Divergent environmental responses of long-term variations in evapotranspiration over four grassland ecosystems in China based on eddy-covariance measurements

•Dominant factor for the IAVs of ET varied among the four grassland ecosystems.•Net radiation dominated the IAV of ET at the alpine marsh meadow.•Water availability mainly regulated the IAVs of ET for relatively arid sites.•Environmental responses of surface conductance varied across the grasslands.