放牧影响下羊草草地主要植物种群生态位宽度与生态位重叠的研究

THE NICHE BREADTHS AND NICHE OVERLAPS OF MAIN PLANT POPULATIONS IN LEYMUS CHINENSIS GRASSLAND FOR GRAZING

本文采用Ｓｈａｎｎｏｎ－Ｗｉｅｎｅｒ和Ｐｉａｎｋａ公式，在土壤水分、土壤含盐量和土壤有机质含量三维生态因子梯度上测定了松嫩草原碱化羊草草地放牧演替系列１２种主要植物种群的生态位宽度和生态位重叠。结果表明，植物种群长期适应由放牧引起的群落和土壤环境因子梯度变化是种群生态位分化的主要原因。优势种羊草种群生态位宽度最大，三维上生态位宽度分别为０．９１０、０．８６９和０．９３０。五脉山黧豆和湿生植物生态位宽度均很窄。增加种表现出较强的适应环境能力，生态位宽度都较大。在放牧演替的先锋植物中，只有虎尾草生态位宽度较大（三维上平均０．７０７），角碱蓬和星星草种群生态位宽度均很窄。生态位宽度较大的物种与其它种群间生态位重叠较大。分布于相同或相邻放牧阶段及具有相同或相似环境要求的物种间生态位重叠较大。放牧条件下，羊草群落的演替过程也就是种群生态位分化的过程。

The niche breadths and niche overlaps of 12 main plant populations grown on the gradients of soil water,soil salt and soil organic content in Leymus chinensis grassland for grazing were measured using the formulas described by ShannonWiener and Pianka.The results show the niche breadths of Leymus chinensis,which were greater than other species,were 0.910,0.869 and 0.930 on the gradients of soil water,soil salt and soil organic respectively.The niche breadths of Lathyrus quinquenervius,Heleochalis intevsita  and Phragmites communities were much narrower.Chloris virgata,which is one of the pioneer plant of grazing succession,had much greater niche breadths(average on the three gradients 0.707) than the other two species(Suaeda corniculata,Puccinellia tenuiflora).The niche overlaps between the species with broad niche breadth and other species were much greater.The niche overlaps among the species distributed in the same/adjacent grazing stages or the species which have the same/similar environment requirements were great.Under grazing condition,the process of community succession was the one of species' niche separate.