Abstract
Warming temperatures in continuous permafrost zones of the Arctic will alter both hydrological and geochemical soil conditions, which are strongly linked with heterotrophic microbial carbon (C) cycling. Heterogeneous permafrost landscapes are often dominated by polygonal features formed by expanding ice wedges: water accumulates in low centered polygons (LCPs), and water drains outward to surrounding troughs in high centered polygons (HCPs). These geospatial differences in hydrology cause gradients in biogeochemistry, soil C storage potential, and thermal properties. Presently, data quantifying carbon dioxide (CO2) and methane (CH4) release from HCP soils are needed to support modeling and evaluation of warming-induced CO2 and CH4 fluxes from tundra soils. This study quantifies the distribution of microbial CO2 and CH4 release in HCPs over a range of temperatures and draws comparisons to previous LCP studies. Arctic tundra soils were initially characterized for geochemical and hydraulic properties. Laboratory incubations at −2, +4, and +8°C were used to quantify temporal trends in CO2 and CH4 production from homogenized active layer organic and mineral soils in HCP centers and troughs, and methanogen abundance was estimated from mcrA gene measurements. Results showed that soil water availability, organic C, and redox conditions influence temporal dynamics and magnitude of gas production from HCP active layer soils during warming. At early incubation times (2–9 days), higher CO2 emissions were observed from HCP trough soils than from HCP center soils, but increased CO2 production occurred in center soils at later times (>20 days). HCP center soils did not support methanogenesis, but CH4-producing trough soils did indicate methanogen presence. Consistent with previous LCP studies, HCP organic soils showed increased CO2 and CH4 production with elevated water content, but HCP trough mineral soils produced more CH4 than LCP mineral soils. HCP mineral soils also released substantial CO2 but did not show a strong trend in CO2 and CH4 release with water content. Knowledge of temporal and spatial variability in microbial C mineralization rates of Arctic soils in response to warming are key to constraining uncertainties in predictive climate models.
| Original language | English |
|---|---|
| Article number | 616518 |
| Journal | Frontiers in Microbiology |
| Volume | 11 |
| DOIs | |
| State | Published - Jan 11 2021 |
Funding
We gratefully acknowledge the assistance of Bob Busey, Larry Hinzman, Kenneth Lowe, Deanne Brice, Ziming Yang, Craig Ulrich, and Tommy Phelps in obtaining and analyzing frozen core samples and field measurements as well as logistical support provided by UIC Science. We thank Hannah Long for developing the soil moisture sensor calibration curve and gravimetric water content profile during a Science Undergraduate Laboratory Internship (SULI) project. Authors deeply appreciate the technical support of Mr. Leo Rivera from Decagon Devices. Finally, we thank Vladimir Romanovsky for sharing continuous subsurface temperature measurements from the Utqiaġvik site and Dami Rich for assistance preparing the illustration in Figure 1. Funding. The Next-Generation Ecosystem Experiments in the Arctic (NGEE Arctic) project was supported by the Biological and Environmental Research program in the U.S. Department of Energy (DOE) Office of Science. Support for the SULI program was also provided by the DOE Office of Science. Oak Ridge National Laboratory was managed by UT-Battelle, LLC, for the DOE under Contract No. DE-AC05-00OR22725.
Keywords
- Arctic tundra
- anaerobic carbon mineralization
- mcrA
- methanogenesis
- permafrost
