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Timber's strength, light weight, and energy-absorbing properties furnish features desirable for bridge construction. Timber is capable of supporting short-term overloads without adverse effects. Contrary to popular belief, large wood members provide good fire resistance qualities that meet or exceed those of other materials in severe fire exposures. From an economic standpoint, wood is competitive with other materials on a first-cost basis and shows advantages when life cycle costs are compared. Timber bridges can be constructed in virtually any weather conditions, without detriment to the material. Wood is not damaged by continuous freezing and thawing and resists harmful effects of de-icing agents, which cause deterioration in other bridge materials. Timber bridges do not require special equipment for installation and can normally be constructed without highly skilled labor. They also present a natural and aesthetically pleasing appearance, particularly in natural surroundings. The misconception that wood provides a short service life has plagued timber as a construction material. Although wood is susceptible to decay or insect attack under specific conditions, it is inherently a very durable material when protected from moisture. Many covered bridges built during the 19th century have lasted over 100 years because they were protected from direct exposure to the elements. In modem applications, it is seldom practical or economical to cover bridges; however, the use of wood preservatives has extended the life of wood used in exposed bridge applications. Using modem application techniques and preservative chemicals, wood can now be effectively protected from deterioration for periods of 50 years or longer. In addition, wood treated with preservatives requires little maintenance and no painting. Another misconception about wood as a bridge material is that its use is limited to minor structures of no appreciable size. This belief is probably based on the fact that trees for commercial timber are limited in size and are normally harvested before they reach maximum size. Although tree diameter limits the size of sawn lumber, the advent of glued-laminated timber (glulam) some 40 years ago provided designers with several compensating alternatives. Glulam, which is the most widely used modem timber bridge material, is manufactured by bonding sawn lumber laminations together with waterproof structural adhesives. Thus, glulam members are virtually unlimited in depth, width, and length and can be manufactured in a wide range of shapes. Glulam provides higher design strengths than sawn lumber and provides better utilization of the available timber resource by permitting the manufacture of large wood structural elements from smaller lumber sizes. Technological advances in laminating over the past four decades have further increased the suitability and performance of wood for modern highway bridge applications.

Increasing numbers of visitors to wilderness have caused resource managers to seek information on good horse-handling techniques and innovative equipment to insure that "the benefits of an enduring resource of wilderness" are preserved.This booklet is for those who travel into wilderness by horseback and who are concerned with minimizing man's impact there. Proper stock-handling, lightweight equipment, and good camp etiquette can do much to protect and preserve wilderness.This booklet illustrates how light, compact gear can be used in the horse camp and emphasizes innovative horse equipment for more comfortable, convenient travel with pack stock. It contains equipment ideas and techniques for "minimum impact" wilderness travel developed over many years by outfitters, packers, horse groups, Forest Service personnel, and other horsemen. The appendixes give detailed information on equipment mentioned in the text.

CONTENTSProgress through Cooperation John R. McGuireSeven Years of Growth Gene W. GreyRESOURCES, UTILIZATION, AND MARKETING Timber Demand and Use James E. Blyth Changing Resource and Utilization Glenn A. Cooper, Eugene F. Landt, Ronald D. Lindmark, and Harold A. Stewart Evaluation of Selected Wood Properties in Relation to Soil-Site Conditions H. E. Wahlgren Federal Trade Commission Guides and Their Effects on the Consumer Donald H. Gott Forest Products Regulatory Legislation John A. Sester The Significance of Log and Tree Grading Systems Robert MassengaleSILVICULTURE Culture: Past, Present, and Future F. Bryan Clark Selecting the Best Available Soils Craig K. Losche Establishment and Early Culture of Plantations Robert D. Burke and Robert D. Williams Weed Control W. R. Byrnes, J. E. Krajicek, and J. R. Wichman Managing Immature Trees for More High-Quality Logs and Related Products Robert E. Phares Tree Culture in the Southeast Warren Giles BoyetteTREE IMPROVEMENT Genetics and Tree Improvement David T. Funk Genetic Variation and Selection Calvin F. Bey Vegetative Propagation: Problems and Prospects R. E. Farmer Tree Improvement Action Programs-The Missouri Story Eugene L. BrunkNUT CULTURE AND PRODUCTION Utilization and Marketing of Nuts R. Dwain Hammons Utilization and Marketing of Shells Clarence C. Cavender Orchard Establishment in Arkansas Max D. Bolar Vegetation Management Increases Production in Nut Orchard Harvey A. Holt and Jack E. Voeller Bluegrass Sod and Trees Jack Weeks Forage and Trees Alan KingPROTECTION Diseases Frederick H. Berry Insects as Related to Wood and Nut Production William E. MillerECONOMICS Evaluating Economic Maturity of Individual Trees Gary G. Naughton Cost and Income Treatment on Small Woodlands Steven E. Lindsey Returns from Two Systems of Multicropping Richard C. SmithInformation and Services Available to the Landowner Burl S. Ashley and John P. Slusher

This book is the first text and reference that specifically addresses the issues and problems of wilderness management. The material is organized into six sections, each intended to present a comprehensive summary and synthesis of pertinent information The book's 16 chapters bring together both previously published as well as new information and viewpoints pertaining to wilderness management-writing which includes philosophy and concepts research data, and management experience in Federal agencies. Specifically, our objectives include the following:1. To sensitize readers to pressing wilderness management issues and the implications of alternative methods of dealing with them.2. To distinguish issues of wilderness management from issues of wilderness allocation and management of related lands, and to describe their important interrelationships.3. To introduce readers to pertinent literature and ongoing research on wilderness, focusing particularly on the management implications of such work4. To describe the evolution of the National Wilderness Preservation System from its philosophical and historical origins to its current size in number of areas and acres, with a speculative look at the future.5. To propose principles and concepts from which management policy and actions to preserve wilderness might be derived, and to describe current management policies, procedures, and techniques that are available. We recognize that among our readers there will be many diverse views about wilderness management, and we do not expect universal agreement with our treatment of a topic as emotion-laden as wilderness. Hopefully, we have avoided some of the polarity of opinion that commonly surrounds discussion of wilderness by attempting to maintain a broad, conceptual perspective on management problems. We have tried to identify alternative wilderness management perspectives and their implications. Where we do advocate a particular management direction, we try to state our position clearly and identify our line of reasoning. Both within individual agencies and among the public, there are varying orientations toward wilderness and its management, but we are gratified by what we think is some convergence of views in the past decade. We hope this book will stimulate the discussions and foster the consensus necessary to meet the challenge of wilderness management that faces government agencies and the interested public.July 1977 John C. Hendee George H. Stankey Robert C. Lucas

The potential value of trees and shrubs, as determined from a study of a variety of shelterbelts and urban screen plantings in southeastern Nebraska, appears to be very good. Reductions of sound levels (attenuations) in the order of 5 to 8 decibels are common, and attenuations of 10 decibels (approximately half as loud) are not unusual for wide belts of tall, dense trees. When the difference in level is based on a comparison of tree-shrub-grass combinations with hard surfaces, the worth of trees and shrubs is even more evident and attenuations of 8 to 12 decibels are common. Occasional reductions of 15 decibels or greater (1/3 as loud) have been noted but these are attributed to exceptionally advantageous temporary atmospheric conditions. The relative effects of tree species, height and belt width are discussed in some detail. In general, wide belts of tall trees are most effective. Species do not appear to differ greatly in their ability to reduce noise levels, provided deciduous varieties are in full leaf. Thus, evergreens are desirable for year-round noise screening. Relative placement of noise screens between sound source and protected area is of great importance; a screen placed relatively close to a noise source is more effective than one placed close to an area to be protected.