短花针茅荒漠草原土壤可培养真菌种群结构及其对放牧强度的响应

Population structure of cultivable soil fungi and its response to grazing intensities in Stipa breviflora desert steppe

为了解荒漠草原生态系统中放牧活动对土壤中真菌种群结构的影响,进而优化放牧方式,在内蒙古短花针茅荒漠草原上人工模拟不同的放牧强度,经过连续8a放牧后,对1个建群种(短花针茅)和2个优势种(冷蒿、无芒隐子草)植物的根际和非根际真菌进行种群结构的研究.应用传统的稀释平板法与菌种分子鉴定技术相结合,对真菌进行计数和物种鉴定.结果表明:随着放牧强度的增加,非根际土壤中可培养真菌的总量呈下降趋势,尤其是表层土壤中的真菌数量急剧下降,深层土壤(20~30cm)中的游离真菌数量则在轻度放牧组中达到最大值.短花针茅根际土壤真菌的数量随着放牧强度的增大而下降,冷蒿和无芒隐子草的根际土壤真菌则分别在轻度和中度放牧强度下数量最多.从非根际土壤中共分离出12种真菌,其中隶属于木霉属和被孢霉属的真菌数量最多,为优势真菌.从短花针茅、冷蒿和无芒隐子草根际土壤中共分离出7种真菌,其中隶属于青霉属、木霉属和链格孢属的真菌数量最多.总的来看,一方面放牧活动降低了根际和非根际土壤中的真菌总量;另一方面适度放牧(轻度或中度)能够促进冷蒿和无芒隐子草根际真菌数量的增加,也有利于某些真菌,如短花针茅、冷蒿、无芒隐子草共有的根际优势真菌—青霉属的生长.

To learn the influence of grazing behavior on the population structures of cultivable soil fungi in desert steppe ecosystem and further optimize the grazing mode in these areas, the population structures of cultivable soil fungi community in the Stipa breviflora desert steppe in Mongolia were studied. The sample plots were continually treated with different grazing intensities in eight years, and the soil fungi were isolated from the rhizosphere and non-rhizospherer soil of one constructive species （Stipa breviflora） and two dominant species （Artemisiafrigida Willd., Cleistogenes songorica）. The traditional dilution-plate method and molecular identification technique were adopted to count and identify the soil fungi. The results showed that the gross quantity of non-rhizosphere soil fungi decreased with the increase of grazing intensity, especially the fungi in the surface soil decreased sharply. While the nou-rhizosphere fungi in deep soil layer （20-30 cm） had the largest amount in the sample plots treated with light grazing intensity. The amount of rhizosphere fungi of Stipa breviflora decreased with the increase of grazing intensity, while the rhizosphere fungi of Artemisiafrigida Willd. and Cleistogenes songorica had the largest amount in the sample plots separately treated with light and medium grazing intensities. Twelve fungi species were isolated from non-rhizosphere soil, among which the species belonging to Trichoderma and Absidia mortierella were the dominant species and had the largest amounts. Seven fungi species were isolated from rhizosphere soil of Stipa breviJlora, A rtemisiafrigida Willd. and Cleistogenes songorica, among which the species belonging to Penicillium, Trichoderma and A lternaria were the dominant species and had the largest amounts. Overall, on the one hand, the grazing behavior decreased the gross amount of fungi of rbizoshpere soil and non-rhizosphere soil; on the other hand, moderate grazing （light or medium） can enhance the amount of fungi in rhizoshpere soil of Artemisiafrigida Willd. and Cleistogenes sortgorica, and also benefited the growth of some species, such as Penicillium, which was the common dominant fungi of Stipa Breviflora, Artemisiafrigida Willd. and Cleistogenes songorica.