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Title: Disappearance of Relict Permafrost in Boreal North America: Effects on Peatland Carbon Storage and Fluxes

Abstract

Boreal peatlands in Canada have harbored relict permafrost since the Little Ice Age due to the strong insulating properties of peat. Ongoing climate change has triggered widespread degradation of localized permafrost in peatlands across continental Canada. Here, we explore the influence of differing permafrost regimes (bogs with no surface permafrost, localized permafrost features with surface permafrost, and internal lawns representing areas of permafrost degradation) on rates of peat accumulation at the southernmost limit of permafrost in continental Canada. Net organic matter accumulation generally was greater in unfrozen bogs and internal lawns than in the permafrost landforms, suggesting that surface permafrost inhibits peat accumulation and that degradation of surface permafrost stimulates net carbon storage in peatlands. To determine whether differences in substrate quality across permafrost regimes control trace gas emissions to the atmosphere, we used a reciprocal transplant study to experimentally evaluate environmental versus substrate controls on carbon emissions from bog, internal lawn, and permafrost peat. Emissions of CO{sub 2} were highest from peat incubated in the localized permafrost feature, suggesting that slow organic matter accumulation rates are due, at least in part, to rapid decomposition in surface permafrost peat. Emissions of CH{sub 4} were greatest from peat incubated in themore » internal lawn, regardless of peat type. Localized permafrost features in peatlands represent relict surface permafrost in disequilibrium with the current climate of boreal North America, and therefore are extremely sensitive to ongoing and future climate change. Our results suggest that the loss of surface permafrost in peatlands increases net carbon storage as peat, though in terms of radiative forcing, increased CH{sub 4} emissions to the atmosphere will partially or even completely offset this enhanced peatland carbon sink for at least 70 years following permafrost degradation.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
939503
DOE Contract Number:
AC36-99-GO10337
Resource Type:
Journal Article
Resource Relation:
Journal Name: Global Change Biology; Journal Volume: 13; Journal Issue: 9, 2007
Country of Publication:
United States
Language:
English
Subject:
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION; 54 ENVIRONMENTAL SCIENCES; 59 BASIC BIOLOGICAL SCIENCES; CANADA; CARBON; CARBON SINKS; CLIMATES; GEOMORPHOLOGY; LITTLE ICE AGE; NORTH AMERICA; ORGANIC MATTER; PEAT; PERMAFROST; STORAGE; SUBSTRATES; TRANSPLANTS; WETLANDS; Hydrogen Technologies and Systems

Citation Formats

Turetsky, M. R., Wieder, R. K., Vitt, D. H., Evans, R. J., and Scott, K. D. Disappearance of Relict Permafrost in Boreal North America: Effects on Peatland Carbon Storage and Fluxes. United States: N. p., 2007. Web. doi:10.1111/j.1365-2486.2007.01381.x.
Turetsky, M. R., Wieder, R. K., Vitt, D. H., Evans, R. J., & Scott, K. D. Disappearance of Relict Permafrost in Boreal North America: Effects on Peatland Carbon Storage and Fluxes. United States. doi:10.1111/j.1365-2486.2007.01381.x.
Turetsky, M. R., Wieder, R. K., Vitt, D. H., Evans, R. J., and Scott, K. D. Mon . "Disappearance of Relict Permafrost in Boreal North America: Effects on Peatland Carbon Storage and Fluxes". United States. doi:10.1111/j.1365-2486.2007.01381.x.
@article{osti_939503,
title = {Disappearance of Relict Permafrost in Boreal North America: Effects on Peatland Carbon Storage and Fluxes},
author = {Turetsky, M. R. and Wieder, R. K. and Vitt, D. H. and Evans, R. J. and Scott, K. D.},
abstractNote = {Boreal peatlands in Canada have harbored relict permafrost since the Little Ice Age due to the strong insulating properties of peat. Ongoing climate change has triggered widespread degradation of localized permafrost in peatlands across continental Canada. Here, we explore the influence of differing permafrost regimes (bogs with no surface permafrost, localized permafrost features with surface permafrost, and internal lawns representing areas of permafrost degradation) on rates of peat accumulation at the southernmost limit of permafrost in continental Canada. Net organic matter accumulation generally was greater in unfrozen bogs and internal lawns than in the permafrost landforms, suggesting that surface permafrost inhibits peat accumulation and that degradation of surface permafrost stimulates net carbon storage in peatlands. To determine whether differences in substrate quality across permafrost regimes control trace gas emissions to the atmosphere, we used a reciprocal transplant study to experimentally evaluate environmental versus substrate controls on carbon emissions from bog, internal lawn, and permafrost peat. Emissions of CO{sub 2} were highest from peat incubated in the localized permafrost feature, suggesting that slow organic matter accumulation rates are due, at least in part, to rapid decomposition in surface permafrost peat. Emissions of CH{sub 4} were greatest from peat incubated in the internal lawn, regardless of peat type. Localized permafrost features in peatlands represent relict surface permafrost in disequilibrium with the current climate of boreal North America, and therefore are extremely sensitive to ongoing and future climate change. Our results suggest that the loss of surface permafrost in peatlands increases net carbon storage as peat, though in terms of radiative forcing, increased CH{sub 4} emissions to the atmosphere will partially or even completely offset this enhanced peatland carbon sink for at least 70 years following permafrost degradation.},
doi = {10.1111/j.1365-2486.2007.01381.x},
journal = {Global Change Biology},
number = 9, 2007,
volume = 13,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
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  • Changes in the spatial distribution of permafrost in the Ouiatchouane palsa peatland (northern Quebec) were monitored from 1957 to present, using aerial photographs taken in 1957 (starting date) and three field surveys in 1973, 1983, and 1993, respectively. Between 1983 and 1993, palsa degradation occurred at about the same rate as between 1957 and 1983, although minor differences in rate of permafrost decay during the three periods (1957-1973, 1973-1983, 1983-1993) may be attributed in part to misidentification of marginal permafrost landforms. Permafrost degradation appeared to be influenced by height of individual palsas and their location within the peatland. Since 1983,more » thermokarst ponds have been progressively invaded by sedges and Sphagnum, a situation promoting successional peatland development and palsa formation as suggested by the presence of a small incipient palsa. Although the main geomorphic process at work is palsa degradation, permafrost aggradation is possible under present climatic conditions. 28 refs., 3 figs., 1 tab.« less
  • The goals of this study were to: (1) measure methane (CH{sub 4}) emissions from peatland soils, (2) improve process models of peatland-atmospheric methane exchange by identifying environmental controls on methane emission, and (3) provide a method of extending CH{sub 4} emissions data from the laboratory to the landscape scale by determining the relationships between plant associations and CH{sub 4} flux. Sites representing a range of parameters were selected for CH{sub 4} sampling and analyses. Linear regression of concentration changes was used to calculate CH{sub 4} flux. In general, calculated methane emissions were larger than those reported for other boreal wetlandmore » sites at a similar latitude. The range of flux measurements showed spatial variation within and among sites as well as seasonal variation among sites. Open graminoid fens had the highest mean seasonal flux, while treed sites had the lowest mean flux. To determine the effects of environmental variables, data on seasonal patterns of water table position and peat temperature were collected and analyzed statistically. A correlation between peat temperature and water table position was observed. A predictive model for methane flux and environmental variables using multiple stepwise regression was developed. The model showed a negative correlation of CH{sub 4} flux with height above mean water table, and a weak correlation of flux with chemistry. The results of the study indicate that multivariate vegetation analyses may be a useful tool for accounting for environmental controls on methane flux and applying chamber measurements to the landscape scale using remote sensing. 43 refs., 8 figs., 3 tabs.« less
  • The fate of carbon stored in permafrost-zone peatlands represents a significant uncertainty in global climate modeling. Given that the breakdown of dissolved organic matter (DOM) is often a major pathway for decomposition in peatlands, knowledge of DOM reactivity under different permafrost regimes is critical for determining future climate feedbacks. To explore the effects of permafrost thaw and resultant plant succession on DOM reactivity, we used a combination of Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), UV/Vis absorbance, and excitation-emission matrix spectroscopy (EEMS) to examine the DOM elemental composition and optical properties of 27 pore water samples gathered frommore » various sites along a permafrost thaw sequence in Stordalen Mire, a thawing subarctic peatland in northern Sweden. The presence of dense Sphagnum moss, a feature that is dominant in the intermediate thaw stages, appeared to be the main driver of variation in DOM elemental composition and optical properties at Stordalen. Specifically, DOM from sites with Sphagnum had greater aromaticity, higher average molecular weights, and greater O/C, consistent with a higher abundance of phenolic compounds that likely inhibit decomposition. These compounds are released by Sphagnum and may accumulate due to inhibition of phenol oxidase activity by the acidic pH at these sites. In contrast, sites without Sphagnum, specifically fully-thawed rich fens, had more saturated, more reduced compounds, which were high in N and S. Optical properties at rich fens were indicated the presence of microbially-derived DOM, consistent with the higher decomposition rates previously measured at these sites. These results indicate that Sphagnum acts as an inhibitor of rapid decomposition and CH4 release in thawing subarctic peatlands, consistent with lower rates of CO2 and CH4 production previously observed at these sites. However, this inhibitory effect may disappear if Sphagnumdominated bogs transition to more waterlogged rich fens that contain very little to no living Sphagnum. Release of this inhibition allows for higher levels of microbial activity and potentially greater CH4 release, as has been observed in these fen sites.« less