草本植物上侵长白山苔原对牛皮杜鹃孤岛化的作用分析

Analysis of the role of herbaceous plant invasion affected the isolationof Rhododendron aureum in the tundra of Changbai Mountain

对近年来长白山出现草本植物上侵灌木苔原,导致牛皮杜鹃(Rhododendron aureum)孤岛化的现象进行了研究.结果表明:草本植物入侵导致苔原带牛皮杜鹃分布范围缩小、重要值下降、生态位总宽度下降,草本植物与牛皮杜鹃生态位重叠程度加重;草本植物入侵使苔原带牛皮杜鹃与岳桦林下牛皮杜鹃隔离加大;苔原带现有草本入侵的景观与牛皮杜鹃景观差异增大;牛皮杜鹃景观破碎程度加重.苔原的低海拔区域受草本入侵影响程度比中高海拔区域强烈.草本植物入侵苔原带并持续扩张,使牛皮杜鹃景观基质面被打散;在苔原带下部出现草甸亚带,使苔原带和岳桦林带成为两个独立的牛皮杜鹃分布区,两个带牛皮杜鹃基因交流的廊道被切断;苔原带上牛皮杜鹃景观破碎程度越来越大,与原来景观的差异越来越大,且这种作用从低海拔逐渐向高海拔推进,在空间上牛皮杜鹃生存范围将越来越小,牛皮杜鹃物种孤岛化问题将越来越严重.

Rhododendron aureum is a polar endemic species,distributed in Changbai Mountain alpine tundra and Betula ermanii forest belt.In recent years,the phenomenon of herbaceous plants invading shrub tundra in Changbai Mountain has strengthened the isolation of Rhododendron aureum.The aim of this study was to study the effect of herbaceous plant invasion on the isolation of Rhododendron aureum.The results showed that the invasion of herbaceous plants led to the reduction of the distribution range of Rhododendron aureum,the decrease of the importance value of Rhododendron aureum,the decrease of the total niche width,and the aggravation of the niche overlap between herbaceous plants and Rhododendron aureum.The invasion of herbaceous plants increased the isolation between Rhododendron aureum in tundra and it under Betula ermanii forest.The difference between the existing herbaceous invasion landscape and the Rhododendron aureum landscape in the tundra was increasing;the fragmentation degree of Rhododendron aureum landscape was aggravated.The influence of herb invasion in low altitude area was stronger than that in middle and high altitude area.Therefore,herbaceous plants invaded the tundra and continued to expand,destroying the substrate surface of the Rhododendron aureum landscape.The meadow subzone appeared in the lower part of the tundra zone,making the tundra zone and the Betula ermanii forest zone become two independent distribution areas of Rhododendron aureum,and the corridors of gene exchange of Rhododendron aureum were cut off.The fragmentation degree of Rhododendron aureum landscape on the tundra belt is increasing,and the difference between the existing landscape and the original landscape is increasing,and this effect is gradually advancing from low altitude to high altitude.In space,the survival range of Rhododendron aureum will be smaller and smaller,and the problem of isolated island of Rhododendron aureum species will be more and more serious.