AUTHORS: Jane Capozzelli*, Masters Student; Dr. Jim Miller, Professor and Director of Graduate Studies – Department of Natural Resources and Environmental Sciences, University of Illinois Urbana-Champaign
ABSTRACT: Due to fire suppression and overgrazing, woody encroachment has emerged as the greatest contemporary source of habitat loss and degradation of grasslands in the region. One strategy that may reduce woody encroachment is the fire-grazing interaction, which has gained traction on large and small reserves because it restores ecosystem function by recoupling fire and grazing. To understand whether this practice reduces woody encroachment we surveyed the composition, abundance, and morphology of woody plants on 11 experimental pastures. We utilized a long-term experiment with three fire and grazing treatments (patch-burn-graze [n = 4], graze-and-burn [n = 4], and burn-only [n = 3]). Each pasture was divided into three patches. In the patch-burn-graze treatment, one patch was burned annually. Cattle had free access to the entire pasture, but preferentially grazed the most recently burned patch more intensively than the other patches. The graze-and-burn treatment had one pasture-wide burn every three years with free access for cattle. The burn-only treatment had one pasture-wide burn every three to five years and no grazing. We established 120 100-x-2-m belt transects (6 – 17 per pasture) and recorded the species, the number of stems, and the maximum height of every plant > 0.5 m tall. In 2017, we sampled 4983 plants of 37 species. The burn-only treatment had the highest abundance of woody plants, driven largely by sprawling patches of Rubus allegheniensis (Allegheny blackberry). Woody plants were slightly less abundant in the patch-burn-graze than in the graze-and-burn treatment. Based on plant morphology, we found that cattle consumed woody plants in the patch-burn-graze treatment, but avoided eating them in the graze-and-burn treatment. Grazing damage likely increases plants’ susceptibility to fire, which may maintain low densities of woody plants long-term.
