Abstract
Plant–microbial feedbacks are important drivers of plant community structure and dynamics. These feedbacks are driven by the variable modification of soil microbial communities by different plant species. However, other factors besides plant species can influence soil communities and potentially interact with plant–microbial feedbacks. We tested for plant–microbial feedbacks in two Eucalyptus species, E. globulus and E. obliqua, and the influence of forest fire on these feedbacks. We collected soils from beneath mature trees of both species within native forest stands on the Forestier Peninsula, Tasmania, Australia, that had or had not been burnt by a recent forest fire. These soils were subsequently used to inoculate seedlings of both species in a glasshouse experiment. We hypothesized that (i) eucalypt seedlings would respond differently to inoculation with conspecific versus heterospecific soils (i.e., exhibit plant–microbial feedbacks) and (ii) these feedbacks would be removed by forest fire. For each species, linear mixed effects models tested for differences in seedling survival and biomass in response to inoculation with conspecific versus heterospecific soils that had been collected from either unburnt or burnt stands. Eucalyptus globulus displayed a response consistent with a positive plant–microbial feedback, where seedlings performed better when inoculated with conspecific versus heterospecific soils. However, this effect was only present when seedlings were inoculated with unburnt soils, suggesting that fire removed the positive effect of E. globulus inoculum. These findings show that external environmental factors can interact with plant–microbial feedbacks, with possible implications for plant community structure and dynamics.
Highlights
Plant species may differentially modify soil microbial community structure through the addition of chemical compounds and organic matter, altering habitat and resources (Ehrenfeld et al 2005)
Eucalyptus globulus displayed a response consistent with a positive plant–microbial feedback, where seedlings performed better when inoculated with conspecific versus heterospecific soils. This effect was only present when seedlings were inoculated with unburnt soils, suggesting that fire removed the positive effect of E. globulus inoculum. These findings show that external environmental factors can interact with plant–microbial feedbacks, with possible implications for plant community structure and dynamics
Our findings suggest that species-specific effects of mature eucalypts on soil microbial communities can lead to plant–microbial feedbacks and that these feedbacks may vary among eucalypt species
Summary
Plant species may differentially modify soil microbial community structure through the addition of chemical compounds and organic matter, altering habitat and resources (Ehrenfeld et al 2005). Negative plant–microbial feedbacks are thought to maintain high levels of tree diversity (Mangan et al 2010; McCarthy-Neumann and Kobe 2010a; Terborgh 2012). In these cases, the performance of conspecific seedlings is reduced in close proximity to adult trees due to an accumulation of host-specific soil pathogens, while the performance of heterospecific seedlings is relatively unhindered (i.e., a Janzen-Connell effect; Connell 1971; Janzen 1970). Little is known regarding the influence of external environmental factors on plant– microbial feedbacks
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