Research On Community And Species Diversity Of Picea Crassifolia Kon Forests In The North Slope Of Qilian Mountain

Picea crassifolia Kom,a special species in the northeast fringe of Tibet Plateau,is mainly distributed in the west of Qinghai,Gansu,Ningxia and Sichuan provinces as well as middle part of Qilian mountains.In this paper, research on the species composition,flora,community structure,distribution pattern and dynamics of Picea crassifolia Kom in Longchanghe,Xishui,Mati, Xiyinghe,Haxi and Chnaglingshan in the north slope of Oianlian mountain was made.Based on the survey concerning 256 samples conducted in 16 sample sites in the 6 forestry areas of Qilian mountains,the species diversity,community structure,relationship among different species of Picea crassifolia Kom forests are analyzed.It is recorded that there are 96 species of vascular plants in the Picea crassifolia Kom community,which belong to 25 families and 51 genuses,including 4 species of arbor,29 species of bush and 62 species of herb plants.Temperate plants,with 31 families and 59 species,the dominate species,which shows the close relationship between Picea crassifolia Kom community and temperate species.The dominate species includes:Picea crassifolia Kom,Dasiphora fruticosa Rydb,Dasiphora dahurica(Nertl)kon.et Klob-Alis,Polygonum viviparum L.,Carex Lanceolata Boott,Pedicularis muscicola Mcisn,etc.The result reveals:a -diversity index changes slightly in the area between 2470m-2800m high altitude,however,it takes a tendency of increasing firstly and then decreasing with the increasing of elevation. And there is obvious vertical change;generally it can be divided into 4 layers: arbor layer,bush layer,herb layer and moss layer.The result shows that the succession relationship of Pinus tabulaeformis-Picea creassifdia mixed forest, Populus dvidana-Picea creassifdia mixed forest,herb-Picea creassifdia mixed forest,moss-Picea creassifdia mixed forest,shurb-Picea creassifdia mixed forest,Pedicularis-Picea creassifdia mixed forest,Sabina przewalskii-Picea creassifdia mixed forest is:the richness indexes from high to low is the mixed forest of Pices crassifolia Kom＞Pedicularis-Picea creassifdia mixed forest＞grass- Picea creassifdia mixed forest＞shurb- Picea creassifdia mixed forest＞moss-Picea creassifdia mixed forest;and Margalef index from high to low is the mixed forest of Picea crassifolia Kom＞Pedicularis- Picea creassifdiamixed forest＞grass-Picea creassifdia mixed forest＞shurb-Picea creassifdia mixed forest＞moss-Picea creassifdia mixed forest.There are big differences among different types of mixed forests concerning vertical structure,species inter-relationship,spatial distribution pattern and community structure.