Forest Condition in Europe - ICP Forests

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72 Forest Condition in Europe 2013 In 2012 compared to 2011 the amount of pine trees damaged decreases from the classes 0 and 2 in favor of the classes 1 and 3, but the classes 0 and 1 are still in majority. Related to defoliation, it was registered a decrease in not defoliated and moderately defoliated trees and an increase in slightly defoliated trees. There were no trees registered in severe defoliation. Results for discolouration showed a very important decrease in not discolouration class (58.3% in 2011 from 13.9% in 2012) and an important increase in slight class (34.7% in 2011 from 77.8% in 2012), and a less important increase in moderate discolouration class. Severe discolouration was not reported. The severe climate conditions of 2012 could explain the deterioration of discolouration. In 2012, the assessment of damage causes showed, as in previous surveys, that the main causal agent was the fungus Cronartium flaccidum which affected 6.9% of the sampled trees and which was distributed in all plots. 5.2. Belarus Not submitted 5.3. Belgium Belgium/Flanders The survey was conducted on 71 plots of the regional 4 x 4 km grid. One transnational 16 x 16 km plot was excluded from the survey because of a clear-cut. The plot design of the Flemish forest inventory was introduced but the ‘Level I’-plots are not part of the NFI. Sample trees were selected on circular plots with a fixed radius of 18 m and the former cross cluster sampling was abandoned. Instead of a fixed number of 24 trees, the number of trees varied between 9 and 132 per plot. On a total of 1778 assessed trees, 56.3% are broad-leaved species and 43.7% are conifers. The main species are Quercus robur, Q. rubra, Fagus sylvatica, Populus sp., Pinus sylvestris and P. nigra subsp. laricio. A sample with ‘other broadleaves’ consists of species like Alnus glutinosa, Castanea sativa, Q. petreae, Fraxinus excelsior, Betula pendula, Acer pseudoplatanus,… 25.0% of the trees were in defoliation classes 2-4. The share of trees with moderate or severe defoliation was 18.5% and 5.0% respectively. 10.2% were considered as healthy and the mortality rate was 1.5%. Broad-leaved tree species revealed a higher defoliation than conifers. 29.0% of the broadleaves and 20.0% of the conifers showed more than 25% defoliation.
Forest Condition in Europe 2013 73 The proportion of moderately to severely defoliated ‘other broadleaves’ was 34.0%. There was a considerable increase of damage in one Alnus glutinosa plot. Defoliation was caused by Phytophthora alni infection, resulting in 21 dead trees and 74.2% of the trees being damaged. Because of the large number of sample trees in this plot, the results influenced the whole survey. The most affected other species were Quercus robur, Pinus nigra subsp. laricio and Populus sp. The crown condition of Populus sp. was comparable to last year but the condition of Q. robur and P. nigra deteriorated. The share of trees in defoliation classes 2-4 was 25.8% for Populus sp., 34.7% for Q. robur and 39.9% for P. nigra. The condition of Fagus sylvatica improved, with only 8.3% of the trees showing more than 25% defoliation. Other less affected species were Q. rubra and P. sylvestris, with 9.7% and 14.0% moderately to severely defoliated trees. Damage by defoliators was observed in several oak plots. On 41.4% of the Q. robur trees, more than 10% of defoliation was caused by insects. In one plot, consecutive years of severe defoliation by Thaumatopoea processionea resulted in tree death. Symptoms of fungi were recorded frequently on Populus sp. (Melampsora larici-populina, rust infection), Q. robur (Microsphaera alphitoides, powdery mildew) and P. nigra (Scirrhia pini, red needle blight). Severe discolouration by Scirrhia pini was recorded on 35.9% of the P. nigra trees. There was a higher incidence of S. pini compared to previous years. Microsphaera alphitoides infection resulted in 32.0% of Q. robur trees with discolouration on more than 10% of the leaf area. The wet summer of 2012 stimulated the spread of fungal diseases like M. alphitoides. Belgium-Wallonia The survey in 2012 concerned 816 trees on 36 plots, on a regional 8x8 km systematic grid. The percentage of trees with a defoliation >=25% shows different long term trend for conifers and broad-leaved: The conifers, which were two time more defoliated in the beginning of the nineties, show this year a rate of 21,6%, lower than last but higher than the last decade. The broad-leaved showed an increase from 10% in 1990 to about 20% in 2005. These damages were mainly due to the degradation of the beech (scolytidae in 2000-2002, drougth in 2003 followed by fruiting in 2004) and of the European oak (drougth in 2003). The rate decrease from 2006 till 2008 with 15,2%, but severely increased in 2009 with 32% and in 2010 with 33,4%; this year the rate is increasing to 39,2 which is the upper level observed! Concerning the mean defoliation observed for the four main species, after an improvement since 2006 for beech and European oak, they increase to about 27,5% for beech and 27,9% for European oak this year. Sessile oak is at a bad condition this year with 22,2%, 5% upper than last year. Spruce shows a non significant increase, with 16,1% this year. Climatic conditions in 2012 do not explain the bad condition of trees; rainfall was at a high level from April to July, with just a dryer period in August and September, with normal temperatures. But the trend is negative since 2008, and we suppose a cumulative effect of stresses in the previous years.
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