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Studying how deadwood mitigates the rockfall hazard in mountain forests is key to understanding the influence of climate-induced disturbances on the protective capacity of mountain forests. Both experimental quantification and numerical process modeling are needed to address this question. Modeling provides detailed insights into the rock–deadwood interaction and can therefore be used to develop effective forest management strategies. Here, we introduce an automatic deadwood generator (ADG) for assessing the impact of fresh woody storm debris on the protective capacity of a forest stand against rockfall. The creation of various deadwood scenarios allows us to directly quantify the mitigation potential of deadwood. To demonstrate the functionality of the proposed ADG method, we compare deadwood log patterns, deadwood effective height, and mesoscale surface ruggedness observed in field surveys in a natural windthrow area with their simulated counterparts. Specifically, we consider two sites near Lake Klöntal, Switzerland, where a major windthrow event occurred in 2019. We perform rockfall simulations for the time (a) before, (b) directly after, and (c) 10 years after the windthrow event. We further compare the results with (d) a simulation with complete clearing of the thrown wood: in other words, a scenario with no standing forest remaining. We showcase an integration of deadwood into rockfall simulations with realistic deadwood configurations alongside a diameter at breast height (DBH)- and rot-fungi-dependent maximum deadwood breaking energy. Our results confirm the mitigation effect of deadwood, which significantly reduces the jump heights and velocities of 400 kg rocks. Our modeling results suggest that, even a decade after the windthrow event, deadwood has a stronger protective effect against rockfall than that provided by standing trees. We conclude that an ADG can contribute to the decision-making involved in forest and deadwood management after disturbances. [ABSTRACT FROM AUTHOR]

Downed and standing deadwood (DW) is a key resource for maintaining forest biodiversity. Although extreme events such as windthrow and fires produce large quantities of DW, this substrate is often drastically reduced by logging activities. To elucidate the respecting consequences of salvage-logging, we assessed both quantity and quality of storm-derived DW (storms Vivian 1990 and Lothar 1999) in Swiss forests using a sample of 90 windthrow sites with ≥3 ha complete windthrow and at elevations ranging from 350 to 1,800 m a.s.l. The majority had been salvage-logged (SL) a few years after the windthrow. On each site, we recorded DW amount and quality on six circular sample plots 20 or 50 m in size. DW volume on SL sites was surprisingly high, with 76.4 m ha on average 20 years after Vivian and 73.8 m ha 10 years after Lothar. In comparison, DW volumes on unsalvaged sites, that is, with no post-windthrow intervention (NI), amounted to 270 m ha. A wide variety of wood decay stages and diameter classes (10 to ≥70 cm) was found on both NI and SL sites, suggesting considerable habitat diversity for DW-associated species irrespective of the treatment. The considerable amounts of DW left after salvage-logging distinctly exceed the minimum DW volumes in forest stands proposed by Müller and Bütler (Eur J For Res 129: 981-992, ) in a conservation context, which demonstrates the importance of wind disturbance for biodiversity. Further studies should quantify DW of individual tree species, since habitat requirements are species-specific. [ABSTRACT FROM AUTHOR]

The article presents a study, which compares forests and wind speed data from 107 winters of 1897-2007 with forest damage in Zurich, Switzerland. It explores the relationships between forest attributes, wind speed and forest damage by evaluating records on forests and wind speed of the said period. It reveals that wind speed increased from the beginning of the 1933 recordings and peaked in the early 1990s.

Abstract: The most severe damage to forests in Central Europe occurs during winter storms caused by Northern Hemispheric mid-latitude cyclones. Storm events in the winter semesters of the past 150 years were investigated to quantify changes and evaluate whether damage rates, forest properties and climate had changed. Records of damage extent (wind throw/snap/breakage), forest area and growing stock in Switzerland were comparatively analysed. Storm damage (m3) was 17 times greater during the period 1958–2007 than during the period 1908–1957 and 22 times greater than in the period 1858–1907. Forest area in Switzerland has increased by 63% and growing stock by 292% over the past 150 years. The significant recent increase in storm damage could only partially be explained by increased growing stock. Weather reports prior to storms indicated that severe storm damage occurred almost always when soils were unfrozen (96%) and wet (96%). During the observation period mean winter temperature has increased by nearly 2°C and winter precipitation has increased by nearly 50% in the study region. In the Zurich region, daily maximum gust wind speed and storm damage were compared. Maximum gust wind speed above 35ms−1 was associated with extensive storm damage. Catastrophic storm damage and maximum gust wind speed measured during storms have increased during recent decades. In conclusion, increasing growing stock, warm winter temperature and high precipitation, and even more markedly, increasing maximum gust wind speed have all contributed to the recent increase in windstorm damage to forests. [Copyright &y& Elsevier]

After a disastrous storm event, quick and reliable information on the extent of forest damage is required. This study evaluated different remote sensing data and methods to detect windthrown forests in mountainous regions as an alternative to the manual analysis of aerial images or terrestrial methods. To this end, both optical satellite sensors (Landsat-7, Spot-4 and Ikonos) and synthetic aperture radar (SAR) data at various frequencies (X-, L-, P- and C-band) were evaluated, and classifications of the windthrown forests were performed. This study was designed to state the advantages and disadvantages of the investigated data and methods. Classification results were compared with aerial images which were interpreted manually on a stereoscopic base. The study showed that the manual interpretation of Ikonos data revealed the most accurate results, followed by an automatic classification of Spot-4 data. Except for ERS-1/2 data, which are too inaccurate in mountainous regions, and SAR P-band data, all sensors and methods investigated have different advantages, so the choice of a specific sensor and method will depend on the question being answered. [ABSTRACT FROM AUTHOR]