Trampling to biocrusts reduced soil microbial biomass and altered soil
microbial communities in vegetation areas of the Tennger Desert, China
Abstract
Biocrusts occupy the surface of soils, house key microbes and
non-vascular plants, and further provide other vital ecological
functions in oligotrophic drylands. However, little is known about the
impact of trampling on fragile biocrusts in temperate deserts,
particularly changes to soil microbial communities. To examine this,
fresh soils from three trampled intensities to biocrusts were sampled in
vegetation areas of the Tennger Desert. Soil microbial biomass carbon
and nitrogen, and microbial communities were studied using chloroform
fumigation and Illumina sequencing, respectively. The results collected
2050 OTUs and 393 species of bacterial communities and 1124 OTUs and 135
species of fungal communities. Severe trampling of biocrusts resulted in
a reduction in soil microbial biomass carbon and nitrogen, and soil
microbial abundance and diversity; changed the relative abundance of
microbial taxa; altered the soil microbial community structures of
cyanobacteria-dominated crusts, and further affected microbial community
functions. Reduced soil moisture and nutrients and enhanced pH were the
factors which caused alteration in soil microbial communities after
trampled biocrusts. In addition, there was a negative correlation
between trampling intensity with soil nutrient content, soil microbial
biomass carbon and nitrogen, and microbial abundance. After similar
trampling intensity, later-succession moss-dominated crusts were
significantly higher in soil nutrients, soil microbial biomass carbon
and nitrogen, soil fungal abundance and diversity, and more distinctive
microbial community structures compared to early-succession
cyanobacteria-dominated crusts. This suggests that there is a positive
correlation between biocrust tolerance to trampling and the successional
stages of biocrusts. Therefore, severe trampling of biocrusts could
modify biocrust fragile structures and functions, which in turn, altered
soil microbial community compositions and structures, and discouraged
their function, leading to a degradation process of surface soils in
temperate desert ecosystems.