## 3 Results
### Ecosystem Respiration and Its Components  
The ecosystem respiration in our study turned out to be a single-peak curve, which peaked between 13:00-16:00 depending on the different land uses of the steppe. The difference of Re between grazed and grazing-excluded steppes was not significant, but they were both significantly lower than the cultivated steppe in every hour (Figure 5a). The Re was divided into Ra and Rh, Rab and Rb according to the different division methods. The Ra of the cultivated steppe, which peaked at 12:00, was substantially higher than that of the grazed and grazing-excluded steppes, which peaked at 14:00 (Figure 5c). The daily variation of the Rh was relatively even, and the difference of Rh between the three use patterns was less distinct than that of Ra (Figure 5d). In addition, the aboveground and belowground respiration of the cultivated steppe was both higher than that of grazed and grazing-excluded steppes (Figure 5e,f). Moreover, the maximum root respiration was occurred in the cultivated steppe at 13:00, reaching 2 umol m\({}^{-2}\) s\({}^{-1}\)).  
The Re of the grazed steppe and the grazing-excluded steppe, both at approximately 17 g CO\({}_{2}\) m\({}^{-2}\) d\({}^{-1}\), was not significantly different (\(p>\) 0.05), while Re of the cultivated steppe reached 26.9 g CO\({}_{2}\) m\({}^{-2}\) d\({}^{-1}\), with a significant increase by 64.3% (\(p<\) 0.05) relative to the grazed steppe (Figure 6). The Ra of the grazed steppe and the grazing-excluded steppe, both at approximately 8 g CO\({}_{2}\) m\({}^{-2}\) d\({}^{-1}\), were not significantly different (\(p>\) 0.05). However, Ra of the cultivated steppe  
Figure 4: Daily average GEP, NPP and NEP on steppes under different land uses during the peak growing period. Vertical bars represent \(\pm\) 1 SD of the mean. Different letters in each bar group indicate significant difference (\(p<\) 0.05). G, grazed steppe; GE, grazing-excluded steppe; C, cultivated steppe.  
reached 14.1 g CO\({}_{2}\) m\({}^{-2}\) d\({}^{-1}\), which was a significant increase by 88.8% (\(p\) < 0.05) relative to the grazed steppe. The Rh of the grazed steppe and the grazing-excluded steppe, both at approximately 9 g CO\({}_{2}\) m\({}^{-2}\) d\({}^{-1}\), were not significantly different (\(p\) > 0.05). However, Rh of the cultivated steppe reached 12.8 g CO\({}_{2}\) m\({}^{-2}\) d\({}^{-1}\), which was a significant increase by 43.7% (\(p\) < 0.05) in comparison with the grazed steppe. The difference in Rab between the grazed steppe and the grazing-excluded steppe was not significant (\(p\) > 0.05), whereas Rab of the cultivated steppe was twice that of the grazed steppe (\(p\) < 0.05). The Rb of the grazed steppe and the grazing-excluded steppe, both at approximately 11 g CO\({}_{2}\) m\({}^{-2}\) d\({}^{-1}\), were not significantly different; however, Rb of the cultivated steppe increased to 14.6 g CO\({}_{2}\) m\({}^{-2}\) d\({}^{-1}\), which was a significant increase by 35.6% (\(p\) < 0.05) relative to the grazed steppe. The Rr of the three grassland-use patterns, all at approximately 2 g CO\({}_{2}\) m\({}^{-2}\) d\({}^{-1}\), were not significantly different between treatments (\(p\) > 0.05).  
Figure 5: Changes of daily dynamics of ecosystem respiration compositions in different grassland-use patterns during the peak growing period. (**a**) ecosystem respiration (Re); (**b**) root respiration (Rr); (**c**) autotrophic respiration (Ra); (**d**) heterotrophic respiration (Rh); (**e**) aboveground respiration (Rab); (**f**) belowground respiration (Rb). G, grazing; GE, grazing-excluded; C, cultivated steppe.