Biology subjects

Joukhajian, A.

Publications and source records attributed to Joukhajian, A..

3 recordsLinked to original sources

bioRxiv2026

Microbial association networks reveal hidden keystone taxa and cross-kingdom interactions after dryland wildfires

How wildfires reorganize soil microbial interactions is a key knowledge gap, particularly for drylands that cover nearly 40% of Earths surface and face increasing wildfire frequency with global change. We compared bacterial, fungal, and cross-kingdom association networks across four timepoints from 2 weeks to 3 years post-fire in two California dryland systems: a high-intensity chaparral shrubland fire and a low-intensity Eastern Joshua tree desert fire, using nearly identical sampling designs and molecular workflows. Wildfire increased bacterial-fungal associations more than bacterial or fungal interactions in both systems, with burned plots consistently shifting toward cooperative over competitive associations. Bacterial-fungal interactions also increased in burned relative to unburned desert plots, suggesting fire promoted microbial associations in desert soils. Although microbial richness declined by up to 61% one year after chaparral wildfire but remained unchanged in the desert, network clustering declined in both systems, indicating reduced community resilience independent of richness loss. Pyrophilous bacteria, including Massilia and Noviherbaspirillum, emerged as keystone taxa after chaparral wildfire, while generalist bacteria and the putatively pyrophilous Pyronemataceae fungus Pseudotricharina structured desert burned networks. Cross-kingdom network analysis revealed shifts in post-fire microbiomes invisible to traditional diversity metrics, highlighting bacterial-fungal interactions and keystone taxa as drivers of dryland post-fire succession.

microbiology↗

bioRxiv2025

Mojave Desert microbial communities show high resistance and resilience over three years despite widespread plant mortality following the Dome Fire

O_LIHigh severity desert fires are uncommon but typically chart a new successional trajectory altering plant communities for at least 65 years. These aboveground vegetation shifts can have large implications for belowground microbial communities that maintain soil structure and nutrient cycling. High severity wildfires in forests or shrublands can severely reduce microbial species richness and biomass and alter microbiomes for decades but impacts on desert soil microbiomes are virtually unknown. C_LIO_LIThe 2020 Mojave Desert Dome Fire burned 43,273 acres of Eastern Joshua tree (Yucca jaegeriana) habitat, burning roughly 1 million trees. To track aboveground and belowground impacts of the Dome Fire, we established 9 plots (6 burned; 3 unburned) and sampled 4 subsamples per plot for 5 time points ranging from 2 weeks to 3 years post-fire. We measured initial ash depth as a proxy of soil burn severity and assessed plant mortality, plant richness, soil chemical characteristics, estimated soil microbial biomass with qPCR, and microbial richness and composition with Illumina MiSeq of 16S and ITS2 amplicons. C_LIO_LIBelowground communities were highly diverse, containing 25,444 bacterial, 269 archaeal, and 6,683 fungal ASVs amplicon sequence variants (ASVs) or microbial taxa. We identified at least 65 plant species and saw 80% Eastern Joshua tree mortality in burned plots over three years, with reduced plant richness post-fire except an abundance of annual herbs at 1-year post-fire, yet the fire did not significantly reduce microbial biomass or richness at any time point. C_LIO_LIMicrobial communities for both bacteria and fungi showed small but significant changes, enriching for pyrophilous microbes in burned plots. We identified increases of pyrophilous microbes such as Tumebacillus, Massilia, Noviherbaspirillum bacteria and Pseudotricharina, Penicillium, Coniochaeta and Naganishia fungi. C_LIO_LISynthesis: We present the first comprehensive above and belowground examination following a natural desert wildfire including Archaea, Bacteria, and Fungi. Despite the widespread mortality of Eastern Joshua trees across 3 years, microbial biomass, richness, and community composition were mostly resistant to change, like microbial responses to low-intensity fast-moving grassland fires. Despite high resistance overall, wildfire still increased several pyrophilous bacterial and fungal taxa common after high severity shrubland and forest wildfires. C_LI

microbiology↗

bioRxiv2025

Eastern Joshua tree arbuscular mycorrhizal fungal mycobiomes largely consistent across roots, soils, and seasons

The Mojave Desert is home to iconic Joshua trees threatened by climate change. Most desert plants form mutually beneficial partnerships with arbuscular mycorrhizal fungi (AMF), yet the AMF of the Eastern Joshua tree (Yucca jaegeriana) remain completely uncharacterized. We tested how Y. jaegeriana AMF spore abundance, richness, and composition varied when sampling 20 trees across 4 seasons from roots versus soils. We confirmed root colonization via staining, assessed spore abundance via microscopy, and used Illumina MiSeq to sequence AMF virtual taxa (VT) with WANDA AML2 primers. We identified 12 spore morphotypes and 47 VTs across 5 families within Glomeromycotina and the most abundant VT Glomus VTX00294 appeared in 87% of soil and root samples. The majority of VTs (26/47) were present across all seasons and were shared among soil and roots (38/47) with more VTs unique to soil. In soil, per tree mean spore abundance and AMF richness was lowest in Summer but consistent across other seasons with richness ranging from 8.8 to 11.5 VTs and mean root richness consistent across seasons. We conclude that sampling from soils rather than roots and any season other than Summer will yield the most diverse AMF communities.

microbiology↗