Soil respiration, globally 68–80 Pg C y−1, represents the second largest carbon flux between ecosystems and the atmosphere (Schimel et al., 1996; Raich et al., 2002). This is more than ten times the current rate of fossil fuel combustion and indicates that each year around 10% of the atmosphere's CO2 cycles through the soil. Thus, even a small change in soil respiration could significantly intensify – or mitigate – current atmospheric increases of CO2, with potential feedbacks to climate change. Despite this global significance and the considerable scientific commitment to its study over the last decades, there is still limited comprehensive understanding of the factors controlling temporal and across-ecosystem variability of soil respiration.
This understanding is largely hampered by the fact that studies are often conducted and compared at different temporal and spatial scales that are not compatible. Since, particularly in large-scale studies, factors influencing soil respiration often correlate with each other, responses of soil respiration to those factors are confounded and only apparent relationships are obtained.
For the purpose of this chapter, methods (and their associated problems) for analyzing soil respiration data from different scales are reviewed and jointly interpreted with emphasis on the temperature dependence of soil respiration.
MODELLING SOIL RESPIRATION: AN OVERVIEW
General modelling approaches
Soil respiration – defined as the CO2 efflux from the soil surface – originates from the metabolic activity of roots (autotrophic respiration), micro-organisms (bacteria, actinomycetes and fungi) and soil meso- and macro-fauna (heterotrophic respiration).