Date of Award

5-2010

Level of Access

Campus-Only Thesis

Degree Name

Master of Arts (MA)

Department

Forest Resources

Advisor

Robert G. Wagner

Second Committee Member

Aaron R. Weiskittel

Third Committee Member

Jeremy S. Wilson

Abstract

American beech (Fagus grandifolia Ehrh.) and sugar maple (Acer saccharum Marsh.) are two major late-successional associates of the northern hardwood forest type that occupies about 40% of Maine's forest. Since the introduction of beech bark disease the timber value of American beech has been substantially reduced, but beech continues to persist and competitively suppress sugar maple and other desirable hardwood species in naturally regenerated stands on many thousands of acres in the Northeast. To better understand the ecology and silviculture of beech dominated understories, I investigated two major aspects of the problem: (1) spatial patterns of beech and sugar maple regeneration in post-harvest stands, and (2) a selective method to control beech while preserving desirable hardwood species (yellow birch, sugar maple, and red maple). Chapter 1 describes the spatial patterns of beech and sugar maple regeneration in north-central Maine at three shelterwood harvested stands that had establishment cuts 5 to 7 years earlier. Three spatial pattern hypotheses were tested by calculating spatial dependence (autocorrelation), and partial Mantel tests were used to test a hypothesis of interspecific repulsion for three height classes (≤30 cm, 31-90 cm, and >90 cm but <4 cm dbh). Autocorrelation was detected for all height classes of both species suggesting contagious (patchy) patterns, but the dominant patterns were overlapping patches of seed-origin advance regeneration beech (>90 cm) and seedling sugar maple (≤30 cm), with average patch sizes of 8.1 and 10.7 m, respectively. The vertical dominance of beech after shelterwood harvesting will likely favor beech dominance over the long term. However, the relatively even spatial distribution of sugar maple seedlings suggests that a selective control method to reduce beech and preserve sugar maple will favor sugar maple dominance. Chapter 2 documents the third-year response of beech, sugar maple, and other hardwood tree species to factorial combinations of glyphosate herbicide (Accord Concentrate®) and surfactant (Entree 5735®) to identify the combination that produced the highest level of beech control and lowest level of sugar maple injury. The most effective treatments (from 0.56 to 1.12 kg/ha a.e. of glyphosate plus 0.25 to 0.5% surfactant) selectively removed 60 to 80% of beech stems while mortality of sugar maple stems was only 10-20%. The five dominant hardwood species showed substantial differences in their susceptibility to the treatments, with the following order of susceptibility from highest to lowest: beech > striped maple > yellow birch > red maple > sugar maple. Results produced using hydraulic nozzles were comparable to those produced using a backpack mistblower, suggesting that these results are transferable to tractor-mounted mistblowers generally used for operational applications.

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