Mast-seeding trees can vary seed output by orders of magnitude among years, but it remains unclear whether high seed production reduces per-seed investment, as predicted by fixed-budget allocation models. We quantified individual seed production with seed mass in European beech across 2792 trees and 123 populations spanning the species' range and quantified seed protein and lipid content in 35 populations. Seed mass increased with seed production, with seeds from high-seeding years being 14% heavier than those from low-seeding years, providing no evidence for a seed size-number trade-off and instead supporting variable reproductive allocation. By contrast, protein content decreased by 31% with increasing seed production, whereas lipid content increased (by 14%), indicating that nitrogen becomes constraining at high reproductive output while carbon-based provisioning is maintained. Climate further structured provisioning: seed mass and protein content were the lowest at climatic range margins, being 28% and 32% lower, respectively, than at the center of the climatic range. European beech can increase seed output without reducing per-seed biomass, but that nitrogen limitation and climatic constraints may strengthen regeneration bottlenecks at both trailing and leading margins, especially as climate warming intensifies.

Beech coppice forests have shaped the mountainous European landscape for centuries. The socio-economical changes occurred over the last 60 years have led to a progressive decline in coppice management, which has resulted in either the abandonment of traditional coppice management, or into active coppice conversion to high forests. Given the long-term process of this process, an ecological, long-term perspective is required to understand the ecological implication of different management practices in these forests. We investigated the influence of conversion management on canopy attributes (leaf litter and seed production, leaf area index). The management options considered were traditional conversion management, based on periodic thinning, and alternative conversion, based on anticipated seed cutting and final harvesting, which were compared against natural evolution (unthinned control). Results showed that the differences between natural evolution and traditional conversion were largest in the years immediately after thinning, and then reduced with full canopy (leaf litter and leaf area index) recovery after 10 years. Conversely, the alternative method with the anticipated seed cutting significantly enhanced canopy heterogeneity and further accelerates the transition to high forest, with dense beech saplings reaching an height over 8 meters eight years post-harvest. ### Competing Interest Statement The authors have declared no competing interest. National Recovery and Resilience Plan (NRRP), Mission 4 Component 2 Investment 1.4 - Call for tender No. 3138 of 16 December 2021, rectified by Decree n.3175 of 18 December 2021 of Italian Ministry of University and Research funded by the European Union - NextGenerationEU; Award Number: Project code CN_00000033, Concession Decree No. 1034 of 17 June 2022 adopted by the Italian Ministry of University and Research, CUP B83D21014060006 and CUP: J33C22001190001, Project title “National Biodiversity Future Center - NBFC”.

In forest ecosystems, soil-plant interactions drive the physical, chemical, and biological soil properties and, through soil organic matter cycling, control the dynamics of nutrient cycles. Parent material also plays a fundamental role in determining soil's chemical properties and nutrient availability. In this study, eight long-time coppice-managed Holm oak forests under conversion to high forest, located under similar climatic condi-tions in Tuscany and Sardinia Regions (Italy), and grown on soils developed from three different lithologies (limestone, biotite granite, and granite with quartz veins) were evaluated. The research aimed to a) estimate the amount of C and nutrients (total N and potentially available P, Ca, Mg, and K) stored both in the organic, organo-mineral, and mineral horizons and at fixed depth intervals (0-0.3 and 0.3-0.5 m), and b) assess the dominant pedological variables driving elemental accumulation. The soils were described and sampled by genetic horizons and each sample was analyzed for its C and nutrient concentration in both the fine earth and skeleton fractions. Despite the different parent materials from which the soils had evolved, the physicochemical properties and the C and nutrient stocks for the 0-0.3 and 0.3-0.5 m layers did not show substantial differences among the eight soils. Conversely, some differences were observed in the stocks of potentially available P and Ca per 0.01 m of mineral horizons. The findings show that over time, plant-induced pedogenic processes (acidification, mineral weath-ering, organic matter addition, and nutrient cycling) almost obliterated the influence of parent materials on soil properties. This resulted in the upper soil horizons that showed similar characteristics, even though derived from different lithologies. However, among the study sites, some differences occurred due to lithology, as in the case of the soils derived from calcareous parent materials that had high concentrations of exchangeable Ca in the mineral horizons and, likely, to environmental variables (e.g., exposure), which possibly influenced litter degradation and the release of nutrients such as N and available P.

The European biodiversity and forest strategies rely on forest sustainable management (SFM) to conserve forest biodiversity. However, current sustainability assessments hardly account for direct biodiversity indicators. We focused on forest multi-taxon biodiversity to: i) gather and map the existing information; ii) identify knowledge and research gaps; iii) discuss its research potential. We established a research network to fit data on species, standing trees, lying deadwood and sampling unit description from 34 local datasets across 3591 sampling units. A total of 8724 species were represented, with the share of common and rare species varying across taxonomic classes: some included many species with several rare ones (e.g., Insecta); others (e.g., Bryopsida) were repre-sented by few common species. Tree-related structural attributes were sampled in a subset of sampling units (2889; 2356; 2309 and 1388 respectively for diameter, height, deadwood and microhabitats). Overall, multi-taxon studies are biased towards mature forests and may underrepresent the species related to other develop-mental phases. European forest compositional categories were all represented, but beech forests were over-represented as compared to thermophilous and boreal forests. Most sampling units (94%) were referred to a habitat type of conservation concern. Existing information may support European conservation and SFM stra-tegies in: (i) methodological harmonization and coordinated monitoring; (ii) definition and testing of SFM in-dicators and thresholds; (iii) data-driven assessment of the effects of environmental and management drivers on multi-taxon forest biological and functional diversity, (iv) multi-scale forest monitoring integrating in-situ and remotely sensed information.

In forest ecosystems, a variety of abiotic and biotic soil forming factors drives soil organic matter (SOM) and nutrients cycling with a profitable outcome on climate change mitigation. As a consequence, type and intensity of forest management, through its impact on carbon (C) and nutrient soil stocks, can be considered as an additional soil forming force. In this study, we investigated the influence of the coppice conversion into high forest on pedogenesis and on soil C and nutrient (N, P, Ca, Mg, and K) stocks, fifty years later the beginning of the conversion-cycle. The trial was established in a Turkey oak forest historically managed under the coppice system in central Italy. Specifically, we considered tree population density (natural evolution - control, moderate thinning, heavy thinning) where soil samples were collected according to genetic horizon to estimate C, N, and P stocks both in the forest floor and at fixed depth intervals (0-30, 30-50 and 50-75 cm). Further, the stocks of exchangeable Ca, Mg, and K were also assessed for the mineral layers. The results showed that litter and the upper layer of mineral soil (0-30 cm) contained a similar quantity of C (about 74-83 Mg ha-1), independently of the trials and no differences were observed also in the whole soil stocks (about 192-213 Mg ha-1). The comparison of the mean stocks calculated per 1-cm of thickness of organic (O), organo-mineral (OM), and mineral (M) layers, although it did not display any difference among trials (excepted for P and Mg), showed a similar capability of the organo-mineral horizons to store C and nutrients compared with the organic ones (e.g., about 6-12 Mg ha-1, 0.3-0.5 Mg ha-1 and 0.5-1.5 kg ha-1 for C, N and P, respectively). Our findings showed that thinning operated on Turkey oak coppice did not affect soil capacity to store C and nutrients. These results suggested that the forest ecosystem itself is the main soil forming force and this is consistent with the target of adopting forest management able to control the global C cycle through the storage of SOM in the mineral soil rather than in forest floor, where SOM turnover is faster.

Old-growth forests play a key-role in reducing atmospheric carbon dioxide (CO2) concentrations by storing large CO2 amounts in biomass and soil over time. This quantifies the carbon pool into different forest compartments in three Mediterranean old-growth forests of Southern Italy populated by Pinus laricio, Fagus sylvatica and Abies alba. Ecosystem carbon pools have been assessed per compartment, i.e., living trees, deadwood, litterfall (foliar and woody), roots and 0-20 cm topsoil, combining the whole old-growth forest mass, (i.e., using tree allometric relationships, deadwood factor conversions, root-to-shoot ratios, litterfall and soil samplings) by the respective organic carbon concentrations. The results show the considerable capacity of these forest ecosystems in storing CO2 in biomass and soil, with carbon pool values ranging from 532.2 to 596.5 Mg C ha(-1). Living trees and 0-20 cm topsoil had larger carbon pool, contributing 53.0 and 22.1%, respectively. In most cases, organic carbon concentration was higher (more than 60%) than the average carbon conversion rate of 50%, especially in living trees, deadwood, and woody litterfall. This study contributes further scientific evidence of the capacity of old-growth forests in storing CO2 in their different compartments, with special evidence on tree biomass, litterfall and mineral soil, thereby highlighting the key role of old-growth forests within the challenge of climate change mitigation.

The goal of this study is to assess the impact of different thinning approaches for coppice conversion into high forest of Turkey oak stands in Italy. The stand structure and the tree/shrub diversity were analyzed in 27 long-term monitoring plots from 7 experimental trials in the Colline Metallifere district (Tuscany, Central Italy) to verify the consistency of the original cultivation goals with the current stand structures. Three different approaches were applied from 1969 onwards: thinning from below, selective thinning, and no-management. Three indexes of specific diversity (Specific Richness, Shannon index and Importance Value) and two indexes of vertical diversity (Vertical Evenness and Coefficient of variation of tree height) were used to analyze and compare the outcome of management practices. The results showed a significantly higher dimensional variability and basal area, and a more complex vertical diversity in control plots and in the plots subject to selective thinning, as compared with plots subject to thinning from below. Tree species richness was high in all plots, independently of the thinning type applied. Based on our results, we suggest Turkey oak-dominated transitory stands to be initially managed by thinning from below, which is easy to be implemented and economically feasible. Selective thinning may be applied later with the aim of promoting sporadic but valuable tree species and increasing tree species diversity.

Epiphytic lichens represent one of the most suitable indicators of forest continuity and management, especially in the context of ancient and old-growth forests. Nevertheless, they have not yet been included among Sustainable Forest Management (SFM) indicators to which Pan-European forest policy and governance refer. In addition, currently adopted SFM indicators are mainly designed for high forests rather than coppice forests, despite the fact that today this management system covers more than 10% of the total European forests. In this study we investigated these two issues by examining epiphytic lichen diversity in three coppice forest stands, located in the two Italian regions of Tuscany and Sardinia. In particular, we addressed: i) the role of lichen diversity as SFM indicator and ii) its relationship with consolidated and new SFM indicators dealing with structural, health, biodiversity, protective and socioeconomic functions. Multivariate Factor Analysis and Generalised Linear Models were adopted for data analysis. We found that lichen diversity and the frequency of single sensitive species were mainly related to the biodiversity of plants and fungi (Criterion 4), the health and vitality of the forests (Criterion 2) and their protective functions (Criterion 5). Furthermore, our results show that the lichen species highlighted by the models may represent suitable indicators in long-term studies, especially in relation to complex and interconnected aspects of sustainable forest management. Although our findings represent a first contribute to this issue, more in-depth researches will be needed to clarify further aspects of the complex interactions among SFM indicators in the context of coppice forests.

We provided long-term stand and canopy structural data from permanent monitoring plots representative of some most diffuse temperate and Mediterranean forests, under different coppice management regimes. Periodic inventories were performed in the surveyed plots since the 1970s. Annual litterfall production and its partitioning (leaf, woody, reproductive parts) and optical canopy measurements using the LAI-2000 Plant Canopy Analyzer were performed every year in fully equipped plots since the 1990s. These data can be used for evaluating the influence of coppice management in the stand and canopy structure, the parametrization of radiative transfer models that require accurate ground truth data, and the calibration of high to medium resolution remotely sensed data. Dataset access is at https://doi.org/10.17632/z8zm3ytkcx.2 . Associated metadata is available at https://agroenvgeo.data.inra.fr/geonetwork/srv/eng/catalog.search#/metadata/2bd2d77f-3cf8-43da-b1b5-9f8196dc017f  .

Tree mortality plays a key role in forest development and function, reducing net annual increments (NAI) even in the absence of major disturbances, although its extent in semi-natural forests is often overlooked. While losses are most commonly quantified as a fraction of stand density, in many cases this could prove misleading due to the non-random nature of competition and mortality, and a quantification of volume mortality rates would provide additional insight. Of great interest is also the quantification of losses relative to gross annual increments (GAI), both from an ecological perspective and in order to better assess net increments and the sustainability margins of forest management. All three perspectives were compared in the present study, based on available data from permanent sample plots across Italy covering a wide range of species, ages and management types. The frequency distribution of all three measures of mortality was highly skewed, with a high number of stands showing little losses; this was apparently not the result of an insufficient monitoring area or time span. Mortality resulted in an average loss of 2.25 m(3) ha(-1) yr(-1), which corresponds to 20.7% of GAI. Mortality rates by number and by volume amounted on average to 1.35% and 0.51%, respectively, demonstrating the need to distinguish between the two perspectives. Two rather distinct clusters were apparent in the relationship between the two mortality rates, with a 1:1 relationship in thinned or disturbed stands but much lower volume mortality rates when self-thinning prevailed, resulting in the loss of many small, suppressed trees. When considering volume mortality rates, however, the relative contribution from dominant or co-dominant trees to total stand mortality was much more important, as a result of their larger volume. If extrapolated to national level, these results could help refine current estimates of net annual increments in Italian forests, and of the margin of sustainability of current harvest levels, which would amount to 45% of NAI.

The present study introduces an exploratory data analysis based on structural indicators with the aim to assess the effect of silvicultural practices on tree stand structure. The study was carried out in three Italian beech forests of different ages with stand structures that originated from dissimilar regeneration and cultivation techniques (Cansiglio, northern Italy, Chiarano, central Italy, and Mongiana, southern Italy). Ten structural indicators were considered when investigating the latent multivariate relationship between stand structure attributes before and after thinning operations by using a multiway factor analysis (MFA). The MFA results identified the older stand at Cansiglio as more homogeneous for cultivation regimes, and more stable to practices when compared with the younger sites (Chiarano and Mongiana). Heterogeneous stands were sensitive to silvicultural practice thus suggesting their possible impact on forest attributes. The proposed approach proved to be an operational tool to evaluate comprehensively the response of forest structure to planned interventions.

The European beech (Fagus sylvatica L.) is a widely distributed tree species across Europe, highly sensitive to climate change and global warming. This study illustrates results of a 5-year monitoring time period from eight sites of the ICP-Forests Level II (intensive monitoring network) along the Italian latitudinal gradient. The tree-level relationship between tree growth dynamics and environmental factors, including seasonal climate fluctuations were investigated by means of tree-level Generalized Additive Mixed Models (GAMMs). Model results revealed that climate was responsible for just a portion of the variability in beech growth dynamics. Even if climatic predictors were highly significant in almost all sites, the model explained nearly 30% of the total variance (with just a maximum value of 71.6%), leaving the remaining variance unexplained and likely connected with forest management trajectories applied to each site (e.g., aged coppice and fully grown high forest). Climate change scenarios were then applied to predict site-specific future responses. By applying climate change scenarios, it was predicted that central and northern Italy would face similar climatic conditions to those currently detected at southern latitudes. A special case study was represented by VEN1 plot (Veneto, Northern Italy) whose current and future climate regimes were grouped in a unique and separated cluster.

Aimed at reducing structural homogeneity and symmetrical competition in even-aged forest stands and enhancing stand structure diversity, the present study contributes to the design and implementation of adaptive silvicultural practices with two objectives: (1) preserving high wood production rates under changing environmental conditions and (2) ensuring key ecological services including carbon sequestration and forest health and vitality over extended stand life-spans. Based on a quantitative analysis of selected stand structure indicators, the experimental design was aimed at comparing customary practices of thinning from below over the full standing crop and innovative practices of crown thinning or selective thinning releasing a pre-fixed number of best phenotypes and removing direct crown competitors. Experimental trials were established at four beech forests along a latitudinal gradient in Italy: Cansiglio, Veneto; Vallombrosa, Tuscany; Chiarano, Abruzzo; and Marchesale, Calabria). Empirical results indicate a higher harvesting rate is associated with innovative practices compared with traditional thinning. A multivariate discriminant analysis outlined significant differences in post-treatment stand structure, highlighting the differential role of structural and functional variables across the study sites. These findings clarify the impact of former forest structure in shaping post-treatment stand attributes. Monitoring standing crop variables before and after thinning provides a basic understanding to verify intensity and direction of the applied manipulation, the progress toward the economic and ecological goals, as well as possible failures or need for adjustments within a comprehensive strategy of adaptive forest management.

High-quality data and long-term time series are the basis of any research activity dealing with natural resources analysis. Adequate sampling designs are fundamental to allow a robust statistical analysis to be representative of a relevant set of target variables. In this work, the sampling strategy of ICP-Forests Level II European network has been proposed to define more efficient and cost-effective procedures under the hypothesis that the average value of single-tree growth (increment) is a proxy of forest health. ICP plots have a fixed spatial structure consisting of a square of 50 x 50 m framed into 25 squared sub-plots. To estimate basal area (G) and increase over time (Delta G), two different sub-sampling methods have been implemented based on a measure of (i) the dominant layer only (i.e. a subset of the highest trees in the plot), and (ii) a random sample of squared sub-plots. While the vertical sampling procedure was performed using a progressive threshold, the horizontal sampling followed a bootstrapping procedure with random extraction without replacement. The mean absolute relative error (MARE) was used to evaluate quality of the two sub-sampling methods. Results highlighted a low predictive power with both methodologies, preventing the possibility to reduce the sampling efforts when estimating AG directly. In this context, the vertical sampling was strictly related to species-specific ecology, spatial structure and forest age, being influenced by vertical distribution of trees. The use of horizontal sampling for direct AG estimation led to systematically high errors. However, the use of horizontal sampling for total G estimation and indirect estimation of AG may reveal as a more effective procedure for a coherent representation of horizontal distribution of trees. Estimate AG as the difference between G values at time t and t + Delta t finally allows for a sensible reduction of costs with a controlled estimation error. An adequate level of MARE should be decided a-priori to select the number of sub-squares to be randomly sampled.