Harden, J. W.

56 items:

Wetland succession in a permafrost collapse: interactions between fire and thermokarst 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... Categories: Publication; Types: Citation; Tags: M3-Improve Permafrost Mapping, Modeling, P1-Predict/Map Impact Changing Permafrost, and Monitoring
Modeling soil thermal and carbon dynamics of a fire chronosequence in interior Alaska Categories: Publication; Types: Citation; Tags: Relationship Understanding 2b-Effects of Fire on Ecosystems
Short-term response of methane fluxes and methanogen activity to water table and soil warming manipulations in an Alaskan peatland 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... Categories: Publication; Types: Citation; Tags: M1-Physical Science, M2-Standardized Stream and Lake Information
Modeling soil thermal and carbon dynamics of a fire chronosequence in interior Alaska Categories: Publication; Types: Citation; Tags: R2b-Effects of Fire on Ecosystems
Bacterial and enchytraeid abundance accelerate soil carbon turnover along a lowland vegetation gradient in interior Alaska Categories: Publication; Types: Citation; Tags: M1-Ecosystems, M1-Physical Science

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