Abstract: Soil respiration is one of the important components in global carbon cycle, and a sensitive indicator of many soil processes that control soil metabolism. In order to understand the dynamics of soil respiration under the Phragmites australis community in dry habitats of Songnen Plain, Northeast China, a field observation on the soil respiration was conducted from May to October 2011 by using LI-6400 automated soil CO₂ flux system. There existed obvious diurnal and seasonal patterns of the soil respiration. The diurnal curve of the soil respiration was unimodal, with the peak appeared at 11:00-13:00, and the seasonal change of the soil respiration was with the maximum (4.8 μmol·m^-2·s^-1) in July and August and the minimum (1.51 μmol·m^-2·s^-1) in October. The main factor affecting the soil respiration was temperature. The soil respiration rate was significantly correlated with the nearground ambient air temperature and the soil temperature at depths 0-10, 10-20, and 20-30 cm, of which, nearground ambient air temperature and the soil temperature at depth 0-10 cm were the two most important controlling factors. The Q₁₀ values of the soil respiration from May to October varied from 1.2 to 1.65, with a mean value of 1.39 and a coefficient of variation of 15.4%. Soil moisture content and near-ground air humidity were not the main environmental factors affecting the soil respiration.

Key words: O₃, Quercus mongolica, leaf litter decomposition, nutrient release.