Soil compaction has become an important issue for forest soil sustainability because the increasing timber demand and the mechanization of all silvicultural operations have led to a higher traffic level. Soil compaction causes a physical degradation which in turn disrupts many other functions e.g. wood production, biodiversity, greenhouse gas emission, surface water quality. Two experimental sites were designed in the North-East of France to study the changes of soils subject to heavy traffic by forest machinery, on the short and the long;term. These sites are representative of highly soils sensitive to compaction. They present the same general functioning (neoluvisol), but they differ on some physical (strength, bulk density, clay content) and chemical properties (pH, chemical saturation). The soil atmosphere composition is directly impacted by soil compaction (change of voids volume, size and connection) but also indirectly by change of other soil properties like water content, temperature and biological activity. On the two sites, we observed a decrease in O2 concentration and an increase in CO2 concentration due to traffic, especially during wet periods. The change of soil atmosphere composition will probably impact root growth, gas emissions, microbial and faunal activity and probably have a negative feedback on soil recovery dynamic.