Elevational gradients are linked with different abiotic and biotic factors, which in turn influence the distribution of plant diversity. In the present study we explored the relative importance of different environmental factors in shaping species diversity and composition of vascular plant species along an elevational gradient in the Chamelia Valley, Api-Nampa Conservation Area in western Nepal. Data were collected from 2,000 to 3,800 m above sea level and analysed using a generalized linear mixed model (GLM) and non-metric multidimensional scaling (NMDS). We recorded 231 vascular plant species consisting of 158 herb species belonging to 55 families, 37 shrub species belonging to 22 families and 36 tree species belonging to 23 families. Species richness and species abundance significantly decreased with increasing elevation. However, species richness increased with the intensity of vegetation cutting. Species richness and abundance also increased with increased annual precipitation and mean annual temperature whereas species abundance decreased with grazing, soil phosphorus and nitrogen. NMDS ordination revealed that mean annual temperature and annual precipitation affect the composition of vascular plant species in opposite ways to elevation. Among the many anthropogenic disturbances, only grazing affected species composition. In conclusion, more than one environmental factor contribute to the shaping of patterns of vascular plant species distribution in western Nepal. Knowledge on species diversity, distribution and underlying factors needs to be taken into consideration when formulating and implementing conservation strategies.

中文翻译：

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尼泊尔西部喜马拉雅中部沿海拔梯度的维管植物多样性

海拔梯度与不同的非生物和生物因素有关，进而影响植物多样性的分布。在本研究中，我们探讨了不同环境因素在塑造尼泊尔西部 Api-Nampa 保护区 Chamelia 山谷沿海拔梯度的维管植物物种多样性和组成方面的相对重要性。从海拔 2,000 到 3,800 m 收集数据，并使用广义线性混合模型 (GLM) 和非度量多维标度 (NMDS) 进行分析。共记录维管束植物231种，其中草本植物55科158种，灌木22科37种，乔木23科36种。物种丰富度和物种丰度随海拔升高而显着降低。然而，物种丰富度随着植被砍伐强度的增加而增加。物种丰富度和丰度也随着年降水量和年平均温度的增加而增加，而物种丰度随着放牧、土壤磷和氮的增加而减少。NMDS 排序显示，年平均温度和年降水量以与海拔相反的方式影响维管植物物种的组成。在众多人为干扰中，只有放牧会影响物种组成。总之，不止一种环境因素促成了尼泊尔西部维管植物物种分布模式的形成。在制定和实施保护战略时，需要考虑物种多样性、分布和潜在因素的知识。