Document Type

Article

Publication Date

2020

DOI

10.1029/2019JG005512

Publication Title

Journal of Geophysical Research: Biogeosciences

Volume

125

Issue

7

Pages

e2019JG005512 (14 pp.)

Abstract

We investigated rates and controls on greenhouse gas (CO2 and CH4) production in two contrasting water‐saturated tundra soils within a permafrost‐affected watershed near Nome, Alaska, United States. Three years of field sample analysis have shown that soil from a fen‐like area in the toeslope of the watershed had higher pH and higher porewater ion concentrations than soil collected from a bog‐like peat plateau at the top of the hillslope. The influence of these contrasting geochemical and topographic environments on CO2 and CH4 production was tested in soil microcosms by incubating both the organic‐ and mineral‐layer soils anaerobically for 55 days. Nitrogen (as NH4Cl) was added to half of the microcosms to test potential effects of N limitation on microbial greenhouse gas production. We found that the organic toeslope soils produced more CO2 and CH4, fueled by higher pH and higher concentrations of water‐extractable organic C (WEOC). Our results also indicate N limitation on CO2 production in the peat plateau soils but not the toeslope soils. Together these results suggest that the weathering and leaching of ions and nutrients from tundra hillslopes can increase the rate of anaerobic soil organic matter decomposition in downslope soils by (1) increasing the pH of soil porewater; (2) providing bioavailable WEOC and fermentation products such as acetate; and (3) relieving microbial N limitation through nutrient runoff. We conclude that the soil geochemistry as mediated by landscape position is an important factor influencing the rate and magnitude of greenhouse gas production in tundra soils.

Comments

An edited version of this paper was published by AGU. Published 2020 by the American Geophysical Union. This article has been contributed to by U.S. Government employees and their work is in the public domain in the United States of America.

Not subject to U.S. copyright.

Original Publication Citation

Philben, M., Taş, N., Chen, H., Wullschleger, S. D., Kholodov, A., Graham, D. E., & Gu, B. (2020). Influences of hillslope biogeochemistry on anaerobic soil organic matter decomposition in a tundra watershed. Journal of Geophysical Research. Biogeosciences, 125(7), 1-14, Article e2019JG005512. https://doi.org/10.1029/2019JG005512

ORCID

0000-0003-2460-838X (Chen)

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