Study On Community Structure And Photosynthetic Characteristics Of Taxus Chinensis Var.Mairei Of Lingchuan In Shanxi

Taxus chinensis var.mairei is an important resource plant for ornamental,medicinal and medicinal purposes,Its taxol is the most abundant plant of anti-cancer drugs in the world.In recent years,the existing species quantity is less and less,has been in an endangered state,was listed as a national rare and endangered plants.Shanxi is the most northern part of Taxus chinensis var.mairei in China.Through the study on the species diversity,main niche and main species associations of Taxus chinensis var.mairei community in Lingchuan,Shanxi,to understand community structure,correlation of species,main position of species and utilization of resources in Taxus chinensis var.mairei community.In addition,by studying the diurnal and seasonal changes of photosynthetic physiological characteristics of Taxus chinensis var.mairei,we learn more the photosynthetic characteristics and ecological factors of affecting its growth.The results of this study will provide the theoretical basis for the protection and breeding of the endangered plant Taxus chinensis var.mairei in natural forests of Taxus chinensis var.mairei national nature in Shanxi.The main findings are as follows:1.Using the richness indices,diversity indices and evenness indices,we studied the species diversity of Taxus chinensis var.mairei community of the Lingchuan,in Shanxi.The results showed that:(1)The 30 communities were classified into 9 associations by TWINSPAN.(2)In vertical structure,the richness index and species diversity index in various synusiae were in order of shrub layer>herb layer>tree layer.(3)Species diversity of Taxus chinensis var.mairei community is affected by habitat conditions and human disturbance.2.By using the formulas of Levins niche breadth,Pianka niche overlap and the niche similarity,we analyzed the niche characteristics of 25 main species of Taxus chinensis var.mairei community of the Lingchuan,in Shanxi.The results showed that:(1)The 25 main species of Taxus chinensi var.mairei community of the Lingchuan in Shanxi,the niche breadth of Carpinus turczaninowii(1.464),Carex spp.(1.450)and Taxus chinensis var.mairei(1.400)were more greater,Epimedium brevicornu(0.049),Callicarpa jaonica var.angu(0.862)and Clerodendrum trichotomum(0.862)were more smaller.(2)The niche overlap among the 25 main species occurred generally,the species having overlap degree being higher than 0.4 reached 186,accounting for 62% of total pairs,suggesting the strong competition between species.(3)The species with niche similarity proportion above 0.4 reached 156,accounting for 52 % in total,indicating that main species had a higher similarity proportion in resource utilization.(4)The main species in the community with larger niche breadth had stronger competitiveness,and the environment and resource utilization ability was stronger,and had greater niche overlap and niche similarity proportion with other populations.3.This paper studied the interspecific relationships among the 300 kinds of species in the 25 main species of Taxus chinensis var.mairei community by using quantitative analysis methods ?2 test,Pearson correlation coefficient and Spearman rank in Lingchuan Nature Reserve in Shanxi.And the detrended correspondence analysis sorting method was used to carry out the division of ecological species groups(ESG)of main species.The results showed that(1)the number of negatively correlated pairs was greater than that of the positively correlated pairs for the main species of Taxus chinensis var.mairei community.This result indicated that interspecific relationships of main species of Taxus chinensis var.mairei community in Lingchuan Nature Reserve did not reach significant levels.(2)The correlation in most species in Taxus chinensis var.mairei community did not reach a significant level and the independence in species is relatively strong,which may be related to the habitat heterogeneity,different biological characteristics of the species and ecological needs.(3)According to the adapting methods the 25 main populations in Taxus chinensis var.mairei community and the leading ecological factors of assisting in DCA sequence,it can be classified into three ecological species groups.4.The photosynthetic characteristics and main influential factors of Taxus chinensis var.mairei seedlings were systematically studied by using the Li-6400 portable photosynthesis system in this paper.The main results were as follows:(1)The net photosynthetic rate(Pn)of Taxus chinensis var.mairei has obvious diurnal and seasonal change.In spring and summer,the diurnal variations of net photosynthetic rates(Pn)of Taxus chinensis var.mairei are all “twin-peaked”,with obvious”midday-depression”of photosynthesis.In autumn and winter,the diurnal variations of net photosynthetic rates(Pn)of Taxus chinensis var.mairei are all ”unimodal-peaked”.(2)The light compensate point(LCP)of Taxus chinensis var.mairei was 11.7 ?mol/m2·s,and the light saturate point(LSP)was 522 ?mol/m2·s.They are very low,indicating that these seedlings required shade condition.(3)By the relative analysis and stepwise multiple regression of net photosynthetic rate and other main physiological-ecological factors in different season,it was found that Pn had the obvious relationship with Cond,Trmmol,and Ci.The main factors influencing net photosynthetic rate(Pn)of stomatal conductance,the second is transpiration rate.