Temperature and endophytes controlled competition of wood-degrading fungi and patterns of decay

Background/Question/Methods

Wood decomposition is primarily fulfilled by brown rot and white rot fungi in temperate and boreal forests. The balance between these fungi determines the patterns of wood decomposition and carbon cycle in forests. But this balance may shift in a warmer environment, especially in high latitude. Additionally, endophyte may assert influence over the fungal competition through priority effect. In this study, we use paper birch and two common fungi to answer two questions 1) How does increased temperature affect the competition between brown rot and white rot fungi? 2) How do endophytes interact with fungi from the soil and influence wood decay?

A microcosm system was used to simulate competition between Piptoporus betulinus (brown rot fungi) and Fomes fomentarius (white rot fungi) on small birch stem in the presence/absence of its endophytes. Microcosms were incubated in 25°C and 30°C for five months. Effect of endophyte was tested by compare microcosms contained autoclaved (no endophyte) and fresh but surface sterilized (endophyte present) wood. Samples were tested for mass loss, water content, dilute alkaline solubility and pH. Quantitative PCR were used to obtain relative abundance of P. betulinus and F. fomentarius.

Results/Conclusions

Presence of endophyte significantly reduced the decay rate when they were competing with external fungi, indicating that part of their energy was allocated to interspecies antagonism from metabolizing wood. In the absence of external fungus, endophytes alone caused significant amount of wood decay. Activity of P. betulinus was slower in higher temperature, but F. fomentarius was not affected. Characters of residue showed that when both fungi were present, wood tend to have white rot in higher temperature. Higher temperature also tends to shift the community of endophyte toward more white rot fungi.

Our results highlighted the role of endophytes in wood decomposition. Major wood-decomposers, not just plant pathogen, may remain dormant in live trees and regain their activity right after tree death. The endophytes also are an important part of assembly history in forming microbial community in dead wood and may have complex interactions with fungi and bacteria in soil. An increased temperature obviously favors white rot fungi, which is in accordance with the theory that brown rot fungi evolved from white rot fungi to adapt to cold environment. Further studies on temperature and endophyte will deepen our understanding on forest carbon cycle under the influence of global change.