Ten-year results from the North American long-term soil productivity study in the Western Gulf Coastal Plain

Forest management operations have the greatest potential to reduce soil productivity through altered soil fertility and air/water balance, which are most affected by organic matter removal and compaction, respectively. The objectives of this study were to assess the early growth response to compaction, organic matter removal, and weed control on the ten locations of the Long-Term Soil Productivity study on the Kisatchie, DeSoto, and Davy Crockett National Forests (Louisiana, Mississippi, and Texas). Three levels of compaction (none, moderate, severe) and three levels of organic matter removal (stem only, whole tree, and whole tree plus forest floor) were applied in a factorial design at each site, and half of each treatment plot was kept free from interspecies competition with herbicides. Soil compaction had no negative impacts on tree growth at ten years; most sites responded positively to compaction due to the reduction of shrub understory competition. Removing more organic matter than the stems reduced stand volume on eight of the ten sites by more than 15 percent. This study indicates that harvesting operations that remove tree branches and foliage, and site preparation operations that remove the forest floor, such as site preparation burns, can have negative impacts on long-term soil productivity.