Forest Condition in Europe - ICP Forests

90 Forest Condition in Europe 2013
conifer bark beetles and a clear one in broadleaves borers. Fungi show a general decrease in
their impact, excepting Dutch elm disease. But the most frequent damaging factors are
drought related damages, which have a high impact in the central, east and south part of the
Iberian Peninsula, excepting Catalonia. “Seca” syndrome damages are concentrated in the
existing focus, not showing a remarkable increment.
The importance of atmospheric pollution in the evolution of forest condition is a factor which
cannot be quantified directly, as it is frequently disguised by other kind of processes which
are more apparent. However, in combination with other agents it can contribute to the degradation
processes of forests.
Sweden
The national results are based on assessment of the main tree species Norway spruce (Picea
abies) and Scots pine (Pinus sylvestris) in the National Forest Inventory (NFI), and concerns,
as previously, only forest of thinning age or older. In total, 7496 trees on 3241 sample plots
were assessed. The Swedish NFI is carried out on permanent as well as on temporary sample
plots. The permanent sample plots, which are 60 percent of the total sample, are remeasured
every 5 th year.
The proportion of trees with more than 25 % defoliation is for Norway spruce 22.8 % and for
Scots pine 10.0 %. In northern Sweden an improvement is seen on Norway spruce while a
decline is observed on Scots pine. In southern Sweden a worsening is seen on both spruce and
pine. The majority of changes seen in defoliation levels during recent years are minor. However,
during the latest years a clear increase of defoliated Scots pine is seen in southern Sweden.
The last year’s outbreak of bark beetles on Norway spruce in central Sweden has decline.
There is however windthrown trees, suitable for colonization, left in the forest since the winterstorm
in 2011, why there is risk of further damage in the near future. In northern Sweden
resin top disease (Cronartium flaccidum) is still a problem in young Scots pine stands. A
special target inventory was undertaken and the results from the inventory show that
damage was found in the entire northern Sweden, but also that no clear changes can be seen
since previous inventories carried out in 2007/2008. The results show no evident spreading of
the disease from the worst affected areas in the northeast. In the northeastern parts of Norrbotten
29 % of young pine forests showed damage (defined as more than 10 % of the trees are
affected). The level of the damage is probably mostly controlled by the presence of favorable
conditions for the fungus, typically due to the weather conditions.
The decline in Ash (Fraxinus excelsior) is continuing in southern Sweden. The large larch
bark beetle (Ips cembrae) has been found in a few areas in southern Sweden. Still, the most
important damage problems are, as previously, due to pine weevil (Hylobius abietis) (in
young forest plantations), browsing by ungulates, mainly elk, (in young forest), and root rot
caused by Heterobasidion annosum.
6.14. Switzerland
In 2012 the Swiss national forest health inventory was carried out on 47 plots of the 16 x 16
km level I grid using the same sampling and assessment methods as in the previous years.
Crown condition in 2012 remained quite similar than in 2011. In 2012 31.4% of the trees had