Human activities are altering a range of environmental conditions, including atmospheric CO2 concentration, temperature, precipitation and nutrient availability. Quantifying and predicting the combined effect of these changes on biogeochemical fluxes is challenging because carbon, nutrient, and water cycles are intricately linked in terrestrial ecosystems. Terrestrial ecosystem models are used for this purpose. These are routinely tested and calibrated against data from ecosystem flux measurements, remote sensing, atmospheric inversions and ecosystem inventories. While these constrain the current mean state of the terrestrial biosphere, they provide limited information on the sensitivity of ecophysiological, biogeochemical, and hydrological processes to environmental changes. As a result, model predictions for terrestrial ecosystem functioning under future climate scenarios still vary widely. Observational and ecosystem manipulation studies (e.g. Free-Air Carbon Dioxide Enrichment (FACE), nutrient addition or warming experiments) can provide unique insights into how ecosystem processes respond to environmental change and hence guide model development and evaluation.

This session focuses on how ecosystem processes respond to changes in CO2 concentration, temperature, water and nutrient availability. It aims at fostering the interaction between experimental and modeling communities by advancing the use of experimental data for model evaluation and calibration. Contributions include both experimental and observational studies, as well as modelling exercises spanning a range of scales and conditions: soil microbial activity, plant ecophysiology, nutrient cycling, and ecosystem level dynamics.