This 2014 Technical Report provides descriptive statistics of the ICP Forests 2013 large-scale (Level I) and 2012 intensive (Level II) monitoring in 25 of the 42 ICP Forests member states, while considering the EEA European forest type classification. It also includes numerical results and national reports of the 2013 national crown condition surveys of 28 member states. Data analyses for this report focus on tree crown condition, including tree damage, and the spatial variation of open field (bulk) and throughfall deposition. The report also contains a description of the new "Aggregated Forest Soil Condition Database" (AFSCDB) of ICP Forests, which will foster integrated evaluations and process-based modelling in the future. Crown condition is one of the most widely applied indicators of tree health and vigor in European forests. One of the variables used for assessing crown condition is foliage density, often referred to as 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 102,115 sample trees on 5672 transnational Level I plots in 25 participating countries in 2013 was 20.3%. Of all trees assessed in 2013 every fifth tree (20.5%) was scored as "damaged", i.e. had a defoliation rate of more than 25%. In general, deciduous trees showed a slightly higher mean defoliation than conifers (23.1% and 20.0%, respectively), and oak species still seemed to be the most vulnerable of all the investigated species. Mediterranean evergreen oak species had the highest mean defoliation rate (25.4%), followed by deciduous temperate oak species (24.0%) and deciduous (sub-) Mediterranean oak species (21.8%). A mean defoliation rate of 21.0% was assessed for European beech (Fagus sylvatica). Coniferous species expressed lower defoliation rates, with Scots pine (Pinus sylvestris) reaching the lowest defoliation rate of all tree species with 18.2%, followed by Norway spruce (Picea abies) with 18.8% and Mediterranean lowland pine species with 20.0%. These defoliation rates are, however, not directly comparable to those of previous reports because of changes in the annual participation of countries and ensuing fluctuations in the plot sample. In consequence, the temporal development of crown condition was calculated separately from the monitoring results for those countries that had submitted data every year without interruption since 1991, 1997, 2002, and 2006, respectively. The report also includes maps that depict species-related trends in mean defoliation on a European-wide scale. Crown condition across Europe did not change significantly from 2012 to 2013. The spatial pattern of the changes in mean defoliation between those two years showed that on 77.5% of the plots no statistically significant differences in mean plot defoliation were detected. The share of plots with an increase in defoliation amounted to 13.4% and the share of plots with a decrease to 9.1%. Evaluations of crown condition also comprise the assessment of tree damage caused by biotic and abiotic factors. In 2013, 40% of the trees included in the damage cause assessments showed some kind of tree damage. As in previous years, insects were the most frequent damage cause and had impaired more than every fourth (28%) of all damaged trees. Abiotic agents caused damage to 14% of the harmed trees and more than half of the symptoms were ascribed to drought (7%), which was also the second most frequent single damage cause. The Aggregated Forest Soil Condition Database (AFSCDB) is a harmonised Level II soil database to better understand processes and changes in forest condition across Europe. It is part of the Forest Soil Condition Databases (FSCDB) of ICP Forests and contains the aggregated soil data of ICP Forests Level II plots of the second soil survey, i.e. soil data collected from 2003 until 2010 with co-funding under different projects. The importance and relevance of this dataset lies in (i) its wide geographical coverage across Europe, (ii) its harmonised methodology, and (iii) its ability to combine soil data with a high number of other forest ecosystem surveys and long-term time series. Despite some limitations of the datasets resulting from analyses conducted by different national laboratories across Europe, this dataset reaches a degree and quality of harmonisation of forest soil data, which has so far not been realized by other international initiatives related to forest soil databases. Measurements of bulk deposition in the open field and throughfall deposition within forest stands belong to the core activities of ICP Forests. These measurements constitute an important source of knowledge about the amount and type of anthropogenic and naturally emitted substances relevant for plants after they have been transported over more or less long distances by air. The following spatial variation of deposition in Europe was found for N-NH4, N-NO3, S-SO4, Ca, and Mg. Maps for the input of calcium and magnesium are depicted with and without sea salt corrections.
− Plots with the highest deposition of N-NH4 are located in central Europe, plots with the lowest deposition in northern and southern Europe, France, and the Baltic states. The highest input with 19.2 kg ha-1 a-1 was found on an oak plot located in northwest Germany.
− Regarding the high and medium deposition fluxes, the spatial pattern for N-NO3 is similar. A maximum value of 14.6 kg ha-1 a-1 was found in the Czech Republic.
− High industry-based deposition of S-SO4 was observed on plots in Belgium and the ridges of the low mountain range extending from Germany to the Czech Republic, Slovakia and southern Poland, with the highest flux of about 19 kg ha-1 on a plot in the Czech Republic. High values were also found on all plots in Greece and on Cyprus, but contrary to individual plots located in the United Kingdom, Norway, and Denmark, their fluxes are not affected by seaborne deposition. The plots in France, Italy, Switzerland, Bulgaria, and most of the plots in Germany and northern Europe are characterized by low deposition.
− The highest values of calcium input were found on plots in the Mediterranean basin and in some regions of eastern Europe. The plots on Cyprus showed the highest fluxes of up to 52.8 kg ha-1 a-1. Low calcium inputs prevail in central and northern Europe.
− The input of magnesium is clearly seaborne. A plot in Italy is the one with the highest input of sea salt corrected magnesium (6.6 kg ha-1 a-1). High deposition was also found on plots in Hungary, Greece, and Cyprus where deposition originates most likely from dust sources.
