Comparison of an autumn biomass harvest with a spring prescribed burn in restored native grass fields

Wildlife managers use spring prescribed burns to set back succession in managed grasslands throughout the prairie pothole region. Yet, prescribed burns are expensive and weather dependent. Autumn biomass harvest of native prairie plants may also simulate natural disturbances and help prevent the invasion of woody species. As such, biomass harvest can be an attractive management option that can augment, and in some cases, replace spring burning programs. We compared vegetation characteristics (vegetation ht and density, and residual litter depth) and changes to the plant community (e.g., species richness, relative abundance of native and exotic plant species) in restored native grasslands of Minnesota, during 2007-2009, in response to spring prescribed burns and autumn biomass harvest. We used a randomized block design to control for site-to-site variability, and compared treatments using mixed models that accounted for this source of variation as well as within-plot repeated measures. This framework also allowed us to consider additional variables (e.g., Julian date, yr effects) thought to influence response patterns, and also additional fields that were treated with an autumn biomass harvest during the same time period. Vegetation characteristics exhibited substantial site-to-site and temporal variability, but, with the exception of litter depths, vegetation characteristics were largely similar in biomass harvest and burned subplots. We conclude that autumn biomass harvests deserve more consideration as a potential grassland management tool.