The objective of this research was to examine the effects of temperature, soil water content and photosynthesis on soil respiration in Populus and Ulmus pumila planting shelterbelts in China’s Junngar Basin.soil respiration was measured during the growing seasons in 2005 and 2006 using an automated CO₂ efflux system (LI-8100). Air temperature (at 50 cm in height) and soil temperature (every 5 cm from 0 to 50 cm depth) were monitored at three points adjacent to the chamber using a digital thermometer (WMY-01C, HuachenMedical Instrument Inc., Shanghai, China) at each site. Gravimetric soil moisture at 0–5, 5–15, 15–30, and 30–50cm depths at three points were measured using the oven-drying method at 105 °C for 48 h.

Soil respiration displayed irregular fluctuation of daytime pattern and significant single-peaked curve of seasonal pattern in the two woodlands. Seasonally, soil respiration was characterized by a maximum in July or August and a minimum in October or May, following the change of soil temperature. The rate of soil respiration was significantly higher in Populus woodland than that in U. pumila woodland with mean rates of 3.71 and 1.82 μmol CO₂·m^–2·s^–1 in two growing seasons, respectively. Soil respiration was significantly correlated with temperature in exponential equation, but uncorrelated with soil water content in the two woodlands.Soil temperature at 50 and 30 cm depths could explain 78.5% and 64.4% of seasonal variations of soil respiration in Populus woodland and U. pumila woodland, respectively, which confirms the common explanation by temperature and soil water content. The difference in soil respiration between the woodlands was influenced by growth state of trees, photosynthesis and soil salinity. Our results suggested that there was significant seasonal variation of soil respiration in oasis shelterbelts in the arid region and soil temperature was the main regulating factor.