Some background...

Strategically integrating small amounts of perennial vegetation (in our case, reconstructed prairie) within row-cropped watersheds offers the opportunity to enhance the health and diversity of Midwestern agricultural landscapes. This project will explore this hypothesis through an integrated watershed-scale approach that uses field experimentation, spatial models, and tradeoff assessments to quantify changes in ecological functioning and economic outputs resulting from different configurations of perennial and annual plants. Integral to the project is the effective communication of project results to catalyze further tests of this practice on the landscape.

Project Objectives

  1. Quantify the influence of different proportions and landscape configurations of annual (e.g., corn and soybean) and perennial (e.g., prairie, savanna, agroforestry) plant communities on the storage, cycling, and output of nutrients, water, and carbon at the field and catchment scale.
  2. Promote greater understanding among diverse groups of people (i.e., the public, policy makers, farmers, environmentalists, etc.) that agroecosystem production and environmental stewardship may be compatible if appropriate combinations and configurations of perennial and annual plants are established.

Hypotheses

  1. The placement of perennial plant communities at strategic locations and of appropriate spatial extent in a watershed will produce disproportionate improvements in ecosystem functioning (e.g., water, nutrient and carbon cycling) without compromising the social and economic viability of agroecosystems.
  2. Small increases in perennial plant cover in watersheds dominated by annual crops will result in disproportionately large increases in species richness and diversity of major taxa (plants, animals, insects, microbes).

Experimental Setup

The systems being studied include a range of percentage and placement of perennial vegetation as shown in Figure 1. The project is being conducted on fourteen small watersheds around the Neal Smith National Wildlife Refuge ranging in size from 1.2 acres to 13 acres.

Figure 1Figure 1. Conceptual design of watersheds.

Watersheds were initially brome grass, and the following treatments were established from Fall 2006 - Spring 2007:

  • Conventional Agriculture (CA): Two-year corn-soybean rotation, without tillage, and with standard herbicide- and fertilizer-based weed and nutrient management practices.
  • Mixed Annual-Perennial system (MAP): Patches and strips of perennial vegetation (native grasses and forbs) are incorporated into the conventional corn-soybean production system, using a combination of modeling and existing knowledge to predict the optimal watershed configuration.
  • Reconstructed Prairie (RP): Native grass and forb seeb (obtained from existing prairie plantings at or near Neal Smith) have been sown. Sites will be maintained by mowing for 2 years, followed by prescribed burning every 2-3 years.

We are measuring the responses of numerous variables, including:

  • Water cycling
  • Nutrient cycling
  • Carbon cycling
  • Biodiversity

Expected Outcomes

  • A demonstration site on the ecological functioning of alternative watershed designs establishe at NSNWR.
  • Quantitative data obtained from the experimental catchments on nutrient, water, and carbon cycling under different annual-perennial plant configurations.
  • Relationship between area of perennial cover and total plant species richness and diversity in agricultural landscapes.
  • Calibration and validation models for predicting watershed and plant community response to alternative agroecosystem designs.
  • Educational and outreach activities: field days oriented towards policy-makers, farmers, the public; a permanent project display at the Neal Smith Learning Center; and an extension brochure with complementary road markers at the site.
  • Network for research-policy linkages established to promote communication and information exchange between the research team and the public.

Figure 2. Aerial photos before and after treatment implementation.