Post Drought Recovery in Malosma laurina after Severe Dieback during California’s Historic Drought of 2012-2016

Malosma laurina is a species of chaparral shrub that dominates coastal exposures of the Santa Monica Mountains of southern California. Between 2012 and 2016, protracted drought with half normal rainfall over a five-year period (175 mm), led to severe dieback, exceeding 50% whole plant mortality at some sites. The drought dissipated in 2017 with an annual rainfall that exceeded the 140-yr normal by 108 mm. As a result of this elevated annual rainfall in 2017, we were interested in documenting the potential for full recovery of Malosma laurina as a keystone species of coastal chaparral shrub communities. We tested the hypothesis of full recovery by comparing plant water relations measured in June 2015 to June 2017. Specifically, we determined if there was a significant increase in the 1) water status of dieback plants (ψpd, predawn water potential), 2) water transport efficiency of stem xylem (ks), 3) rate of photosynthesis (A), and 4) rate of stomatal conductance to water vapor diffusion (gs)