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The acidity regimes of representative soils on the north slope of the Changbai Mountains were examined through determinations of PH and pCa of the soil paste as well as in-site determinations. For soils under broad-leaf forest or broad-leaf-Korean pine forest, the pH decreased from the litter to lower layers gradually until it did not change or decreased further slightly. For soils under coniferous forest or Ermans birch forest,there was a minimum in pH at a depth of 3～6 cm where the content of humus was high. The pCa increased gradually from the soil surface downward to a constant value. The lime potential (pH-0.5pCa) showed a similar trend as the PH in its distribution. For a given soil, the measured pH value of the thick paste, ranging from 4.5 to 5.5, was lower by about 0.5 units than the value determined by the conventional method with a water to soil ratio of 5:1. The PH determined in site was even lower. It was found that there was a fairly close relationship between soil acidity and the type of vegetation. The pH showed a trend of decreasing from soils under broad-leaf forest through broad-leaf-conifer mixed forest and coniferous forest to Ermans birch forest, and the pCa showed an opposite trend in variation.
The acidity regimes of representative soils on the north slope of the Changbai Mountains were examined through determinations of PH and pCa of the soil paste as well as in-site determinations. For soils under broad-leaf forest or broad-leaf-Korean pine forest, the pH decreased from the litter to lower layers yet until it did not change or decreased further slightly. For soils under coniferous forest or Ermans birch forest, there was a minimum in pH at a depth of 3 ~ 6 cm where the content of humus was The lime potential (pH-0.5pCa) showed a similar trend as the PH in its distribution. For a given soil, the measured pH value of the thick paste, ranging from 4.5 to 5.5, was lower by about 0.5 units than the value determined by the conventional method with a water to soil ratio of 5: 1. The PH determined in site was even lower. It was found that there was a fairly close relationship between soil acid ity and the type of vegetation. The pH showed a trend of decreasing from soils under broad-leaf forest through broad-leaf-conifer mixed forest and coniferous forest to Ermans birch forest, and the pCa showed an opposite trend in variation.