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If we look at the algal crusts, there is a poorly developed algal crust that will consolidate the soil, but it's very fragile. It is just a few of millimeters thick. It's the thinnest crust I've ever seen. My current thinking is that there's a very good chance that this crust doesn't really protect the soil against erosion like some of the other crusts do. Maybe it doesn't fix nitrogen. In our preliminary studies it appears that the crust cover is much less abundant in the Mojave. It's thinner and more easily disrupted. Nitrogen fixation is much slower than in some of our cool desert sites like the Great Basin. And we suspect that protection from erosion is less important. I find the same algae, Microcoleus and Schizothrix, although there are some species differences among the rare species. In fact, we've even found some things that we think are new species. We find new species in almost every site that we study in detail. This is an area of research where people just haven't done the work. The essential biodiversity questions are yet to be addressed.

I'm going to close with this shot from Australia. I recently went to Western Australia and I just had to get into the outback and see what the crusts were like. The crusts are completely different because the desert is completely different. It's not like anything I've seen in North America. They have trees in their deserts, such as Eucalyptus and Acacia. You can see that the soil is darkened by microbiotic crusts. There are very few lichens and mosses. They are mostly cyanobacterial. One of the ideas I want to leave with you today is that it's been a real interesting trip this last quarter of a century with microbiotic crusts. We found that the crusts were very significant to the ecosystems in the Great Basin Desert and Colorado Plateau for a number of different reasons. We thought we knew their species composition, but we really are only beginning to assay the biodiversity in these fascinating communities.

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