Shedding some light

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By Molly McGovern

Have you ever taken a mid-summer walk though your favorite woodland and wondered why the soil was mostly bare? Or thought it was too bad that the beautiful display of forest wildflowers was limited to springtime? These characteristics of our woodlands are not natural. They are relatively new phenomena, coinciding with the cessation of fire in our woodlands approximately 150 years ago.

Iowa's natural landscape was once a great mosaic of prairie, savannas, wetlands, woodlands and forests. The mosaic was sculpted by fire and mediated by topography, soils, water, habits of Iowa fauna and other local factors. In drier years, fire would've permeated nearly every part of Iowa's landscape including our deepest woodlands. Carried primarily by cool season sedges, grasses and leaf litter, these fires were characteristically less intense than prairie fires. The effect was the periodic removal of fire-intolerant brush and young saplings. The product was an open, traversable landscape housing a diverse array of flowering plants from early spring to late fall.

For the last 150 years, fire has ceased to be a component in our woodlands and forests. The result is a dramatic increase in brush and fire intolerant trees. This condition allows enough light in the spring to produce an attractive assortment of spring wildflowers. Once the leaves of trees and shrubs have emerged, the atmosphere becomes choked of light. The summer and fall blooms of sunflowers, goldenrods, asters and others have now been relegated to the edges of our woodlands or eek out an existence along a path or other such opening. Oak regeneration has diminished in many of our woodlands due to oak species greater than average light requirements for germination and growth.

The lack of summer and fall ground cover has exposed our woodlands to intense erosion. Studies conducted at the Morton Arboretum in Chicago by Gerould Wilhelm suggest that not only does this lead to erosional ditches, but carried away with the soil are precious native plant seeds, perpetuating the degradation. Also contributing to woodland erosion and degradation is the invasion of many aggressive, non-native plant species such as garlic mustard, tartarian honeysuckle and common buckthorn.

When considering the health of our woodlands, it is best to remember that nature did not draw firebreaks between the prairie, savanna and more timbered areas of our state. The firebreaks were drawn by rivers, wetlands, rocks, bison trails, steep slopes and factors we can't begin to envision. Opening our woodlands and returning fire to the landscape is a step towards greater plant and animal biodiversity, soil retention and a step back onto the path of plant and animal evolution that have been occurring in Iowa's woodlands for the last 4000 years.

Molly McGovern is a botanist and prairie/savanna enthusiast. She and her family live on INHF's Snyder-Heritage Farm, where they witness daily progress on the site's 80-acre savanna restoration.

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