Extended Data Fig. 9: The response ratio relationship between subordinate species richness and dominant species cover (a), and the characters of community composition.

b, relative cover of each subordinate species functional group in ambient plots. c, Relative frequency-relative cover curve in Eurasian grasslands. d, relative frequency-relative cover curve in North American grasslands. Lines are mixed-effects model fits for each trend. The black, purple, and yellow lines indicate the trends averaged across all sites, the trends for each Eurasian grassland site, and the trends for each North American grassland site, respectively (see Supplementary Table 6 for detailed summary statistics). Values are mean ± s.e.m of the relative cover of each functional group in subordinate species in ambient plots across the six Eurasian grasslands (n = 6) and six North American grasslands (n = 6), and significance was assessed by t-tests (two-sided). Relative cover of perennial forb (PF) was significantly higher (t = 2.60, P = 0.04) in Eurasian grasslands compared with North American grasslands. No significant difference in relative cover was found for annuals and biennials (AB, t = −1.23, P = 0.26), perennial grass (PG, t = 0.48, P = 0.64), and shrubs and subshrubs (SS, t = −1.20, P = 0.28) between Eurasian and North American grassland sites. Relative frequency and relative cover are calculated based on the values over four years in ambient plots for each species at each site. Light pink and green represent dominant and subordinate species, respectively. □, ○, △, ◇, ▽, × represent TAR, ERG, XLL, XLS, MUR and URA in Eurasian grasslands, as well as KNZ, HYS, CHY, SGS, SBL and SBK in North American grasslands. Species with a relative frequency greater than 0.8 and a relative cover greater than 12% are dominant species, and the rest are subordinate species.