Physiological response of moss/cyanobacteria crusts along a precipitation gradient from semi-arid to arid desert in China

Aims Desert regions are regarded as highly sensitive to climatic changes. In arid and semi-arid desert, photosynthetic organisms from biological soil crusts are poikilohydric and sensitive to fluctuations in precipitation. How do physiological properties such as concentration of biochemical constituents and enzymes respond to a precipitation gradient from semi-arid to arid desert regions? Methods We sampled cyanobacteria and moss crusts from four desert regions with distinctly different amounts of annual rainfall. Subsequently, the contents of photosynthetic pigments, malondialdehyde (MDA), osmotic adjustment substances, and antioxidative enzyme activities were correlated with the means of annual precipitation, evaporation, and temperature at the various sites. Results Crust type, precipitation level, and their interaction had significant influences on many physiological properties (photosynthetic pigments, proline, soluble sugar, and superoxide dismutase). The contents of soluble protein, proline, and soluble sugar of cyanobacteria/moss crusts decreased with increasing precipitation level. Superoxide dismutase and catalase activities of cyanobacteria crusts decreased significantly with increasing annual precipitation. No significant variations in MDA were observed between different precipitation regions in the two crusts. Conclusions Among the environmental variables tested, the annual amount of precipitation had the strongest effect on the physiological properties of moss/cyanobacteria crusts in different regions. Crust type combined with particular precipitation level influenced the physiological properties of crusts. Moreover, both moss and cyanobacteria crusts exhibited strong physiological adaptability to changes in precipitation. This result needs to be incorporated into future ecological models, which will help in understanding the function and vulnerability of biocrusts in the face of climate change.