Dynamic Changes of Rhizosphere Soil Microbial Community Along A Karst Coniferous Plantation Chronosequence

Soil microorganisms are essential for establishing plant diversity and supporting various ecosystem functions throughout the process of plantation development. However, there is still limited knowledge regarding how the rhizosphere soil microbial communities change during forest vegetation restoration in the Karst area. This study examined the rhizospheric soil properties and microbial community composition along a chronosequence of Pinus armandi plantations in a karst mountain region of southwest China. Rhizospheric soil samples were collected from plantations of P. armandi aged 10, 16, 22, and 47 years old. High-throughput sequencing was employed to analyze the composition of bacterial and fungal communities. The results indicated that the plantation growth dramatically changed the rhizosphere soil characteristics and microbial community patterns. With the age of the stand, the contents of TP, TK, AN and AK increased gradually, while the contents of TC, TN and SOC decreased first and then increased, and reached the lowest level at 16 years old. As the stand age increased, bacterial community diversity indexes increased, whereas diversity indexes for fungal communities 10-year increased, peaked at 16 years old, and then decreased. The relative abundances of bacterial and fungal phyla varied significantly among different stand ages. Proteobacteria(38.14%) and Acidobacteria(33.98%) were the most prevalent bacterial phyla in the rhizosphere soil, while the dominant fungal phyla were Basidiomycota(46.53%), Ascomycota(40.48%), and Mortierellomycota(9.92%). The abundance and diversity of bacterial and fungal communities were significantly correlated with soil nutrient levels. A redundancy analysis (RDA) results indicated that soil total nitrogen (TN), total phosphorus (TP) and available nitrogen (AN) were key regulators of rhizosphere bacterial communities, and soil AN, TP and available phosphorus (AP) were key regulators of rhizosphere fungal community. Our findings provide valuable insights into the response of rhizosphere microbiota to long-term afforestation, contributing to a better understanding of the mechanisms underlying vegetation succession driven by soil microbes in the Karst area of southwest China.