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Grassland ecosystems are an important component of global terrestrial ecosystems and play a crucial role in the global carbon cycle. Therefore, it is important to study the carbon dioxide (CO2) process in the Middle Tien Shan grassland ecosystem, which can be regarded as a typical representative of the mountain grasslands in Xinjiang. Eddy covariance (EC) and the global carbon fluxes dataset (GCFD) were utilized to continuously monitor the Middle Tien Shan grassland ecosystem in Xinjiang throughout the 2018 growing season. The findings revealed notable daily and monthly fluctuations in net ecosystem exchange (NEE), gross primary productivity (GPP), and ecosystem respiration (Reco). On a daily basis, there was net absorption of CO2 during the day and net emission during the night. The grassland acted as a carbon sink from 6:00 to 18:00 and as a carbon source for the remaining hours of the day. On a monthly scale, June and July served as carbon sinks, whereas the other months acted as carbon sources. The accumulated NEE, GPP, and Reco during the growing season were −329.49 g C m−2, 779.04 g C m−2, and 449.55 g C m−2, respectively. On the half-hourly and daily scales, soil temperature (Ts) was the main contributor to CO2 fluxes and had the greatest influence on the variations in CO2 fluxes. Additionally, air temperature (Ta) showed a strong correlation with CO2 fluxes. The grassland ecosystems exhibited the strongest CO2 uptake, reaching its peak at soil temperatures of 25 °C. Moreover, as the air temperatures rose above 15 °C, there was a gradual decrease in NEE, while CO2 uptake increased. The applicability of GCFD data is good in the grassland ecosystem of the Middle Tien Shan Mountains, with correlations of 0.59, 0.81, and 0.73 for NEE, GPP, and Reco, respectively, compared to field observations. In terms of remote sensing spatial distribution, the Middle Tien Shan grassland ecosystem exhibits a carbon sink phenomenon. [ABSTRACT FROM AUTHOR]

• Vortex-related data using continuous observations at Kelameili Station in the Gurbantunggut Desert. • The correlation analysis of NEE, GPP, Reco and various environmental factors was carried out. • Assess the carbon sequestration capacity of China's second largest desert and largest fixed semi-fixed desert (Gurbantunggut Desert). • The comparison of carbon source/sink functions in different terrestrial ecosystems provides a reference. • a new direction for finding "carbon failures". Although previous studies have illustrated the variation of CO 2 fluxes in different terrestrial ecosystems, more needs to be reported on desert ecosystems. This study, based on the eddy covariance (EC) measurements data over the Gurbantunggut Desert, analyzed the controlling factors and variations of net ecosystem exchange (NEE), gross primary production (GPP), and ecosystem respiration (Reco) during the growing season (April-September2021) in Gurbantunggut Desert. The results were as follows: 1) Carbon fluxes in the Gurbantunggut Desert had prominent daily and seasonal variations during the growing season. On the daily scale, it showed a net uptake during the day and a net release at night, and the monthly average daily change curve of NEE was "U" shaped; on the seasonal scale, carbon uptake was observed in all months, with a peak of −37.76 gC m−2 month−1 in May. 2)The cumulative amounts of NEE, GPP, and Reco in the Gurbantunggut Desert were −193.74, 235.43, and 41.69 g C m−2, respectively, throughout the growing season, showing carbon sinks. 3) Correlation analysis with environmental factors revealed that NEE, GPP, and Reco of desert ecosystems were highly significantly correlated with photosynthetically active radiation (PAR) at different time scales (p < 0.01). Second, at the half-hourly scale, all environmental factors showed vital significance, with a high correlation with air temperature (Tair) and soil temperature (Tsoil); at the monthly scale, they were significantly correlated with Precipitation (p < 0.05). 4) Photosynthetically active radiation is the dominant factor affecting the daily net ecosystem carbon exchange rate. The two are consistent with the rectangle hyperbola model where the daily net ecosystem carbon exchange rate decreases with increasing photosynthetically active radiation. The results indicate that carbon fluxes in the growing season of the Gurbantunggut Desert ecosystem are more sensitive to the response of photosynthetically active radiation. The results have significant reference value for further understanding and research in predicting the source-sink function and influence mechanism of desert ecosystems. [ABSTRACT FROM AUTHOR]