低剂量混合稀土积累对黄褐土微生物主要类群的生态效应

采用田间小区试验和室内低剂量模拟叠加试验相结合的方法，研究低剂量混合稀土在黄褐土中积累对土壤微生物主要类群的生态效应．结果表明，低剂量稀土的持续积累对土壤细菌、放线菌产生刺激、抑制、再刺激的交替作用；对真菌也产生类似的作用，但抑制作用不显著，而刺激作用持续、明显．混合稀土对3类土壤微生物数量抑制程度顺序为：细菌>放线菌>霉菌．稀土积累至150mg·kg^-1时，土壤各类微生物的种群结构均发生显著的改变，耐稀土微生物数量大幅度增加，细菌中的G^-细菌、链霉菌的白孢类群、真菌中青霉分别成为优势种群．对低浓度稀土积累的田问土壤微生物学参数模拟计算结果表明，稀土对土壤细菌、放线菌和真菌的EC50(半抑制浓度)值分别为24．1、41．6～73．8和55．3～150．1mg·kg^-1，30mg·kg^-1值可以初步确定为稀土在黄褐土中积累的安全临界值．

Ecological effects of low dosage mixed rare earth elements accumulation on major soil microbial groups in a yellow cinnamon soil

A combination of field plot experiment and simulated low dosage accumulation test was adopted to study the ecological effects of low dosage mixed rare earth elements (REE) accumulation on major soil microbial groups in a yellow cinnamon soil. The continuous accumulation of REE had the alternative effects of stimulation, inhibition and re-stimulation on soil bacteria and actinomycetes, and a continuous stimulation on soil fungi. The inhibitory intensity of REE on the three groups of soil microorganisms was in the order of bacteria > actinomycetes > fungi. At the accumulation of 150 mg x kg(-1) of REE, the population structure of three groups changed remarkably. The number of REE-tolerant microbes increased, with gram negative bacteria, white spore group and penicillium being predominant in bacteria, actinomycetes and fungi population, respectively. The median effect concentration (EC50) of REE was 24.1, 41.6-73.8 and 55.3-150.1 mg x kg(-1) for soil bacteria, actinomycetes and fungi, respectively. The EC50 value of 30 mg x kg(-1) might be taken as the critical value of mixed REE in yellow cinnamon soil.