EFFECT OF SOIL CHARACTERISTICS ON SUCCESSION IN SITES RECLAIMED AFTERACID-RAIN DEFORESTATION

Change in dominant species on sites reclaimed after the forest decline in the Krusne hory Mountains, Czech Republic. is explained by changes in soil characteristics. A 15-year course of succession was inferred from comparing sites of different ages. Succession was studied in two contrasting habitat types: (1) plots from which the vegetation cover w ith top soil and diaspores was completely removed in order to make rep lanting of spruce (Picea abies) saplings possible, and (2) mounds orig inating from accumulating the removed material. At the beginning of su ccession in the plots, Calamagrostis villosa was the main colonizer an d retained its dominance up to 5 years, after which it was gradually r eplaced by Deschampsia flexuosa. In contrast, revegetation from C. vil losa rhizomes occurred in mounds and no dominant species exchange was observed during the first 15 years of succession. Differences in conte nts of soil chemicals and in their trends over time were found between habitat types. Organic matter and nitrogen levels were higher in moun ds than in plots during the whole period of succession studied. Soil a cidity decreased in plots but increased in mounds. It appears that C. villosa is outcompeted from plots because of its high requirements for the organic matter content, a factor that was found to be the best pr edictor of trends in the species' successional behaviour. Occurrence o f D. flexuosa was correlated with soil acidity and calcium and potassi um contents.