Journal
FRONTIERS IN MICROBIOLOGY
Volume 6, Issue -, Pages -Publisher
FRONTIERS MEDIA SA
DOI: 10.3389/fmicb.2015.00817
Keywords
land cover; land use legacies; low molecular weight carbon compounds; microbial community function; microbial community composition; root exudates
Categories
Funding
- U.S. National Science Foundation [DEB-1021098, DEB-1021222]
- Virginia Tech's Open Access Subvention Fund
- Direct For Biological Sciences [1021222] Funding Source: National Science Foundation
- Division Of Environmental Biology [1021222] Funding Source: National Science Foundation
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Inputs of low molecular weight carbon (LMW-C) to soil primarily via root exudates are expected to be a major driver of microbial activity and source of stable soil organic carbon. It is expected that variation in the type and composition of LMW-C entering soil will influence microbial community composition and function. If this is the case then short-term changes in LMW-C inputs may alter processes regulated by these communities. To determine if change in the composition of LMW-C inputs influences microbial community function and composition, we conducted a 90 day microcosm experiment whereby soils sourced from three different land covers (meadows, deciduous forests, and white pine stands) were amended, at low concentrations, with one of eight simulated root exudate treatments. Treatments included no addition of LMW-C, and the full factorial combination of glucose, glycine, and oxalic acid. After 90 days, we conducted a functional response assay and determined microbial composition via phospholipid fatty acid analysis. Whereas we noted a statistically significant effect of exudate treatments, this only accounted for 3% of the variation observed in function. In comparison, land cover and site explained 46 and 41% of the variation, respectively. This suggests that exudate composition has little influence on function compared to site/land cover specific factors. Supporting the finding that exudate effects were minor, we found that an absence of LMW-C elicited the greatest difference in function compared to those treatments receiving any LMW-C. Additionally, exudate treatments did not alter microbial community composition and observable differences were instead due to land cover. These results confirm the strong effects of land cover/site legacies on soil microbial communities. In contrast, short-term changes in exudate composition, at meaningful concentrations, may have little impact on microbial function and composition.
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