Studies on forest regeneration dynamics in the world focus on studying the topics like density, regeneration tree composition and the relationship between regenerated trees[r]
Trang 1MINISTRY OF EDUCATION
AND TRAINING
VIETNAM ACADEMY
OF SCIENCE AND TECHNOLOGY
GRADUATE UNIVERSITY SCIENCE AND TECHNOLOGY
-
Nguyen Tien Dung
STUDY ON STRUCTURAL DYNAMICS OF THE EVERGREEN
BROADLEAF FOREST
IN HANG KIA - PA CO NATURE RESERVE
AND XUAN SON NATIONAL PARK
Trang 2The thesis was completed at:
Graduate University of Science and Technology - Vietnam Academy
of Science and Technology
Supervisors:
1 Assoc Prof Dr Tran Van Con
2 Assoc Prof Dr Nguyen Van Sinh
The thesis can be found at:
- Library of Academy of Science and Technology
- National Library of Vietnam
Trang 3INTRODUCTION
1 The urgency of the thesis
Forests play an important role to regulate the climate; maintain the ecological environment; preserve and regulate water sources; protect soil against erosion; and prevent and minimize natural disasters In Vietnam, forest area has changed dramatically over time In 1943, the forest area in Vietnam was 14.1 million ha (coverage reached 43%); however, by 1990 the forest area was severely reduced to 9.18 million ha (coverage reached 27.2%); in the years 1980 - 1990, on average, our country lost 100,000 ha of forest each year Since 1995, thanks to the great efforts of the State and Government of Vietnam, the forest area has increased to 14.6 million
ha with the national coverage reaching 41.89% However, the quality
of the natural forest is currently low and continues to decline in timber volume and biodiversity Deterioration of forest quality leads
to a decline in the role of forests in people's lives Natural disasters continuously occur and severely affect lives of people
The forestry basis for sustainable forest management includes classification of natural forests, structural features of natural forests, rules of growth and yield of natural forests, rules of forest succession and regeneration The dynamics taking place in the forest can be divided into three groups of processes: (i) tree growth; (ii) additional regeneration process; and (iii) natural death process in diameter classes Information on the growth and regeneration rules of forest trees should be obtained from long-term observations by positioning plots, by monitoring those rules over the long term This requires specialized knowledge, great time and finance Up to now, in Xuan Son National Park and Hang Kia - Pa Co Nature Reserve, there are
Trang 4very few studies on the PL of the location of forest dynamics, and no studies on structural dynamics of forests For the above reasons, the
topic: " Study on structural dynamics of the evergreen broadleaf forest
in Hang Kia - Pa Co Nature Reserve and Xuan Son National Park"
has been conducted
2 The study objectives of the thesis
- General objective: To contribute to understanding the rules and structural dynamics of evergreen broadleaf natural forests as a basis for proposing some solutions for sustainable forest management
- Specific objective: To identify some structural characteristics and forest structural dynamics characteristics in Hang Kia - Pa Co Nature Reserve and Xuan Son National Park; and propose some solutions for sustainable forest management
3 The main study contents of the thesis
- Study on forest structure characteristics and species diversity
- Study on canopy layer structure dynamics
- Study additional regeneration dynamics; and level transition and death process
- Proposed application of study results
- Proposal of some solutions for forest management
4 Layout of the thesis
Introduction: Explaination of the necessity, objectives, and scientific and practical significance of the thesis (3 pages)
Chapter 1 Study overview (30 pages)
Chapter 2 Subject, scope, content limitation and study method (14 pages)
Chapter 3 Characteristics of the study area (10 pages)
Trang 5Chapter 4 Study results and discussion (65)
Conclusions and recommendations: presenting conclusions drawn from study results, stating existing shortcomings and recommendations (3 pages)
The thesis includes 27 tables and 39 pictures Refer to 92 documents in Vietnamese and foreign languages
CHAPTER 1 STUDY OVERVIEW
1.1 Study on forest dynamics worldwide
1.1.1 Study on regeneration dynamics
Studies on forest regeneration dynamics in the world focus on studying the topics like density, regeneration tree composition and the relationship between regenerated trees and the canopy layer; regeneration forms of tropical forests; additional regeneration capacity of regenerating tree layer for the canopy layer and factors affecting regeneration ability; the variation in plant diversity of regenerated tree layers after different harvesting time; growth of regenerated plants under different ecological conditions; using mathematical models to predict the rate of additional regeneration, etc Studies on regeneration dynamics in the world are conducted on the standardized positioning plots and long-term study This method
of study has not been used much in Vietnam
1.1.2 Study on growth dynamics of forests
Studies on growth dynamics of forests in the world focus on the following topics like study on growth dynamics in diameter and total cross section at the diameter levels; the relationship between growth in diameter and mortality, between the rate of regeneration and mortality; using mathematical models to calculate the rate of
Trang 6addition and mortality and simulating dynamics of growth for forest objects These studies have been all conducted on standard positioning plots For growth dynamics, there have been many different authors using mathematical models to simulate this behavior This is an issue that needs to be further studied in Vietnam
1.1.3 Study on dynamics succession
Studies on forest succession in the world focus on the following topics like the change of species composition, the diversity
of plants, the regeneration and growth of forest trees in different successive stages Some authors have also used mathematics to simulate the process of forest dynamics, including Modul on forest succession Forest succession studies have been followed for a very long time, methodical, time and effort consuming Additional studies and findings on the rules of the typical successive behavior of tropical forests are of great significance to current forest management practices
1.2 Study on forest dynamics in Vietnam
1.2.1 Study on forest regeneration dynamics
Studies on forest regeneration dynamics in Vietnam have been condcuted for a long time The authors have focused on the regeneration dynamics on forest land after shifting cultivation and regeneration under the canopy of natural forests, effects of factors on regeneration process, etc In general, studies on forest regeneration dynamics in Vietnam have not been carried out much There are very few studies on the positioning PLs; therefore, it is necessary to continue additional studies on regeneration dynamics issues on the positioning PLs for understanding this process with different specific subjects
Trang 71.2.2 Study on growth dynamics
The foundation of dynamics studies are studies of basic silvicultural principles in forest ecosystems Prior to 1990, the authors focused on forest growth issues with the widely used method of tree analysis After 1990, the authors focused on tree growth dynamics There have been studies that simulate the laws of structure and dynamics during this period Recently, dynamics studies have been conducted on permanent plots (PL), but still few Therefore, it is important to carry out to studies on the process of forest dynamics on the positioning PLs
1.2.3 Study on dynamics succession
Studies on forest succession dynamics are often conducted in a long time and are time and effort consuming In the absence of long-term monitoring, it is possible to use the method of reseaching space instead of through time, studying on forest ecosystems with many similarities, and recovering after many different stages This issue needs to be studied in a long term on the positioning PLs for the most accurate information about those processes
1.3 Discussion and identification of study questions
After the general study, the questions are posed are: according
to which law does the evergreen broadleaf natural forest dynamics occur? Does a relationship exist between the dynamics and structural factors of the forest? Can math functions be used to simulate those processes? What equations can represent those relationships? To test these hypotheses, the thesis focuses on the following issues:
- Study on forest structure characteristics at the beginning of PLs establishment at Xuan Son National Park and Hang Kia - Pa Co Nature Reserve
Trang 8- Study on structural dynamics in order to notice a change of composition over time of dominant species in the forest
- Study on structural dynamics N/D1.3 in order to determine the changing trend of this structural factor in the future
- Study on additional regeneration dynamics, transition and death process for an overview of the structural dynamics of the forest
- Proposal of some solutions for forest management based on the study results of the thesis
CHAPTER 2 SUBJECT, SCOPE, CONTENT LIMITATION
AND STUDY METHOD 2.1 The subject, scope and limitation of the study
2.1.1 The subject of the study
From the point of phylogenetic vegetation, the study subjetc of the thesis is evergreen broadleaf natural forest in Hang Kia - Pa Co Nature Reserve, Hoa Binh Province and in Xuan Son National Park, Phu Tho province
2.1.2 Scope and limitation of the study
- Limitation of study subject: to only focus on study on structural dynamics of the canopy layer (including layers A1, A2, and A3) of the stand For additional regenerated trees, only the number of regenerated trees added to the tall tree layer is concerned
- Content limitation: study on structural characteristics, structural dynamics, additional regeneration, and transition and death process of the canopy canopy
- Limit on study time: from 2007 to 2018
2.2 Study content
Trang 92.2.1 Study on forest structure characteristics and species diversity 2.2.2 Study on dynamics of the canopy layer structure
(Composition, N/D1.3)
2.2.3 Study on additional regeneration dynamics, transformation and death process of the canopy layer
2.2.4 Proposal of application of study results
2.2.5 Proposal of some solutions for forest management
2.3 Study methods
2.3.1 Method of data collection
Establishing permanent plots with a size of 100x100m Measuring diameter at breast height (D1,3): All trees have D1.3> 10cm
in the PL Measuring the peak height (Hvn) of the trees with D1.3> 10cm in the plot In the second measurement (in 2018), statistic and measurement of regenerated trees were further done to the tall tree layer of dead trees in reality
2.3.2 Information processing methods and tools used
All data collected from the permanent plots are collected, adjusted, analyzed, processed and calculated by Excel and SPSS softwares with necessary criteria for the study content Testing of specific types of mathematical functions is performed to find suitable types of functions that simulate the dynamic process MM&S software is used to simulate the process of dynamics
CHAPTER 3 CHARACTERISTICS OF THE STUDY AREA 3.1 Characteristics of natural conditions
3.1.1 Geographical location
3.1.1.1 Hang Kia - Pa Co Nature Reserve
Trang 10Located in the north of Mai Chau District, west of Hoa Binh Province, within the administrative boundaries of 6 communes: Hang Kia, Pa Co, Tan Son, Bao La, Cun Pheo, and Pieng Ve with the total area of 7,091 ha, including 2 subdivisions:
- Strictly protected subdivision: 2,680 ha
- Ecological rehabilitation subdivision: 4,411 ha
3.1.1.2 Xuan Son National Park
Xuan Son National Park is located to the west of Tan Son District, on the triangular boundary between three provinces Phu Tho, Hoa Binh and Son La The total natural area is 15,048 ha; of which agricultural production land is 312.4 ha; 14,617.5 ha of forest land; and 118.1 ha of non-agricultural land
3.1.2 Topography and terrain
3.1.3 Geology and pedology
3.1.4 Climatic and hydrological conditions
to management and protection of the Nature Reserve's natural resources
- In Xuan Son National Park: within the scope of the park, there are 2 subjects managing the same area of land, making the management of land use complicated and difficult In addition, some locations in functional subdivisions are not properly managed
Trang 11CHAPTER 4 RESULTS AND DISCUSSION 4.1 Forest structure characteristics in the study area
4.1.1 Forest composition, structure and diversity
4.1.1.1 Forest composition and structure
a, Canopy layer (timber)
The research results show that the forest composition in the study area is fundamentally different The difference is shown in dominant species and number of species in the community An overview of the structural characteristics of each cell is shown as follows:
Table 0.1 Botanical composition in the study area
Plot Area
Num
of species
Density (tree/ha) HL Botanical composition
17,3 Castanopsis indica + 9,6
Garcinia fagraeoides + 6,8 Hopea chinensis + 5,8 Diospyros sylvatica, + 5,6 Manglietia dandyi
24,8 Diospyros sylvatica + 10,0
Lithocarpus dealbatus + 8,2 Garcinia fagraeoides + 7,3 Vatica odorata ssp + 5,6 Lithocarpus ducampii + 44,1 others
20,8 Saraca dives + 6,8 Aglaia
lawii + 5,9 Pometia pinnata + 5,8 Barringtonia acutangula + 60,7
others
9,2 Saraca dives + 6,9 Bhesa
robusta + 6,5 Barringtonia acutangula + 77,4 others
6,6 Nephelium cuspidatum + 5,7
Aglaia argentea + 5,2 Wrightia tomentosa + 82,5 others
Trang 12- In Xuan Son National Park, tree species composition is more diverse and plentiful in the Hang Kia - Pa Co area The number of species in the PL varied from 71 to 106 species corresponding to the density from 344 to 487 plants/ha In the area of Hang Kia - Pa Co, the number of species varied from 56 (HB03) to 70 species (HB06), density varied from 466 to 608 trees/ha
- In the area of Hang Kia - Pa Co, the dominance is more pronounced than that of Xuan Son, reflected through the large formation coefficient, the total composition coefficient of the dominant species is high In the Xuan Son area, most of the plant species in the PLs do not show their dominance
- In terms of composition, there is also a difference between the two areas due to the difference in geography and flora
b, Shrub and vegetation layer
There are also significant differences in the characteristics of the shrub and vegetation layer in the two areas The shrub layer at Hang Kia - Pa Co is from 1.2 to 2.0 m high Coverage from 20 - 30% Xuan Son area has a remarkable difference The shrub layer has an average height of 0.5 - 1.2m, coverage from 10-20% In general, the shrub and vegetation layer in Hang Kia - Pa Co area is taller and denser than Xuan Son due to the higher degree of light fall under the forest canopy at Hang Kia - Pa Co
Thus, at the two study sites there is a fundamental difference in the species composition and dominance level For a more comprehensive view, there is a need for in-depth research on plant diversity in the study area
4.1.1.2 Species diversity in the study area
Trang 13Questioning: is the 1 ha area of each PL sufficiently representative of the study area? Test results for the PLs based on the minimum representative area method proposed by MÜLLER-DOMBOIS and ELLENBERG, (1974) [85], are presented as follows:
Figure 0.1: Changes of the
species in Hang Kia - Pa Co
when the area of the PL changed
Figure 0.2: Changes of the species in Xuan Son when the PL area changes
Through the statistics of the number of new species appearing when the PL area increases, we can see that: When increasing the PL area from 7,600m2 to 8,400m2 (an increase of 800m2 is equivalent to> 10% of the area of the PL), the number of species exported the new level in each PL is below 10% Thus, it can be seen that only the area of each PL reaching 8,400m2 is enough to represent the research object
Results of the calculation of species diversity indicators are as follows:
Table 0.2 Botanical diversity in the study area
Ordinal Location Num of
species
Density (trees/ha) HL H D
0 20 40 60 80