Objective This study aimed to explore the effects of precipitation reduction on leaf litter decomposition of tree and shrub species and their mixed litter in south China.

Methods In Pinus massoniana and Camellia oleifolia mixed forest, three kinds of penetration reduction intensity treatments were set up: blank control (CK), throughfall reduction by 30% (R30) and throughfall reduction by 60% (R60), and the field decomposition bag experiment was carried out for 18 months. The decomposition and structural carbohydrate degradation dynamics of three leaf litter types of leaf litter-P. massoniana litter, C. oleifolia litter and a mixed litter in equal proportions were monitored.

Results (1) Both R30 and R60 treatments significantly increased the litter mass remaining ratio and decreased the decomposition constant (k) of P. massoniana (p < 0.05). In contrast, only the R60 treatment significantly increased the litter mass remaining ratio of C. oleifolia and the mixed leaf litter (p < 0.05). (2) The R30 and R60 treatments significantly increased the remaining ratio of lignin and cellulose during the P. massoniana litter decomposition (p < 0.05), while only R60 treatment increased the remaining ratio of lignin and cellulose during the C. oleifolia litter decomposition (p < 0.05). (3) Correlation analysis indicated a positive linear relationship between the litter mass remaining ratio and the remaining of lignin and cellulose (p < 0.05).

Conclusion The throughfall reduction inhibited the decomposition of P. massoniana, C. oleifolia, and their mixed leaf litter, leading to a decreased degradation of structural carbohydrates. The inhibitory effect was influenced by both the type of litter and the intensity of throughfall reduction. These findings provide theoretical basis for the rational management of litter in mixed P. massoniana and C. oleifolia forests under precipitation reduction.