Dans la salle de conference du centre INRA.

Predicting plant-soil feedback across plant functional groups and its role in overyielding.

Gerlinde B. De Deyn
Wageningen University, The Netherlands

Soils host a tremendous biodiversity which governs functions essential for sustaining plant productivity and diversity. Decomposers in the soil ensure the release of plant growth-limiting mineral nutrients, and mutualistic symbionts can facilitate nutrient acquisition, while plant pathogens reduce plant growth. Different plant species develop different soil communities in their rhizosphere and thereby develop plant-species specific plant-soil feedback (PSF) effects that selectively suppress or stimulate the growth of specific plant species. To date, it remains hard to predict PSF effects, yet it is expected that soil biota respond to plant traits such that plant traits can be indicative for the PSF a plant develops. The development of negative PSF appears to be most common so that plant species combinations in space or time could promote plant productivity via the release of negative PSF. We tested the hypotheses that 1) plant traits indicative for high resource acquisition (high RGR, SLA, SRL, low % AMF colonisation) trade-off with more negative PSF, and that 2) the higher yield in plant species mixtures as compared to in monocultures can be (at least in part) explained by the dilution of negative PSF. We used the long-term Jena grassland biodiversity experiment, quantified plant species-specific plant traits and PSF values of 49 plant species, and related the species-specific PSF to plant species-specific relative yield and to the diversity effects in the species-rich plant communities in the field. We found that PSF across species ranged from negative to positive and that SRL and % AMF colonisation played a significantly role in PSF, even when accounting for plant functional groups. In contrast to our expectations, species with neutral to positive PSF contributed most to overyielding and to complementarity effects. These results point at the importance of beneficial soil organisms not only to support plant productivity in monoculture but also in species mixtures.