Global change is driving biodiversity loss and altering the distribution and intensity of biotic interactions within communities. One example is the increasing population of bark and root beetles that kill thousands of trees annually that ultimately become coarse woody debris (CWD). This CWD is uniquely pre-inoculated with ophiostomatoid (bluestain) fungi, which attracts some invertebrates like mites and termites. Increases in potential prey in CWD likely increases predatory species such as ants, but how bluestain fungi impacts decomposer communities remains largely unexplored. We predicted that CWD with bluestain would have increased abundance of microbi-detritivores and subsequently increased ant diversity than CWD without bluestain. Additionally, we predicted ant communities in CWD would differ from the local ant species pool. To test this, loblolly pine trees were inoculated with one of five bluestain treatments or water as a control in 2011. In October 2012, two trees from each treatment were felled and left out until 2015. After 3 years, logs were harvested from each tree and invertebrates were extracted and identified. Lastly, to determine if CWD harbors distinct ant communities within the forest, we collected and identified ants from the 16-ha plot in 2017 and 2018 to determine the ant species pool.
Results/Conclusions
Bluestained CWD decomposer communities differed from control CWD. In total, 24 ant species were found in CWD and ant richness was ~2 fold greater in bluestained wood than controls. Wood inoculated with Ophiostoma ips fungi had the highest ant diversity and trended toward 72% greater average ant richness (9 ± 2.8) than controls. Bluestained CWD had a 2.4-fold higher abundance of decomposer organisms. Specifically, bluestained CWD had ~4- and 63-fold more collembolans and psocopterans respectfully and more predators in general than controls, with pseudoscorpions having ~2-fold greater abundance in bluestained CWD than controls. Ant species in CWD represented a specific subset of species from the total ant species collected in the forest. This suggests that CWD serves as an environmental filter by selecting against certain ant species. However, the majority of ant species from CWD tended to be generalist predators reflecting the general increase in microbi-detritivores and suggesting that bluestain inoculated wood has a strong bottom-up effect on decomposer communities. CWD constitutes a significant carbon store in forest ecosystems. Changes in bluestained CWD detrital communities will likely impact wood decomposition rates and nutrient cycling.