Authors : Jie Li, Bin Wang, Xiaoqin Liu, Lulu Feng, Rongrong Ma, Ben Niu, Liang Zhao, Yingnian Li, Yanhong Tang, Mingyuan Du and Song Gu
Abstract: To accurately estimate the magnitude and seasonal dynamics of Evapotranspiration (ET) over an important alpine winter pasture in the Northeastern Qinghai-Tibetan Plateau, researchers employed the Food and Agriculture Organization (FAO) Penman Monteith (P-M) Model. The model was also used to investigate changes in the crop coefficient (kc) which was calculated as the ratio of the measured actual ET (ETa from the Eddy Covariance (EC) System) to the reference ET (ET0 from the P-M Model). The results indicated a reference ET of 900 mm year-1 from the alpine meadow pasture which was significantly higher than the actual ET (426 mm year-1). In addition, the seasonal dynamics of these two ET values differed. The reference ET peaked from April to July while the actual ET was primarily in growing season. The value of kc exhibited significant seasonal variations within the range 0.3-1.0 with a mean kc of 0.55 during the growing season. The correlation analysis of the relationship between daily kc and its primary environmental factors indicated that the Vapor Pressure Deficit (VPD), net Radiation (Rn) and air Temperature (Ta) were the major influencing factors of the daily kc. The daily kc showed a linear increase with Rn and Ta and a linear decrease with the VPD. With respect to the biotic factors, the biomass exhibited a significant positive correlation with kc. Thus, a daily kc Model is developed as a function of the VPD, Rn, Ta and biomass. This ET Model was validated using 2005 data and showed a satisfactory consistency between the simulated and measured ET.
Jie Li, Bin Wang, Xiaoqin Liu, Lulu Feng, Rongrong Ma, Ben Niu, Liang Zhao, Yingnian Li, Yanhong Tang, Mingyuan Du and Song Gu, 2014. A Study of Fitting an Alpine Winter Pasture Evapotranspiration to a Model Based on the Penman-Monteith Equation. Journal of Animal and Veterinary Advances, 13: 123-131.