Ecological responses of Stipa steppe in Inner Mongolia to experimentally increased temperature and precipitation. 3: Soil respiration

The response of soil respiration to simulated climatic warming and increased precipitation was evaluated on the arid-semi-arid Stipa steppe of Inner Mongolia. Soil respiration rate had a single peak during the growing season, reaching a maximum in July under all treatments. Soil temperature, soil moisture and their interaction influenced the soil respiration rate. Relative to the control, warming alone reduced the soil respiration rate by 15.6 +/- 7.0%, whereas increased precipitation alone increased the soil respiration rate by 52.6 +/- 42.1%. The combination of warming and increased precipitation increased the soil respiration rate by 22.4 +/- 11.2%. When temperature was increased, soil respiration rate was more sensitive to soil moisture than to soil temperature, although the reverse applied when precipitation was increased. Under the experimental precipitation (20% above natural rainfall) applied in the experiment, soil moisture was the primary factor limiting soil respiration, but soil temperature may become limiting under higher soil moisture levels.