About This Project

Soil organic matter, rich in plant polymers, comprises a large fraction of the global carbon budget, but the processes driving its degradation are not well understood. Our team combines organic geochemistry, molecular biology, and plant metabolic engineering to study how plant biomass is degraded by soil microbes, building towards an improved understanding of how carbon may increase—or decrease—in a changing world.

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Motivating Factor

Soil organic matter (SOM) makes up the largest terrestrial carbon reservoir, though its precise size remains uncertain due to limited understanding of molecular mechanisms driving carbon cycling in soils. ‘Carbon-use efficiency’ (CUE)--the ratio of stored to respired carbon-- has been positively correlated with increased C sequestration in soils. Recent research challenges traditional views that chemical structure alone determines organic matter persistence in soils, suggesting that broader ecosystem traits play a crucial role in preserving plant-derived polymers. An improved mechanistic understanding of polymer degradation is central to understanding carbon sequestration in a changing world: If we cannot fully understand the mechanisms as they operate now, it is impossible to assert with any confidence how global climate change will affect these processes.

Specific Bottleneck

Mechanistic studies of CUE have largely focused on monomer catabolism, overlooking the complex nature of soil organic matter (SOM) and its degradation pathways. Three key factors remain understudied: (1) The extent to which microbial community composition and physiology determine organic matter accessibility; (2) The role of plant polymer structures in resistance to decomposition - a topic traditionally studied by plant biologists rather than soil ecologists; and (3) The interaction between biotic factors and abiotic conditions like oxygen levels, mineral binding, and metal-catalyzed reactions in SOM preservation and breakdown. Understanding these interconnected processes is crucial for predicting SOM dynamics.

Actionable Goals

Our understanding of the soil carbon cycle hinges on improved mechanistic studies that will provide constraints on the rates of degradation of plant-derived polymers. Work should be carried out to constrain: (1) polymer versus monomer degradation in soils; (2) the phylogenetic diversity of enzymes responsible for breaking down polymers and their mechanisms; and (3) potential chemical fingerprints of these biotic mechanisms that can be traced into SOM residues within soils. Fully addressing all these distinct aims requires an interdisciplinary approach that spans geochemistry, molecular biology, microbial ecology, and plant synthetic engineering.