Abstract:

Based on daily observational data from ten national meteorological stations in the Chishui River basin (1981–2024) , the vapor pressure deficit (VPD) was calculated using the Tetens formula. To assess the effect, annual data on sowing area, yield and the long−term average growth period of liquor−making sorghum in Renhuai (2006–2024) were utilized. The temporal–spatial characteristics of VPD were analyzed using trend analysis, Mann–Kendall test and wavelet analysis, followed by a quantitative assessment of the VPD−induced stress on liquor−making sorghum production in Renhuai. The results showed that: (1) from 1981 to 2024, the VPD in the Chishui River basin exhibited a highly significant increasing trend at the annual, spring and summer scales (P<0.01), with rates of 0.005kPa·10y⁻¹, 0.007kPa·10y⁻¹ and 0.007kPa·10y⁻¹, respectively. A significant increase was also observed in winter (0.004kPa·10y⁻¹, P<0.05), while the autumn trend was not significant. The greatest change occurred in summer (0.105 to 0.207kPa), and the smallest in winter (0.074 to 0.124kPa). Following an abrupt change observed from 2001 to 2004 across annual and seasonal scales, the VPD showed a consistent increase, and its variability increased over the subsequent decades. (2) From 1981 to 2024, annual and seasonal VPD consistently showed a spatial pattern of low in the northwest and high in the southeast. This pattern was projected to strengthen over the next 3–7 years of annual and seasonal VPD in the Chishui River basin. (3) During the period of 2006–2024, every 0.01kPa increase in the mean VPD of the liquor−making sorghum growing season (April–August) in Renhuai reduced the yield by 108.8kg·ha⁻¹. The increase of VPD had a direct negative effect on the yield and indirectly amplified the yield loss by intensifying the combined stresses of air temperature and relative humidity. Soil−water conservation and irrigation infrastructure are recommended to mitigate the risks associated with rising VPD.

Key words: the Chishui River basin, Dry?wet evolution, Relative humidity, Liquor?making sorghum, Climate change