Dry years and mound-pool landscape response: Observations at Jepson Prairie and simulations in a geomorphological model

Background/Question/Methods
Many vernal pool landscapes are mound-pool landscapes, where the isolated pools are separated by isolated mounds, at scales of meters to tens of meters. Isolation from year-round water, and the high edge-to-area ratio characteristic of many small pools compared to few large ones, support the flora and fauna endemic to vernal pool ecosystems. There is increasing evidence that much mound-pool topography is maintained by fossorial rodents' response to the seasonal inundation characteristic of temporary pools. Mound-pool density and organization are not identical on all landforms inhabited by the same rodent species; possible explanations of the differences include differences in the original landscape, or changes with age, or responses to climate variation in the short and long term. I combine simulations of rodent-plant-water feedback, which generate mound-pool topography, with observations of rodents, plants, and water in Jepson Prairie, CA. The recent low-rainfall years showed rapid rodent response to rare rainfall, a behavior which has been added to the model.

Results/Conclusions
The simulated landscapes with drought periods can tend towards increasing density and regularity over time, a pattern seen in the largest surviving chronosequence of mound-pool landscapes near Merced, CA. The effect depends on the parameterization of climate variability and rodent response, within historical records. This suggests that currently observable processes may be adequate to explain the organization of vernal pool landscapes tens of thousands to millions of years old. The simulation can also estimate how climate variability caused by climate change might affect vernal pool landscapes in the medium-term future.