Understorey vegetation along a heavy-metal pollution gradient in SW Finland

Understorey vegetation of Scots pine forests was studied along a 8-km trans ect running SE from a Cu-Ni smelter at Harjavalta, SW Finland. Long-term ac cumulation of heavy metals and sulphur in the forest ecosystem has drastica lly changed plant communities. Vegetation was almost absent up to a distanc e of 0.5 km from the smelter. The total coverage and the number of plant sp ecies increased with increasing distance from the smelter. Ordination by gl obal non-metric multidimensional scaling (GNMDS) indicated that the florist ic composition was differentiated in response to the pollution level. The m ain compositional gradient of GNMDS was correlated with the heavy metal con centrations in the organic soil layer and with the size of the overstorey t rees. Vascular plants were more pollution-resistant than ground lichens, wh ereas mosses were the most sensitive plant group. In addition to heavy meta ls, nutrient imbalances and the considerably reduced water-holding capacity of the surface soil also restrict plant recolonisation on the degraded sit es. (C) 2001 Elsevier Science Ltd. All rights reserved.