Regional signatures of plant response to climate across North American deserts: Forecasts for management and planning

Background/Question/Methods

Future warming and changes in the patterns of precipitation predicted by climate models can have a strong impact on plant species already stressed by low water availability in North American deserts. Accurate forecasts of climate-induced changes in desert plant species assemblages are needed by managers because dryland ecosystems are prone to abrupt and potentially irreversible degradation and reductions in productivity. To better inform management responses to broad-scale climate change impacts, we have synthesized over a century (1906-2012) of climate and vegetation monitoring results from nearly 1500 plots across the Colorado Plateau, Sonoran, Chihuahuan, and Mojave Deserts.

Results/Conclusions

In all deserts, we demonstrate both linear and nonlinear responses of dominant plant species and plant diversity to drought and elevated temperature. Our results from the Colorado Plateau reveal large declines of cool-season perennial bunchgrasses primarily driven by high temperatures. In the Sonoran Desert, there were increases in cacti with hotter temperatures, as well as reductions in warm-season perennial grasses and subshrubs with less annual precipitation. Trees and shrubs were less responsive to changing climatic conditions, but many species were sensitive to warmer temperatures and less winter precipitation, especially on south-facing slopes. In the Chihuahuan Desert, many grasses and forbs had large responses to summer precipitation, whereas most woody vegetation had small responses to winter precipitation. Our results from the Mojave Desert show declines of shrubs at some sites related to reductions in winter precipitation. Cross-site and cross-desert comparisons reveal differences in how plants respond to climate, and the importance of soil, landscape, and biotic characteristics in modifying responses. We highlight “climate pivot points” that mark important shifts from increases to decreases in plant abundance along climatic gradients. These results are being used to assist with management decisions, improve monitoring protocols, and inform climate change vulnerability assessments for land managers.