Changes in Litter Organic Acid Release Characteristics During Litter Decomposition in Plantations Comprising Different Tree Species

Phosphorus deficiency restricts the productivity of plantation forests in southern China. Low-molecular-weight organic acids (LMWOAs) can promote insoluble P activation and improve P availability in red soils. However, few studies have investigated organic acids (OAs) released during litter decomposition under field conditions. A one-year litterbag decomposition experiment with monthly sampling was conducted using four common plantation tree species in subtropical China, namely, Phoebe bournei, Michelia macclurei, Schima superba, and Cunninghamia lanceolata, to determine changes in LMWOA composition, content, and release characteristics during decomposition. Seventeen LMWOAs were detected during litter decomposition, and OA types differed among tree species. The total amount of litter-derived OAs varied among species, following the order S. superba > P. bournei > C. lanceolata > M. macclurei, with the amount in S. superba being 1.15 times that in M. macclurei. The release characteristics of OAs differed significantly. C. lanceolata, S. superba, and M. macclurei exhibited a net release pattern, whereas P. bournei exhibited a release–enrichment–release pattern. S. superba and M. macclurei litter released significantly more OAs than C. lanceolata. Overall, this study provides field-based evidence for interspecific differences in litter-derived OAs dynamics and offers a basis for tree species selection in mixed plantations with potential implications for nutrient return and phosphorus cycling.