关键词: 半干旱草原, 碳交换, 生态系统呼吸模型, 涡度相关法

Abstract:

The turbulence data observed by eddy covariance system combined with soil temperature and soil volumetric water content (VWC) data from Xilinhot National Climate Observatory were used to analyze respiration process and its key climatic influencing factors of the semi-arid stipa grassland ecosystem in Xilin Gol during the growing season from 2010 to 2012. The applicability of four different ecosystem respiration models over this ecosystem was compared, including three multiplication models and a Q₁₀ model. Based on this research, the interannual variability of net ecosystem exchange (NEE), ecosystem respiration (R_eco) and gross primary productivity (GPP) were discussed. The respiration was affected by soil temperature and soil water content, in which soil water content was an important limiting factor. The precipitation in 2010 and 2011 was less than normal, so this ecosystem suffered from different degrees of drought stress. The respiration rate increased significantly with soil water content in the range of 12%?20%, while it was not sensitive to the change of soil water content in the range of <12% and >20%. In 2012, when the precipitation was abundant, respiration rate was more correlated with the trend of soil temperature. The fitting results indicated that Q₁₀ model had better performance (R² = 0.64) than other three models, and the cumulative total ecosystem respiration during growing season in these three years simulated by the Q₁₀ model was 157.32, 138.75 and 246.32 gC/m². The total amount of NEE was −110.28, −68.79 and −310.05 gC/m², while the total amount of GPP was 267.52, 207.57 and 555.85 gC/m². The effect of drought stress on photosynthesis was greater than that of respiration. Therefore, the inter-annual difference of net carbon exchange due to drought stress was more obvious than that of total primary productivity and respiration.

Key words: semi-arid grassland, carbon exchange, ecosystem respiration model, eddy covariance