LB 32-269 - Smoke without fire: Wildfire smoke affects phenolic compounds of a wild Alaskan berry

Wildfire smoke is a major contributor to air pollution and may cause physiological stress on plants, inducing the synthesis of phenolic compounds, decreasing photosynthesis, and/or changing fruit, flower, or leaf phenology. The frequency and intensity of wildfires has increased over the last thirty years in Alaska and has led to concerns about the impact of smoke on bog blueberry (Vaccinium uliginosum L., Ericaceae). This is an important subsistence berry due to its high nutritional and cultural value for rural and Indigenous communities in Alaska, and an important food source for many animals. We exposed plots of bog blueberry plants to smoke at different stages in berry development (early-season when the plants were flowering, mid-season when berries were unripe, and late-season when berries were fully ripe). We measured anthocyanins, proanthocyanidins, and total phenolic compound concentration in the fully ripe berries, as well as yearly branch growth, leaf anthocyanin levels, and fruit, flower, and leaf phenology. Berries from plants exposed to smoke early-season had a 40% increase of anthocyanin content. Berries from plants exposed to smoke mid-season had a 57% increase of anthocyanin content and a 44% increase of proanthocyanidin content. Plants exposed late-season showed no significant changes compared to the control. While timing mattered for anthocyanin and proanthocyanidin production, overall phenolic compound content remained unchanged, suggesting the production of some compounds were stimulated while others were inhibited in response to smoke exposure. Increases in anthocyanins in berries may have benefits to consumers as birds have been shown to preferentially select food containing higher concentrations of anthocyanins to potentially increase their intake of dietary antioxidants. Plants exposed to smoke early-season started to lose leaves earlier than other treatments, while plants exposed mid- and late-season lost leaves at a faster rate, shortening the photosynthetic period of an already short growing season, and potentially limiting flower and fruit production the following year. Smoke showed no effect on leaf anthocyanin levels, branch growth, fruit and flower phenology, and leaf color change, indicating that the stress of smoke exposure has minimal impact to the overall health of the plant during the same season. Bog blueberry plants are responding to smoke by increasing certain phenolic compounds, likely as a stress response. These changes might have positive impacts on consumers, and as berry abundance is not affected, smoke exposure is unlikely to impact availability of wild Alaskan bog blueberries to both humans and wildlife.