Wood decomposing fungal community structure and function differ across decay stages of wood, but respond similarly to temperature

Background/Question/Methods

Microbial activity and thus decomposition respond to changes in temperature as well as wood quality. Thus, we explored how temperature and decay stage (a proxy for quality) interact to alter wood decomposition and fungal communities. Fungal communities in decomposing wood are fairly simple but differ between logs and vary between decomposition stages. Differences in fungal community structure may result in differences in fungal activity, and thus wood decomposition. Here, we address the questions: 1) Does decomposition stage effect fungal abundance, community structure, or potential enzyme production? 2) Does the response of microbial activity to temperature vary across stages of wood decomposition? And 3) Does warming alter fungal community structure or abundance in wood of varying decomposition stages?

We used Pinus taeda wood of varying decomposition stages collected from a common site. Each log was incubated in 3-gallon buckets in growth chambers at different temperatures (15 - 35℃ ) encompassing natural seasonal variation in eastern TN. To assess wood characteristics we measured wood density and pH. To assess fungal community structure and abundance we performed T-RFLP and qPCR, and to assess microbial activity we measured wood respiration rate, total C evolution, mass loss, and potential enzyme activity of 4 important enzymes.

Results/Conclusions

Fungal communities differed in structure and abundance between decay stages, and these differences resulted in altered activity but a similar response of activity to warming. The fungal community differed across decay stages and changed after six week incubation at different temperatures (15 - 35℃ ). Fungal abundance differed between decay stages and was 250% greater in stage 3 logs than stage 2 logs on average. Both decay stage and temperature altered microbial activity in our samples, however we observed no interaction between the effects of decay stage and temperature on microbial activity. While respiration increased with temperature, we observed the highest respiration rates in early (stage 1) and late (stage 4) stages of decay. These changes in fungal community and activity may be related to observed differences in wood characteristics across decay stages. Wood density decreased by 40% with increasing stages of decay. This research links fungal community structure to function and addresses a critical uncertainty in carbon cycling models, the response of wood decomposition to warming.