Abstract: Soil acid buffering capacity plays an important role in preventing soil acidification induced by fertilization and atmospheric nitrogen deposition, and thus is critical for maintaining soil functioning. Arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) plants differ greatly in functional traits, but how the differences of their impacts on soil acid buffering capacity are still poorly understood. In this study, forests with dominant tree species associated with AM and ECM fungi in subtropical China were selected, aiming to investigate soil acid buffering capacity and the relevant physicochemical properties of forest soils. The results showed that AM-dominated forest soils had significantly higher soil acid buffering capacity than ECM-dominated forest soils. In comparison, pH, exchangeable base cations, cation exchange capacity, exchangeable K⁺, Na⁺, Ca²⁺, organic matter and nitrate concentrations were significantly higher in AM-dominated forest soils, but ammonium concentrations were lower than ECM-dominated forest soils (P<0.01). Soil acid buffering capacity was positively correlated with pH, soil organic matter, exchangeable calcium, cation exchange capacity and base saturation (P<0.01), the exchangeable base cations and exchangeable magnesium (P<0.05), while it was significantly negatively correlated with the exchangeable acid content (P<0.01). In addition, 47.4% of the variation in soil acid buffer capacity could be explained by the contents of exchangeable calcium and organic matters. Therefore, AM tree species can improve soil acid buffering ability by promoting accumulation of organic matters and exchangeable base cations (mainly Ca²⁺) in soils. Moreover, AM-dominated forests could prevent soil acidification better than ECMdominated forests in subtropical regions when exposed to chronic atmospheric nitrogen deposition.

Key words: soil acidification, exchangeable base cation, mycorrhizal type