Effects of interplanting Liquidambarformosana on soil microbial derived and plant derived carbon in pure Pinus massoniana plantation

<bold>Objective</bold> This study aims to explore the effects of interplanting on soil microbial-derived and plant-derived carbon in pure <italic>Pinus massoniana</italic> forests，addressing whether such silvicultural practice could enhance soil carbon storage in subtropical low-productivity coniferous forests. <bold>Method</bold> We conducted a matched-pair experiment in 15-year-old pure <italic>P. massoniana</italic> forests and adjacent mixed plantations interplanted with native <italic>Liquidambar formosana</italic> for 6 years in southern Jiangxi Province.Three replicate plots（20 m×20 m）were established for each forest type.Soil samples were collected from four soil layers（0-10 cm，10-20 cm，20-40 cm，and 40-60 cm）to analyze：soil physical and chemical properties，enzyme activities，microbial residues carbon（MRC）and plant residues carbon concentrations.These measurements allowed us to examine the effects of interplanting on vertical distribution patterns of soil carbon components and elucidate the underlying mechanisms. <bold>Result</bold> Interplanting with mixed <italic>L. formosana</italic> significantly influenced MRC and lignin phenols（VSC）content in <italic>P. massoniana</italic> forests，as well as the characteristics of soil lignin degradation.Compared to the pure forest，the mixed forest exhibited a significant increase of 14.9% and 11.9% in fungal residues carbon （FRC） and MRC，respectively，in the 0-10 cm soil layer.The contents of vanillyl and VSC increased significantly by 32.7% and 13.8%，respectively，while the syringyl content decreased significantly by 15.9%.，soil organic carbon（SOC）content was significantly increased by 13.5%.Interplanting significantly decreased both the syringyl/vanillyl ratio in 0-10 cm soil and the syringic acid/aldehyde ratio in 10-20 cm soil.Key drivers of microbial residues and plant residues carbon dynamics included particulate organic carbon（POC），total nitrogen（TN），ammonium nitrogen（NH4⁺-N），nitrate nitrogen（NO₃^--N）content，and the activities of acid phosphatase（AP），β-glucosidase（BG），cellobiohydrolase（CB），and N-acetyl-β-glucosaminidase（NAG）. <bold>Conclusion</bold> Interplanting <italic>L. formosana</italic> into pure <italic>P. massoniana</italic> forests significantly increased the content of both microbial and plant-derived carbon in the topsoil，thereby activating its carbon sequestration potential.<italic>L. formosana</italic> as a promising species for interplanting is recommended to enhance the soil carbon storage capacity of low-efficiency <italic>P. massoniana</italic> plantations.