Research

The daily maximum uptake of CO2 was 2. 38 g C•m- 2•d - 1 on July 30. The ratio of daily uptake and emission in August were observed , - 6. 82 and 2. 95μmol CO2•m- 2•s - 1 , respectively. In the growing seasons , daily NEE was dominated by the variation of photo synthetically active radiation ( PAR) . At the same time , daily NEE combined with leaf area and community diversity to control photosynthetic rate and photosynthetic efficiency. Maximum photosynthetic rate was 2. 46 - 10. 39μmol CO2•m- 2•s - 1 , and the apparent quantum yield ( denoting the maximum efficiency of light utilization in photosynthesis) was 0. 013 -0. 070μmol CO2•μmol - 1 PAR. The influence of temperature , Q10 (1. 8) in the growing season was less than in the non - growing season. The respiration of the ecosystem was mainly dominated by temperature and leaf area. Carbon absorption was not dominated by the larger temperature difference of the day and night in the growing season. Our study proved that the artificial grassland ecosystem was a carbon sink with a carbon absorption of - 49. 35 g C•m- 2•a - 1 . Our study also proved that the source and sink function of carbon was influenced by the amount , intensity and seasonal allocation of annual precipitation , as well as by plant community diversity.