高寒小嵩草草甸暖季草场主要植物种群的生态位

对高寒小嵩草草甸不同放牧强度下20种植物种群的优势度、生态位宽度及生态位重叠规律进行了研究。结果表明,经过2年的放牧实验,对照、轻度和中度放牧组的主要优势种均为小嵩草和垂穗披碱草,重度放牧组的主要优势种为鹅绒委陵菜和阿拉善马先蒿;由于小嵩草、矮嵩草和线叶嵩草具有耐牧和耐践踏等生物学特点,它们的生态位宽度很大（0．938,0．824,0．815）;垂穗披碱草由于其耐牧和耐旱性较差,生态位宽度相对较小（0．805）,且青海野青茅、异针茅、针茅、紫羊茅和双叉细柄茅等禾本科牧草的生态位宽度在放牧强度梯度上均较小（0．226,0．448,0．445,0．608,0．605）,说明放牧抑制了高大禾草层片的发育,为植株矮小的莎草科牧草的生长创造了条件;异针茅和针茅之间、甘肃马先蒿和阿拉善马先蒿之间生态位重叠较小（0．500,0．572）,这是种间对资源利用上分化的结果。分布于放牧演替系列2个极端的种群间生态位重叠较小,表明物种的分布是既间断又连续的。

Niche of main plant populations on a warm-seasonal pastureland of alpine Kobrecia parva meadow

The study on the dominance,niche breadth and niche overlap of twenty main plant populations on a warm-seasonal pastureland of alpine Kobrecia parva meadow under four grazing intensities showed that after two years grazing,K.parva and Elymus natans were the dominated plants in the control,light grazing,and moderate grazing plots,while Potentilla anserine and Pedicularis alaschanica dominated in heavy grazing plot.Because of their high endurance in grazing,drought,and tramping,K.parva,K.humilis and K.capillifolia had a wide niche breadth,with the values being 0.938,0.824 and 0.815,respectively.The niche breadth of E.natans was relatively narrow(0.805) owing to its bad biological characters in enduring grazing,drought and tramping.The niche breadths of D.kokonorica,Stipa aliena,S.purpurea,Festuca rubra and Ptilagrostis dichotoma based on grazing gradients were all very narrow,with the values being 0.226,0.448,0.445,0.608 and 0.605,respectively,indicating that grazing restricted the growth of high grasses and created a good environment for the growth of short sedges.The niche overlaps between S.aliena and S.purpurea,and P.kansuensis and P.alaschanica were relatively narrow(0.500,0.572),which could be seen as the results of resource utilization differentiation between plant species.The species with grater niche breadth generally had greater niche overlap with other species,while the species distributed on the two extremeness of the grazing gradient had narrower niche overlap with each other,suggesting that the distribution of the species was both continuous and discontinuous.