原状土与非原状土对土壤自养微生物碳同化能力的影响

Effect of disturbed and undisturbed soils on the carbon assimilation capacity of autotrophic microbes

自养微生物在土壤中广泛存在,但原状土与非原状土对其CO2同化能力的影响尚不明确。因此,本研究采用14C连续标记示踪技术,选取亚热带区4种典型土壤进行室内模拟培养,探讨了原状土与非原状土对农田土壤自养微生物碳同化能力及其对土壤碳库活性组分的影响。结果表明：连续标记培养110 d后,原状土与非原状土样均表现出可观的CO2同化能力,根据估算,非原状土、原状土的CO2同化速率分别为0.015-0.148、0.007-0.050 g·m^-2·d^-1,说明土壤受扰动可能加剧自养微生物的活性,增强土壤自养微生物的CO2同化能力。相关分析表明,土壤自养微生物同化碳（14C-SOC）与其微生物截留碳（14CMBC）呈极显著正相关（R2=0.955）。而且,土壤可溶性有机碳（DOC）、微生物量碳（MBC）和土壤有机碳（SOC）的更新率分别为：0.9%-4.5%、2.2%-9.7%和0.09%-0.43%（原状土）;0.26%-1.09%、3.6%-20%和2.9%-5.7%（非原状土）。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。本研究丰富和扩大了土壤微生物的基本功能和在土壤碳循环过程中作用的认识。

Assimilation of atmospheric carbon dioxide（ CO2） by autotrophic microbes is an integral process in the soil environment. However,the influence of disturbed and undisturbed soils on CO2-assimilation capacity remains poorly understood. In this study,we incubated four types of disturbed and undisturbed soil samples for 110 days in a closed,continuously14C-labeled CO2atmosphere and measured the amount of14C-labeled carbon（ C） incorporated in the microbial biomass during this period. The allocation of14C-labeled-assimilated C in labile soil C pools such as dissolved organic C（ DOC） and microbial biomass C（ MBC） was analyzed over the14C-labeling span. Significant amounts of14C-SOC were detected in both disturbed and undisturbed soils. The assimilative rate ranged from 0. 015 to 0. 148 g·m- 2·d- 1in the disturbed soils and from 0. 007to 0. 050 g·m- 2·d- 1in the undisturbed soils. A significant positive linear relationship was detected between the concentrations of14C-SOC and14C-MBC（ R2= 0. 955,P〈 0. 01）. The proportions of14C-DOC,14C-MBC,and14C-SOC to the total DOC,MBC,and SOC were 0. 9%-4. 5%,2. 2%- 9. 7%,and 0. 09%- 0. 43% in the undisturbed soils,and 0. 26%- 1. 09%,3. 6%- 20%,and 2. 9%- 5. 7% in the disturbed soils,respectively. Furthermore,the distribution and transformation of microbe-assimilated C had much greater influence on the dynamics of DOC and MBC than on those of SOC. These results offer new insights into the importance of microbes in the assimilation of atmospheric CO2and of the potentially significant contributions made by microbial autotrophy to terrestrial C cycling.