Pearson correlation analysis between 8-day averages or sums of LUE and environmental factors at each site.

TS: typical steppe; DS: desert steppe; Tmin: minimum temperature (°C); Ta: average temperature (°C); Ts5: soil temperature at 5 cm depth (°C); VPD: vapor pressure deficit (kPa); SWC10: soil water content at 10 cm depth (m3 m−3); AET: actual evapotranspiration (mm); PET: potential evapotranspiration calculated using Penman-Monteith equation (mm); EF: evaporative fraction; AET/PET: the ratio of actual evapotranspiration to potential evapotranspiration; PRECP, precipitation (mm).R2 is determination coefficient; n is sample number.*P**P