Research On Phenotypic Traits Of Germplasm Resources And Superior Tree Selection Of Quercus Gilva

Quercus gilva is an evergreen tree of Quercus section Cyclobalanopsis(Fagaceae).Its hard and well-textured heartwood provides quality materials for high-end furniture and fine artware production.Besides,this deep-rooted tree species provides essential ecological services,including water conservation and soil protection.In addition,its seeds are rich in starch,which can be utilized as an economic tree species.Q.gilva has been therefore considered to be ecologically,economically,and ornamentally valuable in subtropical China.However,the once widespread Q.gilva populations have greatly diminished as a consequence of human disturbance.It is desperately needed to better protect and utilize natural germplasm resources of Q.gilva.Therefore,in order to effectively protect and utilize Q.gilva genetic resources,we carried out this study from three aspects:investigating the characteristics of natural Q.gilva communities,studying the phenotypic diversity of Q.gilva,and building a comprehensive evaluation system for superior trees of Q.gilva.The main results are as follows:(1)The characteristics of natural community of Q.gilva:Through the investigation of the characteristics of Q.gilva communities in Jiangxi Wuyuan,Hunan Longshan,and Fujian Jianou,we found that dicotyledonous plants were dominant in three Q.gilva natural communities.The seed plants in the investigated natural communities mainly belonged to tropical and temperate distribution types,which was consistent with the fact that Q.gilva mostly distributed in middle subtropical China.The analysis of size-class of Q.gilva and other dominant species revealed that there were difficulties in the natural regeneration of Q.gilva in Jiangxi Wuyuan and Fujian Jianou communities.The Margalef species richness index,Shannon-Wiener diversity index,and Pielou evenness index in three Q.gilva communities were herb layer>shrub layer>tree layer.(2)The phenotypic diversity of Q.gilva natural populations:Fifteen growth and leaf traits of 115 individuals from 14 natural populations were measured and then the phenotypic diversity and variation pattern were studied.Results showed that the average variation coefficient and the average Shannon-Wiener index of 15 phenotypic traits were 35.07%and 1.998,respectively.Variation coefficient and Shannon-Wiener index of 14 populations ranged from 14.94%(Dongkou)to 35.56%(Longshan)and from 1.127(Songyang)to 1.980(Changning),respectively.These results indicated that Q.gilva showed a relatively high level of phenotypic diversity.Significant differences in 15 phenotypic traits were found among and within populations(P<0.01),with an average phenotypic differentiation coefficient of 41.49%.This elucidated that the phenotypic variation within populations was greater than that among populations.Correlation analysis showed that there were significant correlations among parts of the traits,whereas no correlation was found between phenotypic traits and geographic factors.Precipitation was the major factor that influenced the phenotypic traits of Q.gilva.Principle component analysis indicated that the first four principal components explained 82.96%of total phenotypic variation of Q.gilva.Cluster analysis revealed that 14 Q.gilva populations were divided into three groups according to their different leaf and petiole size,which was not related to the geographic distribution of populations.(3)Comprehensive evaluation system for superior trees of Q.gilva:Firstly,68 individuals with similar age,straight trunk,vigorous growth,and no obvious diseases were selected from 115 investigated Q.gilva individuals.Fifteen phenotypic traits as the main indices were measured from 68 individuals and then were comprehensively analyzed to screen out the core evaluation indices.Through principal component analysis,weight analysis,and stepwise regression analysis,the comprehensive evaluation formula of Q.gilva superior trees was obtained:Y=-1.310*10-7+0.044X1+0.097X2+0.063X3+0.071X5+0.088X6+0.146X9+0.156X11+0.226X13(R2=0.99,P<0.01).In the equation,Y refers to the final score of Q.gilva superior trees,the core indicators X1,X2,X3,X5,X6,X9,X11,and X13 are tree height,diameter at breast height,volume,crown diameter,leaf length,leaf area,petiole length,and petiole area,respectively.Finally,35 superior trees of Q.gilva were selected.