贵州韭菜坪山区不同海拔草地群落植物多样性和生产力

Plant diversity and productivity of grassland communities at different altitudes of Jiucaiping Mountain, Guizhou

草地群落特征和生产力反映草地对环境的适应，影响草地生态系统的稳定性、物质循环、能量流动和第二性生产. 为了解贵州韭菜坪山区天然草地群落特征和生产力在垂直梯度上的变化规律，以4个不同海拔梯度（2 385 m、2 503 m、2 553 m和2 648 m）天然草地为研究对象，通过野外植物群落调查，采用样方法、刈割法和数据处理探讨不同草地群落的物种组成、密度、盖度、生物多样性、地上生物量、载畜量及它们与海拔之间的关系. 结果表明，4个草地群落植物共有27种，隶属于16科27属. 随海拔升高，各草地群落物种数目由14种降低到5种，群落优势种（含共优势种）的密度分别为113.70、237.30、155.00、32.34株/m^2，盖度分别为88.60%、87.10%、89.70%和63.60%，生物量分别为2 597.40、3 851.90、3 274.90、387.70 kg/hm^2，草地载畜量分别为2.16、2.72、1.64、0.13羊单位/hm^2. 此外，物种数目、Pielou均匀度指数、Margalef丰富度指数、Simpson多样性指数随海拔升高均呈现逐渐减小的趋势；草地群落随海拔升高的Cody多样性分别为10.00、7.00、7.50；物种数目S、Margalef丰富度指数和Simpson多样性指数与海拔高度均呈负二次函数关系. 因此，可对中低海拔（2 500 m以下）草地采取划区轮牧或季节性轮牧，对高海拔草地（2 500 m以上）采取禁牧或少牧的方式，以保证该区域草地生态系统的生物多样性和稳定性. （图1 表5 参33）

The characteristics and productivity of grassland communities reflect its adaptation to the environment, and affect the stability, substance circulation, energy exchanges, and secondary productivity of grassland ecosystems. To investigate the characteristics and productivity of natural grassland communities in vertical gradients in Jiucaiping mountainous regions, Guizhou Province, four natural grassland communities of different altitude gradients （2 385, 2 503, 2 553, and 2 648 m） were selected. On the basis of field data and analysis, the species composition, number of species, species density, plant height, coverage, and above-ground biomass were investigated. In addition, the relationships between biodiversity and altitude gradients of the four grasslands were analyzed by calculating derivative biodiversity indices comprising Pielou’s evenness index, Margalef’s richness index, Simpson’s biodiversity index, and Cody’s biodiversity index. The results showed that there were 27 species, belonging to 16 families, and 27 genera. With increasing elevation, the number of species decreased from 14 to 5; the densities of dominant species （included co-dominant species） were 113.70, 237.30, 155.00, and 32.34 plants/m^2, respectively; coverage were 88.60%, 88.60%, 89.70%, and 63.60%, respectively; the above-ground biomass were 2 597.40, 3 851.90, 3 274.90, 387.70 kg/hm^2, respectively; and the potential stock capacity were 2.16, 2.72, 1.64, and 0.13 sheep units/hm^2, respectively, in the four grassland communities. The number of species, Pielou’s evenness index, Margalef’s richness index, and Simpson’s biodiversity index all presented a decreasing trend with increasing elevation; meanwhile, Cody’s diversity between two adjacent grassland communities were 10.00, 7.00, and 7.50. The relationship between the number of species, Pielou’s evenness index, Margalef’s richness index, Simpson’s biodiversity index, and elevation were all negative quadratic functions. Therefore, to ensure the biodiversity and stability of grassland ecosystems in Jiucaiping mountainous regions, regional or seasonal rotation grazing should be practiced in low altitude （〈 2 500 m） areas, and no or light grazing should be practiced in high altitude （〉 2 500 m） areas.