宁夏荒漠草原不同封育年限优势种群的生态位特征

Niche Characteristics of Dominant Plant Populations in Desert Steppe of Ningxia with Different Enclosure Times

以宁夏荒漠草原为研究对象,采用空间梯度代替时间梯度的方法,对不同封育年限及未封育草地的植被进行调查,并运用生态位宽度和生态位重叠指数对不同恢复演替阶段优势种群的生态位特征进行计测。结果表明:草地封育后,植物种群的生态位宽度发生变化,未封育草地以一年生植物刺蓬(Salsola pestifer)的生态位宽度最大,短花针茅(Stipa breviliora)和牛枝子(Lespedeza potaninii)种群的生态位宽度均以封育7年的草地最高,分别为3.153和4.058,中亚白草(Pennisetum centrasiaticum)种群的生态位宽度在各封育年限草地及未封育草地中均较高,是该区域的泛化种。封育草地恢复演替过程中种群之间生态位重叠总体较高,大多物种间生态位重叠指数在0.4～0.8之间;其中,未封育草地的种群重叠指数较低,封育5年的草地种群重叠指数最高。不同封育年限草地中生态位宽度最大的物种不一定和其他的物种有最大的重叠值,植物群落较高的生态位重叠和种群生态位宽度之间不存在线性关系。

The vegetation of unenclosed and enclosed desert steppes were investigated after three, four, five, six, and seven years using the method of spatial sequence replacing time series. Niche breadth and o- verlap indices were used to measure the niche characteristic of dominant plant populations. Results showed that the niche breadth of plant population changed after enclosure. In the 0-year fenced grassland, the niche breadth of Salsola pestifer was the highest one. The niche breadth of Stipa breviliora and Lespede- za potaninii were the largest in 7-year fenced grassland. The niche breadth of Pennisetum centrasiaticum was larger than that of other species in different fencing years. The niche breadth of dominant species nar- rowed with increasing fencing years, whereas that of other species broadened. The population overlapping index of 0-year fenced grassland was the lowest one and that of 5-year fenced grassland was the highest. Species having high niche breadth didn＇t have large niche overlap with other species. There was no rela- tionship between niche breadth and niche overlap of dominant species.