Monitoring of forest biodiversity from forest resource inventory data

Forest biodiversity has become a new concern for society. It has introduced new regulations and new ways of thinking in areas of forest use and planning. In Sweden the Forestry Act of 1993 states that timber production and maintenance of biodiversity are objectives of equal dignity. This results in a need for monitoring the maintenance of biodiversity in order to know if the policy intentions are followed. The problem of maintenance of biodiversity can be looked at from different scales, such as species, ecosystem, landscape, regional and national. On the national and regional level it is possible to use forest resource inventory data to get an overview of the forest biodiversity changes. The method used was to analyse the relative changes of variables related to biodiversity over time. The changes are compared to a reference period (1983-1987) and can be calculated as either an annual change or as a moving average of three years data. The variables studied were proportion of the broadleaved species in middle aged forests, amount of dead or windthrown trees, amount of big trees, amount of old unmanaged forest, proportion of wet forests, clear-cut area and habitat diversity. These variables are considered important substrata to produce and maintain a high forest biodiversity. The results show that it is possible to follow the changes of the substrata (prerequisites) which indicate a high forest biodiversity on a broader scale. By introducing new variables more directly related to biodiversity and combining different information sources more effective methods can be developed.