Drought resistance and resilience in Mediterranean oaks appear to be structured along axes of variation linked to leaf habit and wood anatomy. Recurrent and intensifying droughts have emerged as a principal driver of decline in Mediterranean oak forests over the past three decades. This review synthesizes current understanding of the functional mechanisms shaping drought impacts in these ecosystems and complements existing work by combining a structured categorical overview with a multivariate functional ordination of oak responses. We assembled a dataset of 240 records derived from 212 studies published between 1994 and 2024, spanning species with contrasting leaf habits (evergreen, deciduous, semi-persistent), diverse wood anatomies (diffuse-, ring-, and semi-ring-porous), and developmental stages ranging from seedlings to mature stands. The studies encompass a broad gradient of drought durations and intensities, enabling comparison of drought resistance and resilience across plant systems. Across the reviewed literature, key ecophysiological mechanisms include stomatal regulation, hydraulic and osmotic adjustment, morpho-anatomical plasticity, and phenological shifts. However, most studies investigate these mechanisms in isolation, and integrative, multi-trait analyses remain rare. Using coarse categorical metrics, we found no clear geographic structuring of resistance, resilience, or response mechanisms, likely reflecting uneven species representation and heterogeneous experimental designs. Nonetheless, the dataset reveals functional patterns linked to plant diversity: deciduous, ring-porous species exhibit higher frequencies of low-resistance and low-resilience states, whereas evergreen, diffuse-porous species tend to display greater hydraulic safety and recovery capacity. Correspondence analysis further highlights major axes of variation associated with leaf habit and wood anatomy, confirming divergent adaptive strategies among Mediterranean oak functional types. Collectively, these findings underscore the importance of functional diversity in shaping drought responses and provide a framework for future mechanistic research and climate-adapted forest management.

Il 21 ottobre 2025 si è svolto a Firenze l’incontro per la presentazione del libro di Orazio Ciancio “Cultura e ricerca forestale”, che è stata anche l’occasione per festeggiare il suo novantesimo compleanno.L’evento, organizzato dai suoi allievi più diretti, ha visto la partecipazione di numerosi colleghi, altri allievi e amici, alcuni dei quali hanno voluto manifestare la loro stima con i contributi che qui riportiamo, insieme agli interventi programmati e alla presentazione del libro da parte di Marco Borghetti. Hanno portato i saluti: Cinzia Gagliardi (Comandante CUFA Regione Toscana), Simone Orlandini (Presidente Unione Nazionale delle Accademie italiane per le scienze applicate allo sviluppo dell’agricoltura, alla sicurezza alimentare e alla tutela ambientale), Massimo Vincenzini (Presidente Accademia dei Georgofili), Enrico Marone (Delegato Rettrice Università di Firenze), Elena Paoletti (Vicepresidente International Union of Forest Research Organizations) e Giorgio Matteucci (Presidente Società Italiana di Selvicoltura ed Ecologia Forestale). Tutti hanno sottolineato la figura del Professor Ciancio e il lavoro da lui svolto a favore delle Scienze Forestali.

Il degrado degli ecosistemi forestali e la perdita di biodiversità rappresentano un rischio per l’equilibrio ecologico ed economico globale. In Italia molte foreste sono state semplificate dalla gestione applicata in passato, in un contesto europeo caratterizzato da habitat spesso in stato di conservazione sfavorevole. Questo lavoro esamina gli indirizzi selvicolturali per il miglioramento ecologico delle foreste semplificate e la valorizzazione della biodiversità con l’obiettivo di fornire elementi utili all’applicazione in Italia del Regolamento UE 2024/1991. L’analisi si articola nella descrizione di approcci metodologici riconducibili a strategie di gestione attiva e conservativa. Sul piano attivo, si evidenzia l'importanza di favorire la rinnovazione naturale, incrementare la complessità strutturale e cronologica dei popolamenti e mantenere livelli adeguati di provvigione legnosa in foresta. Particolare rilievo è attribuito al rilascio in bosco di necromassa legnosa e di alberi a invecchiamento indefinito per sostenere o ripristinare la diversità biologica. Sul piano conservativo, si promuove la tutela delle dinamiche naturali nelle aree protette e la salvaguardia delle foreste vetuste. L’integrazione di tali strategie, supportata da una governance multilivello, è essenziale per accrescere la resilienza ecosistemica e raggiungere gli obiettivi ambientali e climatici dell’UE.

Old-growth forests (OGFs) provide key benchmarks for biodiversity and ecosystem functioning, yet relationships among stand structural heterogeneity, topographic gradients, and multilayered understorey composition remain insufficiently quantified in Mediterranean mountain systems. This study aimed to (i) quantify forest structural heterogeneity in Southern Apennine OGFs, (ii) examine relationships among site conditions, vascular plant diversity and forest structure and (iii) identify the structural attributes most strongly associated with vascular plant species composition while disentangling their contribution from that of topography. Location: Pollino National Park, southern Italy. Structural attributes, topographic variables and vascular plant species composition were recorded across nine candidate OGF sites. After exclusion of one site, the analytical dataset comprised 142 subplots from eight sites. Structural complexity was quantified using a Structural Heterogeneity Index (SHI). Linear mixed-effects models accounted for subplot nesting within site, while canonical correspondence analysis (CCA), principal coordinate analysis (PCoA) and variation partitioning (VP) assessed structural-topographic-floristic relationships. Floristic sampling completeness and sensitivity to the taxon-frequency threshold were also evaluated. SHI values varied markedly among forest types, with beech and mixed forests exhibiting the highest structural heterogeneity. Across the full multivariate gradient, topographic variables explained 18.8% of variation in structural attributes. In site-adjusted mixed models, aspect had a significant joint association with SHI, whereas elevation and slope were not significant. Floristic ordination was highly stable across taxon-frequency thresholds, and pooled sample coverage was 98.65%. VP analysis revealed that the forest-structure predictor set had a larger unique contribution to floristic variation (23.5%) than topography alone (12.8%), with a substantial shared fraction; large-tree abundance, canopy cover and decay-class diversity were among the structural variables significantly associated with vascular plant composition. The ecological complexity of Southern Apennine OGFs reflects an interplay of structural, topographic, historical and floristic dimensions. Integrating stand structure, topographic context and vascular plant composition provides a more robust framework for interpreting and conserving old-growth forests than any single structural metric.

Riparian ecosystems in Mediterranean landscapes are critical for biodiversity conservation and ecosystem services. This study investigates riparian vegetation change dynamics in a Mediterranean ecosystem in southern Italy, focusing on the potential relationship with environmental and anthropogenic factors contributing to the observed dynamics over the study period. We used 25-year of Landsat imagery to assess riparian vegetation cover and surface water changes, analyzing temporal trends of Normalized Difference Vegetation Index (NDVI) and Modified Normalized Difference Water Index (MNDWI), respectively. Statistical trend analysis revealed for the 96% of the changing areas a significant increase in riparian vegetation cover classified between "light" to "moderate improvements" in terms of trend's magnitude. The greening process is particularly pronounced in areas with gentler slopes and higher Strahler stream orders. Conversely, we found a decrease in the surface area covered by water over the observed period. We used Structural Equation Model (SEM) to identify the relationship between water availability (surface water, precipitation, soil moisture) and riparian vegetation change trends. Reduction in surface water appears as the primary factor influencing vegetation change. Although the contribution to vegetation dynamics of topography, environmental conditions, land use and reduced anthropogenic pressure e.g. decline in traditional agriculture and land abandonment remain negligible outside the core of conceptualized model, their role in creating favourable conditions for riparian vegetation expansion cannot be overlooked. An understanding of these patterns and interactions is important for the development of effective adaptive management strategies to sustain both ecosystem functions and conservation efforts in riparian areas.

Heat and drought stress have triggered forest dieback episodes worldwide, affecting oak forests, particularly in hotspots of climate change such as the Mediterranean Basin. However, forecasting dieback is not straightforward. In this study, we used the earlywood anatomy to improve dieback forecasts in five oak species characterized by different drought sensitivity (i.e. from high to low Quercus robur, Q. cerris, Q. frainetto and Q. canariensis, Q. humilis, Q. pubescens) across Italy and Spain. We measured radial growth, expressed as basal area increment (BAI), earlywood hydraulic diameter (Dh) and vessel area of coexisting non-declining (ND) and declining (D) trees in each stand. Then, we calculated the product between the coefficient of variation (CV) of vessel area and a spatial aggregation index (AI). High CV × AI values indicate regularly spaced vessels with variable area of vessels, while low values correspond to clustered vessels with similar area. ND trees showed higher BAI values than D trees from 10 to 40 years before the dieback onset, when ND trees grew 20-50 % more than the D trees. We observed a decline in the vessel area CV several decades prior to dieback in D trees, with the exception of Q. cerris. The AI showed higher values in ND than in D trees. Consequently, the CV × AI product was consistently higher in ND than in D trees. The CV × AI divergence between ND and D trees was pronounced in the wettest sites, specifically for Q. robur and Q. humilis. Time series of CV × AI effectively differentiated trees based on their vigor. Wood anatomy variables could be used to enhance predictions of vulnerability to drought-induced dieback. This study can help identify vulnerable trees before the onset of dieback symptoms, serving as a tool to support the management of forests prone to drought.

The health status of forests is becoming increasingly endangered by drought-induced climate change. In recent decades, widespread forest decline has been reported worldwide in all biomes. The reports of forest mortality across Italy and the need to be better aware of the extent and magnitude of the phenomenon were the assumptions that led to the development of a web-application called SilvaCuore. A team of researchers from the University of Basilicata has carried out this project to safeguard Italian forests. The aim is to combine scientific research and active community participation (Citizen Science project) through the use of new technologies, in order to better monitor and manage Italy’s forest heritage. The SilvaCuore web-application seeks to census the declining forest sites located in Italy and to create a database that can be used as a basis to improve the forest management. SilvaCuore has been developed as a Progressive Web Application and can be accessed from smartphones, tablets and PCs due to its responsive user interface. The user, after registering in to the web-application, is guided by a user-friendly step-by-step procedure in the reporting process that, besides a brief description or more complex data, allows to take some photos and the GNSS position of the site. The report outcomes will be automatically collected in a cloud web database, immediately accessible to the research team. Verified reports will become publicly accessible from the same web-application, ready to provide a concrete insight into the health of our forests. The application is also linked to a website that provides additional information about the project, the rationale behind the app, and the research activities carried out by the SilvaCuore team. It is crucial to improve the citizen's approach to nature and environmental issues: a more aware citizen will be a citizen who cares more about the environment and its preservation. An case in point is the agreement with PEFC Italy (Program for the Endorsement of Forest Certification Schemes): first, PEFC-certified forest owners will be able to utilize the web-application, in order to implement adaptive forest management and second, this will provide useful alert reporting. The challenge here is to be able to create a monitoring network that not only monitors the current state of forest health but also evaluates potential future dynamics, and becomes increasingly capable of responding to the threat of forest decline.

Water transport, mechanical support and storage are the vital functions provided by the xylem. These functions are carried out by different cells, exhibiting significant anatomical variation not only within species but also within individual trees. In this study, we used a comprehensive dataset to investigate the consistency of predicted hydraulic vessel diameter widening values in relation to the distance from the tree apex, represented by the relationship D-h proportional to L-beta (where D-h is the hydraulic vessel diameter, L the distance from the stem apex and beta the scaling exponent). Our analysis involved 10 Fagus sylvatica L. trees sampled at two distinct sites in the Italian Apennines. Our results strongly emphasize that vessel diameter follows a predictable pattern with the distance from the stem apex and beta similar to 0.20 remains consistent across cambial age and climates. This finding supports the hypothesis that trees do not alter their axial configuration represented by scaling of vessel diameter to compensate for hydraulic limitations imposed by tree height during growth. The study further indicates that within-tree variability significantly contributes to the overall variance of the vessel diameter-stem length exponent. Understanding the factors that contribute to the intraindividual variability in the widening exponent is essential, particularly in relation to interspecific responses and adaptations to drought stress.

Previous favorable climate conditions stimulate tree growth making some forests more vulnerable to hotter droughts. This so-called structural overshoot may contribute to forest dieback, but there is little evidence on its relative importance depending on site conditions and tree species because of limited field data. Here, we analyzed remote sensing (NDVI) and tree-ring width data to evaluate the impacts of the 2017 drought on canopy cover and growth in mixed Mediterranean forests (Fraxinus ornus, Quercus pubescens, Acer monspessulanum, Pinus pinaster) located in southern Italy. Legacy effects were assessed by calculating differences between observed and predicted basal area increment (BAI). Overall, the growth response of the study stands to the 2017 drought was contingent on site conditions and species characteristics. Most sites presented BAI and canopy cover reductions during the drought. Growth decline was followed by a quick recovery and positive legacy effects, particularly in the case of F. ornus. However, we found negative drought legacies in some species (e.g., Q. pubescens, A. monspessulanum) and sites. In those sites showing negative legacies, high growth rates prior to drought in response to previous wet winter-spring conditions may have predisposed trees to drought damage. Vice versa, the positive drought legacy found in some F. ornus site was linked to post-drought growth release due to Q. pubescens dieback and mortality. Therefore, we found evidences of structural drought overshoot, but it was restricted to specific sites and species. Our findings highlight the importance of considering site settings such as stand composition, pre-drought conditions and different tree species when studying structural overshoot. Droughts contribute to modify the composition and dynamics in mixed forests.

This study provides an overview of the forests of Basilicata, Southern Italy, including their recent history, dominant forest types, current management, and vulnerability to climate change and wildfire. It outlines silvicultural and management proposals that can be implemented in the new forest plan that the Basilicata Region is about to adopt. The proposals are based on the principle of adaptive management to support forest functionality, biodiversity and ecosystem services. Silvicultural methods include continuous cover forestry, natural regeneration, species richness and functional diversity, structural diversification, imitation of natural disturbances, tree retention to increase biodiversity. The characteristics of the forest-wood supply chain have been analyzed, highlighting weaknesses and possible improvements.

Forests around the world are facing climate change. Increased drought stress and severe heat waves in recent decades have negatively impacted on forest health, making them more vulnerable and prone to dieback and mortality phenomena. Although the term vulnerability is used to indicate an increased susceptibility of forests to climate change with a worsening of their vigour status that can compromise their ability to respond to further climate extreme events, there are still uncertainties on how to evaluate it. Indeed, evaluation of forest vulnerability is complex both because of some critical issues in the estimation methods used and because of the multiple factors influencing the response of forests to ongoing climate change. A way to assess the vulnerability to environmental stresses is by combining remote sensing and dendroecological data. However, these two approaches entail multiple uncertainties, including growth/photosynthetic relationships, carbon allocation dynamics, biases of tree-ring data and noisy remote sensing data, which require further clarification for proper monitoring of pre- and post-drought forest trajectories. Our review aims to create an overview of the current literature and knowledge to understand the critical issues, needs and possible solutions that forest vulnerability research is addressing. We focus on Mediterranean forests located in a climate warming hotspot and showing a high vulnerability to increased aridification.

Post-fire natural regeneration of Aleppo pine forest in the Gargano promontory (Southern Italy) is documented by means of photographs taken soon after fire and some years later. The potential of pine for adaptation to climate change and fire disturbance through its phenotypic plasticity is highlighted, and future dynamics of Aleppo pine forests and management perspectives are considered.

We investigated the dendroclimatic response of a Pinus heldreichii metapopulation distributed over a wide elevation interval (from 882 to 2143 m a.s.l.), spanning from low mountain to upper subalpine vegetation belts in the southern Italian Apennines. The tested hypothesis is that wood growth along an elevational gradient is non-linearly related to air temperature. During three years of fieldwork (2012-2015) at 24 sites, we collected wood cores from a total of 214 pine trees with diameter at breast height from 19 to 180 cm (average 82.7 & PLUSMN; 32.9 cm). We used a combination of tree-ring and genetic methods to reveal factors involved in growth acclimation using a space-for-time approach. Scores from ca-nonical correspondence analysis were used to combine individual tree-ring series into four composite chronologies re-lated to air temperature along the elevation gradient. Overall, the June dendroclimatic response followed a bell-shaped thermal niche curve, increasing until a peak around 13-14 & DEG;C. A similarly bell-shaped response was found with previ-ous autumn air temperature, and both dendroclimatic signals interacted with stem size and growth rates, generating a divergent growth response between the top and the bottom of the elevation gradient. Increased tree growth in the upper subalpine belt was consistent with the consequences of increasing air temperature under no drought stress. A positive link was uncovered between pine growth at all elevations and April mean temperature, with trees growing at the lowest elevations showing the strongest growth response. No elevational genetic differences were found, hence long-lived tree species with small geographical ranges may reverse their climatic response between the lower and upper bioclimatic zones of their environmental niche. Our study revealed a high resistance and acclimation capa-bility of Mediterranean forest stands, and such low vulnerability to changing climatic conditions highlights the poten-tial to store carbon in these ecosystems for the coming decades.

The link between biodiversity and ecosystem function can depend on environmental conditions. This contingency can impede our ability to predict how biodiversity-ecosystem function (BEF) relationships will respond to future environmental change, causing a clear need to explore the processes underlying shifts in BEF relationships across large spatial scales and broad environmental gradients. We compiled a dataset on five functional traits (maximum height, wood density, specific leaf area [SLA], seed size, and xylem vulnerability to embolism [P-50]), covering 78%-90% of the tree species in the National Forest Inventory from Italy, to test (i) how a water limitation gradient shapes the functional composition and diversity of forests, (ii) how functional composition and diversity of trees relate to forest annual increment via mass ratio and complementarity effects, and (iii) how the relationship between functional diversity and annual increment varies between Mediterranean and temperate climate regions. Functional composition varied with water limitation; tree communities tended to have more conservative traits in sites with higher levels of water limitation. The response of functional diversity differed among traits and climatic regions but among temperate forest plots, we found a consistent increase of functional diversity with water limitation. Tree diversity was positively associated with annual increment of Italian forests through a combination of mass ratio and niche complementarity effects, but the relative importance of these effects depended on the trait and range of climate considered. Specifically, niche complementarity effects were more strongly associated with annual increment in the Mediterranean compared to temperate forests. Synthesis: Overall, our results suggest that biodiversity mediates forest annual increment under water-limited conditions by promoting beneficial interactions between species and complementarity in resource use. Our work highlights the importance of conserving functional diversity for future forest management to maintain forest annual increment under the expected increase in intensity and frequency of drought.

<p>Some tree species have shown to be very vulnerable to drought and heat waves in the Mediterranean Basin, causing a loss of important socio-economic and ecosystem forest services.  In this regard, oaks are important but vulnerable species which are showing losses in terms of productivity and growth and rising mortality rates. Dendroecological studies using retrospective analysis of wood anatomical traits and tree rings have demonstrated their potential to assess long-term patterns of growth and vigor in several Mediterranean oak species. Moreover, the long-term reconstruction of wood anatomical traits such as transversal lumen area, allows investigating hydraulic adjustments of trees through time.</p> <p>In this study, we reconstructed changes in wood anatomy for a 38-year long period (1980-2017) to investigate how drought impacted the hydraulic functionality and triggered dieback in five ring-porous oak species from Italy and Spain (<em>Quercus robur, </em><em>Quercus frainetto,</em><em> </em><em>Quercus cerris</em>, <em>Quercus canariensis, Quercus pubescens</em>). We compared non-decaying (ND) and decaying (D) coexisting trees of each species showing low and high defoliation levels, respectively. We analyzed earlywood anatomical traits (vessel area, hydraulic diameter, vessel density, theoretical hydraulic conductivity, etc.) in these species and analysed them considering a ranking of increasing drought tolerance: <em>Q. robur, </em><em>Q. frainetto,</em><em> </em><em>Q. cerris</em>, <em>Q. canariensis, </em>and<em> Q. pubescens</em>.</p> <p>We observed differing growth patterns and xylem conduit area responses in D trees compared with ND trees. The D trees formed narrower EW vessels than ND and the Dh were lower in D trees compared with ND trees. We discuss the relationships between radial growth, changes in wood anatomy and hydraulic functioning of trees focusing on those proved more sensitive to growth decline and mortality in order to highlight the climatic triggers of dieback in ring-porous oak species as related to hydraulic failure.</p>

Drought reduces canopy cover, productivity and tree growth in forests. However, there is still little knowledge on how drought affects coupling between canopy greenness assessed by remote sensing and hydraulic conductivity detected by wood anatomy. This combination could improve the understanding of forest response to climate change. Thus, we investigated the impacts of a hot drought, which occurred in summer 2017, on radial growth, earlywood hydraulic diameter (Dh), a proxy of conductivity, and several remote-sensing indices in mixed Mediterranean hardwood forests (Quercus pubescens Willd. - Fraxinus ornus L.). In general, growth showed a higher coherence among trees and a higher responsiveness to climate. Growth decreased during the drought year, particularly for Q. pubescens, which showed high defoliation and dieback intensity. Both species showed a decline of Dh in 2018 after the drought and subsequent warm winter conditions. We found positive relationships between Dh and remote-sensing data for Q. pubescens in some of these vulnerable sites, where (i) growth was constrained by dry spring-summer conditions and (ii) Dh and growth covaried. These findings indicate a high variability among sites and tree species in their responses to drought considering earlywood anatomy, growth canopy cover and water content. However, some common patterns emerge such as links between potential hydraulic conductivity (Dh), tree cover and Dh-growth covariation in the most impacted sites. Further, F. ornus seem to perform better in terms of growth under drought conditions, showing less mortality and dieback than Q. pubescens. Future studies could explore how water transport and changes in canopy cover respond to dry and warm conditions and if that covariation indicates vulnerability to drought.

<p>Increasing drought severity can affect the healthy status of forests and determine changes in structural and ecophysiological responses to such extreme climate events. Reduced canopy cover, productivity and tree growth and recent dieback phenomena are widespread responses to drought. However, favourable climatic conditions can improve the post-drought recovery capacity of forests, but also make them vulnerable to drought damage through structural overshoot by altering the root to shoot ratio due to wet conditions. Due to the lack of integrated and retrospective field data, the patterns and responses of forests to wet-dry climate variability are still poorly understood. In this work we used remote sensing data (NDVI) to characterise the canopy conditions and combined them with field and tree-ring width data to assess the effects of the summer 2017 drought on Mediterranean tree species in southern Italy (<em>Fraxinus ornus, Quercus pubescens, Acer monspessulanum, Pinus pinaster</em>). By comparing radial growth and resilience indices we found that growth responses to drought depended not only on tree species but also on site conditions. Overall, the growth decline due to drought was followed by a rapid recovery, while negative legacies to drought were found at lower quality sites, which corresponded to sites with the lowest NDVI values. Indeed, trees at these sites showed high growth rates before drought, in response to wet winter-spring conditions, and then suffered more from drought stress. Our results demonstrated how structural overshoots predisposes to drought damage and induced negative legacies. Specific knowledge on the effects of drought overshoot over time is important for analysing and understanding current forest responses and dynamics.</p>

Wildfires represent one of the primary disturbance agents in the Mediterranean, significantly affecting the ecological integrity of forests. Therefore, understanding the spatial patterns of post-fire vegetation recovery is crucial to improving forest restoration planning and assessing the regeneration capacity of different forest stands that have been impacted by wildfires. In this study, we analysed post-fire vegetation recovery rates within the context of fire severity, pre-fire vegetation, and post-fire climate conditions, for different Mediterranean forest classes, namely, Mediterranean pine, holm, deciduous oak forests, sclerophyllous vegetation, and thermophilous shrublands. Basilicata, in Italy, was chosen as a study area, as it represents a wide range of forests. The Relative Recovery Indicator (RRI) was derived from Normalized Burn Ratio (NBR) patterns extracted from 30-meter Landsat time series for different wildfires that occurred during the 2004-2016 within Google Earth Engine (GEE) environment. A Linear Mixed Model (LMM) was used to test the effect of the different variables on the RRI. Results showed a general decrease in recovery rate within five-years post-fire for each forest cover class, which is mainly related to pre-and post-fire conditions. Pre-fire vegetation conditions significantly influenced post-fire vegetation recovery, especially in sclerophyllous and deciduous oak forests. Post-fire climate conditions (e.g., temperature) were also important predictors of vegetation recovery explaining the variation in post-fire RRI patterns. The proposed method could provide new insights into the restoration and management of forest eco-systems in the Mediterranean.

•Floodplain and riparian forests are among the most vulnerable ecosystems.•We compared growth of coexisting trees in a temperate and Mediterranean conditions.•Climate and tree-ring data were combined with growth models to detect growth decline.•Warmer springs and drier summers reduce oak and ash growth.•Alder was the most drought resistant species.