Study On The Community Structure Of Hopea Hainensis In Limu Mountain Nature Reserve Of Hainan Province

Hopea Hainanensis,as a precious tree species in the Limu Mountain Nature Reserve in Hainan Province,is one of the national rare and endangered protected species at the first level.Its survival is also greatly threatened with the increase of human interference.In the paper,the wild resource of The Limu Mountain Forest farm in Hainan is regarded as the research object.We do some researches that matched protection countermeasures are given on the basis of distributions and renewal characteristics of Hopea Hainanensis base population,including the analysis of the species composition and structure of the base community,the relationship between the diversity of the plant type of the Hopea Hainanensis base community and the occurrence of pests and diseases,.The results are of great significance for understanding the population distribution of slopes in the Lima mountain forest,carrying out the conservation of species diversity in forest areas and maintaining the stability of the ecosystem of tropical mountain rainforests.The results are as follows:(1)Population distribution and seedling regeneration regularity of hill base.The distribution pattern of the age structure in the hillside and barrier distribution area of Limu Mountain Forest Farm is as follows:middle-aged tree group>young tree group>old tree group,showing a hammer-shaped structure distribution,and the population of hillside and barrier belongs to the growth-type population.The number of seedlings under the mother tree decreases with the increase of the distance from the mother tree,and varies with the direction.The seedling survival rate is the highest in the range of 0-5 m from the mother tree to the south.The difference of relative distance from the mother tree had significant effect on the total number of seedlings on the hillside.The difference was most significant when the distance from the south to the mother tree was 5-10 m and 15-20 m,and the distance from the east to the mother tree was 10-15 m.This may be due to different directions of light,wind and other reasons.The mean number of seedlings and the mean height of seedlings reached the minimum at 782 m and 748 m,respectively.The maximum difference of the average height was 18.42(+0.01).(2)Species composition and structure analysis of hillside community in Limu Mountain.A total of 46 families,84 genera and 122 species of vascular plants were found in the sample plots including 2 families,4 genera and 4 species of ferns,44 families,80 genera and 118 species of seed plants.From the perspective of families,the family and genera of community plants are not concentrated,which shows the richness of the species of community plants.In the aspect of genera,dicotyledons are dominant in the angiosperm phylum of this region,and the dominant genera are common tropical genera such as Syzygium and Elaeocarpus.The arbor layer of the slope base community is mainly composed of Vatica mangachapoi,Gironniera subaequalis,Schefflera octophylla,Cinnamomum tsoi and some plants of Fagaceae;the dominant species in shrub layer are Tabernaemontana divaricata,Mallotus hookerianus?Nephelium lappaceum?Polyalthia laui is dominated by Arbor palm,single-leaf crescent fern,Selaginella tamariscina?Pandanus austrosinensis?Caryota ochlandra,etc.The number of plant community species in the natural protection area of Limu Mountain slope base decreases with the increase of altitude,which may be due to the decrease of temperature with the increase of altitude,and the change of environmental factors such as light,precipitation and air humidity affects the distribution of plant species.(3)Relationship between population structure,plant species diversity and occurrence of diseases and insect pests in Hopea hainanensis community.Diameter of mother trees on Hopea hainanensis,height,elevation,Margalef index,Simpson index and Pielou index have different relationships with the occurrence of diseases and insect pests.With the increase of diameter of mother trees on Hopea hainanensis,the damage rate of pests and diseases on the whole showed a downward trend with the highest value of 24.3%and the lowest value of 8.9%.With the increase of mother trees,the damage rate of pests and diseases on mother trees showed a downward trend gradually,and the incidence of diseases and insects first decreased and then increased between 5 and 20 m.After 20 m,the damage rate of diseases and insects tended to be stable,averaging about 9.9%.So mature trees had better resistance to pests and diseases.The altitude is not completely positively correlated with the incidence of pests and diseases.With the gradual increase of altitude,the damage rate of Hopea hainanensis gradually decreases,but when the altitude reaches 650 m,the damage rate of trees gradually stops decreasing.The average is 16.6%.With the increase of species richness,the damage rate of Hopea hainanensis decreased gradually.When richness reaches 0.75,the damage rate decreases to about 14.45%.With the increase of evenness,the damage rate of pests and diseases increased first and then decreased.At 1.3,the maximum damage rate was 24.3%,and then maintained at about 12.4%.With the increase of Simpson index,the damage rate also showed a decreasing trend.At 0.96,the average damage rate dropped to 12.18%.Therefore,by adjusting the diversity of plant types in the sample plot of Hopea hainanensis community,the risk of trees being damaged by pests and diseases can be effectively reduced.According to the distribution and renewal characteristics of Hopea hainanensis population,the relationship between the species composition and structure of Hopea hainanensis community and the occurrence of diseases and insect pests,this paper puts forward some effective measures,such as protecting the population of Hopea hainanensis,optimizing the spatial distribution structure of natural forest on Hopea hainanensis,removing unfavorable factors such as mother tree seedlings and surrounding environment and reducing human disturbance activities,so as to make more contributions to the healthy utilization and sustainable development of Hopea hainanensis wild resources in Li Mu mountain nature reserve.