Issue At Hand

There is a growing recognition that intensive row crop agriculture as currently practiced in the Upper Midwest does little to sustain rural communities or environmental quality. One way that intensive agricultural landscapes might be improved is to establish perennial vegetation at key locations.

Although perennials are known to be beneficial, there is insufficient information about the type, quantity, and spatial arrangements of perennials to recommend optimal landscape designs. We are members of a team of scientists working to fill these information needs.

What We Hope to Accomplish

In an experiment conducted at Neal Smith National Wildlife Refuge in Prairie City, Iowa, we are assessing the benefits and costs associated with integrating perennial vegetation into annual rowcrops.

This experiment is conducted within multiple, small watersheds at the refuge. Studying multiple sites allows the experiment to be scientifically robust. Studying the integration of row crop production and perennial plants over watersheds will allow the results to be realistically applied to farming systems in the Midwest.

Some scientists are studying agricultural yield, water quality and quantity, and soil properties within these watersheds. This specific component assesses how biodiversity responds to strips of prairie vegetation positioned within corn and soybean fields.

How We Go About It

Biodiversity is important in agricultural landscapes because it can contribute to enhanced water quality, the suppression of insect pest and weed populations, and aesthetic and recreational opportunities.

We keep track of the abundance and diversity of plants, insects, and birds within each watershed. With greater amounts of perennial habitat, we anticipate greater number of species within a watershed.

Plants

Intact prairie communities can contain a rich diversity of plant species, but how many plant species can be found in patches and strips of reconstructed prairie interspersed with corn and soybean? How does the size of prairie patches and strips affect the density of plants species within them? How many years does it take for each species to appear after prairie reconstruction has been initiated?

To find answers to these questions, we conduct vegetation surveys in each of the 12 experimental watersheds. These surveys are conducted in late summer, when evidence of both cool season and warm season species can be found most readily.

Insects

The most diverse component of any ecosystem are the insect species found in the soil, on the plants, and flying throughout the refuge. This community changes with time of year requiring us to survey for them at multiple times of the growing season.

The perennial habitats can offer a refuge for beneficial insects that do not survive the frequent disturbances associated with row crop agriculture. In addition to monitoring overall insect biodiversity, we will measure the contribution of beneficial insects, like this hover fly larvae (left) that feed on pest like this aphid.

Birds

We measure bird response to the experimental treat-ments by surveying for individual birds and bird nests.

All of the 12 watersheds are walked and any bird seen or heard while censusing is tallied. These censuses are conducted in the early morning, eight times during the breeding season (May through early July). Surveys for bird nests are conducted every two weeks during the breeding season.

In both cases, we are especially interested in how birds are using the cropland and perennial habitat within the experimental watersheds.