As one of the important constituents of the carbon cycle, soil respiration is the primary mechanism by which soil carbon is released and an important source of atmospheric CO₂, which plays a critical role in regulating atmospheric CO₂ concentration and world climate dynamics. Even a small change in soil respiration could profoundly affect the concentration of atmospheric CO₂. Numerous studies have been conducted into the relationship between soil respiration, environmental factors (eg. temperature, soil moisture) and anthropogenic disturbance (eg. land use change). However, most of these studies have focused on forest and steppe ecosystems, rather than on desert ecosystems. There is little available information on the effect of vegetation succession on soil respiration in a desert ecosystem. The establishment of artificial sand-binding vegetation in the Shapotou region has changed the landscape from moving dunes to stabilized dunes covered by shrubs, which has, in turn, modified soil respiration patterns. This study has characterized soil respiration patterns and the effects of soil moisture and temperature on soil respiration during vegetation restoration of a desert ecosystem.
The study was conducted in the Shapotou revegetated area, located on the southeast fringe of the Tengger Desert (37°32'N, 105°02'E). Soil respiration rates were measured, using the alkali absorption method, in revegetated enclosures, which were constructed in 1956, 1964, 1981, 1987, 1989 and the area was revegetated with Caragana korshinskii in 2007. Soil respiration was also investigated in a sandy area stabilized with straw checkerboard in 2007 and in an area of shifting sand dunes. Based on the traditional space-for-time succession approach, these study plots represented vegetations of different successional stages. The results showed that: 1) In general, soil respiration rates gradually increased with the increasing age of the revegetation. This trend was significant when the soil volume moisture were higher than the mean value (0.0487 cm³ /cm³) for the whole of the experimental period (P<0.05). Soil respiration in the revegetated areas established in 1956, 1964, 1981 was significantly higher than in the areas revegetated in 2007, the area stabilized in 2007 with straw checkerboard and in the shifting sand dunes (P<0.05). No significantly increase was detected when soil volume moisture was lower than the mean value (P>0.05); 2) Soil moisture is an important environmental factor influencing soil respiration. Positive correlations were found between soil volume moisture and the soil respiration rates in every study plot and the correlation coefficients progressively increased with increasing age of the revegetation (P<0.05) and 3) An exponential model has been used to describe the relationship between soil respiration rates and soil temperature. Soil temperature only had a significant effect on soil respiration in the revegetated areas established in 1987 and 1989, but not in the other revegetated enclosures. In every study plot, the Q₁₀ values were uniformly lower than the mean values for temperate regions (1.57). These results suggest that the vegetation restoration process can alter the magnitude of soil respiration rate as well as its response to soil moisture and temperature variations.