Long-term research on storm areas demonstrates the potential and the limits of natural regeneration After windthrow, questions arise about the appropriate silvicultural management. Answers can be derived from long-term studies on 19 storm-damaged areas caused by Vivian (1990) and Lothar (1999), which encompass cleared, cleared and planted as well as uncleared subareas. Forest succession on these areas was studied using repeated regeneration inventories. Ten resp. 20 years after the storms, the resulting young forests were 3–12 m tall and had a stem density of 500 to 31,400 per ha. Many tree species grow in the storm areas, with climax species like European beech (in the lowlands) and Norway spruce (in high-altitude forests) being most frequent. Advance regeneration has only a small share of the young stands, since seedlings were scarce in the pre-storm stands. Regeneration is slightly more dense on cleared than on uncleared storm areas. The yearly increase in seedling density ranged from 25 to 4,000 trees per ha, with low values occurring mainly if dense vegetation of tall forbs, bramble or bracken covered the ground. The increase in density has fallen since the storms, and in thickets with high stem numbers, the regeneration density has even started to decrease. Pionieer trees as well as sycamore maple and ash grow fastest, and climax species like Norway spruce and silver fir slowest. For spruce, planting results in an advance of 1.0 to 2.4 m after 20 years in high montane storm areas; moreover, gaps, which are widespread in storm areas even 10 or 20 years after the storm event, can be avoided. On areas with total damage, cluster planting should be considered, in particular in protection forests and in cases with scarce advance regeneration, missing seed trees and dense ground vegetation.

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Silver fir is a highly desirable species in European mountain forests from a management and conservation point of view, but it is also highly palatable for ungulates. We planted Abies alba saplings along natural light gradients to explore under natural browsing: (1) the light conditions under which saplings grow best in the absence of browsing; (2) when and by which ungulate species which saplings are browsed; and (3) under which conditions saplings react most vigorously to browsing. The experiment was carried out in a Swiss forest using four fenced plots each containing about 30 saplings planted in 2001, which were between 17 and 100 cm tall in 2009. For half of the saplings, browsing was allowed and filmed from April 2009 to January 2010. Saplings grew better with more light (13 % rather than 10 % canopy openness). Browsing was not a single event per sapling but a continuous process during the winter months. Almost all saplings exposed to browsing suffered heavy browsing by chamois and red deer, but no roe deer browsing was observed. The remainder of the browsed shoots were longer and contained more buds under 13 % canopy openness. The browsinginduced height differences between browsed and unbrowsed trees increased over time under all light conditions, and almost no diameter growth was measured in the years after browsing. In cases with severe browsing, management aimed at letting in more light does not lead to a substantially better tolerance of browsing. We thus recommend integrating the ''feeding strength'' in the assessment of browsing.

Früher Laubfall der Buche während der Sommertrockenheit 2018: Resistenz oder Schwächesymptom? Die Sommertrockenheit 2018 führte in verschiedenen Regionen der Schweiz zum vorzeitigen Laubfall bei Bu-chen (Fagus sylvatica L.). Es stellte sich die Frage, ob dieser Laubfall als Resistenzreaktion aufgefasst werden soll, die den Buchen einen physiologischen Vorteil verschafft, oder als ausgeprägtes Schwächesymptom. Zur Beantwortung dieser Frage führten wir im Spätsommer 2018 Zustandserhebungen bei 781 ausgewachsenen Buchen mit frühem und 138 mit normalem Laubfall (insgesamt 919 Bäume) in den Regionen Aargau/Zürich (AG/ZH), Baselland (BL) und Schaffhausen (SH) durch. Erneute Begutachtungen und Probenahmen verschiedener Parameter im Frühling und Sommer 2019 zeigten, dass von den Buchen mit frühem Laubfall regional zwischen 1.4% und 4.7% abstarben. Die mittlere Kronenmortalität im Sommer 2019 betrug für Bäume mit frühem Laubfall in BL 35.6%, in SH 30.0% und in AG/ZH 17.4%. Bei Bäumen mit normalem Laubfall in der Nachbarschaft lagen die Werte nur bei 13.0% (BL) und 5.3% (AG/ZH). Die mittleren Mortalitätsraten stiegen 2019 vom Frühling bis zum Sommer an. Bäume mit frühem Laubfall trugen generell mehr Früchte (Mast-Effekt). In BL traten bei Bäumen mit frühem Laubfall signifikant mehr Rindenschäden und Nekrosen auf als bei Bäumen mit normalem Laub-fall. Bäume mit frühem Laubfall wurden dort häufiger von Buchenwollschildläusen befallen, und deren Blätter im Kronendach wurden stärker durch Insekten und Pilze beeinträchtigt. In AG/ZH wiesen die Bäume mit frühem Laubfall deutlich häufiger Schleimfluss auf, und sie standen öfter am Waldrand. Aufgrund unserer Resultate stellt der verfrühte Laubfall bei Buchen, wie er sich während der ausgeprägten Sommertrockenheit 2018 ereignete, ein Schwächesymptom dar, das durch die Beobachtung gestützt wird, dass viele Zweige und Äste im Jahr nach der Trockenheit nicht mehr ausgetrieben haben bzw. abstarben.

In anticipation of more severe summer droughts, forestry in temperate Europe is searching for drought-resistant ecotypes of native tree species that might maintain ecosystem services in the future. We investigated how spring precipitation and soil conditions interact with summer drought and affect the establishment of conifer seedlings from different climatic origin. Emergence, establishment and subsequent performance of seedlings originating from autochthonous, Central Alpine, continental Eastern European, and Mediterranean Pinus sylvestris and Picea abies populations were studied in the dry Alpine Rhine valley, Switzerland, at three sites with differing soil water holding capacities and in 3 years with contrasting weather conditions. In addition to this natural inter-annual variation, precipitation was manipulated within sites with throughfall reduction roofs. Seedling establishment and growth were principally affected by the spring weather in the year of emergence. In years with average to positive spring water balance, seedlings grown at the site with the highest water holding capacity had 2-5 times more aboveground biomass than seedlings grown at sites with less favourable soils. Effects of seed origin were marginal and only detectable at the drier sites: contrary to our expectations, seedlings from the Central Alpine Rhone valley, where the climatic spring water deficit is large, outperformed those from the Mediterranean. Consequently, plantation of non-native populations from dryer origin will mitigate the effects of increased summer drought at driest sites only, while the inter-annual variability of spring precipitation will continue to enable temperate conifers to regenerate on a wide range of forest soils independent of seed origin.