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Weighing grazing, riparian area exclosures

By Doug Warnock

For the Capital Press

Grazing expert Doug Warnock discusses "exclosures" to keep livestock away from water.

Fencing to exclude livestock is often recommended for the protection of riparian areas. Total exclusion of grazing in riparian areas is not as desirable as properly managed grazing in them.

“There is an abundance of research on what constitutes an effective filter (protective) strip and the common denominators are high stem density, vigorous roots and no bare soil,” reports Tip Hudson, Washington State University Extension regional rangeland and livestock specialist.

“We have known for centuries that periodic plant tissue removal, as from grazing, stimulates the formulation of new stems, thus increasing the stem density of grass plants. Moderate removal of plant tissue stimulates plant growth, while leaving adequate material to protect the soil and absorb moisture,” Hudson said.

When stem removal is done by mechanical means, a heavy thatch is left. This thatch can result in the growth of bacteria. Moderate removal of plant tissue from periodic, short-term grazing has the effect of depositing nutrients and organic matter, which invigorates the plants, stimulating growth and development. A stand of dense and vigorous perennial grasses provides a stabilizing effect for the soil, resulting in better water quality.

Livestock, when improperly managed, have the potential to negatively impact riparian areas. When there is excessive removal of plant tissue, the soil surface is exposed and precipitation is not retained at the point of contact, but can move across the soil surface. Erosion leads to siltation and lowered water quality.

Certainly, establishing closed riparian areas removes the possibility of the direct depositing of livestock manure into streams, but it also eliminates the many beneficial aspects of well managed grazing in those areas.

Ungrazed, fenced areas can provide a place for noxious weeds to develop and cause problems for wildlife movement, limiting their access to streams. Rather than limit the use of a potentially effective management tool, like grazing animals, it is more appropriate to allow the use of it and other tools that can help create the desired landscape.

The health and vigor of the plant population in a riparian zone should be the object of the management plan and the manager should develop and implement the plan, while monitoring for results. When monitoring suggests changes need to be made to ensure the well-being of the plants, the manager should respond and adapt accordingly.

Prescription-type, inflexible approaches are restrictive and don’t allow managers the adaptability that can be so effective when dealing with the complex biological ecosystems that we have in riparian areas. Adaptive management, which includes continuous monitoring and adjusting as needed, is the most practical and successful approach to enhancing riparian area health and high water quality.

Doug Warnock, retired from Washington State University Extension, lives in the Touchet River Valley where he consults and writes on grazing management. He can be contacted at dwarnockgreenerpastures@gmail.com.



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