ORCID Profile
0000-0002-5671-7209
Current Organisation
University of New Hampshire
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Publisher: Copernicus GmbH
Date: 12-2017
Abstract: Abstract. Soil erosion plays a crucial role in transferring sediment and carbon from land to sea, yet little is known about the rhythm and rates of soil erosion prior to the most recent few centuries. Here we reconstruct a Holocene erosional history from central India, as integrated by the Godavari River in a sediment core from the Bay of Bengal. We quantify terrigenous fluxes, fingerprint sources for the lithogenic fraction and assess the age of the exported terrigenous carbon. Taken together, our data show that the monsoon decline in the late Holocene significantly increased soil erosion and the age of exported organic carbon. This acceleration of natural erosion was later exacerbated by the Neolithic adoption and Iron Age extensification of agriculture on the Deccan Plateau. Despite a constantly elevated sea level since the middle Holocene, this erosion acceleration led to a rapid growth of the continental margin. We conclude that in monsoon conditions aridity boosts rather than suppresses sediment and carbon export, acting as a monsoon erosional pump modulated by land cover conditions.
Publisher: Springer Science and Business Media LLC
Date: 05-10-2021
DOI: 10.1038/S41467-021-25983-9
Abstract: Northern post-glacial lakes are significant, increasing sources of atmospheric carbon through ebullition (bubbling) of microbially-produced methane (CH 4 ) from sediments. Ebullitive CH 4 flux correlates strongly with temperature, reflecting that solar radiation drives emissions. However, here we show that the slope of the temperature-CH 4 flux relationship differs spatially across two post-glacial lakes in Sweden. We compared these CH 4 emission patterns with sediment microbial (metagenomic and licon), isotopic, and geochemical data. The temperature-associated increase in CH 4 emissions was greater in lake middles—where methanogens were more abundant—than edges, and sediment communities were distinct between edges and middles. Microbial abundances, including those of CH 4 -cycling microorganisms and syntrophs, were predictive of porewater CH 4 concentrations. Results suggest that deeper lake regions, which currently emit less CH 4 than shallower edges, could add substantially to CH 4 emissions in a warmer Arctic and that CH 4 emission predictions may be improved by accounting for spatial variations in sediment microbiota.
Publisher: Cold Spring Harbor Laboratory
Date: 10-02-2020
DOI: 10.1101/2020.02.08.934661
Abstract: Northern post-glacial lakes are a significant and increasing source of atmospheric carbon (C), largely through ebullition (bubbling) of microbially-produced methane (CH 4 ) from the sediments 1 . Ebullitive CH 4 flux correlates strongly with temperature, suggesting that solar radiation is the primary driver of these CH 4 emissions 2 . However, here we show that the slope of the temperature-CH 4 flux relationship differs spatially, both within and among lakes. Hypothesizing that differences in microbiota could explain this heterogeneity, we compared site-specific CH 4 emissions with underlying sediment microbial (metagenomic and licon), isotopic, and geochemical data across two post-glacial lakes in Northern Sweden. The temperature-associated increase in CH 4 emissions was greater in lake middles—where methanogens were more abundant—than edges, and sediment microbial communities were distinct between lake edges and middles. Although CH 4 emissions projections are typically driven by abiotic factors 1 , regression modeling revealed that microbial abundances, including those of CH 4 -cycling microorganisms and syntrophs that generate H 2 for methanogenesis, can be useful predictors of porewater CH 4 concentrations. Our results suggest that deeper lake regions, which currently emit less CH 4 than shallower edges, could add substantially to overall CH 4 emissions in a warmer Arctic with longer ice-free seasons and that future CH 4 emission predictions from northern lakes may be improved by accounting for spatial variations in sediment microbiota.
Publisher: Springer Science and Business Media LLC
Date: 11-09-2023
Publisher: Elsevier BV
Date: 08-2017
No related grants have been discovered for Joel Johnson.