Biology subjects

Pulido Barriga, M. F.

Publications and source records attributed to Pulido Barriga, M. F..

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↗

bioRxiv2026

The response of leaf litter bacterial communities to simulated drought depends on temperature

Microbial communities regulate carbon and nitrogen (N) cycling, yet their long-term responses to chronic global changes remain unclear. Using 12 years of grassland litter samples from the Loma Ridge Global Change Experiment in Irvine, California, we tested whether interactions between experimental drought and N deposition, and previously observed temporal variability are driven by background climatic conditions, including precipitation and temperature. Consistent with short-term studies, drought and N addition had relatively small effects on bacterial community composition compared to pronounced seasonal and interannual variability, with drought-by-year interactions explaining more variation than drought alone. Seasonal shifts were largely driven by short-term fluctuations in rainfall and temperature, whereas the substantial interannual variability in community composition was not captured by site-level climate metrics. Contrary to expectations, drought effects were influenced more by background temperature than precipitation, with the strongest effects observed in cooler years. Lastly, a bacterial taxons sensitivity to climate variability under ambient conditions did not predict its response to chronic drought. Together, our findings show that bacterial responses to drought are temporally dynamic and influenced by background temperature, underscoring the need for long-term longitudinal studies of soil microbial communities to better predict microbial responses under future global change. ImportanceMicrobial responses to global change, particularly drought and nitrogen addition, are often inferred from short-term studies (< 2 years), yet natural temporal variability may overshadow experimental effects. Using a 12-year dataset of grassland leaf litter communities, we show that temporal variability, both seasonal and interannual, exert a stronger influence on bacterial community composition than chronic drought or nitrogen deposition. These findings challenge assumptions about the magnitude of drought effects, particularly in naturally drought-affected ecosystem such as California grasslands and highlight the importance of long-term datasets for predicting microbial responses to climate change. By demonstrating that bacterial communities are strongly shaped by background climatic variability (baseline precipitation and temperature independent of imposed chronic treatments) and may be buffered to sustained drought, this work improves forecasts of ecosystem responses and informs the design of global change experiments and restoration strategies in future research studies.

microbiology↗

bioRxiv2026

Differential impacts of fall versus spring prescribed burns on microbial biomass, richness, and composition in young mixed conifer forests

Prescribed burns aim to restore ecological processes and mitigate high-severity wildfire risks. Historically, California wildfires occur in summer or fall, but due to limited burning opportunities, prescribed burns occur in fall and spring. Yet, whether the burn season affects ecological outcomes is largely unknown. Here, we test prescribed burn season impacts on soil burn severity, bacterial and fungal abundance, richness, and composition as assessed with 16S and 18S qPCR and 16S and ITS2 Illumina MiSeq. We implemented a Before-After-Control-Impact design with 9 California montane mixed conifer forest stands (4 fall, 4 spring, 1 unburned control). We assessed resilience by collecting 6 sub-samples per stand at 6 time points ranging from pre-fire to 3 days, 1 and 6 months, and 1 and 2 years after fall and spring burns. Fall burns significantly reduced bacterial and fungal abundance and richness, whereas spring burns did not. Indeed, at 24 days after fall burns compared to pre-fire, bacterial and fungal richness were reduced by 24-30%, with richness of ectomycorrhizal fungi reduced by 45% and saprobic fungi by 28%. After the fall burn, fungal richness recovered within a year and fungal abundance within 6 months, whereas bacterial abundance and richness recovered in 2 years. Bacterial and fungal communities experienced compositional turnovers after both burns, with the emergence of several genera of "fire-loving" pyrophilous bacteria (Massilia, Paenibacillus) and fungi (Geminibasidium, Pyronema, Neurospora). Our findings suggest that, although seasonal differences were evident, both fall and spring prescribed burns mitigate wildfire impacts while promoting the succession of pyrophilous microbes.

microbiology↗