Report - ICP Forests

4. National Survey Reports in 2009 99
Damage due to various factors was observed at 14.2% of the sample trees. 1.5% of the trees
died. Most frequent damage was recorded at Fraxinus excelsior (at 45.4% of the trees), Populus
tremula (37.3%) and Quercus robur (32.7%), and more rarely on Pinus sylvestris (9.8% of the
observed trees).
The most frequently observed causes of damage were fungi (4.5%), direct influence of men
(3.4%), and abiotic factors (1.7% of the observed trees). The greatest share of trees with signs of
damage by fungi was noted at Fraxinus excelsior (38.6%, by Armillaria spp.), Populus tremula
(22.8%, mostly by Phellinus tremulae) and Quercus robur (11.6%, mostly by Phellinus robustus).
Mechanical and abiotic damage types were assessed on Picea abies (5.6% and 3.0%) and on
Betula pendula (4.8% and 3.2% of the observed trees).
Unfavourable weather conditions in June were caused by frequent thunderstorms. In some cases
they were accompanied by hail and high wind speeds. On 12th and 13th of June wind speed
reached 110 km/hour in some areas in the eastern part of the Republic. About 4.5 thousand
hectares of wood were thrown by strong winds. Two Level I plots were lost and one was badly
damaged.
4.3 Belgium
Flanders
The large scale survey was conducted on the plots of the former Level I 4 x 4 km grid. On 72
plots, a total of 1 730 sample trees were assessed.
The mean defoliation in the survey was 19.9% and the share of damaged trees was 15.1%.
19.5% of the trees were considered as healthy and the mortality rate was 0.1%. Discolouration
was observed on 8.8% of the sample trees. Broad-leaved trees showed a higher defoliation than
conifers. In broadleaves, average defoliation level was 20.5% with 17.8% of the trees in
defoliation classes 2 to 4. Conifers revealed a better condition, with a mean defoliation of 18.7%
and 9.7% of the trees being damaged.
Populus spp. and Quercus robur were the main broad-leaved species with the highest
defoliation. Mean defoliation was 26.8% in poplar stands and 21.7% in Quercus robur. The
share of damaged trees was 36.7% and 20.2%, respectively. As in previous surveys, defoliation
was lower in Fagus sylvatica and Quercus rubra. Mean defoliation was 15.7% in Fagus
sylvatica and 17.0% in Quercus rubra. Less than 10% of the trees were in defoliation classes 2
to 4 (7.7% and 5.5%). The least affected coniferous species was Pinus sylvestris with 6.4% of
the trees being damaged and a mean defoliation of 17.4%. Mean defoliation in Pinus nigra
subsp. Laricio was 23.4%, with 21.7% of the trees showing moderate to severe defoliation.
Some sample trees were replaced after thinning but there were no removals due to storm
damage. The dry weather in August and September did not have a negative impact on the crown
condition of the most common tree species. Seed production was high in comparison to 2008,
especially in Quercus robur and Fagus sylvatica.
Trees were affected by defoliators in several Quercus forests. Quercus robur showed an
increased level of insect damage, and nests of oak processionary moth (Thaumetopoea
processionea) were observed in more Quercus robur plots. As in 2008 severe infestation of
Populus spp. by rust (Melampsora spp.) was causing discolouration and defoliation.