Search Results (49)

The cork oak (Quercus suber L.), an emblematic species of Mediterranean biodiversity, is the focus of this study, which aimed to characterize the relationships between abiotic factors and variations in its secondary metabolites. Rhizospheric soil samples (collected at two depths: 0–15 cm and 15–25 cm), roots, and leaves were gathered in Azouza forest (Kabylia, Algeria) during the winter and summer seasons of 2019. Analyses were conducted on total polyphenol (TPP), flavonoid (FLAV), and tannin (TT) contents, and their antioxidant activities were assessed using DPPH, FRAP, and TAC assays. The results reveal seasonal and soil-depth variability, with the highest concentrations observed in leaves (170.2 mg GAE/g DW for TPP, 14.15 mg TAE/g DW for TT, and 6.4 mg QE/g DW for FLAV). Antioxidant activity was also more pronounced in leaves, with IC50 values of 130.90 µg/mL (DPPH) and 61.22 µg/mL (FRAP). Roots from the deeper layer (15–25 cm) exhibited higher phenolic compound levels and greater antioxidant activity compared to those from the superficial layer (0–15 cm). Principal component analysis showed that 93% of the variance was explained by seasonal factors and sampling depth, confirming their key role in secondary metabolite synthesis and biological activity. The cork oak’s biochemical adaptability to environmental changes reveals climate adaptation strategies, highlighting soil–plant influences on its metabolic responses in Mediterranean ecosystems. Full article

This study presents a green and solvent-free methodology based on thermal desorption coupled to gas chromatography-mass spectrometry (TD-GC-MS) to characterise cork’s volatile aromatic (VOC) profile. Samples from three geographical origins—Catalonia, Extremadura, and Sardinia—were analysed at different extraction temperatures. Cork stoppers from Sardinia were also analysed after two washing procedures (immersion and spray) and thermal treatment. The results showed that temperature and geographical origin significantly influenced the quantity and intensity of extracted VOCs, with higher extraction temperatures yielding a more comprehensive volatile profile. Vanillin was the most abundant compound in all samples. A multivariate analysis showed that cork from Extremadura was associated with carboxylic acids, Catalonia with furan derivatives and sugar-related compounds, and Sardinia with phenolic compounds linked to lignin degradation. Immersion-washed stoppers retained more lignin-derived and phenolic compounds, while spray-washed samples were characterised by a higher alkane content. Thermal treatment notably altered the VOC profile, increasing ketones such as acetophenone and 2-nonadecanone and reducing alkanes and fatty acids. These findings highlight the influence of the geographical origin and manufacturing process on the aromatic composition of cork, with potential applications in industries seeking natural active compounds. Full article

The resilience and regeneration of cork oak (Quercus suber L.) play a central role in sustaining the European oak landscape, particularly within the socio-economic and ecological frameworks of the Western Mediterranean. This species has a noticeable ability to withstand drought and temperature extremes. However, its natural regeneration is increasingly challenged by climate change and associated extreme weather events, as well as by competition among individuals for light, water, and nutrients. Monitoring this process in the field can be time-consuming, requiring the use of sampling techniques and the identification of appropriate inventory sampling design (ISD) schemes. Line transect (LT) and radial cluster (RC) inventory designs are widely used in ecological studies, botanical research, and plant species distribution assessments, as well as other environmental forestry studies. This research compares two inventory sampling designs (line transect vs. radial cluster) for inventorying and monitoring the dynamics of natural regeneration at the initial development stages of cork oak. In particular, this study evaluates the influences of inventory sampling design, time, and acorn density on the total living and dead seedlings over a two-year period, using the cork oak as a reference species in the Mediterranean climate of Northern Portugal. The results confirm the critical role of acorn availability in seedling regeneration dynamics within cork oak ecosystems and emphasize a temporal increase in the death of seedlings, markedly influenced by the day of year. The temporal component had a substantial impact on seedling mortality, which increased by 5.00‰ per day, meaning that one seedling died approximately every 200 days, whereas mortality spikes occur on specific days, suggesting temporal factors affecting seedling viability. The study also shows differences in regeneration estimates between the inventory designs. The line transect design records lower acorn density and seedlings than the radial cluster design. The results highlight an important but often overlooked source of variation in forest regeneration studies, emphasizing the need for careful consideration of inventory methods to ensure effective data collection and accurate representation of natural regeneration dynamics, ultimately supporting efforts to enhance cork oak regeneration and resilience against climate change and competitive pressures. Full article

In Mediterranean ecosystems, a thorough understanding of seedling regeneration dynamics as well as a good predictive ability of the process is essential for sustainable forest management. Leveraging the predictive capacity of the multilayer perceptron (MLP) as recognized as artificial intelligence methodology, the authors analyzed a real case study with a dataset encompassing environmental, ecological, and forestry variables. The study focused on the cork oak (Quercus suber, L.) seedling regeneration dynamic, which is a critical process for maintaining ecosystem resilience. A set of 10 MLP with a block from 5 to 50 neurons with hyperbolic tangent (TanH), linear (LIN), and Gaussian (GAUS) activation function were tested and their performance for predictive purposes was compared with traditional quantitative approaches. The MLP configured with 40–50 neurons per activation function (TanH, LIN, GAUS) demonstrated outstanding predictive performance, achieving an area under the curve (AUC) of the receiver operating characteristic and precision-recall scores above 0.80. These models made few prediction errors, effectively explaining the majority of the data variance, as indicated by a high generalized R² and a low mislearning ratio. This approach outperformed traditional statistical models in predicting seedling regeneration. Tree density, stand density index, and acorn number played an important role, influencing the cork oak seedling prediction. In conclusion, the results of this research determined the importance of an AI classification modeling technique in the prediction of cork oak regeneration, providing practical references for future forest management strategy decisions. Full article

Quercus suber L. (Q. suber) is an evergreen tree species known for producing high-quality cork. Traditional seed propagation of Q. suber has low viability and is time-consuming. Therefore, we used young stem segments of 2~3-year-old seedlings as explants, and optimized protocols for tissue culture and rapid micropropagation of Q. suber. The best disinfection method was 0.10% HgCl₂ (v/v) for 5 min. 0.50 g·L⁻¹ Poly Vinyl Pyrrolidone (PVP) is the best anti-browning agent with a significant reduction in browning by nearly 1.76-fold (58.89% → 33.33%). Woody Plant Medium supplemented with micronutrients and vitamins from Murashige and Skoog Medium (WPMS) was found to be the most suitable for shoot formation. The optimal hormone ratio for development of shoots from axillary buds was 0.60 mg·L⁻¹ 6-benzyladenine (6-BA). Among the cytokinins tested, 0.50 mg·L⁻¹ 6-BA was the most suitable for development of shoots from axillary buds. In additon, the highest percentage of rooting explants (66.67%) and rooting number (3.03) was obtained on WPM basal medium supplemented 0.20 mg·L⁻¹ IBA and 0.20 mg·L⁻¹ NAA. In summary, we have established a set of protocols for tissue culture and rapid micropropagation of Q. suber. These findings lay the foundation for rapid micropropagation and genetic improvement. Full article

The cork oak (Quercus suber L.) woodlands, known as montados in Portugal, hold significant economic, cultural, social, and environmental value. They are found in the Mediterranean Sea basin, particularly in the Iberian Peninsula, and sustain various activities like silvopastoralism, with cork being a primary product. Despite its economic significance, challenges such as climate change threaten its sustainability. This study aimed to analyze the edaphoclimatic variables affecting cork yield, thickness, price, and gross income in the Alentejo region of Portugal. A total of 35 farmers were selected for the data collection included in this study. Multivariable linear regressions were performed to establish relationships between cork yield, thickness, price, and gross income as dependent variables, various edaphoclimatic factors, and tree densities. A higher tree density correlates with an increased cork yield but a decreased cork thickness. Soil pH affects cork yield and thickness, with a lower pH favoring higher cork yields but thinner cork. A higher clay and silt content in horizon soil C enhances cork thickness and raises the price but reduces the cork yield. Higher accumulated precipitation and temperatures contribute to higher yields and thicknesses of cork. It is concluded that the relationships between the dependent and the independent variables are complex but partially explainable. Understanding these relationships is paramount to ensure sustainable management practices are adopted that are capable of addressing issues raised in the current context of climate change. Full article

Agglomerated cork is a natural cork that has gone through a process of crushing and pressing using heat and binders. One of its applications is thermal insulator in construction. The design of these materials is becoming an essential part of building. The raw materials currently used to make insulators consume a large amount of energy, which has created the need to increase the use of renewable and ecological resources such as plant fibers to reduce the environmental problems generated. The objective of this study was to determine the different properties of experimental particleboard panels made from cork and Canary Island date palms without using any binder at minimum energy consumption. The produced cork–palm boards (density of 850 kg/m³, reached a MOR 8.83 N/mm², MOE 794.5 N/mm², and IB 0.38 N/mm²) are higher values than the traditional cork particleboards with UF made from cork. The thermal conductivity values obtained 0.069 to 0.096 W/m·K are higher than cork boards with UF. Ecological boards that can be used as rigid thermal insulators in the construction industry have been achieved to improve the mechanical properties of the traditional agglomerated cork. Full article

Acorn flour is a rich source of nutrients and is beneficial to human health due to, among other things, its low glycemic index and polyphenol content. In order to obtain more accurate data on the levels and activities of the substances tested after ingestion and digestion, it may be beneficial to use a simulated in vitro digestion method. Therefore, the objective of the present study was to elucidate the content of polyphenols, individual phenolic acids, flavonoids and antiradical properties of acorn flour and pasta enriched with acorn flour before and after simulated in vitro gastrointestinal digestion. The results indicate that the total polyphenol content (TPC), flavonoid content and radical scavenging activity exhibited an increasing trend following the initial digestion stage and a decreasing trend following the second stage. Nevertheless, the levels of phenolic acids demonstrated an increase in both digestion phases. The digestion processes of polyphenols in acorn flour differ significantly from those in pasta. In the case of pasta, total polyphenols, phenolic acids and flavonoids, as well as free radical scavenging properties, demonstrated a decreasing trend following each digestion stage. Full article

Near-surface soil hydraulic properties (SHPs) are fundamental for describing and predicting water and energy exchange processes, particularly at the soil–atmosphere interface, and regulating evapotranspiration, infiltration, and runoff in different ecosystems. In this study, a new method was proposed to estimate near-surface SHPs by combining sensor-based soil infiltrability measurements with inverse modeling using HYDRUS-2D. The infiltration rate (IR) was estimated by combining the linear source inflow method with image processing, and K_s was estimated from the near-surface steady-state IR (NSIRM). The SWRC parameters described by the van Genuchten model were estimated using the inverse modeling method of HYDRUS-2D for the fitting of sensor-measured infiltration data. Subsequently, the parameters of the van Genuchten model, including $\alpha$, $n$, and $l$, were inversely estimated. Three undisturbed soils, including two stand humus samples from cork oak (Quercus suber L.) and oleander (Pinus tabuliformis L.) stands and one sandy loam from a farmland, were sampled near the soil surface to validate the proposed method. The estimated K_s was evaluated by the constant head method (CHM). The estimated parameters of the SWRC were validated by those determined through the simultaneous measurement of the soil moisture content and water potential using sensor techniques. The results showed that the K_s estimated from the NSIRM for each soil sample were 23.40 ± 1.21, 23.86 ± 1.83, and 22.99 ± 2.26 mm h⁻¹, respectively. In comparison, the K_s determined by the CHM were 24.41 ± 1.53, 24.26 ± 0.37, and 23.81 ± 0.10 mm/h, respectively. The relative errors of the proposed method were 4.14%, 1.64%, and 3.42%, respectively. For the SWRC estimation, the normalized root mean square errors (NRMSEs) between the measurements and the estimates for each soil sample were 0.1724, 0.1454, and 0.0606, respectively. Based on this, the AWC was obtained, and K_u was deduced from the estimated K_s and SWRC parameters for each soil sample. In general, the proposed method successfully estimates near-surface SHPs, simplifies the measurement device, and provides a new perspective for the in situ determination of near-surface SHPs under field conditions in the near future. Full article

The cork tree, Quercus suber L., is a characteristic species of the Dehesa agrosilvopastoral system, typical of western Spain. Defoliating insects are an important component of these ecosystems. This study assessed the presence and impact of defoliators feeding on Q. suber soft leaf tissue and their relationship with foliar monoterpene emission profiles. Samplings consisted of weekly tree beating (15 times per tree per sample) during the flight period of key species. We studied 26 cork trees with known profiles of foliar monoterpene emission (13 pinene and 13 limonene chemotypes). We identified a total of 272 larvae from 9 species. The main species were Catocala nymphagoga Esper (40.8%) and Periclista andrei Know (27.6%). Notably, 70.6% of larvae were found on trees with a pinene chemotype. The combined abundance of the four key defoliator species (C. nymphagoga L., P. andrei, Bena bicolorana L., and Cyclophora punctaria L.) was 62.7% lower on limonene-chemotype trees than pinene-chemotype trees. Significant differences were found in defoliation damage between leaves with distinct terpene emission profiles. These results suggest that both the abundance and damage caused by defoliators differ with trees’ emission profiles, and this may indicate differences in palatability and/or nutritional quality between Q. suber trees with distinct foliar monoterpene emission profiles. Full article

Cork is a natural and renewable material extracted from the cork oak Quercus suber L. (1) Background: The cellular structure and chemical composition of the plant wall give cork its physical and mechanical properties. Chemically, the composition of cork is principally dominated by the presence of suberin as the main structural cell wall component and affected by its close association with other components. The usual chemical analysis of cork has been partially adapted from wood and other lignocellulosic analytical methods and it is a method with extensive procedures. This study aims to (i) find quicker and more sustainable methods for testing the cork chemical composition, (ii) conduct extraction tests using alternative techniques, (iii) optimize alternative methodologies, and (iv) validate the proposed sustainable methodologies. (2) Methods: Microwave-assisted extraction (MAE) and accelerated solvent extraction (ASE) are explored as alternative systems to the traditional method. The percentages of the extractives obtained via MAE are lower than the percentages obtained by means of the classical composition. (3) Results: However, the percentages of suberin are very similar in both methods: 46.39% in the case of the classical composition and 45.11% in the case of microwave-assisted extraction. No significant differences are observed between the content of the extractives in the dichloromethane, ethanol, and water obtained via ASE and the results obtained with the classical methodology. (4) Conclusions: MAE and ASE are faster methods; they use less solvents and provide more reproducible results than the classical chemical composition methodology. These data pave the way for novel sustainable alternatives relative to the studies of the chemical composition of cork. Full article

Quercus suber L. is an evergreen cork oak tree that can produce cork, one of the most important valuable natural bioresources in Portugal, with a high impact for the bioeconomy. Given its socio-economic relevance and the upcoming biotic and abiotic threats cork oak faces, it is of extreme importance that genetic conservation of its genetic variability occurs so that cork oaks can adapt to new conditions. This work represents a review of the current knowledge on Quercus suber genetic resources, focusing on the existing genetic variability and the strategies for its conservation. Furthermore, we highlight genetic knowledge on tolerance and response to abiotic and biotic stresses and cork quality, which are useful for further studies on stress response pathways and mechanisms and improvement regarding stress tolerance. Full article

The cork oak tree (Quercus suber L.) symbolizes the Montado landscape in Portugal and is a central element in the country’s social and economic history. In recent decades, the loss of thousands of cork oaks has been reported, revealing the ongoing decline of these agroforestry ecosystems. This emblematic tree of the Mediterranean Basin is host to the soil-born root pathogen Phytophthora cinnamomi, an active cork oak decline driver. In this framework, the early diagnosis of trees infected by the oomycete by non-invasive methods should contribute to the sustainable management of cork oak ecosystems, which motivated this work. Gas exchange and visible/near-infrared (400–1100 nm) reflectance spectroscopy measurements were conducted on leaves of both control and P. cinnamomi inoculated plants. These measurements were taken at 63, 78, 91, 126, and 248 days after inoculation. Additionally, at the end of the experiment, biochemical assays of pigments, sugars, and starch were performed. The spectroscopic measurements proved effective in distinguishing between control and inoculated plants, while the standard gas exchange and biochemistry data did not exhibit clear differences between the groups. The spectral data were examined both daily and globally, utilizing the PARAFAC method applied to a three-way array of samples × wavelengths × days. The separation of the two plant groups was attributed to variations in water content (4v (O−H)); shifts in the spectra red edge; and structural modifications in the epidermal layer and leaves’ mesophyll. These spectral signatures can assist in the field identification of cork oaks that are interacting with P. cinnamomi. Full article

Competition indices may improve tree growth modelling in high-density stands, found often in new cork oak plantations. Distance-dependent competition indices have hardly been considered for juvenile cork oak plantations since existing models were developed for low-density mature stands. This study aims at inspecting the potential of including distance-dependent competition indices into diameter at breast height (d) and total height (h) growth models for Quercus suber L., comparing several distance-dependent and distance-independent competition indices. Annual d and h growth were modelled with linear and non-linear growth functions, formulated as difference equations. Base models were initially fitted considering parameter estimates depending only on site index (S) and/or stand density (N). They were refitted, testing the significance of adding each competition index to the model parameters. Selected models included the best-performing distance-dependent or -independent competition indices as additional predictors. Best base d and h growth models showed a modelling efficiency (ef) of ef = 0.9833 and ef = 0.9900, respectively. Adding a distance-dependent competition index slightly improved growth models, to an ef = 0.9851 for d and ef = 0.9902 for h. Best distance-dependent competition indices slightly overperformed distance-independent ones in diameter growth models. Neither S nor N were included on best fitted models. If inter-tree competition is present in juvenile undebarked cork oak plantations, it does not yet strongly impact individual tree growth, which may diminish the importance of using, at this stage, more complex spatially explicit competition indices on predicting individual tree growth. Full article

In this study, an analysis of the influence of extractives, suberin and lignocellulosic components on the pyrolysis decomposition and fire reaction mechanisms of a cork oak powder from Quercus suber L. is presented. The summative chemical composition of cork powder was determined. Suberin was the main component at 40% of the total weight, followed by 24% of lignin, 19% of polysaccharides and 14% of extractives. The absorbance peaks of cork and its individual components were further analyzed by means of ATR-FTIR spectrometry. Thermogravimetric analysis (TGA) showed that the removal of extractives from cork slightly increased the thermal stability between 200 °C and 300 °C and led to the formation of a more thermally stable residue at the end of the cork decomposition. Moreover, by removing suberin, a shift of the onset decomposition temperature to a lower temperature was noticed, indicating that suberin plays a major role in enhancing the thermal stability of cork. Furthermore, non-polar extractives showed the highest flammability with a peak of heat release rate (pHRR) of 365 W/g analyzed by means of micro-scale combustion calorimetry (MCC). Above 300 °C, the heat release rate (HRR) of suberin was lower than that of polysaccharides or lignin. However, below that temperature it released more flammable gases with a pHRR of 180 W/g, without significant charring ability, contrary to the mentioned components that showed lower HRR due to their prominent condensed mode of action that slowed down the mass and heat transfer processes during the combustion process. Full article