放牧率对高寒混播草地主要植物种群生态位的影响

对垂穗披碱草/星星草混播草地不同放牧率下22种植物种群优势度和生态位分化规律的研究结果表明:不同放牧率下混播草地的建群种相同,而次优势种和伴生种发生了明显变化;不同放牧率下混播草地的建群种垂穗披碱草因其高度和发达的根系成为竞争的优胜者,抑制了星星草的生长,因而其生态位宽度最大,为0.956,星星草次之,为0.821;不同放牧率下混播草地的建群种垂穗披碱草、星星草和侵入种早熟禾与其他植物种之间(除了草、紫羊茅和乳白香青)及彼此之间的生态位重叠均较大,而同属的鹅绒萎陵菜、多裂萎陵菜和雪白萎陵菜之间以及生活型相近的小嵩草、矮嵩草和青海苔草之间的生态位重叠也较大。这说明具有相同形态特征或生活型的物种之间生态位重叠较大,且生态位宽度较大的物种与其他种群间也有较大的生态位重叠,但分布于放牧演替系列两个极端的种群间生态位重叠较小。

Grazing rate effect on major plant population niches in artificially mixed-sown alpine grassland

Dominance and polarizing rule of niche for twenty-two main plant populations in Elymus nutans/Puccinellia tenuiflora mixed-sown alpine grasslands with different stocking rates were studied.Results show that after three grazing seasons,Elymus nutans and Puccinellia tenuiflora are still the dominant plants in plots with different grazing rates,whereas sub-dominant and concomitant plants are highly variable if not vulnerable.Under different grazing conditions,planted Elymus nutans plant is the competitive winner and restrains growth of Puccinellia tenuiflora due to its high height,deep and well-developed roots,hence widest niche breadth(0.956),which closely followed by Puccinellia tenuiflora(0.821).Planted Elymus nutans and Puccinellia tenuiflora plants and invading Poa spp.have larger niche overlaps with other plants,except for Koeleria cristata,Festuca rubra,Anaphalis lacteal and among each other.There are also larger niche overlaps among Potentilla anserina,P.multifida and P.nivea;and Kobresia humilis,K.parva and Carex ivanavoe,which exhibit similar phenology.This indicates that larger niche overlaps exist among plant species with similar morphology and phenology,and between species with greater niche breadths over others.Species distributing in two extremities along stocking rate gradients show narrower niche overlaps.