National Park, MT, the Indian Peaks Area, CO, and Taos Ski Valley, NM. Elements of alpine slopes were identified and transformed into ordinal variables. Two indicators of insolation were calculated from slope angle, slope aspect, and latitude, and soil depth indicators and elevation were recorded. In each region, the contribution of these variables to the variation in the plant community composition were compared using nonmetric multidimensional scaling and random forest models.The partitioned variance explained by the topographic and topography-derived climatic variables differed among the three regions. Variables related to moisture conditions were more important in the snowiest, northern region and the central region, while those related to energy were more important in the southern region with higher radiation and temperature. Lower correlations of mesoscale variables set microrefugia in a hierarchical context.The more extreme regional topographically derived climatic variables better explain the differentiation of alpine plant communities. These variables may not play the same role in potentially novel future climates. Because topographic features mediate regional climates to niche dimensions, setting microrefugia in a multiscale framework can focus research on climate change impacts.