This book arises out of a symposium on forest and woodland terrestrial ecosystems which was held in Florence on 20-24th May 1991. It was organised jointly by the Commission of the European Communities (CEC) and the European Science Foundation (ESF) in association with the Italian Research Council (CNR). The symposium brQughUogether most -Of the internationally recognized groups working on forest ecosystems including biologists, botanists, ecologists, soil scientists, modellers, foresters and policy makers. All the CEC countries were represented. In addition, there was a broad audience from Eastern and Central Europe and from EFfA countries. Outstanding experts from outside Europe (US, Australia, Canada, Japan, China, etc.) were also present. In total, the symposium was attended by more than 500 participants. The structure of this book reflects the main elements of the meeting. As such it includes three main sections. The first consists of six major state-of-the-art reviews corresponding to the six plenary sessions, each followed by a discussion which has been summarized by rapporteurs. The reviews were prepared to assess critically the state of current knowledge in ecosystem research and to provide a scientific basis both for policy decisions and for further research.

In the concluding session of the symposium "Acid Deposition, a Challenge for Europe" held in Karlsruhe in September 1983, Dr. GINJAAR, the former Minister of Health and Environmental Protection of the Netherlands, emphasised the need for setting up a concerted research programme including the effects of air pollution on terrestrial and aquatic ecosystems. The Council of Ministers of the European Community in 1984 adopted a revision of the 3rd Community Programme on Environment comprising contract research and concerted action in the field of the effects of air pollution in eco systems. These research areas were also introduced in the 4th R-D Community Programme on Environment, adopted by the Council of Ministers in 1986 and are subject again to contract research and concerted action. The Commission of the European Community is very concerned to increase the effectiveness of researcn projects carried out within the national programmes, and those undertaken at the Community level. The Commission tends to develop an integrated scientific approach, including not only the physico-chemical behaviour, the transport and the deposition of airborne pollutants but also the effects of these pollutants, in particular on living organisms and ecosystems. With regard to the specific issue of the effects, the Commission is trying to develop and strengthen a multi-disciplinary approach associating biologists, pathologists, eco physiologists, and specialists of soil sciences, within the concerted action, as well as within coordinated research projects."