Study On The Natural Population Structure And Niche Of Phoebe Bournei In Central Jiangxi Province

Phoebe bournei is a national level II key protected wild plant,belonging to rare and endangered species,which has high ecological and economic value.This paper aims to analyze the size structure of the population by taking the natural population of Phoebe bournei in central Jiangxi as the research object.The data collection from the sample-plot survey,by using diameter structure instead of age structure,it is divided into 16 diameter grades.The population characteristics were studied based on the survivorship curve and quantitative analysis method and the population distribution pattern was analyzed by the theoretical distribution model and the aggregation intensity index.The niche quantitative analysis method was used to analyze the niche characteristics of the main populations in the community.It provided a reference for the rational management and protection of the natural population of Phoebe bournei.The main findings and conclusions was as follows:?1?The proportion of seedlings?D<2 cm?,saplings?2 cm?D<5 cm?,small trees?5 cm?D<10 cm?,medium trees?10 cm?D<20 cm?,large trees?20 cm?D<40 cm?and old trees?D?40 cm?accounted for 57.93%,13.14%and 12.91%respectively of the total plants.The diameter structure of the population as a whole presents was generally an inverse-J type.The mortality of the population at three stages of D<2 cm and H>1 m,5 cm?D<10 cm and 60 cm?D<65 cm were all exceed 50%.The life expectancy was the highest at 25 cm?D<30 cm?e_x=4.50?.The survivorship curve of the population tended to be the Deevey-II type,which generally belongs to the growing and stable population.?2?The spatial distribution pattern of the population at the sampling scales of 5m×5 m,5 m×10 m and 10 m×10 m indicates that the population was generally aggregated,,and the aggregation intensity decreased with the scale.The distribution pattern of populations at different growth stages showed that from the stage of seedlings,saplings,small trees,medium trees,large trees to old trees,the distribution pattern was from high aggregation to low aggregation,and the aggregated distribution developed in a random direction.The population showed a clustering distribution from the sapling to the big tree stage,and the old tree stage showed a random distribution.But the 10th diameter grade?35 cm?D<40 cm?was the turning point from the individual aggregation distribution to the random distribution.?3?Phoebe bournei was widely distributed in the community and had strong adaptability.It was important values?51.51%?and niche breadth?B_i=1.22,B_a=0.86?were higher than other populations.By analyzed the niche overlap?NO?,there were 94pairs of NO=0,accounting for 49.47%of the total logarithm,indicating that these pairs in the community did not appear in the same resource level;NO<0.6 pairs accounted for more than 80%of all species,indicating that most tree species were less obvious for each resource level.By analyzing the proportion of niche similarity(C_ih),there were 94 pairs of C_ih=0,accounting for 78.42%of the total logarithm,indicating that most of the populations had low similarity to environmental resource utilization.At the same time,the similarity ratio of Phoebe bournei to the species with wide niche was between 0.29 and 0.41,indicating that the adaptability of these niches to the environment was highly similar to that of Phoebe bournei.