The research, published in the journal Biogeosciences, was carried out at the Leipzig Canopy Crane, a research facility operated by the German Centre for Integrative Biodiversity Research (iDiv) in one of the largest remaining floodplain hardwood forests in Central Europe. The site, located in the floodplain of the Elster, Pleiße, and Luppe rivers near Leipzig, Germany, is dominated by sycamore maple, common ash, English oak, and hornbeam, and hosts a continental climate with an annual mean temperature of 9.7 degrees Celsius. From March 2019 to February 2020, a team of researchers led by Ettore Fedele of Leipzig University and Swansea University, together with colleagues from Justus Liebig University Giessen and iDiv, collected passive air samples every week at three different heights above the forest floor: 3, 15, and 28 meters. Nine Durham-type spore traps, each fitted with a sterile Petri dish coated in a thin layer of Vaseline, were deployed across three sampling stations separated by 40 to 60 meters, capturing whatever fungal material the air delivered.

Rather than relying on microscopy, which can identify only a fraction of airborne fungi, the team turned to DNA metabarcoding of the fungal internal transcribed spacer (ITS) region, a genetic barcode widely used to distinguish fungal species. DNA was extracted from the collected samples, amplified with three different primer combinations chosen to maximize taxonomic coverage, and sequenced on an Illumina MiSeq platform. The resulting reads were processed with the DADA2 pipeline, which infers exact amplicon sequence variants with single-nucleotide resolution, and taxa were assigned using the IDTAXA classifier against the UNITE database, supplemented by BLASTN searches against the NCBI reference database. After quality filtering and removal of contaminants and low-abundance variants, the final dataset comprised more than 1.4 million fungal sequencing reads and 760 distinct sequence variants, providing an unusually rich census of the forest’s aerial mycobiome.

The results paint a clear taxonomic picture. Ascomycota, the most species-rich fungal phylum, dominated the airborne community with 74.3 percent of all reads, followed by Basidiomycota at 25.1 percent, with all remaining phyla together accounting for less than one percent. Three genera stood out as the consistent workhorses of the air: Cladosporium, which alone made up 30.52 percent of total reads, Epicoccum at 11.58 percent, and Alternaria at 5.62 percent. All three belong to the class Dothideomycetes and are familiar names in aerobiology, not least because they rank among the best-known triggers of allergic reactions and plant diseases worldwide. Their dominance in the Leipzig air mirrors patterns reported from other temperate environments, from Havana to Salamanca to Bratislava, underscoring how consistent the major players in the airborne fungal world are across regions.

The study’s central finding concerns temperature. When the researchers compared community composition across the twelve monthly sampling periods using permutational multivariate analysis of variance, average air temperature emerged as the only meteorological variable significantly correlated with shifts in the fungal aerosol community. Neither humidity, which ranged from 50.3 percent in June to 84.3 percent in December, nor rainfall, nor wind speed showed significant associations. When the team split the year into warm and cold months around the study period’s mean temperature of 13.29 degrees Celsius, a striking pattern emerged: Ascomycota became significantly more abundant during warmer months, while Basidiomycota dominated the colder ones. Wilcoxon rank-sum tests confirmed both differences were highly significant. The three dominant genera all peaked in summer, with Cladosporium reaching its maximum in July and Epicoccum and Alternaria in August, while the basidiomycete yeasts Vishniacozyma and Itersonilia peaked in January, the coldest month of the study.

Digging deeper with differential abundance analysis, the researchers identified 68 sequence variants belonging to 66 different genera, roughly 21 percent of the genera analyzed, whose abundance shifted significantly with seasonal temperature. Nearly 40 percent of Ascomycota genera responded positively to warmer conditions, whereas only 15 percent of Basidiomycota genera did so. Among the temperature-responsive taxa were several of considerable practical concern. The genus Erysiphe showed the strongest positive response to warming, and one variant was identified as Erysiphe alphitoides, the invasive pathogen responsible for oak powdery mildew, a disease that poses a significant threat to forest health and productivity across Europe. The dataset also contained Zymoseptoria tritici, a major pathogen of wheat, suggesting that nearby agricultural areas contribute fungal propagules to the forest air. On the allergen front, the summer peaks of Cladosporium and Alternaria, both potent respiratory allergens linked to asthma exacerbations, align with earlier work connecting these genera to high temperatures and low humidity.

One of the study’s more surprising results was what it did not find: any meaningful vertical structure in the fungal community. Despite sampling at heights spanning 25 meters, from near the ground to the upper canopy, neither trap height nor sampling location had a significant effect on fungal diversity, and height explained only a trivial two percent of the variation in community composition. The researchers attribute this to the continuous turbulent mixing of air within the planetary boundary layer, the lowest part of the atmosphere, which effectively homogenizes airborne particles across altitudes below the canopy top. Backward air-mass trajectory modeling using the HYSPLIT system confirmed that air arriving at the three sampling heights followed substantially overlapping paths, indicating that the fungi collected at different elevations originated from the same regional sources. This finding contrasts with studies in the Amazon rainforest, where bioaerosol concentrations declined markedly from understory to above the canopy, and highlights how boundary-layer dynamics can override the vertical stratification of source communities on the forest floor.

The team also defined a core mycobiome for the site: 27 sequence variants that appeared in every single sample collected throughout the year, representing the constant airborne fungal background of the Leipzig floodplain forest. At the class level, this core community was composed of Dothideomycetes, Tremellomycetes, Agaricomycetes, and Leotiomycetes, drawing members from both major fungal phyla. Establishing such a baseline matters, the authors argue, because knowing the stable background community makes it easier to identify local sources of bioaerosols and to separate their signal from the effects of external drivers such as weather and climate. Interestingly, the dataset also included taxa previously reported mainly outside Europe, such as Alanphillipsia aloetica, originally described from South Africa, a reminder that airborne fungal communities are shaped by long-distance dispersal as well as local sources.

The implications extend well beyond one forest. Because bioaerosols make up more than ten percent of atmospheric particulate matter, influence cloud formation and the hydrological cycle, and serve as sensitive indicators of ecosystem change, understanding what controls their composition is essential for predicting how ecosystems and human health will fare under climate change. The temperature-driven patterns documented here suggest that as summers warm, allergenic and pathogenic ascomycetes may become increasingly prominent in the air we breathe, with consequences for respiratory health, crop disease pressure, and forest management costs. The authors caution, however, that temperature effects on aerosol dynamics are entangled with temperature effects on the phenology of the source species themselves, making it difficult to disentangle direct influences on spore release from indirect effects mediated through fungal life cycles and host plant development.

For that reason, the researchers emphasize that a single year, however intensively sampled, is only a beginning. They call for multi-year monitoring with higher temporal resolution, potentially separating daytime and nighttime periods to capture the influence of diel temperature fluctuations, boundary-layer dynamics, and spore-release phenology. Such extended records would allow scientists to determine whether the temperature-mediated shifts in fungal abundance and composition observed at Leipzig persist or intensify under continuing climate change and increasingly frequent extreme events. In the meantime, the study stands as the first comprehensive assessment of meteorological influences on airborne fungi across seasonal cycles in a Central European floodplain forest, and as a benchmark against which future changes in the air’s invisible fungal cargo can be measured. The raw sequencing data have been deposited in the European Nucleotide Archive, ensuring that this aerial census of a hidden world remains open to the researchers who will build upon it.

Subject of Research: Seasonal dynamics of airborne fungal communities in a temperate floodplain forest assessed by DNA metabarcoding

Article Title: Unlocking the air: DNA metabarcoding sheds light on seasonal fungal dynamics in a temperate floodplain forest

Article References: Fedele, E., Müller, C. M., Wissemann, V., Gemeinholzer, B., Wirth, C., & Sánchez-Parra, B. (2026). Unlocking the air: DNA metabarcoding sheds light on seasonal fungal dynamics in a temperate floodplain forest. Biogeosciences, 23(19), 6931-6945. https://doi.org/10.5194/bg-23-6931-2026

Image Credits: AI Generated

DOI: 10.5194/bg-23-6931-2026

Keywords: airborne fungi, DNA metabarcoding, bioaerosols, floodplain forest, seasonal dynamics, temperature, Ascomycota, Basidiomycota, Cladosporium, allergens, plant pathogens, climate change