Garden waste deposits as a source for non-native plants in mixed deciduous forests

摘要

Question: Is illegal garden waste dumping in mixed deciduous forests a source for establishment of non-native plants in deciduous forests?Location: Northwestern Switzerland.Methods: We quantified the amount of illegally dumped garden waste at 20 sites over 1 yr and compared the soil conditions, species richness and abundance of plants in the ground vegetation at disposal sites with those at 20 control sites in urban deciduous forests.Results: We found that illegal garden waste dumping frequently occurs in urban forests. At single sites, 0.1-12.5 m~3 (mean: 2.6 m~3) garden waste was dumped per month, resulting in a total annual amount of 2.2-35.8 m~3 (mean: 17.8 m~3) waste deposited.Thirty-seven of the 163 plant species recorded were not native to Switzerland. All 37 non-native species were recorded in waste disposal sites, but only three of them in control sites. Thus, garden waste dumping sites harboured a larger number of non-native species than control sites, but the two groups of sites did not differ in number of native species. The species composition also differed between disposal and control sites: larger proportions of species typical of disturbed habitats, more therophytes and species with autochorous seed dispersal were recorded in disposal sites than in control sites.Conclusions: We provide evidence that numerous non-native horticultural plant species escape from dumping sites and colonize forests. There is an urgent need to increase awareness of garden owners concerning problems associated with illegal garden wastedumping.