Kurzbeschreibung
(Englisch)
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Climate and atmospheric deposition are affecting tree growth and carbon allocations in forests. While tree stem growth is partially increasing in Europe, allocation to crown foliage seems to decrease. Mast and seed years seem to increase in frequency. The question of how global warming, increased nitrogen deposition and CO2 concentrations are influencing the frequency and intensity of seed production is highly important for the estimation of forest development under global change. The proposed project intends first to estimate the reoccurring fruit and mast years of the main European tree species using the available large-scale ICP Forests data base (level I plots) and literature studies of the main European tree species, i.e. common beech, Norway spruce, Scots pine and oak species. In a second step the Swiss and the European ICP Forests level II plots with available litterfall, crown condition and tree growth data will be used to quantify the amount of carbon that is allocated in different years to stem wood growth, leaf/needle growth and seed and cone production. Relationships between fruit production and climatic conditions, nutrient supply, atmospheric deposition and general forest conditions will be derived. Finally, the information will be fed back into prediction models.
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Abstract
(Englisch)
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Climate change has an influence on tree growth and carbon sequestration in woody compartments. However, changes of environmental conditions may not only influence total primary production, but also its allocation to stem wood growth, compared to leave and fruit production. This project investigated the effects of temperature on frequency and intensity of fruit production of trees based on (i) visual assessment of fruiting intensity on the ICP Forests Level I plot network and similar surveys and (ii) quantitative measurements of stem growth, foliage and fruit litterfall on the ICP Forests Level II plot network in Europe. The results show that the year to year variations in the fruit production of the trees on a plot is much less synchronous for Pines than for Beech, Spruce and Oak trees. For Beech and Spruce we found patterns of synchronous mast year occurrence with a spatial scale of the European geographical regions. Increasing frequency of mast year was prevalent in UK, North Rhine Westphalia (Germany), Norway and for parts of the dataset from Switzerland. On average fruit production was on 8%, 4%, 12% and 6% of the total C-allocation to above ground tree compartments, for Beech, Oak, Pine, and Spruce trees, respectively. In mast years this percentage was typically two or more time higher than in non-mast years. On average, the absolute stem growth and foliage production were lower in mast years than in other years, except for stem growth of Spruce. Temperature during the 7 days period after 1st April of years preceding mast years were typically higher than in the periods preceding non-mast years in many regions. There were however, regions were the contrary was observed, which might be explained by more frequent water shortage at higher temperatures. Further, there were also regions with mixed or no such relations found in the ICP Forests level I dataset.
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