Changes in functional gene structure and metabolic potential of the microbial community in biological soil crusts along a revegetation chronosequence in the Tengger Desert

Biological soil crusts (BSCs), the pioneers of restoration of degraded vegetation, act as an organizing principle in drylands largely through metabolic activities of microbial communities. However, little is known about the microbial functional potential involved in biogeochemical processes during BSC succession in desert ecosystems. Here, we utilized a functional gene array (GeoChip 5.0) in conjunction with determinants of microbial community compositions of BSCs along a revegetation chronosequence in the Tengger Desert, to address the following: (a) how the functional structure of the microbial community changes with BSC age in different soils and (b) how genes involved in carbon (C)- and nitrogen (N)-cycling change and whether they promoted an increased microbial metabolic potential during BSC succession in desert revegetation. The results showed that the relative abundance of functional genes was determined by the microbial community compositions in the BSC development process, and the significant differences in microbial functional genes were detected in 61-year-old BSCs from other aged BSCs. Redundancy analysis indicated that the abundance of fungi and moss and soil physicochemical properties were the important factors determining differences in microbial functional structures. Functional genes associated with C degradation and N denitrification were the major components involved in C and N cycles, which were closely related to the increased fungal abundance during succession. The increased gene abundance of 61-year-old BSCs in both C and N cycles promoted microbial metabolic potential. These results indicated that fungi might be the key microbial mediators in C and N cycling in the later development of BSCs, and microbial functional structure could be a potential indicator of revegetation sustainability in desert ecosystems.