Impoverishment of vegetation in a coniferous forest polluted by copper and zinc

Abstract

Copper and Zn concentrations in raw humus were elevated > 400 and > 80 times, respectively, near an old and a new foundry emitting Cu and Zn but virtually no SO2. Effects on the vegetation were most evident in the ground layer. Four response stages were recognized. (i) Common mosses of mature coniferous forest (Pleurozium schreberi, Hylocomium splendens, Ptilium crista-castrensis, Dicranum polysetum) began to decrease in cover where the Cu and Zn levels in the tissues were 3–5 and 2 times those measured at remote sites, respectively, (ii) Lichens typical of mature dry forest communities (Cladonia subgen. Cladina and C. uncialis) were reduced in cover. (iii) Pioneers typical of successional communities (especially Cladonia subgen. Cladonia) increased slightly in cover, while tolerant mosses retained their cover, (iv) Even the tolerant mosses and lichens disappeared, except for Pohlia nutans. The occurrence of epiphytic lichens decreased. Hypogymnia physodes suffered a reduction in cover and thallus size. The grass Deschampsia flexuosa tended to increase somewhat towards the foundries, but the other field-layer species were unaffected. However, much dead Deschampsia flexuosa has been observed recently close to the new foundry. Environmental variables modified the response of the vegetation to the pollution. Deterioration of the ground layer makes the polluted, thin soil prone to erosion.