RECOVERY OF EVERGREEN CLONAL DWARF SHRUB VACCINIUM-VITIS-IDAEA AFTER SIMULATED MICROTINE HERBIVORY IN A BOREAL FOREST

The evergreen dwarf shrub lingonberry (Vaccinium vitis-idaea L.) was s ubjected to microtine herbivory simulations to investigate its recover y in a boreal forest. Beside the control (A), the study included three levels of herbivory: clipping of half the annual branches from 50% of ramets (B), removal of 50% of ramets (C), and removal of 100% of rame ts (D). Density, growth, and fecundity of the ramets were monitored du ring the study. New ramets emerged rapidly from dormant basal buds at the base of the removed ramets in groups C and D. After three growth s easons, 60-117% and 42-112% of density and biomass, respectively, had been regained in the groups damaged relative to the control, the diffe rence being insignificant between the treated groups apparently becaus e of the small sample size. Survival, fecundity and net growth of rame ts were not affected by the treatment. Mean dry weight of annual branc hes in new ramets was lower in the damaged groups than the control. Th e recovery of the lingonberry was unexpectedly good. The results sugge st that, since natural herbivory seldom is as heavy as in this work, t he time between population density peaks of microtine rodents is usual ly long enough for the lingonberry to recover in boreal ecosystems.