Forest planting as a way of species dispersal

Abstract

Fortuitous introductions of plant species with forestry planting material used in areas deforested by air pollution were studied in the Krušné hory Mountains, Czech Republic. The number and abundance of species of higher plants accompanying spruce saplings were recorded at three stages of the afforestation process: (1) before planting; (2) after planting; (3) after the first growing season. The reduction in the number of species and individuals during these stages of afforestation process was monitored. In total, 39 species were brought into the site with pre-grown saplings and 14 (36%) became successfully established; the corresponding figures for the total number of individuals were 524 (i.e. 1.024 per sapling) and 56 (i.e. 10.7% of the original number), respectively. In terms of the number of species, the planting procedure itself accounted for 72% of total losses, whereas the remaining 28% died during the first year of growth on the site. In terms of the mortality of individuals, the corresponding figures were 90% and 10%. Annuals were reduced to a greater extent than perennials. Epilobium adenocaulon and Betula pendula were the most successful species in terms of the size of established population. Eight species previously not reported from the area under study were found accompanying the transported saplings. The importance of introductions for the ruderalisation of forest sites is discussed. Considering the extent (millions of saplings being planted each year) and duration (two centuries in Europe) of afforestation efforts, it is suggested that this form of dispersal has caused an important enrichment to the local flora.