Twenty years after treatments designed to simulate soil compaction from logging equipment were applied to research plots in the Sierra Nevada, researchers found little difference in root growth and expansion among conifers within treatment areas and those unexposed to logging activities. The findings shed light on the resiliency of forests to weather disturbances from land management.
In the early- to mid-1990s, research plots were established on land that had been clear-cut logged. Although the specific study sites hadn’t been compacted by logging equipment, researchers came in six months post-harvest with a vibrating drum roller weighing more than 17 tons to make 21 passes across the research plots.
Soil density and strength measurements were taken 10 and 20 years post-treatment at various depths up to a foot from the surface. While compaction readings remained at thresholds previously believed to limit root growth, the trees told a different story.
“When we dug a 3-foot-deep trench to look at what the roots were doing beneath the surface, we found no noticeable difference in the amount or size of fine root structures or lateral roots between conifer trees in the compacted sites and those undisturbed,” said Matt Busse, a soil scientist with the Forest Service’s Pacific Southwest Research Station.
The findings corroborate other studies that have found little difference in long-term vegetation growth following ground-compacting activities.
“While we can’t say that these findings hold true in all cases across all landscapes,” Busse said, “it does illustrate how resilient productive soils with moderately high porosity and organic matter, such as those found in the Sierra Nevada, can be to compaction.”