OutdoorNebraska

5 P rincipal investigator Dirac Twidwell and a team of research scientists from his lab including Victoria Donovan, Caleb Roberts, and Carissa Wonkka have been conducting studies in the Pine Ridge to address critical needs that the interagency Pine Ridge Conservation Planning Committee deemed most important for research and for improving conservation planning. Their research focuses on the impact of wildfire and invasive herbaceous and woody plants on the native plant community in the Pine Ridge. They found that the series of wildfires in ponderosa pine forests have collectively contributed to a dynamic, fire-driven community that varies in space with time since fire. Some large forest patches were severely burned and transitioned to a non-forest state, but many areas escaped damage from high severity fires and continued to persist. In burned ponderosa forest patches, unique herbaceous communities were maintained up to 27 years post fire, whereas community composition in burned and unburned grasslands were similar at all times since fire. The plant community composition in burned forests did not differ among high and low severity burned forests at all times since fire. Understory shrub communities, tree densities, and coarse woody debris were all strongly associated with differences in burn severity. Invasive species' abundances were highly variable, and no strong patterns were detected with regard to time since fire or vegetation categories. Cheatgrass was the most prominent invasive species and occurred across all surveyed areas. These findings, coupled with other results from the project, reveal that all wildfires over the last three decades exhibited patterns of severity and vegetation responses consistent with a mixed severity wildfire classification. The ecological impacts of wildfire in the Pine Ridge are of mixed severity, which differ from high severity wildfire impacts. The collective impact of wildfires from previous decades and the more recent wildfires have resulted in a series of unique community assemblages that change with time since fire and the fire severity that occurs in new wildfires. The implication is that wildfire is increasing landscape level biodiversity. ✔ By Dirac Twidwell, Assistant Professor, Rangeland Ecologist at UNL It is often assumed that the entire forest is severely burned and lost after wildfire. This is not the case in the Pine Ridge. Many areas persist after wildfire. Severely burned areas do occur but constitute the minority of the burned landscape Across the Pine Ridge, mixed severity fires have resulted in a mixture of vegetation transitional states across the landscape interspersed with areas of forest and grassland. MAPS BY TWIDWELL LAB Wildfire, Invasions, and the Trajectory of Plant Communities It is often assumed that the entire forest is severely burned and lost after wildfire F I R E S E V E R I T Y YEAR FIRE % SEVERELY BURNED 1989 Fort Robinson 28% 2000 Sawlog 2% 2006 Dawes 8% 2006 Sioux 35% 2007 Soldier Creek 20% 2012 Douthit 5% 2012 Wellnitz 17% 2012 West Ash 6%

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