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Growing season CH4 fluxes were monitored over a two year period following the start of ecosystem-scale manipulations of water table position and surface soil temperatures in a moderate rich fen in interior Alaska. The largest CH4 fluxes occurred in plots that received both flooding (raised water table position) and soil warming, while the lowest fluxes occurred in unwarmed plots in the lowered water table treatment. A combination of treatment and soil hydroclimate variables explained more than 70% of the variation in ln-transformed CH4 fluxes, with mean daily water table position representing the strongest predictor. We used quantitative PCR of the -subunit of mcr operon to explore the influence of soil climate...
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To determine the influence of fire and thermokarst in a boreal landscape, we investigated peat cores within and adjacent to a permafrost collapse feature on the Tanana River Floodplain of Interior Alaska. Radioisotope dating, diatom assemblages, plant macrofossils, charcoal fragments, and carbon and nitrogen content of the peat profile indicate ~600 years of vegetation succession with a transition from a terrestrial forest to a sedge-dominated wetland over 100 years ago, and to a Sphagnum-dominated peatland in approximately 1970. The shift from sedge to Sphagnum, and a decrease in the detrended tree-ring width index of black spruce trees adjacent to the collapse coincided with an increase in the growing season temperature...
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To test the effects of altered hydrology on organic soil decomposition, we investigated CO2 and CH4 production potential of rich-fen peat (mean surface pH = 6.3) collected from a field water table manipulation experiment including control, raised and lowered water table treatments. Mean anaerobic CO2 production potential at 10 cm depth (14.1 ± 0.9 μmol C g−1 d−1) was as high as aerobic CO2 production potential (10.6 ± 1.5 μmol C g−1 d−1), while CH4 production was low (mean of 7.8 ± 1.5 nmol C g−1 d−1). Denitrification enzyme activity indicated a very high denitrification potential (197 ± 23 μg N g−1 d−1), but net NO 3 − reduction suggested this was a relatively minor pathway for anaerobic CO2 production. Abundances...
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In an effort to characterize the species and production rates of various upland mosses and their relationship to both site drainage and time since fire, annual net primary production of six common moss species was measured. Several stands located near Delta Junction, interior Alaska, were located. These stands ranged from one to 116 years since fire in well-drained (dry) and moderately to somewhat poorly drained (wet) black spruce (Picea mariana)-feathermoss systems. Moss species composition varied greatly during the fire cycle, with Ceratodon purpureus dominating the earliest years after a fire, Aulacomnium palustre dominating the transitional and older stages, and Hylocomium splendens dominating the oldest, mature...
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To determine the influence of fire and thermokarst in a boreal landscape, we investigated peat cores within and adjacent to a permafrost collapse feature on the Tanana River Floodplain of Interior Alaska. Radioisotope dating, diatom assemblages, plant macrofossils, charcoal fragments, and carbon and nitrogen content of the peat profile indicate approximately 600 years of vegetation succession with a transition from a terrestrial forest to a sedge-dominated wetland over 100 years ago, and to a Sphagnum-dominated peatland in approximately 1970. The shift from sedge to Sphagnum, and a decrease in the detrended tree-ring width index of black spruce trees adjacent to the collapse coincided with an increase in the growing...
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Abstract. To determine the influence of fire and thermokarst in a boreal landscape, we investigated peat cores within and adjacent to a permafrost collapse feature on the Tanana River Floodplain of Interior Alaska. Radioisotope dating, diatom assemblages, plant macrofossils, charcoal fragments, and carbon and nitrogen content of the peat profile indicate ~600 years of vegetation succession with a transition from a terrestrial forest to a sedge-dominated wetland over 100 years ago, and to a Sphagnum-dominated peatland in approximately 1970. The shift from sedge to Sphagnum, and a decrease in the detrended tree-ring width index of black spruce trees adjacent to the collapse coincided with an increase in the growing...
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Changes in vegetation and soil properties following permafrost degradation and thermokarst development in peatlands may cause changes in net carbon storage. To better understand these dynamics, we established three sites in Alaska that vary in permafrost regime, including a black spruce peat plateau forest with stable permafrost, an internal collapse scar bog formed as a result of thermokarst, and a rich fen without permafrost. Measurements include year-round eddy covariance estimates of carbon dioxide (CO2), water, and energy fluxes, associated environmental variables, and methane (CH4) fluxes at the collapse scar bog. The ecosystems all acted as net sinks of CO2 in 2011 and 2012, when air temperature and precipitation...
    map background search result map search result map Effects of Experimental Water Table and Temperature Manipulations on Ecosystem CO2 Fluxes in an Alaskan Rich Fen Differential response of carbon fluxes to climate in three peatland ecosystems that vary in the presence and stability of permafrost Bacterial and enchytraeid abundance accelerate soil carbon turnover along a lowland vegetation gradient in interior Alaska Modeling soil thermal and carbon dynamics of a fire chronosequence in interior Alaska Short-term response of methane fluxes and methanogen activity to water table and soil warming manipulations in an Alaskan peatland Molecular investigations into a globally important carbon pool: permafrost-protected carbon in Alaskan soils Wetland succession in a permafrost collapse: interactions between fire and thermokarst Wetland succession in a permafrost collapse: interactions between fire and thermokarst Exploring the sensitivity of soil carbon dynamics to climate change, fire disturbance and permafrost thaw in a black spruce ecosystem Wetland succession in a permafrost collapse; interactions between fire and thermokarst Changes in Species, Areal Cover, and Production of Moss across a Fire Chronosequence in Interior Alaska Response of anaerobic carbon cycling to water table manipulation in an Alaskan rich fen Assessment of boreal forest historical C dynamics in the Yukon River Basin: relative roles of warming and fire regime change Fire effects on soil organic matter content, composition, and nutrients in boreal interior Alaska Decadal and long-term boreal soil carbon and nitrogen sequestration rates across a variety of ecosystems Exploring the sensitivity of soil carbon dynamics to climate change, fire disturbance and permafrost thaw in a black spruce ecosystem Effects of Experimental Water Table and Temperature Manipulations on Ecosystem CO2 Fluxes in an Alaskan Rich Fen Short-term response of methane fluxes and methanogen activity to water table and soil warming manipulations in an Alaskan peatland Decadal and long-term boreal soil carbon and nitrogen sequestration rates across a variety of ecosystems Differential response of carbon fluxes to climate in three peatland ecosystems that vary in the presence and stability of permafrost Wetland succession in a permafrost collapse: interactions between fire and thermokarst Wetland succession in a permafrost collapse: interactions between fire and thermokarst Wetland succession in a permafrost collapse; interactions between fire and thermokarst Response of anaerobic carbon cycling to water table manipulation in an Alaskan rich fen Changes in Species, Areal Cover, and Production of Moss across a Fire Chronosequence in Interior Alaska Fire effects on soil organic matter content, composition, and nutrients in boreal interior Alaska Molecular investigations into a globally important carbon pool: permafrost-protected carbon in Alaskan soils Bacterial and enchytraeid abundance accelerate soil carbon turnover along a lowland vegetation gradient in interior Alaska Assessment of boreal forest historical C dynamics in the Yukon River Basin: relative roles of warming and fire regime change Modeling soil thermal and carbon dynamics of a fire chronosequence in interior Alaska