Molecular screening of microorganisms associated with discolored wood in dead European beech trees suffered from extreme drought event using next generation sequencing

Drought events weaken trees and make them vulnerable to attacks by diverse plant pathogens. Here, we propose a molecular method for fast screening of microorganisms associated with European beech decline after an extreme drought period (2018) in a forest of Thuringia, Germany. We used Illumina sequencing with a recent bioinformatics approach based on DADA2 to identify archaeal, bacterial, and fungal ASVs (amplicon sequence variants) based on bacterial and archaeal 16S and fungal ITS genes. We show that symptomatic beech trees are associated with both bacterial and fungal plant pathogens. Although the plant pathogen sequences were detected in both discolored and non-discolored wood areas, they were highly enriched in the discolored wood areas. We show that almost each individual tree was associated with a different combination of pathogens. Cytospora spp. and Neonectria coccinea were among the most frequently detected fungal pathogens, whereas Erwinia spp. and Pseudomonas spp. were the dominant bacterial plant pathogens. We demonstrate that bacterial plant pathogens may be of major importance in beech decline

Habitat properties are key drivers of Borrelia burgdorferi (s.l.) prevalence in Ixodes ricinus populations of deciduous forest fragments

Background: The tick Ixodes ricinus has considerable impact on the health of humans and other terrestrial animals because it transmits several tick-borne pathogens (TBPs) such as B. burgdorferi (sensu lato), which causes Lyme borreliosis (LB). Small forest patches of agricultural landscapes provide many ecosystem services and also the disservice of LB risk. Biotic interactions and environmental filtering shape tick host communities distinctively between specific regions of Europe, which makes evaluating the dilution effect hypothesis and its influence across various scales challenging. Latitude, macroclimate, landscape and habitat properties drive both hosts and ticks and are comparable metrics across Europe. Therefore, we instead assess these environmental drivers as indicators and determine their respective roles for the prevalence of B. burgdorferi in I. ricinus. Methods: We sampled I. ricinus and measured environmental properties of macroclimate, landscape and habitat quality of forest patches in agricultural landscapes along a European macroclimatic gradient. We used linear mixed models to determine significant drivers and their relative importance for nymphal and adult B. burgdorferi prevalence. We suggest a new prevalence index, which is pool-size independent. Results: During summer months, our prevalence index varied between 0 and 0.4 per forest patch, indicating a low to moderate disservice. Habitat properties exerted a fourfold larger influence on B. burgdorferi prevalence than macroclimate and landscape properties combined. Increasingly available ecotone habitat of focal forest patches diluted and edge density at landscape scale amplified B. burgdorferi prevalence. Indicators of habitat attractiveness for tick hosts (food resources and shelter) were the most important predictors within habitat patches. More diverse and abundant macro- and microhabitat had a diluting effect, as it presumably diversifies the niches for tick-hosts and decreases the probability of contact between ticks and their hosts and hence the transmission likelihood.[br/] Conclusions: Diluting effects of more diverse habitat patches would pose another reason to maintain or restore high biodiversity in forest patches of rural landscapes. We suggest classifying habitat patches by their regulating services as dilution and amplification habitat, which predominantly either decrease or increase B. burgdorferi prevalence at local and landscape scale and hence LB risk. Particular emphasis on promoting LB-diluting properties should be put on the management of those habitats that are frequently used by humans. In the light of these findings, climate change may be of little concern for LB risk at local scales, but this should be evaluated further

Comparing fungal richness and community composition in coarse woody debris in Central European beech forests under three types of management.

Managing forests by selection cutting is a promising silvicultural technique for maintaining forest biodiversity. Despite the importance of fungi in decomposition and nutrient cycling in forest ecosystems, no study to date has investigated the effects of selection cutting on fungal communities, especially using a culture-independent molecular technique to assess more than just the species that are fruiting at the time of sampling. Based on operational taxonomic units (OTUs) found in coarse woody debris, we compared the richness and community composition of wood-inhabiting fungi from selection cutting, age-class, and unmanaged European beech-dominated forests. We found that fungal OTU richness in selection cutting and unmanaged forests was not significantly different (P > 0.05), but it was higher, in both cases, than that in the age-class forest (P = 0.0002). Fungal community composition was not significantly different among the three forest types (P > 0.05). Abundances of common, wood-inhabiting fungal OTUs in different forest types were significantly correlated: the highest and lowest correlations were found between unmanaged forests and selection cutting (ρ = 0.52, P < 0.0001, n = 94), and between unmanaged and age-class forests (ρ = 0.30, P = 0.0080, n = 79), respectively. © 2014 German Mycological Society and Springer-Verlag Berlin Heidelberg