Understanding plant species interactions, including facilitation and competition, is fundamental to improve the success of woody seedling establishment. This is particularly important for the ...restoration of sclerophyllous oak forests, one of the main forest types in Mediterranean Europe currently facing a severe lack of oak natural regeneration. However, the effects of shrub communities dominated by different species and diverse shrub communities on the establishment of Mediterranean oaks remains poorly understood. We conducted a 3-year experimental study in cork oak (Quercus suber L.) woodlands in Portugal to assess the effects of species dominance and diversity of the shrub community and associated abiotic resources on cork oak seedling emergence and survival. We hypothesized that the emergence and survival vary with the identity of the dominant shrub, due to distinct shrub functional traits affecting understory abiotic conditions. Additionally, we predict that the survival of seedlings increases with shrub diversity, driven by net facilitation processes. We sowed 960 cork oak acorns across five replicated microhabitats: four with distinct shrub species dominance and diversity and one without shrub cover. We used Bayesian statistics to model cork oak seedling emergence and survival as a function of microhabitat type and abiotic variables (soil water and temperature, soil characteristics and leaf area index). Seedling emergence and survival varied with species dominance and diversity of the shrub microhabitat. The highest survival was observed in microhabitats characterized by higher shrub diversity, and the lowest survival in microhabitats dominated by Cistus ladanifer. Maximum soil temperature was associated with higher emergence but lower survival in open conditions or areas with sparser shrub cover. Water logging constrained emergence and survival, but higher soil potassium was associated with higher survival, for all microhabitats. Our study shows that interactions between cork oak seedlings and their shrub neighbors are species and community dependent, and that a more diverse shrub composition improves cork oak seedling survival, likely due to distinct shrub traits that ameliorate the physical environment and promote facilitation. Management and restoration of Mediterranean sclerophyllous oak forests need to consider the specificity and diversity of the understory plant community, as well as the different stages of oak early life-cycle, to identify the most favorable conditions for oak establishment. This becomes particularly important under more frequent climatic extremes predicted for Mediterranean Europe.
•Cork oak seedling emergence and survival varied with shrub dominance and diversity.•Cork oak seedling survival increased with higher shrub diversity.•Water logging in winter negatively affected seedling emergence and survival.•Distinct shrub traits seem to favor or inhibit cork oak seedling establishment.•Seedlings died at high rates, particularly during the first year.
•We manipulated predator distributions through fencing in a longleaf pine savanna.•After 10years we compared vegetation in areas with and without predators.•Woody browse was released and preferred ...forage was reduced in predator exclosures.•We found support for the Behaviorally-mediated trophic cascade hypothesis.•Scared deer help suppress hardwood encroachment in frequently burn pine savannas.
Ecologists increasingly recognize the importance of trait-mediated indirect interactions and suggest behavioral traits aimed to reduce predation risk can induce trophic cascades. However, the application of theory developed in simple experimental systems to complex natural systems has spurred debate regarding whether predation risk, independent of direct killing, can structure ecosystems. We examined the effects of white-tailed deer (Odocoileus virginianus) foraging under the risk of predation by coyotes on oak (Quercus spp.) regeneration and the abundance of palatable understory species in a frequently burned longleaf pine savanna. Oaks represent a common but relatively low quality forage item for deer, and are an important component of this system because oak encroachment into pine-dominated uplands can reduce biodiversity. In frequently burned ecosystems oaks and other fire-impeding species often exist in a demographic fire-trap, where they sprout following fire but rarely escape into the midstory, because they are repeatedly top-killed by subsequent fires. Many factor including herbivory stress can influence the probability of fire survival for oak saplings. Other Cervids, including elk (Cervus canadensis) and moose (Alces alces) are known to increase use of woody browse with predation risk because of selection for brushy areas that offer concealment cover. We experimentally manipulated predation risk for 10years, by establishing 4 approximately 40-ha predator exclosures and 4 control plots to test the effects of predation risk on aspects of the plant community. Reduced predation risk resulted in increased oak recruitment and decreased abundance of palatable forage. A density-mediated trophic cascade does not explain the release of oaks and our results provide support the behaviorally-mediated trophic cascade hypothesis. We offer evidence that frequent disturbance can facilitate trophic cascades and that predator-sensitive foraging can enhance fire suppression of oaks and influence groundcover composition in longleaf pine savannas.
A középkori Kesztölc településsel azonosítható helyszínen2007-ben feltárásra került többek között a Q174-es objektumszámú tölgyfa bélésű kút. A megfigyelések szerint, a településen belüli helyzete ...alapján, a nagy szakmai gondossággal épített kutat a teljes közösség használhatta. Az egykori hadi- és a Jeruzsálembe vezető zarándokúttól csak pár méterre ásott kútról feltételezhető, hogy nem csak a helyieket, de az átutazókat is szolgálta.
Holm oak is a key tree species in Mediterranean ecosystems, whose populations have been increasingly threatened by oak decline syndrome, a disease caused by the combined action of
and abiotic ...stresses. The aim of the present study was to produce holm oak plants that overexpress the Ginkbilobin-2 homologous domain gene (
) that it is known to possess antifungal properties. Proembryogenic masses (PEMs) isolated from four embryogenic lines (Q8, E2, Q10-16 and E00) were used as target explants. PEMs were co-cultured for 5 days with
EHA105pGnk2 and then cultured on selective medium containing kanamycin (kan) and carbenicillin. After 14 weeks on selective medium, the transformation events were observed in somatic embryos of lines Q8 and E2 and a total of 4 transgenic lines were achieved. The presence of the
gene on transgenic embryos was verified by PCR, and the number of transgene copies and gene expression was estimated by qPCR. Transgenic plants were obtained from all transgenic lines after cold storage of the somatic embryos for 2 months and subsequent transfer to germination medium. In an in vitro tolerance assay with the pathogen
, we observed that transgenic plants were able to survive longer than wild type.
ObjectiveDuring the last decade, about 20-30% of the Zagros forests have faced a problem called oak decline. The aim of present study was to investigate the bacterial diversity in the healthy and ...declined forest areas by comparing two methods culture-dependent and culture-independent methods.Materials and methodsSampling was done from different tissue and soil of oak trees in the forests of Ilam province. In the culture-based method, using microbiological and molecular methods the bacteria in the samples were isolated and identified to the genus and species level. In order to study metagenomics in culture-independent method, total microbial DNA was extracted directly from the samples and prepared metagenomic library using conventional and index primer, the diversity of bacterial was examined using Illumina's Miseq platform and then the results of the two methods were compared.ResultsBased on the culture-based method, only 3 phylum were identified, while in the metagenomics method, 9416 OTUs were obtained, that were divided into 12 phylum. In both methods, 3 families of Bacillaceae, Enterobacteriacea and Xanthomonadaceae were observed as the dominant families. The species diversity within a sample (Alpha diversity) was higher in the rhizosphere sample and in the Eyvan and Gale jar areas than other samples. The species diversity between samples (Beta diversity) was in Eyvan, Gale jar, Chavar, Tangedalab and Arghavan appear more similar to each other than the sites samples. Bacterial community of stems and leaves were more similar and also bulk and rhizosphere were more similar in bacterial species composition.ConclusionsIn the metagenomics method, very few species are identified, while in the culture method, the probability of this is low. Also, in the culture-independent method, alpha and beta diversity can be studied more comprehensively. In the culture-based method, the bacterial population can be identified up to the species level, while in the culture-independent method, it is usually identified up to the genus level. Therefore, it is suggested to use a combination of two methods simultaneously in studies of microbial communities.
•Acorn dispersal is a hierarchical and selective process at different spatial scales.•Decisions at coarse scale drive decisions at finer ones.•Habitat of the tree and distance to the forest edge ...drives dispersal habitat.•Dispersal distance depends on the origin and caching habitats of the acorns.•Woody species drive the specific sites of acorn dispersal in and out of the forest.
Seed dispersal is key to forest regeneration and often depends on the behavior of seed scatter-hoarding animals. However, our understanding of the decision-making of scatter-hoarders and how vegetation structure at different spatial scales affects dispersal patterns remains limited. We studied seed dispersal at the forest edge across multiple spatial scales (habitat, sub-habitat, microsites) between and within habitats with distinct vegetation structure. Our model system is a mixed-oak forest dominated by holm oak (Quercus ilex) and an adjacent shrubland dominated by the shrub Retama sphaerocarpa. For three years, we tracked the movement of acorns by a keystone scatter-hoarder, the Eurasian jay (Garrulus glandarius). At the coarse scale, jays did not show a preference for caching acorns either in the forest or in the shrubland when the source tree was within the forest. However, when the source tree was on the forest edge or was an isolated oak tree in the shrubland at < 200 m from the forest, jays showed a preference for caching in the forest. Conversely, when isolated oak trees were > 200 m from the forest, all acorns were dispersed in the shrubland. Dispersal distances were shorter within the forest than within the shrubland. At an intermediate scale, within the shrubland jays preferred to cache acorns under large retamas while avoiding gaps. In the forest, jays also avoided gaps and preferred certain woody species and vertical vegetation structures, although these preferences varied across feeders. At the finest scale, jays selected stones as cache microsites. Thus, the selection of acorn caching sites followed a hierarchical and selective top-down process across different spatial scales. The position of the source trees in the landscape determined habitat preference and dispersal distance. We detected different preferences in response to similar vegetation structure and composition, indicating that the decision-making process is flexible at an intermediate scale that generates diverse spatial patterns of dispersal. This study sheds light on the intricate decision-making process of seed caching by scatter-hoarders, and the consequences for the spatial patterns of seed dispersal as well as the expansion and regeneration of oak forests.
Veneer checking is a common enough occurrence in woodworking. It appears as cracks in the veneer and generally following the grain. Their appearance and the variation of their depth and frequencies ...have tremendous impact on their utilization. Finding a means of identifying and characterizing the veneer checks is an important ongoing challenge. An automated device, named SMOF, was developed in LABOMAP (Arts et Metiers - France) and achieves this task. By using the SMOF device, the lathe checks occurred in veneers of two species: zeen oak (Quercus canariensis Willd.) and afares oak (Quercus afares Pomel) were detected, automatically imaged and then, the depth and intervals of checks measured. The results were described by statistical distributions that exhibited abnormalities, such as skewness and kurtosis, which were assessed by mode analysis. It has been established that hot soaking temperature (from 60°C to 90°C) reduce slightly the cutting forces for both species, no produce significant heart checks within the loose side of veneers. However, low soaking temperature (from 50°C to 65°C) allow avoiding deeper lathe checking, producing shallower ones acceptable for veneer production.
PDF
