Linking soil microbial community with the changes in soil physicochemical properties in response to long-term agricultural land use change of different chronosequences and depth layers

Agricultural land use changes are essential in addressing global urbanization demands. The improper management of agricultural land may lead to the alteration of the microbial ecosystem, which ultimately affects soil quality. Here, we assessed how soil microbial diversity, communities, and physicochemical properties in three layers of soil; upper (0-15 cm), middle (15-30 cm), and lower (30-45 cm), responded to a long-term land use change from paddy land (PL) to dry land of different chronosequences; PD3 (3 years), PD5 (5 years), and PD10 (10 years). We found PL conversion into dry lands increased soil pH, soil 3 phase R-value, bulk density (BD), organic matter (OM), total phosphorus (TP), total nitrogen (TN), and decreased electrical conductivity (EC), water holding capacity (WHC), and moisture content (MC) in all three layers. The land use change from PL to dry lands initially (PD3) decreased (11-25 %) bacterial diversity, while it significantly increased in PD5 (0.1-16 %), and PD10 (1-14 %) in all three layers. Unlike bacterial diversity, fungal diversity was high in PD5 in the upper layer, while the middle and lower layer was the least affected. We also found the conversion of PL to dry land altered relative abundance (RA) of bacteria on the upper layer, while RA of fungi was reshaped in all three layers. The Pearson's correlation coefficient showed that MC, OM, pH, R-value, TN, TP, and WHC were important physicochemical factors, which significantly (P < 0.05) influenced Nitrospirae, Chloroflexi, Proteobacteria, and Basidiomycota composition. Briefly, our study show that land use change initially (3 years) caused huge changes in the microbiome, which improved somehow in further years (5 and 10 years), and we conclude that land use changes impact positively on functional biodiversity and biological quality of the soil.