Population Ecology Of Natural Japanese Yew

The Japanese yew(Taxus cuspidata Sieb.et.Zucc.) is a survivor tertiary species and national level endangered species.Study on the natural population ecology of Japanese yew will be helpful to reveal its endangered mechanism,and it is greatly important in theory and applied values on conservation,plantation and restoration of the population effectively.This study revealed corresponding regulations about the scalar and stucture characteristics, intraspecific and interspecific competition,community characteristics,reproductive and treering characteristics of Japanese yew population.The results showed:1.Although the scalar of natural Japanese yew population in Muling Nature Reserve was pretty large,the age structure of the natural population was not optimal.The number of seedlings(76.81%) and trees(20.87%) was much more than that of saplings(2.32%),and the trees were mostly old.This kind of structure would affect the population development in the future.The scalar of Japanese yew(Taxus cuspidata) population and the relationship between individual distribution and site factors were analyzed,The result showed that the distribution rules of Japanese yew population were correlated to elevation, slope position,slope aspect and slope gradient.The optimal distribution range in elevation for the natural Japanese yew population was at the attitudes of 700-800 m.The amounts of Japanese yew individuals on shady slope were more than those on sunny slope.On top slope and mid-slope,the individual amounts of Japanese yew were more than those on toe slope.Most of Japanese yew individuals occurred on slope gradient of less than 15.The scalar of the population was decreased with the slope gradient increasing.2.The intraspecific competition of Japanese yew population was weak,accounting for 4 percent of total competition,and the main stress to the Japanese yew population came from interspecific competition,which accounted for 96 percent of the total.The main competitors were the dominant species of the zonal vegetation types,including Abies nephrolepis,Tilia amurensis,Acer mono and Pinus koraiensis.The competition intensity of Japanese yew declined with increasing DBH,and the stress was more intense for trees less than 20 cm in DBH.The relationship between competition intensity and individual growth of target trees followed the equation y = 289.03x^-1.5012.Along the site gradient such as elevation,slope gradient,slope aspect and slope position,the competition intensity and competitor type changed notably.3.Quantitative classification(Two-way Indicator Species Analysis.TWINSPAN) and ordination analysis(detrended correspondence analysis,DCA:canonical correspondence analysis,CCA ) were used to examine the ecological characteristics of Japanese yew communities.From TWINSPAN analysis,we classified the 72 plots into 4 types,that was Dryopteris crassirhizoma-Corylus mandshurica-Taxus cuspidata-Abies nephrolepis-Pinus koraiensis,Athyrium multidentatum-Corylus mandshurica-Taxus cuspidata-Abies nephrolepis-Pinus koraiensis,Hippochaete hyemale- Corylus mandshurica- Taxus cuspidata-Abies nephrolepis-Pinus koraiensis,Carex callitrichos- Corylus mandshurica-Taxus cuspidata-Abies nephrolepis-Pinus koraiensis.The DCA analysis provided us with similar results.Both classification and ordination analysis of the plots reflected the spatial distribution of shrub communities.The first axis of DCA appeared to be related to slope position and slope gradient,the second axis to the changes of elevation and aspect.The result of CCA showed,elevation,Slope location and slope gradient were three important factors restrict the distribution of Japanese yew communities,and reflected the relationships between community types and ecology factors.4.In the life history of Japanese yew population,the hearty reproduction for tree was during 20cm～60cm in DBH.The number of blooming individuals was about the same as that of unblooming individuals for sampled trees more than 10cm in DBH,the ratio of blooming female and male was near to 1:2,a male tree with 1.5cm in DBH was the youngest blooming tree.Most of female and male strobilus grew in young twigs,The quantity of female and male strobilus in crown declined downward,and the quantity of male strobilus was about 1.5～5 times than that of female strobilus.The quantity of female strobilus in east and south crown more than that of in west and south crown,the quantity of male strobilus was on the contrary.The relationship between quantity of male strobilus and DBH of male trees followed the equation:Y = 8.0021X^2.3872(R = 0.8755, P<0.001),for female trees it followed the equation:Y= 2.5892X^2.3826(R = 0.6871, P<0.001 ).1000-seed weight of Japanese yew was 45.41g～55.60g,and hardly affected by trees in DBH,slope aspect and slope position.Seed moisture content and embryo development varied in different years.Crude fat,crude protein and starch were main components in the seeds.The contents of soluble carbohydrate,crude protein and starch in Japanese yew seeds were higher than that of in Taxus mairei.The quantity of Japanese yew seeds in soil existed unnotably variance in orientation,most of them existed in the range of 1m to the female trees,and the quantity decreased with the distance increasing. The quantity of Japanese yew seeds in soil declined following the depth increasing,most of them(83.97%) existed in soil less than 5cm in depth.The most important factors affecting soil seed bank were predation by insects and animals,the proportion of the viable seeds accounted for less than 1%.5.Based on the relationship between the tree-ring data and temperature from 1961 to 2004of Muling in Heilongjiang Province,the minimum spring temperature from October of prior year to January of current year was the primary factor affecting radial growth of Japanese yew,and annual precipitation was a relative lesser factor.the minimum spring temperature was reconstructed for 300 years from 1700 to 2004 using a standard tree-ring chronology of Muling in Heilongjiang Province,the equation was Y=8.6564X-30.23(F = 20.67,P < 0.0001,r²= 0.32 ),the retrieve values matched the measured values in tendency and the extreme values basically.In the past 300 years in Muling,the minimum spring temperature existed obviously periodical change with periods of 2-4 years and 8 years,it had also longer periods of 20 years in a few series,this might be affected by ENSO,Asian Monsoon and abnormal activities of macula.