Fires transform soil microbial communities directly via heat-induced mortality and indirectly by altering plant and soil characteristics. Emerging evidence suggests the magnitude of changes to some plant and soil properties increases with burn severity, but the persistence of changes varies among plant and soil characteristics, ranging from months to years post-fire. Thus, which environmental attributes shape microbial communities at intermediate time points during ecosystem recovery, and how these characteristics vary with severity, remains poorly understood. We identified the network of properties that influence microbial communities three years after fire, along a burn severity gradient in Sierra Nevada mixed-conifer forest. We used phospholipid fatty acid (PLFA) analysis and bacterial 16S-rDNA amplicon sequencing to characterize the microbial community in mineral soil. Using structural equation modelling, we applied a systems approach to identifying the interconnected relationships among severity, vegetation, soil, and microbial communities. Dead tree basal area, soil pH, and extractable phosphorus increased with severity, whereas live tree basal area, forest floor mass, and the proportion of the ≥53 μm soil fraction decreased. Forest floor loss was associated with decreased soil moisture across the severity gradient, decreased live tree basal area was associated with increased shrub coverage, and increased dead tree basal area was associated with increases in total and inorganic soil nitrogen. Soil fungal abundance decreased across the severity gradient, despite a slightly positive response of fungi to lower soil moisture in high severity areas. Bacterial phylogenetic diversity was negatively related to severity and was driven by differences in nutrients and soil texture. The abundance of Bacteroidetes increased and the abundance of Acidobacteria decreased across the severity gradient due to differences in soil pH. Overall, we found that the effects of burn severity on vegetation and soil physicochemical characteristics interact to shape microbial communities at an intermediate time point in ecosystem recovery.
Bibliographical noteFunding Information:
This work was supported by the USDA National Institute of Food and Agriculture , McIntire Stennis project 1006839 and by Michigan State University . JA was supported by an NSF Graduate Research Fellowship Program award. We thank Bernardo Maestrini and Joshua James for field assistance, and Katherine Walker and Thanwalee Sooksa-Nguan for laboratory assistance. We thank Hugh Safford (USDA Forest Service) and Erin Alvey for providing shrub coverage data. We thank Kyle Merriam and Michelle Coppoletta (USDA Forest Service, Plumas National Forest) for assistance in obtaining sampling permits and facilitating sampling logistics. We thank Jeffrey Doser from the Michigan State University Statistical Consulting Center for statistical assistance.
- Forest soils
- Microbial community composition
- Microbial community structure
- Microbial diversity
- Soil properties
PubMed: MeSH publication types
- Journal Article