VIETNAM NATIONAL UNIVERSITY OF FORESTRY QUOC MINH DUNG STUDY ON STRUCTURE OF EVERGREEN BROADLEAF FOREST AND WOODY SPECIES DIVERSITY IN PHIA OAC-PHIA DEN NATIONAL PARK, CAO BANG PROVIN
Trang 1VIETNAM NATIONAL UNIVERSITY OF FORESTRY
QUOC MINH DUNG
STUDY ON STRUCTURE OF EVERGREEN BROADLEAF FOREST AND
WOODY SPECIES DIVERSITY
IN PHIA OAC-PHIA DEN NATIONAL PARK, CAO BANG PROVINCE
Field: Silviculture Code: 9 62 02 05
ABTRACT OF DOCTORAL THESIS
HA NOI, 2025
Trang 2Academic supervisors:
The first: ASSOC PROF DR TRAN QUOC HUNG
The second: ASSOC PROF DR NGUYEN HONG HAI
Reviewer 1: Reviewer 2: Reviewer 3:
The dissertation is defending at exam committee at Vietnam National University of Forestry on am date month year 2025
The dissertation can be found at National library and Library of Vietnam National University of Forestry
Trang 3PUBLICATIONS
1 Nguyễn Văn Quý, Quốc Minh Dũng, Nguyễn Thị Hương Ly, Lê Anh Thanh,
Nguyễn Văn Hợp, 2023 Mô hình phân bố độ phong phú của các loài cây gỗ trong rừng lá
rộng thường xanh ở tỉnh Cao Bằng Tạp chí Khoa học và Công nghệ Lâm nghiệp Số 6: 36-45
https://doi.org/10.55250/jo.vnuf.12.5.2023.036-045
2 Quốc Minh Dũng, Nguyễn Thị Hương Ly, Lê Anh Thanh, Nguyễn Văn Quý,
2023 Động thái cấu trúc của rừng lá rộng thường xanh ở Vườn quốc gia Phia Oắc - Phia
Đén, tỉnh Cao Bằng, giai đoạn 2015-2020 Tạp chí Khoa học và Công nghệ Lâm nghiệp Số
6: 27-35
https://doi.org/10.55250/jo.vnuf.12.6.2023.027-035
3 Quoc Minh Dung, Nguyen Thi Huong Ly , Le Anh Thanh, Nguyen Van Quy,
2023 Effects of forest structure on woody plant diversity in an evergreen broadleaved forest
in Cao Bang province Journal of Forestry Science and Technology No 16: 67-76
https://doi.org/10.55250/jo.vnuf.8.2.2023.067-076
4 Quốc Minh Dũng, Nguyễn Thị Hương Ly, Lê Anh Thanh, Nguyễn Văn Quý,
2023 Cấu trúc, đa dạng loài và sinh khối trên mặt đất của rừng lá rộng thường xanh ở Vườn
quốc gia Phia Oắc-Phia Đén Tạp chí Khoa học Lâm nghiệp Số 6: 88-97
http://vafs.gov.vn/vn/wp-content/uploads/sites/2/2024/01/Bai-10.-Quoc-Minh-Dung.pdf
Trang 4PREFACE
1 The necessity of the study
Cao Bang is a border highland province in Northeast Vietnam, with a natural area of 670,785.6 hectares, of which 79.68% is forest and forest land (https://caobang.gov.vn) Phia Oac - Phia Den National Park located at Nguyen Binh district, Cao Bang province, was established under Decision No 57/QD-TTg dated January 11, 2018, based on the upgrade
of Phia Nature Reserve Oac - Phia Den Total area of the national park is about 10,593.5 hectares and belonging to Vietnam's special-use forest system, with forest coverage of 81% Phia Oac - Phia Den National Park is valueable for scientific research, genetic resource conservation, environmental education and is important to the local community in regulating climate, protecting soil and water resource
Of the total 6,146.5 hectares of natural wood forests, poor forests account for the largest proportion with 4,147.91 hectares (67.4%), in addition, depleted forests cover 154.92 hectares (2.5%) and no woody volume forests cover 73.33 hectares (1.1%) However, due to limitations in forest management and protection, negative impacts on forests and deforestation are becoming more and more serious Other causes such as encroaching forest land for farming and building roads into villages increase the rate of deforestation; Biodiversity has been declining in both quantity and quality, many rare and endemic species
of animals and plants are at risk of extinction Natural forests in the National Park area have become poor in volume, the flora and fauna have been seriously damaged over a long period
of time, leading to a sharp decline in quantity and quality, especially the woody tree layer
A number of scientific research has been carried out in the area such as developing a sustainable forest management plan for Phia Oac - Phia Den National Park [2]; Program to investigate, evaluate and monitor developments in forest resources nationwide in cycles I-
IV [6]; Research on the structure of closed evergreen mountain forests [5], Diversity of medicinal plant species [14]; Identification of taxa of the Coffee family (Rubiaceae) [1];
Note the species Begonia wenshanensis [3] However, previous studies were mostly at
initial investigations and assessments, on a narrow scale, and not fully systematical and comprehensive evaluated plant resources in the National Park area Phia Oac - Phia Den Therefore, systematic in-depth research on the structure and diversity of forest ecosystems
in the National Park is really necessary
The thesis entiled "Study on the structure of evergreen broad-leaved forests and the diversity of woody plants in Phia Oac - Phia Den National Park, Cao Bang province" was
Trang 5set out to provide scientific basis on structure and diversity of woody plants of this forest type, as well as proposing solutions to restore and sustainably develop woody plant resources in Phia Oac - Phia Den National Park
2 Objectives of the study
3.2 Practical significance
(i) Initially proposed some solutions to restore poor and depleted secondary forests in Phia Oac - Phia Den National Park;
(ii) Thesis is a reference for scientific research and teaching
4 New contributions of the study
(i) Identified some characteristics and structural changes of poor and very poor evergreen broadleaf secondary forests at Phia Oac - Phia Den National Park in the period 2015-2020
(ii) Assessed diversity levels of woody tree species on poor and very poor evergreen broadleaf secondary forests at Phia Oac - Phia Den National Park
Trang 6(iii) Proposed solutions to restore and develop poor and very poor evergreen broadleaf secondary forests in the study area
5 Objects and limitation of the study
The thesis focuses on studying following contents:
(i) Poor and depleted evergreen broadleaf forest structure
(ii) Diversity of woody plant species in poor and depleted evergreen broadleaf forests (iii) Changes in the structure of poor and depleted evergreen broadleaf forests in the period 2015-2020
(iv) Propose solutions to restore and develop poor and depleted evergreen broadleaf natural forests
b) Study area
Selecting typical samples of two poor and depleted evergreen broadleaf forest communities in Phia Oac-Phia Den National Park
c) Time
The research was carried out from 2015 to 2020, then completing the thesis
6 Structure of the thesis
The main part of the thesis consists of 132 pages, including 18 tables, 20 figures, one list of published articles and 178 references, presented in the following parts: Chapter 1 Literature review; Chapter 2 Research content and methods; Chapter 3 Characteristics of the research area; Chapter 4 Results and discussion; Conclusions, problems and recommendations
Trang 7Chapter 1 LITERATURE REVIEW
Forest ecosystems, especially tropical natural forests, have a very complex structure, leading to a great challenge in research on forest structure for forestry scientists The structure and species diversity of natural forest stands greatly affect forest functions such as protection, environmental protection, and biodiversity conservation Therefore, research on the structure and diversity of forest ecosystems is a basic and important topic This overview presents some results of domestic and foreign research on the structural characteristics and diversity of woody plant species as well as the structural fluctuations of natural forests
1.1 In the world
Researching of forest structure is understanding the rules of arrangement and combination of components of forest plant communities in space and time [11] Spatial forest structure is related to the location and spacing of trees, mainly reflecting horizontal distribution, degree of species mixture and differences in tree size And temporal structure is often associated with regeneration, growth and afforestation, often including independent factors such as tree age, height, diameter, density, basal area, biomass, height canopy width, leaf area and wood biomass
Species composition is a frequently used variable to describe how species occupy the growing space of a forest stand because it is easy to estimate, interpret, and apply in growth and productivity research as well as practice in forestry Diversity indices such as species richness, Shannon–Weaver index and Simpson index are commonly used because they can
be easily estimated These indices increase with the number of species and the number of trees distributed evenly across all species, while the evenness index provides information about the uniformity of species richness [7]
Forest dynamics refers to the processes of recruitment, growth, death and turnover of constituent tree species of a forest community These processes are driven by both natural and anthropogenic disturbances McDowell et al [7] review recent advances in understanding the drivers of forest dynamics and how they interact and change in the context of global climate change The authors show that changes in forest dynamics are ongoing and that the emerging pattern is that global forests are trending toward younger populations with faster turnover rates while old forests have stability dynamics are declining
Trang 81.2 In Vietnam
Vietnam's natural forests are tropical forests, very rich and diverse in species composition, and complex in structure Research on forest structure has been conducted since the early 20th century, with contributions from many domestic and foreign researchers
Nguyen Van Quy & colleagues (2022) [10] studied the spatial relationship of the LRTX forest type in Tan Phu, Dong Nai province, to better understand the ecological characteristics of the species Sen mu - a tree species named in the List of IUCN Among the total of 100 species belonging to 49 families identified, the density, basal area and IVI% of Sen mu are the highest, but the average diameter at breast height of the species is average compared to the 16 main tree species in OTC The spatial pattern of the plant is clustered distribution in the sapling stage, random distribution in the pole and mature stages In the spatial relationship between the 16 main tree species of the OTC, Sen mu has a mutualistic relationship with 5 species, a competitive relationship with 4 species and an independent relationship with 7 species
Conserving biodiversity is of great significance for sustainable development At Than
Sa - Phuong Hoang nature reserve - a specialty forest with great potential for biodiversity When analyzing a number of biodiversity indicators: IVI, insect ratio, H', Cd, Hα, it shows that: Sub-system of tropical green rainy season broad-leaved trees recover naturally on land with many exposed rocks At altitudes > 500 m, there are more high species than other subpopulations, whereas forest vegetation on limestone mountains has many low species The Hα index can be used to analyze computationally diverse entities instead of other numbers [9]
1.3 Studies of natural forests at Phia Oac – Phia Den National park
Phia Oac - Phia Den National Park, Cao Bang province, has a natural area of 10,593.5 hectares, located in 5 communes and towns The National Park's terrain has steep slopes, with diverse vegetation, including low mountain tropical humid evergreen closed forests and medium and high mountain subtropical closed evergreen humid forests
Some structural characteristics of low mountain tropical humid evergreen forests have been studied by Cao Thi Thu Hien and colleagues (2019) through measurement data from 09 1-ha ONC of three forest types in the Phia Oac – Phia Den National Park The results show the presence of 8,641 trees representing for 119 species and 45 families, in which Euphorbiaceae, Lauraceae and Moraceae families predominate The tree species
Trang 9diversity indices between forest types do not differ much, with the Shannon-Wiener and Simpson diversity indices range from 2.572 to 2.974 and from 0.840 to 0.904 [2]
In addition, other studies also recorded rich biodiversity with 1,199 plant species belonging to 611 genera and 177 families, in which the Magnolia phylum dominates [6] Research on the diversity of medicinal plant resources in Phia Oac - Phia Den National Park, the results show that: total number of medicinal plant species found is 472 species, belonging to 323 genera, 128 plant families, of which the Angiosperm accounts for superiority The main parts of the plant used to make medicine are the leaves, roots, and essential oils, which are used to treat 21 different groups of diseases, especially skin diseases [7]
Results of research on endangered plant species in Phia Oac - Phia Den National Park, Cao Bang province have identified 78 plant species that need conservation priority, of which 61 species are listed in the Vietnam Red Book
1.4 General assessment
(i) Research on natural forest structure: Research on natural forest structure, domestically and internationally, is increasingly detailed when considering the carbon storage capacity and stability of trees, species, and status of forest ecology in space and time, and explore the distribution and spatial relationships among forest trees to support sustainable forest management
(ii) Research on woody plant species diversity: Assess biodiversity using popular indices such as Simpson, Margalef, and Shannon-Wiener and develop a formula for tree species composition Moreover, research structure and phylogeny provide a deeper understanding of the evolution and distribution of tree species, and apply species richness distribution (SAD) to predict and manage forest ecosystems
(iii) Research on natural forest structure changes: Forest dynamics is a complex process, the result of ecological processes taking place in communities, promoting the growth, regeneration and formation of species tree species, can last hundreds of years Understanding forest dynamics, including factors such as regeneration rates, mortality rates and growth rates of tropical forest trees, is the basis for conservation and predicting development trends of plant communities in the future
(iv) Research on plants in Phia Oac - Phia Den National Park: With its important ecological role and great economic and social value, Phia Oac - Phia Den National Park has attracted attention by many scientists researching forest structure, biodiversity and endangered species However, additional research needs to continue to preserve and sustainably develop forest ecosystems in the context of climate change
Trang 10Chapter 2 CONTENTS AND METHODOLOGY 2.1 Contents
2.1.1 Structural characteristics of poor and depleted LRTX forests
Study the structure of poor and depleted forest stands in the study area
2.1.2 Diversity of woody plant species in poor and depleted LRTX forests
Study the diversity of woody plant species in poor and depleted forest stands in the study area
2.1.3 Structural dynamics of poor and depleted forests in the period 2015-2020
Study changes in the structure of poor and depleted forest stands in the study area during the period 2015-2020
2.1.4 Propose some solutions to restore and develop poor and depleted natural forests
2.2 Methods
2.2.1 Point of view and approach
- Point of view: the research goal is to identifying some scientific bases for the recovery and sustainable development of woody plant species of poor and depleted natural forests in Phia Oac-Phia Den National Park Therefore, researching and simulating nature on the basis of forestry characteristics, regeneration, growth and development of forest tree species in their natural distribution area is the most effective approach The approach of the project is to describe the structure, species diversity and structural changes over time of these two forest types to find the natural laws that have been regulating forest structure in order to propose solutions methods to restore and develop natural forests in a manner suitable to the natural conditions of the study area
- Approach
+ Experimental approach: Based on monitoring data of two types of poor and depleted forests on permanent plots, the project describes the current status and changes in forest structure over time to find growth and develop rules
+ Systematic approach: Based on ecological studies of natural forest species with the same ecological conditions and legal documents as a basis for proposing measures to restore and develop forests in the study area
Trang 112.2.2 Secondary data
- Documents on natural conditions such as topography, climate, hydrology, land, forest resources; Socio-economic conditions such as: population, labor, ethnic composition
of Phia Oac-Phia Den National Park, Cao Bang province
- Report, data and maps of the results of forest investigation and inventory in Cao Bang province in 2016 under the project "National forest census and inventory for the period 2013-2016" according to Decision No 594/QD-TTg April 15, 2013 by the Prime Minister Data and maps monitoring developments in Cao Bang province's forest resources in 2015 and 2020
- Legal documents such as Circular No 29/2018/TT-BNNPTNT [7] and amended Circular No 17/2022/TT-BNNPTNT [8] regulate Silvicultural measures; Recent research results on Forestry plant species
- Recorded data 2015 on 02 national ecological location plots No 12 and 13 in Phia Oac-Phia Den National Park, Cao Bang province by the Northeast Forest Inventory and Planning Sub-Institute Information about 02 national ecological ODVs is as follows:
+ 02 ODVs cover a large enough area (200 hectares) and are established on 02 main forest states of the National Park: depleted (ODV 13) and poor (ODV 12) forests so they represent the research object of the project is LRTX natural forest in Phia Oac-Phia Den National Park
+ The collected data in 2015 from 02 ODVs were in detail and accurately on the woody and regenerating tree layers, and also allowed comparison with the data of ODV's second survey cycle in 2020 to evaluate forest dynamics in the period 2015-2020 Thus, the data of 02 ODVs in space and time are consistent with the scope and research objectives
+ Each ODV covers an area of 100 hectares (1000 m x 1000 m), including 03 ONCs, each cell has an area of 1 hectare (100 m x 100 m), established on the status plot with the largest area
+ Each ONC is divided into 25 ODDs with an area of 400 m2 (20 m x 20 m) to measure all trees with D1.3 ≥ 6 cm, including determining species name, diameter at breast height, total height, tree position In addition, 05 regeneration research plots with an area of 16 m2 (4 m x 4 m) were established in the 4 corners and in the middle of ONC, all regenerated trees have a height from < 0.5 m to > 5.0 m m are measured for total height and quality assessment
Trang 122.2.3 Data collection
Collecting data on 02 ODVs 12 and 13 in 2020: Each ODV covers an area of 100 hectares and 03 research plots (ONC) with an area of 10,000 m2 (size 100 x 100 m) are set
up Each ONC is divided into 25 subplots (ODD), numbered consecutively from 1 to 25, left
to right and top to bottom Each ODD covers an area of 400 m2 (size 20 x 20 m), all trees, in the tall tree layer with a diameter at breast height (DBH) ≥ 6 cm, are numbered and measured, including: identify species name; Measure DBH using a tape measure with an accuracy of 0.1 cm; Measure the total height (HVN) of all trees in odd-numbered plots using
a Blumeleiss ruler with an accuracy of 0.5 m; Determine the relative position of the tree in ODD using a Leica Disto D2 laser ruler In 2020, PhD student participated in re-surveying all trees, recording additional trees and dead or missing trees compared to 2015
Investigating regenerated trees: on each ONC, 05 plot plots of 16 m2 (4m x 4m), are set up at the corners of ODD numbers 1, 5, 13, 21, 25 (Figure 2.1), measure the following indicators: total height (Hvn) and classifying regenerated trees into 7 levels (<0.5 m, 0.5 - 1.0
m, 1.1 - 1.5 m, 1.6 - 2.0 m, 2.1 - 3.0 m, 3.1 - 5.0 m, >5.0 m); Species name, origin of regenerated tree Quality of regenerated trees: (i) Tree quality A: Healthy tree, straight and even trunk, balanced canopy, no pests or hollow intestines (ii) Quality tree B: The tree has the characteristics of a slightly bent trunk, a lopsided canopy, may have tumors or some small defects but still has the ability to grow and develop to maturity; or the tree is mature, has some minor defects but does not greatly affect the ability to grow or utilize the wood (iii) Quality trees C: Mature trees with severe defects (such as pests, bent, hollow, missing tops ) have almost no ability to take advantage of wood; Immature trees with many defects (such as pests, bent, hollow, missing tops, abnormal growth ) are unlikely to continue to grow and develop to maturity
2.2.4 Data analysis
All tree species names were standardized using the online tool Taxonomic Name Resolution Service 4.0 (Boyle et al (2013) [1], https://tnrs.biendata.org/) to check compatibility with the discovery group Angiosperm Phylogeny Group IV (AGP IV)
Applying statistical methods in forestry to process and analyze data, based on the use
of Microsoft Excel 2016, Past 4.14, Programita, SPSS 26, Phylocom 4.2 and other related softwares
Trang 13Chapter 3 STUDY AREA
3.1 Natural condition
Phia Oac - Phia Den National Park is located in Nguyen Binh district, Cao Bang province, with an area of 10,593.5 hectares of 5 communes Thanh Cong, Quang Thanh, Phan Thanh, Hung Dao and Tinh Tuc town, Nguyen district Binh, Cao Bang province Phia Oac - Phia Den National Park has geographical coordinates: from 22o31'44" to 22o39'41" North latitude, from 105o49'53" to 105o56'24" East longitude
Phia Oac - Phia Den National Park is an area with diverse terrain and typical climate
of high mountains, including many soil types and rich hydrological systems According to the results of the forest inventory in 2016 and updated in 2022, Phia Oac - Phia Den National Park has 8,886.52 hectares of forest land (83.89% of the total area) and 1,706.98 hectares of unforested land (16,000 hectares) 11% of total area) This national park currently records up to 1,287 plant species, of which 90 are in danger of extinction
3.2 Characteristics of 02 ODV
The two national forest ecological ODVs No 12 and 13 established by the Northeast Forest Investigation and Planning Sub-Institute since 2015 according to instructions attached to Decision No 200/QD-TCLN-KH&HTQT dated May 15, 2015 2014 of the General Department of Forestry, described as follows:
(i) ODV 12 has UTM coordinates: X = 592,000; Y = 2,501,001 (Figure 3.1); was established in Lung Muoi Village, Quang Thanh Commune, Nguyen Binh District, Cao Bang Province; belongs to the strictly protected zone of the National Park and is in a state of poor natural forest The North is surrounded by the Phia Oac - Phia Den range, the highest peak in the area has an altitude of 1,888.8 m (compared to sea level) and gradually lowers to Southeast direction, relatively complex divided terrain, average slope 270 to 350
ODV 13 has UTM coordinates: X = 592,000 ; Y = 2,493,002 (Figure 3.1); was established in Khau Cang Village, Thanh Cong commune, Nguyen Binh district, Cao Bang province; belongs to the ecological restoration sub-zone of the National Park and is in poor natural forest status The area's terrain is mainly medium mountain terrain The average altitude is from 800 - 1,100 m, the terrain is quite complicated, the average slope is from 20
- 28o The topographical system of hills and mountains is in and around the area and runs north and gradually lowers to the east