藏东南是我国泥石流灾害分布最集中,危害严重的区域之一,泥石流堆积扇广布.泥石流沉积区植被恢复是生物治理泥石流和生态恢复措施的重要内容,也是高寒区生态恢复关注的焦点.对林芝县扎西岗、鲁朗定位站和芽依3个不同年代形成的泥石流沉积区植物群落结构和物种进行了多样性调查,结果表明:植物群落结构与泥石流发生的年限、所处的海拔和发生的强度有密切关系.泥石流沉积区植物群落主要为云南沙棘+云南锦鸡儿+蕨麻萎陵菜群落、糙皮桦+高丛珍珠梅+西南草莓群落和糙皮桦+云南锦鸡儿+西南草莓群落组成,包含糙皮桦、云南锦鸡儿等29种植物.泥石流沉积区形成时间越长,群落物种多样性水平有下降趋势,群落优势度C值有一定程度的提高.泥石流沉积区植物群落层次多样性表现为一般草本层多样性水平较高,乔灌层较低.乔灌草均匀度指数Jsw值略大于草本层.泥石流暴发时间过长或过短,Jsw值较小.优势度C值与丰富度指数Ma值呈负相关性,与泥石流沉积区形成时间呈正相关系.%Debris flow is one of most disasters on the southeastern Tibetan Plateau,China.Many alluvial fans induced by debris flow widely distribute in the region.Ecological restoration is usually used to control debris flow.In the study,we investigated effects of age on the community structure and species diversity of the alluvial fans in Zhaxi Gang,Research Station and Yayi.The results showed that the community structures have been strongly influenced by occurrence period and intensity of debris flow.There are two main community structures including Hippophae rhamnoides Linn.subsp.yunnanensis Rousi + Caragana franchetiana Kom.+ Potentilla anserina Linn.and Betula utilis D.Don + Sorbaria arborea Schneid.+ Fragaria moupinensis (Franch.) Card.and Betula utilis D.Don + Caragana franchetiana Kom.+ Fragaria moupinensis (Franch.) Card.Twenty-nine species such as Betula utilis D.Don and Caragana franchetiana Kom et al were found in the alluvial fans induced by debris flow.We detected a significant negative correlation between the age of alluvial fans and species diversity,but degree of dominance (C value) increased with the age.Compared with the herbaceous layer,tree and shrub layers have lower diversity index.The evenness index (Jsw) in the tree + shrub + grass structure is larger than that in the herb layer.The dominance degree (C value) is negatively correlated to the richness index (Ma values),but a positive correlation to the age of debris flow deposition.
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