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1. Does Emerald Ash Borer Infestation Alter Ash Phloem Microbial Communities Over Time?

   https://doi.org/10.1094/PBIOMES-06-25-0046-R  

   Mann, Andrew J; Mogouong, Judith T; Showlater, David N; Held, Benjamin W; Bushley, Kathryn E; Blanchette, Robert A (December 2025, Phytobiomes Journal)

   The emerald ash borer (EAB), Agrilus planipennis, is a destructive invasive insect of North American ash (Fraxinus). While microorganisms associated with the beetle may contribute to tree decline and death, the microbial community succession during an EAB attack is unknown. We repeatedly sampled the bottom two meters of green ash (Fraxinus pennsylvanica) and black ash (Fraxinus nigra) in seven stands across an infestation gradient over four years. Amplicon libraries were sequenced from control phloem tissue of trees showing no symptoms of infestation, uninfested phloem of trees with EAB, infested phloem (galleries), frass, and larvae to determine if there are shifts in the fungal and bacterial communities as trees succumb to EAB attack. We found that the control phloem communities significantly differed from the beetle-infested phloem in both tree species. Furthermore, as EAB progressed in its attack from the top limbs to the tree’s base, the microbial communities in uninfested phloem outside the galleries shifted away from communities in phloem of control trees. In infested phloem, more than 80% of the detected taxa were absent from control trees (i.e., most taxa were non-latent). However, the relative abundance of latent taxa in infested phloem was higher than the relative abundance of the non-latent taxa, especially for potential canker-causing fungi, which increased 21-fold and 32-fold in black ash and green ash trees, respectively. These findings provide valuable insight into how a woodboring beetle shapes the microbial environment within trees over time, influencing the overall microbial diversity, such as canker-causing and wood decay taxa. 

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2. Population dynamics of ash across the eastern USA following invasion by emerald ash borer

   https://doi.org/10.1016/j.foreco.2020.118574  

   Ward, Samuel F.; Liebhold, Andrew M.; Morin, Randall S.; Fei, Songlin (January 2021, Forest Ecology and Management)

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3. Phases in fine volcanic ash

   https://doi.org/10.1038/s41598-023-41412-x  

   Hornby, Adrian; Gazel, Esteban; Bush, Claire; Dayton, Kyle; Mahowald, Natalie (September 2023, Scientific Reports)

   Abstract Volcanic ash emissions impact atmospheric processes, depositional ecosystems, human health, and global climate. These effects are sensitive to the size and composition of the ash; however, datasets describing the constituent phases over size ranges relevant for atmospheric transport and widely distributed impacts are practically nonexistent. Here, we present results of X-ray diffraction measurements on size-separated fractions of 40 ash samples from VEI 2–6 eruptions. We characterize changes in phase fractions with grainsize, tectonic setting, and whole-rock SiO₂. For grainsizes < 45 μm, average fractions of crystalline silica and surface salts increased while glass and iron oxides decreased with respect to the bulk sample. Samples from arc and intraplate settings are distinguished by feldspar and clinopyroxene fractions (determined by different crystallization sequences) which, together with glass, comprise 80–100% of most samples. We provide a dataset to approximate glass-free proportions of major crystalline phases; however, glass fractions are highly variable. To tackle this, we describe regressions between glass and major crystal phase fractions that help constrain the major phase proportions in volcanic ash with limited a priori information. Using our dataset, we find that pore-free ash density is well-estimated as a function of the clinopyroxene + Fe-oxide fraction, with median values of 2.67 ± 0.01 and 2.85 ± 0.03 g/cm³for intraplate and arc samples, respectively. Finally, we discuss effects including atmospheric transport and alteration on modal composition and contextualize our proximal airfall ash samples with volcanic ash cloud properties. Our study helps constrain the atmospheric and environmental budget of the phases in fine volcanic ash and their effect on ash density, integral to refine our understanding of the impact of explosive volcanism on the Earth system from single eruptions to global modeling. 

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4. Wildfire Ash Composition and Engineering Behavior

   https://doi.org/10.1061/JGGEFK.GTENG-11683  

   Wirth, Xenia; Antunez, Vanessa; Enriquez, Dezire; Arevalo, Zuleyma; Kanaan, Ramzieh (June 2024, Journal of Geotechnical and Geoenvironmental Engineering)

   After a wildfire event, ash is a newly formed surficial soil layer with microscale properties such as roughness, morphology, and chemical composition that may impact how ashes form fabrics in situ and so affect the overall hydrological conditions of a burned area (infiltration capacity, permeability, etc.). To examine the effects of ash microscale properties on macroscale behavior, eight wildfire ash samples from California were characterized physically (specific gravity, specific surface area, particle size, etc.), chemically (elemental composition, organic and inorganic carbon content, etc.), and geotechnically (strength, compaction, saturated hydraulic conductivity, etc.). The tested ashes were found to contain predominantly organic unburned carbons and carbonates derived from the combustion of calcium-oxalate rich fuels in temperatures likely ranging from 300°C to 500°C. Ashes had high specific surface areas because morphologically, particles had highly texturized and porous surfaces. Additional water was necessary to coat the particle surfaces, which led to high liquid limits and compaction optimum moisture contents. Hydraulic conductivity values were within range for silty sands (10^−5–10^−3  cm/s), and specimens had friction angles near 30°. However, tested ashes consistently demonstrated high void ratios and low bulk densities during testing for strength, hydraulic conductivity, and compaction. These anomalies were attributed to unusual carbonate morphologies; the high interparticle friction of these phases allowed ashes to form looser fabrics than a typical silty sand and contributed to the measured high void ratios, low maximum dry unit weights, and high friction angles. Overall, we hypothesize that the relative amounts of inorganic versus organic constituents in our wildfire ash samples affected how the ashes formed fabrics and so affected their geotechnical properties. 

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5. The Role of Phenylpropanoids and the Plant Microbiome in Defences of Ash Trees Against Invasive Emerald Ash Borer

   https://doi.org/10.1111/pce.15534  

   Zhang, Bin; Koski, Tuuli‐Marjaana; Wang, Hualing; Chen, Zhenzhu; Li, Huiping; Mogouong, Judith; Bushley, Kathryn E; Xing, Longsheng; Sun, Jianghua (August 2025, Plant, Cell & Environment)

   ABSTRACT Plants have coevolved with herbivorous insects for millions of years, resulting in variation in resistance both within and between species. Using a manipulative experiment combined with untargeted metabolomics, microbiome sequencing and transcriptomics approaches, we investigated the roles of plant metabolites and the microbiome in defence mechanisms in native resistant Manchurian ash (Fraxinus mandshurica) trees and non‐native susceptible velvet ash (Fraxinus velutina) trees against the highly invasive emerald ash borer (EAB,Agrilus planipennis). Comparative transcriptomics and metabolomics analyses show that the phenylpropanoid pathway, which is enriched in differentially expressed genes and differentially abundant metabolites, may serve as a potential regulator of resistance. Additionally, the microbiome is distinctly shifted in two ash species. Indicator taxa analysis reveals that the distinct genera are dominant in the galleries of two ash species, for example,Pseudomonasin velvet, andHafnia‐Obesumbacteriumin Manchurian. The strong correlation between indicator taxa and metabolites suggests that the chemical compounds might impact the microbial community in phloem directly or indirectly, or vice versa. This study significantly enhances our understanding of the variation in resistance between ash species and its contribution to the invasion success of EAB, providing valuable insights for the development of pest management strategies. 

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