Soil respiration is studied on both croplands (Lonzée, Longs Tours and Bordia) and forests (Vielsalm).
Crop sites (Lonzée Terrestrial Observatory)
In agricultural ecosystems, the influences of environmental variables (temperature, soil water content, rain events,…) and crop management on soil respiration are studied, respectively, at the Lonzée and Bordia + Longs Tours sites. To assess the response of soil respiration to environmental drivers with a good temporal resolution, an experimental set-up composed of automated soil chambers (dynamic closed chamber system, Fig. 1) and usual meteorological instruments was implemented at the Lonzée site, both in cultivated areas and in root exclusion zones, so as to separate out the two components of soil respiration. The measurement frequency is half-hourly. These measurements allowed partitioning of Total Ecosystem Respiration between its heterotrophic, aerial autotrophic and below ground autotrophic components (Suleau et al., 2011).
Figure 1 – Automated soil CO2 flux measurements in a winter wheat crop at the Lonzée site.
The specific question of soil organic matter loss, associated to the process of soil heterotrophic respiration, was also specifically investigated at the Longs Tours (owned by the Walloon Agricultural Centre, Fig. 2) and Bordia (in collaboration with Unit of Crop science, Solrésidus project). At the Long Tours site, soil respiration was compared on soil plots submitted to similar pedoclimatic conditions but to different fertilisation procedures, since more than 50 years (Buysse et al., 2011).
Figure 2 – Manual soil CO2 flux measurements in root exclusion zones at the Longs Tours site.
Complementary to field investigations, a laboratory experiment was carried out with Lonzée soil samples to better understand the short-term temperature impact on soil heterotrophic respiration. Three incubators were built (Fig. 3) and the samples were incubated at three different pre-incubation temperatures, before the temperature was increased and decreased to perform daily temperature cycles between 5 and 35 °C. The CO2 fluxes were measured on the samples after each temperature change, using a dynamic closed chamber system. The experiment highlighted very different impacts of temperature at short and longer terms