Long term repeated prescribed burning increases evenness in the basidiomycete laccase gene pool in forest soils

Abstract

Repeated prescribed burning alters the biologically labile fraction of nutrients and carbon of soil organic matter (SOM). Using a long-term (30 years) repeated burning experiment where burning has been carried out at a 2-or 4-year frequency, we analysed the effect of prescribed burning on gross potential C turnover rates and phenol oxidase activity in relation to shifts in SOM composition as observed using Fourier-transform infrared spectroscopy. In tandem, we assessed the genetic diversity of basidiomycete laccases. While the overall effect of burning was a decline in phenol oxidase activity, Shannon diversity and evenness of laccases was significantly higher in burned sites. Co-correspondence analysis of SOM composition and laccase operational taxonomic unit frequency data also suggested a strong correlation. While this correlation could indicate that the observed increase in laccase genetic diversity due to burning is due to increased resource diversity, a temporal replacement of the most abundant members of the assembly by an otherwise dormant pool of fungi cannot be excluded. As such, our results fit the intermediate disturbance hypothesis. Effects were stronger in plots burned in 2-year rotations, suggesting that the 4-year burn frequency may be a more sustainable practice to ensure the long-term stability of C cycling in such ecosystems.

Frequency of prescribed burning in an upland oak forest determines soil and litter properties and alters the soil microbial community

“…The technique we used to assay the SMC did not give us resolution to identify specific bacteria with known roles in different nutrient cycle processes. However, the shift in Gram negative bacterial PLFA abundance signified community differences occurring at broad taxonomic levels that may alter ecosystem function, specifically carbon cycling, as supported by other studies measuring soil microbial function (Giai and Boerner, 2007;Artz et al, 2009;Ponder et al, 2009).…”

“…A previous study suggested low intensity prescribed burning could cause moderate changes to the SMC in savannas and forests likely due to changes in nutrient and substrate availability (Ponder et al, 2009). It has also been found that decreases in carbon-cycling extracellular enzyme activity and SOC can occur with increasing burn frequency (Artz et al, 2009). There are very few studies reporting effects of long-term repetitive prescribed burning on soil microbial community composition.…”

“…However, there have been few studies to our knowledge that examine the relationship between changes in soil properties and the SMC due to frequent prescribed burning in oak forests. Some studies have looked at differences between microbial extracellular enzymes in response to prescribed burning and have found relationships between soil microbial biomass, SOC and decreased functioning (Eivazi and Bayan, 1996;Giai and Boerner, 2007;Artz et al, 2009). The longterm indirect effects in the soil microenvironment such as release of available nutrients, increased soil pH, warmer exposed soil and reduced organic matter may be critical to the abundance, functioning and composition of SMC along with nutrient availability.…”

Response of soil microbial communities to management strategies for enhancing Scots pine (Pinus sylvestris) establishment on heather (Calluna vulgaris) moorland

“…Although the effect of repeated prescribed burning on heather moor soil fungal communities has not been investigated, there is good evidence that soil fungal communities, including symbiotic mycorrhizal and decomposer fungi, along with microbial biomass and physiological activities, are altered in certain forests if long term burning is conducted more frequently than quadrennially (Bastias et al 2006a,b;Campbell et al 2008;Artz et al 2009). Since we observed no evidence for altered fungal communities at Abernethy Forest ca 6 years following the experimental burn, our data suggest that burning heather moors on a typical muirburn cycle is unlikely to have an adverse impact on soil fungal communities.…”

“…The structure of communities of soil fungi (Bettucci and Alonso 1995;Chen and Cairney 2002;Bastias et al 2006b), along with those of ectomycorrhizal and arbuscular mycorrhizal fungi (eg Gibson and Hetrick 1988;Stendell et al 1999;Grogan et al 2000;Bastias et al 2006a), have, however, frequently been shown to change following burning. Importantly, these changes in soil fungal communities may be associated with altered diversity of fungi that produce enzymes involved in the turnover of major soil C pools such as cellulose or phenolic compounds (Artz et al 2009;Bastias et al 2009), suggesting that fungus-driven decomposition processes can be affected by some burning regimes.…”