Site #1: The Alluvial Mima Mounds

Cladonia spp. from alluvial mima mounds, Turnbull National Wildlife Refuge. may 2, 2012. Photo by Therese Addis.

Last Wednesday Therese and I headed out to our first site, the alluvial Mima Mounds. Pronounced Mee-mah Mounds, these are some of the most bizarre geological formations found in prairies around the world – Texas, China, and here at Turnbull too. The Mima Mounds, also called prairie or pimple mounds, are named after the mounds over near Olympia, Washington. When I first walked through the mounds last winter out on the west side of the state, I was shocked — the mounds over there are 8-12 feet tall, about the same in diameter, and they look like a giant permaculture or agricultural project. Perhaps that sounds like a ludicrous idea, but it sounds just as crazy as them being constructed by ancient giant gophers, and there are many of geologists and scientists who support that hypothesis, Note: check the resources list below for some popular science articles about the mima mounds. In sum, the mima mounds are mysterious, and Therese and I were excited to find out what lichen are living in the soil crusts out there. I knew that there wouldn’t be the Reindeer Moss kind of Cladonia lichen like on the mounds in Olympia, but exactly what would be there, neither of us were really too sure.

Alluvial Mima Mounds

Alluvial mima mounds, walking west towards Stubblefield Lake. May 2, 2012.

So what did we find? Well, at first there were many grasses as we walked west towards Stubblefield Lake. And the intermound areas were very filled in with soil making the mounds look less distinct than the typical mima mounds — the tops of the mounds only poked out about 3-4 feet, and the mounds were most visible due to the clump of dead woody forbs on the top of each mound. As we walked further into the refuge the density of the grasses decreased, small granite rocks increased, and the cryptogamic crusts became more abundant. At our trial location we plopped down our bags and began collecting some soil crusts, and a few rock crusts.

And what lichen did we find? Well, I’m still keying them out but here is a sneak peek:

Diploschistes spp.

The first one we found was a Diploschistes spp. which was very abundant. Therese’s first comment was that she would have thought that they were just some sort of poop, and they did look like poop because they are parasitic and grow over other lichens, and it looks like they may be parasites of mosses too.

We also found a Cladonia, a black crust with tiny apothecia, a very leprose lichen growing on a rock (Lepraria?), a possible Leptogium growing within moss, and others. And we found a couple possibly different species of squamulose lichen with no reproductive features, no pruina, no cephalodia, no distinctive features besides typical colors (brown or green top with white bottom) that we could see in the field. Or were we just looking at the primary thallus of a Cladonia, perhaps, not sure yet,

Checking out the cryptogamic soil crusts

Only a few rock crust lichen were collected, but we’ll be back on site next week after we key these 9 soil crusts out, so we’ll focus on rocks, and gather any additional soil crust lichen that we may have overlooked. We may also check to see if there is any difference in the  diversity and composition of different slopes of a mound – NESW sides. But I’m also super excited for the rock crusts. It’s so neat to me that endolithic lichen can actually grow within the rock matrix, in some cases up to 2mm deep. Intense critters! For more information of endolithic lichen, check out the Discussion of Lichen Biology: Chapter 4.


“Heaps of confusion”. By Beth Geiger. Earth, Aug98, Vol. 7 Issue 4, p34, 4p.

“Mystery of the Mima mounds”. By Daryl Gray. Current Science, 1/8/99, Vol. 84 Issue 9, p10, 2p

“Soil properties and microbial activity across a 500m elevation gradient in a semi-arid environment”, Soil Biology and Biochemistry. By Jeffrey L. Smith, Jonathan J. Halvorson, Harvey Bolton Jr.

“Engineering properties of Mima Mound soils from Turnbull National Wildlife Refuge, Eastern Washington”. by Toni Voile and Richard Orndorff from the Department of Geology at Eastern Washington University. Presented at the 2004 annual meeting of the Geological Society of America.

Spatial Modeling of Biological Soil Crusts to Support Rangeland Assessment and Monitoring” by Matthew A. Bowker, Jayne Belnap, and Mark E. Miller in Rangeland Ecology Management 59:519–529; September 2006.

Biological Soil Crusts: Ecology & Management” Technical Reference 1730-2 for the U.S. Department of the Interior (2001). By Jayne Belnap, Julie Hilty Kaltenecker, Roger Rosentreter, John Williams,Steve Leonard and David Eldridge.

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