| Zhayun Township is located in the central mountainous area of Hainan, the vegetation is an important part of Yinggeling Nature Reserve, as an important water resource conservation forest for Hainan, it also plays an important role to link different protected regions in east, west, south, and north of Hainan, so this area is very important for ecological security. With route, quadrate and interview methods, we studied the plant diversity and the types of secondary forest communities, results as follows:(1) Natural landscape was the main composition, with diversity landscape but serious landscape fragmentation. There were five landscape types in Zhayun, they are forestland, grassland, farmland, home garden and garden, with high landscape diversity, but low evenness to the dominant forestland. And the forestland can be divided into near primitive forest, secondary forest, plantation and shrub. Among them, near primitive forest, secondary forest, shrub and grassland were belonged to natural landscape, while plantation, garden, home garden and farmland were artificial landscape. The whole landscape was divided into north and south by Changhua River which is the largest corridor throughout the landscape.The preliminary analysis for the relationship between human activities on landscape diversity showed that human activities increased the fragmentation of the landscape in one hand and reduced in the other hand, which depended on the content and manner of human activities. In the central of Zhanyun, garden landscape was growing and tended to gradually occupy secondary forest and grassland. And in the south and the north plantation appeared in a large scale, showing a trend to replace the secondary forest and grassland gradually from north and south directions. Artificial landscape is growing and becoming more and more continuous while natural landscape is decreasing and more fragmented.(2) With high species diversity, clear dominance, and many important species. There were 1493 vascular species in natural ecosystem, which belonged to 172 families,739 genus. There were 40 dominant families with more than 10 species, contained 433 genus (58.59%), 1029 species(68.92%,). Above families and genus play dominant role in this plant flora. And there were 136 endangered and protected species and 104 species endemic to Hainan. There were 314 vascular species in artificial ecosystem, which belonged to 96 families,240 genus. Among them,139 species including 52 wild species and 87 cultivated species were new species that could not be found in natural ecosystem.87 cultivated plants included 70 species with only one variety and 17 species with several varieties. Study on plant using showed that medicinal plant was the largest accounting for 30.50%. Artificial ecosystem and natural ecosystem was similar to the composition of plant forms, all of them were herb> tree> shrub> vine, but herb occupied a higher proportion while tree and shrub declined in proportion in artificial ecosystem. Families or genus with 1 spice in artificial ecosystem is higher than the proportion of natural ecosystem, which means artificial ecosystem flora is more vulnerable. Therefore, artificial ecosystem protection must be paid more attention.Coastal hilly area of Sanya was in south of Hainan, Haikou volcanic area was in north of Hainan, compared to these two regions, the plant forms composition of Zhayun was relatively modest proportion, and Zhayun's community was more complex and stable. The proportion of families and genus with 1 specie in Zhayun was lower than Sanya and Haikou, but the proportion of families with more than 20 species and genus with more than 5 species was higher, that showed there were higher plant diversity and more stable plant flora in Zhayun.(3) Floristic geographic element was multiple, with significant tropical characteristics and a certain proportion of temperate element, showing a transition trend from tropical to subtropical.147 spermatophyte families of natural ecosystem were divided into 10 areal-types and 8 subtypes,685 genus were divided into 14 areal-types 13 subtypes. In which tropical family accounted for 62.57% of total family number and tropical genera accounted for 87.23% of total number of non-cosmopolitan distributional genera. of 90 spermatophyte families of artificial ecosystem were divided into 7 areal-types and 4 subtypes,234 genus were divided into 13 areal-types and 8 subtypes, in which tropical family accounted for 65.56% of total family number and tropical genera accounted for 85.84% of total number of non-cosmopolitan distributional genera. Compared with natural ecosystem, artificial ecosystem lack of Chinese endemic genera, only one genera, Cunninghamia, and had more many exotic plants, these exotic plants had enriched Zhayun's plant diversity on the one hand, while pose a threat on original plant diversity on the other hand.Compared to Sanya and Haikou, the proportion of tropical flora in Zhayun was ranged between these two regions, and the proportion of temperate flora was higher than them. With some ancient families and containing more Chinese endemic genera showed that Zhayun flora originated earlier and had a longer history. All above matched to high-altitude central mountainous location of Zhayun.(4) By TWINSPAN classification and DCA ordination, secondary forest were divided into seven community types. They are Form. I Cyclobalanopsis kerrii+Albiza odoratissima+ Diospyros strigosa, Form. II Liquidambar formosana+ Garcinia oblongifolia + 2Litsea variabilis, Form.â…¢Cratoxylum cochinchinense + Psychotria rubra + Vatica mangachapoi, Form.â…£Schefflera octophylla+Schima saperba+ Lithocarpus fenestratus, Form. V Neolitsea oblongifolia+Cyclobalanopsis insularis, Form.VI Castanopsis fissa and Form.â…¦Xanthophyllum hainanense+Dasymaschalon trichophorum+ Radermachera frondosa. The first axis of DCA expressed the formations'spatial distribution and the gradient of temperature, while the second one depicted inconspicuous environmental information. Study on species diversity showed that species diversity of communities with stronger human disturbance intensity is lower than others. P diversity index is very small between any two community types showed a high habitat heterogeneity among secondary forest communities of Zhayun.(5) The protection object of natural ecosystem is Yinggeling Nature Reserve located in the northwest, secondary forest and shrub outside NR. Secondary forest protection is difficult, but the protection is of great significance, so it is necessary to control the plantation's increase and to strengthen the protection of secondary forest. Grassland's ecological quality was poor, worse than plantation, therefore, grassland outside NR could be developed for plantation. Shrub below 25 degree can be properly developed for mixed agro-forestry project, but protected plants inside should be protected strictly. Protection measures was different between outside NR and NR, NR should be strictly protected by NR staff, outside NR can be protected with paid responsibility system by local villagers. To carry out assessment and quantification on the ecosystem service value of Hainan central mountainous area, and then to legally incorporated it into the economic accounting system. For artificial ecosystems, In situ conservation under PAPDM is the effective to protect plant diversity. To protect the plant diversity of home garden ecosystem and enhancing land-use efficiency of the existing garden ecosystem also play an important role to protect the plant diversity of Zhayun Township.
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