Abstract of talk

The global area of cultivated land has increased considerably over the past five decades, accompanied by an increase in use of agrochemicals. Despite the many ecosystem services provided by soils, there is very little understanding on how land-use intensification (including use of pesticides) influences soil microbiome and the related services that humans rely upon. The presence of pesticide residues in soils is well-known, but an understanding of its impact on soil microorganisms is still lacking at a large scale.
Here we used an extensive soil DNA dataset derived from the last European Union (EU) LUCAS survey (2018). A total of 715 sampling locations distributed across Europe were included and classified according to a gradient of increasing land-use intensification: from woodlands (less anthropic), to grasslands and croplands (more anthropic). We assessed how this intensification gradient influenced the diversity, structure and predicted functions of bacterial and fungal communities (e.g., plant symbiosis and human and plant pathogenicity).
We found that more anthropic habitats (croplands and grasslands) had higher microbial richness than natural ones (woodlands). However, high diversity was not necessarily correlated with beneficial functions carried out by microorganisms, as croplands were characterised by a higher presence of fungal plant pathogens that could have been selected by pesticide input. Anthropogenic activities (chemical application) may have been selected for some bacterial functional groups in more intensified land types, as nitrogen-fixing bacteria were more abundant there, and could have been favoured through fertiliser applications. We also observed that differences in community structure were the most important between croplands and woodlands, indicating that anthropogenic activities can effectively shape soil bacterial and fungal communities.
In addition, in over 400 sites, we combined LUCAS soil biodiversity data with pesticide residue concentrations (over 110 active ingredients) in order to explore how pesticide inputs may affect soil microbial biodiversity. Impacts of pesticides on the diversity, structure and predicted functions of bacterial and fungal communities in croplands will be presented.
Our findings represent a step forward to a more comprehensive assessment on the anthropogenic factors shaping soil microbial communities. They can contribute to the development of policy recommendations for better preserving soil microbiomes in Europe.