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The relation of some physical and chemical soil characteristics to cryptogamic crust development was determined from sites in semidesert regions of southern Utah. The effects of grazing on cryptogamic crust development also was examined. Electrical conductivity, percentage silt, and soil phosphorus were found to be correlated with well-developed cryptogamic crusts. Both total cryptogamic cover and the number of cryptogamic species decreased under grazing pressure. The management of rangelands, especially in arid regions, would be strengthened by understanding the role of cryptogamic crusts and considering them in range management decisions. Published in Journal of Range Management, volume 35, issue 2, on pages 180...
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Chlorophyll degradation and electrolyte leakage were measured for the umbilicate desert lichen Rhizoplaca melanophthalma (Ram.) Leuck. & Poelt in the vicinity of a coal-fired power plant near Page, Arizona. Patterns of lichen damage indicated by chlorophyll degradation were similar to those indicated by electrolyte leakage. Regression analyses of chlorophyll degradation as well as electrolyte leakage on distance from the power plant were significant (p < 0.001), suggesting that lichen damage decreased with increasing distance from the power plant. Mean values for both variables at the two sites closest to the power plant (7 and 12 km) differed significantly from values for the two sites farthest from the plant (21...
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Soil surfaces dominated by cyanobacteria and cyanolichens (such as Collema sp.) are widespread in deserts of the world. The influence of these biological soil crusts on the uptake of bioessential elements is reported for the first time for six seed plants of the deserts of Utah. This sample almost doubles the number of species for which the influence of biological soil crusts on mineral uptake of associated vascular plants is known. These new case studies, and others previously published, demonstrate that cyanobacterial or cyanobacteria- Collema crusts significantly alter uptake by plants of many bioessential elements. In studies now available, these crusts always increase the N content of associated seed plants....
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Cryptobiotic soil crusts are an important component of semiarid and arid ecosystems. An important role of these crusts is the contribution of fixed nitrogen to cold-desert ecosystems. This study examines the residual effects of various intensities and combinations of different surface disturbances (raking, scalping, and tracked vehicles) on nitrogenase activity, chlorophyll content, and chlorophyll degradation in these soil crusts. Nine months after disturbance chlorophyll content of disturbed soils was not statistically different from undisturbed controls, except in the scalped treatments, indicating recovery of this characteristic is fairly quick unless surface material is removed. Differences in chlorophyll degradation...
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Sixty uniformly distributed stands in adjacent areas, 40 in Virginia Park (virgin) and 20 in Chesler Park (grazed), were analyzed. Cryptogamic and vascular species were recorded; cover was analyzed by the point sampling method, and frequency by means of 25 quadrats (each 0.125 m2) per stand. The prevalent species (26 in Virginia, 23 in Chesler) were selected on the basis of a constancy?times?frequency index. Interspecific association patterns were determined by means of simple procedures based on quadrat frequency values for each species in the individual stands. Major environmental variables were recorded at each stand, and soil samples from four depths were collected at each site. Soil samples were analyzed for...
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