关键词: 蒙古栎, 土壤呼吸, 异养呼吸, 根际呼吸, 坡向

Abstract: The division of soil respiration (R_S) components is a key step for understanding forest carbon cycle models. Uncovering the influence of slope aspect would help understand the mechanism of water and heat effects on soil respiration. The aim of this study was to quantify seasonal dynamics and flux of soil respiration components in two slope aspects, and to explore influencing factors and mechanisms. The trenching approach was used to partition R_S into heterotrophic respiration (R_H) and rhizospheric respiration (R_R) in a Mongolian oak forest. The dynamic infrared gas analyzer was used to in situ monitor soil respiration and its components in two slope aspects during the growing season. The results showed that R_S, R_H, and R_R all showed a bimodal peak curve, with significant differences between two slope aspects. The proportion of R_R was approximately the same. R_S, R_H, and R_R had a significant exponential relationship with soil temperature (T₅). The temperature sensitivity coefficient (Q₁₀) of R_H was higher than that of R_R. The Q₁₀ of R_S, R_H, and R_R of the sunny slope were all higher than that of the shady slope. Adding the variable of volume of soil water content (W₅) to the model could improve the prediction ability of soil respiration and its components. The response of different respiratory components to T₅ and W₅ was different for the same slope aspect, while the response of the same respiratory components to T₅ and W₅ for different slope aspects was different. The R_H fluxes of sunny slope and shady slope in Mongolian oak forest were 249.22 and 291.82 g C·m^-2, and R_R flux was 149.00 and 179.17 g C·m^-2, respectively. The soil respiration flux (F) showed a typical single peak curve on the monthly scale, both flux of R_H (F_RH) and flux of R_R (F_RR) showed exponential function relationship against average soil temperature (T_a) for both slope aspects, and showed a linear relationship against the precipitation. Binary linear regression was significant, but the variables and parameters were different between slope aspects and different respiratory components. The results indicated that slope variables had significant influence on R_S, R_H, R_R and their flux in same forest type. The mechanism underlying the effects of hydrothermal conditions on respiratory components was different. The parameters and variables in the model at different temporal scales reflected different ecological processes.

Key words: Quercus mongolica, soil respiration, heterotrophic respiration, rhizospheric respiration, slope aspect.