Warming treatments shift the temporal dynamics of diversity and composition of bacteria in wild blueberry soils

Soil bacterial communities are a crucial biological indicator of soil health and crop performance; however, their response to climate change remains poorly understood. In Maine, wild blueberry farms are experiencing unprecedented temperature changes, which may exacerbate microbial responses and potentially harm the crop. To elucidate the response of bacterial communities to warming during the growing season, we employed passive and active open-top chambers to simulate climate warming scenarios in wild blueberry fields. Warming treatments elevated atmospheric temperatures by 1.2 and 3.3 °C (passive and active warming), respectively, but did not affect soil temperatures. Nevertheless, soils in the active warming treatment exhibited significantly lower water content than ambient conditions. Overall, soil bacterial diversity and richness (June, July, and August data combined) under the warming (passive and active) treatments and ambient controls did not demonstrate significant differences after two years of experimental warming. However, significantly higher bacterial evenness and diversity under warming treatments were observed in the early growing season (June). Our study also reveals pronounced seasonal shifts in the evenness and diversity of bacteria in wild blueberry soil, suggesting that the variation in bacterial community structure may be more influenced by seasonal changes in temperature and plant activity during the growing season than by warming treatments. The increased bacterial evenness and diversity under warming treatments in June may be attributed to advanced plant phenology, indicating a potential future shift in seasonal dynamics of bacterial activity under global warming.