Resilience and Heterogeneity Following Fire in the Nebraska Sandhills

The Nebraska Sandhills grassland is an expansive, semi-arid ecosystem characterized by vegetation-stabilized rolling sand dunes. The Sandhills grassland is managed for livestock production by seeking to minimizing disturbances, such as fire, that increase bare ground. The increase in bare ground following fire has contributed to the fear of fire leading to the emergence of a mobile sand dune state. We tracked vegetation response following a growing season wildfire that occurred during extreme drought conditions. In wildfire and drought conditions are when one would expect resilience to be overcome leading to a lack of vegetation recovery and a transition to a mobile sand dune state. However, aboveground herbaceous biomass recovered to unburned levels after two years and resisted a transition to an undesirable plant community. Next, we assessed the potential for focal fire and grazing to create heterogeneity of grassland structure and composition in order to increase biodiversity. Using patch burning, discrete patches were burned annually and grazers were allowed to select between recently burned and unburned areas. We found the Sandhills grassland is spatially homogeneous in vegetation structure and composition with greater structural heterogeneity emerging temporally in the transition from growing to dormant season. However, temporal heterogeneity manifests as an artifact of how vegetation was classified. Although live herbaceous vegetation decreases in the transition to dormant season, grassland vegetation structure is only slightly affected because herbaceous standing dead vegetation increases as a result of herbaceous vegetation senescence. Advisors: Dirac Twidwell and Walter H. Schach