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Effect of Elevated CO 2 and Drought on Soil Microbial Communities Associated with Andropogon gerardii
Author(s) -
Kassem Issmat I.,
Joshi Puneet,
Sigler Von,
Heckathorn Scott,
Wang Qi
Publication year - 2008
Publication title -
journal of integrative plant biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.734
H-Index - 83
eISSN - 1744-7909
pISSN - 1672-9072
DOI - 10.1111/j.1744-7909.2008.00752.x
Subject(s) - andropogon , biomass (ecology) , microbial population biology , ecosystem , agronomy , stomatal conductance , soil water , water content , soil carbon , biology , botany , ecology , bacteria , photosynthesis , genetics , geotechnical engineering , engineering
Our understanding of the effects of elevated atmospheric CO 2 , singly and in combination with other environmental changes, on plant‐soil interactions is incomplete. Elevated CO 2 effects on C 4 plants, though smaller than on C 3 species, are mediated mostly via decreased stomatal conductance and thus water loss. Therefore, we characterized the interactive effect of elevated CO 2 and drought on soil microbial communities associated with a dominant C 4 prairie grass, Andropogon gerardii Vitman. Elevated CO 2 and drought both affected resources available to the soil microbial community. For example, elevated CO 2 increased the soil C:N ratio and water content during drought, whereas drought alone decreased both. Drought significantly decreased soil microbial biomass. In contrast, elevated CO 2 increased biomass while ameliorating biomass decreases that were induced under drought. Total and active direct bacterial counts and carbon substrate use (overall use and number of used sources) increased significantly under elevated CO 2 . Denaturing gradient gel electrophoresis analysis revealed that drought and elevated CO 2 , singly and combined, did not affect the soil bacteria community structure. We conclude that elevated CO 2 alone increased bacterial abundance and microbial activity and carbon use, probably in response to increased root exudation. Elevated CO 2 also limited drought‐related impacts on microbial activity and biomass, which likely resulted from decreased plant water use under elevated CO 2 . These are among the first results showing that elevated CO 2 and drought work in opposition to modulate plant‐associated soil‐bacteria responses, which should then influence soil resources and plant and ecosystem function.