Quantitative assessment of biocrust distribution patterns using landscape indices benefits the study of their soil conservation functions

Abstract

Biological soil crusts (biocrusts) are widely distributed covers and show obvious differences in coverage, composition, and distribution patterns under field conditions. To date, it is still difficult to assess the ecological function of biocrusts in different distribution patterns due to challenges in quantitatively assessing their patterns. Landscape ecology inspired us to characterize and describe landscape distribution patterns through a series of indices. Accordingly, this study developed a method to quantitatively characterize the distribution pattern of biocrusts at the plot scale. Our results demonstrated that optimum grain size selection is important. The first inflection point determines the optimum grain size of 5 mm. Based on this grain size, four landscape indices were selected out of fifteen, including the percentage of the landscape (PLAND), edge density (ED), patch cohesion index (COHESION), and splitting index (SPLIT), which represented 91.6 % of the total distribution characteristic information of biocrusts within 58 squares of 1.5 × 1.5 m. The four landscape indices were validated for applicability by describing biocrust characteristics for various patterns, scales, and coverage levels both in the laboratory and field plots. This method for quantitatively assessing the distribution characteristics of biocrusts lays a foundation for the study of the relationship between the distribution pattern of biocrusts and ecological functions and processes.