Abstract

In the evaluation of soil remediation efficiency, the integrity of the soil's functional capacities is not usually considered. It is well known that soil microorganisms and enzymes play an essential role in the cycling of nutrients and the stabilization of the soil structure. Several ecotoxicological tests have been developed and used to evaluate the impact of a contaminant on individual soil animals or populations. However, few, if any, can evaluate the damage a contamination causes on the soil's functional capacity or, in other words, on soil health.

Soil health is a key component of sustainability. Health is defined as the condition of an organism, or one of its parts in which it performs its vital functions normally or properly. The specificity and integrative nature of enzymatic activity measurements provide a unique advantage in assessing soil health. Soil, as a whole, can be thought of as a living biological entity carrying biochemical reactions. Enzymatic activities are attractive as indicators because of their central role in the soil's capacities to function. A healthy soil implies a healthy microbial community that is able to sustain its vital functions, that is resistant to naturally occurring disturbances or stresses and that can recover from degradation. In order to evaluate its capacity to maintain functional integrity, it is therefore essential to monitor a system over time, following an environmental disturbance. The capacity of a system to withstand an environmental perturbation is called stability. The functional stability is described using three parameters: resistance, recovery and recovery rate. Resistance is inversely proportional to loss of function after perturbation. For its part, recovery is the return of a system to its original state after release from stress or perturbation.

The research hypothesis of this thesis is as follows: Soil health evaluation is related to a soil's capacity to resist to perturbations and to its recovery dynamics.

Therefore, the main objective of the thesis was to be able to evaluate a soil's functional stability and to relate it to the soil's health. (Abstract shortened by UMI.)