Clear-cutting-based forest management facilitates plant invasions in Estonian hemiboreal forest landscapes
摘要
Land-use intensification generally facilitates non-native species invasion, but the mechanisms may be region-specific and often remain obscure in early stages of the invasions. We investigated the spread of three conspicuous non-native plants into 23 variably managed hemiboreal forest and mire landscapes in Estonia: eastern galega (Galega orientalis), large-leaved lupine (Lupinus polyphyllus), and Canadian goldenrod (Solidago canadensis). Their distribution varied across the studied landscapes but was generally sparse. The species were found only in open areas, young forests, or at linear anthropogenic elements. Correspondingly, we did not detect any of these species in undrained and unlogged landscapes. The area occupied by each species in a landscape increased primarily along with its prevalence in the surrounding zone (propagule pressure). Additional facilitative effects were a higher proportion of open areas and young forests (goldenrod) and the length of roads (galega; lupine). Interestingly, we found no significant effect of ditches located away from roads. Our findings indicate that clear-cutting-based forestry creates pathways for non-native plants in hemiboreal forests, though these invasions are in their early stages in Estonia, and their spread into older forests remains uncertain. Dense road networks pose a threat of plant invasion in forests on mineral soils, while intact peatlands apparently resisted the studied species. Forestry experiments and adaptive management could help develop region-specific silvicultural systems that better prevent invasive species establishment.