Crown condition survey: a health barometer of trees and forests
INBO monitors forest health using the Level I crown condition survey. In Europe, this large scale survey is carried out simultaneously using a harmonized methodology. The results are reported internationally (www.icp-forests.net).
In Flanders, we investigated the health status of 1473 trees in the summer of 2023. We assessed defoliation and symptoms of damage by biotic or abiotic agents.. A tree is considered as damaged , when more than a quarter of the leaves or needles are missing. 22.6% of the trees in the sample plots were damaged. Among deciduous species, damage was highest in Quercus robur and among conifers in Pinus nigra subsp. laricio. Compared to 2022, we notice an improvement in crown condition. Only in Quercus rubra the proportion of damaged trees increased.
Short-term evolutions in crown condition are often caused by varying weather conditions. Not only do they have a direct impact, they also influence the occurrence of insects and fungi. For example, the hot and dry summer months in 2020 and 2022 resulted in poorer crown condition for most tree species.
Acidification, eutrophication and climate change with associated hazards like storms, drought, heat and forest fire remain the biggest threats to forests, as do newly introduced diseases and infestations.
Geert Sioen, Pieter Verschelde, Peter Roskams
Image above: Quercus robur in De Merel public forest (Level I plot n°85069, Brecht) (INBO photo)