Biological soil crust is composed of lichens, cyanobacteria, green algae, mosses, and fungi. Although crusts are a dominant source of nitrogen (N) in arid ecosystems, this study is among the first to demonstrate their contribution to N availability in xeric temperate habitats. The study site is located in Lucas County of Northwest Ohio. Using an acetylene reduction technique, we demonstrated potential N fixation for these crusts covering sandy, acidic, low N soil. Similar fixation rates were observed for crust whether dominated by moss, lichen, or bare soil. N inputs from biological crusts in northwestern Ohio are comparable to those in arid regions, but contribute substantially less N than by atmospheric deposition. Nitrate and ammonium leaching from the crust layer were quantified using ion exchange resin bags inserted within intact soil cores at 4 cm depth. Leaching of ammonium was greater and nitrate less in lichen than moss crusts or bare soil, and was less than that deposited from atmospheric sources. Therefore, biological crusts in these mesic, temperate soils may be immobilizing excess ammonium and nitrate that would otherwise be leached through the sandy soil. Moreover, automated monitoring of microclimate in the surface 7 cm of soil suggests that moisture and temperature fluctuations in soil are moderated under crust compared to bare soil without crust. We conclude that biological crusts in northwestern Ohio contribute potential N fixation, reduce N leaching, and moderate soil microclimate.

A survey of biological crust components (bryophytes, lichens, chlorophyta, bacteria), soil fauna (nematodes, collembolans, mites) and vascular plants was conducted in a dry sand savanna in northwestern Ohio between 1995 and 2001. In soil, six free-living chlorophytes and seven cyanobacteria taxa were identified. Chlorophyta were more abundant than cyanobacteria with Desmococcus olivaeus and Stichococcus bacillaris being the most common species. For bryophytes, the most common species were Polytrichum piliferum and Ceratodon purpureus, and for lichens, Cladonia species. Notably, we found lichen species in the crusts have chlorophytes not cyanobacteria, as their photobionts. Twenty-seven families and 29 genera of nematodes, and four collembolan species were identified in crust and rhizosphere communities. Autotrophic denitrifying bacteria were not detectable with the method employed. The biological crust occurred among a vascular plant community with Robinia pseudoacacia, Rubus flagellaris, Bromus inermis, and Vicia villosa as the most abundant tree, shrub, graminoid, and non-grass herbaceous plants, respectively. To our knowledge, this is the first report of microbial crust community composition in xeric patches of northwestern Ohio. Moreover, our report includes a report of soil nematode or collembolan communities associated with soil biological crust communities.