Search Results (22)

Integrating ground-based and aerial remote sensing for individual tree-level stem volume modeling remains underexplored in Mediterranean mixed forests, despite the growing need for cost-effective, automated forest inventory approaches. This study evaluated the combined use of Handheld Laser Scanning (HLS) and Unmanned Aerial Vehicle (UAV)-based Structure from Motion (SfM) photogrammetry for individual-tree stem volume modeling in a mixed stand in Castilla y León, Spain, dominated by Pinus halepensis, Pinus pinea, Quercus faginea, and Cupressus sempervirens. Two open-source HLS processing tools; the Forest Structural Complexity Tool (FSCT) and 3D Forest Inventory (3DFin), were compared for individual tree attribute extraction, with FSCT outperforming 3DFin across all species. Reference stem volumes were derived by applying species-specific Spanish National Forest Inventory (SNFI) allometric equations to FSCT-extracted diameter and height values. Random Forest models were then built using UAV-SfM crown metrics as predictors, testing two image overlap configurations: 80 × 80 F (80% front and side overlap) and 80 × 60 CF (80% front, 60% side, cross-flight). The 80 × 80 F configuration produced the best-performing model (R² = 0.730), with 80 × 60 CF achieving comparable accuracy (R² = 0.688), results confirmed by spatially independent leave-one-plot-out cross-validation (LOPO-CV R² = 0.627 and 0.613, respectively). These results show that combining HLS and UAV-SfM through a predominantly open-source workflow offers a viable, reproducible approach to stem volume modeling in structurally complex Mediterranean mixed forests. Full article

Mediterranean agroforestry systems (AFSs), typified by the Iberian Dehesas and Portuguese Montados, are multifunctional landscapes where Quercus species act as ecological keystones sustaining biodiversity, soil fertility, and rural livelihoods. These systems are increasingly affected by complex oak decline syndromes driven by drought, soil degradation, and climate-induced pathogen outbreaks. Conventional chemical controls are often ineffective and environmentally detrimental, underscoring the need for ecologically sound management alternatives. This review synthesizes recent advances in the application of microbial biological control agents (MBCAs) to manage diseases in Mediterranean Quercus species, including Q. ilex, Q. suber, Q. faginea, and Q. pyrenaica. We conducted a structured literature review using predefined keyword searches in Web of Science and Scopus, followed by the screening of records to identify 22 relevant peer-reviewed studies on microbial disease control in Mediterranean Quercus species. We identified 20 peer-reviewed studies that reported that MBCAs—primarily from Bacillus, Serratia, Streptomyces, Trichoderma, Simplicillium and Alternaria—exert biocontrol effects through antibiosis, mycoparasitism, competition for ecological niches, and the induction of host defense responses. Although most experiments were conducted in vitro, some demonstrated significant disease suppression in seedlings infected by Phytophthora cinnamomi, Diplodia corticola, and Biscogniauxia mediterranea. Future research should integrate field-based validation and microbiome-oriented forest management approaches to enable the operational use of microbial-based disease control strategies in AFS landscapes. Full article

Quercus faginea Lam., a winter-deciduous oak native to the Iberian Peninsula, typically grows under a Mediterranean climate. To identify the main drivers influencing radial wood increment, we analyzed the climatic signals in tree-ring width and wood anatomical traits using increment cores. Winter conditions influenced both latewood width and earlywood vessel size in the first row. Latewood was positively correlated with precipitation and temperature, with the long-term positive effect of winter water supply supported by SPEI. In contrast, vessel size showed negative correlations, also reflecting a long-term negative effect of winter precipitation. Consequently, conditions that enhanced latewood width and overall tree-ring growth appear to be associated with the formation of smaller earlywood vessels. Although ample winter precipitation replenishes soil water reserves and supports prolonged wood formation, it may also induce anaerobic soil conditions that promote root fermentation, depleting carbohydrates needed for cell turgor and expansion, and ultimately regulating earlywood vessel size. This physiological decoupling may help explain the lack of a significant correlation between latewood width and earlywood vessel size, underscoring their independent responses to environmental influences. Our findings highlighted the complex interplay between various climatic conditions affecting Q. faginea, with implications for understanding its adaptive capacity in changing climates. Full article

The southeast of Spain is one of the most arid and desertification-prone areas in continental Europe, with climate change contributing to this situation. Climatic conditions affect the availability of water in the plant structures of wild species, facilitating the onset and/or spread of forest fires and increasing aridity. The Region of Murcia, in southeastern Spain, has small forest stands of gall oak (Quercus faginea Lam.) with relict value. It is of interest to investigate the situation of these stands, allowing us to know about their distribution and their evolution in the face of climate change. For this purpose, previous dendrometric studies, available from a specific stand, are considered to be contrasted with current data, individual trees were geolocated, and distribution maps of contrasting environmental conditions were created. In general, gall oak has been observed to be distributed up to 1200 m altitude, especially in shady areas and embedded valleys and north-northeast orientations. Importantly, there was a positive evolution of vegetative development, with increments in the number of trees during the study period, despite some negative affections in specific areas due to climate change. Full article

Oaks are characterized by high plasticity and intense interspecific gene flow due to natural hybridization. This generates a wide phenotypic spectrum, which creates taxonomic confusion within the genus. We compared the acorn traits across a temperature gradient in two types of Mediterranean Quercus (Quercus faginea Lam. and Q. pyrenaica Willd.) and their hybrids. Genetic groups were identified using amplified fragment length polymorphism (AFLPs) analysis. Acorns sampled from each of the three genetic groups were used for comparative purposes by means of 15 morphological characteristics. Eight of the traits showed discriminant value among the three groups. The acorn height tended to decrease with decreasing temperatures across the gradient, whereas the acorn width exhibited the opposite response. However, fruit traits allowed discrimination between the three groups, and the differences were consistent in the different zones. Both the number of acorns produced and the individual acorn size were larger for Q. pyrenaica. Hybrids showed intermediate traits between both parent species. Traditionally, the persistence of parental species in the absence of reproductive barriers has been explained by the lower fitness of the hybrids. Our results, however, do not reveal the presence of transgressive characteristics in the hybrids that could justify a lower competitive capacity. Full article

Acorns, the seeds of oak trees, are pivotal in the Mediterranean region, historically serving as vital sustenance for wildlife and humans. Although traditionally used for livestock, in times of scarcity, acorns were also used in human diets together with their use in traditional medicine. In this review, we explore and deepen the multifaceted significance of oak species, consolidating nutritional data while emphasizing sustainable practices for modern dietary integration and potential applications in other areas, promoting long-term ecological balance. In the Mediterranean region, notable species are Quercus ilex, Q. faginea, Q. suber, and Q. coccifera, which differ in flavor, texture, and nutritional content. Rich in carbohydrates, acorns can contain up to 50% starch as well as amino acids, proteins, and lipids. This nutritional composition favors the preparation of flour for use in bread doughs or even diverse types of processing such as roasting, which makes it a substitute for coffee. Furthermore, acorn by-products, containing tannins, find applications in leather processing. This review highlights and summarizes in detail the nutritional potential, culinary adaptability, and diverse applications of acorns, emphasizing the need to preserve and utilize natural resources sustainably. In doing so, it sheds light on the often-overlooked value of these humble seeds. Full article

The valid deciduous Quercus L. species from North Africa have been largely discussed by many authors. The current species remain yet uncertain. In this study, we compare several populations of presumably Q. canariensis Willd. and Q. faginea Lam. from Algeria with pure populations of these species from the northeast of the Iberian Peninsula. Different morphological characters from leaves have been analyzed. Principal components analysis and a canonical analysis of principal coordinates have been used to observe the relationship between samples, groups and the seven quantitative variables. Distances among centroids have been reported and a SIMPER procedure has also been executed to better explain the different variability within and between groups. PERMANOVA has been applied to test for significant differences between the groups. For the trichomes study, ANOVA models have been used. From our analysis, we conclude that in Algeria, we have a single Q. canariensis Willd. population, different from the Iberian population we examined. It probably corresponds morphologically to Q. mirbeckii Durieu, currently considered a synonymy of Q. canariensis Willd., and for the “Q. faginea” group we have two Algerian populations: Q. faginea Lam. subsp. faginea, found in the northeast Iberian Peninsula, and Q. tlemcenensis (A.DC.) Maire and Weiller ex Greuter and Burdet. Previous results from other authors have also been discussed. Full article

The distribution and abundance of the various truffle species are influenced by the climate, soil, and vegetation conditions. The setting of these characteristics is necessary for the potential species’ cultivation. Here, we describe the ecological characteristics of Moroccan truffles and desert truffles and their associations with host plants. We also determine the climate and soil parameters relating to the geographic distribution and fructification of truffles and desert truffles. In contrast to truffles, which are found in sub-humid environments, desert truffles are found in semi-arid and arid regions of Morocco. The dissemination of desert truffles in the Mamora forest and oriental regions of Morocco is typically linked to the presence of Helianthemum sp., whereas the existence of truffles (Tuber spp.) in the Middle Atlas depends on the subsistence of Quercus ilex and Q. faginea. The truffles’ and desert truffles’ fructification depends mainly on the precipitation frequency. Terfezia arenaria and Tuber oligospermum, the two major desert truffles of Mamora forest, require an annual rainfall of 435 mm on average in slightly acidic soil. While the oriental and Highland desert truffles, namely Terfezia boudieri, T. claveryi, and Tirmania spp., require an annual precipitation average of 123 to 267 mm and a high CaCO₃ content. Otherwise, there is Tuber aestivum, localized in humid regions with a rainfall rate of more than 650 mm, and found under calcareous soil rich in organic matter with the presence of potential host plants, such as oaks, cedars, and pines. Our findings open up the possibility of successful cultivation of truffles and desert truffles having an economic interest through understanding their ecological requirements in Morocco. Full article

Among the main objectives of Natura 2000 Network sites management plans is monitoring their conservation status under a reasonable cost and with high temporal frequency. The aim of this study is to assess the ability of single-photon light detection and ranging (LiDAR) technology (14 points per m²) and Sentinel-2 data to classify the conservation status of oak forests in four special areas of conservation in Navarra Province (Spain) that comprise three habitats. To capture the variability of conservation status within the three habitats, we first performed a random stratified sampling based on conservation status measured in the field, canopy cover, and terrain slope and height. Thereafter, we compared two metric selection approaches, namely Kruskal–Wallis and Dunn tests, and two machine learning classification methods, random forest (RF) and support vector machine (SVM), to classify the conservation statuses using LiDAR and Sentinel-2 data. The best-fit classification model, which included only LiDAR metrics, was obtained using the random forest method, with an overall classification accuracy after validation of 83.01%, 75.51%, and 88.25% for Quercus robur (9160), Quercus pyrenaica (9230), and Quercus faginea (9240) habitats, respectively. The models include three to six LiDAR metrics, with the structural diversity indices (LiDAR height evenness index, LHEI, and LiDAR height diversity index, LHDI) and canopy cover (FCC) being the most relevant ones. The inclusion of the NDVI index from the Sentinel-2 image did not improve the classification accuracy significantly. This approach demonstrates its value for classifying and subsequently mapping conservation statuses in oak groves and other Natura 2000 Network habitat sites at a regional scale, which could serve for more effective monitoring and management of high biodiversity habitats. Full article

Within-stem variation in the mechanical properties of Portuguese oak wood was analysed, considering different locations (three sites in the centre and north of Portugal—Site 1, Site 2, Site 3) and positions within the tree (two distances to pith—P1, P2). The study comprised compression parallel to the grain, bending strength and modulus of elasticity. Ultimately, this study aims at assuring the building of a body of knowledge on the technological quality and processing options for this species. The results showed for one provenance, Site 1, a significant effect of the distance to pith in the mechanical properties, which can be related to a different soil composition. For this provenance, a decrease in the compression and bending strength was verified from pith to bark. For the other provenances (Site 2 and Site 3), no effect was noticed. The overall behaviour showed noticeable correlations between the mechanical properties and density. Full article

Tree growth takes place at different time scales ranging from hours to days. To understand growth responses to climate, continuous high-resolution measurements of tree diameter variations are needed, which are usually obtained with automatic dendrometers. Here, we monitored stem diameter increment of Quercus faginea Lambert growing in central Portugal to determine the effect of climate on daily and seasonal growth dynamics during the 2013 growing season. Stem diameter variation presented a unimodal seasonal pattern characterized by an exponential phase in spring followed by a plateau during summer, interrupted by an abrupt increase in autumn caused by rainfall. Stem diameter increment started in March when the temperature was above 10 °C. Stem diameter variation showed a double climatic constrain, with temperature limiting growth in spring and precipitation in summer. The amplitude of the daily cycles of stem variation was higher in summer, as well as the expansion phase length, meaning that trees needed longer to replenish the water lost through transpiration during the day. The absence of a pronounced stem shrinkage during the summer suggests that Q. faginea has access to water over the whole growing season. Our results indicate that this species relies on deep soil water reserves and can be physiologically active during summer drought. Full article

The achievement of goals in forest landscape restoration strongly relies on successful plantation establishment, which is challenging in drylands, especially under climate change. Improvement of field performance through stock quality has been used for decades. Here, we use machine learning (ML) techniques to identify key stock traits involved in successful survival and to refine previous specifications that were developed under more conventional stock quality assessments carried out at the lifting–shipping phases in the nursery. Two differentiated stocklots in each species were used, both fitting in the regional quality standard. ML was used to infer a set of attributes for planted seedlings that were subsequently related to survival at the short-term (two years) and mid-term (ten years) in six different species planted in a harsh site with shallow soil that suffered the driest year on record during this study. Whilst stocklot quality, as measured in the lifting–shipping stage, had very poor importance to the survival response, individual plant traits presented a moderate to high diagnostic ability for seedling survival (area under the receiver operating characteristic (ROC) curve between 0.59 and 0.99). Early growth traits catch most of the importance in these models (≈40%), followed by individual morphology traits (≈28%) and site variation (≈2%), with overall means varying across species. Aleppo pine and Phoenician juniper stocklots presented survival rates of 66–78% after ten years, and these rates were below 27% for the remaining species that suffered during the historical drought. In Aleppo pine, the plant attributes related to early field performance (growth in the first growing season) were more important in the drought-mediated mid-term performance than stock quality at the nursery stage. Within the technical framework of this study, our results allow for both testing and refining the regional quality standard specifications for harsh conditions such as those found in our study. Full article

In Mediterranean environments, light and water are clearly dominant ecological drivers of seedling growth and survival, and their interaction could modify productivity and forest composition. We examine the early response of seedlings of four co-occurring Mediterranean tree species (Pinus pinea, Juniperus thurifera, Quercus ilex and Quercus faginea) grown in the nursery to differing light and water availability conditions. Morphological (survival, height, biomass) and physiological (shoot midday water potential, net photosynthesis, transpiration rate, stomatal conductance, Fv/Fm, PSII and ETR) traits were studied, along with biomass allocation traits and drought resistance and plasticity indices. A significant effect of both factors was mainly shown for growth and morphological traits, while survival, physiological traits and allometry were affected by either water availability or light, being more remarkable the effect of water availability over light. Drought severely limited Q. faginea’s survival under both light intensities. The high plasticity of J. thurifera and Q. ilex seedlings to different light and water availability environments will confer these two species with an adaptive advantage in the early growth stages in comparison with P. pinea and Q. faginea seedlings. Thus, to maintain the codominance of the four species, silvicultural interventions should focus on the joint management of all of them. Full article

Seed predation is an antagonistic interaction that negatively affects the performance of individual plants and can limit plant population dynamics. In animal-dispersed plants, crop size is an important determinant of plant reproductive success through its effect on seed dispersers and predators. Seed traits, such as size or chemical composition, can also increase the tolerance to seed predators or reduce their performance. We investigated the interaction between Quercus faginea and two specialized pre-dispersal insect seed predators (weevils and moths) during two years of contrasting crop size to determine the consequences of oak reproductive investment on seed production and insect performance. Crop size was 44% lower and acorns were 32% smaller in the second year, although acorn predation by insects was proportionally similar between both years at the population level. Individual trees producing larger crops showed a lower incidence of insect predators during the year of abundant acorn production, whereas trees producing bigger acorns experienced higher seed predation rates by insects, and acorns held more insect larvae in the low crop year. Competition between insects increased when acorn production was low, and higher tannin content in acorns further constrained the number of weevil larvae developing together in the same acorn. However, the abundance and size of insect larvae produced per tree were similar between the two crop years, and this was due to larvae often depleting acorn reserves when resources were low. Oak reproductive output increased nearly two-fold during the large crop year. Crop size variation, acorn production in a given year and acorn size and chemical composition seem to be important traits for reducing damage by insect predators in Quercus faginea and improve oak reproductive success. Full article

Tree biomass and the diversity relationship in mixed forest have an impact on forest ecosystem services provisions. Tree biomass yield is driven by several aspects such as species identity, site condition, stand density, tree age and tree diversity expressed as species mingling and structural diversity. By comparing diverse degrees of tree mixtures in natural forests, we can gain insight into the ecosystem services provision level and dynamic. Two monitoring sites in the Castilian Northern Plateau (Spain) have been analyzed to disentangle the relationships between biodiversity levels and tree biomass yield. Two permanent one hectare (ha) squared plots were established at Llano de San Marugán and Valdepoza. In each plot, all individual trees were measured (diameter and height), georeferenced and its species identity defined. Tree species in the two sites were Pinus sylvestris, Pinus nigra, Pinus pinea, Quercus pyrenaica, Quercus ilex, Quercus faginea and Juniperus thurifera. From these datasets, ten diversity indices that fall in three categories (species richness indices, species compositional/mingling indices and vertical structural indices) were used as predictor variables to fit several candidate models. By merging the trees by site (without considering the species identity) selected models include individual tree basal area as an explanatory variable combining by addition or interaction with diversity indices. When species are analyzed independently, structural diversity impacts on biomass yield in combination (additive or multiplicative) with tree size is negative for Pinus nigra and positive for the other species. Full article