土壤自养微生物同化碳向土壤有机碳库输入的定量研究：14C连续标记法

自养微生物在土壤中广泛存在,但其CO2同化能力及其向土壤碳库的输入机制尚不明确.应用14C连续标记示踪技术,选取亚热带区4种典型稻田土壤在密闭系统模拟培养,探讨了土壤自养微生物同化碳向土壤碳库的输入过程和机制及其对土壤碳库活性组分的影响.结果表明,土壤微生物具有客观的CO2同化能力.标记培养110 d后,供试土壤的14C-SOC含量范围为69.06～133.81 mg.kg-1,而14C-DOC、14C-MBC含量范围为2.54～8.10 mg.kg-1、19.50～49.16 mg.kg-1.土壤自养微生物同化碳(14C-SOC)与其微生物截留碳(14C-MBC)呈极显著的正相关关系.土壤可溶解性有机碳(DOC)、微生物量碳(MBC)和SOC的更新率分别为5.65%～24.91%、4.23%～20.02%和0.58%～0.92%.而且,土壤自养微生物同化碳的输入对土壤活性碳组分的DOC、MBC含量变化影响较大,而对SOC影响较小.对微生物在土壤碳循环过程的基本功能的认识在本研究中得以丰富和加深.

Quantifying Soil Autotrophic Microbes-Assimilated Carbon Input into Soil Organic Carbon Pools Following Continuous 14C Labeling

Soil autotrophic microbe has been found numerous and widespread. However, roles of microbial autotrophic processes and the mechanisms of that in the soil carbon sequestration remain poorly understood. Here, we used soils incubated for 110 days in a closed, continuously labeled ¹⁴C-CO₂ atmosphere to measure the amount of labeled C incorporated into the microbial biomass. The allocation of ¹⁴C-labeled assimilated carbon in variable soil C pools such as dissolved organic C (DOC) and microbial biomass C (MBC) were also examined over the ¹⁴C labeling span. The results showed that significant amounts of ¹⁴C-SOC were measured in paddy soils, which ranged from 69.06-133.81 mg·kg^-1, accounting for 0.58% to 0.92% of the total soil organic carbon (SOC). The amounts of ¹⁴C in the dissolved organic C (¹⁴C-DOC) and in the microbial biomass C (¹⁴C-MBC) were dependent on the soils, ranged from 2.54 to 8.10 mg·kg^-1, 19.50 to 49.16 mg·kg^-1, respectively. There was a significantly positive linear relationship between concentrations of ¹⁴C-SOC and ¹⁴C-MBC (R²=0.957^**, P<0.01). The ¹⁴C-DOC and ¹⁴C-MBC as proportions of total DOC, MBC, were 5.65%-24.91% and 4.23%-20.02%, respectively. Moreover, the distribution and transformation of microbes-assimilated-derived C had a greater influence on the dynamics of DOC and MBC than that on the dynamics of SOC. These data provide new insights into the importance of microorganisms in the fixation of atmospheric CO₂ and of the potentially significant contributions made by microbial autotrophy to terrestrial C cycling.