Print PageThe intensification of aridity due to climate change in the southwestern U.S. is likely to have a large impact on the growth and survival of plant species that may already be vulnerable to water stress. To make accurate predictions of plant responses to climate change, it is essential to determine the long-term dynamics of plant species associated with past climate conditions. Here, we highlight preliminary research results from National Parks in the Sonoran Desert that relate past regional patterns in climate to changes in plant species and functional types.
Results/Conclusions
Our initial findings indicate that warmer and drier conditions differentially affected plant species and functional types, and these responses were moderated by past land use, landscape position, and soil characteristics. Sixty years of monitoring results in Organ Pipe Cactus National Monument suggest a northward expansion of an endemic cactus in relation to an increase in frost-free days and shifts in land use. Cacti in other protected areas have also increased, but the succulent plant, Fouquieria splendens, has decreased with increasing temperatures. Perennial grasses and subshrubs have significantly declined in response to drier conditions. Shrubs and trees have shown a mixed response to climate variability, depending on their drought tolerance traits and the physical characteristics of sites that may have affected water availability. Acacia species have largely increased with increases in aridity, whereas Cercidium microphyllum on steep hillslopes and Atriplex species have largely decreased in shrublands where they are dominant. Larrea tridentata was responsive to winter precipitation, and increases in Prosopis velutina for much of the 20th century have ceased, most likely due to decreases in water availability. These results suggest that climate change has been affecting dryland plant communities for a number of decades and provide critical information for regional management decisions.
