Report - ICP Forests

4. National Survey Reports in 2009 111
Visible damage symptoms were observed for 16.1% of the assessed trees (18.8% in 2008).
Similarly to the previous years most frequently recorded damage was caused by insects (29.6%
of all cases), followed by others – direct action by man (12.5%), abiotic factors (mostly wind)
(12.1%), fungi (10.6%). The proportion of damaged trees of the most common tree species was
quite similar and constituted 14.1-16.5% of the assessed trees. No serious and extensive attacks
of biotic agents were recorded in 2009. Pinus sylvestris stands in western regions were still
slightly damaged by Neodiprion sertifer and the crowns had not fully recovered from the attacks
of the previous years as well. A local outbreak of Lymantria dispar has continued for the second
year in south-western Latvia. A decline of Alnus was observed in different regions of Latvia, but
the causing agent has not yet been ascertained.
4.17 Lithuania
The national forest inventory and the regional forest health monitoring grids (4 × 4 km) in
Lithuania were combined since 2008. The transnational Level I grid (16 × 16 km) was kept. In
2009 the forest condition survey was carried out on 983 sample plots from which 72 plots were
on the transnational Level I grid and 911 plots on the national forest inventory grid. In total
5 961 sample trees representing 19 tree species were assessed. The main tree species assessed
were Pinus sylvestris, Picea abies, Betula pendula, Betula pubescens, Populus tremula, Alnus
glutinosa, Alnus incana, Fraxinus excelsior, and Quercus robur.
In general, the mean defoliation of all trees species has slightly increased since 2007. However,
mean defoliation of all tree species has varied inconsiderably from 1997 to 2009 and the
condition of Lithuanian forests can be defined as relatively stable.
The mean defoliation of all tree species slightly increased up to 21.3% in 2009 (20.5% in 2008).
18.6% of all sample trees were not defoliated (class 0), 63.7% were slightly defoliated and
17.7% were assessed as moderately defoliated, severely defoliated and dead (defoliation classes
2–4). Mean defoliation of conifers was 20.8% (20.3% in 2008) and for broadleaves 22.1%
(20.8% in 2008).
Mean defoliation of Pinus sylvestris was 20.8% (20.4% in 2008). Starting from 1998 mean
defoliation of Pinus sylvestris has not exceeded 22.0%. The number of trees in defoliation
classes 2-4 decreased to 14.9% (16.4% in 2008). Mean defoliation of Picea abies was only 0.3
percent points higher than in 2008 (20.3%) and the share of trees in defoliation classes 2-4
decreased to 20.9% (24.5% in 2008).
Populus tremula had the lowest mean defoliation and the lowest share of trees in defoliation
classes 2-4. Mean defoliation of Populus tremula was 17.8% (16.3% in 2008) and the
proportion of trees in defoliation classes 2-4 was 9.3% (10.3% in 2007). Mean defoliation of
Alnus glutinosa increased up to 25.1% (18.5% in 2008) and the share of trees in defoliation
classes 2-4 up to 27.9% (16.5% in 2008). It was the worst condition of Alnus glutinosa in the
whole assessment period (1989 – 2009). Mean defoliation of Alnus incana was 1.2 percent
points lower than in 2008 (24.4%). The share of trees in defoliation classes 2-4 decreased to
19.6% (28.9% in 2008). Mean defoliation of Betula spp. Slightly increased to 19.8% (19.1% in
2008) and the share of trees in defoliation classes 2-4 decreased to 13.8% (16.5% in 2008).
The condition of Fraxinus excelsior remained the worst. This tree species had the highest
defoliation since 2000. Mean defoliation of Fraxinus excelsior has been gradually decreasing in
the last few years, but increased again in 2009. Mean defoliation was 39.8% (36.5% in 2008).