Fertility indicators in temperate forest soils: issues, approaches and prospects

The fertility of a soil classically refers to an aptitude to produce plant biomass, under a given set of climatic and topographic conditions; it therefore contributes to an ecosystemic supply service (MEA, 2005). It is generally subdivided into three components – chemical, physical and biological – which are closely linked (Genot et al., 2009). The chemical component describes the ability of the soil to supply the nutrients that are essential to the plant, in the appropriate forms, quantities and proportions; it is itself broken down into three components that target fertility in the short, medium and long term, respectively. It also considers the risks of toxicity linked to some elements, such as aluminium. The physical component takes into account the properties that influence the soil water regime (storage capacity and infiltration), as well as root prospection and biological activity (porosity, compactness, stoniness and aeration). Lastly, the biological component corresponds to the influence exerted by living organisms on the availability of mineral elements (through weathering, recycling or symbioses) and on the physical condition of the soil.