Chin J Plant Ecol ›› 2009, Vol. 33 ›› Issue (6): 1023-1033.DOI: 10.3773/j.issn.1005-264x.2009.06.002

Special Issue: 碳水能量通量

• Original article • Previous Articles     Next Articles

EFFECTS OF CO<sub>2</sub> ENRICHMENT, HIGH NITROGEN DEPOSITION AND HIGH PRECIPITATION ON A MODEL FOREST ECOSYSTEM IN SOUTHERN CHINA

DENG Qi1,2, ZHOU Guo-Yi1, LIU Ju-Xiu1, LIU Shi-Zhong1, DUAN Hong-Lang1,2, CHEN Xiao-Mei1,2, ZHANG De-Qiang1,*()   

  1. 1 South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China
    2 Graduate University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2009-03-06 Accepted:2009-06-25 Online:2009-03-06 Published:2009-11-30
  • Contact: ZHANG De-Qiang

Abstract:

Aims Responses of soil respiration to global change play an important role in global carbon cycling, but the effects of increasing atmospheric carbon dioxide concentration ([CO2]), nitrogen (N) deposition and precipitation on soil respiration in subtropical China are unclear. Our objective was to test the effects of increased [CO2], N deposition and precipitation on soil respiration and to determine how they influence soil respiration in subtropical China.
Methods A model forest ecosystem was constructed of six tree species native to South China. The species were exposed to four experimental treatments in open-top chambers beginning March 2005. Three chambers were used for elevated [CO2] (CC), two for high N treatment (NN) and the control (CO) and one for elevated precipitation (HR). The CC treatment was achieved by supplying additional CO 2 from a tank until the chambers had a concentration of (700 ± 20) μmol CO 2·mol-1. The NN treatment was achieved by spraying seedlings once a week for a total amount of NH4NO3 of 100 kg N·hm-2·a-1. The HR treatment was achieved by weekly irrigation with 100 L water.
Important findings For two years, soil respiration displayed strong seasonal patterns with higher values observed in the wet season (April to September) and lower values in the dry season (October to March) in the control chambers (CO) and the CC and NN treatments (p<0.001). There was no seasonal difference in the HR treatment (p>0.05). The CC enrichment affected soil respiration significantly (p<0.05), and there were no significant differences in annual CO2effluxes between CO and the other two treatments. The annual CO2 effluxes reached 4 241.7, 3 400.8, 3 432.0 and 3 308.4 g CO2·m-2·a-1 in the CC, NN, HR and CO treatments, respectively. Soil respiration showed diverse responses between dry and wet seasons under different treatments. Higher soil respiration in the CC and NN treatments occurred in the wet season (p<0.05). In the dry season, soil respiration increased in the HR treatment (p<0.05) and decreased in the NN treatment (p<0.05). We found significant exponential relationships between soil respiration rates and soil temperature and significant linear relationships between soil respiration rates and soil moisture (below 15%).

Key words: CO2 enrichment, open-top chamber (OTC), nitrogen deposition, precipitation, soil respiration