Response Characteristics of Biological Soil Crusts Under Different Afforestation Measures in Alpine Sandy Land.

Desertification, which may lead to land degradation, is a significant global ecological issue. Biological soil crusts (BSCs) can play a role in sand fixation, carbon sequestration, and the improvement in soil functions in the ecological restoration of sandy soil. Therefore, elucidating the responses of BSCs to afforestation measures in alpine sandy areas is necessary to guide vegetation configuration in sandy ecosystems and enhance the effectiveness of sand fixation measures to prevent desertification. Herein, we determined the physicochemical properties and enzyme activities of bare sand (no crust) and algal and moss crusts collected from four sites subjected to different afforestation measures, including + (WLYY), + (SLWL), + (SHNT), and (NT80) plantations. High-throughput sequencing was also employed to analyze bacterial community structure in BSCs. The results revealed that fine particle contents in algal and moss crusts were higher than in bare sand. During the succession from bare sand to algae to moss crust, their enzymatic activities and water and nutrient contents tended to increase. And the diversity of bacterial communities changed little in the SLWL sample points, while the richness showed a trend of first decreasing and then increasing, but bacterial community richness and diversity first decreased and then increased at the other sites. Among the four measures, SLWL enhanced nutrient contents, enzyme activities, and bacterial community richness and diversity in BSCs relatively more effectively. Alkaline-hydrolyzable nitrogen and soil organic matter were the key factors impacting bacterial community structures in BSCs under the four afforestation measures. From the perspective of BSCs, the results can provide a reference for the prevention and control strategies of other alpine sandy soils.