关键词: 川西亚高山, 火烧迹地, 川滇高山栎林, 土壤呼吸, 异养呼吸

Abstract: [Objective] To analyze the influence of environmental factors on total soil respiration rate (R_s) and heterotrophic respiration rate (R_h) and their seasonal dynamics of burned forest area in the subalpine regions in western Sichuan, China. By comparing the rate of R_s and R_h between burned area and control plot (CK), the results would provide a basis for comprehending the forest carbon cycle and estimation of soil C fluxes under the condition of fire disturbance.[Method] In this study,the burned area (8 years since fire) Quercus aquifolioides and control plots (CK) of subalpine forest in Western Sichuan were studied. Using a field setup through root exclusion method and LI-8100 automated soil CO₂ flux system, we measured R_s and R_h, soil temperature (T₅) and soil gravimetric water content (W₅) at 5 cm depth from September 2010 to December 2011. Relationships of R_s and R_h with abiotic factors were determined by fitting both an exponential model and a two-factor model.[Result] In dormant season, R_s and R_h rates for the burned area were obviously higher than those of control plot (P < 0.05), respectively. However, R_s and R_h were not different between the burned area and the control plot in growing season and whole year (P > 0.05). A significant exponential relationship was found between R_s or R_h and T₅ in different seasons, respectively (P < 0.01). There was a significant relationship between R_s or R_h and W₅, but no significant effect was observed of W₅ on R_s or R_h in the CK plot during growing season. We found that R_s or R_h appeared to be a inhibition phenomenon by W₅ when it was low than 25.8%, but there was no significant relationship when it was over 37.7% (P > 0.05). Notably, T₅ and W₅ two-way model was better than the single factor model. Therefore, soil carbon emission was significantly affected by T₅ and W₅ in the subalpine forest. Furthermore, the soil temperature sensitivity (Q₁₀) values of Rs and Rh from the burned area were lower than those of in the CK plot, whereas Rs are more sensitive to T₅ in different seasons. Moreover, R_s and R_h of burned area and CK were strongly correlated to nitrate nitrogen, light fraction organic carbon and particulate organic carbon at 0-30 cm soil layers. The estimated values of R_s and R_h for burned area was 13.9% and 1.8% higher than those for control plot.[Conclusion] Our study indicated that R_s and R_h were dominated by interaction of T₅ and W₅.We can infer that soil carbon emission of burned area may be less sensitive to temperature variations than the CK under global warming scenarios. Our results emphasize that fire disturbance in forest land and associated carbon metabolisms should be taken into consideration in the model construction under climate change scenarios.

Key words: subalpine of western Sichuan, burned area, Quercus aquifolioides forest, soil respiration, heterotrophic respiration