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In Europe, forest management has controlled forest dynamics to sustain commodity production over multiple centuries. Yet over‐regulation for growth and yield diminishes resilience to environmental stress as well as threatens biodiversity, leading to increasing forest susceptibility to an array of disturbances. These trends have stimulated interest in alternative management systems, including natural dynamics silviculture (NDS). NDS aims to emulate natural disturbance dynamics at stand and landscape scales through silvicultural manipulations of forest structure and landscape patterns. We adapted a "Comparability Index" (CI) to assess convergence/divergence between natural disturbances and forest management effects. We extended the original CI concept based on disturbance size and frequency by adding the residual structure of canopy trees after a disturbance as a third dimension. We populated the model by compiling data on natural disturbance dynamics and management from 13 countries in Europe, covering four major forest types (i.e., spruce, beech, oak, and pine‐dominated forests). We found that natural disturbances are highly variable in size, frequency, and residual structure, but European forest management fails to encompass this complexity. Silviculture in Europe is skewed toward even‐aged systems, used predominately (72.9% of management) across the countries assessed. The residual structure proved crucial in the comparison of natural disturbances and silvicultural systems. CI indicated the highest congruence between uneven‐aged silvicultural systems and key natural disturbance attributes. Even so, uneven‐aged practices emulated only a portion of the complexity associated with natural disturbance effects. The remaining silvicultural systems perform poorly in terms of retention compared to tree survivorship after natural disturbances. We suggest that NDS can enrich Europe's portfolio of management systems, for example where wood production is not the primary objective. NDS is especially relevant to forests managed for habitat quality, risk reduction, and a variety of ecosystem services. We suggest a holistic approach integrating NDS with more conventional practices. [ABSTRACT FROM AUTHOR]

Context: Since the nineteenth century, rural areas have experienced progressive abandonment mostly due to socioeconomic changes, with direct and indirect effects on forest disturbance regimes occurring in these human-dominated landscapes. The role of land abandonment in modifying disturbance regimes has been highlighted for some types of disturbances, albeit being still somewhat overlooked compared to climate change. Objectives: This literature review is aimed at highlighting the most relevant effects of land abandonment and land-use legacy on the regime of different types of forest disturbances, providing insight into land-use change/disturbances interactions. Methods: We searched in the Scopus and Web of Science databases for relevant studies at the global scale dealing with eight major natural disturbances: avalanche, flooding, herbivory, insect outbreak, landslide, rockfall, wildfire and windthrow. We classified papers into five relevance classes, with the highest score (4) assigned to studies quantitatively measuring the interactions between abandonment dynamics and disturbance regimes. Results: Most papers focused on wildfires in Mediterranean Europe in the twentieth century, where landscape homogenisation and fuel build-up contributed to worsening their frequency, size and severity. Dense forests developed following land abandonment instead exert inhibiting effects toward mass movements such as avalanches, rockfalls and landslides. Regarding the other investigated disturbances, we found only a few studies presenting site-specific and partly contrasting effects. Conclusions: Land abandonment triggers ecological processes at the landscape scale, altering land cover patterns and vegetation communities, which in turn affect disturbance regimes. Implications for land and resource management mostly depend on the stage at which post-abandonment secondary succession has developed. [ABSTRACT FROM AUTHOR]

European larch is a dominant species in the subalpine belt of the western Alps. Despite recent increases in wildfire activity in this region, fire ecology of European larch is poorly understood compared to other larch species around the world. This study aims to assess whether European larch forests are resilient to fires, and to find out the factors that drive such resilience. We assessed the recovery of larch forests along a gradient of fire severity (low, moderate, high) based on the abundance and dominance of post-fire larch regeneration. We established 200 plots distributed among burned larch forests in nine wildfires that occurred between 1973 and 2007 in the western Alps. We included variables regarding topography, climate, fire severity, fire legacies, ground cover, grazing intensity, and time since fire. To evaluate potential drivers of larch recruitment, we applied generalized linear mixed models (GLMM) and random forests (RF). Larch regeneration was much more abundant and dominant in the moderate- and high-severity fire classes than in the low-severity class. More than half of the plots in the moderate- and high-severity classes were classified as resilient, i.e., post-fire larch regeneration was enough to recover a larch stand. GLMM and RF produced complementary results: fire severity and legacies, such as snags, canopy cover and distance to seed source, were crucial factors explaining post-fire larch recruitment. This study shows that fire has a positive effect on larch regeneration, and we conclude that European larch forests are highly resilient to mixed-severity fires in the western Alps. [ABSTRACT FROM AUTHOR]

Scots pine ( Pinus sylvestris L.) and European beech ( Fagus sylvatica L.) dominate many of the European forest stands. Also, mixtures of European beech and Scots pine more or less occur over all European countries, but have been scarcely investigated. The area occupied by each species is of high relevance, especially for growth evaluation and comparison of different species in mixed and monospecific stands. Thus, we studied different methods to describe species proportions and their definition as proportion by area. 25 triplets consisting of mixed and monospecific stands were established across Europe ranging from Lithuania to Spain in northern to southern direction and from Bulgaria to Belgium in eastern to western direction. On stand level, the conclusive method for estimating the species proportion as a fraction of the stand area relates the observed density (tree number or basal area) to its potential. This stand-level estimation makes use of the potential from comparable neighboring monospecific stands or from maximum density lines derived from other data, e.g. forest inventories or permanent observations plots. At tree level, the fraction of the stand area occupied by a species can be derived from the proportions of their crown projection area or of their leaf area. The estimates of the potentials obtained from neighboring monospecific stands, especially in older stands, were poorer than those from the maximum density line depending on the Martonne aridity index. Therefore, the stand-level method in combination with the Martonne aridity index for potential densities can be highly recommended. The species' proportions estimated with this method are best approximated by the proportions of the species' leaf areas. In forest practice, the most commonly applied method is an ocular estimation of the proportions by crown projection area. Even though the proportions of pine were calculated here by measuring crown projection areas in the field, we found this method to underestimate the proportion by 25% compared to the stand-level approach. [ABSTRACT FROM AUTHOR]

Aerial LiDAR (Light Detection and Ranging) derived data are widely adopted for the study and characterization of forests. In particular, LiDAR derived-CHM (Canopy Height Model) has proved essential in identifying tree height variability and estimating many forest features such as biomass and wood volume. However, CHM quality may be affected by internal limits and anomalies caused by raw data (point cloud) processing (i.e., vertical errors), which are quite often disregarded by users, thus generating potentially erroneous results in their applications. In this work, an auto-consistent procedure for the fast evaluation of CHM accuracy has been developed based on the assessment of internal anomalies affecting CHM data obtained by differencing gridded DSM (Digital Surface Model) and DTM (Digital Terrain Model). To this purpose, a CHM was generated using the gridded DTMs and DSMs provided by the Cartographic Office of the Piemonte Region (north-western Italy). We estimated the local potential CHM error over the whole region, and demonstrated its strictly dependence on the terrain morphometry, particularly slope. The relationship between potential CHM error and slope was modeled separately for mountain, hill and flat terrain contexts, and used to produce a potential error map over the whole region. Our results showed that approximately 20% of the regional territory suffers from CHM uncertainty (in particular high elevation areas, including the treeline), though the majority of regional forest categories was affected by negligible CHM error. The potential consequences of CHM error in forest applications were evaluated, concluding that the tested LiDAR dataset provide a reliable basis for forest applications in most of the regional territory. [ABSTRACT FROM AUTHOR]

Abstract: Pattern analysis of tree stems in forests stands is commonly used to assess the type and intensity of tree-to-tree interactions. Crowns are directly involved in competition for light, and plastically react by growing asymmetrically. We tested the hypothesis that the spatial pattern of crown centers is different than that of stem bases, and specifically more regular due to optimal foraging. We also postulated that shift to regularity in crown spatial pattern was directly related to individual crown asymmetry and the intensity of competition in the stand. We computed point pattern statistics in four long-term forest monitoring plots, established in Scots pine forests of the Alps, and the intensity of spatial association of crown centroids versus stem locations. Crown asymmetry was significantly correlated to competitive status. Crowns were more regularly distributed than stems in mature stands, but not so in a young stand where competition was at a lower intensity. At the stand level, the shift towards regularity was related to relative density and mean crown asymmetry. We propose that studies of competition in mature forests routinely analyze spatial pattern of crowns in addition to that of stems, in order to collect stronger evidence of competitive processes. [Copyright &y& Elsevier]

Abstract: The role of deadwood on biodiversity conservation of forest ecosystems is widely recognised. Interest on deadwood has increased in the last years, and forest management policy regards deadwood as indicator of sustainable forest management. This study took place in mixed montane forests in Eastern Italian Alps. The objective was to determine how past forest management, topography and forest structure influenced coarse woody debris (CWD) accumulation. 124 sampling points were established in four forest reserves, where time since active management activities ranges from 12 to more than 50 years. A multivariate analysis was performed to investigate the connections among site, stand characteristics, and CWD. Coarse woody debris volume in the reserves was similar to other forests withdrawn from regular management in last decades in central Europe. However, CWD stocking was much lower than in old-growth montane mixed forest. Both site and stand characteristics determined CWD accumulation. Elevation, basal area of living trees and human impact emerged as the most important factors. These aspects are connected with the accretion (density-dependent mortality) and the depletion (harvesting, decay) of deadwood in the stand. In the next decades we expect an increase of deadwood stocking, due to density-dependent mortality and disturbances. [ABSTRACT FROM AUTHOR]

Testing the relations between tree parameters and the richness and composition of lichen communities in near-natural stands could be a first step to gather information for forest managers interested in conservation and in biodiversity assessment and monitoring. This work aims at evaluating the influence of tree age and age-related parameters on tree-level richness and community composition of lichens on spruce in an Alpine forest. The lichen survey was carried out in four sites used for long-term monitoring. In each site, tree age, diameter at breast height, tree height, the first branch height, and crown projection area were measured for each tree. Trees were stratified into three age classes: (1) <100 years old, immature trees usually not suitable for felling, (2) 100-200 years old, mature trees suitable for felling, and (3) >200 years old, over-mature trees normally rare or absent in managed stands. In each site, seven trees in each age class were selected randomly. Tree age and related parameters proved to influence both tree-level species richness and composition of lichen communities. Species richness increased with tree age and related parameters indicative of tree size. This relation could be interpreted as the result of different joint effects of age per se and tree size with its area-effect. Species turnover is also suspected to improve species richness on over-mature trees. Similarly to species richness, tree-level species composition can be partially explained by tree-related parameters. Species composition changed from young to old trees, several lichens being associated with over-mature trees. This pool of species, including nationally rare lichens, represents a community which is probably poorly developed in managed forests. In accordance to the general aims of near-to-nature forestry, the presence of over-mature trees should be enhanced in the future forest landscape of the Alps especially in protected areas and Natura 2,000 sites, where conservation purposes are explicitly included in the management guidelines. [ABSTRACT FROM AUTHOR]

Abstract: Density management diagrams (DMD) are graphical tools used in the design of silvicultural regimes in even-aged forests. They depict the relationship between stand density, average tree size, stand yield and dominant height, based upon relevant ecological and allometric relationships such as the self-thinning rule, the yield-density effect, and site index curves. DMD effectively summarize stand structural descriptors, and are therefore helpful in determining stand characteristics needed to achieve a range of management goals. We constructed a DMD for Scots pine (Pinus sylvestris L.) forests in the western Italian Alps. We used 210 sample plots from a region-wide forest inventory to determine the maximum density line and volume and top height isolines. Site index curves were used to assess the time taken by stands to progress along their development trajectories. The protection provided by Scots pine stands is most effective against rockfall, due to the frequent occurrence of such forests in active source or transition areas. We used the DMD to identify combinations of size and density representing optimal and sub-optimal protection from rockfall. An actual pine stand was used as a case study to illustrate how the diagram can be used to assess current functionality of the forest, forecast its likely development and compare alternative management strategies. [Copyright &y& Elsevier]

1. The tree-ring growth response of stone pine ( Pinus cembra L.) to climatic variability was studied in the Alps. The aims were (i) to assess tree-ring growth patterns at different spatial-temporal scales; (ii) to identify the climate parameters that explain most of the variability in radial growth at different time domains; and (iii) to study past and current trends in radial growth and climate–growth relationships at different locations. 2. High- and low-frequency stone pine chronologies were compiled for 30 treeline sites on the French and Italian Alps. We used gridded climate data computed from 200 years of instrumental records from an extensive Alpine network. Climate–growth relationships were computed with bootstrap correlation functions and their stationarity and consistency over time assessed with moving correlation. 3. No spatial patterns were detected in stone pine chronology statistics despite the regional clustering observed in tree-ring series and climate responses. This can be attributed to (i) local weather variability; (ii) different biophysical conditions caused by soil moisture, solar radiation, snowmelt dynamics and growing season length; and (iii) forest stand history and age structure, the expression of long-term land use and disturbances. 4. The exceptionally long-term climate records allowed significant stone pine growth response changes to be assessed at both annual and decadal time scales. Winter conditions and spring–summer temperatures mainly affected the growing season length, in addition to site carbon and water balance. Most of these limiting factors varied spatially and temporally along the latitudinal and longitudinal gradients in response to the corresponding changes in local conditions. 5. Our results show evidence of a clear response variability of Pinus cembra to climate limiting factors, at both spatial and temporal scale. Such knowledge extended to other species and regions will provide better estimates of the effect of climate variability on species distribution and dynamics within global change scenarios and more accurate past climate reconstruction and forest ecosystem modelling. [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]

Abstract. A study of the forest lines, tree lines and the structures of the sub-alpine forest was performed in Vallone Vallanta and in Alevé forest in the Varaita Valley (Cottian Alps, Piedmont, Italy). Forest- and tree lines were analysed over 1728 ha while forest structures were studied on six 3000-m 2 plots located at the tree line (2), at the forest line (2) and inside the sub-alpine forest (2). Dendro-ecological analysis of living plants and stumps showed that Larix decidua was more abundant in the past than today and that Pinus cembra has expanded, both upwards and within sub-alpine forests. Age structure analysis revealed that the current sub-alpine forest stands were established 200 - 220 yr ago, probably following a clearcut. At the forest lines the tree density decreases, and some trees are more than 500 yr old, whereas at the tree lines most of the trees (almost exclusively Pinus cembra) are younger than 100 yr. Growth dynamics were investigated both by observing Basal Area Increment (BAI) in the old and dominant trees, and by comparing the BAIs of classes of trees with a given cambial age range in different time periods. The results showed that the growth rates of mature Pinus cembra and Larix decidua had increased. These increments are more substantial for Pinus than for Larix. The growth rate of young trees (100 yr) of both species has decreased over recent decades. This could be due to competition caused by increased tree densities that have resulted from a decrease in grazing. [ABSTRACT FROM AUTHOR]

In the southern part of the Alps the intensive use of forests for domestic animals has declined this century and particularly during the last few decades. After the Second World War wild ungulates, rare or absent at the beginning of this century, increased in number and expanded their range. Mountain forests are very vulnerable to ungulate damage owing to the long periods needed for regeneration processes. In this study, the impact of ungulate browsing on forest regeneration was investigated in 10 areas of the Italian Alps. The incidence of browsing damage on forest regeneration (10-150 cm height) was found to vary between 52.8% in the most severely damaged area and 6.9%, in the least affected area. The lethality of browsing damage (used as index of browsing intensity) was found to he nil in 4 areas out of ten and up to 17.2170 in the areas with the highest ungulate density. Ungulate density is not the only factor influencing degree of browsing damage; winter tourism and land and road settlements in potential ungulatewinter ranges also play an important role. Naturalistic silvicultureis the most profitable system for the conservation and the sustainability of the whole forest ecosystem but high ungulate densities prevent its application. [ABSTRACT FROM AUTHOR]