Abstract:

By using an infrared gas analyzer(IRGA) with a 6400-09 chamber, the diurnal, seasonal and interannual dynamics of soil CO₂ efflux rate was measured in a Caragana plantation located in Taiyuan basin over four years from January 2005 to December 2008. The soil temperature (T) at 10 cm depth and the soil water content (W) over top 10 cm were also measured at the same time. The results showed that soil respiration rate(R) of the Caragana plantation had an asymmetric diurnal pattern, with the minimum appearing about 6: 00 and the maximum around 14: 00. The CO₂ efflux exhibited pronounced seasonal variations that clearly followed the seasonal change in T, with high values appearing in August, and low value in early spring and winter. Cumulative annual respiration amount from March to December was 1 145.7, 1 224.7, 814.9 and 904.7 g C·m^-2a^-1, respectively, in 2005, 2006, 2007 and 2008, and there was an obvious difference between years. The relationships between R and T at 10 cm depth could be described by exponential equation (R = ae^bT), with a determination coefficient (R²) of 0.41, 0.31, 0.67 and 0.54, respectively, for 2005, 2006, 2007 and 2008, and calculated Q₁₀ (Q₁₀ = e^10b) varied from 1.70 to 2.02 over four years and was 0.64 and 2.11 for growing season and non-growing season, respectively. The relationships between R and W over top 10 cm depth had significant correlation (P< 0.01) in 2005 and 2006, with a determination coefficient (R²) about 0.30,however the relationship was not significant (P ＞ 0.05) in 2007 and 2008. The four two-variable models of linear and non-linear were able to predict relationships of R with both T and W, with the R² ranging from 0.51 to 0.83.

Key words: Caragana plantation, soil respiration, temporal variation, soil temperature and soil moisture, loess plateau