In the European Alps the importance of forests as protection against ava lanches and soil erosion is becoming ever clearer with the continuing increase in population and development of tourism. The protective potential of the moun tain forests can currently only be partially realised because a considerable propor tion of high-altitude stands has been destroyed in historical times by man's extensive clearing ofthe forests. The forests still remaining are of limited effec tiveness, due to inadequate density of trees and over-maturity. Considerable efforts, however, are now being made in the Alps and other mountains of the globe to increase the high-altitude forested area through reforestation, to raise depressed timberlines, and to restore remaining protection forests using suit able silvicultural methods to their full protective value. This momentous task, if it is to be successful, must be planned on a sound foundation. An important prerequisite is the assembly of scientific facts con cerning the physical environment in the protection forest zone of mountains, and the course of various life processes of tree species occurring there. Since the introduction of practical field techniques it has been possible to investigate successfully the reaction of trees at various altitudes to recorded factors, and the extent to which they are adapted to the measured situations. Such ecophysio logical studies enable us to recognize the site requirements for individual tree species, and the reasons for the limits of their natural distribution.

Klappentext

In the European Alps the importance of forests as protection against ava­ lanches and soil erosion is becoming ever clearer with the continuing increase in population and development of tourism. The protective potential of the moun­ tain forests can currently only be partially realised because a considerable propor­ tion of high-altitude stands has been destroyed in historical times by man's extensive clearing ofthe forests. The forests still remaining are of limited effec­ tiveness, due to inadequate density of trees and over-maturity. Considerable efforts, however, are now being made in the Alps and other mountains of the globe to increase the high-altitude forested area through reforestation, to raise depressed timberlines, and to restore remaining protection forests using suit­ able silvicultural methods to their full protective value. This momentous task, if it is to be successful, must be planned on a sound foundation. An important prerequisite is the assembly of scientific facts con­ cerning the physical environment in the protection forest zone of mountains, and the course of various life processes of tree species occurring there. Since the introduction of practical field techniques it has been possible to investigate successfully the reaction of trees at various altitudes to recorded factors, and the extent to which they are adapted to the measured situations. Such ecophysio­ logical studies enable us to recognize the site requirements for individual tree species, and the reasons for the limits of their natural distribution.

Inhalt
General Features of the Upper Timberline.- Reasons for Occurrence of Timberlines and Their Experimental Investigation.- Some Milestones in the History of Ecophysiological Research Concerning Alpine Timberline.- 1. Natural Regeneration of Tree Stands at Timberline.- 1.1 Seed Production. Frequency of Seed Years, Quantity, and Quality of Seed.- 1.2 Dispersal of Seed.- 1.3 Maturation of Seed.- 1.4 Germination.- 1.5 Vegetative Propagation.- 2. Growth of Trees at Timberline.- 2.1 Height Growth.- 2.2 Growth of Leaves.- 2.3 Diameter Growth.- 2.4 Root Growth and Mycorrhizae.- 3. Dry Matter Production of Trees at Timberline.- 3.1 Photosynthesis.- 3.2 Dark Respiration with Respect to Altitude and Timberline.- 3.3 Carbon Balance of Trees at Timberline.- 3.4 Net Carbon Gain and Biomass Increment at Elevations up to Timberline.- 3.5 Primary Production and Nitrogen Nutrition.- 4. Water Relations of Trees at Timberline.- 4.1 Water Relations in Summer.- 4.2 Water Relations in Winter.- 5. Climatic Resistance and Damage of Trees at Timberline.- 5.1 Frost Damage.- 5.2 Ultraviolet and High Intensity Radiation Damage.- 5.3 Heat Damage.- 5.4 Mechanical Damage.- 5.5 Winter Desiccation or Frost-drought Damage.- 6. Synopsis.- 6.1 Carbon Budget.- 6.2 The Course of Developmental Phases.- 6.3 Climatic Resistance.- References.- Taxonomic Index.