Soil CO2 concentration and efflux as affected by heavy traffic in forest in northeast France
Résumé
An experimental site was set up in northeast France on a Luvisol (ruptic) soil to examine the duration of physical, chemical and biological disturbances in the soil following mechanized forest harvesting. Soil carbon dioxide (CO2) efflux (SE) and concentration ([CO2]) in the silt loam layer (050 cm) were measured from March 2008 to March 2010 in the trafficked (T) and control (C) plots of this site. This study aimed to validate these two measurements as indicators for long-term soil monitoring following disturbance by heavy traffic in 2007. Throughout the sampling period, SE in the T-treatment was significantly reduced relative to that in the C-treatment. The response of [CO2] to traffic depended on the season; it decreased during summer and increased during winter and spring. The combination of the two measurements indicated an increase in the frequency and duration of anoxic conditions resulting from poor gas diffusion after heavy forest traffic. The relationships between soil climatic properties (temperature, water content and water table level) on one hand and SE or [CO2] on the other, demonstrated a strong control of SE by soil biological activity and a double control of [CO2] by gas production/consumption and gas transfer. Our findings suggest that [CO2] and SE are sensitive to soil degradation by forest harvesting and that the impact of soil compaction provides complementary information on the processes involved in regulating CO2 production and efflux. However, their use as simple indicators is questionable as the impact varied with time and was probably dependent on the soil type.