Ecological gradients on the contact of xerothermic grassland and woodland in the Bohemian karst

The gradients of floristic composition and environmental factors (temperature, soil moisture, pH, light intensity) were followed on three transects delimited in the contact zone between woodland and xerothermic grassland on the NW. slope of the Velká hora Hill in the Bohemian Karst. The densities of the more frequent plants and corresponding values of environmental factors are presented in graph form. Three different ecotopes, e.g. woodland, thermophilous grassland, contact between woodland and grassland, could be traced. The values of temperature, soil moisture, light intensity grouped according to the three ecotopes show significant differences in the respective mean. Furthemore, the association between species has been calculated and thechi-square matrix for the 11 most frequent species is given. On the basis of these calculations, a diagram of assumed relations between species was constructed. On the ground of data obtained, a significant regression of the density of thermophilous herbaceous plants on the temperature of the soil surface was found. The type of gradient on this experimental site is discussed and noticeable step-like, discontinuous character of both the floristic and environmental gradient is shown.