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给出了雨季(7月)鼎湖山季风常绿阔叶林两个土壤剖面(DHLS和DHS)中CO2气体的碳同位素组成和更新特征,探讨了土壤CO2气体的来源比例.结果表明:该林区土壤CO2气体含量变化范围为6120～18718μL.L-1,随深度增加而增大,75cm以下则逐渐减少.在DHLS剖面,土壤CO2气体的δ13C值的变化范围为-24.71‰～-24.03‰,与同层位气体含量呈显著负相关(R2=0.91),模拟结果显示该剖面中的CO2气体主要来源于根系呼吸作用(>80%);而在DHS剖面,土壤CO2气体的δ13C值变化范围为-25.19‰～-22.82‰,模拟结果显示除表层(20cm)90%来源于根系呼吸作用外,深部(40～105cm)主要来源于微生物的分解作用(51%～94%).14C年龄显示,DHLS和DHS剖面中土壤CO2气体中的碳均为现代碳,14C年龄之间最大差值分别为8和14个月,DHLS剖面中土壤CO2气体更新速率较快.在DHLS和DHS剖面中,土壤CO2气体△14C值的变化范围分别为100.0‰～107.2‰和102.5‰～112.1‰,高于现代大气CO2和同层位土壤有机碳的△14C值,土壤CO2气体可能是大气核爆14C的一个重要储库.
The carbon isotope composition and renewal characteristics of CO2 in two soil profiles (DHLS and DHS) of the monsoon evergreen broad-leaved forest in Dinghu Mountain during the rainy season (July) are presented, and the sources of CO2 gas in the soil are also discussed. The results show that: The range of soil CO2 gas content was 6120 ~ 18718μL.L-1, which increased with the increase of depth and decreased gradually under 75cm.The δ13C value of soil CO2 gas ranged from -24.71 ‰ to -24.03 ‰ (R2 = 0.91). The simulation results show that the CO2 gas in this section mainly comes from the root respiration (> 80%). In the DHS section, the δ13C value of the soil CO2 gas changes The results showed that the depth (40 ~ 105cm) was mainly derived from microbial decomposition (51% ~ 94%), except that 90% of surface layer (20cm) was derived from root respiration. Shows that the carbon in soil CO2 gas in DHLS and DHS profiles are all modern carbon and the maximum difference between 14C ages is 8 and 14 months, respectively, and the soil CO2 gas renewal rate in DHLS profile is faster. In the DHLS and DHS profiles , And the range of △ 14C value of soil CO2 gas was 100.0 ‰ ~ 107.2 ‰ and 102.5 ‰ ~ 112.1 ‰, which is higher than the △ 14C value of the modern atmospheric CO2 and the soil organic carbon in the same layer. The soil CO2 gas may be an important reservoir for atmospheric nuclear explosion14C.