Friday seminar: Predicting terrestrial ecosystem processes in Earth System Models from ecological first principles
By Dr. Han Wang, Northwest Agriculture and Forestry University, Yangling and Tsinghua University, Beijing, China.
Earth System Models (ESMs) incorporating the interactions of terrestrial ecosystems and climate are used to predict the future feedback between climate and anthropogenic carbon dioxide. However, the overlook of ecological and evolutionary first-principles in ESMs leads to incorrect assumptions and problematic representations of plant functional traits, which play a key role in mediating large-scale terrestrial ecosystem processes, and therefore eventually creates large uncertainties in model predictions. Here, a new modeling strategy is proposed to predict trait variation along environment gradients based on optimality concepts. Rooting in natural selection, optimality concepts hypothesize that plants coordinate different eco-physiological processes to maximize reproductive fitness, and can generate testable relationships between traits and environments from maximization criteria. Over the past several years, Dr. Wang has been successfully applying this new modeling strategy to predict the acclimation behaviors of photosynthetic and respiration traits, which were supported by extensive independent observations. A universal trait-based light-use efficiency model (Pmodel) for terrestrial ecosystem productivity was then developed with only two parameters but perform as well as complex models. This simple model’s predictive skill suggests a route towards an improved predictive understanding and modeling approach for terrestrial carbon cycling. It is argued that in the light of evolution, optimality approach may lead to a more robust basis for understanding and modeling both the coordination of plant traits among species and biological controls of the emergent functional properties of ecosystems as represented in ESMs.