skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Longer thaw seasons increase nitrogen availability for leaching during fall in tundra soils

Abstract

Climate change has resulted in warmer soil temperatures, earlier spring thaw and later fall freeze-up, resulting in warmer soil temperatures and thawing of permafrost in tundra regions. While these changes in temperature metrics tend to lengthen the growing season for plants, light levels, especially in the fall, will continue to limit plant growth and nutrient uptake. We conducted a laboratory experiment using intact soil cores with and without vegetation from a tundra peatland to measure the effects of late freeze and early spring thaw on carbon dioxide (CO 2) exchange, methane (CH 4) emissions, dissolved organic carbon (DOC) and nitrogen (N) leaching from soils. We compared soil C exchange and N production with a 30 day longer seasonal thaw during a simulated annual cycle from spring thaw through freeze-up and thaw. Across all cores, fall N leaching accounted for similar to 33% of total annual N loss despite significant increases in microbial biomass during this period. Nitrate(NO 3 -) leaching was highest during the fall (5.33 ± 1.45 mgNm -2 d -1) following plant senescence and lowest during the summer (0.43 ± 0.22 mg Nm -2 d -1). In the late freeze and early thaw treatment, we found 25% highermore » total annual ecosystem respiration but no significant change in CH 4 emissions or DOC loss due to high variability among samples. The late freeze period magnified N leaching and likely was derived from root turnover and microbial mineralization of soil organic matter coupled with little demand from plants or microbes. Furthermore, large N leaching during the fall will affect N cycling in low-lying areas and streams and may alter terrestrial and aquatic ecosystem nitrogen budgets in the arctic.« less

Authors:
ORCiD logo [1]; ORCiD logo [2];  [3];  [4]
  1. Univ. of New Hampshire, Durham, NH (United States). Earth Systems Research Center, Inst. for the Study of Earth, Oceans and Space; Univ. of Alaska Fairbanks, Fairbanks, AK (United States)
  2. Univ. of New Hampshire, Durham, NH (United States). Earth Systems Research Center, Inst. for the Study of Earth, Oceans and Space, Dept. of Natural Resources and Environment
  3. Univ. of New Hampshire, Durham, NH (United States). Earth Systems Research Center, Inst. for the Study of Earth, Oceans and Space, Dept. of Earth Sciences
  4. Univ. of Vermont, Burlington, VT (United States). Rubenstein School of Environment and Natural Resources
Publication Date:
Research Org.:
Univ. of New Hampshire, Durham, NH (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
OSTI Identifier:
1257286
Grant/Contract Number:
AC05-06OR23100; administered by ORISE-ORAU under co
Resource Type:
Journal Article: Published Article
Journal Name:
Environmental Research Letters
Additional Journal Information:
Journal Volume: 11; Journal Issue: 6; Journal ID: ISSN 1748-9326
Publisher:
IOP Publishing
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; nitrogen; carbon; permafrost thaw; tundra soils; changing seasonality; arctic tundra; microbial biomass; permafrost carbon; alpine ecosystem; growing-season; Alaskan tundra; forest soils; temperature; vegetation; dynamics

Citation Formats

Treat, Claire C., Wollheim, Wilfred M., Varner, Ruth K., and Bowden, William B. Longer thaw seasons increase nitrogen availability for leaching during fall in tundra soils. United States: N. p., 2016. Web. doi:10.1088/1748-9326/11/6/064013.
Treat, Claire C., Wollheim, Wilfred M., Varner, Ruth K., & Bowden, William B. Longer thaw seasons increase nitrogen availability for leaching during fall in tundra soils. United States. doi:10.1088/1748-9326/11/6/064013.
Treat, Claire C., Wollheim, Wilfred M., Varner, Ruth K., and Bowden, William B. 2016. "Longer thaw seasons increase nitrogen availability for leaching during fall in tundra soils". United States. doi:10.1088/1748-9326/11/6/064013.
@article{osti_1257286,
title = {Longer thaw seasons increase nitrogen availability for leaching during fall in tundra soils},
author = {Treat, Claire C. and Wollheim, Wilfred M. and Varner, Ruth K. and Bowden, William B.},
abstractNote = {Climate change has resulted in warmer soil temperatures, earlier spring thaw and later fall freeze-up, resulting in warmer soil temperatures and thawing of permafrost in tundra regions. While these changes in temperature metrics tend to lengthen the growing season for plants, light levels, especially in the fall, will continue to limit plant growth and nutrient uptake. We conducted a laboratory experiment using intact soil cores with and without vegetation from a tundra peatland to measure the effects of late freeze and early spring thaw on carbon dioxide (CO2) exchange, methane (CH4) emissions, dissolved organic carbon (DOC) and nitrogen (N) leaching from soils. We compared soil C exchange and N production with a 30 day longer seasonal thaw during a simulated annual cycle from spring thaw through freeze-up and thaw. Across all cores, fall N leaching accounted for similar to 33% of total annual N loss despite significant increases in microbial biomass during this period. Nitrate(NO3-) leaching was highest during the fall (5.33 ± 1.45 mgNm-2 d-1) following plant senescence and lowest during the summer (0.43 ± 0.22 mg Nm-2 d-1). In the late freeze and early thaw treatment, we found 25% higher total annual ecosystem respiration but no significant change in CH4 emissions or DOC loss due to high variability among samples. The late freeze period magnified N leaching and likely was derived from root turnover and microbial mineralization of soil organic matter coupled with little demand from plants or microbes. Furthermore, large N leaching during the fall will affect N cycling in low-lying areas and streams and may alter terrestrial and aquatic ecosystem nitrogen budgets in the arctic.},
doi = {10.1088/1748-9326/11/6/064013},
journal = {Environmental Research Letters},
number = 6,
volume = 11,
place = {United States},
year = 2016,
month = 6
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1088/1748-9326/11/6/064013

Save / Share:
  • Climate change has resulted in warmer soil temperatures, earlier spring thaw and later fall freeze-up, resulting in warmer soil temperatures and thawing of permafrost in tundra regions. While these changes in temperature metrics tend to lengthen the growing season for plants, light levels, especially in the fall, will continue to limit plant growth and nutrient uptake. We conducted a laboratory experiment using intact soil cores with and without vegetation from a tundra peatland to measure the effects of late freeze and early spring thaw on carbon dioxide (CO 2) exchange, methane (CH 4) emissions, dissolved organic carbon (DOC) and nitrogenmore » (N) leaching from soils. We compared soil C exchange and N production with a 30 day longer seasonal thaw during a simulated annual cycle from spring thaw through freeze-up and thaw. Across all cores, fall N leaching accounted for similar to 33% of total annual N loss despite significant increases in microbial biomass during this period. Nitrate(NO 3 -) leaching was highest during the fall (5.33 ± 1.45 mgNm -2 d -1) following plant senescence and lowest during the summer (0.43 ± 0.22 mg Nm -2 d -1). In the late freeze and early thaw treatment, we found 25% higher total annual ecosystem respiration but no significant change in CH 4 emissions or DOC loss due to high variability among samples. The late freeze period magnified N leaching and likely was derived from root turnover and microbial mineralization of soil organic matter coupled with little demand from plants or microbes. Furthermore, large N leaching during the fall will affect N cycling in low-lying areas and streams and may alter terrestrial and aquatic ecosystem nitrogen budgets in the arctic.« less
  • Current and future warming of high-latitude ecosystems will play an important role in climate change through feedbacks to the global carbon cycle. This study compares 6 years of CO 2 flux measurements in moist acidic tundra using autochambers and eddy covariance (Tower) approaches. Here, we found that the tundra was an annual source of CO 2 to the atmosphere as indicated by net ecosystem exchange using both methods with a combined mean of 105 ± 17 g CO 2 C m-2 y-1 across methods and years (Tower 87 ± 17 and Autochamber 123 ± 14). Furthermore, the difference between methodsmore » was largest early in the observation period, with Autochambers indicated a greater CO 2 source to the atmosphere. This discrepancy diminished through time, and in the final year the Autochambers measured a greater sink strength than tower. Active layer thickness was a significant driver of net ecosystem carbon exchange, gross ecosystem primary productivity, and Reco and could account for differences between Autochamber and Tower. The stronger source initially attributed lower summer season gross primary production (GPP) during the first 3 years, coupled with lower ecosystem respiration (Reco) during the first year. The combined suppression of GPP and Reco in the first year of Autochamber measurements could be the result of the experimental setup. Root damage associated with Autochamber soil collar installation may have lowered the plant community's capacity to fix C, but recovered within 3 years. And while this ecosystem was a consistent CO 2 sink during the summer, CO 2 emissions during the nonsummer months offset summer CO 2 uptake each year.« less
  • The few prethaw observations of tundra carbon fluxes suggest that there may be large spring releases, but little Is lmown about the scale and underlying mechanisms of this phenomenon. To address these questions, we combined ecosystem eddy flux measurements from two towers near Barrow, Alaska, with mechanistic soil-core thawing experiment During a 2week period prior to snowmelt In 2014, large fluxes were measured, reducing net summer uptake of CO2 by 46% and adding 6% to cumulative CH4 emissions. Emission pulses were linked to unique rain-on-snow events enhancing soli cracking. Controlled laboratory experiment revealed that as surface Ice thaws, an immediate,more » large pulse of trapped gases Is emitted. These results suggest that the Arctic C02 and CH4 spring pulse is a delayed release of biogenic gas production from the previous fall and that the pulse can be large enough to offset a significant fraction of the moderate Arctic tundra carbon sink.« less
  • The few prethaw observations of tundra carbon fluxes suggest that there may be large spring releases, but little is known about the scale and underlying mechanisms of this phenomenon. To address these questions, we combined in this paper ecosystem eddy flux measurements from two towers near Barrow, Alaska, with mechanistic soil-core thawing experiment. During a 2 week period prior to snowmelt in 2014, large fluxes were measured, reducing net summer uptake of CO 2 by 46% and adding 6% to cumulative CH 4 emissions. Emission pulses were linked to unique rain-on-snow events enhancing soil cracking. Controlled laboratory experiment revealed thatmore » as surface ice thaws, an immediate, large pulse of trapped gases is emitted. Finally, these results suggest that the Arctic CO 2 and CH 4 spring pulse is a delayed release of biogenic gas production from the previous fall and that the pulse can be large enough to offset a significant fraction of the moderate Arctic tundra carbon sink.« less