Spatiotemporal variations in the water use characteristics and efficiency of Potentilla fruticosa shrubs found in the Qinghai Tibet Plateau

Analysis of the characteristic changes in water use efficiency in alpine meadows and its influencing factors plays an important role in improving the water use efficiency of these alpine meadows. Our study used gross primary productivity (GPP) and evapotranspiration as calculated by the latent heat flux (LE) and the latent heat of evaporation (latent heat of evaporation, λ) to evaluate the water dynamics of Potentilla fruticosa shrub meadows in Haibei, Qinghai Province between 2003 and 2010. The water use efficiency (WUE) of these shrub meadows was evaluated across eight consecutive years, allowing for a robust evaluation of their response to meteorological factors. Our results showed the following: 1) On an interannual scale, the gross primary productivity, evapotranspiration, and water use efficiency increased at an annual rate of 98.55 g·m⁻², 40.15 mm, and 138.70 g·(m²·mm)⁻¹, respectively. While gross primary productivity, evapotranspiration, and water use efficiency all reached their maximum in July and their minimum in January when evaluated on a seasonal scale. 2) The annual average temperature, relative humidity, and net radiation have the highest relative contribution to the annual water use efficiency, and these factors can explain up to 73.50% of the variation in the annual water use efficiency values. The following three environmental factors: photosynthetically active radiation, air temperature, and relative humidity contribute as much as 74.14% to the values on the growth season scale. The annual average temperature and photosynthetically active radiation rates are both relatively important contributing factors to both the annual and growing season scales, with these values accounting for up to 43.09% and 30.79% of the total, respectively. Correlation analysis revealed that relative humidity was the main factor affecting water use efficiency. Annual average temperature and vapor pressure deficit also exerted some effect on the annual scale values under these conditions. The main influencing factors for the growing season scale also included photosynthetically active radiation and net radiation. The results of this study make a significant contribution toward clarifying the underlying regulatory mechanisms mediating the dynamic changes in water use efficiency in shrub meadows in response to changing environmental conditions.