Element composition of leaves and wood of beech (Fagus sylvatica L.) on SO₂-polluted sites of the NE-Bavarian Mountain

Abstract

Element composition of leaves and wood from healthy and declining beech (Fagus sylvatica L.) growing on SO₂-polluted sites in the NE-Bavarian Mountains was studied. The wood and foliar Mg contents was significantly lower for declining than for healthy beech. Within the period between 1956 and 1985 the Mg concentrations in year rings of moderately damaged (declining site) and healthy beech declined significantly. No such change was observed for severely damaged beech (declining site), indicating that the Mg supply of those trees had reached a minimum already before 1956. Symptoms of forest decline, however, appeared first in the late seventies and early eighties. It is assumed that the decrease of the Mg concentration in year rings of healthy and moderately declining trees during the past three decades was caused by increasing acid emissions. The significant increase of the wood S contents especially at the declining high elevation site confirms this assumption.The decrease of the wood Mg contents was paralleled by a decrease of the annual increments in diameter for healthy and declining beech, which started in 1972 and became accelerated in 1976. The reduction of growth in the early seventies at the high elevation site coincided with an elongation of chimneys at power stations and steel works and higher filtering of basic dust relative to acid emissions. In the extremely hot and dry summer 1976 drought and a drastical drop of soil pH due to an excess nitrification are supposed to have accelerated the declining of growth and Mg availability. We, therefore, believe that the long-term acid input and the accelerated soil internal H⁺ production due to an excess nitrification are mainly responsible for the sustained symptoms of forest decline in the NE-Bavarian Mountains during the late seventies and early eighties.