Chin J Plant Ecol ›› 2006, Vol. 30 ›› Issue (2): 295-301.DOI: 10.17521/cjpe.2006.0039

• Original article • Previous Articles     Next Articles


ZHAO Shuang_Ju1,3(), ZHANG Yi_Ping1,*(), YU Gui_Rui2, SONG Qing_Hai1,3, SUN Xiao_Min2   

  1. 1Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Kunming 650223, China
    2Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
    3Graduate school of Chinese Academy of Sciences, Beijing 100039, China
  • Accepted:2005-06-02 Published:2006-03-30
  • Contact: ZHANG Yi_Ping


Tropical forests play an important role in altering the carbon budgets of terrestrial ecosystems. We examined patterns of diurnal and seasonal net ecosystem CO2 exchange (NEE) in a tropical seasonal rainforest of Xishuangbanna on clear days between November 2003 and October 2004. We found that the diurnal dynamics of NEE showed a single_peaked curve. During daytime throughout the year, NEE increased with solar radiation after sunrise, but fluctuated after sunset. Values of NEE (absolute values) in the foggy_cool and wet seasons were greater than those in the dry_hot season during daytime. During the night, NEE values were dominated by soil temperature and soil water content and were highest in the wet season, followed by those in the dry_hot season and lowest in the foggy_cool season. NEE, water vapor deficit (VPD) and air temperature (Ta) curves all showed pronounced seasonal variation, but photosynthetically available radiation (PAR) did not vary significantly. Maximum photosynthesis rates (Pmax) and dark respiration rates (Re) were greater when VPD≥16 hPa than whenVPD<16 hPa, whereas photon density (α) was the opposite. Re was also greater when Ta≥25 ℃ than whenTa<25 ℃ in the three seasons.α was reduced when Ta≥25 ℃ in the dry_hot and wet seasons. ThePmax increased in the dry_hot season and decreased in the wet season when Ta≥25 ℃. Our data suggested thatPAR is the main factor influencing NEE diurnal dynamics, whereas both VPD and Ta play a major role in regulating NEE seasonal dynamics.

Key words: Xishuangbanna tropical seasonal rainforest, Net ecosystem CO2 exchange, Eddy covariance, Diurnal and seasonal variation