Ten Years of Change in Beech Stand in North Central Maine Long Affected with Beech Bark Disease

In Maine, northern hardwood stands long affected by beech bark disease often still have high numbers of beech trees. This is mostly due to sprouting, and most new stems become severely infected with the disease. Beech that are resistant to the scale insect, Cryptococcus fagisuga Lind., the inciting factor for the disease complex, do exist and often occur in clumps of root sprout origin. In 1989 a long-term study of the effects of commonly used seasonal harvesting regimes on regeneration initiation and survival was established in north central Maine. Treatments included harvest season (winter or summer) and intensity (clearcut or partial cut). Resistant trees were paired with nearby susceptible trees that were of similar height and diameter, and then the trees were randomly chosen as a pair to be cut or left standing. The numbers of seedlings and sprouts that occurred in 174 15-foot radius plots around these study trees were counted annually fiom 1992- 1994. The annual growth of over 3 100 sprouts and seedlings were monitored. Initial results showed that the season of harvest, degree of overstory removal, and the cutting or leaving of trees had no effect on the numbers of sprouts initiated as a result of harvesting. In the summer of 2002, the original plots were re-established to determine sprout mortality associated with seasonal harvesting regimes. Out of the 174 original study trees, 172 were located, and the total number of sprouts and seedlings that occurred within the plots were recorded. Height and diameter measurements were taken on the monitored sprouts, seedlings within each plot. Summer harvests, and clearcut treatments, resulted in the highest regeneration mortality; 71% mortality in the summer harvests and 69% mortality in the clearcuts. By 2002, resistant study trees that originally were left after harvest had 67% mortality in winter clearcuts and 78% mortality in summer clearcuts, suffering no mortality in any of the partial cut or uncut stands. This demonstrates the importance of protecting resistant trees with uncut islands to insure their survival. Understanding the consequences of seasonal harvesting practices on root disturbance and resistant trees may hold the key to improving the quality of beech in stands affected with beech bark disease