Environmental Studies Program


Date of this Version

Spring 5-2014


Environmental Studies Undergraduate Student Thesis, University of Nebraska–Lincoln, 2015


Copyright © 2015 Amanda Hefner


In late July 2012, the Region 24 Complex fire consumed over 76, 000 acres of north central Nebraska. This area consists of ponderosa pine forest with high densities of eastern redcedar, deciduous hardwood forest, and Sandhills prairie. This incredible event provided an occasion to examine the effect of the fire on soil nitrification and soil erosion at The Nature Conservancy’s Niobrara Valley Preserve. Eighteen 900m2 plots were established in regions chosen for their topographic location (footslope, midslope, and ridgetop), forest density, and directional slope (north vs. south facing slope). Each plot was split into nine subplots with 25 erosion pins installed in the center subplot. These pins displayed soil activity per month. Soil samples were taken in all subplots, except in the center subplot where erosion pins were installed. Erosion data was highly variable, but a correlation was shown between tree density and soil activity. Each soil sample was comprised of three soil core samples (15cm) randomly selected in each subplot. Using KCl extraction, results showed that high nitrate and ammonia rates correlate with slope, soil pH, and tree density. The available soil nitrogen was shown to increase with basal area of eastern redcedar, indicating that ladder fuels like cedar add to the intensity of the fire and therefore the lasting impacts on the area’s resources. A mini-disk infiltrometer was used to test for soil hydraulic conductivity and hydrophobicity. The results indicated that further testing of the soil profile was needed to evaluate hydrophobicity, but soils within areas of higher densities of trees were indicating hydrophobic characteristics. Further research is needed to understand the complete relationship between the soil health and the wildfire, especially when it comes to eastern redcedar encroachment on these ecosystems.