Carlos A. Sierra1
1Theoretical Ecosystem Ecology Group, Max Planck Institute for Biogeochemistry
Models of soil organic matter (SOM) dynamics have become essential for integrating concepts and observations on different aspects of the cycling of carbon and elements in soils. Every year, a large number of models are proposed in the literature addressing new ideas on the biology, chemistry, and physics of SOM dynamics such as the role of microorganisms, mineralogy, and vertical transport. From this large variety of models, it is difficult to assess main model differences that would lead to very different qualitative dynamics; or, on the contrary, to equifinal predictions among models. Here, we will present an effort to generalize models of SOM dynamics with the aim to extract common concepts and principles among models. In addition, we will introduce a set of metrics to assess system-level properties among models. These metrics include: SOM age, transit time, and entropy. We propose SOM age as a meaningful metric to assess persistence of carbon and nutrients in soils, and SOM transit time as a metric to assess time-scales of carbon sequestration in soils. SOM entropy is introduced as a metric to assess complexity of models, and as a tool for parsimonious model selection. Overall, these metrics contribute to system-level understanding of the SOM system.
Carlos A. Sierra is a research scientist at the Max Planck Institute for Biogeochemistry in Jena, Germany, where he leads a group on Theoretical Ecosystem Ecology. The group, funded by the German Research Foundation through the Emmy Noether Programme, focuses its research on the mathematical understanding of the global carbon cycle, particularly on the time-scales of carbon storage and how global change modifies process rates in the terrestrial biosphere. He obtained his PhD degree from Oregon State University, studying in his dissertation theoretical aspects of terrestrial biogeochemical models. Dr. Sierra has made contributions to the theory of soil organic matter dynamics by proposing mathematical generalizations of models with their main ecological principles. He is active in the development of software for the analysis of ecosystem properties. In addition, he has contributed to the development of the theory of time scales of biogeochemical cycling by developing mathematical tools for the estimation of ages and transit times of elements in ecosystems.