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.