河西走廊西段荒漠戈壁灌木群落物种多样性的海拔格局

Patterns of Altitudinal Distribution of Species Diversity of Desert Gobi Shrub Communities in West Hexi Corridor of China

【目的】分析河西走廊西段灌木群落结构特征在海拔梯度上的分布规律,探讨荒漠戈壁灌木群落物种多样性的空间分布格局。【方法】以甘肃荒漠戈壁灌木群落为对象,在800~3200 m的海拔范围内设置12个海拔梯度,探讨物种多样性沿海拔的变化特征。【结果】荒漠戈壁灌木群落类型沿海拔从低到高依次有沙拐枣+梭梭群落、泡泡刺群落、沙拐枣+泡泡刺群落、泡泡刺+红砂+沙拐枣+膜果麻黄群落、合头草+红砂群落、泡泡刺+红砂群落、合头草+盐爪爪+红砂群落、灌木亚菊+细枝盐爪爪群落、合头草群落、盐爪爪群落、盐爪爪+红砂群落、红砂群落,其中,红砂、合头草和泡泡刺等为分布范围较大的优势种;群落的α多样性指数沿海拔梯度从低到高呈先增加后降低的单峰型分布格局,最大值出现在海拔2000~2200 m内,其中,丰富度Gleason、Margalef指数和多样性Shannon-Wiener、Simpson指数随海拔上升表现出显著的单峰型格局(P<0.05),海拔显著影响荒漠戈壁灌木群落的物种多样性(P<0.05);虽然年均降水量和年均气温与海拔极显著相关(P<0.01),但物种多样性与年均降水量和年均气温的相关性均未达到显著水平(P>0.05);群落物种多样性指数偏低,群落结构简单,物种组成稀少;大多数相邻海拔梯度间灌木群落的Jaccard相似水平较低。【结论】河西走廊西段荒漠戈壁以灌木为优势种的群落呈区域性的斑块状分布格局。不同海拔梯度内灌木群落的建群种都发生了变化。物种多样性在海拔梯度上呈先升后降的单峰分布格局。

【Objective】The altitudinal patterns of distribution of structural characteristics of shrub communities in the western part of Hexi Corridor was analyzed in order to explore the spatial distribution patterns of species diversity in shrub communities in desert gobi.【Method】12 plots were set up in the shrub communities within an altitudinal range of 800-3200 m in the desert gobi to investigate the changes of species diversity along elevation.【Result】From low to high altitudes,the types of shrub communities were in turn Calligonum mongolicum+Haloxylon ammodendron,Nitraria sphaerocarpa,C.mongolicum+N.sphaerocarpa,N.sphaerocarpa+Reaumuria soongarica+C.mongolicum+Ephedra przewalskii,Sympegma regelii+R.soongaric a,N.sphaerocarpa+R.songarica,S.regelii+Kalidium foliatum+R.soongarica,Ajania fruticulosa+K.gracile,S.regelii,K.foliatum,K.foliatum+R.soongarica,R.soongarica,among which R.soongarica,S.regelii and N.sphaerocarpa were dominant species with large distribution range,playing an important role in the desert gobi ecosystem.Theαdiversity index showed a unimodal distribution pattern that increased first and then decreased along the altitudinal gradient,with the maximum value occurred at 2000-2200 m.The richness index(Gleason,Margalef)and the diversity index(Shannon-Wiener,Simpson)showed a significant unimodal pattern with the altitudinal gradient(P<0.05).The vertical distribution pattern of diversity in the shrub communities in desert gobi was significantly affected by the altitudes(P<0.05).Although the mean annual precipitation and the mean temperature were extremely significantly correlated with the altitude(P<0.01),the correlation between species diversity and precipitation or temperature was not significant(P>0.05).The species diversity indices of desert gobi shrub communities were low,with simple structure and few species.Most Jaccard similarity levels of different shrub communities were low between altitudinal gradients.【Conclusion】The distribution pattern of desert gobi shrub community was patchiness in regional scale in West Hexi Corridor.The constructive species of shrub communities changed within different altitudinal gradients.The distribution pattern of species diversity was unimodal on the altitudinal gradients,which rose first and then descend.This study will help to understand the spatial distribution pattern of shrub communities in arid region,and provide a basis for scientific conservation and management.