Structural characteristics of old-growth, maturing, and partially cut northern hardwood forests

Live tree diameter distributions, and abundance and quality of standing and downed coarse woody debris (CWD), were compared among three northern hardw ood stand types in the Adirondack Mountains of New York, USA: old growth; p artially cut, uneven-aged with 40-50 cm maximum residual diameters; and mat uring, even-aged, 90-100 yr old, postfire. Downed CWD (stumps less than or equal to 1 m tall and logs) volumes in the old-growth, partially cut, and m aturing stands were 139, 69, and 61 m(3)/ha, respectively. Large (greater t han or equal to 50 cm diameter) CWD comprised 17%, 13%, and 4% of the total downed CWD volume in the old-growth, partially cut, and maturing stands re spectively. Approximately one-half the large CWD in the partially cut stand s was in the form of cut stumps. Standing CWD (stumps >1 m tall and standin g dead trees) basal areas averaged 8.6, 1.2, and 4.1 m(2)/ha in the old-gro wth, partially cut, and maturing stands, respectively. Basal area of large (greater than or equal to 50 cm diameter) standing CWD averaged 70%, 0%, an d 5% of the total in the old-growth, partially cut, and maturing stands. Bo th downed and standing CWD loads were influenced by mortality due to beech bark disease. Decay distributions of downed CWD were similar in all stand t ypes. The old-growth stands averaged 55 live trees greater than or equal to 50 cm dbh/ha, including 14 trees greater than or equal to 70 cm dbh/ha. Th e partially cut stands contained 5 trees greater than or equal to 50 cm dbh /ha, with none >55 cm dbh. The maturing, even-aged, stands averaged 1.3 ste ms greater than or equal to 50 cm dbh/ha in the postdisturbance cohort but also had similar to 8 postfire residuals/ha with diameters up to 70 cm dbh. Implementing forest ecosystem management guidelines to emulate the structur al characteristics of old-growth northern hardwoods should retain at least 16 live trees/ha greater than or equal to 50 cm dbh including 6 trees/ha gr eater than or equal to 70 cm dbh. Target levels for downed CWD volume would be less (perhaps 25% less) than the 139 m(3)/ha reported here, considering the influence of beech bark disease on the stands we studied. These goals can be accomplished by increasing diameter limits in selection systems, by extending even-aged rotations beyond 100 yr, and implementing "reserve shel terwood" cuts that retain large trees in regenerated, even-aged stands. Ret aining large trees will provide more future options to increase the proport ion of large standing and downed CWD in managed stands.