Order Number 9509389 Effects of pruning on growth of western hemlock (Tsuga heterophylla (Raf.) Sarg.) and Sitka spruce (Picea sitchensis (Bong.) Carr.) in southeast Alaska Petruncio, Markian Demetrius, Ph.D. University of Washington, 1994 Copyright ©1994 by Petruncio, Markian Demetrius. All rights reserved. UMI 300 N. ZeebRd. Ann Aibor, MI 48106 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Effects of Pruning on Growth of Western Hemlock (Tsuga heterophylla (Raf.) Sarg.) and Sitka Spruce (Picea sitchensis (Bong.) Carr.) in Southeast Alaska by Markian Demetrius Petruncio A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy University of Washington 1994 Approved by_ (Chairperson of Supervisory Committee) ~ r7 ) a A w J Program Authorized College of Forest Resources to Offer Degree____ Date. / . / W Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. © Copyright 1994 Markian Demetrius Petruncio Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. In presenting this dissertation in partial fulfillment of the requirements for the Doctoral degree at the University of Washington, I agree that the Library shall make its copies freely available for inspection. I further agree that extensive copying of this dissertation is allowable only for scholarly purposes, consistent with "fair use” as prescribed in the U.S. Copyright Law. Requests for copying or reproduction of this dissertation may be referred to University Microfilms, 1490 Eisenhower Place, P.O. Box 975, Ann Arbor, MI 48106, to whom the author has granted "the right to reproduce and sell (a) copies of the manuscript in microform and/or (b) printed copies of the manuscript made from the microform." Signature. Date. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. University of Washington Abstract Effects of Pruning on Growth of Western Hemlock (Tsuga heterophylla (Raf.) Sarg.) and Sitka Spruce (Picea sitchensis (Bong.) Carr.) in Southeast Alaska by Markian Demetrius Petruncio Chairperson of the Supervisory Committee: Professor Chadwick D. Oliver College of Forest Resources Permanent study plots were established in Southeast Alaska in 1990, 1991, and 1992 to monitor and quantify the growth responses of western hemlock (Tsuga heterophylla (Raf.) Sarg.) and Sitka spruce (Picea sitchensis (Bong.) Carr.) to thinning and pruning. Young trees in mixed stands were thinned to 170 trees per acre (420 trees/ha) and pruned to three different heights -- 8,12, and 17.4 feet (2.4, 3.7, and 5.3 m). Branch sizes and time-and-motion data were recorded and analyzed to determine the functional relationships between time required to prune and branch characteristics. Pruned height and stem diameter were significant variables for predicting time required to prune. Epicormic branching, sunscald, and tree mortality were monitored to determine how pruning to various heights affects stem quality and tree survival. Epicormic sprouts increased on spruces but differences in numbers of epicormics between treatments were statistically nonsignificant in the first two years after treatment. Stem diameter, basal area, and butt log volume growth differences between treatments were statistically significant in the first year; and diameter growth differences were significant in the second year after treatment. Height growth differences between treatments were statistically nonsignificant in the first two years after treatment. Percent live crown length removed in combination with initial stem diameter and Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. live crown ratio in combination with initial stem diameter were significant variables in multiple regression models for predicting posttreatment stem diameter, basal area, and volume growth. Growth was significantly reduced when 40 percent or more live crown length was removed and when live crown ratios were reduced below 50 percent. Mean stem diameter growth in the 17.4-foot (5.3 m) lift was significantly reduced at 4.5 feet (1.4 m) above the ground but not at 17.4 feet (5.3 m) resulting in significant changes in stem taper after treatment. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table of Contents Page List of Figures ....................................................................................... iv List of Tables .......................................................................................... viii Part I. Introduction to Forest Pruning .............................................. 1 Axioms ....................................................................................... 3 Postulates ................................................................................... 4 Hypotheses ................................................................................. 4 Part II. Review of Forest Pruning Literature ................................... 8 Natural Pruning and Clear Wood Production in Conifers .... 11 Developments in Pruning Equipment ....................................... 14 Early Equipment Developments in Europe ............................... 15 Early Equipment Developments in North America ................. 15 Recent Developments in Pruning Equipm ent .......................... 18 Choosing the Right Equipment ................................................ 22 Western Hemlock and Sitka spruce Branch Characteristics .. 24 Pruned Branch Stub Occlusion ................................................ 26 Importance of the Branch Collar .............................................. 28 Empirical Research on Branch Stub Occlusion ........................ 29 Effects of Pruning on Diameter G row th ................................... 32 Effects of Pruning on Stem F o rm .............................................. 32 Effects of Pruning on Height G row th ....................................... 33 Sunscald Injury on Conifers ....................................................... 34 Potential Pathogens of Pruned T rees ....................................... 35 Insects Attracted to Pruning Wounds ............................... 36 Economic Analyses of Pruning .................................................. 37 Pruning in North America ......................................................... 40 Part IH. Experimental Design and Procedures ................................. 42 Site Characteristics .................................................................... 42 Plot Layout ....................................... 48 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Selection of Leave Trees .............................................................. 49 Thinning O peration .................................................................... 50 Treatments ................................................................................. 50 Measurements ............................................................................. 52 Time-and-Motion D a ta ...................... ................. ....................... 53 Data Analysis ............................................................................. 54 Part IV. Experimental Results and Discussion ................................. 56 Species Composition .................................................................... 56 Diagnostic Stand Variables ....................................................... 56 Branch Characteristics .............................................................. 69 Time Required for Pruning ....................................................... 71 Immediate Effects of Pruning Treatm ents ............................... 79 Sunscald and M ortality ................................... .......................... 82 Epicormic Shoots on Spruce ....................................................... 82 Height Growth Responses ......................................................... 83 Diameter Growth Responses ..................................................... 87 Stem Taper Two Years After Pruning ...................................... 101 Basal Area Growth Responses ........................ 106 Butt Log Volume Growth Responses ........................................ 113 Conclusions ................................................................................. 120 Part V. Applications to Management ................................................. 124 Recommendations for Pruning Western Hemlock and Sitka Spruce ......................................................................... 128 Planning, Implementing, and Monitoring Forest Pruning Operations .................................................................... 131 Determining Suitability of Stands for Pruning ........................ 131 Design Alternatives: Fixed-Lift and Variable-Lift Pruning ... 132 Implementation .......................................................................... 133 Pruning Time and Costs ................. 133 Monitoring and Evaluation ....................................................... 135 ii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Environmental Considerations...........................