Nematode community indices


Enrichment Index: This index indicates the level of nutrient availability and activity of primary detrital consumers in soil. EI is based on the weighed abundance of the opportunistic non-herbivorous guilds indicators of enriched conditions (Ba1 and Fu2). EI increases with nutrient availability in soil (nitrogen in particular).

EI = e/(e + b) × 100 e = ∑Ke × n b = ∑Kb × n (a)


Structure Index: SI provides indication on the complexity and the trophic connectance in soil food web, thus informing about the stability of the environment. SI is based on the weighed abundance of the nematode indicators of undisturbed conditions and structured food web (nematodes with long generation time and high sensibility to disturbance). The higher the Structure Index, the higher the complexity of the soil food web, indicating a more stable environment.

SI = s/(s + b) × 100 s = ∑Ks × n (a)


Nematode Channel Ratio: It is calculated from bacterivores (Ba) and fungivores (Fu) abundances. As Channel Index, NCR provides information on decomposition channel of soil organic matter. High value indicates that bacterial channel is dominating in soil.

NCR = Ba/(Ba + Fu) (b)


Maturity Index: It informs about maturity of the soil food web and stability of the environment. It is calculated from free living nematodes abundances and their respective cp-class; the higher the Maturity Index, the higher the stability of the environment.

Vi × Pi (c)

Diversity indices


Taxonomic richness: Number of nematode genera identified in a sample. This parameter informs about the level of patrimonial diversity.


Shannon index of diversity: This index is calculated by taking number of genera and equitability among taxa identified in a sample. It informs about the level of patrimonial diversity. The higher the Shannon index, the higher the diversity of a sample.

H' = ∑Pi × lnPi Pi = Ni/N (d)

Metabolic footprints

Footprints give a measure of the metabolic impact of the nematofauna concerned (enrichment fauna, structure fauna, herbivore fauna and total community). They are calculated by taking into account the production component (amount of carbon partitioned into growth and eggs) and respiration of the concerned nematodes. The higher the value of metabolic footprint, the higher the activity of the functional group.


Enrichment footprint

F = ∑[Ni × (0.1 × Wi/Vi) + (0.273 × Wi0.75)] µg C. kg−1 de sol sec (e)


Structure footprint


Herbivore footprint


Composite footprint