Abstract:

Veratrum nigrum can be used as an indicator of steppe degradation, and is often a companion species in natural steppes. As steppe degradation increases, it irreversibly replaces the native plants and becomes the dominant species. However, the mechanism by which V. nigrum spreads affect vegetation and soil properties remains unclear. To investigate the effects of the spread of Veratum nigrum on vegetation characteristics and soil physicochemical properties in mountain meadow steppes, and the relationship between them. We selected Inner Mongolia mountain meadows steppe as the research object, and set up four hazard levels according to Veratrum nigrum coverage level: control C₀ (coverage=0), mild hazard C₁ (coverage≤20%), moderate hazard C₂ (20%<coverage ≤40%), and severe hazard C₃ (coverage>40%), and investigated and analyzed the composition of the mountain meadow steppe plant community and the physicochemical characteristics of soils under the different Veratrum nigrum hazard levels. The results showed that compared with the control C₀, the species richness and Shannon and Simpson indices of the plant community in C₃ decreased significantly, whereas the total aboveground biomass showed a decreasing trend and then an increasing trend with the increase in Veratrum nigrum hazard; compared with C₀, the aboveground biomass of plants other than Veratrum nigrum and dominant plants in C₁, C₂, and C₃ decreased significantly by 9.93%, 57.7%, and 46.9%, respectively. Additionally, with an increase in Veratrum nigrum hazard, soil pH significantly decreased, whereas the total nitrogen, total phosphorus, ammonium nitrogen, nitrate nitrogen, available phosphorus, and available potassium content in the soil were significantly higher in the C₃ treatment than in the C₀ treatment. Correlation analysis indicated that soil pH, total phosphorus, ammonium nitrogen, nitrate nitrogen, and available phosphorus content were important environmental factors affecting the aboveground biomass of Veratrum nigrum, and soil pH, total phosphorus, nitrate nitrogen, ammonium nitrogen, and available phosphorus content were significant environmental factors affecting the species richness and Shannon diversity index of plant communities. In summary, Veratrum nigrum promotes its own population spread by increasing soil nutrient content, lowering soil pH, and decreasing the richness and species diversity of grassland plant communities.

Key words: Veratrum nigrum, Mountain meadow steppe, vegetation characteristics, soil physicochemical properties

摘要：

藜芦（Veratrum nigrum）可作为草地退化的指示指标，其在天然草地中常为伴生种，随着草地退化程度的加剧，不可逆地取代本土植物演化为优势物种。然而，藜芦扩散对植被与土壤性质的影响机制仍不清楚。为探明藜芦扩散蔓延对山地草甸草地植被特征和土壤理化性质的影响，以及植被特征与土壤理化性质间的关系。以内蒙古山地草甸草地为研究对象，根据藜芦覆盖度等级设置对照C₀（无藜芦）、轻度危害C₁（盖度≤20%）、中度危害C₂（20%<盖度≤40%）、重度危害C₃（盖度>40%）4个危害度等级，调查分析不同藜芦危害程度下山地草甸草地植物群落组成和土壤理化变化特征。结果表明，与无藜芦对照C₀相比，C₃处理植物群落的物种丰富度、Shannon和Simpson指数均显著下降；总地上生物量随着藜芦危害度的增加呈现出先降低后增加的趋势；相比C₀，C₁、C₂和C₃处理除藜芦与优势植物以外的其他植物地上生物量分别显著下降9.93%、57.7%、46.9%；同时，随着藜芦危害度的增大，土壤pH显著下降，而土壤全氮、全磷、铵态氮、硝态氮和速效磷和速效钾含量在C₃处理下均显著高于C₀；相关性分析表明，土壤pH值、全磷、铵态氮、硝态氮和速效磷含量是影响藜芦地上生物量的重要环境因子；土壤pH值、全磷、硝态氮、铵态氮和速效磷含量是影响植被群落物种丰富度和Shannon多样性指数的重要环境因子。综上所述，藜芦通过增加土壤养分含量，降低土壤pH，同时降低草地植物群落丰富度与物种多样性，加速自身种群数量的扩散。

关键词: 藜芦, 山地草甸草地, 植被特征, 土壤理化性质