Local range boundaries versus large-scale tradeoffs: climatic and competitive constraints on tree growth

Species often respond to human‐caused climate change by shifting where they occur on the landscape. To anticipate these shifts, we need to understand the forces that determine where species currently occur. We tested whether a long‐hypothesised trade‐off between climate and competitive constraints explains where tree species grow on mountain slopes. Using tree rings, we reconstructed growth sensitivity to climate and competition in range centre and range margin tree populations in three climatically distinct regions. We found that climate often constrains growth at environmentally harsh elevational range boundaries, and that climatic and competitive constraints trade‐off at large spatial scales. However, there was less evidence that competition consistently constrained growth at benign elevational range boundaries; thus, local‐scale climate‐competition trade‐offs were infrequent. Our work underscores the difficulty of predicting local‐scale range dynamics, but suggests that the constrai...

物种通常会通过改变其在陆地景观中的分布范围，来应对人为气候变化。为了预判这类分布变化，我们需要厘清决定物种当前分布格局的核心驱动因素。我们针对“长期以来被提出的气候与竞争限制之间的权衡（trade-off）能否解释树木物种在山坡上的分布格局”这一假说开展了实证检验。我们利用树木年轮（tree rings），重建了三个气候特征迥异的区域内，处于分布中心（range centre）与分布边缘（range margin）的林木种群对气候与竞争的生长敏感性。研究发现，在环境严苛的海拔分布边界（elevational range boundaries）处，气候通常会限制林木生长；而在大空间尺度上，气候限制与竞争限制之间存在权衡关系。然而，鲜有证据表明，在环境适宜的海拔分布边界处，竞争会持续约束林木生长；因此，局地尺度上的气候-竞争权衡现象并不常见。本研究凸显了预测局地尺度分布动态的难度，但研究表明，约束[原文内容未完整提供]。