Soil Rehabilitation Promotes Resilient Microbiome with Enriched Keystone Taxa than Agricultural Infestation in Barren Soils on the Loess Plateau

SIMPLE SUMMARY: Soil degradation accompanied by agricultural intensification is threatening the existence of dryland areas globally. However, improvement in soil quality in these areas through plant restoration has been greatly successful. Under this practice, soil microorganisms, especially keystone taxa, exert positive feedback on soil bio-functionality by recycling nutrients. Nevertheless, to date, it remains unclear as to how similar are the changes in these keystone taxa in dryland barren soils and agricultural soils, with comparison perspective. The earlier longer-term experiments in Loess soils have shown profound positive effects of plant restoration and establishment of more complex soil microbial networks in the presence of higher nutrient accumulation. The current work shows more keystone taxa that tend to exist in rehabilitated conditions when compared to their agricultural soil counterparts. ABSTRACT: Drylands provide crucial ecosystem and economic services across the globe. In barren drylands, keystone taxa drive microbial structure and functioning in soil environments. In the current study, the Chinese Loess plateau’s agricultural (AL) and twenty-year-old rehabilitated lands (RL) provided a unique opportunity to investigate land-use-mediated effects on barren soil keystone bacterial and fungal taxa. Therefore, soils from eighteen sites were collected for metagenomic sequencing of bacteria specific 16S rRNA and fungi specific ITS2 regions, respectively, and to conduct molecular ecological networks and construct microbial OTU-based correlation matrices. In RL soils we found a more complex bacterial network represented by a higher number of nodes and links, with a link percentage of 77%, and a lower number of nodes and links for OTU-based fungal networks compared to the AL soils. A higher number of keystone taxa was observed in the RL (66) than in the AL (49) soils, and microbial network connectivity was positively influenced by soil total nitrogen and microbial biomass carbon contents. Our results indicate that plant restoration and the reduced human interventions in RL soils could guide the development of a better-connected microbial network and ensure sufficient nutrient circulation in barren soils on the Loess plateau.