Effects of temperature and soil water-content on soil respiration of grazed and ungrazed Leymus chinensis steppes, Inner Mongolia

The dynamics and the controlling factors of soil respiration measured with a closed static chamber method for continuous 2 years in grazed and ungrazed typical Leymus chinensis steppes, Inner Mongolia, PR China were analysed. There were similar diurnal and seasonal dynamics between the grazed and ungrazed plots. The diurnal patterns of soil respiration could be expressed as one-humped curves, reaching to the maximum at 11:00–14:00 and falling to the minimum at 1:00–3:00. During the growing season, the rates of soil respiration increased from the middle of June to the end of July and then gradually decreased. The seasonal changes of soil respiration were mainly influenced by moisture and temperature. When temperature was an independent controlling factor, it played a good role under the conditions of lower temperature (<15 °C) and lower moisture (<12%). However, the temperature models (e.g. linear, quadratic, power, exponential and Arrhenius models) did not reflect the stimulation effect of moisture on soil respiration with increasing temperature and moisture. Moisture was the single best predictor of hourly soil respiration rate in the arid and semi-arid grassland, but the mutual regulation by temperature and moisture did improve the predictive capacity of the models. Linear models could give better simulations than others did, and account for above 82% of the variation in soil respiration at the ungrazed plot. Although there was no further improvement in exponential, exponential-power and exponential-Arrhenius models for the simulation at the ungrazed plot, they did enhance the predictive capacity of soil respiration at the grazed plot (R2=0.87–0.88R2=0.87–0.88).