黄河首曲-玛曲县高寒草甸沙化演替进程中群落结构及种群生态位特征

以甘肃省玛曲县高寒沙化草甸为对象,应用空间序列代替时间序列的方法,对其不同沙化演替阶段植物群落主要种群结构及其生态位特征进行了研究.结果表明:(1)随着沙化演替的进行,物种组成数呈单峰式曲线变化规律,在轻度沙化阶段物种数最多(43种),禾草类和豆科类物种的重要值和生态位宽度均呈逐渐减少规律,优势度逐渐减弱；在极度沙化阶段(除垂穗披碱草外)几乎完全消失,莎草类和杂类草一些物种的重要值和生态位宽度则均呈逐渐增大规律,优势度逐渐增加,并在重度或极度沙化阶段成为优势种、次优势种或重要伴生种；随沙化演替进程,蒲公英、狼毒和乳白香青等物种则表现出波动性,最后消失,物种组成和数量的变化导致沙化演替进程中高寒草甸草场质量逐渐降低.(2)相邻沙化演替阶段植物群落的物种组成相似性指数较高,而相距较远的沙化演替阶段植物群落的物种组成相似性指数较小,沙化演替系列两个极端阶段的植物群落的物种组成相似性指数最小.(3)垂穗披碱草在整个沙化演替过程中重要值和生态位宽度均逐渐减小,但其值都较大.(4)生态位总宽度占前5位的物种依次是:垂穗披碱草、莓叶委陵菜、矮嵩草、高山唐松草和苔草,其值分别为1.653、1.438、1.387、1.295和1.204.(5)种群之间生态位重叠系数的平均值随沙化程度加深呈单峰式曲线变化规律,轻度沙化阶段种群的生态位重叠程度较高,为0.824.

Population Structure and Niche Dynamics Characteristics of Plants Communities in the Sandy Succession of Maqu Alpine Meadow in First Meander of Yellow River

With the application of space instead of time-series sequence method,the desertification of alpine meadow succession of different stages of plant community structure and niche of main population characteristics were studied in Maqu.The results showed that:(1)With the succession of the desertification,species composition showed a single peak-type curve number variation.In the mild stages of desertification,there are the largest number of species,43 species.The important value and niche breadth of grasses and leguminous species showed the law of diminishing,the dominance gradually weakened.In extreme desertification stages,grasses and leguminous species(except Elymus nutans) almost completely disappeared,the important value and niche breadth of sedges and forbs class showed the law of increasing,the dominance gradually increased.In severe or extreme desertification stage,sedges and forbs class became the dominant species,sub-dominant species or important associated species.With the deepening of sandy succession,some species such as dandelion,euphorbia and white Hong Qing and other species are unstable and finally disappeared,which resulted in desertification process of succession,the quality of alpine meadow decreased;(2)In adjacent sandy succession stages,the similarity index of species composition in plant community is higher,while far away from the sandy stage,the similarity index of species composition in plant community is smaller.In the two extremes of sandy succession series,the similarity index of species composition in plant community minimum;(3)In the entire sandy succession process,the important value and niche breadth of Elymus nutans were gradually reduced,but the values are still large;(4)Niche accounted for the total width of the top five species were:Elymus nutans,Potentilla fragarioides,Kobresia humilis,Thalictrum alpinum and Carex kansuensis,and their total width of the niche were 1.653,1.438,1.387,1.295 and 1.204,respectively;(5)The average niche overlap coefficient between populations showed a single peak-type curve variation during the desertification process.In mild stages of desertification,there is a higher niche overlap(0.824) between populations.