Phosphorus cycling characteristics and soil microbial responses in different uneven-aged mixed forests of Pinus massoniana
Description
This study aimed to elucidate the regulatory mechanisms underlying phosphorus (P) characteristics, P cycling functional taxa, genes, and their co-occurrence networks in uneven-aged mixed Pinus massoniana plantations. Furthermore, it identified the optimal mixing mode to provide a theoretical basis for alleviating P limitation and facilitating the sustainable management of subtropical P. massoniana forests. Four uneven-aged mixed forests formed by P. massoniana with Schima superba (PS), Elaeocarpus sylvestris (PE), Phoebe bournei (PP), and Taxus wallichiana (PT) were investigated, with a pure P. massoniana forest (CK) as the control. By quantifying plant-soil-microbe P indicators, combined with metagenomic sequencing and co-occurrence networks to evaluate the effects of uneven-aged mixing on P cycling and the associated functional taxa and genes. The results indicate that soil microorganisms in all stands exhibited P limitation. Mixed planting significantly increased litter P (LP) and soil total P (TP) content, but it did not enhance soil available P (AP) content. Among the mixed stands, PT showed relatively higher microbial biomass P (MBP) and P use efficiency (PUE), exerting a better effect on alleviating P limitation. Distinct differentiation was observed in the P cycling functional taxa among different stands. Acidoferrum acted as the core taxon for P cycling across all stands, while PT harbored a unique taxon, CAIMXF01, facilitating P uptake and transport. Notably, Streptomyces predominantly mediated inorganic P solubilization, while Rhizobium regulated organic P mineralization. The co-occurrence network between P cycling functional taxa and genes was relatively intricate in PT, and exhibited relatively high synergistic efficiency. Uneven-aged mixing of P. massoniana influenced P cycling by regulating the differentiation of functional taxa and genes, as well as the structure of their co-occurrence networks, and PT was more effective in alleviating P limitation and enhancing P cycling efficiency.