The response of plant interactions to manipulations of water and consumer pressure during extreme climate events in California

We experimentally tested the hypothesis that the mechanism of facilitation depends on the dominant driver of plant productivity. During an extreme drought year (2014) and a year of above-average rainfall (2016) we experimentally manipulated soil moisture and consumer pressure at 240 plots in the San Joaquin Desert. Water was added at different levels in each year to reflect average precipitation patterns. Animal exclosures were erected to deter mammals and grazers in the system. Plant abundance for each identified species was measured in shrub and open microsites with each of the crossed treatments in both years at the end of the growing season. Each plot was a 50 cm x 50 cm quadrat and biomass was collected from the center 10 cm area. The dominant shrub in the system used in the study was Ephedra californica. Full paper available: Filazzola, A., Liczner, A. R., Westphal, M. and Lortie, C. J. (2018), The effect of consumer pressure and abiotic stress on positive plant interactions are mediated by extreme climatic events. New Phytol, 217: 140â 150. doi:10.1111/nph.14778