放牧强度对大针茅根际和非根际土壤中细菌数量和群落特征的影响

Effects of Grazing Intensity on the Bacterial Number and Community Characteristics in Bulk and Rhizosphere Soil of Stipagrandis

利用涂布平板法和变性梯度凝胶电泳(denatured gradient gel electrophoresis,DGGE)技术,检测4个放牧强度(对照、轻度放牧、中度放牧和重度放牧)下,大针茅(Stipagrandis)植物根际和非根际土壤中细菌数量和群落特征的变化。结果表明,放牧对细菌群落多样性及组成有显著影响,但对细菌数量没有明显影响。随着放牧强度的增加,根际和非根际土壤细菌数量及群落多样性的变化趋势不同。根际土壤中,在中度放牧强度下,细菌数量最高,轻度放牧强度下,细菌多样性最高。说明细菌群落多样性比细菌数量敏感。而在非根际土壤,细菌数量和群落多样性随着放牧强度的增加而逐渐降低。说明根际细菌较非根际细菌群落有更好的抗干扰能力。同一放牧强度下,根际土壤细菌数量及群落多样性高于非根际土壤,但根际和非根际土壤细菌群落结构差异较小。总之,与非根际细菌相比,根际细菌群落具有更好的抗干扰能力,及其与非根际土壤细菌群落组成的相似性说明在生态恢复过程中,根际细菌群落可能作为一个菌种库存在。

In order to explore the effects of grazing intensity on the bacterial number and community char- acteristics in bulk and rhizosphere soil of Stipagrandis, we investigated the sizes and community structures of bacteria in the rhizosphere and bulk soils of Stipagrandis under four grazing intensities using spread plate method and denatured gradient gel electrophoresis （DGGE）. Four grazing intensities were non-graz- ing （CK）, lightgrazing（LG）, moderate grazing（MG） and heavy grazing（HG）, respectively. The results showed that grazing intensity had significant effect on bacterial community diversity and structure, but bacterial number was not significantly impacted by grazing intensity. Bacterial number and community characteristic in rhizosphere soil or bulk soil showed different patterns along with grazing intensity. In rhi- zosphere soil, bacterial number was the highest in MG plot and bacterial community diversity was the highest in LG plot. However, in the bulk soil, bacterial number and community diversity gradually de- creased with increasing the grazing intensity. This meaned rhizosphere bacteria were more resistant against grazing than non-rhizosphere bacteria. Rhizosphere bacteria might be a pool of bacteria in the process of ecological restoration.