This book is published as part of the broad area of research on the changing global climate and its impact on the environment. The upper timberline is the most conspicuous vegetation limit in high-mountain areas of all continents and islands, except for the Antarctic. The dynamics of timberline establishment and maintenance could well be affected by global warming in a number of ways. From a global viewpoint, the present timberline is far from being caused only by the current climate, but instead reflects also history of climate and local site conditions. Thus, the main objective of the book is to explain mountain timberlines as space- and time-related phenomena. After an introduction into the complexities of the subject, the history and present state of timberline research are outlined. Chapters on the tree species at timberline and on the relationship of timberline elevation to macroclimate, climate character and the mass-elevation effect follow.
The main chapter deals with the physiognomic and ecological differentiation of upper timberlines, in particular with the timberline controlling physical and biological factors, their interactions and their influence on the spatial structures and temporal dynamics in the timberline ecotone. Also, the influences of trees and tree stands on site conditions are considered. This is the base for understanding the response of timberlines to climatically driven changes, which are considered in the last chapters.