Soil respiration across scales: the importance of a model-data integration framework for data interpretation

Soil respiration represents the second largest CO₂ flux of the terrestrial biosphere and amounts 10 times higher than the current rate of fossil-fuel combustion. Thus, even a small change in soil respiration could significantly intensity-or mitigate-current atmospheric increases of CO₂, with potential feedbacks to climate change. Consequently, to understand future dynamics of the earth system, it is mandatory to precisely understand the response of soil respiration to changing environmental factors. Among those changing factors, temperature is the one with clearest and most certain future trend. The relationship of soil respiration to environmental factors and particular temperature has been tackled at a variety of scales-from laboratory via field to global scale, with each of the approaches having its particular problems, where results from different scales are sometimes contradictory. Here, we give an overview of modeling approaches to soil respiration, discuss the dependencies of soil respiration on various environmental factors, and summarize the most important pitfalls to consider when analyzing soil respiration at the respective scale. We then introduce a model-data synthesis framework that should be able to reconcile and finally integrate apparently contradictory results from the various scales