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Abstract In Iran, native oak species are under threat from episodes of Charcoal Disease, a decline syndrome driven by abiotic stressors (e.g. drought, elevated temperature) and biotic components, Biscogniauxia mediterranea (De Not.) Kuntze and Obolarina persica (M. Mirabolfathy). The outbreak is still ongoing and the country’s largest ever recorded. Still, the factors driving its’ epidemiology in time and space are poorly known and such knowledge is urgently needed to develop strategies to counteract the adverse effects. In this study, we developed a generic framework based on experimental, machine-learning algorithms and spatial analyses for landscape-level prediction of oak charcoal disease outbreaks. Extensive field surveys were conducted during 2013–2015 in eight provinces (more than 50 unique counties) in the Zagros ecoregion. Pathogenic fungi were isolated and characterized through morphological and molecular approaches, and their pathogenicity was assessed under controlled water stress regimes in the greenhouse. Further, we evaluated a set of 29 bioclimatic, environmental, and host layers in modeling for disease incidence data using four well-known machine learning algorithms including the Generalized Linear Model, Gradient Boosting Model, Random Forest model (RF), and Multivariate Adaptive Regression Splines implemented in MaxEnt software. Model validation statistics [Area Under the Curve (AUC), True Skill Statistics (TSS)], and Kappa index were used to evaluate the accuracy of each model. Models with a TSS above 0.65 were used to prepare an ensemble model. The results showed that among the different climate variables, precipitation and temperature (Bio18, Bio7, Bio8, and bio9) in the case of O. persica and similarly, gsl (growing season length TREELIM, highlighting the warming climate and the endophytic/pathogenic nature of the fungus) and precipitation in case of B. mediterranea are the most important influencing variables in disease modeling, while near-surface wind speed (sfcwind) is the least important variant. The RF algorithm generates the most robust predictions (ROC of 0.95; TSS of 0.77 and 0.79 for MP and OP, respectively). Theoretical analysis shows that the ensemble model (ROC of 0.95 and 0.96; TSS = 0.79 and 0.81 for MP and OP, respectively), can efficiently be used in the prediction of the charcoal disease spatiotemporal distribution. The oak mortality varied ranging from 2 to 14%. Wood-boring beetles association with diseased trees was determined at 20%. Results showed that water deficiency is a crucial component of the oak decline phenomenon in Iran. The Northern Zagros forests (Ilam, Lorestan, and Kermanshah provinces) along with the southern Zagros forests (Fars and Kohgilouyeh va-Boyer Ahmad provinces) among others are the most endangered areas of potential future pandemics of charcoal disease. Our findings will significantly improve our understanding of the current situation of the disease to pave the way against pathogenic agents in Iran.

Oak decline is a complex disorder that seriously threatens the survival of Zagros forests. In an extensive study on taxonomy and pathology of fungi associated with oak decline in the central and northern part of Zagros forests, 462 fungal isolates were obtained from oak trees showing canker, gummosis, dieback, defoliation, and partial or total death symptoms. Based on inter-simple sequence repeat (ISSR) fingerprinting patterns, morphological characteristics, and sequences of ribosomal DNA (28S rDNA and ITS) and protein coding loci (acl1, act1, caM, tef-1a, rpb1, rpb2, and tub2), 24 fungal species corresponding to 19 genera were characterized. Forty percent of the isolates were placed in eight coelomycetous species from seven genera, namely, Alloeutypa, Botryosphaeria, Cytospora, Didymella, Gnomoniopsis, Kalmusia, and Neoscytalidium. Of these, four species are new to science, which are introduced here as taxonomic novelties: Alloeutypa iranensis sp. nov., Cytospora hedjaroudei sp. nov., Cytospora zagrosensis sp. nov., and Gnomoniopsis quercicola sp. nov. According to pathogenicity trials on leaves and stems of 2-year-old Persian oak (Quercus brantii) seedlings, Alternaria spp. (A. alternata, A. atra, and A. contlous), Chaetomium globosum, and Parachaetomium perlucidum were recognized as nonpathogenic. All coelomycetous species were determined as pathogenic in both pathogenicity trials on leaves and seedling stems, of which Gnomoniopsis quercicola sp. nov., Botryosphaeria dothidea, and Neoscytalidium dimidiatum were recognized as the most virulent species followed by Biscogniauxia rosacearum. [ABSTRACT FROM AUTHOR]

Xylophagous insects play a crucial role in forest ecosystems, contributing to population dynamics. The "Cerambyx complex" (CC) constitutes an emerging pest in Mediterranean oak woodlands. We studied the fragmentation and connectivity of holm and cork oak stands in Andalusia (Spain), and the relationships with the current dispersion of CC, as well as the effect on the connectivity and dispersion patterns with the implementation of nests of a predator bird (Garrulus glandarius) to reduce insect populations in highly connected areas. The Kernel Density Estimation (KDE) was used to assess the spatial distribution of CC. Connectivity was assessed using graphs theory (Graphab 2.6) to characterize the importance of patches and linkages for contributing to dispersal. We selected the Eurasian jay (G. glandarius) as a reference bird species to generate "barriers" to the dispersion of the CC. We used the probability of connectivity (PC) and the flux (F) to compare the effect of the introduction of Eurasian jay nets. Results showed an increasing trend in the distribution and incidence of CC during the period 2001–2016, resulting in 7.3% and 13.1% mortality rates for Q. ilex and Q. suber, respectively. The connectivity model using only Q. ilex and Q. suber forests as reference habitats was not enough to explain the distribution of CC. The value of PC and F metrics decreased by 38.09% and 20.59% by introducing 300 nests of Eurasian jay. Our methodology provides a pest management tool using connectivity metrics, which can be integrated with other variables to control pest outbreaks and pest dispersion. [ABSTRACT FROM AUTHOR]

Brenneria goodwinii is a bacterial pathogen causing severe decline in Quercus brantii. We explored the effects of B. goodwinii on physiological traits of Q. brantii seedlings and assessed differences between families in the response to the pathogen. We examined 210 seedlings from 14 half-sib families. To evaluate disease resistance, foliar symptoms and several physiological traits, including chlorophyll fluorescence and electrolyte leakage were measured in pathogen-inoculated and mock-inoculated seedlings. In addition, seven EST-SSR markers associated with stress resistance were genotyped in two resistant and two susceptible families. All physiological traits were negatively affected by pathogen inoculation. There was significant genetic variation among the families, with the most susceptible ones showing a worse physiological condition. The heritability and coefficient of genotypic variation of the resistance increased during the experimental period reaching relatively high values (0.49 and 35%, respectively) five weeks after inoculation. EST-SSR analysis revealed that resistant families showed the highest heterozygosity. Two of the seven evaluated loci were associated with the measured physiological traits and showed high FST values. Our results support that resistant mother trees can be selected for disease management. The putative alleles of FIR053 locus could be useful for identifying resistant Q. brantii families to the pathogen. [ABSTRACT FROM AUTHOR]

Oak decline is a complex disorder that seriously threatens the survival of Zagros forests. In an extensive study on taxonomy and pathology of fungi associated with oak decline in the central and northern part of Zagros forests, 462 fungal isolates were obtained from oak trees showing canker, gummosis, dieback, defoliation, and partial or total death symptoms. Based on inter-simple sequence repeat (ISSR) fingerprinting patterns, morphological characteristics, and sequences of ribosomal DNA (28S rDNA and ITS) and protein coding loci (acl1, act1, caM, tef-1α, rpb1, rpb2, and tub2), 24 fungal species corresponding to 19 genera were characterized. Forty percent of the isolates were placed in eight coelomycetous species from seven genera, namely, Alloeutypa, Botryosphaeria, Cytospora, Didymella, Gnomoniopsis, Kalmusia, and Neoscytalidium. Of these, four species are new to science, which are introduced here as taxonomic novelties: Alloeutypa iranensis sp. nov., Cytospora hedjaroudei sp. nov., Cytospora zagrosensis sp. nov., and Gnomoniopsis quercicola sp. nov. According to pathogenicity trials on leaves and stems of 2-year-old Persian oak (Quercus brantii) seedlings, Alternaria spp. (A. alternata, A. atra, and A. contlous), Chaetomium globosum, and Parachaetomium perlucidum were recognized as nonpathogenic. All coelomycetous species were determined as pathogenic in both pathogenicity trials on leaves and seedling stems, of which Gnomoniopsis quercicola sp. nov., Botryosphaeria dothidea, and Neoscytalidium dimidiatum were recognized as the most virulent species followed by Biscogniauxia rosacearum.

Extended Abstract Introduction and Objective: For about two decades, the Zagros forests have been facing a declining issue, and the effects of this crisis are visible in various regions. Material and Methods: In the current study, the effect of climate change on the decline of Persian oak in the Zagros forest stands is probed using meteorological data and sample plots over time. To conduct this research, in order to collect field data, a regular random sampling model with fixed sample plots with two sampling periods in 1998 and 2018 was used. Furthermore, the trend of four climatic elements of precipitation, temperature, frost, and relative humidity in Gilan-e-Gharb station from 1988 to 2018 was studied. Results: The results showed that the frequency and stock of Persian oak species in the second period compared to the first period was decreased. The cross-sectional per hectare of Iranian oak was decreased from 5.2 in the first stage sampling to 4.4 in the second sampling. The results of comparing the quality and health conditions in two samples showed that in the first period, 11.9% of Persian oak trees were decayed and dried, while in the second period it was 71.55%. The oak decline rate in the second-period sampling was higher in health and quality grades 2 and 1 (41.9% and 28.5%, respectively) and was decreased in grades 4 and 5 (8.2% and 3/1%, respectively). However, the deterioration in higher degrees leads to the death of Persian oak trees. The Mann-Kendall analysis results of climatic elements showed that during the study period, the trend of precipitation, frost, and relative humidity was decreasing and the temperature was increasing. In the first decade and to some extent in the second decade, noticeable stability was observed in the studied indices, but in the third decade, there were many fluctuations. Conclusion: According to the obtained results, it can be said that climate change and the occurrence of severe drought stresses cause oak trees to suffer from physiological weakness. By creating physiological weakness in the trees, the conditions for the invasion of pests and various diseases are provided to them and the oak tree goes to dryness and decay.

The decline and mortality of Quercus species worldwide are interpreted through the interactions of several factors in space and time. Among these factors, Phytophthora cinnamomi has been identified as a major biotic agent triggering mortality of Quercus ilex and Q. suber in the Mediterranean basin. However, there are few examples in the literature studying the interaction between P. cinnamomi and site environmental factors or assessing the effects of environmental drivers on the host-pathogen system. In this study, we examined how both characteristics and spatial distribution of soil and topography influence the effects of P. cinnamomi over the disease status of Q. ilex and Q. suber plantations using spatial analysis by distance indices and structural equation modelling. Results showed the high influence of soil (texture, nutrients, chemical composition and moisture) and topography (orientation, solar incidence and hydrology) over the pathogen availability, as well as lower mortality and defoliation of Q. suber, but more related to the colony forming units (cfu) distribution, compared with Q. ilex. These differences highlighted the convenience of mixed afforestation compared with monospecific ones, increasing afforestation resilience, and the importance of a precise scale for the characterization of soil and topography, preventing afforestation failure. [ABSTRACT FROM AUTHOR]

The 2015–2018 outbreak of spongy moth (Lymantria dispar) in southern New England initiated a severe oak decline and mortality event. While defoliation was a primary driver, increased secondary pest and pathogen activity contributed to decline and death. Following this large defoliation event, Diplodia was frequently recovered from northern red oaks (Quercus rubra) with serious outbreaks of twig cankering. Given the many recent reports of Diplodia corticola on oak in eastern North America, it was presumed to be the causal agent. To confirm, a limited survey was conducted from five states in the region (Maine, Massachusetts, New Hampshire, New York, and Vermont). Based on ITS, tef1 and tub2 sequences generated from 28 isolates collected primarily from northern red oak, Diplodia gallae, two potentially novel Diplodia species and Diplodia sapinea were identified. Surprisingly, D. corticola was not found in this study. ITS sequences alone failed to discriminate among isolates of D. gallae and D. corticola, creating uncertainty over previous reports of D. corticola in eastern North America. Only a combined ITS + tef1 dataset successfully distinguished D. gallae and D. corticola along with two other closely related species that also occur on oak (Diplodia quercicola and Diplodia quercivora). Additional cankering and endophytic fungi (Coryneum, Dendrostoma, Gnomoniopsis, Pestalotiopsis and Tubakia) were also found on symptomatic oaks in the region. Identification of Diplodia isolates from non‐Quercus hosts also detected Diplodia neojuniperi on Juniperus chinensis and Microbiota decussata, which has not been reported previously in North America. [ABSTRACT FROM AUTHOR]

Brenneria goodwinii is a Gram‐negative bacterium associated with the phenomenon of Acute Oak Decline (AOD), which has played a very important role in the decline of oak populations in Europe in recent years. In this paper, the Maxent model was developed to detect the trend in the distribution of B. goodwinii in Europe. Generated from confirmed location data and bioclimatic variables, the Maxent model achieved high predictive accuracy as measured by parameters such as AUC and AUCdiff. Nineteen bioclimatic variables available on the WorldClim portal for the years 1970–2000 were used to create the model. The generated model allows to determine the most useful bioclimatic variables to assess the maximum entropy of the habitat in terms of the occurrence of B. goodwinii. In addition, the model identified areas of Europe where the probabilities of fit for bacteria are >.7. These areas include Great Britain, France, Belgium, the Netherlands, Germany, Denmark, Spain, Portugal and Italy. [ABSTRACT FROM AUTHOR]

Most forests are recovering from human land use, making it critical to understand the effect of disturbance on forest recovery. Forests of the eastern United States have a long history of land use, but it is unknown whether historical disturbances have contributed to their transition from ectomycorrhizal (ECM) to arbuscular mycorrhizal (AM) tree dominance. Disturbance may promote nitrogen (N)‐fixing trees in early succession, which can elevate soil N availability even after they die. Higher soil N availability may facilitate the competitive success of AM trees over ECM trees, but such 'N fixer founder effects' have not been empirically tested.Here, we analysed data from three land‐use disturbances in a temperate forest historically dominated by ECM trees: selective‐cutting (ranging from 0 to 52 m2 ha−1), clear‐cutting and agricultural abandonment. These disturbances occurred at different times, but long‐term data capture 3–7 decades of forest recovery.We found that the AM tree fraction in contemporary forests was 2, 4, and 6‐fold higher following selective‐cutting, clear‐cutting and agricultural abandonment, respectively, compared to forest composition in 1934. Across these disturbances we also observed an increasing abundance of the N fixer black locust immediately following disturbance. Using a simulation model parameterized by data from black locust, we estimated historical rates of symbiotic N fixation to understand the relationship between N fixation and AM dominance in individual plots. We found that N fixation was positively associated with the growth of ECM trees generally, and oak and hickory specifically, only following light selective‐cutting (<12 or <18 m2 ha−1 basal area extraction, respectively). Following higher levels of selective‐cutting and clear‐cutting, N fixation was positively associated with the growth of AM trees, particularly red maple and tulip poplar. Agricultural abandonment led to AM dominance regardless of N fixation rates.Synthesis and applications. Our findings suggest that common land use practices and black locust, a native N fixer, can reduce the dominance of ECM trees. If N fixers are likely to proliferate following disturbance, we might maintain ECM dominance by cutting trees at low densities and by applying prescribed fire to remove N. [ABSTRACT FROM AUTHOR]

Phytophthora cinnamomi and Phytophthora multivora are considered important forest pathogens globally. The presence of P. cinnamomi is widely reported, but little is known about the presence of Phytophthora multivora in the Mediterranean evergreen oak forests and its possible role in their decline syndrome. The present study was conducted to identify the presence of P. cinnamomi, P. multivora, and other Phytophthora species in the Castelporziano Presidential Estate in Italy using both soil-baiting and metabarcoding approaches. A total of 52 rhizosphere soil samples were collected from declining oak stands, from which 254 isolates of oomycetes taxa were obtained among which Phytophthora cinnamomi, P. multivora, P. plurivora, P. gonapodyides, and P. bilorbang were identified based on morphological traits. The results of HTS analysis revealed the presence in the rhizosphere of 20 different Phytophthora spp. including all the taxa obtained through baiting. Interestingly, the Phytophthora community did not differ among tree hosts. Phytophthora cinnamomi was the most common species in the investigated site. The pathogenicity of P. multivora to holm and cork oaks was evaluated on 3-month-old seedlings using P. cinnamomi as the positive control. Soil inoculation test demonstrated the aggressiveness of P. multivora on both holm oak and cork oak. Phytophthora multivora resulted by far less aggressive than P. cinnamomi. Among the host tree species, holm oak had a higher susceptibility to both tested pathogens. While P. multivora seems to play a relevant role in the decline of forest and urban ecosystems in Australia, its role in evergreen oak decline seems to be limited at the moment. Considering the nature of P. multivora as a fine root feeder and adaptation to dry environments, its role in holm and cork oaks decline could become more relevant in the medium term specifically in association with climate change. [ABSTRACT FROM AUTHOR]

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Pedunculate (Quercus robur L., 1753) and sessile (Q. petraea (Matt) Liebl., 1784) oak are long living trees, of great ecological and economic importance, consisting in significant components of the hardwood forests in Romanian lowlands and hilly regions. Even oak forests are resilient, over the last decades they have been affected several times by episodes of decline, followed by significant levels of mortality. These episodes are more frequent lately and have very rich facets. The important role of Agrilus spp. in the decline phenomenon is due to the participation in the final phase of the causative chain that leads to the mortality of oaks. Since, there is a lack of data on Agrilus oak infestation in Romania. The paper aims to review the information on the characteristics of the oak Agrilus spp. and the symptoms exhibited by the decline affected oak trees infested with Agrilus spp., to better understand the relationship between these species and oak decline and to facilitate the identification of the Agrilus infestations. [ABSTRACT FROM AUTHOR]

Massive propagation of cork oak (Quercus suber) individuals tolerant to Phytophthora cinnamomi (Pc) is probably the most important challenge for cork production. Screening for resistance to Pc of ca. 200 seedlings obtained from a single cork oak tree that has survived the epidemic was performed by soil infestation. Twenty months after Pc inoculation, 33 seedlings survived from Pc infection and the four most vigorous seedlings were selected. The plants were forced to produce new shoots under controlled climatic conditions, and the new shoots were used to establish the plants in vitro by axillary budding. High axillary shoot proliferation rates were achieved by culturing the new shoots on Lloyd and McCown (WPM) medium, followed by subculturing for 2 weeks on 0.22 µM benzyladenine (BA) and for 2 weeks further on 0.04 µM BA. Addition of 20 µM silver thiosulphate (STS) increased the proliferation rates and improved the appearance and development of shoots. Rooting rates of 80–100% were obtained by culturing the shoots for 24 or 48 h on Gresshoff and Doy medium with ⅓ macronutrients plus 122.5 µM indole-3-butyric acid and subsequent transfer to root expression medium containing 20 µM STS. The results of this study optimize the micropropagation of a relevant and recalcitrant tree species in forestry. [ABSTRACT FROM AUTHOR]

Oak decline is a general term used for the progressive dieback and eventual mortality of oak trees due to many compounding stressors, typically a combination of predisposing, inciting, and contributing factors. While pinpointing individual causes of decline in oak trees is a challenge, past studies have identified site and stand characteristics associated with oak decline. In this study, we developed a risk map of oak decline for the Daniel Boone National Forest (DBNF), combining GIS, remote sensing (RS), and public reporting (citizen science, CS). Starting with ground reports of decline (CS), we developed a site-scale model (GIS and RS) for oak decline based on four previously identified predisposing factors: elevation, slope, solar radiation, and topographic wetness. We found that areas identified in the model as having a high oak decline risk also reflected areas of observed oak decline (CS). We then optimized and expanded this risk model to the entire range of the DBNF, based on both site characteristics (as piloted for the case study site) and stand inventory data. The stand inventory data (including species composition and age) further improved the model, resulting in a risk map at the landscape level. This case study can serve as a planning tool and highlights the potential usefulness of integrating GIS, remote sensing, and citizen science. [ABSTRACT FROM AUTHOR]

Root rot affecting holm oak is a cause of high ecological and economic losses in the Iberian Peninsula, highlighting the relevance of developing disease control methods. The aim of this work was to assess the effect of a biological treatment composed of beneficial organisms (Trichoderma complex, T-complex) on holm oak seedlings infected by Phytophthora cinnamomi in two contrasted holm oak ecotypes, one considered highly susceptible (HU) and another considered tolerant to the pathogen (GR). For this purpose, a complete multifactorial test was carried out in a greenhouse, and seedlings were monitored for survival analysis and morphological and physiological attribute evaluation. Mortality began earlier in the susceptible (HU) than in the tolerant (GR) ecotype, and survival showed different trends due to the inoculation with beneficial microorganisms depending on the ecotype of the plants. The tolerant ecotype showed a high survival rate and better response to the treatment with beneficial microorganisms. GLM showed that the main reason for differences between treatments was ecotype, followed by T-complex and irrigation, and a weak interaction between ecotype and P. cinnamomi was found. The linear relationship between photosynthesis (A) and transpiration (Tr) showed an increase in the A/Tr rates for infected and inoculated plants under drought conditions for the GR ecotype. The tolerant ecotype was benefited more by the beneficial microorganism treatment. The understanding of the genetic diversity of Q. ilex and water stress influence on the efficacy of biological treatments against root rot provides useful information to develop environmentally friendly disease control methods to address the holm oak decline. [ABSTRACT FROM AUTHOR]

Oak open woodlands (dehesas) have outstanding socioeconomic and ecological values, sustain traditional agro-silvo-pastoral uses, provide high-value ecosystem services, and constitute key biodiversity hotspots. Cerambyx cerdo and Cerambyx welensii are two large, oak-living, wood-boring, sympatric longhorn beetles (Coleoptera: Cerambycidae) that may reach pest status in SW Spain, contributing to oak decline. Understanding species-specific habitat requirements determining occupancy–abundance patterns is needed to develop management or control strategies. We conducted a large-scale, four-year study using 1650 feeding traps to ascertain longhorn abundance and species-specific habitat suitability in relation to 18 ecological variables, 9 biotic (oak species, forest mass, trunk diameter, tree density, basal area, forest cover, shrub cover, ground cover, oak renewal), and 9 abiotic (bedrock outcrops, altitude, ground slope, aspect, mean temperature: annual/July/January, annual precipitation, insolation). Results showed that longhorn abundance was sensitive to most ecological variables and to many interactions between them. Interestingly, interactions between ecological variables and longhorn species were widespread, signifying that responses were species-specific and therefore predictive Generalized Linear Mixed Models (GLMMs) were different between species. Our research contributes to the understanding of the ecological factors that shape longhorn species-specific occupancy–abundance patterns, delves into their sympatric relationship, and contributes toward improving sustainable forest practices that will mitigate longhorn impact in oak open forests. [ABSTRACT FROM AUTHOR]

Background and Objective Over the past decade, the Zagros region, specifically its Zagros oak trees, has experienced significant impacts from droughts and climate change. Climate change has resulted in heightened desertification and oak forest decline. This study examines and analyzes meteorological droughts and their correlation with climate change. This is a prominent contributing factor to oak tree decline in Ilam Province. The focus is on study sites in the northern and southern Serabaleh regions, where oak decline has been observed. Methodology For this study, comprehensive data on daily precipitation and minimum and maximum temperature were obtained from the synoptic station in Ilam, covering the period from its establishment until 2019. The Standardized Precipitation Evapotranspiration Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI) were developed to assess meteorological drought and identify wetter and drier years. The SPI measures the deviation of precipitation from the mean value and normalizes it by the standard deviation. In contrast, the SPEI considers the discrepancy between precipitation and evapotranspiration. These indices were calculated on various time scales, including 3, 6, 12-month, and annual periods, and drought status was analyzed based on their respective classifications. To examine the role of climate change and identify influential precipitation and temperature patterns in drought occurrence, a set of four precipitation indices and eight temperature indices were calculated using ClimPACT software. These indices, developed by climate change experts, capture changes in mean or extreme weather conditions. The analysis also included wind speed. The relationship between drought indices and climate change was assessed through regression analysis and the Pearson correlation coefficient. Moreover, the study employed the Mann-Kendall and Pettitt Test to identify change points or significant abrupt changes in the time series. These tests were conducted at 5% significance and 95% confidence levels. Results The study findings indicate a decreasing trend in the highest consecutive 5-day rainfall since 1995. In addition, there are insignificant reductions in the annual sum of wet days and the highest rainfall events of one or two days since 1998. This decrease in rainfall has been accompanied by increased maximum air temperatures since 1998, with a significant intensification observed from 2007 to 2015. Additionally, there has been a slight increase in minimum temperatures since 2002 and a significant wind speed since 1996. These factors have contributed to increased evaporation since 1998 and the occurrence of droughts on different time scales, ranging from six and twelve months since 1998 to three months since 2003. Global warming has influenced droughts. Three-month droughts have resulted in milder six- and twelve-month droughts, but more severe three-month droughts in oak decline, primarily due to significant changes in maximum temperatures since 2007. The occurrence of these droughts has been associated with an increase in the percentage of days with temperatures above the average since 2007, leading to more severe droughts from 2007 to 2015, with the peak in 2008 coinciding with the highest level of oak decline during the study period and under the influence of climate change phenomena. Conclusion The SPEI drought index indicates a higher frequency and longer duration of droughts during the study periods, albeit with less severity than the SPI index. This suggests that the rising temperatures during cold months, in addition to dry months, have played a role in influencing the drought conditions. The results demonstrate that drought and climate change are the primary influential factors contributing to oak tree dryness in the forests of Ilam Province. Considering the decreasing precipitation trend and increasing temperature trend observed in the studied region, the occurrence of climate and environmental hazards, such as heatwaves, droughts, and floods, may further increase. [ABSTRACT FROM AUTHOR]

Wood-boring insects are considered potential contributing/inciting factors to oak decline. Cerambyx cerdo (Cc) and C. welensii (Cw) are two sympatric oak-living large sapro-xylophagous longhorn beetles with different pest/legal status, whose larvae bore into living wood of healthy/decayed trees, and whose impact has increased alarmingly in recent years. We conducted a regional-scale multi-year (2017–2020) field study to model Cc and Cw distribution and to explore species-specific occupancy-abundance patterns. Records were obtained with 1650 feeding traps placed throughout the region of Extremadura (SW Spain) (41,634 km2) in holm, cork and pyrenean oak woodlands. Catch number (a proxy of abundance) was analysed through GLMMs, LMs and geostatistical interpolation (IK algorithm) to generate catch probability maps. Catch number was extremely variable between trees (traps), stands and years (Cc: 0–252, Cw: 0–219 adults/trap) with no repulsive interspecific association at the tree scale. Explanatory factors in the models (species, sex, year and host oak) and several interactions among them significantly affected catch number. As a whole, Cw was more abundant than Cc, but catch number greatly depended on host tree (Cw: cork > holm > pyrenean oak, Cc: holm > cork > pyrenean oak). Occupancy-abundance patterns were positive with significant occupancy x species interaction. Niche breadth was more than double in Cw (Levins' BA = 0.42) than in Cc (BA = 0.19) and niche overlap almost complete (Pianka's O = 0.98). Our large-scale pioneer study shows that Cc and Cw are widespread in SW Spain, but with huge host-mediated intra- and interspecific geographic variation in abundance, which has critical implications in population management/control strategies. [ABSTRACT FROM AUTHOR]

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.

Iii Portugal. fungal symbionts of the ambrosia beetle Plaoria' crlindrus inoculaaffect tree vigor of cork oak (Quercia· suber) and are linked with the cork decline process. Fungal symbionts play cnicial role.4 in the life history of and ambrosia beetles and recent work indicates complex interactions on chefungal and plant metabolic level. Colonized trees may respond with an array infocurrently unknown volatile metabolites being indicative of such interactions, acting as infochemicals with their environment. In this study. we examined volatile organic compounds (VOCK) of cork oak seedlings wound inoculated interwith strains of three fungal associates of P. cvli, ith·us (Ridtbelea, nonteou, quercina, and Cemton'stiopsis sp. nov.) over a 45-day period by means thermodesorption gas chromatography-mass spectrometry techniques. Fungal strains induced largely quantitative but species-specific changes among 58 VOCs characterized. Overall. monoterpenes-the major volatiles cork oak foliage-were significantly reduced. possibly a result of fungal ophiostransformation. Acetophenone, sulcatone. and nonanal-volatiles known mediating ambrosia beetle behavior-increased in response to fungal inoculaaffect lion. Qualitative VOC profiles of excised tissue of wood lesions (21 VOCs) and pure ftingal cultures (60 VOCs) showed little overlap with seedling VOCs. indicating their plant-derived but fungal-induced origin. This chefungal moecological study expands on the limited knowledge of VOCs as infocurrently chemicals emitted from oak trees threatened by oak decline in relation to beetle-vectored ophiostomatoid fungi. It opens new avenues of research to clarify mutualistic or pathogenic aspects of these complex symbiotic interwith actions and develop new control strategies for P. o, lindrus. including its mycobiota. [ABSTRACT FROM AUTHOR]

One of the environmental problems of the Zagros forests, especially in the last two decades, is the occurrence of oak decline phenomenon in Zagros Forest. The intensity of oak decline in the North Zagros is slower than in the Middle and South Zagros. The purpose of this study was to investigate the trends of oak decline in forests of Baneh city (Kurdistan province) from 2019 to 2020.Four sites including Belveh and Gandman (southern aspect) and Saraki and Mirhesam (northern aspect) were selected and 100 trees were evaluated in each site. Oak decline status was recorded during two years of research in five classes: healthy trees, dieback in crwon, dieback up to 50%, dieback more than 50% and standing dead tree. Wilcoxon and Friedman (non-parametric tests) were used to compare the decline codes at each site for two consecutive years and to compare the decline codes at four sites per year (separately). The results showed that the greatest change of oak decline class was in Saraki site (with 0.27 change). At all four sites, the trees were shifting to oak decline classes in the second year of the research, and the change in oak decline classes at each site for two consecutive years (Wilcoxon test) was statistically significant. Besides, the change of dieback trees (dieback and dieback up to 50%) from 24% of trees in 2019 to 44% of trees in 2020 had changed. Most oak decline was observed on the southern aspect. Overall, it is suggested that human intervention and deforestation be controlled as much as possible to control the Oak decline. [ABSTRACT FROM AUTHOR]

To study the relationship between some physico-chemical properties of soil and ecophysiological properties of oak trees on dieback, Meleshabanan area in Lorestan Province was selected. Using the geographic information system (GIS), the landform map of study area was prepared. In this forest, 30 square sample plots with 2500 m2 area, in a random systematic grid (200*200) were selected. The percent dieback was measured and recorded. In each sample plot, soil and leaves of oak trees were sampled. Some soil properties such as texture, electrical conductivity, acidity, bulk density, porosity, organic carbon, organic matter, and concentrations of calcium, magnesium, nitrogen, phosphorus, potassium, and sodium were measured. Also peroxidase, catalase, and ascorbate peroxidase enzymes, MDA, proline, chlorophyll a, b, carotenoid pigment, and concentrations of calcium, magnesium, nitrogen, phosphorus, potassium, and sodium in leaves were measured. The results showed that there was a significant difference in clay, sand, soil texture, Ca content, N/P ratio, and, MDA concentration between different dieback classes. Leaf Ca concentration with increasing dieback increased, while MDA first increased and then decreased. Also, the results of canonical correspondence analysis (CCA) showed that the frequency of trees in high dieback classes and the number of dead trees were directly related to bulk density and %clay and inversely related to %porosity, %sand, Mg, K, and N content.

Massive propagation of cork oak (Quercus suber) individuals tolerant to Phytophthora cinnamomi (Pc) is probably the most important challenge for cork production. Screening for resistance to Pc of ca. 200 seedlings obtained from a single cork oak tree that has survived the epidemic was performed by soil infestation. Twenty months after Pc inoculation, 33 seedlings survived from Pc infection and the four most vigorous seedlings were selected. The plants were forced to produce new shoots under controlled climatic conditions, and the new shoots were used to establish the plants in vitro by axillary budding. High axillary shoot proliferation rates were achieved by culturing the new shoots on Lloyd and McCown (WPM) medium, followed by subculturing for 2 weeks on 0.22 µM benzyladenine (BA) and for 2 weeks further on 0.04 µM BA. Addition of 20 µM silver thiosulphate (STS) increased the proliferation rates and improved the appearance and development of shoots. Rooting rates of 80–100% were obtained by culturing the shoots for 24 or 48 h on Gresshoff and Doy medium with ⅓ macronutrients plus 122.5 µM indole-3-butyric acid and subsequent transfer to root expression medium containing 20 µM STS. The results of this study optimize the micropropagation of a relevant and recalcitrant tree species in forestry.

Oak decline presenting symptoms of tracheomycosis have been observed globally over long periods of time. Since the 1990s, oak decline has been considered to be a multifactorial process where abiotic predisposing factors play a significant role. Nevertheless, biotic factors, such as subcortical insects and fungal pathogens, may influence the decline process, as some insect species transmit spores of tracheomycotic pathogens. We investigated biotic agents (subcortical insects, Ophiostoma spp. and Phytophthora spp.) in six declining oak stands located within mesophytic and thermophytic zones in the Czech Republic, where five dry years occurred from 2015 to 2019. The spectrum of insect pests of oak stands was investigated using two methods: reared from logs from each stand and window traps. The presence of Ophiostoma fungi was assessed from cultivated woodblocks; Phytophthora pathogens were isolated from soil samples. In total, 2931 subcortical insect individuals were captured during the 2021 vegetation period. The most species-rich group of the subcortical insect complex involved in oak decline consisted of the families Cerambycidae: Xylotrechus antilope; Curculionidae: Scolytus intricatus, Xyleborus monographus; and Buprestidae: Agrilus biguttatus, A. sulcicollis. The presence of Ophiostoma was detected in all stands with different intensities between tree parts. Several important oak pests were positively correlated with the occurrence of Ophiostoma. On the contrary, from all soil samples, Phytophthora plurivora was found at only one studied oak stand. Based on the results, a new modified model of biotic and abiotic factors involved in the oak decline is proposed. [ABSTRACT FROM AUTHOR]

Dieback has affected oak forests ecosystems of Iran in recent years. In order to understand this phenomenon, we selected 12 healthy and 16 dead trees of Quercus brantii Lindl in Dalab forest of Ilam. The responses of ring width chronologies to climatic factors were investigated in the living and dead trees. We also established the interrelationships between earlywood vessel features including vessel density, average vessel lumen area, the percentage of total vessel lumen area within the surface analyzed, the hydraulically weighted diameter, and ring width for 6 living and 6 dead trees. The results of crossdating showed that death occurred from 2008 onwards in most decayed trees. We found important differences in the effects of climatic factors on ring width chronologies between the living and dead trees, whereby water availability was the main factor controlling the radial growth of dead trees, which were more sensitive to drought. The analysis of earlywood vessels showed that the hydraulically weighted diameter and the vessel density are the anatomical features differing most strongly between the living and dead trees. From the difference of the hydraulically weighted diameter and the vessel density series between the living and dead trees, we concluded that dead individuals had the higher vulnerability to water stress. Moreover, by monitoring the annual variations of xylem anatomical features in the years before tree death, we propose the most critical timings of processes related to dieback. [ABSTRACT FROM AUTHOR]

Oak (Quercus) species are a major component of much of the eastern forest. Unfortunately, multiple species have experienced well-documented episodes of decline and mortality over the past century. A mortality event in chestnut oak (Q. prinus) across southern Indiana in 2016 sparked concern about the health of chestnut oak, leading to an effort to identify factors that triggered and contributed to the event. We evaluated stand conditions, tested for the presence of Phytophthora cinnamomi , and collected tree cores from chestnut oak trees within diseased stands and nearby healthy stands. We found no evidence that P. cinnamomi was associated with mortality. Instead, our dendrochronological analysis suggests that a series of dry June conditions followed by wet March conditions weakened vulnerable trees, allowing the exceptional drought in 2012 to incite decline. Greater basal area increment prior to growth decline, along with a higher probability of decline on mesic north-northeastern slopes, suggest that vulnerable individuals may have been those that preferentially allocated carbon into above ground growth at the expense of developing drought resilient root systems. • Chestnut oak mortality in southern Indiana followed a drought-induced decline sequence incited by the drought of 2012. • Faster growing trees were more likely to die than slower growing trees. • More mesic sites saw proportionately greater rates of mortality. [ABSTRACT FROM AUTHOR]

Root rot affecting holm oak is a cause of high ecological and economic losses in the Iberian Peninsula, highlighting the relevance of developing disease control methods. The aim of this work was to assess the effect of a biological treatment composed of beneficial organisms (Trichoderma complex, T-complex) on holm oak seedlings infected by Phytophthora cinnamomi in two contrasted holm oak ecotypes, one considered highly susceptible (HU) and another considered tolerant to the pathogen (GR). For this purpose, a complete multifactorial test was carried out in a greenhouse, and seedlings were monitored for survival analysis and morphological and physiological attribute evaluation. Mortality began earlier in the susceptible (HU) than in the tolerant (GR) ecotype, and survival showed different trends due to the inoculation with beneficial microorganisms depending on the ecotype of the plants. The tolerant ecotype showed a high survival rate and better response to the treatment with beneficial microorganisms. GLM showed that the main reason for differences between treatments was ecotype, followed by T-complex and irrigation, and a weak interaction between ecotype and P. cinnamomi was found. The linear relationship between photosynthesis (A) and transpiration (Tr) showed an increase in the A/Tr rates for infected and inoculated plants under drought conditions for the GR ecotype. The tolerant ecotype was benefited more by the beneficial microorganism treatment. The understanding of the genetic diversity of Q. ilex and water stress influence on the efficacy of biological treatments against root rot provides useful information to develop environmentally friendly disease control methods to address the holm oak decline.

Oak decline is a general term used for the progressive dieback and eventual mortality of oak trees due to many compounding stressors, typically a combination of predisposing, inciting, and contributing factors. While pinpointing individual causes of decline in oak trees is a challenge, past studies have identified site and stand characteristics associated with oak decline. In this study, we developed a risk map of oak decline for the Daniel Boone National Forest (DBNF), combining GIS, remote sensing (RS), and public reporting (citizen science, CS). Starting with ground reports of decline (CS), we developed a site-scale model (GIS and RS) for oak decline based on four previously identified predisposing factors: elevation, slope, solar radiation, and topographic wetness. We found that areas identified in the model as having a high oak decline risk also reflected areas of observed oak decline (CS). We then optimized and expanded this risk model to the entire range of the DBNF, based on both site characteristics (as piloted for the case study site) and stand inventory data. The stand inventory data (including species composition and age) further improved the model, resulting in a risk map at the landscape level. This case study can serve as a planning tool and highlights the potential usefulness of integrating GIS, remote sensing, and citizen science.

Holm oak populations are severely affected by oak decline syndrome, and reliable methods of conserving the plant material are required. A vitrification-based cryopreservation method was used for the first time for the long-term conservation of holm oak embryogenic cultures. Successful cryopreservation was achieved after determining the best developmental stage of the somatic embryos used and the optimal incubation period in plant vitrification solution 2 (PVS2). Embryos were recovered from individual nodular embryogenic structures (NES) derived from four embryogenic lines after preculture on a medium containing 0.3 M sucrose, incubation in PVS2 vitrification solution for 15 min at 25 °C and direct immersion in liquid nitrogen (LN). Embryo recovery rates of 16.7–63.3% were obtained after cryostorage for four years in LN. In addition to the embryo developmental stage and the PVS2 treatment time, the genotype can also significantly affect embryo recovery after LN storage. There were no significant differences in plant regeneration or polyploid stability between somatic embryos and plants derived from control embryos (not cryopreserved) and cryopreserved embryos. The findings indicate that embryo proliferation, plant conversion and polyploid stability are maintained in material recovered from the vitrification solution and subsequently cryopreserved. [ABSTRACT FROM AUTHOR]

In Portugal, the oak pinhole borer Platypus cylindrus and its mycobiota have been associated with cork oak (Quercus suber) death, but no knowledge exists regarding the associated bacterial community. However, it is known that some bacteria are important for ambrosia beetle symbiosis and play a role in oak tree health. To explore the bacteria associated with this beetle and its host, with the ultimate goal of highlighting potential roles in oak decline, this study used a culture‐dependent approach for strain isolation and phylogenetic identification using 16S rRNA gene sequencing and multilocus sequence analysis (MLSA). The bored galleries of different cork oak trees from a cork stand in Alentejo, together with the body and mycangia of adult beetles, were investigated. The samples revealed a diverse community comprising 500 isolates with 64 distinct types of bacterial colonies. Sixty‐eight strains were selected for sequencing and used for phylogenetic analysis, 40 from wood galleries and 28 from beetles. Thirty‐two genera of bacteria were identified, 18 of which were described for the first time within oak–beetle interactions. Major taxonomic groups were Actinobacteria in beetles and Enterobacterales in wood galleries. Although specific oak bacterial pathogens were not detected, a group of distinct strains detected in wood galleries, potentially belonging to a new Pectobacteriaceae species, were able to produce mild symptoms on cork oak plantlets. This study reports for the first time the biodiversity of culturable bacteria associated with the Q. suber–P. cylindrus interaction, their relevance to both organisms and the possible contribution to oak decline. [ABSTRACT FROM AUTHOR]

Structural dynamics of the shrub layer were analysed in a Hungarian oak forest after the serious oak decline pandemics. Vertical foliage distribution changed in the understory and a new subcanopy layer appeared below the oak canopy in the last decades. This paper focuses on the following questions: (1) how have the new foliage layer developed after oak decline? (2) Which woody species are the most frequent in this layer? (3) How have the mean sizes of these species changed? The forest association in the monitoring site is Quercetum petraeae-cerridis with Quercus petraea Matt. L. (sessile oak) and Quercus cerris L. (Turkey oak). The site was subdivided into 144 permanent subplots. Woody individuals were classified as subcanopy trees between 8.0-13.0 m in height. Measured structural parameters were carried out in the period 1982-2017. Three woody species, Acer campestre L. (field maple), Acer tataricum L. (Tatar maple) and Cornus mas L. (European cornel) played a key role in the new layer and their height was between 8.0-13.0 m or higher than 13.0 m. The density of species in this layer increased considerably between 1982 and 2002. The most frequent woody species was A. campestre. The mean height, diameter and mean cover of the dominant woody species increased significantly after the decreasing oak density. Our results suggest that the mixed oak forest responded to oak decline with significant structural rearrangement in the shrubs and three woody species compensated for the remarkable foliage loss in the canopy. These species formed a new subcanopy layer. [ABSTRACT FROM AUTHOR]

Objective During 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 methods Sampling 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. Results Based 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. Conclusions In 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. [ABSTRACT FROM AUTHOR]

The dehesa is a traditional agrosilvopastoral ecosystem characterized by a savanna-like structure. It has been in decline since the middle of the last century, in particular in agricultural environments where it has been relegated to isolated forests. This paper presents a study into the reduction over the past 50 years. One of the main causes of this decline has been identified as xylophagous insects, specifically the wood borer Cerambyx welensii Kuster (Coleoptera: Cerambycidae). Based on estimations in both the population size, using Jolly Seber models, and the level of tree injury, using a single-index model, the study investigates the role the insect has played in the decline of the dehesa. Surface area loss was found to be greater than 50%, while canopy cover has diminished linearly over the period studied, with the risk of disappearance of the woodland increasing in the same magnitude as borer population density. The highest wood borer population densities observed corresponded to stands with an average canopy cover loss of 1.68% a year, indicating a risk of completely losing the forest cover in the short term (10–30 years). The proposed tree injury index was successful in categorizing the size of the insect population, and seems to be a useful indicator for describing the relationship between the two variables. According to this indicator, woodlands with more than 10% of trees with severe or very severe injuries are at risk. Follow-up work should be undertaken to investigate long-term demographic changes in wood borer populations, and management practices should be developed to reduce the population size, minimize forest loss and preserve these relict oak trees in unconnected landscapes. [ABSTRACT FROM AUTHOR]

Key Message: The patterns of induced chemical defences in Quercus ilex leaves are specific to the biotic stress factor that causes them. Interactive effects between stressors depend on provenance. Quercus forests are suffering serious decline worldwide, closely linked to the consequences of climate change. The increase of biotic stressors threatens the survival of the holm oak (Quercus ilex), a dominant tree species in the Mediterranean Basin. A better understanding of its resistance mechanisms is urgently required to enable a better control of its decline. In this work, the ability of holm oaks from six Iberian provenances to respond to multiple biotic damage is studied through an analysis of their induced chemical defence patterns. Using 2016 seedlings established in a common garden trial (6 regions × 12 families/region × 7 seedlings/family × 4 treatments), biotic damage was induced at the root level (by infection with the widespread pathogen Phytophthora cinnamomi) and at the above-ground level (by mechanical defoliation). The levels of constitutive and induced total phenols, total tannins and condensed tannins were measured. Results showed that (1) the defensive chemical patterns present significant local and geographical variation, (2) survival to stress is more related to constitutive defences than induced ones, (3) the induced response is stressor-specific, and (4) there is an interactive effect amongst stressors whose sign (induction/inhibition) depends on the provenance. These findings on biotic stressor effects on the chemical defences and survival of holm oak can contribute to the development of genetic material selection programs in the integrated control of the widespread decline of Quercus. [ABSTRACT FROM AUTHOR]

The oak decline phenomenon, causes crown dieback, decreasing the radial growth and eventually the death of oak trees. The first step to control this phenomenon is conduction a management program. Identification of the factors which are related to oak decline, is a key factor in management of this phenomenon in Zagros oak forests. The aim of this study was collecting and identifying the oak borer beetles in the forests of Gilane Gharb region in southwestern of Kermanshah province. The required data were obtained by direct observation and field sampling. The samples were collected based on a systematic sampling pattern in 90 square plots (50* 50 m) and all trees were surveyed in each plot. The borer beetles were collected by splitting the dried branches, cutting the trunk and branches and keeping them in a proper condition. In this study, the damage symptoms from the borer beetles were observed on 61.3% of oak trees. The collected buprestid borer beetles on the oak trees were identified as following: Acmaeodera (Acmaeotethya) degener (Scopoli, 1763), Acmaeodera (Acmaeotethya) ottomana (Frivaldszky von Frivald, 1840), Acmaeodera (Acmaeotethya) undulata (Abeille de Perrin, 1891), Acmaeodera (Acmaeodera) wethloi (Obenberger, 1940), Acmaeoderella (Carininota) impunctata (Abeille de Perrin, 1891), Capnodis anthracina (Fischer, 1830), Capnodis cariosa hauseri (Obenberger, 1928), Chalcophorella (Stigmatophorella) bagdadensis (Laporte & Gory, 1836), Chalcophorella (Stigmatophorella) escalerae (Abeille de Perrin, 1904), Perotis lugubris longicollis (Kraatz, 1880), Svatactesis johanidesi (Bily, 1997). The most abundant species were P. lugubris, C. cariosa, A. undulata and A. wethloi, respectively. [ABSTRACT FROM AUTHOR]

Information about the occurrence of shrubby individual's relation with oak decline is fundamental to developing knowledge from forest stand. This paper focuses on the following questions: (1) how are the shrub's occurrences changed after oak decline? (2) Which shrubs have the highest occurring in the subplots? The mixed oak stand is located in the Bükk Mountains of Hungary. The monitoring plot (48 m × 48 m) was subdivided into 144 permanent subplots; the measured parameter was observed in the period 1972-2017. The shrub layer was divided into low (< 1.0 m in height) and high (= 1.0 m) layer. High shrub specimens were randomly distributed and had become more homogeneous by 2017; there was no subplot with 10 or more specimens in the last decade. In the subplots the policormon forming shrubs were present with a higher occurrence. Correlation analysis showed that occurrence of Acer tataricum, Cornus mas and Euonymus verrucosus in the high and Cornus sanguinea and Ligustrum vulgare in the low shrub layer changed significantly after the oak decline. High shrubs with the highest occurrence were E. verrucosus and C. mas. The most occurrent low shrub species were E. verrucosus and L. vulgare. Our results suggest that after the oak decline the most shrubs' occurrence decreased considerably and the distribution was more homogeneous. [ABSTRACT FROM AUTHOR]

Holm oak populations have deteriorated drastically due to oak decline syndrome. The first objective of the present study was to investigate the use of axillary budding and somatic embryogenesis (SE) to propagate asymptomatic holm oak genotypes identified in disease hotspots in Spain. Axillary budding was achieved in two out of six tolerant genotypes from the south-western region and in two out of four genotypes from the Mediterranean region. Rooting of shoots cultured on medium supplemented with 3 mg L−1 of indole-3-acetic acid plus 0.1 mg L−1 α-naphthalene acetic acid was achieved, with rates ranging from 8 to 36%. Shoot cultures remained viable after cold storage for 9–12 months; this procedure is therefore suitable for medium-term conservation of holm oak germplasm. SE was induced in two out of the three genotypes tested, by using nodes and shoot tips cultured in medium without plant growth regulators. In vitro cloned progenies of the tolerant genotypes PL-T2 and VA5 inhibited growth of Phytophthora cinnamomi mycelia when exposed to the oomycete in vitro. Significant differences in total phenol contents and in the expression profiles of genes regulating phenylpropanoid biosynthesis were observed between in vitro cultured shoots derived from tolerant trees and cultures established from control genotypes. [ABSTRACT FROM AUTHOR]

Thanks to their ability to generate ecosystem services, forest ecosystems have a significant social, economic and environmental impact on the development of many regions in the world, especially those located in urban and peri-urban areas. Today, increased forest vulnerability is reflected in an increased number of episodes of severe decline associated mainly with drought. In this context, the Mediterranean area shows high forest vulnerability and a subsequent decline in its natural renewal rate. In this scenario, the aim of this research is to assess the sustainability of a protected pristine deciduous oak forest near Rome via the development of a forest health condition monitoring tool based on the application of multispectral satellite data and the identification of silvicultural models suitable to promoting natural forest renewal. Data and results from research in the case study area, the Natural State Reserve of Castelporziano (Rome), have potential as an important decision making tool in sustainable forest management.

Brenneria goodwinii, Rahnella victoriana and Gibbsiella quercinecans are three bacterial species frequently isolated together from oak displaying symptoms of Acute Oak Decline (AOD), which include weeping patches on trunks. All three bacterial species play a role in lesion formation in the current episode of AOD in Britain, although B. goodwinii is the most dominant. The ongoing research into stem lesion formation characteristic of this polybacterial syndrome has been focussed primarily on the pathogenicity, identification and taxonomy of these bacteria. As all three species were newly classified within the past ten years, there are many unanswered questions regarding their ecology and interactions with each other. To determine the effect of bacterial interactions on fitness in vitro, we examined pairwise (diculture) and multispecies (triculture) interactions between B. goodwinii, R. victoriana and G. quercinecans in oak leaf media microcosms. Additionally, the effect of co-culturing on the evolution of these species was determined and the evolved B. goodwinii strains were examined further by whole genome sequencing. Our results indicate that B. goodwinii thrived in monoculture with significantly higher viable cell counts than the other two species. Additionally, B. goodwinii performed well in pairwise culture with mutually competitive interactions observed between B. goodwinii and R. victoriana, and between B. goodwinii and G. quercinecans. In the multispecies triculture, B. goodwinii and R. victoriana appeared to exhibit co-ordinated behaviour to outcompete G. quercinecans. After four weeks B. goodwinii grown in co-culture with the other two species developed greater evolved fitness than the strain grown in monoculture as reflected by the increased viable cell counts. The competitive interactions taking place between the threes species indicated evolving improved fitness of B. goodwinii in vitro, that gave it a growth advantage over both R. victoriana and G. quercinecans which showed no significant changes in fitness. Overall, B. goodwinii gains greater benefit in terms of fitness from in vitro competitive interaction with the other two species.

The first and most important issue in forest drought management is knowledge of the location and severity of forest decline. In this regard, we used geostatistics and artificial neural network methods to map the dieback intensity of oak forests in the Ilam province, Iran. We used a systematic random sampling with a 250 × 200 m grid to establish 100 plots, each covering 1200 m2. The percentage of the declined trees in each plot was measured and recorded. Also, a composite soil sample was extracted from the center and the four corners of each plot in order to determine their physical and chemical properties. After examining the normality of the data, the dieback intensity map was made using interpolation methods and the artificial neural network. The results showed that the best method for dieback intensity estimation was the artificial neural network with an accuracy of 85 %, by using the multilayer perceptron algorithm. Oak decline was found to be mainly related to the slope, soil moisture, soil organic content and soil bulk density.

Although forest areas have been growing in Europe, some forest types have been declining regionally. Since the 1980 s, there have been reports of defoliation and mortality in evergreen oak woodlands of the Iberian Peninsula. However, long-term and large-scale trends of Iberian oak decline are still poorly understood. We quantified trends in canopy cover for cork oak (Quercus suber) and holm oak (Q. rotundifolia) woodlands in mainland Portugal for a 50 year period (1965 to 2015). We considered loss of canopy cover a proxy of forest degradation and asked how it changed over time, in association with human activity and climate. Between 1965 and 2015, both cork oak and holm oak canopy cover showed declining trends (57.9% and 71.1% of sampling points, respectively). Canopy cover dynamics, however, differed across time. Between 1965 and 1990, canopy cover gains (over 35% of sampling points) prevailed over losses (under 20%), with larger differences for cork oak than holm oak. Between 1990 and 2015, canopy cover losses (over 70% of sampling points) were much higher than gains (under 9%). Oak canopy cover decrease was associated with flatter areas (usually having more intensive land use) for both oak species, higher cattle numbers (holm oak only) and higher mean temperature (cork oak only). Contrastingly, loss of holm oak canopy cover seems to have occurred in less hot and dry regions that enable more intensive land uses. Active restoration is urgently needed to reverse the current decline in canopy cover in Mediterranean evergreen oak woodlands. [ABSTRACT FROM AUTHOR]

Key message: The physical and chemical properties of soil are not a determinant of oak decline. Under stress, trees keep their vital activities by changing their physiological performance. The phenomenon of oak decline has been reported widely in various regions in the world. Although, many studies have addressed this problem, further studies are required to accurately identify the influencing factors. In this regard, we measured and analyzed some physiochemical properties of soil and some ecophysiological attributes of oak trees in different classes of dieback in Zagros Forest. We also used the Standardized Precipitation Evapotranspiration Index (SPEI) to determine the occurrence of drought in the study site. The findings indicated that dead trees and trees with a high rate of dieback were mostly present in soils with heavy texture. Besides, a significant difference in malondialdehyde (MDA) was found in various dieback classes. Moreover, with increasing dieback, the content of Ca in the leaf increased and the N/P ratio decreased. In these conditions, oak trees change their absorption and consumption of required elements. [ABSTRACT FROM AUTHOR]

Interactions among plant species and their soil biota drive plant–soil feedbacks (PSFs) that play a major role in the dynamics and diversity of plant communities. Among the different components of the soil community, pathogens are considered to be the main drivers of negative PSFs. Despite this, the number of studies that have experimentally quantified the contribution of soil pathogens to PSFs remains considerably low. Here we conducted a greenhouse experiment with oomycete‐specific fungicide to quantify the contribution of soil pathogens, and particularly oomycete pathogens, to individual and pairwise PSFs in forest communities. We used as a case study Mediterranean mixed forests dominated by Quercus suber and invaded by the oomycete pathogen Phytophthora cinnamomi. The fungicide treatment was crossed with a competition treatment to explore how conspecific neighbors might modify pathogen effects. To place the results of the experiment in a wider context, we also conducted a systematic review of published papers that explicitly used fungicide to explore the role of pathogens in PSF experiments. Our experimental results showed that oomycete pathogens were the main drivers of individual PSFs in the study forests. Oomycete effects varied among tree species according to their susceptibility to P. cinnamomi, driving negative PSFs in the highly susceptible Q. suber but not in the coexistent Olea europaea. Oomycete‐driven PSFs were not modified by intraspecific competition. Oomycete pathogens were also major contributors to negative pairwise PSFs assumed to promote species coexistence. Results from the systematic review supported the novelty of our experimental results, since only three studies had previously used oomycete‐specific fungicide in a PSF context and none in systems invaded by exotic oomycetes. Overall, our results provide novel evidence of oomycete pathogens (including the exotic P. cinnamomi) as fundamental drivers of negative individual and pairwise PSFs with implications for species coexistence in invaded communities. Although in the short‐term invasive pathogens might contribute to species coexistence by causing self‐limitation in dominant species, strong inter‐specific variation in self‐limitation might undermine coexistence in the long‐term. Because of the increasing number of exotic oomycetes worldwide, further attention should be given to oomycetes as drivers of PSFs in plant communities. [ABSTRACT FROM AUTHOR]

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The presence of Cryphonectria parasitica (Murrill) M.E. Barr was studied in six natural and planted stands of sweet chestnut in Serbia. The fungus was detected on the sweet chestnut in five localities and on the sessile oak in one locality. In total, 77 isolates from the sweet chestnut and five isolates from the sessile oak were obtained. Based on the culture morphology, all the obtained isolates were proven to be free from Cryphonectria (Saccardo) Saccardo & D. Saccardo hypovirus. The isolates of C. parasitica from the sweet chestnut were compatible with three different vegetative compatibility types, EU-12, EU-2, and EU-1, while the isolates from the sessile oak belonged to EU-12. After inoculation in laboratory conditions, the isolate from the sweet chestnut and sessile oak caused the decline in 88 and 76% of the sweet chestnut plants, respectively. In the case of the sessile oak, both isolates caused the decline in 52% of the plants. In field conditions, both isolates were aggressive to sessile oak trees after previous bark wounds and they were statistically significantly different compared to the control trees. The isolate from the sweet chestnut caused significantly larger cankers compared to both the isolate from the sessile oak and the control.

Oak decline presenting symptoms of tracheomycosis have been observed globally over long periods of time. Since the 1990s, oak decline has been considered to be a multifactorial process where abiotic predisposing factors play a significant role. Nevertheless, biotic factors, such as subcortical insects and fungal pathogens, may influence the decline process, as some insect species transmit spores of tracheomycotic pathogens. We investigated biotic agents (subcortical insects, Ophiostoma spp. and Phytophthora spp.) in six declining oak stands located within mesophytic and thermophytic zones in the Czech Republic, where five dry years occurred from 2015 to 2019. The spectrum of insect pests of oak stands was investigated using two methods: reared from logs from each stand and window traps. The presence of Ophiostoma fungi was assessed from cultivated woodblocks; Phytophthora pathogens were isolated from soil samples. In total, 2931 subcortical insect individuals were captured during the 2021 vegetation period. The most species-rich group of the subcortical insect complex involved in oak decline consisted of the families Cerambycidae: Xylotrechus antilope; Curculionidae: Scolytus intricatus, Xyleborus monographus; and Buprestidae: Agrilus biguttatus, A. sulcicollis. The presence of Ophiostoma was detected in all stands with different intensities between tree parts. Several important oak pests were positively correlated with the occurrence of Ophiostoma. On the contrary, from all soil samples, Phytophthora plurivora was found at only one studied oak stand. Based on the results, a new modified model of biotic and abiotic factors involved in the oak decline is proposed.

An increase in tree mortality rates as a consequence of biotic disturbances has been detected worldwide. Biotic disturbances in forests might cause significant impacts at ecosystem-level, with strong effects on soil biological activity and organic matter transformation. However, very few empirical studies have explored to date the consequences of biotic disturbances for soil microbial communities and C and N cycles. Here, we assessed the effects of Quercus suber dieback, caused by the exotic root pathogen Phytophthora cinnamomi, on the soil microbial community and key components of the C and N cycle. We used a spatially explicit neighborhood approach to analyze the effects of Q. suber trees with different health status and non-declining coexistent species on soil variables. The study was replicated in the two main Q. suber forest types of the region (closed forests and open woodlands) with contrasting soil texture characteristics. Pathogen-induced tree dieback did not affect microbial functional diversity or biomass, but translated into lower soil microbial respiration. Tree mortality induced changes in several variables of the C and N cycle, but the sign and magnitude of these effects varied depending on the local characteristics of soil texture. Coexistent species differed strongly from Q. suber in their effects on the C and N cycle. Overall, our results show that tree dieback due to invasive pathogens translates into complex short- and long-term effects on different components of the C and N cycles, despite no effects on microbial functional diversity and biomass. [ABSTRACT FROM AUTHOR]