Location, Location, Location

Scientists, including those at the National Agroforestry Center (NAC) in Lincoln, NE, are studying the effects different land management and conservation practices have on the delivery of nonpoint-source contaminants into streams and lakes. From this research have come best management practices, conservation practice design specifications, policy changes, and incentive program guidelines. State and Federal programs target conservation practices near streams and lakes to intercept sediment and water runoff from agricultural fields. These practices, commonly called riparian buffers, involve establishing vegetation, sometimes rows of fast-growing trees, to serve as living water filters. These and other buffer practices have been key elements in U.S. Department of Agriculture programs and initiatives for nearly 20 years.

So why don't we just install vegetative buffers along every stream and lake in the United States as a matter of course? First of all, the necessary money and resources just aren't available for an undertaking that large. Secondly, results are inconclusive as to whether 100 percent buffering of streams will provide 100 percent pollution control, though research shows that even installing some buffers can significantly improve water quality. Perhaps the answer lies in locating and designing the buffers to be as efficient as possible.

Not All Buffers Should Be Created Equal

To find out how to get the biggest bang for the buffer buck, NAC scientists in Lincoln, NE, get down to the basics, looking at how tree-based buffers work, how to design them for greatest effect, and where to place them on the landscape.

NAC riparian ecologist Mike Dosskey researches the mechanisms that allow grass and tree buffers to filter runoff from crop fields. "Much of the filtering effect is a result of plant material aboveground slowing down the surface water runoff, " says Dosskey. "This gives water more time to soak into the soil. Sediments, often with chemicals and nutrients attached to them, are then deposited within the vegetation. The longer that runoff water stays in the buffer, the more likely contaminants are to get taken up into the plants instead of rushing directly into the stream or lake or down into the ground water."

The typical buffer is a uniformwidth strip of grass, trees, or shrubs between a field and stream. This works well if the water is flowing off the field in a uniform sheet, but that rarely happens. Usually the runoff entering the buffer is more concentrated in some areas and almost nonexistent in others. In the areas where it is concentrated, runoff can overwhelm the buffer, which ends up providing little benefit to the stream.

In other words, not all buffers are created equal. The NAC technology transfer staff is working with Dosskey to develop guidelines to help conservationists design variable-width buffers to improve buffer function as part of larger, landscape-level efforts. "Riparian buffers are only a part of the water-quality solution," says Dosskey. "To be most effective, they need to be part of a comprehensive plan that includes upland conservation practices as well."

More Bang For the Buck

Water quality isn't the only bang we can get from the buffer buck investment. Incorporating Working Trees into agricultural landscapes produces many environmental benefits such as more diverse wildlife habitat, carbon storage, odor moderation, and soil erosion reduction. There are also other potential benefits for the landowner such as aesthetics, income from alternative crops and products, protection of roads from drifting snow, recreational opportunities, and energy conservation.

NAC researchers Gary Bentrup and Todd Kellerman are working with Dosskey to develop a suite of planning tools which natural resource professionals can use to create buffer designs that provide more than just water-quality benefits. Limited funding for conservation means that practices that offer landowners more than just one benefit will be more widely supported and adopted. But it can get very complicated very quickly. "We all want conservation buffers to simultaneously provide multiple benefits like clean water, wildlife habitat, and maybe some additional income. However, some desirable benefits require designs that are mutually exclusive," says Bentrup, a research landscape planner.

Imagine the amount of information it would take to run a buffer design software program that could work through all the possibilities to determine the plant species, appropriate spacing, and location of practices to achieve all the potential benefits listed earlier. Even if all of the information existed and was easily accessible, the program would require extensive technical information from the land manager about field conditions and landowner objectives- and would probably take forever to run.

Instead of creating one interface or software program, NAC has chosen to create a coordinated, but independent collection of tools to approach issues at the regional, landscape, and site scales. These independent tools are still usable even if someone wants to examine only one aspect of installing a conservation practice. However, if someone wants to look at the potential for other benefits or try to understand conservation issues at a different scale, other tools are also available.

NAC's goal is to provide more than just the information; the goal is to create tools that people will use. To increase the usability of these tools, the scientists use input from natural resource professionals, land use planners, and landowners throughout the research development phases. This input ensures that the new tools are addressing real problems in practical ways.

For more information:
Richard Straight at 402-437-5178 x24
or rstraight@fs.fed.us.

Richard Straight, an agroforester with the National Agroforestry Center, is based in Lincoln, NE.