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30 years of forest health monitoring


Photo: Volkmar Timmermann.

There are over 11 billion trees in the Norwegian forest. The timber value alone amounts to several hundred billion Norwegian crowns. To protect these values, researchers follow the forests’ state of health and monitor harmful fungi and insects.

The Norwegian Monitoring Programme for Forest Damage was started up as a result of extensive forest death in central Europe in the mid-1980s, among other things. As part of the European forest health monitoring, tree health is measured at 2600 measurement points around the country. It’s like a national health survey, in which a group of people are followed throughout their lives, and in which blood samples are taken which may say something about the population's health status.

But trees do not have blood vessels, so it’s the condition of the tree crown that is evaluated. Branches and needles or leaves make up the crown, and the trees’ health is therefore judged from observation of the crowns’ condition.

- Low crown density reflects the degree of stress or damage the tree has been subjected to, explains NIBIO-biologist and expert on fungi Volkmar Timmermann.

In three places in the country researchers have established monitoring sites where much more intensive and detailed surveys are carried out. Samplers have been set up that collect rain or snow to check among other things the acidity (pH) of the precipitation. In addition, measurements are made in the water that falls through the canopies, throughfall. Water in the soil under the trees is also collected and analysed for contents of nutrients, aluminium, pH and sulphur and nitrogen compounds. In addition, measurements are made of needle chemistry, tree growth, and changes in vegetation.

However, the monitoring programme’s regular registrations are not always enough to be able to detect new pests. Thus, it is important that those who visit the forests are observant and report damage they have seen. One way to report damage is through the Web portal skogskader.no.