Climate change impacts on vernal pool hydrology and vegetation in northern California

Vernal pools are seasonal wetlands that have a high diversity of endemic and native plant species, yet they are threatened by agricultural conversion and urban development and face threats posed by climate change resulting from altered precipitation and temperature regimes. We developed an approach to investigate the potential impacts of climate change on hydrology and vegetation communities of vernal pools by creating a mass-balance hydrologic model that is coupled to a statistical model of plant community distribution. The hydrologic and vegetative models were calibrated using field measurements from a vernal pool in northeastern California that experiences snow-dominated hydrology and is larger than vernal pools in more studied areas like Central California, but representative of other northern California vernal pools. Using downscaled data from global climate models, the coupled model suggests that warmer conditions will lead to the pool being inundated for a shorter time, but with little change in maximum depth. Reduced hydroperiods suggest possible declines in vernal pool specialist species with future climate change. The coupled model is an integrated approach for understanding the impact of altered environmental conditions on unique hydrology and plant community composition of vernal pool ecosystems, but the model approach could be improved with longer term data and by applying it at more sites to broaden the applicability of the approach and to enable better process representation.