Date of Award

12-2016

Level of Access Assigned by Author

Open-Access Thesis

Language

English

Degree Name

Master of Science (MS)

Department

Forest Resources

Advisor

Shawn Fraver

Second Committee Member

Laura S. Kenefic

Third Committee Member

Alan S. White

Additional Committee Members

Jean-Claude Ruel

Abstract

Northern white-cedar (Thuja occidentalis; hereafter white-cedar) communities have received relatively little research attention, and managers lack the tools used in the management of other commercial tree species. This includes the recognition of old-growth characteristics and the differentiation between old-growth and partially harvested stands, particularly in the context of Forest Stewardship Council (FSC-US) certification. Specifically, there is very little information about characteristics that define old-growth white-cedar stands despite the species’ abundance and wide distribution. Regional indices for late-successional or old-growth stands (Whitman and Hagan, 2007) do not include white-cedar. Forests dominated by white-cedar represent a type that currently lacks quantitative benchmarks for old-growth characteristics.

To identify the structural characteristics unique to old-growth white-cedar stands, we inventoried 16 old-growth and 17 partially harvested stands in Maine and New Brunswick. In Chapter 1, we report the outcomes from a range of structural metrics commonly used in forest management such as basal area (BA, m² ha-1), quadratic mean diameter (QMD, cm), large tree (≥ 40 cm dbh) density, and volumes of coarse woody material (CWM, m³ ha-1), along with a set of structural complexity indices (e.g., diameter distribution index, mingling index). Two significant predictors were identified that, in combination, differentiate old-growth from partially harvested white-cedar stands: advanced-decay coarse woody material volume (logs in decay stages 4 and 5 using a 5-stage system) and live tree QMD. No structural complexity indices were useful in predicting old-growth status. Our research improves the understanding of old-growth characteristics in white-cedar stands and provides an important tool for the successful management of white-cedar.

In Chapter 2, we present a practitioner-oriented guide to aid in the application of our findings by forest managers. Specifically, we provide an equation for determining the probability that a white-cedar stand has old-growth characteristics, as well as supporting information about how to collect and prepare the data needed to use this prediction tool. Illustrations and photographs are used to demonstrate the forest attributes of interest, and to aid the practitioner in measuring and determining the decay classes of coarse woody material. In addition, we discuss the relevance of our findings to ecological forestry prescriptions. This guide will prove useful for forest managers working under FSC guidelines, wherein the recognition of old-growth characteristics is institutionalized in requirements for reserving old-growth stands and maintaining old-growth characteristics where they are found in managed stands.

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