Windstorms represent one of the main large-scale disturbances that shape the European landscape and influence its forest structure, so post-event restoration activities start to gain a major role in mountainous forest management. After a disturbance event, biological legacies may enhance or maintain multiple ecosystem services of mountain forests such as protection against natural hazards, biodiversity conservation, or erosion mitigation. However, the conservation of all these ecosystem services after stand-replacing events could go against traditional management practices, such as salvage logging. Thus far, the impact of salvage logging and removal of biological legacies on the protective function of mountain stands has been poorly studied. Structural biological legacies may provide protection for natural regeneration and may also increase the terrain roughness providing a shielding effect against gravitational hazards like rockfall. The aim of this project is to understand the dynamics of post-windthrow recovery processes and to investigate how biological legacies affect the multifunctionality of mountain forests, in particular the protective function. To observe the role of biological legacies we performed 3000 simulations of rockfall activity on windthrown areas. Results show the active role of biological legacies in preventing gravitational hazards, providing a barrier effect and an energy reduction effect on rockfall activity. To conclude, we underline how forest management should take into consideration the protective function of structural legacies. A suggestion is to avoid salvage logging in order to maintain the multifunctionality of damaged stands during the recovery process.
<p>Shallow landslides are one of the most frequent gravitative natural hazards in the Alpine region that could affect human infrastructures. Forests can play a direct protective function, preventing the triggering of such events thanks to the role they play in water regulation and mechanical effects, in particular with root reinforcement. Few studies, however, report empirical assessments, based on after-events shallow landslides inventory, of the protective effects given by the presence of the forest on this natural hazard. With this study, an attempt was made to assess the possible influence of the presence of the forest on the topographic triggering conditions and the magnitude of the landslides respect to those triggered in open lands. A comparison was then developed between the structural characteristics of forest stands, in which landslides were recorded, and the reference parameters of the protection forests guidelines. In addition, it has been evaluated how root reinforcement can have an influence at a local scale on the location of shallow landslide triggering. Finally, a subsample of the forest landslides was selected for field surveys, in order to analyze the influence of stand structure on the magnitude of landslides. The study area corresponds to the territory of upper Agordino valley (405 km<sup>2</sup>), in the Veneto Region (Italy), which was severely affected by storm Vaia in October 2018 that caused widely the trigger of numerous shallow landslides and large windthrows. Through the analysis of the orthophotos pre and post-event and the Dem of Difference of DTMs, overall 469 (116 triggered in the forest) shallow landslides were identified with median values of area of 177 m<sup>2</sup> and volume of 163 m<sup>3</sup>. In terms of density, forest landslides are less frequent than those in open lands and are triggered on slopes with higher inclination. Forest stands where landslides were recorded show median values of coverage of 60%, gap area of 551 m<sup>2</sup>, gap length of 18 m, and gap width of 16 m. It turned out that comparing to the silvicultural guidelines on the management of protection forests, the most important parameter appears to be the gap length. Such gaps represent the weakest zone in terms of root reinforcement where the landslides can be triggered more easily. This has been confirmed by the application, at the plot scale, of the SOSlope model (Cohen and Schwarz, 2017) which results that most of the landslide scarps (42 out of 53) were located in the zones with the lowest lateral root reinforcement. A multivariate analysis carried out on data collected in the field on a subsample of 20 forest landslides highlights that landslides with higher volume and area were recorded mostly in young forests with high density. A stand with a good amount of large trees and an uneven-aged structure seems to be the most effective in these terms. These results emphasize the protective effects of forests against shallow landslides and suggest the need for their optimal silviculture management, taking also into account the increasing susceptibility to other natural disturbances which could compromise the protective function.</p>
<p>Forests provide many important ecosystem services. Natural disturbances, such as wildfires, pest outbreaks and windrows, are the main phenomena shaping forest ecosystems. Due to both climate and global changes, extreme events are increasing in frequency and forests are thus increasingly being affected by stand replacing disturbances. Mountain forest dynamics and ecosystems services are critically influenced by disturbances, in particular storm. In this framework, is crucial to understand these environmental modifications, finding the best management strategies to restore or maintain ecosystem services provided by forests. After large disturbance, there are two different issues to deal with: the large amount of deadwood on the ground, and the needs of&#160; regeneration in order to re-establish the forest cover. To face these problems different management strategies can be adopted. Salvage logging (total or partial) and no-intervention are the two opposite approaches to handle the large amount of deadwood. Natural regeneration or reforestation, instead, are the main strategies to consider to re-establish forest cover. In this study we focused on post-windstorm conditions, in particular concerning large windthrows caused by the Vaia storm, occurred in October 2018 on Eastern Italian Alps. After such large-scale event, natural regeneration is the most convenient strategy to regenerate forest. This process should take place in an area with a high amount of coarse wood debris (CWD). For this reason is crucial to understand the interaction between windthrown timber and regeneration dynamics. In this study we analyzed how CWD is able to create a favorable regeneration microsite enhancing seedling establishment probability. In particular, we focused on two different facilitative mechanisms provided by CWD: microsite amelioration and seedling protection. The former has been analyzed measuring temperature and SWC in the proximity of seedling planted in the surrounding of deadwood elements, the latter by recording browsing evidence at the end of the season. &#160;In order to infer the CWD contribution, control sites have been established in empty sites (no CWD presence in the surrounding). Our results showed that in southern slopes, microsite with significative lower temperature are found northern to the logs, decreasing water stress for saplings. The ameliorative function of logs and CWD in general contribute to decrease the transplanting shock, increasing the probability to establish for saplings. Moreover, the presence of lying deadwood decreased significantly the browsing on saplings. The result of our study highlighted the importance of favorable regeneration microsites provided by deadwood, both for natural regeneration dynamics and for increasing the survival probability for planted saplings. Favorable microsites and nurse biological legacies should be considered in defining post-disturbance management strategies, promoting only a partial salvage logging or non-intervention &#160;approaches as much as possible.</p>
<p>The RESILIENCE project aims at developing&#160; an integrated methodology for assessing the impact of climatic variations and changes on the intense precipitation and wind regimes, and on the consequent triggering of flash floods, debris-flows and wind-related forest damages. A significant increase of short and intense precipitation is expected in the next future due to global warming, with consequent impacts on flash floods and hydro-geomorphic hazards such as shallow landslides and debris flows. Despite their societal importance, only few studies have explored potential climate change effects on these hydrological and hydro-geological processes. In fact, no accepted estimates of such changes to be used in engineering practice or environmental management planning exist so far, nationally or regionally.</p><p>The RESILIENCE project tries to address this specific knowledge gap. Two recent scientific advances are at the basis of the development of RESILIENCE. The first advance is the advent of high-resolution climate models, also called Convection-Permitting Climate Models (CPM), which improve the representation of both precipitation and wind field at the sub-daily scales compared to the standard coarser resolution Regional Climate Models. However, due to their computational costs, simulations are currently available for only short (typically ten years) time slices and few emission scenarios. These time series are too short to provide reliable statistics of extremes if analyzed using the classical extreme value methods. A second recent advance in the field of extreme value theory, the Metastatistical Extreme Value Distribution (MEVD), allows to overcome this limitation: it provides reliable extreme event probability estimates even from short time series, as in the case of CPM outputs, since it is based on all &#8220;ordinary events'' in the series instead of just yearly maxima or a few &#8220;peak-over-threshold&#8221; values per year as in the traditional methods.</p><p>Given this background, and focusing on the Veneto region in Italy as a study area, the specific objectives of RESILIENCE are 1) to quantify near (2041-2050) and far (2090-2099) future changes in precipitation and wind extremes probability at sub-daily temporal scales with respect to the baseline (1996-2005) using the MEVD approach&#160; and high-resolution COSMO-CLM simulations, 2) to quantify the associated future impacts on flash floods, debris flows and forest damages, 3) to provide data and hazard models to support flood and forest risk management plans in the Italian North-East accounting for future climate changes.</p><p>RESILIENCE brings together an interdisciplinary group of scientists, from hydrologists, to climate modelers, to statisticians, to forest science experts, and is based on the interaction with three key Project Stakeholders. The project results will be communicated and disseminated to a wide audience of residents in the Veneto region and beyond, through collaborations with Museums, Academies and Local Authorities.</p>
<p>The interaction of forests and wind disturbances is a topical issue in scientific research, especially considering that the ongoing climate change will lead to a probable increase in the frequency of natural disturbances of high severity (e.g., storms).</p><p>The study of wind-tree interaction has led to the development of various models for predicting wind risk damage to forest stands. Of these models, ForestGALES is the most widely adopted across forest species and geographical locations. Initially developed in the UK as a management tool to assess the susceptibility of plantations to windstorm damage, this semi-empirical, process-based wind risk model has since been expanded and used in other contexts, both European and non-European. Recently ForestGALES has been updated and developed in the R framework (fgr package), in order to be easily applicable to different scenarios. However, the original ForestGALES reference database used to derive empirical coefficients of tree anchorage is limited to a relatively flat area and small size trees (Diameter at Breast Height -DBH- less than 30 cm).</p><p>In this context, the first objective of this research was to investigate the anchorage of standing trees with large diameters by means of pulling tests. Therefore, 44 spruce trees (<em>Picea abies</em> (L.) Karst.), an important species for alpine silviculture and particularly susceptible to wind damage, were subjected to destructive pulling tests.</p><p>&#160;Using a load cell, inclinometers and strain gauges the tree felling was monitored in all its phases. Of the 44 plants tested (DBH> 40 cm), 13 were selected in sloped terrain in order to test if slope may affect stability, in a comparison with trees with similar characteristics on flat terrain. The first results showed that trees on a slope have a higher overturning coefficient and are therefore more resistant to uprooting.</p><p>The data obtained from the field were translated into input parameters for ForestGALES model, allowing to differentiate the parameters for spruce according to the slope of the terrain. The parametrisation was further complemented with physical parameters (MOE and MOR) typical of spruce trees grown in the mountain/dolomitic environment. Using these new parametrisations, wind risk assessment maps were created for a case study area located in the north-eastern Italian Alps. This area was strongly affected by storm Vaia in October 2018, the mapping, therefore, aims to observe the susceptibility of stands before and after the disturbance event.</p>
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