Abstract
Global wildfire activity has increased since the 1970s and is projected to intensify throughout the 21st century. Wildfires change the composition and biodegradability of soil organic matter (SOM) which contains nutrients that fuel microbial metabolism. Though persistent forms of SOM often increase postfire, the response of more biodegradable SOM remains unclear. Here we simulated severe wildfires through a controlled “pyrocosm” approach to identify biodegradable sources of SOM and characterize the soil metabolome immediately postfire. Using microbial amplicon (16S/ITS) sequencing and gas chromatography-mass spectrometry, heterotrophic microbes (Actinobacteria, Firmicutes, and Protobacteria) and specific metabolites (glycine, protocatechuate, citric cycle intermediates) were enriched in burned soils, indicating that burned soils contain a variety of substrates that support microbial metabolism. Molecular formulas assigned by 21 T Fourier transform ion cyclotron resonance mass spectrometry showed that SOM in burned soil was lower in molecular weight and featured 20 to 43% more nitrogen-containing molecular formulas than unburned soil. We also measured higher water extractable organic carbon concentrations and higher CO2 efflux in burned soils. The observed enrichment of biodegradable SOM and microbial heterotrophs demonstrates the resilience of these soils to severe burning, providing important implications for postfire soil microbial and plant recolonization and ecosystem recovery.
| Original language | English |
|---|---|
| Pages (from-to) | 4167-4180 |
| Number of pages | 14 |
| Journal | Environmental Science and Technology |
| Volume | 58 |
| Issue number | 9 |
| DOIs | |
| State | Published - Mar 5 2024 |
Funding
This research was funded by M.J.W. and T.B. from the National Science Foundation under grant number 2114868 and the United States Department of Agriculture (USDA) National Institute of Food and Agriculture through AFRI grant number 2021-67019-34608. The Table of Contents artwork was created with BioRender.com. We thank Troy Bauder, Karl Whitman, and the Poudre Fire Authority for providing a safe location for the pyrocosm burns. We thank Daniel Reuss and the EcoCore facility at Colorado State University for assisting with soil CO2 measurements and total soil C and N measurements. GC-MS was performed at the CSU ARC-BIO facility (RRID: SCR_021758). Thanks to Dr. Prithwiraj De for helping with GC-MS derivatization and sample preparation. Thanks to Dr. Robert Young for providing code for the FT-ICR MS data analysis. Thanks to researchers at the Rocky Mountain Research Station biogeochemistry lab, owned by the USDA Forest Service, for conducting dissolved organic carbon, dissolved total nitrogen, and ammonium measurements. Thanks to researchers at the National High Magnetic Field Laboratory ICR User Facility which is supported by the National Science Foundation Division of Chemistry and Division of Material Research through DMR-1644779 and DMR-2128556. Data for this research were provided by the Niwot Ridge LTER program (NWT VII: NSF DEB-1637686, NWT VIII: NSF DEB-2224439). Use of firm, trade, or product names is for descriptive purposes only and does not imply indorsement by the U.S. government. This research was funded by M.J.W. and T.B. from the National Science Foundation under grant number 2114868 and the United States Department of Agriculture (USDA) National Institute of Food and Agriculture through AFRI grant number 2021-67019-34608. The Table of Contents artwork was created with BioRender.com. We thank Troy Bauder, Karl Whitman, and the Poudre Fire Authority for providing a safe location for the pyrocosm burns. We thank Daniel Reuss and the EcoCore facility at Colorado State University for assisting with soil CO measurements and total soil C and N measurements. GC-MS was performed at the CSU ARC-BIO facility (RRID: SCR_021758). Thanks to Dr. Prithwiraj De for helping with GC-MS derivatization and sample preparation. Thanks to Dr. Robert Young for providing code for the FT-ICR MS data analysis. Thanks to researchers at the Rocky Mountain Research Station biogeochemistry lab, owned by the USDA Forest Service, for conducting dissolved organic carbon, dissolved total nitrogen, and ammonium measurements. Thanks to researchers at the National High Magnetic Field Laboratory ICR User Facility which is supported by the National Science Foundation Division of Chemistry and Division of Material Research through DMR-1644779 and DMR-2128556. Data for this research were provided by the Niwot Ridge LTER program (NWT VII: NSF DEB-1637686, NWT VIII: NSF DEB-2224439). Use of firm, trade, or product names is for descriptive purposes only and does not imply indorsement by the U.S. government. 2