Early effects of agroforestry practices on soil microbial communities in vineyards

Some vineyard practices (tillage, chemical weeding or pest management) are generally known to impact the environment by water, atmospheric and soil pollution with particular negative effects on the diversity and the abundance of soil microorganisms. In an agro-ecological context, innovative cropping systems have been developed to reduce environmental footprint and improve ecosystem services. Among them, agroforestry offers strategies of sustainable land management practices. It consists in intercropping trees with annual/perennial/fodder crop on the same plot but it is weakly referenced with grapevine. The present study assesses the effects of intercropped young trees (8 years old) on the soil quality of agroforestry vineyards, in south-western France regions.More precisely soils of the different plots were sampled according to the distance to the tree (from 1 m to 19m) and soil microbial abundance, diversity and community structure have been characterized by a soil metagenomic approach. Our technical approach consisted in extracting and quantified soil DNA to evaluate the molecular microbial biomass, then in calculating the soil fungi/bacteria ratio – obtained by qPCR - and in characterizing the soil microbial diversity – through Illumina sequencing of 16S and 18S regions.Our results showed a few effect of tree on microbial abundance and diversity conversely to the microbial community structure. In addition, the comparison of microbial co-occurrence networks inside vine plots according to distance to the tree revealed also significant differences. Altogether our study allows building up the first references systems concerning the impact of agroforestry practices on vineyards which will be interpreted in terms of soil quality, functioning and sustainability.