Abstract: Soil microbial communities play a crucial role in forest ecological processes, but the differences between rhizosphere and non-rhizosphere soils, as well as their variations with stand ages remain unclear. We collected rhizosphere and non-rhizosphere soils in Castanopsis hystrix plantations at ages (6, 10, 15, 25, 30 and 34 years) in the southern subtropics and analyzed soil microbial communities using the phospholipid fatty acid (PLFA) method. There were significant differences in microbial communities between the two. Rhizosphere soils had higher total PLFAs and fungal to bacterial (F:B) ratios, and lower arbuscular mycorrhizal fungi to ectomycorrhizal fungi (AMF:EMF) ratios in the 34-year-old stand but microbial communities in non-rhizosphere soils showed no changes with stand age. Rhizosphere soils had higher total PLFAs and F:B ratios but lower AMF:EMF ratios. Further analysis revealed a strong correlation between fine root nutrients and rhizosphere soil PLFAs, indicating a closer interaction between root exudates and microbial communities. In contrast, non-rhizosphere soil PLFAs appeared to be more influenced by soil nitrogen availability. Overall, soil microbial communities exhibited significant differences between rhizosphere and non-rhizosphere soils over various stand ages. A strong correlation was observed between rhizosphere soil PLFAs and fine root nutrients, which may improve our understanding of forest management strategies.

Key words: Total PLFAs, Soil microbial communities, Plant nutrients, Rhizosphere soil