2014 GSA Annual Meeting in Vancouver, British Columbia (19–22 October 2014)

Paper No. 295-16
Presentation Time: 12:45 PM

SOIL MICROBIAL RESPIRATION AND BIOMASS AS A FUNCTION OF SOIL MOISTURE CONTENT IN A LENXINGTON SILT LOAM FROM WEST TENNESSEE


DRIVER, Damani A.1, O'DELL, Kaela2, PARADIS, Charles J.3, MAHMOUDI, Nagissa2, FORTNEY, Julian L.4, SCHAEFFER, Sean M.5 and HAZEN, Terry C.6, (1)Earth & Planetary Sciences, University of Tennessee, Knoxville, Nashville, TN 37204, (2)Knoxville, TN 37901, (3)Earth & Planetary Sciences, University of Tennessee Knoxville, 306 EPS Building, 1412 Circle Drive, Knoxville, TN 37996-1410, (4)Civil and Environmental Engineering, University of Tennessee Knoxville, 325 John D. Tickle Building, Knoxville, TN 37996-2313, (5)Biosystems Engineering and Soil Science, University of Tennessee, 2506 EJ Chapman Dr, Knoxville, TN 37996, (6)Earth & Planetary Sciences, University of Tennessee Knoxville, 306 EPS Building, 1412 Circle Drive, Knoxville, TN 37996

Observations, experimentation, and models suggest that recent and severe weather events, e.g. drought and heavy precipitation, are due to anthropogenic climate change. The effects of severe weather on microbial soil respiration are thought to be dependent on the ecosystem of interest. In this study, we quantified changes in microbial respiration and biomass as a function of soil moisture in a Lexington silt loam from West Tennessee. We hypothesized that microbial respiration and biomass are dependent on the magnitude and duration of changes in moisture content.

Soil moisture was controlled by weekly water addition to simulate ambient and heavy moisture conditions, which were held at 16% and 32%, respectively. Drought treatment received no water. CO2 was measured continuously for six weeks. Microbial biomass and soil moisture were measured pre and post-incubation.

Cumulative CO2 production was significantly higher in the drought treatment than in the heavy moisture treatment after one week. After two weeks, cumulative CO2 production failed to increase in the drought treatment while continuing to increase in ambient and heavy moisture treatments. Cumulative CO2 production was significantly less in the drought treatment than in the heavy moisture treatment after six weeks. Post-incubation moisture measurement verified that ambient and heavy moisture contents were maintained at approximately 16% and 32%, respectively. The drought treatment soil moisture content was below detection limits at the end of the experiment. Biomass data analysis is underway and will provide additional information on the response of the microbial community to changes in moisture.

This study strongly suggests that extended periods of drought may negatively impact microbial respiration rates in West Tennessee soils. Furthermore, the effect of moisture content on soil respiration may not be apparent after one week and drought conditions may initially facilitate increased respiration. Finally, this study demonstrated that after an extended period, increased moisture content may not result in a significant increase in respiration. These results may support future studies of larger scale soil microbial respiration resulting from new patterns in anthropogenic-driven precipitation and drought regimens in various ecosystems.

Session No. 295

Environmental and Engineering Geology (Posters)
Wednesday, 22 October 2014: 9:00 AM-6:30 PM
Exhibition Hall C (Vancouver Convention Centre-West)
Geological Society of America Abstracts with Programs. Vol. 46, No. 6, p.717
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