Assessment of vegetation performance on semicoke dumps of Kohtla-Järve oil shale industry, Estonia.

The performance of vegetation was assessed at semicoke dumping sites of Kohtla-Jarve oil shale industry in summers 2004 and 2006. The condition of tree species and the presence of herbaceous species were recorded in areas where the vegetation had been planted or had developed naturally. Betula pendula and Populus balsamifera were the most abundant tree species on the semicoke dumps covering 0.54 and 0.11 km 2 , respectively. Herbaceous vegetation had the highest coverage in stands dominated by Alnus glutinosa, but the species composition of herbs was homo- geneous under different tree species. Most of the herbaceous species were typical of wasteland areas (ruderal strategy type) or adapted to stressful conditions (stress-tolerant strategy type), including seven protected orchid species. The species composition of herbs was affected by the slope of the dump. Our results indicate that planting with Alnus glutinosa gives the best result for the reclamation of semicoke dumps as this tree species promotes the growth of herbaceous vegetation.