Elevated atmospheric CO2 concentrations caused a shift of the metabolically active microbiome in vineyard soil

BackgroundElevated carbon dioxide concentrations (eCO(2)), one of the main causes of climate change, have several consequences for both vine and cover crops in vineyards and potentially also for the soil microbiome. Hence soil samples were taken from a vineyard free-air CO2 enrichment (VineyardFACE) study in Geisenheim and examined for possible changes in the soil active bacterial composition (cDNA of 16S rRNA) using a metabarcoding approach. Soil samples were taken from the areas between the rows of vines with and without cover cropping from plots exposed to either eCO(2) or ambient CO2 (aCO(2)).ResultsDiversity indices and redundancy analysis (RDA) demonstrated that eCO(2) changed the active soil bacterial diversity in grapevine soil with cover crops (p-value 0.007). In contrast, the bacterial composition in bare soil was unaffected. In addition, the microbial soil respiration (p-values 0.04-0.003) and the ammonium concentration (p-value 0.003) were significantly different in the samples where cover crops were present and exposed to eCO(2). Moreover, under eCO(2) conditions, qPCR results showed a significant decrease in 16S rRNA copy numbers and transcripts for enzymes involved in N-2 fixation and NO2- reduction were observed using qPCR. Co-occurrence analysis revealed a shift in the number, strength, and patterns of microbial interactions under eCO(2) conditions, mainly represented by a reduction in the number of interacting ASVs and the number of interactions.ConclusionsThe results of this study demonstrate that eCO(2) concentrations changed the active soil bacterial composition, which could have future influence on both soil properties and wine quality.