| Plantations are one of the most important components of forest ecosystems.To solve the existing forest resource problems and environmental problems,it is necessary to vigorously develop plantations and increase the plantation area on the one hand,and improve the breeding quality of plantations on the other hand.In recent years,with the concept of sustainable management of plantations,a large number of individual trees with excellent characteristics in plantations have received the attention of breeders.While establishing breeding strategies,accurate and high-throughput access to phenotypic characteristics of trees is an important prerequisite for improving the breeding quality of plantations and maintaining the long-term productivity of plantations.Traditional phenotype acquisition methods have limitations of being labor-intensive,destructive,and time-consuming and are usually inefficient to meet the needs of large-scale work.Terrestrial Laser Scanning(TLS)can obtain fine three-dimensional structural information of forests and perform the non-destructive measurement of individual tree trunk profiles and tree branch structures,providing accurate and efficient technical ways to obtain structural characteristics of forest tree growth,which is of great significance to realize the selection and breeding of superior ginkgo species and gene mining.Meanwhile,the genetic diversity of forest trees is also an important issue that must be considered in plantation breeding,especially for plantations without seed source information.In China,there are a large number of plantations without seed source information,and if breeding materials are selected only based on phenotypes while the genetic background is unknown,it will affect the level of genetic diversity of the breeding population.Studying the genetic diversity of plantations and revealing the population’s genetic structure is an important theoretical and technical basis for formulating strategies to improve the utilization of plantations and guiding the scientific management of plantation resources.Ginkgo biloba,which is resistant to diseases and pests,has a beautiful tree appearance and has yellow leaves in autumn and green leaves in spring.It is a valuable ornamental and timber species,commonly cultivated in the world,and is also one of the most important plantation species in China.This study was conducted in a ginkgo timber plantation without seed source information.We used Simple Sequence Repeats(SSR)molecular markers for analyzing the genetic background and extracting growth structural characteristics based on high-density point clouds(obtained by TLS),aiming to explore the possibility of applying remote sensing technology in the forest breeding process.First,this study used SSR markers to analyze the genetic diversity and population structure of 102 individual trees in the Ginkgo biloba plantation and grouped the trees according to genetic distance.Then,individual tree growth structural characteristics were extracted separately:tree height,diameter at breast height,crown width,crown area,crown volume,height to living crown,trunk volume,Biomass of all components(leaf biomass,branch biomass,stem biomass,aboveground biomass,root biomass,and whole plant biomass).Principle Component Analysis(PCA)was used to evaluate the growth structural characteristics of the trees in each genetic group and to select the trees with the best growth structural characteristics.This study provides guidance for the scientific management of plantations and technical and methodological support for the sustainable management of plantations,precise cultivation of forests,and acceleration of the forest breeding process.The results of the study indicate that:(1)The results of genetic diversity and population structure analysis showed that the screened 14 pairs of SSR primers amplified 114 alleles,and the average effective number of alleles(Ne)of the population was 4.76,the average observed heterozygosity(Ho)was 0.477,the average expected heterozygosity(He)was 0.749,the average Shannon’s information index(I)was 1.672,and the average polymorphism information content index(PIC)was 1.672.The observed heterozygosity of all 12 loci was lower than the expected heterozygosity,and most loci in the population deviated significantly from the Hardy-Weinberg equilibrium(HWE).Based on the genetic distance matrix,a Neighbour-joining(NJ)dendrogram was drawn,and the 102 samples could be divided into three populations,and the three populations could be further divided into six subpopulations.The individual trees G311,G724,and G115 were clustered into one group,which were more distantly related to the remaining individual trees.The result of Bayesian clustering algorithm was consistent with the NJ dendrogram result,and the population structure showed that no individual tree was 100%from one group,and there were large genetic differences among different individual trees.(2)The results of individual tree growth structural characteristic extraction showed that TLS point cloud data could be used for non-destructive estimation of individual tree growth structural characteristics.Based on the accurate individual tree segmentation results,the field measured height and Li DAR estimated height have a good consistency.TLS extracted height of individual trees from three genetic groups with high accuracy(Adj-R~2 ranging from 0.80 to1.00,RMSE ranging from 0.07 to 0.69m,and r RMSE ranging from 0.82%to 9.19%%);the same for diameter at breast height(Adj-R~2 ranging from 0.83 to 0.99,RMSE ranging from 0.76to 1.19cm and r RMSE ranging from 5.19%to 9.48%).Meanwhile,the quantitative structure model(QSM)reconstruction based on TLS point cloud could fit the individual tree morphology well.According to the statistical analysis,there were considerable differences in the growth structural characteristics of individual trees in this plantation,especially in crown width,crown volume,trunk volume,and biomass of all components.All growth structural characteristics were positively correlated with each other,including biomass of all components.And diameter at breast height was all significantly positively correlated with biomass of all components,thus diameter at breast height has great potential for estimating biomass of all components.(3)A total of 11 individual trees with excellent growth structure were selected from 102 individual trees in three genetic groups.In Group 1,comprehensive scores of the selected individual trees were G115(625.772);In Group 2,comprehensive scores of the selected individual trees were G135(453.014),G132(417.009),and G111(388.172),respectively.In Group 3,comprehensive scores of the selected individual trees were G334(323.253),G122(267.457),G138(263.639),G415(260.405),G231(256.858),G534(255.062),G1110(252.367). |
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