铅胁迫对黄褐土微生物区系和功能多样性的影响

为了筛选出黄褐土中对铅污染敏感的指示微生物，本研究采用室内培养试验研究不同铅浓度对土壤微生物区系和功能多样性的影响。结果表明，向土壤中添加硝酸铅显著降低了可培养细菌、放线菌和真菌微生物的种群数量，这种抑制作用随着铅浓度的升高而增强，随着培养时间的延长而减弱。铅浓度、细菌、真菌和放线菌数量两两间呈极显著负相关关系。低浓度铅处理（100 mg kg?1）在培养初期（1 d）显著减少了可培养细菌和放线菌的数量，降低率分别为27.43%和30.89%；高浓度铅处理（2500 mg kg?1）在整个培养期内均对真菌数量产生显著抑制作用，且抑制率维持在90%左右。从培养初期到中期（1 ~ 14 d），随着铅浓度升高土壤微生物群落活性和功能多样性指数显著下降（中浓度铅处理除外），培养后期（28 d）各个浓度铅处理的土壤微生物的丰富度和优势度均显著增加。与对照、低浓度铅和高浓度铅处理相比，中浓度铅处理（500 mg kg?1）更有利于保持黄褐土较高的微生物的群落代谢活性和功能多样性。本研究中3 种可培养微生物功能群对黄褐土添加硝酸铅的敏感度依次是放线菌，细菌和真菌。研究表明，在黄褐土地区真菌可以用来指示较为严重的土壤铅污染状况，放线菌和细菌可以用来指示铅污染程度较轻的土壤环境状况。

Effect of Lead Stress on Microbial Flora and Functional Diversity in Yellow-cinnamon Soil

The effects of lead addition on soil microbial flora and functional diversity were studied under simulated conditions to screen out the sensitive microbial indicators of lead pollution in yellow-cinnamon soil. The results showed that lead nitrate significantly inhibited the populations of soil bacteria, actinomycetes and fungi. The inhibitory effect increased with the increasing lead concentration, and the inhibition influence decreased at late stage of incubation. Extremely significant negative correlations were observed between lead concentration and the number of bacteria, fungi and actinomycetes. The addition of lead at a low concentration (100 mg kg?1) significantly reduced the number of culturable bacteria and actinomycetes, with the inhibition rates at 27.43% and 30.89%, respectively; the high concentration of lead (2500 mg kg?1) addition significantly inhibited fungal population during the whole incubation stage, and the inhibition rate was about 90%. The metabolic activities and functional diversity indexes of soil microbial community were significantly inhibited by the lead treatments from the initial to the middle stage (1 ~ 14 d), except for the medium concentration lead addition treatment. At late stage (28 d), the richness and dominance of soil microbial community were significantly increased. Compared with the control, and low as well as high concentration of lead addition treatments, medium concentration lead addition treatment (500 mg kg?1) was more conducive to maintain the higher metabolic activity and functional diversity of microbial community. Among the three culturable microorganisms, functional groups of actinomycetes were the most sensitive, followed by bacteria, and fungi were the least sensitive. Our study suggested that fungi could be applied as an indicator in reflecting the soil suffering from more serious lead pollution, while actinomycetes and bacteria could indicate the more light ones in yellow-cinnamon soil.