The Qinghai-Tibetan Plateau (QTP) is generally considered to be the water source region for its surrounding lowlands. However, there have only been a few studies that have focused on quantifying alpine meadow evapotranspiration (ET) and its partitioning, which are important components of water balance. This paper used the Shuttleworth–Wallace (S–W) model to quantify soil evaporation (E) and plant transpiration (T) in a degraded alpine meadow (34°24′ N, 100°24′ E, 3963 m a.s.l) located at the QTP from September 2006 to December 2008. The results showed that the annual ET estimated by the S–W model (ET_SW) was 511.5 mm (2007) and 499.8 mm (2008), while E estimated by the model (E_SW) was 306.0 mm and 281.7 mm for 2007 and 2008, respectively, which was 49% and 29% higher than plant transpiration (T_SW). Model analysis showed that ET, E, and T were mainly dominated by net radiation (R_n), while leaf area index (LAI) and soil water content at a 5 cm depth (SWC_5cm) were the most important factors influencing ET partitioning. The study results suggest that meadow degradation may increase water loss through increasing E, and reduce the water conservation capability of the alpine meadow ecosystem.

The Northeast China maize belt is one of the three major golden maize belts in the world and has been severely affected by climate change, however, the evapotranspiration (ET) partitioning is not clear. It is important to study ET and its components under climate change. In this paper, the water balance model SOILWAT2 was used to estimate ET partitioning in drought and humid years, seasons, and maize growth stages from 1989 to 2018 over rainfed maize farmland. The results indicated that the SOILWAT2 model performed well for the prediction of ET and its partitioning compared with eddy covariance measurements. The mean yearly ET, transpiration (T), soil evaporation (Es), and canopy interception evaporation (Int) were 432.3 mm, 197.6 mm, 204.7 mm and 19.2 mm, respectively, over 30 years. Es/ET was 6.3% lower in drought years than in humid years, T/ET was conversely higher (6.2% higher in drought years). There was no clear difference of Int/ET between humid and drought years. In the growing season, T/ET, Es/ET, and Int/ET varied from 40.0% to 75.0%, 22.8% to 55.7%, and 0.7% to 7.0%, respectively. T/ET decreased along with the growth of maize and was greatest at the greening–jointing stage. Es/ET was smallest at the greening–jointing stage. We found a power function relationship between T/ET, Es/ET, and leaf area index (LAI) and above-ground biomass. Our results indicated that for the rainfed farmland, drought may limit maize yield by increasing water loss of maize through increasing T under climate change conditions. Therefore, securing food yield will depend on increases in water-use efficiency and other adaptive strategies, such as drought-resistant varieties, and irrigation.

Terrestrial ecosystem water balance refers to the state between precipitation inputs, and outputs via evapotranspiration, groundwater recharge and runoff. The Three River Source Region (TRSR) is known as the “water tower of Asia” and is an important water source region for much of southeast Asia. Spatial and temporal distributions of water balance across the TRSR have been affected by recent changing climatic conditions. However, the status and variation of water balance under the influence of environmental factors remain unclear. We employed SOILWAT2, a daily time step ecosystem water model, along with 35 years of climate data from 29 meteorological stations to characterize the hydrological dynamics of the region. Our results revealed that 15 of the sites exhibited evidence of a net water source (precipitation > actual evapotranspiration) between 1981 and 2015. These stations were predominantly located at intermediate elevations (3,400–4,100 m) and low latitudes (<34°N), while stations at lower and higher elevations as well as higher latitudes were not sources because of moisture limitations by a dry climate. In contrast to a strong spatial pattern, we found no obvious temporal trend of the net water source. The interannual and seasonal variability of the net water source is dependent on the temporal fluctuations in potential evapotranspiration and precipitation. We therefore conclude that there is an elevation and latitude dominated spatial pattern of the water balance on the TRSR, with important implications for the availability of water resources.

To elucidate the photosynthetic physiological mechanisms influencing alfalfa (Medicago sativa L.) yield and quality under varying planting densities, the cultivar ‘Zhongmu No.1’ was used as experimental material. The effects of different row spacing (R1, R2, R3) and seeding rate (S1, S2, S3, S4, S5) combinations on chlorophyll content (ChlM), nitrogen flavonol index (NFI), chlorophyll fluorescence parameters, forage quality, and hay yield were systematically analyzed. Results showed that alfalfa under R1S3 treatment achieved peak values for ChIM, NFI, EE, and hay yield, whereas R1S4 treatment yielded the highest Fv/Fm and CP content. Redundancy analysis further indicated that yield was most strongly associated with ChlM, NFI, Y (II), and qP. Y (II), and qP significantly influenced alfalfa forage quality, exerting negative effects on ADF and NDF, while demonstrating positive effects on CP and EE. In conclusion, narrow row spacing (15 cm) with moderate seeding rates (22.5–30 kg·hm⁻²) optimizes photosynthetic performance while concurrently enhancing both productivity and forage quality in alfalfa cultivated, establishing a theoretical foundation for photosynthetic regulation in high-quality and high-yield alfalfa cultivation.

Terrestrial ecosystem water balance refers to the state between inputs from precipitation, and outputs including evapotranspiration, groundwater recharge and runoff. The Three River Source Region (TRSR) is known as the “water tower of Asia” and is an important water source region for much of southeast Asia. Spatial and temporal distributions of water balance have changed within the TRSR under recent changing climatic conditions. However, the status and variation of water balance under the influence of environmental factors remain unclear. We used a daily time step ecosystem water model (SOILWAT2) and 35 years data for 29 meteorological stations to describe water balance across the TRSR and found that 15 of the sites represented a net water source (precipitation > actual evapotranspiration) between 1981 and 2015. Stations at intermediate elevations (3400 to 4100 m) and low latitudes (< 34°N) were net water sources; stations at lower and higher elevations as well as higher latitudes were not sources because of moisture limitations by a dry climate. In contrast to a strong spatial pattern, we found no obvious temporal trend of the net water source. The interannual and seasonal variability of the net water source is dependent on the temporal fluctuations in potential evapotranspiration and precipitation. We therefore suggest that there is an elevation and latitude dominated spatial pattern of the water balance on the TRSR, with important implications for the availability of water resources.