Restoration of broadleaved forest vegetation : early plant colonization in plantations on former fields

The purpose of this study was to evaluate the colonization patterns of forest herb layer species in newly established plantations on former arable fields. Among six stands surveyed the following hypotheses were tested: 1. Species richness is higher in new stands adjacent to older forest than in isolated ones 2. Oak stands provide better conditions for colonization than beech stands due to more suitable light conditions 3. Differences in migration rates are related to the diaspore dispersal mode of the plant species The maximum possible migration rates for the stands measured varied between 4.7 m year-1 and 69.9 m year-1. The maximum realized migration rates ranged from 0.37 to 66.0 m year-1 and the mean migration rates varied from 0.37 to 8.2 m year-1. These migration rates are consistently higher than the results presented in previous similar studies. The species richness was higher in adjacent stands compared to isolated stands and new oak stands contained more species than beech stands where only a few of the fast colonizers were found. The results showed that the migration of different forest herb layer species is influenced by the diaspore dispersal mode, special border characteristics between older forest and young plantations and the light conditions depending on the tree species planted. The fringe between the older stand and the new plantation should be long and without roads and open vegetation in order to enhance successful forest plant colonization. Concerning the ability of plants to colonize new stands soon after canopy closure, conditions are generally more favorable in oak stands than in beech stands, probably mainly due to differences in light availability