Long-term Response of Hemlock-Northern Hardwoods Forests
to Windthrow and Salvage Logging
Principal investigators: Lisa Schulte Moore, Iowa State University
Glenn R. Guntenspergen, United States Geological Survey
Katie (Derr) Lang, US Forest Service Northern Research Station
Key Partner: Wisconsin DNR Flambeau State Forest
Issue At Hand Windthrow is a common natural disturbance in many forest ecosystems. By removing trees from the overstory, windthrow changes the light and soil environments of the forest, creating sites for the establishment of new plants. Windthrow is sometimes followed by salvage logging, as landowners attempt to recover some of the value associated with the trees that were blown over. What We Hope to Accomplish We are quantifying the response of hemlock-northern forest to these disturbances. We expect forests to respond differently to windthrow alone than to the combination of windthrow and salvage logging. Under-standing this response will help foresters manage salvaged logged forests sustainably into the future.
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How We Go About It The Flambeau River Hemlock-Hardwood Scientific Area (Winter, WI) and nearby areas were struck by a severe thunderstorm on July 4, 1977. Winds associated with this storm reached 253 km/h and almost completely removed the forest overstory on the Flambeau. Some of the Flambeau was thereafter salvage logged. In 1979, a long-term study was initiated to assess the effects of windthrow and salvage logging on the Flambeau. Basic tree, sapling, shrub, and herb data were collected from sampling plots. These sites were resurveyed in 1990, 1999, and 2004. Soils and micro-topographic data were also collected in 2004.
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What We Are Finding Both salvaged and unsalvaged sites are regenerating into forests dominated by sugar maple, yellow birch, American basswood, and American elm. Eastern hemlock, which was common in the area prior to the storm, is not a component of the current forest. We are finding some differences between salvaged and unsalvaged forests. Unsalvaged forests have more biomass in canopy trees, but there are fewer tree saplings. The microtopography of the forest floor is more pronounced in unsalvaged versus salvaged forests. Patterns of understory herbs vary with disturbance type and microtopographic position.
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Funding for this work has been provided by USGS and Iowa State University. For more information, see the following publications, or contact Lisa Schulte Moore (lschulte@iastate.edu).
Lang, K.D., L.A. Schulte, and G.R. Guntenspergen. 2009. Forest dynamics in mesic northern hardwoods following windthrow and salvage logging. Forest Ecology and Management 259:56-64.
Derr, K.D. 2006. Forest Dynamics in mesic northern hardwoods following windthrow and salvage logging. M.S. thesis, Iowa State University, Ames, IA. (pdf)
Dunn, C.P., G.R. Guntenspergen, and J.R. Dorney. 1983. Catastrophic wind disturbance in an old-growth hemlock-hardwood forest, Wisconsin. Canadian Journal of Botany 61:211-217.
