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Many scientists and managers have an interest in describing the environment following a fire to understand the effects on soil productivity, vegetation growth, and wildlife habitat, but little research has focused on the scientific rationale for classifying the post-fire environment. We developed an empirically-grounded soil post-fire index (PFI) based on available science and ecological thresholds. Using over 50 literature sources, we identified a minimum of five broad categories of post-fire outcomes: (a) unburned, (b) abundant surface organic matter (>85% surface organic matter), (c) moderate amount of surface organic matter (≥40 through 85%), (d) small amounts of surface organic matter (<40%), and (e) absence of surface organic matter (no organic matter left). We then subdivided each broad category on the basis of post-fire mineral soil colors providing a more fine-tuned post-fire soil index. We related each PFI category to characteristics such as soil temperature and duration of heating during fire, and physical, chemical, and biological responses. Classifying or describing post-fire soil conditions consistently will improve interpretations of fire effects research and facilitate communication of potential responses or outcomes (e.g., erosion potential) from fires of varying severities. OPEN ACCESSForests 2012, 3 446

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.

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