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Controls on ecosystem and root respiration across a permafrost and wetland gradient in interior Alaska

Environmental Research Letters

By:
, , , , , and
DOI: 10.1088/1748-9326/8/4/045029

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Abstract

Permafrost is common to many northern wetlands given the insulation of thick organic soil layers, although soil saturation in wetlands can lead to warmer soils and increased thaw depth. We analyzed five years of soil CO2 fluxes along a wetland gradient that varied in permafrost and soil moisture conditions. We predicted that communities with permafrost would have reduced ecosystem respiration (ER) but greater temperature sensitivity than communities without permafrost. These predictions were partially supported. The colder communities underlain by shallow permafrost had lower ecosystem respiration (ER) than communities with greater active layer thickness. However, the apparent Q10 of monthly averaged ER was similar in most of the vegetation communities except the rich fen, which had smaller Q10 values. Across the gradient there was a negative relationship between water table position and apparent Q10, showing that ER was more temperature sensitive under drier soil conditions. We explored whether root respiration could account for differences in ER between two adjacent communities (sedge marsh and rich fen), which corresponded to the highest and lowest ER, respectively. Despite differences in root respiration rates, roots contributed equally (~40%) to ER in both communities. Also, despite similar plant biomass, ER in the rich fen was positively related to root biomass, while ER in the sedge marsh appeared to be related more to vascular green area. Our results suggest that ER across this wetland gradient was temperature-limited, until conditions became so wet that respiration became oxygen-limited and influenced less by temperature. But even in sites with similar hydrology and thaw depth, ER varied significantly likely based on factors such as soil redox status and vegetation composition.

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Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Controls on ecosystem and root respiration across a permafrost and wetland gradient in interior Alaska
Series title:
Environmental Research Letters
DOI:
10.1088/1748-9326/8/4/045029
Volume
8
Issue:
4
Year Published:
2013
Language:
English
Publisher:
IOP Publishing
Contributing office(s):
Coop Res Unit Seattle
Description:
11 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Environmental Research Letters
Country:
United States
State:
Alaska
Other Geospatial:
Bonanza Creek Experimental Forest
Online Only (Y/N):
Y