Relationship between community composition and water infiltration of biological soil crusts in the hilly Loess Plateau, China

Abstract

Biological soil crusts (biocrusts) are the mixed community composed of different ratios of cyanobacteria, mosses, and lichens at the slope scale in the Hilly Loess Plateau region. Biocrusts significantly affect water infiltration in this area. The relationship between infiltration rate and community structure of mixed biocrusts is unknown, which would hinder the assessment of soil permeability of biocrusts at the slope scale. We measured the stable infiltration rate of cyanobacteria, moss, and mixed biocrusts with different proportions of cyanobacteria and moss including moss coverage of <15%, 15%-30%, 30%-45%, 45%-60% and >60%, respectively. The principal component analysis and path analysis were used to understand the influencing factors of stable infiltration rate of mixed biocrusts, and to clarify the relationship between the stable infiltration rate and the community structure of mixed biocrusts. The results showed that the saturated hydraulic conductivity of cyanobacteria and moss crusts was 0.66 mm·min-1 and 2.40 mm·min-1, respectively. The stable infiltration rates of mixed biocrusts with moss coverage <15% to >60% were 0.80-2.30 mm·min-1. The stable infiltration rate of mixed biocrusts at the slope scale depended on moss coverage and its improvement on soil pore structure, with the correlation coefficients being 0.636 (P=0.011) and 0.835 (P=0.000) respectively. Herein, the saturated hydraulic conductivity and coverage of cyanobacteria and moss confirmed the weighted prediction of water infiltration volume (y) i.e., a significant correlation (r=0.945) with the measured water infiltration volume (x) of mixed biocrusts. The linear fitting of measured and predicted water infiltration volume of mixed biocrusts was y=0.85x (R2=0.98, P<0.05). This study clarified the relationship between water infiltration of mixed biocrust community composition and individual biocrust composition, which provided a scientific basis for accurately evaluating the hydrological process of biocrusts in this area.