Integrated diurnal soil respiration model during growing season of a typical temperate steppe: Effects of temperature, soil water content and biomass production

Soil respiration was measured with the enclosed chamber method in an ungrazed Leymus chinensis steppe during the growing seasons of 2001 and 2002. Soil respiration rate (RS) was significantly influenced by air temperature (T) at the diurnal scale, and could be described by Van't Hoff's equation (RS = R10 exp(β(T − 10))). At the seasonal scale, the normalized soil respiration rate at 10 °C (R10) was mainly controlled by soil water content (R2 = 0.717, P < 0.001), while the sensitivity of soil respiration to temperature (Q10) was partially affected by absolute growth rate (R2 = 0.482, P = 0.004). Thus, soil respiration could be described as RS = (20.015W − 84.085) (0.103AGR + 1.786)(T−10)/10 during the growing seasons, integrating soil water content (W) and absolute growth rate (AGR) into the temperature-dependent soil respiration equation. It was validated by the observed soil respiration rates in this study (R2 = 0.890, P < 0.001) and observations from near-field experiment (R2 = 0.687, P = 0.011). It implied that accurately evaluating annual soil respiration should include the effects of plant biomass production and other abiotic factors besides air temperature.