Does Soil Legacy Affect Root Activity in Species Mixtures?

In species-rich plant communities, the distribution of soil biota is patchy as plant species develop their own communities of soil biota over time. There is increasing evidence that these communities are predominantly pathogenic. When plant individuals die, this results in a microbial legacy effect in the soil. The remaining microbial community may affect the belowground exploitation of these patches, i.e. root placement and root activity, and subsequent invasion by other species.

The objective of this experiment was to assess the effect of plant-soil feedback in soil patches on the root activity of species grown in mixtures. We hypothesise that root growth of species is more negatively affected in soil in which the species has grown before (“own soil”) than soil conditioned by other plant species (“foreign soil’) or mixed soil.

In 2016, a mesocosm experiment was set up with mixed plant communities (50 x 50 cm) containing eight different plant species: four grasses and four forbs. Within each compartment we created four soil patches of 12.5 cm diameter by 20 cm depth, containing soil preconditioned by one out of four plant species (two grasses and two forbs from the plant communities) or a mixture of all four soils. In June, a tracer solution containing ¹⁵NO₃, Rb, Li and Sr was injected into the patches to assess nutrient uptake activity of the different species as affected by patch type.

Analyses of the tracer concentrations in the aboveground plant material, indicate significant differences in tracer uptake among the species and patch types and evidence of interaction between patch type and plant species. This suggests that the root activity of species is differentially affected by the history of the soil they are growing on.

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under Marie Sklodowska-Curie grant agreement No 655771