Seasonal Changes of a and Pmax on Tibetan Plateau Alpine Meadow Ecosystem
会议名称：《第四届青藏高原国际学术研讨会》
会议日期：2004年
学科分类：07[理学] 070601[理学-气象学] 0706[理学-大气科学]
摘 要：The Alpine meadow is one of the vegetation types widely distributed on the Tibetan Plateau with the area about 1.2 million square kilometers. The dangxiong grass station located in hinterland of Tibetan Plateau is covered with this typical vegetation. The continuous carbon flux data measured with the open-path eddy covariance systems during growing season in 2003 were used to analyze the diurnal variation patterns of the Net Ecosystem carbon dioxide Exchange (NEE) and the seasonal changes of its apparent quantum yield αas well as maximum ecosystem assimilation P. Results showed that the Net Ecosystem carbon dioxide Exchange presented obvious diurnal variation patterns with single-peak of diurnal maximum carbon assimilation at 11: 00-12: 00 (local time).The diurnal maximum carbon assimilation was highest in exuberance period (-0.288 mg COms i.e.-6.538μmol COms) and lowest in withering period (-0.18mg COms i.e.-4.086μmol COms). During the daytime, NEE fitted fairly well with PAR in a rectangular hyperbola function, with apparent quantum yield declining in the order of exuberance period (0.0244μmolCO μmol PAR) early exuberance period seed maturing period withering period (0.0098μmolCO μmol PAR). The maximum ecosystem assimilation didn’t change much during the first three period with an average of 0.433 mgCOms i.e.9.829μmolCOms. But during withering period, it was only 0.35 mg COms i.e.7.945μmolCOms.