Forest Ecology and Management

Large old trees are of eminent importance for organic carbon storage in forest ecosystems and thus play a role in mitigating climate change. Such trees also have an increased risk of internal stem decay and tree cavity formation, which promotes biodiversity, but complicates the prediction of their biomass and carbon stocks, which is usually done from stem diameter and tree height data applying allometric biomass functions. Since the extent of internal stem decay is known to vary widely between different forest ecosystems and data from moist temperate forests exhibited low significance of internal stem decay, we studied dry, frequently fire-exposed Pinus ponderosa forests in central Oregon to capture the other climatic extreme of temperate forests. We hypothesized high significance of internal stem decay for stand aboveground tree biomass, as we assumed widespread stem injury from fire. In addition, we tested the hypothesis that far more than the largest 1% of trees are necessary for 50% stand biomass, as this hypothesis is found in the literature, but has been challenged in other studies. We found low biomass loss due to internal stem decay by only ca. 1% suggesting that also for fire-prone temperate forests of western North America, biomass estimates based on allometric regression are reliable. The 1% largest trees-50% stand aboveground biomass hypothesis has to be rejection for our forests as long as only trees of a size are included that noteworthily contribute to stand biomass. This metrics strongly depends on regeneration density, which is not relevant for stand biomass.

Human land use has greatly affected the natural landscapes in most parts of the world, and Scandinavian industrial forestry has substantially altered the age structure of the boreal forest over the last 75 years. In this study, we analyzed 44 years of line transect counts of Capercaillie and Black grouse collected in an industrial forest landscape in central Sweden between 1980 and 2024. The area was heavily logged in the 1960s and 1970s, followed by large-scale replanting. A hierarchical Gompertz state-space model to assess long-term population dynamics of both species. The adult state model included a brood production submodel, and forest age structure, snow depth, vole abundance, and spring frost were covariates. Our results reveal strong density dependence and temporally variable environmental effects. Capercaillie and Black grouse exhibited contrasting decadal trends: Capercaillie increased markedly during the early study years, whereas Black grouse declined steeply before recovering later in the series. Increasing proportions of forest aged 21-40 years had a clearly positive effect on Capercaillie, whereas snow depth in the previous winter negatively influenced Capercaillie but not Black grouse. Brood production exhibited substantial interannual unexplained variation, although late spring frost reduced brood size in Capercaillie. Toward the end of the study, the two species reached similar levels of latent adult abundance, demonstrating that both can persist at sustainable densities across a broader range of forest structures than suggested in earlier studies.

Habitat fragmentation disrupts metapopulation dynamics by altering environmental conditions and constraining demographic processes critical for persistence and recruitment. In the dry Afromontane forests of northern Ethiopia, we investigated how natural and anthropogenic drivers affect seedlings, saplings, and mature tree dynamics of Olea europaea subsp. cuspidata across 34 patches. We used dynamic occurrence models to quantify effects of patch area, altitude, browsing, and disturbance. Our results indicate that high disturbance reduces seedling occurrence probability lower disturbance sites has seedling in 30% of survey plots, high disturbance would bring this down to 10% (median = -1.322, 95% CI: -2.703 to -0.283). Disturbance makes seedling less likely to persist, while large patch size help seedling persists (median = -0.93, 9 5 % CrI -1.87 - -0.02). For mature individuals, disturbance was the only significant predictor of occurrence probability, suggesting greater resistance to environmental and spatial variability compared to earlier life stages. These findings emphasize that while mature trees display resilience, the successful regeneration of Olea europaea is constrained by disturbance, but current level of browsing is not a threat. Management strategies for conservation should prioritise reducing disturbance through community engagement and forest stewardship to enhance regeneration potential and ensure long-term population viability.

Ectomycorrhizal (ECM) fungi are well-known for their crucial roles in forest health and productivity, yet their responses to various forest management practices are understudied, particularly in oak-dominated forests. The purpose of this study was to better understand the effects of silvicultural treatments on the diversity and community composition of ECM fungi in an oak-hornbeam forest in northern Hungary. We analyzed ITS2 rDNA metabarcoding data of soil-borne fungi to compare richness and community composition of ECM fungi among forest treatment types (clear-cutting, gap-cutting, preparation-cutting, tree retention in clear-cut areas, and control) and between sampling years (2020 and 2021). We found 268 ECM fungal genotypes, with the most diverse phylogenetic clades being /russula-lactarius (52), /tomentella-thelephora (47), /inocybe (40), /sebacina (27), and /cortinarius (20). We found significant compositional difference of ECM fungi among silvicultural treatments in both years, with some variations in richness. There were also small, but still significant compositional differences between the two years. Treatment effect was partly explained by altered environmental variables, such as relative humidity and soil temperature. These results highlight the importance of forest structure and the abiotic environment in driving community dynamics of plant-symbiotic fungi, with potential implications for forest health and productivity.

Primary and old-growth forests are globally valued for their biodiversity, ecosystem services, and cultural significance. The EU Biodiversity Strategy and EU Forest Strategy for 2030 require strict protection of remaining primary and old-growth forests, yet they cover only about 3% of EU forest area and remain highly threatened. The European Commissions guidelines define old-growth forests using three main indicators--native tree species, deadwood, and large/old trees--supported by five complementary indicators. Implementing these indicators for boreal and hemiboreal old-growth forests in northern Europe currently lack science-based operational criteria that meet EU legal standards. We provide recommendations for implementing European Commissions indicators with science-based operational criteria and thresholds to minimize misclassification and ensure cost-effective conservation. Key thresholds include native species dominance, [≥]5% deadwood of the total wood volume, and [≥]20 large/old trees per hectare. Additional guidance is offered for regeneration patterns, structural complexity, microhabitats, and indicator species, emphasizing that all indicators should be applied collectively.

Internal decay in living trees is an important component of carbon and nutrient cycling as well as species and structural diversity maintenance in forest ecosystems. We used sonic and electrical resistance tomography to evaluate and compare the prevalence and severity of stem decay in 57 living trees among four common species (Acer rubrum L., Nyssa sylvatica Marsh., Quercus rubra L., and Tsuga canadensis (L.) Carriere)) with overlapping and non-overlapping distributions across wetland and upland habitat types at the Harvard Forest in Petersham, MA, USA. Independent of tree size, site identity best explained variation in the prevalence of decay across trees sampled, whereas species identity best explained the severity of decay. We categorized trees as having no decay, incipient decay, active decay, or cavities based on combined sonic and electrical resistance metrics, the latter generated by a custom image analysis application. About 31% of wetland trees exhibited incipient decay (compared to 11% in the upland), whereas about 32% of upland trees exhibited active decay (compared to 10% in the wetland). Our study highlights a new quantitative framework for decay categorization through normalized principal component analysis (PCA) and decay analysis software that complements dual tomographic methodology for future investigations of ecological drivers of decay presence and susceptibility.

Maple syrup production is strongly influenced by spring weather conditions, particularly the frequency and intensity of freeze-thaw cycles. However, marked individual differences in sap and sugar yields persist among trees growing under similar stand conditions, indicating additional tree-level sources of variation. This study aimed to explain inter-individual variability in maple yields in commercial high-vacuum syrup production using structural, morphological, and growth characteristics. We used terrestrial light detection and ranging to derive variables describing crown, stem, and whole-tree size, biomass, and structure in 38 mature sugar maples. We related these variables to individual yields, including sap volume, sugar content, and syrup production. Our models explained substantial inter-individual variability: 52% in sap sugar content, 44% in sap volume, and 47% in syrup production. Laterally expanded crowns were associated with higher sap sugar content, as were lower growth rates in the first 25 mm of wood. Sap volume was highest in large, heavily branched trees with crowns extending vertically along the stem. Projected crown surface area was the strongest predictor of syrup yield, with an estimated increase of 250 mL per 5.6 m2. These findings highlight the importance of multidimensional crown development in maximizing individual yields in maple syrup production.

Longitudinal data on disease susceptibility in forest trees are rare but essential for understanding host-pathogen dynamics and genetic variation in susceptibility traits. We present a long-term multisite common garden dataset quantifying susceptibility of Scots pine (Pinus sylvestris) to Dothistroma needle blight. The dataset comprises annual disease assessments collected from the same trees across 11 years, spanning 168 families and 21 Scottish provenances. This design enables partitioning of genetic and environmental sources of variation, evaluation of temporal stability in host response, and estimation of variance components and narrow-sense heritability of susceptibility. The data support analyses of phenotypic plasticity, provenance-level responses, and interactions between disease susceptibility and other adaptive traits. This resource will facilitate predictive modelling of host susceptibility under current and future environmental conditions.

SummaryO_LIIn woody perennials, reproductive allocation considered as a fraction of NPP (RA) has been rarely quantified, especially tracked across plant lifetimes, measured in biologically meaningful currencies, and separated from standing biomass. C_LIO_LIWe addressed this gap by measuring dry mass, nitrogen, and phosphorus for every aboveground tissue type for 14 iteroparous perennial shrubs tracked across their full lifetimes, calculating RA using four accounting schemes and three currencies. C_LIO_LIRA was substantially higher by mid-life than typical estimates from ecosystem-scale studies. Distinguishing standing biomass from yearly production further revised RA upwards. Using a nutrient currency (especially P) increased the perceived costs of reproduction. Propagules were highly nutrient-enriched and reproductive accessory costs consumed more nutrients than did the propagules themselves. Considering N and P resorption from senescing leaves and wood shrank the effective vegetative nutrient budget, further concentrating net annual nutrient demand in reproductive tissues. C_LIO_LIOur results highlight high investment in RA for woody perennials, especially using nutrient currencies. Broadly similar allocation patterns were observed across species with different functional traits and lifespans, suggesting generality that may apply across biomes. Widespread underestimation of RA in forest growth models likely overestimates the proportion of NPP available for vegetative growth, leading to substantial errors in predictions. C_LI

O_LICalluna vulgaris is often managed in the UK by rotational burning, but this practice has recently been banned on peat with depth greater than 30-40 cm. It is unclear how then to manage the large areas of Calluna on blanket bogs used for sport shooting because without managed burning, fuel loads and wildfire risk will increase as the Calluna ages within the artificially narrow age distributions created by burn management. C_LIO_LIWe developed a model of Calluna mortality and management to understand duration and persistence of post-management effects. This allows us to assess how long it will take to reach a more natural age structure which would allow increased diversity if management ceases. C_LIO_LIOur results show that management effects persist for around 50 years depending on site-specific mortality rates. Active management may therefore be needed either to mitigate the elevated risk of severe wildfire or to speed up this transition. C_LIO_LISome studies have employed, as unmanaged analogues, Calluna stands that were last managed <50 years ago, but such studies may have unintentionally biased their results by observing Calluna still in post-management recovery leading to an over-estimation of wildfire risk associated with more natural blanket bogs. C_LIO_LISynthesis and applications: with the banning of burning as a management tool for Calluna on deep peat, alternative management is now likely needed as our model shows it could take around 50 years for the Calluna to reach a more natural age distribution. Mowing can replicate some of the effects of managed burning but requires repeated intervention and may compress the peat surface from repeated machine tracking. Rewetting and Sphagnum reintroduction may offer a more sustainable management approach to lowering Calluna fuel loads and reducing severe wildfire risk by creating wetter sub-optimal conditions for Calluna growth and thereby altering the competitive balance between Sphagnum and Calluna. Further work is needed to assess the efficacy of rewetting in controlling fuel loads and how this varies with climate and local pressures. More broadly, this work highlights the need to quantify the persistence of past management regimes to understand ecological trajectories. C_LI

Species have optimal environmental conditions, and ongoing climate warming is reshaping community composition. In particular, many ecosystems exhibit thermophilization, a shift toward species adapted to warmer conditions. However, this process is often slower in forests, leading to a mismatch between community composition and ambient temperature, referred to as climatic debt. Despite increasing attention, its effects on forest productivity remain unclear. Quantifying tree community responses to warming is therefore essential for predicting future forest dynamics and informing biodiversity conservation. In this study, we analyzed natural forests across Japan using data from the 3rd and 4th National Forest Inventory periods (2009-2018). We first assessed compositional consistency between survey periods using the Bray-Curtis index and excluded plots with high dissimilarity ([&ge;] 0.8). Species-specific thermal optima were estimated using species distribution models and used to calculate the Community Temperature Index (CTI). Thermophilization was quantified as the temporal change in CTI, while climatic debt was defined as the difference between CTI and mean annual temperature. We then examined the relationship between climatic debt and changes in aboveground biomass, used as a proxy for productivity, using linear mixed-effects models. We found a mean thermophilization rate of 0.005 {degrees}C yr-{superscript 1}. Despite this shift, climatic debt increased at an average rate of -0.022 {degrees}C yr-{superscript 1}, indicating a growing mismatch between climate warming and community thermal composition. Although thermophilization showed no statistically significant association with stand structure, it tended to vary with the proportion of small-diameter trees, suggesting the influence of multiple interacting drivers. Importantly, increasing climatic debt was significantly associated with declines in forest primary productivity, even after accounting for stand structure and regional variation. These results demonstrate that delayed thermal adjustment of tree communities can constrain forest productivity under ongoing climate warming, highlighting the importance of evaluating community-level thermal responses for sustaining forest ecosystem functioning.

Tropical forest succession can reorganize biodiversity not only by changing species richness, but also by filtering the functional traits that represent ecological strategies. Harvestmen are highly sensitive to microclimatic and structural changes in Neotropical forests, yet their functional diversity remains poorly explored. We investigated taxonomic and functional diversity of harvestmen in a local scale, an Atlantic Forest remnant in southeastern Brazil containing forest patches at different successional stages. Standardized nocturnal active searches and leaf-litter sampling yielded 384 individuals belonging to 14 morphospecies. Functional diversity was quantified from four morphological traits using Hill numbers (q = 0, 1 and 2), morphofunctional ordination, beta-diversity partitioning and environmental models based on forest-structure variables and PCA-derived gradients. Functional diversity was highest when rare species were weighted equally and declined strongly from q = 0 to q = 2, indicating that uncommon species carried much of the regional morphofunctional variation. Functional alpha diversity was positively associated with taxonomic alpha diversity, and Mantel tests showed that taxonomic and functional dissimilarities among sampling points were significantly correlated. However, formal beta-diversity partitioning refined this interpretation: functional beta diversity was dominated by nestedness-resultant dissimilarity rather than turnover, suggesting that functionally poorer assemblages represented contracted subsets of the regional trait space. Morphofunctional analyses identified compact, robust and long-legged species groups, and environmental models showed that lower vegetation structure, litter depth and forest-maturity gradients significantly influenced functional diversity. These findings indicate that mature, structurally complex Atlantic Forest patches help maintain the full spectrum of harvestman morphofunctional strategies and highlight harvestmen as promising models for trait-based conservation ecology. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=105 SRC="FIGDIR/small/731358v1_ufig1.gif" ALT="Figure 1"> View larger version (53K): org.highwire.dtl.DTLVardef@1f91597org.highwire.dtl.DTLVardef@1f89aa6org.highwire.dtl.DTLVardef@7141b8org.highwire.dtl.DTLVardef@191accc_HPS_FORMAT_FIGEXP M_FIG C_FIG

Accurate estimation of forest growing stock volume (GSV) at fine spatial scales is essential for sustainable forest management, carbon accounting, and local decision-making. However, traditional forest inventories often lack sufficient sampling density to provide reliable estimates for small areas. This study evaluates the performance of two small area estimation approaches: the Empirical Best Predictor (EBP) based on a nested-error linear regression model, and the Mixed-Effects Random Forest (MERF) for estimating GSV at the forest stand level using multi-source remote sensing data. The analysis was conducted in the Vallombrosa Nature Reserve (Italy), integrating field measurements from 101 plots with auxiliary variables derived from Sentinel-2 imagery and airborne LiDAR. Both methods were applied to estimate the mean and total GSV across 658 forest stands, many of which lacked direct observations. Model performance was assessed using spatial cross-validation, and uncertainty was quantified using root-mean-square error (RMSE). Results show that MERF outperformed EBP in predictive accuracy, achieving higher R2 (0.67 vs. 0.37) and lower RMSE (151 vs. 202 m3 ha{square}1). MERF also produced more stable and precise uncertainty estimates, with improved coverage of observed values. While both methods yielded comparable total GSV estimates, EBP exhibited greater variability and sensitivity to model assumptions. In contrast, MERF effectively captured non-linear relationships and handled multicollinearity among predictors, though at the cost of reduced interpretability and higher computational demand. Overall, findings highlight the advantages of integrating machine learning with mixed-effects modeling for SAE in forestry, particularly under conditions of sparse sampling and complex ecological variability.

Climatic and biogeographic variables are often used as a proxy for tree genetic diversity, but local factors can also influence it. We propose that woodland age, presence of ancient trees, and population size could impact genetic diversity. Using the RBG Kew UK National Tree Seed Project as a study case, we examined how these factors are accounted for during seed collection. We found 42% of tree seed collections come from ancient woodlands and that 8.4% overlap with ancient trees. Sampled forest patches size ranges from few individuals to several thousand. We then carried out a pilot to examine the role of population size on functional traits variation, testing the relationship between population size and seed germination and seedling thermal stress sensitivity in three populations of the Betula pubescens Ehrh. complex. We found that seeds and seedlings from larger populations showed higher fitness and stress resistance. Our results highlight the importance of local factors to predict variation in functional traits, relevant for tree resilience. Existing seed collections of native species stored in conservation seed banks offer a valuable resource to explore these factors and improve our understanding of genetic diversity in tree populations, with implications for biodiversity conservation and forestry production.

Atmospheric inorganic nitrogen (N) deposition has been linked to increased tree phosphorus (P) deficiency and shifts in ectomycorrhizal (ECM) fungal community composition across Europe, but the underlying mechanisms remain poorly understood due to the scarcity of species-level studies of fungal physiology at large spatial scales. Here, we characterized ECM communities in nine Scots pine (Pinus sylvestris L.) stands across Europes largest N deposition gradient to gain mechanistic insight into N-driven ECM community shifts, by assessing morpho-physiological traits (i.e. soil exploration types and ECM root-tip level exoenzyme activities involved in organic N and P acquisition) on individual ectomycorrhizas. Our data revealed high functional variation in foraging strategies across species and sites, including within dominant ECM genera (Cortinarius, Elaphomyces, Lactarius, Piloderma, Russula). Shifts in community-level exoenzyme activities along the N deposition gradient were consistent with increasing P limitation, with a buffering effect of phosphomonoesterase activity on host nutritional status (i.e. reduced foliar N:P). These trends were mainly driven by interspecific differences in enzymatic profiles and species turnover along the gradient, rather than intraspecific variation within widespread species. Dominant low-biomass species in high N sites (e.g. E. citrinopapillatus, L. subdulcis, R. ochroleuca) were efficient P-foragers, with some displaying high oxidative activity, potentially hampering soil carbon storage under elevated N loads. These findings highlight the role of ECM species-specific traits in mediating ecosystem processes and can help understand the future of pine forests under chronic N pollution, with potential implications for applied forestry.

Forest regeneration depends not only on how many seeds trees produce, but on the physiological quality of those seeds. Yet while climate-driven shifts in seed quantity and masting have received sustained attention, the parallel question of whether climate change degrades seed quality remains poorly resolved. Using a nationwide dataset of seed mass and viability in European beech (Fagus sylvatica L.) collected between 1996 and 2024 (13,349 seed lots from 381 forest districts across Poland), with climate-quality analyses focused on 5,374 freshly harvested seed lots from 353 districts (2004-2023), we asked whether the two components of seed quality respond to different seasonal climatic windows, and whether harvest-year climate also shapes seed performance during long-term cold storage. Seed mass and seed viability were only weakly correlated (Spearmans {rho} = 0.15), acting as two independent dimensions of seed quality. Both revealed substantial temporal variation over the study period, but along distinct trajectories. Seed mass declined markedly between segmented-regression breakpoints in 2009 and 2019, more steeply at higher latitudes, coinciding spatially and temporally with the masting breakdown reported at the species northeastern range margin. Climatic associations were correspondingly divergent. Viability was positively associated with previous summer temperature, consistent with temperature-cued flower initiation, and negatively with spring temperature in the harvest year, plausibly reflecting thermal disruption of early embryogenesis. Seed mass showed no significant association with any seasonal climatic predictor, indicating control by slower or unmeasured processes. Storage duration progressively reduced viability, and this decline was further modulated by climate during seed development, with seeds developing under climatically suboptimal conditions losing viability faster. These results expose a hidden decoupling between seed quantity and seed quality under contemporary climate change, with direct consequences for forest regeneration and for ex situ conservation strategies that assume mast-year seeds will remain viable for decades.

QuestionsEcological monitoring, repeated collection of ecological data, is essential to document how ecosystems respond to change. In grasslands, different vegetation monitoring protocols are used across disciplines, making it difficult to address multiple management objectives or research questions. We asked four questions about how three common vegetation monitoring protocols compare. (1) How do the protocols differ in how they collect data? (2) How do the protocols differ in their utility? (3) In what ways do vegetation measurements quantitatively differ across protocols? (4) What are each protocols strengths? LocationThis study was conducted on working ranches in the Southern Great Plains with vegetation consisting mainly of native forbs and grasses. MethodsWe implemented three protocols at each site: (1) the Rangeland Analysis Platform (RAP), (2) the Grassland Effectiveness Monitoring (GEM) protocol, and (3) a typical pollinator ecology survey protocol. We qualitatively compared each protocols utility and quantitatively compared cover measurements that each produced. ResultsAll three protocols displayed positive associations within cover categories, but differed in actual cover measurements. The RAP protocol, which uses remote sensing, measured the highest total vegetation cover. The GEM protocol, a line-point intercept method, had more capability to capture fine-scale cover patterns. The GEM protocol measured the most bare ground while the Pollinator protocol measured more forb coverage. ConclusionFine-scale methods like the GEM protocol are most appropriate to address objectives that require capturing small patterns that would otherwise be overlooked with methods like quadrats or remote sensing. Remote sensing is advantageous when monitoring large areas or inaccessible land, but may over-estimate cover. The Pollinator protocol is best equipped to address questions regarding flower abundance and richness. Similarities among protocols can facilitate synergy across disciplines for more effective monitoring. We emphasize the importance of denoting a clear scale and scope of monitoring objectives before selecting methods.

The Northwest Forest Plan (NWFP) Passive Acoustic Monitoring (PAM) program is a large-scale interagency biodiversity monitoring framework designed to assess the status and trends of northern spotted owls (Strix occidentalis caurina), barred owls (Strix varia), marbled murrelets (Brachyramphus marmoratus), and broader forest biodiversity across federally administered lands in the Pacific Northwest. In 2025, we deployed autonomous recording units at 2,095 sampling stations within 532 5-km2 hexagons randomly selected across approximately 24 million acres of federal forest lands in Washington, Oregon, and California. These deployments generated 1.37 million hours of acoustic recordings that we processed using the convolutional neural network PNW-Cnet v5 for automated species identification and subsequent human validation of focal species detections. Northern spotted owls were detected in 28% of sampled hexagons range-wide, including 16% in Washington, 25% in Oregon, and 60% in California. Occupancy patterns remained consistent compared to previous years, with higher occupancy concentrated in southern portions of the geographic range and continued low occupancy across much of the Washington Cascades and Oregon Coast Range. Barred owls were detected in 86% of sampled hexagons and remained broadly distributed throughout most of the NWFP area. Marbled murrelets were detected in 50% of reviewed hexagons within NWFP marbled murrelet management zones, with highest occupancy occurring in coastal forests of Oregon and Washington. The 2025 field season occurred under substantial operational constraints that reduced sampling effort by approximately half relative to 2023 and 2024 because of staffing limitations affecting participating federal agencies. Despite these reductions, the NWFP-PAM framework continued to provide broad-scale, spatially representative ecological information across the NWFP area. Results highlight the growing importance of passive acoustic monitoring and machine learning approaches for long-term biodiversity monitoring under changing environmental and operational conditions.

Early management decisions in operational forestry are critical for plantation success because it strongly influences seedling quality at planting. Beyond shaping seedling morphology, nursery inputs can also restructure root-associated fungal communities which has consequences for nutrient acquisition, stress tolerance and disease suppression after planting. In this study, we altered nutrient and fungicide inputs based on mycorrhizal ecological theory and quantified the effects of these treatments on key dimensions of the growth performance of radiata pine seedlings. In parallel, we profiled the root-associated mycobiome, assigning fungal taxa to functional guilds and summarizing their richness, diversity, relative abundance and community structure. Using a composite performance index that integrates the key morphological and health measures into a single response variable, together with conventional statistical models with machine learning approaches, we identified management practises that promote both plant performance and a favourable root fungal community and determined the consistent microbiome changes linked to overall quality of the seedlings. These results suggest that microbial feedback loops occur even in highly managed nursery conditions. More broadly, by combining a composite performance index with predictive modelling, we provide a practical way to test complex management combinations and identify microbiome features associated with high-quality planting stock.

Forests play a crucial role in mitigating climate change as primary terrestrial carbon sinks. While some studies suggest that global warming enhances forest productivity, a growing body of evidence highlights detrimental impact primarily driven by increased water stress. Yet the extent to which positive effects of climate change offset its negative impacts on tree species productivity remains unclear at large spatial extents. We assessed forest growth and mortality for the 21 most abundant tree species in Europe using National Forest Inventory data from more than 50,000 plots and 700,000 trees to disentangle the relative importance of climate and forest structure. Specifically, we examined how vapor pressure deficit (VPD) anomalies across species climatic edges and stand developmental stages affect forest growth and mortality occurrence and intensity (i.e. whether mortality occurred and the amount of basal area lost). Then, we aggregated the responses across species and separately for broad-leaved and needle-leaved species to assess whether forest growth and mortality differed between major functional groups. Although the importance of forest growth and mortality drivers varied markedly among species, climate had a stronger influence on mortality than on growth, particularly in needle-leaved species. Forest growth declined and mortality increased along VPD anomaly in most species and forests studied. Responses were most pronounced at arid species edges in early-stage broad-leaved forests and at wet edges in late-stage needle-leaved forests, where differences between functional groups were also highest. We evidence the need to parametrise species-specific models of forest growth and mortality across large spatial extents to better understand and predict effects of climate change on forest productivity. In addition, our results emphasize the importance of improving the understanding of forest mortality processes given the strong influence of climate on mortality, while also further studying vulnerable populations to climate change in arid edges of species distributions.