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Premise: Examining community turnover across climate gradients at multiple scales is vital to understanding biogeographic response to climate change. This approach is especially important for alpine plants in which the relative roles of topographic complexity and nonclimatic or stochastic factors vary across spatial scales. Methods: We examined the structure of alpine plant communities across elevation gradients in the White Mountains, California. Using community climatic niche means (CCNMs) and measures of community dissimilarity, we explored the relation between community composition and elevation gradients at three scales: the mountain range, individual peaks, and within elevation contours. Results: At the mountain range scale, community turnover and CCNMs showed strongly significant relations with elevation, with an increase in the abundance of cooler and wetter‐adapted species at higher elevations. At the scale of single peaks, we found weak and inconsistent relations between CCNMs and elevation, but variation in community composition explained by elevation increased. Within the elevation contours, the range of CCNMs was weakly positively correlated with turnover in species identity, likely driven by microclimate and other site‐specific factors. Conclusions: Our results suggest that there is strong environmental sorting of alpine plant communities at broad scales, but microclimatic and site‐specific, nonclimatic factors together shape community turnover at finer scales. In the context of climate change, our results imply that community–climate relations are scale‐dependent, and predictions of local alpine plant range shifts are limited by a lack of topoclimatic and habitat information. [ABSTRACT FROM AUTHOR]

Premise of the Study: With biodiversity and rates of climate change among the highest, the eastern Himalaya are critical for understanding the interaction of these two variables. However, there is a dearth of longitudinal data sets that address the effects of climate change on the exceptional alpine biodiversity of the Himalaya. Methods: We established permanent alpine vegetation monitoring plots in three mountain chains of the Hengduan Mountains, the easternmost Himalaya, which have warmed 0.03–0.05°C yr−1 since 1985. Recently, we resampled plots (176 1‐m2 quadrat plots and 88 sections of 11 summits in three Hengduan mountain chains) to measure changes in vegetation after 7 years. Key Results: Over 7 years, Tibetan alpine vegetation increased in number of species (+8 species/summit; +2.3 species/m2), in frequency (+47.8 plants/m2), and in diversity (+1.6 effective species/m2). Stepwise regressions indicated that warmer temperatures, southerly aspects, and higher elevations were associated with greater increases in these vegetation metrics. Unexpectedly, Himalayan endemic species increased (+1.4 species/m2; +8.5 plants/m2), especially on higher‐elevation summits. In contrast, the increase in relative abundance of non‐alpine species was greater at lower‐elevation summits. Plants used by local Tibetans also increased (+1.3 species/m2; +32 plants/m2). Conclusions: As in other alpine areas, biodiversity is increasing with climate change in the Himalaya. Unlike other areas, endemic species are proliferating at the highest summits and are indicators of change. [ABSTRACT FROM AUTHOR]