不同坡向高寒草甸土壤理化特性和微生物数量特征

阐明不同坡向草地土壤性质的空间分异格局,为退化草地的精准修复和科学管理提供参考。研究了青藏高原东缘高寒草甸退化草地不同坡向(北坡N、西北坡NW、西坡W、东坡E、东北坡NE、西南坡SW和南坡S)土壤理化性质和微生物数量特征。结果发现:从N→S坡向上,土壤有机质、碳氮比和全氮含量均呈下降趋势,土壤全磷含量和pH值在不同坡向间均无显著差异(P0.05),E坡向全磷含量最高((2.83±0.95)g/kg),NW坡向含量最低((2.07±0.12)g/kg);土壤细菌、真菌和放线菌数量变化呈波动现象,NW坡向的细菌((13.0×10~5±1.0×10~5)个/g)、真菌((14.0×10~3±0.0)个/g)和放线菌((24.0×10~4±1.0×10~4)个/g)数量最低,E坡向的细菌数量最高((85.5×10~5±2.5×10~5)个/g),S坡向的真菌((24.0×10~3±0.0)个/g)和放线菌((209.5×10~4±4.5×10~4)个/g)数量最高;回归分析表明,在E→S坡向上,随土壤含水量、有机质、碳氮比和全氮含量的增加,土壤细菌和放线菌数量均显著降低(P0.05),而土壤真菌数量随含水量、pH值、土壤养分含量的增加略有降低(P0.05)。可见,不同坡向高寒草甸土壤理化特征差异明显,也导致了土壤微生物数量分配格局的不同。

Soil physical and chemical characteristics and microbial proportions in an alpine meadow with different slopes

The alpine meadow is the main type grassland ecosystem which has several unique characteristics. Slope direction is one of the important topographic factors in the alpine meadow which plays an important role in the spatial differentiation of soil properties. The difference in soil nutrients and microorganisms between different slope directions may lead to different landscape qualities, and the difference in landscapes will determine the nature of the soil which finally affects the vegetation structure and growth. Therefore, understanding the role of slop effects in driving soil microbes and functions is essential for formulating sustainable ecosystem management and conservation policies. The aim of the current study is to clarify the spatial distribution pattern of grassland soil properties under different slope directions and to provide a basis for the precise restoration of degraded grassland. The soil physical and chemical properties and microbial quantity changes in the degraded meadow of the alpine meadow in the eastern margin of the Qinghai Tibetan Plateau (N, northern slope; NW, northwest slope; W, west slope; E, eastern slope; NE, northeast slope; SW, southwest slope; S, south slope) were studied. The results showed that the soil organic matter, carbon and nitrogen ratio, and total nitrogen content decreased from north to south (N to S). The total phosphorus content and pH value of the soil were not significantly differed between the seven slopes. The content of total phosphorus in the E slope was the highest ((2.83±0.95)g/kg), and the content of the NW slope was the lowest ((2.07±0.12)g/kg); the counts of soil bacteria, fungi, and actinomycetes fluctuated with slope differences. The count of bacteria ((13.0×10⁵±1.0×10⁵)cfu/g), fungi ((14.0×10³±0.0)cfu/g) and actinomycetes ((24.0×10⁴±1.0×10⁴)cfu/g), was the lowest in the NW slope, highest in the E slope for bacteria ((85.5×10⁵±2.5×10⁵)cfu/g) and actinomycetes ((209.5×10⁴±4.5×10⁴) cfu/g), and on the S slope fungus ((24.0×10³±0.0)cfu/g) was the highest. The regression analysis showed that with the increase of soil water content, organic matter, C/N ratio, and total nitrogen content, the counts of soil bacteria and actinomycetes decreased significantly from the gradient of the N slope to the S, and there was no significant influence on the count of fungi. The change in soil pH value and total phosphorus had no significant influence on the number of microbes (P > 0.05). It could be concluded that soil nutrient contents were different under different slope directions. When the soil nutrient content was high, the demand for plant growth may be given priority. Therefore, during the period of high soil nutrient contents, the count of microorganisms remain relatively small.