Changes since 1950 of mineral pools in the upper C-horizon of Swedish deciduous forest soils

Abstract

Soils from the C-horizon of deciduous forests in southern Sweden, originally sampled in 1947-52, were resampled in 1988. Air-dried soil from both periods were extracted in 1991 using M NH4Ac, pH 4.8, and 0.2 M HNO3 for analysis of exchangeable and acid soluble pools of Na, Mn, Ca, Mg, K, Sr, Zn, Fe, S, P, and Al. Using acid NH4Ac as extractant nine elements had changed significantly (p 0.90 for Na, K, Mg, and Sr), but with the exception of S, values for HNO3 were higher or much higher. It is concluded that a decided decrease of the exchangeable pools of base cations and an equally decided increase of exchangeable Al has occurred even in the C-horizon, well below the main rhizosphere. That also the acid soluble pools of base cations have decreased indicates mineralogical changes which may counteract a complete reversibility of the current soil acidification.