Biology subjects

Bogar, L. M.

Publications and source records attributed to Bogar, L. M..

3 recordsLinked to original sources

bioRxiv2025

Fire severity drives shifts in ectomycorrhizal fungal communities and Pseudotsuga menziesii seedling performance

Background and AimsHigh-severity wildfires are increasing in western North America, disrupting soil conditions and mutualisms between plants and ectomycorrhizal fungi (EMF), which support seedling nutrient uptake, stress tolerance, and survival. This study investigates how fire severity and recency affect fungal communities and Pseudotsuga menziesii (Douglas-fir) seedling performance, and whether live-soil inoculation or stress priming improve post-fire outcomes. MethodsIn a greenhouse experiment, Douglas-fir seedlings were grown in soils from high-severity burns, recent and historic low-severity burns, and unburned sites in the Sierra Nevada. Each soil was applied as a live or autoclaved inoculum. Drought stress and abscisic acid priming treatments were imposed before a final 3-week dry-down. We measured seedling biomass, chlorophyll fluorescence (Fv/Fm), EMF colonization, and fungal community composition using ITS amplicon sequencing. ResultsHigh-severity soils reduced seedling growth, EMF colonization, and fungal richness. Low-severity burns supported more rich, diverse fungal communities and greater seedling performance. Stress priming treatments had minimal effects. Fungal community composition varied significantly by burn severity. ConclusionFire severity drives changes in fungal community structure that influence seedling outcomes. Low-severity soils retain beneficial microbial legacies, supporting stronger mycorrhizal associations that result in seedling performance comparable to unburned soils. Targeted microbial restoration may enhance post-fire forest regeneration in high-severity burn areas

ecology↗

bioRxiv2024

Functional composition of deep soil microbial communities changes with oak mortality

Tree mortality in oak savannas is increasing under climate change, but its impact on microbial communities and soil carbon below the top 20 centimeters is relatively unknown. Deep tree roots, their ectomycorrhizal fungi, and associated bacteria may have a particularly important effect on landscape carbon storage, as they mediate the transfer of recently fixed plant carbon into deep soil and subsoil layers. To investigate how tree mortality impacts microbes and soil carbon, we sampled under living and recently dead Quercus douglasii trees in a California oak savanna, gathering depth-resolved soil cores to 45 cm below the surface. We captured finely resolved biological detail on these soil samples, comparing living (RNA-based) to potential and historical (DNA-based) microbial communities and assessing microbial biomass with phospholipid fatty acid analysis. Tree mortality greatly reduced the abundance of ectomycorrhizal fungi, particularly in subsoils. Fungal niches were more variable at depth under dead trees than under living ones, and RNA-based profiling captured substantially different communities than DNA, especially under living trees. However, tree mortality three years prior to our study did not impact the overall quantity of carbon stored in the soil. Tree mortality can have profound effects on the interactions between tree roots, mycorrhizal fungi, and soil bacteria, which may shift soil carbon dynamics over long time scales. Understanding the mechanisms of these interactions, and their time scales, will improve our ability to predict and manage soil carbon in savanna landscapes as drought and heat events kill more oaks in arid climates. HighlightsO_LIRibosomal RNA, from living cells, revealed different communities than from DNA. C_LIO_LIMicrobial functions changed more with depth and tree health than taxonomy. C_LIO_LIDifferences were most extreme below 20 cm depth. C_LIO_LIMicrobial population distributions changed under living and dead trees. C_LIO_LITotal microbial biomass and carbon were similar beneath living and dead trees. C_LI

ecology↗

bioRxiv2018

Keystone mutualists can facilitate transition between alternative ecosystem states in the soil

Symbioses between plants and microbial organisms can fundamentally alter the structure of ecosystems, from their species diversity to rates of nutrient cycling. Yet, many aspects of how differences in the prevalence of microbial symbioses arise are unclear. This is a key knowledge gap, as if co-variation in plant and microbial distributions are primarily determined by extrinsic abiotic factors then symbioses should exert little independent control over ecosystems. To examine the potential for alternative symbiotic communities to arise under similar conditions we examined biogeochemical cycling and microbial community structure in a coastal landscape where historical patterns of vegetation transition are known, allowing us to eliminate abiotic determinism. We found that alternative states in microbial community structure and ecosystem processes emerged under different plant species. Greenhouse studies further demonstrated that plant selection of symbiotic microbes is central to emergence of these alternative states and occurs independent of soil abiotic conditions. Moreover, we provide evidence that transition between states may be highly dependent on the presence of a small set of ruderal symbionts that are rare in mature systems but may act as keystone mutualists. Because differences between these alternative states can be directly linked to plant-microbe symbioses, independent of initial conditions, our results suggesting that biotic feedbacks between keystone symbiotic microbes and plants play a foundational role in the diversity and function of soils.

ecology↗