The dynamics of energy flow of yak population was studied at the Haibei Alpine Meadow Ecosystem Eeseach Station (Lat. 37°29'- 37°47'N, long. 101°12' -101°33'E) during 1984. Owing to the high altitute of the studying area (3,200 -3,800 m above sea level),the four seasons in the year are not as distinct as the phenophases of the meadow vegetation so we carried on our experiments according to the three main phenophases. green up, exuberance and withering of vegetations instead of the four seasons. The daily fo...