Influence of mechanized timber harvesting on soil compaction in northern hardwood forests

Evaluating and refining methods to minimize soil compaction during timber harvesting is important for maintaining soil health and long-term forest productivity. This is especially important when harvesting methods change over time. In this study, a hybrid harvesting method was used with the trees cut by one machine, in-forest processing of trees by other machines, and transporting the wood to the roadside by a forwarder on silt loam soils during the summer months. Two methods for sampling soils with mixed horizons in logging trails were developed to determine the baseline values of soil bulk density for long-term monitoring and to compare soils from nonmixed B horizons with those of B horizons from nontrafficked areas. For both methods, paired soil samples, in and outside of logging trails, were collected to determine the difference in bulk density between trails and nontrafficked areas. Soil compaction in trails was greatest where the soils adjacent to trails had low bulk densities and for locations that were closest to landings. These results are important in the context of climate change, as more summer logging is expected to occur in areas traditionally cut in the winter because of longer frost-free periods and more winter precipitation occurring as rain. More logging during the expanding snow-free season could translate to a greater degree of compaction and longer soil recovery times over a larger portion of the forested landscape.