Plant functional groups have contrasting effects on soil water availability by affecting interception, uptake, and transpiration.
Whether changes in plant functional groups exacerbate or mitigate climate-related drought has received little attention. Researchers modeled the effects of different plant functional groups and climate change on ecological drought in 340 semiarid grasslands over 30-year periods. Relative to a mixed perennial grassland, frequency and duration of drought decreased beneath annual grasses, yet drought increased beneath shrubs and under high biomass. This finding indicates that increased plant biomass through invasions or management, such as fertilization or respite from grazing, could exacerbate drought conditions. Results suggest that factors that increase biomass, or cause the replacement of perennial temperate grasslands by shrubs, can intensify ecological drought both in current and future climates.
Wilson, S.D., Schlaepfer, D.R., Bradford, J.B., Lauenroth, W.K., Duniway, M.C., Hall, S.A., Jamiyansharav, K., Jia, G., Lkhagva, A., Munson, S.M., Pyke, D.A., Tietjen, B., 2018, Functional group, biomass, and climate change effects on ecological drought in semiarid grasslands: Journal of Geophysical Research - Biogeosciences, https://doi.org/10.1002/2017JG004173.