スギ樹幹の近傍と遠方における土壌溶液の化学組成とアルミニウムの形態

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It is well known that stemflow of the Japanese cedar tree is strongly acidic, which causes severe acidification of soils close to the trunk of the tree. However, the possible effects of this acidification on aluminum species distribution in soil solutions is virtually unknown. Thus, in order to conduct aluminum speciation, soil solutions were collected for one year from the Ah horizon at plots close to (-10 cm) and far from (>100 cm) the trunk of a Japanese cedar tree in Gunma Prefecture, Japan. Throughfall and stemflow samples were also collected to elucidate the dominant process that controls soil solution chemistry. The results obtained are summarized below: 1) The pH of soil solutions close to the trunk (referred to as C samples) and far from the trunk (referred to as F samples) ranged from 4.40 to 4.65 and 5.65 to 6.15, respectively. The difference between the two was 1.3 pH units on average. 2) The speciation of monomeric aluminum was conducted using HPLC with fluorescence detection of the Al-lumogallion complex in combination with equilibrium calculations. For F samples, only organic aluminum was detected, with a low level (1.2μmol L^<-1> on average). For C samples, however, Al^<3+> was dominant throughout the year, having an average concentration of 27.1μmol L^<-1>. 3) The dominant ion species for F samples were calcium and nitrate, showing that the chemistry of the samples was governed primarily by nitrification. During the dry winter season, the total ion concentration became two- or three-fold due to evaporation. 4) For C samples, the concentrations of calcium and nitrate fell to 38 and 56%, respectively, of those of F samples, because internal nitrate production was suppressed due to acidification. In the winter, the Al^<3+> level rose to 75.8μmol L<-1>, probably because the increases in calcium and hydrogen ion concentrations caused by evaporation enhanced the ion exchange with exchangeable aluminum in the soil.
社団法人日本土壌肥料学会の論文
2000-10-05

スギ樹幹の近傍と遠方における土壌溶液の化学組成とアルミニウムの形態

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