Conservation Biology Of Erythrophleum Fordii Oliv., A Rare And Endangered Tree Species In South China

Erythrophleum fordii O. is a valuable broad-leaved timber species with medical and ecological values in tropical and sub-tropical zones in south China. The natural forest of this species has been heavily destroyed due mostly to long-term over-exploitation and utilization, and alteration to croplands and fast-growing plantations. The species has thus been listed as of national second key protected plants, and been included in the IUCN Red List of Endangered Species as the endangered species. Here its natural geographical distribution, environmental properties for its suitable sites,and current status of its conservation were surveyed in south China; Its population structure and dynamics and their variation along altitude were studied in a large area of natural forests in Wuming County, Guangxi; Damage characteristics of a shoot borer in E. fordii plantations were investigated so as to follow the effects of this pest on conservation of this tree species; Germplasm resources were collected and phenotypic variation of fruite and seed, and their offspring seedlings were measured as well as genetic diversity and population genetic structure were estimated using SSR makers; Plantations were established using collected germplasm resources and their growth were investigated for purposes of ex situ conservation and breeding at two sites in Guangdong and Guangxi, respectively. Endangered status and mechanism and potential way for conservation of E. fordii were discussed at two aspects of population ecology and population genetics. The findings will provide evidences and basic data for making conservation and breeding strategy of this species. The main results were as follows:1. E. fordii was mainly distributed in Guangdong, Guangxi, Fujian and Taiwan Provinces in China, ranging from 24°N to south with altitude under 600m. The species grows mostly at the lower parts of mountains or hills, and human disturbances such as illegal logging, large-scale alteration into croplands and fast-growing plantations resulted in severe fragmentation of its natural forests and habitats. 2. Distributing pattern of seed and individual are cluster in E. fordii natural populations,population were regenerated by seeds and sprouts,but extended population were depend on seed spread. population age structure and dynamic were done by static life tab., seedlings and sapling was mass,but which have higher mortality rate,Survival numbers and mortality rates were descended in young and mature stages,following age increased, survival rate, mortality density,hazard rate were decline,but cumulative mortality rate ascend. so E. fordii population survive-shape curve remain with Deevey survive-shapeⅢtype.3. As surveyed on a slope of Wuming County, Guangxi, frequency and density of E. fordii in plots increased and then slightly decreased with the increasement of altitude. Similar to this was the way that soil chemical properties varied along with altitude. Population dynamics analysis showed that populations developed differently at all sorts of altitudes, populations at middle and upgrade altitude belonged to growing populations (plotⅠ,Ⅱ,Ⅲ;V_pi>0,V′_pi>0), while populations at low altitude to declining populations (plotⅣ,Ⅴ; V_pi<0,V′_pii<0).4. Shoot borer attack is one of main factors that poorly influence natural regeneration and even population maintanance, and survival and early growth performances of plantations of this species. It occurs very often in natural forests as well as plantations of E. fordii. In the present studies, the shoot borer was identified as Cryptophlebia ombrodelta L. at the first time. As investigated in germplasm resources conservation pools and coppice plantations of this species, the pest could harm above 90% of buds and tender branchs, even petiole at tree top. The damaged trees were distributed in cluster pattern within plots. The occurrence of insect damage was preliminarily concluded, and relationship between insect attack and site condition need be further studied.5. Phenotypic variation of seeds and pods in 8 natural populations,and seed germination and seedling growth of progenies from 6 natural populations were analyzed,the results showed that there were abundant variations of phenotypic traits of seeds, pods and seedlings within and among populations, and significant differences among populations. Variation of pod traits among populations was higher than that of seeds, variation of seedling height among populations was higher than that of stem collar diameter, and seedling performance was remarkably correlated with seed size and seed mass. Pod morphology was in significantly negative correlation to longitude, seed mass positive to latitude, and seedling collar diameter and height negative to mean annual rainfall and altitude, respectively. These indicated that temperature was the main factor that restricted the natural distribution of E. fordii.6. Genetic diversity and structure of E. fordii were analyzed using SSR markers in nine populations. Five polymorphic loci were obtained with totally 34 alleles,among which seven were private alleles, and one or two common alleles per locus. The mean number of alleles per locus(A), the mean number of efficient alleles per locus(Ae), the expected and observed heterozygosities,Shannon index(I) were 3.9, 2.50, 0.5313, 0.5783 and 1.0088, respectively. F_IS was on average 0.0349, most loci were on Hardy-Weinberg equilibrium in the nine populations. F_ST was 0.1792, which was indicated that there existed 17.92% genetic variation among populations. Gene flow between populations (Nm) was 1.1452, and significant differentiation occurred among populations. And correlation between genetical and geographical distance was not significant by Mantel test (P>0.05).7. Two plantations were established for ex situ conservation and utilization of germplasm resources of E. fordii in Guangdong and Guangxi, respectively. Earlier evaluation were conducted according to their growth performance of height and collar diameter, and damage rate by shoot borer. There were more variation within than among populations,in accordance to results at DNA level. Through two-year observations, the gerplasm resource pool were preliminarily proved to be well established, and progenies from two populations grew better, which should be further proved. And from the findings of phenotypic and SSR variations it was indicated that more populations and as many families as possible in each population should be collected for ex situ conservation of germplasm resources of this species in the future.