Free-living soil nematodes: diversity, functions and bioindication

Abstract :

Nematodes, microscopic roundworms, are a major group of soil animals, involved in many functions. Bacterivorous nematodes, which mainly consume bacteria, play key roles in nutrient recycling by interacting with plant roots and microorganisms via the soil microbial loop. Laboratory experiments have enabled us to quantify the effects of bacterivorous nematodes on P fluxes and plant growth, and to identify the main mechanisms of the microbial loop. Several agronomic levers likely to control the soil microbial loop are emerging as promising, including bio-organo-mineral fertilization, plant diversity and crop genetic diversity. These nematodes also appear to play a role in the regulation of plant-parasitic nematodes via apparent competition. Our analysis of the effects of agricultural practices worldwide on free-living soil nematodes has enabled us to propose a freely-available decision-support tool, SIPANEMA, which can be used to raise users' awareness of the roles played by nematodes. This tool estimates the risks of parasitic pressure and loss of biological functioning, and enables the user to compare different agronomic scenarios.