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

The specifics of forest ecosystems require a strategy of soil fertility assessment distinct from that commonly used in agro-ecosystems. Existing indicators fall into three main approaches. The first is to estimate the availability of resources (water, minerals) considering the size of the pools and the dynamics of supply. A second is based on the quantification of the response of communities of organisms other than arboreal plants in terms of presence / absence, abundance and / or activity. The third assesses fertility by analyzing the response of the forest stand / tree itself, in terms of productivity or foliar nutrient contents. For each approach, a series of indicators are presented, stating: their principles and indications, how to acquire them, their interests and limits, their links with other indicators and few prospects for improvement.