Chestnut Orchards Research Articles

Omitting the Application of Nitrogen or Potassium Reduced the Growth of Young Chestnut (Castanea sativa) Trees, While a Lack of Boron Decreased Fruit Yield

The chestnut tree (Castanea sativa Mill.) is gaining importance in the mountainous regions of southern Europe due to the high value of its fruits. It is essential to establish effective cultivation protocols, considering that this species is still relatively understudied. In this study, we present the outcomes of the initial establishment of a chestnut orchard conducted through a nutrient omission trial for four years. The treatments included a fertilization plan with nitrogen, phosphorus, potassium, and boron (NPKB), the control, and four other treatments corresponding to the omission of each nutrient (-NPKB, N-PKB, NP-KB, NPK-B). The -NPKB and NP-KB treatments showed significantly lower trunk circumferences and canopy volumes compared to the other treatments. The NPK-B treatment resulted in the lowest fruit production, with a total accumulated yield (2020–2022) of 0.56 kg tree–1, a value significantly lower than that of NPKB (1.12 kg tree–1) and N-PKB (1.19 kg tree–1). The assessment of nutrient concentrations in the leaves revealed plants with deficient levels of B and K in treatments that did not receive these nutrients. Conversely, N levels in the leaves in the -NPKB treatment fell within the sufficiency range (20 to 28 g kg–1). This suggests that the sufficiency range should be adjusted to higher values, given the treatment’s effect on tree growth. It was also observed that the -NPKB treatment led to lower soil organic matter compared to the other treatments, likely due to reduced herbaceous vegetation development under the canopy, leading to decreased organic substrate deposition in the soil. The main findings of this study are that N and K were crucial elements for the optimal growth of chestnut trees, while B played a significant role in fruit production.

Metagenomic characterization of soil bacterial communities in young chestnut orchards in northern Portugal

Metagenomic characterization of soil bacterial communities in young chestnut orchards in northern Portugal

Pheromone-Based Mating Disruption of Conogethes punctiferalis (Lepidoptera: Crambidae) in Chestnut Orchards.

Chestnuts (Castanea crenata Siebold and Zucc.) are one of the major agroforestry products in Korea, and Conogethes punctiferalis is a major pest of the chestnut fruit. Pheromone-based mating disruption (MD) has emerged as a promising eco-friendly approach to reduce population levels and ultimately mitigate fruit damage. Field trials were conducted over two years (2022-2023) in two commercial chestnut orchards in Central Korea that were infested with C. punctiferalis. Compared with the control treatment, the MD treatment effectively reduced the number of male C. punctiferalis captured in the MD treatment plots. Male catch inhibition (MCI) rates ranged from 70.5% to 82.7% in 2022 and from 87.8% to 95.1% in 2023. The MD efficacy (%) was calculated based on the total number of chestnut fruits collected and the number of fruits damaged by C. punctiferalis. In 2022, the MD efficacy of the single-dosage treatment (TS, 50 g/ha) was 63.9% in Orchard A and 73.6% in Orchard B. In 2023, the MD efficacies of the double-dosage treatment (TD, 100 g/ha) and the two-application treatment (TT, 50 g/ha in June and August) were 60.2% and 77.9% in Orchard A and 50.9% and 64.8% in Orchard B, respectively. This study confirms the efficacy of pheromone-based MD in reducing the C. punctiferalis numbers in chestnut orchards and damage to chestnut fruits.

Quantifying Asian chestnut gall wasp (Dryokosmus kuriphilus Yasumatsu) impact on fruit yield and on tree growth using terrestrial LiDAR

The Asian chestnut gall wasp is an invasive pest that causes ecological and economic losses in the management of the sweet chestnut (Castanea sativa Mill.). The pest therefore needs to be monitored in order to assess its impact on tree growth and fruit yield. As part of this work, we propose an infestation level classification based on the number of galls per branch. For two sweet chestnut orchards infested by the wasp, terrestrial light detection and ranging (LiDAR) data were used to calculate tree growth and fruit yield was quantified in terms of nuts and burrs. The tree growth and fruit yield variables were statistically analysed to determine the impact of different infestation levels on these variables, and differences between pairs of infestation levels were tested for significance. Negative correlations were found for the fruit yield variables with infestation indicators, while positive correlations were found for the tree growth variables. Significant differences were observed in fruit yield and tree growth variables associated with different infestation levels.

First report of Bretziella fagacearum infecting chestnut in Michigan.

In the summer of 2021, a 20-year-old 'Colossal' (Castanea sativa × C. crenata hybrid) tree in a commercial chestnut orchard in northwest Michigan suddenly declined. Until 2023, an additional 26 adjacent trees declined, suggesting the occurrence of root-graft transmission of the pathogen. The initial wilting of leaves progressed to complete tree death in about 10 days. Symptoms included wilting, and bronzing, followed by tanning starting at leaf apex and margins, with significant defoliation. Sometimes black-to-brown streaks of discoloration appear in the sapwood, with no signs of mycelial mat production on dead trees. Branches from symptomatic trees in two different areas of the orchard were submitted to Plant and Pest Diagnostics at Michigan State University. Bretziella fagacearum (Bretz) Z.W. de Beer, Marinc., T.A. Duong & M.J. Wingf. was detected in both samples using nested PCR (Wu et al. 2011) and qPCR (Bourgault et al. 2022). The products of the nested PCR were sequenced (GenBank accession nos. OR522695-OR522696) and BLASTn search results showed 100% identity to an ex-type strain of B. fagacearum (MH865866). Surface-sterilized discolored sapwood chips were plated on acidified potato dextrose agar (aPDA). Bretziella fagacearum was consistently recovered; colony and endoconidia morphology aligned with the description of the pathogen (De Beer et al. 2017). A pure culture (BF277) was obtained for inoculation experiments. To confirm pathogenicity, 10 'Colossal' chestnut seedlings (average stem diameter of 9 mm) were inoculated in the greenhouse with a 14-day old culture of BF277. Using a conical drill bit, two 0.4 mm diameter holes were drilled, one was 5 cm above the soil line at a 45° angle and the other was on the opposite side of the stem at least 10 cm above the soil line. A 50-µl conidial suspension (1 × 107 conidia per ml) was applied and the holes were sealed with Parafilm. Five 'Colossal' seedlings were inoculated with sterile water. Leaf epinasty with bent petioles was observed 14 days later. Leaf wilting and necrosis similar to natural infection in the orchard were observed at 24 and 34 days after inoculation, respectively. Water-inoculated control plants showed no symptoms. Bretziella fagacearum was reisolated from symptomatic plants by surface sterilizing leaf petioles with 75% ethanol (30 s), followed by 10% (v/v) bleach (1 min), and two rinses with sterile deionized water (>1 min). Petiole pieces (~1 cm) were plated on aPDA. The pathogen was reisolated from six symptomatic plants and detected using qPCR in the remaining four seedlings. Bretziella fagacearum was not detected in control plants. The identity of the recovered fungus was confirmed following the amplification of the internal transcribed spacer (ITS) from extracted genomic DNA, as described in Chahal et al. 2022. The resulting PCR product was sequenced and assembled into a consensus sequence using Geneious Prime. The consensus sequence (accession no. OR515809) revealed 100% identity to the ex-type of B. fagacearum (KU042044). This is the first record of B. fagacearum infecting chestnut trees in Michigan. Previously, B. fagacearum has been reported infecting Chinese chestnut (C. mollissima) in Missouri (Bretz and Long, 1950). Oak wilt is widely distributed in Michigan and is the predominant disease afflicting red oaks in the Midwestern U.S. Consequently, constant vigilance and monitoring are essential in chestnut orchards to promptly detect and effectively manage potential infections.

A Handheld Laser-Scanning-Based Methodology for Monitoring Tree Growth in Chestnut Orchards.

Chestnut and chestnut byproducts are of worldwide interest, so there is a constant need to develop faster and more accurate monitoring techniques. Recent advances in simultaneous localization and mapping (SLAM) algorithms and user accessibility have led to increased use of handheld mobile laser scanning (HHLS) in precision agriculture. We propose a tree growth monitoring methodology, based on HHLS point cloud processing, that calculates the length of branches through spatial discretization of the point cloud for each tree. The methodology was tested by comparing two point clouds collected almost simultaneously for each of a set of sweet chestnut trees. The results obtained indicated that our HHLS method was reliable and accurate in efficiently monitoring sweet chestnut tree growth. The same methodology was used to calculate the growth of the same set of trees over 37 weeks (from spring to winter). Differences in week 0 and week 37 scans showed an approximate mean growth of 0.22 m, with a standard deviation of around 0.16 m reflecting heterogeneous tree growth.

Effects of the Abandonment of Traditional Cultural Practices on Epiphytic Bryolichenic Communities in Chestnut Orchards in North-West Spain

This study delves into the impact of contrasting management practices on epiphytic bryolichenic communities, shedding light on their divergent responses to management regimes on Castanea sativa Mill. orchards. Lichens and bryophytes were sampled in managed and abandoned plots, in 95 trees, in north and south sides and at two heights in Galicia (NW Spain). The studied groups exhibited opposing reactions to these management practices; bryophytes suffered adverse effects in managed stands, experiencing reduced cover and species richness compared to abandoned orchards, while lichens displayed heightened cover and species diversity. The size of trees, included as a covariate in our analyses, displayed no significant impact on the overall species richness of lichens or bryophytes, although it did influence the cover of specific functional traits. These differing outcomes may be linked to alterations in environmental conditions brought by management interventions. Furthermore, the study uncovered divergent responses within the taxonomic and functional composition of epiphytic communities. Different species and functional groups exhibited varying reactions to changing environmental conditions, making predictions a complex endeavour. In conclusion, this research emphasizes the need for management strategies that account for the diverse ecological requirements of different species and functional groups since no single management regime will suit all species or functional groups.

Guardians of quality: advancing Castanea sativa traceability using DNA analysis from seed to processed food

Castanea sativa is one of the most appreciated species in Italy, due to timber and fruit quality; nuts are usually intended for fresh consumption, but also for the production of industrial foods. The demand for an efficient traceability system to identify Castanea species and cultivars along the supply chain, from the chestnut orchard to the processed product, is crucial to protect consumers and producers from frauds. Here we present a traceability protocol to identify the species of the Castanea genus and trace the cultivars of Castanea sativa, based on DNA markers (SSRs and SNPs) analyses. Microsatellites were applied to identify the cultivar in plant material (leaves, seed, and episperm) and processed food (creams, beverages, flour, and cookies). Although SSRs made it possible to trace cultivar starting from somatic tissues (e.g.: leaves), the presence of foreign paternal DNA from pollenizer plants in seed and processed food, interferes with the identification of the maternal one. To overcome this issue, we Illumina sequenced six C. sativa cultivars to highlight maternal-inherited markers. A set of SNP/INDEL markers in two chloroplastic regions were identified, able to effectively distinguish and trace C. sativa from C. mollissima and C. crenata. The High Resolution Melting (HRM) analysis was performed as a practical and efficient method for SNP/INDELvalidation and to develop a fast, reliable, and reproducible protocol for chestnut traceability in food.

Post-Transcriptional Gene Silencing of Glucanase Inhibitor Protein in Phytophthora cinnamomi.

Ink disease is considered one of the most significant causes contributing to the decline of chestnut orchards. The reduced yield of Castanea sativa Mill can be attributed to two main species: Phytophthora cinnamomi and Phytophthora cambivora, with the first being the main pathogen responsible for ink disease in Portugal. P. cinnamomi is a highly aggressive and widely distributed plant pathogen, capable of infecting nearly 1000 host species. This oomycete causes substantial economic losses and is accountable for the decline of numerous plant species in Europe and worldwide. To date, no effective treatments are available to combat these pathogens. Given chestnut's economic and ecological significance, particularly in Portugal, it is crucial to investigate the molecular mechanisms underlying the interaction between Phytophthora species and host plants. This can be achieved through the study of the glucanase inhibitor protein (GIP) produced by P. cinnamomi during infection. The technique of RNA interference (RNAi) was employed to suppress the GIP gene of P. cinnamomi. The resulting transformants, carrying the silenced gene, were used to infect C. sativa, allowing for the assessment of the effects of gene silencing on the plant's phenotype. Additionally, bioinformatics tools predicted the secretion of GIP protein. The obtained results validate RNAi as a potential alternative tool for studying molecular factors and for controlling and managing P. cinnamomi.

Artificial intelligence unveils key interactions between soil properties and climate factors on Boletus edulis and B. reticulatus mycelium in chestnut orchards of different ages

The main objective of this study was to determine the possible interaction of two important abiotic factors (soil and climate) on the mycelial concentration and frequency of the ectomycorrhizal fungi Boletus edulis and B. reticulatus, using traditional statistics and artificial neural network tools. The frequency and concentration of Boletus mycelium were determined over three months (September, October, and November), and two years (2018 and 2020), in three hybrid chestnuts (Castanea × coudercii) orchards of 40-, 10-, and 3- years-old, using real-time qPCR. Statistical analysis revealed a significant effect of the year on B. edulis mycelium concentration and of the sampling plot (different tree ages) on B. reticulatus frequency. The combination of artificial intelligence networks (ANN) with fuzzy logic, named neurofuzzy logic (NF), allowed the construction of two robust models. In the first, using year, month, and sampling plot as inputs, NF identified hidden interactions between year and month on B. edulis mycelium concentration and between sampling plot and sampling month on B. reticulatus mycelium frequency, thus improving the information obtained from the statistical analysis. In the second model, those three factors were disaggregated into 44 inputs, including 20 soil properties and 24 climatic factors, being NF able to select only 8 as critical factors to explain the variability found in both ectomycorrhizal Boletus species regarding mycelial frequency and concentration. Specifically, NF selected two chemical soil properties (cation exchange capacity and total carbon) and three physical properties (macroaggregates, total porosity, and soil moisture at field capacity), as well as their interactions with three climatic elements (cumulative difference between precipitation and potential evapotranspiration (P-PET-1-2) and water deficit (WD-1-2) in the previous two months and excess water (WE-1) in the month prior to sampling. These results provide a much deeper understanding and new insights into the ecology and the role of abiotic factors which explain the different mycelial development patterns of ectomycorrhizal fungi such as B. edulis and B. reticulatus in chestnut agroecosystems.

SOME BIOTIC LIMITING FACTORS OF DRYOCOSMUS KURIPHILUS (HYMENOPTERA CYNIPIDAE): A SURVEY IN CHESTNUT ORCHARDS NEAR FLORENCE (ITALY)

The biological control of the Asian Chinese gall wasp (ACGW) Dryocosmus kuriphilus, is influenced by several factors. In 2013, a survey was carried out in three chestnut orchards near Florence (Italy) to investigate ACGW parasitization by native parasitoids and the introduced Torymus sinensis. The following two methods were adopted: the first based on the dissection of cynipid galls with the aim of inspecting cells within each gall and the second based on monitoring adult emergence from galls. Parasitization patterns due to gall position related to plant height were also evaluated. Native parasitoids were more abundant in the upper part of tree crowns in June, while in July and August their activity was more evident in the middle and lower parts of chestnut trees. Conversely, parasitization of T. sinensis, was detected at all plant heights. Plant position within stands also affected the performance of both native parasitoids and T. sinensis, with parasitization that progressively decreasead moving toward the interior of the orchards. Gall necrosis was equally evaluated as a limiting factor of ACGW survival. Among the isolated fungal species, Gnomoniopsis castaneae (Tamietti), an endophyte fungus harmful to fruits, colonized both healthy and necrotic galls together with ubiquitous components of fungal communities such as Alternaria sp., Aspergillus sp., Fusarium sp. and Colletotrichum fioriniae. Our results evidenced that T. sinensis was able control the ACGW, while native parasitoids played only a secondary, though non-negligible, role. Conversely, gall necroses had a minor impact on pest control, as their efficacy was limited to the early stages of gall development. Key words: biodiversity, gall-inducing insects, native parasitoids, fungal species

Strong pollen limitation in genetically uniform hybrid chestnut orchards despite proximity to chestnut forests

Key messageIn arboriculture, the number and diversity of pollen donors can have a major impact on fruit production. We studied pollination insurance in hybrid chestnut orchards (C. sativa × C. crenata) provided by nearby wild European chestnuts (C. sativa) in southwestern France. Most fruits were sired by hybrid pollenizers rather than by wild chestnuts. When these hybrid pollenizers were too scarce, a frequent situation, pollen produced by wild chestnut trees did not compensate for the lack of compatible pollen and fertilization rates and fruit production collapsed.ContextThe demand for chestnuts has been increasing in recent years in many European countries, but fruit production is not sufficient to meet this demand. Improving pollination service in chestnut orchards could increase fruit production.AimsInvestigate pollination service in chestnut orchards. Evaluate the contribution to pollination of trees growing in chestnut woods and forests.MethodsWe investigated five orchards planted with hybrid chestnuts (C. sativa × C. crenata) cultivars in southwestern France. We combined fruit set data, which provide information about pollination rate, with genetic data, which provide information about pollen origin. We used this information to estimate the contribution of nearby C. sativa forest stands to the pollination of each orchard.ResultsPollination rates vary considerably, being fivefold higher in orchards comprising numerous pollen donors than in monovarietal orchards. Because of asymmetric hybridization barriers between hybrid and purebred cultivars, the surrounding chestnut forests provide very limited pollination insurance: less than 14% of the flowers in these monovarietal orchards had been pollinated by forest trees.ConclusionBecause chestnut orchards are now increasingly relying on hybrid cultivars, surrounding wild European chestnut trees are no longer a reliable pollen source. To achieve maximal fruit set, efforts must therefore concentrate on orchard design, which should include enough cultivar diversity.

Control Efficacy of UAV-Based Ultra-Low-Volume Application of Pesticide in Chestnut Orchards.

Pesticide spraying using unmanned aerial vehicles (UAVs) has been utilized in many crops, including fruit tree crops, because of its merits in terms of labor-saving and the low risk to the operator. However, its relevance to chestnut, one of the commercially significant fruit trees grown throughout Europe and Asia, has not been studied. In this work, we assessed the effectiveness of UAV-based ultra-low-volume pesticide application in chestnuts. We demonstrated the efficiency of three insecticides applied by a UAV on young chestnut trees. Interestingly, using a reduced amount of one of the pesticides, UAV-based spraying had greater control efficacy than conventional methods. The efficacy of ultra-low-volume pesticide application to adult trees was equivalent to using an air-blast sprayer. The spray coverage was compared in terms of spray volume (20 L vs. 40 L ha-1), flight method (straight flight vs. rotating flight for each tree), the size of the UAVs (8 L vs. 30 L in payload capacity), flow rate (3.8 L vs. 6.0 L min-1), and tree age in order to characterize the droplet deposition of UAV-based spraying. Overall, we showed that spraying pesticides using a UAV could effectively protect chestnut trees. It was debated how tree training, or tree height, affected pest control.

The effects of chestnut orchard microclimate on burr development

Chestnut crop is regaining its fame worldwide with powerful investment perspectives. Unluckily the climate change effects are posing high threat to its cultivation with less available resources and increased production cost both in traditional and specialized orchards. Additionally, the chestnut physiological knowledge is still limited, especially as concern the burr development (i.e., the economical production target) and its relationship with the environmental parameters. The aim of the present study was to evaluate the seasonal, daily, and hourly burr growth pattern associated to environmental parameters for improving physiological knowledge on this species. The study was carried out in a traditional rainfed sweet chestnut orchard located in the Tuscan-Emilian Apennines (Monterenzio, Italy). The chestnut burr growth was measured, along the entire season, both with a digital calliper and through the use of plant-based sensors (fruit-gauges) that permitted to measure, in real-time, the burr growth pattern. Environmental data were recorded by a weather station placed in the middle of the orchard. Results evidenced a higher burr growth rate, in the last part of the season (from middle-end of August to full fall) while the daily growing pattern was characterized by increased oscillation, along the season, of night-swelling and daily-shrinkage. The night-swelling was found to be influenced by high nocturnal air relative humidity while the daily-shrinkage was influenced by the higher wind speed, solar radiation and vapour pressure deficit. Thus, the burr daily net growth can be associated, depending on the phenological stages, to environmental parameters. Precipitation but especially the atmosphere humidity, in September and October, were the main external drivers of burr daily net growth. These results could be promising for the adoption of sustainable (e.g., late season grass mowing, sprinkler irrigation) and smart practices for improving chestnut management in both traditional and specialized orchards.

Soil Organic Carbon Stock Assessment for Volunteer Carbon Removal Benefit: Methodological Approach in Chestnut Orchard for Fruit Production

The implementation of a protocol for supporting a reliable soil C market is needed. This paper aims to propose a methodology for evaluating soil organic C (SOC) stock changes for the C credit market. A 15-year-old chestnut orchard (CO) and a chestnut coppice (CC) as reference land were selected in the northern part of the Apennine chain (Italy). The CO is the result of the CC conversion carried out in 2005. The soil sampling by pedogenetic horizons till parent material was carried out in 2005, 2010, 2015 and 2020 in CO and in 2005 and 2020 in CC. For each sample, the concentration and stock of the total SOC and of the most recalcitrant SOC form were estimated. Unlike the CC, in CO, an increase over time of SOC stocks was observed throughout the entire soil profile indicating the suitability of CO for C credit gaining. Most of the SOC was stored within the deepest soil horizon. The methodology can be considered eligible for the C credit market because, replicable, the CO was intentionally realized by humans after 1990, and the additionality was evaluated. Moreover, soil functionality was considered through the evaluation of SOC forms and of the pedogenetic horizons.

Leaf Trait Hyperspectral Characterization of Castanea sativa Miller Affected by Dryocosmus kuriphilus Yasumatsu

While populations of the Asian chestnut gall wasp (Dryocosmus kuriphilus Yasumatsu), an invasive pest affecting the European chestnut (Castanea sativa Miller), have started to be controlled biologically, this pest still conditions chestnut tree development. With the aim of assessing plant health status as a means of monitoring gall wasp infestation, we used a field spectroradiometer to collect data from leaves taken from 83 trees in two chestnut orchards. We calculated characteristic spectral signatures for pest infestation, and after training and validation, developed classifiers to distinguish between different infestation levels. Several partial least square discriminant analysis (PLS-DA) and random forest (RF) models were fitted with reflectance and transformed values to obtain characteristic curves reflecting infestation. Four wavelengths (560 nm, 680 nm, 1400 nm, and 1935 nm) were identified as showing the greatest differences between curves. The best overall accuracy (69.23%) was achieved by an RF model fitted with reflectance transformed values. Lower overall accuracy (26.92%) was achieved in distinguishing between infestation levels. In conclusion, while more specific differences in infestation levels were not detectable, our method successfully discriminated between gall absence and presence.

Plant Functional Dispersion, Vulnerability and Originality Increase Arthropod Functions from a Protected Mountain Mediterranean Area in Spring.

Plant diversity often contributes to the shape of arthropod communities, which in turn supply important ecosystem services. However, the current biodiversity loss scenario, particularly worrying for arthropods, constitutes a threat for sustainability. From a trait-based ecology approach, our goal was to evaluate the bottom-up relationships to obtain a better understanding of the conservation of the arthropod function within the ecosystem. Specifically, we aim: (i) to describe the plant taxonomic and functional diversity in spring within relevant habitats of a natural protected area from the Mediterranean basin; and (ii) to evaluate the response of the arthropod functional community to plants. Plants and arthropods were sampled and identified, taxonomic and functional indices calculated, and the plant-arthropod relationships analyzed. Generally, oak forests and scrublands showed a higher plant functional diversity while the plant taxonomic richness was higher in grasslands and chestnut orchards. The abundance of arthropod functional groups increased with the plant taxonomic diversity, functional dispersion, vulnerability and originality, suggesting that single traits (e.g., flower shape or color) may be more relevant for the arthropod function. Results indicate the functional vulnerability of seminatural habitats, the relevance of grasslands and chestnut orchards for arthropod functions and pave the way for further studies about plant-arthropod interactions from a trait-based ecology approach.

Soil microbiota impact on Boletus edulis mycelium in chestnut orchards of different ages

Biotic factors (host plant age and soil microbiota) influencing Boletus edulis mycelium frequency and concentration have been investigated. The study was carried out in September, October and November 2018 and 2020, using six orchards of chestnut hybrid Castanea × coudercii of 40-, 10- and 3-years-old. Taxonomical identity of bacterial and fungal species was ascertained by DNA metabarcoding. Mycelium frequency and concentration of B. edulis were studied through quantitative PCR (qPCR) of soil samples. It was hypothesized that mature plants (40-years-old) have a greater soil microbiota associated at the rhizosphere, in comparison with young plants (10- and 3-years-old). This situation may reverberate on B. edulis mycelium that should be more abundant in 40-years-old orchards, also thanks to the higher number of beneficial interactions whit soil microbiota. It was found that host plant age significantly altered bacterial and fungal assemblages in both years. Bacterial fraction was dominated by the phylum Proteobacteria, Acidobacteria and Actinobacteria and showed a higher species richness and diversity in orchards of 10- and 3-years-old. Fungal phylum such as Basidiomycota was more abundant in 40- and 10-years-old orchards, whereas Ascomycota and Mortierellomycota were more abundant in the 10- and 3-years-old orchards. Mycelium frequency of B. edulis in soil samples was higher in 2020 (97 %) than in 2018 (19 %), although without differences between plant age and sampling month in each year. Boletus edulis mycelium concentration was higher in 2020 than in 2018, and in September 2020, whereas plant age did not have any effect. Of 173 bacterial taxa considered, the 12 %, 54 % and 82 % of the significant correlations with B. edulis mycelium concentration were found in 40-, 10- and 3-years-old orchards, respectively. On the other hand, of 180 fungal taxa, the 12 %, 24 % and 42 % of the significant correlations occurred in 40-, 10- and 3-years-old orchards, respectively. This investigation represents the first report about the role of soil microbiota on the ecology of B. edulis in Castanea agro-ecosystem.

Relationship between Leaf Scorch Occurrence and Nutrient Elements and Their Effects on Fruit Qualities in Chinese Chestnut Orchards

Chinese chestnut (Castanea mollissima) is a multipurpose tree providing nuts and timbers, which holds an important position in the mountainous villages in China. However, leaf scorch disease is becoming more and more serious in the chestnut orchards of Yanshan Mountain areas, but the cause of occurrence is still unclear. In this study, the nutrient elements were analyzed from the leaves, roots, and surrounding soils of roots as well as the nut qualities in the healthy and scorched trees from two adjacent chestnut orchards. The results showed that the elements of nitrogen (N), iron (Fe), boron (B), and zinc (Zn) in leaves significantly increased in the scorched trees as well as N and B in roots, and potassium (K), and available potassium (AP) in soils, but leaf magnesium (Mg), root manganese (Mn), and soil Mg, copper (Cu), Fe, and B significantly decreased. Correlation analysis demonstrated that B, Zn, Mg, and Fe had a greater influence on the status of leaf health, and soil AK, K, Fe, B, and Cu had an impact on leaf B concentration. In addition, the occurrence of leaf scorch affected the nut sizes, contents of total soluble proteins and ascorbic acid as well as the catalase activity in the nuts. These results indicated that the disruption of soil-element balance may be one of the main causes resulting in the occurrence of leaf scorch, which would provide a theoretical basis and practical guidance for the prevention of chestnut leaf scorch disease.

Distribution and habitat of the Eurasian Treecreeper (Certhia familiaris) in Corsica

The Eurasian Treecreeper is a forest bird distributed from South-Western Europe up to Northern Asia. Two phylogenetic groups have been recently identified within this species, one restricted to Corsica Island (Mediterranean) and the Caucasus region, the other distributed over most of Eurasia and in Northern Asia. Little is known on the natural history of the Corsican population. We present here new comprehensive data on its distribution and habitat. The Eurasian Treecreeper is found from sea level to the upper limit of the forest but absent from the treeless macchia, a dominant vegetation in Corsica. Breeding occurs in a variety of tree species with a strong preference for mature stands and large trees. Its preferred habitat consists of old stands of Corsican Pines and of Sweet Chestnuts, although they are not the commonest tree species in Corsica. The current decline of Sweet Chestnut orchards confers a particular importance to the future preservation of mature stands of Corsican Pine, a patrimonial habitat of great value hosting several endemic bird taxa.