Soil nematodes: a key group for regulating ecosystem processes
Author: Eligio Malusa, INHORT
Nematodes, known commonly as roundworms, are one of the most abundant, common, and diverse multicellular organisms on Earth. They generally have an prolonged, cylindrical body shape tapering at both ends. Diverse morphological, physiological, and behavioural adaptations allow nematodes to pervade nearly every habitat. We can find them in soil, marine and freshwater sediments, and as parasites in plants, invertebrates and vertebrates.
Soil nematodes belong to the soil micro-fauna, with a body length ranging from 0.1 to 2.5 mm and a diameter ranging from 5 to 100 μm. They occur in soil in high densities. For example, each square meter of soil may contain millions of individuals and several hundred species of nematodes.
The significance of soil fauna in many ecosystem processes has prompted ecologists to seek biological indicators by which to assess soil condition. Soil health is defined as the capacity of a soil to function within ecosystem boundaries to sustain biological productivity and promote plant and animal health. Nematodes are certainly a key group for regulating many ecosystem processes, as well as bioindicators of contamination and degradation of the natural environment. Nematodes are represented in all heterotrophic levels in soil food web. Based on their morphology we can specify five main feeding types: bacterial feeders, fungal feeders, omnivores, predators (Fig.1.) and plant parasites (Fig.2.).
In Excalibur we are using soil nematodes communities to assess the impact of new multifunctional soil microbial inoculants and bio-effectors on soil biodiversity. Soil samples are collected and, after extraction, each nematode taxon, usually at family or genera level, is classified into functional guilds defined as a matrix of nematode feeding habits, specifically characterized by biological, ecological and life cycle features. We assess all the ecological indexes based on the weighted proportion of nematodes in the samples.
The nematodes communities analysis combined with chemical, physical and other biological analyses is expected to support the development of valuable tools for farmers and advisors and to better understand how innovative biodiversity-driven soil management practises can promote a sustainable agroecological approach to fruits and vegetable productions.