Quercus Ilex Research Articles

A new species of Rhadinobracon Szépligeti (Hymenoptera: Braconidae: Braconinae) from Spain, with probable host record

Rhadinobracon hispanicus sp. n. is described and illustrated from specimens reared from dead and dying wood of Quercus rotundifolia Lamarck collected in Huelva province, S. W. Spain. The only xylophagous insects also reared were the buprestid beetle Acmaeodera octodecimguttata (Piller & Mitterpacker) (Buprestidae), which is considered to be almost certainly the host. Rhadinobracon is largely Afrotropical, Middle Eastern and Indian in distribution and the new species represents a large expansion of the known range of the genus. The new species exhibits considerable sexual dimorphism in respect of the hind leg, and an earlier male specimen (now lost) from a different locality in Spain clearly, from photographs and an outline description, belongs to the same species.

Microarthropod responses to fire: vegetation cover modulates impacts on Collembola and Acari assemblages in Mediterranean area

BackgroundIn the Mediterranean region, fire is a recurring disturbance that impacts both surface and underground organisms. While the effects on plants and surface animals are well-studied, the consequences for soil microarthropods are often overlooked. This research addresses the microarthropod responses to fire by comparing post-fire Collembola and Acari assemblages in soils with different vegetation covers. Three years post-fire, surface soils were sampled within the Vesuvius National Park (Southern Italy) from a total of 24 sites, comprising 6 sites each under holm oak (HO), pine (P), black locust (BL), and herbaceous (H) vegetation. Within each vegetation cover, sites were further categorized into three unburnt (NB) and three burnt (B) sites for comprehensive analysis. Collembola and Acari were extracted, identified at the family and suborder level, respectively and analyzed for density and taxa richness.ResultsThe results highlighted that fire alone did not impact microarthropod communities, but its effects varied according to the vegetation covers. Microarthropod abundance declined in burnt soils under P, and increased in burnt soils under BL. Furthermore, eu-edaphic organisms (Onychiuridae, Oribatida), typical of stable environments, decreased in soils under P, and increased in soils under black locust.ConclusionsFire impact on microarthropod communities changed according to the vegetation covers, highlighting the importance of considering vegetation type when managing post-fire landscapes. The rapid recovery of microarthropod communities under some vegetation covers suggests that fire may not universally impair soil biodiversity in Mediterranean environments.

Bioreduction of aromatic ketones catalyzed by oak fruits (Quercus Ilex L ) fruit grown in north Algeria

The present work primarily aims to investigate and establish a method for the bioreduction of aromatic ketones to produce corresponding alcohols. This process is crucial for the production of various industrially important chemicals, including pharmaceuticals, agrochemicals, and natural products, and supports the principles of green chemistry. Additionally, this study seeks to valorize the vegetation cover in southern Algeria as a source of biochemical catalysts. Our research focused on the bioreduction of several acetophenone derivatives using the fruits of Oak (Quercus ilex L.) which is cultivated in northern Algeria. The findings indicate that these plant tissues can effectively reduce acetophenone derivatives. Specifically, a chemical yield of approximately 90% was achieved for acetophenone, while yields ranged from 60% to 75% for 4'-haloacetophenones (where X = F, Cl, and Br) and 4'-nitroacetophenone. These results demonstrate that (Quercus ilex L).fruits from northern Algeria can serve as effective biocatalysts in the reduction of aromatic ketones to their corresponding alcohols. This approach not only supports the sustainable production of pharmaceuticals but also provides significant health, environmental, economic, and medical benefits.

Stem Growth and Dehydration Responses of Mediterranean Tree Species to Atmospheric and Soil Drought.

Stem growth responses to soil and atmospheric drought are critical to forecasting the tree carbon sink strength. Yet, responses of drought-prone forests remain uncertain despite global aridification trends. Stem diameter variations at an hourly resolution were monitored in five Mediterranean tree species from a mesic and a xeric site for 6 and 12 years. Stem growth and dehydration responses to soil (REW) and atmospheric (VPD) drought were explored at different timescales. Annually, growth was determined by the number of growing days and hours. Seasonally, growth was bimodal (autumn growth ≈ 8%-18% of annual growth), varying among species and sites across the hydrometeorological space, while dehydration consistently responded to REW. Sub-daily, substantial growth occurred during daytime, with nighttime-to-daytime ratios ranging between 1.2 and 3.5 (Arbutus unedo ≈ Quercus faginea < Quercus ilex < Pinus halepensis in the mesic site, and Juniperus thurifera < P. halepensis in the xeric site). Overall, time windows favourable for growth were limited by soil (rather than atmospheric) drought, modulating annual and seasonal growth in Mediterranean species, and stems maintained non-negligible growth during daytime. These patterns contrast with observations from wetter or cooler biomes, demonstrating the growth plasticity of drought-prone species to more arid climate conditions.

Life cycle assessment of common urban trees - The environmental performance of three Mediterranean cities

Given the increasing pressure from extreme events due to climate change, the planting of new trees has become a priority in the political agendas of cities. However, the rush to plant trees often fails to account for the reduced performance and lifespan of trees in heavily urbanized areas and the environmental impact of their production, maintenance, and eventual disposal. By means of the Life Cycle Analysis, this study aims to investigate the potential environmental benefit and impact of trees planted in three European cities located in Mediterranean areas (Perugia, Thessaloniki, and Cascais), that have adhered to the management guidelines of the LIFE Clivut project. The environmental performance of each tree is mainly affected by the tree management operations performed, by the climatic conditions, and by the tree performance in carbon dioxide (CO2) uptake and Particulate matter (PM) capture. The impact assessment obtained by ReCiPe 2016 Endpoint (H) methodology evidenced that the trees' beneficial effects widely overcome the impact of the operations carried out during the tree management. Broadleaved species showed an average environmental performance higher than conifers. The best results have been obtained by Tilia cordata Mill., Quercus ilex L., Populus spp. and Celtis australis L. in the case of broadleaved trees, and by Calocedrus decurrens (Torr.) Florin and Cedrus spp. for Conifers. The results of the Environmental Footprint (EF 3.1) method highlighted the urban trees' potentiality to mitigate Human Health problems and to improve Ecosystem Quality. Future studies may explore other management scenarios to optimize energy and materials use, reduce emissions, hence obtaining an increase of the environmental benefit for the urban areas.

Microclimatic effects of tree shelters on the early establishment and resilience of seeded acorns vs. outplanted seedlings

Little is known about the effects of tree shelters on the early response of oak seedlings produced by acorn seeding. In this paper, we explore the effects on holm oak (Quercus ilex L. subsp. ballota (Desf.) Samp.) seedlings of the microenvironment created by the tree shelters and the restoration method (seeding vs. outplanting) in terms of emergence, survival, growth, and resilience after harvesting. For this purpose, seedling height [H], root collar diameter [RCD], number of leaves, and aerial biomass were monitored. We made two sowings of acorns in February 2017 and February 2018, together with a seedling outplanting in February 2018 in a common garden site in semiarid SE Spain. In total, 600 acorns were randomly sowed and 300 nursery-grown seedlings were outplanted and studied until 2022. Mother tree and initial acorn mass were also monitored as additional variables in the analyses. Tree shelters consisted of closed plastic Tubes, Mixed tubes, Cork shelters, Tiles, and a Control with no shelter. Emergence rate was positively influenced by the Tube shelter (86%) as compared to the Control (64%), and especially by the initial acorn mass. By contrast, mother tree or year of sowing seemed to have no effect. The survival rate for the emerged acorns (88%) was statistically similar to that of outplanted seedlings (91%), and was unaffected by mother tree, tree shelter, or acorn mass. In terms of growth, the slenderness ratio (H:RCD) was considerably higher in seedlings from directly seeded acorns than for those that were outplanted. With the exception of Tile, all the shelters showed a higher slenderness ratio than the Control, especially the Tube shelter, which also showed a lower number of leaves and a lower aboveground dry biomass than the Control, Cork, and Tile shelters. Virtually no interactions were observed between the mother tree and the tree shelter. At harvesting, all the growth-related parameters were still strongly dependent on the acorn mass and the initial seedling features recorded after the first growing season. Resprouting rate and growth were also highly dependent on the acorn mass and the plant features at the beginning of the experiment and at harvesting. In summary, we did not find evidence to support tree shelters to improve the microclimate of holm oak seedlings both seeded or outplanted. Direct acorn seeding can be as successful as outplanting of nursery-grown seedlings. Selection of heavy acorns from mothers with a high germination and emergence rate is highly advisable.

Acorn removal and seedling age determine oak (Quercus ilex L. and Q. suber L.) restoration outcome in ungulate-dominated Mediterranean environments

Key messageWe test the potential benefits of planting 2-year vs. 1-year-old seedlings to restore Mediterranean oak-dominated systems. Planting 2-year-old Quercus suber L. seedlings is recommended for improved survival and resilience against wild boar (Sus scrofa L.) and drought in dry sandy soils. The removal of acorns in seedlings did not apparently influence leaf biochemical traits and could reduce wild boar damage, particularly in 1-year-old seedlings.ContextIn the face of anthropogenic global change, Mediterranean oak-dominated ecosystems confront increased biotic (ungulate herbivory) and abiotic (drought) stressors, compromising forest regeneration. Restoration measures are imperative to address this scenario.AimsThis study assesses the impact of different mitigation measures on the survival and biochemical traits of two oak species.MethodsWe planted Quercus ilex L. and Q. suber L. seedlings in Cabañeros and Doñana National Parks (Spain), subjecting them to three treatments: cotyledon/acorn removal, seedling age (1- vs. 2-year-old), and herbivore protection (fenced vs. non-fenced).ResultsWild boar (Sus scrofa L.) damage peaked in winter and early spring, while drought prevailed from late spring to fall. In sandy soils, wild boar uprooted 1-year-old more often than 2-years-old seedlings (40% vs. 18%). One-year-old seedlings without acorns showed higher survival rates against wild boar only in sandy soils. The removal of acorns in seedlings did not influence plant biochemical traits.ConclusionsPlanting 2-year-old seedlings in sandy soils may mitigate wild boar damage and improve drought resilience. Seedling age seems more important than acorn removal against biotic and abiotic stressors although acorn removal could reduce wild boar damage in 1-year-old seedlings. Our results underscore the importance of considering multiple stressors in oak restoration strategies.

Contribution to the Iberian thermomediterranean oak woods (Spain, Portugal): the importance of their teaching for the training of experts in environmental management

The study of the holm oak forests of the lower and upper mesomediterranean of the south of the Iberian Peninsula, and new syntaxons of holm oak forests not assigned until now are contributed. The plant dynamics is provided and completed, and the importance of the learning of plant description and dynamics by university students, future environmental managers, is specified. Taking into account the strong anthropic action with the consequent destruction of holm oak forests, it is necessary to enhance the knowledge of plant dynamics to decipher the potential vegetation, and to be able to apply the vegetation series as a basis for agronomic and forestry management. In this work, we propose a new vegetation series. We propose the association Aristolochio baeticae-Quercetum rotundifoliae nova for the biogeographic sector Granadino-Almijarense (Montes de Málaga) and as a first dynamic stage of the microforest of Olea europea var. sylvestris obtained by deforestation. The study of the Iberian olive groves allows us to propose two new associations Aristolochio baeticae-Oleetum sylvestris and Ephedro fragilis-Oleetum sylvestris.

Fatty acid composition and antioxidant capacity of defatted, non-defatted and oils extracts of &lt;i&gt;Quercus ilex&lt;/i&gt; fruit from Algeria

Fatty acid composition and antioxidant capacity of defatted, non-defatted and oils extracts of &lt;i&gt;Quercus ilex&lt;/i&gt; fruit from Algeria

Genetic variation in susceptibility of Phytophthora cinnamomi-infected holm oak in the absence or presence of severe drought

Abstract The evergreen oaks Quercus ilex and Quercus suber are exposed to widespread Phytophthora infestation in natural forests. To restore diseased forests, deploying trees less susceptible to combined stress is the most promising approach. We aimed to determine whether drought affects the susceptibility of Q. ilex and Q. suber seedlings to Phytophthora cinnamomi (Pc) differently. Additionally, to provide scientific support for a genetic improvement program to reduce the susceptibility of holm oak to decline, genetic variation and heritability in susceptibility to Pc in Q. ilex in the absence or presence of drought were estimated. About 7000 seedlings of 66 Q. ilex and 9 Q. suber trees from the Extremadura region (Spain) were inoculated with Pc at age 1. The following year, half the experimental blocks were regularly watered and half were exposed to severe drought, and inoculated again with Pc. In the absence of drought, Q. ilex was more susceptible than Q. suber to Pc (mortality 97% and 59%, respectively), but in the presence of drought after Pc infection the species were equally susceptible (~97% plant mortality). It could therefore be expected that under the climate change scenarios predicted for the south of the Iberian Peninsula, offspring of Q. suber will be as compromised as offspring of Q. ilex to soil infestation by Pc. Significant additive genetic variation and heritability in the susceptibility of Q. ilex to combined Pc infection and drought were observed (hi2 = 0.46 for time to death of plants), indicating that breeding for tolerance to combined stress is possible. Family variance component estimates of time to death in Q. ilex were highest in the presence of drought, and genetic control of susceptibility in Q. ilex decreased over time as plant stress increased. This is the first study to define a production population against combined stress in oak.

Unravelling DNA methylation dynamics during developmental stages in Quercus ilex subsp. ballota [Desf.] Samp.

BackgroundDNA methylation is a critical factor influencing plant growth, adaptability, and phenotypic plasticity. While extensively studied in model and crop species, it remains relatively unexplored in holm oak and other non-domesticated forest trees. This study conducts a comprehensive in-silico mining of DNA methyltransferase and demethylase genes within the holm oak genome to enhance our understanding of this essential process in these understudied species. The expression levels of these genes in adult and seedling leaves, as well as embryos, were analysed using quantitative real-time PCR (qRT-PCR). Global DNA methylation patterns were assessed through methylation-sensitive amplified polymorphism (MSAP) techniques. Furthermore, specific methylated genomic sequences were identified via MSAP sequencing (MSAP-Seq).ResultA total of 13 DNA methyltransferase and three demethylase genes were revealed in the holm oak genome. Expression levels of these genes varied significantly between organs and developmental stages. MSAP analyses revealed a predominance of epigenetic over genetic variation among organs and developmental stages, with significantly higher global DNA methylation levels observed in adult leaves. Embryos exhibited frequent demethylation events, while de novo methylation was prevalent in seedling leaves. Approximately 35% of the genomic sequences identified by MSAP-Seq were methylated, predominantly affecting nuclear genes and intergenic regions, as opposed to repetitive sequences and chloroplast genes. Methylation was found to be more pronounced in the exonic regions of nuclear genes compared to their promoter and intronic regions. The methylated genes were predominantly associated with crucial biological processes such as photosynthesis, ATP synthesis-coupled electron transport, and defence response.ConclusionThis study opens a new research direction in analysing variability in holm oak by evaluating the epigenetic events and mechanisms based on DNA methylation. It sheds light on the enzymatic machinery governing DNA (de)methylation, and the changes in the expression levels of methylases and demethylases in different organs along the developmental stages. The expression level was correlated with the DNA methylation pattern observed, showing the prevalence of de novo methylation and demethylation events in seedlings and embryos, respectively. Several methylated genes involved in the regulation of transposable element silencing, lipid biosynthesis, growth and development, and response to biotic and abiotic stresses are highlighted. MSAP-seq integrated with whole genome bisulphite sequencing and advanced sequencing technologies, such as PacBio or Nanopore, will bring light on epigenetic mechanisms regulating the expression of specific genes and its correlation with the phenotypic variability and the differences in the response to environmental cues, especially those related to climate change.

Microbial controls on seed germination

Germination onset is the first stage in the phenological plant cycle, influenced by abiotic and biotic factors. Both soil and seed microbiota are key drivers of germination, influencing seed storage, dormancy release, and germination rates. Interactions between plants and soil microbes contribute to plant adaptation to their environment. Therefore, plants could benefit more from interacting with soil microbes from the local (‘home’) environment than with those from other origins. As crucial germination drivers, plants may select for specific microbial taxa that provide them with a home-field advantage, regardless of microbial richness and diversity in their surroundings. Here, we looked at the role of seed-associated microorganisms on holm oak (Quercus ilex) germination, whether seed or soil microbes have a greater impact on this process, and how the interaction between seed and soil microbiotas influence holm oak germination. We found that microbes on Q. ilex seeds have a significant effect on germination, with non-sterilised seeds having higher germinated acorns than sterilised ones. Moreover, when co-occurring, soil microorganisms enhance the effect of seed-associated microbes on holm oak germination. Overall, our results evidence a home-field advantage where local soil communities, along with seed-associated microorganisms, enhance Q. ilex germination over that of different soil or plant species, evidencing the importance of local adaptation for plant fitness.

Different drought-tolerance strategies of tree species to cope with increased water stress under climate change in a mixed forest.

Trees' functional strategies to cope with extreme drought are essential under climate change. In a mixed Mediterranean forest, we analyzed the functional strategy in response to drought of four co-occurring species (Pinus pinea, Pinus pinaster, Juniperus oxycedrus, and Quercus ilex) during two years. Specifically, we assessed functional traits related to tree water status, leaf water relations, and gas exchange. Different trait-syndrome metrics and the functional strategies under water stress observed suggested a species drought-tolerance differentiation, with the more anysohidric Q. ilex and J. oxycedrus showing a much higher drought tolerance than the more isohydric P. pinea and P. pinaster. All species recovered from negative leaf turgor reached during peak water stress in summer. Q. ilex and J. oxycedrus kept lower leaf osmotic potentials and lower sensitivity of leaf gas exchange and leaf photochemistry to water stress. In contrast, the pine species exhibited more drought-avoidant and water-conservative strategies, yet this behavior was less effective in mitigating water stress's impact on their physiology. The pine species were the most affected by drought, with prolonged near-zero net photosynthesis during summer. P. pinaster was more isohydric than P. pinea and exhibited a lower capacity to maintain leaf turgor. Physiological processes regulating leaf turgor under drought constitute a key functional strategy involved in the carbon and water-related mechanisms, ultimately inducing mortality under hot drought. The currently observed mortality dynamics for P. pinaster, and to a lower extent in P. pinea, may be exacerbated by loss of functional homeostasis.

Effect of Pinus halepensis Mill. Reforestation on the Above-Ground Biomass and Internode Elongation and Leaf Size of Native Species in Morroco

This study aims to determine the effect of the reforestation of Pinus halepensis Mill. on the above-ground biomass and morphological characteristics of native species (internode elongation and leaf size) in the Beni Sohane forest. Plant biomass of the herbaceous layer was harvested on randomly selected 2 m2 quadrats in reforested plots of ± 12, ± 25, and ± 45-year-old, and native forest controls. The internode length and leaf size (length and width) were measured on plants randomly selected belonging to four native species Quercus ilex L., Pistacia lentiscus L., Phillyrea angustifolia L., and Cistus creticus L.. The results showed that P. halepensis reforestation had no significant effect on the above-ground biomass and the leaves and internodes dimensions in the young plantations ± 12-year-old. However, as the pine trees mature, the average dry matter weight decreases, especially in stands 45 years old, where this weight was significantly lower than that of natural forests. This fact has led to herders abandoning important pastures previously used by their cattle. In addition, the fast growth of P. halepensis trees formed a canopy above all indigenous species resulting in changes in the dimensions of internodes and leaves. For the two oldest plantations, the internode length, leaf width, and length of the 4 species have been significantly increased. However, the leaf length-to-width ratio decreased significantly, with leaves in reforested plots being larger rather than longer compared to control samples in native forests. Planting P. halepensis can negatively impact the long-term growth of native plants, so we recommend periodically removing some of the pines (thinning) to restore the balance of these ecosystems. Thus, species selection for reforestation should consider maximizing rather than destroying ecological and socioeconomic services.

Effect of Pinus halepensis Mill. Reforestation on the Above-Ground Biomass and Internode Elongation and Leaf Size of Native Species in Morroco

This study aims to determine the effect of the reforestation of Pinus halepensis Mill. on the above-ground biomass and morphological characteristics of native species (internode elongation and leaf size) in the Beni Sohane forest. Plant biomass of the herbaceous layer was harvested on randomly selected 2 m2 quadrats in reforested plots of ± 12, ± 25, and ± 45-year-old, and native forest controls. The internode length and leaf size (length and width) were measured on plants randomly selected belonging to four native species Quercus ilex L., Pistacia lentiscus L., Phillyrea angustifolia L., and Cistus creticus L.. The results showed that P. halepensis reforestation had no significant effect on the above-ground biomass and the leaves and internodes dimensions in the young plantations ± 12-year-old. However, as the pine trees mature, the average dry matter weight decreases, especially in stands 45 years old, where this weight was significantly lower than that of natural forests. This fact has led to herders abandoning important pastures previously used by their cattle. In addition, the fast growth of P. halepensis trees formed a canopy above all indigenous species resulting in changes in the dimensions of internodes and leaves. For the two oldest plantations, the internode length, leaf width, and length of the 4 species have been significantly increased. However, the leaf length-to-width ratio decreased significantly, with leaves in reforested plots being larger rather than longer compared to control samples in native forests. Planting P. halepensis can negatively impact the long-term growth of native plants, so we recommend periodically removing some of the pines (thinning) to restore the balance of these ecosystems. Thus, species selection for reforestation should consider maximizing rather than destroying ecological and socioeconomic services.

Diversity patterns of herbaceous community in environmental gradients of dehesa ecosystems

Dehesa is a unique ecosystem associated with high biodiversity, that integrates trees, livestock, and pasture, making agro-pastoral production compatible with sustainability. However, in the last few decades, a manifold of factors have caused a decline in tree vitality, density, and coverage, leading to long-term changes in species composition and ecosystem structure. This study aims to determine changes in the diversity of the herbaceous plant community in relation to environmental characteristics, the phytosanitary state of the holm oak (Quercus ilex L. subsp. ballota (Desf.) Samp.), and possible interactions with biotic agents, including Phytophthora cinnamomi. For this purpose, the floristic composition and alpha diversity of the understory were assessed in two dehesa stands in Southern Spain. Additionally, the spatial heterogeneity (beta diversity) patterns of herbaceous plants were evaluated in relation to a climatic gradient and subplot orientation at the regional, plot, tree, and subplot scales. Our findings show that microsite features and climate substantially impact the herbaceous plant community in dehesa stands. Annual precipitation is a crucial factor affecting the diversity and biomass of herbaceous plants on a broader, regional scale, consistent with its role as a limiting factor in the Mediterranean climate. However, site-level differences, such as soil clay content and plot slope angle, positively correlate with plant biodiversity, growth, and richness, varying with the Biodiversity Index considered. Moreover, microsites resulting from the combined effects of plot and tree are the main drivers of dissimilarities between samples, as expressed by beta diversity. Contrary to our initial hypothesis, our results reveal no significant association between tree health and herbaceous biodiversity decline.

Predicting the climatic suitability of non-native drought resistant trees in the face of desertification – A case study with Argania spinosa in the Iberian Peninsula

Climate change is driving a poleward shift in the optimal distributions of terrestrial organisms, including trees. Consequently, trees are expected to decrease in climatically unfavourable areas as their optimal climatic conditions shift poleward. This is the case of Mediterranean High Nature Value agroforestry systems in Iberian Peninsula, dominated by holm oaks (Quercus rotundifolia) and cork oaks (Quercus suber), which are expected to shift their future distribution northward. Failure to keep pace with climate warming poses a heightened risk of extinction for these tree species, as well as the loss of crucial ecosystem services they provide. A similar situation is found for argan trees (Argania spinosa) in the southwestern region of Morocco, where it also supports an agroforestry system. The optimum climate for these trees is also shifting northward, toward the Iberian Peninsula. As the argan tree thrives in more arid conditions with irregular precipitation, the future climatic conditions in the Iberian Peninsula may become favourable for the persistence of this tree. In light of this situation, the assisted colonization of the argan tree could potentially contribute to protecting and preserving the tree-associated ecosystem services in Iberian Peninsula. We conducted climate suitability modelling using maximum entropy approach, for both the current and future timeframes, for North of Morocco and Algeria (native range) and the whole Iberian Peninsula (non-native range). Accordingly, there appears to be a significant area with highly suitable climatic conditions (>80 %) for argan tree occurrence, covering approximately 6.7 % of the territory, over 38,000 km2. This area is projected to increase significantly in the future, covering 9–22 % of the territory, or about 55,000 and 127,000 km2. With this study, we aim to contribute to the discussion on the benefits of assisted colonization of argan trees into Iberian Peninsula, as well as potential drawbacks such as the risk of this species becoming invasive.

High heat tolerance, evaporative cooling, and stomatal decoupling regulate canopy temperature and their safety margins in three European oak species.

Heatwaves and soil droughts are increasing in frequency and intensity, leading many tree species to exceed their thermal thresholds, and driving wide-scale forest mortality. Therefore, investigating heat tolerance and canopy temperature regulation mechanisms is essential to understanding and predicting tree vulnerability to hot droughts. We measured the diurnal and seasonal variation in leaf water potential (Ψ), gas exchange (photosynthesis Anet and stomatal conductance gs), canopy temperature (Tcan), and heat tolerance (leaf critical temperature Tcrit and thermal safety margins TSM, i.e., the difference between maximum Tcan and Tcrit) in three oak species in forests along a latitudinal gradient (Quercus petraea in Switzerland, Quercus ilex in France, and Quercus coccifera in Spain) throughout the growing season. Gas exchange and Ψ of all species were strongly reduced by increased air temperature (Tair) and soil drying, resulting in stomatal closure and inhibition of photosynthesis in Q. ilex and Q. coccifera when Tair surpassed 30°C and soil moisture dropped below 14%. Across all seasons, Tcan was mainly above Tair but increased strongly (up to 10°C > Tair) when Anet was null or negative. Although trees endured extreme Tair (up to 42°C), positive TSM were maintained during the growing season due to high Tcrit in all species (average Tcrit of 54.7°C) and possibly stomatal decoupling (i.e., Anet ≤0 while gs >0). Indeed, Q. ilex and Q. coccifera trees maintained low but positive gs (despite null Anet), decreasing Ψ passed embolism thresholds. This may have prevented Tcan from rising above Tcrit during extreme heat. Overall, our work highlighted that the mechanisms behind heat tolerance and leaf temperature regulation in oak trees include a combination of high evaporative cooling, large heat tolerance limits, and stomatal decoupling. These processes must be considered to accurately predict plant damages, survival, and mortality during extreme heatwaves.

Short range shifts in plant physiological responses to induced water stress: Experimental evidence of intraspecific trait variability differentiating neighbouring Mediterranean plant populations

Mediterranean plants are facing increased periods of drought, potentially jeopardizing their survival. Despite the known influence of intraspecific variability on plants’ responses to the environment, most studies focus on differences between species and overlook short distances. Following the observation of three nearby populations of Quercus ilex and Cistus salviifolius inheriting different sets of drought-related functional traits in common garden, we tested if these populations could perform differently under water stress. We observed drought responses on plantlets from both species, measuring key physiological traits such as gas exchanges and spectrometric indexes. Our results show similar responses from populations of C. salviifolius while Q. ilex had high intraspecific variability, with increased drought-resistance in plants hailing from dry provenances, reflected by improved water use efficiency, photosynthetic capacity, and reduced metabolic response to stress. These observations support the idea that, despite the short distances, neighbouring plant populations can adapt differently to drought, changing the way they withstand climate and its changes.

An extraordinary jewel beetle species (Perotis unicolor (Olivier, 1790)) from Northeastern Algeria: re-discovery of this species in North Africa after more than half a century

Jewel beetles (Buprestidae), also known as metallic wood-boring beetles, predominantly inhabit forest environments. Several taxa within this family hold heritage status in both broadleaf and conifer forests. The larvae of most species undergo development within the inner, living part of tree bark, while some species can behave as opportunistic pests, causing considerable damage to weakened host trees. Notably, in Algeria, Lamprodila festiva on Barbary thuja (Tetraclinis articulata), and Agrilus biguttatus on oak trees were recognized as significant pests. Given the potential impact of climate change on forest jewel beetles, there were two key concerns: i) many of these species prefer warmer climates, making them thermophilic, and shifts in temperature patterns can affect their distribution and abundance, ii) following severe droughts, forest declines and diebacks may occur, offering an opportunity for these beetles to exploit weakened trees. In the context of this study, a Buprestidae (Coleoptera) species was re-discovered in the northeastern region of Algeria within holm oak (Quercus ilex) shrub lands, Perotis unicolor (Olivier, 1790). This is an important finding as it has not been reported in the fauna of North Africa for more than half a century.