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Forests and Streams

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Published on: Jun. 2, 2002

Last revision: Nov. 12, 2010

Wooded areas near streams or on the banks of streams are called riparian forests. They prevent erosion and trap sediment and runoff. They also cool water, provide underwater habitat and produce food for fish and wildlife. Eventually, the trees that are improving the health and quality of the waterway can be converted to useful wood products.

In rural Missouri, woody corridors often serve as buffers between cropland and pasture land and streams. In heavily forested areas, the border between riparian and upland forests is distinguished by a change in species and composition.

Riparian forests almost always occupy areas of moist, fertile soils. Streamside forests also tend to have larger trees with more dens and snags, and they are more likely to have a variety of tree heights. Typical riparian tree species include sycamore, cottonwood, bur oak, silver maple, ash, pecan and black walnut. Other common riparian plants include greenbriar, poison ivy, false rue anenome, stinging nettle and spicebush.

Historically, riparian forests protected most of the rivers and streams of the state. However, agricultural and urban development have reduced the amount of streambank that is now protected by trees, lowering water quality and reducing aquatic habitat.

When it rains, soil from unprotected areas washes into riparian areas. These areas are often referred to as creek and river bottoms. If there is nothing to slow or stop this soil, it will eventually end up in the stream itself. Too much sediment suspended in the water can reduce or block sunlight, which is necessary for the growth and reproduction of beneficial aquatic plants. Sediment on stream bottoms can disrupt the feeding and reproduction habits of fish and aquatic insects. Large sedimentary deposits can fill streams and increase the threat of flooding.

Riparian forests diminish the threat and effects of erosion and siltation. The protection begins with the tree canopy, which protects the soil from the hammering impact of rain. The leaf layer on the forest floor also protects the soil, and it acts as a sponge, soaking up water and slowing runoff from nearby fields and hills. Tree roots help prevent streambank erosion by holding soil in place.

Streamside forests also have a filtering effect. With slower runoff, more water soaks into the ground. Pesticides and fertilizers attached to soil particles aren't carried into the waterway. Filtering nitrogen and phosphorus is especially important because these can fuel excessive algal growth in the water, depleting

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