Metagenomic analysis of microbial community and function reveals the response of soil respiration to the conversion of cropland to plantations in the Loess Plateau of China

As an effective method to control soil erosion and increase vegetation coverage in the Loess Plateau of China, the conversion of cropland to plantations also influences soil respiration (Rs). A lot of research work has been performed on the response of Rs to land use change in this region. Nevertheless, the microbiological mechanism on the response of Rs to land use change has not been elucidated. In this study, Rs was measured during the conversion of cropland to plantations. Moreover, soil microbial community and metabolic function were analyzed by metagenomic sequencing. When the conversion of cropland to plantations was implemented, Rs significantly increased. Metagenomic analysis indicated that the conversion of cropland to plantations had a stronger impact on microbial abundance than microbial composition, which was reflected in the abundance of dominant phyla, such as Actinobacteria, Proteobacteria, Acidobacteria, Chloroflexi, Firmicutes, Cyanobacteria, Gemmatimonadetes, Planctomycetes and Verrucomicrobia. Carbon metabolic pathways and genes also had a remarkable response to land use change. Although the abundance of some carbon metabolic genes decreased with the conversion of cropland to plantations, the abundance of CAZy (Carbohydrate-Active Enzymes) genes increased. Moreover, carbon metabolic genes with significant differences affiliated to above dominant phyla. All results indicated that the conversion of cropland to plantations changed microbial abundance, which in turn affected abundance of carbon metabolic and CAZy genes. The increase in the storage of organic matter caused by the above changes promoted microbial catabolism for producing a large amount of CO2 in plantations soil, which was reflected by high Rs. Our study provides insights into the microbiological mechanism on the response of Rs to land use change during the conversion of cropland to plantations in the Loess Plateau of China.