Álvaro Rubio-Cuadrado

Why neighbouring trees exposed to the same climatic extremes follow contrasting decline trajectories remains a central question in understanding climate‐driven forest dieback. Here, we reconstructed the processes underlying drought‐induced decline in a rear‐edge European beech ( Fagus sylvatica ) forest by integrating dendroecology, wood anatomy, stable isotopes, leaf physiology, fine‐root traits and soil fungal community analyses. Tree vulnerability was primarily linked to long‐term functional divergence driven by microsite heterogeneity rather than recent climatic stress. Vigorous trees occupied deeper soils and experienced higher local competition, exhibiting safer hydraulic architecture, greater stem storage capacity, deeper water uptake, lower long‐term intrinsic water‐use efficiency and stronger ectomycorrhizal mediation of resource acquisition. In contrast, trees on shallower soils and under low competition displayed more vulnerable hydraulic trajectories, reduced access to deep water sources and weaker drought buffering. These differences were detectable decades before growth trajectories diverged. Extreme droughts and compound drought–frost events exposed pre‐existing vulnerabilities. Following a critical drought–frost event in 1995, declining trees failed to recover and entered a self‐reinforcing cascade involving crown dieback, reduced carbon assimilation, constrained growth, diminished formation of conductive and storage tissues, and weaker carbon allocation to ectomycorrhizal fungi. The contrasting trajectories emerged from organ‐specific adjustments, rather than from a uniform shift along a single whole‐plant strategy. Our results show that forest decline often reflects the delayed expression of long‐standing vulnerabilities shaped by fine‐scale microsite heterogeneity.

The timing of budburst is a key determinant of a tree’s fitness within its environment. While numerous studies have investigated the environmental drivers of phenology, less attention has been paid to how phenological traits influence individual tree performance within the forest. Here, we assessed at the individual-tree scale whether earlier budburst is associated with enhanced growth and how intra-annual growth dynamics differ between early- and late-flushing trees. We analyzed annual and intra-annual growth together with budburst phenology across the Spanish plots of the ICP Forests intensive monitoring network (Level II) representative of major forest ecosystems in Spain, which include Mediterranean and temperate forests. Annual growth data were obtained from 296 trees monitored over 28 years, while phenological observations covered 13 years and intra-annual growth 11 years for a subset of 127 trees. On average, trees with earlier budburst exhibited higher annual growth, and the relationship was positive in seven of the nine species, although it was individually significant only in Pinus sylvestris and P. pinaster , and the differences among species were not statistically conclusive. No significant relationship was found in P. halepensis , P. pinea , P. nigra , Quercus ilex , Q. suber , Q. petraea , or Fagus sylvatica ; in F. sylvatica the tendency was negative, possibly owing to its high sensitivity to late frosts. Neither leaf habit nor any single climatic or edaphic variable significantly modified the relationship, although the plots of the two species with a significant relationship all belonged to the group of cooler sites, and none of the species from the warmer and drier sites showed it. The seasonal course of growth differed between early- and late-flushing trees: the higher growth of early-flushing trees was not restricted to the onset of the growing season but extended over the whole growth period.

Climatic and socioeconomic changes are driving widespread tree decline in abandoned Mediterranean coppices, a process potentially modulated by their clonal structure. However, the influence of belowground clonal size on aboveground physiological performance in resprouting species remains unknown. We integrated genetic, physiological and dendrochronological approaches within a one-hectare experimental plot of Quercus pyrenaica Willd. to test the effect of clonal size on shoot vigour and physiological performance. We studied 48 vigorous and decaying shoots from 24 size-contrasted clones, characterized by clonal area, shoot number, cumulative basal and sapwood area, and leaf area index. During the prolonged 2022 summer drought, we monitored leaf water potential, water content and gas exchange across seven measurement campaigns. These measurements were complemented with analyses of leaf pressure–volume traits, leaf minimum conductance, branch vulnerability to embolism, stem non-structural carbohydrates and long-term stem radial growth. Vigorous and declining shoots did not differ in monitored leaf-level variables or leaf hydraulic traits. However, declining canopy vigour was reflected in decadal stem growth stagnation and reduced stem xylem soluble sugars after leaf flush. Increasingly negative leaf water potential during the dry season limited long-term stem growth, more markedly for declining shoots. Both leaf hydration during summer drought and leaf area per unit sapwood area increased with clonal size. Concurrently, large clones exhibited higher branch vulnerability to embolism, with no differences in leaf osmoregulatory capacity. Our findings suggest that, in this coppiced clonal system, (i) stem-level measurements better captured differences between vigorous and declining shoots than leaf-level measurements, likely due to non-uniform branch dieback, (ii) single-time-point physiological measurements can provide insight into long-term growth trends and (iii) centennial coppicing has driven clonal-size-dependent allometric adjustments that favour root water uptake while increasing embolism vulnerability. Clonal structure and size are therefore overlooked factors that should be integrated into management strategies for these ecosystems.

Anthropogenic pressure has led to the degradation of most natural areas in Europe. However, there is growing concern amongst both citizens and public administrations regarding the need to improve the conservation status of natural spaces through ecological restoration projects. The greatest challenge faced by ecological restoration managers is determining the most appropriate measures to ensure successful restoration, given the highly variable case-specific conditions, differing interests and objectives amongst stakeholders and limited knowledge of which measures have succeeded or failed in past restoration projects. The objective of this study is to address this issue by compiling an exhaustive database of European ecological restoration initiatives through surveys targeting stakeholders (including managers, landowners, workers, researchers and interested citizens) in relation to restoration projects already implemented, in progress or planned. The questionnaire was designed to cover all aspects related to restoration projects: general characteristics (e.g. geographic scope, duration, funding sources), ecological restoration approaches (e.g. techniques applied, target species), socio-economic and governance dimensions (e.g. stakeholder engagement, policy frameworks) and standardised success indicators for quantifying project outcomes. The published database includes responses from a total of 404 participants. This database contains extensive information on ecological restoration practices across Europe, including the reported causes of success or failure and captures the diverse perspectives associated with respondents’ different roles in restoration. It is, therefore, of interest to researchers, policy-makers and other stakeholders involved in ecological restoration.

Summary: Land-use changes are fueling the transformation of formerly grazed European landscapes. Abandoned grasslands and woodlands are undergoing rapid processes of shrub encroachment (“shrubification”), but data on the patterns and paces of these dynamics are lacking. To fill this research gap, the common hawthorn ( Crataegus monogyna ), a widely distributed thorny shrub species dominating succession in many formerly grazed woodlands, was studied. To quantify age and growth rates, dendrochronological analyses were conducted on six hawthorn populations exposed to varying climate conditions in northern Spain. To test whether growth and aboveground phenology were coupled, data on leaf phenology were obtained for two study sites and related it to radial-growth indices. Lastly, growth indices were correlated with climate (temperature, precipitation) and hydrological (river flow) variables. A positive correlation between growth indices and the leaf flush date was found in one site. Warmer spring conditions lead to earlier leaf flushing, whereas leaf fall was delayed by warm autumn conditions. Growth was enhanced by low winter and summer temperatures, and by wet winter-to-spring conditions. However, a high river flow in spring reduced growth in a floodplain forest site. In the case of hawthorn, encroachment in dry sites could be slowed down by warmer spring and summer temperatures, which constrain its radial growth, whereas wetter spring conditions could accelerate it. The pace of ongoing “shrubification” across formerly grazed regions could be modulated by aridification.

Climate models forecast warmer winter conditions, which could lead to an earlier spring xylem phenology in trees. Localized stem heat experiments mimic this situation and have shown that stem warming leads to an earlier cambial resumption in evergreen conifers. However, there are still few comprehensive studies comparing the responses to stem heating in coexisting conifers and hardwoods, particularly in drought-prone regions where temperatures are rising. We addressed this issue by comparing the responses (xylem phenology, wood anatomy, growth, and sapwood concentrations of non-structural carbohydrates—NSCs) of two pines (the Eurosiberian Pinus sylvestris L., and the Mediterranean Pinus pinaster Ait.) and a ring-porous oak (Quercus pyrenaica Willd.) to stem heating. We used the Vaganov-Shashkin growth model (VS model) to simulate growth phenology considering several emission scenarios and warming rates. Stem heating in winter advanced cambial phenology in P. pinaster and Q. pyrenaica and enhanced radial growth of the three species 1–2 years after the treatment, but reduced the transversal lumen area of earlywood conduits. P. sylvestris showed a rapid and high growth enhancement, whereas the oak responded with a 1-year delay. Heated P. pinaster and Q. pyrenaica trees showed lower sapwood starch concentrations than non-heated trees. These results partially agree with projections of the VS model, which forecasts earlier growth onset, particularly in P. pinaster, as climate warms. Climate-growth correlations show that growth may be enhanced by warm conditions in late winter but also reduced if this is followed by dry-warm growing seasons. Therefore, forecasted advancements of xylem onset in spring in response to warmer winters may not necessarily translate into enhanced growth if warming reduces the hydraulic conductivity and growing seasons become drier.