Wildfire impact: Natural experiment reveals differential short-term changes in soil microbial communities

Abstract

A wildfire which overran a sensor network site provided an opportunity (a natural experiment) to monitor short-term post-fire impacts (immediate and up to three months post-fire) in remnant eucalypt woodland and managed pasture plots. The magnitude of fire-induced changes in soil properties and soil microbial communities was determined by comparing (1) variation in fireadapted eucalypt woodland vs. pasture grassland at the burnt site; (2) variation at the burnt woodland-pasture sites with variation at two unburnt woodland-pasture sites in the same locality; and (3) temporal variation pre-and post-fire. In the eucalypt woodland, soil ammonium, pH and ROC content increased post-fire, while in the pasture soil, soil nitrate increased post-fire and became the dominant soluble N pool. However, apart from distinct changes in N pools, the magnitude of change in most soil properties was small when compared to the unburnt sites. At the burnt site, bacterial and fungal community structure showed significant temporal shifts between pre-and post-fire periods which were associated with changes in soil nutrients, especially N pools. In contrast, microbial communities at the unburnt sites showed little temporal change over the same period. Bacterial community composition at the burnt site also changed dramatically post-fire in terms of abundance and diversity, with positive impacts on abundance of phyla such as Actinobacteria, Proteobacteria and Firmicutes. Large and rapid changes in soil bacterial community composition occurred in the fire-adapted woodland plot compared to the pasture soil, which may be a reflection of differences in vegetation composition and fuel loading. Given the rapid yet differential response in contrasting land uses, identification of key soil bacterial groups may be useful in assessing recovery of fire-adapted ecosystems, especially as wildfire frequency is predicted to increase with global climate change.

Wildfire effects on the microbial activity and diversity in a Mediterranean forest soil

“…In both, QQ1 and QQ2 areas Actinobacteria and Firmicutes phyla were detected. In previous studies using analysis of the 16S rRNA gene clone libraries the presence of Firmicutes in burnt soils (Belova et al, 2014) and an increase in Actinobacteria in burnt soils compared with control soil was reported (Ferrenberg et al, 2013;Prendergast-Miller et al, 2017). Concerning to the Bacteroidetes phylum its presence is very abundant in QQ1 in contrast with that in QQ2 in which it was not detected.…”

Frequent fire reorganizes fungal communities and slows decomposition across a heterogeneous pine savanna landscape

“…Fungi tend to be more susceptible to fire than bacteria are (Dooley & Treseder, 2012), but their responses to fire vary among taxa and ecological guilds (Dumontet et al, 1996;Mabuhay et al, 2003). Most fire-fungus studies have assessed the effects of high-intensity wildfires, which cause large declines in fungal biomass and result in strong compositional shifts in fungal communities (Treseder et al, 2004;Dooley & Treseder, 2012;Holden et al, 2013;Prendergast-Miller et al, 2017). Although fire responses may vary among biomes, fungal community shifts in managed pyrogenic ecosystems may differ from wildfire effects because prescribed fires often have very different characteristics (e.g.…”

Effects of fire frequency on litter decomposition as mediated by changes to litter chemistry and soil environmental conditions

“…Previous work has documented shifts in soil enzyme activity in response to the reintroduction of fire in deciduous forests in Ohio [24], which may impact decomposition of soil organic matter. Fire can also impact litter decomposition if decomposer microbe populations shift [25] or if the local microbial community is best-adapted to decomposing local litter [26]. Finally, post-fire changes to nutrient availability in mineral soil [19, 27] may alleviate nutrient-limitation and increase activity of decomposing microbes.…”