u ._.:. I i ECOLOGY AND SILVICULTURE OF WESTERN LARCH FORESTS WYMAN C. SCHMIDT RAYMOND C. SHEARER ARTHUR L. ROE FOREST SERVICE U.S. DEPARTMENT OF AGRICULTURE ACKNOWLEDGMENTS We acknowledge with appreciation the many scientists, technicians, and managers in the USDA Forest Service who have had a part in the research that provides the basis for this report. We specifically want to acknowledge former scientists of the Western Larch Silvic~lture research unit in Missoula, Montana-Kenneth N. Boe, Russell K. LeBarron, A. E. Squillace, and David Tackle. In addition we want to acknowledge the support and continuing interest of the staffs of the St. Regis Paper Company, Champion International (formerly Anaconda Forest Products), Burlington Northern, University of Montana, Bureau of Land Management, and Bureau of Indian Affairs. The use of trade names in this publication is solely for the convenience of the reader. Such use does not constitute an official endorsement by the U.S. Department of Agriculture of any product or service to the exclusion of others that may be suitable. PESTICIDES PRECAUTIONARY STATEMENT This publication reports research involving pesticides. It does nut contain recommendations for their use, nor does it imply that the uses discussed here have been registered. All uses of pesticides must be registered by appropriate State and/or Federal agencies before they can be recommended. CAUTION: Pesticides can be injurious to humans. domestic animals, desirable plants. and fish or other wildlife-if they are not handled or applied properly. Use all pesticides selectively and carefully. Follow recommended practices for the disposal of surplus pesticides and pesticide containers. ( l Digitized by Coogle ECOLOGY AND SILVICULTURE OF WESTERN LARCH FORESTS ( by Wyman C. Schmidt, Project Leader and Principal Silviculturist, and Ray­ mond C. Shearer, Principal Silviculturist, USDA Forest Service, Intermoun­ tain Forest and Range Experiment Station, Ogden, Utah 84401; Schmidt stationed at the Forestry Sciences Laboratory in Bozeman, and Shearer at the Forestry Sciences Laboratory in Missoula; and Arthur L. Roe, USDA Forest Service, retired, formerly Principal Silviculturist, Intermountain Forest and Range Experiment Station, Ogden, Utah. ( Technical Bulletin No. 1520 March 1976 U.S. Department of Agriculture Forest Service Digitized by Coogle RESEARCH SUMMARY Western larch forests are valued not only for the to outgrow them in height for most of the life of the high quality wood they produce-wood used for a stand. However, the initial seedbed preparations, multiplicity of products-but also for their esthetic stocking, and insects and diseases can alter this beauty. A wide variety of wildlife, including grizzly pattern. For example, prescribed burning for seed­ bear, moose, and elk, find protection and food in bed preparation generally creates conditions highly larch forests. Deep winter snows dramatize the suitable for early larch growth. Larch grows faster watershed values. and gains a more dominant position on burned than Westerr,t larch is the largest of the North on other types of seedbeds. American larches. It is deciduous, and the most The majority of natural stands in larch forests shade-intolerant species in the northern Rockies. are heavily overstocked-30,OOO to 40,000 trees per Although always seral, it has a wide ecological acre at age 10 are not uncommon. Larch growth amplitude, growing in association with most con­ potential nearly always exceeds its actual growth in ifers native to the northern Rocky Mountains. natural stands because larch is very sensitive to Deficient moisture defines its lower elevational overcrowding. Diameter and height growth reduc­ limits, while low temperatures mark the upper ex­ tions, even of the dominant trees, are readily ap­ treme. Larch grows best on north exposures, valley parent in stands under 10 years old. This illustrates bottoms, benches, and rolling topography; the need to thin very early in the life of the stand to southwest exposures are usually unfavorable for take full advantage of its rapid juvenile-growth larch. potential. Without early thinning, the highly in­ Dwarf mistletoe is the most serious disease­ tolerant crowns are reduced, and overall vigor causing parasite, and larch casebearer and western declines. Maintaining good vigor also results in spruce budworm the most serious insect pests greater resistance to snow and wind as well as in­ damaging western larch. All three are widespread sect and disease damage. throughout the type and can substantially reduce Larch response to thinning in older stands is growth. directly related to the degree of overstocking and Even-aged management methods, including associated tree vigor at the time of thinning. clearcutting, shelterwood, and seed-tree cuttings, Moderately overstocked stands respond rapidly essentially mimic conditions historically created by while heavily overstocked stands, with their smaller wildfires and create conditions needed to crown ratios and reduced vigor, respond propor­ regenerate harvested larch forests. Natural tionately slower. Dominant and codominant trees regeneration can usually be relied upon with any of consistently respond most favorably to thinning these cutting methods if a mineral soil seedbed has and should be featured in management. been prepared by prescribed burning or mechanical Overmature larch forests generally show scarification. Because larch cone crops are predic­ negative or little net volume growth because mor­ table a year in advance, seedbeds can be prepared tality exceeds or approximates growth. Partial cut­ before seed dispersal. A I-to-I ratio of fair or better tings in old-growth forests produce only minor net versus poor cone crops generally precludes the growth increases, principally on species other than necessity of artificial regeneration methods, but larch. However, immature larch forests possess where natural seedfall fails, direct seeding and substantial growth potential under management. planting methods are good substitutes. This bulletin provides growth and yield infor­ Characteristically, larch grows in mixed-species mation-stratified by site indices, physiographic stands with several other conifers, gains an early site, and ecological habitat type-for predicting height advantage over its associates, and continues this potential growth. ii Digitized by Coogle CONTENTS Page Page RESEARCH SUMMARy.......... .......... ....... ii Even-Aged Cutting Methods. .. .. ... 31 INTRODUCTION. 1 Clearcutting . .. 32 IMPORTANCE OF WESTERN LARCH ............. 2 Seed-Tree Cutting. .. .. .. 34 Range ........................................... 2 Shelterwood Cutting ........................... 36 Resource......................................... 3 Comparison of Cutting Methods .................. 38 Mature and Overmature Stands.. ............... .. 3 STAND MANAGEMENT .......................... 40 Immature Stands ............................... 4 Composition. .. 40 Nonstocked Lands .............................. 4 Stocking .... .. 40 Products ......................................... 4 Factors Affecting Development ..................... 42 TREE AND FOREST DESCRIPTION ............... 6 Cultural Treatments . .. 44 Tree Characteristics ............................... 6 Thinning ...............................'. .. 45 Associated Vegetation ............................. 6 Seedlings and Saplings .. .. .. .. .. .. .. .. .. .. .. ... 46 Habitat Types .................................. 7 Poles ........................................ 47 Timber Types .................................. 8 Methods ..................................... 48 ENVIRONMENTAL FACTORS..................... 9 Pruning ........................................ 50 Climate .......................................... 9 GROWTH AND YIELD ............................ 51 Precipitation. .. 9 Overmature Stands . .. 51 Temperature. .. 9 Diameter ....................................... 51 Edaphic .......................................... 10 Volume ........................................ 51 Land Characteristics .............................. 10 Vigor ........................................ 53 Soil ........................................... 10 Immature Stands ................................. 53 Damage ......................................... 10 Height ......................................... 53 Physical ....................................... 10 Diameter. .. 55 Fire ......................................... 10 Age and Site Index ........................... 55 Wind ........................................ 11 Vigor ........................................ 55 Snow and Ice. .. II Ecological Habitat Type and Stand Density ...... 57 Temperature. .. II Basal Area . .. 58 Noxious Fumes . .. 11 Volume ........................................ 58 Biological ...................................... 12 Transmission Poles . .. .. 59 Diseases ..................................... 12 Sapwood Depth . .. 59 Insects ....................................... 14 Spirality ..................................... 59 Animals ..................................... 17 Pole Class ................................... 59 STAND REGENERATION ......................... 18 FUTURE RESEARCH ............................. 60 Seed Production .................................. 18 PUBLICATIONS CiTED ........................... 61 Flowering ....................................... 18 APPENDIXES ..................................... 67 Maturity ......................................