The integration of nematode communities into the soil biological health framework by factor analysis

A critique of the soil health framework is that biological indicators currently lag behind chemical and physical indicators of soil health. Incorporating nematode communities into the soil health framework could help to better reflect key aspects of soil food web structure and function and significantly contribute to ecosystem processes. However, little is understood regarding how nematode communities relate to soil biological health indicators such as permanganate oxidizable carbon (POXC), soil protein, mineralizable C, and enzyme activities in agroecosystems. Here, we use an exploratory factor analysis (EFA) to quantitatively explore which set of soil health indicators best explain a given factor (i.e. soil health trait) using data from two long term experimental trials and 44 farm fields across Ohio. Specifically, this paper aims to 1) integrate our understanding of nematode structure and function with other soil biological health indicators to describe soil health traits; and 2) determine how management practices alter soil health traits. We found that soil biological health indicators represented four underlying soil health traits: fungal organic matter processing pathway, the rate of nutrient cycling, trophic complexity, and cumulative disturbance. Results indicated that soil biological health indicators, such as enzyme activities, POXC, mineralizable C and soil protein were more integrated with nematode feeding groups than with nematode indices. Additionally, tillage intensity had a significant effect on the fungal organic matter processing pathway and the rate of nutrient cycling. This study indicates that nematode feeding groups can be readily incorporated into the soil health framework and future soil health assessments.