Forest decline became a matter of public and scientific concern in France in 1983 when conifers in the Vosges mountains were found to exhibit unusual crown deterioration. An impassioned controversy on a supposedly large scale forest health problem was then in full swing in Central Europe. A co-ordinated research programme entitled DEFORPA ("Deperissement des For~ts et Pollution AtmospMrique") was launched in 1984. This programme ran from 1984 to 1991 and a number of projects are still in progress. The Programme was sponsored by three French ministries (Enviroument, Agriculture and Forestry, Research and Technologyl), several state agencies, various regional authorities and the Commission of the European Communities (DO xn and DG VI). Initially, emphasis was solely laid on the understanding of forest decline in the mountainous areas - because damage was most obvious there - in relation to natural and man-made factors. Air pollution was given high but not overwhelming priority. Thus, the DEFORPA Programme was not in its essence a nation-wide assessment of air pollution effects, unlike a number of national acidification research programmes in Europe and North America. During. the programme, however, the areas of concern expanded. In particular, research into water acidification in the Vosges mountains was developed in parallel with the DEFORPA Programme, and possible eutrophication of the ground flora in northeastern France became the subject of new research.

Over the past decade there has been considerable interest in the effects of atmospheric deposition on forest ecosystems. This volume summarizes the results of the Integrated Forest Study (IFS), one of the most comprehensive research programs conducted. It involved intensive measurements of deposition and nutrient cycling at seventeen diverse forested sites in the United States, Canada, and Norway. The IFS is unique as an applied research project in its complete, ecosystem-level evaluation of nutrient budgets, including significant inputs, outputs, and internal fluxes. It is also noteworthy as a more basic investigation of ecosystem nutrient cycling because of its incorporation of state-of-the-art methods, such as quantifying dry and cloud water deposition. Most significantly, the IFS data was used to test several general hypotheses regarding atmospheric deposition and its effects. The data sets also allow for far-reaching conclusions because all sites were monitored over the same period using comparable instruments and standardized protocols.

Maintaining or increasing stand productivity is the concern of forest land managers worldwide. Consequently, there is increasing interest in understanding the impact of environmental stress on productivity and the development of management strategies that ameliorate or reduce the deleterious effects. Invited scientists gathered in Fort Collins, Colorado on July 30, 1985, to present the current state of knowledge regarding the impact of environmental stress on forest stand productivity. Particular attention was given to elucidating the mode of action by which individual stress elements reduce productivity. Environmental factors and the levels that constitute stressed (suboptimal) conditions in forest stands were identified, and the effects of stress intensity and duration on key stand parameters, including photosynthesis, respiration, assimilate partitioning, senescence and mortality, were emphasized. The role of genetics and silvicultural treatments in lessening the stress impact on stand productivity was presented, particularly in regards to alternative methods for environmental stress management. Modeling of stand dynamics in response to environmental stress was explored as an effective research and management tool. VIII Improved forest management practices will develop as we improve our understanding of the nature of important environmental stresses and as we comprehend their impact on tree and stand performance, manifested through physiological processes and genetic potential. This book is dedicated to such an understanding and comprehension.