Range exclosures located throughout Utah in cool desert shrub communities were analyzed to determine, (1) response of cryptogamic crusts to grazing, (2) soil variables that influence development of cryptogamic crusts and (3) time needed for reestablishment of cryptogamic communities after disturbance. The amount of lichen, moss and algal cover was found to be considerably reduced by domestic grazing. Sites with moderate to high as opposed to light cryptogamic cover were characterized by significantly heavier textured soils and greater salinity. Cryptogamic cover increased from 4% to 15% during first 14-18 years of exclusion from grazing, but increased only 1% during next 20 years. Reestablishment of a cryptogamic occurs in at least 14-18 years and possibly sooner. Until recently little attention has been given soil stabilizing role of nonvascular plants (cryptogams). Studies in semidesert regions of Utah in past decade have made it increasingly clear that such plants (particularly lichens, mosses and algae) exert a significant impact on soil stability and rates of water infiltration (Anderson et al., 1982; Kleiner and Harper 1972; Kleiner and Harper 1977; Loope and Gifford 1972). The control of wind erosion is of primary importance in arid West. Many desert ranges are sparsely vegetated, resulting in large amounts of exposed soil surface. Brady (1974) suggested the presence of a stable soil crust or a rough soil surface decreased severity of wind erosion. Cryptogamic soil crusts have such a double protective influence at soil surface, since they cement soil fragments into cohesive units and produce roughened surfaces. Filamentous blue-green algae associated with soil crusts produce thick gelatinous sheaths (Durrell and Shields 1961) that render them more tolerant to desiccating conditions of desert (Fig. 1). These gelatinous sheaths coupled with intertwinning growth habit of algal filaments effectively bind surface soil particles, forming a distinct felt-like surface or shallow subsurface meshwork on many desert soils. Moss and lichen constituents of cryptogamic crusts are also important soil stabilizers. Thalli of these plants often cover much of soil surface and small ventral rhizoids penetrate surface in much same way that algal filaments do. Lichens and mosses thus become anchored on soil surface and shield soil from erosive winds and rain. The irregular soil surface caused by algal growth and lichen and/or moss thalli (Fig. 2) breaks up micro-patterns of wind flow, reduces windborne soil losses and traps drifting soil particles. The stabilizing effect of cryptogamic crusts as described here lacks quantitative analysis, thus our conclusions are based on personal Authors are, respectively, senior staff ecologist, Native Plants, Inc., Salt Lake City, Utah 84108, professor, and associate professor, botany and range science, Brigham Young University, Provo, Utah 84602. Research supported by a grant from Intermountain Forest and Range Experiment Station under a cooperative agreement supplement to 12-1 1-204-31. The collaboration of Ralph C. Homgren ofthe IFRES is gratefully acknowledged. Manuscript received June 2, 1979. Fig. 1. This filamentous blue-green alga is a common constituent of cryptogamic soil crusts. Note unusually thick sheath. experience and observations of others (Anantani and Marathe 1974, Durrell and Shields 1961, Fletcher and Martin 1948, Kleiner and Harper 1972, Kleinerand Harper 1977, Singh 1950). However, there is little question that cryptogamic communities are of importance in stabilization of many arid regions of western North American. Wind erosion on arid ranges is probably intensified by grazing during dry periods. Although hooved grazing animals are destructive to highly developed cryptogamic soils crusts, it seems possible that grazing programs can be developed that minimize damage to Fig. 2. The pinnacling of soil surface seen here isa common characteristic of more highly developed cryptogamic soil crusts. JOURNAL OF RANGE MANAGEMENT 35(3), May 1982 355 This content downloaded from 207.46.13.86 on Fri, 14 Oct 2016 04:20:13 UTC All use subject to http://about.jstor.org/terms
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Jul 1, 1992
M.A Karam + 3
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