Population Dynamics And Community Diversity Of Emmenopterys Henryi In Primary And Secondary Forest

Emmenopterys henryi Oliv.,native to China,is a tertiary relict tree species.It is the only extant species of the monotypic genus Emmenopterys,Currently it is distributed in 16 provinces in China.However,most ofthe populations of E.henryi are small,and the majority of them are scattered in the remote mountainous areas.Under the influence of human activities,there are different types of E.henryi community habitats in the wild,which can be divided into two categories.One is the secondary forest disturbed by certain human activities and the other is the primary forest with no or little human interference.According to the second key protected wild plant resources survey,there are several wild populations of E.henryi in the mountainous area of Liyang,Jiangsu.Suffered from severe artificial deforestation in 1990s,the community where these populations occur is considered as secondary forest.Meanwhile,a mass of wild populations of E.henryi is found in the mountainous area of Chun'an,Zhejiang.Because of the scarcity of population,the steep terrain and high altitude,these populations have been subject to little human interference in the past several decades.Accordingly,their communities are preserved better than those from Liyang,and they can be classified as primary forest.To compare their ecological difference between primary and secondary forests,we sampled E.henryi populations from Dayuan village in Chun'an,Zhejiang and Nanshan Bamboo Sea-Longtan Forest Farm in Liyang,Jiangsu respectively.Through field survey,the age structure,quantity dynamics,regeneration strategy,distribution pattern and community diversity of E.henryi populations were studied.The purpose of this study is to compare the distribution and development trend of the E.henryi in the two different habitats.Moreover,this study can also provide baseline for further understanding of its growth habits and reasonable protection.The results are as follows:(1)Age structure:First,25 tree cores with different size classes were collected at the height of 1.30 meter of sample trees in primary and secondary forest totally.Then,we made them dry,polish and record their actual age.Finally,the DBH-Age curve was fitted.The formulation was:y=7.14e0.052x((R2= 0.91,P<0.01).The actual age cf every tree were estimated according to the fitted formulation.The maximum DBH of E.henryi was 74.20 cm,with a height of 26 m,and its corresponding age was 338.43 years in primary forest.In secondary forest,the maximum DBH of E.henryi was 50.64 cm,with a height of 16 m,and its corresponding age was 99.37 years.We divided these populations of E.hmyi into nine age classes(every 10 years as an age class)according to their actual age.We then made statistics concerning the number of each age class and analyzed their age structure dynamics.The results showed that both populations in primary and secondary forest were of growing types collectively.However,some small populations in secondary forest were of senescent type due to few individuals,absence of the saplings,and deficient seedlings.In addition,the result of population structure from the height class was similar to that from age class.(2)Population demography:The results of static life table showed that the maximum expected longevity of the E.henryi population was at the age class ?,and there was a small peak of mortality rate at the age class ? and ?.The survival curve of E.henryi populations in primary forest accorded with Deevey ? type.In secondary forest,the maximum expected longevity of the E.henryi population was at the age class ? and ?,with the peak of mortality rate at age class I and VI.Its survival curve also accorded with Deevey ? type.(3)Regeneration strategy:E.henryi populations are often distributed in gullies and hillsides nearby with bare rock and barren soil.The populations had two types of regeneration in the wild,and they were seedling and sprouting respectively.Furthormore,the latter can be divided into three categories:root sprouts,stem base sprouts and crown sprouts.Due to poor habitat and low germination rate,there are considerable sprouting individuals both in primary and secondary forest.The number of sprouting individuals in primary forest was lower than in secondary forest,probably resulting from human disturbance in secondary forest.This suggested that the proper human disturbance could be beneficial to its sprouts regeneration.(4)Spatial pattern:1500 m2 plots were established in primary forest and secondary forest respectively.The spatial distribution pattern,pattern dynamics and spatial association of different age classes in the two communities were compared by applying point pattern analysis method.The results showed that the overall distribution pattern of E.henryi in primary and secondary forests was clumped.Their dynamics of the population pattern were also similar in the two forests.Namely,distribution pattern presented a trend from clump to random along with the increasing of the age class in each forest type.The results of spatial correlation showed that the advanced trees promoted the juveniles in the sampled stand.(5)Community diversity:There were significant difference in species composition between primary and secondary forest.The species in primary forest were richer than in secondary forest.There were 170 vascular plants,belonging to 132 genera and 75 families in primary forest.In contrast,there were only 76 vascular plants,belonging to 69 genera and 47 families in secondary forest,due to human disturbance and bamboo invasion.Except for Pielou community evenness index(PW),Species richness index(S)?Shannon-Wiener species diversity index(SW)and Simpson ecological dominance index(SN)in primary forest were higher than those in secondary forest.Concerning taxonomic diversity,average taxonomic difference index(?+)and the taxonomic difference variation index(?+)in primary forest were lower than in secondary forest.Therefore,it indicated that although the species in primary forest were rich,their relationship were relatively closer than in secondary forest with more homogeneous communities.Based on the results stated above,it is suggested to reduce the interference intensity in secondary forests.Specifically,we could consider felling some bamboos in secondary forest,and promoting the sustainable and stable development of the community.In addition,it may be also practicable to transplant some seedlings of E.henryi in certain patch with more individuals into other patches with few seedling with the aim to keep the populations stable in the long run.