Shrub Wetland
Willow, red-osier dogwood, meadowsweet, and alder – often called “tag alder” – are some of the shrubs that grow in wet soils in Wisconsin. These shrubs are less than 20 feet tall and, when young, can be quite dense.
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combination of thick young shrubs as well as some older shrubs. When cutting in shrub wetlands, remember to keep a few trees to provide singing perches for golden-wings and other songbirds. The Wisconsin Young Forest Partnership can give more details on how to refresh shrub wetlands, plus inform landowners about programs to cover the cost of management.
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Two good places to see active alder management are Lake Tomahawk Demonstration Area in Oneida County and Ackley Demonstration Area in Langlade and Marathon Counties.
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Learn more about managing old farmland to help wildlife in Best Management Practices for Woodcock and Associated Bird Species. Also see Best Management Practices for Golden-winged Warbler Habitats in the Great Lakes Region, including the supplement Shrub Wetlands. A good general reference is A Landowner’s Guide to Woodland Wildlife Management.
Sun-loving trees like red maple, tamarack, balsam poplar, and aspen (popple) may add to the mix. At ground level grow plants such as bunchberry, ferns, sedges, Canada mayflower, blueberry, and cranberry. Shrub wetlands occur in the floodplains of rivers and streams (biologists refer to those areas as “riparian zones”) and in bogs, marshes, swamps, and swales.
People may find shrub wetlands inhospitable and sometimes even impassable, but wild creatures love them. Such habitats offer diverse food, in the form of shoots, stems, buds, fruits, seeds, and insects, in a dense setting where animals can evade predators and find shelter during storms or cold weather.
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A host of songbirds from alder flycatchers to golden-winged warblers breed in shrub wetlands. Ruffed grouse often hunker down there, and woodcock probe the damp soil to feed on earthworms and other invertebrates. Snowshoe hares lurk along the edges of thickets, and foxes and bobcats tour those margins in search of a meal. Many human hunters look for deer among the dense shrubs, especially when hunting pressure becomes intense.
Biologist inspects alder stand just on the verge of being too old. After mowing or shearing, shrubs will grow back thickly and offer prime habitat to young forest wildlife./C. Fergus
During winter, a machine shears an overmature alder stand at Ackley Habitat Demonstration Area, in Langlade and Marathon Counties, northern Wisconsin.
After shearing, this five-year-old alder stand in Marathon County offers excellent dense regrowth for wildlife from tiny songbirds to big buck deer./A. Roth
Shrubs may grow very slowly in damp soils. Some shrub wetlands may not need to be managed if they have many small openings grown up with herbaceous plants and sedge tussocks, or scattered patches or clumps of woody shrubs that don’t exist in large blocks, or if natural processes such as floods, fires, or beaver activities regularly set the vegetation back to a stage featuring thick and vigorous stem growth.
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Often, though, wetlands shrubs become overmature. When alder stands get too old, their stem density decreases substantially, and the ground beneath them becomes overgrown with grasses so that ground-dwelling birds like woodcock can’t move about and feed freely. An alder stand is usually too old to provide high-quality habitat when the shrubs’ limbs become thick and grow horizontally instead of vertically. Overmature alder stands should be cut back and allowed to regenerate. Alders sprout vigorously from their stumps when cut.
Alder can be regenerated by manual cutting with a chainsaw. An efficient way to refresh a large alder stand is to employ a tracked vehicle with a high-speed rotating head that chews the shrubs down. (It’s important to do such work in winter when the ground is frozen to avoid damaging the shrubs’ roots, digging deep ruts in the soil, and bogging down equipment.) Cutting can be designed in different patterns. One option is to cut a series of long strips along stream corridors, chewing down around 25 percent of the alder in the stand every five years. Another strategy is to cut individual patches within sprawling shrub swamps, also cutting about 25 percent of the alder every five years.
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Meandering cutting patterns that follow the topography while keeping shrub patches throughout an area will attract songbirds such as the golden-winged warbler. Running strips perpendicular to a stream will let woodcock find earthworm prey by shifting uphill or downhill, depending on the soil moisture content. These types of management patterns yield and perpetuate a
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