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Natural disturbances play an important role in shaping the dynamics of mountain forests, yet their effects on essential ecosystem services, such as protection against natural hazards, can be significant. With the challenges posed by climate change and increasing disturbances, as well as the complexities of salvage logging, there is a growing interest in understanding post-disturbance development in unsalvaged mountain forests, alongside the advancement of decision support systems aimed at ensuring sustained provision of ecosystem services. In this study, we combined a space-for-time substitution approach with long-term monitoring data to evaluate regeneration processes and development of deadwood decay following three distinct windthrow events in Central European mountain forests that were locally unsalvaged (specifically Vaia in 2018, Kyrill in 2007, and Vivian in 1990). Our unique dataset additionally provided insights into the long-term effects of disturbance legacies and tree regeneration on protection against natural hazards. Deadwood cover gradually decreased with time since disturbance, from an average of 50% two years after Vaia to 25% twelve years after Kyrill and 15% thirty years after Vivian. Similarly, deadwood height above ground significantly decreased over time, with median values dropping from 1 to 2 m immediately after the disturbance to 25–30 cm three decades later. The decay stage and diameter of deadwood significantly influenced tree regeneration, with larger diameters of logs and deadwood in more advanced decay stage (especially less solid/soft to very loose stage), facilitating seedling establishment, thus a second wave of tree regeneration. About a quarter of saplings grew on deadwood thirty years after disturbance. The analysis of post-windthrow stand development showed an increase in tree cover and height with time since disturbance, with distinct patterns observed across different windthrow events and sites. Three decades post-disturbance, the number of trees had notably increased, with tree cover reaching 50%. Although Norway spruce remained the dominant species, the forest composition had shifted towards a predominance of broadleaves, particularly evident at lower elevations and areas with moderate browsing pressure. Our findings underscore the critical role of post-disturbance forest recovery and deadwood dynamics in promoting uneven-aged mixed forest structures, thereby enhancing forest regeneration, structural diversity, and protection against natural hazards. Emphasizing the vital importance of retaining deadwood, our study suggests that its role as a valuable substrate for enhancing resilience and ecosystem services is likely to grow in the future. • Deadwood cover and height above ground decreased with time since windthrow. • Decay stage and diameter of deadwood significantly influenced tree regeneration. • At lower elevations, windthrow led to higher shares of broadleaves. • Deadwood supports tree establishment and heterogeneity of forest structure. • Avoiding salvage logging enhanced forest recovery and avalanche protection. [ABSTRACT FROM AUTHOR]

Understanding the processes that shape forest functioning, structure, and diversity remains challenging, although data on forest systems are being collected at a rapid pace and across scales. Forest models have a long history in bridging data with ecological knowledge and can simulate forest dynamics over spatio‐temporal scales unreachable by most empirical investigations.We describe the development that different forest modelling communities have followed to underpin the leverage that simulation models offer for advancing our understanding of forest ecosystems.Using three widely applied but contrasting approaches – species distribution models, individual‐based forest models, and dynamic global vegetation models – as examples, we show how scientific and technical advances have led models to transgress their initial objectives and limitations. We provide an overview of recent model applications on current important ecological topics and pinpoint ten key questions that could, and should, be tackled with forest models in the next decade.Synthesis. This overview shows that forest models, due to their complementarity and mutual enrichment, represent an invaluable toolkit to address a wide range of fundamental and applied ecological questions, hence fostering a deeper understanding of forest dynamics in the context of global change. [ABSTRACT FROM AUTHOR]

Forests of the Apennines are characterised by high canopy cover and high tree species diversity (being at the interface between two major climatic zones of Europe), and provide important ecosystem functions to millions of people. They exemplify cutting-edge themes such as forest ecology in warmer climates, consequences of heavy land use, and resilience at the trailing edge of the distribution of many European forest species (Silver fir, Norway spruce, Beech, Black pine, Birch). We introduce the setting under the geological and climatological point of view and review the literature on the interactions between these long-term drivers and the specific, structural, and genetic diversity of these forest communities (e.g., effects of glacial refugia or tectonic/volcanic activity), followed by a brief outline of what little is known about natural disturbance regimes and their range of variability. Anthropogenic disturbances (fire, grazing) and land use changes (abandonment of cropland and pasture) have been by far the main drivers of forest dynamics at least for the last two millennia, determining for examples overageing of coppices, treeline advances, forest encroachment on former agricultural land. We suggest considerations about the interplay between these land use changes and disturbance drivers (e.g. fuel continuity), summarize comparisons between managed and unmanaged forests (e.g., increase in tree size, deadwood, biodiversity indicators), and elaborate on current proposals for climate-adapted management, highlighting specific and genetic diversity as an important source of resilience and adaptive potential. [ABSTRACT FROM AUTHOR]

Knowledge about the stand structure and dynamics of subalpine forests is crucial to preserve their multifunctionality. In the present study, we reconstructed the spatiotemporal dynamics of a subalpinePinus cembraforest in the eastern Italian Alps in response to natural disturbances and forest management. We adopted a concurrent point pattern, dendroecological and growth dominance (GD) analysis. We mapped and measured all trees ofPinus cembraandLarix deciduain a 1 ha plot. We analyzed intra- and interspecific spatial patterns and spatial autocorrelation of tree size and age. We explored establishment dynamics and shifts in competition by analyzing growth suppression/release patterns and GD trends. Results showed a clumped, uneven-aged, multilayered structure where pine was dominant. The synergic action of ecological and human-induced factors is discussed to explain the prevalence of pine over time. Spatial pattern and autocorrelation analyses suggest a different colonization strategy of the two species, in which pine established after small-scale perturbations and experienced a stronger inter- and intra-specific competition. The interruption of tree establishment and shift in GD toward large trees resulting from the lack of forest management are the most important findings of this research. This highlights the importance of an active management to avoid the homogenization of the forest structure that is generally associated with a reduction in biodiversity and protective ability of forests. [ABSTRACT FROM PUBLISHER]

Abstract: As a consequence of the recent change in human land-use intensity in mountain territories in the Italian Alps, many Norway spruce (Picea abies (L.) Karst.) subalpine forests have recently developed without significant anthropogenic disturbance. Even so, their structure and dynamics are still influenced by past human activity. In order to analyze the interactions between past management and current stand dynamics, competition among trees was studied in two 1-ha permanent plots in the Valbona Forest Reserve, located within the Paneveggio-Pale di San Martino Natural Park (eastern Italian Alps). The plots were established in 1993 in two stands with similar age, density and structure but different management history. Tree measurement was repeated in 2005. We carried out the analysis both on the stand- and on the individual tree scale. We computed maximum Stand Density Index (SDI) for Norway spruce in Paneveggio Park (SDImax 1380) based on an ancillary sample plot network. The intensity of stand-level competition and its course through time was assessed in each study area computing percent relative SDI (SDI%) for the two inventory years. Competition at individual level was studied using known individual-based competition indices (CIs) as well as a new set of Crown Area Indices (CAI), all of them based on tree variables such as dbh, height, crown area and inter-tree distance. We assessed the performance of each index by evaluating its explanatory power in forecasting individual tree basal area growth (Δg) in a 10-year period. In the more recently thinned plot, competition did not induce mortality rates comparable to the second plot, that has been unmanaged for the last 60 years. We expect the intensity of competition-induced mortality of the two stands to increase its similarity in the next future. Individual CIs based solely on tree diameter produced the best performance in plot 1 (e.g., Daniels’ CI, ). In plot 2 different CIs, including tree height, crown area and inter-tree distance as base variables also, proved the most explanatory ones, including CAI6 (), which not consider dbh. We attributed the differential role of tree spatial location and dominance-related descriptors in predicting growth to the time when the stand experienced the last anthropogenic disturbance. The competition relationships still experience the effect of the artificial alteration of forest structure: after human disturbance, mature Norway spruce subalpine forests need several decades to approach more natural dynamics. [Copyright &y& Elsevier]

• Harmonised freely-available data is crucial to model forest impacts on climate change. • We summarise available datasets on forest functioning and underlying drivers. • Data for key demographic mechanisms are available at the short-term at EU level. • Lack of high-resolution harmonised EU data for genetic and physiological tree responses to climate change. • Need for Pan-European data integration effort. Climate change is expected to cause major changes in forest ecosystems during the 21st century and beyond. To assess forest impacts from climate change, the existing empirical information must be structured, harmonised and assimilated into a form suitable to develop and test state-of-the-art forest and ecosystem models. The combination of empirical data collected at large spatial and long temporal scales with suitable modelling approaches is key to understand forest dynamics under climate change. To facilitate data and model integration, we identified major climate change impacts observed on European forest functioning and summarised the data available for monitoring and predicting such impacts. Our analysis of c. 120 forest-related databases (including information from remote sensing, vegetation inventories, dendroecology, palaeoecology, eddy-flux sites, common garden experiments and genetic techniques) and 50 databases of environmental drivers highlights a substantial degree of data availability and accessibility. However, some critical variables relevant to predicting European forest responses to climate change are only available at relatively short time frames (up to 10-20 years), including intra-specific trait variability, defoliation patterns, tree mortality and recruitment. Moreover, we identified data gaps or lack of data integration particularly in variables related to local adaptation and phenotypic plasticity, dispersal capabilities and physiological responses. Overall, we conclude that forest data availability across Europe is improving, but further efforts are needed to integrate, harmonise and interpret this data (i.e. making data useable for non-experts). Continuation of existing monitoring and networks schemes together with the establishments of new networks to address data gaps is crucial to rigorously predict climate change impacts on European forests. [ABSTRACT FROM AUTHOR]

Projections of landscape dynamics are uncertain, partly due to uncertainties in model formulations. However, quantitative comparative analyses of forest landscape models are lacking. We conducted a systematic comparison of all forest landscape models currently applied in temperate European forests (LandClim, TreeMig, LANDIS-II, iLand). We examined the uncertainty of model projections under several future climate, disturbance, and dispersal scenarios, and quantified uncertainties by variance partitioning. While projections under past climate conditions were in good agreement with observations, uncertainty under future climate conditions was high, with between-model biomass differences of up to 200 t ha−1. Disturbances strongly influenced landscape dynamics and contributed substantially to uncertainty in model projections (~25–40% of observed variance). Overall, model differences were the main source of uncertainty, explaining at least 50% of observed variance. We advocate a more rigorous and systematic model evaluation and calibration, and a broader use of ensemble projections to quantify uncertainties in future landscape dynamics. • The first systematic comparison of forest landscape models is presented. • Variance of model projections under several future scenarios is substantial. • Model differences explain most of the simulated variance. [ABSTRACT FROM AUTHOR]