About the Forest Condition Survey

The National Forest Condition Survey (WZE) is a terrestrial sample inventory based on a permanent systematic sampling grid (Level I network). The condition of the tree crowns serves as an indicator of the vitality of the forests. The WZE has been conducted annually in the old federal states since 1984 and in the new federal states since 1990.

Since January 1, 2014, it has been carried out on the basis of the Federal Ordinance ForUmV, which is anchored in the Federal Forest Act (§41a paragraph 6BWaldG).

The nationwide survey is conducted on a grid of 16 × 16 kilometers and currently covers over 420 points at which approximately 10,000 trees are assessed. This enables representative results for the most important tree species at the federal level. The federal states have densified this network as needed in order to be able to make statements at the state level and for individual regions. The field surveys and initial examination of the data are carried out by the federal states. The data is compiled and evaluated at the Thünen Institute of Forest Ecosystems. The nationwide findings are published annually by the Federal Ministry of Food, Agriculture, and Consumer Protection and are included in excerpts in various reports, e.g., the Federal Government's Forest Condition Report, the Agricultural Report, or the Statistical Yearbook on Food, Agriculture, and Forestry. The data is also used in the international forest condition survey (UNECE ICP Forests).

The forest condition survey procedure consists of a visual assessment of the externally visible health or damage status of individual trees. The key parameter here is crown thinning, which is assessed in 5% increments based on needle or leaf loss in relation to a reference tree. In addition, other characteristics are recorded that can provide information about the vitality of the trees and the causes of crown thinning. These include, for example, the intensity of fruiting, yellowing of leaves or needles, insect and fungal infestation, and trunk and crown damage.

Data collection is based on an internationally agreed manual. In order to ensure methodologically comparable data collection within the framework of the WZE, additional quality assurance and control measures are carried out. An important component is the annual national coordination course for state inventory managers. Following this, the Thünen Institute of Forest Ecosystems analyzes the results of the coordination courses and compiles a report that is made available to the participants.

Further information can also be found on the Thünen website.