The topographic signature of ecosystem climate sensitivities in the western U.S.

It has been suggested that hillslope topography can promote the persistence of hydrologic refugia, sites where ecosystem productivity is relatively insensitive to climate variation. Currently, the mechanisms that promote the persistence of these locations and their spatial distributions are poorly resolved across gradients in climate. We quantified the response of ecosystem net primary productivity to variability in the annual climatic water balance for 30 years across the western U.S. The standardized slope of this pixel-specific linear regression represents ecosystem-climate sensitivity and provides a means to identify ecosystems that are buffered from droughts. Environmental conditions produced by hillslope convergence reduced ecosystem sensitivity to climate across the majority of the region. We observed the greatest topographic effect in semi-arid climates, while vulnerability to drought was maximized in flat, arid landscapes. In aggregate, spatial patterns of ecosystem sensitivity can be implemented for regional planning to maximize conservation in landscapes more resistant to perturbations.

已有研究表明，坡面地形（hillslope topography）可促进水文避难所（hydrologic refugia）的存续——这类区域的生态系统生产力相对不受气候波动影响。当前，维持这类区域存续的机制及其空间分布在气候梯度上仍未得到充分厘清。本研究量化了美国西部30年间生态系统净初级生产力（net primary productivity）对年气候水分平衡变异性的响应。该逐像元线性回归的标准化斜率表征了生态系统-气候敏感性，同时为识别受干旱缓冲的生态系统提供了可行途径。坡面汇流形成的环境条件，降低了该区域大部分区域的生态系统对气候的敏感性。本研究在半干旱气候区观测到最为显著的地形效应，而平坦干旱景观的干旱脆弱性达到峰值。总体而言，生态系统敏感性的空间格局可应用于区域规划，以在抗扰动能力更强的景观中最大化保护效益。