Year of Award

2010

Document Type

Thesis

Degree Type

Master of Science (MS)

Degree Name

Forestry

Department or School/College

College of Forestry and Conservation

Committee Chair

Christopher Keyes

Commitee Members

Charles Palmer, LLoyd Queen

Keywords

Pinus ponderosa, old-growth forest, ecological res

Publisher

University of Montana

Abstract

When applying prescribed fire to long-unburned but fire-dependent ecosystems managers require better decision-support models to determine appropriate conditions for achieving desired effects. Prolonged combustion in duff accumulations at the base of large conifers can lead to fine root mortality, cambial injury, enhanced susceptibility to bark beetle attack, and possibly tree death. Pre-burn sampling to predict duff mound consumption from measurable attributes is vital in order to limit the deleterious effects of prolonged smoldering combustion. The objective of this study was to determine the conditions that influence duff consumption and analyze the variability of these factors in the field. Duff moisture content, mineral content, bulk density, composition and depth were spatially quantified to inform prescribed burning decisions. Variability in factors influencing consumption was analyzed within and between duff mounds to improve pre-burn sampling procedures. Results show that a significant amount of variability in properties that could influence consumption due to differences between and within duff mounds. Duff properties did not vary significantly between uphill and downhill sampling locations. There was a positive relationship between tree size and duff depth. There was no association between lower duff moisture content and duff depth. Sampling recommendations were developed for the most appropriate protocols of efficient and meaningful duff sampling on an operational basis. A laboratory experiment was conducted to investigate how measurable attributes of duff affect smoldering combustion in duff mound fuels. Samples were divided between upper and lower duff for a total of 100 burn tests. Moisture content was adjusted to observe the transition through the ignition and spread limit. Bulk density, mineral content and percent consumption were recorded for each burn. The moisture content threshold for smoldering combustion was 57% and 102% respectively for upper and lower duff. Percent consumption was inversely related to moisture content for both layers of duff, and partially dependent on mineral content for lower duff. Results from this study aim to identify important attributes of duff that control the burning process in order to inform prescribed burning decisions.

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© Copyright 2010 Emily Claire Garlough