The Phenological Dynamics Of The Plant Species With Extremely Small Populations Ostrya Rehderiana

As one of the Plant Species with Extremely Small Populations,Ostrya rehderiana is distributed only in the Western Tianmu Mountain Zhejiang Province.At present,there are only 5 wild individuals.The branching pattern,phenological dynamics and biomass allocation of O.rehderiana,including its seedlings,the planted individuals and the natural individuals,are studied in the paper by field observation and indoor detection.The results are as follows:The overall bifurcation ratio,the stepwise bifurcation ratio,the branch length(from the first order to the third order)and he branch angle(from the first order to the third order)of O.rehderiana seedlings are higher than those of adults.Comparied to the planted individuals and natural individuals,O.rehderiana seedlings show the different growth strategy.Both natural and planted individual's branch length have an increasing trend with the increasing in the branch grade.The bifurcation ratio of the planted individuals(especially the upper canopy)is higher than that of the natural individuals,the ratio of the branches with leaves in the planted individuals is also higher than that in the natural individuals.Meanwhile,the branch length of the planted individuals show increasing trendence from the upper canopy to the lower canopy.There is a certain transformation relationship between the branch angle and branch length.The leaves dynamic of O.rehderiana also observed in the paper.The results suggest O.rehderiana leaves emerge in March and fall after October,all withered in early December.The mixed buds are germinated in June,which sprout into branches,leaves and inflorescences from late February to early March in the next year.The male inflorescences appeared in June,which will bloom in the early or middle March of the next year and pollinate to the newly-born female inflorescences.The female inflorescences appeared earlier than male inflorescences in current year,but its flowering period is relatively short.The number of modules in the upper canopy,including bud,leaf inflorescence and fruit,generally are higher than those in lowe canopy,on the other side,the number of modules in the planted individuals are also higher than those in the natural individuals.In the early growing season,there is a significant negative correlation between leaf mass per area and leaf area,but there is no significant correlationbetween them with the leaves development.The biomass allocation of the branches in one four-branch system increase with the increasing in the branch grade,othersie,the biomass allocation of the branches show no obvious difference between the first order branchs and the second order branchs.their biomass allocation are about 10%,and their coefficient of variation are low,too.Whithin one four-branch system,the biomass allocation of leaves are the largest among the different modules,which occupied nearly 50% of the biomass and its coefficient of variation are relatively low and stable in summer.However,The reproductive allocation of O.rehderiana is very low comapring to the other modules.The lower fruits number of O.rehderiana is key factor limting its population generation and distrbution in nature.