PLANTS DIVERSITY AND FOREST STRUCTURE DIFFERENTIATION BY ELEVATION IN NGOC LINH MOUNTAIN RANGE, KON TUM PROVINCE, VIETNAM

Ngoc Linh mountain range with Ngoc Linh peak of 2598m.a.s.l is an important part of forest ecosystems in Central – Highlands, Vietnam. Located on the complex terrain with stable and long-term geological components, the plant communities here contain the diversity and originality of the high mountains and contiguous areas between Central and Central Highlands Vietnam. The study area covers 65571 hectares, of which Ngoc Linh Nature Reserve covers about 40500 hectares, spread over medium and high mountain terrain. Strongly divided terrain has created the richness, diversity, and originality of ecosystems, especially the structure of natural vegetation. The article presents characteristics and differentiation of forest plantations in Ngoc Linh mountain area; study diversity, and conservation value of regional plant diversity resources; analyzing the characteristics and relationships of plants with geographical factors, especially the rules of elevation, slope, terrain direction, soil and drainage capacity of forest land. Comparison of similarities and differences with some other areas of the Central Highlands, especially the communities with the participation of coniferous plants. To implement the scientific content, various methods have been used. Among them are the main methods: Mapping method and Geographic Information Systems, Field survey methods and Phytogeography (Plant Geography) methods. The study results recorded 1128 species of vascular plants, belong to 627 genera, 175 families, 59 orders, 10 classes, 6 divisions. The flora of Ngoc Linh mountainous area fully converges the vascular plants of the plants in Vietnam, in which the species mainly focus on Magnoliophyta. This is the most diverse division with a total of 145 families, 571 genera and 1032 species, accounting for 82,39 % of families, 91,07 % of genera, and 91,48 % of species. The comparison results show that the proportion between sectors in the plants of Ngoc Linh and the plants of Vietnam has the same structure, with quite similar proportions of dominant species group. Accordingly, the absolute advantage of the Magnoliophyta is from 91.48 % and 92.62 % respectively. 80 rare and precious species have been identified in the IUCN Red List and Vietnam’s Red Data Book 2007. There are 189 endemic species of 135 genera of 66 families. In which there are 107 endemic species of Central Vietnam, the rest belong to Vietnam endemic. Some endemic species with high conservation significance is: Panax vietnamense, P. dalatensis, Quercus langbianensis. The rules of distribution according to elevation are shown in the structure of plant communities through species composition and canopy structure of the forest. Accordingly, plant communities have a high diversity with complex structures, including 3–4 layers. At 900 m.a.s.l elevation, in mixed forests, broadleaf trees form multi-dominant and diverse species. From 1000–1500 m.a.s.l, on the mountainside terrain, the dominant vegetation with P. kesiya in the emergent layer. High diversity in forest structure clearly manifests at 2000–2300 m.a.s.l. Plants are strongly differentiated; some places are multi-dominant, and some places are dominant with P. dalatensis. The most diversity of plants is concentrated at an elevation of 2000–2300 m.a.s.l and the number of the most canopy spread from 1500–2000 m.a.s.l. Gymnosperms, especially P. kesiya and P. dalatensis, participate in single dominant and codominance roles in mixed forest communities. There are differences in the distribution of major conifer species forming plant communities in Ngoc Linh mountain range compared to Chu Yang Sin National Park and Bidoup – Nui Ba National Park in Central and South – Central Highlands. Accordingly, in Ngoc Linh, P. dalatensis has a wider distribution area, higher dominance with a clear role in the formation of plant communities at elevations above 2000 m.a.s.l.