Simplifying Soil Organic Carbon Model Structures with First-Order Linear Decay: When, How, and Why?

Soil organic matter is the largest terrestrial pool of carbon on Earth, containing more carbon than terrestrial vegetation and more carbon than even the atmosphere. Most Earth System Models (ESMs), designed to integrate and examine how the interdependent systems of the planet interact, represent soil organic carbon with multiple pools and linear decay term. Despite this soil model structure’s prevalence in ESMs since its debut in the 1980s, some recent work has shown that these models’ results can often be closely replicated using a simpler one-pool model structure for soil carbon stocks under certain conditions. In this talk we will review how examining time scales of interest and the assumption of mature soil stocks being close to steady state can allow us to create models that use only a single soil carbon pool with comparable results, as well as some numerical simulations to compare how this reduced complexity model fairs against a full feedback linear model under multiple scenarios. In addition, we will discuss how even these model structures do not always tell the full story of the inherent complexity of the biological, physical, chemical, or geological processes in soil.