Ecological effects of soil compaction and initial recovery dynamics: a preliminary study

Skid trails of regular harvest operations with time delays up to 24 years between tracking and examination were investigated in order to characterize the status of recovery of essential soil functions. The study was focused on the ability of soils to serve as an effective rooting space. The gas diffusion coefficient and the fine root distributions of comparable sensitive silty loams were used to describe the disturbances of soil functions still detectable after decades. Tracking with heavy loaded machines severely reduced the soil aeration and in consequence the ability of the soil to act as a rooting space. Reduction of gas diffusivity and rooting was found on the whole skidding trail area and even expanded to the close vicinity of the margin zone. Up to 14 years after machine impact, gas diffusion coefficients and root densities beyond 4 cm depth under wheel tracks showed no signs of restoration. Soil aeration and root densities comparable to the control plot were found in the top soil layer 18 years after tracking at the site Ettenheim. At that location 24 years after machine impact, significantly reduced root densities occurred only in soil depths beyond 54 cm. In the long run, only concentration of machine traffic on permanent skid trail systems guarantees an adequate soil preservation. This applies especially under Middle European site conditions and management practices. This prescription must be underlined in guidelines for machine use in forests.