期刊
JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES
卷 123, 期 8, 页码 2627-2642出版社
AMER GEOPHYSICAL UNION
DOI: 10.1029/2018JG004396
关键词
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资金
- J.M.W.'s Fulbright Distinguished U.S. Arctic Chairship-Norway
- Faculty of Biosciences, Fisheries, and Economics of the Department of Arctic and Marine Biology, University of Tromso (UiT)
- National Science Foundation [OPP 0909538]
Currently, there is a lack of understanding on how the magnitude and sources of carbon (C) emissions from High Arctic tundra are impacted by changing snow cover duration and depth during winter. Here we investigated this issue in a graminoid tundra snow fence experiment on shale-derived gelisols in Svalbard from the end of the growing season and throughout the winter. To characterize emissions, we measured ecosystem respiration (R-eco) along with its radiocarbon (C-14) content. We assessed the composition of soil organic matter (SOM) by measuring its bulk-C and nitrogen (N), C-14 content, and n-alkane composition. Our findings reveal that greater snow depth increased soil temperatures and winter R-eco (25 mg C m(-2) d(-1) under deeper snow compared to 13 mg C m(-2) d(-1) in ambient conditions). At the end of the growing season, R-eco was dominated by plant respiration and microbial decomposition of C fixed within the past 60 years (Delta C-14 = 62 +/- 8%). During winter, emissions were significantly older (Delta C-14 = -64 +/- 14%), and likely sourced from microorganisms decomposing aged SOM formed during the Holocene mixed with biotic or abiotic mineralization of the carbonaceous, fossil parent material. Our findings imply that snow cover duration and depth is a key control on soil temperatures and thus the magnitude of R-eco in winter. We also show that in shallow Arctic soils, mineralization of carbonaceous parent materials can contribute significant proportions of fossil C to R-eco. Therefore, permafrost-C inventories informing C emission projections must carefully distinguish between more vulnerable SOM from recently fixed biomass and more recalcitrant ancient sedimentary C sources.
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