Abstract: Field monitoring was conducted to study the annual dynamics of soil heterotrophic respiration and soil temperature and moisture in Liquidambar formosana and Pinus massoniana forests in hilly areas of southeast Hubei Province, China. At the same time, laboratory experiment was performed to study the heterotrophic respiration rate along soil profile, and the sensitivity of surface soil (0-5 cm) heterotrophic respiration to soil temperature and moisture. Then, a model was established to valuate the potential effects of warming change on the soil heterotrophic respiration in study area. In L. formosana and P. massoniana forests, the soil heterotrophic respiration rate in 0-5 cm layer was 2.39 and 2.62 times, and 2.01 and 2.94 times of that in 5-10 cm and 10-20 cm layers, respectively, illustrating that soil heterotrophic respiration  mainly occurred in 0-5 cm surface layer. The temperature sensitivity factor (Q₁₀) of soil heterotrophic respiration in 0-5 cm, 5-10 cm, and 10-20 cm layers was 2.10, 1.86, and 1.78 in L. formosana forest, and 1.86, 1.77, and 1.44 in P. massoniana forest, respectively. The relationship between surface soil heterotrophic respiration and temperature (T) well fitted exponential function R=αexp (βT), and that between surface soil heterotrophic respiration and moisture (W) well fitted quadratic function R=a+bW+cW². Therefore, the relationship of surface soil heterotrophic respiration with soil temperature and moisture could be described by the model lnR=a+bW+cW²+dT+eT², which suggested that the response of soil heterotrophic respiration to soil moisture was depended on soil temperature, i.e., the sensitivity decreased with decreasing soil temperature. The calculation of the annual soil heterotrophic respiration rate in the two forests with the established model showed that the calculated respiration rate was a slightly higher in L. formosana forest but close to the measured one in P. massoniana forest, illustrating the applied importance of the model. Our results suggested that the soil heterotrophic respiration in the L. formosana and P. massoniana forests in hilly areas of southeast Hubei Province would have an obvious increase under the background of global warming.

Key words: Liquidambar formosana forest, Pinus massoniana forest, soil heterotrophic respiration, Q₁₀