As forests decline in temperate and tropical climates, highly-developed countries and those striving for greater economic and social benefits are beginning to utilize marginal forests of high-latitude and mountainous regions for resources to satisfy human needs. The benefits of marginal forests range from purely aesthetic to providing resources for producing many goods and services demanded by a growing world population. Increased demands for forest resources and amenities and recent warming of high latitude climates have generated interest in reforestation and afforestation of marginal habitats in cold regions. Afforestation of treeless landscapes improves the environment for human habitation and provides for land use and economic prosperity. Trees are frequently planted in cold climates to rehabilitate denuded sites, for the amenity of homes and villages, and for wind shelter, recreation, agroforestry, and industrial uses. In addition, forests in cold climates reduce the albedo of the earth's surface in winter, and in summer they are small but significant long-lived sinks for atmospheric carbon dioxide. Finally, growth and reproductive success of forests at their geographic limits are sensitive indices of climatic change. As efforts to adapt forests to cold climates increase, however, new afforestation problems arise and old ones intensify. Austral, northern, and altitudinal tree limits are determined by many different factors. Current hypotheses for high-latitude tree limits are based on low growing-season temperatures that inhibit plant development and reproduction.

Zusammenfassung
Proceedings of a NATO ARW held in Laugarvatn, Iceland, June 18-23, 1991

Inhalt
Socioeconomic Importance of Forests in Iceland.- Biochemical and Physiological Requirements of Trees for Forest Development beyond Tree Limits.- Molecular Bases for Adaptation of Coniferous Trees to Cold Climates.- Growth and Development of Northern Forest Trees as Affected by Temperature and Light.- Testing Winter Desiccation Resistance for Species and Provenance Selection at Timberlines.- Growth of Mountain Birch (Betula Pubescens Ehrh.) in Response to Changing Temperature.- Performance of Mountain Birch in Different Environments in Sweden and Iceland: Implications for Afforestation.- Environmental Limitations of Forest Development at and beyond Tree Limits.- Causes of Alpine Timberline: A Review of the Hypotheses.- Physiology of Trees at Treeline.- Treeline in Relation to Climate, with Special Reference to Oceanic Areas.- Pliocene Fossil Nothofagus (Southern Beech) from Antarctica: Phytogeography, Dispersal Strategies, and Survival in High Latitude Glacial-Deglacial Environments.- Predicting Afforestation Success during Climatic Warming at the Northern Limit of Forests.- Climate Change as Seen by Trees and by Climate Modelers.- Effects of Wind on Boreal Forests.- Long-Term Biometeorological Monitoring at Two Forest Sites in Iceland and Newfoundland: Initial Results.- Potential Tree Species and Provenances for Forest Development in Cold Climates.- Genetic Diversity of Tree Populations at Their Arctic Limits.- Potential Species and Provenances for Forest Development in Cold Climates.- Species and Provenance Choice at Northern Tree Limits in Maritime Climates.- Seed Collections from North American Trees for Marginal Sites in the Nordic Countries.- The Uses of Lignoses in Horticulture in Iceland.- Provenance Selection, Testing, and Breeding to Accelerate Adaptation and Growth of Trees and Shrubs.- Accelerating Adaptation of Trees at Tree Limits by Selective Breeding.- Selection and Breeding of Scots Pine for Northern Sweden.- Provenance and Individual Variation in Climatic Hardiness of Scots Pine in Northern Finland.- Hybridization among Provenances of Lodgepole Pine.- Genetics, Cytogenetics, and Molecular Genetics of Icelandic Birch: Implications for Breeding and Reforestation.- Chloroplast DNA Diversity, Phylogenetics, and Hybridization in Picea.- Genetic Variation in Early Frost Tolerance of Spruce from Northwestern North America.- Case Histories of Forest Development beyond Tree Limits.- History of Tree Planting on the Aleutian Islands.- Afforestation of Lutz Spruce, Sitka Spruce, and Norway Spruce in the Vesteraalen Islands, Norway.- Development of an Environmental Forest and Arboretum on the Outer Coast of Finnmark County, Norway.- Forest Development in Iceland.- Potential Treeline in the Faroe Islands.- Forest Trials at High Elevations in Britain.- Wind and Wave Forests: A Case Study and Implications for Silviculture.- The Alpine Timberline of Tibet.- Forestry in New Zealand's Southern High Country.- Summaries of Working Group Sessions.- Species Index.