Gloria Great Basin, Oroville, CA, USA.
Department of Ecology, Montana State University, Bozeman, MT, USA.
Am J Bot. 2020 Feb;107(2):239-249. doi: 10.1002/ajb2.1376. Epub 2019 Nov 12.
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.
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.
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.
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.
在多个尺度上检查气候梯度下的群落周转率对于理解生物地理对气候变化的响应至关重要。对于高山植物来说，这种方法尤其重要，因为地形复杂性和非气候或随机因素的相对作用在空间尺度上有所不同。
我们研究了加利福尼亚白山的海拔梯度上高山植物群落的结构。使用群落气候生态位均值（CCNMs）和群落差异度量，我们在三个尺度上探索了群落组成与海拔梯度之间的关系：山脉、单个山峰和海拔轮廓内。
在山脉尺度上，群落周转率和 CCNMs 与海拔呈显著相关，随着海拔升高，较凉爽和较适应潮湿的物种丰度增加。在单个山峰的尺度上，我们发现 CCNMs 与海拔之间的关系较弱且不一致，但由海拔解释的群落组成变化增加。在海拔轮廓内，CCNMs 的范围与物种身份的周转率呈弱正相关，可能是由小气候和其他特定于地点的因素驱动的。
我们的结果表明，在广泛的尺度上，高山植物群落存在强烈的环境分类，但微气候和特定于地点的非气候因素共同塑造了更精细尺度上的群落周转率。在气候变化的背景下，我们的结果意味着群落-气候关系是尺度依赖性的，并且由于缺乏地形气候和栖息地信息，对当地高山植物分布变化的预测受到限制。
