biologie des sols

The course examines the soil as a living ecosystem, exploring the conditions that support life (abiotic factors: temperature, moisture, pH, texture, organic matter; and biotic factors: competition, predation, mutualism) and the central role of organisms in pedogenesis — shaping soil structure, chemistry, and fertility.

Chapter 1 establishes the ecological framework: the importance of the edaphon, the dual influence of abiotic and biotic factors, the action of fauna on soil physical, chemical, and biological properties, and the quantitative tools used to analyse biocenoses (density, diversity indices such as Shannon and Simpson, and biological indicators including relict species).

Chapter 2 provides a detailed study of each major faunal group: protozoa regulate bacterial populations through the microbial loop, mineralising nitrogen for plant uptake; nematodes occupy five trophic niches and serve as sensitive soil health indicators via Nematode Fauna Analysis; oligochaetes (especially earthworms) are the dominant engineers of temperate soils, transforming organic matter, improving structure, and enhancing nutrient availability; insects — particularly ants and termites — are major bioturbators and decomposers; arachnids (especially mites) fragment litter and regulate food web dynamics; isopod crustaceans decompose plant residues; and vertebrates influence soil through burrowing and foraging.

Throughout, the course emphasises how human activities — tillage, pesticides, compaction, acidification — degrade soil biological communities, and how sustainable management can restore them.