Bird Calendars

NOTES FROM NATURE

By Jerry Toll

Prescribed Burning—

It's a Natural for Prairie Management

Once again we experienced a hot dry summer here in eastern Nebraska, and once again there was quite a bit of media coverage on the forest fires in the west. Thankfully, no major fire was begun by a prescribed burn as happened last year.

The advantages of prescribed burning as a forest management tool was covered. However, we in the prairie states also benefit from prescribed burning when managing prairie remnants such as our own ASO Prairie Preserve (originally Jensen Prairie)

There are those idealists who think a hands-off approach is the best way to preserve a prairie, as in "let nature take its course."

This approach is appropriate when preserving large isolated intact ecosystems such as the Arctic National Wildlife Refuge.

However, if the wish is to simulate and try to recreate the biodiversity once found there, it will not work because a preserve surrounded by land used for economic purposes will continue to degrade. It must be managed by thoughtful land managers who have learned to work with nature.

Fire is a major influence that shaped the formation of the Great Plains. The Eastern Tall Grass Prairie is considered a derived grassland because tall grass prairies such as are found in our region can support woodlands.

It is thought that the burning of the prairie by Native Americans and the natural high incidence of lightning strikes in the region historically kept the Eastern Woodlands from encroaching into the prairie states.

There are two basic ways to manage prairies with fire, depending on the desired results. Ranchers use prescribed burning in the spring because they want to maintain grass production for grazing. Yearly spring burning favors the production of warm grasses like bluestem but is detrimental to the broadleaf flowering plants. This practice is used extensively in the Flint Hills region of Kansas.

Those managing for biodiversity use a mosaic approach in their burn regimen. They burn plots in different seasons. They burn less frequently, closer to a three-year cycle. They divide the managed area into plots so that not all plots are burned simultaneously, and they vary the burn application for each plot. This practice encourages biodiversity of native species for various reasons.

All native prairie plants are adapted to fire but respond differently. By changing the timing from season to season and year to year, no one group of plant types is favored over other types.

The insects and all other living things that inhabit the prairie can be maintained. Most biota in soils and on the surface is integral to the community and is a measure of its health. By providing unburned plots to serve as refuges, the community will recover when the plant habitat returns.

The biota in the soil is generally unaffected. Soil temperature changes little except in the top inch or so during a burn. A burn does increase the absorption of solar radiation until the plant community recovers. It also affects the absorption and evaporation of moisture in the soil. For these reasons, winter burns are not recommended because the soil surface will remain exposed for a long period.

The control of invasive nonnative plants is an important component of maintaining a diverse prairie. A flexible prescribed burn schedule enables the manager to target specific problems.

For example, a late spring burn when the non-native cool weather grasses are already green will set them back, allowing the warm-season grasses to compete when they begin to grow.

The seeds of most native plants are adapted to fire, but fire reduces the high production of seeds typical of invasive annuals.

Seasonal timing has an effect on what will be accomplished. A spring burn provides nutrients to warm season grasses and controls invasive annuals. A summer burn tends to retard both desirable warm and undesirable cool season grasses.

However, 80% of lightning strikes occur in June and July, so it is thought that perhaps the smaller, cooler, naturally occurring fires typical of summer reigned historically. This helps to explain the natural diversity of our prairie. Fall burns are good for controlling woody vegetation.

The effects of a prescribed burn cannot be generalized to other types of ecosystems. An eastern deciduous forest will respond differently from a western coniferous forest.

In fact, a prescribed burn in the Sandhills will respond differently from a burn at ASO's Prairie Preserve.

Different soil types, plant community, or annual rainfall are just a few of the variables that need to be considered.

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