Divscaling - Flächenabhängigkeit von Diversität im Wald

The main objective of this project is to elaborate how different diversity components in Swiss forests change with increasing area and how they depend on changing heterogeneity.

The main task of the Swiss National Forest Inventory (NFI) is to monitor the development of the Swiss forest with regard to all its services and its sustainability, including diversity. For example, the occurrence of all tree species from a height of 40 cm is surveyed in a sample area of 200 m2. Other forest inventories in Switzerland (forest enterprises, regional inventories) and national inventories of other countries work with different sample area sizes. The comparability of diversity indicators between different inventories is considered important, but is only permitted to a limited extent because diversity does not linearly relate to the sample area.

The main goal of DivScaling is to find out how exactly diversity in Swiss forests changes in relation to sample area, and how additional factors influence this relationship. This is to be achieved using diversity area curves. Diversity-area curves have their origin in species-area curves, a tool with a long-lasting history in ecology to describe how diversity is related to sample area. Basically, species-area curves show that species numbers increase relatively steeply with increasing area, before gradually approaching a maximum. Recent studies show that the increase in diversity is determined not only by increasing sample area but also by increasing heterogeneity of environmental conditions. The DivScaling project aims to use this knowledge to analyze the relationship between sample area, heterogeneity and diversity for the Swiss forests in order to come up with reliable statements on diversity (and its uncertainties) in Swiss forests for any unit with a given size.

The second goal is to assess the area-dependence not only for taxonomic diversity, but also for additional diversity components such as structural, functional, and phylogenetic diversity. Structural diversity is crucial for the existence of micro-habitats for countless forest animal species, functional diversity is used in connection with the functioning of the forest ecosystem, and phylogenetic diversity can show how much evolutionary diversity is accumulated in a forest community.

The third objective is to compare the relationships between area, heterogeneity and diversity components determined for Switzerland in greater depth using international data sets (Europe, North America). This will show how well the approach proposed here can solve the problem of comparing diversity across sample areas of different sizes across the various inventories.