Chin J Plant Ecol ›› 2007, Vol. 31 ›› Issue (6): 1119-1131.DOI: 10.17521/cjpe.2007.0140

Special Issue: 碳水能量通量

• Research Articles • Previous Articles     Next Articles

MODELING SEASONAL VARIATION OF CO2 FLUX IN A SUBTROPICAL CONIFEROUS FOREST USING THE EALCO MODEL

MI Na1,2, YU Gui-Rui2,*(), WANG Pan-Xing1, WEN Xue-Fa2, SUN Xiao-Min2, ZHANG Lei-Ming2, SONG Xia2, WANG Shu-Sen3   

  1. 1Nanjing University of Information Science and Technology, Nanjing 210044, China
    2Synthesis Research Center of Chinese Ecosystem Research Network, Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
    3Canada Centre for Remote Sensing, Ottawa, Canada
  • Received:2006-10-16 Accepted:2007-02-22 Online:2007-10-16 Published:2007-11-30
  • Contact: YU Gui-Rui

Abstract:

Aims Seasonal drought frequently occurs in the mid-subtropical region of China and commonly combines with high temperature. Our objectives were to test the sensitivity of carbon exchange to this seasonal drought and discuss the influence of seasonal drought on carbon assimilation.

Methods We used flux measurements obtained from eddy covariance technology since October 2002 over a human-planted forest ecosystem at Qianyanzhou (QYZ) (26°44' N, 115°03' E, 110.8 m als.). The EALCO (ecological assimilation of land and climate observations) model is parameterized to simulate the ecosystem carbon exchange process in the human-planted evergreen forest. Simulation results were validated using half-hourly carbon fluxes and daily and annualGPP (gross primary production), NEP (net ecosystem production) and TER (total ecosystem respiration) estimated from eddy covariance measurements.

Important findings In general, the model can effectively simulate the two years' carbon fluxes among soil-plant-atmosphere on hourly, daily and annual scales. Both simulations and observations showed strong impact of drought on GPP in 2003. Compared with 2004, the annual GPP in 2003 was 12.9% lower according to observations (1 610 vs. 1 865 g C·m-2) and 11.2% lower according to model results (1 637 vs. 1 844 g C·m-2). The diurnal variations of NEP from both observations and simulations during the period of soil water deficit showed asymmetric format, i.e., the peak value of carbon exchange accrued at a certain time in the morning and then decreased with time. Modeling results indicated that water stress has more influence on photosynthesis than TER, which led to the decrease of NEP. Further analysis suggested that deep soil water content controls canopy photosynthesis in sunny days before noon during soil water stress. Afternoon, both high temperature and deep soil water content eliminate the GPP, and their elimination percents are equal. On cloudy days, radiation and deep soil water content primarily determine the photosynthesis, and temperature becomes a generally minor controlling factor.

Key words: coniferous plantation, carbon flux, EALCO model, ecosystem processes, seasonal drought