The project "Growth trends of European forests - has site productivity changed?" will give a retrospective view of the development of forest site productivity in Europe. All institutions and scientists involved in long-term growth research are invited to contribute to this project.
Data quality and evaluation methods are of central importance. Three data sources will be used in the project: tree analysis data, permanent plot data, and inventory data. Since mainly existing data will be analyzed some limitations have to be accepted: Data may not always be representative for larger areas, stand structure and stand history may not always be well documented in full detail. Data will be checked, evaluated and interpreted by each scientist individually according to common standards. Standardization of methods and presentations are required. Since methods of collecting data differ considetably, evaluation methods have to be adapted to each case. Some standards are recommended. The results of the project will be published in a report consisting of the individual contributions.
The terms "site", "forest site productivity" and "growth trend" are defined. The standards of data quality and evaluation are grouped according to the three data sources. Methods for the detection of growth trends are described and illustrated by examples. Growth trends are defined as deviation of actual growth from expected growth over several decades. The definition of expected growth is therefore important. Past experience on comparable sites will be used as a "growth reference". The paper includes an extensive list of relevant literature. The planned activities and other organizational aspects are presented. Finally, abstracts of papers presented at the workshop in Joensuu 1994 are attached.