PS 68-72 - Drought-induced dieback and post-drought recovery of desert perennials in southern California

Friday, August 11, 2017
Exhibit Hall, Oregon Convention Center
Roger A. Anderson and Britta J. Fast, Biology, Western Washington University, Bellingham, WA

Desert scrub habitat in the Sonoran Desert of southern California flourished with healthy perennials, visually observed, measured, and photographed by RA Anderson from the late 1970's through 2000. In 2002 and 2003, the desert scrub plant communities in southern California suffered a severe "once-in-a-century" drought and as a result, the mortality and dieback rates of perennial plants spiked throughout the Mojave and Sonoran Deserts in 2002. In 2005, after near-record rains, the plants already appeared to be in recovery from dieback, thus plant ecologists began documenting the recovery. After another substantial rainy season, in spring 2010 on our site near Desert Center in Riverside County, we were able to document and measure over 1500 dead and live plants, and documented plant-to-plant and plant-to-wash distances on a 4 hectare plot on which the plants had been mapped and measured in the early 1980's.


All 46 Ambrosia salsola and 68% of 806 A. dumosa died. Virtually 100% of Larrea tridentata stems died, but 538 of 544 plants survived, with about 30% of those having regained their former diameter by 2010. Similarly, by 2010 about 30% of the desert ironwood Olneya tesota regained their former diameter. The essential correlates revealed that more smaller shrubs died and shrub death was more likely if it was further from washes or closer to other shrubs.