Understanding the impact of climate change and elevated CO2 on tree microbial diversity

Many trees, such as oak, are crucial to the British economy, environment, and culture. They support many species, providing a habitat that encourages rich woodland biodiversity. However, they are threatened by climate change, which alters the abundance and distribution of tree pathogens, increasing the likelihood of new disease breakouts. Acute Oak Decline (AOD) is caused by multiple factors, including several bacterial species that become key members of the pathogenic oak microbiome. Environmental changes could increase trees' susceptibility to pathogens, raising AOD prevalence.
A core component of climate change is a rise in carbon dioxide concentration, affecting tree growth and disease susceptibility. Elevated levels of atmospheric CO2 (e[CO2]) cause changes in leaf composition and increase biomass through higher levels of photosynthetic carbon fixation. There are well-established links between microbiome composition and the physiology of the host plant. Microbiomes typically extend an organism's functional capabilities, importantly increasing tolerance to stress and disease. However, the effect of e[CO2] on tree physiology and microbiome community structure is somewhat unexplored.
Utilising the Birmingham Institute of Forest Research (BIFoR) Free Air Carbon Dioxide (FACE) facility, we can investigate e[CO2] effects on microbial community diversity (including bacteria, fungi, and bacteriophage) on different tree species (including Oak and Cherry), and how these microbes interact with tree pathogens. We hypothesise that as trees grow larger under e[CO2], there may be higher microbial abundance, but leaf chemistry compositional changes will alter the diversity of the microbes, potentially negatively impacting the microbiomes' ability to suppress pathogen establishment. We will examine how individuals and microbial consortia interact with key pathogens, such as a polymicrobial consortium of Gram-negative Enterobacteriaceae (e.g., Brenneria sp., Gibbsiella sp., Rahnella sp.) that cause Acute Oak Decline (AOD). This approach is essential for making accurate predictions regarding future tree health and disease.