IMPACT OF GRAZING AND NEIGHBOR REMOVAL ON A HEATH PLANT COMMUNITY TRANSPLANTED ONTO A SNOWBED SITE, NW FINNISH LAPLAND

A transplant experiment was carried out to test hypotheses on forces o rganizing plant communities in a mountain snowbed. Particularly the ro les of competition and grazing, as determinants of snowbed vegetation composition were examined. Blocks of heath vegetation dominated by Vac cinium myrtillus, a deciduous-evergreen dwarf shrub, were transplanted into a snowbed site near the altitudinal distribution limit of V. myr tillus. Experimental treatments on the snowbed included grazer exclosu res and neighbour removal. V. myrtillus declined in the snowbed as com pared to controls during seven growing seasons. Removal of competing p lants did not have significant effect on the projected plant area of V . myrtillus. Grazing tended to reduce the area of V. myrtillus with ca 40% when compared to exclosures. In contrast to V. myrtillus, gramino ids, such as Deschampsia flexuosa, increased in the snowbed, presumabl y due to increased moisture from melting snow. A tall herb (Solidago v irgaurea), virtually absent initially, started to increase within excl osures but not in unfenced plots. It cannot be ruled out that in the l ong term, tall, broad-leaved herbs can assume dominance on moderate sn owbeds in the absence of grazing. The results suggest that the harsh s nowbed environment is a major cause for the decline of V. myrtillus. a nd grazing may promote this decline. This is partially compatible with Grime's CSR hypothesis, but supports also the prediction of the explo itation ecosystems hypothesis that grazing limits potentially competit ive species, and release from grazing leads to their increase.