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Timber management techniques benefit oaks, wildlife in southern Iowa forests

  • 3/5/2019 12:43:00 PM
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The tracks jumped out from the old, crusty snow - they were big - likely from a trophy - and some of the largest Jeff Glaw has seen.

“That’s a pretty good sized tom turkey that left these tracks,” said the long-time wildlife biologist with the Iowa Department of Natural Resources (DNR). Glaw was visiting the 780-acre Soap Creek Wildlife Area with district forester and co-worker Ray Lehn to check on an area that had its tree make up manipulated as part of their forest stewardship plan.

Lehn and Glaw have partnered on forest stewardship plans at Soap Creek and the Eldon wildlife areas, in northern Davis County, in an effort to perpetuate the oaks in the forest and encourage other mast producing species, like walnuts, hackberries and cherries.

Forest stewardship plans stretch long into the future and each one begins with inventorying what trees are currently on the area. Tree inventories are broken down by tree stands, which are simply natural breaks in the landscape, fences, ravines, or where the tree make up changes. At the Eldon area, its 800 acres of forest is broken into 88 individual stands. And the stands are prioritized.

Once the forest stewardship plan is written, approved and discussed at a public meeting, the work begins.

Most of the timber stand improvement is achieved by identifying mast producing trees, like oaks and walnuts, or other target trees and getting rid of the trees around it that are competing for sunlight. This technique is called crop tree release and the competing trees can either be felled or girdled. Girdling is a method where the tree is cut around but not completely through and although it’s dead, is allowed to remain standing to provide valuable habitat for woodpeckers and, later, for bats.

Lehn occasionally uses another technique called shelterwood harvest that removes the understory and mid story stems in combination with a partial harvest of overstory trees, leaving oak trees with the best genetic material in the timber to naturally regenerate. The purpose of shelterwood harvest is to put sunlight on the forest floor to promote oak seedlings becoming established in the understory. After about five years, the remaining overstory is removed to allow the young oaks to thrive.

Timber harvest is limited along rivers or roads and where threatened and endangered species may be found. Wildlife staff does some of this timber stand improvement work, but most is contracted to private forestry contractors who submit bids to purchase the timber.

Money from these projects is deposited into the Wildlife Forest Fund which is used to pay for some of the additional timber improvements. To date, nearly $110,000 has been invested to improve the forests at Soap Creek and Eldon wildlife areas with the majority of the cost paid by this fund. The National Wild Turkey Federation Super Fund and Wildlife Diversity habitat grants have also been used to help pay for timber improvements on both areas.

The stewardship plan identified fragmentation in the timber, like old farm fields, and calls for these areas to be planted with state nursery stock trees to connect the forests. Eliminating this fragmentation reduces the impact of cowbird parasitism on the nests of songbirds.

As an agency, the Iowa DNR has placed a priority for promoting oaks in the public timber because of the mast production benefits for wildlife and added benefits found on an oak floor versus the floor of a shade tolerant timber.

A forest with a healthy mast production will benefit acorn eaters, like deer, turkey, squirrels, woodpeckers and quail. A healthy oak timber is also attractive for resident and migrating neotropical birds.

The Eldon and Soap Creek wildlife areas are part of the Soap Creek-Stephens Forest Bird Conservation Area which has identified 256 bird species, including 88 listed as a species of greatest conservation need. It is also home to all nine Iowa bat species, including nursery colonies of the federally endangered Indiana bat. The wildlife diversity on these areas is extensive.

Private landowners can discuss forest stewardship plans by contacting their local district forester. There may be funding available to help offset the cost for doing the work.

While the forest stewardship plan is being carried out at the Eldon and Soap Creek wildlife areas, Lehn has turned his attention to mapping timber stands at the Selma and Van Buren wildlife areas in Van Buren County. The process of improving forests in southeast Iowa continues with new drafts, of new comprehensive forest stewardship plans, for new areas.

“Through these plans, we are doing what’s best for the timber and what’s best for the wildlife,” Lehn said.