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Treeline position, structure, and composition are shaped by natural and anthropogenic factors. At human-disturbed treelines, it is particularly difficult to disentangle the specific role of natural and anthropogenic drivers controlling tree recruitment dynamics following land abandonment. We tested for a possible common regeneration pattern of Pinus nigra Arn. at four upper treeline ecotones in the central Apennines (Italy). The sites were selected based on (1) the occurrence of natural encroachment of P. nigra above 1600 m a.s.l., and (2) the mountain top elevation higher than 2000 m a.s.l. We assessed structure and spatiotemporal patterns of P. nigra advancing regeneration using point and surface pattern analyses. We mapped, measured, and dated 845 trees sampled on a total surface area of 336 ha. P. nigra is the only tree species expanding at high altitude and features a scattered process that started 35-40 years ago, with a maximum recruitment frequency between 1995 and 2003. Pinus regeneration appeared over-dispersed along the slope at a scale range of 12-18 m. We found spatial segregation between saplings and young trees at intermediate distances (8-17 m) and small patches of young trees distributed along the treeline ecotone. The spatial pattern of P. nigra encroachment in the central Apennines revealed a replicable model independent of treeline topography and local disturbance histories. [ABSTRACT FROM AUTHOR]

Resilience against fire disturbance of Mediterranean vegetation has been frequently described. However, due to climatic change and abandonment of local land use practices, the fire regime is changing, probably leading to higher intensities and frequencies of disturbance events. The forthcoming scenario calls for a full understanding of post-disturbance tree recruitment processes, structural resilience and possible consequences on the overall forest biodiversity. In particular, knowledge on severe crown fires' effects on forest stand structural attributes needs to be further explored. In this work, we describe and quantify fire impact and short-term response of a Mediterranean forest affected by high severity crown fires, focusing on the compositional and structural diversity of living and dead trees, spatial pattern of fire-induced mortality, recovery dynamics of tree species. The analysis, based on a synchronic approach, was carried out within four burned and two not burned fully stem-mapped research plots located in NW Italy, belonging to two forest categories differing for their main tree restoration strategies. Distance-dependent and distance-independent indices were applied to assess structural diversity dynamics over time since fire occurrence. Within the analyzed forests fire was found to affect mostly forest structure rather than its composition. Number of snags largely increases immediately after the fire, but it levels off due to their fall dynamics. Regeneration strategies and fire severity influenced species abundance and consequently diversity patterns. Stem diameter and height diversity were modified as well, with a strong increase in the first post-fire year and a sharp reduction six years after the disturbance. Fire determined also a higher heterogeneity in crown cover and vertical structure. Spatial patterns of surviving trees and snags were greatly affected by fire, producing an increase in aggregation and segregation mechanisms. Autosuccessional processes are supposed to preserve current forest structure and composition, but the ecosystem selfrestoring capability should be analyzed in the light of the possible changes in fire regime. [ABSTRACT FROM AUTHOR]

a consequence of land abandonment and marginalization, open areas and traditionally managed wood pastures are disappearing from many alpine valleys. Landscape and stand scale dynamics were analyzed in two neighboring inner valleys of central Italian Alps (Valmalenco, SO) dominated by larch ( Larix decidua Mill.) forests and experiencing different historical land use intensities. Land cover mapping obtained from object-oriented analysis of aerial photographs was used to quantify land cover changes between 1961 and 2003. Spatial statistics were used to quantify landscape patterns, and intensive sampling in permanent plots was employed to perform point pattern analysis at the stand scale. Expansion of forested area at the expense of wood pastures was the main land cover transition observed. Differences in land use intensities were responsible for different patterns at the landscape scale: (1) heavier grazing and human pressure created a more diverse and fragmented mosaic of meadows, open woodlands, forests and wood pastures, (2) lower human impact favored a more homogeneous and stable system. A decline in grazing pressure in the late 1970s favored the establishment of larch and spruce in a clustered pattern, typical of the subalpine belt. Subalpine wood pastures, likewise many other semi-natural environments, are in danger of disappearing and lose their productive and cultural characteristics, because they are developing into more closed and dense stands. [ABSTRACT FROM AUTHOR]

Abstract: It is frequently believed that a post-fire environment requires immediate actions in order to be restored. Salvage logging followed by plantation is a common post-fire restoration practice in many forests of the northwestern Italian Alps. The objectives of this study were to assess the impact of active and passive management techniques on the restoration of a burned area of the Aosta Valley and to determine which approach is the most suitable for enhancing Pinus sylvestris regeneration after stand replacing wildfires. The influence of five management options (no intervention; salvage logging; broadleaves plantation; Larix decidua plantation; P. sylvestris or Pseudotsuga menziesii plantation) and environmental variables on natural regeneration structure and composition was evaluated through direct gradient analysis. Pinus sylvestris and Populus tremula were the dominant tree species (40 and 29%, respectively) in the regeneration layer. Density, size, and structural diversity of natural regeneration were higher in the no intervention area. The proximity to forest edge was found to be the most important environmental variable. This study provided evidence that taking advantage of natural restoration processes may be a suitable alternative strategy to the active restoration practices adopted according to the Aosta Valley policy of post-fire management. [ABSTRACT FROM AUTHOR]

The multitemporal acquisition of images from the Sentinel-1 satellites allows continuous monitoring of a forest. This study focuses on the use of multitemporal C-band synthetic aperture radar (SAR) data to assess the results for forest type (FTY), between coniferous and deciduous forest, and tree species (SPP) classification. We also investigated the temporal stability through the use of backscatter from multiple seasons and years of acquisition. SAR acquisitions were pre-processed, histogram-matched, smoothed, and temperature-corrected. The normalized average backscatter was extracted for interpreted plots and used to train Random Forest models. The classification results were then validated with field plots. A principal component analysis was tested to reduce the dimensionality of the explanatory variables, which generally improved the results. Overall, the FTY classifications were promising, with higher accuracies (OA of 0.94 and K = 0.86) than the SPP classification (OA of 0.66 and K = 0.54). The use of merely winter images (OA = 0.89) reached, on average, results that were almost as good as those using of images from the entire year. The use of images from a single winter season reached a similar result (OA = 0.87). We conclude that multiple Sentinel-1 images acquired in winter conditions are feasible to classify forest types in a hemi-boreal Swedish forest. [ABSTRACT FROM AUTHOR]

Questions: What is the structure of the anthropogenic upper forest-grassland ecotone and are there differences in the spatial relationships between the tree species involved? Location: Valfurva Valley, Italian central Alps. Methods: We conducted a spatial distribution and structure analysis in three 1-ha permanent plots along an altitudinal gradient, from the treeline to the sub-alpine forest. We reconstructed the age structure from cores from each individual with diameter > 4 cm at 50 cm height. Results: All tree species and age classes examined had a clumped structure. The cluster tendency was more evident at the treeline where the environmental conditions are more severe. In the sub-alpine forest there was a repulsion between Pinus cembra and Pious mugo but at the treeline P. cembra was frequently found downslope from P. mugo. Conclusions: Although human influence has been the main driving force in shaping the present forest structure, in the last few decades natural dynamics have become the predominant force acting on forest structure and processes, showing a higher magnitude as altitude increases. Our results emphasize the existence of facilitating and interfering mechanisms between different species. P. cembra seems to be favoured compared to the other tree species. [ABSTRACT FROM AUTHOR]

Spatiotemporal development and human impact on dynamic processes were investigated in the mixed European larch (Larix decidua Mill.) and Swiss stone pine (Pinus cembra L.) subalpine forest of Lago Perso (Piedmont, Italy). We mapped and measured all 295 trees (DBH ≥4 cm) and 914 saplings (>10 cm height, <4 cm DBH) in a permanent plot (1 ha). One core per tree was extracted upslope at 50 cm height, and dendrochronological techniques were applied to reconstruct age structure and growth patterns. All of the data collected were stored in a GIS, and tree and stem crown maps were generated and analysed to quantify spatial patterns. Ripley's K(t) univariate and bivariate point pattern analyses were employed to assess the degree of spatial autocorrelation. Documentary research was conducted to reconstruct human land use. The stand is uneven-aged, and there were no obvious age cohorts or other evidence of major disturbances in the past. Stone pine saplings and trees and larch saplings exhibited a clumped structure. The same clumping was not so evident in larch trees. The observed structural changes are mainly related to human land use and grazing regime. Although human influence is still manifest, in the recent decades natural dynamics have become the predominant influence on the forest's structure and processes. [ABSTRACT FROM AUTHOR]

Due to the associated fire risk, the wildland–urban interface (WUI) has drawn the attention of researchers and managers from a range of backgrounds. From a land management point of view, it is important to identify the WUI to determine areas to prioritise for fire risk prevention. It is also important to know the fire risk mitigation measures available to select the most appropriate for each specific context. In this systematic review, definitions of the WUI were investigated and physical mitigation measures for reducing the risk of fire were examined from a land management perspective. The PRISMA 2020 Statement was applied to records published until 31 December 2022 and retrieved from the Web of Science, Scopus, and other research engines. A total of 162 publications from scientific journals and the grey literature were scrutinised and selected for analysis. Only publications providing an original definition of the WUI or proposing physical measures to reduce fire risk at the interface were retained, while those relating to emergency management and social perception were not considered. The risk of bias was reduced by internal cross-assessment by the research team. Definitions of the WUI (n = 40 publications) changed according to the research objective, varying broadly in identification of the anthropogenic and the wildland components of the interface. Terminology varied according to the definition, and the term wildland–human interface (WHI) was found to be more comprehensive than WUI. Methodological definitions of the interface ranged from using aggregated data through to identification of the buildings at risk in the interface with considerable precision. Five categories of physical fire risk mitigation measures (n = 128 publications) were identified: clearance distances, landscaping, wildland fuel management, land planning, and buildings design and materials. The most effective measures were those applied at early stages of urban development, and maintenance of assets and vegetation is crucial for preparedness. This review represents an analysis of scientific evidence on which land managers can base their actions to reduce the fire hazard risk in the WUI. The number of studies investigating the WUI is considerable, but experimental studies and quantitative results are scarce, and better communication and coordination among research groups and land management agencies is advisable. This systematic review was not registered. [ABSTRACT FROM AUTHOR]

We present the first high-resolution Holocene pollen, plant-macrofossil, and charcoal records from the upper-montane zone in the central Dinaric Alps. Drawing on these new records from well-dated lacustrine sediments of Zminje Jezero (ca. 1500 m a.s.l.; Montenegro) and on independent chironomid-inferred summer temperatures, we explore long-term ecosystem responses to variations in climate, fire disturbances and land use, as well as legacy effects of past environmental changes. A mixed spruce-fir forest established in the upper-montane zone around 9500 cal BP, and Fagus sylvatica became co-dominant with the two conifers after 5000 cal BP. Prehistoric land-use pressure was overall remarkably low, but increased since 2000 cal BP and was highest after the Middle Ages. We found a significant positive relationship between biomass burning and summer temperature, indicating that fires were mostly climate driven. Picea abies was insensitive to summer temperature, biomass burning and human impact, which supports the view that spruce forests may not be significantly impacted by fire. In contrast, Abies alba and other disturbance-sensitive trees (Tilia, Ulmus, Fraxinus excelsior -type) show significant negative responses to land-use pressure and positive responses to summer temperature. This supports the notion that these species may be well-adapted to warmer-than present summer temperatures and that their populations declined in recent millennia due to land-use activities. Conversely, F. sylvatica was sensitive to summer temperatures but was promoted by low biomass burning, indicating that its expansion in the spruce-fir dominated forest was enhanced by the onset of cooler and possibly also moister climatic conditions as well as by fire disturbances. [ABSTRACT FROM AUTHOR]

The efficiency of forest logging operations can be strongly affected by the layout of the harvesting pattern, which is usually based on silvicultural constraints and technical feasibility. Specifically, individual tree volume and the spatial distribution of trees significantly impact the overall harvesting performance. Spatial optimization of tree selection at the forest stand level may improve timber harvest efficiency by maximizing key performance indicators, such as the economic benefit, under given operational and silvicultural constraints. In this study, we applied two harvesting operation-optimization approaches based on integer programming for uphill cable yarding operations in mountain areas, including tree selection and load maximization. The first approach involves tree selection based on single tree harvest, while the second one performs tree selection based on tree clusters harvest per work cycle. As input elements a productivity model, derived by time-motion study with a Mounty MT50-2 and individual tree parameters extracted from high-resolution airborne laser scanning data, were prepared. Single tree information was further rated by financial value, and subsequently combined with the productivity model, allowing a detailed breakdown of operational costs. The results showed that optimizing the tree selection while respecting the allowable cut timber volume established in the harvesting plan can improve the efficiency of forest operations. The cluster approach was shown to be more efficient in terms of economic benefit compared to the actual selection, with an increase of 24.94%. However, the single tree approach resulted in a decrease of economic benefit compared to the actual selection, with a decrease of 22.85%. [ABSTRACT FROM AUTHOR]

Deriving burn severity from multispectral satellite data is a widely adopted approach to infer the degree of environmental change caused by fire. Burn severity maps obtained by thresholding bi-temporal indices based on pre- and post-fire Normalized Burn Ratio (NBR) can vary substantially depending on temporal constraints such as matched acquisition and optimal seasonal timing. Satisfying temporal requirements is crucial to effectively disentangle fire and non-fire induced spectral changes and can be particularly challenging when only a few cloud-free images are available. Our study focuses on 10 wildfires that occurred in mountainous areas of the Piedmont Region (Italy) during autumn 2017 following a severe and prolonged drought period. Our objectives were to: (i) generate reflectance composites using Sentinel-2 imagery that were optimised for seasonal timing by embedding spatial patterns of long-term land surface phenology (LSP); (ii) produce and validate burn severity maps based on the modelled relationship between bi-temporal indices and field data; (iii) compare burn severity maps obtained using either a pair of cloud-free Sentinel-2 images, i.e. paired images, or reflectance composites. We proposed a pixel-based compositing algorithm coupling the weighted geometric median and thematic spatial information, e.g. long-term LSP metrics derived from the MODIS Collection 6 Land Cover Dynamics Product, to rank all the clear observations available in the growing season. Composite Burn Index data and bi-temporal indices exhibited a strong nonlinear relationship (R 2 > 0.85) using paired images or reflectance composites. Burn severity maps attained overall classification accuracy ranging from 76.9% to 83.7% (Kappa between 0.61 and 0.72) and the Relative differenced NBR (RdNBR) achieved the best results compared to other bi-temporal indices (differenced NBR and Relativized Burn Ratio). Improvements in overall classification accuracy offered by the calibration of bi-temporal indices with the dNBR offset were limited to burn severity maps derived from paired images. Reflectance composites provided the highest overall classification accuracy and differences with paired images were significant using uncalibrated bi-temporal indices (4.4% to 5.2%) while they decreased (2.8% to 3.2%) when we calibrated bi-temporal indices derived from paired images. The extent of the high severity category increased by ~19% in burn severity maps derived from reflectance composites (uncalibrated RdNBR) compared to those from paired images (calibrated RdNBR). The reduced contrast between healthy and burnt conditions associated with suboptimal seasonal timing caused an underestimation of burnt areas. By embedding spatial patterns of long-term LSP metrics, our approach provided consistent reflectance composites targeted at a specific phenological stage and minimising non-fire induced inter-annual changes. Being independent from the multispectral dataset employed, the proposed pixel-based compositing approach offers new opportunities for operational change detection applications in geographic areas characterised by persistent cloud cover. • We mapped burn severity using Sentinel-2 paired images and reflectance composites. • Bi-temporal indices benefit from a reduction in non-fire induced spectral changes. • Reflectance composites exhibit spectral consistency in space and time. • Our approach increased the overall classification accuracy up to 5.2%. • Gaining contrast between healthy and burnt vegetation improves burn severity maps. [ABSTRACT FROM AUTHOR]

Worldwide, mountain forests represent a significant factor in reducing rockfall risk over long periods of time on large potential disposition areas. While the economic value of technical protection measures against rockfall can be clearly determined and their benefits indicated, there is no general consensus on the quantification of the protective effect of forests. Experience shows that wherever there is forest, the implementation of technical measures to reduce risk of rockfall might often be dispensable or cheaper, and large deforestations (e.g. after windthrows, forest fires, clear-cuts) often show an increased incidence of rockfall events. This study focussed on how the protective effect of a forest against rockfall can be quantified on an alpine transregional scale. We therefore estimated the runout length, in terms of the angle of reach, of 700 individual rockfall trajectories from 39 release areas from Austria, Germany, Italy and Slovenia. All recorded rockfall events passed through forests which were classified either as coppice forests or, according to the CORINE classification of land cover, as mixed, coniferous or broadleaved dominated high forest stands. For each individual rockfall trajectory, we measured the forest structural parameters stem number, basal area, top height, ratio of shrub to high forest and share of coniferous trees. To quantify the protective effect of forests on rockfall, a hazard reduction factor is introduced, defined as the ratio between an expected angle of reach without forest and the back-calculated forest-influenced angles of reach. The results show that forests significantly reduce the runout length of rockfall. The highest reduction was observed for mixed high forest stands, while the lowest hazard reduction was observed for high forest stands dominated either by coniferous or broadleaved tree species. This implies that as soon as one tree species dominates, the risk reduction factor becomes lower. Coppice forests showed the lowest variability in hazard reduction. Hazard reduction due to forests increases, on average, by 7% for an increase in the stem number by 100 stems per hectare. The proposed concept allows a global view of the effectiveness of protective forests against rockfall processes and thus enable to value forest ecosystem services for future transregional assessments on a European level. Based on our results, general cost–benefit considerations of nature-based solutions against rockfall, such as protective forests as well as first-order evaluations of rockfall hazard reduction effects of silvicultural measures within the different forest types, can be supported. [ABSTRACT FROM AUTHOR]

• Wind damage can heavily impact montane forests. • Models can be used to produce wind vulnerability maps for montane forests. • New parametrisations can be validated and added to existing models. • Mapping vulnerability to wind damage can help forest managers and practitioners. The risk of wind damage to European forests is expected to increase due to the changed climate. Research efforts in forestry have been focussing on the development of analytical and modelling tools to aid with the evaluation and the prediction of forests' vulnerability to wind damage, and ultimately to inform forest management decisions aimed at promoting wind-resistance in forest stands. Recent catastrophic wind damage to European forests has shown that wind damage risk applies also to montane forests. These are of particular importance for the various ecosystem services they provide, including protection from gravitational hazards and defence against soil erosion. At present, the available forest wind risk models have been tested and used mainly on production or planted forests in different countries, but never in the complexity of mountainous terrains. The aim of this study is to introduce a methodology for the validation of a new parametrisation of the ForestGALES wind risk model, specifically designed for the alpine scenario. To do so, we used parameters from pulling tests in the field, and laboratory mechanical tests. We also developed a workflow that, starting from data obtained by LiDAR, aims at producing wind damage vulnerability maps. After validating this new parameterisation, we investigated the variations in wind vulnerability for a case study in the Italian Alps by introducing the Difference of Vulnerability (DoV) raster. Among our results, the DoV proves to be an innovative tool whose future use can increase understanding of the factors predisposing a forest stand to wind instability. [ABSTRACT FROM AUTHOR]

Protection forests effectively preserve people and infrastructures against natural hazardssuch as rockfall, snow avalanches, landslides, debris flows, soil erosion and floods.Consequently, a reduction of this protective effect due to changes in forest structurecan drastically increase the degree of risk related to these phenomena. The Vaiawinter storm (29-30 October 2018) affected 41000 ha of forest in North-EasternItaly, with an amount of windthrow timber volume of 8.6•106 m3, compromisingthe protective function of a large portion of the forests. The aim of this study is toevaluate changes in the protective effect against rockfall of a forest located on thesouthern slope of the Mt. Pore after the damages of the Vaia winter storm. Threescenarios have been considered: 1) forest before the windstorm (condition at summer2018), 2) uncleared windthrow (current status after the windstorm), and 3) clearedwindthrow (removal of all fallen dead stems). Rockfall numerical simulations have beenpursued considering these three scenarios using the 3D rockfall trajectory modelRockyfor3D. The protective effect of the forest in the three scenarios has been evaluatedusing the model outputs to calculate quantitative indicators at the distance of theinfrastructures at risk. Field surveys and a UAV survey carried out during summer 2018allowed the collection and the spatialization of the model input parameters, includingthe forest characteristics before the wind storm. Furthermore, after event on-siteinvestigations allowed the estimation of the windthrow damages and the calibration ofthe model parameters in the second and third scenarios. Modelling results showthat the great amount of dead stems lying on the ground after windthrow (secondscenario) can provide protection against rockfall comparable to the living forest (firstscenario) in the short period. Effectively, even though the forest and the elements onthe ground are not able to stop all the boulders, they can significantly decreasethe kinetic energy of the boulders, reducing the speed and rebound height, anddecreasing the magnitude of the phenomenon. On the other hand, clearing the windthrow(scenario 3) increase the rockfall risk, especially for the infrastructures at higherdistances from the rock cliff. Finally, field surveys supported by remote sensingsurveys are revealed essential in order to achieve simulations adherent to reality. [ABSTRACT FROM AUTHOR]

Large crown fires in the Aosta Valley mostly occur in south-facing slopes where xeric conditions favour the presence of highly flammable conifer stands dominated by Pinus sylvestris. North-facing slopes are less affected by the occurrence of wildfires but the availability of large fuel amounts and prolonged drought periods can raise the fire risk also in these areas. Although stand-replacing wildfires affected about 20% of the total burned forest area from 1989 to 2017, the scarce fire adaptations of Pinus sylvestris pose serious problems for the regeneration of this species and a suitable post-fire management strategy is thus required to enhance this process. Long and mid-term forest regeneration dynamics of Pinus sylvestris were explored using both field surveys and remote sensing techniques in 12 stand-replacing wildfires occurred between 1989 and 2006 in the Aosta Valley. Tree regeneration at different development stages was sampled during 2017 and its fractional cover was also assessed. Time series of Landsat derived spectral vegetation indices were employed to track forest regeneration over time and temporal trajectories were modelled using robust regression methods to assess the magnitude and the direction of spectral changes throughout the years. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Wildfires, insect outbreaks, and windstorms are increasingly common forest disturbances. Post-disturbance management often involves salvage logging, i.e., the felling and removal of the affected trees; however, this practice may represent an additional disturbance with effects on ecosystem processes and services. We developed a systematic map to provide an overview of the primary studies on this topic and created a database with information on the characteristics of the retrieved publications, including information on stands, disturbance, intervention, measured outcomes, and study design. Of 4341 retrieved publications, 90 were retained in the systematic map. These publications represented 49 studies, predominantly from North America and Europe. Salvage logging after wildfire was addressed more frequently than after insect outbreaks or windstorms. Most studies addressed logging after a single disturbance event, and replication of salvaged stands rarely exceeded 10. The most frequent response variables were tree regeneration, ground cover, and deadwood characteristics. This document aims to help managers find the most relevant primary studies on the ecological effects of salvage logging. It also aims to identify and discuss clusters and gaps in the body of evidence, relevant for scientists who aim to synthesize previous work or identify questions for future studies. [ABSTRACT FROM AUTHOR]

Remote sensing supports carbon estimation, allowing the upscaling of field measurements to large extents. Lidar is considered the premier instrument to estimate above ground biomass, but data are expensive and collected on-demand, with limited spatial and temporal coverage. The previous JERS and ALOS SAR satellites data were extensively employed to model forest biomass, with literature suggesting signal saturation at low-moderate biomass values, and an influence of plot size on estimates accuracy. The ALOS2 continuity mission since May 2014 produces data with improved features with respect to the former ALOS, such as increased spatial resolution and reduced revisit time. We used ALOS2 backscatter data, testing also the integration with additional features (SAR textures and NDVI from Landsat 8 data) together with ground truth, to model and map above ground biomass in two mixed forest sites: Tahoe (California) and Asiago (Alps). While texture was useful to improve the model performance, the best model was obtained using joined SAR and NDVI (R² equal to 0.66). In this model, only a slight saturation was observed, at higher levels than what usually reported in literature for SAR; the trend requires further investigation but the model confirmed the complementarity of optical and SAR datatypes. For comparison purposes, we also generated a biomass map for Asiago using lidar data, and considered a previous lidar-based study for Tahoe; in these areas, the observed R² were 0.92 for Tahoe and 0.75 for Asiago, respectively. The quantitative comparison of the carbon stocks obtained with the two methods allows discussion of sensor suitability. The range of local variation captured by lidar is higher than those by SAR and NDVI, with the latter showing overestimation. However, this overestimation is very limited for one of the study areas, suggesting that when the purpose is the overall quantification of the stored carbon, especially in areas with high carbon density, satellite data with lower cost and broad coverage can be as effective as lidar. [ABSTRACT FROM AUTHOR]

Foundation species can change plant community structure by modulating important ecological processes such as community assembly, yet this topic is poorly understood. In alpine systems, cushion plants commonly act as foundation species by ameliorating local conditions. Here, we analyze diversity patterns of species' assembly within cushions and in adjacent surrounding open substrates (83 sites across five continents) calculating floristic dissimilarity between replicate plots, and using linear models to analyze relationships between microhabitats and species diversity. Floristic dissimilarity did not change across biogeographic regions, but was consistently lower in the cushions than in the open microhabitat. Cushion plants appear to enable recruitment of many relatively stress-intolerant species that otherwise would not establish in these communities, yet the niche space constructed by cushion plants supports a more homogeneous composition of species than the niche space beyond the cushion's influence. As a result, cushion plants support higher adiversity and a larger species pool, but harbor assemblies with lower β-diversity than open microhabitats. We conclude that habitats with and without dominant foundation species can strongly differ in the processes that drive species recruitment, and thus the relationship between local and regional species diversity. [ABSTRACT FROM AUTHOR]

Facilitative effects of some species on others are a major driver of biodiversity. These positive effects of a benefactor on its beneficiary can result in negative feedback effects of the beneficiary on the benefactor and reduced fitness of the benefactor. However, in contrast to the wealth of studies on facilitative effects in different environments, we know little about whether the feedback effects show predictable patterns of context dependence., We reanalyzed a global data set on alpine cushion plants, previously used to assess their positive effects on biodiversity and the nature of the beneficiary feedback effects, to specifically assess the context dependence of how small- and large-scale drivers alter the feedback effects of cushion-associated (beneficiary) species on their cushion benefactors using structural equation modelling., The effect of beneficiaries on cushions became negative when beneficiary diversity increased and facilitation was more intense. Local-scale biotic and climatic conditions mediated these community-scale processes, having indirect effects on the feedback effect. High-productivity sites demonstrated weaker negative feedback effects of beneficiaries on the benefactor., Our results indicate a limited impact of the beneficiary feedback effects on benefactor cushions, but strong context dependence. This context dependence may help to explain the ecological and evolutionary persistence of this widespread facilitative system. [ABSTRACT FROM AUTHOR]

Facilitative interactions are defined as positive effects of one species on another, but bidirectional feedbacks may be positive, neutral, or negative. Understanding the bidirectional nature of these interactions is a fundamental prerequisite for the assessment of the potential evolutionary consequences of facilitation., In a global study combining observational and experimental approaches, we quantified the impact of the cover and richness of species associated with alpine cushion plants on reproductive traits of the benefactor cushions., We found a decline in cushion seed production with increasing cover of cushion-associated species, indicating that being a benefactor came at an overall cost. The effect of cushion-associated species was negative for flower density and seed set of cushions, but not for fruit set and seed quality. Richness of cushion-associated species had positive effects on seed density and modulated the effects of their abundance on flower density and fruit set, indicating that the costs and benefits of harboring associated species depend on the composition of the plant assemblage., Our study demonstrates 'parasitic' interactions among plants over a wide range of species and environments in alpine systems, and we consider their implications for the possible selective effects of interactions between benefactor and beneficiary species. [ABSTRACT FROM AUTHOR]

Abstract: The capacity of a forest ecosystem to recover following major disturbances depends on the regeneration characteristics of the species and the environment at the time of establishment, resulting from several interacting biotic and abiotic factors. At climatically stressed sites major drivers of recruitment are the presence of a seed source and the availability of ‘safe sites’ for germination, particularly in the harsh conditions resulting after a stand-replacing wildfire. Post-fire rehabilitation and restoration treatments can produce a deep ecological impact on recruitment processes, acting on biotic legacies and altering the variety and abundance of microsites. Two common post-fire management strategies, salvage logging and the absence of any post-fire intervention, were contrasted in a burned area located in Aosta Valley (North-Western Italy) to identify main environmental variables affecting seedlings and to quantify the effect of shelter elements on tree recruitment. Our hypothesis is that post-fire burned wood management may greatly affect microhabitat suitability for seedling survival in a dry mountain Pinus sylvestris forest. Regeneration density five years after the fire was still low, even though tree species recruitment started immediately following the disturbance. Differences in species composition were found among the investigated treatments. Regeneration density and diversity were positively associated with deadwood. An exception was represented by Populus tremula, regenerating mostly vegetatively, whose behaviour differed from the other tree species. Ground cover conditions contributed to patterns of seedling occurrence. The strong spatial association of seedlings with deadwood suggests that deadwood produces microsites that enhance establishment of regeneration. The relationship between nurse deadwood elements and regeneration was found to be highly anisotropic, as a consequence of the higher protection from radiation and reduced soil moisture loss in the shady sides of the shelter element. In this context post-fire management, particularly when removing burned wood, should be implemented with an understanding of its potential to affect the capacity of the ecosystem to restore, influencing both directly and indirectly recruitment. [Copyright &y& Elsevier]

Knowledge on the range of variability of montane European forests is hampered by limited data on the natural disturbance regime and by the small size of old-growth remnants. We studied the mixed -- Lom forest reserve (55.8 ha) in Bosnia and Herzegovina at three different scales: a grid of 40 sampling points to describe the structural characteristics and their range of variability, three transects to analyse gap size and gap fraction, and a 1.1 ha permanent plot to reconstruct age structure and disturbance history. The forest is characterized by a high volume of living trees (763 m3·ha-1 in the 55.8 ha core area and 1160 m3·ha-1 in the permanent plot) and of coarse woody debris (327 and 383 m3·ha-1, respectively). The percentages of forest area in canopy and expanded gaps are 19% and 41%, respectively. The median canopy gap size is 76.9 m2 and ranges from 11.1 to 708.0 m2. There are large (up to 120 cm diameter at breast height) and very old trees (441, 432, and 416 years for silver fir ( Mill.), Norway spruce ( (L.) Karst.), and European beech ( L.), respectively). During the last three centuries, the disturbance patterns have been characterized by single-tree or small group mortality. In central Europe, this forest is at the end of a gradient from forests characterized by intermediate disturbances to those where very small-scale processes predominate. [ABSTRACT FROM AUTHOR]

This paper reports a semi-automated workflow for detection and quantification of forest damage from windthrow in an Alpine region, in particular from the Vaia storm in October 2018. A web-GIS platform allows to select the damaged area by drawing polygons; several vegetation indices (VIs) are automatically calculated using remote sensing data (Sentinel-2A) and tested to identify the more suitable ones for quantifying forest damage using cross-validation with ground-truth data. Results show that the mean value of NDVI and NDMI decreased in the damaged areas, and have a strong negative correlation with severity. RGI has an opposite behavior in contrast with NDVI and NDMI, as it highlights the red component of the land surface. In all cases, variance of the VI increases after the event between 0.03 and 0.15. Understorey not damaged from the windthrow, if consisting of 40% or more of the total cover in the area, undermines significantly the sensibility of the VIs to detecting and predicting severity. Using aggregational statistics (average and standard deviation) of VIs over polygons as input to a machine learning algorithm, i.e., Random Forest, results in severity prediction with regression reaching a root mean square error (RMSE) of 9.96, on a severity scale of 0–100, using an ensemble of area averages and standard deviations of NDVI, NDMI, and RGI indices. The results show that combining more than one VI can significantly improve the estimation of severity, and web-GIS tools can support decisions with selected VIs. The reported results prove that Sentinel-2 imagery can be deployed and analysed via web-tools to estimate forest damage severity and that VIs can be used via machine learning for predicting severity of damage, with careful evaluation of the effect of understorey in each situation. [ABSTRACT FROM AUTHOR]

Chilean territory is recurrently affected by severe wildfires, which drastically reduce the forest cover and promote runoff, soil erosion and slope instabilities. To understand how the geomorphic system responds to wildfires in terms of sediment dynamics, the assessment of sediment connectivity, i.e. the property describing the relationships between compartments of a geomorphic system, is crucial. This study aims to quantify the spatial linkages between fire severity and sediment connectivity to identify common patterns and driving factors. The compound use of field data and open-source satellite imagery helped to apply the Relative differenced Normalized Burn Ratio (RdNBR) and the Index of Connectivity (IC) in the context of two consecutive wildfires, occurred in 2002 and 2015, in the Rio Toro catchment (Chile). The fire severity assessment showed that the 2002 event affected 90% of the catchment, with high severity areas representing around 70%. The 2015 wildfire instead, affected 76% of the catchment with moderate severity around 42%. Accordingly, as result of the sudden reduction in forest cover in severely affected areas, the IC changed after both wildfires with an overall increase of 1.07 and 0.54, respectively. However, only for the second disturbance, it was possible to observe a clear relationship between the RdNBR and the IC variations. The different degree of vegetation cover heterogeneity between the two pre-wildfire scenarios contributed to different fire severity and IC variability between the two disturbances. The use of open-source satellite data and the development of a weighting factor (W), to be used in IC and able to capture the land cover change driven by the wildfires, could make the application of this approach straightforward, promoting its reproducibility in other catchments for land management and risk mitigation purposes. Unlabelled Image • Burned catchments show sudden ecological and hydro-geomorphic alterations. • Fire severity and sediment connectivity interaction is assessed using RdNBR and IC. • An approach to involve post-wildfire vegetation changes in the IC is presented. • Fire severity and sediment connectivity maps share similar patterns. [ABSTRACT FROM AUTHOR]

Natural disturbances act as a driver in forest communities at different scales shaping both structure and species composition. In a climate change perspective, disturbances are meant to increase both in frequency and in severity, highlighting the necessity for forest managers of quick decision-making for adequate resource planning. Among the recent extreme events in the Alps, the ice-storm that took place during the late winter 2014 was noticeable for its extension, affecting three Countries, one of which got damaged for more than 50% of its forest cover. In the last decades, the use LiDAR technology proved the capability of providing reliable information on forest structure at a landscape scale. A procedure was developed for the assessment and quantification of ice storm damages on stands of three typical Alpine species: Norway spruce (Picea abies Karst.), silver fir (Abies alba Mill.) and European beech (Fagus sylvatica L.). The approach was tested at three different point densities in order to take advantage of the extremely high-resolution of the original point cloud (200 pts/m2) and then to assess the feasibility of a possible wider application to commonly available datasets (i.e. 5 and 10 pts/m2). A direct comparison between measured and derived stand structural parameters did not show satisfactory correlations, while analysing the differences between pre- and post- event in terms of basal area and volume showed the potential of LiDAR in correctly identifying variations of the single parameters. Furthermore, the use of the Leaf Area Density index (Bouvier et al., 2015) showed the possibility of identifying the damage across the vertical profile of the stand and describing how each species was affected. On a wider perspective, this methodology applied to multi-temporal LiDAR scans may allow for rapid assessment of damage intensity and typology over landscapes and future regeneration dynamics. [ABSTRACT FROM AUTHOR]