Multitrophic interactions can impact ecosystem processes via direct and indirect mechanisms. Bark beetle outbreaks are increasing in frequency and intensity and ultimately generate massive quantities of wood input to forest ecosystems. Trees attacked by bark beetles are often inoculated with bluestain (Ascomycota: Ophiostomataceae) fungi that do not decompose trees but can be attractive to subterranean termites like Reticulitermes spp., which are major wood decomposers and often have complex interactions with fungi. If bark beetle-attacked trees attract and increase termite activity, then this is likely to impact biogeochemical cycles during decomposition as termites can accelerate wood decomposition. We used laboratory and field experiments to investigate how wood experimentally inoculated with bluestain fungi affects subterranean termite presence and feeding on loblolly pine wood. In laboratory experiments, termites were given a choice between wood inoculated with Ophiostoma minus bluestain fungi species or without, after which wood consumption was measured. In field studies, we measured termite presence in 0.5 m deadwood inoculated with O. minus bluestain fungi vs. deionized water after one year. Wood and soil chemistry was measured in the field.
Results/Conclusions
In laboratory studies, we found that termites consume wood inoculated with Ophiostoma minus 20% more than controls. Twenty-five percent of deadwood in field trials had termites present after 1 year. Of these, termites were present in deadwood inoculated with O. minus 4-times more than controls. Termite presence was associated with 6% less C in sapwood and 11% more N in sapwood and heartwood. This suggests that bark beetle activity may indirectly influence wood decomposition through trophic interactions among bluestain fungi and termites, and these interactions may be widespread and complex.