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To improve our understanding of farmland surface process and agricultural water management in arid oasis area, we analyzed the characteristics of water and heat fluxes at different time scales, and the influence of arid advection and canopy conductance (Gc) on water and heat fluxes at different growth stages. In addition, we used path analysis to study the influence path of environmental factors on latent heat flux (LE) . In this paper, the water and heat fluxes were measured by eddy-covariance in 2017. The results were as follows: (1) LE showed multiple peaks, while the other fluxes were basically unimodal shapes at the daily scale. On the whole, the values of daily net radiation (Rn) were maximum, followed by LE, sensible heat flux (H) and soil heat flux (G) at each growth stage. The variation of diurnal G showed obvious lagged effect compared to that of Rn. (2) LE and H accounted for 86% and 14% (respectively) of daytime energy during the whole growing stages, indicating that LE was the main energy consumption item. The contribution of arid advection to daytime LE ranged from 5% to 59% with an average value of 28% at whole growing season. The influence of Gc on LE was stronger at the new shoot and leaf-fall stages than that in the middle growing season. (3) LE was mainly affected by Rn, followed by vapor pressure deficit (VPD) and air temperature (Ta), and the influence degrees of VPD and Ta on LE were similar. Furthermore, the path analysis showed that Rn directly affected LE; VPD and Ta mainly affected LE indirectly through Rn. As a whole, the water and heat fluxes in vineyards of arid desert oasis in Northwest China display significant diurnal and seasonal variations, and the influences of environmental factors on these exists great discrepancies in magnitude and path. [ABSTRACT FROM AUTHOR]

Grapes are one of the main economic crops in the arid area of Northwest China. Understanding its photosynthetic production process is very important for planting and cultivation. In order to analyze the physiological characteristics of grape photosynthesis and the main influencing factors affecting grape photosynthesis under natural conditions in the field, the daily variation of net photosynthetic rate of grape(variety: Seedless White) leaf and its daily variation of physiological and ecological factors in typical season of grape were measured from June to September in 2019. The path analysis method is used to analyze the direct and indirect effects of various factors on the net photosynthetic rate of grape leaf, and to determine its main influencing factors. In addition, the response of the net photosynthetic rate of grape leaf to various physiological and ecological factors was further analyzed in the whole day time-phased mode. The results were as follows: (1) The daily variation of net photosynthetic rate of grape leaf showed a single peak pattern, which first increased and then decreased; (2) The net photosynthetic rate of grape leaf was positively correlated with photosynthetic active radiation, vapor pressure deficit, air temperature, stomatal conductance and transpiration rate, and negatively correlated with relative humidity and intercellular CO2 concentration. Among them, the correlation coefficient with stomatal conductance and transpiration rate was the largest; (3) The main determinant that affected the variation of net photosynthetic rate of grape leaf was the transpiration rate in June, August and September, and the stomatal conductance in July; (4) The net photosynthetic rate of grape leaf in each month showed a “hysteretic loop” relationship with air temperature, photosynthetic active radiation, vapor pressure deficit, and a good linear relationship with transpiration rate and stomatal conductance(R²>0.85), and an exponential function relationship with intercellular CO2 concentration(R²=0.53). Studies have shown that grapes have a strong ability to adapt to the environment in the arid area of Northwest China. In cultivation, we can optimize management and increase yield by controlling transpiration rate and stomatal conductance, but the direct and indirect effects of other factors need to be considered. [ABSTRACT FROM AUTHOR]