Diversity and Nitrogen Experiment (DIVN)
The purpose of the DIVN experiment is to examine the relationships between functional diversity and nitrogen fertilization on the productivity and phenology of prairies. The four broadly defined functional groups in prairies are warm-season (C4) grasses, cool-season (C3) grasses, legumes, and forbs. Warm-season grasses are often the dominant grasses in prairies and include big bluestem, switchgrass, and Indiangrass. Warm-season grasses often become dominant later in the growing season - during the hot and dry parts of the summer. Cool-season grasses in prairies begin growing earlier in the growing season than warm-season grasses. Legumes are plants that have mutualistic relationships with nitrogen-fixing bacteria and can add limiting nitrogen to prairie systems. Forbs are broad-leaved plants flowering plants. In the DIVN experiment, we include warm-season grasses, cool-season grasses, and legumes. We examine whether functional diversity can be used to increase resource use complementarity in prairie systems thereby increasing aboveground productivity and whether nitrogen fertilization affects these relationships. A corn treatment is also included in the DIVN experiment in order to compare these prairie systems to our current status quo in biofuel feedstocks.
The first image is of the functional diversity treatments in the DIVN experiment. There are three species plants in each functional group. The three species of cool-season grasses are Canada wildrye, slender wheatgrass, and prairie brome. The three species of warm-season grasses are big bluestem, switchgrass, and Indiangrass. The three species of legumes are Illinois bundleflower, showy ticktrefoil, and round headed bushclover. The mixtures contain all nine species.
The DIVN experiment was located at the Bruner Farm in Boone County, IA. We started the DIVN experiment in the field in May 2008 using prairie seedlings that had been grown in a greenhouse. By October 2008 the prairie plants were nearly full size. This experiment continued through November 2010.
Peer-reviewed articles from the DIVN experiment: