Martin Lorenz

Forest Health Status in Europe

Forest health status in Europe is assessed by the International Cooperative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests). Established by the Convention on Long-Range Transboundary Air Pollution (CLRTAP) under the United Nations Economic Commission for Europe (UNECE), the ICP Forests has been monitoring forest condition in close cooperation with the European Commission (EC) for 20 years. The present paper describes the latest results of the deposition measurements on permanent monitoring plots and of the extensive defoliation sample survey. The findings reveal marked spatial patterns in bulk and throughfall depositions of nitrate (N-NO3), ammonium (N-NH4), and sulfate (S-SO4), as well as an obvious decrease in bulk and throughfall deposition of sulfate. Latest analyses of defoliation data confirm previous results, indicating a high correlation with weather extremes.

Exceedance of critical loads and of critical limits impacts tree nutrition across Europe

Key messageExceedance of critical limits in soil solution samples was more frequent in intensively monitored forest plots across Europe with critical loads for acidity and eutrophication exceeded compared to other plots from the same network. Elevated inorganic nitrogen concentrations in soil solution tended to be related to less favourable nutritional status.ContextForests have been exposed to elevated atmospheric deposition of acidifying and eutrophying sulphur and nitrogen compounds for decades. Critical loads have been identified, below which damage due to acidification and eutrophication are not expected to occur.AimsWe explored the relationship between the exceedance of critical loads and inorganic nitrogen concentration, the base cation to aluminium ratio in soil solutions, as well as the nutritional status of trees.MethodsWe used recent data describing deposition, elemental concentrations in soil solution and foliage, as well as the level of damage to foliage recorded at forest plots of the ICP Forests intensive monitoring network across Europe.ResultsCritical loads for inorganic nitrogen deposition were exceeded on about a third to half of the forest plots. Elevated inorganic nitrogen concentrations in soil solution occurred more frequently among these plots. Indications of nutrient imbalances, such as low magnesium concentration in foliage or discolouration of needles and leaves, were seldom but appeared more frequently on plots where the critical limits for soil solution were exceeded.ConclusionThe findings support the hypothesis that elevated nitrogen and sulphur deposition can lead to imbalances in tree nutrition.

Forest Condition in Europe: 2013 technical report of ICP Forests. Report under the UNECE Convention on Long-Range Transboundary Air Pollution (CLRTAP)

Of the 42 countries that have participated in ICP Forests since 1986, 27 countries reported largescale monitoring data from Level I plots and more detailed forest ecosystem related monitoring data from Level II plots for the year 2012. In total, the participating countries provided information on more than 15,000 plots and more than 220,000 trees. Data analyses for this 2013 Technical Report focused on the impact of air pollution on tree crown condition and on sulphate and nitrogen deposition to forests. In addition, the impact on individual trees of factors other than air pollution, e.g., biotic agents, was assessed. Crown condition is the most widely applied indicator for forest health and vitality of European forests. One of its primary parameters is the rate of defoliation, which is assessed as the percentage of needle/leaf loss in the crown compared to a reference tree with full foliage. The mean defoliation of 114,361 sample trees on 6,168 transnational Level I plots in 2012 was 19.7%. Of all trees assessed in 2012 every fourth to fifth tree (22.9%) was scored as damaged, i.e., had a defoliation rate of more than 25%. In general, broadleaved trees showed a higher mean defoliation rate than conifer species (23.6% and 20.2%, respectively). Oak species still seem to be the most vulnerable of all the investigated species. Of the main species groups, deciduous temperate oak species had the highest mean defoliation (26.5%), closely followed by Mediterranean evergreen oak species (25.2%), and deciduous (sub-) temperate oak species (24.6%). A mean defoliation rate of 19.6% was assessed for European beech (Fagus sylvatica). Coniferous species expressed lower defoliation rates on average, with European spruce (Picea abies) reaching 19.2%, followed by Scots pine (Pinus sylvestris) with 19.3%, and Mediterranean lowland pine species with 20.7%. These figures are, however, not directly comparable to those of previous reports because of fluctuations in the plot sample that are primarily due to changes in the annual participation of countries. Therefore, the temporal development of crown condition was calculated separately from the monitoring results for those countries which have submitted data every year without interruption since 1993, 1998, and 2002, respectively. In addition, maps were drawn that depict temporal species trends in defoliation. The presented results suggest that there was no overall improvement of crown condition for the longest analyzed time period from 1993 to 2012. Over the last 20 years the percentage of plots with clearly increasing mean defoliation (17.2%) even exceeded the share of plots with decreasing defoliation (12.5%) but most of the investigated plots showed no statistically significant change in crown condition (70.3%). Compared to the previous year only, the investigated trees showed on average similar rates of defoliation in 2012. More than three out of four plots (78.7%) showed no statistically significant difference in mean defoliation between those two years. Defoliation increased on 13.8% and decreased on only 7.5% of the plots.

Pan-European Forest Monitoring: An Overview

Abstract Forest assessments aim at meeting a variety of information needs, such as forest health, forest volume and growth, carbon sequestration, biodiversity, as well as relationships between forests, climate change, and air pollution. Respective forest assessments have been implemented in Europe on different scales with different intensities. The ICP Forests has been established in 1985. With its currently more than 6800 large-scale and more than 760 intensive monitoring plots in Europe and with 40 countries of Europe as well as with Canada and the United States of America also participating, ICP Forests constitutes one of the largest forest monitoring programs in the world. It contributes cooperates with numerous scientific and political institutions and programs. In this context, an overview on current forest information needs and on monitoring approaches and initiatives is provided. Examples of main results are provided.Forest assessments aim at meeting a variety of information needs, such as forest health, forest volume and growth, carbon sequestration, biodiversity, as well as relationships between forests, climate change, and air pollution. Respective forest assessments have been implemented in Europe on different scales with different intensities. The ICP Forests has been established in 1985. With its currently more than 6800 large-scale and more than 760 intensive monitoring plots in Europe and with 40 countries of Europe as well as with Canada and the United States of America also participating, ICP Forests constitutes one of the largest forest monitoring programs in the world. It contributes cooperates with numerous scientific and political institutions and programs. In this context, an overview on current forest information needs and on monitoring approaches and initiatives is provided. Examples of main results are provided.