Bark beetle outbreaks are increasing in frequency and intensity, generating massive inventories of dead trees across the landscape. Although decomposition is a biotic process, little is understood about how the presence, turnover, and interactions among saproxylic organisms impact rates of decomposition. During bark beetle attacks, trees are pre-inoculated with ophiostomatoid fungi, which has been linked to increased termite presence and feeding. This may, in turn, alter biogeochemical cycles during decomposition. We examined these relationships by experimentally inoculating dead wood with bluestain fungi in a temperate pine forest. Across 10 replicate plots, 8 0.5 m-long logs were inoculated with Ophiostoma minus and 8 with distilled water. Half of the logs from each inoculation treatment were covered with mesh barrier to exclude aboveground beetles while permitting access by belowground decomposers. A subset of samples were collected following one and two years of in situ decomposition to determine changes in wood and soil carbon and nitrogen.
Results/Conclusions
After one year of decomposition, termite were observed 4-times more frequently in logs inoculated with bluestain fungus and were positively associated with N concentrations in bark, sapwood, and heartwood and negatively associated with C and subsequently C:N ratios in sapwood. Wood samples at two years are still being analyzed. Soils below logs had 17% more N (p < 0.001) and C (p = 0.022) following two years of decomposition compared to one. Additionally, the increase in soil C was 33% larger when the inoculated fungus was not present in overlying logs (p = 0.028). These results demonstrate both fundamental changes in carbon and nitrogen biogeochemistry during decomposition as well as the potential role of bark beetle-fungal-termite interactions in further changing the distribution of nutrients.