蘑菇圈形成对高寒草甸群落植被结构及稳定性的作用

蘑菇圈作为青藏高原高寒草甸一种常见生态学现象,也是草地群落植被更新重要场所。通过对青藏高原高寒草甸蘑菇圈区域群落植被特征和经济类群、生活型及演替顶极成分功能群生物量构成、Raunkiaer频度系数、演替度及Spearman秩相关特征进行分析,明晰蘑菇圈不同区域草地植被分异特征,解析蘑菇圈形成对草地植被变化和群落稳定性的作用。结果表明:1)蘑菇圈形成明显改变物种构成,圈上群落优势种为垂穗披碱草和赖草,而圈上和圈外群落皆无绝对优势种;2)蘑菇圈环的形成显著提高了圈上禾草、地下芽植物和降低种的生物量比例,降低其物种多样性;3)蘑菇圈圈上群落处于更高演替阶段,其植物种重要值与经济类群和演替顶极成分的生物量构成变化一致;4)圈上群落主要植物种对正负关联比为0.89,多数种对的种间联结松散,群落稳定性较低;圈内和圈外群落主要植物种对的正负关联比皆>1,多数种对间关联性较强,群落稳定性较强;且蘑菇圈群落中显著关联种对发生在亚优势种与伴生种或伴生种与伴生种之间。研究认为,蘑菇圈形成促进高寒草甸由莎草/杂类草群落向禾草/杂类草群落演替,但降低高寒草甸稳定性。

Effects of fairy ring formation on community vegetation structures and stability in alpine meadows

Fairy rings is a common ecological phenomenon in alpine meadows on the Qinghai-Tibet Plateau and is an important site for vegetation regeneration.In order to explore the effects of fairy ring formation on vegetation change and community stability in the Plateau's alpine meadows,we studied the vegetation characteristics of different ring zones,functional group biomass composition by economic category,the life form and succession climax component,the Raunkiaer frequency coefficient,succession degree and Spearman rank correlations within the plant community surrounding the fairy ring zone.The results indicated that:1) fairy ring formation significantly changed species composition.The dominant species on the fairy ring were Elymus nutans and Aneurolepidium dasystachys but there were no clearly dominant species either within and outside the rings;2) fairy ring formation significantly increased the biomass ratios of grasses,geophytes and decreaser on the fairy ring,but reduced its species diversity;3) the community on the fairy ring was at a higher successional stage,and the importance value of plant species accorded with their economic category and succession climax component type's biomass composition;4) on the fairy ring,the positive to negative associations ratio of the main species-pairs was 0.89,the interspecific association of most species-pairs was not significant and the community was in a lower stable state;while within and outside the fairy rings the ratios were both ＞1,the association between most species-pairs was stronger and the community was more stable.The respective associated species-pairs occurred mainly between sub-dominant species or companion species and the companion species of fairy ring communities.This research shows that fairy ring formation can encourage alpine meadow succession from sedges/forbs communities to grass/forbs communities,but that they also reduce the stability of alpine meadows.