Analysis of proton generation and consumption of forest surface soils in Hokkaido, northern Japan

摘要

We determined proton budgets of surface soils in a deciduous forest (Df) and a coniferous forest (Cf) of Volcanogenous Regosols in Tomakomai, Hokkaido of northern Japan. The total H{sup}+ source was 12.9 and 11.6 kmol{sub}cha{sup}(-1)y{sup}(-1) at Df and Cf respectively, and the external H{sup}+ was 1% at Df and 2% at Cf. The primary H{sup}+ sources were vegetation uptake of base cations and nitrification, while the major H{sup}+ sinks were release of base cations and NO{sub}3{sup}- uptake by vegetation. Leaching incubation experiments using A horizon soils including Df and Cf with NH{sub}4{sup}+ solutions (5.3, 15.9 mg N L{sup}(-1)) showed that H{sup}+ from nitrification was generally higher in the Df soil than Cf soil, and nitrification of Tomakomai Df soil was the highest in both treatments. Results of multiple regression analyses suggested that p H{sub}(KCl) and exchangeable Ca{sup}(2+) contributed to the H{sup}+ generation via nitrification. leaching experiments with dilute HCl (pH 3.3) revealed that cation release (mainly Ca{sup}(2+)) occurred, and the proportion of release by decrease of exchangeable cations was higher than that by mineral weathering. Mineral weathering in the Tomakomal soil was higher than the other soils.