Woody debris as a component of ecological diversity in thinned and unthinned northern hardwood forests

We examined the effects of management on coarse woody debris, both standing and downed, in thinned and unthinned northern hardwood forests in upper Michigan. The unthinned conditions included old growth and second growth, while the thinned conditions included both even- and uneven-aged management. The structural features analyzed were stem diameter, density, basal area, and height of snags and live trees, as well as volume, diameter, and decay state of downed woody debris (DWD). As measured by these features, the relative structural complexity among the forest conditions was generally old growth > uneven-aged > second growth ~ even-aged. Although snag density was highest in second-growth forests, old growth had the highest snag basal area. Old growth also had the largest volume of DWD, second growth and even-aged had the least, and uneven-aged had an intermediate value. Unlike old growth, other treatments lacked large diameter (> 40 cm) snags and DWD. If prescriptions are changed to allow for the creation of larger snags and DWD, particularly those > 60 cm in diameter, stands can be managed to more closely resemble these structural aspects of old-growth forests.