Title: Adding Depth to Our Understanding of Nitrogen Dynamics in Permafrost Soils

Abstract

Losses of C from decomposing permafrost may be offset by increased productivity of tundra plants, but nitrogen availability partially limits plant growth in tundra ecosystems. In this soil incubation experiment carbon (C) and nitrogen (N) cycling dynamics were examined from the soil surface down through upper permafrost. We found that losses of CO ₂ were negatively correlated to net N mineralization because C-rich surface soils mineralized little N, while deep soils had low rates of C respiration but high rates of net N mineralization. Permafrost soils released a large flush of inorganic N when initially thawed. Depth-specific rates of N mineralization from the incubation were combined with thaw depths and soil temperatures from a nearby manipulative warming experiment to simulate the potential magnitude, timing, and depth of inorganic N release during the process of permafrost thaw. Our calculations show that inorganic N released from newly thawed permafrost may be similar in magnitude to the increase in N mineralized by warmed soils in the middle of the profile. The total release of inorganic N from the soil profile during the simulated thaw process was twice the size of the observed increase in the foliar N pool observed at the manipulative experiment.more » Here, our findings suggest that increases in N availability are likely to outpace the N demand of tundra plants during the first 5 years of permafrost thaw and may increase C losses from surface soils as well as induce denitrification and leaching of N from these ecosystems.« less

Authors:

Salmon, Verity G.  ^[1];

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Schädel, Christina  ^[2];

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Bracho, Rosvel ^[3]; Pegoraro, Elaine ^[2]; Celis, Gerardo  ^[2];

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Mauritz, Marguerite  ^[2];

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Mack, Michelle C. ^[2]; Schuur, Edward A. G. ^[2]

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+ Show Author Affiliations

1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2. Northern Arizona Univ., Flagstaff, AZ (United States)
3. Univ. of Florida, Gainesville, FL (United States)

Publication Date:

2018-07-14

Research Org.:

Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE

OSTI Identifier:

1468280

Alternate Identifier(s):

OSTI ID: 1465909

Grant/Contract Number:  

AC05-00OR22725; SC0006982; 1203777; 1026415

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Geophysical Research. Biogeosciences

Additional Journal Information:

Journal Volume: TBD; Journal ID: ISSN 2169-8953

Publisher:

American Geophysical Union

Country of Publication:

United States

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES; permafrost thaw; nitrogen availability; soil depth; moist acidic tussock tundra; mineralization