Table 3 Results of the curve estimation of the relationship between water additions and total biomass, aboveground biomass, belowground biomass and R: S ratio (i.e. the ratio of aboveground biomass and belowground biomass) of species Artemisia frigidawith linear, quadratic, power and exponential equations, where R2, F, Df1, Df2, significance, constant, b1 and b2 were showed. A larger R2 with a significant value is a better estimation, which is marked in red