THE EFFECT AND EXTENT OF HEAVY GRAZING BY REINDEER IN OLIGOTROPHIC PINE HEATHS IN NORTHEASTERN FENNOSCANDIA

Thirty and fifty years old exclosures established in northeastern Fenn oscandia in lichen-rich oligotrophic pine Pinus sylvestris forests on podzolised soil were used to study the effect of reindeer grazing on p ine fine roots, microbial activity, and on bryophyte, dwarf shrub and lichen biomasses. There were significantly less lichens, especially Cl adina stellaris, at grazed than at ungrazed sites. Coverage of other l ichens like C. arbuscula and C. rangiferina and bryophytes, especially Dicranum spp., benefitted from grazing. The biomass of vascular plant s, mainly Calluna vulgaris, Empetrum nigrum and Vaccinium vitis-idaea, was reduced at grazed sites, although their coverage was not influenc ed. Microbial activity was significantly lower at grazed sites. The in fluence of grazing is most obviously mediated by reduced soil moisture during dry periods at grazed sites. Fine root parameters (per soil an d stem volumes) were lower at grazed sites (pPCA = 0.072), the first p rincipal component consisting of a number of fine root tips, length an d weight. Grazing decreased all exchangeable nutrients by 30-60% in or ganic layer. Based on PCA the decrease was significant for exchangeabl e nutrients, although of individual elements only P and S showed stati stically significant difference. The extent of heavy grazing in northe astern Fennoscandia coniferous forest was revealed by remote sensing. It revealed extensive area in which reindeer lichens are reduced in no rtheastern Finland. The Finnish-Russian border can be clearly distingu ished in the satellite image composite.