Cork Oak Research Articles

Developing translucent emulsions using sustainable NADES-based extracts

In this work, we explored natural deep eutectic solvents (NADES) for developing translucent NADES-in-oil emulsions (TEs) for cosmetic applications. NADES, composed of lactic acid and glycerol (1:1 and 1:4 ratios), were selected for their natural origin, non-toxicity, and compatibility with living organisms. These green solvents facilitated the extraction of bioactive compounds from Lavandula angustifolia, Corymbia citriodora, Thymus vulgaris, Quercus suber, Allium sativum, and Origanum vulgare. The resulting NADES-extracts were characterized using LC-MS for compound identification and incorporated into TEs formulations. The content of phenolics, flavonoids, chelating power, and the antioxidant activity were assessed for both NADES-extracts an TEs. The produced TEs (50 wt% egg L-α-phosphatidylcholine (EPC), 20 wt% ethanol, 20 wt% olive oil, and 10 wt% NADES/NADES-extracts) effectively hindered the activity of enzymes responsible for skin melanin regulation and aging, namely tyrosinase (IC50 ≈ 0.18 mg/mL for eucalyptus) and elastase (IC50 ≈ 0.23 mg/mL for thyme). Gram-negative bacteria, particularly K. pneumoniae, were found to be more susceptible to NADES-extracts and TE-extracts, resulting in larger zones of inhibition. The study reported no toxic effects in the larval model, with a noticeable decrease (2-fold) in melanization in G. mellonella larvae after TE application. Cytotoxicity results indicated that TEs could be tolerated in skin cells at concentrations up to 5 %. Transdermal testing showed TEs permeation into the skin of 1–5 %, suggesting their use for cosmetic purposes without significant cellular damage. This study highlights the potential of NADES combined with natural extracts as sustainable, non-toxic ingredients in cosmetic formulations, paving the way for innovative skin regeneration products.

Genetic and epigenetic control of dormancy transitions throughout the year in the monoecious cork oak.

Bud dormancy plays a vital role in flowering regulation and fruit production, being highly regulated by endogenous and environmental cues. Deployment of epigenetic modifications and differential gene expression control bud dormancy/break cycles. Information on how these genetic and epigenetic mechanisms are regulated throughout the year is still scarce for temperate trees such as Quercus suber. Here, the expression levels of CENTRORADIALIS-LIKE (CENL) and DORMANCY-ASSOCIATED PROTEIN 1 (QsDYL1) during seasonal cycles of bud development, suggesting that QsCENL may be implicated in growth cessation in Q. suber and that QsDYL1 is a good dormancy marker. As gene expression can be regulated by the activity of chromatin modifiers, we have analysed the expression of these genes and the deposition of epigenetic marks in dormant versus non-dormant bud meristems. The DNA methyl transferases CHROMOMEHTYLASE 3 (QsCMT3) and METHYLTRANSFERASE 1 (QsMET1) were more expressed in the transition between dormancy to bud swelling. QsCMT3 was also highly expressed during the late stages of active bud formation. Conversely, the HISTONE ACETYLTRANSFERASE 1 (QsHAC1) was up-regulated during growth cessation and dormancy when compared to bud swelling. These results indicate that epigenetic regulation is implicated in how bud development progresses in Q. suber, which can be observed in the different profile deposition of the repressive and active marks, 5mC and H3K18Ac/H3K4me, respectively. The identification of bud-specific genetic and epigenetic profiling opens new possibilities to predict the relative rate of dormancy/growth of the bud stages, providing tools to understand how trees respond to the current challenges posed by climate change.

Development of Biodegradable and Recyclable FRLM Composites Incorporating Cork Aggregates for Sustainable Construction Practices.

Reducing energy consumption in the building sector has driven the search for more sustainable construction methods. This study explores the potential of cork-modified mortars reinforced with basalt fabric, focusing on optimizing both mechanical and hygroscopic properties. Six mortar mixtures were produced using a breathable structural mortar made from pure natural hydraulic lime, incorporating varying percentages (0-3%) of cork granules (Quercus suber) as lightweight aggregates. Micro-computed tomography was first used to assess the homogeneity of the mixtures, followed by flow tests to evaluate workability. The mixtures were then tested for water absorption, compressive strength, and adhesion to tuff and clay brick surfaces. Adhesion was measured through pull-off tests, to evaluate internal bonding strength. Additionally, this study examined the relationship between surface roughness and bond strength in FRLM composites, revealing that rougher surfaces significantly improved adhesion to clay and tuff bricks. These findings suggest that cork-reinforced mortars offer promising potential for sustainable construction, achieving improved hygroscopic performance, sufficient mechanical strength, internal bonding, and optimized surface adhesion.

Robust Trend Analysis in Environmental Remote Sensing: A Case Study of Cork Oak Forest Decline

We introduce a novel methodological framework for robust trend analysis (RTA) using remote sensing data to enhance the accuracy and reliability of detecting significant environmental trends. Our approach sequentially integrates the Theil–Sen (TS) slope estimator, the Contextual Mann–Kendall (CMK) test, and the false discovery rate (FDR) control. This comprehensive method addresses common challenges in trend analysis, such as handling small, noisy datasets with outliers and issues related to spatial autocorrelation, cross-correlation, and multiple testing. We applied this RTA workflow to study tree cover trends in Los Alcornocales Natural Park (Southern Spain), Europe’s largest cork oak forest, analysing interannual changes in tree cover from 2000 to 2022 using Terra MODIS MOD44B data. Our results reveal that the TS estimator provides a robust measure of trend direction and magnitude, but its effectiveness is dramatically enhanced when combined with the CMK test. This combination highlights significant trends and effectively corrects for spatial autocorrelation and cross-correlation, ensuring that genuine environmental signals are distinguished from statistical noise. Unlike previous workflows, our approach incorporates the FDR control, which successfully filtered out 29.6% of false discoveries in the case study, resulting in a more stringent assessment of true environmental trends captured by multi-temporal remotely sensed data. In the case study, we found that approximately one-third of the area exhibits significant and statistically robust declines in tree cover, with these declines being geographically clustered. Importantly, these trends correspond with relevant changes in tree cover, emphasising the ability of RTA to detect relevant environmental changes. Overall, our findings underscore the crucial importance of combining these methods, as their synergy is essential for accurately identifying and confirming robust environmental trends. The proposed RTA framework has significant implications for environmental monitoring, modelling, and management.

Climate change and exotic pathogens shift carbon allocation in Mediterranean mixed forests

Abstract Forecasting the effects of global change drivers on ecosystems is one of the most pressing challenges for scientists worldwide. Particularly, climate change and exotic pathogens might have a large impact on plant community dynamics and ecosystem functioning through changes in carbon uptake and sinks. Nevertheless, we still have a poor understanding of the combined effects of these two drivers on plant communities. Here, we explored the impact of rainfall reduction and exotic pathogens on the carbon balance of Mediterranean tree species. For this, we performed a 3‐year field experiment taking advantage of rainfall exclusion infrastructures (30% exclusion) installed in the southernmost European oak forests invaded by the aggressive exotic pathogen Phytophthora cinnamomi. We measured a set of 10 variables representative of tree carbon sources (photosynthetic rates) and sinks (primary production, reproduction, defence, and reserves) in adult trees of three species in two forest types: closed forests of Quercus suber and Q. canariensis, and open woodlands of Q. suber and Olea europaea. We found a large variability in the sensitivity of the different carbon sources and sinks to the effects of drought and pathogens, from variables highly sensitive to both factors (carbon fixation and reproduction, root chemistry) to variables only responsive to drought (litter production) or totally unresponsive (tree trunk, leaf chemistry). Although negative effects predominated, positive effects of rainfall exclusion were also detected in wet years, likely due to a reduction of pathogen abundance in drier soil. Trade‐offs between carbon sinks appeared in all tree species, but rainfall exclusion only modified trade‐offs in Q. suber, the species most susceptible to P. cinnamomi. Synthesis. We provide evidence on the complexity of the combined effects of abiotic (drought) and biotic (pathogens) global change drivers on carbon source and sinks of adult trees, including both negative direct effects and positive indirect effects. Our results showed that these effects varied among co‐existing species, particularly for carbon sinks directly related to tree demography (reproduction). Therefore, long‐term changes in the structure of Mediterranean mixed forests might be expected towards the dominance of species highly resistant to both drought and pathogens.

Effects of plantations on rainfall redistribution in a rocky mountain area of North China

AbstractRainfall redistribution plays a crucial role in the water cycle. However, the main factors affecting the redistribution of rainfall remain uncertain. We chose three different plantations—cork oak (Quercus variabilis Bl.), oriental arborvitae (Platycladus orientalis L.) and black locust (Robinia pseudoacacia L.)—to investigate the role of plantations in rainfall redistribution and to determine the main factors influencing rainfall redistribution. The results indicated that cork oak exhibited the highest stemflow (0.34%) and the lowest canopy interception (12.58%), whereas black locust had the lowest stemflow (0.21%), and oriental arborvitae displayed the greatest canopy interception (32.8%). Under different density conditions for cork oaks, the stemflow was highest (0.39%) in low‐density forests with 750 trees ha−2 and lowest (0.34%) in medium‐density forests with 1100 trees ha−2. Meanwhile, the highest canopy interception (17.68%) was observed in high‐density forests (1300 trees ha−2), while the lowest interception rate (9.22%) was found in low‐density forests. The main factors affecting rainfall redistribution and their contribution rates were as follows: bark roughness index (35%), wind speed (18.6%), tree species (14.2%), diameter at breast height (11.2%), stand density (9.6%) and rainfall amount (5.4%). Our findings suggested that structural characteristics of trees are the primary factors affecting rainfall redistribution. Planting cork oak in the rocky mountain regions of North China is recommended because of its substantial stemflow production, particularly under low‐density growth conditions. Therefore, this study has significant guiding implications for the selection of afforestation tree species in similar rocky mountain areas globally.

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.

Lack of Small-Scale Changes in Breeding Birds after a Fire: Does the Resilience of Cork Oaks Favor Rapid Recolonization in Suburban Wood Patches?

Forest fires are disturbance events that can impact biological assemblages at multiple scales. In this study, the structures of breeding bird communities in cork oak patches located in an agro-mosaic suburban landscape of central Italy (Rome) were compared at the local scale with a fine-grained mapping method before (2018) and after (2023) a fire event occurred in July 2022. The analyses did not reveal any significant changes in the density of territorial pairs or in the diversity metrics, both univariate (Shannon–Wiener index, evenness, Margalef normalized richness) and bivariate (Whittaker and k-dominance plots, abundance/biomass curves) of diversity. Even when the guilds of strictly forest-related species were compared, no differences emerged before and after the fire. This counterintuitive phenomenon may be due to the characteristics of the dominant tree, the cork oak (Quercus suber), a sclerophilous tree that is very resilient to fires and able to recover foliage in the following spring season, thus allowing rapid bird recolonization. However, other small-scale phenomena (e.g., the ‘crowding effect’ and local dispersal of territorial pairs from remnant wood patches not affected by fire) may explain this lack of change in breeding bird density and diversity. Further studies should be carried out at larger spatial and temporal scales and at different levels of fire frequency and intensity to confirm these responses at the guild/community level in suburban cork oak wood patches.

Study of cork from Quercus suber L. with and without yellow spot: aromatic fraction and cellular structure

Study of cork from Quercus suber L. with and without yellow spot: aromatic fraction and cellular structure

Aluminum Phosphate Nanoplates Synthesized via Green Method Using Cork Oak Somatic Embryo-Derived Phytates

Aluminum Phosphate Nanoplates Synthesized via Green Method Using Cork Oak Somatic Embryo-Derived Phytates

Comparative analysis of Quercus suber L. acorns in natural and semi-natural stands: Morphology characterization, insect attacks, and chemical composition

Comparative analysis of Quercus suber L. acorns in natural and semi-natural stands: Morphology characterization, insect attacks, and chemical composition

Effects of Biophysical Factors on Light Use Efficiency at Multiple Time Scales in a Chinese Cork Oak Plantation Ecosystem

Light use efficiency (LUE) characterizes the efficiency of vegetation in converting photosynthetically active radiation (PAR) into biomass energy through photosynthesis and is a critical parameter for gross primary productivity (GPP) in terrestrial ecosystems. Based on the eddy covariance measurements of a Chinese cork oak plantation ecosystem in northern China, the temporal variations in LUE were investigated, and biophysical factors were examined at time scales ranging from hours to years. Our results show that diurnal LUE first increased sharply before 8:30 and then decreased gradually until 12:00, thereafter increasing gradually and reaching the maximum value at sunset during the growing season. The daily and monthly LUE first increased and then decreased within a year and showed a substantial drop around June. The annual LUE ranged from 0.09 to 0.17 g C mol photon−1, and the multiyear mean maximal LUE was 0.30 g C mol photon−1 during 2006–2019. Only GPP (positive) and clearness index (CI) (negative) had consistent effects on LUE at different time scales, and the effects of the remaining biophysical factors on LUE were different as the time scale changed. The effects of air temperature, vapor pressure deficit, precipitation, evaporative fraction, and normalized difference vegetation index on LUE were mainly indirect (via PAR and/or GPP). When CI decreased, an increased ratio of diffuse PAR to PAR produced a more uniform irradiance in the canopy, which ultimately resulted in a higher LUE. Due to climate change in our study area, the annual LUE may decrease in the future but improving management practices may slow or even reverse this trend in the annual LUE in the studied Chinese cork oak plantation.

A highly efficient and environmentally friendly approach to utilizing Quercus suber pericarp subfractions to remove metallic cations from aqueous solutions

Increasing water contamination from metal cations is a significant environmental challenge for humans. This has sparked extensive research into the development of adsorbents with superior removal efficiencies. This study assessed the adsorption capacity of crude and lignocellulosic fractions obtained from the pericarp of Quercus suber acorns, specifically focusing on the removal of Pb(II), Cd(II), Ni(II), and Cu(II) ions from aqueous solutions. The lignocellulosic fraction was separated from the crude fraction after extraction of cell wall polysaccharides using water and alkaline solutions. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were used to characterize the crude and lignocellulosic fractions. Data from equilibrium adsorption experiments were analyzed using the Langmuir and Freundlich isotherm models. The study found that the lignocellulosic fraction removed Pb(II) ions more efficiently than the crude fraction, with qmax values of 500.0 mg.g−1. Crude fractions exhibited a considerable retention potential for Cd(II), Ni(II), and Cu(II) ions with qmax values of 95.2 mg.g−1, 333.3 mg.g−1 and 200 mg.g−1 respectively. Crude and lignocellulosic fractions extracted from the acorn Q. suber pericarps could be environmentally friendly biosorbents for the removal of metal cations from aqueous solutions.

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.

Enhanced Production of Therapeutic Metabolites in Cork-Oak Somatic Embryos under Abiotic Stress Conditions

This study investigates the enhanced production of key therapeutic metabolites (ellagic acid, serotonin, and chlorogenic acid) in response to abiotic stress in in vitro cultures of Quercus suber somatic embryos. Findings indicate significant increases in metabolite levels under various stress conditions, highlighting the potential for commercial-scale production of these compounds, known for their antioxidant, anticancer, and anti-COVID-19 properties. Under osmotic/saline stress, ellagic acid production significantly increased, representing an 80% increase compared to control conditions. In embryos exposed to different stressors, serotonin accumulation showed a six-fold increase under osmotic/saline stress. Although the elicitors used did not increase chlorogenic acid levels, exploring alternative stress types may enhance its production. This research paves the way for sustainable, large-scale production of health-beneficial metabolites, addressing global health challenges and promoting resource sustainability.

Revealing local adaptation of Quercus suber L. populations under climate change through Genome Scans and Environmental Association Analysis

Revealing local adaptation of Quercus suber L. populations under climate change through Genome Scans and Environmental Association Analysis

Seasonality in embolism resistance and hydraulic capacitance jointly mediate hydraulic safety in branches and leaves of oriental cork oak (Quercus variabilis Bl.).

Seasonality in temperate regions is prominent during the era of increased climatic variability. A hydraulic trait that can adjust to seasonally changing climatic conditions is crucial for tree safety. However, little attention has been paid to the intraspecific seasonality of drought-related traits and hydraulic safety of keystone forest trees. We examined seasonal variations in the key morphological and physiological traits as well as multiple hydraulic safety margins (SMs) at the branch and leaf levels in oriental cork oak (Quercus variabilis Bl.), which is predominant in Chinese temperate forests. Pneumatic measurements indicated that, as seasons progressed, the water potential at which 50% of branch embolisms occur (P50_branch) decreased from -3.34 to -4.23MPa, with a coefficient of variation (CV) of 9.08%. Sapwood capacitance ranged from 48.19 to 248.08kgm-3MPa-1, peaking in autumn and reaching minimum in winter (CV 60.58%). Rehydration kinetics confirmed higher leaf embolism vulnerability (P50_leaf) in spring and autumn than those in summer, with values ranging from -1.06 to -3.02MPa (CV 39.85%). All leaf pressure-volume (PV) traits shifted with growth, with CVs ranging from 6.95% to 46.69%. Sapwood density had significant negative correlations with P50_branch and hydraulic capacitance for elastic water storage, whereas leaf mass per area was linearly associated with PV traits but not with P50_leaf. Furthermore, the branch typical SMs (difference between branch midday water potential and P50_branch) were consistently >1.84MPa, and vulnerability segmentation was prevalent throughout, implying a plausible hydraulic foundation for the dominance of Q. variabilis. Diverse hydraulic response patterns existed across seasons, leading to positive SMs mediated by the aforementioned physiological traits. Although Q. variabilis exhibits a high level of hydraulic safety, its susceptibility to sudden summer droughts may increase due to global climate change.

Monitoring ink disease epidemics in chestnut and cork oak forests in central Italy with remote sensing

Forests provide multiple ecosystem services including water and soil protection, biodiversity conservation, carbon sequestration, and recreation, which are crucial in sustaining human health and wellbeing. Global changes represent a serious threat to Mediterranean forests, and among known impacts, there is the spread of invasive pests and pathogens, often boosted by climate change and human pressure. Remote sensing can provide support to forest health monitoring, which is crucial to contrast degradation and adopt mitigation strategies. Here, different multispectral and SAR data are used to detect the incidence of ink disease driven by Phytophthora cinnamomi in forest sites in central Italy, dominated by chestnut and cork oak respectively. Sentinel 1, Sentinel 2, and PlanetScope data, together with ground information, served as input in Random Forests to model healthy and disease classes in the two sites. The results indicate that healthy and symptomatic trees are clearly distinguished, whereas the discrimination among disease classes of different severity (moderate and severe damage) is less accurate. Crown dimension and sampled spectral regions are a critical factors in the selection of the sensor; better results are obtained for the larger chestnut crowns with Sentinel 2 data. In both sites, the red and near infra-red bands from multispectral data resulted well suited to monitor the spread of the ink disease.

Modeling and spatialization of biomass and carbon stock using unmanned Aerial Vehicle Lidar (Lidar-UAV) metrics and forest inventory in cork oak forest of Maamora

Recently, the concerns about climate change have heightened the need for effective methods for estimating and mapping Biomass and Carbon stock at local, national, continental, and global scales. Reliable Biomass and Carbon stock quantification and spatialization is a challenge, especially in degraded Mediterranean Cork oak forest. To estimate and map Biomass (Btree−Total) and Carbon stock (Cst−total), we explored an improved approach using extracted metrics collected by Lidar-UAV (unmanned aerial vehicles Lidar), combined with forest inventory data. We approach three types of models for data analysis: Simple linear regression, multiple linear regressions, and stepwise multiple linear regression. The best Biomass and Carbon stock model fit is the Stepwise multiple linear regressions, involving the following metrics: maximum elevation, canopy cover and point cloud density and intensity. Our finding provides a quantification and spatialization Biomass and Carbon stock model based on Lidar-UAV metrics in Cork Oak Mediterranen forest and the results confirm the degraded state of Maamora Forest with a Biomass and Carbon stock relatively medium to low.

Uncovering miRNA-Mediated Regulation in Phellem Versus Xylem Differentiation in Quercus suber L.

Uncovering miRNA-Mediated Regulation in Phellem Versus Xylem Differentiation in Quercus suber L.