Study On Population Structure Dynamics Of Dominant Species In Natural Forest Of Tropical Coastal Hills In Tongguling And Photosynthetic Characteristics Of Seedling Under Forest Gap

In order to further understand the northeastern hainan tropical coastal hilly natural superiority species in the forest structure characteristics,survival present situation,the update mechanism and dynamic change characteristics of the future,in this study,the fixed sample plots of the coastal secondary forest in Tongguling,northeast hainan were reviewed,and the methods of important value calculation,static life table,quantitative analysis of population structure and variance analysis were mainly adopted to compare and analyze the dynamic change rules of the forest in this area.the forest community in the young plant response to different light environment and adapt to quantitative analysis,revealing the different tree species seedling update micro environment microclimate condition of forest gap,especially the response of the light environment,To understand the internal driving mechanism of forest regeneration,community dynamics and succession of natural forest in tropical coastal hills from the perspective of physiology and ecology.The results are as follows:1.There are 151 species of plants,belonging to 97 genera and 51 families,in the natural forest of tropical coastal hills in Tongguling.There were 104 species of trees,46 species of shrubs and 22 species of woody lianas.Gymnosperms have 1family,1 genus,1 species,150 species of angiosperms,belonging to 50 families,97genera.The top 25 species in importance value of this sample are respectively:Schefflera octophylla、Aeronychia oligophlebia、Olea dioica、Syzygium buxifolioideum、Syzygium championii、Syzygium odoratum、Stertulia lanceolata Cav、Syzygium buxifolium、Acmena acuminatissima、Litsea variabilis、Choerospondias axillaris、Symplocos chunii Merr、Eurya nitida、Koilodcpas hainanense、Dillenia turbinata、Xantolis longispinosa、Mallotus hookerianus、Aporosa yunnanensis、Antirhea chinensis、Eiacocarpus sylvestri、Sarcosperma laurinum、Hydnocarpus hainanensis、Bridelia balansae、Drypetes arcuatinervia.Compared with the dominant species composition of the community in 2012,this study found that a total of 13species with an important value greater than 1 were added in the natural forest sample plots of the tropical coastal hills,respectively are Choerospondias axillaris、Eurya nitida、Dillenia turbinata、Koilodcpas hainanense、Mallotus hookerianus、Antirhea chinensis、Eiacocarpus sylvestri、Bridelia balansae、Hydnocarpus hainanensis、Drypetes arcuatinervia、Olea brachiata、Lithocarpus corneus、Cryptocarya concinna.2.The Schefflera octophylla population size level structure dynamic index（without considering external environmental interference）V_pi=030.685>0,dynamic index of population age structure（subject to random disturbance）V_pi’=0.236>0;the quantitative index of the Aeronychia oligophlebia population shows that:V_pi=44.600>0,V_pi’=0.312>0;The quantitative index of the Olea dioica population shows that:V_pi=42.375>0,V_pi’=0.994>0;The quantitative index of the Syzygium championii population shows that:V_pi=25.098>0,V_pi’=0.239>0;The quantitative index of the Stertulia lanceolata Cav population shows that:V_pi=32.733>0,V_pi’=1.966>1;The quantitative index of the Syzygium odoratum population shows that:V_pi=41.463>0,V_pi’=0.107>0;The quantitative index of the Syzygium buxifolioideum population shows that:V_pi=10.772>0,V_pi’=0.065>0.the life expectancy of the seven dominant populations showed a single peak characteristic of increasing first and then decreasing,showing a"low-high-low"change pattern.It shows that these populations are in the growth stage and relatively stable.According to the prediction of time series model,the number of individuals in the population of canard foot wood will increase in the next 3,6 and 9years.As the main dominant species of natural forest in the tropical coastal hills of Tongguling in hainan,canard foot wood has a large number of young individuals and abundant reserve resources,which can well supplement the loss caused by natural death of individuals at all ages and is in a stable development stage.3.The maximum light intensity in the window center of natural forest in Tongguling tropical coastal hills ranges from 1600 to 1700 Lux,the maximum light intensity in the edge of the window ranges from 1400 to 1650 Lux,and the maximum light intensity in the forest ranges from 1200 to 1350 Lux.The light intensity in the three habitats is shown as:forest understory>forest gap central>the forest edge.Due to the difference of illumination intensity in different habitats,air temperature and humidity and soil water content in different environments are not the same.The air humidity in the forest decreases gradually from the forest to the center of the forest gap.The air temperature at the edge of the forest window was the highest,then it went to the center of the forest gap,and the air temperature under the forest was the lowest.The soil relative water content was shown as:forest undetstory（31.15%）>the forest edge（17.21%）>forest gap central（13.83%）.4.Plants growing in different light environments show certain differences in plant morphology,growth,photosynthetic characteristics and physiological characteristics.The results showed that the average growth of plant height and base diameter of the seedlings of Ardisia humilis,Arytera littoralis,Fissistigma oldhamii,Litsea variabilis and Schefflera octophylla were higher than those in the forest.However,the growth and change trends of basal diameter and plant height of the seedlings in different light environments were opposite,the height growth was higher in the forest gap environment than in the forest,and the growth of basal diameter was higher in the forest than in the forest gap environment.Under three different light environments,the net photosynthetic rate of Bridelia tomentosa,Arytera littoralis and Ardisia humilis was as follows:forest gap central>forest understory>the forest edge.the net photosynthetic rate of Schefflera octophylla,Hancea hookeriana and Fissistigma oldhamii was as follows:forest gap central>the forest edge>forest understory.And Litsea variabilis and Laurocerasus phaeosticta is shown as:forest understory>forest gap central>the forest edge.5.In this study,the least significant difference（LSD）method of variance analysis was used to compare the photosynthetic differences of plant seedlings in different habitats,and the results showed that there were significant differences in the net photosynthetic rates of different species in different light environments.The significant differences in photosynthetic physiological characteristics of different species are a reflection of the different ecological strategies used by different plants to obtain resource utilization.In the natural forest of the tropical coastal hills,the photosynthetic capacity of Schefflera octophylla,Fissistigma oldhamii,Hancea hookeriana,Ardisia humilis,Bridelia tomentosa and Arytera littoralis seedlings in the forest gap environment was higher than that of the undergrowth.even though these six plants could live in the low-light environment in the forest,the light energy of the leaves was mostly used for survival.since the net photosynthetic rate determines the accumulation capacity of plant material and affects the rate of plant growth,it indicates that the seedlings of the above six plants are more able to use the accumulated effective materials for growth in the forest window environment.The seedlings of Laurocerasus phaeosticta and Litsea variabilis belong to the plants with strong shade tolerance and plasticity.They can adapt well in the forest gap environment and canopy environment,but the growth of Laurocerasus phaeosticta and Litsea variabilis under the canopy is more beneficial to the growth of Laurocerasus phaeosticta and Litsea variabilis under the canopy.