Extended Data Fig. 4: The patterns of abiotic factors in Eurasian and North American grasslands.

a, Frequency of historical extreme drought, normal precipitation, and extreme precipitation years (n = 6). b, Ambient precipitation (n = 6). c, Effects of extreme drought on soil moisture in Eurasian (n = 36) and North American grasslands (n = 60). d, Effects of extreme drought on soil moisture for each site in Eurasian grasslands (n = 6). e, Effects of extreme drought on soil moisture for each site in North American grasslands (n = 10). Values are mean ± s.e.m. Significance was assessed by t-tests (two-sided) in a, and no significant difference was found (all p > 0.05). The frequencies and precipitation are based on 37-year historical weather data from 1982 to 2018 for each site (see Methods). Purple and yellow dashed lines represent averaged precipitation across all Eurasian grassland sites and North American grassland sites, with their 95% CI, respectively. Statistical significance of the values between treatments is depicted as *(p < 0.05), which was assessed by Tukey’s HSD tests (two-sided).