No abstract

Live tree diameter distributions, and abundance and quality of standing and downed coarse woody debris (CWD), were compared among three northern hardwood stand types in the Adirondack Mountains of New York, USA: old growth; partially cut, unevenaged with 40-50 cm maximum residual diameters; and maturing, even-aged, 90-100 yr old, postfire. Downed CWD (stumps Յ1 m tall and logs) volumes in the old-growth, partially cut, and maturing stands were 139, 69, and 61 m 3 /ha, respectively. Large (Ն50 cm diameter) CWD comprised 17%, 13%, and 4% of the total downed CWD volume in the old-growth, partially cut, and maturing stands respectively. Approximately one-half the large CWD in the partially cut stands was in the form of cut stumps. Standing CWD (stumps Ͼ1 m tall and standing dead trees) basal areas averaged 8.6, 1.2, and 4.1 m 2 /ha in the old-growth, partially cut, and maturing stands, respectively. Basal area of large (Ն50 cm diameter) standing CWD averaged 70%, 0%, and 5% of the total in the old-growth, partially cut, and maturing stands. Both downed and standing CWD loads were influenced by mortality due to beech bark disease. Decay distributions of downed CWD were similar in all stand types. The old-growth stands averaged 55 live trees Ն50 cm dbh/ha, including 14 trees Ն70 cm dbh/ha. The partially cut stands contained 5 trees Ն50 cm dbh/ha, with none Ͼ55 cm dbh. The maturing, even-aged, stands averaged 1.3 stems Ն50 cm dbh/ha in the postdisturbance cohort but also had ϳ8 postfire residuals/ha with diameters up to 70 cm dbh.Implementing forest ecosystem management guidelines to emulate the structural characteristics of old-growth northern hardwoods should retain at least 16 live trees/ha Ն50 cm dbh including 6 trees/ha Ն70 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 shelterwood'' cuts that retain large trees in regenerated, even-aged stands. Retaining large trees will provide more future options to increase the proportion of large standing and downed CWD in managed stands.

Live tree diameter distributions, and abundance and quality of standing and downed coarse woody debris (CWD), were compared among three northern hardwood stand types in the Adirondack Mountains of New York, USA: old growth; partially cut, unevenaged with 40-50 cm maximum residual diameters; and maturing, even-aged, 90-100 yr old, postfire. Downed CWD (stumps Յ1 m tall and logs) volumes in the old-growth, partially cut, and maturing stands were 139, 69, and 61 m 3 /ha, respectively. Large (Ն50 cm diameter) CWD comprised 17%, 13%, and 4% of the total downed CWD volume in the old-growth, partially cut, and maturing stands respectively. Approximately one-half the large CWD in the partially cut stands was in the form of cut stumps. Standing CWD (stumps Ͼ1 m tall and standing dead trees) basal areas averaged 8.6, 1.2, and 4.1 m 2 /ha in the old-growth, partially cut, and maturing stands, respectively. Basal area of large (Ն50 cm diameter) standing CWD averaged 70%, 0%, and 5% of the total in the old-growth, partially cut, and maturing stands. Both downed and standing CWD loads were influenced by mortality due to beech bark disease. Decay distributions of downed CWD were similar in all stand types. The old-growth stands averaged 55 live trees Ն50 cm dbh/ha, including 14 trees Ն70 cm dbh/ha. The partially cut stands contained 5 trees Ն50 cm dbh/ha, with none Ͼ55 cm dbh. The maturing, even-aged, stands averaged 1.3 stems Ն50 cm dbh/ha in the postdisturbance cohort but also had ϳ8 postfire residuals/ha with diameters up to 70 cm dbh.Implementing forest ecosystem management guidelines to emulate the structural characteristics of old-growth northern hardwoods should retain at least 16 live trees/ha Ն50 cm dbh including 6 trees/ha Ն70 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 shelterwood'' cuts that retain large trees in regenerated, even-aged stands. Retaining large trees will provide more future options to increase the proportion of large standing and downed CWD in managed stands.