Biocrust recovery improves soil fertility after 10-year sand-fixation using reed checkerboard barriers on reshaped dunes in an arid sandy desert in central Asia

Biological soil crusts (BSCs; biocrusts) are well developed in drylands, which are crucial to the stability and resilience of dryland ecosystems. In the southeastern Gurbantunggut Desert, a typical sandy desert in the middle part of central Asia, engineering development has an increasing negative impact on ecosystems. Fortunately, ecological restoration measures are being implemented, but the exact effect on soil quality is still unclear. In artificial sand-fixing sites on reshaped dunes along the west-east desert road, a total of 80 quadrats (1 m × 1 m) of reed checkerboards after the implementation of sand-fixing measures for 10 years were investigated to determine the BSC development status and soil properties. The algal and lichen crusts accounted for 48.75 % and 26.25 % of the total quadrat number, respectively, indicating an obvious recovery effect of BSC (only 25 % for bare sand). The developmental level of BSC gradually increased from the top to the bottom of the dunes (Li 0 → Li 6),which was consistent with the distribution pattern of BSCs on natural dunes. Compared with bare sand, the soil organic carbon (13.85 % and 23.07 % increases), total nitrogen (12.55 % and 23.95 % increases), total potassium (9.30 % and 8.24 % increases), and available nitrogen (23.97 % and 61.41 % increases) contents of algal and lichen crusts were significantly increased, and lichen crusts had markedly higher increase effect than algal crusts. The BSC development markedly reduced soil pH (0.49 % and 0.50 % decreased) and increased electrical conductivity(11.99 % and 10.68 % increases), resulting in improved soil microenvironment. Soil properties showed significant linear relationships with BSC development level, and an optimal fitting (R² = 0.770 or 0.780) was detected for the soil fertility index. Based on the soil property matrix, the bare sands, algal, and lichen crusts were markedly separated along the first axis in the PCA biplot, which once again confirmed the significant positive effect of BSC recovery on soil fertility improvement. Consequently, in the early stage of sand-fixation (e.g., < = 10 years) by reed checkerboards on the damaged desert surface, BSC recovery can well promote and predict soil fertility in this area. The results provide a reliable theoretical basis for the restoration technology and scientific management of degraded sandy desert ecosystems.