Modelling the influence of snowfall on cyanobacterial crusts in the Gurbantunggut Desert, northern China

摘要

Biological soil crusts (BSCs) are widespread in arid and semiarid regions. They have long been regarded as a key biotic component of desert ecosystems. However, little information is available regarding the influence of snowfall on BSCs in desert ecosystems. Therefore, we conducted the present work in the largest fixed and semi-fixed desert in China, the Gurbantunggut Desert, where snowfall is a special form of precipitation, and snow cover is a prerequisite for BSC survival during the harsh winter. We investigated the effects of altered winter snowfall on biomass, chlorophyll (Chl) fluorescence, moisture content, and soluble-protein and malondialdehyde (MDA) concentrations in cyanobacterial crusts in the early (March) and late (October) periods after snowfall in 2014. The results indicated that biomass (indicated by Chl a), Chl fluorescence (i.e. maximum photochemical efficiency, fluorescence yield and rates of electron transport) and the concentration of soluble protein of cyanobacterial crusts declined as a result of lower soil water content resulting from snow removal or reduction. Increased snowfall had positive effects on physiological properties associated with photosynthesis but induced dramatic decreases in the MDA concentration in cyanobacterial crusts. In addition, photosynthesis of cyanobacterial crusts was obviously higher in the late than in the early period after snowfall, which can be attributed to increases in the cover of cyanobacteria in the crust communities. These findings provided evidence that increased snowfall in the Gurbantunggut Desert could favour and help maintain the development of BSCs.