Airborne and Terrestrial Laser Scanning Data for the Assessment of Standing and Lying Deadwood: Current Situation and New Perspectives

LiDAR technology is finding uses in the forest sector, not only for surveys in producing forests but also as a tool to gain a deeper understanding of the importance of the three-dimensional component of forest environments. Developments of platforms and sensors in the last decades have highlighted the capacity of this technology to catch relevant details, even at finer scales. This drives its usage towards more ecological topics and applications for forest management. In recent years, nature protection policies have been focusing on deadwood as a key element for the health of forest ecosystems and wide-scale assessments are necessary for the planning process on a landscape scale. Initial studies showed promising results in the identification of bigger deadwood components (e.g., snags, logs, stumps), employing data not specifically collected for the purpose. Nevertheless, many efforts should still be made to transfer the available methodologies to an operational level. Newly available platforms (e.g., Mobile Laser Scanner) and sensors (e.g., Multispectral Laser Scanner) might provide new opportunities for this field of study in the near future

Numerical evaluation of the forest protective role against rockfall after a windthrow: the case study of the Mt. Pore (North-Eastern Italy)

Protection forests effectively preserve people and infrastructures against natural hazards such as rockfall, snow avalanches, landslides, debris flows, soil erosion and floods. Consequently, a reduction of this protective effect due to changes in forest structure can drastically increase the degree of risk related to these phenomena. The Vaia winter storm (29-30 October 2018) affected 41000 ha of forest in North-Eastern Italy, with an amount of windthrow timber volume of 8.6\u2022106 m3, compromising the protective function of a large portion of the forests. The aim of this study is to evaluate changes in the protective effect against rockfall of a forest located on the southern slope of the Mt. Pore after the damages of the Vaia winter storm. Three scenarios have been considered: 1) forest before the windstorm (condition at summer 2018), 2) uncleared windthrow (current status after the windstorm), and 3) cleared windthrow (removal of all fallen dead stems). Rockfall numerical simulations have been pursued considering these three scenarios using the 3D rockfall trajectory model Rockyfor3D. The protective effect of the forest in the three scenarios has been evaluated using the model outputs to calculate quantitative indicators at the distance of the infrastructures at risk. Field surveys and a UAV survey carried out during summer 2018 allowed the collection and the spatialization of the model input parameters, including the forest characteristics before the wind storm. Furthermore, after event on-site investigations allowed the estimation of the windthrow damages and the calibration of the model parameters in the second and third scenarios. Modelling results show that the great amount of dead stems lying on the ground after windthrow (second scenario) can provide protection against rockfall comparable to the living forest (first scenario) in the short period. Effectively, even though the forest and the elements on the ground are not able to stop all the boulders, they can significantly decrease the kinetic energy of the boulders, reducing the speed and rebound height, and decreasing the magnitude of the phenomenon. On the other hand, clearing the windthrow (scenario 3) increase the rockfall risk, especially for the infrastructures at higher distances from the rock cliff. Finally, field surveys supported by remote sensing surveys are revealed essential in order to achieve simulations adherent to reality

Forest fuel assessment by LiDAR data. A case study in NE Italy

Fuel management is a crucial action to maintain wildland fires under the threshold of manageability; hence, in order to allocate resources in the best way, wildland fuel mapping is regarded as a necessary tool by land managers. Several studies have used Aerial Laser Scanner (ALS) data to estimate forest fuels characteristics at plot level, but few have extended such estimates at a zonal level. In the context of the EU Interreg Project CROSSIT SAFER, a test of the possibilities of ALS data to predict fuels attributes has been performed in three different areas: an alpine basin, a coastal wildland-urban interface and a karstic highland. Eighteen sampling plots have been laid out over 6 forest categories, with a special focus on Pinus nigra J. F. Arnold artificial forests. Low density (average 4 points/m2) discrete return LiDAR data has been analysed with FUSION, a free point cloud analysis software tailored to forestry purposes; field and remote sensing data have been connected with simple statistical modelling and results have been spatialised over the case study areas to provide wall-to-wall inputs for FLAMMAP fire behaviour simulation software. Resulting maps can be of relevance for land managers to better highlight the most vulnerable or fire prone areas at a mesoscale administrative level. Limitations and room for improvement are pointed out, in the view that land management should keep updated with the latest technology available

Natural disturbances and protective effect: the role of biological legacies in protection forests

Natural disturbance regimes are expected to be greatly altered in the next future byclimatechanges (e.g.increase in frequency and intensity, changing in seasonality). Among natural disturbances, windstorms represent one of the main large-scale factor that shape European landscape and that influence European forest structure. Moreover, windstorms may affect ecosystem services that are normally provided by mountain forests such as protection against natural hazards, conservation of biodiversity or erosion mitigation. However, after a disturbance event, structural biological legacies, like deadwood, may enhance or maintain some of these ecosystem services. After a stand-replacing event, the conservation or fast restoration of all these services should be the target of post disturbance management, but currently traditional practices (mainly salvage logging) are often leading to their depletion. The study of the impact of salvage logging (i.e. the removal of almost all the biological legacies) on the protective function of mountain stands has been poorly addressed. Structural biological legacies (i.e. snags, logs, stumps) may provide protection for the natural regeneration as well as they may increase the terrain roughness, providing a shielding effect against gravitative hazards like rockfall. The aim of the present study was to investigate how biological legacies affect the multifunctionality of mountain forests, focusing on the protective function. To observe the role of biological legacies we performed software simulations of rockfall activity on windthrown areas located in the Dolomites, region highly affected by the Vaia windstorm in October 2018. Results showed the short-term important role of biological legacies in mitigating rockfall propagation, mainly as barrier effect rather than an energy reduction effect. After a natural disturbance, forest management should take into consideration the residual protective function of structural legacies. Salvage logging operations should be limited in areas where rockfall hazard is high, in order to take advantage on the multifunctionality of biological legacies during the recovery process