in mosses has declined the most for lead (77%), followed by vanadium (55%), cadmium 74 (51%), chromium (43%), zinc (34%), nickel (33%), iron (27%), arsenic (21%, since 75 1995), mercury (14%, since 1995) and copper (11%). Between 2005 and 2010, the 76 decline ranged from 6% for copper to 36% for lead; for nitrogen the decline was 5%.

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Occurrence of mast years, i.e. the synchronous production of vast amounts of fruits or seeds, has an important impact on forest ecosystems, their functioning and their services. We investigated the mast patterns of the forest tree species common beech, common and sessile oak, Norway spruce and Scots pine in Central and Northern Europe over the last two to three decades. We analysed data from the International Co-operative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests) and additional Danish, German, Flemish and Swiss datasets.Within-plot synchrony of fructification intensity in individual trees was high in beech and spruce and lower in oak species and pine. Mast frequency increased in most regions for beech, whereas the other species showed mixed or no trends. Beech, oak species and spruce showed strong mast year (MY) synchrony, but pine did not. MY synchrony between species was only significant in Bavaria, in Switzerland and between beech, oak species and spruce in Denmark. The deciduous species showed bimodal normal masting, while the conifers had switching normal masting. Oak species and the conifers supported the large seed and the accessory costs hypotheses, and beech and spruce supported the economy of scale, predator satiation and resource allocation hypotheses.

& Key message Volume predictions of sample trees are basic inputs for essential National Forest Inventory (NFI) estimates. The predicted volumes are rarely comparable among European NFIs because of country-specific dbh-thresholds and differences regarding the inclusion of the tree parts stump, stem top, and branches. Twenty-one European NFIs implemented harmonisation measures to provide consistent stem volume predictions for comparable forest resource estimates. & Context The harmonisation of forest information has become increasingly important. International programs and interest groups from the wood industry, energy, and environmental sectors require comparable information. European NFIs as primary source of forest information are well-placed to support policies and decision-making processes with harmonised estimates. & Aims The main objectives were to present the implementation of stem volume harmonisation by European NFIs, to obtain comparable growing stocks according to five reference definitions, and to compare the different results. & Methods The applied harmonisation approach identifies the deviations between country-level and common reference definitions. The deviations are minimised through country-specific bridging functions. Growing stocks were calculated from the unharmonised, and harmonised stem volume estimates and comparisons were made. This article is part of the topical collection on Forest information for bioeconomy outlooks at European level

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