Differential Controls of Greenhouse Gas (CO2, CH4, and N2O) Concentrations in Natural and Constructed Agricultural Waterbodies on the Northern Great Plains

Published by American Geophysical Union (2023) © 2023. The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.Government of Saskatchewan (Award 200160015), Natural Sciences and Engineering Research Council of Canada Discovery grants (to K.F., G.L.S., H.M.B., and P.R.L.), the Canada Foundation for Innovation, University of ReginaPeer ReviewedInland waters are hotspots of greenhouse gas (GHG) cycling, with small water bodies particularly active in the production and consumption of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). However, wetland ponds are being replaced rapidly by small constructed reservoirs in agricultural regions, yet it is unclear whether these two water body types exhibit similar physical, chemical, and environmental controls of GHG content and fluxes. Here, we compared the content and regulatory mechanisms of all three major GHGs in 20 pairs of natural wetland ponds and constructed reservoirs in Canada's largest agricultural region. Carbon dioxide content was associated primarily with metabolic indicators in both water body types; however, primary production was paramount in reservoirs, and heterotrophic metabolism a stronger correlate in wetland ponds. Methane concentrations were correlated positively with eutrophication of the reservoirs alone, while competitive inhibition by sulfur-reducing bacteria may have limited CH4 in both waterbody types. Contrary to expectations, N2O was undersaturated in both water body types, with wetlands being a significantly stronger and more widespread N2O sink. Varying regulatory processes are attributed to differences in age, depth, morphology, and water-column circulation between water body types. These results suggest that natural and constructed water bodies should be modeled separately in regional GHG budgets

Seasonal variability of CO2, CH4, and N2O content and fluxes in small agricultural reservoirs of the northern Great Plains

©2022 Jensen, Webb, Simpson, Baulch, Leavitt and Finlay. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.Government of Saskatchewan (Award 200160015), Natural Sciences and Engineering Research Council of Canada Discovery grants (to KF, GS, HB, and PL), the Canada Foundation for Innovation (Award RGPIN–2018- 0490), University of ReginaPeer ReviewedInland waters are important global sources, and occasional sinks, of CO2, CH4, and N2O to the atmosphere, but relatively little is known about the contribution of GHGs of constructed waterbodies, particularly small sites in agricultural regions that receive large amounts of nutrients (carbon, nitrogen, phosphorus). Here, we quantify the magnitude and controls of diffusive CO2, CH4, and N2O fluxes from 20 agricultural reservoirs on seasonal and diel timescales. All gases exhibited consistent seasonal trends, with CO2 concentrations highest in spring and fall and lowest in mid-summer, CH4 highest in mid-summer, and N2O elevated in spring following ice-off. No discernible diel trends were observed for GHG content. Analyses of GHG covariance with potential regulatory factors were conducted using generalized additive models (GAMs) that revealed CO2 concentrations were affected primarily by factors related to benthic respiration, including dissolved oxygen (DO), dissolved inorganic nitrogen (DIN), dissolved organic carbon (DOC), stratification strength, and water source (as δ18Owater). In contrast, variation in CH4 content was correlated positively with factors that favoured methanogenesis, and so varied inversely with DO, soluble reactive phosphorus (SRP), and conductivity (a proxy for sulfate content), and positively with DIN, DOC, and temperature. Finally, N2O concentrations were driven mainly by variation in reservoir mixing (as buoyancy frequency), and were correlated positively with DO, SRP, and DIN levels and negatively with pH and stratification strength. Estimates of mean CO2-eq flux during the open-water period ranged from 5,520 mmolm−2 year1 (using GAM-predictions) to 10,445 mmolm−2 year−1 (using interpolations of seasonal data) reflecting how extreme values were extrapolated, with true annual flux rates likely falling between these two estimates

Distribution patterns of fungal taxa and inferred functional traits reflect the non-uniform vertical stratification of soil microhabitats in a coastal pine forest

In boreal systems, soil profiles typically consist of distinct stratified horizons, with organic layers at the surface overlying deeper mineral horizons providing microhabitat variation along a depth gradient, and vertical stratification of fungal communities along such soil profiles is commonly observed. We studied fungal community structure in a coastal pine forest along a gradient of decreasing influence from the coast. In this system, the vertical stratification pattern of soil microhabitats (defined here as organic, mineral with roots and mineral without roots: O, MR and MN, respectively) is non-uniform; organic horizons are sometimes buried under drifting sand dunes. Our results show that soil microhabitats are distinct with respect to physiochemical characteristics, community composition and OTU richness. While community composition was partly related to depth and distance from the coastal forest edge, microhabitat appeared to have the strongest influence. A closer inspection of the OTUs with the highest relative sequence abundance within each microhabitat revealed that microhabitats support functionally distinct fungal communities with respect to trophic mode and growth morphology. These results suggest that in coastal pine forests, variation in soil microhabitats contributes to the high fungal diversity found belowground and may play an important role in optimizing nutrient cycling