Abstract
Riverine floodplains are ecologically and economically valuable ecosystems that are heavily threatened by anthropogenic stressors. Microbial communities in floodplain soils mediate critical biogeochemical processes, yet we understand little about the relationship between these communities and variation in hydrologic connectivity related to land management or topography. Here, we present metagenomic evidence that differences among microbial communities in three floodplain soils correspond to a long-term gradient of hydrologic connectivity. Specifically, all strictly anaerobic taxa and metabolic pathways were positively associated with increased hydrologic connectivity and flooding frequency. In contrast, most aerobic taxa and all strictly aerobic pathways were negatively related to hydrologic connectivity and flooding frequency. Furthermore, the genetic potential to metabolize organic compounds tended to decrease as hydrologic connectivity increased, which may reflect either the observed concomitant decline of soil organic matter or the parallel increase in both anaerobic taxa and pathways. A decline in soil N, accompanied by an increased genetic potential for oligotrophic N acquisition subsystems, suggests that soil nutrients also shape microbial communities in these soils. We conclude that differences among floodplain soil microbial communities can be conceptualized along a gradient of hydrologic connectivity. Additionally, we show that these differences are likely due to connectivity-related variation in flooding frequency, soil organic matter, and soil N. Our findings are particularly relevant to the restoration and management of microbially mediated biogeochemical processes in riverine floodplain wetlands.
Original language | English |
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Pages (from-to) | 630-644 |
Number of pages | 15 |
Journal | Microbial Ecology |
Volume | 73 |
Issue number | 3 |
DOIs | |
State | Published - Apr 1 2017 |
Externally published | Yes |
Funding
We thank Genevieve Leet for assistance with field work, as well as Zachary Freedman and Rima Upchurch for their analytical and bioinformatics insights. We also thank other members of both the Wiley lab and Zak lab who provided advice and support throughout this project, as well as Robert Lyons and Jeanne Geskes for their guidance with DNA sequencing. We thank Eric Dunton, Steve Kahl, and several additional members of the SNWR staff for refuge access, assistance with materials and equipment for sampling, and valuable ecological insights about our study system. We also thank two anonymous reviewers for their thoughtful comments on a previous draft of this manuscript. Funding for our work was provided by the Horace H. Rackham School of Graduate Studies and the School of Natural Resources and Environment at the University of Michigan, as well as the United States Fish and Wildlife Service.
Keywords
- Hydrologic connectivity
- Microbial community
- Riverine floodplain
- Soil
- Wetland restoration