Table 2 Network metrics applied at experimental fields to assess soil biodiversity, trophic complexity and energy pathways of the soil food web63,64.

From: Analysis of complex trophic networks reveals the signature of land-use intensification on soil communities in agroecosystems

Metric

Scope

Definition

Biological relevance

Node richness

Community

Number of nodes \(S\)

Food web size. Indicator of potential relationships

Trophic group richness

Community

Number of distinct trophic groups present in a community.\(|G|\)

Functional diversity

Trophic group entropy

Community

Distribution of read counts among groups in an observed community using Hill numbers framework

Indicator of equitability

Average degree

Node

Number of interactions in which the OTU or group is involved

Centrality index: indicator of complexity

Mean trophic level

Node

Ordinal classification based on the relative position in the network, defined as 1 + the weighted average of the trophic levels of its resources/hosts

Centrality index: Indicator of the variety of trophic levels/ resources exploited as a food source

Omnivory level

Node

Variety in the trophic levels of a consumer’s food

Centrality index: Indicator of the degree of specialization

Link density

Network

Average number of edges per node

L/S

Connectivity index: indicator of quantity of relationships

Average path length

Network

Mean distance (d) between any pair of nodes in the network

Σi,j dij/S2

Connectivity index: indicator of trophic redundancy and food web resilience

Maximum path length

Network

Longest path between any pair of nodes in the network

max┬((i,j) ∈ 1..S)〖d_ij 〗

Connectivity index: indicator of network length

% parasitic links

Energy pathways

Proportion of total links that are parasitic

Diversity of interaction types

Bacteria:Fungi path ratio

Energy pathways

Ratio of decomposer-bacteria chains to saprotroph-fungi total pathway lengths

Indicator of bacterial dominance and N cycling efficiency

Detritivore:Herbivore path ratio

Energy pathways

Ratio between detritivore and root herbivory total pathway lengths

Indicator of importance of the detrital food path (dead vs. living organisms as a resource)

Node turnover

(hill number: q = 0, 1,2)

Network stability

Turnover in the composition of the network (OTU or group)

β-diversity

  1. The interaction network is described by nodes (N), which are either OTUs or trophic groups (G), and edges (L, links from a resource node to a consumer node). Edges are described by their type (predator, parasitic, symbiotic), and weighted by the probability of occurrence of the resource and consumer pair.
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