Desertification induced changes in soil bacterial and fungal diversity and community structure in a dry-hot valley forest

Increase in aridity is a global phenomenon due to climate change. Understanding soil microbial communities' response to aridity induced desertification is essential to predict the regulation of microbial processes under climate change and to develop feasible restoration plans. Therefore, to elucidate desertification effects, we investigated the changes in soil properties and, shifts and drivers of soil microbial diversity and community composition of a dry-hot valley-based Pinus densata forest located in south-east Tibetan Plateau of China. Amplicon sequencing of bacterial and fungal communities were used to determine soil bacterial and fungal community composition and diversity patterns. The results revealed that soil bacterial and fungal alphadiversities were lower in desertified P. densata forest soils. Soil total carbon content (TC) was the major predictor of bacterial Pielou index. Whereas fungal Chao 1 and Simpson diversity indices were mainly influenced by total nitrogen contents (TN) of the soil. Differential response between soil bacterial and fungal communities' structures were observed between the desertified and non-desertified soils. Soil pH mainly regulated the overall microbial community structures in addition to TC determining bacterial and TN determining fungal community structures, respectively. Changes in the relative abundance of bacterial phylum Chloroflexi and Actinobacteria, and the ratio of fungal phylum Ascomycota/Basidiomycota were the indicators of intensity of soil desertification in the studied forests. The relative abundance of pathogenic microbial communities in soils was more in desertified soils in comparison to the non-desertified soils of P. densata forests, such as the bacterial genus Conexibacter and fungal genera Penicillium and Ilyonectria. This study evidences the differential response of soil bacterial and fungal communities to changes in soil biotic and abiotic properties indicating differential adaptive mechanism in a forest ecosystem currently experiencing adverse effects of rapid desertification.