Cultivation profile: a visual evaluation method of soil structure adapted to the analysis of the impacts of mechanical site preparation in forest plantations

Mechanical site preparation (MSP) is widely used in forestry to improve plantation success. Although it is known to alter soil properties, its direct effects on soil structure have rarely been described. The cultivation profile is a visual soil evaluation (VSE) method developed in agricultural research to analyse the impacts of cultivation practices on soil structure. The objective of the study was to adapt the method to forest plantations in order to analyse the effects of MSP on soil quality. Cultivation profiles were performed in six experimental plantation sites located in Northern France. The method made it possible to compare the impacts on soil structure of three MSP methods. It provided a schematic representation of the soil structural quality and a quantitative estimation of the volume of soil favourable to seedling root growth. It also highlighted unexpected negative effects of some MSP methods on soil structure, such as the creation of small cavities, the presence of compacted soil volumes due to wheel tracks or smeared soil volumes due to tool pass, and the pseudogleisation of soil zones due to changes in water circulation in the soil. The relevance and limitations of VSE methods in the context of forest plantation as well as the expected future development of the methods are discussed.