Document: DON-3-87-2

Modeling the ecological consequences of an alternative management regime for northern hardwoods.

BRAGG, D.C.* ¹, D.W.ROBERTS ² and T.R.CROW ¹

University of Michigan, Ann Arbor, MI 48109 USA ¹
Utah State University, Logan, UT USA ²

Abstract:
Managing-for-old-growth (MOG) characteristics has been proposed to meet ecosystem management objectives. Using the NORTHWDS model, we evaluated MOG as applied to second- growth, hardwood-dominated, even-aged stands of the Ottawa National Forest (Michigan, USA). A synthetic 225 ha stand was assembled from 50 - 70 yr old 0.09 hectare sugar maple-dominated stand elements and simulated (10 replicates per scenario) for 250 yr. Two traditional forest management regimes, clearcutting (CC) and uneven-aged selection (UA), were compared to MOG and an unmanaged control. Eight scenarios were considered: four harvest treatments (unmanaged, MOG, UA, and CC) at two deer browsing levels (high and low). MOG aboveground live tree biomass patterns were comparable to unmanaged old-growth, with both treatment types reaching or exceeding the ~ 250 Mg/ha threshold noted for similar old-growth northern hardwood stands. Long-term average tree species richness (~ 7.0) for MOG and UA treatments closely matched the unmanaged control, while clearcutting produced significantly higher richness (~ 7.5 - 8.0, depending on deer browsing intensity). The MOG scenario averaged 12 - 15 Mg/ha of coarse woody debris (CWD) biomass, which, while lower than the 15 - 24 Mg/ha average of unharvested conditions, exceeded the CWD stocks of both the UA and CC scenarios (7 - 11 Mg/ha and 3 - 7 Mg/ha, respectively). With the exception of tree species richness in clearcut scenarios, white-tailed deer browsing only minorly impacted the reported parameters. Although dominated by sugar maple, MOG stand structure and composition can emulate old-growth in some respects.

Keywords: NORTHWDS model, old-growth, northern hardwoods, management

This abstract is being presented at: 1:45 PM in session:
Oral Session #51: Disturbance Ecology: Harvesting, Grazing and Roads.