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1. Exploring Trait Trade-Offs for Fungal Decomposers in a Southern California Grassland

   https://doi.org/10.3389/fmicb.2021.655987  

   Alster, Charlotte J. ; Allison, Steven D. ; Glassman, Sydney I. ; Martiny, Adam C. ; Treseder, Kathleen K. ( April 2021 , Frontiers in Microbiology)

   null (Ed.)

   Fungi are important decomposers in terrestrial ecosystems, so their responses to climate change might influence carbon (C) and nitrogen (N) dynamics. We investigated whether growth and activity of fungi under drought conditions were structured by trade-offs among traits in 15 fungal isolates from a Mediterranean Southern California grassland. We inoculated fungi onto sterilized litter that was incubated at three moisture levels (4, 27, and 50% water holding capacity, WHC). For each isolate, we characterized traits that described three potential lifestyles within the newly proposed “YAS” framework: growth yield, resource acquisition, and stress tolerance. Specifically, we measured fungal hyphal length per unit litter decomposition for growth yield; the potential activities of the extracellular enzymes cellobiohydrolase (CBH), β -glucosidase (BG), β -xylosidase (BX), and N-acetyl- β - D -glucosaminidase (NAG) for resource acquisition; and ability to grow in drought vs. higher moisture levels for drought stress tolerance. Although, we had hypothesized that evolutionary and physiological trade-offs would elicit negative relationships among traits, we found no supporting evidence for this hypothesis. Across isolates, growth yield, drought stress tolerance, and extracellular enzyme activities were not significantly related to each other. Thus, it is possible that drought-induced shifts in fungal community composition may not necessarily lead to changes in fungal biomass or decomposer ability in this arid grassland. 

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2. Decoupling of functional traits from intraspecific patterns of growth and drought stress resistance

   https://doi.org/10.1111/nph.18937  

   Kerr, Kelly_L ; Fickle, Jaycie_C ; Anderegg, William_R_L ( May 2023 , New Phytologist)

   Intraspecific variation in functional traits may mediate tree species' drought resistance, yet whether trait variation is due to genotype (G), environment (E), or G×E interactions remains unknown. Understanding the drivers of intraspecific trait variation and whether variation mediates drought response can improve predictions of species' response to future drought.

   Using populations of quaking aspen spanning a climate gradient, we investigated intraspecific variation in functional traits in the field as well as the influence of G and E among propagules in a common garden. We also tested for trait‐mediated trade‐offs in growth and drought stress tolerance.

   We observed intraspecific trait variation among the populations, yet this variation did not necessarily translate to higher drought stress tolerance in hotter/drier populations. Additionally, plasticity in the common garden was low, especially in propagules derived from the hottest/driest population. We found no growth–drought stress tolerance trade‐offs and few traits exhibited significant relationships with mortality in the natural populations, suggesting that intraspecific trait variation among the traits measured did not strongly mediate responses to drought stress.

   Our results highlight the limits of trait‐mediated responses to drought stress and the complex G×E interactions that may underlie drought stress tolerance variation in forests in dry environments.

    

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3. Temperate trees locally engineer decomposition and litter‐bound microbiomes through differential litter deposits and species‐specific soil conditioning

   https://doi.org/10.1111/nph.19900  

   Yates, Caylon ; King, William_L ; Richards, Sarah_C ; Wilson, Cullen ; Viddam, Vedha ; Blakney, Andrew_J_C ; Eissenstat, David_M ; Bell, Terrence_H ( June 2024 , New Phytologist)

   Leaf decomposition varies widely across temperate forests, shaped by factors like litter quality, climate, soil properties, and decomposers, but forest heterogeneity may mask local tree influences on decomposition and litter‐associated microbiomes. We used a 24‐yr‐old common garden forest to quantify local soil conditioning impacts on decomposition and litter microbiology.

   We introduced leaf litter bags from 10 tree species (5 arbuscular mycorrhizal; 5 ectomycorrhizal) to soil plots conditioned by all 10 species in a full‐factorial design. After 6 months, we assessed litter mass loss, C/N content, and bacterial and fungal composition. We hypothesized that (1) decomposition and litter‐associated microbiome composition would be primarily shaped by the mycorrhizal type oflitter‐producing trees, but (2) modified significantly by underlying soil, based on mycorrhizal type of theconditioning trees.

   Decomposition and, to a lesser extent, litter‐associated microbiome composition, were primarily influenced by the mycorrhizal type of litter‐producing trees. Interestingly, however, underlying soils had a significant secondary influence, driven mainly by tree species, not mycorrhizal type. This secondary influence was strongest under trees from the Pinaceae.

   Temperate trees can locally influence underlying soil to alter decomposition and litter‐associated microbiology. Understanding the strength of this effect will help predict biogeochemical responses to forest compositional change.

    

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4. Routes and rates of bacterial dispersal impact surface soil microbiome composition and functioning

   https://doi.org/10.1038/s41396-022-01269-w  

   Walters, Kendra E. ; Capocchi, Joia K. ; Albright, Michaeline B. N. ; Hao, Zhao ; Brodie, Eoin L. ; Martiny, Jennifer B. H. ( July 2022 , The ISME Journal)

   Recent evidence suggests that, similar to larger organisms, dispersal is a key driver of microbiome assembly; however, our understanding of the rates and taxonomic composition of microbial dispersal in natural environments is limited. Here, we characterized the rate and composition of bacteria dispersing into surface soil via three dispersal routes (from the air above the vegetation, from nearby vegetation and leaf litter near the soil surface, and from the bulk soil and litter below the top layer). We then quantified the impact of those routes on microbial community composition and functioning in the topmost litter layer. The bacterial dispersal rate onto the surface layer was low (7900 cells/cm2/day) relative to the abundance of the resident community. While bacteria dispersed through all three routes at the same rate, only dispersal from above and near the soil surface impacted microbiome composition, suggesting that the composition, not rate, of dispersal influenced community assembly. Dispersal also impacted microbiome functioning. When exposed to dispersal, leaf litter decomposed faster than when dispersal was excluded, although neither decomposition rate nor litter chemistry differed by route. Overall, we conclude that the dispersal routes transport distinct bacterial communities that differentially influence the composition of the surface soil microbiome.

    

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5. Contrasting geochemical and fungal controls on decomposition of lignin and soil carbon at continental scale

   https://doi.org/10.1038/s41467-023-37862-6  

   Huang, Wenjuan ; Yu, Wenjuan ; Yi, Bo ; Raman, Erik ; Yang, Jihoon ; Hammel, Kenneth E. ; Timokhin, Vitaliy I. ; Lu, Chaoqun ; Howe, Adina ; Weintraub-Leff, Samantha R. ; et al ( December 2023 , Nature Communications)

   Abstract Lignin is an abundant and complex plant polymer that may limit litter decomposition, yet lignin is sometimes a minor constituent of soil organic carbon (SOC). Accounting for diversity in soil characteristics might reconcile this apparent contradiction. Tracking decomposition of a lignin/litter mixture and SOC across different North American mineral soils using lab and field incubations, here we show that cumulative lignin decomposition varies 18-fold among soils and is strongly correlated with bulk litter decomposition, but not SOC decomposition. Climate legacy predicts decomposition in the lab, and impacts of nitrogen availability are minor compared with geochemical and microbial properties. Lignin decomposition increases with some metals and fungal taxa, whereas SOC decomposition decreases with metals and is weakly related with fungi. Decoupling of lignin and SOC decomposition and their contrasting biogeochemical drivers indicate that lignin is not necessarily a bottleneck for SOC decomposition and can explain variable contributions of lignin to SOC among ecosystems. 

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