Description

Pyric-herbivory is a process that is widely assumed to create greater habitat heterogeneity in grasslands at the land- scape scale than could be achieved by either fire or grazing alone. Yet, few studies have actually quantified the effects of pyric- herbivory on vegetation structure within layers of the grass canopy. Here we quantify the effects of pyric-herbivory on a pasture at Tallgrass Prairie National Preserve in Kansas. We subdivided the pasture into three patches and burned one patch each year in a three-year rotation. We estimated visual obstruction for 25-cm strata and recorded maximum vegetation height. We found that recently burned patches exhibited less visual obstruction in comparison to patches burned 13 and 25 months prior, creating heterogeneity at the landscape scale, and we noted that structure recovered at half the length of the fire return interval. We did not observe an intermediate vegetation structure (consisting of an open understory with a canopy cover), which pyric-herbivory has been hypothesized to create. We found almost no differences among years, indicating that pyric-herbivory operated similarly within the observed range of precipitation, topography, fire intensity, and stocking rate. Despite these consistencies, the effects of pyric-herbivory on vegetation structure may vary with different stocking levels.