Date of Award

Summer 5-20-2016

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Forest Resources (MFR)

Department

Forest Resources

Advisor

Robert Wagner

Second Committee Member

Brian Roth

Third Committee Member

Jeffrey Benjamin

Abstract

Whole-tree (WT) and cut-to-length (CTL) harvesting systems are commonly used in the spruce-fir forests of Maine. While these mechanized systems have significantly improved the productivity of forest harvesting, there are potential negative consequences of these harvest systems, including damage to residual stands and soil. Residual stand damage and soil disturbance can lead to reduced growth rates, soil productivity, and log value. Understanding the effects of WT and CTL harvesting systems can help protect future stand values and long-term site productivity in Maine spruce-fir stands.

We used two studies to investigate the impact of residual stand damage and soil disturbance on Maine spruce-fir stands. In the first study, an experiment in west-central Maine was used to quantify stem, root, and crown damage following commercial thinning (CT) at 33, 50, and 66% levels of relative density reduction in stands that had previously received precommercial thinning (PCT) or no PCT. We found that prior PCT with CTL harvesting was the most important factor predicting the level of residual stand damage after CT. Higher initial stand densities associated with no-PCT and WT harvesting increased the probability of machine-to-tree or tree-to-tree contact that resulted 86% more residual stem damage. We found that higher CT removal levels (>33%) resulted in higher rates of stem and root damage. We also found that trees closer to harvest trails had a higher probability of stem and root damage, along with the higher probability of high or medium severity wounds.

In the second study, we used a long-term experiment in northern Maine to quantify stand composition and growth 32 years after clearcutting using a WT harvest system. Soil disturbance measurements were made on 100 transects that were installed immediately after the site was harvested in 1981. We found no influence of soil disturbance on tree- and stand-level variables, including basal area, density, percent hardwood, volume, DBH, and height. We also examined annual radial growth rates using tree cores from a subset of balsam fir crop trees (>6.35 cm DBH) that had grown on the most and least disturbed soil conditions. No differences were found in growth rate over the entire growth period. Despite severe soil rutting and mineral soil exposure from WT harvesting, we were unable to detect any differences in subsequent forest composition, structure, or growth from soil disturbance at the Weymouth Point study site 32 years after harvest.

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