The pollen/vegetation relationship in broadleaved forests dominated by Castanea sativa was analysed using an empirical approach. The pollen content of surface sediments of three lake basins of different sizes (6.3, 22.2, and 101.2 ha) in Ticino (southern Switzerland) was used for a comparison with the surrounding vegetation. We surveyed the vegetation around the two small lakes, Lago di Origlio and Lago di Muzzano, and estimated the relative crown coverage of tree species. The regional vegetation outside the lake catchment (ca. >1 km) was determined with the data from the first Swiss National Forest Inventory. For the third large lake, basin of Ponte Tresa, we used only this latter approach for comparison with pollen data. We compare uncorrected and corrected pollen percentages with vegetational data that were processed with distance-weighting functions. To assess the degree of correspondence between pollen and vegetation data we define a ratio pollen/vegetation, which allows a comparison at the taxon level. The best fit between total pollen load and vegetation is reached for a distance from the lake shore of ca. 300 m for Lago di Origlio (150 × 350 m in size) and of ca. 600 m for Lago di Muzzano (300 × 750 m in size). Beside these general patterns, our analysis reveals taxon-specific pollen dispersal patterns that are in agreement with results from previous studies in northern Europe. Ratios of species with local (proximal) and long-distance (distal) pollen dispersal provide evidence that pollen dispersal mechanisms can influence the size of the taxon-related pollen source area, from small (100-400 m) to large (>5 km) for the same lake. The proportion of distal species increases with increasing lake size, highlighting the predominance of atmospheric pollen transport. We conclude that the large species-related differences in pollen source areas have to be taken into account when the provenance at a site is estimated and discussed.

Forest development models have been used to predict future harvesting potentials and forest management reference levels under the Kyoto guidelines. This contribution aims at presenting the individual-tree simulator MASSIMO and demonstrating its scope of applications with simulations of two possible forest management reference levels (base or business as usual) in an example application. MASSIMO is a suitable tool to predict timber harvesting potentials and forest management reference levels to assess future carbon budgets of Swiss forests. While the current version of MASSIMO accurately accounts for legacy effects and management scenarios, effects of climate and nitrogen deposition on growth, mortality, and regeneration are not yet included. In addition to including climate sensitivity, the software may be further improved by including effects of species mixture on tree growth and assessing ecosystem service provision based on indicators.

Timber-harvesting potential of Swiss forests: simulation of management scenarios Growing stock in Swiss forests has, during the past 10 years, increased by 3% overall, with large regional variation. The increase in Alpine regions has been considerable, while growing stock has decreased on the Plateau. We simulated 5 different 100-year management scenarios with the forest development model Massimo. In the base scenario “constant growing stock”, 7.7 million m3 of merchantable timber could be harvesting annually. In the scenario “increasing growing stock”, the harvesting potential was lower (6.3 million m3), but it was higher in the scenarios “continually high increment” (7.8 million m3), “high demand for coniferous timber“ (8.5 million m3) and “high demand for wood fuel or chemical timber” (8.1 million m3). With time, timber-harvesting costs increase for all scenarios, with the least increase for the base scenario. If the prevailing management system continues (scenario “increasing growing stock”), stands will become denser and growing stock increase, with the risk of more disturbances, e.g. wind, snow-breakage, or bark beetles. In the Plateau, however, the regional overuse of recent decades could limit the overall timber-harvesting potential. In Alpine regions, stabilizing growing stock (scenario “constant growing stock”) could improve the resistance of forests, but the harvesting costs per cubic meter might be higher. These management scenarios provide decision makers with indications of how particular forest management strategies could affect the development of growing stock, harvesting amounts and costs.

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