Journal
GLOBAL CHANGE BIOLOGY BIOENERGY
Volume 13, Issue 11, Pages 1814-1830Publisher
WILEY
DOI: 10.1111/gcbb.12893
Keywords
diazotroph; free-living nitrogen fixation; marginal land; plant nitrogen demands; sustainable bioenergy; switchgrass
Funding
- U.S. Department of Energy [DE-FC02-07ER64494, DE-SC0014108, DE-SC0018409]
- National Science Foundation Long-term Ecological Research Program [DEB 1832042]
- Michigan State University AgBioResearch
- U.S. Department of Energy (DOE) [DE-SC0014108] Funding Source: U.S. Department of Energy (DOE)
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Climate variables are found to be strong drivers of FLNF rates in switchgrass systems, while a weak correlation between diazotrophic community composition and FLNF rates is observed. Seasonal contributions of FLNF have the potential to meet up to 80% of switchgrass nitrogen demands.
Free-living nitrogen fixation (FLNF) represents an important terrestrial N source and is gaining interest for its potential to contribute plant available N to bioenergy cropping systems. Switchgrass, a cellulosic bioenergy crop, may be particularly reliant on FLNF when grown on low N systems, like marginal lands. However, the potential contributions of FLNF to switchgrass as well as the controls on this process are not well understood. In this study, we evaluated drivers of FLNF rates and N-fixing microbial (diazotrophic) community composition in field-grown switchgrass systems over two growing seasons with high temporal sampling. We found that climate variables are strong drivers of FLNF rates in switchgrass systems, compared to other environmental and biological factors including soil nutrients and diazotrophic community composition. Increased soil moisture availability generally promoted FLNF rates, but extreme rainfall events were detrimental. These climate-related responses suggest a potential for loss of FLNF-derived N contributions under projected climate shifts. We found a significant, but weak correlation between diazotrophic community composition and FLNF rates. We also observed a significant shift in the diazotrophic community composition between 2017 and 2018 and similarly measured a significant difference in FLNF rates between growing seasons. Lastly, we found that seasonal FLNF N contributions, based on measurement with high temporal resolution, has the potential to meet up to 80% of switchgrass N demands suggesting that FLNF measurements extrapolated from fewer time points or locations may underestimate these potential N contributions.
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