An Ecoregional Context for Forest Management on National Wildlife Refuges of the Upper Midwest, USA

Abstract

To facilitate forest planning and management on National Wildlife Refuges, we synthesized multiple data sources to describe land ownership patterns, land cover, landscape pattern, and changes in forest composition for four ecoregions and their associated refuges of the Upper Midwest. We related observed patterns to ecological processes important for forest conservation and restoration, with specific attention to refuge patterns of importance for forest landbirds of conservation priority. The large amount of public land within the ecoregions (31–80%) suggests that opportunities exist for coarse and meso-scale approaches to conserving and restoring ecological processes affecting the refuges, particularly historical fire regimes. Forests dominate both ecoregions and refuges, but refuge forest patches are generally larger and more aggregated than in associated ecoregions. Broadleaf taxa have increased in dominance in the ecoregions and displaced fire-dependent taxa such as pine (Pinus spp.) and other coniferous species; these changes in forest composition have likely also affected refuge forests. Despite compositional changes, larger forest patches on refuges suggests that they may provide better habitat for area-sensitive forest landbirds of mature, compositionally diverse forests than surrounding lands if management continues to promote increased patch size. We reason that although fine-scale research and monitoring for species of conservation priority is important, broad scale (ecoregional) assessments provide crucial context for effective forest and wildlife management in protected areas.

Appendices

Appendix 1: Tree taxa used in this study

 

Deciduous species	Coniferous species
American basswood (Tilia americana L.)	Balsam fir (Abies balsamea (L) Mill.)
American beech (Fagus grandifolia Ehrh.)	Eastern hemlock (Tsuga canadensis (L.) Carriere)
American hornbeam (Carpinus caroliniana Walter)	Jack pine (Pinus banksiana Lamb.)
Black ash (Fraxinus nigra Marsh.)	Red pine (P. resinosa Sol.)
Green ash (F. pennsylvanica Marsh.)	White pine (P. strobus L.)
White ash (F. americana L.)	Black spruce (Picea mariana Mill.)
Balsam poplar (Populus balsamifera Rehder)	White spruce (P. glauca (Moench) Voss)
Eastern cottonwood (P. deltoids Marsh.)	Tamarack (Larix laricina K. Koch)
Bigtooth aspen (P. grandidentata Michx.)	Northern white cedar (Thuja occidentalis L.)
Trembling aspen (P. tremuloides Michx.)
Paper birch (Betula papyrifera Marsh.)
Yellow birch (B. alleghaniensis Britt.)
Black cherry (Prunus serotina Ehrh.)
Choke cherry (P. virginiana L.)
Pin cherry (P. pensylvanica L.)
American elm (Ulmus americana L.)
Rock elm (U. thomasii Sarg.)
Slippery elm (U. rubra Mulh.)
Hop-hornbeam (Ostrya virginiana (Mill) K. Koch)
Mountain maple (Acer spictatum Lamb.)
Red maple (A. rubrum L.)
Silver maple (A. saccharinum L.)
Sugar maple (A. saccharum Marsh.)
Black oak (Quercus velutina Lamb.)
Bur oak (Q. macrocarpa Michx.)
Northern pin oak (Q. ellipsoidalis E.J. Hill)
Pin oak (Q. palustris Muenchh.)
Northern red oak (Q. rubra L.)
Swamp white oak (Q. bicolor Willd.)
White oak (Q. alba L.)
Butternut (Juglans cinerea L.)

Appendix 2. National Land Cover Data (NLCD 2001) class definitions for land covers found covering >10% of the area of refuges and ecoregions of study

Deciduous Forest: Areas dominated by trees generally >5 m tall, and >20% of total vegetation cover. More than 75% of the tree species shed foliage simultaneously in response to seasonal change.

Evergreen Forest: Areas dominated by trees generally >5 m tall, and >20% of total vegetation cover. More than 75% of the tree species maintain their leaves all year. Canopy is never without green foliage.

Woody Wetlands; Areas where forest or shrubland vegetation accounts for >20% of vegetative cover and the soil or substrate is periodically saturated with or covered with water.

Shrub-Scrub: Areas dominated by shrubs; >5 m tall with shrub canopy typically >20% of total vegetation. This class includes true shrubs, young trees in an early successional stage or trees stunted from environmental conditions.

Herbaceous: Areas dominated by herbaceous vegetation, generally >80% of total vegetation. These areas are not subject to intensive management such as tilling, but can be utilized for grazing.

Emergent Herbaceous Wetlands: Areas where perennial herbaceous vegetation accounts for >80% of vegetative cover and the soil or substrate is periodically saturated with or covered with water.

Open Water: Areas of open water, generally with <25% cover of vegetation or soil.