Population Structure of Shrub in the Southern Five Islands of Miaodao Archipelago and Its Response to the Environmental Factors
The shrubs of islands also play a significant role in ecosystem since they are resistant to climatic conditions,especially to drought and salinity.The quantitative research on ecological relationship between vegetation and the environment at landscape and region scale has been developed rapidly,and that became one of the focuses of vegetation science.The paper aims to describe the composition and distribution of shrub in the southern five islands of Miaodao Archipelago and explain the influence of environment factors on the shrub population and give the reference for vegetation recovery.Based on the investigations of shrub vegetation species and environmental factors of southern five islands of Miaodao Archipelago in Shandong Province,the relationship between eco-environmental factors and the shrub species composition as well as their population structure in the survey area was investigated by using correlation analysis,canonical correspondence analysis (CCA),and two-way indicative species analysis (TWINSPAN).The result showed that:(1)27 shrub vegetation species belonging to 15 families and 23 genera were observed during the study period in the islands.The dominant families are Leguminosae and Moraceae.The highest frequency of the species is Vitex negundo var.heterophylla,which contributed up to 66.67％ of the stations.Ziziphus jujuba var.spinosa and Grewia biloba var.parviflora were also found in more than 50％ of the stations.(2)By using TWINSPAN,the population of shrub layer were classified into six types,they are Morus alba population,Robinia pseudoacacia-Cudrania tricuspidata population,Ziziphus jujuba var.spinosa population,Grewia biloba var.parvi flora population,Vitex negundo var.heterophylla population and Amorpha fruticosa population.(3)Multivariate ordination techniques were used to analyze the effects of environment variables on the shrub community by CANOCO version 4.5.The environmental factors were analyzed,which include slope,aspect,coverage,soil water,pH,available nitrogen and available potassium,available phosphor,respectively.All of these environmental variables were ln (x+1) transformed before analysis except for pH.The results of canonical correspondence analysis (CCA) with forward selection indicates that tree coverage(F=3.19,P=0.004) and pH (F=2.01,P=0.014) were the most important environmental factors which influence shrub distribution in the southern five islands of Miaodao Archipelago during the study periods.
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万方数据
维普
