Geology Club Seminar

The metabolic activity of soil microbiomes plays a central role in global nutrient cycles. Understanding how soil metabolic activity responds to climate-driven environmental perturbations is a key challenge. However, the ecological, spatial, and chemical complexity of soils complicates understanding how these communities respond to perturbations. Here, we address this complexity by combining dynamic measurements of respiratory nitrate metabolism with modeling to reveal functional regimes that define soil responses to environmental change. Measurements on >1500 soil microcosms subjected to pH perturbations reveal regimes where a few key mechanisms govern the response of soils to perturbations. A minimal mathematical model with two parameters, the quantity of biomass activity and the available growth-limiting nutrients, predicts nitrate utilization dynamics across soils and pH perturbations. Changes in model parameters under perturbations reveal three functional regimes with distinct proposed mechanisms: an acidic regime causing cell death and reduced metabolism, a nutrient-limited regime where dominant taxa utilize soil matrix-released nutrients, and a resurgent growth regime where rare taxa grow exponentially with excess nutrients. The model-proposed mechanisms governing each regime are validated through amendment experiments, nutrient measurements, sequencing, and experiments with isolates. Experiments and meta-analyses suggest functional regimes are prevalent in soils exposed to pH perturbations.