EFFECT OF HABITAT AND TIME OF CLIPPING ON THE RECOVERY OF THE BILBERRY (VACCINIUM-MYRTILLUS)

The growth of the bilberry (Vaccinium myrtillus L.) was investigated i n two boreal forest types (moderately dry pine heath forest, EM, and m esic spruce heath forest, HM) after being clipped at ground level in J uly, August or September 1985. The treatments simulated herbivory dama ge caused by small rodents. The emergence and growth of new ramets was monitored for five growing seasons. Regrowth during the same season o ccurred after clipping in July, but the survival of these ramets was l ow, especially in the HM forest. The two later clipping times prevente d current-year regrowth, but allowed new shoots to emerge in the follo wing years. Calculated as a percentage of the original value, the biom ass that had accumulated by 1989 was greater in the HM forest than in the EM forest. In the EM forest, the density and the biomass reached t he control level in the plots clipped in July, growth decreasing as th e time of clipping became later. In the HM forest, the control level w as reached in the plots clipped in August and September. No clear patt ern of ramet growth was observed to be caused by the different treatme nts. Ramet size was slightly reduced in the plots clipped in September in the HM forest, possibly owing to the great density. The ramets wer e smaller in the EM forest, but the percentage ratio of leaf biomass t o total biomass was somewhat greater than in the HM forest. The result s suggested that the ability of the bilberry to recover completely fro m severe herbivory between the years of peak rodent populations depend s both on the timing of the damage and on the growing site.