Comparative Study On Effects Of Undergrowth Vegetation Diversity Of Eucalyptus Grandis×E. Urophylla And Castanopsis Hystri Plantations In Guangxi Qinlian Forestry Farm

The plantations especially the large-scale development of eucalyptus plantations have re suit in a series of environmental issues that cause widespread public concern in the communi ty and also touches off a controversy over the development of eucalyptus.At present,local g overnments and forest farms have begun to adjust the structure of the afforestation tree speci es in order to ease the dispute.However the effects on plant species diversity caused by Euca lyptus plantation is one of the main environmental issues.In this paper,compared to the orig inal Pinus massoniana plantation before afforestation,we intend to show a comparative stud y on the effects on the biological diversity of undergrowth plants caused by Eucalyptus grandis×E.urophyllaand Castanopsis hystri plantation in State-owned Forest Farm of Qingli ang Guangxi,by using a method of replacing time with space.The main researches are as fol lows:(1)Compared with the original Pinus "massoiniana plantation after 6 years of afforestation,the number of understory plant species has been increase both in the forests of Eucalyptus urophylla plantation and Castanopsis hystri plantation.Especially the number of herbaceous species has significant increase,but the increase of woody plants is not obvious.A further analysis of the composition of the dominant plants in the understory shows that the construction in Eucalyptus urophylla plantation and Castanopsis hystri plantations both decrease the dominant of some woody plants but increase herbaceous plants domination in the original Pinus massoniana plantation.(2)Eucalyptus grandis×E.urophylla plantation and Castanopsis hystri plantations change the dominant species of understories in the original Pinus massoniana forest.The important value of the main dominant species has been obviously changed in the original Pinus massoniana.The oringinal dominant species are replaced by the drought-resistant plants and some dominant species even disappear.(3)Conpared to the species in the original Pinus massoniana plantation,the species rich ness has slightly increase in the shrub layer of Eucalyptus grandis×E.urophylla pla ntation(6 species more)and Castanopsis hystri plantation increased(4 species more),but ha s obvious increase in the herbaceous layer,8 more in Eucalyptus grandis×E.urophylla and 13 more in red vertebrate.Similarly,whether it is the Shannon-Wiener diversity index(H')o r the Simpson dominance index(D),the index of Eucalyptus grandis×E.urophylla plantatio n and Castanopsis hystri plantations both increase more than the oringinal Pinus massonian a plantations.However the change of diversity of shrub layer is not obvious,but the herbace ous layer diversity is changed significantly.(4)Eucalyptus grandis×E.urophylla plantation and Castanopsis hystri plantation both have impact on the diversity of understory plants but the effect of Eucalyptus grandis×E.urophylla plantation is more significant than red cone plantation.