Abstract:

The exchange of matter and energy between earth and air can guide the function and stability of local ecosystem. In order to reveal the dynamic change process of energy in the warm desert steppe in the photovoltaic area and its response to environmental factors， this study took the warm desert ecosystem under the photovoltaic construction in Talatan， Republican County， Qinghai Province as the research object， and adopted vortex-correlation technology to study the change characteristics and regulatory factors of energy flux and distribution in the growing season. The results show that net radiation （R_n）， latent heat flux （LE）， sensible heat flux （H） and soil heat flux （G） all show a unimodal pattern on the daily scale. Among them， the monthly mean values of R_n， LE and G reached their peak in July， while H reached its peak in October. R_n has the highest mean monthly flux， while G has the lowest. In addition to H's upward trend at the end of October， R_n， LE and G all showed a downward trend after that. The energy distribution during the observation period showed that the dominant period of LE was relatively longer， and the energy closure ratio was 71%. During the observation period， net radiation was the most important meteorological factor for LE， H and G， followed by soil water content and air temperature， and G was more sensitive to net radiation （path coefficient 0.93）. Soil water content positively regulated LE （0.18）， but negatively regulated H （-0.26）. The contribution degree of saturated water vapor pressure difference to LE is significantly higher than that of H. Meanwhile， air temperature has an indirect effect on LE， but a direct effect on H. In addition to the net radiation， the soil heat flux is also affected by the significant positive effect of air temperature， with a coefficient of 1.52. The quantitative results of this study can improve our cognition and understanding of the law and internal mechanism of energy exchange in desert steppe under the background of photovoltaic facility construction.

Key words: warm desert, vorticity correlation technique, photovoltaic construction, water and heat flux, energy balance