Probing the Impact of Deep Roots on Soil Function
Deeply rooted plants are common in dry landscapes all over the world, but most studies of roots and root-associated microbes explore only the top 20cm of the soil profile. We are exploring diverse approaches to sampling deeper soils to a meter or more, with the goal of coupling DNA-based community characterizations (bacterial and fungal amplicons, and broader metagenomics) with RNA-based metatranscriptomics, and tying this functional information about the microbial communities to soil properties such as carbon storage.
Deep oaks: Functional composition of subsoil microbial communities changes with oak mortality
What happens to soil microbes and carbon stocks after a tree dies? We recently posted a preprint describing a project in which we investigate how tree mortality alters microbial communities. Using finely depth-resolved soil samples beneath living and dead Quercus douglasii trees, we combined RNA- and DNA-based profiling with phospholipid fatty acid analysis to show that oak death strongly reshapes microbial communities, particularly for ectomycorrhizal fungi. By contrast, soil carbon stocks remain unchanged three years post-mortality. Our results highlight the importance of deep soil microbial processes in mediating ecosystem responses to climate-driven tree decline.
The influence of fire on root and microbial carbon cycling in deep soils in a pine-oak forest
While wildfires dramatically change what we see aboveground, their impacts extend meters below the surface, where tree roots and their microbial partners interact in ways that shape soil processes and long-term carbon storage. In this project, funded collaboratively by the National Science Foundation and the Paul G. Allen Frontiers Group, we are exploring what happens deep underground in forests after fire. Our team is investigating how roots, fungi, and bacteria influence deep soil communities while trees are alive, and how these underground networks change when fire kills the canopy. By studying soils and weathered rock layers up to five meters deep, we aim to reveal how these hidden ecosystems respond to disturbance, and to build models that connect microbial activity to the cycling and storage of carbon across forest landscapes.