樹幹流と土壌の酸性化の実態(<シンポジウム特集>酸性雨と森林衰退,研究の現場から)

概要

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(1) Top soil acidification around Sugi (Cryptomeria japonica) trees were studied by grid sampling method. The pH (H_2O) values of near-trunk points were much lower than that of outer sampling points. The isoclines of pH were shapes of concentric circles. (2) Results from trench soil samplings showed that stem flow effects on soils and soil acidification extended hemispherically from the trunk base. High concentrations of aqueous Al were detected in soil solution at a heavily damaged Sugi stand. (3) Changes in stem flow characteristics were measured and nutrient inputs by stem flow were estimated. Average pH values of upper, middle, and lower samples were 5.0, 4.1, and 3.2 respectively. Nutrient concentrations in stem flow rose up 1 or 2 orders higher as the stem flow flowed downward. (4) nutrient inputs by stem flow were 817 (cation) and 577 (anion) mmol_c・tree^<-1>・yr^<-1>. Main cations were NH_4-N (34% of total cation charge), Na (25%), and Ca (16%). Anion comprised Cl (48% of total anion charge), SO_4-S (33%) and NO_3-N (19%). Dry and wet deposition caught by the emergent part of the crown consists of 80-90% of total stem flow input. (5) This study suggests that the nitrogen input by stem flow in urban forests is equivalent to the annual litter fall N input in montane forest ecosystems.
森林立地学会の論文
1992-06-30