FOREST DEFINITIONS IN LARGE-SCALE INVENTORIES

When designing forest inventories several definitions on the subject to be inventoried have to be fixed. The issue is particularly important in large scale inventories as these inventories cover a broad variety of forest types and conditions. The definitions must be observed when reporting the inventory results. The paper deals with 1 type of the basic definitions: The definition of forest. This definition is important - for the interpretation of inventory results, - for the comparison of results from different inventories: - to assess changes in follow uo inventories, - to compare inventory results of e.g. adjacent inventories, and - for the compilation of results of several inventories. The paper discusses the techniques to assess forest area and the principal quantitative criteria used in forest definitions in large scale inventories. The forest definitions of 15 National Forest Inventories are compared. The comparison showed clearly that it is hardly possible to bring the inventory results in a strictly compatible form. In a quantitative (simulation) study it is examined under different forest definitions what the differences in the resulting forest areas are. A forest definition based on a minimum crown coverage is used in this study. It showed that the differences are mainly due to the structure of the forest distribution and the forest cover percent. The differences are particularly clear in open forest formations as they exist e.g. in upper montane areas and in arid-regions.