Biological soil crusts decrease soil erodibility of economic fruit forests land through its consolidation effect in the Three Gorges Reservoir area.

• (1) The impacts of biocrusts on soil erodibility were investigated in the humid region of TGRA. • (2) CSEI decreased as a threshold-based nonlinear function with the increase of biocrusts coverage. • (3) Variation in soil erodibility was controlled by the differences in BC th , soil texture, and SOM. • (4) Biocrusts decreased soil erodibility was dominant through its consolidation effect in TGRA. Biological soil crusts (Biocrusts) play a significant role in controlling soil erosion by regulating soil erodibility. Nevertheless, affected by the regional climate, soil types, and biocrusts types, the influence mechanism of biocrusts on soil credibility, may be completely different in different regions. Most previous studies regarding the effects of biocrusts on soil erodibility were carried out in dryland regions, and little is known in humid regions where biocrusts are well developed. Therefore, this study was conducted to quantify the variation in soil erodibility, reflected by soil cohesion (Coh), penetration resistance (PR), saturated hydraulic conductivity (K s), mean weight diameter (MWD), mean number of drop impact (MND), soil erodibility of K factor (K), structural stability index (SSI), and a comprehensive soil erodibility index (CSEI), with biocrusts coverage and reveal the influence mechanism of biocrusts on soil erodibility of economic fruit forests land in the Three Gorges Reservoir area (TGRA). Six economic fruit forests land of Citrus sinensis with different biocrusts coverages (0–20%, 20%-40%, 40%-60%, 60%-80%, 80%-100%) and without biocrusts (as control) were selected as the testing sites. The results showed that the development of biocrusts significantly decreased soil erodibility. Compared to Citrus sinensis land without biocrusts, the development of biocrusts increased Coh , K s, MWD , MND , and SSI significantly, whereas decreased PR , K , and CSEI significantly. The reductions in CSEI varied from 19% to 66%. Moreover, with the increase of biocrusts coverage, CSEI exhibited a changing pattern of decreasing first and then reaching a stable stage when coverage was approximately greater than 20%. In particular, variation in CSEI with biocrusts coverage was dominantly controlled by the differences in biocrusts thickness, soil particle distribution, and organic matter content. Biocrusts thickness played the most critical role via directly bonding or binding soil particles and aggregates. The result is helpful for understanding the process and mechanism of soil erosion controlled by biocrusts, also provides a new idea for the prevention of soil erosion under economic fruit forests in the TGRA. [ABSTRACT FROM AUTHOR]