Soil compaction from cut-to-length thinning operations in young redwood forests in northern California

In northern California, United States, a cut-to-length (CTL) system was recently used for the first time to harvest young redwood (Sequoia sempervirens (Lamb. ex D. Don) Endl.) forests. Landowners and public agencies in this region have been concerned about the potential negative impacts of CTL on soils during wet-season harvest operations. To determine soil impacts, we measured changes in soil bulk density (BD) and hydraulic conductivity (HC) after CTL operations in May and August. Soil samples were collected at two locations (track and center) along forwarder trails and at a reference point at three soil depths (0–5, 10–15, and 20–25 cm), and HC samples were collected only at the 0–5 cm soil depth from the same sample points. We found a significant difference in BD between the reference point and track at 0–5 cm, which decreased as soil depth increased. There was a negative correlation between initial BD values and percent increase of BD, supporting the fact that the percent increase in BD was high at the soil surface (25%–30%), but BD did not exceed 1.13 Mg·m^–3 at the 0–5 cm depth. However, our HC results were different from what we expected and were not as consistent as the BD results, as the HC data had much higher variability.