Temperature sensitivity of soil heterotrophic respiration is altered by carbon substrate along the development of Quercus Mongolica forest in northeast China

Soil heterotrophic respiration was profoundly correlated with the decomposition of soil organic carbon and the global carbon balance. It was liable to be affected by temperature and carbon substrate availability. To investigate the effects of different carbon substrate inputs on organic carbon decomposition and the temperature sensitivity of soil heterotrophic respiration along the forest stand ages, we sampled surface soils (0-20 cm) from three Quercus Mongolica forest stands (20, 30 and 40 years old) in Northeast China. The microcosms were established to incubate the soil under three carbon substrate treatments (glucose, amylopectin, and the combination of glucose and amylopectin) at 13, 23, and 33 degrees C, respectively. The carbon substrates were 320 mu mol g(-1) and 40 mu mol g(-1) fresh soil for glucose and amylopectin, respectively. The combined treatment was 160 mu mol glucose g(-1) and 20 mu mol amylopectin g(-1) fresh soil. The results showed that rates of basal respiration (BR), substrate-induced respiration (SIR), and specific growth rate (SGR) significantly increased with the increasing forest ages. After the addition of carbon substrates, the stimulation effects of SIR and SGR were higher at 23 degrees C than 13 degrees C and 33 degrees C, especially the addition of amylopectin. The Q(10) values of SIR were lower after the addition of glucose than those of amylopectin at lower temperature intervals (13-23 degrees C), but higher at higher temperatures (23-33 degrees C). The Q(10) linearly increased with increasing rates of substrate availability. The Q(10 )values of SIR stimulated by amylopectin were higher at lower temperature intervals (13-23 degrees C), suggesting the responses of Q(10) were not only adjusted by carbon substrates but also the ranges of temperature change. The exogenous stable organic carbon inputs greatly increased the Q(10) values of soil heterotrophic respiration in the older forest stands. These results indicated that the decomposition of stable carbon substrate will be more sensitivity to temperature in boreal successional Quercus Mongolica forest.