EFFECTS OF IRRIGATION AND FERTILIZATION ON THE GROUND VEGETATION IN A 130-YEAR-OLD STAND OF SCOTS PINE

Seven years of irrigation and liquid fertilization brought about drastic changes in the vegetation of the field layer (vascular plants) and bottom layer (lichens and mosses) in a mature pine-heath community. Forty new vascular plant species became established. The five most abundant new species had abundant seed sources in the vicinity of the experimental area and were species with effective seed dispersal and (or) a persistent seed bank. Many of the new species, however, dispersed long distances to colonize the experimental area. Wind was the dominant dispersal mechanism among the species that established early, whereas most of the species that established during the later part of the study period had no obvious adaptation for wind or animal dispersal. Two new species with rapid vegetative spread and tall stature, Rubus idaeus L. and Epilobium angustifolium L., dominated the field layer at the end of the study period. Of the original field layer species, Calluna vulgaris (L.) Hull decreased, while the other two dwarf shrubs, Vaccinium myrtillus L. and Vaccinium vitis-idaea L., remained largely constant. The bottom layer as a whole decreased. All reindeer lichens (Cladina spp.) disappeared, and the dominant moss, Pleurozium schreberi (Brid.) Mitt., decreased markedly. Some new litter-growing moss species became established.