Date of Award

2006

Level of Access

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Forest Resources

Advisor

Laura S. Kenefic

Second Committee Member

Ivan J. Fernandez

Third Committee Member

Walter C. Shortle

Abstract

The objective of this retrospective study was to quantify the long-term effects of tree harvesting intensity on red spruce-flats in northern Maine. Six stands harvested approximately 30 years ago with volume removals of 30, 50, and 80 percent and two unharvested reference sites were selected. All of the stands were originally harvested during the winter with in-woods delimbing. Soil physical and chemical properties, stand basal area, species composition, and forest floor cover type were evaluated. Increment cores were extracted to look at growth and chemical indicators of tree response to harvesting and associated changes in soil solution chemistry. Dendrochemistry has not been used in this context before. Ion exchange resin membranes (IERMs) were employed to characterize relative differences among sites in current pools of plantavailable nutrients in soil solution. Though total BA does not currently differ among stands, the 80% removal stands have the most balsam fir and the least red spruce. The proportion of the forest l-loor covered with bryophytes declined with decreasing proportions of overstory red spruce, which was in turn related to harvest intensity. O horizon mass and thickness were lowest in the 80% removal, while thickness was greatest in reference stands and mass was greatest in the 50% removal. Harvesting resulted in significant differences in soil chemistry that were pervasive in the Oea horizons, but nearly absent in the mineral soil. Exchangeable Ca, K, Ca and base saturation, Ca:Al ratios, pH, and CEC, were highest in the 50% removal. Percent organic matter and C:N ratios were significantly lower in the 80% removal than the reference, suggesting that harvesting decreases these variables. Observed changes in soil chemistry were attributed to harvest-induced changes in O horizon decomposition dynamics and the presence of slash after the harvest, although there were possible pre-treatment differences important to our interpretation. There was no evidence of a stand-level increase in radial growth in response to harvesting, though a post-1960 regional decline in red spruce growth rates may have masked a growth response. Presumed changes in post-harvest soil solution chemistry were not detected in sample tree cores. Additionally, sample trees were codominants at the time of harvesting, and light may not have been limiting. A high frequency of cores exhibiting a Ca enrichment in the 1970s may be indicative of an increase in Ca availability in the 1990s. Current labile pools of plant available nutrients, as measured by IERMs, do not appear to have been significantly altered by harvesting. However, Ca as a proportion of the base cations Ca, K, Mg is higher in the more heavily harvested stands, suggesting that Ca has increased disproportionately to K and Mg. This study used methods for field implementation of IERMs that were adapted from other studies for use in coniferous forests. We found that DI water that is typically used for transport can potentially desorb measurable amounts of ions, particularly K, from the IERMs. This needs to be further investigated to improve interpretation of data obtained from IERMs.

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