Contrasting fungal responses to wildfire across different ecosystem types

Abstract

Wildfire affects our planet's biogeochemistry both by burning biomass and by driving changes in ecological communities and landcover. Some plants and ecosystem types are threatened by increasing fire pressure while others respond positively to fire, growing in local and regional abundance when it occurs regularly. However, quantifying total ecosystem response to fire demands consideration of impacts not only on aboveground vegetation, but also on soil microbes like fungi, which influence decomposition and nutrient mineralization. If fire‐resistant soil fungal communities co‐occur with similarly adapted plants, these above‐ and belowground ecosystem components should shift and recover in relative synchrony after burning. If not, fire might decouple ecosystem processes governed by these different communities, affecting total functioning. Here, we use a natural experiment to test whether fire‐dependent ecosystems host unique, fire‐resistant fungal communities. We surveyed burned and unburned areas across two California ecosystem types with differing fire ecologies in the immediate aftermath of a wildfire, finding that the soil fungal communities of fire‐dependent oak woodlands differ from those of neighbouring mixed evergreen forests. We discovered furthermore that the latter are more strongly altered compositionally by fire than the former, suggesting that differences in fungal community structure support divergent community responses to fire across ecosystems. Our results thus indicate that fire‐dependent ecosystems may host fire‐resistant fungal communities.

Soil microbial communities are not altered by garlic mustard in recently invaded central Illinois forests

“…We also compared the relative abundance and species richness of saprotrophic, pathogenic, and mycorrhizal functional guilds among garlic mustard treatments and between sampling dates using FUNGuild (Nguyen et al, 2016) to assign functional guild to taxa. Assignments with “probable” or “highly probable” confidence scores were included, and in cases where taxa were assigned to more than one guild, mycorrhizal classification was given higher priority than pathogenic, which was given higher priority than saprotrophic guild (Smith et al, 2021).…”

Woodland wildfire enables fungal colonization of encroaching Douglas‐fir

“…We do not observe that Douglas-firs facilitate oak colonization to the same extent, potentially due to stricter hostspecificity in Douglas-fir root fungal communities (Figure 4). Third, we observed significant but variable effects of fire on root fungal colonization (Figure 1), richness (Figure 2) and community structure (Figure 3), demonstrating that fire-driven shifts in soil fungal communities (Smith et al, 2021) translate to differences in root-associated fungal community assembly. In support of H3, we found negative effects of fire on fungal species richness with both Douglas-fir and oak when growing in Douglas-fir forest soil, and a negative effect of fire on root fungal colonization in oak seedlings in Douglas-fir forest soil.…”

“…We chose this distance because prior investigation of ectomycorrhizal fungi found that spatial autocorrelation was limited to approximately 3 m distance (Lilleskov et al, 2004). Moreover, a prior study in this system found that the minor influence of geography on soil fungal community composition relative to other predictors increased most rapidly among the shortest pairwise distances (Smith et al, 2021). This indicates that even small spatial distances between samples create differences in community composition that are large relative to the maximum potential impact of geography, minimizing the potential statistical challenge of spatial autocorrelation in this system.…”

Soil microbial communities are not altered by garlic mustard in recently invaded central Illinois forests

“…We also compared the relative abundance and species richness of saprotrophic, pathogenic, and mycorrhizal functional guilds among garlic mustard treatments and between sampling dates using FUNGuild (Nguyen et al 2016) to assign functional guild to taxa. Assignments with “probable” or “highly probable” confidence scores were included and in cases where taxa were assigned to more than one guild, mycorrhizal classification was given higher priority than pathogenic, which was given higher priority than saprotrophic (Smith et al 2021).…”