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1. Nutrient and stress tolerance traits linked to fungal responses to global change

   https://doi.org/10.1525/elementa.2020.00144  

   Treseder, Kathleen K.; Alster, Charlotte J.; Cat, Linh Anh; Gorris, Morgan E.; Kuhn, Alexander L.; Lovero, Karissa G.; Hagedorn, Frank; Kerekes, Jennifer F.; McHugh, Theresa A.; Solly, Emily F. (January 2021, Elementa: Science of the Anthropocene)

   null (Ed.)

   In this case study analysis, we identified fungal traits that were associated with the responses of taxa to 4 global change factors: elevated CO2, warming and drying, increased precipitation, and nitrogen (N) enrichment. We developed a trait-based framework predicting that as global change increases limitation of a given nutrient, fungal taxa with traits that target that nutrient will represent a larger proportion of the community (and vice versa). In addition, we expected that warming and drying and N enrichment would generate environmental stress for fungi and may select for stress tolerance traits. We tested the framework by analyzing fungal community data from previously published field manipulations and linking taxa to functional gene traits from the MycoCosm Fungal Portal. Altogether, fungal genera tended to respond similarly to 3 elements of global change: increased precipitation, N enrichment, and warming and drying. The genera that proliferated under these changes also tended to possess functional genes for stress tolerance, which suggests that these global changes—even increases in precipitation—could have caused environmental stress that selected for certain taxa. In addition, these genera did not exhibit a strong capacity for C breakdown or P acquisition, so soil C turnover may slow down or remain unchanged following shifts in fungal community composition under global change. Since we did not find strong evidence that changes in nutrient limitation select for taxa with traits that target the more limiting nutrient, we revised our trait-based framework. The new framework sorts fungal taxa into Stress Tolerating versus C and P Targeting groups, with the global change elements of increased precipitation, warming and drying, and N enrichment selecting for the stress tolerators. 

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2. Temporal and Spatial Variations in Subterranean Estuary Geochemical Gradients and Nutrient Cycling Rates: Impacts on Groundwater Nutrient Export to Estuaries

   https://doi.org/10.1029/2022JG007132  

   Wilson, Stephanie J.; Anderson, Iris C.; Song, Bongkeun; Tobias, Craig R. (June 2023, Journal of Geophysical Research: Biogeosciences)

   Abstract Subterranean estuaries (STEs) form at the land‐sea boundary where groundwater and seawater mix. These biogeochemically reactive zones influence groundwater‐borne nutrient concentrations and speciation prior to export via submarine groundwater discharge (SGD). We examined a STE located along the York River Estuary (YRE) to determine if SGD delivers dissolved inorganic nitrogen (DIN) and phosphorus (DIP) to the overlying water. We assessed variations in STE geochemical profiles with depth across locations, times, and tidal stages, estimated N removal along the STE flow path, measured hydraulic gradients to estimate SGD, and calculated potential nutrient fluxes. Salinity, dissolved oxygen (DO), DIN, and DIP varied significantly with depth and season (p < 0.05), but not location or tidal stage. Ammonium dominated the DIN pool deep in the STE. Moving toward the sediment surface, ammonium concentrations decreased as nitrate and DO concentrations increased, suggesting nitrification. Potential sediment N removal rates mediated by denitrification were <8 mmoles N m⁻² d⁻¹. The total groundwater discharge rate was 38 ± 11 L m⁻² d⁻¹; discharge followed tidal and seasonal patterns. Net SGD nutrient fluxes were 0.065–3.2 and 0.019–0.093 mmoles m⁻² d⁻¹for DIN and DIP, respectively. However, microbial N removal in the STE may attenuate 0.58% to >100% of groundwater DIN. SGD fluxes were on the same order of magnitude as diffusive benthic fluxes but accounted for <10% of the nutrients delivered by fluvial advection in the YRE. Our results indicate the importance of STE biogeochemical transformations to SGD flux estimations and their role in coastal eutrophication and nutrient dynamics. 

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3. Antibiotics and temperature interact to disrupt soil communities and nutrient cycling

   https://doi.org/10.1016/j.soilbio.2021.108437  

   Lucas, Jane M.; Sone, Bronte M.; Whitmore, Dana; Strickland, Michael S. (December 2021, Soil Biology and Biochemistry)
4. Resilience of phytoplankton dynamics to trophic cascades and nutrient enrichment

   https://doi.org/10.1002/lno.11913  

   Carpenter, Stephen R.; Arani, Babak M. S.; Van Nes, Egbert H.; Scheffer, Marten; Pace, Michael L. (August 2021, Limnology and Oceanography)

   Abstract Resilience was compared for alternate states of phytoplankton pigment concentration in two multiyear whole‐lake experiments designed to shift the manipulated ecosystem between alternate states. Mean exit time, the average time between threshold crossings, was calculated from automated measurements every 5 min during summer stratification. Alternate states were clearly identified, and equilibria showed narrow variation in bootstrap analysis of uncertainty. Mean exit times ranged from 13 to 290 h. In the reference ecosystem, Paul Lake, mean exit time of the low‐pigment state was about 100 h longer than mean exit time of the high‐pigment state. In the manipulated ecosystem, Peter Lake, mean exit time of the high‐pigment state exceeded that of the low‐pigment state by 30 h in the cascade experiment. In the enrichment experiment mean exit time of the low‐pigment state was longer than that of the high‐pigment state by about 100 h. Mean exit time is a useful measure of resilience for stochastic ecosystems where high‐frequency measurements are made by consistent methods over the full range of ecosystem states. 

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5. Nutrient addition increases grassland sensitivity to droughts

   https://doi.org/10.1002/ecy.2981  

   Bharath, Siddharth; Borer, Elizabeth T.; Biederman, Lori A.; Blumenthal, Dana M.; Fay, Philip A.; Gherardi, Laureano A.; Knops, Johannes M. H.; Leakey, Andrew D. B.; Yahdjian, Laura; Seabloom, Eric W. (February 2020, Ecology)

   Abstract Grasslands worldwide are expected to experience an increase in extreme events such as drought, along with simultaneous increases in mineral nutrient inputs as a result of human industrial activities. These changes are likely to interact because elevated nutrient inputs may alter plant diversity and increase the sensitivity to droughts. Dividing a system’s sensitivity to drought into resistance to change during the drought and rate of recovery after the drought generates insights into different dimensions of the system’s resilience in the face of drought. Here, we examine the effects of experimental nutrient fertilization and the resulting diversity loss on the resistance to and recovery from severe regional droughts. We do this at 13 North American sites spanning gradients of aridity, five annual grasslands in California, and eight perennial grasslands in the Great Plains. We measured rate of resistance as the change in annual aboveground biomass (ANPP) per unit change in growing season precipitation as conditions declined from normal to drought. We measured recovery as the change in ANPP during the postdrought period and the return to normal precipitation. Resistance and recovery did not vary across the 400‐mm range of mean growing season precipitation spanned by our sites in the Great Plains. However, chronic nutrient fertilization in the Great Plains reduced drought resistance and increased drought recovery. In the California annual grasslands, arid sites had a greater recovery postdrought than mesic sites, and nutrient addition had no consistent effects on resistance or recovery. Across all study sites, we found that predrought species richness in natural grasslands was not consistently associated with rates of resistance to or recovery from the drought, in contrast to earlier findings from experimentally assembled grassland communities. Taken together, these results suggest that human‐induced eutrophication may destabilize grassland primary production, but the effects of this may vary across regions and flora, especially between perennial and annual‐dominated grasslands. 

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