Soil microeukaryotic communities, soil properties, and plant biomass production in the DivResource experiment, 2022

The study was conducted in the DivResource Experiment, established in 2011 at the experimental field station of the Helmholtz Centre for Environmental Research (UFZ) in Bad Lauchstädt, Germany. The experiment comprises eight perennial grassland species (four grasses and four herbs) arranged in monocultures, two-species mixtures and four-species mixtures under fertilized and unfertilized conditions, resulting in 48 plots distributed across four blocks. During peak biomass (10 June 2022), six soil cores (1 cm diameter, 10 cm depth) were collected per plot, pooled, sieved (2 mm), and divided into subsamples. One subsample was frozen at −20 °C for DNA analyses, while the remainder was stored at 4 °C for soil analyses. DNA was extracted from 1 g soil. The SSU–ITS–LSU rRNA region was amplified using the universal eukaryotic primers V4F and 21R and sequenced using Oxford Nanopore technology. Fungal OTUs were assigned to functional groups using the FungalTraits database, whereas protist OTUs were classified according to Lentendu et al. (2025) and expert knowledge. We measured soil pH, total carbon and nitrogen, plant-available phosphorus, exchangeable potassium, and aboveground plant biomass using standard methods. Biomass was harvested during peak biomass in 2022. Community-weighted means (CWMs) of specific leaf area (SLA) and specific root length (SRL) were calculated from published trait data (Siebenkäs et al. 2016), weighted by species relative biomass.