Abstract
Forest disturbance increases soil nitrification rates in temperate ecosystems, but little is understood regarding contributions of newly discovered complete ammonia-oxidizing bacteria (i.e., comammox) to this important ecosystem process. We sampled soils across eight historically disturbed and adjacent reference forested watersheds at the Coweeta Hydrologic Laboratory in North Carolina and used qPCR to determine abundance of three groups of nitrifiers: canonical ammonia-oxidizing bacteria (AOB), ammonia-oxidizing archaea (AOA), and comammox bacteria (CAOB). All three groups exhibited significantly higher abundance in disturbed soils, though CAOB were more abundant than either AOA or AOB. Further, CAOB showed similar correlations with soil variables compared with AOB, suggesting similar niche requirements. CAOB were better predictors of soil NO3 − relative to AOA and AOB, suggesting CAOB are functionally relevant to nitrification in temperate forests.
| Original language | English |
|---|---|
| Article number | 107801 |
| Journal | Soil Biology and Biochemistry |
| Volume | 145 |
| DOIs | |
| State | Published - Jun 2020 |
Bibliographical note
Publisher Copyright:© 2020
Funding
This work was funded by the Coweeta LTER, funded by National Science Foundation grant DEB-1637522 and by the Virginia Tech Global Change Center. We thank the Coweeta Hydrologic Laboratory, Southern Research Station, USDA Forest Service for support and Angela Weisel for assistance with field soil sampling and laboratory analyses. We also thank Bobbie Niederlehner for help with analytical chemistry and Steve McBride for thoughtful feedback on the manuscript. Finally, we thank two anonymous reviewers, whose thoughtful comments greatly improved this manuscript. Linear regression models showed all nitrifier groups as significant predictors of soil NO3−, though CAOB abundance explained more variation in soil NO3− than either AOB or AOA (R2 = 0.65 vs .26 and .32, respectively, Fig. 2D, E, F). This apparent coupling of CAOB to soil NO3− may reflect higher energy efficiency of CAOB (Costa et al., 2006), which perform both the rate-limiting step (ammonia-oxidation) and the nitrate-producing step (nitrite-oxidation) of nitrification. Additionally, we used model selection with AICc to compare models with all possible combinations of nitrifier groups as predictors of soil NO3−, selecting the model with the highest AICc weight (Table S3). The best-supported model retained CAOB and AOB abundance as predictors, which is consistent with a recent modeling study that suggested AOB are more important than AOA to nitrification in these soils, despite higher abundance of AOA relative to AOB (Lin et al., 2017). Future work should utilize methods to directly attribute nitrification rates to different nitrifier groups to mechanistically test the relationships observed here (e.g., stable isotope probing). However, overall, our results demonstrate that CAOB are more abundant than other ammonia-oxidizers in our soils and strong relationships between CAOB and NO3− suggest that CAOB are functionally important to soil N-cycling in temperate forests of the eastern US.This work was funded by the Coweeta LTER, funded by National Science Foundation grant DEB-1637522 and by the Virginia Tech Global Change Center. We thank the Coweeta Hydrologic Laboratory, Southern Research Station, USDA Forest Service for support and Angela Weisel for assistance with field soil sampling and laboratory analyses. We also thank Bobbie Niederlehner for help with analytical chemistry and Steve McBride for thoughtful feedback on the manuscript. Finally, we thank two anonymous reviewers, whose thoughtful comments greatly improved this manuscript.
| Funders | Funder number |
|---|---|
| CAOB | |
| Virginia Tech Global Change Center | |
| National Science Foundation Arctic Social Science Program | 1637522, DEB-1637522 |
| U.S. Dept. of Agriculture Forest Service |
Keywords
- AOA
- AOB
- Comammox
- Disturbance
- Forest
- Nitrification
ASJC Scopus subject areas
- Microbiology
- Soil Science