Simulated Mima mounds emerge from small interactions

TL;DR

This study demonstrates that Mima mounds can form and persist through simple, local interactions between soil, water, plants, and rodents, modeled via cellular automata.

Contribution

It introduces a cellular automata model showing that small-scale interactions can produce and sustain Mima mound topography.

Findings

Mound-pool topography emerges from local interactions in the model.

The model reproduces mound shapes on slopes and flat terrain.

Mound formation is robust to initial conditions.

Abstract

The Mima-mound-and-vernal-pool topography of California is rich in endemic plant and invertebrate species, but we do not know how this unusual environment is created or maintained. Burrowing rodents have been observed to move soil upwards at annual rates sufficient to maintain the mounds despite erosion, but there is no tested explanation of this behavior. We propose that the mounds are an emergent effect of small-scale (10 cm, 1 day) interactions between topography, hydrology, plant growth, and rodent burrowing. A cellular automata simulation of these processes both generates and maintains mound-pool topography with minimal dependence on initial conditions, and can also describe mound morphogenesis on slopes, where observed mound geometry is distinct from that on level ground.