Abstract: It is important to explore the differences in acid buffering capacity of leaf litter and its controlling factors for forest restoration and management in subtropical region. It is unclear whether leaf litter traits can be used to predict acid buffering capacity. In this study, the leaf litters of 12 tree species in subtropical forests were selected for simulated acid rain extraction experiments. The pH value and base ions content of the extraction solution and the initial physicochemical traits of litters were examined. The main regulating factors of acid buffering capacity of litters were tested through the relationships between initial traits and acid buffering capacity. The results showed that leaf litters of all the species significantly increased pH value of simulated acid rain solution. The acid buffering capacity (>4) of most broadleaved species (e.g., Toona sinensis (A. Juss.) Roem., Sassafras tzumu（Hemsl.) Hemsl. and Vernicia fordii (Hemsl.) Airy Shaw), except for Sapium discolor (Champ. ex Benth.) Muell. Arg (<1), was significantly higher than that coniferous species (including Cunninghamia lanceolata (Lamb.) Hook. and Pinus massoniana Lamb.). The extraction time significantly affected the acid buffering capacity of litters. The strongest acid buffering capacity of Pinus massoniana litter occurred at 1 day of extraction, while that of the other species occurred at 5 days of extraction. Acid buffering capacity was positively correlated with initial pH value of litters (the correlation coefficients at 1 d, 5 d and 15 d were 0.84, 0.80 and 0.83, respectively; P<0.05), and negatively correlated with lignin content (the correlation coefficients at 1 d, 5 d and 15 d were -0.68, -0.75 and -0.69, respectively; P<0.05). Stepwise regression analysis confirmed that initial pH value was the most important driving factor of acid buffering capacity. Our results indicated that initial leaf litter traits, especially pH value, can predict their acid buffering capacity. Therefore, pH value should be given priority when selecting species from the perspective of acid buffering capacity in the future.

Key words: acid rain, forest litter, leaf litter trait, acid buffering capacity, screening of species.