SURFACE DISTURBANCE OF CRYPTOBIOTIC SOIL CRUSTS - NITROGENASE ACTIVITY, CHLOROPHYLL CONTENT, AND CHLOROPHYLL DEGRADATION

Cryptobiotic soil crusts are an important component of semiarid and ar id ecosystems. An important role of these crusts is the contribution o f fixed nitrogen to cold-desert ecosystems. This study examines the re sidual effects of various intensities and combinations of different su rface disturbances (raking, scalping, and tracked vehicles) on nitroge nase activity, chlorophyll content, and chlorophyll degradation in the se soil crusts. Nine months after disturbance chlorophyll content of d isturbed soils was not statistically different from undisturbed contro ls, except in the scalped treatments, indicating recovery of this char acteristic is fairly quick unless surface material is removed Differen ces in chlorophyll degradation among treatments were not statistically significant. However, nitrogenase activity in all treatments showed t remendous reductions, ranging from 77-97%, when compared to the contro l, indicating this characteristic is slow to recover. Consequently, as sessment of crustal recovery, from disturbance must include not only v isual and biomass characteristics but other physiological measurements as well. Areas dominated by these crusts should be managed conservati vely until the implications of crustal disturbance is better understoo d.