Forest Condition in Europe - ICP Forests

84 Forest Condition in Europe 2013
by direct action of men (34.2% of all cases), insects (23.0%), animals (21.2%), fungi (11.7%)
and abiotic factors (7.6%). Other damage causes were recorded for 0.6% of all cases and unknown
cause – for 1.6% of all cases. The distribution of damage causes was considerably different
than last year when damage by abiotic factors constituted 21.3% of all cases, by direct
action of man - 17.7% and by fungi - 15.1%. The proportion of insect damages has increased
considerably since last year. Differences in the distribution of damage causes are most likely
induced by the change of dataset and expected maximum of outbreak of Lymantria monacha
that started in the vicinity of Riga city in 2011. The greatest share of trees with damage symptoms
was recorded for Populus tremula (19%) and the smallest – for Betula spp. (10.5%).
6.5. Lithuania
In 2012 forest condition survey was carried out on 1011 sample plots from which 79 plots
were on the transnational Level I grid and 932 plots on the National Forest Inventory grid. In
total 5732 sample trees representing 18 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, Quercus robur.
The mean defoliation of all tree species slightly increased to 22.6% (21.2% in 2011). 16.3%
of all sample trees were not defoliated (class 0), 59.2% were slightly defoliated and 24.5%
were assessed as moderately defoliated, severely defoliated and dead (defoliation classes 2-4).
Mean defoliation of conifers slightly increased to 23.0% (21.1% in 2011) and for broadleaves
– to 22.1% (21.3% in 2011).
Populus tremula had the lowest mean defoliation and the lowest share of trees in defoliation
classes 2-4. Mean defoliation of Populus tremula was 17.1% (17.3% in 2011) and the proportion
of trees in defoliation classes 2-4 was only 3.6% (4.4% in 2011). Due to spring frost in
2009 condition of Alnus glutinosa was the worst in 2009 – 2010. Condition of Alnus glutinosa
was finally regenerated in 2012. Mean defoliation decreased to 18.7% (25.1% in 2009; 23.4%
in 2010; 19.4% in 2011) and the share of trees in defoliation classes 2-4 was 10.3% (27.9% in
2009; 25.0% in 2010; 9.5% in 2011).
Condition of Fraxinus excelsior remained the worst between all observed tree species. This
tree species had the highest defoliation since year 2000. Assessed mean defoliation was
39.0% (43.5% in 2011). The share of trees in defoliation classes 2-4 increased up to 55.7%
(58.3% in 2011). The reasons for such significantly bad condition, has not been defined yet.
19.6% of all sample trees had some kind of identifiable damages symptoms. The most frequent
damages were caused by abiotic agents (about 6.0 %) in the period of 2010 – 2012. It is
closely connected with the storm that hitted the South-Eastern part of Lithuania in
08.08.2010. The highest share of damages symptoms were assessed for Fraxinus excelsior
(44.3%), Populus tremula (30.6%) and Alnus incana (28.4%), the least for Alnus glutinosa
(12.7%) and for Pinus sylvestris (14.9%).
In general, mean defoliation of all tree species has varied inconsiderably from 1997 to 2012
and the condition of Lithuanian forests can be defined as relatively stable.