Nematode data

Sample.data Plot.ID consecutive numbers for plots (in total 36 plots) Treatment One restoration treatment and two reference treatments. Topsoil+Propagules= Topsoil removal (upper 10-30 cm) combined with introduction of target plant species; Initial=intensively managed grasslands; Target= species-rich semi-wet to semi-dry grasslands treat.yr Treatment abbreviation. For restored grasslands: Treatment abbreviation + time since restoration; Initial + Target = NA yr.trt year when topsoil was removed; Initial + Target = NA Age time since restoration (sampling year 2018 - yr.trt); Initial + Target = NA Age.class restored sites of similar age grouped into four age classes. Y.4 = Year 3+4 (recently restored); Y.18 = Year 17+19 (mid-term); Y.24 = Year 23+25 (long-term); Y.30 = Year 27+32 (long-term); Initial + Target = NA Cluster clustered spatial arrangment of sites in the field (see Supporting Information Fig. S1) Site clustered spatial arrangment (replicates) of plots per site (see Supporting Information Fig. S1)

Taxonomy
ASV.ID unit number.letter code per amplicon sequence variant (in total 904) Taxonomic rank Phylum, Class, Order, Family, Genus, Species

Abundance
columns Plot.ID (see Sample.data) rows ASV.ID (see Taxonomy)