Oribatid mites are invisible indicators of soil health

Minute living organisms in the soil work unceasingly to maintain ecosystem equilibrium and dynamics. Oribatid mites play an important role in this setting. They participate in organic matter decomposition and nutrient cycling, two processes that are essential to soil health. Their sensitivity to environmental changes also means that they are valuable bioindicators of soil health.

A rigid shell, or exoskeleton, protects the bodies of these mites and facilitates their movement. They can be smaller than a millimetre and they live in soil, forest litter or amongst mosses and lichens. They account for around 40% of the microarthropods present in soil, feeding from dead plant matter, fungi and algae and contributing directly to the recycling of these materials. Oribatids chew and partially digest organic matter, transforming it into a resource that is more easily used by microbes and thus accelerating the decomposition process.

An international research team, comprising scientists from France and from Algoma University in Canada and the University of São Paulo in Brazil, recently studied the effects of farming practices on these communities in Mediterranean vineyards. The researchers compared the soils of conventional and organic vineyards, with or without plant cover (permanent or temporary) between the rows, against natural garrigue soils used as a reference. More than 7500 mites were collected in order to analyse their abundance, diversity and richness.

Their results showed that natural ecosystems are home to communities that are much richer than those found in cultivated soils. However, the presence of permanent plant cover between vine rows favours communities similar to those found in natural soils. By contrast, bare soils, or those with only temporary cover, are home to fewer individuals and display less diversity. The differences between organic and conventional vineyards appeared to be less marked: abundance and richness varied little, but diversity was slightly higher under organic farming methods.

These observations, published in Applied Soil Ecology, thus confirm that oribatid mites are valuable allies to monitor the impact of farming practices on soil biodiversity and to favour ecological restoration. By maintaining plant cover and limiting chemical inputs, wine growers can preserve soil diversity and reinforce the resilience of their plots.