Swamp Hardwoods
Swamp hardwoods occur in low areas with wet soils but are distinct from
floodplain hardwoods, which typically only occur in the lower 2/3rds of
the state. Black ash, red maple, and American elm typically dominate swamp
hardwoods, and commonly associated species include balsam poplar, bur
oak, and white birch. Swamp hardwood sites are typically characterized
by a seasonally fluctuating water table including occasional flooding.
The depth to the water table is one of the most critical factors affecting
the development of individual swamp hardwood stands, and that varies widely
from site to site. Better growth is achieved in swamp hardwood sites where
the water moves through the stand, but closed hardwood swamps are common.
Loss of a significant percentage of the overstory can cause a significant
rise in the local water table, which can seriously inhibit the establishment
of new tree seedlings, so an understanding of the local water table dynamics
is critical for successful management of these swamp hardwood forests.
For more details on the growth and characteristics of swamp hardwood stands,
see the USDA
Manual of Silvics.
Swamp hardwood stands can be managed for timber products. Black ash sawlogs are particularly valuable. However, consistently successful prescriptions for the regeneration of swamp hardwoods are not well developed because of the wide range of conditions across swamp hardwood sites. When attempting to manage swamp hardwoods for timber, make certain to work closely with an experienced professional forester. Timber management of swamp hardwood stands would typically involve thinning stands to maintain 80 percent crown occupancy by releasing the crowns of the best crop trees. Shelterwood silvicultural prescriptions can be used in some circumstances to regenerate swamp hardwoods, but the consistent reliability of this technique is not well established. Jim and Marlene Zdanovec have some lowland hardwoods on their woodlands in Marathon County. The Zdanovecs have not had an opportunity for a commercial harvest in their swamp hardwoods, but they have been doing some of their own non-commercial timber stand improvement thinning (the removal of some of the trees to promote the growth of the remaining trees) to promote the development of high quality trees and high quality wildlife habitat.
For more details on how to actively manage a swamp hardwood stand, see the DNR Silviculture and Forest Aesthetics Handbook.