Few studies have evaluated how variability in both the amount and timing of precipitation affect the structure and physiology of shrubs in these systems. Idaho State University and USGS scientists quantified changes in big sagebrush shrubs following 20 years of experimental manipulations in amount and seasonal timing of precipitation. Most of the responses entailed changes in plant structure, where shrub sizes increased in winter-irrigated compared to control plots. Summer irrigation had few effects. Irrigation, particularly in winter, affected structural and stand-level abundance of big sagebrush, while physiological changes in the shrubs were less evident. Thus, it appears for sagebrush that seasonal timing is at least as important as the amount of precipitation, and that responses to changes in precipitation timing occur through changes in carbon allocation more so than changes in leaf-level carbon gain.

Reinhardt, K., McAbee, K., Germino, M.J., 2018, Changes in structure and physiological functioning due to experimentally enhanced precipitation seasonality in a widespread shrub species: Plant Ecology, https://doi.org/10.1007/s11258-018-0845-z.