Cause-effect Relationships of Forest Ecosystems

For more than 20 years the Convention on Long-range Transboundary Air Pollution (CLRTAP) has been striving to control air pollutant emission in Europe and North America. Its Working Group onEffects (WGE) has been responsible for the scientific underpinning. The International CooperativeProgrammes (ICPs) identify air pollution effects on the environment through monitoring, modellingand scientific review. The scientific network of the ICPs and the monitoring and modelling resultshave been promoting the development of the Convention and are an essential component for itssuccess in the future.The International Cooperative Programme on Assessment and Monitoring of Air Pollution Effectson Forests (ICP Forests) collects in close cooperation with the European Commission data anddetermines cause effect relationships of changes in forests due to air pollution and other stresses bymeans of monitoring both at the large scale and at the scale of ecosystems. The International CooperativeProgramme on Integrated Monitoring of Air Pollution Effects on Ecosystems (ICP IM)determines and predicts the state of ecosystems or catchments and their changes from a long-termperspective with respect to the regional variation and impact of air pollutants.Both ICPs have been co-operating closely for a number of years now although the objects understudy are different at first sight. ICP IM is focusing on catchments in undisturbed ecosystems whileICP Forests monitors forest ecosystems which are managed regularly. As most ICP IM sites arewithin forest areas and as many countries have linked their plots of both programmes within onemonitoring system, it is common agreement to intensify the co-operation. One result of this intensiveco-operation is the harmonisation of assessment methods. As the next level of cooperation, thisreport reviews the outstanding data and information gathered by both programmes and presents forvarious areas of research the main findings. In addition results and information were contributed bya large number of participating countries. All support received from the countries in the preparationof the report is gratefully acknowledged.It is expected that this report will intensify the co-operation between the National Focal Centres(NFCs) in all participating countries and help to intensify the work in those areas which will be ofhighest priority for the two programmes in future