Short-term response of soil microbial communities associated to different native vegetation type to wildfire

FERNÁNDEZ, GUILLERMO; BARBERO, FLORENCIA; FILIPPINI, EDITH; TORRES, ROMINA C.; GARCÍA, GABRIELA; MLEWSKI, CECILIA; ARGIBAY, DAIHANA; MERILES, JOSE

La Serena

Congreso; XLIV Congreso Chileno de Microbiología; 2022

Sociedad Chilena de Microbiología

In different ecosystems around the world, fire is considered an important disturbing agent that affects the structure of vegetation, the physicochemical properties of soils, biodiversity and the deterioration of ecosystem services. At a local scale, fires can modify vegetation physiognomies by partial or total elimination of the flora and increasing the spatial heterogeneity. In addition, wildfires affect and modify the edaphic communities and the biogeochemical cycles of nutrients and trace elements. In the Pampean ranges of central Argentina, most fires are caused accidentally or intentionally, because fire is used as a management tool for the regrowth of pastures. By using remote sensing, high-throughput amplicon sequencing, fatty acid methyl ester (FAME) analysis and geochemical measurements, we studied the effect of wildfire on soil microbial communities from Sierras Chicas of Córdoba, Argentina, after seven days of ceasefire. We hypothesized that vegetation type (forest, shrubland and grassland), soil pH and fire severity would be the most important determinants of microbial community composition. Results showed that, despite specifically selecting paired visibly burned vs. visibly not burned sites, fire had no significant effect on overall microbial community composition, with changes limited to a small number of taxa. However, the phylum Actinobacteria with representatives of Thermoleophilia class were identified as significant positive fire responders in the system. The remotely-sensed normalized burn ratio (NBR) combines satellite imagery from before and after burns, capturing changes in reflectance due to vegetation combustion and mortality. NBR ranges from low to moderate in our study, affecting the communities? distribution. Further, there were no significant differences between soil properties. This suggests that soil microbial response to low-moderate severity fires may be primarily mediated by vegetation, rather than a direct death from heat or changes in soil properties. Thus, effects in post-fire microbial communities may need more than one week to emerge.Future investigations are needed to strengthen our understanding of the microbial fire-response framework including direct death from fire exposure, temporal response to fire-induced changes to soil environment, and response to different fire regimes or return intervals.