Study On Conservation Biology And Restoration Technique Of The Relict Plant Glyptostrobus Pensilis

Glyptostrobus pensilis(Staunt.)Koch,now unique in the Glyptostrobus,is at the risk of becoming extinct in the wild.It has been listed as a first-class threatened plant species,one of handful species of highest conservation concern in China.As a living fossil plant,G. pensilis was widely distributed in the Northern Hemisphere.After the Quaternary glaciation,because of natural geographical factors and human activities,majority populations have extincted except Southeast China.G. pensilis has important scientific value in many research fields such as the phylogenesis of family Taxodiaceae,paleobotany and the Quaternary glacial climate.Dues to the climatic change,human interference,habitat destruction,succession pressure and other factors,the distribution range of G. pensilis is still shrinking and become isolated and scattered.The population size are decreasing sharply,G. pensilis is in danger of extinction.How to protect rare gene resources,and expand population size of G. pensilis becomes an urgency matter.Therefor,research on conservation biology and recovery assessment of G. pensilis aims to provide necessary data for the establishment of scientific and effective conservation strategy for this endangered species.This study focus on nature geographic distribution,population quantitative characteristics,genetic diversity and cutting propagation technique of G. pensilis systematically and comprehensively from the views of population ecology,reproductive ecology and conservation genetics.Research on population ecology and quantitative characteristics could reveal population structure,dynamic law and trends of evolution of G. pensilis.ISSR markers was used to detect genetic diversity and genetic composition of wild and artificial G. pensilis populations to compare the differences of genetic diversity and genetic structure between wild and artificial G. pensilis populations,evaluate recovery genetic consequences of G. pensilis.The seedling growth rule was discussed through experiment of sowing,and the cuttage propagation techniques of G. pensilis was also explored by testing various factors.The endangered mechanism of G. pensilis was discussed and some suggestions on species recovery and conservation strategies were provided.The conclusions are as follows:(1)The relationship between geographical distribution and climate factors was discussed using relation index of vegetation and climate.In China,G. pensilis was disconnectedly distributed in Pearl River delta,the middle and lower reaches of Changjiang River and Minjiang River.It mainly distributed in north latitude 13°21'～37°36' and longitude 102°40'～121°29',in the altitude ranged from 25 m to 2000 m.It requires moist but well drained soil and a warm,sunny position,where annual mean temperature varied from 12.10℃～22.60℃,the annual mean precipitation varied from1199.60 mm～2231.00 mm,the annual mean relative humidity varied from 62.00%～82.00% and the annual average sunshine hours varied from 1589.20 h～2781.60 h.Low temperature,humidity,high temperature,sunlight and precipitation were the most important factors that affect the distribution of G. pensilis.(2)By using the principles and methods of population ecology,the population structure and dynamic law of G. pensilis were analyzed.Several aspects were discussed about the wild populations.â‘ Five probability models were applied to analyze the structure features on diameter distribution of main tree populations in G. pensilis forest.The results showed that normal distribution model was the best fitness to express the structure of diameter distributions of G. pensilis population,which suggested that the range of diameter distributions were wider and the number of mid-size wood was in the majority.The fitting effect of Weibull distribution model,Γdistribution model and lognormal distribution model were not so perfect.There was obvious linear relationship between the parameters of normal distribution and tree diameter,and the model was effective by using forest characters to forecast the parameter values of normal distribution.â‘¡The population age structure characteristic of G. pensilis was studied using space for time method.The result showed that populations had opposite pyramid age structure,which had abundant old trees,relatively few seedlings and young trees.The age structure of G. pensilis in the community was declining,and ability to resist disturbance and regenerate was weak.Biological characteristics and habitat conditions were the critical elements for the age structure of G. pensilis.â‘¢In order to determine the population state of G. pensilis,analyze its past population structure and pre-disturbance situation and forecast its future population dynamics,the population life table were analyzed by space deducing time method.The static life table,survivorship curve,mortality rate curve and danger rate were compiled using the diameter at breast height class to represent the age class structure and smooth out technique.The survival cure of the population belonged to the type of Deevey-â…¢,and the dynamics trend showed that the mortality rate of population was high in early age,while the accumulative mortality and livability had emerged after the former high-low trend.The death density function had emerged high on edges and low in the center.â‘£Spectral analysis of the population dynamics was made to revel the renewal process and stability of G. pensilis.The natural renewal process of G. pensilis population could be represented by the fluctuation of trees number distribution in different age grades . The natural renewal of G. pensilis indicated harmonics superposition characteristics,which large cycle contains small cycle.Minor cycle was coincident with the periodic fluctuation of annual growth of G. pensilis.⑤The spatial distribution pattern of G. pensilis population was determined using for aggregate indices and Iwao's equation,and the causes of the evolved pattern was also determined.The results showed that the spatial distribution of G. pensilis population presented an aggregating distribution,and the degree of diffusion was related to the different habitats.The effects of different scales showed the highest aggregating intensity when quadrat was 25 m².â‘¥The growth law of basic area of G. pensilis population was studied by the methods of Logistic model.And a new model was optimized from the modified simplex method.The optimized results showed that the Hong-Logistic model was more suitable than other models to simulate the actual growth trend of G. pensilis population.The residual sum of squares was 1.7831,and the intrinsic growth rate was 0.7604,and the Tr value was 1.3116 diameter class year.The highest growth rate of basal area was the eighth age classes,namely the phase when breast diameter was 48～54 cm,and the basal area reached 58.1991 m²/hm².It was thus clear that the growth of G. pensilis population was retarded,and it needed long time to recover after suffering damages.⑦The competition of G. pensilis and its associated species were discussed with the Lotka-Volterrra equation.The result showed that dominant degree of G. pensilis and its associated species was 63396 cm²Â·hm^-2 and 15877 cm²Â·hm^-2,respectively.Interspecific competition modulus was 0.8231 by calculating importance value.The relative dominant degree of G. pensilis and associated species was 69.21% and 30.79% respectively when reaching their balance.The mixed trees could jointly dominate this community,and the whole community was controlled by G. pensilis population.But the number of G. pensilis would be constantly decline.⑧The method of R-cluster analysis was used to analyze the 25 quantitative traits cluster of G. pensilis population and the interaction of the quantitative traits.The quantitative traits'infection to growth,heredity and economic character of G. pensilis were also discussed.The results showed that the volume and tree height,crown length,diameter at breast height were significantly correlated.The growth traits were correlate with photosynthesis area,and tree height was the first element of volume,and the heredity was stable in tree shape and self-pruning.⑨The DBH and tree height mean growth of G. pensilis from different provenances were studied by combining geographical statistical methods with fractal theory.The fractal dimensions of DBH and tree height growth of G. pensilis were calculated in order to revealed the rule of spatial distribution variation.The results showed that the fractal dimensions of DBH and tree height were 1.635 and 1.824, respectively.The fractal dimensions of DBH was lower than fractal dimensions of tree height.The diameter breast height should be selected as evaluating indicator of different provenances.Several aspects were discussed about artificial population.â‘ Five probability models were applied to analysis the structure feature on chest height diameter distribution of G. pensilis-aged and pure plantation.The results showed that the majority were middle and small diameter class.The population was currently in the primary stage of forest development,the symmetrical distribution of diameter change within a certain range.Weibull distribution model was the best fitting model for the smaller error probability and more accurate fitting.The eigenvalue such as coefficient of variation,skewness,kurtosis consistent with the characteristics of the artificial aged and pure plantation.The artificial population embodied special law on diameter distribution compared to natural populations.It showed that the populations different in communities,density,average diameter and growth phase had differences in diameter struture feature.â‘¡The interrelated relation between competitive index and growth of breast-height diameter was analyzed with method of regression analysis.The competitive index reflecting objectively the competition and growth pattern of G. pensilis plantation was selected,and stand growing models were established.The results showed that the relationship between diameter growth and distance was very weak,the main key elements composing competition index were relative tree height,relative crown and rate of crown length.The individual tree growing models can fitting the grow rule of G. pensilis accurately.The factors such as average height,average breast diameter,growing stock of sub-compartment and basal area would be estimated by using the growth model and estimation methods.â‘¢The self thinning model of G. pensilis population was studied by regression analysis.The relationship between total stand basal area and population density,and the relationship between singleplant volume and population density were also studied.The accuracy of models were significantly high and had a good prospect in plantation management density control.â‘£In order to forecast accurately height of each diameter class of G. pensilis,the height-diameter model was established.The Weibull function was chosen to develop height-diameter models.By verified,this equation might be applied to estimate the tree height growth of G. pensilis.⑤The community stability of G. pensilis was discussed and conservation strategy was suggested according to the protection status of G. pensilis artificial population in Doumen.(3)Samples from the main distribution regions of G. pensilis were analyzed by ISSR(Inter simple sequence repeats)molecular marker.10 ISSR primers were used to amplify 136 individuals of 8 populations,a total of 95 discernible DNA fragments were detected.Of these,37(P = 38.95%)were polymorphic loci , which indicated that very low level of genetic variation existed in the populations.The difference of the genetic diversity among all the populations was evident.The percentage of polymorphic loci(P),Nei's gene index(He)and Shannon information index(I)were 33.56%,0.1078 and 0.1902,while those at the species level averaged 38.95%,0.1608 and 0.2360,respectively.Moreover,the genetic differential index(G_ST = 0. 3982)indicated that there was strong genetic differentiation among populations.The dendrograms of genetic relationships among populations was constructed based on Nei's genetic distance.The mean genetic parameters of wild populations(P = 39.92%,He = 0.1499,I = 0.2202)were much higher than artificial populations(P = 26.98%,He = 0.1113,I = 0.1558).Coefficient of gene differentiation and genetic distance of wild populations(G_ST = 0.4513,D = 0.0301)were much higher than artificial populations(G_ST = 0.2836,D = 0.0192).The change of genetic diversity had obvious positive correlation with population age and elevation in specific limit.The results indicated that although the quantity has been successfully restored,the genetic diversity and genetic structure of G. pensilis have not recovered appropriately,given the loss of genetic variation and low genetic diversity in artificial populations.The combined results of the analysis of population genetic structure and community investigation suggested that establishing a conservation spot in the optimal habitat of G. pensilis,and to cross-transplant adult plants or seedlings mutually among populations in order to enhance the gene flow.By these means,the genetic diversity resources of the species can be preserved to the greatest extent.(4)The cuttage propagation techniques of G. pensilis was explored by testing various factors including hormone types,soaking time,medium and concentrations and cuttings.The best way for cottage of G. pensilis was that cuttings came from the top part of 1-years-old branch,cuttings soaked in ATB1 150 mg/L solution for 2 h before inserting in the medium with combination of peat∶pearlite = 2∶1,spacing 3 cm×4 cm.The depth of the cutting insert for 3～4 centimeters distance to the top.Water the cuttings in time and keep sunshine resistant,antisepsis,sterilization and so on.The rooting ratio of cutting under these treatments above could reach 39.89%.The tree height and ground diameter growth rhythms of G. pensilis sowing seedling were fitted using Logistic equation to study seedling growth rule.The correlation coefficients was above 0.95.The seedling growth pattern displayed"S"curves for height while ground diameter growth had positive correlation with height. (5)The endangered characteristics,ecological suitability and endangered mechanism of G. pensilis was discussed after macroscopic and microscopic analysis.It was the process of temporal and spatial change and had been resulted from different factors.On the surface,the habitat fragmentation that human activities caused and deforestation was important factors threatened this species.Essentially,it resulted from the comprehensive effects of human activities and natural factors,such as drastic climate changes , low genetic diversity , habitat destruction , ecological stress factors and species competition.The endangered reasons of G. pensilis indicated that species conservation was a complex and systematic project.It should consider all the various factors to carry out the relevant protection and population recovery of G. pensilis systematically and comprehensively.