CAVITY TREES AND COARSE WOODY DEBRIS IN OLD-GROWTH AND MANAGED NORTHERN HARDWOOD FORESTS IN WISCONSIN AND MICHIGAN

The effects of uneven-aged management on the availability of coarse wo ody debris habitat were examined in northern hardwood forests (with an d without a hemlock component) in north-central Wisconsin and adjacent western Upper Michigan. Snags, cavity trees, fallen wood, and recent tip-up mounds in 15 managed uneven-aged (selection) stands were compar ed with levels in 10 old-growth stands and six unmanaged even-aged sec ond-growth stands. Amounts of coarse woody debris in selection stands were generally intermediate between old-growth and even-aged stands. D ensity of snags >30 cm DBH in northern hardwood selection stands avera ged 12/ha, approximately double that found in even-aged northern hardw oods, but only 54% of the level in old-growth northern hardwoods. High est densities of snags >30 cm DBH occurred in old-growth hemlock-hardw ood stands, averaging over 40 snags/ha. For combined forest types, the volume of fallen wood (>10 cm in diameter) was significantly lower in selection stands (60 m(3)/ha) and even-aged stands (25 m(3)/ha) than in old-growth stands (99 m(3)/ha). Volume differences were even more p ronounced for large-diameter debris (>40 cm). Cavity tree density in s election stands averaged 11 trees/ha, 65% of the mean number in old-gr owth stands. Densities of snags (>30 cm DBH) and large-diameter cavity trees (>45 cm) present in selection stands exceeded current guideline s for wildlife tree retention on public forests.