Transitions within agroecosystems impact protists diversity and soil multifunctionality

Soil protists are key contributors to ecosystem functions. The impacts of transitions within agricultural systems on the soil biota and functionality receive less attention than that among distinct ecosystems including forest, grassland, and cropland. Here, we investigated the impacts of transitioning from open field (OF) to greenhouse (GH) agriculture on soil protist communities and multifunctionality across multiple paired sites. Our results revealed that the transition from OF to GH reduced protist phylogenetic diversity, with a greater impact on rare protists (42.1% reduction). Latitude was the strongest predictor of phagotrophic protist community variation in paired OF and GH soils across regions. The soil multifunctionality index declined by an average of 17.7%, mostly due to the loss of rare protists in GH soils. Reconstitution experiments confirmed that inoculating GH soils with rare protists from OF soils significantly restored multifunctionality. Our work highlights the critical role of low-abundant protists in modulating soil functioning.