SOIL ACIDITY IN 1970 AND 1989 IN A CONIFEROUS FOREST IN SOUTHWEST FINLAND

Forest soil pH in southwest Finland was measured with identical sampli ng and analysing methods in 1970 and 1989. The acidity of the organic humus layer increased significantly as pH values measured on water and on salt suspensions decreased between the two sampling dates. For the mineral soil layers, no unambiguous trend was found, pH values measur ed on salt suspension tended to be unchanged or lower, while pH on wat er suspension in some soil layers were even higher in 1989 than in 197 0.