不同状态高寒草甸土壤微生物分布及其变化

Distribution and Change of Soil Microorganism in Alpine Meadow under Different States

【目的】了解藏北高寒草甸不同退化阶段土壤微生物的变化特征。【方法】采用涂抹平板法对藏北南部不同状态高寒草甸(包括正常草地、轻度和严重退化草地)土壤微生物及其变化进行了研究。【结果】(1)不同退化程度高寒草甸中3种土壤微生物数量均表现出放线菌>细菌>真菌的特征,放线菌在3种微生物中占绝对优势;放线菌与细菌随着草地退化程度的加剧表现出先下降再上升的趋势,而真菌则随着草地的退化表现出先急剧上升又显著下降的趋势。(2)不同退化程度高寒草甸表层(0~10 cm)和亚表层(10~20 cm)土壤中微生物的分布各不相同,真菌在正常草甸和重度退化草甸中表现为表层小于亚表层,而在轻度退化草甸中却表现为表层大于亚表层的趋势;放线菌在正常草甸和轻度退化草甸中表现为表层大于亚表层,而在重度退化草甸中却表现为表层小于亚表层的趋势;细菌则均表现出表层大于亚表层的趋势。(3)不同退化程度高寒草甸表层和亚表层土壤中微生物的变化趋势亦不尽相同,土壤细菌在表层和亚表层均表现出随着土壤退化程度的逐步加深呈先减少再增加的变化趋势;真菌在表层表现出随着土壤退化程度的逐步加深呈先增加再减少的变化趋势,而在亚表层土壤中却表现为先下降再轻微上升的趋势;放线菌数量则表现为表层土壤中随草地退化程度的加剧逐步下降的趋势,亚表层土壤中却呈现先轻微下降又显著上升的变化趋势。【结论】放线菌为藏北高寒草甸土壤中的优势微生物种类,随着草地退化程度的加剧,藏北高寒草甸不同退化阶段土壤微生物的变化规律各不相同,不同微生物种类在表层和亚表层土壤中的分布规律亦不尽相同。

[ Objective] Soil microbes and their changes in alpine meadows （including normal grassland, mild and severely degraded grass- land） in southern Tibet were studied. [ Method ] The smear plate method was used. [ Result ] （i） The number of soil microbes in alpine mead- ow showed different characteristics of actinomycetes 〉 bacteria 〉 fungi, and actinomycetes had the absolute superiority among the three kinds of microorganisms. As for Actinomycetes and bacteria, the degree of degradation increased first and then increased, while the fungi showed a sharp increase and a significant decrease with the degradation of the grassland. （ii） The distribution of microbes in the surface of alpine meadow （0 -10 cm） and sub-surface layer （10 -20 cm） in different degrees of degradation was different. The fungi were expressed in the normal meadow and severely degraded meadow with the surface less than the sub-surface. In the mild degraded meadow, the surface layer was larger than the sub-surface layer, while the normal meadow and the mild degraded meadow showed that the surface layer was larger than the sub-surface layer, but in the severe degraded meadow, Sub-surface of the trend ; bacteria were showing that the surface layer was greater than the sub-surface trend. （iii）The trend of microbes in the surface and sub-surface soils of alpine meadows with different degrees of degradation was different. The soil bacteria showed a tendency to decrease first and then increase with the gradual degradation of soil degradation in the surface and sub-surface. The number of actinolnycetes showed that the number of actinolnycetes in the sub-surface soil decreased with the in-crease of the degree of soil degradation. The degree of degradation of grassland gradually decreased, and the sub- surface soil showed a slight decrease and a significant increase trend. [ Conclusion] Actinomycetes were the dominant microbial species in alpine meadow soil. With the aggravation of grass- land degradation, the changes of soil microorganisms were dif- ferent under degraded stages of alpine meadow in northern Ti-bet. The distribution law of different microbial species in surface and subsurface soil is also not identical.