Chloe P. H. Lewis @ Harte Lab, UCBerkeley

Feedbacks in the soil

Landscape topography from small interactions

Mounds in pools after first heavy rain, Dec. 2012

Subtle undulations in the grassland turn into mounds and pools with about 3″ of rain (Dec. 3rd, 2012)

Mima mounds are an unusual landscape topography which occur in the Americas and Africa. They were extensive in California’s Central Valley before intensive farming and settlement. Mima mounds are regular undulations of the soil, half a meter or a meter tall (a few feet), three to ten times as wide. Especially in California, Mima mounds usually alternate with vernal pools, micro-ecosystems that support many endemic species of plants and invertebrates.

There are dozens of theories of what built or maintains the Mima mound landscapes. My dissertation research is following up the increasingly solid evidence that fossorial (burrowing) creatures, e.g. pocket gophers, actively maintain Mima mounds. I have hypothesized a feedback between gophers, plants, hydrology, and topography, composed of small-scale, short-term interactions, which spontaneously develops Mima mound topography over decades and maintains them over millennia.

I am testing this in three ways:

  • simulating that region and others with cellular automata;
  • closely recording the phenomona involved in one mound-pool region, to test the strength of the small interactions; and
  • comparing the simulated results to the recorded extent and patterns of mound-pool topography, to see if the association with edaphic factors holds true.

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