スギ林土壌における酸の生成および緩衝作用の定量的把握

概要

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A monitoring study was carried out at a Japanese cedar (Cryptomeria japonica) stand in Minamitonai, Shichinohe Town, Aomori Prefecture, to estimate acid load and buffering reaction using tension-free lysimeters. The term was 16 months from July 1998 to October 1999. Proton (H^+)and other nutrient budgets were examined. Ammonium (NH_4^+) deposition was higher in summer than in winter(P<0.05). Conversely, sulfate(SO_4^<2->) deposition was higher in winter than in summer (P<0.05). Annual inputs were 0.56kmol(+) ha^<-1>y^<-1> for NH_4^+ and 0.70kmol(-) ha^<-1>y^<-1> for SO_4^<2->. High NH_4^+ input contributed to acid load, which was larger than associated atmospheric acid deposition. Base cation exchange, chemical weathering of minerals, and uptake of nitrate(NO_3^-) were the main acid buffer reactions in summer. Base cation mobilization was proportional to total acid production and silica mobilization was proportional to acid production associated with nitrogen transformation. Although there was a high total nitrogen (NH_4^+ + NO_3^-)input, NH_4^+ output at the depth of 80 cm was negligible and NO_3^- output at the depth of 80 cm was 0.23 kmol(-) ha^>-1<y^<-1>, which was 34% of total input. In the case of winter, sulfate adsorption contributed to buffer reactions, which made annual acid production negative. We, therefore, concluded that intensive soil acidification hardly occurred.
社団法人日本土壌肥料学会の論文
2000-12-05