Comparative physiological responses of Microcoleus vaginatus and Bryum argenteum to enhanced UV-B radiation under field conditions.

UV-B radiation is an important environmental factor affecting the composition and function of biological soil crusts (BSCs). The aim of this study was to compare the effects of enhanced UV-B radiation on BSCs from Tengger Desert, north-western China, which are dominated by the cyanobacterium Microcoleus vaginatus Gom. and moss Bryum argenteum Hedw. The BSCs were exposed to four UV-B supplemental treatments, including 2.75 (control), 3.08, 3.25, and 3.41Wm-2, for 40 days under field condition. In both the studied organisms, UV-B radiation significantly affected the physiological properties (total flavonoids, soluble proteins, soluble sugars, and proline contents). While marginally enhanced UV-B radiation for a short period favoured the growth of M. vaginatus and B. argenteum, excessively high and prolonged UV-B radiation suppressed the physiological properties of the two organisms. Moreover, response index revealed that UV-B radiation had more detrimental effects on B. argenteum, suggesting that B. argenteum is more sensitive to UV-B radiation than M. vaginatus. The findings of this study could help to predict and evaluate the possible changes in the structure and function of desert ecosystems, based on the variation in physiological responses of M. vaginatus and B. argenteum to enhanced UV-B radiation.