Nutrient Changes in Ozark Highland Soils Due to Forest Harvest Management.

The Missouri Ozark Forest Ecosystem Project (MOFEP) is a long-term experiment established to investigate forest management influence on a host of ecosystem components. Mixed hardwood systems at MOFEP are managed with even-aged (EAM), uneven-aged (UAM), and no harvest (NHM) management; all treatments are replicated in triplicate. Soils at MOFEP and elsewhere in the Ozark Highlands are dominated by highly weathered Ultisols and Alfisols. However, the effects of timber removal on soil nutrients in the three management systems have not been investigated. This study seeks to elucidate the effect of management practices on surface soil nutrient pools in particular soils present at MOFEP. Three soils were selected based on relative nutrient status as indicated by subsoil percent base saturation (% BS): low, less than 20 % BS; medium, 20 – 50 % BS; and high, greater than 50 % BS. In 2007, ten years after harvest, samples were collected in 10 cm increments from 0 to 30 cm in each treatment and soil using a paired sampling approach (i.e., samples were collected in treated and nearby non-treated locations). Treatments sampled were EAM clear cuts, UAM single tree removals and NHM sites. Samples were analyzed for a variety of soil chemical properties including pH, potentially mineralizable nitrogen, organic carbon content, and concentrations of base cations. Statistical analyses performed to date indicate that many of these parameters are significantly different (α=0.10) between EAM and UAM sites. Nutrient concentrations are consistently decreasing in UAM relative to EAM treated soils, particularly at the 0 – 10 cm depth. Disparity between the treated soils is attributed to differences in slash distribution within the treatments. Additional results from total soil nitrogen, water soluble nitrogen, and labile and stable nitrogen pools analyses will be presented.