Change of plant diversity of Populus davidiana,Quercus liaotungensis and their mixed forest in Ziwuling area of Loess Plateau

QIN Juan1,WANG Kai-bo1,SHANGGUAN Zhou-ping1,2(1 State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau,Northwest A & F University,Yangling,Shaanxi 712100,China;2 Institute of Soil and Water Conservation,Chinese Academy of Science,Yangling,Shaanxi 712100,China)

Populus davidiana;Quercus liaotungensis;Populus davidiana-Quercus liaotungensis mixed forest;plant diversity;community stability;Ziwuling forest area

The plant diversity of the three types of forests:Populus davidiana,Quercus liaotungensis,and Populus davidiana-Quercus liaotungensis mixed forest in Ziwuling forest area of the Loess Plateau was studied.The results showed that in the proccss of from the vanguard community(Populus davidiana) to the climax community(Quercus liaotungensis) succession,the plant species richness index and plant diversity index assumed the drop tendency,but the mixed forest type was in the middle stage of succession,therefore its species richness index and plant diversity index was also between the two kinds of forest types,namely,Populus davidiana > Populus davidiana-Quercus liaotungensis mixed forest>Quercus liaotungensis.Each of the change of plant species richness index(Gleason index and Margalef index),and diversity index(Shannon-Wiener index) in herbage layer、shrub layer and arbor layer both assumed the drop tendency.There are little difference of pielou evenness index in the arbor layer,shrab layer and herbage layer,except in the arbor layer of cuercus liaotangensis.In the study of the plant diversity and relation of community′s stability of forest,we found an advantageous point exist between the plant diversity and stability of the forest community,namely,the plant diversity can not totally represent the stability of community,but it is an essential index to show the forest community's stability.