Preliminary Study on the Population Structure Characteristics of Symplocos in Xiaolingjiao Area of Huangshan Mountain

Rui CONG Kaiwen ZHANG Fangfang SUN

Abstract [Objectives] This study was conducted to understand the species diversity of plant communities in the Xiaolingjiao area of Anhui Province， and to analyze the current status of the plant resources of Symptocos.

[Methods] Quadrats with a total area of 3 600 m2 were set up in typical evergreen broad-leaved forests in the Xiaolingjiao area of Huangshan Mountain.

[Results] There were 79 species of woody plants in the quadrats， belonging to 53 genera of 29 families. As seen from the age class structure， evergreen trees such as Castanopsis eyrei and Eurya nitida were growing populations， and Cyclobalanopsis glauca， Cunninghamia lanceolata， Pinus massoniana and Loropetalum chinense were declining populations. The age class structure of each species in Symplocos was of the growing type， and the various populations had not reached a stable state and would grow continuously. The communities had a tendency to develop to evergreen broad-leaved forests.

[Conclusions] This study provides a scientific basis for the protection， development and utilization of Symplocos plants.

Key words Symplocos; Population structure; Xiaolingjiao area of Huangshan; Protection

Since the beginning of the 20th century， certain foundation has been laid for the research on vegetation types， distribution characteristics， and flora composition of the Huangshan Mountains in Anhui， especially for the succession and population protection of Pinus taiwanensis communities[1]. Xiaolingjiao is a part of Huangshan National Nature Reserve. The plants of Symplocos are excellent evergreen or deciduous trees or shrubs with flowers and fruits. There are about 300 species in the world， and about 77 species are distributed in China[2]， which are more common in the south of the Yangtze River Basin， and of which 6 species are distributed in Anhui[3]. The plants in Symplocos have rich resources and play an important role in medicinal and garden applications， but there are few reports on their population structures. In this study， through community investigation of wide plants in Symplocos in Xiaolingjiao area of Anhui Province， according to the investigation on community species composition and population age structure[4]， the basic characteristics and development trends of the communities in this area were systematically analyzed， and the competition mechanism between Symplocos populations and other populations was explored. This study will provide a scientific basis for the protection and utilization of Symplocos plants.

Materials and Methods

Generation situation of the research area

Xiaolingjiao is located in the western part of Huangshan Scenic Area （118°11′E， 30°14′N） in Anhui Province. It covers an area of about 16.55 km2 and has an altitude between 380 and 1 130 m[5]. The Xiaolingjiao area is a nature reserve. The degree of natural plant landscape development in this area is low， and the vegetation approaches natural forest communities. However， the local communities near the Huangshan Scenic Area are subject to severe human disturbance， and the forest communities in Xiaolingjiao area have formed a pattern of coexistence of natural succession and different degrees of man-made disturbance. However， these forest communities at different succession stages have large differences in species composition， flora characteristics， age class structure， etc.[6]. Due to the significant differences in vertical height in Xiaolingjiao area， different plant communities such as secondary forests， evergreen broad-leaved forests， evergreen deciduous broad-leaved mixed forests， and mountain dwarf forests and mountain shrubs are distributed from bottom to top[7]， and the dominant species include Castanopsis eyrei， Symplocos sumuntia， S. setchuensis， Rhododendron ovatum， Eurya nitida， Quercus glauca， Loropetalum chinense， Cunninghamia lanceolata， etc.

Research methods

Quadrat investigation

This investigation and research was carried out in August 2018. In the wild plant communities of Xiaolingjiao area， Anhui， representative sections where a lot of Symplocos plants were distributed were selected， and 36 large quadrats of 10 m×10 m were set up. Each large quadrat was divided into four small quadrats of 5 m×5 m， and the total investigated area was 3 600 m2. The community investigation included records of the species name， number， diameter， height， branchlets， crown， coordinates and growth status of DBH ≥1 cm standing wood.

Data statistics and analysis

Species composition： The names and numbers of the families， genera and species of woody plants in the quadrats were recorded in detail， and their proportions were calculated.

Analysis of importance value[8]： The importance value in the tree layer was calculated according to Important value IV = （Relative abundance+Relative frequency+Relative significance）/3.

Analysis of population age class structure： The population age classes were divided according to the following method[9-10]： age class I： DBH<2.5 cm， age class II： 2.5 cm≤DBH<7.5 cm， age class III： 7.5 cm≤DBH<15 cm， age class IV 15 cm≤DBH<22.5 cm， and age class V： DBH≥22.5 cm.

Results and Analysis

Community tree species composition

According to the investigation and statistics， there were 79 woody plant species， belonging to 53 genera in 29 families. Among them， gymnosperms include Pinus massoniana， C. lanceolata and Juniperus formosana; there were 76 angiosperm species， mainly evergreen tree species in the Symplocaceae （S. sumuntia， S. setchuensis ， S. stellaris， S. anomala， S. paniculata）， Aquifoliaceae （Ilex chinensis， I. rotunda， I. wilsonii， etc.）， Fagaceae （C. eyrei， Q. glauca， C. stewardiana， etc.） and Theaceae （E. nitida， Camellia cuspidata， C. fraterna）， and the deciduous tree species included Dalbergia hupeana， R. simsii， Lindera glauca， Styrax japonicus， S. odoratissimus. There were 2 833 plants in the quadrats， and the number of individuals per unit area was 7 869 plants/hm2.

There were 16 species of arbor plants with an important value greater than 1.5% in the quadrats， among which 5 species belonged to Symplocos. The total relative frequency， relative significance and relative abundance of these species were 74.90%， 91.60%， and 85.32%， respectively， which meant that they accounted for 83.94% of the importance value， so these species could basically reflect the main characteristics of the communities. Among them， C. eyrei， S. sumuntia， L. chinense， Q. glauca and S. setchuensis were the main constructive species of these communities. The importance values of Symplocos plants were 10.54%， 7.01%， 2.97%， 2.63%， and 1.70%， respectively. S. anomala showed the highest resprouting rate （28.57%） among the 5 Symplocos species， followed by S. paniculata  （17.31%） and S. setchuensis （16.10%）.

Analysis of age class structure of dominant populations

According to the V-class standing tree division standard， the age class structure characteristics of the main plants in the quadrats are shown in Fig. 1.

It can be seen from Fig. 1 that C. glauca， C. lanceolata， P. massoniana and L. chinense were the declining populations in these communities， especially the C. lanceolata and P. massoniana populations. Adult trees of these species mostly occupied the arbor layer， and the young trees had weak competitiveness in the auxiliary species with higher canopy density and showed inhibited growth， thereby exhibiting a declining tendency. Evergreen tree species such as C. eyrei and E. nitida were growing populations， which was because of the number of young trees much more than that of adult trees and being fast-growing species. Symplocos plants were mostly young trees， which had greater advantages in the arbor and shrub layers and enhanced the characteristic of evergreen broad-leaved forests to a certain extent.

Based on the age class structure and the characteristics of plant growth， a static life table was prepared for Symplocos plants in the quadrats， and division of classes was performed according to the diameter at breast height （DBH）： class I： 0-0.9 cm， class II： 1.0-1.9 cm， class III： 2.0-2.9 cm， III. Level， and so on， 10 levels in total （sprouting seedlings with a DBH less than 1 cm were more and not counted）. It can be seen from the above figure that there were many young trees of S. anomala and S. stellaris in the communities， with the proportions of individuals at 72.45% and 62.24%， respectively， and the age classes II， III and IV were dominant in the populations. Therefore， both the S. anomala and S. stellaris populations were increasing populations. However， due to the enrichment of tall and large trees in the top space， the growth of Symplocos plants is limited inevitability， which leads to the unstable growth of the entire populations. Proper thinning of forests will help the growth of seedlings， and can promote natural reproduction of Symplocos plants and other plants.

Conclusions

Analysis of community characteristics

Through field surveys and data analysis， there were 79 species of woody plants in 53 genera of 29 families in the quadrats， and symplocaceae， Fagaceae， Theaceae and Ericaceae are common families. Evergreen tree species such as P. massoniana， C. lanceolata and C. fraterna and deciduous tree species such as R. simsii ， Liquidambar formosana， S. paniculata， Albizia kalkora and S. japonicus were common in the communities of C. eyrei+E. nitida+S. stellaris， C. glauca+R. ovatum+S. anomala and S. sumuntia+S. setchuensis+L. chinense. These dominant and constructive species could basically reflect the nature of these communities. In addition， if C. eyrei possesses certain advantages in a community structure， the communities may develop into evergreen broad-leaved forests with C. eyrei as the dominant species in the succession of the community. From the analysis of the age class structures of dominant species in the communities， dominant growing populations of evergreen tree species such as C. eyrei， E. nitida， S. sumuntia， S. setchuensis and S. stellaris may replace declining populations mainly including P. massoniana， C. lanceolata and L. chinense， the entire communities continue to develop into evergreen broad-leaved forests.

Regeneration， conservation and utilization of Symplocos plants

All Symplocos plants were companion species of the communities. Among the investigated quadrats， S. sumuntia， S. setchuensis and S. stellaris having high adaptability showed large proportions of young trees reproducing continuously， and low proportions of adult trees， and the populations had the opportunities to show a continuously growing trend. Once dead standing trees forms a window， the populations will grow rapidly and may become stable populations in the communities. S. anomala had higher rate of resprouts （28.57%）， and showed more one-year-old and two-year-old seedlings， but fewest young trees， indicating that the individuals are greatly affected by the environment in their growing process and prone to death. The total number of S. paniculata was small， in which the number of young individuals was larger， and the resprouting rate was high （17.31%）， so the demand for light was large. Due to inter- and intra-species competition， there were fewer middle-age young trees， which were in dispersive distribution in quadrats. Due to the abundant young tree resources of Symplocos plants and their strong regeneration ability， the age class structures of the plants were all of a typical pyramid growth type. However， because of the impact of the dense forest environment and intra-species competition mechanism， it is difficult for the one-year-old or two-year-old seedlings to become young trees through environmental screening， which may lead to the decline of the population richness， and it is necessary to properly thin the forests to promote their regeneration.

There are many species of Symplocos resource plants with high ornamental and medicinal value. As native tree species， they have strong adaptability， and are suitable for urban garden applications， thereby having broad development prospects. At present， there are few studies on Symplocos plants in China， and even fewer in terms of germplasm resources， introduction and domestication. Therefore， it is necessary to pay more attention to the research and protection of Symplocos plants， and to carry out in-depth research in biology and reproductive physiology， so as to introduce， domesticate， cultivate and breed good varieties. In addition， we should try to establish the best asexual fast propagation system to expand production， so as to meet market demand and make it play a good environment and economic benefits.

References

[1] SU SJ， LIU JF， LAN SR， et al. A review of Pinus taiwanensis studies （1960-2014） and the knowledge domain analysis[J]. Journal of Fujian Agriculture and Forestry University： Natural Science Edition， 2015， 44（5）： 478-486. （in Chinese）

[2] LIU B， RAO Q， SHI MJ， et al. Traditional value of Symplocos plants by ethnobotanical studies[J]. Journal of Minzu University of China： Natural Sciences Edition， 2017， 26（2）： 1-10. （in Chinese）

[3] HU JQ， LIANG SW. Yellow Mountain plants[M]. Shanghai： Fudan University Press， 1996. （in Chinese）

[4] CONG R， ZHANG KW， XIE MM， et al. Community composition structure and diversity of Meliosma oldhamii Maxim. in the Baohua Mountain of Jiangsu Province[J]. Journal of Sichuan Agricultural University， 2017， 35（2）： 214-219. （in Chinese）

[5] YI XG， DING H， FANG YM， et al. Species diversity of forest at different altitudes based on fixed plot in Huangshan Mountains[J]. Journal of Nanjing Forestry University： Natural Sciences， 2018， 42（1）： 150-155. （in Chinese）

[6] ZHAO LJ. Structure characteristics and influencing factors of Lithocarpus glaber-Cyclobalanopsis glauca community in subtropical evergreen broad-leaved forest[D]. Changsha： Central South University of Forestry and Technology， 2014： 96. （in Chinese）

[7] GONG J， LU L， JIN CL， et al. Impacts of tourist disturbance on plant communities and soil properties in Huangshan Mountain scenic area[J]. Acta Ecologica Sinica， 2009， 29（5）： 2239-2251. （in Chinese）

[8] LI WH， YANG GD， LI YF， et al. Pattern and environmental interpretation of Osmanthus delavayi and O. yunnanensis communities [J]. Journal of Plant Resources and Environment， 2018， 27（4）： 53-62. （in Chinese）

[9] CAO J， YANG TH， ZHANG JH， et al. Population structure and regeneration types of Ilex spp. in Tiantong National Forest Park， Zhejiang Province[J]. Journal of Zhejiang A&F University， 2015， 32（1）： 76-83. （in Chinese）

[10] WANG HS. Floristic plant geography[M]. Beijing： Science Press， 1992. （in Chinese）