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In situ measurement of microbial activity and controls on microbial CO 2 production in the unsaturated zone
Author(s) -
Wood Brian D.,
Keller C. Kent,
Johnstone Donald L.
Publication year - 1993
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/92wr02315
Subject(s) - environmental science , nutrient , carbon dioxide , abundance (ecology) , hydrology (agriculture) , carbon cycle , soil science , ecology , geology , biology , ecosystem , geotechnical engineering
Carbon dioxide concentrations were measured at various depths and times in the unsaturated zones of two hydraulically and geochemically contrasting field sites, one in southeastern Washington state, and the other in south central Saskatchewan. In situ CO 2 production rates were calculated from a mass balance that accounted for diffusive fluxes and partitioning of CO 2 into an advecting aqueous phase. Production rates were compared with (1) microbial abundance and (2) subsurface temperature to determine whether subsurface CO 2 production rates could be expressed as a simple function of these two variables. At the Washington site, subsurface production was successfully expressed as a function of microbial abundance and temperature for a large portion of the year, but not near the end of the growing season. Although subsurface microbes and organic carbon were more abundant at the Saskatchewan site, subsurface CO 2 production rates were generally several orders of magnitude lower than at the Washington site, and no correlation could be established between microbial numbers, temperature, and production rate. The cases where production rates could not be expressed as a function of microbial numbers and temperature suggested conditions in which some other factor, such as nutrient limitations, was controlling.