Vegetation and soil effects from prescribed, wild, and combined fire events along a ponderosa pine and grassland mosaic

We describe the efficacy of prescribed fires after two wildfires burned through and around these fires located in eastern Montana within the Missouri River Breaks. The objectives of the prescribed fires were to decrease tree density and favor increased herbaceous cover, thus decreasing the potential for crown fire. Our objective was to evaluate post-fire tree density, herbaceous cover, soil surface, and burn severity to determine if the prescribed fires fulfilled management objectives and if they affected post-wildfire outcomes. Because there is no information available on pre-fire conditions, we used a draft of the handbook Forest Descriptions and Photographs of Forested Areas Along the Breaks of the Missouri River in Eastern Montana (RMRS-GTR-186) of unburned sites as our frame of reference. We compared sites burned by prescribed fire alone, wildfire alone, and prescribed fire followed by wildfire to the unburned sites from the handbook. Statistical analysis showed no significance in tree density, herbaceous cover, and crown scorch, but we do report observed trends. Depending on the physiographic position, more trees survived in places burned by the combination of prescribed and wildfire than places burned only by the wildfire. The prescribed fires tended not to fulfill prescription objectives, particularly in tree density, until the second fire occurred. However, the wildfire tended to exceed prescription objectives because it killed too many trees. Compared to the unburned sites, all the fires tended to decrease litter and favor higher amounts of grass cover, thus fulfilling prescription objectives. Heterogeneity in vegetation characteristics such as canopy base height increased as a function of the combined fires. This CD describes detailed results and outcomes among the different fires and the unburned sites, and its accompanying photograph handbook provides examples of burned and unburned sites to use as a communication, calibration, and/or monitoring tool. Although the information is unique to a series of fires, the concepts and methods we used are applicable in other locales required to evaluate efficacy of fuel treatments.