Chin J Plant Ecol ›› 2022, Vol. 46 ›› Issue (12): 1448-1460.DOI: 10.17521/cjpe.2021.0428

• Special feature: Ecosystem carbon and water fluxes in ecological vulnerable areas of China • Previous Articles     Next Articles

Seasonal and interannual variations in energy balance closure over arid and semi-arid grasslands in northern China

WANG Yan-Bing, YOU Cui-Hai, TAN Xing-Ru, CHEN Bo-Yu, XU Meng-Zhen, CHEN Shi-Ping()   

  1. State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
    University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2021-11-22 Accepted:2022-04-22 Online:2022-12-20 Published:2023-01-13
  • Contact: *CHEN Shi-Ping(
  • Supported by:
    National Key R&D Program of China(2017YFA0604801);National Natural Science Foundation of China(32071565);National Natural Science Foundation of China(41773084)


Aims Eddy covariance (EC) systems are widely used for measuring the fluxes of carbon, water, and energy, as well as meteorological factors. As one important reference of independently evaluating scalar flux by EC technique, energy balance closure is widely used for evaluating data quality of carbon, water, and energy fluxes.

Methods Using the data of energy fluxes and meteorological variables retrieved from 56 site-year, the energy balance closure of six sites across three ecosystems (i.e. desert steppe, typical steppe, and meadow steppe) was analyzed by two widely used methods: linear regression from the ordinary least squares (OLS) and the energy balance ratio (EBR). The overall evaluation of energy balance closure, the seasonal and interannual variations and the related influencing factors were investigated.

Important findings The results show that: 1) the multiple-year EBR and OLS slope over the six sites had a mean value of 0.89 ± 0.11 and 0.96 ± 0.04, respectively, which are better than the results of the FLUXNET and ChinaFLUX. 2) There were significant differences over different sites and grassland types, with EBR of desert steppe (1.01 ± 0.09) and typical steppe (0.90 ± 0.11) both higher than meadow steppe (0.83 ± 0.05). There were seasonal variations of EBR over the six studied sites, and with better and stable results in growing season than non-growing season. The air temperature (Ta), vapor pressure deficit (VPD), soil moisture (SWC), and Albedo regulated the seasonal variation of EBR, with the low Ta and high Albedo remarkably reducing EBR during the non-growing season. 3) There were significant interannual variations of EBR across different sites and grassland types. The latent heat fraction (the ratio of latent heat flux to net radiation, LE/Rn), mean annual air temperature (MAT) and growing season Albedo significantly influenced interannual variation of EBR. The LE/Rn showed the strongest impact and explained 44% of the interannual variation of EBR. The significantly increasing in leaf area index (LAI) strongly regulated the upward of the available energy (net radiation minus ground heat flux, Rn- G0), which contributes to the significant downward of EBR during observed years. It should be noted that EBR and OLS slope should be combined to better evaluate the energy balance closure. In conclusion, this study help improve our understanding of the potential linkage between energy balance closure and environmental factors, evaluate the quality of scalar flux estimates from EC technique, as well as improve the data processing protocol of flux data in the semi-arid and arid grassland region.

Key words: energy balance closure, eddy covariance, seasonal variation, interannual variation, grassland