Moderate disturbance increases the PLFA diversity and biomass of the microbial community in biocrusts in the Loess Plateau region of China

Abstract

Biological soil crusts (biocrusts) play key roles in dryland ecosystems. Examining the effects of different intensities of disturbance on biocrusts and exploring appropriate disturbance levels can provide important information about ecosystem processes and services in drylands. Five disturbance intensities ranging from 10% to 50% based on the percentage of broken biocrusts were implemented to examine the effects of simulated goat trampling on microbial communities; microbial community structure was measured with the phospholipid fatty acid method. The effects of disturbance on the biocrusts were closely related to disturbance intensity. Surprisingly, moderate disturbance had a weak effect on total biocrust coverage but increased cyanobacterial coverage by 2 ~ 3%. Consequently, there was an increase in total N, a reduction in the C/N ratio and improvements in soil moisture, and these effects led to 13 ~ 21% and 5 ~ 6% increases in microbial biomass and diversity, respectively, compared with those in undisturbed biocrusts. However, high-intensity disturbance substantially reduced biocrust coverage and microbial abundance. The study supports the intermediate disturbance hypothesis and suggests that moderate disturbance has positive effects on the microbial communities of biocrusts. These findings provide vital information for the ecological management of drylands.