EFFECTS OF WOODLOT ISOLATION ON THE DISPERSION OF PLANTS WITH FLESHY FRUITS

By relating species presence, number and density to the perimeter and isolation of small (0.1 - 2.75 ha) homogeneous woodlots (n = 43), indications were obtained that some fleshy-fruited species are negatively affected by woodlot isolation. The number of fruit-bearing herbaceous perennial species increased with woodlot area, probably because of the increasing heterogeneity of the herb layer. The density of individuals of the investigated species were negatively correlated to woodlot area. There were also some indications that the presence/absence of species was related to the length of the forest edge (e.g. Hedera helix). Because woodlot area and shape index were strongly correlated, the effects of increased forest area and forest edge were hard to separate. The probability of occurrence of Lonicera periclymenum and the density of IIex aquifolium decreased with an increasing degree of isolation of present forest islands. The chance of occurrence of L. periclymenum decreased also with the degree of isolation in the past, measured from topographical maps of about 60 yr ago. The total area of broad-leaved forest within a radius of 500 m, as well as the distance to the nearest connecting landscape element, seem to be good indicators of woodlot isolation.