Infodoc : Sciences, Techniques et Culture

Soil organic matter is the largest carbon reservoir of the terrestrial ecosystems and is a main driver of soil fertility. Its evolution driven by climate and atmosphere changes is a main issue in the medium and the long term, on a global scale and on a local scale. We present a literature synthesis on this topic, focused on forest SOM. The main study methods are the comparisons of soil inventories, the interpretation of spatial correlations with climate into temporal trends, the monitoring of the inputs and outputs of soil carbon in forest as well as in laboratory, and a diversity of models that link the knowledge’s and foresee the evolutions of SOMs. The results confirm that a decrease in SOM content is to be expected sooner or later in the boreal and temperate forests, due to the gl[...]

Soil organic matter is the largest carbon reservoir of the terrestrial ecosystems and is a main driver of soil fertility. Its evolution driven by climate and atmosphere changes is a main issue in the medium and the long term, on a global scale and on a local scale. We present a literature synthesis on this topic, focused on forest SOM. The main study methods are the comparisons of soil inventories, the interpretation of spatial correlations with climate into temporal trends, the monitoring of the inputs and outputs of soil carbon in forest as well as in laboratory, and a diversity of models that link the knowledge’s and foresee the evolutions of SOMs. The results confirm that a decrease in SOM content is to be expected sooner or later in the boreal and temperate forests, due to the global warming. However, nitrogen deposition has a positive effect on SOM storage, which is not yet included in the carbon models at a global scale. In addition, the free air carbon dioxide experiments (FACE) could not detect any change in SOM storage up to now, but it is likely that positive effects will occur later. Qualitatively, nitrogen deposition and warming are reducing the limitation of fertility by nitrogen, and it is expected that phosphorus limitation will become relatively more important.