Microbial Community-Level Physiological Profiles and Genetic Prokaryotic Structure of Burned Soils Under Mediterranean Sclerophyll Forests in Central Chile

Abstract

Forest fires alter soil microbial communities that are essential to support ecosystem recovery following land burning. These alterations have different responses according to soil abiotic pre- and post-fire conditions and fire severity, among others, and tend to decrease along vegetation recovery over time. Thus, understanding the effects of fires on microbial soil communities is critical to evaluate ecosystem resilience and restoration strategies in fire-prone ecosystems. We studied the state of community-level physiological profiles (CLPPs) and the prokaryotic community structure of rhizosphere and bulk soils from two fire-affected sclerophyll forests (one surveyed 17 months and the other 33 months after fire occurrence) in the Mediterranean climate zone of central Chile. Increases in catabolic activity (by average well color development of CLPPs), especially in the rhizosphere as compared with the bulk soil, were observed in the most recently affected site only. Legacy of land burning was still clearly shaping soil prokaryote community structure, as shown by quantitative PCR (qPCR) and Illumina MiSeq sequencing of the V4 region of the 16S rRNA gene, particularly in the most recent fire-affected site. The qPCR copy numbers and alpha diversity indexes (Shannon and Pielou’s evenness) of sequencing data decreased in burned soils at both locations. Beta diversity analyses showed dissimilarity of prokaryote communities at both study sites according to fire occurrence, and NO3– was the common variable explaining community changes for both of them. Acidobacteria and Rokubacteria phyla significantly decreased in burned soils at both locations, while Firmicutes and Actinobacteria increased. These findings provide a better understanding of the resilience of soil prokaryote communities and their physiological conditions in Mediterranean forests of central Chile following different time periods after fire, conditions that likely influence the ecological processes taking place during recovery of fire-affected ecosystems.

Impact of prescribed fire on soil microbial communities in a Southern Appalachian Forest clear-cut

“…Correlation analyses revealed significant associations between specific bacterial phyla and soil properties. Soil pH, a fundamental soil characteristic, exhibited positive correlations with Acidobacteria and Chloroflexi, emphasizing their potential preference for specific pH ranges ( Fierer and Jackson, 2006 ; Aponte et al, 2022 ). Conversely, Acidothermus, Acidipila, Mycobacterium, and Bradyrhizobium genera displayed negative correlations with soil pH, suggesting their sensitivity to pH fluctuations.…”

Forest Wildfires in Chile: Effects on Soil Degradation and Damage Mitigation

“…Legacy of land burning was still shaping soil microbial activity (i.e., microbial respiration) eight months after the fire, which was also reflected in lower carbon contents in burned soils [35]. Moreover, land burning still clearly shape soil prokaryotic community structure during the first three years after fire occurrence [23].…”

“…In Chile, despite the recurrence of extreme wildfires (e.g., Mataix-Solera et al [22], Úbeda and Sarricolea [10]), there is still very limited research focused on the impact of land burning on soil properties and biodiversity ( [8,[22][23][24][25][26][27][28]. Direct effects of fires shift soil microorganism's community structure (see below), reducing vegetation cover and altering soil's chemical and physical properties [20].…”

“…These changes can affect plant nutrition and carbon sequestration in the short and medium term [24]. In Mediterranean forest ecosystem of central Chile, even low-severity fires have altered soil microbial diversity and carbon storage capacity [23,35]. The effect of fire in soil communities has been reported.…”

Rising awareness to improve conservation of microorganisms in terrestrial ecosystems: advances and future directions in soil microbial diversity from Chile and the Antarctic Peninsula

“…Therefore, soil microbial diversity can only be fully understood through the integration with these connected disciplines. Despite some efforts to combine soil microbial diversity and geochemical data (e.g., Mandakovic et al, 2018;Aponte et al, 2022;Barret et al, 2022;Aguado-Norese et al, 2023), integrated studies are scarce. As an example, in our survey the type of soil was rarely explicitly indicated, despite the great diversity of soil orders identified in Chile (Casanova et al, 2013).…”