SULFUR INPUTS AND OUTPUTS FOR 2 EUROPEAN BEECH FORESTS GROWING ON DIFFERENT SOIL SUBSTRATES

Using a flux-balance approach, the S budget of two heavily polluted be ech (Fagus sylvatica L.) forest ecosystems growing on acid and calcare ous soil substrates was investigated. Total S deposition (dry and wet fall) at both sites was large (2.3 and 3.2 kequiv..ha-1.year-1 at the calcareous and acidic beech forest sites, respectively). The contribut ion of dry deposition to the total S deposition in-both stands was sig nificant; dry deposition of S exceeded the deposition of S even in bul k precipitation. The atmospheric input of S exceeded, at both sites, t he forest S requirements by 6-7 times. Consequently, at the acidic bee ch forest site, phytotoxins like Al3+ (2 kequiv..ha-1.year-1) were rel eased with seepage water, neutralizing the acid input. At the calcareo us beech forest site, leaching of huge amounts of Ca2+ (15 kequiv..ha- 1.year-1) and HCO3- (12 kequiv..ha-1.year-1) was significant enough to offset the effects of acid precipitation. About 20% of the atmospheri c S input in both beech stands accumulated in the vegetation. The S in put-output balance in the acidic beech forest indicated a slight tende ncy towards S accumulation in the soil in the form of AlOHSO4. The S b udget in the calcareous beech forest stand was more or less balanced.