Effects of climate on interactions between wood-decomposing microbes and insects at a global scale

• Applicants: Professor Dr. Claus Bässler; Professor Dr. Sebastian Seibold
• Subject Area: Forestry
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 500899582

Deadwood decomposition represents an important process in the global forest carbon cycle. The main biotic agents of wood decomposition are microbes and insects, but while insects accelerate wood decomposition in the tropics, they have neutral or even negative effects in the temperate and boreal zone. Insects interact closely with wood-decomposing microbes, including symbiotic associations, facilitation and competition. However, it remains unclear how effects of insects on microbial communities change along global climate gradients. While local field studies and lab experiments showed that insect-microbe interactions can either accelerate or decelerate wood decomposition, it has not been analyzed whether this mechanism explains why effects of insects on decomposition change so strongly from tropical to boreal forests. In the proposed project, we will conduct the first global study of insect-fungal interactions in deadwood by using wood samples from a global experiment which included treatments that either gave access to insects or excluded insects (Seibold et al. 2021, Nature). Wood samples have already been collected and we will only need to identify fungal and bacterial communities by next-generation sequencing and compare the recorded microbial communities between both treatments. This approach allows studying how global climate gradients moderate effects of insects on wood-decomposing fungi and bacteria and will provide a better understanding of how insects affect microbial biodiversity and how these effects translate into ecosystem functioning, i.e. wood decomposition. We will test five hypotheses in relation to the microbial assembly processes affected by insects along the global climate gradients. We thereby consider different diversity measures at alpha and beta level as well as specialization metrics based on network analyses and phylogenetic diversity. Considering global climate change and the ongoing loss of biodiversity, including forest insects, a better understanding of climate effects on the complex relationships between wood-inhabiting insects and microbes is needed to predict the future of the global forest carbon sink. We are confident that the proposed project will be an important step to close this knowledge gap and thus be of major importance not only for science but also for environmental and carbon policies.

• DFG Programme: Research Grants