3.3 Plant community composition
Inter-annual precipitation fluctuation strongly shaped plant community composition through altering the relative aboveground biomass of main plant species (Table S2; Y: all p < 0.01). In particular, the relative plot biomass of C. aristatum was drastically decreased in the dry year (Fig. 4a–d). Mycorrhizal suppression had no significant impact on plant community composition across the two experimental years (Table S3; all p > 0.05). P input alone greatly enhanced the relative aboveground biomass of C. aristatum and A. mongolicum (Table S2, Fig. 3). Inter-annual precipitation fluctuation strongly changed species richness and plant Shannon index (Table S3; Y: all p < 0.01), which was higher in 2019 than in 2020 (Fig. S2). P input alone significantly increased plant species richness from 2019 to 2020 (Fig. S2a and b; F 1, 28 = 21.06, p < 0.01; F 1, 28 = 22.50, p < 0.01, respectively), but N addition alone and fungicide application did not change it (Table S3, all p > 0.05).