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Title: Switchgrass cultivars alter microbial contribution to deep soil C in Nebraska

Author
item ROOSENDAAL, DAMARIS
item Stewart, Catherine
item DENEF, KAROLIEN - COLORADO STATE UNIVERSITY
item FOLLETT, RONALD - RETIRED ARS EMPLOYEE
item Pruessner, Elizabeth
item VARVEL, GARY
item SAATHOFF, AARON - LI-COR, INC.
item Palmer, Nathan - Nate
item Sarath, Gautam
item Jin, Virginia
item Schmerr, Martin
item SOUNDARARAJAN, MADHAVAN - UNIVERSITY OF NEBRASKA

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 8/16/2013
Publication Date: N/A
Citation: N/A

Interpretive Summary: SUMMARY NOT NECESSARY, MEETING ABSTRACT ONLY.

Technical Abstract: Switchgrass (Panicum virgatum L.) is a C4, perennial grass that is being developed as a bioenergy crop for the United States. While aboveground biomass production is well documented for switchgrass ecotypes (lowland, upland) and cultivars, there has been little focus on the impact of plant belowground productivity on microbial communities at subsurface soil depths. Differences in belowground productivity by switchgrass ecotypes could lead to distinct differences in belowground microbial biomass and microbial community composition. In this study, stable isotope probing of phospholipid fatty acids (PLFA) was used to measure microbial community abundance and composition for two switchgrass cultivars, lowland cultivar ‘Kanlow’ and upland cultivar ‘Summer’, following 13CO2 pulse-chase labeling. Total PLFA abundance decreased with soil depth and was greater for Kanlow compared to Summer. Community structure also changed with depth. The relative abundance of PLFA biomarkers for actinomycetes and gram-positive bacteria increased with depth to 60-90 cm in depth then decreased throughout the remainder of the depth profile (>90 cm). The opposite was observed for gram-negative bacteria, fungi, and arbuscular mycorrhizal fungi (AMF). Although we observed differences in microbial biomass that were correlated to plant productivity, small differences in microbial community composition were detected between cultivars, with Summer having more AMF markers at depth and fewer gram negative markers compared to Kanlow. We also detected more neutral lipid fatty acids (NLFAs) for AMF deeper in the profile for Summer. Fungi and AMF comprised less than 10% of biomass, but were predominantly involved in rhizodeposit C metabolism although all other groups metabolized rhizodeposit C. For bioenergy production systems, variation between switchgrass ecotypes could impact C sequestration and storage as well as potentially other belowground processes by altering microbial communities.