On the recovery of mountain birch afterEpirritadamage in Finnish Lapland, with a particular emphasis on reindeer grazing

:The effectiveness of recovery of mountain birch forests defoliated by Epirrita autumnata in 1965 in Inari Lapland, northern Finland, was studied by monitoring seedling and basal sprout formation in eight fenced areas and corresponding control plots, 400 m2 each. The number of seedlings and the abundance of basal sprouts were measured in 1973, 1979, 1982, 1987 and 1990/1991. The results indicate that tree recovery from seeds is in theory possible in the damaged birch forests almost everywhere in the study area, and that the changes occurring in the undergrowth after the damage may actually support the development of seedlings. However, in practice this process is disturbed by the adverse effect of reindeer grazing on seedling establisment. The formation of sprouts from dormant basal buds in damaged trees is not so greatly affected by reindeer grazing, but sprouting has been successful and the forest will totally recover only in a few areas where sprouting was abundant soon after the Epirrita damage. Sprout formation is disturbed by rot, which spreads from the dead mother tree into the sprouts, and recovery has been rather limited in most of the damaged areas. Tree density can be expected to decrease greatly in most of these areas.